The influence of alloying elements on properties of centrifugally cast high-speed steel rolls

Alloying elements has the influence on the microstructure, hardness, and fracture toughness of centrifugally cast high-speed steel (HSS) rolls. Emphasis was placed on therole of hard carbides located along solidification cell boundaries and the type of the tempered martensitic matrix. Microstructural observation, X-ray diffraction analysis, hardness and fracture-toughnessmeasurements, and fractographic observations were conducted on the HSS rolls. The constitution and morphology of carbides observed within the intercellular boundaries varied depending upon the predominant alloying elements that comprised them. These massive carbide formations strongly influenced the bulk material hardness and fracture toughness due to their high hardness. The effects of alloying elements were analyzed on the basis of the liquidus-surface diagram which and indicated that the proper contents of the carbon equivalent (CE), tungsten equivalent, and vanadium, The roll material, containing a small amount of intercellular carbides and lathtype tempered martensitic matrix, had excellent fracture toughness, since carbides were well spaced. Therefore, it was suggested that the optimization of alloying elements was required to achieve the homogeneous distribution of carbides.