Study On The Effect Of Electromagnetic Levitation Current On The Solidification Structure Of 600 MPa Steel

Compared with the traditional equilibrium solidification,the electromagnetic suspension solidification technology is a vacuum refining technology with good dynamic conditions,which can realize the non-equilibrium rapid solidification of high melting point alloy and produce ultra-fine microstructure materials.Some quality defects often appear in the solidification process of 600 MPa steel during continuous casting.Based on the mechanism of vacuum electromagnetic suspension,the effect of current on the solidification structure of 600 MPa steel was explored in this study,which provides a reference for the evolution of solidification structure of metals and metal alloys under the condition of electromagnetic suspension.In this study,the method of combining theory,experiment and simulation was used to study the principle of the effect of electromagnetic suspension current on the solidification structure of alloy,the simulation study of the effect of electromagnetic suspension current on the control condition of 600 MPa steel,and the test of the effect of different suspension conditions on the solidification structure of 600 MPa steel.The main research conclusions are as follows:(1)The principle of influence of electromagnetic suspension current on solidification structure of alloy shows that:when the metal sample is in a strong magnetic field,due to the suspension principle,the metal sample will cut the magnetic induction line,generate the induced electromotive force,and form a closed current loop on the surface of the metal sample.At the same time,the electromagnetic force is generated between the induced magnetic field and the induced current.The longitudinal nonspinning component provides the suspension effect,while the horizontal spinning component produces the driving and stirring effect,so as to achieve the purpose of suspension and grain refinement.After applying AC magnetic field,forced convection is formed in the metal melt due to the effect of magnetic field,which breaks the first formed dendrite and brings the broken dendrite to the interior of the melt,so that the dendrite is evenly distributed in the melt,and the nucleation rate is increased,and the grain is refined.(2)The simulation results of the influence of electromagnetic suspension current on the suspension control conditions of 600 MPa steel show that the temperature field decreases gradually from the inside to the outside due to the influence of skin effect,and the Joule heat generated by electromagnetic stirring is uniformly distributed.When the input frequency is fixed,the size of the input current is proportional to the size of the magnetic field.The larger the magnetic field is,the stronger the eddy current effect is,and the more Joule heat is generated.When the frequency of the sample is 334 k Hz,the optimal suspension current of the sample suspended about 2 g should be about 50 A.(3)The stability test of 600 MPa electromagnetically suspended steel shows that the sample vibrates,falls and sticks to the test tube wall during suspension.When the inner diameter of the suspension coil is 20 mm,the outer diameter is 26 mm,the suspension coil is 3 turns,the stabilization coil is 2 turns,the suspension mass is 2.66g,the air flow is 1.0 L/min,and the 600 MPa steel is stable in suspension.(4)The test results of the influence of current intensity on the solidification structure of 600 MPa grade steel show that different current intensities cause different temperatures on the surface of the sample,and different temperatures have different effects on the solidification structure of the droplets.When in levitation,the cooling atmosphere is 100%H₂,the gas flow is 2.0 L/min,the power frequency is 334 k Hz,and the current is 50.8 A.Electromagnetic levitation,through high-speed camera shooting and calculating the number of frames per second,it can be known that 600MPa steel The droplet melted from solid to liquid within 6.453 s,and the droplet changed from liquid to solid within 15.938 s.This shows that the 600 MPa grade steel droplet melts and solidifies,and the growth rate of primary dendrites is very fast.On the one hand,the forced convection effect generated by the alternating magnetic field is strong;on the other hand,the magnetic field generated by electromagnetic levitation must be accompanied by electromagnetic stirring.Electromagnetic stirring will break the developed dendrites,significantly reduce the size of the crystal grains,make the temperature in the droplets more uniform,and help control the uniformity of the solidification structure during solidification.