| 摘要 |
Prodn. of a filling bush for a pressure die casting machine involves lining the melt-contacting inside of a hollow steel cylinder with an at least 0.2 mm. thick W-contg. or ceramic protective layer by powder metallurgical hot isostatic pressing. Alternatively, the entire filling bush is sintered by hot isostatic pressing of a metal powder, of compsn. 30-60% W, 0.5-5% Co, 0.2-20% Mo, 10-20% Cr, 2-10% V, less than 2.5% C and balance Fe, in a cylindrical metal die. The lining is pref. about 2mm thick and may consist of (i) an alloy of compsn. 80-99.5 wt.% W, 0.5-5 wt.% Co, 0.01-20 wt.% Mo and less than 2.5 wt.% C, (ii) an alloy of compsn. 30-60 wt.% W, 0.5-5 wt.% Co, 0.2-20 wt.% Mo, 10-20% Cr, 2-10 wt.% V, less than 2.5 wt.% C and balance Fe; or (iii) a ceramic selected from SiAlON, AlN, AlON or Al2TiO5. The lining or bush is pref. hot isostatically pressed at at least 10 (pref. 100) MPa and at least 1200 (pref. 1300) deg. C. The total prodn. cycle time is about 9 hrs. the sintering time being 3 hrs.. ADVANTAGE - The filling bush has long term resistance to attack by molten Al or Zn and the lining is resistant to exfoliation.
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