AHSS Attributed as a Success Enabler on 2005 Ford Freestyle/500 Platform

The 2005 Ford Freestyle and Ford 500, two sister vehicles that are part of Ford's Year of the Car, owe a piece of their success to the use of Advanced High-Strength Steels (AHSS). AHSS is credited as the key enabler for weight efficiency and world class performance for this global vehicle platform.

The Freestyle/500 architecture and energy management strategy evolved from Volvo P2X Platform (S60, S80, V70), and the vehicles carry a common front structure, front floor and bill of process.

2005 Ford Freestyle (top) and 500 (bottom) share global platform using AHSS

Fifteen percent of the Ford 500's mass is made up of DP 600 steel with another 26 percent made up of varying grades of HSLA steels. DP 600 steel was used in the dash cross member, B-Pillar and front rail closeout. DP 600 also was used as part of tailor-welded blanks in the side member inner where it was teamed with HSLA 250 and the side member outer, where it was combined with mild steel. HSLA 250 and 350 were used in the front rail tailor-welded blanks. HSLA 350 also was used in the rear rails.

A five-star full frontal crash rating was achieved for both vehicles. The full frontal load path carries crash energy from the tailor-welded blank front rails (HSLA250/HSLA 350) into the A-Pillar (DP 600 and HSLA 250 steel), dash cross member (DP 600) and along the side member (DP600).

Ford 500 Material usage and full front crash load path

Green: HSLA 250 Blue: HSLA 350 Yellow: HSLA 550 Red: DP 600 Purple: Inner: Top DP 600 / Bottom: HSLA 250 Outer: Top DP 600 / Bottom: Mild Steel

A five-star crash rating also was achieved for both the front and rear seat without the use of side airbags. Side impact load is managed by the B-Pillar DP600 tailor-welded blank inner and outer panels, the HSLA 550 center roof bow, HSLA 350 cross members and the DP 600 side members.

Freestyle Material Usage and Side Impact Load Path

Green: HSLA 250 Blue: HSLA 350 Yellow: HSLA 550 Red: DP 600 Purple: Inner: Top DP 600 / Bottom: HSLA 250 Outer: Top DP 600 / Bottom: Mild Steel

Both vehicles were designed to meet the new FMVSS 208 front impact requirements, which include both full frontal and offset crash specifications.

Ford 500 body structure

Freestyle body structure

As well, they have been designed to meet upcoming FMVSS 301 rear impact requirements, which are aimed at reducing the chances of fuel-fed fires caused by fuel system breaching in vehicle crashes.

The Freestyle/500 design exercise produced some specific AHSS lessons learned that are not unlike the experiences shared in AutoCo's recently released Advanced High-Strength Steel (AHSS) Application Guidelines v2.3.:

• Excellent work hardening co-efficient in DP steels make them difficult to re-draw, and consequently, final part geometry should be obtained in the initial draw.
• DP steels require blanker holder forces that are 20-30% higher than HSLA 350.
• Consideration needs to be given when developing dies, and may constitute revised or upgraded die materials, as well as a revised press tonnage strategy.
• Incremental die tryout time is required to manage spring-back corrections.
• An intensive dimensional control strategy should be implemented including production draws and production assembly tooling at CP prototype build.

Another factor that Ford attributes as a success enabler for these vehicles is early and intensive supplier involvement.