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A heat treatment process for improving temper brittleness of martensitic heat-resistant steel

A tempering brittle, martensite technology, applied in the field of heat-resistant steel, can solve the problems of scrapped workpieces and economic losses, and achieve the effect of improving strength and toughness, obvious benefits, and inhibiting crack nucleation

Active Publication Date: 2020-05-26
XIJING UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Once temper brittleness occurs, the workpiece will be scrapped, resulting in large economic losses. Therefore, how to avoid temper brittleness is very important

Method used

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  • A heat treatment process for improving temper brittleness of martensitic heat-resistant steel

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0025] Processing material: Cr12Ni2 martensitic heat-resistant steel, weight 10Kg;

[0026] After the steel ingot undergoes high-temperature solution treatment, high-temperature forging and quenching, the billet is tempered. Tempering temperature is 620 ℃, heat preservation 2 hours.

[0027] The impact energy was tested to be 65J, the toughness was significantly reduced, and a certain amount of M23C6 carbide particles were observed to be distributed on the boundaries of martensite laths, resulting in temper brittleness.

[0028] The brittle sample was tempered again, and the tempering temperature was raised to 650° C., and kept for 3 hours. The mechanical properties of the sample after secondary tempering were tested, and the impact energy was determined to be 115J, the hardness was 335HBW, and the tensile strength was 917Mpa. At the same time, the diffuse distribution of carbonitrides distributed in the matrix can be observed by SEM and TEM. The results show that after sec...

Embodiment 2

[0030] The processing material is Cr12Ni2 martensitic heat-resistant steel with a weight of 15Kg.

[0031] After the steel ingot undergoes high-temperature solution treatment, high-temperature forging and quenching, the billet is tempered. Tempering temperature is 630 ℃, heat preservation 5 hours. The mechanical properties of the workpiece in Example 2 were tested, and the impact energy was 102J, the hardness was 340HBW, and the tensile strength was 938Mpa. At the same time, it is observed that carbides such as M2X and M7C3 are distributed in the matrix. The results show that although the tempering is carried out in the brittle temperature region, due to the prolonged tempering time, the toughness of the sample is not significantly reduced, and the performance is improved to avoid temper brittleness.

Embodiment 3

[0033] The processing material is Cr12Ni2 martensitic heat-resistant steel with a weight of 18Kg.

[0034] After the steel ingot undergoes high-temperature solution treatment, high-temperature forging and quenching, the billet is tempered. Tempering temperature is 660°C, heat preservation for 1 hour, then lower the temperature to 625°C and heat preservation for 2 hours. The mechanical properties of the workpiece of Example 3 were tested, and the impact energy was 114J, the hardness was 337HBW, and the tensile strength was 925Mpa. It can be observed that carbides such as M2X and M7C3 are distributed in the matrix. The results show that after pre-tempering, even at T 脆 Tempering within the range will also not produce temper brittleness.

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Abstract

The invention discloses a heat treatment technology for improving the temper brittleness of martensitic heat-resistant steel. The precipitation of carbides is controlled through a tempering technology, and complicated process regulation is not required; and not only can the strength and toughness of the martensitic heat-resistant steel can be improved, but also the temper brittleness of the martensitic heat-resistant steel is avoided. The main reasons for improvement of the strength and toughness of the martensitic heat-resistant steel and improvement or repair of the temper brittleness include: (1) stabilization of M23C6 carbides; (2) further recovery of martensitic laths; and (3) dispersed precipitation enhancement of MX, M2X, M7C3 and M6C and other carbides. Under the combined action ofthe three factors, the nucleation, growth and development of cracks are inhibited, and finally the strength and toughness of the martensitic heat-resistant steel are improved. The technology is low in cost, high in efficiency, and the benefits are obvious; and the purpose of waste reutilization can be achieved.

Description

technical field [0001] The invention belongs to the technical field of heat-resistant steel and relates to a heat treatment process for improving the temper brittleness of martensitic heat-resistant steel. Background technique [0002] Martensitic heat-resistant steel usually contains 9-14% of Cr elements. In order to further improve its toughness and high-temperature durability, a small amount of alloy elements such as Ni, Mo, Mn, Si, V, Nb, and W are added on this basis. Form martensitic heat-resistant steel series. Among them, the most widely used is the Cr12Ni series martensitic heat-resistant steel, which has a high hardness after quenching. Different tempering processes are implemented, and it has different combinations of strength and toughness; it is mainly used in the field of power plant boilers, such as steam turbine blades and rotors. , Steam boiler body, valve, reheating body, high temperature steam pipe, cylinder and other high temperature working parts have g...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D1/18C21D6/00
CPCC21D1/18C21D6/004C21D2211/008Y02P10/20
Inventor 乔勋王琳淋王德文刘守法孟东容白旭峰朱炎
Owner XIJING UNIV
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