| 摘要 |
1342417 Heat treating steel USS ENGINEERS & CONSULTANTS Inc 31 Aug 1971 [31 Aug 1970] 40619/71 Heading C7A Steel is given an ultra-fine grain structure by preconditioning it at a temperature in the range (A 1 -150‹ F.) to just below A 1 for 5-30 minutes, followed by rapid heating to above the A 3 temperature for just sufficient time for austenilisation to occur, followed immediately by cooling at a rate not less than that required to form a fine ferrite-pearlite structure; the cycle may be repeated a number of times. As exemplified, steels containing were preheated at 1300‹F., heated at 16‹ F. /sec. to 1580‹ F. and air cooled, while steels containing were preheated at 1100-1150‹ F., heated e.g. at 16‹ F./sec. to 1500‹ F. and water quenched, the cycle being repeated 5 times. |
