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A. Addition of methane to the furnace atmosphere reduces decarburising by hydrogen
B. Nitrogen in presence of steam decor-burises high carbon steel, whereas hydrocarbon gases
carburise the surface of steel at annealing temperatures
C. Active nitrogen (formed by cracking ammonia at the metal surface) cause nitride formation
with increase in surface hardness
D. None of these

Correct Answer: None of these

Last Updated: March 11, 2019