Guide to 4140 Steel Bar Products

AISI 4140 steel bar is a low-alloy steel that contains specific amounts of molybdenum, chromium, and manganese. The presence of chromium improves the product’s wear resistance, molybdenum improves its strength and toughness, and manganese decreases the metal’s brittleness.

The AISI designation given by the American Iron and Steel Institute of 4140 is based on the composition of the steel and can be broken down as such: 

  • 41XX – Indicates that the steel is in the chromium-molybdenum low alloy family.
  • 40 – Indicates a nominal carbon concentration of 0.40%.

Putting all the numbers in the AISI designation together, 4140 can be interpreted as a low alloy molybdenum-chromium steel containing 0.40% carbon.


4140 steel is known for having exceptional properties. Read the tables below for more information.


Carbon 0.38-0.43
Manganese 0.75-1.00
Sulfur (Max) 0.040
Silicon 0.15-0.35
Chromium 0.80-1.10
Molybdenum 0.15-0.25


4140 steel can be heat treated to a wide range of tensile strength, yield strength, and hardness. This means it is suitable for an array of applications with specific strength, wear, and fatigue requirements. Tensile strength is how well the steel can withstand tensile (pulling) forces without breaking, while yield strength refers to the maximum stress a material can handle before it undergoes plastic deformation.  Fatigue relates to a material’s ability to resist cyclic loading.


Since 4140 steel bars have exceptional wear resistance and high strength, they are often used to produce heavy-duty equipment, including bulldozer blades, crankshafts, and gears. 4140 steel can also withstand high stress and wear, making it a good material for oil and gas refinery equipment.

When 4140 steel has been quenched in a liquid medium and tempered for greater toughness, it is used to manufacture a wide range of fasteners, including nuts and bolts, guides, valves, pins, couplings, reamers, cams, and more.

King Steel’s Capabilities

As a leading 4140 steel bar supplier, King Steel has developed partnerships with manufacturers in many industries. Our success is built on our commitment to first-class quality and service. 

We can produce 4140 steel bars in the following sizes and shapes:

  • Sizes: .25″ to 15″ 
  • Shapes:
    • Flats
    • Hexagon
    • Rounds
    • Rounded Cornered Square
    • Square

Purchase 4140 Steel Bars From King Steel Today

King Steel has over 40 locations throughout North America.  As an industry-leading steel supplier, we are ready and prepared to provide you with the high-quality products you need. Contact us today to get help selecting the right size and shape for your 4140 steel bars or to request a product quote.