KR101833216B1 - Pickling agent for grain oriented electrical steel sheet, pickling process of grain oriented electrical steel sheet - Google Patents

Abstract

The present invention provides a pickling solution for a directional electric steel sheet, and a pickling method for a directional electric steel sheet, which improves the surface roughness of a rolled material so as to prevent rolling slip caused by rapid abrasion of a rolling roll when cold rolling is performed in a process of manufacturing a directional electric steel sheet. According to an embodiment of the present invention, the pickling solution for a directional electric steel sheet includes 10 to 30 wt% of inorganic acids, 1 to 10 wt% of hydrogen peroxide (H_2O_2), and the remaining of water.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a pickling method for an electric steel sheet for a directional electric steel sheet and a pickling method for a directional electric steel sheet,

Acid pickling solution for a directional electric steel sheet and a pickling method for a directional electric steel sheet.

In general, a grain-oriented electrical steel sheet is a steel sheet containing a Si component of about 3.1%, and has an aggregate structure in which the grain orientations are aligned in the {100} < 001 > direction and has extremely excellent magnetic properties in the rolling direction Electrical steel sheet.

Directional electrical steel sheets are divided into two steel types, antimony (Sb) and non-Sb. Recently, the production proportion of Sb-added steels with superior magnetic properties has been increased. However, as the line speed decreases due to the rolling slip caused by abrasion of a large amount of rolling rolls during cold rolling of Sb-added steels, It is very heated.

It is an object of the present invention to provide an acidic solution for a directional electric steel sheet which improves the surface roughness of the rolled material in order to prevent rolling slip caused by abrupt abrasion of the rolling roll during cold rolling in a directional electric steel sheet manufacturing process.

It is an object of the present invention to provide a pickling method of a directional electric steel sheet which improves the surface roughness of the rolled material in order to prevent rolling slip caused by rapid abrasion of the rolled roll during cold rolling in a directional electric steel sheet manufacturing process.

The pickling solution for a directional electric steel sheet according to an embodiment of the present invention comprises 10 to 30% by weight of inorganic acid, 1 to 10% by weight of hydrogen peroxide (H ₂ O ₂ ) and the remainder.

The grain-oriented electrical steel sheet may contain 0.001 to 0.15% by weight of Sb and the balance of Fe and other unavoidable impurities.

The inorganic acid may include hydrochloric acid, nitric acid or hydrofluoric acid.

The pickling solution for the directional electric steel sheet may further contain 1 to 10% by weight of iron chloride (FeCl ₃ ).

A method for pickling a directional electrical steel sheet according to an embodiment of the present invention includes: preparing a hot rolled steel sheet; And spraying an acid washing liquid containing 10 to 30 wt% of inorganic acid, 1 to 10 wt% of hydrogen peroxide and the remainder on the surface of the hot-rolled annealed hot-rolled sheet.

In the step of preparing the hot-rolled annealed hot-rolled sheet, the hot-rolled sheet may be a hot-rolled sheet having an Sb layer formed on its surface.

The Sb segregation layer may contain 0.3 to 1% by weight of Sb.

Preparing the hot-rolled annealed hot-rolled sheet comprises preparing a slab comprising 0.001 to 0.15% by weight of Sb and the balance of Fe and other unavoidable impurities; Heating the slab; Hot rolling the heated slab to produce a hot rolled steel sheet; And hot-rolled annealing the hot-rolled sheet.

The inorganic acid may include hydrochloric acid, nitric acid or hydrofluoric acid.

The acid solution may further contain 1 to 10% by weight of iron chloride (FeCl ₃ ).

According to an embodiment of the present invention, in the production of a grain-oriented electrical steel sheet, an acid taxane and / or a soda-lime slag that can effectively remove the Sb segregation layer formed on the surface of the hot rolled steel sheet to prevent rolling slip in the cold rolling process, A pickling method can be provided.

In addition, the rolling operation at the time of cold rolling is stabilized, and the magnetic properties such as iron loss and magnetic flux density can be improved by ensuring high temperature workability.

FIG. 1 is a scanning electron microscope (SEM) photograph of the hot-rolled sheet section after hot-annealing in the embodiment and the Sb concentration in the thickness direction analyzed by an electron probe micro analyzer (EPMA).
Fig. 2 shows the results of analysis of the surfaces of the steel sheets picked up in Examples and Comparative Examples 1 and 2 by an electron probe micro-analyzer (EPMA).

The terms first, second and third, etc. are used to describe various portions, components, regions, layers and / or sections, but are not limited thereto. These terms are only used to distinguish any moiety, element, region, layer or section from another moiety, moiety, region, layer or section. Thus, a first portion, component, region, layer or section described below may be referred to as a second portion, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified and that the presence or absence of other features, regions, integers, steps, operations, elements, and / It does not exclude addition.

When referring to a portion as being "on" or "on" another portion, it may be directly on or over another portion, or may involve another portion therebetween. In contrast, when referring to a part being "directly above" another part, no other part is interposed therebetween.

In the present invention, 1 ppm means 0.0001%.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Commonly used predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Antimony (Sb) is a typical material forming segregation zone in Fe base material. Sb contained in Sb-added steel is also not segregated as steel and segregated on the surface. Particularly, when a large amount of hot-rolled oxide layer is formed, the amount of segregation will be larger because the oxide layer is a ceramic material, the solubility of Sb is lower than that of the metal matrix, and the Sb supersaturated in the oxide layer region is an interface It is segregated after spreading.

The most basic principle of the pickling on the surface of an alloy material can be explained by electromotive force. Electromotive force refers to a force that moves electrons at two points of different potentials and generally tends to move electrons toward the lower (reduction potential) side in the oxidation-reduction reaction . A well-known example of this effect is cathodic protection. For example, when Mg metal is connected or welded to prevent corrosion of a service gas oil tank, which is Fe metal, Mg metal (E ^o = -2.73 V) with a small potential value is first oxidized and ionized, Electrons move toward the Fe metal (E ^o = -0.44 V) having a large potential value. Then, the surface of Fe is reduced by the electrons moved, so that the surface is not corroded.

The change of the oxidation-reduction reaction by the potential difference can be applied to the pickling process of Sb-added steel. Is a process in which a metal atom is ionized and eluted by reaction with an anion (e.g., Cl ^- , OH ^-, etc.) in a solution. All the components contained in the Sb unreinforced steel have a smaller reduction potential than that of hydrogen and can be eluted into the solution, and the excess free electrons generated by ionization of the metal are transferred to the hydrogen ions and reduced to hydrogen gas (H ₂ ) do. However, in the case of Sb-added steels, Sb segregated on the surface of the steel sheet is a substance having a larger potential value than hydrogen. Therefore, the Fe atoms are ionized, and some of the released electrons move to the Sb rather than the hydrogen ions, and the Sb atoms are not eluted into the ion state by the extra electrons. That is, the Sb segregation layer is picked up in the acidic liquid and not removed. Also, the oxide layer existing in the segregated portion of Sb is not allowed to fall off, and the acidity deteriorates and the scale remains. In the case where Sb having a relatively large potential value exists as compared with the case where Fe is present singly, free electrons move toward Sb, so that electrons are not concentrated on the Fe surface, and the relative dissolution rate of Fe is increased do.

H ₂ O ₂ (hydrogen peroxide), which is a substance having a higher reduction potential than Sb, is added to the acidic solution to prevent the phenomenon that Sb is not eluted as excess electrons are generated in the Sb segregation layer as described above, And the generated electrons are taken by hydrogen peroxide instead of Sb. As a result, since no extra electrons are generated in the Sb segregation layer, the Sb atoms can also react with the anions in the acid solution and can be eluted.

As shown in Reaction Scheme 1 below, H ₂ O ₂ serves as a source for providing Fe ^{3 +} ions in the acidic solution.

[Reaction Scheme 1]

FeCl ^{3 -} &^gt; Fe ^{3 +} + 3Cl ^-

^{_{2Fe 2 + + H 2 O 2}} + 2H + → 2Fe 3 + + 2H 2 O

At this time, as shown in Table 1 below, the reduction potential of Fe ^{3 +} is +0.77 V which is larger than Sb (+0.20 V). Therefore, Fe ^{3 +} ions tend to be reduced to Fe ^{2 +} by bringing electrons around them. Therefore, the Fe ions are ionized and the electrons released by Fe ^{3 +} ions, not Sb. Finally, if Fe ^{3 +} ions are present in the acidic solution, Sb can be removed during the pickling process.

Reaction formula E ⁰ (V) Fe ^{2 +} + 2e ^- ? Fe -0.44 2H ⁺ + 2e ^- &gt; H ₂ 0.00 ^{SbO + + 2H + + 3e -} → Sb + H 2 O +0.20 Fe ^{3 +} + e ^- &gt; Fe ^{2 +} +0.77

The pickling solution for a directional electric steel sheet according to an embodiment of the present invention comprises 10 to 30% by weight of inorganic acid, 1 to 10% by weight of hydrogen peroxide (H ₂ O ₂ ) and the remainder.

The inorganic acid can be used without restriction as long as it is an inorganic acid used in an acidic solution. Specifically, the inorganic acid may include hydrochloric acid, nitric acid or hydrofluoric acid. More specifically, hydrochloric acid can be used.

The inorganic acid may be contained in an amount of 10 to 30% by weight based on 100% by weight of the acidic tax solution. If the amount of the inorganic acid is too small, pickling may not be sufficient. If the amount of the inorganic acid is too large, defects may occur on the surface of the steel sheet due to over-pickling. More specifically, 15 to 20 wt% of inorganic acid may be included.

Hydrogen peroxide (H ₂ O ₂ ) is added to efficiently remove Sb segregated on the surface of the steel sheet. The hydrogen peroxide may be contained in an amount of 1 to 10% by weight based on 100% by weight of the acid tax. If too little hydrogen peroxide is contained, Sb can not be sufficiently removed. If too much hydrogen peroxide is contained, the surface of the steel sheet becomes rough, which may lead to poor workability in the subsequent rolling. More specifically, hydrogen peroxide may be contained in an amount of 2 to 6% by weight.

The acidic solution according to an embodiment of the present invention may further contain 1 to 10% by weight of iron chloride (FeCl ₃ ) relative to 100% by weight of the acid tax solution. By further containing an appropriate amount of iron chloride, the Sb removal efficiency can be further improved.

The acid solution according to an embodiment of the present invention is used as an acidic solution of a grain-oriented electrical steel sheet. As described above, since the detailed liquid according to one embodiment of the present invention is excellent in the Sb removal efficiency in the Sb-added steel, the directional electrical steel sheet can be used as the directional electrical steel sheet, It can be used more effectively in electric steel sheet.

Specifically, the grain-oriented electrical steel sheet may contain 0.001 to 0.15% by weight of Sb and the balance of Fe and other unavoidable impurities.

In the present invention, the inclusion of Sb means that Sb is essentially included, and does not mean that components such as Si, Al, Mn, C, and N are generally excluded from the other orienting electrical steel sheets.

In one embodiment of the present invention, the components of the grain-oriented electrical steel sheet will be described in detail as follows.

Si: 2.8 to 6.8 wt%

Silicon (Si) increases the resistivity of the steel to reduce iron loss. When the content of Si is too small, the resistivity of the steel becomes small and the iron loss characteristic deteriorates. In the high temperature annealing, The door can be opened. If the content of Si is too large, the brittleness is increased and cold rolling may become difficult. Therefore, the content of Si can be controlled within the above-mentioned range. More specifically, Si may be contained in an amount of 3.8 to 5.8% by weight.

Al: 0.020 to 0.040 wt%

Aluminum (Al) is finally a component that acts as an inhibitor by being made of nitride of (Al, Si, N), (Al, Si, Mn) N type. When the content of Al is too small, it is difficult to expect a sufficient effect as an inhibitor. When the content of Al is too large, the nitride of the Al system precipitates and grows too much, so that the effect as an inhibitor may become insufficient. Therefore, the content of Al can be controlled within the above-mentioned range.

Mn: 0.01 to 0.20 wt%

Manganese (Mn) has the effect of reducing the iron loss by increasing the resistivity as Si and reacting with the nitrogen introduced by the nitriding treatment together with Si to form precipitates of N (Al, Si, Mn) It is an important element for suppressing the growth of sizing and causing secondary recrystallization. However, when the content of Mn is too large, it accelerates the austenite phase transformation during hot rolling so that the size of the primary recrystallized grains is reduced to make the secondary recrystallization unstable. When the content of Mn is too small, the effect of increasing the austenite fraction during hot-rolling reheating as the austenite forming element to increase the amount of precipitates and thus to make the primary recrystallization through MnS formation not too much It can occur insufficiently. Therefore, the content of Mn can be controlled within the above-mentioned range.

Sb: 0.001 to 0.15 wt%

Since Sb is an element which interferes with the movement of grain boundaries as a grain boundary segregation element, generation of goss grain in {110} < 001 > orientation is promoted as a grain growth inhibitor, and secondary recrystallization is well developed. If the content of Sb is too small, the effect may be deteriorated. If the Sb content is too large, the grain boundary segregation becomes severe and the brittleness of the steel sheet becomes large, so that plate breakage may occur during rolling.

And more specifically 0.01 to 0.08% by weight of Sb.

Sn: 0.01 to 0.15 wt%

Since Sn is an element that interferes with grain boundary movement as a grain boundary segregation element together with Sb, generation of goss grain in the {110} < 001 > orientation is promoted as a grain growth inhibitor so that secondary recrystallization is well developed. It is an element. More specifically, Sn may be contained in an amount of 0.01 to 0.12% by weight.

C: not more than 0.01% by weight

C is a component which does not greatly contribute to the improvement of the magnetic properties of the grain-oriented electrical steel sheet in the embodiment of the present invention, and is preferably removed as much as possible. However, if it is contained above a certain level, the austenite transformation of the steel is promoted in the rolling process, and the hot rolled structure is miniaturized during hot rolling to help form uniform microstructure. Therefore, the C content in the slab is 0.03 weight % Or more. However, when the C content is excessive, coarse carbide is produced and it is difficult to remove the carbonaceous material during decarburization, so that it is preferably 0.08 wt% or less. The carbon is decarburized through the decarburization annealing process in the course of producing the grain-oriented electrical steel sheet, and C is contained in the grain-oriented electrical steel sheet to be produced at a final content of 0.01 wt% or less.

N: 0.001 to 0.005 wt%

N is an element that reacts with Al or the like to refine the crystal grains. When these elements are appropriately distributed, it is possible to appropriately finely structure the structure after cold rolling as described above, thereby assuring proper primary recrystallization grain size. However, if the content is excessive, the primary recrystallized grains are excessively refined, and as a result, the driving force causing crystal grain growth during the secondary recrystallization increases due to the fine crystal grains, so that the crystal grain can grow to an undesired orientation. Also, if the N content is excessive, it takes a long time to remove it in the final annealing process, which is not preferable. Therefore, the upper limit of the nitrogen content should be 0.005 wt%, and the nitrogen content of the slab should be 0.001 wt% or more when reheating the slab, so that the lower limit of the nitrogen content is preferably 0.001 wt%. Nitrogen is partially penetrated through the steep annealing process in the production of the grain-oriented electrical steel sheet, and N is included in the final grain-oriented electrical steel sheet in an amount of 0.005 to 0.05% by weight.

A method for pickling a directional electrical steel sheet according to an embodiment of the present invention includes: preparing a hot rolled steel sheet; And spraying an acid washing liquid containing 10 to 30 wt% of inorganic acid, 1 to 10 wt% of hydrogen peroxide and the remainder on the surface of the hot-rolled annealed hot-rolled sheet.

Hereinafter, each step will be described in detail.

First, a hot rolled sheet which is hot-rolled is prepared. The hot-rolled annealed hot-rolled sheet can be used without particular limitation as long as it is a hot-rolled sheet produced in the course of manufacturing a directional electric steel sheet. More specifically, the hot-rolled sheet hot-rolled has a slab containing 0.001 to 0.15% by weight of Sb and the balance of Fe and other unavoidable impurities; Heating the slab; Hot rolling the heated slab to produce a hot rolled steel sheet; And hot-rolled annealing the hot-rolled sheet.

The composition of the slab is the same as the reason for limiting the composition of the above-described directional electrical steel sheet, and therefore, a repeated description thereof will be omitted. The detailed process conditions in each of the other processes are the same as those in the directional electric steel sheet. If the person skilled in the field of directional electric steel sheet can expect the condition without specific explanation, It is omitted.

The hot-rolled annealed hot-rolled sheet can also be subjected to a mechanical pre-treatment such as shot blasting.

In the hot-rolled steel sheet thus produced, Sb in the steel is segregated and an Sb segregation layer is formed on the surface. The existing acid solution can not efficiently remove the Sb segregation layer, which causes the rolling slip to occur in the cold rolling process, resulting in deterioration of the rolling productivity. In an embodiment of the present invention, an appropriate amount of hydrogen peroxide is added to an acidic solution, whereby the Sb segregation layer can be efficiently removed.

The Sb segregation layer means a layer in which Sb is segregated and has a higher content of Sb than other portions of the steel sheet, and specifically includes 0.3 to 1% by weight of Sb.

Next, an acidic solution containing 10 to 30% by weight of inorganic acid, 1 to 10% by weight of hydrogen peroxide and the remainder is sprayed onto the surface of the hot-rolled annealed sheet. The constitution of the acid tax liquid is the same as that described above, and a duplicate description will be omitted.

The details of the process conditions for the acid liquid spray are the same as those of the directional electric steel sheet, and those having technical knowledge in the field of directional electric steel sheet can be expected without specific explanation, so a detailed description thereof will be omitted .

The steel sheet thus picked is then made into a grain-oriented electrical steel sheet by cold rolling, decarburization, nitriding annealing and high temperature annealing. Further, the magnetic domain refinement can be carried out if necessary.

Hereinafter, the present invention will be described in more detail with reference to examples. However, these embodiments are only for illustrating the present invention, and the present invention is not limited thereto.

Example

A hot-rolled sheet containing 850 ppm (0.085% by weight) of Sb was prepared. Hot rolled, and shot blast pretreated. A scanning electron microscope (SEM) photograph of the section of the hot-rolled steel sheet and the Sb concentration in the thickness direction were analyzed by an electron probe micro analyzer (EPMA) to identify the Sb segregation layer present in the hot-rolled steel sheet and are shown in FIG. As shown in FIG. 1, the concentration of Sb rapidly increases at the interface between the oxide layer and the base material, and it can be confirmed that the Sb segregation layer is formed.

An acid washing solution containing 17 wt% of hydrochloric acid, 5 wt% of hydrogen peroxide and the remainder was sprayed onto the surface of the hot-rolled plate by a nozzle and pickled. The pickled hot-rolled sheets were analyzed by an Electron Probe Micro Analyzer (EPMA) and are shown in Fig.

Comparative Example  One

And acid pickling was carried out in the same manner as in Example except that 17% by weight of hydrochloric acid and an acid washing liquid containing the remainder were used as the acid washing liquid. The pickled hot-rolled sheets were analyzed by an Electron Probe Micro Analyzer (EPMA) and are shown in Fig.

Comparative Example  2

Except that acidic solution containing 17% by weight of hydrochloric acid, 5% by weight of ammonium thiosulfate and the remainder was used as the acidic tax solution. The pickled hot-rolled sheets were analyzed by an Electron Probe Micro Analyzer (EPMA) and are shown in Fig.

FIG. 2 shows the results of analysis of the surfaces of the steel sheets picked up in Examples and Comparative Examples 1 and 2 by an electron probe microanalyzer (EPMA). In Fig. 2, the red color indicates a higher Sb concentration, and the blue color indicates a lower Sb concentration. As shown in Fig. 2, almost no Sb was detected in the examples.

On the other hand, in Comparative Example 1, a large amount of red dots were observed in comparison with the Examples, and in Comparative Example 2, the result was worse than Comparative Example 1. The maximum concentration of Sb was 100 for Comparative Example 1, 99 for Example, and 110 for Comparative Example 2. [ As to the maximum concentration of Sb, there is no significant difference between Comparative Example 1 and Example, but in the case of Examples, since the area having a high concentration of Sb is much smaller than that of Comparative Examples 1 and 2, it can be confirmed that Sb is efficiently removed in the Examples have.

It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents. It will be understood that the invention may be practiced. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (10)

Wherein the acidic solution for an electric steel sheet comprises 10 to 30% by weight of inorganic acid, 1 to 10% by weight of hydrogen peroxide (H ₂ O ₂ )
Wherein said grain oriented electrical steel sheet comprises 0.001 to 0.15% by weight of Sb and the balance of Fe and other unavoidable impurities. delete The method according to claim 1,
Wherein the inorganic acid comprises hydrochloric acid, nitric acid or hydrofluoric acid. The method according to claim 1,
An acid taxane for a directional electric steel sheet further comprising 1 to 10% by weight of iron chloride (FeCl ₃ ). 0.001 to 0.15% by weight of Sb and the balance of Fe and other unavoidable impurities;
Heating the slab;
Hot rolling the heated slab to produce a hot rolled steel sheet;
Preparing a hot-rolled sheet hot-rolled and annealed by hot-annealing the hot-rolled sheet; And
A step of spraying an acidic solution containing 10 to 30 wt% of inorganic acid, 1 to 10 wt% of hydrogen peroxide, and the remainder on the surface of the hot-rolled and annealed hot-rolled steel sheet. 6. The method of claim 5,
Wherein the hot-rolled annealed hot-rolled sheet in the step of preparing the hot-rolled annealed hot-rolled sheet is a hot-rolled sheet having a surface of Sb on the surface thereof. The method according to claim 6,
Wherein the Sb segregation layer comprises 0.3 to 1% by weight of Sb. delete 6. The method of claim 5,
Wherein the inorganic acid comprises hydrochloric acid, nitric acid or hydrofluoric acid. 6. The method of claim 5,
Wherein the acid solution further comprises 1 to 10% by weight of iron chloride (FeCl ₃ ).

Images