Differences in Basic Composition

• The 41L40 designation refers to 4140 grade chromium-molybdenum alloy steel that includes 0.15 to 0.35 percent by weight of lead added. It is a high-carbon steel, with 0.38 to 0.43 percent carbon by weight, its chromium content is 0.8 to 1.1 percent, and it contains 0.15 to 0.25 percent molybdenum. Ledloy, which is a common name for 12L14, also contains 0.15 to 0.35 percent lead by weight. It is a low-carbon alloy with only 0.15 percent carbon, and no significant amount of chromium or molybdenum is found in this steel.
  
  

Additional Differences in Composition

• Sulfur and phosphorus are present in 41L40 steel at 0.035 percent and 0.04 percent of weight, respectively. These elements are also found in 12L14 steel, at the rate of 0.04 to 0.09 percent of phosphorus and 0.26 to 0.35 percent of sulfur by weight. The percentage of manganese by weight in 41L40 steel is 0.75 to 1, and that of silicon is 0.15 to 0.35. Significant amounts of silicon are not found in 12L14 steel, which includes 0.85 to 1.15 percent of manganese by weight.
  
  

Differences in Physical Characteristics

• The chromium-molybdenum base of 41L40 makes it a far harder steel than the more malleable 12L14 alloy. The Brinell hardness index of the former is 200, whereas the latter is tested at an index of 160. On the other hand, the machinability index of 41L40 steel is 66 percent of the reference alloy B1112, whereas 193 percent of B1112 is the rating for 12L14. This translates to an average cutting speed of 110 feet per minute for 41L40 versus 325 feet per minute for 12L14.
  
  

Difference in Usage

• As it is a much harder steel, 41L40 is used to manufacture parts and assemblies that will be subject to wear and tear in harsh conditions. Its uses include the manufacture of joints for oil well tools, axle shafts, high-temperature bolts and other fasteners, hydraulic assembly shafts and tractor parts, as well as die-casting dies. The main use for 12L14 is in automatic screw machines, where rods of steel are machined into common screws and bolts. Hose fittings, inserts, bushings, clamps and other crimped, riveted or highly machined parts are also made of 12L14 because of its flexibility.