Stainless steel is a steel alloy that contains 10.5% chromium with or without other alloying elements and has a maximum of 1.2% carbon by mass. It is mainly known for its corrosion resistance properties, which can be enhanced by adding nickel and molybdenum. Its ability to resist corrosion makes the alloy “stainless.” The resistance of the metallic alloys in stainless steel to corrosion is based on passivation. The prevalence and stability of passivation depend on the condition that Fe-Cr alloy must have a minimum chromium content of about 10.5% by weight. Chromium forms a thin layer of chromium oxide on the steel surface. It forms a “passive layer” that acts as a reliable protective coating for stainless steel. The passive layer has self-healing capability. The presence of chromium also hardens and then toughens stainless steel.
You can roll stainless steel into sheets, plates, bars, wire, and tubing. 316 stainless steel tube is a popularly used grade in various industries and belongs to the austenitic stainless-steel family. It shows excellent corrosion resistance, weldability, machinability and is helpful in different applications at high temperatures. It finds use in food processing components, pharmaceutical, and chemical equipment.
The presence of varying alloying elements in differing compositions ascribes to it its various pertinent properties. The metallic alloy has an iron base. Pure iron is very soft, and its mechanical strength improves only by adding different alloying elements like carbon, manganese, or silicon. The alloys support engineering construction. The commonly used alloying elements in stainless steel include:
Carbon is a non-metallic element present in all grades of stainless steel. Its austenitizing solid and increasing carbon content improves the hardness and strength of stainless steel. In stainless steel, carbon is the principal hardening element. You cannot harden or strengthen pure iron by heat treatment. The addition of carbon, however, enables a wide range of hardness and strength. But the presence of a higher amount of carbon makes stainless steel brittle and reduces its weldability.
The presence of chromium in stainless steel increases its hardness, strength, and corrosion resistance. Chromium is critical in the manufacturing of stainless steel. It increases steel’s resistance to oxidation. It forms a self-repairing passive layer of Chromium Oxide on the steel surface. At higher temperatures, it increases the strength of stainless steel.
Nickel is a commonly used alloying element in the production of stainless steel. Nickel enhances its essential properties such as formability, weldability, and ductility. At elevated temperatures, it improves stainless steel’s resistance to oxidation and corrosion. It also reduces thermal expansion for better dimensional stability. Nickel helps in stabilizing the austenitic structure of the steel at room temperature and below.
Like chromium, molybdenum impacts the corrosion resistance of steel. It also increases stainless steel’s hardenability and strength, generally at high temperatures. It has a high melting point, due to which it gives strength to steel at high temperatures. Molybdenum also increases steel’s high-temperature tensile and creep strengths. It improves stainless steel’s resistance to pitting and crevice corrosion, generally in chlorides and sulfur-containing environments.
The presence of these alloying elements in varying compositions determines the properties of stainless steel. It renders it useful for different end-uses to serve essential purposes across various industries.