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Method for improving low-temperature impact toughness of low-nickel ferrite-austenitic stainless steel

A low-temperature impact toughness, stainless steel technology, applied in the field of steel alloy materials, can solve the problems of low strength and elongation, low corrosion resistance element content, poor corrosion resistance and other problems

Active Publication Date: 2022-02-15
CHINA WEAPON SCI ACADEMY NINGBO BRANCH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The low-nickel type medium chromium ferritic stainless steel obtained by the present invention has excellent low-temperature toughness and high strength, the tensile strength is above 445MPa, the impact energy at -40°C is above 106J, and the impact energy at 20°C is above 143J ; Although the low-nickel type medium chromium ferritic stainless steel in this patent has better impact energy at low temperature, the content of corrosion resistance elements such as Cr and N in the ferritic stainless steel is relatively low, and the corrosion resistance is poor. and low strength and elongation
Ferritic-austenitic stainless steel is a mixed structure of ferrite and austenite. Alloy composition, preparation process, and two-phase ratio control all have important effects on its strength, plasticity, toughness, and corrosion resistance. The low-temperature impact toughness control process for ferritic stainless steel (full ferritic structure) is not applicable to ferritic-austenitic stainless steel

Method used

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  • Method for improving low-temperature impact toughness of low-nickel ferrite-austenitic stainless steel

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0022] Such as figure 1 Shown is the first preferred embodiment of the present invention.

[0023] The low-nickel ferritic-austenitic stainless steel involved in this embodiment includes the following components in terms of mass percentage: C: 0.03%, Cr: 21.5%, Mo: 0.25%, Ni: 1.5%, Mn: 4.9%, Si: 0.2%, N: 0.24%, and the balance is iron and other unavoidable impurities.

[0024] The above stainless steel is placed in a vacuum induction melting furnace and melted under a nitrogen atmosphere to obtain an ingot, which is then forged with an initial temperature of 1150°C and a final forging temperature of 1000°C, followed by air cooling to obtain a forged billet.

[0025] The method for improving the low-temperature impact toughness of the above-mentioned low-nickel ferritic-austenitic stainless steel comprises the following steps in sequence:

[0026] 1) Hot rolling: the above-mentioned forged billet is subjected to multi-pass hot rolling, the starting rolling temperature is con...

Embodiment 2

[0033] The main difference between this example and Example 1 is that the process parameters are different, specifically, in step 1), the starting rolling temperature is 1200°C, the finishing rolling temperature is 950°C, and the total reduction rate is 95%; step 2) In step 3), the solution temperature is 1000°C, the holding time is 40min, and the ferrite ratio is 45%, and the austenite ratio is 55%; in step 3), the low temperature tempering temperature is 350°C, and the tempering time is 30min.

[0034] After the ferritic-austenitic stainless steel of this embodiment is tempered at 350° C. for 30 minutes, its low-temperature impact energy at -40° C. reaches 80 J. The tensile strength is 950MPa, the yield strength is 600MPa, the elongation is 45%, and the pitting potential in 3.5% NaCl aqueous solution is 460mV.

Embodiment 3

[0038] The main difference between this embodiment and Embodiment 1 is: 1. The low-nickel ferrite-austenitic stainless steel is different, specifically, the low-nickel ferrite-austenitic stainless steel involved in this embodiment, according to In terms of mass percentage, it includes the following components: C: 0.02%, Cr: 22.8%, Mo: 0.30%, Ni: 0.9%, Mn: 6.7%, Si: 0.3%, N: 0.28%, and the balance is iron and other unavoidable impurities.

[0039] 2. The process parameters are different. Specifically, in step 1), the starting rolling temperature is 1230°C, the finishing rolling temperature is 1000°C, and the total reduction rate is 95%; in step 2), the solution temperature is 1100°C, and the holding time is 20 minutes, the proportion of ferrite is 46%, and the proportion of austenite is 54%. In step 3), the low-temperature tempering temperature is 350° C., and the tempering time is 30 minutes.

[0040] After the ferritic-austenitic stainless steel of this embodiment is tempere...

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Abstract

The invention relates to a method for improving the low-temperature impact toughness of low-nickel ferrite-austenitic stainless steel. The method comprises the following steps that 1) hot rolling is conducted, specifically, the low-nickel stainless steel obtained after smelting is forged, and then hot rolling is conducted to obtain a hot-rolled material; 2) solid solution annealing is conducted, specifically, the hot-rolled material is subjected to solid solution annealing treatment, the solid solution temperature ranges from 1000 DEG C to 1100 DEG C, the heat preservation time ranges from 20 min to 40 min, and then water cooling is conducted; and 3) low-temperature tempering is conducted, specifically, the plate obtained after the step 2) is subjected to tempering, the tempering temperature ranges from 300 DEG C to 400 DEG C, the heat preservation time ranges from 10 min to 60 min, and then air cooling is conducted. According to the method, the low-temperature impact toughness is effectively improved while the strength of the low-nickel ferrite-austenitic stainless steel is guaranteed, so that the service safety of the low-nickel ferrite-austenitic stainless steel is improved, and the service life is prolonged.

Description

technical field [0001] The invention belongs to the technical field of iron and steel alloy materials, and in particular relates to a method for improving low-nickel ferrite-austenite stainless steel low-temperature impact toughness. Background technique [0002] The microstructure of the current ferritic-austenitic stainless steel is composed of a certain proportion of ferrite and austenite, chemical composition design, forging and rolling process, heat treatment state, etc. The ratio of the two phases and the distribution of elements have an important impact on the performance of the stainless steel. The main alloying elements in this type of stainless steel are Fe, Cr, Mn, Ni, Mo, C, N and a small amount of Si. In recent years, in order to save Ni resources and respond to the impact of Ni metal price fluctuations on the stainless steel market, the method of replacing Ni with Mn and N can be used to reduce the cost of raw materials on the one hand, and on the other hand, ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21D8/02C21D1/26C21D1/18C21D9/46C22C38/44C22C38/58C22C38/02
CPCC21D8/0226C21D1/26C21D1/18C21D9/46C22C38/44C22C38/58C22C38/02C22C38/001Y02P10/20
Inventor 赵岩高永亮陈达宇李一舒陈巍
Owner CHINA WEAPON SCI ACADEMY NINGBO BRANCH
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