JP-2026076342-A - A punch for ironing and a metal cylinder obtained by ironing using the punch.

Abstract

[Problem] To provide a punch for ironing that has excellent pull-out properties after ironing, and a metal cylindrical body obtained by ironing using the punch. [Solution] The metal cylinder has a hollow cylindrical shape and is obtained by ironing, wherein numerous dot-shaped protrusions are distributed on its inner circumferential surface, and when viewed in a longitudinal cross-section along the axial direction, each of the dot-shaped protrusions has a shape in which the apex is biased toward the direction opposite to the processing direction. [Selection Diagram] Figure 2

Inventors

• 神山 昂大
• 田村 政臣
• 中村 友彦
• 高木 翔平

Assignees

• 東洋製罐株式会社

Dates

Publication Date

20260511

Application Date

20260218

Claims (5)

1. A metal cylinder having a hollow cylindrical shape, obtained by ironing, characterized in that numerous dot-shaped protrusions are distributed on its inner circumferential surface, and, when viewed in a longitudinal cross-section along the axial direction, the apex of each of these dot-shaped protrusions is offset in the direction opposite to the machining direction.
2. The metal cylindrical body according to claim 1, wherein an organic resin layer is laminated on the inner circumferential surface, and the dot-shaped protrusions are distributed on the surface of the organic resin coating layer.
3. The metal cylinder according to claim 2, wherein the organic resin is a thermoplastic resin.
4. In a punch used for ironing metal, The punch for ironing is characterized in that a large number of dot-shaped recesses are distributed on the outer surface of the punch, and when viewed in a cross-section along the sliding direction of the punch, it has an arc-shaped raised portion on the side opposite to the tip of the punch.
5. A metal cylinder having a hollow cylindrical shape, obtained by ironing using the ironing punch described in claim 4, characterized in that a large number of dot-shaped protrusions are distributed on its inner circumferential surface, and when viewed in a longitudinal cross section along the axial direction, the apex of each of the dot-shaped protrusions is offset in the direction opposite to the processing direction.

Description

This invention relates to a punch used in ironing processes, and further to a metal cylindrical body, such as a seamless can, obtained by ironing using this punch. Ironing is a harsh plastic deformation process performed to thin metal walls, and is applied to the manufacture of thin-walled, high-height metal cylinders, such as thin-walled seamless cans. This ironing process is carried out by passing a hollow metal cylinder through a narrow space between an annular die and a rod-shaped punch. Specifically, a punch is inserted into the metal cylinder to be thinned, and the cylinder is sandwiched between the punch and the annular die. The metal cylinder is then thinned by relatively moving (sliding) the punch and the annular die in this state. For example, Patent Documents 1 and 2 disclose a technology for manufacturing seamless cans (drawn ironed cans) using this type of ironing process. By the way, in this type of ironing process, the punch must be withdrawn from the thinned metal cylinder after the ironing process is complete. The problem here is that, in ironing, the metal cylinder, which is the workpiece, is pressed firmly against the outer surface of the punch, resulting in a large frictional resistance. This makes it difficult to withdraw the punch smoothly, which not only reduces productivity but can also cause problems such as deformation of the inner surface of the formed metal cylinder due to the withdrawal process. In reality, the ease of punching out punches during this type of ironing process has hardly been considered. For example, Patent Document 3 discloses a seamless metal can in which a thermoplastic resin layer is formed on the inner surface, and a number of dot-like protrusions are formed on the thermoplastic resin layer on the inner surface. This technology mitigates the molecular orientation of the thermoplastic resin layer caused by ironing by forming dot-like protrusions, thereby suppressing the decrease in dent resistance caused by molecular orientation in the thermoplastic resin layer. In other words, in Patent Document 3, ironing is performed using a punch with dot-like recesses formed on its outer surface in order to form dot-like protrusions on the thermoplastic resin layer on the inner surface of the can. As can be understood from this, Patent Document 3 also does not consider the pullability of the punch for ironing at all. International Publication No. 2017/033791Japanese Patent Publication No. 2018-69256Patent No. 3327137 A diagram illustrating the thinning of a workpiece (metal cylinder) by ironing.Partially enlarged axial cross-sectional view (X-X cross-sectional view) of the ironing punch of the present invention.Figure 2 is a partially enlarged schematic plan view of the outer surface of the ironing punch shown.A partially enlarged cross-sectional view of a thinned workpiece (metal cylinder).A schematic longitudinal cross-sectional view showing the positional relationship between the ironing punch and the thinned seamless can at the end of the ironing process when the workpiece is a metal seamless can.This diagram shows the engagement relationship between the dot-shaped recesses formed on the punch and the dot-shaped protrusions formed on the workpiece (metal cylinder) during punch withdrawal.A diagram illustrating the rollback pattern generated by the withdrawal of a punch used for ironing.A diagram illustrating an example of a press forming process utilizing ironing.A diagram illustrating an example of a molding process when ironing is performed in multiple stages. <About the ironing process> Ironing is a well-known method of plastic deformation of metals and is widely used, for example, in the manufacturing of high-height, thin-walled seamless metal cans. As shown in Figure 1, in this ironing process, the ironing die C is pressed against the outer surface of the metal cylinder B, which is the workpiece, and rubbed against it while the ironing punch A moves the cylinder B in the processing direction, thereby thinning the cylinder B. Therefore, in this type of ironing process, the inner surface of the metal cylinder B is firmly in contact with the outer surface of the ironing punch A. In this type of ironing process, the ironing ratio is expressed by the following formula, where t0 is the thickness of the metal cylinder before ironing and t1 is the thickness after ironing. The larger this ironing ratio, the greater the surface pressure applied to the ironing die C and then to the punch A, resulting in a harsher molding process. Hazing rate (%) = 100 × ( t0 - t1 ) / t0 The ironing punch A has a tubular (cylindrical) shape, but is generally made of the same cemented carbide as the ironing die C described later, and is made relatively thick to prevent deformation during ironing. Furthermore, a drive shaft S (not shown in Figure 1, but indicated as S in Figure 5) for moving the punch A in the machining direction is connected to the inner surface of one end of the punch A (the