Additives to Reduce Veining and Avoid Refractory Coatings

摘要

It is well known that the European and US foundry industry has been facing intense pressure on costs and strong competition for many years now. Direct competitors cannot only be found far away in China or India but also in Europe, or much closer to home. Environmental and industrial safety regulations along with complaints from nearby residents are making life difficult for many foundries. Meeting these requirements often entails massive investment with little financial payback. Castings have also become real works of art. Increasingly, foundries must be able to realize and implement the ideas of creative designers regarding a component's mechanical properties, geometry, weight and so on. On top of this, buyers ruthlessly focus on price when making their contract award decision, regardless of whether they are buying for the automotive industry or for medium-sized mechanical engineering companies. Reasonable quality and on-time delivery are considered a matter of course and absolutely essential. This paper shows foundry men ways in which they can respond to these challenges by using not only brand-new but also tried-and-tested means, such as selecting the right sand, additives, binders and coatings. The use of sand additives to avoid veining defects is very common in cold box applications. Sand additives in combination with refractory coatings that improve the surface quality and reduce or prevent penetration of the metal are normally used for this purpose. This common practice enables high-quality castings to be produced, although foundries are well aware that this is accompanied by a greater amount of time and effort needed in the process chain. ASK Chemicals has now developed a solution that combines the positive effects of additives and coatings in a single product. This new type of additive mainly consists of low-density alumina silicate ceramics (LDASC) and a small quantity of flux. Test results have shown in a reproducible manner that this material has unique expansion and shrinkage properties that not only prevent veining but also produce outstanding casting surfaces, even without the use of coatings. A series of castings for the automotive industry, such as brake disks, brake cylinders and steering knuckles, have been produced without coating the cores and the results are good. Quality and economic benefits speak to the use of the newly developed sand additive. Hence, ISOSEAL™ 2011 offers foundries key technical and economic competitive advantages.