KR860000178B1 - Manufacture of tinplate and tinplate containers - Google Patents

Abstract

An unreflowed solderable electrolytic tinplate is produced by the Halogen process. Initially coatings of tin are applied on opposite faces of the strip steel(12) from an electrolyte containing stannous tin and fluoride ions. The material is then rinsed with an agent containing less than 8 g/l of fluoride ions and due to carry-over, stannous ions. 0.95-2.5 g/sq. m. of tin is applied on at least one of the strip faces, while the ratio of fluoride ions to stannous tin ions in the rinse solution, is not less than 10:1. Pref., the current density, during electrodeposition, is 600-1600(800-1200) amps/sq. meter.

Description

Tin can steel for manufacturing can

1 is a schematic diagram of a halogen type electro tin plating line.

2 is a cutaway view of a typical can with double ends and two joints longitudinally welded together.

3 is a cross-sectional view of the longitudinal seam of the can of FIG. 2.

4 is a cross-sectional view of the joints at both ends of the can of FIG.

5 is a fine longitudinal cross-sectional view of a steel strip electrodeposited with tin.

6 and 7 are fine longitudinal cross-sectional views showing the plated surface of the reflowed steel strip.

8 is a fine longitudinal cross-sectional view of a steel strip showing the structure resulting from the reflow.

9 to 14 show the results of various tests of reflowed and unreflowed steel sheets.

The present invention relates to a steel plate used for producing tubular containers or cans and the like.

Generally, tin steel sheets for cans are produced by electrodepositing tin on a continuous steel strip. Steel strips are typically used in electrolytic tin plating lines for electrolytic cleaning, pickling processes (immersing them in acidic or alkaline solutions to remove oxides or scales from metal surfaces), electrotin plating, reflow processes, and final chemical or The electrochemical passivation process (the process of lowering the activity of the metal surface by immersing the chemically active metal surface in an aqueous solution of the electropolarization or passivating solvent) is successfully passed. The reflow process known as flow brightening melts the plated tin to temperatures above the melting point of the tin by conduction, radiation, or induction heating at high frequencies to provide a smooth gloss surface, while combining a portion of the tin with the face of the steel strip to Form a layer.

Electrically tin-plated lines can be classified into three types: phenolsulfonic acid type lines, alkali or stenitite lines, and halogen type lines, which are classified according to the type of electrolyte used. The principles are identical to each other.

The present invention employs a halogen type electroplating plating line. The halogen type electrolyte is stored in a series of small cells each having a self-circulation system, a rolling mill, and an anode chamber. The steel strip is plated horizontally across the top surface of the electrolyte in a series of small cells and only the bottom surface is plated. The steel strip then rises upwards and again in the opposite direction, turning the original top face into the bottom face and passing across another series of small cells so that the other side is plated with tin. The halogen-type tin plating line operates at high speed, and may also apply different thicknesses of plating amounts on both sides of the steel strip.

Manufacturers of fine steel sheets have to produce better quality products due to recent high-speed can manufacturing lines, and this demand is required to produce better quality products by manufacturing lines with cans with welded joints. This is especially true when manufacturing steel barrels with seams. The biggest problem when manufacturing cans at high speed is that the welding force is lowered.

Currently, cans with longitudinal seams are usually made of reflowed steel sheets with plating amounts in the range of approximately 2.5 g / m ² . This has been considered necessary to obtain adequate welding force and corrosion resistance.

The present invention can be produced relatively low-cost unreflowed plated steel sheet and at the same time has the same effect as that of a polished stone plate with a large amount of uncontrolled plating, the problem of welding force in the high-speed tin cans It is from the research that pointed out that it alleviates the problem.

According to the present invention there is provided a fine-grained steel sheet further enhanced the welding force and corrosion resistance. Wherein the steel sheet is an unreflowed steel sheet having a plating amount of ² g / m ² or less, preferably having a plating amount in the range of 0.5 to 1.5 g / m ² .

The steel plate may have the same plating amount on both sides, or one side may be thicker.

In halogen type electro tin plating lines, it is most important to minimize the hydration of the tin compound hydrated in the rinse step on the tin plated surface of the sintered steel sheet, which keeps the highly concentrated fluoride ions in the rinse solution. At the same time it has been found that this can be achieved by keeping the ratio of fluoride ions to stannous ions at a very high level.

Halogenated steel sheet according to the present invention is plated with a tin fluoride ion and a tin tin ion to the opposite sides of the steel strip with a halogen to pass the plated steel strip through the fluoride ions in the rinse solution The type is manufactured by line. As the steel strip passes through the electrolyte, the electrolyte is carry-over on the steel strip and at least one side of the steel strip is electrodeposited with a plating amount of 2.5 g / m ² or less, and the plated steel The strip passes through a rinse solution in which the ratio of fluoride ions to stannous ions is maintained at least 10: 1.

Preferably, the concentration of concentrated fluoride in the rinse solution is maintained in the range between 8 g / l and 20 g / l.

The ratio of the fluoride ion to the tin tin ion in the electrolyte may be maintained in the range of 8: 1 to 15: 1, and the electrolyte is composed of tin tin ions, fluoride ions, ferrous cyanide, a brightener, and the like. Can be.

Rinse solution may be composed of sodium bifluoride (NaHF ₂ ) or sodium fluoride (NaF) aqueous solution.

More preferably, at least one side of the steel strip is electrodeposited with a plating amount of 0.5 to 1.5 g / m ² . The precipitation of the hydrated tin compound on the plated surface in the rinsing step is most effectively reduced when the fluoride ions in the rinse solution are present in a suitable form as a compound with the tin, and this phenomenon only occurs when the environment is acidic. In particular, the pH value of the rinse solution should be kept well below 4 by adding hydrochloric acid, and commercial concentrated hydrochloric acid has been found to be suitable here.

Other various features according to the invention will be described in detail below with reference to the accompanying drawings.

Figure 1 shows the overall electroplating line of the halogen type. The steel strip 12 is fed to the accumulator or loop 13 via a pair of unwinding devices 11 that flatten the strip, from which the steel strip 12 is subjected to a stamping machine. High speed feed to the electroplating apparatus generally indicated by reference numeral 19 via a 14, alkaline electrolytic cleaning tank 15, rinsing tank 16, pickling tank 17, and other rinsing tanks 18. do.

The accumulator or loop 13 allows the steel strip to be continuously supplied in the line even when the steel strip coil is replaced. At the exchange of the steel strip coils, the ends of the unwrapped steel strips and the front of the newly exchanged steel strips are welded to each other in the shear welder 20, after which the new steel strips are continuously fed into the line.

In the electroplating apparatus 19, the steel strip 12 passes through a series of electrolyzers 21 each having a self-circulation system, a rolling mill and a tin anode bank and the like. The electrolytic cell 21 is designed so that the steel strip 12 is slightly submerged in the electrolyte so that only the bottom part is plated. The steel strip is then plated backside as it passes through another series of electrolyzers 22 in the opposite direction.

The steel strip plated as described above passes through the electroplating apparatus 19 and passes through the rinsing tank 23 and the passivation tank (not shown). The steel strip is also rewound to an apparatus for winding the steel strip after passing through the oil coating device and the accumulator (not shown).

The electrolyte in the electrolytic cell 21 may generally be configured as follows.

Tin Ion (Sn ⁺⁺ ) 12-25g / l

Chloride ion (Cl ^-) 38g / l

Fluoride ions (F ^-) 34g / l

Ferrous Cyanide 0.75g / l

Polish 3.5g / l

The ratio of fluoride ions (F ⁻ , Sn ⁺⁺ ) to stannous ions in the electrolyte while the line is running is generally maintained in the range between 8: 1 and 15: 1.

The rinse solution in the rinse tank 23 may consist of pure water demineralized and dissolved sodium bifluoride (NaHF ₂ ) or sodium fluoride (NaF).

In addition, the rinsing solution during line operation may contain some of the first and second tin, chloride ions, and fluoride ions due to the electrolyte introduced by the steel strip from the electroplating apparatus 19. Thus, a suitable apparatus is provided for recovering these electrolytes and returning them to the electrolytic cell of the electroplating apparatus 19.

The halogen type electro tin plating line of FIG. 1 is conventional and the details thereof are well known to those skilled in the art of electro tin plating.

FIG. 2 shows a typical can 24 made of masonry steel, which consists of a tubular outer wall 25 and both ends 26, 27. The outer wall 25 has joints 28 welded to each other in the longitudinal direction, and both ends 26 and 27 are connected to the outer wall 25 by double joints 29. The seams 28 of the outer wall 25 are shown in FIG. 3, and the double seams 29 are shown in FIG.

The structure of the can shown in FIGS. 2 to 4 is conventional, which can be produced as a modern high speed forming machine. Here, the stone plate steel that will form the outer wall 25 is supplied to the can body manufacturing machine, where it forms a tubular shape while forming a longitudinal seam 28. The can body is then subjected to a welding bead 31 along the outside of the seam 28 as it passes through the high speed welder.

The can body manufactured as described above has an edge which is bent outwardly from both ends of the can body while passing through the end bending machine, and then the can body is transferred to the double joint and only one end is connected to the double. A sealing member is generally applied before the double jointed joint is formed. In general, the cans are transferred to the canner production line with the top open, and the top end is connected by double splicing in the last process.

In general, lacquer is applied to protect the interior of the can, in which case the lacquer is applied to only one side of the stone plate before forming the can. The application of lacquer for external decoration on such containers, such as beverage cans, is also performed before forming the cans.

Machines for making cans as described above are well known, and the procedure for making cans is also common and is not described in detail here. The present invention mainly describes the features of tin can steel sheets for cans manufactured as such machinery.

Relief of base surface of steel strip as current is distributed evenly over special roughness (0.2 to 1.00 μm CLA with 25 to 150 peaks / cm) on the fine surface of steel when tin is deposited by halogen type electro tin plating line Tin is plated in the same shape as (see FIG. 5).

Invisible fine non-metallic particles are attached to the base surface of the steel strip, which is covered by the precipitated tin during the deposition of tin and forms a small space 35 as shown in FIG. do. Referring to FIG. 6, the plated juicer 31 is covered by the passivation film 33, and the non-metallic particles 34 are covered by the plated tin to form a small space 35.

Reflowing the plated surface of the steel plate as in the conventional method to give it a smooth gloss is provided with a familiar gloss on the plated surface, but the uniformity of the plated surface is lost and the surface tension is shown in FIG. As shown in Fig. 8, a small hole is vibrated, and as shown in FIG. 8, a portion of tin is combined with the base surface of the steel strip to form an alloy.

As a result of the reflow, the amount of plating distributed on the steel strip becomes very uneven and at the same time the amount of plating is reduced at the vertices, and in some cases the vertices may be covered only with alloyed tin.

Also, the "dewetting" phenomenon that occurs on the surface of nonmetallic inclusions depends on the thickness ratio of tin to the width of the inclusion, and the surface tension of tin, and when the tin plating amount is as low as E 05 (2.8g / m ² ), "Wetting" phenomenon is easy to occur, and as the amount of tin plating decreases, the "dewetting" phenomenon becomes more and more severe, and the welding strength and corrosion resistance of the masonry steel sheet are also drastically reduced. The "dewetting" areas of the steel strip's foundation and their associated holes are blocked by chromium compounds during the passivation stage of the steel sheet, while at the same time these areas are welded together with the thin alloy-covered vertices during welding. It acts as a pinch point to block the, so the steel plate with a plating amount of less than E 05 was difficult to use in high-speed can manufacturing line.

If the precipitated tin is not reflowed, the nonmetallic content covered by the deposited tin will continue to be covered with tin, further reducing pinch points and improving weldability. 9, the proportion of pores increases with decreasing tin plating amount, and it can be seen from this point that the unreflowed stone plate is better than the reflowed stone plate.

FIG. 10 shows the results of an Iron Dissolution Value Test (ISV) taken and measured of reflowed and unreflowed steel sheets with varying tin plating amounts. The iron dissolution test is a measure of the exposure of iron, and the results of the test revealed that the iron exposure increased even more after the reflow process. Therefore, if the tin plating amount is reduced, the exposure of iron is much more reflowed than that of the non-reflowed steel. Therefore, it can be seen that the surface of the non-reflowed steel plate is far superior to that of the reflowed steel plate.

The results of this study can be summarized as follows: The extent of tin coverage on the base surface of the steel strip is a major factor affecting the welding force, and reflowing the deposited tin results in steel As the "dewetting" phenomenon occurs at the base of the strip, tin flows out of the vertices, resulting in a very thin coating of the vertices, which severely affects the welding force.

In summary, the non-reflowed steel plate with a small amount of non-reflowed plating has an excellent gloss surface compared to the reflowed steel plate with a high amount of plating, and at the same time, a very satisfactory welding power is achieved even with a non-reflowed steel plate with a very small tin plating amount. You can get In order to test the steel sheet according to the present invention, the unreflowed steel sheet in the range of 3.36 g / m ² (E 06) to 0.56 g / m ² (E 01) was divided into six stages for various tests. And the results are shown in FIGS. This is the result of the comparative test between the stone plate of the present invention and the conventional stone plate.

Referring to FIG. 11, satisfactory welding force is achieved with unreflowed steel sheets having a low plating amount of 0.5 g / m ² (E 01 is 0.56 g / m ² ), while reflowed steel sheets are described above. Excessive tin of at least 2.0 g / m ² is required to achieve a weld comparable to that.

The above "dewetting" phenomenon not only affects the welding force, but also affects the corrosive effect of the steel plate. Figures 12, 13 and 14 show the relative performance of unreflowed and reflowed and reflowed steel sheets that have been variously tested to measure corrosion resistance. The test results demonstrate that the corrosion performance of unreflowed steel sheets is superior to that of reflowed steel sheets. The corrosion tests between the tin coating weight is E 02 (1.1g / m ²⁾ of the corrosion resistance of the tin coating weight Tin ripple plate are not the low E 04 (2.2g / m ²⁾ and E 05 (2.8g / m ²⁾ Point out that it is comparable to the corrosion resistance of reflowed steel sheets.

The results of the test were obtained by a steel sheet produced in a halogen type electro tin plating line shown in FIG. It has been found that it is very important to keep the fluoride in the rinsing tank 23 at a high level in order to produce a low-grade steel sheet having excellent welding force. Since unreflowed fine steel sheet depends on the state of the deposited amount of plating, great attention must be paid to the rinsing step in order to prevent the hydrated tin compound from depositing on the plated surface. It has also been found that the welding force is reduced when the ratio of fluoride ion to stannous ion in the rinse solution drops below 10: 1. In addition, the reduction in welding force occurs when the concentration of fluoride in the rinse solution drops below 8 g / l, and the best result is obtained when the concentration of fluoride is maintained between 10 g / l and 20 g / l.

As a result of extensive testing, the decrease in welding force caused by the deposition of tin compounds in the rinsing solution on the tin plated surface during the rinsing step can be most effectively prevented when fluoride ions in the rinse solution are present in the proper form with the tin compounds. It is found that is only possible if the acid is acidic, especially that the pH value of the rinse solution should be kept below 4 for the best results. This can be achieved very simply by adding an appropriate amount of concentrated hydrochloric acid.

Unexpectedly high welding force and corrosion resistance of low reflowed unrefracted steel sheets resulted in excellent deposition of tin in uniform thickness along the contour of the base surface of the steel strip and very low impurities on the tin plated surface. Caused by. This fact is the coating weight to produce an appropriate amount of Tin plate that are not low of 0.95g / cm ² to this ripple in the laboratory, and demonstrate the desk in a high speed tin manufacturing line. For the can manufacturing test, three tons of steel sheets were cut into a size of 800 × 858 mm and divided into two groups and supplied through a conventional high speed can manufacturing line.

Beverage cans from the first group were successfully manufactured from test materials. Lacquer painting and welding performance were very satisfactory. The lacbuer baking cycle was very difficult in terms of time and temperature, and about half of the useful tin was alloyed. This means that the level of glass tin before welding was 0.5 g / m ² , which is only 20% of the level of glass tin that is always found in E 05, but the welding force was satisfactory. During this particular test, the fabrication losses were not as severe as in the E 05 stone plate, and it was proved that applying an opaque lacquer provided a can of E 02 which is almost indistinguishable from the can of E 50.

In addition, the second group of test materials was used to make beverage cans, which were also very satisfactory for lacquer painting and welding performance, and were found to be better or nearly equivalent to E 05's stone plate.

The shelf life test on the cans produced in this test indicates that there is no fundamental difference between the shelf life of cans made of E 02 and the shelf life of conventional cans made of E 05.

After the two successful cans manufacturing tests described above, about 35 cans of fabrication tests were carried out, each containing at least 3 tons of unreflowed low-grade plated steel sheet at each recovery: a total of 400 tons of test material were produced. Was evaluated. About 33,000 beer and beverage can bodies and about 32,000 food can bodies were produced from unreflowed stone plates, all of which successfully completed at least three months shelf life testing. In the second group of tests, the cans were welded with pure tin welds. The tin welds are not only difficult to use compared to the conventional lead-tin welds, but also have a high failure rate when used in conventional stone steel sheets. It is not only difficult to use compared to pure tin welds, but also has a high failure rate when used in conventional stone steel sheets. The minimum plating amount of reflowed steel sheet to use pure tin weld is E 05, and most can manufacturers use E 07 or higher to work with pure tin weld. However, the non-reflowed steel sheet having a plating amount of E 02 produced according to the present invention was consistently and satisfactorily welded with a pure tin weld in a conventional can manufacturing line.

Manufacturing tests have also demonstrated the importance of carefully controlling the current density in the electrolyzer to produce homogeneous products. This current density ranges from 600 to 1,600 Amps / m ² , preferably 800 to 1,200 Amps / m ² . With a tine speed of 550 m / min, only six to twelve electrolyzers will be used within the range of the best current density. For the reflowed conventional steel sheet of E 05, the current density used in 16 decontamination lines is 1,500 Amps / m ² .

As described above, according to the present invention, a steel plate capable of producing a good can at a high speed in a good manner, that is, a steel plate having a tin plating amount reduced by 66% is provided, and at the same time, the welding faced by the conventional stone plate used in the can manufacture Power problems can be solved. In addition, it can be produced without mechanical or electrical changes to the current tin-plating line and can reduce power consumption by about 60%.

The test results are presented in one embodiment only, and the particular fine steel sheet used in the test does not limit the present invention. Tin plated steel plates with the same tin plating on both sides are generally used for the manufacture of cans to which lacquer is applied, but for cans without lacquer used for canning fruits or fruit juices, they can be made with different plating amounts, ie It is possible to achieve the welding force and the corrosion resistance according to the present invention by making the inside of the thickening amount of plating and the outside of the can thin.

In the typical can shown in FIGS. 2-4, the longitudinal seam is a lock joint, but the low reflow non-reflowing steel plate according to the present invention is intended for storing non-corrosive or non-pressurized contents. It is also possible to have overlapping joints that can be used in cans.

In addition, the above-described good results can be obtained even when the non-reflowed uncoated steel sheet produced by the electro tin plating line other than the halogen type electro tin plating line is low.

Accordingly, the present invention may be practiced in various ways within the scope of the appended claims.

Claims (1)

A tin plate for making tin electrode with tin deposited on a continuous steel strip, wherein the amount of unreflowed tin plating deposited on one side of the steel strip is at least 0.95 g / m ² and up to 2.5 g / m ² Stone plate for manufacturing.

Images