Reducing Surface Defects With Proper Vein Reduction
While green sand foundry vein reduction compounds can lead to improvements in iron castings — such as reduction in metal penetration and core erosion — they can result in varying degrees of tensile property reduction.
As casting surface quality becomes increasingly important to end-users, foundries have to find new and effective methods of eliminating surface defects in iron castings.
One method — vein reduction compounds — is used primarily to reduce or eliminate expansion defects, which show up as “veins” on the surface of the casting. Foundries have achieved reductions in expansion defects and imprints in casting quality with mixtures of 90% prepared sand and 10% vein compounds.
However, the key to vein reduction compound use is to be careful when adding the compounds into core sand mixtures, as they can result in varying degrees of reduction in mold tensile properties. This reduction is due primarily to the composition of the materials and the sizing.
This article will take a look at the process of vein reduction and what casting surface quality improvements can result.
Fig. 1. The middle location on this test casting was made with a phenolic urethane binder without the addition of a vein reduction compound. The locations at the left and right both used vein reduction compounds.Read More