| 摘要 |
PROBLEM TO BE SOLVED: To eliminate an annealing treating stage for softening by cooling a steel contg. a specified ratio of C at a specified cooling rate in the magnetic field with a specified magnetic field gradient in succession to hot working. SOLUTION: As for the compsn. of a steel to form into a stock, the content of C is regulated to <=0.8 mass %, and, as the suitable one from the viewpoint of the subsequent secondary working, a low caron low alloy steel for structural purpose or the like can be given. At the time of cooling this steel in succession to hot rolling, it is cooled at a cooling rate of <=10 deg.C/sec while being applied with the magnetic field. Thus,γ-αtransformation is promoted to remarkably increase the amt. of ferrite to be generated, by which the elimination of a softening treating stage is made possible. But, in this case, the presence of a magnetic field gradient of 0.1 to 10 T/cm by absolute value is essential, and such effect is not recognized in the uniform magnetic field. Moreover, the magnetic field to be applied in the process of the cooling is preferably regulated to 1 to 40 T by magnetic flux density.
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