| Technology of electric pulse modification, an advanced technology for the solidification control, has been paid more and more attentions by improving solidification structure and refining grain significantly. Since the majority of researches concentrate on refining grain by technology of electric pulse modification,seldom reports can be found about the effects on element segregation and inclusions.Therefore, it has a very important significance in studying the effects of technology of electric pulse modification on refining solidification structure, element segregation and inclusions.In this paper, technology of electric pulse modification was applied to treat medium carbon steel for studying the influences of carbon distribution, solidification structure and inclusions under different process parameters. Besides, the mechanism of technology of electric pulse modification on medium carbon steel was also preliminarily discussed and the results obtained described as follows:(1)Inhibition of central carbon segregation and uniform distribution of carbon,related to the parameters of electric pulse modification, can be obtained by using treatment of electric pulse modification. With the increasing of the imposed pulse energy, including the voltage, treatment time and the pulse frequency, the carbon distribution was more uniform and carbon segregation was also improved, but when the imposed pulse energy reached to some of extent, the improvement of carbon segregation began to decrease.(2)Treatment of electric pulse modification can refine solidification structure of medium carbon steel and inhibit the development of dendrite, then developing from coarse dendrite to granular particle. With the increasing of the imposed pulse energy,the dendrite became coarsening, then the secondary dendrite arm spacing decreased finally, the developed dendrite completely changed to granular crystal.After treatment of electric pulse modification, the morphology of pearlite significantly changed, interlamellar pearlite spacing became small, lamellar structure became twisted and pearlite in the shape of short rod and granular also could be foundin local area.With pulse energy increasing, the massive pearlite gradually transfered into fine or granular pearlite and the pearlite interlaminar spacing decreased. Besides, the structure of pearlite interlaminar has experienced twist deformation in a certain degree under different pulse energy. Without pulsed electric field, the pearlite interlaminar spacing was 1.57?m, but changed to 0.56?m when the voltage was 6V, frequency was900 Hz and acting time was 30 s.( 3) Treatment of electric pulse modification has significant effect on the inclusion size and inclusion distribution of medium carbon steel by decreasing inclusion size and making its distribution dispersed. As an increase of pulse energy,the average diameter of inclusions in the sample decreased first and then increased and the number of inclusions in unit area increased with the decreasing of the inclusion size.The average diameter in the sample without treatment of electric pulse modification was 6.29?m and the number of inclusions in unit area was 84 /mm2;While the voltage was 6V, frequency is 300 Hz and the action time was 30 s, the average diameter decreased to 2.70?m and the number increased to 123/mm2. Without treatment of electric pulse modification, diameter of the inclusions under 5?m account for 52.86%, 5~10?m, 10~20?m and >20?m accounted for 28.77%, 14.75% and3.62% respectively, it could be found that the diameter above 5?m almost made up half of the total inclusions. However, the inclusion size decreased rapidly after applying pulsed electric field and the diameter of the inclusions under 5?m accounted for above 90%. It was also concluded that these changes were related to the imposed pulse energy and only suitable pulse energy could promote refining inclusions. |
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