A two-step tempering process for improving the impact toughness of large nuclear power forgings

A technology of impact toughness and large forgings, which is applied in the field of two-step tempering process, can solve the problems that the impact absorption energy cannot be achieved and the impact performance is not enough to achieve the effect of improving impact toughness

Active Publication Date: 2018-11-16
SHANGHAI JIAO TONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] After literature search, Kim J T and others wrote "Improvement of impact toughness of the SA 508 class 3 steel for nuclear pressure vessel through steel-making and heat-treatment practices" on Nuclear engineering and design magazine (1997, Vol.174(1), P51-58). (Improving the impact toughness of SA508Gr.3 steel for nuclear power pressure vessels by improving the production and heat treatment process)", the paper proposes that the impact toughness of nuclear power pressure vessel forgings can be significantly improved by improving the vacuum carbon deoxidation technology and reducing the Si content, but it is still insufficient To ensure 100% qualified impact performance
[0004] Directly heating the quenched SA508Gr.3 forgings to 600-660°C and tempering for 4-12h is a commonly used tempering process in actual production, but this traditional tempering process often leads to the decomposition of retained austenite into size The mixed structure of larger elongated carbides and ferrite makes the impact absorption energy often fail to reach the 48J required by the technical specification

Method used

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  • A two-step tempering process for improving the impact toughness of large nuclear power forgings
  • A two-step tempering process for improving the impact toughness of large nuclear power forgings
  • A two-step tempering process for improving the impact toughness of large nuclear power forgings

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Embodiment 1

[0021] use as figure 1 The two-step tempering process shown treats large nuclear power forgings. The specific steps are:

[0022] The forging of the lower cylinder has an outer circle of φ4417mm, a wall thickness of 113mm, and a length of 4267mm. It is required that the hardness after tempering heat treatment should be higher than HB180, and the impact absorption energy at -21°C should be greater than 48J. After the workpiece is austenitized and kept at 890°C, it is water-cooled and quenched; tempering adopts a two-step tempering process: first hold at 400°C for 2 hours, then raise the temperature to 650°C for 4 hours, and cool to room temperature with the furnace. Samples were taken at the specified position to test its hardness and impact toughness. The measured hardness was HB202, the impact absorption energy was 79, 95, and 118J respectively, and the average value was 97.33J, meeting the technical requirements.

[0023] The structure of the forging before and after tempe...

Embodiment 2

[0028] The forging of the lower cylinder has an outer circle of φ4417mm, a wall thickness of 113mm, and a length of 4267mm. After tempering and heat treatment, the hardness is higher than HB180, and the impact absorption energy at -21°C is greater than 48J. After the workpiece is austenitized and kept at 890°C, it is water-cooled and quenched; tempering adopts a two-step tempering process: first hold at 350°C for 2 hours, then raise the temperature to 650°C for 4 hours, and cool to room temperature with the furnace. Samples were taken at the specified position to test its hardness and impact toughness. The measured hardness was HB200, the impact energy absorbed was 72, 90, and 128J respectively, and the average value was 96.67J, meeting the technical requirements.

Embodiment 3

[0030] For the cone forging, the outer circle at one end is φ5626mm, the outer circle at the other end is φ4467mm, the wall thickness is 168mm, and the length is 3187mm. After the workpiece is austenitized and kept at 890°C, it is water-cooled and quenched; tempering adopts a two-step tempering process: first hold at 450°C for 2 hours, then raise the temperature to 660°C for 6 hours, and cool to room temperature with the furnace. Samples were taken at the specified position to test its hardness and impact toughness. The measured hardness was HB193, the impact absorption energy was 97, 105, and 86J respectively, and the average value was 96J, which met the technical requirements.

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Abstract

The invention relates to a two-step method tempering process for improving impact toughness of a nuclear power large forging. The process includes the following steps that (1) the quenched nuclear power large forging is heated to 300-450 DEG C for heat preservation; and (2) the forging is heated to 600-660 DEG C continuously for heat preservation, then the forging is cooled in a furnace, and the process is completed. Compared with the prior art, the impact absorbing energy average value of steel treated by the two-step method tempering process can reach about 100J. The impact toughness is obviously improved compared with the nuclear power large forging treated by a traditional tempering process. Moreover, the process is simple, easy to operate and implement and the like.

Description

technical field [0001] The invention relates to the field of metal heat treatment technology, in particular to a two-step tempering process for improving the impact toughness of SA508Gr.3 steel nuclear power large forgings. Background technique [0002] As a commonly used structural material, SA508Gr.3 steel is widely used in the manufacture of key components of nuclear power plants such as nuclear power pressure vessels, tube sheets, and cylinders. For this kind of steel, the most important thing is to provide enough high strength and high impact toughness to overcome the safety hazards caused by instantaneous impact caused by accidents. It is worth noting that the impact toughness of steel will gradually deteriorate due to radiation embrittlement during the operation of nuclear power plants. Therefore, it is crucial to ensure the safe operation of nuclear power plants to make steel have higher initial impact toughness through heat treatment. [0003] After literature sear...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D1/18C21D9/00
CPCC21D1/18C21D9/0068C21D2211/002C21D2211/004C21D2211/005
Inventor 顾剑锋韩利战晏广华李传维潘健生
Owner SHANGHAI JIAO TONG UNIV
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