Effect of Heat Treatment on Properties of Narrow-gap Welded Joints of 25Cr2Ni2MoV Steel for Nuclear Power Rotors

YANG Feipeng; WU Haitao; FAN Yangyang

doi:10.3969/j.issn.1674-6457.2026.06.008

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Journal of Netshape Forming Engineering ›› 2026, Vol. 18 ›› Issue (6) : 75-84. DOI: 10.3969/j.issn.1674-6457.2026.06.008

Joining of New Materials and Dissimilar Materials

Effect of Heat Treatment on Properties of Narrow-gap Welded Joints of 25Cr2Ni2MoV Steel for Nuclear Power Rotors

YANG Feipeng¹, WU Haitao^1,*, FAN Yangyang^2,3

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Abstract

The work aims to investigate the influence law of heat treatment parameters on the microstructure and properties of welded joints, and provide a theoretical and experimental basis for further performance optimization. Welding of 40 mm thick nuclear power rotor test plates was completed by narrow-gap GTAW horizontal welding. The properties of weld metal under four heat treatment conditions (as-welded, 590 ℃×16 h, 590 ℃×20 h, 590 ℃×28 h) were compared. Quantitative microstructural characterizations including optical microstructure analysis, SEM scanning and electron backscatter diffraction (EBSD) were carried out on the specimens after mechanical property tests. Compared with the as-welded state, the yield strength of weld metal after heat treatment decreased by about 100 MPa on average, and the tensile strength decreased by approximately 70 MPa. The toughness of weld metal also decreased significantly after heat treatment, and the impact toughness at room temperature (20 ℃) and 0 ℃ decreased by more than 50% in general. Prolonging the holding time led to a gentle decline in weld strength and room-temperature impact toughness, while the impact toughness at 0 ℃ was reduced by over 50% with stronger dispersion. In conclusion, the carbide morphology at grain boundaries changes remarkably; the precipitation quantity and density of carbides increase obviously, forming continuous carbide precipitation networks. Under external loading for mechanical properties, the dislocation blocking effect of original grain boundaries is greatly weakened, and the rapid crack propagation macroscopically results in serious deterioration of tensile and impact properties of the joint.

Key words

low-alloy high-strength steel / heat treatment / narrow-gap GTAW / carbide

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YANG Feipeng, WU Haitao, FAN Yangyang. Effect of Heat Treatment on Properties of Narrow-gap Welded Joints of 25Cr2Ni2MoV Steel for Nuclear Power Rotors[J]. Journal of Netshape Forming Engineering. 2026, 18(6): 75-84 https://doi.org/10.3969/j.issn.1674-6457.2026.06.008

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Funding

Open project of State Key Laboratory of Precision Welding & Joining of Materials and Structures (AWJ-24M09); LAM-ANSTEEL Advanced Metallic Materials Innovation Center Major Project (LAC2023ZSC300)