United States Patent [191
[11]
Patent Number:
4,875,947
Nakayama et a1.
[45]
Date of Patent:
Oct. 24, 1989
[54] METHOD FOR PRODUCING
GRAIN-ORIENTED ELECTRICAL STEEL
3,932,201
SHEET HAVING METALLIC LUSTER AND
[21] Appl. No.: 239,191
[22] Filed:
Aug. 31, 1988
Howe et al. ..
4,543,134
9/1985 Tanaka et al.
148/113
.. 148/113
.. 148/113
Tanaka et al. .................... .. 148/113
3/1978 Japan .
7/1980 Japan .
6/1981 Japan .
59-96278
6/1984 Japan .
60-89521
1426150
5/1985
2/1976
Japan .............. ..
United Kingdom .
148/111
.. 148/113
Primary Examiner-—John P. Sheehan
Japan .............................. .. 62-215224
Japan
.......... .. 62-215225
Japan
.......... .. 63-193297
[51]
Int. Cl.‘ ............................................. .. H01F 1/04
[52]
[58]
US. Cl. ................................... .. 148/113; 148/112
Field of Search ...................... .. 148/111, 112, 113
References Cited
U.S. PATENT DOCUMENTS
3,039,902
6/1962 Miller et a1. ...................... .. 148/ 113
3,582,407
6/1971
3,615,918 10/1971
4/1985
53-22113
55-89423
56-65983
[73] Assignee: Nippon Steel Corporation, Tokyo,
Japan
[56]
148/113
148/113
FOREIGN PATENT DOCUMENTS
of Kitakyushu, Japan
Foreign Application Priority Data
4,512,823
4,775,430 10/ 1988
Youichi Zaizen; Kouji Yamasaki, all
Aug. 31,1987 [JP]
Aug. 31, 1987 [JP]
Aug. 2, 1988 [JP]
Steger ............................... .. 148/113
Miller ......... ..
Maucione ....... ..
4,242,155 12/1980 Morita et al.
EXCELLENT PUNCHING PROPERTY
[75] Inventors: Hisanobu Nakayama; Osamu Tanaka;
Yasumoto;
Senoo;
[30]
1/ 1976
4,171,994 10/1979
4,186,038 l/ 1980
Steger et a1. . . . . .
. . . . . ..
148/113
Evans et a1. .
..... .. 148/113
3,697,322 10/1972 Lee et a1. .................. .. 148/113
3,841,925 10/ 1974 Steger ............................... .. 148/ 113
Attorney, Agent, or Firm-Kenyon & Kenyon
[57]
ABSTRACT
A method for producing grain-oriented electrical steel
sheet having metallic luster and excellent punching
property comprises the steps of decarbonization anneal
ing a grain-oriented electrical steel sheet which has been >
cold rolled to a ?nal thickness, coating the decarboniza
tion-annealed sheet with an annealing separator consist
ing of magnesium blended with one or more salts of
alkali metal or alkaline-earth metal, and ?nish annealing
the coated sheet.
4 Claims, No Drawings
1
4,875,947
-
2
closed in Japanese Published Unexamined Patent Appli
METHOD FOR PRODUCING GRAIN-ORIENTED
ELECTRICAL STEEL SHEET HAVING METALLIC
LUSTER AND EXCELLENT PUNCHING
PROPERTY
cation No. 55(l980)-89423 which uses an annealing
separator consisting of ?ne alumina powder blended
with 5—30% hydrated silica mineral powder, an Sr com
pound, a Ba compound, calcium oxide and calcium
hydroxide, the annealing separator being applied to the
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for producing
glass-less grain-oriented electrical steel sheet exhibiting
10
steel sheet prior to ?nish annealing. As another there is
known that disclosed in Japanese Published Unexam
ined Patent Application No. 56l98l)-65983 which uses
an annealing separator consisting alumina hydroxide
metallic luster and more particularly to such a steel
blended with of 20 parts by weight of an impurity re
sheet having very superior punching property.
moving additive and 10 parts by weight of a suppressing
agent, the separator being applied to the steel sheet to
2. Description of the prior art .
Grain-oriented electrical steel sheet is generally pro
form a thin glass ?lm of a thickness of 0.5 mm or less.
duced as follows. A silicon steel slab containing not 15
Further, Japanese Published Unexamined Patent Ap
more than 4.0% Si is hot rolled, optionally annealed,
plication No. 59(l984)-96278 discloses an annealing
subjected to a single cold rolling or two or more cold
separator consisting of A1203, which has low reactivity
rollings alternately with intermediate annealing, and
toward the SiO; in the oxide ?lm formed during decar
then cold rolled to the ?nal sheet thickness. It is then
bonization annealing, and MgO calcined at more than
20
subjected to decarbonization annealing to produce a
l,300° C. to reduce its reactivity. The method of this
SiOz-containing oxide ?lm on its surface, whereafter an
application
produces a useful effect in that it suppresses
annealing separator consisting mainly of MgO is applied
the
formation
of a forsterite ?lm (glass ?lm).
to the surface thereof and dried. The sheet is then
On
an
actual
production line, however, ?uctuations
wound into a coil and subjected to high-temperature
?nish annealing. As a result, the formation of Goss 25 sometimes arise in the dew point or constitution of the
gas atmosphere during decarbonization annealing, for ,
texture secondary recrystallization grains is promoted
example. Also, local variations arise in the thickness of
and a glass ?lm is formed on the sheet surface. If re
the oxide ?lm formed on the surface of the steel plate.
quired, the sheet is coated with an insulating coating
Furthermore, depending on its history, the steel plate
liquid and then baked to form an insulating ?lm thereon.
itself undergoes variation in oxidation in the widthwise
Grain-oriented electrical steel sheet is used as a mate
or lengthwise direction. On the other hand, methods for
rial for the iron cores of dynamos, transformers and
removal of glass film are known but entail the risk of
other electrical equipment. Ordinarily such a core is
non-uniform removal. At any rate, up to the present
fabricated by punching or shearing the sheet into appro
there has been no method for consistent production of
priately shaped core plates by use of a steel die and then
laminating the core plates to obtain the core. In fabricat 35 grain-oriented electrical steel sheet exhibiting metallic
ing an iron core for a turbine generator, for example, the
luster.
number of core plates required amounts to 100 to 200
SUMMARY OF THE INVENTION
thousand. Moreover, it is necessary to hold the punch
ing burr height of these plates to not more than, for
The object of the present invention is to provide a
instance, 15 pm. This is important for the purpose of 40 method for producing grain-oriented electrical steel
preventing an abnormal increase in core loss caused by
sheet having metallic luster and excellent punching
shorting of the edges of the core plates after they have
been laminated to form the core.
The surface of grain-oriented electrical steel sheet is
coated with a glass ?lm or with both a glass ?lm and an 45
insulating ?lm. As the glass ?lm has high hardness, it
increases the wear of the die during the punching opera
tion. For this reason, punching burr tends to occur after
several thousand punching operations and it becomes
necessary to repolish the die or to replace it with a new
one. This greatly reduces the ef?ciency of the work and
leads to an increase in cost.
property.
DETAILED DESCRIPTION OF THE
INVENTION
In the production of grain-oriented electrical steel
sheet, hot rolling is generally followed by optional an
nealing, a single cold rolling or two or more cold roll
ings alternately with intermediate annealings, cold roll
ing to the ?nal sheet thickness, decarbonization anneal
ing, application of an annealing separator, winding into
a coil, and ?nish annealing. The present invention does
A method for producing grain-oriented electrical
not
particularly specify the steel constituents or the
steel sheet having metallic luster is disclosed, for exam
steps
up to that in which the steel sheet is rolled to the
ple, in Japanese Published Unexamined Patent Applica 55
?nal thickness, and these can be freely selected.
tion No. 53(l978)-22l 13. According to the disclosed
The grain-oriented electrical steel sheet which has
method, the thickness of the oxide ?lm produced during
been cold rolled to the ?nal sheet thickness is decarbon
decarbonization annealing is held to not more than 3 pm
ization annealed. This decarbonization annealing re
and ?ne alumina powder blended with 540% of hy
moves carbon from the steel, causes primary recrystalli
drated silica mineral powder is used as the annealing
zation and forms an oxide ?lm containing SiOz on the
separator. After being coated with this separator, the
surface of the sheet.
steel sheet is ?nish annealed. This method produces
After decarbonization annealing, the grain-oriented
electrical steel sheet is coated with an annealing separa
obtained, the presence of the hydrated silica makes it
possible to form a glass ?lm that separates easily, and 65 tor. At this time it is important that the composition of
the annealing separator be such that no glass ?lm forms
the product has a metallic luster.
during ?nish annealing but instead the sheet surface
As one known annealing separator which suppresses
the formation of a glass ?lm, there is known that dis
comes to exhibit a metallic luster.
certain good effects such as that a thin oxide ?lm is
3
4,875,947
In the present invention there is used an annealing
separator consisting of 100 parts by weight (hereinafter
referred to simply as “pa ”) of magnesia (MgO)
4
Experiments were conducted for ?nding a way to
eliminate this problem and it was found that a marked
improvement in punching property and good electrical
blended with 2-40 parts of one or more salts of members
properties can be obtained by coating the surface of the
selected from among such alkali metals as Li, Na, K and
Rb and such alkaline-earth metals as Ca, Ba, Mg and Sr.
When there is used an annealing separator consisting
grain-oriented electrical sheet having metallic luster
with an inorganic coating, then carrying out ?attening
annealing, and thereafter applying an organic coating to
ofnot less than 2 parts ofa salt ofan alkali metal or an
the sheet surface.
alkaline-earth metal blended with 100 parts of magnesia,
reaction between the magnesia and the SiO; during
sisting of one or more of, for example, phosphates such
?nish annealing is suppressed, whereby glass ?lm is not
As the inorganic coating there can be used one con
as phosphoric acid, aluminum phosphate, magnesium
formed. This is because the salt in the annealing separa
phosphate, calcium phosphate, zinc phosphate and man
tor decomposes the SiO; in the oxide ?lm. To realize
ganese phosphate, chromates such as chromic acid,
this effect, it is necessary for the annealing separator to
15 magnesium chromate, aluminum chromate, calcium
contain not less than 2 parts of the salt per 100 parts of
chromate and zinc chromate, dichromate and colloidal
the magnesia. When less salt is contained, an adhesive
silica. A coating weight of 0.5-2.5 g/m2 is preferable.
glass ?lm is formed or glass ?lm is locally formed, giv
The inorganic coating can have boric acid, borate or
ing a non-uniform appearance and degrading the quality
silicate added thereto.
of the product. On the other hand, when the amount of 20 Following application of the inorganic coating, ?at
the salt blended with the magnesium is too great, stick
tening annealing is carried out at 800°-870° C. This
ing occurs during the ?nish armealing. Also, where an
temperature range is selected as the most effective for
insulating ?lm is to be formed by coating with an insu
lating coating liquid followed by baking, it becomes
straightening the shape of sheet. In this invention, since
the steel sheet is covered with the aforesaid coating, it
difficult to remove the annealing separator in the pre 25
experiences absolutely no oxidation by the gas atmo
ceding step of light pickling. To preclude these prob
sphere, which results in improved punching property
and ensures good electrical properties.
40 parts.
Next, an organic insulating coating is applied to the
When grain-oriented electrical steel sheet is coated
sheet
and baked thereon at, for example, 250°-350° C. to
with this annealing separator and ?nish annealed, the 30
form
an insulating ?lm. As the organic coating there
entire surface of the sheet will be free from glass ?lm
lems, the content of the salt is speci?ed as not more than
over the entire length thereof, not withstanding any
variation that may exist in the thickness of the oxide ?lm
at the time of decarbonization annealing, and will ex
hibit metallic luster and superior punching property.
In the method of the present invention, since use of
too low an annealing temperature causes the time re
quired for decarbonization to become impracticably
long and may result in incomplete decarbonization, the
annealing temperature is speci?ed as not less than 800°
C. On the other hand, since use of too high a tempera
can be used, for example, one of acrylic type or of sty
rene, polyvinyl, melamine, phenol, silicon, vinyl ace
tate, epoxy or the like. An organic coating blended with
35 an inorganic coating is also usable. Use of the organic
coating by itself improves the punching property of the
grain-oriented electrical steel sheet. A further dramatic
improvement in punching property can be realized,
however, by ?rst preventing the formation of an oxide
?lm through the provision of the inorganic coating and
then further applying and baking on the organic coat
ing.
Any method can be used for applying the annealing
separator to the grain-oriented electrical steel sheet. For
the probability of a nonuniform glass ?lm remaining
after ?nish annealing, this temperature is further speci 45 example, it can be applied in the form of a slurry or by
electrostatic painting.
?ed as not more than 850' C. While there is no need to
ture hinders the decarbonization and increases the
amount of oxide layer formed, which in turn increases
prescribe the decarbonization annealing time, it is pref
erably 90-180 sec. The annealing is carried out in an
atmosphere of H2, N2, Ar, H20 and a small amount of
CO and CO2. It is important to control the rate of oxidi
zation by this gas atmosphere. When the oxidization
rate PHZO/PHZ is low, the decarbonization becomes
EXAMPLE 1
A grain-oriented electrical steel sheet consisting of
0.046% C, 3.12% Si, 0.057% Mn, 0.022% S and the
balance of Fe and unavoidable impurities was hot rolled
to a thickness of 2.3 mm. The hot-rolled sheet was then
insuf?cient, which has an adverse effect on the electri
cold rolled twice to a sheet thickness of 0.35 mm, with
cal properties of the sheet. Thus PHZO/PHZ is speci?ed
intermediate annealing at 980° C. for three minutes
being carried out between the two cold rollings. The
as not less than 0.25. When the oxidization rate is too
high, a large amount of oxide layer is formed and an
cold-rolled sheet was then decarbonization annealed in
irregular glass ?lm is likely to remain following ?nish
a wet hydrogen atmosphere. Next specimens of the
annealing. Thus the upper limit on this rate has been set
at 0.55.
sheet were coated with annealing separators of the com
After ?nish annealing, the grain-oriented electrical
steel sheet is subjected to ?attening annealing for
straightening it into sheet form. At this time, an oxide
positions shown in Table 1 and subjected to ?nish an
nealing at l,200° C. for 20 hours. In the ensuing continu
ous heat ?attening step, a coating of phosphate plus
colloidal silica was applied to and baked on the speci
layer will form on the sheet surface with metallic luster
mens in such amount as to obtain a coating weight after
even though every effort is made to maintain the atmo 65 baking of 2 g/mz.
sphere as dry as possible. This oxide layer degrades both
the punching property and the electrical characteristics
of the sheet.
The resulting specimens were examined for appear
ance, punching property and electrical properties. The
results are also shown in Table l.
4,875,947
.5
'
6
TABLE 1
Punching
Specimen
property"
(after coating
Annealing separator tparts by weight!
No.
MgO
1
100
A1203 Additives
Magnetic properties
B10
W17/50
Appearance
with phosphate)
(T)
(W/kg)
Remarks
LiCl: 5
Completely free of
3.8 (104 times)
1.87
1.30
Invention
KCl: 5
metallic luster
Completely free of
3.6 (104 times)
1.87
1.30
"
5 (104 times)
1.88
1.28
"
3.5 (104 times)
1.87
1.29
"
6 (104 times)
1.87
1.29
"
6.2 (104 times) -
1.88
1.29
"
6.5 (104 times)
1.88
1.28
"
0.6 (104 times)
1.87
1.33
Comparative
3 (104 times)
1.87
1.30
example
Comparative
glass film; uniform
2
"
glass ?lm; uniform
3
"
metallic luster
Completely free of
CaClg: 5
»
glass ?lm; uniform
4
"
metallic luster
Completely free of
BaClz: 5
glass ?lm; uniform
metallic luster
5
"
6
"
CaCl2: 5 +
Completely free of
LiCl: 5
glass ?lm; uniform
CaClg: 5 +
metallic luster
Completely free of
KCl: 5
glass ?lm; uniform
metallic luster
7
"
CaCl;_: 5 +
Completely free of
BaCl: 5
glass ?lm; uniform
metallic luster
Comparative
100
example 1
Comparative
MgO calcined
example 2
at 1,700‘ O: 60
O
100
0
, Complete glass ?lm
MgSO4.7I-I1O:
Meta?ic luster
6
but somewhat
example
irregular
‘Number of punching operations with a 5 mm diameter steel die before heigh of punching-burr became 50 pm.
As can be seen from Table 1, all specimens prepared
coated with annealing separators of the component
using an annealing separator satisfying the component
30 content ratios shown in Table 2 at the rate of 8 g/m2 per
content ratios of this invention (No. l-7) were free of a
glass ?lm and exhibited metallic luster as well as good
punching property, as compared not only with Com
side and were then subjected to ?nish annealing at
l,200° C. for 20 hours. In the ensuing continuous heat
?attening step, a coating of aluminum phosphate plus
parative Example No. 1 prepared using a conventional
colloidal silica was applied to the specimens at the rate
annealing separator for providing a complete coating
35
?lm but also with Comparative Example No. 2 pre
pared using an annealing separator claimed not to pro
duce a substrate coating ?lm.
Specimen
of 2 g/m2 and baked thereon. The appearance, punching
property and magnetic properties of the so-obtained
products are shown Table 2. The punching property
was evaluated by the same method as in Example 1.
TABLE 2
Annealing separator
gparts by weight)
Punching property“
(after coating
Magpetic proErties
B10
W17/50
No.
MgO
CaClz
Appearance
with phosphate)
(T)
(W/kg)
Remarks
Comparative
example 1
100
0
Uniform glass ?lm
0.6 (104 times)
1.85
1.32
Comparative example
2
3
"
"
2
5
Almost no glass ?lm
Completely free of glass
4.2 (104 times)
5.1 (104 times)
1.86
1.87
1.30
1.27
Invention
"
4
"
l0
6.3 (104 times)
1.87
1.25
"
6.7 (104 times)
1.87
1.26
"
6.5 (104 times)
1.87
1.28
"
?lm; grains exposed
Completely free of glass
?lm; grains exposed
5
"
2O
Completely free of glass
6
"
30
Completely free of glass
?lm; grains exposed
?lm; grains exposed
Moreover, the specimens prepared according to the
method of the present invention exhibited good electri 55
cal properties (magnetic ?ux density B10 and core loss
As the grain-oriented electrical steel sheet according
to the present invention has no glass ?lm on its surface
whatsoever, it not only exhibits improved punching
dition of ?ve or more parts of CaCl; resulted in a sheet
60
property but is also provided with enhanced electrical
properties by facilitating the movement of the magnetic
having no glass ?lm whatsoever, complete uniform
exposure of the metal surface, good appearance and
highly superior punching property.
domain walls in the process of magnetization.
EXAMPLE 2
While slight formation of a glass ?lm was noted in the
case of adding only 2 parts CaClZ, the improvement in
punching property was nevertheless considerable. Ad
W17/so)
EXAMPLE 3
There was used a 0.35 mm decarbonization-annealed
A grain-oriented electrical steel sheet consisting of
0.045% C, 3.08% Si, 0.060% Mn, 0.024% S and the
sheet obtained in the same manner as that in Example 1.
balance of Fe and unavoidable impurities was hot rolled
Specimens of the decarbonization-annealed sheet were
to a thickness of 2.3 mm. The hot-rolled sheet was then
65
4,875,947
7
8
cold rolled twice to a sheet thickness of 0.35 mm, with
zation annealed at 820° C. for 150 seconds in an atmo
sphere
of N2+H2 at
an
oxidation
rate
-
intermediate annealing at 950° C. for three minutes
being carried out between the two cold rollings. Speci
PHzO/PH2=0.35. Specimens of the so-obtained sheet
mens of the cold-rolled sheet were then decarboniza
were coated with the annealing separators shown in
Table 5 and subjected to ?nish annealing at l,200° C. for
20 hours. Then, on a continuous coating line, the speci
tion-annealed under the conditions shown in Table 3.
The specimens were coated with annealing separators
" of the compositions shown in Table 3 and subjected to
mens were subjected to heat ?attening and treatment to
?nish annealing at 1,200° C. for 20 hours. A coating
liquid of phosphate plus colloidal silica was applied to
bake a coating consisting primarily of colloidal silica
and orthophosphate thereon. The properties of the so
the specimens and baked thereon in a step that also 10 obtained products are shown in Table 5.
TABLE 5
No.
Additive per 100 pans by
weight of MgO
(in parts by weight)
1
2
3
4
5
6
BaClz 10
MgCl; 10
CaCl; 10
LiCl 10
KCl 10
None (comparative example)
served the
Appearance
Uniform metallic luster over entire surface
Uniform metallic luster over almost entire surface
Uniform metallic luster over entire surface
Uniform metallic luster over entire surface
Uniform metallic luster over entire surface
Uniform glass ?lm
Punching property
(after coating
with phosphate)
Magpetic propgrties
B3
W17/50
(T)
(W/kg)
6.7 (104 times)
4.8 (104 times)
7.6 (104 times)
5.9 (104 times)
1.89
1.87
1.89
1.28
1.88
1.87
62(10“ times)
0.5 (104 times)
pmp°se of ?attening annealing . The result
1.28
1.32
1.28
1.30
1.32
1.38
EXAMPLE 5
ing specimens were examined for appearance, punching
property and magnetic properties. The results are
A slab consisting of 0.04% C, 3.1% Si, 0.06% Mn,
0.02% S, 0.001% A1, 0.005% N and the balance of Fe
shown in Table 4.
TABLE 3
Decarbonization annealing"
Specimen Temperature
Additive per 100 parts by weight of MgO
(in parts by weight)
CaClz l0
No.
('C.)
PHZO/PHZ
1
810
0.28
Remarks
2
"
0.45
"
Invention
3
4
5
"
800
865
0.58
0.35
0.35
"
"
"
Comparative example
Invention
Comparative example
6
810
0.35
No addition
Comparative example
Invention
‘Uniform heating time: 150 sec
TABLE 4
Punching property"
Magpetic properties
C content after
Appearance
(after coating
with phosphate)
B3
(T)
W17/50
(W/kg)
Free from uniform ?lm over entire
Free from uniform ?lm over entire
6.3 (104 times)
5.8
1.87
1.88
1.32
1.28
3
Some irregularity along edges; slight ?lm formation
2.3
1.87
1.36
8
4
Free from uniform ?lm over entire
5.9
1.88
1.30
16
No.
1
2
decarbonization
(ppm)
22
14
5
irregularity along edges; slight ?lm formation
1.4
1.87
1.35
33
6
Uniform glass ?lm
0.7
1.86
1.36
18
‘Number of punching operations with a 5 mm diameter steel die before height of punching-burr became 50 um.
All specimens prepared under the conditions of 810°
C., PH2O/PH2=0.28, 0.45, and 800° C., 50
PH2O/PH2=0.35, which conditions satisfy the present
and unavoidable impurities was heated to 1,400“ C. and
invention, incurred no formation of glass ?lm, exhibited
?nished as a 21 mm hot-rolled coil. After pickling, the
metallic luster and had good punching property. In
coil was reduced to 0.75 mm by primary cold rolling,
contrast, the specimen according to the comparative
subjected to intermediate annealing at 950° C. for 60
example was uniformly formed with a glass ?lm and 55 seconds, and reduced to 0.35 mm by ?nal cold rolling.
exhibited poor punching property. More speci?cally, in
The cold-rolled sheet was decarbonization annealed at
specimen No. 3 which was prepared using too high a
value of PHZO/PHZ and in specimen No. 5 which was
prepared using too high a temperature, because of the
and ?nish annealed The sheet was then washed with
water to remove MgO and subjected to ?attening an
840° C., coated with MgO containing 10 wt% CaClg,
occurrence of such irregularities as the formation of 60 nealing (at 850° C. for 90 sec) and insulation coating
?lm at the edge portions and slight formation of ?lm
throughout, the punching property was poor. Further,
(300° C. for 10 sec), whereafter specimens thereof were
treated in the following four ways:
analysis conducted to determine residual C after decar
bonization revealed an abnormality in specimen No. 5.
Case 1: The specimen was coated with an aluminum
EXAMPLE 4
A cold-rolled sheet of a ?nal thickness of 0.35 mm
prepared after the manner of Example 3 was decarboni
65
phosphate inorganic coating at a coating weight
after drying of 2 g/m2 and then flattening annealed.
Case 2: The specimen was ?attening annealed in a dry
atmosphere of 98% N2 plus 2% H2, coated with an
organic coating consisting of a magnesium phos
4,875,947
9
had excellent punching property.
- weight of 2 g/mZ, and baked.
Case 3: A speciment treated as in Case 1 was coated
with an organic coating consisting of a magnesium
phosphate base containing organic acryl at a coat
ing weight of 2 g/m2, and baked.
10
were all free of glass ?lm, exhibited metallic luster and
phate base containing organic acryl at a coating
What is claimed is:
5
1. A method for producing grain-oriented electrical
steel sheet having metallic luster and excellent punching
property comprising the steps of decarbonization an
nealing, at a temperature of 800° to 850° C. and in an
Case 4: A specimen treated as in Case 1 was coated
atmosphere whose rate of oxidation PHZO/PHZ is 0.25
with an organic epoxy resin at a coating weight of
2 g/mz, and baked.
The so-obtained specimens were tested for punching
to 0.55, a grain-oriented electrical steel sheet which has
been cold rolled to a ?nal thickness, coating the sheet
property and electrical properties. The results are
shown in Table 6.
weight of magnesia blended with 2 to 40 parts of one or
more chlorides of members selected from the group
with an annealing separator consisting of 100 parts by
consisting of Li, Na, K, Rb, Ca, Ba, Mg, and Sr, and
TABLE 6
15 ?nish annealing the sheet.
Punching property
punching-burr height
annealing separator consists of 100 weight parts of mag
nesium blended with 2-40 parts of CaClg.
3. The method as claimed in claim 1 further compris
Maggetic propgrties
No.
reached 30 pm (in tens
of thousands of times)
W17/50
(W/kg)
B3
('1')
Remarks
1
2
1.31
1.85
Comparative
2
32
1.45
1.83
Comparative
20
example
71
75
1.31
1.30
1.85
1.86
Invention
Invention
ing the steps of coating the surface of the ?nish annealed
sheet with an inorganic coating, ?attening annealing the
coated sheet, and coating the ?atten annealed sheet
with an organic coating.
4. The method as claimed in claim 1 further compris
example
3
4
'
2. The method as claimed in claim 1 wherein, the
Number of punching
operations before
25
ing the steps of coating the surface of the ?nish annealed
sheet with an inorganic coating, ?attening annealing the
coated sheet, and coating the ?attening-annealed sheet
Punching conditions: Steel die; punching diameter, 5 mm; clearance, 9%; 400
strokes/min
with a coating consisting of an inorganic coating agent
base having an organic coating agent blended there
uniform glass ?lm and exhibited poor punching prop 30 with.
While the comparative examples were formed with a
i
erty, the specimens according to the present invention
35
50
55
65
i
*
*
$
UNITED STATES PATENT AND TRADEMARK OFFICE
CERTIFICATE OF CORRECTION
PATENT NO.
:
4,875,947
DATED
;
Oct.
|NVENTUR($) ;
24, 1989
H. Nakayam, et a1 .
It is certified that error appears in the above-identified patent and that said Letters Patent is hereby
corrected as shown below:
Column 2, line 9, change "561981)" to ——56(l98l)——.
Column 2, line 10, between "consisting" and
_"alumina" insert ——of—-.
Column 5, line 25 (Table 1), change "MgSO4-7" to
——MgSO4'7—-.
Column 5, line 27, change "heigh" to ——height——.
Column 7, Table 4, numbers 1, 2, and 4, after
"entire" insert ——surface—-.
Column 10, line 22, change "flatten" to
——flattening-—.
Signed and Sealed this
Twelfth Day of February, 1991
Aztest:
HARRY F. MANBECK. JR.
Arresting Officer
Commissioner of Patents and Trademarks