Abstract:

The generating reason of the surface soot was analyzed by comparison of carburized and quenched 20CrMnTiH steel workpiece surface states with and without soot. Surface hardness, hardened depth and microstructure of the workpieces with soot were measured. Compared to that without soot, the results show that the hardened depth of the workpiece with soot is a little deeper, the surface hardness is more or less the same, and there are many non-granular carbides near the sharp corner of the soot-containing workpiece surface, and their morphologies are very different, among them the longest rod-like carbide is up to 12 μm in length. The analysis shows that temperature arising and strong carburizing periods too much propane during are the reason of the soot formation.

Key words: carburized and quenched workpiece, soot, 20CrMnTiH steel, carburizing temperature, carbon potential, carbide