Protective gas used in the annealing furnace for steel coil comprises of__________________?
A. 95% N2 + 5% H2
B. 5% H2 + 9% N2
C. 100% CO
D. 100% H2
A. 95% N2 + 5% H2
B. 5% H2 + 9% N2
C. 100% CO
D. 100% H2