In 1967, 500 million tons of steel were produced; by 2016, the figure had grown to over 1.6 billion. Steel is a widely used material all around the world, found in dozens of ordinary objects in our daily lives, such as cutlery or screws.
There are about 35,000 types of steel, each with its own applications and uses. In this post, we will focus on carbon steels.
What is steel?
Steel is a material that widely used in various types of manufactures thanks to its mechanical properties such as strength, ductility, malleability, hardness, etc. It is an alloy of a metal —iron— and carbon. The branch of metallurgy that works with steel is known as siderurgy.
The reason that it has been used for thousands of years and that it has so many applications is that its basic elelments can be easily found in the earth’s crust. If a ranking were made of the most abundant materials on our planet, iron would be number 14; if the ranking were of the materials found in the universe, it would occupy fourth place, as it is also abundant in stars.
In general, all grades of steel are composed of two elements: iron and carbon. Those known as “carbon steels” account for about 90% of steel grades. The difference between carbon steels and the others begins when additional elements are added to modify the properties. For example, manganese and phosphorus determine a steel’s durability and strength.
How is steel different from iron?
- Iron is a hard, ductile metal with a melting point of 1535 ºC.
- Carbon is a very versatile nonmetal that, when fused with iron, allows it to retain its characteristics as a metal while improving its physico-chemical properties.
Carbon steel: definition and types
Depending on the alloying element or elements added to the iron, numerous types of steel can be obtained. Within this variety, carbon steels are those in which carbon is the only alloying element or, if they contain other elements, these are found in low concentrations. The percentage of carbon is fundamental to defining their mechanical properties.
Increasing carbon creates changes in the metal’s structure and mechanical properties: it becomes harder and stronger, and its ductility, weldability and elongability are reduced.
Within the composition of carbon steels, there are other elements such as silicon or manganese that are essential to the composition, and others that have been called “impurities” because it is difficult to exclude them completely, such as sulfur, oxygen or hydrogen.
How can you recognize a carbon steel? It has a matte appearance and is sensitive to corrosion.
Carbon steel types
The various types of carbon steel can be classified by their low, medium or high carbon content.
Steels are considered to have a low percentage of carbon when the proportion is under 0.25%. These are referred to as “sweet” or “ferrous.” They are generally ductile, malleable, and manipulable, have good weldability, and do not respond to the heat treatment of quenching. They heat up a little if temperatures are low or if they are thicker than 25 mm. They are used to manufacture structural profiles, wires, nails, screws, bars, etc.
Steels with a medium percentage of carbon have a slightly higher percentage of this non-metal than the previous category, ranging from 0.25% to 0.55%. They accept a certain degree of hardening treatment, and are more resistant and harder naturally, but they are also more difficult to weld.
These are used to manufacture vehicle axles, machines, springs, gears, agricultural tools, cables and wires with excellent results or railroad rails.
High-carbon steels have a carbon percentage higher than 51%. They are harder and more resistant than medium-carbon steels, and have a good disposition to hardening. However, their weldability is so low that they are not welded at all.
They are used to manufacture cutting and machining tools such as drill bits, saw bands, springs, plow discs, lathe blades, files, etc.
At ULMA Forged Solutions we manufacture flanges of different materials and different types of steel such as carbon steel or stainless steel, among others. If you are looking for a company specialized in manufacturing this type of parts, do not hesitate to contact us.