JPS61174329A - Method for stress relief annealing of grain oriented magnetic sheet - Google Patents

Abstract

PURPOSE:To accelerate stress relief and to decrease iron loss, by giving a specified strain to the titled sheet, next carrying out stress relief annealing. CONSTITUTION:Strain causing 0.05-5.0kg/mm<2> residual stress is given to said sheet having about 3.2% Si content and about 0.225mm thickness, cold rolled at 2 times and finish annealed in coil state. Brush, ball pen, shot blast projection, light draft, etc., by gear roll and dull roll are used for giving strain. It is favorable to give strain so that glass film is not fractured or even if fractured, it is light and the film is hardly damaged in appearance. Next, said sheet is stress relief annealed by continuous annealing or box annealing at about 800 deg.C. By such a method, iron loss of said steel sheet can be decreased.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a strain relief annealing method for grain-oriented electrical steel sheets,
This is to promote strain release and reduce iron loss.

(Prior art) Grain-oriented electrical steel sheets are produced by processing slabs containing 2 to 4% St through processes such as hot rolling, cold rolling, intermediate annealing, decarburization annealing, and final annealing. .

The finished annealed coil is hot straightened and flattened to remove the coil set.

In order to recover the deterioration of magnetic properties caused by the strain introduced at this time, strain relief annealing is performed, and an insulating coating liquid is applied and baked to produce a product. In the other case, after final annealing, the magnesia, etc. that have adhered to the surface are washed with water, and the product is shipped to customers as a coil set product with a glass film formed during final annealing.

In this case, it is generally processed into a wound core by the customer, and this processed product is annealed at a temperature of approximately 800°C to recover from deterioration in magnetic properties due to processing strain, and is used as an iron core product. In either case, it is important to recover the deterioration of magnetic properties due to strain in order to maintain the magnetic properties of the product at a good level.

A grain-oriented electrical steel sheet that is finished annealed in a coiled shape has an oxide layer called a glass coating tightly bonded to the surface of the base steel. On the other hand, strain relief annealing after processing improves magnetic properties by releasing or rearranging and recovering defects such as dislocations introduced as processing strains. This annealing is continuous annealing and is 750
~900℃ for 30 seconds to several minutes or box annealing to 750~90
It is carried out at 0°C for 1 to several hours.

It is important that this annealing sufficiently recovers from the deterioration in magnetic properties caused by strain. For this purpose, for example, JP-A-59-9622
In the method described in Publication No. 7, the tension during annealing is set to 0.3 to 0.7.
The iron loss is reduced by lowering it to kl/ws2.

(Problems to be Solved by the Invention) However, this annealing often does not sufficiently recover the magnetic properties, and the original magnetic properties of the steel sheet may not be utilized. The present inventors investigated a method for promoting recovery from such deterioration of magnetic properties due to strain, and found that by performing preliminary treatment to impart slight strain before strain relief annealing, recovery is quick and sufficient, resulting in a reduction in iron loss. was found to be stable.

(Means for Solving the Problems) The present invention has been made based on this knowledge, and its gist is that when finish annealing grain-oriented electrical steel sheets are annealed to remove strain, brushes, shot blasts, gears, etc. are applied to the steel sheets. 0.05-5.
The present invention provides a strain relief annealing method for a grain-oriented electrical steel sheet, characterized in that a strain that produces a residual stress of 0 #/w is applied, and then strain relief annealing is performed.

The present invention will be explained in detail below.

First, the explanation will be given with reference to experimental data. The present inventors conducted an experiment in order to promote the release of strain during strain relief annealing of a grain-oriented electrical steel sheet and stably reduce iron loss.

As a test material, 3.20% S was finish annealed in the form of a film.
1. A grain-oriented electrical steel sheet having a thickness of 0.225 m and subjected to two-time cold rolling was used. A strain producing a residual stress of 9/m in the range of 0.2 to 3.5' was applied to the entire surface of the steel plate using a steel wire brush at intervals of 10 cm using a galvanic brush. 8 for the steel plate treated in this way and the steel plate as finished annealed for comparison.
Strain relief annealing was performed at 00°C for 120 seconds using continuous annealing.
Next, the iron loss value W17150 was measured. The result is the first
As shown in the figure, it was found that the iron loss value w and 7Ao of the steel plate (1) and (2) strained with a steel wire brush and sol-in were lower than that of the steel plate (3) without strain. That is, The steel plate without strain (3) has an average iron loss value W17150 of 1.
Even though it is 105WA, it is steel plate (i) with strain imparted,
@) U 1.060 x, o7oW/kf,
When strain is applied and then strain relief annealing is performed, the release of strain is promoted and the effect of reducing iron loss is achieved. Note that the glass coating formed by final annealing was not damaged by applying this strain.

The reason why iron loss decreases when strain is applied and then strain relief annealing is applied is that when the dislocations introduced by strain application disappear at grain boundaries, the steel plate surface, etc. when heated in strain relief annealing,
This is thought to be to induce and promote the release of strain.

The degree of strain applied to reduce iron loss is 0.0 in terms of residual stress.
Requires at least 5 kg and 7 m2. On the other hand, as the degree of strain increases, the iron loss does not decrease due to the applied strain, so the upper limit of the residual stress is 5.0i.

In addition to the above-mentioned brush and sol-in methods, methods for applying strain include shot blasting, light rolling with gear rolls and dull rolls, and the like. Further, it is preferable that the applied strain is such that it does not destroy the glass coating, or even if it does, it is so slight that it hardly causes any damage to the coating in terms of appearance.

Regarding the grain-oriented electrical steel sheet subjected to strain relief annealing in the present invention, there is no need to limit its steel composition or manufacturing method up to strain relief annealing. Also, strain relief annealing may be continuous annealing or box annealing. Any annealing method may be used.

(Example) Next, an example will be described.

Example 1 C: 0.078%, Sl: 3.28%, Mn:
A silicon steel slab consisting of Q, 075%, At: 0.028%, S: 0.025cm, N: 0.0080cm, balance iron was hot-rolled, annealed and cold-rolled in the usual manner. .225m
A steel plate of m thickness was used. Then, it was decarburized and annealed, coated with an annealing separator containing MgO as a main component, and finished annealed in a coiled form.

Brushing with a steel wire brush on the steel plate after finish annealing,
Strain was applied by shot blasting and 1% reduction by gear-shaped rolls. Next, these steel plates and
For comparison, 11 steel plates that were finish annealed without being strained were subjected to strain relief annealing at 800° C. for 2 hours, and their magnetic properties were measured. The results are shown in Table 1.

Table 1 Example 2 b■C: 0.055%, Sl: 3.23%, Mn:
A silicon steel slab consisting of 0.065%, S: 0.025%, and the balance iron was hot rolled, annealed, cold rolled, annealed, and cold rolled in a conventional manner to obtain a 0.225% thick steel plate. . Next, decarburization annealing is performed, and an annealing separation agent containing MgO as the main component is applied.
Finish annealed in coil form.

After final annealing, the steel plate with coil sections was subjected to the same strain imparting treatment as in Example 1, and after box annealing at 800° C. for 2 hours, the magnetic properties were measured. The results are shown in Table 2.

As shown in Table 2 and above, according to the present invention, by imparting strain to a grain-oriented electrical steel sheet and then subjecting it to strain relief annealing, the effect of reducing iron loss is achieved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between strain imparting treatment and iron loss during strain relief 9 annealing of a grain-oriented electrical steel sheet.

Claims (1)

[Claims] When performing strain relief annealing on a grain-oriented electrical steel sheet that has been finish annealed, it is recommended to apply strain that produces a residual stress of 0.05 to 5.0 kg/mm^2 to the steel sheet, and then perform strain relief annealing. Distortion relief annealing method for grain-oriented electrical steel sheets.