| 摘要 |
A strip of composite metal laminate material embodying a thin inner layer of stainless steel sandwiched between and metallurgically bonded to two relatively thicker outer layers of low carbon steel is subjected to a brief, high temperature heat treatment followed by a relatively much longer heat treatment at much lower temperature for substantially eliminating the yield point in the laminate and for maximizing formability of the laminate while permitting some reduction in the corrosion resistance properties of the stainless steel layer of the laminate. The composite strip material is then readily formed into two, concentrically disposed convolutions of the strip material while the laminate material is in this highly formable condition. The convolutions of the strip material are then brazed together to provide a double-walled tubing, the brazing procedure being regulated to effect selected heat treatment of the formed composite material for substantially restoring the corrosion resistance properties of the stainless steel layer of the laminate within the finished tubing.
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