GB654922A - Improvements in and relating to machine parts - Google Patents

Abstract

Machine parts which when in use are subjected to high temperatures and which comprise a body more nearly adjacent the source of high temperature welded to a body situated more remotely from the said source, have the first mentioned body formed of an alloy of the following composition: C 0.08-1.0 per cent; Si 0.1-2.0 per cent; Mn 0.1-5 per cent; Ni 5-30 per cent; Cr 5-21 per cent; W and/or Mo 1.5-15 per cent; Nb 0.25-15 per cent, the Nb being partly replaceable by Ta, the minimum quantity of Nb being 0.05 per cent when Ta is present, with the optional presence of V in substitution for part of the Nb or Ta and Nb, the quantity of Nb or Ta and Nb not falling below 1.0 per cent when V is present; Co 3-30 per cent; N 0-0.3 per cent; Cu 0-6 per cent; Fe not less than 33 per cent and constituting, with unavoidable impurities, the balance, the total content of Ni and Cr being not less than 24 per cent. A steel of like composition may be used in which Ti wholly or partially replaces Nb. The second mentioned body is formed of a steel of the following composition: C 0.03-0.25 per cent; Si 0.2-2 per cent; Cr 15-25 per cent; Ni 7-16 per cent; one or more of the metals Nb, V, Zr, Ta 5-30 times the weight of the carbon content; Fe, and unavoidable impurities, the balance. The first mentioned body may be formed with a boss to which the second mentioned body is welded, e.g. by flash butt welding. The welded machine part may then be stress relieved by heating at about 500 DEG C. The production of valves for high duty internal combustion engines, and rotors and bearing shafts for high temperature gas turbines and compressors is referred to. Specifications 647,701 and 653,311 are referred to.