JPS55117516A - Manufacture of double-ply pipe - Google Patents

Abstract

PURPOSE: To make possible the manufacture of high accurate double-ply pipe comprising the outer pipe and inner pipe being tightly bound to each other over entire length, by inserting the cooled and thermally contracted inner pipe into the heated and thermally expanded outer pipe, by applying the expansion work to the inner pipe, and then, by giving the thermal contraction to the outer pipe and thermal expansion to the inner pipe.

CONSTITUTION: The outer pipe 1 made of carbon steel, etc., is heated by the coil heater 2, etc., and the inner pipe 3 made of stainless steel, etc., is inserted into the outer pipe 1. The hydraulic and cooling medium is introduced into inside 4 of inner pipe 3 through the hole 6 bored in the plug 5, and the diameter of inner pipe 3 is cooled and thermally contracted. Next, the hydraulic pressure is impressed to the inside 4 of inner pipe 3 to expand its diameter; hereby, the outer pipe 1 is also expanded together with the inner pipe 3. When the diameter is expanded so far as the suitable value for mutual tightening, the pressure rise is interrupted, and the hydraulic medium is drained away from the inner pipe 3; hereafter, the diameter of inner pipe 3 increases owing to thermal expansion. Meantime, the outer pipe 1 is naturally cooled to cause the thermal contraction; as a result, the interference is formed between the outer pipe 1 and inner pipe 3. According to this method, the combination of various materials becomes possible, the tightening becomes uniform, and the product yield is improved.

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