KR101110257B1 - Non-oriented electrical steel sheet with high magnetic flux density and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a non-oriented electrical steel sheet having a high magnetic flux density and a method for manufacturing the same, in terms of weight% C: 0.005% or less, Si: 0.1 to 4.5%, Mn: 0.1 to 0.7%, P: 0.1% or less, sol. A magnetic flux density characterized by Al: 0.0003 to 0.003%, S: 0.0009 to 0.005%, N: 0.004% or less, Ti: 0.005% or less, V: 0.0060% or more and 0.05% or less, balance Fe and other unavoidable impurities High non-oriented electrical steel sheet and its manufacturing method are the technical gist. In the present invention, Al is added only the minimum necessary amount in the form of sol.Al necessary for the deoxidation of steel, and at the same time, V is added to form VN precipitates to suppress the formation of AlN, and the optimum process conditions are derived and appropriate. By adjusting to a level, it is possible to provide a non-oriented electrical steel sheet having excellent magnetic properties, in particular magnetic flux density, without significantly increasing the amount of added elements.

Non-oriented, electrical steel, magnetic properties, magnetic flux density, AlN

Description

Non-oriented electrical steel sheet with excellent magnetic flux density and its manufacturing method {NON-ORIENTED ELECTRICAL STEEL SHEET WITH HIGH MAGNETIC FLUX DENSITY AND MANUFACTURING METHOD THEREOF}

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 the like, and more particularly, to a non-directional excellent magnetic flux density produced by appropriately controlling the steel component and its processing conditions. It relates to an electrical steel sheet and a method of manufacturing the same.

Non-oriented electrical steel sheet is widely used as an iron core of electric equipment such as various motors and transformers, and is an important component necessary to convert electrical energy into mechanical energy in rotating equipment. High magnetic flux density is required.

Among these, iron loss is energy that disappears as heat during the energy conversion process, so the lower the efficiency, the higher the efficiency of the rotor, and the higher the magnetic flux density, the higher the efficiency of the rotor, the higher the efficiency of the rotor. The copper wire is wound and used for power equipment after being punched and stacked. In particular, according to the recent energy saving trend, magnetization is easy, and a miniaturized motor and transformer are required. The copper wire can be wound less and the amount of iron core can be reduced, which greatly reduces the energy loss. In particular, when a miniaturized motor is loaded in an electric vehicle, it is known that not only the energy loss can be minimized due to the reduction of the overall weight, but also the ripple effect on the entire apparatus including the same is very large.

Conventionally, in order to realize low iron loss, various methods for improving the deteriorated magnetic flux density have been separately performed instead of increasing the amount of Al or the like from the viewpoint of reducing eddy current loss.

For example, Japanese Patent Laid-Open No. 40-016653 discloses a technique in which As, Ni, Co, Cu, Mo, Cr, and the like are added. However, such a special element has a problem in that the cost is increased. In Japanese Patent Laid-Open No. 1-42050, a technique containing a combination of Cr, Ni, B, and Cu is described. However, since the Al content is large, the improvement of the magnetic flux density is still not satisfactory with the above technique alone. -136626 discloses a method of performing annealing rate of 5 ° C./sec or more at the time of final annealing of the cold rolled plate. However, since the addition amount of Al is high and the coiling temperature is set to 600 ° C. or less after hot rolling, The problem is that the image can be bad.

Therefore, in order to solve the problems caused by such a high amount of Al, Japanese Patent Laid-Open Publication No. 2000-160306 improves the workability by increasing the S content, which is an impurity element, instead of lowering the amount of Al, but the magnetic properties are increased by increasing the fine precipitates. There is a problem of deterioration.

In order to solve the above problems, the present inventors have repeatedly studied and experimented and proposed the present invention based on the results. Al is added only the minimum necessary amount in the form of sol.Al necessary for deoxidation of steel. The purpose of the present invention is to provide a non-oriented electrical steel sheet having excellent magnetic properties, in particular magnetic flux density, by deriving VN precipitates to suppress the formation of AlN by adding V among the components, and deriving optimum process conditions.

In the present invention, C: 0.005% or less, Si: 0.1 to 4.5%, Mn: 0.1 to 0.7%, P: 0.1% or less, sol.Al: 0.0003 to 0.003%, S: 0.0009 to 0.005%, N: It provides a non-oriented electrical steel sheet having excellent magnetic flux density, characterized in that it is composed of 0.004% or less, Ti: 0.005% or less, V: 0.0060% or more and 0.05% or less, balance Fe and other unavoidable impurities.

At this time, the total weight of one kind or two kinds of Sn, Sb by weight% is further contained in 0.005 ~ 0.2%, it is characterized by the composition.

In addition, the sol.Al: 0.001% or less by weight%, and the sol.Al / V value is 0.002 ~ 0.2 also has the characteristics.

In addition, the AlN inclusions in steel having a particle diameter of 0.07 to 0.5 µm are also characterized by being 1200 pieces / cm 2 or less.

In addition, C: 0.005% or less, Si: 0.1 to 4.5%, Mn: 0.1 to 0.7%, P: 0.1% or less, sol.Al: 0.0003 to 0.003%, S: 0.0009 to 0.005%, N: 0.004 by weight% % Or less, Ti: 0.005% or less, V: 0.0060% or more and 0.05% or less, steel slabs composed of residual Fe and other unavoidable impurities are hot rolled after reheating to form a hot rolled sheet, and then cold rolled and finally annealed. It provides a non-oriented electrical steel sheet having excellent magnetic flux density.

At this time, the steel slab is characterized in that the composition of one or two kinds of Sn, Sb by weight% is further included as 0.005 ~ 0.2%.

In addition, in the case where the Si is 1.0 to 4.5% by weight, the hot roll annealing is performed at 850 to 1,100 ° C. after the hot rolling.

Furthermore, the final annealing is also characterized in that it is carried out at 750 ~ 1,100 ℃.

According to the present invention as described above, Al is added only a minimum necessary amount in the form of sol.Al for the deoxidation of the steel, and at the same time, V is added to form VN precipitates to suppress the formation of AlN, the optimum process By deriving conditions and adjusting them to an appropriate level, there is an effect of providing a non-oriented electrical steel sheet having excellent magnetic properties, particularly magnetic flux density, without excessively increasing the amount of added elements.

In general, N precipitates as AlN in steel, and since AlN is fine at 0.1 μm or less and long in shape, greatly inhibiting the growth of crystal grains. While adding only the minimum necessary amount in the form of .Al, V is added to form VN precipitates, and the formation of AlN is suppressed, and an appropriate amount of S is added to prevent N from penetrating into the steel sheet to suppress grain growth. By providing a non-oriented electrical steel sheet with improved magnetic flux density.

Hereinafter, the reason for numerical limitation of the steel component of the present invention will be described in detail.

C not only causes magnetic aging in the final product to lower magnetic properties during use, but also forms carbide to deteriorate iron loss, so it is desirable to control the slab not to exceed 0.005% by weight.

Since Si is an element that lowers iron loss by increasing specific resistance, it is preferable to add 0.1% by weight or more to secure the strength of the material and increase the specific resistance, but when it exceeds 4.5% by weight, the punchability of the steel sheet is increased by increasing the hardness of the steel sheet. Degrades. Therefore, the content of Si is limited to 0.1 to 4.5% by weight.

Mn is added because it increases resistivity, develops texture, and suppresses the formation of fine precipitates. When it is added less than 0.1% by weight, the texture becomes worse. Since the cost increases compared to the decrease, the Mn content is limited to 0.1 to 0.7 wt%.

P is an element that forms a texture that favors magnetism, and serves to improve in-plane anisotropy and improve strength. However, considering the cold rolling property, the content is limited to 0.1% by weight or less.

Since sol.Al forms fine and long AlN precipitates to suppress the growth of crystal grains, sol.Al is not added but is contained in the form of sol.Al for deoxidation at the steelmaking stage. However, if it contains too much, the specific resistance is increased to decrease the magnetic flux density, so it should be contained in 0.0003 ~ 0.003% by weight. In this case, more preferably, sol.Al may be contained in an amount of 0.001% by weight or less, thereby further reducing a decrease in magnetic flux density.

S is controlled so as not to exceed 0.005% by weight because it is advantageous to manage as low as possible because it forms a fine precipitate MnS deteriorates the magnetic properties. However, if the S content is too small, at least 0.0009% by weight or more is added since N penetrates into the steel sheet and suppresses grain growth. Therefore, the content of S is limited to 0.0009 ~ 0.005% by weight (9 ~ 50 ppm).

N is an element which should be suppressed as much as possible because it forms fine and long AlN precipitates, and thus the content thereof is limited to 0.004% by weight or less.

Ti is an element that forms fine carbide of TiC or nitride of TiN to inhibit grain growth, so the content of the Ti is limited to 0.005% by weight or less.

V combines with C or N to form carbides or nitrides, but in the present invention, V and N combine to form VN precipitates when contained in excess of 0.0060% by weight, thereby greatly reducing the amount of fine and long precipitates such as AlN. In order to improve the magnetic properties, it is controlled to contain at least 0.0060% by weight. However, if the content is excessively large, the workability is reduced, so it is limited to 0.05% by weight or less. Therefore, the content of V is limited to more than 0.0060% and 0.05% by weight or less.

At this time, sol.Al is contained in 0.001% by weight or less in the steel added with V, sol.Al/V has a value of 0.002 to 0.2, and 1200 Al / inclusions in steel having a particle diameter of 0.07 to 0.5 µm As a result of the control, the magnetic flux density was significantly improved and the magnetic properties of the non-oriented electrical steel sheet were excellent. This is because Al and N are reduced by more easily bonding with V and N in the above conditions to precipitate as VN.

Since Sn and Sb segregate at grain boundaries and suppress aggregates that are detrimental to their magnetic properties, thereby improving the aggregates, one or two kinds are added so that the sum of one or two kinds is 0.005 to 0.2% by weight. This is because when the sum of one or two kinds of Sn and Sb is less than 0.005% by weight, the effect of improving the texture is insignificant, and when it exceeds 0.2% by weight, the cold rolling property and the punching property deteriorate.

In addition to the above composition, the present invention is composed of the remaining Fe and other unavoidable impurities.

Hereinafter, the manufacturing method of the electrical steel sheet using the steel slab of the above components will be described in detail.

The steel slab formed as described above is made of molten steel in steelmaking and then solidified into slabs in a continuous casting process. In the present invention, the slab is charged into a hot pre-rolling furnace and heated at a temperature of 1250 ° C. or lower under normal conditions. do. At this time, when heated to more than 1250 ℃ because the precipitates harmful to the magnetic, such as AlN can be re-dissolved and finely precipitated after hot rolling, the slab is heated at a temperature of 1250 ℃ or less and then hot rolled.

The hot rolling is subjected to finishing rolling after rough rolling, the finishing rolling of the finishing rolling is finished on ferrite, and the final rolling rate is 20% or less for correcting the plate shape. When the hot rolling is carried out on the ferrite, there is more residual stress than the finish of rolling on the austenitic phase, and thereafter, the grains are easily grown in the final product because the grains are easily grown during winding and annealing.

In addition, the hot rolled sheet manufactured as described above is wound at 700 ° C. or lower and cooled in air. When the coiling temperature exceeds 700 ° C., AlN having low solubility is redissolved so that fine precipitates are formed during air cooling after winding. have. Therefore, in the present invention, the hot rolled sheet can be wound at 700 ° C. or lower to coarsen the precipitate of AlN as much as possible.

The cold-rolled hot rolled sheet is subjected to hot rolled sheet annealing if necessary, and then cold rolled sheet annealing (final annealing).

At this time, the hot-rolled sheet annealing is carried out if necessary when the content of Si is 1.0 to 4.5% by weight or more. This is because, when the Si content is high, performing hot-rolled sheet annealing coarsens the crystal structure to increase the magnetic flux density. However, if the temperature of the hot-rolled sheet annealing is less than 850 ℃ the structure does not grow or grow finely, the magnetic flux density is less synergistic effect, when the annealing temperature exceeds 1100 ℃, the magnetic properties may rather deteriorate, plate-like Because of the problem of deterioration of rolling workability due to deformation, the temperature range is limited to 850 ~ 1,100 ℃.

In the cold rolling, the final rolling is performed in a thickness of 0.1 to 0.7 mm, and if necessary, after the first cold rolling, the secondary cold rolling may be performed after the intermediate annealing, and the final rolling rate may be in the range of 50 to 95%.

The cold-rolled cold rolled sheet is subjected to final annealing. When the final annealing temperature is less than 750 ° C., recrystallization does not occur sufficiently. When the final annealing temperature is above 1,100 ° C., the surface layer oxide layer is deeply formed and the magnetism is deteriorated. The temperature of the final annealing of the present invention is limited to 750 ~ 1,100 ℃.

The final annealed annealing plate is shipped to the customer after the insulation coating treatment in a conventional manner.

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 heated at 1,180 ° C, and finish rolling at hot rolling was performed at 850 ° C. The rolling reduction in the last stand during the hot rolling of the hot rolling was 17%, rolled to a thickness of 2.0 mm, and then air-cooled after winding. The hot rolled sheet was subjected to hot rolled sheet annealing at the temperature shown in Table 2, pickled, and then cold rolled to a thickness of 0.35 mm, and the final annealing was performed at 1050 ° C., and then the magnetic properties such as iron loss and magnetic flux density were examined. It is described in.

[Table 1]

TABLE 2

As shown in Table 2, Inventive Materials 1 to 6 prepared by the production method of the present invention using the invention steel A to invention steel E satisfying the component range of the present invention shows that the magnetic flux density is higher than the comparative material And iron loss was low. Comparative material 1 had a high sol.Al and a low V content, so that the sol.Al/V value was 1.75, so that the magnetic flux density was relatively low, and comparative material 2 had a high sol.Al/V value of 0.5 and an excessive S. Although the iron loss was slightly improved, the magnetic flux density was lower than that of the inventive material. The comparative material 3 was the inventive steel but the hot-rolled sheet annealing temperature was high, indicating that the magnetic flux density was low due to the increase of AlN-containing inclusions. In addition, Comparative 4 was found to have a low magnetic flux density due to high sol.Al and low contents of S and V.

Example 2

By weight% C: 0.0028%, Si: 0.6%, Mn: 0.25%, P: 0.045%, S: 0.0021%, sol.Al: 0.0006%, N: 0.0014%, Ti: 0.0015%, V: 0.008%, Sb: 0.03%, sol.Al/V value is 0.075, steel slab composed of the remaining Fe and other unavoidable impurities is reheated to 1,200 ℃, and finishing rolling temperature of finishing rolling at hot rolling is 880 ℃, and reduced The rate was 15% to prepare a 2.5 mm thick hot rolled sheet. The hot rolled plate was wound at 680 ° C., then air cooled, pickled and cold rolled to a thickness of 0.50 mm. As a result of the final annealing of the cold rolled sheet, the number of AlN-containing inclusions was 1,080, the magnetic flux density (B50) was 1.78T (Tesla), and the iron loss (W15 / 50) was 4.0W / kg. Therefore, when Si is less than 1.0 wt%, sol.Al is contained in an amount of 0.001 wt% or less even when hot-rolled sheet annealing is not performed, and the value of sol.Al/V is in the range of 0.002 to 0.2 of the present invention. The AlN inclusions in the steel having a particle diameter of 0.07 to 0.5 µm exhibited good values of 1,080, indicating that the magnetic flux density was very good.

Example 3

By weight% C: 0.0027%, Si: 3.1%, Mn: 0.185%, P: 0.008%, S: 0.0011%, sol.Al: 0.0008%, N: 0.0015%, Ti: 0.0016%, V: 0.007%, Sn: 0.015%, sol.Al/V value is 0.085, and the slab composed of the remaining Fe and other unavoidable impurities is reheated to 1,160 ℃, and the finishing rolling temperature of finishing rolling during hot rolling is 900 ℃, 2.0 mm thick. The hot rolled steel sheet was prepared. The hot rolled steel sheet was wound at 660 ° C. and then air cooled, and the hot rolled sheet was annealed at 980 ° C. for 2 minutes, followed by pickling to cold roll 0.20 mm thick. The number of AlN-containing inclusions in the final annealed steel sheet was 880, the magnetic flux density (B50) was 1.68T, and the iron loss (W10 / 400) was 9.8 W / kg. Therefore, when Si contained high Si of 1.0% by weight or more, it can be seen that the magnetic flux density is further improved by performing hot-rolled sheet annealing in the range of 850 to 1,100 ° C, and sol.Al is contained in 0.001% by weight or less. In the case of sol.Al/V value of 0.085 in the range of 0.002 to 0.2 of the present invention, the number of AlN inclusions in steel having a particle diameter of 0.07 to 0.5㎛ was considerably low, and thus the magnetic flux density was also excellent. there was.

Claims (8)

By weight% C: 0.005% or less, Si: 0.1 to 4.5%, Mn: 0.1 to 0.7%, P: 0.1% or less, sol.Al: 0.0003 to 0.003%, S: 0.0009 to 0.005%, N: 0.004% or less The non-oriented electrical steel sheet having excellent magnetic flux density, characterized by Ti: 0.005% or less, V: 0.0060% or more and 0.05% or less, balance Fe and other unavoidable impurities. The method of claim 1, The non-oriented electrical steel sheet having excellent magnetic flux density, characterized in that the composition is further comprised of 0.005 to 0.2% by weight of one or two of Sn and Sb in weight%. The method according to claim 1 or 2, The non-oriented electrical steel sheet having excellent magnetic flux density, wherein the sol.Al is contained in an amount of 0.001% or less and the sol.Al/V value is 0.002 to 0.2 by weight. The method of claim 3, Non-oriented electrical steel sheet having excellent magnetic flux density, characterized in that the AlN inclusions in the steel having a particle diameter of 0.07 to 0.5 µm are 1200 pieces / cm 2 or less. By weight% C: 0.005% or less, Si: 0.1 to 4.5%, Mn: 0.1 to 0.7%, P: 0.1% or less, sol.Al: 0.0003 to 0.003%, S: 0.0009 to 0.005%, N: 0.004% or less , Ti: 0.005% or less, V: 0.0060% or more, 0.05% or less, steel slab composed of residual Fe and other unavoidable impurities, after reheating, hot rolling to make a hot rolled sheet, and then cold rolling and final annealing Method for producing non-oriented electrical steel sheet having excellent density. The method of claim 5, The steel slab is a method of producing a non-oriented electrical steel sheet having excellent magnetic flux density, characterized in that the composition is further comprised by weight% of one or two of Sn, Sb in a total of 0.005 ~ 0.2%. The method according to claim 5 or 6, When the Si is 1.0 to 4.5% by weight, the hot rolled sheet annealing at 850 ~ 1,100 ℃ after the hot rolling, characterized in that the magnetic flux density excellent non-oriented electrical steel sheet manufacturing method. The method according to claim 5 or 6, The final annealing is a method for producing a non-oriented electrical steel sheet having excellent magnetic flux density, characterized in that carried out at 750 ~ 1,100 ℃.