Steel 20MnB4 +AC+C
Supply condition · default condition
EN 20MnB4
+AC+C = spheroidize annealed then cold drawn
The standard cold-heading wire delivery condition: annealed for ductility, drawn to size and phosphate/soap coated for die life.
Values for the +AC+C condition
Other 20MnB4 tempers and conditions
20MnB4 is listed in 6 conditions; see the grade overview at 20MnB4.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose for the softest, most ductile state before severe multi-station cold heading or cold extrusion of complex parts. | 310 | 460 | 26 | 135 HB | — |
Treated to ferrite-pearlite structure | Isothermally treated for uniform ferrite-pearlite and consistent drawing behaviour; a middle ground between +U and +AC. | 370 | 540 | 22 | 155 HB | 8.8 % IACS |
Hot rolled | Mill hot-rolled condition; the cheapest input for further annealing, drawing or hot forging, not for direct severe cold heading. | 390 | 580 | 20 | 170 HB | — |
+AC+CDefaultThis page Spheroidize annealed then cold drawn | The standard cold-heading wire delivery condition: annealed for ductility, drawn to size and phosphate/soap coated for die life. | 450 | 550 | 13 | 160 HB | — |
Cold drawn from untreated hot-rolled stock | Drawn without prior spheroidizing — higher strength and better straightness/tolerance, but limited upset ratio; suits light heading and machined parts. | 580 | 660 | 9 | 195 HB | — |
Supplied with specified hardenability, quenched and tempered after… | Pick when the finished fastener must be oil/water quenched and tempered to 800–1000 MPa; the guaranteed Jominy band ensures reproducible core hardness. | 750 | 900 | 13 | 28 HRC | — |
What is 20MnB4 +AC+C?
20MnB4 +AC+C is 20MnB4 supplied in the +AC+C condition — the standard cold-heading wire delivery condition: annealed for ductility, drawn to size and phosphate/soap coated for die life. 20MnB4 +AC+C has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 550 MPa (79.8 ksi) — stronger than 52% of steel grades. Elongation at break is 13% and the elastic modulus is 207 GPa (30 Msi). 20MnB4 +AC+C 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
- Forms and bends easily — 85/100, better than 96% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
- Limited ductility — 13%, worse than 78% of steel grades
20MnB4 +AC+C properties
Typical room-temperature values for 20MnB4 +AC+C; 15 are specific to this condition. Other listed values are 20MnB4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20MnB4 +AC+C 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
20MnB4 +AC+C has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 550 MPa (79.8 ksi) — stronger than 52% of steel grades. Elongation at break is 13% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
20MnB4 +AC+C is rated for continuous service to 250°C (482 °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 µm/m·K (6.67 µin/in·°F).
Electrical3
20MnB4 +AC+C 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 20MnB4 +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 25%.
Manufacturability7
20MnB4 +AC+C's machinability is good (55/100, better than 62% of steel grades); weldability good (55/100); formability excellent (85/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20MnB4 +AC+C
Is 20MnB4 easy to machine?
Machines like 1020/1518 in the annealed state (~60–65 % of 1212); use sharp positive tooling and chip breakers because low-sulphur cold-heading steel produces stringy chips.
Can 20MnB4 be welded?
Weldable with CE_IIW ≈ 0.45 using low-hydrogen consumables; preheat 100–150 °C above ~16 mm and avoid welding on quenched-and-tempered fasteners as boron martensite is crack-sensitive.
Can 20MnB4 be formed, bent or molded?
Excellent cold heading, extrusion and thread rolling in +AC/+AC+C with phosphate-soap or polymer lubricant; upset ratios above ~2.5:1 need the spheroidized condition.
What surface finishes work on 20MnB4?
No corrosion resistance bare — zinc electroplate, zinc-nickel, zinc flake (Dacromet/Geomet) or phosphate-and-oil; bake at 190–220 °C within 4 h after plating parts harder than ~32 HRC to relieve hydrogen.
20MnB4 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 | 0.18 – 0.23 | 0.2 |
| Simax per EN 10263-4 | ≤ 0.3 | 0.15 |
| Mn | 0.9 – 1.2 | 1.05 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Bboron for hardenability; effective B requires Ti/Al nitrogen fixation | 8×10⁻⁴ – 0.01 | 0 |
| Altotal Al, for nitrogen binding and grain refinement | ≥ 0.02 | 0.04 |
| Tioptional, common producer practice to protect boron | ≤ 0.05 | 0.03 |
| Fe | balance | — |
20MnB4 +AC+C — frequently asked
What is 20MnB4 +AC+C used for?
20MnB4 +AC+C is typically used for bolts, screws and cold-formed fasteners. In short: most formable boron steel; weldable cold-heading grade; economical medium-strength fasteners.
What is the yield strength of 20MnB4 +AC+C?
20MnB4 +AC+C has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 550 MPa (79.8 ksi) — stronger than 52% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 20MnB4 +AC+C easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like 1020/1518 in the annealed state (~60–65 % of 1212); use sharp positive tooling and chip breakers because low-sulphur cold-heading steel produces stringy chips.
Can 20MnB4 +AC+C be welded?
Yes — weldability is rated good (55/100). Weldable with CE_IIW ≈ 0.45 using low-hydrogen consumables; preheat 100–150 °C above ~16 mm and avoid welding on quenched-and-tempered fasteners as boron martensite is crack-sensitive.
What surface finishes work on 20MnB4 +AC+C?
No corrosion resistance bare — zinc electroplate, zinc-nickel, zinc flake (Dacromet/Geomet) or phosphate-and-oil; bake at 190–220 °C within 4 h after plating parts harder than ~32 HRC to relieve hydrogen.
Can 20MnB4 +AC+C be formed, bent or molded?
Excellent cold heading, extrusion and thread rolling in +AC/+AC+C with phosphate-soap or polymer lubricant; upset ratios above ~2.5:1 need the spheroidized condition.
What is the maximum service temperature of 20MnB4 +AC+C?
20MnB4 +AC+C 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 10263-4: Steel rod, bars and wire for cold heading and cold extrusion — Part 4: Steels for quenching and tempering — CEN (2018)
- EN 10263-1/-2: Cold heading steels — general technical delivery conditions and delivery conditions for untreated/soft-annealed steels — CEN (2018)
- ISO 898-1: Mechanical properties of fasteners made of carbon steel and alloy steel — 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 (boron hardenability) — ASM International (2013)
- Cold heading quality boron steel wire rod datasheets (20MnB4 / 1.5525) — European & Chinese 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.