4100 series steel is a chromium and molybdenum steel commonly known as chromoly steel. Chromoly steels are used in aircraft tubing, gears, piston wrist pins, crankshafts, structural tubing and firearms components along with other applications. Due to the popularity of 4100 series steels mix-ups of metal grades frequently occur requiring an organization to perform a metal sort.

Verichek Technical Services, Inc. routinely conducts Positive Metal Identification (PMI) on 4100 series steel for grade differentiation. Customers who need the PMI analysis often own a handheld XRF unit but handheld XRF can only differentiate 4130 based on an accurate Manganese analysis. What if 4140 and 4150 are mixed up? If that’s the case organizations need a mobile Optical Emission Spectrometer (OES) to sort based on carbon values.

Grade Carbon Chromium Manganese Moly Phos Silicon Sulfur Fe
4130 0.28-0.33 0.80-1.10 0.40-0.60 0.15-0.25 0.035Max 0.15-0.35 0.04Max 97.03-98.22
4140 0.380-0.430 0.80-1.10 0.75-1.0 0.15-0.25 0.035Max 0.15-0.35 0.04Max 96.785-97.77
4150 0.480-0.530 0.80-1.10 0.75-1.00 0.15-0.25 0.035Max 0.15-0.35 0.04Max 96.745-97.67

Iron and other elements share multiple minimum and maximum ranges and the only reliable way to differentiate 4140 from 4150 is by accurately measuring the element carbon. Carbon for 4140 is a minimum of .380 to a maximum of .430 vs 4150 which has a minimum of .480 to a maximum of .530 for carbon. The two steels are separated by 0.05 percent carbon.

We hope you’ve enjoyed reading how to sort 4140 from 4150. For more information regarding PMI sorting visit our blog or complete the contact us form to speak with a service professional.


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