Effect of quenching and tempering on microstructure and microhardness of 34CrNiMo6 steel forged connecting rods was studied by means of microstructure characterization,microhardness testing and phase diagram calculation.Based on the evolution of microstructure,the change regulation of surface and internal microhardness before and after quenching and tempering of the forged connecting rods was revealed.The results show that the forged connecting rod is composed of pearlite and sorbite,with slight decarburization on the surface.After quenching and tempering,the grain size of the forged connecting rod decreases and its local strain uniformity gets well.There is a non-significant decarburization layer and dispersed carbide particles on the near surface,thus the hardness variation of the near surface is obvious.Although the average micro-hardness after heat treatment is lower than that before heat treatment,the internal microstructure is uniform tempered sorbite,which reduces the dispersion of hardness.
alloy steelforged connecting rodquenching and temperingmicrostructuremicrohardness
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