レーザー硬化処理における亜共析鋼の組織変化

抄録

The heat-affected-zone microstructure was analyzed both theoretically on S45C carbon steel as an example of hypo-eutectoid steel irradiated with CO₂ laser beams. The affected zone was examined with the Nomarski microscope, SEM, EPMA and micro-hardness tester. The micro-hardness in the hardened layer varies remarkably, depending on carbon contents of the regions. The distribution of carbon contents is subject to the diffusion process of carbon atoms from the prior-pearlite colonies to ferrite phase after Ac₁ transformation. Final microstructure is formed below the Ms point in the rapid cooling period. Experimental results could be explained well with the theoretical thermal history at each part of hardened layers. Microstructural change can be estimated by theoretical analysis on hardening process as well as the shape and size of transverse cross-section of the hardened layers.