Low vs Medium vs High Carbon Steel – Difference Between Low, Medium and High Carbon Steels

The main difference between low, medium, and high carbon steels is the carbon content, which results in differences in their properties and applications. 

Low carbon steel, includes most ordinary carbon structural steel and some high-quality carbon structural steel. Most of them are used for engineering structural parts without heat treatment, and some are used for mechanical parts requiring wear resistance after carbon and other heat treatment. Easy to accept all kinds of processing, such as forging, welding, and cutting. It is often used to manufacture chains, rivets, bolts, shafts, etc.

Low carbon steel has good cold formability and can be cold formed by crimping, bending, stamping, and other methods. This kind of steel fin has good weldability. Low carbon steel with low carbon content has low hardness and poor machinability. Quenching treatment can improve its machinability. Low carbon steel is generally rolled into angle steel, channel steel, I-beam, steel pipe, containers, boxes, furnace bodies, agricultural machines, and tools, etc. High-quality low-carbon steel is rolled into thin plates to make deep drawing products such as automobile cab and generator cover; it is also rolled into bars to make mechanical parts with strength requirements. Low carbon steel generally does not undergo heat treatment before use, and those with a carbon content of more than 0.15% are carburized or cyanidated to meet the requirements shaft, shaft sleeve, sprocket, and other parts with high layer degree and good wear resistance.

The use of low-carbon steel is limited due to its low strength. Properly increasing the content of manganese in carbon steel and adding trace alloying elements such as vanadium, titanium, and niobium can greatly improve the strength of steel. If the carbon content in steel is reduced and a small amount of aluminum, boron, and carbide forming elements are added, ultra-low carbon bainite can be obtained, which has high strength and maintains good plasticity and toughness.

Medium carbon steel is a grade of ferrous metal, in addition to carbon, it can also contain a small amount of manganese (0.60% to 1.65%). according to the product quality, it is divided into ordinary carbon structural steel and high-quality carbon structural steel. It has good hot working and cutting performance and poor welding performance. Its strength and hardness are higher than that of low carbon steel, while its plasticity and toughness are lower than that of low carbon steel. It can be used directly without heat treatment, hot rolled and cold drawn materials, or after heat treatment. The medium carbon steel after quenching and tempering has good comprehensive mechanical properties. The maximum hardness that can be achieved is about HRC55. Therefore, medium carbon steel is the most widely used in various applications with a medium strength level. In addition to being used as building materials, medium carbon steel is also widely used to manufacture various mechanical parts. Medium carbon steel has higher carbon content than low carbon steel, higher strength, and poor weldability. 

High carbon steel is often called tool steel. Hammer and crowbar are made of steel with a carbon content of 0.75%; cutting tools such as drill bit, tap and reamer are made of steel with a carbon content of 0.90% to 1.00%. High carbon steel has poor welding performance due to high carbon content. High carbon steel is more prone to thermal cracks than medium carbon steel.