REPARATION DE MOULES A LINGOTS

REPAIR OF INGOT MOULDS

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
The invention provides a composition for use in the
repair of ingot mould bottom or stool plates, which com-
position comprises aluminium foil in particulate form,
iron oxide and a granular refractory material.

Revendications

1. A composition for use in the repair of ingot mould
bottom or stool plates, which composition comprises, by weight,
10% to 40% aluminium foil in particulate form, 40% to 80% iron
oxide and 5% to 40% granular refractory material.
2. A composition according to claim 1, wherein the
aluminium foil has a maximum particle size of 2 mm.
3. A composition according to claim 1 wherein the
granular refractory material is selected from zircon sand and
zircon flour.
4. A composition according to claim 1, which includes
a sensitiser selected from fluorspar and borax.
5. A composition according to claim 1, which includes
up to 10% by weight of fluorspar.
6. A composition according to claim 1, which includes
an additive selected from nitrates and alloying additives.
7. A composition according to claim 1, which includes
an alloying additive selected from ferrosilicon, ferromanganese
and ferrochromium.
8. A composition according to claim 1, which includes
up to 10% by weight of a nitrate.
9. A composition according to claim 1, wherein the
iron oxide is provided as millscale.
10. A composition according to claim 1, wherein the
iron oxide is selected from magnetite and red hematite.
11. A composition for use in the repair of ingot
mould bottom or stool plates, said composition comprising the
following ingredients:

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said percentages being by weight, based on the composition.
12. A composition for use in the repair of ingot
mould bottom or stool plates, said composition comprising the
following ingredients:
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said percentages being by weight, based on the composition.
13. A composition for use in the repair of ingot
mould bottom or stool plates, said composition comprising the
following ingredients:
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said percentages being by weight, based on the composition.
14. A method of repairing a bottom or stool plate of an
ingot mould containing a cavity, which method comprises locating
in the cavity a composition according to claim 1, reacting the
composition exothermically to form a molten slag, and allowing
the slag to solidify.

Description

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The invention relates to the repair of ingot moulds
and, in particular, to the repair of bottom or stool plates as
used in ingot moulds.
The bottom plates of ingot moulds tend to undergo
severe erosion in use, and there is a need to repair the cavities
formed in the plates which tends to be expensive. Various
exothermic compositions have been proposed for this purpose but
they have a tendency to generate fume. Some exothermic compositions
have been formulated which tend to reduce the evolution of fume
but fume evolution still occurs. Fume is not acceptable in steel-
works since it is generally inconvenient to workers and tends to
rise in the tall steelworks, the upper regions of which have
working parts, e.g. cranes, the windows of which get dirty.
In Japanese Patent Publication No. 52.106323 of
Foseco Japan Limited, published September 6, 1977, there is
described and claimed a method of repairing a stool plate of an
ingot mould comprising locating in a hole in the plate a mixture
comprising an exothermic composition and a refractory material in
granular form such as zircon sand or zircon flour, reacting the
mixture exothermically to form a molten slag and allowing the slag
to solidify. In the mixture the exothermic composition comprises
aluminium powder and iron oxide.
It has now been discovered that if aluminium foil
~ in particulate form is used in lieu of all or part of the
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aluminium powder there is less tendenc~ for fu~e to be evolYed.
According to this invention, in one aspect thereof, there
is provided a composition for use in the repair of ingot mould
bottom or stool plates, which composition comprises, by weight,
10% to 40% aluminium foil in particulate form, 40% to 80% iron
oxide, and 5% to 40% granular refractory material.
In the compositions of the invention the iron oxide
may be provided by millscale, magnetite, red hematite or mixtures
thereof. Since the purity of millscale affects the evolution of
fume, it is preferred to employ either a purer form of iron oxide
or, generally to minimize fume evolution, to use millscale
obtained in uncontaminated form. Suitable millscale is that
formed on ingots during soaking and removed prior to rolling.
:Preferably, millscale when employed will have a sieve
grading such that no more than 5% by weight will pass a - 100 mesh
BSS sieve and no more than 5% by weight will pass a +10 mesh BSS
~sieve. In the case of magnetite and some other iron oxides the
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sieve grading may be much finer, for example, up to 30% below
-100 mesh BSS sieve without being detrimental to the level of fume
evolved.
The granular refractory used in the compositions of the
invention may be any of the well known refractory materials,
preferably zircon sand or flour, or grog, and may be a powdered
material or of a coarser grade.
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The aluminium foil preferably has a particle size of
2mm maximum, e.g. from Q.OS to 2 mm, and is preferably in granular
form.
The compositions of the invention may include other
materials, e.g. those associated with exothermic compositions
such as a sensitiser e.g. fluorspar or borax, a nitrate, or an
alloying additive such as ferrosilicon, ferromanganese or ferro-
chromium or mixtures thereof.
The proportion of the ingredients in the compositions of
the invention may be adjusted to give any desired degree of repair
efficiency, refractoriness and fume evolution. Preferably the
following proportions are used, percentages being by weight:
aluminium foil pieces10 to 40%
iron oxide 40 to 80%
granular refractory5 to 40%
fluorspar 0 to 10%
nitrate 0 to 10%
In the compositions of the invention aluminium powder
may also be employed together with aluminium foil, but this of
course increases the risk of fume evolution. In some applications,
however, a small amount of aluminiu~ powder may be tolerated.
The invention, in another aspect, resides in a method of
repairing a bottom or stool plate of an ingot mould containing a
cavity, which method comprises locating in the cavity a
composition
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; according to the invention, reacting the composition
exothermically to form a molten slag, and allowing the
slag to solidify.
Following is a description by way of example o~
compositions in accordance with the invention and their
- use, all percentages being by weight.
An ingot mould repair composition was formulated
¦ by blending ingredients as follows: ;
, 10 Aluminium foil pieces 17%
¦ Iron oxide 60%
~¦ Zircon sand or flour 20%
. .
- Fluorspar 2%
~ -- Sodium nitrate 1%.
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. EXAMPLE 2
Another ingot mould repair composition was formula-ted
by blending ingredients as follows:
Aluminium foil pieces 18%
Magnetite 59%
Zircon sand or flour 20%
: . Fluorspar 2%
~¦ Sodium nitrate 1%.
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¦ ~ 25 A further ingot mould repair composition was formulated
by blending ingredients as follows:
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F.S. 976
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Aluminium foil granules
22 BSS mesh to
~ 100 BSS mesh 17%
; Millscale 70%
Grog 10%
Fluorspar 3%.
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EXAMPLE 4
, Compositions as set out in Examples 1 -to 3 were
', formulated using blown aluminium powder in place of the
particulate aluminium foil. In comparative tests using
the blown aluminium powder compositions on the one hand
and the compositions of Examples 1 to 3 on the other, burn
i.e. ignition of the compositions, was top initiated by
placing on top of a heap of each composition on a bottom
plate to be repaired a starter powder which was then ignited.
In the case of the aluminium powder compositions the heat
spread uniformly down the heap, and much fume was evolved
throughout a burn period of 45 seconds. In the case of
the compositions of the invention the burn time was 90
seconds but the heat seemed to be confined more within the
¦ heap and there was little or no fume until the last few
seconds,
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