非磁性鋼の冷間加工硬化特性について
タービン発電機用非磁性鋼の研究-I
1964 年 50 巻 1 号 p. 37-42
詳細
1964 年 50 巻 1 号 p. 37-42
Influences of various factors such as solution treatment, cold work and stress relief on flow stress, cold work hardening characteristics and mechanical properties were tesed with the austenitic cold work hardening steels, 8Mn-8Ni-4Cr, 18Mn-4Cr, and 14Mn-6Ni-4Cr, which have been most widely utilized for non-magnetic retaining ring of turbo-generator.After tensile cold working up to 30% redaction of area at various temperatures from 20°C to 500°C tensile properties were studied at room temperature.The results obtained are as follws.
1) At the cold working temperature between 300°C and 500°C 8Mn-8Ni-4Cr showed the highest flow stress and 18Mn-4Cr the lowest, but at room temperature 18Mn-4Cr showed the highest flow stress on the contrary.
2) The investigation of the influence of cooling rate on the mechanical properties of the specimen with a 30mm squre bar cooled from solution temperature revealed that there was no difference between air cooling and water quenching with all of the specimens, except with the steel 18Mn-4Cr cold-worked at a relatively lower temperature, which showed better properties after water quenching.
3) As the result of changing the cold working temperature, tensile and proof strength were increased and elongation and reduction of area were decreased with increasing working temperature for 8Mn-8Ni-4Cr and 14Mn-6Ni-4Cr, but for 18Mn-4Cr, tensile and proof strength were the highest when the specimen was cold worked at room temperature.Therefore cold work hardening was the most remarkable for 8Mn-8Ni-4Cr at the temperatures between 300°C and 500°C and for 18Mn-4Cr at the room temperature.
4) Influence of stress relieving temperature on the mechanical properties of these specimens after cold working at 400°C and 500°C was studied.There was no changes of the mechanical properties when stress relieved at the temperature below cold working temperature, but when stress relieved above cold working temperature, proof strength, elongation and reduction of area were all decreased and especially when relieving at 600°C remarkable brittleness was caused because of carbide precipitation at grain boundary.
