JPH0711035B2 - Strain relief annealing method for grain-oriented electrical steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a strain relief annealing method for grain-oriented electrical steel sheets,
It is intended to promote strain relief and reduce iron loss.

(Prior Art) A grain-oriented electrical steel sheet is produced by treating a slab containing 2 to 4% of Si by processes such as hot rolling, cold rolling, intermediate annealing, decarburizing annealing, and finish annealing. The coil-like finish annealed coil is hot straightened and flattened to remove the coil set. In order to recover the deterioration of the magnetic properties due to the strain entered at this time, strain relief annealing is performed, and then an insulating coating solution is applied and baked to obtain a product. The present invention provides the above strain relief annealing method for improving magnetic properties. In the other case, after finish annealing, the magnesia attached to the surface is washed with water and shipped to customers as a product with a coil set, which has a glass film formed during finish annealing. In this case, it is generally processed by a customer into a wound core, and the processed core is annealed at a temperature of about 800 ° C. to recover the magnetic characteristic deterioration due to the processing strain, to obtain an iron core product. In either case, it is important to recover the deterioration of the magnetic properties due to strain in order to keep the magnetic properties of the product at a good level.

The coil-shaped finish-annealed grain-oriented electrical steel sheet has a layer of oxide called a glass coating that is tightly bonded to the surface of the base iron. On the other hand, the strain relief annealing after being processed improves the magnetic characteristics by releasing or rearranging and recovering defects such as dislocations that have entered as working strain. This annealing is continuous annealing at 750 to 900 ° C for 30 seconds to several minutes,
Alternatively, it may be box annealed at 750 to 900 ° C for 1 / several hours. It is important to sufficiently recover the deterioration of magnetic properties due to strain by this annealing. For this reason, for example, in the method described in JP-A-59-96227, the tension during annealing is reduced to 0.3 to 0.7 kg / mm ² to reduce the iron loss.

(Problems to be solved by the invention) However, in many cases, the annealing may not sufficiently recover the magnetic properties, and the original magnetic properties of the steel sheet may not be utilized. The present inventors have studied a method of promoting recovery of deterioration of magnetic properties due to such strain, and recovery is fast when a pretreatment for imparting a slight strain before the strain relief annealing is performed, resulting in sufficient reduction of iron loss. Found to be stable.

(Means for Solving Problems) The present invention has been made on the basis of this finding, and the gist thereof is to distort-anneal a finish-annealed grain-oriented electrical steel sheet by brushing, shot blasting, or gearing the steel sheet. 0.05 ~ 5.0kg / mm by roll roll, dull roll, ballpoint pen, etc.
^2. A strain relief annealing method for a grain-oriented electrical steel sheet, which comprises applying a strain causing residual stress and then performing strain relief annealing.

The present invention will be described in detail below.

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

As a test material, a grain-oriented electrical steel sheet having a coil shape and annealed by 3.20% Si and a sheet thickness of 0.225 mm by a double cold rolling method was used. Strain that causes a residual stress of 0.2 to 3.5 kg / mm ² on the steel sheet,
It was applied to the entire surface with a steel wire brush at intervals of 10 mm with a ballpoint pen. For comparison, the steel sheet thus treated and the steel sheet that had been subjected to finish annealing were subjected to strain relief annealing at 800 ° C. for 120 seconds by continuous annealing, and then the _iron loss value W _17/50 was measured. The results are shown in Fig. 1. Steel plates (1) and (2) strained with a steel wire brush and a ballpoint pen are strain-free steel plates.
It was _found that the _iron loss value W _17/50 was lower than that of (3). That is, the steel sheet without distortion (3) had an _iron loss value W _{17/50 of 1.105} on average.
W / kg, whereas the strained steel plates (1) and (2) are 1.060
And 1.070 W / kg, when strain is applied and then strain relief annealing is performed, the release of the strain is promoted and the iron loss is reduced. Note that the glass film formed by finish annealing was not damaged by the application of this strain.

In this way, the reason why iron loss is reduced by applying strain and then strain relief annealing is that the dislocations introduced by the strain application are extinguished on the grain boundaries heated by strain relief annealing, the steel plate surface, etc.,
It is considered to induce and promote the release of distortion.

The degree of strain that reduces iron loss is 0.05 kg residual stress
/ mm ² or more is required. On the other hand, when the degree of strain is too large, the iron loss does not decrease due to the applied strain, so the upper limit of the residual stress is 5.0 kg / mm ² .

In addition to the brush and the ballpoint pen, shot blast projection, light reduction with a gear-shaped roll or a dull roll, or the like is adopted as a method of imparting strain. Further, it is preferable that the strain to be applied does not destroy the glass coating, or is mild even if it is destroyed, and causes almost no damage to the coating in appearance.

Regarding the grain-oriented electrical steel sheet that is strain-relieved and annealed in the present invention, it is not necessary to limit the steel components and the manufacturing method until the strain-relief annealing.

The strain relief annealing may be either continuous annealing or box annealing, and any annealing method can be applied.

(Example) Next, an example will be described.

Example 1 C: 0.078% by weight, Si: 3.28%, Mn: 0.075%, Al: 0.028
%, S: 0.025%, N: 0.0080%, silicon steel slab consisting of balance iron is subjected to hot rolling-annealing-cold rolling 0.225m
It was a steel plate with a thickness of m. Then, decarburization annealing was performed, an annealing separating agent containing MgO as a main component was applied, and finish annealing was performed in a coil shape.

Brushing with steel wire brush on the steel sheet after finish annealing,
Strain was imparted by shot blast projection and 1% reduction by a gear-shaped roll. Then, with these steel plates,
For comparison, strain relief annealing was performed on a steel sheet that had been subjected to finish annealing without applying strain under the condition of 800 ° C. × 2 hours, and the magnetic properties were measured. The results are shown in Table 1.

Example 2 C: 0.055% by weight%, Si: 3.23%, Mn: 0.065%, S: 0.025
%, The silicon steel slab consisting of the balance iron was hot-rolled-annealed-cold-rolled-annealed-cold-rolled into a 0.225 mm thick steel plate by a conventional method. Then, decarburization annealing was performed, an annealing separating agent containing MgO as a main component was applied, and finish annealing was performed in a coil shape.

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

As described above, according to the present invention, by imparting strain to the grain-oriented electrical steel sheet and then performing strain relief annealing, the effect of being able to reduce iron loss is exhibited.

[Brief description of drawings]

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

Claims (1)

[Claims] 1. When strain-relieving annealing of a grain-oriented electrical steel sheet after finish annealing, a strain corresponding to a residual stress of 0.05 to 5.0 kg / mm ² is applied to the steel sheet, and then strain-relieving annealing is performed to obtain iron loss. And a method for strain relief annealing of a grain-oriented electrical steel sheet characterized by improving a magnetic flux density.