WO2020110750A1 - Surface-treated steel sheet, and method for manufacturing surface-treated steel sheet - Google Patents

Abstract

A surface-treated steel sheet is provided, which comprises a steel sheet and a deposited layer formed on one surface or both surfaces of the steel sheet and containing metal zinc, wherein the deposited layer further contains at least one component selected from the group consisting of a vanadium oxide, a vanadium hydroxide, a zirconium oxide and a zirconium hydroxide, and the ratio of the area S₂ of a peak appearing at 3600 cm^-1 which attributes to a hydroxide to the area S₁ of a peak appearing at 1600 to 650 cm^-1 which attributes to an oxide, i.e., S₂/S₁, is 0 to 0.3 inclusive in an infrared absorption spectrum obtained by measuring the surface of the deposited layer by reflection method of FT-IR spectroscopy.

Description

Surface-treated steel sheet and method for manufacturing surface-treated steel sheet

The present invention relates to a surface-treated steel sheet, and more particularly to a surface-treated steel sheet used for automobiles, home appliances, building materials, civil engineering, machinery, furniture, containers, etc., and a method for producing the same.
The present application claims priority based on Japanese Patent Application No. 2018-223492 filed in Japan on November 29, 2018, and the content thereof is incorporated herein.

BACKGROUND ART Conventionally, surface-treated steel sheets having electrogalvanized layers (electrogalvanized steel sheets) have been used in various fields such as home appliances, building materials, and automobiles. In recent years, it has been required to further improve the corrosion resistance of electrogalvanized steel sheets.
As a method of improving the corrosion resistance of the electrogalvanized steel sheet, it is conceivable to increase the coating amount (basis weight) of the galvanized layer. However, if the plating amount of the electrogalvanized steel sheet is increased, the workability and weldability are deteriorated.

Also, forming an alloy plating layer in place of the zinc plating layer of an electrogalvanized steel sheet is an effective means for improving the corrosion resistance. Depending on the type and composition of the alloy plating layer, the corrosion resistance of the steel sheet is improved and the weldability is also excellent (see Non-Patent Document 1, for example). However, when forming an alloy plating layer instead of a zinc plating layer, it is difficult to avoid an increase in manufacturing cost. For this reason, it is required to reduce the areal weight by further improving the performance of the alloy plating layer.

It has been studied to improve the corrosion resistance by adding vanadium element to the galvanized layer of the electrogalvanized steel sheet. For example, Patent Documents 1 to 5 describe techniques for complex electrodeposition of Zn—V oxide on the surface of a steel plate that is a cathode.
The deposited layer obtained by such a technique usually contains hydroxide. For example, when the inventors of the present invention evaluated the surface of the deposited layer of the surface-treated steel sheet obtained by the technique described in Patent Document 5 by the reflection method of the FT-IR method, oxides were found on the surface of the deposited layer. The ratio of the peak area of 3600 cm ⁻¹ showing hydroxide to the peak area of 1600 to 650 cm ⁻¹ shown was about 0.4 or more (Test No. 44 and test in Table 2-1 and Table 2-2). No. 45).

Japanese Patent No. 5273316 JP, 2011-236471, A JP, 2013-185199, A JP, 2014-114503, A JP, 2013-108183, A

In the surface-treated steel sheet on which a layer (precipitation layer) containing zinc and vanadium oxide and hydroxide or zirconium oxide and hydroxide is formed on the steel sheet surface by electroplating, Vanadium or zirconium contained contributes to the plane corrosion resistance of the surface-treated steel sheet. However, in the conventional surface-treated steel sheet, it is required to further improve the adhesiveness at the interface between the deposited layer and the steel sheet. In particular, in the case of a surface-treated steel sheet, it is desired that the deposited layer does not peel off from the steel sheet when subjected to bending or other processing.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a surface-treated steel sheet excellent in flat surface corrosion resistance and adhesion of a processed portion, and a manufacturing method thereof.

The inventors of the present invention have earnestly studied in order to achieve both the plane corrosion resistance of the surface-treated steel sheet and the adhesion of the processed part, and as a result, the following new findings have been obtained. The "adhesion of the processed portion" means the adhesion between the steel sheet and the deposited layer in the processed portion when the processing such as bending is applied. Hereinafter, in this specification, it may be referred to as "processed portion adhesion".

For example, if the content ratio of zinc in the deposited layer is increased, the adhesion of the processed portion is improved, but the flat corrosion resistance is reduced. Therefore, it has been difficult to achieve both the adhesion of the machined portion and the planar corrosion resistance in the conventional surface-treated steel sheet having a precipitation layer containing zinc and vanadium or zirconium.
Therefore, in order to solve the above problems, the present inventor has conducted diligent research by paying attention to the composition of the deposited layer, particularly the hydroxide and oxide of vanadium or zirconium. As a result, surprisingly, the adhesion of the processed part is excellent when the ratio of hydroxide to oxide is less than a certain value, and this ratio of hydroxide and oxide affects the flat corrosion resistance. I did not find it.

The present invention has been made based on the above findings, and its gist is as follows.

[1] Steel plate,
A precipitation layer containing metallic zinc formed on one or both sides of the steel sheet;
The deposition layer further contains one or more selected from the group consisting of vanadium oxide, vanadium hydroxide, zirconium oxide and zirconium hydroxide,
In the infrared absorption spectrum obtained by measuring the surface of the deposited layer by the reflection method of FT-IR method, the peak area S _{1 at} 1600 to 650 cm ⁻¹ indicating an oxide and the peak area S ₁ at 3600 cm ⁻¹ indicating a hydroxide. A surface-treated steel sheet having a ratio S ₂ /S ₁ with respect to a peak area S ₂ of 0 or more and 0.3 or less.
[2] The amount of metallic zinc contained in the deposited layer is a (g/m ² ), and the total amount of the vanadium oxide and vanadium hydroxide contained in the deposited layer, or the zirconium oxide and the zirconium. The surface-treated steel sheet according to [1], wherein 100b/(a+b) is 0.1 or more and 50 or less, where b (g/m ² ) is the total amount of hydroxides in terms of metal. ..
[3] The amount of metallic zinc contained in the deposited layer is a (g/m ² ), and the total amount of the vanadium oxide and vanadium hydroxide contained in the deposited layer, or the zirconium oxide and the zirconium. The surface-treated steel sheet according to [1], wherein 100b/(a+b) is 1.0 or more and 20 or less when the total amount of hydroxides is b (g/m ² ) in terms of metal. ..
[4], wherein the adhered amount of the deposition layer is 1.0 g / ^{m 2} or more 50.0 g / ^{m 2} or less, [1] the surface treated steel sheet according to any one of - [3] ..
[5] The deposition layer has a first phase containing the metallic zinc and a second phase containing at least one of vanadium oxide and vanadium hydroxide, or at least one of zirconium oxide and zirconium hydroxide. Then
The first phase is a plurality of dendrite-like columnar crystal phases grown in the thickness direction of the steel sheet, and the second phase is an amorphous phase formed around the first phase. The surface-treated steel sheet according to any one of [1] to [4].
[6] The surface-treated steel sheet according to any one of [1] to [5], which has one or more coatings on the surface of the deposited layer.
[7] A step of forming a deposit layer on one or both surfaces of the steel sheet by cathodic electrolysis treatment,
Heat-treating the deposited layer,
Equipped with
The cathodic electrolysis solution contains a zinc compound and at least one of a vanadium compound or a zirconium compound,
The ratio of V ion concentration (g/l) or Zr ion concentration (g/l) to Zn ion concentration (g/l) in the cathodic electrolytic treatment solution is 0.2 to 0.9,
The pH of the cathodic electrolytic treatment solution is 1.0 to 4.0,
Between the start and the end of the cathodic electrolysis treatment, a non-energization time of 0.01 seconds or more is provided once or more,
The flow rate of the cathodic electrolysis solution during the non-energization time of the cathodic electrolysis treatment is 0.05 m/sec or more and 5.00 m/sec or less,
The maximum temperature of the deposited layer in the heat treatment is 100° C. or higher and 350° C. or lower,
The average heating rate in the heat treatment is 40° C./sec or more,
In the heat treatment, a non-heating time of 0.5 seconds or more and 5 seconds or less is provided between when the temperature of the deposition layer is 100° C. or higher and when the cooling of the deposition layer is started. Method for producing surface-treated steel sheet.

According to the present invention, it is possible to provide a surface-treated steel sheet excellent in flat surface corrosion resistance and adhesion of a processed portion, and a manufacturing method thereof.

It is a schematic diagram of the cathode electrolysis apparatus suitably used when manufacturing the surface-treated steel plate of this embodiment. It is a schematic diagram explaining the IR spectrum of the precipitation layer of the surface-treated steel plate of this embodiment.

The surface-treated steel sheet according to one embodiment of the present invention will be described in detail below.

The surface-treated steel sheet of the present embodiment includes a steel sheet and a deposition layer containing zinc metal formed on one side or both sides of the steel sheet, and the deposition layer further includes vanadium oxide, vanadium hydroxide, and zirconium oxide. And 1600 to 650 cm showing an oxide in an infrared absorption spectrum obtained by measuring the surface of the deposited layer by a reflection method of FT-IR method, containing at least one selected from the group consisting of and zirconium hydroxide. ^The surface-treated steel sheet has a ratio S ₂ /S ₁ of the peak area S ₁ of ^{−1 to} the peak area S _{2 of} 3600 cm ⁻¹ indicating a hydroxide of 0 to 0.3.

In the present embodiment, the steel sheet that serves as the base for forming the precipitation layer is not particularly limited. For example, as a steel sheet, ultra low C type (ferrite-based structure), Al-k type (structure containing pearlite in ferrite), two-phase structure type (eg structure containing martensite in ferrite, bainite in ferrite) are used. Any type of steel sheet may be used, such as a microstructure that includes retained microstructure, a microstructure that includes retained austenite in ferrite, a microstructure that includes retained austenite in ferrite, and there is no limitation on the plate thickness.

In the present embodiment, metal zinc on the steel plate, one or more selected from the group consisting of vanadium oxide, vanadium hydroxide, zirconium oxide and zirconium hydroxide (at least one of vanadium oxide or hydroxide, Alternatively, a deposited layer containing zirconium oxide and/or hydroxide is formed. By including metallic zinc in the deposit layer, sacrificial corrosion resistance can be imparted to the deposit layer, and further, one or more selected from the group consisting of vanadium oxide, vanadium hydroxide, zirconium oxide and zirconium hydroxide. Therefore, flat corrosion resistance can be secured.

Further, in the present embodiment, in the infrared absorption spectrum obtained by measuring the surface of the deposited layer by a reflection method of FT-IR method (Fourier transform infrared spectrophotometry), 1600 showing oxide is shown. ratio _S 2 / _{S 1} between the peak area _{S 2} of the absorption of 3600 cm ^-1 indicating the hydroxide to the peak area _{S 1} of the absorption of ~ 650 cm ^-1 it is 0.3 or less.

As a result of diligent studies by the present inventors, when the ratio of hydroxide to oxide in the deposited layer is reduced to a certain value or less, between the deposited layer and the steel sheet after working without affecting the planar corrosion resistance. It was found that the adhesion (adhesion of the processed portion) can be improved. That is, in the present embodiment, the ratio of hydroxide to oxide is reduced so that the S ₂ /S ₁ is 0.3 or less, whereby the surface having both the adhesion of the processed portion and the flat corrosion resistance is obtained. A treated steel plate can be obtained. When S ₂ / _{S 1} is at greater than 0.3, the adhesion between the deposited layer and the steel sheet in the processing section after machining is _poor, S 2 / _{S 1} is set to 0.3 or less, preferably 0.2 or less And In addition, it is preferable that the amount of hydroxide in the deposited layer is small from the viewpoint of the adhesion of the processed portion, and S ₂ /S ₁ may be 0, but from the viewpoint of cost increase due to stricter control conditions in the manufacturing method described later, S ₂ /S ₁ may be 0.1 or more.

Note that the deposited layer contains zinc metal and vanadium and/or zirconium. Here, the above-mentioned "oxide" when the deposition layer contains vanadium, and "hydroxide" are vanadium oxide and vanadium hydroxide, respectively, and the above-mentioned "oxide" when the deposition layer contains zirconium. The terms "and hydroxide" refer to zirconium oxide and zirconium hydroxide, respectively. When the deposited layer contains metallic zinc, vanadium, and zirconium, "oxide" indicates a mixture of vanadium oxide and zirconium oxide, and "hydroxide" means vanadium hydroxide and zirconium hydroxide. Shows a mixture of.

Incidentally, the In measuring S 2 _/ S _1, performs a measurement in more than 10 points of the surface of the surface-treated steel sheet, intended to calculate the average value. Here, the distance between the measurement points is 1 mm or more. However, if the size of the test material is insufficient and it is difficult to perform measurement at 10 points while ensuring a sufficient measurement interval, shorten the measurement interval or reduce the number of measurement points. Is acceptable.
In the FT-IR reflection method, the surface of the deposited layer is measured in principle. Further, as a measuring method, in principle, a high-sensitivity reflection method (RAS method: Reflection Absorption Spectrometry) is used. However, when a film such as a coating film is applied to the surface of the deposition layer, it may be difficult to remove the coating film and measure the surface of the deposition layer by the high-sensitivity reflection method. In this case, after the cross section of the deposited layer is cut out by CP (cross section polisher) processing or the like, a carbon-free layer derived from the coating film such as a coating film is analyzed by a generally known elemental analyzer such as EPMA. It is advisable to identify the deposited layer and measure the deposited layer by the microscopic reflection method of the FT-IR method.

In the present embodiment, the amount of metallic zinc (adhesion amount) contained in the deposited layer is a (g/m ² ), and the total amount of vanadium oxide and hydroxide contained in the deposited layer or zirconium oxide. When the total amount (adhesion amount) of the hydroxide is b (g/m ² ) in terms of metal, 100b/(a+b) is preferably 0.1 or more and 50 or less. When 100b/(a+b) is less than 0.1, the effect of improving planar corrosion resistance by vanadium or zirconium is not sufficiently exhibited, and the planar corrosion resistance of the deposited layer is poor. On the other hand, when 100b/(a+b) is more than 50, the corrosion resistance of the deposited layer on the flaws is poor. Note that 100b/(a+b) is particularly preferably 1.0 or more and 20 or less because the flat surface corrosion resistance and the flaw corrosion resistance are excellent. When the deposited layer contains both a vanadium compound and a zirconium compound, b is the total amount of vanadium oxide, vanadium hydroxide, zirconium oxide, and zirconium hydroxide in terms of metal.

The amount of metallic zinc a (g/m ² ) contained in the deposited layer, the total amount of vanadium oxides and hydroxides, or the total amount of zirconium oxides and hydroxides b (g/m ^{2 in} terms of metal). ) Can be determined by dissolving the deposited layer with an acid and measuring the amount of Zn, the amount of V, and the amount of Zr in the solution after the dissolution by ICP (Inductively Coupled Plasma) emission spectroscopy. When analyzing the deposited layer, it is advisable to dissolve the deposited layer with hydrochloric acid prepared by adding an inhibitor to hydrochloric acid or the like so that the steel sheet does not dissolve.

Further, the adhesion amount of deposition layer is preferably 1.0 g / ^{m 2} or more 50.0 g / ^{m 2} or less. By setting the amount of deposition to be 1.0 g/m ² or more, the planar corrosion resistance of the surface-treated steel sheet can be further improved. In addition, by controlling the deposition amount to be 50.0 g/m ² or less, the manufacturing cost can be suppressed and the adhesion between the deposition layer and the steel sheet can be improved. From these viewpoints, it is more preferred amount of adhesion of the deposited layer is 3.0 g / ^{m 2} or more 40.0 g / ^{m 2} or less.

The deposited amount of the deposited layer is the amount of mass change of the surface-treated steel sheet before and after removing the deposited layer from the surface-treated steel sheet by dissolving the deposited layer with hydrochloric acid containing an inhibitor so that the steel sheet does not dissolve. The amount of deposition of the deposited layer can be obtained from this.

In addition, the deposition layer of the surface-treated steel sheet of the present embodiment includes a first phase containing metallic zinc and a second phase containing at least one of vanadium oxide or vanadium hydroxide, or at least one of zirconium oxide or zirconium hydroxide. It may have a form having a phase. Furthermore, the first phase containing metallic zinc is a plurality of dendrite-like columnar crystal phases grown in the thickness direction of the steel sheet, and the second phase is an amorphous phase formed around this first phase. May be. In such a precipitation layer, the dendrite-like columnar crystal phase that is the first phase is first precipitated, and then the second phase is precipitated around the columnar crystal phase.

The dendrite-shaped columnar crystal phase of the first phase may be formed only of metallic zinc, or may contain other metallic components such as iron and nickel together with metallic zinc. It is preferable that the deposition layer contains 0.1% by mass or more and 7% by mass or less of iron as a metal element because the weldability is excellent. The dendrite-like columnar crystal phase of the first phase has a structure that grows from the steel sheet side toward the precipitation layer surface side along the thickness direction of the precipitation layer and branches toward the precipitation layer surface.

The second phase may contain zinc oxide in addition to at least one of vanadium oxide or vanadium hydroxide, or at least one of zirconium oxide or zirconium hydroxide. The second phase is formed around the dendrite-shaped first phase. During the formation of the precipitation layer, the first phase composed of dendrite columnar crystals is formed first, and then the second phase composed of the amorphous phase is formed around the first phase. By containing vanadium oxide and hydroxide, or zirconium oxide and hydroxide, and zinc oxide, barrier properties can be imparted to the deposited layer. Further, since the second phase is mainly composed of oxide or hydroxide, it is possible to secure coating adhesion when a coating film is formed on the second phase.

The first phase of the dendrite-like columnar crystal phase containing metallic zinc gives a diffraction pattern due to the crystal structure when electron beam diffraction is performed from the cross section of the deposited layer using a transmission electron microscope (TEM). On the other hand, regarding the second phase, a diffraction pattern due to the crystal structure is not obtained, and it is judged that the second phase is amorphous.

The deposition layer as described above may be provided in only one layer, or may be provided in a state where a plurality of layers are laminated. When a plurality of deposition layers are provided, at least one of the plurality of deposition layers may be the deposition layer of the present embodiment.

Further, in the case where the surface-treated steel sheet is used for applications having a black appearance, and when a plurality of deposition layers are provided, the deposition layer of the present embodiment may be provided as the outermost layer. preferable.

A base layer may be provided between the steel plate and the deposit layer. The underlayer is provided as necessary to improve the adhesion between the steel sheet and the deposited layer. In this embodiment, it is preferable to provide an underlayer made of a crystal containing zinc, nickel, and iron having a thickness of 1 to 300 nm.

A chemical conversion treatment film, a coating film, an organic resin film, and a film containing an organosilicon compound containing a silane coupling agent may be further formed on the deposition layer of the surface-treated steel sheet of the present embodiment. When forming a coating film, it is preferable to form a non-chromated film as a base layer on the surface of the deposition layer. By forming these coatings on the surface of the deposited layer, the planar corrosion resistance of the surface-treated steel sheet can be further improved.

The surface-treated steel sheet of this embodiment has an L* value of 40 or less, which represents lightness, and has a black appearance. By having a black appearance, it can be used for various purposes such as a material for products having a black appearance.

Further, the surface-treated steel sheet of the present embodiment has been described as an example in which a precipitation layer is formed on the steel sheet, but the present embodiment is not limited to this, and an electrogalvanized steel sheet, a hot-dip galvanized steel sheet, an alloyed hot-dip galvanized steel sheet. The deposit layer of the present embodiment may be formed on the galvanized layer. That is, another galvanized layer may be formed between the steel plate and the deposited layer. By forming another galvanized layer, the planar corrosion resistance of the surface-treated steel sheet can be further improved. For example, even when the corrosive substance passes through the deposition layer, the sacrificial anticorrosion effect can be exhibited by another galvanized layer, and the planar corrosion resistance of the surface-treated steel sheet can be improved.
Further, as a matter of course, the deposition layer of the surface-treated steel sheet according to the present embodiment contains both the vanadium compound (at least one of vanadium oxide and hydroxide) and the zirconium compound (at least one of zirconium oxide and hydroxide). May be included. As described above, the vanadium compound and the zirconium compound have the same action and effect with respect to the corrosion resistance and the flat surface corrosion resistance of the surface-treated steel sheet. Further, the vanadium compound and the zirconium compound do not interfere with each other's action and effect. Even when the deposited layer contains both the vanadium compound and the zirconium compound, S ₂ /S ₁ can be measured by the procedure described above. When the deposition layer contains both a vanadium compound and a zirconium compound, the second phase of the deposition layer contains at least one of vanadium oxide or vanadium hydroxide and at least one of zirconium oxide or zirconium hydroxide. It may be in the form.

Next, a method for manufacturing the surface-treated steel sheet of this embodiment will be described.
The surface-treated steel sheet of the present embodiment is a method in which a zinc compound and a solution containing a vanadium compound or a zirconium compound are used to form a deposition layer by cathodic electrolysis on one or both surfaces of the steel sheet, and then the deposition layer is heat-treated. Can be manufactured by Specifically, the method for producing a surface-treated steel sheet according to the present embodiment, by cathodic electrolysis treatment, a step of forming a deposition layer on one or both sides of the steel sheet, and a step of heat treating the deposition layer, cathodic electrolysis The treatment solution contains a zinc compound and at least one of a vanadium compound and a zirconium compound, and the V ion concentration (g/l) or Zr ion concentration (g/l) and the Zn ion concentration (g /L) is 0.2 to 0.9, the pH of the cathodic electrolysis treatment solution is 1.0 to 4.0, and the pH of the cathodic electrolysis treatment is not less than 1 time. A non-energization time is provided, the flow rate of the treatment liquid during the non-energization time of the cathodic electrolysis treatment is 0.05 m/sec or more and 5.00 m/sec or less, and the maximum temperature of the deposition layer in the heat treatment is 100° C. or more and 350° C. or less. In the heat treatment, the average rate of temperature rise is 40° C./sec or more, and 0.5 seconds or more and 5 seconds or less between the temperature of the precipitation layer is 100° C. or more and the cooling of the precipitation layer is started. No heating time is provided.

As a solution used in the cathodic electrolysis treatment (cathodic electrolysis treatment solution), a solution containing Zn ions and V ions and/or Zr ions can be used. Precipitation is obtained by subjecting a steel sheet to cathodic electrolysis treatment using this solution. Layers can be made. As the solution containing Zn ions, V ions and/or Zr ions, a solution containing Zn compounds, V compounds and Zr compounds is used. As an example of the cathodic electrolytic treatment solution, specifically, it can be obtained by dissolving Zn sulfate, vanadyl oxide or zirconyl nitrate in an aqueous solution of an inorganic acid such as sulfuric acid.

The Zn compound, a metal _{Zn, ZnSO 4 · 7H 2 O} , include soluble salts such as ZnCO _3. These may be used alone or in combination of two or more.

Further, the Zr compound is preferably one that forms ZrO ²⁺ ions in a solution, and examples thereof include soluble salts such as zirconyl nitrate, zirconyl sulfate, and zirconium oxynitride chloride. These may be used alone or in combination of two or more.

As the V compound, vanadyl oxide, ammonium metavanadate (V), potassium metavanadate (V), sodium metavanadate (V), VO(C ₅ H ₇ O ₂ ) ₂ (vanadyl acetylacetonate (IV)) , VOSO ₄ · _5H 2 O (vanadyl sulfate (IV)) and the like. Among these vanadium compounds, oxidation _{vanadyl, VO (C 5 H 7 O} 2) 2 ( vanadyl acetylacetonate _(IV)), it is preferable to use a VOSO 4 · _5H 2 O (vanadyl sulfate (IV)). These vanadium compounds may be used alone or in combination of two or more.

Ratio of V ion concentration (g/l) and/or Zr ion concentration (g/l) and Zn ion concentration (g/l) in the solution for cathodic electrolysis ((V ion and/or Zr ion)/ Zn ion) is 0.2 to 0.9. When (V ions and/or Zr ions)/Zn ions are less than 0.2 or more than 0.9, V ions or Zr ions are not taken into the deposition layer, and vanadium or zirconium oxide or hydroxide in the deposition layer is not incorporated. You may not be able to secure enough items.

The pH of the solution for cathodic electrolysis is 1.0 to 4.0 in order to secure the amount of deposition in the deposited layer and the content of vanadium and zirconium oxides and hydroxides in the deposited layer. If the pH is less than 1.0, vanadium and/or zirconium will not be incorporated into the deposited layer, and the oxides and hydroxides of vanadium and/or zirconium in the deposited layer may not be sufficiently secured. If the pH exceeds 4.0, V ions and/or Zr ions will precipitate in the solution as oxides, and vanadium and/or zirconium oxides and hydroxides will not be incorporated in the precipitation layer.

In addition to the Zr compound, the V compound, and the Zn compound, the solution for the cathodic electrolysis treatment may further contain a pH adjusting agent, a Zr compound, a V compound, and another metal compound other than the Zn compound, an additive, and the like, if necessary. You may add. Examples of the pH adjusting agent include H ₂ SO ₄ and NaOH. Examples of the additive include Na ₂ SO ₄ which stabilizes the conductivity of the solution for cathodic electrolysis. Other metal compounds include nickel compounds such as NiSO ₄ .6H ₂ O.

The solution for cathodic electrolysis may contain Na ^{+ in an amount} of 0.1 mol/l or more. In this case, the conductivity of the solution can be increased, and the precipitation layer of this embodiment can be easily formed.

The temperature of the solution for the cathodic electrolysis treatment is not particularly limited, but is preferably in the range of 40 to 60° C. in order to easily and efficiently form the deposition layer of this embodiment.

In the present embodiment, when forming the deposited layer by cathodic electrolytic treatment, it is preferable that the a current density of 2A / dm ² or more 150A / dm ² or less. By setting the current density within the above range, it is possible to easily form the deposition layer of the present embodiment in which the contents and the amount of the vanadium and/or zirconium oxide and hydroxide are sufficiently secured. If the current density is less than 2 A/dm ² , it is not efficient because the electrolytic treatment speed is low. When the current density exceeds 150 A/dm ² , the so-called hydrogen generation reaction proceeds remarkably, and it becomes difficult to obtain a plating layer having a vanadium and/or zirconium content of 50% by mass or less. The time for performing the cathodic electrolysis treatment is not particularly limited, and can be appropriately set depending on the current density and the required deposition amount of the deposited layer.
Furthermore, when forming the deposited layer by the cathodic electrolysis treatment, a non-energization time of 0.01 seconds or more is provided once or more between the start and the end of the cathodic electrolysis treatment. The flow rate of the cathodic electrolytic treatment solution must be 0.05 m/sec or more and 5.00 m/sec or less. The start of the cathodic electrolysis treatment is when the first energization of the steel sheet is started. The termination of the cathodic electrolysis treatment is when the final energization of the steel sheet is terminated. The non-energization time is a period during which no voltage is applied between the steel plate and the cathodic electrolytic treatment solution. In other words, the cathodic electrolysis treatment including one non-energization time is a cathodic electrolysis treatment in which energization is performed twice. The flow velocity of the cathodic electrolysis solution is the relative flow velocity between the cathodic electrolysis solution and the steel sheet.
The present inventors have found that by providing the cathodic electrolysis solution with a non-energized time and flowing the solution at a flow rate within a predetermined range during this non-energized time, the effect of further suppressing the generation of hydroxide can be obtained. .. It is presumed that this is because the pH of the solution increases near the surface of the steel sheet as the formation of the deposited layer progresses (that is, dendrite growth). It is presumed that by stopping the dendrite growth and allowing the solution to flow during this period, the local increase in pH is eliminated and the generation of hydroxide is suppressed.
As a result of an experiment, the present inventors provided a non-energization time of 0.01 seconds or more once or more, and defined the flow rate of the cathodic electrolysis solution during the non-energization time as 0.05 m/sec or more and 5.00 m/sec or less. did. If the non-energization time of 0.01 seconds or more is not provided, even if the solution is flowing during the energization time, the increase in pH will not be sufficiently eliminated. Further, when the flow rate of the cathodic electrolysis solution during the non-energization time is less than 0.05 m/sec, the same result as when the non-energization time is not provided is obtained. On the other hand, if the flow rate of the cathodic electrolytic treatment solution during the non-energized time is more than 5.00 m/sec, the dissolution of the deposited layer becomes large, which is not suitable.

As described above, in a solution containing Zn ions and V ions and/or Zr ions, a steel plate as a raw material is electrolyzed as a cathode to form a deposition layer, and then the deposition layer is further heated in the present embodiment. It is then necessary to control the ratio of hydroxide to oxide in the deposited layer.

When manufacturing a surface-treated steel sheet, it is not easy to control the ratio of hydroxide to oxide in the deposited layer simply by adjusting the electrolysis conditions. The reason is related to the pH of the solution (bath) used for electrolytic treatment. Specifically, during electrolysis, vanadium ions and/or zirconium ions in the bath are precipitated as oxides and/or hydroxides. It depends on whether the precipitates are oxides or hydroxides during electrolysis. Of the local pH rise of the bath. Therefore, it is not easy to control the ratio of hydroxide to oxide in the deposited layer simply by adjusting the electrolysis conditions. Therefore, as a result of investigating a method for easily controlling the ratio of hydroxide to oxide in the deposited layer, it was found that the ratio can be controlled by performing heat treatment under a predetermined condition after forming the deposited layer.

In the present embodiment, after the deposit layer is formed on the surface of the steel sheet by the cathodic electrolytic treatment, the deposit layer is heated at an average heating rate of 40° C./sec or more. Then, a period of 0.5 seconds or more and 5 seconds or less without heating is provided between the temperature of the steel sheet becoming 100° C. or more and the time of cooling. By performing such heat treatment, while changing the hydroxide of the deposition layer to an oxide, it is possible to prevent the steam generated at that time from continuing to expand in the deposition layer, and to form a cavity in the deposition layer. It becomes possible to suppress the occurrence of.

In the present embodiment, after the precipitation layer is formed on the surface of the steel sheet as described above, heat treatment is performed at an average temperature rising rate of 40° C./sec or more. Further, a time period of 0.5 seconds or more and 5 seconds or less without heating is secured from when the temperature of the deposition layer (steel plate) reaches 100° C. or higher until cooling is started. When the average rate of temperature rise is less than 40° C./sec, the amount of change of the hydroxide in the precipitate layer to the oxide is small, and the peak area S ₁ showing the hydroxide is different from the peak area S ₁ showing the oxide in the IR spectrum. the ratio S _{2 /} S ₁ between the ₂ will not be sufficiently reduced, processability portion adhesiveness may be deteriorated. Therefore, the average heating rate in the heat treatment is 40° C./sec or more, preferably 50° C./sec or more.

Moreover, after the temperature of the precipitation layer (steel plate) reaches the ultimate temperature of 100° C. or higher, heating is stopped for a certain period of time and then held, and then cooling is started, so that the peak area S ₁ showing oxides in the IR spectrum is The ratio S ₂ /S ₁ with respect to the peak area S ₂ indicating a hydroxide is easily reduced, which is preferable. By setting the ultimate temperature to 100° C. or higher, the change from hydrate to oxide can be promoted. Further, if the time during which the heating is not performed is too long, the gas (mainly water vapor) may stay and the S ₂ /S ₁ may not be reduced, so the heating stop time is set to 5 seconds or less. On the other hand, if the non-heating time is too short, the gas (mainly water vapor) may expand in the deposition layer, making the deposition layer brittle and lowering the adhesion of the processed part. Moreover, the upper limit of the ultimate temperature of the precipitation layer (steel plate) is preferably 350° C. or lower. When heated to over 350°C, a part of the deposited layer may be dissolved.

“The average heating rate” is the value obtained by dividing the temperature rise range of the steel sheet from the start of heating to the stop of heating by the time required from the start of heating to the stop of heating. Further, the “time without heating” after reaching the ultimate temperature is the time from when heating is stopped to when cooling is started, during which the steel plate temperature may or may not be fixed. Although good, it is preferable to maintain the steel plate temperature at 100° C. or higher during this period.

High-frequency induction heating or laser heating is preferable as the above heat treatment method, and in the case of high-frequency induction heating, the precipitation layer is heated from the steel sheet side, which is more preferable. The cooling after the heat treatment is preferably water cooling from the viewpoint of productivity, and may be water cooling by a spray method, for example.

Although the method for manufacturing the surface-treated steel sheet according to the present embodiment has been described above, the cathode electrolysis apparatus shown in FIG. 1 is a manufacturing apparatus that can be suitably used for carrying out one cathodic electrolysis treatment in the manufacturing method. Will be described as an example.
In the present invention, the cathodic electrolysis treatment is performed twice or more by using two or more of these devices connected to each other, and the time and the flow rate during non-energization are controlled between them.

FIG. 1 is a schematic diagram showing an example of a cathode electrolysis device. In FIG. 1, reference numeral 1 indicates a steel plate, reference numeral 2 indicates an electrolytic bath, reference numeral 21 indicates an electrolytic bath, and reference numeral 3 indicates an anode. The electrolytic bath 2 is preferably the above-mentioned solution for cathodic electrolysis.

In FIG. 1, reference numerals 4a, 4b, 5a, and 5b indicate rolls for moving the steel sheet 1 in the direction of the arrow in FIG. The rolls 4a and 4b arranged on the steel plate 1 are conductor rolls. The steel plate 1 serves as a cathode by being electrically connected to the rolls 4a and 4b.

The electrolysis tank 21 has an upper tank 21 a arranged above the steel plate 1 and a lower tank 21 b arranged below the steel plate 1. A plurality of anodes 3 made of platinum or the like are arranged in the upper tank 21a and the lower tank 21b adjacent to the steel plate 1 with a predetermined space between the anode 3 and the steel plate 1. The surface of each anode 3 facing the steel plate 1 is arranged so as to be substantially parallel to the surface of the steel plate 1.

The upper bath 21a and the lower bath 21b are filled with the electrolytic bath 2. As shown in FIG. 1, a horizontally moving steel plate 1 is arranged between the upper tank 21 a and the lower tank 21 b of the electrolytic bath 21, and the steel plate 1 is immersed in the electrolytic bath 2. .. Then, by transporting the steel sheet 1, the electrolytic bath 2 becomes the electrolytic bath 2 in a fluid state in which the electrolytic bath 2 is relatively fluidized with respect to the steel sheet 1.

The upper tank 21a is provided with an upper supply pipe 2a for supplying the electrolytic bath 2 to the upper tank 21a so as to penetrate the upper surface of the upper tank 21a. The upper supply pipe 2a is branched into a plurality of outer peripheral branch passages 2c and a plurality of intermediate branch passages 2d (only one is shown in FIG. 1) in the upper tank 21a. A plurality of intermediate branch paths 2d are arranged along the width direction of the steel plate 1 between the adjacent anodes 3 in a plan view. The intermediate branch 2d has an opening for supplying the electrolytic bath 2 between the anode 3 and the steel plate 1 on both sides. A plurality of outer peripheral branch paths 2c are arranged along the width direction of the steel sheet 1 between the anode 3 and the rolls 4a and 4b in a plan view. The outer peripheral branch passage 2 c has an opening for supplying the electrolytic bath 2 between the anode 3 and the steel plate 1.

Further, the upper tank 21a is provided with a discharge port (not shown) for discharging the electrolytic bath 2, and is connected to the upper supply pipe 2a via a pipe (not shown) equipped with a pump. Therefore, in the upper tank 21a, the electrolytic bath 2 supplied from the upper supply pipe 2a and discharged from the outlet is supplied by the pump again from the upper supply pipe 2a and circulated. It is an electrolytic bath 2.

Further, the lower tank 21b is provided with a lower supply pipe 2b for supplying the electrolytic bath 2 to the lower tank 21b so as to penetrate the lower surface of the lower tank 21b. The lower supply pipe 2b is branched into a plurality of outer peripheral branch passages 2e and a plurality of intermediate branch passages 2f (only one is shown in FIG. 1) in the lower tank 21b. A plurality of intermediate branch passages 2f are arranged along the width direction of the steel plate 1 between the adjacent anodes 3 in plan view. The intermediate branch passage 2f has an opening for supplying the electrolytic bath 2 between the anode 3 and the steel plate 1 on both sides. A plurality of outer peripheral branch passages 2e are arranged along the width direction of the steel plate 1 between the anode 3 and the rolls 5a and 5b in a plan view. The outer peripheral branch passage 2 e has an opening for supplying the electrolytic bath 2 between the anode 3 and the steel plate 1.

Further, the lower tank 21b is provided with a discharge port (not shown) for discharging the electrolytic bath 2, and is connected to the lower supply pipe 2b through a pipe (not shown) equipped with a pump. Therefore, in the lower tank 21b, the electrolytic bath 2 supplied from the lower supply pipe 2b and discharged from the outlet is supplied by the pump again from the lower supply pipe 2b and circulated. It is an electrolytic bath 2.

The relative flow velocity of the electrolytic bath 2 with respect to the steel plate in the electrolytic bath 21 is preferably in the range of 3 to 300 m/min, more preferably in the range of 20 to 300 m/min, or more preferably in the range of 30 to 200 m/min. .. When the average flow velocity of the electrolytic bath 2 is in the range of 3 to 300 m/min, it is possible to prevent the occurrence of cracks in the deposited layer and supply ions from the electrolytic bath 2 to the surface of the steel sheet 1 without any trouble. ..

The cathodic electrolysis apparatus shown in FIG. 1 is always energized. Two or more of these apparatuses are connected and used, and a deposition layer is formed by controlling the time and the flow rate during which there is no energization. By performing the above-mentioned heat treatment on the above, the deposition layer according to the present embodiment can be formed.

The surface-treated steel sheet of the present embodiment can be produced by the above production method, but both surfaces of the steel sheet may be subjected to pretreatment, if necessary, before forming the above-mentioned precipitation layer. As a pretreatment, it is preferable to perform nickel plating with a thickness of 1 to 300 nm on both surfaces of the steel sheet.

Also, after forming the deposited layer, a chemical conversion treatment film, a coating film, an organic resin film, a film containing an organic silicon compound containing a silane coupling agent may be further formed. As an example of forming such a film, for example, there is a method of applying a coating composition containing each component forming the film and curing the coating composition. Specifically, each component constituting the film is added to a solvent such as water and dissolved or dispersed to apply a coating composition on the deposition layer, and the coating film is heat dried by far infrared rays or induction heating. A method of curing by curing is preferable.

Examples of the present invention will be shown below, but the examples shown below are examples of the present invention, and the present invention is not limited to the examples described below.

(1. Steel plate)
As the steel plate, SPCD for drawing a general cold rolled steel plate described in JIS G 3141 having a plate thickness of 0.8 mm was used.

(2. Deposition layer)
First, a solution containing Zn ions and V ions, a solution containing Zn ions and Zr ions, and some of the solutions (solutions 32 to 34) were prepared containing Fe ions. These solutions were prepared by mixing ZnSulfate and vanadyl oxide or zirconyl nitrate (for solutions 32 to 34, further iron sulfate) in sulfuric acid. The details of the solutions 1 to 34 are as shown in Table 1. In addition, the solution composition (mass (g/l) of each ion) in Table 1 was converted from the masses of Zn sulfate, vanadyl oxide, zirconyl nitrate, and iron sulfate used. The components of the deposited layer were adjusted by the amount of these solution components. The pH of the solution was adjusted by the amount of sulfuric acid and the amount of Na hydroxide.

Next, the above-mentioned steel plate as a cathode is immersed in these solutions 1 to 34, a platinum anode is placed opposite to the surface of the steel plate, and the electrolytic solution can be made to flow in one direction between the steel plate and the platinum electrode. Cathodic electrolysis treatment was performed using the apparatus to form a deposited layer. The electrolysis conditions were: solution temperature: 50° C., electrolysis time (total): 1 to 5 seconds, current density: 80 to 120 A/dm ² , and average flow rate of the electrolytic solution was 80 mpm (m/min). In addition, the flow rate when the power was not applied was the value described in Table 2-1. The number of energizations was within the range of 1 to 4 times. The components of the formed precipitation layer are shown in Table 2-1.

After that, the deposited layer was heat-treated by high frequency induction heating. In the heat treatment, heating was performed at a predetermined average rate of temperature increase to an ultimate temperature of 100° C. or higher, and after the ultimate temperature was raised, a “non-heating time” was provided, and then cooling was performed by spray-type water cooling. The heat treatment conditions are shown in Table 2-1. Regarding the heat treatment conditions shown in Table 2-1, when the average heating rate is 40° C./sec or more, “◯” is given, and when it is less than 40° C./sec, “x” is given. Also, "○" indicates that the heating time of 100°C or more is 0.5 seconds or more and 5 seconds or less, and "x" indicates that the heating time is 100°C or more and less than 0.5 seconds or more than 5 seconds. And The ratio of the amount of oxide and hydroxide in the deposited layer was changed by controlling the maximum temperature and the time during which heating was not performed. In this way, various surface-treated steel plates (plate thickness t: 0.8 mm) were manufactured.

The ratio of the amount of oxide and hydroxide in the deposited layer was determined by a high-sensitivity reflection method using a Fourier transform infrared spectrophotometer (“FT/IR-6100” manufactured by JASCO Corporation). Specifically, in the obtained IR spectrum, the ratio S ₂ / of the peak area S ₂ of absorption indicating hydroxide near 3600 cm ⁻¹ to the peak area S ₁ of absorption indicating oxide at 1600 to 650 cm ^−1. S ₁ was determined. As shown in FIG. 2, the peak area of absorption is defined by dividing the absorption peak by the baseline of the IR spectrum, and defining the area of the region defined by the baseline (the area of the shaded area in FIG. 2) as the peak area. did.

Further, the deposition amount of the deposited layer is the mass of the surface-treated steel sheet before and after removing the deposited layer by removing the deposited layer from the surface-treated steel sheet by dissolving the deposited layer with hydrochloric acid containing an inhibitor so that the steel sheet does not dissolve. The amount of deposition of the deposited layer was obtained from the amount of change.
Further, each component in the deposited layer was determined by measuring the amount of Zn, the amount of V and the amount of Zr in the solution after dissolving the deposited layer by ICP emission spectroscopy.

Further, the amount of zinc contained in the deposited layer is a (g/m ² ), and the total amount of vanadium oxide and vanadium hydroxide contained in the deposited layer or the total amount of zirconium oxide and zirconium hydroxide contained in the deposited layer is vanadium. Alternatively, Table 2-2 shows 100b/(a+b) when b (g/m ² ) is calculated in terms of zirconium metal. The "100b/(a+b)" was obtained from the analysis result of each component in the deposited layer.

Also, the obtained surface-treated steel sheets (Test Nos. 1 to 49) were evaluated by the methods shown below for the following items.

"Adhesion of processed part"
An evaluation sample cut out from a surface-treated steel sheet was overhanged by 9 mm with an Erichsen tester, and the outside of the overhanging convex portion that was processed was used with an adhesive tape (Nichiban Co., Ltd.: trade name Cellotape (registered trademark)). And a tape peeling test was performed. The peeling state of the deposited layer after the test was observed, the peeling rate of the deposited layer at the crown of the overhanging convex portion was determined, and the adhesion of the processed portion was evaluated according to the following criteria. In addition, the evaluation "2" or more was passed.

(Standard)
4: No peeling 3: Peeling rate less than 10% 2: Peeling rate 10% or more and less than 50% 1: Peeling rate 50% or more

"Plane corrosion resistance"
In accordance with the salt spray test method described in JIS Z 2371, a 5% NaCl aqueous solution was sprayed onto an evaluation sample (edge and backside tape-sealed) cut from a surface-treated steel sheet at an ambient temperature of 35° C., and 12 The white rust generation area ratio of the non-sealed portion after the lapse of time was visually observed and measured, and evaluated according to the following criteria, and "2" or more was determined to be acceptable. The white rust occurrence area ratio is the percentage of the area of the white rust occurrence area to the area of the observed area.

(Standard)
4: No white rust occurred 3: White rust occurrence area ratio less than 10% 2: White rust occurrence area ratio 10% or more, less than 50% 1: White rust occurrence area ratio 50% or more

"Paint adhesion"
A coating (Amillac #1000, manufactured by Kansai Paint Co., Ltd.) was applied to the evaluation sample cut out from the surface-treated steel sheet by bar coating, and baked at 140° C. for 20 minutes to form a film having a dry film thickness of 25 μm. The obtained coated plate was immersed in boiling water for 30 minutes and then left in a room at room temperature for 24 hours. After that, 100 squares of 1 mm square were cut into the sample with an NT cutter, and this was extruded with an Erichsen tester for 7 mm, and then the extruded convex portion was subjected to a peeling test with an adhesive tape, and painting was performed according to the following standards. Adhesion was evaluated and "2" or more was passed.

(Standard)
4: No peeling 3: Peeling number of 1 or more and less than 10 2: Peeling number of 10 or more, less than 50 1: Peeling number of 50 or more

"Defect corrosion resistance"
For the evaluation sample cut out from the surface-treated steel sheet (the edge and the back surface are tape-sealed), use a cutter knife to make a flaw in the shape of "X" with the force reaching the underlying steel sheet, and then perform the "planar corrosion resistance". The corrosion resistance of the flaws was evaluated by the salt spray test. The corrosion resistance of the scratches was evaluated according to the following criteria according to the presence or absence of red rust on the scratches, and "2" or more was regarded as passing.

3: No red rust generation 2: Red rust generation less than 5% 1: Red rust generation 5% or more

"Weldability"
The appropriate current range was measured under a pressure of 1.96 kN and an energization time of 12 cycles/50 Hz. The electrode used was Cr-Cu. The lower limit value of the appropriate current range is a current value that secures a button diameter of 4√t or more (t is the plate thickness (mm) of the surface-treated steel sheet), and the upper limit value is a current value at which dust is generated. Spot welding was performed at a current value lower than the determined appropriate current upper limit value by 0.5 kA, and the button diameter was measured at every 50 dots. The button diameter was obtained by peeling off the two welded steel plates and measuring the button diameter left on the steel plate on one side. The button diameter is less than 4√t or 50 points is subtracted from the number of points where no current has passed, and the number of points is set as the number of continuous points. Weldability (continuous pointability) is evaluated according to the following criteria, and a score of "2" or more is passed. And

4: 100 or more continuous RBIs: 50 or more RBIs and less than 100 RBIs: 2 or more RBIs and less than 50 RBIs: 1 or less RBIs

As shown in Table 2-2, all of the surface-treated steel sheets of the invention examples were excellent in the adhesion of the processed part and the flat surface corrosion resistance, and further were excellent in the adhesion of the coating, the corrosion resistance of the flaw part, and the weldability.

On the other hand, as shown in Table 2-1 and Table 2-2, the test No. In Nos. 7 and 8, vanadium oxide and vanadium hydroxide were not deposited in the deposition layer because the composition of the electrolytic solution was not appropriate, and as a result, the flat corrosion resistance and coating adhesion were insufficient.

Test No. In Nos. 12, 13, and 18, the composition of the electrolytic solution was not appropriate, so that zirconium oxide and zirconium hydroxide were not deposited in the deposition layer, and the flat corrosion resistance and coating adhesion were insufficient.

Test No. No. 41 had an average rate of temperature rise during heat treatment of less than 40° C./second, so vanadium oxide and vanadium hydroxide were deposited in the deposited layer, but the ratio of oxide to hydroxide in the deposited layer ( _S 2 _/ S ₁₎ can not be sufficiently lowered, resulting it becomes insufficient processability part adhesion and coating adhesion.

Test No. In No. 44, the “time without heating” was 6 seconds, which exceeded the upper limit of 5 seconds which is an appropriate manufacturing condition. Therefore, the ratio (S ₂ /S ₁ ) of oxide and hydroxide in the deposited layer should be sufficiently reduced. Was not possible, and as a result, the adhesion of the processed part and the adhesion of the coating became insufficient.

Test No. In No. 45, the “non-heating time” was 0.4 seconds, which did not satisfy the lower limit of 0.5 seconds which is the lower limit of the appropriate manufacturing conditions. Therefore, the ratio of oxide to hydroxide in the deposited layer (S ₂ /S ₁ ) Could not be sufficiently lowered, and as a result, the adhesion of the processed portion and the adhesion of the coating became insufficient.
Test No. Reference numeral 58 is an example in which the cathodic electrolysis treatment was performed by one energization, so that there was no non-energized time. The oxide/hydroxide ratio (S ₂ /S ₁ ) in the deposited layer could not be reduced sufficiently, and the adhesion of the processed part and the adhesion of the coating became insufficient.
Test No. No. 59 was not suitable because the flow rate of the solution during the non-energized time was too large, so that the dissolution of the plating was large and the quality control at the manufacturing stage could not be performed.

The pH of the solution 15 in Table 1 was too high at 4.5, so that a precipitate was generated in the solution and it was unsuitable as an electrolytic solution.

Further, the obtained deposited layer was observed with a field emission transmission electron microscope (FE-TEM) (JED-2100F manufactured by JEOL Ltd.). In all of Nos. 1 to 59, a plurality of dendrite-like columnar crystal phases (first phase) grown in the thickness direction of the steel sheet and an amorphous phase (second phase) formed around the precipitate layer were formed in the precipitation layer. It was confirmed that it was done. The dendrite columnar crystal phase (first phase) contains metallic zinc by elemental analysis and electron beam diffraction analysis by an energy dispersive X-ray analyzer (EDS (JED-2300T) manufactured by JEOL Ltd.), It was also found that the amorphous phase (second phase) contained vanadium oxide and/or vanadium hydroxide, or zirconium oxide and/or zirconium hydroxide.

DESCRIPTION OF SYMBOLS 1... Steel plate, 2... Electrolyte bath, 2a... Upper supply piping, 2b... Lower supply piping, 3... Anode, 4a, 5a, 4b, 5b... Roll, 21... Electrolyzer, 21a... Upper tank.

Claims (7)

1. Steel plate,
   A precipitation layer containing metallic zinc formed on one or both sides of the steel sheet;
   The deposition layer further contains one or more selected from the group consisting of vanadium oxide, vanadium hydroxide, zirconium oxide and zirconium hydroxide,
   In the infrared absorption spectrum obtained by measuring the surface of the deposited layer by the reflection method of FT-IR method, the peak area S _{1 at} 1600 to 650 cm ⁻¹ indicating an oxide and the peak area S ₁ at 3600 cm ⁻¹ indicating a hydroxide. A surface-treated steel sheet having a ratio S ₂ /S ₁ with respect to a peak area S ₂ of 0 or more and 0.3 or less.
2. The amount of metallic zinc contained in the deposited layer is a (g/m ² ), and the total amount of the vanadium oxide and vanadium hydroxide contained in the deposited layer, or the zirconium oxide and the zirconium hydroxide. The surface-treated steel sheet according to claim 1, wherein 100b/(a+b) is 0.1 or more and 50 or less, where b (g/m ² ) is a total amount of the above in terms of metal.
3. The amount of metallic zinc contained in the deposited layer is a (g/m ² ), and the total amount of the vanadium oxide and vanadium hydroxide contained in the deposited layer, or the zirconium oxide and the zirconium hydroxide. The surface-treated steel sheet according to claim 1, wherein 100b/(a+b) is 1.0 or more and 20 or less, where b (g/m ² ) is a total amount of the above in terms of metal.
4. Wherein the adhered amount of the deposition layer is 1.0 g / ^{m 2} or more 50.0 g / ^{m 2} or less, surface-treated steel sheet according to any one of claims 1 to 3.
5. The deposition layer has a first phase containing the metallic zinc and a second phase containing at least one of vanadium oxide or vanadium hydroxide, or at least one of zirconium oxide or zirconium hydroxide,
   The first phase is a plurality of dendrite-like columnar crystal phases grown in the thickness direction of the steel sheet, and the second phase is an amorphous phase formed around the first phase. The surface-treated steel sheet according to any one of claims 1 to 4.
6. (6) The surface-treated steel sheet according to any one of (1) to (5), wherein the surface of the deposited layer has one or more coatings.
7. By the cathodic electrolysis process, a step of forming a deposition layer on one or both sides of the steel sheet,
   Heat-treating the deposited layer,
   Equipped with
   The cathodic electrolysis solution contains a zinc compound and at least one of a vanadium compound or a zirconium compound,
   The ratio of V ion concentration (g/l) or Zr ion concentration (g/l) to Zn ion concentration (g/l) in the cathodic electrolytic treatment solution is 0.2 to 0.9,
   The pH of the cathodic electrolytic treatment solution is 1.0 to 4.0,
   Between the start and the end of the cathodic electrolysis treatment, a non-energization time of 0.01 seconds or more is provided once or more,
   The flow rate of the cathodic electrolysis solution during the non-energization time of the cathodic electrolysis treatment is 0.05 m/sec or more and 5.00 m/sec or less,
   The maximum temperature of the deposited layer in the heat treatment is 100° C. or higher and 350° C. or lower,
   The average heating rate in the heat treatment is 40° C./sec or more,
   In the heat treatment, a non-heating time of 0.5 seconds or more and 5 seconds or less is provided between when the temperature of the deposition layer is 100° C. or higher and when the cooling of the deposition layer is started. Method for producing surface-treated steel sheet.

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