A team in South Korea has developed a warm-forging process for the manufacture of an aluminium alloy automotive differential case—usually produced from ductile cast iron. The as-forged aluminium alloy differential case not only provides a net shape but also has a crack-free volume internally, while reducing the total weight by about 40% based on the proposed design.
Their paper on the process is published in the Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering.
To replace conventional ductile cast iron with a lightweight material in the differential case, the team used aluminium alloy 6082 in the warm-forging process. Aluminium alloy 6082 is a medium-strength alloy with excellent corrosion resistance; it features the highest strength of the 6000-series alloys. In plate form, 6082 is the alloy most commonly used for machining.
Experimental warm forging using aluminium alloy 6082 was conducted in a 1600 tonf (8.9 kN) press to evaluate the proposed design in the die and the punch as well as the forgeability of the aluminium alloy differential case.
The automotive industry’s interest in using light metals in both structural and body parts continues to increase. The use of aluminum alloys (5000 and 6000 series) is of special interest to them because the material represents a cost-effective solution for reducing weight while maintaining functional requirements for structural strength and crash resistance.
Aluminum alloys have low formability compared to draw-quality steel, however. Stampers now are presented with new challenges in obtaining good part definition (corner and fillet radii, draw depth) and formability (failure due to fracture or wrinkling) when working with these aluminum alloys.
Warm forming of aluminum sheet has emerged as a way to increase ductility and formability. In fact, elevating the temperature (or warm forming) of aluminum sheet at reasonable production rates and acceptable costs has become a realistic alternative to straight stamping.—“R&D Update: Warm forming of alloys in the auto industry”, Stamping Journal
Sangik Lee, Byungmin Kim, Hye-Jin Lee, Jonghun Yoon (2015) “Warm forging of an aluminium alloy for the differential case in an automobile transmission” Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering doi: 10.1177/0954407015600900