Stainless steel

Austenitic stainless steel[24][25] is the largest family of stainless steels, making up about two-thirds of all stainless steel production (see production figures below). They possess an austenitic microstructure, which is a face-centered cubic crystal structure. This microstructure is achieved by alloying with sufficient nickel and/or manganese and nitrogen to maintain an austenitic microstructure at all temperatures from the cryogenic region to the melting point. Thus austenitic stainless steels are not hardenable by heat treatment since they possess the same microstructure at all temperatures.

Their yield strength is low (200 to 300 MPa), which limits their use for structural and other load bearing components. Duplex stainless steels tend to be preferred in such situations because of their high strength and corrosion resistance. Their elongation is high, which allows very important deformation in fabrication processes (such as deep drawing of kitchen sinks). They are weldable by all processes. The most frequently used is electric arc welding (see welding section below). They are essentially non-magnetic and maintain their ductility at cryogenic temperatures.

Thin sheets and small diameter bars can be strengthened by cold working, with an associated reduction of elongation; however, if they are welded, the welded area will return to the low strength level of the steel before cold working. This limits the use of cold-worked austenitic stainless steels.

They can be further subdivided into two sub-groups, 200 series and 300 series:

• 200 series[26] are chromium-manganese-nickel alloys, which maximize the use of manganese and nitrogen to minimize the use of nickel. Due to their nitrogen addition, they possess approximately 50% higher yield strength than 300 series stainless steels.
  • Type 201 is hardenable through cold working,
  • Type 202 is a general purpose stainless steel. Decreasing nickel content and increasing manganese results in weak corrosion resistance.[27]
• 300 series are chromium-nickel alloys, which achieve their austenitic microstructure almost exclusively by nickel alloying; some very highly alloyed grades include some nitrogen to reduce nickel requirements. 300 series is the largest group and the most widely used.
  • Type 304: The best known grade is Type 304, also known as 18/8 and 18/10 for its composition of 18% chromium and 8%/10% nickel, respectively.
  • Type 316: The second most common austenitic stainless steel is Type 316. The addition of 2% molybdenum provides greater resistance to acids and to localized corrosion caused by chloride ions. Low-carbon versions, for example, 316L or 304L, are used to avoid corrosion problems caused by welding. The "L" means that the carbon content of the alloy is below 0.03%.

Ferritic stainless steels possess a ferrite microstructure like carbon steel, which is a body-centered cubic crystal structure, and contain between 10.5% and 27% chromium with very little or no nickel. This microstructure is present at all temperatures, due to the chromium addition, and like austenitic stainless steels, these are not hardenable by heat treatment. They cannot be strengthened by cold work to the same degree as austenitic stainless steel. They are magnetic like carbon steel.

Additions of niobium (Nb), titanium (Ti), and zirconium (Zr) to grade 430 allow good weldability (see welding section below).

As they do not contain nickel, they cost less than austenitic grades and are now present in a wide range of industries.

Common grades are 409 and 409 Cb (Cb columbium is the US name for niobium) with about 10.5% chromium, the latter being used mostly for automobile exhaust pipes in North America, while stabilized grades 439 and 441 are used in Europe.[28]

Ferritics such as 430 (17% Cr) are used for architectural applications and structural applications.[29]

Swiss Army knives are made of martensitic stainless steel.

They are used for kitchenware,[30] sinks, slate hooks, roofing, white goods (dishwashers, refrigerator doors, etc.), chimney ducts, solar water heaters and others.

Higher chromium ferritics (22% Cr) are now used for power plates for solid oxide fuel cells (SOFC) operating at temperatures around 700 °C.[31]

Electrical resistance ferritic grades Fr-Cr-Al are not included in these groups, as they are designed for oxidation resistance at elevated temperatures.[32]

Martensitic stainless steels offer a wide range of properties and are used as stainless engineering steels, stainless tool steels, and creep resisting steels. They fall into four categories (with some overlap):[33]

1. Fe-Cr-C grades: They were the first grades used and they are still widely used in engineering and wear-resistant applications.
2. Fe-Cr-Ni-C grades: In these grades, some of the carbon is replaced by nickel. They offer a higher toughness and higher corrosion resistance. Grade EN 1.4303 (Casting grade CA6NM) with 13% Cr and 4% Ni is used for most Pelton, Kaplan and Francis turbines in hydroelectric power plants[34] because it has good casting properties, a good weldability and a good resistance to cavitation erosion.
3. Precipitation hardening grades: Grade EN 1.4542 (a.k.a. 17/4PH), the best known grade, combines martensitic hardening and precipitation hardening. It achieves high strength and good toughness and is used in aerospace among other applications.
4. Creep-resisting grades: Small additions of niobium, vanadium, boron, and cobalt increase the strength and creep resistance up to about 650 °C.

Martensitic stainless steels form a family of stainless steels that can be heat treated to provide an adequate level of mechanical properties.

The heat treatment typically involves three steps:[35]

1. Austenitizing, in which the steel is heated to a temperature in the range 980–1050 °C depending on the grades. The austenite is a face centered cubic phase.
2. Quenching. The austenite is transformed into martensite, a hard body-centered tetragonal crystal structure. The as-quenched martensite is very hard and too brittle for most applications. Some residual austenite may remain.
3. Tempering, i.e. heating to around 500 °C, holding at temperature, then air cooling. Increasing the tempering temperature decreases the yield strength and ultimate tensile strength but increases the elongation and the impact resistance.

Replacing some of the carbon in martensitic stainless steels by nitrogen is a fairly recent development. The limited solubility of nitrogen has been increased by the pressure electroslag refining (PESR) process in which melting is carried out under a high nitrogen pressure. Up to 0.4% nitrogen contents have been achieved leading to higher hardness/strength and higher corrosion resistance. As the PESR is expensive, lower but significant nitrogen contents have been achieved using the standard argon oxygen decarburization (AOD) process.[36][37][38][39][40]

They are magnetic. They are not as corrosion resistant as the common ferritic and austenitic stainless steels due to their low chromium content.

Duplex stainless steels have a mixed microstructure of austenite and ferrite, the aim usually being to produce a 50:50 mix, although in commercial alloys the ratio maybe 40:60. They are characterized by high chromium (19–32%) and molybdenum (up to 5%) and lower nickel contents than austenitic stainless steels. Duplex stainless steels have roughly twice the yield strength of austenitic stainless steel. Their mixed microstructure provides improved resistance to chloride stress corrosion cracking in comparison to austenitic stainless steel Types 304 and 316.

Duplex grades are usually divided into three sub-groups based on their corrosion resistance: lean duplex, standard duplex, and super duplex.

The properties of duplex stainless steels are achieved with an overall lower alloy content than similar-performing super-austenitic grades, making their use cost-effective for many applications. The pulp and paper industry was one of the first ones to use extensively duplex stainless steel. Today, the oil and gas industry is the largest user and has pushed for more corrosion resistant grades, leading to the development of super duplex and even so-called hyper duplex grades. More recently, the less expensive (and slightly less corrosion-resistant) lean duplex has been developed, chiefly for structural applications in building and construction (concrete reinforcing bars, plates for bridges, coastal works) and for the water industry.

Precipitation hardening stainless steels have corrosion resistance comparable to austenitic varieties, but can be precipitation hardened to even higher strengths than the other martensitic grades.

There are based on three types:[41]

- Martensitic 17-4 PH[42] (AISI 630 EN 1.4542) contains about 17% Cr, 4% Ni, 4% Cu, and 0.3% Nb.

Solution treatment at about 1040 °C followed by quenching results in a relatively ductile martensitic structure. Subsequent aging treatment at 475 °C precipitates Nb and Cu-rich phases that increase the strength up to above 1000 MPa yield strength. This outstanding strength level finds uses in high tech applications such as aerospace (usually after remelting to eliminate non-metallic inclusions and thereby to increase fatigue life). Another major advantage of this steel is that aging, unlike tempering treatments, is carried out at a temperature that can be applied to (nearly) finished parts without distortion and discoloration.

- Semi-austenitic 17-7PH[42] (AISI 631 EN 1.4568) contains about 17% Cr, 7.2% Ni, and 1.2% Al.

Typical heat treatment involves first solution treatment and quenching. At this point, the structure remains austenitic. Martensitic transformation is then obtained either by a cryogenic treatment at −75 °C or by severe cold work (over 70% deformation, usually by cold rolling or wire drawing). Aging at 510 °C – which precipitates the Ni₃Al intermetallic phase – is carried out as above on nearly finished parts. Yield stress levels above 1400 MPa are then reached.

- Austenitic A286[43](ASTM 660 EN 1.4980) has the following typical analysis Cr 15%, Ni 25%, Ti 2.1%, Mo 1.2%, V 1.3%, and B 0.005%.

The structure remains austenitic at all temperatures.

Typical heat treatment involves solution treatment and quenching, followed by aging at 715 °C. Aging forms Ni₃Ti precipitates and increases the yield strength to about 650 MPa at room temperature. Unlike the above grades, the mechanical properties and creep resistance of this PH steel remain very good at temperatures up to 700 °C.

A286 is in fact a Fe-based superalloy, used in jet engines and gas turbines, turbo parts, etc.

The designation "CRES" is used in various industries to refer to corrosion-resistant steel. Most mentions of CRES refer to stainless steel, although the correspondence is not absolute, because there are other materials that are corrosion-resistant but not stainless steel.[44]

There are over 150 grades of stainless steel, of which 15 are most commonly used. There are a number of systems for grading stainless and other steels, including US SAE steel grades.

Uniform corrosion takes place in very aggressive environments, typically chemical production or use, pulp, and paper industries, etc. The whole surface of the steel is attacked, and the corrosion is expressed as corrosion rate in mm/year (usually less than 0.1 mm/year is acceptable for such cases). Corrosion tables provide guidelines.[47]

This is typically the case when stainless steels are exposed to acidic or basic solutions. Whether stainless steel corrodes depends on the kind and concentration of acid or base and on the solution temperature. Uniform corrosion is typically easy to avoid because of extensive published corrosion data or easily performed laboratory corrosion testing.

However, stainless steels are susceptible to localized corrosion under certain conditions, which need to be recognized and avoided. Such localized corrosion is problematic for stainless steels because it is unexpected and difficult to predict.

Stainless steel is not completely immune to corrosion as shown in this desalination equipment.

Acidic solutions can be put into two general categories: reducing acids, such as hydrochloric acid and dilute sulfuric acid, and oxidizing acids, such as nitric acid and concentrated sulfuric acid. Increasing chromium and molybdenum content provides increased resistance to reducing acids while increasing chromium and silicon content provides increased resistance to oxidizing acids.

Sulfuric acid is one of the largest-tonnage industrial chemicals manufactured. At room temperature, Type 304 stainless steel is only resistant to 3% acid, while Type 316 SS is resistant to 3% acid up to 50 °C and 20% acid at room temperature. Thus Type 304 SS is rarely used in contact with sulfuric acid. Type 904L SS and Alloy 20 are resistant to sulfuric acid at even higher concentrations above room temperature.[48][49] Concentrated sulfuric acid possesses oxidizing characteristics like nitric acid, and thus silicon-bearing stainless steels also find application.

Hydrochloric acid damages any kind of stainless steel and should be avoided.[2]^:118[50]

All types of stainless steel resist attack from phosphoric acid and nitric acid at room temperature. At high concentration and elevated temperature attack will occur, and higher-alloy stainless steels are required.[51][52]

In general, organic acids are less corrosive than mineral acids such as hydrochloric and sulfuric acid. As the molecular weight of organic acids increases, their corrosivity decreases. Formic acid has the lowest molecular weight and is a weak acid. Type 304 SS can be used with formic acid, though it tends to discolor the solution. Acetic acid is probably the most commercially important of the organic acids, and Type 316 SS is commonly used for storing and handling acetic acid.[53]

Type 304 and Type 316 stainless steels are unaffected by any of the weak bases such as ammonium hydroxide, even in high concentrations and at high temperatures. The same grades of stainless exposed to stronger bases such as sodium hydroxide at high concentrations and high temperatures will likely experience some etching and cracking.[54]

Increasing chromium and nickel contents provide increased resistance.

All grades resist damage from aldehydes and amines, though in the latter case Type 316 is preferable to Type 304; cellulose acetate damages Type 304 SS unless the temperature is kept low. Fats and fatty acids only affect Type 304 SS at temperatures above 150 °C (302 °F) and Type 316 SS above 260 °C (500 °F), while Type 317 SS is unaffected at all temperatures. Type 316L is required for processing of urea.[2]

Localized corrosion can occur in a number of ways, e.g. pitting corrosion and crevice corrosion. Such a localized attack is most common in the presence of chloride ions. Increasing chloride levels require more highly alloyed stainless steels.

Localized corrosion can be difficult to predict because it is dependent on many factors, including:

• Chloride ion concentration (however, even when the chloride solution concentration is known, it is still possible for chloride ions to concentrate, such as in crevices (e.g. under gaskets) or on surfaces in vapor spaces due to evaporation and condensation).
• Increasing temperature increases susceptibility.
• Increasing acidity increases susceptibility.
• Stagnant conditions increase susceptibility.
• The presence of oxidizing species, such as ferric and cupric ions.

This is probably the most frequent form of corrosion. The corrosion resistance of stainless steels to pitting corrosion is often expressed by the PREN (pitting resistance equivalent number) obtained through the formula

PREN = %Cr + 3.3 %Mo + 16 %N,

where the terms correspond to the contents proportion by mass of chromium, molybdenum, and nitrogen respectively in the steel.

The higher the PREN, the higher the pitting corrosion resistance. Increasing chromium, molybdenum and nitrogen contents provide increasing resistance to pitting corrosion.

While the PREN is a property of the stainless steel, crevice corrosion occurs when poor design has created confined areas (overlapping plates, washer-plate interfaces, etc.), or when deposits on the material have created same, and when the PREN is not high enough for the service conditions. Design and good fabrication techniques combined with correct alloy selection can prevent such corrosion.[55]

Stress corrosion cracking (SCC) is a sudden cracking and failure of a component without deformation.

It may occur when three conditions are met:

• The part is stressed (by an applied load or by residual stress).
• The environment is aggressive (high chloride level, temperature above 50 °C, presence of H₂S).
• The stainless steel is not sufficiently SCC-resistant.

The SCC mechanism results from the following sequence of events:

1. Pitting occurs.
2. Cracks start from a pit initiation site.
3. Cracks then propagate through the metal in a transgranular or intergranular mode.
4. Failure occurs.

Whereas pitting leads in most cases to unsightly surfaces and in the worst case to perforation of the stainless sheet, failure by SCC can lead to very damaging consequences. It is therefore considered as a special form of corrosion.

As SCC requires several conditions to be met, it is relatively easy to avoid it:

• Reduce the stress level (the oil and gas specifications provide requirements for maximal stress level in H₂S-containing environments).
• Assess the aggressiveness of the environment (high chloride content, temperature above 50 °C, etc.).
• Select the right type of stainless steel: superaustenitics such as grade 904L or super-duplex (ferritic stainless steels and duplex stainless steels are very resistant to SCC).

Left nut is not stainless and is rusty

Galvanic corrosion[56] (also called "dissimilar-metal corrosion") refers to corrosion damage induced when two dissimilar materials are coupled in a corrosive electrolyte. The most common electrolyte is water, ranging from freshwater to seawater. When a galvanic couple forms, one of the metals in the couple becomes the anode and corrodes faster than it would all by itself, while the other becomes the cathode and corrodes slower than it would alone. Stainless steel, due to its superior corrosion resistance relative to most other metals, including steel and aluminium, becomes the cathode, accelerating the corrosion of the anodic metal. An example is the corrosion of aluminium rivets fastening stainless steel sheets in contact with water.[57]

The relative surface areas of the anode and the cathode are important. In the above example, the surface of the rivets will be small compared to that of the stainless-steel sheet. However, if stainless-steel fasteners are used to assemble aluminium sheets, galvanic corrosion will be much slower because the galvanic current density on the aluminium surface will be order of magnitude smaller.

A similar, but frequent mistake, is to assemble stainless-steel parts with carbon-steel fasteners; whereas using stainless steel to fasten carbon-steel plates is usually acceptable. Providing electrical insulation between the dissimilar metals, where possible, is effective at preventing this type of corrosion.

At elevated temperatures all metals react with hot gases. The most common high-temperature gaseous mixture is air, and oxygen is the most reactive component of air. Carbon steel is limited to approximately 900 °F (480 °C) in air. Chromium in stainless steel reacts with oxygen to form a chromium oxide scale, which reduces oxygen diffusion into the material. The minimum 10.5% chromium in stainless steels provides resistance to approximately 1,300 °F (700 °C), while 16% chromium provides resistance up to approximately 2,200 °F (1,200 °C). Type 304, the most common grade of stainless steel with 18% chromium, is resistant to approximately 1,600 °F (870 °C). Other gases such as sulfur dioxide, hydrogen sulfide, carbon monoxide, chlorine, and others also attack stainless steel. Resistance to other gases is dependent on the type of gas, the temperature and the alloying content of the stainless steel.[58][59]

Oxidation resistance increases with chromium, as well as silicon and aluminum, content. Small additions of cerium and yttrium increase the adhesion of the oxide layer on the surface.[60]

Fe-Cr-Al ferritic stainless steels with aluminum up to 5% are used for electrical-resistance alloys, such as Kanthal, in the form of wire or ribbons.

Properties of a few common grades are listed below.

Like steel, stainless steels are relatively poor conductors of electricity, with significantly lower electrical conductivity than copper.

Martensitic and ferritic stainless steels are magnetic.

Ferritic steels are made up of ferrite crystals, a form of iron with up to 0.025% carbon. It only absorbs a small amount of carbon because of its cubic crystalline structure, which consists of one iron in each corner and a central iron atom; the central atom is what gives it magnetic properties.

Grades with low coercitive field Hc have been developed for electrovalves used in household appliances and for injection systems in internal combustion engines

Annealed austenitic stainless steels are usually non-magnetic.

Some applications require non-magnetic materials, such as magnetic resonance imaging.

Work hardening can make cold-formed austenitic stainless steels slightly magnetic. Sometimes if austenitic steel is bent or cut, it creates magnetism along the edge of the stainless steel because the crystal structure rearranges itself.

Galling, sometimes called cold welding, is a form of severe adhesive wear, which can occur when two metal surfaces are in relative motion to each other and under heavy pressure. Austenitic stainless steel fasteners are particularly susceptible to thread galling, although it also occurs in other alloys that self-generate a protective oxide surface film, such as aluminum and titanium. Under high contact-force sliding, this oxide can be deformed, broken and removed from parts of the component, exposing the bare reactive metal. When the two surfaces are of the same material, these exposed surfaces can easily fuse together. Separation of the two surfaces can result in surface tearing and even complete seizure of metal components or fasteners.[62][63]

Galling can be mitigated by the use of dissimilar materials (bronze against stainless steel) or using different stainless steels (martensitic against austenitic). Additionally, threaded joints may be lubricated to provide a film between the two parts and prevent galling. Also, Nitronic 60, made by selective alloying with manganese, silicon, and nitrogen, has demonstrated a reduced tendency to gall.

• Gas metal arc welding also known as metal inert gas (MIG} welding
• Gas tungsten arc welding also known as tungsten inert gas (TIG) welding
• Plasma arc welding
• Flux-cored arc welding
• Shielded metal arc welding (covered electrode)
• Submerged arc welding

MIG and TIG welding are the most common methods used.

• Stud welding
• Resistance spot welding
• Resistance seam welding
• Flash welding
• Laser beam welding

Adhesive bonding has recently gained interest with the development of high preformance glues.[66]

Electric arc welding of ferritic stainless steels type 430 results in grain growth in the heat-affected zone (HAZ) which in turn leads to brittleness. This has been largely overcome with stabilized ferritic grades (with niobium, titanium and zirconium forming precipitates that prevent grain growth).[67][68]

Most of the world's stainless steel production is produced by the following processes.

• Electric arc furnace (EAF) in which stainless steel scrap, other ferrous scrap and ferro alloys (Fe Cr, Fe-Ni, Fe Mo, Fe Si) are melted. The molten metal is then poured into a ladle and transferred into the AOD
• Argon oxygen secarburization (AOD) allows the removal of carbon in the molten steel and other composition adjustments to achieve the desired chemical composition of the steel
• Continuous casting (CC) in which the molten metal is solidified into slabs (typical section is 20 cm thick and 2 m wide) for flat products or blooms (sections vary widely but 25 cm × 25 cm is about the average).
• Hot rolling (HR): The slabs and blooms are reheated in a furnace and then hot rolled. Hot rolling reduces the thickness of the slabs to produce about 3-mm thick coils. Blooms, on the other hand, are hot rolled into bars (that are cut into lengths at the exit of the rolling mill) or wire rod which is coiled.
• Cold finishing (CF): This is a very simplified overview.

Hot rolled coils are pickled in acid solutions to remove the oxide scale on the surface, then subsequently cold rolled (Sendzimir rolling mills), annealed in a protective atmosphere until the desired thickness and surface finish is obtained. Further operations such as slitting, tube forming, and others can be carried out in downstream facilities.

Hot rolled bars are straightened, then machined to the required tolerance and finish.

Wire rod coils are subsequently processed to produce cold finished bars on drawing benches, fasteners on boltmaking machines and wire on single or multipass drawing machines.

World stainless steel production figures re published every year by ISSF.[69]

Overall stainless steel production (flat and long products):

The stainless steel production in China accounted for more than 50% of the world production in 2017. Breakdown of production by families of stainless steels in 2017:

• Austenitic stainless steels Cr-Ni (also-called 300*-series): 54%
• Austenitic stainless steels Cr-Mn (also called 200*-series): 21%
• Ferritic and martensitic stainless steels (also called 400*-series): 23%

This breakdown is quite stable over the years.

• 300, 200 and 400 refer to the ASTM/AISI grade numbering system for stainless steels

The use of stainless steel in buildings can be both practical and aesthetic. In vogue during the Art Deco period, the most famous use of stainless steel during this period is the upper portion of the Chrysler Building. Because of its durability, many of these buildings have retained their original appearance.

Stainless steel is used in the construction of modern buildings, such as the exterior of the Petronas Twin Towers and the Jin Mao Building.[70] The Parliament House of Australia in Canberra has a stainless steel flagpole weighing over 220 metric tons (240 short tons).[71] The largest stainless steel building in North America is the aeration building in the Edmonton Composting Facility, the size of 14 hockey rinks.[72] La Geode in Paris has a dome composed of 6433 polished stainless steel equilateral triangles that form the sphere that reflects the sky.[73] The development of high-strength stainless steel grades such as the "lean duplex" grades, has led to its increasing use in structural applications.[74][75]

Stainless steel is used as a roofing material for airports, due to its low reflectance, which helps to stop pilots from being dazzled, and for its ability to keep the surface of the roof close to ambient temperature. Examples of such airports include the Sacramento International Airport in California and the Hamad International Airport in Qatar.

Stainless steel is used for pedestrian and for road bridges, in the form of tubes, plates, or reinforcing bars.[76] Examples include: the Cala Galdana Bridge in Menorca (Spain), the first stainless steel road bridge to be built; the Champlain Bridge, Montreal;[76] the Oudesluijs bridge in Amsterdam, a bridge made using Construction 3D printing;[77] the Padre Arrupe Bridge in Bilbao, which links the Guggenheim Museum to the University of Deusto campus.[78] the Sant Fruitos Pedestrian Bridge in Spain; Stonecutter's Bridge, Hong Kong;[76] and The Helix Bridge, a pedestrian bridge in Singapore.

• 
  Stainless steel cladding is used on the Walt Disney Concert Hall
• 
  The 630-foot-high (190 m), stainless-clad (type 304) Gateway Arch defines St. Louis's skyline
• 
  The pinnacle of New York's Chrysler Building is clad with Nirosta stainless steel, a form of Type 302[79][70]
• 
  An Art Deco sculpture on the Niagara-Mohawk Power building in Syracuse, New York
• 
  The Cala Galdana Bridge, Menorca
• 
  Helix Bridge, Singapore

• The aluminium cladding of the spheres and tubes of the Atomium in Brussels was renovated with stainless-steel cladding in 2006.
• The Blossom pavilion in Shanghai by Zhan Wang, was created in 2015.
• Cloud Gate, a sculpture by Anish Kapoor in Chicago.
• Jaime Latapí López's Cristo de Chiapas, created in 2007 (Tuxla Guttierez, Mexico).
• Gateway Arch (pictured) is clad entirely in stainless steel: 886 tons (804 metric tons) of 0.25 in (6.4 mm) plate, #3 finish, type 304 stainless steel.[80] (St. Louis, Missouri)
• Juraj Jánošík monument (Terchova, Slovakia)
• La danse de la fontaine émergente (Paris, France) by Chen Zhen. Created in 2008
• Man of Steel (sculpture) under construction (Rotherham, England)
• Metamorphosis (Charlotte, NC, USA) by David Černỳ. Created in 2011[81]
• Sibelius Monument is made entirely of stainless steel tubes (Helsinki, Finland)
• Sun Voyager (Reykjavik, Iceland) by Jon Gunnar Arnason 9 m × 18 m × 7 m. Created in 1990
• The Big Elk (Stor-Eldval, Norway) by Linda Bakke. Created in 2015
• The Kelpies (Falkirk, Scotland)
• Unisphere, constructed as the theme symbol of the 1964 New York World's Fair, is constructed of Type 304L stainless steel as a spherical framework with a diameter of 120 feet (37 m) (New York City)
• United States Air Force Memorial has an austenitic stainless steel structural skin (Arlington, Virginia)

Stainless steels have a long history of application in contact with water[82] due to their excellent corrosion resistance. Applications include a range of conditions from plumbing,[83] potable[84] and waste water treatment[85] to desalination and brine treatment.[86][87] Types 304 and 316 stainless steels are standard materials of construction in contact with water. However, with increasing chloride contents higher alloyed stainless steels such as Type 2205 and super austenitic and super duplex stainless steels are utilized.[88]

Important considerations to achieve optimum corrosion performance are:[89]

• choose the correct grade for the chloride content of the water;
• avoid crevices when possible by good design;
• follow good fabrication practices, particularly removing weld heat tint;
• drain promptly after hydrotesting.

The use of stainless steel piping has helped to reduce the losses of drinking water in the cities of Tokyo, Seoul and Taipei.[90]

Stainless steels are used extensively in the Pulp and Paper industry for two primary reasons, to avoid iron contamination of the product and their corrosion resistance to the various chemicals used in the papermaking process.[91][92]

A wide range of stainless steels are used throughout the papermaking process. For example, duplex stainless steels are being used in digesters to convert wood chips into wood pulp. 6% Mo superaustenitics are used in the bleach plant and Type 316 is used extensively in the paper machine.

Stainless steels are used extensively in these industries for their corrosion resistance to both aqueous, gaseous and high temperature environments, their mechanical properties at all temperatures from cryogenic to the very high, and occasionally for other special physical properties.[93][94][95][96]

Stainless steel is used for industrial equipment when it is important that the equipment lasts and can be kept clean

Austenitic (300 series) stainless steel, in particular, Type 304 and 316 or sometimes 400 series is used, is the material of choice for the food and beverage industry. Stainless steels do not affect the taste of the product, they are easily cleaned and sterilized to prevent bacterial contamination of the food, and they are durable.

Stainless steels are used extensively in cookware, commercial food processing, commercial kitchens, brewing beer, wine making, and meat processing.[97]

Acidic foods with high salt additions, such as tomato sauce, and highly salted condiments, such as soya sauce may require higher alloyed stainless steels such as 6% Mo superaustenitics to prevent pitting corrosion by chloride.

Automobiles

The Allegheny Ludlum Corporation worked with Ford on various concept cars with stainless steel bodies from the 1930s through the 1970s to demonstrate the material's potential. The 1957 and 1958 Cadillac Eldorado Brougham had a stainless steel roof. In 1981 and 1982, the DMC DeLorean production automobile used Type 304 stainless steel body panels over a glass-reinforced plastic monocoque. Intercity buses made by Motor Coach Industries are partially made of stainless steel.

The largest use of stainless steel in cars is the exhaust line. Environment protection requirements of reducing pollution and noise for the whole life of cars led to the use of ferritic grades typically AISI409/409Cb in North America, EN 1.4511 and 1.4512 in Europe. They are used for collector, tubing, muffler, catalytic converter, tailpipe. Heat resisting grades typically EN1.4913 or 1.4923 are used in parts of turbochargers, other heat resisting grades for EGR (Exhaust gas recirculation) and for inlet and exhaust valves. In addition, common rail injection systems and particularly the injectors rely on stainless steels.

Stainless steel has proved to be the best choice for miscellaneous applications, such as stiffeners for windshield wiper blades, balls for seat belt operation device in case of accident, springs, fasteners, etc.

The aft body panel of the Porsche Cayman model (2-door coupe hatchback) is made of stainless steel. It was discovered during early body prototyping that conventional steel could not be formed without cracking (due to the many curves and angles in that automobile). Thus, Porsche was forced to use stainless steel on the Cayman.

Some automotive manufacturers use stainless steel as decorative highlights in their vehicles.

Light commuter trains (Tram links)

Stainless steel is now used as one of the materials for tramlinks, together with Aluminum alloys and Carbon steel. Duplex grades tend to be preferred thanks to their corrosion resistance and higher strength, allowing a reduction of weight and a long life in maritime environments[98]

Passenger rail cars

Rail cars have commonly been manufactured using corrugated stainless steel panels (for additional structural strength). This was particularly popular during the 1960s and 1970s, but has since declined. One notable example was the early Pioneer Zephyr. Notable former manufacturers of stainless steel rolling stock included the Budd Company (USA), which has been licensed to Japan's Tokyu Car Corporation, and the Portuguese company Sorefame. Many railcars in the United States are still manufactured with stainless steel. India is developing its rail infrastructure and has started to put new stainless steel coaches in service.[99] South Africa is also commissioning stainless steel coaches.[100]

Aircraft

Budd also built two airplanes, the Budd BB-1 Pioneer and the Budd RB-1 Conestoga, of stainless steel tube and sheet. The first, which had fabric wing coverings, is on display at the Franklin Institute, being the longest continuous display of an aircraft ever, since 1934. The RB-2 Was almost all stainless steel, save for the control surfaces. One survives at the Pima Air & Space Museum, adjacent to Davis–Monthan Air Force Base.

The American Fleetwings Sea Bird amphibious aircraft of 1936 was also built using a spot-welded stainless steel hull.

Due to its thermal stability, the Bristol Aeroplane Company built the all-stainless steel Bristol 188 high-speed research aircraft, which first flew in 1963. However, the practical problems encountered meant that Concorde employed aluminium alloys. Similarly the experimental mach 3 American bomber, the XB70 Valkyrie, made extensive use of stainless steel in its external structure due to the extreme heat encountered at those high speeds.

The use of stainless steel in mainstream aircraft is hindered by its excessive weight compared to other materials, such as aluminium.

Spacecraft

Stainless steel also has an application in spaceflight. The early Atlas rockets have used stainless steel (this formed their fuel tanks). The outer cladding of the modules and the Integrated Truss Structure of the International Space Station use stainless steel alloys. Components of the future Space Launch System, and the structural shell of the SpaceX Starship will be the second and third rockets respectively to use stainless steel.

Surgical tools and medical equipment are usually made of stainless steel, because of its durability and ability to be sterilized in an autoclave. In addition, surgical implants such as bone reinforcements and replacements (e.g. hip sockets and cranial plates) are made with special alloys formulated to resist corrosion, mechanical wear,[101] and biological reactions in vivo.

Stainless steel is used in a variety of applications in dentistry. It is common to use stainless steel in many instruments that need to be sterilized, such as needles,[102] endodontic files in root canal therapy, metal posts in root canal–treated teeth, temporary crowns and crowns for deciduous teeth, and arch wires and brackets in orthodontics.[103] The surgical stainless steel alloys (e.g., 316 low-carbon steel) have also been used in some of the early dental implants.[104]

Stainless steels are extensively used in all manner of power stations, from nuclear[105] to solar.[106] Furthermore, stainless steels are ideally suited as mechanical supports for power generation units when the permeation of gases or liquids are required, such as filters in cooling water or hot gas clean up[107] or as structural supports in electrolytic power generation.[108]

Stainless steel is used in electrolysers (PEM - proton exchange membranes and SOEL - solid oxide electrolysers being the most common) that convert electrical energy into hydrogen gas by water electrolysis. Conversely, stainless steel is used in fuel cells that do the opposite, react hydrogen with oxygen to produce water and electrical energy.

Stainless steel is often preferred for kitchen sinks because of its ruggedness, durability, heat resistance, and ease of cleaning. In better models, acoustic noise is controlled by applying resilient undercoating to dampen vibrations. The material is also used for cladding of surfaces such as appliances and backsplashes.

Cookware and bakeware may be clad in stainless steels, to enhance their cleanability and durability, and to permit their use in induction cooking (this requires a magnetic grade of stainless steel, such as 432). Because stainless steel is a poor conductor of heat, it is often used as a thin surface cladding over a core of copper or aluminium, which conduct heat more readily.

Cutlery is normally stainless steel,[109] for low corrosion, ease of cleaning, negligible toxicity, as well as not flavoring the food by[110] electrolytic activity.

Stainless steel is used for jewelry and watches, with 316L being the type commonly used for such applications. Oxidizing stainless steel briefly gives it radiant colors that can also be used for coloration effects.[111] Valadium, a stainless steel, and 12% nickel alloy is used to make class and military rings. Valadium is usually silver-toned, but can be electro-plated to give it a gold tone. The gold tone variety is known as Sun-lite Valadium.[112] Other "Valadium" types of alloy are trade-named differently, with such names as "Siladium" and "White Lazon".

Some firearms incorporate stainless steel components as an alternative to blued or parkerized steel. Some handgun models, such as the Smith & Wesson Model 60 and the Colt M1911 pistol, can be made entirely from stainless steel. This gives a high-luster finish similar in appearance to nickel plating. Unlike plating, the finish is not subject to flaking, peeling, wear-off from rubbing (as when repeatedly removed from a holster), or rust when scratched.

Some 3D printing providers have developed proprietary stainless steel sintering blends for use in rapid prototyping. One of the more popular stainless steel grades used in 3D printing is 316L stainless steel. Due to the high temperature gradient and fast rate of solidification, stainless steel products manufactured via 3D printing tend to have a more refined microstructure; this, in turn, results in better mechanical properties. However, stainless steel is not used as much as materials like Ti₆Al₄V in the 3D printing industry; this is because manufacturing stainless steel products via traditional methods are currently much more economically competitive.

There is extensive research indicating some probable increased risk of cancer (particularly lung cancer) from inhaling welding fumes while welding stainless steel.[126][127][128][129][130][131] Stainless steel welding is suspected of producing carcinogenic fumes from cadmium oxides, nickel, and chromium.[132] According to Cancer Council Australia, "In 2017, all types of welding fumes were classified as a Group 1 carcinogen."[132]

Stainless steel is generally considered to be biologically inert. However, during cooking, small amounts of nickel and chromium can leach out of stainless steel cookware. Nickel can contribute to cancer risks -- particularly lung cancer and nasal cancer.[133][134]. However, a connection between such cookware and cancer has not been firmly established[135]