Silicon Carbide Ceramic Foam Filters
Technical field
The invention relates to the purification of molten metal, in particular to a foam ceramic filter. More specifically, the present invention relates to a ceramic foam filter containing silicon carbide as a ceramic component, and the filter prepared by the present invention is used for filtering and purifying ferrous metal melts.
Background technique
During the smelting and pouring process of various metal liquid alloys, the casting reject rate caused by casting defects such as non-metallic inclusions and shrinkage holes is generally as high as 50-60% of the total rejects. Inclusion defects not only seriously reduce the mechanical properties and casting properties of castings, but also have harmful effects on the machining and appearance of castings. Purifying liquid casting alloys, reducing or eliminating various non-metallic inclusions and exhaust gases are undoubtedly important technical measures to obtain high-quality castings.
Filtration technology has been used in foundry production for decades, but initially simple filters such as barbed wire, perforated steel plates, and porous mud cores were inserted into the gating system to filter out large inclusions. Since the 1960s, aluminum silicate fiber, molybdenum silk, boron nitride fiber and other two-dimensional structural inner filter screens have appeared in Russia, the United States, the United Kingdom, and other countries, and have been applied in production. had a certain effect. However, all these filter screens can only filter out large inclusions and very few small inclusions in molten metal through mechanical sieving. Due to the low refractoriness and strength of the aluminum silicate fiber filter, it can only be used for filtering non-ferrous alloys, cast iron and small steel castings, and it is difficult to withstand the impact of high-temperature metal fluid for a long time; the molybdenum wire and Although the boron nitride fibrous filter screen developed in the United States can be used to filter high-temperature alloys such as cast steel, its application is limited because of its high price. There are also straight-hole core-type ceramic filters and refractory particle filters used for casting alloy filtration, but their porosity is small, and the filtration efficiency of the former is still low, and the filtration effect is unstable. The bonding effect makes it easy to leak particles and is inconvenient to use. Although the sintered porous ceramic filter first successfully developed in the United States in the early 1970s solved the problems of easy particle leakage and inconvenient use of the refractory particle filter, it is different from the honeycomb straight-hole ceramic filter successfully developed in the early 1980s in the United States. As in the case, the porosity is still small, generally less than 50%, so that the flow rate of molten metal is low.
Ceramic foam filter is the third generation filter product after refractory fiber filter screen and honeycomb straight-hole ceramic filter. The earliest ceramic foam filter was a ceramic foam filter for aluminum alloy successfully developed by Consolidated Aluminum Company of the United States in 1978. The trade name is Selee/Al. In 1984, Selee/Fe, a ceramic foam filter for filtering ferrous metals, was developed. The development of ceramic foam filters for casting alloys in China began in the early 1980s. The first ceramic foam filters successfully developed by Harbin University of Science and Technology in 1982 can only be used for filtering aluminum alloys.
