TH55419A - Methods of manufacturing heat transfer pipes. - Google Patents

Abstract

DC60 (12/09/45) This invention relates to a method for fabricating heat exchanger tubes for heat exchangers such as automotive radiators. The tubes should ideally be formed from copper or a copper alloy. Thin sheets of material are folded into B-shaped forms and joined together with a flux-free brass solder. The solder is in the form of a foil or paste. A typical paste consists of a powder filler, a binder, and a carrier, which may be a liquid or wax. This invention relates to a method for fabricating heat exchanger tubes for heat exchangers such as automotive radiators. The tubes should ideally be formed from copper or a copper alloy. Thin sheets of material are folded into B-shaped forms and joined together with a flux-free brass solder. The solder is in the form of a foil or paste. A typical paste consists of a powder filler, a binder, and a carrier, which may be a liquid or wax.

Claims (17)

1. The method of forming tubes for heat exchangers involves preparing thin sheets of metal or alloy with a base and two end sections. The ends of the sheets are folded to form legs, each with opposite sides and the other side opposite the base. The ends are further folded together to form a pair of fluid channels. A brass bonding material, which can be flux-free bonded to the sheets, is introduced between the opposite sides of the legs and between the base and the side of the leg opposite the base of the sheet. The sheets and the brass bonding material are heated sufficiently to melt and bond to the legs and base, connecting the legs to the base and forming the tube. 2. Method of Claim 1 in which thin sheets are assembled with copper or a copper alloy and a welding material; brass is assembled with a copper alloy which has been formulated to have a melting temperature lower than the melting temperature of the thin sheet. 3. Method of Claim 2, in which a thin sheet is heated to a temperature no more than approximately 20% above the melting point of the material for brass welding. 4. Method of claim 2 where the material for brass welding is in the form of a paste or foil. 5. Method of Claim 2 where the material for brass welding is in the form of a paste composed of a powdered metal or alloy filler, binder and carrier. 6. Method of claim 5 where the powdered filler has a particle size between 15 and 30 microns. 7. Method of Claim 5 where the powdered filler is an alloy of copper, nickel, tin, and phosphorus. 8. Method of claim 6, in which the filler consists of approximately 1% to 5% nickel, approximately 15% to 20% tin, approximately 4% to 7% phosphorus, and copper. 9. Method of Claim 5 where the carrier, consisting of a liquid or paste, is applied by brushing, spraying, or dispersing the brass bonding material. 10. The method of claim 9 where the carrier consists of water or alcohol. 11. The method of claim 9, which includes additional drying of the tube after spraying or brushing of the brass paste welding material onto a thin sheet to allow the carrier to evaporate. 12. Method of Claim 5 where the carrier compound, including wax and bonding material, is heated during application to thin sheets. 13. Method of claim 12 where the binder is a thermoplastic material. 14. The method of claim 13, which includes the melting of the wax carrier and thermoplastic material before applying the brass bonding material to the legs and base of the thin sheet, followed by cooling of the thin sheet to hold the brass bonding material in place. 15. Method of claim 4 where the material for welding brass is in the form of foil with a thickness between approximately 0.01 and 0.5 mm and is applied by placing the foil between opposite sides of the leg sections and between the base and the side of the leg section opposite the base of the thin sheet. 16. The method of manufacturing automotive radiators involves preparing a number of heat exchanger tubes according to claim 1 and shaping the tubes into automotive radiators. 17. The boiler is manufactured in accordance with the methods of claim 16.