[862] Low nickel, multi-purpose alloy.
For casting:
• Very little boric acid flux is recommended. Do not use carbon flux such as soda ash, saltpeter etc. No flux needed in bottom pour automatic casting unit.
• Flouric based investment removers are the best for silicon oxide invisible coating. Use of aggresive acid causes corrosion and surface damage. Brite cast investment removers works effectively.
• To calculate the weight of the metal needed (in grams), multiply density (gm/cc) with weight of wax (grams) . Add 10% of the total weight for button.
• Gypsum bonded investment is recommended. Follow manufacturer's instruction for burnout cycle.
For sheet and wire:
Composition and Melting:
• The alloy and fine gold should be melted together in a clean crucible. Place alloy in the bottom of the crucible and fine gold on top.
• Initial melting temperature should be obtained then reduced to the suggested ingot temperatures.
• The alloy should be mixed well with a stirring rod to ensure a good mix.
• Alloy should be poured into a preheated, vertical or lightly lubricated iron mold.
• Use a steady, even pouring motion slowing down at the end of the pour to preventshrinkage at the top of the ingot.
• Use a round rod mold for wire and a 2-piece L shaped mold for plate and sheet.
Quenching:
• The metal ingotshould be removed from the mold and quenched immediately into a pickle solution or water.
• For heavy ingots a one-minute cooling period is recommended to avoid quench cracking.
Fabrication:
• The metal ingot should be cleaned of all adhering oxides or fluxes before rolling.
• The ingot should be rolled or drawn to a 50% reduction in size before annealing.
• After initial annealing continue the reduction at 50% before annealing again.
• Clean the ingot after each anneal.
• Keep rolls, dies and metal clean to prevent defects in the finished stock.
Annealing:
• Annealing temperature is 710°C/1310°F for 20 minutes & Air cool in front of fan or moving air. Do not over anneal.
• A boric acid fire coat should be applied before annealing in open atmospheres.
• Over annealing can cause excessive grain growth and orange peel effect on the surface
