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before degassing or during degassing were close, with 21% and 18%, respectively. Of the respondents, 11% said that there was no definitive chronology to the addition, with respect to degassing. A follow up question indicated that 70% of the foundries will stick to the same pro- cessing chronology, with 25% saying they will add after degassing and fluxing as a variation to their standard procedure.


Approximately how long before pouring is the eutectic modi- fier added?


As with grain refiner additions, the majority of metalcast- ers (90%) responded that modifier additions should be made within 30 minutes of pouring. When asked to provide tips on adding eutectic modifiers,


respondents had this to say: “Monitor additions, it’s easy to add too much strontium


(and you CAN add too much). It needs time to take effect, but will also fade over long periods of rest.” “Add after fluxing, but before degassing so the flux does


not remove the strontium, and the degassing can remove added gas from the strontium.” “Experience with modification is limited, foundry


personnel don’t know why they add Sr.” Te last few questions on this survey were open ended


questions with regard to using strontium as a modifier. Spe- cifically, those that do not, why not? And those that do, why? For those that do not, the majority said that it was just not required for their castings, while others saw no benefit from the additions or negative effects in the form of too much porosity. Some even answered that they didn’t know why not, it just hasn’t been done in their plant. For those that add strontium as a modifier, 7% add based


on customer requirements, 30% find it helps counteract shrink by adding in gas porosity, 13% are adding for the improved flow-ability, heat-treatability, mechanical proper- ties benefit, or a mix of similar reasons that they see within the end casting. Te rest, 48%, cited “modifying the eutectic” as the main reason. While this is clearly the goal of a eutec- tic modifier, what seems to be unclear to the respondents is what that actually means in terms of the resulting casting. Perhaps it stems from a lack of information on the “best practices” for the metalcaster and relying on experience and “as it’s always been done” mentality. In either case, seeing what procedures and practices others in the industry are following may help those who are curious about improving their practices find a place to start.


Fig. 3. Shown are the breakdown of responses to the question, “When do you most add eutectic modifications relative to other additions?” November 2016 MODERN CASTING | 47


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