Steel 37Cr4 +AC (Spheroidize annealed)
Heat-treated state
EN 37Cr4
Choose for cold heading, cold extrusion of fasteners and for the best drill/tap behaviour before hardening.
Values for the +AC condition
Other 37Cr4 tempers and conditions
37Cr4 is listed in 10 conditions; see the grade overview at 37Cr4.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
+ACThis page Spheroidize annealed | Choose for cold heading, cold extrusion of fasteners and for the best drill/tap behaviour before hardening. | 350 | 580 | 25 | 180 HB | — |
Annealed | Softest supply condition for heavy machining or as a pre-condition before hardening. | 380 | 620 | 22 | 200 HB | — |
Treated to ferrite-pearlite structure and hardness range | Ordered when a specified machining hardness band with a controlled F/P microstructure is needed for automatic machining lines. | 400 | 660 | 20 | 14 HRC | 8 % IACS |
Normalized | Uniform fine ferrite-pearlite structure for stock removal, forging clean-up and stress relief before final Q&T. | 420 | 700 | 19 | 210 HB | — |
+QT | Heavier bar/forging class; reduced core strength because 37Cr4 hardenability limits full martensite above ~40 mm. | 450 | 720 | 19 | 18 HRC | — |
+QTDefault Quenched and tempered | Standard stocked condition: balanced strength and toughness for shafts, connecting rods and highly loaded machine parts. | 520 | 780 | 17 | 22 HRC | — |
Induction hardened | Pick when a wear-resistant 50–56 HRC surface and compressive residual stress are needed over a tough Q&T core (journals, splines, cams). | 540 | 800 | 15 | 53 HRC | — |
Cold drawn | Bright cold-drawn bar with close tolerance and higher as-supplied strength for shafts machined without further heat treatment. | 620 | 760 | 10 | 230 HB | — |
+QT | Highest EN 10083-3 property class for small-diameter bar, pins and bolts where full through-hardening is achieved. | 700 | 920 | 15 | 29 HRC | — |
Specified hardenability band / hardened | Order +H when the Jominy hardenability band must be guaranteed; as-quenched (830–870 °C, oil) it reaches full martensitic hardness and must be tempered before service. | 1,400 | 1,800 | 3 | 54 HRC | — |
What is 37Cr4 +AC?
37Cr4 +AC is 37Cr4 heat treated to +AC — choose for cold heading, cold extrusion of fasteners and for the best drill/tap behaviour before hardening. 37Cr4 +AC has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 74% of steel grades. Elongation at break is 25% and the elastic modulus is 210 GPa (30.5 Msi). 37Cr4 +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). +QT is the default condition FabDigit quotes; +AC is available on request or by drawing note.
Advantages
- Easy to machine — 66/100, better than 95% of steel grades
- Forms and bends easily — 62/100, better than 78% of steel grades
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
37Cr4 +AC properties
Typical room-temperature values for 37Cr4 +AC; 14 are specific to this condition. Other listed values are 37Cr4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
37Cr4 +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).
Mechanical16
37Cr4 +AC has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 74% of steel grades. Elongation at break is 25% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
37Cr4 +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 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
37Cr4 +AC conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 37Cr4 +AC takes about 28 MJ of energy and emits 2 kg of CO₂ — less than 56% of steel grades. Typical recycled content is 25%.
Manufacturability8
37Cr4 +AC's machinability is good (66/100, better than 95% of steel grades); weldability fair (42/100); formability good (62/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 37Cr4 +AC
Is 37Cr4 easy to machine?
Machine in +A/+AC or +FP condition (≈60–70% of 1212); in +QT at 235 HB use coated carbide, moderate speed and rigid setup, finish-grind after hardening.
Can 37Cr4 be welded?
CE ≈ 0.65–0.70 — preheat 200–300 °C, low-hydrogen consumables, and temper/stress-relieve at 550–650 °C after welding; avoid welding in the hardened condition.
Can 37Cr4 be formed, bent or molded?
Hot forge 1100–850 °C then normalize; cold heading only in the spheroidized +AC condition, bending in +QT is limited to large radii.
What surface finishes work on 37Cr4?
Not corrosion resistant — protect with phosphate + oil, black oxide, zinc/zinc-nickel plating, hard chrome, or nitriding for wear; grind and polish easily to Ra < 0.4 µm.
37Cr4 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 | 0.34 – 0.41 | 0.37 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| Cr | 0.9 – 1.2 | 1.05 |
| Pmax per EN 10083-3 | ≤ 0.03 | 0.02 |
| S0.020–0.040 for +S free-machining variants | ≤ 0.04 | 0.02 |
| Fe | balance | — |
37Cr4 +AC — frequently asked
What is 37Cr4 +AC used for?
37Cr4 +AC is typically used for shafts, gears and axles. In short: higher-carbon 34Cr4 upgrade; Q&T automotive shaft steel; takes induction hardening.
What is the yield strength of 37Cr4 +AC?
37Cr4 +AC has a typical yield strength of 350 MPa (50.8 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 74% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 37Cr4 +AC easy to machine?
Reasonably — machinability is rated good (66/100, better than 95% of steel grades). Machine in +A/+AC or +FP condition (≈60–70% of 1212); in +QT at 235 HB use coated carbide, moderate speed and rigid setup, finish-grind after hardening.
Can 37Cr4 +AC be welded?
With care — weldability is rated fair (42/100). CE ≈ 0.65–0.70 — preheat 200–300 °C, low-hydrogen consumables, and temper/stress-relieve at 550–650 °C after welding; avoid welding in the hardened condition.
What surface finishes work on 37Cr4 +AC?
Not corrosion resistant — protect with phosphate + oil, black oxide, zinc/zinc-nickel plating, hard chrome, or nitriding for wear; grind and polish easily to Ra < 0.4 µm.
Can 37Cr4 +AC be formed, bent or molded?
Hot forge 1100–850 °C then normalize; cold heading only in the spheroidized +AC condition, bending in +QT is limited to large radii.
What is the maximum service temperature of 37Cr4 +AC?
37Cr4 +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.
What is the difference between 37Cr4 +QT and 37Cr4-IH?
+QT is the default condition — standard stocked condition: balanced strength and toughness for shafts, connecting rods and highly loaded machine parts. IH: pick when a wear-resistant 50–56 HRC surface and compressive residual stress are needed over a tough Q&T core (journals, splines, cams). Yield strength is 520 MPa in +QT versus 540 MPa in IH.
Sources
- EN 10083-3 Steels for quenching and tempering — Alloy steels — CEN (2006)
- EN 10277 Bright steel products — technical delivery conditions — CEN (2018)
- GB/T 3077 (35Cr equivalent) — SAC (2015)
- ASM Handbook Vol.1 Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 Fatigue and Fracture — ASM International (1996)
- Chromium quenched and tempered steel 1.7034 data sheet — European long-products mill (typical) (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.