Research on Heat Treatment Process for Grain Size Improvement of 35CrNi3MoV Steel
35CrNi3MoV is a kind of medium carbon low alloy tempered steel,due to large ingot size,insufficient forging and high forging temperature,it often shows serious problem relates to microstructure heredity.Although application of 990℃high temperature normalizing is able to dissolve the alloy cementite in the 35CrNi3MoV steel,weaken the pinning effect of the alloy cementites which distribute along the acicular orientation of the original coarse acicular bainite and refine the grain,over-high temperature will lead to secondary grain growth and even increase the driving force of grain growth;while isothermal annealing at 600℃is able to form equilibrium structure,the original orientation disappears and the structural dispersion increases,leading to beneficial results for grain refinement.Due to the short holding time,if the temperature selected is inappropriate,there will be a mixture of bainite and pearlite which is unfavorable for subsequent grain size refinement.
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