KR19980017729A - Non-oriented electrical steel sheet having excellent magnetic properties and manufacturing method thereof - Google Patents

Abstract

The present invention is, by weight%, C: 0.015% or less, Si: 1.5-3.5%, Mn: 0.5% or less, P: 0.1% or less, S: 0.01% or less, Al: 1.0% or less, N: 0.007% or less The present invention provides a non-oriented electrical steel sheet having excellent magnetism, which is composed of Sn: 0.03-0.3%, Cr: 0.05-0.7%, Ni: 0.05-0.5%, balance Fe, and other unavoidable impurities. , In weight%, C: 0.015% or less, Si: 1.5-3.5%, Mn: 0.5% or less, P: 0.1% or less, S: 0.01% or less, Al: 1.0% or less, N: 0.007% or less, Sn: Heating a sleeve composed of 0.03-0.3%, Cr: 0.05-0.7%, Ni: 0.05-0.5%, balance Fe and other unavoidable impurities to 1250 ° C. or less; Hot rolling the heated slab on a ferrite having a finish rolling temperature of finishing rolling during hot rolling at 800 ° C. or higher; Winding at a temperature of 800 ° C. or lower; Continuously annealing the hot rolled steel sheet at a temperature of 900-1100 ° C .; It provides a method for producing a non-oriented electrical steel sheet having excellent magnetic properties, including pickling, cold rolling, and hot annealing at 900-1050 ° C.

Description

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

The present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same, which are used as iron cores of electric machines such as various motors, small transformers, and more particularly to a non-oriented electrical steel sheet having a low iron loss and high magnetic flux density and a method of manufacturing the same. .

In general, non-oriented electrical steel sheet is used as a core material of various electrical equipment, and more than 60% of the electrical energy is consumed by a rotor such as various motors, the electrical steel sheet accounts for more than 25% of the motor energy loss. These non-oriented electrical steel sheets may be classified according to the amount of Si element added in the material, and may be classified into low grade materials when the amount of Si is included in 1.5% or less and high grade materials in the case of 1.5% or more. Increasing the Si content increases the resistivity, which reduces the eddy current loss during the loss.

Among the magnetic properties of the non-oriented electrical steel sheet, the iron loss is expressed in watts of electric loss per kilogram of iron core, and the smaller the value, the better. The magnetic flux density is expressed in Tesla as the amount of magnetic flux induced according to the magnitude of the magnetic field generated by applying electricity. The method of improving the magnetic properties is to change the composition of the steel or to control properly in the rolling and annealing process, and to develop the aggregated structure such as the (100) and (110) planes on the rolled plate, which is advantageous for the magnetism in the material. By increasing the grain size or by growing the grains. Such a manufacturing method is a method of reducing the hysteresis loss during iron loss, and when a component such as Si is determined, the vortex loss is fixed and the iron loss can be reduced by reducing the hysteresis loss.

Non-oriented electrical steel sheet can be roughly divided into semi-process and pulley process according to the manufacturing process. The pulley process is a process in which the hot rolled plate is cold rolled after pickling and finally annealed, and then processed by demand. The semi process is a hot rolled plate after the pickling, cold rolled, and after an intermediate annealing, usually a skin pass rolled at a rolling reduction of 15% or less. It is a process that the consumer processes and heats afterwards. Skin pass rolling not only increases the process but also has the disadvantage that the consumer must heat treatment after processing.

Japanese Patent Laid-Open No. 63-317627 is added with a small amount of alloying elements and a large amount of Mn to improve the magnetic field by rolling on austenite during hot rolling, but the hot rolled sheet is subjected to annealing for a long time, and also cold rolled in order to grow large grains. After the annealing of the plate is manufactured in a semi-process that is shipped after rolling the skin pass, which is light rolling, in the high-grade steel having a high Si content, the hardness of the material is so high that the skin pass rolling is difficult.

Japanese Unexamined Patent Publication No. 64-142050 is also manufactured by a semi-process in which a large amount of Mn is added and skin pass rolling is applied, and is applied only to a material having a low Si content.

The present invention has been made to solve the problems of the prior art described above, and when the Si content is 1.5% or more, the non-oriented non-oriented electrical steel sheet is properly selected, and the non-aromatic excellent magnetic properties are low iron loss and high magnetic flux density by the pulley process It is an object to provide an electrical steel sheet.

Moreover, an object of this invention is to provide the manufacturing method of the non-oriented electrical steel plate excellent in the magnetism with low iron loss and high magnetic flux density.

The non-oriented electrical steel sheet having excellent magnetic properties of the present invention for achieving the above object, in weight%, C: 0.015% or less, Si: 1.5-3.5%, Mn: 0.5% or less, P: 0.1% or less, S: 0.01 % Or less, Al: 1.0% or less, N: 0.007% or less, Sn: 0.03-0.3%, Cr: 0.05-0.7%, Ni: 0.05-0.5%, balance Fe and other inevitable impurities. .

Moreover, the manufacturing method of the non-oriented electrical steel plate excellent in the magnetic property of this invention is C: 0.015% or less, Si: 1.5-3.5%, Mn: 0.5% or less, P: 0.1% or less, S: 0.01% by weight%. 1,250 or less of Al: 1.0%, N: 0.007%, Sn: 0.03-0.3%, Cr: 0.05-0.7%, Ni: 0.05-0.5%, balance Fe, and other unavoidable impurities. Heating to C or lower; Hot rolling the heated slab on a ferrite having a finish rolling temperature of finishing rolling during hot rolling at 800 ° C. or higher; Winding at a temperature of 800 ° C. or lower; Continuously annealing the hot rolled steel sheet at a temperature of 900-1100 ° C .; Pickling, cold rolling, and a high temperature annealing at 900-1050 ℃.

Cr is known to form carbides and lower the magnetism, but in the present invention, the C is 0.015% or less, and the addition of Sn, a grain boundary segregation element, and Ni, an element for improving the texture of the slab, to bring the slab heating temperature to 1250 ° C or less. After the rolling in the ferrite phase (Phase) during hot rolling, grain growth was possible and improved.

Hereinafter, the non-oriented electrical steel sheet having excellent magnetic properties and a method of manufacturing the same will be described in detail with reference to the preferred embodiment.

First, the reason for numerical limitation of the component elements of the non-oriented electrical steel sheet excellent in the magnetic property of this invention is demonstrated.

C causes magnetic aging and degrades magnetism during use, so it may be 0.015% or less in slab and 0.003% or less in the final product.

Si is added as a major element to increase the resistivity at least 1.5% or more, up to 3.5% in consideration of cold rolling properties.

Mn lowers iron loss by increasing specific resistance, but it needs to be suppressed because it combines with S to form MnS, which is a fine precipitate, to refine grains and is limited to 0.5% or less in the present invention.

P forms an aggregate structure favorable for magnetism but decreases cold rolling property, so it is added up to 0.1%.

S is advantageously contained as low as possible because it precipitates fine emulsions to refine crystal grains and adversely affect magnetic properties. In the present invention, S is preferably 0,01% or less.

Al adds up to 1.0% because it increases the resistivity, reducing iron loss and reducing the effect of N.

N is an invasive element, which inhibits the development of aggregates, and therefore it is preferable that the content is as small as possible. In the present invention, N is 0.007% or less.

Sn segregates at grain boundaries to control the shape of the grains. In addition, the formation of aggregated tissue on the surface 222 that is disadvantageous to magnetism is suppressed to improve the magnetism. If it is 0.03% or less, the effect is small. If it is 0.3% or more, the cold rolling property is lowered. Therefore, it is added in the range of 0.03-0.3%.

Cr was found to increase the corrosion resistance, form nitrides, and improve the magnetism when added with Sn. It should be added at least 0.05% to have the effect, and considering the degree of magnetic improvement compared to the added amount, add up to 0.7% to make 0.05-0.7%.

Ni is added because it improves the texture, and in particular, by adding Sn and Cr in combination, superior properties can be obtained rather than the properties of the respective winso. The addition amount must be added at least 0.05% to have the effect. The upper limit of the effect is added at 0.5% or less to make 0.05-0.5%.

Hereinafter, the manufacturing method of this invention is demonstrated in detail.

Steel slabs having the above composition are made of molten steel in a converter, an electric furnace, etc., solidified into slabs, charged into a heating furnace before hot rolling, and heated to 1250 ° C. or less. When heated to a temperature higher than this, the precipitates may be re-dissolved and a large amount of fine precipitates may be generated after hot rolling, thereby degrading magnetic properties.

The heated slabs are finish rolled, at which time they are hot rolled in a ferritic phase (Phase) of 800 ° C. or higher during finish rolling. It is possible to roll at a temperature of at least 800 ° C. or more, and also, by hot rolling on a ferrite, there is little recrystallization in the hot rolled sheet, so that a large residual stress remains. Thus, grains are greatly grown during annealing of the hot rolled sheet in a later step.

Winding after hot rolling can be carried out at 800 ° C. or lower to maintain the residual stress in the hot rolled sheet, and to maintain the precipitate at an appropriate size.

The hot-rolled cold rolled sheet is continuously annealed at a temperature of 900 ° C. or more and 110 ° C. or less.

This is because the annealing effect is less at a temperature of 900 ° C. or lower, and a surface flaw occurs in the hot rolled sheet at a temperature of 1100 ° C. or higher. Annealing time is 10 minutes or less, and productivity improves.

Subsequently, the hot rolled sheet is annealed and cold rolled. Such pickling and cold rolling are performed on the same conditions as before.

The cold rolled sheet is subjected to high temperature annealing at 900 ° C. or more and 1050 ° C. or less so that sufficient grain growth by recrystallization and development of an advantageous structure for magnetism is developed, but grain growth is insufficient at 900 ° C. or less, and the surface oxide layer is more than 1050 ° C. This is because it is severely generated and the surface scratches are also severe. The annealing time should be 5 minutes or less to ensure beautiful surface quality.

As described above, according to the present invention, by adding Sn, Cr, and Ni to the general component system of steel and setting the manufacturing conditions according to the components, the grain size is large, and the texture of the (100) plane and the (110) plane, which is an advantageous structure for magnetism, The well-developed non-oriented electrical steel sheet can be manufactured with excellent magnetic properties in the final product.

Hereinafter will be described in more detail according to a preferred embodiment of the present invention.

Example 1

Steel slabs having the components as shown in Table 1 below were dissolved, and hot rolling, hot rolled sheet annealing, and pickling cold rolling were performed under the production conditions as shown in Table 2. Since the Si content, which is a ferrite forming element, was high and hot rolling, the conditions of this embodiment were all rolled on ferrite.

The cold rolled sheet was annealed and cut for 120 seconds at a temperature of 1000 ° C. in a dry mixed gas atmosphere containing 20% of hydrogenated 80% nitrogen for grain growth, and then examined for magnetic properties and materials.

Comparative steel A does not have Ni, unlike the present invention steel, Comparative steel B does not contain Ni and Cr. Comparative steel C has Mn outside the scope of the present invention.

Comparative materials 1 to 3 were selected as comparative steel A, comparative steel B and comparative steel C as shown in Table 2, and Comparative materials 4 to 6 were selected as inventive steel B as a steel grade, but the manufacturing conditions of the production method of the present invention It is different from the condition.

As a result of the investigation, in the invention material satisfying the component range and manufacturing conditions of the inventive steel, the crystal grains were larger than those of the comparative material.

TABLE 1

TABLE 2

* W _15/50 (W / kg): Iron loss when magnetized to 1.5 Tesla at 50 Hz

* B ₅₀ (Tesla): Magnetic flux density induced when magnetizing at 5000 A / m

Example 2

By weight, C: 0.006%, Si: 3.05%, Mn: 0.25%, P: 0.015%, S: 0.005%, Al: 0.41%, N: 0.002%, Sn: 0.11%, Cr: 0.35%, Ni The slab composed of: 0.17%, residual Fe and other impurities was heated to 1180 ° C, rolled to a thickness of 21 mm at a temperature of 880 ° C which is a ferrite phase during finishing of finishing rolling during hot rolling, and wound up at 650 ° C. The cooled hot rolled sheet was continuously annealed and pickled for 3 minutes at a temperature of 1050 ° C. The pickled plate was cold rolled five times to prepare a thickness of 0.35 mm. The cold rolled sheet was annealed at a temperature of 1000 ° C. for 1 minute in a dry atmosphere containing 20% hydrogen and 80% nitrogen for grain growth, and the annealing plate was examined for magnetic properties after cutting. The magnetic properties were the iron loss value when the magnetic flux density of 1.5 Tesla was maintained at 50 Hz and was investigated at 2.01 W / kg, and the grain size was 112 μm.

In the non-oriented electrical steel sheet produced by the manufacturing method of the present invention described above, as shown in Examples and Table 2, the effect of obtaining a non-oriented electrical steel sheet excellent in magnetism is achieved by reducing iron loss and improving magnetic flux density.

Claims (2)

By weight%, C: 0.015% or less, Si: 1.5-3.5%, Mn: 0.5% or less, P: 0.1% or less, S: 0.01% or less, Al: 1.0% or less, N: 0.007% or less, Sn: 0.03 An excellent magnetic non-oriented electrical steel sheet, characterized in that the composition is composed of -0.3%, Cr: 0.05-0.7%, Ni: 0.05-0.5%, balance Fe and other inevitable impurities. By weight%, C: 0.015% or less, Si: 1.5-3.5%, Mn: 0.5% or less, P: 0.1% or less, S: 0.01% or less, Al: 1.0% or less, N: 0.007% or less, Sn: 0.03 Heating to below 1250 ° C. a slab composed of -0.3%, Cr: 0.05-0.7%, Ni: 0.05-0.5%, balance Fe and other unavoidable impurities; Hot rolling the heated slab on a ferrite having a finish rolling temperature of finishing rolling during hot rolling at 800 ° C. or higher; Winding at a temperature of 800 ° C. or lower; Continuously annealing the hot rolled steel sheet at a temperature of 900-1100 ° C .; Pickling, cold rolling, and Method for producing an excellent non-oriented electrical steel sheet comprising the step of annealing at 900-1050 ℃ high temperature.