KR20160077568A - The slag coated steel sheet with high hardness and corrosion resistance and manufacturing method thereof - Google Patents

Abstract

The present invention provides a manufacturing method of a slag coated steel sheet with high hardness and corrosion resistance to coat powder for coating which has furnace slag, ferronickel slag, or a compound thereof to a surface of the steel sheet and, more specifically, provides a slag coated steel sheet with high hardness and corrosion resistance manufactured thereby. Thus, slag treated as waste to be discarded is utilized as a surface treatment material of a steel sheet, and the steel sheet is surface treated with the slag to increase corrosion resistance and hardness of the steel sheet.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slag coated steel sheet having excellent hardness and corrosion resistance,

The present invention relates to a slag-coated steel sheet excellent in hardness and corrosion resistance, and a method for producing the same.

In general, slag, which is a by-product of the steelmaking process, is divided into blast furnace slag and steel slag. A part of the iron ore that does not contain iron is melted and comes out of the blast furnace is called blast furnace slag. In order to make steel from iron, By-products generated in the process of removing silicon components and the like are referred to as steelmaking slag.

The blast furnace slag is formed by melting a non-iron component contained in iron ore, coke, limestone, and the like, which is charged in a blast furnace, and is made of a ceramic material whose main component is lime (CaO) and silica (SiO ₂ ). Such blast furnace slag is quenched into high pressure water in a molten state to form a shape like a sand bar. This form is called granulated slag-water cooled, while the form in which cooling is gradually cooled in a natural cooling- It is called slat (Palletized Slag-Air cooled). Such blast furnace slag has been applied to cement raw material, fertilizer, paint, and aggregate for civil engineering so far and is mainly used as a construction material.

The steel slag is mainly composed of lime and silica, similar to blast furnace slag. The slag is produced by refining furnace slag (BOF slag) and scrap iron produced in the refining process by blowing high-pressure oxygen to the slag produced in the blast furnace. (EAF Slag). These steelmaking slag are recycled for use as building materials, similar to blast furnace slag, but most of them are classified as industrial wastes and are being reclaimed.

In addition, ferronickel slag is generated during the ferronickel production process, and its main component is composed of silica and magnesium oxide (MgO). The ferronickel slag is classified into a gravel-like carbonaceous slag, which is cooled slowly by natural air-cooling, and a sand-type waterglass slag, which is produced by spraying water into molten slag. In the case of ferronickel granule slag, it is known that it has high hardness and abrasion resistance when used as aggregate for civil engineering. In case of ferronickel water slag, it has superior characteristics than natural sand and can be used as concrete sand. It is known that concrete with high strength can be manufactured.

As described above, steelmaking and ferronickel slag are used as building materials for cement or concrete, but a considerable part of them are still disposed of at the landfill site. Therefore, recycling measures are urgently needed.

In the present invention, waste treated slag is used as a surface treatment material of the steel sheet, and the steel sheet is surface treated with the slag to improve the corrosion resistance and hardness of the steel sheet

According to an embodiment of the present invention, there is provided a method for manufacturing a slag coated steel sheet excellent in hardness and corrosion resistance by coating a surface of a steel sheet with a coating powder comprising blast furnace slag, ferronickel slag or a mixture thereof.

The powder for coating has a spherical shape, and the average particle size may be 10 to 90 탆.

The coating powder may be produced by spray drying a blast furnace slag, a ferronickel slag, or a mixture thereof, followed by classification.

The coating may be performed by at least one coating method selected from the group consisting of spray coating, chemical vapor deposition, physical vapor deposition, low temperature spraying and aerosol deposition.

The spray coating method may be at least one method selected from the group consisting of plasma coating method, high speed flame spraying, flame spraying, arc spraying and explosion spraying.

The plasma coating method may have an applied current of 300 to 700 A.

In the plasma coating method, the distance between the spray gun inlet to be radiated and the steel sheet may be 10 to 200 mm.

According to another embodiment of the present invention, there is provided a steel sheet and a coating layer formed on at least one surface of the steel sheet, wherein the coating layer comprises a blast furnace slag, a ferronickel slag, or a mixture thereof, and a slag coated steel sheet excellent in hardness and corrosion resistance do.

The steel sheet may be a hot-rolled steel sheet, a cold-rolled steel sheet, a coated steel sheet, an alloy coated steel sheet, or a stainless steel sheet.

The coating layer may have a thickness of 50 to 500 mu m.

The present invention has the effect of increasing the corrosion resistance and hardness of the steel sheet by using the slag to be treated as a surface treatment material of the steel sheet and treating the steel sheet with the slag.

Fig. 1 is a photograph of a granulated blast furnace slag particle subjected to refinement and sphering.
FIG. 2 is a photograph of a granulated and spheronized ferronickel slag particle for spray coating.
3 is a photograph of the surface of the steel sheet after the brine spray test is performed on the blast furnace slag-coated steel sheet of Example 1. Fig.
4 is a photograph of the surface of a steel sheet after the saline spray test is performed on the ferronickel slag-coated steel sheet of Example 2. Fig.
5 is a photograph of the surface of the steel sheet after the brine spray test was performed on the blast furnace-ferronickel slag-coated steel sheet of Example 3. Fig.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention relates to a slag-coated steel sheet excellent in hardness and corrosion resistance to be coated and a method for producing the same, and more particularly to a slag-coated steel sheet having excellent hardness and corrosion resistance to coat a steel sheet with a coating powder containing blast furnace slag, ferronickel slag, A slag-coated steel sheet manufacturing method is provided. When the steel sheet is coated using the powder for coating, the corrosion resistance of the steel sheet is greatly improved, and the hardness of the slag-coated steel sheet can be excellent.

The steel sheet with improved corrosion resistance and hardness can be used for various rolls, various pumps, pipes, piping, valve parts and construction materials of the steel industry, which require properties such as corrosion resistance and wear resistance. The recycling effect of such slag is not only economical in terms of recycling waste from steel and ferronickel processes but also has advantages of environmental preservation and also it is possible to omit the galvanizing process of steel sheet, .

As a by-product generated in the blast furnace slag is a steel manufacturing process used in the present _{invention, CaO 42%, SiO 2 34} %, Al 2 O 3 14%, MgO 6.4%, TiO 2 1.3%, S 0.4% and the Total-Fe 0.4 % And the like, and since the constituent material of the blast furnace slag is substantially free of iron component and is made only of a ceramic oxide, it can be very advantageous in terms of ensuring corrosion resistance.

Ferronickel slag, which is a byproduct produced in the ferronickel manufacturing process, contains 55% SiO ₂ , 33% MgO, 2.2% Al ₂ O ₃ , 7% total-Fe and 0.4% CaO, MgO can easily react with H ₂ O or CO ₂ in water and in the atmosphere to form magnesium hydroxide (Mg (OH) ₂ ) or magnesium carbonate (MgCO ₃ ). At this time, since the magnesium hydroxide and magnesium carbonate formed are in a very stable form, they can serve as a barrier layer for preventing penetration of the corrosion factor into the steel sheet when the magnesium hydroxide and magnesium carbonate are present on the surface of the steel sheet.

When such a blast furnace and ferronickel slag are coated on a steel sheet, the steel sheet acts as a corrosion preventing layer to prevent oxidation or corrosion by being exposed to the atmosphere and has a merit that the hardness is remarkably increased due to the hardness unique to ceramics. 3 to 5, a steel sheet coated with a blast furnace slag, a ferronickel slag, or a mixture thereof was subjected to a spray test for 600 hours. As a result, corrosion (redness) was not generated on the surface, It can be seen that it has.

When coating the surface of the steel sheet with a coating powder containing blast furnace slag, ferronickel slag, or a mixture thereof, the kind of the coating method can be carried out without limitation in the case of the ceramic coating method. However, spray coating, chemical vapor deposition, A low temperature spraying method and an aerosol deposition method.

Among the above coating methods, the spray coating method is simple and costly to manufacture, and thus is widely used for coating ceramic materials. Spray coating is a coating technique in which materials such as rods, wires, and powders having superior characteristics to the base material are melted or semi-melted by a high-temperature heat source such as gas or electricity, and collided and laminated on the surface of the base material at high speed. Such a spray coating can select a wide range of coating materials such as metals, non-metals, and ceramics (mainly metal oxides), has no work restrictions on the dimensional shape of parts, and can obtain excellent coating properties such as abrasion resistance, corrosion resistance, electric shielding and heat resistance.

The blast furnace and ferronickel slag have a particle size of several micrometers to several hundreds of micrometers, and have a non-uniform particle size and an irregular shape for use as coating powders. Particularly, for use as a powder for spray coating in the coating method, the particle size and particle shape must be uniform.

If the particle size of the spray coating powder is small, the uniformity of the spray is lowered due to the low feedability to the spray gun, and when the particle size of the powder is large, fine particles are generated and it is difficult for the spray to smoothly proceed. Therefore, the particle size of the sprayed powder should be adjusted to an appropriate size, and the powdering property of the powder is determined according to the shape of the particles.

The blast furnace and ferronickel slag used in the present invention can also be manufactured into a spherical powder for spray coating by using a spray dryer facility to control particle size and make the shape uniform. In general, a spray dryer is a device used to obtain spherical particles having a size of several tens of micrometers. As a liquid or paste material is sprayed by a sprayer, it is dried with hot air to obtain spherical particles of fine and uniform size in a short time . The spray-coating powder thus obtained can be classified by using a vibrating body, and powder having an average particle size of not more than 90 탆 can be classified into powder for final coating.

The average particle size of the coating powder is preferably in the range of 10 to 90 占 퐉. When the size of the coating powder is less than 10 占 퐉, the drag force due to the gas is weakened in the gas flow field during the particle injection, And the coating efficiency may be lowered and quality deterioration may be worse. If it exceeds 90 탆, the complete melting of the particles may be deteriorated and the moving speed may be slowed to lower the coating efficiency, as well as the surface quality due to an increase in the roughness of the coating layer. Figs. 1 and 2 are photographs of powder particles for final coating produced by spray-drying and granulating blast furnace slag and ferronickel slag.

The spray coating method may be at least one method selected from the group consisting of a plasma coating method, a high-speed flame spraying, a flame spraying, an arc spraying, and an explosive spraying, although the method is not limited.

The plasma coating method has a wide range of spray reselection in the spray coating method and forms an excellent coating, and is the most efficient method in slag coating, and has a very high adhesion strength of the coating material and a very dense coating structure. If the amount of applied current is less than 300 A, a sufficient melting temperature is not reached, so that the adhesion and uniformity of the coating are deteriorated due to the partial melting of the powder, and the 700 A If it exceeds this value, some cracks may be generated in the formed slag film or the adhesion of the film may be deteriorated.

If the distance is less than 10 mm, the distance between the spray gun and the substrate becomes too close, so that a part of the coating particles collide with the substrate There is a problem in that the slag particles tend to be repelled out again or that the uniform thickness of the material coating layer is lowered due to the increase in the local thickness. When the thickness exceeds 200 mm, the deposition rate of the slag particles starts to decrease remarkably, An increase in the amount of current to be applied may be required, thereby decreasing the efficiency.

According to another embodiment of the present invention, there is provided a steel sheet and a coating layer formed on at least one surface of the steel sheet, wherein the coating layer comprises a blast furnace slag, a ferronickel slag, or a mixture thereof, and a slag coated steel sheet excellent in hardness and corrosion resistance do.

If the thickness of the coating layer is less than 50 탆, the pores existing in the coating layer are not completely melted due to the thin thickness, so that the corrosion factors penetrate into the surface of the steel sheet The corrosion resistance of the steel sheet may deteriorate. If it exceeds 500 탆, further improvement in corrosion resistance can not be expected, and a cost loss may occur or an excessive cracking may occur in the coating layer due to excessive coating thickness, have.

The kind of the steel sheet is not limited, but may be, for example, a hot rolled steel sheet, a cold rolled steel sheet, a coated steel sheet, an alloy coated steel sheet, or a stainless steel sheet.

Hereinafter, the present invention will be described more specifically by way of specific examples. The following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

In order to liquefy the obtained blast furnace slag and ferronickel slag powder, a polyethylene 5L bottle containing zirconia balls (3 mm size) was weighed so that the volume ratio of distilled water and slag was 85:15, the total weight of distilled water and slag was 2 kg, Ball-milling was performed for a period of time. Thereafter, the ball-milled liquid slag was charged to the spray dryer equipment using a metering pump and a spherical slag granule was prepared. The slag granules prepared by spray drying were placed in an alumina crucible and sintered by heating at 1400 ℃ for 4 hours. Then, the slag granules were filtered through 90 ㎛ or more through a vibrator to prepare final slag powder for spray coating. The slag powders prepared for spray coating were classified into blast furnace slag, ferronickel slag, or mixtures thereof (weight ratio of blast furnace slag and ferronickel slag was 1: 1).

The substrate used to spray-coat the slag was a 2.5 mm thick hot-rolled steel sheet cut into 75 x 150 (width x length) mm ² . Among them, some hot-rolled steel sheets were prepared under conditions that no coating treatment was carried out or that the thickness of the coating layer was not provided according to the present invention. The remaining hot-rolled steel sheets were subjected to spray drying and classification processes using a plasma spray coating method, Slag, ferronickel slag, or a mixture thereof. The equipment used for the plasma spray coating was a METCO 9M system. The gas used for spray coating was a mixture of argon (Ar) 80% and hydrogen 20% and was sprayed at a speed of 650 m / s. At this time, the amount of applied current was 500A, the slag powder was supplied 30g per minute, and the distance from the specimen was maintained at 100mm. The thickness of the coating layer was adjusted to 20, 50, 100, 300, 500 and 700 ㎛ for all three kinds of slag by controlling the number of coatings and coating time.

≪ Evaluation of corrosion resistance &

Evaluation of the corrosion resistance of the slag coated steel sheet was carried out using a salt spraying apparatus of Suga Co., Ltd. The evaluation of the corrosion resistance of the slag coated steel sheet, the coating thickness, and the corrosion resistance evaluation results are shown in Table 1 below. The above-mentioned plate corrosion resistance evaluation was carried out under the conditions of a salt concentration of 5%, a temperature of 35 ° C and a spray pressure of 1 kg / cm ² in a flat plate state, and the time required for elongation of 5% or more was measured. The evaluation criteria of corrosion resistance were evaluated as follows based on 120 hours. The results are shown in Table 1, and photographs of the surfaces of the steel sheets after spraying with salt water of Examples 1 to 3 are shown in Figs. 3 to 5, respectively.

○: Red chute occurred more than 120 hours

X: Less than 120 hours of red generation

<Hardness evaluation>

For hardness evaluation, the section hardness was measured using a Vickers micro-hardness meter. The section hardness is measured on the portion near the surface layer of the hot-rolled steel sheet, the middle portion and the uppermost portion of the coating layer, and the results are averaged to determine whether the section hardness is good or not based on the section hardness 100 HV.

○: Cross section hardness 100 Hv or more

X: Less than 100Hv in section hardness

division Slag type Coating Thickness (탆) Corrosion resistance Section hardness Comparative Example 1 - - X X Comparative Example 2 blast furnace 20 X X Example 1 blast furnace 50 ○ ○ Example 2 blast furnace 100 ○ ○ Example 3 blast furnace 300 ○ ○ Example 4 blast furnace 500 ○ ○ Comparative Example 3 blast furnace 700 X ○ Comparative Example 4 Ferronickel 20 X X Example 6 Ferronickel 50 ○ ○ Example 7 Ferronickel 100 ○ ○ Example 8 Ferronickel 300 ○ ○ Example 9 Ferronickel 500 ○ ○ Comparative Example 5 Ferronickel 700 X ○ Comparative Example 6 Blast furnace-ferronickel 20 X X Example 11 Blast furnace-ferronickel 50 ○ ○ Example 12 Blast furnace-ferronickel 100 ○ ○ Example 13 Blast furnace-ferronickel 300 ○ ○ Example 14 Blast furnace-ferronickel 500 ○ ○ Comparative Example 7 Blast furnace-ferronickel 700 X ○

(Blend-ferronickel: mixture of blast furnace slag and ferronickel slag)

As can be seen from the above Table 1, since the hot-rolled steel sheet of Comparative Example 1 had no coating layer to prevent the corrosion factor, redness was immediately started as soon as the salt spray test was started, and the hot- And a low hardness value.

In Comparative Example 2, since the thickness of the coating layer of the blast furnace slag was thinner than the range controlled by the present invention, the slag coating was not sufficiently filled, and the corrosion resistance was lowered due to the penetration of the corrosion factor due to the internal micro pores. Of the hardness value.

In Comparative Example 3, the hardness value was higher than the reference value, but the coating layer thickness of the blast furnace slag was thicker than the range controlled by the present invention, resulting in corrosion due to microcracks in the slag coating layer, and corrosion resistance was lowered.

The ferronickel slag of Comparative Example 4 was also thin as in the case of blast furnace slag, so that adherence factor penetration was caused by micropores in the coating layer and the corrosion resistance was lowered and the hardness value was also low.

In Comparative Example 5, the hardness of the ferronickel slag coating layer was more than the standard value, but the thickness of the coating layer was also decreased due to the microcracks in the coating layer caused by the increase in thickness as in the case of the blast furnace slag.

The blast furnace-ferronickel slag of Comparative Example 6 had the same corrosion resistance and hardness values as those of Comparative Examples 2 and 3 due to its thin thickness.

As in Comparative Examples 3 and 5, the blast furnace-ferronickel slag of Comparative Example 7 had a hardness value higher than a reference value, but the corrosion resistance was lowered due to microcracks caused by a thick coating layer.

On the other hand, in Examples 1 to 14, redness did not occur even for 120 hours, and the hardness value also showed an excellent hardness of 100 Hv or more.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

Claims (10)

A method for producing a slag-coated steel sheet excellent in hardness and corrosion resistance by coating a coating powder containing blast furnace slag, ferronickel slag or a mixture thereof on the surface of a steel sheet.
The method for manufacturing a slag-coated steel sheet according to claim 1, wherein the coating powder has a spherical shape and an average particle size of 10 to 90 탆.
The slag-coated steel sheet manufacturing method according to claim 1, wherein the coating powder is produced by spray drying and blending a blast furnace slag, a ferronickel slag, or a mixture thereof, and is excellent in hardness and corrosion resistance.
The method according to claim 1, wherein the coating is performed by at least one coating method selected from the group consisting of a spray coating method, a chemical vapor deposition method, a physical vapor deposition method, a low temperature spraying method and an aerosol deposition method.
[6] The method of claim 4, wherein the spray coating method is at least one method selected from the group consisting of a plasma coating method, a high-speed flame spraying method, a flame spraying method, an arc spraying method, and an explosion spraying method.
6. The method of claim 5, wherein the plasma coating method has a hardness and an excellent corrosion resistance with an applied current of 300 to 700 A.
[6] The method of claim 5, wherein the plasma coating method has a hardness and corrosion resistance of 10 to 200 mm between the inlet of the spray gun and the steel plate.
Steel plate and
And a coating layer formed on at least one surface of the steel sheet,
Wherein the coating layer comprises a blast furnace slag, a ferronickel slag, or a mixture thereof, and is excellent in hardness and corrosion resistance.
The slag-coated steel sheet according to claim 8, wherein the steel sheet is a hot-rolled steel sheet, a cold-rolled steel sheet, a coated steel sheet, an alloy-coated steel sheet or a stainless steel sheet.
The slag-coated steel sheet according to claim 8, wherein the coating layer has a thickness of 50 to 500 탆 and is excellent in hardness and corrosion resistance.

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