EP1225993B1

EP1225993B1 - Heat treatment and sand removal for castings

Info

Publication number: EP1225993B1
Application number: EP00952228A
Authority: EP
Inventors: Scott P. Crafton; Paul M. Crafton; Volker R. Knobloch; James L. Lewis, Jr.; Ian French
Original assignee: Consolidated Engineering Co Inc
Current assignee: Consolidated Engineering Co Inc
Priority date: 1999-07-29
Filing date: 2000-07-27
Publication date: 2008-06-11
Anticipated expiration: 2020-07-27
Also published as: JP3817476B2; JP2006061988A; MXPA02000936A; HK1048085B; KR20020026552A; EP1225993A1; CN1172760C; HK1080784A1; CN1672835A; AU6496600A; CA2391349C; CN1364104A; ATE397986T1; HK1048085A1; WO2001008836A1; CN1315601C; EP1225993A4; DE60039180D1; KR100805514B1; AU781487B2

Abstract

A system and method for heat treating castings (13, 53) and removal cores (54) therefrom. The castings (13, 53) are initially located in indexed positions with their x, y, and z coordinates known. The castings (13, 53) are passed through a series of nozzle stations (41, 63) each having a series of nozzles (42, 64, 64') mounted in present positions corresponding to the known indexed positions of the castings passing through the nozzle stations (41, 63). The nozzle (42, 64, 64') apply heated fluids to the castings (13, 53) for heat treating the castings (13, 53) and dislodging the sand cores (54) for removal from the castings (13, 53).

Description

This invention generally relates to metallurgical casting processes, and more specifically to a method and apparatus for removal of a sand core from a casting and the heat treatment of the casting.
A traditional casting process for forming metal castings employs, for example, a cast iron flask-type mold or sand mold, also known as a die, having the exterior features of a desired casting, such as a cylinder head, formed on its interior surfaces. A sand core comprised of sand and a suitable binder material and defining the interior features of the casting is placed within the die. Sand cores generally are used to produce contours and interior features within the metal castings, and the removal and reclaiming of the sand materials of the cores from the castings after the casting process is completed is a necessity. Depending upon the application, the binder for the sand core and/or sand mold, if used, may comprise a phenolic resin binder, a phenolic urethane "cold box" binder, or other suitable organic binder material. The die is then filled with a molten metallic alloy. When the alloy has solidified, the casting generally is removed from the die and is then moved to a treatment furnace (s) for heat-treating, reclamation of the sand from the sand cores, and aging. Heat treating and aging are processes that condition metallic alloys so that they will be provided with different physical characteristics suited for different applications.
In accordance with some of the prior art, once the casting is formed, several distinctly different steps generally must be carried out in order to heat treat the metal casting and reclaim sufficiently pure sand from the sand core. A first step separates portions of sand core from the casting. The sand core is typically separated from the casting by one or a combination of means. For example, sand may be chiseled away from the casting or the casting may be physically shaken or vibrated to break-up the sand core and remove the sand. JP03000465 discloses in its abstract a method and a system for removing sand cores out of a casting. Thereby the casting remains in the die after casting and solidification and air is blown through core openings of the die into the cores of the casting. By passing the air through the cores the organic binder of the core sand is burned away and the sand can be removed. Once the sand is removed from the casting, heat treating and aging of the casting generally are carried out in subsequent steps. The casting is typically heat treated if it is desirable to strengthen or harden the casting. An additional step consists of purifying the sand that was separated from the casting. The purification process is typically carried out by one or a combination of means. These may include burning the binder that coats the sand, abrading the sand, and passing portions of the sand through screens. Therefore, portions of sand may be re-subjected to reclaiming processes until sufficiently pure sand is reclaimed.
There is, therefore, a desire in the industry to enhance the process of heat treating castings and reclaiming sand core materials therefrom such that a continuing need exists for a more efficient method, and associated apparatus, that allow for more efficient heat treatment, sand core removal, and reclamation of sufficiently pure sand from the sand core.
Briefly described, the present invention comprises a system and method for heat treating castings, such as for use in a metallurgical plant, and for removing the sand cores used during the casting processes. The present invention encompasses multiple embodiments for efficiently removing and reclaiming the sand of sand cores using high pressure fluid media, and for in-die heat treatment of the castings.
In one embodiment of the invention, the castings will be left in their dies for "in-die" heat treatment of the castings. The dies typically are pre-heated before the molten metal of the castings is poured into them to maintain the metal close to a heat treatment temperature for the castings, so as to partially heat treat the castings inside the dies while the castings solidify. Thereafter, the dies, with their castings therein, typically are located or placed in indexed orientations or positions with their x, y and z coordinates known for heat treatment of the castings therein and removal of the sand cores.
For heat treatment and the removal and reclamation of the sand cores of the castings, the dies and castings generally are passed through a heat treatment furnace of a heat treatment station; The heat treatment station further includes a plurality of nozzle stations each having a series of nozzles oriented or positioned in a pre-defined manner corresponding to the known positions of the dies and castings for applying high pressure fluids thereto. The nozzle stations also can include robotically operated nozzles that move along a pre-defined path around the dies, into various application positions corresponding to the positions or orientations of die access openings or apertures in the dies for access to the castings for dislodging the sand cores from the castings. Alternately, the heat treatment station can also include alternative energy sources, such as inductive or radiant energy sources, or an oxygen chamber, for supplying energy to the dies or mold packs to raise their temperature for heat treating the castings therewithin. Thereafter, the castings are removed from their dies and passed through subsequent core removal stations or processes to further remove and potentially reclaim the sand cores from the castings.
In a further embodiment, the dies are pre-heated to a pre-defined temperature. Thereafter, as molten metal is poured into the dies, the dies continue to be heated to heat treat castings as they are solidified without removing the castings from the dies. The dies can then be transferred to a quenching station for quenching of the castings and removal of the sand cores therefrom. In this embodiment, the dies generally are maintained in a known, fixed position or orientation at or adjacent to the pouring station. The dies are heated by the application of heated fluids from a series of nozzles positioned about the dies, typically in alignment with die access openings thereof. The nozzles further are subsequently moved about the dies between a series of nozzle positions set according to the position or orientation of the dies, for heating the dies to heat treat the castings within the dies.
Various objects, features, and advantages of the present invention will become apparent upon reading and understanding this specification, taken in conjunction with the accompanying drawings.
Fig. 1 is a schematic illustration of an embodiment of the present invention for in-die heat treating with sand core removal process.
Figs. 2A-2B are side elevational views illustrating movement of the air nozzles to various application positions about a die for in-die heat treatment.
Fig. 3 is a side elevational view schematically illustrating an alternative embodiment of a heating chamber for in-die heat treatment of castings.
Fig. 4 is a side elevational view schematically illustrating another alternative embodiment of a heating chamber for in-die heat treatment of castings.
Figs. 5A-5B are side elevational views schematically illustrating further alternative embodiments of heating chambers for in-die heat treatment of castings.
An embodiment of the present invention illustrating the in-die heat treatment of castings is illustrated in Figs.1-5B. As illustrated in Fig. 1, in this embodiment of a casting process 50, a molten metal or alloy M is poured into a die 51 at a pouring or casting station 52. As indicated in Figs. 1-2B, the dies, 51 in this embodiment typically include flask type molds formed from a metal such as cast iron or similar material or can be green sand type molds formed from a sand material mixed with an organic binder as is known in the art, and generally include an internal chamber in which the castings 53 (Fig. 3-5B) are formed.
Each of the dies 51 further generally includes a sand core 54, as illustrated in Fig. 4, generally formed from a sand material mixed with an organic binder for forming bores and or core apertures or access openings in the castings formed within the dies and for creating casting details or core prints. The dies 51 in this embodiment, further typically include ports or die access openings 56 (Fig. 2B) that are formed at selected, desired positions or locations about the dies and extend through the side walls of 57 of the dies 51 so as to provide access to the castings 53 being formed within the dies (Figs. 3-5B) for direct application of heat to the castings while in-die and for dislodging and removal of the sand cores therefrom.
A heating element such as a heated air blower or other suitable gas or electric fired heater mechanism 58 (Fig. 1) also can be provided adjacent the pouring or casting station 52 for preheating the dies as the molten material M is introduced therein. Alternatively, the dies can be formed with cavities adjacent the castings within the dies, in which a heated gas, thermal oil or other heated medium, can be received for preheating the dies and further heating the castings within the dies. Typically, the dies are preheated to a desired temperature depending upon the heat treatment temperature required for the metal or alloy being used to form the casting, i.e., 400 - 600 °C for aluminum. The pre-heating of the dies tends to substantially maintain and minimize loss of the temperature of the castings being formed within the dies at or near the heat treatment temperature for the castings as the dies are transferred from the pouring station and to at least partially heat treat the castings as they solidify, and to enhance the heat treatment of the castings by reducing heat treatment times since the castings do not have to be significantly reheated to raise their temperature to levels necessary for heat treatment.
Thereafter, once each die 51 has been filled with a molten material M, the die typically is transferred from the casting or pouring station 52 by a die transfer mechanism 59 into a loading station 61. The die transfer mechanism 59 generally can include a die transfer robot, winch, conveyor or other type of conventionally known transfer mechanism for moving the dies from the pouring station to the loading station. The transfer mechanism positions each die in a known, indexed position at the loading station, with the x, y and z coordinates of the dies being located in a known orientation or alignment prior for heat treatment.
In the present embodiment of the invention, the dies thereafter generally are moved into and through a heat treatment station 62 to at least partially heat treat the castings and break down their sand cores for removal. As discussed above, the heat treatment station 62 generally includes a heat treatment furnace, typically a gas fired furnace, having a series of treatment zones or chambers for applying heat to the dies for at least partial heat treatment of the castings "in-die". The number of treatment zones or chambers can be divided into as many or as few zones as an individual application may require, depending upon the castings being processed. Additionally, following at least partial heat treatment of the castings while in-die, the castings can be removed from their dies and passed through the heat treatment station for continued heat treatment, sand core removal and possibly for sand reclamation.
An example of a heat treatment furnace for the heat treatment and at least partial breakdown and/or removal of the sand cores from the castings while the castings remain "in-die", or the continued heat treatment, sand core removal, and possibly reclamation of the sand of the cores, from the castings after removal from their dies, is illustrated in U. S. Pat. Nos. 5,294,994 ; 5,565,046 ; and 5,738,162 . A further example of a heat treatment furnace for use with the present invention is illustrated and disclosed in U. S. Patent Application serial no. 09/313,111, filed May 17, 1999 . These heat treatment furnaces further enable the reclamation of sand from the sand cores of the castings that are dislodged through the die access openings during heat treatment of the castings while they remain in their dies.
As illustrated in Figs. 1-2B, the heat treatment station 62 further generally includes a series of nozzle stations 63 or assemblies each equipped with a plurality of nozzles 64. The nozzles of each of the nozzle stations generally are oriented at known, preset positions and/or orientations in registration with the known positions of certain ones or sets of die access openings 56 of the dies 51. The number of nozzle stations and the number of nozzles at each station can be varied as needed for providing heat in varying degrees and/or amounts to the dies for heat treating the castings therewithin to enable control of the heating of the dies and thus the castings, and the adjustment of the heating to different stages of heat treatment of the castings.
Each of the nozzles generally supplies a fluid flow or blast of a heated fluid that is directed toward the dies and typically toward a specific die access opening or set of die access openings of each die as indicated in Figs. 2A and 2B. The fluid medium applied to the dies typically includes water, air, thermal oils, salt or other conventionally known fluids that are supplied under high pressure and at varying temperatures to heat the dies, with the temperature of the fluid flows supplied by the needles being controlled to conform to different heat treatment stages as the casting is passed through the different nozzle stations of the heat treatment station. The introduction of the heated fluids into the dies through the die access openings further generally tends to cause a breakdown of the binder for the sand cores of the castings so as to cause the sand cores to at least partially degrade and be dislodged and/or removed from the castings during heat treatment, with the dislodged sand material passing through the die access openings with the draining of the fluids therefrom. In addition, the dies also potentially can be at least partially opened as they pass through the nozzle stations for more direct application of the heated fluids to the castings and core openings thereof for heat treatment and sand core removal.
In addition to having the castings pass through a series of nozzle stations that include nozzles mounted in fixed positions in registration or corresponding to the known positions of the dies, and thus the known positions of the die access openings, it is further possible to maintain the dies in a fixed casting position at a single nozzle station or at the pouring station for application of heated fluids thereto. In such an embodiment, nozzles 64' (Figs. 2A and 2B) typically are robotically operated so as to be movable between a series of predetermined fluid application or nozzle positions as illustrated by arrows 66 and 67 in Figs. 2A and 2B. As the nozzles 64' move about the dies in the direction of arrows 66 and 67, they apply a heated, pressurized fluid media F against the dies, typically directed toward and into the access openings 56, so as to raise and maintain the temperature of the dies at a sufficient temperature for heat treating the metal casting therewithin as the molten metal of the castings is solidified. The various application or nozzle positions of the movable nozzles generally are determined or set according to the known x, y and z coordinates of the dies, and thus their die access openings, at the pouring station or upon the positioning or locating of the dies at the loading station by the die transfer mechanism.
The dies 51 of the present invention typically have the ability to be heated up to approximately 450 - 650°C or greater depending upon the solution heat treatment temperatures required for the alloy or metal of the casting that is required, and typically are preheated to a temperature sufficient to enable at least partial heat treatment of the casting during pouring of the molten metal. The heating of the dies further is controlled through control of the temperature of the fluid media applied to the dies so as to heat and maintain the dies at the desired temperatures needed for heat treating the metal of the castings being formed therein to minimize heat loss during transfer to the heat treatment station and thus minimize the amount of reheating required to raise the castings back to their heat treatment temperatures.
In alternate embodiments of the heat treatment stations shown in Figs. 3 - 5B, the nozzle stations can be supplemented or replaced with additional heat treatment chambers in which energy is supplied or directed toward the dies for raising and maintaining the temperature of the dies at the required temperature for heat treating the castings therein. In a first example of a heat treatment chamber 70, illustrated in Fig. 3, the dies or sand mold packs 51 generally are placed on a conveyor or transport mechanism 71 for movement through the heating chamber 70 as indicated by arrows 72. The heating chamber 70 typically is an elongated furnace chamber having an insulated floor, sides, and ceiling and, as illustrated in the embodiment of Fig. 3, includes a radiant energy source 73. The radiant energy source 73 typically is mounted in the ceiling of the heating chamber 70, although it will be understood by those skilled in the art that the radiant energy source can also be mounted in side walls, and that multiple radiant energy sources can be used, mounted in the side walls, overhead and/or below the dies as they are moved through the heating chamber 70 on the conveyor or transport mechanism. Typically, the radiant energy source will be an infrared emitter or other known type of radiant energy source.
The radiant energy source generally will direct radiant energy at approximately 400 - 650°C toward the dies passing through the heating chamber, typically being directed against the sides and/or top of each die as illustrated by arrows 74. The dies, and thus the castings therewithin, are subjected to the radiant energy source for a desired length of time, depending upon the metal of the castings being heat treated. The radiant energy generally is absorbed by the dies, causing the temperature of the dies to correspondingly increase so as to heat the dies and thus the castings there within from the inside out.
Fig. 4 shows a further alternative heating chamber 80 for use in the in-die heat treatment of the present invention. As shown in Fig. 4, the heating chamber 80 generally is an elongated furnace having an insulated floor, ceiling and side and includes a conveyor or other transport mechanism 84 for moving the dies, with their castings therewithin, through the heating chamber 80 in the direction of arrows 82. The heating chamber 80 further includes an induction energy source 83 for applying induction energy to the dies or mold packs, and thus to the castings and sand cores 53 and 54 contained therewithin. The induction energy source generally can include a conduction coil, microwave energy source or other known induction energy sources or generators, and, as with the radiant energy source of Fig. 3, can be positioned in the ceiling of the heating chamber 80, above the dies, along the sides of the heating chamber, or both. The induction energy source will create a high energy field of waves, indicated by arrows 84, that are directed toward the top and/or sides of the dies 51 and are of a particular frequency or frequencies that will be absorbed by the sand cores 54 so as to cause the temperature of the sand cores and thus the castings to be increased to correspondingly heat treat the metal castings within the mold packs by heating the casting and thus the dies from the inside out.
Still a further alternative construction of a heating chamber 90 for use in the present invention for heat treatment of the castings while "in-die" by adding energy to the dies and thus the castings to increase the temperature thereof is shown in Figs. 5A and 5B. In this embodiment, the dies typically will comprise sand mold pack type dies, although flask type molds also could be used. As shown in Figs. 5A and 5B, the heating chamber 90 typically is an elongated furnace chamber that includes a conveyor or transport mechanism 91 for conveying the dies 51 with their castings 53 contained therein in the direction of arrows 92. As the dies and castings are moved through the heating chamber 90, they are passed through a low velocity oxygen chamber 93. The oxygen chamber generally includes a high pressure, upstream side 94 and a low pressure, downstream side 96 that are positioned opposite each other to assist in the drawing of the oxygen flow through the dies. As indicated by arrows 97 (Fig. 5A) and 97' (Fig. 5B), as the dies pass through the low velocity oxygen chambers of the heating chambers 90 heated oxygen gas is directed at and is forced through the dies or mold packs. As the oxygen gas is drawn or flows from the high atmospheric pressure' side to the low atmospheric pressure side, of the oxygen chamber, flowing through the dies or mold packs, a percentage of oxygen is combusted with the binder material of the sand mold packs and sand cores, so as to enhance the combustion of the binder material within the heating chamber. As a result, the mold packs and their castings are further supplied with energy from the enhanced combustion of the binder material thereof and the oxygen, which thus increases the temperature of the castings in the mold packs, while at the same type breaking down the binder of the mold packs and sand cores for ease of removal and reclamation. As shown in Figs. 5A and 5B, the low velocity oxygen chamber can be oriented in either a vertical orientation (shown in Fig. 5A) or a substantially horizontal orientation (shown in Fig. 5B) for forcing the hot oxygen gasses through the mold packs, depending upon size and space configurations for the heating chamber.
Further, it is also possible to carryout the increasing of the temperature of the dies or sand mold packs for in-die heat treatment of the castings, while reducing the potential heat loss transfer between the molten material and die surfaces, and the atmosphere, by including an energy source within the die itself.
In such an embodiment, the dies typically are formed with cavities or chambers in close proximity to the internal cavity in which the casting is formed. A heated fluid media, such as thermal oils, water, or similar or other material capable of readily retaining heat is then be supplied to the die structure being received within these cavities. This heated fluid tends to increase and help maintain the temperature of the casting at a desired level needed for heat treatment.
As a result of applying energy to the die or mold packs themselves, the dies are heated to desired temperatures and can be maintained at a such temperatures as needed for heat treating the castings being formed therewithin as the molten metal of the casting is solidified within the dies. Such in-die heat treatment of the castings can significantly cut the processing time required for heat treating castings, for example, from approximately 250 minutes to as low as approximately 50 minutes, as the metal of the castings is generally elevated and stabilized at the heat treatment temperature shortly after pouring of the molten metal material into the dies, so that heat treatment of the castings can take place in a relatively short period of time following the pouring of the molten metal material into the dies. The raising of the temperature of the dies to the heat treatment temperature for heat treating the castings, further enhances the breakdown and combustion of the combustible organic binders of the sand cores and/or sand molds, if used, so as to further reduce the time required for the heat treatment and dislodging and reclamation of the sand cores and sand molds of the casting process.
Following the heat treatment of the castings in their dies within the heat treatment station 62, the castings typically are removed from their dies and can be moved to an additional heat treatment station for completion of the heat treatment of the castings, as needed, and for sand core removal and possible reclamation of the sand materials of the cores. The castings are then moved into a quenching station 100 for quenching and cooling of the castings. Alternatively, as shown in Fig. 1, the castings can be removed from their dies and transferred directly to the quenching station. The quenching station 100 typically includes a quench tank having a cooling fluid such as water or other known coolant material, but the quenching station can also comprise a chamber having a series of nozzles, indicated at 101 in Fig. 1, that apply cooling fluids such as air or water to the castings. The quenching also can take place in contiguous ancillary quenching equipment that is in close proximity to the pouring station so that cycle time and heat variations can be minimized for the setting and treatment of the molten metal material of the casting within the dies.
After heat treatment and sand removal of the castings is completed, the castings can be removed from the dies and then immersed in the quench tank of the quench station for cooling the castings before further processing, and sand removed from the castings then can be reclaimed for later reuse. In addition, as indicated in dashed lines in Fig. 1, it is also possible to transfer the dies directly from the pouring station to the quenching station. For example, where the dies from the pouring station are heated to a heat treatment temperature at or adjacent the pouring station for heat treating the castings, the dies can then be transferred directly to the quenching station.
Accordingly, the present invention enables the reduction or elimination of a requirement for further heat treating of the castings once removed from the dies, which are heated to provide solution heating time and cooled to provide the quenching effect necessary, while in-die, so as to significantly reduce the amount of heat treatment/processing time required for forming metal castings. The present invention further enables an enhanced or more efficient heat treatment and breakdown and removal of sand cores within the castings by directing fluid flows at the castings at preset positions, corresponding to known orientations or alignments of the castings and/or the dies with the castings contained therein as they are passed through a heat treatment station.

Claims

A method of processing a metal casting (53), comprising:
pouring a metal (M) in molten form into a die (51);

retaining the metal within the die (51) for a time and to a temperature sufficient to at least partially solidify the metal to form the casting (53) having a core and core openings therein;

placing the die (51) in a heat treatment station (62) for heat treating the casting (53) within the die (51) with the casting (53) aligned in a defined, indexed position; and

applying energy to the die (51) to increase the temperature of the casting (53) within the die (51) and at least partially heat treat the casting (53) while the casting (53) is within the die (51).
The method of claim 1, wherein placing the die (51) in a heat treatment station (62) comprises placing the casting (53) in its indexed position with a plurality of the core openings of the casting (53) and a series of die access openings (56) formed in said die (51) aligned in known, predefined alignment, and further heat treating the casting (53).
The method of claim 2, further comprising:
aligning the core openings of the casting (53) and/or the die access openings (56) formed in said die (51) with a plurality of nozzles (64, 64'); and

directing a heated media from the plurality of nozzles (64, 64') at and into the core

openings and/or said die access openings (56).
The method of claim 2, further comprising:
moving a plurality of nozzles (64, 64') to a first nozzle position in alignment with at least a plurality of core access openings formed in the casting (53); and

moving at least a portion of the plurality of nozzles (64, 64') to a second nozzle position, wherein the portion of the plurality of nozzles (64, 64') is in alignment with at least a second plurality of core openings formed in the casting (53).
The method of claim 1, wherein applying energy to the die (51) comprises directing radiant energy against the die (51), and heating the die (51) and casting (53) from outside the die (51) inwardly.
The method of claim 1, wherein applying energy to the die (51) mold comprises directing inductive energy from an induction energy source against the die (51) to heat the casting (53) from inside the die (51) outwardly.
The method of claim 1, wherein applying energy to the die (51) comprises moving the die (51) through a pressurized chamber, drawing a flow of oxygen gas through the die (51) to promote combustion of a combustible binder material of the die (51), and heating the casting (53) with the combustion of the binder and oxygen gas.
A system, for manufacturing of metal castings (53), comprising:
at least one die (51) in which a metal material (M) is received for forming the casting (53) having a core and core openings;

a heat treatment station (62) including a heat treatment chamber (70, 80, 90) in which said dies (51) are subjected to application of heat for at least partially heat treating the castings (53) within said dies (51); and

wherein said heat treatment station (62) includes a means for heating said dies (51) to a temperature sufficient to at least partially heat treat the castings (53) therewithin.
The system of claim 8 wherein said means for heating comprises at least one nozzle station (63) positioned along said heat treatment station (62) and having at least one nozzle (64, 64') initially mounted in alignment with a series of die access openings (56) formed in said die (51) for applying a fluid media (F) to said die (51) for heating said die (51) and dislodging core material of a core (54) within the casting (53).
The system of claim 8 wherein said means for heating comprises a radiant energy source (73) mounted in said heating chamber (70) so as to direct radiant energy toward said die (51).
The system of claim 8 wherein said means for heating comprises an induction energy source (83) mounted within said heating chamber (80) for transmitting inductive energy to said die (51).
The system of claim 8 wherein said means for heating comprises an oxygen chamber (93) positioned along said heat treatment station (62) for directing a flow of oxygen through said dies (51) for reacting and combusting with a binder material, in order to increase the temperature of the castings (53) within said dies (51).
The system of claim 9 wherein said means for heating further includes an energy source positioned in said heating chamber (70, 80, 90) for applying energy to said die (51) to heat said die (51) from inside out.
The system of claim 8 further comprising a quenching station (100) for quenching the heat treated castings (53).