Options for Updated Sand System Sand System


L


Phenolic-based, olivine/silica system, mechanical reclamation (the existing system)


ess than fi ve years ago, the mining of olivine sand ceased in the U.S., leaving


North American metalcasters looking for alternative sources. Some chose to import olivine sand from Norway, though the increased shipping costs when compared to a domestic supplier made this an expensive option. For voestalpine Nortrak’s met-


alcasting facility in Decatur, Illinois, importing its olivine sand more than doubled in cost, from $140 per ton in 2011 to $280 in 2012. T e facil- ity’s fl askless molding system for manganese steel trackwork castings relied on new olivine facing sand for surface quality and reclaimed olivine/ silica backing sand to minimize costs. Plant expansion plans were developed to increase production by nearly 60% in the short-term and 115% in the long-term. voestalpine Nortrak contacted an


engineering fi rm (GEMCO, Son, Netherlands) that had installed a turnkey casting facility in 2010 for a company site in France. Company offi - cials hoped the project for the Decatur site could be partially paid for with cost savings realized from an improved sand molding system.


Choosing a New System


The molding system was assigned top priority in the phased expansion. Sand system scenarios compared were: • Ester-cured phenolic-based, olivine/silica system, mechanical reclamation (the existing system at the time of study). • Ester-cured phenolic-based, 100% olivine system, mechanical reclamation.


• Ester-cured phenolic-based, 100% olivine system, mechanical and thermal reclamation.


• Ester-cured phenolic-based, chromite/silica system, mechani- cal reclamation and magnetic separation.


• Furan-based, chromite/silica sys- tem, with mechanical reclamation and magnetic separation.


• Ester-cured phenolic-based, chro- Fig. 2. The schematic shows the fl ow of sand through the new system. February 2016 MODERN CASTING | 33


Phenolic-based, 100% olivine system, mechanical reclamation


Phenolic-based, 100% olivine system, mechanical and thermal reclamation


Phenolic-based, chromite/silica system, mechanical reclamation


Furan-based, chromite/silica system, mechanical reclamation separation


Phenolic-based, chromite/silica, mechanical and thermal reclamation


Reclamation Rate(s)


Facing 0% Backing 75%


Facing 60% Backing 60%


Facing 80% Backing 80%


Facing 70% Backing 70%


Facing 87.5% Backing 87.5%


Facing 90% Backing 70%


Cost (compared to existing system)


N/A 110% 60% 110% 45% 45%


Investment Not


Applicable Minor


$620,000 $780,000 $960,000 $1,400,000 Fig. 1. Engineers chose the furan-based sand system (in green) from the various options available.


mite/silica, mechanical reclamation, magnetic separation and chromite thermal reclamation. Figure 1 shows the sand, treat- ment costs and investment require- ments for each scenario. The furan bonded chromite/silica system offered the best payback. Although chromite costs about double the high cost of silica, the ability to magnetically separate chromite from silica and the high reclamation rate associated with furan binder made this system the low-cost choice. In addition to the cost benefi ts associated with the switch, voestalpine Nortrak also could reduce its landfi ll contribution by increasing reclamation,


which would prove environmentally responsible. Figure 2 contains a sche- matic showing the sand fl ow diagram for this system. Even though two sister casting


facilities in Europe were successfully running this system, voestalpine Nor- trak still had two concers: • Would the furan bonded chromite make rangy, manganese steel track- work castings more crack prone?


• Would the silica separate from the chromite to avoid manganese silicate formation that produces unacceptable surface quality? Initial trials with furan bonded


chromite revealed some unexpected cure time issues. T ese issues were


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