JP3527414B2 - Electromagnetic steel sheet for laminated adhesive core with extremely excellent adhesive strength stability - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic steel sheet for a laminated bonded iron core which can form an iron core by punching or shearing and then bonding the steel sheets by pressing and heating. Things. 2. Description of the Related Art When manufacturing an iron core of an electric device or the like used for a stator of a motor or the like, electromagnetic steel sheets are punched or sheared, laminated, and the end faces are fixed by a method such as welding or caulking. It is common to use iron cores. Recently, as disclosed in Japanese Patent Publication No. 55-9815 or Japanese Patent Application Laid-Open No. 2-208034, as an iron core fixing method which does not require the above-mentioned welding method and caulking method, an insulating film having adhesiveness is previously formed. A method has been proposed in which a steel sheet is formed on a steel sheet surface, punched or formed into a predetermined shape by shearing, and then laminated and pressed and heated to fix the steel sheets to form an iron core. [0003] If the bonding strength between the steel plates in the laminated bonded iron core is insufficient, there is a possibility that peeling may occur when the iron core is rotating. Therefore, the degree of adhesion between the steel sheets, that is, the so-called adhesive strength, is very important. The adhesive strength is affected by the material of the film, the amount of the film, the drying temperature, and the like. When the coating material is the same, the adhesive strength is particularly affected by the amount of the coating and the drying temperature. Until now, the production control has been performed by precisely adjusting these. However, there has been a problem that even if the film is dried with the same film amount and the same drying temperature, the adhesive strength varies. [0004] It is an object of the present invention to provide an electromagnetic steel sheet for a laminated bonded iron core which has the above-described variations in quality and has stable bonding strength. SUMMARY OF THE INVENTION The present invention provides a stamping or
After shaping into a predetermined shape, these are laminated
And then press and heat to fix the steel sheets together.
An electromagnetic steel sheet for a laminated adhesive core, wherein an insulating film having an adhesive action is formed on a steel sheet for forming a core.
Film is an organic material film containing a constituent element of oxygen, the steel sheet surface oxide content after removal of the film is less than steel per surface 0.005 g / m ² or more 1.0 g / m ² oxygen basis weight This is an electromagnetic steel sheet for laminated adhesive iron cores with extremely excellent adhesive strength stability. As a result of intensive studies to solve the above-mentioned problems, the inventors found that the amount of surface oxide of a steel sheet before forming an insulating film having an adhesive effect was affected. I came to think that I was doing it. In order to confirm this idea, a sample was prepared under the following conditions, and the adhesive strength was examined. First, a large number of magnetic steel sheets having a thickness of 0.5 mm are prepared and subjected to heat treatment under various conditions of varying the degree of oxidation of the atmosphere and the heating time to obtain samples having different oxide amounts in terms of oxygen amount per one side of the steel sheet. Produced. In this sample, the resin composition was acrylic resin: epoxy resin: phenol resin = 1.
9: 4: 3 film weight using a roll coater solids mass fraction 20 mass% of water emulsion type coating liquid by (mass%) was applied so that the per side 8 g / m ^2.
These were dried at a drying temperature of 160 ° C. [0008] A test piece was cut out from the sample thus produced. Then, two test pieces were piled up and 10 kgf / cm ²
The sample was heated to 200 ° C. in a state of being pressurized and held for 60 seconds to prepare a test piece for measuring adhesive strength. The adhesive strength of this test piece was measured using a tensile tester. The results are shown in FIG. In FIG. 1, the amount of oxide is 0.005.
Under the conditions of less than g / m ^{2 and more} than 1.0 g / m ² , the variation in the adhesive strength is about ± 20 kg / cm ² , whereas the amount of oxide is not less than 0.005 g / m ^{2 and} 1.0 g / m ^2.
Under the condition of m ² or less, the variation in the adhesive strength is about ± 10.
kg / cm ² . Furthermore, when comparing the average value of the adhesive strength, the condition subjected to the heat treatment is about 10 kg / cm ² higher than the condition not subjected to the heat treatment (0.001 g / m ^{2 of} oxide) before coating the film. I understood that. As described above, the inventors consider as follows why the adhesive strength of the adhesive film can be stabilized by defining the amount of oxide on the steel sheet surface. When two steel plates with an adhesive layer sandwiched therebetween are separated by an external force, there are roughly two types of separation methods.
One is that the coating itself breaks and peels off, which is called cohesive failure. The other is destruction occurring at the interface between the coating and the steel sheet and peeling off, which is called interfacial destruction. The inventors have focused on the latter, namely, an intermediate that mediates between the steel sheet and the coating, in consideration of suppressing interfacial fracture. The insulating film having an adhesive action is mainly composed of an organic substance. One of the constituent elements is oxygen. On the other hand, oxides present on the steel sheet are Fe
Naturally, oxygen is also included as a constituent element in addition to Si and Si. At this time, the adhesion between the oxide and the steel sheet is generally good. Therefore, if oxygen atoms can be shared between the oxygen in the insulating film and the oxygen in the oxide formed on the steel sheet, interface destruction can be suppressed, and the improvement and stabilization of the adhesive strength can be expected. On the other hand, when the amount of oxide on the surface of the steel sheet exceeds a certain amount, it is considered that there is less room for oxygen in the film to be bonded on the steel sheet, and thus the adhesive strength varies.
The present invention can be applied to any type of non-oriented electrical steel sheet, such as a unidirectional electrical steel sheet and a non-oriented electrical steel sheet, as long as it is an electrical steel sheet manufactured by ordinary rolling and annealing, but is particularly applied to a non-oriented electrical steel sheet for a motor core. The best. Further, the present invention is applicable irrespective of the resin composition of a coating liquid for forming an insulating film exhibiting an adhesive function. For example, when bonding steel sheets to each other by pressing and heating such as phenolic resin and epoxy resin, it can be applied not only to thermosetting resins that cause a curing reaction, but also to heating such as acrylic resins and methacrylic resins. The present invention can also be applied to a thermoplastic resin which does not undergo a curing reaction. As an example, the resin composition, acrylic resin: epoxy resin: phenol resin = 19: 4: 3 solids in (mass%) Weight fraction 2
0 there is mass% of water emulsion type coating liquid. There is no particular limitation on the method of causing the coating liquid to adhere to the steel sheet. For example, a roll coater or a bar coater may be used, or a spray method may be used. 1 g / m ² or more per side 20
g / m ² or less is desirable. When the coating amount can not be obtained a sufficient adhesion strength for difficult to sufficiently cover the entire steel sheet surface as the less than 1 g / m ^2, whereas the pressure and heat is more than 20 g / m ^2, resin oozing from the end face The problem is that the space factor is easily reduced, and the space factor decreases. for that reason,
The coating amount is preferably 1 g / m ² or more and 20 g / m ² or less. Since the optimum drying temperature varies depending on the organic resin used, a temperature at which the adhesive strength is maximized may be selected. In order to remove only the insulating film from the steel sheet on which the insulating film having an adhesive action is formed, the coated steel sheet may be immersed in an appropriate organic solvent to dissolve the film. The organic solvent selected at this time may be selected from those having good solubility depending on the type of the film. Examples include toluene, ethyl acetate, and methyl ethyl ketone, but other solvents may be used. Further, the temperature of the organic solvent may be raised above room temperature to promote dissolution. The oxygen concentration is then measured by chemical analysis. Example 1 First, an electromagnetic steel sheet having a thickness of 0.5 mm, having an oxide of 0.14 g / m ^{2 in} terms of oxygen per side on a steel sheet, I prepared something without things. Then
These resin is an acrylic resin: epoxy resin: phenol resin = 15: 3: 3 solids in (mass%) Ratio 2
0 coating amount mass% of water emulsion type coating liquid using a roll coater was applied so that the per side 6 g / m ^2. These were dried at a drying temperature of 150 ° C. and cooled. A test piece was cut out from the sample thus prepared. Then, the two test pieces were stacked and heated to 200 ° C. under a pressure of 10 kgf / cm ² , and held for 60 seconds to prepare a test piece for measuring adhesive strength. The adhesive strength of this test piece was measured using a tensile tester. Table 1 shows the results
Shown in [Table 1] Comparative Example having no oxide from [0017] Table 1, the average value of the adhesion strength is as low as 165 kg / cm ^2, while the variation in adhesive strength as high as ± 15 kg / cm ^2, oxide content is 0. 14 g / M ² , the average value of the adhesive strength is 1
It is as high as 71 kg / cm ² and the variation in adhesive strength is ± 10 kg / cm ^2.
It is excellent as small as cm ^2. <Example 2> First, an electromagnetic steel sheet having a thickness of 0.35 mm, having an oxide of 0.01 g / m ^{2 in} terms of oxygen per one side on a steel sheet, and an electromagnetic steel sheet having no oxide were prepared. did. Then
These resin is an acrylic resin: epoxy resin: phenol resin = 18: 3: 4 (mass%) per one surface coating weight using a roll coater solids mass fraction 20 mass% of the coating solution at 9g / M ² . These were dried at a drying temperature of 160 ° C. and cooled. A test piece was cut out from the sample thus prepared. Then, two test pieces were stacked and pressed under a pressure of 10 kgf / cm ² for 20 minutes.
A test piece for measuring adhesive strength was prepared by heating to 0 ° C. and holding for 60 seconds. The adhesive strength of this test piece was measured using a tensile tester. Table 2 shows the results. [Table 2] [0019] Table 2 Comparative Example having no oxide from the average value of the adhesion strength is low and 166kg / cm ^2, while the variation in adhesive strength as high as ± 16 kg / cm ^2, oxide content is 0.
In the example of 01 g / m ² , the average value of the adhesive strength was 172 kg.
/ Cm ² and the variation in adhesive strength is as small as ± 11 kg / cm ² and excellent. According to the present invention, it is possible to obtain an electromagnetic steel sheet for a laminated bonded iron core having a stable bonding strength.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a relationship between an oxide amount in terms of an oxygen amount per one surface and an adhesive strength.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-1443963 (JP, A) JP-A-10-261535 (JP, A) JP-A-11-246981 (JP, A) JP-A-9-99 31545 (JP, A) JP-A-9-41043 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02K 1/18

Claims (1)

(57) [Claims] [Claim 1] Predetermined by punching or shearing
After they are shaped, they are laminated and pressurized and heated.
An electromagnetic steel sheet for a laminated bonded iron core in which an insulating film having an adhesive action is formed on the steel sheet to fix the steel sheets to each other to form an iron core, wherein the film contains oxygen as a constituent element.
It is composed of an organic film, and the amount of oxide on the surface of the steel sheet after removing the film is 0.005 g per one side of the steel sheet as an oxygen basis weight.
/ M ² or more and 1.0 g / m ² or less, an electromagnetic steel sheet for laminated adhesive cores having extremely excellent adhesive strength stability.