抄録
This experiment was carried out in order to find out conditions for ausforming Mn-Cr-B spring steel. The steel was ausformed in either stable or metastable phase of austenite, and tempered at 480°C for one hour, and then its various properties have been investigated by subjecting the material to tension test, hardness test and optical microscopy. The results obtained are as follows:
(1) The steel, as it is ausformed at 480°∼550°C, increases in yield strength and in tensile strength, but decreases considerably in elongation. In the relationship between tensil strength and elongation the ausformed steel is found second-rate to the steel conventionally treated.
(2) The greater is the improvement that can be attained in hardening steel by raising the temperature in operation, when the process of ausforming it is carried on in the stabe phase of austenite. Though there is but small increase in strength after tempering it, there is scarcely any decrease in elongation. Though the relationship between tensile strength and elongation is nearly equal in both the kinds of steel after their heat treatment, the yield ratio in ausformed steel is higher than that in the steel convetionally treated.
(3) Developing bainite in austenite in the course of ausforming steel has bad effect on elogation of the material, but it scarcely appears that developing pearlite in austenite will anywise affect elongation.
(4) It is recommended that ausforming spring steel will be processed in the stable phase of austenite.
