Tool steels are groups into six types: high speed, hot work, cold work, shock resisting, special purpose and water hardening.
High-speed steels are very efficient with heavy cuts and high speeds they are incapable, at slow speeds and lighter cuts, of holding the keen edge necessary for obtaining a very smooth finish on certain articles.
Special steels have been produced for this purpose, known as finishing steels, which are capable of retaining a keen cutting edge for much longer periods than carbon steel used under similar conditions.
This steel has good resistance to oxidation at elevated temperatures, high hardness and good wearing properties.
lt is suitable for intricate sections, dies for blanking, coining, toller threading and drop forging hard materials.
High Tungsten-chromium Steel is the best type of steel for hot work except where resistance to scaling or oxidation is important.
lt is used for hot-drawing, hot-forging, extrusion dies and dies for die casting aluminium, brass and zinc alloys.
Die-casting die steels often fall through surface cracking caused by cyclic expansion and contraction, aggravated by the erosive action of the molten metal.
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