Ultra-High Strength Steels (UHSS): what are they and how they improve vehicles

Ultra-high strength steels (UHSS) in cars are simply advanced high-strength steels (AHSS) with significantly higher minimum tensile strengths. Viewed another way, UHSS (aka “ultra-high tensile steels”) are a subset of the boarder category of AHSS steels.

There is no generally accepted tensile strength that makes a grade into an ultra-high strength steel: some companies say 780 MPa, others say 980 MPa, 1180 MPa or 1270 MPa.

Previously, WorldAutoSteel, the association of steelmakers focused on AHSS for cars, proposed the following approximate definitions based on minimum tensile strengths (TS):

Advanced high-strength steels (AHSS) ≥ 550 MPa TS
Ultra-high strength steels (UHSS) ≥ 780 MPa TS
GigaPascal steels ≥ 1000 MPa or 1 GPa TS

However, WorldAutoSteel’s 2021 AHSS Application Guidelines puts the minimum tensile level for AHSS steels at 440 MPa, while acknowledging no agreed-upon level for UHSS steels. It could be that the less frequently used term “GigaPascal” will become more popular because there is no ambiguity regarding its definition: steels with tensile strengths of 1000 MPa or greater.

Types of ultra-high strength steels

The metallurgical types of steels capable of achieving UHSS strengths can include:

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Why the “UHSS” designation matters

If there is no generally accepted definition for ultra-high strength steel, why even use the term? The answer is that “UHSS” is useful for both steelmakers and automakers as shorthand for designating stronger AHSS steel grades.

And as UHSS steels continue to increase in strength, more thought has to go into how they are formed into car parts, including anticipating issues such as springback. That said, most of these forming issues can be addressed through the proper selection of UHSS steel properties, advanced forming simulations, correct tooling parameters, and car part design.

Automotive applications for AHSS/UHSS steels

Increased impact protection and safety

Advanced and ultra-high strength steels enable you meet new, more stringent safety standards — or provide an extra (and marketable) margin of product safety.

Lightweighting and energy efficiency

Each year, more and more advanced and ultra-high strength steel is being specified by automaker as they further optimize their cars for lightweighting — while meeting increasingly rigorous crash standards. Lightweighting with AHSS and UHSS steel can help your vehicle meet future government mandates, as well as customers’ current needs for lower energy expenses.

Increased vehicle capacity and performance

Upgrading to AHSS/UHSS steel grades can make your vehicles stronger, with higher payloads and increased durability. Advanced and ultra-high strength steels can also improve torsional stiffness for improved car handling and responsiveness. They can also create more internal space (for wiring, electronics, etc.) by replacing thicker materials with strong grades of thinner AHSS/UHSS steels.

Car assembly

Increased sustainability

While aluminum and carbon fiber materials are strong and light, they are also CO2 intensive and harder to recycle than steel. When selecting structural materials, ask yourself if your choices are aligned with your customers’ sustainability goals.

Right now, you can specify AHSS/UHSS steel grades that are made in some of the world’s most CO2-efficient steel mills — at costs that are 40% to 400% less than non-ferrous high strength materials. Even better: SSAB is on track to make commercially-available fossil-free Docol® AHSS steels, already in 2026.

Collaborating on lighter, safer, more efficient steel BIW

Higher strength steels do require more design and pre-production planning. That’s why our AHSS/UHSS experts can help you optimize your designs by modeling product performance, forming, and joining.

And we have in-house steel production technicians to advise you every step of the way, whether your AHSS/UHSS fabrication includes cold forming, 3D roll forming, tailor welding blanks or coils, or hot-stamping of PHS steels.

Joining conventional steels to AHSS steels? Have questions about spot resistance welding or laser welding of AHSS? Check out our AHSS/UHSS Welding Guidebook.

Looking to use mixed materials, and possibility structural adhesives, with AHSS/UHSS steels? We can help with all of your AHSS/UHSS joining needs.

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