JP2000234183A - Steel sheet for film laminated welded can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel sheet for a film laminated welded can large in ACR (weldable range in which a sound nugget free from the generation of scattering at the time of welding and welding peeling in a can expanding test is formed) in the case a steel sheet for a welded can laminated with a film is subjected to seam welding to form into a can barrel and also free from the generation of a defective can caused by scratches even in the case of welding at a high speed. SOLUTION: This invention is a steel sheet for a welded can in which a tinning layer is formed on at least either surface of the steel sheet, and the upper layer is provided with a film laminated layer composed of an organic resin film, the average surface roughness Ra of the steel sheet is 0.2 to 0.4 μm, and in the tinning layer, metallic tin is contained in the range of >250 to 600 mg/m2, and alloy tin is contained in the range of 400 to 1,500 mg/m2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film-laminated steel sheet used for a three-piece weld can (hereinafter simply referred to as "weld can") obtained through a seam welding process. The present invention relates to a steel plate for a film-laminated welded can having no flaw on a can body.
In addition, the present invention relates to a steel sheet which is particularly suitable for being applied to a case where the steel strip is formed into a cylinder whose axial direction is the longitudinal direction of the steel strip to finish the welded can.

[0002]

2. Description of the Related Art Steel plates for cans include Sn, Cr, Ni on the surface of the steel plate.
These are processed into three-piece cans or two-piece cans, and are supplied as beverage cans, food cans, and the like. Above all, the three-piece can consists of three parts: the top lid, the bottom lid, and the seam-welded can body. The manufacturing process is simpler than the two-piece can, making it easier to rationalize, and suitable for the production of small lots and many kinds. It has the advantage of being.

[0003] In the production of such three-piece cans, particularly three-piece cans using tin-plated materials, major technological advances brought about by recent mass consumption include increasing the tensile strength of the steel sheet used and reducing the weight by reducing the thickness. Increasing the speed of seam welding and rationalizing can manufacturing and improving productivity by employing a film-laminated steel plate (a state in which an organic resin film such as a polyethylene terephthalate film (PET) is baked on a steel plate).

[0004] In the production process of a three-piece can, the seam welding process of the can body plate plays an important role in determining the quality and productivity of the can body. In the seam welding operation, problems that generally occur are splash (splash) and peeling of a welded portion in a can open test. Scattering is basically caused by the flow of overcurrent, and peeling is caused by the necessary current not sufficiently flowing to the joint surface between the steel plates. In seam welding, there is a proper current range (a weldable range, hereinafter simply referred to as “ACR”) for preventing both of these defects from occurring, and the larger the range, the better. If the ACR is small, peeling is likely to occur if the current value is reduced in order to prevent the occurrence of scattering. Conversely, if the current value is increased so that peeling does not occur, scattering will occur. For this reason, a material having a large ACR is basically required for a steel plate for a welding can.

[0005] In the case of seam welding, when a high-strength, ultra-thin (thickness: 0.2 mm or less) steel plate is used as the material of the three-piece can body, the welding operation becomes more difficult in the following points. That is, in an ultra-thin steel plate, the air resistance of the joint surface becomes relatively large, and the contact resistance becomes large. Also, when the sheet thickness is small, the heat generated by seam welding is carried away by the welding can body, so that the temperature of the steel sheet increases and the electric resistance increases. Such an increase in contact resistance and electric resistance tends to cause frequent spattering during seam welding. Thus, high-speed welding is increasingly more difficult than with normal thickness because ultra-thin steel sheets have a narrower ACR and it is increasingly difficult to stably avoid both spalling and flaking.

[0006] As described above, recent technological advances along with the extremely thinning of the can body material include a change in the method of painting and printing on the can body plate. That is, conventionally, after a sheet is coated (4 to 6 rows × 5 to 6 rows with a wide sheet), it is baked by a heating oven (a high temperature and long time treatment at 190 to 210 ° C. for 10 to 20 minutes). Was. An alternative to this was the film lamination method. In this method, a gravure-printed film is laminated on the outer surface of the can at the same time, and a plain transparent film is laminated on the inner surface of the can at the same time. In addition, there is an advantage that the flavor of the contents can be secured. Since the lamination to the steel plate is performed while leaving a portion to be seam-welded, the metal is exposed at the portion to be welded (the width edge of the slit material). This method is described in, for example,
In the publication No. 868, from the coil wrapped with the can body blank material, both sides of the long can body blank material (narrow coil corresponding to the circumferential length of one can) supplied continuously are welded to both sides. A method of thermocompression bonding a film while leaving exposed portions of metal Cr at corresponding end edges is disclosed.

[0007] This film laminating method is not only environmentally friendly because it does not use a heating oven, it is also capable of high-speed passing, and even in the case of multiple colors, it can be finished with one passing and the plate change is only for film replacement. In addition, since printing on the can body plate can be performed by heating for a short time, the welding machine can be directly connected to the film laminating line, and this is a technology expected to further improve productivity.

[0008]

However, even if a high-efficiency and high-productivity production system is adopted by employing these recent technologies, when a defective can having some defect occurs, the material in operation is not treated. The operation will be stopped due to replacement of the line or the repair of the line, and the expected effect will not be sufficiently exhibited. Therefore, in the new production system, it is particularly important to avoid troubles of defective products.

However, in reality, when the above-mentioned recent technology is adopted and a film is laminated on a surface of a high-strength ultra-thin steel sheet having a thickness of 0.20 mm or less and high-speed welding is performed,
About several hours after the start of the operation, the strength of the welded portion is insufficient, so-called poor welding is likely to occur. In addition, there is also a problem that a poor appearance can occur such as abrasion on the outer surface and the inner surface of the can body. There was also a tendency that such defective cans frequently occur as the welding speed increases. Among the laminated cans, the method of cylindrically forming the steel strip in the longitudinal direction with the longitudinal direction of the steel strip as the axial direction of the cylindrical body is such that the non-laminated part for welding is located at the end of the slit coil width, so that the laminating process is easy and the productivity is high. Is high. However, since the yield strength in the width direction of the material steel plate is generally high, the springback during cylindrical forming is large. For this reason, the width of the overlap margin of the welded portion is not stable, and welding defects are more likely to occur, which is a problem.

Accordingly, a main object of the present invention is to solve such a problem in the prior art, and when a steel plate for a welding can laminated with a film is seam-welded to form a can body, the ACR is used. (The weldable range in which a sound nugget is formed without spattering during welding and no peeling during welding test) is large, and no welding failure occurs even when welding at high speed, and appearance defects due to flaws etc. An object of the present invention is to provide a steel plate for a film-laminated welding can that does not generate a can.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to achieve the above-mentioned problems, and as a result, the spark behavior at the time of welding, which has not received much attention, has affected welding defects and flaws. It has been found that in order to optimize the sparking behavior, it is necessary to appropriately control the amounts of metal tin and alloying tin and the surface roughness of the steel sheet. In addition, it has been found that since the laminating conditions in the film laminating method are different from the conventional printing and baking conditions, the amounts of tin metal and tin alloy are likely to be in a region disadvantageous to spark generation. That is, in the present invention, a tin plating layer is formed on at least one surface of the steel sheet,
A steel plate for a welding can having a film laminate layer comprising an organic resin film as an upper layer, wherein the steel plate has an average surface roughness Ra of 0.2 to 0.4 μm, and the tin plating layer has a metal tin of 200 to 600 μm. mg / m ² and alloy tin 400
A steel sheet for a film-laminated welded can, characterized in that the steel sheet is contained in a range of up to 1500 mg / m ² .

In the above invention, the average surface roughness is
A particularly preferable range is 0.28 to 0.38 μm, the amount of metallic tin is more than 250 to less than 500 mg / m ² , and the amount of alloy tin is more than 550 to 1100 mg / m ² . Further, in the above invention, it is particularly preferable to adopt a layer configuration in which a Ni base plating layer is formed on the surface of the steel sheet, a reflow-processed tin plating layer is formed thereon, and a chromate layer is further formed thereon. In addition, the average surface roughness of the steel sheet in the present invention refers to the value of the material surface immediately before tin plating. Therefore, when Ni plating is performed, the value is in a state after Ni plating (when diffusion processing is performed after Ni plating, a state after diffusion processing).

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a description will be given of the research results that led to the development of the present invention. After Ni plating on a cold rolled steel sheet with a thickness of 0.150 mm at a nickel content of 80 ± 20 mg / m ² ,
Ni diffusion treatment by continuous annealing at 0 ℃ or Ni amount 200 mg
After Ni plating at / m ² , the surface roughness Ra was adjusted to about 0.3 μm and the degree of temper was adjusted to T5 by a temper rolling mill without performing a diffusion treatment. Next, after flattening electrodeposition with a tin basis weight of 1340 mg / m ² , a tin alloying heat treatment (reflow treatment;
The temperature was raised to 280 ° C., and then put into a water tank at 50 to 80 ° C. within 1 second after heating. Furthermore, on the upper layer, the amount of metallic Cr is 8 mg / m ² ,
Plating was performed at a Cr content of 6 mg / m ² to obtain a thin tinned steel sheet. In this reflow process, by controlling the time from temperature increase to water cooling and the temperature reached, the alloying amount of tin,
The amount of metal tin was adjusted to various ranges. This plated steel sheet is coated with (1) a conventional sheet coating method (210 ° C x 20 minutes), (2) a plain PET film on the inner surface of the can, and a pre-printed PET film on the outer surface of the can. They were laminated and baked in a heating furnace (220 ° C. × 1 minute) to form steel plates for welding cans, respectively, by a film lamination method.

[0014] After slitting these steel plates for cans to the size of a can unit, the welding speed (copper wire feed speed) is set to 120 m.
Per minute, the operation of continuous can production was carried out at an ultra-high speed, and the flaws on the plating surface of the can body and the occurrence of defective welding cans were examined in detail. The direction of can forming was set such that the longitudinal direction of the steel strip was the axial direction of the cylindrical body (the same applies hereinafter). As a result, in the steel sheet for cans finished by the conventional sheet coating method, no poorly welded can was generated even after the passage of time. On the other hand, flaws are hardly conspicuous due to the rigidity of the printed surface, but when closely observed, the flaws were observed over time. On the other hand, some of those finished by the film laminating method were automatically removed as defective welding cans by the inspection and sorting device as the continuous operation time passed. In addition, flaws appeared on the plating surface of the can body, and some were generated within several hours at an early stage.

The present inventors have observed the surface of the flawed can, the welding machine and its surroundings in detail in order to pursue the cause of flawing. As a result, the following facts were confirmed.・ Plating film laminating line with no ground (plating
It seems that tin clumps adhere to the end of the steel sheet conveyed by the unmelted tin sheet and before lamination), which seems to be related to the cause of the flaw. -When the cans removed as defective welding cans are examined in detail by observation, analysis, cross-sectional microscopic observation, etc., in most cases, tin clumps are caught in the welding lap. (In addition, a small number of tin-based masses were sandwiched instead of tin.)-When closely observing the vicinity of the electrode wheel of the welding machine, white powder was found around the Z bar and cylinder. Has a white lump (tin lump) of the same size as that found in the removal can, which falls for some reason and becomes a poorly welded can when it adheres to the weld joint thing. Note that Z
The bar is a guide rod having a substantially Z-shaped cross section for guiding both ends to be welded to the position of the electrode wheel, and its tip extends to the vicinity of the electrode wheel.

Therefore, the tin weight and the reflow treatment conditions were changed in various ranges, and for the steel sheet for cans manufactured by the same film laminating method as described above, the relationship between the metal tin amount of the steel sheet before welding and the tendency of defective cans was observed. The relationship was investigated. The result is shown in FIG. From FIG. 1, in order to prevent the generation of defective cans, the amount of metal tin is set to 200 to 600 mg / m ² , preferably 250 mg / m ² .
It can be seen that it is necessary to make the range of super-less than 500 mg / m ² . In the range of 200 mg / m ² or less, the ACR was out of the range (strong welding), a sufficient welded portion could not be obtained, and dust was frequently generated. On the other hand, if it exceeds 600 mg / m ² , defective welding cans frequently occur. According to the investigation described below, the cause of defective welding cans was that sparks became remarkable when the amount of tin exceeded 600 mg / m ² , and particles consisting mainly of tin scattered by the sparks accumulated on Z bars and the like. It became impossible to withstand its own weight, and as a result of insufficient welding as a result of dropping and adhering to the welded joint due to vibration during operation.

In resistance welding of steel sheets for cans, sparks, that is, scattering of (melted) metal particles due to electric discharge (short-circuit current) have been conventionally observed, but the particles thus dispersed form a red fireball. In particular, the effect on the quality of the can, such as poor welding and flaws, is hardly considered as a problem (spark is a phenomenon different from scattering in which molten weld metal is scattered by pressure). However, the present inventors presumed that the above-mentioned white chunk of tin was also caused by sparks, and photographed the welding situation with a high-speed video camera. As a result, in addition to the red fireball-shaped particles that can be observed with the naked eye, it was found that white powdery particles were also scattered by the spark. As a result of collecting and analyzing these particles, red fireball-shaped particles were 50 to 300 μmφ.
It was found that the white powdery particles were spherical, having a size of 30 μmφ or less, and mainly composed of tin. The spark particles in the form of fireballs mainly composed of iron have a long scattering distance, and since most of them are scattered on the floor of the welding machine, they do not adhere so much around the electrode wheels, and thus have not been a serious problem in the past. However, in this survey, some of the causes of poor welding were found, and it was found that there was no problem. This is presumably because some tin is mixed in the iron spark, and due to the high adhesion of the tin, the iron spark also partially adheres around the electrode wheel. On the other hand, white powdery spark particles mainly composed of tin adhered to the periphery of the electrode wheel, such as Z bars, and as a result, some particles were deposited and grown to a mass. It was considered that such a lump dropped due to vibration or its own weight, and when the drop position was a portion to be welded, it hindered welding and resulted in poor welding.

It is considered that the reason why the scratches on the groundless surface (steel sheet after plating and before lamination) increased as the amount of metal tin increased was due to these sparks. That is, although it is assumed that a part of the spark particles had also adhered to the can body in the past, since the steel plate was painted and printed (the surface was relatively hard), no noticeable flaw was generated. Conceivable. On the other hand, in the case of the laminated can, since a considerable amount of soft metal tin is present on the surface, the flaws become deep and thick, and it is considered that the flaws have a level of scratches that may be a problem in appearance. In the manufacturing process of the laminated can, in many cases, a slit plate, which is a material steel plate, is conveyed on a cemented carbide plate at the time of feeding the steel plate on the entrance side of the film laminator. It seems to be a factor.

In order to prevent the occurrence of defective cans due to such causes, it is necessary to reduce the generation of sparks, especially the generation of white spark particles mainly composed of tin. For this purpose, as described above, it is important to optimize the amount of metallic tin. However, investigations by the inventors have revealed that it is necessary to further optimize the amount of alloying tin and the surface roughness. First, it is necessary to set the upper limit of the amount of metallic tin to 600 mg / m ² or less, as already shown in FIG. At 600 mg / m ² or less, poor welding and flaws do not often occur, but at more than 600 mg / m ² , a large amount of tin-based white sparks are generated, and the occurrence of poor welding and flaws increases. In addition, the number of scratches increases due to the surface softening accompanying an increase in the amount of metal tin on the surface. As shown in FIG. 1, by setting the amount of metal tin to less than 500 mg / m ² , the occurrence of poor welding and flaws can be reduced to almost zero. It is necessary that the amount of metallic tin be 200 mg / m ² or more. When the amount of metal tin is 200 mg / m ² or more, the occurrence of poor welding is considerably small. However, when the amount of metal tin is less than 200 mg / m ² , the contact area with the electrode ring is small and the welding current is locally concentrated.
CR becomes small and poor welding occurs frequently. In particular, when the degree of softening due to welding heat is small, the adaptation to the electrode ring becomes poor, and the contact area is further reduced, so that the adverse effect is large. On the other hand, if the amount of metal tin is too small, the amount of heat generated by the can body itself during welding becomes small, the temperature of the welding machine increases, and the electrical resistance (specific resistance) increases. . In addition, metal tin amount is 250
By setting it to be over mg / m ² , the occurrence of poor welding becomes almost zero. Therefore, the amount of metallic tin is 200 mg / m ² -600 mg /
m ² , with a preferred upper limit of less than 500 mg / m ² and a preferred lower limit of more than 250 mg / m ² .

In FIG. 1, "large" indicates about 10%, "small" indicates about 1%, and "quitely small" indicates about 0.2% of welding defects due to the ACR factor. Is less than 0.1%. In addition, welding failures caused by sparks are substituted by almost the same aging effect evaluation. Regarding the operation time until maintenance work (removal of spark particles) such as Z-bar is required, "large" is about 30 minutes and "less".
Means about 120 minutes, "very little" means about 240 minutes, and "none" means that no operation requires maintenance even if it exceeds 300 minutes. In addition, as for the scratches, “a lot” is such that the flaws can be seen at a glance visually, “small” the degree that can be found by searching a little, and “none” if it is not easily understood by the naked eye. And

Next, the effect of alloy tin on the weldability is shown in FIG. ◎, ○,
The evaluation criteria for Δ and × are the same as those in FIG. Although alloy tin does not have the same effect as metal tin as sensitively, the presence of a large amount of tin increases the occurrence of tin-containing sparks and tends to cause poor welding. For this reason, the upper limit of the amount of alloy tin is set to 1500 mg / m ² . If alloy tin is present in an amount exceeding 1500 mg / m ² , spark-induced welding failures frequently occur, and flaws easily occur. In addition, the amount of alloy tin was 1500 mg / m ²
If it is less than 1, welding failure will not occur much, 1300 mg
/ M ² in the following without the flying etc. occurs, occurs almost at 1100 mg / m ² or less is zero. On the other hand, if the alloy tin amount is too small, the suitable range of the metal tin amount between the welding failure due to the shortage of the ACR region and the welding failure due to the spark tends to narrow, and the welding failure also tends to increase. For this reason, the lower limit of the amount of alloy tin is set to 400 mg / m ² . In addition, when it exceeds 550 mg / m ² , the occurrence of poor welding becomes almost zero, which is particularly preferable. It is presumed that the reason why welding defects easily occur when the amount of alloy tin is small is related to the fact that the temperature of the welding machine becomes high and the electrical resistance increases as in the case of metal tin.

In order to control the amount of metal tin and the amount of alloy tin during plating within the above-mentioned appropriate ranges, the conditions of the reflow treatment after sprinkling may be adjusted mainly. In particular, the lamination process is often low temperature or short time compared to the print coating process, and considering that tin alloying is difficult to progress, adjust the metal tin slightly less than the coating material, and after lamination process It is preferable that an appropriate amount remains. Therefore, the amount of tin alloy should be in the range of 400 to 1500 mg / m ² , with the preferred upper limit being 1300 mg / m ² , more preferably
1100 mg / m ² , and a preferable lower limit is more than 550 mg / m ² .

Next, the effect of surface roughness on spark generation is shown in FIG. Spark "Large" is about 30 minutes, "Medium"
Indicates a level that requires care in about 180 minutes,
Did not require maintenance for more than 300 minutes of operation. When the surface roughness (plate surface roughness) is less than 0.2 μm, tin-based white sparks occur frequently. This is presumably because the surface area of the steel sheet becomes small at a low roughness, so that the area covered with metal tin relatively increases, and tin sparks are easily generated. Further, when the surface roughness is small, the flaws are relatively conspicuous, so that the occurrence of scratches increases. Therefore, the surface roughness needs to be 0.2 μm or more. In addition,
By setting the surface roughness to 0.2 μm or more, the generation of sparks is considerably reduced. However, when the surface roughness is set to 0.28 μm or more, it is possible to reduce to a level at which little influence on poor welding and scratches is observed. On the other hand, when the surface roughness exceeds 0.4 μm, sparks increase, although iron sparks having less influence are mainly contained. This is presumably because the electrical resistance increases due to the reduction in the contact area, but there is also a possibility that iron is exposed due to the increase in the steel sheet surface area. In any case, when the surface roughness is set to 0.4 μm or less, the generation of sparks is considerably reduced. In addition, when it is 0.38 μm or less, it can be reduced to a level at which the effect on poor welding and abrasion is hardly observed. Therefore, the surface roughness is set in the range of 0.2 to 0.4 μm, and more preferably, 2.8 to 3.8 μm.

Next, a specific example of the method for producing a steel sheet for a can according to the present invention will be described. As the material for the steel sheet for cans, a low carbon aluminum killed continuous cast steel of C: 0.1 wt% or less or an ultra low carbon aluminum killed continuous cast steel of C: 0.004 wt% or less, which has been conventionally used as a material for can steel sheets, is used. Is preferred. This material is hot-rolled, pickled, and cold-rolled by a conventional method, and then continuously annealed to produce a cold-rolled steel strip, which is then dry-tempered without lubricating oil (total rolling reduction is 3% or less). ) Is performed on two stands. Temper rolling is performed by appropriately adjusting the surface roughness of the rolling rolls of the first and second stands of the temper rolling mill. Dry temper rolling can be performed with one stand or two or more stands, or in some cases, with three or more stands. The method of forming the surface roughness of the rolling roll is a method of polishing with a grindstone, a method of injecting fine super-hard steel powder at high speed after polishing the roll surface, a method by discharge dull processing, a method by laser dull processing etc,
Either method may be used.

In producing the steel sheet for a can of the present invention, it is desirable that the tin of the tin plating layer be distributed in an island shape in order to further improve the weldability.
In order to achieve such a distribution, Ni plating is performed as a base treatment of the plating material before tin plating,
Subsequently, it is necessary to perform a Ni diffusion process and further perform a reflow process after the tin plating. In order to further improve the corrosion resistance, it is also desirable to perform a chromate treatment on the tin plating layer on which the reflow treatment has been performed. That is, in the layer configuration of the present invention, on the surface of the steel sheet, there is a base plating CAL diffusion layer of Ni, on which a reflow-treated tin plating layer is further formed, and further thereon, a chromate layer made of metal Cr and Cr oxide is formed. Are particularly suitable. As described above, when a base treatment by Ni plating is performed before the tin plating step, the average surface roughness of the steel sheet according to the present invention is in a state immediately before the tin plating, that is, after the Ni plating (diffusion treatment after the Ni plating). , The average surface roughness measured after the diffusion treatment).

[0026]

Next, the present invention will be specifically described based on examples. Low-carbon aluminum-killed continuous cast steel or ultra-low-carbon aluminum-killed continuous cast steel, which is generally used as a steel sheet for cans, is hot-rolled (finishing temperature
900 ± 30 ° C), pickled with hydrochloric acid, cold rolled into cold-rolled steel strips of various thicknesses, and the Ni plating amount was 20 to 500 mg / m ² per side at the continuous annealing line entry side, Ni plating was performed in a weight ratio of Ni / (Ni + Fe) of 0.01 to 0.30 and a thickness of the Ni + Fe alloy layer in a range of 10 to 4000 °, and diffusion treatment was performed in a continuous annealing heating furnace and a soaking furnace. Thermal cycle of annealing is 680 ~ 760 ° C × 10
Second, HNX gas atmosphere (10% H ₂ + 90% N ₂ )
And The other part was plated with Ni on the entry side of the tin plating line and was not subjected to diffusion treatment.

The surface-treated steel sheets were made to have a surface roughness Ra:
The surface roughness was adjusted to Ra: 0.1 to 0.6 μm by temper rolling (without rolling oil) using a work roll of 0.2 to 0.6 μm. These steel sheets have a total tin content of 770-2100 mg / m ^2.
, And the amount and tin of alloy were changed by controlling the temperature and time of the reflow treatment. At that time, the shape of the metal tin was made convex using a flux. Subsequently, the amount of metallic Cr was in the range of 1 to 30 mg / m ² , and the amount of Cr oxide was 1 to 30 mg / m ² .
Chromate treatment was performed in the range of 30 mg / m ² . Next, a lamination process was performed. Lamination processing conditions are PET
After laminating the film, the temperature is lower than the melting point of tin (190 ~
(230 ° C) for 1 minute or less. The film for the outer surface of the can was printed in advance, and the film for the inner surface was laminated without any solid color.

The respective plating baths used for Ni plating and tin plating, and the respective conditions of reflow and chromate treatment are as follows.

From the obtained test material, an analysis sample was collected, and the total amount of tin; X-ray fluorescence method, the amount of metallic tin;
Alloy tin amount = total tin amount-metal tin amount, Ni amount; fluorescent X-ray method, metal Cr amount; electrolytic peeling method, total Cr amount; fluorescent X-ray method, oxidation
Cr content = total Cr content-metal Cr content was determined by each method. Also,
The flaws on the plain material surface in the laminating line were investigated and evaluated. In addition, using a copper wire type electric resistance heating seam welder (commercial machine), welding of n number of 1000 pieces under the following conditions, and investigating the occurrence of defective welding cans due to the drop and adhesion of spark particles to the welded part And after welding 190 g
A two-stage neck-in process was performed on the beverage can body, and the occurrence of cracks after the flange process was investigated to evaluate high-speed weldability. In addition, the upper limit current value that does not cause scattering and the peel welding strength (peel test in which a cut is made at one end of the welded part and the welded part is peeled off from the can body, it is determined that the one that can tear the entire length of the welded part has sufficient strength, (A case where the joint surface peels off during the peeling is determined to be insufficient strength)) is obtained as the weldable range ACR. When this value was 5 A or more, preferably 6 A or more, it was determined that the high-speed welding process was possible, and the weldability was evaluated. In addition, in the peel test, before making a cut, the inner and outer surfaces of the can were visually observed, and the evaluation of the poor welding can due to the adhesion of the spark mass and the flaw resistance were also confirmed.

The results of these investigations were comprehensively evaluated to evaluate the flaws and the occurrence of defective welding cans. The eaves coverage was evaluated based on the same criteria as in FIG. 1 on the solid ground and the inner and outer surfaces of the can. The results were evaluated as ○, and those judged as “none” were evaluated as ◎. Also,
Regarding poorly welded cans, those with obvious welding defects, those with cracks (peeling) observed in the welded part during flange processing, and those with peeling failures that appear to be due to lumps due to sparks in the welded part in the peel test X was evaluated. In addition, although there was no problem with quality, particles having sparks clearly adhering to the welded portion were marked with a circle in consideration of prolonged use. Those which did not correspond to any of these were evaluated as ◎.

Welding conditions : Can type; 190 g drink can body, 350 g drink can body ・ Copper wire diameter: 1.3 mmφ ・ Passing speed: 120 m / min ・ Welding pressure: 40 kg ・ Frequency: 700 Hz ・ Weld wrap allowance: 0.5 mm

The results of the study are summarized in Table 1.
As can be seen from this table, although the invention example was wound in the plate width direction to form a cylinder, there were no flaws, no defective welding cans due to adhesion of spark lumps, etc., and the proper welding current range was 5 A or more. High-speed welding can be performed stably despite the fact that it is a high-strength ultra-thin steel sheet having a thickness of 0.150 mm, preferably as large as 6 A or more. These effects are obtained by appropriately setting the plate surface roughness before plating and the amounts of metal tin and alloy tin immediately before welding. On the other hand, in Nos. 2 and 3 of the comparative examples, since the amount of residual metal tin was large, a poorly welded can was generated, and abrasions frequently occurred. In Nos. 4 and 5, conversely, the amount of metal tin was too small, and the ACR was narrowed due to scattering. Also,
In Nos. 8 and 10, since the plate surface roughness was small,
In Nos. 6 and 9, conversely, since the plate surface roughness was large, the flawing property was poor, and poor welded cans and abrasions were observed. Also,
In Nos. 1 and 7, the amount of alloy tin was excessive or insufficient, and poor welded cans occurred in both cases.

[0033]

[Table 1]

[0034]

As described above, according to the present invention,
Even when welding is performed at a high speed, a defective can due to abrasions and spark lumps does not occur, and a steel plate for a film laminated welding can having a wide weldable range can be provided. Such an effect is exhibited in the case of a high-strength, ultra-thin steel sheet which is more severe in conditions, and greatly contributes to high quality and high productivity of a three-piece can.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of the amount of residual tin on the occurrence of defective cans.

FIG. 2 is a graph showing a relationship between a residual metal tin amount, an alloy tin amount, and properties such as weldability and rust resistance.

FIG. 3 is a graph showing the effect of the surface roughness of a steel sheet on rust resistance and flaws on the surface of a can body.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hideo Kukuminato 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Chiba Works, Ltd. (72) Inventor Tatsuyuki Okazaki 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba F-term (reference) 3E061 AA16 AB07 AB13 BA02 DA02 DB04 DB20 4K024 AA03 AA07 AB01 AB02 BA03 BB24 DA01 DB01 DB02 DB04 DB10 GA14 4K044 AA02 AB02 BA02 BA10 BA15 BB03 BC08 CA16 CA17 CA18 CA42 CA44 CA48 CA67

Claims (1)

[Claims] A steel plate for a welding can having a tin plating layer formed on at least one surface of a steel plate and a film laminate layer formed of an organic resin film on the tin plating layer, wherein the steel plate has an average surface roughness Ra of 0.2 Wherein the tin-plated layer contains 200 to 600 mg / m ^{2 of} metal tin and 400 to 1500 mg / m ² of tin alloy. steel sheet.