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Alloy Steel 4340
Material Type
Metal
Material Name
Alloy Steel 4340
Alternative Names
G43400 | 1.6511 | 36CrNiMo4 | EN24
Process Compatibility
CNC Milling, CNC Turning
introduction
Alloy Steel 4340 in CNC Machining
Alloy Steel 4340 belongs to the AISI 4000 series of steels, a heat-treatable, low-alloy steel with high strength and toughness.
The machinability of Alloy Steel 4340 depends on its heat treatment condition. In its annealed state, it machines relatively easily. However, when heat-treated for increased strength, it becomes more challenging to machine. It is common to machine the material in the annealed state and then heat-treat it to achieve the desired mechanical properties. It can achieve high strength through heat treatment while maintaining toughness, wear resistance, fatigue strength, atmospheric corrosion resistance, and overall strength.
Due to its toughness, cutting tools with high-speed steel or carbide inserts are commonly used. We use coolant during machining to dissipate heat and improve tool life. Lubrication helps reduce friction and extend tool life. It cannot be anodized, but we can do other post-processing treatments, such as tempering and annealing. We can also do surface finishing for a smoother surface.
Properties
Properties Table of Alloy Steel 4340
| MECHANICAL PROPERTIES | |
|---|---|
| Ultimate Tensile Strength | 690-1080 MPa |
| Yield Strength | 470-630 MPa |
| Young's Modulus(Elasticity) | 205-213 GPa |
| Elongation at Break | 15-22 % |
| Physical Properties | |
| Corrosion Resistance | Moderate to Poor |
| Magnetism | Semi-Magnetic |
| UV Resistance | Excellent |
| Weldability | Moderate |
| Thermal Properties | |
| Maximum Service Temperature | 613-652°C |
| Thermal Expansion Coefficient | 11.5-13 x 10^-6/°C |
| Thermal Conductivity | 35-50W/(m·K) |
| Electrical Properties | |
| Electrical Resistivity | 18-27 μΩ*cm |
TECHNOLOGY OVERVIEW
Basic Knowledge of Alloy Steel 4340
What is Alloy Steel 4340?
4340 steel is a strong, durable steel with medium carbon and low alloy content. It has exceptional strength, ductility, toughness, creep resistance, and fatigue resistance compared to many other types of steel.
The hardness of 4340 steel can range from 24 to 53 HRC, depending on the applied heat treatment. In terms of chemical composition, it contains a minimum of 95.10% iron, 1.65% nickel, 0.7% chromium, 0.65% manganese, 0.38% carbon, 0.15% silicon, and 0.2% molybdenum, with slight variations within defined maximum limits.
This steel is widely used in various applications, including heavy shafting, fasteners, aircraft, automotive, and hydraulic systems.
Advantages of Alloy Steel 4340
- Exhibits high tensile strength
- Good toughness and impact resistance, even at lower temperatures
- Good ductility
- Good wear resistance
- Balanced combination of properties for various applications
- Relatively machinable with appropriate tooling and techniques
- Responds well to heat treatment for optimizing mechanical properties
- Weldable with proper procedures and precautions
Applications of Alloy Steel 4340
- Aircraft landing gear components
- Automotive crankshafts and connecting rods
- Oil and gas drilling equipment
- Power generation turbine shafts and gears
- Heavy machinery axles and shafts
- Automotive transmission gears and axles
- Tool and die making molds and dies
- Marine propeller shafts
- Sporting goods like bicycle crankshafts
FAQ
Machining Alloy Steel 4340 Buying FAQ
Yes, Steel 4340 is wear-resistant and has excellent resistance to abrasion, shock, and impact. It also shows impressive atmospheric corrosion resistance.
Yes, 4340 steel is easily hardenable. It can be heat-treated to achieve high levels of hardness and strength. The most common method for hardening 4340 steel involves heating it to a specific temperature range and then quenching it in oil. This process helps enhance its mechanical properties.
4340 steel is stronger than 4130 steel. When normalized, 4340 has a tensile strength of about 110,000 lbs, higher than 4130 or 4140. Additionally, 4340 can be heat-treated in thick sections, a capability that 4130 and 4140 lack.
Yes, but it requires careful attention during the welding process. Preheating and post-weld heat treatment are often recommended to avoid issues like cracking and to ensure the desired mechanical properties in the welded joints. Proper welding procedures and expertise are essential when working with 4340 steel to maintain its integrity and performance.
Other Materials
Aluminum 7075
Aluminum 7075 is a strong and lightweight alloy often chosen because of its high strength-to-weight ratio. It is widely used in CNC machining
More info about Aluminum 7075
Alloy Steel 4140
Alloy Steel 4140, also known as chromoly steel, is a versatile low-alloy steel that contains chromium, molybdenum, and manganese.
More info about Alloy Steel 4140
Copper C101
Copper C101, also known as oxygen-free electronic (OFE) copper, is a high-purity copper alloy with excellent electrical conductivity and thermal conductivity.
More info about Copper C101
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