Hot Rolling Treatment and Cold Stretching Treatment

　　After hot rolling or casting, the steel is no longer specialized for heat treatment and deliver directly after cooling, that is called hot rolling treatment. The terminal temperature of hot rolled is generally 800 to 900 degrees Celsius. After that, steel is generally cooling in the air, thus the state is equivalent to normalizing treatment. Due to the terminal temperature is high or low, different from normalizing heating temperature controlled strictly, The fluctuation of steel with hot rolling is greater than normalizing treatment on structure and properties.

　　The surface of steel with hot rolling is covered with a layer of iron oxide, which has a certain corrosion resistance. Therefore, requirements of storage and transportation is less strict than that of cold stretching and large and medium steel plate can be stored in the open yard.

　　Hot rolling treatment and cold stretching treatment

　　The steel, which is through cold stretching, without any heat treatment and direct delivery, is known as cold stretching. Compared with the state of hot rolled, cold stretching steel has high precision, good surface quality and higher mechanical properties. Due to the surface of steel with cold stretching is without oxide layer covered, and there are a lot of internal stress, it is extremely easy to suffer corrosion or rust. As a result, the packaging and storage of steel with cold stretching have strict requirements. It’s generally to be kept in the warehouse and the warehouse temperature and humidity should be pay attention.