There are many kinds of alloy steel, usually according to the content of alloy elements into low alloy steel (content <5%), medium alloy steel (content 5% ~ 10%), high alloy steel (content >10%); According to the quality is divided into high quality alloy steel, special alloy steel; According to their characteristics and uses, they can be divided into alloy structural steels, stainless steels, acid-resistant steels, wear-resistant steels, heat-resistant steels, alloy tool steels, rolling bearing steels, alloy spring steels and special performance steels (such as soft magnetic steels, permanent magnetic steels, non-magnetic steels), etc. In addition to iron, carbon and a small amount of inevitable silicon, manganese, phosphorus, sulfur elements in steel, also contains a certain amount of alloying elements, the alloying elements in steel are silicon, manganese, molybdenum, nickel, chromium, alum, titanium, niobium, boron, lead, rare earth and so on one or several of them,…