KR101059215B1 - Non-oriented electrical steel sheet having excellent magnetic properties and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a non-oriented electrical steel sheet having excellent magnetic properties by lowering iron loss and further improving magnetic flux density by appropriately controlling the content of Nb and P in the impurity elements of the steel sheet material in the production of non-oriented electrical steel sheet, and a method of manufacturing the same. It is about.

In the present invention, by weight%, C: 0.005% or less, Si: 3.5% or less, Mn: 1.0% or less, P: 0.005 to 0.04%, S: 0.005% or less, Al: 0.005 to 1.5%, N: 0.003% or less , Nb: 0.001% or less, O: 0.003% or less, to provide a non-magnetic electrical steel sheet excellent magnetic properties, characterized in that it is composed of the remaining Fe and other unavoidable impurities.

The present invention also reheats the steel slab of the composition to 1050 ~ 1250 ℃ and then hot rolled, wound up to 750 ℃ or less hot rolled sheet annealing or hot rolled sheet annealing, pickling, cold rolling, 800 ~ 1070 It provides a non-oriented electrical steel sheet having excellent magnetic properties, characterized in that the final gas in a dry atmosphere and a mixed gas consisting of more than 3% hydrogen and the remaining nitrogen at a temperature of ℃.

Description

Non-oriented electrical metal sheets with improved magnetic property and method for manufacturing the same

1 is a graph comparing iron loss of steel containing P higher than that of component steels of Table 1 containing P of the present invention;

2 is a magnetic flux density comparison graph of steels containing high P compared to the magnetic flux density of the component steels of Table 1 containing P of the present invention.

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, by lowering the iron loss by appropriately controlling the content of Nb and P in the impurities of the steel sheet material The present invention relates to a non-oriented electrical steel sheet further improved magnetic flux density and a method of manufacturing the same.

Non-oriented electrical steel sheet is an important component constituent material 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 the energy that turns into heat and disappears in the process of energy conversion, and the 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 related electric device can be reduced, so that miniaturization is possible.

In order to manufacture a material with low iron loss and high magnetic flux density, it is necessary to manufacture with clean steel with few impurities.

Japanese Patent Application Laid-Open No. 7-305114 is a conventional technique for improving magnetic properties of clean steel in non-oriented electrical steel sheet. In the prior art, Sn, Cu, Ni, Cr components must be added, and when these elements are added, it is shown that impurities deteriorate magnetic properties. Another prior art is U.S. Patent No. 5,730,810, which is limited to Ti, Zr, etc. among the impurities, there is a problem of increasing the cost by adding a REM element.

The present invention has been studied in this background. In the manufacture of non-oriented electrical steel sheet, by investigating the elements that greatly affect the magnetic properties among the impurities of the steel sheet material, and by controlling the content appropriately to lower the iron loss and magnetic flux density To further improve the non-oriented electrical steel sheet and its manufacturing method, the object is.

In order to achieve the above object, the present invention first investigated the influence of each impurity element in the non-oriented electrical steel sheet material component, and among them, Nb significantly reduced the magnetic properties. It was observed that Nb is contained as an impurity in the manufacture of steel and its magnetic properties are greatly changed by the amount contained. Nb binds to N and C in the steel to form fine nitrides and carbides of NbN and NbC, inhibiting grain growth and encouraging the growth of (222) planes that are harmful to magnetism. Therefore, if possible, reduce the amount of N and C, and reduce the amount of Nb can be a way to lower the iron loss and increase the magnetic flux density. In particular, when Nb is contained below 0.001%, the magnetic flux density may be rapidly increased, and the iron loss may be greatly reduced. In addition, Nb has a property of strongly binding to O in molten steel to form precipitates such as Nb ₂ O ₅ , NbO ₂ , and Nb ₂ O ₃ . In order to reduce the influence of O, it is preferable to add Al as much as possible, and such Al suppresses the formation of fine AlN of N, thereby reducing the influence of N. As described above, in steels with a low Nb content, P must be contained in an amount of 0.005 to 0.04%. If the content of P is too low, less than 0.005%, the effect of Nb should be made lower. If P is added more than 0.04%, grain refinement will occur due to grain boundary growth inhibition.

The present invention is in weight percent, C: greater than 0% and less than 0.005%, Si: greater than 0% and 3.5% or less, Mn: greater than 0% and 1.0% or less, P: 0.005 to 0.04%, S: greater than 0% and 0.005% or less, Al: 0.005 to 1.5%, N: more than 0% and less than 0.003%, Nb: more than 0% and less than 0.001%, O: more than 0% and less than 0.003%, non-directional electricity characterized in that it is composed of the remaining Fe and other unavoidable impurities Provide the steel sheet. In another possible embodiment of the present invention, in weight%, C: greater than 0% and 0.005% or less, Si: greater than 0% and 3.5% or less, Mn: greater than 0% and 1.0% or less, P: 0.005 to 0.04%, S: More than 0% and less than 0.001%, Al: 0.005 to 1.5%, N: more than 0% and less than 0.003%, Nb: more than 0% and less than 0.001%, O: more than 0% and less than 0.003%, remaining Fe and other inevitable impurities It provides a non-oriented electrical steel sheet, characterized in that.

In addition, the present invention is reheated to a slab formed as described above to 1050 ~ 1250 ℃ hot rolled, wound at 750 ℃ or less and then hot rolled sheet annealing or hot rolled sheet annealing, pickling, cold rolling, 800 It provides a non-oriented electrical steel sheet production method comprising the final annealing in a dry gas and a mixed gas consisting of more than 3% hydrogen and the remaining nitrogen at a temperature of ~ 1070 ℃.

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

First, in the manufacture of the non-oriented electrical steel sheet of the present invention, the reason for the content limitation of steel sheet material components will be described.

C: 0.005 wt% or less

The C is known to be preferable for the magnetic properties because the lower the content of C, since C causes magnetic aging in the final product, thereby lowering the magnetic properties during use. Therefore, the amount is reduced in the refining step of the steel, the magnetic content is improved by containing less than 0.005% by weight in the slab. When C is contained in the slab at more than 0.005% by weight, decarbonization annealing should be performed before hot-rolled sheet or final annealing. In this case, water is used. . In the final product, containing less than 0.003% by weight, if possible, can suppress self-aging.

Si: 3.5 wt% or less                     

The Si is a component that decreases the eddy current loss during iron loss by increasing the specific resistance, but is preferably limited to 3.5% by weight since cold rolling is difficult when 3.5% by weight or more is added.

Mn: 1.0 wt% or less

The Mn is a component that not only increases specific resistance but also improves texture, and when added in excess of 1.05% by weight, the magnetic enhancement effect is saturated, so that the content thereof is preferably limited to 1.0% by weight or less.

P: 0.005-0.04 weight%,

P increases resistivity, segregates at grain boundaries, and needs to be added at least 0.005% by weight to see the effect as an element that develops texture. If too much is added, cold rolling becomes difficult, and segregation increases, and magnetic Since this is lowered, it is preferable to limit the content to 0.04% by weight or less. In particular, when P is contained in an amount of 0.005% or less, the effect is only shown when Nb is lowered, so P is added at least 0.005%.

S: 0.005 wt% or less

The S forms a fine precipitate, MnS, which deteriorates the magnetic properties, so it is advantageous to manage the content as low as possible, and when the content exceeds 0.005% by weight, the magnetic properties are very deteriorated, so the content is limited to 0.005% by weight or less. do. In addition, the lower the S, the iron loss is reduced, so the content is preferably less than 0.001% by weight.

Al: 0.005-1.5 wt%

The Al is an effective component for reducing the eddy current loss by increasing the specific resistance, and when added less than 0.005% by weight has no effect of the addition, the addition of more than 1.5% by weight is lower in the degree of magnetic improvement compared to the added amount, cold rolling property is also lowered It is preferable to limit the content to 0.005 to 1.5% by weight. In addition, when Al is added in an amount of 0.2% or more and 1.5% or less, the effect is further increased, the effect of O is greatly reduced, and finely precipitated AlN is formed as coarse AlN precipitate.

N: 0.003 wt% or less

The N forms a fine and long AlN precipitates, so as to contain as little as possible because it combines with Nb to form a fine precipitate of NbN, it is preferable to limit to 0.003% by weight or less.

Nb: 0.001 wt% or less

The Nb inhibits the growth of grains by forming fine NbN precipitates and inhibits the growth of aggregates on the (222) plane, which is detrimental to magnetism, and combines with Nb to form fine precipitates of NbN. It is also necessary to reduce C in the slab as much as possible because Nb combines with C to produce fine carbides. Since Nb is very much influenced by the amount of addition, it is to be contained less than 0.001%, because when added more than 0.001% iron loss is greatly increased, the magnetic flux density is sharply lowered. Nb contains at least 0.005% or more of P, so that the effect is large, and even if P is too large, grain growth is difficult and magnetism is deteriorated.

O: 0.003% by weight or less

The O is preferably made of various oxides to suppress grain growth, so the content thereof is preferably as low as possible, and it is preferable to reduce the amount of oxygen by deoxidation with Al addition or the like. In addition, since the oxide is formed in molten steel by combining with Nb, it is to be contained as little as possible, and in the present invention, it is preferable to limit it 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 slab formed as described above is reheated to 1050-1250 ° C. and then hot rolled. If the reheating temperature is less than 1050 ° C, the rolling load is too great and the steel is not homogenized when rolling, and if it exceeds 1250 ° C, the impurity element is precipitated as a fine precipitate to suppress grain growth of the final product, so the reheating temperature is 1050 ~ It is preferred to limit to 1250 ° C.

The hot rolled sheet prepared as described above is wound up at 750 ° C. or lower, and then cooled in air in a coiled state or in a non-oxidizing atmosphere. When the coiling temperature exceeds 750 ° C., oxidation may increase during cooling, and pickling may deteriorate. Therefore, the coiling temperature is preferably limited to 750 ° C. or less. It is not a problem to lower the coiling temperature, but if the temperature is excessively low, a lot of cooling water may occur.

The wound hot rolled sheet is pickled and cold rolled. It may also be pickled after hot-rolled annealing at 800 ° C. or higher before pickling. When the hot rolled sheet annealing temperature is less than 800 ° C., the annealing effect is small. Therefore, the hot rolled sheet annealing temperature is preferably limited to 900 ° C. or more. 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. Cold rolling can be 0.15 ~ 0.7mm thick. The thinner the lower the iron hand.

The cold rolled steel sheet to the target thickness is annealed at 750 ~ 1070 ℃. If the annealing temperature is less than 750 ℃ grain growth is insufficient, if the temperature exceeds 1070 ℃ excessive surface temperature not only can cause surface defects on the surface of the plate but also worse magnetic properties, the cold rolled sheet annealing temperature is It is preferable to limit to 750-1070 degreeC. In addition, the annealing atmosphere during annealing is performed in a dry atmosphere without humidity in a non-oxidizing atmosphere. If there is moisture, O in the water may be decarburized by bonding with C of the steel, but by bonding with Si and Al of the steel sheet to form an oxide layer inside the steel sheet to lower the magnetic properties, annealing in a dry non-oxidizing atmosphere. If possible, annealing is carried out with a mixed atmosphere of hydrogen and nitrogen used for at least 3% hydrogen. This is because a trace amount of oxygen in the annealing atmosphere penetrates into the steel sheet and causes internal oxidation in a hydrogen atmosphere of 3% or less.

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 1130 ° C., hot rolled to 2.0 mm, and wound up at 660 ° C. The wound hot rolled sheet was annealed at 1000 ° C. for 2 minutes, pickled, and cold rolled to a thickness of 0.5 mm. The cold rolled steel sheet was annealed at 1000 ° C. for 10 minutes in hydrogen, at 90% in nitrogen and in a dew point or less for 1 minute. After the annealing plate was cut magnetic properties were investigated, the results are shown in Table 2 below.

division Ingredient (% by weight) C Si Mn P S Al N Nb O Inventive Steel A 0.0021 2.05 0.19 0.013 0.0023 0.30 0.0012 0.0004 0.0015 Inventive Steel B 0.0022 2.01 0.18 0.013 0.0028 0.31 0.113 0.0007 0.0018 Invention Steel C 0.0020 2.03 0.19 0.012 0.0023 0.29 0.0014 0.0009 0.0017 Comparative Steel A 0.0022 2.03 0.18 0.013 0.0024 0.32 0.0012 0.0012 0.0015 Comparative Steel B 0.0021 2.06 0.19 0.013 0.0025 0.30 0.0013 0.0025 0.0016 Comparative Steel C 0.0023 2.02 0.18 0.012 0.0027 0.32 0.0012 0.0040 0.0015 Comparative Steel D 0.0022 2.00 0.19 0.012 0.0026 0.31 0.0011 0.0052 0.0016 Comparative Steel E 0.0021 2.00 0.19 0.0002 0.0026 0.31 0.0011 0.0009 0.0015

division Steel grade _Iron loss (W _15/50 )
(W / kg) Magnetic flux density (B ₅₀ )
(Tesla) Crystal grain
Size (μm) Invention 1 Inventive Steel A 2.82 1.752 120 Invention 2 Inventive Steel B 2.87 1.750 112 Invention 3 Invention Steel C 2.91 1.745 105 Comparative Material 1 Comparative Steel A 3.32 1.725 86 Comparative Material 2 Comparative Steel B 3.45 1.723 80 Comparative Material 3 Comparative Steel C 3.54 1.720 80 Comparative Material 4 Comparative Steel D 3.65 1.715 75 Comparative Material 5 Comparative Steel E 3.28 1.725 78

-W _15/50 : Loss generated when magnetizing to 1.5 Tesla at 50 Hz

-B ₅₀ : Induced magnetic flux density when a magnetic field is added at 5000 A / m at ₅₀ Hz

As shown in Table 2, the invention materials (1 to 3) manufactured under the manufacturing conditions of the present invention using the invention steel (A to C) 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. It can be seen that Nb has a magnetic flux density that is significantly improved in the range of 0.001% or less and iron loss is low. Since nitride and carbides by Nb are suppressed as much as possible, magnetism is particularly shown to be improved.

In addition, Figure 1 is a result of comparing the iron loss characteristics according to the amount of P in the steel containing P as in the embodiment of the present invention and the steel containing P in the range of 0.07 to 0.072% by weight as in the embodiment, Figure 2 is a magnetic flux This is the result of investigating and comparing the density. In the case where P is larger than the scope of the invention, it was found that the iron loss is higher and the magnetic flux density is lower in the scope of the invention of Nb.

Example 2

The steel slab formed as shown in Table 3 below was reheated to the reheating temperature shown in Table 4 below, hot rolled to 2.3 mm, and wound up at 700 ° C. The wound hot rolled sheet except for Inventive Material 6, the rest were annealed at 900 ℃, pickled and cold rolled to a thickness of 0.5mm. The cold rolled steel sheet was annealed at 1000 ° C. for 2 minutes in an atmosphere as shown in Table 4 below. The annealing plate was investigated after the magnetic properties and grain size, the results are shown in Table 4 below.

division Ingredient (% by weight) C Si Mn P S Al N Nb O Inventive Steel D 0.0022 0.50 0.40 0.021 0.0012 0.25 0.0016 0.0007 0.0017 Inventive Steel E 0.0023 1.12 0.25 0.016 0.0011 0.30 0.0015 0.0006 0.0015 Inventive Steel F 0.0023 1.13 0.74 0.013 0.0009 0.65 0.0014 0.0009 0.0016 Comparative Steel E 0.0022 1.11 0.26 0.014 0.0007 0.31 0.0014 0.0015 0.0015 Comparative Steel F 0.0022 1.12 0.25 0.070 0.0008 0.32 0.0015 0.0014 0.0018 Comparative Steel G 0.0120 1.12 0.27 0.013 0.0007 0.30 0.0014 0.0009 0.0014

division Steel grade sleeve
Reheating temperature
(℃) Cold rolled plate
Annealing Temperature
(℃) Cold rolled plate
Annealing atmosphere Iron loss
(W _15/50 )
(W / kg) Magnetic flux density
(B ₅₀ )
(Tesla) Crystal grain
Size (μm) Invention 4 Inventive Steel D 1200 800 30% hydrogen, 70% nitrogen 5.30 1.795 42 Invention 5 Inventive Steel E 1120 950 5% hydrogen, 95% nitrogen 4.20 1.772 85 Invention 6 Inventive Steel E 1120 950 30% hydrogen, 70% nitrogen 4.12 1.761 78 Invention Material7 Inventive Steel E 1120 1000 50% hydrogen, 50% nitrogen 1.05 1.773 88 Invention Material 8 Inventive Steel F 1150 950 30% hydrogen, 70% nitrogen 3.65 1.765 92 Comparative Material 5 Comparative Steel E 1120 950 30% hydrogen, 70% nitrogen 4.56 1.750 75 Comparative Material 6 Comparative Steel F 1120 950 30% hydrogen, 70% nitrogen 4.66 1.748 70 Comparative Material7 Comparative Steel G 1120 950 30% hydrogen, 70% nitrogen 4.98 1.701 55 Comparative Material 8 Comparative Steel G 1120 950 30% hydrogen, 70% nitrogen, dew point 3.40 1.732 75

-W _15/50 : Loss generated when magnetizing to 1.5 Tesla at 50 Hz

-B ₅₀ : Induced magnetic flux density when a magnetic field is added at 5000 A / m at ₅₀ Hz

Comparative material 5 had a high Nb in the comparative steel, and comparative material 6 had an excessively high P, which deteriorated the magnetism. Comparative material 7 added a dew point to decarburize C, but the magnetic enhancement was limited. Materials other than Comparative Material 7 were annealed in a dry atmosphere.

Example 3

By weight, C: 0.0026%, Si: 3.02%, Mn: 0.16%, P: 0.009%, S: 0.0009%, Al: 1.3%, N: 0014%, Nb: 0.007%, O: 0.0018%, rest A slab composed of Fe and other unavoidable impurities was reheated to 1140 ° C. and then hot rolled to prepare a 1.8 mm thick steel sheet. The steel sheet was wound at 620 ° C. and then annealed at 1000 ° C. for 2 minutes in a non-oxidizing atmosphere. The steel sheet was cold rolled to a thickness of 0.35 mm after pickling. The cold rolled sheet was cold-annealed at 1070 ° C. for 30 seconds in a dry 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 1.97 W / kg, the magnetic flux density (B ₅₀ ) was 1.67 Tesla, and the grain size was 152 μm.

As described above, the present invention provides a non-oriented electrical steel sheet and a method for manufacturing the non-oriented electrical steel sheet by lowering the iron loss and further improving the magnetic flux density by appropriately controlling the content of Nb and P in the sheet material impurity elements in the production of non-oriented electrical steel sheet It is effective.

Claims (5)

By weight%, C: greater than 0% and less than 0.005%, Si: greater than 0% and less than 3.5%, Mn: greater than 0% and less than 1.0%, P: 0.005 to 0.04%, S: greater than 0% and less than 0.005%, Al: 0.005 ~ 1.5%, N: more than 0% and less than 0.003%, Nb: more than 0% and more than 0.001%, O: more than 0% and less than 0.003%, excellent magnetic non-directional electricity, characterized in that it is composed of the remaining Fe and other unavoidable impurities Grater. By weight%, C: greater than 0% and less than 0.005%, Si: greater than 0% and 3.5% or less, Mn: greater than 0% and 1.0% or less, P: 0.005 to 0.04% by weight, S: greater than 0% and less than 0.001%, Al: 0.005 to 1.5%, N: more than 0% and less than 0.003%, Nb: more than 0% and less than 0.001%, O: more than 0% and less than 0.003%, excellent magnetic non-directional, characterized in that it is composed of the remaining Fe and other unavoidable impurities Electrical steel sheet. By weight%, C: greater than 0% and less than 0.005%, Si: greater than 0% and 3.5% or less, Mn: greater than 0% and 1.0% or less, P: 0.005 to 0.04% by weight, S: greater than 0% and less than 0.005%, Al: 0.2-1.5%, N: more than 0% and less than 0.003%, Nb: more than 0% and more than 0.001%, O: more than 0% and less than 0.003%, excellent magnetic non-directional, characterized in that it is composed of the remaining Fe and other unavoidable impurities Electrical steel sheet. By weight%, C: greater than 0% and less than 0.005%, Si: greater than 0% and 3.5% or less, Mn: greater than 0% and 1.0% or less, P: 0.005 to 0.04% by weight, S: greater than 0% and less than 0.001%, Al: 0.2-1.5%, N: more than 0% and less than 0.003%, Nb: more than 0% and more than 0.001%, O: more than 0% and less than 0.003%, excellent magnetic non-directional, characterized in that it is composed of the remaining Fe and other unavoidable impurities Electrical steel sheet. By weight%, C: more than 0% and less than 0.005%, Si: more than 0% and more than 3.5% or less, Mn: more than 0% and more than 1.0%, P: 0.005 to 0.04%, S: more than 0% and less than 0.005%, Al: 0.005 ~ 1.5%, N: more than 0% and less than 0.003%, Nb: more than 0% and more than 0.001%, O: more than 0% and more than 0.003%, reheat the slab composed of remaining Fe and other unavoidable impurities to 1050 ~ 1250 ℃ Hot rolled, wound up to 750 ° C or lower, then omitted or hot rolled annealed, pickled, cold rolled, and finished in a mixed gas atmosphere consisting of at least 3% hydrogen and the remaining nitrogen at a temperature of 800-1070 ° C. Method for producing a non-oriented electrical steel sheet excellent magnetic properties, characterized in that the annealing.

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