Patent GB-795994-A (GB)
Title: Improvements in or relating to method of making metal fabrications
Inventor: JOHNSON ARTHUR FREDERICK
IPC: B21D53/04
Filed: 1956-06-08
Abstract: 795,994. Making heat exchangers. OLIN MATHIESON CHEMICAL CORPORATION. June 8, 1956, No. 17758/56. Class 83 (2). A method of making metal fabrications adapted to be inflated by fluid pressure to make a hollow metal article such as a heat-exchanger comprises positioning a pattern of stop-off material on a metal sheet, bending and folding the sheet into layers lying in face-to-face relationship and having said pattern lying therebetween, and thereafter, while the layers are secured against relative slippage by the folded edge, pressure welding by rolling those areas not protected by stop-off material. A sheet 1 of copper alloy is grooved at 2, is degreased, cleaned, rinsed and dried and then has a foreshortened pattern of stop-off material 5 applied, e.g. by a silk screen, to one half 3 of the surface of the sheet not containing the groove 2. The stop-off material 5 comprises a mixture of 13 per cent colloidal graphite, 40 per cent calcium carbonate having a granulation of less than 325 mesh, and the balance water. The sheet 1 is then folded about the groove 2 so that the pattern is interposed between adjacent surfaces of the folded sheet. This assembly is then heated to about 900‹ C. in a reducing atmosphere and while hot passed through a rolling mill in the direction of foreshortening of the pattern to reduce its thickness about 50 per cent in a single pass, thus welding those parts 9 of the sheet not separated by the pattern of stopoff material into a unitary structure. The assembly is then cleaned, rinsed and dried and cold rolled to bring the length to that desired. The structure is then annealed at 750‹ C. for half and hour and, after cleaning and drying, trimmed along its edges removing the folded edge 6. The unwelded areas are then expanded by fluid pressure applied through a tube 7. In another embodiment, Fig. 7, two grooves are cut in opposite faces of a sheet to divide it into three equal areas 11, 12, 13, foreshortened patterns are applied to the areas 11, 13 and the sheet is bent over to Z form and then pressed flat. The assembly is then pressurewelded by hot rolling, then cleaned, cold-rolled, annealed and trimmed. The unwelded patterns are then expanded by fluid pressure. In a further embodiment, Fig. 9, two grooves are formed on the same surface of the sheet, dividing the sheet into three areas 31, 32, 33, the area 33 being equal to, or greater than, the sum of the areas 31, 32. Patterns 34, 35 are applied to the areas 31, 32 which are then bent over on to the area 33. The assembly is hot rolled and treated as in the other embodiments and may be slit into two along the abutting edges 36, 37. In a further embodiment, Fig. 10 (not shown), a folded edge is introduced through the rollers first. One part of a pattern may be placed on one opposing surface and the remainder on the other opposing surface or duplicate patterns may be placed on each surface. Sheets of copper, copper alloy, bronze, brass or aluminium may be used. For copper alloy the reduction in one pass of the hot rolling must be at least 35 per cent and for aluminium at least 60 per cent.