42CrMo Alloy Steel | GB 42CrMo 1.7225 4140 | High-Strength Chromium-Molybdenum Steel Supplier

42CrMo is a premium chromium-molybdenum medium-carbon alloy steel manufactured to GB/T 3077 standards. With 0.38-0.45% carbon, 0.90-1.20% chromium, and 0.15-0.25% molybdenum, it offers an exceptional combination of high strength, excellent toughness, and superior hardenability. What sets this grade apart is its versatility and balanced performance profile: high fatigue strength, good wear resistance, and maintained mechanical properties at elevated temperatures. It exhibits minimal distortion during heat treatment with no significant temper embrittlement tendency—making it ideal for heavily stressed components.

This grade is also designated as AISI 4140, DIN 1.7225 (42CrMo4), JIS SCM440, and 708M40 in the UK. Whether for crankshafts, heavy-duty gears, hydraulic machinery components, or high-strength fasteners, it delivers reliable performance under demanding conditions. Available annealed (≤217 HB) for machinability, quenched and tempered for immediate use, or normalized as required.

Material Shape and Size

1.Round Bar

Flat Bar

Equivalent Grade

Standard System	Country/Region	Equivalent Grade	Common Search Terms
DIN EN	Germany	1.7225, 42CrMo4, 41CrMo4	42CrMo4 steel, DIN 1.7225, 1.7225 steel
AISI/ASTM	USA	4140	4140 steel, AISI 4140, 4140 alloy steel
JIS	Japan	SCM440, SCM4	SCM440 steel, JIS SCM440
GB	China	42CrMo	42CrMo steel, GB 42CrMo, 42CrMo alloy steel
BS	UK	708M40, 709M40	708M40 steel, EN19
ISO	International	42CrMo4, 683-1	ISO 42CrMo4
AFNOR	France	40CD4, 42CD4	40CD4 steel

Note: 42CrMo corresponds to AISI 4140 in the USA, DIN 42CrMo4 (1.7225) in Germany, and JIS SCM440 in Japan

Chemical Composition

Element	C	Si	Mn	P	S	Cr	Mo
Content (%)	0.38-0.43	0.15-0.30	0.60-0.90	≤0.020	≤0.020	0.90-1.20	0.15-0.30

Mechanical Property

MECHANICAL PROPERTY	METRIC VALUE	IMPERIAL VALUE
Hardness (Annealed)	147 – 241 HB	147 – 241 HB
Hardness (Quenched & Tempered)	28-34 HRC	28-34 HRC
Tensile Strength (σb)	≥1080 MPa	≥156.6 ksi
Yield Strength (σ0.2)	≥930 MPa	≥930 MPa
Elongation (δ5)	≥12 %	≥12 %
Reduction of Area (ψ)	≥45 %	≥45 %
Impact Toughness (KV, 20°C, Longitudinal)	≥63 J	≥46.5 ft·lb

Delivery Condition

Black Surface, Bright Surface, Turned Surface, Grinded Surface, Poblished surface.

Application

Automotive Industry: Crankshafts, connecting rods, camshafts, axle shafts, transmission gears, steering knuckles, universal joints, torsion bars for high-performance vehicles
Heavy Machinery Components: Gears and pinions for industrial gearboxes, heavy-duty shafts, spindles, rollers, drums, cylinders, columns for mining and construction equipment
Oil and Gas Industry: Drill collars, drill pipe connectors, tool joints for 2000m+ deep wells, blowout preventer components, pumping parts, valve bodies for high-pressure service
Power Generation: Turbine shafts, generator rotors, pump shafts, bolting for pressure vessels and flanges in power stations and refineries
Hydraulic and Pneumatic Systems: Hydraulic cylinder rods, pistons, plungers, valve components for high-pressure hydraulic systems
Fasteners and Connectors: High-strength bolts, studs, nuts for pressure vessel and structural applications, requiring high tensile strength and fatigue resistance
Mold and Die Industry: Large and medium plastic molds requiring strength and toughness, die holders, bolster plates, backing blocks for stamping and forming tools
Aerospace Components: Landing gear parts, structural components, engine mounts requiring high strength-to-weight ratio and fatigue resistance
Railway Equipment: Locomotive traction gears, supercharger drive gears, axles, couplers for heavy-duty rail applications
General Engineering: Highly stressed shafts, gears, spindles, mandrels, collets, and machine tool components requiring strength and wear resistance

Heat Treatment & Processing

Heat Treatment:

Soft Annealing: Heat to 760±10°C, hold 2-4 hours, furnace cool to 400°C at ≤20°C per hour, then air cool. Resulting hardness 220-230 HB, optimized for extensive machining
Normalizing: Heat to 840-880°C, hold adequate time, air cool. Refines grain structure, improves machinability, and reduces internal stress before hardening
Stress Relieving: Heat to 500-650°C, hold 1-2 hours, slow cool in furnace to 400°C, then air cool. Relieves machining stresses before final heat treatment
Preheating: Recommended at 500-600°C for complex or large parts to minimize thermal shock during austenitizing
Hardening (Austenitizing): Temperature 840-880°C (typical 850°C) . Soak time proportional to section size (minimum 1 hour). Protect against oxidation and decarburization using controlled atmosphere or anti-scale compounds
Quenching: Oil quench (40-60°C) for most sections; polymer quench possible for complex shapes; water quench for simple sections requiring maximum hardness (risk of distortion) . Quench to 50-70°C, then temper immediately. Hardness after quenching: 52-56 HRC
Tempering: Temper immediately after quenching while component is still warm. Hold minimum 1 hour per 25mm section thickness. Cool in air or oil (for larger sections) .

Processing Guide:

Forging: Hot forming temperature 1150-1200°C (heating), start forging at 1130-1180°C, finish forging >850°C. For sections >50mm, slow cool in furnace or insulating media to prevent cracking
Welding: Requires preheat 200-300°C; use low-hydrogen processes and matching filler metals (ER80S-B2). Post-weld heat treatment at 550-650°C recommended to relieve stresses
Nitriding: Gas nitriding at 525°C achieves surface hardness 600-700 HV with case depth 0.20-0.50mm; enhances wear resistance for specialized applications
Induction Hardening: Surface hardening possible achieving 54-60 HRC with case depth control; temper at 150-180°C after hardening

Quality Inspection & Control

Full-process control: Raw material inspection (certificate, composition); production inspection (composition, mechanical properties, 100% UT, dimensional, surface); finished product inspection (MTC EN 10204 3.1, reports).

Our Advantages

Strong Production Capacity: 10,000 tons/year, advanced equipment.
Adequate Stock: 600+ tons standard specs (3-7 days delivery); custom specs 15-30 days.
Custom Processing: One-stop sawing, milling, drilling, polishing, heat treatment.
Strict Quality Control: Full-process inspection, professional team/equipment.
Global Supply: Container/LCL shipment, anti-rust packaging, on-time delivery.
Professional Technical Support: Senior engineers guide material selection, heat treatment, processing.