JP2006045590A - Steel sheet coated with organic resin film for di can, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a steel sheet coated with an organic resin film for DI (drawn and ironing) cans which causes no PET (polyethylene terephthalate) hair and has excellent can characteristics and also to provide its manufacturing method. <P>SOLUTION: The steel has a composition consisting of, by weight, 0.001 to 0.010% C, ≤0.05% Si, ≤0.9% Mn, ≤0.1% P, ≤0.04% S, 0.010 to 0.100% Al, ≤0.0050% N, ≤0.050% Nb and/or ≤0.10% Ti and the balance Fe with inevitable impurities. Further, grain sizes in directions parallel to and perpendicular to the rolling direction are made to 3.0 to 10.0μm, respectively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a steel plate for DI cans coated with an organic resin film used for container materials such as food cans and beverage cans and a method for producing the same, and is excellent in DI (Drwan and Ironing) processability. It relates to a steel plate for DI cans coated with an organic resin film suitable for DI can applications, which eliminates the phenomenon that the resin film is peeled off in the form of a thread at the cut end, has a low rough surface roughness after processing, and has a low ERV value. is there.

  Conventionally, as a method for forming side seamless cans, a method of applying an organic paint to the inside and outside of a can after forming a surface-treated steel sheet, and coating a resin film on the steel sheet before forming a kind of resin film There is a so-called thinned drawn ironing can molding method in which the steel plate of the portion that becomes the side wall of the can is thinned.

  In recent years, in applications of side seamless cans, there has been a demand for further reducing the thickness of the side wall of the can, and high reduction in can molding is required. Therefore, when forming a DI can coated with an organic resin film made of PET, a high surface pressure is generated between the steel plate and the forming tool during ironing, and the PET hair problem that the cut end of the organic film is peeled off into a thread shape occurs. . Conventionally, as a method for preventing part of the organic resin film from peeling off, there is a method for changing the shape of the opening of the metal can (see, for example, Patent Document 1). However, it cannot be applied to a DI processing method with a very severe processing degree.

  Prior art document information relating to the present application includes the following.

JP 2004-26306 A

  Usually, a DI can is obtained by punching a coated steel plate into a disk shape and drawing it to obtain a drawn can first. This squeezed can reduces the thickness of the side wall of the can through several ironing processes, and finally obtains a DI can.

  In the above processing method, the coated steel sheet is punched into a disk shape, and then cup drawing and ironing are performed. However, the material with high strength of the original plate has a high surface pressure at the ironing process, and the cut surface of the organic film is very Although it is very fine, it tears into filaments, and during continuous canning, the flakes of the filamentous film (hereinafter referred to as PET hair) peel off and accumulate on the can-making line, which significantly impairs workability. Therefore, a soft material is desirable until the ironing process of the can.

  Moreover, it is necessary to make ERV value small from the point of reducing iron elution.

  An object of the present invention is to solve the above-mentioned problems, and an organic resin film suitable for use in DI cans, in which a coated metal disk is soft until ironing, has excellent workability, and does not cause large skin roughness during molding. It aims at providing the steel plate for DI cans which coat | covered, and its manufacturing method.

  The present inventor limited that the PET hair is a soft material until the ironing process of the can, so that the hair is limited to an extremely low carbon steel sheet, and the crystal grain needs to be reduced in order to reduce the ERV value. I found out. Therefore, the present inventor has found that by adding Nb and / or Ti to an ultra-low carbon steel, there is no PET hair and excellent ERV characteristics if the material is soft and has small crystal grains.

  The steel plate for DI cans coated with the organic resin film of the present invention according to claim 1 has C: 0.001 to 0.010 wt%, Si: ≤ 0.05 wt%, Mn: ≤ 0 as steel components. .9 wt%, P: ≦ 0.1 wt%, S: ≦ 0.04 wt%, Al: 0.010 to 0.100 wt%, N: ≦ 0.0050 wt%, and Nb: ≦ 0.05% by weight and / or Ti: ≦ 0.10% by weight, further comprising the balance Fe and inevitable impurities, and the crystal grain size in the direction parallel to and perpendicular to the rolling direction is 3. It is 0-10.0 micrometers, It is characterized by the above-mentioned.

  The manufacturing method of the steel plate for DI cans which coat | covered the organic resin film of this invention of Claim 2 is C: 0.001-0.010 weight%, Si: <= 0.05 weight%, Mn as a component of steel. : ≦ 0.9 wt%, P: ≦ 0.1 wt%, S: ≦ 0.04 wt%, Al: 0.010 to 0.100 wt%, N: ≦ 0.0050 wt%, and A heat cycle including an overaging treatment after cold rolling a hot-rolled steel sheet containing Nb: ≦ 0.050 wt% and / or Ti: ≦ 0.10 wt% and further comprising the balance Fe and inevitable impurities Annealing is performed, and temper rolling is performed at an elongation of 0.5 to 2.0%.

  The manufacturing method of the steel plate for DI cans which coat | covered the organic resin film of this invention of Claim 3 is C: 0.001-0.010 weight%, Si: <= 0.05 weight%, Mn as a component of steel. : ≦ 0.9 wt%, P: ≦ 0.1 wt%, S: ≦ 0.04 wt%, Al: 0.010 to 0.100 wt%, N: ≦ 0.0050 wt%, and A hot-rolled steel sheet containing Nb: ≦ 0.050% by weight and / or Ti: ≦ 0.10% by weight and further comprising the balance Fe and inevitable impurities is subjected to annealing after primary cold rolling and further rolling. Secondary cold rolling is performed at a rate of 5 to 30%.

  By using a soft ultra-low carbon steel sheet having C of 0.01% by weight or less, the surface pressure during the final ironing process was reduced, and the occurrence of PET hair was suppressed. Moreover, in order to suppress the coarsening of a crystal grain diameter by adding any one or both of Nb and Ti, ERV value can be reduced.

  The steel plate of the present invention is coated with a resin film such as polyester, punched into a disk shape, squeezed into a cup, and can be processed continuously and at high speed by the DI processing method, no PET hair problem occurs, DI cans can be molded.

  In recent years, this DI can is used in order to further reduce the thickness of the side wall, so that high reduction in DI molding is required. Therefore, a high surface pressure is generated between the steel sheet and the forming tool during ironing, and the organic film is cut. The PET hair problem occurs in that it peels off in the form of threads. Therefore, the present inventors have proposed to minimize the PET hair by softening the material to reduce the surface pressure during the ironing process and reducing the load on the molding. Therefore, a soft ultra-low carbon steel plate having C of 0.01% by weight or less is used as the steel plate.

  In addition, the ultra-low carbon steel sheet generally has large crystal grains and becomes rough after the can is formed, thereby deteriorating the ERV value. Therefore, Nb and / or Ti were added to the ultra-low carbon steel sheet to refine the crystal grains without impairing the soft properties, and at the same time as improving the PET hair, the ERV value was improved.

  The range of the other detailed steel component and the reason are shown below.

(Components of hot-rolled steel sheet)
C: 0.001 to 0.010 wt%, Si: ≤ 0.05 wt%, Mn: ≤ 0.9 wt%, P: ≤ 0.1 wt%, S: ≤ 0.04 wt%, Al: Including 0.010 to 0.100% by weight, N: ≦ 0.0050% by weight, Nb: ≦ 0.050% by weight, and / or Ti: ≦ 0.10% by weight, with the balance Fe and Consists of inevitable impurities.

The reasons for regulating steel components are described below.
(C amount)
If C exceeds 0.01% by weight, it hardens and causes PET hair problems. Therefore, the C amount is 0.01% by weight or less. Moreover, it is preferably 0.001% by weight or more in view of can strength and suppression of coarsening of crystal grains.
(Si amount)
Si is an element harmful to corrosion resistance as a material for cans, but is an element inevitably contained as Al killed steel, and the upper limit was set to 0.05% by weight.
(Mn amount)
Mn is a component necessary to prevent red heat brittleness during hot rolling due to the impurity S, but if it exceeds 0.9% by weight, the drawability deteriorates, so the upper limit was made 0.9% by weight. .
(P amount)
P is an effective component for crystal grain refinement. However, in the present invention, crystal grains are refined with Nb and Ti, so that it is desirable that P is less in terms of softening during molding. . Therefore, P is 0.1% by weight or less.
(S amount)
S is an impurity component that causes red hot brittleness during hot rolling, and it is desirable that S be as small as possible.
(Al content)
Al is indispensable for obtaining a steel plate having high cleanliness as a deoxidizer in steelmaking, and the lower limit was set to 0.01% by weight. Further, the upper limit is set to 0.10% by weight or less in order to suppress hardening due to excessive solute Al.
(N amount)
N is a solid solution N and has a high effect of increasing the strength. In the present invention, N is not desirable if it is contained in a large amount. In addition to Ti and Al, some form Nb and precipitates to suppress the strength increase. However, when the precipitates are excessive, the crystal grains become excessively fine and the strength is increased. Therefore, the upper limit was made 0.0050% by weight or less.

  Although the slab heating temperature and hot rolling conditions are not specified in the present invention, the slab heating temperature is 1100 ° C. or higher because hot rolling is good in shape and finish rolling is performed in the γ region. It is desirable to do. However, it is not necessarily limited to γ region rolling. In addition, the coiling temperature in the hot rolling is set to 450 ° C. in consideration of the quality stability in the coil width direction and the longitudinal direction during hot rolling, and when the temperature exceeds 650 ° C., the crystal grains become coarse and rough skin occurs. The coiling temperature is preferably in the range of 450 to 650 ° C.

Cold rolling process When the rolling reduction is less than 75%, the annealing process leads to coarsening or mixing of the crystal grains of the steel sheet, and the crystal grains cannot be sufficiently refined. % Is preferably the lower limit. Further, when forming a DI can made of an organic resin film, anisotropy to extreme forming of the steel sheet with respect to the rolling parallel direction due to drawing and ironing is not preferable. Therefore, it is more desirable to make the rolling rate 85 to 93%.

Annealing Step In the present invention, in order to soften the steel plate, it is desirable to perform an overaging treatment for annealing, but since it is an ultra-low carbon steel plate and added with carbide forming elements such as Nb and Ti, The aging effect is not fully exhibited. Therefore, if necessary, when using a steel sheet having a high C content (0.007 to 0.01% by weight), annealing in a heat cycle including an overaging treatment may be performed.

  After the annealing, the following secondary cold rolling (temper rolling or DR rolling) is performed.

Temper rolling In the case of temper rolling, if the elongation is in the range of 0.5 to 2.0%, generation of stretcher strain is prevented, so this range is appropriate.
In the present invention, the solid solution C and N in the steel is reduced by overaging treatment, and the workability in deep drawing is improved by suppressing the occurrence of constriction and the connection of voids, and is the object of the present invention. Strength is imparted by performing temper rolling in the range of 0.5 to 2.0% elongation while satisfying the DI processing conditions, whereby the steel sheet of the present invention has a high degree of processing required for DI processing. In addition to the properties, it is possible to provide a plate strength that does not cause the occurrence of broken bodies during processing. Thus, in the present invention, these two steps can be combined to achieve the conditions of workability and sheet strength. The temper rolling also achieves the required can strength required for an extremely thin can.

DR rolling DR rolling may be performed particularly when giving the can strength after molding, but the rolling reduction is 5 to 30%. If it is less than 5%, rolling is difficult, and if it exceeds 30%, the steel sheet has high strength, which makes it difficult for can molding.
This DR (Double Reduce Rolling) rolling is a rolling method in which the plate strength is increased in order to decrease the plate thickness more positively than the temper rolling.
In the present invention, secondary cold rolling is performed including the temper rolling and DR rolling.

  Next, examples of the steel sheet used in the present invention include sheet-shaped and coil-shaped steel sheets, steel foils, and steel sheets subjected to surface treatment. In particular, for electrolytic chromic acid-treated steel sheets having a two-layer structure in which the lower layer is metallic chromium and the upper layer is chromium hydrated oxide, or tinplate, ultrathin tin-plated steel sheets, nickel-plated steel sheets, galvanized steel sheets, and these plated steel sheets A hydrated chromium oxide or a surface treatment having a two-layer structure in which the upper layer is a chromium hydrated oxide and the lower layer is a metallic chromium layer is excellent in adhesion to an organic resin film such as a polyester resin. As the organic resin film laminated on the steel plate, the following resin films can be used.

Lamination of Resin Film The resin film applied to the present invention can be either a single layer film or a multilayer film of two or more layers, and is preferably a film made of a thermoplastic resin, particularly a polyester resin. The polyester resin preferably has an ester unit such as ethylene terephthalate, ethylene isophthalate, butylene terephthalate, butylene isophthalate, and is a polyester mainly composed of at least one ester unit selected from these. Is preferred. At this time, each ester unit may be copolymerized, and further, a homopolymer or copolymer of two or more types of ester units may be blended and used. Other than the above, those using naphthalenedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, etc. as the acid component of the ester unit, and the alcohol component of the ester unit include propylene glycol, diethylene glycol, neopentyl glycol, Those using cyclohexanedimethanol, pentaerythritol, or the like may be used.

  This polyester may be a laminate of two or more polyester layers made of homopolyester or copolyester, or a blend of two or more thereof. For example, the lower layer of the polyester film can be a copolymerized polyester layer excellent in thermal adhesion, and the upper layer can be a polyester layer or a modified polyester layer excellent in strength, heat resistance, and barrier properties against corrosive components.

  In the present invention, it is preferable to use a film made of an unstretched polyester resin. In the operation of laminating the polyester resin film on the surface-treated steel sheet, the resin is cut or the surface-treated steel sheet laminated with the polyester resin film is drawn or drawn. Even if a severe molding process such as ironing is performed, the resin will not be scraped or wrinkled, and cracks will not be generated, cracked or further peeled off. It is necessary to strengthen the resin.

  For this reason, it is preferable to make the intrinsic viscosity of said polyester resin into the range of 0.6-1.4, and it is more preferable to set it as the range of 0.8-1.2. When a polyester resin having an intrinsic viscosity of less than 0.6 is used, the strength of the resin is extremely lowered, and it cannot be applied to a can formed by drawing or drawing and ironing. On the other hand, if the intrinsic viscosity of the resin exceeds 1.4, the melt viscosity when the resin is heated and melted becomes extremely high, and the operation of laminating the polyester resin film on the surface-treated steel sheet becomes extremely difficult.

  In the case of a single layer film, the thickness of the resin film is preferably 5 to 60 μm, and more preferably 10 to 40 μm. If the thickness is less than 5 μm, the process of laminating the surface-treated steel sheet becomes extremely difficult, and the resin layer after drawing or drawing and ironing is likely to be defective, and the can is molded into a can and filled with the contents. However, the permeation resistance to corrosive components is not sufficient. When the thickness is increased, the permeation resistance is sufficient, but it is economically disadvantageous to have a thickness exceeding 60 μm. In the case of a multilayer film, the ratio of the thickness of each layer varies from the viewpoints of molding processability, permeation resistance, or the effect on the flavor of the contents, but each layer has a total thickness of 5 to 60 μm. Adjust the thickness.

  Further, when the resin film is formed into a film, the resin film may be formed by adding a coloring pigment, a stabilizer, an antioxidant, a lubricant, and the like as long as necessary properties are not impaired in the resin.

  As a method of laminating the organic resin film, the organic resin film may be directly or with an adhesive interposed in the heated surface-treated steel sheet. Moreover, you may apply the extrusion laminating method which laminates the melted resin directly on a surface treatment steel plate. As these laminating methods, known methods can be applied.

Using ultra-low carbon steel plates having the chemical components shown in Table 1, all the steel plates are subjected to primary rolling at a rolling rate of 85%, followed by continuous annealing at a temperature higher than recrystallization (annealing temperature of 730 ° C. or higher, desirably 750). And annealing time: 30 seconds, desirably 60 seconds or more), and temper rolling was performed at an elongation rate of 1.5%. Thereafter, the steel plate having a thickness of 0.225 mm was subjected to electrolytic chromic acid treatment (metal chromium 120 mg / m ² as the lower layer and chromium hydrated oxide 15 mg / m ^{2 in} terms of chromium as the upper layer), and then the can 20 wt% of a titanium oxide white pigment is added to a copolymerized polyester resin (inherent viscosity: 0.8) made of ethylene terephthalate (88 mol%) and isoterephthalate (12 mol%) on the outer surface when molded into When a non-stretched film having a thickness of 15 μm is formed into a can, the surface that becomes the inner surface side when formed into a can is 30 μm in thickness made of ethylene terephthalate (88 mol%) and isoterephthalate (12 mol%). The stretched transparent copolyester resin films were brought into contact with each other and pressed to obtain PET film-coated steel sheets. Examples 1-4 are within the component range of the present invention, and Comparative Examples 1-5 are outside the component range of the present invention. The evaluation method is shown below.

Mechanical property of steel plate The threshold of strength at which PET hair does not become prominent is that the tensile strength (TS) in the tensile test of JIS No. 5 piece is 450 MPa (= N / mm ² ) or less. Also, the lower limit is 250 MPa or more from the can strength. In addition to the tensile strength, the average r value (average Rankford value, (r value parallel to the rolling direction + r value perpendicular to the rolling direction + r value in the 45 ° direction relative to the rolling direction) (Value x 2) / 4) is 1.45 or more.

Crystal grain size The crystal grain size is rough at the time of molding, and due to this ERV defect due to the rough skin, the upper limit is 10.0 μm or less in both the direction parallel to the rolling direction and the direction perpendicular to the rolling direction. Is desirable. Further, excessive fine particles increase the bottom withstand voltage, so the lower limit is desirably 3.0 μm.

Bottom pressure resistance of molded DI cans Blanks with a diameter of 150 mm were punched out from the samples prepared in the examples and comparative examples, and then a punch with a diameter of 90 mm was made so that the surface on which the white colored film was laminated became the outside of the container. A drawing process (drawing ratio 1.67) followed by a drawing process (redrawing ratio 1.36) of redrawing with a 66 mm diameter punch was performed. This cup was molded into a DI can having a can diameter of 66 mm and a can wall upper end of 0.15 mm using an ironing apparatus comprising three stages of ironing dies. Next, the upper end portion was trimmed to a height of 122 mm, and heat treatment was performed at 215 ° C. for 30 seconds to remove the distortion of the film, and then the upper end portion was reduced in diameter to make the diameter of the open end portion 57 mm. Next, the opening end portion was stretched toward the outside of the can, the flange portion was formed so that the diameter of the flange end portion was 62 mm, and the bottom pressure resistance of the can before filling the contents was measured.

  In this case, the bottom pressure resistance is preferably 660 MPa or more from the viewpoint of can strength. On the other hand, if the bottom pressure resistance is too high, for example, when the contents expand at a high temperature, the bottom is not easily deformed, and a phenomenon of bursting at the cap portion of the can occurs. Therefore, the upper limit of the bottom pressure resistance is set to 780 MPa. That is, the range of an appropriate bottom pressure resistance was set to 660 to 780 MPa.

Generation of PET hair in molded DI can In the above-mentioned bottom pressure resistance section, immediately after molding into a DI can, the state of occurrence of PET hair was examined by visual observation of the opening of the can. The case where the occurrence of PET hair was not recognized was evaluated as “no”, and the case where even a little was observed was evaluated as “present”.

ERV Value In the above-mentioned bottom pressure resistance, the ERV of the DI can after heat treatment was measured. A case of 0.1 mA or less was evaluated as having no ERV defect, and a case of exceeding the value was evaluated as having an ERV defect.

  Table 2 shows the evaluation results of the characteristics. The overall judgment in Table 2 is T.W. S. , R value, crystal grain size, bottom pressure resistance, presence / absence of occurrence of PET hair, presence / absence of occurrence of ERV defect were evaluated as “good”, and if any one was satisfied, “x” was satisfied. In Comparative Example 1, Nb and Ti were not added, the crystal grains in the rolling direction were large, and ERV failure was caused. Further, Comparative Examples 2 and 3 each had a high Nb amount and Ti amount, were hard due to insufficient recrystallization during continuous annealing, had a high bottom pressure resistance, and generated PET hair. Since Comparative Example 4 had a high amount of C, it was hard and had a high bottom pressure resistance, and PET hair was also generated. Comparative Example 5 had a high secondary rolling rate, was hard, had a high bottom pressure resistance, and generated PET hair.

  According to the present invention, since softening at the time of molding, PET hair does not occur even during DI processing at a continuous high speed, and since coarsening of the crystal grains is suppressed, the skin roughness is small and the problem of ERV failure does not occur. The steel plate suitable for DI can use which coat | covered the resin film can be provided.

Claims (3)

  As steel components, C: 0.001 to 0.010 wt%, Si: ≤ 0.05 wt%, Mn: ≤ 0.9 wt%, P: ≤ 0.1 wt%, S: ≤ 0.04 Wt%, Al: 0.010-0.100 wt%, N: ≦ 0.0050 wt% and Nb: ≦ 0.050 wt% and / or Ti: ≦ 0.10 wt% Further, a DI can coated with an organic resin film comprising the remaining Fe and unavoidable impurities, wherein the crystal grain size in the direction parallel to and perpendicular to the rolling direction is 3.0 to 10.0 μm. Steel plate.   As steel components, C: 0.001 to 0.010 wt%, Si: ≤ 0.05 wt%, Mn: ≤ 0.9 wt%, P: ≤ 0.1 wt%, S: ≤ 0.04 Wt%, Al: 0.010-0.100 wt%, N: ≦ 0.0050 wt% and Nb: ≦ 0.050 wt% and / or Ti: ≦ 0.10 wt% Further, the hot-rolled steel sheet composed of the remaining Fe and inevitable impurities is subjected to annealing in a heat cycle including overaging treatment after cold rolling, and further subjected to temper rolling at an elongation of 0.5 to 2.0%. A method for producing a steel plate for DI cans coated with an organic resin film, characterized in that:   As steel components, C: 0.001 to 0.010 wt%, Si: ≤ 0.05 wt%, Mn: ≤ 0.9 wt%, P: ≤ 0.1 wt%, S: ≤ 0.04 Wt%, Al: 0.010-0.100 wt%, N: ≦ 0.0050 wt% and Nb: ≦ 0.050 wt% and / or Ti: ≦ 0.10 wt% Further, an organic resin film characterized by subjecting a hot-rolled steel sheet comprising the remaining Fe and inevitable impurities to annealing after the primary cold rolling, and further performing secondary cold rolling at a rolling rate of 5 to 30%. Manufacturing method of coated steel plate for DI can.