Performance Heat Treatment Method for Improving the Strength and Toughness of Large Forgings Used in Nuclear Capacitors

Abstract

The invention discloses a property thermal treatment method for improving the toughness of a large forging used in a nuclear power container. The method is applied to property thermal treatment on the forging used in the nuclear power container that the material is SA508-3, the outer diameter is 3.5-6.5 m, the height is not higher than 5 m, and the wall thickness is 100-250 mm; an electric heating annular furnace is adopted; the temperature control precision of the electric heating annular furnace is + / -10 DEG C. The method comprises the following steps: 1, performing subcritical quenching; 2, quenching; 3, tempering. According to the method, one-time subcritical quenching is added before quenched-tempered heat treatment, as the temperature is low in subcritical quenching, a forging material is not completely austenitized, the unmelted ferrite can prevent crystal particles from growing up, superfine austenite crystal grains can be formed along an original large austenite crystal boundary before quenching, a good crystal grain refining effect can be achieved, and good tissue preparation is provided for later quenching-tempering treatment. Through the adoption of the method, the low-temperature toughness of the forging is improved on the basis of ensuring the qualified strength, so as to meet the requirements on properties of large nuclear power forgings.

Description

technical field [0001] The invention relates to a heat treatment method, in particular to a performance heat treatment method for improving the strength and toughness of large forgings for nuclear capacitors. Background technique [0002] Nuclear capacitors play a vital role in ensuring the safe operation of nuclear power plants throughout the 40-60-year service cycle, so nuclear capacitors are generally assembled and welded by high-performance large forgings. [0003] General requirements for SA508-3 large forgings for nuclear capacitors are as follows: [0004] 1. It has high room temperature strength and high temperature strength, and the technical index is measured by room temperature tensile test and high temperature tensile test; [0005] 2. Sufficient toughness, especially low temperature toughness, which is generally measured by Charpy impact test or drop weight test. From the perspective of safety, it is generally required that the toughness of the forging materia...

AI Technical Summary

Problems solved by technology

[0014] The above-mentioned heat treatment process of conventional quenching + high temperature tempering can meet the performance requirements of most large nuclear power forgings, but there are still some forgings due to defects (such as poor composition and serious segregation) caused by the previous process. Conventional properties Toughness after heat treatment is lower than specification requirements

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