Hot tops and risers - mixts based on mill dust giving exothermic reactions

摘要

Material for the mfr. of hot tops, risers and runners etc. for foundry work contains 20-50% ball mill dust of up to 30% Al content, 3-12% finely divided Al0.4 mm, 0-15% organic fibrous material such as rayon fibre, 0-40% inorganic fibrous material eg. asbestos, 1-10% binder and inert filler e.g. pheny formaldehyde resin and burnst slag; an oxidant such as mill scale and a chemical initiator e.g. a fluoride if required. Parts made from this mixt. are formed by reaction of a slurry onto the required former and then removal and drying in an oven before storage. The parts produce a controlled exothermic reaction and are also easy to store, providing good insulation to the solidifying metal after the exothermic reaction has ceased.