KR20020016025A - A method for manufacturing non-grain oriented electric steel sheet with superior magnetic property - Google Patents

Abstract

PURPOSE: A method for manufacturing a non-grain oriented electric steel sheet is provided which improves magnetic characteristics by properly controlling heating temperature and speed during annealing of a cold rolled steel sheet. CONSTITUTION: The method for manufacturing a non-grain oriented electric steel sheet with superior magnetic property comprises the processes of coiling to a temperature of 620 to 800 deg.C a hot rolled steel sheet comprising 0.008 wt.% or less of C, 1.5 wt.% or less of Si, 0.6 wt.% or less of Mn, 0.15 wt.% or less of P, 0.015 wt.% or less of S, 0.005 wt.% or less of Al, 0.0040 wt.% or less of N and a balance of Fe and other inevitable impurities; pickling and cold rolling the coiled hot rolled steel sheet; and annealing the pickled and cold rolled steel sheet at a heating temperature of 700 to 950 deg.C and a heating rate of 8 to 40 deg.C/sec.

Description

Method for manufacturing non-oriented electrical steel sheet having excellent magnetic property {A METHOD FOR MANUFACTURING NON-GRAIN ORIENTED ELECTRIC STEEL SHEET WITH SUPERIOR MAGNETIC PROPERTY}

The present invention relates to a method for manufacturing non-oriented electrical steel sheet used as an iron core of an electronic device such as a motor, a transformer, and more particularly, to a method for manufacturing a non-oriented electrical steel sheet having low magnetic loss and high magnetic flux density. .

Non-oriented electrical steel sheet used as an iron core in electric equipment such as motors and transformers is a component that rotates a motor by converting electrical energy into mechanical energy.In order to reduce energy, magnetic properties are improved by improving magnetic properties. High and iron loss should be low.

In order to improve the magnetic properties, it is necessary to lower impurities in the steel to clean the steel or to add special elements to change the properties of the material. In addition, the manufacturing conditions should change the magnetic properties by changing the rolling and annealing conditions.

For example, Japanese Patent Application Laid-Open No. 63-137122 provides a method of cooling a cooling rate of 10 ° C./sec after annealing a cold rolled sheet. However, in this case, the cooling device needs to be long, which leads to high space and high productivity. There is a problem of deterioration. In addition, Japanese Patent Application Laid-Open No. 61-136626 provides a method of performing a heating rate of 5 ° C./sec or more at the time of final annealing of a cold rolled plate. Therefore, there is a problem that the plate shape may be deteriorated by quenching.

In order to solve the above problems of the prior arts, the present inventors have conducted research and experiments and proposed the present invention based on the results, and the present invention provides a heating temperature and a heating rate during annealing of a cold rolled plate. The present invention provides a method of manufacturing a non-oriented electrical steel sheet with improved magnetic properties by appropriately controlling the above object.

The present invention for achieving the above object, in weight%, C: 0.008% or less, Si: 1.5% or less, Mn: 0.6% or less, P: 0.15% or less, S: 0.015% or less, Al: 0.005% or less, N: 0.0040% or less, hot rolled sheet composed of residual Fe and other unavoidable impurities is wound to a temperature of 620-800 ° C, pickled and cold-rolled, and then heated at annealing temperature of 700-950 ° C and heated at annealing The present invention relates to a method for producing a non-oriented electrical steel sheet excellent in magnetic properties, characterized in that the annealing at a speed of 8 ~ 40 ℃ / sec.

Hereinafter, the present invention will be described in more detail.

The present inventors, while studying a method for lowering the iron loss and increasing the magnetic flux density in the non-oriented electrical steel sheet, by adjusting the component system of the non-oriented electrical steel sheet appropriately, the winding temperature after hot rolling and the heating temperature and heating rate at the time of annealing It has been found that the optimization can form well the (200) and (110) planes, which are favorable to the magnetism. Therefore, in the component system of the non-oriented electrical steel sheet, in order to lower the content of Si, to suppress the growth of grains and to suppress the AlN precipitates that inhibit the texture that is beneficial to magnetism, the contents of Al and N were set low, and the windings were manufactured under the manufacturing conditions. The temperature is in the range of 620 ~ 800 ℃, the annealing heating temperature is set to 700 ~ 950 ℃ and the annealing heating rate is set to 8 ~ 40 ℃ / sec.

Hereinafter, the components and the manufacturing method of the non-oriented electrical steel sheet will be described.

In the non-oriented electrical steel sheet of the present invention, since the C component causes magnetic aging in the final product and degrades the magnetic properties during use, the slab is 0.008% or less in the slab and decarbonized annealing in the final product to 0.005% or less in the final product. It is desirable to manage.

Si is an element that decreases the eddy current loss during iron loss by increasing the specific resistance, and the content thereof is preferably set to 1.5% or less. The reason is that if the content of Si is more than 1.5%, Al must be added for improving the magnetism.

Since Mn combines with S to form MnS which is a fine precipitate, it is preferable to manage it to 0.6% or less.

P is an element which increases the resistivity and forms a texture that is advantageous for magnetic, and is preferably added at 0.15% or less for improving punching workability.

Since S forms a fine precipitate, MnS, which adversely affects the magnetic properties, S is preferably contained as low as possible. Therefore, the content is preferably managed at 0.015% or less.

Al plays a role of lowering eddy current loss by increasing the non-resistance, but in the present invention, it is preferable to manage it to 0.005% or less in order to suppress AlN precipitate formation.

Since N also forms fine and long AlN precipitates, it is desirable to suppress as much as possible and to manage it to 0.004% or less.

It is preferable to wind the hot rolled steel sheet formed as described above at a temperature of 620 to 800 ° C. to prevent coarse growth of precipitates harmful to magnetism such as AlN and MnS. If the coiling temperature is less than 620 ° C., the size of the precipitate inside the hot rolled sheet. If it is small and higher than 800 degreeC, winding operation is difficult and there exists a problem that a hot rolled sheet shape worsens.

The coiled hot rolled coil is air cooled, and then pickled and cold rolled without hot rolled sheet annealing. The cold rolled steel is used as a single cold rolling method to obtain a final product. On the other hand, when C component is high among slab components, decarbonization annealing can be performed.

Then, the cold rolled annealing plate, the heating temperature is preferably set to 700 ~ 950 ℃ and heating rate of 8 ~ 40 ℃ / sec. When the annealing heating temperature is less than 700 ° C., grain growth is insufficient, and if the heating temperature is higher than 950 ° C., the surface temperature is excessively high, which may cause surface defects on the surface of the plate and may cause deterioration of magnetic properties. In addition, if the heating rate during the annealing is less than 8 ℃ / sec, the texture is not well developed, if faster than 40 ℃ / sec plate shape of the product worsens and the texture is poor. Therefore, it is preferable to set the heating rate at the time of annealing at 8 to 40 ° C./sec to advantageously develop the aggregate structure of the annealing plate in magnetic. On the other hand, the annealing atmosphere may be hydrogen, nitrogen or a mixed atmosphere thereof.

The annealing plate is shipped at a demand price after the insulation coating treatment, and the insulation coating may be made of organic, inorganic and organic-inorganic composite coatings, and may be coated with other insulating coatings.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

The components shown in Table 1 below were heated to 1230 ° C. in a steel slab and hot pressed to 2.3 mm in thickness, then wound and cooled according to the conditions in Table 2. The cooled hot rolled plate was pickled and cold rolled to a thickness of 0.50 mm, and then subjected to annealing by applying an annealing temperature and annealing rate shown in Table 2 below. At this time, the annealing atmosphere was atmosphere of 25% hydrogen and 75% nitrogen, which was carried out for 1 minute. Thereafter, the annealing plate was cut and the magnetic properties and the texture strength were investigated, and the results are shown in Table 2 below.

division Component (wt%) C Si Mn P S Al N Inventive Steel 1 0.003 0.41 0.26 0.071 0.0025 0.0021 0.0012 Inventive Steel 2 0.003 0.40 0.25 0.070 0.0030 0.0008 0.0014 Comparative Steel 1 0.003 0.40 0.26 0.070 0.0024 0.0078 0.0014 Comparative Steel 2 0.003 0.41 1.05 0.071 0.0025 0.0020 0.0012

division Steel grade used Manufacture conditions Measurement result Winding temperature (℃) Annealing Temperature Heating rate during annealing (℃ / sec) _Iron loss (W _15/50 ) W / kg Magnetic flux density (B ₅₀ ), Tesla (200) facet tissue strength Invention 1 Inventive Steel 1 650 850 10 5.21 1.80 0.41 Invention 2 700 850 15 5.15 1.81 0.60 Invention 3 740 750 15 5.20 1.79 0.50 Invention 4 740 850 15 5.05 1.81 0.75 Invention 5 Inventive Steel 2 740 800 15 4.78 1.83 0.88 Invention 6 740 800 25 4.72 1.82 0.85 Comparative Material 1 560 800 15 5.62 1.766 0.35 Comparative Material 2 740 800 5 5.60 1.757 0.29 Comparative Material 3 Comparative Steel 1 740 800 15 5.95 1.752 0.25 Comparative Material 4 Comparative Steel 2 740 800 15 5.32 1.745 0.22 1) W _15/50 : Loss generated when magnetizing to 1.5 Tesla at ₅₀ Hz 2) B ₅₀ : Magnetic flux density induced when a magnetic field is added at 5000 A / m at ₅₀ Hz 3) Surface texture strength (Holta equation) Surface strength of (200) face by

As shown in Table 1 and Table 2, the comparative material (1) having a low winding temperature of the hot rolled sheet and the comparative material (2) having a low heating rate during annealing deteriorate magnetic properties and texture strength of the (200) plane. It was. In addition, the comparative material (3) made of the comparative steel (1) in which Al was excessively added, and the comparative material (4) made of the comparative steel (2) in which Mn was excessively added, are also the present invention materials (1) to (6). ) The magnetic properties and the texture strength of the (200) plane were also degraded.

(Example 2)

Slabs composed of C: 0.0025%, Si: 0.60%, Mn: 0.54%, P: 0.082%, S: 0.0072%, Al: 0.0006%, N: 0.0012%, Residual Fe and other unavoidable impurities. After heating to 1150 ℃ hot rolling to make a thickness of 2.5mm. Then, it was wound up and pickled at 700 ° C. and cold rolled to a thickness of 0.5 mm. The cold rolled plate thus prepared was annealed for 30 seconds, the heating temperature was 900 ℃, the heating rate was 30 ℃ / sec. At this time, the annealing atmosphere was a mixed atmosphere of 20% hydrogen and 80% nitrogen. After annealing, the organic and inorganic composite insulating coating was continuously coated and then cut, and the magnetic properties and the texture strength of the (200) plane were measured. As a result, the iron loss (W _15/50 ) was _4.25 W / kg, the magnetic flux density (B ₅₀ ) was 1.81 Tesla, and the texture strength of the (200) plane was 1.25.

As described above, if the non-oriented electrical steel sheet is manufactured by controlling the annealing conditions of the steel component and the cold rolled sheet according to the present invention, the iron loss is low and the magnetic flux density is high, thereby improving the magnetic properties.

Claims (1)

By weight%, C: 0.008% or less, Si: 1.5% or less, Mn: 0.6% or less, P: 0.15% or less, S: 0.015% or less, Al: 0.005% or less, N: 0.0040% or less, balance Fe and others The hot rolled sheet composed of unavoidable impurities is wound at a temperature of 620 to 800 ° C, pickled and cold rolled, and then annealed at an heating temperature of 700 to 950 ° C and a heating rate of 8 to 40 ° C / sec. Method for producing a non-oriented electrical steel sheet excellent magnetic properties, characterized in that.