What Causes Metal Casting Defects?
The cause of metal casting defects depends on the components and how they are cast.
A variety of irregularities can affect metal castings. The most common defect is porosity. Porosity refers to the voids—the empty spaces—on or within what should be a solid metal casting. The cavities in porous metal castings will cause leaking, plating problems, and performance issues in pressure applications.
A cavity in the middle of a casting may be caused by axial shrinkage. All metal shrinks as it solidifies, but the outside metal solidifies faster than metal at the center. From pouring speed to pouring temperature, several steps in the casting process will affect the size and shape of the defects.
Pinhole voids result when gas is trapped in the metal casting during solidification. Either the gas was insufficiently evacuated from the mold, or turbulence during gating created the air pockets.
Instead of simply being trapped, sometimes gas is created by variations in the components of the metal. High nitrogen, low carbon, elevated aluminum, or the formation of carbon monoxide in the melt can create this metallurgical porosity.
A number of defects can occur on the surface of the casting, caused by gases, venting, pattern design, melting practice, pouring practice, and more. Defect-free castings can be very difficult to make, especially when a solution for one problem causes a different problem.
The best solution is to seal the porosity using vacuum pressure impregnation. Imprex is the leading provider of casting impregnation services and systems to seal your leaky castings and eliminate the porosity.
Do you need to fix the defects in your metal castings? Contact Imprex today.