Large-diameter seamless steel pipe steel is no longer specially heat treated after hot rolling or forging, and is delivered directly after cooling, called hot rolling or hot forging state, the termination temperature of hot rolling (forging) is generally 800 ~ 900 °C, and then generally cooled naturally in the air, so 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 control is strict, so the fluctuation of steel structure and properties is greater than that of normalizing. Many steel enterprises use controlled rolling, because the final rolling temperature control is very strict, and after the final rolling to take forced cooling measures, so the grain of steel is refined, the delivered steel has high comprehensive mechanical properties. Non-torsional control cold and hot rolled wire rod performance is superior to ordinary hot ro…