MX2011002943A - Method of improving quality of quartz foundry sand. - Google Patents

Abstract

The invention relates to the art of a sand having characteristics making the sand useful in producing molds for casting of metal parts and, more particularly, to a method of improving the quality of a quartz sand having natural characteristics making the sand a "foundry sand.' The invention is a method of improving a naturally occurring quartz foundry sand.

Description

METHOD TO IMPROVE THE QUALITY OF FOUNDATION SAND IN QUARTZ FIELD OF THE INVENTION The invention relates to a sand having characteristics that make the sand useful in the production of molds for casting metal parts and, more particularly, to a method for improving the quality of a quartz sand having natural characteristics that they make the sand a "foundry sand". The invention is a method for improving a natural quartz casting sand.

BACKGROUND OF THE INVENTION In the casting of metal parts, a mold is formed by means of a mixture of a casting sand and a binder so that the mold defines the desired shape of the hard part resulting from a molten metal poured into the mold and solidified. These molds are made from a variety of granular materials; however, there are only a few areas in the world that have high-grade natural quartz castings. That quartz sand has necessary characteristics for its sufficient and cheap use as a foundry sand and is used directly to produce a casting mold. The quartz casting sand is substantially less expensive than the alternative chromite and zirconium. The lowest cost of casting sand. Natural quartz in several places in the world results in the ability to make a sand mold for metal casting at low cost; however, since those locations are not necessarily adjacent to the smelting facilities, the low cost advantage of high quality natural quartz sand is mitigated by the cost of transporting the sand to the end-use site. As a result, some of the quartz foundry sand located closer to the foundry industry is used commercially, although it does not have optimum characteristics for the process of producing a mold. This more easily accessible natural quartz casting sand has no physical characteristics that allow it to be used primarily to form the external structure or armor of a sand mold. This portion of the mold usually employs an inorganic binder. In castings having a central opening, it is necessary to use a core also formed by a casting sand; however, the core of the mold has more demanding properties and is usually formed from a casting sand different from that of quartz which is held together by an organic binder, such as a phenolic resin or furan resin. In this way, the core of a mold is more expensive to produce than the outer shell of the mold. In short, a foundry that want to use quartz sand faces the dilemma of using expensive quartz sand from limited areas of the world or lower quartz casting sand from nearest veins. Although those local foundry sands are less advantageous in the casting process. In addition, this lower quality quartz casting sand from closer sources is not easily useful for producing the internal core of a mold for the casting process. Accordingly, the background of the present invention is the availability of high quality quartz casting sand from remote areas or a more available but lower quality casting sand. This limiting property of the local, lower quartz smelting sand makes that sand generally unacceptable to produce the core of a mold. As a result, cheap but more readily available quartz casting sand was used primarily for the external shell of a mold, but not for a core of a casting mold. The physical limitations of that local smelting sand, even when used for the framework of a mold, increased the permeability in the mold and had a low tensile strength, thus increasing the percentage of rejects in the casting process.

Consequently, improvements in the quality of locally available silica smelting sand are necessary.

SUMMARY OF THE INVENTION The present invention relates to a method for producing an improved local smelting sand which has similar characteristics to expensive quartz casting sand. Using the invention, the local casting sand of lower quality can be used for the mold framework, but more importantly, it can be used in the core of a sand casting mold. This new method comprises providing a quartz casting sand of lesser quality as a feedstock. The melting sand of the feed material is 1 commercial casting sand with a Grain Finish Number (GFN) in the range of 40-70 and has particles with a roundness greater than 0.40 with improved tensile strength.

Broadly, the invention involves a method for producing higher grade casting sand which includes the steps of providing an existing casting sand and processing the existing casting sand to increase the obtainable tensile strength.

In the process of the invention, the initial material is natural quartz casting sand with a given roundness level, and certain natural surface contaminants. By this invention, the extracted foundry sand is modified so that it is better to be used as chemically agglutinated core sand. The extracted sand is first washed to remove the bonded and graded clay to approximately the size range required for a final core sand.

The foundry sand is subjected to a special mechanical process where the particles are subjected to abrasion by particle-to-particle interaction, but more importantly, they are struck with a metal member at a relatively high speed. The particle-to-particle interaction removes minerals that adversely affect the resins while the collision of particles with the metal members tends to increase the roundness.

In the preferred embodiment, a rapidly moving blade moves through a mass of semi-wet particles which moves in the opposite direction. This is high intensity purification (HIS). After the sand has been processed for the required period of time, it is then taken to another washing step to remove fine particles and materials generated by the attrition process. The sand is then dried and sieved to a specification, the size of the final product for a chemically bonded core sand.

The removal of minerals from the surface of the natural foundry sand improves the sand to make it a better or improved quartz casting sand for be used in the nucleus. The increase in tensile strength obtainable improves the quartz casting sand so that it has a higher quality.

The invention is a method that produces a satisfactory melting sand of common silica sand using a highly aggressive mechanical attrition device for processing the feedstock in a semi-dry state. Semi-dry is a moisture content in the general range of 5-20 percent. This device intensifies the abrasion between the particles and the semi-dry mass, so that the small material product of the abrasion of the regular surface of the particles can be separated by a washing process. The washing of the processed mass removes the fines to improve the quality of the final product, the final product which has been converted from a particle of common silica sand to a particle having an improved sphericity and roundness and an increase in the resistance to traction obtainable. This novel process that converts a common silica sand into a high quality casting sand employs an aggressive mechanical attrition device operated at high speed. In the preferred embodiment, the attrition device is an inclined rotating mixing container that tumbles a silica sand feedstock while forcing the feedstock into a path of a rotor tool driven in the direction of rotation opposite to that of the mixing tray or container. This device includes a detector that removes material from the; Cylindrical inner wall of the container and deflects the particles towards the path of the high speed rotor. That; Mechanical action provides abrasion and intensive homogenization of the feed material particles. The rotor includes outwardly extending blender blades which cause the individual particles to be mechanically tumbled by the container to become 'rounder'. The lower blender blades prevent accumulation in the lower wall of the tilted container, when it rotates. Adjacent to the lower wall of the container, the highly compressed particles are tumbled; and forced against each other by the weight of the material in the container or rotating tray.

According to the present invention, there is provided a method for producing a high-grade silica smelting sand comprising providing an existing silica sand useful as foundry sand, and feedstock, subjecting the feed material to aggressive mechanical attrition. using blades that pass through the feed material until the feed material is converted into a high quality casting sand with an improved obtainable tensile strength when used, a foundry sand and graded sand. high quality casting the desired GFN. Water is added to the feed material before the aggressive mechanical attrition to create a semi-dry mass for the attrition operation. The amount of water, according to one aspect of the present invention, creates a dough where the water content is in the range of 5-20% by weight of the dough. The existing foundry sand is a silica sand that has a roundness of more than 0.40.

According to the preferred embodiment of the invention, the existing foundry sand is a natural silica sand graded to give a given GFN and the aggressive mechanical attrition is effected during a process time of less than 10 minutes and preferably about 5 minutes . The aggressive mechanical attrition is carried out in a rotating container and the blades are whisk blades that rotate rapidly in the rotating container. The blades are rotated in a first direction and the container is rotated in a second direction opposite the first direction with the container being inclined and the blades and the container are rotated about parallel axes.

According to another characteristic of the invention, the particles having a grain size of less than one size in the range of 50-80 microns are removed from the high quality casting sand.

According to another aspect of the present invention there is provided a method for producing a high quality silica melting sand of a silica sand feedstock having a roundness of at least 0.40. This method comprises loading the feedstock into a rotating container to create a feedstock to which water is added so that the dough has a moisture content in the range of 5-20%. Then the semi-dry standard mass is subjected to aggressive mechanical attrition by rapidly moving the blades through the feed mass and continuing the aggressive mechanical attrition for a time to form a high quality casting sand. In the preferred embodiment, the processed foundry sand has a sphericity greater than 0.50 and a roundness of more than 0.40. The process time is less than 10 minutes and preferably about 5 minutes and the particles having a grain size of less than SOSO microns are removed from the sand to create the final product .: In summary, the present invention relates to a method for converting a natural sand capable of being used in foundry into a high quality casting sand where the impurities around the particles of the foundry sand are removed and the tensile strength obtainable using the sand in a mold, mainly the core of a mold, it increases. The details in the preferred embodiment for carrying out the invention are set forth in this application and are defined by the claims.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a cross-sectional view of a portion of molten or molded metal resulting from a casting operation employing a mold having the core of the foundry sand of Figure 2 and the casting sand of the outer shell of the Figure 3; Figure 4 is a block diagram illustrating the process cycle of a representative casting operation or casting system employing a core as shown in Figure 2 and a coating as shown in Figure 3; Figure 5 is a block diagram illustrating a common process for reclaiming the foundry sand used in operation d. cast iron illustrated in Figure 4; Figure 6 is a reproduction of a Krumbein / Sloss diagram showing the roundness and sphericity interval used in determining the characteristics of a foundry sand; Figure 7 is a block diagram describing the method for producing high quality casting sand from according to the present invention; Figure 8A is a block diagram describing the use of the method described in Figure 7; Figure 8B is a block diagram of a method similar to the method of Figure 8A that describes a slightly modified version of the novel discovery that constitutes the invention, as described in Figure 7. '| Figures 8C-8D are tables comparing foundry sand produced disagreement with the method described in Figure 7 with a high quality casting sand located in a remote area of the world.

Figure 8E is a table showing the extent to which the invention changes the contamination of the natural feedstock used in the novel method; Figure 9 is a schematic representation of the system used in the practice of the method described in Figure 7; Figures 10 and 11 are cross-sectional views of the preferred device for aggressive mechanical attrition of a silica sand feedstock in the preferred system of Figure 9 and the method of Figure 7; Figure 12 is a cross-sectional view taken, generally, along Figures 12-12 of Figure 10; Figure 13 is a schematic side view illustrating the lower portion of the device for aggressive mechanical attrition used in the preferred system of Figure 9 and the method of! Figure 7; Figures 13A-13C are schematic representations that explain certain aspects of the method and system used in the present invention which tend to increase the roundness of the individual particles of a silica sand feed; Figure 14 is a schematic representation of the inclined containers used in the method and systems of the present invention illustrating the compacting action on the semi-dry mass of the feedstock produced by the filling of the container inclined to its capacity, which is preferably greater than about 70% by volume; Figure 14A is a partial view taken, generally, along the line 14A-14A of Figure 14 and schematically illustrating the tumbling action on the semi-dry mass caused by the tilting and rotation of the container, drumming action which improves the operation of the aggressive mechanical attrition device shown in Figures 10-12; Figure 15 is a side elevational view illustrating the movement of particles caused by the operation of the aggressive mechanical attrition device used in the practice of the preferred embodiment of the present invention; Y Figure 16 is a top view schematically illustrating the movement of the particles in the device shown in Figures 10-12.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the Figures where what is shown is for purposes of describing the invention and illustrating the preferred embodiments of the invention and not for the purpose of limiting the invention, Figures 1-3 schematically illustrate casting or metal casting technology. wherein the present invention is a constituent component that is to say that the invention is in the specific art of providing foundry sand for use by the metal smelting industry, not the metal smelting industry itself. In the metal casting industry a molten metal part, such as the schematic part P, is formed in a casting operation and includes an outer body 2 and an inner core 4 created by the core C formed of foundry sand and a binder, usually an organic binder. The core has the shape of the hole 4. According to the practice of standard casting, the core C is located inside the cladding S, also produced by foundry sand and a binder, usually an inorganic binder. The internal profile 6 of cladding C is coupled to the external profile of the part P. The mold M for the part P is contained in an outer casing or frame B, so that when the core C is located in the cladding S, the metal melt is poured into the mold M to conform to the shape of the part P. After solidification of the part, the mold M is separated into halves A, B and the part P is removed. Due to the different physical dynamics experienced by the inner core C and the outer cladding S, the foundry sand to produce those two components has different physical demands. The core C must also escape the gases generated from the inner part P. Consequently, the sand must have a high level of permeability and a high resistance to traction. The sand must be of high quality and the binder for the high-quality casting sand of the core is usually organic. The coating S is less demanding and requires a lower quality of foundry sand and usually includes an inorganic binder. The physical properties of the sand and the core and the coating are different. Mainly, the lining requires extremely high quality casting sand, where the liner can use a lower quality, common casting sand, of the generally available type of sand extracted near the casting operation. Because of this In fact, most smelting operations throughout the world employ a different mineral for the foundry sand used in the core. For economic reasons, it is common practice to use a lower grade silica sand for the coating! S and more expensive sand for the C core In the foundry industry, a preferred process for producing cores and coatings of a casting mold is to use silica sand for both components. To achieve the goal of using silica sand for both mold components, a high quality silica sand is compared! a company of the technique of sand casting. That; High quality sand is available only in limited places in the world and is very expensive to be transported to remote casting sites. When the high quality silica smelting sand is obtained, locally, at a reasonable cost or from a remote area at an extremely high cost, the FS smelting system of the Figure 4 is employed in a general manner. In this system, the silica sand > High quality obtained from a supplier of foundry sand and in its onboard state ("new sand") is used with organic binders to form the core. Due to the lower demands of the coating, a small amount of high quality silica sand ("new sand") is combined with "reclaimed" silica sand to be formed in the S coating using an inorganic binder, such as clay. After the casting operation is carried out by the FS system and part P is removed, the used casting sand of the cladding and the core are mixed together and recovered by a standard "recovery device" schematically illustrated in Figure 4. The "reclaimed" sand and the "new" high quality sand are used for the coating. To recover the silica sand from the liner and the core, the industry often uses a recovery system, such as the RS recovery system, schematically illustrated in Figure 5. In the normal recovery system, the used core sand and the coating is crushed. This particulate smelting sand is subjected to attrition, which removes the binder by abrading the particles together. This abrasion action removes fine particles and some of the binder, mainly the inorganic binder, from the clay. The foundry sand used is then subjected to a heating operation to remove the organic binders from the foundry sand as "fines". After removing the organic and inorganic binders, the used foundry sand is again subjected to attrition until the small particles can be removed as "fines" to produce a reclaimed silica sand, which sand is generally free of residual binders. This sand "reclaimed or recovered" is added to "new" high quality sand as shown in system F of Figure 4 to produce the S coating of the M mold for later use in a casting or casting operation. Those procedures depicted in Figures 4 and 5 are used in smelting operations when high quality silica sand is available either locally or at a high cost to a smelter sand supplier. The present invention relates to a situation where the smelting company does not want or can not economically pay for the cost of high quality silica smelting sand and when that high quality silica smelting sand is not locally available. In that situation, the smelter uses sand for the core that is different from the mold casting sand, which is often low quality silica sand. Alternative smelting sands are used in the core, while cheap smelting sand is used in the siding at all expense and difficulty in recovery associated with that smelting operation. The present invention solves that particular problem and employs method 10 of Figure 7 and system 200 of Figure 9 to produce a high quality silica sand cast from low silica sand: natural quality, locally available and / or cheap In this presentation of the general background, the term "quality" is used to define the type of sand of casting. The quality of the sand is related to the shape as defined by the roundness of the particles and the tensile strength, obtained when the sand is used. The roundness of any foundry sand is at least 0.4. A high quality sand has a tensile strength obtainable from more than 100 PSI (7.031 gF / cm2) to 15 minutes. The natural foundry sand processed by the invention has a drastically low tensile strength obtainable. The physical properties of the particles in a foundry sand are somewhat subjective, but are generally defined by the Krumbein / Sloss diagram of Figure 6. When those particular physical characteristics of the foundry sand particles are discussed in this application , reference can be made to the diagram of Figure 6 for the evaluation of the description.

Method 10 and System 200 (Figures 7 and 9) Silica smelting sand is relatively inexpensive and is received by a smelter in containers, such as bags, which contain simply extracted, natural silica sand having the characteristics required for use in the coating core or both. Those bags of sand are not processed, except for being extracted, washed and graduated. This procedure defines the supply of sand silica for use in the foundry industry. The technique of providing foundry sand to the foundry industry of the technique of the invention. As discussed, the available natural sand useful for foundry applications, known as "foundry sand", varies in quality defined by physical characteristics, such as roundness and sphericity. Although silica "foundry sand" is available throughout the world, high quality silica sand is obtainable only in certain places that require a high transportation cost and a high cost based on supply and demand. In this industry casting sand was provided, the inventors have developed a novel method. The discovery is a novel method to provide silica smelting sand to be; used by the foundry industry. This novel method is the method described in Figure 7. The system 200 for effecting this novel method is described in Figure 9. The fused silica sand of the type useful for a low quality silica smelting sand is extracted and supplied. to a place relatively close to the foundry. The silica melting sand is loaded into a hopper or supply 12 and then graded to the desired GFN number, as a number in the range of 40-70. This number is determined by the desired degree of foundry sand needed for casting. This graduation process is illustrated by a hydrodimensioner 14 which produces a feed material through line 18 at an aggressive attrition operation by blocks 20 where the sand is subjected to the action of moving knives of an aggressive mechanical attrition device of the type illustrated in FIGS. Figures 10 -12. In this way, the operation of the process 20 is carried out as a batch operation where the feed material! Silica sand entering the line 18 is converted to a semi-dry or wet mass of silica sand by the addition of water, indicated by the block or water supply 22. Preferably, the mass of the silica sand in step 20 has a moisture content in the range of 5-20% obtained by adding water. The operation of semi-dry batches 20 is carried out for the desired time controlled by the timer 50 to remove contaminants from the surface and increase the tensile strength obtainable, as well as slightly increase the roundness of the particles. The method 10 employs the device 202 of the system 200 of Figure 9. This device is an aggressive mechanical attrition device, referred to as a High Density Debug (HIS) device, as illustrated in Figures 10-12. The timer 50 is set at the desired process time which allows this aggressive attrition to increase the quality of the sand. In practice, the time is less than 10 minutes and preferably about 5 minutes. Accordingly, the feedstock is aggressively treated by the HIS device illustrated in Figures 10-12 for a short time to produce a casting sand having a high quality, essentially defined by the level of tensile strength obtainable. The silica sand, after being aggressively treated by the device 202 in operation 20, is passed by means of a transport or line 30 to a temporary storage silo 40. The temporary storage silo, the high melting sand quality is passed to the hydrodimensioner 60 by means of the conveyor or line 42 to remove smaller particles and generally record the semi-dry processed melting sand. The sand is then dried by a liquid bed dryer in the form of a fluid bed dryer and the cooler 70. Then the processed foundry sand is screened by the net 100 and bagged or otherwise prepared for distribution according to as indicated by block 80. As explained, the new method 10 performed by the system 200 shown in Figure 9 achieves a goal hitherto not achieved in the art of providing foundry sand for the foundry sample. The quality of the foundry sand is enhanced by an aggressive, rapid mechanical attrition of a low grade silica sand to be used as a casting by a casting device. high density depuration or HIS 202 shown in detail in Figures 10-12 and explained in the section discussing the "preferred embodiment".

The broad concept of method 10 is illustrated schematically by the simple block diagram identified by a process 120 in Figure 8A. This process, in the technique of providing casting sand, an existing furidation sand having a roundness and a sphericity for the foundry sand but with a tensile strength drastically obtainable less than 100 as measured for a time 15 minutes of sedimentation for: the mold is transported to the site where the method 100 is made. This site is relatively close to the smelter that uses the sand. This incoming smelter sand is a low quality silica smelting sand 122. That smelter sand of low quality is passed through block 124, which is method 10 of Figure 7. Method 100 produces a sand casting grade silica having a PSI of more than 90. The drastic increase in tensile strength obtainable is caused by the removal of contaminants from the surface and / or by a slight increase in the roundness imparted to the foundry sand incoming by the use of method 10.

Improve the quality of cheap foundry sand to duplicate scarce high quality casting sand face, is novel in the technique of production of foundry sand, especially the silica sand casting technique. A slight modification of the process 120 shown in Figure 8A is illustrated as the process 120A in Figure 8B. In this slight modification, the rounded quartz particles are screened and graded, as indicated by block 130. This silica sand is processed by method 10 and system 200 as indicated by block 132. The method 10 is modified by increasing the time of the timer 50 so that the roundness of the particles is increased to produce the desired roundness of a high quality silica smelting aroma. Subsequently, the improved, desired high quality silica melting sand is graded, as indicated by block 134, and has particles with a roundness greater than 0.6. This increase in roundness can be measured periodically to readjust the time for the process time required by the particular type of natural rounded quartz particles that are being supplied by method 100. In both of process 120 and process 120A, sand High quality cast iron has a high obtainable tensile strength, a roundness greater than 0.40. Process 120A can start with a wide range of silica particles.

The Incast 55 is foundry sand extracted in Canoitas, Mexico and is a sand of lower quality than some other foundry sands. This lower quality smelting sand is processed by the method 10 using the 200 system. The results of this processing are documented in the Tables of Figure 8C, 8D and 8E where the processed smelting sand is compared with the smelting sand of High quality Oregon 55 of the United States. The speed of the blades of the HIS device described in Figures 10-12 was 3117; RPM for a tangential speed of approximately 100 feet / second (30.48 meters / second). The drum or container of the HIS device was noted in the opposite direction at a speed of 35 RPM. The lot was approximately 250 kilograms. After a 5 minute process time, the lower grade silica smelting sand (Incast 55) was converted to a higher quality silica smelting sand having the physical characteristics in the center column of Figures 8C and 8D .

According to the tabulated in Figure 8C, the INCAST 55 of the material; incoming sifted feed has a GFN of 55.04 and a clay content of 0.23%. After processing by method 10 for 5 minutes, the GFN did not change and is comparable to the GFN of Oregon 55. In a similar way, the only effect on the clay is the reduction of the amount of clay in the foundry sand INCAST 55 processed Turning now to Figure 8D, the important characteristic of the tensile strength obtainable from the components of the mold is compared to the tensile strength obtainable from Oregon 55. A standard tensile strength measurement is normally 15 minutes. The lower quality silica sand, Incast 55 has a roundness of at least 0.40 and a sphericity of at least 0.5 to give a tensile strength at 15 minutes of 44 PSI (3.09 KgF / cm2). This is compared to a higher quality smelting sand, bregón 55, with a tensile strength of 93 PSI (6.53 KgF / cm2). When INCAST 55 is processed by system 200 performing method 10, the sand experiences an increase in tensile strength at 15 minutes at a value of 99 PSI (6.96 KgF / cm2). This indicates that the lower grade silica smelting sand has been converted into a high quality silica smelting sand comparable to the Oregon 55 extracted in a remote place in the Mexican smelter. This increase in tensile strength is a major advantage for foundry sand and illustrates the results obtained using a unique method and system of the present invention. Another feature of the present invention is the reduction of surface contamination. The mined INCAST 55 foundry sand has the surface contaminations exposed in the table in Figure 8E. After processing for 5 minutes, contaminations of the surface of the feedstock are reduced to the levels shown in the right column of Figure 8E. This same advantage has been obtained by increasing the size of the device 202 to process a batch of approximately 50 metric tons as well as a smaller batch of 250 kilograms.

In summary, the present invention converts a lower quality casting sand, Incast 55 extracted in Mexico into a casting sand of higher quality comparable to the Oregon 55 simply by processing the lower quality casting sand for 5 minutes using aggressive mechanical attrition. by the high density purification device (HIS 202). The tensile strength is obtained by increasing the characteristics of the INCAST 55 lower quality casting sand using the present invention. The smelter using the new foundry sand is near Mexico at the INCAST mine. In this way, the smelter can reduce its costs and still have the advantage of Oregon 55 cast iron sand.

PREFERRED MODALITY OF THE INVENTION The main objective of the present invention is to provide a method and system for converting sand of natural silica foundry, somewhat common, into sand of casting of high quality and reproduce sparse, expensive silica smelting sand.

According to another aspect of the present invention is the novel device in which aggressive mechanical attrition is effected by means of one or more mobile members passing through a mass of semi-dry particles moved in the opposite direction under compressive forces in a rotating container.

The invention involves the concept of producing an improved high-quality casting sand from a natural, somewhat common silica sand feed material with a different particle shape and size by an "abrasive attrition of the type" which it submits to aggressive abrasion the incoming smelting sand. The preferred modality processes the sand with "aggressively mechanical attrition". This general process is illustrated in Figure 7, where the incoming extracted casting sand is a particular feed material which is semi-dry. This feedstock is subjected to aggressive mechanical attrition by the device illustrated in Figures 10-12. Then the particles of aggressive aggressive attrition are introduced into a hydrodimensioner to remove fines and then dried before being sieved to the GFN of the a desired grade of sand 1 of casting. The aggressive mechanical attrition in the particles that collide with each other by the movement in a trajectory and driven by a moving member in an opposite direction. Aggressive mechanical attrition includes particle-to-particle collision, the collision of moving particles with a moving metal member through the mass of feed particles, as illustrated in Figures 13, 13A, 13B and 13C. The particles are driven in the trajectories shown in Figures 15 and 16.

The preferred system for practicing the present invention is illustrated schematically in Figure 9 which involves slight modifications of the method, shown in Figure 7. Figure 7 is presented solely for the purpose of showing a general method. In Figures 7 and 9, the feedstock is a natural quartz casting sand. The particle feed mass is loaded into the aggressive mechanical attrition device, which is schematically illustrated in Figures 10-12 for aggressive movement that changes the shape of the particle, as illustrated in Figures 13A, 13B, 13C. , 14'A, 15 and 16.

Figure 7 shows a preferred method 10 for converting common extracted silica melt sand into improved high quality casting sand by generally reproducing available silica melting sand in limited places. Method 10 involves transporting melted silica sand extracted with the minus 80% silica dioxide to the processing site as indicated by hopper 12. Natural sand is silica sand which includes silica in the form of particles having a hardness of more than 6.0 Mohs. From the hopper 12, the extracted casting sand which is directed to a processing operation 14 which involves a hydrodimensioner to convert the incoming extracted silica sand into a feedstock having a desired size for the size of the casting sand to be produced. The extracted sand is mechanically divided into individual particles. In this way, the feedstock has particles in the general range of more than 350 to the desired approximate amount determined by the desired grade or size of the resulting foundry sand. However, this feed material usually has individual silica particles of less than about 5-10 mesh. The sieves can remove larger or smaller particles if desired to give the desired grade size. The processing operation divides the particles into individual grains with the small particles removed, so that each particle can be processed into individual desired particles. For a high quality casting sand having an improved roundness characteristic and, more importantly, an increased obtainable tensile strength.

The feed material from the foundry sand is directed through the outlet 18 to the aggressive batching attrition operation where the aggressive attrition is effected using a moving blade to produce High Intensity Purification. This action is effected by a device shown better in Figures 10, 11 and 12. This device is operated at a rotating speed greater than the speed for which it was designed. The device performs the method of operation 20. In the aggressive attrition device used to effect high density purification (HIS), an operation 20, water is added by step 22 to produce semi-dry feed material. The processed material has approximately 5-20% by weight of water. This moisture content aids in the use of the device of Figures 10-12 to perform the aggressive mechanical attrition operation on the semi-dry feed material which had hitherto not been carried out on rock particles, such as silica particles. Operation 20 is a batch that continues for a "process time", which time is controlled to obtain the desired improvement in smelting sands so that the sand has characteristics such as that of the scarce, expensive silica smelting sand. The final product is then added to the mass of processed particles or the final product is taken through line 30 to a silo Temporary Storage 40. The appropriate mass or final product of particles is retained in the temporary storage silo 40 to allow its metered feeding through the line 42. The operation 20 is stopped by the timer 50 which adjusts to a desired type of processing obtained by experience. In practice, the fixed process time is less than about 10 minutes and preferably about 5 minutes. After the processing time has expired, the operation 20 discharges the mass of particles processed through line 30 to the temporary storage silo 40. The silo is necessary to convert the batch processing of the semi-dry feed material into a continuous operation for the i hydrodimensionadpr 60. The silo is an equilibrium chamber, as a process accumulator for successive batches of the I processed food material. After the fixed processing time, the final product of the aggressive mechanical attrition operation 20 is emptied through the line I 30 towards the temporary storage silo 40. At that time, the mass of final processed product is dosed from the temporary storage silo 40 to a hydrodimensioner 60 where the product is graduated and the small undesirable particles are removed, so that the larger round particles are dried and cooled in the dryer 70. This method produces a final product to be stored in trays or the silo 80. The final product can be subsequently graduated either before or after the tray or silo 80. However, according to the preferred embodiment, the final product of the dryer 70 is directed to a sieve network 100. The net 100 removes the large particles, and the small particles to deposit a selected grade of foundry sand in the receptacle 80 for shipment to the desired time. In the system 200 of Figure 9, the improved foundry sand is graded after being deposited in the silo 80 by the sieve network 110. The user determines the grade of the foundry sand. The smelting sand of the dryer 80 can be used to produce a variety of different graduated values of smelting sands according to what is required by the final consumer. The method 10 of Figure 7 and the system 200 of Figure 9 convert the extracted natural cast sand 1 from silica sand into an improved foundry sand.

The preferred method 10 produces a final product as the content of the hopper 90, or preferably, as a graded casting sand determined by the screening network 100. After the aggressive mechanical attrition operation 20 processes the incoming casting sand, the converted final product can be used as a sand Improved smelting which is probably high quality natural casting sand from limited areas of the world. Several iron smelting operations require i casting chains of different size; consequently, the final product is a graded casting sand. One aspect of the invention is therefore to grade the foundry sand by a screening network 100, or network 110 of the system 200.

In practice, the grade selected for the arena I The cast iron has a maximum particle size of just over 1.0 mm and a minimum size of about 0.5 mm. Thus, the foundry sand is a mass of particles which are very large so that they can exhibit high permeability when the foundry sand is in a core or mold as shown in Figures 2 and 3. The core or mold | is subjected to extreme temperatures (the temperature of steel or cast iron) in the range of more than 1500 ° C. In addition, those temperatures ensure that the organic binder is typically used. in the molds and cores (in the molding without baking) it volatilizes and the gases that it produces can escape from the core and the cavity of the mold without damaging the core or mold, that is to say, cause cracks or fissures in the mold before the solidification of iron or steel. Consequently, the high temperatures involved in iron / steel smelting create high pressures in the core and the mold, both directly and indirectly. The Desired casting sand should have a sufficiently high sphericity to overcome those problems.

Method 10 of Figure 7 is effected by system 200 of Figure 9, where the aggressive attrition operation of method 10 is schematically illustrated as device 202. This device is shown in detail in Figures 10, 11 and 12. According to the preferred embodiment of the system, the dryer 70 is a fluid bed dryer and cooler in which it does not have a final output product deposited in the silo or hopper 80 then sieved by the network 110.

According to the invention, the aggressive attrition device 202 is employed to perform the HIS operation 20 of the method 10. As shown in Figures 10-12, the abrasive attrition device 202 includes a supporting frame 300 on the floor 302 The frame has a lower portion 304 and a fixed upper arm, which extends 306. This support frame rotatably assembles the container 310 having a cylindrical wall 302 and a lower circular wall 314. The upper circular lip or edge 316 of the container 310 rotates in the circular groove 322 of the cover or fixed cover 320 mounted on the arm 306. The fixed cover 320 has an opening 324 with a nut 325 that allows the loading of the batch of the sand feed material FS in the container 310. The container is assembled from rotating manner on the bearing 330 which is inclined on the frame 300 so that the container 310 is rotatably mounted on the bearing 330 which is inclined on the frame 300 so that the container 310 is rotatably mounted around a first X axis inclined to the right as shown in Figures 10, 11 and 12. The container 310 is driven around the X axis by the mechanism 340 which includes the associated wheel 342 of the lever actuated with the container 310 and rotated by a motor 344 The first axis x is concentric with the bearing 330 and is orthogonal to the bearings, so that the fixed axis defines the rotation of the container 310. To pour the finished product FP from the container 310, there is a lower drain opening: 350 concentric with the x axis and closed by the door 352 rotating on the stump 354 supported by the fixed arm 308. The door 352 is opened and closed by the actuating cylinder 356. Within the cylinder 310 there is a rotor 400 supported by the axis 402 concentric with the second axis and which is parallel to the first axis x. In this way, both axes are inclined in a direction from the first axis x to the second axis, and, as shown in Figures 10 and 11. The bottom of the rotor 400 is slightly spaced above the bottom wall 314 and includes vertically spaced assemblies. of axially extending blender blades 410, 412 and 414, blades each of which are placed circumferentially deflected, as best shown in Figure 12. Each set or set of blender blades preferably includes at least two diametrically opposed blades. However, more than two blades can be used in a set or set in the practice of the present invention. The motor 420 drives the rotor 400 rotatably mounted on the arm '306 and with respect to the fixed cover 320. The inner wall or the adjacent bottom 314 is an arched deflector 340 fixed on the cover 320 by a support bar which is vertically extends 432 which has a very small profile, so as not to interfere with the feed material in the container 310 when the container is rotating around the x-axis. The detector 430 surrounds the lower blender blades of the game 410 as shown in Figure 12, so that the rotation of the container 310 in the direction of the arrow m causes the lower portion of the mass of the feed material to be directed towards the blender blades rotating opposite from the bottom set 410. At a small end 434 and scraper edges 436, the deflector 430 forces the particles adjacent to the bottom wall 314 toward the action diameter of the blades in the bottom set 410. The motor 420 drives the rotor 400 so that the external tip of the whipping blades exceeds approximately 20 meters per second and acts against the compressed feeding material in the lower portion of the rotating container 310. As shown in Figures 10 and 11, the knife sets are mounted on the cylindrical support member 402 with a more vertical end 404. This member is located in the lower portion of the container so that the container is filled with at least about 70% of the feed material FS .. The whipping blades act against the compressed feed material in the rotating container 310. In practice, the conveyor 330 empties the processed feed material FS into the container 310 through the open door 326 as shown in Figure 10. The container 310 is then rotated in the m direction while the whipping blades on the rotor 400 rotate in the opposite direction n. The baffle 430 keeps the particles in the bottom wall or bottom 314 moving more than the other particles. The particles are removed from the wall 314 and diverted towards the rotor blades of the set or set 410. After the processing time of the method 10 has expired, the rotation of the container and the rotor stop and the cylinder 356 empties the mass final processed or final product FP for its subsequent removal of small particles and preparation for drying for its graduation by network 100 of method 10. Inclining container 310 in the direction between the first x axis and the small axis, the feed material is compressed in container 310 by gravitational force. The weight of the feed material occupying at least 70% of the volume of the container 210 also improves compression in the lower part of the container that interacts with the rotating whip blades below the end 404 of the member 402. It has been found that the attrition device aggressive mechanics 202 can be operate at high speed and during a i time to effect the conversion of silica sand into smelting sand as explained here. This method is an aggressive attrition of the semi-dry feed material by High Intensity Purification.

Figure 13 illustrates the overall structure and function of the arched baffle 430. The baffle forces the particles of the feed material towards the lower setting area 410 of the illustrated whip blades as two axially extending blades 410a and 410b with external tips 410c and optional lower separators 410d. When the container 410 rotates in the m direction about the x axis, the rotor 400 rotates to an opposite direction m around the deviation axis y. The baffle 430 deflects the material adjacent the bottom wall 310 to the whirling blades that rotate in the opposite direction 410a, 410b. Actually, more than two blender blades can be used. Using an inclined rotating container, the feeding material is tumbled and forced towards the rotor path rotating in the opposite direction 400. Baffle 430 moves the material of inner surface 312 and deflects it towards the rotating rotor. The high speed operation of the rotor provides an intensive abrasive action, ie, HIS and also produces homogenization. The lower blender blades prevent the accumulation of material on the lower wall 314. This action is improved by increasing the rotational speed of the rotor blade so that it has a velocity at tip 410c in the defined circle1 by the action of this tip of at least 20 meters per second. The surface 416 of the support bar 432 removes the material from the inner surface of the wall of the rotating container 312. This description explains the general operation in the lowermost portion of the inclined or skewed rotating container.

Figures 13A, 13B and 13C illustrate schematically the action of abrasive formation of individual particles in the feed material to subject the surfaces of the particles to aggressive abrasion. The individual particles are moved in opposite directions as illustrated by the solid arrows (address m) and the open arrows (address n). When a whipping blade 500 moves in the direction n the particles of the feedstock are forced by the container 310 in the direction m. This action makes the side 502 of the blender blades 500 force some particles in direction n while the other particles are moving in m direction. The movement of particles in opposite directions of collision produces abrasion between the particles; mobile, indicated schematically by arrow 510 in Figure 13B. The movement of the particles in opposite directions by the interaction of the whipping blades adjacent to the lower portion of the rotating container 310 affects the aggressive mechanical attrition of the particles. When the whipping blade 500 moves in the ma direction through the particles moving in the n direction, the abrasive action between the particles as illustrated in Figure 13A and Figure 13B is augmented by the action illustrated schematically in Figure 13C. . In this Figure, the particles moving in the m direction are coupled to the edge 502 and move abrasively along the surface 504. In this way, there is an abrasive action represented by the arrow 512 between the surfaces of a mobile blender blade when it attaches to the surfaces of the particles. ' that move in the direction m. This interaction occurs in the lower portion of the sloping container where the particles are compressed together to improve the abrasive action between the moving particles and between the surfaces of the whipping blade and the particles moving in the opposite direction. Those abrasive actions by the device 202 tend to increase the: roundness of the casting sand particles that are being processed by the rotating container and the whirling blades rotating in the opposite direction.

The abrasive action is improved by loading the sloped container 310 with at least 70% feed material FS, as illustrated in Figure 14. Since the container is rotated at an inclined angle a, which angle is generally about 60. °, the particles in the lower portion of the container 310 below approximately the line L of Figure 4 are highly compressed. The line L represents, in general, the upper part of the support member of the blender blade 402 of the rotor 400. In this way, the particles within the area below the level L are subjected to the action of the whipping blades as well as to the the abrasive action of drumming caused by the rotation of the tumbling container 310! highly compressed particles adjacent to the lower portion of the container. This concept is illustrated schematically in Figure 14A. What is shown in Figures 13A, 13B, 13C, 14 and 14A is not at scale given that they are only used for the purposes of the theoretical abrasive action caused by the device 2, when the device operates on the drums fed particles loaded in their container. The; particles move along the paths indicated by the arrows in Figures 15 and 16 that illustrate; the side view and top view, respectively, of how the particles are moved by the rotating cylindrical container 310. These trajectories are intercepted by the blender blades as already described. This interaction of the driven movement of the particles produces the surface action of the particles and thus the increased roundness created in the silica sand particles processed by the device 202, which is the preferred mechanism for operation 200 in the method 10 of Figure 7. ' The invention converts particles from the natural cast sand feed material into the improved foundry sand method 10 shown in Figure 7 and the system 200 shown in Figure 9. The foundry sand is graded, preferably by the sieve network 100 before storage or after storage by network 110 in system 200.

The extracted silica melting sand can be washed and sized by any combination of operations to provide the "semi-dry" feed material with; the initial dimensioned particles desired. This procedure is used to convert the sand of cast iron extracted in a semi-dry particulate feed material. That feed material is loaded into the device that performs aggressive mechanical attrition to slightly change the shape of the particles and remove impurities. Washing and / or adding water creates a wet process. The incoming feed material is screened in number and then introduced as a particulate mass referred to as "feed material". This semi-dry FS feed material is used in the method of the present invention to convert the extracted foundry sand into a better quality casting sand with the desired degree and improved quality which reproduces the expensive and difficult high quality casting sand from to locate. According to what is indicated in this specification, the process defined in the claims has been carried out and can be duplicated using the information data presented here by any expert in the technique of silica sand processing. In addition, the process used to produce foundry sand can be used to produce improved foundry sand on natural, common foundry sand used as the feedstock.

It has been found that the invention can use various aggressive mechanical attrition devices to effect abrasive attrition, such as HIS to create acceptable casting sand having better characteristics. Attrition abrasive to increase the quality of sand casting sand of common silica smelting, the HIS process on silica for foundry sand, has not been previously practiced. Actually, this process on the semi-dry cast iron sand feed material is novel. Its application produces a foundry sand having an improved obtainable tensile strength in the inventive main discovery of the invention. The local foundry sand is converted to high quality cast iron sand.

As a feature of the novel process, water is added to the feed material, as shown in Figures 7 and. 9. A water quantity of 5-20 percent of the feed material and water mixture is used to convert the aggressive mechanical attrition process into an aggressive "semi-dry" attrition process at a dry process or process site. wet resuspension. The container 310 rotates in one direction with a moist feed material compressed by its own weight caused by filling the container to approximately 70-90%. The blender blades of the vertically spaced sets 410, 412 and 414 are rotated through the mass of compressed particles to bring the particles back into the compressed mass of approaching feedstock. The particle-to-particle interaction removes the sharp edges and It makes the individual particles more round. The blades also interact with particles to smooth the surface of the particles. The container is tilted as shown in Figures 10, 11 and 12 to force the particles towards a stronger frictional grinding action as shown in Figure 14A. To effect this aggressive attrition to affect the shape of the particles, the rotor blades are rotated at a linear tip speed of more than 20 meters per second, and preferably approximately 30 meters per second for the tip speed of the blade. At this very high speed, the blender blade cuts through the mass of compressed particles from the lower portion of the feed material loaded into the container or rotating holder to produce mechanical abrasive attrition in a form to improve the silica sand particles. in a very short time.

The novel procedure that HIS uses on a semi-dry silica sand improves the physical characteristics of the common natural foundry sand, so that the sand can compete with the high quality casting sand available only in a few places.

OVERVIEW OF THE INVENTION The present invention, according to the implemented in the embodiments explained above, it involves the aggressive mechanical attrition of a natural silica melting sand by the use of an attrition device, where the individual particles of the incoming smelting sand are subjected to the action of moving metal members quickly. In the preferred device, the implementation of this novel concept involves rapidly moving blender blades that pass through a semi-dry compact or wet mass of natural smelting sand. The action of the whipping blades that move through the compacted mass of particles produces an aggressive attrition of the sand particles of cast iron.

The present invention employs aggressive mechanical attrition, which is referred to as High Intensity Debug (HIS). This aggressive mechanical attrition can be effected effectively in a very short time, such as less than about 10 minutes; however, the time may be extended to increase the roundness of the particles that are being processed in an HIS device and remove contamination. The aggressive mechanical attrition and, in fact, the process carried out by the HIS device, has been used until now to process foundry sand. The advance of the present invention involves the use of that aggressive process to increase the quality of the low cost casting sand. The incoming feed material of this invention is a natural common foundry sand of the type which may be useful for the lining or reinforcement of a mold with inorganic binders but not generally useful for the core of a mold, where the demands for properties are more critical and where binders are normally used organic A satisfactory core of a casting mold requires higher quality silica sand, which is generally not available at low cost. Thus, in the core casting industry they often employ an alternative to expensive silica smelting sand; like Olivine, chromite or Zirconium.

The present invention improves the natural silica melting sand so that it can be used as a core sand by converting this sand into a sand with the high quality only obtainable in the silica sand extracted in several remote places throughout the world. Although the invention anticipates the use of an existing natural casting sand, other similar silica deposits with high roundness can be used as a feedstock to produce high quality casting sand of the type available for use in the core of a mold. metal casting. Accordingly, the incoming silica feedstock is a natural silica sand having characteristics normally associated with foundry sand, with roundness greater than about 0.40.

This type of rounded silica sand allows the novel aggressive mechanical attrition method of the present invention to improve! roundness The improvement of roundness as well as cleanliness; The sand produces a casting sand that has higher tensile strength with less binder.

As described above, by the use of the invention, the incoming feedstock is a locally available, low quality silica melting sand, which can be used as a foundry sand for the coating or frame of the mold. foundry. The higher quality casting sand produced by the present invention is processed so that it can satisfy the requirements of the core. Obviously, that high quality sand to be used in the core can also be used in the frame or coating of the mold with some advantage. Consequently, the novel processed casting sand is cheap, so that it can be used economically both in the core and in the cladding or reinforcement. When the high-quality casting sand produced by the present invention is used in the core, as shown in Figure 2, and a lower quality casting sand is used in the coating or shell, and as shown in the Figure 3 The recovery of the two different sands used is difficult. These recovery difficulties can be modified using the sand, produced by the method of Figure 7. The improved silica melting sand can be used in both components. See Figure 4. It is an economic advantage when both components of the operation. castings use a common high quality casting sand. In this way, the present invention useful for the core of the casting operation allows a better recovery process of the sand used after the casting has been completed.

When the silica sand processed by the present invention is a low quality casting sand or a sand which can be used for casting operations, the aggressive mechanical attrition process of the present invention is effected by the high purification device. intensity of Figures 10-12. The roundness of the incoming silica is increased. In this way, the silica sand produced; by the invention is a foundry sand having a drastically higher quality than the incoming silica sand. That processed foundry sand has a higher tensile strength using at the same time less binder. The invention converts the feed material into a semi-dry mass, adding water of approximately 5-20% of the dough. Accordingly, the aggressive mechanical attrition contemplated for use in the invention is effected on the semi-dry mass of silica sand.

The natural silica sand is first washed to remove any bonded deposited clay and is graded in approximately the size range required for the final silica sand to be used as a core melting sand. The particles of the feedstock are not only subject to interaction abrasion but, more importantly, collide with the metal member driven at a relatively high speed through the semi-dry, compressed mass of silica sand. The particle-to-particle interaction of the present invention removes minerals that adversely affect the amount and type of resin binder that must be used. The increase in roundness reduces the binder requirements and increases the tensile strength of the core using the improved, high quality casting sand produced by the present invention. In practice, aggressive mechanical attrition is a drastic high-energy action of the metal against particles that require less than about 10 minutes. However, if necessary, the processing time can be increased to obtain a larger desired roundness. One advantage is that a short process time is made possible by the dramatic mechanical action of the metal member, moving through a compressed mass of wet particles.

In the; preferred modality, mechanical attrition Aggressive by the high intensity purification device is effected for a time necessary to increase the roundness of the individual particles by at least about 0.10. More importantly, the tensile strength at 30 minutes of the melting sand constituting the finished product of the present invention is increased to a value greater than about 100 psi (7.0311 KgF / cm2). As another feature of the invention, the; particles in the 50-80 micron range are removed from the process sand melt feed material to increase the permeability of the resulting high quality casting sand. This is advantageous for the foundry sand used in the core of the mold. The processed feed material constitutes natural silica sand which is converted to a mass of particles having a moisture content in the range of 5-20%, so that the aggressive mechanical attrition process is effected on a semi-dry mass. This procedure is different from the operation on a dry mass or on a suspension. Performing aggressive mechanical attrition on a semi-dry mass allows the mass to be compressed by its own weight to force the particles together in a form not obtainable in a dry mass. In the preferred embodiment, the aggressive mechanical attrition of the present invention is effected by a number of blades rotating driven at high speed through a semi-dry mass to physically collide with and form the individual particles that make up the mass of semi-dry compressed silica sand. In the practical embodiment, the semi-dry dough is rotated in a container around a set of rotating whipping blades which are driven at high speeds through the semi-dry dough. The container is driven in one direction and the blades are driven rapidly in the opposite direction. In the preferred embodiment of the invention as shown in Figures 10-12, these two rotating actions occur around parallel axes, separated.

In the preferred embodiment of the present invention the cast sand feed material is a natural coarse sand; however, it may be of other types of quartz casting sand of lower quality, common or silica sand having the characteristics of a foundry sand. Since the incoming silica sand that can be used in foundry sand applications has a roundness of more than 0.40, the resulting final product has a substantially greater roundness of 0.40 since aggressive attrition tends to increase the roundness of the individual particles . Processing the silica sand with that roundness, or otherwise, by the aggressive mechanical attrition of the present invention is novel and highly suggested in the Sand casting technique. In this technique the natural silica sand is simply extracted, washed and graded and used as foundry sand. High-quality silica smelting sand is not readily available, so core sand often demands the use of alternative hard minerals.

Those characteristics of the novel process for increasing the quality of a sand of the low quality casting type in a high quality casting sand constitute the invention as defined in the appended claims which are considered part of the description and are incorporated as reference here in reduced form for [practice by the inventors.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (22)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property.

1. A method to increase the quality of an existing natural silica smelting sand, the method is characterized in that it comprises subjecting the existing smelting sand to mechanical attrition during the process time necessary to remove contaminants from the surface and improve the tensile strength. obtainable from the existing foundry sand.

2. The method according to claim 1, characterized in that the mechanical attrition is aggressive mechanical attrition that involves more than just particle to particle abrasion.

3. The method according to claim 1, characterized in that it comprises: (a) provide an existing silica smelting sand as a feedstock; (b) subjecting the feed material to aggressive mechanical attrition using blades that pass through the feed material until the feed material is converted into high quality casting sand with improved obtainable tensile strength when used as a . foundry sand; Y (c) grade the high quality casting sand in the desired GFN.

4. The method in accordance with the claim 3, characterized in that it includes adding water to the feed material before the aggressive mechanical attrition to create a semi-dry mass by attrition.

5. The method according to the claim 4, characterized in that the semi-dry mass has a water content in the range of 5-20 weight percent of the dough.

6. The method according to claims 1-5, characterized in that the existing foundry sand is a silica sand with a roundness of more than 0.40.

7. The method according to claims 1-6, characterized in that the existing foundry sand is a silica sand with a sphericity of at least about 0.50.

8. The method according to claims 1-5, characterized in that the existing foundry sand is a silica sand with a sphericity of at least about 0.50.

9. The method according to claims 1 - 8, characterized in that the existing foundry sand is a natural silica sand graduated to a given GFN.

10. The method according to claims 2-9, characterized in that the aggressive mechanical attrition is carried out during a process time of less than 10 minutes.

11. The method according to claims 3 - 10, characterized in that the high quality cast iron sand is dried before being graded

12. The method according to claims 3 - 11, characterized in that the aggressive mechanical attrition is carried out in a rotating container and the blades are whipping blades that rotate rapidly in the rotating container.

13. The method of compliance with the claim 12, characterized in that the blades are rotated in a first direction and the container is rotated in a second direction opposite the first direction.

14. The method according to the claim 13, characterized in that the container is tilted and the blades and the container are rotated about parallel axes.

15. The method according to claims: 3-14, characterized in that the particles have a grain size of less than one size in the range of 50-80 microns are removed from the sand of high quality casting.

16. The method according to claims 3 - 15, characterized in that the mechanical attrition increases the roundness of the high quality casting sand by at least 0.10.

17. A method for producing a high quality silica melting sand from a silica sand feedstock having a roundness of at least 0.40 and a sphericity of at least 0.50, the method is characterized in that it comprises: (a) loading the feed material into a rotating container to create a mass of the feed material; (b) adding water to the feed material to form a mass of semi-dry feed material with a moisture content of 5-20 percent; (c) subjecting the mass of semi-dry feed material to aggressive mechanical attrition by rapidly moving the blades through the mass of feed material; Y (d) continuing the abrasive attrition for a time to form foundry sand having a higher quality than the feed material.

18. The > method according to claim 17, characterized in that the time is less than 10 minutes.

19. The method according to claims 17-18, characterized in that it includes: (e) removing high quality casting sand particles having a particle size of less than one value in the range of 50-80 micrometers.

20. The method according to claims 17-19, characterized in that the mechanical attrition increases the roundness of the high quality casting sand by at least 0.10 on the roundness of the feedstock .;

21. The method according to claim 17, characterized in that the time is set to increase the roundness of the feed material to a desired level.

22. The method according to claim 21, characterized in that the fixed time is substantially greater than 10 minutes.