| 摘要 |
PURPOSE:To form a wear-resistant double-wall pipe at a low cost by superposing a non hardenable outside pipe having a low yield point and high toughness and an inside pipe in an annealed state having high hardenability and high yield point so as to contact tightly with each other and subjecting the pipes to quick heating, bending and quench hardening. CONSTITUTION:The inside pipe 1 consisting of a high-carbon steel or the like which is a material having high hardenability and having the high yield point in the hardenable state is relatively superposed in the annealed state on the outside pipe 2 consisting of a low-carbon steel or the like which is a non-hardenable material having the low yield point and high toughness including low hardenability. The pipes are then plastically deformed by rollers 3 from the outside of the outside pipe 2 and are drawn in an arrow direction to diametral reduce body pipes 1, 2 so as to contact with each other, by which the double-walled pipe stock is obtd. The double-walled pipe stock is annularly and quickly heated from the inside by a high-frequency induction heating means 4 and right thereafter, the pipe stock is subjected to quick cooling by a cooling means 5 to harden the inside pipe 1. The double-walled pipe stock is passed through a die 7 by a bending and drawing means 6, by which the pipe stock is diametrally reduced and bent. Both pipes 1, 2 are thereby self-tightened and the wear-resistant double-walled pipe 8 is obtd.
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