Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(vol.43 no.501 October 2002)
Rolling Characteristics of Dull Finished Ceramic Rolls
Ken-ichi YASUDA, Osamu SHITAMURA and Tamihito KAWAHIGASHI
(Received on October 1, 2001)
Among many kinds of ceramics, sialon was selected as the most suitable roll material for cold rolling. Sialon rolls were developed and their rolling performance was demonstrated during cold rolling of stainless steel and other hard materials. These rolls have been used mainly as bright rolls. In order to expand the application field, dull finished sialon rolls were also developed, and their rolling characteristics were studied through experiments. There are two ways to obtain a rough surface:one is by polishing with coarse grinding powder slurry and the other is by shot blasting. A maximum roughness of Ra3.6micro-meter can be obtained with the latter method. Roughness drop during rolling of sialon rolls is almost the same as that of steel rolls. Roughness change can be minimized with a roughness drop prevention treatment that involves polishing with fine grinding powder slurry after surface roughening. Roll coating occurs such that the surface color changes uniformly unlike the case of bright rolls. In dull rolling with sialon rolls, roll coating does not spoil the durability of surface roughness. The possible reduction range is wider in sialon rolls than in steel rolls because the former has higher Young's modulus. Strip surface brightness changes with a change in reduction ratio. The controllable range of strip surface brightness thus becomes wider in sialon rolls. Print rolls were also developed by application of the shot blasting technique. The roll surface is dented to have the desired mark by shot blasting after photolithographic masking. It is confirmed that the marks are printed clearly on the strip surface by rolling with the print rolls under a wide reduction range.
Key words : cold rolling, ceramic roll, sialon, dull roll, roll coating, strip surface brightness
Measurement of Deformation of Extrusion Die in Hot Extrusion of Aluminum
-- Deformation of Extrusion Die in Aluminum Hot Extrusion 2 --
Tsutomu MORI, Norio TAKATSUJI, Kenji MATSUKI,
Tetsuo AIDA, Kazuo MUROTANI and Kouichi UETOKO
(Received on October 23, 2001)
The deformation of extrusion die in a rod (diameter=32.0mm, extrusion ratio=10) of 1050 aluminum and 6063 aluminum alloy extrusion at 573~623K is measured at the position 27~45mm away from the die center by using a laser displacement meter. Because the part around the extrusion die is restrained by the binding force produced by the friction force between the container wall and the billet, it is found that the deformation angle of extrusion die decreases as the measurement point approaches the container wall. The distribution of the deformation angle of the extrusion die in the vicinity of the bearing part in 1050 aluminum extrusion is hardly changed. On the other hand, that in the vicinity of the bearing part in 6063 aluminum alloy extrusion is changed markedly. Since the binding force in the part around the extrusion die decreases as the billet length decreases, and it is assumed that the total deflection of the extrusion die increases gradually.
Key words : aluminum extrusion, deflection of extrusion die, measurement, 1050 aluminum, 6063 aluminum alloy
Prediction of Mechanical Property of Ferrite-Pearlitic Microalloyed Steel in Controlled Forging
-- Process Modeling in Controlled Forging 2 --
Hiroaki YOSHIDA, Sachihiko ISOGAWA, Yoshinori KANEKO,
Yasuhiro YOGO and Takashi ISHIKAWA
(Received on October 31, 2001)
Controlled forging is greatly effective in the weight reduction of automobile components as mentioned in the previous report, because of the fine microstructure. On using the controlled forging, prediction of the microstructure and mechanical properies by the finite element method (FEM) is very useful for process designing. For the purpose of weight reduction of automobile components by strengthening, predictions of yield strength, fatigue strength and reduction in area are very important, becaue the design of the components is based upon these properties. However, most process modeling systems proposed previously can predict only the microstructure, or hardness and tensile strength. In this paper, the predictions of yield strength, fatigue strength and reduction in area are discussed in addition to hardness and tensile strength. Hardness and tensile strength can be prodicted simply by the volume fraction of ferrite. On the other hand, yield strength and reduction in area can be predicted by the combined equation based on Hall-Petch's law, consisting of the volume fractions of ferrite and pearlite and their grain sizes. It is cofirmed that the fatigue strength does not have any interrelation with tensile strength, but does with yield strength.
Key words : forging, mechanical property, thermomechanical heat treatment, microalloyed steel, process modeling
Square-Shell Deep Drawability and Dynamic Explicit FEM Simulation of Titanium Sheets
-- A Study of Formability of Titanium Sheets 1 --
Tetsuro OHWUE, Hideki FUJII,
Masao KIKUCHI and Teruhiko HAYASHI
(Received on November 12, 2001)
Uniaxial tensile tests, square shell deep drawing tests and simulations utilizing a dynamic explicit code "PAM-STAMP" are carried out in order to investigate the formability of pure titanium sheets. Materials used are four types of pure titanium sheets (JIS class 1 and JIS class 2) and an IF steel sheet. In the FEM simulation, anisotropy of r-value by the Hill equation is adopted. As a result, the square shell deep drawability of pure titanium sheets is significantly enhanced by teflon lubricants, compared with that by rust-preventive oil lubricants. This shows that the friction between material and tool surface is very important in the deep drawing of pure titanium sheets. In addition, for the square shell deep drawing of pure titanium sheets, material draw-in from flange changes with the rolling direction of material. These phenomena coincide with the FEM simulations.
Key words : deep drawability, titanium sheet, anisotropy, lubricant, FEM simulation
Effects of Extrusion Conditions on Hot Extruding Characteristics of Magnesium Alloy
Norio TAKATSUJI, Kenji MATSUKI, Tetsuo AIDA,
Kazuo MUROTANI and Jun SYOBO
(Received on November 15, 2001)
The effects of extrusion conditions on the surface qualities of extruded AZ31 magnesium alloys and the extrusion load are investigated. The extrusion load increases under low-temperature or high-speed conditions. The surface qualities of AZ31 magnesium alloys extruded with no lubricant are poor, and many minute cracks are produced. The minute cracks grow into large and deep crater-like cracks under high-temperature and high-speed conditions. The cause of deterioration in the quality of surfaces is a discontinuous metal flow in the neighborhood of the die exit. The surface qualities of AZ31 magnesium alloys extruded with graphite lubricant are good up to the middle of extrusion processing, and minute cracks are not observed.
Key words : magnesium alloy, hot extrusion conditions, surface quality, graphite lubricant
Effect on Pass Schedule of Cross-Sectional Shapes of Circular Seamless Tubes Reshaped into Square Shapes by Hot Roll Sizing Mill
Takuo NAGAMACHI, Yoshitomi ONODA, Eiji WAKAMATSU,
Takaaki TOYOOKA, Takuya NAGAHAMA and Nobuhiko MORIOKA
(Received on November 19, 2001)
In order to manufacture a heavy gauge square steel pipe, a hot roll sizing process is introduced because of difficulty in manufacturing it with sharp corners by cold roll forming. In this paper, the effect of pass schedule on a cross-sectional shape is discussed by referring to the experimental measurements and the results calculated by the rigid-plastic finite element method. The experiment was carried out at the last part of the sizing process of seamless pipes. The corners of a product become sharper as the magnitude of total reduction increases. In the case of two roll type, the corner near the roll flange becomes sharper than the corner near the groove bottom. The hollow depth at the sides will be small when the incremental reduction at each sizing stand is high at the early reshaping stage with a large bending curvature ((D0/2)/Ri, Ri:bending radius, D0:initial external diameter of a circular seamless pipe) and low at the late reshaping stage with a small bending curvature.
Key words : hot roll forming, tube forming, seamless pipe, heavy gauge square pipe, rigid-plastic FEM
Application of Volume Loss Recovery and Incremental Volume Control to Multistage Forging and Slab Extension-by-Forging Process
-- Volume Loss in Non-Steady-State Analysis by Rigid/Viscoplastic Finite Element Method --
Jian SHANG, Shiro TOYOSHIMA and Manabu GOTOH
(Received on November 29, 2001)
Large volume loss is induced when a large increment per step is imposed in the numerical simulation of the forging process by the rigid/viscoplastic FEM (Finite Element Method). Two methods are proposed to suppress such volume loss:one is IVC (incremental volume control) and the other is VLR (volume loss recovery). In our previous work, the validity of both methods was examined by analyzing the simple upsetting and single-stage extrusion of a cylindrical billet with a flat or straight die. In this study, we apply these two methods to more complex forging processes. First, a cold multistage axisymmetric forging process with curved dies is analyzed, and the volume loss and strain distribution are examined. Next, the slab extension-by-forging process is analyzed under the plane strain condition, in which a single-step/multi-step procedure with IVC and VLR is contrived to reduce the computation time, and volume constancy and thickness distribution are examined. Moreover, the effect of the so-called rigid zone on the slab thickness distribution is discussed, when the single-step procedure is employed. From the results, it is confirmed that the volume loss is effectively reduced by the use of both methods even in such complex processes, and that around the curved portion of the die, VLR keeps the volume constancy more accurately than IVC does.
Key words : numerical simulation, rigid/viscoplastic FEM, volume loss, forging, extension-by-forging, rigid region
Improvement of Filling Ratio and Reduction of Forming Pressure
-- A Trial for Forming of a Spur Gear Made from the Drawn Cup 2 --
Yukihiro KAKISHIMA, Yukihiko UCHIDA and Michihiko HOSHINO
(Received on December 13, 2001)
In a previous report, a new production method was proposed in which a spur gear was made from a drawn cup by plastic working. This forming method consists of four processes, namely, drawing, re-striking, ironing and compressing. However the forming of steel gears is not suitable for the actual production because the forming pressure in the compressing process is too high and the filling ratio is not sufficient. Therefore it is examined to reduce the forming pressure and improve the filling ratio by two versions of the divided flow forging method. One consists of flowing material into the opposite side of a tooth using a cushion punch with grooves. The other consists of flowing material into the clearance between the cushin punch and the compressing plate which enlarges the bore. It is found that the divided flow methods are able to improve the filling ratio and reduce the forming pressure. A deformation mechanism by FEM simulation is very similar to the experimental result, and it can be used to estimate the filling ratio and forming pressure.
Key words : sheet metal forming, cold die forging, rigid-plastic FEM, deformation-load property, spur gear