Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
SK:[D R~II,
Background
Reheat furnaces are used to heat heavy slabs of metal
(work pieces) which are moved through the furnace supported on
water cooled structural members called skid rails. These skid
rails include a wear bar secured to the top oE the skid rails
for contact with the slabs. The contact between the wear bars
and the slabs allows heat transfer from the slabs to the skid
rails which produce lines of chilling sometimes called "tiger
stripes"O Elimination of such tiger stripes is desired par-
ticularly where the slabs are to be used in producing steel
strips so that a uniform gauge strip may be produced.
An example of the work of the prior art -to eliminate
these tiger stripes is shown in U.S. Pat. No. ~,354,~24
wherein the wear bars secured to the top of the structured
member are staggered~ spaced apart and the top surface oE the
structural member covered between the wear bars with a metal
honeycomb reinforced insulation. While such structure has
been very successful in minimizing the heat transfer from the
slab to the skid railJ the wear bars still allow some cooling
of the slabO
Another example of the prior art is disclosed in UOS.
Pat. No. 3,214,15~ which discloses a work engaqing means
supported from a rail on two stacked blocks made of ceramic
material with the lower block which engages the structural
member having a density substantially less than th~ upper
block. It also suggests that the work engaging means may be
made of a material having a very high resistance to heat such
as cobalt or molybdenum. The use of low density ceramics as a
support may provide heat insulation but is subject to damage
when heavy work pieces are moved over the work engaging means.
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Summary
An object of -the present inven-tion is to provide an
improved skid rail to reduce the heat transfer from -the work
piece to the skid rail.
Another object is to provide an improved wear bar
structure for a skid rail which has a minimum of heat transfer
with respect to the work piece.
According to one aspect of the invention there is pro-
vided a skid rail for a reheat furance comprising a hollow
structural member having an upper flat sur:Eace, a support block
having a leg secured to said flat upper surface of said structural
member and flanges extending outward at the upper end of said
leg, a wear bar having an axial openinq extending therethrough
which is open at its lower portion and wider at its upper portion
to receive said suppor-t block therein, and means for securing
said wear bar on its support block to prevent axial movement of
the wear bar with respect to said upper surface of said hollow
structural member, said wear bar being of a material having low
thermal conductivity at elevated temperatures.
According to another aspect of the invention there is
provided a skid rail for a rehea-t furnace comprising a hollow
structural member having an upper flat surface, a wear bar, a
plurality of support blocks, and means coacting with said sup-
port blocks for securing said wear bar on the upper surface of
said structural member, said wear bar being of a material having
low thermal conductivity at elevated temperatures, said securing
means includes a plurality of cleats secured to the upper sur-
face of said structural member and positioned to engage said
blocks to secure said wear bar to said upper surface with a
space under said wear bar between blocks, said cleats each being
U-shaped and including a base, a pair of legs, and a pai.r of
caps secured -to said legs in overlying relationship to -the
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blocks positioned bet~een -the legs oE said base -to preven-t the
blocks from moving on said surface, and a stop posi-tioned on -the
other side of said block.
According to a further aspec-t of the invention there
is provided a skid rail comprising a hollow structural member,
a wear bar being of a material having low thermal conductivity
and high strength at elevated temperatures, said wear bar being
a different ma-terial than said structural member, and means for
securing said wear bar in a position above and along the length
of the upper surface of said structural member wherein said
securing means includes a plurality of brackets extending
across the upper surface o:E said structural member, said brackets
having a recess into which said support blocks are received, and
means for securing said brackets to said struc-tural member.
_ief Description of the Drawings
~ hese and other ob~ects and advan-tages oE -the present
invention are hereinafter set forth and explained wi-th reference
to the drawings wherein:
FIGURE l is a transverse sectional view of the preferred
embodiment of -the improved furnace skid rail of the present in-
vention taken along line l-l of FIGURE 2.
FIGURE 2 is a plan view of the improved skid rail shown
in FIGURE l.
FIGURE 3 is an elevation view of the improved skid rail
of FIGURES l and 2.
FIGURE 4 is a longitudinal sectional view of ano-ther
embodiment of the improved furnace skid rail of the present
invention taken along line 4-4 in FIGURE 3.
FIGURE 5 is a transverse sectional view of -the improved
skid rail shown in FIGURE 4.
FIGURE 6 is a plan view of the improved skid rail shown
in FIGURES 4 and 5 illustrating the wear bar retaining means.
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FIGURE 7 is a plan view of still another mocli:Eied ~orm of
skid rail.
FIGURE 8 is a transverse sec-tional view of the modified
form of skid rail taken along line 8-~ in FIGURE 7.
FIGURE 9 is a vertical longitudinal sectional view of -the
modified skid rail taken along line 9 ~ in FIGURE 7.
Brief description of the Preferred Embodiment
The preferred embodiment of the present invention is best
shown in FIGU~ES 1, 2 and 3 wherein skid rail llO includes
truncated triangular pipe 111 having flat upper surface 112 on
which wear bars 114 are mounted in intermittent parallel
relationship as shown. Insulation 115 is placed on the sides
and bottom of pipe 111, as shown in FIGURE 1 bu-t omitted for
clarity in FI~URES 2 and 3. T-shaped bars or blocks 116 which
are welded to surface 112 vertically secure wear bars 11~ to
pipe lllo Wear bars 114 are longitudinally secured by thrust
pads 118, which are welded to top surface 112 of pipe 111.
For ease of manufacture and assembly it is preferred that wear
bars 114 be comprised of short sections approximately
15 inches long with a thrust pad 118 being at each
section-to-section joint and each end. Wear bars 114 have a
T-shaped opening so they can be inserted onto T-shaped
bars 116 without requiring intimate thermal conducting con~act
as would result if bars 114 were welded directly to pipe 111.
Thermal conductivity is further impeded by inserting
insulation 117 between bars 116 and 11~ as shown in FIGURE 1.
It is preferred that insulation 117 be of an alumina silica
type, such as that manufactured by Babcock and Wilcox Company
of Augusta, Georgia under the trademark Kaowool ST. An
additional reduction in high temperature thermal conductivity
is obtained ~y manufacturlng wear bars 114 from an iron,
chrome, cobalt alloy which has low thermal conductivity at the
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high temperatures e~perienced in the metallurclic~l reheat
furnace. A suitable alloy ~or wear bars l14 would be one
havin~ the following composition C-0.12%, Mn-0.60~;
Si-0.07~; Cr-28.00~; Fe 21.00% and Co-~9.58%.
Insula~ing material 126 is embedded in reinforcing
frame 128 and is in physical contact with upper surface 112 of
pipe 111 and further reduces the heat transfer between -the hot
slab work piece (not shown) and pipe 111. Insulating
material 126 is preferred to be a dual material giving a
combination of high thermal resistance, high radiant
emissivity and high strength. Such a material is manufactured
by A.P. Green Refractory Co. of Mexico, Missouri under the
trademark Jade Pak 88P. It is preferred that the wear bars
and insulating material be arranged in two separate
alternating rows, as best seen in FIGURE 2, to further
minimize heat transfer -from the hot slab and eliminate tiger
stripes.
Brief Description of other Embodiments
A second embodiment of the invention is shown in
FIGURES 4, 5 and 6, wherein skid rail 10 includes truncated
triangular pipe 11 having flat top surface 12 on which wear
bar 14 is mounted and with insulation 15 on the bottom and
sides of pipe 11. Blocks 16 support and help secure wear
bar 14 by welding. Blocks 16 are uniformly spaced along wear
bar 14 with the spacing being provided so -that wear bar 14 is
not subject to damage due to the slabs or work pieces being
moved thereon. Means 18 is provided to retain wear bar 14 and
blocks 16 in the desired position relative to surface 12.
Such retaining means 18 includes cleats 20 and stops 21 which
are secured to surface 12. Cleats 20 and stops 21 are welded
on surface 12 in position and sized to secure blocks 16 to
skid rail 10 and to allow sufficient space for differences in
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thermal e~pansion. Cleat 20 includes V-shaped base 22 and
caps 24 on legs 25 of base 22. Caps 24 are secured -~o le~s 25
by welding so that they overhang the outer por~ions of
block 16 as shown. Suitable insulatlon material 26 is placed
within and around reinforcing frame 28 whlch is secured to
surface 12 of pipe 11 by welding. Portions of insulating
material 26 have been omitted in FIGURE 6 to show reinforcing
frame 28. This type of insulation 26 is disclosed in U.S.
Pat. No. 4,354,824 and such disclosure is incorporated herein
by reference. Pipe 11 is also coated with suitable
insulation 27.
As can be seen in FI~URES 4 and 6, insula-tion 26 extends
under wear bar 14 between blocks 16~ It is preferred that
insulation 26 not be in physical contact with wear bar 14.
Also clea-ts 20 and stops 21 are spaced along surface 12 to
engage opposite sides of blocks 16 on wear bar 14 so that
blocks 16 fit within the space bounded by legs 25, bases 22
and stops 21. It is preferred that bases 22 with blocks 16
positioned therein are secured to surface 12, then caps 2~ are
secured to bases 22 to secure blocks 16 in position and thus
secure wear bar 14 in place.
With the structure shown and described the material of
wear bar 14 and blocks 16 is preferred to be a material having
low thermal conductivity and high strength at elevated
temperatures such as the nickel based alloy sold by
International Mickel Company under the trademark
"Incoloy ~02".
Insulating material 26 is preferred to be a dual material
giving a cor~ination of high thermal resistance, high radiant
emlssivity and high strength. Cleats 20 and stops 21 are
steel and are used since the material of wear bar 14 and
block 16 cannot be readily welded to carbon steel, such as
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pipe 11, due to its chemical incompatibility and diIferent
coefficient oE thermal expansion. This structure provides a
load bearing insulation separating the hot slab -from the "heat
sink" of the water cooled pipe 11 to thereby eliminate tiger
stripes on the ho-t slab.
Still another embodiment of the invention is shown in
FIGURES 7, 8 and 9, wherein skid rail 30 includes truncated
triangular pipe 32 with suitable insulation 31 on i~s lower
surface and sides and having flat top sur-face 3~ on which
wear bar 36 is mounted. Blocks 38 support and secure wear
bar 36 by welding. Blocks 38 are uniformly spaced along wear
bar 36 with the spacing being provided so that wear bar 36 i5
no-t subject to damage due to the slabs or work pieces being
moved thereon. Means 40 is provided to retain wear bar 36 and
blocks 38 in the desired position relative to surface 34.
Such retaining means 40 includes bracke-t 42 which extends
across top surface 34 of skid rail 30 and has its outer
ends ~4 depending into slots 46 in flanges 48 of skid rail 30
and secured therein by suitable securing means 50. Such
securing means 50 may be spring loaded pins which extend into
holes in flange 48. Bracket 42 includes recess 52 in its
central portion into which block 38 is positioned. As can be
seen from FIGURE 4, brackets 42 are alternatively positioned
so that recesses 52 of adjacent brackets ~2 Eace in opposite
directions to secure blocks 38 and wear bar 36 as best shown
in FIGURE 7. Caps 54 are secured to hrackets 42 in position
to cover the outer edge of blocks 38 as shown in FIGURES 7 and
8.
Suitable insulating material 56 is placed within and
around reinforcing frame 58 which is secured to surface 34 of
pipe 32 by welding. In FIGURE 7 portions of insulating
material 56 have been omitted to show rein-Eorcing frame 58.
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Insulation material 56 is simil.ar to .insulation material 26
and extends under wear bar 36 between blocks 38. Also the
material of the other components of this modi-fied form are the
same as those in the preferred form previously described.
