JP5354872B2 - Stainless steel can body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance pressure resistance of a can without using a rainforcement member, restrict occurrence of defects such as wrinkles at the time of press forming an end plate and reduce wall thickness and weight. <P>SOLUTION: This stainless steel can member has a ratio of the plate thickness t<SB>1</SB>of a barrel part 1/the inner diameter D of the barrel part 1 of at least 0.0008, wherein the plate thickness t<SB>2</SB>of an end plate 2/the plate thickness t<SB>1</SB>of the barrel part 1 is 0.4 or more and 1 or less, the radius r at a corner inner surface of an end plate 2/the inner diameter D of the barrel part 1 is 0.15 or more and 0.35 or less and at the same time the radius R at the central inner surface of the end plate 2/the inner diameter D of the barrel 1 is 0.7 or more and 1.15 or less. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a stainless steel can body including a cylindrically formed barrel portion and press-molded end plates provided at both ends of the barrel portion, and particularly to optimize the shapes of the barrel portion and the endplate. Thus, while improving the pressure resistance of the can body without using a reinforcing member, it is possible to suppress the occurrence of defects such as wrinkles during press molding of the end plate, and relates to a new improvement that can realize thinning and weight reduction. is there.

Direct pressure cans that are directly subjected to the water pressure of tap water are subject to water leakage, deformation, and damage for 1 minute at a water pressure (positive pressure) of 17.5 kgf / cm ² (1.75 MPa), which is the standard approval standard value of the Japan Water Works Association. It is necessary to satisfy the requirement, and generally the pressure resistance is secured by increasing the plate thickness used for the can body. Therefore, the plate thickness is currently set to 1.2 mm or more. On the other hand, the can body intended for hot water storage instead of the direct pressure type can be made thinner than the direct pressure type can body because the Japan Water Works Association's type approval standard value is as low as 3 kgf / cm ² (0.3 MPa). Become. At present, the plate thickness is set to 0.8 mm or more in order to set the pressure resistance standard higher than 0.3 MPa in consideration of the safety factor.

  Here, the current market trend is to reduce the weight of the can, and in order to reduce the weight, it is necessary to make the plate thickness thinner. However, when the plate thickness is reduced, the pressure resistance of the can body is lowered. Therefore, a technique described in Patent Document 1 below can be cited as a technique for improving the pressure resistance. That is, in the conventional can body, in order to improve the pressure resistance of the can body, a plurality of reinforcing rings are screwed on the outer peripheral surface of the cylindrical body with the upper and lower openings closed at equal intervals in the length direction of the cylindrical body. It is fixed.

Japanese Patent No. 3436011

  In the conventional can as described above, since a plurality of reinforcing rings (reinforcing members) are used to improve pressure resistance, the material and the manufacturing cost increase, and the reinforcing ring is heavier. In addition, simply reducing the plate thickness not only reduces the pressure resistance of the can body, but also tends to cause body wrinkling (puckering) during press molding of the end plate. If it is enlarged, cracks will occur.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to improve the pressure resistance of the can body without using a reinforcing member, and to solve problems such as wrinkles during press molding of the end plate. It is an object of the present invention to provide a stainless steel can body capable of suppressing the occurrence of thinning and realizing a reduction in thickness and weight.

A stainless steel can body according to the present invention includes a barrel portion formed in a cylindrical shape and end plates press-molded at both ends of the barrel portion, and the barrel portion and the end plate are made of ferritic stainless steel. In the can body in which the thickness t _{1 of the} barrel portion / the inner diameter D of the barrel portion is at least 0.0008, the thickness t _{2 of the} end plate / the thickness t ₁ of the barrel portion is set to 0.4. The radius r of the corner inner surface of the end plate / the inner diameter D of the barrel portion is set to 0.15 or more and 0.35 or less, and the radius R of the center inner surface of the end plate / the inner diameter D of the barrel portion. Was 0.7 or more and 1.15 or less.

According to the stainless steel can body of the present invention, in the can body in which the plate thickness t _{1 of the} barrel portion / the inner diameter D of the barrel portion is at least 0.0008, the thickness t _{2 of the} end plate / the thickness t ₁ as 0.4 or more and 1 or less, the inner diameter D of radius r / the body of the corner inner surface of the end plate with 0.15 or more and 0.35 or less, the radius of the central inner surface of the end plate R / Because the inner diameter D of the body portion is 0.7 or more and 1.15 or less, the pressure resistance of the can body is improved without using a reinforcing member, and the occurrence of defects such as wrinkles during press molding of the end plate is generated. It is possible to reduce the thickness and weight.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is an explanatory view showing the shape of a stainless steel can body according to Embodiment 1 of the present invention.
The pressure acting on the can for the purpose of hot water storage includes positive pressure and negative pressure. As a result of the study by the inventor of the present application, a cylindrical portion 1 is formed at both ends of the cylindrical portion 1. If the can body has the end plate 2 provided, the positive pressure is determined by the ratio of the radius (corner portion radius) r of the inner surface of the end plate 2 to the inner diameter D of the body portion 1 and the inner diameter D of the body portion 1. It has been found that the negative pressure is most influenced by the plate thickness t _{1 of the} body ₁ / the inner diameter D of the body 1.

  In the present embodiment, the component values shown in Table 1 (the balance is Fe and inevitable impurities) as a test material, using a high corrosion resistance ferritic stainless steel having a 0.2% proof stress of 360 MPa and a tensile strength of 525 MPa, The shapes of the body 1 and the end plate 2 were examined. From the viewpoint of characteristics, the preferred component range of the ferritic stainless steel applied to the present invention is the range shown in Table 2 below (the balance is Fe and inevitable impurities). The body portion 1 is formed by processing plate-like stainless steel into a cylindrical shape and welding both ends thereof, and the end plate 2 is formed by pressing.

FIG. 2 is a graph showing the relationship between the plastic deformation starting negative pressure and the plate thickness t _{1 of the} body ₁ / the inner diameter D of the body 1. The deformation of the can body due to the negative pressure occurs in the body 1 rather than the end plate 2. However, in the experiments of the inventors of the present application, the plastic deformation start negative pressure and the plate of the body 1 are shown in FIG. It can be seen that there is a high correlation with the thickness t ₁ / the inner diameter D of the body 1, and the pressure resistance against negative pressure increases as the plate thickness t _{1 of the} body ₁ / the inner diameter D of the body increases. To do. That is, when the thin plate thickness t ₁ of the barrel 1, it can be seen that in order to secure pressure resistance, it is effective to miniaturize the internal diameter D of the barrel 1. Although the set reference value of the negative pressure varies depending on the use situation, in the present embodiment, considering the pressure reduction in the can during hot water supply, the set reference value of the negative pressure is set to a negative pressure value of 0.018 MPa, and The plate thickness t ₁ / the inner diameter D of the body portion 1 is assumed to be 0.0008 or more.

In practice, if the thickness t _{1 of the} barrel ₁ / the inner diameter D of the barrel 1 is greater than 0.0025, the thickness t ₁ increases and the cost of the can increases. In addition, if the inner diameter D of the body portion 1 is reduced, the hot water storage capacity is reduced, and there is a concern that the hot water will run out during use of the hot water. Therefore, the thickness of the body portion t ₁ / body portion 1 of the present invention is intended. The inner diameter D is 0.0025 or less. In addition, since the present invention is intended to reduce the thickness, the thickness t ₁ of the body portion 1 intended by the present invention is a value of 0.4 mm or more and 0.8 mm or less.

Next, FIG. 3 is a graph showing the relationship between the plastic deformation start pressure at positive pressure and the radius r of the inner surface of the corner plate 2 / the inner diameter D of the body 1, and FIG. 4 is the plastic deformation start pressure at positive pressure. 4 is a graph showing the relationship between the radius R of the center inner surface of the end plate 2 / the inner diameter D of the body 1. As shown in the figure, the plastic deformation starting pressure becomes maximum when r / D and R / D are 0.5. That is, in order to improve pressure resistance against positive pressure, a hemispherical end plate in which the radius R of the central inner surface of the end plate 2 and the radius r of the corner inner surface of the end plate 2 are the same as the inner diameter D / 2 of the body 1 is optimal. It is. However, since the forming of the end plate is a drawing process, and a compressive force acts in the circumferential direction of the blank, the hemispherical end plate 2 having the largest area of the overhang portion where the blank does not contact the punch and the die at the initial stage of press processing is The body wrinkle is most likely to occur in the overhang portion that is not restrained by the punch or die. Therefore, as the plate thickness t2 of the end plate ₂ is made thinner, body wrinkles (puckering) are more likely to occur, and cracks will occur if the wrinkle restraining force is increased to prevent the body wrinkles. In addition, when the radius R of the center inner surface of the end plate 2 is increased, the press formability (inhibition of body wrinkles) is improved and the internal capacity is increased, but the pressure resistance is decreased. Further, even if the radius r of the corner inner surface of the end plate 2 is reduced, the press formability is improved and the internal capacity is increased, but the pressure resistance is lowered.

Hereinafter, specific experimental results on the shape of the end plate 2 will be shown.
Experiment 1.
FIG. 5 is a diagram showing a state during press molding of the end plate 2 of FIG. FIG. 6 is an explanatory diagram showing a range in which the pressure resistance of the can body and the press formability of the end plate 2 are normal under the conditions of Experiment 1. FIG. In Experiment 1, the ferritic stainless steel having a plate thickness of 0.4 mm was used as a test material. In press working of the end plate 2, a blank diameter of 500 mm, a punch diameter of D300 mm, a die R (Rd) = 4 mm, and wrinkles. The holding force (BHF) was set based on the well-known Siebel semi-theoretical formula, and was pressed to a drawing height of 170 mm. R at the center of the punch of the end plate 2 is changed within a range of 150 to 360 mm (R / D = 0.5 to 1.2), and r at the shoulder of the punch is 30 to 150 mm (r / D = 0 to 0). .5) and the changed ones were combined and press molding of the end plate 2 was performed. As shown in FIG. 6, the radius r of the inner surface of the end plate 2 / the inner diameter D of the body portion 1 is larger than 0.35, and the radius R of the center inner surface of the end plate 2 / the body portion 1. When the inner diameter D was made smaller than 0.7, body wrinkles occurred during press molding.

  When body wrinkles did not occur, the body portion 1 having the same thickness as the end plate 2 was joined by welding, and a pressure resistance test was performed as a can body having a height of L 1200 mm. The positive pressure reference value was 0.6 MPa (the Japan Water Works Association's model approval reference value was 0.3 MPa) in consideration of the safety factor, and the one without water leakage, significant deformation and destruction was accepted. In this pressure resistance test, as shown in FIG. 6, when the radius r of the corner inner surface of the end plate 2 / the inner diameter D of the barrel portion 1 is smaller than 0.15, and the radius R / of the center inner surface of the end plate 2 When the inner diameter D of the body 1 was made larger than 1.15, non-uniform deformation occurred in the end plate.

Experiment 2.
FIG. 7 is an explanatory diagram showing a range where the pressure resistance of the can body and the press formability of the end plate 2 are normal under the conditions of Experiment 2. FIG. In Experiment 2, the ferritic stainless steel having a plate thickness of 0.5 mm is used as a test material for both the end plate and the body, and in press working of the end plate 2, a blank diameter of 1000 mm, a punch diameter of D600 mm, and a die R (Rd) = 4 mm. The wrinkle restraining force was set based on the well-known Siebel semi-theoretical formula, and was pressed to a drawing height of 300 mm. R at the center of the punch of the end plate 2 is changed within a range of 300 to 720 mm (R / D = 0.5 to 1.2), and r at the shoulder of the punch is 60 to 300 mm (r / D = 0 to 0). .5) and the changed ones were combined and press molding of the end plate 2 was performed. As shown in FIG. 7, even in this condition, as in Experiment 1, when the radius r of the inner surface of the corner plate 2 / the inner diameter D of the body portion 1 is larger than 0.35, and the inner inner surface of the end plate 2 When the radius R / the inner diameter D of the body portion 1 is smaller than 0.7, body wrinkles occurred during press molding.

  Further, when the body wrinkle did not occur, the pressure resistance test was conducted as in Experiment 1. As shown in FIG. 7, in this pressure resistance test, as in Experiment 1, the radius r of the corner inner surface of the end plate 2 / the inner diameter D of the body portion 1 was made smaller than 0.15, and the center of the end plate 2 When the radius R of the inner surface / the inner diameter D of the body portion 1 was larger than 1.15, non-uniform deformation occurred in the end plate.

In Experiments 1 and 2, the case in which the body 1 and the end plate 2 are made of the same ferritic stainless steel as described above has been described. However, the thickness t ₁ of the body 1 is increased according to the negative pressure reference value. In this case, the thickness t _{2 of the} end plate 2 may be changed from the thickness of the body 1. Optimum shape of the end plate as described above also thickness t ₂ of the end plate 2 as was changed to a thin plate thickness than the plate thickness t ₁ of the barrel 1 is unchanged. This is because the negative pressure is influenced not by the end plate 2 but by the plate thickness t _{1 of the} body ₁ / the inner diameter D of the body 1 as described above. When the end plate 2 is made thinner than the body portion 1, if it is made too thin, body wrinkles and cracks are likely to occur at the time of press molding, and the pressure resistance is lowered. Therefore, the thickness t _{2 of the} end plate / the thickness t _{1 of the} body portion is It is set to about 0.4 or more and 1 or less.

Accordingly, in a can body having a body thickness t _{1 of the} body portion ₁ / an inner diameter D of the body portion 1 of at least 0.0008, the thickness t ₂ of the end plate ₂ / the thickness t ₁ of the body portion ₁ is 0.4 or more and 1 In the following, the radius r of the corner inner surface of the end plate 2 / the inner diameter D of the barrel 1 is 0.15 or more and 0.35 or less, and the radius R of the center inner surface of the end plate 2 / the inner diameter D of the barrel 1 is set to 0. By setting it to 7 or more and 1.15 or less, it is possible to suppress the occurrence of problems during press molding while improving the pressure resistance of the can body without using a reinforcing member, and it is possible to realize a reduction in thickness and weight.

It is explanatory drawing which shows the shape of the stainless steel can body by Embodiment 1 of this invention. Is a graph showing the relationship between the inner diameter D of the thickness t _{1 /} barrel of plastic starts to change the negative pressure and the body. FIG. 3 is a graph showing the relationship between the plastic deformation starting pressure at a positive pressure and the radius r of the corner inner surface of the end plate / the inner diameter D of the body 1. It is a graph which shows the relationship between the plastic deformation start pressure in positive pressure, the radius R of the center inner surface of the end plate / the inner diameter D of the body part 1. It is a figure which shows the state at the time of press molding of the end plate 2 of FIG. It is explanatory drawing which shows the range where the pressure resistance of a can and the press moldability of the end plate 2 are normal in the conditions of Experiment 1. It is explanatory drawing which shows the range where the pressure resistance of a can and the press moldability of the end plate 2 are normal in the conditions of Experiment 2.

Explanation of symbols

  1 body, 2 end plate

Claims (1)

A barrel (1) formed in a cylindrical shape;
An end plate (2) provided at both ends of the body (1) and press-molded,
The barrel (1) and the end plate (2) are made of ferritic stainless steel, and the thickness (t ₁ ) of the barrel (1) / the inner diameter D of the barrel (1) is at least 0.0008. In the can body, the thickness t ₂ of the end plate (2) / the thickness t ₁ of the body portion (1) is 0.4 or more and 1 or less, and the radius r of the corner inner surface of the end plate (2) / the body The inner diameter D of the part (1) is 0.15 or more and 0.35 or less, and the radius R of the central inner surface of the end plate (2) / the inner diameter D of the body part (1) is 0.7 or more and 1. and 15 or less, a stainless steel can body plate thickness _{t 1,} characterized in that a 0.4mm or more and 0.8mm or less of the barrel (1).

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