| 摘要 |
PURPOSE:To easily improve the thermal impact resistance of the nozzle for casting consisting of refractories contg. a specific ratio of carbon contg. graphite by disposing a oxide layer of which carbon is annihilated by oxidation by prescribed amt. more on the inside surface of a nozzle hole at prescribed depth. CONSTITUTION:Sintered alumina powder, electromelted zirconia powder, graphite powder, Si3N4 powder, resin, etc., are mixed and the mixture is subjected to CiP molding to produce the nozzle body 1 consisting of the refractories contg. 5 to 40wt.% graphite-contg. carbon. The outer periphery of the nozzle body 1 is then lathed and after the outer periphery and tuyeres are coated with pyrophyllite and water glass, the nozzle body is subjected to oxidation calcination at a high temp. to provide an oxide layer 3 in which the above-mentioned carbon is annihilated by oxidation by >=10wt.% at 2 to 10mm depth on the inside surface of a nozzle hole 2. The nozzle for casting is thus produced. The formed oxide layer has the rough structure, the low elasticity of modulus and the thermal conductivity lower than the thermal conductivity of the base material. The layer exhibits the effect of absorbing and relieving thermal impact in the initial period of casting. |
