The Mechanical and physical properties of steel Can vary greatly depending on their composition and percentage of impurities (such as phosphorus or sulfur).
Thus, in order to achieve better mechanical and physical properties over others, steel can be alloyed with chromium, cobalt, copper, molybdenum, nickel, nitrogen, selenium, tantalum, titanium, tungsten or vanadium.
The composition and properties of steel vary widely. Steel in general has a lower carbon content than that found in iron, and a lower number of impurities than those found in other metals.
In general, physical properties such as density, electrical and thermal conductivity do not vary widely from one alloy to another.
However, the mechanical properties such as strength, ductility and hardness depend greatly on the type of alloy and steel composition.
Main mechanical properties of steel
1- Plasticity
It is the ability of steel to retain its shape after being subjected to stress. The steels that are alloyed with small percentages of coal, are more plastic.
2- Fragility
Fragility is the ease with which steel can be broken when subjected to stress. When steel is alloyed, with a high percentage of coal, it tends to be more brittle.
3- Malleability
Malleability is the facility of steel to be rolled. In this way, some stainless steel alloys tend to be more malleable than others.
4- Hardness
Hardness is the resistance that a metal opposes against abrasive agents. The more coal is added to a steel alloy, the harder it will be (Kailas, s.f.)
5- Tenacity
Tenacity is the concept that denotes the ability of steel to withstand the application of an external force without breaking.
In the case of steel with a medium carbon concentration, the tenacity tends to be higher (Chapter 6. Mechanical Properties of Metals, 2004).
Main physical properties of steel
1- Body
They include properties related to the weight of the steel, its volume, mass and density.
2- Thermal
It refers to three fundamental aspects of steel: its ability to conduct temperature (conduction), its potential to transfer heat (convection), and its ability to emit infrared rays in the medium (radiation).
3- Electrical
They refer to the ability of steel to conduct electric current.
4- Opticians
These properties in the case of steel denote its ability to reflect light or emit brightness. To the extent that stainless steel is alloyed with a higher percentage of aluminum, better optical properties will have.
5- Magnetic
It refers to the ability of the steel to be induced or to induce an electromagnetic field.
The higher the percentage of iron in the steel alloy, the greater its ability to act as a magnet (Sandhyarani, 2016).
Types of steel
Different types of steel are produced according to their application, therefore, the mechanical and physical properties of these types of steel must be different.
In this way, different scales have been created to classify the steel according to its properties (elasticity, density, melting point, thermal conductivity, strength, hardness, among others).
To manufacture different types of steel, manufacturers use different concentrations of other metals to make alloys.
The production process and the way in which the steel is worked also exerts a significant influence on the final product obtained.
According to the American Iron and Steel Institute (AISI), steel can be categorized into four major groups, according to their chemical composition:
- Carbon Steel
- Alloy steel
- Stainless steel
- Tool steel
Properties of carbon steel
Carbon steel is derived from the alloy between iron and coal. By varying the percentage of carbon, it is possible to produce steels with different qualities. In general, the higher the percentage of carbon, the more tenacious and rigid the steel.
Steel with a low percentage of carbon is known in the market as wrought iron. This type of steel is easy to handle as it is highly plastic.
For this reason, it is widely used to produce bars, decorative applications or lamp poles.
Steel with an average carbon content is highly tenacious, which is why it is used to make bridges or structural parts capable of withstanding enormous loads.
For its part, high carbon steel is used to make cables. When the percentage of coal is greater than that of iron, it is referred to as cast iron, which is worked for the manufacture of vases and other types of articles.
Although the latter type of steel is quite hard, it is also highly brittle (Materials, 2014).
Properties of Alloy Steel
Alloyed steel is one that is made with a small percentage of one or more metals other than iron.
Those metals added to the alloy have the ability to change the properties of steel.
For example, steel made from iron, chromium and nickel results in stainless steel. When aluminum is added to this alloy, the result is more malleable and uniform in appearance.
When steel alloys are added manganese, they can achieve strength and exceptional hardness.
Properties of stainless steel
Stainless steel contains between 10 and 20% chromium, a factor that allows it to be highly resistant to corrosion and oxidation.
When steel contains 11% chromium, it is approximately 200 times more corrosion resistant than steel that does not contain chromium. There are three groups of stainless steel:
Austenitic Steel : It is the one that has a broader concentration of chromium and a small percentage of nickel and carbon.
It is commonly used for food processing and piping. It is easy to recognize because it is not magnetic.
Ferritic steel : Is the type of steel containing approximately 15% of chromium, but only a few strokes of coal and other metals such as molybdenum, aluminum or titanium.
This type of steel is magnetic, highly hard and resistant. It can be hardened when working in cold.
Martensitic steel : Is one containing moderate amounts of chromium, nickel and carbon. It is highly magnetic and treatable at high temperatures.
Martensitic steel is commonly used to make cutting tools such as knives and surgical equipment.
Properties of tool steel
The tool steel is highly durable, temperature resistant, and with a fairly high hardness.
Contains tungsten, molybdenum, cobalt and vanadium. It is the one used to make the drill bits of the drills (Bell, 2017).
References
- Bell, T. (March 17, 2017). Retrieved from"What Are the Types and Properties of Steels?: thebalance.com.
- Chapter 6. Mechanical Properties of Metals. (2004). Retrieved from"Mechanical Properties of Metals: virginia.edu".
- Guru, W. (2017). Weld Guru. Obtained from Guide to the Mechanical Properties of Metals: weldguru.com.
- Kailas, S. V. (s.f.). Chapter 4. Mechanical Properties of Metals. Retrieved from Material Science: nptel.ac.in.
- Materia, T. (August 2002). Total Matter. Obtained from Mechanical Properties of Metals: totalmateria.com.
- Materials, A. (December 2, 2014). Retrieved from MECHANICAL AND PHYSICAL PROPERTIES: worldstainless.org.
- Sandhyarani, N. (August 4, 2016). Obtained from Physical Properties of Steel: buzzle.com.