Question

How are carbon steels classified as either low, medium, or high carbon steels?

Answer 1

Hint: Steel is mainly an alloy of iron and carbon along with some other metals like manganese and sulphur. Carbon steel is one of the different types of steel. The three types of carbon steels differ in the chemical composition of the carbon content which results in different structural properties.

Complete answer:
An alloy is composed of different types of elements and compounds. Similarly, carbon steel is also an alloy of iron, carbon, and in very small amounts of manganese, copper, and silicon.
Carbon steel classification is based on the carbon content present in the alloy. There are mainly 3 types of carbon steels:
1) – Low carbon steel: It contains up to $0.30%$ carbon and is also known as mild carbon steel. It makes up the largest group of carbon steels and is used more frequently than high carbon steels. This is due to their easily weldable and ductile nature. They are used in making automobile body panels, wire products, etc.
2) – Medium carbon steel: Its carbon content ranges from $0.30%$ to $0.60%$. Due to an increase in the carbon content, their tensile strength and hardness increase but ductility decreases. This category of carbon steel is used in making shafts, axels, gears, etc.
3) – High carbon steel: Its carbon content ranges from $0.60%$ to $1.50%$. These carbon steels are extremely difficult to weld, and their tensile strength is so high that they are used in making springs and metal cutters.
Hence, the carbon steels are classified on the basis explained above.

Note: Though the high carbon steels are very tensile and hard, they can be welded and used for machinery purposes by preheating and post-heating techniques. Also, these 3 types of carbon steels do not only differ in carbon content but there is a very little difference in the amount of manganese present in them.