Title of Invention

AN IMPROVED PROCESS AND DEVICE OF BONDING OF BABBITT METAL ON A SUBSTRATE OF PRODUCE BABBITTED BEARIING

Abstract This invention relates to a process and device of bonding of babbitt metal on a substrate to produce babbitted bearing by pouring molten babbitt metal in the molding space (8 and 10) in a bearing shell assembly (S) to form an integrated bonding of the babbitt metal with a HP liner (7) on directional solidification of the said metal to form an edge defect free bonding (8) with the HP liner circumferentially at the inner side of the bearing surface of the HP liner and also at the edges of the bearing shell (HP liner) by forming a collar (10). The bearing shell is attached to fixture plates (6) at both side and the bearing shell assembly is fixed on a centrifugal casting machine, wherein the molten metal is poured in the integrated molding space (8 and 10) of the preheated bearing shell assembly through preheated ladle to form a babbitted bonding of the HP liner on solidification on cooling.
Full Text -2-
AN IMPROVED PROCESS AND DEVICE OF BONDING OF BABBITT METAL ON A SUBSTRATE TO PRODUCE BABBITTED BEARING
FIELD OF THE INVENTION
This present invention relates to development of an improved process and device of bonding of babbitt metal on a substrate. More particularly the present invention relates to an improvement of babbitting process for bearings to achieve permanent adhesion / bonding of babbitt material with thin section base steel, metallic or alloy material.
The present invention is useful particularly for thin section bearings of large size / higher ratings steam turbine, generator motor and hydropower products.
BACKGROUND OF THE INVENTION
Babbitting in the existing process for thin .section is unsuccessful due to failure of the bonding of babbitt material (an alloy of tin, copper, antimony and lead) at

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the edges of thin substrate. As a consequence the production line is hampered through loss of time due to rejections and repeated works for putting up the bearing in order. Not only that, on going through such repeated works the base steel bearing shell is discarded and replaced due to dimensional shortage in length during repeated machining and subsequent processing.
In the existing art the substrate (base material) the inner surface of which required to be bonded with babbitt metal is fixed on a centrifugal machine with a fixture and the bearing shell surface is tinned in a furnace before fixing it on the centrifugal machine. The babbitt metal is melted and the molten metal is poured in the bearing shell fixture assembly which is mounted on rotating centrifugal machine and the bearing shell is subsequently cooled. Due to shrinkage of the metal on cooling, the adjacent zone to the fixture plate become prone to result a non adherent / non bonding surface. Thus the HP liner is failing due to its non bonding with the babbitt metal at its edges.
The present invention is aimed to remove the aforesaid difficulty of prior art by developing an improved process and device.

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DESCRIPTION OF THE INVENTION
The proposed invention has been developed on thorough prior art literature survey and experiments for optimized bonding of babbitt metal on steel and other metal alloys substrate (H.P. liner and other thin section bearings) through modification of the existing fixture and characterize evaluated the resulted bearings.
According to one objective of the invention the problem of the prior art was analyzed with data collections, process parameters were studied and root cause of the failure of the bonding of babbitt metal was studied and remedial measures were found out on test trials.
Another objective of the invention is to develop and use collar for the base bearing shell.
A further objective of the invention is to develop a suitable fixture to reduce heat loss during cooling with lesser surface coritact with the bearing shell.

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A still another objective of the invention is to modify process of temperature measurement with instrument going through radiation during its direct contact to prevent heat loss instead of using instrument involved with conduction of heat.
A still further objective of the invention is that when the molten Babbitt metal was poured at 510 ± 10° C it is ensured that the temperature of the end metal during pouring does not drop below 480° C.
The resulted bonded babbitt metal to the substrate (usually steel base) is characterize evaluated by ultrasonic testing and any defect occurring at edges of the substrate (HP liner) is cut off to prevent any non-bonding defect to result improved babbitted bearing in the first attempt itself.
According to the invention there is provided an improved process of bonding babbitt metal on a substrate to produce a babbitted bearing comprising the steps of: pouring molten babbitt metal in the molding space in a bearing shell assembly having a fixture to form an integrated bonding of the babbitt metal with a HP liner on solidification of the said metal; forming an edge defect free

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bonding of the babbitt metal with a cleaned, shot blasted, tinned HP liner fixed in fixture plates at both sides of the HP liner and the solidified babbitt metal (8) on cooling; the said bonding being formed by plurality of protruded sections (12) of the molded metal on to the plurality of matching grooves maintained throughout the circumferential surface of the HP liner (3) and by forming a collar (10) at both the edges of the HP liner (7); matching the bearing shell to the required thickness of babbitt metal to form a babbitted bearing and; characterize evaluated the bearing for its non bonding edge defect by ultrasonic testing.
In industrial use in order to minimize the friction associated with the sliding movement of plane bearing a fluid lubricant is almost invariably used. Under ideal condition of lubrications a continuous oil film would be maintained between the sliding surface and the material used for bearing surface would be unimportant. However under the actual condition of bearing operation, some direct contact between the shaft and bearing surface in unavoidable. As a result the property of bearing material forming the bearing surface are actually of great practical importance. Hence the properties.of babbitt material and its adhesion quality to the base material plays important role for better operation for a longer

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service period. The bearing shell is cleaned of oil / grease and acid pickled to get rid of corrosive product if any. The bearing surface is then shot blasted with angular steel grit to make the surface conducive for adhesion. The fixture is designed to suit the designed thickness of babbitt metal required on the inner surface of bearing. The fixture along with bearing shell is fixed on centrifugal machine. The tinning is carried out on the shot blasted surface for adhesion of babbitt metal. The uniform temperature for tinning is achieved in heat treatment furnace maintained at suitable temperature with the temperature recorder. The tin based babbitt metal as per desired material grade is melted in the induction furnace which has time temperature recorder.
The molten tin based babbitt metal is poured through preheated ladle to the preheated bearing shell fixture assembly mounted on rotating centrifugal casting machine. After pouring the metal, the bearing shell is cooled at faster rate to get directional solidification.
After solidification the bearing shell is machined to the required thickness of babbitt metal. The adhesiveness is checked by ultrasonic test for non bonding defect. The surface is subjected to dye penetrant test to confirm crack free surface as per specification.

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The invention will be better understood from the following description of one embodiment with reference to the accompanying drawings in which
Figure 1 relates to a schematic cross sectional elevational view of a bearing shell with fixture of prior art.
Figure 2 relates to a schematic cross sectional elevational view of the bearing shell with fixture and collar according to the present invention.
In Figure 1 inner bearing surface of a HP liner (3) used in a steam turbine or generator or hydro power parts after being cleaned, shot blasted and tinned is provided on a bearing shell assembly (1) having a fixture plate (2) to clamp the bearing shell (3), the babbitt metal (4) to be bonded with the HP liner, on solidification of the molten metal (4) when the molten metal is poured in the bearing shell fixture assembly (1) provided with hollow mold space with plurality of protrusions at the top of the said mold chamber.

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The bearing surface of the HP liner being similarly matchingly grooved at plurality of joining points in which the said plurality of grooves of the liner are press fitted with the protrusions of the mold chamber for molten babbitt metal.
As hereinbefore described the said processing of bonding is supported for the circumferential surface of the substrate (HP liner) but the said processing does not provide any means of supporting the bonding of babbitt metal with a substrate at its edge of the bearing shell which are prone to non-adhesion from the cracks developed at the edge due to shrinkage of the babbitt metal during solidification of the molten metal resulting defected zone (5) at the edge and thus resulting frequent stoppage of the running line and replacement of bearing on repeated working.
The improved processing and the device to remove the above difficulties of the existing art is explained below in the exemplary embodiment shown in Figure 2.
As shown in Figure 2 the improved bearing shell fixture assembly (S) comprises optimized fixture plate (6) with a groove at the top of the fixture plate to engage in the groove the projected matching top part (11) of the HP liner (7) in fitting relationship and a thin collar (10) encircling the fixture plate and the HP liner and provided within fixture plate and the HP liner in register with circumferential

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surface of the HP liner and the collar being extended from the lower surface of the top projected part (11) of the HP liner to the top surface of the molding space (8) of the babbitt metal, thus extending the mold (8) combined with space (10) contiguous with the mold space (8).
The mold (8) has plurality of protrusions (12) at the top of the said mold chamber to be press fitted with matching plurality of grooves maintained at the HP liner.
The molten babbitt metal being melted in an induction furnace controlled by time temperature recorder is poured in the molding space to the preheated bearing shell fixture assembly (S) through preheated small capacity ladle. The molten metal is shown in the fixture assembly as + signs and it is cooled at faster rate to get directional solidification with chilling arrangement. Appropriate measures are taken through preheating of the bearing shell along with fixture at optimum temperature so that the last molten metal temperature of the babbitt metal does not reach below 480° C during pouring at the molding space of the bearing shell fixture assembly.

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After solidification of the metal the bearing shell (the HP liner bonded with babbitt metal) (11, 10 and 8) is machined to the required thickness of babbitt metal. The adhesiveness / bonding of the babbitt metal is checked by ultrasonic testing for non-bonding defect if any.,, The surface is also checked by dye penetrant test to confirm crack free surface of the bonding surface.
The improved bearing shell with collar and fixture does not show any edge defect (9) at the edge of the HP liner as it was occurring in the prior art with edge defect zone (5).
The present invention has the following advantages over prior art:
1. Improvement in bonding / adhesion quality.
2. Productivity saving.
3. Cycle time reduction.
4. Reduction in rework and rejection.
5. Cost reduction
The present invention has herein narrated should not be read and construed in a restrictive manner as some modifications and alterations in dimensions of babbitt metal thickness, fixture plates, collar are possible within the scope and limit of the invention as defined and encampused in the appended claims.

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WE CLAIM
1. An improved process of bonding babbitt metal on a substrate to produce a babbitted bearing comprising the steps of:
- pouring molten babbitt metal (8) in the molding space (8 and 10) in a
bearing shell assembly (S) having a fixture (6) to form an integrated
bonding of the babbitt metal with a HP liner (7) on solidification of the
said metal;
- forming an edge defect free bonding of the babbitt metal with a
cleaned, shot blasted, tinned HP liner fixed in fixture plates (6) at both
sides of the HP liner and the solidified babbitt metal (8) on cooling;
- the said bonding being formed by plurality of protruded sections (12)
of the molded metal on to the plurality of matching grooves
maintained throughout the circumferential surface of the HP liner (7)
and by forming a collar (10) at both the edges of the HP liner (7);
- matching the bearing shell (7) to the required thickness of babbitt
metal to form a babbitted bearing and;
- characterize evaluated the bearing for its non bonding edge defect by
ultrasonic testing.

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2. A process of bonding babbitt metal on a substrate as claimed in claim 1,
wherein the babbitt metal is melted in an induction furnace and the molten
metal is poured at 510 ± 10° C on preheating the bearing shell along with the
fixture at optimum temperature so that the last molten metal poured through
a preheated ladle does not reach below 480° C during pouring.
3. A process of bonding babbitt metal on a substrate wherein temperature
measure is carried through instrument based on radiation to prevent any heat
loss due to direct contact of the instrument with the substrate.
4. A process of bonding babbitt metal on a substrate wherein the bearing shell
with the fixture plates were constructed with optimized design to reduce heat
loss during cooling due to lesser surface area of contact of the substrate with
the fixture plate.
5. A process as claimed in the preceeding claims wherein the substrate is a steel
HP liner used in large size steam turbine, generator, motor or hydropower
products or other thin section bearings.

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6. An improved device of bonding babbitt metal on a substrate to produce a babbitted bearing comprising of:
- a bearing shell fixture assembly (S) consisting of a HP liner (7) an
optimized fixture plate (6) at both the ends of the bearing shell with
grooves at the top of the fixture plates (6) to engage in the grooves a
projected matching top part (11) of the HP liner (7) in fitting relation,
a thin collar (10) encircling the fixture plate and the bearing shell (7)
and provided within the fixture plate and the HP liner in register with
circumferential surface of the HP liner and the collar (10) being
extended from the lower surface of the top projected part (11) of the
HP liner to the top surface of molding space (8) of the babbitt metal,
thus combining the mold space (8) contiguous with the space (10);
- the mold (8) has plurality of protrusions (12) at its top to be press
fitted with matching plurality of grooves provided at the bottom
surface of the HP liner;

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- the combined molding space (8 and 10) being casted by pouring molten babbitt metal melted in an induction furnace to the optimized preheated bearing fixture assembly mounted on rotating centrifugal casting machine through preheated small ladle to form edge defect free bearing shell bonded with collar (10) and babbitted metal (8) at the inner surface of the HP liner on solidification.
7. A device as claimed in claim 6, wherein the casting of the Babbitt metal to be
bonded with the bearing shell in the molding space (8 and 10) is carried
through faster cooling with chilling arrangement provided on the mold space
(8).
8. A device as claimed in claim 6, wherein the cleaned, acid pickled shot blasted
and thinned bearing shell is put up in the fixture and fixture along with the
bearing shell is fixed on a centrifugal casting machine in which the bearing
shell is babbitted by pouring molten babbitt metal through preheated ladle in
the optimized preheated bearing shell assembly mounted on rotating
centrifugal casting machine and cooled on directional solidification.

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9. A process of bonding babbitt metal on a substrate to produce a babbitted bearing as herein described and illustrated in the accompanying drawings.
10.A device of bonding babbitt metal on a substrate to produce a babbitted bearing as herein described and illustrated in the accompanying drawings.

This invention relates to a process and device of bonding of babbitt metal on a substrate to produce babbitted bearing by pouring molten babbitt metal in the molding space (8 and 10) in a bearing shell assembly (S) to form an integrated bonding of the babbitt metal with a HP liner (7) on directional solidification of the said metal to form an edge defect free bonding (8) with the HP liner circumferentially at the inner side of the bearing surface of the HP liner and also at the edges of the bearing shell (HP liner) by forming a collar (10). The bearing shell is attached to fixture plates (6) at both side and the bearing shell assembly is fixed on a centrifugal casting machine, wherein the molten metal is poured in the integrated molding space (8 and 10) of the preheated bearing shell assembly through preheated ladle to form a babbitted bonding of the HP liner on solidification on cooling.

Documents:

01301-kol-2006 abstract.pdf

01301-kol-2006 assignment.pdf

01301-kol-2006 claims.pdf

01301-kol-2006 correspondence others.pdf

01301-kol-2006 description (complete).pdf

01301-kol-2006 drawings.pdf

01301-kol-2006 form-1.pdf

01301-kol-2006 form-2.pdf

01301-kol-2006 form-3.pdf

1301-KOL-2006-ABSTRACT 1.1.pdf

1301-KOL-2006-AMANDED CLAIMS.pdf

1301-KOL-2006-CANCELLED PAGES.pdf

1301-KOL-2006-CLAIMS 1.1.pdf

1301-KOL-2006-CORRESPONDENCE 1.1.pdf

1301-KOL-2006-CORRESPONDENCE.pdf

1301-KOL-2006-DESCRIPTION (COMPLETE) 1.1.pdf

1301-KOL-2006-DRAWINGS 1.1.pdf

1301-KOL-2006-FORM 1.1.1.pdf

1301-KOL-2006-FORM 1.1.pdf

1301-KOL-2006-FORM 2.1.1.pdf

1301-KOL-2006-FORM 2.1.pdf

1301-KOL-2006-FORM-27-1.pdf

1301-kol-2006-form-27.pdf

1301-KOL-2006-OTHERS DOCUMENTS.pdf

abstract-01301-kol-2006.jpg


Patent Number 245142
Indian Patent Application Number 1301/KOL/2006
PG Journal Number 01/2011
Publication Date 07-Jan-2011
Grant Date 04-Jan-2011
Date of Filing 04-Dec-2006
Name of Patentee BHARAT HEAVY ELECTRICALS LIMITED
Applicant Address 3rd FLOOR,KARUNAMOYEE,SALT LAKE CITY,KOLKATA-700091 NEW DELHI-110049
Inventors:
# Inventor's Name Inventor's Address
1 Prabhat Kumar Srivastava Dinesh Kumar,Ashish Ranjan Metallurgy Engineering,HEEP,BHEL,Haridwar,249403
PCT International Classification Number b23k3/00,f28d
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA