TECHNICAL FIELD
[0001] The present invention relates to an
electrical steel sheet.
BACKGROUND ART
[0002] An electrical steel sheet is used or
transported under a corrosive environment. For
example,' the electrical steel sheet is used in hot
and humid regions or transported by sea. During the
transportation by sea, a large amount of salt comes
flying. Therefore, the electrical steel sheet is
required to have rust resistance. To obtain the rust
resistance, an insulating film is formed on the
surface of the electrical steel sheet. An example of
the insulating film is a chromite-based insulating
film. Though the chromite-based insulating film
exhibits good rust resistance, hexavalent chromium
used as the raw material of the chromite-based
insulating film is carcinogenic. Therefore, it is
required to develop an insulating film that can be
formed without using hexavalent chromium as a raw
material.
[0003] Examples of the insulating film that can be
formed without using hexavalent chromium as a raw
material include a phosphate-based insulating film, a
silica-based insulating film, and a zirconium-based
insulating film (PATENT LITERATURES 1 to 12).
However, with these insulating films, the rust
resistance at the same level as that of the chromitebased
insulating film cannot be obtained. Though the
rust resistance is improved by thickening the
insulating film, the weldability and the caulking
property decrease more with a thicker insulating
film.
CITATION LIST
PATENT" LITERATURE
[0004] Patent Literature 1: Japanese Examined Patent
Application Publication No. 53-028 375
Patent Literature 2: Japanese Laid-open Patent
Publication No.. 05-078855
Patent Literature 3: Japanese Laid-open Patent
Publication No. 06-330338
Patent Literature 4: Japanese Laid-open Patent
Publication No. 11-131250
Patent Literature 5: Japanese Laid-open Patent
Publication No. 11-152579
Patent Literature 6: Japanese Laid-open Patent
Publication No. 2001-107261
Patent Literature 7: Japanese Laid-open Patent
Publication No. 2002-047576
Patent Literature 8: International Publication
Pamphlet No. 2012/057168
Patent Literature 9: Japanese Laid-open Patent
Publication No. 2002-47576
Patent Literature 10: Japanese Laid-open Patent
Publication No. 2008-303411
Patent Literature 11: Japanese Laid-open Patent
Publication No. 2002-249881
Patent Literature 12: Japanese Laid-open Patent
Publication No. 2002-317277
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0005] An object of the present invention is to
provide an electrical steel sheet capable of
obtaining good rust resistance without using
hexavalent chromium as a raw material of an
insulating film.
SOLUTION TO PROBLEM
[0006] The present inventors earnestly studied to
solve the above problem. As a result, it has been
revealed that good rust resistance is obtained when
the phosphate exhibiting a specific peak in a solid
31P-NMR spectrum is contained in an insulating film.
It has also been revealed that use of a coating
solution containing a chelating agent is important
for forming the insulating film.
[0007] The present inventors have reached the
aspects of the present invention described below as a
result of further earnest studies based on the above
findings.
[0008] (1)
An electrical steel sheet, including:
a base material of electrical steel; and
an insulating film formed on a surface of the
base material,
wherein the insulating film contains a phosphates
of one or more selected from the group consisting of
Al, Zn, Mg and Ca, and
wherein the phosphate exhibits a specific peak
having a top within a range of -26 ppm to -16 ppm in
a solid 31P-NMR spectrum, and a proportion of an
integrated intensity of the specific peak relative to
an integrated intensity of all peaks in the solid 31p-
NMR spectrum is 30% or more.
[0009] (2)
The electrical steel sheet according to (1),
wherein a half width of the specific peak is 20 ppm
or more.
[0010] (3)
The electrical steel sheet according to (1) or
(2), wherein the insulating film contains an organic
resin.
ADVANTAGEOUS EFFECTS OF INVENTION
[0011] According to the present invention, good rust
resistance can be obtained without using hexavalent
chromium as the raw material of the insulating film
because the phosphate exhibiting a specific peak in a
solid 31P-NMR spectrum is contained in the insulating
film. This can avoid a decrease in weldability and
caulking property accompanying an increase in
thickness of the insulating film.
BRIEF DESCRIPTION OF DRAWINGS
[0012] [Fig. 1] Fig. 1 is a cross-sectional view
illustrating a structure of an electrical steel sheet
according to an embodiment of the present invention;
[Fig. 2] Fig. 2 is a view illustrating an
example of a measurement result of a solid 31P-NMR
spectrum;
[Fig. 3A] Fig. 3A is a view illustrating an
example of a test result of rust resistance when a
concentration of sodium chloride was 1.0 mass%;
[Fig. 3B] Fig. 3B is a view illustrating an
example of a test result of rust resistance when a
concentration of sodium chloride was 0.3 mass%;
[ Fig. 3C] Fxg. 3C is a view illustrating a~n
example of a test result of rust resistance when a
concentration of sodium chloride was 0.1 mass%;
[Fig. 3D] Fig. 3D is a view illustrating an
example of a test result of rust resistance when a
concentration of sodium chloride was 0.03 mass%;
[Fig. 3E] Fig. 3E is a view illustrating an
example of a test result of rust resistance when a
concentration of sodium chloride was 0.01 mass%;
[Fig. 4A] Fig. 4 A is a view illustrating an
example of a test result of rust resistance when an
insulating film was formed using a coating solution
not containing a chelating agent; and
[Fig. 4B] Fig. 4B is a view illustrating an
example of a test result of rust resistance when an
insulating film was formed using a coating solution
containing a chelating agent.
DESCRIPTION OF EMBODIMENTS
[0013] Hereinafter, an embodiment of the present
invention will be described in detail referring to
the accompanying drawings. Fig. 1 is a crosssectional
view illustrating a structure of an
electrical steel sheet according to the embodiment of
the present invention.
[0014] As illustrated in Fig. 1, an electrical steel
sheet 1 according to the embodiment of the present
invention includes a base material 2 of electrical
steel and an insulating film 3 formed on a surface of
the base material 2. The base material 2 includes a
composition suitable for a grain-oriented electrical
steel sheet or a non-oriented electrical steel sheet.
[0015] The insulating film 3 contains a phosphate of
one or more selected from the group consisting of Al,
Zn, Mg and Ca. The phosphate exhibits a specific
peak having a top within a range of -26 ppm to -16
ppm in a solid 31P-NMR spectrum, and the proportion of
the integrated intensity of the specific.peak
relative to the integrated intensity of all peaks in
the solid 31P-NMR spectrum (integrated intensity
ratio) is 30% or more. The half width of the
specific peak is preferably 2 0 ppm or more.
Hereinafter, M sometimes denotes Al, Zn, Mg or Ca or
any combination thereof.
[0016] The insulating film 3 exhibiting the above
specific peak is denser and has better rust
resistance than the insulating film included in a
conventional electrical steel sheet. Therefore,
according to the electrical steel sheet 1, good rust
resistance can be obtained without decreasing the
weldability and the caulking property without using
hexavalent chromium as the raw material of the
insulating film 3.
[0017] The solid 31P-NMR spectrum can be analyzed as
follows for instance. The solid 31P-NMR spectrum of
the insulating film containing phosphate reflects a
molecular structure around the P atom in the
insulating film as illustrated in F ig~ 2~, and the
position of the peak (chemical shift) and the half
width of the peak depend on the molecular structure.
Further, a plurality of components overlap to
constitute the spectrum in some cases. In peak
separation of the solid 31P-NMR spectrum, for example,
assuming that the solid 31P-NMR spectrum is made by
overlapping of Gauss functions, an optimization
calculation is performed so as to be able to
reproduce the solid 31P~NMR spectrum using the area
fraction, the peak position, and the half width of
the individual Gauss function as fitting parameters.
The integrated intensity ratio, the peak position,
and the half width of each component can be decided
from the result of the optimization calculation. In
the above manner, the integrated intensity ratio of
the specific peak can be obtained.
[0018] Next, a method of manufacturing the
electrical steel sheet 1 will be described. This
method includes applying a coating solution composed
of an M-containing polyvalent metal phosphate, a
chelating agent and water to the base material of the
electrical steel, and baking the coating solution.
Water with a total concentration of Ca ions and Mg
ions of 100 ppm or less is used as the water in the
coating solution. Examples of the polyvalent metal
phosphate include an aluminum monophosphate, a zinc
monophosphate, a magnesium monophosphate, and a
calcium monophosphate. Hereinafter, an aluminum
phosphate, a zinc phosphate, a magnesium phosphate,
and a calcium phosphate represent the aluminum
monophosphate, the zinc monophosphate, the magnesium
monophosphate, and the calcium monophosphate
respectively.
[0019] In baking the coating solution, the ends of
the phosphate are cross linked by the
dehydration/condensation reaction' to form an
insulating film. Examples of the. reaction formula of
the dehydration/condensation reaction include the
followings. The chelating agent is described as "HOR-
OH" and the metal is described as "M".
P-OH + HO~P -> P-O-P (Reaction formula 1)
P-OH + HO-P + HO-R-OH
-> P-O-R-O-P ( R e a c t i o n f o r m u l a 2)
P-OH + HO-P + HO-R-OH + M
-> p_o-M-0-R-0-P (Reaction formula 3)
P-OH + HO-P + HO-R-OH + 2M
-> p_o-M-0-R-0-M-0-P (Reaction formula 4)
[0020] On the other hand, when a coating solution
composed of the polyvalent metal phosphate and water
but not containing the chelating agent is used, the
reaction of Reaction formula 1 occurs but the
reactions of Reaction formula 2 to Reaction formula 4
do not occur. Therefore, in the case of using the
coating solution containing the chelating agent, much
more crosslinking points exist in the insulating film
and higher rust resistance "can" be obtained than in
the case of using the coating solution not containing
chelating agent. With more bonds of the chelating
agent, a larger number of crosslinking points exist
and higher rust resistance can be obtained.
[0021] As the chelating agent, for example, an
oxycarbonic acid-based, dicarboxylic acid-based or
phosphonic acid-based chelating agent is used.
Examples of the oxycarbonic acid-based chelating
agent include a malic acid, a glycolic acid and a
lactic acid. Examples of the dicarboxylic acid-based
chelating agent include an oxalic acid, a maIonic
acid and a succinic acid. Examples of the phosphonic
acid-based chelating agent include an
aminotrimethylene phosphonic acid, a
hydroxyethylidene monophosphonic acid, and a
hydroxyethylidene diphosphonic acid.
[0022] The amount of the chelating agent contained
in the coating solution is 1 mass% to 30 mass%
relative to the mass of the insulating film after
baking. Since the coating solution containing
phosphate is acidic, Fe elutes from the base material
into the coating solution while the drying of the
coating solution is not completed and the coating
solution is kept acidic. When Fe elutes excessively
to exceed the reaction limit of the chelating agent,
an iron phosphate and an iron hydroxide are
generated, so that the insulating film exhibiting the
specific peak cannot be" obtained. This phenomenon is
remarkable when the amount of the chelating agent is
less than 1 mass%. Accordingly, the amount of the
chelating agent is 1 mas s% or more relative to the
mass of the insulating film after baking. On the
other hand, when the amount of the chelating agent is
more than 30 mass%, the phosphate in the coating
solution is less than 70 mass%, so that sufficient
heat resistance cannot be obtained in the insulating
film. Accordingly, the amount of the chelating agent
is 30 mass% or less relative to the mass of the
insulating film after baking.
[0023] The chelating agent is an active compound
but, once reacted with metal, becomes stable in terms
of energy and does not exhibit sufficient activity
any longer. Accordingly, to keep the activity of the
chelating agent high, metal other than the metal
contained in the phosphate is prevented from reacting
with the chelating agent before the baking of the
coating solution is completed. Therefore, it is
preferable that the concentration of metal ions
having high reactivity with the chelating agent in
water is low. Examples of the metal ion include a Ca
ion and a Mg ion. When the total concentration of
the Ca ions and the Mg ions is more than 100 ppm, the
activity of the chelating agent decreases.
Therefore, the total concentration of the Ca ions and
the Mg ions is 100 ppm or less, and more preferably
7 0 ppm or less . "A" smaller amount of alkaline-earth'
metal ions other than the Ca ions and the Mg ions is
more preferable.
[0024] The chelating agent contains a hydroxyl group
at an end, and is likely to take an association state
(hydrogen bond) expressed by Reaction formula 5.
R-OH...O=R (Reaction formula 5)
[0025] When the degree of association (degree of
hydrogen bond) of the hydroxyl group in the chelating
agent increases, the crossi inking reactions expressed
by Reaction formula 2 to Reaction formula 4 hardly
occur. Therefore, the application of the coating
solution is preferably performed to make the degree
of association as low as possible. For example, in
- 11 -
the case of performing application using a roller
(roll coating), it is preferable to apply the coating
solution while giving a shear stress to the coating
solution to decrease the degree of association of the
chelating agent. Decreasing the diameter of the
roller and increasing the moving speed of the base
material can give the shear stress suitable for
releasing the association state. For example, it is
preferable to use a roller having a diameter of 7 00
mm or less and set the moving speed of the base
material to 6 0 m/min or more, and more preferable to
use a roller having a diameter of 50 0 mm or less and
set the moving speed of the base material to 70 m/min
or more.
[0026] The "1b~a1^ing of the coating solution is
performed at a temperature of 250°C or higher, the
heating rate (first heating rate) from the
temperature of the base material at the application,
for example, the room temperature of about 30 ° C f to
100°C is 8 °C/sec or more, and the heating rate
(second heating rate) from 150 ° C to 250°C is lower
than the first heating rate. The temperature at the
application is substantially equal to the temperature
of the coating solution.
[002 7] The progress of the above-described
association of the chelating agent occurs no longer
if the flowability of the coating solution is lost.
Accordingly, to make the degree of association as low
12 -
as possible, it is preferable to increase the first
heating rate up to the boiling point of water
(100°C). When the first heating rate is less than
8 ° C/sec, the degree of association of the chelating
agent rapidly increases during temperature increase
to make the crossi inking reactions expressed by
Reaction formula 2 to Reaction formula 4 hardly
occur. Therefore, the first heating rate is 8 ° C/sec
or more.
[0028] The crosslinking reactions of the phosphate
and the chelating agent and the decomposition of the
chelating agent of Reaction formula 1 to Reaction
formula 4 occur in a temperature range of 15 0 ° C to
250 c C. The crosslinking reactions are carried out
preferably to prevent the decomposition of" the
chelating agent from being excessively rapid, and the
second heating rate from 150CC to 250°C is preferably
as low as possible. Capturing of the chelating agent
into the phosphate structure and the crosslinking
reactions are affected by the above-described degree
of association of the chelating agent. Accordingly,
when the first heating rate is high and the degree of
association of the chelating agent is low, the .
crosslinking reaction of the phosphate and the
chelating agent can be accelerated even if the second
heating rate is increased. Inversely, when the first
heating rate is low and the degree of association of
the chelating agent is high, the crosslinking
- 13 -
reaction of the chelating agent and the phosphate
needs to be accelerated by accordingly decreasing the
second heating rate. From the study by the present
inventors, it has been revealed that when the first
heating rate is 8 °C/sec or more and the second
heating rate is lower than the first heating rate,
the crosslinking reaction of the phosphate and the
chelating agent proceeds according to the degree of
association of the chelating agent and good rust
resistance can be obtained. However, when the second
heating rate is excessively high, for example, more
than 18 °C/sec, the crosslinking is not sufficiently
completed, so that good rust resistance cannot be
obtained even if the first heating rate is 8 ° C/sec
o~r more. Accordingly, the second heating rate is
18 °C/sec or less. On the other hand, with a lower
second heating rate, the productivity becomes lower,
which is remarkable at less than 5 °C/sec.
Accordingly, the second heating rate is preferably
5 °C/sec or more.
[0029] The electrical steel sheet 1 can be
manufactured through the application of the coating
solution to the base material of the electrical steel
and baking of the coating solution.
[0030] The coating solution may contain an organic
resin. The organic resin contained in the coating
solution has an action of suppressing abrasion of a
punching die. Therefore, use of the coating solution
_ 1 4 _
containing the organic resin improves the punching
workability of the electrical steel sheet. The
organic resin is preferably used as a waterdispersible
organic emulsion. In the case where the
water-dispersible organic emulsion is used, it is
more preferable that less alkaline-earth metal ions
such as Ca ions, Mg ions are contained therein.
Examples of the organic resin include an acrylic
resin, an acrylic styrene resin, an alkyd resin, a
polyester resin, a silicone resin, a fluorocarbon
resin, a polyolefin resin, a styrene resin, a vinyl
acetate resin, an epoxy resin, a phenol resin, an
urethane resin, and a me1amine resin.
[0031] Next, the action of the chelating agent will
be described.
[0032] To reveal the action of the chelating agent,
the present inventors measured the solid 31P-NMR
(nuclear magnetic resonance) spectrum for the
insulating film formed using the coating solution
containing the chelating agent and the insulating
film formed using the coating solution not containing
the chelating agent. Fig. 2 illustrates an example
of the "measurement result of the solid ~ P-NMR
spectrum. In Fig. 2, the first or third spectrum
from the top is of the insulating film formed using
the coating solution containing the chelating agent
(Example 1, Example 3), and the second, fourth, or
fifth spectrum from the top is of the insulating film
- 15 -
formed using the coating solution not containing the
chelating agent (Reference example 2 , Reference
example 4, Reference example 5). The aluminum
phosphate was used as the polyvalent metal phosphate
contained in the coating solution in Example 1,
Reference example 2 and Reference example 4 , and the
aluminum phosphate was used as the polyvalent metal
phosphate in Example 3 and Reference example 5.
[0033] As illustrated in Fig. 2, in the insulating
film formed using the coating solution not containing
the chelating agent, a spectrum containing a
component exhibiting a peak having a top near -30 ppm
and a small half width (Reference example 2,
Reference example 4 ) , or a spectrum containing a
component exhibiting a peak having a top near +13 ppm
and a large half width (Reference example 5) was
obtained. On the other hand, in the insulating film
formed using the coating solution containing the
chelating agent in Example 1, a spectrum containing a
component exhibiting a peak having a top' at -23 ppm
and a large half width in addition to such a
component as in Reference example 2 or Reference
example 4 was obtained. In the insulating film
formed using the coating solution containing the
chelating agent in Example 3, a spectrum containing a
component exhibiting a peak having a top at -18 ppm
and a large half width in addition to such a
component as in Reference example 5 was obtained.
- 16 -
[0034] The present inventors focused on the
different points in the above solid 31P-NMR spectrum
and considered that the peak contained in the solid
31P-NMR spectrum greatly contributes to the
improvement in rust resistance of the insulating
film, and investigated the relationship between them.
[0035] Here, a method of evaluating the rust
resistance will be described.
[0036] Examples of the test of evaluating the rust
resistance of the electrical steel sheet include the
humidity cabinet test defined in JIS K 2246 and the
salt spray test defined in JIS Z 2371. However,
since the corrosive environments in these tests are
greatly different from the corrosive environment
where the electrical: steel sheet rusts, the rust
resistance of the electrical steel sheet cannot be
appropriately evaluated by these tests.
[0037] Hence, the present inventors studied the
method capable of appropriately evaluating the rust
resistance in the corrosive environment where the
electrical steel sheet rusts. As a result, it has
been found that the following method can
appropriately evaluate the rust resistance. In this
method, liquid droplets of sodium chloride solutions
different in concentration are attached by 0.5 ul to
the surface of the electrical steel sheet having the
insulating film and dried, and the electrical steel
sheet is held in an atmosphere with constant
- 17 -
temperature and humidity of a temperature of 50°C and
a relative humidity RH of 90% for 48 hours. A
thermo-hygrostat may be used. Thereafter, the
presence or absence of rust is observed, and the
concentration of the sodium chloride solution with
which the electrical steel sheet does not rust is
identified. The rust resistance is evaluated based
on the concentration of the sodium chloride solution
with which the rust does not form.
[0038] More specifically, in this method, after the
attachment and drying of the liquid droplets of the
sodium chloride solutions, the electrical steel sheet
is exposed to a moist atmosphere. Such process is
similar to a corrosive environment to which the
electrical steel sheet is exposed. In the corros ive
environment, salt adheres to the surface of the
electrical steel sheet during storage, transportation
and use and then the salt deliquesces due to an
increase in humidity. With a higher concentration of
the sodium chloride solution, a larger amount of
sodium chloride remains after drying and the rust is
more likely to form. Accordingly, by making an
observation while decreasing stepwise the
concentration of the sodium chloride solution, and
specifying the concentration where the rust does not
form (hereinafter, sometimes referred to as a "limit
sodium chloride concentration"), the rust resistance
in the corrosive environment to which the electrical
- 18 -
steel sheet is actually exposed can be quantitatively
evaluated based on the limit sodium chloride
concentration.
[0039] Fig. 3A to Fig. 3E illustrate examples of the
test result by the above method. In this test, the
concentration of sodium chloride was 1.0 mass% (Fig.
3A), 0.3 mass% (Fig. 3B), 0.1 mass% (Fig. 3C), 0.03
mass% (Fig. 3D), or 0.01 mass% (Fig. 3E). As
illustrated in Fig. 3A to Fig. 3E, rust was observed
when the concentration of the sodium chloride was 1
mass%, 0.3 mass%, 0.1 mass%, or 0.03 mass%, and rust
was not observed when the concentration of the sodium
chloride was 0.01 mass%. Therefore, the limit sodium
chloride concentration of the electrical steel sheet
is 0.01 mass%. The present inventors hate confirmed
that the rusting state rarely changes even when the
hold time in the atmosphere with constant temperature
and humidity is over 48 hours.
[0040] Fig. 4A illustrates an example of a test
result by the above method about the electrical steel
sheet having the insulating film formed using the
coating solution not containing the chelating agent,
and Fig. 4B illustrates an example of a test result
by the above method about the electrical steel sheet
having the insulating film formed using the coating
solution containing the chelating agent. Each of the
coating solutions contains the aluminum phosphate as
the polyvalent metal phosphate. On the electrical
- 19 -
steel sheet having the insulating film formed using
the coating solution not containing the chelating
agent, rust was observed in the case of using the
sodium chloride solution having a concentration of
0.03 mass% as illustrated in Fig. 4A. On the other
hand, on the electrical steel sheet having the
insulating film formed using the coating 'solution
containing the chelating agent, no rust was observed
even in the case of using the sodium chloride
solution having a concentration of 0.2 mass% as
illustrated in Fig. 4B.
[0041] As described above, the limit sodium chloride
concentration is higher and better rust resistance
can be obtained in the case of forming the insulating
film'U'sing the coating solution containing the
chelating agent than in the case of forming the
insulating film using the coating solution not
containing the chelating agent.
[0042] The effect of improving the rust resistance
by addition of the chelating agent to the above
coating solution can be explained in association with
the solid 31P-NMR spectrum. The insulating film of
the phosphate which is formed using the coating
solution not containing the chelating agent has a
structure containing a simple bond expressed by the
right side of Reaction formula 1. In the solid 31p-
NMR spectrum, this structure exhibits a peak having a
top about -30 ppm and a narrow width when the
- 20 -
phosphate is crystallized, and exhibits a peak having
a top near +13 ppm and a broad width when the
phosphate is amorphous. On the other hand, the
insulating film of the phosphate which is formed
using the coating solution containing the chelating
agent also includes an amorphous structure containing
a complex bond expressed by the right sides of
Reaction formula 2 to Reaction formula 4. In the
solid 31P-NMR spectrum, the amorphous structure
exhibits a peak having a top in -2 6 ppm to -16 ppm,
and the half width of the peak is, for example, 2 0
ppm or more. Though details will be described later,
when the proportion of the integrated intensity of
the peak exhibited by the amorphous structure
""("specific peak) relative to the""""i"ntegrated intensity
of all peaks in the solid 31P-NMR spectrum is 30% or
more, good rust resistance can be obtained.
[0043] The insulating film 3 according to the
embodiment of the present invention exhibits the
above specific peak in the solid 31P-NMR spectrum.
Therefore, good rust resistance can be obtained
without using hexavalent chromium as the raw material
of the insulating film 3 by the electrical steel
sheet 1. For example, the electrical steel sheet 1
exhibits sufficient rust resistance even under a high
airborne salt environment during transportation by
sea or the like or under a hot and humid environment
corresponding to the subtropical zone or the tropical
- 21 -
zone. Since the insulating film 3 does not need to
be formed thick, a decrease in weldability and
caulking property can be avoided.
[0044] It should be noted that the above embodiment
merely illustrate concrete examples of implementing
the present invention, and the technical scope of the
present invention is not to be construed in a
restrictive manner by the embodiment. That is, the
present invention may be implemented in various forms
without departing from the technical spirit or main
features thereof.
EXAMPLES
[0045] Next, examples of the present invention will
be described- The condition in examples is one
condition example employed for confirming the
feasibility and the effect of the present invention,
and the present invention is not limited to the one
condition example. The present invention can employ
various conditions without departing from the scope
of the present invention and within achieving the
object of the present invention.
[0046] The present inventors prepared coating
solutions each composed of phosphate, a chelating
agent, an organic resin and water listed in Table 1
and applied to both surfaces of a base material of
electrical steel and baked. The total concentration
(total ion concentration) of Ca ions and Mg ions
contained in the water is also listed in Table 1.
- 22 -
The application condition and the baking condition
are also listed in Table 1. The first heating rate
is the heating rate from 30°C to 100°C, and the
second heating rate is the heating rate from 15 0 °C to
250°C. The base material contained 0.3 mass% of Si,
and the thickness of the base material was 0.5 mm.
In Sample No. 17, an insulating film was formed using
chromate in place of phosphate.
[0047] [Table 1]
[0048] Then, measurement of the solid 31P-NMR
spectrum and evaluation of the rust resistance and
the weldability of the insulating film were
performed.
[0049] In the measurement of the solid 31P-NMR
spectrum of the insulating film, the position of the
peak (chemical shift), the half width of the peak,
and the proportion of the integrated intensity were
obtained. The results are listed in Table 2 . The
underlined portion in Table 2 represents that the
numerical value is out of the range of the present
invention.
[0050] In the evaluation of the rust resistance, a
test piece was prepared from each electrical steel
sheet, liqu~i~d~~ droplets of sodium chloride solutions
different in concentration were attached by 0.5 ul to
the surface of the test piece and dried, and the test
piece was held in an atmosphere with constant
temperature and humidity of a temperature of 50°C and
a relative humidity RH of 90% for 48 hours. The
concentrations of the sodium chloride solutions were
0.001 mass%, 0.01 mass%, 0.02 mass%, 0.03 mass%, 0.10
mass%, 0.20 mass%, 0.30 mass%, and' 1.0 mass%.
Thereafter, the presence or absence of rust was
observed, and the limit sodium chloride (NaCl)
concentration of each test piece was identified.
This result is also listed in Table 2.
[0051] In the evaluation of the weldability, the
- 25 -
welding current was 12 0A, a La-W (2.4 mm 4> ) was used
as an electrode, the gap was 1.5 mm, the flow rate of
an Ar gas was 6 1/min, and the clamping pressure was
50 kg/cm2, welding- was performed at various welding
speeds. Then, the maximum welding speed at which
blow hole was not generated was specified. The
result is also listed in Table 2.
[0052] [Table 2]
[0053] As listed in Table 2, both of a limit sodium
chloride concentration of 0.10 mass% or more and a
welding speed of 100 cm/min were obtained in Samples
No. 10 to No. 16 within the range of the present
invention. In other words, good rust resistance and
weldability were obtained.
[0054] Since the top of the peak was not in the
range of -2 6 ppm to -16 ppm in Samples No. 1 to No.
4, the limit sodium chloride concentration was 0.03
mass% or less or the welding speed was 50 cm/min. In
other words, the rust resistance or the weldability
or both of them were low.
[0055] Since the top of the peak was in the range of
-2 6 ppm to -16 ppm but the proportion of the
integrated intensity was less than 3 0% in Samples No.
5 to No. 9, the limit sodium chloride concentration
was 0.03 mass% or less. In other words,, the rust
resistance was low.
[0056] Since the top of the peak was in the range of
-26 ppm to -16 ppm but the proportion of the
integrated intensity v/as less than 30% in Samples No.
18 to No. 21, the limit sodium chloride concentration
was 0.03 mass% or less. In other words, the rust
resistance was low.
INDUSTRIAL APPLICABILITY
[0057] The present invention is applicable, for
example, in an industry of manufacturing an
electrical steel sheet and an industry using the
electrical steel sheet.

[Claim 1]
And the base material of the electromagnetic steel, and an insulating film formed on the surface of the base material
　has,　the insulating coating, Al, Zn, 1 or more phosphate salts selected from the group consisting of Mg and Ca containing,
　the phosphate salt, the solid 31 in the P-NMR spectrum, the vertex represents a specific peak in the range of -26ppm ~ -16ppm, the solid integrated intensity of the specific peak 31 all in P-NMR spectrum electrical steel sheet, wherein the ratio of the relative integrated intensity of the peak is 30% or more.
[Claim 2]
　Electrical steel sheet according to claim 1, wherein the half width of the specific peak at 20ppm or more.
[Claim 3]
　Electrical steel sheet according to claim 1 or 2, wherein the insulating coating, characterized in that it contains an organic resin.