Agitating – Jet or spray impinging free-falling stream
Patent
1996-09-04
1998-06-30
Soohoo, Tony G.
Agitating
Jet or spray impinging free-falling stream
366127, 266234, 266233, 75 1016, 420590, B01F 1502, C21C 700, C22C 100, C21B 1500
Patent
active
057723206
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and apparatus for mixing a metal matrix composite and in particular, but not exclusively, relates to a method and apparatus for mixing a metal matrix composite in either a liquid or semi-solid state. The method and apparatus may also find use in the formation of metal matrix composites which are produced by controlled cooling and stirring to stimulate precipitation of intermetallic compounds or other reinforcing phases which are then created in-situ.
A metal matrix composite as herein defined is a material which comprises a continuous metallic matrix phase throughout which there is deliberately dispersed during processing reinforcing particles, whiskers or fibres to achieve properties unobtainable by manipulation of the parent material alone. The reinforcing phases can be metallic, ceramic or intermetallic and are generally harder and stiffer than the continuous metallic phase. As a result the metal matrix composite typically exhibits better wear resistance and a higher specific stiffness than the unreinforced alloy.
In the past, metal matrix composites have been produced by mechanically mixing ceramic reinforcement materials such as particulate, whiskers or short fibres with a liquid metal contained in a suitable vessel. This mixing has been carried out using a variety of paddles which stir the liquid metal creating a vortex into which the reinforcement material is introduced. Once the reinforcement material has been introduced, it must then be prevented from segregating from the parent metal by settling or flotation, by means of further mixing. In the past this also has been achieved by means of mechanical mixing.
The mechanical mixing of metals, whether they be in the liquid state or in a semi-solid state at a temperature between the liquidus and solidus of the base alloy, gives rise to a number of disadvantages. Typically, stirring devices not only suffer from mechanical breakdown or errosion but also occupy regions of the melt surface which limits access to the melt for dispensing or other applications. In addition, mechanically stirred liquid metal systems are typically unable to eliminate stagnant zones or stable vortices within the mixing vessel so that in these regions centrifugal or gravitational forces tend to separate the reinforcement materials from the liquid alloy. The scaling up of laboratory mixing systems has also proved to be quite difficult for mechanical systems since larger systems typically require several mixers to operate simultaneously and so require constant supervision and/or maintenance if they are to achieve the desired effect. Furthermore, it goes without saying that mechanical impellers are susceptible to breakage during melt down of the solid charge.
The present invention is intended to go some way towards addressing the above-mentioned problems associated with the prior art.
According to a first aspect of the present invention there is provided an apparatus for mixing solid particulates in a molten metal matrix to form a metal matrix composite, the apparatus comprising a refractory vessel for containing the metal matrix in a molten state and defining an inlet and an outlet; refractory conduit means in communication with both the inlet and outlet so as to define with the vessel a closed loop flow path, the inlet and outlet being so spaced as to encourage mixing within the vessel; and pump means disposed within the flow path and operative to circulate the metal matrix and particulates around the closed loop path so as to effect a mixing thereof. This apparatus has the advantage of reducing the dependence on mechanical stirring devices as in the majority of cases the liquid, or semi-solid, metal constitutes the only moving component within the flow path. Furthermore, provided the metal is forced to circulate in such a way as to prevent settling under gravity and avoids the formation of stable vortices, it can be readily scaled to suit a desired holding capacity or composite throughput.
Advantageously, the pump means may comprise an el
REFERENCES:
patent: 1771918 (1930-07-01), Fry
patent: 2655550 (1953-10-01), Zvanut
patent: 3490896 (1970-01-01), Steinke
patent: 3591698 (1971-07-01), Howard et al.
patent: 3987840 (1976-10-01), Birat
patent: 4007921 (1977-02-01), Zingg
patent: 4572673 (1986-02-01), Porter et al.
patent: 4589637 (1986-05-01), Bamji et al.
patent: 4704162 (1987-11-01), Bamji et al.
patent: 5322417 (1994-06-01), Ottinger et al.
EA Technology Limited
Soohoo Tony G.
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