KR102006129B1 - Pre-treatment agent for metal stainless steel drawing process and method for preparing the same - Google Patents

Abstract

The present invention relates to a pretreatment coating agent for a stainless steel drawing process excellent in moisture resistance, which comprises 75 to 90% by weight of a sulfate, 3 to 25% by weight of a borate and 0.01 to 0.1% by weight of a desiccant. The pretreatment coating film of the stainless steel drawing process of the present invention is greatly improved in the moisture-proofing property and has the effect of preventing the adhesion of the film to deterioration or detachment or peeling of the film even in a high temperature and high humidity environment.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-treatment agent for a steel strip,

The present invention relates to a pretreatment coating agent for a stainless steel drawing process and a method for producing the same, and more particularly, to a pretreatment coating agent for improving the hygroscopicity of a surface pretreatment film before cold rolling of stainless steel and a method for producing the same.

Generally, metal products used in almost all industrial fields, for example, machine parts tools such as bolts and nuts, and metal parts such as automobile parts are manufactured through plastic working such as cold drawing, cold pressing and the like.

In the plastic working of a metal material, for example, in cold pressing and drawing, an lubricating film is required at the friction interface between the metal mold and the metal material (material to be processed). If the lubricating coating is insufficient, it is difficult to work into a desired shape, and there arises a problem such that a small portion (pressing and sticking) occurs.

Accordingly, most of the metal material (the material to be processed) is subjected to pretreatment such as acid washing to remove impurities and scale on the surface of the metal material prior to plastic working such as cold drawing, have. At this time, in the course of the coating process, a coating method in which a metal film is coated with a phosphate film such as zinc phosphate on the surface thereof and a soap-based lubricant is used as a bonding method, lubricant coating method is widely used. Specifically, a phosphate coating agent containing a phosphate and a zinc salt is reacted with a surface of a metal material to form a phosphate coating, and then a soap-based lubricant is applied to form a lubricating layer on the phosphate coating.

In general, a phosphate film is applied to a steel material, but since a stainless steel material does not form a phosphate film due to its high corrosion resistance, a polymer material film using physical adhesion or a salt material film chemically reactive with a stainless material surface .

For example, in Korean Patent Publication No. 10-2013-0124148, Korean Patent No. 10-1523546, and Japanese Patent No. 3533015, any one of K ₂ SO ₄ and Na ₂ SO ₄ , 3 to 25% by weight of Na ₂ B ₄ O ₇ , and 2 to 10% by weight of a nonionic surfactant.

In the high temperature and high humidity environment where the ambient temperature is near or above 30 ℃ or the relative humidity is close to or exceeds 60% in the drawing process, the pretreatment film formed on the surface of the stainless steel drawn material is hygroscopic due to the inherent hydrophilic property, The adhesiveness is deteriorated, and in severe cases, the coating film is detached and peeled off, thereby deteriorating the usability of the coating agent.

Therefore, in order to reduce the occurrence of such a problem in a high temperature and high humidity environment, hot air is applied to the surface of the stainless steel drawn material after coating to alleviate the problem of moisture absorption, but energy consumption and troublesome process are encountered.

Korea Patent Publication No. 2013-0124148 Korean Patent No. 10-1523546 Japanese Patent No. 3533015

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a pretreatment coating agent for drawing a stainless steel having improved moisture resistance and a method of manufacturing the same.

According to an aspect of the present invention, there is provided a pretreatment coating agent for drawing a stainless steel having excellent moisture resistance, which comprises 75 to 90% by weight of a sulfate, 3 to 25% by weight of a borate and 0.01 to 0.15% by weight of a desiccant.

The desiccant may be xanthan gum.

The sulfuric acid salt may be at least one selected from the group consisting of sodium sulfate, potassium sulfate, magnesium sulfate, copper sulfate, chromium sulfate and iron sulfate.

The coating agent may further comprise 2 to 10% by weight of a surfactant.

The surfactant may be at least one selected from the group consisting of fatty acid soda, glucoside series and amino acid series.

The coating agent may be used at a temperature of 25 ° C or higher and a humidity of 60% or higher.

According to another aspect of the present invention, there is provided a method for preparing a mixed solution comprising: preparing a first mixed solution by adding a sulfate and a borate to water and stirring the mixture; Adding a desiccant to water and stirring to prepare a second mixed solution; And a step of adding and stirring the second mixed solution to the first mixed solution, and a method for producing a pretreatment coating agent for drawing a stainless steel having excellent moisture resistance.

The desiccant may be xanthan gum.

The temperature of water in the step of preparing the second mixed solution may be 20 to 90 캜.

The method may further include the step of adding a surfactant in the step of adding and stirring the second mixed solution to the first mixed solution.

The pretreatment coating film of the stainless steel drawing process of the present invention is greatly improved in the moisture-proofing property and has the effect of preventing the adhesion of the film to deterioration or detachment or peeling of the film even in a high temperature and high humidity environment.

Fig. 1 is a view showing the surface properties of the coating film within 60 minutes after use of the coating agent of Comparative Example 1, using an optical microscope.
Fig. 2 is a photograph of the surface properties of the coating film observed within 500 minutes after using the coating agent of Comparative Example 1 using an optical microscope.
3 is a graph showing the moisture absorption rate test results when the coating agents of Examples 1 to 4 and Comparative Example 1 were used.

Hereinafter, preferred embodiments of the present invention will be described with reference to various embodiments. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention relates to a pretreatment coating agent for a stainless steel draw process and a method for producing the same.

According to an aspect of the present invention, there is provided a pretreatment coating agent for a stainless steel drawing process excellent in moisture resistance, which comprises 75 to 90% by weight of a sulfate, 3 to 25% by weight of a borate and 0.01 to 0.1% by weight of a desiccant.

The coating agent of the present invention comprises 75 to 90% by weight of a sulfate. When the content of the sulfate is less than 75% by weight, the reactivity with the surface of the stainless steel is weak and the degree of formation of the film becomes weak. On the other hand, when the content exceeds 90% by weight, the reactivity with the stainless steel surface and the film- Is lowered.

The kind of the sulfate is not particularly limited, but potassium sulfate, sodium sulfate, magnesium sulfate, copper sulfate, chromium sulfate, iron sulfate and the like can be used, and potassium sulfate and / or sodium sulfate can be preferably used .

On the other hand, the coating agent of the present invention comprises 3 to 25% by weight of a borate salt. When the content of the borate salt is less than 3% by weight, the lubricity of the coating is lowered, while when it is more than 25% by weight, the moisture resistance after coating treatment is increased, but dusts which are harmful to the environment during the drawing process tend to occur.

The kind of the boric acid salt is not particularly limited, but for example, sodium borate, potassium borate, tetraborate, and anoborate salt can be used, and sodium borate is preferably used.

As described above, the coating agent used in the stainless steel cold-drawing industrial field, which contains sulfate and borate, is easily dissolved in hot water. Also, when the stainless steel drawn material is immersed in a solution in which a certain amount of the coating agent is dissolved in hot water, which is excellent in reactivity with the stainless steel surface, and then dried in the air, a hard and dense salt film is formed on the surface of the stainless steel material. This coating enhances the embossability of the lubricant during the drawing process and can act to reduce the frictional force between the die surface and the surface of the workpiece.

In such a coating process and drawing process, in a high temperature and high humidity environment in which the drawing process environment is close to or above ambient temperature of 30 ° C or relative humidity is close to or above 60%, the pretreatment coating formed on the surface of the stainless steel draw- Hygroscopicity occurs due to hydrophilicity, so that the adhesion of the coating is deteriorated, and in severe cases, the coating peels off.

Accordingly, the inventors of the present invention have focused on a method of adding a small amount of moisture-resistance improving material to a coating agent used in a stainless steel cold drawing to reduce the hygroscopicity of the coating film in a high temperature and high humidity environment after coating.

The coating agent of the present invention comprises 0.01 to 0.1% by weight of a desiccant. The desiccant used in the present invention must be soluble in hot water such as the sulfate and borate and be uniformly dispersed in an aqueous solution and be uniformly dispersed in the coating and on the surface layer when the drawn material is immersed in the coating agent solution.

In the present invention, xanthan gum can be used as a desiccant. Zinc black is particularly preferable because it has a water-soluble, moisture-retaining property and is dispersed evenly in a solution in a very small amount.

The content of the desiccant is preferably 0.01 to 0.15% by weight. When the content is less than 0.01% by weight, the moisture-proof effect is insufficient. On the other hand, when the content exceeds 0.15% by weight, the degree of improvement of the moisture-proof effect is insignificant.

On the other hand, the coating agent of the present invention may further comprise 2 to 10% by weight of a surfactant. When the amount of the surfactant added is less than 2% by weight, the wettability between the surface of the stainless steel material and the coating liquid is insufficient and a non-uniform coating can be formed. When the amount is more than 10% by weight, This can cause problems.

Examples of such surfactants include sodium cocoyl apple amino acids of the amino acid series, sodium cocoyl glutamate, potassium cocoyl glycinate, and decyl glucoside, lauric glucoside, palm kernel / coco glucoside, Preferably, decyl glucoside can be used.

The coating agent according to the present invention can be used particularly under high-temperature and high-humidity conditions such as a temperature of 25 ° C or more and a humidity of 60% or more. As described above, according to the present invention, since the pretreatment film formed on the surface of the stainless steel drawn material has moisture absorption due to hydrophilic nature of the material, the adhesion of the film deteriorates and the film peels off in severe cases .

According to another aspect of the present invention, there is provided a method for preparing a mixed solution, comprising: preparing a first mixed solution by adding a sulfate and a borate to water and stirring the mixture; Adding a desiccant to water and stirring to prepare a second mixed solution; And a step of adding and stirring the second mixed solution to the first mixed solution, and a method for producing a pretreatment coating agent for drawing a stainless steel having excellent moisture resistance.

The method for producing a coating agent of the present invention is started from the step of adding a sulfate and a borate to water and stirring to prepare a first mixed solution. Such a step can be carried out according to a generally known production method, and more particularly, by adding a sulfate and a borate to water at about 75 to 85 DEG C and dissolving it by stirring.

The kind of the sulfate is not particularly limited, but potassium sulfate, sodium sulfate, magnesium sulfate, copper sulfate, chromium sulfate, iron sulfate and the like can be used, and potassium sulfate and / or sodium sulfate can be preferably used .

The kind of the boric acid salt is not particularly limited, but for example, sodium borate, potassium borate, tetraborate, and anoborate salt can be used, and sodium borate is preferably used.

Next, a desiccant is added to the water and stirred to prepare a second mixed solution. As the desiccant, xanthan gum can be used. Zinc black is particularly preferable because it has a water-soluble, moisture-retaining property and is dispersed evenly in a solution in a very small amount.

In preparing the second mixed solution, the temperature of water may be room temperature or less than 90 ° C. More preferably 20 to 90 ° C. The desiccant of the present invention dissolves even at room temperature, but the higher the temperature of water, the better the dissolution is. However, when the temperature of the water is 90 ° C or higher, there is a problem that the molecular structure of the moisture-proofing agent is changed.

The concentration of the desiccant added to the water is preferably 1 to 2%. If added less than 1%, there will be no problems in use and application. However, since the concentration of aqueous solution is low, storage and circulation may become uncomfortable due to increase in volume. If it exceeds 2%, viscosity of the mixed solution is increased and added to the coating solution There is a problem of slow dispersion. That is, when the addition concentration of the desiccant is 1 to 2%, the viscosity of the mixed solution and the degree of dispersion when added to the final coating agent are satisfactory.

Finally, a second mixed solution is added to the first mixed solution and stirred to prepare a pretreatment coating agent for a stainless steel drawing process excellent in moisture resistance.

More specifically, the sulfuric acid salt and the boric acid salt are completely dissolved in water, and the second mixed solution is added to the uniform first mixed solution and stirred to prepare a coating agent. The content of the desiccant is preferably 0.01 to 0.15 wt% . When the content is less than 0.01% by weight, the moisture-proof effect is insufficient. On the other hand, when the content exceeds 0.15% by weight, the degree of improvement of the moisture-proof effect is insignificant.

At this time, 2 to 10% by weight of the surfactant may be added and stirred. Examples of such surfactants include sodium cocoyl apple amino acids of the amino acid series, sodium cocoyl glutamate, potassium cocoyl glycinate, and decyl glucoside, lauric glucoside, palm kernel / coco glucoside, Preferably, decyl glucoside can be used.

Example

Hereinafter, the present invention will be described in more detail with reference to examples. The following examples are intended to further illustrate the present invention and are not intended to limit the present invention.

Example

After adding 0.5 liter of distilled water to the first beaker and heating it to about 85 DEG C on a hot plate, 42.5 g of potassium sulfate, 5.5 g of sodium sulfate and 2 g of sodium borate were added and dissolved by stirring.

Next, 0.5 liter of distilled water was added to the second beaker, and the mixture was heated to about 85 占 폚 on a hot plate, and 2.5 g of xanthan gum was added thereto and dissolved by stirring.

Thereafter, the solution of the second beaker was added to the first beaker of the coating agent 1 and stirred. The content of the xanthan gum in the solution was 0.01 to 0.15 wt% based on 100 parts by weight of potassium sulfate, sodium sulfate and sodium borate (1 to 4).

However, in Comparative Example 1, only the solution of the beaker 1 was used.

The contents of the coating agent and xanthan gum used in the following Table 1 are summarized.

division Coating solution concentration Comparative Example 1 Example 1 Example 2 Example 3 Example 4 density
(weight%) Encapsulation 10% 10% 10% 10% 10% Xanthan gum 0% 0.01% 0.05% 0.1% 0.15%

On the other hand, a slide glass for experiments (L 76.2 mm x W 25.4 mm x t 1 to 1.2 mm) was used for easily observing the coating film attached to the surface and for giving the surface condition under a constant condition. For the formation of the film, the slide glass was immersed in Examples 1 to 4 and Comparative Example 1 for about 10 seconds, taken out, and dried with a dryer for about 20 seconds.

The dried specimen after immersion in Comparative Example 1 was exposed to a hygroscopic environment with a humidity of 75% and a temperature of 26 ° C by an optical microscope, and the weight increase due to moisture absorption was measured with time to observe changes in the surface properties of the coating. The surface properties of the film after the surface treatment using Comparative Example 1 corresponding to the existing film agent were exposed to a hygroscopic environment at a humidity of 75% and a temperature of 26 ° C, and the surface properties of the film within about 60 minutes were shown in FIG. 1, Are shown in Fig. 2, respectively. In Fig. 1, which is the initial stage of moisture absorption of the treated film layer, the crystalline state of the film is comparatively clear and the surface property is maintained while maintaining the state of a thick resinous crystal grain. In Fig. 2 where the moisture absorption degree is high, The roughness of the coating film and the roughness of the coating film are decreased due to moisture absorption after the treatment, and the deterioration of the coating performance will become apparent.

Fig. 3 shows the results of measurement of the moisture absorption rate with time at a temperature of 26 DEG C and a humidity of 75% with respect to a specimen coated by immersing the slide glass in Examples 1 to 4 and Comparative Example 1. Fig.

Referring to FIG. 3, when xanthan gum is added in the range of about 0.05 to 0.15% as in Examples 1 to 4, it can be confirmed that the moisture absorption rate can be reduced more than twice. The moisture absorption rate seems to be saturated when exposed for about 200 to 250 minutes.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

Claims (10)

And 0.01 to 0.15 part by weight of xanthan gum based on 100 parts by weight of a mixture of 3 to 25% by weight of a borate salt and a balance of a sulfuric acid salt.
delete The method according to claim 1,
Wherein the sulfates are at least one selected from the group consisting of sodium sulfate, potassium sulfate, magnesium sulfate, copper sulfate, chromium sulfate and iron sulfate.
The method according to claim 1,
And 2 to 10% by weight of a surfactant.
5. The method of claim 4,
Characterized in that the surfactant is at least one selected from decyl glucoside, lauric glucoside, palm kernel coco glucoside, sodium cocoyl sodium amino cocoyl glutamate, potassium cocoyl glycinate and fatty acid soda. Process Pretreatment.
The method according to claim 1,
Characterized in that it is used at a temperature of 25 DEG C or more and a humidity of 60% or more.
Adding a sulfate and a borate to water and stirring to prepare a first mixed solution;
Adding xanthan gum to water and stirring to prepare a second mixed solution; And
And adding the second mixed solution to the first mixed solution and stirring the mixed solution.
delete 8. The method of claim 7,
Wherein the water of the step of preparing the second mixed solution has a temperature of 20 to 90 ° C.
8. The method of claim 7,
Further comprising the step of adding a surfactant in the step of adding and stirring the second mixed solution to the first mixed solution.

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