Aside from their commercial names, transmission steels are named according to their tensile and ultimate strength, rather than their chemical composition. These materials are specified as St37-2, St44-2, St52-3 etc. in order to display their tensile strength. Since their Carbon (C) content is low, the strength is increased by their Manganese (Mn) content.
For example, St37 material has to provide 370 N/mm² tensile strength. The term transmission steel is generally used for SAE 1008 – SAE 1010 – SAE 1012 – SAE 1013 VE ST-37 grade steels. The cold drawn form (which means calibrated) of this material is known as transmission in the commercial market.
Transmission steels provide high weldability, thanks to their low carbon content. This facilitates their use in machine parts that require welding after processing or during assembly, shafts in automobile equipment and many parts in manufacturing, and makes them preferrable.
Transmission steel is machined easily since it is not hard. But the machining time gets longer since the chips don’t break like in free cutting steel. The reason for preferring it to free cutting steel is mainly because it is cheaper.
St44 and St52 materials contain a stronger structure. This is due to the increase in their carbon and manganese content. For example, the strength value o SAE 1050 material without heat treatment is almost the same as St52 material, which contains almost half the carbon.