1045 vs 4140 Steel Comparison

Our 1045 and 4140 grade steels are both very popular options here at Capital Steel & Wire, and we often get questions related to their differences. 1045 and 4140 have distinct chemical and mechanical characteristics which make them valuable for different applications.

Chemical Makeup

It is easiest to see the differences chemical differences between 1045 and 4140 by doing a side by side comparison with a chart.

  1045 4140
Iron, Fe 98.51-98.98% 96.79-97.78%
Carbon, C 0.45% 0.40% 
Manganese, Mn 0.60-0.90% 0.75-1.00% 
Phosphorus, P (max) 0.04% 0.035% 
Sulfur, S (max) 0.05% 0.040% 

The carbon content of both 1045 and 4140 determines the last two digits of their grade number. The carbon content of 1040 steel is 0.40%, while 1045 has a carbon content of 0.45%. The first digit "1" identifies that they are both carbon steels, and the second digit "0" identifies that there were no modifications to the alloy. Note the higher concentration of Manganese in 4140 than 1045.

Mechanical Properties

Whether a steel is hot rolled or cold drawn determines many of the mechanical properties. The majority of 1045 and 4140 steel is purchased in cold drawn state, but we provided two graphs of both hot rolled and cold drawn mechanical properties for both 1040 and 1045.

Here is a comparison chart of 1040 and 1045 hot rolled steel mechanical properties:

   1045 Hot Rolled 4140 Hot Rolled
Tensile Strength 82,000 psi  90,000 psi
Yield Strength  45,000 psi  65,000 psi 
Elongation in 2"  16%  35% 
Reduction in Area  40% 40% 
Brinell Hardness  163  25 

Here is a comparison chart of 1040 and 1045 cold drawn steel mechanical properties:

   1045 Cold Drawn 4140 Cold Drawn
Tensile Strength 91,000 psi  95,000 psi
Yield Strength  77,000 psi  60,200 psi 
Elongation in 2"  12%  25% 
Reduction in Area  35% 35% 
Brinell Hardness  179  197 

Real Life Applications

4140 steel is chromium, molybdenum, manganese steel with good toughness, impact resistance and fatigue strength. 1045 has slightly increased tensile strength and yield strength numbers than 1045 as a result of a slightly higher carbon content. Also, as a result of higher carbon content, 1045 is not as easy to weld as 4140.