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Warm-forged aluminum alloy differential case reduces weight by about 40%

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.


  • 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



Using new aluminum alloys for ICE, power trains assemblies, wheels, frame units, other body parts etc could reduce the total weight of our 4,000 lbs gas guzzler by 40% or to about 2,400 lbs or less. Smaller engines, tires, gas tanks etc could also be used to futher reduce weight and fuel usage.

Of course, the same could apply (to a slightly lesser extend) to HEVs, PHEVs and BEVs/FCEVs.

Aluminum @ $1/lb is low cost and would NOT realy increase total cost.


They don't say how much weight you might save in a typical operation and how much extra it would cost.
Also, how many similar parts could they replace - and what would they typical total weight (or mass) per car be?

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To reduce the weight of a car means using more expensive materials and fabrication techniques so the benefits in terms of reduced fuel consumption more range need to be balanced against those costs. This cost benefit tradeoff will not change much until we get self driving battery electric taxis. Self driving BEV taxis changes everything because they can easily be made to last for 1,000,000 miles without repairs on drive train or battery instead of gassers that can only last for 200,000 miles before mayor repairs on engine and transmission is needed. That means the capital cost per mile driven for an autonomous taxi BEV is only 20% of the capital cost of a gasser per mile driven. That means you can spend 5 times as much money on lightweight materials on a BEV as you can on a gasser and still have the same cost of capital per mile as the gasser. In other words, the economics of using low weight materials is much better for autonomous BEVs than for gassers. So gassers will stay more or less the same with regard to weight whereas autonomous BEVs will get far more low weight materials in order to reduce electricity spending and increase their range.

So once again we need to make autonomous cars before we will see any huge leap forward with regard to using low weight materials for cars. The reality is that the auto industry will be business as usual with little technological progress until we start seeing the first self driving cars selling miles on public roads. After that the industry is going to explode driven by a profound technological transformation that will change the auto industry forever.


Yes Henrik, driverless extended range (e-UBER type) vehicles available 24/7, at a reasonable rate, could greatly reduce the number of vehicles (at home and on roads) and probably reduce accidents, property damages, insurance cost, injuries and fatalities.

During peak hours, larger driverless e-vehicles could pick-up 10+ passengers on the same route to further reduce the number of vehicles in use and reduce rates accordingly.

Vehicles with one passenger (driver) only could be restricted to slow lanes etc.


This article is quite misleading. Most contemporary cars are front wheel drive (or AWD and based on a FWD) and do not have a separate differential case. The differential is enclosed in the transmission housing which is almost always made from an aluminum alloy. Maybe pickup trucks are still using a cast iron differential housings but even rear drive cars already have aluminum differential housings.

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