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techniques and parameters are used. The study indicated all of the alloys are suitable for die casting. However, particular alloys require
special treatment in some instances. For example, when the iron and manganese contents of the alloys are small, precautions have to be taken against possible die soldering problems. Alloy #4 in this study, which contained 0.7% iron and 0% manganese and was predicted to have high thermal conductivity, also had a high die soldering tendency. For this type of alloy, the iron and manganese contents should be kept at their allowable upper level and/or nickel reduced to a minimum. Based on previous studies, manganese and nickel additions in the ranges of manganese 0-0.5% and nickel 0.05- 0.5% do not affect the variation of the alloy’s thermal conductivity. So, for the alloy to keep the required thermal conductivity, manganese can be raised to 0.25-0.5%, and nickel can be reduced to a minimum.
Evaluating Alloy Options Like most design challenges,
choosing a custom alloy requires balancing the alloy chemical content and benefi ts against the cost. As one die caster noted, the customer needs to be aware of the tradeoffs and feel comfortable that the solution is worth its costs. While the decision point may be different in each case, a 5% increase in strength may not be worth an additional cost. The graph in Fig. 1 shows the fl ex-
ibility of die casting alloys available to meet specifi c strength requirements. The graph shows alloy 380 with two different magnesium compositions and plots stress vs. strain for those alloys in a tensile test. Alloy #7 has higher magnesium content and exhibits a higher tensile strength than alloy #1, which has a more typical alloy 380 magnesium composition.
METAL
Adam E. Kopper, Mercury Cast- ings, Fond du Lac, Wis., and Naoyuki
MarCh/aPril 2010 Metal Casting Design anD PurChasing 45
Fig. 1. The typical stress vs. strain curve shows how alloy 380 with two different magne- sium compositions perform in a tensile test.
Tsumagari, Briggs & Stratton Mil- waukee, Brown Deer, Wis., con- tributed to this article. Additional information was extracted from “A Study of Aluminum Alloy-Micro-
structure-Performance Interaction,” Diran Apelian, Makhlouf Makhlouf and Libo Wang, and “Casting Char- acteristics of Aluminum Die Casting Alloys,” Makhlouf and Apelian.
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