Friday August 13, 2021’s Smile of the Day: Stainless Steel
On this Day:
In 1913, Harry Brearley of Sheffield, England invented stainless steel. Well, we can polish up that claim a bit to see if it remains stainless…
Stainless steel is a group of ferrous alloys that contain a minimum of approximately 11% chromium, a composition that prevents the iron from rusting and also provides heat-resistant properties. Different types of stainless steel include the elements carbon (from 0.03% to greater than 1.00%), nitrogen, aluminium, silicon, sulfur, titanium, nickel, copper, selenium, niobium, and molybdenum. Specific types of stainless steel are often designated by their AISI three-digit number, e.g., 304 stainless. The ISO 15510 standard lists the chemical compositions of stainless steels of the specifications in existing ISO, ASTM, EN, JIS, and GB (Chinese) standards in a useful interchange table.
Stainless steel’s resistance to rusting results from the presence of chromium in the alloy, which forms a passive film that protects the underlying material from corrosion attack, and can self-heal in the presence of oxygen. Corrosion resistance can be increased further by the following means:
- increase chromium content to more than 11%
- add nickel to at least 8%
- add molybdenum (which also improves resistance to pitting corrosion)
The addition of nitrogen also improves resistance to pitting corrosion and increases mechanical strength. Thus, there are numerous grades of stainless steel with varying chromium and molybdenum contents to suit the environment the alloy must endure.
Resistance to corrosion and staining, low maintenance, and familiar luster make stainless steel an ideal material for many applications where both the strength of steel and corrosion resistance are required. Moreover, 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 material’s corrosion resistance, the ease with which it can be steam-cleaned and sterilized, and the absence of the need for surface coatings have prompted the use of stainless steel in kitchens and food processing plants.
The invention of stainless steel followed a series of scientific developments, starting in 1798 when chromium was first shown to the French Academy by Louis Vauquelin. In the early 1800s, James Stoddart, Michael Faraday, and Robert Mallet observed the resistance of chromium-iron alloys (“chromium steels”) to oxidizing agents. Robert Bunsen discovered chromium’s resistance to strong acids. The corrosion resistance of iron-chromium alloys may have been first recognized in 1821 by Pierre Berthier, who noted their resistance against attack by some acids and suggested their use in cutlery.
In the 1840s, both Sheffield steelmakers and Krupp were producing chromium steel with the latter employing it for cannons in the 1850s. In 1861, Robert Forester Mushet took out a patent on chromium steel.
These events led to the first production of chromium-containing steel by J. Baur of the Chrome Steel Works of Brooklyn for the construction of bridges. A U.S. Patent for the product was issued in 1869. This was followed with recognition of the corrosion resistance of chromium alloys by Englishmen John T. Woods and John Clark, who noted ranges of chromium from 5–30%, with added tungsten and “medium carbon”. They pursued the commercial value of the innovation via a British patent for “Weather-Resistant Alloys”.
In the late 1890s, German chemist Hans Goldschmidt developed an aluminothermic (thermite) process for producing carbon-free chromium. Between 1904 and 1911, several researchers, particularly Leon Guillet of France, prepared alloys that would be considered stainless steel today.
In 1908, the Essen firm Friedrich Krupp Germaniawerft built the 366-ton sailing yacht Germania featuring a chrome-nickel steel hull in Germany. In 1911, Philip Monnartz reported on the relationship between chromium content and corrosion resistance. On 17 October 1912, Krupp engineers Benno Strauss and Eduard Maurer patented as Nirosta the austenitic stainless steel known today as 18/8 or AISI Type 304.
Similar developments were taking place in the United States, where Christian Dantsizen of General Electric and Frederick Becket (1875-1942) at Union Carbide were industrializing ferritic stainless steel. In 1912, Elwood Haynes applied for a US patent on a martensitic stainless steel alloy, which was not granted until 1919.
While seeking a corrosion-resistant alloy for gun barrels in 1912, Harry Brearley of the Brown-Firth research laboratory in Sheffield, England, discovered and subsequently industrialized a martensitic stainless steel alloy, today known as AISI Type 420. The discovery was announced two years later in a January 1915 newspaper article in The New York Times.
The metal was later marketed under the “Staybrite” brand by Firth Vickers in England and was used for the new entrance canopy for the Savoy Hotel in London in 1929. Brearley applied for a US patent during 1915 only to find that Haynes had already registered one. Brearley and Haynes pooled their funding and, with a group of investors, formed the American Stainless Steel Corporation, with headquarters in Pittsburgh, Pennsylvania.
In the beginning, stainless steel was sold in the US under different brand names like “Allegheny metal” and “Nirosta steel”. Even within the metallurgy industry, the name remained unsettled; in 1921, one trade journal called it “unstainable steel”. In 1929, before the Great Depression, over 25,000 tons of stainless steel were manufactured and sold in the US annually.
Major technological advances in the 1950s and 1960s allowed the production of large tonnages at an affordable cost:
- AOD Process (argon oxygen decarburization), for the removal of carbon and sulfur
- Continuous casting and hot strip rolling
- The Z-Mill, or Sendzimir cold rolling mill
- The Creusot-Loire Uddeholm (CLU) process, which bypasses the need for argon
Unlike carbon steel, stainless steels do not suffer uniform corrosion when exposed to wet environments. Unprotected carbon steel rusts readily when exposed to a combination of air and moisture. The resulting iron oxide surface layer is porous and fragile. In addition, as iron oxide occupies a larger volume than the original steel, this layer expands and tends to flake and fall away, exposing the underlying steel to further attack. In comparison, stainless steels contain sufficient chromium to undergo passivation, spontaneously forming a microscopically thin inert surface film of chromium oxide by reaction with the oxygen in the air and even the small amount of dissolved oxygen in the water. This passive film prevents further corrosion by blocking oxygen diffusion to the steel surface and thus prevents corrosion from spreading into the bulk of the metal. This film is self-repairing, even when scratched or temporarily disturbed by an upset condition in the environment that exceeds the inherent corrosion resistance of that grade.
The resistance of this film to corrosion depends upon the chemical composition of the stainless steel, chiefly the chromium content. It is customary to distinguish between four forms of corrosion: uniform, localized (pitting), galvanic, and SCC (stress corrosion cracking). Any of these forms of corrosion can occur when the grade of stainless steel is not suited for the working environment.
The designation “CRES” refers to corrosion-resistant steel.
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 can be seen in the upper portion of the Chrysler Building. Thanks to 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. The Parliament House of Australia in Canberra has a stainless steel flagpole weighing over 220 metric tons (240 short tons). The largest stainless steel building in North America is the aeration building in the Edmonton Composting Facility. La Geode in Paris has a dome composed of 6433 polished stainless steel equilateral triangles that form the sphere that reflects the sky. The development of high-strength stainless steel grades, such as “lean duplex” grades, has led to increasing use in structural applications.
Thanks to its low reflectivity, stainless steel is used as a roofing material for airports, which prevents pilots from being dazzled. It is also used 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 road bridges in the form of tubes, plates, or reinforcing bars. Examples include: the Cala Galdana Bridge in Menorca, the first stainless steel road bridge to be built; the Champlain Bridge in Montreal; the Oudesluijs bridge in Amsterdam, a bridge made using Construction 3D printing; the Padre Arrupe Bridge in Bilbao, which links the Guggenheim Museum Bilbao to the University of Deusto. the Sant Fruitos Pedestrian Bridge in Spain; Stonecutter’s Bridge, Hong Kong; and The Helix Bridge, a pedestrian bridge in Singapore (per Wikipedia).
First, a Story:
Where does stainless steel wool come from? Sheep metal.
Second, a Song:
Ash Woodrow of the UK states:
“The great songwriters always say ‘[W]rite about what you know.’
When I wrote this song I was working in stainless steel sales, so maybe I took the advice too literally…….
Anyway, this song was the result and I learned how to (painstakingly) create a video for it today. So. Much. Work!
Recorded on an old digital 8 track recorder using a classical guitar, Fender Jazz Bass, Kala Ukulele and a small pot of rice to shake the beat.
This song owes more than a little to Gilbert & Sullivan and the great Tom Lehrer.
Enjoy, and sing along if you know it…” (per YouTube.com)
Here is Ash Woodrow’s performance of “304”. I hope you enjoy this!
Thought for the Day:
“Each material has its specific characteristics which we must understand if we want to use it. This is no less true of steel and concrete.” – Ludwig Mies van der Rohe
Have a great day!
Dave & Colleen
© 2021 David J. Bilinsky and Colleen E. Bilinsky