We investigated injection molding characteristics by carrying out comparative tests using an aluminum alloy mold coated using iron plating and a steel mold. In this study, a rapid heating and cooling mold temperature system was applied to the method of controlling mold temperature aiming at weldless molding. The weldless molding was made possible using an aluminum alloy mold coated by iron plating with a rapid heating and cooling mold temperature system. However, it is necessary to increase the injection start temperature by a higher value when using the aluminum alloy mold than when using the steel mold. The temperature in the aluminum alloy mold during molding was almost uniform. About 40% was what reduced in the aluminum alloy mold as a result of comparing the cycle times under weldless molding conditions. The transcript of the mold surface pattern to the product with the aluminum alloy mold was worse than that with the steel mold. However, the value was small. It was clarified that injection molding that uses an aluminum alloy mold and a rapid heating and cooling mold temperature system is effective for weldless molding.
This study is conducted to carry out the compression forming of aluminum films using a diamond mold in atmosphere and vacuum without the use of lubricant, in order to evaluate the transcription quality and metallographic structure of such films formed under the two conditions. In the diamond mold, three-dimensional microcavities are formed on the culets of a pair of diamond anvils, using a focused ion beam (FIB) system. Ultrahigh-pressure can be applied to the culets. A high-pressure plastic forming of an aluminum film was carried out using the fabricated diamond mold. The transcription quality of the aluminum film formed in atmosphere was poor because air remained in the mold. In contrast, when plastic forming was carried out in vacuum, the transcription quality of the aluminum film formed was good, because the amount of air remaining in the diamond mold was minimized. It was also confirmed that the average grain size of the aluminum film, which was 20-30 µm when a conventional diamond die was used, was reduced to 1 µm or less after the high-pressure plastic forming. It is considered that an equivalent strain of 4 or more was generated as a result of applying high-pressure, and that the forming conditions were the same as those under a strong strain.
Coating techniques utilizing the collision and adhesion of microparticles on a substrate have recently been attracting attention. However, the bonding between particles deposited on the substrate at room temperature and atmospheric pressure is weak because the kinetic energy of particles during their collision with a substrate is small. The aim of this study is to form ceramic films under these conditions, which is considered difficult. Concretely, the pressurized gas at the surface of the workpiece to be processed is released by the pulsed injection of helium gas using alumina microparticles to form coatings, while preventing the collision speed of the alumina microparticles from decreasing. By pulsed gas injection for 5 min, we succeeded in forming 10-µm-thick alumina ceramic films with a hardness of approximately 40% of that of a sintered alumina body. The results of a friction wear experiment indicated that the coefficient of friction of the films was stable and low (0.15). In addition, the quenched steel balls used in the experiment were worn out, demonstrating that the formed films have good abrasion resistance and adhesion.
The shaping conditions for a spur gear with an inner spline by cold extrusion by reducing the outer diameter or expanding the inner diameter of the workpiece were examined experimentally. The specifications of the spur gear examined are as follows: module m=1.0-2.0, number of teeth Z=22-13, and tooth depth h=2.25m; those of the inner spline are as follows: module ms=1.0, number of teeth Z=8-16, and tooth depth hs=1.25m. The tested material is low-carbon steel, S15C. The outer and inner diameters of the workpiece, inner spline tip diameter, and mandrel small and large diameters were varied to examine the effect of the reduction in area. It is found that well-shaped spur gears and inner splines can be produced. The shaping conditions are closely connected with the reduction in area. The accuracy of the shaped spur gear was about 6~8 Grade in the old JIS. The punch and mandrel needed pressure for the shaping are much lower than the strength of the material.
A mash seam welder is widely used for a continuous annealing and galvanizing line, but it is not applied to a continuous cold rolling line. The cross section of mash seam welding is characterized by steps at the edge of the lap seam. Analyzing by FEM and experimentally, the steps are found to be transformed to surface defects by rolling. There are two forms of defects: double-deformed and open. The former appears at the stepping-up part of the edge, and the latter appears at the stepping-down part. The potential of rolling fracture in double-deformed defects increases when the angle of step forms more steeply. The conventional flattening mechanism of steps at the lap seam is a swage by narrow wheels after welding, but a conventional swaging mechanism forms double-deformed defects. By crossing the upper and lower swaging wheels, shear force at the surface smoothen the steps without forming double-deformed defects. By using a mash seam welder with a cross swaging mechanism, lapped welding sheet specimens of 6 mm thickness are flattened without causing surface defects. The welded specimens can be rolled to 3.4 mm thickness without inducing fracture.
Hole expansion test using a flat-bottomed cylindrical punch was carried out to clarify the effects of the difference in microstructure between two types of complex-phase high-strength hot-rolled steel sheet on stretch flangeability, in which ferrite-pearlite steel and ferrite-bainite steel of 590 MPa tensile strength were used. The results showed that the hole expansion ratio λ in the case of the hole of a reamer edge depended on fracture limit strain, which changed with the fracture behavior. Moreover, by investigating the correlation between the quality of material around the hole and λ of the sheared hole, it was clarified that the λ of ferrite-bainite steel is affected by work hardening, and that the λ of ferrite-pearlite steel is affected by microvoids generated in piercing.