Papers by Keyword: Warm Stamping

Abstract: This paper investigates the galling behaviour of a range of hard coatings applied to tooling surfaces during the sheet forming of an aluminium alloy workpiece. A total of three types of tooling materials were investigated, two of which were subject to PVD deposited coatings of AlCrN, CrN and DLC applied to the working surface. The third tooling material had undergone induction heating, plasma-nitriding and polishing. To evaluate the galling behaviour of the applied coatings, a tribological evaluation was conducted using a pin-on-disc test set-up at a constant load and varying temperature. The coated discs, replicating the tooling material, were tested against aluminium alloy pins AA6082 and AA7075 representing the workpiece material. This investigation indicated that the friction and galling behaviour of aluminium is highly dependent on temperature, and the use of two different aluminium pins had no significant effect. At room temperature, it was found that carbon-based coatings provide the lowest friction and the best protection against galling, whilst nitride-based treatments exhibit better performance at high temperature. Moreover, at elevated temperatures, coated tools exhibit superior anti-galling properties compared to uncoated tools.

Abstract: The advantages and disadvantages of the conventional hot stamping steel and the hot tamping technology were shortly reviewed. It was proposed that new type steel with relative low austenization temperature and air hardening ability should be designed and produced to overcome the surface oxidation and avoid the complexity of cooling system of the stamping dies. In this study, it was shown that the 3rd generation sheet steel with medium-Mn composition could be austenized and pressed at 700-750°C and air cooled into automobile parts with strength no less than 1.5GPa and ductility larger than 12%. This new steel and corresponding forming technology were called warm stamping technology, which overcomes the disadvantages of the conventional hot stamping steel. The fabrication trials of the automobile parts in the automobile industries were demonstrated with high strength and relative good ductility. It was concluded that the 3rd generation sheet steel and the warm stamping technology could be applied to replace the conventional hot stamping steel and conventional hot stamping technology in near future.

Abstract: This paper describes the research status of the warm stamping at home and abroad. The status of aluminum alloy and magnesium alloy is introduced in warm stamping respectively, using the tensile test, the drawing test, and bending experiments to prove the temperature and other factors have effect on the formability of materials. It also presents the status that using warm forming to solve the spring-back problem of the high strength steels. In addition, the mold and lubrication are also the key problems in warm stamping; they have a corresponding development with the development of warm forming though there are a few scholars specializing in the content.

Abstract: The stamping process for manufacturing cell phone cases with magnesium alloy AZ31 sheets was studied using both the experimental approach and the finite element analysis. The formability of AZ31 magnesium-alloy sheet at elevated temperatures was studied first. The experimental results reveal that the forming of AZ31 sheets becomes possible as long as the sheet is heated to an elevated temperature and 200oC is an optimum forming temperature to start with. An optimum stamping process, including die geometry, forming temperature, and blank dimension, for manufacturing the cell phone cases was examined by the finite element analysis. The finite element analyses performed for the cell phone were validated by the good agreement between the simulation results and the experimental data. It also confirms that the cell phone cases can be produced with AZ31 magnesium-alloy sheets at elevated temperature by the stamping process. It provides an alternative to the electronics industry in the application of magnesium alloys.

Abstract: Uniaxial tensile test of a cross rolled magnesium alloy sheet was conducted under different temperatures and strain rates. The mechanical propriety of AZ31 magnesium alloy sheet was analyzed according to the true strain-stress curves. Then the non-thermal drawing process, during which the temperature of die, blankholder and blank is 200°C while the punch is kept at room temperature, was simulated by the thermo-mechanical coupled finite element method. The deformation behavior and the temperature change in the drawing process was investigated. Due to the heat conduction, there was non-uniform distribution of temperature along flange area, force transfer area and deformation area. Therefore the resistance of the force transfer area is enhanced and the warm formability of magnesium alloy sheet can be further improved. The thermo-mechanical coupled simulation provides a good guide for the development of non-isothermal drawing techniques.