A SPECIAL AGING PHENOMENON IN ALLOY STEEL.

Abstract

The elongation and reduction of area of the tensile specimen newly taken from a considerably large alloy steel forging may increase strikingly according as the specimen is tested after few days, with no change in the tensile strength but a remarkable alteration of the fracture. The author studied on this special aging phenomenon and obtained the following results:
(1) This aging phenomenon appears clearly in tension test and less in impact test. (2) Heating the specimen, even at 100°C., remarkable effect is produced. (3) With the increasing cross-section of specimen, it is found necessary to apply a longer time, proportional to crossectional area, to eliminate the aging phenomenon perfectly. (4) The elongation and reduction of area of the steel in cast condition are raised and almost attained the values for the forged condition provided that the time and temperature of heating are sufficient. (5) This aging phenomenon appears conspicuously in the steel forging with flakes. (6) Before and after aging of the specimen, there is considerable difference in hydrogen content. (7) By heating the aged specimen in hydrogen gas for 1 hour at 500°C., the mechanical properties, the hydrogen content and the apperance of the fracture of specimen are returned to their original states.