Patents
A process for preparation of thermally conducting metallic multi layers useful for the manufacture of industrial components, which comprises: i) heating a metallic backing substrate such as steel to remove exiting hydrogen, providing grooves on the surface to be joined, cleaning the said substrate by a known method, characterised in that providing ceramic coating capable of withstanding high temperature on the surfaces not to be joined, heating the said grooved substrate to a temperature in the range of 260 ?C to 300 ?C, spraying the preheated grooved surface with a flux capable of removing oxide layers, dipping the said substrate in a conventional tin bath maintained at a temperature in the range of 260-290 ?C for a period in the range of 4 minutes to 6 minutes per dip and repeating the tinning process till the formation of intermetallic phase to obtain a tinned backing substrate takes place, ii) machining one or more metallic intermediate substrates such as copper and copper alloy, cleaning the said machined substrates by a known method, heating the cleaned substrate to a temperature in the range of 260-300 ?C, spraying the preheated substrate with a flux capable of removing oxide layers, dipping the resultant substrate in a conventional tin bath maintained at temperature in the range of 260-280 ?C for a period in the range of 4 minutes to 6 minutes per dip and repeating the tinning process, if required, to obtain a tinned intermediate substrate, iii) cleaning the tinned backing and intermediate substrates by a known method, preheating to a temperature in the range of 190?-210 ?C, cleaning the tinned substrates, spraying the surfaces to be joined with a flux, placing the said preheated tinned backing substrate with the surface to be joined facing upward in a conventional tin bath maintained at a temperature in the range of 280 ?C-300 ?C, placing the said preheated one or more tinned intermediate substrates in the said tin bath in such a manner that the surfaces to be joined are in contact with each other, applying pressure in the range of 0.2 kg/cm2 to 0.5 kg/cm2 to the said substrates for a period in the range of 5 minutes to minutes and removing the joined substrates from the tin bath followed by cooling to semi solid state. v) pouring molten babbitt on to the top surface of the intermediate substrate, followed by unidirectional cooling by applying heat on to the top surface of the babbitt layer and coaling from the bottom side of the backing substrate till complete solidification occurs.