Note: Descriptions are shown in the official language in which they were submitted.
2I4~972
R~cR~ouND OF THE INVENTION
Field of the Invention
The present invention relates to an amorphous iron
based alloy having excellent magnetic characteristics as
well as resistance to brittleness. The invention further
relates to a method of manufacturing the amorphous iron
based alloy.
Description of the Related Art
As disclosed in Japanese Patent Unexamined
Publications No. 54-148122 (1979), No. 55-9460 (1980) and
No.57-137451 ( 1982), when a molten alloy composed of Fe-B-
Si or the like is ejected onto the surface of a cooling
roll rotating at high speed, using the single roll method
or the like, and is quenched and solidified at a cooling
speed of about 10 _ 106 C/sec., a so-called amorphous
alloy sheet can be produced with a thickness of about
several dozens of microns and wherein the atoms are
disposed in a disorderly arrangement.
Such an amorphous alloy sheet has low iron loss and
high magnetic flux density and has excellent so-called soft
magnetic characteristics when attempted to be put into
practical use as a core material of a transformer.
Nevertheless, such a sheet composed of the Fe-B-Si
ternary amorphous alloy has disadvantages. Although the
sheet can achieve an iron loss value which is low to some
degree, the improvement of iron loss is limited. A further
reduced iron loss cannot be expected from a ternary alloy.
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To cope with this problem, attempts have been made to add
various elements to the ternary amorphous alloy as a fourth
~component.
For example, Japanese Patent Examined Publication No.
1-54422 (1989) proposed an amorphous iron based alloy
obtained by the addition of Mn, Ni and the like to an Fe-B-
Si alloy in an amount of 0.5 - 3 at% (atomic percent) and
the thus obtained amorphous iron based alloy had a low iron
loss and excellent insulating film processing properties.
However, when Mn is added in an amount of 0.5 at% or more,
the material becomes brittle. Further, reduction of
magnetic flux density becomes a problem in practical use.
Japanese Patent Unex~mined Publication No. 62-192560
(1987) proposed an amorphous alloy obtained by adding one
element or two or more selected from Cr, Mo, Ta, Mn, Ni,
Co, V, Nb and W to a Fe-B-Si alloy, in an amount of 0.05 -
5 at%, and further subjecting the resulting alloy to a
process such as rolling or the like for adjustment of
surface roughness of the alloy.
However, Japanese Patent Unexamined Publication No.
62-192560 (1987) does not take brittleness into
consideration. Further, even if the surface roughness of
the alloy made into a sheet is adjusted by rolling or the
like, such a process is doubtfully effective for reduction
of brittleness. In addition, adjustment of surface
roughness is industrially very ineffective and also
disadvantageous as to manufacturing cost.
The present invention is directed to overcoming the
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aforesaid problems advantageously, and relates to an
amorphous iron based alloy having excellent magnetic
characteristics as well as resistance to brittleness. It
is further directed to a method of manufacturing such a
superior amorphous iron based alloy.
SUMMARY OF THE lNV~:NlION
To improve the iron loss of an Fe-B-Si amorphous iron
based alloy, it is effective in some ways to add a slight
amount of Mn to the alloy, as described above. However,
this is disadvantageous because it is accompanied by
reduction of magnetic flux density and increase of
brittleness of the material.
As a result of a zealous examination for overcoming
the above disadvantage, the inventors have obtained the
following knowledge:
(1) when a Mn content is 0.2 at% or more to less than
0.5 at~, iron loss can improved without so much reducing
magnetic flux density;
(2)when molten alloy is quenched and solidified in a
reducing atmosphere, in particular, in a CO2 atmosphere
cont~ining a small amount of H2, the surface roughness of
the sheet is greatly improved as compared with molten alloy
quenched and solidified in the atmosphere and thus the
cooling speed of the alloy is increased as well as the
oxidized state of the sheet surface is also improved, and
as result, cracks are difficult to be produced and material
can be effectively ductile;
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(3) when the surface roughness is improved, since a
demagnetizing field due to magnetic poles which is caused
by irregular surface is reduced, magnetic flux density is
improved; and
(4) when the surface property of the sheet is improved
by effecting a quenching and solidifying process in the (H2
+ CO2) atmosphere, the disadvantage such as the reduction of
magnetic flux density and/or the embrittlement which are
caused by the addition of Mn can be completely overcome.
More specifically, the present invention relates to
an amorphous iron based alloy having excellent magnetic
characteristics as well as resistance to brittleness, and
is composed of a component represented by the following
chemical formula and having a surface roughness of about
0.8 ~m or less in terms of a mean roughness along the
centerline Ra. The formula is FexBySizMna,
where about 75 S X S 82 at%
7 S Y ~ 15 at%
7 S Z S 17 at%
0.2 S a < 0.5 at%
The amorphous iron based alloy can effectively be bent
in intimate contact in a critical bending test.
Further, the present invention relates to a
method of manufacturing an amorphous iron based alloy
having excellent magnetic characteristics as well as
resistance to brittleness, comprising the step of quenching
and solidifying a molten alloy composed of a component
represented by the following chemical formula, wherein the
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quenching and solidifying process is effected in a CO2
atmosphere cont~ining H2 in an amount of about 1 - 4% by
volume.
The formula is FexBySizMna,
where about 75 ~ X ~ 82 at%
7 ~ Y ~ 15 at%
7 ~ Z ~ 17 at%
0.2 ~ a < 0.5 at%.
BRIEF DESCRIPTION OF THE DRAWINGS
Results of actual test work giving examples how the
present invention is achieved will be described below, and
in the drawings, wherein:
Fig. 1 is a chart showing determined relationships
between iron loss W13/so and Mn content in an amorphous iron
based alloy composed of Fe78aB13Si~na.
Fig. 2 is a chart showing determined relationships
between magnetic flux density B1o and Mn content in an
amorphous iron based alloy composed of Fe78aB13SigMna.
Fig. 3 is a chart showing determined relationships
between iron loss W13/50 and Mn contents in an amorphous iron
based alloy composed of Fe81aB12Si7Mna.
Fig. 4 is a chart showing determined relationships
between magnetic flux density B1o and Mn contents in an
amorphous iron based alloy composed of Fe81aB12Si7Mna.
Fig. 5 is a chart showing determined relationships
between magnetic flux density B1o and mean centerline
roughness Ra both in an amorphous iron based alloy composed
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of Fe~.7B12Si7MnO.3 and in an amorphous iron based alloy
composed of Fe77.7B13SigMnO3.
Fig. 6 is a chart showing relation between an amount
of Mn content and the bending limit heights in an various
atmosphere at the time of rapid solidification of an
amorphous iron based alloy with a sheet thic~ness of 30 ~m
composed of Fe81aB12Si7Mna.
Fig. 7 is a chart showing relation between an amount
of Mn content and the bending limit heights in an various
atmosphere at the time of rapid solidification of an
amorphous iron based alloy with a sheet thickness of 20 ~m
composed of Fe81aBl2Si7Mna.
Fig. 8 is a chart showing relation between a mean
roughness Ra and the bending limit heights of at different
sheet thicknesses each in an amorphous iron based alloy
composed of Fe~.7Bl2Si7MnO3.
Fig. 1 shows a result of actual tests on the
relationship between amount of Mn and iron loss W13/50
(iron loss value when the frequency was 50 Hz and the
magnetic flux density was 1.3T) of an amorphous iron based
alloy composed of Fe~aB13SigMna.
The molten alloy was quenched and solidified in air,
in air and CO2, and in a CO2 atmosphere containing H2 up to
4%. The resulting amorphous iron based alloy was 25 ~m
thick and 20 mm wide and was annealed at 400C for one hour
in a magnetic field. The resulting samples were
investigated.
73461-57
2l~8972
Fig. 2 shows results of tests on the relationship
between Mn content and magnetic flux density B1o (magnetic
flux density in a magnetic field of 1000 A/m) of an
amorphous iron based alloy having the same components. The
band-shaped dispersion of the magnetic flux density to the
Mn content in Fig. 2 is caused by dispersion of surface
roughness of the samples.
It is found from FIGS. 1 and 2 that a low iron loss
can be obtained and the reduction of a magnetic flux
density can be also suppressed by the addition of a small
amount of Mn to Fe-B-Si ternary alloy.
Figs. 3 and 4 show the relationship between Mn content
and iron loss W13/so and the relationship between Mn content
and magnetic flux density B1o of an amorphous iron based
alloy composed of Fe81aB12Si7Mna, respectively in the same
way as in Figs. 1 and 2.
A sheet made of an amorphous iron based alloy composed
of Fe81aB12Si7Mna was annealed at 360C for one hour in a
magnetic field. The band-shaped dispersion of the magnetic
flux density to the Mn content in Fig. 4 is caused by
dispersion of surface roughness of the samples.
As apparent from FIGS. 3 and 4, a low iron loss can be
obtained and the reduction of a magnetic flux density can
be also suppressed by the addition of a small amount of Mn
also in this case.
Further, in particular, when a large amount of Fe
exceeding 80~ is contained as the case of this alloy
composition, there is also an advantage that the effect of
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reducing an iron loss resulting from the addition of Mn is
more remarkably increased.
Fig. 5 shows the relationship between mean roughness
along the centerline Ra and magnetic flux density when a is
controlled to be 0.3 at% in the amorphous iron based alloys
composed of Fe78aB13SigMna and Fe81aB12Si7Mna.
The Ra is an average value obtained by measuring the
surface contacted to a quench roll three times at the
center part of the sheet in a sheet width direction
according to JIS B0601.
It is shown in Fig. 5 that when the average roughness
on the centerline Ra is reduced, the magnetic flux density
can be greatly improved.
When an amorphous iron based alloy with a sheet
thickness of 30 ~m composed of Fe81aB12Si7Mna was quenched
and solidified in air, the bending limit height was
increased as the Mn content was increased as shown by the
dotted line in Fig. 6.
The bending limit height is an index for indicating
degree of brittleness of a material. It is represented by
the distance between the inner surfaces of a sheet 150 mm
long just before the sheet is broken when it is being bent
with the surface thereof in contact with a roll directed to
the outside. When the bending limit height is 0, the sheet
can be bent upon itself in intimate contact.
On the other hand, when the same amorphous iron based
alloy was quenched and solidified in a CO2 atmosphere
cont~in;ng 3% H2, the resulting bending limit height of the
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alloy was greatly reduced. This is shown by the solid line
of Fig. 6.
Further, FIG. 7 shows the case that a sheet having the
same composition, is 20 ~m thick in the same way. When the
molten alloy was quenched and solidified in the CO2
atmosphere cont~ining 3% H2 in the same way as FIG. 6, it is
found that the bending limit height of the amorphous alloy
is reduced and brittleness is improved.
A difference of characteristics of the sheet may be
caused by a difference of the atmosphere in which the sheet
is processed. This affects the condition of the surface of
the sheet. We have found that when the sheet was made in
air, the sheet had a surface roughness of about 0.8 - 1.2
~m, expressed as Ra, on the surface of the sheet in contact
with a roll, whereas when the sheet was made in a CO2
atmosphere cont~ining 3% H2, the sheet had a surface
roughness of about 0.4 - 0.8 ~m and less irregularity.
FIG. 8 shows the relationship between Ra and
brittleness. It can be found that when the Ra is reduced,
the sheet become less brittle. The number of irregular
portions from which cracks start, when the sheet is bent,
is very small and the sheet is difficult to be cracked
accordingly.
Further, when the Ra is reduced, since heat is
effectively transmitted from the alloy to a cooling roll
when the alloy is quenched and solidified, a cooling speed
is increased so that the alloy reaches the ideal amorphous
state.
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Further, a reason why the CO2 + H2 atmosphere is
effective to the improvement of brittleness is that an
effect of improving the oxidized state of sheet surface is
also obtained by the reducing atmosphere, in addition to
the effect of improving the Ra.
Next, reasons why the components of the novel alloy
are limited to the above ranges will be described below.
Fe: about 75 - 82 at% (hereinafter, atomic percentages are
simply shown as %)
Fe is an important element for determining magnetic
properties. When the Fe content is less than about 75%,
the magnetic flux density of the alloy is too low, whereas
when the Fe content exceeds about 82%, iron loss is
increased and thermal stability deteriorates. Thus, the Fe
content is limited to a range of about 75 - 82%. A more
preferable range is about 80 to 82%.
B: about 7 - 15%
Although B is useful to make the material amorphous,
when B is less than about 7%, it is difficult to make the
material amorphous, whereas when the B content exceeds
about 15%, magnetic flux density is reduced and the Curie
temperature is also reduced. Thus, the B content is
limited to a range of about 7 - 15%. A more preferable
range of the content is about 9 - 13%.
Si: about 7 - 17%
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Although Si promotes making the material amorphous and
achieves thermal stability, when the Si content is less
than about 7%, the Curie temperature is low and not
practically usable, whereas when the Si content exceeds
about 17%, iron loss is increased. Thus, the Si content is
limited to a range of about 7 - 17%. A more preferable
range of the content is about 7 - 10%.
Mn: about 0.2% or more to less than about 0.5%
Although Mn is effective to reduce iron loss, when Mn
is less than about 0.2%, there is little effect upon iron
loss. When the Mn content is about 0.5% or more, magnetic
flux density is reduced as the Mn content is increased and
the material becomes more brittle. Thus, the Mn content is
limited to a range of from about 0.2% or more to less than
about 0.5%.
When a material is quenched and solidified in air, the
material becomes more brittle as shown in Figs. 6 and 7.
When, for example, a transformer winding is made,
difficulties such as breaking of the sheet are likely to be
caused by the brittleness of the material.
The bending limit height should be as small as
possible to prevent these difficulties. A sheet that is
capable of being bent upon itself in intimate contact is
most effective.
When a material can be bent in intimate contact, no
breaking of the sheet is caused when winding a transformer.
12
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More specifically, when the bending limit height is about
0.10 mm, this defect occurs at a rate of 0.2%, whereas when
the bending limit height is about 0.25 mm, defects occur at
a rate of 0.8%.
Thus, the present invention effectively controls and
limits the brittleness of a material by keeping its surface
roughness to about 0.8 ~m or less (Ra) as well as reducing
the oxidation of the surface of a sheet by effecting
quenching and solidifying in a CO2 atmosphere containing H2
in a range of about 1 - 4%.
The atmosphere used in quenching and solidification is
m~ i n ly composed of CO2 because the gas is inactive and
available at low cost and has a high radiation capability
because it is a ternary gas and has a high specific
gravity. Thus, the gas effectively acts to reduce surface
roughness by entrapment of the gas.
It is important to maintain the H2 gas content of the
CO2 gas to a range of about 1 - 4%. When the H2 gas content
is less than about 1%, surface roughness (Ra) cannot be
kept to about 0.8 ~m or less. Also the reduction of
surface oxidation is not sufficient because a sufficient
reducing atmosphere cannot be obtained. In sharp
distinction, when the H2 gas content exceeds about 4%, the
handling of the gas becomes a serious problem because there
is danger of explosion. Further, when the H2 gas content is
further increased the gas invades the sheet surface and
makes the sheet brittle.
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DET~TT~n DESCRIPTION OF PREFERRED EMBODIMENT
Example 1
Molten alloys containing Fe in an amount exceeding 80
at% and various components shown in Table 1 were injected
onto the surface of a Cu roll rotating at high speed in a
vessel of a CO2 atmosphere containing 3%H2 and made to
amorphous alloy sheets of 25 ~m thick and 20 mm wide and
then the sheets were annealed at 340 - 420C for an hour in
a magnetic field.
Annealing in a magnetic field is a well-known method
of annealing a sheet while a magnetic field is applied to
the sheet in a direction toward which the sheet is desired
to be magnetized so that the soft magnetic properties of
the sheet are improved.
Table 1 shows the result of measurements of iron loss
values, magnetic flux density and surface roughness of the
surface in contact with the roll of the resulting amorphous
iron based alloy sheets.
As is apparent from Table 1, the amorphous alloy
sheets obtained by the present invention had low iron
losses and magnetic flux densities excellently adapted to
be used for transformers.
Further, the sheets could easily be bent upon
themselves in intimate contact in critical bending tests,
and had excellent resistance to brittleness.
Whereas, although the comparative examples could be
subjected to an intimate contact bending, all of them had
high iron loss or low magnetic flux density.
14
Table 1
Sample C~ lt~- (at%)~13/50 Blo Surface P-ug' -99 Critlcsl BendLng HeLght Reference
No. (W/kg) (T) Ra (~m) (mm)
1 ~egl.6 Bll SL7 Mn0A 0-109 1.550 0.7 LntLmate bendLng possLble Example of the Present LnventLon
2 ~e8155 Bll SL8 MnO.45 0.087 1.546 0.8 - dLtto - - dLtto
3 Pegl.7 BlO SL3 Mno.3 0.104 1.547 0.6 - dLtto - - dLtto
4 Pegl.6 Blo SL8 Mn0A 0.091 1.542 0.7 - dLtto - - dLtto
Ee80~8 B12 SL7 Mn0.2 0-095 1.538 0.6 - dLtto - - dLtto
6 ~ego.6 B12 SL7 Mno.4 0.084 1.530 0.7 - dLtto - - dLtto
7 ~e81.0 B12 SL7 0.213 1.545 0.7 - dLtto - C~ t~ve Example
8 Pe8l.9 Bll MnO.l 0.162 1.540 0.7 - ditto - - ditto
9 Ee80.3 B12 Si7 Mno.7 0.082 1.515 0 7 - ditto - - ditto
~80.1 Bl2 Si7 Mno.g 0.081 1.493 0.7 - ditto - - ditto
00
CD
214897~
Example 2
Molten alloys containing Fe in an amount 80 at% or
less and various components shown in Table 2 were evaluated
in the same way as the embodiment 1 and the result of the
evaluation is shown in Table 2.
As apparent from Table 2, all of the amorphous alloy
sheets obtained according to the present invention had low
iron loss and excellent bendability.
Whereas, the comparative examples had high iron loss
or low magnetic flux density although they could be
subjected to intimate contact bending.
According to the present invention, the iron loss of
an Fe-B-Si amorphous iron based alloy can be reduced and
its magnetic flux density can be increased.
Further, according to the present invention, the
brittleness of a material after addition of Mn can be
effectively reduced and sheet breakage in manufacture of
winding transformers can be prevented by effecting the
quenching and solidifying process in a CO2 atmosphere
contA; n ing a slight amount of H2.
16
Table 2
Sample Composition (at%)W13~50 B1o Surface P~ L ~ Critical Bending ~eight Reference
No. (W/kg) (T)Ra (~m) (mm)
11 PeM,8 B13 Si9 Mn0.2 0.0891.515 0.6intLmate bending possible Exsmple of the Present invention
12~e77.7 B13 Si9 Mno.3 0.0821.512 0.7 - ditto - - ditto
13~e77,6 B13 Si9 Mno4 0.0801.508 0.7 - ditto - - ditto -
14~e7755 B13 Si9 Mno.45 0.0801.505 0.7 - ditto - - ditto
15Pe7765 B13 Si9 Mno.35 0.0801.510 0.8 - ditto - - ditto
16Ee79,7 B12 Si8 Mno30.098 1.5200.7 - ditto - - ditto
17Ee796 B12 Sig Mno40.091 1.5180.7 - ditto - - ditto
18~e767 B9 Si14 Mno30.092 1.4930.6 - ditto - - ditto -
19 Ee766 B9 Si14 Mno,4 0-0901.490 0.7 - ditto - - ditto -
l?e78 B13 Si9 0.1151.520 0.6 - ditto - C~ tive Example
21 Ee779 B13 Si9 MnQl 0.1131.511 0.7 - ditto - - ditto -
22 Pego Bl2 Sig 0.231 1.5350.6 - ditto - - ditto -
23 ~eM Bg Si14 0.203 1.4950.7 - ditto - - ditto -
24 ~eM 2 B13 Si9 Mn0.80.080 1. 463 0 . 6 - ditto - - ditto
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Example 3
Amorphous iron alloy sheets each composed of
' Fe80.6B12Si7MnO.4 (thickness: 30 ~m) were made by the same
method as Example 1 except that the atmospheres used in
quenching and solidification were variously changed as
shown in Table 3.
Surface roughnesses of the surfaces in contact with
the roll and bending limit heights of each of the thus
obtained sheets were investigated. Table 3 shows the
results of the investigation, together with iron loss and
magnetic flux density.
As is apparent from Table 3, the surface roughnesses
and the bending limit heights of the sheets were changed
depending upon differences of the atmospheres used in
quenching and solidification. When the sheets were made in
atmospheres according to the present invention, the sheets
had small mean roughnesses along centerlines Ra of 0.7 ~m
and had excellent resistance to brittleness more than
sufficient to enable intimate contact bending.
When an atmosphere contained H2 in an amount less than
1%, all of the mean centerline Ra surface roughnesses
exceeded 0.8 ~m, and further, as the Ra increased, the
limit bending height increased and brittleness proceeded.
Further, when an excessive amount of H2 was contained
(Sample No. 28), although the Ra was 0.7 ~m, intimate
contact bending could not be effected.
Table 3
SampleAtmosphere in Wl3/50 Blo RaCritical Bending Height Reference
No.Quenching and (W/kg) (T) (~m)
Solidification
Air 0.085 1.524 1.2 0.25 Comparative Example
26 C02 0.085 1.529 0.9 0.13 Comparative Example
270.5%H2 + C02 0.084 1.530 0.9 0.10 Comparative Example
28 lOZH2 + C02 0.084 1.536 0.7 0.05 Comparative Example
_O 29 1.0%H2 + C02 0.084 1.537 0.7 intimate contact Example of the Present
bending achieved Invention
4-0%H2+ C02 0.084 1.537 0.7 intimate contact Example of the Present
- bending achieved Invention
31 60%C02 + Air 0.085 1.525 1.1 0.20 Comparative Example
32 30ZC02 + Air 0.085 1.525 1.0 0.16 Comparative Example
