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CN-121976133-A - 800 MPa-level low-alloy high-strength steel and preparation method and application thereof

CN121976133ACN 121976133 ACN121976133 ACN 121976133ACN-121976133-A

Abstract

The invention discloses 800 MPa-level low-alloy high-strength steel and a preparation method and application thereof, and relates to the technical field of welding steel. The 800 MPa-level low-alloy high-strength steel comprises C, si, mn, nb, ti, cr, B, N, P, S and the balance of Fe and unavoidable impurity elements, B-Cr element coupling is adopted to replace expensive Mo, ni and other elements in the traditional easy-to-weld steel by optimizing the chemical components and the proportion of the steel, ferrite matrix Gao Jiangyi welding steel is obtained by precisely matching alloy elements with a rolling process, the alloy cost of the ton steel can be obviously reduced by the improved components, the prepared low-alloy high-strength steel has high strength, easy welding and low softening rate of welding joints, the production cost is greatly reduced while the excellent performance is ensured, and the application field is wider.

Inventors

  • JIN JINWEN
  • WANG SHUIZE
  • WANG HONGXING
  • LIU GANG
  • CHANG HAITAO
  • LI RONG
  • HUANG YUHE
  • LU JUN

Assignees

  • 宁波钢铁有限公司
  • 北京科技大学

Dates

Publication Date
20260505
Application Date
20260316

Claims (10)

  1. 1. The 800 MPa-level low-alloy high-strength steel is characterized by comprising the following components ：C:0.065wt.%-0.085wt.%,Si:0.06wt.%-0.20wt.%,Mn:1.5wt.%-2.0wt.%,Nb:0.04wt.%-0.08wt.%,Ti:0.10wt.%-0.18wt.%,Cr:0.20wt.%-0.60wt.%,B:0.0010wt.%-0.0035wt.%,N≤0.0040wt.%,P≤0.010wt.%,S≤0.005wt.%, in percentage by weight, and the balance of Fe and unavoidable impurity elements.
  2. 2. The 800 MPa-grade low-alloy high-strength steel according to claim 1, wherein the yield strength Re 1 is not less than 720MPa and the tensile strength R m is not less than 800MPa.
  3. 3. A method for preparing 800 MPa-level low-alloy high-strength steel according to any one of claims 1-2, comprising the steps of: Heating the casting blank with the thickness of 50-80 mm; performing rough rolling treatment on the casting blank, and rolling the casting blank into an intermediate blank with the thickness of 10mm-25 mm; Carrying out finish rolling treatment on the intermediate blank, and rolling the intermediate blank into a steel plate with the thickness of 4mm-8 mm; and (3) carrying out water cooling on the steel plate to 575-625 ℃ at the speed of 60-100 ℃ per second, and then carrying out coiling treatment to obtain the 800MPa low-alloy high-strength steel.
  4. 4. A method according to claim 3, wherein the temperature of the heat treatment of the cast slab is 1200 ℃ to 1250 ℃ for 1.5h to 2h.
  5. 5. A method according to claim 3, wherein the initial rolling temperature is 1175 ℃ to 1225 ℃ and the final rolling temperature is 980 ℃ or more; Preferably, the finishing temperature of the rough rolling is 1020 ℃ to 1080 ℃.
  6. 6. The method according to claim 5, wherein the rough rolling treatment is carried out for 3 to 5 passes, and the average reduction per pass is 25 to 35%.
  7. 7. The method according to claim 3, wherein after the rough rolling treatment is completed, the intermediate billet is air-cooled for 10s to 30s and then subjected to finish rolling treatment; preferably, the initial rolling temperature of the finish rolling treatment is 880-930 ℃, the final rolling temperature is 800-850 ℃, the finish rolling treatment is 3-4 times, and the average reduction of each time is 30-40%.
  8. 8. A method according to claim 3, wherein the temperature of the coiling treatment is 600 ℃ to 625 ℃ and the holding time is 0.8h to 1.5h, and then the coiling treatment is cooled to room temperature along with the furnace.
  9. 9. Use of a 800 MPa-grade low-alloy high-strength steel according to any one of claims 1-2 or a 800 MPa-grade low-alloy high-strength steel produced by the production method according to any one of claims 3-8 in the field of welding.
  10. 10. The use according to claim 9, wherein the welding conditions comprise the following: Performing shielded welding under the condition of mixed gas of 80% Ar and 20% CO 2 , wherein the diameter of a welding wire is 0.8-1.5 mm, the dry extension of the welding wire is 10-18 mm, the gas pressure is 0.2-0.8 MPa, the gas flow is 18-25L/min, and the heat input of a filling welding bead is 5-kJ/cm-12 kJ/cm; Preferably, no preheating treatment is needed before welding, and the welding softening rate is less than or equal to 12.2 percent.

Description

800 MPa-level low-alloy high-strength steel and preparation method and application thereof Technical Field The invention relates to the technical field of welding steel, in particular to 800 MPa-level low-alloy high-strength steel, and a preparation method and application thereof. Background With the continuous improvement of the level of modern equipment, the performance requirements on engineering structural materials are increasingly severe, and the strength of steel is promoted to be continuously improved. While satisfying high strength (for example, above 800MPa level), the steel material is required to have excellent comprehensive properties including good weldability, lower welding softening rate, and the like. Conventional high strength steels employ a martensitic or bainitic structure with a high carbon content, and an increase in the carbon equivalent severely impairs the weldability of the material. Meanwhile, in order to ensure the uniform structure of the steel plate core, high hardenability is realized by adding a large amount of alloying elements Mo, ni and the like, and the carbon equivalent is further improved. The higher the strength grade requirement of the steel is, the higher the content of the added alloy elements is, the cost of the alloy elements is increased, and the welding performance and the softening rate of the steel are reduced. However, the strong market competition and price competition pressure forces steel enterprises to reduce the cost by optimizing alloy design and production process on the premise of ensuring the material performance. At present, low-alloy high-strength steel obtained by adding alloy elements and controlling rolling and cooling is published at home and abroad, and easy-to-weld steel with strength of more than 800MPa adopts high alloy elements such as Mo, ni, V and the like for ensuring welding performance, so that the market competitiveness of steel types is not high, and the production pressure of steel enterprises is high. According to the Chinese patent CN119876775A, the high-strength and easy-to-weld ultra-fine grain steel with the strength and the performance of a welded joint are improved by adding a large amount of noble metals such as Ni, V and the like into the steel, wherein the content of Ni element is up to 2.0% -3.5%, and the alloy cost is high. The Chinese patent CN115948699B discloses a manufacturing method of 800MPa grade high strength steel plate for a stress corrosion resistant spherical tank, which adopts high-quality elements such as 1.03 percent Cr, 0.35Mo, 0.34Ni and the like, and has the advantages of 690 MPa tensile strength, unexplained welding performance, high alloy cost and unobvious strength. A Chinese patent is a 800MPa grade low yield ratio easy-welding steel plate and a production method thereof, mainly adopting Nb-V-Cr-Mo-Ni and other elements with high cost, wherein the concrete components of the steel plate are 0.08%-0.10%,Si：0.15%-0.40%,Mn：1.1%-1.50%,P：≤0.010%,S：≤0.005%,Alt：0.020-0.050%,Nb:0.030%-0.060%,Ti:0.010%-0.025%,V：0.030%-0.050%,Cr:≤0.50%,Mo：≤0.50%,Ni：≤0.6%, and the balance of Fe and unavoidable impurities. The content of V+Mo+Ni exceeds 1.10, and the alloy cost is high. Under the background that the cost of raw materials is high and the price of a steel product is continuously low, the optimization production cost is urgent while the performance of the steel is ensured. In view of this, the present invention has been made. Disclosure of Invention The invention aims to provide 800 MPa-level low-alloy high-strength steel and a preparation method and application thereof, so as to solve the technical problems. The invention is realized in the following way: In a first aspect, an embodiment of the present invention provides 800 MPa-grade low alloy high strength steel, including, in weight percent, ：C:0.065wt.%-0.085wt.%,Si:0.06wt.%-0.20wt.%,Mn:1.5wt.%-2.0wt.%,Nb:0.04wt.%-0.08wt.%,Ti:0.10wt.%-0.18wt.%,Cr:0.20wt.%-0.60wt.%,B:0.0010wt.%-0.0035wt.%,N≤0.0040wt.%,P≤0.010wt.%,S≤0.005wt.%,, the balance Fe and unavoidable impurity elements. In a second aspect, an embodiment of the present invention provides a method for preparing 800 MPa-grade low-alloy high-strength steel, including the following steps: Heating the casting blank with the thickness of 50-80 mm; performing rough rolling treatment on a casting blank, and rolling into an intermediate blank with the thickness of 10mm-25 mm; carrying out finish rolling treatment on the intermediate blank, and rolling the intermediate blank into a steel plate with the thickness of 4mm-8 mm; and (3) water-cooling the steel plate to 575-625 ℃ at the speed of 60-100 ℃ per second, and then carrying out coiling treatment to obtain the 800MPa low-alloy high-strength steel. In a third aspect, embodiments of the present invention provide an application of 800 MPa-grade low-alloy high-strength steel as described above or 800 MPa-grade low-alloy high-strength steel prepared by the preparat