| 摘要 |
PURPOSE:To manufacture a clad pipe having a well adhered mating surface of inner and outer pipes by extracting air in the clearance between inner and outer piper stocks through a groove formed in the peripheral direction between both pipe stocks and a vent hole communicated to the groove. CONSTITUTION:An outer pipe stock 1 is provided with a vent hole 3 communicated to its inside space, and an inner pipe stock 2 is provided with a groove 4 in the peripheral direction of a position opposite to the vent hole 3. The outer pipe stock 1 is put in a vessel 5 in a state of inserting the inner pipe stock 2 into its inside space, and the inside of vessel 5 is evacuated into vacuum to extract air in the clearance between both pipe stocks 1, 2. After completing the air extraction, both ends of pipe stocks 1, 2 are sealed by welding 6 and the vent hole 3 is blocked 7, in the inside of vessel 5 kept in vacuum, to manufacture a billet for double-ply pipe.
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