| 摘要 |
<p><PICT:0985022/C6-C7/1> In a continuous process for heat-treating steel strip or wire, the strip is passed through a liquid heat transfer medium contained in two baths 1, 2, Fig. 3, over guide rolls 4, 5 and 6; the strip 3 is heated to a maximum temperature between the two baths, and the heat transfer medium is circulated in counter-current to the moving strip in the second bath, from which the hot medium flows into the first bath, preheating the incoming strip. Heating is effected by electrical induction through a transformer 11, the secondary circuit of which is preferably the heat transfer medium consisting of a liquid metal, which is circulated by a pump through pipes 7, 8. The bath 1 is at 350 DEG C. and on emerging into the short path over insulated guide roll 5, the temperature of the strip rises to 700 DEG C. due to its high resistance in relation to the metal bath. The strip is then quenched by liquid metal flowing in counter-current to it. The top guide roll 5 is surrounded by a casing containing an inert atmosphere. Suitable bath metals are lead, lead/antimony or lead/bismuth alloys or a molten barium salt. Baffles 35 enhance the counter-current cooling effect and maintain a uniform temperature gradient; the liquid metal in pipe 7 is at 600 DEG C. and in pipe 8 at 200 DEG C. Pipe 7 may be in convoluted form. The strip may be mild or alloy steel, tin plate, or aluminium-coated steel.</p> |
