C. Cabrera, C. Morón, A. Garcia

Universidad Politecnica de Madrid (SPAIN)
The present work has as main aim to make a small introduction about the types of steels, specially the ones used in the construction industry. This material is appreciated in construction due to its many advantages as strengths, resistance, adaptability and flexibility in design, durability, recyclability,…; even though it also has week points like a low resistance to fire, weak against corrosion and a high initial cost compared with other materials.

There are a high variety of ways to classify steel. So, it is very important to the building engineering students to know the classification of steel will be focused on the chemical composition of the steel, as it is the most common way of classifying it. The different types of steel will be grouped in four types: carbon steel, alloy steel, stainless steel and tool steel.

In carbon steel the main alloying constituent is carbon, in a range between 0.12% and 2%. It may also content small amounts of other elements like manganese, sulphur, phosphorus and silicon. Variations in the carbon content of carbon steel can modify its mechanical properties, for example, with an increase in the carbon content from 0.01 to 1.5% in the alloy, its strength and hardness increases but still such an increase beyond 1.5% causes appreciable reduction in the ductility and malleability of the steel.

Alloy steel is a term used referring to steels with other alloying elements in addition to the carbon. The content of this alloying element is between 1.0% and 50% by weight. The most common alloying elements used in this type of steel are manganese, nickel, chromium, molybdenum, vanadium, silicon, and boron; Less common alloyants are aluminum, cobalt, copper, cerium, niobium, titanium, tungsten, tin, zinc, lead, and zirconium. By varying the alloy proportions steel properties such as hardenability, corrosion resistance, strength, formability, weldability or ductility can be manipulated.

Stainless steel is the alloy of any type of iron that contains at least 10.50 % of chromium and no more than 1.20 % of carbon. It also may content other alloy elements such as nickel or molybdenum. These steels can be divided into four groups based on their crystalline structure.
Tool steels is a variety of carbon and alloy steels, its carbon content ranges between 0.7% and 1.5%, it also contains tungsten, molybdenum, cobalt and vanadium in varying quantities to increase heat resistance and durability. They are ideal for cutting and drilling equipment, this suitability comes from their distinctive hardness, resistance to abrasion, their ability to hold a cutting edge, and/or their resistance to deformation at elevated temperatures (red-hardness).