Product Introduction
When your machinery requires strength, durability, and reliability under heavy loads and continuous operation, 40Cr alloy steel is a proven choice. 40Cr (equivalent to AISI 5140) is widely used in automotive transmissions, industrial reducers, construction machinery, and agricultural equipment. With proper heat treatment, it delivers excellent toughness, wear resistance, and fatigue strength.
At our facility, we combine CNC hobbing, gear shaping, milling, turning, and grinding processes to produce high-precision gears and custom 40Cr alloy steel mechanical parts. Whether you need spur gears, helical gears, gear shafts, spline shafts, or non-standard mechanical components, we provide consistent quality and tight tolerances.
Key Features of Our 40Cr Alloy Steel Gears & Mechanical Parts
Optimized Hardness & Strength
Through quenching and tempering (usually 850°C oil quench + 550–600°C temper), 40Cr achieves a hardness of 28–32 HRC in the core, with surface hardness up to 50–55 HRC after induction hardening. This gives excellent resistance to contact fatigue and tooth breakage.
Superior Wear Resistance
The chromium content (0.8–1.1%) enhances hardenability and forms stable carbides, making these parts ideal for high-load, high-sliding applications such as gear pairs in heavy trucks or rolling mill drives.
High Fatigue Strength
With a tensile strength of ≥ 810 MPa and yield strength ≥ 660 MPa (after QT), 40Cr components withstand cyclic stresses much better than standard carbon steels like 45#. Many customers choose it as a cost-effective alternative to more expensive alloy steels.
Precision Machining Capability
Our 5-axis CNC machining centers, gear grinders, and CNC lathes allow us to achieve:
- Gear accuracy grade: DIN 6–7 or AGMA 12–13
- Surface roughness: Ra ≤ 0.8 μm on tooth flanks
- Dimensional tolerance: ±0.005 mm for critical bores and shafts
Flexible Heat Treatment Options
We offer normalizing, quenching & tempering, induction hardening, and carburizing (though 40Cr is not a true carburizing steel, we can recommend surface hardening where needed). For high-demand gears, nitriding is also available upon request.
Surface Finishing for Protection
To prevent rust and improve appearance, we can apply black oxide, phosphating, zinc plating, or oil coating – especially important for export shipments in humid environments.
Typical Applications
| Industry | Application Examples |
| Automotive | Transmission gears, transfer case gears, differential gears, gearbox shafts |
| Industrial machinery | Reducer gears, sprockets, couplings, heavy-load camshafts |
| Agricultural equipment | Tractor PTO gears, harvester drive gears, tiller shafts |
| Construction machinery | Excavator swing gears, crane winch gears, concrete mixer drive parts |
| Energy sector | Wind turbine yaw gears, mining conveyor drive sprockets |
- If you need custom 40Cr alloy steel machined gears or mechanical parts like bushings, collars, stepped shafts, or flanges – just send us your drawing (PDF, DWG, STEP, or even a sketch). We provide OEM & ODM services with low MOQ and fast prototyping.
Technical Data
- Chemical composition (wt%): C 0.37–0.44, Si 0.17–0.37, Mn 0.50–0.80, Cr 0.80–1.10
- Tensile strength: ≥ 810 MPa
- Yield strength: ≥ 660 MPa
- Elongation: ≥ 9%
- Impact toughness (AkU): ≥ 47 J/cm²
- Hardness after QT: 28–32 HRC (core), up to 55 HRC (surface induction hardened)
Product Images
Frequently Asked Questions
What gear accuracy grades can you achieve?
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We produce gears to DIN 6–7 or AGMA 12–13, with tooth profile and lead errors controlled within 0.01mm.
Can you make custom gears not listed on your website?
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Yes. Send us your drawing (PDF, DWG, STEP) or a sample, and we will provide a feasibility analysis and quotation.
What is the maximum gear size you can machine from 40Cr?
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Our CNC lathes handle parts up to 800mm diameter, and gear hobbing machines up to 1,200mm. For larger sizes, contact us for custom solutions.
Do you provide heat treatment for 40Cr gears?
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Yes, in-house heat treatment includes normalizing, quenching & tempering, induction hardening, and nitriding.
What surface treatments do you offer for 40Cr parts?
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Black oxide, phosphating, zinc plating, and anti-rust oil coating are available.
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