JPS61174334A - Method for subjecting grain-oriented electrical steel sheet to strain relief annealing - Google Patents

Abstract

PURPOSE:To accelerate the relief of a strain in a grain-oriented electrical steel sheet and to reduce the iron loss by applying a prescribed etchant to the convex part of the steel sheet formed during finish annealing and by subjecting the steel sheet to strain relief annealing. CONSTITUTION:A steel sheet obtd. by rolling a silicon steel slab having a prescribed composition is subjected to decarburization annealing, coiling and finish annealing. An etchant is applied to the convex part of the coil set formed during the finish annealing by about 1.5g/m<2>, and the coil set is subjected to strain relief annealing under prescribed conditions. The etchant is selected among phosphoric acid, phosphates, chromic acid, chromates, sulfuric acid, sulfates, hydrochloric acid, chlorides, nitric acid, nitrates, boric acid, borates, etc. By this strain relief annealing method, the iron loss of the grain-oriented electrical steel sheet is reduced, and the magnetic characteristics are improved.

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) A grain-oriented electrical steel sheet is manufactured by treating a slab containing 2 to 4 inches of Sl 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, a glass film formed during final annealing is applied, and the product is shipped to customers as a product with a coil set. 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 form has an oxide layer called a glass coating that is closely 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 to 900
℃ for 30 seconds to several minutes or box annealing at 750 to 900℃
It is held for one 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, in the method described in JP-A-59-96227, the tension during annealing is lowered to 0.3 to 0.7 kg/.2 in order to reduce iron loss.

(Problems to be Solved by the Invention) However, recovery of the magnetic properties is often insufficient in this annealing, and the original magnetic properties of the steel sheet may not be utilized. The present inventors have studied methods to promote recovery from such deterioration of magnetic properties due to strain, and have found that chemical treatment of the surface of the steel sheet before strain relief annealing results in faster recovery, is carried out sufficiently, and the decrease in iron loss is stabilized. I found out what to do.

(Means for Solving the Problems) The present invention has been made based on this knowledge, and its gist is that when strain relief annealing is applied to a coil of a finish annealed grain-oriented electrical steel sheet, the finish annealing of the steel plate is performed. Phosphoric acid, phosphate, chromic acid, chromate on the convex part of the coil set (coiled deformation) that occurred when.

Sulfuric acid, sulfate, hydrochloric acid, chloride, nitric acid, nitrate, boric acid,
A strain relief annealing method for a grain-oriented electrical steel sheet is characterized in that one or more types of etching agents such as borates are applied in the form of an aqueous solution, slurry, or as a single substance, and then strain relief annealing is performed.

The present invention will be explained in detail below.

The inventors of the present invention have conducted various studies to reduce iron loss by promoting strain release in strain relief annealing of grain-oriented electrical steel sheets, and the description will be made with reference to experimental data.

The test material used was a grain-oriented electromagnetic steel plate having a finish annealing of 3.25% S1 and a plate thickness of 0.25 am in the form of a coil. The glass coating is applied to the convex surface of the coil set without flattening the steel plate on which the glass coating is formed.

An aqueous solution of phosphoric acid having a tinging effect and a mixture of phosphoric acid and a phosphate salt was applied 1 to 12 times each. , Strain relief annealing was performed at 800° C. for 2 hours on the steel sheet coated with the etching agent and the steel sheet that had been finish annealed for comparison.
Next, the iron loss value W1V5o was measured. The result is the first
As shown in the figure. As is clear from this figure, steel plate 1 coated with phosphoric acid and steel plate 2 coated with a mixture of phosphoric acid and phosphates have iron loss values W17A compared to steel plate 3 which is not coated.
o becomes significantly lower. In other words, for a steel sheet that has been finish annealed to form a glass coating, without flattening annealing, an etching agent is applied to the convex surface of the coil set, and then annealing is performed to remove strain. It has been found that this has the effect of significantly reducing losses.

Etching agents include phosphoric acid, phosphates, chromic acid, chromates, sulfuric acid, sulfates, hydrochloric acid, and chlorides.

Substances that have an etching effect on the glass coating are used, such as nitric acid, nitrates, boric acid, and borates. Substances other than those mentioned above may be used as long as they produce an etching effect on the glass coating. In the grain-oriented electrical steel sheet to be strain-relief annealed in the present invention, its steel composition, strain-relief annealing There is no need to limit the manufacturing method until the process is completed.

Further, strain relief annealing may be continuous annealing or box annealing, and any annealing method may be applied.

(Example) Next, an example will be described.

Example 1 C in weight%: 0.07.3%, St: 3.25
%, Mn: 0.068, At: 0.030%, S: 0
．． 024%.

A silicon steel slab consisting of N: 0.0079%, balance iron was hot rolled, annealed and cold rolled to 0.225%.
Made of thick steel plate.

After decarburization annealing, an annealing separator containing MgO as a main component was applied, and finish annealing was performed in a coiled state.

After final annealing, the etching agent shown in Table 1 was applied to the convex surface of the coil set produced during final annealing of the steel plate in an amount of 1.5.
It was applied so that the area was 97m2. Next, strain relief annealing is performed at 8
The magnetic properties were measured under the conditions of 00°C x 2 hours. The results are shown in Table 1.

Table 1 Example 2 C: 0.052%, Sl: 3.32%, Mn in weight %
: 0.060 mm, S: 0.024 A silicon steel slab made of residual iron was subjected to hot rolling, cold rolling, annealing, and cold rolling in a conventional manner to obtain a steel plate with a thickness of 0.225 m. After decarburization annealing and applying an annealing separator, final annealing was performed. After final annealing, an etching agent was applied to the convex surface of the coil set of the steel plate in the same manner as in Example 1 so that the amount of etching was IFI/m2. The magnetic properties were measured by applying strain relief annealing at 800° C. for 2 hours. The results are shown in Table 2.

(Effects of the Invention) As described above, according to the strain relief annealing method of the present invention, it is possible to reduce the core loss and improve the magnetic properties of grain-oriented electrical steel sheets, which is of great industrial benefit. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between chemical treatment conditions and iron loss during annealing for strain relief of grain-oriented electrical steel sheets. Figure 1 Chemical treatment conditions

Claims (1)

[Claims] When strain-relieving annealing a grain-oriented electrical steel sheet after finish annealing, phosphoric acid, phosphate, chromic acid, chromate, sulfuric acid, sulfate, A strain relief annealing method for grain-oriented electrical steel sheets, which comprises applying an etching agent such as hydrochloric acid, chloride, nitric acid, nitrate, boric acid, or borate, and then performing strain relief annealing.