Distortion in case hardened JIS-SCM420 specimenswas investigated with relation to the shape of continuous castingmolds. Hot rolled bars made from two cast blocks, where one ofthe blocks has round section (Steel A) and the other hasrectangular section (Steel B), were prepared. Macro-etched patternin a cross section of the bars has round shape for Steel A andrectangular shape for Steel B, respectively.After carburized, ring specimens produced from Steel B weredistorted to an oval shape, whose line on upside was correspondentto the longitudinal direction of the rectangular macro-etchedpattern. On the other hand, the ring specimens of Steel A did notshow conspicuous change in shape. It was also confirmed that theshape change in gears of Steel A was smaller than that of Steel B.Furthermore, it was found that the specimens cut from theinner part of the macro-etched pattern expanded less than ones cutfrom the outer. And a FEM analysis was carried out to check thedistortion in mesh models that consisted of a round or rectangulararea surrounded by an area with higher expansion coefficient. Thecalculated shape changes were consistent with the shape changeobserved in ring specimens and gears.
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