Aluminum Sand Casting Porosity
Defect formation caused by gas entrapment and volume contraction during solidification in sand casting, minimized through process-adapted venting.
Pores in aluminum castings are caused by gases that can no longer escape during solidification, or by the shrinking of the metal as it cools. In welding, these pores are a real problem: they can melt, release gases, and then lead to bubbles and cracks in the weld. The porous areas are also often dirty or oxide-containing, which further disrupts the welding process. Before welding, you must grind or mill the area around the pores generously until you have clean, dense material. If you weld deeper into the porous structure, you only burn the dirt and draw bubbles into the weld. A clean weld on dense base material is the be-all and end-all.