KR100479992B1 - A non-oriented steel sheet with excellent magnetic property and a method for producing it - Google Patents

Abstract

The present invention relates to a non-oriented electrical steel sheet used as an iron core of an electric machine and a method for manufacturing the same, the element that does not improve the magnetic properties by adjusting the content of the components is suppressed as much as possible, hot rolling temperature, in the production of non-oriented electrical steel sheet, By controlling the annealing temperature and the atmosphere, to provide a non-oriented electrical steel sheet and a method for manufacturing the steel that can be produced clean steel and improve the magnetic, the purpose is.

The present invention is in the midrange%, C: 0.01% or less, Si: 3.5% or less, Mn: 1.2% or less, Al: 1.3% or less, Sn: 0.03 to 0.3%, Cr: 0.05 to 0.5%, Ti: 0.0005 to 0.009 %, N: 0.005% or less, O: 0.005% or less, and the sum of Cu, Ni, Sb, and Ca elements is 0.2% or less, and P, S, Mo, V, B, Zr, W, As, Mg, Te, Technically, the present invention relates to a non-oriented electrical steel sheet in which the sum of Zn elements is 0.1% or less, and the present invention also reheats the slab formed as described above to 1250 ° C or less, and then hot-rolls the ferrite to 600 ° C or more. Winding in the temperature range, pickling the hot rolled sheet without annealing or annealing, cold rolling to the final thickness, and annealing the cold rolled sheet in an atmosphere of at least 10% hydrogen in the temperature range (Ac ₁ -150 ° C) to Ac ₁ The technical gist of the non-oriented electrical steel sheet having excellent magnetic properties is described.

Description

Non-oriented electrical steel sheet having excellent magnetic properties and manufacturing method thereof {A NON-ORIENTED STEEL SHEET WITH EXCELLENT MAGNETIC PROPERTY AND A METHOD FOR PRODUCING IT}

The present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same used for iron cores of electrical equipment such as motors, transformers, and more particularly, non-oriented electrical steel sheet having excellent magnetic properties to properly control the steel components and the same It relates to a manufacturing method.

Non-oriented electrical steel sheets used as iron cores in electric equipment such as motors and transformers should be magnetized at low magnetic fields, and should be able to obtain high power even with a small amount of electricity. In other words, the efficiency must be high. This requires low iron loss and high magnetic flux density in the non-oriented electrical steel sheet. Iron loss appears as heat when applying a magnetic field, and the magnetic flux density represents the strength and efficiency of the magnetic field delivered to it. It is easy to reduce the copper wire at the core part, and the low amount of copper means less copper loss, which is a major loss in the motor. Losses in the motor include copper loss, iron loss, and mechanical loss. Among them, the ratio of copper loss is high.

Non-oriented electrical steel sheets are generally graded by the amount of silicon, because Si has a high resistivity, which lowers the eddy current loss during iron loss. Al is another element that increases the vortex loss, but has the disadvantage of being expensive. The element which increases such a specific resistance has a disadvantage in making rolling difficult when it is added in excess, and there is a limitation in addition. Therefore, there is a need for a method of suppressing impurity elements and improving materials so as to add alloying elements that increase specific resistance, but improve properties of materials.

In order to solve this problem, Japanese Patent Laid-Open No. Hei 7-268568 suppresses impurity elements as much as possible, but has a disadvantage in that magnetic properties are disadvantageous by adding V. Japanese Patent Laid-Open No. Hei 7-54044 is also disadvantageous in magnetism, such as As and P. Impurity of is added. In addition, these patents have no limit on the amount of O harmful to magnetism.

Accordingly, the present invention controls the elements that do not improve the magnetism by adjusting the content of components, and in the manufacture of non-oriented electrical steel sheet, by controlling the hot rolling temperature, the annealing temperature and the atmosphere, the non-directional electrical which can improve the magnetism To provide a steel sheet and a method of manufacturing the same, the purpose is.

The present invention is in the midrange%, C: 0.01% or less, Si: 3.5% or less, Mn: 1.2% or less, Al: 1.3% or less, Sn: 0.03 to 0.3%, Cr: 0.05 to 0.5%, Ti: 0.0005 to 0.009 %, N: 0.005% or less, O: 0.005% or less, and the sum of Cu, Ni, Sb, and Ca elements is 0.2% or less, and P, S, Mo, V, B, Zr, W, As, Mg, Te, The present invention relates to an electrical steel sheet having excellent magnetic properties, characterized in that the sum of Zn elements is 0.1% or less, and the present invention also hot-rolls after reheating a slab having such a composition to 1250 ° C. or less, and ferrite temperature of 600 ° C. or more. Winding in the range, pickling the hot rolled sheet without annealing or annealing, cold-rolled to the final thickness, and annealing the cold rolled sheet in an atmosphere of at least 10% hydrogen in the temperature range (Ac ₁ -150 ℃) ~ Ac ₁ It relates to a method for producing non-oriented electrical steel sheet having excellent magnetic properties.

The inventors of the present invention have attempted to produce an advantageous non-magnetic electrical steel sheet by suppressing impurity elements as much as possible and producing steel cleanly in order to manufacture non-oriented electrical steel sheets having excellent magnetic properties. Elements that are not harmful due to magnetism and are not added include C, P, S, N, O, Mo, V, B, Zr, W, As, Mg, Te, and Zn. As the furnace, Cu, Ne, Sb, Ca, and the like are harmful to magnetism, but Ti is an element inevitably added to suppress other impurity elements. However, according to the results of analyzing the molten steel before the steelmaking converter, the following results can be obtained. That is, C is 6% or less, P is 0.2% or less, S is 0.3% or less, N is 0.03% or less, O is 0.035 or less, Mo is 0.01% or less, V is 0.1% or less, B is 0.01% or less, Zr Silver is 0.005 or less, W is 0.5% or less, As is 0.01% or less, Mg is 0.01% or less, Te is 0.005% or less, Zn is 0.01% or less, Cu is 0.05% or less, Ni is 0.05% or less, Sb is 0.005% Hereinafter, Ti is 0.5% or less. Therefore, it can be seen that elements not added are also contained in small amounts in the final product analysis. Among the elements, elements that easily react with O, etc., remain low in the steel because they are oxidized and float as inclusions when oxygen is blown in the converter.

Elements which are not removed or added in the present invention are Si, Mn, Al, Sn, Cr, Ti. In addition, other elements are not added, and the trace elements present in the steel are contained in the elements inevitably added from the molten iron of the blast furnace or the impurities of the scrap metal added as the refrigerant during the converter operation. The steel of the present invention composed of such components sets an upper limit of impurities which can be added in molten iron or scrap metal during the converter operation.

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

The above C causes magnetic aging to decrease the magnetic properties during use by the iron core of the electric equipment, so it is 0.01% or less in the slab and 0.003% or less in the final product. If the content is higher than 0.003%, decarbonization annealing is performed, but decarbonization annealing can be performed during cold rolling annealing.

The Si is an element that decreases the eddy current loss during iron loss by increasing the resistivity, but if excessive, plate breakage may occur, so that it is added in the steel of the present invention for less than 3.5% for one-time rolling during cold rolling.

The Al is an element that increases the specific resistance and lowers the eddy current loss. When Al is added more than 1.3%, the Al is limited to 1.3% or less because the degree of improvement in magnetism is small.

The Sn segregates at the grain boundaries to suppress diffusion intrusion of oxygen elements from the steel surface upon annealing, to be densely distributed on the surface of the final product, to inhibit oxidation, and to suppress the texture of the (222) surface which is disadvantageous to magnetism. Play a role. In the present invention, the addition amount is 0.03 to 0.3%, since the effect is less when the amount is 0.03% or less, and the cold rolling property becomes worse when the amount is 0.3% or more.

Cr is an element that reduces N in steel and suppresses corrosion of the surface of the product, and at least 0.05% is added to the effect, and when it exceeds 0.5%, the effect is reduced compared to the added amount, so it is added at 0.05 to 0.5%. .

Ti is an element that easily combines with oxygen and nitrogen to suppress precipitate formation in steel, and the amount of Ti is 0.0005 to 0.009%. The reason is that when 0.009% or more is added, oxygen or nitrogen is excessively combined, and steel cleanliness is lowered, and when it is less than 0.0005%, O and N become high and steel cleanliness decreases.

Since N forms fine and long AlN precipitates to suppress the growth of crystal grains, it is preferable to suppress them as much as possible, and in the present invention, the content is made 0.005% or less.

The O is easily combined with other elements to form an oxide to rise as slag in molten steel, but some uninjured inclusions remain in the steel to remain as fine precipitates, thereby inhibiting the movement of magnetic domains in the final product, thereby lowering the magnetism. In addition, since the non-oxidized oxygen remaining in the slab is combined with other elements during the heat treatment of the subsequent process to lower the magnetism, in the present invention, it is 0.005% or less.

Cu and Ni are elements that are difficult to oxidize, and remain even after scrap metal is not used. Sb and Ca did not degrade the magnetism even when they remained as impurities. However, such a sum of Cu, Ni, Sb, and Ca is preferably contained in an amount of 0.2% or less so as to easily control other impurities.

Other P, S, Mo, V, B, Zr, W, As, Mg, Te, Zn elements can be removed by floating as slag in combination with oxygen or other elements in the converter operation. The sum and the elements contained in the scrap metal, etc., put into cold ingot before the converter work should be 0.1% or less. If it is more than 0.1%, the magnetism is low, so the element added to the cold iron scrap should be suppressed as much as possible. Among these elements, especially P and S remain as a segregation element to the product, and when the magnetic field is applied, the movement of the magnetic domain is suppressed, thereby lowering the magnetism. Therefore, the elements should be contained as low as possible.

Hereinafter, the manufacturing method of this invention is demonstrated.

The steel slab formed as mentioned above is a cold ingot obtained by putting at least 70% or more of the molten iron brought from a furnace, and putting the remaining 30% or less of scrap metal into a converter. Deoxidation and denitrification by Al, Ti, etc. is performed on the molten steel refined in steelmaking, after addition of other elements, solidified into slabs in a continuous casting process, charged into a heating furnace before hot rolling, and then to 1250 ° C or lower. Heat. When reheating to a temperature higher than 1250 ℃ redissolves the harmful particles such as AlN and MnS may be finely precipitated after hot rolling, it is preferable to hot rolling after reheating to a low temperature range.

After hot rolling, the hot rolled sheet is wound in a coil state in air and cooled. In order to improve the magnetic properties can be wound in the temperature range of (Ar ₁₎ of 600 ℃ ~ ferrite station. If the coil is wound as high as possible, fine precipitates generated in the hot rolled sheet may coarse to clean the steel, but if wound in the austenite zone, the temperature may be excessively high to increase oxidation, and the precipitate may be reduced to 600 ° C. to a temperature range of (Ar ₁₎ of the ferrite station it is preferred.

In order to further improve the magnetic properties, the wound-rolled hot rolled sheet may be subjected to hot rolled sheet annealing. Since fine precipitates still remain in the hot rolled sheet, the hot rolled sheet may be annealed for 1 minute or more in a temperature range of 850 to 11250 ° C. in order to further improve magnetic properties. At this time, annealing at less than 850 ° C is less annealing effect, when annealing at a temperature higher than 1150 ° C is bad plate shape, and precipitates can be rather dissolved in the plate, it is limited to the above temperature range. Such hot-rolled sheet annealing is not necessarily performed, and after hot-rolled sheet annealing, cold rolling is performed after pickling. In addition, even if hot-rolled sheet annealing is not performed, it is cold-rolled after pickling.

The annealed hot rolled sheet is continuously rolled and cold rolled to the final product thickness, followed by annealing. Preferably, the annealing temperature is annealed below the Ac ₁ temperature, which is the upper limit of the 100% ferrite phase upon heating given by the steel component. Above this temperature, the austenite phase may appear in the tissue, and thus, the (111) and (211) surfaces, which are aggregates that are disadvantageous to magnetism, may develop. Therefore, the austenite phase should be annealed on the ferrite to prevent grain refinement. In addition, the lower limit temperature at the time of cold annealing should be higher than (Ac ₁ -150 ° C) in order for the grain to grow. Therefore, the annealing temperature should be at least a temperature range higher than (Ac ₁ -150 ° C) and lower than Ac ₁ .

When oxygen enters the surface, an oxide is formed by combining with elements such as Al, Si, Mn, etc. in the material, and therefore, it is preferable to anneal it in a non-oxidizing atmosphere containing at least 10% or more of hydrogen. Annealing time is carried out continuously for 30 second-5 minutes. After that, the annealing plate is shipped at the demand price after the insulation coating treatment.

Hereinafter, the present invention will be described in detail through examples.

Example 1

Steel slabs having the components shown in Table 1 below were prepared through an external refining process after the converter. In Table 1, the A-based element is the sum of elements of Cu, Ni, Sb, and Ca, and the B-based element is the sum of elements of P, S, Mo, V, B, Zr, W, As, Mg, Te, and Zn. Was. The steel made of slabs was heated at 1150 ° C. for 1.5 hours, hot rolled, and then wound at a winding temperature as shown in Table 2 to cool in air. The cooled hot rolled sheet was annealed or annealed without cold annealing under the conditions shown in Table 2, and then annealed under the conditions shown in Table 2 in a reducing atmosphere of 40% hydrogen and 60% nitrogen. Then, after cutting the annealing plate to investigate the magnetic properties and the results are shown in Table 2 below.

Steel grade C Si Mn Al Sn Cr N O Ti A system B series Inventive Steel a 0.003 0.85 0.25 0.22 0.10 0.27 0.0012 0.0021 0.0032 0.072 0.025 Inventive Steel b 0.003 0.87 0.24 0.32 0.09 0.25 0.0018 0.0024 0.0012 0.031 0.009 Comparative Steel a 0.003 0.86 0.25 0.22 0.11 0.22 0.0012 0.0045 0.0003 0.071 0.252 Comparative Steel b 0.003 0.89 0.23 0.31 0.09 0.26 0.0017 0.0023 0.0109 0.230 0.010 Comparative Steel c 0.002 0.85 0.24 0.32 0.10 0.03 0.0041 0.0052 0.0013 0.049 0.121

As shown in Table 1, the comparative steel (a) contains a lot of B-based elements, O was also high, while Ti was low. Comparative steel (b) was excessively high in Ti, overall cleanliness in the steel was low, and A-based elements were also high. Comparative steel (c) had a low Cr component and a high B-based element. On the other hand, invented steels (a) and (b), the components of the slab satisfy the composition of the invention steel.

Sample Number Steel grade Hot Rolled Sheet Winding Temperature (℃) Hot Rolled Annealing Temperature (℃) Ac1 (℃) Cold Rolled Annealing Temperature (℃) _Iron loss (W _15/50 ) W / kg Magnetic flux density (B ₅₀ ) Tesla Invention 1 Inventive Steel a 650 950 972 950 3.49 1.77 Invention 2 Inventive Steel b 800 none 1009 980 3.65 1.74 Invention 3 Inventive Steel b 750 950 1009 960 3.45 1.76 Comparative Material 1 Inventive Steel b 550 950 1009 960 3.72 1.73 Comparative Material 2 Inventive Steel b 600 none 1009 840 4.15 1.72 Comparative Material 3 Comparative Steel a 750 950 975 950 4.24 1.71 Comparative Material 4 Comparative Steel b 750 950 1012 960 3.86 1.73 Comparative Material 5 Comparative Steel c 700 950 1005 960 4.31 1.72 W _15/50 : Loss caused by applying a magnetic field at 1.5 Tesla at 50 Hz B ₅₀ : Magnetic flux density induced when magnetic field is applied at 5000 A / m

As can be seen in Table 2, the comparative material (1) was low in the hot rolled sheet winding temperature appeared low magnetic. The cold-rolled sheet annealing temperature (Ac ₁ -150 ℃) lower than the comparative material 2 was also poor magnetism. Comparative materials (3) to (5) were manufactured under appropriate manufacturing conditions, but were made of comparative steels (a) to (b) to have low magnetic properties. On the other hand, the invention materials were manufactured in the scope of the invention, the magnetic properties were excellent.

Example 2

By weight, C: 0.004%, Si: 2.95%, Mn: 0.16%, Al: 0.82%, Sn: 0.11%, Cr: 0.31%, N: 0.0013%, O: 0.0019%, Ti: 0.0023%, A The system element is Cu: 0.01%, Ni: 0.03%, Sb: 0.009%, Ca: 0.0012%, and the B element is P: 0.008%, S: 0.0015%, Mo: 0.0012%, V: 0.0003%, and B: A slab containing 0.0009%, Zr: 0.0005%, W: 0.0012%, As: 0.001%, Mg: 0.0007%, Te: 0.0008%, Zn: 0.0006%, and the balance of Fe and other impurities is heated to 1150 ° C. After the hot rolled to a thickness of 2.3mm, wound at 720 ℃ temperature, the hot rolled sheet was annealed for 10 minutes at 1100 ℃ and then pickled. The annealed hot rolled sheet was cold rolled to a thickness of 0.5 mm after pickling. The cold rolled sheet was divided into 5% hydrogen and 50% hydrogen in a dry atmosphere, and the remainder was nitrogen, followed by annealing for 2 minutes at 1030 ° C. This steel had only a ferrite phase within the annealing range. After annealing, the coating was continuously coated with an organic-inorganic mixture, followed by cutting to measure magnetic properties. As a result, the material worked with 5% hydrogen during annealing of the cold rolled sheet had an iron loss (W _15/50 ) of 2.65 W / kg and a magnetic flux density (B ₅₀ ) of 1.66 Tesla. Also, the grain size was grown to 120 mu m. In comparison, the material with 50% hydrogen was _2.34 W / kg in iron loss (W _15/50 ) and the magnetic flux density (B ₅₀ ) was 1.68 Tesla. In addition, the crystal grain size was largely grown to 150 µm to improve magnetism. Therefore, it was found that annealing in an atmosphere containing a large amount of hydrogen is preferable for the improvement of magnetic properties.

As described above, the present invention was able to clean the steel and improve the magnetic properties of the product by controlling the steel component and appropriately producing the annealing temperature and the atmosphere in the manufacturing process.

Claims (2)

At midrange%, C: 0.01% or less, Si: 3.5% or less, Mn: 1.2% or less, Al: 1.3% or less, Sn: 0.03 to 0.3%, Cr: 0.05 to 0.5%, Ti: 0.0005 to 0.009%, N : 0.005% or less, O: 0.005% or less, the sum of Cu, Ni, Sb, and Ca elements is 0.2% or less, and P, S, Mo, V, B, Zr, W, As, Mg, Te, and Zn elements Non-oriented electrical steel sheet having excellent magnetic properties with a sum of 0.1% or less. At midrange%, C: 0.01% or less, Si: 3.5% or less, Mn: 1.2% or less, Al: 1.3% or less, Sn: 0.03 to 0.3%, Cr: 0.05 to 0.5%, Ti: 0.0005 to 0.009%, N : 0.005% or less, O: 0.005% or less, the sum of Cu, Ni, Sb, and Ca elements is 0.2% or less, and P, S, Mo, V, B, Zr, W, As, Mg, Te, and Zn elements Slabs whose sum is 0.1% or less After reheating to 1250 ℃ or lower, hot rolling, winding in ferrite temperature range of 600 ℃ or higher, pickling hot rolled sheet without annealing or annealing, cold rolling to final thickness, and annealing cold rolled sheet (Ac ₁ -150 ℃) Method for producing an excellent non-oriented electrical steel sheet characterized in that the annealing in an atmosphere of at least 10% hydrogen in the temperature range ~ Ac ₁ .