We should first understand some basic knowledge about moulds, which is the classification of moulds. According to the classification, moulds are generally divided into hot work moulds, cold work moulds and plastic moulds. In addition, it can also be classified according to the service life: Grade 1: more than 1 million times; Grade 2: 500,000-000,000 times; Grade 3: 300,000-~500,000 times; Grade 4: 100,000-300,000 times; Grade 5: less than 100,000 times; Form 1 and 2 require mold steel can be heat treated, hardness in about 50 HRC, otherwise it is more likely to wear. So the choice of steel should have both good heat treatment performance and high hardness. Domestic mold steel manufacturers, more grades, grades are more confusing, can not be used as a reference for comparative studies, the following materials are imported materials. Since the reform and opening up, China has produced a large number of industrial molds, when the mold technology import countries are mainly Japan, Europe and the United States, Hong Kong and Taiwan, Hong Kong usually use European and American technology and materials, while Taiwan is using Japanese materials and technology.