Preparation method of high-uniformity cold-rolled phase-change high-strength steel

Abstract

The invention relates to the technical field of steel preparation, in particular to a preparation method of high-uniformity cold-rolled phase-change high-strength steel. The preparation method comprises the following steps: sequentially coiling and slowly cooling a cooled hot-rolled plate to obtain a hot-rolled coil; wherein the coiling temperature meets the relation that the first coiling temperature T1 for cooling the head of the hot-rolled plate, the second coiling temperature T2 for cooling the tail of the hot-rolled plate and the third coiling temperature T3 for cooling the central area of the hot-rolled plate meet the relation that T1 is larger than T3, and T2 is larger than T3; performing cold rolling on the hot-rolled coil to obtain a cold hard coil; and the cold hard roll is subjected to continuous annealing treatment under the condition of the gradient heating rate and the gradient cooling rate, and an annealed plate is obtained. According to the preparation method, the coiling temperature and the annealing treatment process are accurately controlled, so that the mechanical properties of the final high-strength steel product are uniformly distributed, and powerful support is provided for improving the steel quality and expanding the application field of the steel.

Description

Technical Field

[0001] The present application relates to the technical field of steel preparation, and in particular to a method for preparing high-uniformity cold-rolled phase-transformed high-strength steel. Background Art

[0002] At present, research shows that for every 10% reduction in the weight of a car, the cruising range of an electric car can increase by 5% to 6%, and the fuel efficiency of a fuel car can increase by 6% to 8%. That is, if the weight of the car body is reduced by 100kg, the fuel consumption per 100 kilometers will be reduced by 0.3L to 0.6L, and the CO2 emissions per kilometer can be reduced by 5g to 8g. In addition, the introduction of multiple safety collision regulations has also put forward higher requirements for the body structure and safety index. Therefore, the use of high-strength steel in the body of the car can not only reduce the weight of the body, but also meet the structural performance requirements of the body.

[0003] However, in the actual production process, due to the different levels of fluctuations in the properties of steel, these fluctuations will increase the risk of cracking of the steel during the stamping stage. At the same time, these fluctuations will seriously affect the uniform distribution of the steel properties, resulting in differences in the performance distribution of the head, middle, tail and edge-center of the steel, making it difficult for the steel to meet the structural performance requirements of the car body. Summary of the invention

[0004] The present application provides a method for preparing a cold-rolled phase-transformed high-strength steel with high uniformity, so as to solve the following technical problem: how to improve the uniformity of the performance distribution of the cold-rolled phase-transformed high-strength steel.

[0005] In a first aspect, the present application provides a method for preparing a cold-rolled phase-transformed high-strength steel with high uniformity, the preparation method comprising:

[0006] The cooled hot-rolled plate is coiled and slowly cooled in sequence to obtain a hot-rolled coil; wherein the coiling temperature satisfies: a first coiling temperature T1 of the head of the cooled hot-rolled plate, a second coiling temperature T2 of the tail of the cooled hot-rolled plate, and a third coiling temperature T3 of the central area of ​​the cooled hot-rolled plate satisfy the relationship: T1>T3, and T2>T3;

[0007] Cold rolling the hot rolled coil to obtain a chilled coil;

[0008] The cold hard coil is subjected to continuous annealing treatment under the conditions of a gradient heating rate and a gradient cooling rate to obtain an annealed sheet.

[0009] Optionally, the first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 satisfy the relationship: T1=T2, and T1-T3=30°C to 50°C.

[0010] Optionally, the third coiling temperature is 550°C to 630°C.

[0011] Optionally, the continuous annealing treatment includes a first heating section, a second heating section and a first holding section in sequence, the terminal temperature of the first heating section is 200°C to 250°C, and the heating rate of the first heating section is 5°C / s to 10°C / s; and / or

[0012] The terminal temperature of the second heating stage is 780°C to 820°C, and the heating rate of the second heating stage is 2°C / s to 6°C / s; and / or

[0013] The first insulation period lasts for 100s to 150s.

[0014] Optionally, the continuous annealing treatment further includes a first cooling section, a second cooling section, a second heat preservation section and a third cooling section in sequence, the terminal temperature of the first cooling section is 700° C. to 750° C., and the cooling rate of the first cooling section is 12° C. / s to 18° C. / s; and / or

[0015] The terminal temperature of the second cooling section is 300° C. to 350° C., and the cooling rate of the second cooling section is 20° C. / s to 30° C. / s; and / or

[0016] The second heat preservation period lasts for 200s to 300s; and / or

[0017] The terminal temperature of the third cooling section is 20°C to 30°C, and the cooling rate of the third cooling section is 5°C / s to 15°C / s.

[0018] Optionally, the step of sequentially coiling and slowly cooling the cooled hot-rolled plate to obtain a hot-rolled coil comprises the following steps:

[0019] The ingot is sequentially heated, rough rolled and finish rolled to obtain a hot rolled plate;

[0020] The hot-rolled sheet is subjected to laminar cooling to obtain a cooled hot-rolled sheet.

[0021] Optionally, the end point temperature of the heating is 1200° C. to 1280° C.; and / or

[0022] The rough rolling temperature is 1010° C. to 1080° C., and the rough rolling time is 30s to 60s; and / or

[0023] The temperature of the finish rolling is 850° C. to 910° C., and the time of the finish rolling is 20s to 50s.

[0024] Optionally, the cold hard coil is subjected to continuous annealing treatment under the conditions of a gradient heating rate and a gradient cooling rate to obtain an annealed sheet, and then the steps of:

[0025] The annealed sheet is flattened to obtain high-strength steel.

[0026] Optionally, the elongation of the flattening treatment is 0.2% to 0.5%.

[0027] Optionally, the cold rolling reduction rate is 45% to 60%.

[0028] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0029] The embodiment of the present application provides a method for preparing a highly uniform cold-rolled phase-transformed high-strength steel. In the preparation method, in the coiling stage of the cooling hot-rolled plate, the coiling temperatures of the head and tail of the cooling hot-rolled plate are controlled to be greater than the coiling temperature of the central area of ​​the cooling hot-rolled plate, so that the temperatures of the head, tail and central area of ​​the cooling hot-rolled plate are differentially distributed, and the different coiling temperatures of the differential distribution can cause the temperature difference between the head and tail of the hot-rolled coil and the temperature of the central area to be maintained at a low level, and can also cause the cooling hot-rolled plate to transform from an austenite region to a full bainite region, so as to obtain a uniform and fine bainite structure, thereby causing the performance and microstructure distribution of the hot-rolled coil to be more uniform, so as to improve the uniformity of the performance distribution of the cold-rolled phase-transformed high-strength steel; in addition, the cold-hardened coil is continuously annealed under the conditions of a gradient heating rate and a gradient cooling rate, and the gradient heating rate and the gradient cooling rate can cause the cold-hardened coil to undergo a uniform microstructure phase transformation under uniform heating and cooling conditions, forming a uniformly distributed martensitic structure, thereby further improving the uniformity of the performance distribution of the cold-rolled phase-transformed high-strength steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0032] Figure 1 A schematic diagram of the main process of a method for preparing a highly uniform cold-rolled phase-change high-strength steel provided in an embodiment of the present application;

[0033] Figure 2 A schematic flow chart of a method for preparing a highly uniform cold-rolled phase-change high-strength steel provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0035] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range; in addition, whenever a numerical range is indicated in this document, it is meant to include any cited number (fractional or integer) within the indicated range.

[0036] In this document, the terms including "including" and "including" mean "including but not limited to". Relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, and "plurality" means two or more; "at least one", "at least one of the following" or similar expressions, refers to any combination of these items, including any combination of single or plural items; for example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should correspond to the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0037] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0038] Figure 1 The main flow diagram of a method for preparing a highly uniform cold-rolled phase-transformed high-strength steel provided in an embodiment of the present application is exemplarily shown;

[0039] like Figure 1 As shown, the embodiment of the present application provides a method for preparing a cold-rolled phase-transformed high-strength steel with high uniformity, the preparation method comprising:

[0040] S1. coiling and slowly cooling the cooled hot-rolled plate in sequence to obtain a hot-rolled coil; wherein the coiling temperature satisfies: a first coiling temperature T1 of the head of the cooled hot-rolled plate, a second coiling temperature T2 of the tail of the cooled hot-rolled plate, and a third coiling temperature T3 of the central area of ​​the cooled hot-rolled plate satisfy the relationship: T1>T3, and T2>T3;

[0041] S2. cold rolling the hot rolled coil to obtain a cold hardened coil;

[0042] S3. The cold hard coil is subjected to continuous annealing treatment under the conditions of a gradient heating rate and a gradient cooling rate to obtain an annealed sheet.

[0043] It should be noted that the first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 can be achieved by controlling the start and end temperatures of the coiling production line.

[0044] It should be noted that the slow cooling method allows the temperature of the edge of the hot-rolled coil in contact with the air to slowly decrease, so that the temperature difference between the edge and the center of the hot-rolled coil is within a relatively low range, thereby improving the performance uniformity in the area from the edge to the center of the hot-rolled coil.

[0045] It should be noted that the embodiment of the present application provides a method for preparing cold-rolled phase-transformed high-strength steel with high uniformity. The core of the preparation method is to accurately control the coiling temperature of the cooled hot-rolled plate and the annealing process of the chilled coil to achieve uniform distribution of the steel structure and properties. The specific principle is as follows:

[0046] (1) During the coiling stage of the cooled hot-rolled plate, the preparation method ensures that the coiling temperature of the head and tail of the hot-rolled plate is higher than the coiling temperature of its central area through fine control. This differentiated temperature distribution design not only effectively maintains the temperature difference between the head and tail of the hot-rolled coil and the central area at a low level, but also promotes the transformation of the cooled hot-rolled plate from the austenite region to the full bainite region, forming a uniform and fine bainite structure. These uniformly distributed bainite structures significantly improve the uniformity of the performance structure of the hot-rolled coil, laying a solid foundation for the subsequent performance optimization of cold-rolled phase transformation high-strength steel.

[0047] (2) The preparation method also pays special attention to the annealing process of the cold-rolled coil. The cold-rolled coil is continuously annealed by adopting a gradient heating rate and a gradient cooling rate. This annealing method allows the cold-rolled coil to undergo a uniform microstructure phase transformation under uniform and controllable heating and cooling conditions, and finally forms a uniformly distributed martensitic structure. The careful design of this step further improves the uniformity of the performance distribution of the cold-rolled phase transformation high-strength steel, ensuring the stability and consistency of the steel in mechanical properties such as strength and toughness.

[0048] In summary, the embodiment of the present application provides a method for preparing highly uniform cold-rolled phase-transformed high-strength steel. The preparation method successfully achieves uniform distribution of the microstructure and properties of the cold-rolled phase-transformed high-strength steel by precisely controlling the coiling temperature and annealing process, providing strong support for improving the quality of steel and expanding its application areas.

[0049] In some optional embodiments, the first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 satisfy the relationship: T1 = T2, and T1-T3 = 30°C to 50°C.

[0050] In these embodiments, the first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 can satisfy the relationship: T1=T2, and T1-T3=30°C~50°C, so that the temperatures of the head, tail and central areas of the cooled hot-rolled plate are differentially distributed, and the different coiling temperatures with differential distribution can cause the temperature difference between the head and tail of the hot-rolled coil and the temperature of the central area to be maintained at a low level, and can also cause the cooled hot-rolled plate to transform from the austenite zone to the full bainite zone, obtaining a uniform and fine bainite structure, thereby causing the performance structure distribution of the hot-rolled coil to be more uniform, so as to improve the uniformity of the performance distribution of the cold-rolled phase transformation high-strength steel.

[0051] The first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 may satisfy the relationship: T1 = T2, and T1-T3 = 30°C, 35°C, 40°C, 45°C or 50°C.

[0052] In some optional embodiments, the third coiling temperature is 550°C to 630°C.

[0053] In these embodiments, the third coiling temperature can be 550°C to 630°C, so that the third coiling temperature is in the bainite transformation zone to promote the metallographic structure of the hot-rolled coil to transform from austenite to bainite. During the continuous annealing process, the bainite can be transformed into a martensite structure, thereby forming a cold-rolled phase transformation high-strength steel with a uniform distribution of metallographic structure, so as to improve the uniformity of the performance distribution of the cold-rolled phase transformation high-strength steel.

[0054] The third coiling temperature may be 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C or 630°C.

[0055] It should be noted that if the third coiling temperature is too high or too low, it will lead to incomplete phase transformation of the metallographic structure, resulting in uneven distribution of the metallographic structure in the final annealed sheet.

[0056] In some optional embodiments, the continuous annealing treatment sequentially comprises a first heating section, a second heating section and a first holding section, the terminal temperature of the first heating section is 200°C to 250°C, and the heating rate of the first heating section is 5°C / s to 10°C / s; and / or

[0057] The terminal temperature of the second heating stage is 780°C to 820°C, and the heating rate of the second heating stage is 2°C / s to 6°C / s; and / or

[0058] The first insulation period lasts for 100s to 150s.

[0059] In these embodiments, the continuous annealing treatment may include a first heating section, a second heating section and a first holding section in sequence, and the terminal temperature of the first heating section may be 200°C to 250°C, and the heating rate of the first heating section may be 5°C / s to 10°C / s, so that the temperature of the chilled coil rises evenly, which is convenient for the subsequent heating of the second heating section; in addition, the terminal temperature of the second heating section may be 780°C to 820°C, and the heating rate of the second heating section may be 2°C / s to 6°C / s, so that the overall temperature of the second heating section is in the ferrite-austenite two-phase region, so as to promote the recrystallization of the ferrite of the chilled coil and the partial austenitization of the chilled coil, so as to finally obtain an annealed sheet with uniform martensite distribution; in addition, the first holding time may be 100s to 150s, so that the process of recrystallization of the ferrite of the chilled coil and partial austenitization of the chilled coil has sufficient time, so as to finally obtain an annealed sheet with uniform martensite distribution.

[0060] The terminal temperature of the first temperature rising section may be 200°C, 210°C, 220°C, 230°C, 240°C or 250°C.

[0061] The heating rate of the first heating section may be 5°C / s, 6°C / s, 7°C / s, 8°C / s, 9°C / s or 10°C / s.

[0062] The terminal temperature of the second temperature rising section may be 780°C, 785°C, 790°C, 795°C, 800°C, 805°C, 810°C, 815°C or 820°C.

[0063] The heating rate of the second heating stage may be 2°C / s, 3°C / s, 4°C / s, 5°C / s or 6°C / s.

[0064] The first insulation time can be 100s, 105s, 110s, 115s, 120s, 125s, 130s, 135s, 140s, 145s or 150s.

[0065] In some optional embodiments, the continuous annealing treatment further includes a first cooling section, a second cooling section, a second holding section and a third cooling section in sequence, the terminal temperature of the first cooling section is 700°C to 750°C, and the cooling rate of the first cooling section is 12°C / s to 18°C / s; and / or

[0066] The terminal temperature of the second cooling section is 300° C. to 350° C., and the cooling rate of the second cooling section is 20° C. / s to 30° C. / s; and / or

[0067] The second heat preservation period lasts for 200s to 300s; and / or

[0068] The terminal temperature of the third cooling section is 20°C to 30°C, and the cooling rate of the third cooling section is 5°C / s to 15°C / s.

[0069] In these embodiments, the continuous annealing treatment may further include a first cooling section, a second cooling section, a second heat preservation section and a third cooling section in sequence, and the terminal temperature of the first cooling section may be 700°C to 750°C, and the cooling rate of the first cooling section may be 12°C / s to 18°C / s, which promotes the formation of oriented epitaxial ferrite of the chilled coil, and at the same time, promotes the enrichment of the stabilizing elements of austenite into austenite, thereby improving the austenite stability of the chilled coil; in addition, the terminal temperature of the second cooling section may be 300°C to 350°C, and the cooling rate of the second cooling section may be 20°C / s to 30°C / s, which promotes the formation of martensite of the chilled coil and the formation of martensite of the chilled coil. The dispersion and uniform distribution of the precipitated phase of the chilled coil can be improved, so that a refined and uniform microstructure can be obtained; in addition, the time of the second insulation section can be 200s to 300s, so that the second insulation section has sufficient time. The second insulation section with sufficient time can further improve the homogenization of the metallographic structure of the chilled coil and obtain an annealed plate with better performance uniformity; in addition, the terminal temperature of the third cooling section can be 20°C to 30°C, and the cooling rate of the third cooling section can be 5°C / s to 15°C / s. The metallographic structure of the chilled coil can be further transformed by the third cooling method, so that an annealed plate with better performance uniformity can be obtained.

[0070] The terminal temperature of the first temperature reduction stage may be 700°C, 710°C, 720°C, 730°C, 740°C or 750°C.

[0071] The cooling rate of the first cooling section may be 12°C / s, 13°C / s, 14°C / s, 15°C / s, 16°C / s, 17°C / s or 18°C / s.

[0072] The terminal temperature of the second temperature reduction stage may be 300°C, 310°C, 320°C, 330°C, 340°C or 350°C.

[0073] The cooling rate of the second cooling section can be 20℃ / s, 21℃ / s, 22℃ / s, 23℃ / s, 24℃ / s, 25℃ / s, 26℃ / s, 27℃ / s, 28℃ / s, 29℃ / s or 30℃ / s.

[0074] The time of the second insulation section can be 200s, 210s, 220s, 230s, 240s, 250s, 260s, 270s, 280s, 290s or 300s.

[0075] The terminal temperature of the third cooling section can be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C.

[0076] The cooling rate of the third cooling section can be 5°C / s, 6°C / s, 7°C / s, 8°C / s, 9°C / s, 10°C / s, 11°C / s, 12°C / s, 13°C / s, 14°C / s or 15°C / s.

[0077] Figure 2 The schematic diagram of the process of preparing a highly uniform cold-rolled phase-transformed high-strength steel provided in an embodiment of the present application is exemplarily shown;

[0078] In some optional embodiments, the step of sequentially coiling and slowly cooling the cooled hot-rolled sheet to obtain a hot-rolled coil comprises the following steps:

[0079] S101. The ingot is sequentially heated, rough rolled and finish rolled to obtain a hot-rolled plate;

[0080] S102. The hot-rolled plate is subjected to laminar cooling to obtain a cooled hot-rolled plate.

[0081] In these embodiments, the cold-rolled phase-transformed high-strength steel ingot is subjected to hot rolling including heating, rough rolling and finish rolling, so that the metallographic structure of the ingot is transformed into the full austenite zone, which is convenient for subsequent coiling and continuous annealing treatment, and a hot-rolled plate with uniform structure can be obtained; in addition, the hot-rolled plate is subjected to laminar cooling, which can improve the uniform deformation of the hot-rolled plate during the laminar cooling process, so that the metallographic structure distribution of the hot-rolled plate is more uniform, thereby obtaining an annealed plate with better performance uniformity.

[0082] In some optional embodiments, the end temperature of the heating is 1200° C. to 1280° C.; and / or

[0083] The rough rolling temperature is 1010° C. to 1080° C., and the rough rolling time is 30s to 60s; and / or

[0084] The temperature of the finish rolling is 850° C. to 910° C., and the time of the finish rolling is 20s to 50s.

[0085] In these embodiments, the terminal temperature of heating can be 1200°C to 1280°C, which prompts the metallographic structure of the ingot to initially transform into austenite; in addition, the temperature of rough rolling can be 1010°C to 1080°C, and the time of rough rolling can be 30s to 60s, and the metallographic structure of the ingot is recrystallized and grain refined by rough rolling; in addition, the temperature of finishing rolling can be 850°C to 910°C, and the time of finishing rolling can be 20s to 50s, and the grains are further refined by finishing rolling to obtain a uniform structure.

[0086] The end point temperature of the heating may be 1200°C, 1210°C, 1220°C, 1230°C, 1240°C, 1250°C, 1260°C, 1270°C or 1280°C.

[0087] The temperature of the rough rolling may be 1010°C, 1020°C, 1030°C, 1040°C, 1050°C, 1060°C, 1070°C or 1080°C.

[0088] The rough rolling time can be 30s, 40s, 50s or 60s.

[0089] The temperature of the finish rolling may be 850°C, 860°C, 870°C, 880°C, 890°C, 900°C or 910°C.

[0090] The finishing rolling time can be 20s, 25s, 30s, 35s, 40s, 45s or 50s.

[0091] In some optional embodiments, the cold hard coil is subjected to continuous annealing treatment under the conditions of a gradient heating rate and a gradient cooling rate to obtain an annealed sheet, and then the steps of:

[0092] S4. Flattening the annealed sheet to obtain high-strength steel.

[0093] In these embodiments, after the annealed sheet is obtained, the annealed sheet is flattened. The flattening process can eliminate the yield platform and surface defects of the annealed sheet, and improve the uniform distribution of the microstructure of the high-strength steel, so that the mechanical properties of the high-strength steel can be more evenly distributed.

[0094] In some optional embodiments, the elongation of the flattening treatment is 0.2% to 0.5%.

[0095] In these embodiments, the elongation of the flattening treatment can be 0.2% to 0.5%, so that the high-strength steel can effectively eliminate the yield platform of the annealing plate after the flattening treatment and improve the uniform distribution of the structure of the high-strength steel, thereby making the mechanical properties of the high-strength steel more evenly distributed.

[0096] The elongation of the flattening process may be 0.2%, 0.3%, 0.4% or 0.5%.

[0097] In some optional embodiments, the cold rolling reduction rate is 45% to 60%.

[0098] In these embodiments, the cold rolling reduction rate can be 45% to 60%. The cold rolling method can optimize the grain structure of the hot-rolled coil, and optimize the mechanical properties of the hot-rolled coil, such as the yield strength and tensile strength, so that the metallographic structure distribution of the hot-rolled coil is more uniform, thereby obtaining an annealed sheet with better performance uniformity.

[0099] The cold rolling reduction ratio may be 45%, 50%, 55% or 60%.

[0100] The present application is further described below in conjunction with specific examples. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards / industry standards; if there are no corresponding national standards / industry standards, they are measured in accordance with common international standards, conventional conditions or conditions recommended by the manufacturer.

[0101] Example 1

[0102] like Figure 2 As shown, a method for preparing a high-uniformity cold-rolled phase-transformed high-strength steel comprises:

[0103] S101. The ingot is sequentially heated, rough rolled and finish rolled to obtain a hot-rolled plate;

[0104] S102. The hot-rolled plate is subjected to laminar cooling to obtain a cooled hot-rolled plate;

[0105] S1. coiling and slowly cooling the cooled hot-rolled plate in sequence to obtain a hot-rolled coil; wherein the coiling temperatures satisfy: a first coiling temperature T1 of the head of the cooled hot-rolled plate, a second coiling temperature T2 of the tail of the cooled hot-rolled plate, and a third coiling temperature T3 of the central area of ​​the cooled hot-rolled plate satisfy the relationship: T1>T3, and T2>T3;

[0106] S2. cold rolling the hot rolled coil to obtain a cold hardened coil;

[0107] S3. The cold hardened coil is continuously annealed under the conditions of a gradient heating rate and a gradient cooling rate to obtain an annealed sheet;

[0108] S4. Flatten the annealed sheet to obtain high-strength steel.

[0109] The first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 satisfy the relationship: T1 = T2, and T1-T3 = 30° C. The first coiling temperature is 610° C.

[0110] The third coiling temperature is 580°C.

[0111] The continuous annealing treatment includes a first heating stage, a second heating stage and a first heat preservation stage in sequence, the terminal temperature of the first heating stage is 200°C, and the heating rate of the first heating stage is 5°C / s;

[0112] The end temperature of the second heating stage is 780°C, and the heating rate of the second heating stage is 2°C / s;

[0113] The first insulation period lasts for 150 seconds.

[0114] The continuous annealing treatment also includes a first cooling section, a second cooling section, a second heat preservation section and a third cooling section in sequence, the terminal temperature of the first cooling section is 720° C., and the cooling rate of the first cooling section is 12° C. / s;

[0115] The end temperature of the second cooling stage is 330°C, and the cooling rate of the second cooling stage is 20°C / s;

[0116] The second insulation period lasts for 250 seconds;

[0117] The terminal temperature of the third cooling stage is 25°C, and the cooling rate of the third cooling stage is 5°C / s.

[0118] The end point temperature of heating is 1260°C;

[0119] The rough rolling temperature is 1010°C and the rough rolling time is 60s;

[0120] The finishing rolling temperature is 885°C and the finishing rolling time is 30s.

[0121] The elongation after flattening is 0.4%.

[0122] The reduction ratio of cold rolling was 60%.

[0123] Example 2

[0124] Based on the contents disclosed in Example 1, the following modifications are further made:

[0125] The first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 satisfy the relationship: T1 = T2, and T1-T3 = 40° C. The first coiling temperature is 600° C.

[0126] The third coiling temperature is 560°C.

[0127] The end temperature of the first heating stage is 250°C, and the heating rate of the first heating stage is 10°C / s;

[0128] The end temperature of the second heating stage is 820°C, and the heating rate of the second heating stage is 6°C / s;

[0129] The first insulation period lasts for 100 s.

[0130] The terminal temperature of the first cooling stage is 700°C, and the cooling rate of the first cooling stage is 18°C / s;

[0131] The end temperature of the second cooling stage is 340°C, and the cooling rate of the second cooling stage is 30°C / s;

[0132] The second insulation period lasts for 250 seconds;

[0133] The terminal temperature of the third cooling stage is 20°C, and the cooling rate of the third cooling stage is 15°C / s.

[0134] The end point temperature of heating is 1255°C;

[0135] The rough rolling temperature is 1060°C and the rough rolling time is 50s;

[0136] The finishing rolling temperature is 895°C and the finishing rolling time is 40s.

[0137] The elongation after flattening is 0.3%.

[0138] The reduction ratio of cold rolling was 50%.

[0139] Example 3

[0140] Based on the contents disclosed in Example 1, the following modifications are further made:

[0141] The first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 satisfy the relationship: T1 = T2, and T1-T3 = 40° C. The first coiling temperature is 640° C.

[0142] The third coiling temperature is 600°C.

[0143] The end temperature of the first heating stage is 230°C, and the heating rate of the first heating stage is 8°C / s;

[0144] The end temperature of the second heating stage is 800°C, and the heating rate of the second heating stage is 4°C / s;

[0145] The first insulation period lasts for 130 seconds.

[0146] The terminal temperature of the first cooling stage is 740°C, and the cooling rate of the first cooling stage is 18°C / s;

[0147] The end temperature of the second cooling stage is 350°C, and the cooling rate of the second cooling stage is 25°C / s;

[0148] The second insulation period is 300s;

[0149] The terminal temperature of the third cooling stage is 30°C, and the cooling rate of the third cooling stage is 12°C / s.

[0150] The end point temperature of heating is 1230°C;

[0151] The rough rolling temperature is 1080°C and the rough rolling time is 30s;

[0152] The finishing rolling temperature is 900°C and the finishing rolling time is 50s.

[0153] The elongation after flattening is 0.3%.

[0154] The reduction ratio of cold rolling was 45%.

[0155] Example 4

[0156] Based on the contents disclosed in Example 1, the following modifications are further made:

[0157] The first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 satisfy the relationship: T1 = T2, and T1-T3 = 40° C. The first coiling temperature is 670° C.

[0158] The third coiling temperature is 630°C.

[0159] The end temperature of the first heating stage is 240°C, and the heating rate of the first heating stage is 7°C / s;

[0160] The end temperature of the second heating stage is 790°C, and the heating rate of the second heating stage is 4°C / s;

[0161] The first insulation period lasts for 120 seconds.

[0162] The terminal temperature of the first cooling stage is 710°C, and the cooling rate of the first cooling stage is 13°C / s;

[0163] The end temperature of the second cooling stage is 310°C, and the cooling rate of the second cooling stage is 22°C / s;

[0164] The second insulation period lasts for 250 seconds;

[0165] The cooling rate of the third cooling stage is 8°C / s.

[0166] The end point temperature of heating is 1220°C;

[0167] The rough rolling temperature is 1040°C and the rough rolling time is 40s;

[0168] The finishing rolling temperature is 850°C and the finishing rolling time is 40s.

[0169] The elongation of the flattening treatment is 0.2%.

[0170] The reduction ratio of cold rolling was 55%.

[0171] Example 5

[0172] Based on the contents disclosed in Example 1, the following modifications are further made:

[0173] The first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 satisfy the relationship: T1 = T2, and T1-T3 = 50° C. The first coiling temperature is 600° C.

[0174] The third coiling temperature is 550°C.

[0175] The end temperature of the first heating stage is 250°C, and the heating rate of the first heating stage is 6°C / s;

[0176] The end temperature of the second heating stage is 800°C, and the heating rate of the second heating stage is 4°C / s;

[0177] The first insulation period lasts for 140 seconds.

[0178] The terminal temperature of the first cooling stage is 700°C, and the cooling rate of the first cooling stage is 14°C / s;

[0179] The end temperature of the second cooling stage is 320°C, and the cooling rate of the second cooling stage is 24°C / s;

[0180] The second insulation period lasts for 280 seconds;

[0181] The cooling rate of the third cooling stage is 10°C / s.

[0182] The end point temperature of heating is 1240°C;

[0183] The rough rolling temperature is 1050°C and the rough rolling time is 50s;

[0184] The finishing rolling temperature is 870°C and the finishing rolling time is 35s.

[0185] The elongation of the flattening treatment is 0.5%.

[0186] The reduction ratio of cold rolling was 50%.

[0187] Example 6

[0188] Based on the contents disclosed in Example 1, the following modifications are further made:

[0189] The first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 satisfy the relationship: T1 = T2, and T1-T3 = 40° C. The first coiling temperature is 650° C.

[0190] The third coiling temperature is 610°C.

[0191] The end temperature of the first heating stage is 240°C, and the heating rate of the first heating stage is 7°C / s;

[0192] The end temperature of the second heating stage is 810°C, and the heating rate of the second heating stage is 5°C / s;

[0193] The first insulation period lasts for 120 seconds.

[0194] The terminal temperature of the first cooling stage is 730°C, and the cooling rate of the first cooling stage is 16°C / s;

[0195] The end temperature of the second cooling stage is 330°C, and the cooling rate of the second cooling stage is 28°C / s;

[0196] The second insulation period lasts for 240 seconds;

[0197] The cooling rate of the third cooling stage is 10°C / s.

[0198] The end point temperature of heating is 1270°C;

[0199] The rough rolling temperature is 1030°C and the rough rolling time is 40s;

[0200] The finishing rolling temperature is 860°C and the finishing rolling time is 30s.

[0201] The elongation after flattening is 0.4%.

[0202] The cold rolling reduction ratio was 58%.

[0203] Comparative Example 1

[0204] Based on the contents disclosed in Example 1, the following modifications are further made:

[0205] The first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 satisfy the relationship: T1 = T2 = T3. The first coiling temperature is 560°C.

[0206] The end temperature of the first heating stage is 210°C, and the heating rate of the first heating stage is 5°C / s;

[0207] The end temperature of the second heating stage is 800°C, and the heating rate of the second heating stage is 4°C / s;

[0208] The first insulation period lasts for 130 seconds.

[0209] The terminal temperature of the first cooling stage is 720°C, and the cooling rate of the first cooling stage is 14°C / s;

[0210] The end temperature of the second cooling stage is 310°C, and the cooling rate of the second cooling stage is 24°C / s;

[0211] The second insulation period lasts for 250 seconds;

[0212] The cooling rate of the third cooling stage is 7°C / s.

[0213] The end point temperature of heating is 1220°C;

[0214] The rough rolling temperature is 1040°C and the rough rolling time is 40s;

[0215] The finishing rolling temperature is 890°C and the finishing rolling time is 35s.

[0216] The elongation after flattening is 0.4%.

[0217] The reduction ratio of cold rolling was 60%.

[0218] Comparative Example 2

[0219] Based on the contents disclosed in Example 1, the following modifications are further made:

[0220] The first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 satisfy the relationship: T1 = T2 = T3. The first coiling temperature is 600°C.

[0221] The end temperature of the first heating stage is 230°C, and the heating rate of the first heating stage is 7°C / s;

[0222] The end temperature of the second heating stage is 820°C, and the heating rate of the second heating stage is 6°C / s;

[0223] The first insulation period lasts for 140 seconds.

[0224] The terminal temperature of the first cooling stage is 700°C, and the cooling rate of the first cooling stage is 16°C / s;

[0225] The end temperature of the second cooling stage is 330°C, and the cooling rate of the second cooling stage is 25°C / s;

[0226] The second insulation period is 300s;

[0227] The cooling rate of the third cooling stage is 12°C / s.

[0228] The end point temperature of heating is 1240°C;

[0229] The rough rolling temperature was 1060°C and the rough rolling time was 40 s;

[0230] The finishing rolling temperature is 900°C and the finishing rolling time is 50s.

[0231] The elongation of the flattening treatment is 0.2%.

[0232] The reduction ratio of cold rolling was 60%.

[0233] Comparative Example 3

[0234] Based on the contents disclosed in Example 1, the following modifications are further made:

[0235] The first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 satisfy the relationship: T1 = T2 = T3. The first coiling temperature is 630°C.

[0236] The end temperature of the first heating stage is 250°C, and the heating rate of the first heating stage is 10°C / s;

[0237] The end temperature of the second heating stage is 780°C, and the heating rate of the second heating stage is 4°C / s;

[0238] The first insulation period lasts for 120 seconds.

[0239] The terminal temperature of the first cooling stage is 740°C, and the cooling rate of the first cooling stage is 12°C / s;

[0240] The end temperature of the second cooling stage is 350°C, and the cooling rate of the second cooling stage is 30°C / s;

[0241] The second insulation period lasts for 220 seconds;

[0242] The cooling rate of the third cooling stage is 14°C / s.

[0243] The end point temperature of heating is 1260°C;

[0244] The rough rolling temperature is 1020°C and the rough rolling time is 40s;

[0245] The finishing rolling temperature is 860°C and the finishing rolling time is 50s.

[0246] The elongation after flattening is 0.3%.

[0247] The reduction ratio of cold rolling was 50%.

[0248] Related experiments and effect data:

[0249] The mechanical properties of the high-strength steels of the embodiments and comparative examples were statistically analyzed, and the results are shown in Table 1.

[0250] Table 1 Mechanical properties of high-strength steel in various embodiments and comparative examples

[0251]

[0252]

[0253] In Table 1, Rp0.2 represents the stress when the non-proportional elongation of the gauge length of the specimen reaches 0.2% of the original gauge length, and the test is carried out in accordance with the standard of GB / T228-2002.

[0254] As can be seen from Table 1, the embodiment of the present application provides a method for preparing a highly uniform cold-rolled phase-changing high-strength steel. The preparation method precisely controls the coiling temperature and annealing process so that the mechanical properties such as yield strength, tensile strength and elongation of the edge, center area and edge to center area of ​​the final high-strength steel product are uniformly distributed, which indicates that the microstructure and properties of the cold-rolled phase-changing high-strength steel are in a uniformly distributed state, and this state provides strong support for improving the quality of steel and expanding its application areas.

[0255] In addition, an embodiment of the present application provides a method for preparing a highly uniform cold-rolled phase-change high-strength steel. The preparation method adopts a higher coiling temperature in the head area and the tail area of ​​the cooled hot-rolled plate, and then uses a slow cooling pit to reduce the temperature difference between the edge and the center of the hot-rolled coil, so that the hot-rolled plate has a uniform performance structure along the length and width directions, and the uniformity of the cold-rolled plate's organizational performance can be further improved by the gradient heating rate and the gradient cooling rate, and finally a cold-rolled phase-change high-strength steel with uniform organizational performance is obtained.

[0256] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. It will be apparent to those skilled in the art that various modifications to these embodiments are possible, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown in the present application, but will conform to the widest range consistent with the principles and novel features applied for by the present application.

Claims

1. A method for preparing a high-uniformity cold-rolled phase-transformed high-strength steel, the preparation method comprising: The cooled hot-rolled plate is coiled and slowly cooled in sequence to obtain a hot-rolled coil; wherein the coiling temperature satisfies: a first coiling temperature T1 of the head of the cooled hot-rolled plate, a second coiling temperature T2 of the tail of the cooled hot-rolled plate, and a third coiling temperature T3 of the central area of ​​the cooled hot-rolled plate satisfy the relationship: T1>T3, and T2>T3; Cold rolling the hot rolled coil to obtain a chilled coil; The cold hard coil is subjected to continuous annealing treatment under the conditions of a gradient heating rate and a gradient cooling rate to obtain an annealed sheet.

2. The preparation method according to claim 1, wherein the first coiling temperature T1, the second coiling temperature T2 and the third coiling temperature T3 satisfy the relationship: T1 = T2, and T1-T3 = 30°C to 50°C.

3. According to the preparation method according to claim 1 or 2, the third coiling temperature is 550°C to 630°C.

4. The preparation method according to claim 1, wherein the continuous annealing treatment sequentially comprises a first heating section, a second heating section and a first holding section, the terminal temperature of the first heating section is 200°C to 250°C, and the heating rate of the first heating section is 5°C / s to 10°C / s; and / or The terminal temperature of the second heating stage is 780°C to 820°C, and the heating rate of the second heating stage is 2°C / s to 6°C / s; and / or The first insulation period lasts for 100s to 150s.

5. The preparation method according to claim 1, wherein the continuous annealing treatment further comprises a first cooling section, a second cooling section, a second heat preservation section and a third cooling section in sequence, the terminal temperature of the first cooling section is 700°C to 750°C, and the cooling rate of the first cooling section is 12°C / s to 18°C / s; and / or The terminal temperature of the second cooling section is 300° C. to 350° C., and the cooling rate of the second cooling section is 20° C. / s to 30° C. / s; and / or The second heat preservation period lasts for 200s to 300s; and / or The terminal temperature of the third cooling section is 20°C to 30°C, and the cooling rate of the third cooling section is 5°C / s to 15°C / s.

6. The preparation method according to claim 1, wherein the cooled hot-rolled sheet is coiled and slowly cooled in sequence to obtain a hot-rolled coil, which comprises the following steps: The ingot is sequentially heated, rough rolled and finish rolled to obtain a hot rolled plate; The hot-rolled sheet is subjected to laminar cooling to obtain a cooled hot-rolled sheet.

7. The preparation method according to claim 6, wherein the terminal temperature of the heating is 1200°C to 1280°C; and / or The rough rolling temperature is 1010° C. to 1080° C., and the rough rolling time is 30s to 60s; and / or The temperature of the finish rolling is 850° C. to 910° C., and the time of the finish rolling is 20s to 50s.

8. The preparation method according to claim 1, wherein the cold hard coil is subjected to continuous annealing treatment under the conditions of a gradient heating rate and a gradient cooling rate to obtain an annealed sheet, and then comprises the steps of: The annealed sheet is flattened to obtain high-strength steel. 9 . The preparation method according to claim 8 , wherein the elongation of the flattening treatment is 0.2% to 0.5%.

10. The preparation method according to claim 1, wherein the cold rolling reduction ratio is 45% to 60%.

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