0001]The present invention relates to an insulating coating of electrical steel sheet.
Background technique
[0002]On the surface of the electrical steel sheet (non-oriented electrical steel sheet and grain-oriented electrical steel sheet), it is common insulating film for the purpose of improving the rust resistance is formed. Conventionally, as the insulation coating, chromate-based insulation coating of the dichromate as a main raw material has been mainly adopted. However, the hexavalent chromium for strong toxicity, from the viewpoint of working environment protection at the time of manufacture (hereinafter referred to as "environmental protection".), An insulating film containing no chromium is required.
[0003]
　As the insulating film to replace the chromate-based insulation coating, salt-based insulating coatings phosphate have been studied (for example, see Patent Document 1). And now, various phosphate-based insulating film has been proposed (e.g., see Patent Documents 2-5). However, salt-based insulating coatings chromic acid, also to reduce the thickness of the coating, sufficient corrosion resistance is obtained, and, because it can ensure excellent weldability and caulking properties, even today, as an insulating coating of electrical steel sheet It has been adopted.
[0004]
　Phosphate-based insulating film (e.g., phosphate Al-based insulating film, phosphate Mg-Al-based insulating film), and, environmental conservation insulation coating containing no chromium (e.g., silica-based insulating film, Zr-based insulating film) the corrosion resistance compared to the chromate-based insulation coating is insufficient. Corrosion resistance when increasing the thickness of the insulating film can be ensured. However, increasing the thickness, a problem that weldability and caulking deteriorates occurs.
[0005]
　In recent years, demand's, has been relocated to severe Southeast Asia and southern China of corrosion environment, electromagnetic steel sheet has come to be exported to the region. And accordingly, the insulating coating of the electrical steel sheet to be exported to severe the local corrosive environment, rust resistance to withstand high airborne salt environments or local hot and humid environment during marine transportation have been required .
[0006]
　For example, Patent Documents 4 and 5, carried out wet test baking an insulating coating at 170 ~ 300 ° C., result of evaluating the corrosion resistance is disclosed. Patent Document 6 and 7, to form an insulating film with a processing solution by adding a synthetic resin to the phosphate compound and the chelating agent is disclosed.
[0007]
　Furthermore, Patent Document 8, the phosphoric acid metal salt having an average particle diameter of 0.05 ~ 0.50 .mu.m acrylic resins, one or more mixtures of epoxy resins and polyester-based resin or copolymer an organic resin comprising, by adding a copolymer of a fluoroolefin and an ethylenically unsaturated compound, the corrosion resistance more enhanced insulating film has been proposed in a wet environment.
CITATION
Patent Literature
[0008]
Patent Document 1: JP-B 53-028375 Patent Publication
Patent Document 2: JP-A 05-078855 JP-
Patent Document 3: JP-A-06-330338
Patent Document 4: JP-A 11-131250 JP
Patent Document 5: JP 11-152579 JP
Patent Document 6: JP 2001-107261 Patent Publication
Patent Document 7: JP 2002-047576 JP
Patent Document 8: WO 2012/057168
Summary of the Invention
Problems that the Invention is to Solve
[0009]
　As described above, in Patent Documents 4 and 5, although the wet test of the insulating film is performed, it is determined to exports, and worth considering is left in order to evaluate the corrosion resistance in high airborne salt environments there.
[0010]
　The insulating film disclosed in Patent Documents 6 and 7, but is excellent in water resistance against condensed water, the rust resistance in hot and humid environment corresponding to the height airborne salt environments and subtropical and tropical during marine transport It is not clear.
[0011]
　Further in the technique described in Patent Document 8, the thickness of the insulating coating is a preferable 0.5 ~ 1.5 [mu] m, the film thickness in the embodiment has a 0.8 [mu] m. User desires, particularly high weldability and caulking properties, the film thickness of the insulating coating is a characteristic that can be secured in the thinner region. Therefore, to achieve an improvement in weldability and caulking properties, while maintaining excellent corrosion resistance, it is required to further reduce the thickness of the insulating film.
[0012]
　Thus, the corrosion resistance of the environmental conservation type insulating film including phosphate-based insulating coating, since it does not reach the level of chromate-based insulating film, the insulating coating of the electrical steel sheet is currently chromate-based insulation and the film and the environmentally friendly insulating film coexist. Therefore, in the production and user both cause a decrease in complexity and productivity of product management, and pressure on revenue.
[0013]
　Users also in environmental conservation insulating film, in addition to the corrosion resistance, the performance at the production technical aspects of weldability and crimping properties also emphasized, seeking performance of conventional chromate-based insulation coating level equivalent .
[0014]
　The present invention, even at a thickness comparable to the salts of chromic acid-based insulating film, excellent corrosion resistance, in particular, high airborne salt environments during sea transport as well as in hot and humid environment corresponding to subtropical and tropical, excellent and to provide an insulating coating environmentally sound electromagnetic steel sheet which exhibits rust resistance was.
Means for Solving the Problems
[0015]
　The present invention has been completed based on the above findings, and the gist of the insulating coating of the electrical steel sheet described below.
[0016]
　(1) an insulating film formed on the surface of the base material of the electromagnetic steel sheet,
　Al, Zn, comprises one or more polyvalent metal phosphate salt selected from Mg and Ca,
　and the surface of the base material in the interface, has a concentrated layer of a divalent metal,
　concentrated amount of the divalent metal contained in the concentrated layer, 0.010 g / m 2 or more 0.20 g / m 2 is less than,
　insulation coating of electrical steel sheet.
[0017]
　(2) said insulating film further contains an organic resin,
　the insulating coating of the electrical steel sheet according to the above (1).
Effect of the invention
[0018]
　According to the present invention, even at a thickness comparable to the salts of chromic acid-based insulating film, excellent for rust resistance can be secured, weldability and caulking excellent in environmental conservation of electromagnetic steel plates insulative coating it is possible to obtain.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019]
FIG. 1 is a graph showing the element concentration distribution in the film thickness direction when using the aluminum phosphate and Ca chelate compound.
FIG. 2 is a graph showing the element concentration distribution in the film thickness direction in the case of using a magnesium phosphate and the Mg chelate compound.
3 is a diagram for explaining a method for separating a peak of Mg derived from a depth direction of the profile in concentrated layer approximated by a Gaussian function of Mg.
4 is a diagram showing an example of an evaluation method of rust resistance test of the insulating coating.
5 is a diagram showing an example of the result of rust resistance test of the insulating coating. (A) is a rust resistance of the formed without adding a chelating agent to the aluminum phosphate insulating film, showing the results of evaluation by the sodium chloride concentration 0.03% sodium chloride aqueous solution, (b) is phosphoric acid the rust resistance of the aluminum in the insulating film formed by adding a chelating agent, and the results of the evaluation with sodium chloride 0.2% aqueous sodium chloride solution.
[6] Test Example No. Is a graph showing the element concentration distribution in the film thickness direction at 9.
Test [7] Example No. Is a graph showing the element concentration distribution in the film thickness direction at 10.
[8] Test Example No. Is a graph showing the element concentration distribution in the film thickness direction at 15.
[9] Test Example No. Is a graph showing the element concentration distribution in the film thickness direction at 20.
Tests [10] Example No. It is a graph showing the element concentration distribution in the film thickness direction of 2.
Tests [11] Example No. It is a graph showing the element concentration distribution in the film thickness direction of 3.
DESCRIPTION OF THE INVENTION
[0020]
　1. For insulating coating
　insulating film according to the present invention are those formed on the surface of the base of the electromagnetic steel sheets. The No particular limitation is imposed on the kind of the base material, it is possible to use steel sheet having a chemical composition and metal structure suitable for use as the base material of the grain-oriented electrical steel sheet or non-oriented electrical steel sheet.
[0021]
　The insulating coating includes Al, Zn, one or more polyvalent metal phosphate salt selected from Mg and Ca. Specifically, as a polyvalent metal phosphate, aluminum primary phosphate, the first zinc phosphate, the first magnesium phosphate and a first calcium phosphate and the like.
[0022]
　However, only the insulating coating comprises the above components, sufficient corrosion resistance, in particular, high airborne salt environments during sea transport as well as rust resistance can not be obtained necessary in hot and humid environment corresponding to subtropical and tropical. Therefore, it said in an insulating film, at the interface between the surface of the base material, it is necessary to form a concentrated layer of a divalent metal.
[0023]
　The concentrated layer has a dense structure, to firmly bonded to both the layer and the base material of the polyvalent metal phosphate, to improve the corrosion resistance and adhesion of the insulating film, resulting in rust resistance It is considered to have greatly improved.
[0024]
　However, (in the following description, simply referred to as "concentrated amounts".) Concentrated amount of the divalent metal contained in the concentrated layer is 0.010 g / m 2 is less than, the divalent metal chelators continuity of the reaction layer is lost, the corrosion resistance improving effect can not be obtained. Meanwhile, the concentrated weight 0.20 g / m 2 to the above, the cost is deteriorated economy become excessive. Thus, the concentrated weight 0.010 g / m 2 or more 0.20 g / m 2 to less than. The concentrated amount, from the viewpoint of improving the corrosion resistance 0.020 g / m 2 is preferably at least, from the viewpoint of economy 0.10 g / m 2 preferably not more than.
[0025]
　In the present invention, thickening amount of the divalent metal contained in the concentrated layer is assumed that determined by the following method. It will be described in detail with reference to specific examples.
[0026]
　First, the glow discharge optical emission spectrometry (GDOES), to measure the concentration distribution in the depth direction of the P and the metal components contained in the insulating film. An example of measurement results, shown in Figures 1 and 2. In the figure, the vertical axis indicates the emission intensity of the element, the horizontal axis represents the discharge time. Luminous intensity is proportional to the concentration of each element, the discharge time corresponds to the depth direction position from the surface.
[0027]
　In the example shown in FIG. 1, the insulating film comprises a first aluminum phosphate, concentrated layer of Ca is formed. In such case, the profile of divalent metal derived from divalent metal profile with phosphate derived from concentrated layer can be clearly distinguished.
[0028]
　On the other hand, in the example shown in FIG. 2, the insulating film comprises a first magnesium phosphate, concentrated layer of Mg is formed. In such a case, as shown in FIG. 3, to separate the peaks of Mg derived from a depth direction of the profile of Mg in concentrated layer approximated by a Gaussian function, derived from the remainder in phosphate Mg to.
[0029]
　(In the drawing, S area surrounded by the curve and the vertical axis and the horizontal axis showing the concentration profiles separated by the above methods I and S C ) from a concentrated amount of the divalent metal contained in the concentrated layer , it is possible to determine the ratio of the amount of divalent metal contained in the insulating film except for the concentrated layer.
[0030]
　Then, the steel plate having a predetermined area where the insulating film is formed on the surface, by immersion in hot alkaline aqueous solution, selectively all dissolve only an insulating film containing a concentrated layer. Then, the alkaline aqueous solution after film dissolution treatment, inductively coupled plasma emission spectrometry by analyzing with (ICP-AES), the total divalent metal weight M contained in the insulating film per unit area T (g / M 2 ) seek.
[0031]
　Thickening amount M of the divalent metal in the concentrated layer in I (g / m 2 ) may be calculated based on the following equation (i).
　M I = M T × S I / (S I + S C ) · · · (i)
　where the meaning of each symbol in the formula is as follows.
　M I : thickening amount of a divalent metal contained in the concentrated layer (g / m
　2 ) M T : total divalent metal content in the insulation coating (g / m
　2 ) S I : the concentrated layer area from which concentration profile
　S C : the area of the concentration profile resulting from an insulating film on excluding concentrated layer
[0032]
　Wherein together with the insulating coating comprises a component described above, by having the concentrated layer, as the membrane thickness was thin, resulting excellent corrosion resistance.
[0033]
　Also, the insulating film may further contain an organic resin. When blanking the electromagnetic steel plates, the inclusion of an organic resin in the insulating film, punching mold wear is suppressed, in order to improve punching processability.
[0034]
　The types of organic resin is not particularly limited, but is preferably a water-dispersible, for example, acrylic resins, acryl styrene resins, alkyd resins, polyester resins, silicone resins, fluorocarbon resins, polyolefin resins, styrene resins, vinyl acetate resins , epoxy resins, phenolic resins, urethane resins, melamine resins, and the like.
[0035]
　2. A method for manufacturing the insulation coating
　for the process for producing the insulation coating according to the present invention, is not provided specifically limited, by using the method shown below, for example, it can be manufactured insulation coating having the above configuration.
[0036]
　First prepared Al, Zn, and polyvalent metal phosphate salt solution contains at least one element selected from Mg and Ca, a coating solution and chelate compounds are mixed comprising a divalent metal. Then, the surface of the base of the electromagnetic steel sheet, baking after coating the coating solution to form an insulating coating. Note that the during the coating liquid may further contain an organic resin as needed, as described above.
[0037]
　Al, Zn, As the polyvalent metal phosphate salt solution contains at least one element selected from Mg and Ca, for example, a first aluminum phosphate aqueous solution, the first zinc phosphate solution, the first phosphoric acid magnesium solution, the one or more selected from a calcium phosphate solution or the like can be used an aqueous solution that is contained in a complex manner.
[0038]
　The divalent metal contained in the chelate compound, Mg, Ca, Sr, Ba, include one or more selected from Zn, and the like. As the chelating component, it can be used oxycarboxylic acid, a chelating agent such as dicarboxylic acid or phosphonic acid.
[0039]
　As oxycarboxylic acid chelating agent, malic acid, glycolic acid and lactic acid are exemplified. As dicarboxylic acid chelating agent, oxalic acid, malonic acid and succinic acid. The phosphonic acid chelating agent, an amino trimethylene phosphonic acid, hydroxy ethylidene mono acid and Hiroki shea diphosphonic acid.
[0040]
　Note that when the chelate compound is mixed with phosphoric acid aqueous salt solution instead of adding a divalent metal and a chelating agent separately, it is preferable to add the one that has been formulated in advance. The addition of a divalent metal and a chelating agent separately, and metal ion chelate constituting the phosphate is reacted, because the formation of the concentrated layer of a divalent metal chelate may be insufficient.
[0041]
　In the coating solution, by the inclusion of the chelating compound in addition to the polyvalent metal phosphate salt solution, in baking process, the divalent metal M, a chelating moiety L and the iron component Fe of the base material in the react, film It believed to form a concentrated layer of a divalent metal having an M-L-Fe bonds at the interface between the base material and.
[0042]
　At this time, in order to a predetermined range the formation of the concentrated layer, the relative amount of the chelating component L of chelate compounds l (mol), incorporation of the added amount of the divalent metal M m (mol) it is preferable that the ratio m / l in the appropriate range. Specifically, by making the value of the blending ratio m / l in the range of 0.1 to 0.9, wherein the concentrated layer is favorably formed, it may improve rust resistance of the insulating coating I understood.
[0043]
　The value of the mixing ratio m / l is more than 0.9, i.e., when a chelate compound close to saturation state divalent metal is constituted almost all of a chelating moiety complexed is contained in the coating solution, most of the chelate compound can not react with the Fe in the base material, concentrated layer having an M-L-Fe bonds becomes difficult to form. On the other hand, wherein when less than the blending ratio m / value of l is 0.1, the chelating compounds, almost all reacts with Fe in the base material, LFE 2 are formed, M-L-aimed concentrated layer having a F bond, becomes too small.
[0044]
　Wherein there is no particular limitation on the amount of the chelating compound in the coating solution, e.g., formation of the entire insulating film is 1 g / m 2 when a polyvalent metal phosphate (anhydrous equivalent) and the organic resin respect of the total amount, the chelating compound may be added 1 mass% or more.
[0045]
　Next, a description will be given of a preferred coating conditions and baking conditions. Baking of the coating solution is performed at temperatures above 250 ° C., the temperature of the base material, for example, the average heating rate of about 30 ° C. from room temperature to 100 ° C. (first heating rate) and 8 ° C. / sec or more at the time of application and average heating rate from 0.99 ° C. to 250 ° C. (second heating rate) lower than the first heating rate. The temperature during coating is equal to the temperature of substantially the coating solution.
[0046]
　Progress meeting chelating agents will not occur if there are no fluidity of the coating solution. Therefore, in order to make the degree of association as low as possible, the first heating rate of up to 100 ° C. equal to the boiling point of water is preferably higher. In a less than 1 heating rate 8 ° C. / sec, since the increased association of the chelating agent is rapidly during warm, the crosslinking reaction hardly occurs. Therefore, the first heating rate is set to 8 ° C. / sec or more.
[0047]
　Crosslinking reaction of phosphate and a chelating agent, and decomposition and volatilization of the chelating agent occurs in the temperature range of 150 ℃ ~ 250 ℃. Therefore, by decreasing the second heating rate from 0.99 ° C. to 250 ° C., it can promote the crosslinking reaction while suppressing the degradation of the chelating agent. However, reduction of the rate of temperature rise can lead to reduced productivity.
[0048]
　On the other hand, the crosslinking reaction of the chelating agent varies depending on the degree of association of the above-mentioned chelating agents. Therefore, to increase the first heating rate, if to reduce the degree of association of the chelating agent, also by increasing the second heating rate, it is possible to accelerate the crosslinking reaction between the phosphate salt and a chelating agent . On the other hand, the first heating rate is low, if the degree of association of the chelating agent is large, unless lower second heating rate accordingly, sufficiently advanced the crosslinking reaction of the chelating agent and the phosphate salt it can not be.
[0049]
　The study of the present inventors, and the first heating rate 8 ° C. / sec or more, if the second heating rate is lower than the first heating rate, phosphate salt and chelate according to degree of association of the chelating agent crosslinking reaction between agent proceeds, it was found that excellent rust resistance can be obtained. However, if the second heating rate is excessively high, for example exceeding 18 ° C. / sec, even first heating rate 8 ° C. / sec or more, crosslinking does not sufficiently complete, excellent rust sex can not be obtained. Therefore, the second heating rate is preferably set to 18 ° C. / sec or less. On the other hand, the second heating rate is higher productivity is lowered low, it becomes significant at less than 5 ° C. / sec. Therefore, the second heating rate is preferably set at 5 ° C. / sec or more.
[0050]
　3. Rust resistance evaluation method for
　the present invention have found that, when offshore long-distance transportation described above, or as a result of investigation of rust resistance of an indicator of the electromagnetic steel sheet which can withstand use under high-temperature humid climate, an insulating film on the surface of the electrical steel sheet, and dried by attaching droplets (0.5 [mu] L) of different sodium chloride aqueous solution of concentration, magnetic steel sheets, constant temperature and humidity condition (50 ° C., RH 90%) for a predetermined time (48 hours) retention and, then, to investigate the corrosion status of the insulating coating, which resulted in the adoption of the method of evaluating at a sodium chloride concentration of rust is not generated.
[0051]
　The reason for adopting this evaluation method is as follows.
[0052]
　Usually, the rust resistance evaluation of magnetic steel sheets, so far, there have been cases where the wet test specified in JIS K 2246 is used. The wet test, the 49 ° C. The temperature, the relative humidity in an atmosphere maintained at 95% or more, the electromagnetic steel sheet a predetermined time, after exposure, a method of evaluating by observing the occurrence state of rust on the steel sheet surface.
[0053]
　However, the wet test, be applied to an electromagnetic steel sheet having an insulation coating, in many cases, corrosion is not observed. Therefore, in the wet test, sea transport at high airborne salt environments, and it is difficult to determine superiority or inferiority of the rust resistance of the insulating coating in the high temperature and high humidity environment corresponding to the subtropical and tropical.
[0054]
　On the other hand, salt spray test specified in JIS Z 2371 are also common corrosion evaluation test. This test, in a thermostat 漕中 maintained at 35 ° C., 5% aqueous sodium chloride solution, fixed time, after adjusting to a predetermined spray amount, performs salt spray a predetermined time the steel sheet surface, rust in a subsequent steel state of occurrence is observed to evaluate test.
[0055]
　The salt spray test, when applied to an electromagnetic steel sheet having an insulation coating, although corroded, salt spray test, a test in a state where the insulating film is always wet, airborne salt of salt damage environment or marine structure or the like of an automobile since is assumed tested corrosion under extremely noisy environment, test environment of salt water spray test, storage of electrical steel sheets hold the like during indoor warehouse or export of land transportation, it is different from the use environment. Described in Patent Document 8, even in a test that combines salt spray, wet-drying step is the same be taken out of the salt spray process.
[0056]
　Upon storage or use of the electromagnetic steel sheets, or saline are immersed in salt water is sprayed, the state in which the surface is completely wet with salt water is that it does not occur under normal use conditions. Further, the corrosion by spraying salt water, the land of indoor warehouse or export during hold corrosive environment (dry and high humidity are repeated), different environments of the steel sheet surface during erosion, corrosion mechanisms along with it It is also different. Thus, studies involving salt spray and salt spray process is not suitable for evaluation of rust resistance of the electrical steel sheet.
[0057]
　The present inventors have studied a method that can properly evaluate the rust resistance of the electrical steel sheet, the method described above, i.e., the surface of the electrical steel sheet having an insulation coating, droplets of different aqueous sodium chloride concentrations (0. dried by adhering 5 [mu] L), the magnetic steel sheets, constant temperature and humidity condition (50 ° C., and held RH 90%) for a predetermined time (48 hours), then examine the corrosion state of the insulating coating, chloride rust does not occur how to evaluate the rust resistance in sodium concentration (rust resistance test method) was confirmed to be correct.
[0058]
　In the case of high concentrations of sodium chloride aqueous solution droplets, depositing the droplets of aqueous sodium chloride solution and dried, corrosion by portions sodium chloride were dry deposit is then exposed to a wet process is caused. The testing process is, salts adhered to the surface during storage transportation of steel plates, then salt deliquescence when a high humidity, optionally, that corrosion occurs, is a technique that makes real environment. With decreasing concentration of sodium chloride, the amount of deposition of salt is reduced, degree of occurrence of rust is mild, eventually rust is not observed. With sodium chloride concentration below which the rust can not be recognized, it is possible to quantitatively evaluate the rust resistance of the insulating coating.
[0059]
　4 shows an example of a method for evaluating rust resistance test of the insulating coating. The sodium chloride concentration, 0.1% increments from 1.0% to 0.1%, continue to reduce in 0.01% increments from 0.1% to 0.01%, the occurrence of rust at each concentration state is a result of observation of the (corrosion state). For the results shown in FIG. 4, the sodium chloride concentration is not observed rust with 0.01%, the limit concentration of sodium chloride is 0.01%. Incidentally, the rust situation even when the retention time of the constant temperature and Shime漕 extending from 48 hours, have confirmed that substantially no change.
[0060]
　The following examples illustrate the present invention more specifically, the present invention is not limited to these examples.
Example
[0061]
　A coating solution containing the ingredients shown in Table 1, the surface of the electrical steel sheet 0.5mm thick containing Si 0.3 mass%, baking after coating under the conditions shown in Table 1 were formed on both sides in the insulating film. Thereafter, the insulating film structure (presence of concentrated layer) and concentrated amount was determined by GDOES and ICP-AES. In addition, we evaluated the rust resistance and weldability of the insulating coating. The results are summarized in Table 1. Chromate insulating coating in Comparative also prepared in the same manner and evaluated.
[0062]
　Measurements thickening amount was performed by the following method. First, the GDOES, to determine the concentration distribution in the depth direction of the P and the metal components contained in the insulating film. Then, the divalent metal thickening layer, for each of the divalent metal of the other insulating coating, was determined area surrounded by the curve and the vertical axis and the horizontal axis showing the concentration profile. Note that when the divalent metal in the phosphates and the chelate compound are the same, divalent metal derived from the concentrated layer approximated by a Gaussian function from the divalent metal in the depth direction of the profile of the concentrated layer the peak was separated and the divalent metal derived from the remainder to phosphate.
[0063]
　Then, the steel plate having a predetermined area where the insulating film is formed on the surface, selection by immersion in aqueous 20% NaOH solution of 80 ° C. 30 minutes, without matrix dissolution, only the insulating film containing a concentrated layer all were dissolved manner. Thereafter, the NaOH aqueous solution after film dissolution treatment, inductively coupled plasma emission spectrometry by analyzing with (ICP-AES), the total divalent metal content in the insulation coating per unit area (g / m 2 ) was determined.
[0064]
　Then, based on the following equation (i), it was calculated thickening amount of a divalent metal contained in the concentrated layer.
　M I = M T × S I / (S I + S C ) · · · (i)
　where the meaning of each symbol in the formula is as follows.
　M I : thickening amount of a divalent metal contained in the concentrated layer (g / m
　2 ) M T : total divalent metal content in the insulation coating (g / m
　2 ) S I : the concentrated layer area from which concentration profile
　S C : the area of the concentration profile resulting from an insulating film on excluding concentrated layer
[0065]
　Rust resistance of the evaluation was conducted by the following method. Test pieces were cut out from the non-oriented electrical steel sheet forming an insulating film on its surface, then dried to adhere 0.001 to 1.0% range of various concentrations of aqueous sodium chloride solution droplets (0.5 [mu] L) , then, constant temperature and humidity condition (50 ℃, RH90%) and held for 48 hours in 漕内 maintained at, was observed corrosion state of the surface. Then, as an index the maximum sodium chloride concentration of rust does not occur was evaluated rust resistance.
[0066]
　The evaluation of the weldability was conducted by the following method. Welding current 120A, electrodes La-W (2.4mmφ), gap 1.5 mm, Ar flow rate of 6L / min, clamping pressure 50 kg / cm 2 in terms of changing the welding speed, the maximum welding speed which blowholes are not generated I was asked. Then, the maximum welding speed as an index to evaluate the weldability.
[0067]
　In the present invention, in the evaluation of the rust resistance, the maximum sodium chloride concentration which rust does not occur in the case of 0.2% or more, it is determined that the rust resistance is excellent.
[0068]
[Table 1]

[0069]
　Table 1, in Test No. 1-7 are the examples of the present invention, it can be seen that the rust resistance is markedly superior. In the examples of the invention, 0.5 g / m 2 (about 0.2 [mu] m) of small thickness, i.e., a thickness comparable to the salts of chromic acid-based insulating film, can be secured equal or superior rust resistance. Furthermore, since it is possible to reduce the film thickness, it can be seen weldability is equivalent to conventional chromate-based insulation coating.
[0070]
　In contrast, in Test Nos. 8-11 of the comparative example was not added to chelate compound in the coating solution, since the concentrated layer of a divalent metal is not formed, to have the film thickness of the insulating film regardless, it was the result of rust resistance is poor. Furthermore, the test No. For the 8, 9 and 11, since the thickness is thick, resulted in weldability is deteriorated.
[0071]
　Test No. In 12 and 13, respectively, the value of the blending ratio m / l of a chelating compound due to being too small and too large, concentrated amount becomes insufficient. Test No. In 14, thickened amount due to the addition amount of the chelate compound in the coating solution is insufficient becomes insufficient. Furthermore, the test No. In 15-18, since the temperature-raising condition during baking was inadequate, concentrated amount becomes insufficient.
[0072]
　In addition, test No. In 19 and 20, due to the addition of the divalent metal and the chelating moiety in a separate diphosphate salt solution, concentrated amount becomes insufficient. Then, concentrated amount was insufficient test No. 12-20, both resulted in rust resistance is poor.
[0073]
　With rust resistance test described above, FIG. 5 shows an example of a result of the divalent metal enriched layer which exists in the vicinity of the interface between the base material of the insulating coating was investigated the effect on rust resistance. In FIG. 5 (a), the test was formed without adding a chelating compound to aluminum phosphate No. The rust resistance of the insulating coating in 8 shows the result of evaluation by the sodium chloride concentration 0.03% aqueous solution of sodium chloride, in FIG. 5 (b), adding a chelate compound containing Zn as a divalent metal aluminum phosphate It was formed by test No. The rust resistance of the insulating coating in 1, the results of evaluation by the sodium chloride concentration of 0.2% sodium chloride solution.
[0074]
　In the insulating film formed without adding a chelating compound to aluminum phosphate, sodium chloride concentration 0.03% sodium chloride aqueous solution, rust greatly occur, whereas, the aluminum phosphate, containing Zn as a divalent metal in the insulating film formed by adding a chelate compound, sodium chloride concentration of 0.2% sodium chloride aqueous solution, rust hardly occurs.
[0075]
　Further, FIGS. 6-11, respectively, are comparative examples Test No. 9, 10 and 20 as well as the invention example Test No. A diagram showing the results of depth analysis in 2 and 3.
[0076]
　Test was not added chelate compound in the coating solution No. In 9 and 10, as shown in FIGS. 6 and 7, the peak of divalent metal was observed. Although chelate compound was added, the test production conditions were not suitable No. In 15 and 20, as shown in FIGS. 8 and 9, although the peak of a divalent metal is observed, was only.
[0077]
　For these test satisfies the requirements of the present invention No. In 2 and 3, as shown in FIGS. 10 and 11, the peak of divalent metal could be clearly confirmed.
Industrial Applicability
[0078]
　According to the present invention, even at a thickness comparable to the salts of chromic acid-based insulating film, excellent for rust resistance can be secured, weldability and caulking excellent in environmental conservation of electromagnetic steel plates insulative coating it is possible to obtain. Therefore, the electromagnetic steel sheet insulating coating is formed according to the present invention, high airborne salt environments during sea transportation, and is suitable for use in hot and humid environment corresponding to subtropical and tropical.

claims

[Claim 1]An insulating film formed on the surface of the base material of the electromagnetic steel sheet,
　Al, Zn, comprises one or more polyvalent metal phosphate salt selected from Mg and Ca,
　at the interface between the surface of the base material has a concentrated layer of a divalent metal,
　concentrated amount of the divalent metal contained in the concentrated layer, 0.01 g / m 2 or more 0.2 g / m 2 is less than,
　the electrical steel sheet insulating coating.
[Claim 2]
　Wherein the insulating film further contains an organic resin,
　the insulating coating of the electrical steel sheet according to claim 1.