201 BROWN & HERON: GEOLOGY AND ORE DEPOSITS OF TAVOY. 



Uses. 



The chief use of tungsten is as an ingredient in the manufacture 

 of tool steels, especially those varieties known as "high-speed" 

 steels. The metals used to impart tensile strength, toughness, 

 hardness and resistance to shock, to iron containing varying quan- 

 tities of carbon, include nickel, chromium, manganese, tungsten, 

 molybdenum, cobalt, vanadium, uranium, and titanium. The 

 famous Damascus steel of the middle ages has been proved to contain 

 both tungsten and chromium, though their addition was probably 

 unintentional. The first modern use of tungsten in steel was made 

 by Mushet in 1857, and his material contained from G pel cent, 

 to 8 per cent, of tungsten, 2 per cent, of manganese and a high 

 percentage of carbon. It possessed the property of hardening 

 without quenching in water and was capable of working at speeds 

 and under conditions unequalled by the best carbon steel tempered 

 with the utmost skill. The credit for the modern development, 

 by heat treatment, of self-hardening steels, is said to be due to 

 Messrs. Taylor and White, who introduced their products to the 

 Paris exhibition in 1900. 



The essential difference between high-speed steel, and ordinary 

 carbon or cutting steel, is that the former is able to withstand very 

 much higher temperatures when cutting. If the temperature of 

 friction due to cutting reaches about 500°F., carbon steel tools begin 

 to lose their hardness, and, as a consequence, the life of the tool on 

 heavy cutting work is a very short one. With high-speed tools, 

 the temperature can rise to, say, 1,150°F., or even higher, without 

 the tool losing its hardness or cutting power, and such tools can 

 consequently cut metals at feeds and speeds greatly exceeding 

 anything obtainable with tools of ordinary carbon steel. This 

 is especially important for exact work on a big scale, such for instance 

 as boring a heavy gun or turning a long length of shafting, when 

 it is necessary for the sake of accuracy to make a continuous finish- 

 ing cut from end to end, without altering the tool and without run- 

 ning the risk of incurring sufficient wear on its edge to impair the 

 exact diameter of the work. 



Another great advantage of the modern high-speed tool lies in 

 the comparative simplicity of its heat treatment, rendering the 

 forging and hardening operations in the smithy considerably easier 

 than when working with carbon tool steels, which must be heated 

 to the correct " critical point " to obtain the best results. In 



