Note: Descriptions are shown in the official language in which they were submitted.
20~7955
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Lubrication System or Casting Moulds
Field of the Invention
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This invention relates to continuous casting moulds,
and more particularly to lubricating systems for effective
lubrication of the mould surface.
Casting moulds are used to shape molten metal and to
- extract heat from this metal to form a solid casting or
ingot. These moulds have two basic characteristics. The
first is to extract heat to effect solidiEication, and the
second is to provide a parting agent or lubricant to
prevent adherence between the molten metal and the mould.
The distribution of the lubricant over the surface of the
inner mould wall has a substantial efeect on the surface
-` ~uality of the ingot.
For example, in continuous casting in insulated or hot
top moulds, it is commonplace to use an insulating head
formed of a heat resistant and insulating material, such as
a refractory material, which resists contact with the
molten metal to be cast. The insulating head is located at
a position contiguous with or adjacent to and extending
around the periphery of the top portion of the mould wall.
The use of an insulating head portion provides for a rela-
tively constant withdrawal of heat from the molten metal
during the casting operation especially when using a short
mould wall.
The lubrication of the walls of moulds with insulating
heads has proven to be difficult. Thus, the point of
contact between the molten metal and cooled mould wall
where the lubricant must be applied is not readily
accessible but is covered by the insulating head.
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Lossack et al U.S. Patent 4,057,100, issued November 8,
` 1977, describes a lubricating system for a continuous
casting mould which represents one attempt at overcoming
the problems of uniform delivery of lubricant to the mould
surface~ They have provided a lubricant reservoir within
the mould itselE, which is arranged such that gravity flow
of li~uid cannot occur between the reservoir and the mould
surface. This design depends upon periodic small pressure
changes within the meniscus area between the molten metal
and the top of the mould cavity to draw lubricant from the
reservoir.
Another attempt at trying to assure the supply of
lubricant along the entire length of a mould surEace is
described in Pryor et al U.S. Patent ~,~20,030, issued
December 13, 1983. This uses discrete lubrican~ Eeed
holes extending through the mould and utilizes delivery
holes of difEering sizes to deliver different amounts of
lubricant.
Typical lubricants (Ised for this purpose include
castor oil, rapeseed oil, other vegetable or animal oils,
esters, paraffins, other synthetic liquids, and any other
suitable lubricants typically utilized in the casting art.
These materials all have a substantial viscosity and moving
them through relatively small conduits results in con-
siderable riction loss or drag. This friction loss is
inversely proportional to the diameter to the fifth power
of the passage.
It is the object of the present invention to provide
an improved lubricant delivery system which compensates
for the friction losses auring lubricant delivery such that
a uniform flow of lubricant is provided along the entire
length of the mould surface.
Summary of the Invention
According to the present invention an apparatus is
provided for casting molten metal. This includes a mould
for effecting solidification of the molten metal into a
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formed metal product, means adjacent to an inlet portion
of the mould for feedin~ the molten metal into the mould
and means for delivering a lubricating agent to a surEace
of the mould contacting the molten metal to substantially
S prevent adhesion of any solidified metal on the surface.
The lubricant delivery system includes at least one
lubricant delivery channel arranged generally parallel to
the mould surface. Inlet means is provided for delivering
a flow of lubricant (oil) under pressure into the delivery
channel. A plurality of small flow passages extend between
the delivery channel and the mould surface for delivery of
lubricant from the channel to the mould surface.
The present inventor has found that when the delivery
channel is required to have a rather small cross sectional
area, e.g. having an effective diameter of less than about
25 mm, there are serious problems in uniform delivery of
lubricant to the mould surface because oE high friction
losses within the delivery channel. According to the
present invention, a system and procedure have been
developed in which the total friction loss of the system
can be proportionally increased downstream from the
delivery channel such that the friction loss from the
lubricant ~low in the delivery channel is negligible
relative to the total friction loss of the system. The
result of this is that lubricant delivered under pressure
to the delivery channel is transferred uniformly from that
channel through the flow passages to the mould surface.
~ preferred embodiment of the novel lubricant delivery
system of the present invention includes at least two
lubricant delivery channels arranged generally parallel to
the mould surface. These include a secondary channel
laterally spaced a predetermined distance from the mould
surface to be lubricated and a primary channel spaced from
the secondary channel. Inlet means aré provided for
delivering a flow of lubricant under pressure into the
primary lubricant channel.
ZO~)'7955
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A plurality of uniformly spaced first restrictive flow
passages extend across between the primary and secondary
channels and a plurality of uniformly spaced second
restrictive flow passages extend across between the
secondary channel and lubricant outlet holes at the mould
surface for delivery of lubricant to the mould surface~
The second restrictive flow passages have effective
diameters smaller than the first restrictive flow passages
and the first restrictive flow passages have effective
diameters smaller than the lubricant channels. In this
manner, the frictional loss from the lubricant ~low in the
primary lubricant channel is negligible relative to the
total friction loss of the total system whereby lubricant
delivered under pressure to the primary lubricant channel
is transferred uniformly through the second restrictive
flow passages to the mould surface.
Typically the second restrictive flow passages have
smaller diameters, are shorter and are more closel~ spaced
than are the ~irst restrictive flow passages. While ~he
required friction losses are typically based on the
diameter of the restrictive flow passages, any combination
of diameters, lengths and spacings of these passages may
be used to obtain the required friction losses. In a
typical example, the first restrictive flow passages have
diameters of 1.2 mm, lengths of 30 mm and lateral spacings
of 100 mm while the corresponding second restrictive
passages have diameters of 0.~ mm, lengths of 6 mm and
; lateral spacings of 12.7 mm. These may be used with
delivery channels having effective diameters of 5.1 mm.
The lubricating agent delivery system of this invention
may be used with moulds for a variety of ingot shapes,
including extrusion and sheet ingot, with or without
insulated or hot tops. It is of particular value with a
casting device having a mould having an inner, axially
;; 35 extending l~all defining a mould cavity, and an insulating
head member formed of a heat insulating
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material having a first portion extending transversely
over at least a part of the mould cavity and a second
portion contiguous with the upper mould surface.
The lubricant delivery channel or channels and the
flow passages can be formed in an oil plate positioned on
top of a mould or directly within the mould itselE or
portions thereof may even be formed within the insulating
head member. The Elow passages extending between the
delivery channel and the mould surface may be discrete
holes formed in one of the above or they may be in the
Eorm of grooves formed either in the top face of the mould
or in the bottom face of an oil plate.
For effective operation of the present invention, the
friction loss of the lubricant flow in the delivery
lS channel is preferably less than 10~ relative to the total
friction loss of the total system, with a ratio oE less
than 5% being particularly preferred.
Brief Description of the Drawings
The invention will be more fully understood from the
following description oE embodiments thereof, given by way
, of example only, with reference to the accompanying
;` drawings, in which:
Figure 1 is a perspective view of an insulated sheet
ingot mould assembly;
Figure 2 is a cross section of an oil plate showing
the lubricant delivery system of the invention;
Figure 3 is a schematic plan view of the lubricant
- delivery system of Figure 2;
Figure 4 is a schematic plan view of an extrusion
ingot mould;
Figure 5 is a schematic plan view of an extrusion
ingot mould with a single delivery channel; and
Figure 6 is a cross section of the system of Figure 5.
Description of the Preferred Embodiments
The embodiment shown in Figure 1 is a mould assembly
having an open-ended rectangular body configuration.
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A mould plate 32 has a vertical mould face 33 which comes
in contact with the molten metal. A coolant manifold ~2 is
fed with coolant through inlet 13 for the purpose of
cooling the mould surface.
The inlet portion of the mould assembly includes an
insulating head 14 which generally conforms to the shape of
the mould with which it is associated. This insulating
head is formed of a heat resistant and insulating material,
such as a refractory material, which will not deteriorate
when in contact with the molten metal to be cast. This
head 14 is located at a position contiguous with or
adjacent to and extending around the periphery of the top
portion o the mould wall face 33. The use of such insu-
lating head provides a relatively constant withdrawal oE
heat from the molten metal durin~ the casting operation
when using a short mould wall.
For casting an ingot, molten aluminum is fed into the
insulating head 1~ and is chilled while passing mould plate
wall face 33 sufficiently to form an outer skin. This is
further cooled by water sprays.
Lubrication System
The oil delivery system of this invention is
illustrated in Figures 2 to 6 and is intended to provide a
uniform distribution of oil on the mould face under all
casting conditions. In the embodiment of Figure 2, an oil
plate 10 on top of mould 32 includes a large primary
channel 20 extending generally parallel to the oil plate
face 11 and mould face 33 and remote therefrom. A
secondary delivery channel 23 of smaller cross sectional
dimension is positioned spaced from primary channel 20 and
also spaced a short distance from oil plate face 11. A
plurality of restrictive passages 21 extend across between
channels 20 and 23. These are drilled from face 29 of oil
plate 10 with a portion 21' extending from end 29 to
channel 20 and the main passage 21 then extending between
channels 20 and 23. After these holes have been drilled,
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; the ends at wall 29 are plugged by means of plugs 22. A
plurality of second restrictive passages 24 extend between
channel 23 and oil plate face 11.
In the bottom face 19 of oil plate 10 slots 25 and 26
are provided for O~rings 27 and 28 respectively. These
O-rings serve to seal the oil plate on top of mould 32.
Figure 3 is a schematic plan view which generaLly
; shows the rectangular mould assembly with the mould cavity
30, primary delivery channel 20, secondary delivery
. 10 channel 23, restrictive passages 21 and restrictive
passages 24. Figure 4 shows an extrusion ingot mould
having a mould cavity 31, together with the prlmary
channel 20, the secondary channel 23, cross passages 21
and oil delivery passages 24.
: 15. In the arrangement shown in Figures 5 and 6, an oil
; plate 35 is position on top Oe a mould 32 having a mould
~; face 33~ The oil plate has an outer edge face 36 and an
inner edge face 37 which con~acts the molten metal. A
lubricant channel 38 of relatively large effective
diameter is provided in the oil plate and a plurality of
equally spaced restrictive passages 39 extend between
. channel 38 and oil plate edge face 37.
;: It has been found that when the diameters, lengths and
; numbers of restrictive passages 39 are selected such that
the total friction loss of the system is sufficiently high
that the friction loss from the cha~nel 38 is less than
10~, preferably less than 5%, of the total friction loss
~ to the total system, the lubricant is delivered uniformly
; through the plurality of restrictive flow passages 39.
Examples
- Example 1
A series of tests were conducted utilizing a system as
illustrated in attached Figure 2.
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The arrangement used had the following characteristics:
Length of primary channel (20) 2600 mm
~iameter of primary channel t20) 5.1-19 mm
Viscosity of oil 346 centistokes
S Oil flow rate 122 ml/min
Spacing between primary restrictions 75 mm
Length of primary restrictions (21) 30 mm
Diameter of primary restrictions (21) 1 mm
Equivalent diameter oE secondary channel (23) 5.1 mm
Spacing between secondary restrictions 25.4 mm
Length of secondary restrictions (24) 6.2 mm
Diameter of secondary restrictions (24) 0O5 mm
Determinations were made on the effect of varying the
diameter of the primary channel. This was varied between
5.1 and 19 mm. The results of this variation in the
diameter of the primary ehannel are shown in Table 1 below.
T lel~
Dia. o~ ~r.imary c~annel~(mm~ 5.1 7 ~ -~ 12.7 19
~otal frlction 10s8 ln primary chann~I (kPa) 56.6 ~r~~ s.a 2~6 --I~- _~ _
2 0 Friction variation - start to end of primary
channel (~)99.899.899.8 99.8 99.8 99.8
Friction lcss in primary restriction ~kPa)25.325.325.3 25.3 25.3 25.3
Friction loss in secondary channel (kPa) 9.5 9.5 9.5 9.5 9.5 9.5
Friction los.e in secondary restriction (kPa~ 13.913.9 13.9 13.9 13.9 13.9
Theoretical total pressure in
: first hole ~PIPT~ (kPa)95.955.245.141.940.7 39.5
2 6 rheoretical total pressure in
last hole "PTDT~ ~kPa)39.339.339.339.239.2 39.2
Uni~ormity variation in percent56.118.67.2 3.3 1.90.37
Rates of primary channel resistance/
total system resistance (~) _ 59.028.912.9 6.2 3.6 l0.7
*The total friction loss in primary channel (kPa) and
friction variation - start to end of primary channel (~)
are caleulated with a uniform flow variation or it is
assuming a uniform variation to establish the primary
channel friction losses.
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From the above results it will be seen that increasing
the effective diameter of the primary channel has a very
dramatic effect on the uniformity of the oil delivery. It
furthermore shows that when space constraints necessitate
the use of an oil delivery channel of small effective
diameter, there are problems in lubricant distribution.
Example 2
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The same system and same general procedure was used as
described in Example 1, but in this case the diameter of
the primary channel was fixed at a rather small size of
5.1 mm and the diameter of the primary restrictions was
varied between 0.4 and 2 mm. The results obtained are
- shown in Table 2.
From the results obtained in Table 2, it is evident
that the problems shown in Table 1 when a small primary
channel diameter of S.l mm was used can be solved by
varying the diameters of the primary restrictions. Thus,
when these were reduced down to a diameter of less than
; .S mm, a very hlgh degree of unlformity was achieved.
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