Steel 27MnCrB5-2 +QT (Quenched and tempered)
Heat-treated state · default condition
EN 27MnCrB5-2
Standard service condition for high-strength fasteners and small shafts up to 16 mm ruling section.
Values for the +QT condition
Other 27MnCrB5-2 tempers and conditions
27MnCrB5-2 is listed in 10 conditions; see the grade overview at 27MnCrB5-2.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Standard wire-rod / drawn-wire condition for multi-station cold heading of bolts and screws. | 360 | 570 | 24 | 170 HB | 8 % IACS |
Annealed | Softest delivery state for machining, deep drawing and heavy cold upsetting of bar stock. | 400 | 620 | 22 | 190 HB | — |
Normalized | Uniform fine-grained structure for hot-formed bar before final machining or hardening. | 500 | 780 | 17 | 21 HRC | — |
Cold drawn | Drawn-to-size bar or wire with improved tolerance and surface; strength raised by cold work. | 660 | 780 | 10 | 21 HRC | 7.9 % IACS |
+QT | Heavier sections — mass effect lowers core strength; choose when section exceeds 40 mm. | 760 | 1,000 | 14 | 31 HRC | 7.8 % IACS |
+QT | Q&T properties for medium ruling sections where the boron effect still gives near-through hardening. | 870 | 1,100 | 13 | 35 HRC | 7.8 % IACS |
+QTDefaultThis page Quenched and tempered | Standard service condition for high-strength fasteners and small shafts up to 16 mm ruling section. | 980 | 1,200 | 12 | 38 HRC | — |
Q&T to bolt property class 10.9 | Cold-headed then Q&T fasteners tempered to 10.9 — the main commercial use of this grade. | 990 | 1,100 | 12 | 34 HRC | 7.8 % IACS |
Q&T to bolt property class 12.9 | Highest standard fastener class from this grade; watch hydrogen embrittlement — avoid electroplating or bake thoroughly. | 1,150 | 1,280 | 10 | 41 HRC | 7.5 % IACS |
Hardened | Intermediate state only — maximum hardness for the carbon level; must be tempered before service. | 1,250 | 1,600 | 4 | 48 HRC | 6.7 % IACS |
What is 27MnCrB5-2 +QT?
27MnCrB5-2 +QT is 27MnCrB5-2 heat treated to +QT — standard service condition for high-strength fasteners and small shafts up to 16 mm ruling section. 27MnCrB5-2 +QT has a yield strength of 980 MPa (142 ksi) and a tensile strength of 1,200 MPa (174 ksi) — stronger than 91% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi). 27MnCrB5-2 +QT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Advantages
- High strength — 980 MPa (142 ksi), better than 91% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
27MnCrB5-2 +QT properties
Typical room-temperature values for 27MnCrB5-2 +QT; 12 are specific to this condition. Other listed values are 27MnCrB5-2 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
27MnCrB5-2 +QT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
27MnCrB5-2 +QT has a yield strength of 980 MPa (142 ksi) and a tensile strength of 1,200 MPa (174 ksi) — stronger than 91% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
27MnCrB5-2 +QT 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 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
27MnCrB5-2 +QT conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 27MnCrB5-2 +QT 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
27MnCrB5-2 +QT's machinability is fair (42/100, worse than 73% of steel grades); weldability fair (35/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 27MnCrB5-2 +QT
Is 27MnCrB5-2 easy to machine?
Machine in +A/+AC (≈190 HB) with carbide at moderate speeds; after Q&T to 35–41 HRC use coated carbide/CBN, rigid setups and grinding for finish features.
Can 27MnCrB5-2 be welded?
CEV ≈ 0.6–0.7, so preheat 200–300 °C, low-hydrogen consumables and post-weld tempering are required; boron promotes HAZ hardening and cold cracking — welding is generally avoided on finished fasteners.
Can 27MnCrB5-2 be formed, bent or molded?
Excellent multi-station cold heading and cold extrusion in spheroidize-annealed condition; hot forming 1050–1150 °C, austenitize 860–900 °C, oil/polymer quench, temper 400–560 °C avoiding the 250–400 °C temper-brittleness window.
What surface finishes work on 27MnCrB5-2?
Not anodizable — protect with zinc or zinc-nickel electroplate (bake 200 °C/4 h against hydrogen embrittlement above 1000 MPa), zinc-flake coating, phosphate + oil, or paint; nitriding or induction hardening can add surface wear resistance.
27MnCrB5-2 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 | 0.24 – 0.3 | 0.27 |
| Simax only | ≤ 0.4 | 0.25 |
| Mn | 1.1 – 1.4 | 1.25 |
| P | ≤ 0.03 | 0.02 |
| Smax; lower for cold-heading quality | ≤ 0.04 | 0.02 |
| Cr | 0.3 – 0.6 | 0.45 |
| Beffective (soluble) boron; Ti/Al additions used to tie up free nitrogen | 8×10⁻⁴ – 0.01 | 0 |
| Fe | balance | — |
27MnCrB5-2 +QT — frequently asked
What is 27MnCrB5-2 +QT used for?
27MnCrB5-2 +QT is typically used for high-strength bolts, cold-headed fasteners and screws. In short: through-hardening fastener steel; class 12.9 capable; boron replaces Cr-Mo alloying.
What is the yield strength of 27MnCrB5-2 +QT?
27MnCrB5-2 +QT has a typical yield strength of 980 MPa (142 ksi) and a tensile strength of 1,200 MPa (174 ksi) — stronger than 91% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 27MnCrB5-2 +QT easy to machine?
Not especially — machinability is rated fair (42/100, worse than 73% of steel grades). Machine in +A/+AC (≈190 HB) with carbide at moderate speeds; after Q&T to 35–41 HRC use coated carbide/CBN, rigid setups and grinding for finish features.
Can 27MnCrB5-2 +QT be welded?
With care — weldability is rated fair (35/100). CEV ≈ 0.6–0.7, so preheat 200–300 °C, low-hydrogen consumables and post-weld tempering are required; boron promotes HAZ hardening and cold cracking — welding is generally avoided on finished fasteners.
What surface finishes work on 27MnCrB5-2 +QT?
Not anodizable — protect with zinc or zinc-nickel electroplate (bake 200 °C/4 h against hydrogen embrittlement above 1000 MPa), zinc-flake coating, phosphate + oil, or paint; nitriding or induction hardening can add surface wear resistance.
Can 27MnCrB5-2 +QT be formed, bent or molded?
Excellent multi-station cold heading and cold extrusion in spheroidize-annealed condition; hot forming 1050–1150 °C, austenitize 860–900 °C, oil/polymer quench, temper 400–560 °C avoiding the 250–400 °C temper-brittleness window.
What is the maximum service temperature of 27MnCrB5-2 +QT?
27MnCrB5-2 +QT 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.
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 — 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.19: Fatigue and Fracture — ASM International (1996)
- EN ISO 18265 Metallic materials — Conversion of hardness values — CEN/ISO (2013)
- Boron steel 27MnCrB5-2 (1.7182) bar and wire rod datasheets — European long-products steelmakers (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.