To provide a cold working tool steel for excavating tool, which is inexpensive and reduced in the number of manufacturing steps and which is prevented of fracture due to crack and chipping and improved in wear resistance to earth and sand, by making a cold working tool steel have high hardness (wear resistance) and toughness, properly regulating the grain size of carbides and the amount of retained austenite, respectively.
The cold working tool steel having high hardness and toughness and excellent earth-and-sand wear property has a composition consisting of, by weight, 0.65-1.40% C, ≤2.0% Si, 0.10-2.0% Mn, 5.0-12.0% Cr, either or both of Mo and W within the range satisfying [Mo equivalent (Mo+1/2W)=0.5 to 5.0 and/or either or both of V and Nb within the range satisfying [V equivalent (V+1/2Nb)]=0.1 to 2.5, and the balance Fe with inevitable impurities and has a structure where the grain size of M7C3-type carbides is regulated to 5-15μm and a retained-austenite structure is allowed to remain by 5-20 vol.% in a martensitic structure.
TSUJII NOBUHIRO
TATE YUKIO
