Magnesium oxide whisker in-situ synthesized spinel reinforced magnesium oxide-based crucible and preparation method of crucible

Abstract

The invention discloses a magnesium oxide whisker in-situ synthesized spinel reinforced magnesium oxide-based crucible which can be sintered under low temperature and is outstanding in chemical stability and thermal shock resistance and a preparation method of the crucible. The method comprises the following steps: (1) mixing 15-25% by mass of nano alumina sol, 0.8-1.5% by mass of a rheological agent, and the balance of nanometer titania sintering additive containing magnesium oxide ceramic powder; adding absolute ethyl alcohol; performing ball milling; uniformly mixing to obtain ceramic sizing containing 65-75% of solid content; (2) preparing a crucible biscuit; (3) preparing a crucible blank; (4) preparing vacuum infiltration on the magnesium oxide-based crucible blank in the aluminum sol; polishing the surface; drying; then sintering for the second time under high temperature of 1350-1550 DEG C; then cooling along with the furnace until room temperature so as to obtain the magnesiumoxide-based crucible.

Description

technical field [0001] The invention relates to a magnesium oxide-based crucible and a preparation method thereof, in particular to a magnesium oxide-based crucible synthesized in situ by magnesium oxide whiskers to enhance spinel and a preparation method thereof, and belongs to the field of metal materials and metallurgy. The magnesium oxide-based crucible prepared by the invention is particularly suitable for smelting magnesium and its alloys. Background technique [0002] In recent years, the demand for lightweight has led to the rapid development of the application of magnesium alloys and aluminum alloys. Whether it is wrought magnesium, aluminum alloys or cast magnesium, aluminum alloys, the production is inseparable from casting equipment. The chemical properties of magnesium are lively, and it is easy to react with oxygen, nitrogen and water vapor. It is easy to be oxidized and burned during the melting and refining process, and the product remaining in the magnesium ...

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Problems solved by technology

Chinese patent document CN103030407B (a kind of preparation method of high-strength, high-density, high-purity magnesia crucible), Chinese patent document CN1011306B (pure magnesia foam ceramic filter and its preparation process) etc. use pure magnesia as raw material to prepare magnesia Ceramics, because MgO has a high melting point and thermal expansion coefficient (13.5×10 -6 / °C) is high, therefore, it leads to difficult sintering (sintering temperature is not lower than 0.8 times its melting point) and poor thermal shock resistance, which limits the application and development of MgO ceramics

add V 2 o 5 In powder form, MgO will react with V at 1190°C 2 o 5 form an approximate composition of Mg 3 V 2 o 8 The liquid phase promotes sintering and can significantly reduce the sintering temperature of MgO foam ceramics, but V 2 o 5 Harmful to the respiratory system and skin during use, and has strict restrictions on operation

with V 2 o 5 Similarly, cobalt oxide is also a good low-temperature sintering aid, but its application is limited as a highly toxic substance and rare resource

Add fluorite (melting point 1423 ℃) and magnesium fluoride ( Melting point 1248°C), the solid solution of fluoride not only increases the lattice distortion of the matrix magnesium oxide during the sintering process, but also easily forms a low melting point liquid phase, thereby reducing the sintering temperature of the magnesia ceramics; however, during the sintering process F in fluoride is combined with Si, Al, Fe, Ca, and most of them (about 70% in ceramic tile production) volatilize in gaseous form, which not only corrodes the green body itself and damages the quality of sintered ceramics, but more seriously, it is discharged to The atmosphere will cause fluoride pollution. Fluoride can enter the human body through the respiratory tract, digestive tract and skin, and has toxic effects on the central nervous system and myocardium. Low-concentration fluorine pollution will cause brittle calcification of teeth and bones. "(GB25464-2010) stipulates that the discharge standard of fluoride must be lower than 5.0mg / m 3 Therefore, using fluoride as a low-temperature sintering aid for magnesia ceramics will inevitably increase the emission of gaseous fluoride and increase the burden of environmental protection investment; in addition, fluoride ions in the residual solid-solution fluoride in ceramics exist in the form of replacing oxygen ions, resulting in crystal The chemical stability of the intergranular bonding is reduced, and it is difficult to resist the long-term erosion of the flux in the magnesium melt

Chinese patent literature CN104496492B (a composite magnesium-carbon refractory crucible and its preparation method) and other disclosed ceramic foam filter preparation slurry adopts silica sol etc. 2 The presence of components makes it easy to react with magnesium and its alloy melts according to formula (4), which also reduces the chemical stability of ceramics

Although the crucible formed by isostatic pressing has the advantages of high density and high yield, and the crucible body is not easily deformed during the sintering process, it is also found that the crucible formed by isostatic pressing has the advantages of high cost, low efficiency, poor thermal stability, rapid heating and During the cooling process, the crucible is prone to cracking and peeling, and the service life is short

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