PURPOSE: To control the quality of a steel material after brazing so as to optimize the same by connecting a metallographic change in structure in the cooling process after the brazing in the furnace quantitatively to chemical components and cooling conditions which are control means thereof.
CONSTITUTION: A model for calculating quantitative ratios of various phase such as ferrite, pearlite, bainite and the like at various temps. in the cooling process in the heat treatment process in the stage of brazing of steel materials in a furnace is made. The cooling curve and chemical components of steel materials by which intended quality is obtained are set by the model which expresses quality with the above-described model and the quantitative ratios of the above- described respective phases transformed at the respective temps. as main parameters in combination with other supplementary parameters. In accordance with the set conditions, the cooling rate is controlled or chemical components are controlled so as to obtain the target quality. The use of an isothermal transformation curve expressing the quantitative ratios of the respective phases in the cooling process quantitatively is convenient in calculating said ratios.
SAKAMOTO YOSHIO
NISHIDA MINORU
