DEVELOPMENT OF DOUBLE-LAYERED CERAMIC FOAM FILTER FOR IRON CASTING

摘要

Production of clean and high quality castings is becoming increasingly important in order to remain competitive in today's global market. In Ms view, use of various type filters during the casting is commonly done for the both of iron and non-iron castings as the means to improve casting processes. In this study the double-layered ceramic foam filter is developed to realize reasonable inoculation reaction and removal of the resultant reaction products from the casting, simultaneously. The filter is made by combination of the first filter containing inoculant and the second one with the porosity finer than the first. In the test experiment, Fe-Si-Ca-Al-Ba alloy is used as the inoculant. The grain distribution of inoculant is ranged 45 to 210 urn. Two kinds of cast iron(FC:3.32wt%C and FCD : 3.61wt%C)are investigated for graphite morphology, matrix structure, mechanical strength and so on. The pouring temperature is 1630 to 1667 K. As the result, graphite is precipitated fully to the shape of A type in grey iron and to the smooth and shapely particles in ductile iron. The oxide generated by inoculation reaction is observed to be entrapped by the second filter, yielding the castings with less inclusions. Tensile strength and elongation are increased for both the grey and ductile iron by the filtration, which is caused not only by the graphite shape control but by the improvement of matrix structure. The proposed filter system is shown to be the reasonable one giving inoculation reaction-filtration space without fading. We have a view that the use of the developed double-layered filter enables us to establish a low-cost and simple casting design in order to obtain clean and high quality products.