THE MAKING AND WORKING OF STEEL 407 



When melted and run into ingots it is termed cast steel, 

 which is the strongest form of steel. These ingots are 

 broken up and melted in crucibles to be cast into any 

 desired shape. 



Crucible steel is used to a large extent for making machine- 

 shop tools and is often spoken of as tool steel. The best 

 grade usually contains fron .9 to 1.1% of carbon and has a 

 wide range of uses. Other grades contain : 



.1 to .5% carbon, used for lathe tools and small drills. 



.5 to .75% " " " battering tools, hot work. 



.75 to 1% " " " dies, axes, large-sized drills. 



The properties of tool steel are due to the carbon they 

 contain. 



464. Tungsten Steel. A number of grades of steel are 

 called alloy steels and owe their properties to the alloy 

 which is added to them. The principal one is tungsten steel, 

 which is made by adding f errotungsten (an alloy of tungsten 

 and iron) to the metal while it is in the crucible. Tungsten 

 steel is also called high-speed steel, because the tools made 

 from it can be used at a higher speed than others. 



465. Steel Castings. Steel castings are made by pouring 

 mild steel into molds. Crucible steel castings are made 

 by melting bar blister steel in crucibles and pouring it into 

 molds. Large steel castings, such as beams for stationary 

 engines, steam chests, large shafts, pistons, cross-heads, 

 stands for steam hammers, large stop valves, etc., are made 

 by simply charging the furnace with pig iron, scrap steel, 

 and broken ingot molds. The disadvantage of this process 

 is that the castings are not perfectly sound because of pores 



