Steel FB780
FB780 is a ferrite-bainite advanced high-strength automotive sheet in the 780 MPa tensile class, strengthened by a fine-grained ferrite matrix with a bainitic second phase to combine strength with very high hole expansion and good sheared-edge/flange formability.
Values for the HR condition
FB780 tempers and conditions
FB780 is supplied in 3 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
HRDefault Hot rolled | Standard supply form for chassis and wheel parts in 1.8–6 mm; best combination of 780 MPa strength and very high hole-expansion. | 660 | 820 | 13 | 245 HB | — |
Cold rolled | Choose for thin gauges (0.8–2.0 mm) and better surface/thickness tolerance, e.g. seat structures and reinforcements. | 685 | 835 | 12 | 24 HRC | 8.2 % IACS |
Thermomechanically controlled processed | For thicker sections (≈4–12 mm) where controlled rolling + accelerated cooling gives 780 MPa class strength with the best low-temperature toughness. | 700 | 810 | 15 | 22 HRC | 8.5 % IACS |
Supply forms, finishes and certifications
Ways FB780 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
Galvanized | Hot-dip zinc (GI) or galvannealed (GA) coated FB780 | Coating |
What is FB780?
FB780 is a ferrite-bainite advanced high-strength automotive sheet in the 780 MPa tensile class, strengthened by a fine-grained ferrite matrix with a bainitic second phase to combine strength with very high hole expansion and good sheared-edge/flange formability. It is used for chassis arms, subframes, control arms, wheel discs and longitudinal members, and replaces thicker lower-strength steel for weight reduction; stocked as HR, CR, galvanized and TMCP coil. Total elongation is below DP or TRIP grades of the same class (A80 about 10–14 %), springback and die wear are high, and HAZ softening plus service above 200 °C on galvanized material need attention. FB780 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,495°C (2,723 °F). FB780 has a yield strength of 660 MPa (95.7 ksi) and a tensile strength of 820 MPa (119 ksi) — stronger than 80% of steel grades. Elongation at break is 13% and the elastic modulus is 210 GPa (30.5 Msi).
What is FB780 used for?
- Automotive wheel discs
- Chassis arms and control arms
- Subframes
- Longitudinal members
- Suspension brackets with flanged holes
- Seat and cross-member structures
- Punched and flanged reinforcements
Advantages
- High strength — 660 MPa (95.7 ksi), better than 80% of steel grades
- Readily welded — 78/100, better than 78% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
- Limited ductility — 13%, worse than 78% of steel grades
FB780 properties
Typical room-temperature values for FB780-HR; bars are the position among steel grades.
Physical3
FB780 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,495°C (2,723 °F).
Mechanical15
FB780 has a yield strength of 660 MPa (95.7 ksi) and a tensile strength of 820 MPa (119 ksi) — stronger than 80% of steel grades. Elongation at break is 13% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
FB780 is rated for continuous service to 350°C (662 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.5 µm/m·K (6.94 µin/in·°F).
Electrical3
FB780 conducts electricity at 8.2 % IACS, better than 61% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of FB780 takes about 27 MJ of energy and emits 2.1 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 25%.
Manufacturability7
FB780's machinability is fair (42/100, worse than 73% of steel grades); weldability very good (78/100); formability good (55/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. FB780 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with FB780
Is FB780 easy to machine?
Drilling/trimming needs coated carbide and rigid setups; punching clearances ~12–15 % of thickness and sharp tools are essential to preserve the high hole-expansion advantage.
Can FB780 be welded?
Very good resistance spot, MAG and laser weldability thanks to low carbon and CE≈0.35; keep heat input moderate to limit HAZ softening, and use higher electrode force / adapted current for galvanized coil.
Can FB780 be formed, bent or molded?
Cold roll-form and stretch-flange well (HER typically 60–100 %), but total elongation is limited — expect large springback, so compensate die geometry and use overbending or post-stretch.
Manufacturability
The process limits FabDigit applies to FB780. Every FB780 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
Sheet metal
| Formability | Better55 / 100 |
|---|---|
| Weldability | Better78 / 100 |
| Bendable | Yes |
FB780 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Clow carbon for weldability | ≤ 0.12 | 0.08 |
| Si | ≤ 0.6 | 0.3 |
| Mnhardenability / bainite formation | ≤ 2.2 | 1.7 |
| P | ≤ 0.03 | 0.01 |
| Slow S for hole-expansion | ≤ 0.01 | 0 |
| Aldeoxidation | 0.02 – 0.08 | 0.04 |
| Nbgrain refinement | ≤ 0.09 | 0.04 |
| TiNb+Ti+V total typically ≤0.22 | ≤ 0.12 | 0.05 |
| Voptional | ≤ 0.1 | |
| Croptional, producer dependent | ≤ 0.6 | |
| Mooptional, promotes bainite | ≤ 0.3 | |
| N | ≤ 0.01 | 0 |
| Fe | balance |
What surface finishes work on FB780?
No anodizing; protect by hot-dip zinc, zinc-nickel plating, phosphate + cathodic e-coat or powder paint; avoid hydrogen-charging pickling/plating routes on highly stressed parts.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
Black / Phosphate
Thermal Spray
How much does FB780 cost?
FB780 is a standard-cost steel ($$), cheaper than about 61% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
FB780 — frequently asked
What is FB780 used for?
FB780 is typically used for automotive wheel discs, chassis arms and control arms, subframes, longitudinal members, suspension brackets with flanged holes and seat and cross-member structures. In short: high-strength FB auto sheet.
What is the yield strength of FB780?
FB780 has a typical yield strength of 660 MPa (95.7 ksi) and a tensile strength of 820 MPa (119 ksi) — stronger than 80% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is FB780 easy to machine?
Not especially — machinability is rated fair (42/100, worse than 73% of steel grades). Drilling/trimming needs coated carbide and rigid setups; punching clearances ~12–15 % of thickness and sharp tools are essential to preserve the high hole-expansion advantage.
Can FB780 be welded?
Yes — weldability is rated very good (78/100). Very good resistance spot, MAG and laser weldability thanks to low carbon and CE≈0.35; keep heat input moderate to limit HAZ softening, and use higher electrode force / adapted current for galvanized coil.
What surface finishes work on FB780?
No anodizing; protect by hot-dip zinc, zinc-nickel plating, phosphate + cathodic e-coat or powder paint; avoid hydrogen-charging pickling/plating routes on highly stressed parts.
Can FB780 be formed, bent or molded?
Cold roll-form and stretch-flange well (HER typically 60–100 %), but total elongation is limited — expect large springback, so compensate die geometry and use overbending or post-stretch.
What is the maximum service temperature of FB780?
FB780 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between FB780-HR and FB780 TMCP?
HR is the default condition — standard supply form for chassis and wheel parts in 1.8–6 mm; best combination of 780 MPa strength and very high hole-expansion. TMCP: for thicker sections (≈4–12 mm) where controlled rolling + accelerated cooling gives 780 MPa class strength with the best low-temperature toughness. Yield strength is 660 MPa in HR versus 700 MPa in TMCP.
How much does FB780 cost?
FB780 is a standard-cost steel ($$), cheaper than about 61% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in FB780?
Yes — FB780 is available for sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- VDA 239-100 Sheet Steel for Cold Forming (HR/CR ...-FB grades) — VDA (2016)
- EN 10338 Hot rolled and cold rolled uncoated products of multiphase steels for cold forming — CEN (2015)
- Advanced High-Strength Steels Application Guidelines v7 — WorldAutoSteel (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Automotive hot-rolled ferritic-bainitic (FB) steel coil datasheets — Baosteel / POSCO / ArcelorMittal (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.