Figure 4: Results of Degas Modelling 357 in 1200 lb. Furnace
Results of New Melt Treatment Method Implementation The new melt treatment procedure was ultimately tested against the incumbent procedure. Specifics of the newly evaluated procedure follow: • Treatments with a Hoist Mount MTS unit and an improved pumping rotor design
• Treatment parameters set according to the degas modeling
• Grain refining and cleaning to be performed via the automatic additions of the grain refining flux
• Argon to remain the purge gas
• Treatment cycle will be automated to 10 mins for 600 lb. crucibles and 15 mins for the 1200 lb. crucibles
• Elimination of TiBor and Hexachloroethane pills
Ultimately, grain refining flux additions of 0.06% the weight of aluminum melt were added via the MTS to both 600 and 1200 lb. melts. The TA testing results are tabulated in Table 4. A perfect GF score of 9.0 was achieved in every cycle using the new procedure. Once the effectiveness of grain
refining was verified, hydrogen tested was completed.
Despite the cycle
time reduction from 30 minutes (for the incumbent) to 13 minutes with the new procedure, every cycle tested matched, or exceeded, the threshold specific gravity specification according to the internal RPT protocol and an in situ hydrogen measurement system used for the evaluation. Significant environmental and safety benefits were also achieved in
eliminating the Hexachloroethane degassing pills, which are dangerous to the touch since they can adsorb to the skin causing a depression to the central nervous system according to Wikipedia. Hexachloroethane has been targeted for obsoletion since 1999. The original evaluation of the new melt treatment was a success so it was implemented, monitored and verified five months later. A tabularized dataset from the adaptation appears in Table 5. The successful adaptation of the new process brought about the following technical & productivity benefits: • Perfect grain refinement every treatment measured with the THERMATEST 5000 NG III unit including 7 more tests run 5 months after implementation as part of the verification process
Continued on pg 30 May 2020 ❘ 29 ®
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