The normal steel grade in this period is carbon structure steel, steel grade code Q235B (Q345B Q345R etc.) in GB standard of China, the relevant international steel grade code is SS400 S235JR St37-2 etc. The regular size of the slab is 200/250*1600* (5000-8000) mm. The regular size of the billet is 130*130/150*150*(8000-12000) mm.