Blog: What makes 3rd generation AHSS grades so unique?

Kate Hicky

Kate Hicky

交流经理,世界汽车用钢联盟

(世界汽车用钢联盟是世界钢铁协会下属汽车用钢项目)

2019年9月17日

Steel evolves.

Now that I have your attention, I’ll tell you how this is true. One of steel’s base elements is Fe, iron. The very makeup of the iron atom (26 electrons with eight in the valence shell) enables it to bond and unbond easily with a wide range of other elements.

How an element bonds with itself and other elements determines, largely, its usefulness as a structural material.

Basic steel is an alloy of iron and carbon. Varying the amount of carbon and many other alloying elements, as well as controlling their chemical and physical makeup in the final steel controls and enhances steel’s qualities.

The full explanation of this process would be a good bedtime story, but to keep it simple, you can make different steels depending on what goes into the chemical and physical recipe. If you’d like to learn more about steelmaking, check out the courses at steeluniversity.

Changing needs drive the material evolution

Metallurgists have been creating these recipes for years, and the result has been a spectrum of new steels engineered to meet specific structural use requirements. Nowhere can this be more clearly seen than in the automotive industry and the steels that are used in vehicle structural applications.

Vehicle design has evolved to meet the strict safety and environmental standards to which they are designed, and steel has contributed to this evolution with new steels to help meet those requirements. 

Consequently, the last two decades have seen an enormous growth in new advanced high-strength steels (AHSS), characterised by unique multi-phase microstructures.

Just to give you an idea of this evolution, twenty-five years ago, the first steel industry collaboration, the UltraLight Steel Auto Body Consortium, launched a global effort to demonstrate what was then the most advanced steels ever produced, high-strength steels (HSS). 

At the time just 11 HSS grades were available for the body structure design. Since that time, the sophisticated steels in the AHSS portfolios have grown to over 50 grades.

These steels change phases as they are worked, such as in the manufacturing process or in a crash, becoming stronger as heat or pressure is applied.

Higher-strength levels mean steel parts can be manufactured at minimum thickness while still meeting the strength requirements for crash and performance. The results are lighter and more environmentally efficient components because less material is used.

The advent of 3rd Gen AHSS

But increasing strength and thinner gauges makes forming complex component shapes a challenge. And because of this, the steel industry introduced Third Generation AHSS (3rd Gen AHSS).

These steels, the third evolution of AHSS, have increased elongation as well as increased strength. Elongation is a material mechanical property that is the degree to which a material may be bent, stretched, or compressed before it breaks.

With high elongation, complex vehicle component shapes can be formed and manufactured more easily, resulting in strong, efficient structures. 

Third Gen AHSS is taking strength levels ever higher while addressing manufacturability. Our members are producing 3rdGen AHSS that can be cold-formed with strength levels upwards of 1200 MPa, with elongations of 20% and greater, which completely opens the manufacturing window of possibilities.

To further assist in the design and manufacture of efficient vehicle structures, new processes such as roll forming and hot stamping help fabricate these stronger materials effectively, while often doubling material use efficiency.

This means less material is produced for each component, resulting in a significant reduction in manufacturing emissions, and coupled with steel’s complete recyclability, ultimately results in an improved vehicle environmental footprint.

Steel E-Motive concepts to demonstrate 3rd Gen AHSS

Third Gen AHSS will have a prominent role in the steel industry’s latest vehicle demonstration programme, Steel E-Motive, which will produce autonomous electric (EV) concepts for Mobility as a Service (MaaS) vehicles.

Steel E-Motive’s broad steel and steel technologies portfolio made available to our engineering partner, Ricardo, ensures that there are ample configurations of materials and processes available.

This portfolio enables the most efficient structures to meet the design and manufacturing challenges of ride sharing, autonomous EVs. 

Steel has and continues to successfully evolve with the family of advanced high-strength steels and steel technologies, engineered to meet ever-changing vehicle design and manufacturing demands.