Pulse Current Treatment Process And Microstructure Research Of Hypereutectic High Chromium Cast Iro

Electric Current Pulse(ECP)processing technology as a metal material treating technology has become a new bright spot of metal solidification technology with advantage of pollution-free,simple equipment,easy to operate and significant effect.However,ECP processing technology is still in the stage of laboratory research and seldom used in industrial production.Therefore,if the ECP is applied in the casting solidification process of specific casting to refine the solidification structure,ECP processing technology will become possible in the actual industrial production.The impact of solidification structure of hypereutectic high chromium cast iron with ECP treating in three different mold(Kiel test block,round bar,slab)during the course of solidification was investigated.The mechanism analysed preliminarily provide a theoretical basis for the production and application of pulse current.First of all,the impact of the solidification structure of hypereutectic high chromium cast iron Kiel test block treaded by ECP electrodes apply mode during the course of solidification was investigated.The results showed that,solidification structure was impacted by ECP electrodes apply mode and structure near the site of the electrode was refined better.In the whole solidification structure of the untreated sample,primary carbides of the lower part organization are small,round and granular,while primary carbides of the middle and upper is in a larger size and multi-rod.Primary carbides of the Kiel test block solidification structure is refined from thick rod into small granular by ECP of middle electrode mode and three positions organizations is not much different.At the same time,the impact of the solidification structure of hypereutectic high chromium cast iron round bar treaded by ECP during the course of solidification was investigated.The results showed that the solidification structure of Φ 50mm hypereutectic high chromium cast iron bars were refined from thick rod to fine granular by ECP,but there are still thick rod-shaped primary carbides in middle the upper part.In addition,the refinement effect of solidification structure is not obvious in Φ 30mm bars.The impact of solidification process of hypereutectic high chromium cast iron slab by different treating times of ECP was investigated.The results showed that solidification structure of slab treated for lmin was no effect.The rod-like carbides were refined and the size is further reduced as the treating time prolonged.When the ECP treating time is 5min,there is optimum refinement effect on the slab solidification structure,and the impact toughness of the slab is gradually increased as the ECP treating time increased.The maximum impact toughness value is 4.75J/cm2.The solidification microstructure of untreated slab is conventional by contrasting untreated and ECP treating time for 5min slab overall solidification structure.The primary carbides near type wall is relatively small with the chilling effect,while primary carbides near the slab center grew up.The solidification microstructure of slab treaded for 5min is refined obviously,and the small particulate primary carbides are evenly distributed in the matrix.