Steel 17MnB4 +U+C
Supply condition
EN 17MnB4
+U+C = cold drawn from as-rolled stock
Straight cold-drawn bar/wire with clean surface and tight tolerance for light heading, machining or straight-length parts.
Values for the +U+C condition
Other 17MnB4 tempers and conditions
17MnB4 is listed in 5 conditions; see the grade overview at 17MnB4.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Softest condition, maximum reduction of area — choose for severe multi-station cold heading and deep extrusion. | 300 | 450 | 27 | 130 HB | — |
Hot rolled | Mill as-rolled coil/bar — the cheapest starting stock, drawn or annealed by the fastener maker before heading. | 350 | 530 | 22 | 155 HB | — |
+AC+CDefault Spheroidize annealed and cold drawn | Standard cold-heading wire delivery: soft spheroidized structure plus drawn size and surface — the default stock for bolt and screw makers. | 450 | 540 | 12 | 160 HB | — |
+U+CThis page Cold drawn from as-rolled stock | Straight cold-drawn bar/wire with clean surface and tight tolerance for light heading, machining or straight-length parts. | 540 | 620 | 10 | 185 HB | — |
Hardenability-controlled (Jominy) / quenched and tempered fastener… | Ordered with guaranteed Jominy band (J1.5 ≈ 40–48 HRC) and used after water/oil quench + temper for property-class 8.8–10.9 fasteners. | 740 | 900 | 14 | 29 HRC | 43 W/m·K |
What is 17MnB4 +U+C?
17MnB4 +U+C is 17MnB4 supplied in the +U+C condition — straight cold-drawn bar/wire with clean surface and tight tolerance for light heading, machining or straight-length parts. 17MnB4 +U+C has a yield strength of 540 MPa (78.3 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 70% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi). 17MnB4 +U+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). +AC+C is the default condition FabDigit quotes; +U+C is available on request or by drawing note.
Advantages
- Easy to machine — 66/100, better than 95% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Limited ductility — 10%, worse than 91% of steel grades
- Limited service temperature — 300°C (572 °F), worse than 78% of steel grades
17MnB4 +U+C properties
Typical room-temperature values for 17MnB4 +U+C; 15 are specific to this condition. Other listed values are 17MnB4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
17MnB4 +U+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).
Mechanical15
17MnB4 +U+C has a yield strength of 540 MPa (78.3 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 70% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
17MnB4 +U+C is rated for continuous service to 300°C (572 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), better than 66% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
17MnB4 +U+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 17MnB4 +U+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
17MnB4 +U+C's machinability is good (66/100, better than 95% of steel grades); weldability good (65/100); formability good (60/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 17MnB4 +U+C
Is 17MnB4 easy to machine?
Machine in the +AC or +AC+C condition (≈65 % of AISI 1212); gummy chips in soft anneal — use sharp positive-rake tools and good chip breakers, and finish-machine before hardening.
Can 17MnB4 be welded?
Weldable with CE_IIW ≈ 0.40–0.45 using low-hydrogen consumables; preheat 100–150 °C on heavier sections and avoid welding hardened parts, which lose temper and can crack.
Can 17MnB4 be formed, bent or molded?
Excellent cold heading, thread rolling and extrusion in +AC/+AC+C with phosphate + soap or polymer lube; keep effective boron intact and avoid over-drawing before multi-blow heading.
What surface finishes work on 17MnB4?
No natural corrosion resistance — zinc electroplate (with bake-out against hydrogen embrittlement above 320 HV), zinc-flake, phosphate + oil or hot-dip galvanizing per ISO 4042/ISO 10683.
17MnB4 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 – 0.2 | 0.17 |
| SiSi ≤ 0.30 (low-Si for cold heading) | ≤ 0.3 | 0.15 |
| Mn | 0.9 – 1.2 | 1.05 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Beffective boron; requires N fixing by Al/Ti | 8×10⁻⁴ – 0.01 | 0 |
| Altotal Al, for nitrogen fixing / grain refinement | ≥ 0.02 | 0.04 |
| Tioptional, added to protect boron from nitrogen | ≤ 0.05 | 0.03 |
| Crresidual | ≤ 0.3 | 0.1 |
| Niresidual | ≤ 0.3 | 0.08 |
| Curesidual | ≤ 0.25 | 0.1 |
| Fe | balance | — |
17MnB4 +U+C — frequently asked
What is 17MnB4 +U+C used for?
17MnB4 +U+C is typically used for cold heading wire, bolts grade 8.8 and case-hardened fasteners. In short: best formability of the MnB group; most weldable boron fastener steel; low-cost hardenable wire rod.
What is the yield strength of 17MnB4 +U+C?
17MnB4 +U+C has a typical yield strength of 540 MPa (78.3 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 70% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is 17MnB4 +U+C easy to machine?
Reasonably — machinability is rated good (66/100, better than 95% of steel grades). Machine in the +AC or +AC+C condition (≈65 % of AISI 1212); gummy chips in soft anneal — use sharp positive-rake tools and good chip breakers, and finish-machine before hardening.
Can 17MnB4 +U+C be welded?
Yes — weldability is rated good (65/100). Weldable with CE_IIW ≈ 0.40–0.45 using low-hydrogen consumables; preheat 100–150 °C on heavier sections and avoid welding hardened parts, which lose temper and can crack.
What surface finishes work on 17MnB4 +U+C?
No natural corrosion resistance — zinc electroplate (with bake-out against hydrogen embrittlement above 320 HV), zinc-flake, phosphate + oil or hot-dip galvanizing per ISO 4042/ISO 10683.
Can 17MnB4 +U+C be formed, bent or molded?
Excellent cold heading, thread rolling and extrusion in +AC/+AC+C with phosphate + soap or polymer lube; keep effective boron intact and avoid over-drawing before multi-blow heading.
What is the maximum service temperature of 17MnB4 +U+C?
17MnB4 +U+C 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 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 — General technical delivery conditions (delivery states +U, +A, +AC, +C, +AC+C, +H) — CEN (2018)
- ISO 898-1 — Mechanical properties of fasteners, property classes 8.8/9.8/10.9 — 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, Jominy) — ASM International (1991)
- Cold-heading boron steel wire rod datasheets (17MnB4 / 20MnB4) — 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.