KR101018487B1 - Clear-coated stainless steel sheet excelling in design and process for producing the same - Google Patents

Abstract

The stainless steel sheet is a ferritic stainless steel sheet containing from 0.2% to 0.8% of Si in mass%, and the steel sheet has a Cr, Si, Al, Fe atomic concentration ratio [(Cr + Si +) at a depth of 50 kPa from the surface thereof. Al) / Fe] has a surface oxide film of 0.6 or more, the chemical conversion treatment agent of the coating film is composed of one or two of aminosilanes and epoxysilanes, and the deposition amount of the chemical conversion agent is 2 to 20 mg / m 2 (fluorescence X The amount of SiO ₂ measured by a line), and has a coating film having a clear coating thickness of 1 to 10 µm.

Stainless steel sheet, coating film, chemical conversion agent, whiteness, surface oxide film

Description

Clear coated stainless steel sheet with excellent design and manufacturing method {CLEAR-COATED STAINLESS STEEL SHEET EXCELLING IN DESIGN AND PROCESS FOR PRODUCING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clear-coated stainless steel sheet used for parts of home appliances, building materials, automobiles, and the like, which are excellent in designability peculiar to metal materials possessed by stainless steel, and which are not colored in yellow at the time of coating.

Stainless steel has been used in a bare state in the fields of home appliances, kitchens, automobiles and building materials because it has excellent corrosion resistance and design. In recent years, the application of the clear-coated stainless steel sheet which added the functions, such as a stain resistance and corrosion resistance, to the advantage of the excellent design, such as metal gloss of a stainless steel plate, is increasing in the home appliance field.

These clear-coated stainless steel sheets have been designed to apply not only colorless clear coating but also clear-coated steel sheets to which a clear coat colored with a pigment or the like and a pigment of pulsate or metallic coat are added. However, the addition of these pigments lowers the transparency of the clear film, thereby lowering the texture with metallic luster peculiar to stainless steel.

On the other hand, in a colorless clear-coated stainless steel sheet, there is a problem in that a chromate treatment, which is a base treatment, gives a yellow color, impairs the design and at the same time, looks blackish depending on the viewing angle. For these problems, Patent Document 1 and Patent Document 2 examine the treatment liquid composition and the coating amount applied to the chromate coating. In patent document 3, examination of the improvement of the external appearance of the base stainless steel plate by phosphoric acid and a silica, the contamination resistance of a coating film, and baking resistance is carried out.

Patent Document 1: Japanese Patent Application Laid-open No. Hei 5-106057

Patent Document 2: Japanese Patent Application Laid-Open No. 11-269660

Patent Document 3: Japanese Patent Application Laid-open No. Hei 8-281864

Patent Document 4: Japanese Patent Application Laid-open No. 56-259

Patent Document 5: Japanese Patent Application Laid-open No. 62-156253

Patent Document 6: Japanese Patent Application Laid-open No. Hei 11-254585

Only the improvement of the chromate treatment method as mentioned above can obtain a clear-coated stainless steel sheet which is excellent in whiteness and high in transparency. An object of this invention is to examine the chemical conversion treatment conditions, the characteristic of the surface of a raw material, and coating conditions, and to provide a clear-coated stainless steel plate excellent in whiteness, and its manufacturing method.

As a result of examination by the inventors, in addition to the chromate treatment, the yellow group coloring (yellowing) of the colorless clear-coated stainless steel sheet, temper color coloring occurs on the surface of the stainless steel sheet during baking of the clear coating film, This temper color coloring also turned out to cause yellowing. A stainless steel sheet excellent in temper color resistance as a stainless steel sheet which changes the chemical conversion treatment from chromate treatment to non-chromate treatment, optimizes the thickness of the chemical conversion coating film, and is applied to a clear-coated stainless steel sheet. It has become clear that by using, the yellowing prevention at the time of clear coating can be realized.

It is known that the temper color of the stainless steel sheet can be suppressed by brightly annealing the stainless steel sheet in which Si and Al are increased to form an oxide film containing SiO ₂ and Al ₂ O ₃ on the steel sheet surface. That is, with the increase of Si or Al content, the oxide film which Si and Al concentrated was easy to form, and the temper color resistance improves. As such stainless steels, high Si steels (Patent Documents 4 and 5), high Al steels (Patent Document 5), and the like are known.

Moreover, patent document 6 is known as a heat resistant transparent coating stainless steel plate which regulated Al or Si on the surface of a ferritic stainless steel plate to 4.5 to 6 atomic%.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining the means which solve the said subject, the clear coating stainless steel plate which used the ferritic stainless steel plate which was excellent in whiteness, and the chemical conversion treatment condition, the characteristic of the surface of a raw material, and coating conditions as mentioned above are examined, and its The manufacturing method was established.

The point which makes a summary of this invention is as follows.

(1) A stainless steel sheet is a ferritic stainless steel sheet containing 0.2% to 0.8% of Si by mass%, and the steel sheet has a Cr, Si, Al, Fe atomic concentration ratio [(Cr) at a depth of up to 50 kPa from the surface thereof. + Si + Al) / Fe] has a surface oxide film of 0.6 or more, the chemical conversion treatment agent of the coating film is composed of one or two of aminosilane-based and epoxysilane-based, the adhesion amount of the chemical conversion treatment agent is 2 to 20 mg / A clear-coated stainless steel sheet excellent in whiteness, having a coating film having a thickness of 1 to 10 µm, which is m 2 (measurement of the amount of SiO ₂ by fluorescence X-ray) and is formed of a clear coating material.

(2) The stainless steel sheet excellent in whiteness as described in (1), wherein the stainless steel sheet further contains 0.005 to 0.15% of Al in mass%.

(3) The said stainless steel sheet further contains Nb: 0.1 to 0.7% by mass%, The clear-coated stainless steel plate excellent in the whiteness as described in (1) characterized by the above-mentioned.

(4) A stainless steel sheet is a ferritic stainless steel sheet containing, in mass%, Si: 0.2 to 0.8%, Al: 0.005 to 0.15%, and Nb: 0.1 to 0.7%, and the steel sheet has a depth up to 50 kPa from the surface thereof. Cr, Si, Al, Fe atomic concentration ratio [(Cr + Si + Al) / Fe] has a surface oxide film of 0.6 or more, and the chemical conversion treatment agent of the coating film is one or two of aminosilane and epoxysilane And a coating amount of 2 to 20 mg / m 2 (measured amount of SiO ₂ by fluorescent X-ray) and a thickness of a clear coating film formed of a clear paint having a thickness of 1 to 10 μm. Clear coated stainless steel plate with excellent whiteness.

(5) Annealing is carried out under conditions in which the final brightness annealing temperature [T 1 (° C.)] and the dew point [T 2 (° C.)] of the annealing atmosphere satisfy one and two equations. Excellent method of manufacturing clear-painted stainless steel plate material.

750 ≦ T1 ≦ 5 × T2 + 1200... … 1 meal

70? T2? … 2 meals

(6) A stainless steel sheet is a ferritic stainless steel sheet containing, in mass%, Si: 0.2 to 0.8% and Al: 0.005 to 0.15%, and the steel sheet is Cr, Si, Al at a depth of 50 kPa from the surface thereof. , Fe atom concentration ratio [(Cr + Si + Al) / Fe] has a surface oxide film of 0.6 or more, the chemical conversion treatment agent of the coating film is composed of one or two of aminosilane-based and epoxysilane-based, It has a coating amount of 2 to 20 mg / m 2 (measured amount of SiO ₂ by fluorescence X-ray), and has a coating film having a clear paint thickness of 1 to 10 μm. Annealing is carried out under the condition that the temperature [T1 (° C.)] and the dew point [T2 (° C.)] of the annealing atmosphere satisfy one and two equations. .

750 ≦ T1 ≦ 5 × T2 + 1200... … 1 meal

70? T2? … 2 meals

(7) A stainless steel sheet is a ferritic stainless steel sheet containing, in mass%, Si: 0.2 to 0.8%, Al: 0.005 to 0.15%, and Nb: 0.1 to 0.7%, and the steel sheet has a depth of up to 50 mm from the surface thereof. Cr, Si, Al, Fe atomic concentration ratio [(Cr + Si + Al) / Fe] has a surface oxide film of 0.6 or more, and the chemical conversion treatment agent of the coating film is one or two of aminosilane and epoxysilane And a coating amount of 2 to 20 mg / m 2 (measured amount of SiO ₂ by fluorescent X-ray) and a thickness of a clear coating film formed of a clear paint having a thickness of 1 to 10 μm. Annealing is performed on a clear-coated stainless steel sheet having excellent whiteness under conditions in which the final brightness annealing temperature [T1 (° C.)] and the dew point [T2 (° C.)] of the annealing atmosphere satisfy formulas 1 and 2. Excellent Method of manufacturing clear-painted stainless steel sheet material.

750 ≦ T1 ≦ 5 × T2 + 1200... … 1 meal

70? T2? … 2 meals

(8) A stainless steel sheet is a ferritic stainless steel sheet containing, in mass%, 0.2% to 0.8% Si, wherein the steel sheet has a Cr, Si, Al, Fe atomic concentration ratio [(Cr) at a depth of up to 50 kPa from the surface thereof. + Si + Al) / Fe] has a surface oxide film of 0.6 or more, the chemical conversion treatment agent of the coating film is composed of one or two of aminosilane-based and epoxysilane-based, the adhesion amount of the chemical conversion treatment agent is 2 to 20 mg / The temperature of the final brightness annealing on the clear-coated stainless steel sheet having excellent whiteness, characterized by having a coating film having a thickness of 1 to 10 μm of m 2 (measured amount of SiO ₂ by fluorescent X-ray) and a clear coating film formed of a clear paint. Annealing is performed under conditions where [T1 (° C.)] and the dew point [T2 (° C.)] of the annealing atmosphere satisfy the formulas 1 and 2, and the surface is polished after the cold rolled ferritic stainless steel sheet is polished. Nieling is performed, The manufacturing method of the clear-coated stainless steel plate material excellent in whiteness.

750 ≦ T1 ≦ 5 × T2 + 1200... … 1 meal

70? T2? … 2 meals

(9) A method for producing a clear-coated stainless steel sheet material having excellent whiteness as described in (6), wherein the cold-rolled ferritic stainless steel sheet is subjected to surface polishing after surface polishing.

(10) A method for producing a clear-coated stainless steel sheet material having excellent whiteness as described in (7), wherein the cold-rolled ferritic stainless steel sheet is subjected to surface polishing after surface polishing.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the relationship between the chemical conversion treatment amount and the discoloration ((DELTA) b *) of a clear-coated stainless steel plate.

Fig. 2 is a change in the atomic concentration ratio [(Cr + Si + Al) / Fe] of Cr, Si, Al, and Fe in the oxide film at a depth of up to 50 GPa from the surface, and discoloration of the clear-coated stainless steel sheet by baking at 224 캜. It is a figure which shows the relationship with ((DELTA) b *).

Fig. 3 is a diagram showing the relationship between the baking temperature of the polished stainless steel sheet and the steel sheet subjected to the bright annealing of the present invention after polishing, and the discoloration (Δb *) of the clear-coated stainless steel sheet.

Fig. 4 shows the atomic concentration ratios of Cr, Si, Al and Fe in the annealing temperature [T1 (° C.)], dew point [T2 (° C.)] of the bright annealing and the oxide film at a depth of up to 50 kPa from the surface [(Cr + Si + Al) / Fe].

MEANS TO SOLVE THE PROBLEM As a result of studying the pretreatment in the designability of a clear-coated stainless steel plate, and the characteristic of a raw material surface, the present inventors discovered that the following two things are important in order to obtain the clear-coated stainless steel plate excellent in whiteness. First of all, an aminosilane-based and epoxysilane-based chemical conversion treatment agent other than a chromate treatment agent is used as the chemical conversion treatment agent as a pretreatment, and the adhesion amount of the chemical conversion treatment agent is in the optimum range. Secondly, as a stainless steel sheet material, Cr, Si, Al components are enriched on the surface to prevent discoloration of the material due to temper color coloring at the time of coating baking. The colorless clear paint may be any of polyester resin, acrylic resin, acrylic urethane resin, epoxy modified polyester resin and the like.

The clear chemical conversion treatment of the present invention will be described.

The clear chemical conversion treatment agent of the present invention comprises one or two of aminosilane and epoxysilane. The reason why the aminosilane-based and epoxysilane-based systems were selected is that the adhesion is good when used, and yellow coloring can be prevented as compared with the case where the chromate treatment agent is used. The adhesion amount of the chemical conversion treatment agent is treated to be 2 to 20 mg / m 2 (the amount of SiO ₂ is measured by fluorescence X-rays), and the surface temperature (MT) of the stainless steel sheet is baked and dried at 60 to 140 ° C.

In Fig. 1, E-206 (aminosilane system) of Nippon Parkerizing Co., Ltd. was changed at 100 DEG C from 2 mg / m 2 to 50 mg / m 2 adhesion amount, roll-coated 2 µm acrylic urethane resin clear paint, and baking temperature was The change of the color tone of the clear-coated stainless steel sheet coated at 200 ° C was investigated. As a stainless steel plate material used for clear coating, temper color coloring by using the SUS430 / bright annealing material whose atomic concentration ratio [(Cr + Si + Al) / Fe] (after-mentioned) in the depth from the surface to 50 kPa is 0.6 or more is used. The yellowing of the cause is doing as little as possible. As shown in the horizontal axis, the vertical axis Δb * in FIG. 1 changes the adhesion amount of the chemical conversion agent and subtracts b * (2) of the steel sheet material from b * (1) when baking coating the clear paint. That is, Δb * = b * (1)-b * (2).

As a result, as shown in Fig. 1, when the deposition amount of the chemical conversion agent exceeds 20 mg / m 2, the gloss of the clear-coated stainless steel is lowered and a slightly yellowish group appears. When the amount of deposition is 20 mg / m 2 or less, Δb * is 0.3 or less, and there is little change in color tone due to chemical conversion treatment. On the other hand, if it is less than 2 mg / m <2> of chemical conversion treatment, a film will become nonuniform and the adhesiveness of a clear coating film and stainless steel will fall. For this reason, in this invention, the adhesion amount of the chemical conversion treatment agent was 2-20 mg / m <2>. In addition, it can be quantified by measuring the amount of Si0 ₂ to the fluorescent X-ray to the stainless steel surface for the coating weight of the chemical conversion treatment agent.

Clear coating film thickness is the range of 1 micrometer-10 micrometers or less. This is because it is difficult to obtain a stable color tone at 1 µm or less, and at 10 µm or more, it is difficult to manufacture a single coating, and the coating film cost also increases. Preferably it is the range of 2 micrometers-5 micrometers.

Next, the raw material of the clear-coated stainless steel sheet of this invention is demonstrated.

In the present invention, the coating baking is carried out by using a steel sheet having a surface oxide film having a Cr, Si, Al, or Fe atomic concentration ratio [(Cr + Si + Al) / Fe] at a depth of up to 50 kPa from the surface, of 0.6 or more. It is characterized in that yellowing is prevented by preventing temper color coloring in the city. By using the ferritic stainless steel sheet containing 0.2% by mass or more of Si, the steel sheet is subjected to bright annealing at a predetermined temperature and atmosphere, whereby the atomic concentration ratio on the surface of the steel sheet can be in the above suitable range.

The stainless steel of a clear-coated stainless steel plate is a ferritic stainless steel plate containing Si: 0.2 to 0.8% by mass%. Since the diffusion rate of the element in the ferritic stainless steel is faster than that of the austenitic system, Cr and Si are easily concentrated in the film. Therefore, this invention was limited to the ferritic stainless steel plate. In particular, it is relatively easy in a special type of steel containing Al or Si (Cr-Al steel or Cr-Si steel), and is described in Patent Documents 4 and 5. However, in the ferritic stainless steel of the present invention, i.e., steel containing 0.2 to 0.8% of Si, a technique for concentrating Cr, Si, and Al described below in a film becomes essential.

In the present invention, in order to form a surface oxide film in which Si is concentrated on the surface of the stainless steel sheet, it is essential to contain Si at least 0.2%, in which case Si is used as the deoxidation element in the solvent of the steel. The upper limit of Si of 0.8% particularly indicates that the present invention is a general-purpose ferritic stainless steel. When Si is contained more than this, it will exceed the component range of general-purpose ferritic stainless steel, for example, SUS430 or SUS430J1L of Nb addition. That is, the Si addition of more than 0.8% deteriorates workability due to the solid solution hardening action and is not suitable for general purpose applications.

In this invention, it is preferable to contain trace amount Al of 0.005% or more and 0.15% or less. This is because Al, like Si, is concentrated in the bright annealing film as described below, thereby having an effect of suppressing an increase in b * during clear coating film baking. Al is added 0.005% or more as a deoxidation element. Addition of large amounts of Al deteriorates workability. Therefore, Al is preferably 0.005 to 0.15%.

In this invention, content of Cr which is a basic component of a ferritic stainless steel plate can be made into the range of 16.0-20.0 mass%. In addition, in order to make the clear stainless steel plate excellent in whiteness, as much as possible, Cr content is good. This is because there is an effect of promoting the thickening of Cr in the film during bright annealing. Moreover, in this invention, it is preferable to contain 0.1 to 0.7% of Nb. This is because the oxide of Nb is more thermodynamically stable than Cr oxide and is considered to have the same action as Cr.

Next, a technique for concentrating Cr, Si, and Al in a surface oxide film in a ferritic stainless steel containing Si: 0.2 to 0.8% will be described.

After cold-roll annealing of ferritic stainless steel SUS430, the material No. 4 polished finish was annealed brightly, and the ratio of Cr, Si, Al, Fe in the oxide film was changed by changing the temperature and atmosphere of the bright annealing. To the material of which the atomic concentration ratio [(Cr + Si + Al) / Fe] was adjusted to the range of 0.15 to 3.5, an aminosilane-based chemical treatment agent was applied as the chemical conversion treatment so that the adhesion amount would be 10 mg / m 2, followed by baking drying at 100 ° C. After that, a roll coating of a 2 μm acrylic urethane resin clear paint was carried out. In Fig. 2, the baking temperature after applying clear paint is 224 ° C, and the relationship between the atomic concentration ratio [(Cr + Si + Al) / Fe] and Δb * is shown. It evaluated by (DELTA) b * which is the difference of b * after baking and a reference material (clear-coated stainless steel plate material). As apparent from Fig. 2, in the material in which the atomic concentration ratio [(Cr + Si + Al) / Fe] is adjusted to 0.6 or more, the change in color tone due to coating and baking is small, and Δb * is less than 1, and there is little discoloration.

Next, the material which adjusted the atomic concentration ratio [(Cr + Si + Al) / Fe] to 0.6 or more and the material which adjusted the atomic concentration ratio [(Cr + Si + Al) / Fe] to less than 0.6 were prepared, and baking temperature Was changed from 150 ° C to 250 ° C to see a change in color tone. The difference is the same as in the case of FIG. In Fig. 3, the atomic concentration ratio [(Cr + Si + Al) / Fe] is set to about 3 for the material of? And?. About ● and ▲, atomic concentration ratio [(Cr + Si + Al) / Fe] is about 0.4 and about 0.2, respectively. As a result, as shown in Fig. 3, in the material in which (Cr + Si + Al) / Fe is adjusted to 0.6 or more by bright annealing, there is little change in color tone due to coating and baking. On the other hand, after polishing finish, the material which does not anneal brightness, and the material which processed in the brightness annealing conditions outside the range of this invention, and adjusted the atomic concentration ratio [(Cr + Si + Al) / Fe] to less than 0.6, at the time of coating and baking The yellowish-colored discoloration is large, especially when the baking temperature is high at 200 ° C or higher.

In the present invention, the components in the surface oxide film are analyzed by AES [Auger Electron Spectroscopy], and the atomic concentration ratio [(Cr + Si + Al) / Fe] at the point where the oxygen concentration is the highest. It was set as. In this invention, it is very important to control (Cr + Si + Al) / Fe to 0.6 or more, and to set it as the surface oxide film which Cr and Si concentrated. In this case, Si is concentrated in the outer layer of the surface oxide film, and Al is concentrated in the inner layer near the bulk. This is because the bright annealing conditions are reduced in Cr, oxidized in Si and Al, and Al ₂ O ₃ has a lower dissociation pressure than Si0 ₂ . In addition, although the appropriate range of (Cr + Si + Al) / Fe may change according to the measuring method of a surface oxide film, the required surface oxide film structure is the same as mentioned above.

The atomic concentration ratio [(Cr + Si + Al) / Fe] in the surface oxide film of the cold rolled annealing material and the polishing finish material is about 0.2. Therefore, the present inventors perform bright annealing on the stainless steel sheet, and the atomic concentration ratio [(Cr + Si + Al) / Fe] of Cr, Si, Al, and Fe at a depth from the surface to 50 kPa becomes 0.6 or more. Bright annealing conditions for forming an oxide film were examined.

Bright annealing is generally carried out in a reducing atmosphere in which hydrogen and nitrogen are mixed in a ratio of H ₂ : N ₂ = (1 to 9): 1, but then the annealing temperature [T1 (° C.)] and the atmosphere dew point [T2 ( Component in the oxide film after annealing changes.

Cold rolled annealing or No.4 finish (JIS G 0203 No.5349) was applied to the cold rolled SUS430J1L and SUS430 steel sheets, and subjected to various annealing temperatures [T1 (° C)] and atmospheric dew point [T2 (° C). )] Shows the results of the bright annealing in FIG. The annealing temperature (T1) is taken as the horizontal axis, and the atmospheric dew point (T2) is taken as the vertical axis, and the (Cr + Si + Al) / Fe atomic concentration ratio at a depth of up to 50 kPa from each surface is stabilized and becomes 0.6 or more. Is,

750 ≦ T1 ≦ 5 × T2 + 1200... … 1 meal

70? T2? … 2 meals

to be.

In the formulas (1) and (2), since Cr is a condition to be reduced and Si is to be oxidized, concentration by selective oxidation of the active ingredients (Si, Al) in the film is effectively performed. When the temperature [T1 (° C.)] of the bright annealing is less than 750 ° C., the diffusion movement of the effective elements (Si, Al) centered on Cr is delayed, so that an oxide film having a sufficient atomic concentration ratio is not obtained. In addition, when the temperature [T1 (° C)] exceeds (5 x T2 + 1200) ° C, since it becomes a condition on the reduction side more than the range of one equation, selective oxidation of Si or Al is suppressed, and a sufficient atomic concentration ratio Does not become an oxide film. Therefore, the brightness annealing temperature [T1 (° C)] is preferably in the range of one equation determined from the relationship with the dew point. Preferably 800 degreeC or more and 1000 degrees C or less are good. More preferably, they are 800 degreeC or more and 900 degrees C or less.

When the dew point [T2 (° C.)] of the bright annealing exceeds −30 ° C., the oxidation of Fe becomes severe, and the concentration of Fe on the surface oxide film cannot be avoided and is discolored by the temper color. Not desirable In addition, gas dew point below −70 ° C. is very difficult industrially. Therefore, the dew point of the bright annealing has a good range of two expressions. Preferably, -60 ° C or more and less than -35 ° C are preferable.

Although the patent document 5 says that there is little temper color coloring in 0.3% of Si concentration, the Example of 0.3% of Si concentration in the same document is temper color coloring grade 3 (yellow). It cannot be made with excellent clear-coated stainless steel sheet. In the present invention, the atomic concentration ratio [(Cr + Si + Al) / Fe] in the oxide film is clearly defined to be 0.6 or more, and the manufacturing conditions which can realize this atomic concentration ratio are made clear, so that the Si concentration is 0.8% or less. It was made possible to set it as the clear-coated stainless steel plate excellent in whiteness even at low Si concentration.

An abrasive finish material imparting a stainless unique surface shape by a polishing mark is useful as a member whose design is important. However, since the surface coating of stainless steel surface-polished very little in concentration of Cr, Si, and Al, it is yellow when it apply | coats a clear coating film, and the high-tension clear coating film stainless steel plate excellent in whiteness cannot be obtained. Therefore, although bright annealing needs to be performed to thicken Cr, Si, and Al in the surface coating, if bright annealing is performed after surface polishing of a ferritic stainless steel sheet subjected to general soft annealing, the manufacturing process becomes complicated, resulting in increased cost. It becomes a factor. Therefore, in the present invention, it is preferable to perform final bright annealing after the surface of the cold rolled ferritic stainless steel sheet is polished. Cold Rolling-Surface Polishing-Bright Annealing to soften annealing to obtain the desired material and to concentrate Cr, Si, Al [High (Cr + Si + Al) / Fe] in the surface coating It can carry out simultaneously by annealing. In particular, in the ferritic stainless steel sheet of the present invention, in order to match the soft nitriding temperature and the concentration temperature of Cr, Si, and Al in the surface coating, it is also possible to control and adjust the recrystallization temperature by the content of Nb. In the case of an austenitic stainless steel sheet, since the solid solution annealing is usually 1000 ° C. or higher, it does not coincide with the temperature at which Cr, Si, and Al are concentrated in the surface coating. Therefore, after cold rolling-polishing, it is necessary to give two annealings of solid solution annealing and bright annealing for oxide film formation.

Table 1 shows Examples and Comparative Examples of the present invention. The surface finish of the ferritic stainless steel sheet was made into three types of No. 4 (fine eye polishing finish), HL (hairline polishing finish), and 2B (surface rolled lightly after pickling). Bright annealing was performed on these ferritic stainless steel sheets under the conditions shown in Table 1. In addition, while the ferritic stainless steel plate of 2B finishing is a manufacturing process which annealed after cold rolling, the other surface finishing does not anneal after cold rolling, and also soft-nitriding is performed simultaneously by bright annealing. In addition, in the conditions suitability of the bright annealing conditions, what is shown by (circle) mark shows the thing suitable for a condition, and the thing shown by the x mark shows that it is not suitable for a condition. Similarly, also in whiteness, what is shown by (circle) mark shows that whiteness is excellent, and what is shown by x mark shows that whiteness deteriorates.

Table 1-1

Table 1-2

Table 1-3

The atomic concentration ratios of Cr, Si, Al, and Fe in the oxide film at a depth from the surface to 50 kPa for each ferritic stainless steel sheet after bright annealing were measured by AES (auger electron spectroscopy) to determine the atomic concentration ratio [ (Cr + Si + Al) / Fe] was obtained.

For each ferritic stainless steel sheet after bright annealing, an aminosilane-based and epoxysilane-based ones were used for the chemical conversion treatment agent (E-206) of Nippon Parkerizing Co., Ltd. as a chemical conversion treatment, and the deposition amount was 2 mg / m 2 to 50 mg / m 2 Changed to the range of. As a comparison, the chemical conversion treatment agent was subjected to the chromate treatment. Then, 1-10 micrometers of the acrylic urethane resin clear film was processed at the baking temperature of 220 degreeC.

The color tone after clear coating was measured by b * (JIS Z8729), and the degree of discoloration was evaluated.

In the example of this invention, when the atomic concentration ratio in the oxide film of the surface of a ferritic stainless steel plate is 0.6 or more, and the chemical conversion treatment which consists of one type or two types of an aminosilane type and an epoxy silane type is made into 2-20 mg / m <2>, On the other hand, a clear coated steel sheet having an excellent whiteness of b * of 2 or less can be obtained, whereas in the comparative example, a b * is a clear coated steel sheet having a yellow group of more than 2, and is shown in a dark hue depending on the viewing angle.

In Comparative Example 20, since the component of Si of the stainless steel sheet was out of the lower limit, (Cr + Si + Al) / Fe in the oxide film was out of the lower limit, and b * deteriorated to 2 or more. In Comparative Examples 21 to 25, since one of the temperature T1 and the dew point T2 of the bright annealing conditions was out of the upper and lower limits, (Cr + Si + Al) / Fe in the oxide film was out of the lower limit, and b * was 2 or more. The whiteness deteriorates. In particular, in Comparative Example 25, since the temper color of the material of the stainless steel sheet was clearly observed, (Cr + Si + Al) / Fe was not measured. In Comparative Examples 26 to 32, (Cr + Si + Al) / Fe of the raw material is 0.6 or more, but the conditions of the chemical conversion treatment agent are outside the scope of the present invention. In Comparative Example 26, the adhesion amount of the chemical conversion treatment agent is beyond the lower limit and is inferior in adhesion. In Comparative Example 27, the deposition amount of the chemical conversion treatment agent was out of the upper limit, whereas in Comparative Example 28, the whiteness was deteriorated to 2 or more because the chemical conversion treatment agent was a chromate agent and not the non-chromate treatment agent of the present invention. In Comparative Examples 29 and 31, the clear paint thickness was out of the lower limit and the color tone was unstable. In Comparative Examples 30 and 32, the clear paint thickness was out of the upper limit, which is difficult to manufacture.

As mentioned above, although preferred Example of this invention was described, this invention is not limited to these Examples. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the invention. The present invention is not limited by the above description, but only by the scope of the appended claims.

According to the present invention which examined the relationship between the design and color tone of a clear-coated stainless steel sheet, it is possible to produce a clear-coated steel sheet excellent in whiteness in the range of b * (color, degree of sulfur / blue, JIS Z 8729) in the range of 0 to 2. It becomes possible. In a general clear-coated stainless steel sheet, b * has a yellow group of about 4 to 6, and it appears dark in color depending on the viewing angle. On the other hand, the clear-coated stainless steel sheet of the present invention has a white color and is not seen as a dark color tone by the viewing direction.

Claims (10)

The stainless steel sheet is a ferritic stainless steel sheet containing from 0.2% to 0.8% of Si in mass%, and the steel sheet has a Cr, Si, Al, Fe atomic concentration ratio [(Cr + Si +) at a depth of 50 kPa from the surface thereof. Al) / Fe] has a surface oxide film of 0.6 or more, the chemical conversion treatment agent of the coating film is composed of one or two of aminosilane-based and epoxysilane-based, and the deposition amount of the chemical conversion agent is 2 to 20 mg / m 2 (fluorescence The amount of SiO ₂ measured by X-ray), the coating having a thickness of 1 to 10 μm formed of a clear paint selected from any one of a polyester resin paint, an acrylic resin paint, an acrylic urethane resin paint, and an epoxy-modified polyester resin paint. Clear coated stainless steel sheet excellent in whiteness, characterized by having a film. The clear-coated stainless steel sheet having excellent whiteness according to claim 1, wherein the stainless steel sheet contains 0.005 to 0.15% of Al in mass%. The clear-coated stainless steel sheet having excellent whiteness according to claim 1, wherein the stainless steel sheet contains Nb: 0.1 to 0.7% by mass%. A stainless steel sheet is a ferritic stainless steel sheet containing, in mass%, Si: 0.2 to 0.8%, Al: 0.005 to 0.15%, and Nb: 0.1 to 0.7%, and the steel sheet is Cr at a depth up to 50 kPa from the surface thereof. , Si, Al, Fe atomic concentration ratio [(Cr + Si + Al) / Fe] has a surface oxide film of 0.6 or more, the chemical conversion treatment agent of the coating film is composed of one or two of aminosilane-based, epoxysilane-based, the coating weight of the chemical conversion treatment agent, and from 2 to 20 mg / ㎡ (measuring the amount of SiO ₂ with X-ray fluorescence), selected from any one of polyester resin-based paint, acrylic resin paint, acrylic urethane resin-based coating, epoxy-modified polyester resin-based paint A clear-coated stainless steel sheet excellent in whiteness, having a coating film having a thickness of 1 to 10 µm formed of a clear paint. To ferritic stainless steel plate material containing Si: 0.2 to 0.8% by mass% Annealing is performed under the condition that the temperature [T1 (° C.)] of the final brightness annealing and the dew point [T2 (° C.)] of the annealing atmosphere satisfy one or two equations, and Cr, Si at a depth from the surface to 50 kPa Steel sheet material having a surface oxide film having a ratio of Al, Fe and atomic concentration ratios [(Cr + Si + Al) / Fe] of 0.6 or more; A chemical conversion treatment in which the deposition amount of the chemical conversion agent is 2 to 20 mg / m 2 (measured SiO ₂ amount by fluorescence X-rays) using the chemical conversion agent composed of one or two kinds of aminosilane-based and epoxysilane-based materials. Then, A coating film having a thickness of 1 to 10 µm is formed by coating a clear paint selected from any one of a polyester resin paint, an acrylic resin paint, an acrylic urethane resin paint, and an epoxy-modified polyester resin paint. The manufacturing method of the clear-coated stainless steel plate excellent in the whiteness described. 750 ≦ T1 ≦ 5 × T2 + 1200... … 1 meal 70? T2? … 2 meals To ferritic stainless steel plate material containing Si: 0.2 to 0.8% and Al: 0.005 to 0.15% by mass% Annealing is carried out under the condition that the temperature of the final bright annealing [T1 (° C.)] and the dew point [T2 (° C.)] of the annealing atmosphere satisfy one and two equations, It is set as the steel plate material which has a surface oxide film whose Cr, Si, Al, Fe atomic concentration ratio [(Cr + Si + Al) / Fe] in the depth from a surface to 50 GPa is 0.6 or more, The plate materials amino silane, an epoxy silane of the first type or of the chemical conversion treatment agent attached amount by using the chemical conversion treating agent composed of two types of 2 to 20 mg / ㎡ (measuring the amount of SiO ₂ with X-ray fluorescence), a chemical conversion that Processing, A clear coating excellent in whiteness, characterized by coating a clear paint selected from any one of a polyester resin paint, an acrylic resin paint, an acrylic urethane resin paint, and an epoxy-modified polyester resin paint to form a coating film having a thickness of 1 to 10 μm. Method of manufacturing painted stainless steel sheet. 750 ≦ T1 ≦ 5 × T2 + 1200... … 1 meal 70? T2? … 2 meals In a ferritic stainless steel sheet material containing Si: 0.2 to 0.8%, Al: 0.005 to 0.15%, Nb: 0.1 to 0.7% by mass%, Annealing is carried out under the condition that the temperature of the final bright annealing [T1 (° C.)] and the dew point [T2 (° C.)] of the annealing atmosphere satisfy one and two equations, It is set as the steel plate material which has a surface oxide film whose Cr, Si, Al, Fe atomic concentration ratio [(Cr + Si + Al) / Fe] in the depth from a surface to 50 GPa is 0.6 or more, Using a chemical conversion treating agent composed of the steel sheet material to one kind or two kinds of amino silane, an epoxy silane, the coating weight of the chemical conversion treatment agent is 2 to 20 mg / ㎡ (measuring the amount of SiO ₂ with X-ray fluorescence) Perform the chemical conversion treatment, Characterized by forming a coating film having a thickness of 1 to 10 μm by coating a clear paint formed of a clear paint selected from any one of a polyester resin paint, an acrylic resin paint, an acrylic urethane resin paint, and an epoxy-modified polyester resin paint. The manufacturing method of the clear-coated stainless steel plate excellent in the whiteness to say. 750 ≦ T1 ≦ 5 × T2 + 1200... … 1 meal 70? T2? … 2 meals After cold rolling a ferritic stainless steel plate material containing Si: 0.2 to 0.8% by mass% and surface polishing Annealing is carried out under the condition that the temperature of the final bright annealing [T1 (° C.)] and the dew point [T2 (° C.)] of the annealing atmosphere satisfy one and two equations, It is set as the steel plate material which has a surface oxide film whose Cr, Si, Al, Fe atomic concentration ratio [(Cr + Si + Al) / Fe] in the depth from a surface to 50 GPa is 0.6 or more, Using a chemical conversion treating agent composed of the steel sheet material to one kind or two kinds of amino silane, an epoxy silane, the coating weight of the chemical conversion treatment agent is 2 to 20 mg / ㎡ (measuring the amount of SiO ₂ with X-ray fluorescence) Perform the chemical conversion treatment, A clear coating excellent in whiteness, characterized by coating a clear paint selected from any one of a polyester resin paint, an acrylic resin paint, an acrylic urethane resin paint, and an epoxy-modified polyester resin paint to form a coating film having a thickness of 1 to 10 μm. Method of manufacturing painted stainless steel sheet. 750 ≦ T1 ≦ 5 × T2 + 1200... … 1 meal 70? T2? … 2 meals 7. The method for producing a clear-coated stainless steel sheet having excellent whiteness according to claim 6, wherein the final bright annealing is performed after surface-grinding the cold-rolled ferritic stainless steel sheet material. 8. The method for producing a clear-coated stainless steel sheet having excellent whiteness according to claim 7, wherein the final bright annealing is performed after the cold-rolled ferritic stainless steel sheet is subjected to surface polishing.

Images