KR20010060652A - A method for manufacturing semiprocess non grain oriented electrical steel sheet with superior magnetic property - Google Patents

Abstract

PURPOSE: Provided is a method for manufacturing non-oriented electrical steel sheet having superior magnetic property by semi-process where Sn, Cr is added to prevent nitrogen infiltration and also Ti is added to form coarse precipitation by combining O, S with N. CONSTITUTION: The non-oriented electrical steel sheet is manufactured by reheating a steel slab comprising C 0.01wt.% or less, Si 1.5wt.% or less, Mn 0.7wt.% or less, P 0.15wt.% or less, S 0.012wt.% or less, Al 0.5wt.% or less, N 0.005wt.% or less, Sn 0.03-0.3wt.%, Cr 0.05-0.5wt.%, Ti 0.005-0.01wt.%, O 0.006wt.% or less, Cu 0.02wt.% or less, V 0.005wt.% or less, Zr 0.005wt.% or less, a balance of Fe, and other inevitable impurities in the temperature range of 1120 to 1250deg.C; hot rolling the steel slab; coiling hot rolled steel sheet at 600deg.C or higher; annealing the hot rolled steel sheet in the temperature range of 800 to 1050deg.C; pickling; cold rolling; annealing the cold rolled steel sheet in the temperature range of 650 to 900deg.C; and then temper rolling it at a reduction rate of 1.5 to 15%.

Description

Method of manufacturing semi-process non-oriented electrical steel with excellent magnetic field {A METHOD FOR MANUFACTURING SEMIPROCESS NON GRAIN ORIENTED ELECTRICAL 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 electric device such as a motor, a transformer, and more particularly, to a method for manufacturing a semi-process non-oriented electrical steel sheet having low magnetic loss and high magnetic permeability. will be.

It is a material that requires low magnetic loss and high magnetic permeability of non-oriented electrical steel used as iron core in electric equipment such as motor and transformer.

The use of non-oriented electrical steel sheet with low iron loss can reduce electrical energy loss, and high permeability can reduce the amount of iron core or copper wire, which can reduce the size or loss of electrical products.

As a method for reducing iron loss in non-oriented electrical steel sheet, there are a method of increasing the specific resistance of Si and Al, and the method of thinning the plate thickness, but they are all manufactured by a semiprocessor.

Methods for manufacturing non-oriented electrical steel sheet can be largely divided into two types: poly-process method and semi-process. The polyprocess method is a method of hot rolling, pickling, cold rolling and final annealing of the slab. The semiprocess method is a method of annealing the cold rolled plate, skin pass rolling under light pressure, and then shipping the product at demand. Since the semi-process method adds light rolling, residual stress is added, and thus the stress relief annealing should be performed after the steel core is processed into a desired core shape. When manufactured by such a semi-process method, the crystal grains can be large, the magnetism can be improved.

On the other hand, in the electrical steel sheet, in order to reduce the iron loss, it is necessary to grow crystal grains appropriately, Japanese Patent Laid-Open Publication No. Hei 1-42050 as a prior art for this. This technique provides a method of manufacturing in a semi-process, but there is a problem in that the manufacturing cost is excessive because a method of increasing the Mn content is used.

In order to achieve the above object, the present inventors have repeatedly conducted research and experiment, and proposed the present invention based on the results. The present invention prevents the intrusion of N by adding Sn and Cr to grain boundaries, and adds Ti. An object of the present invention is to provide a method for producing a semi-process non-oriented electrical steel sheet having low iron loss and excellent permeability by generating coarse precipitates by combining with O, S and N to clean steel.

In the present invention, C: 0.01% or less, Si: 1.5% or less, Mn: 0.7% or less, P: 0.15% or less, S: 0.012% or less, Al: 0.5% or less, N: 0.005% or less, Sn: 0.03 ~ 0.3%, Cr: 0.05 ~ 0.5%, Ti: 0.005 ~ 0.01%, O: 0.006% or less, Cu: 0.02% or less, V: 0.005% or less, Zr: 0.005% or less, residual Fe and other unavoidable impurities The slabs to be formed are reheated to a temperature of 1120 to 1250 ° C, hot rolled and wound up to a temperature of 600 ° C or higher, and then hot-rolled sheet annealing is carried out at a temperature range of 800 to 1050 ° C, if necessary, or wound at 750 ° C or higher. After the magnetic annealing and pickling, cold rolling, cold-rolled annealing at a temperature of 650 ~ 900 ℃ and skin pass rolling at 1.5 ~ 15% of the excellent magnetic properties of semi-process non-oriented electrical steel sheet It relates to a manufacturing method.

Hereinafter, numerical limitation of the component system which concerns on this invention is demonstrated.

The C is a magnetic aging in the final product, the iron loss may be increased by magnetic aging when used after processing into electrical products, it is preferable to manage less than 0.01% in the slab, 0.003% or less in the final product.

The Si is an element that increases the specific resistance to lower the eddy current loss during iron loss, but in the present invention, it is preferable to add it to 1.5% or less in consideration of the effect of skin pass rolling.

Mn combines with S to form MnS, which is a fine precipitate, but grows crystal grains, so the upper limit thereof is preferably limited to 0.7%. If the content exceeds 0.7%, the degree of magnetic improvement is reduced compared to the amount added.

P is an element that increases specific resistance and forms an advantageous texture for magnetic, and it is preferable to add P below 0.15% in consideration of cold rolling property.

S is advantageously contained as low as possible to form a fine precipitate MnS adversely affect the magnetic properties, it is preferable in the present invention to limit the content to 0.012% or less.

The Al is an element that increases the specific resistance, lowers the eddy current loss and reduces the amount of oxygen in the steel. When the content exceeds 0.5%, the improvement in magnetic field is small compared to the added amount, and the price is limited, so it is limited to 0.5% or less. It is desirable to.

Since N forms fine and long AlN precipitates, it is preferable to suppress N as much as possible. In the present invention, the content is set to 0.005% or less.

Sn is an element that segregates at the grain boundary and suppresses diffusion of N. If the content is less than 0.03%, the effect is less. If the content exceeds 0.3%, the cold rolling property is deteriorated. Therefore, the composition range is set to 0.03 to 0.3%. It is desirable to.

Cr is an element that promotes ferrite formation and combines with N to form nitride. Its effect is only when the content is at least 0.05%, but when the content exceeds 0.5%, the degree of improvement of magnetic properties is small compared to the amount of addition, so the component range is preferably set to 0.05 to 0.5%.

Since the Cu is combined with S in steel to form fine impurities such as CuS, the content of Cu should be as low as possible. In the present invention, the Cu content is preferably limited to 0.02% or less.

Since V is combined with C to form a fine precipitate, the content thereof is preferably limited to 0.005% or less.

Since Zr combines with oxygen to form a fine precipitate, the content of Zr is preferably limited to 0.005% or less so that possible inhibition.

Hereinafter, the manufacturing method of this invention is demonstrated.

The steel slab formed as described above is made of molten steel in steelmaking and then solidified into slabs in a continuous casting process, charged into a heating furnace before hot rolling, and heated to a temperature range of 1120 ° C to 1250 ° C. In order to facilitate hot rolling, the heating temperature is 1120 ° C. or higher, but when the temperature is higher than 1250 ° C., precipitates harmful to magnetism, such as AlN and MnS, may be re-dissolved to precipitate finely after hot rolling. It is preferable to set the range to 1120-1250 degreeC.

Thereafter, the hot rolled hot rolled sheet is wound at a temperature of 600 ° C. or higher for magnetic enhancement, and cooled in a coil state in air.

The wound-rolled hot rolled sheet may be subjected to hot rolled sheet annealing as needed, the temperature is preferably set to 800 ~ 1050 ℃. The reason is that the effect is less when the temperature is less than 800 ℃, the plate shape may worsen when it is higher than 1050 ℃.

Meanwhile, the hot rolled plate may be annealed by using the heat of the wound hot rolled plate itself after being wound at 750 ° C. or higher. This is called self-annealing, and if necessary, may be slowly cooled by putting in a sealed furnace.

Thereafter, pickling and cold rolling are performed, followed by cold rolling annealing, preferably continuous annealing for 30 seconds to 5 minutes at a temperature range of 650 to 900 ° C. If the annealing temperature is lower than 650 ℃ grain growth is insufficient, if higher than 900 ℃ grain growth may be excessive and the magnetic properties may be worse. In addition, the annealing time is also important for recrystallization, if too long, there is a disadvantage that the skin pass rolling is high, if short, grain growth is insufficient, it is preferable to limit to 30 seconds to 5 minutes as described above.

Next, 1.5-15% of skin pass rolling is performed on the annealing plate. If the skin pass rolling is less than 1.5%, the residual stress imposed on the recrystallized grains is small, and the grain growth is insufficient when the heat treatment is demanded. On the other hand, if the skin pass reduction ratio is higher than 15%, the recrystallized grains are nuclei. This is undesirable because fine particles can be formed to form.

In this way, the skin pass-rolled material is shipped with the rolled oil applied or at the demand price after the insulation coating treatment. The insulating coating may be treated with an organic, inorganic, and organic / inorganic composite coating, and may be coated with other insulating coating.

After that, the demand heat treatment is carried out in a temperature range of 700 ~ 850 ℃ in a non-oxidizing atmosphere.

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

(Example)

To prepare a steel slab having the chemical composition of the following Table 1, heated for 2.5 hours at a temperature of 1150 ℃, hot rolling to 2.2m and then wound and cooled as shown in Table 2, and then hot-rolled sheet annealing or hot rolled annealing for 10 minutes After the pickling, cold rolling was performed and the cold rolled sheet was annealed. At this time, cold-rolled sheet annealing was performed for 2 minutes in the atmosphere of 25% hydrogen and 75% nitrogen.

Thereafter, the thickness after the final skin pass rolling was 0.47 mm. The skin pass rolled material was 760 ° C. for 1.5 hours in a non-oxidation atmosphere, and then cooled by annealing to remove stress.

Then, the magnetic properties were measured and the results are shown in Table 2 below.

Steel grade C Si Mn P S Al N Sn Cr Ti O Cu V Zr Inventive Steel a 0.003 0.92 0.25 0.010 0.002 0.26 0.0016 0.11 0.25 0.0051 0.0010 0.005 0.0021 0.0020 Inventive Steel b 0.003 0.95 0.50 0.015 0.002 0.25 0.0017 0.15 0.30 0.0070 0.0009 0.009 0.0009 0.0015 Comparative Steel a 0.003 0.94 1.15 0.015 0.002 0.24 0.0014 0.01 0.03 0.0007 0.0010 0.008 0.0042 0.0009 Comparative Steel b 0.003 0.95 0.25 0.015 0.002 0.24 0.0015 0.15 0.30 0.0003 0.0075 0.008 0.0025 0.0015 Comparative Steel c 0.003 0.96 0.24 0.015 0.002 0.24 0.0019 0.15 0.25 0.0023 0.0040 0.035 0.0003 0.0003 Comparative strength d 0.002 0.95 0.25 0.015 0.002 0.25 0.0018 0.15 0.30 0.0075 0.0045 0.052 0.0065 0.0003

Sample Number Hot rolled sheet winding method Hot Rolled Sheet Winding Temperature (℃) Hot Rolled Annealing Temperature (℃) Cold Rolled Annealing Temperature (℃) Skin pass reduction rate (%) _Iron loss (W / kg, W _15/50 ) Permeability (μ _1.5 ) Steel grade Invention 1 Self-annealing 800 none 750 6 2.90 3850 Inventive Steel a Invention 2 Air cooling 700 950 750 2.92 3800 Invention 3 Air cooling 650 950 750 2.90 3605 Invention 4 Self-annealing 850 none 800 8 2.65 3800 Inventive Steel b Comparative Material 1 Air cooling 600 950 1000 2 3.62 2920 Comparative Material 2 Self-annealing 700 none 600 8 3.33 2600 Comparative Material 3 800 750 6 3.62 2700 Comparative Steel a Comparative Material 4 800 750 3.88 2800 Comparative Steel b Comparative Material 5 800 750 3.98 2670 Comparative Steel c Comparative Material 6 800 750 4.25 2860 Comparative strength d 1) W _15/50 : Loss generated when magnetizing to _1.5 Tesla at 50 Hz 2) μ _1.5 : Permeability induced when magnetizing to _1.5 Tesla at 50 Hz

As shown in Table 2, the invention materials (1), (4) subjected to self-annealing after hot rolling, and the invention materials (2) and (3) subjected to hot rolling annealing after hot rolling were all It can be seen that it has excellent magnetic properties.

The annealing temperature of the cold rolled sheet was too high because the annealing temperature of the comparative material 1 was too low.

Comparative materials (3) to (6) had poor magnetic properties due to component conditions outside the scope of the present invention.

Example 2

By weight C: 0.003%, Si: 1.15%, Mn: 0.25%, P: 0.009%, S: 0.002%, Al: 0.35%, N: 0.0011%, Sn: 0.15%, Cr: 0.35%, Ti: Slab composed of 0.004%, O: 0.002%, Cu: 0.005%, V: 0.001%, Zr: 0.001% is heated to 1130 ° C, hot rolled, hot rolled to a thickness of 2.0 mm, and wound up at a temperature of 850 ° C. After cooling in a closed furnace. After cooling, the hot rolled sheet was cold rolled to a thickness of 0.515 mm, annealed at 750 ° C. for 15 minutes, and then skin pass rolled to 0.47 mm.

The skin pass-rolled material as described above was cut, and subjected to stress relief annealing at 750 ℃ and then to measure the magnetic properties.

As a result, the magnetic loss (W _15/50 ) was 2.66W / kg and magnetic permeability was 3500.

Example 3

By weight C: 0.001%, Si: 0.45%, Mn: 0.45%, P: 0.075%, S: 0.001%, Al: 0.001%, N: 0.0012%, Sn: 0.11%, Cr: 0.33%, Ti: A slab composed of 0.005%, O: 0.001%, Cu: 0.006%, V: 0.0009%, Zr: 0.0008%, balance Fe and other impurities, was heated to 1150 ° C, hot rolled to a thickness of 2.0mm, and 700 ° C temperature. After winding in the furnace, annealing at 1000 ° C. for 5 minutes, pickling, cold rolling, annealing at 800 ° C. for 2 minutes, and skin pass rolling at a thickness of 0.475 mm. The magnetic properties after stress relief annealing at 100% nitrogen for 2 hours at 790 ° C were investigated. The magnetic properties were iron loss (W _15/50 ) of 3.52W / kg and permeability of 5500. The grain size after heat treatment was 105 μm.

As described above, the present invention has the effect of producing a non-oriented electrical steel sheet having low iron loss and high permeability by adjusting the steel component by adding Sn, Cr, Ti, and appropriately controlling the coiling temperature and annealing conditions. will be.

Claims (3)

By weight% C: 0.01% or less, Si: 1.5% or less, Mn: 0.7% or less, P: 0.15% or less, S: 0.012% or less, Al: 0.5% or less, N: 0.005% or less, Sn: 0.03 to 0.3 %, Cr: 0.05 ~ 0.5%, Ti: 0.005 ~ 0.01%, O: 0.006% or less, Cu: 0.02% or less, V: 0.005% or less, Zr: 0.005% or less, remainder Fe and other inevitable impurities Is reheated to a temperature of 1120 ~ 1250 ℃, hot rolled, wound up to a temperature above 600 ℃, pickled, cold rolled and cold-annealed at a temperature of 650 ~ 900 ℃, and skin pass at 1.5 ~ 15%. Method for producing a semi-process non-oriented electrical steel sheet having excellent magnetic properties, characterized in that rolling The method according to claim 1, further comprising the step of annealing the hot rolled sheet at a temperature in the range of 800 to 1050 ° C after winding the hot rolled sheet. By weight% C: 0.01% or less, Si: 1.5% or less, Mn: 0.7% or less, P: 0.15% or less, S: 0.012% or less, Al: 0.5% or less, N: 0.005% or less, Sn: 0.03 to 0.3 %, Cr: 0.05 ~ 0.5%, Ti: 0.005 ~ 0.01%, O: 0.006% or less, Cu: 0.02% or less, V: 0.005% or less, Zr: 0.005% or less, remainder Fe and other inevitable impurities Is reheated to a temperature of 1120 ~ 1250 ° C, hot rolled, and then wound up to a temperature of 750 ° C or higher, followed by self-annealing, pickling, cold rolling, and annealing of the cold rolled plate at a temperature range of 650 ° C to 900 ° C. Method for producing a semi-process non-oriented electrical steel with excellent magnetic properties, characterized in that the skin pass rolling in%