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TTTG Article Tool Steels: an Historical Survey of Types, Brands and Makers John Bates ♠ Wednesday, 7Th of October 2015

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TTTG Article Tool Steels: an Historical Survey of Types, Brands and Makers John Bates ♠ Wednesday, 7Th of October 2015 TTTG Article Tool Steels: An Historical Survey of Types, Brands and Makers John Bates ♠ Wednesday, 7th of October 2015 INTRODUCTION There existed for many years an air of mystery surrounding the selection, heat treatment and use of tool steels. Started by the secretiveness of the early makers, it has been fostered somewhat by the seemingly never-ending introduction of new grades. Today the term tool steel commonly means hard steel of a quality used for making tools for cutting and other purposes. More specifically it refers to varieties of carbon and alloy steels that are particularly well-suited to be made into tools. For the purposes of this historical survey the author has divided the tool steels into five basic types or groups: water-hardening carbon tool steels, oil hardening tool steels, shock-resisting tool steels, air hardening tool steels; and high-speed steels. (/Content/Articles/2015-06- The survey also covers the non-ferrous cutting tool 13.ToolSteels/HalcombSteel.jpg) Fig 1: alloys. Although technically not steels, they are a group Halcomb Steel Company, Syracuse, of tool alloys which crop up more often than may be New York - Dreadnought tool steel expected. Furthermore, they are quite useful for certain purposes and operations in the metal shop. advertisement - 1913. A BRIEF OUTLINE OF HSS CLASSIFICATION During the 1970s the American Society for Testing and Materials (the ASTM is now ASTM International) introduced a unified numbering system for steel comprising 11 main classes each designated by a letter as follows: W:Water-Hardening (https://en.wikipedia.org/wiki/Tool_steel#Water-hardening_group) S: Shock-Resisting (https://en.wikipedia.org/wiki/Tool_steel#Shock-resisting_group) O: Cold-Work (Oil-Hardening) (https://en.wikipedia.org/wiki/Tool_steel#Oil-hardening) A: Cold-Work (Medium-Alloy, Air-Hardening) (https://en.wikipedia.org/wiki/Tool_steel#Air-hardening) Cold-Work (High-Carbon, High-Chromium) (https://en.wikipedia.org/wiki/Tool_steel#High_carbon- D: chromium.2C_D-type) L: Low-Alloy (http://www.azom.com/article.aspx?ArticleID=6139#) F: Carbon-Tungsten (https://en.wikipedia.org/wiki/Tool_steel#Special_purpose_group) P1- P: Low-Carbon Mould Steels P19: P20- Other Mould Steels P39: H1- Chromium-Base Hot Work (http://www.totalmateria.com/page.aspx? H: H19: ID=CheckArticle&site=kts&NM=234) H20- Tungsten-Base Hot Work (http://www.totalmateria.com/page.aspx? H29: ID=CheckArticle&site=kts&NM=234) H40- Molybdenum-Base Hot Work (http://www.totalmateria.com/page.aspx? H59: ID=CheckArticle&site=kts&NM=234) T: High-Speed (Tungsten-Base) M: High-Speed (Molybdenum-Base) (https://en.wikipedia.org/wiki/High-speed_steel) The current ASTM standard recognises 7 tungsten types and 21 molybdenum types of HSS. In this unified numbering system the tungsten-type HSS grades (e.g. T1, T15) are assigned numbers in the T120xx series, while molybdenum (e.g. M2, M48) and intermediate types are T113xx. The current standard (ASTM A600) covers types T1, T2, T4, T5, T6, T8, and T15 and molybdenum- type high-speed steels M1, M2, M3, M4, M6, M7, M10, M30, M33, M34, M36, M41, M42, M43, M44, M46, M47, M48, and M62 in the form of annealed, hot-rolled bars, forgings, plate, sheet, or strip, and annealed, cold-finished bars or forgings used primarily in the fabrication of tools. Two intermediate high speed tool steels designated as M50 and M52 are also covered. Water-Hardening Tool steels include all class W tool steels. These steels do not retain hardness well at elevated temperatures, but they do have high resistance to surface wear. Typical applications include blanking dies, files, drills, taps, countersinks, reamers, jewellery dies, and cold-striking dies. THE HIGH SPEED STEELS (HSS) Just what is high speed steel or HSS? Well when tool steels contain a combination of more than 7.0% tungsten, molybdenum and vanadium, along with more than 0.6% carbon, they are referred to as high speed steel. HSS is a highly-alloyed tool steel capable of maintaining hardness at elevated temperatures better than the high carbon and low alloy steels. This good hot hardness permits tools made of HSS to be used at higher cutting speeds (hence the name “High-Speed”). Since the early 1900s a wide variety of high speed steels has been and continues to be available. For the most part these steels can be divided into two basic types: Tungsten-type, designated T-grades by the AISI; and Molybdenum-type, designated M-grades by the AISI. The term HSS includes all the molybdenum (M1 to M52) and tungsten (T1 to T15) class alloys. These steels require high temperatures for hardening. The molybdenum types are usually hardened from a range of 1200°C (2200°F) to 1235°C (2250°F), the tungsten types as a rule from 1260°C (2300°F) to 1290°C (2350°F) when heat treated in an atmosphere controlled furnace. High-speed tools steels may be hardened to 62- 67 HRc and maintain that hardness in service temperatures as high as 540°C (1000°F) making them very useful in high-speed machining. Tungsten-type HSS: The tungsten steels form the oldest class and are an outgrowth of the even older Mushet steels. Their development started in the 19th century with Robert Mushet in UK and reached a technical flowering with the work of F W Taylor and M White in the USA just as the 20th century dawned. Robert F Mushet practiced the addition of manganese to the steel. But he didn’t stop there; he continued (/Content/Articles/2015-06- experimenting and sometime in 1868 eventually 13.ToolSteels/ArmstrongWhitworth.jpg) discovered self-hardening steel. This new steel was Fig 2: Armstrong Whitworth & Co., immediately put into the market under the name “R Manchester, U.K. - Three Celebrated Mushet’s Special Steel” or "R.M.S". A typical analysis of Brands of HSS - 1911. this steel was 2.4% carbon, 5.9% tungsten, and 2.5% manganese (these were the proportions of the original R.M.S made at Coleford - the R.M.S made at Sheffield contained 0.55% chromium). Unfortunately for Mushet, the company organised to manufacture and sell his new steel did not succeed well in business. Some three years later the production of Mushet steel was taken over by Samuel Osborn & Co Ltd at the Clyde Works, Sheffield. With a better business model the wide introduction of the new steel into engineering works and its imitation under the name of air-hardening or self-hardening steel quickly followed. Clearly a substantial advance had been made in the art of cutting metals. It was now possible to turn or plane at double or triple the former speeds; and to machine pieces which were formerly just too hard for the tools available or so hard as to make the cost of operation prohibitive. But even after gaining general use in engineering works, Mushet tools were little used for increasing speeds – most usually they were only used to save frequent grindings (/Content/Articles/2015-06- or to permit doing jobs previously impossible. 13.ToolSteels/Mushet.jpg) Fig 3: Samual It took a further 25 years after ‘Mushet’ or ‘self- Osbourne & Co., Sheffield, U.K. - hardening’ steel had become an established fact in Mushnet HSS advertisement - 1903. engineering before the marvellous properties latent in it were clearly appreciated and the industrial world caught a glimpse of what promised to be a revolution in machine shop methods. Frederick W Taylor had begun experimenting with Mushet and other self-hardening steels as far back as 1894. His aim was to determine which steels were best suited to special kinds of work. So shortly after taking charge of the Bethlehem steel works in 1898 he formed an association with Maunsel White and others in order to better undertake the work at hand. Before the introduction of HSS in the USA the term ‘Mushet steel’ meant self-hardening tool steels containing tungsten. These early ‘Mushet’ steels contained from 5-8% tungsten, up to 2.5% manganese, and very high carbon (1.5-2.4%) with sometimes 0.5% chromium. The Mushet steel made by Samuel Osborn & Co Ltd in 1868 and branded ‘Self-Hard’ or R.M.S. had a typical analysis of 8% tungsten, 2% carbon, and 1% manganese. The Taylor and White experiments from 1893 to 1898 led to a new steel with less carbon. Taylor-White steel (/Content/Articles/2015-06- of c.1900 contained 1.85% carbon, 8% tungsten, 3.8% 13.ToolSteels/OsbornsDrills.jpg) Fig 4: chromium, and 0.3% manganese. Finally, on 19 Samual Osbourne & Co., Sheffield, February 1901, Taylor and White received a patent for U.K. - Mushnet HSS advertisement - a ‘Metal-Cutting Tool and Method of Making Same’ 1912. such a tool being "specially adapted for cutting very hard metal and capable of running efficiently when cutting such metals at higher speeds and greater temperatures than has heretofore been practicable". The investigations by Taylor and White, which culminated in the development of ‘high speed steel’, required a very large amount of money to be spent and infinite patience to be exercised. Something like 50,000 recorded tests were made, a great many more were not recorded, and close to one million pounds of steel and iron was cut into chips; the estimated total cost was almost $200,000. However, this was by no means the end of experiments with HSS. In 1904 the addition of vanadium was patented by the Crucible Steel Company and this led to the formulation of what is perhaps the best-known grade, the 18-4-1 steel (later known simply as T1). Cobalt in HSS was first reported in 1912 by Becker in Germany.
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