KR101873963B1 - Black color plated sheet and manufacturing method thereof - Google Patents

Abstract

Embodiments of the present invention provide a technique for forming a coating having a high value-added appearance quality and excellent hardness on a steel sheet surface in a short time.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black-

To a black plated steel sheet and a method of manufacturing the same.

In general, iron-based steel sheets have high mechanical strength and dimensional stability, and are one of the materials used in the manufacture of automobile parts and the like.

In recent years, steel sheets having high value-added appearance quality and excellent hardness have been required in the fields of building materials, household appliances, automobiles, and the like. In this connection, there is known a method of plating a Zn or Zn-based alloy on the surface of a steel sheet, but the plating layer color is not uniform or the strength is weak.

 Embodiments of the present invention provide a technique for forming a coating having a high value-added appearance quality and excellent hardness on a steel sheet surface in a short time.

In one embodiment of the present invention, a steel plate; And a coating disposed on the surface of the steel sheet.

However, in the above-mentioned black-plated steel sheet, the coating is formed of a Zn matrix; And ZnO, Al ₂ O ₃ , and MgO mixed in the Zn matrix, and the lightness L value on the surface is 40 or less (but excluding 0).

Specifically, the thickness of the coating film may be 2 to 4 占 퐉.

The ZnO may be present to a depth of 1.5 to 3.5 탆 from the surface of the coating.

The MgO and Al ₂ O ₃ Respectively, to a depth of 3-4 [mu] m from the surface of the coating, in an embodiment of the present invention

The coating may further comprise Al and Mg. In this case, the amounts of Al and Mg may gradually increase from the depth of 1.5 to 2.5 占 퐉 from the surface of the coating to the interface with the steel sheet.

In the film of the final steel sheet, ZnO, Al ₂ O ₃ and MgO are each present in an amount of 20 wt% or less (excluding 0 wt%), and the remainder is a hydrate of ZnO, a hydrate of Al ₂ O ₃ , Or a mixture thereof.

On the other hand, the steel sheet may be a ternary alloyed steel sheet containing Zn, Al and Mg.

According to another embodiment of the present invention, there is provided a method of removing air, comprising the steps of: removing air partially or entirely inside a sealed container; An oxygen-introducing step of introducing oxygen (O ₂ ) into the closed container through the air removing step; And a humidity and heat treatment step of heat-treating the Zn-plated steel sheet or the Zn alloy-based coated steel sheet in the sealed container through the oxygen-introducing step.

However, in the method for producing a black-plated steel sheet, the lightness L value on the surface of the coated steel sheet is controlled to be 40 or less (but excluding 0) in the humidity and heat treatment step.

Specifically, the air removing step may be to remove all the air inside the sealed container until the pressure inside the sealed container reaches 0 bar.

The oxygen introduction step may be to introduce oxygen into the closed vessel through the air removal step until the pressure inside the closed vessel reaches 0.5 to 1.5 bar.

The humidity and heat treatment step may be performed at a constant humidity ranging from 50 to 100% RH or less in a temperature range of 100 ^° C to 160 ^° C. Also, the above-described moisture-resistance heat treatment step may be performed within 2 hours (but excluding 0 hour), specifically 0.5 to 2 hours.

On the other hand, the Zn alloy-based plated steel sheet may be a ternary plated steel sheet of Al, Mg, and Zn. Specifically, the Zn alloy-based plated steel sheet may be a magnesium-based or magnesium alloy-based steel sheet having a plated layer composed of 1.0 to 22.0 mass% of Al and 1.3 to 10.0 mass% of Mg as a balance, Zn and other unavoidable impurities on the surface of the magnesium- .

In the humidity and heat treatment step, the plating layer is oxidized to form a Zn matrix; And a ZnO, Al ₂ O ₃ , and MgO mixed in the Zn matrix.

It is possible to form on the surface of the steel sheet a film having a high value-added appearance quality and excellent hardness in a short time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the surface brightness L value according to the conditions under which the coated steel sheet is heat-treated under constant humidity in Examples 1 to 3 of the present invention. FIG.
Fig. 2 shows the distribution of the substance according to the film thickness of Example 4 of the present invention.
3 shows the results of EDS analysis of the surface of Example 4 of Example 4 of the present invention.
4 is a FIB-TEM and a schematic diagram of the films before and after the heat treatment of Examples 4 and 5 of the present invention.
Fig. 5 shows the appearance evaluation results according to the constant-humidity heat treatment conditions extended from Examples 1 to 5 of the present invention.
Fig. 6 shows the appearance evaluation results according to the pretreatment conditions and the humidity and heat treatment conditions of the plated steel sheets extended from Examples 1 to 5 of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described in detail below. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims.

In one embodiment of the present invention, a steel plate; And a coating disposed on the surface of the steel sheet. However, in the above-mentioned black-plated steel sheet, the coating is formed of a Zn matrix; And ZnO, Al ₂ O ₃ , and MgO mixed in the Zn matrix, and the lightness L value on the surface is 40 or less (but excluding 0).

Further, in another embodiment of the present invention, an air removing step of removing part or all of the air inside the sealed container; An oxygen-introducing step of introducing oxygen (O ₂ ) into the closed container through the air removing step; And a humidity and heat treatment step of heat-treating the Zn-plated steel sheet or the Zn alloy-based coated steel sheet in the sealed container through the oxygen-introducing step. However, in the method for producing a black-plated steel sheet, the brightness L value on the surface of the coated steel sheet is controlled to be 40 or less (but excluding 0) in the humidity and heat treatment step.

Hereinafter, the method for producing a black-plated steel sheet provided by embodiments of the present invention and the finally obtained black-plated steel sheet will be described in detail.

In general, as described above, in recent years, there has been a demand for a steel sheet having a high value-added appearance quality and excellent hardness in the fields of building materials, household appliances, automobiles, and the like.

In this connection, there is known a method of plating the surface of a steel sheet with a Zn or Zn-based alloy, but it is known that the surface quality is not good such as the surface is not uniform.

However, according to one embodiment of the present invention, when the Zn-plated steel sheet or the Zn alloy-based coated steel sheet is heat-treated in a closed container in which humidity is constantly controlled, the plating layer is oxidized and can be converted into a film having a uniform surface have.

Specifically, the coated steel sheet may be a Zn alloy-based coated steel sheet, and may be, for example, a ternary coated steel sheet of Al, Mg, and Zn. Thus, the coating may comprise a Zn matrix; And ZnO, Al ₂ O ₃ , and MgO mixed in the Zn matrix.

Particularly, according to one embodiment of the present invention, when the inside of the closed vessel is subjected to the heat treatment under the oxygen elevation condition, the coating film can be formed within a short time. Specifically, when oxygen (O ₂ ) is added after removing a part or all of the air inside the closed vessel, the lightness L value is lower than or equal to 40 within a short period of time , Except for 0). Thus, the color of the surface of the coating film is uniformly blackened, and the appearance quality with high added value can be obtained. In addition, the internal structure of the coating is dense and can have a high hardness.

Specifically, the air removing step may be to remove some or all of the air inside the sealed container until the pressure inside the sealed container reaches 0 bar.

However, if the pressure inside the sealed container after the air removal is in excess of the above range, even if oxygen is introduced at a later stage, the concentration is not sufficient and the time for reaching the lightness L value to 40 or less (but excluding 0) is delayed , The surface color can not be uniformly blackened, and the internal structure of the film may not be formed precisely.

The oxygen introduction step may be to introduce oxygen into the closed vessel through the air removal step until the pressure inside the closed vessel reaches 0.5 to 1.5 bar.

When the pressure inside the sealed container after the oxygen introduction is less than the above range, the oxygen concentration is insufficient and the time for reaching the lightness L value to 40 or less (but excluding 0) is delayed, the surface color is not uniformly blackened , The internal structure of the film may not be formed precisely.

The humidity and heat treatment step may be performed at a constant humidity ranging from 50 to 100% RH or less in a temperature range of 100 ^° C to 160 ^° C. Also, the above-described moisture-resistance heat treatment step may be performed within 2 hours (but excluding 0 hour), specifically 0.5 to 2 hours.

Under such internal gas atmosphere, temperature, and humidity conditions, the plating layer is oxidized to form a Zn matrix; And a ZnO, Al ₂ O ₃ , and MgO mixed in the Zn matrix.

However, the time required for the L value of the surface to reach 40% or less may be different within the above range. Specifically, the higher the humidity and the higher the humidity, the shorter the time required for the L value of the surface to reach 40% or less.

More specifically, the thickness of the coating may be 2 to 4 탆. The Zn matrix may be distributed throughout the entire film. However, in the Zn matrix, ZnO, Al ₂ O ₃ , and MgO may exist to a certain depth from the surface of the coating, respectively.

Specifically, the ZnO may be present to a depth of 1.5 to 3.5 탆 from the surface of the coating. Further, the MgO and Al ₂ O ₃ may each be present to a depth of 3 to 4 탆 from the surface of the plating layer. That is, the MgO and Al ₂ O ₃ may exist in a region deeper than the ZnO, respectively.

On the other hand, since the coating is derived from a Zn-based plating layer containing Al and Mg, it may further contain Al and Mg. In this case, the amounts of Al and Mg may gradually increase from the depth of 1.5 to 2.5 占 퐉 from the surface of the coating to the interface with the steel sheet.

In the film of the final steel sheet, ZnO, Al ₂ O ₃ and MgO are each present in an amount of 20 wt% or less (excluding 0 wt%), and the remainder is a hydrate of ZnO, a hydrate of Al ₂ O ₃ , Or a mixture thereof.

 On the other hand, when the steel sheet is a ternary alloyed steel sheet of Al, Mg and Zn, a coating layer composed of 1.0 to 22.0 mass% of Al and 1.3 to 10.0 mass% of Mg and the balance of Zn and other unavoidable impurities may be formed on the surface of the steel sheet have.

The inside of the plating layer (that is, the steel sheet) may be a ternary plated steel sheet of Al, Mg, and Zn.

Hereinafter, examples of the present invention, comparative examples thereof, and evaluation examples thereof will be described. However, the following embodiments are only a part of the embodiments of the present invention, and thus the scope of rights of the present invention is not limited thereto.

Example  One ( Humidity  Heat treatment conditions: temperature 160 ° C , Humidity 79 RH% )

(1) Plated steel plate preparation

A ternary alloy steel plate on which a Zn-based plating layer containing molten Al and Mg was formed on the surface was used. (2) Atmosphere atmosphere control inside the sealed container before the heat treatment

The airtight container was prepared, the air was withdrawn by using a pump until it reached 0 bar, and then another pump was used to introduce oxygen until it reached 1 bar.

(3) Hydrothermal heat treatment

The coated steel sheet was placed inside the sealed container in which the inner gas atmosphere was formed. The sealed container was heat-treated at a temperature of 160 캜 while controlling to maintain a constant humidity of 79 RH% in a sealed state.

The coating layer of the plated steel sheet was oxidized by the above-described humidity and heat treatment, and the surface color was converted into a blackened film.

Example  2 ( Humidity  Heat treatment conditions: temperature 140 ° C , Humidity 75 RH% )

The surface of the coated steel sheet was blackened in the same manner as in Example 1, except that the temperature was changed to 140 캜 and 75 RH% in a constant-humidity heat treatment condition.

Example  3 ( Humidity  Heat treatment conditions: temperature 135 ℃ , Humidity 90 RH% )

The surface of the coated steel sheet was blackened in the same manner as in Example 1, except that the temperature was changed to 135 캜 and 90 RH% in a constant-humidity heat treatment condition.

Example  4 ( Humidity  Heat treatment conditions: temperature 150 ℃ , Humidity 95 RH% )

The surface of the coated steel sheet was blackened in the same manner as in Example 1, except that the temperature was changed to 150 ° C and 95% RH in the humidity-conditioning heat treatment condition and the treatment was conducted for 1 hour.

Example  5 ( Humidity  Heat treatment conditions: temperature 150 ℃ , Humidity 95 RH% )

The surface of the coated steel sheet was blackened in the same manner as in Example 1, except that the temperature was changed to 150 캜 and 95% RH under the conditions of the constant-humidity heat treatment and the treatment was conducted for 0.2 hour.

Evaluation example  One

For each of Examples 1 to 3, the brightness L value of the formed film was measured according to the constant-humidity heat treatment time and is shown in Fig.

According to Fig. 1, it can be confirmed that the L value of the surface within 2 hours reached 40% or less in all of Examples 1 to 3 as a result of performing the heat treatment under the condition that the oxygen concentration in the closed vessel was made high.

Further, it can be confirmed that when each of the examples 1 to 3 reaches a specific value where the L value of the surface is 40% or less, it is no longer lowered. Specifically, the L value of the finally obtained black plated steel sheet converges to 25 to 30.

On the other hand, the time required for the L value of the surface to reach 40% or less is different in Examples 1 to 3, which is caused by the difference in humidity and the heat treatment temperature. Specifically, the higher the humidity and the higher the humidity, the shorter the time required for the L value of the surface to reach 40% or less.

Evaluation example  2

Fig. 2 shows a distribution diagram of the substance according to the film thickness of Example 4. Fig.

In FIG. 2, the Zn oxide is present to a depth of about 2 탆 from the surface, the Zn metal increases in abundance from the surface, each oxide of Al and Mg exists from the surface to a depth of about 3.5 탆, And Mg in the depth of about 2 탆 from the surface, the abundance increases. In addition, it can be seen that the depths where the respective oxides of Al and Mg exist are deeper than the Zn oxide. Overall, the oxide appears to be distributed from the surface to a depth of about 3-4 μm.

3 shows the results of EDS analysis on the surface of Example 4. Fig.

In FIG. 3, it is seen that the zone in which the Zn oxide is present and the zone in which the oxides of Zn, Al, and Mg are present are mixed.

4 is a FIB-TEM and a schematic diagram of the coating films before and after the heat treatment for heat treatment in Examples 4 and 5.

In Figure 4, a and d is a constant humidity before heat treatment characteristics, b and e are 150 ^o C, 95RH%, and a humidity cabinet after the heat treatment characteristics of 0.2 time conditions (Example 5), c and f is 150 ^o C, 95RH %, And 1 hour (Example 4). Accordingly, it is possible to grasp the influence of the heat treatment time under the same temperature and humidity conditions.

Evaluation example  2

 Specifically, the influence from the humidity and heat treatment conditions was confirmed by extending from Examples 1 to 5. 5, the surface characteristics (film thickness and color) of the black-coated steel sheets were measured in terms of temperature, humidity, and time. And time.

More specifically, the higher the heat treatment temperature, the higher the humidity at the same heat treatment temperature and time, the longer the heat treatment under the same temperature and humidity condition, the more the degree of blackening becomes, and the thicker the film becomes thicker Can be confirmed.

Therefore, it can be seen that the film thickness and the color diversification are possible by controlling the conditions of the moisture-proof heat treatment.

Evaluation example  3

From the results of Examples 1 to 5, the influence of the pretreatment conditions and the humidity and heat treatment conditions of the coated steel sheet was confirmed.

Specifically, for each coated steel sheet surface-treated with a chromate (CL), an inorganic substance (NT), and a hairline, and a non-surface treated coated steel sheet, the temperature, humidity, And subjected to a heat treatment under a constant humidity condition.

In FIG. 6, it can be seen that the surface L value of the black plated steel sheet obtained varies depending on the pretreatment conditions and the humidity and heat treatment conditions of the coated steel sheet.

Therefore, it can be seen that color diversification is possible by controlling the pretreatment conditions and the humidity and heat treatment conditions of the coated steel sheet.

While the present invention has been described in connection with certain exemplary embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (18)

An air removing step of removing part or all of the air inside the sealed container;
Introducing oxygen (O ₂ ) into the closed container through the air removing step until the pressure inside the closed container reaches 0.5 to 1.5 bar;
And a humidity and heat treatment step of heat-treating the Zn-coated steel sheet or the Zn alloy-based coated steel sheet in the sealed container through the oxygen-introducing step,
Wherein the lightness L value on the surface of the coated steel sheet is controlled to be 40 or less (but excluding 0) in the humidity and heat treatment step.
A method for producing a black plated steel sheet.
The method according to claim 1,
The black plated steel sheet
Steel plate; And a coating disposed on the surface of the steel sheet,
Wherein the coating comprises:
Zn matrix; And ZnO, Al ₂ O ₃ , and MgO mixed in the Zn matrix
A method for producing a black plated steel sheet.
3. The method of claim 2,
The thickness of the film is,
2 to 4 [mu] m.
A method for producing a black plated steel sheet.
The method of claim 3,
In the ZnO,
Lt; RTI ID = 0.0 > um < / RTI >
A method for producing a black plated steel sheet.
The method of claim 3,
The MgO and Al ₂ O ₃ , respectively,
Lt; RTI ID = 0.0 > 3 < / RTI > to 4 &
A method for producing a black plated steel sheet.
The method of claim 3,
Wherein the coating comprises:
Al and < RTI ID = 0.0 > Mg. ≪
A method for producing a black plated steel sheet.
The method according to claim 6,
The Al and Mg, respectively,
The abundance increases gradually from the depth of 1.5 to 2.5 占 퐉 from the surface of the film to the interface with the steel sheet,
A method for producing a black plated steel sheet.
delete The method according to claim 1,
Wherein the air removing step comprises:
Until the pressure inside the sealed container reaches 0 bar,
And removing all the air inside the sealed container.
A method for producing a black plated steel sheet.
delete 10. The method of claim 9,
The humidity and heat treatment step may include:
Is performed in a temperature range from 100 < ⁰ > C to 160 < ⁰ > C.
A method for producing a black plated steel sheet.
10. The method of claim 9,
The humidity and heat treatment step may include:
Is carried out at a constant humidity within a range of 50 to 100% RH.
A method for producing a black plated steel sheet.
10. The method of claim 9,
The humidity and heat treatment step may include:
Is performed within 2 hours (except 0 hours)
A method for producing a black plated steel sheet.
14. The method of claim 13,
The humidity and heat treatment step may include:
0.5 to 2 hours.
A method for producing a black plated steel sheet.
The method according to any one of claims 1, 9 and 11 to 14,
In the Zn alloy-based plated steel sheet,
Al, Mg, and Zn.
A method for producing a black plated steel sheet.
16. The method of claim 15,
In the Zn alloy-based plated steel sheet,
Wherein a coating layer composed of 1.0 to 22.0 mass% of Al, 1.3 to 10.0 mass% of Mg, and Zn and other unavoidable impurities is formed on the surface of the steel sheet,
A method for producing a black plated steel sheet.
17. The method of claim 16,
In the humidity and heat treatment step,
Wherein the plating layer is oxidized.
A method for producing a black plated steel sheet.
delete

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