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针对秦沈线17处钢轨闪光焊焊接接头轨面产生的横向裂纹,通过在伤损部位取样,分别进行洛氏硬度、金相组织和显微硬度等试验,结合焊轨生产的实际,分析裂纹形成原因。认为所检闪光焊焊接接头的裂纹起源于钢轨表面的白亮层马氏体组织,并在外力作用下扩展进入正常的珠光体组织区域,裂纹深度达到5mm。研究钢轨精磨方式与焊缝凸起之间的关系,得出:对矫直后具有明显焊缝凸起的焊接接头进行精磨时有可能因打磨中进刀量过大,引起钢轨局部机械热损伤,造成局部金属的急速高温和急速冷却,形成高硬度的脆性白亮层马氏体组织,是导致焊接接头轨面产生裂纹的根本原因。建议进一步研究钢轨焊接生产打磨工艺规范以及客运专线铁路钢轨的预打磨规范,避免钢轨及焊接接头出现马氏体组织。
Aiming at the transverse cracks produced on the rail surface of 17 joints welded by rail flashover in Qin Shen Line, the Rockwell hardness, microstructure and microhardness were sampled from the damaged parts, and the crack was analyzed based on the actual production Formed reason. It is considered that the crack in the welded joint of flashlight welding originates from the white-bright martensite on the rail surface and expands into the normal pearlite region under the action of external force, and the crack depth reaches 5mm. Studied the relationship between the rail refining method and the weld bump, and concluded that it is possible that when the welded joint with obvious weld protrusion after straightening is refined, the amount of feed in the grinding process may be too large, Thermal damage, resulting in rapid local high temperature metal and rapid cooling, the formation of high hardness of brittle white bright-layer martensite, welded joints is the leading cause of cracks in the rail surface. It is suggested to further study the grinding process specification for rail welding production and the pre-grinding specification for railway rails on passenger dedicated lines so as to avoid the occurrence of martensite in the rails and welded joints.