JPS6056437B2 - Drawing and ironing can made of surface-treated steel plate and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drawn and ironed can made of a surface-treated steel plate and a method for manufacturing the same, and more specifically, the present invention relates to a drawn and ironed can made of a surface-treated steel plate, and more particularly, the amount of tin plating is lower than that of a conventional drawn and ironed can made of a tinned steel plate. The present invention relates to a drawn and ironed can which has significantly improved paint adhesion and corrosion resistance while maintaining a significantly low level of corrosion, and a method for manufacturing the same.

The can body obtained by drawing the metal material between a punch and die and then ironing it has no seams in the can body and the connection between the can body and the can bottom, and has a good appearance and bottom. It has the advantage of not requiring operations such as tightening the lid or forming seams, and the can body is thin, requiring less metal material, making it ideal for applications such as beverage canning. widely used. Naturally, the metal material for this drawing and ironing can must be a material with good workability, and from this point of view relatively expensive metal materials such as aluminum plate and tin-plated steel plate (tin plate) are generally used. There is. Among these materials, there is a problem with tin-plated steel sheets due to the depletion of tin resources.
Due to the economic constraints that the cost of tin increases year by year, it is desirable to reduce the amount of tin plating as much as possible. However, the tin-plated layer acts as a solid lubricant during the 7-draw ironing process of the tin-plated steel plate, and acts as a protective coating layer against corrosion of the casing after processing. Attempts to reduce the amount of tin plating in this manner are subject to limitations from the viewpoints of workability and corrosion resistance.

Thus, at present, only #50 to #100 tin plate (tinning amount: 5.6 to 11.2 y/d) is used as a tinned steel plate for drawing and ironing.
The present inventors have developed a metal material for drawing and ironing that has a tin plating amount of 0.05 to 2, which is considerably lower than conventional materials.
．． Even when using a tinned steel plate within the range of 809/d, when the drawn and ironed cup obtained by drawing and ironing is heated to a certain temperature, the tinned coating layer on the surface of the side wall of the cup is heated. If the tin-iron alloy layer is easily converted into a tin-iron alloy layer and the tin-iron alloy layer is formed on the surface of this side wall, the paint on the casing will be more difficult to coat than when the tin-plated coating layer remains on this surface. It was discovered that the adhesion and corrosion resistance were rather significantly improved, and the present invention was achieved. By making this tin plating layer extremely thin, it is possible to
A feature of the present invention is that the tin-plated coating layer on the surface of the side wall of the case can be converted into a tin-iron alloy layer when heated for a short period of time to a certain temperature, which is particularly advantageous for industrial production such as aluminum alloys. This makes it especially advantageous for industrial production. That is, the object of the present invention is to maintain the amount of tin plating at a significantly lower level compared to conventional drawn cans made of tin-plated steel plates, and to significantly improve paint adhesion and corrosion resistance. An object of the present invention is to provide a drawing and ironing can and a method for producing the same.

Another object of the present invention is to maintain the surface of a metal material for drawing and ironing in a state of a metal tin plating layer sufficient to exhibit a sufficient solid lubricant action during drawing and ironing,
On the other hand, after the drawing and ironing process is completed! Another object of the present invention is to provide a method for producing a drawn and ironed can that can be converted into a tin-iron alloy layer having excellent paint adhesion and corrosion resistance.

According to the present invention, the can bottom is made of a thick surface-treated steel plate, and the can body is made of a thinner-walled surface-treated steel plate than the can bottom, and the can body and the can bottom are connected to each other. At the connection part,
In a drawn ironing can without a seam, the drawn ironing can has a surface layer containing 0.01 to 1.70y/i tin on the side wall of the case, and the surface layer has an exposed area ratio of 20% or more. There is provided a drawing and ironing can having a tin-iron alloy layer of 4, wherein the surface of the bottom of the can is made of a tin-plated coating layer.

The present invention further provides a method for manufacturing a drawn and ironed can, which comprises subjecting a tinned steel plate to drawing and ironing between a punch and a die, wherein the tinned steel plate has a tin coating of 0. .05 to 2.80y/d (7) Using a tin-plated steel plate, heat a drawn cup obtained by drawing and ironing to a temperature of 150°C or higher to form a tin-plated coating layer on the surface of the side wall of the cup. Provided is a method for producing a drawn and ironed can, which is characterized by converting a tin-iron alloy layer into a tin-iron alloy layer. The present invention will be described in detail based on specific examples shown in the accompanying drawings.

1 No. 11A showing the overall structure of the squeezing ironing can of the present invention
In the figure, the can body 1 is composed of a can body section generally designated by 2 and a can bottom section generally designated by 3.

There is virtually no seam between the side surface of the can body 2 and the connecting portion 4 between the can body 2 and the can bottom 3. As will be described in detail later, the can body 2 is formed by drawing a metal material between a punch and a die and then ironing it, and as a result, its thickness is thinner than that of the can bottom 3. There is. A thick flange 6 is provided on the upper edge of the can body 2 via a neck 5 if desired, and double seaming is possible between it and the peripheral edge of the can end member (not shown). It is becoming.

In addition, a smooth spherical protrusion (dome) 7 is provided inward on the can bottom 3 to prevent the can bottom 3 from protruding outward due to the pressure of the contents and to prevent the can from sitting. I'm starting to get better. Further, the case 1'' shown in Fig. 1-B shows the entire structure of the squeezer of the present invention in a negative internal pressure can. A thin flange 6' is provided through the flange 5'', and double seaming is possible between the flange 6' and the peripheral edge of the can end member (not shown). Furthermore, the can bottom 3'' is provided with a planar recess 7'' facing inward to prevent the can bottom 3'' from protruding inward due to atmospheric pressure and negative pressure inside the can, thereby improving the seating of the can. The important feature of the squeeze ironing can of the present invention is that the straining ironing can as a whole has a diameter of 0.05 to 2.80.
In particular, the outer surface has a surface layer containing tin at 0.20 to 1.70 V/d, and the inner surface has a surface layer containing tin at 0.01 to 1.70 V/d, and the inner and outer surfaces of the can bottom 3 are coated with tin. The inner and outer surfaces of the can body 2 have a tin-iron alloy layer with an exposed area ratio of 20% or more, particularly 25% or more.

That is, conventional tin-plated steel sheets for drawing and ironing had a relatively large amount of tin plating as already mentioned above, but according to the present invention, the total amount of tin present on the surface of the drawing and ironing can is reduced. This makes it possible to easily form a tin-iron alloy without impairing processability while significantly lowering the level of tin-iron alloy compared to conventional ones, and also significantly improves the paint adhesion and corrosion resistance of the case. .

From the standpoint of the effects of the present invention, it is extremely important that the surface of the can body substantially consist of a tin-iron alloy layer. That is, in FIG. 2, which shows an enlarged cross section of the can bottom 3, the bottom wall 3 has a steel plate substrate 8, a tinned coating layer 9,
and a tin-iron alloy layer 10 interposed between the substrate 8 and the tin-plated coating layer 9.

Further, in FIG. 3 showing an enlarged cross section of the side wall of the can body 2, the side wall 2 is made up of a steel plate substrate 11 and a tin-iron alloy layer 12 on the steel plate substrate. A metallic tin layer 13 and an exposed iron surface 14 may be partially present. This exposed iron surface requires surface treatment to prevent pitting corrosion caused by iron-corrosive contents such as cola. Therefore, in order to improve corrosion resistance, it is necessary to passivate the exposed parts of the steel surface by applying general surface treatments such as phosphate treatment, phosphochromic acid treatment, and chromic acid treatment. It is. In the present invention, the exposed area ratio of the tin-iron alloy layer 12 of the can body side wall 2 refers to the value SA obtained by the following measuring method.

That is, using a potentiostat (constant voltage electrolyzer),
A saturated calomel electrode was used as a reference electrode, platinum was used as a counter electrode, and the pH was adjusted to 9.5 with sodium hydrogen carbonate. In a 0.05N anhydrous sodium carbonate aqueous solution, the can body surface of the object to be measured with a certain area (for example, 1 cm) exposed is first heated at -2
Polarize from 00rT1■ to -1450n1V, then from -1450rT1V to +400n1■, and finally from +400rT1■ to -13 while obtaining the polarization curve.
Polarize to 00n1V.

In either case, polarization is carried out continuously at a constant rate of 1000 n1 V/min. This polarization curve is shown in FIG. Note that, prior to measurement, a pre-operation is performed as necessary to remove dirt, oxide film, and surface treatment film on the surface of the object to be measured. -1000rT1V to -1200rT1V of this polarization curve
A maximum of three peaks were observed between the two, with the first peak appearing attributable to tin, the second peak to iron, and the third peak to tin-iron alloy. The exposed area ratio SA of the tin-iron alloy layer can be determined by setting the peak height of the tin-iron alloy layer of the sample to be measured near -1130rT]V to HspA/d, as shown in Fig. 4. Define.

The exposed area ratio of the tin-iron alloy layer defined here is 20
% or more, especially 25% or more is desirable.

As is clear from comparing Figures 2 and 3, the can body 2
is thinner than the thickness of the can bottom 3 because it undergoes the drawing and ironing process, and related to this, the thickness of the tin-plated layer remaining on the surface of the can body after the drawing and ironing process is also smaller than that of the tin on the can bottom surface. It is naturally thinner than the thickness of the plating layer. According to the invention,
Rather than leaving the thinned tin-plated layer as it is on the surface of the can body, it is possible to convert the tin-plated layer into the tin-iron alloy layer 12 by heating, so that paints, etc. It was discovered that adhesion and corrosion resistance were rather markedly improved. The tin-iron alloy layer is formed by thermal diffusion of metallic tin, which is a plating layer, and iron, which is a substrate.

In the present invention, the degree of this thermal diffusion is controlled so that the above-mentioned exposed area ratio is 20% or more, particularly 25% or more. This tin-iron alloy layer 12 dissolves only slightly in carbonated drinks such as cola.

Also, for the base metal iron. Although the potential is noble, the potential difference between the tin-iron alloy and iron is small, and the degree of corrosion of the iron base metal is small, with only slight planar corrosion. Also, for juices, this tin-iron alloy protects the underlying iron. The tin-iron alloy layer on the side wall of the can body, which has a small amount of tin plating, is extremely thin, has excellent workability, and has good paint adhesion, so the paint film is difficult to crack during processing.

As the tin-iron alloy layer 12 is formed on the can body side wall 2, the tin-iron alloy layer 10 is also formed on the can bottom 3. The thickness of the tin-plated layer on the can bottom is Since the tin-iron alloy layer 10 is significantly larger and more uniform than that of the side wall of the body, it rarely reaches the surface, and the tin-plated coating layer 9 tends to remain on the surface.

In the drawing and ironing can of the present invention, the thickness of the can bottom 3 is set to D1.
When the thickness of the can body 2 is d, it is defined by the formula.

It is desirable that the ironing rate (RO) is generally in the range of 40 to 80%, particularly 50 to 70%, and that the thickness of each of these parts is in the range of.

Furthermore, the average thickness of the tin-iron alloy layer 12 is generally 0.005
Preferably, the range is from 0.2 microns to 0.2 microns, and the atomic ratio of tin to iron is preferably from 2:1 to 1:3.

The drawn and ironed can of the present invention has a tin plating amount of 0.05 to 2.
．． 80y/i (defined herein as the amount of tin plating and the amount of plating per side), especially the surface that becomes the outer surface of the drawing ironing can is 1.00 to 2.80y/i, and the inner surface and A tin-plated steel plate having a surface of 0.05 to 2.80y/a is used, and this steel plate is subjected to drawing and ironing between a punch and a die in accordance with a well-known operation. It is formed by heating the resulting drawn and ironed cup to a temperature of 150° C. or higher to convert the tin-plated coating layer on the surface of the side wall of the cup into a tin-iron alloy layer.

The tin-plated steel plate used is a low-carbon rolled steel plate electroplated with the amount of tin described above. However, bright plates that are melted after being plated (
It may also be a reflow board).

From the viewpoint of drawing and ironing workability, the former matte board is particularly advantageous. Also, the latter bright plate is advantageous for conversion into a tin-iron alloy layer. In the present invention, if the amount of plating is less than the range mentioned above, the drawing and ironing workability tends to decrease significantly, while if the amount of plating is more than the range mentioned above, it will take a long time to form an alloy to the surface. This requires a heat amount of 3 and is not suitable for the purpose of the present invention, which is to save the amount of expensive tin used. The drawing and ironing process can be easily carried out by means known per se, using a combination of a punch and a die, which are known per se, and supplying a lubricant between the material and the die if necessary.

The ironing rate of the ironing process is preferably within the range described above. The drawn and ironed cup after processing is heated to a temperature of 150° C. or higher to convert the tinned layer on the side wall surface into a tin-iron alloy layer. Formation of an alloy layer due to diffusion of metal tin and iron occurs actively above the melting temperature of tin (23's), but if the temperature is lower than this melting temperature, but above 150°C, the formation of an alloy layer in all stages will occur. As in the case, the formation of an alloy layer by thermal diffusion proceeds. The heating conditions under which the exposed area ratio of the above-mentioned tin-iron alloy layer on the side wall of the can body is 20% or more depends on the amount of tin plating remaining on the side wall of the can body. The smaller the amount of heat energy required, the less heat energy needs to be applied. In the case molded from the above-mentioned #50 to #100 tin-plated steel plate that is currently in use, there is a large amount of tin plating remaining on the side wall of the can body, so the tin-iron alloy layer is exposed. 20% area ratio
In order to achieve the above, it is necessary to provide a large amount of thermal energy, which is not practical. In comparison, if the amount of residual tin plating on the side wall of the can body falls within the claimed range, the temperature ranges from 150°C to 300°C.
By selecting an appropriate combination of heating conditions between 1 minute and 1 minute at °C, the exposed area ratio of the tin-iron alloy layer can be reduced to 20%.
It's easier than ever and has great practical value.

The heat treatment is usually performed in one treatment to increase the exposed area ratio of the tin-iron alloy layer to 20% or more, but it may be performed in multiple stages of two or more stages if desired.

Further, instead of performing the heat treatment as a separate process, a heating process during the production of the squeeze and iron can can be used instead.

For example, by changing the heating and drying process after degreasing and the baking process of paint and ink so that the above-mentioned conditions are satisfied, it is also possible to make the process also serve as a process for forming a tin-iron alloy layer. . The invention will be explained using the following example.

Example 1 Base plate thickness 0.32Tm1 hardness T-2, surface roughness RalμM
．． ．． A bright-plated steel plate with a tin coating amount of 1.68 q/d (inner and outer surfaces) is punched into a disc with a diameter of about 130 Trrfn, and formed into a cup shape with an inner diameter of about 53 mm between a drawing punch and a drawing die according to the usual method. .

Next, it was ironed using a combination of ironing punch and ironing die.

The dimensions and physical properties of this can body are as follows. Bottom wall thickness (D) 0.32wgn Trunk wall thickness (d) 0.10wgn Squeezing rate (
RD) 68.7% Can body inner diameter
537m Can body height 1357 nm Can body volume
300m1 tin-iron alloy layer exposed area ratio 2
~5% After degreasing and cleaning the inner and outer surfaces of this can body, an aqueous sodium salt solution of phosphoric acid having a concentration of 2.5% was sprayed on the inner and outer surfaces of the can body for 208' at 80 DEG C. to form a surface treatment film.

Then I painted it with epoxy urea paint. As for the heat treatment conditions for forming the alloy layer, a treatment was performed at 210° C. for 3 minutes before painting. The exposed area of the tin-iron alloy layer at this time is
It was about 30%. The T-beer strength, which indicates coating film adhesion, was 1.5 to 2.0 kg/Cwi. Thereafter, the can body was filled with a carbonated beverage (cola), the can lid was double-sealed, the can was filled, and the can was subjected to a storage test at 50°C. 1 week and 6
After storage for several months, the can was opened and the inner surface of the can was observed and evaluated.

As a result, the housing of the present invention can be used not only after one week but also after 6 days.
Even after storage for several months, no pitting corrosion was observed on the can body, and no abnormalities such as peeling of the paint film were observed.

In addition, in order to evaluate the adhesion with the external paint, we filled the can of the present invention with a white coat and finishing varnish on the outside of the can, filled it with the contents of a carbonated beverage containing low fruit juice, and then placed it in a can warmer. Alternatively, the housing of the present invention was subjected to heating and heat sterilization treatment using a pasteurizer or the like, but the case of the present invention did not exhibit any abnormalities such as peeling of the white coat or finishing varnish even after undergoing these heat cycles. Furthermore, in order to emphasize the excellent effects of the present invention, a control case other than the present invention was prepared in the same manner as in Example 1 above, except for the following changes.

(1) Control case A: Same case as Example 1, except that the amount of tin attached was 11.2y/771' (2) Control case B, except that the amount of tin attached was 5.6y/7TI Comparison of exposed area ratio of tin-iron alloy layer and coating film adhesion (T-beer strength) on the inner surface of the can body for the two types of control cases and the case of Example 1, which are the same cases as in Example 1. evaluated.

As is clear from the above comparison results, it has been confirmed that the exposed area of the tin-iron alloy layer affects the coating adhesion, and by selecting it within the scope of the present invention, an excellent case can be obtained. It became clear that Example 2 A can body was prepared by drawing and ironing a blank plate similar to Example 1, with the amount of tin deposited on the inner and outer surfaces being 1.70 y/d on the outer surface and 0.56 y/d on the inner surface. A casing was made using the same process and the adhesion of the coating was measured, and it was found to have a strength of 1.3k9/CTn or more.

At this time, the exposed area ratio of the tin-iron alloy layer was as high as 70% on the outer surface and 80% on the inner surface. Example 3 In order to evaluate suitability for contents resistance, the can bodies of Example 1 and the can bodies of Controls A and B were washed and then tested at pH 4.5. An aqueous sodium salt solution of phosphoric acid having a concentration of 2.5 was sprayed on the inner and outer surfaces of the can body at 80° C. for 20 seconds to form a surface treatment film and passivate the iron surface.

Heating was performed at 255° C. for about 9 to 2 hours to form an alloy layer. After that, epoxy urea paint was applied to the can body. For comparative evaluation, the cans were filled with carbonated drinks (cola-based, citric acid-based), stored in a storage room at 50°C for 6 months, and then opened to measure the amount of dissolved iron and check the state of pitting corrosion. Observed. The corroded parts of the cola-based contents of these can bodies were near the seam of the neck-in part and the seam-processed part.

The pitting corrosion occurred near the seaming of the neck-in part. From the above results, it was confirmed that the case of the present invention had sufficient can performance with no abnormality observed in the suitability for contents resistance.

Example 4 Base plate thickness 0.30WL1 hardness T-2112, surface roughness Ra
lμM. ．． A matte plated steel plate with a tin coating amount of 2.24y/a (inner and outer surfaces) with a diameter of 145Tfr! Punch out a disc of Fi, using the usual method, to make an inner diameter of approximately 72.2 between the drawing punch and die.
Form into a T1Un cup shape.

Next, this cup-shaped molded product was subjected to a re-processing process, and then the cup-shaped molded product (inner diameter of about 65.4 wm) was subjected to the same stiffening process as in Example 1.

The dimensions and physical properties of this can body are as follows. Bottom wall thickness (D) 0.30T! Un trunk wall thickness (d
) 0.0gIrgn pumping rate (Rd)
70% Can body inner diameter 65.4 mm Can body height 122 order Can body volume 410 m1 Tin-iron alloy layer exposed area ratio 0% This can body was subjected to a heating cycle in the same manner as in Example 3.

At this time, the exposed area ratio of the tin-iron alloy layer was as high as 25 to 30%. After coating this can body in the same manner as in Example 3, the coating adhesion was measured, and the beer strength was 1.5.
It was confirmed that the adhesive exhibited excellent adhesion of k9/Cm or more, and was also good in a case using a matte board.

Example 5 The tin coverage was prepared according to Example 2.

External adhesion amount 1.70y/Nf, internal adhesion amount 1.12y/Nf
d, with the aim of improving workability on the outer surface and secondary corrosion resistance on the inner surface, and increasing the coating amount on both sides. Adjusted different matte plated steel sheets. The can body was manufactured according to the method of Example 1.

As a result, no trouble occurred during ironing, the diffusion condition during the heating cycle was good, and the exposed area ratio of the tin-iron alloy layer was 35% on the inner surface and 35% on the outer surface. Similar to Example 3, carbonated beverages were filled and stored for long-term storage.
When the can was opened two months later, no abnormalities were found on the inside of the can.

In addition, a 1.5% salt water spray test was conducted to evaluate the adhesion of the paint to the outer surface.

As a result of the test, no peeling of the outer coating film was observed even after one week.

Example 6 When the can body prepared in Example 4 was subjected to a heating cycle of 250°C and approximately 308°C, excellent promotion results were obtained with an exposed area ratio of the tin-iron alloy layer of 70% or more on both the inner and outer surfaces. Ta.

When a coating film adhesion test was conducted using the can body, it showed a T-beer strength of 1.5k9/Cm or more.

Furthermore, no abnormality was observed in either the cola or the liquid in the corrosion resistance test.

[Brief explanation of the drawing]

Figure 1-A is a diagram showing the overall structure of the squeezing can of the present invention when the can bottom has a curved surface, Figure 1-B
The figure shows the overall structure of the squeezed can of the present invention when the can bottom has a flat surface, and Figure 2 is an enlarged cross-sectional view of the bottom of the squeezed can of the present invention. Fig. 3 is an enlarged sectional view showing the side wall of the can body of the squeezed can of the present invention, and Fig. 4 shows the polarization curve of the can body surface. is the can body, 3 is the can bottom, 4 is the connection between the can body and the can bottom, 5 is the neck, 6 is the flange,
7 is a projection (dome), 8 is a steel plate substrate, 9 is a tin-plated coating layer, 10 is a tin-iron alloy layer, 11 is a steel plate substrate, 12 is a tin-iron alloy layer, 13 is a metal tin layer, 14 is exposed iron Show each side.

Claims (1)

[Scope of Claims] 1. A can body obtained by subjecting a surface-treated steel plate to drawing and ironing, and consisting of a relatively thick-walled can bottom and a relatively thin-walled can body; In a drawn ironing can which has no seam at the connection part between the part and the bottom of the can, the can body of the drawn ironing can has a surface layer containing 0.01 to 1.70 g/m^2 of tin; A drawing and ironing can, characterized in that the surface layer forms a tin-iron alloy layer with an exposed area ratio of 20% or more, and the surface of the bottom of the can consists of a tin-plated coating layer. 2 The can body of the drawn and ironed can has a surface layer containing 0.20 to 1.70 g/m^2 of tin on the outer surface, and a surface layer containing 0.0 g/m^2 on the inner surface.
The drawing and ironing can according to claim 1, characterized in that it has a surface layer containing 1 to 1.70 g/m^2 of tin. 3. In a method for manufacturing a tin-plated can, which involves subjecting a tin-plated steel plate to drawing and ironing between a punch and a die, the amount of tin plating is 0.05 to 2.80 g/ A drawn and ironed cup obtained by ironing using a tin-plated steel plate of m^2 is heated to a temperature of 150°C or higher to convert the tin-plated coating layer on the surface of the side wall of the cup into a tin-iron alloy metal. A method for manufacturing a squeezed iron can. 4. As a tin-plated steel plate, the amount of tin plating is 1.00 to 2.80 g/m^2 on the outer surface of the drawing and ironing can, and 0.05 to 2.80 g/m^ on the inner surface. 4. The manufacturing method according to claim 3, wherein a tin-plated steel plate having a tin plating amount of 2 is used.