kyle brown, danavi wollin Studies on Hot Tearing Tendencies of Aluminum Cast Alloys Poured into Sand Molds kyle brown, danavi wollin

Introduction High strength alloys, particularly aluminum, are commonly used in the casting industry due to their superior mechanical properties However, high strength aluminum alloys have a higher tendency to form a defect called hot tear when cast Hot tear leads to increased scrap rates which in turn reduces the profitability and competitiveness of castings produced from these alloys The aim of this study was to isolate the variables which govern the formation of hot tears in cast aluminum alloys

What is Hot Tearing? Hot tears are defects that occur in castings that are subject to mechanical restraints Hot tears occur when thin sections of a casting solidify before larger, isolated sections of a casting The presence of this defect greatly reduces the structural integrity of the casting in which it occurs and commonly results in the casting being scrapped

Experimental Procedure A model of the test pattern was created and imported into the magma 5.3 software suite where its solidification was simulated at both superheated and non- superheated casting temperatures A sand mold of the pattern was created and cast at the specified temperatures. Results were analyzed and compared with predicted results from the simulation Figure 1: Fraction Solid Results from AlMg9 Poured at its Superheated Temperature into a Furan Sand Mold

Results Simulations were run at various pouring temperatures using two different mold compositions Time to complete solidification and cooling rates were measured at two points in the casting The difference in solidification time and rate between the two points was calculated and tabulated Figure 2: Tabulated Simulation Results Showing Difference in the Time Required to Reach 100% Fraction Solid at two Separate Points in the Casting with Varying Pouring Temperatures and Mold Types

Conclusions Results from the simulation were gathered and analyzed statistically to isolate the factors relevant to the formation of hot tears The primary factors assessed were pouring temperature and mold type From the results we were able to conclude that the primary factor affecting the formation of hot tears in cast aluminum alloys was the pouring temperature of the alloy

Special Thanks To Dr. Pradeep Rohatgi for the use of the UWM foundry laboratory for the casting of test molds To Dr. Hathibelegal Roshan for his knowledge of Magma 5.3 and the formation of hot tear defects To Dr. Benjamin Schultz and Regs Schiller for their assistance in designing the patterns for the production of the test mold And to MagmaSoft for the provision of Magma 5.3 licenses to UWM

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