U75V轨道钢线性摩擦焊工艺研究

目的 提高及改善目前轨道连接与修复的质量。方法 采用线性摩擦焊（LFW）的方法，对高碳轨道钢（U71Mn）在不同参数下进行了焊接试验，并对其微观组织和力学性能进行了表征。结果 焊接参数对接头质量起着决定性的作用。根据焊后接头的微观组织差异，可将其分为4个部分：焊缝中心区（WCZ）、热力影响区（TMAZ）、热影响区（HAZ）和母材（BM）。BM为珠光体和上贝氏体的混合组织，TMAZ由珠光体和少量马氏体组成。在WCZ中，由于受到的热力耦合作用的增强和更高的冷却速率，该区域马氏体含量进一步增加。在拉伸试验中，所有试样均在WCZ处发生断裂，接头的最大抗拉强度达到BM强度的86.6%。此外，WCZ中存在大量马氏体，在增加焊缝显微硬度的同时也降低了焊缝的冲击韧性。结论 采用LFW的方法可以得到焊接质量优良的轨道钢接头。

Linear Friction Welding Process of U75V Rail Steel

In order to improve the connection and repair quality of the rail, linear friction welding (LFW) was used in this study to conduct welding tests on a kind of high carbon rail steel (U71Mn) with different parameters, and the microstructure and mechanical properties of the welded joint were characterized. The experimental results showed that welding parameters played a decisive role in joint quality. According to the microstructure difference of the welded joint, it could be divided into four parts: weld center zone (WCZ), thermo-mechanical affected zone (TMAZ), thermal affected zone (HAZ) and base material (BM). BM was a mixture of pearlite and upper bainite; and TMAZ was composed of pearlite and a small amount of martensite. In WCZ, the martensite content was further increased due to the stronger thermo-mechanical coupling and higher cooling rate. In the tensile test, all samples fractured at WCZ; and the maximum tensile strength of the joint reached 86.6% of BM strength. In addition, there was a large amount of martensite in WCZ, which not only increased the microhardness but also reduced the impact toughness of the weld. Therefore, rail steel joints with good welding quality can be obtained by the LFW method.