Steel 35B2 +QT-HS (+QT high strength)
Hardness band
EN 35B2
Select for property-class 10.9 fasteners and highly loaded pins in small sections; watch hydrogen embrittlement when plating.
Values for the +QT-HS condition
Other 35B2 tempers and conditions
35B2 is listed in 8 conditions; see the grade overview at 35B2.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Lowest-hardness machining condition (max ~197 HB) for pre-machined parts hardened afterwards. | 330 | 560 | 23 | 8 HRC | 8.2 % IACS |
Spheroidize annealed | Pick for cold-heading wire and cold-extruded blanks; globular carbide structure gives maximum cold upsetting ability before final Q&T. | 340 | 540 | 24 | 160 HB | — |
Normalized | Use to homogenize grain size after forging and before machining or hardening. | 370 | 620 | 20 | 9 HRC | 8 % IACS |
Hot rolled | Cheapest mill condition; buy when you will anneal, spheroidize or Q&T in-house. | 380 | 640 | 18 | 10 HRC | 8 % IACS |
Treated to specified hardness range | Ordered when a mill-guaranteed hardness band (typically 170–230 HB) is needed for automatic machining or cold forming. | 420 | 660 | 17 | 14 HRC | 8.2 % IACS |
Cold drawn | Choose for close tolerance, bright surface pins and shafts used without further heat treatment. | 600 | 720 | 9 | 17 HRC | 7.9 % IACS |
+QTDefault Quenched and tempered | Standard delivery/final condition for high-strength bolts, pins and shafts up to ~16 mm section. | 760 | 950 | 12 | 31 HRC | — |
+QT-HSThis page +QT high strength | Select for property-class 10.9 fasteners and highly loaded pins in small sections; watch hydrogen embrittlement when plating. | 950 | 1,100 | 10 | 36 HRC | — |
What is 35B2 +QT-HS?
35B2 +QT-HS is 35B2 heat treated to +QT-HS — select for property-class 10.9 fasteners and highly loaded pins in small sections; watch hydrogen embrittlement when plating. 35B2 +QT-HS has a yield strength of 950 MPa (138 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 91% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi). 35B2 +QT-HS 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). +QT is the default condition FabDigit quotes; +QT-HS is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 950 MPa (138 ksi), better than 91% of steel grades
Limitations
- Limited formability — 12/100, worse than 92% of steel grades
- Limited ductility — 10%, worse than 91% of steel grades
- Difficult to machine — 35/100, worse than 84% of steel grades
- Limited service temperature — 300°C (572 °F), worse than 78% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
35B2 +QT-HS properties
Typical room-temperature values for 35B2 +QT-HS; 13 are specific to this condition. Other listed values are 35B2 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
35B2 +QT-HS 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).
Mechanical16
35B2 +QT-HS has a yield strength of 950 MPa (138 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 91% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
35B2 +QT-HS is rated for continuous service to 300°C (572 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
35B2 +QT-HS conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 35B2 +QT-HS takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
35B2 +QT-HS's machinability is fair (35/100, worse than 84% of steel grades); weldability poor (25/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 35B2 +QT-HS
Is 35B2 easy to machine?
Machine in +A/+AC/+TH (170–210 HB) with carbide at moderate feeds; in +QT above 300 HB expect ~50 % of 1212 rates and use coated carbide with rigid setups.
Can 35B2 be welded?
Weldable only with care in the annealed state (CEV ≈ 0.5): preheat 150–250 °C, low-hydrogen consumables and post-weld temper; avoid welding hardened fasteners.
Can 35B2 be formed, bent or molded?
Spheroidize-anneal (+AC) plus phosphate/soap or polymer lubricant for multi-station cold heading and thread rolling; hot forge 1100–1200 °C, finish above 900 °C, then normalize.
What surface finishes work on 35B2?
No corrosion resistance bare — zinc, zinc-nickel or zinc-flake coat, or phosphate plus oil; bake within 4 h after acid pickling/electroplating above ~1000 MPa to avoid hydrogen embrittlement.
35B2 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 |
|---|---|---|
| C | 0.32 – 0.39 | 0.35 |
| Sisome mills to 0.40 max on wire rod | ≤ 0.3 | 0.2 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | — |
| Slower S for cold-heading wire | ≤ 0.04 | — |
| Crresidual | ≤ 0.3 | 0.1 |
| BTi or Al added to fix free nitrogen so boron stays effective | 8×10⁻⁴ – 0.01 | 0 |
| Fe | balance | — |
35B2 +QT-HS — frequently asked
What is 35B2 +QT-HS used for?
35B2 +QT-HS is typically used for high-strength bolts, fasteners and structural pins. In short: strongest boron fastener grade; limited cold formability; quench-and-temper only.
What is the yield strength of 35B2 +QT-HS?
35B2 +QT-HS has a typical yield strength of 950 MPa (138 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 91% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 35B2 +QT-HS easy to machine?
Not especially — machinability is rated fair (35/100, worse than 84% of steel grades). Machine in +A/+AC/+TH (170–210 HB) with carbide at moderate feeds; in +QT above 300 HB expect ~50 % of 1212 rates and use coated carbide with rigid setups.
Can 35B2 +QT-HS be welded?
Not readily — weldability is rated poor (25/100). Weldable only with care in the annealed state (CEV ≈ 0.5): preheat 150–250 °C, low-hydrogen consumables and post-weld temper; avoid welding hardened fasteners.
What surface finishes work on 35B2 +QT-HS?
No corrosion resistance bare — zinc, zinc-nickel or zinc-flake coat, or phosphate plus oil; bake within 4 h after acid pickling/electroplating above ~1000 MPa to avoid hydrogen embrittlement.
Can 35B2 +QT-HS be formed, bent or molded?
Spheroidize-anneal (+AC) plus phosphate/soap or polymer lubricant for multi-station cold heading and thread rolling; hot forge 1100–1200 °C, finish above 900 °C, then normalize.
What is the maximum service temperature of 35B2 +QT-HS?
35B2 +QT-HS is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- EN 10083-3 Steels for quenching and tempering — Alloy steels — CEN (2006)
- EN 10263-4 Steel rod, bars and wire for cold heading — Steels for quenching and tempering — CEN (2018)
- EN ISO 898-1 Mechanical properties of fasteners — Bolts, screws and studs — ISO (2013)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals and Processes — ASM International (2013)
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.