TAILIEUCHUNG - Foseco Ferrous Foundryman's Handbook Episode 11

Tham khảo tài liệu 'foseco ferrous foundryman's handbook episode 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 240 Foseco Ferrous Foundryman s Handbook SEMCOPERM M66 has been developed for coating EPS patterns used for making iron castings by the lost foam process. It is particularly suitable for vacuum assisted casting. The permeability is such that metal pull-through is unlikely to take place. The coating is supplied as a heavy slurry at 95-100 Baumé. It must be diluted with water to 55-65 Baumé for application by dipping or overpour methods. Coatings for the full-mould process This process uses polystyrene patterns to make large one-off castings. The patterns are usually machined from large blocks of expanded polystyrene. After coating the patterns are surrounded with a self-setting resin bonded sand to form a rigid mould. The process is widely used to make large grey iron press-tool castings sometimes many tonnes in weight having metal sections as much as 100-150 mm thick. The coating in such cases must be capable of being applied in a thick layer without cracking or peeling to provide an adequate barrier to the metal. Foseco supplies STYROMOL 702FM coating developed specially for this purpose. Spirit based coatings must not be used for this application since burning off the coating would result in loss of the pattern before the sand mould was formed. STYROMOL 702FM is a dense thixotropic water based slurry containing a blend of graphite and refractories which can be applied by spray or brush. To facilitate application a small amount of water can be added to give a Baumé of 90-100 . This will give a coating thickness of mm. The most effective method of application is via a spray system. Once applied the coating must be completely dried prior to ram-up and casting. The coating must be air dried using warm air circulation but the temperature must not exceed 45 C or there is a risk that the polystyrene pattern may be damaged . It may take 2-3 days before all the moisture is removed. The TRIBONOL process Green sand moulding is the most widely used moulding process for

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