Steel 36MnB4 QT-10.9
Hardness band
EN 36MnB4
QT-10.9 = q&T to property class 10.9
Tempered high (≈500–560 °C) for 10.9 bolts — best balance of strength, toughness and hydrogen-embrittlement safety.
Values for the QT-10.9 condition
Other 36MnB4 tempers and conditions
36MnB4 is listed in 8 conditions; see the grade overview at 36MnB4.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Softest condition with globular carbides — pick for severe multi-station cold heading/extrusion of bolt blanks before quench and temper. | 380 | 560 | 22 | 165 HB | — |
Normalized | Used to refine grain and homogenize hot-rolled bar before machining or subsequent hardening; not a cold-heading condition. | 430 | 700 | 18 | 205 HB | — |
Specified hardenability (Jominy band), as-rolled delivery | Choose when the fastener/part maker needs a guaranteed Jominy hardenability band for through-hardening of thick sections; delivered hot-rolled/untreated unless combined with +AC. | 460 | 730 | 16 | 215 HB | — |
+AC+CDefault Spheroidize annealed and cold drawn | Standard fastener wire/bar delivery: spheroidized then lightly cold drawn to size, straightness and surface for cold heading or bar turning. | 500 | 640 | 12 | 190 HB | — |
Cold drawn | Plain cold-drawn bar for machined parts where good size tolerance and surface matter and the part will be hardened afterwards. | 650 | 780 | 9 | 235 HB | — |
QT-10.9This page Q&T to property class 10.9 | Tempered high (≈500–560 °C) for 10.9 bolts — best balance of strength, toughness and hydrogen-embrittlement safety. | 950 | 1,060 | 12 | 34 HRC | — |
Quenched and tempered | Standard through-hardened bar condition for high-strength shafts, pins and machined fasteners; specify section size, hardenability falls off above ~25 mm. | 980 | 1,200 | 11 | 38 HRC | — |
Q&T to property class 12.9 | Peak-strength condition for 12.9 socket-head cap screws; tempered ≈400–450 °C — highest load capacity but most sensitive to hydrogen embrittlement and notches. | 1,140 | 1,280 | 9 | 41 HRC | — |
What is 36MnB4 QT-10.9?
36MnB4 QT-10.9 is 36MnB4 heat treated to QT-10.9 — tempered high (≈500–560 °C) for 10.9 bolts — best balance of strength, toughness and hydrogen-embrittlement safety. 36MnB4 QT-10.9 has a yield strength of 950 MPa (138 ksi) and a tensile strength of 1,060 MPa (154 ksi) — stronger than 91% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi). 36MnB4 QT-10.9 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). +AC+C is the default condition FabDigit quotes; QT-10.9 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
- Forms and bends easily — 65/100, better than 81% of steel grades
Limitations
- Limited ductility — 12%, worse than 84% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
- Limited service temperature — 300°C (572 °F), worse than 78% of steel grades
36MnB4 QT-10.9 properties
Typical room-temperature values for 36MnB4 QT-10.9; 16 are specific to this condition. Other listed values are 36MnB4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
36MnB4 QT-10.9 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
36MnB4 QT-10.9 has a yield strength of 950 MPa (138 ksi) and a tensile strength of 1,060 MPa (154 ksi) — stronger than 91% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
36MnB4 QT-10.9 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
36MnB4 QT-10.9 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 36MnB4 QT-10.9 takes about 24 MJ of energy and emits 1.9 kg of CO₂ — less than 97% of steel grades. Typical recycled content is 30%.
Manufacturability7
36MnB4 QT-10.9's machinability is fair (42/100, worse than 73% of steel grades); weldability poor (20/100); formability good (65/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 36MnB4 QT-10.9
Is 36MnB4 easy to machine?
Machine in +AC or +AC+C (about 60% of AISI 1212); after Q&T above 38 HRC use carbide or CBN with rigid setups and expect heavy tool wear.
Can 36MnB4 be welded?
Poor — high hardenability from boron gives hard martensitic HAZ; if unavoidable use low-hydrogen consumables, 200–250 °C preheat and immediate post-weld temper.
Can 36MnB4 be formed, bent or molded?
Excellent multi-station cold heading and thread rolling in the spheroidized (+AC/+AC+C) condition with phosphate+soap or polymer lubricant; hot forge 1100–1200 °C, do not forge below ~850 °C.
What surface finishes work on 36MnB4?
Not anodizable; use zinc or zinc-nickel plating with a 190–220 °C hydrogen bake within 4 h (or zinc-flake / Delta-type coatings on 12.9 parts to avoid embrittlement), black oxide + oil for indoor use.
36MnB4 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 | 0.36 |
| Si≤0.30 typical for cold-heading grades per EN 10263-4 | ≤ 0.4 | 0.25 |
| Mn | 0.8 – 1.1 | 0.95 |
| P | ≤ 0.03 | 0.02 |
| S≤0.025 for cold-heading wire (EN 10263-4) | ≤ 0.04 | 0.02 |
| Crresidual | ≤ 0.3 | 0.15 |
| Beffective boron; Ti/Al added to fix N | 8×10⁻⁴ – 0.01 | 0 |
| Tinitrogen fixing, producer practice | ≤ 0.05 | 0.04 |
| Fe | balance | — |
36MnB4 QT-10.9 — frequently asked
What is 36MnB4 QT-10.9 used for?
36MnB4 QT-10.9 is typically used for property class 12.9 bolts, socket head cap screws, high-strength studs and threaded rod, cold-headed engine fasteners, wheel bolts and cold-forged pins and sleeves. In short: 12.9-capable boron steel; high carbon, deep hardening; poor weldability by design.
What is the yield strength of 36MnB4 QT-10.9?
36MnB4 QT-10.9 has a typical yield strength of 950 MPa (138 ksi) and a tensile strength of 1,060 MPa (154 ksi) — stronger than 91% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 36MnB4 QT-10.9 easy to machine?
Not especially — machinability is rated fair (42/100, worse than 73% of steel grades). Machine in +AC or +AC+C (about 60% of AISI 1212); after Q&T above 38 HRC use carbide or CBN with rigid setups and expect heavy tool wear.
Can 36MnB4 QT-10.9 be welded?
Not readily — weldability is rated poor (20/100). Poor — high hardenability from boron gives hard martensitic HAZ; if unavoidable use low-hydrogen consumables, 200–250 °C preheat and immediate post-weld temper.
What surface finishes work on 36MnB4 QT-10.9?
Not anodizable; use zinc or zinc-nickel plating with a 190–220 °C hydrogen bake within 4 h (or zinc-flake / Delta-type coatings on 12.9 parts to avoid embrittlement), black oxide + oil for indoor use.
Can 36MnB4 QT-10.9 be formed, bent or molded?
Excellent multi-station cold heading and thread rolling in the spheroidized (+AC/+AC+C) condition with phosphate+soap or polymer lubricant; hot forge 1100–1200 °C, do not forge below ~850 °C.
What is the maximum service temperature of 36MnB4 QT-10.9?
36MnB4 QT-10.9 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 — Part 3: Alloy steels — CEN (2006)
- EN 10263-4 Steel rod, bars and wire for cold heading and cold extrusion — Part 4: quenched and tempered steels — CEN (2017)
- 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. 4: Heat Treating (boron hardenability) — ASM International (1991)
- Cold heading steel wire rod grade datasheets (boron steels 30MnB4/36MnB4) — European wire rod producers (2022)
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.