| 摘要 |
<p>1409794 Graphite compositions HOWMET CORP 6 Sept 1972 [17 Sept 1971] 41393/72 Heading C1A [Also in Division C3] A core for use in the casting of metals is formed by moulding a composition containing graphite, a polysiloxane and a catalyst for curing the polysiloxane to a pre-formed core configuration, curing, baking and firing the pre-formedcored configuration to convert the polysiloxane to a siliceous material to bond the filler together and define a dimensionally stable core. Suitable catalysts include zinc acetate, lead stearate, lead 2-ethylhexoate, calcium stearate, dibutyl triacetate, stannous octoate, lead oxide, zinc oxide, benzyltrimethyl ammonium 2-ethyl hexoate, tetramethyl ammonium acetate and benzoyl peroxide. In the specific Examples 9 and 10 where graphite is used it may be all of size -200 mesh (Tyler) or a mixture of -200 mesh (Tyler) flour and 30-100 mesh (Tyler) particles. The composition is formed into the desired core shapes and heated, suitably at 100‹ F. per hour to 1200‹ F., which temperature may be maintained for 4 hours; thereafter the core is heated at 100‹ F. per hour until the core reaches 2050‹ F. and is held at this temperature to complete the baking and firing cycle and convert the polysiloxane to a siliceous material to bond the ceramic filler particles together.</p> |
