鋼材再現溶接熱影響部の変態挙動におよぼす成分元素の影響(第 3 報) : 溶接用 SH-CCT 図におよぼす Mo の影響

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The effect of Mo on transformation behaviour in synthetic weld heat-affected zone of steel was investigated using simplified steels made of pure metals and graphite. Mo element displaced the SH-CCT diagram for ferrite and pearlite transformation regions to a longer time, and extended Zwischenstufengefuge (Zw) transformation region to a longer time. Each critical cooling time Cf', Cp' and Ce' increased with Mo content. Morphologies of ferrite, pearlite and Zw were strongly influenced by Mo. In the region of longer cooling time (cooling time from A_3 to 500℃; above 60sec), the growth of massive ferrite and ferrite sawteeth were controlled by the addition of Mo, and fine colony pearlite formed between both ferrite sideplates or both rodlike ferrites precipitated more easily than lamellar or degenerate pearlite. In the case of middle and shorter colling time (cooling time; under 60sec), ferrite sideplate and rodlike ferrite or needlelike ferrite were more liable to develop than massive ferrite and ferrite sawteeth, and fine colony pearlite formed more easily than other pearlite. Zw accompanied with fine carbide precipitated easily in this region of cooling time. Mo element rasied the hardenability curves in synthetic weld heat-affected zone of steels. It seemed that the hardness is influenced considerably by the morphological change of ferrite. The effect of Mo on the hardness of martensite was a little.
1975-03-05