Ultra-high strength steels (UHSS) are sophisticated materials with carefully controlled compositions and microstructures that result in a unique combination of strength, ductility, toughness and fatigue properties. UHSS include dual phase, complex phase, ferritic-bainitic, martensitic, transformation-induced plasticity, hot-formed and twinning-induced plasticity steels. They are increasingly being used in automotive applications like crash zones where they provide benefits like high energy absorption and strength with formability. UHSS also show promise for use in civil engineering and infrastructure due to their high strength and potential to reduce costs through lower alloy contents.

2. What is UHSS?
Types Of UHSS
General Properties
Applications

3. Ultra High-Strength Steels (UHSS) are complex,
sophisticated materials, with carefully selected
chemical compositions and multiphase
microstructures resulting from precisely controlled
heating and cooling processes.
Various strengthening mechanisms are
employed to achieve a range of strength, ductility,
toughness, and fatigue properties.
These steels aren’t the mild steels of yesterday;
rather they are uniquely light weight and
engineered to meet the challenges of today’s
vehicles for stringent safety regulations,
emissions reduction, solid performance, at
affordable costs.

4. • Ultra-high-strength steels are :
• UHSS are multiphase steels with
excellent combination of strength and
formability.
• UHSS with (YS)> 780 MPa are called
ULTRA HIGH STRENGTH STEELS.

5. The UHSS family includes :
• Dual Phase (DP)
• Complex-Phase (CP)
• Ferritic-Bainitic (FB)
• Martensitic (MS or MART)
• Transformation-Induced Plasticity (TRIP)
• Hot-Formed (HF)
• Twinning-Induced Plasticity (TWIP)
DP
TRIP
CP

6. • DP and TRIP steels are excellent in the crash zones of the
car for their high energy absorption, where TRIP steels have
the advantage of better formability in conjunction with greater
component strength .
• CP steels demonstrate a significantly higher tensile yield
strength at the same tensile strength.
• Martensitic and boron-based Press Hardened
Steels (PHS) result in improved safety performance, where
MS have high basic strength and are extremely difficult to
form .
These UHSS grades are uniquely qualified to meet the
functional performance demands of certain parts.
For example :

7. The broad range of properties is best illustrated by
the famous Global Formability Diagram, captured in
Figure -1 following.
UHSS
FIG-1 Steel Strength Ductility Diagram for Today’s AHSS Grades (includes
comparison of traditional low-strength and high-strength steels)

8. Steels with yield strength levels in excess of 550
MPa are generally referred to as AHSS.
These steels are also sometimes called
“ultrahigh-strength steels” for tensile strengths
exceeding 780 MPa.
AHSS with tensile strength of at least 1000 MPa
are often called “Giga Pascal steel” (1000 MPa =
1GPa).
Please note another category of steels,
represented in Figure-1 following as Austenitic
Stainless Steel.

9. Third Generation AHSS (3rd Gen) seek to offer
comparable or improved capabilities at
significantly lower cost. However, because they
are so new, there is yet no clear definition of
what they comprise.
The primary objectives in developing 3rd Gen
steels are:
• Use steels with lower alloying content to reduce costs.
• Target minimum strength and ductility levels to
1200 MPa .
• 30% elongation.
These materials have excellent strength combined with excellent
ductility, and thus meet many vehicle functional requirements.

10. • High strength
• Weight saving
• Easy forming and weldability Ultra 690
• Cost efficiency
• Easy machinability
• Excellent ductility
• High energy absorption
•
•
• ….etc...
We conclude these properties

11. • UHSS has been preferred to a great
extent in bridges.
• engineering and high rise buildings.
• UHSS has been recently introduced
in civil engineering applications.
• has already been widely used in the
automotive industry.
• As it is already known, most of the
high and ultra high strength steel
grades derive their strength by
quenching.