JP3282498B2 - Surface-treated Al-Zn-based alloy plated steel sheet excellent in roll forming workability and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated material of an Al--Zn alloy-plated steel sheet which is mainly used without painting for applications such as building materials and home appliances, and particularly to a so-called 55% Al--Zn alloy-plated steel sheet. The present invention relates to a surface treatment material suitable for a high-Al-Zn-based alloy-plated steel sheet and a method for producing the same.

[0002]

2. Description of the Related Art High-Al-Zn-based alloy-coated steel sheets represented by so-called 55% Al-Zn-based alloy-coated steel sheets have a beautiful plating appearance and excellent corrosion resistance. All of them are used as unpainted, for exterior walls, etc., and for home appliances, for example, for back plates of refrigerators. In these applications, not only long-term corrosion protection is required for the plated steel sheet, but also because the plated surface is used directly where it can be seen, the beautiful surface appearance of the plated steel sheet without discoloration over a long period of time It needs to be maintained. In addition, in the case of building materials, the plated steel sheet is formed by roll forming, so it is required that the plating surface is not damaged and that the plating does not pick up on the roll (that is, the roll forming property is good). Can be

Conventionally, the following proposals have been made for the purpose of improving the characteristics of such a high Al-Zn alloy plated steel sheet. Japanese Patent Publication No. Hei 4-2672 discloses a method of treating the surface of a 55% Al-Zn-based alloy-plated steel sheet using a treatment liquid containing a water-dispersible or water-soluble organic resin as a main component, and mixed with chromic acid. It discloses a method for improving corrosion resistance and roll forming property. In this method, a specific resin film is formed on the plating surface to avoid direct contact between the roll and the plating surface, thereby improving the roll forming property, and at the same time, obtaining corrosion resistance by chromic acid in the resin film.

With respect to a method for preventing blackening, Japanese Patent Publication No. 53353/1993 discloses that the surface of a 55% Al—Zn alloy plated steel sheet is treated with a treatment liquid in which chromic acid and an organic resin are mixed at a specific ratio. A method is disclosed in which chromic acid is prevented from directly reacting with plating to improve blackening resistance. Regarding a method for preventing blackening of a galvanized steel sheet other than a 55% Al-Zn-based alloy-coated steel sheet, for example, a 5% Al-Zn-based alloy-coated steel sheet, JP-A-59-177381 and JP-A-63-65088 disclose a method for preventing blackening. For example, a method of treating a plating surface with Ni or Co at a stage after plating and before a chromate treatment is disclosed.

[0005]

Conventionally, 55% Al-Z
The roll forming properties and corrosion resistance of n-type alloy plated steel sheets are improved by treating the plating surface with a treatment liquid that is mainly composed of a water-dispersible organic resin and mixed with chromic acid, as represented by the above technology. Has been planned. However, such a method using a treatment liquid mainly composed of an organic resin has the following problems. That is, an emulsifier is generally used to disperse the organic resin in the processing liquid, but when the processing liquid contains chromic acid, it is difficult to ensure long-term stability of the processing liquid. It is an effective means to add a large amount of nonionic emulsifier to improve the stability of the processing solution, but when such an emulsifier is used, the stability of the processing solution is improved, but the resin is formed into a film. However, there arises a problem that the drying temperature required for the drying is high or the drying time is long, and as a result, the burden on facilities is increased. In any case, since the storage time is limited in terms of the stability of the processing liquid, there is a problem that a large amount of chromium waste liquid is generated.

[0006] Organic resins that can be formed in a short time at a low temperature generally have a low Tg and have a limit in water resistance. They may adhere to each other and cause a so-called blocking phenomenon, which may impair the appearance of the steel sheet. Also, even after molding, when stored in a stacked state, the adhesive strength increases,
There is a problem that the workability during construction is reduced. Further, the above-mentioned method has the same problem as in the case of the stability of the processing solution and the blocking resistance. In addition, the above-described method requires two steps of production, which is not only disadvantageous in terms of production cost, but also has no effect of improving characteristics other than blackening resistance. Therefore, an object of the present invention is to solve such problems of the prior art, and to form rolls,
An object of the present invention is to provide a surface-treated Al-Zn alloy-plated steel sheet which is excellent in blocking resistance, corrosion resistance, appearance uniformity, and can obtain excellent blackening resistance without performing special pretreatment, and a method for producing the same.

[0007]

The features of the present invention for solving such a problem are as follows. [1] A single-layer or multiple-layer film containing colloidal silica having an average particle diameter of 80 to 200 nm and a chromium compound on the surface of an Al—Zn-based alloy plating film containing 25 to 75% by weight of Al, roll forming machining adhesion amount of the colloidal silica is characterized by having a surface treatment coating 200~6000mg / ^{m 2} in terms of SiO _2, the amount of deposition of the chromium compound is 7~50mg / ^{m 2} reckoned as metal chromium Surface-treated Al-Zn-based alloy-plated steel sheet with excellent heat resistance.

[ 2 ] Al containing 25 to 75% by weight of Al
-The average particle diameter is 80 to
A treatment liquid containing 200 nm of colloidal silica and a chromium compound and having a pH of 3 or less, wherein the molar ratio of the amount of trivalent chromium to the total amount of chromium is trivalent chromium / total chromium: 0.1 to 0.7. A method for producing a surface-treated Al-Zn-based alloy-plated steel sheet having excellent roll-forming properties, wherein the surface-treated film according to [1] is formed on the surface of the plated film by coating and drying.

[ 3 ] Al containing 25 to 75% by weight of Al
-A treatment solution containing a chromium compound and having a pH of 3 or less on the surface of the Zn-based alloy plating film, wherein the molar ratio of the amount of trivalent chromium to the amount of total chromium is trivalent chromium / total chromium: 0.1 to 0.7. After applying a certain treatment liquid and drying, the average particle diameter is 80
By applying and drying a treatment liquid containing colloidal silica having a thickness of ~ 200 nm,
A surface-treated Al-Z excellent in roll forming processability, characterized by forming the surface-treated film according to [1].
A method for producing an n-based alloy plated steel sheet.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION
We have been studying ways to improve the roll formability of high Al-Zn alloy plated steel sheet represented by alloy plated steel sheet without using a film mainly composed of organic resin.
As a result, it has been found that the roll forming property can be effectively improved by forming a specific surface treatment film mainly composed of colloidal silica on the surface of the plating film. Therefore, the feature of the present invention is that a roll formed by a surface treatment film mainly formed of colloidal silica is used without using a film mainly composed of an organic resin such as water dispersibility which has been used for obtaining roll forming properties in the prior art. The purpose is to improve the formability.

[0011] The roll forming property is effectively improved by such a surface treatment film mainly composed of colloidal silica because of the high Al-Zn alloy plated steel sheet represented by the 55% Al-Zn alloy plated steel sheet. Since the surface has fine irregularities formed by α and β layers peculiar to this type of plated steel sheet, the colloidal silica fills the concaves on the irregular surface, and the deformation resistance of the convexes in contact with the roll Is increased, and as a result, the plating surface is less likely to be damaged. Therefore, such an effect of the present invention is an effect peculiar to a high-Al-Zn alloy-coated steel sheet in which irregularities are formed on the plating surface due to the structure of the plating film. -Since a plated steel sheet such as a Zn-based alloy plated steel sheet has a smooth plated surface, the effect is hardly obtained.

The details of the present invention and the reasons for limitation will be described below. The plated steel sheet serving as a base of the surface-treated Al-Zn-based alloy-plated steel sheet of the present invention contains 25 to 25 Al in the plating film.
It is an Al-Zn-based alloy-plated steel sheet containing 75% by weight, and a so-called 55% Al-Zn-based alloy-plated steel sheet is known as the most typical one. As mentioned earlier, the plated film of such a high Al-Zn alloy coated steel sheet because it has fine irregularities on the surface, the effect of the present invention can be appropriately obtained. On the other hand, when the amount of Al in the plating film is less than 25 wt%, the effect of the present invention cannot be sufficiently obtained because the plating film surface is smooth. Normally, Si is contained in the plating film of this type of Al—Zn-based plated steel sheet at 0.5 wt% of the Al content.
It is included above.

A so-called 55% Al—Zn alloy plated steel sheet usually means that the amount of Al in the plating film is 50 to 60 watts.
about t% Al-Zn-based alloy-plated steel sheet (in the following description, 55% Al-Zn-based alloy-plated steel sheet refers to the Al-Zn-based alloy-plated steel sheet having the Al content described above); The plating film usually contains Si
Is contained at about 1-3 wt%. As described above, the effect of improving the characteristics according to the present invention is as follows.
It can be obtained remarkably in a 5 wt% Al-Zn-based alloy-plated steel sheet.
Particularly remarkable property improving effects are obtained in a Zn-based alloy plated steel sheet. When a 55% Al-Zn alloy plated steel sheet is used without painting, the plated surface is used in a state of having a so-called spangle design property from an aesthetic point of view. Therefore, in such an application, the skin pass is not performed, or even if it is performed, a slight skin pass is performed, whereby the unevenness of the plating surface is maintained almost as it is, and the spangle is clearly observed visually. Is preferred.

The surface treatment film formed on the surface of the Al—Zn-based alloy plating film is a single-layer or multiple-layer film containing colloidal silica and a chromium compound. 200mg adhered amount of the colloidal silica in the coating in terms of SiO ₂ / m ²
If less than 6000 mg / m ² , a sufficient improvement effect on roll forming properties cannot be obtained, while if more than 6000 mg / m ² , colloidal silica coats the surface of the plating film thickly, so that scratch resistance and roll forming properties are rather deteriorated. Would. Deposition of the colloidal silica in this order in the film is 200~6000mg / m ² in terms of SiO _2, preferably 300~4000mg / m ^2.

Colloidal silica is advantageous in that it has excellent stability in a processing solution and can be used without causing a thickening of the processing solution, and has a drying temperature at which water evaporates, that is, a sheet temperature. At a drying temperature of about 80 ° C., it tightly adheres to the plating surface and exhibits a desired effect. In addition, since the formed film has releasability, and is excellent in thermal stability and corrosion resistance, a film that does not block even when placed in a high temperature and high humidity environment in a coil state can be formed. The characteristics of the surface treatment film are greatly affected by the average particle size of the colloidal silica used. That is, when the average particle diameter of the colloidal silica exceeds 200 nm, the appearance that powder is attached to the film surface (powder appearance)
And a film having poor adhesion and easy to peel off. On the other hand, even when the average particle size of the colloidal silica is less than 80 nm, the average particle size is not as large as when the average particle size exceeds 200 nm,
Again, there is a similar tendency. On the other hand, when the average particle diameter of the colloidal silica is in the range of 80 to 200 nm, there is no such a problem, and a film having excellent transparency and excellent adhesion can be formed. In addition, it is possible to mix colloidal silica having a particle diameter of less than 80 nm or exceeding 200 nm with colloidal silica having a particle diameter of 80 to 200 nm, but even in such a case, the content should be limited to about 20 wt% of the entire colloidal silica. is there.

The chromium compound is contained in the surface treatment film in order to secure corrosion resistance and blackening resistance. The chromium compound improves the corrosion resistance and blackening resistance by:
The effect of the passivation film mainly composed of trivalent chromium formed by the reaction between the surface of the plating film and hexavalent chromium is large.
In order to sufficiently satisfy these characteristics, it is necessary that the amount of the chromium compound adhered is 7 mg / m ² or more in terms of chromium metal. If the amount is less than 7 mg / m ² , a sufficient effect cannot be obtained. On the other hand, when the amount of the chromium compound attached increases, the corrosion resistance and blackening resistance are improved, but even when added in an amount exceeding 50 mg / m ² , the effect of improving the corrosion resistance and blackening resistance is saturated, and conversely, the solubility is poor. An increase in the amount of Cr causes environmental problems. Therefore, the adhesion amount of the chromium compound is 7 to 50 mg / m ^{2 in} terms of chromium metal, preferably 10 to 30 m / m ² .
g / m ² .

The surface treatment film may contain additives other than the above-mentioned colloidal silica and chromium compound as long as the effects of the present invention are not impaired. For example, additives such as metal ions such as Al, Zn, Ca, Mg, and Cd, organic lubricants such as polyethylene wax, water-dispersible or water-soluble resin, and resin beads are used as additives for improving roll forming properties and scratch resistance. Etc. can be added. The metal ions added to the film serve to bridge between the colloidal silicas and enhance the film strength. The organic lubricant, water-dispersible or water-soluble resin, resin beads, and the like added to the film serve to reduce the frictional force generated at the time of contact with the roll, which causes scratches. However, excessive addition of metal ions reduces blackening resistance and stability of the processing solution, and excessive addition of an organic lubricant or water-dispersible or water-soluble resin reduces the stability of the processing solution or foams the processing solution. May cause problems such as
Therefore, it is necessary to keep the amount of these additives within an appropriate range where the above-mentioned adverse effects are not observed. Specifically, in the case of a water-soluble or water-dispersible resin, 300 mg /
It is preferable that the adhesion amount is not more than m ² .

As a method of dispersing a relatively small amount of resin or the like in the treatment liquid, it is effective to adjust the viscosity of the treatment liquid to prevent sedimentation of the resin. According to this treatment method, when a relatively small amount of resin or the like is to be added, the resin can be dispersed without using an emulsifier, so that a treatment liquid having excellent foaming resistance can be obtained. Further, an anion such as phosphoric acid can be added to the surface treatment film. For example, the addition of phosphoric acid is effective in suppressing coloring by chromium and forming an uncolored film, whereby a particularly beautiful appearance can be obtained without impairing the plating appearance. The effect of suppressing the coloring of other anions is also recognized, but if these are added excessively, they have an adverse effect on blackening resistance and corrosion resistance. Therefore, it is necessary to keep the addition amount within an appropriate range.

Next, a method for producing the surface-treated Al—Zn-based alloy-plated steel sheet of the present invention will be described. As a method for producing the surface-treated Al—Zn-based alloy-plated steel sheet of the present invention, a first method is to apply a treatment liquid containing colloidal silica and a chromium compound to the surface of a plating film and to dry the same. As a method, there is a method in which a treatment liquid containing a chromium compound is applied and dried, and then a treatment liquid containing colloidal silica is applied and dried.

In the first method, colloidal silica is dispersed in a treatment solution containing a chromium compound, and this is applied to the surface of a plated steel sheet and dried. In the second method, a treatment liquid containing a chromium compound is applied and dried, and then a treatment liquid in which colloidal silica is dispersed in water is applied to the surface of the plated steel sheet and dried. In the second method, the treatment liquid containing colloidal silica may further contain a chromium compound. In order to form a passivation film early with chromic acid, the pH of the processing solution has a great influence. When the pH of the treatment liquid exceeds 3, passivation takes a long time, and a case occurs in which blackening occurs during storage after production. For this reason, the pH of the processing solution containing the chromium compound needs to be 3 or less. Therefore, when the treatment liquid containing colloidal silica in the second method also contains a chromium compound, it is necessary that the pH of the treatment liquid is also 3 or less.

For the purpose of forming a film having a high solubility, a treatment liquid containing a chromium compound, in which a part of hexavalent chromium is reduced to trivalent chromium, is used. In the case of using such a treatment solution containing trivalent chromium, if the pH of the treatment solution exceeds 3, the solution may gel and a problem may occur in the stability. It is necessary to make it 3 or less. Further, the amount of trivalent chromium in the treatment liquid is represented by a molar ratio with respect to the total amount of chromium.
The range is 0.1 to 0.7. When the molar ratio is less than 0.1, a film having high solubility is not obtained. On the other hand, when the molar ratio is more than 0.7, corrosion resistance and blackening resistance are reduced, and the stability of the processing solution is also reduced.

Therefore, when the treatment liquid containing colloidal silica also contains a chromium compound in the second method, the molar ratio of the amount of trivalent chromium to the total amount of chromium in the treatment liquid also needs to be within the above range. There is. There is no special restriction on the method of applying the processing liquid in both the first method and the second method. For example, a method in which the processing liquid is applied by spraying or dipping, and the amount of the applied processing liquid is adjusted by roll squeezing or gas squeezing. A method of applying with a roll coater or the like can be used.

In a method using a treatment liquid mainly composed of a water-dispersible organic resin as in the prior art, once the treatment liquid is dried in the treatment tank, the resin solid content in the treatment liquid becomes insoluble in the tank. However, it is difficult to wash off with water, but in the method of the present invention using a treatment liquid mainly composed of colloidal silica, the inside of the treatment tank after the treatment can be easily washed. Also, unlike a treatment liquid mainly composed of a water-dispersible organic resin, the treatment liquid used in the method of the present invention has excellent resistance to foaming, and thus can be applied by spraying. Also,
Since the stability of the processing solution with respect to the solution temperature (bath temperature in the case of immersion treatment) is much better than the conventional method using a processing solution containing a large amount of a water-dispersible organic resin, a normal chromate treatment solution is used. There is no problem even if the liquid temperature is about 50 to 60 ° C., and therefore, there is an advantage that the furnace capacity and energy required for drying in the next step can be reduced, and the equipment cost and operation cost can be reduced.

The method of drying each processing solution in the first method and the second method is optional, and for the drying treatment, for example, an electric furnace, a hot air furnace, an induction heating furnace, or the like can be used. The drying temperature is also not particularly limited, but if the drying is performed at an excessively high temperature, the corrosion resistance and the blackening resistance tend to be reduced. Therefore, it is preferable to dry at an ultimate plate temperature of 60 to 150 ° C. which is a normal drying condition.

[0025]

【Example】

[Embodiment 1] In this embodiment, a hot-dip galvanized steel sheet (thickness 0.3 mm) or a hot-dip Al-containing steel sheet containing 0.3 wt%, 5 wt%, and 55 wt% of Al in a plating film, respectively.
After applying a treatment liquid having the composition shown in Table 1 to the surface of a Zn-based alloy-plated steel sheet (thickness: 0.3 mm), it was dried to prepare a test material. The treatment liquid containing the colloidal silica or the water-dispersible organic resin applied to the plated steel sheet was dried using a hot air drying furnace at a reaching plate temperature of 80 ° C. and a drying time in the furnace of 10 seconds. In addition, the test materials which were previously subjected to chromate treatment (Table 2,
For the test material using the plated steel sheet “D” in Table 3), chromic acid having a Cr reduction ratio of 20% was sprayed on the surface of the plated steel sheet while being heated to 50 ° C., squeezed by a roll, and then heated in a hot air oven. Was used at a final plate temperature of 80 ° C., to which a chromium compound adhered at 15 mg / m ^{2 in} terms of chromium metal was used.

As the colloidal silica to be added to the treatment liquid, one having an average particle diameter of 120 nm was used. As the organic resin to be added to the treatment liquid, a polymethacrylic acid-based organic resin stabilized with a nonionic emulsifier was used. Phosphoric acid and ammonia were used to adjust the pH of the processing solution. The adhesion amounts of the chromium compound and colloidal silica in the surface treatment film were determined by measuring their intensities using fluorescent X-rays. The amount of the organic resin adhered was determined by measuring the strength of C using EPMA. The following characteristic tests were performed on each test material.

(A) Corrosion resistance A salt spray test was conducted for 240 hours, and evaluated according to the following evaluation criteria according to the degree of rust generation. 10: No rust 8: Rust area is less than 10% 6: Rust area is 10% or more and less than 25% 4: Rust area is 25% or more and less than 50% 1: Rust area is 50% or more

(B) Resistance to blackening: 15 in a wet tester (HCT) at 50 ° C. and 98% relative humidity.
A test material of 0 mm × 150 mm was left in a stacked state for 6 days so that the surface of the steel sheet became wet in the tester, and the degree of discoloration due to blackening was evaluated according to the following evaluation criteria. 10: No change in appearance 8: Slight discoloration when viewed diagonally 6: Discoloration in an area of less than 10% when viewed directly 4: Discoloration in an area of 10% or more and less than 25% when directly viewed 1: Directly viewed Over 25% area

(C) Resistance to Cr dissolution The test material was immersed in boiling water for 120 seconds,
The amount of eluted Cr was measured by measuring the amount of r attached, and evaluated by% of [residual Cr amount] / [initial attached Cr amount]. (D) Roll forming resistance (scratch resistance) A bead pull-out test was performed using a bead having a tip diameter of 5 mmR and pressed against a test material having a width of 30 mm with a load of 20 kgf, and the appearance was visually observed. Observe at
The following evaluation criteria were evaluated according to the degree. ：: No scratch or change in appearance can be confirmed. い な い: No scratch, but slightly higher gloss. ×: Clear scratch or metal adhered to bead.

(E) Blocking resistance The test material cut into 70 mm × 150 mm was subjected to a surface pressure of 0.2 k.
gf / cm ^{2 and} a load of 80
The adhesion state after leaving for 24 hours in a humid environment of 98 ° C. and 98% RH was evaluated according to the following evaluation criteria. ○: No adhesive feeling at all △: Clearly adhered, requiring peeling force ×: Clearly adhered, abnormal appearance when peeled off (F) Film adhesion immediately after drying Test A tape peeling test was performed on the test material immediately after being taken out of the drying furnace when preparing the material, and the presence or absence of peeling of the film was examined. The stability of the treatment liquid was evaluated by observing the state of the treatment liquid at 40 ° C. and observing the state of the liquid on the following day, one week, two weeks, and four weeks.

Table 1 shows the processing solutions used for processing the plated steel sheets.
Tables 2 and 3 show the results of the film configuration and property evaluation of the obtained test materials. N among the treatment liquids shown in Table 1
o. 2, No. 3, No. 8, No. 10, No. 1
1, No. No. 12 is a treatment liquid not satisfying the conditions of the present invention. 1, No. 4, No.
5, No. 6, No. The liquid stability is clearly inferior to the processing liquid of No. 7.

N of the examples shown in Tables 2 and 3
o. 1, No. 2, No. No. 17 is inferior in roll forming property because the amount of colloidal silica adhered in the film is out of the range of the present invention. In addition, No. 4, no. 13
Is inferior in corrosion resistance and blackening resistance because the amount of the chromium compound adhered in the film is too small. In addition, No. 14,
No. 15, No. No. 16 is inferior in blocking resistance and film adhesion immediately after drying because a large amount of a water-dispersible resin is added to the film. In addition, No. 20, no. 21
Is intended for a plated steel sheet other than the Al—Zn-based alloy-plated steel sheet targeted by the present invention, so that the effects of the present invention cannot be obtained, and therefore, the roll forming property is poor. On the other hand, the examples satisfying the conditions of the present invention have excellent properties in all of roll forming properties, blocking resistance, corrosion resistance, blackening resistance, and Cr dissolution resistance. However, no. Sample No. 3 was prepared using a treatment solution outside the conditions of the present invention, and thus had a high Cr solubility.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

Example 2 55 W of Al in the plating film
After applying a treatment liquid satisfying the production conditions of the present invention to the surface of a hot-dip Al-Zn-based alloy-plated steel sheet (sheet thickness 0.3 mm) containing t%, the sheet temperature reached 80 using a hot air drying furnace.
The sample was dried at a temperature of 10 ° C. and a drying time in a furnace of 10 seconds to prepare a test material having a film configuration shown in Table 4. With respect to these test materials, the powdery appearance of the film surface (whether or not the appearance was such that powder adhered) was visually determined. Further, an adhesive tape was stuck on the surface of the film and then peeled off, and it was examined whether or not the peeled film adhered to the tape adhesive surface. The results are shown in Table 4 together with the film configuration. According to Table 4, the influence of the average particle diameter of the colloidal silica becomes remarkable especially when the amount of the adhered colloidal silica is large, and the average particle diameter is 80 nm.
When it is less than 200 nm or more than 200 nm, the powdery appearance is obtained, and the film itself is easily peeled off. On the other hand, the average particle size of the colloidal silica is 80 to 2
In the range of 00 nm, even if the coating amount is 3 g / m ² or more, a glass-like coating having excellent adhesion is obtained.

[0037]

[Table 4]

As described above, according to the present invention, a surface-treated Al-Z having excellent roll forming properties, corrosion resistance, blackening resistance, blocking resistance and Cr dissolution resistance is excellent.
An n-based alloy-plated steel sheet can be obtained. In addition, since the treatment liquid used for the production shows unprecedented liquid stability and is also excellent in operability, a surface-treated Al-Zn-based alloy-plated steel sheet excellent in the above-mentioned various properties can be efficiently and inexpensively manufactured. Can be manufactured.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-72887 (JP, A) JP-A-63-65088 (JP, A) JP-A-3-161333 (JP, A) JP-A 57-78 203796 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00-22/86 C23C 28/00

Claims (3)

(57) [Claims] An Al— containing 25 to 75% by weight of Al.
The average particle diameter is 80 to 2 on the surface of the Zn-based alloy plating film.
A single-layer or multi-layer film containing colloidal silica having a thickness of 00 nm and a chromium compound, wherein the adhered amount of the colloidal silica is ₂₀₀ to 6000 mg / m ^{2 in} terms of SiO ² ;
The amount of the chromium compound attached is 7 to 50 in terms of chromium metal.
mg / m ² , characterized in that it has a surface treatment film and is excellent in roll forming processability.
n-based alloy plated steel sheet. 2. Al-containing 25 to 75% by weight of Al
The average particle diameter is 80 to 2 on the surface of the Zn-based alloy plating film.
P containing 00 nm colloidal silica and a chromium compound
H3 or less treatment liquid having a molar ratio of trivalent chromium to total chromium of trivalent chromium / total chromium: 0.1 to 0.7 is applied and dried to form a plating film A method for producing a surface-treated Al-Zn-based alloy-plated steel sheet having excellent roll forming workability, comprising forming the surface-treated film according to claim 1 on the surface of the steel sheet. 3. Al-containing 25 to 75% by weight of Al
P containing chromium compound on the surface of Zn-based alloy plating film
H3 or less treatment liquid, wherein the molar ratio of the amount of trivalent chromium to the total amount of chromium is trivalent chromium / total chromium: 0.1 to 0.7, dried, and then coated with an average particle Diameter 80 ~
Applying a treatment liquid containing 200 nm of colloidal silica,
A method for producing a surface-treated Al-Zn-based alloy-plated steel sheet having excellent roll formability, characterized by forming the surface-treated film according to claim 1 on the surface of the plated film by drying. .