| 摘要 |
A method, and an apparatus for practicing the method, for producing heavy pure aluminum coatings on small diameter steel tubing are disclosed. The coating has an average thickness of 0.004 inch to 0.008 inch (100-200 mu m), to provide outstanding resistance to corrosion, and to maintain integrity in the face of abrasive action, and with coating ductility and adherence sufficient to permit double flaring. The method and apparatus are highly useful in the manufacture of Bundyweld tubing for automotive brake lines, and single wall tubing for refrigeration or air conditioner heat exchangers. Various surface preparations are disclosed; and after surface preparation the tube is uniformly heated to a carefully regulated peak temperature in a non-oxidizing high intensity direct fired furnace, followed by passing the tube vertically upward through a shallow pool of molten aluminum, whereby to cast on a thick coating, followed by "free exit" finishing, air quenching, and, if desired, redrawing.
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