| 摘要 |
<p>Elongated ferrous material is heat treated by passing it through a liquid heat transfer medium, and heating it by induction between its entry to and final exit from the bath, the temperature characteristic to which the material is subjected being controlled in accordance with the hardness of the treated strip to maintain the latter uniform. In one embodiment Fig. 1 (not shown) the strip is preheated in a liquid bath, passed out of the latter and through an induction heater, and returned to a liquid quench bath, the liquid being circulated between the quench and preheat baths in closed cycle. In another embodiment, Fig. 2 (not shown) the material remains in a circulating liquid bath throughout the heat treatment and is heated by induction while passing therethrough. The hardness of the strip may be detected by magnetizing to saturation followed by magnetizing in the opposite sense, the coercive force or remanent magnetism giving a measure of hardness. The heat treatment may be carried out in an oxygen-free atmosphere containing a predetermined amount of water vapour whereby the strip is slightly oxydized and dragout losses from the metal bath are reduced.</p> |
