MXPA99000704A - Procedure for obtaining non-ferrous metals through colada in sand molds ve - Google Patents

Abstract

The procedure consists of drying the cavity of the green sand molds, in which molten metal is deposited by casting to obtain respective pieces, so that the drying of said cavity is done prior to the filling phase thereof to eliminate the moisture and prevent the formation of porosities in the resulting piece, to achieve the drying of the cavity of the molds has been provided that are affected by recesses, so that the application of hot air through a top bell corresponding to a station of drying and the application of a negative pressure or vacuum through a lower collector, produces a current of hot air that circulates between the cavities of the molds, going towards the emptied drains, I understand the humidity of such molds and redirecting the extracted water towards the lower manifold, in another embodiment, the molds have their through passages, which are made in the section of the installation in which the transport of the molds (I ') takes place from the molding chamber to the filling station, said through-holes (2') being made by means of the ends or punches (21) of corresponding rods (20) that are displaceable in an upward direction and descend

Description

PROCEDURE PE OBTAINING DETIEZES PE METALS NOT FERREOS MEPIANTE COLAPA IN MOLPES PE ARENA VERPE PESCRIPTION OBJECT OF THE INVENTION The invention relates to a method for obtaining pieces of non-ferrous metal, such as aluminum, where the molten metal is cast on molds or specks of green sand, essentially based on the fact that prior to the casting of the metal a drying takes place of the molds to eliminate the humidity present in them and thus avoid the formation of micro-porosities in the resulting piece. The object of the invention is to obtain a type of mold or speck of green sand in vertical with hollows or voids, through which and by vacuum, is subjected to the corresponding mold cavity to a stream of hot air to dry it. It is also the object of the invention the particular way to effect the drying of the mold, as well as perform the filling thereof and a subsequent and unique plugging of the casting channel, using a cooled piston to cause the rapid solidification of said casting channel and power perform the removal of the mold promptly. It is also the object of the invention to perform the recesses in such a way as to facilitate the vacuum operation throughout the mold, with the purpose of achieving that the molten metal in its casting in the mold perfectly fills all the interstices or conduits of the latter, percussing in an increase in production. The realization of the castings to obtain the function that has just been referred to, will be carried out when the molds are in the transport line of the filling station.

ANTECEPENTES PE THE INVENTION The obtaining of pieces of non-ferrous metals by casting in molds or specks of sand in green, presents the disadvantage that the green sand incorporates a large amount of water, between 3.5% and 4%, which will suppose that the The resulting piece presents a series of porosities on its external surface. The porosity of the resulting piece is due to the fact that fundamentally on the outer surface of the mold in contact with the molten metal at high temperature, a strong heating occurs which causes the evaporation of the water present in the mold, so that the aluminum absorbs the hydrogen from the water causing a lot of micro-porosities on the surface of the pieces. One way to improve the outer surface of the pieces obtained is to achieve that the solidification of the molten metal inside the mold occurs quickly, various techniques are known which allow rapid cooling of the molten metal, being able to mention among others the following : - Carry out the casting of the molten metal in metal molds, which allows to obtain a rapid cooling, this technique has the disadvantage of the high cost of manufacturing the molds, as well as the limited productive capacity obtained. - Obtaining the mold from a magnetic mineral that also allows a rapid cooling and solidification of the molten metal, obtaining pieces with a better microstructure. This technique is described in PCT patent W096 / 11761. - Obtaining the mold from several pieces of different materials, in such a way that one of them is formed by a metal of high thermal conductivity that acts as a means of extracting the heat of the molten metal. This technique is described in European Patent No. 0 557374.

In the foundry industry, males with hollows or voids are known whose purpose is to lighten them by weight or to reduce them, but nevertheless, there have never been any specks of green sand provided with holes or voids to facilitate the elimination of the water contained in the sand. green. On the other hand, when it comes to aluminum casting, the practice demonstrates that it is convenient to maintain the natural humidity of the green sand molds, since based on such humidity an acid surface film is instantaneously formed in the casting process. self-protects the cast part. However, given the formal complexity of the pieces that are currently melted in aluminum, there are usually difficulties for the molten aluminum to completely fill all the nooks and crannies of the mold, filling that can be promoted and enhanced by the application of vacuum, for which It is extremely useful to obtain emptying or through holes in the mold.

DESCRIPTION PE THE INVENTION The procedure recommended is designed to solve the problem described above, based on carrying out a drying of the molds, prior to the casting process of the molten metal, all in order to eliminate the moisture present in the molds and avoid the formation of porosities on the external surface of the obtained or resulting pieces. For this, the method of the invention consists in the following: Obtaining the molds of green sand with a series of holes or voids that allow the circulation of a stream of hot air through them and thereby cause the elimination of moisture of the green sand.

Incorporate, forming part of the casting installation, a drying station in which the mold is subjected to a current of hot air that drags the moisture contained therein, entrainment that is made towards the voids or voids for the elimination of said humidity, with the special particularity that said drying station incorporates an upper hood, side plates and a lower extraction manifold, in such a way that the molds will be arranged inside a perfectly sealed chamber, allowing the application of a Negative pressure through an extractor produces a circulation of hot air that drags moisture from the mold, from the internal walls of the cavity thereof, to the voids or voids and from these to the extractor itself. The method also includes the introduction of the mold, once dried, into a chamber formed by an upper closing plate (operated by hydraulic cylinders), side plates and a lower gas extraction system, all in such a way that before the said chamber is subjected to a vacuum that eliminates the air and gases that could be found inside the cavities of the mold. The method also includes the step of plugging the pouring channel, once the mold is filled, this plugging is effected by means of a piston driven by a cylinder, the piston incorporating an inner chamber through which a stream of air or liquid is circulated. that allows to cool its end in order to cause the rapid solidification of the casting channel, thus being able to quickly remove the mold and start a new cycle, all in order to achieve that the productivity of the machine is high. In order that when aluminum is melted this metal completely fill all the nooks and holes of the mold, it is important that the aforementioned recesses are through in the mold, in order to promote and enhance the application of vacuum, it is also foreseen that these recesses in the mold, they are made once they are in the transport line to the filling or casting station, where the casting of the molten aluminum reacts with the application of a vacuum that favors the filling of the mold.

In this case, the recesses or holes obtained in the mold are intended to facilitate the vacuum operation throughout the mold, in order that the molten metal perfectly fill all the conduits or recesses thereof. Another feature of the invention relates to the device for making these passages in the mold, the device being based on a series of rods provided with a piercing tip, rods that are driven by a motor in order to perform the drilling of the same. the molds, giving rise to through holes in these. The device for carrying out the emptyings or through holes, is complemented by a central piston and guides that allow the rise / fall of the rod properties by means of which the repeated through-holes or holes are made, also incorporating a lateral piston that allows to vary at will the positioning of the rods with respect to the molds, thus allowing to perform more suitable perforations according to their size, foreseeing for this that the base of support and sliding of the row of molds has longitudinal grooves that allow the passage of the rods in the different possible positions that these may occupy.

PESCRIPTION PE LOS PIBUJOS To complete the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical realization thereof, an assembly of drawings is included as an integral part of said description. with an illustrative and not limitative character, the following has been represented: Figure 1 shows the mold that intervenes in the process of the invention.

Figure 2 shows the advance of the mold towards the area where the drying station is established. Figure 3 shows a sectional view corresponding to the cutting line A-A of the previous figure. Figure 4 shows the mold once dried and introduced into the filling station, this one comprising a top closure plate, side plates and a vacuum and gas extraction system located in the lower part. Figure 5 shows the mold in the filling phase, after the closure of the upper and lateral plates that are represented in the previous figure separately from the mold. Figure 6 shows the mold once filled and plugged the pouring channel. Figure 7 shows the release of the mold, after the depressurization of the corresponding pouring ladle and after the cooling time of the pouring channel has elapsed. Figure 8 shows a view corresponding to an installation in which the execution of the recesses or through holes on the molds takes place, an operation that is carried out prior to the casting of the metal. Figure 9 shows a sectional view corresponding to the cut line B-B of the previous figure. Figure 10 shows, finally, an elevation view of the device by means of which passages or holes are made in the molds according to the embodiment shown in figures 8 and 9.

PREFERRED EMBODIMENT OF THE INVENTION The procedure for obtaining pieces of non-ferrous metals is based, as has been said previously, on producing a drying of the molds prior to the casting of the molten metal, so that the moisture present in the drying process is eliminated in the drying process. the molds and avoid the formation of microporosities in the resulting pieces. For this, according to the aforementioned figures, it is necessary that the molds (1) used are obtained by means of a series of cavities or recesses (2), distributed along that, using to effect those recesses or cavities (2) a plate lower end with barbs that act like males. Obviously, the recesses or cavities (2) can be obtained using, instead of a lower plate, a side plate provided with tines, leaving, in this case, the recesses (2) of the molds (1) arranged horizontally. The mold obtained enters the corresponding filling machine, attaching itself to the end of the row of molds, as shown in figure 2, in which a drying station is established. The recesses or cavities (2) of the molds (1) allow the circulation of hot air from the internal cavity (3) of each mold (1) towards those recesses or recesses (2), so that to cause that air circulation hot is for what the drying station has been foreseen, constituted this one from an upper bell (4) and some closing lateral plates (5) that keep the molds (1) hermetically closed, complementing the drying station with a lower collector (6) for collecting and extracting water, so that by blowing hot air through the hood (4) and applying a negative pressure or vacuum through the collector (6) there will be a hot air current flowing from the internal cavity (3) of the respective mold (1) towards the recesses or recesses (2) thereof, dragging the moisture contained in such mold towards the extraction manifold (6). With this technique, a drying of the internal walls of the cavity (3) of the mold takes place., with which the outer surface of the pieces obtained will present a better finish. Once the described drying phase has been carried out, the molds (1) are passed unitarily to the filling station, in which, as shown in FIG. 1, the mold appears positioned between an upper closing plate (7), operated by means of hydraulic cylinders, side plates (8) and a vacuum and gas extraction system (9) located in the lower part, as shown in figure 4. The mold (1) is provided with the corresponding filling duct ( 10) facing the pouring channel (11), observing in this figure 4 the pouring spoon (12) in communication with the molten metal deposit in which a closing element (13) is provided, so that once hermetically fixed the plates (7) and (8), and by pressurizing the ladle (12), through the conduit (14), pressurization that can be carried out by means of a pneumatic and electromagnetic pump system, the metal is cast cast on the mold (1), as 5 is shown in FIG. 5, and once said filling is effected, the plugging of the pouring duct (10) is effected by means of a piston (15) which is driven by a hydraulic or pneumatic cylinder (16), and whose piston (15) defines a inner chamber (17) through which a stream of air or liquid is circulated that allows the end (18) to cool to cause rapid solidification of the pouring duct (10), thus being able to quickly remove the mold (1) and Start a new cycle. After the cooling time of the pouring duct (10) and depressurization of the pouring spoon (12), the plates (7) and (8) are removed to allow the exit of the mold (1) from the filling station and start a new cycle. In an alternative embodiment, shown in figures 8, 9 and 10, the recesses (2 ') of the molds (1') are through, so that said molds (1 ') coming from the molding chamber, referenced with (29) in figure 8, they pass to the filling or pouring station of molten metal, so that in the section referenced with (18) of said station, where the execution of the annotated comments (2 ') takes place. which have to be through holes, as clearly shown in figures 8 to 10, those recesses or through holes (2 ') being provided to facilitate the vacuum operation through the entire mold (1'), so that the molten metal fill perfectly all the interstices, gaps or recesses of this one.

Said recesses (2 ') are made by means of a device generally referenced with (19) and represented in figures 8 and 10, which includes a plurality of rods (20) provided at their free end with a piercing tip (21) , so that starting from a motor (22), and after the corresponding transmission based on pulleys and toothed belts (23), the rotation of such rods (20) and therefore the perforation will take place, by means of their tips ( 21), of the corresponding mold (1 '), thus obtaining the aforementioned through-cuts (2'), as clearly shown in figures 8 to 10, all in such a way that in order to effect such perforations or through-holes it is necessary that rods (20) move upwards, driven by a central piston (242), collaborating in the upward and downward displacements guides (25). A lateral piston (26) is also provided, which makes it possible to vary the positioning of the rods (20) relative to the molds (1 '), so as to effect the through-cuts (2'), in the most suitable position, depending on the of the morphological characteristics of the mold. The base on which the molds support and slide (1 ') will be provided in the section (18) corresponding longitudinal grooves (27) that allow the passage of the rods (20) in the possible distances positions they can occupy. As can be seen in figures 8 and 9, each mold (1 ') is kept perfectly airtight by closing the corresponding upper plates (7') and side (8 '), also providing a collector for vacuum (28), through which a vacuum can be applied that will improve the casting of molten metal inside the molds, filling all the interstices thereof, since that vacuum is made through the through-flushes (2 ') of each mold (! ') •

Claims (3)

NOVEPAP PE THE INVENTION REIVTNPICATIONS

1. - Method for obtaining pieces of non-ferrous metals by casting in green sand molds, characterized in that it comprises the following operational phases; obtain the molds (1-1 ') of green sand with recesses (2-2'), to allow the circulation of a stream of hot air through them to cause the removal of moisture from the green sand, or to get a vacuum that allows to fill all the interstices and cavities in the mold; entering the mold (1-1 ') in a drying station established in the corresponding filling machine, said drying station comprising an upper bell (4) and side plates (5) that maintain a series of molds (1-1') ) hermetically sealed to each other; apply a negative pressure or vacuum through a lower manifold (6) and simultaneous blowing of air through the hood (4), producing a current of hot air circulating between the cavities (3) of the molds (1-1) ') to the recesses (2-2') of these, extracting the humidity and redirecting the extracted water towards the lower collector (6); passing the mold (1-1 '), after drying, to the corresponding filling station, formed by a top closing plate (7-7'), side plates (8-8 '), and a vacuum and gas extraction (9) located at the bottom; filling the mold by pressurizing the corresponding pouring spoon (12), simultaneously extracting gases contained in the internal cavities of each mold (1-1 ') through the vacuum and lower gas extraction system (9); clogging the pouring duct (10), after filling the mold (1-1 '), by means of a piston (15) driven by a hydraulic cylinder (16), simultaneously applying a gas or liquid inside a chamber (17) established in the plunger (15) to produce the cooling and corresponding solifi cation of the duct (10) entering the mold (1-1); depressurizing the ladle (12), maintaining the seal of the inlet conduit (10) to the mold (1- 1 '), as well as the extraction of gases; removal of the top plate (7-7 ') and side plates (8-8') in the filling station, after the cooling time of the pouring or inlet pipe has elapsed (10) to the mold (1-1 '), to allow the extraction of this and start a new cycle. 2.- Procedure for obtaining pieces of non-ferrous metals by casting in green sand molds, according to claim 1, characterized in that the recesses (2 ') are through the mold itself (1'), carried out in the section (18) wherein the transport of such molds (1 ') from the corresponding molding chamber (29) to the filling or casting station of the molten metal takes place, through-flushes (2') which are obtained by means of punched tips (21) provided in the respective free end of corresponding rods (20) rotating simultaneously driven by a motor (22) and displaced in a vertical direction by a piston (24). 3. Process for obtaining pieces of non-ferrous metals by casting in green sand molds, according to claim 2, characterized in that the rods (20) can be varied in position with respect to the molds (1 '), to realize the through-castings ( 2 '), there being provided in the base support and sliding of the molds (1'), longitudinal grooves (27) for the passage of the rods (20) in the different positions they can occupy.