General Information about 4130 Steel and 4130 Round Bar

4130 steel is part of the SAE (Society of Automotive Engineers) family of steel grades.  4130 round bar contains alloying elements including both chromium and molybdenum, and is sometimes referred to as chromoly or CRMO. It is considered a low alloy steel because its percentage of metals is low in proportion to its main component, iron.

4130 round bar may be supplied as hot rolled, cold drawn, rough turned or turned and polished. 4130 steel may also be annealed or heat treated depending on the end application.

4130 steel is readily machined by conventional methods. To increase its machinability, 4130 round bar may be normalized and tempered. It may also be supplied in a fully heat treated condition making the machinability of 4130 steel more difficult with the increased hardness. Tempering may be done to restore some of the ductility after heat treatment and quench.  A typical length for 4130 round bar is 20′, although many mills have the capacity to roll a variety of lengths depending on the application. It is also supplied in a wide range of diameters. 4130 steel may also be supplied in wire rod form, with a typical package weighing around 4,000 #.


4130 round bar is commonly used in forging as well as hot and cold working type applications.


4130 steel consists of carbon, .28/.33, manganese, .40/.60, phosphorus, .035 (max.), sulfur, .04 (max.), silicon, .15/.35, chromium, .80/1.10 and molybdenum, .15/25. The carbon content makes the steel easier to weld and also helps it to respond to heat treatment. The manganese contributes to the strength of the alloy. Silicon helps to remove oxygen during steel making and also contributes to the overall hardness of the alloy. The chromium & molybdenum contents are strengthening agents that may be useful in certain applications.