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42CrMo4 1.7225 JIS G4053 Alloy Structural Steel

42CrMo4 alloy steel delivers high hardenability and superior strength‑toughness. Featuring outstanding fatigue resistance, ideal for wind turbine gearbox components, heavy‑duty machine spindles, pressure vessel flanges and high‑strength bolting.

Standard: DIN 42CrMo4(1.7225), GB/T 3077 (42CrMo), JIS G4053
Technique: EAF + LF + VD, forged or hot-rolled, multi-directional forging ratio ≥4, quenched and tempered as required
Shape: Round, Flat, Plates, Blocks
Heat treatment: Supplied in quenched and tempered (QT) condition with hardness 28–34 HRC typical; annealed or normalized condition available on request
Surface Treatment: Turned, milled / ground, sawn ends. Black (hot-rolled / forged surface) available for large sections
Tolerance: flat bars & plates thickness: +0.5/-0.0 mm (turned); forged blocks: ±0.2 mm
MOQ: 1 Ton

We supply DIN 42CrMo4 in various custom sizes

Chemical Composition (%)

Grade	C	Si	Mn	P (≤)	S (≤)	Cr	Mo
42CrMo4	0.38–0.45	≤0.40	0.60–0.90	0.035	0.035	0.90–1.20	0.15–0.30
4140	0.38–0.43	0.15–0.35	0.75–1.00	0.035	0.035	0.80–1.10	0.15–0.25
1.7225	0.38–0.45	≤0.40	0.60–0.90	0.035	0.035	0.90–1.20	0.15–0.30
SCM440	0.38–0.43	0.15–0.35	0.60–0.90	0.035	0.035	0.90–1.20	0.15–0.30
42CrMo	0.38–0.45	0.17–0.37	0.50–0.80	0.030	0.030	0.90–1.20	0.15–0.25

Main characteristics of 42CrMo4 alloy steel

High hardenability - uniform properties for large‑size parts
Good strength‑toughness - high tensile strength with impact resistance
Excellent fatigue resistance - reliable under heavy alternating loads
Favorable machinability ‑ easy processing after heat treatment

42CrMo4 alloy steel applications

42CrMo4 steel for Wind Turbine Gearbox Components

Deep hardenability and high fatigue strength make 42CrMo4 the trusted choice for gear and shaft components under fluctuating loads, ensuring decades of reliable operation.

42CrMo4 steel for Heavy-Duty Machine Spindle

After quenching and tempering, 42CrMo4 offers an excellent strength-toughness balance, providing lasting precision and shock resistance for large machine tool spindles.

42CrMo4 steel for Pressure Vessel Flanges & High-Strength Bolting

Widely used in European pressure vessel construction, 42CrMo4 resists creep and relaxation at elevated temperatures, ensuring leak-free flange connections.

Our Production Technology For 42CrMo4 (1.7225 / SCM440 / 42CrMo) High-Strength Alloy Steel

Quality Control:
Ultrasonic testing (UT) 100% as per SEP 1921 or ASTM A388 (upon request)
Micro Cleanliness as per ASTM E45
Grain size as per ASTM E112 (typically ≥5 for critical applications)
Delivery condition options:
Soft annealed (+A): max. 241 HB
Normalized (+N): 197 – 235 HB
Quenched and tempered (+QT): 248 – 302 HB (or 255 – 341 HB for higher strength)
Mechanical properties as per EN 10083-3 or ASTM A29 / A322

mechanical properties & heat treatment of 42CrMo4 steel

Heat temperature	Start forging temperature	Finish forging temperature	Cooling method
1050 – 1080 °C	1050 – 1000 °C	≥ 850 °C	Pit, sand, or furnace cooling

Annealing

Hardening

42CrMo4 is a through-hardening alloy steel. Proper preheating and austenitizing are critical to achieve the desired hardness without cracking.
Pre-heating (recommended): Preheat to 600 – 650°C to reduce thermal shock during austenitizing
Austenitizing temperature: 830 – 880°C.
Lower range (830–850°C): For thinner sections and complex shapes
Upper range (850–880°C): For heavier sections requiring deeper hardness
Preferred range: 840 – 860°C
Holding time: At least 30 minutes per 25mm of section thickness (minimum 30 minutes)
Quenching media:
Oil (preferred for most sections) — provides good hardness with moderate distortion
Water — for larger sections or when maximum hardness is required (increased crack risk)
Polymer (PAG) — for controlled cooling rate and reduced distortion
Salt bath (180 – 220°C) — for martempering complex shapes
Hardness after quenching: 52 HRC (typical); 50 – 52 HRC achievable.
End-quench (Jominy) results: 5mm → 56.4 HRC, 9mm → 53.5 HRC, 15mm → 50.1 HRC, 30mm → 48.6 HRC

Stress relieving

Perform after rough machining, heavy stock removal, or welding to reduce residual stresses
Heat carefully to 600 – 650°C (below the tempering temperature)
Hold at temperature for 1 hour per 25mm of section thickness (minimum 2 hours)
Air cool after holding
This operation reduces the risk of distortion during final heat treatment and improves dimensional stability

Tempering

Temper immediately after the workpiece cools to handwarm temperature (approx. 50–70°C). Delayed tempering may cause cracking
Number of tempers: Minimum 1 time for standard applications; 2 times recommended for critical components
Holding time: 1 hour per 20mm of section thickness (minimum 2 hours)
Cooling method: Air cool after each tempering cycle
Tempering temperature range: 470 – 700°C, depending on final hardness requirement

Normalizing

Normalizing temperature: 860 ± 10°C.
Hold at temperature until uniformly heated (approx. 30 minutes per 25mm of section thickness).
Cool in still air.
Hardness after normalizing: 197 – 235 HB.
Purpose: Refine grain structure, eliminate forging stresses, and prepare for final heat treatment.

Why Choose NSPM as Your 42CrMo4 alloy steel Supplier

Source Direct

Direct mill cooperation ensures stable supply, competitive pricing, and consistent quality. Global resource integration and strong supply chain management guarantee reliable material sourcing and long-term availability.

Stock Ready

50,000+ tons inventory across 11 warehouses enables fast delivery. Flexible cutting, short lead times, and ready stock support urgent demands and improve customers’ production efficiency.

Expert Team

600+ professionals, including R&D specialists and technical engineers, provide application-driven support. Fast response and deep tooling knowledge ensure accurate solutions for diverse industrial needs.

Fully Inspected

Strict quality control system with full traceability, UT testing, and heat treatment records. Certified standards (ISO, CE) ensure every material meets high-performance and reliability requirements.

Full-Chain Machining

From steel supply to precision machining, heat treatment, and equipment manufacturing, NSPM offers integrated solutions that enhance accuracy, efficiency, and overall tooling performance.