JP5752880B2 - Surface-treated plated steel sheet and manufacturing method thereof - Google Patents

Description

  The present invention relates to a surface-treated plated steel sheet and a method for producing the same.

  Plated metal plates such as aluminum-zinc alloy plated steel plates are widely used in fields such as building material products, home appliances, and automobile parts. Such a plated steel sheet is surface-coated in order to improve the corrosion resistance and chemical resistance (alkali resistance, acid resistance, etc.) of the plating layer and workability. For example, Patent Document 1 discloses that a resin film is formed on a plating layer with a composition containing hexavalent chromium in an aqueous resin having an acid value of 10 to 200, and Patent Document 2 discloses a plating layer. On the other hand, it is disclosed to form a lubricant-blended silicone resin film containing a small amount of chromium.

  In these prior arts, the corrosion resistance and chemical resistance of the plating layer are improved by treatment with chromium (chromate treatment). In addition, by simultaneously coating the plating surface with a resin film using a resin composition, the lubricity between the production roll and the press die during molding processing is improved, and the plating layer is destroyed during molding processing, This prevents the plating layer caused by frictional heat from being fused with a forming roll or a press die. This prevents the metal powder generated from the plating layer from adhering to the molding roll and the press mold, thereby preventing the metal powder from accumulating on the corners of the molded product and causing the baking phenomenon, and scratches and abrasions. The occurrence of defects is prevented, for example, and appearance defects are prevented. However, in the chromate treatment as described in Patent Documents 1 and 2, when condensation occurs on the plated metal plate or the plated metal plate is exposed to rain water, chromium ions are eluted from the film, resulting in environmental pollution. There is a fear. Therefore, in recent years, it has been studied to impart corrosion resistance, chemical resistance, and good workability to a plated metal plate by a treatment that does not use chromium (chromate-free treatment). For example, Patent Documents 3 and 4 attempt to impart corrosion resistance, chemical resistance, and lubricity to the plating layer by coating the plating layer with a urethane resin film in which a silane coupling agent and a zirconium compound are blended. .

  However, in these chromate-free treatments, the corrosion resistance and chemical resistance imparted to the plating layer has not yet reached the level of chromate treatment, and further improvement of corrosion resistance and chemical resistance by chromate-free treatment. Was desired.

Japanese Patent Publication No.4-2672 JP 7-251128 A JP 2003-151578 A JP 2004-204333 A

  The present invention has been made in view of the above points, and is a surface-treated plated steel sheet capable of imparting excellent corrosion resistance, chemical resistance and workability to a plating layer without using chromium, and a method for producing the same. The purpose is to provide.

As a result of repeated examination of a surface-treated plated steel sheet and a method for producing the same that can impart excellent corrosion resistance, chemical resistance, and workability to a plating layer without using chromium, the present inventors have performed hot dip plating. It has been found that the corrosion resistance and chemical resistance of the plating are remarkably improved by applying an aqueous coating material containing a zirconium compound and / or zirconium ions to the surface of the steel sheet immediately after the treatment. The means for applying is preferably a spraying method. In addition to spraying, there are coating methods such as roll coating, but there are problems such as complicated equipment.

In addition, after applying a water-based coating material containing a zirconium compound and / or zirconium ions to the surface of the steel sheet immediately after the hot dipping treatment, if a resin film layer is further formed thereon, the corrosion resistance and chemical resistance are improved. And found that processability is improved. This upper resin film can be formed by a coating method such as spray coating and / or roll coating.

  The metal compound layer formed as the first layer of the hot dip plating layer contains a metal compound and / or metal ions in a state where the hot dip surface temperature immediately after the steel plate is pulled up from the hot dip bath is 150 to 350 ° C. Good corrosion resistance and chemical resistance can be obtained only by applying an aqueous coating material. Although the details of the reason are unknown, it is presumed that there is some relationship with the metal compound formation state of the first layer. That is, when the temperature of the hot-dip plating surface when applying the aqueous coating material is less than 100 ° C., a metal compound composed of the hot-plating component itself is formed, and the aqueous coating material is difficult to wet, and a uniform coating film is formed. Since it cannot be formed, it is considered that sufficient performance is not exhibited. Further, if the temperature exceeds 350 ° C., the volatilization or evaporation of water in the coating material is too intense, which inhibits the formation of the metal compound layer on the steel sheet surface, or the formed metal compound layer is very Since it becomes brittle, it is considered that sufficient performance is not exhibited. Therefore, in order to form the metal compound layer formed in the first layer of the hot-dip plating upper layer, the hot-dip surface temperature at which the aqueous coating material containing the metal compound and / or metal ions is applied is 100 ° C to 350 ° C, Preferably it is set as the range of 150 to 300 degreeC.

  According to the present invention, excellent corrosion resistance, chemical resistance, and workability can be imparted to a plated steel sheet without using chromium.

  Hereinafter, modes for carrying out the present invention will be described.

  The present invention is a manufacturing method in which a hot-dip plated layer is provided on one or both surfaces of a cold-rolled steel plate, and further a metal compound layer and / or a resin layer are sequentially laminated, and the surface-treated plated steel plate manufactured by the manufacturing method It is.

  As the cold-rolled steel sheet, for example, a so-called low carbon steel sheet having a C (carbon) content concentration of 0.1 wt% or less in the steel may be mentioned, but any steel sheet capable of hot dipping may be used.

Examples of the hot dipping include aluminum-zinc alloy plating. This includes aluminum in the range of 4 to 95% by mass, the balance is made of zinc, and may further contain Si, Mg, Sr, Cr, other trace amounts of third components, and other inevitable. Impurities may be included. Examples of such hot dipping include low aluminum-zinc alloy plating containing aluminum in the range of 4 to 10% by mass and high aluminum-zinc plating containing 20 to 95% by mass of aluminum.

  The metal compound layer does not contain chromium. This metal compound layer is formed by applying an aqueous coating material containing a metal compound and / or metal ions to the plating surface immediately after hot dipping. The application method is not limited, but it is preferably applied by spraying. As this water-based coating material, an appropriate material exhibiting rust prevention can be used, and examples of the metal element to be contained include Zr, Si, Mg, Sr, Ba, V, and Ca. Zr is preferred.

  The thickness of the metal compound layer can be adjusted by the concentration of the metal compound and / or metal ions of the aqueous coating material and the spray amount of the aqueous coating material. In order to give excellent corrosion resistance and chemical resistance to the surface-treated plated steel sheet and to give good workability, the thickness of the metal oxide layer is 0.02 μm or more and 2 μm or less. 0.02 μm or more and 1 μm or less. If it exceeds 1 μm, the hard metal compound layer is likely to break, and when subjected to processing, it may become a base point of damage to the underlying hot-dip plated layer.

  The surface-treated plated steel sheet on which the metal compound layer is formed has excellent corrosion resistance and chemical resistance compared to a hot-dip plated steel sheet that is not subjected to any treatment, and exhibits good workability. Furthermore, by providing a resin layer on the metal compound layer, it is possible to obtain performance comparable to chromate treatment that can withstand severe corrosive environments and processing conditions. The resin layer can be formed by applying a resin coating material by spray coating and / or roll coating, and then baking and drying. The component of the resin coating material is preferably an acrylic emulsion and / or a polyurethane dispersion. Moreover, the resin coating material may contain a rust preventive agent.

  The thickness of the resin layer is 0.5 μm or more and 5 μm or less, and preferably 1 μm or more and 3 μm or less. If it is less than 1 μm, the barrier effect of the resin layer is reduced, and sufficient performance improvement cannot be expected. If it exceeds 3 μm, it will be difficult to apply in terms of cost and equipment.

  In a continuous hot dip galvanizing production facility, the cold-rolled steel sheet was drawn from the hot dipping bath, and immediately after the plating on the steel sheet surface solidified, various coating materials were sprayed. The hot dipping was 55% aluminum-zinc alloy hot dipping. For the metal compound layer formed on the plating surface, a zirconium-based rust inhibitor and an acrylic emulsion (Aquabrid NT-201-J27 manufactured by Daicel Finechem Co., Ltd.) were used. The thickness of the metal compound layer was adjusted by the amount sprayed with the zirconium-based rust inhibitor, and as shown in Table 1, the metal compound layer was adjusted in the range of 0.005 to 2 μm. In order to further provide a resin layer on the upper layer of the metal compound layer, an acrylic emulsion coating material (Aquabrid NT-173-244J, manufactured by Daicel Finechem Co., Ltd.) is coated with a roll coater, and then at a steel plate temperature of 80 ° C. A resin layer was formed by baking and drying under the following conditions. The thickness of the resin layer was adjusted according to the resin solid content concentration in the coating material and the coating conditions of the roll coat, and was adjusted in the range of 0.5 to 5 μm.

  The performance of the material manufactured in the above manufacturing process was evaluated.

<Wetting evaluation test>
Each surface-treated plated steel sheet is placed in a humidity test apparatus with a humidity of 98% and an atmospheric temperature controlled to 50 ± 2 ° C., and the state of the surface-treated plated steel sheet after 30 days is visually observed. Based on a surface-treated plated steel sheet subjected to a certain chromate treatment, a case where the appearance was equivalent to this was evaluated as ◯, and a case where the degree of corrosion such as generation of white rust was larger was evaluated as ×.

<Salt spray evaluation test>
Based on the salt spray test method defined in JIS Z2371, each surface-treated plated steel sheet was sprayed with salt water for 240 hours. Observe the condition of the surface-treated plated steel sheet after treatment, and if the appearance is equivalent to this, based on the surface-treated plated steel sheet subjected to the chromate treatment as a reference, it is inferior to the chromate treatment, In comparison with 55% aluminum-zinc alloy-plated steel sheet without any surface treatment, the case where the degree of corrosion such as white rust is small is Δ, and the degree of corrosion is 55% aluminum-zinc without surface treatment. The case of the same grade as an alloy plating steel plate was evaluated as x.

<Chemical resistance evaluation test>
(1) Each surface-treated plated steel sheet was immersed in an aqueous sodium hydroxide solution having a concentration of 1% by mass at 20 ° C., taken out after 1 hour, washed with deionized water, and further dried with a drier. Observe the condition of the surface-treated plated steel sheet after treatment, and if the appearance is equivalent to this, based on the surface-treated plated steel sheet subjected to the chromate treatment as a reference, it is inferior to the chromate treatment, In comparison with 55% aluminum-zinc alloy plated steel sheet without any surface treatment, Δ is the case where the degree of discoloration is small, and the degree of discoloration is the same as 55% aluminum-zinc alloy plated steel sheet without surface treatment. The case of degree was evaluated as x.
(2) Each surface-treated plated steel sheet is immersed in dilute sulfuric acid with a concentration of 1% by mass at 20 ° C., taken out at each time point of 1 hour and 5 hours, washed with deionized water, and further with a dryer. Dried. Observe the condition of the surface-treated plated steel sheet after treatment, and if the appearance is equivalent to this, based on the surface-treated plated steel sheet subjected to the chromate treatment as a reference, it is inferior to the chromate treatment, In comparison with 55% aluminum-zinc alloy plated steel sheet without any surface treatment, Δ is the case where the degree of discoloration is small, and the degree of discoloration is the same as 55% aluminum-zinc alloy plated steel sheet without surface treatment. The case of degree was evaluated as x.

<Workability evaluation test>
By roll forming, adhesion bending processing is performed, and the degree of damage of the steel sheet surface that has been in contact with the bent part and the mold is visually observed, and the surface-treated plated steel sheet subjected to chromate treatment as a reference is used as a reference. A case where the appearance is equivalent to this, ◯, which is inferior to the chromate treatment, but △, a case where the degree of damage is small in comparison with a 55% aluminum-zinc alloy plated steel plate which is not subjected to any surface treatment, A case where the degree was the same as that of a 55% aluminum-zinc alloy-plated steel sheet not subjected to surface treatment was evaluated as x. Roll forming (also called roll forming, cold roll forming, etc.) is a series of forming rolls arranged in tandem, through a metal base plate or a metal strip such as a coil material, a hoop material, a cutting plate, It refers to a method of forming a plate material that is gradually and continuously subjected to bending in the width direction to produce a tube or shape having a desired cross-sectional shape from a flat base plate.

  In Comparative Example No. 1 in Table 1. In comparison with 25 untreated 55% aluminum-zinc alloy plated steel sheet, Invention Example No. 1 in which the thickness of the zirconium compound layer is in the range of 0.02 μm to 1 μm. 2-No. No. 5 showed excellent corrosion resistance, chemical resistance and processability. On the other hand, no. No. 1 has a zirconium compound layer as thin as 0.005 μm. No superiority was found compared to 24. No. No. 6 is a case where the oxide layer is as thick as 2 μm. No advantage was seen with 24. No. Nos. 7 to 9 are comparative examples in which the steel plate temperature during spraying is less than 150 ° C., but the corrosion resistance and chemical resistance are No. No superiority was found compared with 25 untreated plated steel sheets.

  No. 10 and no. 23 is a comparative example of only an organic resin film layer without a zirconium compound layer. No. In comparison with 24 chromate treatment, the performance is not sufficient. No. Nos. 12 to 18 are examples in which an appropriate zirconium compound layer and a resin film layer were formed thereon, and showed performance equivalent to chromate treatment.

  No. 11 and no. Nos. 19 to 22 are examples in which a zirconium compound layer and an organic resin film were formed. No. 11 is a case where the resin film is slightly thin. 19 to 22 are examples when the zirconium compound layer is slightly thin. Both of these are slightly inferior in performance to the chromate treatment. Compared to 24, there was a clear improvement in performance in all performance evaluations.

Claims (7)

A cold-plated steel sheet is immersed in a hot-dip plating bath while continuously conveying the cold-rolled steel sheet, and immediately after the cold-rolled steel sheet is drawn out of the hot-dip bath, a zirconium compound and / or Alternatively, by applying a water-based coating material containing zirconium ions and drying the water-based coating material with residual heat immediately after the hot dipping treatment, the hot-rolled steel sheet is coated on the surface of the cold-rolled steel sheet and a metal compound thin film is formed thereon A method for producing a surface-treated plated steel sheet, wherein the layer is continuously formed.   The method for producing a surface-treated plated steel sheet according to claim 1, wherein the water-based coating material contains an acrylic emulsion and / or a polyurethane dispersion.   The method for producing a surface-treated plated steel sheet according to claim 1 or 2, wherein a resin thin film layer is formed by further applying a resin coating material on the upper layer of the metal compound thin film layer and baking and drying.   The method for producing a surface-treated plated steel sheet according to claim 3, wherein the resin coating material is an acrylic emulsion and / or a polyurethane dispersion. The method for producing a surface-treated plated steel sheet according to claim 3 or 4, wherein the resin thin film layer contains a metal compound.   The method for producing a surface-treated plated steel sheet according to claim 5, wherein the metal compound contained in the resin thin film layer is a Zr oxide. A surface-treated plated steel sheet produced by the method for producing a surface-treated plated steel sheet according to any one of claims 1 to 6.