抄録
Recently a high pressure and temperature have been used for land and marine turbines. Accordingly Cr-Mo steel castings are used for the turbine castings and their attachments. But cracks that differ from hot tear are often seen in these castings. These cracks are resemble with white spot or hair cracks which occur in the special steel, forgings by their characteristics, that is, their sharp from, aging Phenomenon, and which were affected by the cooling velocity or stress. Cracks which happen in the test piece that is forged and water cooled by 800°C, resemble with the cracks of castings. The cause of these cracks are not clear, but if these cracks are same as white spot, alloy steel castings, especially in large and complex form with high alloy elements, are very dangerous, so that mamufacturing of these castings must be done most cautiously.
