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4130 vs 4140 vs 4340 Steel

4130 vs 4140 vs 4340 Steel

4000 grade steels are Molybdenum steel alloys, meaning they have a small amount of Molybdenum (Mo) in them. 

However, most of these alloys only have a very small percentage—a maximum of ~0.5%. Molybdenum has a very high melting point (4,753°F) which makes it useful for aircraft parts, military armor, and engines. It’s commonly used in steel alloys to increase strength, corrosion resistance, and weldability.

4130, 4140, and 4340 steel alloys are very similar, and commonly used for precision machined steel parts. This article will compare the 3 different alloys and help you decide which one is best for your next project.

What are 4000-grade steel alloys used for?

4xxx steel alloys are stronger than many other steel alloys. These alloys are commonly used for gears, tooling, automotive parts, and high-strength pins, nuts, and bolts. The added Molybdenum gives the steel similar strength to titanium, at a much lower cost.

Most 4000 alloy steels can also be easily formed and welded.

41xx steel alloys have added Chromium, which further increases their strength and gives them better corrosion resistance. Chromium is the element added to stainless steel to make the metal rust-resistant, but the amount of Chromium in 4130 and 4140 steels is ~90% less compared to stainless steel alloys.

4130 steel

4130 steel is one of the best options for steel parts that require strength and fatigue resistance. 4130 steel also has an impressive tensile strength of 97200 PSI. It also has great ductility in its annealed state, which makes it easy to draw it into wires.

The difference between 4130 and 4140 steel is the Carbon content. 4130 steel has ~0.3% carbon, while 4140 steel has ~0.4% carbon. That might seem like an insignificant difference, but it has a noticeable impact on the strength, machinability, and weldability of the steel parts.

Because 4130 steel has less carbon, it’s easier to machine and slightly lower tensile strength. 4130 steel also has better weldability. Out of these 3 steel alloys, 4130 has the best machinability and weldability, but the lowest strength.

Common applications:

  • Valve components
  • Automotive parts
  • Aircraft parts

4130 Chemical Composition

Element Percentage
Iron (Fe)
97.03 - 98.22
Chromium (Cr)
0.80 - 1.10
Manganese (Mn)
0.40 - 0.60
Carbon (C)
0.28 - 0.33
Silicon (Si)
0.15 - 0.25
Molybdenum (Mo)
0.15 - 0.25
Sulfur (S)
0 - 0.04
Phosphorus (P)
0 - 0.035

4140 steel

4140 steel is a popular general-purpose alloy. It’s ideal for parts that require high tensile strength and toughness. It has considerable atmospheric corrosion and wear resistance, and doesn’t become brittle. Because of this, 4140 is commonly used for parts that require extra toughness like crankshafts, gears, and high-strength bolts.

4140 steel still has good machinability despite the higher carbon contents, however, extensive welding can be challenging. To improve weldability, the parts should be heat treated. 4140 steel in its annealed state means the parts are in their most stable state.

Common applications:

  • Crankshafts
  • Sprockets
  • Gears
  • Nuts and bolts
  • Pins
  • Pump and valve components

4140 Chemical Composition

Element Percentage
Iron (Fe)
96.93 - 98.12
Chromium (Cr)
0.80 - 1.10
Manganese (Mn)
0.75 - 1.0
Carbon (C)
0.38 - 0.43
Silicon (Si)
0.15 - 0.25
Molybdenum (Mo)
0.15 - 0.25
Sulfur (S)
0 - 0.04
Phosphorus (P)
0 - 0.035

4340 steel

4340 steel is more different from 4130 and 4140. This alloy is a 43xx rather than a 41xx steel, which puts it in a different category—Nickel-chromium-molybdenum steel. 4130 and 4140 alloys are both chromium-molybdenum steel. 

4340 steel has ~1.8% Nickel added to the composition, which isn’t in 41xx steels. 

Because of the added Nickel, 4340 steel is the hardest and more durable alloy compared to the 41xx alloys. 4340 steel has good shock and impact resistance as well as wear and abrasion resistance in the hardened condition. It also offers good ductility in the annealed condition, allowing it to be bent or formed. 4340 is often used in cases where steel alloys don’t have the hardenability to meet the strength requirements.

The added Nickel does make this alloy more expensive as a raw material, and more expensive to machine. The price difference can be offset because of the increased durability, the parts have a longer lifespan.

Common applications:

  • Automotive parts
  • Crankshafts
  • Fasteners
  • Heavy machinery
  • Military aircraft
  • Rotor shafts
  • Transmission components
  • Turbine shafts

4340 Chemical Composition

Element Percentage
Iron (Fe)
95.19 - 96.33
Nickel (Ni)
1.65 - 2.0
Chromium (Cr)
0.70 - 0.90
Manganese (Mn)
060 - 0.80
Carbon (C)
0.37 - 0.43
Molybdenum (Mo)
0.20 - 0.30
Silicon (Si)
0.15 - 0.30
Sulfur (S)
0 - 0.04
Phosphorus (P)
0 - 0.035
4130
Low
4140
Low

Spex is an ISO 9001:2015 certified company. Organizations use this standard to demonstrate the ability to consistently provide products and services that meet customer and regulatory requirements.

We incorporate world-class excellence in every step of the process, in our ongoing efforts to ensure your success.

Reach out to our team to get a quote for CNC machined steel parts for your next project. 

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