HK1080784B - Heat treatment and sand removal for castings - Google Patents

Description

Apparatus and method for heat treatment and desanding of castings

The present application is a divisional application of the invention patent application entitled "Heat treatment and Sand removal of castings" filed on 24/1/2002 and having application number 00810835.8.

Referenced related application

The present invention claims benefit from united states provisional patent applications No. 60/146,390 (filed 29/7 1999), No. 60/150,901 (filed 26/8/1999), and No. 60/202,740 (filed 10/5/2000).

Technical Field

The present invention relates to metallurgical casting processes, and more particularly to methods and apparatus for removing sand cores from castings and heat treating the castings.

Background

Conventional casting processes for forming metal castings, for example, use cast iron flask-type molds or sand molds (commonly referred to as dies) that mold the external features of the desired casting (e.g., cylinder head) on the internal surface. A sand core, comprising sand and a suitable binder material, defining internal features of the casting is disposed in the mold. Sand cores are commonly used to produce contours and internal features within metal castings, and the core sand material must be removed and recovered from the castings after the casting process is completed. Depending on the application, the sand core and/or sand mold, if a binder is used, may include a phenolic resin binder, a phenolic polyurethane "cold box" binder, or other suitable organic binder material. The mold is then filled with a molten metal alloy. When the alloy solidifies, the casting is typically removed from the mold and sent to a heat treatment furnace for heat treatment, sand reclamation from the sand core, and aging. Heat treatment and aging are processes for improving metal alloys to have physical properties suitable for a variety of applications.

According to some prior art techniques, once the castings are formed, several distinct steps are typically required in order to heat treat the metal castings and to adequately recover the pure sand from the sand cores. The first step is to separate the core portion from the casting. The sand cores are typically separated from the castings by one or a combination of means. For example, the sand may be chiseled from the casting or may be physically vibrated or shaken to break apart and break apart to remove the sand. Once the sand is removed from the casting, the casting is typically heat treated and aged in a subsequent step. If it is desired to strengthen or harden the casting, the casting is typically heat treated. Another step involves cleaning the sand separated from the casting. The above-described purification operation is usually performed by one or a combination of methods. These may include burning the binder coated on the sand, grinding the sand, and passing the sand portions through a mesh screen. Thus, the sand fraction can be subjected to a reclamation step until a sufficiently clean sand is reclaimed.

Accordingly, there is a long felt need in the industry for improved methods of heat treating castings and recovering sand core materials therefrom, and there is a long felt need for effective methods and related apparatus for more efficiently heat treating, removing sand cores, and recovering substantially cleaned sand from the sand cores.

Disclosure of Invention

Briefly, the present invention comprises a system and method for heat treating castings (such as those used in metallurgical plants) and removing sand cores from the casting process. The invention has a plurality of functions of effectively removing and reclaiming sand core molding sand by using high-pressure fluid medium and heat treating the casting in the mold

Examples are given.

In one embodiment of the invention for removing the sand and heat treating the castings, molten metal is poured into a mold that is typically preheated to maintain the metal at a temperature near the heat treatment temperature at which the castings are formed. The castings are then removed from the mold and each is placed in a predetermined position on a saddle having known x, y, z axes and coordinates. Each saddle is generally configured to receive a casting in a fixed orientation or position having an axis and coordinates of X, Y, Z, and the casting is positioned at a known indexing location such that the core apertures of the castings formed with the sand cores are positioned or aligned at the known indexing location. The saddle can also include a locating feature to guide and assist in maintaining the casting in a desired known, calibrated position.

Each saddle passes through a heat treatment furnace or chamber of a heat treatment station with a casting positioned within it, for heat treatment and sand removal and possible reclamation of the sand cores. A series of nozzles having x, y, z coordinates fixed or positioned in alignment with the casting locations direct a high pressure flow of a heated fluid medium, such as air, water, or heat transfer oil, onto and into the castings during heat treatment in the heat treatment station. The fluid facilitates and helps remove and facilitates the removal of the sand core molding sand from the internal cavities of the casting after the sand core is broken up during heat treatment. Typically, the nozzles are arranged in nozzle stations positioned sequentially through the heat treatment chamber, with the nozzles in each nozzle station being positioned at predetermined orientations relative to known locations of the core holes of the castings, and each nozzle combination being remotely controllable by a control system or console.

In another embodiment of the invention, the casting can be retained in its mold for "in-mold heat treatment". These molds are typically preheated prior to pouring the molten casting metal to maintain them at a temperature near the heat treatment temperature of the casting so as to partially heat treat the casting within the mold while the casting is partially solidified. The castings with the molds communicating therein are then typically placed or positioned in a nominal orientation, or position known in the x, y, z coordinates, for heat treatment of the castings therein and removal of the sand cores.

The molds and castings generally pass through a heat treatment furnace at a heat treatment station for heat treatment and for the removal and reclamation of the sand cores of the castings. The heat treatment station also includes a plurality of nozzle stations, each having a series of nozzles positioned and arranged in a predetermined manner corresponding to known locations of the mold and the casting to facilitate the use of a designed high pressure fluid thereto. The nozzle station also includes nozzles operable by automated machinery and movable along a predetermined path around the mold into various application positions corresponding to the positions or orientations of the mold entrances or openings to facilitate access to the castings for removal of the sand cores therefrom. Alternatively, the heat treatment station can also include an alternative heat source, such as an inductive or radiant energy source, or an oxygen chamber for providing energy to the mold or mold as a whole for elevating the temperature to heat treat the castings therein. The casting is then removed from the mold and passed through a subsequent core removal station or through a subsequent core removal step to further remove and possibly reclaim the sand core from the casting.

In another embodiment, the mold is preheated to a predetermined temperature. Subsequently, while the molten metal is poured into the mold, the mold is continuously heated so that the casting is heat-treated while it is solidified without removing the casting from the mold. The mold can then be transferred to a quenching station for quenching the castings and removing the sand cores therefrom. In this embodiment, the mold is typically maintained in a known fixed position or orientation at or near the casting table. The mold is heated using heat jets from a series of nozzles arranged around the mold and generally aligned with the mold inlet. The nozzle is then further moved around the mold between a series of nozzle positions set according to the mold position or orientation to heat the mold to heat treat the casting therein.

Various objects, features and advantages of the present invention will become more apparent upon a reading of the specification when taken in conjunction with the accompanying drawings.

Drawings

FIG. 1 is a schematic view of a first embodiment of the present invention;

FIG. 2 is a side view showing the introduction of molten metal into the mold;

FIG. 3 is a perspective view showing the position of the casting within the saddle;

FIG. 4 is a schematic diagram illustrating another embodiment of the present invention for performing in-mold heat treatment and removing sand molds;

FIGS. 5A-5B are side views showing the air nozzle moving around the mold to various application positions for in-mold heat treatment;

FIG. 6 schematically illustrates another heat treatment chamber for heat treating a casting within a mold

A side view of an embodiment;

FIG. 7 schematically illustrates another heat treatment chamber for heat treating a casting within a mold

A side view of an embodiment;

fig. 8A-8B schematically illustrate side views of other embodiments of heat treatment chambers for heat treating castings within molds.

Detailed Description

Reference will now be made in detail to the drawings in which like reference numerals refer to like parts throughout. FIG. 1 generally illustrates a metallurgical casting process 10. Since the casting process is prior art, the conventional casting process is only briefly described herein for reference.

As shown in fig. 1 and 2, according to the present invention, molten metal or metal alloy M is poured into a mold 11 at a pouring station or casting station 12 to form a casting 13 such as a cylinder head or a cylinder of an automotive engine. Typically, the cores are received or positioned to form hollow cavities and/or casting details or core prints within the casting in each mold. Each mold 11 is typically a sand box type mold and can be made of a metal such as cast iron or other prior art material and may have a clam shell design to facilitate opening and removal of the casting therefrom. The mold may also be a green sand mold made of a sand material mixed with a binder such as a phenolic resin or other suitable organic binder as is known. Similarly, the casting cores typically comprise sand cores formed from a sand material and a suitable binder such as a phenolic resin, phenolic urethane "cold box" binder or other suitable organic binder material of the current art.

As shown in fig. 3, each mold 11 generally includes a series of side walls 14, a top or upper wall 16, and a bottom or bottom wall 17, thereby defining an interior cavity 18 for receiving the molten metal M. The internal cavity 18 is generally formed with a relief pattern for forming internal features of the casting 13 within the mold to define the shape or contour of the final casting. A gate 19 is typically formed in the upper wall or roof 16 and communicates with the cavity 18 for pouring or introducing the molten metal M into the mold as shown in fig. 1 and 2. The resulting casting features a mold cavity, and in addition a core opening or inlet 21 is formed at the location of the core in the mold.

It is also common to provide a heating element, such as a hot air blower or other suitable gas or electric furnace heating mechanism 22, near the pouring station 12 to preheat the mold 11. Alternatively, the mold can be provided with a heat source or element that heats the mold. For example, the mold can include a chamber adjacent the casting for receiving a heating medium, such as hot oil, that heats the mold. Typically, the mold is preheated to a desired temperature depending on the metal or alloy from which the casting is formed. For example, for aluminum, the mold needs to be preheated to within about 400-600 degrees Celsius. The various preheating temperatures required to preheat various metal alloys are familiar to those skilled in the art and can include a wide range of temperatures, including about 400-. Preheating the mold helps to maintain the cast metal at or near the heat treatment temperature to minimize heat loss as the molten metal is poured and solidified within the mold, and then transferring the mold to a subsequent processing station for heat treating the castings.

Once the molten metal or metal alloy has been poured into the molds and has at least partially solidified, a mold transfer mechanism 25 removes the molds and castings from the pouring station 12 and transfers them to a loading station 26, as shown in fig. 1. The mold transport mechanism includes an automated machine (not shown) that transports the molds, a winch or other type of conventional transport mechanism for transferring the molds from the pour station to the load station. In the first embodiment of the invention, after the molten metal M has solidified within the mold to form a casting, the casting 13 (FIG. 3) is removed from the mold 11 at a load station 26 (FIG. 1), for example using a robotic arm or similar mechanism, and placed within a predetermined indexed position having known x, y, z coordinates within the saddle 27. As a result, the core openings 21 (FIG. 3) of the castings are likewise positioned or aligned in known locations for removing the sand cores from the castings.

As shown in FIG. 3, each saddle is typically a basket or rack, typically made of a metallic material and having a base 28 and a series of side walls 29, thereby defining an open casting cavity or container 31 that receives casting 13 with an exposed core hole or inlet. The casting will typically be secured in a known nominal or aligned orientation or position when placed within the receptacle 31 of its saddle 27. Additionally, as shown in FIG. 3, the saddle 27 can also include a positioning member 32 mounted on each saddle base and/or wall 28 and 29 for guiding and maintaining the casting in a desired, indexed position within the saddle 27. The locating member comprises a guide pin 33 as shown in FIG. 3, or can comprise a notch or groove as shown by dashed line 34 in FIG. 3, or other similar means for guiding and locating the casting in the desired indexed position or orientation. Typically, the guide pins 33 are made of a metal material, such as cast iron or similar high temperature resistant material, and are mounted on the bottom or either side wall of the saddle. During the casting process, corresponding locator or guide openings 36 (shown in phantom) are formed in the casting, for example, by using guide pins mounted on the bottom or side walls of the saddle, or by using a degradable sand core material. When the castings are placed in their saddles, the guide pins will be received in the respective guide openings of the castings to position and maintain the castings in a desired calibrated position having known and defined x, y, z coordinates, and to similarly position or align the locations of the core inlets in the castings in known positions to more effectively and directly heat the casting sand cores to facilitate the removal and removal of the core sand for reclamation.

Additionally, in some applications, the mold may include a steel or iron "die" (hill) or core (insert) having various design features allocated on the casting for the purpose of improving its grain structure. These metal molds can be removed after casting or can be left behind and become part of the casting as the molten metal of the casting solidifies. The metal mold, if left in the casting, can also be used as a locator to position the casting in its desired alignment or position within the saddle. The features or details left by the removal of the metal molds can also be used as locating points for engaging guide pins or other locating members in the saddles to secure each casting in its desired indexed position.

After each casting 11 has been loaded in its saddle with a known x, y, z coordinate position or orientation, as shown in FIG. 1, each casting will then be heat treated in the saddle in a heat treatment station 40 to remove the cores and recover the core sand, if necessary. The saddle is typically transported on a conveyor belt or track through the heat treatment station so that the castings will be maintained in known, indexed positions as they pass through the heat treatment station. The heat treatment station 40 typically includes a heat treatment furnace, which is typically a gas-fueled furnace and has a series of treatment sections or chambers for heat treating and de-coring each casting and recovering core sand. Wherein the treatment section can be divided into as many or as few sections as possible while each application may require heat treatment and core removal, and each casting is typically held inside the mold until a saddle can carry it through a heat treatment station. It is also possible to age the castings within the heat treatment station 40 if desired.

In U.S. patent No. 5,294,094; 5,565,046 and 5,738,162, which are incorporated herein by reference, disclose heat treatment furnaces for heat treating castings and for removing sand cores from the castings, and possibly for recovering the sand cores from the sand cores of the castings. Another heat treatment furnace disclosed in U.S. patent application No. 09/313,111, filed on 17.5.1999, which also is incorporated herein by reference, can heat treat metal castings as well as remove sand cores and recover the core sand.

As shown in FIG. 1, the heat treatment station 40 includes a series of nozzle stations 41 positioned at spaced intervals therealong to facilitate the heat treatment operation and removal of the sand cores from the castings. The number of nozzle stations placed along the heat treatment station may vary depending on the core print or design of the casting. The series of nozzles 42 included in each nozzle station or assembly 41 are mounted and positioned in known or aligned positions corresponding to known nominal positions of the castings within the saddles being traversed therethrough. The number of nozzles in each nozzle station may vary depending on the core print of the casting, so that different types of castings having different core designs may be used with different arrangements or numbers of nozzles at will in each nozzle station. The nozzles are typically controlled by a remotely controllable control system to engage or disengage the individual nozzles at the different nozzle stations depending on the design or core print of the castings passing through the heat treatment station.

Each nozzle 42 is typically mounted in a predetermined position and/or orientation and is formed to align with one of a core hole or entry or core print or with a set of core holes in the mold based on the known nominal position of the casting in the saddle. The high pressure hot stream supplied to each nozzle typically comprises air, hot oil, salt, water or other known fluids and is directed to the core openings at high pressures, typically in the range of approximately 1,000FPM to about 15,000FPM, although higher or lower pressures can be used depending on the particular casting application. The pressurized fluid applied to the casting through the nozzles tends to impact or contact the cores within the casting to at least partially crack or break the binder material of the sand cores. When the sand core is broken up or dislodged by the fluid, the core sand of the sand core may tend to be dislodged or cleaned from the casting through the core opening or inlet by the passage of the fluid through the casting to recover the core sand.

The nozzles 42 of each nozzle assembly or nozzle station 41 can also be adjusted to different nozzle positions depending on the characteristics of the casting, as can the pressure of the fluid. Remote adjustment of the nozzle can be achieved, for example, by using a nozzle that can be moved or positioned automatically. The fluid from the nozzles can also have different temperatures depending on the section of the heat treatment station in which the nozzles dispensing the fluid are located so that the fluid will not negatively impact the heat treatment of the castings through the heat treatment furnace or station. In addition, the nozzles of each nozzle station are movable between various positions, including from a rest position to an application position, or between several application positions, and toward the core apertures or inlets once the castings are moved to each of the various zones or stations within the heat treatment station, so as to strategically direct streams of hot, high pressure fluid to the various core apertures or inlets to cause the cores to break and be dislodged from the castings and for the removal of the cores. In this manner, the use of the nozzle station within the heat treatment furnace or station may enhance and make more efficient the breaking up and removal of the sand cores from each casting as the castings are heat treated, and facilitate the reclamation of the sand material from the sand cores for reuse.

As shown in FIG. 1, after each casting has been heat treated and the cores removed, each casting is removed from the heat treatment station 40 and typically moved to a quench station 45. The quench station 45 generally comprises a quench tank filled with a cooling fluid such as water or other known casting into which the casting may be immersed for cooling and quenching. The volume and size of the quench tank is generally a function of the specific heat of the castings and metal or metal alloy being formed, including the temperature to which the castings and each casting have been heated. Alternatively, the quench station may include a series of air nozzles for injecting cooled air into the quenched castings.

Another embodiment of the present invention illustrates heat treating a casting in a mold as shown in fig. 4-8B. As shown in fig. 4, in an embodiment of a casting process 50, molten metal or alloy M is injected into a mold 51 at a pouring or casting station 52. As shown in fig. 4-5B, the mold 51 in this embodiment typically comprises a flask-type mold made of, for example, cast iron or the like, or may be a green-sand mold made of a sand material mixed with an organic binder as is well known in the art, and typically includes an internal chamber within which a casting 53 is formed (fig. 6-8B).

Each mold typically includes a sand core 54, as shown in fig. 7, which is typically formed of a sand material mixed with an organic binder for forming apertures and or core apertures or inlets in the castings formed in the mold and for forming casting details or core patterns. The mold 51 in this embodiment further includes ports or mold access ports 56 (fig. 4-5B) that may be formed at optional, desired locations or places around the mold and extend through the sidewalls 57 of the mold 51 to provide access to the castings 53 formed within the mold (fig. 6-8B) for directly applying heat to the castings within the mold and breaking up and removing the sand cores.

Heating elements, such as hot air blowers or other suitable gas or electric heating mechanisms 58 (fig. 4), are disposed adjacent the pouring or casting station 52 to preheat the mold as molten metal M is introduced into the mold. Alternatively the mold may be formed with a cavity adjacent the casting within the mold, wherein heated gas, hot oil or other heating medium may be contained for preheating the mold and further heating the casting within the mold. Typically, the mold is preheated to a desired temperature, i.e., 400-600 degrees Celsius for aluminum, depending on the desired heat treatment temperature for the metal or alloy to form the casting. Preheating the mold tends to: substantially maintaining the temperature of the casting formed within the mold at or near the heat treatment temperature of the casting and minimizing heat loss thereof while the mold is being transferred from the pour table; at least partially heat treating the casting while the casting is solidifying; and enhancing the heat treatment of the castings by reducing the heat treatment time since the castings need not be significantly reheated to the temperature levels required for heat treatment.

Thereafter, each mold 51, once filled with molten material M, is transferred by a mold transfer mechanism 59 from the casting or pouring station 52 to a loading station 61. The mold transport mechanism 59 typically comprises a mold transport robot, winch, conveyor, or other type of conventional transport mechanism for transferring molds from the pour station to the load station. The transport mechanism positions each mold within a known predetermined nominal position at the load station with the x, y, z coordinates of the mold in a known orientation or position prior to heat treatment.

In a preferred embodiment of the invention, the mold is then typically moved into and through a heat treatment station 62 to at least partially heat treat the castings and to break and remove the cores. As noted above, the heat treatment station 62 typically comprises a heat treatment furnace, typically a gas-fueled furnace, having a series of treatment sections or chambers for heating the molds to at least partially heat treat the castings "within the molds". Wherein the number of treatment sections or chambers can be divided into as many or as few sections as possible in each application, depending on the casting to be treated. In addition, after at least partial heat treatment of the castings within the molds, the castings can be removed from their molds and passed through a heat treatment station for continued heat treatment, removal of the sand cores and possibly reclamation of the core sand.

In U.S. patent No. 5,294,994; 5,565,046 and 5,738,162 disclose heat treatment furnaces that heat treat castings while they remain "in the mold", at least partially break up and/or remove sand cores from the castings, or continue to heat treat, remove and possibly recover the sand cores. Reference is made herein to the incorporation of these publications. Another heat treatment furnace for use with the present invention is disclosed in U.S. patent application No. 09/313,111, filed on 17.5.1999, which is also incorporated herein by reference. These treatment furnaces are capable of recovering core sand from the sand cores of castings removed through the mold inlets during heat treatment of the castings while the castings remain within the castings.

As shown in fig. 4-5B, the heat treatment station 62 also typically includes a series of nozzle stations 63 or assemblies each equipped with a number of nozzles 64. The nozzles of each nozzle station are typically positioned at a known predetermined location and/or orientation in alignment with known locations of some or some group of inlets 56 on the die 51. The number of nozzle stations and the number of nozzles on each nozzle station can be varied as desired to heat the mold to heat treat the castings therein to varying degrees and/or amounts to control the heating of the mold and thereby the castings and to adjust the heating to the various stages of heat treatment of the castings.

Each nozzle typically supplies a heated liquid or gas stream, as shown in fig. 5A and 5B, which is directed onto the dies, typically at a particular die inlet or set of die inlets of each die. The fluid medium applied to the nozzles typically comprises water, air, hot oil, salt or other known fluids at high pressure and at different temperatures that heat the mold, the temperature of the heat flux applied by the needles as the castings pass through the different nozzle stations of the heat treatment station being controlled to correspond with the different stages of the heat treatment. Directing the heat flux into the mold through the mold inlet also typically tends to cause the binder of the sand cores of the castings to break down so that the sand cores at least partially disintegrate and are removed and/or extracted from the castings during the heat treatment, and the removed core sand material flows through the mold inlet upon removal of the fluid. In addition, the mold may also be at least partially opened while passing through the nozzle station to more directly apply the heat flux to the casting and core hole for heat treatment and core removal.

In addition to passing the casting through a series of nozzle stations including being mounted in fixed positions aligned with or corresponding to known positions of the mold and thereby aligned with known positions of the mold inlets, it is also possible to maintain the mold in a fixed casting position at a nozzle station or at a pouring station to apply the heat flux. In such an embodiment, the nozzle 64' (fig. 5A and 5B) may be generally operated by an automated machine so as to be movable between a series of predetermined fluid applications or nozzle positions as indicated by arrows 66 and 67 in fig. 5A and 5B. As the nozzles 64' move around the mold in the direction of arrows 66 and 67, they apply a high pressure heat stream F to the mold, generally directed to and through port 56, to raise and maintain the temperature of the mold to a temperature sufficient to heat treat the metal castings as the molten metal of the castings solidifies. The various applications or nozzle positions of the movable nozzle are typically determined or set according to the known x, y and z coordinates of the mold and thus of its inlet, either on the casting table or once the mold is positioned or placed on the loading table by the mold transport mechanism.

The mold 51 of the present invention is generally capable of being heated to temperatures approaching 450-650 degrees celsius or higher depending on the temperature required for alloy or metal solution treatment of the casting, and is typically preheated to a temperature sufficient to partially heat treat the casting as it is poured. The heating of the molds is also controlled by controlling the temperature of the heat flux applied to the molds to heat the molds and maintain their temperature at the desired temperature for heat treatment of the metal of the formed castings to minimize heat loss during transfer to the heat treatment station, thereby minimizing the amount of re-heat required to re-raise the castings to the heat treatment temperature.

In an alternative embodiment of the heat treatment station as shown in fig. 6-8B, the nozzle station can be supplemented or replaced by an additional heat treatment chamber in which energy is supplied or directed to the mold to raise and maintain the mold temperature at the desired temperature for heat treatment of the castings. In a first embodiment of the heat treatment chamber 70, shown in fig. 6, the molds or sand molds 51 are typically placed on a conveyor belt or conveyor mechanism 71 for movement through the heating chamber 70 as indicated by arrow 72. The heating chamber 70 is generally an elongated furnace chamber having insulated bottom, sides and top and includes a radiant energy source 73 as shown in fig. 6. The radiant energy sources are typically mounted at the top of the heating chamber 70, but it will also be appreciated by those skilled in the art that the radiant energy sources can be mounted at the sides as they move through the heating chamber 70 on a conveyor or conveyor mechanism, as well as at the side walls, above and/or below the mold using a plurality of radiant energy sources. Typically, the radiant energy source is an infrared emitting source or other type of radiant energy source.

The radiant energy source typically directs about 400-650 degrees celsius radiant heat to the molds passing through the heating chamber, typically to the sides and/or top of each mold as indicated by arrows 74. The mold is thereby exposed to radiant energy with its castings for a desired period of time, which is dependent upon the metal from which the castings are heat treated. This radiant energy is generally absorbed by the mold, which correspondingly raises the temperature of the mold to heat the mold and its casting from the inside outward.

Fig. 7 illustrates another alternative embodiment of a heating chamber 80 for use in heat treatment in the mold of the present invention. As shown in FIG. 7, the heating chamber 80 is typically an elongated furnace having insulated bottom, top and sides and includes a conveyor or other transport mechanism 84 for moving the molds and their castings through the heating chamber 80 in the direction of arrow 82. The heating chamber 80 also includes an inductive energy source 83 for applying inductive energy to the mold or mold and thus to the castings and the sand cores 53 and 54 therein. The inductive energy source can typically comprise a conductive coil, microwave energy source, or other known inductive energy source or generator, as in the radiant energy source of fig. 6, which can be placed along both sides of the heating chamber on top of the heating chamber 80 above the mold, or on both sides. The induction energy source is capable of generating a high energy magnetic field as indicated by arrows 84 which is directed to the top and/or sides of the mold 51 and has one or more predetermined frequencies which are absorbed by the sand cores 54 to raise the sand cores and the temperature of the castings to correspondingly heat treat the castings within the mold by heating the castings and the mold from the inside to the outside.

Fig. 8A and 8B illustrate another alternative embodiment of a heating chamber 90 for use in the present invention to "in-mold" heat treat castings by applying energy to the molds to thereby increase the temperature of the castings. In this embodiment, the molds typically comprise sand mold fill molds (sand mold pad type dies), although sand type molds (flash type dies) are also possible. As shown in fig. 8A and 8B, the heating chamber is generally an elongated heating chamber that includes a conveyor belt or conveyor mechanism 91 for conveying the molds 51 with the castings 53 therein in the direction of arrow 92. As the molds and castings move through the heating chamber 90, they pass through the low flow oxygen chamber 93. The oxygen chamber generally includes a high pressure upstream side 94 and a low pressure downstream side 96 that face each other to facilitate oxygen flow through the die. As the mold passes through the low flow oxygen chamber of heating chamber 90, heated oxygen is introduced to and through the mold or filled mold as depicted by arrows 97 (fig. 8A) and arrows 97' (fig. 8B). When the oxygen flows through the mold or filled mold, is drawn or directed from the high pressure side of the oxygen chamber to the low pressure side, a portion of the oxygen combusts with the mold filling and the binder of the sand core, thereby promoting combustion of the binder material within the heating chamber. As a result, the mold filling and its casting are further provided with a binding material to improve the energy provided by the combustion, thereby increasing the temperature of the casting within the mold filling, while breaking up the binder and sand cores of the mold filling to facilitate removal and reclamation of the sand cores. As illustrated in fig. 8A and 8B, depending on the size and configuration of the heating chamber, the low flow rate oxygen chambers may be oriented in a vertical direction (as in fig. 8A) or a substantially horizontal direction (as in fig. 8B) for forcing hot oxygen through the mold fill.

In addition, the internal mold casting may also be heat treated by providing an energy source within the mold itself to increase the temperature of the mold or sand mold fill while reducing potential heat transfer losses between the molten metal, the mold surface and the air. In such an embodiment, the mold is formed with a cavity or chamber proximate to the internal cavity in which the casting is formed. Such as hot oil, water or other heated fluid medium capable of retaining heat, is supplied to the mold structures contained in these cavities. These heating fluids tend to increase and help maintain the temperature of the castings at the desired level required for heat treatment.

As a result of the application of energy to the mold or the mold filling itself, the mold is heated to a desired temperature and maintained at a temperature necessary to heat treat the casting formed therein as the molten metal of the casting solidifies. When the metal of the casting is generally raised to a temperature and stabilized at the heat treatment temperature just after the molten metal is poured into the mold, heat treatment of such castings in the mold can significantly reduce the machining time required to heat treat the casting from 250 minutes to as low as about 50 minutes as possible so that heat treatment of the casting can be carried out in a short period of time after the molten metal is poured into the mold. If used, raising the temperature of the mold to the heat treatment temperature of the heat treated casting also increases the breakdown of the sand cores and or sand molds and the combustion of combustible binders therewith to further reduce the time required for heat treating and removing and reclaiming the sand molds during the sand core and casting process.

After the castings within the molds have been heat treated in the heat treatment station 62, the castings generally are removed from the molds and moved to additional heating stations to complete the heat treatment of the castings as desired, as well as to remove the sand cores and possibly reclaim the sand material of the sand cores. The casting then moves to the quench station 100 for quenching and cooling the casting. Alternatively, as shown in FIG. 4, the casting is removed from the mold and transferred directly to a quench station. The quench station 100 typically includes a quench tank filled with a cooling fluid (e.g., water or other cooling material), but also has a series of nozzles, indicated at 101 in fig. 4, for applying a cooling fluid (e.g., air or water) to the castings. Quenching may also be performed in an auxiliary quenching apparatus adjacent to the casting table so that cycle time and thermal variations may be minimized to set and process the molten metal material within the mold.

After the heat treatment of the castings and the removal of the sand cores, the castings can be removed from the molds and then immersed in a quench tank of a quench station for cooling the castings prior to further processing, and the sand removed from the castings for reclamation for later use. Alternatively, the mold may be transferred directly from the pouring table to the quenching table, as indicated by the broken line in fig. 4. For example, the mold may be transferred directly to the quench station after heating the mold from the pour station to a heat treatment temperature at which the casting is heat treated near the pour station.

Accordingly, the present invention reduces or eliminates the need for further heat treating the casting once removed from the mold, the casting being heated to provide a solution heating time and cold extruded to provide the necessary in-mold quenching effect, so as to significantly reduce the amount of heat treatment/processing time to form the metal casting. The present invention also provides for a method of forming a cast article by directing a fluid stream at the cast article in a predetermined location, which corresponds to a known orientation or location of the cast article and its mold as it passes through the heat treatment station,

it will be understood by those skilled in the art that while the present invention has been discussed above with reference to the accompanying drawings, various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as described in the following claims.

Claims (21)

1. A method of machining a casting of a known metal comprising:

pouring molten metal into a mold;

holding the metal in the mold for a period of time sufficient to at least partially solidify the metal to form a casting having a sand core and a sand core opening therein;

placing the casting in the indexing position with the X, Y, Z axis of the casting oriented in a known orientation such that the orientation of at least the plurality of sand core openings is in a known position aligned with the plurality of nozzles;

directing a stream of fluid from the nozzle into the sand core opening and into the opening to remove the sand core from the casting; and

moving the plurality of nozzles to a first nozzle position aligned with at least the plurality of openings into the sand core; and

at least a portion of the plurality of nozzles is moved to a second nozzle position, wherein the portion of the plurality of nozzles is aligned with the core opening.

2. A method of machining a casting of a known metal comprising:

pouring molten metal into a mold;

the metal is held in the mold for a period of time sufficient to at least partially solidify the metal to form a casting having a sand core and sand core openings therein;

transferring the casting from the mold to a saddle;

placing the casting in a nominal position within the saddle, the X, Y, Z axis coordinate of the casting being known such that the orientation of at least the plurality of sand core openings is in a known position aligned with the plurality of nozzles;

fluid streams are directed from the nozzles at and into the sand core openings to remove the sand cores from the castings.

3. A system for producing castings from molten metal, comprising:

a series of molds receiving molten metal therein to define and form castings;

a series of saddles adapted to receive a casting in a desired orientation having known nominal coordinates; and

a heat treatment station having a saddle received therein with castings in known indexed positions therein for heat treating the castings and removing the sand cores, the heat treatment station comprising:

a plurality of nozzle stations, each nozzle station provided with a plurality of nozzles positioned in alignment with known indexed positions of the castings for applying fluid streams to the castings to substantially dislodge the sand cores from the castings.

4. The system of claim 3 wherein each of the nozzle stations includes a series of automatically controlled nozzles adapted to move about the castings between at least first and second nozzle positions for directing fluid streams onto the castings from different directions to substantially dislodge and remove the sand cores from the castings.

5. The system of claim 3 wherein each said saddle includes a series of walls defining a casting pocket and a plurality of locating members positioned within said casting pocket for engaging and guiding said casting into its known nominal position at said saddle having known position coordinates.

6. The system of claim 5 wherein said locating members comprise guide pins, said castings being formed in said molds, said molds having corresponding locating openings in which said guide pins are received for locating the castings in their known, indexed positions in said saddles.

7. The system of claim 3 wherein said molds comprise sand box molds having a heat source for preheating said molds and at least partially heat treating said castings.

8. The system of claim 3 further comprising a quenching station for quenching said castings.

9. A system for making metal castings, comprising:

a mold containing a metal material therein to form a casting;

a heat treatment station through which the mold with the castings therein is moved at known indexed positions for heat treating the castings;

the heat treatment station includes a heat treatment chamber in which the mold is subjected to applied heat to at least partially heat treat the castings within the mold; and

wherein said heat treatment station includes a means for heating said mold to a temperature sufficient to at least partially heat treat the castings therein.

10. The system of claim 9 wherein said heating means includes at least one nozzle station disposed along said heat treatment station and having at least one nozzle originally mounted in alignment with a series of mold inlets formed in said molds for applying a fluid medium to said molds to heat said molds and remove core material from cores within said castings.

11. The system of claim 9, further comprising at least one nozzle station disposed along said heat treatment station and having at least one nozzle originally mounted in alignment with a series of mold inlets formed in said molds for applying a fluid medium to said molds to remove core material from cores within said castings.

12. The system of claim 9, wherein said heating means comprises a radiant energy source mounted within said heating chamber for directing radiant energy onto said mold.

13. The system of claim 9, wherein said heating means comprises an induction energy source mounted within said heating chamber for directing induction energy onto said mold.

14. The system of claim 9 wherein said heating means includes an oxygen chamber mounted along said heat treatment chamber whereby a flow of oxygen is directed through said mold to react with the binder and combust to raise the temperature of the casting within said mold.

15. The system of claim 9, wherein said heating means further comprises an energy source located within said heating chamber for applying energy to said mold to heat said mold from inside and outside.

16. The system of claim 9 further comprising a quenching station for quenching the heat treated castings.

17. The system of claim 9, further comprising means for directing a fluid medium to the casting to decompose at least a portion of the mold.

18. The system of claim 17, wherein the fluid medium is selected from the group consisting of air, water, and thermal oil.

19. The system of claim 17 wherein the means for directing the fluid medium further comprises means for directing the fluid medium onto the casting under high pressure.

20. The system of claim 17, wherein the mold comprises a sand core, and wherein the means for introducing the fluid medium to the casting to break down at least a portion of the mold comprises means for applying the fluid medium to break down at least a portion of the sand core.

21. The system of claim 17 and further comprising means associated with the heat treatment station for placing the mold in the heat treatment station to heat treat the castings within the mold in the defined, indexed position.