Ferritic stainless steel is plain chromium (10.5-28%) alloy, usually with low carbon content. It is magnetic and ductile, and as the name suggests it has high resistance to corrosion and oxidation. They are generally resistant to stress corrosion cracking. However, its welding tendency has some limitations, which restrict its use to thinner gauges. 3CR12, a special grade, which is developed and patented by Columbus Stainless, largely overcomes this problem. These grades can be buffed in order to provide luster to the final cut of stainless steel.
This stainless steel contains chromium and nickel grades with very low carbon content. They are non-magnetic but can become slightly magnetic when cold-worked. Cold working also enhances their strength. They have excellent corrosion resistance, especially to atmospheric corrosion; good formability; good weldability, and excellent mechanical properties over a wide range of temperatures. In addition, these steel are easy to clean, which enhances their use in applications in hygienic and sterile environments.
Austenitic Stainless Steel is divided further into 2 broad categories:
This category of stainless is popularly known as the 300 series. Currently, it is the largest produced stainless grade globally. Application ranges from food processing plants, chemical plants, architectural equipment, kitchenware, hospitals.
The 200 series of stainless steel is considered as the fastest growing and highest revenue earning steel. The Stainless steel is used for applications which include kitchenware, cutlery, sinks, and automobiles.
This grade of stainless steel contains high level of chromium and nickel. The amount of chromium may vary from 18-28%. Duplex gets its identity from the combination of ferritic and austenitic grade of stainless steel. According to the needs and demands, this grade may also contain elements like molybdenum (1-5%), nitrogen (0.05-0.3%), copper, and tungsten (up to 2%). These grades are extremely corrosion resistant and are even tolerant to chloride stress and attack, which makes them a perfect companion for marine applications, offshore platforms, paper and pulp industries, and desalination plants. It has a higher welding and fabrication range than any of its parent stainless steel. The combination can lead to significant cost and weight savings compared to a solution in austenitic stainless steels.
Through heat therapy, only the martensitic stainless steels can be treated to enhance hardness of the alloy. The most popular method to harden the surface of stainless is by precipitation hardening, but martensitic stainless grade goes through a different procedure for the same purpose. In this process, small particles are formed by the appropriate heat treatment and these particle acts as the strengthening agent in the steel matrix.
They are high carbon containing (0.1-1.2%), plain chromium contacting stainless steel grades. The main motto to create martensitic grade was to develop cutlery items, but it performs best under hardened conditions and mildly corrosive environment. Their common uses are knife blades, instruments, fasteners, shafts.