Carbon Steels
Introduction
Carbon steel is a common type of steel that is an alloy of iron and carbon with carbon content from about 0.05 up to 2.1 percent by weight. It does not contain any minimum amount of other alloying elements, such as chromium, cobalt, molybdenum or tungsten. The American Iron and Steel Institute (AISI) defines carbon steel as:
- No minimum content is specified or required for chromium, cobalt, molybdenum, nickel, niobium, titanium, tungsten, vanadium, zirconium, or any other element to be added to obtain a desired alloying effect
- The copper minimum stated cannot exceed 0.40%.
- Or the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65%; silicon 0.60%; copper 0.60%.
The more carbon in steel, the harder and stronger it becomes after heat treatment, and the lower its melting point. As a result, carbon steel has a lower melting point and higher durability compared to stainless steel. But as the carbon content increases, the ductility of carbon steel after heat treatment will become worse, which means that it has less strength compared to stainless steel. In addition, the higher carbon content will reduce the weldability of the carbon steel, whether or not it has been heat-treated.
Type & Property & Application
Carbon steel are classified by their content of carbon into the four types: low-carbon steel, medium-carbon steel, high-carbon steel and ultra-high-carbon steel. The different types of carbon steel are different in their carbon content, microstructure, properties and applications. The details are as follows:
- Low-carbon steel: Low-carbon steel has a carbon content of between 0.05% and 0.15% with microstructure of ferrite and pearlite. It has the characteristics of low hardness and cost, high ductility, toughness, machinability and weldability. The low-carbon steel cannot be hardened by heat. Thus, the alloy is usually treated by cold work. Low-carbon steel is widely used in the automobile industry, structural shapes, pipes, construction, bridge components, etc.
- Medium-carbon steel: Medium-carbon steel has a carbon content of between 0.30% and 0.50% with microstructure of martensite. It has the characteristics of low hardenability, medium ductility, strength and toughness, and good wear resistance. Unlike low-carbon steel, medium-carbon steel can be heat treated, however only thin sections. Medium-carbon steel is widely used in railway tracks, train wheels, crankshafts, machinery parts, etc.
- High-carbon steel: High-carbon steel has a carbon content of approximately 0.6% to 1.0% with microstructure of pearlite. It has the characteristics of low ductility, high hardness and strength. In most cases, high-carbon steel is hardened and tempered. Thus, it has high wear resistant and is very suitable for the production of cutting tools.
- Ultra-high-carbon steel: Ultra-high-carbon steel has a carbon content of approximately 1.25%–2.0%. The alloy has great hardness by tempering. Therefore, it is widely used for special purposes like (non-industrial-purpose) knives, axles, and punches.
As a leading supplier of metals and alloys, Alfa Chemistry now can provide various carbon steels in the shapes of bar, wire, strip, foil, pipe, tube, sheet, plate, forgings, pipe fittings, flanges, etc. The main products include: