Aaron Middleton

Developing new alloys for safer, longer lasting and lightweight e-vehicles

Hydrogen induced delayed fracture is a significant barrier to the widespread application of martensitic steels over 1500MPa ultimate tensile strength in structural applications in the automotive industry. Charging of Hydrogen during processing, such as can occur in press hardening and electro-galvanising, can result in subsequent cracking and splitting caused by hydrogen diffusion at high residual stress part features such as trimmed edges and pierced holes. As a result, manufacturers are… Show more

Hydrogen induced delayed fracture is a significant barrier to the widespread application of martensitic steels over 1500MPa ultimate tensile strength in structural applications in the automotive industry. Charging of Hydrogen during processing, such as can occur in press hardening and electro-galvanising, can result in subsequent cracking and splitting caused by hydrogen diffusion at high residual stress part features such as trimmed edges and pierced holes. As a result, manufacturers are required to use restrictive countermeasures to avoid the risk hydrogen induced delayed fracture in these types of steels, which reduce their robustness and breath of application.

Several studies in the last two decades [Asahi 2003, Szost 2013, Turk 2018, Cho 2018] have demonstrated that Vanadium additions to steels with highly dislocated microstructure can yield carbides which act as functional trapping sites for diffusible Hydrogen, with apparent benefits in resistance to hydrogen induced delayed fracture. In this paper, we explore the practicalities of alloy design and processing to form these Vanadium carbides using computational thermodynamic methods and propose a composition and processing concept for an 1800MPa ultimate tensile strength press hardening steel with enhanced delayed fracture resistance via an optimal carbide structure. Show less

A knowledge sharing conference presentation dedicated to the decarbonisation of the transport and infrastructure sectors, with special focus on lightweight steel solutions for electric vehicles. Presentation encompassed metallurgical principles, load cases, design concept through to lifecycle analysis. Example use case:

https://www.ssab.com/news/2019/03/ssabs-docol-steel-used-in-gacha-allweather-autonomous-shuttle-bus

For assistance in choosing the right grade of steel and the design, McConnel turned to SSAB.

“McConnel is a long-time SSAB customer, and for this development project, they attended many seminars to gain knowledge about what is really possible with high strength steel,” explains Aaron Middleton, Tech Support Special Steels, SSAB. “For the design concept, we looked to known principles based on the technical literature, focusing in on an optimal shape, and then identified the right… Show more

For assistance in choosing the right grade of steel and the design, McConnel turned to SSAB.

“McConnel is a long-time SSAB customer, and for this development project, they attended many seminars to gain knowledge about what is really possible with high strength steel,” explains Aaron Middleton, Tech Support Special Steels, SSAB. “For the design concept, we looked to known principles based on the technical literature, focusing in on an optimal shape, and then identified the right steel.”

Strenx® 700 MC Plus was chosen as the most optimal grade for the boom and auxilirary structures, based on its excellent formability, which enabled the optimized shape to be realized. The areas exposed to wear, in the vicinity of the flail head, are made from cold-rolled Hardox® 450.

“The complexity of the design required that we needed to get the tooling correct and the welding order was critical,” says Henry-Lefort. “It was a challenging process, but the result is worth it – and could not have been done without high strength steel.” Show less

SSAB’s new Hardox steel is being used in containers that offer a boost in sustainability for the transport sector