Steel 33B2 +AC (Spheroidize annealed)
Heat-treated state
EN 33B2
Pick for the softest, most ductile state before multi-station cold heading or deep cold extrusion of larger parts.
Values for the +AC condition
Other 33B2 tempers and conditions
33B2 is listed in 8 conditions; see the grade overview at 33B2.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
+ACThis page Spheroidize annealed | Pick for the softest, most ductile state before multi-station cold heading or deep cold extrusion of larger parts. | 320 | 510 | 24 | 150 HB | — |
Annealed | General soft condition for machining or moderate cold forming when full spheroidizing is not specified. | 340 | 550 | 22 | 160 HB | — |
Hot rolled | Cheapest mill condition; feedstock for further annealing or for hot forging, not for severe cold heading. | 390 | 640 | 20 | 190 HB | — |
+AC+CDefault Spheroidize annealed and cold drawn | Standard stocked cold-heading wire: sized, straight, phosphate/soap coated and soft enough to head, then quench-tempered as a finished part. | 520 | 620 | 12 | 180 HB | — |
Cold drawn | Use where dimensional accuracy and higher as-delivered strength matter more than heading ductility (turned parts, light upsetting). | 580 | 680 | 10 | 200 HB | — |
+QT | The workhorse condition for headed M5–M16 bolts and screws: quench from ~870 °C, temper ~500–550 °C. | 720 | 880 | 14 | 29 HRC | — |
+QT | High-strength option for small-diameter boron-steel fasteners (temper ~420–470 °C); watch hydrogen embrittlement after electroplating and limit section size. | 960 | 1,080 | 10 | 35 HRC | — |
Hardenability-controlled quality, hardened | Order +H when the Jominy band must be guaranteed; the as-quenched (water/oil from 860–890 °C) martensite reaches ~50 HRC and must be tempered before use. | 1,300 | 1,650 | 4 | 50 HRC | — |
What is 33B2 +AC?
33B2 +AC is 33B2 heat treated to +AC — pick for the softest, most ductile state before multi-station cold heading or deep cold extrusion of larger parts. 33B2 +AC has a yield strength of 320 MPa (46.4 ksi) and a tensile strength of 510 MPa (74 ksi) — weaker than 81% of steel grades. Elongation at break is 24% and the elastic modulus is 210 GPa (30.5 Msi). 33B2 +AC 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; +AC is available on request or by drawing note.
Advantages
- Forms and bends easily — 90/100, better than 98% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Low strength — 320 MPa (46.4 ksi), worse than 81% of steel grades
33B2 +AC properties
Typical room-temperature values for 33B2 +AC; 15 are specific to this condition. Other listed values are 33B2 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
33B2 +AC 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
33B2 +AC has a yield strength of 320 MPa (46.4 ksi) and a tensile strength of 510 MPa (74 ksi) — weaker than 81% of steel grades. Elongation at break is 24% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
33B2 +AC is rated for continuous service to 400°C (752 °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
33B2 +AC 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 33B2 +AC takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability6
33B2 +AC's machinability is good (60/100, better than 83% of steel grades); weldability fair (45/100); formability excellent (90/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 33B2 +AC
Is 33B2 easy to machine?
Machines like 1035 in the +AC/+AC+C states (≈65 % of 1212); it is low-sulphur so use sharp positive tooling and good chip control, and expect a drop to ~40–50 % after quench-tempering.
Can 33B2 be welded?
Weldable with care but boron plus 0.33 %C gives a hard, crack-prone HAZ — use low-hydrogen consumables, 150–250 °C preheat and post-weld temper; welding after Q&T destroys the fastener properties.
Can 33B2 be formed, bent or molded?
Designed for cold heading and cold extrusion in the spheroidize-annealed condition with phosphate+soap or polymer lubricant; upset ratios of 2.5–3 diameters are routine, and inter-stage annealing is rarely needed.
What surface finishes work on 33B2?
No inherent corrosion resistance: zinc electroplate (with 190–220 °C bake within 4 h for ≥1000 MPa parts), zinc-flake (Dacromet/Geomet), zinc-nickel or manganese phosphate + oil are the usual protective systems.
33B2 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 |
|---|---|---|
| Cgrade-defining carbon level | 0.3 – 0.36 | 0.33 |
| Sikept low for cold heading | ≤ 0.3 | 0.15 |
| Mn | 0.5 – 0.8 | 0.65 |
| P | ≤ 0.03 | 0.02 |
| Smax; low-S for cold formability | ≤ 0.03 | 0.01 |
| Beffective (soluble) boron gives the hardenability boost | 8×10⁻⁴ – 0.01 | 0 |
| Altotal Al (or Ti) to fix nitrogen and protect the boron effect | ≥ 0.02 | 0.03 |
| Curesidual, max | ≤ 0.25 | 0.1 |
| Crresidual, max | ≤ 0.3 | 0.1 |
| Niresidual, max | ≤ 0.3 | 0.08 |
| Fe | balance | — |
33B2 +AC — frequently asked
What is 33B2 +AC used for?
33B2 +AC is typically used for bolts, cold-headed fasteners and automotive hardware. In short: low-cost boron hardenability; cold-heading fastener steel; cheaper than 41Cr4.
What is the yield strength of 33B2 +AC?
33B2 +AC has a typical yield strength of 320 MPa (46.4 ksi) and a tensile strength of 510 MPa (74 ksi) — weaker than 81% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 33B2 +AC easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Machines like 1035 in the +AC/+AC+C states (≈65 % of 1212); it is low-sulphur so use sharp positive tooling and good chip control, and expect a drop to ~40–50 % after quench-tempering.
Can 33B2 +AC be welded?
With care — weldability is rated fair (45/100). Weldable with care but boron plus 0.33 %C gives a hard, crack-prone HAZ — use low-hydrogen consumables, 150–250 °C preheat and post-weld temper; welding after Q&T destroys the fastener properties.
What surface finishes work on 33B2 +AC?
No inherent corrosion resistance: zinc electroplate (with 190–220 °C bake within 4 h for ≥1000 MPa parts), zinc-flake (Dacromet/Geomet), zinc-nickel or manganese phosphate + oil are the usual protective systems.
Can 33B2 +AC be formed, bent or molded?
Designed for cold heading and cold extrusion in the spheroidize-annealed condition with phosphate+soap or polymer lubricant; upset ratios of 2.5–3 diameters are routine, and inter-stage annealing is rarely needed.
What is the maximum service temperature of 33B2 +AC?
33B2 +AC is rated for continuous use to about 400°C (752 °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)
- EN 10263-1 — General technical delivery conditions (delivery states +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 (boron steels, carbon steel physical data) — ASM International (1990)
- ASM Handbook Vol. 4 — Heat Treating (hardenability of boron steels, Jominy behaviour) — ASM International (1991)
- Cold-heading quality boron steel wire rod datasheets (ovako / Saarstahl / Ø CHQ wire producers) — various steel 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.