Steel 18MnB4 +AC+C
Supply condition · default condition
EN 18MnB4
+AC+C = spheroidize annealed and cold drawn
The standard fastener-wire supply condition: soft ductile core with sized, clean drawn surface for high-speed cold heading.
Values for the +AC+C condition
Other 18MnB4 tempers and conditions
18MnB4 is listed in 5 conditions; see the grade overview at 18MnB4.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Softest condition with globular carbides — pick for the most severe cold heading, extrusion or thread rolling. | 310 | 470 | 26 | 140 HB | — |
Hot rolled | Cheapest mill condition — pick for further in-house annealing/drawing or for hot-formed parts. | 380 | 570 | 20 | 168 HB | — |
+AC+CDefaultThis page Spheroidize annealed and cold drawn | The standard fastener-wire supply condition: soft ductile core with sized, clean drawn surface for high-speed cold heading. | 470 | 560 | 13 | 172 HB | — |
Untreated (hot rolled) and cold drawn | Drawn straight from hot-rolled rod without annealing — pick for moderate upsetting, machined parts and cost-driven bar stock. | 560 | 640 | 9 | 195 HB | — |
Hardened and tempered | Final in-service condition of cold-headed parts: austenitize ~880–920 °C, quench, temper 400–500 °C for 8.8 or 340–420 °C for 10.9. | 940 | 1,050 | 12 | 33 HRC | — |
What is 18MnB4 +AC+C?
18MnB4 +AC+C is 18MnB4 supplied in the +AC+C condition — the standard fastener-wire supply condition: soft ductile core with sized, clean drawn surface for high-speed cold heading. 18MnB4 +AC+C has a yield strength of 470 MPa (68.2 ksi) and a tensile strength of 560 MPa (81.2 ksi) — stronger than 57% of steel grades. Elongation at break is 13% and the elastic modulus is 207 GPa (30 Msi). 18MnB4 +AC+C 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).
Advantages
- Forms and bends easily — 82/100, better than 94% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Easy to machine — 62/100, better than 89% of steel grades
Limitations
- Limited ductility — 13%, worse than 78% of steel grades
18MnB4 +AC+C properties
Typical room-temperature values for 18MnB4 +AC+C; 15 are specific to this condition. Other listed values are 18MnB4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
18MnB4 +AC+C 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).
Mechanical14
18MnB4 +AC+C has a yield strength of 470 MPa (68.2 ksi) and a tensile strength of 560 MPa (81.2 ksi) — stronger than 57% of steel grades. Elongation at break is 13% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
18MnB4 +AC+C is rated for continuous service to 350°C (662 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 12.1 µm/m·K (6.72 µin/in·°F).
Electrical3
18MnB4 +AC+C conducts electricity at 9 % IACS, better than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 18MnB4 +AC+C 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
18MnB4 +AC+C's machinability is good (62/100, better than 89% of steel grades); weldability good (55/100); formability very good (82/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 18MnB4 +AC+C
Is 18MnB4 easy to machine?
Machines like 1018/15B21 in the annealed or drawn state (≈65 % of AISI 1212); after +H hardening use coated carbide, rigid setups and expect noticeably lower tool life.
Can 18MnB4 be welded?
Weldable by resistance and MAG but boron sharply raises HAZ hardenability — limit heat input, preheat 100–150 °C on thicker sections and avoid welding fully hardened high-class fasteners.
Can 18MnB4 be formed, bent or molded?
Designed for cold heading, extrusion and thread rolling in +AC or +AC+C; phosphate/lubricate the wire, and heat treat after forming since only the +H condition develops rated strength.
What surface finishes work on 18MnB4?
No anodizing; use zinc or zinc-nickel electroplating, zinc-flake coating or hot-dip galvanizing, plus hydrogen-relief bake within 4 h for parts ≥1000 MPa.
18MnB4 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 | 0.15 – 0.21 | 0.18 |
| Sioften ≤0.10 for Si-killed cold-heading wire | ≤ 0.3 | 0.15 |
| Mn | 0.7 – 1.1 | 0.9 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Bhardenability agent; must be protected from N by Ti/Al | 8×10⁻⁴ – 0.01 | 0 |
| TiN-fixing addition, optional per melting practice | 0.02 – 0.05 | 0.04 |
| Altotal Al, deoxidation/N control | 0.02 – 0.06 | 0.04 |
| Crresidual | ≤ 0.3 | 0.1 |
| Niresidual | ≤ 0.3 | 0.08 |
| Curesidual | ≤ 0.25 | 0.1 |
| Fe | balance | — |
18MnB4 +AC+C — frequently asked
What is 18MnB4 +AC+C used for?
18MnB4 +AC+C is typically used for fasteners, bolts and cold heading wire. In short: consistent through-hardening; cold-heading grade; between 17MnB4 and 22MnB4.
What is the yield strength of 18MnB4 +AC+C?
18MnB4 +AC+C has a typical yield strength of 470 MPa (68.2 ksi) and a tensile strength of 560 MPa (81.2 ksi) — stronger than 57% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is 18MnB4 +AC+C easy to machine?
Reasonably — machinability is rated good (62/100, better than 89% of steel grades). Machines like 1018/15B21 in the annealed or drawn state (≈65 % of AISI 1212); after +H hardening use coated carbide, rigid setups and expect noticeably lower tool life.
Can 18MnB4 +AC+C be welded?
Yes — weldability is rated good (55/100). Weldable by resistance and MAG but boron sharply raises HAZ hardenability — limit heat input, preheat 100–150 °C on thicker sections and avoid welding fully hardened high-class fasteners.
What surface finishes work on 18MnB4 +AC+C?
No anodizing; use zinc or zinc-nickel electroplating, zinc-flake coating or hot-dip galvanizing, plus hydrogen-relief bake within 4 h for parts ≥1000 MPa.
Can 18MnB4 +AC+C be formed, bent or molded?
Designed for cold heading, extrusion and thread rolling in +AC or +AC+C; phosphate/lubricate the wire, and heat treat after forming since only the +H condition develops rated strength.
What is the maximum service temperature of 18MnB4 +AC+C?
18MnB4 +AC+C 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: steels for quenching and tempering — 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. 4A/16 — Steel Heat Treating and Machining — ASM International (2013)
- Boron cold-heading wire grades (17MnB4/20MnB4 family) data sheets — 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.