Abstract
The influences of added C, Mo, and N contents on precipitation hardening were investi-gated. There were 23 kinds of samples with varying chemical composition of C, Mo, and N. For the purpose of studying the influence of varied contents of added elements on precipitation hardening, 13 group were made by various combinations of all samples. After hot forging to bars, all samples were solution treated at 1200°C for 1 hour. Then, they were aged at 800°C up to 150 hours. Hardening was measured by hardness at 1, 3, 15, 30, 50, 75, 100, and 150 hours. And, the microstructure of such aged samples was also observed.
It was concluded from this experiments as follows;
(1) Carbon contents had more remarkable influences on precipitation hardening than Mo or N contents. If the carbon contents increased, hardness was raised and phenomena of double peaks on hardening process became more evident.
(2) Although influence of Mo contents was not found immediately after solution treatment, more Mo meant more hardening when it was aged at 800°C. If Mo content was much less than 6%, softening was indicated after 150 hours aging at 800°C.
(3) In the experiment of Reports (IX), the influence of N content on precipitation hardening was not apparent. This was already investigated in Reports (V) in much more details.
