SSAB and the automotive industry: Lightweight solutions for Chrysler
Iroquois Industries Inc., of Warren, MI, USA is a leading manufacturer of stamped automotive parts in the USA. Iroquois Industries had made a front suspension upper control arm, the DR UCA, for the Dodge Ram Pick-up truck for the previous two years. Chrysler’s demand was to reduce the mass of the UCA of the Dodge Ram Pick-up Truck 2009. That arm was referred to as the DS UCA.
With the ever increasing cost for gasoline, one of the enablers to assist in improving fuel economy for their full size pick up truck, the Dodge Ram, was to put this truck on a massive mass reduction program. The mass reduction had to be accomplished without giving up Dodge Ram pick up truck load carrying or towing capability—two very critical reasons why customers purchase full size pick-up trucks. Chrysler Purchasing and Engineering dictated that the DR UCA had to have its mass reduced to match the mass of a proposed wire form UCA made from cold drawn steel wire. This wire form arm was 1.3 kg lighter than the DR UCA that Iroquois was then producing for the production Dodge Ram pick-up.
What to do?
The answer was clear, the only way to reduce the mass of Iroquois’ DR UCA was to utilize a new design that had a smaller section modulus and made from significantly higher strength steel.
The steel Iroquois selected was SSAB’s Domex 700 MC. Domex 700 MC steel is an ultra high strength HSLA steel having a yield strength of 700 MPa or more than twice the 340 MPa yield strength HSLA steel used on the Dodge Ram, DR UCA. Since the loading on the UCA was along the plane of the arm, it was clear that a design that maintained about the same plan view shape as the DR UCA but having a thinner section would offer a more efficient design. The result is that the DS UCA is 1.36kg (3 lbs) lighter than the DR UCA and it achieved the Chrysler mass target for the arm which was based on the steel wire form arm design proposal. This saves 2.72 kg (6 lbs) per vehicle.
Iroquois is now pursuing other control arms and stamped steel products made from Domex 700MC. Higher fuel economy standards are already on the books so lighter components are becoming more and more the mandate for the industry. Iroquois’ studies have shown that steel stampings made from Domex 700 MC steel can be designed to have about the same mass as forged or cast aluminum control arms. And, while Domex 700 MC is more expensive than lower strength steel alternatives, control arms made from Domex 700 MC are still about 20% less expensive than aluminum control arms.