We applied hot-dip aluminium coating under the following conditions on the mild steel wire (rimmed steel containing 0.07%C) and the steel wire (containing 0.5%C) each cold drawn to 0.5mm diameter and examined the mechanical properties of those aluminium coated wires.
The fluxes utilized in this coating process are ammonium chloride vapour and staurated zinc chroride and amonium chroride (ZnCl
2: NH
4Cl=87:13 by weight) aqueous solution held at 80°C. Thee molten bath of aluminium is maintained at 680, 700, 720 and 750°C, and immersion time in it is 1, 2 and 5 seconds at every temperature.
When a cold drawn steel wire having 162kg/mm
2 tensile strength and 1% elongation (100mm G. L.) is aluminium coated by hot-dip process, the tensile strength decreases to 100, 90 and 87kg/mm
2 at 680, 700 and 730°C of the metal bath temperature respectively, and the elongation increases 5-6%. Accordingly, it is difficult to obtain an aluminium coated high strength steel wire by the hot-dip process.
When a cold drawn mild steel wire having 95kg/mm
2 tensile strength and 1% elongation is coated by the same process, the tensile strength decreases to around 50kg/mm
2, while the hot-dip galvanized same wire has about 80kg/mm
2 tensile strength. But such a hot-dip aluminium coated wire has a little higher tensile strength than that of the same wire only passed through a molten lead bath under the same condition, because the hard and brittle alloy layer is formed on the surface of wire by the hot-dip aluminium coating process. The elongation increases to 10% by coating but this value is only a half of that of the wire passed through the molten lead bath at the same temperature and same speed.
It is desirable to maintain the molten metal bath temperature as low, and the immersion time as short as possible.
抄録全体を表示