GB717164A - Improvements in or relating to hollow metal bodies - Google Patents

Abstract

717,164. Pistons; cylinder liners. DEUTSCHE EDELSTAHLWERKE AKT.-GES. May 30, 1951 [Oct. 4, 1948; March 3, 1948; March 3, 1949], No. 12673/51. Class 122(1) [Also in Groups VIII and XXVIII] A hollow metal body 1, such as a cylinder liner or a piston, is subjected to a hardening treatment so that at least one surface of the wall of the body comprises hardened portions 2 spaced by relatively soft portions 3. The portions 2, 3 may be alternately arranged with respect to each other in the axial or circumferential direction of the body, or in both directions. The portions 2 may merge into the portions 3 and preferably extend through the full thickness of the wall of the body, and may be in the form of axially-spaced annular bands, Fig. 1, or spiral bands, Fig. 2 (not shown), or spiral bands of opposite pitch, Fig. 3 (not shown). The ends la, 1b of the body may be completely hardened or locally hardened in ring-like or spiral bands and surrounded by sleeves 4 of soft metal, e.g. steel. The hardened annular portions 2 may be produced by bringing the whole thickness of the wall of the body to the hardening temperature using an electric-induction coil or a gas burner surrounding the tube, the coil or burner being advanced in steps in the axial direction of the body which is quenched internally or externally; alternatively, a heating element only partly surrounding the body is used while the body is rotated. When hardened bands of spiral formation are required, a spiral-shaped heating element partly surrounds the body which is rotated and moved axially relatively to the element. The body may be given a heat treatment to produce a body with both faces having alternately arranged hardened and tempered portions, or one face may be completely hardened.