38 0115 AMP features.indd 38 ADVANCED MATERIALS & PROCESSES | JANUARY 2015 F METALLURGY LANE alloys were austenitic . Thefirst timean and nickel. Withsufficientnickel, these he studied alloyswithbothchromium steel andcalled martensitic . Finally, carbon thatcould behardened asany therefore called ferritic. Anotherwas higher thatcould notbehardened and types: Onewas lowcarbon withhigh Guillet’s workshowedthree basic alloy the commercial range ofstainless steel. additions thatwouldlater bealloyswithin 1906 covering thefull range ofchromium He publishedhisresearch during1904- was aFrenchman namedLeon Guillet. of thisnew low-carbon chromium use The first metals researcher to make chromium content andlowcarbon. the way to studying alloyswithmuchhigher without carbon contamination. Thispaved heat to separate thechromium metal heavy-walled container to generate enough chromium ore withaluminumpowderina the thermite process, whichcombines chemist HansGoldschmidtinvented chromium steels. German At thispoint, is themostimportant factor inmaking added to iron. Further, controlling carbon producing low-carbon chromium to be Before 1895,there was noprocess for treatment to achieve higherstrength. the 2%to 5%range andrequired heat 1890s. Thesealloyadditionswere in combining chromium withnickel inthe 1890s, whileGermanresearchers began THAT DOESNOT RUST, WHICHOCCURREDAFTERRESEARCH INTO HIGHCHROMIUM STEELSBEGAN. ONE OFTHEGREATEST ADVANCES INMODERNMETALLURGY WAS THEDISCOVERY OFASTEEL : THESTEEL THAT DOESNOT RUST —PART 1 and materials milestones industriesalongwithkey anddevelopments. Metallurgy Lane,authored byASMlife memberCharlesR.Simcoe, isayearlong seriesdedicated to oftheU.S. theearly metals history alloy steels duringthe1880sand chromium ornickel to heat treated rench researchers began adding process. invented thethermite Hans Goldschmidt the well-knownFrench metallurgist alloys justafew years after Guillet include chromium andiron-chromium-nickel Two otherresearchers whostudied iron- place ofthesealloys. inthediscovery International, 1949)awarded himfirst in hisclassicStainless Steels book(ASM classified asstainless steels, CarlZapffe to publishonalloysthatwouldlater be “stainless.” Because Guillet was thefirst and thenormalatmosphere. They were were resistant to corrosion inbothacids missed thefact thatsomeofhisalloys during hisera. However, hecompletely properties thatcould bemeasured metallographic andmechanical steels. Guillet’s studies covered the define therange oftoday’s stainless These three categories continue to occurred atambienttemperature. all-austenitic microstructure was seen,it chromium-nickel alloys. iron-chromium andiron- metallurgist tostudy Leon Guilletwasthefirst on stainless steels.” Monnartz First, piece ofworkasstands intheliterature steels—and provided asbrillianta disclosed thestainlessness ofstainless 1911. Quotingfrom Zapffe, “His research published inthejournalMetallurgie in Germany. Hebegan hisworkin1908and resistance was PhilipMonnartzof groundbreaking property ofcorrosion The first researcher to discover the STAINLESS STEEL DISCOVERY OF Scholarship Memoirs, Vol 1,1909. of theIron andSteel Institute’s Carnegie published theirresults inthesameedition steels, whichhadto belowcarbon. Both on theiron-chromium-nickel austenitic high carbon. Giesendidmostofhiswork iron-chromium alloyswithbothlowand Giesen. Portevin studied thestraight Albert Portevin andanEnglishman,W. inventor ofstainlesssteel. Philip Monnartz,the 1/9/2015 3:58:08PM 39 ADVANCED MATERIALS & PROCESSES | JANUARY 2015 determined that when the chromium this alloy a few years later for steam content exceeded 12%, the steel resisted “IT’S NOT SURPRISING turbine blades. attack by nitric acid and did not corrode in the normal atmosphere. Next, he found THAT IT TOOK SO Another American, Elwood Haynes, that the metal surface needed to be LONG TO DISCOVER worked on stainless steel with a higher prepared to form a protective film. This carbon content to produce a martensitic extremely thin film was the formation of STAINLESS STEEL. microstructure upon quenching from an oxide with a combination of iron and a high temperature. Haynes was an chromium when the chromium exceeded WHAT’S SURPRISING automobile manufacturer with an interest 12%. The tightly adherent film prevented IS THAT IT WASN’T in developing alloys for spark plugs. He further oxidation or corrosion. had already invented Stellite, a cobalt- DISCOVERED SOONER.” chromium-tungsten-carbon alloy used to He also found that low carbon content make hard and wear-resistant surfaces, is necessary to prevent formation of long to discover stainless steel. What’s such as valve seats. He applied for a chromium carbides and that carbon surprising is that it wasn’t discovered sooner.” patent in 1911 on a stainless steel alloy can be controlled by adding stronger that contained 13% chromium with 0.30% carbide formers, such as titanium, carbon, but it was held up for many years columbium, vanadium, molybdenum, STAINLESS STEEL due to interference with a British patent. or tungsten to form carbides of these APPLICATIONS ABOUND alloys rather than of chromium. Finally, The years from 1904 to 1911 were a major The British patent was held by Harry Monnartz learned that the addition of discovery period, while the following Brearley who had been searching for a 2% to 3% molybdenum greatly increased decade witnessed development of wear and corrosion-resistant alloy for gun the corrosion resistance of austenitic alloys for specific applications. The first barrels. This led him to a 13% chromium, stainless. His research provided the basic patent for a stainless steel alloy was 0.25% carbon hardenable stainless steel. He information for all future developments in German #246015, issued in 1910 to W. promoted his alloy—the forerunner of AISI practical alloys for the many applications Borchers and P. Monnartz, although the 420—for cutlery. It was a natural application that would develop for stainless steel. first application for stainless steel was for hardened knives and his employers for lead-in wires for electric lamp bulbs. were in , UK, the capital of tool For his discovery, Monnartz must be The research was done by Christian and knife making. Brearley is credited with considered the one true inventor of stainless Dantsizen at the General Electric Research starting the first production of hardenable steel. While the other researchers, especially Laboratories in Schenectady, N.Y. Using stainless. The British military found that Guillet, were the pioneers of iron-chromium very low-carbon chromium made by the Brearley’s alloy was the answer for aircraft and iron-chromium-nickel steels, they Goldschmidt thermite process, he engine exhaust valves and requisitioned the completely missed the only property that developed an alloy containing 14% to available supply for the years 1914-1919. makes these alloys useful today. The mystery 15% chromium and 0.07% to 0.15% Thomas Firth and Sons made 50 tons for is this: How did they not notice that some carbon. His goal was resistance to knives before the war, a production lot of their alloys were so difficult to etch for oxidation at high temperature and considered to be the dawn of the stainless metallographic examination? As Zapffe the chromium provided that in a steel industry. quipped, “It’s not surprising that it took so ferritic microstructure. GE would use One of the most important patents issued for stainless steel went to Eduard Maurer and Benno Strauss working at the Friedrich Krupp Works in Essen, Germany. Their German patent #304159 issued in 1912 included, for the first time, austenitic stainless steel. One of their alloys contained 20% chromium and 7% nickel. With slight modification, this alloy became 18-8, the single most important stainless steel alloy ever produced. Elwood Haynes invented Harry Brearley launched Eduard Maurer patented martensitic stainless steel the production of the first austenitic For more information: Charles R. with 13% chromium and martensitic stainless for stainless steel in 1912. Simcoe can be reached at crsimcoe1@ 0.30% carbon. cutlery and tableware. gmail.com. For more metallurgical history, visit metals-history.blogspot.com.

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