Round steel is no longer specially heat treated after hot rolling or forging, and is directly delivered after cooling, which is called hot rolling state or hot forging state.
The termination temperature of hot rolling (forging) is generally 800 to 900 ° C, and then generally is naturally cooled in the air, so that the hot rolling (forging) state is equivalent to normalizing treatment. The difference is because the hot rolling (forging) termination temperature is high or low, unlike the normalizing heating temperature, the fluctuation of the microstructure and properties of the steel is larger than the normalizing. At present, many steel companies adopt controlled rolling. Since the final rolling temperature control is very strict and forced cooling measures are taken after the final rolling, the grain of the steel is refined, and the delivered steel has a high comprehensive mechanical property. This is the reason why the non-twist-controlled cold-rolled wire rod is superior to the ordinary hot-rolled wire rod.
The seamless steel pipe delivered in hot-rolled (forged) condition has a certain corrosion resistance due to the surface covered with a scale of iron oxide. The requirements for storage and transportation are not as strict as the seamless steel pipe delivered in the cold-rolled (rolled) state. Large and medium-sized steel and medium-thick steel plates can be stored in open storage yards or after being covered.
