Experimental Research On Solidification Structure And Carbide Morphology Of High Carbon High Speed Steel With Electromagnetic Stirring

High carbon high speed steel roll containing high carbon and high alloy is easy to form a lot of network carbides. This network carbide is hard and crisp, which seriously reduces the performance of roll. The network carbide is difficult to be eliminated by conventional heat treatment. So it is very crucial to modify the carbide size and distribution in high carbon high speed steel composite roll during the casting. Electromagnetic stirring has the role of refining grains, reducing macro-segregation and micro-segregation in crystal, and increasing the solubility of elements in the matrix. Fabrication of high carbon high speed steel roll with electromagnetic stirring is expected to obtain better micro structure high carbon high speed steel.This thesis focuses on the effect of electromagnetic stirring on the microstructure of casting and morphology of carbides in high carbon high speed steel for composite roll. The microstructure of casting and morphology of carbides in high carbon high speed steel with different components are systematically studied using the method of metallographic examination, SEM, and EDS. The results show that the carbides of high carbon high speed steel are mainly the MC, M2C and M6C carbides. MC carbides distributed mainly by granular, M2C carbides distributed by strip and massive, and most of the network carbides are M6C carbides. With electromagnetic stirring carbides mainly distributed on the boundary becomes to dispersively distribute in the cell and along the boundary. And with the increase of the applied current, distribution of carbides are more uniform. As compared with no electromagnetic stirring, the initial solidification rate in cast center is higher than that at the edge of cast. At cast center, the main carbides are MC type carbides and MC-M2C compound carbides. Rotary electromagnetic stirring can tend to form the MC carbides, break network carbides and reduce the size of carbides. There exists an optimal electromagnetic stirring current intensity. As for the element content, improving C content will make carbides more diverse and generate more carbides; improving V content will inhibit the formation of W, Mo carbides; improving W content will promote other types of carbides converted to itself carbides.