Stainless steel is an extensively-used material, used in domestic goods as well as industrial ones. However, it is not a single material. Stainless steel is the name given to a collection of corrosion-resistant materials. Almost all the variants of stainless stall have a minimum of 10.5% chromium. Chromium, on reacting with oxygen forms chrome-oxide, a complex surface-layer oxide, that cannot be seen. However, the oxide is strong enough to prevent rusting of the surface.
Stainless steel has various grades, and the hardness and properties depend on the composition of each variant. The common elements used to make stainless steel include carbon, chromium, nickel, nitrogen, manganese, copper and other materials.
Important properties of stainless steel
Stainless steel has several advantages over normal or mild steel. Apart from resistance to corrosion and greater strength, the material comes with several other advantages:
High resistance to corrosion
As mentioned, stainless steel has
an oxide layer, that makes it resistant to corrosion. This layer serves as a
protective covering, self-healing in nature. This indicates that regardless of
what fabrication methods you incorporate, the level of corrosion resistance
will remain intact. Even when stainless steel is damaged or cut, it will remain
resistant to corrosion. On the other hand, normal steel can be protected by
providing it with a coating or galvanizing the material. If any modification is
made on the surface, the underlying material becomes susceptible to corrosion.
Greater cryogenic toughnessStainless steel comes with greater
cryogenic toughness, as compared to normal steel. This is gauged by the
toughness or ductility of the material and temperatures below zero. At such
temperatures, austenitic stainless steel has a significantly higher tensile
strength, than that at ambient temperatures. At the same time, they have a
greater degree of toughness.
Higher rate of work hardening
One of the advantages of using stainless steel is that the strength of the metal can be increased through cold working. It has a higher rate of work hardening, as compared to normal steel. A calculated combination of annealing stages and cold working can be used to deliver a specific strength to the fabricated component.
For instance, you might consider the drawing of wire. In springs, certain wires are used, which get the desired level of tensile strength through work hardening. However, if the same wire serves the function of bendable tie wire, the material would be softer as a result of annealing.
Greater hot strength
Austenitic grades of stainless
steel are capable of retaining higher strengths at greater temperatures.
Particularly, the grades of stainless steel that have high levels of silicon,chromium, rare earth elements or nitrogen. For instance, stainless steel grades like 446, with chromium ferritic ingredients have high hot strength. Due to the high content of chromium, stainless steel can resist high temperatures.
Greater strengthStainless steel, in comparison to
mild steel, has greater strength. The tensile strength in this type of steel is greater than normal steel. Particularly, in the precipitation hardening and martensitic grades of stainless steel, you can find the highest tensile strength. Even this type of stainless steel has double the strength of 304 and 316, two of the most common variants of stainless steel.
Depending on the purpose and properties required, one can choose the desired grade of stainless steel. Ferric stainless steel, austenitic stainless steel, martensitic stainless steel, and duplex stainless steel are some of the popular grades. A proper customization process ensures that the right grade is used for a specific purpose.