defects are usually revealed during machining as sub-surface defect voids.
Check venting at specific areas where gas holes
occur and increase where possible.
The permanent mold process used to produce Dura-Bar XL is designed to virtually eliminate casting defects such as gas holes
, inclusions, and hard spots.
Bates also proposed that the results of resonant frequency analysis will often correlate to overall strength; it can show shrinkage, gas holes
, surface cracks and inclusions.
Naik described pinhole defects by stating, "Hydrogen pinholes are spherical or pear-shaped gas holes
However, the use of the sleeves with cookies created gas holes
and pock mark defects on the surface of the casting underneath the sand of the cookies.
It helps eliminate gas holes
, porosity and metal oxides while increasing fluidity, resulting in more successful castings.
7% in gray iron require correspondingly low S contents and higher pouring temperatures to avoid slag reaction gas holes
(subsurface blow holes) caused by MnS interactions at the cope surface of the casting.
05% and greater) were effective in tying up N as Ti compounds (TiCN or TiN) and preventing re-precipitation as gas holes
Defect: After being machined by an outside facility, four different defects appeared in this casting--cold shut, gas holes
, sand inclusions and stress cracks.
Because steam and other gases are evolved in green-sand molding when molten metal is poured into the mold, the sand must be permeable--porous--to permit the gases to pass or else the casting may contain gas holes
and other defects.
Morgan, "The Nature and Origin of Gas Holes
in Iron Castings," AFS Transactions, p 17-33 (1965).