抄録
Pure Fe-C-Si-Ti alloy(0.1∼0.4% Ti) was melted in an alumina crucible, using a Tamman furnace. Adding 0.001∼0.020% of Te to molten iron at 1380°C, it was cooled in the furnace at a rate of 60°C/min. Relation between thermal analysis curves and microscopic structures was investigated. For subsequent experiment, Fe-C-Si alloys or coke pig irons containing 0.2% Ti were remelted in a graphite crucible in a kriptol furnace. After tellurium addition, molten iron was poured into sand mould to investigate the structure and hardness.
The results obtained are as follows : —
1). Up to a critical amount of tellurium addition, the graphite structure changes from eutectic to coase flaky form. But excess additions produce fine eutectic graphite again.
2). Thermal analysis curves show that tellurium addition of critical amount slightly lessen undercooling in the eutectic solidification.
3). It is suggested that the change in the graphite structure of titanium cast iron by tellurium additon is due to the differences in the growth rates of eutectic austenite and graphite during solidification.
4). The eutectic graphite in coke pig iron containing about 0.2% Ti changed to coase flaky form with addition of 0.003∼0.005% Te, and then it was promoted with the inoculation of ferro-silicon.
5). With excess addition of tellurium, a ferrite matrix was formed around fine graphites in titanium cast iron, and the hardness decreased considerably.
