Effect of Rolling and Heat Treatment Process on Mechanical Properties of Extra-thick 3Cr2NiMo Steel Plate

KONG Lingyi; LUO Zongan; FENG Yingying; WU Zaoqin

doi:10.3969/j.issn.1674-6457.2025.07.006

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Journal of Netshape Forming Engineering ›› 2025, Vol. 17 ›› Issue (7) : 52-61. DOI: 10.3969/j.issn.1674-6457.2025.07.006

Composite Material Rolling Technology and Equipment

Effect of Rolling and Heat Treatment Process on Mechanical Properties of Extra-thick 3Cr2NiMo Steel Plate

KONG Lingyi¹, LUO Zongan^1,*, FENG Yingying¹, WU Zaoqin²

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Abstract

The work aims to fabricate extra-thick 3Cr2NiMo steel plate, in order to solve the problems of weld cracking, poor interface strength and toughness and uneven hardness of 3Cr2NiMo steel during welding. After preheating of 2 pieces of 3Cr2NiMo steel, the blank edges were sealed by vacuum electron beam welding under 5×10^-2 Pa vacuum condition, and then the composite billets were combined by different rolling processes. Next, tempering heat treatment was carried out to solve the problem of uneven hardness. With the increase of the rolling reduction rate, the size of the oxide at the composite interface became smaller. At a reduction rate of 70%, there was no obvious oxide at the interface, and the matrix structure on both sides of the interface was lower bainite. After tempering at 630 ℃ for 3 h and cooling with the furnace, the microstructure on both sides of the interface was relatively uniform, and the oxide size of the composite interface decreased, which was conducive to the improvement of the interface strength. After tempering, the hardness of the blank with the reduction rate at 50% and 70% was between 28HRC-32HRC along the thickness direction, meeting the requirements of the mold industry. After tempering, the z-tensile fracture position of the specimen with the reduction rate at 70% was not at the interface and the neck shrinkage appeared, which was ductile fracture. The tensile strength reached 971 MPa and the elongation reached 22.5%, showing good metallurgical bonding quality. The problems of poor interface strength and toughness and uneven hardness of 3Cr2NiMo steel are solved successfully by the rolling process with 70% reduction rate and the furnace cooling method after tempering at 630 ℃ for 3 h.

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composite process of vacuum rolling / composite interface / hot rolling / reduction rate / microstructure

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KONG Lingyi, LUO Zongan, FENG Yingying, WU Zaoqin. Effect of Rolling and Heat Treatment Process on Mechanical Properties of Extra-thick 3Cr2NiMo Steel Plate[J]. Journal of Netshape Forming Engineering. 2025, 17(7): 52-61 https://doi.org/10.3969/j.issn.1674-6457.2025.07.006

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