Q: I’ve always known veining to be problem that is addressed by mold coatings and additives. Yet, even using these products the problem never seems to go away completely. Please explain to me what “veining” is, what new method — if any — are available to eliminate this defect.
A: Veining is caused by the non-linear expansion of silica sand during the casting process, which forms veins or “fins” on the casting surface, resulting in positive metal. There are several options in order to overcome veining, including mixing different aggregates in with the sand, applying coatings, and introducing sand additives.
Different types of sand additive options are available. Some contain starches, wood flours, iron oxides, and microspheres that act in varying ways from burning out to fluxing to collapsing, allowing room for the sand to expand.
It’s important to remove veins that form, and it is especially critical to eliminate them in a casting’s internal cavities, such as in a water jacket, so its performance will not be impeded.
As a result of extensive research and development, a more effective line of sand additives have been developed, called engineered sand additives (ESAs).
VEINO ULTRA™ RS2 was developed for warm box molding operations, and VEINO ULTRA™ RS4 was specifically designed for phenolic urethane cold box (PUCB) and no bake molding. Either VEINO UTLRA™ I 900 or VEINO ULTRA™ I 950 can be used in all three of these processes. All of these ESAs are based on readily available industrial minerals that are mined locally.
These newer ESAs offer many advantages. They are effective in severe applications. They are more cost effective as they are used at low addition rates, compared to previously developed ESAs. Most of these sand additives contain red iron oxide (Fe2O3), and have the ability to scavenge various mold gases during the casting process. In addition, they contain ingredients that do not significantly affect the blowability of the sand core, and high tensile levels can be maintained at low resin levels.
The VEINO ULTRA series will save you money in the cleaning room, and help reduce the cost-per-ton of castings shipped.
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