Note: Descriptions are shown in the official language in which they were submitted.
WO 94/17217 ~ ~ r~ V S i 3 PCTIGB94/00108
Alloyi~g A~ditivo
This invention relates to an alloying additive. More particulary it relates to a method of making an alloying additive of fine metallurgical structure. ;;
It has for many years been appreciated that it can be advantageous for an
allcying additive to have such a structure, and that such a structure can be achieved by
castilg a melt of the alloy in such a way that the cooling to which the alloy is subJected
when passing from the molten to solid states is relatively rapid.
'::
For example, our French Patent Specifica~ion No. 2133439 relates to
aluminum-based alloying additives comprising a transition metal, normally titanium,
and boron. Such alloying additives are added to aluminium-based melts to providegrain refinement. The main active component of ~he alloying additive is boride
par~icles, normally titanium diboride, TiB2. In order to ma~imise the effectiveness of
those particles, the specification teaches subjecting the melt of the alloying material, as
soon as ~ossible after formation of the TiB2 particles, to rapid cooling to form the solid
alloy, thereby minimising the extent to which the TiB2 particles can grow in size. The
preferred method of rapid cooling taught in I:R 2133439 is casting into a mould of
thermally conducting material such as copper, which is preferably water cooled. A less
preferred alternative suggested is a splat qu~nching process comprising atomising the
melt to form droplets and projecting the molten droplets by means of a current of inert
gas against a cooled smooth surface, ~o that the molten droplets are rapidly solidified
by impact against the smooth surface without adhering to it. The former method entails
the danger that the rate of cooling will be insufficient, and als~ the moulded product
will not be of suitable form for many applications. The latter method is expensive to
operate.
European Patent Specifications Nos. 0398449 Al and 0421549 Al disclose
methods of producing strontium-aluminium alloying additives to be used as modifiers
for aluminium-silicon alloys. They both make use of the knowledge that solidification
of the melt at a relatively high rate of cooling will result in a fine metallurgical
structure in the solidified alloying additive. In both cases the process for achieving the
required rate of cooling involves atomisation of the melt. In EP 0398449 Al, theatomised droplets are quick cooled to obtain solid particles which are subsequently
processed to consolidate them. In EP 0421549 Al the atomised particles are collected
as solid material on a collecting surface. The atomisation process is e~cpensive to
operate, and in many cases requires steps, such as the provision of a special
atmosphere, to guard against air contamination of the alloying material.
WO 94/172t7 ~ 3 i ~ PCTIGB94/OOlOP~
-2 -
According to the present invention there is provided a method of making an
alloying additive of fine metallurgical structure, comprising providing a melt of
alloying material, providing cooling means comprising a cooling surface, applying one
or more substantially unatomised streams of the melt to the cooling surface to pr~duce
a splat product, and arranging the splat product into a dosage form suitable for making
- measured alloying additions.
Thus, it will be appreciated that the process of the invention provides a
relatively ine~pensive to operate process which is capable of reliably producing an
alloying additive of fine metallurgical structure. We have discovered that with many
alloying materials which are such that when subjected to atomisation they need aspecial atmosphere to prevent unacceptable contamination of the melt, the process of
the preænt invention can be practised in an ambient atmosphere. However, in certain
cases it may nevertheless be desirable to provide a suitable protective atmosphere for
the melt of alloying material as the unatomised melt is applied to the cooling surface.
We have found that employing the method of the invention it is possible to
produce alloying additives in which the alloying component content is higher than can
be achieved using more conventional casting techniques. Also, because of the
relatively high cooling rates involved, where a melt of alloying material would undergo
unaccep~able segregation if conventionally cast, as would be the case with a 20
weight % strontium-aluminium alloy or a 20 weight % titanium-aluminium alloy, for
example, it is often possible to make an alloying additive of the same composition by
the method of the invention, by arranging that the atomised stream or streams applied -
to the cooling surface are above the liquidus of the melt.
Conveniently, the splat product is comminuted, for e~ample by granulation, as
described later, before it is arranged into the dosage form suitable for making alloying
additions.
Tn order to achieve a desirable fineness in the metallurgical structure of the splat
product, the rate of cooling of the atomised stream or streams by the cooling means is
preferably from 20 to 1000 C per second, most preferably from 50 to 500 C per
second. In order to maintain a rate of cooling within those ranges it is generally
necessary to apply a flow of cooling fluid, such as air or water for e~ample, in thermal
communication with the alloying material applied to the cooling surface. Preferably
the cooling means comprises thermally conductive material so as to facilitate the
removal of heat from the alloying material on the cooling surface, and it desirably
WO 94117217 ~ 3 o " ~ 9 PCT/GB94tO0108
-3-
should also be such as rea iily to permit the release of the splat product from that
surface; suitable materials are steel and copper, for example. -
The techniques employed in the manufacture of amorphous metals can produce
cooling rates of the order to 106 C per second, but such techniques are relatively
expensive to operate, and, if applied to a melt of alloying material, generally would not
produce a worthwhile improvement in the fineness of the metallurgical structure of the
alloying material, as compared with that achievable by the splat cooling uæd in the
present invention.
The temperature of the alloying material when applied to the cooling surface
will, of couræ, be above its solidus. It should preferably not be more than 200 C
above the liquidus.
Preferably, the cooling means comprises a cooling surface which moves in an
endless path. Such a cooling means may comprise, for example, a rotating cylinder or
recirculating belt having an e~ternal cooling surface. Where the cooling surface is one
which moves in an endless path, we have found that it is beneficial to cool it by
applying a flow of cooli;ng fluid, for example a water spray, to an internal surface of
the cooling means, the internal surface being in thermal communication with the
cooling surface. The required thermal communication can be achieved by arrangingthat the cooling means comprises a suitable thermally conductive material such as steel
or copper, for example. This arrangement can provide efficient, even removal of heat
from the alloying material impinging on the cooling surface.
According to a preferred embodiment of the invention, impurities in the melt
are concentrated at an upper zone in the melt, and the unatomised stream or streams are
fed to the cooling surface from below the said upper wne. That has the advantage that
impurities in that wne are not included in the melt applied to the cooling surfa~. The
unatomised stream or streams can be fed from below the upper zone by underpouring
from below it. In a preferred arrangement, the melt is held in a metallurgical vessel
and is released through one or more apertures in the vessel below the upper wne. We
have found that it is advantageous to oscillate the melt so as to urge impurities in it to ~ -
rzse towards the upper wne. The oscillation is preferably in a generally vertical plane.
In certain cases, where the aUoying material is a high melting one and
impurities in the melt are not concent~ated at an upper wne in the melt, it may be of
benefit to feed the unatomised stream or streams to the cooling surface by pouring the
WO 94il7217 PCT/GB94/0010~
~ i 3 ~
melt from its surface, such as by lip pouring, for example. In such cases, where more
than one stream is required, this can be achieved by lip pouring from a vessel having
castellations formed along the width of a surface over which the melt is to be poured.
With such an arrangement, one can avoid the problems of hole blockagec which canarise when a high melting alloying material is fed by the arrangement described in the
previous paragraph, and one can also achieve a higher rate of feeding.
As a result of tests, we have found that in order to obtain splat product having a
reasonably fine metallurgical structure which is also sufficiently thin as to be easily
granulated, while at the same time not e~ccessively restricting the rate of production, the
thickness of the splat product desirably should be from 0.1 to 5 mm, preferably less
than 3 mm. The width of the splat product is of less importanoe, and can conveniently
be from 2 to 200 mm, for example. Its length can be unlimited, but generally will also
be from 2 to 200 mm.
There are several ways in which the splat product produced in the method of the ~ -
invention can be iarranged into a dosage form suitable for making measured alloying
additions, for e~cample:
. P~clc~gi~g into UIIit qu~tities.
Splat material in loose form is packaged into unit qualltities. Where the unit
quantities are relatively small, for e~cample, 250 g, 500 g or 1 kg, the alloying
addition can be made by adding the required number of packaged unit quuntities
directly to the melt. In such cases the unit quantities of splat material are
conveniently packed into suitable packages that can release the splat materiial,for e~ample by being melted or burnt away when the package is added to the
melt to which the alloying addition is to be made. Where the package is to be
added to the melt in this way, care should be taken to select it such that it will ~-
not give rise to products which will be deleterious from the health and safety -
point of view or from the point of view of the chemical analysis of theialloyed
material. As regards health and safety, it will be appreciated that if the -
packaging is of combusdble materiall suitable precaudons will have to be
provided to prevent operators being e~cposed to e~cessive amounts of
combusdon products, whatever the nature of the combusdble material. Bearing
that in mind, suitable combusdble packaging materials are plasdcs such as a
chlorine-free, low melt, low density polyethylene. An alternadve approach in `~
cases where packaged unit ~uanddes are to be added directly to the melt to be
alloyed is to package the splat material in material which can add a useful
WO 94/17217 PCTIGB94100108
-S
component to the melt which is being alloyed; aluminium foil is an example of
such a packaging material which would be appropriate in many instances. The -- packaged unit quantities may be substantially larger than as described above,
e.g. 10 kg or more. In such cases it may be convenient to add the splat materialto the melt which is to be alloyed by means of suitable dosing apparatus such asinjection apparatus.
2. compre~ g into u~it qu~ntities.
Splat material in loose form is compressed into unit quantities. There are
several possibilities for this~
(i) Briquetting.
The splat material in loose form is formed into suitable self-suppor~ng
unit bodies by means of any of the various kinds of briquetting apparatus
known in the art. If desired, any suitable binders or other desired
additives may be added to the splat material before briquetting. The
briquetted product may be of any suitable form, for e~cample cylinders,
pucks, pillows, lumps or cubes. We prefer cylinde~s between 50 and
2û0 mm in diameter and between 5 and 20Q mm in height. Suitable unit
weights of the briquetted products are 100 g, 250 g, 500 g or 1 kg, for
e~ample.
(ii) Compressing to a metallurgical bulk shape. -
This may be achieved by techniques similar to the briquetting techniques
described above. However, the shapes produced are somewhat larger,
e.g. S kg, 10 kg or 25 kg. The bulk shapes may be waffle plates or
ingots, for e~ample. They may be added directly to the melt which is to --
be alloyed. Alternatively, they may be e~ctruded to an elongated form,
such as rod or wire, for e~ample, which is suitable for continuous
feeding to the melt which is to be alloyed. A rod of about 9 mm
diameter i3 a preferred form.
(iii) Cold e~ctruding to an elongated form.
Splat material in loose form is cold extruded through a die to an
elongated form, rod or wire for e~cample, suitable for continuous feeding -
to a melt. Again rod of about 9 mm diameter is prefe~red. A suitable
cold e~trusion prwess is lalown as the Conform p~ocess; see the paper
by J. A. Padre "The continuous e~ctrusion of wire and sections from
non-ferrous metal powders by the CONPORM processn, presented at the
International Powder Metallurgy Conference, Washington, U.S.A., on
24th June 1980.
wo 94117217 ~1 t3 u 319 PCT/GB94loolnx
For all of the above ways of arranging the splat product produced in the method
of the invention into a dosage fonn, we very much prefer that the splat material in
loose form which is employed has been produced by a process comprising comminuting
the splat product. Preferably the comminuted splat product has a mean ma~imum
dimension of from 0.5 to 10 mm, more preferably from 1 to 5 mm. The required
comminution of the splat product can be achieved by means of a metaUurgical
granulation machine, which has rotating blades which can reduce the size of the splat
product pieces to the required degree.
The aUoying material used to produce the aUoying additive in accordance with
the method of the invention may be of any suitable kind. Preferably it is an aluminium
based material, where the alloying additive is to be used to make aUoying additions to
an aluminium-based melt. E~amples of aluminium-based alloying materials are:
1. A mo~if ior co~pri~ing strontiu~.
Such aUoying materials are suitable for mal~ing alloying additions to
hypoeutectic and eutectic aluminium-silicon alloy melts for the purpose of
improving the crystal structure of the aluminium-silicon eutectic crystals when
the alloy solidifies. The preferred such alloy is a stron~um-aluminium alloy
containing strontium in the range from 3 to 30 weight %, preferably from 8 to
20 weight %, more preferably about 10 weight %. Because of the fine
metallurgiGIl structure of strontium-aluminium alloying additives produced by ;
the method of the invention, it is possible to produce the alloying additions inrod form, even at higher strontium levels than can be formed to rod from
strontium-aluminium alloys produced by more conventional metnods.
The strontium-aluminium modifier may additionally comprise titanium, and
boron; such an alloying addition can be added to hypoeutectic aluminium-silicon `
melts ~o produce grain refinement of the aluminium component as well as
modification of the aluminium-silicon component of the solidified
aluminium-silicon alloy. Such an alloying addition may comprise, in weight %:
5% to 25% strontium, 0.5% to 12% titanium, 0.1% to 2% boron. Three
preferred compositions comprise in weight %: (a) about 10% strontium, about
1% titanium and about 0.2% boron; (b) about 10% strontium, about 5%
~tanium and about 1% boron; and (c) about 5% strontium, about 10% titanium
and about 1% boron.
~ b i 3
wo 94/17217 pcTlGBs
-7-
2. A grain r~ er.
Grain refiners for adding to aluminium-based melts may comprise titanium; they
usually comprise boron as well as titanium. When produced by the method of
the invention their activity can be enhanced as a result of the improvemer.t in
the fineness of the metallurgical structure. The rate of dissolution may also beenhanced. With those comprising boron as well as titanium, this is especially
the case when the melt of the alloy,ing material is applied to the cooling su~face
within a short time of the beginning of the co e~istence of the boron and the
titanium in the melt. FR 2133439 describes techniques which can readily be
adapted to ~he method of the present invention whereby it will be possible to
minimise the length of that time period. E~camples of suitable composi~ons of
alun~inium-based grain refiners which can be produeed by the method of the
invention are those comprising, in addition to the alun~inium, in weight ~:
(a~ 5% to 25% titanium, preferably about 10% titanium;
(b) about 3% titanium, plus boron; e.g.
(i) about 3% titanium and about 1 9to boron; ~ ~`
(ii) about 3% titanium and about 0.196 boron;
(iii) about 3% titanium and about 0.2% boron, and
(iv) about 3% titanium and about 0.5% boron.
(c) about 5% titanium, plus boron; e.g.
(i) about 5 % titanium and abost l ~i boron; ~ -
(ii) about 5% titanium and about 0.1% boron; `
(iii) about 5 % titanium and about 0.2% boron; and
(iv) about 5% titanium and about 0.6% boron.
3. A con~uctivity-enh~nci~g ~itive.
Such additives generally comprise alun~inium and boron, and are added to
alun~inium melts to precipitate out conductivity-impairing impurities such as
vanadium. When produced by the method of the invention, they can have an
improved rate of dissolution and rate of preeipitating out of the --
conductivity-impairing impurities. The preferred such alloy is a
boron-aluminium alloy comprising boron in the range from 3 to 10 weight %,
preferably about 4 weight %.
.. An ~lloying ~itiv~ for ~ing ~n ~lloying ~et~l.
Such alloying additives can be employed to add an alloying metal such as
- zirconium, manganese, copper, vanadium, iron or chromium, for e~ample, to
an aluminium-based melt. When produced by the method of the invention their
wo g4~l72l7 ~ 3~ 8- PCT/GB94100iQ~ ~
rate of dissolution may be enhanced. Preferred compositions for such alloying :
additives are:
(a) zirconium-alun~inium, comprising zirconium in the range from 5
to 30 weight ~o, preferably about 15 weight ~o;
(b) manganese-aluminium, comprising manganese in the range from S to 40
weight %, preferably about 20 weight %; `
(c) co~er-aluminium, comprising copper in the range from 20 to
60 weight %, preferably about 50 weight %;
~d) vanadium-aluminium, comprising vanadium in the range from S to 30
weight %, preferably about 10 weight ~
(e) iron-aluminium, comprising iron in ~e range from S to 40 weight %,
preferably about 20 weight %; and
(f) chromium-aluminium, comprising chromium in the range from ~ to
40 weight %, preferably about 20 weight %.
Where it is desired to make an alloying additive by the method of the invendon such
that the additive contains more than one alloying component, one can arTange that the
original melt of a11oying ma~ial contains all of the required alloying components, as -~
illustrated in the following E~ample 3. However, we have found that in many
circumstances the same object can be achieved with greater convenience by a~anging
that a splat product having a first composition is n~i~ed with at least one additional splat
product having a different composi~on to provide a mi~ced splat product for arranging~:*
into a dosage form in accordance with the invention. This is illustrated in the following
E~cample 4. The first and addidonal splat products are prefe~ably comminuted as
descdbed above, either before or after they are mi~ed together. :
, .~
The present invention also comprehends a method of ma~ing an alloying addidon to an
aluminium melt, comprising adding to the melt a dosage form whiclt has been produced ;
by a method in accordance with the invendon. ~-
-
In order that the invention may be more fully understood, some embodiments in
accordance therewith will now be descnbed with reference to the accompanying
d wings. Figures l(a) and l(b) are photographs at the same size as the original. The
~: rest of the Pigures are all photomicrographs at a magnification of S00. In the
drawings:
- WO 94117217 PCT/GB94/00108 ~-
g
Fig. l(a) shows the structure of untreated aluminium metal as used in E~ample 1.Fig. l(b) shows the structure of aluminium metal after being grain refined with the
grain refiner alloying briquettes produced in accordlan~e with Example 1. -
Fig. 2(a) shows the structure of untreated LM24 alloy as used in E~xamples 2
to4.
Fig. 2(b) shows the structure of LM24 alloy after being modified with modifier
alloying briquettes produced in accordance with E~cample 2.
Fig. 3 shows the structure of LM24 alloy after being modified and gra n refined with `
modifier and grain refiner alloying briquettes produced in accordance with
E~cample 3. -
Fig.4 shows the structure of LM24 alloy after being modified and grain refined with
modifier and grain refiner alloying briquettes produced in accordance with
EJ~ample 4.
Example 1
A 300 kg melt of alloying material comprising 5 weight % titanium, 1 weight ~;
% boron balance aluminium of 99.7 weight % purity (511 TiBAI) was pre~red by
reacting potassium fluotitanate, K2TiF6, and potassium borofluoride, K~F4, with
molten aluminium in an induction furnace.
The alloying material was then converted to a splat product in an apparatus
comprising a tundish which was mounted vertically above cooling means comprising a
water~ooled, standard cylindrical metallurgical packaging drum of 1 mm thick mild
steel having a length of 880 mm and a diameter of 660 mm. It was mounted for
rotation about its cylindrical axis, with the axis disposed ho~izontally, and was
connected to a motor arranged to drive it at a rate of 30 r.p.m. The drum was
open-ended, and was cooled by means of a spray bar which projected from the openend within the drum's interior so as to direct a spray of water to the interior of the
drum, centred at appro~cimately the 1 o'clock position.
The tundish having a capacity of 10 kg of alloying material was arranged about
400 mm above the 12 o'clock position. It comprised a steel body of substantiallyV-section and e~ctending over almost the whole of the a~cial length of the drum, and was
lined intemally with suitable refractory material. The base of the "V~ of the tundish
included a horizontal intemal floor section 50 mm wide which was provided with a line
of 8 evenly spaced 6 mm diameter circular apertures to enable the contents of the
wo 94117217 pcTlGs94lool~R
tundish to exit in a line of streams which could be directed to the drum along its axial -
length at the 12 o'clock position.
The tundish was mounted so that it could be oscillated ver~cally, perpendicular '
to the axis of the drum, and was connected to an oscillator arranged to move it in that '-
direction over a distance of 20 mm, at a rate of 100 oscillations per minute.
The splat producing apparatus had been prepared to receive the molten alloying
material, by activating the drum drive motor and the oscillator, and supplying cooling
water at a temperature of 15 C at a rate of 100 kg per minute. Molten alloying
material at 850 C was supplied to the tundish ~rom the induction furnace continuously '
at a rate such as to keep it approximately three quarters full. The melt e~ited the holes
in the base of the tundish, thus being underpoured. It then fell in a series of
semi-continuous streams onto the surface of the drum at the 12 o'clock position, that
surface acting as a cooling surface causing the melt to solidify at an estimated rate of
about 400 C per second, to form splat pieces of mean dimensions apDro~imately 50
mm wide x 100 mm long ~c 1 mm thick. The solidified splat pieces fell away from the - -
drum at appro~timately the 3 o'clock position, and were continuously removed forprocessing in a granulator. Appro~imately 300 kg of splat product were produced, -
over a period of-40 mi~utes. The final 3 kg to e~it the tundish were discarded, as they ~
would have contained a large part of the impurities which had been accumulating at the "
surface of the melt of alloying material. -
The granulator used was a Blackfriars granulator, and comprised rotating blades
for comminuting the splat product. It had been manufactured by Blackfriars Ro~ary
Cut~ers Ltd., of Redhill, Surrey, E~lgland, and was designated as their 18 inch ASHD
Rotary Cutter. The comminuted splat product exiting the granulator had a mean
ma~imum dimension of 3 mm. '~
It was then fed' to a metallurgical briquetting apparatus comprising a hydraulicpress for formation into dosage units. The press cold compacted the comminuted splat
product into the dosage units, each of which comprised a tablet in the form of acylinder 90 mm in diameter and 2S mm long. Each tablet weighed 300 g. The tablets
were used as a grain refiner alloying additive. They were added to molten aluminium ~ '
of 99.7 weight % purity at an addition rate of 2 kg per tonne. A sample of the treated ' ' ~'
melt was then solidified in accordance with a comparative test based on the AA TPl
grain refiner test; the structure of the solidified sample is shown in Fig. l(b); Fig. l(a)
shows the structure of an untreated sample of the aluminium.
WO 94117217 '' 1 ~3 0 ~ 1 3 PCTIGB94100108
- 1 1 - ~,
,~,
Example 2
A 300kg melt comprising 10 weight % strontium, balance aluminium of 99.7 -
weight % puriey (lOSrAI) was prepared by alloying 30 kg of strontium metal into a
melt of 270 kg of molten aluminium in an induction furnace.
The alloying material was then converted to a splat product in the apparatus P
described in Example 1, under substantially the same conditions, with the exception
that the temperature of the strontium-alun~inium melt supplied to the splat cas~ng
apparatus was 8 70 C.
:.
The resulting splat product was then granulated and briquetted, as in Example 1, -
the comminuted splat product exiting the granulator having a mean maximum
dimension of 3 mm, and the cylindrical briquetted tablets each being 90 mm in
diameter x 25 mm in length, and weighing 300 g.
A trial was conducted in which the briquetted tablets were used as an alloying
additive to modify a melt of LM24, being added at the rate of 3 kg/tonne. LM24 is a
hypoeutectic aluminium-silicon alloy containing copper, and conforms to the
specification, in weight %: 3.0 to 4.0 copper, 7.5 to 9.5 silicon, maximum 1.3 iron,
ma~cimum 3.0 zinc and maximum 0.5 manganese. Although this alloy is generally used
in the un-modified state, it is an alloy which can be used to show modification
par~cularly well.
The structure of the modified alloy on solidification is shown in Fig. 2(b);
Fig. 2(a) shows the structure of an untreated sample of the alloy.
~ample 3
A 300 kg melt of an alloying material comprising 10 weight % strontium, 1
weight % ~tanium, 0.2 weight % boron, balance aluminium of 99.7 weight % purity
(10/1/0.2 SrTiBAl) was prepared by reac~ng the appropriate amounts of K2TiF6 andKBF4 with molten aluminium as in Example 1 and alloying 30 kg of strontium metal as
in EJtample 2.
The alloying material was then converted to a splat product in the apparatus
described in Example 1, under substantially the same conditions, with the exception
wo 94/17217 ~1~ U d :~ ~ PCT/GB94/oolov
-12- ~-
that the temperature of the strontium-alum~ruum melt supplied to the splat cashng
apparatus was 870 C.
The resulting splat product was then g~nulated and briquet~d, as in Example 1,
the comminuted splat product exiting the granulator having a mean maximum
dimension of 3 mm, and the cylindrical briquetted tablets each being 90 mm in
diameter x 25 mm in length, and weighing 300 g.
. .
A trial was conducted in which the briquetted tablets were used as an alloying
additive to modify and grain refine a melt of LM24, being added at the rate of
3 kg/toMe.
The ~tructure of the modified and grain refined alloy on solidification is shownin Fig. 3.
Examplç 4
A melt of 5/1 TiBAl alloying material was prepared and converted to a splat
product and then granulated, as described in Example 1, and a melt of lOSrAI wasprepared and converted to a splat product and then granulated as described in
Example 2. Portions of the 5tl TiBAl and lOSrAl splat products after comminution in
the granulator were mixed in a weight ratio of 80 to 20, so that the resulting mixture
was, in weight %: 4% ~tanium, 0.8% boron, 2% strontium, balance aluminium. The
resulting mLxture was briquetted as described in Example 1 to produce cylindrical
briquetted tablets, each being 90 mm in diarneter x 25 mm in length, and weighing
300 g.
A tlial was conducted in which the briquetted tablets were used as an alloying
additive to modify and grain refine a melt of LM24, being added at the rate of
5 kg/tonne.
The structure of the modified and grain refined alloy on solidification is shownin Fig. 4.
. .
