FIELD OF THE INVENTION
The present invention relates to providing a fixture for manufacturing of skid pipes for
transporting slabs in walking beam furnaces. More particularly, the present invention is directed
to providing a fixture for assembly and welding of skid pipes for walking beam furnace adapted to
ensure required geometrical accuracy of these skids including the spacers and buttons attached
to it by maintaining the required narrow manufacturing tolerances in assembly and also to avoid
uneven warping of pipes during welding inside the special fixture, thus favouring fast and
accurate in-house production of the skid pipes for periodic replacement of the damaged ones.
BACKGROUND OF THE INVENTION
In the Hot Strip Mill and Plate Mill of the applicants' steel plant, slabs are rolled into coils and
plates respectively. To do so, cold slabs which are received from slab casting machines, are
heated to the rolling temperature (~1200°C) in furnaces. These furnaces are walking beam type
having two sets of so called "skids", namely fixed and movable. The movement of slabs inside the
furnace is facilitated by controlled movement of movable skids. They move in a rectangular
closed path. This movement is achieved by coordinated articulation of hydraulic cylinders.
The skids carry and move slabs inside the furnace. These are basically seamless tubes on which
mushroom shaped buttons are welded at regular intervals. Cooling water flows inside the tubes.
Buttons are made of special material which are directly exposed to flame inside the furnace.
They also carry the weight of the slabs.
It is evident from above that these buttons are subjected to extreme boundary conditions of heat
and strain. This results in wear and tear. Thus, these skids have a finite life of around 7-8 years
before they are replaced by new ones.
As the skid pipes are necessarily manufactured with very precise tolerance required for their
application and the buttons are made of special material, the prices of skid pipes procured from
outside sources are exorbitantly high.
There has been thus a need in the operation of walking beam type furnaces to provide means for
inhouse production of skid pipes with desired accuracy of dimensions and tolerances at required

rate to meet the requirement of replacement of damaged skids at reasonable cost with minimum
chances of rejection.
OBJECTS OF THE INVENTION
The object of the present invention is directed to providing a fixture for production of skid pipes
for walking beam furnaces involving assembly and welding of components with desired accuracy
and dimensional tolerance of the finished product.
Another object of the present invention is directed to providing a fixture for production of skid
pipes for walking beam furnace, involving simple and easy- to-make components produced with
inhouse resources at reasonable cost.
A further object of the present invention is directed to providing a fixture for production of skid
pipes for walking beam furnace which would able to ensure narrow tolerances of skid pipes and
also to avoid uneven warping of pipes during welding.
A further object of the present invention is directed to providing a fixture for production of skid
pipes for walking beam furnace wherein components including the spacers and buttons can be
assembled at fast rate with desired dimensional accuracy.
A further object of the present invention is directed to providing a fixture for production of skid
pipes for walking beam furnace which is composed of various components and clamping bolts
which are simple, safe and user friendly to operate and can be handled with less manpower.
A further object of the present invention is directed to providing a fixture for production of skid
pipes for walking beam furnace so that manufacturing process become fast and accurate using
multiple fixtures of same design.
A further object of the present invention is directed to providing a fixture for production of skid
pipes for walking beam furnace which would ensure producing skid pipes which are distortion free
and true to dimensions, within stipulated tolerances with zero rejection.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to providing a fixture for manufacturing
furnace skid pipes to carry and move slabs inside walking beam furnaces, comprising
a left fixture component and an identical right fixture component, each of which is
welded structure, provided with releasable clamping means ;
each of said left and right component comprising a plurality of holding plates adapted
to hold a pair of skid pipes at proper distance by tightening said clamping bolts;
means to assemble weld-in-pieces including skid buttons and distance pieces placed
in position and maintained with releasable clamping means for facilitating welding
of said weld in pieces to said skid pipes to thereby produce the skid pipes in said
fixture.
A further aspect of the present invention is directed to providing said fixture wherein the
said releasable clamping means comprises of any clamping means including clamping
bolts, U-bolts bolts, clamp plate.
A still further aspect of the present invention is directed to said fixture wherein said left
fixture component and an identical right fixture components have welded holding plates
with cut to shape apertures for holding the skid pipes at proper distance.
A still further aspect of the present invention is directed to said fixture comprising
a left fixture component and an identical right fixture component, each of which is
welded structure, provided with clamping bolts;
each of said left and right component comprising a plurality of holding plates
arranged longitudinally on top of I-sections to accommodate length of skid pipes;
said holding plates are having cut-to-shape apertures to hold a pair of skid pipes at
proper distance by tightening said clamping bolts;

means to assemble weld-in-pieces like skid buttons and distance pieces placed in
position and clamp.
A still further aspect of the present invention is directed to said fixture wherein skid
buttons are clamped one by one after placing them on the upper pipe at a pre defined
distance and clamped by clamp plate and U bolts.
A still further aspect of the present invention is directed to said fixture wherein after all the
weld-in-pieces are welded, fixture is opened and the skid pipe is removed ready for further
processing.
A still further aspect of the present invention is directed to said fixture adapted to maintain
narrow tolerances as per QAP laid down in manual supplied by OEM and also to avoid
uneven warping of pipes during welding.
Yet another aspect of the present invention is directed to said fixture adapted to produce
Skid pipes which are distortion free and true to dimensions, within stipulated tolerances to
ensure zero rejection.
A still further aspect of the present invention is directed to said process for manufacture of
furnace skid pipes involving the fixture comprising:
providing said left fixture component and an identical right fixture component, each
of which is welded structure having said cut-to -shape holding aperture such as to
hold the skid pipes at proper distance and thereafter together involving clamping
means ;
assembling the weld-in-pieces including skid buttons and distance pieces placed in
position and clamping with releasable clamping means ;
carrying out welding of the said weld in pieces to said skid pipes to thereby produce
the skid pipes in said fixture; and
finally releasing the clamped fixture to thereby provide the furnace skid pipes.

The objects and advantages of the present invention are described in greater details with
reference to the following accompanying non limiting illustrative drawings.
BRIEF DECSRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is the schematic view of the walking beam mechanism wherein skid pipes are used to
carry and moving the slabs through the furnace.
Figure 2: is the schematic view of the Construction details of the skid involving two parallel pipes
one above the other separated by spacers and a plurality of buttons along the top pipe at defined
spacing.
Figure 3: is the schematic perspective view of the fixture according to the present invention for
production of skid pipe assembly involving fitting and welding of the components.
Figure 4: is the schematic end view of the fixture shown in Figure 3, showing the fitting of
spacers and buttons in position in relation to pipes and the different clamping arrangements used
in the fixture.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention relates to a fixture for production of skid pipes for transporting slabs in
walking beam furnaces adapted to ensure required geometrical accuracy of these skids including
the spacers and buttons attached to it by maintain the required narrow manufacturing tolerances
in assembly and also avoiding unwanted uneven warping of pipes during welding.
In Hot strip mill, cold slabs which are received from slab casting machines, are heated to the
rolling temperature (~1200°C) in furnaces. These furnaces are walking beam type having two
sets of so called "skids", namely fixed and movable. Accompanying Figure 1 shows the
schematic view of the walking beam mechanism wherein skid pipes are used to carry and moving
the slabs through the furnace. The movement of slabs inside the furnace is facilitated by
controlled movement of movable skids. They move in a rectangular closed path. This movement
is achieved by coordinated articulation of hydraulic cylinders.

Accompanying Figure 2 shows the schematic view of the construction details of the skid
involving two parallel pipes one above the other separated by spacers and a plurality of buttons
along the top pipe at defined spacing. The skids carry and move slabs inside the furnace. These
are basically seamless tubes on which mushroom shaped buttons are welded at regular intervals.
Cooling water flows inside the tubes. Buttons are made of special material which are directly
exposed to flame inside the furnace. They also carry the weight of the slabs. Buttons are
subjected to extreme boundary conditions of heat and strain. This results in wear and tear. Thus,
these skids have a finite life of around 7-8 years before they are replaced by new ones.
Geometrical accuracy of these skids is of paramount importance. Manufacturing tolerances are
very close. To achieve these narrow tolerances and also to avoid uneven warping of pipes during
welding, a specially configured fixture has been developed by way of the present invention.
Accompanying Figure 3 shows the schematic perspective view of the fixture according to the
present invention for production of skid pipe involving fitting/assembly and welding of the various
components ensuring desired precise manufacturing tolerance.
This is made in two identical left and right components. Each component is a welded structure.
Holding plates are having cut- to-shape apertures to hold skid pipes at proper distance. Clamping
bolts are then tightened. Weld-in-pieces like skid buttons and distance pieces are placed. Buttons
are clamped one by one after placing them on the upper pipe at a pre defined distance and
clamped by clamp plate and U bolts as shown in accompanying Figure 4. Welding is carried out
using special electrodes recommended as per applicable standards based on material
specification. Proper spacing is also maintained in the fixture so that the welding of components
can be carried out in position. After all the weld-in-pieces are welded, fixture is opened and the
skid pipe is ready for further processing.
It is thus possible by way of the present invention to providing a fixture for assembly and welding
of skid pipes used for moving slabs in walking beam type furnaces, which ensure cost effective
production of skid pipe assemblies with desired precise dimensional tolerance and avoiding
distortion due to welding of various components of the skid pipe at required rate with no rejection
to replace the damaged skids.

We Claim:
1. A fixture for manufacturing furnace skid pipes to carry and move slabs inside walking
beam furnaces, comprising
a left fixture component and an identical right fixture component, each of which is
welded structure, provided with releasable clamping means ;
each of said left and right component comprising a plurality of holding plates adapted
to hold a pair of skid pipes at proper distance by tightening said clamping bolts;
means to assemble weld-in-pieces including skid buttons and distance pieces placed
in position and maintained with releasable clamping means for facilitating welding
of said weld in pieces to said skid pipes to thereby produce the skid pipes in said
fixture.
2. A fixture as claimed in claim 1 wherein the said releasable clamping means comprises
of any clamping means including clamping bolts, U-bolts bolts, clamp plate.
3. A fixture as claimed in anyone of claims 1 or 2 wherein said left fixture, component
and an identical right fixture components have welded holding plates with cut to
shape apertures for holding the skid pipes at proper distance.
4. A fixture as claimed in anyone of claims 1 to 3 comprising
a left fixture component and an identical right fixture component, each of which is
welded structure, provided with clamping bolts;
each of said left and right component comprising a plurality of holding plates
arranged longitudinally on top of I-sections to accommodate length of skid pipes;
said holding plates are having cut-to-shape apertures to hold a pair of skid pipes at
proper distance by tightening said clamping bolts;
means to assemble weld-in-pieces like skid buttons and distance pieces placed in
position and clamp.

5. A fixture as claimed in anyone of claims 1 to 4 wherein skid buttons are
clamped one by one after placing them on the upper pipe at a pre defined distance
and clamped by clamp plate and U bolts.
6. A fixture as claimed in anyone of claims 1 to 5 wherein after all the weld-in-
pieces are welded, fixture is opened and the skid pipe is removed ready for further
processing.
7. A fixture as claimed in anyone of claims 1 to 6 adapted to maintain narrow
tolerances as per QAP laid down in manual supplied by OEM and also to avoid
uneven warping of pipes during welding.
8. A fixture as claimed in anyone of claims 1 to 7 adapted to produce Skid
pipes which are distortion free and true to dimensions, within stipulated tolerances
to ensure zero rejection.
9. A process for manufacture of furnace skid pipes involving the fixture as claimed in
anyone of claims 1 to 8 comprising:
providing said left fixture component and an identical right fixture component, each
of which is welded structure having said cut-to -shape holding aperture such as to
hold the skid pipes at proper distance and thereafter together involving clamping
means ;
assembling the weld-in-pieces including skid buttons and distance pieces placed in
position and clamping with releasable clamping means ;
carrying out welding of the said weld in pieces to said skid pipes to thereby produce
the skid pipes in said fixture; and
finally releasing the clamped fixture to thereby provide the furnace skid pipes.

ABSTRACT

There is provided a fixture for manufacturing of skid pipes for transporting slabs in walking beam
furnaces. More particularly, the present invention is directed to providing a fixture for assembly
and welding of skid pipes for walking beam furnace adapted to ensure required geometrical
accuracy of these skids including the spacers and buttons attached to it by maintaining the
required narrow manufacturing tolerances in assembly and also to avoid uneven warping of pipes
during welding inside the special fixture, thus favouring fast and accurate in-house production of
the skid pipes with minimum/no rejection, required to meet periodic replacement of the
damaged ones.