Effect Of Pulse Current On The Mirostructure Of W6Mo5Cr4V2 High Speed Steel And Its Mechanism

In industrial production, the production process of high speed tool steel is very complicated. The effect of traditional improving method is not significant, and its operation is very complex. So new processing methods need to be explored. The technology of pulse current treatment for improving production processing emerges.In this work, the pulse current was applying on W6M5C4V2 high speed tool steel to study the influence of voltage, frequency, pulse width and the temperature of pulse current treatment on the composition, shape, size, number and distribution of the carbide in the microstructure. And the influence of voltage, frequency and pulse width on the content of alloying elements, the segregation degree of alloying elements and the hardness of the matrix was also studied.By applying pulse current on W6M5Cr4V2 high speed tool steel at 1320℃ in the solid-liquid zone and 1220℃ in the solid zone, we found that the microstructure of high speed steel treated by pulse current in the solid zone was more closer to the requirements of industrial production than which in the solid-liquid zone.After pulse current treatment, the phase species of the carbides in the steel were not changed, but their shapes tended to break from mesh, and there was obvious trend to be isolation and ball. The herringbone eutectic carbides disappeared and the content of carbide also decreased. The content of alloying elements in matrix increased and the segregation degree of alloying elements reduced, which all leaded to the increasing of hardness of the matrix.The influence of pulse current parameters on the microstructure of high speed steel was also studied by the single variable method. It was found that when the pulse width was fewer than 50μs, the broken network trend of carbides in W6M5Cr4V2 high speed tool steel enhanced and the content of carbide decreased with the pulse width increasing. Distribution of the carbides became evenly. When the pulse width was larger than 50μs, the broken network trend of carbide declined and the content of carbide decreased with the pulse width decreasing. Distribution of the carbides became unevenly. With the pulse voltage and pulse frequency increasing, the broken network trend of carbide became obvious and the content of carbide decreased. Distribution of the carbides became evenly.Based on the analysis, the influence of pulse current on microstructure of W6M5Cr4V2 high speed tool steel is mainly result from Joule heating effect and electromagnetic effect coupling of pulse current.