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Alloy Steel 4140 is a low-alloy steel containing chromium, molybdenum and manganese. It is valued for its high fatigue strength, toughness and resistance to wear and impact. For UK engineers and product designers, CNC machining Alloy Steel 4140 is a reliable route from prototype to finished part.
It machines well in the annealed condition and can be heat treated to raise strength and hardness, making it popular for demanding mechanical components. Common examples are heavy-duty shafts, connecting rods and high-tensile bolts. Its quoted tensile strength of around 1130 MPa gives a useful guide when sizing parts.
Parts are produced by CNC milling or turning. Although it resists atmospheric corrosion better than plain carbon steel, a protective finish is recommended for harsh environments. Get an instant online quote for Alloy Steel 4140 CNC parts and have them delivered to your door in the UK.
Material
Alloy Steel 4140
Description
Strengths
Lead time 10 business days. Cr-Mo alloy steel with high fatigue and torsional strength, good toughness and wear resistance.
Weaknesses
Needs care when welding
Silver grey
Ultimate tensile strength
1130 MPa
Yield strength
715 MPa
Modulus of elasticity
210 GPa
Elongation at break
21.5%
Density
7.85 g/cm³
Hardness
28–32 HRC
Shear modulus
80 GPa
Corrosion resistance
Good (atmospheric)
UK equivalent
EN19 (709M40)
Maximum service temperature
Melting point 1416°C
Thermal expansion coefficient
11.5–13.5 × 10⁻⁶ /°C
Thermal conductivity
Not specified
Electrical resistivity
Not specified
Heat treatment
Hardening & tempering
Recommended finish
Black oxide, plating or oil
Heavy-duty shafts
Connecting rods
High-tensile bolts
Gears & spindles
Values shown are typical supplier figures for Alloy Steel 4140 and may vary with stock condition. Please confirm critical properties before production.
4140 (EN19) machines well in the annealed or pre-hardened condition. It is tougher than mild steel, so cycle times are longer, but it gives a good finish.
4140 is commonly used for precise shafts, spindles and gears. Achievable tolerances depend on part size, geometry and features, so mark any critical tolerances on a 2D drawing with your upload and they will be reviewed and confirmed in your quote.
Yes. 4140 can be hardened and tempered for higher strength and wear resistance. Black oxide, plating or oil is recommended for corrosion protection. Welding needs care.
Typical uses include heavy-duty shafts, connecting rods, high-tensile bolts, and gears and spindles.
4140 (EN19) is a versatile chromium-molybdenum steel for most high-strength parts. 4340 (EN24) adds nickel for greater toughness in large sections and is preferred for the most demanding parts, such as landing gear and drive shafts.
The typical lead time shown for 4140 steel is 10 business days from an approved order. Heat treatment can add time. Quantity, finishing and any heat treatment can affect this, and your quote confirms the date before you order.
Parts in as fast as 10 business days
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