Unit Cell Titanium Casting

Abstract

A system (5) and method (800) for unit cell casting of titanium or titanium-alloys is disclosed herein. The system (5) comprises an external chamber (45), a crucible (10) positioned within the external chamber (45), an induction coil (15) positioned around the crucible, an internal chamber (40) positioned within the external chamber (45), and a mold (30) positioned within the internal chamber (40). The external chamber (45) is evacuated and a pressurized gas is injected into the evacuated external chamber (45) to create a pressurized external chamber (45). An ingot (20) is melted within the crucible utilizing induction heating generated by the induction coil (15). The internal chamber (40) is evacuated to create an evacuated internal chamber (40). The titanium alloy material of the ingot (20) is completely transferred into the mold (30) from the crucible (10) using a pressure differential created between the external chamber (45) and the internal chamber (40).

Claims

1. A method for unit cell casting of titanium or titanium-alloys, the method comprising: positioning a mold within an internal chamber; evacuating an external chamber to create an evacuated external chamber wherein a ceramic crucible containing a titanium alloy ingot is positioned therein; evacuating the internal chamber to create an evacuated internal chamber having a pressure no greater than 310.sup.2 atmosphere; injecting a pressurized gas into the evacuated external chamber to create a pressurized external chamber with a pressure in excess of 1 atm; melting the titanium alloy ingot within the ceramic crucible utilizing induction heating generated by an induction coil to superheat the titanium alloy material in excess of its melting temperature; transferring the completely melted titanium alloy material into the mold from the crucible using a pressure differential created between the external chamber and the internal chamber; wherein the crucible is not cooled; wherein a high pressure differential in maintained between the external chamber and the internal chamber during the transfer of the melted titanium alloy material; wherein the PLC controls power to the induction coil to position the induction coil relative to the titanium alloy ingot; wherein the pressure of the internal chamber and the pressure of the external chamber are monitored and communicated to the PLC during the casting process, and wherein the PLC controls the casting process based on the pressure of the internal chamber and the pressure of the external chamber.

2. The method according to claim 1 wherein the pressurized gas is argon.

3. The method according to claim 1 wherein the centering feature is a seat.

4. The method according to claim 1 wherein an atmospheric pressure of the evacuated internal chamber ranges from 310.sup.2 atmosphere to 9.8710.sup.7 atmosphere.

5. The method according to claim 1 wherein the crucible is a single Yttria-based barium infused shell layer having a thickness ranging from 0.015 inch to 0.060 inch, and comprised of a binder with a slurry ratio between 1:1.5 and 1:3.5.

6. The method according to claim 1 wherein a power level to the induction coil is more than 70 kiloWatts.

7. The method according to claim 1 wherein the centering feature is a plurality of stand-offs in a wall of the ceramic crucible.

8. The method according to claim 1 wherein a power level to the induction coil is more than 90 kiloWatts.

9. The method according to claim 1 wherein an atmospheric pressure of the evacuated internal chamber ranges from 9.8710.sup.7 atmosphere to 9.8710.sup.13 atmosphere

10. A system method for unit cell casting of titanium or titanium-alloys, the system comprising: an external chamber; a ceramic crucible positioned within the external chamber; an induction centered on the upper third of the titanium alloy ingot in the ceramic crucible; an internal chamber positioned within the external chamber; and a mold positioned within the internal chamber; wherein a ceramic crucible containing a titanium alloy ingot is positioned therein, wherein the titanium alloy ingot is centered within the ceramic crucible using a centering feature; wherein the pressure of the internal chamber and the pressure of the external chamber are monitored and communicated to the PLC during the casting process, and wherein the PLC controls the casting process based on the pressure of the internal chamber and the pressure of the external chamber; wherein the external chamber is evacuated to create an evacuated external chamber; wherein a pressurized gas is injected into the evacuated external chamber to create a pressurized external chamber; wherein the titanium alloy ingot is melted within the ceramic crucible utilizing induction heating generated by an induction coil to superheat the titanium alloy material in excess of its melting temperature; wherein the crucible is composed of Silica and coated with a Yttria based slurry and stucco system; wherein the internal chamber is evacuated to create an evacuated internal chamber; wherein the titanium alloy material is completely transferred into the mold from the crucible using a maximum pressure differential created between the external chamber and the internal chamber.

2. A method for unit cell casting of titanium or titanium-alloys, the method comprising: positioning a mold within an internal chamber; pre-heating a titanium alloy ingot; evacuating an external chamber to create an evacuated external chamber wherein a ceramic crucible containing the pre-heated titanium alloy ingot is positioned therein; evacuating the internal chamber to create an evacuated internal chamber having a pressure no greater than 310.sup.2 atmosphere; injecting a pressurized gas into the evacuated external chamber to create a pressurized external chamber with a pressure in excess of 1 atm; melting the titanium alloy ingot within the ceramic crucible utilizing induction heating generated by an induction coil; transferring the completely melted titanium alloy material into the mold from the crucible using a pressure differential created between the external chamber and the internal chamber; wherein a high pressure differential in maintained between the external chamber and the internal chamber during the transfer of the melted titanium alloy material; wherein the PLC controls power to the induction coil to position the induction coil relative to the titanium alloy ingot; wherein the pressure of the internal chamber and the pressure of the external chamber are monitored and communicated to the PLC during the casting process, and wherein the PLC controls the casting process based on the pressure of the internal chamber and the pressure of the external chamber.

12. The method according to claim 11 wherein the pressurized gas is argon.

13. The method according to claim 11 wherein a frequency generated in the induction coil ranges from 1 kilo-Hertz to 50 kilo-Hertz.

14. The method according to claim 11 further comprising a plurality of titanium alloy ingots ranging from 2 to 6 ingots.

15. The method according to claim 14 wherein each of the plurality of titanium alloy ingots has a thickness ranging from 1 mm to 10 mm, and a height ranging from 2 cm to 20 cm.

16. The method according to claim 11 wherein the internal chamber is preheated at a temperature ranging from 1150 C. to 1250 C.

17. The method according to claim 11 wherein a PLC determines when to melt the titanium alloy based on the pressures of the internal chamber and the external chamber.

18. The method according to claim 11 wherein the PLC determines when to change the pressure of internal chamber and the external chamber.

19. The method according to claim 11 wherein an atmospheric pressure of the evacuated internal chamber ranges from 9.8710.sup.7 atmosphere to 9.8710.sup.13 atmosphere

20. The method according to claim 11 wherein a power level to the induction coil is more than 60 kiloWatts.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0016] FIG. 1 is an illustration of a unit-cell casting system.

[0017] FIG. 2 is an isolated view of an interior chamber, crucible, induction coils and mold of the unit-cell casting system, showing placement of the induction coils at a lower section of the crucible.

[0018] FIG. 2A is an isolated view of an interior chamber, crucible, induction coils and mold of the unit-cell casting system, showing placement of the induction coils at an upper section of the crucible.

[0019] FIG. 2B is an isolated view of an interior chamber, crucible, induction coils and mold of the unit-cell casting system, showing an insulation material wrapped around the mold.

[0020] FIG. 3A is an illustration of a technician pre-heating a mold in an oven.

[0021] FIG. 3B is an illustration of a technician attaching the pre-heated mold to a lid of the internal container.

[0022] FIG. 3C is an illustration of a technician attaching the lid to the internal container.

[0023] FIG. 3D is an isolated view of the internal container.

[0024] FIG. 3E is an isolated view of the lid of the internal container.

[0025] FIG. 3F is an isolated view of the internal chamber of the internal container showing infrared heaters.

[0026] FIG. 4 is an illustration of a unit-cell casting system during an external chamber evacuation step.

[0027] FIG. 4A is an illustration of a unit-cell casting system during an external chamber pressurization step.

[0028] FIG. 4B is an illustration of a unit-cell casting system during an ingot melting step.

[0029] FIG. 5 is an illustration of a PLC unit and computer for a unit cell casting system.

[0030] FIG. 6 is a block diagram of a unit cell casting method.

[0031] FIG. 7 is an isolated view of a crucible for a unit cell casting system.

[0032] FIG. 8 is a flow chart of a method for unit cell titanium casting.

[0033] FIG. 9 is a flow chart of a method for unit cell titanium casting.

[0034] FIG. 10 is a flow chart of a method for unit cell titanium casting.

[0035] FIG. 11 is an illustration of a PLC unit, an operator's computer for a unit cell casting system, an internal chamber with monitoring connections.

[0036] FIG. 12 is an illustration of a PLC unit, an operator's computer for a unit cell casting system, an internal chamber with monitoring connections.

DETAILED DESCRIPTION OF THE INVENTION

[0037] In the two chamber casting system, when utilizing Titanium as the target material to melt and fill a pattern mold or molds, there can be difficulties to fill those molds due to the relative viscosity of titanium. In order to overcome the challenge of completely filling the pattern mold, the titanium is heated to a temperature past its melt point and preferably the material is superheated. This is done in the two-chamber casting system type of equipment where the crucible is not cooled (as in typical casting practices). Heating the material past its melt point and approaching and/or exceeding the superheated state increases the fluidity of the material and allows the opportunity to fill complex and/or thin-wall pattern molds.

[0038] In the two chamber casting system, the target material (placed in the crucible, and subsequently melted through the use of an induction coil) is typically a single ingot cut from bar stock utilized at room temperature. In order to accelerate the melting of the target material and reduce cycle times, it is necessary to preheat the ingot to higher temperatures (>300 C). This causes a faster heating and subsequent melting of the target material thus reducing the time necessary to evacuate the material from the crucible into the pattern mold. The accelerated process also reduces the potential for reaction of the target material and may allow for more complete fill of complex geometries.

[0039] Utilizing the two chamber casting system, one of the primary tenets is the use of a crucible in order to contain the target material during melt and prior to evacuation into the pattern mold. In order to reduce operating costs while still allowing the electromagnetic forces from the induction coil to act upon the target material, the crucible should be formed of a molded crucible formed of >90% Yttria. This will allow for the crucible to be reused and also minimize any reaction between the crucible and the target material during melt.

[0040] Utilizing the two chamber casting system, one of the primary tenets is the use of a crucible in order to contain the target material during melt and prior to evacuation into the pattern mold. In order to reduce operating costs while still allowing the electromagnetic forces from the induction coil to act upon the target material, the crucible should be formed of a molded crucible formed of >90% Zirconia. This will allow for the crucible to be reused and reduce overall cost due to crucible usage and materials.

[0041] Utilizing the two chamber casting system, one of the primary tenets is the use of a crucible in order to contain the target material during melt and prior to evacuation into the pattern mold. In order to reduce operating costs while still allowing the electromagnetic forces from the induction coil to act upon the target material, the crucible is preferably formed of a molded crucible formed of Yttria and infused with Barium. This will provide the benefits of a molded Yttria crucible (reusable, low reactivity) with the benefit of the target material being less apt to stick to the surface thus providing better evacuation and higher chance of reuse.

[0042] As shown in FIG. 1, a unit cell titanium casting system 5 comprises an external container 44, an internal container 39, a vacuum mechanism 60, a crucible 10, an induction coil 15, a coil electrical generation mechanism 25, and a mold 30. The external container 44 defines an external chamber 45. The internal container 39 defines an internal chamber 40. The vacuum mechanism 60 includes a vacuum line 71, a vacuum connector 70 and pressure gauges 75a and 75b. The vacuum mechanism 60 is utilized to evacuate and pressurize the external chamber 45 and the internal chamber 40 in order to create a pressure differential between the internal chamber 40 and the external chamber 45.

[0043] The crucible 10 is preferably composed of a ceramic material. In a most preferred embodiment, the crucible 10 is composed of a first layer 11a, a second layer 11b and a silica based third layer 11c, as shown in FIG. 7. A metal ingot 20 is placed within the interior of the crucible 10. The metal ingot 20 is preferably a titanium alloy material. The volume of the crucible 10 preferably corresponds to the amount of metal necessary for forming the article. The interior of the crucible 10 preferably has a diameter ranging from 15 centimeters (cm) to 90 cm, more preferably from 35 cm to 60 cm. A height of the crucible 10 preferably ranges 30 cm to 200 cm, and more preferably from 60 cm to 100 cm.

[0044] A connection nozzle 27 is connected between a bottom opening (not shown) of the crucible 10 and an opening to the mold 30. The connection nozzle 27 allows the melted metal material from the ingot 20 to flow into the mold 30 for casting of the article. Specifically, the size of connection nozzle 27 is determined based on the size and shape of the cavity of the mold 30, and is preferably from 5 cm to 100 cm, and more preferably from 15 cm to 50 cm.

[0045] The induction coil 15 is wrapped around the crucible 10. The induction coil 15 is energized to generate an electromagnetic force to melt the metal ingot 20 (e.g., titanium alloy ingot) within the crucible 10. The coil electrical generation mechanism 25 provides the electricity to the induction coil 15. As shown in FIG. 2, the induction coil 15 is wrapped around a bottom section 10b of the crucible 10. This melts the bottom of the ingot 20 first. As shown in FIG. 2A, the induction coil 15 is wrapped around an upper section 10a of the crucible 10. This melts the top of the ingot 20 first.

[0046] In order to optimize the ability of the target material to seal around the port of a ceramic crucible 10, the induction coil 15 is preferably centered on the upper third of the ingot 20. This positioning allows the induction coil 15 to first act on the upper portion of the ingot 20 (melting the material from the top down), causing molten material to cascade around the still-solid ingot 20 and forming a seal before the electromagnetic forces of the induction coil 15 affect the remaining material.

[0047] Alternatively, in order to fully utilize the electromagnetic forces of the induction coil 15, to include the electromagnetic stirring of the melt, the induction coil 15 is positioned towards the bottom 10b of the ceramic crucible 10. This positioning allows for a uniform melt as molten material cascades onto itself and also increased homogeneity of the pour as the electromagnetic forces can better act on the molten material prior to it being evacuated from the crucible 10.

[0048] Melting of the ingot 20 of titanium alloy is carried out in a vacuum condition for induction melting. The induction coil 15 is connected to the coil electrical generation mechanism 25.

[0049] The ceramic crucible 10 is utilized for vacuum induction melting of the titanium alloy. The ceramic material does not interfere with the fielding effect of the electromagnetic force, and the electro-magnetic induction energy generated by the induction coil 15 is fully focused on melting the ingot of titanium alloy.

[0050] In an embodiment shown in FIG. 2B, an insulating material 31 is wrapped around the mold 30. During casting pattern molds are preheated prior to use in order to improve the flow of material into the mold itself and to better allow the mold 30 to fill completely. Due to the nature of titanium materials, and the melting process itself, the more that heat loss is minimized, the greater time the material has to flow and fill the mold 30 prior to solidification. To this end, pattern mold heat is retained through the use of an insulating material 31 (e.g.: Kaolin wool) thereby extending the useful period of the mold 30 prior to the pour and allowing for better fill, including filling of more difficult molds (e.g., thin walled castings).

[0051] As shown in FIGS. 3A, 3B, 3C, 3D and 3E, the mold 30 is preheated in an oven 80. During unit cell casting, pattern molds 30 are preheated prior to use in order to improve the flow of material into the mold 30 itself and to better allow the mold 30 to fill completely. Due to the nature of titanium materials, and the melting process itself, there is a likely correlation between the temperature of the mold 30 and the ability to fill complex and/or thin walled pattern molds 30. Temperatures testing include 1050 C., 1060 C., 1100 C., 1150 C., 1200 C., 1250 C. and 1260 C. The pre-heated mold is removed from the 80 and attached to a lid 35 of the internal container 39.

[0052] In an alternative embodiment shown in FIG. 3F, infrared heaters 50a and 50b are used to maintain the heat of the mold 30 within the internal chamber 40. Due to the nature of titanium materials, and the melting process itself, the more that heat loss is minimized, the greater time the material can flow and fill the mold 30 prior to solidification. To this end, pattern mold heat is retained through the use of infrared heaters 50a and 50b placed within the internal walls of the internal chamber 40 of the internal container 39 in order to minimize pattern mold cool down and improve the ability to cast complex and/or thin-walled parts.

[0053] FIGS. 4, 4A and 4B illustrate the casting process using a pressure differential between the external chamber 45 and the internal chamber 40 to assist in the flow of melted titanium alloy materials into a mold 30.

[0054] FIG. 5 illustrates a programmable logic computer (PLC) and operator computer 91 utilized with the unit cell casting system 5.

[0055] FIG. 6 is a block diagram of a unit cell casting method 600. At step 601, an ingot 20 is prepared for casting. The single ingot 20 is utilized to manufacture a single article such as a golf club head 29. As opposed to manufacturing multiple articles in a single process, which results in the loss of material, the present invention manufactures only a single article in each process. At step 602, the mold 30 is preheated in an oven. At step 603, the external chamber 45 is evacuated. At step 604, the external chamber 45 is pressurized with an argon gas. At step 605, the internal chamber 40 is evacuated. At step 606, the induction coil 15 is energized and at step 607 the ingot 20 is melted within the crucible 10. At the step 608, the melted material flows into mold 30. At step 609, the de-molding process occurs. At step 610, the article (golf club head) 29 is finished. A frequency generated in the induction coil ranges from 1 kilo-Hertz to 50 kilo-Hertz, and a power ranges from 15 kilo-Watts to 50 kilo-Watts. An atmospheric pressure of the evacuated internal chamber ranges from 310.sup.2 atmosphere to 9.8710.sup.7 atmosphere. An atmospheric pressure of the evacuated internal chamber ranges from 9.8710.sup.7 atmosphere to 9.8710.sup.13 atmosphere.

[0056] As shown in FIG. 7, the first layer 11a and the second layer 11b are preferably composed of yttrium oxide and other materials. Yttrium oxide is highly inert to titanium in a high-temperature environment resulting in no chemical reaction between the two materials. Yttrium oxide also isolates the ceramic material from the titanium during the melting process to prevent reaction between them to ensure the smooth melting of the titanium-alloy. The third layer 11c of the crucible 10 is preferably composed of silicon dioxide and other materials. The silicon dioxide resists the metallic expansion and thermal stress during the melting process to ensure strength of the crucible.

[0057] A preferred thickness of the first layer 11a is from 0.5 mm to 1.5 mm and the preferred thickness range of the crucible 10 is from 5 mm to 15 mm.

[0058] A method 800 for unit cell casting of titanium or titanium-alloys is shown in FIG. 8. At block 801, a pressure of an internal chamber is monitored utilizing a first vacuum gauge. At block 802, a pressure of an external chamber is monitored utilizing a second vacuum gauge. At block 803, the pressure of the internal chamber and the pressure of the external chamber are transmitted to a programmable logic controller (PLC). At block 804, a mold is positioned within the internal chamber. At block 805, an external chamber is evacuated to create an evacuated external chamber having a pressure no greater than 310.sup.2 atmosphere, wherein a ceramic crucible containing a titanium alloy ingot is positioned therein. At block 806, the internal chamber is evacuated to create an evacuated internal chamber having a pressure no greater than 310.sup.2 atmosphere, wherein the external chamber and the internal chamber have an equal pressurization. At block 807, the titanium alloy ingot is melted within the ceramic crucible utilizing induction heating generated by an induction coil positioned around the ceramic crucible. At block 808, the completely melted titanium alloy material is transferred into the mold from the crucible using a pressure equalization between the external chamber and the internal chamber. A pressure equalization is maintained between the external chamber and the internal chamber during the melting of the titanium alloy ingot. The pressure of the internal chamber and the pressure of the external chamber are monitored and communicated to the PLC during the casting process, and wherein the PLC controls the casting process based on the pressure of the internal chamber and the pressure of the external chamber.

[0059] A method 900 for unit cell casting of titanium or titanium-alloys is shown in FIG. 9. At block 901, a pressure of an internal chamber is monitored utilizing a first vacuum gauge. At block 902, a pressure of an external chamber is monitored utilizing a second vacuum gauge. At block 903, the pressure of the internal chamber and the pressure of the external chamber are transmitted to a programmable logic controller (PLC). At block 904, a mold is positioned within the internal chamber. At block 905, an external chamber is evacuated to create an evacuated external chamber having a pressure no greater than 310.sup.2 atmosphere, wherein a ceramic crucible containing a titanium alloy ingot is positioned therein. At block 906, the internal chamber is evacuated to create an evacuated internal chamber having a pressure no greater than 310.sup.2 atmosphere, wherein the external chamber and the internal chamber have an equal pressurization. At block 907, the titanium alloy ingot is melted within the ceramic crucible utilizing induction heating generated by an induction coil positioned around the ceramic crucible. At block 908, a pressurized gas is injected into the evacuated external chamber to create a pressurized external chamber with a pressure in excess of 1 atm, wherein the pressure differential between the external chamber and the internal chamber is maximized. At block 909, the completely melted titanium alloy material is transferred into the mold from the crucible using a pressure equalization between the external chamber and the internal chamber. A high pressure differential in maintained between the external chamber and the internal chamber during the transfer of the melted titanium alloy material. The pressure of the internal chamber and the pressure of the external chamber are monitored and communicated to the PLC during the casting process, and wherein the PLC controls the casting process based on the pressure of the internal chamber and the pressure of the external chamber.

[0060] A method 1000 for unit cell casting of titanium or titanium-alloys is shown in FIG. 10. At block 1001, a mold is positioned within an internal chamber of a casting chamber. At block 1002, an external chamber is evacuated to create an evacuated external chamber wherein a ceramic crucible containing a titanium alloy ingot is positioned therein. At block 1003, the internal chamber is evacuated to create an evacuated internal chamber having a pressure no greater than 310.sup.2 atmosphere. At block 1004, the titanium alloy ingot is melted within the ceramic crucible utilizing induction heating generated by an induction coil positioned around the ceramic crucible, wherein the external chamber and the internal chamber are at an equal pressurization. At block 1005, a pressurized gas is injected into the evacuated external chamber to create a pressurized external chamber with a pressure in excess of 1 atmosphere. At block 1006, a high pressure differential is utilized between the external chamber and the internal chamber to flow the completely melted titanium alloy material into the mold from the crucible.

[0061] FIG. 11 illustrates a PLC 90, an operator's computer 91 and an apparatus 5 for a system for unit cell titanium casting.

[0062] FIG. 12 illustrates a PLC 90, an operator's computer 91 and an internal chamber with an optical pyrometer for a system for unit cell titanium casting. The optical pyrometer monitors the temperature of the internal chamber.

[0063] Those skilled in the pertinent art will recognize that materials other than titanium and titanium alloy may be cast in the unit cell casting system without departing from the scope and spirit of the present invention.

[0064] From the foregoing it is believed that those skilled in the pertinent art will recognize the meritorious advancement of this invention and will readily understand that while the present invention has been described in association with a preferred embodiment thereof, and other embodiments illustrated in the accompanying drawings, numerous changes, modifications and substitutions of equivalents may be made therein without departing from the spirit and scope of this invention which is intended to be unlimited by the foregoing except as may appear in the following appended claims. Therefore, the embodiments of the invention in which an exclusive property or privilege is claimed are defined in the following appended claims.