WO2019118723A1

WO2019118723A1 - High pressure metal melt and solidification process and apparatus

Info

Publication number: WO2019118723A1
Application number: PCT/US2018/065444
Authority: WO
Inventors: Vivek M. Sample; Michael J. CARDINALE; Raymond J. Kilmer; Evan C. WAITKUS
Original assignee: Arconic Inc
Current assignee: Howmet Aerospace Inc
Priority date: 2017-12-14
Filing date: 2018-12-13
Publication date: 2019-06-20
Anticipated expiration: 2020-06-14

Abstract

An apparatus and process for continuous formation of a metal product in which metal powder feedstock, under a high pressure to prevent boiling of low boiling point elements, is formed into a melt which is then passed through an engineered orifice into a splat cooling chamber to form a solid product shape such as flakes, spherical powders, rods or sheets.

Description

HIGH PRESSURE METAL MELT AND SOLIDIFICATION PROCESS AND

APPARATUS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of United States Provisional Application Serial Number 62/598,589 filed December 14, 2017, which is incorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

[0002] This disclosure generally relates to apparatuses for manufacturing metal products and more particularly to metal alloys such as aluminum alloys produced by melting various metal components and ingredients together.

BACKGROUND

[0003]The Aluminum Association Global Advisory Group defines“aluminum alloys” as“aluminum which contains alloying elements, where aluminum predominates by mass over each of the other elements and where the aluminum content is not greater than 99.00%.” (Global Advisory Group GAG - Guidance, GAG Guidance Document 001 , Terms and Definitions, Edition 2009-01 , March 2009, § 2.2.2.) An“alloying element” is a“metallic or non-metallic element which is controlled within specific upper and lower limits for the purpose of giving the aluminum alloy certain special properties” (§ 2.2.3). For example, a casting alloy is defined as“alloy primarily intended for the production of castings,” (§ 2.2.5) and a“wrought alloy” is“alloy primarily intended for the production of wrought products by hot and/or cold working” (§ 2.2.5).

SUMMARY OF THE DISCLOSURE

[0004]As used herein,“multi-component alloy product” and the like means a product with a metal matrix, where at least four different elements making up the matrix, and where the multi-component product comprises 5-35 at. % of the at least four elements. In one embodiment, at least five different elements make up the matrix, and the multi- component product comprises 5-35 at. % of the at least five elements. In one embodiment, at least six different elements make up the matrix, and the multi- component product comprises 5-35 at. % of the at least six elements. In one embodiment, at least seven different elements make up the matrix, and the multi- component product comprises 5-35 at. % of the at least seven elements. In one embodiment, at least eight different elements make up the matrix, and the multi- component product comprises 5-35 at. % of the at least eight elements. As described below, additives may also be used relative to the matrix of the multi-component alloy product.

[0005] This disclosure describes a novel apparatus and process for continuous formation of a metal alloy granulated product, wire, sheet or ingot via an isothermal process in which powdered metal feedstock, such as a finely granulated metal feedstock, under a high pressure inert environment, is introduced into a two stage melting furnace, melted, and then rapidly cooled into a solid form product, all under a high pressure environment. The apparatus and process may be utilized to form binaries, ternaries, intermetallic and multicomponent alloy products.

[0006]A feedstock supply of at least a low boiling point element and a high melting point element is gathered in a pressurizable receiver. This feedstock may be in any form such as fine or course granulated material or powder. This feedstock is first introduced into the receiver through a first valve which is then closed, and the receiver pressurized to ensure a nonreactive environment. This feedstock is then passed through a second valve into a two stage melting furnace.

[0007] The first stage of the melting furnace includes an induction melting chamber. This chamber experiences large thermal gradients as the feedstock is introduced at room temperature and heated to form a molten mass. The second stage of the melting furnace is an accumulator that is maintained at essentially isothermal conditions so as to provide a uniform mixture and distribution of constituent elements within the melt. The melt is then passed through a discharge device into a cooling chamber, preferably a splat cooling chamber where it is rapidly cooled while at pressure to a solid state product structure that maintains a uniform distribution of constituent elements within the solid state structure. The solid state product may be in the form of flakes, spheres, wire, or sheet depending on the configuration of the discharge device and the cooling mechanism within the splat cooling chamber. The product is then collected, pressure reduced, and the product discharged for subsequent processing and use. One such use of the solid state product produced via the apparatus and process described herein is as feedstock for additive manufacturing processes.

[0008] . The process and apparatus may be operated in essentially a continuous manner by introducing a feedstock portion into a pressurizable receiver, removing air from the receiver and pressurizing the receiver with a nonreactive gas such as an inert gas, transferring the pressurized feedstock portion from the receiver into a melting furnace pressurized with the inert gas, heating the feedstock portion to form a melt, passing the melt into a pressurized accumulator chamber, discharging a portion of the melt from the accumulator chamber through a discharge device into a splat cooler where the portion of the melt is very rapidly cooled into a solid state while at pressure, and sequentially repeating the introducing, pressurizing, transferring, melting, passing, discharging and cooling operations until a desired quantity of solidified product is produced. The solidified product is then collected, pressure reduced to atmospheric, and the collected product released for further processing and/or use.

[0009] An apparatus in accordance with an exemplary embodiment of the present disclosure preferably includes a pressurizable feedstock receiver connected via a first valve to a feedstock supply of feedstock for producing a metal product that includes at least a low boiling point element and a high melting point element. The feedstock preferably includes the low melting point element and the high melting point element. The apparatus also includes a pressurizable feedstock induction melting chamber for producing a melt. The melting chamber is connected to the receiver via a second valve. A pressurizable accumulator chamber is connected to the feedstock induction melting chamber via an internal stem plug valve. The accumulator chamber is configured to maintain the melt therein at a constant temperature. The apparatus also includes a discharge device and a pressurizable cooling chamber connected to the accumulator chamber through the discharge device. During operation, the induction melting chamber, the accumulator chamber, the discharge device and the cooling chamber are pressurized to a predetermined pressure at least greater than a boiling point of the low boiling point element of the feedstock. The second valve is preferably remotely operated such that the valve may be opened only when the receiver and melting chamber are at the

predetermined pressure.

[00010] The apparatus may also include a pressurizable collection chamber connected to the cooling chamber via a third valve. The discharge device preferably includes a divergent nozzle and may include multiple orifices opening into the cooling chamber. The internal plug valve is preferably operable to maintain a predetermined level band of melt in the accumulator chamber. Preferably

pressurization of the various chambers is accomplished with a nonreactive gas such as argon. In addition, the nonreactive gas may be accompanied by an additive gas, for example, such as nitrogen or hydrogen.

[00011] The melt is preferably driven from the melt chamber to the accumulator chamber during operation by a differential pressure applied between the melting chamber and the accumulator chamber.

[00012] A process in accordance with the present disclosure may be viewed as including introducing a portion of feedstock including at least one of a low boiling point element and at least one of a high melting point element into a pressurizable receiver via a first valve, pressurizing the receiver with a nonreactive gas to a predetermined pressure greater than a boiling point of the low boiling element to provide a portion of pressurized feedstock, transferring the portion of pressurized feedstock into a pressurized induction melting chamber connected to the receiver via a second valve at the predetermined pressure, heating the portion of pressurized feedstock to form a melt, passing the melt to a pressurized accumulator chamber connected to the feedstock induction melting chamber through a third valve, passing the melt accumulated in the accumulator chamber through a discharge device to a pressurized cooling chamber, and cooling the melt to a solid form product in the cooling chamber. This method or process may further include repeating the introducing, pressurizing, transferring, melting, passing, and cooling operations for a next portion of feedstock thereby continuously forming product.

[00013] In some embodiments, pressurizing includes introducing a partial pressure of another gas selected from the group consisting of nitrogen and hydrogen. In one or more embodiments the predetermined pressure is also sufficient to prevent boiling of any additive introduced into the melt in addition to the feedstock. This feedstock may be granulated or may be a powder or may be a combination of both.

[00014] The process may further include operations of cooling the melt in the cooling chamber by passing the solidifying melt between parallel rollers. The process may alternatively include cooling the melt in a splat cooling chamber by passing the solidifying melt over rotating cold drums. The nonreactive gas may be an inert gas. In some embodiments, the inert gas and the additive gas are both introduced in one or more of the receiver, the melting chamber, the accumulator chamber and the cooling chamber. [00015] In some embodiments, the inert gas and the additive gas may pressurize the accumulator chamber prior to passing the melt into the accumulator chamber. In another exemplary embodiment, the nonreactive gas may be an inert gas such as Argon. The operation of passing may include controlling differential pressure within a narrow band to drive the melt into the cooling chamber. The flow of melt into the splat cooling chamber may preferably be controlled by maintaining a required differential pressure.

[00016] In one or more embodiments of the present disclosure an exemplary apparatus may include a pressurizable feedstock receiver connected via a first valve to a feedstock supply of feedstock for producing a metal product that includes at least a low boiling point element and a high melting point element.

[00017] In any one or more of the above embodiments, the feedstock may preferably include both the low melting point element and the high melting point element.

[00018] In one or more of the above embodiments, the apparatus also includes a pressurizable feedstock induction melting chamber for producing a melt.

[00019] In one or more of the above embodiments, the melting chamber is connected to the receiver via a second valve.

[00020] In one or more of the above embodiments, the pressurizable accumulator chamber is connected to the feedstock induction melting chamber via an internal stem plug valve. The accumulator chamber is configured to maintain the melt therein at a constant temperature.

[00021] In any one or more above embodiments the apparatus may also include a discharge device and a pressurizable cooling chamber connected to the accumulator chamber through the discharge device.

[00022] In one or more of the above embodiments, during operation, the induction melting chamber, the accumulator chamber, the discharge device and the cooling chamber are pressurized to a predetermined pressure at least greater than a boiling point of the low boiling point element of the feedstock.

[00023] In one or more of the above embodiments, the second valve is preferably remotely operated such that the valve may be opened only when the receiver and melting chamber are at the predetermined pressure. [00024] In one or more embodiments of the present disclosure the apparatus may also include a pressurizable collection chamber connected to the cooling chamber via a third valve. The discharge device preferably includes a divergent nozzle and may include multiple orifices opening into the cooling chamber.

[00025] In one more of the above embodiments the internal plug valve is operable to maintain a predetermined level band of melt in the accumulator chamber. In one or more of the above embodiments pressurization of the various chambers is accomplished with a nonreactive gas such as argon. In one or more of the above embodiments, the nonreactive gas may be accompanied by an additive gas, for example, such as nitrogen or hydrogen.

[00026] In one or more of the above embodiments, the melt may be driven from the melt chamber to the accumulator chamber during operation by a differential pressure applied between the melting chamber and the accumulator chamber.

[00027] In one or more of the above embodiments a process in accordance with the present disclosure may be viewed as including introducing a portion of feedstock including at least one of a low boiling point element and at least one of a high melting point element into a pressurizable receiver via a first valve, pressurizing the receiver with a nonreactive gas to a predetermined pressure greater than a boiling point of the low boiling element to provide a portion of pressurized feedstock, transferring the portion of pressurized feedstock into a pressurized induction melting chamber connected to the receiver via a second valve at the predetermined pressure, heating the portion of pressurized feedstock to form a melt, passing the melt to a pressurized accumulator chamber connected to the feedstock induction melting chamber through a third valve, passing the melt accumulated in the accumulator chamber through a discharge device to a pressurized cooling chamber, and cooling the melt to a solid form product in the cooling chamber.

[00028] In one or more of the above embodiments, a method or process in accordance with this disclosure may further include repeating the introducing, pressurizing, transferring, melting, passing, and cooling operations for a next portion of feedstock thereby continuously forming product.

[00029] In one or more of the above embodiments, pressurizing includes introducing a partial pressure of another gas selected from the group consisting of nitrogen and hydrogen. In one or more embodiments of the present disclosure the predetermined pressure preferably sufficient to prevent boiling of any additive introduced into the melt in addition to the feedstock.

[00030] In one or more of the above embodiments, this feedstock may be granulated or may be a powder or may be a combination of both.

[00031] Furthermore, in any one or more of the above embodiments the process may further include operations of cooling the melt in the cooling chamber by passing the solidifying melt between parallel rollers.

[00032] In any one or more of the above embodiments, the process may alternatively include cooling the melt in a splat cooling chamber by passing the solidifying melt over rotating cold drums.

[00033] In one or more of the above embodiments, the nonreactive gas may be an inert gas. In some embodiments, the inert gas and the additive gas are both introduced in one or more of the receiver, the melting chamber, the accumulator chamber and the cooling chamber.

[00034] In other embodiments, the inert gas and the additive gas may be separately introduced.

[00035] In one or more of the above embodiments, the inert gas and the additive gas may pressurize the accumulator chamber prior to passing the melt into the accumulator chamber.

[00036] In any one or more of the above exemplary embodiments, the nonreactive gas may be an inert gas such as Argon.

[00037] In any one or more of the above embodiments, the operation of passing may include controlling differential pressure within a narrow band to drive the melt into the cooling chamber.

[00038] In any one or more of the above embodiments, the flow of melt into the splat cooling chamber may be controlled by maintaining a required differential pressure.

BRIEF DESCRIPTION OF THE DRAWING

[00039] FIG. 1 is a vertical sectional schematic view of an exemplary apparatus for producing a product in accordance with the present disclosure.

[00040] FIG. 2 is an enlarged view of the feed section of the apparatus shown in FIG. 1 . [00041] FIG. 3 is an enlarged view of the two stage melting furnace section of the apparatus shown in FIG. 1.

[00042] FIG. 4 is an enlarged view of one embodiment of a splat cooling chamber in accordance with the apparatus shown in FIG. 1.

[00043] FIG. 5 is an enlarged view of the product collection section of the apparatus shown in FIG. 1.

DETAILED DESCRIPTION

[00044] T urning now to the drawing, a side elevation schematic sectional view of one embodiment of an exemplary apparatus 100 in accordance with the present disclosure is shown in FIG. 1. Apparatus 100 includes a feedstock ingest section 102, a furnace section 104, a discharge device 106, a splat cooling section 108 and a product collection section 110.

[00045] Throughput of feedstock, melt and product processed through the sections 102 through 1 10 is controlled by a remotely operated series of valves 1 12, 1 14, 1 16, 1 18, and 120. Operation of each of these valves will be explained in further detail below. The control circuitry for these valves is not shown.

[00046] An enlarged view of the feed section 102 is shown in FIG. 2. The feedstock section includes a feedstock hopper 122 in series with a feedstock receiver 124 that can be isolated via inlet valve 1 12 and outlet valve 1 14, air removed, and then pressurized with an inert gas along with selected additives such as nitrogen and/or hydrogen. The vacuum system and gas pressurization system is not shown, for ease of explanation of the subject apparatus of the present disclosure.

[00047] Feedstock 126 is placed in the hopper 122. Valve 1 12 is opened and valve 124 closed, permitting a portion of the feedstock 126 to drop into the receiver 124. Valve 1 12 is then closed and air within the receiver 124 is purged with an inert gas such as argon or a vacuum drawn in the receiver 124 to remove the air. The receiver 124 is then pressurized to a predetermined pressure with the inert gas and selected additives such as nitrogen and hydrogen may be introduced into the receiver 124.

[00048] At the same time, each of the furnace section 104 and the splat cooling section is, or has already been, pressurized to the predetermined pressure with the inert gas and/or inert gas with selected additives such that the pressure within these sections is the same. When the receiver 124 reaches the predetermined pressure, valve 1 14 is opened, permitting the feedstock 126 within the receiver 124 to drop into the first stage of the furnace section 104. The valve 1 14 is then closed, readying the receiver 124 to accept another portion of feedstock 126.

[00049] An enlarged view of the furnace section 104 is shown in FIG. 3. The furnace section 104 includes an upper melting chamber 128 and a lower accumulator chamber 130 surrounded by induction heating coils 132. The melting chamber 128 experiences large thermal gradients as feedstock, at room temperature, is cyclically introduced into the chamber 128 and heated to form a melt 134. The lower chamber, or accumulator chamber 130 is isolated from the upper chamber 128 by a stem valve 1 16. This stem valve 1 16 separates the melt portion that experiences large temperature variations from the melt in the accumulator chamber 130 so as to maintain the melt in the accumulator chamber at constant temperature. The stem valve 1 16 is periodically opened to permit melt 134 to pass into the accumulator chamber 130 so as to maintain a narrow band level of melt 134 within the accumulator so as to maintain a constant differential pressure head on the discharge device 106. The temperature of the melt 134 within the accumulator chamber 130 is maintained constant so that the melt 134 therein is maintained essentially at isothermal conditions. This helps to ensure that the elemental composition of the melt in the accumulator chamber 130 remains uniform as it passes into the discharge device 106 and into the splat cooler section 108.

[00050] The discharge device section 106 and splat cooler section 108 is shown in FIG. 4. During steady state operation, the melt 134 continually passes out of the accumulator chamber 130 through a discharge device such as a divergent nozzle 136, a convergent-divergent nozzle, a series of holes, slits or other structure designed to disperse the melt 134 into the chamber 108 in a desired manner. In the illustrated embodiment of the discharge section 106 of the apparatus 100 shown in FIGS. 1 and 4, a divergent nozzle 136 is shown. This nozzle 136 atomizes and disperses the melt 134 as it enters the splat cooling chamber 108.

[00051] The driving force on the melt 134 passing into the splat cooling chamber 108 via the device 106 is the differential pressure on the melt 134 due to the height of the melt 134 within the accumulator chamber 130. In order to maintain a constant flow rate into the splat cooling chamber 108 this level of melt 134 must be tightly controlled to remain within a narrow band as mentioned above. It is this narrow level band that establishes the differential pressure required and essentially controls the operational sequencing of valves 1 12, 1 14 and 1 16 and hence the throughput of feedstock 126 through the apparatus 100 during steady state operation of the apparatus 100. Use of the differential pressure to maintain constant flow rate conserves energy and eliminates the need for a high volume gas flow otherwise needed to accelerate the melt 134 into the splat cooling chamber.

[00052] The splat cooling chamber 138 of cooling section 108 is maintained at the same pressure as the furnace section 104 with the inert gas with additives as above described. The splat cooling chamber 138 houses, in the shown exemplary embodiment 100, a pair of rotating cooling drums 140 or wheels that spin on axles 142. These cooling drums 140 are preferably internally cooled drums with copper exteriors and are spun at a relatively high speed such that the melt 134 that hits the drum surfaces and solidifies is flung off of those surfaces by centrifugal force, resulting in formation of flakes 144 that fall to the conical bottom portion 146 of the chamber 138. The solidification rate can be changed by using drums 140 of appropriate materials in order to produce equilibrium structures can be obtained by using low cooling rates and non-equilibrium structures, such as metallic glasses, super- saturated alloys or matrix structure with high defect densities such as vacancies and dislocation.

[00053] These flakes 144 then pass through open valve 1 18 into the collection section1 10 as is shown in FIG. 5. Collection section 110 includes the bottom portion 146 of the cooling chamber 138, valve 1 18, a collection chamber 148, and valve 120. The purpose of the collection section 1 10 is to receive and collect the solidified product, in this case flakes 144, and transition the content of collection chamber 148 to atmospheric pressure for removal and subsequent processing.

[00054] Not shown in FIG. 5, is a gas recycling system that removes the inert gas from the collection chamber 148 once valves 1 18 and 120 are closed, and replaces that gas with normal air. While the flakes 144 are in the collection chamber 148, they may be additionally cooled to about normal atmospheric temperature. Valve 120 is then opened to release the product, in this case, accumulated flakes 144.

[00055] The processes described above with reference to sections 102, 104, 106 and 108 are repeated until the collection chamber 148 is full, at which point the valve 1 18 is closed, pressure brought to atmospheric, and valve 120 opened to remove the product. Valve 1 18 is then reclosed, inert gas pressure restored within collection chamber 148, and valve 1 18 reopened to receive accumulated flakes 144 from the bottom portion 146 of the splat cooling chamber 138. Operational sequencing of section 110 may differ from that of sections 102-108 depending on the size of the collection chamber 148.

[00056] In the apparatus 100, primary control is the rate of flow through the discharge device 106, which necessarily controls the level variation rate of melt 134 in the accumulator chamber 130. Thus secondarily, the timing is controlled by the level in the accumulator 130 to maintain a constant head or differential pressure on the discharge device 106. Hence the discharge device flow rate controls all the other valve sequences in order to maintain a desired throughput of the apparatus 100.

[00057] The splat cooler 108 as shown incorporates rotating cooling drums 140. Depending on the product being produced, these drums along with the discharge device 106 may be changed. For example, the discharge device nozzle 136 may be replaced by a convergent nozzle to generate a thin stream of melt and this melt stream passed between rotating cooling spools to form a wire or a sheet product. The above described apparatus and process may be utilized to produce unique microstructures in the product while combining elements with low boiling point and high melting point. Because the pressure head driving the molten metal stream of melt 134 is used to pass the melt into the splat cooling section 108, minimal energy is used, the amount of inert gas is minimized, and chamber volume is minimized. Because it is fully enclosed, process safety is also enhanced. Different product shapes such as rods, sheets, flakes and powders may be produced utilizing the apparatus 100 as above described.

[00058] While various embodiments of the new technology described herein have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. It is to be expressly understood that such modifications and adaptations are within the spirit and scope of the presently disclosed technology.

Claims

1. An apparatus comprising:

a pressurizable feedstock receiver connected via a first valve to a feedstock supply of feedstock for producing a metal product that includes at least a low boiling point element and a high melting point element, the feedstock including the low melting point element and the high melting point element;

a pressurizable feedstock induction melting chamber for producing a melt connected to the receiver via a second valve;

a pressurizable accumulator chamber connected to the feedstock induction melting chamber via an internal stem plug valve, wherein the accumulator chamber is configured to maintain the melt therein at a constant temperature;

a discharge device; and

a pressurizable cooling chamber connected to the accumulator chamber through the discharge device;

wherein during operation, the induction melting chamber, the accumulator chamber, the discharge device and the cooling chamber are pressurized to a predetermined pressure at least greater than a boiling point of the low boiling point element of the feedstock.

2. The apparatus according to claim 1 further comprising a pressurizable collection chamber connected to the cooling chamber via a third valve.

3. The apparatus according to claim 1 wherein the second valve is remotely operated such that the valve may be opened only when the receiver and melting chamber are at the predetermined pressure.

4. The apparatus according to claim 3 wherein the discharge device includes a divergent nozzle.

5. The apparatus according to claim 3 wherein the discharge device includes multiple orifices opening into the cooling chamber.

6. The apparatus according to claim 1 wherein the internal plug valve is operable to maintain a predetermined level band of melt in the accumulator chamber.

7. The apparatus according to claim 1 wherein pressurization is accomplished with a nonreactive gas.

8. The apparatus according to claim 7 wherein the nonreactive gas is

accompanied by an additive gas.

9. The apparatus according to claim 1 wherein the melt is driven from the melt chamber to the accumulator chamber during operation by a differential pressure applied between the melting chamber and the accumulator chamber.

10. The apparatus according to claim 8 wherein the additive gas is selected from a group including nitrogen and hydrogen.

1 1. A process comprising:

introducing a portion of feedstock including at least one of a low boiling point element and at least one of a high melting point element into a pressurizable receiver via a first valve;

pressurizing the receiver with a nonreactive gas to a predetermined pressure greater than a boiling point of the low boiling element to provide a portion of pressurized feedstock;

transferring the portion of pressurized feedstock into a pressurized induction melting chamber connected to the receiver via a second valve at the predetermined pressure;

heating the portion of pressurized feedstock to form a melt;

passing the melt to a pressurized accumulator chamber connected to the feedstock induction melting chamber through a third valve;

passing the melt accumulated in the accumulator chamber through a discharge device to a pressurized cooling chamber; and

cooling the melt to a solid form product in the cooling chamber.

12. The process according to claim 1 1 further comprising repeating the introducing, pressurizing, transferring, melting, passing, and cooling operations for a next portion of feedstock thereby continuously forming product.

13. The process according to claim 1 1 wherein pressurizing includes introducing a partial pressure of another gas selected from the group consisting of nitrogen and hydrogen.

14. The process according to claim 1 1 wherein the predetermined pressure is sufficient to prevent boiling of any additive introduced into the melt in addition to the feedstock.

15. The process according to claim 1 1 wherein the feedstock is granulated.

16. The process according to claim 1 1 wherein the feedstock is a powder.

17. The process according to claim 1 1 further comprising cooling the melt in the cooling chamber by passing the solidifying melt between parallel rollers.

18. The process according to claim 1 1 further comprising cooling the melt in a splat cooling chamber by passing the solidifying melt over rotating cold drums.

19. The process according to claim 12 wherein the inert gas and the additive gas are both introduced in one or more of the receiver, the melting chamber, the accumulator chamber and the cooling chamber.

20. The process according to claim 18 wherein the inert gas and the additive gas pressurize the accumulator chamber prior to passing the melt into the accumulator chamber:

21. The process according to claim 18 wherein the inert gas is Argon.

22. The process according to claim 1 1 wherein passing further comprises controlling differential pressure within a narrow band to drive the melt into the cooling chamber.

23. The process according to claim 22 wherein flow rate of melt into the splat cooling chamber is controlled by maintaining a required differential pressure.