Study on Microstructure and Mechanical Properties of G20Mn5 Cast Steel Joints by MAG Repair Welding

SUN Jia; LIANG Juxing; MA Chuanping; ZHANG Zhenlin

doi:10.7512/j.issn.1001-2303.2024.06.11

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Study on Microstructure and Mechanical Properties of G20Mn5 Cast Steel Joints by MAG Repair Welding
Vol. 54, Issue 6, Pages: 66-73(2024)
Published： 25 June 2024 ，
DOI： 10.7512/j.issn.1001-2303.2024.06.11
稿件说明：

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孙佳，梁炬星，马传平，等.G20Mn5铸钢件MAG焊焊补接头组织与力学性能研究［J］.电焊机，2024，54（6）：66-73.

SUN Jia, LIANG Juxing, MA Chuanping, et al.Study on Microstructure and Mechanical Properties of G20Mn5 Cast Steel Joints by MAG Repair Welding[J].Electric Welding Machine, 2024, 54(6): 66-73.
孙佳，梁炬星，马传平，等.G20Mn5铸钢件MAG焊焊补接头组织与力学性能研究［J］.电焊机，2024，54（6）：66-73. DOI： 10.7512/j.issn.1001-2303.2024.06.11.

SUN Jia, LIANG Juxing, MA Chuanping, et al.Study on Microstructure and Mechanical Properties of G20Mn5 Cast Steel Joints by MAG Repair Welding[J].Electric Welding Machine, 2024, 54(6): 66-73. DOI： 10.7512/j.issn.1001-2303.2024.06.11.

摘要

为研究G20Mn5铸钢件最优的焊补工艺，以提高铸钢件质量和降低生产成本。对G20Mn5铸钢件进行MAG焊焊补，比较了5种焊补工艺（包括焊前预热、焊后保温、热处理等条件）的接头显微组织和力学性能。试验结果显示，所有焊补工艺接头的焊缝区和热影响区粗晶区均未出现淬硬的马氏体组织和粗大的魏氏组织；焊补接头的抗拉强度均超过480 MPa，断后伸长率均大于20%，硬度峰值均低于250 HV，焊缝和热影响区的冲击功值均大于母材；各焊补接头的拉伸试样和疲劳试样均断裂于母材，疲劳裂纹源为铸钢件内部的显微缩松缺陷。试验证明，5种工艺焊补接头的显微组织和力学性能均满足使用要求，综合考虑各方面因素，焊补前不预热+焊补后覆盖保温缓冷+不热处理为最优焊补工艺。

Abstract

To investigate the microstructure and mechanical properties of the welded joints of G20Mn5 cast steel for determining the optimal welding repair process

enhancing the quality of cast steel parts

and reducing production costs

G20Mn5 cast steel parts were welded using the MAG welding method. Five different welding repair processes (including preheating before welding

post-weld heat preservation

and heat treatment conditions) were compared for the mechanical properties of the joints. The test results showed that none of the welded joints exhibited hardened martensitic structures or coarse Widmanstätten structures in the weld zone and the coarse grain area of the heat-affected zone; the tensile strength of all welded joints exceeded 480 MPa

the elongation after fracture was greater than 20%

the peak hardness was below 250 HV

and the impact energy of the weld zone and heat-affected zone was greater than that of the base material; the tensile and fatigue samples of each welded joint all fractured in the base material

with the fatigue crack source being the micro-shrinkage porosity defect inside the cast steel part. The tests have proven that the microstructure and mechanical properties of the welded joints of the five processes meet the requirements for use. Considering all factors

the optimal welding repair process is "no preheating before welding

post-weld covering for heat preservation and slow cooling

and no heat treatment."

关键词

G20Mn5铸钢焊补热处理显微组织力学性能

Keywords

G20Mn5 cast steelwelding repairheat treatmentmicrostructuremechanical properties

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