JP3363033B2 - Electro-galvanized steel sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrogalvanized steel sheet having a bright surface color tone.
It is useful as a zinc-based plated steel sheet that is used without coating as an outer coating material for automobiles, home electric appliances, office automation equipment, and building materials.

[0002]

2. Description of the Related Art Electrogalvanized steel sheets have excellent corrosion resistance and appearance, so
It has been widely put to practical use as an outer plate material for equipment A, etc., and as a building material.

Heretofore, electrogalvanized steel sheets have been mainly used as coating bases by taking advantage of their excellent corrosion resistance, and since the surface thereof is hidden by overcoating, the appearance characteristics of the surface of the plating layer. Was not particularly emphasized. However, in recent years, in order to simplify the process and reduce the cost on the user side, the overcoating process has been omitted or simplified, and the number of cases where the electrogalvanized steel sheet is used as it is without coating is increasing. At this time, various chemical conversion treatments such as chromate treatment and thin film type organic or inorganic clear film treatment are applied to the surface of the electrogalvanized steel sheet to further enhance corrosion resistance, workability, fingerprint resistance and lubrication. Property, weldability, grounding property (conductivity), etc. are used, and it is used without top coating.

In that case, the surface appearance of the electrogalvanized steel sheet appears as it is as the appearance of the product, so that the appearance characteristics of the plated steel sheet become extremely important. Regarding the color tone of the appearance characteristics of the plated steel sheet, it is natural that a brighter color is preferred, so that the user's request for a particularly bright color tone (that is, a characteristic with high brightness) is becoming more severe.

Under these circumstances, several methods for manufacturing electrogalvanized steel sheets with high brightness have been proposed.
For example, Japanese Examined Patent Publication (Kokoku) No. 5-36514 defines the orientation of a specific crystal plane in an electrogalvanized layer, specifically, the (00 · 2) plane orientation index is 0.5 or more, and (1
It is described that a chromate-treated electrogalvanized steel sheet having a bright color tone can be obtained by suppressing the (0.1) plane orientation index to 1.0 or less.

In Japanese Patent Publication No. 7-11071,
A technique for defining the orientation of a specific crystal plane in the electrogalvanized plating layer is disclosed in the same manner as described above, and specifically, the (10-3) plane orientation index is 1.0 or more, and the (10-1) plane is disclosed. The orientation index is 1.0 or less, or the (11.0) plane orientation index is 0.6 or more and the (10 • 1) plane orientation index is 1.0.
In addition, the chromate-treated electrogalvanized steel sheet with a bright color tone is obtained by suppressing the (00 · 2) plane orientation index to 1.0 or less while satisfying any of the above plane orientation indexes.

The method described in the above publication is a technique for increasing the brightness of the surface of the plating layer by defining the orientation of a specific crystal plane in the electrogalvanized plating layer. The surface of the plating layer is subjected to chemical conversion treatment such as chromate. This is characterized in that the reduction in lightness is suppressed as much as possible even when an organic clear film is formed or further formed, and as a result, an electrogalvanized steel sheet with a bright color tone is obtained. In addition, according to these publications, the specific criteria for "bright color tone" are as follows:
It is described as "55 or more in lightness (L value)", and those satisfying this criterion are evaluated to sufficiently satisfy the user's requirement for color tone.

[0008]

However, as the inventors of the present invention have made various studies, the color tone (brightness) of the electrogalvanized plating layer is certainly the orientation of a specific crystal plane as described in the above publication. However, it is not always possible to obtain stable brightness by defining their orientations, and it cannot be said that the certainty is always satisfactory. Further, in recent years, the level of lightness required by users has become more and more severe, and it is the actual situation that it is not possible to satisfy the user's demands with a standard such as “lightness of 55 or higher”. Specifically, the L value is 80 or more in the as-galvanized state, the L value is 75 or more even after the chromate treatment, and the L value after the thin clear film is formed is 70 or more. Lightness is needed.

The present invention has been made by paying attention to the above-mentioned circumstances, and its purpose is to exceed the conventional level of lightness, to obtain an L value of 80 or more in an as-galvanized galvanized state, and after chromate treatment. It is an object of the present invention to provide an electrogalvanized steel sheet capable of satisfying the requirements of a high level of lightness such as an L value of 75 or more and an L value of 70 or more after a thin film clear film treatment.

[0010]

Means for Solving the Problems The electrogalvanized steel sheet according to the present invention capable of solving the above-mentioned problems is an electrogalvanized steel sheet having an electrogalvanized plating layer formed on one side or both sides of the steel sheet. The feature is that the orientation index of each crystal plane in the zinc-based plating layer satisfies the following relational expression. A = [I _co (00 ・ 2) + I _co (00 ・ 4) + I _co (10 ・ 3)] ≧ 8.0 B ＝ [I _co (10 ・ 0) + I _co (10 ・ 1) + I _co (10 ・ 2) + I _co (11 ・ 0)] ≦
1.0 However, I _co (hk · l) represents the orientation index of the (hk · l) plane.

In the present invention, the orientation index of each crystal face is "A / B≥" under the condition that the above requirements are satisfied.
13.0 "is preferable because an electrogalvanized steel sheet having a higher brightness can be obtained.

Due to its excellent brightness (brightness), this electrogalvanized steel sheet can be effectively used as it is as an outer plate material or building material for automobiles, home electric appliances, OA equipment, etc. It is also effective to use chromate film treatment or organic or inorganic thin film clear film treatment for further improvement in corrosion resistance, workability, fingerprint resistance, etc., which is preferable when performing chromate film treatment. It is desirable that the adhesion amount is 50 mg / m ² or less in terms of Cr, and the preferable adhesion amount when performing the clear film treatment is 2 g / m ² or less in terms of dry weight.

According to the present invention, the brightness of the surface of the as-galvanized zinc-based plating can be 80 or more as the L value measured by JISZ 8730, and the same L after the chromate treatment can be obtained. Even with a value of 75 or more, and even when a thin film clear film treatment is applied, an excellent brightness of 70 or more is obtained at the same L value.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the history of experiments leading to the present invention. The present inventors have used a sulfuric acid-based electrolytic zinc-based plating bath that uses an insoluble electrode that is widely used as a general industrial manufacturing method for electrolytic zinc-based plated steel sheets, and has a bath pH, a bath temperature, a current density, and a bath flow velocity. The relationship between the color tone of the obtained electrogalvanized steel sheet and the crystal plane orientation of the plating layer was investigated in detail by changing the plating treatment conditions such as the plating bath composition.

At this time, the color tone of the plating layer surface is JIS Z
The lightness (L value) specified in 8730 was evaluated, and the crystal plane orientation of the plating layer was calculated from the diffraction peak obtained by X-ray diffraction measurement by the following method.

[Calculation Method of Crystal Plane Orientation Index] The diffraction peak intensity value (cps) of each crystal plane (hk · l) obtained by X-ray diffraction measurement of the electrogalvanized plating layer is I.
(Hk · l). Next, each crystal plane (hk ·
The standard diffraction peak intensity value (cps) of 1) is I _s (hk ·
l) (the subscript s means standard).

From these values, the orientation index of each crystal plane of the electrogalvanized plating layer was calculated by the following formula: I _co (hk
・ L) is defined (the subscript co is crystal orientation)
Means). I _co (hk · l) = I / I _s However, I = I (hk · l) / {I (00 ・ 2) + I (00 ・ 4) + I (10 ・ 0) + I (10 ・ 1) + I (10
2) + I (10 ・ 3) + I (11.0)} I _s = I _s (hk ・ l) / {I _s (00 ・ 2) + I _s (00 ・ 4) + I _s (10 ・0) + I _s (10
1) + I _s (10 ・ 2) + I _s (10 ・ 3) + I _s (11 ・ 0)} That is, the orientation index I _co (hk ・ l) in the crystal plane (hk ・ l) of the electrogalvanized plating layer the l), the crystal plane of the galvanized layer relative diffraction intensity I (hk · l), means a value corrected by dividing the relative intensity I _s of the same crystal plane (hk · l) in the zinc powder .

Regarding I _s (hk · l) shown in the above formula, its data is described in ASTM (and JCPD), and when it is transcribed, it is as shown in Table 1 below.

[0019]

[Table 1]

As is clear from Table 1, the diffraction angle 2
When θ is in the range of 30 to 80 degrees, a total of 7 types of diffraction intensities from Miller index planes (crystal planes) can be obtained. Based on this value, the orientation index of each crystal plane [I _co (hk · l)] Can be calculated. Here, the index plane angle (deg) described in Table 1 means the angle formed by the basal plane of zinc hexagonal crystal and each Miller index plane, and in the case of hexagonal crystal form, : A, c ・ Crystal plane (Miller index plane): (h ₁ K ₁ · l ₁ ) and (h ₂ K ₂ · l ₂ ) ・ Angle formed by both crystal planes: φ (deg), ・ 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 ) ・ Z = h ₂ ² + Assuming that k ₂ ² + (h ₂ × k ₂ ) +3/4 (a / c) ² × (l ₂ ² ), both crystals can be obtained from the relational expression of cos φ = X / (Y × Z) ^1/2. The angle φ (deg) formed by the surface is calculated, and the value always falls within the range of 0 to 90 °.

When the correlation between the color tone of the surface of the electrogalvanized plating layer obtained as described above and each crystal plane orientation index was investigated, it was found that between the magnitude of the individual crystal plane orientation index and the lightness or darkness of the color tone. It was not always possible to find a unique correlation. That is, when the orientation index of a certain crystal plane is high, no clear correlation such that the color tone is always very bright or vice versa is not recognized.

Therefore, the orientation index of each crystal plane is not considered, but the base plane of hexagonal zinc shown in Table 1 above is used as a base (0 °), and the base plane and each crystal plane are formed. Find the angle (hereinafter referred to as the exponential plane angle (deg)),
Within the range of the index plane angle (0 to 90 °), the index plane angle is in the range of 0 to 35.5 °, which is small (00 · 2),
A group consisting of three crystal planes (10 · 3) and (00 · 4) and (10 · 0) and (10 ·
1), (10 ・ 2), (11.0) divided into two groups of 4 crystal planes, and investigated the relationship between the sum of orientation indices and the lightness and darkness of the color tone of the galvanized surface in both groups. As shown below, we have obtained new knowledge that has never been recognized so far.

That is, the orientation index of the (hk · l) plane is I
_{If co} (hk · l), A = [I _co (00 ・ 2) + I _co (00 ・ 4) + I _co (10 ・ 3)] ≧ 8.0 B = [I _co (10 ・ 0) + I _co (10 ・ 1) + I _co (10 ・ 2) + I _co (11 ・ 0)] ≦
It has been found that when both relational expressions of 1.0 are satisfied at the same time, an electrogalvanized steel sheet having a very bright color tone can be surely obtained.

FIG. 1 is a graph showing the experimental results of examining the relationship between them. As is apparent from this figure, the electrozinc system satisfying the two relational expressions A and B at the same time. It can be seen that the color tones of the surface of the plated steel sheet all show a very excellent lightness with an L value of 80 or more.

That is, in the present invention, the orientation index of each crystal plane is not specified, but (00 · 2), (10 ·
3), (00/4), (10.0), (10.1),
Of the total of 7 types of crystal faces of (10 ・ 2) and (11.0), (00 ・ 2), (10 ・ 3), which has a small exponential plane angle,
Treating the three crystal faces of (00 ・ 4) as one group,
The sum of the orientation indices of these three crystal planes is 8.0 or more, and the index face angles are large (10 · 0), (10 ·
1), (10 ・ 2), (11.0) 4 crystal planes
By treating them as a group and suppressing the total value of the orientation indices of these four crystal planes to 1.0 or less, it is possible to secure an electrogalvanized steel sheet with outstanding brightness far exceeding conventional materials and having an L value of 80 or more. It has been successfully obtained.

The orientation indices of the respective crystal planes are independent of each other. For example, the index plane angle is small (00 · 2),
Considering three crystal plane orientation indices (10-3) and (00-4), if one of them (for example, the (10-3) plane) has a high (or low) orientation index, the rest. The orientation index of two (eg, (00 ・ 2), (00 ・ 4) planes) does not necessarily have a high (or low) dependency, and these things have a large index plane angle. (10.
0), (10 ・ 1), (10 ・ 2), (11.0) 4
The same is true for the two crystal planes.

In the present invention, each crystal plane in the electrogalvanized plating layer is divided into two groups, a group that exerts a positive influence on the brightness and a group that exerts an adverse influence on the brightness, and the sum of the orientation indices of these groups is defined. By introducing a new concept, we have succeeded in obtaining an electrogalvanized steel sheet that exhibits more excellent brightness.

The specific means for achieving the above-mentioned relational expression of the orientation index defined in the present invention is not particularly limited, and the orientation index of each crystal plane varies depending on various factors. Cannot be uniquely determined. For example, in an electrolytic zinc-based plating method using an acidic bath that is generally adopted on an industrial scale, plating current density, continuous increase / decrease of current or intermittent energization, conductivity as a plating bath composition, pH, impurities in the bath, etc. Type (organic or inorganic) and its concentration, type and concentration of additives in the bath, plating bath-
Various factors such as the relative flow velocity between the raw steel sheets are considered to affect the orientation index of each crystal plane.Therefore, depending on the situation at the site, set those conditions so that the above relational expression of the orientation index can be achieved. A method of controlling each individually or in combination is adopted. In this case, sufficient reproducibility can be secured by setting the conditions in advance by a preliminary experiment that takes into consideration the situation at the site.

According to a further study conducted by the present inventors on the premise of the above two groupings, in addition to the sum of the crystal plane orientation indices of the groups represented by the formulas A and B, the Those having a ratio (A / B) of 13.0 or more show particularly excellent brightness, and the crystallographic planes of the above two groups have an orientation index of (00 · 2) plane of 4.0 or more. And the orientation index of the (10 · 1) plane is 0.
It was confirmed that those having a value of 3 or less show a more stable and high level of brightness, and by adding these requirements, an electrogalvanized steel sheet having an L value of 83 or more and having an excellent brightness can be obtained. ing.

By the way, FIG. 2 is a graph showing the effect of the A / B ratio on the brightness in the electrogalvanized layer satisfying the requirements of the above formulas A and B. The A / B ratio is 13 The lightness is further increased beyond that, and L shows an excellent lightness of 83 or more. Also, FIG. 3 shows that among the plating layers that also satisfy the requirements of the formulas A and B, (00 It is a graph showing the effects of the orientation indexes of the (2) plane and the (10.1) plane on the brightness, and the orientation index of the (00/2) plane is 4.0 or more. Further, it can be seen that those in which the orientation index of the (10 · 1) plane is 0.3 or less, more preferably 0.2 or less, have an outstanding lightness of 83 or more in L value.

As described above, in the present invention, the sum of the orientation indices of the crystal planes of the group represented by the formula A in the electrogalvanized layer is 8.0 or more, and the orientation of each crystal plane of the group represented by the formula B is adjusted. By setting the sum of exponents to 1.0 or less,
The feature is that it secures a high level of brightness that surpasses the conventional level, and there is no particular limitation on the coating amount, but if the coating amount is too small, the original corrosion resistance becomes insufficient. I hate it, so 3g is preferable
/ M ² or more, more preferably 10 g / m ² or more, and further preferably 20 g / m ² or more. On the other hand, regarding the upper limit of the coating amount, it is preferably 100 g / m in consideration of the electric power cost and the like accompanying the increase of the coating amount.
^It can generally be said that the amount is ² or less, more preferably 60 g / m ² or less, and further preferably 40 g / m ² or less.

The zinc-based plating layer having high brightness is
It can be formed on only one side of the steel sheet or on both sides depending on the application. Further, prior to the formation of the zinc-based plating layer, Ni, as a base plating layer,
Ni-based plating such as Ni-Co, Ni-P, Zn-Ni,
Zn-based plating such as Zn-Fe, Zn-Cr, Fe-P,
Of course, it is also possible to have a multilayer plating structure in which Fe-based plating such as Fe-B is applied.

The electrogalvanized steel sheet of the present invention having the above-mentioned electrogalvanized layer of high brightness formed on the surface layer can be commercialized as it is because of its excellent brightness.
If necessary, it is also effective to form a chemical conversion treatment film such as chromate or a thin organic or inorganic clear film on the surface in order to further improve the corrosion resistance, workability and fingerprint resistance. Is.

In this case, when a chemical conversion treatment film or a clear film is formed, the lightness of the surface tends to be slightly decreased as described below, but the L value is still 70 or more, and the conventional electrogalvanic plating method is used. Compared with a steel plate, a much superior brightness is secured.

By the way, FIG. 4 is a graph showing the result of examining the relationship between the amount of chromate film adhered and the lightness. As the amount of chromate adhered increases, the lightness tends to slightly decrease, and the amount of adhesion increases. After that, the decrease cannot be neglected. The lightness after forming the chromate film is L
In order to secure a value of 75 or higher, it is desirable to keep the amount of the chromate film deposited in terms of Cr to 50 mg / m ² or less, more preferably about 30 mg / m ² or less. B, which is a measure of color tone other than
There is no problem that the value increases and the appearance becomes yellowish.

The main purpose of forming the chromate film is to improve the white rust resistance (corrosion resistance) of the surface of the electrogalvanized plating layer. From such a purpose, the amount of Cr conversion is 10 to 30 mg / m ² Since the degree is sufficient, there is no concern that the corrosion resistance is sacrificed to avoid the decrease in brightness.

The method for forming the chromate film is not particularly limited, and any of so-called reactive chromate treatment, electrolytic chromate treatment, coating chromate treatment and the like may be adopted, and depending on the case, they may be used in combination. It is also possible to do so. In order to further improve the corrosion resistance, scratch resistance, and blackening resistance of the chromate film, various oxides such as silica and organosilane compounds, as well as reactions of phosphoric acid, nitric acid, fluorides, silica, fluorides, etc. It is also effective to use a chromate treatment liquid containing an appropriate amount of an accelerator and the like.

Next, FIG. 5 is a graph showing the effect on the lightness when a thin clear film is further formed on the chromate film, and the decrease in lightness can be recognized by the formation of the clear film. If the amount of the clear film deposited exceeds 2 g / m ² , the L value, which is the tentative target lower limit value of the lightness of the present invention, may fall below 70. Therefore, the amount of the clear film deposited is 2 g by dry weight. / M ² or less, more preferably 1 g / m ² or less. The main purpose of forming a clear film is to further improve corrosion resistance, workability (lubricity), fingerprint resistance, etc., and such purpose is generally 0.
About 1 to ² g / m ² is sufficiently achieved. Therefore, there is no concern that the original purpose and performance of the clear film will be sacrificed in order to avoid a decrease in brightness, and there is no risk of impairing the groundability, weldability, etc. within this adhesion amount range.

There is no particular limitation on the constituent material of the clear film, but preferred examples include an epoxy resin, a polyester resin, a polyurethane resin and an ethylene copolymer containing an ethylenically unsaturated carboxylic acid as a polymerization component. Mainly composed of organic resins such as united resins, polyvinyl resins, polyamide resins, acrylic resins, and fluorine resins,
Inorganic materials such as various oxide particles such as silica and various phosphates for further improvement of corrosion resistance, lubricity, scratch resistance, workability, weldability, electrodeposition paintability, coating adhesion, etc. Organic clear film forming agent containing pigments, wax particles, organic silane compounds, naphthenates, etc .; or silicates such as sodium silicate, potassium silicate, lithium silicate, etc. Inorganic pigments and waxes such as colloidal silica and various oxide particles and various phosphates with the aim of further improving lubricity, scratch resistance, processability, weldability, electrodeposition paintability, and coating adhesion. Examples include inorganic clear film forming agents containing particles, organic silane compounds and the like. Among these, one kind or two or more kinds can be arbitrarily selected and used. The base steel sheet used in the present invention is not particularly limited, and includes ordinary mild steel sheets, high-strength steel sheets and various alloy steel sheets.

[0040]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited by the following examples, and changes may be made within the scope not departing from the gist of the preceding and the following. Of course, it is possible to carry out, and they are all included in the technical scope of the present invention.

Example Using a cold-rolled steel sheet as a plating base sheet, an electrogalvanized steel sheet was manufactured by the following procedure. In addition, a part of them was subjected to reactive chromate treatment to form a chromate film, and further a clear film was formed on the chromate film.

(1) Immersion degreasing in alkaline aqueous solution: 3% by weight caustic soda aqueous solution, 60 ° C. × 2 seconds (2) Electrolytic degreasing in alkaline aqueous solution: 3% by weight caustic soda aqueous solution, 60 ° C. × 2 seconds 20 A / dm ² (3) Washing with water ( 4) Pickling: 5 wt% sulfuric acid aqueous solution, 40 ° C x 2 seconds (5) Washing with water (6) Electrogalvanizing: ・ Plating cell: Horizontal plating cell ・ Plating bath composition ZnSO ₄ / 7H ₂ O 300-350 g / liter Na ₂ SO ₄ 50~100 g / l H ₂ SO ₄ 3~ 30 g / l ^{Ni 2+ 0~ 200 ppm Fe 2+ 0~2000} ppm Sn 2+ 0~ 10 ppm In 3+ 0~ 200 ppm Pb 2 ⁺ 0 ~ 5 ppm Cu 2 ⁺ 0 ~ 1 ppm ・ Current density: 25 ~ 200 A / dm ²・ Plating bath temperature: 20, 40, 60 ° C ・ Plating bath flow rate: 1, 2 m / sec ・ Electrode (anode): Pb Alloy electrode-Amount of plating: 20 g / m ² (per surface) (7) Washing (post-treatment of (8) to (10) shown below is performed for some ) (8) Chromate treatment: Reactive chromate treatment, Cr equivalent adhesion amount 10 to 100 mg / m ² (9) Washing with water (10) Thin film organic resin film treatment: Crosslinking polyethylene resin (colloidal silica, addition of wax particles), adhesion amount 0.5 to 5.0 g / m ² (Adhesion amount is adjusted by the solid content concentration of the coater coating liquid, the rotation speed of the coater roll, and the nip pressure) (11) Drying

The obtained electrogalvanized steel sheet was subjected to X-ray diffraction measurement under the following conditions, and the orientation index was calculated from the diffraction intensity of each crystal plane of the zinc plating. Also, using a color difference meter,
The brightness (L value) of the obtained electrogalvanized steel sheet (including the chromate-treated material and the thin-film organic coating material) was measured,
The brightness of the color tone was ranked according to the criteria shown in Table 2 below.

[Conditions for X-ray Diffraction] Apparatus: Rotating anticathode X-ray diffractometer manufactured by Rigaku Target: Cu (monochromatic ratio by flat plate monochrome crystal; Cu-Kα ray) Tube voltage: 40 kV Tube current: 300 mA Measuring angle: 2θ 30 ° to 80 ° Scanning speed: 2 ° / min Sampling angle: 0.02 ° Divergence slit: 1 ° Scattering slit: 1 ° Light receiving slit: 0.15 mm In-plane rotation: 100 rpm The results are shown in Tables 3 to 6. .

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

[Table 4]

[0048]

[Table 5]

[0049]

[Table 6]

From Tables 3 to 6, the following can be considered. In the examples in which the values of the formulas A and B defined in the present invention both satisfy the requirements, both have a very high lightness with an L value of 80 or more, and chromate treatment or Even if a thin film organic clear film treatment is applied,
Although a slight decrease in brightness is recognized, the L value maintains a high brightness of 70 or more.

On the other hand, in the comparative example in which one of the values of the expressions A and B deviates from the specified value, the L value of 80 which is intended in the present invention.
The brightness of the above level is not obtained. Further, if the amount of the chromate film deposited is too large and exceeds 50 mg / m ^{2 in} terms of Cr, the L value of 75 or more cannot be ensured after the chromate treatment (Reference Examples 34 and 35). It can be seen that in order to secure the level of brightness, it is desirable to suppress the Cr-equivalent deposition amount of the chromate film to 50 mg / m ² or less. In addition, a reference example (No. 45, 46) in which the amount of the organic clear film adhered exceeds 2.0 g / m ^2.
Then, since the decrease in the brightness becomes large, it is understood that it is desirable to suppress the adhesion amount of the clear film to 2.0 g / m ² or less in order to secure the L value of 70 or more in the state after the clear film treatment.

In Tables 3 to 6, the formula A of the crystal plane group which is divided into two groups in the electrogalvanized plating layer,
The sum of the orientation indices obtained in B is shown. Table 7 shows the orientation indices of the individual crystal planes of some of these plating layers.

[0053]

[Table 7]

[0054]

The present invention is constituted as described above, and each crystal plane in the electrogalvanized plating layer is divided into two groups, a crystal plane that exerts a favorable influence on the brightness and a crystal plane that exerts an adverse influence on the brightness. By providing the sum of the orientation indexes of the respective groups defined by the formulas A and B, it is possible to provide an electrogalvanized steel sheet having a high level of lightness, which exceeds the conventional example of L value of 80 or more. Became. Also,
In addition to these requirements, by defining the A / B ratio, and further by defining the orientation indices of the (00 ・ 2) and (10 ・ 1) planes among the crystal planes, the lightness can be increased to 83 or more as an L value. It is possible to raise up to. This electrogalvanized steel sheet can be used as it is as various outer panel materials, building materials, etc., and by applying chromate film treatment or thin film clear film treatment as needed, corrosion resistance, lubricity, Defect, workability, weldability,
It is also effective to further improve the electrodeposition coatability, coating film adhesion, etc. for practical use.

[Brief description of drawings]

FIG. 1 is a graph summarizing the effect of the sum of orientation indices defined by formula A and formula B on the brightness of the surface of a plated steel sheet.

FIG. 2 is a graph showing the relationship between A / B ratio and lightness (L value).

FIG. 3 is a graph showing the influence of the orientation index of the (00.2) plane and the (10-1) plane on the brightness.

FIG. 4 is a graph showing the relationship between the amount of chromate film deposited on the surface of a plating layer and brightness.

FIG. 5 is a graph showing the relationship between the amount of clear film adhesion and lightness when a chromate film is adhered to the surface of the plating layer and a thin organic clear film is further formed.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kuniyasu Araga               1 Kanazawa-cho, Kakogawa-shi, Hyogo Co., Ltd.               Kobe Steel Kakogawa Steel Works                (56) Reference JP-A-4-110489 (JP, A)                 JP-A-6-2193 (JP, A)                 Japanese Patent Publication 7-11071 (JP, B2)                 Japanese Patent Publication 5-36512 (JP, B2)                 "Materials and Processes" Vol. 8               (1995) No. Page 6,1420 (Company) Nippon Steel               Published by Steel Society

Claims (7)

(57) [Claims] 1. An electrogalvanized steel sheet in which an electrogalvanized plating layer is formed on one surface or both surfaces of the steel sheet, wherein the orientation index of each crystal face in the zinc based plating layer satisfies the following relational expression: An electrogalvanized steel sheet with a bright color tone. A = [I _co (00 ・ 2) + I _co (00 ・ 4) + I _co (10 ・ 3)] ≧ 8.0 B ＝ [I _co (10 ・ 0) + I _co (10 ・ 1) + I _co (10 · 2) + I _co (11 · 0)] ≦ 1.0 However, I _co (hk · l) represents the orientation index of the (hk · l) plane. 2. The galvanized steel sheet according to claim 1, wherein the orientation index of each crystal plane satisfies the relationship of the following formula. A / B ≧ 13.0 3. The electrogalvanized steel sheet according to claim 1 or 2, wherein a chromate film of 50 mg / m ² or less in terms of Cr is formed on the surface of the zinc-based plating layer. 4. A clear film having a dry weight of 2 g / m ² or less is formed on the chromate film.
The electrogalvanized steel sheet according to 3. 5. The galvanized steel sheet according to claim 1, which has a lightness (L value) of 80 or more as measured by JIS Z 8730. 6. The electrogalvanized steel sheet according to claim 3, which has a lightness (L value) of 75 or more as measured by JIS Z 8730. 7. The galvanized steel sheet according to claim 4, which has a lightness (L value) of 70 or more as measured by JIS Z 8730.