Simulation Research On The Heavy Ingot Solidification Process

With the upsizing of major equipment forgings,a high quality level is required for the heavy ingot.The heavy ingot has the characteristics of long solidification time and complicated solidification process,which brings serious defects to the grain structure.Since the second industrial revolution,the western developed countries have been insisting on the anatomical work of heavy ingot,and obtained amount of research results.Since the 1980s,China has begun to pay attention to the anatomy of heavy ingot.There are two main quality problems in heavy ingot:coarse grain structure and severe components macrosegregation.Both are closely related to the"temperature gradient"and"convective motion"conditions of heavy ingot during solidification.In this paper,a"thermal simulation"method to study the solidification process of large ingots under laboratory conditions is presented.Heavy ingot casting prototype based on the size,the calculation of the temperature field of casting solidification process,according to the big ingot casting from the center to the outside temperature characteristics of different regions,in the thermal simulation experiment,completed the"no temperature gradient condition","low temperature gradient condition","high temperature gradient condition"and""the condition of high temperature gradient thermal simulation experiments.According to the experimental results,the effects of different temperature gradient conditions on shrinkage cavity location,grain morphology,element segregation,inclusion species,morphology and quantity were analyzed.The morphology and microstructure of a 100-ton ingot were compared with the thermal simulation results.The effect of horizontal rotation on thermal simulation results was investigated,the mechanism of forced convection to change grain morphology was studied,and the mechanism of convection?flow and heat transfer?to refine solidified microstructure was discussed.The cafe organization module of Procast is used to simulate the microstructure results.Compared with the results of"thermal simulation",the microstructure of"no temperature gradient condition","low temperature gradient condition","higher temperature gradient condition"and"high temperature gradient condition"were simulated respectively.Determine the appropriate numerical simulation parameters,respectively for the surface nucleation parameters Nmax=5×10⁷,?Tmax=0.5,sigma?T=0.1,the shape parameters of nucleation Nmax=7.5×10⁸,?Tmax=2.5,sigma?T=1,growth parameters a₂=8.9×10^-6,a₃=4.5×10^-6.The effects of different temperature gradients on grain morphology were analyzed.The macroscopic segregation module in procast software is used to simulate the composition segregation of tissues under different temperature gradients.The numerical simulation results provide a basis for simulating the solidification process of large ingot.Using the flow characteristics of liquid steel in 1500?or so and water at 20?when the characteristics of the flow characteristics of similar,independent set up water simulation rotating experiment platform,combined with the thermal simulation experiment level spinning process parameters,were measured under the condition of forced convection"level"fluid shear strain and the normal strain,fluid tangential motion is analyzed and the normal movement of the influence of the initial solidification dendrite growth.The growth process of dendrites at different temperature gradients was recorded by using ammonium chloride precipitation apparatus.The effect of increasing nucleation core on nucleation process was investigated by tracer particles.The effects of temperature gradient on dendrite growth and morphology transformation were considered.Finally,combined with the thermal simulation and numerical simulation,the research methods of thermal simulation experiment result?grain morphology,element segregation,inclusion distribution and so on?verified in comparison with the numerical simulation results,according to appropriate simulation parameters?initial conditions,boundary conditions,the crystal nucleation and growth parameters,etc.?to simulate and predict the 22 ton ingot solidification process.The temperature field,flow field and solute field are coupled in the simulation.The simulation results are in good agreement with the published results.It provides an effective method to study the solidification process of large ingot.