JP3149752B2 - Manufacturing method of steel plate with excellent white rust resistance and lubricity - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a steel sheet having a coating excellent in white rust resistance and lubricity and containing no hexavalent chromium at all.

[0002]

2. Description of the Related Art Steel sheets used for automobiles, home appliances, building materials, etc., particularly zinc and zinc-based alloy-plated steel sheets, are used without painting or painting.
In the meantime, it is left unpainted for a considerably long time. Therefore, rust is generated during that time, and various substances are adsorbed and adhered to the surface of the steel sheet, so that the quality is greatly reduced. In order to suppress the generation of rust, various post-treatments are widely performed after the zinc-based plating. As a typical method of the post-treatment, there is a chromate treatment method in which chromic acid or a salt thereof is a main component and various other additives are added. This chromate treatment is an economical treatment which has excellent corrosion resistance and can be performed relatively easily.

[0003]

However, the chromate treatment uses highly toxic hexavalent chromium. In the treatment process, there are problems such as the adverse effect of chromate on the human body and the disposal of chromium sludge after wastewater treatment. In addition, there are various problems such as elution of hexavalent chromium from the product after the chromate treatment.

[0004] In view of the above, in order to prevent the generation of white rust on a steel sheet, particularly a zinc-based plated steel sheet, a number of pollution-free treatment techniques that do not rely on chromate treatment have been proposed.

[0005] For example, a thin film is formed by a method such as immersion, coating, or electrolytic treatment using an inorganic compound, an organic compound, an organic polymer, or a solution in which these are combined. Specifically, the following techniques have been proposed.

(1) A method using a polymetal oxide such as molybdenum and tungsten (for example, Japanese Patent Application Laid-Open No. 57-587)
No. 5) (2) A method using tannic acid (see, for example,
(3) A pollution-free chromate treatment method using a treatment solution containing trivalent chromium and containing no hexavalent chromium (for example, JP-A-61-587). According to the method, the stable area against corrosion of polymetal oxides such as molybdenum and tungsten is narrower than that of chromium, and it is impossible to obtain the same corrosion resistance as chromate.

In the method (2), there is a problem that coloring by tannic acid occurs when sufficient corrosion resistance is to be obtained.

Further, in the above method (3), the treatment time (reaction time) needs to be relatively long, and its corrosion resistance is not sufficiently high.

Further, from the viewpoint of environmental protection, it is desirable that the film has lubricity in addition to corrosion resistance. If there is no lubricity, lubricating oil must be applied at the time of molding, and a large amount of oil is discharged into the degreasing liquid in the degreasing step after molding.

The present invention has been made in view of the above circumstances, and is intended to provide a steel sheet which forms a safe and harmless chemical conversion film in a manufacturing process and a use process, and is excellent in white rust resistance and lubricity. The aim is to provide a method that can be manufactured.

[0011]

According to the present invention, in order to solve the above-mentioned problems, first, a silicate ester and an aluminum inorganic salt are used in an Al / (Al + Si) molar ratio of 0.0
A solution in which an organic solid lubricant is mixed in a weight ratio of 0.1 to 1 inclusive with Si in the silicate ester is applied to a steel plate. After that, a method for producing a steel sheet having excellent white rust resistance and lubricity, characterized by forming a coating having an adhesion amount of 50 mg / m ² or more in terms of (Al + Si) metal, after heating and drying.

Secondly, the present invention provides a method for producing a steel sheet having excellent white rust resistance and lubricity, wherein aluminum nitrate is used as the aluminum inorganic salt in the above method.

Thirdly, there is provided a method for producing a steel sheet excellent in white rust resistance and lubricity, characterized in that the heating and drying temperature is less than 200 ° C. in any of the above methods.

Fourth, in any one of the above methods, the solution may contain one or more of inorganic salts of nickel, cobalt, and magnesium in a molar ratio of 0.01 to Al.
As described above, the present invention provides a method for producing a steel sheet excellent in white rust resistance and lubricity, which is a solution containing the same mole number or less as Al.

Fifth, in any one of the above-mentioned first to third methods, the solution may contain phosphoric acid or a phosphoric acid compound in terms of the number of moles of phosphoric acid and the total number of moles of aluminum and silicate. A method for producing a steel sheet having excellent white rust resistance and excellent lubricity, characterized in that it is contained in a range of 5% to 200%.

Sixth, in any one of the above-mentioned first to third methods, the solution may be such that the trivalent chromium compound is defined as 0.1 mole of chromium metal and 0.1 mole based on the total mole number of aluminum and silicate ester. Provided is a method for producing a steel sheet having excellent white rust resistance and lubricity, characterized in that the steel sheet is contained so as to be twice to three times as large.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as described above, a solution containing a silicate ester, an inorganic salt of aluminum, and an organic solid lubricant is applied to a steel sheet to provide corrosion resistance,
A film excellent in lubricity can be formed. Although the reason is not necessarily clear, it is considered that silicic acid and aluminum oxide form a network structure, form a dense composite oxide thin film, and provide white rust suppressing ability. Further, it is considered that the addition of the organic solid lubricant to the film lowers the friction coefficient of the film surface and improves lubricity.

As the aluminum inorganic salt, aluminum nitrate, aluminum chloride, aluminum sulfate and the like can be used. Among them, aluminum nitrate is preferable. The reason is not always clear at the moment,
It is conceivable that nitrate promotes the formation of the network structure of the film or does not hinder the formation of such a network structure.

As the silicate ester, for example, methyl silicate, ethyl silicate and n-butyl silicate can be used. From the viewpoint of cost, it is preferable to use inexpensive ethyl silicate,
There is no particular limitation.

As the organic lubricant, lubricating particles composed of polyolefin wax, modified polyolefin wax and fluorocarbon can be used. When the particle size exceeds 20 μm, the lubricating particles easily fall off from the film, so that it is desirable to use a fine powder having a particle size of 20 μm or less.

The ratio between the silicate ester and the aluminum inorganic salt is in the range of 0.015 or more and 0.75 or less in terms of Al / (Al + Si) molar ratio. This is because this value is 0.01
If it is less than 5, the corrosion resistance is greatly reduced, and a problem occurs in the white rust suppressing ability. If it exceeds 0.75, the white rust suppressing ability is similarly insufficient. Here, Al
The reason why the corrosion resistance changes depending on the / (Al + Si) molar ratio is considered to be that the corrosion resistance depends on the denseness of the obtained film structure.

Further, the solid content of the organic solid lubricant is 0.1 to 1 in weight ratio with respect to Si in the silicate ester.
Mix so that: This is because the addition ratio is 0.
If it is less than 1, little improvement in lubricity is observed, and if the addition ratio is more than 1, it causes mold seizure during pressing.

In the present invention, the silicate ester
In addition to the aluminum inorganic salt and the organic solid lubricant, one or more of nickel, cobalt, and magnesium inorganic salts are contained in the solution in a molar ratio to Al of 0.01 or more and the same mole number or less as Al. Is preferably contained.
By adding the inorganic salts of nickel, cobalt and magnesium in this way, the corrosion resistance of the Al—Si-based coating in a defective portion (including both a defect generated during film formation and a relatively small defect generated during forming a steel sheet) is improved. The drop can be significantly reduced.

Here, the content of one or more of these is set to 0.01 or more in terms of molar ratio with respect to Al. If the content is less than this, the effect of suppressing the decrease in the corrosion resistance of the film defect portion is almost lost. This is because it is not observed.
This is because the proportions of Si and Si decrease, and the nickel, cobalt and magnesium interfere with the film-forming action of the Al-Si based film, resulting in a film having a poor coverage and deteriorating the corrosion resistance.

The inorganic salts of nickel, cobalt and magnesium to be added include nitrates, sulfates and chlorides, but are not particularly limited.

Further, in the present invention, the phosphoric acid or the phosphoric acid compound is contained in the solution in the range of 5% to 200% as the number of moles of phosphoric acid based on the total number of moles of aluminum and silicate ester. Is preferred. Thereby, white rust resistance can be further improved.

Here, the content is set to 5% or more and 200% or less. When the content is less than 5%, almost no effect due to the addition of the phosphoric acid compound is observed, and when it exceeds 200%, the white rust suppressing effect is obtained. Is no longer visible. The reason is 2
If it exceeds 00%, it is presumed that phosphate ions inhibit the growth of a dense Al-Si network structure and cause film defects. Although the mechanism by which the effect of the addition of the phosphoric acid compound is exerted is not clear at present, it is considered that the plating surface is inactivated by the phosphoric acid compound and the Al-Si network structure is strengthened by the phosphoric oxide. Can be

As the phosphoric acid compound, for example, primary ammonium phosphate, secondary ammonium phosphate, tertiary ammonium phosphate
Ammonium, sodium phosphate, and the like can be used, but are not limited thereto.

Furthermore, in the present invention, the trivalent chromium compound (trivalent chromium ion) is defined as the mole number of chromium metal, and based on the total mole number of aluminum and silicate ester.
It is preferably contained in the solution in a range of 0.1 to 3 times. This can further improve the white rust resistance.

Here, the content is set in the range of 0.1 times to 3 times. When the content is less than 0.1 times, the effect of adding the chromium compound is hardly observed, and when the content exceeds 3 times, the white content increases. This is because the effect of suppressing rust is no longer observed. It is presumed that the reason for this is that if the ratio exceeds three times, chromium ions inhibit the growth of a dense Al-Si network structure and cause film defects. Also, the mechanism by which the effect is exhibited by the addition of the trivalent chromium compound is not always clear at present, but inactivation of the plating surface by the chromium compound,
It is considered that the chromium oxide enhances the Al-Si network structure.

As the trivalent chromium compound, for example, chromium nitrate, chromium chloride, chromium sulfate, chromium acetate and the like can be used, but it is not limited to these.

The organic solvent used to form the solution is not particularly limited, but for example, methanol, ethanol,
Butanol, propanol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, ethylene glycol,
Organic solvents capable of dissolving silicate esters, aluminum salts, organic solid lubricants such as diformaldehyde methoxyethanol can be used, and non-polar solutions such as 1,4 dioxane can be used as polar solvents such as alcohol. It can be used in combination with a solvent. Water can also be used in combination with alcohol or the like.

As a method of applying the above solution to a steel sheet, a method using a roll coater, a method of immersing the steel sheet in the solution or spraying the solution on the plated steel sheet, and then removing an excessive solution by a roll are used. Can be applied.

After the solution is applied in this manner, heating and drying are performed, and the temperature at that time is preferably lower than 200 ° C. The heat treatment temperature after application to the steel sheet affects the corrosion resistance of the Al-Si coating, and even if the temperature is 200 ° C or more, the ability to suppress white rust can be obtained, but the corrosion resistance tends to decrease by increasing the heat treatment temperature. It is in. This is presumably due to an increase in the number of pinholes caused by rapid evaporation of the organic solvent and an increase in cracks caused by hardening of the film. Heating and drying temperature is no problem as long as the solvent used is volatile,
The lower limit is determined by the volatility of the solvent.

When the coating of the present invention is applied to a galvanized steel sheet, the treatment temperature must be a temperature at which the galvanizing and the thermal diffusion of the steel sheet as the substrate do not occur rapidly. It is believed that 350 ° C. is a practical upper limit.

The coating weight of the film formed after heating and drying was
(Al + Si) 50 mg / m ² or more in terms of metal.
This is because if it is less than 50 mg / m ² , the corrosion resistance is insufficient. There is no particular upper limit on the amount of adhesion, but if the amount of adhesion is too large, the flexibility is deteriorated, and cracks and peeling are likely to occur, so that the film thickness is about 1.0 μm, which is about 1.0 g / m ² or less. Is preferred.

As the steel sheet applied in the present invention, various surface-treated steel sheets including a cold-rolled steel sheet can be used.
There is no particular limitation. For example, examples of the zinc-based plated steel sheet include a galvanized steel sheet by an electroplating method, a zinc-nickel alloy-plated steel sheet, a galvanized steel sheet by a hot-dip plating method, and an aluminum-zinc-based alloy-plated steel sheet.

[0038]

【Example】

(1st Example) Adhesion amount of 0.7 mm plate thickness 20 per side
g / m ² electrogalvanized steel sheet, 0.7 mm thick coated surface 20 g / m ² per galvanized nickel-nickel alloy coated steel sheet (13% nickel content), 0.7 mm thick coated surface 60g / m ² hot-dip galvanized steel sheet,
Alloyed hot-dip galvanized steel sheet with a coating thickness of 0.7 mm per side of 45 g / m ² per side, hot-dip aluminum-zinc alloy coated steel sheet with a coating thickness of 0.7 g per side of 80 g / m ² (aluminum content 55% ) Were prepared, and the silicates, aluminum salts, and organic lubricants shown in Table 1 were used in Table 2
Was applied by a roll coater, and then subjected to a heating treatment by changing the heating temperature in a hot-air drying furnace to form films of Examples 1 to 36 and Comparative Examples 1 to 8. Table 2 shows the heating temperature at that time.
It was also described in. At this time, the amount of the chemical conversion film deposited can be changed depending on the amount of the solid component in the treatment liquid or the application conditions such as a roll coater.

Regarding the steel sheet, of the above steel sheets, Examples 1 to 30, Comparative Examples 1 to 8 are electrogalvanized steel sheets, Examples 31 to 33 are hot-dip galvanized steel sheets, and Example 34 is an electrogalvanized nickel-plated alloy. A steel sheet, Example 35 used a hot-dip aluminum-galvanized steel sheet, and Example 36 used an alloyed hot-dip galvanized steel sheet.

Next, the corrosion resistance and lubricity of the sample thus prepared were evaluated by the following methods, and are shown in Table 2.

(1) Corrosion resistance For each sample, a salt spray test (JIS-Z-23)
71) was carried out, and the area ratio of white rust occurrence after 24 hours and 48 hours was examined, whereby white rust resistance was evaluated.

The white rust resistance was evaluated according to the following criteria.

Evaluation of white rust generation area ratio 0% to less than 5% ◎ 5% to less than 25% ○ 25% to less than 50% △ 50% to less than 80% × 80% to 100% xx (2) Lubricity Draw bead test Each sample was pulled out while being deformed by a machine (tip of a male die: 10R, horizontal pressing load: 50 kg / m ² , deformation height: 1 mm), and evaluated by the pulling resistance value shown below.

Pull-out resistance value = (pull-out load) / (pushing load)

[Table 1]

[0045]

[Table 2]

As shown in Table 2, Examples 1 to 36, which are within the scope of the present invention, exhibited good white rust resistance and lubricity, whereas Comparative Examples 1 to 8 all exhibited resistance to white rust. It was confirmed that white rust and lubricity were poor.

(Second Example) An electrogalvanized steel sheet having a thickness of 0.7 mm and an adhesion amount of 20 g / m ² per side was coated on a steel sheet having a thickness of 0.7 mm.
As shown in Table 3, a silicate ester, an aluminum salt and an organic lubricant were used, various solvents shown in Table 3 were used, and the molar ratio of Al / (Al + Si) was 0.2 as shown in Table 4. Then, a solution containing the solid content of the organic solid lubricant in a weight ratio to Si in the silicate ester of 0.5 was applied by a roll coater, and then heated by a hot air drying furnace. Processing was performed, and Examples 37 to
Forty-three films were formed.

The samples were subjected to a salt spray test (JIS-Z-2371) in the same manner as in the first embodiment, and the area ratio of white rust occurrence after 24 hours and 48 hours was examined. evaluated. Further, the lubricity of each sample was evaluated in the same manner as in the first example. Table 4 shows the results. The evaluation criteria were the same as in the first embodiment.

[0049]

[Table 3]

[0050]

[Table 4]

As shown in Table 4, it was confirmed that within the range of the present invention, good corrosion resistance was exhibited without being largely influenced by the type of the solvent.

(Third Embodiment) An electrogalvanized steel sheet having a thickness of 0.7 mm and an adhesion amount of 20 g / m ² per side was prepared.
After dissolving a silicate, an aluminum salt and an organic lubricant shown in Table 5, and further applying a methyl cellosolve solution in which any of inorganic salts of magnesium, nickel, and cobalt is dissolved in a composition shown in Table 6, using a roll coater, Heat treatment was performed by changing the heating temperature in a hot air drying furnace to form films of Examples 44 to 58 and Comparative Examples 9 to 17. The heating temperature at that time is also shown in Table 6. At this time, the amount of the chemical conversion film deposited can be changed depending on the amount of the solid component in the treatment liquid or the application conditions such as a roll coater.

Next, the corrosion resistance and lubricity of these samples were evaluated in the same manner as in the first example. In addition, in order to evaluate the corrosion resistance of the cut portion, the surface of the sample after the chemical conversion treatment was scratched with a cutter knife to reach the ground iron, and the degree of white rust generation after 24 hours of the salt spray test was examined.
It is described together.

The corrosion resistance of the cut portion was evaluated according to the following criteria.

Evaluation of rust occurrence in cut part No white rust generated ◎ White rust generated in part of cut part ○ White rust generated in part of cut part △ White rust started to flow ・ Part of cut part White rust occurs and a large amount of white rust flows

[Table 5]

[0056]

[Table 6]

As shown in Table 6, Examples 44 to 58, which are within the scope of the present invention, showed good white rust resistance, good corrosion resistance at cut portions, and good lubricity.
It was confirmed that all of Comparative Examples 9 to 17 were poor in white rust resistance, corrosion resistance of cut portions, and lubricity.

(Fourth Embodiment) An electrogalvanized steel sheet having a thickness of 0.7 mm and an adhesion amount of 20 g / m ² per one side was prepared.
After applying a methyl cellosolve solution in which a silicate ester, an aluminum salt, an organic lubricant, and a phosphoric acid compound shown in Table 7 are dissolved in the composition shown in Table 8, using a roll coater, the heating temperature is changed by a hot air drying furnace to perform heat treatment. To form films of Examples 59 to 73 and Comparative Examples 18 to 24. The heating temperature at that time is also shown in Table 8. At this time, the amount of the chemical conversion film deposited can be changed depending on the amount of the solid component in the treatment liquid or the application conditions such as a roll coater.

The samples were subjected to a salt spray test (JIS-Z-2371) in the same manner as in the first embodiment.
After 48 hours and 72 hours, the area ratio of white rust occurrence was examined, and the white rust resistance was evaluated. Further, the lubricity of each sample was evaluated in the same manner as in the first example. Table 8 shows the results. The evaluation criteria were the same as in the first embodiment.

[0060]

[Table 7]

[0061]

[Table 8]

As shown in Table 8, Examples 59 to 73 within the scope of the present invention all showed good white rust resistance and lubricity. On the other hand, among Comparative Examples, Comparative Examples 18 to 20 in which the phosphoric acid compound is out of the appropriate range have poor white rust resistance,
Comparative Examples 21 to 24 in which the amount of the organic lubricant is out of the appropriate range.
Was found to have poor lubricity.

(Fifth Embodiment) An electrogalvanized steel sheet having a thickness of 0.7 mm and an adhesion amount of 20 g / m ² per one side was prepared.
After applying a silicate ester, an aluminum salt, an organic lubricant, and a trivalent chromium compound having the composition shown in Table 10 in a methyl cellosolve solution shown in Table 9 by a roll coater, the heating temperature was changed by a hot air drying furnace to heat the solution. The coatings of Examples 74 to 87 and Comparative Examples 25 to 31 were formed by performing the treatment. The heating temperature at that time is also shown in Table 10. At this time, the amount of the chemical conversion film deposited is the solid component amount in the processing solution,
Alternatively, it can be changed according to application conditions such as a roll coater.

The samples were subjected to a salt spray test (JIS-Z-2371) in the same manner as in the first example.
After 48 hours and 72 hours, the area ratio of white rust occurrence was examined, and the white rust resistance was evaluated. Further, the lubricity of each sample was evaluated in the same manner as in the first example. Table 10 shows the results. The evaluation criteria were the same as in the first embodiment.

[0065]

[Table 9]

[0066]

[Table 10]

As shown in Table 10, Examples 74 to 87 within the scope of the present invention all showed good white rust resistance and lubricity. On the other hand, among Comparative Examples, Comparative Examples 25 to 27 in which the trivalent chromium compound is out of the appropriate range have poor white rust resistance, and Comparative Example 28 in which the organic lubricant is out of the appropriate range.
Nos. 31 were confirmed to have poor lubricity.

[0068]

As described above, according to the present invention,
A solution containing silicate ester, aluminum inorganic salt, and organic solid lubricant within a certain range is applied to a steel sheet, and then heat-dried to form a chemical conversion coating, which is safe in the manufacturing process and in the use process. It is harmless and sanitary, and the chemical conversion coating formed in this way is excellent in white rust suppressing ability and lubricity in a healthy portion of the coating. Therefore, the present invention is extremely useful industrially.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masaru Sagiyama 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (56) References JP-A-9-118989 (JP, A) JP-A-59 -177377 (JP, A) JP-A-53-102934 (JP, A) JP-A-59-35682 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00- 22/86 B05D 7/14

Claims (6)

(57) [Claims] 1. A silicate ester and an aluminum inorganic salt having an Al / (Al + Si) molar ratio of 0.015 or more and 0.75 or less, and an organic solid lubricant having a solid content in the silicate ester of A solution mixed so as to have a weight ratio of 0.1 to 1 with respect to Si is applied to a steel sheet, and then heated and dried, and the adhesion amount is 5 in terms of (Al + Si) metal.
A method for producing a steel sheet having excellent white rust resistance and lubricity, characterized by forming a coating of 0 mg / m ² or more. 2. The method for producing a steel sheet having excellent white rust resistance and lubricity according to claim 1, wherein aluminum nitrate is used as the aluminum inorganic salt. 3. The method for producing a steel sheet having excellent white rust resistance and lubricity according to claim 1, wherein the heating and drying temperature is lower than 200 ° C. 4. The solution according to claim 1, wherein the solution contains one or more of inorganic salts of nickel, cobalt and magnesium in a molar ratio to Al of 0.01 or more and the same mole number or less as Al. The method for producing a steel sheet excellent in white rust resistance and lubricity according to any one of claims 1 to 3. 5. The solution contains phosphoric acid or a phosphoric acid compound in a molar number of phosphoric acid in a range of 5% to 200% with respect to the total molar number of aluminum and silicate ester. The method for producing a steel sheet excellent in white rust resistance and lubricity according to any one of claims 1 to 3, characterized in that: 6. The method according to claim 1, wherein the solution contains the trivalent chromium compound as a mole number of chromium metal in a range of 0.1 to 3 times the total mole number of aluminum and silicate. The method for producing a steel sheet having excellent white rust resistance and lubricity according to any one of claims 1 to 3.