Note: Descriptions are shown in the official language in which they were submitted.
DE5CRIPTION
PREPARATION OF PHOSPHOR~S-CONTAINING METAhLIC
GL~SS-FO~I~NG ~LOY MEL1'S
. . ~
BACKGROU~D OF TH~ INVENTION
... .
Recent advances in the metallurgical ar.s in-
clude development of alloys which, ~ihen rapidly quench-
ed from the melt at rates in excess of about 104 to 106C
per second, form glassy ~amorphous) solids. Such glass-
forming alloys commonly are based on transition metals,
usually iron, nickel and/or cobalt, in conjunction with
one or more metalloids of phosphorus, boron and carbon.
- Glass-forming alloys are, for examplel described in U.S.
Pat. 3,856,513 issued December 24, 1974 to Chen et al.
Preparation of phosphide based melts of glass-
formin~ alloys under ambient atmosphere leads to oxide
inclusions in the glassy metal product. The conventional
method of excluding the ambient atmosphere by vacuum
melting leads to possible losses of phosphorus values
from the melt due to evaporation-. Iron phosphide is a
basic ingredient in many glass-forming metallic alloy
compositions, and in the high purity form required for
such purpose, it is quite costly. Inexpensive forms of
iron phosphide available are impure and contain phosphorus
in form which can evaporate upon heatin~, and which tends
to form volatile phosphorus pentoxide, and which poses a
safety hazard and results in changes of the alloy compo-
sition. Glassy solid structures are obtained from such
alloys by processes such as the melt spin process wherein
a fine jet o~ the molten alloy is impinc3ed upon a rapidly
movinc~ chill surface for solidification. Orifice dia-
meters in this process are exceedingly s~nall, and orifice
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pluggage on account of solid impurities contained in the
melt can represent seri~us problems. Iron, cobalt or
niekel based phosphorus-containing glass-forming alloys
whieh additionally contain boron as a metalloid are
particularly prone to contamination with solid partieles.
In such alloy, these particles were found to be pre-
dominantly small partieles of TiO2 and/or TiBo3, both of
whieh have high melt points, and both of whieh are rela-
tively insoluble in the melt. It was ~ound that titanium
is an impurity commonly contained in ferrophosphorus,
which is used as a source of phosphorus in making these
alloys, although titanium may also be present as contami-
nant in other raw materials employed in making these
alloys.
The present invention provides refining flux for
redueing oxidation of and loss of phosphorus values from
phosphorus-containing alloys, espeeially phosphorus-eon-
taining iron, niekel and~or cobalt-based alloys.
- SVMM~RY OF THE INVENTIO~
Phosphorus-containing metallic glass-forming
alloy melts are covered with a layer o~ molten boron tri-
oxide flux. Such layer protects the melt from oxidation,
dissolves oxide partieulates and impurities from the
molten metal alloy and prevents the evaporation of p~os-
phorus values. The flux floating on the alloy melt will
not interfere with subsequent easting or spinning opera-
tions, and the alloy melt can be replenished direetly
through the flux layer. Alloys prepared according to the
process of the present invention leave minimum residues in
the jetting crucible in subsequent melt spin operations~
Phosphorus-containing iron, nickel and/or cobalt-
based alloys are desirably melted under a boron trioxide
flux additionally comprising oxides o iron, niekel and/or
eobalt. The ~lux layer protects the molten alloy from
oxidationt reduces or eliminates contamination of the melt
with particulate matter, especially metal oxides, and pre-
vents loss of phospllorus values by vaporization.
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--3--
DETAILED ~ESCRIPTION OF THE INVENTION
.
Metallic glass-formin~ alloys which benefit
from protection by boron trioxide flux contain phosphorus
as a metalloid component, alone or together with other
metalloids, such as boron, ca:rbon and silicon. The
phosphorus component of such alloys is usually contributed
by ingredients having the formulas FePx, NiPX, CoPx, MnPx,
wherein x is between abut 0.3 and 1.1 and preferably bet-
ween about 0.5 and 1. Preferred alloy compositions include
alloys utilizing as source of phosphorus FePx wherein x is
between about 0.5 and 1. Pre:Eerred allo.y compositions in-
clude transition metal alloys containing between about 3
- and 25 weight percent phosphorus. These alloys have a
phosphorus partial pressure of less than 20 micron, and
melting points of between about 900C and 1200C.
Phosphorus-containing alloys based on one or
more of iron~ nickel and/or cobalt which benefit from
melting under the refining boron trioxide flux which
additionally contains oxides of iron, nickel and/or cobalt
have the general formula MaPbYC wherein M is a metal se-
lected from one or more of the group consisting of iron,
cobalt and nickel; P represents phosphorus; Y represents
a metalloid selected from one or both of the group con-
sisting of boron and carbon; and a, b and c are in atomic
percent, wherein a is about 70 to 90, b is 0-20, but
desirably at least 1, the sum of b + c is about 10 to 30,
the sum of a ~ b ~ c being 100. In the above formula,
- up to about 80 percent of M may be replaced by one or
more of any transition metal other than iron, cobalt and
nic~el. Suitable replacements include silicon, chromium,
vanadium, aluminum, tin, antimony, germanium, indium,
beryllium, molybdenum, titanium, manganese, tungsten,
zirconium, hafnium and copper, for example. The phos-
phorus content of the alloy will ordinarily be derived
35 from ferrophosphorus, which may be of any suitable phos- :
phorus content, such as commercially available grades con-
taining about 18 and 25 percent by weight phosphorus.
The boron trioxide flux comprises compositions
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of the formula B2O3 of about 95 weight percent purity,
preferably better than about 98 weight percent purity, the
balance being represented by incidental impuritiess or
intentional additives which are substantially inert, that
is to say, that they do not materially interfere with the
intended function of the boron trioxide flux.
Suitable boron trioxide fluxes have a melting
point between about 400C and 600C, preferably between
about 400 and 500C, and have a vapor pressure of below
about 20 micron.
In the fluxes of the present invention which
additionally contain an oxide of iron, cobalt and/or
nickel, the oxide is suitably chosen to correspond to the
major metal component of the alloy. For example, if iron
is the only or major metal component of the alloy, the
oxide component in the flux desirably, but not neces-
sarily, is an oxide of iron. Nic~el-containin~ melts
desirably are refined under a flux-containing nickel
oxide. The flux desirably contains from about 20 to ~0
percent by weight boron trioxide.
In the melting operation the metal oxide (e.g.
iron, cobalt or nic~el oxide) coacts with the boron
trioxide to obtain the desired result. I~ is believed
that oxygen from the metal oxide combines with titanium
metal contained in the melt as an impurity, perhaps
forming TiO2, which is then bound in the molten flux.
The boron trioxide seems to act as a coagulant for the
titanium dioxide as well as for other particulate matter
which may be contained in the melt. Moreover, the boron
trioxide, because of its acidic character, seemingly tends
to prevent oxidation of phosphorus, if present, to the
five valent oxide state, as might occur due to presence
of small amounts of oxygen in the melt. In the five va-
lent state, phosphorus is volatile under refining condi-
tions encountered in ma~ing the alloys here under con-
sideration.
Of the oxides of iron, namely FeO, Fe2O3 and
Fe3O~, all are suitable, FeO being preferred. Likewise,
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any of the oxicles of cobalt, CoO, Co2O3, as well as
Co3O~, may be employed. However, for reasons of high
cost, use of oxides of cobalt is not ordinarily preferred.
Nickel oxide, for reasons of availability as well as
efectiveness, is the preferred metal oxide. Metal oxides
of commercial degree of purity are suitable for use.
The boron trioxide (B2O3) similarly may be of
any degree commercial purity.
In the metal oxide containing fluxes, the boron
trioxide is desirably employed in amount of 20 to 80 per-
cent by weight, preferably 30 to 70 percent by weight,
most preferably 40 to 60 percent by weight of the flux,
the balance being represented by the metal oxide. Of
course, if desired, other components which do not mate-
rially interfere with the protective and refining func-
tions of the flux may be included in the flux composition
for any desired purpose, e.g. melting point reduction,
although addition of other components is not ordinarily
preferred.
The flux compositions are employed in amount
sufficient to provide a flux layer of between about 1 and
50 millimeter thickness, preferably between about 2 and
10 millimeter thic~ness on top of the molten metal alloy.
It is an advantage of these flux compositions that their
solubility in the alloys is generally low, so that grosscontamination of the alloy with the flux is avoided.
Furthermore, minor contamination of the alloy with boron
values from the flux is generally not deleterious, that is
to say that such contamination would not adversely affect
the glass-forming capabilities of the alloy, nor its
properties in the solid state.
The temperature of the alloy melt can be bet-
ween about 1000C and 1500C, and preferably between
about 1100C and 1~00C~ The temperature of the boron
trioxide flux can be between about 900C and 1400C.
To prevent oxidation and loss of phosphorus
value from the alloy, the boron trioxide flux should be
present at tempelatures leading normally to oxidation
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and/or evaporation of phosphorus values, and in particular
the boron trioxide should be present when the alloy is in
the molten state. The boron trioxide, to obtain the full
benefit of its function, is desirably added to the cold
charge. If it is added after the alloy is melted, con-
siderable amounts of phosphorus can be lost.
To fulfill its refininy function, the flux
should remain in contact with the surface of the melt at
melting temperature for a tim~ period for at least about
one minute, desirably of at least about 5 minutes. Con-
tact times of, say, between about 5 min~tes and 5 hours,
desirably of between about 30 minutes and about 3 hours
are eminently suitable. If desired, the melt may be
agitated. Suitable melting furnaces include those lined
with high temperature ceramic materials. Preferred fur-
nace linings are ma~e from magnesia, zirconia and alumina.
If desired, suitable inert atmospheres may be provided
above the flux, including such as those provided by helium
or argon. Alternatively, the melting operation may be
conducted under vacuum~ However, provision of inert
atmospheres is not essential. If an inert atmosphere is
supplied, argon is preferred.
EXAMPLES 1-5
Iron, nickel, phosphorus, and boron containiny
glass-~orming alloy compositions were prepared by melting
together under vacuum raw materials of the following
purity: iron, 99.9 weight percent pure; nickel, 99.9
weight percent pure; nickel boride, 99 weight percent
pure having boron content of between about 17 and 19
weight percent; ferrophosphorus (Type I) containin~ 61.43
weight percent iron and 20.39 weight percent boron; ferro-
phosphorus (Type II) containing 79 weight percent iron
and 21 weiyht percent phosphorus. To each charge there
was added an amount of Fe40Ni40Pl4 6 (
metal alloy to provide an initial susceptor for induction
heatiny of the charge. No Fe40Ni~OP14B6 was
of sample 5 since the ferrophosphorus employed coupled
suEficiently with the racliation. The charye was contained
.
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72~3
in a m~gnesia crucible covc-red with boron trioxide and
heated by means oE induction heatiny coils. The melt of
Examples 1, 2, 4, 5 was maintained under vacuum under a
layer of B2O3 flux at a temperature of 1200C for one
hour, before casting it into ingots. The melt o~ Example
3 was soaked at 1300~C for 1 hour. The amounts of
materials charged are summarized in Table 1 below:
Table 1
Char~e (~rams)
Ferro-
Example phosphorus Fe Ni P B alloy Fe Ni NiB B2O3
- 40 - 40-14~
1915 (I)~00 263 895 193 136
21200 (I) 1030
3823 (I)707 35~ 895 199 154
44937 (I)2265 2151 5370 llG0 300
5381~ (II) ~98 3654 773
The cast ingots were subjected to analysis for
insolubles, oxygen, silicon, calcium, iron, nickel, phos-
phorus, and boron. The ingot obtained in Example 3 was
further subjected to a second melt cycle at 1200C for 1
hour in vacuum under a flux of B2O3. The remelted alloy
was again cast into an ingot and subjected to analysis.
The results of the analysis are shown in Table ~I below.
Iron, nickel, boron and phosphorus were deter-
mined by wet chemistry; oxygen was determined by placing
pieces of raw alloy in a graphite boat in a Leco oxygen
analyzer. This method determines only dissolved oxygen,
but not chemically bonded oxygen. The procedure for
determining insolubles involved dissolving a 2 ~ram sample
of the solid ingot in 100 milliliter of a reagent solu-
tion composed of 50 milliliter nitric acid (70~ H~03);
10 milliliter of sulfuric acid (100~ H2SO4) and ~0 milli-
liter of water. The alloy was refluxed in the reagent
solution until disso ved. The resultant solution was
filtered thro~gh an analytical filter to determine in-
soluble content as ash residue. Silicon and calcium were
determined by takiny an aliquot part of the solution,
evaporating the solution, mixing the residue with spec-
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trographic grade graphite and determining the traces by
emissions spectroscopy.
Table 2
Analytica] Results
Weight Percent
Insoluble
S~MPLE Test Oxy~en Si Ca Fe Ni P B
1 1.29 0.031 0.05 less 40014 49.51 9.82 0.79
than
0.03
3 0.65 0.14 0.03 less 41.99 47.64 9.19 1.1
than
0.01
4 1.1 0.17 0.51 less 41.52 47.87 9.11 0.~9
than
0.05
0.03 0.01 0.03 less 44.21 45.52 8.93 1.35
than
0.03
EXAMPLE 6
This example illustrates production of an alloy
containing Fe: 45.9 -~ 1 percent by weight; Ni: 44.6 + 1
percent by weight; P: 7.85 + 0.32 percent by weight;
- B: 1.45 + 0.11 percent by weight. The raw materials
charged are iron, electrolytic fragments~ 99.9 percent
pure; nickel pellets, 99.9 percent pure; ferrophosphorus,
low silicon grade (less than about 0.5 percent silicon~; -
nickel~boron, low aluminum grade tas available, for
example, from Shieldalloy Company). Prior to and during
the charging operation the furnace is purged with argon
gas. The required amounts of ironl nickel and ferrophos-
phorus are charged to the furnace, and the charge is
gradually heated until melting. At that point, an oxi-
dizing acid flux consisting of about 50 weight percent
nickel oxide and about 50 weight percent B2O3 is added
to the molten charge in an amount of about 8 lbs. per
2,500 lb. metal charge to produce about a 1/8 inch thick
layer of flux. The melt is refined under this flux at
a temperature of about 1,180 to l,200C for 20 to 30
minutes r takin~ care to avoid temperatures in excess of
1200C during the refining operation. Thereafter, the
flux is skin~ed and the nickel boron is added to the melt.
The heat is finished under an argon blanket. Total
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refining and holding time at the 1,180 to l,200C isabout 45 to 60 minutes. The refined alloy is then cast at
about l,000C.
Using identical raw materials, alloy of the
above composition prepared using the NiO/B2O3 flux as
above described had a titanium content of only 0.04 per-
cent by weight, whereas an alloy obtained under other-
wise identical conditions from the same raw materials,
but without use of the flux, had a titanium content about
0.16 percent by weigh~. Furthermore, alloy prepared under
conditions of the present invention had significantly
lower contamination with other oxidizable elements which
tend to form insoluble solid oxides. As a consequence,
metal refined in accordance with the present invention r
as above described, caused substantially less restric-
tion of a casting nozzle in a subsequent spin casting
operation.
