18-8系ステンレス鋼の熱損傷による高温特性の変化
1964 年 13 巻 132 号 p. 683-692
詳細
1964 年 13 巻 132 号 p. 683-692
This experiment concerning the changes in mechanical strength at the room and elevated temperatures showed that after inflicting thermal damage, that was, the repeated heating and cooling rapidly on the austenitic stainless steels, the thermal cycles did not always weaken the strength of the materials.
The following results were obtained:
(1) By the damage caused by rapid heating and cooling, what is called“strain enhanced precipitation” occurs with increase of hardness due to the slip for thermal stress. The influence of this damage is more remarkable on the bending fatigue characteristics than on the tensile.
(2) When the accumulative thermal damage is moderate, its strength breeds a negative damage and gains at the room and at the high temperature. When it exceeds a certain value, however, the strength drops due to the growth of precipitation particles. Their effect on the strength is more remarkable at the high temperature than at the room temperature.
(3) The precipitation caused by the thermal damage is different in nature from that of ordinary heating, fine precipitation particles occurring within each grain itself, and increasing their resistance to the dislocation movement. However, the cracks due to the damage become the source of fatigue cracks.
(4) The thermal resistance to the repetition of rapid heating and cooling is greater in the type 304 stainless steel than in the types 321 and 347.
