船用钢丝绳断裂失效分析

Fracture Failure Analysis of Marine Steel Wire Rope

目的了解某船用ϕ76 mm锚泊定位镀锌钢丝绳累计使用寿命较短、多处出现单丝断裂现象的原因。方法采用宏观分析、硬度测试、力学性能试验、断口分析、化学成分分析、扫描电镜显微组织观察等方法对该钢丝绳的断裂原因进行分析。结果拉伸试验断口为杯锥状断口,其放射区面积较纤维区更大,表明材料塑性差,硬脆性大,断口中包含有夹杂,这些因素会导致钢丝发生断裂;试样心部的显微硬度最高,钢丝断裂是从钢丝心部开始产生之后,裂纹向四周开始扩散直至整根钢丝断裂,纤维区硬脆性最大,断裂源位于纤维区。结论钢丝绳断裂为韧性断裂。实际工况下,钢丝绳断口为劈裂状断口,符合韧性断裂的滑移分离特征,其主要原因是钢丝的屈服强度不能适应工作应力要求从而发生断裂。观察断口发现,断口的放射区面积占比较大,纤维区面积占比小,表明材料塑性差,硬脆性大,断口中包含夹杂,钢丝绳易在此处发生断裂。试样心部的显微硬度最高,距离心部越远,显微硬度越低,可知钢丝绳断裂源是由心部产生的,断裂源位于纤维区。

The work aims to clarify the reasons why the accumulated service life ofϕ76 mm galvanized steel wire rope for ship anchorage position is short and single wire fracture occurs in many places.Macro analysis,hardness test,mechanical property test,fracture analysis,chemical composition analysis and microstructure observation by scanning electron microscope were used to analyze the fracture reason of the steel wire rope.The fracture face in tensile test was in cup-cone form and its radiation area was larger than the fiber area,indicating that the material had poor plasticity and high hardness and brittleness,and the fracture contained inclusions.Therefore,the wire fracture occurred.The core of the sample had the highest microhardness.The fracture of wire started at its center and then the crack spread all the way around until the whole wire broke.The fiber area had the greatest hard brittleness,and the source of fracture was located in the fiber area.The fracture of steel wire rope is ductile fracture.In actual working conditions,the fracture of steel wire rope is in split fracture form,which is consistent with the characteristics of slip separation of ductile fracture.Its main reason is that the yield strength of steel wire rope cannot meet the requirements of working stress and thus fracture occurs.By observing the fracture,it is found that the radiation area of the fracture accounts for a large proportion,while the fiber area accounts for a small proportion,indicating that the material has poor plasticity and high hardness and brittleness and the fracture contains inclusions.Therefore,the steel wire rope is prone to fracture here.The microhardness of the core of the sample is the highest.The farther away from the core is,the lower the microhardness is.It is concluded that the fracture source of the steel wire rope is generated from the core,and the fracture source is located in the fiber area.