1. Hot rolled state
After the steel is hot-rolled or forged, no special heat treatment is required, and it is delivered directly after cooling. It is called hot-rolled or hot-forged state. The termination temperature of hot-rolling (forging) is generally 800～900℃, and then it is generally natural cooling in the air, so the hot-rolled (forged) state is equivalent to normalizing treatment. The steel delivered in the hot-rolled (forged) state has a certain degree of corrosion resistance because the surface is covered with a layer of oxide scale. The storage, transportation and storage requirements are not as strict as the steel delivered in the cold-drawn (rolled) state. Large and medium-sized steel , Medium and thick steel plates can be stored in the open yard or after being covered.
2. Cold drawn (rolled) state
The state of cold-drawn or cold-rolled steel that is directly delivered without any heat treatment is called cold-drawn or cold-rolled state. Compared with the hot-rolled (forged) state, the steel in the cold-drawn (rolled) state has high dimensional accuracy, good surface quality, low surface roughness, and higher mechanical properties. The packaging, storage and transportation of cold drawn (rolled) steel have strict requirements, and generally need to be kept in a warehouse and should pay attention to the temperature and humidity control in the warehouse.
3. Normalizing state
The steel is normalized and heat treated before leaving the factory, and this delivery state is called normalized state. Since the normalizing heating temperature is more strictly controlled than the hot rolling termination temperature, the structure and properties of the steel are uniform. Compared with the annealed steel, due to the faster normalizing cooling rate, the number of pearlite in the steel structure increases, the pearlite layer and the steel grain are refined, so it has higher comprehensive mechanical properties and is beneficial to improvement The widmanstatten structure of low carbon steel and the cementite network of hypereutectoid steel can prepare the structure for further heat treatment of the finished product. Carbon steel and composite steel are often delivered in a normalized state.
