A study of centrifugal cast high boron high speed steel

摘要

In the present study a high-boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high-boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high-boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high-boron high speed steel roll consisted of M_2(B,C), (W,Mo)_2(B,C), M_3(B,C), M_(23)(B,C)_6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 ℃, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 ℃, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high-boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm~2. The single groove steel rolling amount of high-boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K_1 mill housing of bar mill.