| 摘要 |
PURPOSE:To obtain a heat exchanger tube having superior erosion resistance and a long service life by working a double-walled tube having a layer of a precipitation hardening alloy by bending and welding and by hardening the alloy layer by aging. CONSTITUTION:A double-walled tube consisting of an outer layer of a precipitation hardening material and an inner layer of an ordinary material for a boiler tube is manufactured by hot extrusion or other method. The precipitation hardening material may be PH stainless steel typified by 17-4 or 17-7. The double- walled tube is worked into the panel of a heat exchanger and aged at a proper temp., preferably <=about 730 deg.C to harden the alloy layer.
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