| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for preventing transformation crack of a steel material, such as martensitic stainless steel, by carrying out cooling while suppressing the occurrence of martensitic transformation by the use of a low- cost equipment easy in time management without heat-treating the steel material, without the necessity of the preparation of a sand cooling field as well as a heat treatment furnace for prevention of transformation crack during cooling of the steel material after hot working. SOLUTION: After a steel material 4 having a possibility of causing transformation crack during cooling, such as martensitic stainless steel, is hot worked, the hot worked steel material 4 is charged into a heat insulating box 1 in such a way that the volume ratio represented by (total volume of the charged material)/(volume within the heat insulating box 1) becomes >=40%, followed by cooling. Further, cooling is performed while retarding cooling velocity by using the heat insulating box 1 in which the inner wall is covered over with a heat insulating material and increasing the heat insulating effect within the box 1.
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