GB769435A - Improvements in, or relating to, the annealing of blackheart iron castings - Google Patents

Abstract

769,435. Annealing cast iron. BIRLEC, Ltd. Dec. 13, 1954 [Dec. 12, 1953], No. 34674/53. Class 72 In a process of annealing blackheart iron castings, the castings are heated to, and soaked at, 850‹-1000‹C. for 15-30 hours and cooled to below the critical range of 760‹- 700‹C., the cooling being controlled through the said critical range, and taking place at least through the critical range, in a reducing atmosphere governed during the soaking stage by reaction of some of the carbon in the castings with air in the furnace. The process may be performed (a) in one furnace, in which case the gaseous products generated during the soaking stage may be discharged to a gas holder where they are stored ready for returning to the furnace during the cooling stage if necessary by the use of a blower, flow control valve and flowmeter or (b) in a high temperature furnace and cooling furnace, of which four modifications are described. In the arrangement of Fig. 1 the high temperature furnace 1 and cooling furnace 2 are connected by pipes 3, 4, the atmospheres within the two furnaces circulating by natural connection and at a speed determined by the throttling valve 5. The circulation may (a) be assisted by a fan, Fig. 2 (not shown) or (b) be forced by a blower Fig. 3 (not shown). In the fourth modification, Fig. 4 (not shown), the gaseous products are forced from the high temperature furnace into the cooling furnace from where they are discharged as waste or to a gas holder.