Stainless steel and its properties

Stainless steel is an iron alloy that is resistant to rust and corrosion. It contains at least 11% chromium and may contain elements such as carbon and other non-metals for other desired properties.Stainless steel's corrosion resistance comes from chromium, which forms a passive film that protects the material and repairs itself in the presence of oxygen.Properties of the alloy, such as luster and corrosion resistance, are useful in many applications.Stainless steel can be rolled into sheet, plate, bar, wire and tube.These are used in cookware, tableware, surgical instruments, major appliances, vehicles, construction materials for large buildings, industrial equipment (eg paper mills, chemical plants, water treatment) and storage tanks and tankers for chemicals and food.

The biological cleaning ability of stainless steel is better than that of aluminum and copper, and it is comparable to that of glass.Its cleanability, strength, and corrosion resistance have led to the use of stainless steel in pharmaceutical and food processing plants.The different types of stainless steel are marked with an AISI three-digit number.The ISO 15510 standard lists the chemical composition of stainless steels specified in existing ISO, ASTM, EN, JIS and GB standards in a useful interchange.

Properties

Conductivity:

Like steel, stainless steel is a relatively poor conductor of electricity, having a significantly lower electrical conductivity than copper. In particular, the non-electrical contact resistance (ECR) of stainless steel is due to the dense protective oxide layer and limits its functionality as an electrical connector application.Copper alloys and nickel-plated connectors tend to exhibit lower ECR values and are the materials of choice for such applications. However, stainless steel connectors are used where ECRs impose lower design criteria and where corrosion resistance is required, such as in high temperature and oxidizing environments.

Melting point:

Like most alloys, the melting point of stainless steel is expressed as a range of temperatures rather than a single temperature.This temperature range is from 1,400 to 1,530 °C (2,550 to 2,790 °F; 1,670 to 1,800 K; 3,010 to 3,250 °R) depending on the specific consistency of the alloy in question.

Hardness:

Stainless steel is a highly durable metal known for its impressive hardness.This quality is mainly due to the presence of two key ingredients: chromium and nickel.Chromium forms an oxide layer on metal surfaces that protects the metal from corrosion and wear. At the same time, nickel helps to increase the strength and ductility of the metal, thereby increasing its overall hardness.Stainless steel can also be hardened by heat treatment processes such as annealing or quenching to further increase its hardness.

Thermal Conduction:

The thermal conductivity of stainless steel depends on its composition and structure.Typically, stainless steel has a thermal conductivity in the range of 15 to 20 W/mK (watts per meter Kelvin).Therefore, it retains more energy to stabilize the surrounding temperature.

Magnetic:

Martensitic, duplex, and ferritic stainless steels are magnetic, while austenitic stainless steels are generally non-magnetic.Ferritic steel owes its magnetic properties to its body-centered cubic crystal structure, in which the iron atoms are arranged in a cube (one iron atom at each corner), with an additional iron atom in the center.This central iron atom determines the magnetic properties of ferritic steels. This arrangement also limits the amount of carbon the steel can absorb to around 0.025%.Grades with low coercivity have been developed for electronic valves used in household appliances and injection systems in internal combustion engines.Some applications require non-magnetic materials, such as magnetic resonance imaging.Austenitic stainless steels, which are normally nonmagnetic, can be made slightly magnetic by work hardening. Sometimes, if austenitic steel is bent or cut, magnetism can develop along the edges of the stainless steel as the crystal structure rearranges itself.