• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a process for producing from a steel blank a steel product with a medium carbon content and a hot-rolled steel product with a medium carbon content containing Fe, unavoidable impurities and residues. The medium-carbon hot-rolled steel product, containing Fe, unavoidable impurities and residues, expressed as a percentage by weight, contains at least the following substances:. where C + Ni + Cr + Mo expressed as a percentage by weight is 2.8 to 5.5% (Fig. 1)
    公开号:SE1351509A1
    申请号:SE1351509
    申请日:2012-06-15
    公开日:2014-01-27
    发明作者:Tommi Liimatainen；David Porter
    申请人:Rautaruukki Oyj；
    IPC主号:
    专利说明:

    the hot rolling step, a holding step after the first cooling step and a second cooling step after the holding step.
    The first step in the process is the step of producing a steel element which, expressed as a percentage by weight, contains 0.3 - 0.7% carbon, C, and Fe, unavoidable impurities and residues.
    The second step in the process is the hot rolling step of hot rolling the steel blank at a temperature in the range 800 - 1250 ° C to obtain a hot rolled steel blank.
    The third step in the process is the first cooling step, which is performed after the hot rolling step, and where cooling, advantageously rapid cooling, the hot rolled steel blank with at least a cooling rate corresponding to a critical cooling rate (CCR) to a temperature in the range l / to 570 ° C, advantageously in the range Md to 570 ° C. This first cooling stage cools, advantageously rapid cooling, the hot-rolled steel blank immediately after the hot-rolling step to a temperature below the austenite-ferrite conversion temperature but exceeding the starting temperature of martensite (l / ls), advantageously higher than the temperature l / ld (the highest temperature at which martensite conversion can occur under load). The critical cooling rate (CCR) is defined as the slowest cooling rate from the curing temperature that produces a substantially fully cured martensitic state. Cooling rates should be understood as average cooling rates.
    The fourth step in the process is the holding step, which is carried out after the first cooling step and in which the hot-rolled steel blank is kept at a temperature in the range l / ls to 570 ° C for a period of 10 to 300 seconds, advantageously in the range l / to 570 ° C. In this holding step, the hot-rolled steel blank is kept at a temperature exceeding lVls, advantageously exceeding l / ld. An object of the holding step is to even out the temperature differences between the interior and the surface of the hot-rolled steel blank. This reduces the probability of hardening cracks in connection with the martensite conversion, which in the process takes place in the fifth stage, the second cooling stage.
    The fifth step in the process is the second cooling step, which is carried out after the holding step and in which the hot-rolled steel blank is cooled at a rate of at least 0.5 ° C / s to a temperature below l / lf to obtain the medium carbon steel product. according to the present invention. By means of the process it is possible to produce a steel product with a medium carbon content, such as tool and / or mechanical steel, which has a part with a microstructure whose martensite content, expressed in volume percent, is preferably higher than 90 ° />, advantageously higher than 95 ° / -. ~.
    A sixth step, ie. a toughening step, may in the process follow the fifth step, the second cooling step. In such a toughening step, the hot-rolled steel blank is hardened.
    This results in a toughened martensitic microstructure. The toughening also reduces the likelihood of cracking in the medium carbon steel product when using the medium carbon steel product.
    All steps of the process, the hot rolling step, the first cooling step, the holding step and the second cooling step can be performed in a hot rolling path.
    The invention also relates to a medium carbon steel product, such as tool and / or mechanical steel, according to claim 25. l lan has selected the composition of the medium carbon steel product so that bainite conversion, perlite conversion or ferrite conversion does not necessarily begin with a medium carbon content using a process according to any one of claims 1 to 24.
    The invention is advantageous because it offers a solution for producing medium-high carbon content without hardening cracks, advantageous for producing tool and / or mechanical steel, by direct rapid cooling in the hot rolling web, which is a cost-effective process compared to the prior art.
    List of figures The invention is described in more detail below with reference to the figures, of which figure 1 shows a part of the heating cycle in a first embodiment of the invention, figure 2 shows a part of the heating cycle in a second embodiment of the invention, figure 3 shows a part of the heating cycle in a third embodiment of the invention, figure 4 shows a part of the heating cycle in a fourth embodiment of the invention, figure 5 shows a part of the heating cycle in a fifth embodiment of the invention, figure 6 shows a part of the heating cycle in a sixth embodiment of the invention.
    Detailed description of the invention First, the process for producing a steel product with a medium carbon content of a steel substance containing Fe, unavoidable impurities and residues, and various embodiments of the process are described in more detail.
    The process contains a step of producing a steel substance which, expressed as a percentage by weight, contains 0.3 to 0.7 ° /> carbon, C.
    The process contains a hot rolling step for hot rolling the steel blank at a temperature of 800 - 1250 ° C to obtain a hot rolled steel blank.
    The process contains a first cooling step, which is carried out after the hot rolling step, and where cooling, advantageously rapid cooling, the hot-rolled steel blank with at least a cooling rate corresponding to the critical cooling rate (CCR) to a temperature in the range 1 μs to 570 ° C, advantageously to a temperature in the range l / ld to 570 ° C.
    The process contains a holding step, which is carried out after the first cooling step and in which the hot-rolled steel blank is kept for a period of 10 to 300 seconds at a temperature in the range l / ls to 570 ° C, advantageously to a temperature in the range l / ls to 570 ° C.
    The process contains a second cooling step, which is performed after the holding step and where the hot-rolled steel blank is cooled at a rate of at least 0.5 ° C / s to a temperature below Mf to obtain the medium carbon steel product according to the present invention.
    The step of producing a steel substance in the process advantageously contains, but not necessarily, producing a steel substance which, in addition to iron, Fe, and unavoidable impurities and residues and said weight percent carbon, C, further, expressed in weight percent, contains: silicon Si 0 , 05 to 2.0%, advantageously 0.10 to 0.7%, manganese l / ln 0.2 to 2.0 ° />, advantageously 0.4 to 1.4%, chromium Cr 0.5 to 3.0 ° />, advantageously 1.0 to 1.8 ° />, vanadium V less than 1.0 ° />, advantageously less than 0.3 ° />, nickel Ni 1.0 to 6.0 ° />, advantageously 1.5 to 3.0 ° />, molybdenum Mo less than 1,0 ° />, advantageously 0.2 to 0.8 ° />, where C + Ni + Cr + l / lo expressed in weight percent is 2.8 to 5.5%. l / clay advantageously, expressed in weight percent, C + Si + l / ln + Cr + Ni + l / lo + V is 3.5 to 6.0 ° />.
    The reasons for the upper and lower limits for the necessary and optional components of the steel blank are as follows: The steel blank contains, expressed as a percentage by weight, 0.3 to 0.7% carbon, C. The lower limit for C has been set at 0.3% to moderate bainite conversion with moderate alloying and further to achieve desired hardness related properties. The upper limit for C has been set at 0.7% because an excessively high carbon content reduces the toughness, which is disadvantageous in tool and / or mechanical steel.
    The steel blank may, expressed as a percentage by weight, contain 0.05 - 2.0%, advantageously 0.10 to 0.7 ° /> silicon, Si. Si improves the hardenability without significantly affecting the weldability and it should be alloyed at least 0.05%, advantageously at least 0.10 ° />. Si is usually included due to treatment for Ca containment. The upper limit has been set at 2 ° />, advantageously 0.7 ° / -. ~ Because the surface quality could otherwise deteriorate.
    The steel blank may, expressed as a percentage by weight, contain 0.2 to 2.0 ° />, advantageously 0.4 to 1.4 ° / -. ~ Manganese, Mn. l / ln improves the hardenability, but it should be less than 2.0%, advantageously less than 1.4 ° />, most advantageously less than 1.0 ° />, in order to avoid segregation of l / ln and C during a medium-carbon steel continuous casting process.
    The steel blank may, expressed as a percentage by weight, contain 0.5 to 3.0 ° />, advantageously 1.0 to 1.8 ° /> chromium, Cr. Cr improves the hardenability and also delays bainite conversion, ie. shifts the bainite conversion boundary to the right the CCT (Continuous Cooling Transformation) diagram and enables the holding step without unwanted bainite.
    The steel blank, expressed as a percentage by weight, may contain less than 1.0%, advantageously less than 0.3 ° /> vanadium, V. Vanadium may increase the hardenability and VC may improve the wear resistance.
    The steel blank, expressed as a percentage by weight, may contain 1.0 to 6.0%, advantageously 1.5 to 3.0% nickel, Ni. Nickel is an advantageous alloying element because it also delays the bainite conversion, ie. shifts the bainite transformation limit to the right in the CCT (Continuous Cooling Transformation) diagram and enables the holding step without unwanted bainite. Nickel further increases the hardenability and it also has a beneficial effect on toughness-related properties, which can be important for tool and / or mechanical steel. Any toughening treatment can be avoided by alloying high nickel levels (1.5 - 3.0 ° />) thanks to the fact that nickel reduces the tendency to crack after direct rapid cooling.
    The steel blank may, expressed as a percentage by weight, contain less than 1.0%, advantageously 0.2 to 0.8% molybdenum, l / l. l / lo can be used, especially when toughening the steel blank to avoid core brittleness, or when the goal is to obtain greater hardness after toughening.
    The steel blank can therefore be toughened at higher temperatures. In one embodiment, the lower limit, expressed as a percentage by weight, of the combination C + Ni + Cr + Mo has been set to 2.8% and the upper limit, expressed as a percentage by weight, to 5.5 ° />. This type of composition combination within these limits gives a steel which can be rapidly cooled immediately after the hot rolling process and kept long enough at a temperature corresponding to Ms to 570 ° C, advantageously l / ld to 570 ° C, without undesired ferrite, perlite or bainite in the microstructure . In other words, this advantageous composition combination forms an opening or at least a bulge above the bainite nose in which austenite cannot be converted into undesired ferrite, perlite or bainite in the microstructure.
    In another embodiment, the lower limit, expressed as weight percent, for the combination C + Si + Mn + Cr + Ni + l / lo + V has been set to 3.5 ° /> and the upper limit, expressed as weight percent, to 6.0 ° />. This kind of composition combination within these limits more advantageously gives a steel which can be rapidly cooled immediately after the hot rolling process and kept long enough at temperatures corresponding to 1 / ls to 570 ° C, advantageously Md to 570 ° C, without undesired errit, perlite or bainite in the microstructure.
    In other words, this advantageous composition combination forms an opening or at least a bulge above the bainitnose and below the perlitnose which austenite cannot be converted to | unwanted ferrite, perlite or bainite in the microstructure.
    The steel blank may, expressed as a percentage by weight, contain less than 0.02% titanium, Ti%. l / lan can alloy titanium to avoid coarse-grained microstructure caused by heat treatment such as arc cutting or welding or during reheating prior to hot working.
    The steel blank may, expressed as a percentage by weight, contain less than 0,03 ° / - niobium, Nb.
    Niobium is not necessarily alloyed intentionally in this steel product, as high carbon content with Nb can impair toughness.
    The steel blank may, expressed as a percentage by weight, contain less than 0,1 ° /> tungsten, W.
    It is advantageous to avoid tungsten because it is very expensive.
    The steel blank may, expressed as a percentage by weight, contain less than 1,0 ° /> copper, Cu. Copper can slightly increase the hardenability.
    The steel blank may, expressed as a percentage by weight, contain less than 0.0005 ° /> boron, B. Boron is not necessarily alloyed intentionally in this steel product, as the hardenability is sufficiently high without boron.
    The steel blank may, expressed as a percentage by weight, contain 0.02 to 0.15 ° /> aluminum, Al.
    Aluminum is necessary to get completely sealed steel and it can also increase the hardening.
    The steel blank may also contain other alloying elements, not mentioned in this description. l / lan performs the first cooling step advantageously, but not necessarily, immediately after the hot rolling step so that the temperature of the hot rolled steel blank is in the range 700 - 1000 ° C at the beginning of the first cooling step. Advantageously, but not necessarily, the hot rolled steel blank is cooled in the first cooling stage at a speed of 5 to 100 ° Cis, advantageously at a speed of 10 to 50 ° C / s, i.e. you quickly cool it.
    In one embodiment of the process, the hot-rolled steel blank is cooled in the first cooling stage to a temperature in the range 421 to 570 ° C. In this embodiment of the process, the hot-rolled steel blank is kept in the holding step at a temperature in the range 421 to 570 ° C. In this embodiment of the method, the second cooling step is performed immediately after the holding step. In this embodiment of the process, the temperature of the hot-rolled steel blank is in the range 421 to 570 ° C at the beginning of the second cooling step. In this embodiment of the process, the hot-rolled steel blank is cooled in the second cooling stage at a speed of 5 to 100 ° C / s, advantageously at a speed of 10 to 50 ° C / s.
    In another embodiment of the process, the hot-rolled steel blank in the first cooling stage is cooled to a temperature in the range 1 / Ice to 421 ° C. In this embodiment of the process, the hot-rolled steel blank is kept in the holding step at a temperature in the range 1 / Ice to 421 ° C. In this embodiment of the method, the second cooling step is performed immediately after the holding step. In this embodiment of the process, the temperature of the hot-rolled steel blank is in the range of 1 / Is to 421 ° C at the beginning of the second cooling step. In this embodiment of the process, the hot-rolled steel blank is air-cooled in the second cooling stage.
    The process may include a leveling step for leveling the hot rolled steel blank, where the leveling step is performed in connection with the holding step, after the first cooling step and before the second cooling step. l / lan performs advantageous leveling at this stage of the process while the hot rolled steel blank is still relatively soft and does not yet have martensitic microstructure. In this regard, reference is made to Figure 6, which shows a part of the heating cycle for an embodiment of the method which contains such a leveling step in connection with the holding step.
    The process may contain a toughening step which is carried out after the second cooling step, in which toughening step the hot-rolled steel blank is toughened at a temperature exceeding l / lf, advantageously at a temperature of l / lf to l / Is, e.g. 150-250 ° C. l / lan can toughen the hot-rolled steel blank at a temperature of l / lf to l / Is, e.g. 150 - 250 ° C, for 20 to 1500 minutes. In this regard, reference is made to Figure 4, which shows a part of the heating cycle of an embodiment of the process which contains such a toughening step. Steel made using such a toughening step has properties associated with a high degree of hardness, which is advantageous for good abrasion resistance.
    The process may alternatively contain a toughening step which is performed after the second cooling step, in which toughening step the hot-rolled steel blank is toughened at a temperature exceeding 1 / Id, e.g. 400 to 450 ° C or 600 to 700 ° C. The hot-rolled steel blank can be toughened at a temperature exceeding 1 / Id, e.g. 400 to 450 ° C or 600 to 700 ° C for 2 to 400 minutes. In this regard, reference is made to Figure 2, which shows a part of the heat cycle for an embodiment of the process which contains a toughening step where the toughening temperature is 600 to 700 ° C. In this regard, reference is also made to Figure 3, which shows a part of the heat cycle for an embodiment of the process which contains a toughening step where the toughening temperature is 400 to 450 ° C.
    A toughening temperature in the range 600 to 700 ° C is particularly suitable for hot-rolled steels with a medium-high carbon content for products which are later surface-hardened by, for example, induction hardening. A toughening temperature in the range 600 to 700 ° C improves the extensibility and impact strength. If the toughening temperature exceeds 650 ° C, the machinability will be better and internal stresses and deformations will decrease, which is advantageous if the hot-rolled steel product with a medium carbon content is machined.
    A toughening temperature in the range 400 to 450 ° C is particularly suitable for hot rolled steel products with a medium carbon content which are later treated by nitriding or gas nitriding.
    If the process contains a toughening step performed after the second cooling step, the toughening step after the second cooling step is advantageously, but not necessarily, performed before the temperature of the hot-rolled steel blank drops below 100 ° C during the second cooling step. This reduces the probability of hardening cracks in comparison with a situation where the hot-rolled steel blank is allowed to cool to room temperature, ie. about 20 ° C. In addition, this reduces the energy requirement at delivery. Referring to Figures 1 to 6, six embodiments of the method are described below.
    Figure 1 shows a part of the heating cycle in a first embodiment of the invention. In the embodiment shown in Figure 1, the steel blank is first hot rolled at a temperature of 800 - 1250 ° C to obtain a hot rolled steel blank. Immediately after the hot rolling step, a first cooling step is performed so that the temperature of the hot rolled steel blank is in the range 700 - 1000 ° C at the beginning of the first cooling step. In the first cooling step, the hot-rolled steel blank is cooled at a speed of at least 5 ° C / s to a temperature in the range 420 to 570 ° C. The first cooling step is followed by a holding step, in which the hot-rolled steel blank is kept at a temperature in the range 420 - 570 ° C for 10 to 300 seconds. Immediately after the holding step, a second cooling step is performed in which the hot-rolled steel blank is cooled at a rate of at least 5 ° C / s to a temperature below 1 / lf to obtain the medium carbon steel product according to the present invention.
    Figure 2 shows a part of the heating cycle in a second embodiment of the invention. The embodiment shown in Figure 2 corresponds to the embodiment shown in Figure 1, with the difference that one toughening step is performed after the second cooling step. In Figure 2, this toughening step is performed before the temperature of the hot-rolled steel blank in connection with the second cooling step drops below 100 ° C. In Fig. 2, the toughening temperature is between 600 and 700 ° C.
    Figure 3 shows a part of the heating cycle in a third embodiment of the invention. The embodiment shown in Figure 3 corresponds to the embodiment shown in Figure 2, with the difference that the toughening temperature is between 400 and 450 ° C.
    Figure 4 shows a part of the heating cycle in a fourth embodiment of the invention. The embodiment shown in Figure 3 corresponds to the embodiment shown in Figure 2, with the difference that the toughening temperature is between 150 and 250 ° C.
    Figure 5 shows a part of the heating cycle in a fifth embodiment of the invention. In the embodiment shown in Figure 5, the steel blank is first hot-rolled at a temperature of 800 - 1250 ° C to obtain a hot-rolled steel blank. Immediately after the hot rolling step, a first cooling step is performed so that the temperature of the hot rolled steel blank is in the range 700 - 1000 ° C at the beginning of the first cooling step. In the first cooling step, the hot-rolled steel blank is cooled at a rate of at least 5 ° C / s to a temperature in the range 1 / Ice to 420 ° C. The first cooling step is followed by a holding step, in which the hot-rolled steel blank is kept at a temperature in the range 1 / Ice to 420 ° C for 10 to 300 seconds. After the holding step, a second cooling step is performed where the hot-rolled steel blank is cooled, e.g. in air at a speed of at least 0.5 ° C / s to a temperature below 100 ° C to obtain the medium carbon steel product.
    Figure 6 shows a part of the heating cycle in a sixth embodiment of the invention. The embodiment shown in Figure 6 corresponds to the embodiment shown in Figure 1, with the difference that a leveling step is performed in connection with the holding step.
    The following describes the hot-rolled steel product with a medium-high carbon content, such as tool and / or mechanical steel, which contains iron, Fe, and unavoidable impurities and residues.
    The medium-carbon hot-rolled steel product, containing Fe and unavoidable impurities and residues, contains, expressed as a percentage by weight, the following additional substances: carbon C 0,3 to 0,7 ° />, silicon Si 0,05 to 2,0%, advantageous 0.10 to 0.7%, manganese l / ln 0.2 to 1.5 ° />, advantageous 0.4 to 1.0%, chromium Cr 0.5 to 3.0 ° />, advantageous 1.0 to 1.8 ° />, vanadium V less than 1.0 ° />, advantageously less than 0.3 ° />, nickel Ni 1.0 to 6.0 ° />, advantageously 1.5 to 3.0%, molybdenum l / lo less than 1.0%, advantageously 0.2 to 0.8%, where C + Ni + Cr + l / lo expressed as a percentage by weight is 2.8 to 5.5 ° />. In another embodiment of the medium rolled hot rolled steel product, expressed as a percentage by weight, C + Si + l / ln + Cr + Ni + l / lo + V is 3.5 to 6.0 ° />.
    The hot-rolled steel product with a medium carbon content, containing Fe and unavoidable impurities and residues, may further, expressed as a percentage by weight, contain less than 0.0005% boron, B.
    The hot rolled steel product of medium carbon content containing Fe and unavoidable impurities and residues may further, expressed as a percentage by weight, contain less than 0.02% of titanium, Ti.
    The medium-carbon hot-rolled steel product containing Fe and unavoidable impurities and residues may further contain, expressed as a percentage by weight, less than 0,03% niobium, Nb.
    The hot-rolled steel product with a medium-high carbon content, which contains Fe and unavoidable impurities and residues, may additionally, expressed as a percentage by weight, contain 0,02 to 0,15 ° /> aluminum, Al.
    The hot-rolled steel product with a medium carbon content, containing Fe and unavoidable impurities and residues, may additionally, expressed as a percentage by weight, contain less than 0,1% tungsten, W.
    The hot-rolled steel product with medium carbon content, containing Fe and unavoidable impurities and residues, may additionally, expressed as a percentage by weight, contain less than 1,0 ° /> copper, Cu.
    The hot-rolled steel product with a medium carbon content, which contains Fe and unavoidable impurities and residues, may also contain other alloying elements, not mentioned in this description.
    The action of the components has been described in connection with the detailed description of the process.
    Composition examples are given in the table below: Example 1 Example 2 C 0.4 0.4 Si 0.25 0.25 l / ln 0.6 0.6 Cr 1.5 0.65 Ni 1.5 2.55 I / IO 0.3 0.55 Al 0.04 0.04 The composition is designed to cause an opening or at least a bulge above the bainitnose and below the perlitnose, in which the austenite can not be converted into unwanted ferrite, perlite or bainite in the microstructure below it. the first cooling stage or the holding stage. This makes it possible to produce hot-rolled steel products with a medium-high carbon content cost-effectively through direct rapid cooling.
    A part of the hot-rolled steel product with a medium carbon content advantageously, but not necessarily, has a microstructure containing more than 90 ° />, advantageously more than 95%, martensite expressed as a percentage by volume.
    A part of the hot-rolled steel product with a medium-high carbon content may also have a microstructure containing more than 90 ° />, advantageously more than 95 ° />, toughened martensite expressed as a percentage by volume.
    When it cools rapidly, the hot-rolled steel with a medium carbon content advantageously has a hardness of 500-800 HB measured 2 mm, advantageously 5 mm from the surface of the steel product with a medium carbon content. Through further toughening, the hardness can be reduced to a level of 300-750 HB depending on the toughening conditions and the steel composition.
    Furthermore, especially when the hot-rolled steel product is toughened in temperatures of at least 400 ° C, the yield strength Rp0.2 of the steel product can exceed 800 l / lPa, its tensile strength can be 1000 - 1300 l / lPa, elongation A5> 10% and further Charpy V (20 ° C)> 45 J.
    The steel product is advantageously a steel plate with a thickness of 5 - 80 mm, advantageously 6 - 60 mm, made in a sheet metal rolling mill. In this embodiment, the said steel blank is a steel plate blank. In one embodiment, the hot-rolled steel product having a medium-high carbon content is produced by means of a process as described in claims 1 to 25.
    It is obvious to a person skilled in the art that the basic idea of the invention, when the technology makes progress, can be realized in different ways. Thus, the invention and its embodiments are not limited to the above examples, but may vary within the scope of the claims.
    权利要求:
    Claims (39)
    [1]
    A process for producing a steel product with a medium-high carbon content from a steel blank, characterized in that it contains a step for producing a steel blank which, expressed as a percentage by weight, contains 0.3 to 0.7% C, Fe and unavoidable impurities and residues, a hot rolling step for hot rolling the blank at a temperature of 800 to 1250 ° C to obtain a hot rolled steel, a first cooling step, which is performed after the hot rolling step and where the hot rolled steel is cooled at at least a cooling rate corresponding to the critical cooling rate (CCR, critical cooling rate) to a temperature in the range l / ls to 570 ° C, advantageously in the range l / ld to 50 ° C, a holding step, which is performed after the first cooling step and where for a period of 10 to 300 seconds, the hot-rolled steel blank maintains at a temperature in the range Ms to 570 ° C, advantageously in the range Md to 570 ° C, and a second cooling step, which is performed after the holding step and then The hot-rolled steel blank is cooled at a rate of at least 0,5 ° C / s to a temperature below 1 / lf to obtain the medium carbon steel product.
    [2]
    Process according to Claim 1, characterized in that the step of producing a steel blank comprises producing a steel blank which, expressed in% by weight, further contains at least the following substances: Si 0.05 to 2.0 ° />, 1 / in 0 , 2 to 2.0%, Cr 0.5 to 3.0 ° />, V less than 1.0 ° />, Ni 1.0 to 6.0 ° / -. ~, L / lo less than 1.0 ° /> where C + Ni + Cr + 1 / lo expressed in weight percent is 2.8 to 5.5 ° />.
    [3]
    Process according to Claim 2, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains 0.10 to 0.7% of Si.
    [4]
    Process according to Claims 2 to 3, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains l / ln 0.4 to 1.4 ° />, advantageously 0.4 to 1.0 ° />.
    [5]
    Process according to one of Claims 2 to 4, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains 1.0 to 1.8 ° /> Cr.
    [6]
    Process according to one of Claims 2 to 5, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains less than 0.3 ° /> V.
    [7]
    Process according to one of Claims 2 to 6, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains 1.5 to 3.0 ° /> Ni.
    [8]
    Process according to one of Claims 2 to 7, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains 0.2 to 0.8% of 10%.
    [9]
    Process according to one of Claims 2 to 8, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains 3.5 to 6.0 ° /> C + Si + l / ln + Cr + Ni + | / lo + V.
    [10]
    Process according to one of Claims 1 to 9, characterized in that the step of producing a steel blank comprises producing a steel blank which, expressed as a percentage by weight, further contains less than 0.02% of Ti.
    [11]
    A method according to any one of claims 1 to 10, characterized in that the step of producing a steel blank comprises producing a steel blank which, expressed in weight percent, further contains less than 0.03% Nb.
    [12]
    Process according to one of Claims 1 to 11, characterized in that the step of producing a steel blank comprises producing a steel blank which, expressed in% by weight, further contains less than 1.0 ° /> Cu.
    [13]
    Process according to one of Claims 1 to 12, characterized in that the step of producing a steel blank comprises producing a steel blank which, expressed as a percentage by weight, further contains less than 0.0005 ° /> B.
    [14]
    A method according to any one of claims 1 to 13, characterized in that the step of producing a steel blank comprises producing a steel blank which, expressed in weight percent, further contains 0.02 to 0.15 ° /> Al.
    [15]
    Method according to one of Claims 1 to 14, characterized in that the first cooling step is carried out immediately after the hot-rolling step, and in that the temperature of the hot-rolled steel blank at the beginning of the first cooling step is in the range from 700 to 1000 ° C.
    [16]
    Process according to one of Claims 1 to 15, characterized in that in the first cooling step the hot-rolled steel blank is cooled at a speed of 5 to 100 ° C / s, advantageously at a speed of a / 10 to 50 ° C / s.
    [17]
    Process according to one of Claims 1 to 16, characterized in that in the first cooling step the hot-rolled steel blank is cooled to a temperature in the range 421 to 570 ° C, in that in the holding step the hot-rolled steel blank is kept at a temperature in the range 421 to 570 ° C, by performing the second cooling step immediately after the holding step, by the fact that the temperature of the hot-rolled steel blank at the beginning of the second cooling step is in the range 421 to 570 ° C, and by cooling in the second cooling step the hot-rolled steel blank at a speed of 5 to 100 ° C / s, advantageously at a speed of a / 10 to 100 ° C / s.
    [18]
    Method according to one of Claims 1 to 17, characterized in that in the first cooling stage the hot-rolled steel blank is cooled to a temperature in the range 1 / ls to 421 ° C, in that in the holding step the hot-rolled steel blank is kept at a temperature in the range l / ls to 421 ° C, in that the temperature of the hot-rolled steel blank at the beginning of the second cooling stage is in the range l / ls to 421 ° C, and in that in the second cooling stage the hot-rolled steel blank is cooled with air cooling.
    [19]
    Method according to one of Claims 1 to 18, characterized by a leveling step for leveling the hot-rolled steel blank, the leveling step being carried out in connection with the holding step, after the first cooling step and before the second cooling step.
    [20]
    Method according to one of Claims 1 to 19, characterized by a toughening step which is carried out after the second cooling step, in which toughening step is hot-hardened the hot-rolled steel blank at a temperature higher than 1 / lf, advantageously at a temperature between 1 lf and lVls, e.g. 150 to 250 ° C.
    [21]
    Process according to Claim 20, characterized in that the hot-rolled steel blank is toughened for 20 to 1500 minutes.
    [22]
    Method according to one of Claims 1 to 21, characterized by a toughening step which is carried out after the second cooling step, in which toughening step the hot-rolled steel blank is toughened at a temperature higher than 1 / ld, e.g. 400 to 450 ° C or 600 to 700 ° C.
    [23]
    Process according to Claim 22, characterized in that the hot-rolled steel blank is toughened for 2 to 400 minutes.
    [24]
    Method according to one of Claims 20 to 23, characterized in that the toughening step is carried out after the second cooling step before the temperature of the hot-rolled steel blank is lowered to below 100 ° C.
    [25]
    A medium-carbon hot-rolled steel product containing Fe and unavoidable impurities and residues, produced by a process according to any one of claims 1 to 24, characterized in that it contains, expressed as a percentage by weight, at least the following substances: C 0.3 to 0.7 ° />, Si 0.05 to 2.0%, l / ln 0.2 to 2.0 ° / -. ~, Cr 0.5 to 3.0%, V less than 1.0 Ni, 1.0 to 6.0%, l / lo less than 1.0% where C + Ni + Cr + l / lo expressed in weight percent is 2.8 to 5.5%.
    [26]
    Medium-carbon hot-rolled steel product according to Claim 25, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains 0.10 to 0.7% of Si.
    [27]
    Hot-rolled steel product with a medium-high carbon content according to Claim 25 or 26, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains 1/4 0.4 to 1.4%, advantageously 0.4 to 1.0%.
    [28]
    Medium-carbon hot-rolled steel product according to one of Claims 25 to 27, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains 1.0 to 1.8 ° /> Cr.
    [29]
    Medium-carbon hot-rolled steel product according to one of Claims 25 to 28, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains less than 0.3% of V.
    [30]
    Medium-carbon hot-rolled steel product according to one of Claims 25 to 29, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains 1.5 to 3.0 ° /> Ni.
    [31]
    Medium-carbon hot-rolled steel product according to one of Claims 25 to 30, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains 0.2 to 0.8 ° /> 1 / lo.
    [32]
    Medium-carbon hot-rolled steel product according to one of Claims 25 to 31, characterized in that a steel blank is obtained which, expressed as a percentage by weight, contains 3.5 to 6.0 ° /> C + Si + l + / ln + Cr + Ni + Mo + V.
    [33]
    Medium-carbon hot-rolled steel product according to one of Claims 25 to 32, characterized in that a steel blank is obtained which, expressed as a percentage by weight, further contains less than 0.0005% B.
    [34]
    Medium-carbon hot-rolled steel product according to one of Claims 25 to 33, characterized in that a steel blank is obtained which, expressed in% by weight, further contains less than 0.02 ° /> Ti.
    [35]
    Medium-carbon hot-rolled steel product according to one of Claims 25 to 34, characterized in that a steel blank is obtained which, expressed as a percentage by weight, further contains less than 0.03 ° /> Nb.
    [36]
    Medium-carbon hot-rolled steel product according to one of Claims 25 to 25, characterized in that a steel blank is obtained which, expressed in% by weight, further contains 0.02 to 0.15% of Al.
    [37]
    Medium-carbon hot-rolled steel product according to one of Claims 25 to 36, characterized in that a steel blank is obtained which, expressed in% by weight, further contains less than 1.0% Cu.
    [38]
    Medium-carbon hot-rolled steel product according to one of Claims 25 to 37, characterized in that a part of the medium-carbon hot-rolled steel product has a microstructure which, expressed as a percentage by volume, contains more than 90%, advantageously more than 95 ° / - martensite.
    [39]
    Medium-carbon hot-rolled steel product according to one of Claims 25 to 37, characterized in that a part of the medium-carbon hot-rolled steel product has a microstructure which, expressed as a volume percentage, contains more than 90 ° />, advantageously more than 95 ° /> hardened martensite .
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    同族专利:
    公开号 | 公开日
    FI20115599A|2012-12-16|
    WO2012172185A1|2012-12-20|
    FI123847B|2013-11-15|
    FI20115599A0|2011-06-15|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    GB773071A|1952-09-06|1957-04-24|Bochumer Ver Fur Guszstahlfabr|An improved method of making steel strip|
    DE19911287C1|1999-03-13|2000-08-31|Thyssenkrupp Stahl Ag|Process for producing a hot strip|CN106319347B|2016-10-27|2018-12-11|钢铁研究总院淮安有限公司|A kind of silicon vanadium steel plate and manufacturing method improving ballistic performance|
    CN111471931B|2020-05-29|2022-01-25|邯郸钢铁集团有限责任公司|Low-alloy wear-resistant steel with good bending and forming performance and production method thereof|
    CN113430459A|2021-06-17|2021-09-24|燕山大学|Vanadium microalloyed medium-carbon carbide-free bainite steel and preparation method thereof|
    法律状态:
    2015-09-29| NAV| Patent application has lapsed|
    优先权:
    申请号 | 申请日 | 专利标题
    FI20115599A|FI123847B|2011-06-15|2011-06-15|METHOD FOR THE MANUFACTURE OF MEDIUM-CARBON STEEL AND HOT-ROLLED MEDIUM-STEEL|
    PCT/FI2012/050619|WO2012172185A1|2011-06-15|2012-06-15|Method for manufacturing a medium carbon steel product and a hot rolled medium carbon steel product|
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