KR20040055905A - Non-oriented electrical sheets with excellent magnetism and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A non-oriented magnetic steel sheet is provided which lowers iron loss and improves magnetic flux density by properly controlling contents of C and P, and a method for manufacturing the non-oriented magnetic steel sheet is provided. CONSTITUTION: The non-oriented magnetic steel sheet with excellent magnetism comprises 0.0010 to 0.0025 wt.% of C, 1.0 to 4.5 wt.% of Si, 0.5 wt.% or less of Mn, 0.005 wt.% or less of P, 0.005 wt.% or less of S, 0.2 to 1.5 wt.% of Al, 0.003 wt.% or less of N and a balance of Fe and other inevitable impurities. The method for manufacturing the non-oriented magnetic steel sheet with excellent magnetism comprises the steps of hot rolling the reheated steel slab after reheating a steel slab comprising 0.0010 to 0.0025 wt.% of C, 1.0 to 4.5 wt.% of Si, 0.5 wt.% or less of Mn, 0.005 wt.% or less of P, 0.005 wt.% or less of S, 0.2 to 1.5 wt.% of Al, 0.003 wt.% or less of N and a balance of Fe and other inevitable impurities; annealing the coiled hot rolled steel sheet at a temperature of 900 to 1,100 deg.C after coiling the hot rolled steel sheet at a temperature of 700 deg.C or less; cold rolling the annealed steel sheet by one cycle cold rolling process or two cycle cold rolling process comprising first cold rolling, intermediate annealing and second cold rolling processes; and annealing the cold rolled steel sheet at a temperature of 950 to 1,100 deg.C.

Description

Non-oriented electrical sheets with excellent magnetism and method for manufacturing the same

The present invention relates to a non-oriented electrical steel sheet used as an iron core of an electric device such as a motor, a transformer and a magnetic shield, and more particularly, a non-oriented to lower the iron loss and improve the magnetic flux density by appropriately controlling the content of C and P It relates to an electrical steel sheet and a method of manufacturing the same.

Non-oriented electrical steel sheet is an important component necessary for converting electrical energy into mechanical energy in electrical equipment. In order to save energy, it is necessary to lower magnetic properties, ie, iron loss and increase magnetic flux density. Iron loss refers to energy that turns into heat and disappears in the process of energy conversion, and magnetic flux density is shown as a power generating force. If the iron loss is low, the energy loss can be reduced, and if the magnetic flux density is high, the copper loss of the electric device can be reduced, thereby miniaturizing.

In order to manufacture a material having low iron loss and high magnetic flux density, it is possible to manufacture a clean steel with few impurities or to add a special element. The impurity elements include elements that generate C, S, P, N and other carbides and nitrides.

The prior art for non-oriented electrical steel sheet is Japanese Patent Application Laid-open No. Hei 10-212555. In the above prior art, P is added to improve punchability. Another conventional technique is Japanese Patent Application Laid-open No. Hei 10-18005. In the above prior arts, P is added to improve mechanical properties.

The prior art for improving the magnetic properties of non-oriented electrical steel sheet is Korean Patent Application No. 2000-45785. In the prior art, although P is added to improve the magnetic properties, there is a problem in that the improvement of the magnetic properties is limited because there is no control of other components that may affect the magnetism in the low P range.

The present invention is to solve the above problems of the prior art, to provide a non-oriented electrical steel sheet and a method of manufacturing the same to reduce the iron loss and improve the magnetic flux density by appropriately controlling the content of C and P, the object.

The present invention for achieving the above object by weight, C: 0.0010 ~ 0.0025%, Si: 1.0 ~ 4.5%, Mn: 0.5% or less, P: 0.005% or less, S: 0.005% or less, Al: 0.2 ~ 1.5%, N: 0.003% or less, including the remaining Fe and other inevitable impurities.

In addition, the present invention is reheated to 1100 ~ 1200 ℃ the slab composition as described above and then hot rolled, wound up to 700 ℃ or less and then hot-rolled annealing at 900 ~ 1100 ℃, once cold rolling method or primary After cold rolling, the intermediate annealing and the second cold rolling are cold rolled by two cold rolling methods, and cold rolling is performed at 950-1100 ° C.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In the non-oriented electrical steel sheet containing Si, Mn and Al, elements such as C, P, S and N, which are known as impurity elements, are preferably contained as little as possible in order to improve magnetic properties. However, in order to remove these elements, it becomes possible only by having a large manufacturing cost. Therefore, it is possible to reduce the manufacturing cost if you leave a few of these impurities and find a way to improve the magnetism.

Therefore, as a result of the present inventor's research to obtain the above-mentioned effect, it was confirmed that grain boundaries exist inside the metal material, and there are many impurity elements, particularly P and C, in the grain boundaries. These elements have a characteristic that many segregation occurs, and these elements exist to some extent inside the grain boundary. Therefore, assuming that an appropriate amount of C and P should be present, the results of experiments varying the content of P and C indicate that if P is contained in an amount of 0.005% or less and the C content is properly controlled, iron loss and magnetic flux density can be increased. Confirmed. That is, the grain size can be greatly increased when manufacturing under the conditions of the present invention can lower the iron loss, and the texture having a (200) plane containing a lot of <100> direction, which is easy to magnetize, is well developed to improve the magnetic flux density. It can increase.

First, look at the reasons for limiting the components of the present invention.

C: 0.0010 to 0.0025 wt%

Since the C causes the magnetic aging in the final product to lower the magnetic properties during use, generally, the lower the content of C, the better the magnetic properties. However, the inventors of the present invention confirmed that the magnetic content is lowered even if the content of C is excessively low at 0.0010% by weight or less. In addition, it was confirmed that even if C is too high, the magnetic properties are lowered. That is, if the content of C is less than 0.0010% by weight, the magnetic properties are lowered, and even if the content is more than 0.0025% by weight, the magnetism is lowered, so the content of C is preferably limited to 0.0010 to 0.0025% by weight.

Si: 1.0-4.5 wt%

The Si is a component that decreases the eddy current loss during iron loss by increasing the specific resistance, but when added less than 1.0% by weight is insufficient in securing the magnetism, when added in excess of 4.5% by weight causes a decrease in cold rolling property, the content is 1.0 ~ It is preferable to limit to 4.5% by weight.

Mn: 0.5 wt% or less

The Mn is a component that not only increases specific resistance but also improves texture, and when added in excess of 0.5% by weight, the improvement effect of the texture is saturated. Therefore, the content is preferably limited to 0.5% by weight or less.

P: 0.005 wt% or less

P is a segregation element, and the impurity element C is managed at 0.0010 to 0.0025% by weight, and the magnetic properties can be improved by controlling P to 0.005% by weight or less. When the content of P is added in excess of 0.005% by weight, segregation increases and the magnetism is lowered, so it is preferable to limit the content to 0.005% by weight or less.

S: 0.005 wt% or less

The S is advantageously managed as low as possible to form a fine precipitate MnS to deteriorate the magnetic properties, it is preferable to limit the content to 0.005% by weight or less because the magnetic properties are very degraded when contained in excess of 0.005% by weight. Do.

Al: 0.2-1.5 wt%

The Al is an effective component to decrease the eddy current loss by increasing the specific resistance, when less than 0.2% by weight of fine AlN precipitates in the steel to decrease the grain size, and when added in excess of 1.5% by weight the degree of magnetic improvement compared to the added amount Since it falls, it is preferable to limit the content to 0.2-1.5 weight%.

N: 0.003 wt% or less

Since N forms fine and long AlN precipitates, it should be contained as little as possible, and in the present invention, it is preferably limited to 0.003% by weight or less.

In addition to the above compositions, the remainder is composed of Fe and other unavoidable impurities.

The steel slabs formed as above are reheated to 1100 ~ 1200 ° C. and then hot rolled. If the reheating temperature is less than 1100 ° C, the rolling load during rolling is too large, and if the reheating temperature is higher than 1200 ° C, impurity elements precipitate as fine precipitates to suppress grain growth of the final product, so that the reheating temperature is limited to 1100-1200 ° C. desirable.

The hot rolled sheet prepared as described above is wound at 700 ° C. or lower, and then cooled in air in a coil state or in a non-oxidizing atmosphere. When the coiling temperature exceeds 700 ° C, oxidation may increase during cooling, and pickling may deteriorate. Therefore, the coiling temperature is preferably limited to 700 ° C or lower. Moreover, the magnetic property is so preferable that the said winding temperature is high within the range of this invention.

The wound hot rolled sheet is hot rolled at 900 to 1100 ° C., followed by pickling and cold rolling. When the hot rolled sheet annealing temperature is less than 900 ℃ annealing effect is less, when the temperature exceeds 1100 ℃ plate shape is worse and the annealing effect is lowered, the hot rolled sheet annealing temperature is preferably limited to 900 ℃ ~ 1100 ℃. The cold rolling may be cold rolled by one cold rolling method, or may be used by cold rolling two times after the first cold rolling and annealing after the second cold rolling. If the intermediate annealing temperature is less than 830 ° C. during the annealing, sufficient recrystallization is not performed. If it exceeds 1100 ° C., excessive grain growth may occur, and grain growth may be insufficient during recrystallization annealing after the second cold rolling. It is preferable to limit to 1100 ° C. In the intermediate annealing, the annealing atmosphere is preferably at least 10% hydrogen and a mixed atmosphere of remaining nitrogen. The reason is that when the hydrogen is less than 10%, fine nonmetallic inclusions Al ₂ O ₃ , MnO and FeO are generated directly under the surface of the steel sheet, resulting in deterioration of the assembly structure and deterioration of magnetic properties.

The cold rolled steel sheet is cold-rolled annealing at 950 ~ 1100 ℃. If the annealing temperature is less than 950 ℃ crystal grain growth is insufficient, if the temperature exceeds 1100 ℃ excessively high surface temperature not only can cause surface defects on the surface of the plate but also deteriorate magnetic properties, the cold rolled sheet annealing temperature is It is preferable to limit to 950-1100 degreeC. In addition, the annealing atmosphere at the time of annealing is preferably at least 10% hydrogen, mixed atmosphere of the remaining nitrogen. The reason is that when the hydrogen is less than 10%, fine nonmetallic inclusions Al ₂ O ₃ , MnO and FeO are generated directly under the surface of the steel sheet, resulting in deterioration of the assembly structure and deterioration of magnetic properties.

The annealing plate is shipped at the demand price after the insulation coating. The insulating coating may be treated with an organic, inorganic and organic-inorganic composite coating, and may be treated with other insulating coating.

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

Example 1

The steel slab, as shown in Table 1 below, was reheated to the reheating temperature shown in Table 2 below, hot rolled to 1.9 mm, and wound up at 660 ° C. The wound hot rolled sheet was annealed at 1000 ° C. for 5 minutes, pickled, and cold rolled to a thickness of 0.35 mm. In addition, the secondary cold rolled material was pickled, cold rolled to 0.8 mm, annealed at 930 ° C., and then cold rolled to a final thickness. Thereafter, the cold rolled sheet was annealed at 1030 ° C. for 1 minute in an atmosphere as shown in Table 2 below. The annealing plate was investigated after the magnetic properties and grain size, the results are shown in Table 2 below.

As shown in Table 2, the invention materials (1 to 5) manufactured by the production conditions of the present invention using the invention steel (A ~ B) satisfying the component range of the present invention to the comparative material (1 to 5) It can be seen that the iron loss is low and the magnetic flux density is high in comparison.

Example 2

Slabs composed of C: 0.0022%, Si: 2.8%, Mn: 0.35%, P: 0.001%, S: 0.0008%, Al: 0.80%, N: 0.0012%, remaining Fe and other unavoidable impurities. Reheated to 1150 ℃ and hot rolled to prepare a 1.8mm thick steel sheet. The steel sheet was wound at 680 ° C. and then annealed at 1000 ° C. for 4 minutes. The steel sheet was cold rolled to a thickness of 0.5 mm after pickling. The cold rolled sheet was cold-annealed at 1070 ° C. for 50 seconds in an atmosphere of 70% hydrogen and 30% nitrogen. After annealing, the organic and inorganic composite insulating coating was continuously coated and then cut to investigate magnetic properties and grain size. Among the magnetic properties of the steel sheet, the iron loss (W _15/50 ) was 2.38 W / kg, the magnetic flux density (B ₅₀ ) was 1.68 Tesla, and the grain size was 158 μm.

Example 3

Slabs composed of C: 0.0015%, Si: 3.23%, Mn: 0.25%, P: 0.004%, S: 0.0015%, Al: 1.3%, N: 0.0015%, remaining Fe and other unavoidable impurities. Reheated to 1120 ° C. and then hot rolled to a thickness of 2.0 mm. The hot rolled sheet was wound at 680 ° C. and then annealed at 980 ° C. After pickling, first cold rolling to 1.0mm, followed by intermediate annealing at 950 ° C. for 30 seconds, and second cold rolling to a thickness of 0.20mm. The cold rolled sheet was annealed at 1070 ° C. for 60 seconds. The steel sheet manufactured as described above was cut and the magnetic properties were measured. The iron loss (W _10/400 ) was 11.02 W / kg, and the magnetic flux density (B ₅₀ ) was 1.66 Tesla. In addition, the grain size was 140 μm, and the texture strength of the (200) plane was 1.62.

As described above, the present invention has the effect of providing a non-oriented electrical steel sheet and a method of manufacturing the same by controlling the content of C and P appropriately to lower the iron loss and improve the magnetic flux density.

Claims (4)

By weight%, C: 0.0010-0.0025%, Si: 1.0-4.5%, Mn: 0.5% or less, P: 0.005% or less, S: 0.005% or less, Al: 0.2-1.5%, N: 0.003% or less, remainder Non-oriented electrical steel sheet having excellent magnetic properties, including the composition of Fe and other unavoidable impurities. By weight%, C: 0.0010-0.0025%, Si: 1.0-4.5%, Mn: 0.5% or less, P: 0.005% or less, S: 0.005% or less, Al: 0.2-1.5%, N: 0.003% or less, remainder The slab composed of Fe and other unavoidable impurities is reheated to 1100 ~ 1200 ℃, then hot rolled, wound up to 700 ℃ or lower, then hot rolled annealed at 900 ~ 1100 ℃, and then cold rolled or cold rolled once. After the intermediate annealing and secondary cold rolling, cold rolling by two cold rolling method, cold-rolled annealing at 950 ~ 1100 ℃ manufacturing method of excellent non-oriented electrical steel sheet comprising a. The method of claim 2, wherein the annealing temperature during the intermediate annealing is 830 to 1100 ° C. 4. The method of claim 2, wherein the intermediate annealing and cold rolling annealing atmosphere is a mixed atmosphere in which hydrogen is at least 10% and the remaining nitrogen.