Study on microstructure and mechanical properties of continuous drive friction-welded joints of bainitic rail steel

IF 2.4 4区材料科学 Q2 METALLURGY & METALLURGICAL ENGINEERING

Welding in the World Pub Date : 2024-05-01 DOI:10.1007/s40194-024-01780-y

Jiaqi Xie, Han Zhang, Chang’an Li, Zhiming Zhu

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Abstract

The U20Mn bainitic rail steel rods with a diameter of 15mm were joined by continuous drive friction welding (CDFW) below the A₁ temperature. The microstructure characteristics of the welded joints without post weld heat treatment (PWHT) were investigated by metallographic observation, scanning electron microscope investigation, and electron backscattered diffraction analysis. Their mechanical properties were evaluated through hardness, tensile, and impact tests. The results show that the welded joints are well-formed without metallurgical defects. They manifest a dense martensitic-bainitic composite phase structure with good mechanical properties attributed to fine-grain and second-phase strengthening effects. The maximum impact energy is 29.2J, with peak hardness increasing to about 124% compared to the base material (BM). Tensile strength reaches 1267±15.1 MPa (102% of BM), and elongation reaches 13.8±0.2% (97% of BM), realizing quasi-equal strength and toughness matching with the BM. These findings provide a basis for the realization of friction welding for bainitic steel rails and the future development of novel rail welding techniques and equipment.

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贝氏体钢轨连续驱动摩擦焊接接头的微观结构和机械性能研究

直径为 15 毫米的 U20Mn 贝氏体钢轨钢棒采用低于 A1 温度的连续驱动摩擦焊（CDFW）进行焊接。通过金相观察、扫描电子显微镜检查和电子反向散射衍射分析，研究了未进行焊后热处理（PWHT）的焊接接头的微观结构特征。通过硬度、拉伸和冲击试验对其机械性能进行了评估。结果表明，焊接接头成形良好，无冶金缺陷。它们表现出致密的马氏体-贝氏体复合相结构，具有良好的机械性能，这归功于细晶粒和第二相强化效应。与基体材料（BM）相比，最大冲击能量为 29.2J，峰值硬度提高了约 124%。拉伸强度达到 1267±15.1 MPa（BM 的 102%），伸长率达到 13.8±0.2%（BM 的 97%），实现了与 BM 的准等强度和韧性匹配。这些发现为实现贝氏体钢轨的摩擦焊接以及未来新型钢轨焊接技术和设备的开发提供了依据。

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来源期刊

Welding in the World METALLURGY & METALLURGICAL ENGINEERING-

CiteScore

4.20

自引率

14.30%

发文量

181

审稿时长

6-12 weeks

期刊介绍： The journal Welding in the World publishes authoritative papers on every aspect of materials joining, including welding, brazing, soldering, cutting, thermal spraying and allied joining and fabrication techniques.