42CrMo4 steel (1.7225): properties, composition, equivalents
42CrMo4 (1.7225) is the Cr-Mo quenched-and-tempered steel of EN 10083-3: 900 MPa yield, 1100–1300 MPa tensile up to 16 mm. Composition, heat treatment, hardness, 4140/SCM440/42CrMo equivalents.
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What is 42CrMo4?
42CrMo4 is Europe's most-used alloy steel for quenched-and-tempered parts: 0.42 % C, 1 % Cr, 0.2 % Mo, Werkstoff number 1.7225, specified in EN 10083-3. The chromium–molybdenum combination gives deep hardenability — a 40 mm bar through-hardens in oil — and resistance to temper embrittlement, so the same bar can be tempered anywhere between 550 and 650 °C to hit a strength band from 900 to 1300 MPa.
It is the steel of crankshafts, gearbox shafts, high-strength bolts (10.9 and 12.9), hydraulic components and drilling tools. Machinability in the soft-annealed condition is fair; most parts are rough-machined at 240–300 HB in the pre-treated (+QT) condition and finished after nitriding or induction hardening.
42CrMo4 and AISI 4140 are the same steel for practical purposes, as are JIS SCM440, GB 42CrMo and BS 708M40; the cross-reference table below grades each match.
42CrMo4 chemical composition
| Element | Mass % | Note |
|---|---|---|
| C | 0.38 – 0.45 | |
| Si | ≤ 0.4 | |
| Mn | 0.6 – 0.9 | |
| P | ≤ 0.025 | |
| S | ≤ 0.035 | 42CrMoS4 (1.7227): S 0.020–0.040 for machinability |
| Cr | 0.9 – 1.2 | |
| Mo | 0.15 – 0.3 |
EN 10083-3:2006 Table 2. No Ni specified; V-modified 42CrMoV4 exists in some mill programmes (not in EN 10083-3).
42CrMo4 mechanical properties
| Thickness / condition | Yield strength ReH / Rp0.2 MPa (ksi) | Tensile strength Rm MPa (ksi) | Elongation A % | Hardness |
|---|---|---|---|---|
| +QT, ≤ 16 mm | 900 (130.5) | 1100–1300 (159.5–188.5) | 10 | ≈ 330–380 HB |
| +QT, 16–40 mm | 750 (108.8) | 1000–1200 (145.0–174.0) | 11 | ≈ 300–350 HB |
| +QT, 40–100 mm | 650 (94.3) | 900–1100 (130.5–159.5) | 12 | ≈ 270–320 HB |
| +QT, 100–160 mm | 550 (79.8) | 800–950 (116.0–137.8) | 13 | ≈ 240–290 HB |
| +QT, 160–250 mm | 500 (72.5) | 750–900 (108.8–130.5) | 14 | ≈ 225–270 HB |
| +A soft annealed | — | ≤ 800 (typ. 650) (≤ 116.0 (typ. 94.3)) | — | ≤ 241 HB |
| +N normalized (typical) | 500 (72.5) | 800–900 (116.0–130.5) | 14 | ≈ 240–270 HB |
EN 10083-3 Table 8 (+QT). Impact: ≥ 35 J (≤ 16 mm) to ≥ 40 J (≥ 40 mm) longitudinal at +20 °C in the Q&T condition. Normalized values are typical, not standardized.
Impact toughness
42CrMo4 requires a minimum Charpy V-notch energy of 35 J at 20 °C (+QT, ≤ 16 mm, longitudinal; ≥ 40 J for 40–250 mm). Charpy energy rises with section because the tempering temperature is higher for the same strength band.
42CrMo4 equivalent grades
| Grade | System | Match | Why / differences |
|---|---|---|---|
| 4140 | AISI / SAE | Identical | AISI 4140 (UNS G41400): C 0.38–0.43, Cr 0.80–1.10, Mo 0.15–0.25, Mn 0.75–1.00. Windows overlap almost completely; mills dual-certify 42CrMo4/4140. |
| 708M40 | BS (superseded British) | Identical | BS 970 708M40: C 0.36–0.44, Cr 0.90–1.20, Mo 0.15–0.25. |
| 42CrMo | GB/T (China) | Identical | GB/T 3077 42CrMo: C 0.38–0.45, Cr 0.90–1.20, Mo 0.15–0.25. |
| SCM440 | JIS (Japan) | Identical | JIS G4053 SCM440: C 0.38–0.43, Cr 0.90–1.20, Mo 0.15–0.30 — matches 42CrMo4 exactly on Cr and Mo. |
| 4140 | AISI / SAE | Near | C 0.40–0.45 — covers the upper half of the 42CrMo4 carbon range. |
| 42CrMoS4 | EN (European) | Near | Same grade with controlled S (0.020–0.040 %) for free machining; slightly lower transverse toughness. |
| 40KhM / 38KhM | GOST (Russia/CIS) | Near | GOST 4543 38KhM (C 0.35–0.42, Cr 0.90–1.30, Mo 0.20–0.30); 40KhM is the nearer Russian practice grade. |
| 080M40 | BS (superseded British) | Functional | The alloy step up, equivalent to 709M40 (EN19). Substitute where hardenability in sections above about 60 mm or genuine toughness is required — 080M40 cannot deliver either. |
| 34CrNiMo6 | EN (European) | Functional | Ni-bearing alternative with deeper hardenability for sections above ~100 mm. |
| C45 | EN (European) | Functional | Unalloyed, cheaper, but through-hardens only in thin sections. |
Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for 42CrMo4 →
Old and superseded designations
| Old name | Standard | Note |
|---|---|---|
| 42CrMo4 (1.7225) | DIN 17200 (withdrawn) | Name and number unchanged since DIN 17200; only the standard moved to EN 10083-3. |
| 708M40 / 708A42 | BS 970 | |
| 42CD4 | NF A 35-552 | |
| 42CrMo4 | UNI 7845 |
Product forms and tolerance standards
Product forms: round bar (hot-rolled, peeled, ground), square and flat bar, forgings and forged blanks, seamless tube (EN 10297, EN 10305), plate (limited, via EN 10083-3 or proprietary).
Dimensional tolerances: hot-rolled round: EN 10060; peeled/ground bar: EN 10278 (h9–h11); forgings: EN 10250-3.
Key property values
42CrMo4 yield strength
In the Q&T condition Rp0.2 is ≥ 900 MPa (130 ksi) ≤ 16 mm, 750 MPa 16–40 mm, 650 MPa 40–100 mm, 550 MPa 100–160 mm and 500 MPa 160–250 mm.
42CrMo4 tensile strength
1100–1300 MPa (≤ 16 mm), 1000–1200 MPa (16–40 mm), 900–1100 MPa (40–100 mm), 800–950 MPa (100–160 mm), 750–900 MPa (160–250 mm).
42CrMo4 hardness
Soft-annealed max 241 HB; Q&T typically 270–350 HB depending on section; as-quenched 54–58 HRC; induction-hardened surface 52–56 HRC; gas-nitrided surface 600–700 HV at 0.3–0.5 mm depth.
Heat treatment
Soft anneal 680–720 °C; normalize 850–880 °C; harden 820–860 °C oil (water only for simple shapes); temper 540–680 °C; stress relieve 550–650 °C. Ac1 ≈ 745 °C, Ac3 ≈ 790 °C, Ms ≈ 310 °C. Ideal critical diameter ≈ 60–80 mm.
Physical properties
Density 7.83 g/cm³, E = 210 GPa, thermal conductivity ≈ 42 W/m·K, expansion 12.1 × 10⁻⁶/K (20–100 °C).
Weldability
Poor weldability: CEV ≈ 0.80 %. Welding is only done on annealed or normalized material with preheat 250–350 °C, low-hydrogen consumables (EN ISO 18276 / Cr-Mo types), interpass control and immediate post-weld tempering at 550–650 °C. Q&T parts should not be welded; design for mechanical joints.
Machining, forming and heat treatment
Machinability index ≈ 50–55 % in the annealed state; 42CrMoS4 improves it to ≈ 60–65 %. Machine at 250–300 HB (pre-treated) with carbide; grinding after hardening. Cold forming limited; hot forging 1100–850 °C then anneal. Surface treatments: induction hardening, gas or plasma nitriding (excellent response), QPQ salt-bath nitrocarburizing.
Typical applications
- Crankshafts, camshafts, gearbox and pump shafts
- High-strength fasteners: property classes 10.9 and 12.9 (EN ISO 898-1)
- Hydraulic cylinder rods and pistons (induction-hardened, chrome-plated)
- Gears and pinions (nitrided or induction-hardened teeth)
- Drill collars, tool joints and downhole equipment (API 7-1 grades)
- Injection-mould frames and machine columns
- Automotive: steering knuckles, axle shafts, connecting rods
42CrMo4 compared with related grades
Frequently asked questions
Is 42CrMo4 the same as 4140?
Yes for practical purposes. AISI 4140 spans C 0.38–0.43, Cr 0.80–1.10, Mo 0.15–0.25; 42CrMo4 spans C 0.38–0.45, Cr 0.90–1.20, Mo 0.15–0.30. Most European bar is dual-certified 42CrMo4 / 4140 / SCM440.
What hardness can 42CrMo4 reach?
As-quenched 54–58 HRC; tempered to a working strength of 1000–1200 MPa it sits at about 300–350 HB (32–38 HRC). Nitriding adds a 600–700 HV case; induction hardening gives 52–56 HRC on the surface.
What is 42CrMo4+QT?
+QT is the quenched-and-tempered delivery condition — the bar is already heat-treated to the EN 10083-3 strength table for its diameter and can be machined and used without further treatment. +A is soft-annealed for machining before the customer heat-treats.
Can 42CrMo4 be welded?
Only in the annealed/normalized state with 250–350 °C preheat and post-weld tempering. Welding Q&T bar destroys the properties in the heat-affected zone and risks cold cracking.
What is the difference between 42CrMo4 and 34CrNiMo6?
34CrNiMo6 (1.6582) adds 1.5 % Ni, which pushes hardenability to sections of 150–250 mm and improves toughness at the same strength. Use it for large shafts and forgings; 42CrMo4 is the economical choice below ~100 mm.
Related grades
Verified against EN 10083-3:2006; EN 10083-3:2006 Tables 2, 8 and 9; EN 10083-1:2006. Last checked: September 2026.