Abstract
Hot-chamber die casting systems for casting aluminum, copper, titanium, and their alloys, as well as other high temperature and/or reactive metals. The hot-chamber die casting system comprises an injection system that includes a cylinder, a plunger reciprocable within the cylinder, and a gooseneck that defines a passage fluidically connected to a cylinder chamber within the cylinder, wherein surfaces of the cylinder, plunger, and gooseneck that contact a molten metal during injection casting are defined by a refractory material that does not react with the molten metal, or have been treated to reduce the rate of dissolution of their surface material into the molten metal during injection casting.
Claims
1. A hot-chamber die casting system for injection casting a molten metal, the hot-chamber die casting system having an injection system that is at least partially immersed in a pool of the molten metal, the injection system comprising: a cylinder having a chamber therein; a plunger reciprocable within the chamber of the cylinder; and a gooseneck defining a passage fluidically connected to the chamber within the cylinder, the passage and the chamber defining a hot chamber of the hot-chamber die casting system; wherein at least surfaces of the cylinder, plunger, and gooseneck that contact the molten metal during injection casting, or optionally the cylinder, plunger, and gooseneck in their entirety, are defined by one or more refractory metals or alloys thereof that do not react with the metal and/or exhibit dissolution rates with the molten metal that are less than the dissolution rates of ferrous alloys with the metal.
2. The hot-chamber die casting system of claim 1, wherein each of the cylinder, plunger, and gooseneck consists of the one or more refractory metals or alloys thereof.
3. The hot-chamber die casting system of claim 1, wherein each of the cylinder, plunger, and gooseneck comprises a bulk material and a shell material on the bulk material that defines the surfaces thereof that contact the molten metal during injection casting.
4. The hot-chamber die casting system of claim 3, wherein the shell material is a coating applied to surfaces of the bulk material.
5. The hot-chamber die casting system of claim 3, wherein the shell material is produced to have a cavity therein that is filled by injecting a liquid volume of the bulk material therein.
6. A method of using the hot-chamber die casting system of claim 1, the method comprising: at last partially immersing the injection system in a pool of the molten metal; and actuating the plunger to force a molten volume of the molten metal through the passage of the gooseneck and into a die mold cavity.
7. The method of claim 6, wherein the molten metal is aluminum, copper, titanium, or an aluminum alloy, copper alloy, or titanium alloy.
8. A casting formed by the method of claim 6.
9. A hot-chamber die casting system for injection casting a molten metal, the hot-chamber die casting system having an injection system that is at least partially immersed in a pool of the molten metal, the injection system comprising: a cylinder having a chamber therein; a plunger reciprocable within the chamber of the cylinder; and a gooseneck defining a passage fluidically connected to the chamber within the cylinder, the passage and the chamber defining a hot chamber of the hot-chamber die casting system; wherein each of the cylinder, plunger, and gooseneck comprises a bulk metallic material, and each of the cylinder, plunger, and gooseneck comprises refractory ceramic surfaces that contact the molten metal during injection casting and do not react with the molten metal.
10. The hot-chamber die casting system of claim 9, wherein each of the cylinder, plunger and gooseneck comprises a shell material on the bulk metallic material thereof that defines the refractory ceramic surfaces thereof that contact the molten metal during injection casting, wherein the shell material comprises the refractory ceramic material.
11. The hot-chamber die casting system of claim 10, wherein the shell material is a coating applied to surfaces of the bulk metallic material.
12. The hot-chamber die casting system of claim 10, wherein the shell material is produced to have a cavity therein that is filled by injecting a liquid volume of the bulk metallic material therein.
13. A method of using the hot-chamber die casting system of claim 9, the method comprising: at last partially immersing the injection system in a pool of the molten metal; and actuating the plunger to force a molten volume of the molten metal through the passage of the gooseneck and into a die mold cavity.
14. The method of claim 13, wherein the molten metal is aluminum, copper, titanium, or an aluminum, copper or titanium alloy.
15. A casting formed by the method of claim 13.
16. A hot-chamber die casting system for injection casting a molten metal, the hot-chamber die casting system having an injection system that is at least partially immersed in a pool of the molten metal, the injection system comprising: a cylinder having a chamber therein; a plunger reciprocable within the chamber of the cylinder; and a gooseneck defining a passage fluidically connected to the chamber within the cylinder, the passage and the chamber defining a hot chamber of the hot-chamber die casting system; wherein the cylinder, plunger, and gooseneck are each formed of a ferrous material and surfaces of the cylinder, plunger, and gooseneck that contact the molten metal during injection casting have surface treatments to reduce the rate of dissolution of the ferrous material into the molten metal during injection casting.
17. The hot-chamber die casting system of claim 16, wherein the surface treatments are nitride or carbo-nitride surface treatments.
18. A method of using the hot-chamber die casting system of claim 16, the method comprising: at last partially immersing the injection system in a pool of the molten metal; and actuating the plunger to force a molten volume of the molten metal through the passage of the gooseneck and into a die mold cavity.
19. The method of claim 18, wherein the molten metal is aluminum, copper, titanium, or an aluminum, copper, or titanium alloy.
20. A casting formed by the method of claim 18.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIGS. 1a and 1b schematically represent a conventional hot-chamber die casting system and steps in the use thereof.
[0020] FIG. 2 schematically represents an injection system comprising a one-piece cylinder and gooseneck in accordance with a nonlimiting embodiment of the invention.
[0021] FIG. 3 schematically represents an injection system comprising a shell-type cylinder and gooseneck in accordance with another nonlimiting embodiment of the invention.
[0022] FIGS. 4a through 4d graphically represent experimental results of weight loss of refractory metals and H13 steel. Weight loss was measured on samples attached on a stirrer at linear speeds given in the x-axis of the diagrams. The samples were submerged into molten A380 aluminum alloy held at 650° C. for various times (10 to 40 min.). FIG. 4a: H13 vs. Ti-6Al-4V. FIG. 4b: W vs. Ti-6Al-4V. FIG. 4c: Mo vs. W. FIG. 4d: Nb vs. Mo.
[0023] FIG. 5 graphically represents a relationship between percent dissolution and submerge time in molten A380 aluminum alloy for H13 samples with six different surface conditions. The temperature of the molten A380 alloy was 650+/−51° C. and the flow rate of the molten A380 alloy was 2.41 m/s.
[0024] FIG. 6 represents soldering area fraction (“Reaction Area”) of different coatings as a function of dipping time (“Time”) when coated samples were subjected to high intensity ultrasonic vibration in a molten A380 aluminum alloy.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The present invention provides hot-chamber die casting systems for casting of aluminum and its alloys, as well as other high temperature metals such as copper, titanium, and their alloys. In particular, the systems include injection systems having a cylinder, plunger, and gooseneck that are capable of surviving contact with molten high temperature and/or reactive metals and provide the ability to cast products therewith. Further, the present invention provides methods of manufacturing and using the hot-chamber die casting systems and their components.
[0026] FIGS. 2 and 3 schematically represent two injection systems suitable for use in casting high temperature metals, such as aluminum, copper, titanium, and their alloys. For convenience, identical reference numerals are used in FIGS. 2 and 3 to denote the same or functionally equivalent elements. Each injection system shown in FIGS. 2 and 3 comprises a cylinder 116, a plunger 114 reciprocable within a chamber 115 of the cylinder 116, and a gooseneck 117 that defines a passage 118 fluidically connected to the cylinder chamber 115. An inlet 128 is provided in a sidewall of the cylinder 116, through which a molten metal (not shown) is able to enter a “hot chamber” 120 defined by the gooseneck passage 118 and the cylinder chamber 115. Hot-chamber die casting systems comprising these components may function in substantially the same manner as described previously in relation to the hot-chamber die casting system of FIGS. 1a and 1b. For example, the plunger 114 may be reciprocated within the chamber 115 of the cylinder 116 to force molten metal from a holding furnace (not shown in FIGS. 2 and 3), into the inlet 128, through the hot chamber 120, through an outlet 119 in the gooseneck 117, and into a cavity of a mold (not shown in FIGS. 2 and 3). As such, the following discussion will focus primarily on certain aspects of the injection systems represented in FIGS. 2 and 3, whereas other aspects not discussed in any detail may be, in terms of structure, function, materials, etc., essentially as was described for the system of FIGS. 1a and 1b. It should be noted that the drawings are drawn for purposes of clarity when viewed in combination with the following description, and therefore are not necessarily to scale.
[0027] FIG. 2 represents an injection system in which the cylinder 116 and gooseneck 117 are part of a one-piece (unitary) construction. The cylinder 116 and gooseneck 117 are preferably formed of a single composition, preferably a metal or alloy, that is capable of surviving prolonged contact with molten high temperature metals, and particularly an aforementioned molten “reactive” metal, i.e., a molten metal that tends to corrode and/or erode ferrous alloys during holding and injection casting and/or ferrous alloys tend to dissolve into the molten metal during holding and injection casting and possibly form intermetallic phases. The plunger 114 is also preferably formed of one or more metals that is/are capable of surviving prolonged contact with molten high temperature metals, and particularly an aforementioned molten “reactive” metal.” In particular, the cylinder 116, gooseneck 117, and plunger 114 may be formed of one or more materials that consist of or include a refractory metal, including but not limited to niobium, molybdenum, tantalum, tungsten, rhenium, titanium, vanadium, chromium, zirconium, hafnium, ruthenium, rhodium, osmium, iridium, and alloys thereof, as a majority constituent of the material. Such refractory metals are substantially nonreactive and/or have a substantially lower dissolution rate in comparison to materials commonly used in the hot-chamber die casting industry, for example, ferrous alloys such as H13 steel and cast irons. Furthermore, the cylinder 116, gooseneck 117, and/or the plunger 114 made of aforementioned refractory metals may have with their surfaces coated with a protective coating, for example, using a surface coating process such as physical vapor deposition (PVD) or chemical vapor deposition (CVD), to reduce or prevent oxidation and/or to further reduce the dissolution rate in the molten metal or alloy to be cast. Alternatively, the cylinder 116, gooseneck 117, and/or the plunger 114 may be formed of more conventional die casting mold materials, such as H13 steel, whose surfaces have been treated to be more resistive to dissolution by a molten high temperature and/or reactive metal. Suitable surface treatments include, but are not limited to, nitriding (ion plasma nitriding) and carbo-nitriding (ion plasma carbo-nitriding). Yet another alternative is to form the gooseneck 117, cylinder 116, and/or plunger 114 of a more conventional die casting mold material, such as H13 steel, and deposit a surface coating thereon of a material that is more resistive to dissolution by a molten high temperature and/or reactive metal. Suitable coating materials and deposition methods include, but are not limited to, chromium carbide (CrC) or W—Cr—Co deposited by high velocity air fuel (HVAF). Preferably, the cylinder 116, gooseneck 117, and/or the plunger 114 are formed of a material, have surfaces formed of a material, or have surfaces treated such that their surfaces have a dissolution rate that is equal to or less than the dissolution rate of titanium in a molten pool of aluminum.
[0028] FIG. 3 represents an injection system whose cylinder 116 and gooseneck 117 are again part of a one-piece (unitary) construction, but modified to have a shell-type configuration as a result of the gooseneck 117 and the cylinder 116 each being formed of at least two materials, one of which is designated a shell material 130 and another designated as a bulk material 132 located within the interior of the shell material 130. Preferably, only the shell material 130 is intended to contact the high temperature or reactive metal during injection casting, such that the bulk material 132 does not as a result of the shell material 130 effectively forming an outer layer on the bulk material 132. The use of the bulk material 132 allows for the use of materials that are not required to be resistant to the molten metal and may reduce the cost of producing the injection system while obtaining high mechanical properties and longer service life for the injection system. In contrast, the shell material 130 is capable of surviving prolonged contact with molten high temperature metals, and particularly a molten reactive metal. As such, the shell material 130 may be formed of a material that consists of or includes a refractory metal, such as those described for the embodiment of FIG. 2. Alternatively, the shell material 130 may be formed of a material that consists of or includes a refractory ceramic material, including but not limited to FeN, FeNC, CrWN, AlCrN, TiN, carbon-based materials including carbides such as VC and WC, and combinations thereof as a majority constituent of the shell material 130. The bulk material 132 may be any suitable material capable of providing support for the shell material 130 thereon, for example, steel. However, if the shell material 130 is formed of a refractory metal and is sufficiently thick to be mechanically strong enough to withstand the die casting process, the bulk material 132 could be omitted, in other words, the one-piece (unitary) construction of the injection system comprising the gooseneck 117 and cylinder 116 is hollow rather than the interior of the shell material 130 being filled with the bulk material 132.
[0029] The injection systems of FIGS. 2 and 3 may be produced with an additive manufacturing process. The additive manufacturing process could include the use of a high energy heat source, such as laser or electron beams, to melt wire or powder feed stock to build the gooseneck 117 and cylinder 116 in their entirety (FIG. 2) or build the shell and/or bulk materials 130 and 132 (FIG. 3) in a layer-by-layer or continuous process.
[0030] The injection system of FIG. 3 may be produced by initially providing the bulk material 132 as a core, and then applying a layer of the shell material 130 thereto using a suitable process, for example, physical vapor deposition, chemical vapor deposition, laser cladding, thermal spraying, additive manufacturing, explosive bonding, or other suitable layer application or deposition process. In the case of explosive bonding, the shell material 130 may be bonded to the bulk material 132 using impact generated by explosion of gun powders applied on a volume of the shell material 130. Alternatively, the shell material 130 may be formed as a hollow mold and the bulk material 132 subsequently cast within the cavity of the shell material 130, for example, through a suitable injection process.
[0031] By forming the cylinder 116, gooseneck 117, and/or plunger 114 entirely of refractory materials and/or their surfaces treated to be more resistive to a molten high temperature and/or reactive metal (FIG. 2) or to have a shell material 130 of a refractory material (FIG. 3), it is believed that the hot-chamber die casting system will have an improved operating life and be capable of producing products of improved quality. Nonlimiting embodiments of the invention will now be described in reference to experimental investigations leading up to the invention.
[0032] FIGS. 4a through 4d are graphs that show measured weight losses of samples formed of metals and alloys in molten A380 aluminum alloy, which is a widely-used die casting alloy. Samples were attached on a stirring apparatus and submerged for various durations (10, 20, and 40 minutes) in the molten A380 alloy held at 650° C. The stirring apparatus was operated at various linear speeds indicated in the x-axis of the graphs. Weight losses of the samples were measured after the indicated durations. The samples were formed of H13 (FIG. 4a), Ti-6Al-4V (FIG. 4a and FIG. 4b; labeled as “Ti”), Anviloy® (a tungsten alloy commercially available from Astaras, Inc.; FIG. 4b and FIG. 4c; labeled as “W”), Mo (FIG. 4c and FIG. 4d), and Nb-1Zr (FIG. 4d; labeled as “Nb”). The nominal composition (weight percent) of the A380 alloy was 7.5-9.5 silicon (Si), 3.0-4.0 copper (Cu), 3.0 or less iron (Fe), 0.5 or less manganese (Mn), and the remaining balance being aluminum (Al). H13 steel was used as a baseline and had a nominal composition (weight percent) of 0.40 carbon (C), 1.00 silicon (Si), 0.020 or less phosphorus (P), 0.003 or less sulfur (S), 5.3 chromium (Cr), 1.40 molybdenum (Mo), 1.0 vanadium (V), and the remaining balance being iron (Fe). Experimental results presented in FIGS. 4a through 4d indicated that the dissolution rate, or weight loss, of H13 steel in molten A380 alloy was 3.4 times higher than that of Ti-6Al-4V, 136 times higher than that of Anviloy®, 366 times higher than that of molybdenum, and 917 times higher than that of Nb-1Zr alloy. Furthermore, no brittle iron aluminide or other iron-based intermetallic phases were formed in the aluminum castings made during the investigations. Consequently, the use of Ti-6Al-4V, Anviloy®, molybdenum, and Nb-1Zr alloy to form the entirety of the gooseneck 117 and cylinder 116 of an injection system, or at least a shell material 130 thereof so that the molten metal only contacts surfaces formed by these refractory materials, can significantly reduce the weight loss and extend the service life of these components in molten A380 alloy.
[0033] FIG. 5 and Table 1 show relationships between the percent dissolution and submerge time in a melt of the A380 alloy for H13 samples with six different surface treatment conditions using a stir test method. The temperature of the molten A380 alloy was 650+/−51° C. and the flow rate of the molten metal was 2.41 m/s. Details of the experimental conditions are given in Q. Han et al., Dissolution of H13 Steel in Molten Aluminum, NADCA Transaction, 2015, Paper T15, Indianapolis, Ind., USA, incorporated herein by reference. These experimental results suggested that surface treatments such as ion plasma nitriding and ion plasma carbo-nitriding and surface coatings such as chromium carbide or W—Cr—Co deposited by HVAF significantly reduced the dissolution amount of H13 samples. Consequently, surface treatment methods of these types can be used for protecting injection systems employed to die cast molten high temperature and/or reactive metals and having components formed of ferrous metals. Boriding was less effective in reducing the weight loss of H13 steel sample under the stirring test.
TABLE-US-00001 TABLE 1 Surface finishing processes. Ion Ion Plasma HVAF: No Plasma Carbide Chromium W-Co- Coating Nitride Nitride Boriding Carbide Cr (NC) (IPN) (IPCN) (B) (CC) (HVAF) 10 min 3 0.06 0.05 2 0.1 1 20 min 11 0.09 0.07 6 0.2 1 40 min 22 0.11 0.08 15 1 6
[0034] FIG. 6 shows relationships of “Reaction Area” and dipping times for H13 samples covered with a layer of one of four different ceramic coatings deposited by PVD. The term “Reaction Area” in FIG. 6 refers to soldering area fraction (SAF), which in the investigation was the ratio of the soldered surface area (the surface area where a coating is damaged by a molten metal) to the total surface area of the coating contacted by the molten metal. The ceramic materials were BALINIT® ALCRONA (AlCrN), BALINIT® D (CrN), BALINIT® FUTURA NANO (TiAlN), and BALINIT® LUMENA (TiAlN), all commercially available from Balzers, Inc. or OC Oerlikon Corporation AG. Published properties of the ceramic coating materials are given in Table 2. Experimental results given in Table 3 were obtained under cavitation conditions in an accelerated soldering test disclosed in Q. Han et al., Accelerated Method for Testing Soldering Tendency of Core Pins, International Journal of Cast Metals Research, 2010, vol. 23, no. 5, pp. 296-302, incorporated herein by reference. Samples (¾ inch (19 mm) diameter) were submerged in molten A380 alloy held in a graphite crucible at 665+/−15° C. High intensity ultrasonic vibration was applied through the sample to the molten A380 alloy to create cavitation conditions which usually occur under die casting conditions. The power of the ultrasonic vibration was 1.5 kW, the amplitude of ultrasonic vibration at the end of each sample was 16 micrometer, and the frequency of the ultrasonic vibration was 20 kHz. The Reaction Area (SAF) value of the uncoated H13 sample was one at an elapsed time of one second, indicating that the surface of the sample was totally covered by a soldered layer. It took almost sixty seconds or longer to reach a SAF value of one for each of the coated samples. These results suggested that a chemical reaction between the molten A380 alloy and the coated H13 sample started on the coated samples much later than that on the uncoated H13 samples. Of the four commercial PVD coatings, BALINIT® LUMENA lasted longest when subjected to high intensity ultrasonic vibration. It took almost thirty to sixty seconds to reach a SAF value of one for the samples coated with a BALINIT® ALCRONA, BALINIT® D (CrN), or BALINIT® FUTURA NANO, respectively, and more than 240 seconds to reach a SAF value of 0.74 for the sample coated with the BALINIT® LUMENA coating. As such, the PVD coatings tested significantly reduced the dissolution rates of H13 in the molten aluminum alloy, and such an effect would also be expected for other aluminum alloys. Consequently, a ceramic layer can substantially reduce the dissolution rates of the gooseneck 117 or cylinder materials in molten aluminum and molten aluminum alloys.
TABLE-US-00002 TABLE 2 Die casting coatings used in investigations. Coating BALINIT ® BALINIT ® FUTURA BALINIT ® ALCRONA BALINIT ®D NANO LUMENA Material AlCrN CrN TiAlN TiAlN Hardness 3200 1750 3300 3400 (HV) Thickness 1-5 1-6 1-4 8-15 (Microns) Max Temp 1080 1300 1600 1650 (° C.) Coating Violet Grey Silver Grey Violet Grey Violet Grey Color Coating Monolayer Monolayer Nano Layer Nano Layer Type
TABLE-US-00003 TABLE 3 Soldering area fractions (SAFs) of commercial coatings after given dipping times. Dipping Time (seconds) Coatings 1 5 10 15 30 60 120 240 H13 Steel 1 BALINIT ® 0.14 0.41 0.56 0.97 1 ALCRONA BALINIT ®D 0.32 0.38 0.40 1 1 BALINIT ® 0.14 0.22 0.58 0.92 0.97 FUTURA NANO BALINIT ® 0.003 0.03 0.15 0.74 LUMENA
[0035] While the invention has been described in terms of specific or particular embodiments and investigations, it is apparent that other forms could be adopted by one skilled in the art. For example, the hot-chamber die casting system and its components could differ in appearance and construction from the embodiments described herein and shown in the drawings, functions of certain components of the system could be performed by components of different construction but capable of a similar (though not necessarily equivalent) function, and appropriate materials could be substituted for those noted. Accordingly, it should be understood that the invention is not limited to any embodiment described herein or illustrated in the drawings. In addition, the invention encompasses additional or alternative embodiments in which one or more features or aspects of the different disclosed embodiments may be combined. It should also be understood that the phraseology and terminology employed above are for the purpose of describing the disclosed embodiments and investigations, and do not necessarily serve as limitations to the scope of the invention. Therefore, the scope of the invention is to be limited only by the following claims.
