An Overview of Carbon Steel

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Carbon steel, an iron-carbon alloy with a carbon content of up to 2.1% of the steel’s total weight, is one of the primary categories of steel. It makes up as much as 90% of steel manufactured globally.

The overarching category of carbon steel can be additionally divided into five sub-categories:

  • Ultra-low-carbon steels: carbon content less than 0.015%;
  • Extra-low-carbon steels: between 0.015% and 0.05% carbon;
  • Low-carbon steels: between 0.05% and 0.19% carbon;
  • Medium-carbon steels: between 0.2% and 0.49% carbon;
  • High-carbon steels: a carbon content over 0.5%.

These must all contain less than 0.6% copper, 0.6% silicon and 1.65% manganese to meet the requirements as carbon steel. They are each uniquely suitable to various applications and technical specifications.

Carbon steel unites the malleability of iron with the high strength of carbon. While it is brittle at first, carbon steel can be heat-treated into a formable state for the production of custom shapes and plates. It preserves its high toughness and tensile strength during the entire heat treatment processes, but its surface layer will afterwards be susceptible to corrosive elements, such as weathering and oxidization.

The issue of weathering and corrosion can be avoided via a carburization processes designed to harden the exterior of the carbon steel, by promoting carbon migration to the surface of the carbon steel component. The spread of carbon throughout the steel will be distorted, with an elevated carbon density at the exterior and a harder, more iron-dense core in the interior. This gives the finished product a unique combination of a wear-resistant skin with a tough core.

Carbon Steel Applications

Due to its high versatility, carbon steel has a broad range of applications and has been employed ubiquitously in a range of industries, especially in the oil, gas, and petrochemical sectors.

As worldwide provider of a variety of steel products, Masteel has obtained and manufactured carbon steel for a wide range of market sectors, with a specialization in the manufacture of low-pressure vessels and industrial boilers for some of the leading fossil fuel energy suppliers in the world.

Carbon Steel Products from Masteel

Masteel provides a range of carbon steel products with ASTM, ASME, and EN specifications, with a variety of carbon steel grades appropriate for manufacture in industrial boilers, pressure vessels, and heat exchangers. These contain excellent notch toughness with tensile strengths in the range of 60-80 ksi to 70-90 ksi.

Masteel also provides hydrogen induced cracking (HIC) resistant carbon steel plates with high durability and performance to combat problems of hydrogen and stress-related corrosion in petrochemical pressure vessels and boilers – especially in sour service settings.

Four Common Carbon Steel Products

Carbon steel is a broad category that includes steel alloys with a carbon content from below 0.015% to over 0.5%. The lower carbon content steels, or ultra-low-carbon steels, are not capable of being heat treated, while ultra-high-carbon steels cannot be toughened by tempering methods.

This is because seemingly minor variations in carbon content can have serious implications on the mechanical properties of a steel alloy, causing widely ranging brittleness and malleability properties. However, they share incredible hardness values, which makes carbon steels appropriate for use in structural, vehicular and domestic purposes.

This article will look at four of the most widespread carbon steel products.

Shipbuilding

Flat-rolled sheets of low-carbon steel and high formability mild carbon steels are applied in the manufacture of numerous lightweight, high-hardness structures. Deck facilities on ships of various sizes regularly use carbon steel to complement the heavier, corrosion resistant hull plating that usually has a higher manganese content.

Several types of steel are used in the manufacture of ship superstructures, with low and mild carbon steels usually working as a base material for tougher steel cladding. Those with a manganese content of as high as 1.65% are commonly formed into steel plates and surface treated to withstand several corrosive elements. These products are regularly used to build the hulls and superstructures of container ships and passenger liners.

Masteel offers a number of grades of shipbuilding carbon steels, such as AH36, DH36, and EH36.

Structural Steels

Steels with intermediate to elevated carbon contents and high levels of additional alloying elements show exceptional degrees of formability and structural integrity, allowing them to be formed into numerous steel profiles and sections. These can be treated and tested to numerous specifications for exacting construction demand and are typically discovered in various engineering applications globally.

Masteel offers structural carbon steels to a range of specifications, such as S355, with a minimum yield strength of 355 N/mm²m.

Pipes and Pressure Vessels

The gas and petrochemical sector are among the biggest users of raw carbon steel products, making millions of miles of carbon steel pipework and pressure vessels for non-vital uses. Low-carbon steel is an appealing possibility for those kinds of uses because of its good weldability for formation into complex, rounded shapes, and its capacity for case hardening.

Case hardening, or carburization, is a treatment method that promotes carbon migration to the exterior of the steel product. This safeguards the tough and ductile inner core while creating a high-hardness crust on the exterior of the vessel or pipe to protect against a range of weathering elements.

Masteel offers a variety of pressure vessel steel grades certified to ASME SA285, and several international standards.

Petrochemical Wells

HIC (hydrogen induced cracking) resistant steel is an ultra-low carbon steel that is widely used for sour service in the oil and gas sector. Steel parts that are in near-endless contact with hydrogen sulfide might eventually show hydrogen embrittlement and related cracking over time. This is an expensive, time-consuming, and possibly hazardous symptom of sour service, which can be circumvented by the use of HIC resistant carbon steel.

HIC resistant steel is exposed to a desulphurization and dephosphorization process to eliminate undesired trace elements and offer a remarkably pure homogenous steel with a carbon content lower than 0.2%.

Masteel offers several grades of HIC resistant steels, such as: MASTERHIC 5; MASTERHIC 10; and MASTERHIC 15.

Carbon Steels from Masteel

Masteel is a top supplier of carbon steel products for a range of applications, offering a variety of steel grades to meet discrete industry demands and offer solutions to application-specific issues.

This information has been sourced, reviewed and adapted from materials provided by Masteel UK Ltd.

For more information on this source, please visit Masteel UK Ltd.

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