AISI 4140 Alloy Steel Data Sheet: What You Really Need to Know
If you’re looking for detailed technical information on AISI 4140 alloy steel, you’re in the right place.
Engineers, manufacturers, and procurement teams often reach out to us with questions like:
- “What are the exact mechanical properties of 4140?”
- “Can I use 4140 for heat-treated components?”
- “Do you have a 4140 data sheet I can use for design?”
Here’s a full breakdown of the most important technical data—and how to use it for real-world applications.
What Is AISI 4140 Alloy Steel?
AISI 4140 is a chromium-molybdenum alloy steel known for its high tensile strength, good fatigue resistance, and excellent toughness. It belongs to the SAE-AISI steel family and is widely used in automotive, oil & gas, toolmaking, and heavy equipment manufacturing.
It’s one of the most popular grades in the 41xx series—and for good reason. You can machine it, heat treat it, and rely on it for demanding structural parts.
Mechanical Properties: AISI 4140 Alloy Steel (Heat Treated Condition)
| Property | Typical Value |
|---|---|
| Tensile Strength | 850–1000 MPa |
| Yield Strength | ~655 MPa |
| Elongation (% in 50 mm) | ~25% |
| Hardness (HRC) | 28–32 (quenched & tempered) |
| Impact Toughness (Charpy V) | Excellent (at low temp) |
| Fatigue Strength | Moderate to High |
| Modulus of Elasticity | 205 GPa |
| Poisson’s Ratio | 0.29 |
| Density | 7.85 g/cm³ |
Note: These values are typical for 4140 in the quenched and tempered condition. For annealed or normalized states, strength and hardness will be lower.
Chemical Composition of AISI 4140
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.38 – 0.43 |
| Manganese (Mn) | 0.75 – 1.00 |
| Chromium (Cr) | 0.80 – 1.10 |
| Molybdenum (Mo) | 0.15 – 0.25 |
| Silicon (Si) | 0.15 – 0.35 |
| Sulfur (S) | ≤ 0.040 |
| Phosphorus (P) | ≤ 0.035 |
This specific chemistry gives 4140 its hardenability, good wear resistance, and ability to perform well after heat treatment.
Heat Treatment Guidelines for 4140 Alloy Steel
One of the most important benefits of 4140 steel is its ability to respond to various heat treatments:
| Process | Typical Range / Notes |
|---|---|
| Annealing | 800–850°C, slow cool in furnace |
| Normalizing | 870–900°C, air cool |
| Quenching | 830–870°C, oil or water quench |
| Tempering | 400–650°C depending on required hardness |
| Nitriding (Optional) | For surface hardness without distortion |
You can achieve surface hardness around HRC 50–55 through nitriding, without affecting core ductility—ideal for wear-prone components like shafts or gears.
Machinability and Weldability
- Machinability: Fair to good, especially in the annealed condition. In hardened condition, use carbide tools and lower speeds.
- Weldability: Can be welded with proper preheating (150–260°C) and post-weld heat treatment to reduce cracking risk.
We often help clients with custom-cut 4140 steel that’s pre-machined and pre-heat-treated to save time and reduce costs in production.
Typical Applications of AISI 4140 Alloy Steel
| Industry | Application Examples |
|---|---|
| Automotive | Drive shafts, crankshafts, steering knuckles |
| Oil & Gas | Drill collars, mud motors, downhole tools |
| Tooling | Molds, die holders, clamp blocks |
| Aerospace (non-flight) | Ground support components |
| Machinery | Gears, axles, tie rods, pins |
Stock Sizes and Services from Otai Steel
We stock a wide range of AISI 4140 alloy steel plates and bars in the following formats:
- Plate Thickness: 6mm to 300mm
- Round bar, flat bar, and block shapes
- Cut-to-size service with tight tolerances
- Optional heat treatment: annealed, quenched & tempered, or nitrided
- UT tested, SGS third-party inspection available
- Rust-proof packaging (wooden box or bundles)
- Fast delivery from over 10,000 tons in inventory
Why Choose Otai Special Steel for 4140 Alloy Steel?
With over 25 years of experience, Otai Steel is your reliable sourcing partner for AISI 4140:
- High inventory availability with mill-direct pricing
- ISO-certified quality control and custom documentation
- Engineering support to help match the right condition to your application
Need a Quote or Expert Advice?
We’re here to help. Whether you need technical clarification or a fast quote, our team is ready.
📧 jack@otaisteel.com
📱 WhatsApp: +8676923190193
Let us know your size, condition, and spec requirements, and we’ll recommend the best solution.
FAQs – AISI 4140 Alloy Steel Data Sheet
- Is AISI 4140 the same as SAE 4140 or EN19?
Yes, they refer to the same base material. SAE 4140 is the U.S. designation; EN19 is the European equivalent. - Can you provide 4140 with specific heat treatment?
Yes. We offer Q&T, annealed, or nitrided conditions upon request. - Do you offer third-party inspection or mill certs?
Absolutely. We can provide SGS, BV, or customer-nominated inspection and full MTC. - What’s the delivery time for 4140 steel?
For stock sizes: usually 3–5 working days worldwide. - Can I request a cut-to-size 4140 plate or block?
Yes! We provide precision cut-to-size and grinding per your drawing.
