Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(Vol.41 No.477 October 2000)
Net Shape Forging of Toothed Products
Utilizing Divided Flow Method
Kyoichi OHGA, Fumio MURAKOSHI, Hiroyuki ANDO,
Koji MIYOSHI and Kazuyoshi KONDO
(Received on December 6, 1999)
The divided flow method was applied to the working of various involute spur machine gears in order to establish it as a practical and useful forging process. A well-shaped gear could be forged under a working pressure of 2000MPa on a low carbon steel such as S10C. When the toothed die was changed to a floating die, the working pressure decreased to 1500MPa. Even in the case of a Ni-Cr-Mo alloyed steel of SNCM, the same well-shaped gear was forged with the pressure of 2330MPa. When the compressive toothed punch was changed to one with a proper projection at the bottom face of the punch, both an external gear with the face width of 10 times the module and an internal gear with the face width of 11 times the module were obtained under a low working pressure. When a newly designed multiaction die set was combined with a single-action press, the divided flow method could be applied within a short working time. In addition, the product having both an internal gear and an external one was successfully obtained.
Key words : net shape, cold forging, divided flow, forming limit, working pressure, spur gear, steel, aluminium, die set
Deformation Mode in Extrusion against Counter Pressure
\ Extrusion against Floating Tool Supported by Pressure@I \
Kozo OSAKADA, Shinji HANAMI and Naoto ARAI
(Received on November 24, 1999)
A cold extrusion method for manufacturing a product with multiple extruded parts (fins) of equal lengths is studied. In this method, a floating tool supported by pressure controls the flow to ensure equal velocities for each extruded part. To analyze this process, a formulation to accommodate the pressure-supported tool into the rigid-plastic finite element method is proposed. The results of the experiments carried out using lead as a model material are compared with those of the finite element simulation. It is found that the pressure necessary to equalize the extruded lengths is as low as 2]3% of the flow stress of the billet. However, with the low pressure, the end surfaces of the extruded parts are not flattened. The pressure necessary to conform the end surfaces to the tool surface is 50]60% of the flow stress. The extrusion pressure increases more steeply than the counter pressure, because the counter pressure significantly affects the frictional stress over the extruded side surfaces.
Key words : extrusion, rigid-plastic finite element method, counter pressure, floating tool
Comparative Evaluation of Various Lubricants by Different Friction
Testing Methods for Cold Forging Processes of Aluminum Alloys
Tamotsu NAKAMURA, Zhi-Liang ZHANG, Masaru ITOH,
Hiroshi KIMURA and Seizaburo IIDA
(Received on January 12, 2000)
Four kinds of friction tests were performed to evaluate various lubricants for cold forging processes of seven kinds of aluminum alloys. Three types of conversion coatings, three paraffinic mineral oils of different viscosity and four types of solid powder lubricants were tested. As a result, the following conclusions were drawn.
(1) An aluminum-fluoride-type conversion coating with zinc stearate gave better lubricity than a calcium-aluminate-type conversion coating in three of the friction testing methods. (2) The higher viscosity mineral oil showed good lubricity in the ring compression type, rod extrusion type and backward extrusion type friction tests. In the forward conical can-extrusion-type friction test, however, the higher viscosity mineral oil gave higher friction coefficients and a severe pick-up on the conical punch surface.@(3) All the solid lubricants had poor lubricity:they gave a higher friction coefficient and severe pick-up than the other lubricants in all four types of friction tests.
Key words : forging, tribology, friction test, upsetting, forward extrusion, backward extrusion, friction coefficient, pick-up
Evaluation Method of Tribological Conditions in Net Shape
Cold Forging of Products with Concave-Convex Profiles
Hiroyuki SAIKI, Yasuo MARUMO, Liqun RUAN and Gracious E.NGAILE
(Received on January 18, 2000)
A tribo-test method is proposed to evaluate the performance of lubricants in cold forging. By this method, the performance of coating-based lubricants was evaluated. Dies with different surface profiles were used to induce various workpiece surface expansions at the tool-workpiece interface. The specimens used were made from two types of steel, JIS-SCM435 and JIS-S15C. The tester includes facilities for heating dies and the workpiece to vary interface temperatures. The tribo-test results indicated that the lubricity of coating-based lubricants is influenced by the interface temperature, the surface expansion and the multistage operations. The coefficient of friction decreased with increasing interface temperature, while it increased above the critical temperature of 300. In the case of large surface expansion, the lubricity deteriorates at a shorter sliding distance. An increase in the sliding velocity led to the increase in the interface temperature, thus the coefficient of friction decreased below 300. The results of the two-stage tribo-tests revealed the effect of the deterioration and the thinning of the coatings upon subsequent forging.
Key words : cold forging, tribo-test, conversion coatings, surface expansion, interface temperature, tool geometry, sliding velocity
Application of 3D Forging Analysis to Optimize
Forging Die Parameters for Helical Gear Forming
Hisayoshi KOJIMA, Shinichiro FUJIKAWA, Kanji UENO
Jun IKEUCHI, Naoki KATO
(Received on March 6, 2000)
Flow-control core forging of helical gears is a popular new forging technology. In this study we show a simulation of this new forming process, the effectiveness of using the Taguchi method for optimizing parameters in the simulation, and the optimization of forging die dimensions. First, the helical gear profiles by the experiment and the simulation compared. An adjustment of the simulation parameters was performed to reduce the difference between experimental and simulation results. The two major die designing parameters were selected to achieve fulfilled gear teeth. In total 25 simulation cases were calculated to obtain underfill quantity distributions on the two-parameter matrix. Then the response surface method, an optimization method, was applied to obtain the optimal combinations of the mandrel diameter and escape hole diameter. In this paper we describe one procedure to achieve optimal die designing parameters using the FEM and optimization methods.
Key words : forging, finite-element method, rigid-plastic FEM, Taguchi method, optimization, flow control method