GB629131A - Improvements relating to the production of elongated metal tubular parts - Google Patents

Abstract

A method of making capillary tubing, e.g., for a hypodermic needle, which splits longitudinally instead of breaking in two when bent, comprises reducing a ductile metal tube in one or more stages, by excessive cold working, each stage being preceded and followed by heating to a temperature below that which would destroy the fibrous structure produced previously. This method may be applied to the metals referred to in Specification 565,061, [Group XXII]. The heating and cold working may be repeated a number of times with an optional final heating. The temperature to which the work is heated and the degree of cold working, for any particular metal or alloy necessary to produce the desired fibrous structure is found by experiment, micro-photographic examination at the various stages of the operation, and by determining the brinell hardness of sufficiently-worked material. Details are given of the treatment required in the case of particular sizes of work pieces made of the steel known under the Registered Trade Mark "Staybrite," stainless steel containing 12 per cent chromium, 12 per cent of nickel and 0.12 per cent of carbon, mild steel containing 0.12 to 0.25 per cent of carbon, 0.5 to 0.8 per cent manganese, and not more than 0.05 sulphur and phosphorus or 0.25 of silicon, and commercial phosphor bronze, containing 95 per cent of copper, 4 of tin and 0.1 of phosphorus, the rest being zinc and impurities. The best temperature for stainless steel is 800 DEG C., for mild steel 715 DEG C., and for the phosphor bronze above 420 DEG C., these temperatures being about 60 per cent of their melting points in the absolute scale. Stainless steel tube made in this way may be finally tempered by heating to 400 DEG -420 DEG C. in a salt bath and quenched.