JP3114642B2 - Black hot-dip Al-Zn alloy plated steel sheet and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to building materials, home electric appliances,
Useful in fields where design is required, such as automobiles, colored surface treated steel sheets with excellent corrosion resistance and design, more specifically blackened molten Al-Zn with a beautiful black or gray black appearance
The present invention relates to an alloy-plated steel sheet and a method for producing the same.

[0002]

2. Description of the Related Art For products in fields where beautiful surface appearance is required, such as building materials and home electric appliances, it is common practice to apply cold-rolled or plated steel sheets to a predetermined shape before painting (post-coating). However, recently, there has been an active movement to apply a pre-coated steel sheet which has been previously coated in the state of a steel sheet to such a product. This is because the steel plate processing maker has the advantage that the production cost can be reduced and the coating quality of the product is improved by omitting the post-coating step. Since the precoated steel sheet undergoes processing after painting, it must have excellent workability in addition to corrosion resistance. To meet this demand, galvanized steel sheets and galvanized steel sheets have been developed and used.

However, in view of the thorough pursuit of cost reduction by steel plate processing manufacturers, there is a demand for an inexpensive surface-treated steel plate having no coloring and excellent design appearance without a costly coating step. became. The quality required for such a colored surface-treated steel sheet is corrosion resistance,
In addition to workability, uniformity of the colored appearance is important, and in some cases, weldability, chemical resistance, fingerprint resistance, and the like are also required. As a color tone, a black color tone is preferred for home electric appliances, small car interior parts and the like.

[0004] As the hot-dip galvanized steel sheet having such a colored appearance or a method for producing the same, the following ones having a black color tone are known. (1) Chlorate, an oxidizing agent such as peroxide and divalent copper ions as main components, and may further contain an organic substance such as polyoxyethylene ether or polyvinyl alcohol.
A zinc or zinc alloy electroplated steel sheet is immersed in a blackening treatment solution having a pH of 5 or less to blacken the plating surface (see JP-A-50-55546, JP-A-52-76237 and JP-A-53-76238). ). (2) Alkaline aqueous solution p containing Co or Ni ions
H: Cathodic electrolysis in an electrolyte solution of 2 to 11 (JP-A-60-190588)
No.).

(3) Anodizing is carried out in an electrolytic solution having a pH of about 4 to which Al ions are added (JP-A-63-157898). (4) A blackening treatment solution containing a predetermined amount of at least two of Ag, Sb and Bi ions and at least one of Ni, Fe and Co ions and having a pH of 0.5 to 7 No. 161176).

(5) Hot-dip Al-Zn plated steel sheet is blackened by steam treatment, and then coated with a clear coating film
-56861). (6) Treatment with an alkaline solution containing Ni ions and NH _{2 and} having a pH of <11.0 (JP-A-2-47273).

(7) Treatment in an aqueous solution containing stannous chloride and a water-soluble Ni or Co compound (JP-A-2-93077). (8) First metal ion selected from Ni, Fe, Co, and Sb, B
After treatment in an aqueous solution containing a second metal ion selected from i, Ag, Cu, Pb, and Sn and fluorine ions, a coating type chromate treatment and a polymer film are applied (JP-A-2-2824).
No. 85).

(9) Treatment with a treating solution having a pH of 5 or more containing at least one compound of Ni ion and Co ion and at least one compound of ammonia and amine to complex the metal ion -31484). (10) It is immersed in an alkaline solution containing a reducing agent, and the treatment time and treatment temperature are controlled to reduce the brightness of the surface layer of the plating (JP-A-6-33269).

[0009] These conventional methods, except for the method (10),
A black film containing a metal element such as Ni or Co is formed, or an oxide or hydroxide of a plating component such as Al is formed, and the adhesion between such a black film and the plating film is formed. The properties, the corrosion resistance of the plating layer itself, and the processing cost become problems. For example, when the method (1) is applied to a plating system having a large amount of oxide such as Al-Zn alloy plating,
The adhesion of the colored film becomes insufficient. (2), (4), (6),
In the methods (7), (8) and (9), the zinc-based plating film is
Corrosion resistance is significantly reduced due to coating with a metal nobler than Zn. In the method (3), a sufficient blackened steel sheet cannot be obtained by Zn-based plating in which a metal element such as Ni or Co does not exist in the plating film. The method (5) has a drawback in productivity because steam treatment is performed at a high temperature for a long time.

On the other hand, when the method (10) is used for plating in which Al and Zn are not uniformly dispersed and solidified, such as Al—Zn alloy plating, the appearance unevenness is large and the processing time is prolonged. , Productivity and quality problems.

[0011]

SUMMARY OF THE INVENTION The present invention provides a low cost,
Provide a blackened hot-dip Al-Zn alloy-coated steel sheet that achieves blackening of a hot-dip Al-Zn alloy-coated steel sheet with excellent corrosion resistance in a short time, has little change in color tone of the processed part, and has excellent adhesion. That is.

[0012]

Means for Solving the Problems The present inventors have proposed molten Al-
As a result of intensive studies on the blackening of Zn alloy plated steel sheets,
The present inventors have found that by treating with a solution containing a transition metal before performing the treatment in a strong alkaline solution, the blackening of the steel sheet is promoted and stabilized as compared with the case where the treatment is not performed, and the present invention has been completed.

The present inventors have also conducted intensive studies on the blackening of a hot-dip Al-Zn alloy-plated steel sheet.
In addition to n and Si, one or more elements of either Sr or V
Plating treatment is performed with a plating bath component having 0.010 wt% or more, and by setting the spangle particle size to 1 mm or less or the secondary Al dendrite crystal spacing (hereinafter abbreviated as DAS) to 15 μm or less, the steel sheet is not blackened. Promoted against the case,
Found to be stable.

The present inventors have further studied the blackening of the hot-dip Al-Zn alloy plated steel sheet. As a result, before the treatment in a strong alkaline solution, the cooling rate of the steel sheet was reduced by a forced cooling device installed after the plating. It has been found that the blackness of the steel sheet is promoted and stabilized by not less than 15 ° C./sec or by setting the secondary Al dendrite crystal spacing (DAS) to 15 μm or less.

The present inventors have further studied the blackening of the hot-dip Al-Zn alloy-plated steel sheet. As a result, before applying the treatment in a strong alkaline solution, the elongation was at least 0.5% or more by a skin pass mill. It has been found that the blackening of the steel sheet is promoted and stabilized as compared to the case where the steel sheet is not treated, by performing the processing by adding a processing of 0.5 μm or less.

That is, the plating film of the hot-dip Al—Zn alloy-plated steel sheet has a film structure in which an Al-rich phase and a Zn-rich phase are mixed because Al and Zn hardly cause mutual solid solution at room temperature. Therefore, when treated in a strong alkaline solution, the Al-rich phase on the plating surface layer is preferentially dissolved (etched), so that fine irregularities are formed on the plating surface,
Generates oxides or hydroxides of Zn. It is considered that the fine unevenness or the product on the plating surface absorbs or interferes with visible light, so that the plating surface becomes grayish black to black visually. When a treatment is performed in a strong alkaline solution, if a transition metal element or an oxide thereof is present on the plating surface, dissolution of Al is further promoted, blackening is realized in a shorter time, and the blackness is more vivid. It turned out to be.

Here, the present invention is as follows. (1) A hot-dip Al-Zn alloy-plated steel sheet, wherein the Al-Zn alloy plating layer has an Al composition of 5 to 95 at% and the surface of the plating layer
The ratio between the Al occupancy and the Al composition of the entire plating layer is 0.5 or less (at
%) And the lightness L ^* is 65 or less.

(2) A black hot-dip Al-Zn alloy-plated steel sheet in which a transition metal element other than Al and Zn or an oxide thereof is adhered to the surface of the black hot-dip Al-Zn alloy-plated steel sheet according to (1). (3) On the Al-Zn alloy plating layer of the black hot-dip Al-Zn alloy-plated steel sheet according to the above (1) or (2), a Cr adhesion amount of 10 to 150.
A black hot-dip Al-Zn alloy-plated steel sheet having a chromate layer of mg / m ² .

(4) The black hot-dip Al-Zn alloy-plated steel sheet according to any one of the above (1) to (3) has an organic resin film having a thickness of 0.2 to 5 μm on the Al-Zn alloy plating layer. A black hot-dip Al-Zn alloy plated steel sheet characterized by the above-mentioned.

(5) Black molten Al according to (1) or (2) above
-First on the Al-Zn alloy plating layer of the Zn alloy plating steel sheet
The chromate layer of 10 to 150 mg / m ² of Cr deposition amount as a layer,
A black hot-dip Al-Zn alloy-plated steel sheet having an organic resin film having a thickness of 0.2 to 5 µm as a second layer.

(6) A hot-dip Al-Zn alloy plated steel sheet having an Al composition of the entire plating layer of 5 to 95 at% is immersed in an acidic solution containing a transition metal element or an alkali solution complexed with a transition metal element. Or after spraying the alkaline solution or performing electrolysis in the alkaline solution, dipping, spraying or electrolyzing the obtained molten Al-Zn alloy plated steel sheet in an alkaline solution having a pH of 11 or more. A method for producing a black hot-dip Al-Zn alloy-plated steel sheet, which is blackened by the method.

(7) Al composition of the entire plating layer is 5 to 95 at%.
A hot-dip Al-Zn alloy-plated steel sheet, wherein the hot-dip Al-Zn alloy-plated steel sheet is plated with a plating bath component having at least 0.010 wt% of at least one element of Sr or V in addition to Al, Zn, and Si. The plated steel sheet with an alkaline solution of pH 11 or higher.
Immersion or immersion electrolysis at a flow rate of 0.1 to 5 m /
blackened by blowing the alkaline solution in countercurrent to s
Kokushoku溶 fusion Al-Zn manufacturing method of the alloy plated steel sheet to perform. .

(8) The hot-dip Al-Zn alloy-coated steel sheet according to the above-mentioned (7), wherein the spangle diameter is 1 mm or less.
Manufacturing method of Zn alloy plated steel sheet. (9) Molten Al-Zn with Al composition of the entire plating layer of 5 to 95 at%
An alloy plated steel sheet, the molten Al-Zn cooling rate after plating of alloy plated steel sheet to 15 ° C. / sec or more, or molten Al-Zn secondary Al dendrite crystals interval (DAS) was 15μm or less Transfer the alloy-plated steel sheet to pH 11 or higher
Immersion or immersion electrolysis in re-solution and flow rate 0.1
By blowing the alkaline solution in a countercurrent of ~ 5 m / s
A method for producing a black hot-dip Al-Zn alloy-plated steel sheet that performs blackening .

(10) As a pre-treatment of the hot-dip Al-Zn alloy-plated steel sheet, a treatment is performed in which at least a skin pass elongation is 0.5% or more and a surface roughness Ra is 0.5 μm or less.
(9) The method for producing a hot-dip Al-Zn alloy-plated steel sheet according to any of (9).

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The blackened hot-dip Al-Zn alloy plated steel sheet of the present invention will be described in detail. (1) Al concentration in the molten Al-Zn alloy plating layer The blackening in the present invention utilizes the difference in the dissolution rate of Zn and Al as described above, so that fine irregularities are formed. It is desirable that Zn and Al have a network structure on the plating surface. Therefore, if the occupation ratio of Al in the plating film is less than 5 at% or more than 95 at%, it is difficult to form a stitch structure that only contributes to blackening. Preferably Al: 20 ~
It is preferably 92 at%, more preferably 40 to 80 at%. In this plating composition region, the network structure on the plating surface has an appropriate size, and the blackening is further promoted.

The optional elements other than Al and Zn constituting the Al—Zn alloy plating layer include Si as a suppressing element of the alloy layer formed at the steel plate / plating interface, and Si for improving the wettability.
La, Ce, Mg for improving corrosion resistance, etc., and the presence of other unavoidable impurities do not affect blackening.

(2) Al occupancy of plating surface layer In the present invention, by treating with a strong alkaline aqueous solution, concentrated Al is preferentially dissolved on the surface, and fine irregularities are formed on the plating surface layer. Accordingly, the surface Al occupancy of the plating surface layer is smaller than before the alkali treatment. The ratio of the Al-Zn alloy coated steel sheet alkali pretreatment of surface Al occupancy and Al content in the coating composition of the entire plating layer of the above composition, i.e. Al reduction ratio is usually 1.
The value is 0 to 1.5, but the present inventors have found that when this value is 0.5 or less, a beautiful black appearance can be obtained. Preferably, when the above ratio is 0.3 or less, a higher degree of blackness is obtained. On the other hand, the lower limit is not particularly specified from the aspect of blackening, but when the treatment is performed below 0.01, the dissolution amount of the plating film becomes excessively large, which adversely affects the corrosion resistance or reduces the unevenness of the dissolved surface. And the blackness decreases. Therefore, it is preferably 0.01 or more. In this specification, the surface Al occupancy of the plating surface layer and the Zn composition of the entire plating layer are defined as follows.

[0028]

(Equation 1)

(3) Effect of adding Sr and V to Al-Zn alloy plating bath One of the pretreatment methods for the blackening treatment used in the present invention is Al
-1 of Sr or V besides Al, Zn and Si of Zn alloy plating bath
Plating is performed with a plating bath component containing at least 0.010 wt% of more than one kind of element. By this processing method, the spangle particle size is set to 1 mm or less, the DAS is set to 15 μm or less, and the Al-rich phase of the plating surface layer is preferentially precipitated, so that the etching is performed in the subsequent blackening treatment by strong alkali treatment. Progresses easily, and a beautiful black appearance is obtained.

(4) Blackening treatment In the blackening treatment method according to the present invention, a hot-dip Al-Zn alloy plated steel sheet is treated with a strong alkaline aqueous solution for a short time to give fine irregularities on the plating surface. in dissolving the Al-rich phase of the plating can layer, that is, by performing etching. For this etching, a strong alkaline solution having a pH of 11 or more, preferably 11.5 or more, is used. Thus, etching is performed in a short time of several seconds to several tens of seconds. However,
It is not necessary to completely remove the Al-rich phase of the coating layer , as long as fine irregularities can be effectively formed in an amount sufficient for blackening.
An Al-rich phase may remain in the layer . When the pH is less than 11, sufficient blackness cannot be obtained in a short time.

Here, the plating surface layer refers to the surface Al occupancy
In relation to the definition, it is the plating layer area from the surface at a depth that can be analyzed by XPS (X-ray photoelectron spectroscopy).

The chemical used in the strong alkaline aqueous solution can be adjusted by dissolving one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium silicate and the like in water. Alkaline components are pH 1 at the application temperature
Other than these can be used as long as they form one or more (eg, a small amount of a water-soluble organic solvent is added).

The treatment method may be any method such as an immersion method, a spray method, and an immersion electrolysis method. In the case of the electrolytic method, an anodic oxidation treatment is performed. Preferred electrolysis conditions, 2 to 15 seconds of the conduction time 1A / dm ² or more, generally a current density of 1 to 10 A / dm ^2. The voltage is preferably 1 to 20V. Preferably 0.1 ~
Perform the electrolytic treatment under a countercurrent of 5 m / s. After the blackening treatment, it is desirable to wash thoroughly with water to prevent color tone unevenness and then sufficiently dry.

The temperature of the processing solution is preferably set at 30 to 90 ° C. If the temperature of the treatment liquid is lower than 30 ° C., a sufficient degree of blackness may not be obtained in a short time. Above 90 ° C, the liquid evaporates violently, hindering operation. Preferably 50-70
° C is good. Further, the contact time between the plated steel sheet and the aqueous alkali solution is preferably 2 seconds or more in any of the above-described immersion method, spray method, and immersion electrolytic method. If the time is less than 2 seconds, blackening may not be uniformly obtained. Since the blackening progresses with the lapse of time, the processing may be stopped when the desired blackness is reached. However, under the above-described conditions, processing for 2 minutes or less (actually 10 seconds or less) is usually sufficient.

(5) Lightness As an index that can be visually evaluated as black or gray black, it is possible to use lightness (L ^* ) as shown in JIS Z 8729. The lightness visually recognized as black or gray black needs to be 65 or less. If it exceeds 65, the surface will be hard to say black or gray-black because some gray or gloss remains.

(6) Pretreatment In the present invention, prior to the above-mentioned strong alkali treatment,
A transition metal or an oxide thereof may be attached.
In other words, a strong alkali treatment is performed after a transition metal element or its oxide is previously adhered to the surface of the hot-dip Al-Zn alloy plated steel sheet.

By such pretreatment, the effect of stabilizing and accelerating the blackening at the time of the blackening treatment with the alkali solution is exhibited, and further, it contributes to the improvement of the post-treatment adhesion and the corrosion resistance after the blackening. The transition metal element at this time is Cr,
Co, Ni, Fe, Cu and the like can be mentioned. These metal elements are
For example the carbonates are added to the alkaline solution as a complex in the form of such sulfates, hydrochlorides, etc. are added to an acidic solution, or Ni (NH _{4) 6} ^2+. By such processing,
Preferably, the spangle diameter of the hot-dip Al-Zn alloy plated steel sheet may be 1 mm or less.

As the surface coating method, there are an immersion method using an acidic or alkaline solution as described above, a spray coating method, an electrolytic method and the like. The electrolysis method in this case may be a cathodic electrolysis. Also in this case, typical electrolysis conditions are as follows:
It is to supply electricity at 10 A / dm ² for 2 to 15 seconds. Voltage is 1
~ 20V is desirable.

Alternatively, these metal components may be added to the plating bath and contained in the plating layer in advance. In other words, when using a system containing the above-mentioned transition metal element as the alloy system of the Al-Zn alloy plating layer,
The -Zn alloy plating process itself constitutes a pretreatment for blackening.

The amount of the transition metal element deposited on the plating layer by the pretreatment, that is, the coating amount, is 5 to 200 mg.
/ m ² , preferably 10 to 100 mg / m ² . Coverage 10
is less than mg / m ^2, hardly then Al dissolution promotion effect of blackening effect by the alkali treatment performed is obtained, whereas, 200 mg
If the coating amount exceeds / m ² , the plating surface will be covered with a strong barrier film, and conversely, the initial reactivity between the alkali and the plating surface will be small, making short-time processing difficult.

Other pre-processing includes the following processing. Plating treatment is performed with a plating bath component containing at least 0.010 wt% of at least one element of Sr or V in addition to Al, Zn, and Si of the Al-Zn alloy plating bath to reduce the spangle particle size to 1.
mm or less and the secondary Al dendrite crystal spacing may be 15 μm or less.

The cooling rate of the steel sheet may be set to 15 ° C./sec or more by the forced cooling device installed after the plating, or the secondary Al dendrite crystal spacing may be set to 15 μm or less. Skin pass mill at least elongation of 0.5% or more, Ra is facilities the following processing 0.5 [mu] m
It may be.

(7) Post-treatment The blackened hot-dip Al-Zn alloy-coated steel sheet of the present invention thus obtained has a uniformly colored surface appearance, and has corrosion resistance equivalent to that of the plated steel sheet before blackening. It is preserved and can be processed as it is and used for manufacturing various products. However, a chromate treatment as a post-treatment or a thin resin film or a chromate treatment as a first layer, a second
It is preferable to apply a thin organic resin film as a layer.

The effect of the chromate treatment is to improve the corrosion resistance and homogenize the surface appearance. The effect of the resin film is the same as that of the chromate treatment. In addition, it was recognized that it had a role of protecting fine irregularities on the plating surface layer, and that the appearance change after molding was small and the corrosion resistance was improved.

The chromate treatment may be a well-known chromate treatment such as a reaction type, an electrolytic type, or a coating type having excellent corrosion resistance. However, a coating type chromate is preferable in that the surface after the blackening treatment is not further reacted (hard to cause). . The amount of the applied chromate film formed is 10 to 150 mg as metal Cr.
/ m ² , especially in the range of ^{20 to} 60 mg / m ² . Adhesion amount is 10
If it is less than mg / m ² , there is no effect on the improvement of color tone and corrosion resistance, and if it exceeds 150 mg / m ² , the blackened steel sheet becomes yellow and its appearance is impaired.

The coating type chromate treatment solution to be used is known for chromium treatment solutions such as acids such as sulfuric acid, phosphoric acid and hydrofluoric acid, and oxides such as silica for improving corrosion resistance, in addition to chromate ions and reducing agents. May be added alone or in combination of two or more. More recently, a water-soluble resin, an emulsion resin, a wax, or the like may be added to improve the corrosion resistance of the processed portion, and these may be used. Cr ⁶⁺ to promote the formation of chromate film
It is preferable to use a partially reduced treatment solution in which some of the ions are reduced to Cr ³⁺ ions. The chromate treatment is
It can be carried out by a conventional method such as coating, spraying, dipping, etc., and after heating and drying the film after the treatment, a coated chromate film is formed. The drying temperature is the highest temperature, usually 50 to 10
Within the range of 0 ° C.

The resin film may be applied directly on the blackened hot-dip Al-Zn alloy plating or on the above-mentioned chromate film by a usual method. The latter is applied when corrosion resistance is required more than the former. The thickness of the organic resin film is limited to 0.2 to 5 μm. When the thickness of this film is less than 0.2 μm, the colored surface is not sufficiently covered, and the effect as a protective film at the time of processing cannot be expected, so that the corrosion resistance may be deteriorated. When the thickness of the resin film exceeds 5 μm, the resin film cannot follow the processing at the time of processing, and peeling in the film may occur, or properties such as adhesion, steel plate weldability, and workability may be deteriorated.

The organic resin to be used is not particularly limited as long as it is a resin capable of forming a transparent film that does not obscure the underlying black color. Examples of suitable resins include acrylic resins, polyester resins, alkyd resins, fluororesins, phenol resins, and epoxy resins. Organic resin film is silica for improving corrosion resistance,
An additive such as wax for imparting lubricity may be contained. Next, the operation and effect of the present invention will be described more specifically with reference to examples.

[0049]

【Example】

(Example 1) Al-Zn alloy hot-dip bath prepared by cutting a cold-rolled steel sheet cut to a thickness of 0.8 mm, a width of 100 mm and a length of 250 mm to a predetermined component using a hot-dip coating tester after solvent degreasing. And plated. The coating weight was adjusted so as to be constant at 80 g / m ² . For example, when Ni is applied as a transition metal to some hot-dip Al-Zn alloy-plated steel sheets, various transition metals were applied by immersion in a nickel sulfate solution of 3 g / l in terms of nickel. In the case of the chromic acid treatment, the cathode electrolysis was further partially performed under the conditions of a current density of 5 A / dm ² × 5 to 10 seconds.

Thereafter, a blackening treatment was performed by an immersion method using a sodium hydroxide aqueous solution (pH = 10 to 15) at 50 to 80 ° C. so that the surface Al occupancy ratio became a predetermined value, and the film was immediately washed and dried. . The plating film of the Al-Zn plated steel plate subjected to such black treatment was analyzed by the following method.

Surface Al occupancy: Quantitative analysis of surface by XPS Al content of the entire plating film: Atomic absorption analysis after dissolving the plating film.
The plated steel sheet was immersed in a coating type chromate treatment solution having a g / l concentration and a Cr ³⁺ / Cr ⁶⁺ ratio of 1, and the steel sheet was rotated to adjust the thickness to a predetermined thickness by centrifugal force. Then, it was dried at 80 ° C. for 30 seconds to form a chromate film.

The resin film was coated on a blackened hot-dip Al-Zn alloy plating or chromate-treated film with an acrylic resin paint in which silica sol was dispersed in an amount of 15% by weight using a bar coater. Baking by heat treatment,
A predetermined film thickness was formed.

This sample was evaluated by the following method. <Evaluation method> (1) Black appearance Lightness (L ^* ) using a colorimeter (CR-300 manufactured by Minolta)
(Value) in the plate surface is black when the average value is 55 or less, and gray black when it exceeds 55 and 65 or less. Those whose measured values fall within a variation of ± 2 are defined as a uniform color tone. ：: Black with uniform color tone (L ^* value of 55 or less) ○: Gray black with uniform color tone (L ^* value of 55 to 65) △: No uniform black color (color tone unevenness) ×: Insufficient black color cannot be obtained (L ^* value is over 65) Even if black is uniformly black in the plane (in the above evaluation, ◎,
○), those with yellowing or interference color
(◎ ^- , ○ ^- )

(2) Appearance after processing Untreated product or chromate-treated product Appearance of tightly bent part ○: Good appearance (no difference in appearance between bent part and flat part) △: Deterioration in appearance of bent part Small ×: Bending part Appearance deterioration Large Thin film resin coated product Appearance after drawing with a cylinder with a drawing ratio of 1.8 (blank diameter 60 mm, no oil coating) ○: Good appearance (no difference in appearance between sliding part and non-sliding part) △: Sliding part Appearance deterioration small ×: Appearance deterioration of sliding part large.

(3) Adhesion of upper layer film Thin film resin coated product Cellophane tape peeling (visual evaluation) on the side surface of the external appearance (blank diameter 60 mm, no oil coating) after cylindrical drawing with a drawing ratio of 1.8. ：: The resin film does not peel at all. Δ: The resin film peeled slightly. ×: 20% or more of the resin film is peeled by area.

(4) Corrosion resistance In a salt spray test (JIS-Z2371), the corrosion resistance was evaluated based on the area where white rust occurred. Untreated or chromate treated (salt spray time 600Hr
After) ◎: No rust generated ○: White rust generated 5% or less △: White rust generated 10% or less ×: White rust generated 10% or more Thin film resin coated product, product without lower layer chromate (after 1200 hours of salt spray time) ◎: No rust generated ○: White rust generated 5% or less △: White rust generated 10% or less ×: White rust generated 10% or more Thin-film resin coated product and product with lower layer chromate (after salt water spraying time of 2400 hours) ◎: No rust generated ○ : White rust generation 5% or less △: White rust generation 10% or less ×: White rust generation 10% or more Table 1 and Table 2 show the coating composition and evaluation results.

As can be seen from these results, Run N
o.1 to 3 and 52 to 54 are hard to be blackened because the Al composition during plating is out of the range of the present invention. Run No.4, 9, 21, 22,
In Nos. 46 and 47, the Al reduction ratio after the blackening treatment exceeded 0.5 (at%), and blackening was difficult. Run Nos. 5, 10, 18, 22, and 46
The pH of the blackening solution is below 11, and it does not turn black enough. Run Nos. 6, 11, 15, 23, and 24 have poor corrosion resistance because chromate and organic resin films do not exist or are not sufficiently adhered.

As described above, the Al composition and the surface Al occupancy in the plating film are the predetermined values, the appropriate blackening treatment conditions, and the black molten Al— The Zn alloy-plated steel sheet not only has a beautiful black appearance, but also has excellent appearance after processing, corrosion resistance, and the like.

[0059]

[Table 1]

[0060]

[Table 2]

(Example 2) A 3 g / l nickel sulfate solution of an Al-Zn alloy hot-dip coated steel sheet having a thickness of 0.8 mm, a width of 900 mm and a Zn content of 80 g / m ² and an Al composition of 50 at% was converted to nickel. And immersed in a facility as shown in FIG. 1 while blowing countercurrent with a sodium hydroxide solution. However, tank length 5m,
The roll diameter of the dam roll was 300 mm and the body length was 2100 mm.

Alkaline conditions: sodium hydroxide (pH = 1
1.5, concentration 5 wt%, temperature 50 ° C) When the flow rate of the aqueous solution was changed, the lightness L ^* became 65 or less at 0.1 m / s or more, and L ^* became 53 at 1 m / s, as shown in Fig. 2. Was not changed.

Example 3 A cold-rolled steel sheet was continuously annealed,
r, the degree of blackness when plating was performed in a 55% Al-Zn bath to which V was added and then alkali treatment was performed under the same conditions.
Table 3 shows the results showing the relationship between the amounts of Sr and V added. The operating conditions at that time are as follows. Cold-rolled steel sheet size: 0.8 mm in thickness, 919 mm in width, Plating bath composition: 55% Al-remaining Zn

[0064]

[Table 3]

Amount of plating: 80 g / m ^{2 on} one side Alkali pretreatment: none Alkaline immersion condition: sodium hydroxide aqueous solution: concentration 5%, pH11, temperature 60 ° C Treatment time: 10 s Treatment method: immersion Even under alkali immersion treatment conditions, a beautiful black appearance can be obtained by adding Sr or V in an amount of 0.010 wt% or more.

(Example 4) A cold-rolled steel sheet was subjected to continuous annealing to obtain 55%.
% Al-Zn bath, then air-cool the plated steel sheet in each condition with a forced cooling device, and then apply alkali treatment under the same conditions, the degree of blackness, cooling rate after plating, DAS 3 and 4 show the results showing the relationship with the above.

・ Cold-rolled steel sheet size: 0.8 mm thick, 919 mm wide ・ Plating bath component: 55% Al-Zn ・ Coating weight: 80 g / m ^{2 on} one side ・ Alkali pretreatment: None ・ Alkaline immersion condition: water Sodium oxide aqueous solution: concentration 5%, pH 11, temperature 60 ° C Treatment time: 10s Treatment method: immersion As described above, even under the same alkali immersion treatment conditions, the cooling rate after plating is 15 ° C / sec or more, or DAS.
Is 15 μm or less, a beautiful black appearance can be obtained.

(Example 5) A cold-rolled steel sheet was subjected to continuous annealing to obtain 55%.
% Al-Zn bath, the skin-pass plated steel sheet is adjusted to a surface roughness Ra of 0.5 μm or less under each condition, and then subjected to alkali treatment under the same conditions. Figure 5 shows the degree and skin pass elongation.
Shown in

The operating conditions at that time are as follows.

· Cold-rolled steel sheet size: 0.8 mm in thickness, 919 mm in width · Plating bath component: 55% Al-Zn · Coating weight: 80 g / m ^{2 on} one side · Surface roughness of plated steel sheet after skin pass: Ra 0.5 μm or less ・ Alkali pretreatment: none ・ Alkali immersion condition: sodium hydroxide aqueous solution… concentration 5%, pH11, temperature 60 ℃ Processing time: 10s Treatment method: immersion method As described above, even under the same alkaline immersion treatment conditions By applying a skin pass with an elongation of 0.5% or more and a surface roughness of the plated steel of 0.5 μm or less, a beautiful black appearance can be obtained.

[0071]

According to the present invention, blackening of a hot-dip Al-Zn alloy plated steel sheet is provided in a relatively short time and at low cost. Accordingly, the blackened molten Al-Zn alloy steel sheet of the present invention is less expensive than the precoated steel sheet, has excellent design properties, and has the high corrosion resistance of Al-Zn alloy plating, so that it can be used without coating. Further, since the blackened film structure according to the present invention does not have a colored layer, even if it is processed, there is no change in the color tone of the processed portion and the appearance is not impaired.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an alkaline solution immersion apparatus of Example 2.

FIG. 2 is a graph showing the results of Example 2.

FIG. 3 is a graph showing a relationship between lightness (L ^* ) and a cooling rate after plating.

FIG. 4 is a graph showing a relationship between lightness (L ^* ) and DAS.

FIG. 5 is a graph showing the relationship between lightness (L ^* ) and skin pass elongation.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mutsugu Sagara 1850 Minato, Wakayama City Sumitomo Metal Industries Co., Ltd. Inside Wakayama Works (72) Inventor Tamotsu Toki 4-5-33 Kitahama, Chuo-ku, Osaka-Sumitomo (72) Inventor Shinya Hikino 1850 Minato, Wakayama City Sumitomo Metal Industries Co., Ltd.Wakayama Works (72) Inventor Hisao Yoshimori 1850 Minato, Wakayama City Sumitomo Metal Industries Co., Ltd.Wakayama Works (72) Inventor Katsuhiro Matsuda Wakayama City 1850 Minato Sumitomo Metal Industries Co., Ltd. Wakayama Works (72) Inventor Minoru Oi 1850 Minato Wakayama City Sumitomo Metal Industries Co., Ltd. Wakayama Works (58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 2 / 00-2/40

Claims (10)

(57) [Claims] 1. A hot-dip Al-Zn alloy plated steel sheet, comprising:
When the Al composition of the entire Zn alloy plating layer is 5 to 95 at%, the surface Al occupancy of the plating layer and the Al reduction ratio of the Al composition of the entire plating layer are 0.5 or less, and the lightness L ^* is 65 or less. A black hot-dip Al-Zn alloy-plated steel sheet. 2. A black hot-dip Al-Zn alloy-plated steel sheet in which a transition metal element other than Al or Zn or an oxide thereof is adhered on the surface of the black hot-dip Al-Zn alloy-plated steel sheet according to claim 1. 3. The black molten Al-Zn according to claim 1 or 2.
Cr adhesion amount on the Al-Zn alloy plating layer of alloy plated steel sheet
A black hot-dip Al-Zn alloy-plated steel sheet having a chromate layer of 10 to 150 mg / m ² . 4. The black hot-dip Al-Zn alloy-plated steel sheet according to any one of claims 1 to 3, on the Al-Zn alloy-plated layer,
A black hot-dip Al-Zn alloy-plated steel sheet having an organic resin film having a thickness of 0.2 to 5 µm. 5. The black molten Al-Zn according to claim 1 or 2.
On the Al-Zn alloy plating layer of the alloy plated steel sheet, having an organic resin film having a thickness of 0.2 5 .mu.m chromate layer of 10 to 150 mg / m ² of Cr deposition amount as a first layer and a second layer A black hot-dip Al-Zn alloy plated steel sheet characterized by the above-mentioned. 6. A method for immersing a hot-dip Al—Zn alloy plated steel sheet having an Al composition of 5 to 95 at% in the entire plating layer in an acidic solution containing a transition metal element or an alkali solution containing a transition metal element as a complex. After spraying the alkaline solution or performing electrolysis in the alkaline solution, the obtained molten Al-Zn alloy plated steel sheet is immersed in an alkaline solution having a pH of 11 or more, or immersion electrolysis, A method for producing a black hot-dip Al-Zn alloy-plated steel sheet in which the alkali solution is blown in countercurrent at a flow rate of 0.1 to 5 m / s to perform blackening. 7. A hot-dip Al—Zn alloy coated steel sheet having an Al composition of the entire plating layer of 5 to 95 at%, wherein the hot-dip Al—Zn alloy coated steel sheet is Sr or V in addition to Al, Zn, and Si. A plated steel sheet plated with a plating bath component having at least one element of at least 0.010 wt% is immersed in an alkaline solution having a pH of 11 or more, or immersion electrolysis, and at a flow rate of 0.1 to 5 m / s.
A method for producing a black hot-dip Al-Zn alloy-plated steel sheet in which blackening is performed by blowing the alkaline solution in a countercurrent to the above. 8. The hot-dip Al-Zn alloy according to claim 7, wherein the spangle diameter of the hot-dip Al-Zn alloy plated steel sheet is 1 mm or less.
Manufacturing method of alloy plated steel sheet. 9. A hot-dip Al—Zn alloy-coated steel sheet having an Al composition of 5 to 95 at% in the entire coating layer, wherein a cooling rate of the hot-dip Al—Zn alloy-coated steel sheet after plating is 15 ° C./sec or more. Or secondary Al dendrite spacing (DAS) of 15μ
m or less, or by dipping the molten Al-Zn alloy plated steel sheet in an alkaline solution having a pH of 11 or more, or by immersion electrolysis and blowing the alkaline solution in a countercurrent flow at a flow rate of 0.1 to 5 m / s to achieve blackening. Production method of black hot-dip Al-Zn alloy plated steel sheet. 10. A hot-dip Al—Zn alloy coated steel sheet having an Al composition of the entire plating layer of 5 to 95 at%, wherein at least a skin pass elongation is 0.5% or more as a pretreatment of the hot-dip Al—Zn alloy coated steel sheet. A hot-dip Al-Zn alloy plated steel sheet with a surface roughness Ra of 0.5 μm or less is immersed in an alkaline solution of pH 11 or more, or immersion electrolysis and flow rate
A method for producing a black hot-dip Al-Zn alloy-plated steel sheet in which blackening is performed by blowing the alkaline solution in a countercurrent flow of 0.1 to 5 m / s.