What Is Stainless Steel? And Its 5 Types?

Stainless steel is an alloy of iron, chromium, and, in some cases, nickel and other metals. The other common additives are carbon, manganese, molybdenum, nitrogen, sulfur, copper, and silicon. Stainless steel is known for its corrosion resistance in varied environments in which carbon and other low alloy steels would easily corrode. The presence of chromium in stainless steel leads to the formation of a tough, adherent, invisible, corrosion-resisting chromium oxide film on the steel surface. More than 60 grades of stainless steel are available today.

Special grades of stainless steel can resist scaling and retain high strength at extremely high temperatures. The easy cleaning ability of stainless steel makes it ideal for maintaining hygiene. Stainless steel can be cut welded, bent, formed, machined, assembled, and fabricated easily. It also has a long life expectancy and is recyclable. Because of its versatile nature, stainless steel is used widely. The global stainless steel market was worth USD 111.4 billion in 2019 and is projected to reach USD 181 billion by 2027 with a growth rate of 6.3% over 2020-2027. Arch City Steel is a top distributor of commonly specified grades and sizes of stainless steel for commercial purposes.

There are mainly five types of stainless steel.

  • Austenitic Stainless Steel

It has austenite as the primary microstructure. When nickel is added to stainless steel in adequate quantity, its crystal structure changes to “austenite”. Austenitic stainless steel consists of 18% chromium and 8% nickel. It is the most commonly used stainless steel and is known for its high toughness and impressive resistance to elevated temperatures. It has excellent formability, fabricability, and ductility. It is used in computer keyboard key springs, kitchen sinks, food processing equipment, architectural applications, chemical plant, and equipment.

  • Ferritic Stainless Steel

Ferritic steel is plain chromium stainless steel. It has varying chromium content between 12% and 18%. As the chromium content increases, its corrosion resistance also increases. It has poor weldability, and its formability is not as good as austenitic. Ferritic Stainless Steels generally have better engineering abilities than austenitic grades. It is used in automotive trim, automotive exhausts, colliery equipment, and hot water tanks.

  • Duplex Stainless Steel

Duplex stainless steels have relatively higher chromium content (between 18 and 28%) and moderate amounts of nickel (between 4.5 and 8%). Hence, it is a mixture of austenitic and ferritic stainless steel. Most duplex steels contain molybdenum in a range of 2.5 – 4%. It shows high resistance to stress corrosion cracking, and has good weldability and formability. It has higher tensile and yield strength than austenitic or ferritic steels. It is used in marine equipment, desalination plants, heat exchangers, and petrochemical plants.

  • Martensitic Stainless Steel

It has high carbon (0.1 – 1.2%) content. These are plain chromium steels containing between 12 and 18% chromium. Martensitic Stainless Steel has moderate corrosion resistance and can be hardened by heat treatment. It shows poor weldability. Like ferritic grades, it is magnetic. It is used in knife blades, surgical instruments, shafts, spindles, and pins

  • Precipitation Hardening Stainless Steels

It provides a combination of austenitic and martensitic properties. It can be hardened after fabrication in a single low temperature “aging” process. It shows moderate to good corrosion resistance and has very high strength. It can be welded easily and has magnetic properties like the ferritic grades.

To Conclude:

The demand for stainless steel is increasing steadily. Different industries utilize stainless steel because of its excellent corrosion resistance, good weldability and formability, and high strength.

5 Things You Should Know About Alloy C-276

Alloy C-276 is a nickel-molybdenum- chromium wrought superalloy with an addition of tungsten. It is the most universally corrosion-resistant material available today. Alloy C-276 also has excellent resistance to pitting, crevice corrosion, and stress corrosion cracking. It is widely used in the chemical process and associated industries.

Alloy C-276 is available in plates, covered electrodes, sheets, strips, billets, bars, wires, pipes, and tubes. Alloy C276 pipe is used in the most severe environments to transfer fluids and fluidized solids. This material is known for its corrosion resistance properties in a wide range of aggressive media.

Here is a list of 5 things you should know about Alloy C-276

· Common Trade Names

Hastelloy C276, Alloy C-276, Nickel C-276; Nickelvac HC-276, Inconel C-276, Nicrofer 5716.

· Applications

Alloy C-276 finds wide applicability across various industries. It is used in digesters and bleach plants in the paper industry. Alloy C-276 is used in chemical processing for multiple components, including heat exchangers, reaction vessels, evaporators, and transfer piping. It is used in components for the recovery of “sour” natural gas. Alloy C-276 is used to manufacture various air pollution control parts, including stack liners, ducts, dampers, scrubbers, stack-gas re-heaters, fans, and fan housings.

Equipment for flue-gas desulfurization plants uses this super-alloy. It is also used in various components which utilize halide or acid catalysts, mixed acid chemical processing, pollution control, pulp and paper production, and municipal waste treatment.

· Characteristics

Alloy C-276 shows exceptional resistance to strong solutions of oxidizing salts, like the ferric and cupric chlorides.

It is one of the few alloys mixes which exhibits resistance to wet chloride gas, hypochlorite, and chlorine dioxide solutions.

Alloy C-276 does not succumb to grain boundary precipitation in welded conditions. Hence it finds extensive use in chemical process applications.

· Resistance to Corrosion

Alloy C-276 shows exceptional resistance to stress corrosion cracking in chloride-bearing solutions, including wet chloride gas, hypochlorite, and chlorine solutions. It also possesses resistance to sulfuric acid, hydrochloric acid, formic acid, acetic acid, chlorides, and solvents. It is much more resistant to stress corrosion cracking than the comparative, austenitic stainless steels. Alloy C-276 exhibits resistance to seawater crevice corrosion. It also has resistance capabilities against phosphoric acid at temperatures below boiling and concentrations lower than 65%. C-276 alloy shows excellent resistance to key, inorganic acids, even in welded form. Because of its high chromium and molybdenum contents, it can withstand both oxidizing and non-oxidizing acids.

· Fabrication and Welding

Alloy C-276 can be hot forged, hot rolled, hot upset, hot extruded, and hot-formed. Hot forming should be done between 1600 and 2250°F (870 and 1230°C), with all heavy forming above 2000°F (1090°C). It can be annealed to optimize the alloy’s corrosion resistance and flexibility. For optimum corrosion performance, cold-worked parts should be re-annealed. Hence, this alloy type can be formed using various cold and hot working processes. Annealing should be practiced at a temperature between 2050°F and 2150°F. A rapid quench should follow this in a protective atmosphere or agitated reducing quench bath.

Alloy C-276 work hardens quickly. However, it can be cold formed again using aggressive methods such as deep drawing, press forming, and punching.

To Conclude:

Alloy C-276 is known for its outstanding corrosion resistance to pitting and crevice attack in the presence of chlorides and other halides and a wide range of aggressive media. It is used in a variety of chemical process environments.