The reason of Cr18Ni9Ti existing is due to existence of intergranular corrosion of Stainless steel tube. There was many concurrency major accidents happened because of the high carbon of 304 Stainless Steel in the early stage, especially in the chemical enterprise. It was found that ntergranular corrosion is the main reason through in-depth study.
The main reason of intergranular corrosion is the precipitation of Cr23C6. In order to prevent the precipitation of Cr23C6, there are two ways: one is to reduce the C content; the other one is to let the C forming other compounds. Because in the smelting level at that time is not fundamentally reduced to below 0.08%, so people take Ti into 18-8 steel to solve the problem of intergranular corrosion， because in stainless steel Ti and C can form TiC can effectively prevent the precipitation of Cr23C6， this leads to what we often call 1Cr18Ni9Ti. In the late last century because smelting technology continues to improve, to produce low carbon and ultra low carbon stainless steel (such as 0Cr18Ni9 304 and 1Cr18Ni9Ti will be replaced, now in foreign countries while retaining its brand, but its proportion is very small, but in the country due to the popularity of stainless steel, in the state-owned enterprises and other places or arsenal in the use of 1Cr18Ni9Ti material, the proportion is reduced year by year.