Prospects for the Control of Solidification Structures from the Viewpoints of Weld, Hot-workability and Near Net Shape Casting

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Solidification structures often determine the quality of final products. In this study, three different phenomena related to solidification processing, which are welding, hot-workability and investment casting, have been summarized.With non-filler welding of SUS836L strips by TIG, segregation of welded material deteriorated corrosion resistance at the bead because of lower Cr and Mo concentrations at the dendrite cores. Employing filler material with higher pitting resistance equivalent (PRE) improved this deterioration. Next, it was confirmed that hot-workability of a stainless steel containing 1.1 mass% boron that has eutectic solidification behavior was more excellent with CC slabs than ingots. This reason is attributed to the fact that the eutectoids consisting of austenite and boride with the CC slab are much finer. Cracks at the stem-like corners of investment casts were often found by the magnetic particle testing. It was considered that the cracks were caused with this position being hot spots. The cracking was improved by changing the size of sprues for molten steel not to hit the corners to prevent hot spots.As a summary, for high alloys, solidification process still depends on the way of try and error and experience base. Therefore far more investigations are expected to predict how molten steels solidify avoiding any defects and deterioration of every property.
社団法人日本鉄鋼協会の論文
2008-03-15