A method for producing a super-thick steel 15MnNi for a nuclear power plant reactor support pressure vessel

By employing specific chemical compositions and production processes, the problems of large performance differences between the upper and lower surfaces and unstable impact energy of 15MnNi steel plates used in nuclear reactor pressure vessels with a thickness of ≥150mm were solved, achieving improved uniformity and low-temperature toughness of the steel plates and meeting the technical requirements of nuclear power plants.

CN118086647BActive Publication Date: 2026-07-03NANYANG HANYE SPECIAL STEEL CO LTD
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
NANYANG HANYE SPECIAL STEEL CO LTD
Filing Date
2023-12-28
Publication Date
2026-07-03

AI Technical Summary

Technical Problem

When existing technologies struggle to produce 15MnNi steel plates for nuclear reactor pressure vessels with a thickness ≥150mm, the performance differences between the upper and lower quarters of the steel plate are significant, resulting in poor stability of the impact energy after simulated stress-relief heat treatment, which makes it difficult to meet the technical requirements of nuclear power plants.

Method used

By employing specific chemical composition design and production processes, including two-stage rolling, controlled cooling, stacking cooling and heat treatment, and by adjusting the quenching cooling method and tempering temperature, the cooling rate of the upper and lower surfaces of the steel plate is ensured to be consistent, the grains are refined, and the uniformity and low-temperature toughness of the steel plate are improved.

Benefits of technology

It achieves balanced performance between the upper and lower quarters of 15MnNi steel plates with a thickness of ≥150mm, with a tensile strength difference of ≤15MPa and a low-temperature impact energy of ≥150J at -60℃, meeting the technical requirements of nuclear power plants and demonstrating stable and reliable performance.

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Abstract

This invention discloses a method for producing extra-thick 15MnNi steel for supporting pressure vessels in nuclear power plant reactors, comprising the following chemical composition (wt%): C: 0.14–0.18, Si: 0.15–0.37, Mn: 1.4–1.55, P: ≤0.008, S: ≤0.003, Nb: 0.015–0.025, V: 0.014–0.020, Ni: 0.75–0.95, Cr: ≤0.20, Al: 0.020–0.030, Ti: 0.01 The carbon content is 5-0.020, with the remainder being Fe and residual elements. The carbon equivalent Ceq is ≤0.49%, and the weld crack sensitivity index Pcm is ≤0.27%. Using a 1000mm thick water-cooled ingot mold, 150-250mm thick 15MnNi steel is obtained through rolling, controlled cooling, stack cooling, and heat treatment. The difference between the tensile strength of the upper and lower quarters and the tensile strength of the upper and lower quarters in the simulated stress-relieved heat-treated state is ≤15MPa. The low-temperature impact energy at -60℃ is ≥150J, and the Z-direction performance is ≥50%. The performance is stable and reliable, fully meeting the requirements for nuclear power steel.
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