KR100805727B1 - Anti-stain and rust formation agent of pickling steel - Google Patents

Abstract

It is an object of the present invention to provide an organic composition that effectively prevents stains and rust from being formed on the surface of a steel sheet by reoxidation by contact of water and air in the process of pickling and washing hot rolled and cold rolled steel sheets.

As a technical configuration for achieving the above object, one or more of alkylamine, alkyldiamine, alkyltetraamine is 40 to 80% by volume, 10 to 50% by volume of tetrahydro-1,4-oxazine as a high temperature stabilizer And at least 10% by volume of anhydrous citric acid as an aqueous solution stabilizer.

Description

Agent for inhibiting stain and rust of pickling steel strip}

1 is a process chart showing a general pickling process.

2 and 3 are graphs showing the results of measuring whiteness and yellowness according to the use of the inhibitor of the present invention.

Figure 4 is a graph showing the results of measuring the transmittance according to the amount of the stabilizer in the inhibitor of the present invention.

The present invention relates to a stain and rust formation inhibitor of pickled steel sheet, and more particularly, to prevent stain and rust on the surface of the steel sheet by reoxidation by contact of water and air in the process of pickling and washing hot rolled and cold rolled steel sheets. It relates to an organic composition.

The present invention is to prevent stains and rust in the pickling process, the following will be briefly described with reference to Figure 1 the pickling process of the hot rolled steel sheet.

Pickling steel sheet (steel plate 24 removed from pickling scale formed on the surface of hot rolled steel sheet) The production equipment is mainly for supplying hot rolled steel sheet, grinding means for rolling hot rolled steel sheet to crush scale layer formed on the surface, hot rolled steel sheet Pickling means is divided into pickling means for removing the crushed scale layer and winding means for cutting and winding the pickling steel sheet to the required length.

The supply means includes a welder 13 and an entry looper 14. The welder 13 welds the preceding steel plate 12 and the trailing steel plate 11 so that the pickling process can be continuously performed, and the entry looper 14 compensates the moving speed of the hot rolled steel sheet which is continuously changed during the welding process. The hot rolled steel sheet in the grinding means and the pickling means allows to proceed at a constant speed.

The grinding means includes a skin pass mill 15 and a scale breaker 16. The hot rolled steel sheet passed by the entry looper 14 at a constant speed is flattened by the skin pass mill 15 and rolled by the scale breaker 16 to mechanically crush the scale layer. The crushing of the scale layer is to allow the acid solution to easily penetrate into the scale layer during pickling, thereby effectively removing the scale.

The pickling means includes a pickling tank 21, a rinsing tank 22, and a hot dryer 23. In the hot rolled steel sheet in which the scale layer is mechanically crushed by the grinding means, the scale is chemically completely removed by pickling in the pickling tank 21. Thereafter, the water is washed while passing through the rinsing tank 22 and then the surface is dried by the hot dryer 23.

The winding means includes an oiler 31, an exit shear 32 and a tension reel 33. The pickling steel sheet 24 whose scale is removed by the pickling means is coated with oil on the surface of the steel sheet by the oiler 31 to prevent further scale formation, and the tension sheath 32 winds up the tension reel 33. According to the capacity, it is cut to an appropriate length and finally wound on the tension reel 33.

During the pickling operation, the pickling steel plate passing through the pickling tank 21 and the washing tank 22 is wound with water in the air to generate stains or rust on the surface. These stains and melted products cause defects, so the line speed to prevent this operation, but not completely prevented. In addition, the line speed of less than 60 MPM (Meter Per Minute) has a significant impact on productivity, such as the generation of a lot of stains and rust due to scrap processing of the product.

In the prior art developed to solve similar problems, the Republic of Korea Patent Publication No. 1994-11374 includes ortho phosphate, azole, polyepoxysuccinic acid and acrylic acid to prevent corrosion of the metal surface in contact with the aqueous medium Although a method of use as a corrosion inhibitor has been published, the composition has to be used separately from the washing solution, and thus it is difficult to use in the washing process of hot rolled and cold rolled steel sheets, and it has been found that the effect is not high.

The present invention has been proposed to solve this problem, and can be used by diluting an amine compound in a washing solution to effectively prevent stains and rust generated by adsorbing on the metal surface to be used directly in the pickling process of hot rolled and cold rolled steel sheet The purpose is to provide stain and rust inhibitors for pickled steel sheets.

The stain and rust inhibitor of the pickled steel sheet according to the present invention for achieving the above object is 40 to 80% by volume of one or more of alkylamine, alkyldiamine, alkyltetraamine, tetrahydro-1, 10 to 50% by volume of 4-oxazine, and at least 10% by volume of anhydrous citric acid as an aqueous solution stabilizer.

The reason why staining or rust occurs during the pickling process of hot rolled and cold rolled steel sheets is because the surface of the pickled steel sheet is activated after pickling, so that the oxidizing material in the washing solution is adsorbed on the surface of the steel sheet. It occurs intensively during the drying step in the illustrated hot dryer 23 or during the winding process in the tension reel 33.

In the present invention, organic components such as alkylamines, alkyldiamines and alkyltetraamines (hereinafter referred to as "amine compounds") are chemically adsorbed on the surface of the pickling steel sheet so that metal corrosion or rust can be suppressed. Consideration should be given to the chemical properties of the components, the properties of the metal surface and their effects on the electrochemical potential.

In the present invention, one or two or more of the amine compounds such as alkylamine, ilkyldiamine and alkyltetraamine are selected and used to contain 40 to 80% by volume in total. These amine compounds prevent the oxides such as oxygen from adsorbing on the surface of the steel sheet in the aqueous solution to suppress the occurrence of stains and rust.

In more detail, the organic compound acts as a second ammonium cation in an acidic aqueous solution when RR′-NH (R and R ′ are alkyl radicals), which is a secondary amine, is used as the adsorptive corrosion inhibitor. . Amine compounds also inhibit anodic reactions, but at this time, they are known as chemisorption, in which unshared electron pairs of nitrogen in amines and empty d orbits in metals are related. As such, the adsorption corrosion inhibitor reduces the area where corrosion reaction proceeds by physical adsorption or chemical adsorption on the surface of the corroded metal, and at the same time, the alkyl radical is coated on the surface of the metal so that the hydrogen cation (H ⁺ ) is removed from the solution. It has the effect of preventing access to or preventing the diffusion of iron cations (Fe ²⁺ ) into the solution.

   This cation is electrostatically chemisorbed when the metal surface charge has a negative charge, thereby mainly suppressing the cathodic reaction. Therefore, the oxidation produced on the surface of the steel sheet does not proceed to exhibit an effect of suppressing the occurrence of rust. As a result, when the amine compound according to the present invention is less than 40% by volume, a small amount of rust is produced and its effect is insignificant, and when it exceeds 80% by volume, the rust generation effect is saturated and does not increase any more, so it is not economical.

In addition, all of the amine compounds used as the alkyl amine exhibits the effect of inhibiting the rust generation, but the experimental results showed that the best effect in the case of ethylamine, ethyldiamine, ethyltetraamine.

Meanwhile, in the present invention, 10 to 50% by volume of tetrahydro-1,4-oxazine is used as a high temperature stabilizer to enable the use of amine compounds at relatively high temperatures. Washing solution, process water, is usually used at room temperature using fresh water as it is. However, in the water washing process of the hot rolled steel sheet, the temperature of the water washing solution sometimes rises higher than the normal temperature (in the case of process water, it is generally considered to be high temperature when used at 35 ° C or higher).

In such a high temperature state, the amine compounds reduce the effect of inhibiting oxidation of the surface of the pickled steel sheet, resulting in a slight amount of rust. Therefore, it is desirable to mix the tetrahydro-1,4-oxazine together with the amine compound so that it can be used more effectively as a stain and rust inhibitor of the pickled steel sheet even at a high temperature. When the content of tetrahydro-1,4-oxazine is less than 10% by volume, high temperature stability is deteriorated, and staining and rust are generated during a high-temperature washing process, and when the content is higher than 50% by volume, the content of amine compounds is relatively low. Rust also occurred after the washing process at room temperature.

On the other hand, in order to ensure the stability in the washing solution of the amine compound of the organic component in the present invention, anhydrous citric acid (Anhydrous citric Acid) is added to 10% by volume or more. This anhydrous citric acid is an amine compound to be more stably adsorbed on the surface of the steel sheet to increase the prevention of rust generation, the experimental results showed that at least 10% by volume or more has a substantial effect. Since more anhydrous citric acid is added, the stabilizing effect increases, so that it may be added to the solubility range in the corresponding inhibitor containing a certain amount of amine compound and tetrahydro-1,4-oxazine. Therefore, in the present invention, the upper limit of the anhydrous citric acid content is not particularly defined.

The inhibitor according to the present invention, in which an amine compound, tetrahydro-1,4-oxazine, and anhydrous citric acid is mixed, is used after dilution in the water washing solutions of hot rolled and cold rolled steel sheets. The dilution ratio of these inhibitors has been shown to have the rust formation prevention effect required in the operation within a wide range, but to dilute to 0.05 ~ 0.15% by volume in consideration of the rust formation prevention effect and the cost of the addition of the inhibitor. It is preferable.

Hereinafter, with reference to the accompanying drawings will be described in detail the experimental results of the effect of the stain and rust inhibitor of the pickling steel plate according to the present invention.

Experiment 1

After pickling the hot-rolled steel sheet, dry specimens without additives and dried specimens treated with the inhibitor of the present invention were compared, and the experiment was performed to measure the whiteness and yellowness through a colorimeter and compare the results. To this end, the specimens of the hot-rolled steel sheet were washed in a clean state by thoroughly washing the surface in 18% hydrochloric acid. And the temperature conditions at the time of pickling are carried out at 75 ~ 85 ℃, experiments were carried out using the inhibitor of the present invention on the basis of the specimen (pickling pickling 40 seconds) once pickled under the same conditions.

   At the time of washing with water, the inhibitor of the present invention was added to pure water at a temperature of 55 to 65 ° C, and the specimens which were pickled under the conditions of no addition and dilution ratio of 0.1% were dried in water of 100 ml or more of each concentration, and dried after 5 minutes of washing with water. Done. After performing three or more times according to each condition, the average value was taken and the performance of the composition product was evaluated. Test items are based on the values of yellowness and whiteness.

As the amine compound, one or two or more of three kinds of alkylamine, ilkyl diamine and alkyltetraamine are selected. In this embodiment, an amine compound in which ethylamine, ethyldiamine and ethyltetraamine are mixed in the same amount is used. Stabilizer was prepared using anhydrous citric acid (molecular weight: 192.13) having a composition as shown in Table 1.

Table 1

Amine compounds Tetrahydro-1,4-oxazine Anhydrous Citric Acid Remarks Comparative Example 1 0 0 0 (No addition) Comparative Example 2 30 60 10   10% stabilizer is used Example 1 40 50 10 Example 2 50 40 10 Example 3 60 30 10 Example 4 70 20 10 Example 5 80 10 10

The composition of Comparative Example was prepared and after the pickling described above, 0.1% of the composition was mixed with the wash water, and then used as the wash water, and the dry specimen was measured for whiteness and yellowness, and the results are shown in FIGS. 2 and 3. .

In the case of whiteness, it can be judged as good quality in the case of 65.0 or more, and becomes the whiteness standard of a product production. As shown in FIG. 2, all of the examples of the present invention showed that the whiteness is more than 65.0, but the addition of the inhibitor (Comparative Example 1) or the case of not mixing in the composition range according to the present invention (Comparative Example 2 ), The whiteness was 53 and 64 respectively.

On the other hand, since the occurrence of rust becomes yellow, the yellowness is closely related to the degree of rust generation, and it can be judged as good quality when the yellowness is 3.0 or less. As shown in FIG. 3, all of the present examples showed good quality with a yellowness of 3.0 or less, but Comparative Example 1 and Comparative Example 2 were poor in quality as 3.8 and 3. 3.

Experiment 2

In the present invention, the following experiment was conducted to determine the rust prevention effect according to the content of anhydrous citric acid added as an aqueous solution stabilizer. In other words, 100 g (g) of anhydrous citric acid as a stabilizer was dissolved in 1 liter (L) of water, and then the amine compound and tetrahydro-1,4-oxazine were mixed in a volume ratio of 1: 1 in a volume ratio, respectively. After adding 0%, 2.5%, 5%, 7.5%, and 10% and maintaining in an oven at 60 ° C. for 7 days, discoloration or formation of precipitates was observed to compare the stability, and the results are shown in FIG. 4.

This is a result of checking the degree of sedimentation and comparing the case of distilled water to 100 and the case of not permeating to 0 based on the permeability. As shown in Figure 4, when the stabilizer addition volume is less than 10%, it is difficult to maintain a stabilized state due to the occurrence of fine white precipitates, and the stability is almost unchanged to 98% only when more than 10% by volume is added. You can see that it maintains state. Therefore, it is preferable to contain 10 volume% or more of anhydrous citric acid which is a stabilizer in this invention.

According to the stain and rust inhibitor of the pickling steel sheet according to the present invention configured as described above, because it is used by mixing in the water washing solution during the pickling process of hot rolled and cold rolled steel sheet is not only convenient to use in the current facilities, but also convenient Excellent stain and rust prevention effect reduces product defect rate and greatly improves product productivity.

Claims (4)

One or two or more of alkylamine, alkyldiamine, alkyltetraamine is 40 to 80% by volume, 10 to 50% by volume of tetrahydro-1,4-oxazine as a high temperature stabilizer, and citric anhydride 10 as an aqueous solution stabilizer The stain and rust inhibitor of the pickling steel sheet, characterized in that the volume% or more. According to claim 1, wherein the alkylamine, alkyldiamine, alkyltetraamine is ethylamine, ethyldiamine, ethyl tetraamine stain and rust inhibitor, characterized in that respectively. A pickling steel sheet, which is produced to have a quality of whiteness of 65 or more and yellowness of 3.0 or less by diluting the stain and rust inhibitor of the pickling steel sheet configured as described in claim 1 to a washing solution. The pickling steel sheet of claim 3, wherein the stain and rust inhibitor of the pickling steel sheet is diluted to 0.05 to 0.15% by volume in a washing solution.

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