| 摘要 |
White metal, whilst molten, has incorporated therein a non-metallic substance which has lubricating properties, is solid at the casting temperature, can be reduced to fine particles and has a specific gravity at least twice that of graphite or within the range 70-110 per cent of that of the molten white metal. Such substance may be lead sulphide, tungsten disulphide, silver sulphide, molybdenum sulphide, silver sulphate or lead iodide. The alloy may have a lead, tin or cadmium base, e.g. Sn 90 per cent, Sb 7.5 per cent, Cu 2.5 per cent; Pb 74.5 per cent, Sn 10 per cent, Sb 15 per cent, Cu 0.5 per cent; Sn 69 per cent, Sb 31 per cent; Sn 74.5 per cent, Sb 25.5 per cent. The non-metallic substance may first be mixed with powdered tin or powdered alloy, the mixture pressed into briquette form and the briquette immersed below the surface of the molten alloy and stirred in. |
