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CN-117721386-B - Multi-element microalloy high-toughness ultrahigh-strength steel and preparation method thereof

CN117721386BCN 117721386 BCN117721386 BCN 117721386BCN-117721386-B

Abstract

The invention relates to a multi-element micro-alloy high-toughness ultrahigh-strength steel and a preparation method thereof, belonging to the technical field of ultrahigh-strength alloy steel. Solves the problem of poor toughness of the existing multi-element micro-alloy ultrahigh-strength steel. The multi-element micro-alloy high-toughness ultra-high-strength steel comprises the following alloy components in percentage by weight: c:0.36 to 0.38 percent of Mn:1.10 to 2.0 percent of Si:0.8 to 1.40 percent of Cr:1.10 to 1.50 percent of Ni:0.15 to 0.40 percent of Mo:0.2 to 0.5 percent of W:0.1 to 0.7 percent, nb is less than or equal to 0.01 percent, V is less than or equal to 0.01 percent, B is less than or equal to 0.001 percent, and the balance is Fe and unavoidable impurities; the preparation process comprises forging-annealing-normalizing-annealing-quenching-tempering. The prepared multi-element microalloy high-toughness ultrahigh-strength steel has low cost, high hardenability and excellent performance.

Inventors

  • LIU GENG
  • SU JIE
  • NING JING
  • GAO QI
  • DING YALI
  • WANG AO
  • CHEN JIAYAN

Assignees

  • 钢铁研究总院有限公司

Dates

Publication Date
20260508
Application Date
20231030

Claims (10)

  1. 1. The multi-element micro-alloy high-toughness and ultra-high-strength steel is characterized in that the alloy components of the multi-element micro-alloy high-toughness and ultra-high-strength steel are ：C：0.36～0.38%、Mn：1.10～2.0%、Si：0.8～1.40%、Cr：1.10～1.50%、Ni：0.15～0.40%、Mo：0.2～0.5%、W：0.1～0.7%、Nb≤0.01%、V≤0.01%、B≤0.001%, percent by weight, and the balance is Fe and unavoidable impurities; the multi-element microalloy high-toughness ultrahigh-strength steel is prepared by the following steps: Step S1, forging, namely heating a billet meeting the requirements of alloy components through a soaking pit, and forging to obtain a first forging stock; Step S2, annealing the first forging stock for the first time, and air-cooling to obtain a second forging stock; step S3, normalizing the second forging stock, and then air-cooling to room temperature to obtain a third forging stock; Step S4, annealing for the second time, heating the third forging stock to perform annealing treatment, and then air-cooling to room temperature to obtain a fourth forging stock; Step S5, quenching, namely heating and preserving heat of the fourth forging stock, quenching, and then cooling to room temperature after gradually cooling with a furnace and oil cooling to obtain a fifth forging stock; Step 6, tempering, namely tempering the fifth forging stock for the first time and tempering the fifth forging stock for the second time, wherein the temperature of the tempering for the second time is not higher than that of the tempering for the first time, so as to obtain the multi-element micro-alloy high-toughness ultra-high-strength steel; in the step S5, the heat preservation temperature is 930-960 ℃ and the heat preservation time is 1-4 hours, wherein the furnace-following slow cooling and oil cooling processes are that the furnace-following slow cooling and oil cooling are carried out after the furnace-following slow cooling is carried out to 830-860 ℃ and then the oil cooling is carried out to room temperature; In the step S6, the first tempering temperature is 235-255 ℃, the tempering time is 3-5 h, the second tempering temperature is 225-235 ℃, and the tempering time is 3-5 h.
  2. 2. The multi-microalloyed high toughness, ultra-high strength steel according to claim 1, wherein the microstructure of the multi-microalloyed high toughness, ultra-high strength steel is comprised of martensite and thin film austenite.
  3. 3. The multi-element microalloyed high toughness, ultra high strength steel according to claim 2, wherein the volume fraction of the thin film austenite is 3% -7%.
  4. 4. A method for preparing a multi-element micro-alloy high-toughness ultra-high strength steel according to any one of claims 1-3, comprising the steps of: Step S1, forging, namely heating a billet meeting the requirements of alloy components through a soaking pit, and forging to obtain a first forging stock; Step S2, annealing the first forging stock for the first time, and air-cooling to obtain a second forging stock; step S3, normalizing the second forging stock, and then air-cooling to room temperature to obtain a third forging stock; Step S4, annealing for the second time, heating the third forging stock to perform annealing treatment, and then air-cooling to room temperature to obtain a fourth forging stock; Step S5, quenching, namely heating and preserving heat of the fourth forging stock, quenching, and then cooling to room temperature after gradually cooling with a furnace and oil cooling to obtain a fifth forging stock; And S6, tempering, namely performing first tempering and second tempering on the fifth forging stock, wherein the temperature of the second tempering is not higher than that of the first tempering, and obtaining the multi-element micro-alloy high-toughness ultrahigh-strength steel.
  5. 5. The method according to claim 4, wherein in the step S1, the initial forging temperature is 1050 ℃ to 1150 ℃ and the final forging temperature is 920 ℃ to 950 ℃.
  6. 6. The method according to claim 5, wherein in the steps S2 and S4, the annealing temperature is 600 to 650 ℃ and the annealing time is 2 to 10 hours.
  7. 7. The method according to claim 6, wherein in the step S3, the normalizing temperature is 950-980 ℃ and the normalizing time is 2-10 h.
  8. 8. The preparation method according to claim 7, wherein in the step S5, the heat preservation temperature is 935 ℃ to 960 ℃ and the heat preservation time is 1 to 2 hours; the following furnace slow cooling and oil cooling processes are that cooling is carried out along with the furnace to 840-860 ℃ and then oil cooling is carried out to room temperature.
  9. 9. The method according to claim 8, wherein in the step S6, the first tempering temperature is 240 ℃ to 255 ℃ and the tempering time is 3 to 5 hours, and the second tempering temperature is 230 ℃ to 235 ℃ and the tempering time is 3 to 5 hours.
  10. 10. The method according to claim 4, wherein in the step S6, a cold treatment operation is further included between the first tempering and the second two-step tempering.

Description

Multi-element microalloy high-toughness ultrahigh-strength steel and preparation method thereof Technical Field The invention relates to the technical field of ultrahigh-strength alloy steel, in particular to a multi-element microalloy high-toughness ultrahigh-strength steel and a preparation method thereof. Background The low-alloy ultrahigh-strength steel has wide market application prospect due to the relatively low alloy cost. The main steel types on the market at present comprise the brands of 4340, D6AC, 300M, 35CrMnSi and the like, the development and the use of the products are more than thirty years, the products are restricted by a plurality of objective factors such as alloy smelting conditions, element cost, thermal deformation, heat treatment conditions and the like at the moment, and are also influenced by subjective factors such as insufficient deep cognition on scientific principles such as physical metallurgy and the like, so that the comprehensive mechanical properties of the materials are generally distributed in the performance interval of high strength and low toughness (the tensile strength is 1900MPa, the fracture toughness is about 70 MPa.m 1/2) and low strength and high toughness (the tensile strength is 1700MPa, the fracture toughness is about 100 MPa.m 1/2). Compared with low-alloy ultrahigh-strength steel, although the high-alloy secondary hardening steel such as A100, M54 and the like can meet the requirements of high strength and high toughness, the high cost and smelting cost severely limit the application of the high-toughness ultrahigh-strength steel in the fields of aerospace and the like in China. Besides the toughness of the material, the hardenability of the low-alloy ultrahigh-strength steel has larger influence on the performance of different parts of the material due to lower alloy content. Hardenability of a material means that the formation of the martensite phase is able to penetrate the entire cross-sectional thickness of the material, not just the surface layer, when the material is subjected to a quenching process. Hardenability is one of the important indicators for measuring the quenching properties of a material, especially in cases where it is desired to obtain a uniform martensitic transformation over the entire material cross-section. How to reasonably adjust the uniformity of the hardenability of the material to match the structural performance of the alloy also has a great challenge. Therefore, under the restriction of low alloy cost and low smelting cost, the development of the alloy steel capable of balancing high strength and high toughness has important significance. Disclosure of Invention In view of the above analysis, the present invention aims to provide a multi-element micro-alloy high-toughness ultra-high strength steel and a preparation method thereof, which are used for solving the problem of poor toughness of the existing multi-element micro-alloy ultra-high strength steel. In one aspect, the present invention provides a multi-element microalloyed high toughness ultra high strength steel having alloy compositions, in weight percent ：C：0.36～0.38％、Mn：1.10～2.0％、Si：0.8～1.40％、Cr：1.10～1.50％、Ni：0.15～0.40％、Mo：0.2～0.5％、W：0.1～0.7％、Nb≤0.01％、V≤0.01％、B≤0.001％,, balance Fe and unavoidable impurities. Further, the microstructure of the multi-element microalloyed high toughness ultra-high strength steel is composed of martensite and thin film austenite. Further, the volume fraction of the thin film austenite is 3% -7%. On the other hand, the invention also provides a preparation method of the multi-element micro-alloy high-toughness and ultra-high-strength steel, which is used for preparing the multi-element micro-alloy high-toughness and ultra-high-strength steel and comprises the following steps of: Step S1, forging, namely heating a billet meeting the requirements of alloy components through a soaking pit, and forging to obtain a first forging stock; Step S2, annealing the first forging stock for the first time, and air-cooling to obtain a second forging stock; step S3, normalizing the second forging stock, and then air-cooling to room temperature to obtain a third forging stock; Step S4, annealing for the second time, heating the third forging stock to perform annealing treatment, and then air-cooling to room temperature to obtain a fourth forging stock; Step S5, quenching, namely heating and preserving heat of the fourth forging stock, quenching, and then cooling to room temperature after gradually cooling with a furnace and oil cooling to obtain a fifth forging stock; And S6, tempering, namely performing first tempering and second tempering on the fifth forging stock, wherein the temperature of the second tempering is not higher than that of the first tempering, and obtaining the multi-element micro-alloy high-toughness ultrahigh-strength steel. Further, in the step S1, the initial forging temperature is 1050 ℃ to 1150 ℃, and the final forging tempera