Chromoly is an abbreviation for “chromium-molybdenum steel”. It is not as lightweight as some steel alloys, but has the advantages of high tensile strength – 90-95 ksi [ksi = 1000 pounds per square inch] in the normalized condition – and malleability. It is also easily welded and is considerably stronger and more durable than standard (1020) steel tubing.
- Wide Range of Sizes– Chromoly can be manufactured to an almost infinite range of OD and wall thickness dimensions by varying the size of the dies and mandrels used.
Chromoly is often called “4130” because the carbon content is nominally 0.30%. With this relatively low carbon content the alloy is excellent from the standpoint of fusion welding . The alloy can be hardened by heat treatment or “normalizing”. This is a process of taking 4130 tube up to a prescribed temperature and cooling it at a precise rate. This removes all strain created in the tube manufacturing process and allows the homogenization of the steel’s grain structure.
Here are the principal benefits you can expect from Chromoly tubing in mechanical applications:
- Strength – Normalizing gives Chromoly high yield and tensile strength.
- Uniformity– Chromoly has uniform wall thickness and concentricity, as well as uniform mechanical properties.
- Close Tolerances– Chromoly offers exceptionally close tolerances for OD, ID and wall thickness dimensions.
- Surface Quality– OD and ID surfaces of Chromoly are free of oxide and scale and have a smooth, dense finish with no trace of the weld.
- Machinability – Chromoly is easily machined and welded.