GB568595A - Improvements in or relating to heat exchange devices - Google Patents

Abstract

568,595. Making heat exchangers and flame traps. COLTMAN, J. L., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. Jan. 9, 1942, No. 339. [Classes 83 (ii) and 83 (iv)] Soldering.-Intercoolers, radiators, oil coolers, flame traps and like heat exchangers for internal-combustion engines, and consisting of thin sheet strip or tubular matrices of nickel or nickel-base alloy containing essentially nickel and copper, such as that sold under the Registered Trace Mark " Monel," or of steel or other ferrous alloy coated with such metal or alloy, are made by coating the surfaces with a thin film of silver, e.g. 0.0001-0.0003" thick, assembling the coated parts and heating in a relatively inert atmosphere to a temperature substantially below the melting point of the parts, but high enough to form a silver alloy therewith which brazes the parts together. The silver alloy may be formed by interdiffusion below the melting point of silver or by melting the silver. Heating may be effected in a furnace at 800-1000‹ C. for 10-20 minutes. The atmosphere may be of burnt coal gas, hydrogen or cracked ammonia. For radiators built up of strips the silver coating may be applied by rolling down a nickel &c. billet sandwiched between sheets of silver which may be secured thereto by silver solder, or the billet and sheet may be packeted prior to rolling. Alternatively, the silver may be applied by electrodeposition and subsequent rolling of the film on the nickel &c. sheets, or by coating with a part formed of silver powder in collodion. For tubular radiators, the parts may be coated electrolytically. For soliddrawn tubes the silver may be applied before the final drawing operation. When the parts are formed of steel &c. coated with nickel &c., the coating is rolled on to prevent pin-holing. Specification 568,567 is referred to.