At present China's large diameter seamless steel pipe, the main production process is hot-rolled and heat expansion of large-diameter seamless steel pipe, hot expanded seamless steel pipe specifications for 325mm-1220mm maximum thickest of 120mm, can produce seamless steel pipe thermal expansion Non-national standard dimensions, thermal expansion seamless is what we often say that thermal expansion, density is relatively low but strong contraction rolled steel with oblique method or drawing method to expand a shortage of pipe diameter pipe finishing processes. In a short period of time for the steel thickening to produce non-standard and special types of seamless pipe, and low cost, high production efficiency, the development trend of international rolling fields today.
Large diameter seamless steel pipe by cold drawing, cold-rolled steel products, such as cold forming, heat treatment and without any direct delivery of state called cold-drawn or cold-rolled condition. Compared with hot-rolled (forging) state, high dimensional accuracy cold-drawn steel (rolled) state, good surface quality, low surface roughness, and a high mechanical properties, due to the cold drawn (rolled) steel delivery status oxide surface is not covered, and there is a lot of stress, vulnerable to corrosion or rust, and thus steel cold drawn (rolled) state, its packaging, storage requirements are more stringent, generally need to be kept in the warehouse, and should pay attention to the temperature and humidity control coffers.
