KR101081295B1 - Method of manufacturing non-oriented electrical steel sheet and non-oriented electrical steel sheet manufactured using thereof - Google Patents

Abstract

The present invention relates to a method for manufacturing a high efficiency non-oriented electrical steel sheet and a non-oriented electrical steel sheet manufactured by the method, comprising the steps of preparing a cold-rolled steel sheet, and at least one element selected from Si, Mn, Al, Ni and Sn A step of preparing a spacer film, and overlapping the cold-rolled steel sheet and the spacer film to form a different winding coil by winding, forming a different winding coil, heat-treating the different winding coil and unwinding the different winding coil (Unwinding After removing the spacer film, the heat-treated cold rolled steel sheet is subjected to insulation coating to facilitate the processing of the initial cold rolled steel sheet, but the Si content in the steel sheet is increased to 3% or more as a result of non-oriented having low iron loss and high magnetic flux density. The present invention relates to an invention in which electrical steel sheets can be manufactured.

Description

METHOD OF MANUFACTURING NON-ORIENTED ELECTRICAL STEEL SHEET AND NON-ORIENTED ELECTRICAL STEEL SHEET MANUFACTURED USING THEREOF}

The present invention relates to a method for manufacturing a non-oriented electrical steel sheet mainly used as iron core material for a small electric motor or a small power transformer, more specifically, by adjusting the content of elements such as Si, Al, Mn, Ni, Sn, steelmaking and The present invention relates to a highly efficient non-oriented electrical steel sheet production method capable of improving the efficiency of a hot rolled / cold rolled process and increasing the efficiency of the electrical steel sheet, and a non-oriented electrical steel sheet manufactured by the method.

Electrical steel sheet (Electrical steel sheet) is a steel sheet to which Si (Si) is added about 3% by weight, and is also referred to as a Si steel sheet because the content of Si is very high compared to a general steel sheet.

The electrical steel sheet can be divided into oriented electrical steel sheet and non-oriented electrical steel sheet according to magnetic properties.

Oriented electrical steel sheet (oriented electrical steel sheet) is manufactured to facilitate magnetization in the rolling direction of the steel sheet has a particularly excellent magnetic properties in the rolling direction, it is mainly used as the iron core of large, small and medium-sized transformers that require low iron loss, high permeability .

On the other hand, non-oriented electrical steel sheet (non-oriented electrical steel sheet) has a uniform magnetic properties regardless of the direction of the steel sheet, it is widely used as iron core materials such as small electric motors, small power transformers, ballasts.

Recently, according to the trend of increasing the efficiency and miniaturization of electrical equipment in terms of energy saving, research is being conducted to reduce iron loss as much as possible in non-oriented electrical steel sheets.

On the other hand, non-oriented electrical steel sheet is largely divided into two types. These are semi-process products, which the buyer must perform after stress relief annealing, and fully-process products, where the buyer does not need to stress relief annealing.

The semi-process products are usually shipped in a modified state in the manufacturing process of steelmaking, continuous casting, slab reheating, hot rolling, winding, hot rolled sheet annealing, cold rolling, annealing, skin-pass rolling and insulation coating. After purchasing the product and processing the product into the desired shape, the stress relief annealing shall be performed to obtain the magnetic properties for the product.

On the other hand, the pulley process products are shipped in a state where deformation is solved through the manufacturing process of steelmaking, continuous casting, slab reheating, hot rolling, winding, hot rolled sheet annealing, cold rolling, recrystallized annealing, and insulation coating. It has the advantage that it can be used without.

Therefore, a pulley process product is mainly used. Here, iron loss means electrical loss per weight of iron core (W / Kg), and the lower the iron loss, the higher the electrical efficiency of the electrical steel sheet.

In general, as the content of Si increases, the specific resistance increases, the iron loss is lowered, and as the iron loss is lowered, it is known that the production of highly efficient non-oriented electrical steel sheet is possible.

However, when the content of Si is added in excess of 3% by weight of the total composition of the electrical steel sheet, the steel sheet has brittleness, so that cold rolling is almost impossible.

Therefore, the content of Si in the steelmaking step is preferably not more than 3% by weight of the total composition of the electrical steel sheet.

To replace this, aluminum (Al) is added to the electrical steel sheet in the steelmaking step instead of Si, but there is a limit in terms of its effectiveness.

In addition, a method for producing a non-oriented electrical steel sheet having excellent magnetic properties such as high magnetic flux density and low iron loss containing Mn, Ni, Sn and the like has been proposed.

However, when an additive element such as Si, Al, Mn, Ni, Sn is added in the steelmaking step, there is a disadvantage in that the subsequent rolling property decreases rapidly as the content thereof increases.

After manufacturing a cold rolled steel sheet with a minimum content of Si, Mn, Al, Ni, and Sn of the present invention, and before heat treatment, a spacer film containing at least one element selected from Si, Mn, Al, Ni, and Sn is described. Provided is a high efficiency non-oriented electrical steel sheet manufacturing method and a non-oriented electrical steel sheet manufactured by the method to be easily produced by superimposing the cold rolled steel sheet and then wound, thereby producing a high magnetic flux density and low iron loss It is for that purpose.

In order to achieve the above object, a high efficiency non-oriented electrical steel sheet manufacturing method according to the present invention comprises the steps of (a) providing a cold rolled steel sheet, and (b) at least one element selected from Si, Mn, Al, Ni, and Sn. Preparing a spacer film included therein; (c) overlapping the cold rolled steel sheet and the spacer film to form a different winding coil by winding and (d) heat treating the hetero winding coil; and e) removing the spacer film while unwinding the dissimilar winding coil, and then performing insulating coating on the heat-treated cold rolled steel sheet.

Here, the cold rolled steel sheet of step (a) is in weight%, C: 0.005% or less, S: 0.005% or less, N: 0.005% or less, Si: 0.8-1.0%, Al: 0.1-0.4%, Mn: 0.1 0.2%, Sn: 0.01% to 0.02%, Ni: 0.02% to 0.10%, and using a steel slab composed of a residual amount of Fe and other impurities, wherein the heat treatment is performed at a temperature of 800 to 1,000 ° C. Characterized in that, the heat treatment is performed for 1 to 2 hours, the spacer film is a three-stage formed with a coating layer containing at least one element selected from Si, Mn, Al, Ni and Sn on both sides of the base material It characterized in that the structure is formed, the base material is characterized in that using a metal substrate or silicon glass fiber substrate coated with a refractory material, the coating layer is selected from one of the hot-dip, electroplating, CVD and PVD method Characterized in that, the coating layer is 0.1 ~ 1mm It characterized by forming a thickness.

In addition, the non-oriented electrical steel sheet according to the present invention is produced by the method described above, characterized in that the content of Si exceeds 3% by weight of the total weight.

The high efficiency non-oriented electrical steel sheet manufacturing method according to the present invention by adding a minimum amount of Si, Mn, Al, Ni and Sn in the cold rolled steel sheet manufacturing, so that the cold rolling process can be easily performed. Accordingly, the present invention provides an effect that can increase the yield of the process for producing high efficiency non-oriented electrical steel sheet.

In addition, the present invention can facilitate the cold rolling using the minimum Si steel sheet as possible as described above, and also before the cold rolling coating layer comprising any one selected from Si, Mn, Al, Ni and Sn and Winding together, it provides an effect that can be produced high-efficiency, non-oriented electrical steel sheet having excellent electrical and magnetic properties during heat treatment.

Hereinafter, a method of manufacturing a high efficiency non-oriented electrical steel sheet and a non-oriented electrical steel sheet manufactured by the method according to the present invention will be described in detail with reference to the accompanying drawings.

In this process, the thickness of the lines or the size of the components shown in the drawings may be exaggerated for clarity and convenience of description.

In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to a user's or operator's intention or custom.

Therefore, definitions of these terms should be made based on the contents throughout the specification.

1 is a flow chart showing an embodiment of a high efficiency non-oriented electrical steel sheet manufacturing method according to the present invention.

Referring to Figure 1, briefly described a high efficiency non-oriented electrical steel sheet manufacturing method according to the present invention.

First, a hot-rolled steel sheet is manufactured by performing a steelmaking / casting / hot rolling process (S100) for manufacturing a steel slab having a minimum addition amount of Si, Mn, Al, Ni, and Sn, and cold rolling (S110) the hot rolled steel sheet. Cold rolled steel sheet is produced. Next, the spacer film including at least one element selected from Si, Mn, Al, Ni, and Sn is stacked on the surface of the cold rolled steel sheet and wound to perform a heat treatment step (S120).

Then, the spacer film is removed while unwinding the coiling coil, and an insulation coating process (S130) is performed on the surface of the cold rolled steel sheet to produce a highly efficient non-oriented electrical steel sheet having excellent electrical / magnetic properties.

Here, the above-described processes will be described in more detail.

First, the steel slab with the minimum addition amount of Si, Mn, Al, Ni, and Sn is weight percent, C: 0.005% or less, S: 0.005% or less, N: 0.005% or less, Si: 0.8-1.0%, Al: A steel slab composed of 0.1 to 0.4%, Mn: 0.1 to 0.2%, Sn: 0.01 to 0.02%, Ni: 0.02 to 0.10% of the remaining amount of Fe and other impurities is prepared.

In more detail, before the composition step for producing steel slab according to the present invention, steelmaking, molten steel and ingot or continuous casting process are typically preceded. First, in the steelmaking step, it is important to control the content of C, N, S low in the molten steel and to add Si, Mn, Al, Ni and Sn to a minimum.

Subsequently, the steel slab containing an appropriate amount of components is manufactured by performing a molten steel in the ingot or continuous casting process. Among the components of the slab steel of the present invention, C, N, and S are elements that interfere with grain growth, so it is necessary to control the content in the steelmaking step at a low level, and Si, Mn, Al, Ni, and Sn lower the iron loss and at the same time the magnetic flux. Since it is an element for increasing the density, it is preferable to add the proper amount into the steel at an appropriate ratio. However, since they play a role of rapidly reducing the rolling property as the amount of addition increases, it is preferable to control the composition range to the minimum.

The reason for limitation of each composition range is as follows.

-C: 0.005 wt% or less

When C is excessively contained, it forms carbides during the manufacturing process of the electrical steel sheet of the present invention, thereby inhibiting grain growth, and it also causes magnetic aging during use as an iron core of an electric device, thereby decreasing the magnetic properties. It is preferable to contain so that it may have a composition of 0.005% or less in steel.

-N: 0.005 wt% or less

Since N tends to react with Al to form AlN precipitates during the steel sheet manufacturing process of the present invention to suppress grain growth, so that it has a minimum amount as much as possible, it is preferable to contain N in a composition of 0.005% or less. .

-S: 0.005 wt% or less

In addition to C and N, S tends to react with Mn to form MnS, which is a fine precipitate, to suppress grain growth, so it is important to have a minimum amount as much as possible. desirable.

Si: 0.8-1.0 wt%

If the Si content is less than 0.8% by weight, the specific resistance of the steel is small and the iron loss characteristics are deteriorated, which is not preferable. If the Si content is excessive, the excellent magnetic flux density is not obtained and the punchability is deteriorated, so the mold wear rate is increased. Not desirable Here, since the content of Si exceeds 1.0% by weight, the Si content may be excessively increased in the subsequent heat treatment process, it is preferable to comply with the limited range.

Al: 0.1-0.4 wt%

When the acid-soluble Al is less than 0.1% by weight, the specific resistance of the steel is small, the iron loss characteristics are not preferable, and if it is more than 0.4% by weight, there is a tendency to excessively increase the Al content in the subsequent heat treatment process according to the present invention, cold Rolling properties may be impaired.

Mn: 0.1-0.2 wt%

In the case of Mn is less than 0.1% by weight, the specific resistance of the steel is small, the iron loss characteristics are not preferred, and if it is more than 0.2% by weight, the content of Mn in the subsequent heat treatment process according to the present invention can be excessively increased, rolls It is not preferable because the load increases and the cold rolling deteriorates.

Sn: 0.01-0.02 wt%

Sn added into steel during steelmaking is an element that reduces (111) surface strength, which is harmful to magnetic properties. When the added amount is less than 0.01% by weight, the effect of improving the magnetic flux density after recrystallization annealing is insignificant. In the subsequent heat treatment step according to the increase in the content of Sn may be excessive, since Sn is ineffective compared to the weight ratio to rise, which can lead to only an increase in the raw material costs, it is preferable to comply with the above range.

Ni: 0.02 to 0.10 wt%

It reduces the iron loss of electrical steel sheet and improves the magnetic flux density. When the added amount is less than 0.02% by weight, the improvement of the magnetic flux density cannot be expected. 0.10% by weight is preferred. In addition, since the Ni content can be supplemented by additional heat treatment if necessary, it is preferable to add a minimum weight.

In addition to the above components, the steel contains Fe and other unavoidable impurities. At this time, Si, Mn, Al, Ni, and Sn is an element for lowering the iron loss and at the same time to increase the magnetic flux density, but is added in the appropriate amount in the steel at an appropriate ratio, in the present invention, the minimum amount is added in consideration of the subsequent heat treatment process.

Steelmaking and playing step according to the present invention is as described above, and then, the steps to the specific hot rolling, cold rolling process and the completion of the non-oriented electrical steel sheet as follows.

[Hot Rolling Step]

The steel slab is charged into a heating furnace and reheated as a pretreatment step of the hot rolling step performed after the composition step. In this case, in order to facilitate hot rolling, the reheating temperature of the steel slab should be 1050 ° C. or higher, but if it exceeds 1250 ° C. Precipitates, which are harmful to iron loss characteristics such as AlN and MnS, are re-dissolved and tend to cause excessive generation of fine precipitates after hot rolling. Such fine precipitates are undesirable because they hinder grain growth and deteriorate iron loss characteristics. Therefore, in the case of the present invention, it is preferable to heat to a temperature of 1050 ~ 1250 ℃.

It is heated as mentioned above and hot-rolled, The operation conditions are performed by a conventional method, At this time, in order to prevent the oxide layer of a hot-rolled steel sheet to generate | occur | produce excessively, it is preferable to adjust finishing rolling temperature to 800-950 degreeC. If the thickness of the hot rolled steel sheet is less than 1.8 mm, the shape of the hot rolled steel sheet is not preferable, and if it is more than 3.0 mm, it is not preferable because a good aggregate structure cannot be obtained and the magnetic flux density deteriorates.

Subsequently, the coiling of the hot rolled steel sheet is preferably performed at a temperature of 800 ° C. or lower so that an oxide layer is not excessively generated on the hot rolled steel sheet, but at a temperature of 650 ° C. or higher for grain growth of the hot rolled steel sheet. After cooling in air in a coiled state, or more preferably furnace cooled.

[Hot Rolled Steel Sheet Manufacturing Steps]

Subsequently, the hot rolled sheet is subjected to hot rolled sheet annealing so as to recrystallize the stretched grains in the center portion and to obtain a uniform grain distribution in the steel plate thickness direction. At this time, if the annealing temperature is lower than 800 ℃, the uniform grain distribution is not obtained, and thus the effect of improving the magnetic flux density and iron loss is insufficient. If the annealing temperature is higher than 1050 ℃, the (111) plane texture which is unfavorable to magnetic Increasing magnetic flux density deteriorates.

Cold Rolled Sheet Manufacturing Steps

Subsequently, the steel sheet on which the hot rolled steel sheet is annealed is subjected to cold rolling after pickling to produce a cold rolled steel sheet. In this case, when rolling at a reduction ratio of less than 64%, rolling productivity is reduced, so it is preferable to roll once at a reduction ratio of 64% or more. At this time, if the thickness of the cold rolled steel sheet is less than 0.20mm, the strength of the (111) plane, which is an unfavorable texture after annealing, is increased, and thus the magnetic flux density decreases. It may not be good because the eddy current loss increases, resulting in an increase in total iron loss.

[Spacer film production step]

Subsequently, in the present invention, a spacer film is prepared as an auxiliary layer for supplementing the Si, Mn, Al, Ni, and Sn contents that are insufficient in the cold rolled steel sheet up to the above step. The spacer film is overlapped with the cold rolled steel sheet and then wound simultaneously to form a heterogeneous winding coil. The spacer film structure includes a coating layer including at least one element selected from Si, Mn, Al, Ni, and Sn on one or both sides of the base material. The structure is preferred. In this case, the base material may be formed using a metal substrate or a silicon glass fiber substrate coated with a refractory material, and the coating layer is preferably formed by one of a method selected from hot dip plating, electroplating, CVD, and PVD methods.

If the base material is a silicon glass fiber substrate may cause acupuncture phenomenon in the subsequent heat treatment process. In addition, when the spacer film is formed on only one surface of the base material, one spacer film may affect only one layer of cold rolled steel sheet, and when formed on both sides, the spacer film may affect multiple layers of cold rolled steel sheet, thus increasing production efficiency. Can be.

In addition, the spacer film of the three-stage structure and the hetero-wound coil structure in combination with the cold rolled steel sheet will be described in more detail with reference to FIGS. 2 and 3.

[Heat treatment step]

In the re-crystallization annealing heat treatment step performed in the subsequent re-crystallization annealing step according to the above method, if the annealing temperature is less than 800 ℃ crystal growth rate is low after recrystallization, iron loss may be deteriorated, if more than 1000 ℃ the surface rather than the advantage of crystal growth Iron loss and magnetic flux density characteristics deteriorate due to the damage caused by an increase in the oxide layer, and therefore, annealing at 800 to 1000 ° C is preferable. At this time, the temperature increase rate influences the strength of the (200) plane, which is an advantageous structure in the steel sheet, to influence the iron loss characteristics and the magnetic flux density values. In order to improve these characteristics, the temperature increase rate is controlled at 5 ° C / sec or more. Preferably, the annealing heat treatment time is preferably adjusted to 1 hour to 2 hours.

In addition, in the present invention, the content of Si, Mn, Al, Ni, and Sn in the final cold rolled steel sheet should be optimally controlled by the spacer film, and all conditions may be satisfied only at the 800 to 1000 ° C. temperature and 1 to 2 hours. there was.

Next, the spacer film is removed by winding the cold rolled steel sheet annealed in the recrystallization annealing heat treatment step in a wound state, treated with organic, inorganic and organic-inorganic composite coating, or coated with an insulating film to be shipped to the buyer. The buyer can then blow into the desired product.

The non-oriented electrical steel sheet according to the present invention is as described above. Looking at the structure and the characteristics of the hetero-wound coil structure and the spacer film which are the core characteristics of the steps are as follows.

2 is a cross-sectional view showing a part of a winding coil for manufacturing a high efficiency non-oriented electrical steel sheet according to the present invention.

FIG. 2 shows a spacer film 250 sandwiched between cold rolled steel sheets 200 for winding immediately after hot rolling of a hot rolled steel sheet. ) And the spacer layer 250 may be unwound and simultaneously wound to form a heterogeneous winding coil.

At this time, the spacer film 250 is preferably formed in a three-stage structure, the specific form of which is as follows.

3 is a cross-sectional view showing a spacer film 250 for manufacturing a high efficiency non-oriented electrical steel sheet according to the present invention.

Referring to FIG. 3, a base material 210 formed of a metal substrate or silicon glass fiber substrate coated with a refractory material is provided, and at least one selected from Si, Mn, Al, Ni, and Sn on both surfaces of the base material 210. The coating layer 220 containing the element is formed. At this time, the coating layer is preferably formed to a thickness of 0.1 ~ 1mm, it is preferable to form by one of the method selected from the hot dip plating, electroplating, CVD and PVD method. If the thickness of the coating layer is formed to less than 0.1mm it may be difficult to control the components of the steel sheet according to the subsequent heat treatment, the winding may not be easily made when the thickness exceeds 1mm.

When the spacer film 250 having such a structure is brought into contact with the cold rolled steel sheet 200, the coating layer 220 is formed on both sides of the cold rolled steel sheet 200. Thus, Si, Mn, Al, Ni, and Sn may be changed according to heat treatment conditions. The content can be easily adjusted.

Therefore, low iron loss can be achieved through high Si content, thereby producing an electric steel sheet having high efficiency.

As described above, the method for manufacturing a high efficiency non-oriented electrical steel sheet according to the present invention enables cold rolling using a Si steel sheet of up to 3% by weight that can be cold rolled.

In addition, the present invention can facilitate the cold rolling by using the minimum Si steel sheet as possible as described above, and wound with a coating layer containing any one selected from Si, Mn, Al, Ni and Sn, the electrical during heat treatment It is possible to manufacture high efficiency non-oriented electrical steel sheet with excellent magnetic properties.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and those skilled in the art to which the art belongs can make various modifications and other equivalent embodiments therefrom. I will understand.

Therefore, the true technical protection scope of the present invention will be defined by the claims below.

1 is a flow chart showing an embodiment of a high efficiency non-oriented electrical steel sheet manufacturing method according to the present invention.

Figure 2 is a cross-sectional view showing a part of the winding coil for producing a high efficiency non-oriented electrical steel sheet according to the present invention.

Figure 3 is a cross-sectional view showing a spacer film for producing a high efficiency non-oriented electrical steel sheet according to the present invention.

Claims (9)

(a) preparing a cold rolled steel sheet; (b) preparing a spacer film containing at least one element selected from Si, Mn, Al, Ni, and Sn; (c) overlapping the cold rolled steel sheet and the spacer film and winding them to form a different winding coil; (d) heat treating the dissimilar winding coil; And (e) removing the spacer film while unwinding the dissimilar winding coil, and then performing insulation coating on the heat-treated cold rolled steel sheet. The method of claim 1, The cold rolled steel sheet of step (a) is by weight%, C: 0.005% or less, S: 0.005% or less, N: 0.005% or less, Si: 0.8-1.0%, Al: 0.1-0.4%, Mn: 0.1-0.2 %, Sn: 0.01% to 0.02%, Ni: 0.02% to 0.10% A method for producing a highly efficient non-oriented electrical steel sheet, comprising using a steel slab composed of Fe and other impurities. The method of claim 1, The heat treatment is a high efficiency non-oriented electrical steel sheet manufacturing method, characterized in that proceeding at a temperature of 800 ~ 1,000 ℃. The method of claim 1, The heat treatment is a high efficiency non-oriented electrical steel sheet manufacturing method characterized in that for 1 to 2 hours. The method of claim 1, The spacer film is a high efficiency non-oriented electrical steel sheet manufacturing method characterized in that it is formed in a three-stage structure formed with a coating layer containing at least one element selected from Si, Mn, Al, Ni and Sn on both sides of the base material. The method of claim 5, The base material is a high-efficiency non-oriented electrical steel sheet manufacturing method characterized in that using a refractory material coated metal substrate or silicon glass fiber substrate. The method of claim 5 The coating layer is a high-efficiency, non-oriented electrical steel sheet manufacturing method characterized in that formed by one of the method of hot-dip, electroplating, CVD and PVD. The method of claim 5, The coating layer is a high efficiency non-oriented electrical steel sheet manufacturing method characterized in that formed to a thickness of 0.1 ~ 1mm. delete

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