Manufacturing method for film-laminated steel sheets and DI cans

Abstract

To further improve punch-release properties while maintaining ironing formability during DI molding. The film-laminated steel sheet according to the present invention comprises a steel sheet as a base material, film layers made of thermoplastic polyester films provided on the front and back surfaces of the steel sheet, and a wax layer provided on the film layer, and the wax layer has a deposition amount of 0.030 to 0.135 g / m per side. 2 and the wax layer adhesion amount differs between the front and back surfaces of the steel plate, and the adhesion amount ratio obtained by dividing the wax layer adhesion amount on the surface with a larger adhesion amount by the wax layer adhesion amount on the surface with a smaller adhesion amount is within the range of 1.05 to 1.35.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a film laminated steel sheet and a DI can.

Background Art

[0002] In recent years, as cans used for food, mainly paper-wound cans and distortion printing cans are often used. Particularly in the case of distortion printing cans, since it is important that the printed pattern is not distorted during forming, the can height is set relatively low, and as forming methods, drawn (DR) forming and drawing and redrawing (DRD) forming are often used. On the other hand, since there is no need to print on the outer surface of the can body of a paper-wound can, in recent years, drawing and ironing (DI) forming, which is more productive, is often adopted.

[0003] DI forming is a forming method in which the wall thickness of a can is reduced to about 40 to 60% of the thickness of the steel sheet used as a material by ironing the portion corresponding to the can wall of a cup obtained by drawing a steel sheet, and the can height is increased. DI forming is characterized in that the amount of deformation in the thickness direction and the can height direction of the steel sheet is very large and the forming speed is fast compared with DRD forming, and the temperature of the steel sheet during forming rises to nearly 200°C. Therefore, for example, in the DI forming of tinplate, which is a kind of tin-plated steel sheet, a coolant containing a lubricant is sprayed onto the ironing die during forming to cool the ironing die. Since the coolant sprayed onto the ironing die also adheres to the formed DI can, a step of washing and removing the coolant from the formed DI can and drying the washed DI can is required. Also, as one of the manufacturing facilities, a treatment facility for such a coolant is required.

[0004] On the one hand, in the manufacturing process of laminated steel sheets, wax can be applied to the film surface of film-laminated steel sheets. Therefore, when manufacturing cans using film-laminated steel sheets, there is no need to apply a lubricant during forming, and the lubricant cleaning and drying process, as well as the lubricant treatment equipment, can be omitted. Due to such advantages, film-laminated steel sheets have been widely used in DRD food cans in recent years.

[0005] However, when applying film-laminated steel sheets to forming processes where the can body is squeezed at high speed, such as DI forming, the film is likely to soften due to the increase in the temperature of the steel sheet during forming, resulting in easy chipping of the film or an increased probability of the can body bursting during forming. In addition, due to the softening of the film, the film on the inner surface of the can adheres to the punch used during processing, making it difficult to remove the punch when pulling it out, that is, the punch removal property deteriorates. When the punch removal property deteriorates, the can end buckles and bites into the space between the punch and the stopper, and the can body is also likely to buckle. In this case, the can-making machine must be stopped to remove the cans with the can ends biting into the space between the punch and the stopper, resulting in a significant decrease in productivity. From this perspective, various film-laminated steel sheets that can be used for DI forming have been proposed.

[0006] For example, in Patent Document 1 below, a laminated metal sheet for a two-piece can body having polyester resin film layers on both sides of a metal sheet is disclosed. The crystallization temperature of the polyester resin film layer on the outer surface side of the can body is 60 to 100°C, and the center line surface roughness (Ra) of the surface is 0.25 to 1.8 μm. Furthermore, in Patent Document 1 below, a laminated metal sheet for a two-piece can body is also disclosed, in which the polyester resin film layer on the outer surface side of the can body is composed of 40 to 100% by mass of a resin having butylene terephthalate as the main structural unit and 0 to 60% by mass of a resin having ethylene terephthalate as the main structural unit, and the center line surface roughness (Ra) of the surface of the film layer on the inner surface side of the can body is 0.2 to 1.8 μm.

[0007] In addition, in Patent Document 2 below, projections with a height of 2 to 10 μm and a circular equivalent diameter d of 0.010 to 0.10 mm are formed at 15 or more per mm on the film surface, and air or an inert gas is entrapped between the resin film directly below the projections and the steel sheet. There is disclosed a laminated steel sheet for containers having excellent draw and ironing workability for can manufacturing, in which a space is present. 2 As described above, in order to improve the ironing formability of the film-laminated steel sheet, conventionally, unevenness has been provided on the film surface to reduce the contact area and reduce friction. However, as described above, when continuous high-speed DI forming is performed, the temperature of the steel sheet increases. As a result, even when using the laminated steel sheets disclosed in Patent Document The laminated steel sheet for containers having excellent draw and ironing workability for can manufacturing, in which a space is present.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] As described above, in order to improve the ironing formability of the film-laminated steel sheet, conventionally, unevenness has been provided on the film surface to reduce the contact area and reduce friction. However, as described above, when continuous high-speed DI forming is performed, the temperature of the steel sheet increases. As a result, even when using the laminated steel sheets disclosed in Patent Document 1 and Patent Document 2, there is still room for improvement from the viewpoint of achieving both ironing formability and punch-through property.

[0010] Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a film-laminated steel sheet capable of further improving the punch-through property while maintaining the ironing formability during DI forming, and a method for manufacturing a DI can using such a film-laminated steel sheet.

Means for Solving the Problems

[0011] In order to solve the above problems, as a result of intensive studies by the present inventors, by optimizing the balance between the slidability on the side that becomes the inner surface of the can of the film-laminated steel sheet and the slidability on the side that becomes the outer surface of the can, while maintaining the ironing formability during DI forming, further, the idea of further improving the punch-through property was conceived. The gist of the present invention completed based on the above idea is as follows. In the following description, the notation "(numerical value A) to (numerical value B)" means "(numerical value A) or more and (numerical value B) or less".

[0012] (1) A steel sheet as a base material, a film layer composed of a thermoplastic polyester film provided on the front and back surfaces of the steel sheet, and a wax layer provided on the film layer, wherein the adhesion amount of the wax layer is On one side of the steel sheet, it is in the range of 0.030 to 0.100 g / m 2 and on the other side of the steel sheet, it is in the range of 0.030 to 0.135 g / m 2 and and the adhesion amount of the wax layer is different between the front side and the back side of the steel sheet, and the adhesion amount ratio obtained by dividing the adhesion amount of the wax layer on the side with the larger adhesion amount by the adhesion amount of the wax layer on the side with the smaller adhesion amount is in the range of 1.05 to 1.35, a film-laminated steel sheet. (2) It has a steel sheet as the base material, a film layer composed of a thermoplastic polyester film provided on the front and back surfaces of the steel sheet, and a wax layer provided on the film layer. The adhesion amount of the wax layer is in the range of 0.030 to 0.135 g / m 2 per side, and the adhesion amount of the wax layer is different between the front side and the back side of the steel sheet. The adhesion amount ratio obtained by dividing the adhesion amount of the wax layer on the side with the larger adhesion amount by the adhesion amount of the wax layer on the side with the smaller adhesion amount is in the range of 1.10 to 1.35. A film-laminated steel sheet (3) It has a steel sheet as the base material, a film layer composed of a thermoplastic polyester film provided on the front and back surfaces of the steel sheet, and a wax layer provided on the film layer. The adhesion amount of the wax layer is in the range of 0.120 to 0.135 g / m 2 per side, and the adhesion amount of the wax layer is different between the front side and the back side of the steel sheet. The adhesion amount ratio obtained by dividing the adhesion amount of the wax layer on the side with the larger adhesion amount by the adhesion amount of the wax layer on the side with the smaller adhesion amount is in the range of 1.05 to 1.35. A film-laminated steel sheet ( 4 ) The melting point of the thermoplastic polyester film constituting the film layer on the side with the smaller adhesion amount is 215°C or more and less than 255°C, the melting point of the thermoplastic polyester film constituting the film layer on the side with the larger adhesion amount is 220 to 260°C, and the melting point of the thermoplastic polyester film on the side with the larger adhesion amount is 5°C or higher than the melting point of the thermoplastic polyester film on the side with the smaller adhesion amount, (1) Any one of ~(3) the film-laminated steel sheet according to the above. ( 5) The penetration of the wax constituting the wax layer, as defined in JIS K2235:2022, is 5 to 20 at a test temperature of 25°C, and the melting point of the wax is 50.0 to 70.0°C. (1) Any one of ~(3) The film-laminated steel sheet according to Any one of ~(3) . ( 6 ) The thickness of the film layer on the side with less adhesion amount is 12 to 40 μm. (1) to ( 3 ) The film-laminated steel sheet according to any one of (1) to ( ( 7 ) The surface roughness of the steel sheet on the side with less adhesion amount is the arithmetic mean roughness Ra as defined in JIS B0601:2013 and is 0.10 to 0.50 μm. (1) to ( 3 ) The film-laminated steel sheet according to any one of (1) to ( ( 8 ) The adhesion amount of the wax layer is more than 0.120 g / m 2 and less than 0.135 g / m 2 per side. (1) or (2) The film-laminated steel sheet according to or (2) . ( 9 )(1) to ( 3 ) A method for manufacturing a DI can using the film-laminated steel sheet according to any one of (1) to (

Advantages of the Invention

[0013] As described above, according to the present invention, while maintaining the ironing formability during DI forming, it is further possible to further improve the punch-through property. As a result, the high-speed formability of the DI can can be improved without reducing the productivity of the DI can.

Brief Description of the Drawings

[0014] [Figure 1]It is an explanatory diagram schematically showing the configuration of a film-laminated steel sheet according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0016] (Regarding the film-laminated steel sheet) <Regarding the configuration of the film-laminated steel sheet> Hereinafter, with reference to FIG. 1, the configuration of the film-laminated steel sheet according to the embodiment of the present invention will be described. FIG. 1 is an explanatory diagram schematically showing the configuration of the film-laminated steel sheet according to the present embodiment.

[0017] The film-laminated steel sheet according to the present embodiment is used as a material for DI cans. As shown in FIG. 1, the film-laminated steel sheet 1 according to the present embodiment includes a base steel sheet 10 that serves as a base material of the film-laminated steel sheet 1, film layers 21 and 22 provided on the front and back surfaces of the base steel sheet 10, and wax layers 31 and 32 provided on the film layers.

[0018] In the film-laminated steel sheet 1 according to the present embodiment, as will be described in detail below, the amount of wax adhered in the wax layer �1 and the amount of wax adhered in the wax layer 32 are different. In FIG. 1, a case where the amount of wax adhered in the wax layer 32 is larger than the amount of wax adhered in the wax layer 31 is illustrated as an example.

[0019] The difference in the amount of wax adhered in the wax layers 31 and 32 as described above is important when manufacturing a DI can using such a film-laminated steel sheet 1 as a material. Although details will be described again below, when manufacturing a DI can using the film-laminated steel sheet 1 according to the present embodiment, the film-laminated steel sheet 1 is arranged so that the wax layer on the side with a larger amount of wax adhered is located on the side that becomes the inner surface of the DI can. That is, in the case of the film-laminated steel sheet 1 shown in FIG. 1, the surface on the side where the wax layer 31 exists becomes the surface on the outer can surface side of the DI can, and the surface on the side where the wax layer 32 exists becomes the surface on the inner can surface side of the DI can, and the film-laminated steel sheet 1 is arranged in the forming apparatus.

[0020] Here, in the following description, for convenience, the film layer located on the outer can surface side of the DI can will be referred to as the "outer can surface side film layer", and the wax layer located on the outer can surface side will be referred to as the "outer can surface side wax layer". Similarly, in the following description, for convenience, the film layer located on the inner can surface side of the DI can will be referred to as the "inner can surface side film layer", and the wax layer located on the inner can surface side will be referred to as the "inner can surface side wax layer".

[0021] Also, when referring to the film layer without distinguishing between the inner can surface side and the outer can surface side, it may be simply abbreviated as the "film layer". Similarly, when referring to the wax layer without distinguishing between the inner can surface side and the outer can surface side, it may be simply abbreviated as the "wax layer".

[0022] ≪Regarding the base steel sheet 10≫ In the film-laminated steel sheet 1 according to the present embodiment, as the base steel sheet 10, various known steel sheets for cans for drawing forming can be used as long as they are suitable.

[0023] Among the steel sheets for cans used for such drawing and ironing forming, it is preferable to use, as the base metal steel sheet 10, those having an r value of 1.00 or more and an absolute value of the Δr value of 0.45 or less. By using such a steel sheet for cans, it is possible to further improve the DI formability of the film-laminated steel sheet 1 according to the present embodiment.

[0024] Drawing and ironing forming is a forming method in which the wall thickness of the can wall of a substantially cylindrical cup is thinned by ironing and drawing. Therefore, if there is variation in the wall thickness of the can wall portion of the cup, the ironing resistance of the thick portion of the wall thickness increases, and the can wall portion may easily break during ironing forming. By setting the r value of the steel sheet used as the base metal steel sheet 10 to 1.00 or more, it is possible to suppress the variation in the wall thickness of the can wall portion in the height direction of the cup, and it becomes possible to prevent the breakage of the can wall portion during ironing forming. The r value of the steel sheet used as the base metal steel sheet 10 is more preferably 1.10 or more. On the other hand, the upper limit value of the r value of the steel sheet used as the base metal steel sheet 10 is not particularly defined, but substantially about 1.20 is the upper limit value.

[0025] Also, by setting the absolute value of the Δr value to 0.45 or less (that is, -0.45 ≤ Δr ≤ +0.45), it is possible to suppress the variation in the wall thickness of the can wall portion in the circumferential direction of the cup, and it becomes possible to prevent the breakage of the can wall portion during ironing forming. The absolute value of the Δr value of the steel sheet used as the base metal steel sheet 10 is more preferably 0.25 or less. The lower limit value of the Δr value of the steel sheet used as the base metal steel sheet 10 is not particularly defined, and the lower it is, the better, and zero is most preferable.

[0026] Note that the above r value and Δr value are defined in JIS Z2254:2021 and can be measured in accordance with JIS Z2254:2021. The r value is also called the plastic strain ratio or the r-value. The initial gauge length, width of the parallel portion, and thickness of the tensile test specimen defined in JIS Z2254:2021 are denoted as L0, W0, and T0 respectively. When the above dimensions after tensile deformation within the range where no necking occurs change to L, W, and T respectively, with L0×W0×T0 = L×W×T, it is a value defined by the following formula. r = ln(W0 / W) / ln(T0 / T) = ln(W0 / W) / ln(LW / L0W0)

[0027] Also, the Δr value is an index indicating in-plane anisotropy. When the angle between the tensile direction of the above tensile test specimen and the rolling direction of the material is θ, the r value is denoted as r θ and is a value defined by the following formula when the deformation characteristics in each direction are measured by changing θ. Here, in the following formula, r0, r 45 , r 90 are the r values at angles corresponding to 0°, 45°, and 90° with respect to the material rolling direction of the tensile direction respectively. Δr = (r0 - 2×r 45 + r 90 ) / 2

[0028] Also, when the steel plate used as the base steel plate 10 is hard, in addition to the fact that the elongation of the steel plate during forming is small and the can body is likely to break during forming, the calorific value of the steel plate during ironing forming increases, and the film layer described later is likely to soften due to heat. Therefore, when forming a DI can with a high ironing rate, it is particularly preferable to use a single-rolled material with a tempering degree of T3 or less as the base steel plate 10.

[0029] Also, in the case of DI cans, if the adhesive strength between the base metal steel sheet and the film layer is low, the film layer may peel off during ironing forming. Therefore, in the film laminate steel sheet 1 according to the present embodiment, it is more preferable that the adhesion between the base metal steel sheet 10 and the film layer is high. Specifically, a test piece with a width of 15 mm × a height of 50 mm is taken from an arbitrary location of the film laminate steel sheet 1 under consideration, and when one of the film layers of the test piece is peeled off at 180° at 20 mm / min, the peel strength is preferably 10 N / 15 mm or more. Such peel strength is more preferably 15 N / 15 mm or more. On the other hand, the higher such peel strength is, the better, and the upper limit value is not particularly defined.

[0030] As will be described in detail below, the film layer in the film laminate steel sheet 1 according to the present embodiment is composed of a thermoplastic polyester. Examples of steel sheets having excellent adhesion to polyester include chromium-based tin-free steel ECCS (Electrolytic Chromium Coated Steel) and chromium-free type tin-free steel.

[0031] Chromium-based tin-free steel is a plated steel sheet in which a metallic chromium layer and a chromium oxide hydrate layer are sequentially formed on the front and back surfaces of the steel sheet as a base material. Since the surface of such tin-free steel easily forms hydrogen bonds with the hydroxyl groups and carbonyl groups possessed by the polyester resin, the adhesion with the film layer can be improved.

[0032] Further, it is preferable that the surface of a chromium-free type tin-free steel sheet, which is composed of one or more elements selected from Zr, Al, Si, P, Ti, Ce, and W, O, and inevitable components, and has a film containing no chromium formed on the front and back surfaces of the steel sheet, has hydroxyl groups. By forming hydrogen bonds between such hydroxyl groups and the hydroxyl groups and carbonyl groups possessed by the polyester resin, the adhesion with the film layer can be improved.

[0033] In addition to the chromium-based tin-free steel and chromium-free type tin-free steel as described above, examples of the base steel plate 10 include a tin plate obtained by subjecting an electrolytic Sn-plated steel plate to chromate treatment, and a chromate-free tin plate having the above-described chromium-free film on the electrolytic Sn-plated steel plate.

[0034] By using the steel plate as described above as the base steel plate 10, the adhesion between the film layer is improved, and it becomes easier to realize the peel strength as described above.

[0035] [Thickness of the base steel plate] In the film laminate steel plate 1 according to the present embodiment, the thickness of the base steel plate 10 as described above (the thickness d in FIG. 1 M ) is not particularly defined as long as it can realize the desired thickness of the can wall portion after the DI forming. The thickness of the base steel plate 10 may be, for example, about 0.15 to 0.26 mm.

[0036] In order to measure the thickness of the base steel plate as described above from the state of the already manufactured film laminate steel plate 1, the following may be done. That is, the film laminate steel plate is immersed in boiling hydrogen peroxide water to peel the film (usually, the film peels within 30 minutes), and the thickness of the base steel plate after the film is peeled may be measured with a micrometer.

[0037] [Surface roughness of the base steel plate] In general deep drawing forming, it is preferable that the surface roughness of the film of the laminate steel plate is somewhat large and the die surface and the film convex surface are in a point contact state because the sliding resistance is low. However, in the case of DI forming focused on in the present embodiment, even if the surface roughness of the film layer is increased, the film softens due to the increase in the steel plate temperature during the drawing and ironing forming, and the unevenness on the surface of the film layer is crushed. Therefore, it can be said that the influence of the surface roughness of the base steel plate 10 is greater than that of the surface roughness of the film layer with respect to the sliding resistance during DI forming.

[0038] Generally, in DI forming, after arranging ironing dies in multiple stages, a steel sheet as a material is formed into a desired shape. When DI forming a film laminate steel sheet with too small surface roughness of the base steel sheet, when passing through the first-stage ironing die, the surface of the film layer is smoothed, and at the same time, the wax accumulated in the depressions caused by the concave portions of the base steel sheet is also likely to fall off. As a result, when passing through the ironing dies in the second stage and subsequent stages, the slidability of the film laminate steel sheet may decrease, and there is a possibility that the film layer is likely to be shaved.

[0039] On the other hand, when DI forming a film laminate steel sheet with too large surface roughness of the base steel sheet, when the film layer softens due to heat generation of the steel sheet when passing through the first-stage ironing die, pinholes are likely to occur in the film layer existing on the convex portions of the base steel sheet.

[0040] The shaving of the film layer and the generation of pinholes in the film layer as described above are events related to the ironing property during high-speed forming of DI cans, and both can occur in the can outer surface side film layer 21 shown in FIG. 1. Therefore, in the film laminate steel sheet 1 according to the present embodiment, on the surface of the base steel sheet 10 on the side that becomes the can outer surface of the DI can (that is, the surface on the side where the can outer surface side film layer 21 is provided), the surface roughness is preferably 0.10 to 0.50 μm in terms of the arithmetic mean roughness Ra defined in JIS B0601:2013. By making the surface roughness of the base steel sheet 10 on the side that becomes the can outer surface be 0.10 to 0.50 μm in terms of Ra, it is possible to prevent shaving of the film and generation of pinholes even when performing DI forming at high speed. The surface roughness of the base steel sheet 10 on the side that becomes the can outer surface is more preferably 0.10 μm or more in terms of Ra. Further, the surface roughness of the base steel sheet 10 on the side that becomes the can outer surface is more preferably 0.30 μm or less in terms of Ra.

[0041] Further, in the film-laminated steel sheet 1 according to the present embodiment, the surface roughness of the base metal steel sheet 10 on the side that becomes the outer surface of the can is 0.10 to 0.50 μm in terms of Ra, and the thickness of the film layer 21 on the outer surface side of the can, which will be described in detail below, is 12 to 40 μm. This further prevents the film from chipping and the occurrence of pinholes, and also prevents the occurrence of indentations on the film layer 21 on the outer surface side of the can, which is more preferable.

[0042] The surface roughness of the base metal steel sheet 10 as described above can be measured using a commercially available surface roughness meter (for example, Surfcom 570A, a surface roughness and shape measuring machine manufactured by Tokyo Seimitsu Co., Ltd.) conforming to JIS B0601:2013. More specifically, from the film-laminated steel sheet 1 of interest, after the wax layer and the film layer are peeled off by immersion treatment using boiling hydrogen peroxide water to expose the base metal steel sheet 10, a measurement sample with a size of 200 mm × 200 mm is collected from an arbitrary location on the surface of the base metal steel sheet 10. Then, for any three locations of such a measurement sample, measurements are taken three times each along the rolling direction of the base metal steel sheet 10 and the direction perpendicular to the rolling direction. The average value of the measurement values obtained in this way may be taken as the surface roughness of the base metal steel sheet 10.

[0043] ≪Regarding the film layer≫ Subsequently, the film layer included in the film-laminated steel sheet 1 according to the present embodiment will be described in detail.

[0044] The film layer in the film-laminated steel sheet 1 according to the present embodiment is a layer provided on the front and back surfaces of the base metal steel sheet 10, as schematically shown in FIG. 1, and is composed of a thermoplastic polyester film. Note that the above-mentioned "thermoplastic polyester" means "a thermoplastic high molecular compound having an ester bond (-COO-).

[0045] [Regarding the melting point of the thermoplastic polyester constituting the film layer] ◇Film layer 21 on the outer surface side of the can As described above, when manufacturing a can by continuously subjecting a laminated steel sheet to DI forming, the temperature of the steel sheet rises to about 200°C at maximum. Therefore, if the melting point of the film layer on the side that becomes the outer surface of the can is low, the film softens when subjected to ironing forming, making it easy to peel off. Therefore, the thermoplastic polyester film that constitutes the film layer on the side that becomes the outer surface of the can of the film-laminated steel sheet 1 (the film layer 21 on the outer surface side of the can in FIG. 1) is preferably a thermoplastic film that does not soften even at around 200°C. If the melting point is 215°C or higher, even when the temperature of the steel sheet reaches 200°C, the degree of film softening is small, and it becomes possible to suppress the occurrence of film peeling. From such a viewpoint, in the film-laminated steel sheet 1 according to the present embodiment, the melting point of the thermoplastic polyester film that constitutes the film layer 21 on the outer surface side of the can is preferably 215°C or higher. The melting point of the thermoplastic polyester film that constitutes the film layer 21 on the outer surface side of the can is more preferably 216°C or higher, and even more preferably 218°C or higher.

[0046] On the other hand, in the film-laminated steel sheet 1, when the melting point of the thermoplastic polyester film that constitutes the film layer 21 on the outer surface side of the can exceeds 260°C, the deformation resistance of the film is large in a state where the mold temperature is still low immediately after the start of DI forming, and in a portion where the bending strain is large, such as the punch shoulder portion or the ring processed portion of the can bottom, the film may tear. By setting the melting point of the thermoplastic polyester film that constitutes the film layer 21 on the outer surface side of the can to 260°C or lower, it becomes possible to prevent such tearing of the film, which is preferable. Further, as will be described below, the melting point of the thermoplastic polyester film that constitutes the film layer 22 on the inner surface side of the can is preferably 5°C or higher than the melting point of the thermoplastic polyester film that constitutes the film layer 21 on the outer surface side of the can. Considering such a difference in melting point, the melting point of the thermoplastic polyester film that constitutes the film layer 21 on the outer surface side of the can is preferably less than 255°C. The melting point of the thermoplastic polyester film that constitutes the film layer 21 on the outer surface side of the can is more preferably 240°C or lower, and even more preferably 235°C or lower.

[0047] ◇ Film layer 22 on the inner surface side of the can Regarding the side that becomes the inner surface of the can of the film laminate steel sheet 1, when the temperature of the steel sheet rises and the film layer softens, the film is likely to be adsorbed by the punch, and as a result, the punch-through property may decrease. As a result of the punch becoming difficult to pass through, the end of the can may get caught on the stopper provided in the mold, and the end of the can may be deformed. However, if the degree of softening of the film is smaller than that of the film layer on the outer surface side of the can, when pulling out the punch, relatively, the slipperiness on the inner surface side of the can is better than that on the outer surface side of the can. From such a viewpoint, the melting point of the thermoplastic polyester film constituting the film layer on the inner surface side of the can of the film laminate steel sheet 1 (that is, the film layer 22 on the inner surface side of the can in FIG. 1) is preferably higher than the melting point of the thermoplastic polyester film constituting the film layer 21 on the outer surface side of the can.

[0048] As a result of the inventors making a detailed study based on the above idea, it was found that when the melting point of the thermoplastic polyester film constituting the film layer 22 on the inner surface side of the can is 5°C or more higher than the melting point of the thermoplastic polyester film constituting the film layer 21 on the outer surface side of the can, the punch-through property becomes good.

[0049] Based on the above findings, in the film laminate steel sheet 1 according to the present embodiment, the melting point of the thermoplastic polyester film constituting the film layer 21 on the outer surface side of the can is preferably 215°C or higher. The melting point of the thermoplastic polyester film constituting the film layer 21 on the outer surface side of the can is more preferably 218°C or higher, and still more preferably 220°C or higher.

[0050] On the other hand, in the film-laminated steel sheet 1, when the melting point of the thermoplastic polyester film constituting the inner-can surface film layer 22 exceeds 260°C, similar to the case of the outer-can surface film layer 21, the deformation resistance of the film is large when the mold temperature is still low immediately after the start of DI forming, and there is a possibility that the film may break at portions where the bending strain is large, such as the punch shoulder and the ring-processed portion of the can bottom. By setting the melting point of the thermoplastic polyester film constituting the inner-can surface film layer 22 to 260°C or lower, it becomes possible to prevent such film breakage, which is preferable. The melting point of the thermoplastic polyester film constituting the inner-can surface film layer 22 is more preferably 255°C or lower, and even more preferably 250°C or lower.

[0051] As described above, in the inner-can surface film layer 22 according to the present embodiment, it is within the range of 220 to 260°C, and it is preferable to use a thermoplastic polyester film having a melting point 5°C or higher than the melting point of the thermoplastic polyester film constituting the outer-can surface film layer 21. The difference in the melting points of the thermoplastic polyester films between the inner-can surface side and the outer-can surface side is more preferably 10°C or higher, and even more preferably 15°C or higher. Note that the upper limit value of the difference in the melting points of the thermoplastic polyester films between the inner-can surface side and the outer-can surface side is not particularly defined, but substantially, about 30°C is the upper limit.

[0052] Here, in order to determine whether a polyester film is used as the film layer in the film-laminated steel sheet 1 from the state of the already manufactured film-laminated steel sheet 1, a sample may be collected from an arbitrary location of the film layer in the film-laminated steel sheet 1 of interest, and the obtained sample may be analyzed by, for example, Fourier transform infrared spectroscopy (FT-IR). In such an analysis result, when a result indicating the presence of an ester bond is obtained, it can be determined that the film layer of interest is composed of a polyester film. Also, by confirming whether the resin constituting the film layer of interest softens when the obtained sample is heated, it is possible to determine whether the resin is thermoplastic.

[0053] In addition, for the melting point of the thermoplastic polyester film as described above, about 5 to 10 mg of sample is collected from an arbitrary location of the film layer in the film-laminated steel sheet 1 of interest, and the obtained sample is analyzed by differential scanning calorimetry (DSC). The temperature that gives the main endothermic peak in the analysis results may be confirmed. For example, using a commercially available differential scanning calorimeter (e.g., DSC7030 manufactured by Hitachi High-Tech Science Corporation), the obtained sample is sealed in an aluminum pan and measured in the range of 50 to 350 °C at a heating rate of 10 °C / min.

[0054] [Details of the thermoplastic polyester film] In the film-laminated steel sheet 1 according to this embodiment, the thermoplastic polyester film used for the film layer is preferably a film that does not elute resin components or adsorb flavor components into the contained food contents even when the can body is formed, baked, or retorted.

[0055] In addition, the elongation of the thermoplastic polyester film used for the film layer is preferably 100% or more when the film is alone. When the elongation of the film is 100% or more when the film is alone, breakage of the film layer when the film-laminated steel sheet 1 is DI-formed can be further prevented.

[0056] ◇ Film layer 21 on the outer surface of the can In the film-laminated steel sheet 1 according to this embodiment, the thermoplastic polyester film constituting the film layer 21 on the outer surface of the can preferably has a melting point of 215 °C or higher in addition to the characteristics to the food contents and the elongation of the film as described above.

[0057] Examples of such thermoplastic polyester films include polybutylene terephthalate resins, copolymers of butylene terephthalate and ethylene terephthalate and / or ethylene terephthalate isophthalate, blend resins of polybutylene terephthalate resins and polyethylene terephthalate resins and / or polyethylene isophthalate terephthalate resins, ethylene terephthalate isophthalate copolymers, blend resins of polyethylene terephthalate resins and polyethylene terephthalate isophthalate copolymers, and the like.

[0058] In particular, in the case of a copolymer resin of butylene terephthalate and ethylene terephthalate and / or polyethylene isophthalate terephthalate, it is particularly preferable that the polybutylene terephthalate is contained in an amount equivalent to 50% by mass or more. Also, in the case of a blend resin of a polybutylene terephthalate resin and a polyethylene terephthalate resin and / or a polyethylene isophthalate terephthalate resin, it is particularly preferable that the polybutylene terephthalate resin is contained in an amount of 50% by mass or more, because it is easy to stretch and has a high breaking strength.

[0059] ◇ Inner film layer 22 on the can inner surface side In the film-laminated steel sheet 1 according to the present embodiment, the thermoplastic polyester film constituting the inner film layer 22 on the can inner surface side preferably has a melting point that is 5°C or higher than the melting point of the thermoplastic polyester film constituting the outer film layer 21 on the can outer surface side, in addition to the characteristics for food contents and the elongation of the film as described above.

[0060] Examples of such thermoplastic polyester films include polyethylene terephthalate resin, polyethylene terephthalate isophthalate copolymer resin, polyethylene terephthalate butylene terephthalate copolymer resin, a blend resin of polyethylene terephthalate resin and polyethylene terephthalate isophthalate copolymer resin, a blend resin of polyethylene terephthalate and polybutylene terephthalate resin, a blend resin of polyethylene terephthalate isophthalate copolymer resin and polyethylene terephthalate butylene terephthalate copolymer resin, a stretched film or an unstretched film of a blend resin of the above resins, and the like.

[0061] In the film laminate steel sheet 1 according to the present embodiment, the thermoplastic polyester film used for the film layer may be a stretched film or an unstretched film. However, since it is better to pay attention to the elongation of the film in DI molding, when using a stretched film, the stretching ratio is preferably 3 or less.

[0062] Also, within a range satisfying the above characteristics, the film used for the film laminate steel sheet 1 may be a multi-layer film of 2 to 3 layers.

[0063] In the film laminate steel sheet 1 according to the present embodiment, various additives such as pigments, lubricants, antioxidants, heat stabilizers, antistatic agents, and crystal nucleating agents may be added to the thermoplastic polyester film used for the film layer, if necessary.

[0064] The elongation of the thermoplastic polyester film as described above can be specified by measuring in accordance with JIS K7161-1:2014 and JIS K7127:1999. Specifically, after removing the wax layer of the film laminate steel sheet 1 of interest with hexane, a tensile test piece may be sampled from an arbitrary location of the film layer in accordance with the above standards. The obtained tensile test piece may be set in a tensile tester and a tensile test may be performed at a measurement temperature of 23 to 25°C.

[0065] [Regarding the thickness of the film layer] ◇Film layer 21 on the outer surface of the can In the DI forming that this embodiment focuses on, the film layer on the side that becomes the outer surface of the can of the film-laminated steel sheet 1 (that is, the film layer 21 on the outer surface of the can) is subjected to strong shear force especially by ironing forming. Therefore, when the thickness of the film layer 21 on the outer surface of the can is too thin, there is a possibility that pinholes are likely to occur because the surface of the film layer is scraped. On the other hand, when the thickness of the film layer 21 on the outer surface of the can is too thick, the film is sheared and displaced when passing through the ironing die, and as a result, the surface of the film layer is scraped, and there is a possibility that pressing defects and streak-like defects due to the generated scrap are likely to be formed.

[0066] According to the detailed study by the present inventors, when the thickness of the film layer 21 on the outer surface of the can of the film-laminated steel sheet 1 (the thickness d in FIG. 1 Fo ) is 12 μm or more, it has become clear that even if a strong shear force is applied to the surface of the film layer in DI forming, the generation of pinholes can be more suppressed. The thickness of the film layer 21 on the outer surface of the can is more preferably 15 μm or more.

[0067] On the other hand, according to the detailed study by the present inventors, when the thickness of the film layer 21 on the outer surface of the can of the film-laminated steel sheet 1 is 40 μm or less, it is possible to prevent the film layer from being scraped when passing through the ironing die, and it has become clear that the formation of pressing defects and streak-like defects can be more suppressed. The thickness of the film layer 21 on the outer surface of the can is more preferably 35 μm or less.

[0068] ◇Film layer 22 on the inner surface of the can In the film-laminated steel sheet 1 according to this embodiment, the thickness of the film layer on the side that becomes the inner surface of the can (that is, the film layer 22 on the inner surface of the can) may be appropriately set to a thickness that can obtain sufficient retort corrosion resistance according to the corrosiveness of the can contents. For example, for contents such as general boiling in water or oil immersion where the pH is not a low value, the thickness of the film layer 22 on the inner surface of the can (the thickness d in FIG. 1 FiBy setting [[ID=]] to 10 μm or more, good retort corrosion resistance can be obtained. In addition, since the can contents showing a low pH value exhibit strong corrosiveness, the thickness of the film layer 22 on the inner surface side of the can is preferably made as thick as possible. For example, by setting the thickness of the film layer 22 on the inner surface side of the can to 20 μm or more, it is possible to ensure good retort corrosion resistance even when containing can contents showing strong corrosiveness.

[0069] However, when the thickness of the film layer 22 on the inner surface side of the can exceeds 100 μm, the film may adhere tightly to the punch during DI forming, making it difficult to slide, and there is a possibility that the punch-through property may deteriorate. Therefore, by setting the thickness of the film layer 22 on the inner surface side of the can to 100 μm or less, it is possible to suppress the deterioration of the punch-through property and ensure good retort corrosion resistance. The thickness of the film layer 22 on the inner surface side of the can is more preferably 50 μm or less.

[0070] In addition, in order to measure the thickness of the film layer as described above from the state of the already manufactured film laminate steel sheet 1, the following may be done. First, a plurality of sample pieces having a size of 100 × 100 mm are collected from an arbitrary position of the sheet-like or coil-like film laminate steel sheet 1. When measuring the thickness of the film layer 21 on the outer surface side of the can for the obtained sample pieces, first, after shaving the side of the film layer 22 on the inner surface side of the can with sandpaper or the like, the film laminate steel sheet 1 is immersed in hydrochloric acid of 17% to 35% to dissolve the base steel sheet, and only the film layer 21 on the outer surface side of the can is peeled and extracted. Then, the thickness of the film layer 21 on the outer surface side of the can may be measured at three arbitrary points using a micrometer while changing the position. The average value of the three obtained measurement values is taken as the thickness of the film layer 21 on the outer surface side of the can. Also, when measuring the thickness of the film layer 22 on the inner surface side of the can, for the obtained sample pieces, after shaving the side of the film layer 21 on the outer surface side of the can with sandpaper or the like, the film laminate steel sheet 1 is immersed in hydrochloric acid of 17% to 35% to dissolve the base steel sheet, and only the film layer 22 on the inner surface side of the can is peeled and extracted. Then, the thickness of the film layer 22 on the inner surface side of the can may be measured at three arbitrary points using a micrometer while changing the position. The average value of the three obtained measurement values is taken as the thickness of the film layer 22 on the inner surface side of the can.

[0071] <<Regarding the wax layer>> Next, the wax layer included in the film laminate steel sheet 1 according to the present embodiment will be described in detail.

[0072] The wax layer in the film laminate steel sheet 1 according to the present embodiment is a layer provided on the film layer as described above, as schematically shown in FIG. 1.

[0073] [Regarding the deposition amount of the wax layer] In the film laminate steel sheet 1 according to the present embodiment, the deposition amount of the wax layer has a great influence not only on the shaving and caging of the film layer 21 on the outer surface side of the can during DI forming, but also on the punch-through property. Therefore, in order to maintain the ironing formability during DI forming and further improve the punch-through property, the deposition amount of the wax layer is an extremely important factor.

[0074] The wax layers provided on the inner surface side and the outer surface side of the can of the film laminate steel sheet 1 melt as the temperature of the steel sheet rises due to DI forming, and a lubricating film is formed on the surface of the laminate steel sheet (which can also be regarded as the surface of the film layer according to the present embodiment), thereby imparting good lubricity to the laminate steel sheet. Further, after the DI forming is completed, the wax that has melted during the DI forming may solidify again and remain on the surface of the film layer.

[0075] In the film laminate steel sheet 1 according to the present embodiment, the deposition amount of the wax layer is in the range of 0.030 to 0.135 g / m per side 2 and the deposition amount of the wax layer is different between the front side and the back side of the steel sheet. Note that the value of 0.030 g / m of the deposition amount per side 2 corresponds to the minimum value of the deposition amount of the wax layer on the side with the smaller deposition amount, and the value of 0.135 g / m of the deposition amount per side 2 corresponds to the maximum value of the deposition amount of the wax layer on the side with the larger deposition amount.

[0076] Hereinafter, the adhesion amounts of the outer can surface wax layer 31 and the inner can surface wax layer 32 will be described in detail respectively.

[0077] ◇ Outer can surface wax layer 31 In the film-laminated steel sheet 1 according to the present embodiment, the adhesion amount of the outer can surface wax layer 31 is 0.030 g / m 2 or more. When the adhesion amount of the outer can surface wax layer 31 is less than 0.030 g / m 2 , the wax film is likely to break (the disappearance of the lubricating film) during ironing forming, and there is a possibility that the film layer may be scraped or nicked at the ironed portion of the outer can surface, which is not preferable. By setting the adhesion amount of the outer can surface wax layer 31 to 0.030 g / m 2 or more, the disappearance of the lubricating film during ironing forming can be prevented, and the scraping or nicking of the film layer at the ironed portion of the outer can surface can be prevented. The adhesion amount of the outer can surface wax layer 31 is preferably 0.040 g / m 2 or more, and more preferably 0.050 g / m 2 or more.

[0078] On the other hand, in the film-laminated steel sheet 1 according to the present embodiment, the adhesion amount of the outer can surface wax layer 31 is less than the value of 0.135 g / m 2 mentioned above, and is 0.100 g / m 2 or less. When the adhesion amount of the outer can surface wax layer 31 exceeds 0.100 g / m 2 , excess wax accumulates in the gap of the ironing die, and streaks or pressing marks are likely to be attached to the surface of the film layer at the portion where the wax accumulates thickly, which is not preferable. By setting the adhesion amount of the outer can surface wax layer 31 to 0.100 g / m 2 or less, the generation of streaks or pressing marks on the surface of the film layer can be prevented. The adhesion amount of the outer can surface wax layer 31 is preferably 0.095 g / m 2 or less, and more preferably 0.090 g / m 2 or less.

[0079] ◇Inner surface side wax layer 32 of the can Regarding the adhesion amount of the inner surface side wax layer 32 in the film-laminated steel sheet 1 according to the present embodiment, the inventors have obtained the following findings. That is, when the adhesion amount of the inner surface side wax layer 32 is too large, as the temperature of the punch increases during continuous can manufacturing, the punch becomes more likely to slip, and distortion concentrates and breaks at the portion where the punch shoulder of the can bottom hits, so-called "punch shoulder breakage" is likely to occur, which is not preferable.

[0080] On the other hand, when the adhesion amount of the inner surface side wax layer 32 is too small, when the punch returns from the bottom dead center to the top dead center, it becomes difficult for the can body to come off the punch. As a result, when the punch retracts, the can body retracts together with the punch, and the can end strongly hits the stopper provided on the die side and is likely to be deformed. Also, in some cases, the can body buckles and can manufacturing has to be interrupted, which is not preferable.

[0081] Based on the above findings, as a result of further studies by the inventors, the buckling of the can body as described above is likely to occur when the adhesion amount of the outer surface side wax layer of the can is less than the adhesion amount of the inner surface side wax layer 32, and the punch shoulder breakage as described above is likely to occur when the adhesion amount of the inner surface side wax layer 32 is much larger than the adhesion amount of the outer surface side wax layer 31.

[0082] As a result of further detailed studies by the inventors regarding this point, in the film-laminated steel sheet 1 according to the present embodiment, the adhesion amount of the inner surface side wax layer 32 (that is, the wax layer on the side with a large adhesion amount) is set within the range of 1.05 to 1.35 times the adhesion amount of the outer surface side wax layer 31 (that is, the wax layer on the side with a small adhesion amount), and it has been found that can body buckling can be suppressed without reaching punch shoulder breakage. Hereinafter, the ratio obtained by dividing the adhesion amount of the wax layer on the side with a large adhesion amount by the adhesion amount of the wax layer on the side with a small adhesion amount will be referred to as the "adhesion amount ratio".

[0083] Based on the above, in the film laminate steel sheet 1 according to the present embodiment, the adhesion amount of the wax layer 31 on the outer surface side of the can is in the range of 0.030 to 0.100 g / m 2 and the adhesion amount of the wax layer 32 on the inner surface side of the can is in the range of 1.05 to 1.35 times the adhesion amount of the wax layer 31 on the outer surface side of the can (in other words, the adhesion amount ratio defined as above is in the range of 1.05 to 1.35). Thereby, in the film laminate steel sheet 1 according to the present embodiment, while maintaining the ironing formability during DI forming, the punch-through property can be further improved. As a result, in the manufacture of DI cans, further improvement in continuous can-making performance can be achieved.

[0084] Note that the adhesion amount of the wax layer 32 on the inner surface side of the can is preferably 1.10 times or more, more preferably 1.15 times or more, the adhesion amount of the wax layer 31 on the outer surface side of the can. Also, the adhesion amount of the wax layer 32 on the inner surface side of the can is preferably 1.30 times or less, more preferably 1.25 times or less, the adhesion amount of the wax layer 31 on the outer surface side of the can.

[0085] In order to measure the adhesion amount of the wax layer as described above from the state of the already manufactured film laminate steel sheet, after dissolving the wax layer on the side of interest in a predetermined solvent, the following treatment may be performed.

[0086] First, a plurality of sample pieces having a size of, for example, 200 mm × 200 mm are collected from an arbitrary position of the film laminate steel sheet 1 in the form of a sheet or a coil. Then, in order to prevent the elution of wax from the wax layer other than the side of interest, a tape seal is applied to the surface of the wax layer on the side not of interest. Next, a solvent (for example, n-heptane, etc.) capable of dissolving wax is poured over the surface on the side where the tape seal is not applied to dissolve the wax layer. The poured solvent is collected in an aluminum foil case (for example, foil case S736210, 11 μm thick, mass: about 0.38 g manufactured by Toyo Aluminium Eco Products Co., Ltd.) whose mass has been measured in advance with a precision balance.

[0087] Subsequently, the aluminum foil case containing the solvent in which the wax has dissolved is placed in a constant temperature bath at 100°C for 30 minutes to completely volatilize the solvent. Then, the mass of the aluminum foil case from which the solvent has volatilized is measured with an analytical balance. From the mass thus obtained, the mass of the wax can be calculated by subtracting the mass of the aluminum foil case before solvent recovery. By dividing the mass of the wax thus obtained by the area of the sample (converted to the unit of m 2 ), the adhesion amount of the wax layer on the surface of interest can be specified.

[0088] In the film-laminated steel sheet 1 according to the present embodiment, the adhesion amount of the wax layer is more than 0.120 g / m per side 2 and less than 0.135 g / m 2 per side may be within the following range. Even in a high adhesion amount state where the adhesion amount of the wax layer per side exceeds 0.120 g / m 2 , the film-laminated steel sheet 1 according to the present embodiment can further improve the punching-out property while maintaining the ironing formability during DI forming. The value of 0.120 g / m for the adhesion amount per side corresponds to the minimum value of the adhesion amount of the wax layer on the surface with a small adhesion amount, and the value of 0.135 g / m 2 for the adhesion amount per side corresponds to the maximum value of the adhesion amount of the wax layer on the surface with a large adhesion amount. 2

[0089] [Regarding the penetration of wax] Next, in order to further prevent the peeling of the film layer 21 on the outer surface of the can that may occur during DI forming as mentioned above, it is more preferable that the wax has a certain degree of hardness. Here, the hardness of the wax can be represented by the penetration defined in JIS K2235:2022 - Item 6.4.

[0090] When the penetration of the wax that constitutes the wax layer according to this embodiment is too small, especially at the molding start stage where the mold temperature has not fully risen, since the wax is in a hard state, the wax is likely to fall off at the squeezing molding part, and push marks caused by the generated wax chips are likely to occur. However, by using a wax with a penetration of 5 or more at a test temperature of 25 °C, it is possible to prevent the wax from falling off at the molding start stage as described above. Therefore, in the wax layer according to this embodiment, the penetration of the wax that constitutes the wax layer at a test temperature of 25 °C is preferably 5 or more. The penetration of the wax at a test temperature of 25 °C is more preferably 10 or more.

[0091] On the other hand, if the penetration of the wax that constitutes the wax layer according to this embodiment is too large, it means that the viscosity of the wax is low. In this case, when continuous can manufacturing is carried out and the temperature of the mold rises, the lubricity of the wax decreases, and it becomes easy for the film layer to be scratched or chipped. However, by using a wax with a penetration of 20 or less at a test temperature of 25 °C, it is possible to prevent the film layer from being scratched or chipped due to the viscosity of the wax as described above. Therefore, in the wax layer according to this embodiment, the penetration of the wax that constitutes the wax layer at a test temperature of 25 °C is preferably 20 or less. The penetration of the wax at a test temperature of 25 °C is more preferably 15 or less.

[0092] Note that the penetration of the wax as described above can be measured according to JIS K2235:2022.

[0093] [Regarding the melting point of wax] In the wax layer 31 on the outer surface side of the can according to the present embodiment, if the melting point of the wax constituting the wax layer is too low, the melted wax will drip onto the outer surface of the can wall during DI molding, and wax stains are likely to occur, which is not preferable. Also, in the wax layer 32 on the inner surface side of the can, if the melting point of the wax constituting the wax layer is too low, it becomes difficult to obtain appropriate lubricity during DI molding, and thus the film layer is likely to be scraped off. However, when the melting point of the wax constituting the wax layer is 50.0 °C or higher, it becomes possible to further prevent indentations and wax stains on the outer surface side of the can, and scraping of the film layer on the inner surface side of the can. In the wax layer according to the present embodiment, the melting point of the wax constituting the wax layer is more preferably 52.0 °C or higher.

[0094] On the other hand, in the wax layer 31 on the outer surface side of the can according to the present embodiment, if the melting point of the wax constituting the wax layer is too high, the wax will adhere and fall off around the ironing die, and indentations are likely to occur on the surface of the outer surface side of the can, which is not preferable. Also, in the wax layer 32 on the inner surface side of the can, if the melting point of the wax constituting the wax layer is too high, it becomes difficult to obtain appropriate lubricity during DI molding, and thus the film layer is likely to be scraped off. However, when the melting point of the wax constituting the wax layer is 70.0 °C or lower, it becomes possible to further prevent indentations on the outer surface side of the can and scraping of the film layer on the inner surface side of the can. In the wax layer according to the present embodiment, the melting point of the wax constituting the wax layer is more preferably 68.0 °C or lower.

[0095] Note that the melting point of the wax constituting the wax layer as described above can be measured by differential scanning calorimetry in the same manner as the melting point of the thermoplastic polyester constituting the film layer described above.

[0096] [Specific Examples of Wax] The wax used for the wax layer according to this embodiment is preferably selected taking into account the removability of the wax after can manufacturing, in addition to the above viewpoints. Examples of waxes with good wax removability after can manufacturing include n-paraffin waxes having 24 to 32 carbon atoms and their urea adducts (for example, various paraffin waxes, candelilla wax, carnauba wax, etc.), micro waxes, mixtures of paraffin wax and micro wax, and the like.

[0097] In the wax layer according to this embodiment, taking into account the wax removability after can manufacturing as described above, it is more preferable to select a wax having an appropriate penetration and melting point from among the waxes whose specific examples are shown above.

[0098] As described above, the film-laminated steel sheet 1 according to this embodiment has been described in detail with reference to FIG. 1.

[0099] (Regarding the manufacturing method of the film-laminated steel sheet) Subsequently, an example of the manufacturing method of the film-laminated steel sheet 1 according to this embodiment will be described.

[0100] (Preparation of the base steel sheet) First, a steel sheet that serves as the base material of the film-laminated steel sheet 1 is prepared. Here, the manufacturing method of the steel sheet that serves as the base material is not particularly limited, and it can be manufactured by various known methods. Also, in the surface conditioning rolling process when manufacturing the base steel sheet, it is possible to achieve the desired surface roughness on the surface of the steel sheet by adjusting the surface roughness of the rolling rolls used. Alternatively, a commercially available steel sheet having desired properties may be purchased and used as the base steel sheet.

[0101] (Formation of the film layer) Next, the base steel plate thus obtained is subjected to various pretreatment processes such as alkali degreasing, water washing, pickling, etc. as necessary to obtain a clean steel plate surface. Thereafter, a film layer is formed on the front and back surfaces of such a base steel plate using a thermoplastic polyester film.

[0102] Here, for the thermoplastic polyester film used to form the film layer, it may be manufactured by oneself based on various known manufacturing methods to have desired properties, or a commercially available product with desired properties may be purchased, or after purchasing a commercially available thermoplastic polyester film, various known treatment methods may be further applied to realize desired properties.

[0103] Next, regarding the method of forming a film layer on the front and back surfaces of the base steel plate as described above, various known film-forming methods can be applied.

[0104] However, it is more preferable to use a method (thermal fusion method) in which the steel strip is heated by passing it through a jacket roll with a built-in heater, an induction heating (IH) furnace, etc., and then a film is continuously fed from both sides of the steel strip and the film is pressed and fused onto the steel strip using a heat-resistant rubber roll. By using the thermal fusion method, it becomes possible to form a film layer with a more uniform thickness on the front and back surfaces of the base steel plate. At this time, by controlling the heating temperature of the base steel plate, the roughness of the roll surface of the film laminating roll, the temperature and pressing force of the roll surface, the thickness of the film layer and the surface roughness of the film layer can be controlled within a desired range.

[0105] Specifically, it is preferable to heat the base steel plate to (film melting point + 15°C) or higher, and the surface temperature of the film laminating roll is within the range of not less than the glass transition point (Tg) of the film and not more than (film melting point + 30°C), and not more than (film glass transition point (Tg) + 20°C).

[0106] In addition, in order to optimize the nip time of the roll for film lamination, the surface hardness of the roll for film lamination is preferably controlled within the range of 30 to 80° as measured by the durometer type A defined in JIS K6253-3:2012. Also, from the viewpoint of making it difficult for bubbles to enter during film formation, the nip pressure of the roll for film lamination is preferably within the range of 100 to 300 N / cm 2 .

[0107] In addition, in order to suppress spheroidization that causes film embrittlement, the steel sheet after film layer formation is preferably rapidly cooled in a water cooling tank within 1 second after lamination.

[0108] <Formation of wax layer> Subsequently, a wax layer is formed on the steel sheet on which the film layer has been formed. Here, the method for forming the wax layer is not particularly limited. A wax layer may be formed by applying a wax that has been heated to a temperature equal to or higher than its melting point and is in a liquid state to the surface of the film layer, or a wax solution in which the wax is dissolved in a volatile solvent may be prepared and such a wax solution may be applied to the surface of the film layer. Also, the steel sheet after wax application may be dried by heating or may be air-dried.

[0109] Note that the method for applying the wax (or wax solution) to the surface of the film layer is not particularly limited, but can generally be performed by known coating methods such as roll coating, curtain flow coating, dipping, bar coating, etc. Also, when drying the wax by heating, the heating method is not particularly limited, and for example, any method such as hot air, near-infrared rays, far-infrared rays, induction heating, or a heating method using a combination of these may be adopted.

[0110] Among the various methods for forming the wax layer as described above, from the perspective of ensuring productivity, in a continuous production line for manufacturing a film-laminated steel sheet, it is more convenient to adopt a method in which wax heated to a temperature equal to or higher than its melting point and melted is applied to the surface of the film layer by a roll coater and air-cooled before the steel sheet is wound up.

[0111] (Regarding the method for manufacturing a DI can using a film-laminated steel sheet) The film-laminated steel sheet 1 according to the present embodiment can be subjected to ironing forming using a commercially available capping press and a DI forming device. More specifically, using the film-laminated steel sheet as described above as a material for a DI can, in the film-laminated steel sheet, the surface on the side with a smaller adhesion amount of the wax layer becomes the surface on the outer side of the DI can, and the surface on the side with a larger adhesion amount of the wax layer becomes the surface on the inner side of the DI can, and the film-laminated steel sheet may be arranged accordingly. Then, DI forming may be performed on such a film-laminated steel sheet. Note that the various conditions during DI forming are not particularly defined, and DI forming may be performed on the film-laminated steel sheet under general conditions in DI forming.

[0112] In the film-laminated steel sheet 1 according to the present embodiment, a wax layer is provided in advance on the film layer. Furthermore, while ensuring both ironing formability and punch-through property during DI forming, and furthermore, since the punch-through property is further improved, during DI forming, forming can be sufficiently performed even without a coolant. Also, when performing DI forming on the film-laminated steel sheet 1 according to the present embodiment, a coolant normally used in ordinary DI forming may be used in combination. Here, the various conditions during DI forming are not particularly limited.

[0113] When manufacturing a paper-wrapped can, after trimming the can end of the DI-formed can body into a desired shape, a DI can can be obtained by performing flange-up processing. Also, when printing on the can body, the can end of the DI-formed can body is trimmed into a desired shape. Subsequently, after performing relief offset printing or flat offset printing on the can body using a curved surface printing machine and then baking, the can end is subjected to flange-up processing to obtain a DI can. After filling the manufactured DI can with contents, the lid can be tightened to seal the DI can.

Example

[0114] Hereinafter, the manufacturing method of the film laminate steel sheet and the DI can according to the present embodiment will be specifically described with reference to examples. However, the various conditions in the examples shown below are one set of conditions adopted for confirming the feasibility and effects of the present invention, and the present invention is not limited to the following examples. Without departing from the gist of the present invention and as long as the object of the present invention is achieved, it is also possible to appropriately modify and implement within a range that conforms to the gist. Therefore, the present invention can adopt various conditions, and all of them are included in the technical features of the present invention.

[0115] <Base metal steel sheet> The steel sheets M1 to M8 shown in Table 1 below were used as the base metal steel sheets. Here, one surface of the base metal steel sheet is referred to as the "first surface", and the surface opposite to the first surface is referred to as the "second surface". In each operation performed hereinafter, the base metal steel sheet was handled so that the first surface side was the side with a small amount of wax layer adhesion and the second surface side was the side with a large amount of wax layer adhesion.

[0116] M1 to M6 are steel sheets with a thickness of 0.225 mm, a temper degree = T3, an r value = 1.05 to 1.1, and a Δr = 0.00 to 0.40. On the surface of the steel sheet, a metal chromium layer (adhesion amount: 80 mg / m per side 2 ) and a chromium hydrated oxide layer (adhesion amount: 10 mg / m per side 2It is a tin-free steel sheet (manufactured by Nippon Steel Corporation) having M7 is a tin-plated steel sheet using a steel sheet with a thickness of 0.24 mm, a tempering degree = T3, an r value = 1.10, and Δr = 0.15. From the steel sheet side in order, there are an Sn-Fe alloy layer (Sn amount: 1.3 g / m per side 2 ), a pure Sn layer (Sn amount: 1.5 g / m per side 2 ), and a chromium hydroxide layer (adhesion amount: 10 mg / m per side 2 ). It is a so-called tinplate (manufactured by Nippon Steel Corporation). M8 is a chromium-free steel sheet (manufactured by Nippon Steel Corporation) having a chemical conversion coating of the chromium-free type mainly composed of Zr hydroxide (Zr amount: 60 mg / m per side 2 ) on a cold-rolled steel sheet with a thickness of 0.195 mm, a tempering degree = T3, an r value = 1.00, and Δr = 0.45.

[0117] Samples with a size of 200 mm × 200 mm were cut out from each base steel sheet, and using a surface roughness and shape measuring machine Surfcom 570A manufactured by Tokyo Seimitsu Co., Ltd., at three locations on the diagonal of the sample, for each of the coil longitudinal direction and the coil width direction, the arithmetic mean roughness Ra was measured three times at a scanning speed of 0.3 mm / second. The average value of the obtained measurement values was taken as the surface roughness Ra of each base steel sheet. The obtained results are shown in Table 1.

[0118]

Table 1

[0119] <Resin film> The resin films used for forming the film layer of the film-laminated steel sheet are shown in Table 2 below. All the films used are commercially available thermoplastic polyester-based stretched films.

[0120] F1 is a biaxially stretched film of a dimethyl terephthalate - ethylene dodecanedioate copolymer resin (DMT / DDA-EG) with a melting point of 210°C, a thickness of 25 μm, and an elongation of 200%. F2 is a biaxially stretched film of a polyethylene terephthalate - polybutylene terephthalate copolymer resin (PET - PBT) with a melting point of 213°C, a thickness of 25 μm, and an elongation of 190%. F3 is a biaxially stretched film of a polyethylene terephthalate - polybutylene terephthalate copolymer resin (PET - PBT) with a melting point of 215°C, a thickness of 25 μm, and an elongation of 190%. F4 is a biaxially stretched film of a polyethylene terephthalate - polybutylene terephthalate copolymer resin (PET - PBT) with a melting point of 218°C, a thickness of 12 μm, and an elongation of 190%. F5 is a biaxially stretched film of a polyethylene terephthalate - ethylene isophthalate copolymer resin (PET - IA) with a melting point of 227°C, a thickness of 19 μm, and an elongation of 160%. F6 is a biaxially stretched film of a polyethylene terephthalate - ethylene isophthalate copolymer resin (PET - IA) with a melting point of 227°C, a thickness of 40 μm, and an elongation of 180%. F7 is a biaxially stretched film of a polyethylene terephthalate - ethylene isophthalate copolymer resin (PET - IA) with a melting point of 240°C, a thickness of 30 μm, and an elongation of 130%.

[0121] F8 is a biaxially stretched film of a polyethylene terephthalate resin (PET) with a melting point of 242°C, a thickness of 20 μm, a draw ratio of 2.9, and an elongation of 100%. F9 is a biaxially stretched film of a polyethylene terephthalate resin (PET) with a melting point of 253°C, a thickness of 20 μm, a draw ratio of 3.0, and an elongation of 100%. F10 is a biaxially stretched film of a polyethylene terephthalate resin (PET) with a melting point of 258°C, a thickness of 19 μm, a draw ratio of 3.1, and an elongation of 100%. F11 is a biaxially stretched film of a polyethylene terephthalate resin (PET) with a melting point of 262°C, a thickness of 19 μm, a draw ratio of 3.3, and an elongation of 100%.

[0122] F12 is a biaxially stretched film of ethylene terephthalate - butylene terephthalate copolymer resin (PET - PBT) with a melting point of 212°C, a thickness of 10 μm, and an elongation of 190%. F13 is a biaxially stretched film of ethylene terephthalate - ethylene isophthalate copolymer resin (PET - IA) with a melting point of 227°C, a thickness of 42 μm, and an elongation of 200%. F14 is a biaxially stretched film of ethylene terephthalate - ethylene isophthalate copolymer resin (PET - IA) with a melting point of 227°C, a thickness of 50 μm, and an elongation of 200%. F15 is a biaxially stretched film of ethylene terephthalate - ethylene isophthalate copolymer resin (PET - IA) with a melting point of 227°C, a thickness of 100 μm, and an elongation of 200%.

[0123] Samples of 5 - 8 mg were taken from the above resin films, and the obtained samples were sealed in aluminum pans. Using a differential scanning calorimeter (DSC7030 manufactured by Hitachi High - Tech Science Corporation), measurements were carried out in the range of 50 - 350°C at a heating rate of 10°C / min, and the temperature of the main endothermic peak was taken as the melting point of each resin film.

[0124]

Table 2

[0125] <Formation of film layer> Using the above - mentioned base steel plate and resin film, film layers were formed on the front and back surfaces of the base steel plate. For the formation of the film layer, a dedicated resin film laminating apparatus equipped with a metal sheet feeding device, a metal hot press for heating the metal sheet, film feeding devices for the front and back surfaces, a heat - resistant rubber laminating roll (the surface temperature of the rubber roll is controlled by a metal heating backup roll), and a cooling water tank was used. Using such an apparatus, steel plates (plate width 200 mm × plate length 200 mm) with film layers formed were fabricated in multiple numbers at each level as shown in Table 4 - 1 and Table 4 - 2 below.

[0126] <Wax> The waxes used for forming the wax layer of the film-laminated steel sheet are shown in Table 3 below. All of the waxes shown below are commercially available.

[0127] W1 is a paraffin wax with a penetration at 25 °C of 29 and a melting point of 48.0 °C. W2 is a paraffin wax with a penetration at 25 °C of 22 and a melting point of 50.0 °C. W3 is a paraffin wax with a penetration at 25 °C of 20 and a melting point of 50.0 °C. W4 is a paraffin wax with a penetration at 25 °C of 15 and a melting point of 52.0 °C. W5 is a paraffin wax with a penetration at 25 °C of 13 and a melting point of 66.3 °C. W6 is a paraffin wax with a penetration at 25 °C of 11 and a melting point of 69.4 °C. W7 is a paraffin wax with a penetration at 25 °C of 5 and a melting point of 75.0 °C. W8 is a candelilla wax with a penetration at 25 °C of 1 and a melting point of 65.0 °C. W9 is a carnauba wax with a penetration at 25 °C of 1 and a melting point of 82.0 °C.

[0128] Note that the penetration at 25 °C of each of the above waxes was measured using an automatic penetration measuring device EX-210ED manufactured by Daiichi Rikagaku Co., Ltd. Also, the melting point of each of the above waxes was measured using 5 - 8 mg of a sample collected from each wax, in the same manner as for the resin film, with a differential scanning calorimeter (DSC7030 manufactured by Hitachi High-Tech Science Corporation). The measurement conditions were a heating rate of 10 °C / min and a measurement temperature range of 50 - 350 °C. The temperature of the main endothermic peak was taken as the melting point of each wax.

[0129]

Table 3

[0130] <Formation of wax layer> First, two laminated steel plates sized 200 mm × 200 mm (two of the same level) on which the film layer was formed by the method described above were handled as a set, aligned with the same film surfaces facing each other, and the end faces were tape-sealed.

[0131] For each wax shown in Table 3 above, hexane (a commercially available general reagent) was used as a solvent, and a predetermined amount was dissolved in hexane to obtain a wax hexane solution. For each such wax, a plurality of types of wax hexane solutions were prepared while varying the wax concentration.

[0132] The steel plates tape-sealed as described above were immersed in the wax hexane solution and then air-dried.

[0133] Next, the tape seal was peeled off, the opposite faces were aligned with each other, and tape sealing was performed again. Thereafter, the steel plates were immersed in wax hexane solutions of different concentrations and air-dried. Then, the tape seal was peeled off to produce film-laminated steel plates with different wax adhesion amounts on the front and back surfaces. By repeating such operations, a plurality of film-laminated steel plates were produced for each level shown in Table 4-1 and Table 4-2 below. In Table 4-1 and Table 4-2 shown below, the waxes used for the front and back surfaces are of the same level.

[0134] <Measurement of wax layer adhesion amount> The adhesion amount of the wax layer was measured as follows. First, for each level of film-laminated steel plate (sized 200 mm × 200 mm), a commercially available tape that does not dissolve in heptane was used to perform tape sealing on the surface on the side where the adhesion amount was not measured. During the tape sealing, the surface on the side where the adhesion amount was not measured and the side surfaces were covered, and further, for the surface on the side where the adhesion amount was measured, regions from both ends up to 5 mm in both the width and length directions were covered. Due to such tape sealing, the size of the region on the surface on the side where the adhesion amount was measured and where tape sealing was not performed was 190 mm × 190 mm.

[0135] Next, for each level of film-laminated steel sheet with the above tape seal, heptane (a commercially available general reagent) was poured over the surface where the adhesion amount was measured to dissolve the wax. The poured heptane was recovered by an aluminum foil case (foil case S736210, deep mouth, 11 μm thick, mass: about 0.38 g, manufactured by Toyo Aluminum Eco Products Co., Ltd.) whose mass had been measured in advance with an analytical balance.

[0136] Subsequently, the aluminum foil case containing the heptane in which the wax had been dissolved was placed in a constant temperature bath at 100 °C for 30 minutes to completely volatilize the heptane. Then, the mass of the aluminum foil case was measured with an analytical balance, and the mass of the wax was calculated from the difference in the mass of the aluminum foil case before and after the heptane recovery. The obtained mass of the wax was divided by the wax application area (190 mm × 190 mm excluding the tape seal part) to determine the wax adhesion amount.

[0137] The configurations of the respective film-laminated steel sheets produced as described above are shown in Tables 4-1 and 4-2 below.

[0138]

Table 4-1

[0139]

Table 4-2

[0140] <Forming of DI cans> For each film-laminated steel sheet produced by the above method, a blank plate with a diameter of 126 mm was punched out. For each of the obtained blank plates, after shallow drawing can forming was performed at a speed of 60 cans per minute using a capping press machine, a drawing and ironing can manufacturing facility (body maker) with a punch stroke of 400 mm and two draws and three ironings was used to continuously iron and form at an average can manufacturing speed of 100 cans per minute. At this time, the blank plates were arranged in the drawing and ironing can manufacturing facility so that the first surface side became the outer can surface side and the second surface side became the inner can surface side. The ironing and forming conditions were a first draw ratio of 1.75, a second draw ratio of 1.35, an ironing punch diameter of 52.80 mm, and a total ironing rate of 48%, and cans with a can height of 100 mm or more were produced.

[0141] <Evaluation method> For each DI can obtained as described above, evaluation was performed from the viewpoints of "DI formability" and "degree of film damage". The details of the evaluation are as follows. Also, the obtained evaluation results are summarized in Tables 5-1 and 5-2 below.

[0142] [Evaluation of DI formability] The evaluation of DI formability was performed from the viewpoints of "degree of deformation of the can end" and "degree of cracking and necking of the punch shoulder of the can bottom". For the evaluation of the degree of deformation of the can end, when there was no deformation of the can end, the score was "A", when slight deformation occurred at the can end, the score was "B", and when jamming occurred, the score was determined as "C". Scores "A" and "B" were considered as passing.

[0143] For the evaluation of the degree of cracking and necking of the punch shoulder of the can bottom, when there was no cracking or necking of the punch shoulder of the can bottom, the score was "A", when slight necking was observed at the punch shoulder of the can bottom, the score was "B", and when cracking of the steel sheet occurred at the punch shoulder of the can bottom, the score was determined as "C". Scores "A" and "B" were considered as passing.

[0144] [Evaluation of the degree of damage to the film surface on the outer can surface of the manufactured can] For the canned products manufactured as described above, the degree of damage to the film surface on the outer can surface was evaluated by visual inspection and by checking for the presence or absence of film pinholes using a pinhole tester. When there were no film flaws or indentation flaws on the film surface on the outer can surface, the rating was "A". When there were independent minute indentation flaws on the film surface on the outer can surface, or when, although no flaws were visible visually, there were 5 or more pinhole reactions detected by the pinhole tester, the rating was "B". When there were scratching flaws on the film surface on the outer can surface, or when indentation flaws causing the steel plate to dent were observed, the rating was determined to be "C". Ratings "A" and "B" were considered passing grades.

[0145] Note that for the detection of pinhole defects using the pinhole tester, a pinhole tester (TRC-250A) manufactured by Sanko Electronics Laboratory Co., Ltd. was used. A carbon brush electrode was attached to the anode side of such a pinhole tester, and the ground side was attached to the part of the film at the end of the can that had been scraped with sandpaper. The entire surface of the can wall was then explored with the carbon brush electrode at 500V.

[0146] [Evaluation of the Degree of Damage to the Film Surface on the Inner Can Surface in Canned Products] For the canned products, the determination of the degree of damage to the film surface on the inner can surface was evaluated by conducting a colored ERV (Enamel Rate Value) test on the canned products manufactured as described above. The determination was as follows: when there was no colored ERV reaction part on the film surface on the inner can surface, the rating was "A"; when there were 5 or fewer independent dot-shaped colored ERV reaction parts per can on the film surface on the inner can surface, the rating was "B"; when there were more than 5 independent dot-shaped colored ERV reaction parts per can, or when there were colored ERV reaction parts in a linear to planar shape, on the film surface on the inner can surface, the rating was determined to be "C". Ratings "A" and "B" were considered passing grades.

[0147] The colored ERV test was conducted as follows. First, the inner surface of the canned product was washed with hexane to remove wax, and then the can was filled with an ERV test solution (ERV test solution composition: CuSO4·5H2O [50 g / L], NaCl [60 g / L]). Next, the positive electrode bar of a digital enamel rate meter (manufactured by Nichia Measuring Industry Co., Ltd., digital enamel rate meter NDE-1200) was immersed, the negative electrode was connected to the can side, and an electric current was applied at 6.3 V for 15 seconds to deposit copper sulfate crystals on the metal exposed part. Then, the damage state of the film surface on the inner surface side of the can was visually determined.

[0148]

Table 5-1

[0149]

Table 5-2

[0150] As is clear from Table 5-1 and Table 5-2 above, the film-laminated steel sheet corresponding to the example of the present invention has good deep drawing formability and film damage degree, while the film-laminated steel sheet corresponding to the comparative example of the present invention has at least one of deep drawing formability or film damage degree inferior. Thus, the film-laminated steel sheet corresponding to the example of the present invention is excellent in ironing workability in deep drawing, particularly has good punch-through property, so it is very useful because it is less likely to cause buckling of the can body during continuous forming and has excellent continuous deep drawing formability.

[0151] As described above, the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that those having ordinary knowledge in the technical field to which the present invention pertains can conceive various modification examples or correction examples within the scope of the technical idea described in the claims, and it is naturally understood that these also belong to the technical scope of the present invention.

[0152] The embodiments disclosed this time are illustrative in all respects and not restrictive. The above embodiments may be omitted, substituted, or changed in various forms without departing from the scope of the appended claims and the gist of the present invention as described below. For example, the constituent elements of the above embodiments can be arbitrarily combined within a range that does not impair their effects. Also, from such an arbitrary combination, the actions and effects of each constituent element involved in the combination can be naturally obtained, and other actions and other effects obvious to those skilled in the art from the description of this specification can be obtained.

[0153] Moreover, the effects described in this specification are merely illustrative or exemplary and not restrictive. That is, the technology according to the present invention can exhibit other effects obvious to those skilled in the art from the description of this specification together with, or instead of, the above effects.

Explanation of Reference Numerals

[0154] 1 Film-laminated steel sheet 10 Base metal steel sheet 21 Film layer on the outer surface side of the can 22 Film layer on the inner surface side of the can 31 Wax layer on the outer surface side of the can 32 Wax layer on the inner surface side of the can

Claims

1. A steel sheet as a base material, A film layer made of a thermoplastic polyester film provided on the front and back surfaces of the steel sheet, A wax layer provided on the film layer, having, the adhesion amount of the wax layer is in the range of 0.030 to 0.100 g / m2 on one side of the steel sheet, and is in the range of 0.030 to 0.135 g / m2 on the other side of the steel sheet, and the adhesion amount of the wax layer is different between the front side and the back side of the steel sheet, A film-laminated steel sheet, wherein the adhesion amount ratio obtained by dividing the adhesion amount of the wax layer on the side with the larger adhesion amount by the adhesion amount of the wax layer on the side with the smaller adhesion amount is in the range of 1.05 to 1.

35.

2. A steel sheet as a base material, A film layer made of a thermoplastic polyester film provided on the front and back surfaces of the steel sheet, A wax layer provided on the film layer, having, the adhesion amount of the wax layer is in the range of 0.030 to 0.135 g / m2 per side, and the adhesion amount of the wax layer is different between the front side and the back side of the steel sheet, A film-laminated steel sheet, wherein the adhesion amount ratio obtained by dividing the adhesion amount of the wax layer on the side with the larger adhesion amount by the adhesion amount of the wax layer on the side with the smaller adhesion amount is in the range of 1.10 to 1.

35.

3. A steel sheet as a base material, A film layer made of a thermoplastic polyester film provided on the front and back surfaces of the steel sheet, A wax layer provided on the film layer, having, the adhesion amount of the wax layer is in the range of 0.120 to 0.135 g / m2 per side, and the adhesion amount of the wax layer is different between the front side and the back side of the steel sheet, A film-laminated steel sheet, wherein the adhesion amount ratio obtained by dividing the adhesion amount of the wax layer on the side with the larger adhesion amount by the adhesion amount of the wax layer on the side with the smaller adhesion amount is in the range of 1.05 to 1.

35.

4. The melting point of the thermoplastic polyester film constituting the film layer on the side with the smaller adhesion amount is 215°C or higher and less than 255°C, The melting point of the thermoplastic polyester film constituting the film layer on the side with the larger adhesion amount is 220 to 260°C, and the melting point of the thermoplastic polyester film on the side with the larger adhesion amount is 5°C or higher than the melting point of the thermoplastic polyester film on the side with the smaller adhesion amount. The film laminate steel sheet according to any one of claims 1 to 3.

5. The penetration of the wax constituting the wax layer as defined in JIS K2235:2022 is 5 to 20 at a test temperature of 25°C, and the melting point of the wax is 50.0 to 70.0°C. The film laminate steel sheet according to any one of claims 1 to 3.

6. The thickness of the film layer on the side with the smaller adhesion amount is 12 to 40 μm. The film laminate steel sheet according to any one of claims 1 to 3.

7. The surface roughness of the steel sheet on the side with the smaller adhesion amount is the arithmetic mean roughness Ra as defined in JIS B0601:2013 and is 0.10 to 0.50 μm. The film laminate steel sheet according to any one of claims 1 to 3.

8. The adhesion amount of the wax layer is 0.120 g / m per side ２ exceeding 0.135 g / m ２ The film-laminated steel sheet according to claim 1 or 2, wherein the above is satisfied

9. A method for manufacturing a DI can using the film laminate steel sheet according to any one of claims 1 to 3, In the film laminate steel sheet, the side with the smaller adhesion amount of the wax layer becomes the side that becomes the outer surface of the DI can, and the side with the larger adhesion amount of the wax layer becomes the side that becomes the inner surface of the DI can. The film laminate steel sheet is arranged so that, DI forming is performed on the film laminate steel sheet. A method for manufacturing a DI can.

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