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CN-121992299-A - Low-cost weldable ultra-high strength steel plate and preparation method thereof

CN121992299ACN 121992299 ACN121992299 ACN 121992299ACN-121992299-A

Abstract

The invention relates to a low-cost weldable ultrahigh-strength steel plate and a preparation method thereof, belongs to the technical field of ultrahigh-strength steel plates, and solves the problems of lower toughness, poorer welding performance and higher cost of steel plates with strength of more than 2300MPa in the prior art. The steel plate comprises the following components in percentage by mass: 0.42-0.47% of C, 0.20-0.50% of Si, less than or equal to 0.20% of Mn, less than or equal to 0.010% of P, less than or equal to 0.003% of S, less than or equal to 0.50% of Cr, 0.80-1.20% of Ni, 0.20-0.40% of Mo, 0.02-0.06% of Ti, less than or equal to 0.04% of Nb, less than or equal to 0.0040% of N, 0.001-0.004% of B, and the balance of Fe. The steel plate has the advantages that the microstructure of the steel plate is provided with a martensitic matrix structure by regulating and controlling the types and the proportions of the constituent elements, so that the strength of the steel plate is improved; through regulating and controlling the contents of elements Ti, nb and N, MC carbide (such as TiC, nbC, (Ti, mo) C) precipitation strengthening phases are formed, martensite grains are refined, and the toughness of the steel is improved; the Mn and Cr contents are reduced, the carbon equivalent is controlled to be less than or equal to 0.70 percent, and the welding performance is improved; the continuous casting and rolling process is adopted for manufacturing, so that the cost is obviously reduced, and the popularization and application of the ultra-high strength steel can be promoted.

Inventors

  • WEI WENCHAO
  • SHI JIE
  • SUN TING
  • YAN YONGMING
  • WANG MAOQIU
  • LI XIAOYUAN
  • XU LE
  • HE XIAOFEI

Assignees

  • 钢铁研究总院有限公司

Dates

Publication Date
20260508
Application Date
20260129

Claims (10)

  1. 1. The low-cost weldable ultra-high strength steel plate is characterized in that the steel plate comprises ：C 0.42-0.47%,Si 0.20-0.50%,Mn ≤0.20%,P ≤0.010%,S ≤0.003%,Cr ≤0.50%,Ni 0.80-1.20%,Mo 0.20-0.40%,Ti 0.02-0.06%,Nb ≤0.04%,N ≤0.0040%,B 0.001-0.004%, balance Fe according to mass percentage.
  2. 2. The steel sheet according to claim 1, wherein the constituent elements of the steel sheet include ：C 0.43-0.47%,Si 0.22-0.38%,Mn ≤0.19%,P ≤0.009%,S ≤0.002%,Cr ≤0.35%,Ni 0.80-1.20%,Mo 0.22-0.35%,Ti 0.025-0.058%,Nb ≤0.04%,N ≤0.0040%,B 0.0015-0.0031%, balance Fe in terms of mass percent.
  3. 3. The steel sheet according to claim 1, wherein the contents of the elements Ti, nb, N in the steel sheet satisfy the following relationship of 0.04% or less Ti+Nb-3.5N or less than 0.07%.
  4. 4. The steel sheet according to claim 1, wherein the prior austenite grain size of the microstructure of the steel sheet is 5.5 μm or less.
  5. 5. The steel sheet according to claim 1, wherein the steel sheet microstructure comprises a martensitic matrix, retained austenite, and a precipitation-strengthened phase, wherein the precipitation-strengthened phase comprises a nano-sized TiC, nbC, (Ti, mo) C, (Nb, mo) C precipitate phase.
  6. 6. A method of making the low cost weldable ultra-high strength steel sheet of any one of claims 1-5, the method comprising: (1) Smelting, refining outside the furnace, vacuum degassing and casting the raw materials in sequence according to the target component content of the steel plate to obtain a casting blank; (2) Heating, rolling, curling and cooling the casting blank, and flattening to obtain a rolled plate blank; (3) And quenching and tempering the plate blank.
  7. 7. The method according to claim 6, wherein in the step (2), the temperature of the heating and maintaining is 1250-1300 ℃ and the time is 1.5-2.0min/mm.
  8. 8. The method according to claim 6, wherein in the step (2), the rolling includes a rough rolling stage and a finish rolling stage, the rough rolling stage has a temperature of 1070 to 1220 ℃, a total compression ratio of 60 to 70%, the finish rolling stage has a primary rolling temperature of 960 to 1000 ℃, and a finish rolling temperature of 820 to 880 ℃, and the total compression ratio of 30 to 40%.
  9. 9. The method according to claim 6, wherein in the step (3), the quenching is performed by maintaining the temperature at 840-880 ℃ for 2.0-3.0min/mm, cooling to 50-100 ℃ below the Mf point at a speed of not less than 100 ℃ per second, and then air cooling to room temperature.
  10. 10. The method according to claim 6, wherein in the step (3), the tempering treatment is performed at a temperature of 150-180 ℃ and maintained for 5-10 min/mm.

Description

Low-cost weldable ultra-high strength steel plate and preparation method thereof Technical Field The invention relates to the technical field of ultrahigh-strength steel plates, in particular to a low-cost weldable ultrahigh-strength steel plate and a preparation method thereof. Background Ultra-high strength steel sheets are widely used in the automotive, mechanical and equipment manufacturing fields. With the continuous improvement of energy saving and emission reduction requirements, the use of a steel plate with higher strength to improve the light weight level and bearing capacity of vehicle equipment is one of the main development trends. The ultra-high strength steel plates mainly used at present mainly comprise wear-resistant steel (NM 450, NM500 and the like) and hot forming steel (MS 1500, MS1800 and the like), the strength reaches 1500MPa-1800MPa, and the ultra-high strength steel plates with higher strength are less in application. The ultra-high strength steel plate applied in the fields of automobiles and machinery is mainly made of medium-low alloy steel by adopting the industrialized flow of converter, continuous casting and continuous rolling, and then a low-temperature tempered martensite structure is obtained by quenching and low-temperature tempering, so that the high strength is obtained, and meanwhile, the ultra-high strength steel plate has better toughness, however, when the strength of the steel plate reaches more than 2000MPa, the process route is difficult to meet the toughness requirement and the welding performance of the steel plate. The ultra-high strength steel such as 300M, aermet and 100 adopts a medium-high alloy component system and is matched with advanced special smelting technology such as vacuum consumable and the like, so that the high strength and high toughness of the material are realized, but the strength of the material only reaches 2000MPa, the comprehensive cost is too high, and the application field is limited. Therefore, there is a need for an ultra-high strength steel sheet having a strength of more than 2300MPa and a method for preparing the same, so as to balance strength, toughness, welding performance and comprehensive cost, and promote popularization and application thereof. Disclosure of Invention In view of the above analysis, the embodiment of the invention aims to provide a low-cost weldable ultrahigh-strength steel plate and a preparation method thereof, which are used for solving the problems of lower toughness, poorer welding performance and higher cost of the steel plate with strength of more than 2300MPa in the prior art. On one hand, the embodiment of the invention provides a low-cost weldable ultra-high strength steel plate, which comprises ：C 0.42-0.47%,Si 0.20-0.50%,Mn ≤0.20%,P ≤0.010%,S ≤0.003%,Cr ≤0.50%,Ni 0.80-1.20%,Mo 0.20-0.40%,Ti 0.02-0.06%,Nb ≤0.04%,N ≤0.0040%,B 0.001-0.004%, parts by mass of Fe as the rest. Further, the steel plate comprises ：C 0.43-0.47%,Si 0.22-0.38%,Mn ≤0.19%,P ≤0.009%,S ≤0.002%,Cr ≤0.35%,Ni 0.80-1.20%,Mo 0.22-0.35%,Ti 0.025-0.058%,Nb ≤0.04%,N ≤0.0040%,B 0.0015-0.0031%, parts by mass of Fe as the balance. Further, the contents of Ti, nb and N in the steel plate satisfy the following relation that Ti+Nb-3.5N is more than or equal to 0.04% and less than or equal to 0.07%. Further, the prior austenite grain size of the microstructure of the steel plate is less than or equal to 5.5 mu m. Further, the steel plate microstructure comprises a martensitic matrix, residual austenite and a precipitation strengthening phase, wherein the precipitation strengthening phase comprises nano TiC, nbC, (Ti, mo) C and (Nb, mo) C precipitation phases. In another aspect, the embodiment of the present invention also provides a method for preparing the low-cost weldable ultra-high strength steel sheet, the method comprising: (1) Smelting, refining outside the furnace, vacuum degassing and casting the raw materials in sequence according to the target component content of the steel plate to obtain a casting blank; (2) Heating, rolling, curling and cooling the casting blank, and flattening to obtain a rolled plate blank; (3) And quenching and tempering the plate blank. Further, in the step (2), the temperature of heating and preserving heat is 1250-1300 ℃ and the time is 1.5-2.0min/mm. Further, in the step (2), the rolling comprises a rough rolling stage and a finish rolling stage, wherein the temperature of the rough rolling stage is 1070-1220 ℃, the total compression ratio is 60-70%, the initial rolling temperature of the finish rolling stage is 960-1000 ℃, the final rolling temperature is 820-880%, and the total compression ratio is 30-40%. Further, in the step (3), the specific quenching process is that the quenching is carried out at 840-880 ℃ for 2.0-3.0min/mm, and then cooled to 50-100 ℃ below the martensite transformation ending temperature (Mf point) at a speed of more than or equal to 100 ℃ per second, and then air-cooled to room