Stainless steel components can be divided into three kinds. Namely: 13 chromium stainless steel, 18 chromium stainless steel, 18-8 stainless steel. Figures represent the amount of chromium steels containing chromium and 18-8 represents the mass fraction of 18%, nickel content of 8%. It can be said from front to rear three grades of stainless steel features: cheap, in general, expensive. Their carbon content rarely, only about 0.1%. Their organizational status, the 13 chromium stainless steel is martensitic, 18 chromium stainless steel is ferritic, austenitic stainless steel 18-8. And the stronger the longer it rust resistance. However, according to the intensity, the martensitic highest, followed ferritic, austenitic weakest.

　　The above is a very rough division of stainless steel, an outsider is difficult to distinguish between them. But there is a very simple distinction, 13 chromium stainless steel and 18 chromium stainless steel will be attracted to a magnet, and 18-8 stainless steel does not. However, the types of stainless steel increased to a degree roughly divided laws inapplicable. For example, there may be hardened, can there carburizing and nitriding, there can be a solution treatment, rapid processability and has improved corrosion resistance, heat resistance and weldability, and so on. In order to correspond to such a wide variety of requirements, little by little changing the chemical composition of stainless steel, manufacture stainless steel material having different uses, these numbers are countless lot of material has been standardized, details JIS standards.

　　In JIS, the United States is now in accordance with the standard 3 digits to represent the characteristics of the type of stainless steel. In the machine shop of the most common stainless steel is SUS304, but its original designation is SUS27. Stainless steel is so widely used, in addition to use it to create sheet metal parts, there is now with the bar by cutting parts is also increasing. Stainless steel has good ductility and toughness, but prone to hardening phenomenon. If you call this hardening misunderstood as high hardness, thus cutting back the amount of food and feed, will result in the cutting edge portion has hardened part is easy to damage the cutting tool is reduced when cutting