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CN-115572908-A - High-elongation complex-phase high-strength steel and production method thereof

CN115572908ACN 115572908 ACN115572908 ACN 115572908ACN-115572908-A

Abstract

The invention belongs to the technical field of high-strength steel manufacturing, and particularly relates to high-elongation complex-phase high-strength steel and a production method thereof. The chemical components of the paint comprise, by weight: 0.09 to 0.12%, si:0.52 to 0.6%, mn:1.7 to 2.0%, cr:0.55 to 0.87%, mo:0.23 to 0.28%, nb:0.03 to 0.05%, V:0.07 to 0.12%, ti:0.14 to 0.18%, P: less than or equal to 0.02 percent, less than or equal to 0.02 percent of S, and the balance of iron and inevitable impurities. The invention introduces Cr with small dispersion into steel 3 C precipitates and plays a role in preventing austenite grains from growing and improving the surface hardness of the steel plate; the alloy elements play a role in coordinating the internal deformation of the steel plate and improving the uniform elongation. Compared with the existing steel grade with the same strength grade, the steel grade has higher elongation.

Inventors

  • MENG QINGGANG
  • KANG HAIJUN
  • LI YIWEI
  • SU CHONGTAO
  • YU LIWEI
  • CUI HONGTAO
  • WANG MENGTAO

Assignees

  • BENGANG STEEL PLATES CO LTD

Dates

Publication Date
20230106
Application Date
20221025
Priority Date
20221025

Claims (7)

  1. 1. The complex phase high-strength steel is characterized by comprising the following chemical components in percentage by weight: 0.09 to 0.12%, si:0.52 to 0.6%, mn: 1.7-2.0%, cr:0.55 to 0.87%, mo:0.23 to 0.28%, nb:0.03 to 0.05%, V:0.07 to 0.12%, ti:0.14 to 0.18%, P: less than or equal to 0.02 percent, less than or equal to 0.02 percent of S, and the balance of iron and inevitable impurities.
  2. 2. The complex phase high-strength steel as claimed in claim 1, wherein the yield strength of the high-strength steel is 722-830 MPa, the tensile strength is 804-940 MPa, and the elongation is 15-22%.
  3. 3. A method of producing a high strength steel according to any one of claims 1-2, characterized in that the method comprises the steps of: (1) Preparing a steel billet by adopting molten iron pretreatment, converter smelting, external refining and continuous casting according to the requirements of chemical components; (2) A heating procedure: heating the steel billet to 1200 ℃, soaking for 40min and discharging; (3) Rough rolling procedure: the initial rolling temperature of rough rolling is higher than 1140 ℃, and the final rolling temperature is higher than 970 ℃; (4) A finish rolling procedure: carrying out finish rolling after rough rolling, wherein the start rolling temperature of the finish rolling is 950 ℃, and the finish rolling temperature is 850-880 ℃; (5) Air cooling and temperature waiting: after finishing rolling, performing air cooling, and cooling to 760 ℃; (6) Laminar cooling: in the laminar cooling process, the temperature is reduced at a cooling speed of 10-13 ℃/s; (7) A coiling step: the coiling temperature is 470-490 ℃, the steel plate is air-cooled and stored to room temperature after coiling, and the final structure of the steel plate is ferrite/lower bainite/martensite/retained austenite.
  4. 4. The production method according to claim 3, wherein in the rough rolling step, a total of 6 passes of rolling are performed, the reduction rate of each pass is more than 20%, and the total reduction rate of rough rolling is more than 85%.
  5. 5. The production method according to claim 3, wherein in the rough rolling process, the rough rolling start temperature is 1146 to 1149 ℃, and the finish rolling temperature is 977 to 980 ℃.
  6. 6. The production method according to claim 3, wherein in the finish rolling step, a total of 7 passes of rolling are performed, and the total rolling reduction rate is more than 90%.
  7. 7. The production method according to claim 3, wherein in the winding step, the winding temperature is 476 to 481 ℃.

Description

High-elongation complex-phase high-strength steel and production method thereof Technical Field The invention belongs to the technical field of high-strength steel manufacturing, and particularly relates to high-elongation complex-phase high-strength steel and a production method thereof. Background With the increasingly fierce competition of the domestic automobile market, the use amount of the high-strength steel on the automobile body is increased by various automobile manufacturers, and the method has the advantages that: (1) When the automobile collides, the high-strength steel can effectively prevent the automobile body from deforming, and the safety of personnel in the automobile is improved. (2) Since the same vehicle body strength can be achieved with a thinner high-strength steel than with a normal steel sheet, it can contribute to weight reduction of the vehicle body. (3) The lighter vehicle body weight can effectively reduce the oil consumption, not only can reduce the use cost of the vehicle, but also is beneficial to reducing the emission of the tail gas of the vehicle, and has extremely high environmental protection significance. (4) Although the unit price of the high-strength steel is slightly higher than that of the common steel, the high-strength steel can reduce the weight of parts, and the calculation result shows that the cost of using the high-strength steel for the same part is lower than that of the common steel after multiplying the weight by the unit price, so that the high-strength steel can effectively reduce the manufacturing cost of a vehicle body. Although high-strength steel has these advantages, the existing high-strength steel contains a large amount of martensite at normal temperature, so that the cold forming capability is poor at room temperature, and the wide application of the high-strength steel is hindered. For example, the three steel grades in table 1 all have decreasing parameters (elongation after break, uniform elongation, strain hardening index and plastic strain ratio) for measuring formability as yield strength and tensile strength increase. TABLE 1 mechanical Property data for different strength steels Disclosure of Invention The invention aims to provide high-elongation complex-phase high-strength steel and a production method thereof. In order to realize the purpose, the technical scheme of the invention is as follows: the invention provides a complex phase high-strength steel, which comprises the following chemical components in percentage by weight: 0.09 to 0.12%, si:0.52 to 0.6%, mn: 1.7-2.0%, cr:0.55 to 0.87%, mo:0.23 to 0.28%, nb:0.03 to 0.05%, V:0.07 to 0.12%, ti:0.14 to 0.18%, P: less than or equal to 0.02 percent, less than or equal to 0.02 percent of S, and the balance of iron and inevitable impurities. The effects of the elements in the steel are as follows: (1) The four elements of C, mn, cr and Ni lower the martensite start transformation point Ms and the end transformation point Mf of the steel, increasing the residual austenite content in the steel. (2) C, mn, cr, ni and Mo, which can increase the hardenability of the steel. (3) Nb, V and Ti, the three elements have the function of strongly hindering the growth of austenite grains, and the smaller austenite grains can also obtain a fine grain structure after phase change. (4) In the production process of steel, hydrogen elements are inevitably mixed, and the hydrogen elements can form hydrogen molecules, so that huge pressure is formed in the steel, and the mechanical property of the steel is reduced. The Ti element added into the steel can not only prevent austenite grains from growing, but also effectively adsorb free hydrogen atoms in the steel by the carbonitride of the Ti, so that the free hydrogen atoms are prevented from being combined into hydrogen molecules, and the risk of hydrogen induced cracking of the steel is reduced. (5) The content ratio of Cr to C in the steel is kept between 6.0 and 7.3, which is beneficial to forming Cr 3 C, the carbide not only has high hardness, but also is tightly combined with a matrix, and can protect the surface of the steel plate during cold deformation. In the technical scheme, the yield strength of the high-strength steel is 722-830 MPa, the tensile strength is 804-940 MPa, and the elongation is 15-22%. In another aspect, the present invention provides a method for producing the above high strength steel, including the steps of: (1) Preparing a steel billet by adopting molten iron pretreatment, converter smelting, external refining and continuous casting according to the requirements of chemical components; (2) A heating procedure: heating the steel billet to 1200 ℃, soaking for 40min and discharging; (3) Rough rolling procedure: the initial rolling temperature of rough rolling is higher than 1140 ℃, and the final rolling temperature is higher than 970 ℃; (4) A finish rolling procedure: carrying out finish rolling after rough rolling, wherein the