JPH0717958B2 - Method of manufacturing ultra-thin high magnetic flux density grain-oriented electrical steel sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an ultrathin unidirectional electrical steel sheet having a high magnetic flux density, which is made of a thin slab containing 2.5 to 4.5% Si.

(Prior Art) A unidirectional electrical steel sheet is used as an iron core material for electric equipment such as a transformer, and must have good magnetic excitation characteristics and iron loss characteristics. Moreover, in recent years, the market demand for low iron loss materials with particularly low energy loss has been increasing.

It is generally well known to reduce the plate thickness as a method for improving iron loss, but it was industrially difficult. In other words, when thinning by chemical polishing, the yield will decrease significantly,
When thinning by cold rolling, there was a problem that secondary recrystallization became difficult.

Recently, the following proposals have been made as methods for reducing the plate thickness. That is, JP-A-59-126722 and JP-A-61-79721 disclose methods of performing cold rolling twice after hot rolling in order to stabilize secondary recrystallization of thin products. Was done. However, this method requires high cost because it requires cold rolling twice. Further, in JP-A-61-217526 and JP-A-61-238916, CBS rolling (Contact-Bend-Stretch rolling) is applied at the time of cold rolling after hot rolling to improve the rolling texture and improve the sheet thickness. Stable even at 0.18 mm or less 2
A method of obtaining secondary recrystallization has been disclosed. But even in this case,
The cost is high because a special rolling mill is required. In addition,
In JP-A 61-238939, as a method for obtaining stable secondary recrystallization even when the plate thickness is 0.15 mm or less, a direct cooling ribbon is formed by a quenching method, and then a final cold rolling reduction ratio is in a range of 55 to 80%. The method of performing one or more cold rollings was disclosed. However, in this case, it is difficult to obtain a high magnetic flux density because the rolling reduction of the final cold rolling is low.

(Problems to be Solved by the Invention) An object of the present invention is to produce an ultrathin unidirectional electrical steel sheet having a sheet thickness of 0.15 mm or less, which is extremely difficult and costly to manufacture, as described above, at a low cost and with extremely high magnetic properties. It is to provide a method of manufacturing the excellent one.

(Means for Solving the Problems) As a result of repeated studies to solve the above problems, the inventors have found that the cold rolling reduction rate is 90% after the molten steel of the electromagnetic steel is made into a thin cast piece by the rapid solidification method. The present invention has been completed by finding that secondary cold recrystallization having a very high Goss degree of integration can be obtained by performing a single cold rolling that exceeds the above level. According to the present invention, not only excellent magnetic properties can be obtained, but also a low cost unidirectional electrical steel sheet can be provided by omitting hot rolling and adopting the single cold rolling method.

The gist of the present invention is to obtain a thin slab by continuously rapidly solidifying a volume steel of an electromagnetic steel containing Si: 2.5 to 4.5%, and the thin slab has a cold rolling reduction of more than 90%. It is a method for producing an ultra-thin high magnetic flux density grain-oriented electrical steel sheet, which is characterized by performing cold rolling once to obtain a final product sheet thickness of 150 μm or less.

The present invention will be described in detail below.

In the conventional method of hot rolling a slab, there is a restriction on the lower limit of the plate thickness due to the problem of the plate temperature lowering that causes the deterioration of the inhibitor due to rolling power and excessive precipitation. However, in order to reduce the plate thickness of the final product having a high magnetic flux density to 150 μm or less by performing ordinary cold rolling by this method, the cold rolling method must be adopted twice so that the rolling ratio does not become too high. By the way, in the case of ordinary hot-rolled sheet, if the final cold rolling reduction exceeds 90%, the Goss nuclei in the sharp are reduced and the magnetic flux density is significantly reduced. However, in the rapid solidification method, a thin material can be easily obtained as compared with the hot rolled sheet. So using this method,
It is possible to manufacture ultra-thin products with a high magnetic flux density of 150 μm or less by one cold rolling, which was impossible in the past. Moreover, the present inventors have found a method for producing an ultrathin grain-oriented electrical steel sheet having an extremely high magnetic flux density by setting the cold rolling reduction rate to be more than 90%. This suggests that the thin cast piece obtained by rapid solidification has less Goss nuclei than the conventional hot-rolled sheet, so that there is an appropriate range for obtaining sharp Goss on the higher rolling rate side.

(Operation) As the starting material of the present invention, a thin slab obtained by continuously and rapidly solidifying molten steel, which is a well-known unidirectional electromagnetic steel material component, is used. For this steel composition, Si is 2.5 to improve iron loss.
% Or more is required, but if it is too large, it easily cracks during cold rolling and processing becomes difficult, so the upper limit is made 4.5%. Other components can be applied as long as they are unidirectional electrical steel material components, but AlN, MnS, Cu ₂ S, MnS as inhibitors
If one or more selected from e, Nb (C, N) and the like are contained in the steel in a known range, secondary recrystallization having a high degree of integration can be obtained. Further, at least one kind of Sn and Sb may be added so as to be 1.0% or less for the purpose of strengthening the inhibitor.

Next, this thin slab material is annealed at 950 to 1200 ° C. for 30 seconds to 30 minutes. Next, cold rolling is performed once such that the cold rolling reduction exceeds 90% to obtain a final plate thickness of 150 μm or less. After this, decarburization annealing is performed in a wet hydrogen atmosphere, an annealing separator such as MgO is further applied, and secondary annealing and finishing annealing at 1100 ° C or higher are performed to obtain a pole with a high magnetic flux density. A thin unidirectional electrical steel sheet is manufactured.

Next, examples of the present invention will be described.

Example 1 Using a twin roll, molten steel containing the components shown in Table 1 was used.
3.0 and 1.2 mm thick thin slabs were made, and continuous cast slabs of the same composition were hot-rolled as comparative materials to make 1.2 mm thick hot-rolled sheets. Then, only 3.0 mm thick thin slabs were pre-cold rolled to a plate thickness of 0.5 mm, all were annealed at 1100 ° C. for 5 minutes, pickled, and then cold rolled to a plate thickness of 0.05 mm.

Next, decarburize annealing in wet hydrogen, apply MgO powder, and then
High temperature annealing was performed at 0 ° C for 10 hours in a hydrogen gas atmosphere.

As shown in Table 2, the ultrathin product obtained by the method of the present invention showed very excellent magnetic properties.

Example 2 Molten steel containing the components shown in Table 3 was prepared using twin rolls.
2.4 and 1.5 mm thick thin slabs were made, and a continuous cast slab of the same composition was hot-rolled as a comparative material to make a 2.4 mm thick hot rolled sheet.
Next, only the 2.4 mm thick thin slab and the 2.4 mm thick hot rolled plate were subjected to intermediate cold rolling to a plate thickness of 0.7 mm, all were annealed at 1070 ° C. for 5 minutes, further pickled, and then cold rolled to 0.10. The plate thickness was mm.

Next, decarburize annealing in wet hydrogen, apply MgO powder, and then
High temperature annealing was performed at 0 ° C for 10 hours in a hydrogen gas atmosphere.

As shown in Table 4, the ultrathin product obtained by the method of the present invention exhibited very excellent magnetic properties.

(Effects of the Invention) According to the present invention, not only excellent magnetic properties are obtained, but also an inexpensive unidirectional electrical steel sheet, especially a pole having a thickness of 0.15 mm or less, by omitting hot rolling and adopting a single cold rolling method. A thin high magnetic flux density grain-oriented electrical steel sheet can be manufactured.

Claims (1)

[Claims] 1. A molten steel of an electromagnetic steel containing Si: 2.5 to 4.5% is continuously rapidly solidified to obtain a thin cast piece, and the thin cast piece is subjected to a cold rolling reduction of more than 90% once. A method for producing an ultra-thin high magnetic flux density grain-oriented electrical steel sheet, which comprises cold rolling to obtain a final product sheet thickness of 150 μm or less.