FIELD OF INVENTION
The invention relates to a system for quick quenching and release of composite materials for producing composite grains, such as alumina-zirconia, with higher performance in abrasive applications.
BACKGROUND
Alumina-Zirconia composite (AZ) grains with near eutectic composition of -42% zirconia by weight and rest alumina produced by fusion of the constituents is known for various applications like abrasives, refractories and metal matrix composites. It is also known that it is critical to quench the fused material below its melting point within seconds to freeze the microstructure and retain a lamellar structure. These fine structures exhibit improvement in performance if the zirconia phase is stabilized in tetragonal form with certain additives like yttria, magnesia, calcia etc., Several researchers have reported the application of the AZ grains in coated and/or bonded abrasives.
The melting point of alumina and zirconia are 2072°C and 2715°C respectively. The eutectic point lies at 42% zirconia with a melting point of 1920°C. In general, the raw materials viz., calcined alumina, monoclinic zirconia, and other additives, if any, are mixed and fused in an electric arc furnace. During the fusion process, the raw materials melt, mix in the liquid phase and form a homogeneous mixture. While quenching this melt and making abrasives, the typical defect in the

grains that hamper the performance is its porosity. Porous grains tend to have lower mechanical strength and high friability.
US 9212097 describes the use of fused grits with composition zirconia:38 to 46%, Silica 0.2 to 0.6%, yttria 0.45 to 0.7%, titania 1 to 2% and rest alumina in grinding wheels and coated abrasive papers. Special emphasis is made on the ratio of Y203/Si02 as between 1.1 and 1.3. The preferred amount of tetragonal content mentioned in this prior art is 70 to 85% with respect to the mass of zirconia.
US 9005323 elaborates about the use of specific amounts of titania and yttria as additives in the AZ abrasive grits with zirconia phase optimized such that it has >70% of high temperature cubic and tetragonal phase, cumulative. The synergistic effect of yttria and titania was highlighted as the key reason for the improved performance of the grains.
In the production of alumina-zirconia (AZ40) composites with eutectic composition, it is known in the prior art that the quenching of the melt is to be done as quickly as possible to maintain the eutectic structure. Slower cooling leads to growth of the crystal size and increase in the lamellar spacing between the alumina or zirconia phase. In extreme cases where the cooling is slower, segregation of the phases can happen leading to alumina rich and/or zirconia rich phases.
Different patents have addressed these issues using various techniques. For example, in US 4059417, the fused mass was poured into a molten chloride of Na, Ca, Ba, or Mg or mixtures. In this method,

there is a possibility of contamination of the AZ40 grains through the cooling media. Further, the cooling process is cumbersome and slower, especially from aboutl400°C. This results in extensive grain growth and the crystallite size thus achieved could be about 50 microns or less.
US 4415510 explains the process of cooling the molten mass by casting it over carbon steel balls. This methods whilst allowing for cooling the material quickly and without contamination from alkali or other materials, it poses challenges in terms of uniformity of the cooling. Since the different portions of the fused mass is cooled at different rates, it leads to anisotropy in the mechanical properties throughout the grains. Further separating the steel balls from the cooled mass would be challenging.
US 4194887 describes an alternate method to cool the mass by lifting the fused material on steel bottle like structures and cooling them rapidly. This process cannot be applied in atmospheric conditions where oxygen will be available in plenty. The properties obtained in these grains are inferior owing to the enhanced oxidation of the titania species; titanium sub oxides impart higher toughness to the AZ40 grains whilst fully oxidized titania presence is not helpful.
US 3993119 describes a different approach to this problem by the introduction of the continuously cycled moulds that can cool the fused mass as thin plates between cast iron plates. This method provides the ability to retrieve the AZ40 composite with homogeneous properties in a scalable process. Further, there is no further processes involved to separate the alkali or steel balls as mentioned in the prior arts. Whilst

this gives good quenching rates, the moulds are too heavy to be used in the manufacturing and hence needs high power drives to cyclically use the moulds. The time that is needed for quenching is difficult to be controlled in this case and hence thicker lamellar structures can be formed in this case.
US 5478510 describes an improvised version of the book mould where the moulds are parallely and vertically maintained in the same level during the poring, discharge and material release stages. This process considerably reduces the power pack requirements to drive the system. However, control of the quenching time from mould filling to release time in this case would be above 2 minutes and hence it is not possible to release the material immediately after it has saturated in terms of heat transfer with the cast iron moulds.
One of the major disadvantage in the patents US 3993119 and US5478510 are the frequent damage to the moulds due to quick thermal cycles and erosion due to high temperature fluid coming in contact with the mould surfaces repeatedly. Further, it is not possible to reduce the retention time within the mould (defined as the time the fused mass is retained in the mould before being discharged to a collector) within the range of few seconds.
SUMMARY OF THE INVENTION
The present disclosure provides a system for quick quenching and release of composite materials for producing composite grains, such as

AZ40. The various embodiments in this disclosure are directed to achieve quick quenching and cooling of the AZ40 fused mass, or the like, to produce crude/quenched AZ40 composites with controlled crystallite and lamellar spacing.
The disclosure relates to a system including a mould assembly, specifically a chill casting mould and a quenching arrangement to maintain the eutectic structure of grains. The property of the grains produced depend on the raw materials, fusion parameters, chill casting mould design, process for quenching the molten mass and the crushing methodology used for making powders. The chemical composition and the microstructure influence the grain properties. Fine grains with eutectic structure as the raw material and the effect of using such material is disclosed herewith. Varied compositions are shown to have comparable performance using this chill casting system.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure la shows the system including the mould assembly according to the invention,
Figure lb shows a partial view of the complete mould assembly according to this invention,
Figure 2 shows the mechanism for mould splitting and filling positions according to the invention,
Figure 3 shows the mould assembly in the opened position for release of quenched crude,
Figure 4 shows the intermediate distributer channel according to an embodiment of the invention.

DETAILED DESCRIPTION:
Figure la shows a system for quick quenching and release of composite materials for producing composite grains. The system includes a furnace (1) from which molten material is poured into a mould assembly (2). The design of the mould assembly (2) is such that the mould blocks (2a) are shaped with grooves of about 5-10 mm. Figure lb shows a partial view of these mould blocks (2a). These mould blocks (2a) are preferably made of cast iron. The complete mould assembly (2) with about 10 to 75 rectangular mould blocks (2a) is rested on rails with a wheel arrangement (4, 5) so that the mould assembly (2) can traverse on the horizontal axis.
Once the mix is fused and enough mixing is ensured, the molten mass may be poured by tilting the furnace (1) to flow the material through the spout and fill the moulds (2a). During the filling stage the mould assembly (2) gradually transverses so that the moulds (2a) are filled sequentially.
In a preferred embodiment, to facilitate release of the solidified material, the spacing between the mould blocks (2a) is increased by pulling the moulds apart with a slotted link system (10) as shown in Error! Reference source not found.. The slotted link system (10) is provided to link adjacent mould blocks (2a) such that each mould block is linked with its adjacent mould block(s). This system (10) helps to maintain the gap (11) between moulds during opening. Also the link system (10) is configured to simultaneously open the moulds (2a) one by

one after pouring. This ensures stripping of solidified products in correct time interval. The arrangement according to this embodiment facilitates the release of material without lifting the moulds independently which enables shorter retention times up to 10 seconds.
Upon activating the slotted link system (10) the mould blocks (2a) of the mould assembly (2) are opened to release the quenched crude, and such released/open position of the mould assembly is shown in Figure 3. Once the pour is completed the solidified material/quenched crude (8) that is released is collected in bins (not shown) located below the mould assembly (2) by gravity.
A hydraulic pulling system (3, 7) enables the full closing of moulds (2a) without any leakage of molten material. The hydraulic pulling system (3, 7) is mounted at one end. This will ensure closing and opening of the moulds (2a) after fixed time interval, thereby ensuring quality of product. A multispeed motion car (6) ensures that the mould assembly (2) can be moved during pouring of the molten material from the furnace (1) according to pre-determined speed. This will ensure right filling of molten material inside mould blocks (2a) without any spillage.
To avoid the solidified material from falling off from the moulds (2a) when it splits, a fast movement option is provided in hydraulic system (3, 7) to move moulds (2a) thereby creating a knocking effect. This is used to clean mould recess for any solidified material trapping, after stripping, without the need for hammering.

In yet another embodiment, two hydraulic pulling systems are provided, one at each end of the assembly so that all the moulds can be filled and then released.
In a further embodiment, to improve the heat transfer kinetics, the moulds (2a) are modified as jacketed moulds which can be cooled continuously by water or other suitable heat transfer fluids flow inside the moulds and thereby facilitate faster quenching.
Deterioration of the mould surfaces due to contact with the fused material could occur frequently. This problem is aggravated when the pour volume is not controlled which increases the chances of spillage and material wastage. Due to the uneven filling pattern in the moulds, the dimensional changes in the mould could be irregular, leading to some pockets of larger thickness. The molten mass that is cooled in the thicker forms typically have slower quenching rates and hence poor mechanical properties. To overcome the mould deterioration and ensure uniform cooling of the material, it is imperative to control the flow of the fused mass into the moulds. According to an embodiment of the invention, this controlled flow of the fused mass into the moulds is achieved by the use of intermediate distribution channels (9) as illustrated in Figure 4 (also Fig. la, lb). Such channels (9) can uniformly fill the moulds (2a) with the fused mass. Figure 4 shows the typical designs of the intermediate distribution channels (9) that can be used for the manufacturing of AZ40 composites, which is only illustrative and not meant to be limiting to these designs.

Typically, the intermediate distributor channels (9) is made of cast iron or graphite. The dimensions of the openings and the shape maybe varied to control the flow of the mass in the desired proportion. For example, it is possible to reduce the mould filling rate in this case without changing the tilting angle.
The uniform distribution and use of mould with releasing mechanism as described above has the following advantages: (i) the mould filling is complete, (ii) reduction in the spillage and scrap formation, (iii) uniform cooling pattern in the entire mould.
This, combined with the ability to quickly release the mould, provides better properties. The incorporation of an intermediate distributor channel (9) between the tilt furnace (1) and the moulds (2) resulted in a uniform distribution of the molten melt, at least 6 % reduction in the scrap being generated from oxidation of the molten melt, and an improved recovery of the crude from 88% to 94%.
The system enables quick quenching followed by quick release in air of the solidified material to facilitate further quenching thereby improving the property of the AZ40 grains effecting finer lamellar structure.

WE CLAIM
1. A system a system for quick quenching and release of composite
materials, said system including a furnace (1) from which molten
material is poured into a mould assembly (2), said mould assembly is
capable of traversing in a horizontal axis and includes mould blocks (2a)
with grooves,
characterized in that a slotted link mechanism (10) is provided to link adjacent mould blocks (2a), wherein spacing between the mould blocks (2a) is increased by pulling the moulds apart with said slotted link system (10) to facilitate quick release of material upon solidification.
2. The system according to claim 1, wherein the slotted link
mechanism (10) is configured to simultaneously open the moulds (2a)
after pouring.
3. The system according to claim 1, wherein at least one hydraulic
pulling system (3, 7) is provided to enable full closing of moulds (2a) to
prevent leakage of molten material and to pull the moulds apart with
said slotted link system (10).
4. The system according to claim 3, wherein a fast movement option is provided in the hydraulic system (3, 7) to create a knocking effect.
5. The system according to claim 3, wherein two hydraulic pulling systems are provided, one at each end of the mould assembly (2).

6. The system according to claim 1, wherein the moulds (2a) are jacketed moulds capable of being water-cooled.
7. The system according to claim 1, wherein said system includes a multispeed motion car (6) for moving the mould assembly (2) during pouring of material from the furnace (1) according to a pre-determined speed.
8. The system according to claim 1, wherein intermediate distribution
channels (9) are provided between the furnace (1) and the mould
assembly (2) for uniform filling of the moulds (2a).