PURPOSE: To efficiently produce intricate tubular articles by using a pipe material of copper (alloy) or Al (alloy) as an arbor and forming a film of boric acid (.salt) on its surface, then inserting the pipe material into a metallic tube and working the tube.
CONSTITUTION: The pipe material 2 consisting of the copper or the alloy is used as the arbor and the film of the boric acid 3 is formed on its surface. This pipe material is inserted into the gold alloy tube 1 to be worked. The composite tube 4 inserted with the arbor tube is drawn by using dies to a prescribed size. The tube is then bent to form a three-dimensionally bent and worked article 5. The worked article 5 is immersed into an alkali or acid to chemically dissolve away the tubular arbor 2. Since the shape of the arbor 2 is tubular, the contact with a liquid chemical covers the entire area of the inside surface in the hollow of the tubular arbor 2. Further, the boric acid film 3 exists on the surface and, therefore, a capillary tube-like spacing is formed between the gold alloy tube 1 and the arbor 2 and the infiltration of the liquid chemical is facilitated. The time required for dissolving away the arbor 2 is drastically shortened by the effects of both.
IJIMA KEIJIROU
AOKI KENJI
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