Overview of Carbon Steel: Types, Pros, And Cons

What is Carbon Steel?

Carbon steel contains between 0.05 and 2.10% carbon by weight. The American Iron and Steel Institute (AISI) defines carbon steel as follows:

 

• There is no minimum content stated chromium, cobalt, molybdenum, nickel, niobium, titanium, tungsten, vanadium, zirconium, or necessary for the addition of any other element to achieve the desired alloying effect.

• The copper minimum stated cannot exceed 0.40%.

• Or the maximum content indicated for any of the elements listed below does not exceed the percentages supplied: Manganese is 1.65%, silicon is 0.60%, and copper is 0.60%.

Carbon steels are made chiefly of iron and carbon and require nearly no alloying components. The carbon content can vary, and there are a few acceptable alloying elements, but these steels are straightforward.

Carbon steel may also refer to steels that are not stainless; in this context, carbon steel may include alloy steels. Unlike carbon steels, low-alloy steels can consist of small amounts of a wide range of alloying elements, allowing them to be tailored according to more uses.

Steel may get harder and more robust by heat treatment as its carbon content increases, but it also becomes less ductile. A higher carbon content diminishes weldability regardless of heat treatment. Higher carbon content in carbon steels reduces the melting point.

Types And Properties of Carbon Steel

Carbon steel is categorized into three types based on its carbon content: low-carbon steel (also known as mild steel), medium-carbon steel, and high-carbon steel. The following is a comparison of their carbon content, microstructure, and properties:

Type	Carbon content (%)	Microstructure	Properties	Examples
Low-carbon steel	0.05 – 0.25	Ferrite, pearlite	Low hardness and cost. High ductility, toughness, machinability and weldability	AISI 304, ASTM A815, AISI 316L
Medium-carbon steel	0.30 – 0.50	Martensite	Low hardenability, medium strength, ductility and toughness	AISI 409, ASTM A29, SCM435
High-carbon steel	0.60 – 1.00	Pearlite	High hardness, strength, low ductility	AISI 440C, EN 10088-3

Low-carbon Steel 

Low-carbon steel, commonly known as mild steel, is by far the most common type of steel. Because of its low cost and material properties, low-carbon steel is suitable for a wide range of applications. Low-carbon steel contains approximately 0.05-0.25% carbon, making it malleable and ductile. Mild steel has a low tensile strength, but it is inexpensive and straightforward to form; carburizing can increase surface hardness.

High-strength, low-alloy steels (HSLA) are also categorized as low-carbon steels, with other ingredients including copper, nickel, vanadium, and molybdenum. Together, these can account for up to 10% of the steel composition. As the name implies, high-strength, low-alloy steels have higher strengths due to heat treatment. They also retain ductility, allowing them to be readily formed and machined. HSLA is more corrosion-resistant than regular low-carbon steel.

Medium-carbon Steel

Medium-carbon steel has 0.30 – 0.50% carbon and 0.60 – 1.65% manganese. This steel’s mechanical properties can be enhanced by a heat treatment involving austenitizing, followed by quenching and tempering, giving them a martensitic microstructure.

Heat treatment is only possible on extremely thin portions. However, steel can add additional alloying elements such as chromium, molybdenum, and nickel to increase its capacity to be heat treated and thus hardened.

Hardened medium-carbon steels have greater strength than low-carbon steels but at the sacrifice of ductility and toughness. This steel is mostly used in manufacturing machine components like shafts, axles, gears, crankshafts, couplings, and forgings. Still, it may also be used in rails and railway wheels.

High-carbon Steel

High-carbon steel has 0.60– 1.00% carbon and 0.30 – 0.90% manganese. It possesses the greatest hardness and toughness of carbon steel but the least ductility. Because they are nearly always hardened and tempered, high-carbon steels are extremely wear-resistant. High-carbon steels might be employed in springs, rope wires, hammers, screwdrivers, and wrenches.

Tool steels and die steels are high-carbon steels containing extra alloying elements such as chromium, vanadium, molybdenum, and tungsten. The incorporation of these elements leads to particularly tough wear-resistant steel, which is a consequence of the production of carbide compounds like tungsten carbide (WC).

Properties And Applications of Common Carbon Steel Grades

Carbon steel comes in various forms and can be used in many industries and sectors. Low-carbon steels are frequently used in vehicle body components, structural forms (I-beams, channel and angle iron), pipelines, building and bridge components, and food cans. Medium-carbon steels are frequently used for railway tracks, train wheels, crankshafts, and gears and machinery parts needing this combination of qualities because of their high strength, resistance to wear, and toughness. High-carbon steels are utilized in cutting tools, springs, great-strength wire, and dies due to their high wear resistance and hardness.

Low-carbon, medium-carbon, and high-carbon steel correspond to some common grades. The following table compares several carbon steel grades’ examples, qualities, and applications.

Type	AISI/ASTM name	Carbon content (%)	Tensile strength (MPa)	Yield strength (MPa)	Ductility (% elongation in 50 mm)	Applications
Low	1010	0.1	325	180	28	Automobile panels, nails, wire
Low	1020	0.2	380	205	25	Pipes, structural steel, sheet steel
Low	A36	0.29	400	220	23	Structural
Low	A516 Grade 70	0.31	485	260	21	Low-temperature pressure vessels
Medium	1030	0.27 – 0.34	460	325	12	Machinery parts, gears, shafts, axles, bolts
Medium	1040	0.37 – 0.44	620	415	25	Crankshafts, couplings, cold-headed parts.
High	1080	0.75 – 0.88	924	440	12	Music wire
High	1095	0.90 – 1.04	665	380	10	Springs, cutting tools

Typical Carbon Steel Products

The carbon content can significantly impact a carbon steel’s mechanical characteristics, leading to a broad range of brittleness and malleability. However, they share extraordinary hardness characteristics, making carbon steel suitable for structural, vehicle, and home applications. Four of the most widely used carbon steel products are described below.

Construction Structure Steels

Steels with intermediate to high carbon contents and high levels of other alloying elements exhibit excellent formability and structural integrity, allowing them to be shaped into a wide range of steel profiles and sections. These may be treated and tested to a variety of specifications for rigorous building demands and are often found in a variety of engineering applications across the world.

Masteel provides structural carbon steels in various specifications, including S355, which has a minimum yield strength of 355 N/mm²m.

Petrochemical Wells

HIC (hydrogen-induced cracking) resistant carbon steel is ultra-low carbon steel that is commonly utilized in the oil and gas industry for sour service. Steel components in near-constant contact with hydrogen sulfide may develop hydrogen embrittlement and associated cracking over time. This is a costly, time-consuming, and sometimes dangerous sign of sour service that may be avoided by employing HIC-resistant carbon steel. HIC-resistant carbon steel is desulphurized and dephosphorized to remove unwanted trace elements and provide a wonderfully pure homogeneous steel with less than 0.2% carbon content.

Masteel provides a variety of HIC-resistant steel grades, including MASTERHIC 5, MASTERHIC 10, and MASTERHIC 15.

Shipbuilding

Flat-rolled sheets of low-carbon steel and high-formability mild steel are utilized in the production of several lightweight and high-hardness constructions. Deck facilities on ships of varying sizes commonly employ carbon steel to complement the heavier, corrosion-resistant hull plating, which typically contains a greater manganese concentration.

Steels of various grades are utilized in the construction of ship superstructures, with low and mild-carbon steels serving as a foundation for harder steel cladding. Those with manganese concentrations as high as 1.65% are routinely produced into steel plates and surface treated to withstand a variety of corrosive substances. These products are commonly utilized to construct the hulls and superstructures of container ships and passenger liners.

Masteel provides a variety of shipbuilding carbon steel grades, including AH36, DH36, and EH36.

Pipeworks And Pressure Vessels

The gas and petrochemical industries are among the most significant users of raw carbon steel materials, producing millions of miles of carbon steel pipework and pressure vessels. Low-carbon steel is an intriguing option for these uses due to its high weldability for forming into complicated, rounded forms and its case hardening capabilities.

Case hardening, also known as carburization, is a treatment process that encourages carbon migration to the steel’s exterior. Carburization protects the solid and ductile inner core while forming a high-hardness crust on the vessel’s or pipe’s exterior to defend against various weathering factors.

Masteel provides many pressure vessel steel grades that are certified to ASME SA285 and several foreign standards.

Pros And Cons of Carbon Steel

Carbon steel accounts for the vast majority of steel types produced and accessible on the worldwide market today. Like every other form of steel, carbon steel has unique properties, advantages, and disadvantages.

Carbon Steel Advantages

• Strong and highly durable

• Higher strength 

• Corrosion resistant properties

• High and low-temperature resistant

• It exists in a large variety of types

• Durable and reasonably inexpensive over the duration of its lifespan

• Environmentally friendly and recyclable

• Low maintenance and easily cleaned

• It can be applied to a particular finish if an attractive cosmetic appearance is desired and does not tarnish readily

Carbon steel has several advantages over traditional steel, one of which is its higher strength. The use of carbon makes iron — or steel — stronger by moving about its crystal lattice. While carbon steel can still stress and crack under pressure, it is less likely than other forms of steel to do so. Therefore, carbon steel is advantageous in situations requiring strength. Many centuries ago, Japanese bladesmiths, for example, fashioned swords using high-carbon steel known as tamahagane steel. Carbon steel is now utilized to create everything from building materials to tools and automobile components.

Carbon Steel Disadvantages

• More prone to rust and corrosion than other steel types

• Difficult to bend and mold into diverse shapes

• High cost, especially at the initial expense

• It can be tough to work with, especially without the most advanced machinery and methods.

• It can often result in costly waste and re-work

There are certain disadvantages to using carbon steel instead of standard steel. Carbon steel is tough to work with since it is so robust, it is difficult to bend and mold into diverse shapes, restricting its applicability in some applications. Carbon steel is also more prone to rust and corrosion than other steel types. Manufacturers add chromium to steel to make it “stainless” — typically 10% to 12%. Chromium acts as a protective coating over the steel, shielding it from moisture that would otherwise cause rusting. On the other hand, carbon steel lacks chromium and may rust if exposed to moisture for an extended period.

Carbon Steel vs. Stainless Steel: What Are Their Differences?

Although the term “steel” refers to an entire family of metal alloys with hundreds of application-specific grades, most people think of steel in two main categories: carbon steel and stainless steel. Below we will compare carbon steel and stainless steel from several aspects.

Carbon Steel vs. Stainless Steel: Alloy Content

Carbon steel and stainless steel share the same iron and carbon constituents. Carbon steel has less than 10.5% alloy, whereas stainless steel must include at least 10.5% chromium. This fundamental distinction gives carbon steel and stainless steel their unique physical properties.

Carbon Steel vs. Stainless Steel: Rusting (Corrosion Resistance)

The primary distinction between stainless steel and carbon steel is their corrosion resistance. Stainless steel is designed to be resistant to rust and corrosion. Stainless Steel has a higher corrosion resistance than Carbon Steel. In stainless steel, a large quantity of chromium is added to form a chromium oxide coating that prevents corrosion. On the other hand, carbon steel lacks sufficient chromium to form such a coating and is therefore susceptible to corrosion and rusting.

Carbon Steel vs. Stainless Steel: Physical Properties

Carbon steel and stainless steel have different physical properties. The parameters are shown in the table below.

Physical parameter	Carbon Steel	Stainless Steel
Average Density	The average Density of Carbon Steel is 7850 Kg/m3	The average Density of Stainless Steel is 8000 Kg/m3. So Stainless Steel is slightly heavier than Carbon Steel
Co-efficient of Linear Thermal Expansion	The thermal expansion coefficient for Carbon Steel is usually less than that of stainless steel and varies in the range of (10.8 – 12.5) X 10-6 m/(m °C)	The expansion coefficient of Stainless Steel is comparatively more than that of Carbon Steel. Depending on grade, the coefficient varies in the range of (10-17.3) X10-6 m/(m °C). So, the thermal growth of Stainless Steel is more than Carbon Steel material.
Melting Point	The melting point of Carbon Steel is more than Stainless Steel. Typically Low Carbon Steel has a melting point of 1410°C. The melting point of high Carbon steel ranges between 1425-1540°C.	The melting point of stainless steel varies between 1375 to 1530 °C.

Carbon Steel vs. Stainless Steel: Mechanical Properties

Ductility: Austenitic stainless steel grades have more ductility than carbon steel grades. Martensitic stainless steel grades, on the other hand, are brittle stainless steel grades that may be more brittle than carbon steel.

Mechanical Strength: Because of the lower carbon content, stainless steel is often softer and weaker in strength. The following table compares the mechanical characteristics of carbon steel with stainless steel:

Mechanical properties	Carbon Steel	Stainless Steel
Yield Strength	Low-carbon Steel: 180 to 260 MPa; High carbon Steel: 325 to 440 Mpa.	Ferritic Steel: 280 Mpa; Austenitic Steel: 230 MPA; Martensitic Steel: 480 MPA
Tensile Strength	Low-carbon Steel: 325 to 485 MPa; High carbon Steel: 460 to 924 Mpa.	Ferritic Steel: 450 Mpa; Austenitic Steel: 540 MPA; Martensitic Steel: 660 MPA
Elastic Modulus	2100000 Mpa	1900000 MPa
Shear Modulus	81000 Mpa	740000 MPa
Poisson’s Ratio	0.3	0.27

Carbon Steel vs. Stainless Steel: Machinability And Weldability

Carbon steel is readily machined and has high welding capabilities. Stainless steel, on the other hand, necessitates specialist welding and machining techniques. Stainless steel is harder than carbon steel for machine tools.

Carbon Steel vs. Stainless Steel: Temperature Capabilities

Stainless steel is capable of containing fluids with temperatures over 426°C. In contrast, graphitization begins around 426°C for carbon steel. Stainless steel is renowned for its superior heat resistance.

Regular carbon steel should not be used at temperatures below -46°C. Below -46°C, a unique LTCS material is employed. On the other hand, stainless steel may be utilized at considerably lower temperatures.

Carbon Steel vs. Stainless Steel: Appearance

In terms of aesthetic appeal, stainless steel is far superior to carbon steel. Stainless steel looks excellent as is. However, carbon steel surfaces must be painted to prevent rusting.

Carbon Steel vs. Stainless Steel: Cost

One of the most significant considerations for carbon steel and stainless steel products is their cost. Stainless steel is often more expensive than carbon steel. However, prices vary according to the grades of the material. The cost of stainless steel rises due to particular alloy additives such as chromium, nickel, and so on, as well as the production processes involved with it.

Carbon Steel vs. Stainless Steel: Application

Carbon steel and stainless steel both have advantages and disadvantages in terms of application, characteristics, and cost. As a result, the choice between stainless steel and carbon steel must always be made depending on the application. Suppose cost is not an issue, and the application demands high temperature (or cryogenic temperature) as well as corrosion resistance. In that case, stainless steel is always the best choice. On the other hand, carbon steel is adequate for regular, non-corrosive conditions.

Carbon Steel vs. Stainless Steel: Other differences

Carbon steel and stainless steel also differ in other ways, such as thermal conductivity, wear resistance, heat treatment, etc. They are compared as follows:

Stainless Steel	Carbon Steel
Thermal conductivity is comparatively lower.	Higher thermal conductivity.
Excellent wear resistance.	Poor wear resistance.
Heat treatment of Stainless steel is difficult.	Carbon Steel can easily undergo heat treatment.
Stainless Steel is easily cleanable.	The cleanability of carbon steel is less than stainless steel.

Compared to low-carbon steel, stainless steel significantly improves strength, hardness, and, most critically, corrosion resistance. High-carbon steel rivals and occasionally surpasses stainless steel in terms of strength. Yet, it is primarily a niche production material in the manufacturing sector. Unlike carbon steel, stainless steel can live and thrive in corrosive or humid situations without oxidizing. However, carbon steel is significantly less expensive than stainless steel and more suitable for major structural components such as tubes, beams, and rolled sheet steel.

Conclusion

Carbon steel combines the malleability of iron with its great strength of carbon. Carbon steel can be heat-treated into a formable state enabling the fabrication of desired shapes and plates. Heat-treating retains its high toughness and tensile strength during all heat treatment processes, however, its surface layer is vulnerable to corrosive factors like weathering and oxidization.

Weathering and corrosion may be avoided by using carburization techniques that promote carbon migration to the exterior of the carbon steel component, which hardens the exterior of the carbon steel. The carbon distribution throughout the steel will be twisted, with an enhanced carbon density at the exterior and a harder, more iron-dense core in the interior. Carburization provides a unique mix of wear-resistant skin and a robust core to the carbon steel.