GB468626A - Improvements in methods of and apparatus for hardening the inner wall surface of hollow metallic bodies - Google Patents

Abstract

468,626. Hardening hollow bodies. LINDE AIR PRODUCTS CO. Jan. 3, 1936, No. 251. Convention date, Jan. 19, 1935. [Classes 72 and 82 (i)] [Also in Group XI] The inner wall of a metallic hollow body is hardened by progressively and uniformly heating successive and relatively narrow circumferential portions of the surface of said wall to a temperature above its critical range and then cooling by utilizing the heat-absorbing capacity of the rest of the body so as to establish a steep temperature gradient over the entire area of the surface. The cooling may be assisted by causing a cooling fluid to impinge on a circumferential portion of the surface in close juxtaposition to the heated portion. In the treatment of the inner wall 11 of a cylinder block 10, the latter is mounted on a hollow support 15 so as to leave openings 14. The water jackets 30 of the block may be filled with a cooling liquid. A star-shaped burner head 17 with a plurality of nozzles 28 and a baffle plate.22 to prevent the upward escape of the heat generated by the nozzles 28 is mounted on the lower end of a hollow shaft 16 provided with a mixing passage for gases entering by pipes 18, 19 and also a passage for cooling medium which enters by the pipe 20 and leaves by the pipe 21. The shaft 16 is in alignment with the axis of the cylinder to be treated and is given a rotary or oscillatory movement by the worm gear 32 and is also moved vertically downward into the cylinder by gear 33 and rack 34. Alternatively the burner may be stationary and the support 15 moved. In a modification, the burner proper is of conical form and provided with a conicalshaped baffle above, or the burner is of inverted conical form and a conical baffle is placed beneath it, the burner in this form being moved upward from the bottom of the cylinder. In a second modification the baffle plate 22, Fig. 1, is arranged below the nozzle 28 and the burner moved upwards from the bottom of the block. In a third modification, a perforated pipe connected to a supply of cold water or air is mounted on the burner either above or below the baffle plate according to where the latter is placed. The cylinder may be made of an alloy steel containing 0À35-0À45 per cent of carbon, 0À5-0À8 of manganese, 0À8-1À1 of chromium and 0À15-0À25 of molybdenum or 0À3-0À4 of carbon, 0À5-0À8 of manganese, 1À0-1À5 of nickel and 0À45-0À75 of chromium.