Indian Patents. 232126:A PROCESS OF MAKING THERMALLY CONDUCTING METALLIC MULTILAYERS USEFUL FOR THE MANUFACTURE OF INDUSTRIAL COMPONENTS

Title of Invention	A PROCESS OF MAKING THERMALLY CONDUCTING METALLIC MULTILAYERS USEFUL FOR THE MANUFACTURE OF INDUSTRIAL COMPONENTS
Abstract	A process for preparation of thermally conducting metallic multi layers useful for the manufacture of industrial components, which comprises:

Full Text	To meet the above requirements, a bearing is made of different materials wherein load is carried by one member while wear characteristics are attained by the other. A bimetallic bearing belongs to this category wherein the load is carried by the steel backing while the bearing lining is meant for better friction and wear characteristics. Although mild steel is most widely used as backing material yet alloy steels, bronzes, brasses and, to a limited extent, aluminium alloys are also used depending on the operating conditions of the bearings. Three main shapes namely half round, full round bush and thrust pad are common in bearing applications. A recent report on "Technology in Indian Bimetal Bearing Industry" has been prepared by the Govt, of India, Dept. of Scientific & Industrial Research, Ministry of Science & Technology, in November, 1990 wherein the different processes of making bimetallic bearings have been discussed. Powder metallurgy route has been found to be the most widely adopted process amongst them. The powder metallurgy process involves the processing of the lining layers in the form of powder through sintering and rolling operations. The sheets are then fixed on to the steel backing mechanically. This is followed by diffusion bonding of the layers to generate good bonding with each other. Available information also indicates that the insertion of a thermally conducting layer in between the steel backing and the babbitt lining could improve the working efficiency of the bearings. This leads to the development of thermally conducting multi metallic layer bearings. The methods of manufacturing thermally conducting multimetallic layer bearings have been described in US Patent No. 4,525,083 dated June 25,1985and US patent NO. 4,33,262 dated Aug 6,1985 wherein steel backing is bonded to the conducting intermediate layer in turn is then bonded with the babbitt layer preferably by welding technique . The drawback of this process is that it comprises a series of operations and is time consuming and costly. There is thus a need for a simpler and less expensive method for producing the thermally conducting multi metallic layer components. The main object of the present invention is to provide a process for making thermally invention is to provide a process for making thermally conducting multi metallic layers useful for the manufacture of industrial components, which obviates the drawbacks as detailed above. Another object of the present invention is to provide improved multimetallic bonding of varying sizes and thicknesses. Yet another object is to provide a process for making multimetallic layers having improved heat transfer and wear properties. Accordingly, the present invention provided 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, i) 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 so 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 JO minutes and removing the joined substrates from the tin bath followed by cooling to a semi solid state; (iv) 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 cooling from the bottom side of the backing substrate till complete solidification. In an embodiment of the present invention, the grooves provided such as gramophone finish may be having pitch to pitch distance in the range of 0.14 +, 0.02 and pitch depth 0.25 +_ 0.05 mm. In another embodiment of the present invention, the cleaning of the substrate surfaces may be affected using known methods such as degreasing, pickling and neutralizing. In another embodiment of the present invention, the molten babbitt used may be IS 25 in the composition range of Sn - 9.0 to 11.0% Sb - 5.0 to 6.0% Cu - In another embodiment of the present invention, the size of the (i) steel backing varies in the range of length 75-200 mm, breadth 50-100 mm and thickness 15-25 mm; (ii) conducting intermediate layer varies in the range of length 75-200 mm, breadth 50-100 mm and thickness 3-6 mm; and (iii) the babbitt lining varies in the range of length 75-200 mm, breadth 50-100 ram and thickness 2-6 mm. In another embodiment of the present invention, the tin bath temperature varies in the range of 260-290°C and the duration of dipping varies in the range of (i) 4-6 minutes per dip during the tinning of the steel backing and the thermally conducting intermediate layer and (ii) 6-10 minutes during joining of the steel backing with the thermally conducting intermediate layer. In its first embodiment of the present invention, the patent describes an improved process of tinning of steel plate and intermediate (thermally conducting) layer. In another embodiment, joining of the intermediate layer with the steel backing and babbitting over the intermediate layer has been described. The process of tinning requires operations like heat treatment, surface preparation and fluxing of the surface prior to tinning. The heat treatment of the steel backing/substrate is carried out at a predetermined temperature for a fixed duration so that existing hydrogen can be removed from the plate. The heat treated steel plate is machined to the required size/finish to remove scale and then its to-be-treated/joined surface subjected to machining to a predetermined finish. The machined surface is polished with the help of emery paper and rubbed with a wire brush to remove burs. Degreasing of the polished surface is done with cotton wet with trichloroethylene. Pickling is the next step in the operation wherein the steel backing is immersed in a freshly prepared solution of HC1 for a fixed duration with a view to attain a clean surface. This is followed by neutralising the after effect of the acid on the to-be-treated surface with a freshly prepared ammonium hydroxide solution with intermediate rinsing with water followed by drying. The surface to be protected from tinning/babbitting is coated with a paste containing Na-silicate, red (FeO) oxide and water in a fixed ratio. The sample so prepared is preheated at a fixed temperature for a predetermined duration prior to fluxing (using a spray gun) with a solution having zinc chloride, ammonium chloride, sodium chloride, hydrochloric acid and distilled water in known quantities. Tinning of the steel backing is carried out by dipping it in molten tin. The top surface of the tin bath is covered with a mixture of zinc chloride and ammonium chloride in a fixed proportion. After holding the plate inside the bath for a predetermined length of time, the sample is taken out. The excess tin is removed from the surface with a hair brush wet with the above mentioned liquid flux. Immediately after brushing, the tinned surface is sprayed with the liquid flux using a spray gun connected with a compressor. Tinning is completed in three successive dips with intermediate cleaning and fluxing as discussed above. A copper/chrome-copper plate is machined to a desired finish/size. The to-be coated surface is then polished with emery paper, degreased with cotton moistened with trichloroethylene and pickled with freshly prepared nitric acid of predetermined concentration for a fixed time period. The pickled surface of the plate is rinsed with running water, dipped in ammonium hydroxide solution and rinsed again with running water and finally dried. The plate is preheated to a desired extent prior to fluxing with a saturated solution of zinc chloride and tinning operations. The copper/chrome copper plate after fluxing is immersed in molten tin; the bath of (molten) tin is covered with a mixture of zinc chloride and ammonium chloride to avoid its oxidation and to remove the oxidized mass. The temperature of the tin bath and the duration of dipping are so fixed that a good bonding forms in between the tin layer and the copper plate. Then the sample is taken out and the excess tin is removed with a hair brush wet with the liquid flux. This cycle is repeated twice for tinning a copper plate. A specially designed mould is used for joining the (tinned) copper with (tinned) steel and babbitting. A graphite plate is fixed at the bottom portion of the mould. The tinned surfaces of steel and copper are degreased with trichloroethylene. The mould and the tinned plates of steel and copper are preheated sufficiently to remove moisture. The tinned surfaces of steel and copper just prior to their joining are fluxed. The steel plate is placed at the base of the mould and immersed in the tin bath maintained at a predetermined temperature for a fixed duration. The copper plate is then put over the steel backing in the mould and pressure on the copper plate is applied through dead weight. The mould assembly is taken out of the bath and the joining medium (tin) is allowed to become semi solid in air. Thereafter, the molten babbitt is poured on to the treated surface of the sample in one step only. Ammonium chloride flux is sprayed on to the surface of the babbitt melt and the melt is cleaned prior to pouring. The top surface of the mould is covered with a preheated steel plate and the mould is cooled with compressed air from the bottom side. Finally, the sample is removed from the mould and subjected to required machining operations. The following examples are given by way of illustration of the process of the present invention and should not be construed to limit the scope of the invention. Example 1 Substrate : Mild steel plate Size: 200 X 100 X 20 mm Intermediate layer: Copper (99.5% purity) plate Size: 200 X 100 X 6 mm Babbitt lining: Tin-base babbitt Composition (element, wt%): IS 25 : Sn - 10.0 Sb- 5.6 Cu- 0.08 As- 0.07 Cd Thickness of the babbitt lining: 5 mm Heat treatment of the steel substrate: Temperature: 650°C Duration: t = (X+l)2 where, X = thickness of the steel substrate in inch t = duration in hrs Samples to be cooled in the furnace after the treatment. Gramophone finishing: Pitch-to-pitch distance = 0.14 mm Pitch depth = 0.25 mm Pickling: Steel substrate/backing: (i) Dipping medium: 7% hydrochloric acid (ii) Duration: 7 minutes Copper layer/plate (i) Dipping medium: 7% nitric acid (ii) Duration: 7 minutes Neutrali zation: (i) Dipping medium (common for the steel substrate and copper plate): 7% ammonium hydroxide (ii) Duration: 4 minutes Surface protection: Composition of the paste: Sodium silicate: 50 cc Red oxide (FeO): 100 gm Water: 200 cc Preheating (common for the steel substrate and copper plate): (a) Temperature: 280°C (b) Duration: 30 minutes Fluxing: (a) Steel substrate: Composition of the flux: Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc (b) Copper plate/layer: (i) Composition of the flux 1: Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc (ii) Composition of the flux 2: Saturated solution of zinc chloride in distilled water (c) Tin bath: Composition of the flux: Zinc chloride = 75 wt.% Ammonium chloride = 25 wt.% (d) Molten babbitt: Composition of the flux: Ammonium chloride Tinning: (a) Steel substrate: (i) Bath temperature: 270°C (ii) Number of dips: 3 iii) duration of each dip: 5 minutes (b) Copper plate/layer (i) Bath temperature: 270°C (ii) Number of dips: 2 (iii) Duration of each dip: 5 minutes Joining of the copper plate/layer with the steel substrate: (a) Preheating (common to the mould, treated steel substrate and copper plate): (i) Temperature: 200°C (ii) Duration: 15 minutes (b) Joining medium: molten tin (i) Temperature of the tin bath: 290°C (ii) Duration: 8 minutes Babbitting (a) Pouring temperature: 450°C (b) Temperature of the steel cover: 280°C Example 2 Substrate : Mild steel plate Size: 200 X 100 X 20 mm Intermediate layer : Chrome copper (Cu - 1% Cr - 0.1 Zr) plate Size: 200 X 100 X 6 mm Babbitt lining: Tin-base babbitt Composition (element, wt%): IS 25: Sn - 10.0 Sb- 5.6 Cu- 0.08 As- 0.07 Cd Thickness of the babbitt lining: 5 mm Heat treatment of the steel substrate: (a) Temperature: 6 5 0°C (b) Duration: t = (X+l)2 where, X = thickness of the steel substrate in inch t = duration in hrs Samples to be cooled in the furnace after the treatment. Gramophone finishing: (a) Pitch-to-pitch distance = 0.14 mm (b) Pitch depth = 0.25 mm Pickling: (a) Steel substrate/backing: (i) Dipping medium: 7% hydrochloric acid (ii) Duration: 7 minutes (b) Chrome copper layer/plate (i) Dipping medium: 7% nitric acid (ii) Duration: 7 minutes Neutralization: (i) Dipping medium (common for the steel substrate and chrome copper plate): 7 % ammonium hydroxide (ii) Duration: 4 minutes Surface protection: Composition of the paste: Sodium silicate: 50 cc Red oxide (FeO): 100 gm Water: 200 cc Preheating (common for the steel substrate and chrome copper plate): (a) Temperature: 280°C (b) Duration: 30 minutes Fluxing: (a) Steel substrate: Composition of the flux: Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc (b) Chrome copper plate/layer: (i) Composition of the flux 1: Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc (ii) Composition of the flux 2: Saturated solution of zinc chloride in distilled water (c) Tin bath: Composition of the flux: Zinc chloride = 75 wt.% Ammonium chloride = 25 wt.% (d) Molten babbitt: Composition of the flux: Ammonium chloride Tinning: (a) Steel substrate: (i) Bath temperature: 270°C (ii) Number of dips: 3 iii) duration of each dip: 5 minutes (b) Chrome copper plate/layer (i) Bath temperature: 270°C (ii) Number of dips: 2 (iii) Duration of each dip: 5 minutes Joining of the chrome copper plate/layer with the steel substrate: (a) Preheating (common to the mould, treated steel substrate and chrome copper plate): (i) Temperature: 200°C (ii) Duration: 15 minutes (b) Joining medium: molten tin (i) Temperature of the tin bath: 290°C (ii) Duration: 8 minutes Babbitting (a) Pouring temperature: 450°C (b) Temperature of the steel cover: 280°C Example 3 Substrate : Mild steel plate Size: 200 X 100 X 20 mm Intermediate layer : Copper (99.5% purity) plate Size: 200 X 100 X 6 mm Babbitt lining: Tin-base babbitt Composition (element, wt%): INDO 84: Sn - 11.6 Sb - 5.7 Cu - 0.5 As - 1.2 Cd - 0.3 Ni Thickness of the babbitt lining: 5 mm Heat treatment of the steel substrate: (a) Temperature: 650°C (b) Duration: t = (X+l)2 where, X = thickness of the steel substrate in inch t = duration in hrs Samples to be cooled in the furnace after the treatment. Gramophone finishing: (a) Pitch-to-pitch distance = 0.14 mm (b) Pitch depth = 0.25 mm Pickling: (a) Steel substrate/backing: (i) Dipping medium: 7 % hydrochloric acid (ii) Duration: 7 minutes (b) Copper layer/plate (i) Dipping medium: 7 % nitric acid (ii) Duration: 7 minutes Neutralization: (i) Dipping medium (common for the steel substrate and copper plate): 7 % ammonium hydroxide (ii) Duration: 4 minutes Surface protection: Composition of the paste: Sodium silicate: 50 cc Red oxide (FeO): 100 gm Water: 200 cc Preheating (comnon for the steel substrate and copper plate): (a) Temperature: 280°C (b) Duration: 30 minutes Fluxing: (a) Steel substrate: Composition of the flux: Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc (b) Copper plate/layer: (i) Composition of the flux 1: Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc (ii) Composition of the flux 2: Saturated solution of zinc chloride in distilled water (c) Tin bath: Composition of the flux: Zinc chloride = 75 wt% Ammonium chloride =25 wt% (d) Molten babbitt: Composition of the flux: Ammonium chloride Tinning: (a) Steel substrate: (i) Bath temperature: 270°C (ii) Number of dips: 3 iii) duration of each dip: 5 minutes (b) Copper plate/layer (i) Bath temperature: 270°C (ii) Number of dips: 2 (iii) Duration of each dip: 5 minutes Joining of the copper plate/layer with the steel substrate: (a) Preheating (common to the mould, treated steel substrate and copper plate): (i) Temperature: 200°C (ii) Duration: 15 minutes (b) Joining medium: molten tin (i) Temperature of the tin bath: 290°C (ii) Duration: 8 minutes Babbitting (a) Pouring temperature: 450°C (b) Temperature of the steel cover: 280°C Example 4 Substrate : Mild steel plate Size: 200 X 100 X 20 mm Intermediate layer : Chrome copper (Cu - 1.0% Cr-.lZr) plate Size: 200 X 100 X 6 mm Babbitt lining: Tin-base babbitt Composition (element, wt%): INDO 84: Sn - 11.6 Sb - 5.7 Cu - 0.5 As - 1.2 Cd - o.3 Ni Thickness of the babbitt lining: 5 mm Heat treatment of the steel substrate: (a) Temperature: 650°C (b) Duration: t = (X+l)2 where, X = thickness of the steel substrate in inch t = duration in hrs Samples to be cooled in the furnace after the treatment. Gramophone finishing: (a) Pitch-to-pitch distance = 0.14 mm (b) Pitch depth = 0.25 mm Pickling: (a) Steel substrate/backing: (i) Dipping medium: 7 % hydrochloric acid (ii) Duration: 7 minutes (b) Chrome copper layer/plate (i) Dipping medium: 7 % nitric acid (ii) Duration: 7 minutes Neutralization: (i) Dipping medium (common for the steel substrate and chrome copper plate): 7 % ammonium hydroxide (ii) Duration: 4 minutes Surface protection: Composition of the paste: Sodium silicate: 50 cc Red oxide (FeO): 100 gm Water: 200 cc Preheating (common for the steel substrate and chrome copper plate): (a) Temperature: 2 8 0°C (b) Duration: 30 minutes Fluxing: (a) Steel substrate: Composition of the flux: Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc (b) Chrome copper plate/layer: (i) Composition of the flux 1: Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc (ii) Composition of the flux 2: Saturated solution of zinc chloride in distilled water (c) Tin bath: Composition of the flux: Zinc chloride = 75 wt% Ammonium chloride =25 wt% (d) Molten babbitt: Composition of the flux: Ammonium chloride Tinning: (a) Stee1 substrate: (i) Bath temperature: 270°C (ii) Number of dips: 3 iii) duration of each dip: 5 minutes (b) Chrome copper plate/layer (i) Bath temperature: 270°C (ii) Number of dips: 2 (iii) Duration of each dip: 5 minutes Joining of the chrome copper plate/layer with the steel substrate: (a) Preheating (common to the mould, treated steel substrate and chrome copper plate): (i) Temperature: 200°C (ii) Duration: 15 minutes (b) Joining medium: molten tin (i) Temperature of the tin bath: 290°C (ii) Duration: 8 minutes Babbitting (a) Pouring temperature: 450°C (b) Temperature of the steel cover: 280°C With the help of above (developed) process, trimetallic bearings with different combinations (i.e. composition, size) of steel backing/copper insert and lining composition and thickness can be developed successfully. The thermally conducting metallic iiiulti layered bearings and such other engineering components could be more effective over the conventionally used bimetallic components in terms of less frictional heating due to increased rate of heat dissipation. This could increase the speed of rotation and load bearing capacity of the member being rotated with the help of the (multi layer) components. The main advantages of the developed process includes less number of processing steps, shorter processing durations and less cost involved. We claim: 1. 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. 2. A process as claimed in claim 1 wherein the grooves provided have pitch-to pitch distance ranging from 0.12 to 0.16 mm and pitch depth ranging from 0.20 to 0.30 mm. 3. A process as claimed in claims 1&2 wherein the cleaning of the substrate surfaces is effected using degreasing, pickling and neutralizing. 4. A process as claimed* in'claims 1 to 3 wherein the molten Babbitt used is IS 25 in the composition range of Sn-9.0 to 11.0% Sb-6.0 to 6.0% Cu- 5. A process of making thermally conducting metallic multi layers useful for the manufacture of industrial components substantially as herein described with reference to the examples.

Full Text

To meet the above requirements, a bearing is made of different materials wherein load is carried by one member while wear characteristics are attained by the other. A bimetallic bearing belongs to this category wherein the load is carried by the steel backing while the bearing lining is meant for better friction and wear characteristics. Although mild steel is most widely used as backing material yet alloy steels, bronzes, brasses and, to a limited extent, aluminium alloys are also used depending on the operating conditions of the bearings. Three main shapes namely half round, full round bush and thrust pad are common in bearing applications.
A recent report on "Technology in Indian Bimetal Bearing Industry" has been prepared by the Govt, of India, Dept. of Scientific & Industrial Research, Ministry of Science & Technology, in November, 1990 wherein the different processes of making bimetallic bearings have been discussed. Powder metallurgy route has been found to be the most widely adopted process amongst them. The powder metallurgy process involves the processing of the lining layers in the form of powder through sintering and rolling operations. The sheets are then fixed on to the steel backing mechanically. This is followed by diffusion bonding of the layers to generate good bonding with each other. Available information also indicates that the insertion of a thermally conducting layer in between the steel backing and the babbitt lining could improve the working efficiency of the bearings. This leads to the development of thermally conducting multi metallic layer bearings.

The methods of manufacturing thermally conducting multimetallic layer bearings have been described in US Patent No. 4,525,083 dated June 25,1985and US patent NO. 4,33,262 dated Aug 6,1985 wherein steel backing is bonded to the conducting intermediate layer in turn is then bonded with the babbitt layer preferably by welding technique . The drawback of this process is that it comprises a series of operations and is time consuming and costly. There is thus a need for a simpler and less expensive method for producing the thermally conducting multi metallic layer components.
The main object of the present invention is to provide a process for making thermally
invention is to provide a process for making thermally conducting multi metallic layers
useful for the manufacture of industrial components, which obviates the drawbacks as
detailed above.
Another object of the present invention is to provide improved multimetallic bonding of
varying sizes and thicknesses.
Yet another object is to provide a process for making multimetallic layers having improved
heat transfer and wear properties.
Accordingly, the present invention provided 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, i) 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 so 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 JO minutes and removing the joined substrates from the tin bath followed by cooling to a semi solid state; (iv) 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 cooling from the bottom side of the backing substrate till complete solidification.
In an embodiment of the present invention, the grooves provided such as gramophone finish may be having pitch to pitch distance in the range of 0.14 +, 0.02 and pitch depth 0.25 +_ 0.05 mm.
In another embodiment of the present invention, the cleaning of the substrate surfaces may be affected using known methods such as degreasing, pickling and neutralizing.
In another embodiment of the present invention, the molten babbitt used may be IS 25 in the composition range of Sn - 9.0 to 11.0% Sb - 5.0 to 6.0% Cu - In another embodiment of the present invention, the size of the (i) steel backing varies in the range of length 75-200 mm, breadth 50-100 mm and thickness 15-25 mm; (ii) conducting intermediate layer varies in the range of length 75-200 mm,
breadth 50-100 mm and thickness 3-6 mm; and (iii) the babbitt lining varies in the range of length 75-200 mm, breadth 50-100 ram and thickness 2-6 mm.
In another embodiment of the present invention, the tin bath temperature varies in the range of 260-290°C and the duration of dipping varies in the range of (i) 4-6 minutes per dip during the tinning of the steel backing and the thermally conducting intermediate layer and
(ii) 6-10 minutes during joining of the steel backing with the thermally conducting intermediate layer.
In its first embodiment of the present invention, the patent describes an improved process of tinning of steel plate and intermediate (thermally conducting) layer. In another embodiment, joining of the intermediate layer with the steel backing and babbitting over the intermediate layer has been described.
The process of tinning requires operations like heat treatment, surface preparation and fluxing of the surface prior to tinning.
The heat treatment of the steel backing/substrate is carried out at a predetermined temperature for a fixed duration so that existing hydrogen can be removed from the plate. The heat treated steel plate is machined to the required size/finish to remove scale and then its to-be-treated/joined surface subjected to machining to a predetermined finish. The machined surface is polished with the help of emery paper and rubbed with a wire brush to remove burs. Degreasing of the polished surface is done with cotton wet with trichloroethylene. Pickling is the next step in the operation wherein the steel backing is immersed in a
freshly prepared solution of HC1 for a fixed duration with a view to attain a clean surface. This is followed by neutralising the after effect of the acid on the to-be-treated surface with a freshly prepared ammonium hydroxide solution with intermediate rinsing with water followed by drying. The surface to be protected from tinning/babbitting is coated with a paste containing Na-silicate, red (FeO) oxide and water in a fixed ratio. The sample so prepared is preheated at a fixed temperature for a predetermined duration prior to fluxing (using a spray gun) with a solution having zinc chloride, ammonium chloride, sodium chloride, hydrochloric acid and distilled water in known quantities.
Tinning of the steel backing is carried out by dipping it in molten tin. The top surface of the tin bath is covered with a mixture of zinc chloride and ammonium chloride in a fixed proportion. After holding the plate inside the bath for a predetermined length of time, the sample is taken out. The excess tin is removed from the surface with a hair brush wet with the above mentioned liquid flux. Immediately after brushing, the tinned surface is sprayed with the liquid flux using a spray gun connected with a compressor. Tinning is completed in three successive dips with intermediate cleaning and fluxing as discussed above.
A copper/chrome-copper plate is machined to a desired finish/size. The to-be coated surface is then polished with emery paper, degreased with cotton moistened with trichloroethylene and pickled with freshly prepared nitric acid of predetermined concentration for a fixed time period. The

pickled surface of the plate is rinsed with running water, dipped in ammonium hydroxide solution and rinsed again with running water and finally dried. The plate is preheated to a desired extent prior to fluxing with a saturated solution of zinc chloride and tinning operations.
The copper/chrome copper plate after fluxing is immersed in molten tin; the bath of (molten) tin is covered with a mixture of zinc chloride and ammonium chloride to avoid its oxidation and to remove the oxidized mass. The temperature of the tin bath and the duration of dipping are so fixed that a good bonding forms in between the tin layer and the copper plate. Then the sample is taken out and the excess tin is removed with a hair brush wet with the liquid flux. This cycle is repeated twice for tinning a copper plate.
A specially designed mould is used for joining the (tinned) copper with (tinned) steel and babbitting. A graphite plate is fixed at the bottom portion of the mould. The tinned surfaces of steel and copper are degreased with trichloroethylene. The mould and the tinned plates of steel and copper are preheated sufficiently to remove moisture. The tinned surfaces of steel and copper just prior to their joining are fluxed. The steel plate is placed at the base of the mould and immersed in the tin bath maintained at a predetermined temperature for a fixed duration. The copper plate is then put over the steel backing in the mould and pressure on the copper plate is applied through dead weight. The mould assembly is taken out of the bath and the joining medium (tin) is allowed to become semi solid in air. Thereafter, the molten babbitt is poured on to the treated

surface of the sample in one step only. Ammonium chloride flux is sprayed on to the surface of the babbitt melt and the melt is cleaned prior to pouring. The top surface of the mould is covered with a preheated steel plate and the mould is cooled with compressed air from the bottom side. Finally, the sample is removed from the mould and subjected to required machining operations.
The following examples are given by way of illustration of the process of the present invention and should not be construed to limit the scope of the invention.
Example 1
Substrate : Mild steel plate
Size: 200 X 100 X 20 mm
Intermediate layer: Copper (99.5% purity) plate
Size: 200 X 100 X 6 mm
Babbitt lining: Tin-base babbitt
Composition (element, wt%): IS 25 : Sn - 10.0 Sb- 5.6 Cu- 0.08 As- 0.07 Cd Thickness of the babbitt lining: 5 mm
Heat treatment of the steel substrate:
Temperature: 650°C
Duration: t = (X+l)2
where, X = thickness of the steel substrate in inch t = duration in hrs
Samples to be cooled in the furnace after the treatment.
Gramophone finishing:
Pitch-to-pitch distance = 0.14 mm Pitch depth = 0.25 mm

Pickling:
Steel substrate/backing:
(i) Dipping medium: 7% hydrochloric acid (ii) Duration: 7 minutes
Copper layer/plate
(i) Dipping medium: 7% nitric acid (ii) Duration: 7 minutes
Neutrali zation:
(i) Dipping medium (common for the steel substrate and copper plate): 7% ammonium hydroxide (ii) Duration: 4 minutes
Surface protection:
Composition of the paste:
Sodium silicate: 50 cc
Red oxide (FeO): 100 gm
Water: 200 cc
Preheating (common for the steel substrate and copper plate):
(a) Temperature: 280°C
(b) Duration: 30 minutes Fluxing:
(a) Steel substrate:
Composition of the flux:
Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc
(b) Copper plate/layer:
(i) Composition of the flux 1:
Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc

(ii) Composition of the flux 2:
Saturated solution of zinc chloride in distilled water
(c) Tin bath:
Composition of the flux:
Zinc chloride = 75 wt.% Ammonium chloride = 25 wt.%
(d) Molten babbitt:
Composition of the flux:
Ammonium chloride
Tinning:
(a) Steel substrate:
(i) Bath temperature: 270°C (ii) Number of dips: 3 iii) duration of each dip: 5 minutes
(b) Copper plate/layer
(i) Bath temperature: 270°C (ii) Number of dips: 2 (iii) Duration of each dip: 5 minutes
Joining of the copper plate/layer with the steel substrate:
(a) Preheating (common to the mould, treated steel
substrate and copper plate):
(i) Temperature: 200°C (ii) Duration: 15 minutes
(b) Joining medium: molten tin
(i) Temperature of the tin bath: 290°C (ii) Duration: 8 minutes
Babbitting
(a) Pouring temperature: 450°C
(b) Temperature of the steel cover: 280°C

Example 2
Substrate : Mild steel plate
Size: 200 X 100 X 20 mm
Intermediate layer : Chrome copper (Cu - 1% Cr - 0.1 Zr) plate
Size: 200 X 100 X 6 mm
Babbitt lining: Tin-base babbitt Composition (element, wt%): IS 25: Sn - 10.0 Sb- 5.6 Cu- 0.08 As- 0.07 Cd Thickness of the babbitt lining: 5 mm
Heat treatment of the steel substrate:
(a) Temperature: 6 5 0°C
(b) Duration: t = (X+l)2
where, X = thickness of the steel substrate in inch t = duration in hrs
Samples to be cooled in the furnace after the treatment.
Gramophone finishing:
(a) Pitch-to-pitch distance = 0.14 mm
(b) Pitch depth = 0.25 mm
Pickling:
(a) Steel substrate/backing:
(i) Dipping medium: 7% hydrochloric acid (ii) Duration: 7 minutes
(b) Chrome copper layer/plate
(i) Dipping medium: 7% nitric acid (ii) Duration: 7 minutes
Neutralization:
(i) Dipping medium (common for the steel substrate and chrome copper plate): 7 % ammonium hydroxide (ii) Duration: 4 minutes

Surface protection:
Composition of the paste:
Sodium silicate: 50 cc
Red oxide (FeO): 100 gm
Water: 200 cc
Preheating (common for the steel substrate and chrome copper plate):
(a) Temperature: 280°C
(b) Duration: 30 minutes
Fluxing:
(a) Steel substrate:
Composition of the flux: Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc
(b) Chrome copper plate/layer:
(i) Composition of the flux 1:
Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc
(ii) Composition of the flux 2:
Saturated solution of zinc chloride in distilled water
(c) Tin bath:
Composition of the flux:
Zinc chloride = 75 wt.% Ammonium chloride = 25 wt.%
(d) Molten babbitt:
Composition of the flux:
Ammonium chloride

Tinning:
(a) Steel substrate:
(i) Bath temperature: 270°C (ii) Number of dips: 3 iii) duration of each dip: 5 minutes
(b) Chrome copper plate/layer
(i) Bath temperature: 270°C (ii) Number of dips: 2 (iii) Duration of each dip: 5 minutes
Joining of the chrome copper plate/layer with the steel substrate:
(a) Preheating (common to the mould, treated steel substrate
and chrome copper plate):
(i) Temperature: 200°C (ii) Duration: 15 minutes
(b) Joining medium: molten tin
(i) Temperature of the tin bath: 290°C (ii) Duration: 8 minutes
Babbitting
(a) Pouring temperature: 450°C
(b) Temperature of the steel cover: 280°C
Example 3
Substrate : Mild steel plate
Size: 200 X 100 X 20 mm
Intermediate layer : Copper (99.5% purity) plate
Size: 200 X 100 X 6 mm
Babbitt lining: Tin-base babbitt
Composition (element, wt%): INDO 84:
Sn - 11.6 Sb - 5.7 Cu - 0.5 As - 1.2 Cd - 0.3 Ni
Thickness of the babbitt lining: 5 mm

Heat treatment of the steel substrate:
(a) Temperature: 650°C
(b) Duration: t = (X+l)2
where, X = thickness of the steel substrate in inch t = duration in hrs
Samples to be cooled in the furnace after the treatment.
Gramophone finishing:
(a) Pitch-to-pitch distance = 0.14 mm
(b) Pitch depth = 0.25 mm Pickling:
(a) Steel substrate/backing:
(i) Dipping medium: 7 % hydrochloric acid (ii) Duration: 7 minutes
(b) Copper layer/plate
(i) Dipping medium: 7 % nitric acid (ii) Duration: 7 minutes
Neutralization:
(i) Dipping medium (common for the steel substrate and copper plate): 7 % ammonium hydroxide (ii) Duration: 4 minutes
Surface protection:
Composition of the paste:
Sodium silicate: 50 cc
Red oxide (FeO): 100 gm
Water: 200 cc
Preheating (comnon for the steel substrate and copper plate):
(a) Temperature: 280°C
(b) Duration: 30 minutes

Fluxing:
(a) Steel substrate:
Composition of the flux:
Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc
(b) Copper plate/layer:
(i) Composition of the flux 1:
Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc
(ii) Composition of the flux 2:
Saturated solution of zinc chloride in distilled water
(c) Tin bath: Composition of the flux: Zinc chloride = 75 wt% Ammonium chloride =25 wt%
(d) Molten babbitt: Composition of the flux: Ammonium chloride
Tinning:
(a) Steel substrate:
(i) Bath temperature: 270°C (ii) Number of dips: 3 iii) duration of each dip: 5 minutes
(b) Copper plate/layer
(i) Bath temperature: 270°C (ii) Number of dips: 2 (iii) Duration of each dip: 5 minutes

Joining of the copper plate/layer with the steel substrate:
(a) Preheating (common to the mould, treated steel substrate and copper plate):
(i) Temperature: 200°C (ii) Duration: 15 minutes
(b) Joining medium: molten tin
(i) Temperature of the tin bath: 290°C (ii) Duration: 8 minutes
Babbitting
(a) Pouring temperature: 450°C
(b) Temperature of the steel cover: 280°C
Example 4
Substrate : Mild steel plate
Size: 200 X 100 X 20 mm
Intermediate layer : Chrome copper (Cu - 1.0% Cr-.lZr) plate
Size: 200 X 100 X 6 mm
Babbitt lining: Tin-base babbitt
Composition (element, wt%): INDO 84:
Sn - 11.6 Sb - 5.7 Cu - 0.5 As - 1.2 Cd - o.3 Ni
Thickness of the babbitt lining: 5 mm
Heat treatment of the steel substrate:
(a) Temperature: 650°C
(b) Duration: t = (X+l)2
where, X = thickness of the steel substrate in inch t = duration in hrs
Samples to be cooled in the furnace after the treatment.
Gramophone finishing:
(a) Pitch-to-pitch distance = 0.14 mm
(b) Pitch depth = 0.25 mm

Pickling:
(a) Steel substrate/backing:
(i) Dipping medium: 7 % hydrochloric acid (ii) Duration: 7 minutes
(b) Chrome copper layer/plate
(i) Dipping medium: 7 % nitric acid (ii) Duration: 7 minutes
Neutralization:
(i) Dipping medium (common for the steel substrate and chrome copper plate): 7 % ammonium hydroxide (ii) Duration: 4 minutes
Surface protection:
Composition of the paste:
Sodium silicate: 50 cc
Red oxide (FeO): 100 gm
Water: 200 cc
Preheating (common for the steel substrate and chrome copper plate):
(a) Temperature: 2 8 0°C
(b) Duration: 30 minutes Fluxing:
(a) Steel substrate:
Composition of the flux:
Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc
(b) Chrome copper plate/layer:
(i) Composition of the flux 1:
Zinc chloride: 240 gm Ammonium chloride: 30 gm Sodium chloride: 60 gm Hydrochloric acid: 9 cc Distilled water: 1000 cc

(ii) Composition of the flux 2:
Saturated solution of zinc chloride in distilled water
(c) Tin bath:
Composition of the flux:
Zinc chloride = 75 wt% Ammonium chloride =25 wt%
(d) Molten babbitt:
Composition of the flux:
Ammonium chloride
Tinning:
(a) Stee1 substrate:
(i) Bath temperature: 270°C (ii) Number of dips: 3 iii) duration of each dip: 5 minutes
(b) Chrome copper plate/layer
(i) Bath temperature: 270°C (ii) Number of dips: 2 (iii) Duration of each dip: 5 minutes
Joining of the chrome copper plate/layer with the steel substrate:
(a) Preheating (common to the mould, treated steel substrate
and chrome copper plate):
(i) Temperature: 200°C (ii) Duration: 15 minutes
(b) Joining medium: molten tin
(i) Temperature of the tin bath: 290°C (ii) Duration: 8 minutes
Babbitting
(a) Pouring temperature: 450°C
(b) Temperature of the steel cover: 280°C

With the help of above (developed) process, trimetallic bearings with different combinations (i.e. composition, size) of steel backing/copper insert and lining composition and thickness can be developed successfully. The thermally conducting metallic iiiulti layered bearings and such other engineering components could be more effective over the conventionally used bimetallic components in terms of less frictional heating due to increased rate of heat dissipation. This could increase the speed of rotation and load bearing capacity of the member being rotated with the help of the (multi layer) components.
The main advantages of the developed process includes less number of processing steps, shorter processing durations and less cost involved.

We claim:
1. 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.
2. A process as claimed in claim 1 wherein the grooves provided have pitch-to pitch distance ranging from 0.12 to 0.16 mm and pitch depth ranging from 0.20 to 0.30 mm.
3. A process as claimed in claims 1&2 wherein the cleaning of the substrate surfaces is effected using degreasing, pickling and neutralizing.
4. A process as claimed* in'claims 1 to 3 wherein the molten Babbitt used is IS 25 in the composition range of Sn-9.0 to 11.0% Sb-6.0 to 6.0% Cu- 5. A process of making thermally conducting metallic multi layers useful for the manufacture of industrial components substantially as herein described with reference to the examples.

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Patent Number

232126

Indian Patent Application Number

374/DEL/1998

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

15-Mar-2009

Date of Filing

13-Feb-1998

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG NEW DELHI-110001 INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	OM PRAKASH MODI	REGIONAL RESEARCH LABORATORY (CSIR), BHOPAL.
2	SATYABRATA DAS	REGIONAL RESEARCH LABORATORY (CSIR), BHOPAL.
3	RUPA DAS GUPTA	REGIONAL RESEARCH LABORATORY (CSIR), BHOPAL.
4	ARIYUR HALASYAM	REGIONAL RESEARCH LABORATORY (CSIR), BHOPAL.
5	YEGNESWARAN	REGIONAL RESEARCH LABORATORY (CSIR), BHOPAL.
6	AMOL KUMAR JHA	REGIONAL RESEARCH LABORATORY (CSIR), BHOPAL.
7	BRAJ KISHORE PRASAD	REGIONAL RESEARCH LABORATORY (CSIR), BHOPAL.

PCT International Classification Number

C30B 29/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA