JPS581085A - Grain pattern generation preventing method of tin electroplated steel strip - Google Patents

Abstract

PURPOSE:To prevent generation of a grain pattern on a tin coated surface, by applying as a flux, a solution of an organic acid or its salt, which has a melting point within a specific temperature range, decomposes at the time of reflow, and is not left on the tin coated surface, on the surface of a strip, before performing the reflow treatment. CONSTITUTION:When performing a reflow treatment to a tin electroplated steel strip, a solution of an organic acid or its salt, which has a melting point of 170-300 deg.C, deocmposes at the time of reflow, and is not left on the tin coated surface is applied as a flux on the surface of the strip prior to said treatment. As for the organic acid or its salt, gluconic acid salt, for instance, gluconic acid sodium, glutamic acid or its salt, for instance, alutamic acid monosodium, tartaric acid or its salt, for instance, tartaric acid potassium are used. They are used in a state of a solution of 1-30g/l.

Description

DETAILED DESCRIPTION OF THE INVENTION In the production of electro-tinning steel strip, the present invention provides
70 - This relates to a method for preventing the occurrence of wood grain patterns on the surface of tin plating due to treatment.

Generally, the plating process for electro-tinned steel strings is often carried out on a ferrostan line.

That is, as shown in the schematic process diagram in FIG. 1, a steel strip 1 is guided by a deflector roll 2 and a non-roll 3 into a plating tank 4 containing tin phenolsulfonate, and then subjected to electrolytic plating. , in a dragaud tank 5 using a dilute phenol sulfonic acid solution, and then passing through a squeezing roll 6 and a dryer 7 to dry the surface. Next, in order to improve corrosion resistance and form a beautiful surface gloss, after performing reflow treatment using 970-device 8,
Product.

This reflow treatment generally involves heating and melting the tin-plated surface to approximately 230 to 300°C using a resistance heating method using direct current using commercial alternating current or a high frequency heating method. The method is adopted in most ferrostane lines because the equipment cost for construction is relatively low, the current efficiency is high, and the heating temperature of the strip is relatively easy to control.

During this reflow process, especially when the amount of tin plating is small, such as on ≠25 tin, the plating surface may have a wood grain pattern (W).
Surface defects called ood-grain may occur. This wood grain pattern often occurs in the resistance heating method, and even in the high frequency heating method, it occurs when the heating rate is slow or the current density is high. Electro-tinned steel strings with wood grain patterns have a slightly cloudy surface, resulting in poor beauty or luster, resulting in a decrease in commercial value.

The occurrence of this wood grain pattern is caused by poor surface quality of the steel strip before plating, improper degreasing of the plating line, and improper pickling treatment, but even if these causes are removed, the wood grain pattern may occur.

The reason for this is that in the resistance heating method using alternating current, the heating temperature is
A period of time appears in which the heating does not increase linearly with respect to time and is virtually stagnant, and this periodic heating and stagnation in heating result in the instantaneous formation of molten and semi-molten portions in the tin layer. This is because the oxide film formed on the semi-molten part becomes fixed and grows rapidly, and even when the heating zone comes again, it does not melt, and the flow of tin is hindered and it cannot be made smooth. It is thought that the luster of that area is poor and a wavy, whitish, dull band appears, which gives rise to the wood grain pattern.

In order to prevent the occurrence of wood grain patterns, increasing the amount of tin plating is an effective method on actual production lines, but with the price of tin soaring and the need to conserve resources, this is not an appropriate method. .

As a means to solve the above problem, for example, when performing reflow treatment, a flux is applied to the surface of the tin plating in advance, which has the function of preventing the progress of local oxidation immediately before the start of melting, or evaporating and removing the oxide film. Method of preventing wood grain patterns by painting (Special Publication No. 5l-289
9) is provided. The fluxes used in this method are potash alum, ammonium chloride, tin chloride, etc., and although they are useful in reducing wood grain patterns to some extent, their effects are not satisfactory.

The inventors of the present invention have conducted extensive research on means to solve the above-mentioned problems and reliably prevent the occurrence of wood grain patterns.

As a result, the occurrence of wood grain patterns is caused by the uneven formation of the tin oxide film just before melting, as described above, so it was found that either the formation of the tin oxide film could be reduced or the formation of a uniform tin oxide film could be achieved. The generation of wood grain patterns is prevented by generating tin, and it decomposes from just before the melting point of tin until it reaches its maximum temperature after melting, producing gases such as CO2, H2O, and NH3 on the plating surface. It has been found that the occurrence of wood grain patterns can be reliably prevented by using a flux that does not remain in the wood.

That is, if such a flux is used, the supply of oxygen to the tin layer coated with the flux is suppressed by the flux, so the generation of tin oxide is suppressed, and
Until just before the flux melts, the temperature rise of the tin layer lags behind the rise of the IJ tag temperature, which reduces thermal pulsations. In this case, the heat retained by tin is used up by the decomposition of 7 lux, and the formation and growth of tin oxide can be inhibited. Therefore, the above action makes it possible to prevent the occurrence of wood grain patterns.

The present invention has been made based on the above knowledge, and when applying a phosphorus treatment to an electro-tin-plated steel string, before applying the reflow treatment, a flux is applied to the surface of the electro-tin-plated steel strip. , 170-30
The method is characterized in that an aqueous solution of an organic acid or its salt is applied, which has a melting point of 0° C. and does not decompose during reflow and remain on the tin-plated surface.

In this invention, the melting point of flux '&170~30
The reason for setting it at 0℃ is that if the temperature is less than 170℃, the flux will melt when drying with a dryer after plating, and the coating will not provide enough protection against oxidation. This is because soaking cannot be achieved by coating protection with 7 lux, and on the other hand, if the temperature exceeds 300°C, the coating material will cause wood grains. Further, the reason why an aqueous solution is used as the flux is that the plated surface can be uniformly coated, and the coating can be easily performed by using a drag aud tank.

Also, when flux is reflowed (230~300℃
) and not to remain on the tin-plated surface is because if 7-lac remains on the tin-plated surface, it will cause wood grain patterns.

In order to obtain a flux that satisfies the above-mentioned conditions, tests were conducted using various types of 7luxes, and the presence or absence of wood grain patterns was investigated, and the following findings were made.

(1) Flux sodium gluconate that does not produce wood grain patterns (melting point: approx. 210°C) Monosodium glutamate (melting point: approx. 248°C) Sodium ethylene diamine tetraacetate (EDTA) (melting point: approx. 240°C)
Potassium tartrate (melting point: approx. 170°C) Glycine (melting point: approx. 290°C) (2) Flux sodium phosphate that produces wood grain patterns (melting point: approx. 40°C) Potassium alum (melting point: approx. 92°C) Citric acid (melting point: approx. 152°C) Glucon Acid (melting point: approx. 155°C) Polyhydric acid* (melting point: approx. 185°C) Sunsulfamino acid* (melting point: approx. 205°C) Tin chloride* (melting point: approx. 247°C) Sodium acetate (melting point: approx. 320°C) Ammonium chloride (melting point: approx. (335℃) (However, the one marked with * decomposed at once and remained on the tin-plated surface.) From the above, it was found that the following is suitable as a flux that can satisfy the above-mentioned conditions. Ta.

(1) Gluconate For example, sodium gluconate.

(2) Glutamic acid and its salts For example, monosodium glutamate.

(3) Ethylene noamine tetraacetate (
EDTA) and its salts such as sodium EDTA.

(1) Tartaric acid and its salts For example, potassium tartrate.

(5) Glycine Next, the method of this invention will be explained with reference to examples.

Example 1 Copper strip ≠2 in ferrostane type tin plating bath
5 plating, coated with a CD aqueous solution of phenolsulfonic acid (1-309/l) as a flux, and sodium gluconate (1-30/l).
A mixture of phenol sulfonic acid and sodium gluconate (phenol sulfonic acid l~30 f/7. curconic acid)'
) and those coated with an aqueous solution of ram 1 to 30'/l) were each subjected to siliflo treatment by a resistance heating method.

As a result, when an aqueous solution of phenolsulfonic acid was applied as a flux, a wood grain pattern appeared on the plated surface and the gloss was poor. On the other hand, those coated with an aqueous solution of sodium gluconate as a flux, or those coated with an aqueous solution of a mixture of sodium gluconate and phenolsulfonic acid, have a wood grain pattern when the content of sodium gluconate is 59/1 or more. A product with excellent gloss was obtained.

Example 2 4P on copper strip in ferrostane type tin plating bath
25 plating and coated with an aqueous solution of L-glutamic acid (3-30?/l) as a flux,
One coated with an aqueous solution of EDTA (1 to 30-), one coated with an aqueous solution of sodium acetate (5 to 30'/l), and an aqueous solution of a mixture of 7 lacs of each of Qji at the same concentration. Each coated material was subjected to a siliflow treatment using a resistance heating method.

As a result, L-glutamic acid was more than 5971, EDTA
is 5 f/171! When the concentration of sodium acetate was 371 or higher, no wood grain pattern was generated and a product with excellent gloss was obtained.

Example 3 +2 on steel strip with tin plating bath of ferrostan tights
5 plating and add 5-3% of sodium gluconate to the dragaud liquid in the dragaud tank 5 shown in Fig. 1.
0 t/l was added and subjected to flux treatment, and the squeezing roll 6,
It was led to a reflow device 8 through a dryer 7 and subjected to a reflow treatment.

In addition, as shown in Fig. 2, using a device in which a flux coating tank 9 is installed next to the drag oud tank 5, a steel strip coated with +25 plating as described above is applied to a drag oud containing ordinary drag oud liquid. After passing through the solution/liquid 5, it is led to a flux coating tank 9 containing an aqueous solution containing 5 to 30 f/l of sodium gluconate, where flux is applied, and passed through a squeezing roll 6 and a dryer 7.
0-Siliflow treatment was performed using apparatus 8.

For comparison, a steel strip coated with +25 plating as described above was passed through a dragaud tank 5 containing phenol sulfonic acid, which is a normal dragaud liquid, passed through a drawing roll 6, a dryer 7, and then passed through a reflow device 8. A reflow process was performed. Note that the line speed was 180 mpm in all cases.

As a result, wood grain patterns appear on the entire surface of items that have been reflowed through a Dragaud tank containing phenol sulfonic acid, which is a normal Dragaud liquid.
The surface gloss was also poor. In addition, sodium gluconate
When treated with Dragaud solution containing t/l, slight graining occurred. However, when treated with Dragoud's solution containing 10 f/1 or more of sodium gluconate, a product with excellent gloss was obtained without any wood grain pattern.

Furthermore, when flux was applied in the flux application tank 9, when an aqueous solution containing 5μ of sodium gluconate was used as the flux, a slight wood grain pattern occurred, but an aqueous solution containing 10μ or more of sodium gluconate was used as the flux. When I used it, no wood grain pattern appeared at all, and the surface was beautiful and had an excellent gloss.

As shown in Examples 1 and 2.3 above, when only phenol sulfonic acid, which is an ordinary dragaud liquid, is used as a flux, the occurrence of wood grain patterns cannot be prevented, but sodium gluconate, L -Glutamic acid, EDTA.

When sodium acetate, glycine, etc. were used as 7x and the content f was 3 to 52/l, a significant effect was exhibited in preventing the occurrence of wood grain patterns.

In addition, when adding the above-mentioned flux to the dragaud liquid in the dragaud tank in the tin plating line, or when performing fluff treatment in a flux application tank installed separately from the dragoud tank, depending on the conditions of the roll squeezing machine. Since the amount of adhesion differs, it is necessary to adjust the flux concentration as appropriate, but a minimum concentration of 52/l is required.

- In addition, in the case of differential thickness plating, wood grain patterns occur only on the +25 plating surface, so as shown in Fig. Roll-coating flux on only one side is extremely economical, as the flux is only applied to one side.

The flux used in this invention does not remain in a gaseous state after decomposition and does not remain on the surface of the tin layer after reflow, so it does not adversely affect chemical conversion treatment properties or one-coatability.

As described above, according to the present invention, during the production of electrolytic tin-plated steel sheets, the occurrence of wood grain patterns on the surface of the tin plating can be appropriately prevented by the reflow treatment.
Industrially significant effects such as a beautiful plated surface with excellent gloss can be obtained.

[Brief explanation of drawings]

FIGS. 1, 2, and 3 are schematic process diagrams showing an example of a tinning line for carrying out the method of this invention. In the drawings: 1... Steel strip, 2... Deflector roll, 3
... Zinc roll, 4... Plated tank, 5...
dragaud tank, 6... drawing roll, 7... dryer, 8... reflow device, 9... flux coating machine, 10... roll coater. Applicant: Keita Tsutsumi, agent for Nippon Kokan Co., Ltd. Figure 2 Figure 1 Indication of the case Patent application No. 1987-97542 Name of the invention (Electro-tinning steel) Method for preventing wood grain patterns on IJ knobs 3 Relationship with the case of the person making the amendment Patent applicant address: 1-2 Marunouchi, Chiyoda-ku, Tokyo rMA<9
, 6> Representative of Nippon Kokan Co., Ltd. Minoru Kaneo 4 Agent (1) Specification, page 2, detailed description of the invention, lines 13 to 14, ``After the reflow treatment, the product ``After performing reflow treatment, it is rapidly cooled in a well-known quench tank (not shown), and then chemical conversion treatment and oiling are performed.
Product. ” he corrected. (2) Specification, Section 3, Detailed Description of the Invention, Section 8
In line 1, the sentence ``The heating rate is slow, but the plating current density is high'' should be corrected to ``The heating rate is slow, but the plating current density is high.'' (3) Specification, page 6, detailed description of the invention, -
Lines 14 to 16, replace the phrase "After plating... is melted" with "
"When drying with a dryer after flux treatment, the flux becomes a semi-molten state." (4) Specification, page 7, detailed description of the invention, “
This is because it causes wood grain patterns to occur. ``This is because it may impede the surface gloss after reflow.In this case, the flux may be completely decomposed or partially decomposed, and in the case of partial decomposition, the remaining flux is It is easily removed in the next step, water cooling treatment.'' (5) Specification, Detailed Description of the Invention, page 7, line 14 to page 8, line 12, ``(1) Flux that does not produce wood grain patterns... ... remained on the tin-plated surface.)" is corrected as follows. (1) Wood grain pattern disappears Franks sodium gluconate (melting point: approx. 210℃) Monosodium glutamate (melting point: approx. 195℃) Ethylene diamine tetraacetate (EDTA) (melting point: approx. 240℃)
) Tartaric acid (melting point: approx. 1'i'O℃) Glycine (melting point: approx. 290℃) (2) Flux sodium phosphate that does not erase the wood grain pattern (melting point: approx. 40℃) Potassium alum (melting point: approx. 92℃) Sebesic acid (melting point: approx. 134℃) Sodium acetate (melting point: approx. 320℃) Ammonium chloride (melting point: approx. 335℃) (3) Flux citric acid (melting point: approx. 152℃) Succinic acid (melting point: approx. 185℃) Sulfamic acid (Melting point: approx. 205°C) Tin chloride (Melting point: approx. 247°C)” (6) Specification, page 9, detailed description of the invention, lines 5-6, “・(5) Glycine Inventing a method..."
(5) Glycine and others, erythorbic acid (melting point approximately 1'72°C). Sodium erythorbate (melting point approximately 200°C). Asparagine (melting point approx. 23.5°C), aspartic acid (
(melting point: approx. 271℃), ascorbic acid (melting point: approx. 192℃)
, alanine (melting point: about 198°C), etc. were found to be able to obtain similar effects. Next, I am corrected to say, ``This invention.'' (7) Specification, page 10, detailed description of the invention,
In lines 12 and 13, "sodium acetate (5-30 f/l) J" should be corrected to "glycine (5-301/l)". (8) Specification, page 10, detailed description of the invention,
In the third to second lines from the bottom, the statement "Sodium acetate is 32/ or more" is corrected to "Glycine is 52/ or more." (9) Specification, page 11, detailed description of the invention,
In the 16th line, the phrase "A reflow treatment was performed." is corrected to "A reflow treatment was performed and the product was rapidly cooled in a well-known quench tank (not shown)." 00) Specification, page 12, detailed description of the invention,
In the first and second lines, the phrase "A reflow treatment was performed." is corrected to "A reflow treatment was performed and quenched in a well-known quench tank (not shown)." 0υ Specification, Section 13, Detailed Description of the Invention, Line 6, "Sodium acetate" is deleted. 02) In the description, No. 13, Detailed Description of the Invention, line 7, correct ``3 to 5 ?/l j to r 5 W/ or more''. 0y Specification, page 14, Detailed Description of the Invention, lines 2-3, "becomes gaseous after decomposition" is deleted.

Claims (1)

[Claims] When performing reflow treatment on the electro-tinned steel strip, before applying the reflow treatment, a flux of 170 to 300% is applied to the surface of the electro-tinned steel strip.
A method for preventing the occurrence of wood grain patterns on electrolytic tin-plated steel strips, which is characterized by applying a water-soluble organic salt or organic salt having a melting point of °C and which decomposes during reflowing and does not remain on the tin-plated surface. .