| 摘要 |
1,269,150. Coating with metals. BRITISH STEEL CORP. Sept. 21, 1970 [Oct. 9, 1969], No.49614/69. Heading C7F. The spot-welding characteristics of a ferrous substrate are improved by hot-dip coating it and directing particles of metallic iron or iron-based alloy on to the coating before it solidifies, so that they are retained at or near the surface of the coating during solidification. The substrate may be a ferrous strip, e.g. of low alloy steel containing Cu and Cr, subjected to a grease burn at about 400‹ C., subjected to a reducing atmosphere at about 700‹ C., and then continuously moved through the hot-dip bath, excess molten coating being removed by a pair of rolls or a controlled air-blast. The coating metal may be zinc, aluminium, or an alloy thereof, e.g. Zn-Al, Al-Mg, or Al-Si. The said particles preferably are -200 mesh, and arrive at the strip at no more than 500 ft/min., preferably 300-500 ft/min., in an amount of 1-3 g/sq.ft., and for heavy gauge, e.g. > 0À048 inch, strip, a second supply of particles may also be used, at higher velocity and in lower quantity than the first, e.g. at 500- 1000 ft. /min. and 0À1 to 0À2 g/sq.ft. The particles may be Fe, mild steel, or 80Fe-20Zn. The coated product may be coated overall with a layer of iron, either electrolytically, or preferably, by immersion plating in a FeCl 2 solution containing 56 g/l Fe at pH 2À2 and 40‹C. for 5 seconds. |
