The Simulation Of Q345Steel Solidification’s Processing And Analysis Of The Casting Microstructure

Solidification process is an important moment of the process of materialpreparation forming stage procedure. It affects not only the rolling and forgingprocedure, but also the performance of the product. Therefore, the controlling of themetal crystallization process becomes an important way to improve mechanicalproperties and process performance of metal.The solidification process included the transfer of heat, mass and the momentum isan opaque and complicated process. It’s difficult for human to accurately analyze thesolidification process. However, by means of the computer to carry out numericalsimulation, we can accurately calculation of the change of each phase field in thecasting forming process to obtain the control parameters for the reasonable castingformation.The research based on Q345steel, uses ProCAST software to carry out simulationcalculation respectively of conventional coagulation and directional solidificationprocess, research the temperature field, solidified structure and the segregation of someelements under different solidification modes, analyse the law of solidification. At thesame time, the research use the vacuum induction melting furnace ZG-0.03A anddirectional growth electromagnetic induction furnace to carry out Q345steelconventional coagulation and directional solidification experiment, use Zeissmetallographic microscope, scanning electron microscope and the energy spectrumanalyzer equipment to observe structure and defects of the test steel. Then throughcomparing simulation results with the test results, in order to get reasonable Q345steelingot form control parameters, provide theoretical guidance for practical production.Via conventional solidification simulation calculation, we can conclude thatsuperheating temperatrure has great influence on the final state casting microstructure,grain mean radius reduces from0.2306mm at75℃to0.1862mm at0℃, and thecenter equiaxial crystal also is greatly improved. Composition has a direct impact to the casting structure of Q345steel, simulation calculation draws that the optimizationcomponents content of C, Mn, Si, P, S respectively is0.18%,1.60%,0.35%,1.60%,0.04%.Simulation the small ingot equiaxed is35.20%and the test steel equiaxed is34.80%. The data is similar. Simulation the ingot macroscopic shrinkage defects’ shapeis a funnel. Its diameter is64.6mm and its height is76.92mm. The actual testingshrinkage also is a irregular funnel. Its diameter is61.34mm and its height is78.53mm.The results of the simulation and experiment are coincided.Directional solidification simulation shows that the secondary dendrite arm spacingdecreases with the increase of solidification rate. When drawing speed increases from50to200μm/s, the secondary dendrite arm spacing reduces from14.49μm to5.80μm,the secondary dendrite refining extent increases. It causes deterioration in concentrationdistribution uniformity at the directional solidification sample’s steady state of soluteelements Si.The secondary dendrite arm spacing of the simulation is that2=11.59μm under100μm/s drawing speed and2=8.69μm under150μm/s drawing speed. The averagesecondary dendrite arm spacing of the experiment is that under100μm/s drawing speedthe2is about14.96μm and at the drawing speed of150μm/s the2is approximatelyequal to8.33μm. The data of the simulation results and the experiment results isapproximate. The energy spectrum of the directional solidification sample’s steadydisplay that the Si segregation is severely compared the drawing speed of150μm/s with100μm/s. Simulation shows that with the casting speed increases, the Si segregation isseverely. Simulation and experiment results are consistent trend, so the simulationprocess is scientific and reasonable.