Steel FB780 · supply condition · default condition
Steel FB780-HR
Properties of the HR condition, compared with the other FB780 tempers.
Standard supply form for chassis and wheel parts in 1.8–6 mm; best combination of 780 MPa strength and very high hole-expansion.
What is FB780-HR?
FB780-HR is FB780 supplied in the HR 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. FB780-HR 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). FB780-HR 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).
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-HR properties
Typical room-temperature values for FB780-HR — 10 properties are specific to this condition; the rest are grade-level values shared by every FB780 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
FB780-HR 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-HR 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-HR 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-HR conducts electricity at 8.2 % IACS, better than 60% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of FB780-HR 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-HR's machinability is fair (42/100, worse than 72% 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.
Other FB780 tempers and conditions
FB780 is also supplied in 3 other conditions. The full side-by-side table is on the FB780 overview.
- HRDefaultStandard supply form for chassis and wheel parts in 1.8–6 mm; best combination of 780 MPa strength and very high hole-expansion.660 MPa yield · 245 HB
- TMCPFor thicker sections (≈4–12 mm) where controlled rolling + accelerated cooling gives 780 MPa class strength with the best low-temperature toughness.700 MPa yield · 240 HB
- CRChoose for thin gauges (0.8–2.0 mm) and better surface/thickness tolerance, e.g. seat structures and reinforcements.685 MPa yield · 250 HB
- GalvanizedPick when the part is exposed to road salt and cannot be fully e-coated; zinc limits service temperature and slightly reduces spot-weld current window.650 MPa yield · 243 HB
Working with FB780-HR
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.
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.
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 | — |
FB780-HR — frequently asked
What is FB780-HR used for?
FB780-HR 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-HR?
FB780-HR 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 4 listed tempers.
Is FB780-HR easy to machine?
Not especially — machinability is rated fair (42/100, worse than 72% 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-HR 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-HR?
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-HR 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-HR?
FB780-HR 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.
Can FabDigit make parts in FB780-HR?
Yes — FB780-HR is available for sheet metal with instant online pricing. 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.