Properties of Stainless Steel
- Stainless steel is an alloy of iron that is resistant to rusting and corrosion.
- It contains at least 10.5% chromium and usually nickel, and may also contain other elements.
- Stainless steel can be rolled into sheets, plates, bars, wire, and tubing.
- It is used in various applications such as cookware, cutlery, surgical instruments, and major appliances.
- Stainless steel is also used in industrial equipment, construction material, and storage tanks.
- Stainless steel rusts only on the outer few layers, while deeper layers are shielded by its chromium content.
- Nitrogen can improve resistance to pitting corrosion and increase mechanical strength.
- Different grades of stainless steel with varying chromium and molybdenum contents are available.
- Corrosion resistance can be increased by increasing chromium and nickel content, and adding molybdenum.
- ISO 15510 standard lists the chemical compositions of stainless steels in various specifications.
- The tensile yield strength of common stainless steel type 304 is around 30,000psi in the annealed condition.
- Cold working can strengthen stainless steel to a tensile yield strength of 153,000psi in the full-hard condition.
- Precipitation hardening alloys like 17-4 PH and Custom 465 can have tensile yield strengths up to 251,000psi.
- Different stainless steel grades have varying strength levels to suit different applications.
- Strength can be tailored through heat treatment and alloy composition.
- Stainless steel has a melting point near that of ordinary steel, higher than that of aluminum or copper.
- The melting point is expressed as a range, typically between 1,400 to 1,530°C (2,550 to 2,790°F).
- The specific consistency of the alloy determines the melting point range.
- Stainless steel melting point is affected by its composition and alloying elements.
- The melting point range is important for processing and fabrication of stainless steel.
- Stainless steels have lower electrical conductivity compared to copper.
- Non-electrical contact resistance (ECR) arises due to the protective oxide layer on stainless steel.
- Copper alloys and nickel-coated connectors have lower ECR values and are preferred for electrical applications.
- Martensitic, duplex, and ferritic stainless steels are magnetic, while austenitic stainless steel is usually non-magnetic.
- Austenitic stainless steel can become slightly magnetic through work hardening.

History of Stainless Steel
- German chemist Hans Goldschmidt developed aluminothermic process for carbon-free chromium in the late 1890s.
- Leon Guillet of France prepared alloys that would be considered stainless steel today between 1904 and 1911.
- Friedrich Krupp Germaniawerft built the sailing yacht Germania with a chrome-nickel steel hull in 1908.
- Philip Monnartz reported on the relationship between chromium content and corrosion resistance in 1911.
- Christian Dantsizen of General Electric and Frederick Becket at Union Carbide industrialised ferritic stainless steel in the United States.
- Harry Brearley discovered and industrialised a martensitic stainless steel alloy in 1912.
- The discovery was announced in a 1915 newspaper article.
- The alloy was marketed under the Staybrite brand by Firth Vickers.
- Brearley applied for a US patent in 1915 but found that Elwood Haynes had already registered one.
- Brearley and Haynes formed the American Stainless Steel Corporation in Pittsburgh, Pennsylvania.
- Harry Brearley initially called his alloy rustless steel.
- The alloy was sold in the US under different brand names like Allegheny metal and Nirosta steel.
- The name stainless steel was given by a local cutlery manufacturer.
- Ford Motor Company continued calling the alloy rustless steel in 1932.
- Over 25,000 tons of stainless steel were manufactured and sold annually in the US in 1929.

Austenitic Stainless Steel
- Austenitic stainless steel is the largest family of stainless steels.
- They possess an austenitic microstructure achieved by alloying steel with nickel and/or manganese.
- Austenitic stainless steels are not hardenable by heat treatment.
- Metastable austenitic stainless steels are widely used in manufacturing cryogenic pressure vessels.
- Cryogenic cold-forming improves wear resistance of austenitic stainless steel.

Ferritic Stainless Steel
- Ferritic stainless steels possess a ferrite microstructure like carbon steel.
- They contain between 10.5% and 27% chromium with little or no nickel.
- Ferritic stainless steels cannot be hardened by heat treatment.
- They are less expensive than austenitic steels and are used in automobile exhaust pipes, architectural applications, and building components.
- Additions of niobium, titanium, and zirconium allow good weldability in ferritic stainless steels.

Martensitic Stainless Steel
- Martensitic stainless steels have a body-centered cubic crystal structure.
- They offer a wide range of properties and are used as stainless engineering steels, stainless tool steels, and creep-resistant steels.
- Martensitic stainless steels are magnetic and less corrosion-resistant than ferritic and austenitic stainless steels.
- They fall into four categories: Fe-Cr-C grades, Fe-Cr-Ni-C grades, precipitation hardening grades, and creep-resisting grades.
- Heat treatment can improve the mechanical properties of martensitic stainless steels.

Note: The content does not provide enough information to create comprehensive groups for the subtopics: Stainless Steel Grades, Quenching Process, Tempering Process, Carbon Replacement with Nitrogen, and Time Frame.

Stainless steel (Wikipedia)

Stainless steel, also known as inox, corrosion-resistant steel (CRES) and rustless steel, is an alloy of iron that is resistant to rusting and corrosion. It contains at least 10.5% chromium and usually nickel, and may also contain other elements, such as carbon, to obtain the desired properties. Stainless steel's resistance to corrosion results from the chromium, which forms a passive film that can protect the material and self-heal in the presence of oxygen.

The alloy's properties, such as luster and resistance to corrosion, are useful in many applications. Stainless steel can be rolled into sheets, plates, bars, wire, and tubing. These can be used in cookware, cutlery, surgical instruments, major appliances, vehicles, construction material in large buildings, industrial equipment (e.g., in paper mills, chemical plants, water treatment), and storage tanks and tankers for chemicals and food products.

The biological cleanability of stainless steel is superior to both aluminium and copper, and comparable to glass. Its cleanability, strength, and corrosion resistance have prompted the use of stainless steel in pharmaceutical and food processing plants.

Different types of stainless steel are labeled with an AISI three-digit number. The ISO 15510 standard lists the chemical compositions of stainless steels of the specifications in existing ISO, ASTM, EN, JIS, and GB standards in a useful interchange table.