The effect of protective gas on annealing of 42CrMo4 steel pipes

Ln this work the effect of protective gas on annealing of cold-rolled 42CrM o4 steel pipes was analysed. The production of protective gas (CO2-CO-H-2-N -2 mixture) and the annealing of pipes at the different temperatures are di scussed. By annealing of pipes in industrial conditions at 920 degreesC a b right steel surface was obtained. Decarburixation of pipes at depth of 0.09 -0.12 mm was observed. However, annealing the pipes at 700 degreesC the dec arburization did not occur. The process of decarburization is explained by means of diffusion of carbon and surface reactions of solid solution of car bon in austenite and some components of protective gas.