JP5272473B2 - DI can molding method - Google Patents

Abstract

A method of forming a DI can is provided in which a steel sheet laminated with an organic resin film is subjected as a raw material to DI forming. In this method, film damage is avoided, and it is easy to pull can bodies out of the punch even when a conventional DI forming machine is used. The angle of ironing die approach is regulated to 2-5°, and ironing forming is conducted so as to satisfy relationship (1), wherein X(n) (%) is the sheet thickness reduction from the original sheet thickness after the n-th ironing operation. Two or more ironing steps are conducted to thereby reduce the sheet thickness. The laminated steel sheet preferably has a yield strength of 300-500 MPa. It is preferred to use a liquid having a viscosity of 0.3-1.0 mPa s as a coolant. X(n)=0.0004X(n-1)3+0.0025X(n-1)2+0.0956X(n-1)+31.1 relationship (1) (provided that X(0)=0)

Description

  The present invention relates to a method for forming a DI can made of a laminated steel sheet coated with an organic resin film.

DRD cans, DTR cans, DI cans and the like are used as two-piece cans for food cans and beverage cans. Among them, DI cans are widely used cans, using both aluminum plates and steel plates as materials.
Here, a method for forming a DI can will be described. First, a metal plate is punched into a circular blank, and then drawn with a cupping press to make a shallow drawn cup. Further, in the DI can molding machine, as shown in FIG. 3, the punch 4 passes through the redrawing die 6 and the ironing dies 7, 8, and 9 at a high speed, thereby performing redrawing processing and ironing processing. Make a DI can. Ironing is usually performed in 3 to 4 steps, and the die is sequentially passed through molding in 5 to 6 steps or more including a drawing step and a redrawing step. At this time, coolant is used for the purpose of lubrication and cooling. Then, after being formed by such a plurality of processes, the traveling direction of the punch 4 is reversed, and the can body is extracted from the punch 4 by the fingers of the stripper 10 disposed at the end of the ironing die at the final stage. Furthermore, after forming with a DI can molding machine, trimming of the upper end of the can, neck forming, flange forming, etc., can be performed to form a DI can that can be wound.

Conventional DI cans were painted after being molded on both aluminum and steel (steel plates). However, in recent years, the omission of the painting process has been aimed at from the viewpoint of environmental measures, food safety, etc., and a material in which an organic resin film is laminated on an aluminum plate or a steel plate has been developed, and attempts have been made to mold the laminated material into a DI can. It has been broken.
However, when the laminated material is used for the DI can, there is a problem that the laminate film is damaged at the time of ironing unique to the DI can. As an attempt to solve this problem, in Patent Document 1, the die surface of the ring-shaped ironing die is narrowed by an inclination angle of 1 to 4 ° (entrance angle θ), and a land having a short length parallel to the cup side wall is formed at the end. An ironing die having a structure with an exit surface that is widened at an inclination angle of 5 to 15 ° from the end is manufactured from an abrasion-resistant material having a thermal conductivity of 50 W / m ° C or more. A method is disclosed in which a cup made of a resin-coated metal plate is ironed and formed into a can body while supplying a cooling liquid using a processing die.

Moreover, when performing DI shaping | molding using an organic resin film laminated steel plate, extraction of the can from the punch was difficult. Regarding punch punchability in DI molding of polyester resin film laminated steel sheet, Patent Document 2 shows that the stripper is improved by placing a stripper before the ironing die for performing the final ironing process. Yes.
Japanese Patent No. 2852403 Japanese Patent Laid-Open No. 2001-300644

  The technology of Patent Document 1 is a technology related to an aluminum plate coated with an organic resin. When this technique is used for an organic resin film laminated steel sheet, the damage to the film surely tends to be reduced. However, what is exemplified in Patent Document 1 as a wear-resistant material having a thermal conductivity of 50 W / m ° C. or higher is a general carbide tool material, and this is used in combination with supplying a cooling liquid. Even when heat generation is suppressed, it is difficult to stably avoid film damage when an organic resin film laminated steel sheet is used.

  On the other hand, the technique of Patent Document 2 relating to extraction of a can body from a punch is certainly considered to be effective. However, this technique can be used for the first time in a DI molding machine with a new mechanism that has not been heretofore, and there is a problem that it cannot be applied to a widely used conventional DI molding machine.

  The present invention has been made in view of such circumstances, and in forming DI using an organic resin film-laminated steel sheet as a raw material, damage to the film is avoided, and a can body from a punch is also used when conventional DI forming is used. An object of the present invention is to provide a method for forming a DI can that can be easily extracted.

The gist of the present invention is as follows.
[1] DI can molding method using laminated steel sheet coated with organic resin film. When reducing sheet thickness by multiple ironing, the angle of entry of the ironing die is 2 ° or more and 5 ° or less. A DI can molding method characterized by satisfying equation (1), where X (n)% is the thickness reduction rate from the original plate thickness in the nth ironing molding.
X (n) ≦ 0.0004X (n−1) ³ + 0.0025X (n−1) ² + 0.0956X (n−1) +31.1 Expression (1)
However, X (0) = 0
[2] The method for forming a DI can according to [1], wherein the laminated steel sheet is a laminated steel sheet in which an organic resin resin film is coated on both surfaces of a steel sheet having a yield strength of 300 to 500 MPa.
[3] A method for molding a DI can according to [1] or [2], wherein a liquid having a viscosity of 0.3 to 1.0 mPa · s is used as a coolant.

  According to the present invention, it is possible to provide a molding method in which damage to the film is avoided and the can body can be easily extracted from the punch even when the conventional DI molding is used.

Hereinafter, the present invention will be described in detail.
In performing DI molding of a laminated steel sheet, the present inventors first disclosed in Patent Document 1 which is an invention related to DI molding of a laminated plate (hereinafter referred to as a laminated aluminum plate) composed of a polyester film and an aluminum sheet or an aluminum alloy sheet. The molding experiment was performed under the conditions.
Specifically, the entrance angle 2 (inlet angle in Patent Document 1) of the ironing die (the ironing ring in Patent Document 1) 1 shown in FIG. 1 is 2 °, and the axial length 3 of the land is 1 mm. The material of the ironing die 1 was tungsten carbide based on cobalt. This is provided with the thermal conductivity under the conditions specified in Patent Document 1. The plate thickness reduction rate of the ironing molding was adjusted to the plate thickness reduction rate described in the specification of Patent Document 1 by adjusting the clearance of the ironing die 1 with the punch. That is, the plate thickness reduction rate in the first ironing was set to 26%, the first to the second to 26%, and the second to the third to 41%. When this plate thickness reduction rate is converted into the plate thickness reduction rate from the original plate, the first round is 26%, the second round is 45%, and the third round is 68%. Hereinafter, in the present invention, unless otherwise specified, the plate thickness reduction rate is the plate thickness reduction rate from the original plate thickness. In the molding, a coolant in which a commercially available tinting material DI can molding lubricant was added to water by 1.5% was used. The laminated steel plate used was a laminate of a PET (polyethylene terephthalate) film having a film thickness of 15 μm on both sides of a steel plate having a plate thickness of 0.2 mm and a yield strength of 400 MPa by a heat fusion method.
As a result of forming experiments under the above conditions, when a laminated steel sheet was used as the material, film damage caused by the film being scraped by the ironing die occurred, and a healthy can body could not be obtained. Upon investigation, it was found that this film damage occurred at the stage of the second ironing process. That is, it was confirmed that the conditions disclosed in Patent Document 1 for a laminated aluminum plate are not necessarily applicable to a laminated steel plate.

Therefore, when the thickness reduction rate in the second ironing was changed from 45% to 40%, the second film damage could be avoided. However, film damage occurred in the third ironing process. This result shows that the film thickness reduction in the second ironing process was avoided by reducing the plate thickness reduction rate in the first to second ironing processes. On the other hand, the second to third processes were avoided. It is probable that film damage occurred due to the high reduction rate of thickness in the ironing process.
Therefore, in order to reduce the plate thickness reduction rate in the second through third ironing, an experiment was performed in which the first and second plate thickness reduction rates were reset. In other words, the first plate thickness reduction rate was 30% higher than the previous experiment, the second plate thickness reduction rate was 45%, and the third plate thickness reduction rate was 68%. As a result, film damage did not occur in each number of ironing moldings, and a healthy can body without film damage could be obtained by ironing molding three times in total.
From the above experiments, even when the laminated aluminum plate can be formed, it may be impossible to form the laminated steel plate due to film damage. It has been found that it is necessary to appropriately set the sheet thickness reduction rate for each number of times in the ironing process. It can be seen that in order not to cause film damage at the plate thickness reduction rate of each number of times, it is necessary to appropriately set the plate thickness reduction rate in the previous stage.

  Therefore, based on the above examination results, in order to determine the conditions necessary for appropriately setting the sheet thickness reduction rate, an experiment was performed in which the sheet thickness reduction rate was changed in multiple ironing operations. At this time, the entrance angles of the ironing dies are 1 °, 2 °, 5 °, and 8 °, and the laminated steel plate is a PET (polyethylene terephthalate) film with a film thickness of 15 μm, the thickness is 0.2 mm, and the yield strength is 400 MPa. What was laminated on both surfaces of the steel plate by the heat fusion method was used. The final plate thickness reduction rate was up to 75%. As a result of the experiment, the following conclusions were obtained.

Intrusion angle of ironing dies: 2 ° or more and 5 ° or less For DI cans using conventional tinting materials, the final plate thickness reduction rate is about 50% to 75%. When using laminated steel plates However, it is necessary to obtain a similar thickness reduction rate. When the entrance angle of the ironing die is 1 °, the plate thickness reduction rate obtained even if the clearance is the same as compared to the case of 2 ° or more becomes extremely low. In order to obtain a sheet thickness reduction rate of 73%, which is the highest level of sheet thickness reduction in DI cans, the number of ironing operations is required 5 times or more when the entrance angle of the ironing die is 1 °. Since a normal DI molding machine is compatible with 3-4 times of ironing, a target sheet thickness reduction rate cannot be obtained with an ironing die with an entry angle of 1 °.
If the entrance angle of the ironing die is 2 ° or more, a sheet thickness reduction rate of about 73% can be obtained, and a can height exceeding the specified value can be obtained. Therefore, in the present invention, the approach angle of the ironing die is set to 2 ° or more. On the other hand, if the entrance angle of the ironing die is 8 °, no matter what the sheet thickness reduction rate is set in multiple times of ironing, film damage will occur and the final sheet thickness reduction rate will be about 30%. It turns out that it can only be obtained. If the entrance angle of the ironing die is 5 ° or less, a plate thickness reduction rate of up to about 75% can be obtained without causing film damage. Therefore, the upper limit of the entrance angle of the ironing die is 5 ° or less.

Conditions for Setting Plate Thickness Reduction Rate FIG. 2 shows the results of experiments conducted by changing the plate thickness reduction rate in three ironing processes. Since it was found from the experiments so far that it is necessary to appropriately set the sheet thickness reduction rate in the previous stage in order to prevent film damage in the ironing molding of each number of times, in FIG. The plate thickness reduction rate in the ironing molding up to the first time, and the plate thickness reduction rate in the ironing molding up to the (n-1) th time on the horizontal axis, showed the presence or absence of film damage.
From FIG. 2, it can be seen that the boundary line of the presence or absence of film damage is the upper limit plate thickness reduction rate that gives an appropriate setting condition for the plate thickness reduction rate so as not to cause film damage. That is, film damage can be avoided if the region is below the boundary line.
Here, when this area is expressed by a polynomial expression with the sheet thickness reduction rate in the ironing forming up to the n-th time being X (n)%, the relationship of Expression (1) is obtained.
X (n) ≦ 0.0004X (n−1) ³ + 0.0025X (n−1) ² + 0.0956X (n−1) +31.1 Equation (1)
However, since X (0) is the sheet thickness reduction rate in the 0th ironing, X (0) = 0.
As described above, in the present invention, when the plate thickness reduction rate from the original plate thickness in the n-th ironing is X (n)%, the above formula (1) is satisfied.

  As is clear from the forming experiment described above, even when the laminated aluminum plate can be formed, the laminated steel plate may not be formed due to film damage. This is considered to be based on the difference in mechanical properties between the aluminum plate and the steel plate. Film damage in the ironing process occurs when the laminated material is stretched while being held in a highly compressed state between the ironing die and the punch, so that the compressive force acting on the film greatly affects. Since the compressive force is generated by the deformation resistance of the material used as the laminate substrate, it is considered that there was a difference in film damage between the aluminum plate and the steel plate. The aluminum plate has a significantly lower yield strength than the steel plate (in the case of the standard 3004 series, the yield strength is about 70 MPa). Therefore, it is considered that the compressive force acting on the film is low and the film damage is difficult to occur. From this point of view, it is considered that there is an applicable range in the yield strength of the steel sheet in the setting condition of the sheet thickness reduction rate shown by the above formula (1) for the laminated steel sheet.

  Therefore, next, a molding experiment was performed using a material whose yield strength was changed. At this time, the entrance angle of the ironing die is 2 °, and the laminated steel plate is a PET (polyethylene terephthalate) film with a film thickness of 15μm on both sides of the steel plate with a thickness of 0.2mm and a yield strength of 260MPa to 550Mpa. What was laminated by the heat sealing | fusion method was used. The sheet thickness reduction rate in the ironing process was set to satisfy the condition (1), and the final sheet thickness reduction rate up to the third time was set to 77%. As a result of the above experiment, the following conclusions were obtained.

Yield Strength of Steel Sheet As mentioned above, film damage occurs when the yield strength is high, and the upper limit of the yield strength of the steel sheet that can avoid film damage was 500 MPa. That is, it is preferable that the yield strength of the steel sheet capable of avoiding film damage at the sheet thickness reduction rate set under the condition of the formula (1) is 500 MPa or less. On the other hand, film damage did not occur when the yield strength was low. However, when the DI can is actually used, it is necessary to provide the necessary can strength. For example, when a DI can is used in a state where the inside of the can is pressurized, if the yield strength of the steel plate is low, the pressure resistance at the bottom of the can is insufficient and the bottom of the can expands. In addition, since the lid is wound around the can body with the lid pressed against the can body, if the yield strength of the steel plate is low, the buckling strength of the bottom of the can is insufficient, and the lower portion of the can is crushed. . Therefore, the yield strength of the steel sheet needs to have a certain value or more, and the yield strength is preferably 300 MPa or more in order to avoid the above problems.

In previous experiments, when the can body after ironing was pulled out from the punch, the upper end portion of the can body was crushed by the finger part of the stripper, and it could not be pulled out normally. That is, the extractability may be inferior. This is a phenomenon that is also known in DI cans using conventional tinting materials. And in the specification of patent document 2, it describes that the extractability of a laminated steel plate is inferior to a tinting material.
As a method for improving the drawability, a means has been used to set the plate thickness reduction rate at the final stage of the ironing multiple times low in the tin DI can. However, when this method is applied to DI cans made of laminated steel sheets, it is necessary to increase the sheet thickness reduction rate in ironing before the final stage, and each time after satisfying the condition of equation (1) It becomes difficult to set the plate thickness reduction rate.
Therefore, we should consider the drawability. Focusing on the fact that the drawability is affected by the lubrication between the inner surface of the can body and the punch, the coolant governing the lubricity in ironing (lubricated / cooled with diluted lubricant with water) The material was subjected to a molding experiment with different conditions.
Specifically, the viscosity of the coolant and the coolant temperature were changed. At this time, in order to change the viscosity of the coolant, the lubricant added in the coolant (commercially used tinplate DI can lubricant) whose concentration was changed to 0% or more was used. The temperature of the coolant was 20 to 80 ° C. Also, the entrance angle of the ironing die is 2 °, and the laminated steel plate is a PET (polyethylene terephthalate) film with a film thickness of 15μm, and is bonded to both sides of a steel plate with a thickness of 0.2mm and a yield strength of 400MPa. A laminate was used. The sheet thickness reduction rate in the ironing process was set to satisfy the condition (1), and the final sheet thickness reduction rate up to the third time was set to 77%. As a result, the following conclusions were obtained.

The viscosity of the coolant is generally better when the concentration of the lubricant in the coolant is higher. In the formation of DI cans using laminated steel sheets, the lower the concentration of the lubricant, the better the drawability. When the viscosity of the coolant used in the experiment was measured using a rotary viscometer, the viscosity was low when the concentration of the lubricant was low, and this viscosity is considered to dominate the drawability. In other words, there is an upper limit to the viscosity of the coolant that exhibits excellent drawability when ironing is performed under the conditions that match the formula (1) using a laminated steel sheet, and 1.0 mPa · s or less is preferable. However, when the viscosity is excessively low, the drawability is excellent, but film damage occurs. This is presumably because during the ironing process, the coolant is not sufficiently held in the contact portion of the laminated steel plate and the ironing die and punch, and the necessary lubricating action cannot be exhibited. In order to avoid film damage, a viscosity of 0.3 mPa · s or more is preferable.
From the above, in order to achieve both excellent drawability and avoidance of film damage when ironing is performed using laminated steel sheets under the conditions that match Equation (1), the viscosity of the coolant is 0.3 to 1.0 mPa · s. Is preferable.

Desirable conditions for the laminated steel sheet used in the present invention are described below.
Steel plate as a substrate of the laminated steel plate of the present invention is not particularly limited. However, the yield strength is preferably 300 MPa or more and 500 MPa or less. The following components and production methods are desirable.
(1) Using low carbon steel having a C content of about 0.01 to 0.10% and recrystallized by box annealing.
(2) A low carbon steel having a C content of about 0.01 to 0.10% and recrystallized by continuous annealing.
(3) Recarbonized and over-aged by continuous annealing using low carbon steel with C content of about 0.01-0.10%.
(4) A low carbon steel having a C content of about 0.01 to 0.10%, which is subjected to secondary cold rolling (DR) after recrystallization annealing by box annealing or continuous annealing.
(5) An ultra-low carbon steel with a C content of approximately 0.003% or less and IF steel with a strong solid solution C-fixing element such as Nb, Ti, etc., and recrystallized by continuous annealing.
As mechanical characteristics other than the yield strength, those having an r value as an index of plastic anisotropy of 0.8 or more are desirable, and the in-plane anisotropy Δr of the plastic anisotropy r value has an absolute value of 0.2. 7 or less is desirable. The plate | board thickness of a steel plate can be suitably set from the shape of the target can and required can body strength. From the viewpoint of suppressing an increase in the cost of the steel plate itself and the can body, it is desirable to use approximately 0.15 to 0.4 mm.

Steel Plate Surface Treatment It is desirable to use a surface-treated steel plate with various surface treatments applied to the laminated steel plate and substrate steel plate used in the present invention. Examples of the surface treatment include tin plating, chrome plating, and metal oxide coating treatment. In particular, a surface-treated steel sheet (so-called TFS) or the like in which a two-layer coating composed of metallic chromium as the lower layer and chromium hydroxide as the upper layer is formed is optimal. When this is used, the amount of adhesion of the metal chromium layer and the chromium hydroxide layer is not particularly limited, but in any case, the metal chromium layer is 70 to 200 mg / m ² and the chromium hydroxide layer is 10 in terms of Cr. It is desirable to be in the range of ˜30 mg / cm ² .

Films The following are preferable as the organic resin film constituting the film-laminated steel sheet used in the present invention.
For example, a polyester resin is a resin layer obtained by condensation polymerization of a carboxylic acid component and a diol component. The carboxylic acid component may contain terephthalic acid as a main component, and the other copolymer component may contain an isophthalic acid component. As a glycol component, ethylene glycol and / or butylene glycol may be the main component, and other copolymer components may include diethylene glycol and cyclohexanedimethanol. Alternatively, the main phase of the polyester resin is the resin, the resin is incompatible with the secondary phase, and contains a resin having a glass transition point Tg of 5 ° C. or lower, polyethylene, polypropylene, and / or an acid-modified product thereof. Or an ionomer. Further, additives such as pigments, lubricants and stabilizers may be added to the resin composition, or a resin layer having other functions in addition to the resin layer may be disposed in the upper layer or the intermediate layer.

  The method of laminating to the steel plate is not particularly limited, and it may be appropriately selected such as a thermocompression bonding method in which a biaxially stretched film or an unstretched film is thermocompression bonded, or an extrusion method in which a resin layer is directly formed on the steel plate using a T die. Can do.

Examples will be described below.
A PET (polyethylene terephthalate) film having a film thickness of 15 μm was laminated on both sides of a steel plate having a plate thickness of 0.2 mm and a yield strength of 400 MPa by a heat fusion method to obtain a laminated steel plate. Next, the resulting laminated steel sheet is punched into a circular blank, drawn with a cupping press at a draw ratio of 1.74, and then formed into a DI can by DI drawing with a DI can forming machine followed by ironing. did. The entrance angle of the ironing die was 2 °, 5 ° and 8 °, and the axial length of the land was 1 mm. In the molding, a coolant in which a commercially available tinting material DI can molding lubricant was added to water by 1.5% was used.

  The target plate thickness reduction rate (original plate thickness standard) in ironing was set to 52% and 73%, and ironing was performed in 1 to 4 steps, and the film damage on the outer and inner surfaces of the can was visually evaluated after forming. . The obtained results are shown in Table 1 together with the plate thickness reduction rate X (n) in each ironing step and the value of the formula (1).

From Table 1, in the case of the conditions defined in the present invention where the entrance angle of the ironing die is 2 °, 5 ° and the plate thickness reduction rate X (n) in each ironing process is lower than the value of the formula (1), Film damage does not occur, and a target plate pressure reduction rate can be obtained in the ironing process in three or four processes.
On the other hand, even when the entrance angle of the ironing die is 2 ° and 5 °, film damage occurs in the comparative example in which the plate thickness reduction rate X (n) in each ironing process is higher than the value of the formula (1). Yes.
In addition, when the ironing die has an approach angle of 8 °, the film thickness is damaged and the target thickness is reduced even if the thickness reduction rate X (n) in each ironing process is lower than the value of equation (1). The reduction rate cannot be obtained.

  A PET (polyethylene terephthalate) film having a film thickness of 15 μm was laminated on both surfaces of a steel plate having a thickness of 0.2 mm and a yield strength of 260 to 550 MPa by a heat-sealing method to obtain a laminated steel plate. The obtained laminated steel sheet was punched into a circular blank, drawn with a cupping press machine at a drawing ratio of 1.74, and then formed into a DI can by DI drawing with a DI can molding machine followed by ironing. At that time, the entrance angle of the ironing die was 2 °, and the axial length of the land was 1 mm. In addition, the number of ironing steps was 3, and the plate thickness reduction rate X (n) at each time was 30.5% for the first time, 45.5% for the second time, and 73.0% for the third time. In this condition, the value of the formula (1) is 31.1% in the first ironing, 47.7% in the second ironing, and 78.3% in the third ironing. It is a condition. In the molding, a coolant in which a commercially available tinting material DI can molding lubricant was added to water by 1.5% was used.

After molding, film damage on the outer surface side and the inner surface side of the can was visually evaluated.
In addition, the bottom of the can after the DI molding is shaped into a bottom conforming to the DI cans used in commercial carbonated beverages, and after trimming the top of the can body, it is attached to a pressure-resistant strength tester and the inside of the can body is Pressure was applied with air, and the pressure resistance at the bottom of the can was measured. Evaluation what breakdown voltage strength of 7 kgf / cm ² or more ○, was × what is less than 7 kgf / cm ^2.
Furthermore, the bottom of the can after DI molding is shaped into a shape that conforms to a commercially available fish meat can, and after trimming the top of the can body, it is flange-formed, wrapped with a lid, and attached to a compression tester. The buckling strength at the bottom of the can was measured by compressing in the can height direction. In the evaluation, a case where the buckling strength was 100 kgf or more was evaluated as ◯, and a case where the buckling strength was less than 100 kgf was evaluated as ×.
The results obtained as described above are shown in Table 2.

  When the yield strength of the steel sheet was 500 MPa or less, film damage did not occur. On the other hand, if the yield strength was 300 MPa or more, the pressure strength and buckling strength were sufficient.

  A PET (polyethylene terephthalate) film having a film thickness of 15 μm was laminated on both sides of a steel plate having a plate thickness of 0.2 mm and a yield strength of 400 MPa by a heat fusion method to obtain a laminated steel plate. The obtained laminated steel sheet was punched into a circular blank, drawn with a cupping press at a drawing ratio of 1.74, and then formed into a DI can by a redrawing with a DI drawing machine at a redrawing ratio of 1.4 followed by ironing. At that time, the entrance angle of the ironing die was 2 °, and the axial length of the land was 1 mm. In addition, the number of ironing steps was 3, and the plate thickness reduction rate X (n) at each time was 30.5% for the first time, 45.5% for the second time, and 73.0% for the third time. In this condition, the value of the expression (1) is 31.1% in the first ironing, 47.7% in the second ironing, and 78.3% in the third ironing. It is a condition. In the molding, in order to change the viscosity of the coolant, the concentration of the lubricant (commercially available lubricant for tinplate DI can) added to the coolant was changed to 0% or more. The temperature of the coolant was 20 to 80 ° C. The viscosity of the coolant was measured using a rotary viscometer.

After molding, film damage on the outer surface side and the inner surface side of the can was visually evaluated.
In addition, the punching ability from the can was evaluated. The punch pullability from the can body was evaluated in a crushed state at the finger part of the stripper, and ◯ indicates that the crushed portion is small and a specified trim height can be secured, and x indicates that it cannot be secured. The obtained results are shown in Table 3.

  When the viscosity of the coolant is 1.0 mPa · s or less, there is no problem in the drawability. On the other hand, when the viscosity of the coolant is 0.3 mPa · s or more, film damage does not occur.

  The present invention is most suitable as a food can or a beverage can. And besides these, using organic resin film laminated steel plate as envisioned in the present invention as a raw material, using conventional DI molding, avoiding damage to the film, for applications where can body pullability is required Are also preferably used.

It is a figure which shows the approach angle of an ironing die. It is a figure which shows the relationship between the plate | board thickness reduction | decrease rate and film damage in ironing. It is a simplified diagram showing a DI can molding machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ironing die 2 Entrance angle of ironing die 3 Land axial length 4 Punch 5 Drawing cup 6 Redrawing die 7 Ironing die (1st process)
8 Ironing dice (2nd process)
9 Ironing dice (3rd process)
10 Stripper

Claims (3)

A method of forming a DI can made of a laminated steel sheet coated with an organic resin film,
In order to reduce the sheet thickness by using multiple independent ironing dies for one ironing forming, and reducing the sheet thickness by multiple ironing forming, the entry angle of the ironing die is set to 2 ° to 5 °, and the nth time A method of forming a DI can characterized by satisfying the formula (1), where X (n)% is the thickness reduction rate from the original sheet thickness in ironing.
X (n) ≦ 0.0004X (n−1) ³ + 0.0025X (n−1) ² + 0.0956X (n−1) +31.1 Formula (1)
However, X (0) = 0   2. The method for forming a DI can according to claim 1, wherein the laminated steel sheet is a laminated steel sheet in which an organic resin resin film is coated on both surfaces of a steel sheet having a yield strength of 300 to 500 MPa.   The method for molding a DI can according to claim 1 or 2, wherein a liquid having a viscosity of 0.3 to 1.0 mPa · s is used as a coolant.

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