JPH11286725A - Manufacture of non-oriented silicon steel sheet excellent in magnetism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a non-oriented silicon steel sheet having a low iron loss and a high magnetic flux density without the necessity of hot rolled plate annealing. SOLUTION: At the time of hot rolling a steel which has a composition containing, by weight, <=0.05% C, <=0.01 N, <=1.5% Si, <=1.5%, Mn, <=1% Al, and <=0.15% P and also containing, if necessary, B in an amount satisfying B/N <=1.5 and <=0.1% Sn, the resultant steel plate is coiled temporarily at a temp. of 1,000 to 750 deg.C under the condition that the difference between the first coiling temperature and finishing temperature is <=100 deg.C, held for 30 sec to 10 min, uncoiled, and coiled again at a temp. of <=250 deg.C. Subsequently, ordinary acid pickling and cold rolling are performed, and the resultant steel sheet is recrystallization-annealed. By this method, the nonoriented silicon steel sheet excellent in magnetism can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density.

[0002]

2. Description of the Related Art In recent years, in the fields of electric machines, especially rotating machines and medium-sized and small-sized transformers in which non-oriented electrical steel sheets are used as iron core materials, worldwide electric power and energy savings, as well as chlorofluorocarbon gas regulations. Among the movements for global environmental conservation, such as the above, the movement for higher efficiency is rapidly spreading. Therefore, there is an increasing demand for non-oriented electrical steel sheets to have improved properties, that is, high magnetic flux density and low iron loss.

By the way, in non-oriented electrical steel sheets,
Conventionally, as a means of reducing iron loss, a method of increasing the content of Si, Al, or the like has been generally adopted from the viewpoint of reducing eddy current loss due to an increase in electric resistance. However, this method has a problem that the magnetic flux density cannot be reduced.

[0004] In addition to simply increasing the content of Si or Al, etc., as described in JP-A-61-231120, the production of high-purity steel by reducing C, N, S, O, etc. Also, measures in the manufacturing process such as devising a finish annealing cycle as described in Japanese Patent Application Laid-Open No. 57-35626 have been taken. Was not as effective.

[0005] Furthermore, high magnetic flux densities have been achieved by controlling the cold rolling reduction rate before the final annealing to an appropriate range, performing hot rolling annealing, or devising hot rolling conditions. Thus, it was not possible to produce a non-oriented electrical steel sheet having a high iron loss and a low iron loss, and it was impossible to meet the above-mentioned demand for a non-oriented electrical steel sheet.

In recent years, in hot rolling of non-oriented electrical steel sheets, the crystal grain size of the hot-rolled sheet has been controlled from the viewpoint of improving the magnetic flux density of the product. The main focus is on increasing the grain size of the hot rolled sheet, that is, the crystal grain before cold rolling, as much as possible. For example, in Japanese Patent Publication No. 57-52410, the finish hot rolling end temperature is set at 750 ° C. or higher to the intermediate temperature of the two-phase region of α phase and γ phase, and the winding temperature is set at 680 ° C. or higher. There is disclosed a method of increasing the coil winding temperature to coarsen the crystal grains of a hot-rolled sheet. In Japanese Patent Publication No. 58-55210, the finish hot rolling end temperature is set to 75.
A technique is disclosed in which the main purpose is to combine the regulation of the C content and the Al content from 0 ° C. or higher to the intermediate temperature of the two-phase region of the α phase and the γ phase.

Further, as described in JP-A-54-76422 and JP-A-58-136718, self-annealing is carried out by the retained heat of a coil that has been wound at a high temperature, and crystal grains of a hot-rolled sheet are reduced. There is also disclosed a technique for improving the magnetic flux density after finish annealing by measuring coarseness. However, a coil kept at a high temperature for a long time has disadvantages in that crystal grains become too coarse, and the sheet passing property is regarded as a problem at the time of cold rolling and the shape of a product plate is deteriorated.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a manufacturing method for improving electromagnetic characteristics without adding an expensive alloy element.

[0009]

Means for Solving the Problems The present inventors have studied the hot rolling and winding conditions in order to solve the above-mentioned problems, and as a result, by specifying these conditions, the characteristics of the non-oriented electrical steel sheet have been remarkably improved. Found that it can be improved. The principle consists of two elements. One is to form a texture favorable to magnetism on the product sheet without deteriorating the shape of the product sheet by making the crystal grain size of the hot-rolled steel sheet an appropriate size.
The other is to leave solid solution C in the hot rolled sheet or to make it into a fine carbide state, and form a texture favorable for magnetism by cold rolling and annealing.

The present invention is based on these ideas, and the gist of the present invention is as follows: C: 0.05% or less, N: 0.01% or less, Si: 3.5% or less, Mn : 1.5% or less, Al: 1% or less, P: 0.15% or less, and if necessary, any one of B or B / N of 1.5 or less, Sn of 0.3% or less or When hot rolling steel containing both,
The first winding is performed at a temperature difference of 100 ° C. or less from the finishing temperature and at a temperature of 1000 ° C. or less and 750 ° C. or more, and is maintained at a temperature in this temperature range for 30 seconds to 10 minutes. And then rewinding, winding again at a temperature of 250 ° C. or less, followed by ordinary pickling and cold rolling, followed by recrystallization annealing, thereby producing a non-oriented electrical steel sheet excellent in magnetism. It is in.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
First, the conditions for limiting the components will be described. C is preferably as small as possible to reduce iron loss, but in the process of the present invention, the effect of improving iron loss up to 0.05% was confirmed, so the upper limit was made 0.05%. The lower limit is not particularly defined, but the effect of the present invention can be achieved within the range of industrially obtainable C level (5 ppm or more).

Si is added for the purpose of improving iron loss.
The larger the amount, the lower the magnetic flux density, and the lower the advantage of the iron loss obtained by the method of the present invention over the iron loss when manufactured by the conventional method, as well as the cost due to the addition of the alloy, which is the gist of the present invention. The upper limit of the addition of Si is set to 3.5% from the viewpoint of suppressing the height.

It is better that N is small in order to improve iron loss. In the steel of the present invention, the upper limit is set to 0.01%. In particular, Al
To reduce the iron loss by suppressing the precipitation of N, add B to
It is desirable to precipitate N. However, when B / N (weight ratio) is 1.5 or more, excess B deteriorates the magnetism.
Was set to 1.5 in B / N.

If the steel of the present invention has a low content of Si, the steel sheet becomes too soft to prevent the punching operation from becoming difficult.
Is added. Although the addition of P also improves iron loss,
Addition of 0.15% or more deteriorates hot workability and may cause hot rolling cracks or the like. Therefore, the upper limit is set to 0.15%.

Al and Mn may be added because they bring about an improvement in iron loss similarly to Si, but the upper limits are set to 1% and 1.5%, respectively, in order to suppress the high cost of alloy addition. Sn
May also be added because it is an element that improves magnetism, but the upper limit is set to 0.3% in order to suppress the high cost of alloy addition.

Next, the limitation of the process conditions will be described.
The feature of the present invention lies in the process conditions of hot rolling and winding. The basic idea is to set the grain size of the hot-rolled sheet to an appropriate size during the first winding and to lower the temperature of the second winding, thereby controlling the state of C to make it cold-rolled and magnetized after annealing. It is to form a preferable texture.

In the first winding, the difference between the winding temperature and the hot rolling finish temperature is set to 100 ° C. or less, and the winding temperature is set to 1000 ° C.
Hereinafter, the temperature is set to 750 ° C. or more, and the temperature is kept in this temperature range for 30 seconds to 10 minutes. This condition is a limiting condition necessary for obtaining the appropriate hot-rolled sheet grain size. The difference between the winding temperature and the finishing temperature is set to 100 ° C. or less because the higher the finishing temperature, the larger the recrystallized grain size and the smaller the driving force required for grain growth. This is because it is necessary to promote grain growth to about 300 μm. The reason why the upper limit of the first winding temperature and the holding time is limited as described above is to prevent the crystal grain of the hot rolled sheet from becoming too large and deteriorating the shape of the product sheet. Further, the reason why the lower limit of the first winding temperature and the holding time is set is that below this, the particle size of the hot rolled sheet is small and the magnetism of the product sheet is not sufficiently improved.

The reason why the second winding temperature is limited to a temperature of 250 ° C. or less is that at a temperature lower than this, the state of C is cold rolled, which is advantageous for forming a texture that improves the magnetic properties of the product sheet during annealing. It works, that is, to suppress the development of (111) oriented grains.

Such a hot rolling and winding process is performed by a coiler which is relatively close to a finishing mill, and then the RO is rolled.
It is realized by rewinding to T (Run-out Table) and rewinding with a conventional coiler. The present process not only improves the electromagnetic properties of the steel of the present invention, but also avoids the drawback of thickening the scale, which has been a problem during conventional high-temperature winding.

[0020]

EXAMPLES Examples of the present invention will be described together with comparative examples.
In the examples, steels having the component compositions shown in Table 1 were used.
Table 2 shows the experimental conditions and the electromagnetic characteristics of the product plate. Also, the first
The first winding processing time is defined as a time from when the coil is wound up to when it is rewound again and separated from the coil. Other manufacturing conditions are as follows.
The temperature is in the range of 250 ° C., and the thickness of the hot-rolled sheet is 2.0 mm to 3.
0 mm and the thickness of the cold rolled sheet was 0.5 mm. 700 ° C annealing
And 850 ° C. for 90 seconds.

Experiment Nos. 1 to 5 satisfying the scope of the present invention
7,10,13,14,16,18,20,21,2
The materials of 3, 24, 26, 28, 30, 32 are the usual 1
Experiment Nos. 12, 15, 17, 19, 2 manufactured by winding
It exhibited excellent electromagnetic characteristics as compared with the same steel type materials of 2, 25, 27, 29, 31, and 33. Further, the material of Experiment No. 6 where the first winding temperature was low, the material of Experiment No. 8 where the difference between the finishing temperature and the first winding temperature was large, and the material of Experiment No. 9 where the first winding time was short. The material, and the material of Experiment No. 11 in which the second winding temperature was high,
Poor electromagnetic properties.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

According to the present invention, a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density can be manufactured, which contributes to the realization of a motor having a low energy loss, and has a high industrial value.

Claims (3)

[Claims] 1. C: 0.05% or less, N: 0.01% or less, Si: 3.5% or less, Mn: 1.5% or less, Al: 1% or less, P: 0 by weight ratio When hot rolling a steel containing 0.15% or less, the first winding is performed at a temperature difference from the finishing temperature of 100 ° C or less, 1000 ° C or less, 750 ° C or more, and After holding for 30 seconds or more and 10 minutes or less in this temperature range, rewinding, winding again at a temperature of 250 ° C. or less, then performing normal pickling and cold rolling, and then performing recrystallization annealing. A method for manufacturing non-oriented electrical steel sheets with excellent magnetic properties. 2. The composition according to claim 1, wherein B is B /
When hot-rolling a steel containing 1.5 or less with N, the first winding was performed at a temperature difference of 100 ° C. or less from the finishing temperature and 10 ° C.
Winding at a temperature of 00 ° C or less and 750 ° C or more, and holding at this temperature range for 30 seconds or more and 10 minutes or less, rewinding, winding again at a temperature of 250 ° C or less, and then usual pickling A method for producing a non-oriented electrical steel sheet having excellent magnetism, which comprises performing cold rolling and then recrystallization annealing. 3. When hot rolling a steel further containing 0.3% or less of Sn in addition to the component according to claim 1 or 2, the temperature difference between the first winding and the finishing temperature is 100 ° C. or less. And
Winding at a temperature of 1000 ° C. or less, 750 ° C. or more, and holding for 30 seconds or more and 10 minutes or less in this temperature range, rewinding, winding again at a temperature of 250 ° C. or less,
A method for producing a non-oriented electrical steel sheet having excellent magnetism, which comprises performing ordinary pickling, cold rolling, and then recrystallization annealing.