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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 intended for crash resistance.
Typical parts for Fortiform® steels
Designation and standard
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| ArcelorMittal name | Generic name | ArcelorMittal Code | VDA 239-100 |
| Fortiform® 980 | HF980Y600 | CR600Y980T-FH | |
| Fortiform® 1050 | HF1050Y700 | Fortiform® 1050 | |
| Fortiform® 1180 | HF1180Y850 | CR850Y1180T-FH |
The above indicative table summarizes the European and VDA standards corresponding to the ArcelorMittal product range.
Mechanical properties
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| ArcelorMittal name | Generic name | Direction | Yield stress Rp0.2 (MPa) | Tensile strength Rm (MPa) | Type 1 Min. A50mm (%) | Type 2 Min. A80mm (%) | Type 3 Min. A50mm (%) | Min. BH2 MPa |
| Fortiform® 980 | HF980Y600 | RD | 600 - 750 | 980 - 1130 | 19 | 19 | 20 | 30 |
| Fortiform® 1050 | HF1050Y700 | RD | 700 - 820 | 1050 - 1180 | 14 | 14 | 15 | 30 |
| Fortiform® 1180 | HF1180Y850 | RD | 850 - 1060 | 1180 - 1330 | 13 | 13 | 14 | 30 |
A80mm %: Percentage elongation after fracture using a specimen with gauge length L0 = 80 mm (ISO 6892-1 type 2 (EN20x80))
A50mm %: Percentage elongation after fracture using a specimen with gauge length L0 = 50 mm (ISO 6892-1 type 1 (ASTM12.5x50) or type 3 (JIS25x50)
A%: Percentage elongation after fracture using a proportional specimen with L0 = 5.65 (So)1/2
Ag %: Percentage plastic extension at maximum force
BH2: Increase in yield strength between a reference condition after a 2% plastic pre-strain and the condition obtained after heat treatment (170°C-20minutes)
Fortiform® 1050 microstructure
Chemical composition
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| ArcelorMittal name | Generic name | Max. C (%) | Max. Si (%) | Max. Mn (%) | Max. P (%) | Max. S (%) | Al (%) | Max. Cu (%) | Max. B (%) | Max. Ti + Nb (%) | Max. Cr + Mo (%) |
| Fortiform® 980 | HF980Y600 | 0.26 | 2.2 | 2.5 | 0.05 | 0.010 | 0.015 - 2.0 | 0.20 | 0.005 | 0.15 | 1.4 |
| Fortiform® 1050 | HF1050Y700 | 0.23 | 1.8 | 2.5 | 0.040 | 0.010 | 0.015 - 1.0 | 0.20 | 0.005 | 0.15 | 0.60 |
| Fortiform® 1180 | HF1180Y850 | 0.26 | 2.2 | 3.0 | 0.05 | 0.010 | 0.015 - 2.0 | 0.20 | 0.005 | 0.15 | 1.4 |
Global availability
Under development Customer trials Commercial unexposed only Commercial exposed and unexposed
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| ArcelorMittal name | Generic name | Uncoated (-UNC) | Extragal® (-GI) | Electrogalvanized (-EG) | Jetgal® (-ZV) |
| Fortiform® 980 | HF980Y600 | ||||
| Fortiform® 1050 | HF1050Y700 | ||||
| Fortiform® 1180 | HF1180Y850 |
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| ArcelorMittal name | Generic name | Uncoated (-UNC) | Extragal® (-GI) | Electrogalvanized (-EG) | Jetgal® (-ZV) |
| Fortiform® 980 | HF980Y600 | ||||
| Fortiform® 1050 | HF1050Y700 | ||||
| Fortiform® 1180 | HF1180Y850 |
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| ArcelorMittal name | Generic name | Uncoated (-UNC) | Extragal® (-GI) | Galvannealed (-GA) |
| Fortiform® 980 | HF980Y600 | |||
| Fortiform® 1050 | HF1050Y700 | |||
| Fortiform® 1180 | HF1180Y850 |
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| ArcelorMittal name | Generic name | Ultragal® (-GI) |
| Fortiform® 980 | HF980Y600 | |
| Fortiform® 1050 | HF1050Y700 | |
| Fortiform® 1180 | HF1180Y850 |
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| ArcelorMittal name | Generic name |
| Fortiform® 980 | HF980Y600 |
| Fortiform® 1050 | HF1050Y700 |
| Fortiform® 1180 | HF1180Y850 |
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| ArcelorMittal name | Generic name |
| Fortiform® 980 | HF980Y600 |
| Fortiform® 1050 | HF1050Y700 |
| Fortiform® 1180 | HF1180Y850 |
Under development
Customer trials
Commercial unexposed only
Commercial exposed and unexposed
Please contact us for products under development.
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® steels 1.5 mm thick.
Forming limit curves for the Fortiform® steel family of 1,5mm thickness (ArcelorMittal model for Europe)
Forming limit curves for the Fortiform® steel family of 1,5mm thickness (Keeler model for North America)
Welding
Resistance Spot Welding
Fortiform® steels are weldable using 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 achieve good spot-weld quality.
For information, here is an example of welding data on Fortiform® 1050 EG steel based on matching joints in accordance with the ISO 18278-2 standard:
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| ArcelorMittal name | Coating | Thickness (mm) | Pure tensile (kN) | Weld diameter (mm) | Tensile-shear (kN) |
| Fortiform® 1050 | Electrogalvanized | 0.8 | 3 | 6 | 10 |
Fatigue strength
Fortiform® steels exhibit excellent fatigue properties on account of their very high mechanical strength. By way of example, the two graphs below show Wöhler curves for Fortiform® steels. The curves plot maximum stress versus number of cycles to failure. They are obtained for two loading ratios: tension-compression R=-1 and tension-tension R=0.1.
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 its customers with a database on the fatigue performance of Fortiform® steels.
Impact strength
As a result of their very high yield and breaking strength, Fortiform® 1050 steel is particularly suitable for safety parts.
Fortiform® steels have 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 positive impact behaviour of these steels. By way of information, the graph below shows the minimum weight-saving potential with these steels relative to a CR340LA steel.
Weight-saving potential relative to a CR340LA steel (reference)
Fortiform® steels have been characterized in a 3-point bending test using top hat cross-section test-pieces impacted at 30 kph. The tests showed excellent behaviour by these steels. By way of information, the graph below shows the minimum weight-saving potential with these steels relative to a CR340LA steel.
Weight-saving potential relative to a CR340LA steel (reference)
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