Why is there still porosity occuring in Argentium casting??

Question

Is heat the issue? Was the alloy to hot during the pour? What is the recomended flow heat?

Answer 1

Hi. Are you following the correct procedure?
"INVESTMENT CASTING
Casting temperature range: 1750-1800°F/955-980°C. Argentium™ Sterling Silver displays a paler color when heated/molten, therefore do not judge casting temperature by eye.

Flask temperature: Lower flask temperatures are recommended. For guidance, drop by a minimum of 85°F/30°C below regular temperatures used for standard sterling silver.

Crucibles: To avoid contamination from other alloys, it is important to use separate crucibles for Argentium™ Sterling Silver. Do no use silicon carbide crucibles.

Protective atmosphere/fluxing: A protective atmosphere is recommended when melting Argentium™ Sterling Silver. If a protective atmosphere is not available, flux can be used (boric acid is recommended). Skim any oxides off the surface before stirring.

Hardness – wet investment removal: Leave flasks to cool for 20-25 minutes before quenching. This will give castings approximately the same hardness as standard sterling silver (70HV). To raise the hardness to approximately 95HV, heat castings at 580°F/300°C for 30-45 minutes and air cool to room temperature.

Hardness – dry investment removal: Leave flasks to cool to room temperature before removing castings from the investment. This will give Argentium™ Sterling Silver a hardness of approximately 100HV.

Precipitation hardening: For hardness above 100HV, follow precipitation hardening instructions.

Remelting: Use at least a 50% fresh/50% scrap mix. For high-quality pieces, using more fresh metal will yield superior results. It is important that used trees and buttons are free from investment powder residue, to avoid contamination."