近来，由于汽车外壳向整体化发展，因此要求冷轧钢板有更高的深冲性能，为此希望钢水经处理后含碳量在0．0020％水平甚至更低。但通常转炉生产的钢水含碳一般在0．020％～0．050％经过RH真空处理后，含碳可降至小于0．0030％。若要进一步降碳，此时脱碳反应速度显著减慢，所以 Recently, as the car shell to the overall development, thus requiring cold-rolled steel sheet has a higher deep-drawing properties, in the hope that after treatment of molten steel carbon content of 0.0020% level or even lower. However, the converter usually produces carbon steel is generally 0.020% ~ 0.050% After RH vacuum treatment, the carbon content can be reduced to less than 0.0030%. To further reduce carbon, decarbonization reaction rate significantly slowed down at this time, so