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After-forging preheat treatment process of large turbine low-pressure rotor forging piece

A pre-heat treatment and low-pressure rotor technology, which is applied in the field of post-forging pre-heat treatment process, can solve problems such as difficult production

Inactive Publication Date: 2012-07-11
ADVANCED MFG TECH CENT CHINA ACAD OF MASCH SCI & TECH +2
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  • Abstract
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  • Application Information

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Problems solved by technology

However, grain inheritance mainly occurs in high-alloy steel, and the austenite of high-alloy steel is extremely stable. For example, the incubation period of isothermal transformation into pearlite in 26Cr2Ni4MoV steel is as long as 7 hours, which is difficult to achieve in production.

Method used

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  • After-forging preheat treatment process of large turbine low-pressure rotor forging piece

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Embodiment Construction

[0013] For a 300MW steam turbine low-pressure rotor forging made of 26Cr2Ni4MoV steel, its rough machining diameter is Φ1850mm, and the forging diameter is Φ1920mm. Firstly, the sample was subjected to 1250°C×1.5h roughening treatment and 350°C×10h bainite treatment to obtain coarse austenite grains and acicular lower bainite structure. After the treatment, the sample grains greater than level 1.

[0014] Then the above treated samples were subjected to high temperature pre-tempering (660°C×20h) + critical zone normalizing treatment (770°C×3h) + normal normalizing (950°C×1h) treatment.

[0015] The treated sample was etched with supersaturated picric acid + sodium dodecylbenzenesulfonate solution to reveal austenite grain boundaries, and its grain size reached 7.5-8.0 grades.

[0016] Using high temperature pre-tempering + critical zone normalizing + normal normalizing process, the grain refinement effect is obvious, the heat treatment cycle is shortened, the heating temperat...

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Abstract

The invention discloses an after-forging preheat treatment process of a large turbine low-pressure rotor forging piece, and provides an after-forging preheat treatment process solving the problem of structural heredity of 26Cr2Ni4MoV steel or 30Cr2Ni4MoV steel used by the large turbine low-pressure rotor forging piece. The after-forging preheat treatment process comprises the steps of: firstly, carrying out 1250DEG C*1.5h roughening and 350DEG C*10h bainite treatment on an experimental material to ensure that rough austenite grains and needle-shaped bainite structures are obtained; and then carrying out high-temperature pre-tempering (660DEG C*20h) and critical region normalizing treatment (770 DEG C*3h) and normal normalizing treatment (950 DEG C*1h) on a test sample treated by the step. After the after-forging preheat treatment process is adopted, the refining effect of the grains is remarkable, the thermal treatment period is shortened, the heating temperature is reduced, the final use performance requirement is ensured, the problem of the structural heredity is solved in the practical production on the premise of ensuring the quality of a rotor, the process is simplified, and the reference basis is provided. The process can be applied in practical production.

Description

technical field [0001] The invention relates to a post-forging preliminary heat treatment process for a large-scale steam turbine low-pressure rotor forging. Background technique [0002] The low-pressure rotor of a large steam turbine is a key part of power generation equipment. The forming and manufacturing of high-quality low-pressure rotor forgings includes smelting, ingot casting, forging, and heat treatment. operational reliability. [0003] At present, the material used for the low-pressure rotor forgings of large steam turbines is generally 26Cr2Ni4MoV steel or 30Cr2Ni4MoV steel. The steel has good hardenability, toughness and comprehensive mechanical properties, but the steel is essentially a coarse-grained steel, and the steel contains high alloying elements such as Ni and Cr, which makes it have a strong structural inheritance phenomenon. After the forging of the rotor forging is completed, before heat treatment, most of the grains inside are coarse, and the who...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21D8/00
Inventor 李永兵王健金嘉瑜谢鲲左玲立陈蕴博
Owner ADVANCED MFG TECH CENT CHINA ACAD OF MASCH SCI & TECH
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