CN-117418212-B - Low-carbon equivalent ultrahigh-strength steel plate and preparation method thereof

CN117418212BCN 117418212 BCN117418212 BCN 117418212BCN-117418212-B

Abstract

The invention relates to a low-carbon equivalent ultrahigh-strength steel plate and a preparation method thereof, belonging to the technical field of ultrahigh-strength steel. The low-carbon equivalent ultrahigh-strength steel plate comprises C：0.32-0.40％,Si：0.10-0.50％,Mn：0.3-1.5％,P≤0.010％,S≤0.005％,Cr≤1.0％,Mo：0.20-0.50％,Ti：0.04-0.10％,Nb≤0.06％,Al：0.01-0.04％,N≤0.005％,B：0.001-0.004％,, mn+Cr is more than or equal to 1.0% and less than or equal to 1.5%, nb+Ti is more than or equal to 0.05% and less than or equal to 0.10%, and the balance is Fe. The carbon equivalent CEV of the obtained steel plate is less than or equal to 0.70%, the tensile strength is more than or equal to 1900MPa, the yield strength is more than or equal to 1600MPa, and the low-temperature impact absorption power KV2 (-40 ℃) is more than or equal to 32J.

Inventors

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

Assignees

钢铁研究总院有限公司

Dates

Publication Date: 20260512
Application Date: 20231018

Claims (8)

1. A low-carbon equivalent ultra-high strength steel plate is characterized by comprising C：0.32-0.40％,Si：0.10-0.50％,Mn：0.3-1.5％,P≤0.010％,S≤0.005％,Cr≤1.0％,Mo：0.20-0.50％,Ti：0.04-0.10％,Nb≤0.06％,Al：0.01-0.04％,N≤0.005％,B：0.001-0.004％, mass percent and meeting the conditions of Mn+Cr of 1.0% or more and Cr of 1.5% or less, nb+Ti of 0.05% or less and Ti of 0.10% or less, and the balance of Fe and unavoidable impurities; the steel plate is obtained through smelting, casting, rolling and heat treatment; the rolling comprises rough rolling and finish rolling, wherein the rough rolling temperature is 1150-1250 ℃, the total compression ratio is more than 60%, the rough rolling finishing temperature is lower than 1100 ℃, the total rolling passes are 3-5, the deformation of the first 1-2 passes is 10-20% and the deformation of the last 2-3 passes is 20-40%; The finish rolling stage comprises a recrystallization zone rolling step and a non-recrystallization zone rolling step, wherein the total rolling steps are 5-7 times, the recrystallization zone is 3-4 times, the non-recrystallization zone is 2-3 times, the rolling temperature of the recrystallization zone is 920-980 ℃, the pass deformation is 20-60%, the rolling temperature of the non-recrystallization zone is 820-920 ℃, and the pass deformation is 10-20%; In the heat treatment stage, the heating temperature is 880-920 ℃ and the heat preservation time is 2-3min/mm, after heating and heat preservation, the temperature is firstly cooled to 50-100 ℃ above Ms point by adopting the cooling speed of 50-200 ℃ per second, then ultra-rapidly cooled to below Mf point by adopting the cooling speed of 500-2000 ℃ per second, and then tempering treatment is carried out for 30-240min at 150-180 ℃; the carbon equivalent CEV of the steel plate is less than or equal to 0.70%, the tensile strength is more than or equal to 1900MPa, the yield strength is more than or equal to 1600MPa, the low-temperature impact absorption power KV2 (-40 ℃) is more than or equal to 32J, the martensite structure in the steel plate is more than 98%, and the grain size is less than 5 mu m.
2. The low-carbon equivalent ultra-high strength steel sheet according to claim 1, wherein the steel sheet comprises C：0.34-0.39％,Si：0.20-0.30％,Mn：0.8-1.3％,P≤0.009％,S≤0.003％,Cr≤1.0％,Mo：0.25-0.35％,Ti：0.05-0.07％,Nb≤0.05％,Al：0.02-0.03％,N≤0.005％,B：0.0015-0.0025％,% by mass and satisfies 1.0% or less of mn+cr 1.5% or less, 0.06% or less of nb+ti 0.10% or less, and the balance of Fe and unavoidable impurities.
3. A method for producing the low carbon equivalent ultra-high strength steel sheet according to any one of claims 1 to 2, comprising the steps of: s1, smelting and casting, namely smelting raw materials according to the component proportion, and casting to obtain a steel billet; S2, rolling, namely heating the billet at 1250-1280 ℃ and then performing rough rolling and finish rolling, wherein the finish rolling temperature is lower than 860 ℃, and coiling when the temperature is reduced to 500-550 ℃, so as to obtain a hot rolled plate; and S3, heat treatment, namely heating, preserving heat, cooling and tempering the hot rolled plate to obtain the steel plate.
4. A method for producing a low carbon equivalent ultra-high strength steel sheet according to claim 3, wherein in step S2, the rough rolling temperature is 1150-1250 ℃, the total compression ratio is more than 60%, and the rough rolling finishing temperature is less than 1100 ℃.
5. The method for producing a low-carbon equivalent ultra-high strength steel sheet according to claim 3, wherein in step S2, the finish rolling stage is divided into a recrystallization zone rolling and a non-recrystallization zone rolling, wherein the temperature of the recrystallization zone rolling is 920-980 ℃, and the temperature of the non-recrystallization zone rolling is 820-920 ℃.
6. The method for producing a low carbon equivalent ultra-high strength steel sheet according to claim 5, wherein the deformation amount of the unrecrystallized rolling is 15 to 30% of the total deformation amount in the finish rolling stage.
7. The method for producing a low carbon equivalent ultra-high strength steel sheet according to claim 3, wherein in step S3, the hot rolled sheet is heated at 880-920 ℃ for a holding time of 2-3min/mm.
8. The method for preparing a low-carbon-equivalent ultrahigh-strength steel plate according to claim 3, wherein the cooling is performed by graded cooling, the hot rolled plate is heated and kept at a temperature of 50-200 ℃ per second, then cooled to 50-100 ℃ above Ms point, then ultra-rapidly cooled to below Mf point at a cooling speed of 500-2000 ℃ per second, and then tempered at 150-180 ℃ for 30-240min.

Description

Low-carbon equivalent ultrahigh-strength steel plate and preparation method thereof Technical Field The invention relates to the technical field of ultra-high strength steel, in particular to a low-carbon equivalent ultra-high strength steel plate and a preparation method thereof. Background Along with the continuous improvement of the social demands for energy conservation and emission reduction, the realization of light weight through the application of the ultra-high strength steel plate becomes one of the main trends of development in the fields of automobiles, mechanical equipment and the like. At present, the ultra-high strength steel plates widely used at home and abroad mainly comprise 450 grades and 500 grades, the strength of the ultra-high strength steel plates respectively reaches 1500MPa and 1700MPa, and the application of the steel plates with 550 grades and higher strength grades is less. As is well known, for steel materials, the strength and toughness are mutually restricted, and as the strength is improved, the toughness of the steel plate is continuously reduced, and the shock resistance is insufficient, so that the development and application of the ultra-high strength steel plate are limited. At present, the ultrahigh-strength steel plate mainly adopts a low-temperature tempered martensite structure, and a great amount of Cr, ni, mo and other alloy elements are added to improve the strength and obtain better toughness storage, particularly Ni element, and the addition amount is generally more than 2%. However, at the same time, too high alloy elements cause the increase of carbon equivalent of the steel plate, reduce the weldability of the steel plate, and increase the production cost, thereby affecting the popularization and application of the steel plate. Therefore, development of 550-grade ultra-high strength steel plates with low carbon equivalent is one of the difficulties in the steel industry. Aiming at the problems, the invention provides an ultra-high strength steel plate with low carbon equivalent and a preparation process thereof, which realize excellent toughness matching under the component system with low carbon equivalent. Disclosure of Invention In view of the above analysis, the invention aims to provide a low-carbon-equivalent ultrahigh-strength steel plate and a preparation method thereof, which are used for solving the problem of unmatched toughness of the existing steel plate. In one aspect, the invention provides a low-carbon equivalent ultrahigh-strength steel plate, which comprises C：0.32-0.40％,Si：0.10-0.50％,Mn：0.3-1.5％,P≤0.010％,S≤0.005％,Cr≤1.0％,Mo：0.20-0.50％,Ti：0.04-0.10％,Nb≤0.06％,Al：0.01-0.04％,N≤0.005％,B：0.001-0.004％, mass percent and satisfies Mn+Cr of 1.0% or more and Cr of 1.5% or less, nb+Ti of 0.05% or less and Ti of 0.10% or less, and the balance of Fe and unavoidable impurities. Further, C：0.34-0.39％,Si：0.20-0.30％,Mn：0.8-1.3％,P≤0.009％,S≤0.003％,Cr≤1.0％,Mo：0.25-0.35％,Ti：0.05-0.07％,Nb≤0.05％,Al：0.02-0.03％,N≤0.005％,B：0.0015-0.0025％,% by mass and 1.0% or more Mn+Cr 1.5% or less, 0.06% or more Nb+Ti 0.10% or less, and the balance of Fe and unavoidable impurities. Further, the carbon equivalent CEV of the steel plate is less than or equal to 0.70%, the tensile strength is more than or equal to 1900MPa, the yield strength is more than or equal to 1600MPa, and the low-temperature impact absorption power KV2 (-40 ℃) is more than or equal to 32J. On the other hand, the invention provides a preparation method of the low-carbon equivalent ultrahigh-strength steel plate, which comprises the following steps of: s1, smelting and casting, namely smelting raw materials according to the component proportion, and casting to obtain a steel billet; S2, rolling, namely heating the billet at 1250-1280 ℃ and then performing rough rolling and finish rolling, wherein the finish rolling temperature is lower than 860 ℃, and coiling when the temperature is reduced to 500-550 ℃, so as to obtain a hot rolled plate; and S3, heat treatment, namely heating, preserving heat, cooling and tempering the hot rolled plate to obtain a finished steel plate. Further, in step S2, the rough rolling temperature is 1150 ℃ to 1250 ℃, the total compression ratio is more than 60%, and the rough rolling finishing temperature is lower than 1100 ℃. Further, in step S2, the finish rolling stage is divided into a recrystallization zone rolling and a non-recrystallization zone rolling, wherein the temperature of the recrystallization zone rolling is 920-980 ℃, and the temperature of the non-recrystallization zone rolling is 820-920 ℃. Further, the deformation amount of the unrecrystallized rolling is 15-30% of the total deformation amount of the finish rolling stage. Further, in step S3, the heating temperature of the hot rolled plate is 880-920 ℃, and the heat preservation time is 2-3min/mm. Further, the cooling adopts graded cooling, after the hot rolled plate is heated and insulated, the hot rolled plate is