Large Forging Defects In Ingot Loose Simulation And Experimental Research

With the development of high performance and high parameters of largeequipments, the need of large castings and forgings becomes more and more,and weight and size of ingots become more and more also. Therefore, it is verynecessary to study the forming mechanisms of internal porosity defects in ingotsand forgings. Porosity defects in ingots can be predicted by analyzingtemperature field calculated using numerical simulation methods. Porositydefects in ingots can be removal by optimizing process parameters. Theseinvestigations have significance for manufacturing high quality steel ingots andforgings.using the method of combining the temperature field and the solid phasefield, solidification process of55tons and234tons steel ingots have beensimulated. The formation mechanisms and laws of porosity defects in largeforging ingots were analyzed and verified by experiments. Porosity defects in55-600tons ingots have been predicted and analyzed by using above optimizedcasting process parameters. By using the relationship of the porosity inProCAST and the relative density in DEFORM, and basing on porosity defectsgot from the casting process simulation, the models in forging processsimulation were established. The reasonable technological parameters of stressesand strains for compacting porosity by WHF method were obtained. The mainconclusions can be drawn as follows.1.By using the method of numerical simulation and experimentalverification, the position distribution of porosity defects in the steel ingot of55tons were predicted. The simulated results are identical to that of the experiment.The transfer coefficient1200w/(m2k) between the ingot and the steel die wereobtained, which provides a reasonable basis for casting process simulation ofother tonnages’ porosity defects.2. In the process of casting and solidification of234tons steel ingot,pouring by the later ladle with low temperature has a great effect onsolidification of the upper part of the ingot, while less influence on the riser and lower of the ingot. Solidification in the upper part of ingot is so fast that the riserloses its feeding capacity earlier, hot point formed in the lower part of the ingot,and then the porosity defect appears at a lower site. At the same height of ingotin the two schemes of double ladle pouring, the speed of the advancing line tothe center is rapidly in the early solidification phase, and the solidification speedslows down with time. In the solidification process of steel ingot, solidificationvelocity is the faster in the area located below the riser line150-300mm. Whentemperatures of two ladles are the same, the porosity defects are slighter thanthat in the other scheme, and the position of porosity moves up.3.With increasing of ingot tonnages, porosity defects are moving far fromthe riser line gradually, toward to the outlet end of ingots, and width and lengthof porosity belt increase significantly. The length increasing rate of porosity is2.296mm/t. For the length of the ingot, the position of porosity defects is nearlyconstant. It located in the10%area along ingot height below the riser line,which has not been affected much more by ingot height. The ingot size hasmuch more influence on the length of porosity defects. The range scale betweenthe length of porosity defects to that of the ingot is21.3%~55.4%. the heavierthe ingot is, the bigger the scale value is, the longer the porosity defect is. Thewidth of Porosity defects relative to the ingot diameter is also more obvious.When the heavy of steel ingot is less than267tons, the width of porosity defectsis1.4%of the diameter of the ingot body. When the steel tonnage is greater than296tons, the width porosity defects to ingot body diameter ratio is greater than3%, and increasing gradually.4.Using the WHF method, the compacting process of the steel ingot with4m length and3m diameters have been simulated under the process parametersof0.7anvil width ratio,20%reduction ratio,10%overlap. The porosity defectof ingots can be compacted fully when the equivalent strain values reach to0.521, equivalent stress value50.8MPa, axial stress value13.7MPa.