KR20200072352A - A degreasing agent for a directional electric steel sheet and a degreasing method using the same - Google Patents

Abstract

The present specification relates to a degreasing agent for a grain-oriented electrical steel sheet and a degreasing method using the same, and more specifically, to a degreasing agent capable of removing a rolling lubricant existing on the surface of a cold-rolled steel sheet prior to decarburization annealing and immersion annealing, and a degreasing method using the same. According to an embodiment of the disclosed degreasing method includes a step of immersing the cold-rolled steel sheet in the degreasing agent. The degreasing agent includes: at least one of 1-5 wt% of glycerin, 7-13 wt% of hydrogen peroxide, and less than 4 wt% of hydrofluoric acid; alcohol having 1 to 8 carbon atoms; and unavoidable impurities.

Description

Degreasing agent for a directional electric steel sheet and a degreasing method using the same}

The present invention relates to a degreasing agent for a grain-oriented electrical steel sheet and a degreasing method using the same, and more particularly, to a degreasing agent capable of removing rolled lubricant existing on the surface of a cold rolled steel sheet before decarburization annealing and entrainment annealing, and a degreasing method using the same. .

The grain-oriented electrical steel sheet is a soft magnetic material having excellent magnetic properties in one direction or in the rolling direction because it exhibits a Goss texture having a aggregation structure of {110}<001> with respect to the rolling direction.

In order to secure excellent soft magnetic properties, precise and accurate control of decarburization annealing and impregnation annealing after cold rolling is important, and for this, the surface treatment state of the cold rolled steel sheet must be maintained at a good level. However, in order to cold-roll the grain-oriented electrical steel sheet, a rolling lubricant is inevitably used, and the rolling lubricant remains on the surface of the cold rolled steel sheet, and there is a problem that the surface treatment state cannot be maintained at a good level.

Korean Registered Patent Publication No. 10-1625982 (Publication date: May 31, 2016)

In order to solve the above problems, the present invention is to provide a degreasing agent and a degreasing method using the degreasing agent capable of degreasing the rolling lubricant remaining on the surface of the cold rolled steel sheet.

Degreasing agent for a grain-oriented electrical steel sheet according to an embodiment of the present invention is at least one of less than 4% of glycerin: 1-5%, hydrogen peroxide: 7-13%, hydrofluoric acid: less than 4%, the balance of 1 to 8 carbon atoms Contains alcohol and unavoidable impurities.

The degreasing method of the grain-oriented electrical steel sheet according to another embodiment of the present invention includes a step of immersing a cold rolled steel sheet in a degreasing agent, wherein the degreasing agent is weight%, glycerin: 1-5%, hydrogen peroxide: 7-13%, hydrofluoric acid: It contains at least one or more of less than 4%, and contains residual alcohols having 1 to 8 carbon atoms and unavoidable impurities.

Further, the step of immersing the cold rolled steel sheet in the degreasing agent may include maintaining the temperature range of the degreasing agent at 20 to 30°C.

In addition, the step of immersing the cold rolled steel sheet in the degreasing agent may include immersing the cold rolled steel sheet in the degreasing agent for 3 to 5 minutes.

In addition, the immersed cold-rolled steel sheet may be further washed with alcohol and then dried.

According to an example of the present invention, since the rolling lubricant remaining on the surface of the cold-rolled steel sheet is removed by a chemical method rather than a mechanical method, reliability in satisfactory surface treatment state can be increased.

According to an example of the present invention, by providing a degreasing agent of a grain-oriented electrical steel sheet and a degreasing method using the same, the target oxidation amount (800±50ppm) and the mass (180±) are achieved by smoothly reacting moisture and ammonia during decarburization and annealing. 10ppm).

Hereinafter, preferred embodiments of the present invention will be described. However, embodiments of the present invention may be modified in various other forms, and the technical idea of the present invention is not limited to the embodiments described below. In addition, embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Terms used in the present application are only used to describe specific examples. Thus, for example, a singular expression includes a plural expression unless the context clearly indicates that it should be singular. In addition, terms such as “comprise” or “include” as used in the present application are used to clearly indicate the existence of features, steps, functions, elements, or combinations thereof described in the specification, and other features. It should be noted that it is not used to preliminarily exclude the presence of a field or step, function, component, or combination thereof.

On the other hand, unless defined otherwise, all terms used in this specification should be regarded as having the same meaning as generally understood by a person having ordinary skill in the art to which the present invention pertains. Accordingly, unless specifically defined herein, certain terms should not be construed in excessively ideal or formal sense. For example, in this specification, a singular expression includes a plural expression unless the context clearly has an exception.

In addition, "about", "substantially", and the like in the present specification are used in the sense of or close to the value when manufacturing and substance tolerances unique to the stated meaning are presented, and are used to help understand the present invention. Or, an absolute value is used to prevent unscrupulous use of the disclosed content by unscrupulous intruders.

In addition, the "cold rolled steel sheet" of the present specification is used as a meaning to refer to the grain-oriented electrical steel sheet before cold-rolled, before decarburization and impregnation annealing.

In order to secure excellent soft magnetic properties, precise and accurate control of decarburization annealing and impregnation annealing after cold rolling is important, and for this, the surface treatment state of the cold rolled steel sheet must be maintained at a good level. However, in order to cold-roll the grain-oriented electrical steel sheet, a rolling lubricant is inevitably used, and the rolling lubricant remains on the surface of the cold rolled steel sheet, and there is a problem that the surface treatment state cannot be maintained at a good level.

In order to solve the above problems, the present invention is to provide a degreasing agent and a degreasing method using the degreasing agent capable of degreasing the rolling lubricant remaining on the surface of the cold rolled steel sheet.

The degreasing agent of the grain-oriented electrical steel sheet according to an embodiment of the present invention comprises at least one of less than 4% by weight of glycerin: 1 to 5%, hydrogen peroxide: 7 to 13%, and hydrofluoric acid: less than 1 to 8 carbons. Contains alcohol and inevitable impurities.

Hereinafter, the reason for limiting the composition will be described in detail. The following composition of the composition means all weight% unless otherwise specified.

Glycerin: 1-5% by weight

Glycerin is a component that acts as a surfactant to increase the degree of activation for decomposing rolling lubricant remaining on the surface of the cold rolled steel sheet by lowering the surface tension between the rolling lubricant and the atmosphere and the steel sheet. In order to exhibit this effect in the present invention, it is preferable that the content of glycerin is 1% by weight or more.

On the other hand, when the content exceeds 5% by weight, the decomposition activity of the rolled milk powder is excessively increased, so that a difference in local degreasing speed is generated, which makes it difficult to degrease the surface uniformly, thereby increasing the surface roughness. Therefore, the content of glycerin in the present invention is preferably controlled to 1 to 5% by weight.

Hydrogen peroxide: 7 to 13% by weight

Hydrogen peroxide is a component for decomposing rolled lubricant remaining on the surface of a cold rolled steel sheet. In order to exhibit this effect in the present invention, it is actively added.

In the present invention, when the hydrogen peroxide content is less than 7% by weight, the degreasing speed of the rolled lubricant is significantly lowered, and rust may occur on the surface of the steel sheet during degreasing. On the other hand, when the content exceeds 13% by weight, the degreasing speed is excessively accelerated, resulting in a difference in the degreasing speed locally, which makes it difficult to degrease the surface uniformly, thereby increasing the surface roughness. Therefore, in the present invention, the content of hydrogen peroxide is preferably controlled to 7 to 13% by weight.

Folic acid: less than 4% by weight

Although hydrofluoric acid decomposes the rolling lubricant remaining on the surface of the cold rolled steel sheet, it is preferable not to use it because it is a very harmful compound for the human body. However, one or more components of glycerin and hydrogen peroxide are added when the degreasing rate of the degreasing agent mixed alone or with the above-described composition is slow or unstable.

In the present invention, when the hydrofluoric acid is 4% by weight or more, since the result of the degreasing treatment is the same as when it is less than 4% by weight, it is preferable to control the content of the hydrofluoric acid to less than 4% by weight.

The remaining component of the invention is alcohol. However, in the normal manufacturing process, unintended impurities from the raw material or the surrounding environment may be inevitably mixed, and therefore cannot be excluded. Since the impurities are known to anyone skilled in the ordinary manufacturing process, they are not specifically mentioned in this specification.

In the present invention, the alcohol may be an alcohol having 1 to 8 carbon atoms, and any of conventional methanol and ethanol may be used.

According to an example of the present invention, the degreasing agent for a grain-oriented electrical steel sheet having the above composition is sufficient to be able to remove the rolling lubricant remaining on the surface of the cold rolled steel sheet, and can be manufactured in various ways as long as there is no adverse effect in terms of chemical reaction.

According to an example of the present invention, when one type selected from the group consisting of glycerin, hydrogen peroxide and hydrofluoric acid is used alone, it is adjusted to the above composition content range and added to alcohol, or when mixed with two or more types, glycerin is added to alcohol. After the injection, hydrofluoric acid may be added to the alcohol, and then hydrogen peroxide may be added to the alcohol in order to prepare the degreasing agent of the present invention.

Hereinafter, a method of degreasing a grain-oriented electrical steel sheet using the degreasing agent of the present invention will be described in detail.

In the present invention, the grain-oriented electrical steel sheet can be variously manufactured by a person skilled in the art from known techniques. According to one example, the grain-oriented electrical steel sheet is a step of heating the slab, the step of hot rolling the slab, the step of annealing the hot rolled steel sheet, the step of cold rolling the heat treated steel sheet, the step of decarburizing and impregnating annealing the cold rolled steel sheet, final And annealing.

The degreasing method of the grain-oriented electrical field of the present invention is to effectively remove the rolling lubricant remaining on the surface of the cold-rolled steel sheet prior to decarburization and impregnation annealing of the cold-rolled steel sheet that has undergone the cold rolling step.

The method for degreasing a grain-oriented electrical steel sheet according to an embodiment of the present invention may include immersing a cold rolled steel sheet in a degreasing agent. The degreasing agent, by weight, contains at least one of glycerin: 1-5%, hydrogen peroxide: 7-13%, and hydrofluoric acid: less than 4%, and may include alcohol with residual carbons 1 to 8 and unavoidable impurities. , The reason for the limitation on the range of ingredients was described above, and thus will be omitted.

In the degreasing method according to one aspect of the present invention, it is preferable that the temperature range of the degreasing agent is maintained at 20 to 30°C. If the temperature of the degreasing agent is less than 20°C, the degreasing agent and the chemical reaction for removing the oil present on the surface of the cold rolled steel sheet may not sufficiently occur, so that the degreasing treatment may not be properly performed. On the other hand, when the temperature of the degreasing agent exceeds 30°C, as a result of the excessively accelerated degreasing reaction rate, a difference occurs in the local degreasing rate, which makes it difficult to degrease the surface uniformly, thereby increasing the surface roughness.

The degreasing method according to an example of the present invention may include immersing a cold rolled steel sheet in a degreasing agent for 3 to 5 minutes. If it is immersed in less than 3 minutes, the degreasing reaction may not be timely, so the degreasing treatment may not be properly performed, and if it is immersed for more than 5 minutes, the degreasing treatment may proceed excessively, resulting in a higher surface roughness.

The degreasing method according to an example of the present invention may further include a step of degreasing the cold rolled steel sheet in a degreasing agent, followed by washing the cold rolled steel sheet with alcohol and then drying.

In addition, after washing with alcohol, the residual degreasing agent is removed after drying, and can be dried at room temperature or dried at a high temperature through hot air at 40 to 100°C.

According to an example of the present invention, since the rolling lubricant remaining on the surface of the cold-rolled steel sheet is removed by a chemical method using a degreasing agent as described above rather than a mechanical method, reliability in satisfactory surface treatment state can be increased.

According to an example of the present invention, by providing a degreasing agent of a grain-oriented electrical steel sheet and a degreasing method using the same, it is possible to remove the rolled lubricant present on the surface of the cold rolled steel sheet, thereby improving the surface treatment state, so that water is dehydrated and dehydrated during annealing. The target ammonia layer (800±50ppm) and needle mass (180±10ppm) can be secured by smoothly reacting with ammonia.

Hereinafter, the present invention will be described in more detail through examples. However, it is necessary to note that the following examples are only intended to illustrate the present invention in more detail and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by matters described in the claims and reasonably inferred therefrom.

{Example}

After preparing each degreasing agent composed of the components of Table 1 and the rest of the alcohol, the temperature of the degreasing agent was maintained at 25° C., and the cold rolled steel sheet was immersed for 4 minutes, then immersed in alcohol for 4 minutes or more to wash, and dried to a natural dry specimen at room temperature. Table 1 shows the amount of the oxide layer and the needle mass obtained by performing decarburization annealing heat treatment. The amount of oxide layer and needle mass are measured by the dry analysis method, and each target value is 800±50ppm and 180±10ppm.

division Degreasing agent composition Oxidation layer amount
(ppm) Needle mass
(ppm) glycerin
(weight%) Hydrogen peroxide
(weight%) Foshan
(weight%) Comparative Example 1 0.5 5.2 0 620 130 Inventive Example 1 2.8 10.4 2.8 810 180 Comparative Example 2 7.3 15.2 5.4 980 160 Inventive Example 2 4.7 11.6 3.5 830 180

Referring to Table 1, it can be seen that as the degreasing agent of Inventive Example 1 and 2, the amount of oxide layer and the amount of needle mass matched the target value, the surface treatment state is good and the Goss texture is well formed to target. Soft magnetic properties can be secured.

On the other hand, in Comparative Example 1, the content of glycerin and hydrogen peroxide was lower than that of the invention, so the degreasing treatment was not properly performed. For this reason, the amount of the oxide layer and the needle mass of Comparative Example 1 were less than the amount of the oxide layer and the needle mass targeted by the present invention. In Comparative Example 1, since the amount of the oxide layer was less than the target value, the formation of an appropriate base coating on the steel sheet was inhibited, resulting in surface defects, and the needle mass was less than the target value, resulting in normal recrystallization of other aggregates other than the goth aggregate. There is a problem that causes a magnetic defect.

In addition, in Comparative Example 2, the content of glycerin, hydrogen peroxide, and hydrofluoric acid was excessive compared to that of the invention, and the degreasing treatment proceeded excessively, resulting in high surface roughness. For this reason, the amount of the oxide layer and the needle mass in Comparative Example 2 were larger than the amount of the oxide layer and the needle mass targeted by the present invention. In Comparative Example 2, since the amount of the oxide layer was larger than the target value, the steel plate was peroxidized, and the color of the base coating was formed unevenly, causing surface defects, and the secondary recrystallization behavior of the grain-oriented electrical steel sheet did not occur properly because the needle mass was greater than the target value. There is a problem in that the magnetic properties are deteriorated due to the second recrystallization of the goth crystal grains having a low degree of integration and, in other words, poor quality.

As described above, although exemplary embodiments of the present invention have been described, the present invention is not limited thereto, and a person having ordinary skill in the art does not depart from the concept and scope of the following claims. It will be understood that various modifications and variations are possible.

Claims (5)

Degreasing agent for grain-oriented electrical steel sheets containing at least one or more of glycerin: 1 to 5%, hydrogen peroxide: 7 to 13%, and hydrofluoric acid: less than 4% by weight, with residual carbon alcohol of 1 to 8 and inevitable impurities. Including; immersing the cold rolled steel sheet in a degreasing agent;
The degreasing agent is at least one of glycerin: 1 to 5%, hydrogen peroxide: 7 to 13%, and hydrofluoric acid: less than 4% by weight, and the aromatic electricity including alcohol having 1 to 8 carbons and unavoidable impurities. Method of degreasing steel sheet. According to claim 2,
The step of immersing the cold rolled steel sheet in the degreasing agent,
Degreasing method of a grain-oriented electrical steel sheet comprising maintaining the temperature range of the degreasing agent at 20 ~ 30 ℃. According to claim 2,
The step of immersing the cold rolled steel sheet in the degreasing agent,
A method of degreasing a grain-oriented electrical steel sheet comprising immersing the cold rolled steel sheet in the degreasing agent for 3 to 5 minutes. According to claim 2,
A method of degreasing the grain-oriented electrical steel sheet further comprising; washing the immersed cold rolled steel sheet in alcohol and then drying it.