JPH0611338A - Weldability evaluation method for electrical steel sheets for laminated cores - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the reliability in laminated welding by accurately evaluating gas escape properties, that is, weldability, during TIG welding of laminated electrical steel sheets. [Structure] An amplitude probability density distribution curve is obtained from a sectional curve of the surface of an electromagnetic steel sheet, and the welding of the steel sheet is performed by using the volume of a valley below a plane passing through a peak of the obtained amplitude probability density distribution curve and parallel to the plate surface as an index. Evaluate sex.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating the weldability of electromagnetic steel sheets for laminated iron cores, and in particular, by accurately grasping the surface condition of the steel sheets, the weldability during the laminated welding of the steel sheets, that is, the escape of generated gas It tries to evaluate sex.

[0002]

2. Description of the Related Art In TIG welding of laminated electromagnetic steel sheets without deteriorating the space factor and magnetic properties, the surface properties of the steel sheets have a great influence. Therefore, various steel sheet surface evaluation methods have been conventionally developed. (For example, Japanese Patent Publication No. 49-6744,
JP-A-54-134043). However, each of the above techniques is a method of evaluating only the amplitude level of the steel plate surface such as the center line average roughness Ra and the maximum height Rmax. On the other hand, we could not obtain valid results. That is, in the electromagnetic steel sheet for laminated iron core, there is a trade-off between securing the space factor as the iron core and improving the air permeability as well, and in order to meet these requirements, the surface shape must be subtly modified. ing. However, comparing the surface properties of steel sheets with different air permeability with the conventional evaluation index,
Often there were cases where no clear difference was observed.

[0003]

As described above, as the surface texture evaluation regarding gas escape between steel plates during welding,
There is a problem in the conventional method that evaluates only the amplitude level. The present invention advantageously solves the above problems, and an object of the present invention is to propose a steel plate weldability evaluation method capable of accurately grasping gas escape properties during TIG welding of laminated electromagnetic steel plates.

[0004]

Means for Solving the Problems Now, the inventors have found that the surface texture having both the space factor and the air permeability has a correlation with the shape and size of the gap. The evaluation method was repeatedly examined. As a result, it was found that the intended purpose can be advantageously achieved by using the volume evaluation technique of the steel sheet surface. The present invention is based on the above findings.

That is, according to the present invention, an amplitude probability density distribution curve is obtained from a sectional curve of a surface of a magnetic steel sheet for laminated iron cores, and a valley below a plane passing through a peak of the obtained amplitude probability density distribution curve and parallel to the plate surface is obtained. A weldability evaluation method for electromagnetic steel sheets for laminated cores, characterized in that the weldability of the steel sheet is evaluated using the volume as an index.

[0006]

In the present invention, first, the surface texture of the electromagnetic steel sheet is measured by a contact type or non-contact type roughness meter to extract a sectional curve.
This measurement was performed by performing parallel line scanning on a certain area.
The dimensional information is collected (see FIG. 1 (a)). Next, an amplitude probability density distribution curve as shown in FIG. 1B is obtained from this sectional curve. Here, the amplitude probability density distribution curve is a graph showing the probability that the extraction curve becomes equal to the cutting level when the cutting level from the highest peak to the lowest valley is taken in the extracted sectional curve. For example, as shown in FIG. 2A, when the measurement length is L and the number of Z-axis divisions is 20, when the amplitude probability density is obtained at a predetermined sampling pitch, it becomes as shown in FIG. . Then, the average peak position of the amplitude probability density distribution curve is obtained, and the volume of the valley below the plane passing through this peak position and parallel to the plate surface is calculated from the three-dimensional information. In other words, the volume of the valley obtained by cutting on the horizontal plane passing through the peak position is obtained, and the weldability, that is, the air permeability at the time of welding is evaluated by this volume value.

[0007]

EXAMPLES The present invention will be specifically described below based on examples. Si: 0.35%, thickness: 0.5 mm, 4 types of electrical steel sheets with the same manufacturing method except for the final finishing treatment were treated with an organic insulating coating (hereinafter simply referred to as Al coating),
It was punched into a donut shape with an inner diameter of 120 mm and an outer diameter of 400 mm. Then, after laminating, while pressing at 100 kgf / cm ² , TIG welding was performed to form a bead having a width of 5 mm with respect to the laminating end face in a direction perpendicular to the plate surface. The welding results are shown in Table 1. As is clear from the table, the results were good except that Sample C had a defect.

[0008]

[Table 1]

Now, for each sample, measurement area: 1.9 mm
Scan a contact type 3D surface roughness meter against × 1.0 mm and
Three-dimensional surface shape data was collected. From the obtained three-dimensional data, the amplitude probability density distribution curve and the surface roughness were obtained, and the frequency of the cross section curve was analyzed. The obtained results are shown in Table 1 and FIGS.

As is clear from the table and FIG. 3, the surface roughness levels of Samples A and B are larger than those of Samples C and D, and if the roughness level of Samples A and B is high, weldability is improved. It is considered that the air permeability becomes a problem in the roughness of the samples C and D levels. Therefore, when the samples C and D were compared, a clear difference was found in the volume V under the peak obtained from the amplitude probability density distribution curve.

This phenomenon is considered to be due to the following mechanism. That is, as shown in FIG. 1 above, the peak position is the height where the surface is most located, and when pressure is applied by stacking, the part above the peak position is almost crushed and loses its volume. A void remains only below the position. Therefore, the passage of gas generated during welding is located below this peak position, and it is considered that if this volume is large, the air permeability will be high.

[0012] The investigation was also conducted by frequency analysis, which is a useful means for investigating the characteristics of the surface shape. That is, FIG.
In the frequency distribution curve obtained by Fourier-transforming the cross-section curve as shown in, the component in the specific wavelength range (PS sum:
The sum of power spectra) was calculated and compared with the weldability, but no clear correlation was observed. The reason for this is that the frequency analysis originally looks at the length of the period of the peaks and valleys, so it is considered that it is not directly linked to the evaluation of the effective volume of the valleys.

As is clear from the results shown in Table 1, the steel type C, which has poor weldability, has a low valley volume of 0.244 mm ³ , while the steel types A and B which have good weldability.
For both and D, the volume of the valley is 0.608, 0.720, 0.478
mm ³ is remarkably high, and therefore the weldability can be effectively evaluated by the volume of the valley.

[0014]

As described above, according to the present invention, the weldability of the electromagnetic steel sheet for laminated core can be evaluated more accurately than before, and the reliability in such laminated welding can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a graph showing a sectional curve and an amplitude probability density distribution curve on a surface of an electromagnetic steel sheet.

FIG. 2 is a diagram showing a procedure for obtaining an amplitude probability density distribution curve from a sectional curve of a surface of an electromagnetic steel sheet.

FIG. 3 is a comparison diagram of three-dimensional surface roughness parameters of each steel type.

FIG. 4 is a graph showing a comparison of power spectrum sums in specific wavelength regions.

FIG. 5 is an explanatory diagram of a calculation procedure of a power spectrum sum.

Claims (1)

[Claims] 1. An amplitude probability density distribution curve is obtained from a sectional curve of a surface of an electromagnetic steel sheet for a laminated iron core, and a volume of a valley below a plane passing through a peak of the obtained amplitude probability density distribution curve and parallel to a plate surface is used as an index. As a method for evaluating the weldability of a magnetic steel sheet for laminated core, the weldability of the steel sheet is evaluated.