10 MECHANICAL AND PHYSICAL PROPERTIES OF STEEL - CHEMISTRY - 2025

The mechanical and physical properties of steel can vary enormously depending on its composition and percentage of impurities (such as phosphorous or sulfur). In this way, when better mechanical and physical properties are desired over others, the 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 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 greatly from one alloy to another. However, mechanical properties such as strength, ductility and hardness are highly dependent on the type of alloy and composition of the steel.

Main mechanical properties of steel

1- Plasticity

It is the ability of steel to retain its shape after being subjected to stress. Steels that are alloyed with small percentages of carbon are more plastic.

2- Fragility

Brittleness is the ease with which steel can be broken under stress. When steel is alloyed, with a high percentage of carbon, it tends to be more brittle.

3- Malleability

The malleability is the ease of the 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 to abrasive agents. The more carbon you add to a steel alloy, the harder it will be.

5- Tenacity

Toughness is the concept that denotes the ability of steel to resist the application of an external force without breaking.

In the case of steel with a medium carbon concentration, the toughness tends to be higher.

Main physical properties of steel

1- Body

They include properties related to the weight of 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 emanate infrared rays in the medium (radiation).

3- Electrical

They refer to the ability of steel to conduct electrical current.

4- Optics

These properties in the case of steel denote its ability to reflect light or emit shine. To the extent that stainless steel is alloyed with a higher percentage of aluminum, it will have better optical properties.

5- Magnetic

It refers to the ability of 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.

Steel types

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, various scales have been created to classify steel according to its properties (elasticity, density, melting point, thermal conductivity, strength, hardness, among others).

To make 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 has a significant influence on the final product obtained.

According to the American Iron and Steel Institute (AISI), steel can be categorized into four main groups, according to its chemical composition:

• Carbon Steel
• Alloy steel
• Stainless steel
• Tool steel

Carbon steel properties

Carbon steel is derived from the alloy between iron and carbon. By varying the percentage of carbon, it is possible to produce steels with different qualities. In general, the higher the percentage of carbon, the tougher and stiffer the steel will be.

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 grating, decorative applications, or lamp posts.

Steel with a medium carbon content is highly tough, which is why it is used to make bridges or structural parts capable of supporting 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 used to make vases and other types of articles.

Although the latter type of steel is quite hard, it is also highly brittle.

Alloy Steel Properties

Alloy steel is one that is manufactured 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 the 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 manganese is added to steel alloys, they can achieve exceptional strength and toughness.

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 resistant to corrosion than steel that does not contain chromium. There are three groups of stainless steel:

Austenitic steel: it is the one with the highest 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, as it is not magnetic.

Ferritic steel: It is the type of steel that contains approximately 15% chromium, but only a few traces of carbon and other metals such as molybdenum, aluminum or titanium.

This type of steel is magnetic, highly hard and resistant. It can be hardened when cold working.

Martensitic steel: it is one that contains 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.

Tool steel properties

Tool steel is highly durable, temperature resistant, and has a fairly high hardness.

Contains tungsten, molybdenum, cobalt, and vanadium. It is the one used to make the drill bits.

References

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