may amp features_am&p master template new QX6.qxt 4/22/2014 6:17 PM Page 40 The Toolmakers: Part I Man is a toolmaker. In fact, the entire progress of mankind has been marked by the ability to develop better tools. Metallurgy Lane, imple tools were first devised for hunting tool steel performance. In authored by purposes, followed by more complex ones the course of their study, ASM life member S for agriculture and construction, and always Taylor and White found that Charles R. Simcoe, included efforts to make better weapons for war. Fi- the higher the heating tem- is a yearlong series nally, with the Industrial Revolution, humans began perature before the steel was dedicated to the early to invent mass-produced machine tools. cooled, the greater the use- history of the U.S. metals During the middle of the 18th century, British fulness and life of the tool. and materials industries clockmaker Benjamin Huntsman rediscovered the “Metals men” had known for along with key ancient Wootz method of melting small quantities years that if steel was heated milestones and of wrought iron in clay pots, with wood chips to at too high a temperature, it developments. supply the carbon, as part of his quest for more uni- would be ruined, or “burnt” form steel to make clock springs. His method was as they described it. Taylor Frederick Taylor further refined years later by the British steelmaker and White simply followed (pictured) and Robert Mushet who simply added pig iron to crude the clues provided by their Maunsel White sponge iron. For more than 175 years (1740 to own experimental data. discovered that heat treatment produces 1920), this process was used for making steels for This led them to tem- secondary tools. The crucible process, as it was called, was peratures in the 2200° to hardening in well suited for making small batches of high-qual- 2400°F range, almost to the tungsten tool steels. ity, controlled-chemistry steel. melting point of their steels. Courtesy of Library of Congress/U.S. The tool steels made in the first 100 years after Alloy steel tools containing public domain. crucible melting became widely used were simple tungsten were so greatly im- iron-carbon alloys. During the 1860s, Mushet was proved when heated to these excessively high tem- doing practical processing work that involved peratures before cooling that they could be adding other metals to tool steel. His studies led operated under conditions so severe that the cut- him to the 1868 discovery that adding tungsten and ting point would glow to a dull red. Later, with manganese in sufficient amounts some refinement in alloy content, these would be caused steel to be extremely hard on called high-speed steels, and would be said to pos- cooling in air from a red heat. At the sess “red hardness.” The use of high-speed steels time, conventional wisdom said revolutionized the machining industry. Heavier hardening could only be done by machine bases were needed to support the stresses rapidly quenching in water. and vibration of the heavier cuts that could now be Mushet’s “Special Steel,” as it was used to remove metal. known, contained 2% carbon, 2.5% manganese, and 7% tungsten. It is Alloy development continues considered the ancestor of all mod- In the meantime, improved alloys that would ern tool steels because it could with- provide maximum response to the Taylor and stand difficult service conditions White heat treatment were being tested in many and required less resharpening due advanced industrial countries. J.A. Mathews of to its greater wear resistance. the Crucible Steel Co. reported the results of a survey he conducted in 1901 on the common Taylor and White tool steels in use, “Modern high-speed steels revolutionize tool steel industry seem to have sprung fairly fully developed from Frederick Taylor, an efficiency a variety of sources at almost the same time.” The expert working on machining stud- change from the old type to the new that Math- Circa 1829, the crucible furnace at ies at Bethlehem Steel Co. with the ews is referring to was a rather drastic change in Abbeydale, England, is the oldest help of experienced metallurgist chemistry from the Mushet steels containing example of the type developed by Benjamin Huntsman. Courtesy of Maunsel White, studied the heat 1.5-2.0% carbon, 2.5-4% manganese and 7-9% www.steelguru.com. treating variables that affected alloy tungsten to the new steels with 0.6-0.8% carbon, 40 ADVANCED MATERIALS & PROCESSES • MAY 2014 may amp features_am&p master template new QX6.qxt 4/22/2014 6:17 PM Page 41 4-6% chromium (manganese was no longer used), and 10-20% tungsten. Mathews was granted a patent in 1905 for the ad- dition of vanadium to high-speed steel. With the ad- dition of about 1% vanadium to the 18% tungsten, 4% chromium, and 0.60-0.80% carbon steel, the first truly universal high-speed steel was born. By 1905, the “18-4-1 high-speed steel” was in commercial pro- Variation of hardness with tempering temperature for four typical tool steels. Cour- duction and would remain the major tool steel for tesy of Wrought Tool Steels, Properties and Selection: Irons, Steels, and High-Per- metal machining during the next 35 to 40 years. formance Alloys, Vol 1, ASM Handbook, ASM International, 1990. Metallurgical research moves forward most recent theory of hardening—slip interfer- One of the first research studies on high-speed ence by precipitated particles. This paper showed, steels was by H.C. Carpenter of England, who believed as concluded earlier by Edwards and Kikkawa, that the high-temperature phase (austenite) was the that the high hardening temperatures are needed source of red hardness. He was led into this error due to dissolve the particles of tungsten-containing to the large amount of austenite he found in samples carbide in the austenite. Bain and Jeffries then after cooling from the hardening temperatures. concluded that the softening of hardened steel Another British metallurgical research study un- during tempering, which occurs in ordinary steel dertaken by C.A. Edwards and H. Kikkawa provided at low temperatures (300° to 900°F), is caused by the first comprehensive understanding of the major grain growth and carbide particle growth beyond metallurgical phenomena in high-speed steel. They the critical size. They reasoned that the greater concluded that chromium imparts the self-hardening, stability of the tungsten carbide forces its forma- and that the extremely high hardening temperature was tion at 1000° to 1200°F, where it increased the Zay Jeffries (pictured) published on the theory needed to dissolve the tungsten. Maximum resistance hardness to a peak called “secondary hardening.” of red hardness in high- to tempering can only be ob- It is only at these temperatures that the larger speed tool steels with tained by getting the tungsten tungsten atoms can move within the iron space Edgar Bain and served as ASM president in 1929. into solution. They also con- lattice to form the alloy carbides. Later studies Courtesy of ASM cluded that careful tempering would confirm the thrust of their theories, al- International. studies with hardness measure- though the details of alloy carbide formation ments could provide valuable would be more complex in detail. information on the relative The following year, 1924, Edgar Bain moved from merits of cutting tools. General Electric Co. to Atlas Steel Co. in Dunkirk, Shortly after Edgar Bain’s N.Y., where he worked with one of America’s most early work using x-rays to de- interesting and prolific metallurgists, Marcus A. termine the crystal structure of Grossmann. The publications of Bain and Gross- austenite (fcc), ferrite (bcc), and mann in 1924 included high-carbon, chromium Edgar Bain, a martensite (bcc), he and Zay steels, chromium in high-speed steel, and their major research Jeffries, while working at the work, “On the Nature of High Speed Steel,” which metallurgist who worked with Marcus GE Lamp Division, published they published in Great Britain in the Journal of The Grossman to publish their famous paper in Iron Age Iron and Steel Institute. This paper was a compilation For more research studies in 1923 on the “Cause of Red of the arts on the manufacturing and metallurgy of information: and a book on high- Hardness of High Speed Steel.” high-speed steel. In some ways, it appears to be a Charles R. Simcoe speed tool steels. can be reached at This paper is considered combination of Grossmann’s practical knowledge Courtesy of Library [email protected]. of Congress/U.S. a classic in the field of metals with the metallurgy and theory reported earlier by public domain. For more metallurgical technology, not because it Bain and Jeffries. Grossmann and Bain expanded this history, changed industrial practices, but because it combined effort in their collaboration in 1931 with the publica- visit www.metals- the latest research tool (x-ray diffraction) with the tion of a textbook entitled “High Speed Steel.” history.blogspot.com. ADVANCED MATERIALS & PROCESSES • MAY 2014 41.