Steel 32CrB4 +AC (Spheroidize annealed)
Heat-treated state
EN 32CrB4
Pick when maximum cold-heading/upsetting formability is needed and the drawer will size the material in-house.
Values for the +AC condition
Other 32CrB4 tempers and conditions
32CrB4 is listed in 8 conditions; see the grade overview at 32CrB4.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
+ACThis page Spheroidize annealed | Pick when maximum cold-heading/upsetting formability is needed and the drawer will size the material in-house. | 370 | 570 | 20 | 167 HB | — |
Annealed | General soft delivery condition for bar to be machined or hot-formed before hardening; cheaper than spheroidizing but less headable. | 390 | 600 | 18 | 180 HB | — |
Supplied with specified (narrow) hardenability band, untreated/as-rolled | Order this when the fastener or part maker must guarantee end-quench (Jominy) hardness after their own quench and temper; delivery is as-rolled with a Jominy band, not hardened bar stock. | 450 | 700 | 15 | 18 HRC | — |
+AC+CDefault Spheroidized (soft) annealed and cold drawn | Standard cold-heading wire/bar condition: spheroidal carbides plus a light draw for size, tolerance and straightness before header/bolt-forming. | 540 | 640 | 12 | 190 HB | — |
Cold drawn | Cold-drawn bar/wire for machined parts and light upsetting where tight tolerance and straightness matter more than maximum headability. | 660 | 760 | 8 | 21 HRC | — |
Quenched and tempered to ~900 MPa | High-tempering condition (≈560–620 °C) for shafts, pins and class 8.8 fasteners where toughness and delayed-fracture safety outrank peak strength. | 750 | 900 | 14 | 28 HRC | — |
+QT | The volume condition for 32CrB4: oil/polymer quench from ~860 °C, temper ≈425–500 °C, for ISO 898-1 property class 10.9 bolts and screws. | 990 | 1,100 | 11 | 35 HRC | — |
+QT | Highest strength condition (temper ≈380–420 °C) for class 12.9 socket screws; use only with strict hydrogen and notch control because delayed-fracture risk rises sharply. | 1,150 | 1,280 | 9 | 41 HRC | — |
What is 32CrB4 +AC?
32CrB4 +AC is 32CrB4 heat treated to +AC — pick when maximum cold-heading/upsetting formability is needed and the drawer will size the material in-house. 32CrB4 +AC has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 570 MPa (82.7 ksi) — weaker than 70% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi). 32CrB4 +AC 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). +AC+C is the default condition FabDigit quotes; +AC is available on request or by drawing note.
Advantages
- Forms and bends easily — 80/100, better than 93% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
32CrB4 +AC properties
Typical room-temperature values for 32CrB4 +AC; 15 are specific to this condition. Other listed values are 32CrB4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
32CrB4 +AC 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).
Mechanical15
32CrB4 +AC has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 570 MPa (82.7 ksi) — weaker than 70% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
32CrB4 +AC is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
32CrB4 +AC conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 32CrB4 +AC takes about 26 MJ of energy and emits 1.9 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 30%.
Manufacturability7
32CrB4 +AC's machinability is good (58/100, better than 75% of steel grades); weldability fair (38/100); formability very good (80/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 32CrB4 +AC
Is 32CrB4 easy to machine?
Machine in +AC/+A/+C condition (≈60 % of AISI 1212) with carbide inserts; after Q&T above 32 HRC expect reduced tool life and prefer grinding or hard turning for finish features.
Can 32CrB4 be welded?
Poor weldability — CE ≈ 0.55–0.65: preheat 200–300 °C, low-hydrogen consumables and post-weld temper are mandatory, and any weld destroys the fastener's Q&T properties, so it is normally not welded.
Can 32CrB4 be formed, bent or molded?
Cold heading/upsetting and thread rolling are done in the +AC or +AC+C condition; keep drawing reductions moderate and phosphate/lubricate wire, then quench from 850–870 °C and temper to the required class.
What surface finishes work on 32CrB4?
No natural corrosion resistance: zinc or Zn-Ni electroplate, zinc-flake (Dacromet/Geomet), phosphate + oil, or hot-dip coat; for parts ≥1000 MPa bake within 4 h of plating to relieve hydrogen and avoid delayed fracture.
32CrB4 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 |
|---|---|---|
| CEN 10263-4 / EN 10083-3 range | 0.3 – 0.34 | 0.32 |
| Si | ≤ 0.3 | 0.2 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | 0.02 |
| Smax; lower for cold-heading quality | ≤ 0.03 | 0.01 |
| Cr | 0.9 – 1.2 | 1.05 |
| Bhardenability booster; needs Ti/Al to fix free N | 8×10⁻⁴ – 0.01 | 0 |
| Tiusual practice to protect the boron effect (not always specified) | ≤ 0.05 | 0.03 |
| Fe | balance | — |
32CrB4 +AC — frequently asked
What is 32CrB4 +AC used for?
32CrB4 +AC is typically used for high-strength bolts, fasteners and small shafts. In short: boron hardenability at low cost; cold-heading fastener steel; poor weldability.
What is the yield strength of 32CrB4 +AC?
32CrB4 +AC has a typical yield strength of 370 MPa (53.7 ksi) and a tensile strength of 570 MPa (82.7 ksi) — weaker than 70% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 32CrB4 +AC easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machine in +AC/+A/+C condition (≈60 % of AISI 1212) with carbide inserts; after Q&T above 32 HRC expect reduced tool life and prefer grinding or hard turning for finish features.
Can 32CrB4 +AC be welded?
With care — weldability is rated fair (38/100). Poor weldability — CE ≈ 0.55–0.65: preheat 200–300 °C, low-hydrogen consumables and post-weld temper are mandatory, and any weld destroys the fastener's Q&T properties, so it is normally not welded.
What surface finishes work on 32CrB4 +AC?
No natural corrosion resistance: zinc or Zn-Ni electroplate, zinc-flake (Dacromet/Geomet), phosphate + oil, or hot-dip coat; for parts ≥1000 MPa bake within 4 h of plating to relieve hydrogen and avoid delayed fracture.
Can 32CrB4 +AC be formed, bent or molded?
Cold heading/upsetting and thread rolling are done in the +AC or +AC+C condition; keep drawing reductions moderate and phosphate/lubricate wire, then quench from 850–870 °C and temper to the required class.
What is the maximum service temperature of 32CrB4 +AC?
32CrB4 +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 10083-3 — Steels for quenching and tempering: alloy steels — CEN (2006)
- ISO 898-1 — Mechanical properties of fasteners: bolts, screws and studs — ISO (2013)
- GB/T 6478 / GB/T 3077 — SAC (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals (boron hardenability) — ASM International (2013)
- Cold-heading quality boron-chromium wire datasheets (32CrB4 / 1.7076) — European & Chinese special-steel wire 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.