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Steels for cold stamping - Fortiform®

Description

The family of Fortiform® steels extends ArcelorMittal's range of Ultra High Strength Steels (UHSS). These steels allow the realization of lightweight structural elements by a cold forming method such as stamping. These Ultra High Strength Steels of third generation are used to provide additional weight reduction thanks to their higher mechanical properties than conventional Advanced High Strength Steels (AHSS) while keeping the same formability.

Position of Fortiform® steels in the ArcelorMittal steel range

Applications

Thanks to their excellent mechanical properties, these grades are particularly suitable for automotive safety parts for crash resistance. Typical parts are shown in the figure below:

Typical parts for Fortiform® steels

Designation and standard

 EuronormsVDA 239-100
Fortiform® 980
Fortiform® 1050CR700Y980T-DH(-UNC,-EG)
Fortiform® 1180
 

Euronorms


VDA 239-100

The above indicative table summarizes the European and VDA standards corresponding to the ArcelorMittal product range.

Technical characteristics

Mechanical properties
Guaranteed for 20x80 mm ISO specimen of uncoated sheet
TD - Tranverse direction (perpendicular to the rolling direction) / RD - Rolling direction

 YS (MPa)UTS (MPa)ef (%)
L0 = 80 mm
th < 3 mm
Direction
 Fortiform® 980600 - 750980 - 1130≥ 19RD
 Fortiform® 1050700 - 8201050 - 1180≥ 14RD
 Fortiform® 1180850 - 10601180 - 1330≥ 12RD

* The guarantees for this grade are subject to change.

Fortiform® 1050 microstructure

Chemical Composition (%)

 CMnSi
 MaxMaxMax
Fortiform® 9800.232.32
Fortiform® 10500.232.32
Fortiform® 11800.232.32

Available coatings and Worldwide availability

 UncoatedElectrogalvanizedExtragal®Zagnelis®
 EURNAMSAMRSACHIEURNAMSAMRSACHIEURNAMSAMRSACHIEURNAMSAMRSACHI
Fortiform® 980              
Fortiform® 1050                 
Fortiform® 1180               

Available in non-visible part quality Undergoing customer testing Under development Available in visible and non-visible part quality (Z)

EUR : Europe Region - NAM : North America Region - SAM : South America Region - RSA : South Africa Region - CHI : China

X  available  / O  under development

Please contact us for products under development.

Recommendations for use and secondary processing

Forming

Fortiform® steels exhibit very good ductility compared with their level of tensile strength.
The figure below shows an example of forming limit curve for Fortiform® 1050 steel 0.8 mm thick. This shows the same formability of Dual Phase 780 steel with lower strength.

Welding

Resistance Spot Welding
Fortiform® steels are weldable with conventional processes by adapting the parameters.
Given the increase of the carbon equivalent, it is necessary to increase welding force and adapt welding cycles to get good quality of spotweld.
For information, here is an example of welding data on  Fortiform® 1050 EG steel tested in homogeneous combination according to ISO 18278-2 standard:

 CoatingThickness (mm)Max. intensity (kA)Nugget diameter (mm)Tensile-shear (kN)
Fortiform® 1050Electrogalvanized0.88.2610

Fatigue

Fortiform® steels exhibit good fatigue properties. The table below gives examples of Wöhler curves for Fortiform® 1050. The curves plot maximum stress versus number of cycles to failure. They are calculated for two loading ratios: tension-compression R=-1 and tension-tension R=0.1.

Wöhler curves or S-N curves for Fortiform® 1050 steel

The graph below shows the low cycle or EN curves for the same steels. These are expressed as strain amplitude versus number of reversals (one cycle equals two reversals). Other high and low cycle fatigue data are available on request.

ArcelorMittal can provide a full database on the fatigue performance of Fortiform® steels.

Impact strength

As a result of their very high tensile strength, Fortiform® 1050 steel is particularly suitable for parts designed to absorb energy in an impact.
Fortiform® 1050 steel has been characterized in dynamic axial compression tests using an omega structure with a spot-welded closure plate at an impact velocity of 56 kph. These tests have demonstrated the very good impact behavior of these steels.

Mass reduction potential compared to that of an HSLA 380 steel (reference)

Complex Phase steels have been characterized in the 3-point bending test using top hat cross-section specimens impacted at 30 kph. The tests showed very good behavior of these steels.

Mass reduction potential compared to that of an HSLA 380 steel (reference)

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