Vibration Excitation Of Liquid Metal Nucleation Theory Of Basic Research

In order to get high proportion of equiaxed grain in metal solidification,liquid metal nucleation stirred by vibration was put forward,based on the theories of crystal dissociation,dendrite smelting and crystal rain.In the process of solidification,a stick with cooling equipment was put into the liquid metal,and continuously put in it cooling agents.Because of the cooling action,there would be some solidification shell in the surface of the stick first.Using the action of the mechanical vibration,the solidified metal should be shattered into pieces and ejected in the liquid metal.These pieces will become the nucleus of the equixed grain growing.In order to finish this paper,the following jobs were done:1)Equipment of nucleation stirred by vibration(ENSV)was assembled and installed.Program of PCI9113 card was compiled for gathering the picture and the data of temperature.2)The object of study was the metal of Zn.The liquid metal was treated by the ENSV in the different degreed of superheat and different cooling agents,so the influence of the vibration and cooling can be observed.3)The object of study was the metal of Zn.In the same degree of superheat,the liquid metal was vibrated and not vibrated separately for observing the phenomenon of liberation on the surface of stick and the shell growing.4)The object of study was the ferritic stainless steel,the effect of vibration and cooling to the solidification was observed.5)The object of study was the iron.Using the computer and the NiCd-NiSi thermoelectric couples to collect the temperature of the stick's surface,bottom and vent port for observing the heat transmission during the ENSV working process,and the mechanics of the nucleation stirred by vibration was disclosure.6)Making use of the heat transmission's calculation,ENSV which is cooled by the water was designed.From the above studies and calculations,we can observe that the proportion of the equixed grain in the Zn-billet was obviously increased to the proportion of 80%, and which was better by the gas cooling agent than the water cooling agent,and the proportion was increased with the time's increasing.Observed and proved the phenomenon of liberation on the surface of stick.Because of the effect of vibration, the mass of the metal chill on the stick was decreased from the 500g to 68g.Because of the effect of cooling and vibration,the proportion of the ferritic stainless steel's equixed grain was increased to 80%.Gathered the temperature,observed the heat transmission's charaCter of the main part of ENSV and calculated the heat transmission and the speed rate of the nucleation.Calculated the temperature of the surface of the stick,and the speed rate of nucleation whose diameter is 100μm,and the amount of which was 3.28×10~6.The phenomenon of the incrustation on the surface of the stick was observed.The ENSV which was cooling by water was designed,From the summary of all the paper,we can conclude that when ENSV treats the liquid metal,there are several innovations as follows.1,Making use of high frequency vibration,the solidification construction can be shattered into pieces,which should be ejected into the liquid metal.These pieces will become the nucleus of the equixed grain growing.2,Because of the temperature on the surface is lower than the inside temperature of the liquid metal,the structure of crystal rain would be formed in advance on the liquid.The vibration can let the liquid fluctuated,so there are some crystal would be descended in the liquid metal and become the nucleus of the equixed grain growing.3,ENSV is an equipment with a cooling system,so it can accelerate the metal solidification.It is better to form the equixed grain.4,Because of the effect of vibration,The ENSV can cause the liquid metal to be flowed,so the result was that the crystal was crashed into lots of pieces which can increase the proportion of the equixed grain.5,The fluxion of the liquid metal can make the crystal grain break away from the mould wall into the metal liquid,and these grain can turn into the nucleuses of the equixed grain growing.The result is that the proportion of the equixed grain in the solidification structure is increased.