High Carbon Tool Steels
Tools are implements such are employed to shape, cut or deform other materials. They are largely made in steel, although other alloys have also been improved. The usual tool steels have C, W, Cr, Mo, V, Mn, and Si in the range of 0.6 to 1.0%. They have hardness and wear resistance. For shock resistance C is limited to 0.5%. W and Mo in between 2 to 18% offer high temperature strength. V in between 0.1 to 2% improves harden-ability whilst Si adds to toughness.
Though the tool and die steels are not generates in as large amount like other steels are, still they are industrially very significant. A variety of steel differing broadly in composition and treatment is utilized for varying reasons. They are employed in such operations as cutting, rolling, shearing and forming. These operations need adequate hardness, toughness, strength wear resistance and heat resistance. For a lot of reasons near-eutecoid and hyper-eutectoid steels have been employed for metal cutting but these plain carbon steels have tendency to lose hardness through tempering while rise in temperature arises during cutting. To overcome such problem high steep tool steel have been improved. The 18.4.1 category of high steel contains 18% W, 4% Cr and 1% V. These steels retain adequate hardness because of carbide formation that is a complex compound Fe4W2C. A tough matrix is provided via Cr. These steel might retain hardness upto a temperature of 500oC.
While 5-12% of cobalt is also added, in addition, the hardness throughout a secondary hardening procedure is increased at temperature around 600oC.