SUS304 is an 18-8 series of austenitic stainless steel, usually used for stamping washer fasteners. Because of its stamping in every part of the material deformation degree of each are not identical, about between 15% ~ 40%, so there are differences in degree of strain hardening material.
 
After cold working, SUS304 stainless steel sheet on the micro slip plane will produce a large number of dislocation and grain boundary, the lattice distortion. The greater the amount of distortion, the dislocation density is higher, the internal stress and the more serious the lattice distortion, the metal deformation resistance and strength and hardness increases with deformation degree, such as plasticity index lower elongation, reduction of area.
 
When work hardening up to a certain degree, if continue to deformation, there is risk of cracking or brittle fracture, its residual stress after forming artifacts caused by explosive rupture extremely easily. Under the effect of environment atmosphere, placed after a period of time, the workpiece will automatically generate intergranular cracking (usually referred to as the "season crack"). So in the process of SUS304 stainless steel stamping, procedures must be carried out between the softening annealing commonly, namely intermediate annealing, to eliminate the residual stress, reduce the hardness, plastic back material, in order to the next processing.
 
304 l is a variation of carbon content lower 304 stainless steel, welding is applied to the occasion. Low carbon content is made in the heat affected zone near the weld in the precipitation of carbide to a minimum, and may result in precipitation of carbide stainless steel intergranular corrosion in some environments (welding erosion). 304 j1 is 304 copper material, mainly used for processing purposes, belongs to the section of nickel series.