KR20090093883A - Phosphate-treated electrogalvanized steel sheet - Google Patents

Abstract

A phosphate treated electrolytic galvanized iron is provided to keep the brightness high after the phosphate treatment. A phosphate treated electrolytic galvanized iron comprises an electric zinc plating layer and a phosphate zinc film. The phosphate zinc film is coated on the electric zinc plating layer. The orientation index Ico(hk.1) of the crystal plane of the electric zinc plating layer is satisfied the following conditions. 4.0<=Ico(00.2), 4.0<=Ico(00.2), 0<Ico(10.0)<=0.020, 0<Ico(10.0)<=0.020, 0<Ico(10.1)<=0.20, 0<Ico(10.1)<=0.20. The Ico is 6 page the orientation index of the Wilson in the crystal plane. The brilliance value of the electrolytic galvanized iron is 70.00 or greater.

Description

Phosphated Electroplated Galvanized Steel Sheet {PHOSPHATE-TREATED ELECTROGALVANIZED STEEL SHEET}

The present invention relates to a phosphate treated electrogalvanized steel sheet having a bright color tone. The galvanized steel sheet of the present invention has a high brightness (L value) after phosphate treatment, and can be suitably used as a material for, for example, a household electrical appliance, a switchboard, an electric exchanger panel, an automobile part, a building material, and the like.

An electrogalvanized steel sheet (hereinafter sometimes referred to as "phosphate-treated steel sheet") having a zinc phosphate coating is often coated with a white paint when used in household electrical appliances or the like described above. However, if the phosphate-treated steel sheet is black (low brightness), a thick white paint must be applied, so that the amount of paint and its cost increase. For this reason, there is a demand for a phosphate treated steel sheet having high brightness from the user. The demand is becoming more and more demanding, and phosphate treatments with a brightness (L value) of 70.00 or more are currently desired. Thus, a technique for increasing the brightness of the phosphate treated steel sheet has been proposed so far.

For example, Japanese Patent Laid-Open No. 1999-61430 discloses a technique for appropriately adjusting the amount of Ni which adversely affects the brightness of the zinc phosphate coating. Specifically, in the technique of Japanese Patent Laid-Open No. 1999-61430, the brightness of the phosphate-treated steel sheet is maintained high by adjusting the ratio of the amount of Ni and Zn in the zinc phosphate film, the amount of zinc phosphate deposited, and the amount of Ni in zinc plating. .

On the other hand, Japanese Patent Application Laid-Open No. 1998-18078 and Japanese Patent Laid-Open No. 2002-256480 disclose techniques for improving the brightness of chromate-treated or non-chromate-treated steel sheets, not phosphate-treated steel sheets. Specifically, such a technique uses zinc by appropriately controlling the orientation index (parameter in Japanese Laid-Open Patent Publication No. 1998-18078) or orientation ratio (parameter in Japanese Laid-Open Patent Publication No. 2002-256480) of each crystal plane of the electrogalvanized layer. The brightness of the plating layer itself is improved.

It is an object of the present invention to provide a phosphate treated galvanized steel sheet having a high brightness (particularly an L value of 70.00 or more).

The phosphate treated electrogalvanized steel sheet having a light color tone according to the present invention which can solve the above problems has a zinc phosphate coating on the electrogalvanized layer, and the crystal faces (00 · 2), (10 · 0) and (10) of the electrogalvanized layer. The orientation index I _co (hk · 1) of 1) satisfies the following formulas (1) to (3).

4.0≤I _co (00 · 2)

0 <I _co (10 · 0) ≤0.020

0 <I _co (10 · 1) ≤0.20

[Wherein, I _co (hk · 1) is in the crystal planes (00 · 2), (10 · 0), (10 · 1), (10 · 2), (10 · 3) and (11 · 0) It is Willson's six-plane orientation index, and the X-ray diffraction peak intensity value (cps) of each crystal plane (hk · 1) of the electrogalvanized layer is called I (hk · 1), and each crystal plane (hk · 1) is calculated by X-ray diffraction peak intensity values _{(cps) I s (hk ·} 1) as to a case where from equation (4) to six.

I _co (hk · 1) = i (hk · 1) / i _s (hk · 1)

i (hk · l) = I (hk · 1) / {I (00 · 2) + I (10 · 0) + I (10 · 1) + I (10 · 2) + I (10 · 3) + I (11 · 0)}

i _s (hk · 1) = I _s (hk · 1) / (I _s (00 · 2) + I _s (10 · 0) + I _s (10 · 1) + I _s (10 · 2) + I _s (10 · 3) + I _s (11 · 0)}]

In a preferred embodiment of the present invention, the brightness (L value) of the phosphate-treated galvanized steel sheet is 70.00 or more.

According to this invention, since the orientation index of the crystal surface of the electrogalvanized layer which is a base is controlled suitably, the brightness after a phosphate treatment can be kept high. As a result, it was possible to provide a high brightness phosphate treated electrogalvanized steel sheet that could satisfy the demanding requirements of the user.

1 is a graph showing a relationship between I _co (00 · 2) of an electrogalvanized layer and the brightness (L value) of a steel sheet after a plating state or zinc phosphate treatment. FIG. 1B is an enlarged graph of part of FIG. 1A.

2 is a graph showing the relationship between I _co (10 · 0) of the _{electrogalvanized} layer and the brightness (L value) of the steel sheet after the plating state or the zinc phosphate treatment. FIG. 2B is an enlarged graph of part of FIG. 2A.

3 is a graph showing the relationship between I _co (10 · 1) of the _{electrogalvanized} layer and the brightness (L value) of the steel sheet after the plating state or the zinc phosphate treatment. FIG. 3B is an enlarged graph of part of FIG. 3A.

MEANS TO SOLVE THE PROBLEM This inventor paid attention to the crystal orientation index of a base plating layer in order to raise the brightness of the phosphate-treated electrogalvanized steel plate which has a zinc phosphate film on an electrogalvanizing layer (base plating layer). In chromate-treated steel sheets and non-chromate-treated steel sheets such as Japanese Patent Application Laid-Open No. 1998-18078 and Japanese Patent Application Laid-Open No. 2002-256480, the relationship between the crystal orientation of the base plating layer and the brightness of the treated steel sheet is studied in detail. This is because the treated steel sheet has not been mentioned at all about the relationship between the crystal orientation index and the brightness.

In particular, the zinc phosphate coating is described in detail in Japanese Patent Application Laid-Open No. 1999-61430, but contains a zinc phosphate crystal having a diameter of about several μm as a main component called a hopeite crystal. Therefore, the color tone of the steel plate after the phosphate treatment is not influenced by the color tone of the base plating layer, and strongly depends on the optical properties of the zinc phosphate crystal. Therefore, in order to increase the brightness of the phosphate treated steel sheet, it is necessary to improve the brightness of the zinc phosphate coating thereon rather than the base galvanized layer. In this regard, as described in Japanese Patent Application Laid-Open No. 1998-18078 and Japanese Patent Application Laid-Open No. 2002-256480, a chromate-treated steel sheet or a bichromate treatment in which the brightness after treatment is improved by increasing the brightness of the zinc-plated layer itself as a base. It is different from the steel plate. This is because these chromate-treated steel sheets and non-chromate-treated steel sheets have an amorphous transparent thin film, and the color tone of the base plating layer is directly reflected in the color tone of the steel sheet after the treatment. Therefore, in order to raise the brightness of the phosphate processed steel plate made into object by this invention, techniques, such as a chromate-treated steel plate, cannot be diverted as it is.

As a result of this inventor's examination, the brightness of the zinc phosphate film has a close relationship with the crystal structure of the specific crystal surface of the electrogalvanized layer which is a base, and the crystal surfaces (00 * 2), (10 * 0), and (10) of the electrogalvanized layer When all of the orientation index _Ico (hk * 1) of * 1) was suitably controlled, it discovered that the brightness after phosphate treatment was kept high, and completed this invention.

That is, the phosphate treated electrogalvanized steel sheet of the present invention has a zinc phosphate coating on the electrogalvanized layer, and the orientation index I of the crystal faces (00 · 2), (10 · 0) and (10 · 1) of the electrogalvanized layer _co (hk · 1) satisfies the following formulas (1) to (3).

[Equation 1]

4.0≤I _co (00 · 2)

[Equation 2]

0 <I _co (10 · 0) ≤0.020

[Equation 3]

0 <I _co (10 · 1) ≤0.20

[Wherein, I _co (hk · 1) is in the crystal planes (00 · 2), (10 · 0), (10 · 1), (10 · 2), (10 · 3) and (11 · 0) Willson's six-sided orientation index. In addition, I _co (hk · 1) denotes the X-ray diffraction peak intensity value (cps) of each crystal plane (hk · 1) of the electrogalvanized layer as I (hk · 1), and each crystal plane of the standard zinc powder (hk · 1). 1) is calculated by X-ray diffraction peak intensity values _{(cps) I s (hk ·} 1) as to a case where from equation (4) to six.

[Equation 4]

I _co (hk · 1) = i (hk · 1) / i _s (hk · 1)

[Equation 5]

i (hk · l) = I (hk · 1) / {I (00 · 2) + I (10 · 0) + I (10 · 1) + I (10 · 2) + I (10 · 3) + I (11 · 0)}

[Equation 6]

i _s (hk · 1) = I _s (hk · 1) / (I _s (00 · 2) + I _s (10 · 0) + I _s (10 · 1) + I _s (10 · 2) + I _s (10 · 3) + I _s (11 · 0)}]

For example, I _co (00 · 2) can be calculated by substituting (00 · 2) into (hk · 1) in the above formulas 4 to 6, that is, as follows.

I _co (00 · 2) = i (00 · 2) / i _s (00 · 2)

i (00 · 2) = I (00 · 2) / {I (00 · 2) + I (10 · 0) + I (10 · 1) + I (10 · 2) + I (10 · 3) + I (11 · 0)}

i _s (00 · 2) = I _s (00 · 2) / (I _s (00 · 2) + I _s (10 · 0) + I _s (10 · 1) + I _s (10 · 2) + I _s (10 · 3) + I _s (11 · 0)}

In addition, "co" and "s" which are subscripts of I _co and I _s represent "crystal orientation" and "standard", respectively.

The X-ray diffraction peak intensity value I (hk · 1) of the electrogalvanized layer is obtained by performing X-ray diffraction under the conditions shown in the following examples. In addition, X-ray data of the diffraction peak intensity value I _s (hk · 1) of the standard zinc powder has been described in ASTM (and JCPD), and electrical (轉記) in Table 1 below it. In the present invention, it is assumed that the value of I _s (hk · 1) shown in Table 1 is used for the above calculation. Accordingly, the value of I _co (hk · 1) can be calculated from the value of I (hk · l) obtained by X-ray diffraction and the value of I _s (hk · l) shown in Table 1 below.

In addition, "exponential-surface angle (deg)" of Table 1 means the angle which the base surface of zinc hexagonal crystal and each mirror index surface (crystal surface) make. In the case of hexagonal crystals, the angle deg formed by both crystal planes can be calculated as follows. In other words,

Grid constants: a, c

, Crystal face (mirror _{jisumyeon): (h 1 k 1 ·} l 1) and _{(h 2 k 2 · l 2} )

The angle formed by the plane crystal plane: φ

X = h ₁ × h ₂ + k ₁ × k ₂ + [1/2 × (h ₁ × k ₂ + h ₂ × k ₁ )] + [3/4 × (a / c) ² × (l ₁ × l ₂ )]

Y = h ₁ ² + k ₁ ² + (h ₁ × k ₁ ) + [3/4 × (a / c) ² × (l ₁ ² )]

If Z = h ₂ ² + k ₂ ² + (h ₂ x k ₂ ) + [3/4 x (a / c) ² x (l ₂ ² )],

Cosφ = X / (Y × Z) ^1/2

From the relational equation, the angle? (Deg) formed by both crystal planes is calculated. The value of the angle phi formed by both crystal planes always falls within the range of 0 to 90 degrees.

The present inventors pay attention to the orientation index of the six surfaces of the electrogalvanized layer, the brightness (L value) in the electrogalvanized steel sheet (plated state) before the phosphate treatment, and the electrogalvanized steel sheet after the phosphate treatment (phosphate treated steel sheet) The brightness (L value) of was measured, respectively. The graph which shows the relationship between the orientation index of the surface specified by this invention and the brightness (L value) after a plating state and a phosphate treatment among the said six surface indexes is shown in FIGS. These graphs are all created based on the graph shown in Table 2 of the Example mentioned later.

1 is a graph showing a relationship between I _co (00 · 2) of an electrogalvanized layer and the brightness (L value) of a steel sheet after a plating state or zinc phosphate treatment. FIG. 1B is an enlarged graph of part of FIG. 1A.

Similarly, FIG. 2 is a graph showing the relationship with the _{electrogalvanized} layer I _co (10 · 0), and FIG. 3 is a graph showing the relationship with the _Ico (10 · 1) of the _{electrogalvanized} layer.

As shown in Figs. 1 to 3, all of the electrogalvanized steel sheets used in this experiment had a high brightness (L value) in the plated state (○ in the figure), and there was a correlation between these values and the orientation index. Did not look. That is, the relationship that the brightness (L value) of the plated state increases or decreases according to the orientation index of the said 6 surface of the electrogalvanized layer was not seen.

However, the brightness (L value) after the phosphate treatment (in the figure) is different from that in the plated state, and as shown in FIGS. 1 to 3, (00 · 2), (10) It was found that the orientation indexes of the (0) and (10 · 1) planes were strongly affected. Specifically, when I _co (00 · 2) is less than 4.0, when I _co (10 · 0) exceeds 0.020, and when I _co (10 · 1) exceeds 0.20, both brightness after phosphate treatment Decreased and the L value became less than 70.00. That is, if the orientation index deviates from the requirements of Equations 1 to 3 above, the brightness (L value) of 70.00 or more cannot be achieved in the phosphate treated steel sheet.

On the other hand, as shown in FIGS. 1-3, even if an orientation index satisfy | fills the requirements of the said Formulas 1-3, the brightness (L value) after phosphate treatment may be less than 70.00. For example, in FIG. 1, there exists an example in which L value becomes less than 70.00 even if _Ico (00 * 2) is 4.0 or more. This means that in order to make the brightness (L value) of the phosphate treated steel sheet more than 70.00, it is insufficient to satisfy only one or two requirements of Equations 1 to 3, and it is necessary to satisfy all three requirements. It is shown. Referring to FIG. 1, even if I _co (00 · 2) is 4.0 or more, the example in which the L value is less than 70.00 does not satisfy the requirements of Equations 2 and 3, so that the brightness (L value) of the phosphate treated steel sheet is It is less than 70.00.

In addition, as shown in Formulas 2 and 3, I _co (10 · 2) and I _co (10 · 1) do not become zero. When these become 0, the brightness (L value) after phosphate treatment falls again (refer to the data whose I _co (10 * 0) = 0 of FIG. 2).

This phenomenon is because the crystal structure of the electrogalvanized layer, which does not satisfy any of the requirements of the above formulas 1 to 3, adversely affects the crystal structure of the zinc phosphate film formed thereon, thereby lowering the brightness of the zinc phosphate film. Is estimated. On the other hand, the crystal structure of the electrogalvanized layer that satisfies all the requirements of the above formulas (1) to (3) has a good effect on the size, shape, and orientation of the zinc phosphate crystal formed thereon, and as a result, the zinc phosphate film reflects incident light. It is thought that it becomes easy to do it.

On the other hand, the orientation index of the crystal plane, which is not defined in the present invention, that is, between I _co (10 · 2), I _co (10 · 3) and I _co (11 · 0) and the brightness (L value) of the phosphate-treated steel sheet As shown in Examples described later, no correlation was observed.

Based on the above basic experiments, the inventor of the present invention Willson in the crystal plane (00 · 2), (10 · 0), (10 · 1), (10 · 2), (10 · 3) and (11 · 0). Among the six-sided orientation indices I _co (hk · 1), _Ico (00 · 2), I _co (10 · 0), and I _co (10 · 1) are considered, and these three orientation indices are controlled. As a result, the brightness of the zinc phosphate coating (that is, the brightness after phosphate treatment) was successfully increased to 70.00 or more. In the present invention, I _co (00 · 2) is preferably 4.5 or more, I _co (10 · 0) is preferably 0.05 or less, and I _co (10 · 1) is preferably 0.15 or less.

Next, the manufacturing method of the phosphate treated steel plate which concerns on this invention is demonstrated.

The base plate to be subjected to electrogalvanization is not particularly limited in the present invention. As the base plate of the galvanized plate, mild steel (eg, Al-killed steel, Ti-killed steel, etc.) having a plate thickness of about 1 mm is generally used. Moreover, cold rolled steel sheets, such as a high tensile strength steel plate, and hot rolled steel sheets etc. which removed black skin by acid washing can be used. In addition, it is preferable to degrease the original disc according to a conventional method before performing plating.

Next, the electrogalvanization conditions are demonstrated. In order to control the crystal structure or orientation of the electrogalvanized layer so as to satisfy the requirements of Equations 1 to 3, it is important to appropriately select a supporting electrolyte (conductive aid) to be added to the plating liquid. For example, in Na ₂ SO _{4 which} is well used conventionally, as demonstrated in Examples described later, it is difficult to control the structure of the plating layer. Therefore, as a supporting electrolyte for producing the phosphate-treated steel sheet of the present invention, Al ₂ (SO ₄ ) ₃ , (NH ₄ ) ₂ SO ₄ , KCl and NaCl are preferable, and Al ₂ (SO ₄ ) ₃ is more preferable.

In addition, the temperature of the plating liquid and the Ni concentration in the plating liquid are also important. Specifically, it is understood that when the temperature of the plating liquid is controlled in the range of about 40 to 50 ° C. and the Ni concentration in the plating liquid is in the range of about 130 to 250 ppm, it is easy to obtain an electrogalvanized layer that satisfies the requirements of Equations 1 to 3 above. (See Examples described later).

In addition, incorporation of high molecular weight organic materials such as dextrin, dextran and amylopectin into the plating solution should be avoided. When such a high molecular organic substance is mixed, it becomes difficult to control the crystal orientation of the electrogalvanized layer.

As the plating liquid, an acid bath (for example, a sulfate bath and a chloride bath) can be used. The pH of the plating liquid is preferably 0.5 or more, preferably 4 or less (more preferably less than 1) in consideration of the crystallographic orientation of the plating layer, current efficiency, plating soot phenomenon, and the like.

In order to control the crystal orientation of the electrogalvanized layer, the pHs of the above-described supporting electrolyte, the polymer organic substance and the plating liquid are important, and plating conditions other than these can be appropriately selected in consideration of other problems (plating soot, etc.). For example, the cell used for plating may be either vertical or horizontal. In addition, the method of energizing the electroplating is not particularly specified, and a known method such as a direct current (constant current) plating method or a pulse plating method can be adopted. The relative flow rate is for example 0.3 to 5 m / sec. In addition, a "relative flow velocity" is a difference between the flow velocity of a plating liquid and the plate | plate speed which considered the flow direction of a plating liquid, and the plate | plate direction of a plating master.

The current density in the plating bath is preferably 30 A / dm ² or more, more preferably 50 A / dm ² or more, in order to ensure a good deposition rate of the zinc plating. On the other hand, if the current density becomes too high, the supply of Zn ions cannot be performed in a timely manner, so that a "plating soot" phenomenon occurs in which the plating appearance becomes black. Therefore, the current density is preferably 200 A / dm ² or less.

The electrogalvanization amount is preferably 1 g / m ² or more (more preferably 3 g / m ² or more), more preferably 100 g / m ² or less (more preferably 60 g / m ² or less, more preferably 40 g / m ² or less). If the electrogalvanized amount is excessively small, the corrosion resistance of the phosphate treated steel sheet is insufficient. On the contrary, when the amount of adhesion is excessively large, the manufacturing cost of zinc plating is increased. Electro-galvanization may be performed only to one side of a disc, and may be performed to both surfaces.

After performing electrogalvanization as above, a zinc phosphate process is performed. As the zinc phosphate treatment liquid, a commercially available treatment liquid containing Zn ions, Ni ions, phosphate ions, nitrate ions and the like can be used (for example, "Pal Bond-3312" manufactured by Nippon Parkarizing Co., Ltd.). In addition, trace amounts of alkaline earth metals, Fe, Co, Mn, Mg, Cr, and Sb may be added to the zinc phosphate treatment liquid, and organic materials such as sodium gluconate and polyether may be added. Therefore, a zinc phosphate film may also contain the impurity derived from these. Zinc phosphate chemical conversion treatment may be performed by immersing an electrogalvanized steel plate in a process liquid, and may also be performed by spraying a process liquid.

The zinc phosphate adhesion amount is preferably 0.8 g / m ² or more (more preferably 1.0 g / m ² or more), preferably 3.0 g / m ² or less (more preferably 2.5 g / m ² or less). When the zinc phosphate adhesion amount is excessively large, peeling resistance and color tone (particularly lightness) of the zinc phosphate film are reduced. On the other hand, when there is too little adhesion amount, there exists a tendency for the adhesiveness of a zinc phosphate film and a coating film to fall.

_Ico (00 · 2), _Ico (10 · 0) and _Ico (10 · 0) of the phosphate-treated steel sheet can be obtained by removing the zinc phosphate film and then diffracting the electrogalvanized layer with X-ray diffraction. Specifically, first, a solution containing 20 parts by mass of ammonium dichromate, 490 parts by mass of 25% by mass of ammonia water and 490 parts by mass of distilled water is prepared. Subsequently, after adjusting this melt liquid at room temperature, a zinc phosphate film can be removed by immersing a phosphate treated steel plate for about 15 minutes. And after removing a zinc phosphate film, the orientation index of an electrogalvanized layer can be computed by performing X-ray diffraction on the conditions shown in the following Example.

The lightness (L value) of the phosphate-treated steel sheet of the present invention is preferably 70.00 or more, more preferably 71 or more. Brightness (L value) in this invention is a value measured by the measuring method shown in the following Example.

EXAMPLE

Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not restrict | limited by the following example, Of course, it is also possible to change suitably and to implement in the range suitable for the said and following, Both of these It is included in the technical scope of the invention.

Example 1

〈Plating Original〉

An Al-killed cold rolled steel sheet was used as the plating disc. After this was degreased and acid washed, electrogalvanization was performed under the following conditions.

<Condition of electro galvanization>

(1) Plating solution (sulphate bath) composition

ZnSO ₄ 7H ₂ O: 350 g / L

Al ₂ (SO ₄ ) ₃ : 170g / L

H ₂ SO ₄ : 20g / L

NiSO ₄ 6H ₂ O: 0 to 0.9 g / L

_{Fe 2 SO 4 · 7H 2 O} : 9g / L

_{Fe 2 (SO 4) 3 ·} 9.5H 2 O: 1.8g / L

Na ₂ MoO ₄ 2H ₂ O: 0.03 g / L

40 mass% Cr ₂ (SO ₄ ) ₃ solution: 0.9 g / L

(2) Current Density: 50A / dm ²

(3) Temperature of plating solution: 20 to 60 ° C

(4) Relative Speed of Plating Solution: 1.5m / s

(5) Electrode (anode): IrO _x electrode

(6) pH of plating bath: less than 1

(7) Zinc plating weight: 20g / m ²

(8) Zinc plating area: 300mm × 180mm

<Condition of X-ray diffraction>

About the electrogalvanized steel plate (plated state) produced as mentioned above, the orientation index of the electrogalvanized layer was computed by the X-ray diffraction of the following conditions.

(1) Apparatus: Rigaku Corporation X-ray Diffraction System

(2) Target: Cu (monochrome ratio by flat monochrome crystals; Cu · Kα rays)

(3) tube voltage: 40kV

(4) tube current: 300mA

(5) Measurement angle: 2θ 30 ° to 80 °

(6) scanning speed: 2 ° / min

(7) Sampling Angle: 0.02 °

(8) diverging slit: 1 °

(9) Scattering Slit: 1 °

(10) Light receiving slit: 0.15mm

(11) In-plane rotation: 100 rpm

<Zinc phosphate treatment>

The electrogalvanized steel sheet produced as described above was washed with tap water, immersed in a zinc phosphate treatment liquid (arm bond 3312) manufactured by Nippon Parkarizing Co., Ltd. (pal bond 3312) at 60 ° C. for 5 seconds, and then washed again with water to dry the phosphate treated steel sheet. Made.

(1) TA (Total Acid): 17 to 20point

(2) Free Acid (FA): 2.0 to 2.5 points

(3) Zinc phosphate adhesion amount: 1.8 to 2.2 g / m ²

<Measurement condition of brightness (L value)>

The brightness (L value) of the electro-galvanized steel sheet (plated state) and the phosphate-treated steel sheet (after zinc phosphate treatment) produced as mentioned above was measured using a color difference meter (SZS-Σ90: manufactured by Nippon Denshoku Co., Ltd.). It measured based on the 0 degree-d method of Z-8722. In this 0 ° -d method, by using an optical trap, the specular light component is released, and only diffused reflected light components other than the specular light are collected into the integrating sphere, and the whiteness is evaluated by the integrated intensity.

In Table 2, manufacturing conditions (plating liquid temperature and Ni concentration in plating liquid), the orientation index of the electrogalvanized layer measured as mentioned above, the plating state, the brightness (L value) after zinc phosphate treatment, and zinc phosphate adhesion amount are described. . Moreover, the graph which shows the relationship between the orientation index of the electrogalvanized layer shown in Table 2, and the brightness (L value) after a plating state or a zinc phosphate process is shown in FIGS.

As shown in Table 2 and FIGS. 1 to 3, when the orientation index of the electrogalvanized layer is controlled to satisfy the above formulas 1 to 3, the brightness (L value) of the phosphate treated steel sheet may be 70.00 or more. In addition, when Al ₂ (SO ₄ ) ₃ is used as the supporting electrolyte, and the temperature of the plating liquid is controlled to 40 to 50 ° C. and the Ni concentration in the plating liquid is 130 to 250 ppm, the orientation index can be controlled to satisfy the above formulas 1 to 3. Can be.

[Reference Example 1 (Comparative Example)]

A phosphate-treated steel sheet was produced under the same conditions as in Example 1 except that Na ₂ SO ₄ was used at 80 g / L instead of Al ₂ (SO ₄ ) ₃ as the supporting electrolyte. Table 3 shows these production conditions (plating solution temperature and Ni concentration in the plating solution) and the orientation indexes (I _co (00 · 2), I _co (10 · 0) and I of the electrogalvanized layer measured as described above). _co (10 · 1)), brightness (L value) after zinc phosphate treatment, and zinc phosphate adhesion amount are described.

As shown in Table 3, when Na ₂ SO ₄ is used as the supporting electrolyte, even if the plating liquid temperature and the Ni concentration in the plating liquid are adjusted to an appropriate range, the orientation index of the electrogalvanized layer is satisfied so as to satisfy the requirements of Equations 1 to 3 above. It was difficult to control, and the brightness of the phosphate-treated steel sheet was all lowered to less than 70.00.

Claims (2)

Has a zinc phosphate coating on the electro galvanized layer, The crystal plane of the electro-zinc plating layer (00, 2), (10, 0) and (10, 1) orientation index I _co (hk, 1) is, to phosphating electrolytic zinc to satisfy the requirements of equations (1) through (3) of the Plated steel plate. [Equation 1] 4.0≤I _co (00 · 2) [Equation 2] 0 <I _co (10 · 0) ≤0.020 [Equation 3] 0 <I _co (10 · 1) ≤0.20 [Wherein, I _co (hk · 1) is in the crystal planes (00 · 2), (10 · 0), (10 · 1), (10 · 2), (10 · 3) and (11 · 0) Willson's six-sided orientation index, The X-ray diffraction peak intensity value (cps) of each crystal plane (hk · 1) of the electrogalvanized layer is called I (hk · 1), and the X-ray diffraction peak intensity value of each crystal plane (hk · 1) of the standard zinc powder When (cps) is set to I _s (hk · 1), it is calculated from the following equations (4) to (6). [Equation 4] I _co (hk · 1) = i (hk · 1) / i _s (hk · 1) [Equation 5] i (hk · l) = I (hk · 1) / {I (00 · 2) + I (10 · 0) + I (10 · 1) + I (10 · 2) + I (10 · 3) + I (11 · 0)} [Equation 6] i _s (hk · 1) = I _s (hk · 1) / (I _s (00 · 2) + I _s (10 · 0) + I _s (10 · 1) + I _s (10 · 2) + I _s (10 · 3) + I _s (11 · 0)}] The method of claim 1, A phosphate treated electrogalvanized steel sheet with a brightness (L value) of 70.00 or more.