Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This ~ nvention relates to iT.lgOt moulds and in particular
lngot m:3uld hs~t topplng practice. Such practlc0 is
adopted ill an e~ ort to malnta1 n a reservo-lr OI molten
metal as long as possi ble whllst the ingot is solidIying.
In this manner the maximum amount of sound steel is
produced because it restricts the ma~nitude OI piping,
and impurity segregation is co~ ined to the top of the
ingot .
From one aspect ~ the present invention provides an ingot
o mould having at its llead a r0cess extellding a~ound the
whole o~ the 1 nner side and a collar supported in the
recess on the shoulder formed thereby, the collar having
an inner surfac~ substantially aligned with that of the
mould and an vuter surface spaced from the r~cessed mould
sur~ace which space :Ls :e illed with a thermally insulating
material.
The i~got mould~ togethcr with the recess and the collar
may be re~tangular or circular in section, an~ the irmer
wall may be fluted~ The mould may conventionally be made
2Q ~rom cast iron, the recess being machined, and the inner
mould sur~ace defined by the recess may have protrusions
in it for locati~g the collar, these protrusions lying
mid-way along the side of t~e mould or at t~e corsers -
: with a rectangular-section mould. Alterl~atively the collar
may be located by a pin a~d slot arrangeme~tO The collar
~: may be made ~rom steel but i~ pre~erably made ~rom cast iro~;
it may be the same as, or dii~erent ~rom the composition
o~ the mould a~d is pre~erably ~lake graphite or modi~ied
iron - the mould may likewise be made ~rom modi~ied 1ake
or spheroidal graphite iron. It may be shaped so as to
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po5sess 1additiollal' wall thickness ln those areas where the
heat ~rom the solidlfy:lng ingot ls more intense.
The thermally insulating mat~rlal may ~e a ceramic ~lbre,
e.g~ Kaowool or Saf~ Regd. Trad~ Mark) O
t~ot top~ moulds in accordance with thi~s invention possess
signi~lcant advantages ln so far as the head assembly may
last the li~e of the mould, but ln any event substantial
savings accrue be~ause the convent~onal heat insulating tiles
consumed w~th every ingot are not employed. Further 7 there is
a marked improvement in ingot y~eld with no deterioration in
internal quality.
In order that the invention may be fully understood two
smbodimen~sthereof will now be described~ by way of e~ample,
. with reference to the accompany ng draw~n~s, in which:-
: 15 Figure 1 illustrates a plan view o~ an ingot mould
according to this inventio~,
~igure 2 illustrates a section on II-II in ~igure 1.
Figure 3 illustrates a plan view with a different
collar;and
~ 20 ~igure 4 illustrates a section on IV-IV in Figure 3
; Referring now to the Fi~ures 1 and 2 in drawings, a rectangular
section ingot mould 1 cast in modified flake graphite iron,
which is tough and resist~nt to surface deterioration during
thermal cycling~ has machined in its upper end a recess.
This recess is def ined by a wall sur~ace 2 which extends
~; around the whole of the inner side of the mould, and a
shoulder 3.
The bottom corner 4 of the recess is pre-~erably curved as
ShQWn SO as to mitigate thermal stresses in use. Mounted in
3~ the recess and supported on the shoulder is a rectangular sectionl
eollar 5 cast in f 1akP graphite iron which has a high thermal
conductivity and is reslstant to distortion. It is machined
on its lower ~ace so 2S to mate closely with the shoulder 3,
and lts upper ~ace is coterminous with the head of the
moul~ 1. The lrlner sur~ace o~ the collar ali~n.s with the
inller sur~ace o~ the mould so as to present a smvoth
continuous profile.
The space between the collar and the wall sur~ace 2
o~ *he mould is filled with a ceramlc ~ibre blanket 7, e.g.
Kaowool or Sa~ll, whic~l is ~irmed into position ~rom above;
~his flbre may alternatlvely be in the ~orm o~ w~ol or loose
~ibres. The assembly may then be completed by securin~ c~ips
(not shown~ over the top o~ the mould to hold the collar in
place throughout the li~e o~ the mould.
Typical dimensions ~or a 3-tonne ingot may be 9 mould
thickness lOOmm, thermally insulating slot width 25mm,
collar thickness 25mm9 collar height 250mm.
This practice may be e~-~ected on either 'blg-end' 9
dowm or 'big-end9 up ingots a~d, in operation, as the
level of molten steel ~8) rises to the head o~ the ingot
the inset collar 5 acts QS a heat sink by reason of the
insul~ti~g fibre backing. The rate o~ cooling of the
head Q~ mol~en s$eel is thus sig~ificantly diminlshed by
this meansj together with the conve~tional anEi-piping
compounds dispensed orl to the upper surface 9 resultlng
in maximis~ng the amount o~ sound steel produced as
mentioned above. hn additional benefit as compare~ with
hot top tiles secured around the top o~ the ingot mould
is that ~here is less surface dressing with the present
arrangement because o~ the compatibility o~ the ingot
mould/collar materials - tile contamination is thus
avoided.
878
Since the heat in-tensity ~rom the solidi:Eying ingot
is greatest ml~way along the sides OI the ingot the collar
may be shaped so as to provide additional 'bodyq in these
arsas to lnhibit local meltlng and/or distortion.
Figllres 3 and 4 dep~ct such arl arrangement. The
collar 10 ls shaped ln a manner which roughly aligrls with
the isothermal contours to be expected so that pronou~ced
bulges are appare~t at the mid-point 1. As be~ore the
collar is supported on the shoulder 3 and the space between ;'
the collar and the mould wall sur~ace 2 is Iilled with
c~ramic Iib~e tnot shown). Plates 12 may be bolted over the
h~ad o~ the ingot mould to hold the collar in place.
Practice according to thls invention has show~ that
the assembly may readily last the liI e OI the mouldl with
little or no special maintenance being required an~ that
. provided a good seal ~s malntained between the lower end
o~ the collar and the shoulder 3 there is no ~lash in this
area; hanger cracks are avoided because the continuous;
mould/collar sur~ace ensures that at no time is the
solidiIying contracting ingot suspended iErom a higher
- ~ level.
Although this hot top practice has been described
with re~erence $o the particular arrangements illustrate~
it is to be understood that various modi~ications may
readily be made without dep~rting ~rom the scope o~ this
lavention~ For ex~mple, the mould need not be cast in
modiiied-~lake graphite iron, it could alternatively be
spheroidal graphite iron or even Ilake graphite; the
collar may l~kewise be made ~rom any o~ these materials or
indeed any other materials, e.g. cast or plate steel,
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provided they are compatible with the mould material and
s~r~e the purpose described. Thinner section collars may
also be utillsed consist0nt with providing a stabl0 shape
with no dis-tortion.
The shape oi the collar generally conforms to the shape
o~ the mould and likewise the shape of the recess is
governed by the mould shape. Any convelliently machineable
recess may be adopted avoiding in particular the ~orma~ion
of sharp corners or other stress-raising ~eatures ~rom
wbioh notch cracks may be propagated by reason o~ the
thermal stresses lmposed in use, As mentioned the inner
mvuld sur~ace de~îned by the recess may have collar-locating
protrusions in lt and ~hese are depicted at the corners (9
ln Figure 1 by way o~ example; they may o~ course be sited
elsewhere. These may indeed take the -~orm o~ separate.
inserts. In Figures 3 and 4 the collar location is e~ected
by pins 13 depending irQm the collar into slots 1.4 where
posltive location is desired. The location may alternatively
be e~fected ~rom pins or the like on the securing clips or
plates (12~
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