Abstract
The authors studied on the effect of aluminum and nitrogen on the graphitization of fine high-carbon steel. Results obtained were as follows:
(1) The presence of acid soluble aluminum had a promoting effect on graphitization. When the high carbon steel were made from electrolytic iron, the graphitization at 650°C after water quenching from 870°C were very markedly accelerated as the arid-soluble aluminum increased up to 0.04%, and the graphitization after cold drawing from 10φ to 8φ were also accelerated as the acid-soluble aluminum increased up to 0.06%.
(2) The nitrogen in solution calculated from total nitrogen, total aluminum, and solubility product for ALN inhibited the breakdown of cementite to graphite after water-quenching from 870°C.
(3) High-carbon steel made from electrolytic iron had a reduced tendency to graphitization at 650°C after air-cooling from 870°C and furnace-cooling from 770°C compared with after water quenching, but this rate of graphitization increased with acid-soluble aluminum up to 0.08%.
(4) The carbide stable rim was noted when austenitizing was carried out in NaCN-BaCl2 salt, and the rim thickness increased with austenitizing time.
(5) Nitrogen dissolved in aluminum-killed high-carbon steel inhibited graphitization after water-quenching, but nitrogen over 0.03% did not produce inhibiting effect on graphitization after cold drawing.
