Steel 23MnB4 +U+C (Untreated, cold drawn)
Supply condition
EN 23MnB4
Cold-drawn from as-rolled rod for tight tolerance and bright finish where only light upsetting or straight machining follows.
Values for the +U+C condition
Other 23MnB4 tempers and conditions
23MnB4 is listed in 5 conditions; see the grade overview at 23MnB4.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Softest condition, spheroidized carbides for maximum cold-heading and deep-extrusion ability before drawing. | 320 | 480 | 24 | 145 HB | — |
Hot rolled | As-rolled coil or bar, the cheapest starting stock when the user will anneal or hot-form it themselves. | 380 | 570 | 20 | 170 HB | — |
+AC+CDefault Spheroidize annealed and cold drawn | The standard cold-heading wire condition: annealed then lightly drawn to size, phosphate-lubricated, ready for multi-station bolt formers. | 480 | 570 | 13 | 175 HB | — |
+U+CThis page Untreated, cold drawn | Cold-drawn from as-rolled rod for tight tolerance and bright finish where only light upsetting or straight machining follows. | 580 | 660 | 10 | 200 HB | — |
Hardened and tempered | Final condition of the formed part: oil/polymer quenched and tempered, using the boron hardenability to reach 800–1100 MPa in small sections. | 880 | 1,000 | 12 | 32 HRC | — |
What is 23MnB4 +U+C?
23MnB4 +U+C is 23MnB4 supplied in the +U+C condition — cold-drawn from as-rolled rod for tight tolerance and bright finish where only light upsetting or straight machining follows. 23MnB4 +U+C has a yield strength of 580 MPa (84.1 ksi) and a tensile strength of 660 MPa (95.7 ksi) — stronger than 75% of steel grades. Elongation at break is 10% and the elastic modulus is 207 GPa (30 Msi). 23MnB4 +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 — 65/100, better than 93% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 580 MPa (84.1 ksi), better than 75% 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
23MnB4 +U+C properties
Typical room-temperature values for 23MnB4 +U+C; 14 are specific to this condition. Other listed values are 23MnB4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
23MnB4 +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
23MnB4 +U+C has a yield strength of 580 MPa (84.1 ksi) and a tensile strength of 660 MPa (95.7 ksi) — stronger than 75% of steel grades. Elongation at break is 10% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
23MnB4 +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 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
23MnB4 +U+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 23MnB4 +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 30%.
Manufacturability7
23MnB4 +U+C's machinability is good (65/100, better than 93% of steel grades); weldability fair (45/100); formability good (55/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 23MnB4 +U+C
Is 23MnB4 easy to machine?
Machines like 1022/15B21 — free-cutting it is not; use sharp tools and good chip control in the annealed state, and expect ~45 % of 1212 rates once quenched and tempered.
Can 23MnB4 be welded?
Weldable with low-hydrogen consumables but boron plus CE ≈ 0.45–0.50 makes HAZ martensite likely; preheat 150–200 °C and post-weld temper, or avoid welding on hardened parts.
Can 23MnB4 be formed, bent or molded?
Designed for cold heading and extrusion in the +AC or +AC+C condition with zinc-phosphate + soap or polymer lubricant; keep reduction schedules moderate to avoid heading cracks.
What surface finishes work on 23MnB4?
No natural corrosion resistance — zinc electroplate (with 190–220 °C hydrogen bake above 1000 MPa), zinc-flake coating, or phosphate-and-oil are the usual finishes.
23MnB4 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 | 0.2 – 0.25 | 0.23 |
| 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 |
| Beffective boron; steel must be Al/Ti killed to protect it from N | 8×10⁻⁴ – 0.01 | 0 |
| Altotal Al, min for nitrogen fixing | ≥ 0.02 | 0.04 |
| Fe | balance | — |
23MnB4 +U+C — frequently asked
What is 23MnB4 +U+C used for?
23MnB4 +U+C is typically used for fasteners, bolts and cold heading wire. In short: most formable boron fastener steel; cold-heading grade, heat treatable; lower carbon than 27MnB4.
What is the yield strength of 23MnB4 +U+C?
23MnB4 +U+C has a typical yield strength of 580 MPa (84.1 ksi) and a tensile strength of 660 MPa (95.7 ksi) — stronger than 75% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is 23MnB4 +U+C easy to machine?
Reasonably — machinability is rated good (65/100, better than 93% of steel grades). Machines like 1022/15B21 — free-cutting it is not; use sharp tools and good chip control in the annealed state, and expect ~45 % of 1212 rates once quenched and tempered.
Can 23MnB4 +U+C be welded?
With care — weldability is rated fair (45/100). Weldable with low-hydrogen consumables but boron plus CE ≈ 0.45–0.50 makes HAZ martensite likely; preheat 150–200 °C and post-weld temper, or avoid welding on hardened parts.
What surface finishes work on 23MnB4 +U+C?
No natural corrosion resistance — zinc electroplate (with 190–220 °C hydrogen bake above 1000 MPa), zinc-flake coating, or phosphate-and-oil are the usual finishes.
Can 23MnB4 +U+C be formed, bent or molded?
Designed for cold heading and extrusion in the +AC or +AC+C condition with zinc-phosphate + soap or polymer lubricant; keep reduction schedules moderate to avoid heading cracks.
What is the maximum service temperature of 23MnB4 +U+C?
23MnB4 +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 10083-3 / ISO 4954 boron steel chemistry references — CEN / ISO (2006)
- ISO 898-1 Mechanical properties of fasteners — property classes 8.8 / 10.9 — ISO (2013)
- ASM Handbook Vol. 1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 14A: Metalworking — Bulk Forming (cold heading) — ASM International (2005)
- Cold heading wire rod grade datasheets (boron steels 19MnB4–37MnB5) — 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.