Steel 34MnB5 · hardness band
Steel 34MnB5-QT50
Properties of the QT50 condition, compared with the other 34MnB5 tempers.
Choose when hardened parts (plough shares, cutting edges, wear plates) need some toughness traded against peak hardness.
What is 34MnB5-QT50?
34MnB5-QT50 is 34MnB5 heat treated to QT50 — choose when hardened parts (plough shares, cutting edges, wear plates) need some toughness traded against peak hardness. 34MnB5-QT50 has a yield strength of 1,400 MPa (203 ksi) and a tensile strength of 1,650 MPa (239 ksi) — stronger than 96% of steel grades. Elongation at break is 8% and the elastic modulus is 210 GPa (30.5 Msi). 34MnB5-QT50 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). CR is the default condition FabDigit quotes; QT50 is available on request or by drawing note.
Advantages
- High strength — 1,400 MPa (203 ksi), better than 96% of steel grades
Limitations
- Difficult to machine — 15/100, worse than 98% of steel grades
- Limited formability — 8/100, worse than 97% of steel grades
- Limited ductility — 8%, worse than 95% of steel grades
- Low fracture toughness — 48 MPa·√m (43.7 ksi·√in), worse than 88% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
34MnB5-QT50 properties
Typical room-temperature values for 34MnB5-QT50 — 12 properties are specific to this condition; the rest are grade-level values shared by every 34MnB5 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
34MnB5-QT50 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical15
34MnB5-QT50 has a yield strength of 1,400 MPa (203 ksi) and a tensile strength of 1,650 MPa (239 ksi) — stronger than 96% of steel grades. Elongation at break is 8% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
34MnB5-QT50 is rated for continuous service to 250°C (482 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.5 µm/m·K (6.94 µin/in·°F).
Electrical3
34MnB5-QT50 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 34MnB5-QT50 takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
34MnB5-QT50's machinability is poor (15/100, worse than 98% of steel grades); weldability poor (25/100); formability not recommended (8/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 34MnB5 tempers and conditions
34MnB5 is also supplied in 7 other conditions. The full side-by-side table is on the 34MnB5 overview.
- CRDefaultStandard stocked condition: soft ferritic-pearlitic cold-rolled coil/blank for blanking and subsequent press hardening or Q&T.420 MPa yield · 185 HB
- PHThe end-use condition for hot-stamped structural/wear parts where ~2000 MPa strength and high hardness are required.1,400 MPa yield · 53 HRC
- QT50Choose when hardened parts (plough shares, cutting edges, wear plates) need some toughness traded against peak hardness.1,400 MPa yield · 50 HRC
- ASAluminium-silicon coated coil/blank: prevents scaling and decarburisation in the austenitizing furnace and gives moderate in-service corrosion protection after press hardening.1,400 MPa yield · 53 HRC
- QT42Higher tempering temperature for impact-loaded hardened components where 50+ HRC would be too brittle.1,150 MPa yield · 42 HRC
- NUniform fine ferritic-pearlitic structure for moderate strength parts and as a pre-treatment before quench and temper.480 MPa yield · 220 HB
- HRHot-rolled coil/plate for thicker press-hardened parts, wear plates and agricultural tool blanks before quenching.450 MPa yield · 200 HB
- APick for maximum cold formability or for machining of thick blanks before hardening.340 MPa yield · 165 HB
Working with 34MnB5-QT50
Is 34MnB5 easy to machine?
Machine and drill in the soft as-delivered or annealed state; after press hardening (50+ HRC) use carbide/CBN, grinding or laser cutting only.
Can 34MnB5 be welded?
Weldable by RSW/laser in the soft state; boron raises hardenability so use low hydrogen consumables, preheat ~150–250 °C on thick sections, and expect HAZ softening/brittleness on hardened parts.
Can 34MnB5 be formed, bent or molded?
Cold form or blank only in the as-delivered condition; final geometry is normally produced by direct hot stamping at 900–950 °C with in-die quenching (>30 °C/s) — hardened parts are essentially non-formable.
What surface finishes work on 34MnB5?
No anodizing; use Al-Si pre-coating for furnace protection, or shot blast plus zinc-phosphate/e-coat, zinc-flake or paint for corrosion protection.
34MnB5 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 |
|---|---|---|
| Chigh-carbon press-hardening variant | 0.3 – 0.37 | 0.34 |
| Si | 0.1 – 0.4 | 0.25 |
| Mn | 1 – 1.4 | 1.2 |
| P | ≤ 0.03 | — |
| Smax (0.025 max on some hot-rolled deliveries) | ≤ 0.01 | — |
| Cr | 0.1 – 0.35 | 0.2 |
| Altotal Al | 0.02 – 0.07 | 0.04 |
| Tities up N so B stays effective | 0.02 – 0.05 | 0.04 |
| Bhardenability booster | 0 – 0.01 | 0 |
| Fe | balance | — |
34MnB5-QT50 — frequently asked
What is 34MnB5-QT50 used for?
34MnB5-QT50 is typically used for press-hardened B-pillar reinforcements, bumper beams, door impact beams, roof and rocker rails, floor and tunnel cross-members and high-strength fasteners. In short: boron-bearing CR steel.
What is the yield strength of 34MnB5-QT50?
34MnB5-QT50 has a typical yield strength of 1,400 MPa (203 ksi) and a tensile strength of 1,650 MPa (239 ksi) — stronger than 96% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 34MnB5-QT50 easy to machine?
Not especially — machinability is rated poor (15/100, worse than 98% of steel grades). Machine and drill in the soft as-delivered or annealed state; after press hardening (50+ HRC) use carbide/CBN, grinding or laser cutting only.
Can 34MnB5-QT50 be welded?
Not readily — weldability is rated poor (25/100). Weldable by RSW/laser in the soft state; boron raises hardenability so use low hydrogen consumables, preheat ~150–250 °C on thick sections, and expect HAZ softening/brittleness on hardened parts.
What surface finishes work on 34MnB5-QT50?
No anodizing; use Al-Si pre-coating for furnace protection, or shot blast plus zinc-phosphate/e-coat, zinc-flake or paint for corrosion protection.
Can 34MnB5-QT50 be formed, bent or molded?
Cold form or blank only in the as-delivered condition; final geometry is normally produced by direct hot stamping at 900–950 °C with in-die quenching (>30 °C/s) — hardened parts are essentially non-formable.
What is the maximum service temperature of 34MnB5-QT50?
34MnB5-QT50 is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 34MnB5-CR and 34MnB5-PH?
CR is the default condition — standard stocked condition: soft ferritic-pearlitic cold-rolled coil/blank for blanking and subsequent press hardening or Q&T. PH: the end-use condition for hot-stamped structural/wear parts where ~2000 MPa strength and high hardness are required. Yield strength is 420 MPa in CR versus 1,400 MPa in PH.
Can FabDigit make parts in 34MnB5-QT50?
Yes — 34MnB5-QT50 is available for sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- EN 10083-3 Steels for quenching and tempering — alloy steels (boron grades) — CEN (2006)
- EN 10346 Continuously hot-dip / Al-Si coated flat steel products — CEN (2015)
- Press-hardening (hot-stamping) steel grades 22MnB5 / 30MnB5 / 34MnB5 data — ArcelorMittal / SSAB / voestalpine (2023)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
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.