Papers in JOURNAL OF THE JAPAN SOCIETY
FOR TECHNOLOGY OF
PLASTICITY
(Vol.41 No.476 September 2000)
Metal Flow in Porthole Die Extrusion
Yuji YAMASHITA, Young-Tae KIM,
Tadasu MURAKAMI and Keisuke IKEDA
(Received on November 9, 1999)
The core in porthole die extrusion is exposed to severe working conditions, and consequently, the life of the core tends to decrease rapidly. An understanding of both metal flow and die pressure is essential to not only to die design but also to high-performance extrusion. In this study, the effects of various extrusion parameters on the metal flow were investigated. The relationship between metal flow and die pressure was examined. The billets for extrusion were composed of two disc-shaped alloys (A1050 and A1100) stacked one-by-one;they exhibit different etching characteristics. After extrusion, the extrusion residue was machined and observed every 10 degrees from 0 to 60. Until completion of the division process, the container friction was relatively small, while it turned sticking condition in the steady-state extrusion process. The change of the extrusion temperature had negligible influence on metal flow. However, it is obvious that metal flow was strongly dependent on friction conditions of the container. The metal flow was also somewhat influenced by the change of the welding chamber depth and division ratio. In addition, three-dimensional shapes of the dead zone were obtained, they would provide information for finite-element analysis.
Key words : porthole die extrusion, die pressure, aluminium, metal flow, dead zone, friction
Method for Suppressing Bending after Asymmetric
Cutting of Cold-Drawn Bar
Satoru WATANABE, Masaaki ABE and Takashi KUBOKI
(Received on December 6, 1999)
A new drawing process to suppress bending after asymmetric cutting of a drawn bar is proposed. The new process involves an additional final pass with ultra-light reduction. The proposition is based on the assumption that the axial residual stress after drawing may be the main factor which causes bending after cutting. The essential point of the new process is to reduce the axial residual stress by performing a final pass with ultra-light reduction. In order to determine the effective drawing conditions, the following approach was adopted. First, the effect of the light reduction pass on the axial residual stress was investigated through laboratory experiments and numerical calculations based on elasto-plastic FEM. Second, bars drawn under several drawing conditions were cut into a shape simulating a rack bar and the bent shape was measured. Third, the correlations between the drawing conditions, the axial residual stress distribution and bent shape were compared. As a result, the critical drawing condition for suppressing bending was found.
Key words : drawing, bending, cutting, rack bar, FEM, light reduction, axial residual stress
Development of Precise Rolling Method in a Mandrel Mill
Tateo YAMADA, Kenji MORIBE,
Masayuki YAMADA and Yoshiaki KUSABA
(Received on December 10, 1999)
A new method of tube rolling in a mandrel mill is proposed. The aim is to eliminate variations in the circumferential wall thickness which occur during mandrel mill rolling, using a 4-roll stand arranged following the conventional mandrel mill. In a mandrel mill, the roll groove center of the finishing stands is designed to correspond to the mandrel bar center so that the wall thickness will be uniform in the circumferential direction. However, in actual operation, a certain range of wall thicknesses must be produced with the same set of rolls and mandrel bar. When rolling a wall thinner than the designed wall, thicker parts appear between the roll groove and flange side of the tube. Because of this, the accuracy of the wall thickness of the rolled tube degrades. A 4-roll stand for rolling these thicker parts after a mandrel mill is proposed in this study. To examine this proposal, an experimental study is carried out with a miniature rolling mill. The effectiveness of the 4-roll stand is confirmed.
Key words : tube rolling, rolling mill, mandrel mill, dimensional accuracy, 4-roll mandrel mill
Experimental Analysis of Material Flow in
Extrusion of C-channel Product
- Die Design Aided by Physical Simulation System ‡T -
Kenji NAKANISHI, Hirofumi KOBA and Shunpei KAMITANI
(Received on December 13, 1999)
Bending, distortion and dimensional variability in the shape and crystallographic structure of an extruded product are closely related to the plastic flow characteristics of the material in the deformation zone of a billet. However, taking into account the three-dimensional plastic flow in an industrial extrusion process for optimum design of the extrusion die involves a relatively complex procedure. Hence, in the present work, a physical simulation system was developed to quantitatively measure and analyze three-dimensional plastic flow in the deformation zone of a billet in a steady-state extrusion process in terms of the flow field and velocity field. As application examples, the material's plastic flow conditions in the extrusion of a C-channel product using a flat die as well as a die with a flow guide were investigated quantitatively using the simulation system. We confirmed that the experimental and analytical results obtained by the physical simulation system yielded useful information for optimum design of the extrusion die. The physical simulation system could be applied to aid in the design of the extrusion die.
Key words : extrusion, flat die, flow guide, die design, visioplasticity method, forming simulation, physical simulation
Influence of Arc Condition on Welding
- Arc Welding of Wire and Terminal -
Toshimitsu FUJIWARA, Hiroyuki IWASAKA, Teruhiko MATSUOKA and Toshio SASAOKA
(Received on December 15, 1999)
Usually, solder containing Pb is used to join many electric components such as relays and switches. Recently, a joining method without Pb has been desired to protect the environment. The main purpose of this trial is to apply arc welding for joining wires and terminals. As a fundamental examination, we investigated the influence of the arc condition on welding when arc welding is applied between a pure copper wire covered by polyurethane and a copper alloy terminal. The result shows that the fusion phenomenon of arc welding can be treated as a heat balance. In other words, the relation between the arc conditions and fusion volume is represented by the regression equation. It is also clarified that the generation of voids in the fusion zone depends on the arc condition. The generation of voids in the fusion zone can be decreased by decreasing the arc current and increasing the arc time.
Key words : joining, arc welding, wire, terminal, nonferrous metal (Cu, Cu-Sn-P, Cu-P)
Influence of Shear Deformation on Grain Coarsening Behaviour
in Hot Working of Medium Carbon Steel
Yutaka NEISHI, Yoshifumi HARUHATA
Masayoshi AKIYAMA and Manabu KIUCHI
(Received on December 20, 1999)
The influence of shear and tensile deformation on the grain coarsening condition during hot working of S45C which the authors presented in the previous paper was investigated using a compression test. The condition is described by two scalar values, temperature and equivalent plastic strain, and no component of the strain tensor is taken into consideration. The purpose of this paper is to examine the validity of describing the condition by the two scalar values, and also to examine whether this condition is valid under tensile testing. In order to realize a large shear deformation, a new specimen geometry was proposed for the compression test. The new specimen geometry was optimized by using the FEM code "ELFEN". Hot compression tests were then carried out using a hot deformation simulator, and tensile testing was carried out with the Gleeble test. Consequently, it was found that the grain coarsening condition may also be described by two scalar values under shear and tensile deformation.
Key words : grain coarsening phenomenon, 3D FEM, S45C, hot deformation simulator, prediction of grain size, narrow band, shear deformation, tensile deformation, equivalent plastic strain, temperature
Simplification of the Manufacturing Process of a High-pressure
Gas Cylinder by Axial-Force-Assisted Redrawing
Nobuhiro KOGA, Tomoyuki OHBUCHI and Takafumi IIJIMA
(Received on December 22, 1999)
To produce a deep-drawn cup depth three to five times greater than its diameter for a small high-pressure gas cylinder from a low-cost, thick steel plate, it is necessary to repeat the redrawing process at least three to five times after deep drawing. In order to reduce the manufacturing cost of a deep-drawn cup, we must reduce the number of redrawing processes. We proposed a new redrawing method which involves redrawing by applying pressure to the edge of the deep-drawn cup. Using this proposed redrawing method, we experimentally produced a deep-drawn cup, and found that the limiting redrawing ratio was significantly improved compared to the case of the conventional redrawing method. In the conventional method, five processes, including deep drawing, are necessary to produce a deep-drawn cup;however, in the proposed redrawing method, the number of processes could be reduced to three. Furthermore, a deep-drawn cup for a 30cc high-pressure gas cylinder could be manufactured via only two processes instead of the four required in the conventional method.
Key words : deep drawing, redrawing, limiting redrawing ratio, high-pressure gas cylinder
Development of Forming Processes of Large Wheel Disks
for Trucks and Buses Using Rocking Die Forging
Kenji YOSHII, Masahiro ABE, Takashi KIMURA,
Kouji IZUMIDA, Osamu EBIHARA and Ken-ichiro MORI
(Received on December 27, 1999)
To reduce material loss in forming of large wheel disks for trucks and buses, forming processes involving the rocking die forging of rings were newly developed. In the present processes, one end of the ring is shrunk and the other is expanded by rocking die forging to form a disk shape. Since the ring is produced by bending a rectangular plate and subsequently welding both ends, the loss of material is small, i.e., the blanking loss is considerably decreased. Rocking die forging was employed to attain a comparatively low forming load for large disks. The two-stage forging process with rocking and fixed dies was designed to obtain the desired disks. The effects of the intermediate shapes of the disks after the 1st stage and the angle of the rocking die in the 2nd stage on the shapes of the disks after the 2nd stage were investigated.
Key words : rocking die forging, material loss reduction, large wheel disk, ring, two-stage forging, deformation-load property
Surface Finish of Aluminium Pipe by Multistage Ironing
with Ultrasonic Vibration
Teruie TAKEMASU, Tatsuo OZAKI, Ryoichi MATSUNAGA
Hiroshi MIYAHARA, Masashi SAKAGUCHI and Kenji TOMITA
(Received on January 6, 2000)
DI (deep drawing and ironing) and EI (extrusion and ironing) processes are widely used to produce cans and photosensitive drums because of their high productivity and their high processing accuracy. However, reduction of the ironing stages is strongly required to lower the production cost. In addition, since the use of fluorocarbon and trichloromethane as detergents of the lubricant is strictly restricted in consideration of environmental conservation, an ironing process with a low-viscosity lubricant or without the need for lubrication is recommended. In this study, multistage ironing experiments with ultrasonic vibration are carried out using a low-viscosity volatile oil as a lubricant to make the washing process of the products unnecessary. The pickup is completely suppressed by polishing the surface of the workpiece using sandpaper before the ironing process. It is experimentally confirmed that the surface finish of the workpiece is considerably improved by applying ultrasonic vibration, and that a sufficient accuracy (Ry<0.2um) can be achieved by a 1-stage or a 2-stage ironing process with vibration.
Key words : sheet metal forming, ironing, surface finish, surface roughness, lubricants, ultrasonic vibration, FEM, photosensitive drum