| 摘要 |
<p>The surfaces of steel articles are heated by induced currents, subjected to a current of gaseous cooling medium for sufficient time to cool the surface to a predetermined temperature and then immediately subjected to the action of a liquid coolant, e.g. water. The predetermined temperature is that temperature at which undesirable structures are formed at the cooling rate attainable by gaseous cooling. In a steel containing 0.3-0.35 per cent carbon, 0.7-1.0 per cent manganese, 0.9-1.20 per cent chromium and the balance iron the liquid coolant is applied when the temperature of the steel has dropped to between 500 DEG C. and 400 DEG C. The gaseous medium may be air supplied at 2 to 4 kgs. per cm.2 for 3 to 15 seconds and it may also be supplied during the application of the liquid.</p> |
