Research On Martensite Transformation Mechanism And Performance Evolution Of 304H Stainless Steel Wire During Cold Drawing

304H austenitic stainless steel wire has the characteristics of good corrosion resistance and excellent mechanical properties,so which has a wide range of applications in the fields of road and bridge steel cables,automobile beads,and precision instruments.In order to meet the requirements of size and strength,stainless steel wire rods are usually applied with a reduction rate of more than 80%.The drawing process is easy to cause the transformation of austenite to martensite,which causes the steel wire to have magnetism.This paper uses tensile testing machine,Vickers hardness tester,OM,SEM,TEM,AFM,finite element simulation and other methods to analyze the mechanical properties,magnetic properties and microstructure evolution laws of steel wires under different pass cross section reducing ratio configuration,and studied the internal relationship between structure evolution and performance changes;the mechanism of martensite transformation was discussed,and the relationship between pass reduction ratio configuration and steel wire properties was explored,and the following main conclusions were(1)Under different pass cross section reducing ratio,the strength and hardness of the drawing process continue to increase with the increase of strain.When the true strain is less than 1.24,the plasticity and torsion properties decrease with the increase of strain.When the true strain is greater than 1.24,due to the effect of grain refinement Reinforced,plasticity and torsion properties are improved.(2)When the total strain is the same,the pass cross section reducing ratio configuration has almost no effect on the final mechanical properties of the steel wire,but it has a significant effect on the magnetic properties;the large reduction area ratio is the first,the steel wire has the strongest magnetism,and the pass cross section reducing ratio configuration is uniform.The magnetism of the steel wire is second,and the surface reduction rate is the second,and the magnetism of the steel wire is the weakest.(3)During the drawing process,as the strain increases,the saturation magnetization(Msa)of drawn austenitic stainless steel wire has a linear relationship with the martensite content(f M).The empirical formula is Msa=99f M-2.9.The martensite content in the steel can be known by measuring the saturation magnetization of the stainless steel.(4)When the strain is small,the martensite nucleates on the shear band and takes the shape of a short rod.When the strain increases,the slip system is activated in a large amount,and the parallel shear bands merge to form a thick slip step.The body gradually grows along the thick slip zone to form striped martensite;during the drawing process,the shear bands in the core of the steel wire are denser,and the texture of the core is favorable for martensite transformation {111}//ND,{110}//ND content is more than the edge,which is conducive to the nucleation of martensite;and the temperature of the core is lower and the strain is large,which is conducive to the growth of martensite,so the martensite content in the core of the steel wire is high.