Note: Descriptions are shown in the official language in which they were submitted.
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GRAIN-O~IENTED ELECTRICAL STEEL SHEET HAVING A LOW
WATT LOSS AND METHOD FOR PRODUCING SAME
BACKGROUND OF TH~ IN~ENTION
1. Field of the Invention
The present invention relates to a grain-
oriented electrical steel sheet having a low watt loss
and a method for produclng the same. More particularly,
the present invention relates to a grain-oriented
electrical steel sheet, in which the magnetic domains
are subdivided and the subdivision effect does not
disappear, even if the steel sheet is subsequently heat
treated. The present invention also relates to a method
for producing the grain-oriented electrical steel sheet
as mentioned above.
2. Description of the Related Art
The grain-oriented electrical steel sheet is-
used mainly as the core material of transformers andother electrical machinery and devices, and must,
therefore, have excellent excitation and watt-loss
characteristics. In the grain oriented electrical steel
sheet, secondary recrystallized grains are developed
which have a (110) plane parallel to the rolled surface
and a <001> axis parallel to the rolling direction.
These grains have the so-called Goss texture formed by
utilizing the secondary recrystallization phenomenon.
Products having improved exciting and watt-loss charac-
teristic~ can be produced by enhancing the orientationdegree of the tllO)'001> orientation and lessening the
deviation of the s001~ axis from the rolling direction.
Note, the enhancement of the (110)~001>
orientation leads to a co~rsening of the crystal grains
and an enlargement of the magnetic domains due to a
passing of domain walls through the grain boundaries.
There occurs accordingly, a phenomenon such that the
watt loss cannot be l~ssened proportionally to enhance
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the orientation.
Japanese Examined Patent Publication No. 58-
5968 proposes to lessen the watt loss by eliminating the
nonproportional phenomenon regarding the relationship
between the orientation enhancement and the watt loss--
reduction. According to this proposal, a ball or the
like is pressed against the surface of a finishing-
annealed, grain-oriented sheet so as to form an
indentation having depth o 5 ~ or less. By this
indentation, a linear, minute strain is imparted to the
steel sheet, with the result that the magnetic domains
are subdivided.
Japanese Examined Patent Publication No. 58-
26410 proposes to form at least one mark on each of the
secondary recrystallized crystal grains by means of
laser-irradiation, thereby subdividing the magnetic
domains and lessening the watt loss.
The materials having ultra-low watt loss can
be obtained, according to the methods disclosed in the
above Japanese Examined Patent Publication Nos. 59-5868
and 58-26410, by means o~ imparting a local minute strain
to the sheet sur~ace of a grain-oriented electrical steel
sheet. Nevertheless, the watt loss-reduction effect
attained in the above ultra-low watt loss materials
disappears upon annealing, for example, during stress-
relie annealing. For example, in the production of
wound cores, the watt loss-reducing effect disappears
disadvantageously ater the stress-relief annealing.
It is also known that the watt loss can be
lessened by refining the crystal grains. For example,
Japanese Examined Patent Publication No. 59-20745
intends to lessen the watt loss by determining an
average crystal-grain diameter in the range of rom 1
to 6 ~n.
It is also known to impart tensional force to
a steel sheet to lessen the watt loss. The tensional
force in the steel sheet can be generated by diffexing
the coefficient o~ thermal expansion between the
insulating coating and the steel sheets.
The above described refining of crystal grains
and strain imparting would not attain a great reduction
in watt loss.
SUMMARY OF THE INVENTION
The materials having an ultra-low watt loss can be
obtained by the methods for subdividing the magnetic
domains. When these materials are annealed, for example,
stress-relief annealed, the watt loss-reduction effect
disappears. It is, therefore, an object of the present
invention to provide a grain-oriented electrical steel
sheet having an extremely low watt loss, and to provide
a method for forming subdivided magnetic domains, in
such a mannex that the watt loss-reducing effect does
not disappear even during a heat treatment, for example,
stress-relief annealing.
The present inventors conducted a number of
e~periments for producing, by the magnetic domain
subdividing method, a grain- oriented electrical steel
sheet which can exhibit an extremely low watt 1GSS even
after a heat ~reatment at a temperature of from 700
to 900C.
In -the experiments, intruders were penetrated into
~he finishing-annealed, grain-oriented electrical steel
sheets. These intruders are distinguished from the
steel of the steel sheets either in components or
stxucture. The intruders were formed as a result of a
reaction, in which the steel sheet or the surface
coating was participated. The intruders were an alloy
la~er, a reaction product of the superficial reaction,
and the like, and the intruders were spaced from one
another.
As a result of the experiments as descrlbed above,
lt was discovered that: the nuclei of magnetic domains
are generated on both sides of the intruders; these
nuclei cause the subdivision of magnetic domains when
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the steel sheet is magneti~ed and, hence, an extremely
low watt loss is obtained; the effect of reducing the
watt loss does not disappear even after the steel sheet
is annealed, for example, stress-relief annealed; and,
an extremely low watt loss is maintained.
The term "intruder" herein expresses clusters,
grains, lines, or the like formed by an intrusion of a
film on the steel sheet into sheet . The film alone may
intrude into the steel sheet. Alternati.vely, -the film
may be combined with the components of a steel sheet
including any surface coating ~ormed during the
production of a grain-oriented electrical steel sheet.
The film may also be combined with the gas atmosphere
of a heating furnace. The films intruded may be those
combined with the components of a steel sheet, or the
gas atmosphere. A preferred intruder is one formed by
Sb metal, Sb alloy, Sb mixture, or Sb compoundl alone
or combined with the steel body of a grain-oriented
electrical steel sheet. The intruder containing Sb can
cause the subdivision of the magnetic domains and
drastically lessen the watt loss.
The effect of watt loss-reduction by the Sb-con-
taining intruder is outstanding, since it does not
disappear cluring a later stress-relief annealing at a
high temperature, for example, from 7~0 to lOOO~C. The
magnetic flux density of steel sheets having the Sb-
containing intruders is high
The term "intrudable means" or "the intrudable
means for subdividing the magnetic domains" herein
represents the material capable of forming the intruder,
and more specifically, is the material to be deposited
on the ~rain-oriented electrical steel sheet by plating.
This material includes Al, Si, Ti, Sb, Sr, Cu, Sn, Zn,
Fe, Ni, Cr, Mn, P, S, B, Zr, Mo, Co~ and other metals
and nonmetals, as well as mixtures, oxides, and alloys
thereof. This material further includes phosphoric
acid, boric acid, phosphate, borate, sulfate, nitrate,
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silicate and the like, and mixtures thereof.
The term "film" hereln collectively indicates a
mechanical coated ~ilm, a chemically deposited film,
e.g., a plating film, and a bonded film; which films are
formed on at least a part of the steel sheet. The term
"film" may include partly a reaction layer and may have
any thickness which is not specified in any way.
The term "surface coating" herein indica-tes the
film, layer or coating ~ormed by the ordinary method for
producing a grain- oriented electrical steel sheet.
The heat-resistant, subdivision of the magnetic
domains can be performed as follows. Strain is imparted
to the grain-oriented electrical steel sheet. The
metallic or nonmetallic powder, the powder of the
metallic or nonmetallic oxide, or agent, such as
phosphoric acid, boric acid, phosphate, borate is
applied, on the~inishing-annealed, grain-oriented
electrical steel sheet, with spaced distances of the
application. When the heat treatment is carried out,
the applied material (intrudable means) is caused to
react with the steel sheet or the surface coating and
is forced into the steel sheet via the strain. The
intruders therefore can be ~ormed spaced from one
another and have components or a structure different
~rom those of steel.
In accordance with the present invention there is
provided a grain-oriented electrical steel sheet having
an ultra low watt loss, characterized in that intruders,
which are spaced from one another and are distinguished
~rom the steel in component or in structure, are formed
on or in the vicinity of the plastic strain region,
thereby subdividing the magnetic domains.
There is also p~ovided a method for producing a
grain-oriented electrical steel sheet by steps including
a subdivision of magnetic domains, characterized in
that, a strain is imparted to the grain-oriented
electrical steel sheet, and an intrudable means for
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forming the intruders being distinguished from the steel
in component or structure, is formed on the grain-
oriented electrical steel sheet prior to or subsequent
to imparting of the strain.
Note, the technique disclosed in Japanese Examined
Patent Publication No. 54-23647 is similar to the present
invention in the point that a metal or compound is
intruded into the steel sheet. It is proposed irl this
technique that, before the finishing annealing, the
compound, metal, or element alone, which is rendered to
slurry form, is applied on the steel sheet and is
thermally diffused into the steel sheet thereby forming,
before the finishing annealing~ the secondary recrystal-
lization-regions in the steel sheet. Principally
speaking, this technique allegedly stops the growth of
grains other than ~110)<001> oriented grains at the
secondary recrystallization regions, thereby attaining a
preferential grcwth of the (110)~001> oriented grains.
The watt loss W17/50 attained in the Japanese Examined
20 Patent Publication No. 54-23647 is approximately
1.00 W/kg which is considerably inferior to ~hat which
the present invention aims to attain. The present
inventors believe that the watt loss according to the
present invention is much less than that of the
publication because diffusing me-tal and the like applied
on the steel sheet at a step prior to the finishing
annealing prevents the coarsening of grains to attain
the watt loss reduction in Japanese Examined Patent
Publication No. 54-23647, while, in the present
invention, after completion of the secondary recrystal-
li~ation, in order to subdivide the magnetic domains the
intruder is forced into the steel sheet, in which the
Goss texture is thoroughly developed.
Method for A~elying an Intrudable Means
The grain-oriented electrical steel sheet, which
is subjected to the subdivision of magnetic domains
according to the present invention, may be produced by
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using any composition and under any conditions of
production steps until the finishing annealing. That
is, AlN, MnS, MnSe, BN, Cu2S and the like can be
optionally used as the lnhibitor. The Cu, Sn, Cr, Ni,
Mo, Sb, W, and the like may be con~ained if necessary.
The silicon steels containing the inhibitor elements are
hot-rolled, annealed, and cold-rolled once or twice with
an intermediate annealing to obtain the final sheet
thickness, decarburization annealed, an annealing
separator applied, and are finally finishing annealed.
The agent which is the intrudable means consists
of at least one member selected from the metal- and
nonmetal-group consisting of Al, Si, Ti, Sb, Sr, Cu, Sn,
Zn, Ni, Cr, Mn, B and their oxides, and of at least one
member selected from the group consisting of phosphoric
acid, boric acid, phosphate, borate, and sulfate, and as
well as these mixtures thereof. The agent is rendered
to a slurry state or solution state and is applied
linearly or spot-like on the finishing-annealed, grain-
oriented electrical steel sheet. The lines are spacedfrom one another.
The metallic or nonmetallic powder has a size of
tens of microns or less. In the slurry, the amount of
metallic, nonmetallic, or oxide powder is preferably in
a concentration from approximately 2 to 100 parts by
weight relative to 100 parts by weight of water, since
the slurry can be applied at a high efficiency at such a
concentration. The metallic or nonmetallic powder or
oxide can be mixed with acid or salt, which may be the
stock solution or may be diluted with water.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a photoyraph showing strain in the steel
sheet;
Figure 2 is an optical microscope photograph
showing an example of the intruder;
Figures 3(a) and (b) are an elevational view and
lateral view, respectively, of an electric plating
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~pparatus;
Figure 4 is a graph showing the relationship
between the current density and cathode-current density
in an electroplating; and
Figure 5 is a graph showing the relationship
between the sheet thickness and watt loss.
Figure 6 is a graph showing a relationship between
the depth of intruder and the reduction percentage in
watt loss.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Method for Imparting Strain
The intrudable means are applied on the finishing-
annealed, grain-oriented electrical steel sheet to form
a film having a weight of from approximately 0.1 to
50 g/m . The application of the intrudable means is
carried out by plating, vapor-depositing, bonding,
fusion-bonding, or the like, preferably by plating.
Prior to or subsequent to the formation of the film, the
strain is imparted by an optical means, such as laser
irradiation, or a mechanical means, such as the yrooved
roll, ball point pen and mark.ing-off methods. The
regions of a grain-oriented electrical steel sheet to
which the strain is imparted are spaced from one another.
The method for imparting the strain is more
specifically described.
The agent is applied on the grain-oriented
electrical steel sheet with a space distance of from 3
to 30 mm. This grain-oriented electrical steel sheet is
preliminarily subjected to a mechanical formation of
minute indentations with a space distance of from 3
to 30 mm by means of a small ball, a ball point pen,
marking-off, a grooved roll, a roller, or the like.
Alterna-tively, the optical method may be used, such as
laser irradiation, for forming the marks~ The appli-
cation amount of the agent can be from 0.1 to 50 g/m2,preferably from 0.3 to 10 g/m2 of area of marks, flaws
and the like, in terms of the film weight after the
application and drying. Subsequently, the heat treatment
is carried out at a temperature of from 500 to 1200C,
after drying the applied agent. During the heat
treatment, the agent is brought into reaction with the
steel sheet and/or the surface coating and forced into
the steel sheet along its width to form the intruders,
such as the alloy layer and/or the surface reaction
product. The intruders so formed are spaced from one
another.
Regarding the laser-irradiation method for imparting
the s-train, the laser may be any one of a CO2 laser,
N2 laser, ruby laser, pulse laser, YAG laser, and the
like. The space distance between the strain-imparted
regions may be from 1 to 30 mm and these regions may be
equi-distant or non-equidistant.
The method for imparting the strain is not to
subdivide the magnetic domains by itself, as in the
conventional method, but to promote~the intruder
formation due to a stably enhanced reaction between the
~0 film and the steel sheet or between the film and the
surface coating. The strain and intrudable means are
further explained with reference to Fig. 1 showing the
strain by black shadow. In this explanation, it is
assumed that the heat treatment is not carried out by
the steel maker but by the user. The intrudable means,
such as the plated Sb, is merely deposited on the steel
sheet and does not exert an effect upon the magnetic
properties until the steel sheet is annealed by the
user. Upon annealing, Sb di~fuses into the steel sheet,
precipitates in the steel sheet, and forms an inter-
metallic compound. The surface of a grain-oriented
electrical steel sheet, to which the laser is applied,
is influenced by the laser so tha-t this surface and its
proximity undergo plastic deformation (black shadow in
Fig. 1). As a result of the plastic deformation,
dislocations, vacancies and other defects increase in
the crystal lattices of deformed region and its
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proximity. During the annealing, the restoration of the
regions influenced by the laser is made in such a manner
that polygonization occurs and subgrains form due to the
rearranging of the dislocations. The grain boundaries
of the subgrains and defects still remaining at the
annealing facilitate the diffusion of the Sb into the
steel. The diffused Sb forms an intermetallic compound
at the grain boundaries of the subgrains and similar
sites of crystals and the intermetallic compound is
precipitated. Unless the defects remain as explained
above, not only does the diffusion occur at a slow rate
but also a uniform diffusion occurs such that Sb
penetrates into the steel in all directions. In the
diffusion under the utilization of regions influenced
by the plastic deformation, the diffusion rate is high
and the diffusion does not spread unlimitedly but is
limited to occur only in the regions mentioned above.
Accordingly, the Sb can penetrate into the steel sheet
to a depth of, for example, from 5 to 30 ~m, and form a
distinct phase which is highly effective for subdividing
the magnetic domains.
The method for imparting the strain is described
more specifically.
The degree of strain is appropriately determined
depending upon the kind of agents used, the temperature-
elevating rate and holding-temperakure of heat treatment,
and the like. The strain-imparting by the laser irradi-
ation can be carried out at an energy density of from
0.05 to 10 J/cm2. The strain-imparting by marking-off
can be carried out at a depth of 5 ~m or less.
According to the discoveries made by the present
inventors during their research into conventional
me-thods of subdividing the magnetic domains by imparting
strain, the effect of subdividing the magnetic domains
can be made to disappear by holding the temperature at
700-900C for a few hours. It is therefore believed
that the stress induced by strain decreases at a temper-
7~
ature of from 700 to 900C~ On the other hand, such atempera-ture range promotes the formation of intruders in
the method utilizing the imparted strain according to
the present invention. It is therefore believed that,
prior to the disappearance of the stress induced by
strain, the material of a film actively propayates into
the steel sheet. The temperature- elevating rate and
the holding time and tempera-ture can therefore be
advantageously determined so that the stress induced by
strain does not disappear during the active propagation.
The appropriate temperature-elevating rate and the
holding time and temperature, as well as their appropri-
ate ranges for stably forming the in-truder, are dependent
upon the component or kind of film, the concentra-tion of
agent in the film, and the like.
Referring to Fig. 2, the intruder is shownO The
intruder was formed by utilizing the stress generated by
a mar~ing off method. As is apparent ~rom Fig. 2, which
is a microscope photograph at the magnification of 1000,
2~ the intruder sharply penetrates into the steel sheet
along its width.
Mote that the laser irradiation can be carried out
after application of the agent, which may be made as
either an entire or partial formation of film on the
finishing annealed, grain- oriented electrical steel
sheet. Also in this case, the strain, which is imparted
to the film, contributes to a stable formation of the
intruder when the subsequent heat treatment is carried
out, since the strain enhances the reactions of film
with the surface coating and steel sheet during the
temperature-elevation and holding. However, the strain-
imparting causes the destruc-tion of a film in many
cases. Such destruction can be prevented by a thick
application of -the agent or by strengthening the film
by, for e~ample, a heat treatment at approximately 500C.
Platin~ Method
A glass film, o~ide film, and occasionally an
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insulating coating (surface coating), are formed on the
finishing annealed, grain-oriented electrical steel
sheet. These films and coating can be removed entirely
or with a space distance by laser-irradiating, grinding,
machining, scarfing, chemical polishing, pickling, shot-
blasting or the like, to expose the steel body o~ the
grain-oriented electrical steel sheet. The intrudable
means, such as metal, nonmetal, a mixture thereof,
alloy, oxide, phosphoric acid, boric acid, phospha-te and
borate, as well as a mixture of phosphoric acid, boric
acid, phosphate and borate, are plated on the steel
sheet. When the glass film and the like are removed
with a space distance, an electroplating, a hot dipping,
or the like is employed for plating. When the glass
film and the like are removed entirely, a partial
electroplating is employed for plating. The building up
amount is 0.1 g/m2 or more.
The oxide film mentioned above is formed during the
decarburization annealing and is mainly composed of SiO~
The glass film is formed by a reaction between the oxide
film and the annealing separator mainly composed of MgO
and is also referred to as the forstellite film. The
insulating coating mentioned above is formed by applying
colloidal silica, chromic acid anhydride, aluminum
phosphate, magnesium phosphate, and the ].ike on the
steel sheet and then baking them. The oxide film, glass
film and the insulating coating suppresses the intrusion
of an intrudable means. By removiny such oxide film and
the like, the reactivity between the intrudable means
and the steel body o~ the grain-oriented electrical
steel sheet is enhanced. The intrudable means deposited
in a building up amount o~ 0.1 g/m2 can then effectively
and stably be caused to penetrate into the steel sheet,
thereby forming the intruder. Since the intrusion depth
and amount can be easily changed by controlling the
building up amount, it becomes also possible to dis-
tinguishably produce products having different grades of
37~'~
watt loss characteristics by controlling the building up
amount. In addition, due to an enhanced reactivity, the
heat treatment after plating may be omitted, but carried
out if necessary to increase the intrusion depth and
amount.
The spaced removal of the oxide film, the glass
film, and the insulating coating can be carried out by
laser-irradiation, grinding, shot-blasting machining,
scarfing, local pickling and the like. The removed
regions are spaced from one another by the distance of
1 mm or more, preferably from 1 ~ 30 mm, with an equal
or nonequal distance, and are oriented preferably at an
angle of from 30 to 90 degrees relative to the rolling
direction of steel sheet. The removal operation may be
continuous, with the aid of pickling or shot-blasting,
or discontinuous. The width of each of the removed
regions is preferably from 0.01 to 5 mm in the light of
an effective formation of the intruder. The steel body
of a grain-oriented electrical steel sheet is exposed by
removing the oxide film and the like. During this
exposure, the steel body is partly slightly recessed and
the s~rain is imparted simultaneously with the recess
~ormation.
After the removal as described above, the electro-
plating of an intrudable means is carried out.
In a case of the spaced remo~al of the surfacecoatiny, the steel sheet is conveyed, for the electro-
plating, through the electrolytic solution, into which
is incorporated an intrudable means, such as metals and
nonmetals, e.g., Al, Si, Ti, Sb, Sr, Sn, Zn, Fe, Ni, Cr,
Mn, P, S, B, Zr, Mo, Co, and a mixture, oxide, or alloy
thereof, as well as phosphate, borate, sulfate, nitrate,
silicate, phosphoric acid, and boric acid. An electro-
chemical reaction occurs, during the electroplating, only
where the surface coating is removed with a distance and
the steel body of a steel sheet is thus exposed. The
intrudable means is therefore electropla-ted on only
, . ..
3~
portions of the steel sheet where the steel body is
exposed, and the other portions are not electroplated
with the intrudable means. The distance between the
portions of electroplating or between the intruders as
well as the location of such portions can be controlled
optionally. Such controlling can be attained without
incurring a reduction in the strip conveying speed of a
plating line at all. No reaction of the remaining
surface coating with the plating solution also brings
about an advantage in that a beautiful appearance of the
surface coating is maintained.
In the case of an entire removal of the surface
coating, the partial electroplating is employed for
plating the intrudable means with a space distance, as
described with reference to Fig. 3. The electroplating
roll shown in Fig. 3 is provided with conductive zones 1,
which ar~ spaced from one another. In the roll body, a
passage 2 for the electrolyte solution is formed.
Injection apertures 3 for the electrolyte solution are
formed through the conductive zones 1 or in their
neighbourhood. By varying the distance between and
arrangement of the conductive zones 1, the distance
between and arrangement of the plated metals also can be
varied. The electrolyte solution, into which the
intrudable means is incorporated as described above, is
also used for the partial electroplating, and the
portions of a steel sheet through which -the current is
conducted are plated with the intrudable means and the
intruder is formed in such portions. The width of each
of the portions mentioned above is preferably from 0.01
to 5 mm.
In the plating method, the building up amount is
important, since, at a small ineffective amount, the
amount of intruder formed is too small to subclivide the
magnetic domains. A-t a building up amount of 0.1 g/m2
or more, a heat-resistant subdivision of the magnetic
domains can be achieved. In addition, by controlling
a
~ 15 ~
the building up amount, the intrusion depth and amount
can be varied~ For example, by increasing the building
up amount, the intrusion depth and amount can be
increased and the watt loss characteristics can thus be
greatly improved and, further, the products having
different grades of watt loss characteristics can be
distinguishably produced.
It is to be noted that, for exposing the steel body
of a steel sheet, either only the glass and o~ide films
or all of the glass and oxide films and the insulating
coating may be removed. The latter removal method is
employed for plating after the formation of the
insulating coating, while the former removal method is
employed for plating directly after forming the glass
film.
Sb-based Intrudable_~leans and Plating Method
According to a preferred method for locating the
intrudable means on the finishing-annealed, grain-
oriented electxical steel sheet, one or more members
selected from the group consisting of Sb alone, Sb-Sn,
Sb-Zn, Sb-Pb, Sb-Bi, Sb-Sn-Zn, Sb~Co, Sb-Ni, other Sb
alloys, a mixture of Sb with one or more of Sn, Zn, Pb,
Bi, Co, Ni, A1 and the like, Sb oxide, Sb sulfate, Sb
borate, and other Sb compounds are incorporated into the
electrolyte solution, through which a steel sheet is
conveyed for electroplating. In a pre~erred electro~
plating method, the plating bath is a fluoride bath
or borofluoride bath which contains fluoric acid,
borofluoric acid, boric acid, and further selectively
~o contains sodium sulfate, salt (NaCl), ammonium chloride,
and caustic soda. A preferred building up amount is
1 g/m or more.
By means of plating with the fluoride bath or
borofluoride bath, a distinctly crystalline electro-
deposition is obtained at a high current efficiency, thedensity of which current, as shown in E'ig. ~, ranges
from a low to a high value. The electrolyte solution
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used in the electroplating solution is a borofluoride
bath which consists of borofluoric acid, and boric acid~
and Sb.
The 0.23 m thick and 914 mm wide grain-oriented
electrical steel sheet is subjected to removal of a glass
film and an insulating coating with a space distance of
5 mm and width of 0.2 mm. The samples obtained from the
steel sheet are then conveyed through the electrolyte
solution, while varying the current density. The
relationship between the apparent current density and
cathode current efficiency is shown in Fig. 4. For
comparison purposes, the electrolyte solution containing
a complex citrate is used for the electroplating.
As is apparent from Fig. 4, the precipitation
efficiency of the intrudable means is high, and the
stability of the precipitation is high, at a high
current density.
Effects similar to this are attained by using a
~luoride bath for the electroplating.
The borofluoride bath and fluoride bath also can be
used for electroplating Sn, Zn, Fe, Ni, Cr, Mn, Mo, Co
and their alloys. The boro~luoride bath contains
borofluoric acid, boric acid, and in addition, one or
more of the conductive salts.
The borofluoride bath and fluoride bath are
advantageous over other baths, such as the sulfate-,
chloride-, and organic salt-baths, in the points as
e~plained with reference -to Fig. 4. The former baths
can therefore attain a low watt loss at a low metal-
deposition amount as compared with the latter baths,
possibly because for the following reasons. ~enerally
speaking, when the glass film and the like of a grain-
oriented electrical steel sheet is subjected to the
removal by laser-irradiating, grinding, machining, shot-
blasting, and the like, part of the glass film and thelike are usually left on the steel sheet. The unremoved
film occasionally impedes during plating of an intruda~le
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means, the forcing of the intrudable means satisfactorily
into the steel sheet. Hydrofluoric acid (HF) as a
component of the fluoride bath etches vigorously the
steel base and slightly dissolves the glass film and
oxide film. Borofluoric acid (HBF4) as a component of
the borofluoride bath is believed to decompose in the
bath and partially generates the hydrofluoric acid ~HF)
according to the ~ollowing ~ormula.
HBF4 + 3H2O ~ ~HF ~ H3BO3
In the fluoride bath and boro~luoride bath, the
general nature of hydrofluoric acid can be advantageously
used for dissolving the surface coating which partially
remains due to a failure of complete removal by the laser
irradiation and the like, and also for etching the steel
base. The metal precipitated in the electroplating
process can be firmly deposited on the steel sheet and
can be brought into direct contact with the steel base
via a broad contact area. ~n improved watt loss can
therefore be attained at a small deposition amount of
metal.
Typical watt loss values W13/50 and W17/50 and
magnetic flux density attained by the present invention
are shown in the following tabl~.
7 ~ L~a
~ 18 -
~ Table 1
Magnetic Sheet Thickness (mm)
Properties 0.18 0.20 0.23 0.27 0.30
W13/50 (W/kg) 0.33 0.37 0.40 0.45 0.51
material W17/50 (W/kg) 0.64 0.67 0.69 0.80 0.87
Blo (T) l.91 1.92 1.93 1.94 1.94
Conven- Wl3/50 (W/kg) 0.40 0.45 0.47 0.52 0.61
tlonal
Material W17/50 (W/kg) 0.80 0.84 0.88 0.94 0.98
plating) Blo (T) 1.92 1.92 1.94 1.94 1.95
The relationships between the W17/50 and ~he
sheet thickness are shown in Fig. 5, in which the solid
and chain lines indicate the Sb plated material and
conventional materials~ respectively, of Table 1. Note
that the grain-oriented electrical steel sheet having
Wl7/50 dependent upon sheet thickness essentially
coincident with ''INVENTIONI' is considerably improved
over the conventional material.
In the case of the borofluoride bath and fluoride
bath, the building up amount is also important as
described hereinabove. A preferred building up amount
is l g/m2 or more.
It is another outstanding feature of the boro-
fluoride bath and fluoride bath that the intruder is
effectively formed in an extremely short period of time,
namely a-t a high productivity, and further, the surface
appearance of the steel sheets is excellent.
The heat treatment can be carried out, if necessary,
to increase the intrusion depth or to further ~orce the
intrudahle means into the steel sheet. The hea~ treat-
ment can be carried out at a temperature of from 500
-- 19 --
to 1200~C~ either by continuous annealing or box
annealing.
Zn is another preferred intrudable means. After
the Zn plating, metal having a vapor pressure lower than
that of Zn is preferably plated on the Zn, and sub-
sequently, the plating is preferably carried out in an
electrolyte solution containing one or more of Ni, Co,
Cr, Cu, and their alloys.
In a case of using the citric acid bath, such an
efficient plating as in the case of using the boro-
fluoride bath can be attained by preliminarily light
pickling prior to the plating.
Heat Treatment Method
During the heat treatment at a temperature of
from 500 to 1200C, a reaction between the agent and
steel body or surface coating of a grain-oriented
electrical steel sheet is advanced. This reaction is
activated by the strain in the temperature-elevating
stage or holding stage of the heat treatment. The
intruders are formed so that they are forced with a
space therebetween, into the steel body and are
structurally distinguished from the secondarily
recrystallized structure having Goss orientation or are
distinguished from the composition of the steel body.
The heat treatment is carried out in a neutral atmos-
phere or a reducing atmosphere containing H2. The
intruder can be an aggregate of the spot-form materials.
As described above, the temperature-elevating rate
and holding temperature are preferably determined
depending upon the kind of intrudable means. This is
because, during t.he intruding procedure, the intrusion
depth and amount are inEluenced by thermal and diffusion
conditions. The intrusion depth and amount appears to
be influenced by whether or not the film thermally
firmly adheres to the steel sheet prior to initiation of
the intrusion. Since the effect of improving the watt
105s characteristics becomes generally great with an
7~
- 20 -
increase in the depth of an intruder measured from the
steel base surface of a grain-oriented electrical steel
sheet, the above described influences should be desirably
used for forming deep intruders. When the temperature-
elevating rate is too slow, the amount of intruderformed becomes small and the total heat treatment-time
becomes long. On the other hand, when the tempera-
ture-elevating rate is too high, there is a danger,
especially for the intrudable means having a low meltlng
temperature-point, that the intrudable means are lost
due to vaporization or the like before completion of a
satisfactory reaction with the surface coating and steel
base of a grain-oriented electrical steel sheet. When
the holding temperature is too low, the reaction of the
intrudable means becomes unsatisfactory. On the other
hand, if the holding temperature is too high, the
electrical insulating propert~ o~ the insulating coating
is impaired, the heat energy is consumed undesirably,
and a failure in the shape of the steel sheets occurs.
Generally, the holding temperature should be in the
range of from 500 to 1200C. The kinds of intrudable
means should be appxopriately selected depending upon
the temperature elevating rate and holding temperature
selected within these ranges.
Film Recoating Method
After the formation of the intrudable means, the
solution for the insulating coating can be applied on
the grain-oriented electrical steel sheet and baked at a
temperature of, preferably 350C or more. The solution
for the insulating coatiny, for example, can contain at
least one member selected from the group consisting of
phosphoric acid, phosphate, chromic acid, chromate,
bichromate, and colloidal silica.
The plated intrudable means do not peel off the steel
sheets during handling due to coil slip and do not
~aporize during the annealing, since the plated in-
trudable means are covered with the insulating coatingO
The formation of in~ruders can therefore be further
stabilized. In addition, the corrosion resistance and
insulating property of portions of the steel sheets
where intruders are formed are improved by the insulating
coating.
Depth of Intruder
Samples having various intruder depths were prepared
by varying the temperature and time of the heat treat-
ment. The composition of the slabs, from which the
0.225 mm thick grain-oriented electrical steel sheets
were manufactured by well known steps starting at the
slab heating and ending at the finishing annealing, was
as follows.
C: 0.05 ~ 0.08~, Si: 2.95 ~ 3.33~, ~In: 0,0
0.12~, Al: 0.010 ~ 0.050~, S: 0.02 ~ 0.03%, N:
0.0060 ~ 0.0090~.
The depth of grains or clusters forced into the
steel sheet was measured. The watt loss W17/50 after
the finishing annealing (W117/50) and the watt
loss W17/50 after the formation of the intruder
(W 17/50~ were measured and the watt loss-improving
percentage (~W) was calculated as follows.
~W = {(W117~50 ~ W 17/50)/W 17/50}
The influence of the depth of the intruders measured
from the surface of steel body of grain~oriented elec-
trical steel sheets upon the watt-loss improving per-
centage (~W) was investigated. The results are shown in
Fig. 6. As is apparent from Fig~ 6, an appreciable
improvement in terms of ~W is obtained at an intruder
depth of 2 ~m or more, and this improvement is enhanced
with an increase in the intruder depth. The improvement
in terms oE ~W saturates at an intruder depth of approxi-
mately 100 ~m. Such a relationship as described above
can be found not only in the steel composition of the
above samples but also in the steel compositions con-
taining one or more of Cu, Sn, Sb, Mo, Cr, Ni and the
like. ~ preferred depth of the intxuders according to
- 22 -
the present inven-tion is 2 ~m or more. The maximum
lntruder dep~h is not specifically limited but is
determined by taking into consideration the thickness of
the steel sheets and the like. Although the intruder
depth should be specified as described above, the
distances therebetween need not be specified at all, and
may be, for example, from approximately 1 to 30 mm. When
the space distance between the intruders is de-termined
narrowly, the grains, clusters and the like of the
intruders appear virtually continuous.
The present inventi~n is now explained with refe-
rence to the examples.
Example 1
Silicon steel slabs, which consisted of 0.077
o C, 3.28% of Si, 0.076% of Mn, 0.030% of Al, 0.024~
of S, 0.15~ of Cu, 0.15% of Sn and iron essentially in
balance, were subjected to well known steps for producing
a grain-oriented electrical steel sheet of hot-rolling,
annealing, and cold-rolling. The 0.250 mm thick cold-
rolled steel sheets were obtained. Subsequently, thewell known steps of decarburization annealing, appli-
cation of annealing separator and finishing annealing
were carried out.
The finishing annealed coils were subjected to
application of an insulating coating and heat-flattening.
Samples of 10 cm in width and 50 cm in length were cut
from these coils and irradiated with laser to Eorm minor
flaws which extended perpendicular to the rolling
direction and were spaced from one another by a distance
of 10 mm, as seen in the rolling direction. These
samples are denoted as "before treatment".
Subsequent to the laser irradiation, the agent A
(ZnO: 10 g -~ Sn: 5 g~, the agent B (Sb2O3: 10 g
+ H3BO3: 10 g), the agent C (Sb: 10 g ~ SrSO4: 20 g),
and the agent D (Cu: 10 g + Na2B4O7: 20 g) were
respectively applied on the samples in an amount of
0.5 g/m2 in terms of weight after application and
7~i~
23 -
drying. The samples were then laminated one upon
another and dried at a furnace temperature of 400C.
The samples were then heat treated at 800C for 30
minutes. The samples subjected to this heat treatment
are denoted as "after treatment". The samples were
further subjected to a stress-relief annealing at 800C
for 2 hours. These samples are denoted as "after
stress-relief annealing". The magnetic properties of
the samples before and after treatment and after stress
relief annealing were measured. The measurement results
are shown in Table 2.
Table 2
Ma~netic Properties
Before trea~t After treatment After stress-
relief annealing
(After laser- (800C x
Agent irradiation 30 minutes,b~d~q) (800C x 2 hours)
BloW17~50 BloW17~50 Blo W17~50
(T~(W/kg) (T)lW/kg) IT) (W/kg)
_ . _ . , .
A 1.925 0.79 1.9260.80 1.926 0.80
B 1.928 0.76 1.9290.77 1.930 0.77
C 1.923 0.75 1.9230.75 1.923 0.75
D 1.931 0.78 1.9320.78 1.933 0.79
E (non-appli- 1.9280.76 - - 1.9350.89
cation of
agent.
ca~xrative
example)
_
Example 2
Silicon steel slabs, which consisted oE 0.077% of
C, 3.30% of Si, 0.076% of Mn, 0.028% of Al, 0.024% of S,
0.16% of Cu, 0.12% of Sn and iron essen-tially in balance,
J'~
- 24 -
were subjected to well known steps for producing a
grain-oriented electrical steel sheet of hot-rolling,
annealing, and cold rolling. The 0.225 mm thick
cold-rolled steel sheets were obtained. Subsequently,
the well known steps of decarburization annealing, appli-
cation of annealing separator and finishing annealing
were carried out. The finishing annealed coils were
subjected to application of an insulating coatin~ and
heat-flattening. Samples of 10 cm in width and 50 cm in
length were cut from these coils and then marked-off to
impart the strain which extended perpendicular to the
rolling direction and were spaced from one another by a
distance of 10 mm. These samples are denoted as "before
treatmentl-.
Subsequent to the mar~ing-off, the Sb2O3 powder
in the powder form, as the agent, was rendered to a
slurry containing the powder in an amount of 10 g/H2O-50
cc. The slurry was applied on the samples in an amount
of 0.6 g/m2 in terms of weight after application and
drying. After drying the heat treatment was carried out
while varying the conditions in a temperature ranging
from 800 to 900C and a time ranging from 5 to 120
minutes so as to vary the intruding depth of the
intruder. The samples subjected to this heat treatment
are denoted as "after treatment". The samples were
further subjected to a stress-relief annealing at 800C
for 2 hours. These samples are denoted as "after
stress-relief annealing". The magnetic properties of
the samples before and after treatment and after stress
relief annealing were measured. The measurement results
are shown in Table 3.
- 25 -
Table 3
Magnetic Properties
Before treat~ent After stress-
Depth of In- (After laser- After treat~ent relief Annealing
truder inadiation)
(~)
BloW17~50 BloW17~50 Blo W17~50
(T)(W/kg) (T)(W/ky) (T) (W/kg)
2 3 3 1.930 0.78 1.923 0.7~ 1.920 0.76
5 ~ 7 1.928 0.76 1.918 0.75 1.913 0.73
10 ~ 12 1.933 0.74 1.915 0.72 1.908 0.69
30 ~ 34 1.930 0.77 1.905 0.75 1.899 0.69
Example 3
Silicon steel slabs, which consisted of 0.077
of C, 3.30~ of Si, 0.076% of Mn, 0.032% of Al, 0.024~
of S, 0.16% of Cu, 0.18% of Sn and iron essentially in
balance, were subjected to well known steps for producing
a grain-oriented electrical steel sheet of hot-rolling,
annealing, and cold-rolling. The 0~225 mm thick cold-
rolled steel sheets were obtained. Subsequently, thewell known steps of decarburization annealing, appli-
cation of annealing separator and finishing annealing
were carried out.
The finishing annealed coils were subjected to
application of an insulating coating and heat-flattening.
Samples of 10 cm in width and 50 cm in length were cut
from these coils and irradiated with laser to Eorm minor
strain which extended perpendicular to the rolliny
direction and were spaced from one another by a distance
of 10 ~n, as seen in the rolling direction. These
samples are denoted as "before treatment".
Subsequent to the laser irradiation, the agent A
- 26 -
(ZnO: 10 g + Sn: 5 g), the agent B (Sb2O3: 10 g +
H3so3: 10 g), the agent C (Sb: 10 g + SrSO4: 20 g),
and the agent D (Cu: 10 g + Na2B4O7: 20 g) were
respectively applied on the entire surface of samples in
an amount of 0.5 g/m in terms of weight after appli-
cation and drying. The samples were dried at a furnace
temperature of 400C, laminated upon one another, and
heat-treated at 800C for 30 minutes. The samples
subjected to this heat treatment are denoted as "after
treatment". The samples were further subjected to a
stress-relief annealing at 800C for 2 hours. These
samples are denoted as "after stress-relief annealing".
The magnetic properties of the samples before and after
treatment and after stress relief annealing were
measured. The measurement resulted are shown in Table 4.
Table 4
Magnetic ProFerties
Eefore treatment After treatment After stre~s-
relief annealing
(After laser (800C x
Agent irradia-tion 30 minutes, ~ing) (800C x 2 hours)
BloW17~50 BloW17~50 BloW17~50
(T)(W/kg) (T)(W/kg) (T)(W/kg)
_
A 1.9400.77 1.9370.73 1.9210.73
B 1.9350.78 1.9250.80 1.9200.69
C 1.9300.77 1.9200.76 1.9050.72
D 1.9350.75 1.9350.71 1.9330~72
E (non-aFpli- 1.9320.78 ~ _ 1.9320.91
cation of
agent.
ccmparative
e~le)
-
7~
- 27 -
Example 4
Silicon steel slabs, which consisted of 0.077~ of
C, 3.15% of Si, 0.076~ of Mn, 0.030% of Al, 0.024~ of S~
0.007~ of N and iron essentially in balance, were
subjected to well known steps for producing a graln
oriented electrical steel sheet of hot-rolling,
annealing, and cold-rolling. The 0.225 mm thick cold-
rolled steel sheets were obtained. Subsequently, the
well known steps of decarburization annealing, appli-
cation oE annealing separator and finishing annealingwere carried out. Samples of 10 cm in width and 50 cm
in length were cut from these coils and stress-relief
annealed. These samples are denoted as "before treat-
ment". Subsequents to the stress-relief annealing, the
agent A IZnO: 10 g + Sn: 5 g), the agent B (Sb2O3:
10 g + H3BO3: 10 g), the agent C (Sb: 10 g + SrSO4:
20 g), and the agent D (Cu: 10 g + Na2B4O7: 20 g) were
respectively applied on the surface, i.e., the ~lass
film, o~ samples in an amount of 0 g g/m2 in terms of
weight after application and drying. These samples were
irradiated with laser in a direction extending virtually
perpendicular to the rolling direction and with distance
spaces of 12 mm, to impart to the samples minute strain.
The samples were heat-treated at 800C for 30 minutes.
The samples subjec-ted to this heat treatment are denoted
as "after treatment". The samples were further subjected
to a stress-relief annealing at 800C for ~ hours. These
samples are denoted as "after stress-relief annealing".
The magnetic properties of the samples before and after
treatment and after stress relief annealing were mea-
sured. The measurement results are shown in Table 5.
3~
- 28 -
Table 5
Magnetic Prop~Xies
Before treatment After treatment After stress-
relief Annealing
(After laser- (800C x
Agent ~ adiation 30 minutes, baking) (800C x 2 hours)
__
BloW17~50BloW17~50 BloW17~50
(T)(W/kg)(T)(W/ky) (T)(W/kg)
A 1.931 0.771.930 0.73 1.931 0.73
B 1.935 0.741.895 0.76 1.880 0.70
C 1.928 0.7~1.903 0.78 1.870 0.71
D 1.925 0.851.925 0.81 1.925 0.81
E (non-appli-1.930 0.80 - - 1.930 0.91
cation of
agent.
o~Lative
example)
Example 5
Silicon steel slabs, which consisted of 0~080%
of C, 3.20~ of Si, 0.068% of Mn, 0.032% of Al, 0.024~
of S, 0.10% of Cu, 0.08% of Sn and iron essentially in
balance, were subjected to well known steps for pro-
ducing a grain-oriented electrical steel sheet of
hot-rolling, annealing, and cold rolling. The 0.250 mm
thick cold-rolled steel sheets were obtained. Sub-
sequently, the well known steps of decarburizationannealing, application of annealing separator mainly
composed of MgO and finishing annealing were carried
out. Samples obtained from the steel sheets, which were
subjected to the finishing annealing, are denoted as
"before treatment".
The steel sheets were irradiated with CO2 laser
in a direction virtually perpendicular to the rolling
- 29 -
direction and with a distance space of 5 mm, so as to
remove the glass film and oxide film. The steel sheets
were then subjected to an electroplating using elec-
trolyte solutions Nos. 1 - 5 containing, as plating
metals, Sb (No. 1), Mn (No. 2), Cr (No. 3), Ni (No. 4),
and none (No. 5), so as to deposit the intrudable means
(plating me-tal) in a building up amount of 1 g/m2.
The samples obtained from the so treated steel sheets
are denoted as "after treatment". The steel sheets were
further subjected to a stress-relief annealing at 800C
for 2 hours. The samples obtained Erom the so annealed
steel sheets are denoted as "after stress-relief an-
nealing". The magnetic properties of the samples before
and after treatment and after stress relief annealing
were measured. The measurement results are shown in
Table 6.
Table 6
Magnetic Prop~rties
After stress-
Before treatment After treatment relief Annealing
Electrolyte (800C x 2 hours)
Solution Nos.
BloW17~50 BloW17~50 BloW17~50
tT)IW/kg) (T)(W/kg) (T)(W/kg)
1 1.938 0.821.937 0.801.940 0.78
2 1.940 0.841.938 0.811.943 0.74
3 1.935 0.821~936 0.791.940 0.75
4 1.948 0.811.947 0.801.949 0.76
5 (non-appli- 1.940 0.83 - - 1.945 0.97
cation of
agent,
ccmparative
example)
_
-
7~
- 30 -
Example 6
Silicon steel slabs, which consisted of 0.078%
of C, 3.25% of Si, 0.068% of Mn, 0.026% of A1, 0.024%
of S, 0.15% of Cu, 0.08% of Sn and iron essentially in
balance, were subjected to well known steps for pro-
ducing a grain-oriented electrical steel sheet of
hot-rolling, annealing, and cold rolling. The 0.225 mm
thick cold-rolled steel sheets were obtained. Sub-
sequently, the well known steps of decarburi2ation
annealing, application of annealing separator mainly
composed of MgO and finishing annealing were carried
out. The samples obtained from steel sheets, which were
subjected to the finishing annealing are denoted as
"before treatment".
The steel sheets were irradiated with CO2 laser
in a direction virtually perpendicular to the rolling
direction and with a distance space of 10 mm~ as seen in
the rolling direction, so as to remove the glass film
and oxide film. The steel sheets were then subjected to
an electric plating using the electrolyte solution
~os. 1 - 5 containing Sb (No. 1), Zn (No. 2), Cr (No. 3),
Sn (No. ~), and none (No. 5, comparative example), so as
to deposit the intrudable means (plating metal) in a
building up amount of 1 g/m2. The solution containing
for insulating coating, containing aluminum phosphate,
phosphoric acid, chromic acid anhydride, chromate, and
colloidal silica was then applied on the surface of
steel sheets and baked at 850C to form an insulating
coating. The samples obtained from the steel sheets
with insulative coating are denoted as "after treat-
ment".
The steel sheets were further subjected to a
stress-relief annealing at 800C for 2 hours. These
samples are denoted as "after stress-relief annealing".
The magnetic properties of the samples before and after
treatment and after stress relief annealing were
measured. The measurement results are shown in Table 7.
7~j;L~
~ 31 -
Table 7
Magnetic Properties
__ _
After Stress-
Before ~eatment After trea~ent relief Annealing
Electrolyte ~800C x 2 hours)
Solution Nos. ~
BloW17~50 Blo W17~50 Blo W17~50
(T)(W/kg) (T) (W/kg) (T) (W/kg)
l 1.943 0.971.939 0.90 1.93~ 0.87
2 1.942 0.981.940 0.92 1.938 0.92
3 1.945 0.961.940 0.91 1.940 0.90
4 1.950 0.961.943 0.90 1.946 0.89
5 Inon-appli- 1.946 0.98 _ _ 1.947 0.98
cation of
agent.
co~r2tive
example)
Example 7
Silicon steel slabs, which consisted of 0.080%
of C, 3.30% of 5i, 0.070% of Mn, 0.028% of Al, 0.025~
of S, 0.0080~ of N and iron essentially in balance were
subjected to well known steps for producing a grain-
oriented electrical steel sheet of hot-rolling,
annealing, and cold-rolling. The 0.225 mm thick cold-
rolled steel sheets were obtained. Subsequently, the
well known steps of decarhurization annealing, appli-
cation of annealing separator mainly composed of MgO and
finishing annealing were carried out. Solution for
forming insulating coating was then applied on the
finishing-annealed steel sheets and baked. During the
baking, the heat-flattening annealing was also per-
formed. The samples obtained from the steel sheets withthe insulating coating, are denoted as "before treat-
ment". These steel sheets were irradiated with CO2
- 32 --
laser in a direction virtually perpendicular to the
rolling direction and with a space distanGe of 5 mm, so
as to remove the glass film and the insulating coating.
The steel sheets were then subjected to an electric
plating using the electrolyte solutions given in Table 8
and containing the intrudable means. The building up
amount of the electric plating was from 0.05 -to 10 g/m2.
The solution for insulating coating aluminum phosphate,
chromic oxide anhydride, and colloidal silica was then
applied on the steel sheets and baked at 350C to form
the insulating coating. The samples obtained from the
steel sheets wi-th an insulative coating are denoted as
"after treatment". The steel sheets were further
subjected to a stress- relief annealing at 800C for
2 hours. The samples obtained from these steel sheets
are denoted as "after stress-relief annealing". The
magnetic properties of the samples before and after
treatment and after stress relie~ annealing were mea-
sured. The measurement results are shown in Table 9.
~lr3~7~
- 33
Table 8
Electrolyte Buildiny up
Solu-tionKind of Plated Metal n
No. ~ /m )
1 - (1) Sb 0.05
(2) " 1.00
(3) " 10.00
2 - (1) Mo 0.05
(2) " 1.00
(3) " 10.00
3 - (1) Cu O.05
(2) i, 1.00
(3~ " 10.00
4 - (1) Sb + Zn 0.05
(2) " 1.00
(3) " 10.00
Non application of agent
IccmParative example)
-- 34 --
I ~ u~ ~ co ~ o ~ ~r o
~n ~1 5: ~.Y I` r~ 1
u~ ~ r-~ .
3 o o o o o o o o o o o o o
U~ X
O In ~ U~0~ 0 U~ CO LO ~D ~ n o r-
~1 o o
~! a) a~ ~ E~ a~
~n
r~ O ~ ~ r~ ~ O In o~
_ ~ ~
:~1 3 o o o o o o o o o o o o
~:4 ~ ~
U ~ ~
~ 1 S~ (~ l ~ O CS~
o ~ ~ t~ ~~r ~ t~) ~ eJI ~r ~')
c~
,, ~ ~ ~
a~
o ~ c;~ ~ ~co o ~ ~ o a~ ~ cc ~ o
E~ ~ r ~ co a~
.~ ~ 3 o o o o o o o o o o O o o
O
~ a
:q ~ ~D CO ~ ~ O ~ O U~ r o a~ co
o ~ er r~ In U~ Lt~ ~ ~r ~r ~ ~r Ln ~ ~r
~ ~ ~ ~ CJ cr~
a
a)
~ O ~
p ~ ~ ~
~ ~ o ~
u~
6~
35 -
Example 8
Silicon steel slabs, which consisted of 0.075%
of C, 3.22% of Si, 0.068% of Mn, 0.030% of A1, 0.02~%
of S, 0.08% of Cu, 0.10% of Sn and iron essentially in
balance, were subjected to well known steps for producing
a grain-oriented electrical steel sheet of hot-rolling,
annealing, and cold rolling. The 0.225 rnm thick cold-
rolled steel sheets were obtained. Subsequently, the
well known steps of decarburization annealing, applica-
tion of annealing separator mainly composed of MgO, and
finishing annealing were carried out.
A solution for forming an insulating coating was
then applied on the finishing-annealed steel sheets and
baked. During the baking, the heat-flattening annealing
was also performed. The samples obtained from the steel
sheets with the insulating coating, aré denoted as "heat
treatment". These stee~ sheets were irradiated with
C2 laser in a direction virtuall~ perpendicular to
the rolling direction and with a space distance of 5 mm.
The steel sheets were then sub~ected to an electroplating
using the electrolyte solutions Nos. 1 - 6 containing Sb
and Zn (No. 1), Sb and Zn (No. 2), Sb and Sn (No. 3), Sb
and SbO (No. ~), Sb (No. 5), and none (No. 6,
comparative example). The building up amounts of
25 electroplating were 0.1, 1, and 10 g/m2. The samples
obtained from the steel sheets plated as above are
denoted as "after treatment". The steel sheets were
further subjected to a stress-relief annealing at 800C
for ~ hours. These samples are denoted as "after
stress-xelief annealing". The magnetic properties of
the samples before and af-ter treatment and after stress
relief annealing were measured. The measurement results
are shown in Table 10.
~ 36 --
u~,~ I oL~o ~
~a x ~ 3 o o o o o o o o o o o o o o o o
~2- ~ ,,~ o~ o
o _ a~ o ~D co co o o ~ co O
~ ~ ~ 3~ 3 o o o o o o o o o o o o o o o
.~ ~ m~ E~ ~ 9 o o ~ ~ ~ ~ o
-~1 ~ _ ,, ,,
~1 o~ ~ o~
g~l 3 o o o o ~ o o o o o o o o o o o
O ~ ~ ~ O ~ O ~ n Lr) Ch O
E~ ~ ~ ~ c~
_
IQ~ ~ ~oo ~0~ ~ ~ ~ ~b~
~ d O ~i u~ o ,i u~ o ~i ui o ~i ~ o ~i u~ ~ o ~
. ~4
O ;~,~ g , ,î ~1 ~ ~1 ~ ~ ,~ ~ ~ ~1 ~ ~ ,~ ~ ~ g ~d ~
~1 ~ '~ Z
7~;~
- 37 -
Example 9
Silicon steel slabs, which consisted of 0.080%
of C, 3.15% of Si, 0.075% of Mn, 0.029% of Al, 0.024%
of S, 0.10% of Cu, 0.08~ of Sn and iron essentially in
balance, were subjected to well known steps for producing
a grain-oriented electrical steel sheet of hot-rolling,
annealing, and cold rolling~ The 0.225 mm thick cold-
rolled steel sheets were obtained. Subsequently, the
well known steps of decarburization annealing mainly
composed of MgO, application of annealing separator and
finishing annealing were carried out.
The samples obtained from the steel sheets having
an insulating coating are denoted as "before t~eatment".
These steel sheets were irradiated with laser in a
direction virtually perpendicular to the rolling direc-
tion and with a space distance of 5 mm, so as to remove
the glass film, insulating coating and oxide film. The
steel sheets were then subjected to an electric plating
using the electrolyte solutions Nos. 1 - 5 containing,
as plating metals, Sb ~No. 1 - borofluoride bath),
Mn ~No. 2 - borofluoride bath), Sn (No. 3 - fluoride
bath); Ni ~No. 4 - fluoride bath), and none (No. 5,
comparative example). The samples obtained from the
steel sheets plated as above are denoted by "after
treatment'l. The steel sheets were further subjected to
a stress-relief annealing at 800C for 2 hours. The
samples obtained from these steel sheets are denoted as
"after stress-relief annealing". The magnetic properties
of the samples before and after treatment and after
stress relief annealing were measured. The measurement
results are shown in Table 11.
_ 38 -
Table 11
_
Magnetic Properties
After Stress-
ElectrolYte sefore treatment After treatment relief An~ealing
Solution Nos.
BloW17~50 BloW17~50 Blo W17~50
(T)(W/kg) (T)(W/kg) (T) (W/kg)
1 1.9380.75 1.9370.74 1.940 0.67
2 1.9400.74 1.9380.73 1.943 0.70
3 1.9350.77 1.9360.75 1.940 0.71
4 1.9480.75 1~9470.75 1.9490 r 72
5 (non-appli- 1.9400.76 - - 1.945 0.97
cation of
agent/
ccmparati~e
example)
_ _
Example 10
Silicon steel slabs, which consisted of 0.078
of C, 3.27% of Si, 0.073% of Mn, 0.029~ of Al, 0.024~
of S, 0.16~ of Cu, 0.008% of Sn and iron essentially in
balance, were subjected to well known steps for producing
a grain-oriented electrical steel sheet oE hot-rolling,
annealing, and cold rolling~ The 0.225 mm thick cold-
rolled steel sheets wexe obtained. Subsequently, the
well known steps of decarburization annealing, applica-
tion of annealing separator and finishing annealing were
carried out. Samples 10 cm in width and 50 cm in length
were cut from the finishing annealed coils and stress--
relief annealed at 800C for 4 hours. These samples,
which are free of stress and coil-set, are denoted as
"before treatment". Each of agents A ~AlPO~), B (Sb pow~
der), C (Sb powder ~ Al powder (1 : 1~) and D (MnSO4)
in an amount of 10 g per 50 ml o H2O, was applied on
the steel sheets and dried to foxm as films. The Eilms
7~i~
- 39 -
were irradiated with an electron beam with a distance
space of approximately 20 mm to impart heat to the films
at 860C for 20 hours. The samples subjected to this
heat treatment are denoted as "after treatment". The
samples were further subjected to a stress-relief
annealing at 800C for 2 hours. These samples are
denoted as "after stress-relief annealing". The magnetic
properties of the samples before and after treatment and
after stress relief annealing were measured. The
measurement results are shown in Table 12.
Table 12
_
Magnetic Properties
After Stress-
Before treatment After treatment relief Annealing
Agent
BloW17~50 BloW17~50 BloW17~50
(T)(W/kg) ~T)~W/kg) (T)(W/kg)
__ . __ _ _
A 1.934 0.891.930 0.831.930 0.82
B 1.945 0.871.943 0.751.885 0.70
C 1.937 0.911.937 0.771.890 0.75
D 1.920 0.921.936 0.841.930 0.85
E ~non-appli- 1.935 0.89 - - 1.935 0.88
cation on of
agent,
comparative
example)
_ _
