12L14 belongs to lead-sulfur composite free-cutting structural steel. In lead free-cutting steel, lead is distributed in the steel as tiny elementary metal particles and is not solid-melted in the steel. During the cutting process, strong friction occurs between the tool and the workpiece, which makes the lead particles in the steel melt. Precipitation, which plays a role of lubrication to improve the cutting performance of steel, make the steel chips finely, reduce tool wear, and ultimately extend tool life. Compared with lead-free steel, the cutting performance of lead-containing steel can be increased by 20-50%, while the mechanical properties and heat treatment performance remain basically unchanged, and it has no effect on cold and hot workability and weldability. 12L14 free cutting steel is a low friction metal that maintains a smooth, machined surface, allowing for increased tool life. This grade of carbon steel is recommended for the manufacturing of high-speed automatic screw machine parts. This standard resulfurized and rephosphorized low carbon steel benefits from the addition of tiny lead particles, providing enhanced machinability. Although 12L14 CF Bar provides excellent machinability, the added lead content reduces the overall strength of the alloy.

Free-cutting steel has been widely used as an important part of manufacturing precision instrument parts, auto parts, and various types of machinery. However, lead free-cutting steel has low contact fatigue, so it is not suitable for parts such as gears and bearings that bear large fatigue stress loads. 12L14 has a tendency to be replaced by it. Its cutting performance is also very good. It is suitable for more stringent occasions where 12L14 cannot be used.