JPS59123719A - Method for annealing iron core for electric apparatus - Google Patents

Abstract

PURPOSE:To obtain an iron core for an electric apparatus having a reduced iron loss and improved magnetic flux density in a weak magnetic field without reducing the magnetic flux density in a strong magnetic field by restricting the time required to heat an iron core at a fixed temp. or above when the iron core is annealed. CONSTITUTION:When an iron core is annealed by induction heating, the temp. T deg.C of the core is adjusted to 720-850 deg.C, and the time the core is heated at a temp. above T deg.C is restricted to -0.37XT deg.C+320min. By the restriction an iron core having superior magnetic characteristics is obtd. without using any special equipment and material. When the upper limit of the temp. of the iron core exceeds 850 deg.C, the interlaminar insulating films are deteriorated, exerting unfavorable influence.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention primarily relates to an annealing method for iron cores used in electrical equipment such as small electric motors and small transformers.

Conventional structure of Shio 11 and its problems Electrical steel sheets are used as the core of AC electrical equipment, but they are often annealed to remove processing distortion and improve magnetic properties. Nowadays, when there is a strong trend towards efficiency, it can be said that annealing of the iron core is indispensable when considering cost.
An indirect heating method is mainly used, in which the entire atmosphere is heated by the combustion heat of gas or oil, and the iron core is further heated.This annealing improves the magnetic properties, although there are some differences depending on the material, and reduces iron loss. , an increase in magnetic flux density occurs at low magnetic fields. In particular, the greatest advantage is the effect of improving the characteristics of electrical equipment by reducing iron loss. However, in conventional annealing,
There are two problems:

First of all, because of indirect heating, the heating efficiency is low and one heating takes a long time (for example, 4 to 6 hours), and the amount of energy consumed is enormous. As a solution to this problem, the annealing method using induction heating is attracting attention as it can greatly shorten the heating time and save energy consumption, and there are also issues that need to be solved in order to obtain iron alloys with excellent magnetic properties. There were many. The second problem is a decrease in magnetic flux density in high magnetic fields due to annealing. The amount of decrease in this magnetic flux density is Bso(5
It is 0.02 to 0.03T at 00°A/m2), which is not large compared to the merit of reducing iron loss, but it is by no means small in view of the strong need for higher efficiency. As a countermeasure against this decrease in magnetic flux density, various methods have been proposed to increase the magnetic flux density of the material in advance, but at present, it is disadvantageous due to high cost. This reduction in magnetic flux density is a major obstacle to achieving this (due to its relationship with product dimensions).

FIG. 1 shows a one-hour cycle pattern of annealing heat in the conventional method. Although there are some differences depending on the structure and capacity of the furnace, the general annealing conditions are heating for 4 to 5 hours.

The total time is 10 to 12 hours, including soaking for 1 to 2 hours at 50°C to 50°C and cooling for 4 to 6 hours. An example of the magnetization characteristics when annealed by this method Q is shown in FIG. Due to annealing, the magnetic flux density increases significantly in a low field (below 10 A/m in Figure 2), but in a high magnetic field (10 A/m or less)
/m (I - H) (d decreases). Generally, it is thought that the decrease in magnetic flux density due to annealing is due to the texture. In other words, annealing causes the growth of crystal grains, and the growth progresses. and (111) planes accumulate from around the two grain boundaries,
This (111) plane does not contain any easy axis of magnetization (oo1). Therefore, it is assumed that the magnetic flux density is particularly low in high magnetic fields. The degree of grain growth during annealing is influenced by the annealing temperature, soaking time, etc. In addition to being determined by the amount of thermal energy received by the treated material, it is also determined by the manufacturing process of the material.In conventional annealing methods, the temperature of 7 vias of each iron core for 1 hour is determined due to productivity and furnace structure. It is impossible to achieve the single-metal control 1, and it is practically impossible to reduce iron loss as much as possible and also prevent a decrease in magnetic flux density.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems.
The present invention provides an annealing method that reduces the magnetic flux density in a high magnetic field, reduces iron loss, and improves the magnetic flux density in a low calm field.

Structure of the Invention The present invention limits the time required for heating and cooling within a certain range when the core temperature is 720°C or higher when annealing the core.
This provides an iron core with excellent magnetic properties.

Description of examples An embodiment of the present invention will be described below with reference to the accompanying drawings.

First, the present invention is based on the fact that in annealing by induction heating, the iron itself generates heat, and the rate of heat generation can be easily controlled by adjusting the input power amount and other factors. By utilizing this advantage, since the degree of crystal grain growth can also be controlled by the uniform control j, it was assumed that it would be possible to suppress the degree of integration of the (111) plane, and this was confirmed through experiments. Figure 3 shows the experimental induction heating annealing cycle pattern.

It was previously confirmed that the growth of crystal grains occurs at temperatures of 720°C or higher within the time range (within 60 minutes) that takes advantage of the induction heating method. Therefore, an example of an experiment conducted on the relationship between time (Tm in Figure 3) and magnetic flux density is shown in Figure 4.80
Although there are some differences depending on the material at temperatures above 0℃, 1
The magnetic flux density decreases after 0 to 16 minutes. In the figure, sample material 1 is one in which the degree of integration of the (100) plane (including the axis of easy magnetization [001]) has been increased in advance, and sample material 2 is a general material (for example, 530). Figure 6 shows that Tm changes with temperature T ('C). From the above results, the time to minimize the decrease in magnetic flux density is expressed as ( 1) It is shown in the formula.

Tm = -0,3 completed・T +320...
... (1) As an example of the present invention, maximum temperature 800°C Tm = 5 minutes, heating 5 minutes, cooling (2oo")
1):) The magnetization characteristics at 45 minutes are shown in FIG. 6, and the iron loss characteristics are shown in FIG. In FIGS. 6 and 7, A shows the characteristics before annealing, B shows the characteristics according to the present invention, and C shows the characteristics according to the conventional method. It's a trench, the test material is JIS.
-C: It is equivalent to S40 of 2554r magnetic steel strip for small electric motors. Commonly used magnetic flux density 1.2~1
．． 7T is superior to a conventional method. In addition, in terms of iron loss characteristics, the conventional method is slightly better at a magnetic flux density of 1.3 to 1.4 T or less, but the present invention is rather lower at magnetic flux densities higher than that. Capacitor motor 2P, 150 with iron core of magnetic properties
A prototype of Wf,z was manufactured and its characteristics were measured. The results are shown in the table below. In the example of the present invention, the magnetic flux density is higher than that of the conventional method, so the excitation current decreases, the -thickness decreases, and furthermore,
Iron JThK is also decreasing. This is because this motor has a relatively high magnetic flux density (1.5 to 1.7 T), so the effect of the present invention is even greater, and this clearly demonstrates the effectiveness of the present invention. .

1QOv50H2 Figure 8 shows the metal structure of the metal shown in Figures 6 and 7. In addition, in Fig. 8, (a) shows the annealing process, and (b) shows the annealing process.
(C) shows the metal structure of the sample material of the present invention, and (C) shows the metal structure of the sample material of the conventional method. As shown in the figure, the crystal grains grow slightly compared to annealing, but the crystal grain size is clearly smaller than that of the conventional method.

As described in detail, according to the present invention, it is possible to supply an iron core with excellent magnetic properties without using special equipment or materials, and it is very advantageous in meeting the need for higher efficiency. still,
The reason why the upper limit of the iron core temperature of the present invention is set as t, (s s o ”C) is because at higher temperatures, the interlayer insulation film on the surface of the electric iron plate will deteriorate significantly, and in some cases, it may peel off. It is.

[Brief explanation of drawings]

Figure 1 is a diagram showing a cycle pattern of annealing by a conventional method, Figure 2 is a diagram showing an example of magnetization characteristics before and after annealing by a conventional method, and Figure 3 is a diagram showing a cycle pattern of an induction heating annealing experiment according to the present invention. Figure 4 is an example of the results of the same experiment, which shows the relationship between the time Tm (minutes) during which the iron core temperature (T'C) is 800°C or higher, and magnetic flux density, and Figure 6 is an example of the results of the same experiment, which shows the relationship between magnetic flux density. Iron core temperature (T″C) and time (Tm
Figure 6 is a diagram showing a comparison of magnetization characteristics between an embodiment of the present invention and a conventional method, and Figure 7 is a diagram showing a comparison of iron loss characteristics between an embodiment of the present invention and a conventional method. Figure - Part <a), (b)
, (Figure c-8 is a micrograph showing the metallographic structure of the sample material used for the same comparison. Name of agent: Patent attorney Toshio Nakao, 1 person @
1 Fig. 2 Fig. H (A/rn) Fig. 5 1■7λi-Seki (minute) M 6 Fig. 7 4 Higashi Kayakubo B CT) '<1

Claims (1)

[Claims] When annealing the iron core by induction heating, the temperature of the iron core is T℃
A method for annealing an iron core for electrical equipment, wherein the temperature is 720'''C or more and 850''C or less, and the time over T'C does not exceed -0.37X T''C, +320 minutes.