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Vol.41, No.5, 288 ~ 297, 2003
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| Title |
| Microstructure and Thermal Fatigue Properties of High Speed Steel Rolls -1. Effects of Alloying Elements on Microstructure, Hardness and Fracture Toughness |
| 김창규 Chang Kyu Kim , 박종일 Jong Il Park , 이성학 Sung Hak Lee , 양정승 Jung Seung Yang |
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| Abstract |
| A study was made of the effects of alloying elements on microstructural factors and fracture properties of five high speed steel (HSS) rolls. Particular emphasis was placed on the role of hard carbides located along solidification cell boundary and the type of the martensite matrix. Microstructural observation, X-ray diffraction analysis, hardness and fracture toughness measurement, and fractographic observation were conducted on the rolls. Various types of carbides mostly segregated in the cell-boundary regions were dependent upon the type and amount of alloying elements, and played an important role in hardness and fracture toughness due to their high hardness. The effects of alloying elements were analyzed on the basis of the liquidus surface diagram, and indicated that the proper contents of carbon equivalent, tungsten equivalent, and vanadium were 1.9∼2.0%, 10∼11%, and 5∼6%, respectively. The roll containing a small amount of cell-boundary carbides and lath-type tempered martensite matrix had excellent fracture toughness since carbides were well spaced. For a better microstructure and fracture properties of the HSS rolls, therefore, it was suggested that the optimization of alloying elements was required to achieve the homogeneous distribution of carbides. |
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| Key Words |
| High speed steel roll, Alloying element, Thermal fatigue, Fracture toughness, Carbide, Solidification cell, Martensitic matrix |
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