Fig. 5. Shown are the level averages for the effects on permeability.
Fig. 6. Shown are the level averages for the effects on smoke opacity.
• V400: A mineral ESA based on red iron oxide with a mixture of hema- tite, magnetite and other minerals, though its particle size is much larger than RIO or BIO.
• V2003: A mineral ESA containing spodumene, a lithium ore.
• IL: A naturally occurring mineral called ilmenite containing primarily iron and titanium oxides.
Core Test Results Work Time/Strip Time Analysis:
Work time/strip time (WT/ST) analysis was measured on each mix and cores were produced and tested in triplicate and averaged. Te data was analyzed from the DOE results for level sums for each variable (Figure 3). Te V400 additive had the greatest effect, extending the WT/ST of the mix very significantly and the RIO and V2 additives had a lesser, but significant effect. Te sand additives
Table 1. Baseline Casting Ratings Veining Penetration Surface Finish
Core 1 1.0 3.0
3.0 40 | MODERN CASTING December 2015
Core 2 3.0 3.0
2.5
Core 3 1.5
2.25 4.0
Core 4 1.0 3.5
4.0
type had the greatest overall effect on the WT/ST with binder level having a smaller, but significant effect. Te sand type had minimal effect on the WT/ ST, high binder levels reduced WT/ ST, and the additive levels had little effect. Te pooled error was relatively large at 13%. Tis may indicate varia- tion from the test method using the “B” hardness scale rather than effects of the variables. Tensile Test Analysis: Level average
charts (Figure 4) also were used to analyze the tensile data. Te RIO, V2 and V400 additives reduced tensile strength while the other additives had lesser effects. Higher binder levels greatly increased strength, which sug- gests the negative effects of some sand additives could be offset with some- what higher binder levels. Additive type had the great-
est impact on the one-hour tensile strength, but a reduced effect on the
24-hour strength. Tis may have to do with related effects on WT/ST. Higher binder levels had the expected significant impact on strength with only minor effects from sand type and addi- tive levels. Te humidity resistance was impacted by binder level, with all other factors having only minor effects. Permeability Analysis: Level aver-
age charts for core permeability are shown in Fig. 5. Sand additives had a minimal effect on permeability. While sand additives certainly can affect the permeability of a mold/core, usage amounts of only 2-4% of the weight of the sand produce only small effects. Te sand type or GFN had the over- whelming effect, with the coarser sand yielding much higher permeability. Smoke Opacity Analysis: Te level
average chart for smoke opacity (Figure 6) showed a surprising result. Several of the sand additives reduced the opac- ity somewhat, but the V400 reduced the opacity about 50%. As expected, the % binder had a major impact.
Casting Results Following shakeout and cooling,
the castings were sectioned through the parting line of the cores and sand
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