hot stamping steel sheet, method for its production

专利摘要:
"hot-stamping steel sheet, method for its production, and hot-stamping steel material". hot stamping steel material, which ensures good resistance to hydrogen embrittlement, said steel plate having the chemical composition of: c: 0.18-0.26%; si: more than 0,02% and not more than 0,05%; mn: 1.0 to 1.5%; p: 0.03% or less; s: 0.02% or less; al: 0.001 to 0.5%; n: 0.1% or less; o: 0.001-0.02%; cr: from 0 to 2.0%; mo: 0 to 1.0%; v: 0 to 0.5%; w: 0 to 0.5%; ni: from 0 to 5.0%; b: from 0 to 0.01%; ti: 0 to 0.5%; nb: 0 to 0.5%; cu: 0 to 1.0%; and equilibrium: fe and impurities, in terms of mass%, the concentration of an inclusion containing mn is not less than 0,010 mass%, and less than 0,25 mass%, and the numerical ratio of an oxide of mn for inclusion having a maximum length of 1.0 to 4.0 µm is 10.0% or more.
公开号:BR112014021801B1
申请号:R112014021801-3
申请日:2013-03-05
公开日:2019-10-29
发明作者:Tanahashi Hiroyuki；Tomokiyo Toshimasa
申请人:Nippon Steel & Sumitomo Metal Corp；Nippon Steel Corp；
IPC主号:

专利说明:

STEEL SHEET FOR HOT STAMPING AND METHOD FOR ITS PRODUCTION.
TECHNICAL FIELD [001] The present invention relates to a hot stamping steel plate, a method for its production, and a hot stamping steel material.
BACKGROUND TECHNIQUE [002] In the field of transport equipment, such as vehicles, an attempt is largely made to reduce mass by using high-strength materials. For example, in automobiles, the use of high-strength steel plates has been steadily increasing with the intention of improving collision safety and enhancing functionality without increasing the car's body mass, and also improving fuel efficiency to reduce carbon dioxide emissions.
[003] In this movement to expand the use of high-strength steel sheets, the biggest problem is the manifestation of a phenomenon called degradation of the capacity of fixing the shape, which is more likely to occur as the strength of the steel sheet is increased. The phenomenon is more likely to occur as the amount of elastic recovery after formation increases with increasing strength, and the phenomenon causes such an additional problem specific to high strength steel sheets that it is not easy to obtain the desired shape.
[004] To solve the problem, a usual method for forming a high-strength steel plate is required, additionally, to carry out a necessary processing step (for example, restored) for a low-strength material free from the problem of degradation the ability to fix the shape, or change the shape of the product.
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2/50 [005] As a method to resolve such situations, a hot forming method called the hot stamping method has received attention. The hot stamping method is a method in which a steel plate (processed material) is heated to a predetermined temperature (in general, the temperature that serves as an austenite phase), and stamped by a die having a temperature (for example, example, room temperature) lower than the temperature of the processed material with the strength of the processed material decreased to facilitate formation, so that a desired shape can be easily provided, and also a rapid cooling (quenching) heat treatment, using the difference of temperature between the processed material and the pressing is carried out to increase the strength of a product after forming.
[006] In recent years, the hot stamping process has been recognized for its usefulness, and a wide range of steel materials have been considered to be applied. Examples of these include steel materials, which are used under a severe corrosive environment, such as automobile chassis components, and steel materials equipped with perforated portions for the purpose of adhering to other components. Thus, steel materials obtained by the hot stamping method were required to have not only resistance, but also resistance to hydrogen embrittlement.
[007] This is because, while it is generally known that resistance to hydrogen embrittlement is reduced with increasing strength of steel materials, a steel material obtained by the hot stamping process in general has a high strength, and, therefore, when applying the hot stamping method to the steel material, the steel material is exposed to a corrosive environment to accelerate the entry of hydrogen into the steel, and massive residual stress occurs as processing, such as drilling is performed,
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3/50 thus raising the possibility that hydrogen embrittlement will occur.
[008] From such a point of view, a technique designed to guarantee resistance to hydrogen embrittlement has also been proposed for steel material, whose strength is increased by the hot stamping method. For example, Patent Literature 1 describes a technique relating to a steel sheet having delayed breaking strength (the same meaning as resistance to hydrogen embrittlement), including a predetermined density of one or more of the oxides, sulfides, crystallized products Composites and precipitated Mg composite products having an average particle size in a predetermined range. Patent Literature 2 describes a technique in which the punching characteristic is improved by performing punching (drilling), in a high temperature (hot) state after heating by hot stamping and before pressing, so that the resistance to breakage delayed is improved.
LITERATURES OF THE PREVIOUS TECHNIQUE
PATENT LITERATURES [009] Patent Literature 1 JP2006-9116A [0010] Patent Literature 2 JP2010-174291A [0011] Patent Literature 3 JP2006-29977A SUMMARY OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION [0012] Although the technique disclosed in Patent Literature 1 is an excellent technique, but it is a technique in which Mg which is not easily included is generally made to exist in steel, and a product containing Mg is highly controlled. Therefore, a more easily practicable technique is desired.
[0013] The technique disclosed in Patent Literature 2 is a technique
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4/50 ca based on hot drilling where punching (drilling) is carried out in a high temperature (hot) state after heating for hot stamping and before pressing. Thus, high dimensional accuracy cannot be ensured on a steel material after hot stamping. In addition, the shape capable of being formed using the technique is restricted. Therefore, it is difficult to expand the range of applications (components) of the hot stamping method by the technique disclosed in Patent Literature 2.
[0014] Thus, a technique that guarantees good resistance to hydrogen embrittlement has not been proposed, even when processing that leads to the remaining tension, such as perforation, is carried out after hot stamping and is easily practicable.
[0015] Therefore, an objective of the present invention is to provide a steel sheet for hot stamping, which ensures a good resistance to hydrogen embrittlement, even when a steel material after hot stamping is subjected to processing which leads to the remainder of the tension, such as drilling; a method for producing it that can be easily accomplished; and a hot-stamped steel material. MEANS TO SOLVE THE PROBLEMS [0016] To achieve the objective described above, the present inventors have conducted studies extensively as described below. The present inventors have paid attention to the inclusion containing Mn and Mn oxide, which are relatively and easily generated in steel, and come up with a new idea of guaranteeing good resistance to hydrogen embrittlement, making these substances serve as a place trap for diffusible hydrogen and non-diffusible hydrogen.
[0017] Then, steel sheets for hot stamping were prepared under various conditions and subjected to a method of
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5/50 hot plugging, and for the steel material obtained, strength and ductility as fundamental characteristics, as well as resistance to hydrogen embrittlement and toughness were examined. As a result, it has recently been discovered that good resistance to hydrogen embrittlement can be fixed on steel material after hot stamping, increasing the inclusion concentration containing Mn and the ratio of Mn oxide for inclusion containing Mn having a size predetermined.
[0018] On the other hand, such a problem has recently been discovered that, when the concentration of the inclusion containing Mn is excessively increased, a reduction in strength becomes apparent in the steel material after hot stamping. That is, it was recently discovered that when the concentration of the Mn-containing inclusion falls within a predetermined range and the number of Mn oxide density for the Mn-containing inclusion having a predetermined size is equal to or greater than a predetermined value, good resistance to hydrogen embrittlement can be ensured and good hardness can be ensured, even when the steel material after hot stamping is subjected to processing that leads to the remainder of the stress, such as punching.
[0019] Next, it was recently discovered that by increasing the winding temperature in a hot rolling step, compared to conventional techniques and performing in cold rolling conditions for the production of steel sheet for hot stamping , the concentration of the Mn-containing inclusion can be made within a predetermined range and the numerical ratio of the Mn oxide for inclusion containing Mn having a predetermined size can be equal to or greater than a predetermined value.
[0020] The present invention was conceived based on the new
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6/50 discoveries described above, and the object of the same is as follows. [0021] A steel plate for hot stamping, in which the steel plate has the chemical composition of: C: 0.18-0.26%; Si: more than 0.02% and not more than 0.05%; Mn: 1.0 to 1.5%; P: 0.03% or less; S: 0.02% or less; Al: 0.001 to 0.5%; N: 0.1% or less; O: 0.0010 to 0.020%; Cr: 0 to 2.0%; Mo: 0 to 1.0%; V: 0 to 0.5%; W: 0 to 0.5%; Ni: 0 to 5.0%; B: 0 to 0.01%; Ti: 0 to 0.5%; Nb: 0 to 0.5%; Cu: 0 to 1.0%; and balance: Fe and impurities, in terms of% by mass, the concentration of an inclusion containing Mn is not less than 0.010% by mass, and less than 0.25% by mass, and the ratio of the number of oxide to Mn for inclusion having a maximum length of 1.0 to 4.0 μΜ is 10.0% or more.
[0022] (2) The steel sheet for hot stamping according to (1), in which the chemical composition comprises one or more selected from the group consisting of Cr: 0.01 to 2.0%; Mo: 0.01 to 1.0%; V: 0.01 to 0.5%; W: 0.01 to 0.5%; Ni: 0.01 to 5.0%; and B: 0.0005 to 0.01%, in terms of mass%.
[0023] (3) The steel sheet for hot stamping according to (1) or (2), in which the chemical composition includes one or more selected from the group consisting of Ti: 0.001 to 0.5% ; Nb: 0.001 to 0.5%; and Cu: 0.01 to 1.0%, in terms of% by mass.
[0024] (4) The steel sheet for hot stamping according to any one of (1) to (3), in which the steel sheet includes on its surface a layer of hot-dip aluminum with a thickness of 50 μm or less.
[0025] (5) The steel sheet for hot stamping according to any one of (1) to (3), in which the steel sheet includes on its surface a hot dip galvanized layer with a thickness of 30 μm or less.
[0026] (6) The steel sheet for hot stamping according to
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7/50 with any one of (1) to (3), in which the steel plate includes on its surface a hot-dip galvanized bonded layer having a thickness of 45 pm or less.
[0027] (7) A method for producing a steel sheet for hot stamping, the method including: a hot rolling step of hot rolling of a steel part having the chemical composition of: C: 0.18 0.26%; Si: more than 0.02% and not more than 0.05%; Mn: 1.0 to 1.5%; P: 0.03% or less; S: 0.02% or less; Al: 0.001 to 0.5%; N: 0.1% or less; O: 0.0010 to 0.020%; Cr: 0 to 2.0%; Mo: 0 to 1.0%; V: 0 to 0.5%; W: 0 to 0.5%; Ni: 0 to 5.0%; B: 0 to 0.01%; Ti: 0 to 0.5%; Nb: 0 to 0.5%; Cu: 0 to 1.0%; and balance: Fe and impurities, in terms of% by mass, and then rolling a piece of steel at a temperature of 690 ° C or higher, to form a hot rolled steel sheet; and a cold rolling continuous cold rolling step of the hot rolled steel sheet in a 10 to 90% reduction to form a cold rolled steel sheet.
[0028] (8) The method for producing a steel sheet for hot stamping according to (7), in which the chemical composition comprises one or more selected from the group consisting of Cr: 0.01 to 2.0%; Mo: 0.01 to 1.0%; V: 0.01 to 0.5%; W: 0.01 to 0.5%; Ni: 0.01 to 5.0%; and B: 0.0005 to 0.01%, in terms of mass%.
[0029] (9) The method for producing a steel sheet for hot stamping according to (7) or (8), in which the chemical composition comprises one or more selected from the group consisting of Ti: 0.001 to 0.5%; Nb: 0.001 to 0.5%; and Cu: 0.01 to 1.0%, in terms of% by mass.
[0030] (10) A method for producing a hot stamping steel plate, in which the hot stamping steel plate, which is obtained through the production method according to
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8/50 any one of (7) to (9), is immersed in a hot dip bath of aluminum in order to form a layer by hot dip of aluminum on the surface of the steel sheet.
[0031] (11) A method for producing a hot stamping steel sheet, wherein the hot stamping steel sheet, which is obtained through the production method according to any of (7) to ( 9), is immersed in a hot dip galvanizing bath to form a hot dip galvanized layer on the steel sheet surface.
[0032] (12) A method for producing a hot stamping steel sheet, wherein the hot stamping steel sheet, which is obtained through the production method according to any of (7) to ( 9), is immersed in a hot dip galvanizing bath, and then heated to a temperature of 600 ° C or lower, to form a hot dip galvanized layer bonded on the surface of the steel sheet.
[0033] (13) A hot-stamping steel material, wherein the hot-stamping steel material has the chemical composition of: C: 0.18 to 0.26%; Si: more than 0.02% and not more than 0.05%; Mn: 1.0 to 1.5%; P: 0.03% or less; S: 0.02% or less; Al: 0.001 to 0.5%; N: 0.1% or less; O: 0.0010 to 0.020%; Cr: 0 to 2.0%; Mo: 0 to 1.0%; V: 0 to 0.5%; W: 0 to 0.5%; Ni: 0 to 5.0%; B: 0 to 0.01%; Ti: 0 to 0.5%; Nb: 0 to 0.5%; Cu: 0 to 1.0%; and balance: Fe and impurities, in terms of% by mass, the concentration of an inclusion containing Mn is not less than 0.010% by mass, and less than 0.25% by mass, and the numerical ratio of an oxide of Mn for inclusion having a maximum length of 1.0 to 4.0 μΜ is 10.0% or more.
[0034] (14) The hot stamping steel material according to (13) above, in which the chemical composition comprises one or more selected from the group consisting of Cr: 0.01 to 2.0% ;
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9/50
Mo: 0.01 to 1.0%; V: 0.01 to 0.5%; W: 0.01 to 0.5%; Ni: 0.01 to 5.0%; and B: 0.0005-0.01%, in terms of% by mass.
[0035] (15) The hot-stamping steel material according to (13) or (14), wherein the chemical composition comprises one or more selected from the group consisting of Ti: 0.001 to 0.5% ; Nb: 0.001 to 0.5%; and Cu: 0.01 to 1.0%, in terms of% by mass. EFFECTS OF THE INVENTION [0036] According to the present invention, good resistance to hydrogen embrittlement can be ensured, even when processing leads to the remaining stress, such as punching, is carried out after hot stamping, and in practice it is easy, so that the range of applications (components) of hot stamping method can be expanded.
BRIEF DESCRIPTION OF THE DRAWINGS [0037] Figure 1 is a view that illustrates a relationship between the amount of diffusible hydrogen and the time to rupture.
[0038] Figure 2 is a view showing a hot stamping method and a die used in the examples.
[0039] Figure 3 is a view showing an aspect of a constant load test piece used in the examples.
[0040] Figure 4 is a view showing an aspect of a steel plate (member) compressed into a hat shape. MODES FOR CARRYING OUT THE INVENTION (1) Chemical Composition [0041] The reason for specifying the chemical compositions of a steel sheet for hot stamping (hereinafter also referred to as the steel sheet of the present invention) and a steel material of hot stamping (hereinafter, also referred to as the steel material of the present invention) according to the present invention will be described. The% in the following descriptions means% by mass.
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10/50 [0042] C: 0.18 to 0.26% [0043] C is an element that is the most important for increasing the strength of a steel sheet through a hot stamping method. When the C content is less than 0.18%, it is difficult to ensure a strength of 1500 MPa or more after hot stamping. Therefore, the C content is 0.18% or more.
[0044] On the other hand, when the C content is more than 0.26%, after hot stamping the ductility becomes low and it is difficult to guarantee a total elongation of 10% or more. Therefore, the C content is 0.26% or less.
[0045] Si: more than 0.02% and not more than 0.05% [0046] Si is an element that is important to control the concentration of an inclusion containing Mn and the numerical relationship of an Mn oxide for inclusion having a maximum length of 1.0 to 4.0 pm. When the Si content is 0.02% or less, the generation of Mn oxide is excessively accelerated, and the concentration of the inclusion containing Mn reaches 0.25% or more, so that the hardness can be significantly reduced. Therefore, the Si content is more than 0.02%. On the other hand, when the Si content is more than 0.05%, the generation of Mn oxide is excessively suppressed, and the numerical ratio of Mn oxide for the inclusion containing Mn having a maximum length of 1.0 to 4.0 pM is less than 10.0%, so it is difficult to obtain good resistance to hydrogen embrittlement with stability. Therefore, the Si content is 0.05% or less.
[0047] Mn: 1.0 to 1.5% [0048] Mn is an element that is the most important in the present invention. Mn acts to increase resistance to hydrogen embrittlement, forming an inclusion containing Mn in steel. Remaining mn that did not form the inclusion acts to improve the hardening capacity. When the Mn content is less than 1.0%, it is difficult for
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11/50 ensure that the inclusion concentration containing Mn is 0.010 mass% or more. Therefore, the Mn content is 1.0% or more. On the other hand, when the Mn content is greater than 1.5%, the effect of the action mentioned above is saturated, being, therefore, economically disadvantageous, and the mechanical characteristics can be deteriorated, due to the Mn segregation. Therefore, the Mn content is 1.5% or less.
[0049] P: 0.03% or less [0050] P is an element that is usually contained as an impurity. When the P content is more than 0.03%, the hot processability is significantly deteriorated. Therefore, the P content is 0.03% or less. The lower limit of the P content does not have to be particularly specified, but is preferably 0.001% or more, because the excessive reduction causes a considerable burden on the steelmaking process.
[0051] S: 0.02% or less [0052] S is an element that is usually contained as an impurity. When the S content is more than 0.02%, the hot processability is significantly deteriorated. Therefore, the S content is 0.02% or less. The lower limit of the S content does not have to be particularly specified, but is preferably 0.0005% or more, because the excessive reduction causes a considerable burden on the steelmaking process.
[0053] Al: 0.001-0.5% [0054] Al is an element that acts to consolidate steel by deoxidation. When the aluminum content is less than 0.001%, it is difficult to perform sufficient deoxidation. Therefore, the Al content is 0.001% or more. On the other hand, when the aluminum content is greater than 0.5%, the generation of Mn oxide is excessively suppressed, and it is difficult to ensure the proportion of Mn oxide described later, so that it is difficult to obtain a good resistance to weakening of hiPetição 870190003912, of 01/14/2019, p. 19/68
12/50 hydrogen. Therefore, the Al content is 0.5% or less.
[0055] N: 0.1% or less [0056] N is an element that is usually contained as an impurity. When the N content is greater than 0.1%, N is easily linked with Ti and B, which are the optional elements described later to consume the elements, so that the effects of such elements are reduced. Therefore, the N content is 0.1% or less, preferably 0.01% or less. The lower limit of the N content does not have to be particularly specified, but is preferably 0.001% or more, because the excessive reduction causes a considerable overload in the steel production stage.
[0057] O: 0.0010-0.020% [0058] O forms an Mn oxide in steel, which acts to increase resistance to hydrogen embrittlement, serving as a trap location for diffusible hydrogen and non-diffusible hydrogen. When the content of O is less than 0.0010%, the generation of Mn oxide is not sufficiently accelerated, and the numerical ratio of Mn oxide for the inclusion containing Mn is less than 10.0%, so that good resistance to hydrogen embrittlement cannot be achieved with stability. Therefore, the O content is 0.0010% or more. On the other hand, when the S content is more than 0.020%, a coarse oxide is formed in the steel to degrade the mechanical characteristics of the steel material. Therefore, the O content is 0.020% or less.
[0059] The steel sheet of the present invention and the steel material of the present invention have the components described above as an essential component composition, and may further contain one or more of Cr, Mo, V, W, Ni, B, Ti, Nb and Cu as needed.
[0060] <Cr: 0 to 2.0%>, <B: from 0 to 0.01%>, <Mo: 0 to 1.0%>, <W: 0 to 0.5%>, <V : 0 to 0.5%> and <Ni: 0 to 5.0%>
[0061] These elements all work to improve the capacity
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13/50 hardening. Therefore, one or more of these elements can be contained. However, when B is contained in an amount that exceeds the aforementioned upper limit, hot processability is degraded and ductility is reduced. When Cr, Mo, W, V and Ni are contained in an amount that exceeds the maximum limit mentioned above, the effect of the aforementioned action is saturated, and is therefore economically disadvantageous. Therefore, the upper limits of the contents of B, Cr, Mo, W, V and Ni are each, as described above. To obtain more reliability of the effect of the above action, it is preferable that the content of B is 0.0005% or more, or the content of any of the elements Cr, Mo, W, V and Ni is 0.01% or more. Ni acts to suppress the degradation of the surface property of the hot rolled steel plate by Cu, and therefore it is preferable that Ni is also contained when Cu described later is contained.
[0062] <Ti: 0 to 0.5%>, <Nb: 0 to 0.5%> and <Cu: 0 to 1.0%>
[0063] Ti, Nb and Cu all act to increase the resistance. Therefore, one or more of these elements can be contained. However, when the Ti content is greater than 0.5%, the generation of Mn oxide is excessively suppressed, and it is difficult to ensure the proportion of Mn oxide described below, so that it is difficult to obtain a good resistance to hydrogen embrittlement. Therefore, the Ti content is 0.5%. When the Nb content is more than 0.5%, hot rolling controllability can be impaired. Therefore, the Nb content is 0.5% or less. When the Cu content is more than 1.0%, the surface property of the hot rolled steel sheet can be impaired. Therefore, the Cu content is 1.0% or less. To obtain the effect of the above mentioned action with greater reliability, it is preferred that any of Ti (0.001% or more), Nb (0.001% or more) and Cu (0.01% or more) is contained. Since Ti is preferably bonded with N in the steel to form a nitride, and thus inhibits B from being released
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14/50 daily consumed by the formation of a nitride, so that the effect of B can be increased even more, it is preferable that Ti is also contained when the aforementioned B is contained. [0064] The balance includes Fe and impurities.
(2) Inclusion [0065] Next, the reason for specifying the inclusion concentration containing Mn and the numerical ratio of the Mn oxide for the inclusion containing Mn having a maximum length of 1.0 to 4.0 μΜ in the present invention to steel sheet and the steel material of the present invention will be described.
[0066] <Inclusion concentration containing Mn: not less than 0.010% by mass and less than 0.25% by mass>
[0067] The inclusion containing Mn plays an important role in suppressing hydrogen embrittlement, along with the numerical ratio of Mn oxide to the inclusion Mn described later having a maximum length of 1.0 to 4.0 μm. When the inclusion concentration containing Mn is less than 0.010%, it is difficult to obtain a good resistance to hydrogen embrittlement. Therefore, the concentration of the inclusion containing Mn is 0.010% or more. On the other hand, when the concentration of the inclusion containing Mn is 0.25% or more, the hardness can be reduced. Therefore, the concentration of the inclusion containing Mn is less than 0.25%.
[0068] The concentration of the inclusion containing Mn is determined according to the following procedure. That is, a steel sheet is electrolyzed at a constant current, in an electrolytic solution with acetylacetone and tetramethylammonium dissolved in methanol, a filter with a pore diameter of 0.2 μm is used for the collection of waste, the mass of waste it is divided by an amount of electrolysis (mass of the steel plate lost by electrolysis), and the value obtained is multiplied by 100 to be described in terms of a percentage.
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It is confirmed that the inclusion extracted by the electrolysis method contains Mn by EDS (energy dispersive X-ray spectroscopy) with a SEM (scanning electron microscope).
[0069] <Numeric ratio of Mn oxide to the number of inclusions containing Mn having a maximum length of 1.0 to 4.0 μΜ: 10.0% or more>
[0070] The numerical ratio of Mn oxide for inclusion containing Mn having a maximum length of 1.0 to 4.0 μM plays an important role in suppressing hydrogen embrittlement, along with the inclusion containing Mn described above. When the ratio of Mn oxide number to the number of inclusions containing Mn having a maximum length of 1.0 to 4.0 μM is less than 10.0%, it is difficult to obtain a good resistance to hydrogen embrittlement . Therefore, the numerical ratio of Mn oxide to the number of inclusions containing Mn having a maximum length of 1.0 to 4.0 μM is 10.0% or more.
[0071] The numerical ratio of Mn oxide to the number of Inclusions containing Mn having a maximum length of 1.0 to 4.0 μM is determined according to the following procedure. The cross section of a steel sheet is observed with a SEM, and the inclusions having a maximum length (for example, the length of the longest side, when the insert is rectangular, and the length of the main axis, when the insert is elliptical. ) from 1.0 to 4.0 μM are selected and defined as exam objects. These inclusions are subjected to EDS analysis, and those for which a characteristic X-ray of Mn and a characteristic X-ray of O (oxygen) are detected at the same time are judged as Mn oxide. Observation / analysis is carried out in a plurality of visual fields until the total number of objects examined exceeds 500, and the numerical ratio of Mn oxide to the total number of objects examined is defined coPetition 870190003912, from 14/01/2019, pg. 23/68
16/50 mo a numerical ratio of Mn oxide.
[0072] Here, the reason why the maximum length of inclusions to be examined is 1.0 pm or more is that, with the smaller inclusion, the precision of the analysis of the constituent elements by EDS becomes insufficient. Here, the reason for the maximum length of inclusions to be examined is 4.0 μΜ or less, which is a larger insert is a union, etc. of a plurality of different inclusions, so that the constituent elements (combinations thereof) are not exclusively defined by local EDS analysis.
(3) Metallization layer [0073] The steel sheet of the present invention and the steel material of the present invention can be a steel sheet with a treated surface or a steel material with a treated surface with a metallization layer formed on a surface of the for the purpose of improving corrosion resistance, etc. The metallization layer can be a hot dip layer, or it can be a galvanizing layer. Examples of the hot dip layer include hot dip galvanized layers, bonded hot dip galvanized layers, aluminum hot dip layers, Zn-Al alloy hot dip layers, Zn hot dip layers -Al-Mg and hot dip layers of Zn-Al-Mg-Si alloy. Examples of the galvanizing layer include zinc electroplating layers and Zn-Ni alloy electroplating layers.
[0074] The thickness of the metallization layer is not particularly limited from the point of view of resistance to hydrogen embrittlement and toughness. For the steel sheet of the present invention, however, it is preferred to restrict the upper limit of the thickness of the metallization layer from the point of view of the press formability. For example, the thickness of the metallization layer is preferably
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17/50 pm or less from the point of view of resistance to seizing in the case of aluminum hot dip, the thickness of the metallization layer is preferably 30 pm or less from the point of view of suppressing Zn adhesion in a matrix, in the case of hot dip galvanizing, and the thickness of the metallization layer is preferably 45 pm or less from the point of view of suppressing the occurrence of cracks in an alloy layer in the case of galvanizing alloy by hot immersion. On the other hand, it is preferred to restrict the lower limit of the thickness of the metallization layer from the point of view of corrosion resistance. For example, in the case of aluminum hot dip and hot dip galvanizing, the thickness of the metallization layer is preferably 5 pm or more, more preferably 10 pm or more. In the case of hot dip galvanizing alloy, the thickness of the metallization layer is preferably 10 pm or more, more preferably 15 pm or more.
(4) Steel Sheet Production Method of the Present Invention [0075] A method for making steel sheets of the present invention will be described.
[0076] The steel sheet of the present invention can be produced by a production method, including: a hot rolling step of hot rolling of a steel part having the chemical composition mentioned above, and then rolling the steel part at a temperature of 690 ° C or higher to form a hot rolled steel sheet; and a continuous cold rolling step by cold rolling the hot rolled steel sheet in a 10 to 90% reduction to form a cold rolled steel sheet. Here, the steel preparation conditions and molding conditions in production of the steel part and conditions for cold rolling applied to the hot rolled steel sheet can be in accordance with a usual method.
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Stripping carried out before cold rolling of hot rolled steel sheets can be according to a usual method.
[0077] The shape of the inclusion described above is obtained by hot rolling a steel piece having the chemical composition mentioned above, then winding the steel piece, at a temperature of 690 ° C or higher, to form a steel plate hot rolled, and cold rolling the hot rolled steel sheet in a 10 to 90% reduction. Therefore, annealing by recrystallization after cold rolling is not necessary from the point of view of resistance to hydrogen embrittlement and toughness after hot stamping. However, it is preferable that after cold rolling, recrystallization annealing is carried out to soften the steel sheet from the point of view of erasure and pre-forming processing capacity, etc., which are performed before the sheet metal. steel to be hot stamped. A metallization layer can be provided after annealing by recrystallization for the purpose of improving corrosion resistance, etc. When hot dipping is carried out, it is preferred to perform the continuous hot dipping treatment carried out using hot dipping equipment subsequent to annealing by recrystallization.
[0078] The reason why a hot stamping steel plate, which is capable of providing a hot stamping steel material that has a good resistance and tenacity to hydrogen embrittlement, is obtained through the production method described above it is not necessarily evident, but this is considered to be related to a state of cementite generation and a microstructure in the hot rolled steel sheet, before being subjected to cold rolling. That is, cementite is crushed together with other inclusions in the rolling stage as a post-stage of the hot rolling stage, but depending on the size of the stage, the size and the
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19/50 state of dispersion after crushing and a state of generation of empty spaces between cementite and steel vary. Depending on the strength (hardness) of the microstructure, the difference in hardness between the microstructure and the inclusion varies, and this also affects the inclusion state and empty spaces. In addition, both cementite and microstructure affect the state of inclusions that are not deformed, but crushed.
[0079] The present inventors assume that by hot rolling a steel part with the chemical composition mentioned above and then winding the steel part, at a temperature of 690 ° C or higher, and cold rolling the steel sheet hot laminate thus obtained in a reduction of 10 to 90%, a cementite generation state and a microstructure are finely combined, and as a result, the form of inclusion described above can be ensured, so that good resistance to embrittlement hydrogen and toughness can be obtained.
[0080] The upper limit of the winding temperature is not particularly restricted from the point of view of maintaining both resistance to hydrogen embrittlement and toughness. However, the winding temperature is preferably 850 ° C or less from the point of view of suppressing an increase in the crystal grain size of the hot-rolled steel sheet to reduce the anisotropy of mechanical properties, such as the ability to stretch or suppress an increase in scale thickness to reduce stripping overhead. The reduction in the cold rolling stage can be appropriately selected according to the capacity of the equipment and a thickness of the hot rolled steel sheet.
[0081] Production conditions other than those described above have little influence on resistance to hydrogen embrittlement and tePetition 870190003912, from 01/14/2019, p. 27/68
20/50 nacity. For example, in the hot rolling stage, at a temperature of 1200 to 1250 ° C, a temperature of the steel part subjected to hot rolling, a toughness of 30 to 90%, and a finishing temperature of about 900 ° C can be selected.
[0082] When annealing by recrystallization is carried out, the annealing temperature is desired to be 700 to 850 ° C from the point of view of moderately softening of the steel sheet, but for the purpose of characterizing other mechanical properties, the hybridization temperature can be less than 700 ° C, or it can be greater than 850 ° C. After annealing by recrystallization, the steel sheet can be directly cooled to room temperature, or it can be immersed in a hot dip bath in the cooling process to room temperature to form a hot dip layer on the surface of the sheet. steel.
[0083] When hot immersion is aluminum hot immersion, Si can be contained in a concentration of 0.1 to 20% in an aluminum hot immersion bath. Si contained in the aluminum hot-dip layer affects the reaction between Al and Fe, which occurs during heating before hot stamping. From the point of view of the moderate suppression of the aforementioned reaction to ensure the press formability of the metallization layer itself, the Si content in the bath is preferably 1% or more, even more preferably 3% or more. On the other hand, from the point of view of moderate acceleration of the aforementioned reaction to suppress Al deposition in a press die, the Si content in the bath is preferably 15% or less, even more preferably 12% or less.
[0084] When hot dip is hot dip galvanizing, the steel sheet is immersed in a hot dip galvanizing bath, and then cooled to room temperature, and when hot dip is galvanizing by immersion in
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21/50 hot alloy, the steel sheet is immersed in a hot dip galvanizing bath, then heated to a temperature of 600 ° C or below and thus subjected to an alloy treatment, and, then cooled to room temperature. Al can be contained in a concentration of 0.01 to 3%, in the hot dip galvanizing bath. Al affects the reaction between Zn and Fe. When hot dip is hot dip galvanizing, the mutual diffusion of Zn and Fe can be suppressed by the Fe and Al reaction layer. When hot dip is hot dip galvanizing , it can be used to perform an adequate plating control composition from the point of view of processability and plating adhesion. These effects are exposed from Al, ensuring that the concentration of Al in the hot dip galvanizing bath is 0.01 to 3%. Therefore, the concentration of Al in the hot dip galvanizing bath can be selected according to a capacity of equipment involved in production, and a purpose.
(5) Method of Production of the Steel Material of the Present Invention [0085] The steel material of the present invention can be obtained by subjecting the steel sheet of the present invention using a usual method.
[0086] Modalities of the present invention described above are merely illustrative, and several changes can be made to the claims.
EXAMPLES [0087] As common tests in the examples below, details of a hydrogen embrittlement acceleration test and measurement of a critical diffusible amount of hydrogen to assess hydrogen embrittlement resistance and details of a Charpy impact test to assess the resistance will be described first.
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22/50 [0088] Diffusable hydrogen was introduced in a test piece (steel plate) by a method of charging the cathode in an electrolyte solution. That is, the test piece was used as a platinum cathode electrode and arranged around the test piece was used as an anode, a predetermined current density was passed between both the first and the last to generate hydrogen on the surface of the test piece, and hydrogen was encouraged to diffuse into the test piece. An aqueous solution formed by dissolving NH4SCN and NaCl in pure water, in concentrations of 0.3% and 3%, respectively, was used as an electrolyte solution.
[0089] The voltage corresponding to the residual voltage as another factor to cause hydrogen embrittlement was applied by a lever-type constant load tester, using a weight (hereinafter referred to as a constant load test; test piece is referred to as a constant load test piece). The constant load test piece has been marked. Once the test piece was broken it was recorded, and the test piece was quickly retracted after it was broken. The electrolyte solution was removed, and an amount of diffusible hydrogen was immediately measured by a hydrogen analysis method by increasing the temperature using a gas chromatograph. The amount of cumulative emission from room temperature up to 250 ° C was defined as a quantity of diffusible hydrogen.
[0090] When changing the current density, while fixing the applied voltage, a relationship between the amount of diffusible hydrogen and a time to rupture as shown in Figure 1 is determined. Here, the with an arrow indicates that the test piece had not broken, even after a predefined time. A 96-hour period was used as a defined time. The median between a minimum Hmin value of the amount of diffusible hydrogen in a part
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23/50 burst test (· in Figure 1.) and a maximum value of Hmax the amount of diffusible hydrogen from an unbroken test piece was defined as a quantity of critical diffusible hydrogen Hc. That is, Hc = (Hmin + Hmax) / 2. Patent Literature 3 (JP2006-29977A) describes a similar test method.
[0091] Resistance to hydrogen embrittlement of a steel sheet with the coating on the surface was evaluated based on the presence / absence of cracks, observing the orifice walls in a drilling test performed with the clearance being changed. That is, a steel plate with a plate thickness of t (mm) was drilled with 10 mmç holes. At this time, the diameter Dp of a punch was fixed at 10 mm, and the internal diameter Di of a die was changed, so that the clearance = (Di - Pd) / 2t χ 100 varied from 5% to 30%. Presence / absence of cracks in the orifice walls was examined, and a crack-free steel plate was evaluated as a steel plate with excellent resistance to hydrogen embrittlement. The number of perforations was 5 or more, by distance, and all the walls of the hole were examined.
[0092] Hardness was assessed by a Charpy impact test in accordance with JIS Z 2242, regardless of the presence / absence of plates. The test piece was molded according to test part No. 4 in JIS Z 2202, and the thickness of the test piece was determined according to a steel plate to be evaluated. The test was conducted in a range of -120 ° C to 20 ° C to determine the transition temperature of ductility brittleness.
(Example 1) [0093] A steel piece having the chemical composition shown in Table 1 has been cast. The steel part was heated to 1,250 ° C and hot rolled to form a 2.8 mm thick hot rolled steel sheet at a finishing temperature of 870-920 ° C. THE
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24/50 winding temperature was adjusted to 700 ° C. The steel sheet was stripped and then cold rolled to a toughness of 50% to obtain a cold rolled steel sheet with a sheet thickness of 1.4 mm. The cold-rolled steel sheet was subjected to annealing recrystallization so that the steel sheet was kept at a temperature ranging from 700 ° C to 800 ° C for 1 minute and at room temperature, thus obtaining a sample material air-cooled (steel sheet for hot stamping).
[0094] A test piece of 50 x 50 mm, was made from each sample material, and electrolyzed to a constant current, in an electrolytic solution with acetylacetone and tetramethylammonium in methanol. The current value was set at 500 mA, and the electrolysis time was adjusted to 4 hours. A filter with a pore diameter of 0.2 pm was used for waste collection, and the mass of the waste was divided by an amount of electrolysis, and described in terms of a percentage. In this way, the concentration of an inclusion containing Mn was determined.
[0095] The cross section of the sample material was observed with an SEM, and inclusion analyzes, that is, counting, measuring and dimension analysis of constituent elements by EDS were performed. In this way, a numerical ratio of an Mn oxide for inclusion having a maximum length of 1.0 to 4.0 μΜ was determined.
[0096] Each sample material was held in air at 900 ° C for 3 minutes, and then sandwiched between experimental flat press dies shown in Figure 2, so that hot stamping was performed. That is, as shown in Figure 2, a steel plate 22 was processed by an upper die 21a and a lower die 21b. An average cooling rate of 200 ° C, as measured by a thermocouple, was about 70 ° C / s. An
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25/50 JIS tensile test piece No. 5, a constant load test piece shown in Figure 3 and a Charpy impact test piece were removed from the steel material after hot stamping. [0097] The constant load test was performed by applying a tension that corresponds to 90% of a tensile strength determined in the tensile test. The current density was adjusted to 0.01 to 1 mA / cm ² .
[0098] Diffusable hydrogen was measured at a heating rate of 100 ° C / hour.
[0099] Charpy's impact test was conducted at a test temperature of 20 ° C, 0 ° C, -20 ° C, -40 ° C, -60 ° C, -80 ° C, -100 ° C and
-120 ° C, and a ductility fragile transition temperature was determined from a change in absorbed energy.
[00100] For the test piece, having direction, the tensile direction was made perpendicular to the bearing direction of the steel plate, in the case of the tensile test piece and the constant load test piece, and the longitudinal direction was parallel to the rolling direction, in the case of the Charpy test piece. The plate thickness of the tensile test piece was adjusted to 1.4 mm, and the plate thickness of other test pieces was adjusted to 1.2 mm by grinding both surfaces. The results are shown in Table 2.
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TABLE 1
Steel Chemical composition (Unit:% by mass, balance: Fe and impurities)Markings Ç Si Mn P s Al N O Others The 0.18 0.015 1.5 0.02 0.004 0.001 0.004 0.007 - Comparative steel B 0.18 0.025 1.5 0.02 0.004 0.001 0.004 0.007 Cr: 0.2, Ti: 0.001, B: 0.0035 Relevant steel ç 0.18 0.045 1.5 0.02 0.004 0.003 0.004 0.007 Nb: 0.01, B: 0.0035 Relevant steel d 0.18 0.055 1.5 0.02 0.004 0.003 0.004 0.007 Cr: 0.2, Ti: 0.005, B: 0.0025 Comparative steel and 0.22 0.015 1.2 0.02 0.004 0.001 0.003 0.0006 Cr: 0.2, B: 0.0025 Comparative steel f 0.22 0.025 1.2 0.02 0.002 0.005 0.003 0.005 - Relevant steel g 0.22 0.025 1.2 0.02 0.002 0.003 0.003 0.009 B: 0.025 Relevant steel H 0.22 0.025 1.2 0.02 0.002 0.003 0.003 0.012 Ti: 0.01, B: 0.005 Relevant steel i 0.24 0.025 1.0 0.01 0.002 0.005 0.003 0.007 Cr: 0.2 Relevant steel j 0.24 0.030 1.0 0.01 0.002 0.005 0.003 0.007 Ti: 0.01, B: 0.003 Relevant steel k 0.24 0.035 1.0 0.01 0.002 0.005 0.003 0.021 Ti: 0.01 Comparative steel l 0.24 0.030 0.9 0.01 0.002 0.005 0.003 0.003 Nb: 0.1 Comparative steel m 0.26 0.010 1.5 0.002 0.004 0.6 0.003 0.010 Nb: 0.3 Comparative steel n 0.26 0.025 1.0 0.002 0.002 0.001 0.002 0.007 Cr: 0.2, B: 0.0030 Relevant steel O 0.26 0.035 1.0 0.002 0.002 0.003 0.003 0.015 - Relevant steel P 0.26 0.030 1.0 0.002 0.004 0.003 0.004 0.010 Cr: 1.0, Ti: 0.03, B: 0.005 Relevant steel
26/50
Underlines in the table indicate values outside the range specified in the present invention
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TABLE 2
No. Steel Inclusion Concentration containing Mn (% by mass) Inclusion containing Mn having a maximum length of 1.0 to 4.0 pm Tensile strength (MPa) Hc(ppm) Ductility brittleness transition temperature (° C) Markings Number of inclusions observed (numbers) Number of Mn oxides (number) Numerical ratio of number of Mn oxides (%) 1 The 0.26 501 261 52.1 1502 0.74 -35 Comparative Example 2 B 0.15 500 69 13.8 1510 0.96 -69 Example of the Present Invention 3 ç 0.12 512 52 10.2 1512 0.90 -70 Example of the Present Invention 4 d 0.10 508 49 9.6 1514 0.45 -55 Comparative Example 5 and 0.13 501 21 4.2 1542 0.30 -70 Comparative Example 6 f 0.16 504 136 27.0 1545 0.92 -68 Example of the Present Invention 7 g 0.14 502 172 34.3 1540 0.91 -66 Example of the Present Invention 8 H 0.18 500 181 36.2 1546 0.94 -67 Example of the Present Invention 9 i 0.15 500 124 24.8 1577 0.90 -71 Example of the Present Invention 10 j 0.13 503 139 27.6 1570 0.92 -68 Example of the Present Invention 11 k 0.32 502 208 41.5 1562 0.72 -29 Comparative Example 12 l 0.11 500 45 9.0 1566 0.32 -65 Comparative Example 13 m 0.02 500 7 14 1582 0.22 -31 Comparative Example 14 n 0.18 500 121 24.2 1590 0.89 -61 Example of the Present Invention 15 O 0.22 500 154 30.8 1596 0.90 -60 Example of the Present Invention 16 P 0.17 507 115 22.7 1598 0.84 -62 Example of the Present Invention
27/50
Underlines in the table indicate values outside the range specified in the present invention
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28/50 [00101] In each example, the steel plate after hot stamping showed a tensile strength of 1500 MPa or more. Samples ^Nos. 2, 3, 6 to 10 and 14 to 16, in which both the concentration of the inclusion containing Mn and the numerical ratio of the Mn oxide for the inclusion having a maximum length of 1.0 to 4.0 pm fell within the specified range in the present invention, they had good resistance to hydrogen embrittlement and toughness with the critical diffusible hydrogen Hc amount of 0.84 ppm or more and the ductility brittleness transition temperature of -60 ° C or below.
[00102] On the other hand, samples N ° ^s . 1 and 11, in which the inclusion concentration containing Mn was outside the range specified in the present invention were weak in resistance to the ductility brittleness transition temperature being very high compared to the examples of the present invention having a comparable tensile strength. Samples ^Nos. 4, 5, 12 and 13 in which the ratio of the number of Mn oxide for inclusion having a maximum length of 1.0 to 4.0 mM that were outside the range specified in the present invention were weak in resistance to hydrogen embrittlement with Hc being significantly less compared to the examples of the present invention. Sample No. 13 has a very high ductility brittleness transition temperature compared to the examples of the present invention that have an equivalent tensile strength, although the inclusion concentration containing Mn is within the range specified in the present invention. It is thought that, due to the fact that the aluminum content is high (outside the range specified in the present invention), an Al oxide is contained in a high concentration.
(Example 2) [00103] A steel piece having the chemical composition shown in Table 3 has been cast. The steel part was heated to 1,250 ° C and rolled
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29/50 hot to form a 3.0 mm thick hot rolled steel sheet at a finishing temperature of 880-920 ° C. The winding temperature was adjusted to 700 ° C. The steel sheet was stripped and then cold rolled to 50% toughness to obtain a cold rolled steel sheet with a sheet thickness of 1.5 mm. The cold rolled steel sheet was subjected to annealing recrystallization so that the steel sheet was kept at a temperature ranging from 700 ° C to 800 ° C for 1 minute and at room temperature, thus obtaining a sample material air-cooled (steel sheet for hot stamping). The concentration of an inclusion containing Mn and a numerical ratio of Mn oxide for the inclusion having a maximum length of 1.0 to 4.0 μΜ were determined in the same way as in Example 1. In addition, a sample material was maintained in air at 900 ° C for 5 minutes, and then compressed into a hat shape shown in Figure 4 using a hot stamping method. An average cooling rate of 200 ° C, as measured by a thermocouple, was about 35 ° C / s. From a test piece and taking position 41 (part of the hat head) shown in Figure 4, a JIS No. 5 tensile test piece, a constant load test piece and a Charpy impact test piece were sockets. The relationship between the test piece taking direction and bearing direction of the steel plate was the same as in Example 1. The thickness of the plate of the tensile test piece was 1.5 mm, and the thickness of the plate of other pieces of test was adjusted to 1.3 mm by grinding both surfaces. The constant load test was conducted by applying a tension that corresponds to 90% of the tensile strength determined in the tensile test. The current density was adjusted to 0.01 to 1 mA / cm ² . Diffusable hydrogen was measured at a heating rate of 100 ° C / hour. Charpy's impact test was conducted at a time 870190003912, of 14/01/2019, p. 37/68
30/50 test temperature of 20 ° C, 0 ° C, -20 ° C, -40 ° C, -60 ° C, -80 ° C, -100 ° C and
-120 ° C, and a ductility brittleness transition temperature was determined from a change in absorbed energy. The results are shown in Table 4.
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TABLE 3
Steel Chemical composition (Unit:% by mass, balance: Fe and impurities)Markings Ç Si Mn P s Al N O Others 2a 0.22 0.015 1.2 0.02 0.002 0.005 0.003 0.005 V: 0.5 Comparative steel 2b 0.22 0.025 1.2 0.02 0.002 0.005 0.003 0.005 V: 0.5 Relevant steel 2c 0.22 0.025 1.2 0.02 0.002 0.005 0.003 0.005 Mo: 0.2 Relevant steel 2d 0.22 0.025 1.2 0.02 0.02 0.005 0.003 0.005 W: 0.2 Relevant steel 2e 0.22 0.025 1.2 0.02 0.02 0.005 0.003 0.005 W: 0.5 Relevant steel 2f 0.22 0.025 1.2 0.02 0.02 0.005 0.003 0.005 Cu: 0.5, Ni: 0.3 Relevant steel 2g 0.22 0.025 1.2 0.02 0.02 0.005 0.003 0.005 Mo: 0.1, W: 0.2, V: 0.2 Relevant steel 2 am 0.22 0.025 1.2 0.02 0.002 0.005 0.003 0.005 B: 0.002, Mo: 0.1, V: 0.2 Relevant steel 2i 0.22 0.030 16 0.02 0.007 0.001 0.003 0.025 B: 0.002, Nb: 0.5 Comparative steel 2j 0.22 0.055 0.6 0.01 0.002 0.003 0.003 0.007 B: 0.002, Cu: 1.0, Ni: 0.5 Comparative steel 2k 0.22 0.025 1.2 0.02 0.002 0.005 0.003 0.005 B: 0.003, Mo: 1.0 Relevant steel 2l 0.22 0.025 1.2 0.02 0.002 0.005 0.003 0.005 Nb: 0.2, V: 0.5 Relevant steel 2 m 0.22 0.060 1.2 0.02 0.002 0.003 0.003 0.005 B: 0.002, V: 0.5 Comparative steel 2n 0.22 0.025 1.2 0.02 0.002 0.002 0.003 0.0007 B: 0.004, Cu: 0.5, Ni: 0.5 Comparative steel 2nd 0.22 0.025 1.2 0.02 0.002 0.005 0.003 0.005 B: 0.002, Nb: 0.2, W: 0.2, V: 0.3 Relevant steel 2p 0.22 0.025 0.6 0.01 0.002 0.001 0.003 0.007 B: 0.003, Mo: 0.2, V: 0.3 Comparative steel
31/50
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TABLE 4
No. Steel Inclusion Concentration containing Mn (% by mass) Inclusion containing Mn having maximum length of1.0 to 4.0 pm Tensile strength (MPa) Hc (ppm) Ductility brittleness transition temperature (° C) Markings Number of inclusions observed (numbers) Number of Mn oxides (number) Numerical ratio of number of Mn oxides (%) 17 2a 0.27 501 113 22.6 1580 0.60 -48 Comparative Example 18 2b 0.15 500 125 25.0 1585 0.98 -68 Example of the Present Invention 19 2c 0.14 512 109 21.3 1588 0.96 -67 Example of the Present Invention 20 2d 0.19 508 126 24.3 1592 0.96 -68 Example of the Present Invention 21 2e 0.16 504 119 23.6 1590 0.96 -69 Example of the Present Invention 22 2f 0.12 500 110 22.0 1586 0.91 -65 Example of the Present Invention 23 2g 0.10 500 118 23.6 1587 1.02 -67 Example of the Present Invention 24 2 am 0.13 502 109 21.7 1591 1.00 -68 Example of the Present Invention 25 2i 0.39 511 302 59.1 1600 0.56 -36 Comparative Example 26 2j 0.005 500 10 7.9 1602 0.55 -65 Comparative Example 27 2k 0.15 500 134 26.8 1588 0.95 -65 Example of the Present Invention 28 2l 0.12 503 123 24.5 1589 1.04 -70 Example of the Present Invention 29 2 m 0.007 504 49 9.8 1594 0.60 -65 Comparative Example 30 2n 0.18 500 103 4.3 1590 0.35 -68 Comparative Example 31 2nd 0.16 512 151 29.4 1587 1.05 -71 Example of the Present Invention 32 2p 0.02 502 47 9.4 1584 0.61 -69 Comparative Example
32/50
Underlines in the table indicate values outside the range specified in the present invention
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33/50 [00104] In each example, the steel plate after hot stamping showed a tensile strength of 1580 MPa or more. Among them, the Nos. 18 to 24, 27, 28 and 31, in which both the inclusion concentration containing Mn and the numerical ratio of Mn oxide for inclusion having a maximum length of 1.0 to 4.0 μΜ were within the range specified in the present invention, they had good resistance to hydrogen embrittlement and Hc toughness of 0.91 ppm or more and the ductility fragility transition temperature of -65 ° C or below.
[00105] On the other hand, samples N ° ^s . 17 and 25, in which the Inclusion concentration containing Mn exceeded the range specified in the present invention were weak in toughness and had much higher ductility brittleness transition temperatures compared to the examples of the present invention. Samples ^Nos. 26, 29, 30 and 32, in which the numerical ratio of Mn oxide for inclusion having a maximum length of 1.0 to 4.0 μm was outside the range specified in the present invention is apparently deficient in resistance to hydrogen embrittlement and had lower Hc compared to the examples of the present invention. Sample No. 25 has a small Hc, although the number of Mn oxides was within the range specified in the present invention. This is thought that due to the fact that the Mn content and the O content are high (outside the range specified in the present invention), the size distribution of the Mn oxide is polarized towards the larger size as compared to examples of the present invention, and therefore the number of voids between Mn oxide and steel is small.
(Example 3) [00106] A steel piece having the chemical composition shown in Table 5 has been cast. The steel part was heated to 1,200 ° C and hot rolled to form a hot rolled steel sheet between 2.0 and
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34/50
4.0 mm thick, at a finishing temperature of 880 to 920 ° C. The steel sheet was wound in a plurality of windings while temperatures were controlled to the cooling conditions on a cooling bed (ROT). The steel sheet was preserved, and then cold rolled by a 50% reduction to obtain a cold rolled steel sheet. The cold rolled steel sheet was subjected to annealing recrystallization so that the steel sheet was kept at 700 ° C to 800 ° C for 1 minute and cooled in air to room temperature, thus obtaining a sample material (steel sheet for hot stamping). A concentration of an inclusion containing Mn and a numerical ratio of an Mn oxide to the inclusion containing Mn having a maximum length of 1.0 to 4.0 μΜ were determined in the same way as in Example 1. Hot stamping was performed using a flat die identical to that of Example 1. A tensile test piece, a constant load test piece and a Charpy impact test piece were made from the steel plate after hot stamping in the same way as in Example 1. For the thickness of the test piece plate, the tensile test piece was identical in thickness to the cold rolled steel plate plate, and other test pieces had a plate thickness obtained by grinding both surfaces of the cold rolled steel sheet to a depth of 0.1 mm. A constant load test, diffusible hydrogen measurement and a Charpy impact test were also carried out in the same manner as in Example 1. The thickness of the hot-rolled sheet finish plate, the winding temperature, the results of the inclusion examination , resistance to hydrogen embrittlement (HC) and toughness are shown together in Table 6.
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TABLE 5
Steel Chemical composition (Unit:% by mass, balance: Fe and impurities)Ç Si Mn P s Al N O Others 3rd 0.20 0.025 1.0 0.02 0.004 0.003 0.003 0.005 B: 0.004 3b 0.26 0.025 1.5 0.02 0.004 0.003 0.003 0.007 Cr: 1.0, Mo: 0.2, W: 0.2, V: 0.5
35/50
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TABLE 6
No. Steel Hot-rolled sheet thickness Cooling temperature (C) Inclusion Concentration containing Mn (% by mass) Inclusion containing Mn having a maximum length of 1.0 to 4.0 pm Tensile strength (MPa) Hc (ppm) Ductility brittleness transition temperature (° C) Markings Number of inclusions observed (numbers) Number of Mn oxides (number) Numerical ratio of number of Mn oxides(%) 33 3rd 2.8 700 0.15 500 89 17.8 1508 0.90 -66 Example of the Present Invention 34 3rd 2.8 690 0.16 500 73 14.6 1516 0.89 -67 Example of the Present Invention 35 3rd 2.8 680 0.14 504 47 9.4 1520 0.48 -47 Comparative Example 36 3rd 3.2 710 0.14 500 78 15.6 1503 0.92 -68 Example of the Present Invention 37 3rd 3.2 700 0.16 501 67 13.4 1510 0.90 -65 Example of the Present Invention 38 3rd 3.2 680 0.13 500 45 9.0 1518 0.44 -45 Comparative Example 39 3rd 4.0 720 0.17 507 77 15.2 1500 0.88 -69 Example of the Present Invention 40 3rd 4.0 690 0.15 500 57 11.4 1506 0.91 -70 Example of the Present Invention 41 3rd 4.0 660 0.15 502 46 9.1 1514 0.46 -44 Comparative Example 42 3b 2.0 710 0.19 500 85 17 1596 1.06 -60 Example of the Present Invention 43 3b 2.0 690 0.20 508 81 15.9 1600 1.03 -59 Example of the Present Invention 44 3b 2.0 670 0.18 500 45 8.9 1606 0.68 -40 Comparative Example 45 3b 2.4 750 0.20 503 58 11.5 1587 1.01 -61 Example of the Present Invention 46 3b 2.4 700 0.21 500 52 10.3 1613 0.98 -63 Example of the Present Invention 47 3b 2.4 645 0.18 500 48 9.5 1622 0.70 -43 Comparative Example 48 3b 3.2 740 0.19 500 82 16.3 1594 1.07 -59 Example of the Present Invention 49 3b 3.2 710 0.22 500 70 13.9 1601 1.02 -58 Example of the Present Invention 50 3b 3.2 680 0.21 500 49 9.8 1618 0.69 -41 Comparative Example
36/50
Underlines in the table indicate values outside the range specified in the present invention
Petition 870190003912, of 14/01/2019, p. 44/68
37/50 [00107] The tensile strength of the steel sheet after hot stamping was independent of the thickness of the finish sheet and steel 3a showed a tensile strength of 1500 to 1520 MPa and steel 3b showed a tensile strength from 1587 to 1622 MPa. When comparing samples that have the same thickness as the plate, it is shown that the tensile strength tends to increase as the coiling temperature decreases, and therefore the resistance of the sample material is thought to be affected by coiling temperature. The concentration of the inclusion containing Mn was within the range specified in the present invention, in all examples, but sample ^Nos. 35, 38, 41, 44, 47 and 50 of comparative examples where the winding temperature was outside the range specified in the present invention, the numerical ratio of Mn oxide for the inclusion containing Mn having a maximum length of 1.0 to 4.0 μΜ was outside the range specified in the present invention (less than 10%), and, consequently, Hc was significantly lower compared to two examples of the present invention with the same finishing thickness of the same steel, which lead to a weak resistance to hydrogen embrittlement, and also the ductility fragility transition temperature was higher compared to two examples of the present invention with the same finish thickness of the same steel, leading to poor toughness. In view of the fact that, in all these comparative examples, the inclusion concentration containing Mn was within the range specified in the present invention, it is thought that, in these comparative examples, Mn oxide grinding was insufficient, so that spaces voids capable of serving as a diffusible hydrogen trap site cannot be sufficiently secured, and therefore the Hc value has become small, and the ductility brittleness transition temperature has been increased because an inclusion stretched without being crushed remains. Samples ^Nos. 33, 34, 36,
Petition 870190003912, of 14/01/2019, p. 45/68
38/50
37, 39, 40, 42, 43, 45, 46, 48 and 49 of examples of the present invention in which the winding temperature was within the range specified in the present invention were excellent in both resistance to hydrogen embrittlement and toughness.
(Example 4) [00108] A steel piece having the chemical composition shown in Table 7 was produced. The steel part was transformed into a 2.8 mm thick hot rolled steel sheet, according to the same conditions as in Example 1, and the steel sheet was pickled and then cold rolled (reduction: 50%) on a steel plate with a plate thickness of 1.4 mm. The cold-rolled steel sheet was heated to 655 ° C at an average heating rate of 19 ° C / s, subsequently heated to 730 to 780 ° C at an average heating rate of 2.5 ° C / s, immediately cooled by an average cooling rate of 6.5 ° C / s, immersed in an aluminum plating bath (containing Si in a concentration of 10% and impurities) to 670 ° C, and then removed 5 seconds. The deposition amount was adjusted with a gas cleaner, followed by the steel sheet cooled by air to room temperature. Analysis of the inclusion of the obtained steel sheet was performed in the same way as in Example 1. In the same way as in Example 2, the hot steel sheet was stamped in the shape of a hat, and a JIS No. tensile test piece. 5, a puncture test piece and a Charpy impact test piece were taken from the hat portion. For heating conditions for hot stamping, the steel sheet was kept at 900 ° C for 1 minute, hydrogen containing nitrogen at a concentration of 3% was defined as an atmosphere, and the dew point was adjusted to 0 ° C. Results of the analysis related to inclusion are shown in Table 8, and test results related to the hot stamping material are presented together in Table 9.
Petition 870190003912, of 14/01/2019, p. 46/68
TABLE 7
Steel Chemical composition (Unit:% by mass, balance: Fe and impurities)Ç Si Mn P s Al N O Others 4th 0.20 0.025 1.5 0.02 0.004 0.003 0.0025 0.007 Cr: 1.0, B: 0.004 4b 0.22 0.025 1.3 0.02 0.002 0.003 0.0025 0.006 B: 0.003, Mo: 0.2, W: 0.1, V: 0.1 4c 0.24 0.040 1.1 0.02 0.002 0.003 0.0025 0.007 Nb: 0.02
39/50
Petition 870190003912, of 14/01/2019, p. 47/68
TABLE 8
No. Steel Al plating layer thickness (pm) Inclusion Concentration containing Mn (% by mass) Inclusion containing Mn having a maximum length of 1.0 to 4.0 pm Number of inclusions observed (numbers) Number of Mn oxides (number) Numerical ratio of number of Mn oxides (%) 51 4th 16.1 0.15 500 60 12.0 52 4th 22.1 0.16 500 64 12.8 53 4th 33.8 0.15 500 63 12.6 54 4th 48.7 0.17 500 66 13.2 55 4th 51.1 0.15 502 63 12.5 56 4b 15.2 0.11 500 73 14.6 57 4b 19.7 0.13 500 70 14.0 58 4b 34.1 0.11 504 71 14.1 59 4b 49.5 0.13 500 86 17.2 60 4b 54.8 0.12 500 74 14.8 61 4c 14.3 0.15 500 56 11.2 62 4c 20.0 0.15 500 61 12.2 63 4c 34.7 0.17 500 55 11.0 64 4c 49.3 0.16 500 57 11.4 65 4c 55.4 0.15 500 66 13.2
40/50
Petition 870190003912, of 14/01/2019, p. 48/68
41/50
TABLE 9
No. Steel Tensile strength (MPa) Number of cracks in the portion of the hole wall (number) Ductility fragility transition temperature (C) Hot stamping status 51 4th 1510 0 -62 Good 52 4th 1512 0 -69 Good 53 4th 1519 0 -67 Good 54 4th 1508 0 -68 Good 55 4th 1511 0 -61 Grip 56 4b 1540 0 -67 Good 57 4b 1543 0 -61 Good 58 4b 1546 0 -69 Good 59 4b 1539 0 -66 Good 60 4b 1544 0 -66 Grip 61 4c 1563 0 -64 Good 62 4c 1560 0 -61 Good 63 4c 1559 0 -60 Good 64 4c 1561 0 -62 Good 65 4c 1558 0 -63 Grip
[00109] In each example, the inclusion concentration containing Mn and the numerical ratio of the Mn oxide to the inclusion containing Mn having a maximum length of 1.0 to 4.0 μΜ were within the range specified in the present invention, and, therefore, no cracks occurred in the orifice walls in the piercing test and the ductility brittleness transition temperature was -60 ° C or below
Petition 870190003912, of 14/01/2019, p. 49/68
42/50 rior, so that a steel plate (member) having both resistance to hydrogen embrittlement and toughness was obtained, but in the samples N ° ^s . 55, 60 and 65 in which the thickness of the Al plating layer was more than 50 pm, abrasions occurred in the hat-shaped longitudinal wall portion with a high frequency. On the other hand, in samples N ° ^s . 51 to 54, 56 to 59 and 61 to 64, in which the thickness of the Al plating layer was 50 pm or less, excoriation did not occur in the hat-shaped portion of the longitudinal wall.
(Example 5) [00110] A steel piece having the chemical composition shown in Table 7 has been transformed into a hot-rolled steel sheet of
2.8 mm thick, according to the same conditions as in Example 1, and the steel sheet was pickled and then cold rolled to form a steel sheet that has a sheet thickness of
1.2 mm. The cold rolled steel sheet was heated to 655 ° C at an average heating rate of 19 ° C / s, subsequently heated to 730 to 780 ° C at an average heating rate of 2.5 ° C / s , immediately cooled by an average cooling rate of 6.5 ° C / s, dipped in a hot dip galvanizing bath (containing a concentration of 0.15% Al and impurities) at 460 ° C, and removed after 3 seconds. The deposition amount was adjusted with a gas cleaner, followed by the air-cooled steel plate to room temperature. Analysis of the inclusion of the obtained steel sheet was carried out in the same way as in Example 1. In the same way as in Example 2, the hot steel sheet was stamped in the shape of a hat, and a JIS No. 5 tensile test piece , a piercing test piece and a Charpy impact test piece were taken from the hat portion. For heating conditions for hot stamping, the steel sheet was kept at 900 ° C for 1
Petition 870190003912, of 14/01/2019, p. 50/68
43/50 minutes, hydrogen containing nitrogen at a concentration of 3% was defined as an atmosphere, and the dew point was set to 0 ° C. Results of the analysis related to inclusion are shown in Table 10, and the test results related to the hot stamping material are presented together in Table 11.
Petition 870190003912, of 14/01/2019, p. 51/68
TABLE 10
No. Steel Galvanized layer thickness (pm) Inclusion Concentration containing Mn (% by mass) Inclusion containing Mn having a maximum length of 1.0 to 4.0 pm Number of inclusions observed (numbers) Number of Mn oxides (number) Numerical ratio of number of Mn oxides (%) 66 4th 6.3 0.15 500 66 13.2 67 4th 12.7 0.16 500 63 12.6 68 4th 23.6 0.15 500 68 13.6 69 4th 28.8 0.17 500 65 13.0 70 4th 31.1 0.15 502 60 12.0 71 4b 11.3 0.11 500 71 14.2 72 4b 19.4 0.13 500 75 15.0 73 4b 24.6 0.11 505 78 15.4 74 4b 29.2 0.13 500 66 13.2 75 4b 33.5 0.12 500 70 14.0 76 4c 10.1 0.15 500 65 13.0 77 4c 17.5 0.15 500 61 12.2 78 4c 19.8 0.17 500 58 11.6 79 4c 29.1 0.16 500 54 10.8 80 4c 32.5 0.15 500 69 13.8
44/50
Underlines in the table indicate values outside the range specified in the present invention
Petition 870190003912, of 14/01/2019, p. 52/68
45/50
TABLE 11
No. Steel Tensile strength (MPa) Number of cracks in the portion of the hole wall (number) Ductility fragility transition temperature (C) Hot stamping status 66 4th 1499 0 -65 Good 67 4th 1504 0 -69 Good 68 4th 1503 0 -61 Good 69 4th 1507 0 -68 Good 70 4th 1511 0 -64 Adhered Zn 71 4b 1543 0 -66 Good 72 4b 1561 0 -61 Good 73 4b 1566 0 -69 Good 74 4b 1569 0 -66 Good 75 4b 1567 0 -62 Adhered Zn 76 4c 1640 0 -64 Good 77 4c 1646 0 -68 Good 78 4c 1640 0 -62 Good 79 4c 1645 0 -62 Good 80 4c 1652 0 -62 Adhered Zn
Petition 870190003912, of 14/01/2019, p. 53/68
46/50 [00111] In each example, the inclusion concentration containing Mn and the numerical ratio of the Mn oxide for the inclusion containing Mn having a maximum length of 1.0 to 4.0 μΜ were within the range specified in the present invention , and therefore cracking did not occur in the orifice walls in the drilling test and the ductility brittleness transition temperature was -60 ° C or below, so that a steel plate (member) having both brittleness resistance of hydrogen and toughness was obtained, but in the samples N ° ^s . of 70, 75 and 80 in which the thickness of the galvanized layer was greater than 30 μm, the adhesion of Zn to the matrix occurred with a high frequency. On the other hand, in samples N ° ^s . 66 to 69, 71 to 74 and 76 to 79, where the thickness of the galvanized layer was 30 μm or less, the adhesion of Zn to the matrix did not occur at all.
(Example 6) [00112] A steel piece having the chemical composition shown in Table 7 has been transformed into a hot-rolled steel sheet of
2.8 mm thick, according to the same conditions as in Example 1, and the steel plate was pickled and then cold rolled (reduction: 50%) on a steel plate with a plate thickness of 1 , 4 mm. The cold-rolled steel sheet was heated to 655 ° C at an average heating rate of 19 ° C / s, subsequently heated to 730-780 ° C at an average heating rate of 2.5 ° C / s, immediately cooled by an average cooling rate of 6.5 ° C / s, dipped in a hot dip galvanizing bath (containing an Al concentration of 0.13%, Fe to a concentration of 0.03 % and impurities) at 460 ° C, and removed after 3 seconds. The deposition amount was adjusted with a gas cleaner, the steel sheet was then heated to 480 ° C from a hot dip galvanized layer, and then cooled to air at room temperature. Analysis of the inclusion of the
Petition 870190003912, of 14/01/2019, p. 54/68
47/50 steel obtained was performed in the same way as in Example 1. In the same way as in Example 2, the hot steel sheet was stamped in the shape of a hat, and a JIS No. dash test piece. 5, a puncture test piece and a Charpy impact test piece were taken from the hat portion. For heating conditions for hot stamping, the steel sheet was kept at 900 ° C for 1 minute, hydrogen containing nitrogen at a concentration of 3% was defined as an atmosphere, and the dew point was adjusted to 0 ° C. Results of the analysis relating to inclusion are shown in Table 12, and the test results related to the hot stamping material are presented together in Table 13.
Petition 870190003912, of 14/01/2019, p. 55/68
TABLE 12
No. Steel Zn-Fe alloy layer thickness (pm) Inclusion Concentration containing Mn (% by mass) Inclusion containing Mn having a maximum length of 1.0 to 4.0 pm Number of inclusions observed (numbers) Number of Mn oxides (number) Numerical ratio of number of Mn oxides (%) 81 4th 15.1 0.15 501 66 13.2 82 4th 22.5 0.16 501 68 13.6 83 4th 31.4 0.15 500 63 12.6 84 4th 39.7 0.17 500 61 12.2 85 4th 46.2 0.15 502 63 12.5 86 4b 15.5 0.11 510 75 14.7 87 4b 21.1 0.13 502 79 15.7 88 4b 39.3 0.11 504 80 15.9 89 4b 44.4 0.13 500 86 17.2 90 4b 49.5 0.12 500 70 14.0 91 4c 14.1 0.15 500 59 11.8 92 4c 20.6 0.15 500 63 12.6 93 4c 34.7 0.17 500 54 10.8 94 4c 42.1 0.16 504 59 11.7 95 4c 45.4 0.15 500 60 12.0
48/50
Underlines in the table indicate values outside the range specified in the present invention
Petition 870190003912, of 14/01/2019, p. 56/68
49/50
TABLE 13
No. Steel Tensile strength (MPa) Number of cracks in the portion of the hole wall (number) Ductility fragility transition temperature (C) Hot stamping status 81 4th 1500 0 -62 Good 82 4th 1507 0 -62 Good 83 4th 1499 0 -60 Good 84 4th 1503 0 -68 Good 85 4th 1507 0 -60 Very small cracks generated 86 4b 1569 0 -67 Good 87 4b 1614 0 -66 Good 88 4b 1619 0 -69 Good 89 4b 1612 0 -63 Good 90 4b 1608 0 -60 Very small cracks generated 91 4c 1681 0 -64 Good 92 4c 1647 0 -61 Good 93 4c 1641 0 -68 Good 94 4c 1646 0 -62 Good 95 4c 1653 0 -60 Very small cracks generated
[00113] In each example, the inclusion concentration containing Mn and the numerical ratio of Mn oxide to the inclusion containing Mn having a maximum length of 1.0 to 4.0 μΜ were within the range specified in the present invention, and, therefore, cracking did not occur in the orifice walls in the piercing test and the ductility brittleness transition temperature was -60 ° C or below, so that a steel plate (member) having both resistance to hydrogen brittleness and toughness was obtained, but in samples N ° ^s . 85, 90 and 95 where the thickness of the hot-dip galvanized, bonded layer was more than 45 μm, very small cracks were generated
Petition 870190003912, of 14/01/2019, p. 57/68
50/50 in the alloy layer after pressing. On the other hand, in samples N ° ^s . 81 to 84, 86 to 89 and 91 to 94, where the thickness of the hot dip galvanized bonded layer was 45 pm or less, very small cracks were not generated at all in the alloy layer after pressing.
INDUSTRIAL APPLICABILITY [00114] According to the present invention, good resistance to hydrogen embrittlement can be ensured, even when processing that leads to the remaining tension, such as punching, is carried out after hot stamping, and in practice it is easy, so that the range of applications (components) of the hot stamping method can be expanded. Accordingly, the present invention is highly usable in steel plate processing industries.
LIST OF REFERENCE SIGNS
21st top matrix
21b lower die steel plate test piece taking position

权利要求:
Claims (14)
[1]
1. Steel sheet for hot stamping, characterized by the fact that the steel sheet has the chemical composition of:
C: 0.18 to 0.26%;
Si: more than 0.02% and not more than 0.05%;
Mn: 1.0 to 1.5%;
P: 0.03% or less;
S: 0.02% or less;
Al: 0.001 to 0.5%;
N: 0.1% or less;
O: 0.0010 to 0.020%;
Cr: 0 to 2.0%;
Mo: 0 to 1.0%;
V: 0 to 0.5%;
W: 0 to 0.5%;
Ni: 0 to 5.0%;
B: 0 to 0.01%;
Ti: 0 to 0.5%;
Nb: 0 to 0.5%;
Cu: 0 to 1.0%; and balance: Fe and impurities, in terms of% by mass, the concentration of an inclusion containing Mn is not less than 0.010% by mass, and less than 0.25% by mass, and the numerical ratio of an oxide of Mn for inclusion having a maximum length of 1.0 to 4.0 μΜ is 10.0% or more.
[2]
2. Hot stamping steel plate, according to claim 1, characterized by the fact that the chemical composition comprises one or more selected from the group consisting of
Cr: 0.01 to 2.0%;
Petition 870190003912, of 14/01/2019, p. 59/68
2/5
Mo: 0.01 to 1.0%;
V: 0.01 to 0.5%;
W: 0.01 to 0.5%;
Ni: 0.01 to 5.0%; and
B: 0.0005 to 0.01%, in terms of mass%.
[3]
3. Hot stamping steel plate, according to claim 1 or 2, characterized by the fact that the chemical composition comprises one or more selected from the group consisting of
Ti: 0.001 to 0.5%;
Nb: 0.001 to 0.5%; and
Cu: 0.01 to 1.0%, in terms of% by mass.
[4]
4. Hot stamping steel sheet according to any one of claims 1 to 3, characterized in that the steel sheet comprises, on its surface, an aluminum hot-dip layer with a thickness of 50 pm or less.
[5]
5. Hot stamping steel sheet according to any one of claims 1 to 3, characterized in that the steel sheet comprises, on its surface, a hot dip galvanized layer having a thickness of 30 pm or any less.
[6]
Steel sheet for hot stamping according to any one of claims 1 to 3, characterized in that the steel sheet comprises, on its surface, a hot dip galvanized alloy layer with a thickness of 45 pm or less.
[7]
7. Hot stamping steel plate according to any one of claims 1 to 6, characterized by the fact that the chemical composition comprises O: 0.0050 to 0.020%, in terms of
Petition 870190003912, of 14/01/2019, p. 60/68
3/5 hands of mass%.
[8]
8. Method for the production of a steel sheet for hot stamping, characterized by the fact that it comprises:
a hot rolling step of a steel part having the chemical composition of:
C: 0.18 to 0.26%;
Si: more than 0.02% and not more than 0.05%;
Mn: 1.0 to 1.5%;
P: 0.03% or less;
S: 0.02% or less;
Al: 0.001 to 0.5%;
N: 0.1% or less;
O: 0.0010 to 0.020%;
Cr: 0 to 2.0%;
Mo: 0 to 1.0%;
V: 0 to 0.5%;
W: 0 to 0.5%;
Ni: 0 to 5.0%;
B: 0 to 0.01%;
Ti: 0 to 0.5%;
Nb: 0 to 0.5%;
Cu: 0 to 1.0%; and balance: Fe and impurities, in terms of% by mass, and then wind the steel part at a temperature of 690 ° C or higher, to form a hot rolled steel sheet; and a cold rolling step of the hot rolled steel sheet in a 10 to 90% reduction to form a cold rolled steel sheet.
[9]
9. Method for the production of a steel sheet for
Petition 870190003912, of 14/01/2019, p. 61/68
4/5 hot plugging, according to claim 8, characterized by the fact that the chemical composition comprises one or more selected from the group consisting of Cr: 0.01 to 2.0%; Mo: 0.01 to 1.0%; V: 0.01 to 0.5%; W: 0.01 to 0.5%; Ni: 0.01 to 5.0%; and B: 0.0005 to 0.01%, in terms of mass%.
[10]
10. Method for the production of a steel sheet for hot stamping, according to claim 8 or 9, characterized by the fact that the chemical composition comprises one or more selected from the group consisting of Ti: 0.001 to 0 , 5%; Nb: 0.001 to 0.5%; and Cu: 0.01 to 1.0%, in terms of% by mass.
[11]
11. Method for producing a hot stamping steel sheet, characterized by the fact that the hot stamping steel sheet, which is obtained through the production method, according to any of claims 8 to 10, is immersed in an aluminum hot dip bath to form a hot aluminum dip layer on the surface of the steel sheet.
[12]
12. Method for producing a hot-stamping steel plate, characterized by the fact that the hot-stamping steel plate, which is obtained through the production method, according to any one of claims 8 to 10, is immersed in a hot dip galvanizing bath to form a hot dip galvanized layer on the surface of the steel sheet.
[13]
13. Method for producing a hot stamping steel plate, characterized by the fact that the hot stamping steel plate, which is obtained through the production method, according to any of claims 8 to 10, is immersed in a hot dip galvanizing bath, and then heated to a temperature of 600 ° C or below, to form a gal layer
Petition 870190003912, of 14/01/2019, p. 62/68
5/5 vanished by hot immersion on the steel sheet surface.
[14]
14. Method for producing a hot stamping steel sheet according to any one of claims 8 to 13, characterized in that the chemical composition comprises O: 0.0050 to 0.020%, in terms of% by mass .

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法律状态:
2018-03-13| B06T| Formal requirements before examination [chapter 6.20 patent gazette]|

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2018-10-16| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]|

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2019-02-26| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]|

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2019-08-20| B25D| Requested change of name of applicant approved|Owner name: NIPPON STEEL CORPORATION (JP) |

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2019-09-17| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2019-10-29| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 05/03/2013, OBSERVADAS AS CONDICOES LEGAIS. (CO) 20 (VINTE) ANOS CONTADOS A PARTIR DE 05/03/2013, OBSERVADAS AS CONDICOES LEGAIS |

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2022-01-04| B21F| Lapse acc. art. 78, item iv - on non-payment of the annual fees in time|Free format text: REFERENTE A 9A ANUIDADE. |

优先权:

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申请号 | 申请日 | 专利标题

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JP2012050935|2012-03-07|

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PCT/JP2013/055992|WO2013133270A1|2012-03-07|2013-03-05|Steel sheet for hot stamping, method for producing same, and hot-stamped steel material|

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