JP2006283182A - Surface-treated stainless steel sheet for metal gasket, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-treated stainless steel sheet for a metal gasket capable of ensuring the long-term liquid anti-freezing property and waterproof adhesiveness after the rubber coating with a chromium-free surface treatment performed thereon. <P>SOLUTION: A surface treatment solution containing an organic resin having a structure shown in the figure, silica, fluoride of Ti and/or Zr of the amount as the metal of Ti and/or Zr being &ge; 1.0 part and &le; 7.0 parts to the total 100 parts of the organic resin and silica, and preferably a coupling agent is coated on at least one side of a stainless steel sheet, and the stainless steel sheet is dried at the highest attained plate temperature of &ge; 200&deg;C at least for 30 seconds to form a surface-treated layer. In the formula, Y<SB>1</SB>, Y<SB>2</SB>are hydrogen, alkyl aminomethyl group, or alkyl ammonium methyl group, which are independent from each other. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a surface-treated stainless steel plate for a metal gasket, and more particularly to a surface-treated stainless steel plate for heat-resistant rubber coating used for a cylinder gasket of an automobile engine or the like. The present invention also relates to a method for producing such a surface-treated stainless steel sheet.

  Cylinder gasket materials for automobile engines and the like must be able to maintain sealability under conditions of high temperature and high pressure. Conventionally, asbestos and carbon have been used. Recently, metal gaskets mainly using stainless steel plates are becoming mainstream mainly due to problems of environmental harm in asbestos and sealing properties in carbon.

  Since a cylinder head such as an automobile engine is subjected to a strong pressure fluctuation cycle in an explosion cycle in the cylinder, the gasket needs to exhibit a sealing characteristic that can sufficiently withstand this pressure fluctuation. In the case of a metal gasket, a heat resistant rubber coating is generally applied to the surface of a stainless steel plate in order to ensure this sealing property.

  Conventionally, in order to ensure adhesion between the rubber coating and the metal, for example, a chromate treatment as described in Patent Document 1 has been performed. The chromate treatment has been generally used for plated steel sheets such as galvanized steel sheets in addition to stainless steel sheets. However, the hexavalent chromium compound contained in the chromate treatment solution is water-soluble, and environmental pollution becomes a problem when it is eluted. Therefore, recently, there is an increasing demand for chromium-free processing.

In the case of so-called chromium-free chemical conversion treatment that does not contain chromium, it is said to be inferior in long-term water-resistant adhesion or antifreeze resistance compared to chromate treatment.
Several techniques have been disclosed so far for examples in which a chemical conversion treatment not containing chromium is performed on a stainless steel plate. For example, Patent Literature 2, Patent Literature 3, and Patent Literature 4 propose a stainless steel plate for gaskets made of phosphoric acid and silica and subjected to chromium-free treatment. However, only a relatively short term antifreeze resistance performance is shown.

  Patent Literature 5, Patent Literature 6, and Patent Literature 7 propose chromium-free surface treatment for coated steel sheets with a transparent coating film. However, there are descriptions such as antifreeze resistance and heat resistance essential for gaskets. However, as it is, it is not suitable as a stainless steel sheet for gaskets that requires long-term antifreeze resistance.

  In recent years, technological development related to chromium-free chemical conversion treatment for metal gaskets has progressed. For example, Patent Document 8 discloses an example in which the surface is treated with hot nitric acid, a baking type adhesive is applied, and baking is performed. Further, Patent Document 9 discloses a chemical conversion treatment technique mainly composed of trivalent chromium that does not contain hexavalent chromium. However, trivalent chromium itself cannot be said to be harmful, and development of chemical conversion treatment using a chromium-free treatment solution is desired from the market. In response to this, Patent Document 10 and Patent Document 11 propose a treated steel sheet in which a film is formed from a treatment liquid obtained by adding a resin or silica to a Ti compound or a Zr compound.

However, even in the techniques proposed in these patent documents, only the antifreeze resistance of the heat-resistant rubber coating has been investigated, and the water-resistant adhesion has not been studied in detail. In recent engine gaskets, LLC (Long Life Coolant, long-life refrigerant) is not always used as a coolant, so water-resistant adhesion is also an important position, combining anti-freeze and water-resistant adhesion. Each manufacturer is improving its performance. When a chromium-free surface treatment solution is used, the problem is that the water-resistant adhesion is particularly inferior to chromate.
Japanese Patent Laid-Open No. 9-122580 JP-A-8-10699 JP-A-8-10700 JP-A-8-58015 Japanese Patent Laid-Open No. 5-169584 Japanese Patent Laid-Open No. 9-10678 Japanese Patent Laid-Open No. 9-24578 JP 2003-246975 A JP 2003-342745 A JP 2002-264253 A JP 2003-105321 A

  The present invention is a stainless steel plate having excellent adhesion to a stainless steel plate and a rubber coating, ensuring long-term antifreeze and water adhesion after rubber coating, and subjected to an environmentally friendly chromium-free surface treatment and a method for producing the same It is an issue to provide.

  The present inventors formed various surface treatment layers on the surface of a stainless steel plate according to the above-described conventional technique, and then applied a fluororubber or NBR rubber coating, and were subjected to long-term water-resistant adhesion and antifreeze-resistant adhesion after 500 and 1000 hours. The adhesiveness with a steel plate and rubber was investigated by testing the property.

  As a result, as will be shown later as a reference example, it has been found that the conventional chromium-free surface treatment has an antifreeze resistance that is as good as that of the chromate treatment, but water adhesion is significantly inferior to that of the chromate treatment. In other words, the investigation of antifreeze resistance alone is not sufficient, and the evaluation of the surface-treated stainless steel sheet for metal gaskets is insufficient unless water resistance adhesion is also evaluated.

  Furthermore, when these results were investigated in detail, it was found that the chromium-free surface-treated product had different locations where peeling occurred when the antifreeze resistance was poor and when the water adhesion was poor. That is, when water resistance is poor, peeling is mainly at the interface between the chromium-free surface treatment layer and the stainless steel plate, whereas when antifreeze resistance is poor, the surface treatment layer and adhesive or rubber are used. Peeling at the interface with the coating was the main. On the other hand, when the adhesion was inferior in the chromate-treated product, it was peeling at the interface between the chromate layer and the adhesive or rubber coating in the antifreeze resistance test, and the water adhesion was not inferior.

  Thus, in the case of chromium-free surface treatment, securing water-resistant adhesion, which was not a problem with conventional chromate products, becomes a problem, and the cause is the lack of adhesion between the steel sheet and the chromium-free surface treatment layer. It was a weak point not found in chromate products.

  According to the present invention, a surface treatment layer containing an organic resin, silica, and a specific amount of one or both of fluorides of Ti and Zr is formed on the surface of the stainless steel plate, thereby improving the resistance after rubber coating. Not only antifreeze properties but also water adhesion can be improved.

  In one aspect, the present invention comprises a surface treatment layer that includes an organic resin, silica, fluoride-derived Ti and / or Zr, and is substantially free of chromium on at least one surface of a stainless steel plate. The amount of Ti and / or Zr derived from fluoride in the layer as a metal is 1.0 part by mass or more and 7.0 parts by mass or less with respect to 100 parts by mass of the total amount of the organic resin and silica. A surface-treated stainless steel sheet for metal gaskets.

  From another aspect, the present invention applies, to at least one surface of a stainless steel plate, a surface treatment liquid containing an organic resin, silica, and a fluoride of Ti and / or Zr and substantially free of chromium, Next, the method is a method for producing a surface-treated stainless steel sheet for a metal gasket, characterized in that drying is performed for 30 seconds or more under a temperature condition where the maximum plate temperature is 200 ° C. or higher.

  “Substantially free of chromium” means that no chromium compound is actively added, but the presence of impurity level chromium is allowed. Specifically, the presence of less than 1% by weight of chromium based on total solids is acceptable.

In preferred embodiments, the present invention further satisfies one or more of the following conditions:
The silica has a specific surface area of 50 m ² / g or more;
The surface treatment layer contains both fluoride-derived Ti and Zr, and the mass ratio of these metals satisfies the following formula:
Zr ≧ 0.3Ti (Formula 1);
-The adhesion amount of the said surface treatment layer is 100 mg / m < ² > or more and 300 mg / m < ² > or less;
-The organic resin is a water-soluble polymer having a structure represented by the following formula (existing as a cross-linked product in the film):

In the formula, Y ₁ and Y ₂ are each independently hydrogen, an alkylaminomethyl group, or an alkylammonium methyl group, and n is 2 to 50;
-Performing the drying multiple times;
-After the drying, cooling the steel sheet without bringing water into contact with the steel sheet surface;
-The surface treatment solution is an aqueous treatment solution having a pH of 2.0 or more and 4.5 or less;
・ Before applying the surface treatment liquid, anneal the steel plate and then pickle.

  According to the present invention, long-term heat resistance, oil resistance, and LLC resistance essential for engine gaskets can be ensured by surface treatment using an environment-friendly chromium-free treatment liquid, thereby ensuring long-term antifreeze and water resistance. Since it is possible to supply engine gaskets that exhibit adhesion, the technical significance of the industrial aspect is high.

In the following, the present invention will be described in detail with respect to particularly preferred embodiments. In the following description, “%” means “% by mass” unless otherwise specified.
[Stainless steel sheet]
The type of the stainless steel plate used for the gasket may be any type such as austenite and ferrite. However, austenitic stainless steel sheets are generally used for gasket applications because they require corrosion resistance under the engine environment, strength as a spring material, and fatigue characteristics of the bead processed portion. In particular, SUS301 (17% Cr-7% Ni), which is a quasi-austenitic stainless steel sheet, is annealed → pickled or brightly annealed and then cold rolled to increase the strength by work hardening. These are also suitable in the present invention.

  In the present invention, since improvement in adhesion between the chromium-free surface treatment layer and the steel plate is a problem, the roughest surface of the stainless steel plate is advantageous in improving the adhesion of the surface treatment layer. Specifically, Ra is preferably 0.10 μm or more, and Rz is preferably 0.50 μm or more. However, since the stainless steel plate used for the metal gasket has the highest priority on the sealing function, a smaller roughness is preferable for this purpose. Therefore, Ra is preferably 0.4 μm or less, and Rz is preferably 1.0 μm or less. In addition, as a steel sheet manufacturing process, the process of removing the scale by annealing → pickling has produced many fine irregularities on the steel sheet surface, rather than the process using bright annealing in the annealing process in the middle process, Since it contributes to improvement in adhesion, it is more preferable for the present invention.

[Surface treatment layer]
The surface treatment layer formed on at least one surface of the stainless steel plate according to the present invention is a chromium-free coating substantially free of chromium. This surface treatment layer is an organic-inorganic composite coating containing an organic resin, silica, and one or both of Ti and Zr derived from fluoride. Therefore, the surface treatment liquid used for the surface treatment contains a fluoride of Ti and / or Zr. The fluorides of Ti and Zr may be titanium tetrafluoride and zirconium tetrafluoride, and hydrates and hydrolysates thereof, which may be used in an aqueous solution state. Hexafluorotitanic acid and hexafluorozirconic acid and salts thereof used in Patent Documents 10 and 11 are not included in the Ti fluoride and Zr fluoride in the present invention.

  The organic resin is a main component of the surface treatment layer, and mainly bears an adhesion function with the stainless steel plate and the surface treatment layer. The silica component has a function of improving adhesion to an adhesive or rubber coating applied to the upper layer of the surface treatment layer.

  The fluoride of Ti and / or Zr is hydrolyzed in the surface treatment liquid to become a hydroxide of Ti or Zr, and fluorine ions are liberated. A highly reactive Ti / Zr hydroxide (eg, Ti-OH) produced by this hydrolysis causes a cross-linking reaction with an organic resin or silica (or silanol), resulting in a fine surface treatment with good adhesion. Form a layer. Further, F ions liberated by hydrolysis etch the steel sheet surface, but fluorine ions are volatilized as HF during drying. As a result, a bond of —O—Ti (Zr) —O—organic resin is formed on the stainless steel plate, and a surface treatment layer composed of a dense film having good water resistance and water adhesion is generated.

  The amount of Ti and / or Zr in the surface treatment layer as a metal is an amount that is 1 part by mass or more and 7 parts by mass or less with respect to 100 parts by mass of the total amount of the organic resin and silica. This amount is calculated on a solid basis for each component. If both Ti and Zr are present, the total amount is calculated.

  When the amount of Ti and / or Zr is below the above range, the crosslinking function due to the function (1) is insufficient, the water resistance and the water-resistant adhesion are inferior, and when it exceeds the above range, the stability of the surface treatment liquid is lost. In many cases, the effect of improving water resistance and water adhesion is saturated. A preferable range of the amount of Ti and / or Zr is 2.0 parts by mass or more and 5.0 parts by mass or less, more preferably 2.5 parts by mass with respect to 100 parts by mass of the total amount of the organic resin and silica. The amount is 4.0 parts by mass or less.

  The type of the organic resin used in the present invention is not particularly limited. For example, an epoxy resin, a phenol resin, an acrylic resin, a silicone resin, or the like can be used. However, in order to obtain higher water-resistant adhesion, a particularly preferable organic resin is , Has the structure represented by the following formula.

In the formula, Y ₁ and Y ₂ are each independently hydrogen, an alkylaminomethyl group, or an alkylammonium methyl group, and n is 2 to 50.

  This resin is a water-soluble oligomer or polymer obtained by polycondensation of alkylaminomethyl or alkylammonium methyl substituted bisphenol A and formaldehyde, and can be called amino or ammonium methyl substituted vinyl bisphenol A resin. Examples of the alkylaminomethyl group include a dimethylaminomethyl group and a diethylaminomethyl group. Examples of the alkyl ammonium methyl group include a trimethyl ammonium methyl group and a triethyl ammonium methyl group.

  In this resin, an alkylamino group or an alkylammonium group reacts with a fluoride of Ti or Zr to introduce a cross-linked structure of —O—Ti (Zr) —O—organic resin into the surface treatment layer. Can contribute to improving the water-resistant adhesion of the surface treatment layer. For the same reason, polyethyleneimine and its derivatives can also be preferably used.

As silica, colloidal particle diameter silica (colloidal silica) is preferable, and both liquid phase silica (colloidal silica or aqueous silica) and gas phase silica (fumed silica, dry silica) can be used. The average primary particle size should be small, and a particle size of 0.1 μm or less is preferably used. Moreover, it is preferable for the specific surface area to be 50 m ² / g or more because the water-resistant adhesion is further improved. The specific surface area is more preferably 150 m ² / g or more. The reason why the adhesiveness is improved when the specific surface area is 50 m ² / g or more is not clear at this time, but as an estimation reason, it has more Si—OH groups, so that the number of hydrogen bond starting points increases. It is conceivable that the adhesiveness is improved and that the specific surface area is increased, so that the surface becomes more complicated and the adhesiveness is improved by the anchor effect.

  From the viewpoint that a larger specific surface area contributes to improvement in adhesion, vapor phase silica is more suitable. As the gas phase silica, Aerosil 130 manufactured by Nippon Aerosil Co., Ltd. is used. The larger the specific surface area, the better the adhesion, so there is no particular upper limit on the specific surface area. However, if silica with a large specific surface area is used, the viscosity of the surface treatment liquid will increase significantly, and the stainless steel plate for the surface treatment liquid will be used. It becomes difficult to apply to. Therefore, it is not preferable to use silica having a specific surface area that makes the thickening effect remarkable.

  The mass ratio of the organic resin to silica is preferably in the range of 95: 5 to 50:50, more preferably in the range of 90:10 to 70:30. When the amount of silica increases, the surface tends to powder and the adhesion tends to be impaired. In addition, the surface treatment liquid is thickened by the above-described thickening action of silica, making application difficult. On the other hand, when there is too little silica, sufficient adhesiveness with the stainless steel plate and rubber coating of a surface treatment layer is not acquired.

  Fluoride-derived Ti and Zr contained in the surface treatment layer may be either one or both of them. When Ti and Zr are used in combination, better performance can be obtained if the mass ratio of Ti and Zr as a metal is in the range of the following formula 1. The reason is unclear, but Zr can improve the water resistance or water-resistant adhesion of the surface treatment layer even if it is quantitatively larger than Ti.

Zr ≧ 0.3Ti (Formula 1)
When Zr <0.3Ti, even if the total amount of Zr + Ti in the surface treatment layer is within the above range, the water resistance and water-resistant adhesion tend to be slightly inferior compared to the case where Zr ≧ 0.3Ti. It can be seen. Particularly preferred is a range of Zr ≧ 0.4Ti. However, when Zr is used alone, sufficient performance may not be obtained. It is also conceivable that the effects of Ti and Zr are slightly different. That is, it can be inferred that among the functions of Ti and Zr described above, Ti contributes a lot to function (2), and Zr contributes a lot to function (1). In function (1) and function (2), function (1) is a function related to the entire surface treatment layer, whereas function (2) is a function to strengthen the interface between the surface treatment layer and the stainless steel plate. Therefore, Ti and Zr related to the function (2) may be small, whereas Ti and Zr related to the function (1) are not much. Therefore, if Ti + Zr is a fixed amount, a higher Zr ratio can obtain better adhesion, and the combined use of Ti and Zr leads to better water-resistant adhesion. it is conceivable that.

The adhesion amount of the surface treatment layer containing an organic resin, silica and fluoride-derived Ti and / or Zr is preferably 100 mg / m ² or more and 500 mg / m ² or less. If it is less than 100 mg / m ² , the water-resistant adhesion is reduced by one rank, and if it exceeds 500 mg / m ² , the rubber adhesion of the bent portion may be lowered. A more preferable range of the adhesion amount is 100 mg / m ² or more and 300 mg / m ² or less.

  In addition to the above components, the surface treatment layer may contain various additives for improving performance. In particular, coupling agents such as silane coupling agents and titanate coupling agents are effective in crosslinking organic resins, strengthening the bond between stainless steel plate and organic resin, and strengthening the bond between the upper layer adhesive and rubber coating. is there. When using a coupling agent, the addition amount is preferably 0.1 parts by mass or more and 2 parts by mass or less, more preferably 0.5 parts by mass or more, with respect to 100 parts by mass of the total amount of the organic resin and silica. 1.5 parts by mass or less. If the addition amount is small, the effect is not seen, and if the addition amount is too large, the stability of the surface treatment liquid used for coating is lost.

  In addition, the surface treatment liquid used for forming the surface treatment layer is added with a wettability improver and an anti-skinning agent for improving coatability, or an acid-based additive for promoting a crosslinking reaction. May be.

[Method for producing surface-treated steel sheet]
The surface-treated stainless steel plate for metal gasket of the present invention having the above-described surface treatment layer contains an organic resin, silica, and Ti and / or Zr fluoride on at least one surface of the stainless steel plate, and substantially contains chromium. It can manufacture by apply | coating the surface treatment liquid which does not contain, and then drying for 30 second or more on the temperature conditions in which the highest ultimate board temperature becomes 200 degreeC or more.

  The above-described components used in the surface treatment liquid and optional components that can be added as desired are as described above. The solvent of the surface treatment liquid is usually water, but a mixed solvent of water and a water-miscible organic solvent in an amount of less than 50% can also be used. This surface treatment liquid etches the surface of a stainless steel plate by the etching function of Ti or Zr fluoride, thereby generating a bond of —O—Ti (Zr) —O—organic resin, thereby improving the water-resistant adhesion of the coating. Improve. In order to increase the etching power of the liquid, it is advantageous that the surface treatment liquid is acidic and the pH is low. However, if the pH is too low, the thickening due to silica increases and the coatability decreases. The preferred pH of the surface treatment solution is 2.0 or more and 4.5 or less, and more preferably in the range of 2.5 to 4.0.

  The surface treatment liquid can be applied by a known method such as roll coating, spray coating, dipping method, dipping → Ringer squeezing method, or curtain flow coating. In consideration of the finished appearance and the ease of control to the above-mentioned preferable adhesion amount range, roll coating is preferable.

  In the above coating method, if the viscosity of the surface treatment liquid is high, foaming of the treatment liquid or a surface pattern after coating is likely to occur. Therefore, the viscosity of the surface treatment liquid used for coating is preferably 20 cp or less. . For that purpose, it is preferable to control the addition amount of Ti and Zr salt and the kind (specific surface area) and addition amount of silica to be added as described above. In order to improve the wettability by the treatment liquid before the application of the surface treatment liquid, it is also effective to subject the stainless steel plate to alkaline degreasing, solvent degreasing, hot water washing or pickling, and these pretreatments are performed according to the present invention. It does not interfere with the effect.

  After applying the surface treatment liquid, drying is performed. In order to obtain sufficient water-resistant adhesion, it is preferable that the temperature during drying is a temperature at which the maximum plate temperature is 200 ° C. or more, and the drying time is 30 seconds or more. In particular, when the amount of Ti and / or Zr is small, stable adhesion can be obtained by increasing the drying temperature and / or increasing the drying time. Further, if the production facility can perform a plurality of times of drying, more stable water-resistant adhesion can be obtained by performing the drying a plurality of times.

  For example, taking an ordinary thin coil coating line as an example, in many cases, two or more roll coaters and two or more drying furnaces are installed. In that case, the surface treatment liquid according to the present invention is applied from the entrance side of the coil with the first roll coater, and the steel sheet is dried at a temperature of 200 ° C. or higher for 30 seconds or longer in one of the two subsequent drying furnaces. . By repeating drying at a steel plate temperature of 200 ° C. or more and 30 seconds or more in two or more drying furnaces, the water-resistant adhesion can be further improved. Further, the higher the drying temperature, the better the water resistant adhesion. The upper limit of the drying temperature is preferably 400 ° C. or less, although it depends on the capacity of the drying furnace. When it exceeds 400 ° C., an oxide scale is generated on the surface of the stainless steel plate, and the adhesion may be impaired. The drying temperature is more preferably 350 ° C. or less, and further desirably 320 ° C. or less.

  If the drying time is too long, the above-mentioned problem of oxide scale occurs and the productivity is also adversely affected. Therefore, the drying time is preferably 3 minutes or less, and more preferably 2 minutes or less. What is necessary is just to determine drying time by the evaluation of the adhesiveness of the surface treatment steel plate manufactured and the capability (heating rate of a drying furnace, the capability of a furnace) of the equipment to manufacture.

  The cooling after drying is desirably left cooling or air cooling. When cooling at a high cooling rate such as water cooling is performed, significant thermal stress is generated at the interface between the stainless steel plate and the surface treatment layer due to the shrinkage of the surface treatment layer, resulting in a decrease in adhesion. In the manufacturing equipment for performing the surface treatment as described above, water cooling may be performed for improving productivity, but it is preferable to keep the cooling rate as low as possible by cooling by air or air cooling. The preferred cooling rate is 50 ° C./s or less, and the smaller the cooling rate, the more effective the prevention of adhesion deterioration. However, it is not desirable to make the cooling rate extremely small because it reduces productivity.

A metal gasket is produced from the surface-treated stainless steel plate of the present invention according to a conventional method. In general, metal gaskets are manufactured in one of the following process sequences:
(1) Steel plate → Adhesive coating → Rubber coating → Punching → Molding → Gasket,
(2) Steel plate → Punch → Molding → Adhesive coating → Rubber coating → Gasket.

  In the gasket manufactured in the order of the above step (1), since rubber is coated on the entire surface of the steel sheet, the rubber is also present at the portion where the cooling water comes into contact, and water-resistant adhesion is required. Since the surface-treated stainless steel sheet of the present invention is excellent in water-resistant adhesion, it is suitable for a gasket manufactured in the order of steps (1) above. Is also applicable.

The following examples illustrate the invention. In the examples, parts and% are parts by mass and% by mass unless otherwise specified.
Example 1
A SUS301 (17% Cr-7% Ni) stainless steel plate having a thickness of 0.4 mm was subjected to bright annealing (in 100% H ₂ ), and then subjected to temper rolling to a plate thickness of 0.2 mm, followed by work hardening. A stainless steel plate was prepared as a base material. The hardness of this stainless steel plate was about 400 Hv. The surface of the base stainless steel plate was alkali degreased with a spray of FC436S (20 g / l, 60 ° C.) manufactured by Nippon Parkering Co., Ltd., and then washed with water and dried.

  Next, a surface treatment solution having the composition shown in Table 1 (the solvent is water) is roll-coated so as to have a predetermined dry film amount, dried at a maximum steel plate temperature of 220 ° C. for 45 seconds, and then cooled by air cooling. It was. The Ti and Zr fluorides used in the surface treatment liquid were titanium tetrafluoride and zirconium tetrafluoride, respectively. The resin and silica used were as follows.

Resin A: Alkylaminomethyl-substituted polyvinyl bisphenol A resin represented by the above structural formula (wherein Y ₁ is a dimethylaminomethyl group, Y ₂ is hydrogen, and n is about 5)
Resin B: Aqueous polyester resin (MD1200 manufactured by Toyobo Co., Ltd.);
Resin C: Epoxy ester resin (CD540 manufactured by Dainippon Ink Co., Ltd.).

Silica A: Gas phase silica (specific surface area 200 m ² / g);
Silica B: Gas phase silica (specific surface area 130 m ² / g);
Silica C: Liquid phase silica (specific surface area 3 m ² / g);
Silica D: Gas phase silica (specific surface area 50 m ² / g).

The following evaluation was performed about the created surface-treated stainless steel sheet. The test results are also shown in Table 1.
<Evaluation of treatment liquid>
Liquid stability evaluation (passed ○ or higher)
The state of the treatment liquid after holding the treatment liquid at 40 ° C. for 10 days was visually evaluated.

A: No suspended matter, no change in viscosity;
○: no suspended matter, viscosity slightly increased;
Δ: no suspended matter, significant increase in viscosity;
X: There is a suspended matter.

<Formation of heat-resistant rubber coating layer>
A heat resistant rubber coating was applied to the upper layer of the prepared surface-treated plate under the following conditions as described below.

Adhesive layer Epoxy adhesive was dip coated to a dry film thickness of 2 μm and dried at 200 ° C. for 3 minutes.

Fluoro rubber (hereinafter also referred to as fluorine)
Paint used: Daikin DPA351, manufactured by Daikin Industries
Dry film thickness 25 μm, vulcanization conditions 200 ° C. × 30 minutes.

NBR (acrylonitrile-butadiene) rubber (hereinafter also referred to as NBR)
Paint used: Nippon Graphite Co., Ltd., Coat Height Dry film thickness 25 μm, vulcanization conditions 200 ° C. × 30 minutes.

<Evaluation of sample with heat-resistant rubber coating layer>
Antifreeze resistance Along with a sample for evaluation of the test steel sheet, an aqueous solution of LLC in which genuine long-life coolant (LLC) manufactured by Toyota Co., Ltd. and ion-exchanged water are mixed in a volume ratio of 50/50 is sealed in a pressure-resistant container and sealed with a fluoro rubber. The container was sealed and heated at 120 ° C. for 500 and 1000 hours. Thereafter, the sample taken out from the LLC aqueous solution was left to stand at room temperature for 24 hours to dry, and then the surface of the rubber layer was scratched with 100 1 mm square grids, the tape was peeled off, and the number of remaining rubber masses was counted. . The evaluation method was as follows (○ or more passed).

☆: Number of remaining cells 100;
A: The number of remaining masses is 90 or more and 99 or less;
○: The number of remaining cells is 70 or more and 89 or less;
Δ: Residual mass number of 50 or more and 69 or less;
X: The number of remaining masses is less than 50.

Hot water A sample for evaluation of ion-exchanged water and a test steel plate was sealed in a pressure vessel, and the vessel was sealed with a fluororubber seal, and heated at 120 ° C. or 150 ° C. for 500 hours and 1000 hours. The sample was taken out and allowed to stand for 2 hours, after which 100 1 mm square grids were scratched on the surface of the rubber layer, the tape was peeled off, and the number of remaining rubber masses was counted. Evaluation was performed as follows (○ or more passed).

☆: Number of remaining cells 100;
A: The number of remaining masses is 90 or more and 99 or less;
○: The number of remaining cells is 70 or more and 89 or less;
Δ: Residual mass number of 50 or more and 69 or less;
X: The number of remaining masses is less than 50.

  As can be seen from Table 1, when the amount of fluoride of Ti and / or Zr is less than 1 part, in terms of metal, with respect to 100 parts of silica + organic resin, the adhesiveness is insufficient, and when more than 7 parts, The liquid stability of the processing liquid deteriorates. Rather than using only one of Ti and Zr alone, by using both in combination and using a large amount of Zr, a stable improvement in adhesion can be obtained with a small amount of Ti + Zr.

Silica has higher adhesion as the specific surface area is larger. Further, the best adhesion can be obtained when the blending ratio of silica: resin is about 10:90 to 30:70. The adhesion amount of the surface treatment layer is preferably 120 to 300 mg / m ² .

(Reference Example 1)
For reference, a stainless steel plate having the same base material as that of Example 1 was surface-treated in accordance with the above-described example of the patent document to prepare a test surface-treated stainless steel plate of the prior art. This test steel sheet was coated with heat-resistant rubber in the same manner as in Example 1 using fluororubber, and in the same manner as in Example 1, antifreeze resistance (heating temperature 120 ° C.) and water resistance (heating temperatures 120 ° C., 150 ° C.). ) Was tested. The test results are shown in Table 2.

In the antifreeze and water resistance tests, the peeled surface was identified by XPS analysis for the test pieces having a residual mass number of less than 90 and evaluations of ◯, Δ, or x. The results are also shown in Table 2. The peel surface is indicated by the following symbol:
R: cohesive failure of rubber film or adhesive layer (adhesion of surface treatment layer is good);
A1: Interface of adhesive layer / surface treatment layer (insufficient adhesion with adhesive);
C: Cohesive failure of the surface treatment layer (insufficient strength of the surface treatment layer);
A2: Steel plate / surface treatment layer interface (insufficient adhesion to steel plate).

  As shown in Table 2, the chromate treatment has very good antifreeze resistance and water resistance. However, the conventional non-chromate surface treatment has a relatively good antifreeze resistance, but has a poor water resistance result. In particular, the phosphoric acid + silica and chromium-free chemical conversion treatment had poor water resistance results. As for the peel surface, when the antifreeze resistance is ○, the peel surface occurred at A1, that is, at the interface between the adhesive layer and the surface treatment layer, but in many cases, the water resistance is ○, Δ, ×. The peeling surface was A2, that is, peeling occurred at the interface between the stainless steel plate and the surface treatment layer.

  On the other hand, despite the fact that the present invention is a chromium-free chemical conversion treatment, as shown in Table 1 of Example 1, not only antifreeze resistance but also water resistance test results are comparable to chromate. Was able to show.

(Example 2)
A SUS301 (17% Cr-7% Ni) stainless steel plate having a thickness of 0.4 mm was subjected to bright annealing (in 100% H ₂ ), and then work hardened to a thickness of 0.2 mm by temper rolling. A material was prepared (Hv: about 400, surface Ra = 0.08 μm). FC436S (20 g / l, 60 ° C.) manufactured by Nippon Parkering Co., Ltd. was sprayed on the surface of the base material for alkaline degreasing, followed by washing and drying.

Next, the surface treatment solution of test number 6 shown in Table 1 was roll-coated so as to have a dry film amount of 150 g / m ² , and the maximum plate temperature (abbreviated as PMT) and drying time shown in Table 2 were 1 After drying 3 to 3 times, air cooling or partial water cooling was performed. The prepared surface-treated stainless steel sheet was evaluated in the same manner as in Example 1, and the results are summarized in Table 3.

  As can be seen from Table 3, a higher drying temperature is preferable, and in order to stabilize the adhesion, a drying temperature of 200 ° C. or higher, particularly 270 ° C. or higher is preferable. However, when drying is performed at an excessively high temperature, Temper color is generated, which causes a decrease in adhesion. Performing drying a plurality of times improves adhesion, but the effect is small unless a drying temperature of 200 ° C. or higher is ensured. Moreover, when water cooling is performed after drying, adhesiveness will fall slightly.

(Example 3)
A base material was prepared by subjecting a 0.4 mm thick SUS301 (17wCr-7wNi) stainless steel plate to bright annealing (in 100% H ₂ ) and then work hardening to a thickness of 0.2 mm by temper rolling. (Hv about 400). FC436S (20 g / l, 60 ° C.) manufactured by Nippon Parkering Co., Ltd. was sprayed on the surface of the base material for alkaline degreasing, followed by washing and drying.

Then, based on the surface treatment solution of Test No. 6 shown in Table 1, the surface treatment solution whose pH was adjusted with 1% acetic acid or phosphoric acid aqueous solution was dried on the steel sheet obtained by the above drying. The surface-treated stainless steel plate was prepared by applying the coating amount to 150 mg / m ² , drying for 40 seconds at a maximum steel plate temperature of 230 ° C., and air cooling. The prepared surface-treated stainless steel sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 4.

  As can be seen from Table 4, by adding an acid to the treatment liquid and adjusting the treatment liquid pH to a range of 2.5 to 4.5, the adhesion is improved while maintaining the liquid stability of the treatment liquid. be able to. If the pH adjustment range is too high or too low, there is a problem that the adhesion improving effect is poor or the liquid stability is deteriorated.

Example 4
A base material obtained by subjecting a 0.4 mm thick SUS301 (17% Cr-7% Ni) stainless steel plate to bright annealing in 100% H ₂ and then work hardening to a thickness of 0.2 mm by temper rolling. Was prepared (Hv approximately 400). Separately, the same stainless steel plate was annealed in a 50% H ₂ + 50% N ₂ atmosphere, and then the surface was descaled by pickling with 10% HNO ₃ + 3% HF, and then subjected to temper rolling. A substrate hardened with a thickness of 0.2 mm was also prepared (Hv: about 400). In each temper rolling, the surface roughness Ra of the base material was changed by changing the surface roughness of the rolling roll.

Next, FC436S (20 g / l, 60 ° C.) manufactured by Nihon Parkering Co., Ltd. was sprayed on the surface of the base material to perform alkaline degreasing, followed by washing and drying.
Thereafter, a treatment liquid whose pH was adjusted with a 1% acetic acid or phosphoric acid aqueous solution based on the surface treatment liquid of Test No. 6 or 15 shown in Table 1 was applied to the base material with an adhesion amount after drying of 150 mg. / M ² , coating was performed at a maximum steel plate temperature of 230 ° C. for 40 seconds, and air cooling was performed. The prepared surface-treated stainless steel sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 5.

  As can be seen from Table 5, the step of pickling after annealing in the production process of the base material can stabilize the adhesiveness higher than that of the bright annealing step. It is estimated that this is not an effect due to the surface roughness, but an effect due to the formation of fine grooves on the surface due to the difference in the process.

Claims (11)

  At least one surface of the stainless steel plate is provided with a surface treatment layer containing an organic resin, silica, and Ti and / or Zr derived from fluoride and substantially free of chromium, and Ti derived from fluoride in the surface treatment layer And / or the amount of Zr as a metal is 1.0 parts by mass or more and 7.0 parts by mass or less with respect to 100 parts by mass of the total amount of the organic resin and silica. Processed stainless steel sheet. The surface-treated stainless steel sheet for metal gasket according to claim 1, wherein the silica has a specific surface area of 50 m ² / g or more. The surface-treated stainless steel sheet for metal gasket according to claim 1 or 2, wherein the surface treatment layer contains Ti and Zr derived from fluoride, and a mass ratio of these metals satisfies the following formula.
Zr ≧ 0.3Ti (Formula 1) The surface treatment stainless steel plate for metal gaskets in any one of Claims 1-3 whose adhesion amount of the said surface treatment layer is 100 mg / m < ² > or more and 300 mg / m < ² > or less. The surface-treated stainless steel plate for metal gaskets according to any one of claims 1 to 4, wherein the organic resin is a cross-linked product of a water-soluble polymer having a structure represented by the following formula.

In the formula, Y ₁ and Y ₂ are each independently hydrogen, an alkylaminomethyl group, or an alkylammonium methyl group, and n is 2 to 50.   At least one surface of the stainless steel plate is coated with a surface treatment solution that contains an organic resin, silica, and fluoride of Ti and / or Zr and does not substantially contain chromium. The manufacturing method of the surface treatment stainless steel plate for metal gaskets characterized by performing drying for 30 seconds or more on the temperature conditions which become.   The method according to claim 6, wherein the drying is performed a plurality of times.   The method according to claim 6 or 7, wherein after the drying, the steel sheet is cooled without bringing water into contact with the steel sheet surface.   The method according to any one of claims 6 to 8, wherein the surface treatment liquid is an aqueous treatment liquid having a pH of 2.0 or more and 4.5 or less. The method according to any one of claims 6 to 9, wherein the organic resin is a water-soluble polymer having a structure represented by the following formula.

In the formula, Y ₁ and Y ₂ are each independently hydrogen, an alkylaminomethyl group, or an alkylammonium methyl group, and n is 2 to 50.   The method according to any one of claims 6 to 10, wherein the stainless steel plate is subjected to annealing and subsequent pickling before applying the surface treatment liquid.