CN-121976009-A - Method for optimizing performance of 20CrMn-N duplex stainless steel based on gradient cold rolling process

Abstract

The invention discloses a method for optimizing the performance of 20CrMn-N duplex stainless steel based on a gradient cold rolling process, which relates to the technical field of steel alloy material reinforcement preparation, and comprises the steps of carrying out solution treatment after preparing the conservation-oriented duplex stainless steel by hot rolling, then adopting a four-roller cold rolling mill to carry out cold rolling deformation, and controlling the gradient of cold rolling deformation amount to enable metastable austenite to generate controllable strain-induced martensitic transformation, so as to regulate and control the volume fraction of martensite, thereby obtaining a 20CrMn-N system LDSS steel plate containing ferrite, austenite and strain-induced martensitic three-phase structure.

Inventors

• LIU ZHENGHONG
• SUN YUMENG
• XU XUEDONG
• DONG HAN
• NI TIANYI
• SUN ZHONGHUI
• CAI XIAOLONG
• LI QINGXI

Assignees

• 长春工程学院

Dates

Publication Date

20260505

Application Date

20260225

Claims (3)

1. 1. The method for optimizing the performance of the 20CrMn-N duplex stainless steel based on the gradient cold rolling process is characterized by comprising the following steps of: Step1, adding raw materials into an AOD furnace, and refining to obtain molten steel with uniform components; step 2, casting the molten steel into a plate blank by adopting a die casting process to obtain a casting blank with the thickness of 150-200 mm, and polishing the surface to remove oxide scales and defects; Step 3, heating a casting blank to 1180-1250 ℃, preserving heat for 2-3 hours, ensuring complete austenitizing and no unconverted original tissue residue, adopting an industrial hot rolling process, controlling the deformation of each pass to 15-25%, and finally hot-rolling to a hot-rolled plate with the thickness of 8-12 mm, and cooling to room temperature after hot rolling to obtain a hot-rolled plate containing an initial ferrite-austenite double-phase structure; Step 4, heating the hot rolled plate cooled to room temperature to 950-1050 ℃, preserving heat for 60-120 min to fully homogenize ferrite and austenite, carrying out rapid water quenching after heat preservation, inhibiting second phase precipitation, eliminating hot rolling stress and hot rolling strip-shaped structures, and finally obtaining a plate containing uniform ferrite and austenite double-phase structures; And 5, performing cold rolling deformation on the sheet subjected to solution treatment by adopting an existing four-roller cold rolling mill, performing multi-pass cold rolling to obtain a preset cold rolling deformation, heating the sheet to 150-200 ℃ for 5-10 min after each cold rolling, eliminating inter-pass internal stress, avoiding edge cracks, and finally obtaining the 20CrMn-N series LDSS steel sheet with ferrite, austenite and strain induced martensite three-phase structure.
2. 2. The method for optimizing the performance of 20CrMn-N duplex stainless steel based on the gradient cold rolling process according to claim 1, wherein the raw materials in the step 1 comprise the following components in percentage by weight: 20.33% Cr, 3.08% Mn, 0.975% Ni, 0.32% Si, 0.24% N, less than or equal to 0.02% C, less than or equal to 0.007% P, less than or equal to 0.001% S, less than or equal to 0.014% O, and the balance Fe.
3. 3. The method for optimizing the performance of 20CrMn-N duplex stainless steel based on the gradient cold rolling process according to claim 1, wherein in the step 4, the cooling rate of rapid water quenching after heat preservation is more than or equal to 50 ℃ per second.

Description

Method for optimizing performance of 20CrMn-N duplex stainless steel based on gradient cold rolling process Technical Field The invention relates to the technical field of reinforced preparation of steel alloy materials, in particular to a method for optimizing the performance of 20CrMn-N duplex stainless steel based on a gradient cold rolling process. Background Duplex stainless steel (Duplex STAINLESS STEELS, DSSS) has excellent strong plasticity, corrosion resistance and fatigue resistance by virtue of the synergistic advantage of ferrite and austenite Duplex structure, has been widely applied to various fields such as petrochemical industry, ocean engineering, environmental protection facilities, automobile manufacturing and the like, gradually replaces part of traditional austenitic stainless steel, and becomes one of the core development directions in the field of advanced structural materials. However, as the global raw material cost rises, conventional Duplex stainless steel relying on expensive alloying elements such as nickel and molybdenum faces the dual challenges of cost pressure and resource constraint, and the development of resource-saving Duplex stainless steel (Lean Duplex STAINLESS STEELS, LDSSS) with manganese and nitrogen instead of nickel and molybdenum is the focus of industry research. The 20CrMn-N saving type duplex stainless steel does not contain molybdenum, reduces noble metals such as nickel and the like, reduces manufacturing cost by optimizing the proportion of chromium, manganese and nitrogen elements, simultaneously shows potential high-strength corrosion resistance by means of the solid solution strengthening effect of nitrogen and manganese and the stabilizing effect of austenite, and meets urgent requirements of fields such as automobile weight reduction, bridge construction, ocean engineering and the like for low-cost and high-performance structural materials. However, the performance regulation and industrialization application of the steel grade still faces a plurality of technical bottlenecks, and the existing production and processing technology is difficult to realize accurate matching of organization and performance: Firstly, the traditional 20CrMn-N system LDSS is mostly prepared by adopting a high-temperature hot forming process, under the process, the difference of the thermodynamic stability of ferrite and austenite is obvious, the growth rate of two-phase grains is inconsistent, the defects of stress concentration, edge cracks and the like are easily generated in the material, the surface smoothness is poor (Ra is more than or equal to 3.2 mu m), the subsequent processing procedures of grinding, polishing and the like are additionally added, the production cost is increased, and the corrosion-resistant layer on the surface of the material is possibly damaged. Although partial researches try to replace thermoforming by adopting a single cold rolling process to enhance the performance through grain refinement and strain induction, a single cold rolling mode with a fixed large deformation is difficult to accurately regulate and control the strain-induced martensitic transformation process of metastable austenite, so that the volume fraction of martensite is uncontrollable, the unbalance problem of 'obviously enhanced strength and sharply reduced plasticity' often occurs, and the requirement of high-end application scenes on the synergy of toughness cannot be met. Secondly, the performance core of the 20CrMn-N system LDSS depends on the proportion coordination and morphological distribution of ferrite, austenite and strain induced martensite three-phase structures, but the prior art lacks effective means for the evolution regulation and control of the three-phase structures. The existing cold rolling process focuses on the optimization of a dual-phase structure (ferrite and austenite), a directional regulation and control scheme aiming at a three-phase structure is not formed, a two-phase cooperative deformation mechanism and a strain distribution rule in the deformation process are not clear, and the influence mechanism of a martensite transformation path and dislocation evolution on the performance is not clear. Meanwhile, in the plastic deformation process of LDSS after the traditional solution treatment, the work hardening behavior mainly depends on the TRIP/TWIP effect of austenite, the effect of improving the yield strength is limited, the great improvement of the yield strength is difficult to realize, and the application of the product in a lightweight bearing structure is restricted. Thirdly, the traditional DSSs performance optimization only depends on component adjustment, for example, the corrosion resistance or strength is improved by increasing the content of alloy elements, so that the original design of 'resource saving' is overcome, new problems of grain boundary segregation, second phase precipitation and the like can be possibly caused, the proc