LT1350涂层线涂布钢辊疲劳断裂失效机理分析

涂布钢辊在工作中同时承受弯矩、扭矩的作用。钢辊的辊轴零件在较小的交变载荷作用下，过早发生了疲劳断裂失效，其断裂类型为脆性断裂。疲劳断裂的发生是多个因素联合作用的结果，主要因素有：交变循环应力；轴径变化引起轴根部的应力集中；因熔化焊接工艺引起的钢辊焊接头区域微观组织改变；焊缝区的焊接缺陷；焊后表面质量，等。这些因素导致焊缝区及零件表面的缺陷成为疲劳微裂纹萌生的起源，而焊接残余应力的存在使平均应力增大，使焊缝缺陷加快扩展到相邻的轴体内部，导致辊轴过早发生疲劳断裂失效。

Analysis of fatigue fracture failure mechanism of a coatedsteel roller of LT1350 coating line

The coated steel roller is subjected to bending moment and torque during operation. Under the effect of a small alternative load, the roller shaft prematurely experiences fatigue fracture failure, and the fracture mode is brittle fracture. The occurrence of fatigue fracture is a result of combined actions of several factors. The main factors are as follows: alternating cyclic stress; stress concentration at the root of the shaft caused by the change in shaft diameter; the change of microstructure in the welded joint region of steel roller caused by the fusion welding process ; the welding defects in weld joint region;surface state after welding. These factors lead to defects in welded joint region and surface of the components to become the origin of fatigue microcrack initiation. Existence of welding residual stress increases the average stress, which causes the weld defects to accelerate toward the inside of the adjacent shaft body and causes the roller shaft to prematurely experience fatigue fracture failure.