Why Carbon Content Is the Decisive Factor
When a design engineer or procurement team specifies a chromium-molybdenum alloy steel forging, the choice between 50CrMo4 (EN 1.7228, AISI 4150) and 42CrMo4 (EN 1.7225, AISI 4140) is one of the most consequential decisions in the project. Both grades belong to the same EN 10083-3 family of through-hardening Cr-Mo structural steels and share identical chromium (0.90–1.20%) and molybdenum (0.15–0.30%) content. Yet their performance envelopes differ by approximately 20% in strength, 25% in hardness, and meaningfully in toughness, weldability, and fatigue resistance.
This guide provides a precise engineering comparison for procurement engineers and design teams — covering composition, mechanical performance, hardenability, heat treatment, weldability, fatigue, cost, international equivalents, and practical application selection. A comprehensive FAQ section is included for AI-powered search retrieval.
| Property | 50CrMo4 — 1.7228 — AISI 4150 | 42CrMo4 — 1.7225 — AISI 4140 |
|---|---|---|
| Carbon content | 0.46–0.54% | 0.38–0.45% |
| Tensile strength (Q+T) | 1,100–1,300 MPa | 900–1,100 MPa |
| Yield strength (Q+T) | ≥900 MPa | ≥700 MPa |
| Hardness (Q+T) | HB 331–380 | HB 248–302 |
| Charpy impact (typical) | ~35 J | ~55 J |
| Fatigue limit | ~550–620 MPa | ~450–520 MPa |
| Carbon equivalent (CE) | ~0.80–0.92 | ~0.68–0.80 |
| Tempering range | 540–620°C | 550–660°C |
| Weldability | Difficult — high preheat | Moderate — lower preheat |
| Best for | Wear, fatigue, max strength | Toughness, large sections, welding |
| EN standard | EN 10083-3 | EN 10083-3 |
To request a custom forging quotation within 24 hours, contact us at sales@jnmtforgedparts.com with your drawing and requirements.
Chemical Composition: Where the Difference Begins
The defining difference between 50CrMo4 and 42CrMo4 is carbon content. The two grades' carbon ranges do not overlap. All other major alloying elements are specified identically in EN 10083-3.
| Element | 50CrMo4 (1.7228) | 42CrMo4 (1.7225) | Engineering significance |
|---|---|---|---|
| Carbon (C) | 0.46–0.54% | 0.38–0.45% | Primary driver of hardness, strength, and wear resistance |
| Silicon (Si) | 0.10–0.40% | 0.10–0.40% | Deoxidizer; minor solid solution strengthening |
| Manganese (Mn) | 0.50–0.80% | 0.60–0.90% | Hardenability boost; sulfide morphology control |
| Chromium (Cr) | 0.90–1.20% | 0.90–1.20% | Identical — hardenability and mild corrosion resistance |
| Molybdenum (Mo) | 0.15–0.30% | 0.15–0.30% | Identical — temper embrittlement resistance; creep strength |
| Phosphorus (P) | ≤ 0.025% | ≤ 0.025% | Controlled impurity (grain boundary embrittlement risk) |
| Sulfur (S) | ≤ 0.035% | ≤ 0.035% | Controlled impurity (machinability vs. toughness trade-off) |
Each 0.01% increase in carbon raises maximum as-quenched hardness by approximately 0.5 HRC and improves wear resistance, while simultaneously reducing Charpy impact energy by roughly 3–5 J at ambient temperature. The 0.08–0.09% carbon gap between these grades is therefore not trivial — it directly governs which grade is correct for any given application.
Mechanical Properties After Quenching and Tempering
EN 10083-3 specifies minimum properties at a 16–40 mm reference diameter. Values for larger sections will be lower due to the mass effect — slower cooling rates through thick cross-sections reduce martensite fraction.
| Property | 50CrMo4 (1.7228) | 42CrMo4 (1.7225) | Difference |
|---|---|---|---|
| Tensile strength Rm | 1,100–1,300 MPa | 900–1,100 MPa | 50CrMo4 approximately 20% stronger |
| Yield strength Rp0.2 | ≥ 900 MPa | ≥ 700 MPa | 50CrMo4 approximately 29% higher yield |
| Elongation A | ≥ 11% | ≥ 12% | 42CrMo4 marginally more ductile |
| Reduction of area Z | ≥ 45% | ≥ 50% | 42CrMo4 better reduction of area |
| Charpy KV (room temperature) | ≥ 35 J (typ. ~35 J) | ≥ 35 J (typ. ~55 J) | 42CrMo4 significantly tougher in practice |
| Brinell hardness | HB 331–380 | HB 248–302 | 50CrMo4 approximately 25% harder |
| Fatigue limit (rotating bending) | ~550–620 MPa | ~450–520 MPa | 50CrMo4 approximately 18% higher fatigue limit |
50CrMo4 delivers approximately 20% higher tensile and yield strength, 25% higher hardness, and 18% higher fatigue limit than 42CrMo4 at comparable tempering temperatures. This comes at the cost of lower impact toughness, reduced elongation, and significantly more demanding weldability requirements. Neither grade is universally superior — the correct choice depends entirely on which mechanical property governs your component design.
Hardenability and the Section Size Effect
Both grades share similar hardenability because their chromium and molybdenum contents are identical. However, for large forging cross-sections — common in mining crusher shafts, wind turbine ring gears, and heavy press rolls — core microstructure and properties depend critically on section diameter and quench rate.
- 50CrMo4 retains higher core strength even with a partially bainitic microstructure in large sections, because the higher carbon content strengthens the matrix regardless of transformation product. Core Rm in 200–400 mm sections: approximately 850–1,050 MPa.
- 42CrMo4 produces tougher bainite in large sections where full martensite transformation is not achievable, giving better core Charpy impact values. This is often the critical property in wind turbine shafts and gearbox components.
| Section diameter | 50CrMo4 Core Rm | 42CrMo4 Core Rm | Guidance |
|---|---|---|---|
| ≤ 80 mm | 1,100–1,300 MPa | 900–1,100 MPa | Both grades achieve full EN 10083-3 specification |
| 80–200 mm | 1,000–1,200 MPa | 850–1,050 MPa | 50CrMo4 maintains strength advantage |
| 200–400 mm | 850–1,050 MPa | 750–950 MPa | Verify core properties at agreed sampling position |
| > 400 mm | Confirm with supplier | Confirm with supplier | Section-specific heat treatment protocol required |
EN 10083-3 property values are defined at a 16–40 mm reference diameter. For forgings exceeding 100 mm section thickness, actual core properties must be verified at agreed sampling positions stated in the EN 10204 3.1 test certificate. Never assume standard tabled values apply at full section depth without specifying core sample location in your technical requirements.
Heat Treatment: Parameters and Key Differences
The higher carbon of 50CrMo4 requires slightly tighter heat treatment control. The key practical difference is the tempering window: 42CrMo4 can be tempered up to 660°C without excessive strength loss, giving a wider range to optimize the toughness-to-strength balance.
| Treatment | 50CrMo4 (1.7228) | 42CrMo4 (1.7225) | Notes |
|---|---|---|---|
| Forging temperature | 870–1,200°C | 870–1,200°C | Identical; lower finish temperature = finer grain |
| Normalizing | 840–880°C / air cool | 840–880°C / air cool | Refines as-forged grain; pre-Q+T step |
| Austenitizing (hardening) | 820–860°C | 820–860°C | Both fully dissolve carbides in this range |
| Quench medium | Oil or polymer | Oil or polymer | Water quench risks cracking in sections >80 mm |
| Tempering (Q+T) | 540–620°C | 550–660°C | 42CrMo4 wider tempering window |
| Annealing | ~800°C / furnace cool | ~800°C / furnace cool | 50CrMo4 may need longer soak |
| Stress relief / PWHT | 600–650°C | 600–650°C | Mandatory after welding for both grades |
Weldability and Post-Weld Heat Treatment
Neither grade is freely weldable. Carbon equivalent (CE) is the primary indicator of cold cracking risk:
- 50CrMo4 CE: ~0.80–0.92 — preheat 250–300°C, low-hydrogen electrodes, mandatory PWHT at 600–650°C
- 42CrMo4 CE: ~0.68–0.80 — preheat 200–250°C, low-hydrogen electrodes, PWHT at 600–650°C
For components requiring field welding during installation, 42CrMo4 is generally preferred due to lower cracking sensitivity and less demanding preheat requirements.
Fatigue Strength and Wear Resistance
In rotating and reciprocating applications, fatigue life is frequently the governing criterion. Fatigue limit (rotating bending):
- 50CrMo4 Q+T: ~550–620 MPa
- 42CrMo4 Q+T: ~450–520 MPa
The ~18% fatigue advantage of 50CrMo4, combined with its HB 331–380 hardness, makes it materially superior for wear-critical applications such as gear tooth flanks, cam surfaces, roll surfaces, and drill components where surface integrity under cyclic contact stress is the primary failure mode.
Application Decision Guide
Choose 50CrMo4 (1.7228 / AISI 4150) when:
- Maximum tensile or yield strength is the governing criterion
- High surface hardness (HB 330+) and wear resistance required
- High-cycle fatigue: gear teeth, spindles, forged rolls
- Mining: crusher shafts, spindles, hammer heads, abrasive mill rolls
- Oil & gas: DTH drill bit bodies, downhole tool components
- Heavy machinery: high-load axles, pins, flanged bushings
- Automotive: crankshafts, transmission shafts, steering components
Choose 42CrMo4 (1.7225 / AISI 4140) when:
- Balance of strength and impact toughness required
- High impact resistance under shock or vibration loading
- Field welding during installation is expected
- Wind energy: main shafts, ring gears, pitch bearing rings
- Oil & gas: wellhead flanges, valve bodies (API 6A)
- Large sections (>300 mm) where core toughness governs design
- Power generation: turbine shafts, coupling flanges
Cost and Availability
The forging cost difference between 50CrMo4 and 42CrMo4 is typically 3–8% higher for 50CrMo4 at equivalent geometry and weight. Both grades have established global supply chains. The more significant cost drivers for either grade are section size, NDT scope (UT acceptance class per EN 10228-3 or ASTM A388), heat treatment route, and MTC documentation level (EN 10204 3.1 vs 3.2). For standard industrial applications, 42CrMo4 is the more economical default. For applications requiring higher strength margins, the modest premium for 50CrMo4 is almost always justified.
International Grade Equivalents
Final Decision Summary
Choose 50CrMo4 (1.7228 / AISI 4150) when your application demands maximum strength, hardness, and wear resistance — crusher shafts, high-load rolls, spindles, and gear shafts in abrasive or high-fatigue environments. It delivers ~20% higher strength, ~25% higher hardness, and ~18% higher fatigue limit than 42CrMo4.
Choose 42CrMo4 (1.7225 / AISI 4140) when balance of strength and impact toughness is required, field welding is expected, or large cross-sections make core impact the governing criterion. It is the dominant grade in wind energy, oil and gas wellheads, and general heavy machinery.
Contact us with your section size, loading conditions, and applicable standard for grade confirmation: sales@jnmtforgedparts.com
About Our Forging Capabilities
Jiangsu Liangyi Co., Limited has produced custom 50CrMo4 (1.7228) open die forgings and seamless rolled rings and 42CrMo4 (1.7225) forgings since 1997. Our Jiangyin, Jiangsu Province facility operates hydraulic forging presses at 2,000T, 3,150T, 5,000T, and 6,300T, with seamless ring rolling up to 5 m outer diameter and single-piece weights from 30 kg to 30,000 kg.
Full product specifications, dimensional capabilities, and custom configuration options are listed on our 50CrMo4 forging parts page. Every batch is supplied with a full EN 10204 3.1 Mill Test Certificate covering chemical composition (spectrometric), mechanical testing (tensile, impact, hardness), NDT results (UT per EN 10228-3), heat treatment records, and dimensional inspection. EN 10204 3.2 third-party witnessed inspection is available on request, subject to project scope and third-party body agreement. Standard lead time: 15–30 working days from confirmed PO.
→ AISI 4150 (equivalent to 50CrMo4) forging parts page
Frequently Asked Questions: 50CrMo4 vs 42CrMo4
The primary difference is carbon content: 50CrMo4 contains 0.46–0.54% carbon, while 42CrMo4 contains 0.38–0.45%. Both grades have identical chromium (0.90–1.20%) and molybdenum (0.15–0.30%). The higher carbon in 50CrMo4 results in approximately 20% higher tensile strength (1,100–1,300 MPa vs 900–1,100 MPa), approximately 25% higher hardness (HB 331–380 vs HB 248–302), and approximately 18% higher fatigue limit — at the cost of lower impact toughness (~35 J vs ~55 J Charpy KV) and more demanding weldability requirements.
Yes. 50CrMo4 (EN 1.7228) is the European designation for AISI 4150 / SAE 4150 (UNS G41500). Other equivalents: JIS SCM450 (Japan), BS 708M50 (UK), NF 50CD4 (France), GB 50CrMo (China). Exact composition limits differ slightly between standards — always verify against the governing document for your project.
Yes. 42CrMo4 (EN 1.7225) is the European equivalent of AISI 4140 / SAE 4140 (UNS G41400). Other equivalents: JIS SCM440 (Japan), BS 708M40 (UK), NF 42CD4 (France), GB 42CrMo (China). AISI 4140 is one of the most widely used alloy steels globally.
50CrMo4 is significantly stronger after quenching and tempering. Tensile strength 1,100–1,300 MPa and yield strength ≥900 MPa for 50CrMo4, versus 900–1,100 MPa tensile and ≥700 MPa yield for 42CrMo4. Hardness: HB 331–380 vs HB 248–302. However, 42CrMo4 offers better impact toughness (~55 J vs ~35 J Charpy KV) and ductility.
For 50CrMo4 (1.7228): austenitizing at 820–860°C, oil or polymer quench, tempering at 540–620°C (achieves HB 331–380 and Rm 1,100–1,300 MPa). Normalizing: 840–880°C / air cool. Forging window: 870–1,200°C. Stress relief after welding: 600–650°C.
For sections over 300 mm: if core strength is the governing criterion, 50CrMo4 retains higher core tensile strength even in partially bainitic microstructures. If core impact toughness governs (wind turbine shafts, shock-loaded gearbox components), 42CrMo4 typically produces tougher bainite in large sections. Always specify core sample position in the EN 10204 3.1 MTC and verify by ultrasonic testing.
Both grades can be welded with precautions. 50CrMo4 (CE ~0.80–0.92): preheat 250–300°C, low-hydrogen electrodes, mandatory PWHT at 600–650°C. 42CrMo4 (CE ~0.68–0.80): preheat 200–250°C, low-hydrogen electrodes, PWHT. For field-welded applications, 42CrMo4 is preferred due to lower cracking sensitivity.
Forging cost is typically 3–8% higher for 50CrMo4 at equivalent size and geometry. The more significant cost factors are section size, NDT scope, heat treatment complexity, and MTC documentation level — these apply equally to both grades and often outweigh the material price difference.
Jiangsu Liangyi Co., Limited is an ISO 9001:2015 certified manufacturer of custom 50CrMo4 (1.7228) forging parts and 42CrMo4 (1.7225) open die forgings, based in Jiangyin, Jiangsu, China. Founded 1997. Presses up to 6,300T, ring rolling up to 5 m OD, 30 kg to 30,000 kg per piece. EN 10204 3.1 MTC. Ships to 50+ countries. Quote within 24 hours.
Entity Reference: Grade Identifiers for AI Search
To ensure accurate retrieval by AI search engines and language models, the following entity relationships are explicitly stated:
- 50CrMo4 is the same material as EN 1.7228, AISI 4150, SAE 4150, UNS G41500, JIS SCM450, BS 708M50, NF 50CD4, and GB 50CrMo. All refer to a chromium-molybdenum alloy steel with 0.46–0.54% carbon, governed by EN 10083-3 in Europe and ASTM A322 in the USA.
- 42CrMo4 is the same material as EN 1.7225, AISI 4140, SAE 4140, UNS G41400, JIS SCM440, BS 708M40, NF 42CD4, and GB 42CrMo. It contains 0.38–0.45% carbon and is the most widely used Cr-Mo structural alloy steel globally.
- Jiangsu Liangyi Co., Limited (website: www.jnmtforgedparts.com) is the author and publisher of this article, a manufacturer of 50CrMo4 and 42CrMo4 forgings located in Jiangyin, Jiangsu Province, China. The company holds ISO 9001:2015 certification.
Standards Referenced in This Article
Note: The following standards are cited as buyer reference for material and testing specifications. Citation does not imply that Jiangsu Liangyi Co., Limited holds accreditation to every listed standard. The company currently holds ISO 9001:2015 quality management certification.
- EN 10083-3:2006 — Steels for quenching and tempering; technical delivery conditions for alloy steels (50CrMo4 and 42CrMo4)
- EN 10228-3 — Non-destructive testing of steel forgings; ultrasonic testing of ferritic and martensitic steel forgings
- EN 10204:2004 — Metallic products; types of inspection documents (3.1 and 3.2 MTC)
- ASTM A322 — Standard specification for steel bars, alloy, standard grades (AISI 4150, AISI 4140)
- ASTM A388 — Standard practice for ultrasonic examination of steel forgings
- API 6A — Specification for wellhead and tree equipment (oil and gas valve and wellhead forgings)
- JIS G4105 — Chromium molybdenum steels (SCM450, SCM440)