WO2006112376A1

WO2006112376A1 - Clear-coated stainless steel sheet excelling in design and process for producing the material

Info

Publication number: WO2006112376A1
Application number: PCT/JP2006/307902
Authority: WO
Inventors: Masuhiro Fukaya; Naoto Ono; Haruki Ariyoshi
Original assignee: Nippon Steel & Sumikin Stainless Steel Corporation
Priority date: 2005-04-15
Filing date: 2006-04-14
Publication date: 2006-10-26
Also published as: AU2006237998A1; CN101098988A; TW200702453A; MY141238A; NZ555633A; JP4606929B2; KR20070087630A; JP2006299299A; TWI370847B; KR101018487B1; CN100585006C; TW201111523A; AU2006237998B2; TWI354029B

Abstract

A clear-coated stainless steel sheet excelling in whiteness degree, characterized in that it includes a stainless steel sheet consisting of a ferrite stainless steel sheet containing 0.2 to 0.8 mass% of Si, the stainless steel sheet from its surface to a depth of 50 Å furnished with a surface oxide film of ≥ 0.6 Cr/Si/Al/Fe atomic concentration ratio [(Cr+Si+Al)/Fe], and further includes a coating film of 1 to 10 μm clear coating material thickness from a chemical treatment agent consisting of one or two members of aminosilane and epoxysilane agents, the chemical treatment agent adhering in an amount of 2 to 20 mg/m2 (amount of SiO2 measured by fluorescent X-ray). Further, there is provided a process for producing the material.

Description

Specification

Clear painted stainless steel plate with excellent design and manufacturing method of the material

TECHNICAL FIELD [0001] The present invention relates to a clear coated stainless steel sheet that is excellent in design characteristics unique to a metal material possessed by stainless steel and is used in parts such as home appliances, building materials, and automobiles that are not colored yellow during painting.

Background art

Stainless steel has been used in the bare state in the fields of home appliances, kitchens, automobiles and building materials because it has excellent corrosion resistance and design properties. Recently, clear coating has added functions such as contamination resistance and corrosion resistance while making the best use of the metallic luster of stainless steel sheets.

RU

[0003] These clear-coated stainless steel sheets are designed to be applied to clear-coated steel sheets that are colored with pigments, pearl-like or metallic-like pigments, as well as colorless clear paints. It has become. However, the addition of these pigments reduces the clearness of the clear film and the texture with the metallic luster unique to stainless steel.

[0004] On the other hand, a colorless clear-coated stainless steel sheet has a problem that it becomes yellowish due to the chromate treatment of the base treatment, impairs the design, and looks black depending on the viewing angle. In order to deal with these problems, Patent Document 1 and Patent Document 2 examine the composition of the treatment liquid and the amount applied to the chromate film. Patent Document 3 discusses improvements in the appearance of the underlying stainless steel sheet with phosphoric acid and silica, and the improvement in the stain resistance and seizure resistance of the coating film.

Patent Document 1: Japanese Patent Laid-Open No. 5-106057

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

Patent Document 3: JP-A-8-281864

Patent Document 4: Japanese Patent Laid-Open No. 56-259

Patent Document 5: Japanese Patent Laid-Open No. 62-156253

Patent Document 6: Japanese Patent Laid-Open No. 11-254585 Disclosure of the invention

Problems to be solved by the invention

[0006] Only by improving the chromate treatment method as described above, it is not possible to obtain a clear coated stainless steel sheet having excellent whiteness and high transparency. It is an object of the present invention to provide a clear-coated stainless steel sheet excellent in whiteness and a method for producing the same, by examining chemical treatment conditions, material surface characteristics, and coating conditions.

Means for solving the problem

[0007] As a result of the study by the present inventors, the yellowish coloring (yellowing) of the colorless clear-coated stainless steel sheet is caused by the chromate treatment, and when the clear coating film is baked, the surface of the stainless steel sheet is colored with temper color. It was found that this temper color coloring also caused yellowing. By changing the chemical conversion treatment from chromate treatment to non-chromate treatment, the thickness of the chemical conversion treatment film is optimized, and a stainless steel plate with excellent temper color resistance is used as a stainless steel plate applied to a clear-coated stainless steel plate. It became clear that yellowing prevention at the time of clear painting can be realized.

[0008] The temper color of the stainless steel sheet can be suppressed by bright annealing the stainless steel sheet with increased Si and A1 to form an acid and aluminum film containing SiO and Al 2 O on the steel sheet surface.

2 2 3

Are known. That is, as the A content increases, an acid film with Si and Al concentrated is likely to be formed, and the temper color resistance is improved. As such stainless steel, high Si steel (Patent Documents 4 and 5) and high A1 steel (Patent Document 5) are known.

Patent Document 6 is known as a heat-resistant transparent coated stainless steel plate in which A1 or Si on the surface of a ferritic stainless steel plate is regulated to 4.5 to 6 atomic%.

[0009] As a result of intensive studies on the means for solving the above problems, the present inventors have studied the chemical conversion treatment conditions, the characteristics of the material surface, and the coating conditions as described above. A clear-coated stainless steel sheet and its manufacturing method were established.

[0010] The gist of the present invention is as follows.

(1) Si stainless steel sheet with a mass ^_0/0:. 0.2 to 0 8% a ferritic stainless steel plate containing, steel sheet is Cr for definitive in depth from the surface to 50A, Si, Al, Fe atomic concentration ratio (Cr + Si + Al) ZFe has a surface oxide film of 0.6 or more. It consists of one or two types of minosilanes and epoxysilanes, and the amount of the chemical conversion treatment agent is 2 to 20 mg / m ² (the amount of SiO is measured by fluorescent X-ray), and the clear paint thickness is 1 to : LO / z

2

A clear-coated stainless steel sheet excellent in whiteness, characterized by having a coating film of m.

(2) The clear coated stainless steel sheet having excellent whiteness according to (1), wherein the stainless steel sheet further contains 8: 0.005-0.15% by mass%.

(3) The clear-coated stainless steel sheet having excellent whiteness according to (1), wherein the stainless steel sheet further contains Nb: 0.1 to 0.7% by mass.

(4) Si in a stainless steel force mass ^{_{0/0:. 0. 2~0 8}} %, A1:. 0. 005~0 15%, Nb:. 0. 1 ~0 ferritic stainless steel containing 7% The steel sheet has a surface oxide film with a Cr, Si, Al, Fe atomic concentration ratio (Cr + Si + Al) ZFe of 0.6 or more at a depth of 50 A from the surface. The chemical conversion treatment agent is composed of one or two types of aminosilane type and epoxysilane type, and the amount of the chemical conversion treatment agent is ² to 20 mgZm ²

A clear-coated stainless steel sheet with excellent whiteness, characterized in that it has a clear paint thickness of 1 to 10; ζ ΐη.

(5) The whiteness described in (1), characterized in that annealing is performed under conditions where the final bright annealing temperature Tl (° C) and the dew point T2 (° C) of the annealing atmosphere satisfy Equations 1 and 2. An excellent method for producing clear-coated stainless steel sheets.

750≤T1≤5 XT2 + 1200 ...... 1 set

-70≤Τ2≤- 30 ...... 2 formulas

(6) Si stainless steel sheet with a mass ^{_{0/0:. 0. 2~0 8}} %, A1:. 0. 005~0 a ferritic stainless steel sheet containing 15% steel plate 50 A from the surface Cr, Si, Al, Fe atomic concentration ratio (Cr + Si + Al) ZFe at a depth of up to 0.6 has a surface acid film, and the coating chemical treatment agent is aminosilane, epoxy 1 type or 2 types of silane

The amount of the chemical conversion treatment agent is ² to 20 mgZm ² (the amount of SiO is measured by fluorescent X-ray), and

2

The temperature of the final bright annealing Tl (° C) and the dew point T2 (° C) of the clear bright stainless steel material with excellent whiteness, characterized by having a coating with a thickness of 1 to 10 μm. ) Is a method for producing a clear-coated stainless steel sheet material having excellent whiteness, characterized in that annealing is performed under conditions satisfying Formulas 1 and 2. 750≤T1≤5 XT2 + 1200 ...... 1 set

-70≤Τ2≤- 30 ...... 2 formulas

(7) Si stainless steel force mass ^{_{0/0:. 0. 2~0 8}} %, A1:. 0. 005~0 15%, Nb:. 0. 1 ~0 ferritic stainless steel containing 7% The steel sheet has a surface oxide film with a Cr, Si, Al, Fe atomic concentration ratio (Cr + Si + Al) ZFe of 0.6 or more at a depth of 50 A from the surface. The chemical conversion treatment agent is composed of one or two types of aminosilane type and epoxysilane type, and the amount of the chemical conversion treatment agent is ² to 20 mgZm ²

2) and a clear-coated stainless steel plate material with excellent whiteness characterized by having a clear paint thickness of 1 to 10; ζ ΐη, and a final bright annealing temperature Tl (° C) and A method of producing a clear coated stainless steel sheet material with excellent whiteness, characterized by annealing under conditions where the dew point T2 (° C) of the annealing atmosphere satisfies Formulas 1 and 2.

750≤T1≤5 XT2 + 1200 ...... 1 set

-70≤Τ2≤- 30 ...... 2 formulas

(8) Si stainless steel sheet with a mass ^_0/0:. 0.2 to 0 8% a ferritic stainless steel plate containing, steel sheet is Cr for definitive in depth from the surface to 50A, Si, Al, Fe atomic concentration ratio (Cr + Si + Al) ZFe has a surface oxide film of 0.6 or more, and the chemical conversion treatment agent for the coating consists of one or two types of aminosilane type and epoxysilane type. The amount of treatment agent attached is 2 to 20 mg / m ² (SiO amount is measured by fluorescent X-ray), and the clear paint thickness is 1 to: LO / z

2

A clear-coated stainless steel plate material with excellent whiteness, characterized by having a coating film of m, and the final bright annealing temperature Tl (° C) and the annealing atmosphere dew point T2 (° C) satisfy Equations 1 and 2. A method for producing a clear-coated stainless steel sheet material with excellent whiteness, characterized by subjecting a ferritic stainless steel sheet that has been annealed under conditions to be cold-rolled and then subjected to final bright annealing.

750≤T1≤5 XT2 + 1200 ...... 1 set

-70≤Τ2≤- 30 ...... 2 formulas

(9) The method for producing a clear-coated stainless steel sheet material having excellent whiteness according to (6), wherein the cold bright rolled stainless steel sheet is subjected to final bright annealing after surface polishing. (10) The method for producing a clear-coated stainless steel sheet material having excellent whiteness according to (7), wherein the cold bright rolled stainless steel sheet is subjected to final bright annealing after surface polishing.

Brief Description of Drawings

[0011] FIG. 1 is a graph showing the relationship between the amount of chemical conversion deposition and the discoloration Ab * of a clear-coated stainless steel sheet.

[Fig.2] Atomic concentration ratio of Cr, Si, Al, Fe (Cr + Si + Al) ZFe in the oxide film at depths up to 50 A from the surface, and 224 ° C baking of clear-coated stainless steel sheet It is a figure which shows the relationship with discoloration Ab *.

FIG. 3 is a graph showing the relationship between the baking temperature of a polished stainless steel sheet and a steel sheet that has been subjected to bright annealing within the scope of the present invention after polishing, and the discoloration Δ b * of the clear-coated stainless steel sheet.

[Fig. 4] Atomic concentrations of Cr, Si, Al, and Fe in the acid film at an annealing temperature T1 (° C), dew point T2 (° C), and a depth of 50 A from the surface of bright annealing FIG. 5 is a diagram showing the relationship with the ratio (Cr + Si + Al) ZFe.

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] As a result of studying the pretreatment and the characteristics of the material surface of the clear coated stainless steel sheet, the present inventors have found that the following two points are important in order to obtain a clear coated stainless steel sheet with excellent whiteness. I found out. First, an aminosilane-based or epoxysilane-based chemical conversion treatment agent that is not a chromate treatment agent is used as a chemical conversion treatment agent as a pretreatment, and the amount of the chemical conversion treatment agent is adjusted to an optimum range. Second, as a stainless steel plate material, the surface is enriched with Cr, Si and Al components to prevent discoloration of the material due to temper color coloring during paint baking. The colorless clear paint may be any of polyester resin, acrylic resin, acrylic urethane resin, epoxy-modified polyester resin, and the like.

[0013] The clear chemical conversion processing of the present invention will be described.

[0014] The clear chemical conversion treatment agent of the present invention comprises one or two types of aminosilane and epoxysilane. The reason for selecting aminosilane type and epoxysilane type is that the adhesion is good when these are used, and yellow coloring can be prevented compared with the case of using a chromate treatment agent. It is also the power that can be. The amount of chemical conversion agent deposited is ² to 20 mgZm ² (measured by X-ray fluorescence.

2) and the surface temperature (MT) of the stainless steel plate material is baked and dried at 60-140 ° C.

[0015] the amount deposited at 100 ° C Nippon Parkerizing Co. E- 206 (aminosilane) in FIG. 1 is changed from 2m gZm ² to 50MgZm ² adhesion amount, 2 mu m of acrylic urethane榭脂system Kurya paints a We investigated the change in color of clear-coated stainless steel sheets that were roll-coated and baked at 200 ° C. As the stainless steel plate material used for clear coating, a tempered SUS43 0Z bright annealed material with an atomic concentration ratio (Cr + Si + Al) / Fe (described later) at a depth of 50 A from the surface of 0.6 or more is used. The yellowing caused by coloration is minimized. The vertical axis (A b *) in Fig. 1 shows the b * (2 ) Is subtracted. That is, A b * = b * (l) —b * (2).

As a result, as shown in FIG. 1, when the adhesion amount of the chemical conversion treatment agent exceeds 20 mgZm ² , the gloss of the clear coated stainless steel is lowered and slightly yellowish. When the adhesion amount is 20 mg Zm ² or less, A b * force .3 or less is obtained, and the change in color tone by chemical conversion treatment is small. On the other hand, if the chemical conversion treatment is less than ² mgZm2, the coating becomes non-uniform and the adhesion between the clear coating and the stainless steel decreases. Therefore, the deposition amount of the chemical conversion treatment agent in the present invention was 2~20mgZ m ^2. The amount of chemical conversion treatment can be quantified by measuring the amount of SiO with fluorescent X-rays on the surface of the stainless steel plate.

2

[0017] The clear coating thickness is in the range of 1 μm force to 10 μm or less. This is because it is difficult to obtain a stable color tone at 1 μm or less, and at 10 m or more, it is difficult to manufacture with one coat, and the coating cost increases. The range is preferably 2 μm to 5 μm.

Next, the material of the clear coated stainless steel sheet of the present invention will be described.

[0019] In the present invention, Cr, Si, Al, Fe atomic concentration ratio at a depth of 50 A from the surface

(Cr + Si + A1)

By using a steel sheet having a surface acid film of 6 or more, it is characterized by preventing yellowing by preventing temper color coloring during paint baking. A ferritic stainless steel sheet containing 0.2% by mass or more of Si is used, and the steel sheet is subjected to bright annealing at a predetermined temperature and atmosphere, so that the atomic concentration ratio on the surface of the steel sheet is increased as described above. It can be within an appropriate range.

[0020] Kurya stainless steel coated stainless steel sheet, Si mass ^_0/0: a ferritic stainless steel sheet containing 0.2 to 0 8%.. Since the diffusion rate of elements in ferritic stainless steel is faster than that of austenite, it is easy to concentrate Cr and Si in the film. Therefore, the present invention is limited to ferritic stainless steel plates. In particular, special steel types containing A1 and Si (Cr—A1 steel and Cr—Si steel) are relatively easy and are described in Patent Documents 4 and 5. However, in the ferritic stainless steel of the present invention, that is, a steel containing 0.2 to 0.8% of Si, a technique for concentrating Cr, Si, and A1 described below is essential. .

[0021] In the present invention, in order to form a surface-oxidized film in which Si is concentrated on the surface of the stainless steel plate, it is essential that Si is contained in an amount of 0.2% or more. This includes those used as deoxidizing elements when steel is melted. The upper limit of 0.8% of Si particularly indicates that the present invention is a general-purpose ferritic stainless steel. If more Si is contained, the composition range of general-purpose ferritic stainless steels such as SUS430 or Nb-added SUS430J1L will be exceeded. In other words, an Si addition strength of more than 0.8% is not suitable for general-purpose use because it degrades the caloric property due to the solid solution hardening action.

[0022] In the present invention, it is desirable to contain a trace amount of A1 of 0.005% or more and 0.15% or less. This is because A1, like Si, has the effect of suppressing an increase in b * during baking of the clear coating film by being concentrated in the bright annealing film as described below. A1 is added in an amount of 0.005% or more as a deoxidizing element. A large amount of A1 strength deteriorates the caulking property. Thus, A1 ί or, from 0.005 to 0.15 ^_0/0 force desirability! /ヽ.

In the present invention, the content of Cr, which is a basic component of a ferritic stainless steel sheet, can be in the range of 16.0 to 20.0% by mass. Furthermore, in order to obtain a Talia stainless steel sheet with excellent whiteness, the Cr content should be as high as possible. This is because it has the effect of promoting the concentration of Cr in the film during bright annealing. Furthermore, in the present invention, it is desirable to contain 0.1 to 0.7% of Nb. This is because the Nb oxide is more thermodynamically stable than the Cr oxide and is considered to have the same effect as Cr.

[0024] Next, in a ferritic stainless steel containing Si: 0.2 to 0.8%, surface oxide skin A technique for concentrating Cr, Si, and Al in the film will be described.

[0025] After cold rolling annealing of SUS430, which is a ferritic stainless steel, No. 4 polished material is brightly annealed, and the temperature and atmosphere of bright annealing are changed to change Cr, Si, The ratio of Al and Fe was changed. Atomic concentration ratio (0: + 31 + 8) 7 6 Aminosilane chemical conversion treatment agent is applied to the material adjusted in the range of 0.15 to 3.5 so that the amount of adhesion is 1 Omg / m ² After being baked and dried at 100 ° C., a 2 / zm acrylic urethane resin clear paint was roll-coated. Figure 2 shows the relationship between the atomic concentration ratio (Cr + Si + Al) ZFe and Ab * when the baking temperature after applying the clear paint is 224 ° C. Evaluation was based on Δ b *, which is the difference between b * and the reference material (talya-coated stainless steel plate material) after baking. As is clear from Fig. 2, the material with the atomic concentration ratio (Cr + Si + Al) ZFe adjusted to 0.6 or more has less color change due to painting and baking * less than 1 and less discoloration.

[0026] Next, a material in which the atomic concentration ratio (Cr + Si + Al) ZFe is adjusted to 0.6 or more and a material in which the atomic concentration ratio (Cr + Si + Al) / Fe ^ O. Then, the baking temperature was changed from 150 ° C to 250 ° C, and the change in color tone was observed. Except for differences in baking temperature and varieties, it is the same as in Fig. 2 above. In Fig. 3, the atomic concentration ratio (Cr + Si + Al) ZFe is about 3 for materials marked with ◯. For 參 and ▲, the atomic concentration ratio (+1 31 + 8) 7 6 is about 0.4 and about 0.2, respectively. As a result, as shown in Fig. 3, the material with (Cr + Si + Al) ZFe adjusted to 0.6 or higher by bright annealing shows little change in color tone due to painting and baking. On the other hand, materials that are not brightly annealed after polishing and processed under bright annealing conditions that are outside the scope of the present invention and whose atomic concentration ratio (Cr + Si + Al) ZFe is adjusted to less than 0.6 are painted and baked. This is particularly noticeable when the yellowish discoloration is large and the baking temperature is higher than S200 ° C.

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) ZFe at the highest oxygen concentration is obtained. . In the present invention, it is extremely important that (0: + 31 + 8) 7 6 is controlled to 0.6 or more to obtain a surface oxide film having a concentration of Cr or Si. In this case, Si is concentrated in the outer layer of the surface oxide film, and A1 is concentrated in the inner layer near Baltha. The reason for this is that the bright annealing conditions are the conditions for reduction for Si, the conditions for oxidation for Si and Al, and more than for SiO. This is because Al 2 O has a lower dissociation pressure. Depending on the method of measuring the surface oxide film,

twenty three

(Cr + Si + Al) ZFe is considered to have a different appropriate range. Required surface oxide film structure is the same as described above.

[0028] The atomic concentration ratio (Cr + Si + Al) ZFe in the surface acid-coated film of the cold-rolled annealed material and the polished finish is about 0.2. Therefore, the present inventors performed bright annealing on the stainless steel sheet, and the atomic concentration ratio of Cr, Si, Al, Fe (Cr + Si + Al) ZFe at a depth of up to 50 A was 0.6 or more. The bright annealing conditions for forming an oxide film were investigated.

[0029] Bright annealing is generally a reducing property in which hydrogen and nitrogen are mixed in a ratio of H: N = (1-9): 1.

twenty two

In the atmosphere, the components in the oxide film after annealing change depending on the combination of annealing temperature Tl (° C) and atmospheric dew point T2 (° C).

[0030] Cold-rolled SUS430J1L and SUS430 steel sheets were subjected to cold-rolling annealing or mechanical polishing equivalent to No. 4 finish (JIS G 0203 No. 5349) to obtain various annealing temperatures Tl (° C). Figure 4 shows the results of bright annealing at the atmospheric dew point T2 (° C). With the annealing temperature T1 on the horizontal axis and the atmospheric dew point T2 on the vertical axis, the range in which the (Cr + Si + Al) ZFe atomic concentration ratio at a depth of up to 50 A from each surface is stable is 0.6 or more. ,

750≤T1≤5 XT2 + 1200 ...... 1 set

-70≤Τ2≤- 30 ...... 2 formulas

It is.

[0031] In the range of Formulas 1 and 2, Cr is a condition for reduction, while Si and Al are conditions for oxidation. Therefore, the concentration of active ingredients (Si, Al) due to selective oxidation into the film is increased. Is effectively done. When the bright annealing temperature Tl (° C) is less than 750 ° C, the diffusion transfer of effective elements (Si, Al) centered on Cr is slow, and the oxide film should have a sufficient atomic concentration ratio. ,. Also, if the temperature T1 (° C) exceeds (5 XT2 + 1200) ° C, the condition on the reduction side is even more than the range of Equation 1, so selective oxidation of Si and A1 is suppressed, and a sufficient atomic concentration ratio It does not become an oxide film. Therefore, the bright annealing temperature T1 (° C) should be in the range of equation 1, which determines the relationship with the dew point. Preferably it is 800 ° C or higher and 1000 ° C or lower. More preferably, it is 800 ° C or higher and 900 ° C or lower.

[0032] The dew point T2 (° C) of bright annealing exceeds 30 ° C, and the oxidation of Fe becomes intense and the surface is oxidized. Since the concentration of Fe in the film is inevitable and discolors due to the temper color, it is not preferable as a material for clear-coated stainless steel sheets. In addition, gas dew points below 70 ° C are very difficult industrially. Therefore, the dew point of bright annealing should be in the range of formula 2. Preferably, it is -60 ° C or higher and lower than 35 ° C.

[0033] Although the temper color coloring is less at the Si concentration of 0.3% in the one described in Patent Document 5, the example of the Si concentration of 0.3% in the same document is the temper color coloring score 3 (yellow). Thus, it is not possible to obtain a clear-coated stainless steel sheet having excellent whiteness. In the present invention, the atomic concentration ratio (Cr + Si + Al) ZFe in the oxide film is clearly defined as 0.6 or more, and the manufacturing conditions that can realize this atomic concentration ratio are clarified. As a result, it became possible to obtain a clear-coated stainless steel sheet with excellent whiteness even at a low Si concentration of 0.8% or less.

[0034] A polished finish with a surface pattern peculiar to stainless steel with polished eyes is useful as a member for which design is important. However, the surface coating of stainless steel that has undergone surface polishing has very little concentration of Cr, Si, and A1, so it turns yellow when applying a clear coating, and has high design with excellent whiteness. No clear-coated stainless steel sheet can be obtained. Therefore, it is necessary to perform bright annealing to concentrate Cr, Si, A1 in the surface coating.However, if bright annealing is performed after surface polishing of a normal stainless steel sheet that has been subjected to soft annealing, the manufacturing process Becomes complicated and causes cost increase. Therefore, in the present invention, it is preferable to subject the cold-rolled stainless steel sheet to the final bright annealing after surface polishing. The cold rolling-surface polishing-bright annealing manufacturing process is used for soft 匕 annealing for material preparation and enrichment of Cr, Si, A1 in the surface coating (high (Cr + Si + Al) Z Fe) Can be performed simultaneously by one bright annealing. In particular, in the ferritic stainless steel sheet of the present invention, the recrystallization temperature can be controlled and adjusted by the Nb content in order to match the softening temperature with the concentration temperature of Cr, Si, A1 in the surface film. Is possible. In the case of an austenitic stainless steel sheet, solid solution annealing is usually 1000 ° C or higher, so it does not match the temperature at which Cr, Si, A1 concentrates in the surface film. Therefore, after cold rolling-polishing, it is necessary to provide two annealing steps, namely, solid solution annealing and bright annealing for forming an acid coating. Example

Table 1 shows examples and comparative examples of the present invention. The surface finish of the ferritic stainless steel sheet was classified into three types: No. 4 (fine, polished finish for eyes), HL (polished hairline), and 2B (skin rolled lightly after pickling). These ferritic stainless steel sheets were brightly annealed under the conditions shown in Table 1. Note that 2B-finished ferritic stainless steel sheet is a manufacturing process that is annealed after cold rolling, while other surface-finished products are not annealed after cold rolling. Softening is also performed at the same time. In addition, those marked with ○ in the condition of bright annealing conditions indicate that the conditions are met, and those marked with X indicate that the conditions are not met. Similarly, in whiteness, those indicated by ◯ indicate that the whiteness is excellent, and those indicated by X indicate that the whiteness is inferior.

[0036] [Table 1-1]

Table 1 ¾ [1

Table 1 (continued) s¾ll

In ¾ 4 «¾¾ft¾ * e¾¼« «* 5« ¾κΜΕΰ ※※ Set * ^^ ※ ¾k One inch zλ! κ;: ..,;-ι1.--,. ,

[0037] For each ferritic stainless steel sheet after bright annealing, the atomic concentration ratios of Cr, Si, Al, and Fe in the oxide film at depths up to 50 A from the surface were measured by AES (Audience Electron Spectroscopy). The atomic concentration ratio (Cr + Si + Al) ZFe was determined by an analysis method.

[0038] For each ferritic stainless steel sheet after bright annealing, chemical conversion treatment (E-206) from Nippon Parkerizing Co., Ltd. was used as the chemical conversion treatment. In the range of ² mg / m ² to 50 mg / m ² . ratio As a comparison, the chemical conversion treatment agent was chromated. Thereafter, 1-10 μm of acrylic urethane resin-based tarilla coating was treated at a baking temperature of 220 ° C.

[0039] The color tone after clear coating was measured by b * QIS Z8729) to evaluate the degree of discoloration.

[0040] In the example of the present invention, the atomic concentration ratio in the acid coating on the surface of the ferritic stainless steel plate is 0.

Clear coating steel sheet with excellent whiteness with b * of 2 or less by applying a chemical conversion treatment of 6 or more, consisting of one or two aminosilanes and epoxysilanes, to an adhesion amount of 2 to 20 mg / m ² In contrast, in the comparative example, b * is a yellowish tara-coated steel sheet with a color value exceeding 2. Depending on the viewing angle, it looks black and has a color tone.

[0041] In Comparative Example 20, since the Si component of the stainless steel plate deviated from the lower limit, (Cr + Si + Al) ZFe in the oxide film deviated from the lower limit, and b * was 2 or more, resulting in poor whiteness. In Comparative Examples 21 to 25, one of temperature T1 and dew point T2 under bright annealing conditions deviated from the upper and lower limits, so (Cr + Si + Al) ZFe in the acid film was outside the lower limit, and b * was 2 or more and white Inferior. In particular, Comparative Example 25 does not measure (Cr + Si + Al) ZFe because the temper color of the stainless steel plate material was clearly observed. In Comparative Examples 26 to 32, (0: + 31 + 8) 76 of the material is 0.6 or more, but the conditions of the chemical conversion treatment agent are out of the scope of the present invention. In Comparative Example 26, the adhesion amount of the chemical conversion treatment agent deviated from the lower limit, resulting in poor adhesion. In Comparative Example 27, the adhesion amount of the chemical conversion treatment agent deviated from the upper limit, and in Comparative Example 28, the chemical conversion treatment agent was a chromate agent and not the non-chromate treatment agent of the present invention. Inferior. In Comparative Examples 29 and 31, the clear paint thickness is outside the lower limit, and the color tone is unstable. In Comparative Examples 30 and 32, the clear paint thickness is outside the upper limit, making it difficult to manufacture.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention. The present invention is not limited by the above description, but only by the scope of the appended claims.

Industrial applicability

[0042] According to the present invention in which the relationship between the design and color tone of the clear-coated stainless steel sheet was examined, b * (chromaticity, yellow Z blue degree, JIS Z 8729) is in the range of 0 to 2, and the whiteness This makes it possible to produce clear-coated steel sheets that excel in the quality. In general clear painted stainless steel sheet, b * is 4 Depending on the viewing angle, it may look dark. On the other hand, the tara-coated stainless steel sheet of the present invention is whitish and does not look dark due to the viewing direction.

Claims

The scope of the claims

[1] Si a stainless steel plate is a mass ^_0/0:. 0.2 to 0 a ferritic stainless steel sheet containing 8% steel plate Cr which definitive in depth from the surface to 50A, Si, Al, Fe Atomic concentration ratio (Cr + Si + A1)

It has 6 or more surface oxide films, and the coating chemical conversion agent consists of one or two types of amino silane type and epoxy silane type, and the amount of the chemical conversion treatment agent is ² to 20 mgZm ² And measure the SiO amount), and the clear paint thickness is l ~ 10 / zm

2

A clear-coated stainless steel sheet with excellent whiteness, characterized by having a coating film.

[2] The clear coated stainless steel sheet having excellent whiteness according to [1], wherein the stainless steel sheet contains A1: 0.005-0.15% by mass.

[3] The clear coated stainless steel plate having excellent whiteness according to claim 1, wherein the stainless steel plate contains Nb: 0.1 to 0.7% by mass.

[4] Si a stainless steel plate is a mass ^{_{0/0:. 0. 2~0 8}} %, A1:. 0. 005~0 15%, Nb: ferritic stainless steel sheet containing from 0.1 to 0.7% The steel sheet has a surface oxide film with a Cr, Si, Al, 6 atomic concentration ratio (0: +31 + 8) 7 6 at a depth of 50 A from the surface of the steel plate of 0.6 or more. The coating chemical conversion treatment agent is composed of one or two types of aminosilane type and epoxysilane type, and the amount of the chemical conversion treatment agent is ² to 20 mgZm ²

[5] The whiteness degree according to claim 1, wherein the annealing is performed under the conditions that the temperature Tl (° C) of the final bright annealing and the dew point T2 (° C) of the annealing atmosphere satisfy the formulas 1 and 2. This is a method of manufacturing a tara-coated stainless steel sheet material that excels in performance.

750≤T1≤5 XT2 + 1200 ...... 1 set

-70≤Τ2≤- 30 ...... 2 formulas

[6] Si a stainless steel plate is a mass ^{_{0/0:. 0. 2~0 8}} %, A1:. 0. 005~0 a full write stainless steel containing 15% steel plate 50 from the surface Cr, Si, Al, Fe atomic concentration ratio at depths up to A (Cr + Si + Al) ZFe has a surface oxide film of 0.6 or more, and the chemical conversion treatment agent of the film is aminosilane type, epoxysilane type The amount of adhesion of the chemical conversion treatment agent is ² to 20 mgZm ² (the amount of SiO is measured by fluorescent X-ray). Clear coating with excellent whiteness, characterized by having a coating thickness of 1 to 10; ζ ΐη. Temperature of final bright annealing Tl (° C) and annealing atmosphere dew point T2 (° C ) Is a method for producing a clear-coated stainless steel sheet material having excellent whiteness, characterized in that annealing is performed under conditions satisfying Formulas 1 and 2.

750≤T1≤5 XT2 + 1200 ...... 1 set

-70≤Τ2≤- 30 ...... 2 formulas

[7] Si a stainless steel plate is a mass ^{_{0/0:. 0. 2~0 8}} %, A1:. 0. 005~0 15%, Nb: ferritic stainless steel sheet containing from 0.1 to 0.7 percent The steel sheet has a surface oxide film with a Cr, Si, A1, 6 atomic concentration ratio (0: +31 + 8) 7 6 at a depth of up to 50 A from the surface. The coating chemical conversion treatment agent is composed of one or two types of aminosilane type and epoxysilane type, and the amount of the chemical conversion treatment agent is ² to 20 mgZm ²

750≤T1≤5 XT2 + 1200 ...... 1 set

-70≤Τ2≤- 30 ...... 2 formulas

[8] Si a stainless steel plate is a mass ^_0/0:. 0.2 to 0 a ferritic stainless steel sheet containing 8% steel plate Cr which definitive in depth from the surface to 50A, Si, Al, Fe Atomic concentration ratio

The coating chemical conversion treatment agent is composed of one or two types of amino silane type and epoxy silane type, and the amount of the chemical conversion treatment agent is ² to 20 mgZm ² (the amount of SiO is measured by fluorescent X-ray). Paint thickness l ~ 10 / zm

2

A clear-coated stainless steel sheet material with excellent whiteness, characterized by having a coating film, on the condition that the final bright annealing temperature Tl (° C) and the annealing atmosphere dew point T2 (° C) satisfy Equations 1 and 2. A method for producing a clear-coated stainless steel sheet material with excellent whiteness, characterized by subjecting a bright stainless steel sheet, which has been annealed and cold-rolled, to surface polishing and then final bright annealing.

750≤T1≤5 XT2 + 1200 ...... 1 set -70≤T2≤- 30 ...... 2 formulas

[9] The method for producing a clear coated stainless steel sheet material having excellent whiteness according to [6], wherein the cold bright rolled stainless steel sheet is subjected to final bright annealing after surface polishing.

10. The method for producing a clear coated stainless steel sheet material having excellent whiteness according to claim 7, wherein the bright bright stainless steel sheet that has been cold-rolled is subjected to final bright annealing after surface polishing.