Physical Properties of Stainless Steel

Stainless steel is also known by many other names like CRES or corrosion-resistant steel, inox steel etc. Stainless steel is a type of metal alloy. The components of stainless steel are iron, chromium, carbon, nickel, molybdenum and small quantities of other metals. These components are present in varied proportion in different varieties of steels. In stainless steel, the chromium content should not be less than 11 percent.

Physical Properties of Stainless Steel

Though the word 'stainless' suggests that it is a stain proof material, actually steel is not completely stain-proof, rather, it does not get stained easily. In all, there are more than 150 grades of steel, out of which 15 are very commonly used. Some of the important physical properties of stainless steel are listed below:

• Stainless steel is a hard and strong substance.
• Stainless steel is not a good conductor of heat and electricity.
• Stainless steel possess high ductile strength. This means it can be easily shaped or bent or drawn in the form of wires.
• Most varieties of stainless steel possess magnetic permeability. They are strongly attracted towards magnets.
• It is highly resistant to corrosion.
• It does not get oxidized very easily.
• Stainless steel can retain its cutting edge for a long period of time.
• Even at very high temperatures, stainless steel is capable of retaining its strength and resistivity towards oxidation and corrosion.
• At cryogenic temperatures, stainless can remain tough.

Why are the Properties of Stainless Steel so Different?

The properties of stainless steel are very different because of its constituents. The high content of chromium in stainless steel is responsible for its corrosion-resistant properties. Therefore, stainless steel used for the purpose of making kitchen cutlery and cookware should have higher amount of chromium, in order to improve its resistivity towards corrosion. In order to increase the level of resistance further, nickel is used. Molybdenum (Mo) present in stainless steel helps in preventing certain types of localized corrosion like pitting.

The iron used for the manufacturing of stainless steel is extracted from its mineral ore. Iron in its purest form, has a natural tendency to react with atmospheric air and water that leads to the formation of rust. Though the primary component of stainless steel is iron, it can resist oxidation. This is because, the chromium present in stainless steel reacts with the oxygen in the air, to give chromium oxide. It adheres to the surface of the stainless steel in the form of a tough, passive coating. In case the surface of this layer is damaged due to some chemical or mechanical effect, the chromium oxide formed, is capable of mending the damage. However, this self-healing process of chromium oxide will work only if there is sufficient amount of oxygen.

The toughness of the stainless steel is on account of the presence of carbon in it. If the carbon content of the stainless steel is increased, it helps make the steel tougher. Carbon enables the stainless steel to get its sharp edges and also facilitates in retaining the sharpness of its edges for a long period of time.

Usually, stainless steel does not rust due to exposure to air and moisture. However, when some liquid substance is kept in a stainless steel container for a long period of time, we may notice the inside the container gets rusted. It happens because the liquid prevents the steel from making any contact with the oxygen. As a result, the damage caused on the layers of chromium oxide by the chemical effect of the liquid cannot be healed up.