With this modification, a new core was produced which was absolutely free of any defects.Ībout software for casting process simulationĬasting process simulation software considers the complete casting process including mold filling, solidification and cooling, and also provides the quantitative prediction of mechanical properties, thermally induced casting stresses and the distortion of cast components. This hypothesis was tested using a silicone rubber band to obtain an improved sealing of the relevant areas of the tool. Air could escape with high speed through the parting lines, resulting in the defect formation. The core blowing simulation results supported the Usiminas conclusion that an improper sealing of the tool was the root cause for these defects. Some of the defects showed a smooth surface, indicating that the sand had been removed by a strong air flow. The flow animation also showed that the problems occurred because these areas had to be filled by a counter flow of the sand (Figure 5).Īnother characteristic of the defects was that they all occurred next to the parting line of the core box. The simulation results showed a very good match between the real defects and areas of low packing density.
Having solved the curing related defects, a further core blowing analysis was carried out. Removing some of the upper and middle vents resulted in a 36% increase in the gas escaping through the lower vents. Total gas mass flow through the lower vents. Since the venting area was reduced, some filling defects were present, as expected.įigure 4. Applying these modifications, Usiminas produced another core, which did not show any gassing defects. Also, the amount of adsorbed curing gas increased in comparison to the original project. The optimization led to a considerable increase of the curing gas concentration in the lower regions of the core (~36%) (Figure 4). However, it was clear that these changes obviously would also influence the core blowing step. Instead of making costly modifications to the core box, Usiminas determined that a possible – and simple – solution was to close some vents in the top and center regions, in order to increase the gas concentration in the bottom. The open venting cross section of the top and central vents was allowing the gas to escape before it reached the bottom of the core. The problematic area corresponds exactly with low concentrations in the simulation.Įvaluating simulated curves for the gas mass flow through the vents made it clear that the catalyzing gas was not reaching the critical area. Core Blown with new parameters in comparison with the local concentration of adsorbed curing gas. The core blowing and curing steps for the PU coldbox process were analyzed, making it possible to draw preliminary conclusions regarding the existing defects.įigure 3. This core, called the thin waist core, represents some of the biggest challenges for Usiminas core production: its length (920 mm), substantial changes in the sand flow direction during blowing, the need to fill certain parts of the core through counter-flow and big variations in the cross section within the core.įirst trials showed problems with the process, which led to a complete collapse of the lower part of the core. The main goal was to optimize the process conditions for the existing tooling layout. The first project on which this software was utilized was already in progress at that time. The bottom of the core collapsed due to a lack of strength.īrazilian steel giant Usiminas recently introduced the new foundry core making simulation software MAGMASOFT® as part of their strategy to establish robust designs and processes for their core production line.