PURPOSE: To improve the producibility, by maintaining various mechanical properties and also settling the reduction of area for securing the texture, and by continuously performing the hydraulic extrusion together with rolling reduction or the stretch- draw forming under unannealed condition all through the processes.
CONSTITUTION: The annealing process 3 is repeated several times after the hydraulic extrusion process 2 or the rolling reduction 2' for the annealed pipe blank 1. Next, the reduction of area by the hydraulic extrusion process 4 is settled at above 50% (preferably 50W75%), on purpose to maintain various mechanical properties as unaltering as possible and also to secure the superior texture. After that, the unannealing section 5 means that the material must not be annealed because the annealing in the process extremely alters the property of the metallic material. In the next rolling reduction or the stretch-draw forming 6, the reduction of area is settled at under 50% (preferably under 15%) which does not damage the effect obtained by the process 4, and then, the processes 4, 5 and 6 are continuously performed; after that, the stress relief annealing 7 is performed according to the conventional method; hereby, the producibility is improved.
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TSUNODA TSUTOMU
FUJITA KAZUMI
