Steel 38B2 +AC (Spheroidize annealed)
Heat-treated state
EN 38B2
Choose for maximum cold-heading and thread-rolling ductility, and as the pre-condition before cold drawing.
Values for the +AC condition
Other 38B2 tempers and conditions
38B2 is listed in 10 conditions; see the grade overview at 38B2.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
+ACThis page Spheroidize annealed | Choose for maximum cold-heading and thread-rolling ductility, and as the pre-condition before cold drawing. | 310 | 520 | 26 | 155 HB | — |
Annealed | General softening treatment for machining or light forming when full carbide spheroidizing is not required. | 330 | 560 | 23 | 165 HB | 8.8 % IACS |
Hot rolled | Mill-delivery hot-rolled coil before any softening; cheapest input for re-heating, forging or subsequent annealing. | 380 | 640 | 19 | 190 HB | 8.5 % IACS |
Normalized | Grain refinement after forging or hot forming, giving uniform ferrite-pearlite before hardening. | 400 | 660 | 19 | 195 HB | 8.5 % IACS |
+AC+CDefault Spheroidize annealed and cold drawn | The standard stocked cold-heading wire condition: sized, straight, lubricant-carrier coated and ready for multi-station header feeding. | 540 | 640 | 12 | 195 HB | — |
+QT | High-temperature temper (600–650 °C) for shafts, pins and machine parts where impact toughness matters more than strength. | 560 | 750 | 18 | 20 HRC | — |
Cold drawn | Sized cold-drawn bar/wire for machined parts and light upsetting where full spheroidized ductility is not needed. | 620 | 720 | 9 | 215 HB | 8.3 % IACS |
+QT | Standard fastener heat treatment for M5–M16 class 8.8 bolts and screws; good toughness with low plating-embrittlement risk. | 720 | 880 | 14 | 27 HRC | — |
+QT | High-strength fastener condition (lower tempering temperature); watch hydrogen embrittlement during electroplating — use zinc-flake coatings. | 990 | 1,100 | 11 | 35 HRC | — |
Hardened | As-quenched martensitic condition used to verify boron hardenability (Jominy) — must be tempered before service. | 1,400 | 1,900 | 3 | 54 HRC | — |
What is 38B2 +AC?
38B2 +AC is 38B2 heat treated to +AC — choose for maximum cold-heading and thread-rolling ductility, and as the pre-condition before cold drawing. 38B2 +AC has a yield strength of 310 MPa (45 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 83% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi). 38B2 +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 — 88/100, better than 98% of steel grades
- Ductile — tolerates forming and impact — 26%, better than 82% of steel grades
Limitations
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
- Low strength — 310 MPa (45 ksi), worse than 83% of steel grades
38B2 +AC properties
Typical room-temperature values for 38B2 +AC; 12 are specific to this condition. Other listed values are 38B2 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
38B2 +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).
Mechanical13
38B2 +AC has a yield strength of 310 MPa (45 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 83% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
38B2 +AC is rated for continuous service to 250°C (482 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
38B2 +AC conducts electricity at 8.5 % IACS, better than 63% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 38B2 +AC takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
38B2 +AC's machinability is good (58/100, better than 75% of steel grades); weldability fair (42/100); formability excellent (88/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 38B2 +AC
Is 38B2 easy to machine?
Machine in +AC or +A condition (≈62–68 % of 1212); after Q&T above 32 HRC use coated carbide, rigid setups and reduced feeds — sulphur is low so chips are stringy.
Can 38B2 be welded?
CE ≈ 0.5–0.55: preheat 200–250 °C, use low-hydrogen consumables and temper after welding; boron aggravates HAZ hardening, so welding of hardened parts is not recommended.
Can 38B2 be formed, bent or molded?
Excellent multi-station cold heading and thread rolling in +AC/+AC+C with phosphate+soap or polymer carrier; hot forging 1100–1200 °C, austenitize 850–880 °C, oil or polymer quench, temper 400–650 °C to the target class.
What surface finishes work on 38B2?
No natural corrosion resistance — zinc or zinc-nickel electroplate (bake 200 °C/4 h if ≥320 HV), zinc-flake (Dacromet/Geomet) for 10.9 parts, or phosphate + oil for as-headed blanks.
38B2 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 | 0.36 – 0.42 | 0.39 |
| Silow Si preferred for cold heading | ≤ 0.3 | 0.15 |
| Mn | 0.5 – 0.8 | 0.65 |
| P | ≤ 0.03 | 0.02 |
| Sup to 0.035 in some Q&T bar specifications | ≤ 0.03 | 0.01 |
| Crresidual | ≤ 0.3 | 0.15 |
| Niresidual | ≤ 0.3 | 0.1 |
| Moresidual | ≤ 0.1 | 0.03 |
| Curesidual | ≤ 0.25 | 0.1 |
| Beffective (soluble) boron controls hardenability | 8×10⁻⁴ – 0.01 | 0 |
| Tiadded to fix nitrogen and protect boron | ≤ 0.05 | 0.03 |
| Algrain refining / N fixing | 0.02 – 0.06 | 0.03 |
| Fe | balance | — |
38B2 +AC — frequently asked
What is 38B2 +AC used for?
38B2 +AC is typically used for high-strength bolts, cold-headed parts and shafts. In short: higher strength than 33B2; boron-hardenable fastener steel; preheat before welding.
What is the yield strength of 38B2 +AC?
38B2 +AC has a typical yield strength of 310 MPa (45 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 83% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 38B2 +AC easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machine in +AC or +A condition (≈62–68 % of 1212); after Q&T above 32 HRC use coated carbide, rigid setups and reduced feeds — sulphur is low so chips are stringy.
Can 38B2 +AC be welded?
With care — weldability is rated fair (42/100). CE ≈ 0.5–0.55: preheat 200–250 °C, use low-hydrogen consumables and temper after welding; boron aggravates HAZ hardening, so welding of hardened parts is not recommended.
What surface finishes work on 38B2 +AC?
No natural corrosion resistance — zinc or zinc-nickel electroplate (bake 200 °C/4 h if ≥320 HV), zinc-flake (Dacromet/Geomet) for 10.9 parts, or phosphate + oil for as-headed blanks.
Can 38B2 +AC be formed, bent or molded?
Excellent multi-station cold heading and thread rolling in +AC/+AC+C with phosphate+soap or polymer carrier; hot forging 1100–1200 °C, austenitize 850–880 °C, oil or polymer quench, temper 400–650 °C to the target class.
What is the maximum service temperature of 38B2 +AC?
38B2 +AC 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: Quench and tempered steels — CEN (2018)
- EN 10083-3 Steels for quenching and tempering — Alloy steels — CEN (2006)
- 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. 4: Heat Treating (boron hardenability) — ASM International (1991)
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.