Steel 23MnB3 +A (Annealed)
Heat-treated state
EN 23MnB3
Sub-critical soft anneal for machining stock and easier straightening.
Values for the +A condition
Other 23MnB3 tempers and conditions
23MnB3 is listed in 8 conditions; see the grade overview at 23MnB3.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Pick this for multi-station cold heading/extrusion of bolts and screws — softest, most ductile delivery condition. | 320 | 470 | 26 | 140 HB | — |
+AThis page Annealed | Sub-critical soft anneal for machining stock and easier straightening. | 340 | 520 | 24 | 155 HB | — |
Hot rolled | Mill-delivered hot-rolled coil, the starting stock before annealing and drawing. | 400 | 600 | 20 | 180 HB | — |
Normalized | Grain refinement after hot forging when parts are not to be hardened. | 400 | 600 | 21 | 10 HRC | 9.5 % IACS |
Cold drawn | Drawn-to-size wire/bar with better surface, straightness and tolerance for automatic heading or turning. | 530 | 620 | 11 | 185 HB | — |
+QT | High-temper condition for class 8.8 bolts where ductility and delayed-fracture safety matter more than peak load. | 720 | 880 | 16 | 26 HRC | — |
+QTDefault Quenched and tempered | Standard service condition for cold-headed fasteners and small shafts after forming — oil/polymer quench plus temper to the required class. | 920 | 1,050 | 13 | 34 HRC | — |
+QT | Highest routine strength level for 23MnB3 fasteners; watch hydrogen embrittlement and keep sections below ~16 mm for through-hardening. | 1,000 | 1,100 | 11 | 36 HRC | — |
What is 23MnB3 +A?
23MnB3 +A is 23MnB3 heat treated to +A — sub-critical soft anneal for machining stock and easier straightening. 23MnB3 +A has a yield strength of 340 MPa (49.3 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 76% of steel grades. Elongation at break is 24% and the elastic modulus is 210 GPa (30.5 Msi). 23MnB3 +A 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). +QT is the default condition FabDigit quotes; +A is available on request or by drawing note.
Advantages
- Forms and bends easily — 75/100, better than 90% of steel grades
Limitations
- Low strength — 340 MPa (49.3 ksi), worse than 76% of steel grades
23MnB3 +A properties
Typical room-temperature values for 23MnB3 +A; 11 are specific to this condition. Other listed values are 23MnB3 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
23MnB3 +A 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
23MnB3 +A has a yield strength of 340 MPa (49.3 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 76% of steel grades. Elongation at break is 24% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
23MnB3 +A is rated for continuous service to 350°C (662 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
23MnB3 +A conducts electricity at 8.6 % IACS, better than 66% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 23MnB3 +A takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
23MnB3 +A's machinability is good (58/100, better than 75% of steel grades); weldability good (55/100); formability very good (75/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 23MnB3 +A
Is 23MnB3 easy to machine?
Machine in +AC or +A condition (≈45–65 % of AISI 1212); in +QT above 32 HRC use coated carbide, rigid setups and reduced feed — the steel is gummy and free-machining additives are absent.
Can 23MnB3 be welded?
Weldable with care (CE ≈ 0.45–0.55): preheat 150–250 °C, low-hydrogen consumables and slow cooling; avoid welding fully hardened fasteners as the HAZ softens and can crack.
Can 23MnB3 be formed, bent or molded?
Designed for multi-station cold heading and cold extrusion in the spheroidized (+AC) phosphate/soap-coated condition; hot forge 1100–1200 °C, then normalize or directly quench and temper.
What surface finishes work on 23MnB3?
Not anodizable — protect with zinc or zinc-nickel electroplating, zinc-flake (Dacromet/Geomet), hot-dip galvanising or phosphate+oil; bake 190–220 °C after plating on ≥10.9 parts to avoid hydrogen embrittlement.
23MnB3 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 | 0.19 – 0.25 | 0.22 |
| Sioften ≤0.10 for Si-killed cold-heading quality | ≤ 0.3 | 0.15 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Bhardenability booster; must stay in solution | 8×10⁻⁴ – 0.01 | 0 |
| Altotal Al, N-fixing and grain refining | 0.02 – 0.06 | 0.04 |
| Tiadded to protect boron from nitrogen | ≤ 0.05 | 0.03 |
| Crresidual | ≤ 0.3 | 0.1 |
| Niresidual | ≤ 0.3 | 0.08 |
| Curesidual | ≤ 0.25 | 0.1 |
| Nkept low so boron stays effective | ≤ 0.01 | 0.01 |
| Fe | balance | — |
23MnB3 +A — frequently asked
What is 23MnB3 +A used for?
23MnB3 +A is typically used for high-strength bolts, fasteners and structural pins. In short: high-hardenability bolt steel; class 10.9 at low alloy cost; cold-heading grade.
What is the yield strength of 23MnB3 +A?
23MnB3 +A has a typical yield strength of 340 MPa (49.3 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 76% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 23MnB3 +A easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machine in +AC or +A condition (≈45–65 % of AISI 1212); in +QT above 32 HRC use coated carbide, rigid setups and reduced feed — the steel is gummy and free-machining additives are absent.
Can 23MnB3 +A be welded?
Yes — weldability is rated good (55/100). Weldable with care (CE ≈ 0.45–0.55): preheat 150–250 °C, low-hydrogen consumables and slow cooling; avoid welding fully hardened fasteners as the HAZ softens and can crack.
What surface finishes work on 23MnB3 +A?
Not anodizable — protect with zinc or zinc-nickel electroplating, zinc-flake (Dacromet/Geomet), hot-dip galvanising or phosphate+oil; bake 190–220 °C after plating on ≥10.9 parts to avoid hydrogen embrittlement.
Can 23MnB3 +A be formed, bent or molded?
Designed for multi-station cold heading and cold extrusion in the spheroidized (+AC) phosphate/soap-coated condition; hot forge 1100–1200 °C, then normalize or directly quench and temper.
What is the maximum service temperature of 23MnB3 +A?
23MnB3 +A 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.
Sources
- EN 10263-4: Steel rod, bars and wire for cold heading and cold extrusion — Part 4: Steels for quenching and tempering — CEN (2018)
- EN 10083-3: Steels for quenching and tempering — Alloy steels — CEN (2019)
- ISO 898-1: Mechanical properties of fasteners made of carbon steel and alloy steel — Bolts, screws and studs — ISO (2013)
- GB/T 6478 (ML23MnB) — SAC (2015)
- 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)
- Cold heading quality boron steel wire rod datasheets (23MnB3 / 1.5507) — European & Asian wire rod producers (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.