Simple Solutions That Work! Issue 16

A luminum and steel foundries use the cooling curve properties provided with their simulation software package or from standard databases; however, those are only guidelines. They can also get the true cooling curve events, like the fraction solid curve and the intermetallic phase transformation temperatures useful for unfamiliar or custom alloys and aerospace applications. That’s because the alloy properties before and after melt treatment are different from the database. For casting simulation and for heat treatment parameters, using the custom melt properties for a given melt procedure versus using the standard database properties is really bringing value especially to complex castings jobbing foundries. This article gives examples for aluminum A201 and A356. The melt and heat treatment were corrected based on the thermal analysis sample results. ALUMINUM A201 COOLING CURVE This foundry first relied on the standard guidelines for the heat treatment cycle (T4). The mechanical properties were on the low side of the norm. The microstructure was analyzed to understand what was going on, and it was determined that the late copper eutectic Are You Still Using Melt Properties from the Standard Database? was burnt-out. To understand why, thermal analysis samples were taken on the molten A201 before and after melt treatment. The late Al-Cu eutectic phase transformation temperature was lower than what the database suggested. The heat-treatment furnace solution temperature was directly at the late eutectic temperature. So, the heat treatment temperature cycles were adjusted accordingly and the problem was solved. It would have saved trials and errors (time and money) to measure the real solidification with thermal analysis in the first place. Now, this foundry takes a thermal analysis sample for each batch of A201 to confirm the cooling curve events are all within their custom parameters. Figure 1 (on next page) shows the simple operator screen for a quick and clear understanding of this complex quality criteria. SIMULATING THE ALLOY CAST ON THE SHOP-FLOOR Non-turbulent gating designs to avoid bifilms oxydes go a long way to improve mechanical properties and casting quality. Still, we need to set the melt quality limits for our simulations and make sure the shop floor melt is within those limits. Figure 2 gives an example FLEXIBLE MANUFACTURING & ENGINEERING TRENDS Continued on next page 7 FRANÇOIS AUDET Solutions Fonderie ARTICLE TAKEAWAYS: • Melt properties from the database are different from shop floor properties • For specific alloys/expensive casting jobs, using the database properties is risky business • Measuring real phase transformation temperatures before casting will save time and money for heat-treatment parameters • Customize the cooling curve in simulation software