| 摘要 |
1,192,799. Heat-treating steel wire or rod. UNITED STATES STEEL CORP. Sept. 21, 1967 [Sept. 27, 1966], No.42975/67. Headings C7A and C7N. Steel wire or rod is subjected to a continuous patenting heat treatment by heating the work in a furnace e.g. containing tubes through which the wire travels to above the steel's upper critical temperature, e.g. to 1600‹ F. in an atmosphere of cracked ammonia to prevent decarburization, then passing it from the furnace without air cooling into a first cascade chamber to quench the work by a liquid medium to below the Ar temperature zone e.g. 400‹-700‹F. to suppress the formation of pro-eutectoid carbides and ferrite, then into a second cascade chamber to reheat the work by a liquid medium to 750-1050‹F. to obtain isothermal transformation to upper bainite and fine pearlite structures. The cascade chambers preferably comprise vigorously agitated quenchant, e.g. NaNO 3 -NaNO 2 eutectic or Pb-Bi alloy, which is pumped from a reservoir up into a tray disposed above where it overflows back into the reservoir. The work may be passed from the second cascade chamber into a holding furnace maintained at the same temperature to complete transformation. The heat treatment may be repeated with intermediate cooling to room temperature and drawing. The wire may be given a copper coating prior to drawing to final gauge. The wire may be of highereutectoid steel containing 0À9-1% of C, max. 0À005% each of P and S, max. 0À1% Si and max. 0À002%N. |
