304 316 stainless steel, which are general type steel, belonging to austenitic stainless steel. It is widely used in the foundry industry. The standard composition of 304 stainless steel is 18% chromium plus 8% nickel. It is non-magnetic. When the impurity content is high, it will occasionally show weak magnetism after processing. This weak magnetism can only be eliminated by heat treatment while the metallographic structure can not be changed by heat treatment.