JPS6030589A - Production of welded can body - Google Patents

Abstract

PURPOSE:To prevent the splash and fissure in the weld zone of a thin steel for a can and to improve the appearance and corrosion resistance thereof by plating a specific amt. or above of tin on the nickel plating layers on both surfaces of said sheet and regulating the remaining free tin on the surface after baking the coated films in a specific range. CONSTITUTION:Tin is plated thinly at >=100mm./m<2> on the nickel plating layers formed on both surfaces of a thin steel sheet for a welded can body and the printed and coated film on the surface is baked then the remaining free tin on the surface is regulated to about 50-200mm./m<2>. If the overlap joint part is subjected to electric resistance welding in this state, the scattering of splash owing to the excessive free tin is eliminated and the generation of the fissure in the weld zone owing to the excessively small free tin is prevented, by which the appearance is improved and the corrosion by the fissure is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a welded can body, and more particularly to a method for manufacturing a welded can body made of a nickel-tin plated steel plate.

Recently, very thin nickel plating has been applied to both sides of thin steel sheets, usually with a plating amount of 10 to 1000 m9/m2, and (if necessary, the nickel layer is alloyed with the base steel), and on top of that, a very thin tin plating (usually with a plating amount of 100 m9/m2) is applied. A nickel-tin plated steel sheet coated with a chromate coating of ~1000 mg/m 2 ) and on which a trace amount of chromate film is formed has been proposed as a material for cans, particularly for welded cans. This type of steel sheet has a thin plating layer made of expensive metal, so it is cheaper than tin-plated steel sheet (usually tin plating amount -2800 mg/m2 or more), and nickel-plated steel sheet is plated with nickel alone. It is said to have the advantage that it is less likely to cause stellash (protrusion or splashing of molten metal) during welding.

Generally, steel plates for welded can bodies are coated (including printing) on both sides, leaving the edges to be welded, to form a paint film (including a printed film), and this paint film is heated at around 200°C. After being baked at a salinity temperature for a predetermined period of time, it is cut into blanks and sent to a welding device.

In the case of nickel-tin plated steel sheets, it is presumed that tin is alloyed with nickel during this baking treatment and the amount of free tin is reduced, but according to the experience of the present inventors, nickel-tin in the same lot Even with galvanized steel sheets, depending on the baking conditions, a large amount of splash may occur during welding, or on the inner surface of the weld (if the diameter of the inner electrode roll is smaller than the diameter of the outer electrode roll), the splash may occur in the circumferential direction. It has been found that a problem often arises in that fissures extending over the pores and opening into the pores often occur.

The inner surface of the welded part is repaired with a protective coating after welding, but the occurrence of splash is undesirable because it tends to leave metal exposed even after the protective coating has been formed, which impairs corrosion resistance against the contents. Furthermore, the splash generated on the outer surface of the welded part spoils the appearance of the product.

In addition, cracks can occur when a welded can body is flanged, necked in, beaded, or stretched (used to form barrel-shaped cans, etc.). This is undesirable because it can cause cracks in the container, which impairs the corrosion resistance of the contents.

It is an object of the present invention to solve the problems of the prior art described above.

In order to achieve the above object, the present invention provides extremely thin nickel plating on both sides of a thin steel plate, and the plate is coated with nickel for 10 minutes without corrosion.
A method for manufacturing a welded can body from a nickel-tin plated steel plate formed by applying a very thin tin plating of 0 m97m or more, and in which the top of the plated steel plate is coated with at least a portion near the weld. coated with a paint film, and the amount of residual free tin in the part after baking treatment is 50 to 50%.
The paint film was burnt to a size of 200m97m2,
A method for manufacturing a welded can body, characterized in that the overlapping portion of a can body molded body, in which the overlapping portion is formed by overlapping the portions, is electrically resistance pine seam welded, hereinafter the present invention. I will explain about it.

In this specification, nickel-tin plated steel sheet refers to a low-carbon thin steel sheet that is coated with very thin nickel plating (usually the amount of plating is -10 to 1000 ru9/nz 2 on one side) on both sides to form a nickel layer. Very thin tin plating (
The amount of plating is usually 100~1ooonvAn on one side to form a tin plating layer, and on top of that, a trace amount of chromate coating (usually 2~100~100 on one side in terms of Cr) is applied to improve corrosion resistance.
2'Omy/m2).

Nickel-tin plated steel sheets also include surface-treated steel sheets similar to those described above, except that the nickel in the nickel layer is alloyed with the base iron by heat treatment before tin plating.

Nickel-tin plated steel sheets are supplied in coiled form, but usually in bushy size (e.g. 1 m x 1 m
) Supplied as cut plates. On this cut plate, leave at least a portion that will become the weld and its vicinity (referred to as the weld portion in this specification, the width of which is usually 3 to 6 wn), and apply inner surface paint to the surface that will become the inner surface. For example, epoxyphenol-based paint) is applied and baked for 8 to 14 minutes at a temperature of approximately 90 to 220 degrees Celsius, and then the surface to be the external surface is painted.
Print or paint and heat at a temperature of about 150 to 170℃.
Bake for 4 minutes. Depending on the application, the inner surface coating, outer surface printing, and painting may be performed two or more times each. In this baking step, tin in the tin layer is alloyed with nickel, reducing the amount of free tin. Next, the cut plate that has undergone the above treatment is cut into a predetermined size to form a blank. Both edges of the blank are areas to be near the welding area, and no coating film or printed film is formed thereon.

Next, as shown in Figure 1, roll up the blank and
are stacked to form a can body molded body 2 having a stacked part 2a, and electricity is applied by pressing the stacked part 2a via the wire electrodes 8a and 8b using the internal electrode roll 6 and the external electrode roll 7 to generate electricity. A welded can body is manufactured by performing resistance pine seam welding. In FIG. 1, 3 is a surface treatment layer such as a nickel layer, a tin layer, and a chromate layer (not shown), 4 is an inner coating film, and 5 is an outer printed film.

In this case, the amount of residual free tin before welding is 50 to 200
It is important to determine the baking conditions so that the amount is mg/m2. If it is less than 50 m9/m2, the tin layer that is soft and melts during welding becomes extremely thin, making it difficult to break the chromate layer, and the so-called compatibility between the wire electrodes 8a and 8b and the overlapping part 2a becomes poor. It is assumed that this is because ssolanosis is more likely to occur.

On the other hand, if the size increases by 200 m97 m2, the above-mentioned fissures are more likely to occur. The reason for this is presumed to be as follows.

When manufacturing welded can bodies for storing food and beverages, etc., solid phase welding is usually used to prevent the formation of cavities and splashes in the welded parts. In this case, if the diameter of the outer electrode roll 7 is relatively small to the extent that it is almost equal to the diameter of each inner electrode roll, the contact length between the roll and the overlapping portion 2a becomes short, so that the zero value of the welding current of the AC waveform The proportion occupied by the relatively low heating temperature part (along the longitudinal direction of the welded part) corresponding to the vicinity becomes large, and as a result, unwelded parts or weak welded parts with low welding strength are likely to occur.This should be prevented. Otherwise, the welding speed must be reduced, sacrificing productivity. [Black X Therefore, when the diameter of the welded can body to be manufactured is relatively small, for example, when the diameter is about 30 to 80 mm, a pair of an outer electrode roll 7 with a relatively large diameter and an inner electrode roll 6 with a relatively small diameter is used. has been adopted.

In this case, as shown in FIG. 2, due to the pressing force applied to the outer electrode roll 7 and the inner electrode roll 6 during welding, that is, due to elastic deformation based on the welding load, the outer electrode roll 7 and the inner electrode roll 6 have flat portions 7a, respectively. and 6a. At the same time, portions 8b of the outer line electrode 8b and the inner line electrode 8a corresponding to the flat portions 7a and 6a, respectively;
and 3a1 also slightly decrease in thickness mainly due to elastic compression. Since the outer electrode roll 7 has a larger diameter than the inner electrode roll 6 (the thicknesses of the wire electrodes 8a and 8b are usually the same), the separation part 10 between the outer wire electrode 8b and the upper surface 9a of the welded part 9 is , the separation part 11 between the inner wire electrode 8a and the lower surface 9b of the welding part 90 is also located on the downstream side, that is, on the right side of the figure. Therefore, the welding current 13 passing near the separation part 10 of the outer wire electrode 8b is The heat is concentrated in the separated portion 11 of the electrode, and the welded portion in the separated portion 11 is particularly likely to be heated to a high temperature.

On the other hand, during the welding operation, the can body formed body 2 is fed by the inner and outer wire electrodes 8a and 8b in the direction of the arrow in FIG. One part is extruded (circumferentially). When a current near the peak of the welding current waveform flows, the extrusion of free tin becomes maximum and builds up in the separation section 11. The more free tin there is, the larger the build-up amount becomes, and the separation part 11
Current concentration is promoted.

Therefore, the heat-affected zone 14 (corresponding to the vicinity of the peak of the welding current waveform and where changes in the structure are observed microscopically) becomes forward downward (that is, toward the inner surface of the can body), and its tip 14a When the lower surface 9b of the welded part 9 is approached, and the amount of free tin is particularly large (200 m9/m), the tip 14a reaches the lower surface 9b, melts locally, and forms the pores 15 and the openings of the pores. It is thought that the cracks 16 are likely to be formed easily.

After welding, the welded portion 9 and the surrounding inner and outer surfaces are usually repaired by forming an organic coating such as paint or plastic film for corrosion prevention. Most of the free tin is alloyed with nickel in the nickel layer during welding, but if free tin remains after welding, no free tin remains during paint baking during this repair process, and all free tin becomes alloyed ( From the viewpoint of corrosion resistance and adhesion to paints, etc., it is desirable to heat the material sufficiently so as to mainly convert it into Ni3SR4).

The present invention is not limited to the above examples; for example, painting and printing may be performed on a coiled steel plate.

According to the present invention, it is possible to manufacture a relatively small diameter welded can body made of painted nickel-roasted tin-plated steel plate without causing spranosis or cracks.

Examples will be described below.

Example External electrode roll (made of copper alloy) has a diameter of 85 mm, internal electrode roll (made of copper alloy) has a diameter of 49 lines, and the thickness of the outer and inner wire electrodes (made of rolled copper wire with a rolling reduction of 50 inches). Electric resistance seam welding machine in column 1,0 (welding current is 400
Hz sine wave)'ff: Nickel-tin plated steel sheets with different amounts of free tin (thickness 0.20++ o
According to n), a welded can body with an inner diameter of 52.3 mm was manufactured by performing pine seam welding with an overlap width of 0.4 mm, a welding load of 45 mm, a welding current of 2800 A, and a welding speed of 45 m/min.

Table 1 shows the measurement results for tin lashing and the occurrence of cracks on the inner surface of the welded part.

Table 1 (Note Xi) Nickel plating amount (one side): 30 rr
U; //m, amount of tin plating (one side, amount of free tin on original plate).

5001rLQ/m2, chromate amount (one side) 7m9/
m2 (Cr equivalent) nickel-tin plated steel plate at 210℃
Heating in an oven for 30 minutes (2) (1) I) The nickel-tin plated steel plate before heating was heated in an oven at 210°C for 20 minutes.

(3) Same as (2) except heating at 210℃ x 15 minutes (
4) 200°C x 10 minutes (5) 200°C x 7 minutes (6) Measuring method of free tin amount: After performing anodization for 3 seconds and cathodic treatment for 60 seconds in a 0.5% sodium carbonate aqueous solution. , JIS G 33
It was measured by the electrolytic peeling method described in 03. Chart speed is 1
25+mm/min.

(7) Judgment was made with the naked eye. n-20° dog is 1
Items with 5 or more splashes in the can, small is 4
There are 1 to 4 of them.

(8) The central part of the welding can with a length of 20 trm was examined using a stereomicroscope.
I observed each can. If a fissure occurs, there is at most one on each pitch, so the occurrence rate is

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view taken perpendicular to the axis, showing the state of a formed can body made of nickel-tin plated steel sheet just before welding. Figure 2 shows the process by which cracks are formed during the welding process. FIG. 1a... Edge (portion that should be near the weld), 2...
- Can body molded body, 2a... overlapped portion, 3... surface treatment layer, 4... inner surface coating film, 5... printed film.

Claims (1)

[Claims] (1) A method for producing a welded can body from a nickel-tin plated steel plate formed by applying a very thin nickel plating to both sides of a thin steel plate and then applying a very thin tin plating of at least 100 m9/m2. A paint film is coated on the plated steel sheet, leaving at least the area near the weld, and the paint film is coated so that the amount of residual free tin in the area after baking is 50 to 200m97m2. 1. A method for manufacturing a welded can body, characterized in that the overlapping portion of a can body molded body is subjected to a baking treatment, and the overlapping portion is formed by overlapping the portions, and the overlapping portion is welded by electric resistance mating seam welding.