 hot-rolled steel sheets, and methods for producing them
专利摘要:
patent pending: "High performance hot rolled steel plate having excellent low temperature impact energy absorption and haz softening resistance, and production method thereof". The present invention relates to hot rolled steel plate having a maximum tensile strength of 600 mpa or more, and has excellent low temperature impact energy absorption and haz softening resistance, and a production method. therein are provided, i.e. sheet containing by weight% c: 0.04 to 0.09%, bs: 0.4% or less, mn: 1.2 to 2.0%, p: 0.1% or less, s: 0.02% or less, al: 1.0% or less, nb: 0.02 to 0.09%, ti: 0.02 to 0.07%, en: 0.005 % or less, where 2.0? mn + 8 [% ti] +12 [% nb]? 2.6, has a remainder of f and inevitable impurities, has a perlite area percentage of 5% or less, has a total area percentage of retained martensite and austenite of 0.5% or less has a remainder of a ferrite and / or bainite metal structure, has a mean ferrite and bainite grain size of 10 µm or less, has an average particle size of alloy carbonitrides with incoherent interfaces containing ti and nb of 20 nm or less, and has a yield ratio of 0.85 or more. 公开号:BR112014002875B1 申请号:R112014002875-3 申请日:2012-08-08 公开日:2018-10-23 发明作者:Naoki Maruyama；Naoki Yoshinaga；Masafumi Azuma；Yasuharu Sakuma；Atsushi Itami 申请人:Nippon Steel & Sumitomo Metal Corporation； IPC主号:
专利说明:
(54) Title: HOT-LAMINATED STEEL SHEETS AND METHODS FOR THE PRODUCTION OF THE SAME (51) lnt.CI .: C22C 38/00; B21B 3/00; C21D 9/46; C22C 38/14; C22C 38/58; C23C 2/02; C23C 2/28 (30) Unionist Priority: 08/09 / 2011JP 2011-173760 (73) Holder (s): NIPPON STEEL & SUMITOMO METAL CORPORATION (72) Inventor (s): NAOKI MARUYAMA; NAOKI YOSHINAGA; MASAFUMI AZUMA; YASUHARU SAKUMA; ATSUSHI ITAMI (85) National Phase Start Date: 06/02/2014 1/41 Descriptive Report of the Invention Patent for HOT-LAMINATED STEEL SHEETS, AND METHODS FOR THE PRODUCTION OF THE SAME. Technical Field [001] The present invention relates to a hot-rolled steel sheet of high yield ratio that has excellent impact energy absorption at low temperature and softening resistance of the ZTA (thermally affected zone) with resistance to maximum stress of 600 MPa or more, and to a method of producing it. Steel sheet is suitable as a base material for construction machinery bars and structures and as a base material for structures, members, etc. of trucks and cars that are mainly shaped by bending and, additionally, as a base material for piping. Background [002] The structures of construction machinery and trucks are assembled by molding hot-rolled steel sheet mainly by bending and arc welding of the molded parts. Therefore, the base material that is used for these parts is required to have excellent curvature and arc weldability. In addition, construction machinery and trucks are sometimes used in low-temperature environments, thus, in particular, with structures for trucks, etc., the properties of being resistant to fragility fracture and being able to absorb sufficiently Impact energy when impact is given, even at a low temperature, is sought. [003] As a steel sheet that has an excellent impact energy absorption, there is the technique revealed in NPLT 1 and PLTs 1 to 2. However, these steel sheets contain structures that include retained austenite or martensite and, in addition, optimize the structures of Petition 870180070307, of 8/13/2018, p. 5/53 2/41 steel sheet metal to achieve excellent impact properties. However, such steel sheet structures have the problems of being inferior in yield stress, and having problems with curvature. [004] Additionally, PLT 3 discloses a method of producing thin steel sheet which has an impact energy absorption capacity at a high yield in a stable cold rolling manner. However, this method suffers from a great softening of the thermally affected zone (ZTA) of the arc welding zone and the inability to obtain sufficient solder joint strength and, in addition, it was disadvantageous in terms of production costs. [005] As a method of obtaining hot-rolled steel sheet that has excellent curvature and a high yield ratio, for example, the dispersion method of Ti, Nb, and other alloy carbides in steel, as shown in PLTs 4 to 6 has been revealed. However, the steel sheet that uses such precipitation reinforcement sometimes suffers from a great softening of the thermally affected zone of arc welding and a drop in the joint strength. In addition, there are problems that sometimes fracture due to embrittlement occurs at a low temperature and, sometimes, the amount of impact energy absorption becomes small. [006] On the other hand, as a technique for suppressing the softening of the thermally affected weld zone, PLT 7 reveals the method of adding Mo and Nb or Ti, while PLT 8 reveals the method of optimizing the ingredients in order to suppress ZTA softening even in Ti-containing precipitation-reinforced steel. However, with these methods, there are problems that, sometimes, embrittlement fracture occur at a low temperature and, sometimes, the amount of impact energy absorption makes it small. Petition 870180070307, of 8/13/2018, p. 6/53 3/41 [007] PLT 9 discloses the method of establishing suitable rolling conditions from the raw rolling to the finishing rolling of the steel plate and a subsequent suitable cooling treatment in order to produce the hot rolled steel sheet for use of high strength electrical resistance welded steel pipe that has excellent hardness and low temperature weldability. This method controls the recrystallization in the rough rolling and finishing rolling of the steel plate to obtain a fine-grained metal structure and to obtain the steel plate that has excellent hardness at low temperature, but does not intend to control the size or distribution of carbonitrides of turns on. As a result, these are not optimized, so there is a problem with a drop in impact energy absorption. [008] PLT 10 reveals a method of establishing an adequate rolling reduction rate and retention time in the rough rolling process of a steel plate, and suitable finishing rolling conditions in order to produce high strength steel plate hot rolled that has excellent hardness and hydrogen cracking resistance. The objective of the optimization of the crude rolling process in this method is to promote the recrystallization of steel, but this does not intend to control the size or distribution of alloy precipitates. As a result, these are not optimized, so there is a problem with a drop in impact energy absorption. Regarding the finishing lamination conditions also, with the method described in PLT 10, there is the problem that it is not possible to control the size or distribution of the alloy precipitates and excellent impact absorption energy cannot be obtained. [009] PLT 11 reveals the technique of properly dispersing precipitated particles in the thermally affected zone of the weld in order to obtain high-strength hot-rolled steel plate that has Petition 870180070307, of 8/13/2018, p. 7/53 4/41 excellent ZTA softening resistance. However, this technique disperses the fine precipitates in the ZTA of the steel plate during arc welding, but the size of the precipitated particles in the steel is not optimized, as a result there is a problem that the steel plate was not excellent in absorption. impact energy. List of Citations Patent Literature PLT 1: Japanese Patent Publication No. 2007-284776A PLT 2: Japanese Patent Publication No. 2005-290396A PLT 3: Japanese Patent Publication No. 10-58004A PLT 4: Japanese Patent Publication No. 2009-185361A PLT 5 : Japanese Patent Publication No. 2007-9322A PLT 6: Japanese Patent Publication No. 2005-264239A PLT 7: Japanese Patent Publication No. 2003-231941A PLT 8: Japanese Patent Publication No. 2001-89816A PLT 9: Publication Japanese Patent No. 2001-207220A PLT 10: Japanese Patent Publication No. 10-298645A PLT 11: Japanese Patent Publication No. 2008280552A Non-Patent Literature NPLT 1: Nippon Steel Technical Reports, vol. 378 (2003), p. Summary of the Invention Technical Problem [0010] The present invention was produced in consideration of the above problems and has as its objective the provision of hot-rolled steel sheet of high yield strength to maximum stress 600 MPa or more which has both a excellent low temperature impact energy absorption and softening resistance Petition 870180070307, of 8/13/2018, p. 8/53 5/41 of ZTA, and a method of producing it. Solution to the Problem [0011] Inventors etc. investigated in detail the factors that influence the softening of the ZTA and impact energy absorption at low temperature of the steel sheet containing Ti and other alloy carbonitrides by which a high yield ratio can be stably achieved. As a result, they found that the amount of ZTA softening can be suppressed by establishing adequate amounts of Ti, Nb, and Mn. [0012] Additionally, the inventors etc. then they intensively studied the method of improving impact energy absorption at low temperature, and found for the first time that by reducing the percentage of perlite area in the metal structure of the steel plate and, preferably, eliminating as much as possible austenite retained and martensite, which in the past was considered advantageous for the improvement of the impact energy absorption capacity, and, additionally, for optimization of the truss equation with the matrix Fe and size of the alloy carbonitrides containing Ti and Nb that are dispersed in steel, in particular by controlling the particle size of alloy carbonitrides with incoherent interfaces, the absorption of impact energy at low temperature, which was a problem in steel reinforced by precipitation, is improved. [0013] In general, in precipitation-reinforced steel containing Nb and Ti, the precipitates are controlled so as to be present in a state of good lattice matching having a specific crystal orientation in relation to the matrix Fe, but at this time , inventors, etc. investigated the relationship with impact energy absorption at low temperature and, as a result, found that precipitated alloy carbonitrides with good lattice matching with matrix Fe tend not to become obstacles to Petition 870180070307, of 8/13/2018, p. 9/53 6/41 start of fracture propagation, while the alloy carbonitrides in an incoherent state with the lowest matrix Fe of the amount of impact energy absorption at low temperature even if relatively small in size. The mechanism by which the lattice matching of the alloy carbonitrides with the matrix affects the amount of impact energy absorption at low temperature is not certain, but it may be that if the alloy carbonitride lattice and the matrix Fe is poor , this becomes a starting point for interfacial peeling or void formation, and promotes both ductile and brittle fractures. [0014] Inventors etc. engaged in extensive studies in the production process and ranges of ingredients for carrying out the above type of structure and, as a result, the hot-rolled steel plate and plated steel plate completed with maximum tensile strength 600 MPa or more, which reaches both a softening resistance of the ZTA and energy absorption at low temperature and, in addition, are high in terms of performance and excellent in curvature. That is, the purpose of the present invention is as follows: (1) A high performance ratio hot rolled steel sheet that has an excellent impact energy absorption at low temperature and softening resistance of ZTA, characterized by comprising, by mass%, C: 0.04 to 0.09%, Si: 0.4% or less, Mn: 1.2 to 2.0%, P: 0.1% or less, S: 0.02% or less, Al: 1.0% or less, Nb: 0.02 to 0.09%, Ti: 0.02 to 0.07%, and Petition 870180070307, of 8/13/2018, p. 10/53 7/41 Ν: 0.005% or less, a remainder of Fe and unavoidable impurities, where 2.0 <Mn + 8 [% Ti] +12 [% Nb] <2.6, and having a metal structure comprising a percentage of area perlite of 5% or less, a percentage of total area of martensite and austenite retained of 0.5% or less, and a remainder of one or both of ferrite and bainite, having an average grain size of ferrite and bainite of 10 pm or less, having an average grain size of alloy carbonitrides with incoherent interfaces containing Ti and Nb of 20 nm or less, having a yield ratio of 0.85 or more, and having a maximum tensile strength of 600 MPa or more. (2) The high performance ratio hot rolled steel sheet which has an excellent impact energy absorption at low temperature and softening resistance of ZTA, according to (1), characterized by additionally comprising, by mass% , V: 0.01 to 0.12%. (3) The high performance ratio hot rolled steel sheet which has an excellent impact energy absorption at low temperature and softening resistance of ZTA, according to claim 1 or 2, characterized by comprising additionally, by% by mass, one or more of Cr, Cu, Ni, and Mo in a total of 0.02 to 2.0%. (4) The high performance ratio hot rolled steel sheet which has an excellent impact energy absorption at low temperature and softening resistance of ZTA, according to any one of (1) to (3), characterized by additionally comprise, by mass%, B: 0.0003 to 0.005%. Petition 870180070307, of 8/13/2018, p. 11/53 8/41 (5) The high performance ratio hot rolled steel sheet which has an excellent absorption of impact energy at low temperature and softening resistance of ZTA, according to any of (1) to (4) , characterized by additionally comprising, by mass%, one or more of Ca, Mg, La, and Ce in a total of 0.0003 to 0.01%. (6) The high performance ratio hot rolled steel sheet which has an excellent low temperature impact energy absorption and softening resistance of ZTA, characterized in that the high performance ratio hot rolled steel sheet of according to any one of (1) to (5) is plated or plated by alloy on a surface. (7) A method of producing hot-rolled steel sheet of high yield ratio that has an excellent absorption of impact energy at low temperature and softening resistance of ZTA, characterized by comprising, heating a steel plate having a composition according to any one of (1) to (5) at 1150 ° C or more, rough rolling of the heated steel plate, finishing of the rough rolling at a temperature between 1000 ° C to 1080 ° C, in which a rolling interval maximum in the rolling mill that is carried out at 1150 ° C or less is 45 sec or less, after the rolling mill, retention of the steel plate for a retention time t1 (sec) that satisfies the following formula (1), then starting the finishing lamination, carrying out the finishing lamination with a final lamination temperature Tf that satisfies the following formula (2) in order to obtain as a steel plate, start of water cooling of the steel plate within 3 seconds after lamination finishing then cooled steel plate at a temperature of 700 ° C or less at a lower cooling rate of 8 ° C / sec or more, and Petition 870180070307, of 8/13/2018, p. 12/53 9/41 steel sheet at a temperature between 530 ° C to 650 ° C. 1000x ([% Ti] + [% Nb])> t1 ..... formula (1) Tf> 830 + 400 ([% Ti] + [% Nb]) · -Formula (2) (8) The production method of the hot-rolled steel sheet of high yield ratio according to (7), characterized in that a final rolling temperature Tf satisfies the following formula (3). Tf> 830 + 800 ([% Ti] + [% Nb]) · -Formula (3) (9) A method of producing high-performance hot-rolled plated steel sheet that has excellent energy absorption from low temperature impact and softening resistance of the ZTA, characterized by comprising, stripping the hot-rolled steel sheet that was obtained by the production method according to (7) or (8), heating the steel sheet at the Ac3 temperature or less then immersing the steel sheet in a plating bath to plate the surface of the steel sheet. (10) The production method of hot-rolled steel sheet of high yield ratio which has an excellent absorption of impact energy at low temperature and softening resistance of ZTA, according to (9), characterized by additionally understanding alloy plated steel sheet after plating. Advantageous Effects of the Invention [0015] According to the hot rolled steel sheet of the present invention, due to the above configuration, it is possible to obtain the high performance ratio hot rolled steel sheet which has a maximum tensile strength of 600 MPa or more, and has excellent ZTA softening resistance, energy absorption at low temperature, and additionally curvature. With steel plate conPetição 870180070307, from 08/13/2018, p. 13/53 In addition, there are the problems that there are restrictions in use and operation at a low temperature, and sufficient joint strength cannot be achieved, but, according to the hot-rolled steel sheet of the present invention, use in regions cold cuts become possible, increased resistance enables products to be reduced in thickness, and the weight-reducing effect of construction machinery, automobiles and trucks, can be expected. [0016] Additionally, according to the production method of the hot rolled steel sheet which has an excellent absorption of impact energy at low temperature and a softening resistance of the ZTA of the present invention, it becomes possible to produce the sheet of high performance ratio hot rolled steel that has a maximum tensile strength of 600 MPa or more, and has excellent ZTA softening resistance, and low temperature energy absorption and additionally curvature. [0017] It is noted that, in the present invention, excellent absorption of impact energy at low temperature means the absorption of impact energy in a Charpy impact test at -40 ° C is 70J / cm 2 or more. Additionally, ZTA's excellent softening resistance means an AHV difference (= HVbm-HVzta) of 40 or less between the Vicker hardness (HVzta) of the most softened part of the thermally affected weld zone (ZTA) and the Vicker hardness (HVbm) ) of the base material in arc welding time by a welding current, voltage, and welding speed selected to give good bead shape, and by a welding heat input of 10000J / cm or less. In addition, excellent curvature means a min / t of 1.0 or less when the thickness of the test piece in a 90 ° V curvature test is the radius of curvature limit where no fracture occurs is ni m . Brief Description of Drawings Petition 870180070307, of 8/13/2018, p. 14/53 11/41 [0018] FIG. 1 A graph that expresses the relationship between Mn + 8Ti + 12Nb and vE-40 and AHV. [0019] FIG. 2 A graph that expresses the effect of the amount of Ti + Nb on the relationship between the retention time t1 and vE-40 from the final rough rolling to the beginning of the finishing rolling. [0020] FIG. 3 A graph expressing the relationship of the mass of Ti + Nb and Tf (° C) of the examples of the invention and two types of comparative examples (A-7 and B-6) between the types of steel that are shown in Table 2. Description of Embodiments [0021] Below, the present invention will be explained in detail. First, the reasons for limiting the steel ingredients of the high-yielding hot-rolled steel sheet which has an excellent low temperature impact energy absorption and softening resistance of the ZTA of the present invention will be explained. Here,% for ingredients means% by mass. C: 0.04 to 0.09% [0022] If the amount of C is less than 0.04%, it is difficult to ensure a maximum tensile strength of 600 MPa or more. On the other hand, if above 0.09%, the coarse and alloy carbonitrides with incoherent interfaces containing Ti and Nb increase and the impact energy absorption at low temperature drops, so the content was limited to 0.04 % to 0.09% reach. Si: 0.4% or less [0023] If the amount of Si exceeds 0.4%, sometimes the retained martensite or austenite remains in the steel plate structure and the low temperature hardness and impact energy absorption drop. For this reason, the appropriate range has been made 0.4% or less. From the point of view of ensuring curvature, 0.2% or less is more preferable. The lower limit on the amount of Si does not adjust particularly. Petition 870180070307, of 13/08/2018, p. 15/53 12/41 te, but if it is less than 0.001%, the cost of production increases, so that 0.001% is the substantive lower limit. Mn: 1.2a2.0% [0024] Mn is used to ensure the strength of the matrix by controlling the metal structure of the steel. Additionally, this is an element that contributes to the suppression of ZTA softening in the weld zone. If less than 1.2%, the percentage of perlite area increases, the impact energy absorption at low temperature drops, and, in addition, the amount of softening of the ZTA increases, so that the strength of the welded joint drops greatly , compared to the matrix resistance. If above 2.0% is contained, sometimes hard martensite is formed, and the impact energy absorption at low temperature drops, so that the appropriate range is made 2.0% or less. From the point of view of ensuring curvature, the content is more preferably 1.8% or less. P: 0.1% or less [0025] P is used to ensure the strength of the steel. However, if above 0.1% is included, the hardness at low temperature drops and, in addition, the absorption of impact energy at low temperature cannot be obtained, so that the appropriate range is made 0.1% or less . The lower limit is not particularly adjusted, but if less than 0.001%, the cost of production increases, so that 0.001% is the substantive lower limit. S: 0.02% or less [0026] S is an element that affects the absorption of impact energy. SE above 0.02% is included, even if controlling the percentage area of the metal structure and the average particle size of the alloy carbonitrides, an impact energy absorption at low temperature cannot be obtained, so the proper range is made 0.02% or less. The lower limit is not particularly adjusted. Petition 870180070307, of 13/08/2018, p. 16/53 13/41, but if less than 0.0003%, the cost of production increases, so that 0.0003% is the substantive lower limit. Al: 1.0% or less [0027] Al is used for deoxidation and control of the metal structure of the steel plate. If above 1.0%, the thermally affected zone in arc welding softens, and sufficient welded joint strength cannot be achieved, so that the proper range is made 1.0% or less. The lower limit is not particularly adjusted, but if less than 0.001%, the cost of production increases, so that 0.001% is the substantive lower limit. Nb: 0.02 to 0.09% [0028] Nb is used as a precipitation reinforcement element to adjust the strength of the steel, and is used to suppress the softening of the weld ZTA. If less than 0.02%, no softening suppression effect of the weld's ZTA is seen, while if above 0.09%, coarse alloy carbonitrides containing incoherent precipitated Ti and Nb increase, and absorption of impact energy at low temperature becomes lower, so the content has been limited to 0.02% to 0.09% in range. Ti: 0.02 to 0.07% [0029] Ti is used as a precipitation reinforcement element to adjust the strength of the steel, and is used to suppress the weld ZTA softening. If less than 0.02%, obtaining the maximum tensile strength of 600 MPa or more is difficult. Additionally, if above 0.07%, incoherent precipitated coarse alloy carbonitrides containing Ti and Nb increase, and the impact energy absorption at low temperature becomes lower, so the content is limited to 0.02% to 0.07% in reach. In order to stably obtain a yield ratio of 0.85 or more, 0.03% is preferably made the lower limit. Petition 870180070307, of 8/13/2018, p. 17/53 14/41 Ν: 0.005% or Less [0030] N contributes to the grain size of the metal structure of the steel plate through the formation of nitrides. However, if above 0.005%, the coarse and alloy carbonitrides with incoherent interfaces containing Ti and Nb increase, and the impact energy absorption at low temperature becomes lower, so the content has been limited to 0.005% or less in range. The lower limit is not particularly adjusted, but if less than 0.0003%, the cost of production increases, so that 0.0003% is the substantive lower limit. 2.0 <Mn + 8 [% Ti] +12 [% Nb] <2.6 [0031] Mn + 8 [% Ti] +12 [% Nb] is the total contribution ratios of the different elements related to absorption impact energy at low temperature and HZ softening due to welding. As shown in FIG. 1, by plotting the relationship of the vE-40 impact energy absorption indicator and the ZTA AHV softening indicator for 11 types of steel that differ in Ti and Nb, if the value of this parameter is less than 2, 0, a sufficient softening resistance of the ZTA cannot be obtained (ie, AHV> 40), and obtaining a maximum tensile strength of 600 MPa or more becomes difficult, while if above 2.6, the coarse and alloy carbonitrides with incoherent interfaces containing Ti and Nb increase, and the impact energy absorption at low temperature becomes lower (ie, vE-4o <7OJ / cm 2 ). For this reason, the appropriate range was limited to 2.0 to 2.6 range. [0032] In the present invention, as steel ingredients, in addition to the essential elements above, it is also possible to selectively include the following such elements. V: 0.01 to 0.12% [0033] V can be used to adjust the strength of the steel. However, if the V content is less than 0.01%, there is no such effect. AdicioPetição 870180070307, of 08/13/2018, p. 18/53 15/41 finally, if above 0.12%, embrittlement proceeds and the absorption of impact energy at low temperature drops. For this reason, the appropriate range was limited to 0.01 to 0.12%. One or more of Cr, Cu, Ni, and Mo in total from 0.02 to 2.0% [0034] Cr, Cu, Ni, and Mo can be used to control the steel structure. However, if the total content of one or more of these elements is less than 0.02%, there is no effect above that accompanies the addition. In addition, if above 2.0%, austenite is retained and the absorption of impact energy at low temperature drops. For this reason, the appropriate range of the total of these elements was limited to 0.02 to 2.0%. B: 0.0003 to 0.005% [0035] B can be used to control the structure of the steel sheet. However, if the amount of B is less than 0.0003%, this effect is not exhibited. Additionally, if above 0.005%, martensite is sometimes formed, and the impact energy absorption at low temperature drops. For this reason, the appropriate range was limited to 0.0003 to 0.005%. [0036] One or more of Ca, Mg, La, and Ce in a total of 0.0003 to 0.01% [0037] Ca, Mg, La, and Ce can be used for steel deoxidation. However, if the total amount of one or more of these elements is less than 0.0003%, there is no such effect, whereas if above 0.01%, embrittlement fracture occurs at a low temperature and the energy absorption of impact falls. For this reason, the appropriate range was limited to 0.0003 to 0.01%. [0038] It is noted that the rest of the ingredients are Fe and unavoidable impurities, but the steel ingredients in the present embodiment are not particularly limited in relation to other elements. Several elements can be properly included to adjust the resistance. Petition 870180070307, of 8/13/2018, p. 19/53 16/41 [0039] Next, the metal structure of the hot rolled steel sheet of the present invention will be explained. [0040] The hot-rolled steel sheet of the present invention may contain ferrite and bainite as the main phases and the remainder of one or more of perlite, martensite, and retained austenite. Percentage of Perlite Area [0041] In precipitation-reinforced steel containing Nb and Ti, if the percentage of perlite area exceeds 5%, embrittlement fracture occurs easily at a low temperature and, in addition, the impact energy absorption falls , so that the upper limit has been made 5%. From the point of view of ensuring curvature, 3% or less is the preferable range. It is noted that the lower limit is not particularly adjusted, but having a percentage of perlite area close to zero is more preferable in relation to the absorption of impact energy. Percentage of Total Area of Martensite and Retained Austenite [0042] In precipitation-reinforced steel containing Nb and Ti, if the percentage of total area of martensite and retained austenite exceeds 0.5%, embrittlement fracture easily occurs at a low temperature and additionally the absorption of pier impact energy. For this reason, the upper limit of the percentage of total area has been increased by 0.5%. It is noted that the lower limit is not particularly adjusted, but having a percentage of total area of martensite and austenite retained close to zero is more preferable in relation to the absorption of impact energy. Metal Structure That Remains of One or Both of Ferrite and Bainite [0043] The area percentages of these are not particularly limited, but from the point of view of ensuring curvature, the PerPetition 870180070307, of 13/08/2018, p. . 20/53 17/41 percentage of bainite area is preferably made 10% or more. Average Grain Size of Ferrite and Bainite [0044] The average grain size of ferrite and bainite is a correlative factor. If the average particle size is above 10 pm, even if you control the average particle size of the alloy carbonitrides that contain Nb and Ti, sometimes the impact energy absorption at low temperature cannot be ensured, so the upper limit was made 10 pm. 8 pm or less is a preferable condition that enables impact energy absorption to be more stable. The lower limit is not particularly adjusted, but if the size is less than 2 pm, the cost of production increases greatly, so that 2 pm is the substantive lower limit. [0045] In the present invention, the metal structure of the steel plate can be observed based on J IS G 0551 by an optical microscope. The observed surface is obtained by polishing the steel sheet, then stripping it with a corrosive Nital solution. [0046] The percentages of ferrite, bainite, perlite, and martensite area can be measured by the method of dot counting or image analysis using structural photographs obtained by an optical microscope or scanning electron microscope (SEM). The percentage of area of austenite retained is measured by X-ray diffraction. [0047] In the present invention, bainite includes upper bainite, lower bainite, and granular bainite. Additionally, the perlite includes perlite and pseudo perlite. [0048] Grain size can be measured by observation with an optical microscope or by analysis of crystal orientation using the EBSD method. Here, the grain size is the average grain size d which is described in J IS G 0551. Average particle size of alloy carbonitrides with Petition 870180070307, of 8/13/2018, p. 21/53 18/41 incoherent interfaces that contain Ti and Nb [0049] The particle size of alloy carbonitrides that contain Ti and Nb and the matching of truss with ferrite or bainite of matrix structure are important factors related to the absorption of impact energy to the low temperature. In general, in precipitation-reinforced steel, it is known to cause the precipitation of fine alloyed carbonitrides with good lattice matching with the matrix structure as fine particles, but for improving hardness at low temperature and improving impact energy absorption, it is important to control the alloy carbonitride particles with poor truss match with the matrix structure. If the average particle size of the alloy carbonitrides with incoherent interfaces that degrade the lattice equation is above 20 nm, the impact energy absorption at low temperature drops, so that the appropriate range has been limited to 20 nm or less. From the point of view of obtaining a better absorption of impact energy, 10 nm or less is the most preferable range. The lower limit is not particularly adjusted, but as a size that enables analysis of the precipitate's crystal orientation, 2 nm is the substantive lower limit. [0050] Here, alloy carbonitrides with incoherent interfaces signify the non-coherent state precipitated in the ferrite or bainite matrix structure, and ferrite and bainite bond not having the following crystal orientation relationships (Baker-Nutting orientation relationships) : (100) MX // (100) Fe (010) MX // (011) Fe (001) MX // (0-11) Fe (Note: -1 is an alternative notation for 1 with a bar above it) [0051 ] Here, M indicates Ti and Nb. The percentages occupied by Ti and Nb are not a problem. Additionally, X indicates C and N. PercentPetição 870180070307, of 08/13/2018, p. 22/53 19/41 cages occupied by C and N are not a problem. When V or Mo is added, sometimes M contains V or Mo. [0052] Note that the alloy carbonitrides with incoherent interfaces were analyzed for crystal orientation and measured for average particle size using a transmission electron microscope (TEM). First, a steel plate sample was made into a thin film of an extension through which electron beams pass, TEM was used to analyze the crystal orientation between the precipitate and the surrounding Fe matrix phase, then the Average particle size of 20 precipitates in order from the larger diameter precipitates in the precipitates that were judged to be incoherent precipitates was measured. Here, the particle size of a precipitate is measured as the equivalent circle diameter when assuming a circle equivalent to a particle's cross-sectional area. Yield Ratio 0.85 or More [0053] If the yield ratio is less than 0.85, sometimes the impact energy absorption at low temperature drops and the curvature drops. For this reason, the lower limit of the yield ratio has been made 0.85. [0054] It is noted that in the present invention, riim / t was used as the criterion for assessing curvature. Here, t is the thickness of the test piece and n> m is the radius of curvature limit at which no fracture occurs in a 90 ° V bend test. A rum / t of 1.0 or less was considered to have good curvature . 0.5 or less is the most preferable range. The upper limit is not particularly adjusted, but if the value is above 1.1, the curvature may fall, so that 1.1 or less is the most preferable range. Maximum Stress Resistance 600 MPa or More [0055] If the maximum tensile strength is less than 600 Petition 870180070307, of 8/13/2018, p. 23/53 20/41 MPa, the steel sheet does not contribute to the weight reduction of the members of cars, trucks, construction machinery, etc., so that in the present invention, the steel sheet of a maximum tensile strength of 600 MPa or more is assumed. [0056] Next, the production method will be explained in detail. [0057] Before hot rolling, it is necessary to heat the steel plate of the ingredients that are prescribed in the present invention to 1150 ° C or more to make the alloy carbonitrides that are present in the steel plate a state of solid solution. If the heating temperature is less than 1150 ° C, it becomes difficult to obtain a resistance of a maximum tensile strength of 600 MPa or more. In addition, the coarse alloy carbonitrides do not dissolve sufficiently and, as a result, the coarse alloy carbonitrides remain, so that the impact energy absorption at low temperature drops. For this reason, the heating temperature of the steel plate was limited to 1150 ° C or more. The upper limit is not particularly adjusted, but if above 1300 ° C, the effect becomes saturated, so that this is the substantive upper limit. [0058] The heated steel plate above is cold rolled into a raw bar. This rough lamination must be completed between 1000 ° C to 1080 ° C. If the finishing temperature is less than 1000 ° C, the coarse alloy carbonitrides precipitate in the austenite, and the impact energy absorption at low temperature drops, whereas if 1080 ° C or more, the austenite grains become coarse, it is not possible to obtain an average grain size of ferrite and bainite of 10 pm or less in the transformed structure after finishing lamination, cooling, and winding, the low temperature hardness deteriorates, and the impact energy absorption drops. Additionally, in the crude lamination performed at 1150 ° C or less, the repeat time 870180070307, from 08/13/2018, pg. 24/53 21/41 tension between reduction lamination passages is an important parameter that affects the average particle size of incoherent alloy carbonitrides. In the method of the present invention, crude lamination is usually carried out by lamination 3 to 10 times or, therefore, more preferably, lamination 5 to 10 times, but if the maximum retention time tO between lamination passages carried out at 1150 ° C or less is 45 s or more, the alloy carbonitrides become coarse to an extent that affects the absorption of impact energy. For this reason, the retention time between lamination reduction passes has been limited within 45 seconds. Within 30 sec is more preferable. [0059] Then, the raw bar is laminated by finishing to obtain a laminated material. [0060] The time (t1) from after finishing the rough rolling to the beginning of the finishing rolling is an important parameter that affects the average particle size of the alloy carbonitrides and the grain size of the ferrite and bainite after transformation. As shown in FIG. 2, the greater the total amount of Ti and Nb, the more the retention time t1 (arrow mark in the figure) where the impact energy absorption (vE-40) changes from good (OK) to not good (NG) increases. The retention time t1 (s) where the absorption changes from good (OK) to not good (NG) substantially corresponds to 1000x ([% Ti] + [% Nb]). Thus, if the retention time t1 (s) of after the rough rolling ends when the finishing rolling starts is 1000x ([% Ti] + [% Nb]) s or more, the coarse alloy carbonitrides precipitate in the austenite, the crystal grains of austenite become coarse, it is not possible to obtain an average grain size of ferrite and bainite of 10 pm or less in the transformed structure after finishing lamination, cooling, and winding, low temperature deteriorates, and energy absorption 870180070307, of 13/08/2018, pg. 25/53 Impact impact falls. 700x ([% Ti] + [% Nb])> t1s is the most preferable range. Consequently, the retention time t1 (s) was defined by the following formula (1): 1000x ([% Ti] + [% Nb])> t1 ..... formula (1) [0061] In addition, in the hot finish laminating, the final laminating temperature Tf has an effect on the average particle size of the alloy carbonitrides and the grain size of ferrite and bainite after transformation, thus being an important condition in the present invention, and changes depend on the contents of Ti and Nb. [0062] It has been learned that if the final rolling temperature Tf is 830 + 400x ([% Ti] + [% Nb]) or less, the coarse alloy carbonitrides with no truss match with the matrix precipitate, and absorption impact energy at low temperature drops. Therefore, the final rolling temperature Tf is adjusted to satisfy the following formula (2). Tf> 830 + 400 ([% Ti] + [% Nb]) · - formula (2) [0063] This relationship (2) is verified from the relationship of the type of steel in Table 2 explained later and the temperature of final lamination Tf. FIG. 3 shows the relationship between the mass% of Ti + Nb and Tf (° C) of an example of the invention and comparative example (A-7 and B-6) in the types of steel that are shown in Table 2. Here, it is it has been learned that the case where the part a coefficient ([% Ti] + [% Nb]) is made 400, that is, formula (2), is the limit at which the impact absorbing energy vE. 4 o -40 ° C becomes 70 J / cm 2 or more. [0064] When the coefficient a is 800, that is, when Tf> 830 + 800 ([% Ti] + [% Nb]) · - formula (3), [0065] compared to when the coefficient a is 400, the impact absorbing energy vE. 4 the -40 ° C changes somewhat from the limit of 70J / cm 2 or more. However, in the region where coefficient a is Petition 870180070307, of 8/13/2018, p. 26/53 23/41 400 to 800, the waiting time until the start of finishing lamination becomes longer, and the possibility of alloying carbonitrides starting to precipitate becomes higher, so that Tf is preferably controlled based on the formula (3 ) where the coefficient a is 800. [0066] The upper limit of the final laminating temperature Tf is not particularly adjusted, but the grain size of the ferrite and bainite tends to become coarse, so that 970 ° C or less is more preferable. [0067] Immediately after the final lamination, the laminated material is cooled with water. The time when the final lamination ends at the beginning of air cooling has an effect on the hardness of the low temperature base material and on the absorption of impact energy through the γ particle size and the average particle size of the alloy carbonitrides. If the air-cooling time immediately after the final lamination exceeds 3 s, the impact energy absorption tends to drop, so that water-cooling starts within 3 seconds. The lower limit is not particularly adjusted, but in general, it is substantially 0.2 s or more. [0068] After cooling with air immediately after the final rolling, the rolled material is cooled to obtain the hot rolled steel sheet. This cooling is an important process for controlling the metal structure. Cooling is performed below 700 ° C or less at the lowest cooling rate of 8 ° C / s or more. [0069] If the cooling cessation temperature exceeds 700 ° C, the alloy carbonitrides precipitate easily roughly at the grain boundaries, the pearlite easily forms, the grain size of the ferrite becomes larger, and the energy absorption of impact at low temperature drops. On the other hand, when the cooling rate more Petition 870180070307, of 8/13/2018, p. 27/53 24/41 down from below 700 ° C is less than 8 ° C / s, alloy carbonitrides precipitate easily roughly at the grain boundaries, pearlite easily forms, the grain size of the ferrite becomes larger, and the impact energy absorption at low temperature drops. [0070] Here, a lower cooling rate of 8 ° C / s or more means that the cooling rate between temperatures from the 700 ° C air-cooled finish temperature never becomes lower than 8 ° C / s. For this reason, for example, this means that air cooling is not carried out in this temperature range. Thus, in the present invention, air cooling is not performed in the middle part of the cooling process using water cooling as opposed to the past. [0071] The cooling cessation temperature is more preferably 680 ° C or less, while the lowest cooling rate is more preferably 15 ° C / s or more. The upper limit of the lowest cooling rate is not particularly adjusted, but if the rate is above 80 ° C / s, uniform cooling in the hot rolled coil becomes difficult, and fluctuations in resistance in the coil become bigger. For this reason, 80 ° C / s or less is preferable. [0072] Then, the cooled hot-rolled steel sheet is wound. The winding temperature is turned from 530 to 650 ° C. If the winding temperature is less than 530 ° C, sometimes retained martensite or austenite are formed, and the drop in hardness at low temperature and a drop in impact energy absorption become noticeable. In addition, if above 650 ° C, the percentage of perlite area becomes greater and the drop in hardness at low temperature and a drop in the absorption of impact energy become noticeable. [0073] The hot rolled steel sheet thus obtained can also be reheated (annealed). In this case, if the reheat temperature exceeds the Ac3 temperature, alloy carbonitrides Petition 870180070307, of 8/13/2018, p. 28/53 Coarse 25/41 precipitate, and the impact energy absorption at low temperature drops. For this reason, the appropriate range of the reheat temperature is limited to the temperature of Ac3 or less. The heating method is not particularly designated, and can be a method using furnace heating, induction heating, atomic heating, high frequency heating, etc. [0074] The heating time is not particularly determined, but if the heating and holding time at 550 ° C or more exceeds 30 minutes, to obtain a tensile strength of 590 MPa or more, the highest heating temperature is preferably 700 ° C or less. [0075] Note that reheating (annealing) can be carried out after winding the hot-rolled steel sheet, and before the temperature drops to room temperature. [0076] Hardening lamination or leveling lamination is effective for correction of shape, aging and improvement of fatigue characteristics, so that it can be performed after blasting or before blasting. If hardening lamination is carried out, the upper limit of the lamination rate is preferably made 3%. This is because if above 3%, the moldability of the steel sheet is impaired. Additionally, stripping can be carried out according to the objective. [0077] Next, the hot-dip galvanized steel sheet and method of production of the same of the present invention will be explained. [0078] The hot-dip galvanized steel sheet of the present invention is the aforementioned hot-rolled steel sheet of the present invention on the surface of which a plating layer or alloy plating layer is provided. [0079] The hot-rolled steel sheet that was obtained by method 870180070307, of 08/13/2018, p. 29/53 26/41 all of the above was stripped off, then a continuous galvanizing facility or continuous annealing and galvanizing facility was used to heat the steel sheet, and hot-dip it to form a plating layer on the surface of the sheet hot rolled steel. [0080] If the heating temperature of the steel plate exceeds the Ac3 temperature, a drop in the tensile strength of the steel plate, and a drop in the impact energy absorption at low temperature occur, so that the appropriate temperature range heating is limited to temperature Ac3 or less. The closer the heating temperature to Ac3, the faster the resistance to voltage drops. The base materials fluctuate greatly in degree, so that Ac3-30 ° C or less is the most preferable range of heating temperature. [0081] Additionally, after hot dip coating, galvanizing can be carried out to obtain a hot dip galvanizing layer. [0082] Note that the type of plating is not limited to galvanizing. It can also be another plating considering that the upper limit of the heating temperature is the temperature Ac3b. [0083] Additionally, in the present invention, the production method that precedes hot rolling is not particularly limited. That is, a blast furnace, converter, electric furnace, etc. can be used for melting, then various types of secondary refining can be used to adjust the ingredients to give the target contents of the ingredients. Then, the steel can be melted by any method, such as normal continuous casting, ingot casting, or also thin plate casting, etc. For feed material, scrap can also be used. When casting a plate that is Petition 870180070307, of 8/13/2018, p. 30/53 27/41 obtained by continuous casting, the high temperature cast plate can be sent directly as it is to the hot rolling mill, or it can be cooled to room temperature, then reheated in a heating furnace and then laminated the hot. Examples [0084] Below, examples will be used to further explain the present invention. [0085] A to AC steels that have the chemical ingredients that are shown in Table 1 were produced by the following method. First, the steels were cast to prepare steel plates, then the steel plates were reheated and rolled cold into rough bars under the conditions of hot rolling and annealing and plating conditions which are shown in Table 2-1 and Table 2-2. Then, the raw bars were laminated by finishing to obtain 4 mm thick laminated materials, then these were cooled and removed as hot rolled steel sheet. Table 1 (Part 1) Steel No. Ç Si Mn P s Al You Nb N THE 0.04 0.3 17 0.01 0.001 0.05 0.03 0.05 0.002 B 0.05 0.3 1.5 0.01 0.001 0.8 0.07 0.04 0.003 Ç 0.08 0.03 1.2 0.02 0.002 0.03 0.06 0.04 0.003 D 0.06 0.03 1.4 0.01 0.003 0.03 0.05 0.04 0.002 AND 0.04 0.3 1.8 0.01 0.003 0.03 0.06 0.05 0.003 F 0.09 0.03 1.3 0.01 0.005 0.03 0.03 0.02 0.002 G 0.02 0.03 1.5 0.01 0.003 0.04 0.05 0.03 0.002 H 0.10 0.03 1.3 0.01 0.003 0.04 0.03 0.04 0.002 1 0.05 0.5 1.3 0.01 0.003 0.04 0.03 0.04 0.002 J 0.05 0.03 1.0 0.01 0.003 0.04 0.03 0.07 0.003 K 0.05 0.03 2.1 0.01 0.003 0.04 0.04 0.04 0.003 L 0.05 0.03 1.3 0.08 0.003 0.04 0.04 0.04 0.003 Petition 870180070307, of 8/13/2018, p. 31/53 28/41 Steel No. Ç Si Mn P s Al You Nb N M 0.05 0.03 1.3 0.12 0.003 0.04 0.04 0.04 0.003 N 0.05 0.03 1.3 0.01 0.015 0.04 0.04 0.04 0.003 0 0.05 0.03 1.3 0.01 0.022 0.04 0.04 0.04 0.003 P 0.05 0.03 1.3 0.01 0.003 1.3 0.04 0.04 0.003 Q 0.05 0.03 1.3 0.01 0.003 0.04 0.005 0.05 0.003 R 0.05 0.03 1.3 0.01 0.003 0.04 0.09 0.06 0.003 s 0.05 0.03 1.3 0.01 0.003 0.04 0.04 0.003 0.003 T 0.05 0.03 1.3 0.01 0.003 0.04 0.04 0.10 0.003 u 0.05 0.03 1.3 0.01 0.003 0.04 0.04 0.04 0.006 V 0.05 0.03 1.3 0.01 0.003 0.04 0.04 0.04 0.003 w 0.05 0.03 1.3 0.01 0.003 0.04 0.04 0.04 0.003 X 0.05 0.03 1.3 0.01 0.003 0.04 0.04 0.04 0.003 Y 0.05 0.03 1.3 0.01 0.003 0.04 0.04 0.04 0.003 z 0.05 0.03 1.3 0.01 0.003 0.04 0.04 0.04 0.003 AA 0.04 0.3 1.9 0.01 0.001 0.05 0.02 0.02 0.002 AB 0.04 0.3 2.1 0.01 0.001 0.05 0.02 0.02 0.002 B.C 0.04 0.3 1.8 0.01 0.001 0.05 0.01 0.003 0.002 Table 1 (Part 2) Steel No. Mn + 8Ti + 12Nb Ac3 Others Comments THE 2.5 853 Invention steel B 2.5 900 Invention steel Ç 2.2 857 Invention steel D 2.3 848 Ca: 0.0015 Invention steel AND 2.9 861 Comparative steel F 1.8 832 Comparative steel G 2.3 866 Comparative steel H 2.0 829 Comparative steel I 2.0 869 Comparative steel J 2.1 857 Comparative steel K 2.9 828 Comparative steel L 2.1 901 Invention steel M 21 929 Comparative steel N 2.1 852 Invention steel O 2.1 852 Comparative steel Petition 870180070307, of 08/13/2018, p. 32/53 29/41 Steel No. Mn + 8Ti + 12Nb Ac3 Others Comments P 2.1 902 Comparative steel Q 1.9 838 Comparative steel R 2.7 872 Comparative steel s 1.7 852 Comparative steel T 2.8 852 Comparative steel u 2.1 852 Comparative steel V 2.1 858 V: 0.06 Invention steel w 2.1 848 Cr: 0.3, Cu: 0.05, Ni: 0.05 Invention steel X 2.1 851 Mo: 0.3, B: 0.002 Invention steel Y 2.1 852 Ce: 0.002, La: 0.001 Invention steel z 2.1 842 Mg: 0.002, Cu: 0.5 Invention steel AA 2.3 842 Invention steel AB 2.5 836 Comparative steel B.C 1.9 841 Comparative steel Table 2 Table 2-1 (1 part) SRT(° C) RR(° C) to(Mon) you(Mon) Tf(° C) t2(Mon) CRmin(° C / s) SCT(° C) TO 1 1230 1020 25 50 900 2 25 680 A-2 1130 1000 25 50 900 2 25 680 A-3 1230 960 25 50 900 2 25 680 A-4 1230 1100 25 50 900 2 25 680 A-5 1230 1020 25 20 900 2 25 680 A-B 1230 1020 25 120 900 2 25 680 A-7 1230 1020 25 50 860 2 25 680 A-8 1230 1020 25 50 900 6 12 680 A-9 1230 1020 25 50 900 2 15 700 A-10 1230 1020 25 50 900 2 5 680 A-11 1230 1020 25 50 900 2 20 720 A-12 1230 1020 25 50 900 2 25 560 A-13 1230 1020 25 50 900 2 25 610 A-14 1230 1020 25 50 900 2 30 580 A-15 1230 1020 25 50 900 2 25 680 Petition 870180070307, of 8/13/2018, p. 33/53 30/41 SRT(° C) RR(° C) 10(Mon) tl(Mon) Tf(° C) t2(Mon) CRmin(° C / s) SCT(° C) A-16 1230 1020 50 50 900 2 25 680 A-17 1230 1020 70 50 900 2 25 680 A-18 1230 1020 120 50 900 2 25 680 B-1 1250 1040 25 60 880 2 50 650 B-2 1250 1000 25 60 880 2 50 650 B-3 1250 970 25 120 880 2 50 650 B-4 1250 1100 25 60 880 2 50 650 B-5 1250 1040 25 60 880 2 50 650 B-6 1250 1040 25 60 850 2 50 650 B-7 1250 1040 25 60 880 6 10 650 B-8 1250 1040 25 60 880 2 5 650 B-9 1250 1040 25 60 880 2 50 680 B-10 1250 1040 25 60 880 2 50 710 B-ll 1250 1040 25 60 880 2 50 510 B-12 1250 1040 50 60 880 2 50 650 B-13 1250 1040 120 60 880 2 50 650 C-1 1250 1040 25 45 880 2 50 570 C-2 1250 1040 25 45 880 2 50 670 Table 2-1 (2nd part) CT (° C) Annealing temperaturemaximum (° C) Plating Type Comments TO 1 600 Example of the invention A-2 600 A-3 600 A-4 600 A-5 600 Example of the invention A-B 600 A-7 600 A-8 600 A-9 640 Example of the invention A-10 600 A-11 680 Petition 870180070307, of 8/13/2018, p. 34/53 31/41 CT (° C) Annealing temperaturemaximum (° C) Plating Type Comments A-12 520 A-13 550 680 Plating Example of the invention A-14 530 680 Electroplating Example of the invention A-15 600 880 Plating A-16 600 A-17 600 A-18 600 B-1 570 Example of the invention B-2 570 Example of the invention B-3 570 B-4 570 B-5 570 Example of the invention B-6 570 B-7 570 B-8 570 B-9 620 Example of the invention B-10 660 B-ll 480 B-12 570 B-13 570C-1 600 Example of the invention C-2 600 730 Plating Example of the invention Table 2-2 D-1 1259 1040 25 45 889 2 50 670 600 Example of the invention E-1 1250 1040 25 60 880 2 50 670 600 F-1 1250 1040 25 60 880 2 50 670 600 G-1 1250 1040 25 60 880 2 50 670 600 H-1 1250 1040 25 60 880 2 50 679 600 1-1 1250 1040 25 60 880 2 50 670 600 J-1 1250 1040 25 60 880 2 50 670 600 K-1 1250 1040 25 60 880 2 50 670 600 L-1 1250 1040 25 45 880 2 50 670 600 Example of the invention Petition 870180070307, of 8/13/2018, p. 35/53 32/41 M-1 1250 1040 25 45 880 2 50 670 600N-1 1250 1040 25 45 880 2 50 670 600 Example of the invention 0-1 1250 1040 25 60 880 2 50 670 600 P-1 1250 1040 25 60 880 2 50 670 600 0-1 1250 1040 25 60 880 2 50 670 600 R-1 1250 1040 25 60 889 2 50 670 600 S-1 1250 1040 25 60 880 2 50 670 600 T-1 1250 1040 25 60 880 2 50 670 600 U-1 1250 1040 25 60 880 2 50 670 600 V-1 1250 1040 25 50 880 2 50 670 600 Example of the invention W-1 1250 1040 25 50 880 2 50 670 600 Example of the invention X-1 1250 1040 25 50 880 2 50 670 600 Example of the invention Y-1 1250 1040 25 50 880 2 50 670 600 Example of the invention Z-1 1250 1040 25 50 880 2 50 670 600 Example of the invention AA-1 1250 1040 25 50 860 2 50 670 600 Example of the invention AB-1 1250 1040 25 50 889 2 50 670 600 AC-1 1250 1040 25 50 880 2 50 670 600 SRT: Plate heating temperature RFT: Crude rolling finish temperature tO: Crude rolling lamination time performed at 1150 ° C or less t1: Time from the end of the rough rolling to the beginning of the finishing rolling Tf: Final finishing lamination temperature t2: Air cooling time after final finishing lamination CRmin: Minimum cooling rate during CFT after air cooling SCT: Water cooling cessation temperature CT: Winding temperature [0086] In Table 1, the chemical compositions are given by mass%. Additionally, in Table 1, Ac3 (° C) is the value that calculated 870180070307, of 8/13/2018, p. 36/53 33/41 side by the following formula: Ac3 = 910-21 0a / [% C] +45 [% Sí] 30 [% Mn] +700 [% P] +40 [% AI] +400 [% Ti] +32 [% Mo] -11 [% Cr] -20 [% Cu] 15 [% Ni] in which,% C,% Si,% Mn,% P,% AI,% Ti,% Mo,% Cr,% Cu, and% Ni respectively indicate the levels in steel of C, Si, Μη, P, Al, Ti, Mo, Cr, Cu, and Ni. [0087] In Table 1, the chemical compositions of the steels correspond to the chemical compositions of the steels of the steel numbers in Table 2 with the same letters of the alphabet as the steel numbers. [0088] In Table 2, SRT indicates the plate's reheat temperature (° C). RFT indicates the finishing temperature of the rough rolling (° C). tO indicates the maximum retention time (s) between rough rolling operations carried out at 1150 ° C or less. t1 indicates the time (sec) from the end of the rough rolling to the beginning of the finishing rolling. Tf 'indicates the final finishing laminating temperature (° C). t2 shows the air cooling time immediately after the last finishing laminate (s). CRmin indicates the minimum cooling rate in the SCT after cooling with air (° C / s). SCT indicates the water cooling cessation temperature (° C). CT indicates the winding temperature (° C). [0089] Steels A-12 to A-14 and C-2 are hot-dip galvanized steel sheets that were produced by stripping the hot-rolled steel sheets, then annealing them in an annealing line and continuous galvanizing at the annealing temperatures that are shown in Table 2, then galvanizing them. [0090] It is noted that the galvanizing immersion temperature has been turned 450 ° C while, for the galvanizing treatment, the alloy temperature has been turned 500 ° C. Petition 870180070307, of 8/13/2018, p. 37/53 34/41 [0091] First, the metal and alloy carbide structures of the prepared steel plate were examined. [0092] The metal structure of the steel plate, as explained above, was observed based on J IS G 0551 for the cross section L by an optical microscope. In addition, the area percentages of the different structures were measured by the method of point counting and analysis using structural photographs in regions of 1 / 4t of thickness in the cross section L (1 / 4t position of the steel plate surface when the thickness of plate is t). The grain sizes of ferrite and bainite were measured by calculating the nominal particle size based on JIS G 0552. [0093] Alloy carbonitrides with incoherent interfaces containing Ti and NB were analyzed for crystal orientation and measured for average particle size by turning the steel plate sample into a thin film of an extension through which the electron beams pass, and using a transmission-type electron microscope (TEM). 20 or more alloy carbonitride particles were examined. [0094] Then, to measure the softening amount of the thermally affected weld zone (ZTA), arc welding was used to prepare an overlapping joint. The welding was carried out in a CO2 atmosphere: 100% with a heat input of about 5000 to 8000J / cm range. After welding, the cross section was polished and the base material and the thermally affected zone of welding (ZTA) were tested for Vicker hardness aiming at softening at 0 or less. The above measurement results are shown in Table 3. Note that in Table 3, F indicates ferrite, B indicates bainite, A indicates retained austenite, M indicates martensite, and P indicates perlite, d (F, b) indicates the average grain size (pm) of ferrite and bainite, dMCN indicates the average particle size (nm) of alloy carbonitrides with interPetition 870180070307, from 13/08/2018, pg. 38/53 35/41 inconsistent faces, and AHV indicates the difference between HVbm and HVzta when the Vicker hardness of the most softened part of the thermally affected weld zone is HVzta and the Vicker hardness of the base material is HVBM. Table 3-1 (1st part) Steel No. YP(MPa) TS(MPa) El (%) YR Percentage ofMetal (%) d (F, B) F + B M THE P TO 1 600 640 25 0.94 98 2 8 A-2 550 590 27 0.93 98 2 9 A-3 590 530 25 0.94 98 2 8 A-4 600 645 25 0.93 98 2 14 A-5 600 640 25 0.94 98 2 7 A-6 600 640 25 0.94 100 12 A-7 590 630 25 0.94 94 6 8 A-8 595 635 25 0.94 98 2 10 A-9 580 620 26 D94 97 3 9 A-10 570 610 27 0.93 94 6 11 A-11 555 600 27 0.93 93 7 13 A-12 490 575 29 0.85 99 1 7 A-13 640 650 24 0.98 98 2 8 A-14 600 610 25 0.98 100 7 A-15 500 550 26 0.91 100 8 A-16 600 635 25 0.94 98 2 8 A-17 590 630 25 0.94 98 2 8 A-18 590 625 25 0.94 98 2 8 B-1 630 630 24 0.93 99 1 8 B-2 630 630 24 0.93 99 1 8 B-3 610 665 25 0.92 99 1 8 B-4 625 675 24 0.93 100 12 B-5 630 680 24 0.93 100 8 B-6 620 670 24 0.93 100 8 B-7 620 670 24 0.93 100 10 B-8 515 665 24 0.92 100 10 Petition 870180070307, of 8/13/2018, p. 39/53 36/41 Steel No. YP(MPa) TS(MPa) El (%) YR Percentage ofMetal (%) d (F, B) F + B M THE P B-9 650 680 24 0.96 97 3 9 B-10 600 640 25 0.94 94 6 12 B-11 480 580 27 0.83 98 2 8 B-12 625 675 24 0.93 99 1 9 B-13 620 670 24 0.93 99 1 9 C-1 560 620 27 0.90 98 2 9 C-2 585 600 25 0.98 98 2 9 Table 3-1 (2nd part) Steel No. dMCN AHV VE_40 Bend-ability Comments TO 1 12 20 120 VG Example of the Invention A-2 25 18 60 VG A-3 22 20 60 VG A-4 14 18 55 VG A-5 13 19 110 VG Example of the Invention A-6 18 20 60 VG A-7 21 22 65 VG A-8 21 20 65 VG A-9 15 18 100 VG Example of the Invention A-10 15 18 65 VG A-11 12 17 55 VG A-12 12 17 64 VG A-13 13 24 110 VG Example of the Invention A-14 13 20 120 VG Example of the Invention A-15 20 16 50 VG A-16 13 20 60 VG A-17 21 18 55 VG A-18 27 18 50 VG B-1 14 21 100 VG Example of the Invention B-2 15 22 85 VG Example of the Invention B-3 22 21 50 VG B-4 13 21 65 VG Petition 870180070307, of 8/13/2018, p. 40/53 37/41 Steel No. dlVICN AHV VE_40 Bend-ability Comments B-5 15 25 90 VG Example of the invention B-6 21 24 60 VG B-7 23 26 60 VG B-8 21 26 65 VG B-9 14 22 80 VG Example of the invention B-10 23 35 55 VG B-11 12 65 G B-12 14 22 55 VG B-13 14 24 50 VG C-1 12 36 80 VG Example of the invention C-2 14 33 70 VG Example of the invention Table 2 1-2 D-1 605 695 25 0.87 98 2 8 15 30 85 VG Example of the invention E-1 620 685 24 0.91 98 2 7 14 8 65 VG F-1 570 595 23 0.96 98 2 8 15 52 65 VG Q-1 545 580 28 0.94 100 10 13 44 75 VG H-1 590 720 24 0.82 97 3 10 15 41 65 P 1-1 595 715 24 0.83 97 2 1 8 15 42 60 P J-1 615 690 24 0.89 96 6 8 22 33 55 VG K-1 605 720 24 0.84 98 2 7 21 6 60 P L-1 625 680 26 0.92 98 2 9 14 38 80 VG Example of the invention M-1 665 700 24 0.95 98 2 8 14 37 40 G N-1 595 640 25 0.93 98 2 9 12 33 75 G Example of the invention 0-1 600 640 25 0.94 98 2 8 13 34 45 P P-1 570 620 27 0.96 98 2 10 13 48 95 VG Q-1 540 595 28 0.91 98 2 8 12 43 110 VG R-1 720 780 21 0.92 98 2 9 21 37 45 VG S-1 615 640 26 0.96 98 2 8 13 56 90 VG T-1 680 720 23 0.94 97 2 8 22 22 65 VG U-1 655 700 24 0.94 98 2 8 21 34 60 VG V-1 665 700 24 0.95 98 2 8 15 36 80 VG Example of the invention W-1 625 675 24 0.93 98 2 7 14 34 90 VG Example of the invention X-1 620 670 24 0.93 100 8 15 34 100 VG Example of the invention Petition 870180070307, of 8/13/2018, p. 41/53 38/41 Y-1 630 680 24 0.93 100 7 15 35 90 VG Example of the invention Z-1 650 700 24 0.93 100 8 15 36 100 VG Example of the invention AA-1 555 635 26 0.87 100 8 13 24 100 G Example of the invention AB-1 525 630 25 0.83 98 2 8 11 42 65 G AC-1 555 580 28 0.96 100 7 11 41 120 VG d (F, B): Average grain size of ferrite and bainite (pm) dMCN: Average particle diameter of incoherent alloy carbonitrides AHV: ZTA softening of arc welding zone (HV) vE-40: Charpy impact energy absorption at -40 ° C (J / cm 2 ) [0095] Then, the steel plate was evaluated for properties resistance, impact energy absorption at low temperature, and curvature. [0096] Steel sheets were evaluated for strength properties by the following method. First, the test material was operated on a test piece No. 5 described in JIS Z 2201. Additionally, this test piece No. 5 was subjected to a stress test according to the method described in JIS Z 2241, and maximum tensile strength (TS), yield strength (YS), and elongation El), were found. [0097] The impact energy absorption at low temperature was evaluated by Charpy impact test. Based on JIS Z 2202, a thickness of 3 mm, notch test piece of 2 mmV has been prepared. The test piece was cooled to -40 ° C, then a Charpy impact test was performed, and the impact energy absorption (J / cm 2 ) was measured. [0098] The bending test was performed using the JIS Z 224 V-block method (bending angle: 90 °). The thickness of the test piece was t. The limit bending radius n> m with no fracture was measured. Petition 870180070307, of 8/13/2018, p. 42/53 39/41 [0099] The measurement results above are shown in Table 3. Note that, as explained above, in Table 3, vE-40 is the impact absorption value of Charpy (J / cm 2 ), while that riim / t is the value of the limit bending radius n> m divided by the thickness of the plate. A riim / t of 0.5 or less is rated as VG (very good), above 0.5 to 1.0 or less in range is rated as G (good), and above 1.0 is rated as P (poor). [00100] Steel A-2 has a plate heating temperature outside the appropriate range, so it is a comparative example where the tensile strength was then less than 600 MPa, and the impact energy absorption at low temperature was low. [00101] Steel A-3 to A-4 and Steel B-3 to B-4 have rough rolling finish temperatures outside the appropriate range, so they are comparative examples where impact energy absorptions at low temperature were low. [00102] Steel A-6 and Steel B-3 have times from the end of rough rolling to the beginning of finishing rolling outside the appropriate range, so they are comparative examples where impact energy absorptions at low temperature were low. [00103] Steel A-7 to A-8, Steel A-10, and Steel B-6 to B-8 have finishing lamination conditions and cooling conditions after finishing lamination outside the appropriate range, so which are comparative examples where low temperature impact energy absorptions were low. [00104] Steel A-11 and Steel B-10 have water cooling finish temperatures after finishing rolling and coiling temperatures of hot rolled steel sheets outside the appropriate range, so they are comparative examples where impact energy absorptions at low temperature were low. [00105] Steel A-12 and Steel B-11 have coil temperatures. Petition 870180070307, from 08/13/2018, pg. 43/53 40/41 to hot rolled steel sheets outside the appropriate range, so they are comparative examples where the tensile strengths were less than 600 MPa, and the low energy impact energy absorptions were low. [00106] Steel A-15 has an annealing temperature of Ac3 or higher, so it is a comparative example where the absorption of impact energy at low temperature was low. [00107] Steels F-1, Q-1, S-1, AB-1, and AC-1 have values of quantities of Mn, amounts of Ti, and amounts of Nb outside the appropriate range, so they are examples comparisons where the amounts of softening of the ZTA were large. Among these, Steels F-1, Q-1, and AC-1 have tensile strengths of less than 600 MPa. [00108] Steel G-1 has a quantity of C outside the appropriate range, so it is a comparative example where the resistance was less than 600 MPa, and the amount of softening of the ZTA was large. [00109] Steels H-1, 1-1, K-1, and AB-1 have amounts of C, amounts of Si, and amounts of Mn outside the appropriate range, so they are comparative examples where martensite or austenite is retained were present, the absorption of impact energy at low temperature was low, and, in addition, the curvature was poor. Steel J-1 has an amount of Mn outside the appropriate range, so it is a comparative example where perlite was present, and the absorption of impact energy at low temperature was low. [00110] Steels M-1 and O-1 have amounts of S and amounts of P that were excessive, so they are comparative examples where impact energy absorptions at low temperature were low. [00111] Steels E-1, R-1, T-1, and U-1 have amounts of Ti, amounts of Nb, and amounts of N outside the appropriate range, so Petition 870180070307, of 8/13/2018, p. 44/53 41/41 which are comparative examples where coarse alloy carbonitrides were present, and the impact energy absorptions at low temperature were low. [00112] Steel P-1 has an excessive amount of Al, so it is a comparative example with softening of the ZTA. [00113] As opposed to this, the examples of the invention all have yield ratios of 0.85 or more, maximum tensile strengths of 600 MPa or more, and excellent low temperature impact energy absorption and ZTA softening resistance . Petition 870180070307, of 8/13/2018, p. 45/53 1/3
权利要求:
Claims (10) [1] 1. Hot-rolled steel sheet, characterized by the fact that it consists of, by mass%, C: 0.04 to 0.09%, Si: 0.4% or less, Mn: 1.2 to 2.0%, P: 0.1% or less, S: 0.02% or less, Al: 1.0% or less, Nb: 0.02 to 0.09%, Ti: 0.02 to 0.07%, and N: 0.005% or less, a remainder of Fe and unavoidable impurities, and optionally consisting of, by mass%, V: 0.01 to 012%, one or more among Cr, Cu, Ni, and Mo in a total of 0.02 to [2] 2.0%, B: 0.0003 to 0.005%, and one or more among Ca, Mg, La, and Ce in a total of 0.0003 to 0.01%, where 2.0 <Mn + 8 [% Ti] +12 [ % Nb] <2.6, and having a metal structure comprising a percentage of perlite area of 5% or less, a percentage of total area of martensite and austenite retained of 0.5% or less, and a remainder of one or both of ferrite and bainite, having an average grain size of ferrite and bainite of 10 pm or less, having an average grain size of alloy carbonitrides with incoherent interfaces containing Ti and Nb of 20 nm or less, Petition 870180070307, of 8/13/2018, p. 46/53 2/3 having a yield ratio of 0.85 or more, and having a strength limit of 600 MPa or more. 2. Hot-rolled steel sheet, according to claim 1, characterized by the fact that it still consists of, by mass%, V: 0.01 to 0.12%. [3] 3. Hot-rolled steel sheet according to claim 1 or 2, characterized by the fact that it also consists of, by mass%, one or more of Cr, Cu, Ni, and Mo in a total of 0, 02 to 2.0%. [4] 4. Hot-rolled steel sheet according to any one of claims 1 to 3, characterized by the fact that it also consists of, by mass%, B: 0.0003 to 0.005%. [5] 5. Hot-rolled steel sheet according to any one of claims 1 to 4, characterized by the fact that it also consists of, by mass%, one or more of Ca, Mg, La, and Ce in a total of 0.0003 to 0.01%. [6] 6. Hot-rolled steel sheet, characterized by the fact that the hot-rolled steel sheet, as defined in any of claims 1 to 5, is plated or plated by alloy on a surface. [7] Method for the production of hot-rolled steel sheet, characterized by the fact that it comprises, heating a steel plate having a composition, as defined in any one of claims 1 to 5, at 1150 ° C or more, crude rolling of the heated steel plate, rough rolling finish at a temperature between 1000 ° C and 1080 ° C, in which a maximum rolling interval in the rough rolling that is carried out at 1150 ° C or less is 45 seconds or less after the rough rolling , retention of the steel plate for a Petition 870180070307, of 8/13/2018, p. 47/53 3/3 retention time t1 (second) that satisfies the following formula (1), then starting the finishing lamination, performing the finishing lamination with a final lamination temperature Tf that satisfies the following formula (2) in order to obtain a steel sheet, start water heating of the steel sheet within 3 seconds after finishing laminating, then cooling the steel sheet to a temperature of 700 ° C or less at a lower cooling rate of 8 ° C / second or more, and winding of the steel sheet at a temperature between 530 ° C and 650 ° C 1000x ([% Ti] + [% Nb])> t1 ..... formula (1) Tf> 830 + 400 ([% Ti] + [% Nb]) · - formula (2). [8] 8. Method for the production of hot rolled steel sheet, according to claim 7, characterized by the fact that a final rolling temperature Tf satisfies the following formula (3) Tf> 830 + 800 ([% Ti] + [% Nb]) · - formula (3). [9] 9. Method for producing hot-rolled plated steel sheet, characterized by the fact that it comprises, stripping the hot-rolled steel sheet that was obtained by the production method as defined in claim 7 or 8, heating of the steel sheet to a temperature of Ac3 or less, then immersing the steel sheet in a plating bath to plate the surface of the steel sheet. [10] 10. Method for the production of hot-rolled plated steel sheet, according to claim 9, characterized by the fact that it also comprises connecting the plated steel sheet after said plating. Petition 870180070307, of 8/13/2018, p. 48/53 1/2 .1 AHV ( 3 'JU ^ / P) O17 “3A NG Ú OK Suitable range «e = -ΞΗ OOKí O oOO £ oNG 60 50 10 0 140 120 100 80 60 40 20 0 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 Mn + 8Ti + 12Nb (mass % 2/2 FI Λ, ο ig.2
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同族专利:
公开号 | 公开日 PL2743364T3|2017-01-31| KR20140026574A|2014-03-05| JP5354130B2|2013-11-27| EP2743364A4|2015-11-04| BR112014002875A2|2017-02-21| CN103732776B|2016-06-08| WO2013022043A1|2013-02-14| CN103732776A|2014-04-16| EP2743364A1|2014-06-18| US20140178712A1|2014-06-26| JPWO2013022043A1|2015-03-05| ZA201400954B|2016-07-27| ES2589640T3|2016-11-15| CN105648311B|2018-03-30| RU2562582C1|2015-09-10| MX349893B|2017-08-18| EP2743364B1|2016-07-27| KR101575832B1|2015-12-08| TW201313920A|2013-04-01| MX2014001501A|2014-05-12| CA2843588C|2018-02-20| CA2843588A1|2013-02-14| TWI453287B|2014-09-21| CN105648311A|2016-06-08|
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法律状态:
2018-05-15| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]| 2018-09-25| B09A| Decision: intention to grant [chapter 9.1 patent gazette]| 2018-10-23| 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 08/08/2012, OBSERVADAS AS CONDICOES LEGAIS. | 2019-11-19| B25D| Requested change of name of applicant approved|Owner name: NIPPON STEEL CORPORATION (JP) |
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申请号 | 申请日 | 专利标题 JP2011173760|2011-08-09| JP2011-173760|2011-08-09| PCT/JP2012/070259|WO2013022043A1|2011-08-09|2012-08-08|Hot-rolled steel sheet having high yield ratio and excellent low-temperature impact energy absorption and haz softening resistance and method for producing same| 相关专利
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