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LOW MAINTENANCE AUTOMOTIVE BATTERY GRID CASTING
Using Low Antimony (2 to 3%) Alloys
A grid made from a low antimony alloy will be softer as cast and will require a little more sensitive handling by the machine from the mold to the trim die and then to the stacker.
Wirtz grid casting machines with electric mold heat and pallet die entry mechanism will cast low antimony alloys without modification since casting temperatures can easily be varied and the handling system from the mold to the die and stacker are designed to handle thin, soft grids.
The melting point of low antimony lead is higher than 4-1/2% antimonial lead, and therefore requires a change in operating temperature. It is possible to adjust for this change by increasing the ladle pour and mold temperatures and/or the amount of the cork insulation. We recommend that the ladle pour temperature not be increased but that the mold temperature and amount of cork insulation be increased. Increased ladle pour temperatures will shorten cork life more rapidly than will an increase in the mold temperature.
In a properly formulated low antimony alloy, hot grid cracking is reduced and casting speeds may be increased.
Notes on Handling Low Antimony Alloys
The lead melting furnace temperature may have to be increased to approximately 850°F (454°C) depending upon the particular alloy being used.
The mold temperature should be approximately 360° to 400° (182° to 204°C).
Extra care must be taken when drossing, solidifying or re-heating the furnace, since the solubility of some alloys, such as copper and sulfur, is reduced at lower temperatures.
1. To dross a low antimony pot, make sure the pot has been at 850°F (454°C) for at least one hour. Stir the dross that has accumulated at the top and try to dissolve it back into solution. After stirring, remove any excess dross.
2. Prior to turning the lead pot off, the pot should be drossed. Follow the procedure shown in 1. above. After drossing the pot, it may then shut down to any temperature which is below the freezing point of the alloy being used. The lead pot should be at 850°F (454°C) or frozen.
3. To re-heat the lead pot, turn the temperature up to 850°F (454°C). After the lead pot reaches temperature, stir the dross which is on top and try to dissolve it back into solution. DO NOT dross the pot after re-heating.
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