钢轨固定闪光焊接头及母材拉伸性能分析

Analysis of Tensile Properties of Stationary Flash Butt Welding Joints and Base Metal for Rails

测试了型式检验不同成套工艺下的钢轨固定闪光焊接头及其母材的拉伸性能,分析了拉伸试样的断裂原因。结果表明:热处理钢轨各部位拉伸强度(Rm和Rp0.2)波动较大,其中轨头最高,但是经过固定焊后的接头各部位拉伸强度趋于一致。钢轨及其固定焊接头的屈强比在0.58~0.63。采用固定焊成型的接头具有优异的拉伸强度,热轧钢轨接头抗拉强度可达到母材的99%~126%,热处理钢轨接头抗拉强度可达到92%~95%。焊后接头的韧性普遍下降明显,接头的断后延伸率(A)占到母材的47%~86%,表明焊接生产工艺尚有优化空间。统计发现,接头拉伸试样一般断在焊缝中心或焊后热处理软化区,如果焊缝没有缺陷,拉伸试样基本都断在软化区,灰斑和MnS夹杂可显著弱化焊缝的拉伸性能。母材的MnS偏析降低了钢轨的焊接性。建议钢厂严格控制钢轨母材轨腰MnS偏析,提高钢轨焊接性;同时建议焊轨厂持续优化生产工艺,减少焊缝灰斑,提高焊接接头的韧塑性。

The tensile properties of stationary welding joints and their base metal for rails under different sets of type inspection processes were tested,and the fracture reasons of the tensile specimens were analyzed.The results show that the tensile strength(Rm and Rp0.2)of each part of the heat treated rail fluctuates greatly,with the rail head being the highest.However,the tensile strength of each part of the joint after stationary welding tends to be consistent.The yield strength ratio of the rail and its stationary welding joint is between 0.58 and 0.63.The joints formed by stationary welding have excellent tensile strength.The tensile strength of hot-rolled rail joints can reach 99%~126%of the base material,and the tensile strength of heat treated rail joints can reach 92%~95%.The toughness of welded joints generally decreases significantly,with the elongation after fracture accounting for 47%to 86%of the base metal,indicating that there is still room for optimization in the welding production process.Through statistics,it is found that joint tensile specimens are generally broken in the center of the weld seam or in the softened zone of post weld heat treatment.If there are no defects in the weld seam,the tensile specimens are mostly broken in the softened zone,gray spots and MnS inclusions can significantly weaken the tensile performance of the weld seam.The MnS segregation of the base material reduces the weldability of the rail.It is recommended that steel mills strictly control the MnS segregation of the rail base material at the waist to improve the weldability of the rail.At the same time,it is recommended that the rail welding factory continuously optimize the production process,reduce gray spots on the weld seam,and improve the plastic toughness of welded joints.