Types Of Carbon Steel Full Analysis-Low/ Medium/ High Carbon Steel

Why is carbon steel the “universal material” of industry?

Carbon steel is an alloy material whose main raw materials are iron and carbon. Carbon steel accounts for more than 90% of the global steel usage. Due to its low cost, high strength and easy processing, it has become the first choice in the fields of automobile manufacturing, construction engineering, mechanical processing, etc. In order to help you better understand carbon steel, this article will systematically analyze the differences in composition, performance characteristics, etc. of the three major categories of low carbon steel, medium carbon steel, and high carbon steel.

The core basis of carbon steel classification

Carbon content determines performance

Types of Carbon Steel

Low carbon steel: economical and practical industrial “foundation”

Ingredients and properties

Low carbon steel is also called mild steel, and its carbon content is usually less than 0.3%. Its characteristics include:
Excellent cold processing performance: suitable for various processing techniques, such as stamping, bending and forming, so low carbon can realize various complex shapes of components.
Good welding performance: no complicated pretreatment is required, welding can be carried out directly, which simplifies the production process and improves work efficiency.
High economic efficiency: the cost is very low, only 1/3 to 1/2 of stainless steel, but the strength and toughness are not low.

Typical application scenarios

Automobile body panels: doors, hoods and chassis, etc., can be easily formed due to excellent cold processing performance, and the welding performance also ensures the firmness and safety of the body structure.
Building structural parts: used to manufacture various structural parts, such as steel bars and H-shaped steel.
Water pipelines: such as pipes that meet ASTM A53 standards, for good pressure resistance and corrosion resistance

Common grades for reference

ASTM A36: This is a general-purpose structural steel used in construction and manufacturing, with a tensile strength range of 400 to 550 MPa.
1018 steel: It has a very low carbon content of about 0.18% and is used in the manufacture of precision parts.

Ingredients and strengthening process

Medium carbon steel has a carbon content of 0.3%-0.6%, which has good mechanical properties and machinability. In order to further improve the performance, it is necessary to optimize the process through quenching + tempering.
Quenching: heating to the critical temperature, transforming into austenite, and then rapidly cooling or high-strength martensite.
Tempering: eliminating the internal stress caused by quenching and improving toughness.

Core Advantages

The tensile strength of medium carbon steel can reach 700MPa, which is 40% higher than that of low carbon steel, and can effectively resist fracture and deformation.
Due to its good cutting performance and processing stability, medium carbon steel is very suitable for precision machining, such as CNC milling and turning.

Typical application scenarios

Transmission shaft (1045 steel)
Gear (4140 alloy steel)
High-strength bolts (SAE Grade 8)

Performance and Challenges

High carbon steel contains more than 0.6% carbon, and its characteristics include:
Hardness can reach HRC 65: close to the level of industrial steel, with strong wear resistance and deformation resistance, and is used to manufacture various tools and cutting tools that require high wear resistance.
Brittleness risk: mainly due to the structural characteristics of the material. After quenching, although the hardness increases, it may also cause an increase in internal stress. Therefore, the heat treatment process needs to be strictly controlled.

Application areas

Cutting tools (1095 steel blades): The carbon content of 1095 steel is about 0.95%, and its hardness and wear resistance are very strong.
Springs (SAE 1080 steel): SAE 1080 steel is a spring steel with a carbon content of about 0.80%, which is excellent in elasticity and strength.
Railway tracks (high carbon high manganese steel): It has excellent strength and wear resistance and can withstand the huge pressure and friction when the train is running.

Key points of rust prevention

The biggest disadvantage of high carbon steel is that it is very easy to rust. In order to extend the service life, the following measures can be taken:
Electrogalvanizing: the most effective and common method, the thickness of the zinc coating must be at least 8 microns.
Regularly apply anti-rust oil: simple and easy, low cost.
Switch to aluminum zinc plate: this material also has excellent corrosion resistance, good mechanical strength and durability.

Comparison of carbon steel types: a quick selection guide