Fracture Analysis of Cold-drawing Steel Wires for Spring

The fracture cause of cold-drawing steel wires for spring during the coiling process was analyzed,and the influencing factors of the coiling process were also summarized.The fracture morphology,microstructure and mechanical property of 1Cr18Ni9Ti cold-drawing steel wires were compared and analyzed by scanning electron microscopy (SEM),energy dispersive spectroscopy (EDS),metallographic microscopy,micro-hardness testing and tensile testing.The analysis results indicate that the fracture mode is ductile fracture,the fracture morphology is mostly dimple,and the fracture cause is related to the coiling process of spring wires.The surface mechanical damage of spring steel wires promoted the initiation of the cracks,the nitride aggregation in the microstructure impaired the continuity of the material,and the higher strength lowered the ductility capacity of the material.The above-mentioned defects increased the fracture inclination of the material,exerting unfavorable influence on the spring processing.Therefore,surface defects,microstructure defects and property defects should be avoided to improve the coiling capability of the spring wires.