US20090064821A1 - Vapor-Reinforced Expanding Volume of Gas to Minimize the Contamination of Products Treated in a Melting Furnace - Google Patents
Vapor-Reinforced Expanding Volume of Gas to Minimize the Contamination of Products Treated in a Melting Furnace Download PDFInfo
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- US20090064821A1 US20090064821A1 US12/271,994 US27199408A US2009064821A1 US 20090064821 A1 US20090064821 A1 US 20090064821A1 US 27199408 A US27199408 A US 27199408A US 2009064821 A1 US2009064821 A1 US 2009064821A1
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- molten metal
- cryogen
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
- B22D21/02—Casting exceedingly oxidisable non-ferrous metals, e.g. in inert atmosphere
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/003—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using inert gases
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/003—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals by induction
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/006—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals with use of an inert protective material including the use of an inert gas
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Definitions
- This invention relates to the minimizing of contamination of molten metal during processing.
- metals In the metal casting industry, metals (ferrous or non-ferrous) are melted in a furnace, and then poured into molds to solidify into castings. In the foundry melting operations, metals are commonly melted in electric induction furnaces. Due to the induced electric current, molten metal in electric induction melting furnaces will typically circulate from the bottom upwards, in the center of the furnace, and circulate downwards along the sidewalls of the furnace, forming a molten metal meniscus with raised center and lower edges. Due to this circulation, molten metal is continually exposed to the atmosphere.
- metal is melted in gas-fired reverberatory furnaces.
- these furnaces will utilize an external side well for charging materials, as opposed to charging materials directly into the main hearth, as this will minimize melt loss (increase recovery) of the charged aluminum, especially for thin pieces of aluminum scrap such as shreds or machine chips.
- Many of these furnaces utilize molten metal pumps to continuously circulate the molten metal between the main hearth and the external well(s).
- the molten metal is circulated through a specially shaped well area which forms a molten metal vortex (meniscus with lowered center and raised outer edges).
- molten metal vortex meniscus with lowered center and raised outer edges.
- These types of charge wells are commonly referred to as “toilet bowls” or “vortex wells”.
- Vortex wells are especially advantageous for charging light gauge scrap such as shreds or chips, since the vortex quickly submerges the light gauge scrap under the molten metal surface, to protect it from atmospheric oxidation. Otherwise this light scrap could float on the molten metal surface, and prolong contact with atmospheric oxygen. So the quick submergence reduces melt loss and improves metal recovery.
- melt furnaces for example electric induction, or gas-fired reverb with vortex charge well
- molten metal holding or transfer vessels such as tundishes or launders
- the molten metal can be exposed to atmospheric air contamination. Due to the special molten metal circulation patterns developed by the melt furnace or vessel (vortex charging well, launder, holding vessel, etc.), often the exposure of fresh molten metal to the atmosphere is exacerbated and continually updated.
- Various processes are utilized to prevent exposure of the metal to the atmospheric air, including vacuum treatment and inerting with a gas or a liquid.
- vacuum treatment a fluid-tight furnace chamber is vacuum evacuated of substantially all ambient oxygen prior to heating the metal.
- This process requires a special vacuum furnace and is generally only suitable for small batch processes.
- the use of a vacuum furnace also results in the need for a substantially long cooling period, which lowers plant productivity.
- the injected inert gas will also entrain ambient air along with it as it is injected into the furnace. Because of these effects, it is difficult, if not impossible, for gas inerting techniques to provide a true inert (0% O 2 ) atmosphere directly at the surface of the metal.
- a liquid cryogen typically N 2 or Ar
- the liquid cryogen has higher density than its gas phase and air, it is much less likely to be pushed up and away from the melt surface by the thermal updrafts.
- the liquid vaporizes into a gas.
- the cryogen boils from liquid to gas, it expands volumetrically by a factor of about 600-900 times as it rises. As a result, the expansion pushes ambient air away from the surface of the metal, inhibiting oxidation.
- One drawback of liquid inerting is the difficulty of efficiently delivering the liquid cryogen to the furnace interior in a liquid state.
- the liquefied gas is extremely cold.
- the liquid inert gas is continually absorbing heat from the surroundings, boiling some of the liquid to vapor inside the storage tank and distribution piping. This vapor must be vented before the liquid is injected into the chamber, otherwise flow sputtering and surging results (caused by the tendency of the gas to choke the flow of liquid in the delivery pipes). As a result, a significant portion of the cryogen supply is lost due to boiling.
- the system includes a container of metal (e.g., hot solid (charge) metal or molten metal) and a system configured to deliver biphasic inert cryogen toward the metal.
- the delivery system may include a lance disposed proximate the top of the container.
- the lance includes a hood that directs both a flow of liquid cryogen and a flow of vaporous cryogen toward the metal surface.
- the liquid cryogen travels to the metal surface, where it vaporizes to generate a volume of expanding gas.
- the vaporous cryogen moreover, is directed downward, toward the expanding gas.
- the vaporous cryogen reinforces expanding gas, slowing its expansion rate to maintain the expanding gas over the metal surface.
- the liquid and vaporous gas work in tandem to inhibit the oxidation of the metal.
- the system can include a number of different features, including any one or combination of the following features:
- a method of providing a vapor blanket over a material processed within a container is also described herein.
- the method can include a number of different features, including any one or combination of the following features:
- FIG. 1 depicts cross-sectional view of an exemplary embodiment of a container with a heated load of metal and a delivery system for a biphasic inert cryogen in accordance with an embodiment of the invention in which the molten metal possesses a generally meniscoid shape with a raised center meniscus portion and a lowered edge meniscus portion.
- FIG. 2 is a close-up view of the delivery system shown in FIG. 1 .
- FIG. 3 depicts cross-sectional view of an exemplary embodiment of a container with a heated load of metal and a delivery system for a biphasic inert cryogen in accordance with an embodiment of the invention in which the molten metal possesses a generally meniscoid shape with a lowered center meniscus portion and a raised edge meniscus portion.
- the present invention provides a system and process wherein a vapor reinforced expanding volume of inert gas (e.g., argon, nitrogen, or carbon dioxide) is developed and maintained over the surface of metal (e.g., molten metal and/or heated metal charge) in a container such as a melting furnace or a transfer system (a ladle, a launder, etc.).
- a vapor reinforced expanding volume of inert gas e.g., argon, nitrogen, or carbon dioxide
- the reinforced expanding volume of inert gas may be generated and maintained from a vaporizing volume of liquid cryogen situated against one or more sides of the inside surface of the container.
- the volumes of expanding gas may be maintained by a continuous stream of liquid cryogen replenishing the vaporizing volume of liquid cryogen from a lance system at the top of the furnace.
- FIG. 1 and FIG. 3 each show a system 10 in accordance with an embodiment of the present invention.
- the system 10 includes a container 100 and a biphasic cryogen delivery system 200 .
- the container 100 includes a bottom wall 105 , a side wall 110 , and an opening 115 defined by a rim 120 .
- the container 100 houses metal 300 (e.g., molten metal and/or heated charge material).
- the container 100 may be a molten metal bath, an induction furnace, a vortex charging well, or a metal containment and/or transfer system such as a ladle, launder, etc.
- convection movements and/or surface tension present in the molten metal may form a converging meniscus with a raised central portion 310 and lower edge portion 320 disposed along the side wall 110 of the container 100 .
- convection movements and/or surface tension present in the molten metal may form a converging meniscus with a lowered center meniscus portion 310 A (the swirling vortex of the molten metal) and an upper edge meniscus portion 320 A disposed along the side wall 110 of the container 100 .
- convection movements and/or surface tension present in the molten metal may form a generally flattened surface shape in which the center portion and the edge portion of the surface lie substantially in the same horizontal plane.
- flattened surface shape the term “generally” refers to those instances where the shape of the molten metal surface does not rise to the level of being considered to have a meniscus having as raised center portion and a lower edge portion as in the embodiment depicted in FIG. 1 , or to have a meniscus having a lowered center meniscus portion and an upper edge meniscus portion as in the embodiment depicted in FIG. 3 .
- the term “substantially” has the same meaning as “generally”.
- the biphasic cryogen delivery system 200 distributes liquid and vaporous inert cryogen into the container 100 .
- the system 200 may include a lance 210 disposed at the top of the container 100 .
- the lance 210 may communicate with an inert liquid cryogen source 400 (e.g., a storage vessel).
- the inert liquid cryogen may include, but is not limited to, argon, nitrogen, or carbon dioxide.
- a diffuser 220 may be coupled to the lance 210 to separate the vaporous component from the liquid component (i.e., the vaporous cryogen from the liquid cryogen).
- the diffuser 220 may include, for example, a sintered 10-80 ⁇ level plug disposed at the discharge end of the lance 210 .
- the diffuser 220 is housed within a shroud or hood 230 configured to channel the liquid and gas components exiting the diffuser, directing them into the container 100 .
- the hood 230 is shaped to direct the biphasic flow or cryogen (i.e., the flow of liquid cryogen 500 A and the flow of vaporous cryogen 500 B) toward the surface of the metal 300 .
- FIG. 2 illustrates a close-up view of the hood 230 illustrated in FIG. 1 .
- the hood 230 includes an inlet end 235 , a first portion 237 , a second portion 239 , and an outlet end 240 .
- the hood 230 curves downward, away from the longitudinal axis of the hood (indicated by X), creating a first or outer bend 245 and a second or inner bend 250 .
- the degree of curvature may include, but is not limited to, downward curvatures in the range of about 0° (where the outlet 240 is generally perpendicular to the axis X) to about 90° (wherein the outlet 240 is generally parallel to the axis X).
- the hood 230 may have an overall length of approximately 4-6 inches (10.16 cm-15.24 cm).
- the first portion 237 (extending from the inlet 235 to the bend 245 / 250 ) may be about 3-5 inches (7.62 cm-12.7 cm) (e.g., 4 inches (10.16 cm)), while the second portion (extending from the bend 245 / 250 to the outlet 240 ) may be about 0.5-3 inches (1.27 cm-7.62 cm) (e.g., about 1.5 inches (3.81 cm)).
- the diameter of the hood channel (indicated as D) may be about 0.5 inches to 2 inches (1.27 cm-5.08 cm) (e.g., 1 inch (3.54 cm)).
- the diameter D of the channel is substantially continuous from the inlet 235 to the outlet 240 .
- the material forming the hood includes, but is not limited to, stainless steel tubing.
- the hood 230 is disposed oriented to introduce the liquid cryogen 500 A and vaporous cryogen 500 B into the container.
- the hood 230 may be disposed at a point proximate the opening 115 of the container 100 .
- the outlet end 240 may be generally coplanar with the opening 115 of the container 100 , or may be positioned slightly below the opening 115 such that it protrudes into the container interior.
- the hood 230 moreover, may be oriented on the container such that the inner bend 250 of the hood is positioned adjacent the sidewall 110 .
- the liquid cryogen 500 A is directed along/adjacent the side wall 110 of the container 100 , permitting the liquid cryogen to reach the metal 300 and create a localized pool or volume 500 C of liquid cryogen along the lower meniscus portion 320 .
- the delivery system 200 of the present invention controls parameters to cause the liquid cryogen 500 A to become localized on the metal 300 . That is, the liquid cryogen 500 A covers only a portion of the metal surface, localizing the liquid cryogen within an area generally adjacent the side wall 110 of the container 100 .
- the pool 500 C of liquid cryogen is formed proximate the side wall 110 of the container. It is more effective to deliver the liquid cryogen 500 A down the side wall 110 of the container (to the lower portion 320 of the meniscus) to maximize the cryogen delivered to the meniscus site, as well as to create a pool 500 C of liquid cryogen at the lowest elevation within the metal environment (e.g., the lowest level of a furnace). In contrast, delivering the liquid cryogen 500 A to the upper portion 310 of the meniscus would inhibit the amount of cryogen actually delivered to the lower portion 320 of the meniscus (along the side wall 110 ) because the cryogen 500 C would become trapped within or above the charge material (solid charge that will melt during the heat cycle).
- placing the delivery system 200 along the side wall 110 of the container 100 provides an additional benefit of automatically facilitating inert protection of the pour of the metal into the transfer ladle, launder, tundish mold, etc.
- the volume 500 C of liquid cryogen is formed proximate the side wall 110 of the container 100 .
- the volume is directed to the upper edge portion 320 A of the meniscus where it then slides down toward the center of the vortex, evaporating as it slides down.
- Delivering the liquid cryogen 500 A to the lowered center portion 310 A of the meniscus in this particular embodiment could potentially create a hazard because the vortex could submerge the liquid cryogen which could potentially lead to an explosion if the liquid cryogen vaporizes below the molten metal surface. It is more advantageous to drip the liquid cryogen 500 A along the upper edge portion 310 A of the meniscus (vortex), where the liquid cryogen 500 A can vaporize to gas as it slides down toward the lowered center meniscus portion 310 A of the center of the vortex.
- the term “drip” includes a conglomeration of droplets which range in size from a tight singular liquid stream to a multiplicity of fairly subdivided small liquid droplets. Note also that the application of the liquid cryogen would be at a location within the vortex, not mixed in as a part of the charge material itself.
- the volume 500 C of liquid cryogen 500 A is either formed proximate the side wall 110 of the container 100 or may be directed into contact with a portion of the molten metal.
- the volume of liquid cryogen is directed to a confined area (particular portion that does not constitute the whole surface of the molten metal) of the surface of the molten metal.
- the volume of liquid cryogen is directed to the edge portion of the surface proximate the side wall. Of these embodiments, the later is the more preferred.
- the flow of liquid cryogen 500 A in each of the embodiments forms a small volume 500 C of liquid cryogen on the surface of the metal 300 , adjacent the side wall 110 with regard to FIG. 1 and FIG. 3 and either adjacent to the side wall 110 or within a particular portion of the flattened surface shape with regard to the flattened condition.
- the pool/volume of liquid cryogen 500 C vaporizes, generating an expanding volume of inert gas 600 that expands across the entire exposed surface of the metal 300 .
- the expansion rate of the gas 600 is generally dependant upon the type of inert gas utilized in forming the inert blanket (e.g., argon, nitrogen, or carbon dioxide).
- inert gas utilized in forming the inert blanket
- argon expands up to 840 times the liquid volume while heating up from ⁇ 302° F. ( ⁇ 185° C.) to room temperature.
- the delivery system 200 further directs a shroud of vaporous cryogen 500 B into the container, where it reinforces the expanding volume of inert gas 600 generated from the pool/volume 500 C of cryogenic liquid, maintaining the expanding volume 600 proximate the exposed metal surface.
- the hood 230 directs the vaporous cryogen 500 B toward the expanding gas 600 , reinforcing the expanding gas and inhibiting its rate of expansion and diffusion into the atmosphere above the container 100 .
- the flow rate of the biphasic cryogen 500 A, 500 B from the source 400 should be effective to provide a continuous volume of expanding inert gas 600 , to maintain a localized pool/volume 500 C of liquid cryogen on the surface of the metal 300 (i.e., to prevent the liquid cryogen 500 A from creating a pool/volume 500 C that covers the entire surface of the metal 300 ), and to maintain the flow reinforcing vaporous cryogen 500 B toward the metal surface.
- the flow rate is determined as a function of the surface area of the metal 300 . This is contrary to the prior art processes, which calculate the flow rate utilizing the volume of the metal.
- the continuous stream of cryogen is maintained at a flow rate of about 0.001 lb/in 2 /min.
- the ratio of liquid cryogen 500 A to vaporous cryogen 500 B exiting the lance 210 may be about 99/1 to about 51/49, depending on the thermal quality of the cryogen distribution system and the working pressure of the cryogen supply tank. Flow rates above the preferred range tend to increase process costs, as well as lead to the “popping” of the metal 300 out of the container 100 due to volumetric and mechanical expansion of the cryogen 500 C as it transitions from a liquid to a vapor. This creates a hazardous situation for users in the area around the container 100 .
- the hood 230 directs the liquid cryogen 500 A into the container 100 , causing the liquid cryogen to fall from the lance 210 adjacent to the side wall 110 and form the small volume (pool 500 C) of liquid cryogen on the surface of the metal 300 , adjacent the side wall of the container 100 .
- the hood directs the liquid cryogen into the container causing the liquid cryogen to fall from the lance either adjacent to the side wall or within a particular confined area on the surface of the molten metal.
- the liquid volume 500 C in each case vaporizes, creating an expanding gas 600 that expands across the entire surface of the metal 300 .
- the hood 230 directs the vaporous gas 500 C downward, toward the metal surface, inhibiting the expansion of the expanding gas 600 , maintaining the reinforced vapor near the surface of the metal 300 .
- This above-describe system is effective to guide the vaporous cryogen 500 B into the container 100 , providing for the complete utilization of the vaporous cryogen, using it to reinforce the expanding gas 600 .
- a 3-15% of the inert cryogen is wasted of the tip of a lance due to flash losses.
- the present system avoids these losses by completely utilizing the vaporous cryogen 500 B, directing it into the container 100 in a manner (at a speed and in an amount) effective to minimize and/or avoid flash losses.
- the hood 230 may possess any dimensions and shape suitable for its described purpose (directing a biphasic flow into the container), and may be modified based on factors such as manufacturing cost, manufacturing method, and application site parameters.
- the flow rate is dependent primarily upon the surface area of the metal 300 in the container 100 requiring protection by the expanding gas 600 , secondary factors may be used to determine the flow rate of the liquid cryogen, such as the reactivity of the alloy or metal being protected, the existence and strength of the ventilation system, and the quality requirements of the end user for the metal being produced.
- a single source 400 of inert cryogen is illustrated, it is understood that multiple sources 400 may be connected to lance 210 to provide multiple types of inert cryogen to the container, including mixtures.
- the systems and methods described can include any one or more suitable controllers and/or sensors to facilitate monitoring and control of various operational parameters during heating of the load in the furnace.
- One or more suitable sensors and related equipment can also be provided to measure and monitor the concentration of the gaseous species within the furnace, preferably at locations in the immediate vicinity of the load surface.
- the induction furnace can include any suitable number and different types of sensors to monitor one or more of the temperature, pressure, flow rate and concentration of nitrogen and/or any other gaseous species within the furnace.
Abstract
Systems and corresponding methods are described herein that provide an effective inert blanket over a metal surface (hot solid (charge) metal or molten metal) in a container such as an induction furnace. The system includes a container of metal and a system configured to delivery biphasic inert cryogen toward the metal. The delivery system may include a lance disposed at the top of the container. The lance has a hood that directs both a flow of liquid cryogen and a flow of vaporous gas toward the metal surface. The liquid cryogen contacts the metal surface, generating a volume of expanding gas over the metal surface. The vaporous cryogen creates a reinforcing vapor that slows the expansion rate of the expanding gas, localizing the expanding gas over the metal surface.
Description
- The present application is a continuation-in-part of U.S. patent application Ser. No. 11/829,115 which claims priority from U.S. Provisional Patent Application Ser. No. 60/839,776, entitled “EGAL” and filed 23 Aug. 2006.
- 1. Field
- This invention relates to the minimizing of contamination of molten metal during processing.
- 2. Related Art
- In the metal casting industry, metals (ferrous or non-ferrous) are melted in a furnace, and then poured into molds to solidify into castings. In the foundry melting operations, metals are commonly melted in electric induction furnaces. Due to the induced electric current, molten metal in electric induction melting furnaces will typically circulate from the bottom upwards, in the center of the furnace, and circulate downwards along the sidewalls of the furnace, forming a molten metal meniscus with raised center and lower edges. Due to this circulation, molten metal is continually exposed to the atmosphere.
- In other types of metal melting operations, for example melting aluminum, metal is melted in gas-fired reverberatory furnaces. Often these furnaces will utilize an external side well for charging materials, as opposed to charging materials directly into the main hearth, as this will minimize melt loss (increase recovery) of the charged aluminum, especially for thin pieces of aluminum scrap such as shreds or machine chips. Many of these furnaces utilize molten metal pumps to continuously circulate the molten metal between the main hearth and the external well(s).
- In one specialized type of side charge well in these types of furnaces, the molten metal is circulated through a specially shaped well area which forms a molten metal vortex (meniscus with lowered center and raised outer edges). These types of charge wells are commonly referred to as “toilet bowls” or “vortex wells”. These vortex charging wells are especially advantageous for charging light gauge scrap such as shreds or chips, since the vortex quickly submerges the light gauge scrap under the molten metal surface, to protect it from atmospheric oxidation. Otherwise this light scrap could float on the molten metal surface, and prolong contact with atmospheric oxygen. So the quick submergence reduces melt loss and improves metal recovery.
- But in order to form this molten metal vortex, a considerable amount of molten aluminum is continually exposed to the atmosphere. A skin of aluminum oxide is continuously generated, and submerged in the vortex. This aluminum oxide (dross) floats to the surface in the adjoining float-out well, and is subsequently skimmed, adding to the overall system melt loss.
- So, in various types of melt furnaces (for example electric induction, or gas-fired reverb with vortex charge well), or in other types of molten metal holding or transfer vessels such as tundishes or launders, the molten metal can be exposed to atmospheric air contamination. Due to the special molten metal circulation patterns developed by the melt furnace or vessel (vortex charging well, launder, holding vessel, etc.), often the exposure of fresh molten metal to the atmosphere is exacerbated and continually updated.
- It is often advantageous to melt and transport the metals without exposure to atmospheric air to minimize oxidation of the metal (including its alloying components), which not only increases yield and alloy recovery efficiency, but also reduces formation of metallic oxides, which can cause casting defects (inclusions), reducing the quality of the finished product. Molten metal, moreover, has a tendency to absorb gases (chiefly oxygen and hydrogen) from the atmosphere (ambient air), which cause gas-related casting defects such as porosity.
- Various processes are utilized to prevent exposure of the metal to the atmospheric air, including vacuum treatment and inerting with a gas or a liquid. In vacuum treatment, a fluid-tight furnace chamber is vacuum evacuated of substantially all ambient oxygen prior to heating the metal. This process, however, requires a special vacuum furnace and is generally only suitable for small batch processes. In addition, the use of a vacuum furnace also results in the need for a substantially long cooling period, which lowers plant productivity.
- With gas inerting, a continuous flow of inert gas is injected into the furnace chamber. This creates a blanket of inert gas that purges ambient oxygen from the chamber, as well as prevents the ambient air from entering the chamber. This process, however, requires an extraordinarily large volume of gas to be used during the process, even with a substantially fluid-tight chamber. The process, moreover, fails to keep the concentration of residual oxygen low enough to prevent the formation of an oxide layer on most metal products. Hot thermal updrafts from within the hot furnace are continually pushing the incoming cold inert gas up and away from the metal surface. Thus, as the hot air and gases rise, the induced draft continually pulls fresh cold air toward the furnace. The injected inert gas will also entrain ambient air along with it as it is injected into the furnace. Because of these effects, it is difficult, if not impossible, for gas inerting techniques to provide a true inert (0% O2) atmosphere directly at the surface of the metal.
- With liquid inerting, a liquid cryogen (typically N2 or Ar) covers the entire exposed surface of the metal (i.e., hot solid metal or molten metal). Since the liquid cryogen has higher density than its gas phase and air, it is much less likely to be pushed up and away from the melt surface by the thermal updrafts. After contacting the metal surface, within a short time, the liquid vaporizes into a gas. As the cryogen boils from liquid to gas, it expands volumetrically by a factor of about 600-900 times as it rises. As a result, the expansion pushes ambient air away from the surface of the metal, inhibiting oxidation. One drawback of liquid inerting is the difficulty of efficiently delivering the liquid cryogen to the furnace interior in a liquid state. The liquefied gas is extremely cold. In the storage tank and distribution piping, the liquid inert gas is continually absorbing heat from the surroundings, boiling some of the liquid to vapor inside the storage tank and distribution piping. This vapor must be vented before the liquid is injected into the chamber, otherwise flow sputtering and surging results (caused by the tendency of the gas to choke the flow of liquid in the delivery pipes). As a result, a significant portion of the cryogen supply is lost due to boiling.
- Thus, there still remains a need in the art to achieve low residual oxygen concentrations through a purging process without losing substantial volumes of inert gases.
- Systems and corresponding methods are described herein that provide an effective inert blanket over a metal surface in a container such as an induction furnace, tundish, etc. The system includes a container of metal (e.g., hot solid (charge) metal or molten metal) and a system configured to deliver biphasic inert cryogen toward the metal. The delivery system may include a lance disposed proximate the top of the container. The lance includes a hood that directs both a flow of liquid cryogen and a flow of vaporous cryogen toward the metal surface. The liquid cryogen travels to the metal surface, where it vaporizes to generate a volume of expanding gas. The vaporous cryogen, moreover, is directed downward, toward the expanding gas. The vaporous cryogen reinforces expanding gas, slowing its expansion rate to maintain the expanding gas over the metal surface. Thus, the liquid and vaporous gas work in tandem to inhibit the oxidation of the metal.
- The system can include a number of different features, including any one or combination of the following features:
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- an open vessel for containing molten metal, the vessel including a bottom wall, a side wall, and an opening;
- an inert cryogen source, the inert cryogen including a liquid flow component and a vaporous flow component;
- a delivery system disposed proximate the opening, the delivery system comprising (1) a lance including an inlet and a outlet, the inlet connected to the inert cryogen source and/or (2) a hood coupled to the outlet end of the lance, wherein the hood directs the components of the inert cryogen toward the molten metal;
- a hood configured to direct the liquid component of the inert cryogen toward the bottom wall of the vessel such that the liquid component contacts the molten metal to form an expanding volume of gas having a rate of expansion;
- a hood further configured to direct the vaporous component toward the molten metal to inhibit the rate of expansion of the expanding volume of gas;
- a hood having a curved housing with an inlet and an outlet located downstream from the outlet;
- a hood positioned such that the outlet of the hood is generally coplanar with or below the opening of the vessel;
- a delivery system operable to generate a flow rate of inert cryogen in the range of about 0.001 lb/in2/min. to about 0.005 lb/in2/min., based upon the surface area of the molten metal;
- diffuser operable to separate the liquid flow component from the vaporous flow component; and
- a hood having a degree of curvature of about 0° to about 90°.
- A method of providing a vapor blanket over a material processed within a container is also described herein. The method can include a number of different features, including any one or combination of the following features:
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- forming molten metal within a container, the molten metal having an exposed surface defining a surface area;
- generating a biphasic inert cryogen, wherein the inert cryogen comprises a liquid flow component and a vaporous flow component;
- directing the liquid flow component into contact with the molten metal to generate an expanding gaseous volume having a rate of expansion;
- directing the vaporous flow component into the container to inhibit the rate of expansion of the gaseous volume;
- directing a flow of biphasic inert cryogen at a flow rate effective to generate the expanding gaseous volume that is substantially coextensive with the exposed surface of the molten metal;
- determining flow rate based upon the surface area of the molten metal;
- providing a flow rate in the range of about 0.001 lb/in2/min. to about 0.005 lb/in2/min., based upon the surface area of the molten metal;
- providing a molten metal possessing a generally meniscoid shape with a raised center meniscus portion and a lower edge meniscus portion, and directing the liquid flow component into contact with the lower meniscoid portion;
- providing a molten metal possessing a generally meniscoid shape with a lowered center meniscus portion and an upper edge meniscus portion, and directing the liquid flow component into contact with the upper meniscoid portion;
- providing a molten metal possessing a generally flattened surface shape, and directing the liquid flow component into contact with a portion of the molten metal, particularly a portion of the outer edge of the generally flattened surface shape proximate the side wall of the container;
- maintaining the flow rate to localize the liquid flow component within a portion of the molten metal exposed surface;
- providing a container including a bottom wall, a side wall, and an opening, and directing the liquid flow component proximate the side wall such that the liquid flow component contacts the molten metal at a point proximate the side wall;
- directing a liquid inert cryogen from a source through a diffuser to separate the liquid flow component from the vaporous flow component; and
- maintaining a flow rate of the inert cryogen such that liquid flow is localized within an area smaller than the molten metal exposed surface.
- The above and still further objects, features and advantages of the systems and methods described herein will become apparent upon consideration of the following detailed description of specific embodiments thereof, particularly when taken in conjunction with the accompanying drawings, wherein like reference numerals designate like components.
-
FIG. 1 depicts cross-sectional view of an exemplary embodiment of a container with a heated load of metal and a delivery system for a biphasic inert cryogen in accordance with an embodiment of the invention in which the molten metal possesses a generally meniscoid shape with a raised center meniscus portion and a lowered edge meniscus portion. -
FIG. 2 is a close-up view of the delivery system shown inFIG. 1 . -
FIG. 3 depicts cross-sectional view of an exemplary embodiment of a container with a heated load of metal and a delivery system for a biphasic inert cryogen in accordance with an embodiment of the invention in which the molten metal possesses a generally meniscoid shape with a lowered center meniscus portion and a raised edge meniscus portion. - The present invention provides a system and process wherein a vapor reinforced expanding volume of inert gas (e.g., argon, nitrogen, or carbon dioxide) is developed and maintained over the surface of metal (e.g., molten metal and/or heated metal charge) in a container such as a melting furnace or a transfer system (a ladle, a launder, etc.). The reinforced expanding volume of inert gas may be generated and maintained from a vaporizing volume of liquid cryogen situated against one or more sides of the inside surface of the container. The volumes of expanding gas may be maintained by a continuous stream of liquid cryogen replenishing the vaporizing volume of liquid cryogen from a lance system at the top of the furnace.
-
FIG. 1 andFIG. 3 each show asystem 10 in accordance with an embodiment of the present invention. As illustrated, thesystem 10 includes acontainer 100 and a biphasiccryogen delivery system 200. Thecontainer 100 includes abottom wall 105, aside wall 110, and anopening 115 defined by arim 120. Thecontainer 100 houses metal 300 (e.g., molten metal and/or heated charge material). By way of example, thecontainer 100 may be a molten metal bath, an induction furnace, a vortex charging well, or a metal containment and/or transfer system such as a ladle, launder, etc. Depending upon the type of container utilized, as shown by the embodiment set forth inFIG. 1 , convection movements and/or surface tension present in the molten metal may form a converging meniscus with a raisedcentral portion 310 andlower edge portion 320 disposed along theside wall 110 of thecontainer 100. In other embodiments as shown inFIG. 3 , where a different type ofcontainer 100 is utilized such as vortex charging wells, convection movements and/or surface tension present in the molten metal may form a converging meniscus with a loweredcenter meniscus portion 310A (the swirling vortex of the molten metal) and an upperedge meniscus portion 320A disposed along theside wall 110 of thecontainer 100. In a still further embodiment (not shown), with a different type ofcontainer 100 such as a ladle or tundish, convection movements and/or surface tension present in the molten metal may form a generally flattened surface shape in which the center portion and the edge portion of the surface lie substantially in the same horizontal plane. As used herein with regard to the phrase “flattened surface shape”, the term “generally” refers to those instances where the shape of the molten metal surface does not rise to the level of being considered to have a meniscus having as raised center portion and a lower edge portion as in the embodiment depicted inFIG. 1 , or to have a meniscus having a lowered center meniscus portion and an upper edge meniscus portion as in the embodiment depicted inFIG. 3 . In addition, with regard to the phrase “in the same horizontal plane”, the term “substantially” has the same meaning as “generally”. - In each of these embodiments above, the biphasic
cryogen delivery system 200 distributes liquid and vaporous inert cryogen into thecontainer 100. Thesystem 200 may include alance 210 disposed at the top of thecontainer 100. Thelance 210 may communicate with an inert liquid cryogen source 400 (e.g., a storage vessel). The inert liquid cryogen may include, but is not limited to, argon, nitrogen, or carbon dioxide. - As discussed above, in traveling from the
source 400 to thecontainer 100, the inert liquid cryogen absorbs heat, forming a vaporous/gaseous component. Consequently, adiffuser 220 may be coupled to thelance 210 to separate the vaporous component from the liquid component (i.e., the vaporous cryogen from the liquid cryogen). Thediffuser 220 may include, for example, a sintered 10-80μ level plug disposed at the discharge end of thelance 210. Thediffuser 220 is housed within a shroud orhood 230 configured to channel the liquid and gas components exiting the diffuser, directing them into thecontainer 100. Specifically, thehood 230 is shaped to direct the biphasic flow or cryogen (i.e., the flow ofliquid cryogen 500A and the flow ofvaporous cryogen 500B) toward the surface of themetal 300. -
FIG. 2 illustrates a close-up view of thehood 230 illustrated inFIG. 1 . In the embodiment illustrated, thehood 230 includes aninlet end 235, afirst portion 237, asecond portion 239, and anoutlet end 240. Thehood 230 curves downward, away from the longitudinal axis of the hood (indicated by X), creating a first orouter bend 245 and a second orinner bend 250. The degree of curvature may include, but is not limited to, downward curvatures in the range of about 0° (where theoutlet 240 is generally perpendicular to the axis X) to about 90° (wherein theoutlet 240 is generally parallel to the axis X). The dimensions of the hood may be any suitable for its described purpose. By way of example, thehood 230 may have an overall length of approximately 4-6 inches (10.16 cm-15.24 cm). By way of specific example, the first portion 237 (extending from theinlet 235 to thebend 245/250) may be about 3-5 inches (7.62 cm-12.7 cm) (e.g., 4 inches (10.16 cm)), while the second portion (extending from thebend 245/250 to the outlet 240) may be about 0.5-3 inches (1.27 cm-7.62 cm) (e.g., about 1.5 inches (3.81 cm)). The diameter of the hood channel (indicated as D) may be about 0.5 inches to 2 inches (1.27 cm-5.08 cm) (e.g., 1 inch (3.54 cm)). Preferably, the diameter D of the channel is substantially continuous from theinlet 235 to theoutlet 240. The material forming the hood includes, but is not limited to, stainless steel tubing. - The
hood 230 is disposed oriented to introduce theliquid cryogen 500A andvaporous cryogen 500B into the container. For example, thehood 230 may be disposed at a point proximate theopening 115 of thecontainer 100. By way of specific example, theoutlet end 240 may be generally coplanar with theopening 115 of thecontainer 100, or may be positioned slightly below theopening 115 such that it protrudes into the container interior. Thehood 230, moreover, may be oriented on the container such that theinner bend 250 of the hood is positioned adjacent thesidewall 110. - With the configuration of
FIG. 1 , theliquid cryogen 500A is directed along/adjacent theside wall 110 of thecontainer 100, permitting the liquid cryogen to reach themetal 300 and create a localized pool orvolume 500C of liquid cryogen along thelower meniscus portion 320. This is contrary to conventional liquid cryogen delivery systems, which direct a blanket of liquid over the entire metal surface. Instead, thedelivery system 200 of the present invention controls parameters to cause theliquid cryogen 500A to become localized on themetal 300. That is, theliquid cryogen 500A covers only a portion of the metal surface, localizing the liquid cryogen within an area generally adjacent theside wall 110 of thecontainer 100. - As noted above, with regard to
FIG. 1 , thepool 500C of liquid cryogen is formed proximate theside wall 110 of the container. It is more effective to deliver theliquid cryogen 500A down theside wall 110 of the container (to thelower portion 320 of the meniscus) to maximize the cryogen delivered to the meniscus site, as well as to create apool 500C of liquid cryogen at the lowest elevation within the metal environment (e.g., the lowest level of a furnace). In contrast, delivering theliquid cryogen 500A to theupper portion 310 of the meniscus would inhibit the amount of cryogen actually delivered to thelower portion 320 of the meniscus (along the side wall 110) because thecryogen 500C would become trapped within or above the charge material (solid charge that will melt during the heat cycle). Also, placing thedelivery system 200 along theside wall 110 of the container 100 (e.g., perpendicular to and adjacent the pouring spout of a furnace) provides an additional benefit of automatically facilitating inert protection of the pour of the metal into the transfer ladle, launder, tundish mold, etc. - As noted with regard to
FIG. 3 , thevolume 500C of liquid cryogen is formed proximate theside wall 110 of thecontainer 100. The volume is directed to theupper edge portion 320A of the meniscus where it then slides down toward the center of the vortex, evaporating as it slides down. By delivering theliquid cryogen 500A to theupper edge portion 320A of the meniscus (along the side wall), it is possible to avoid creating a pool ofliquid cryogen 500A at the lowest elevation within the metal environment (e.g., the lowest level of a furnace). Delivering theliquid cryogen 500A to the loweredcenter portion 310A of the meniscus in this particular embodiment could potentially create a hazard because the vortex could submerge the liquid cryogen which could potentially lead to an explosion if the liquid cryogen vaporizes below the molten metal surface. It is more advantageous to drip theliquid cryogen 500A along theupper edge portion 310A of the meniscus (vortex), where theliquid cryogen 500A can vaporize to gas as it slides down toward the loweredcenter meniscus portion 310A of the center of the vortex. As used herein, the term “drip” includes a conglomeration of droplets which range in size from a tight singular liquid stream to a multiplicity of fairly subdivided small liquid droplets. Note also that the application of the liquid cryogen would be at a location within the vortex, not mixed in as a part of the charge material itself. - As noted with regard to the embodiment where the molten metal has a generally flattened surface shape, the
volume 500C ofliquid cryogen 500A is either formed proximate theside wall 110 of thecontainer 100 or may be directed into contact with a portion of the molten metal. In one embodiment, the volume of liquid cryogen is directed to a confined area (particular portion that does not constitute the whole surface of the molten metal) of the surface of the molten metal. In another particular embodiment, the volume of liquid cryogen is directed to the edge portion of the surface proximate the side wall. Of these embodiments, the later is the more preferred. - Thus, with the above noted hood configuration, the flow of
liquid cryogen 500A in each of the embodiments forms asmall volume 500C of liquid cryogen on the surface of themetal 300, adjacent theside wall 110 with regard toFIG. 1 andFIG. 3 and either adjacent to theside wall 110 or within a particular portion of the flattened surface shape with regard to the flattened condition. Due to the heat generated by the surface of themolten metal 300, as well as the heat radiated by thefurnace walls 110, the pool/volume ofliquid cryogen 500C vaporizes, generating an expanding volume ofinert gas 600 that expands across the entire exposed surface of themetal 300. This expansion pushes ambient air away from the surface of themetal 300, and infiltrates any charge material melting at the molten surface. This, in turn, provides a true inert atmosphere directly at the metal surface. The expansion rate of thegas 600 is generally dependant upon the type of inert gas utilized in forming the inert blanket (e.g., argon, nitrogen, or carbon dioxide). By way of example, as the pool/volume 500C of liquid cryogen boils from liquid to gas, it may expand volumetrically by a factor of about 600-900 times as it rises. By way of specific example, argon expands up to 840 times the liquid volume while heating up from −302° F. (−185° C.) to room temperature. - The faster the expanding
gas 600 expands, the quicker it escapes thecontainer 100, becoming lost into the surrounding environment. Such a loss not only reduces the effectiveness of the inert blanket, but also alters the surrounding atmosphere (e.g., exposing users to inert gas). To minimize and/or eliminate the rate of loss of the expanding volume ofgas 600 from thecontainer 100, thedelivery system 200 further directs a shroud ofvaporous cryogen 500B into the container, where it reinforces the expanding volume ofinert gas 600 generated from the pool/volume 500C of cryogenic liquid, maintaining the expandingvolume 600 proximate the exposed metal surface. Specifically, thehood 230 directs thevaporous cryogen 500B toward the expandinggas 600, reinforcing the expanding gas and inhibiting its rate of expansion and diffusion into the atmosphere above thecontainer 100. This alleviates a major drawback of conventional liquid inerting (discussed above), where a large portion of the inert cryogen is lost (e.g., when vented off to avoid lance sputtering). - The flow rate of the
biphasic cryogen source 400 should be effective to provide a continuous volume of expandinginert gas 600, to maintain a localized pool/volume 500C of liquid cryogen on the surface of the metal 300 (i.e., to prevent theliquid cryogen 500A from creating a pool/volume 500C that covers the entire surface of the metal 300), and to maintain the flow reinforcingvaporous cryogen 500B toward the metal surface. Preferably, the flow rate is determined as a function of the surface area of themetal 300. This is contrary to the prior art processes, which calculate the flow rate utilizing the volume of the metal. Preferably, the continuous stream of cryogen is maintained at a flow rate of about 0.001 lb/in2/min. to about 0.005 lb/in2/min. (about 0.07 g/cm2/min. to about 0.35 g/cm2/min.), alternatively from about 0.002 lb/in2/min. to about 0.005 lb/in2/min. (about 0.14 g/cm2/min. to about 0.35 g/cm2/min.) of the exposed metal surface area in thecontainer 100. This maintains a flow of cryogen at a rate effective to generate a beneficial amountvaporous cryogen 500B capable of reinforcing the expandinggas 600. For example, the ratio ofliquid cryogen 500A tovaporous cryogen 500B exiting thelance 210 may be about 99/1 to about 51/49, depending on the thermal quality of the cryogen distribution system and the working pressure of the cryogen supply tank. Flow rates above the preferred range tend to increase process costs, as well as lead to the “popping” of themetal 300 out of thecontainer 100 due to volumetric and mechanical expansion of thecryogen 500C as it transitions from a liquid to a vapor. This creates a hazardous situation for users in the area around thecontainer 100. - In operation, the
hood 230 directs theliquid cryogen 500A into thecontainer 100, causing the liquid cryogen to fall from thelance 210 adjacent to theside wall 110 and form the small volume (pool 500C) of liquid cryogen on the surface of themetal 300, adjacent the side wall of thecontainer 100. In the embodiment that deals with a generally flattened surface shape, the hood directs the liquid cryogen into the container causing the liquid cryogen to fall from the lance either adjacent to the side wall or within a particular confined area on the surface of the molten metal. Theliquid volume 500C in each case vaporizes, creating an expandinggas 600 that expands across the entire surface of themetal 300. At the same time, thehood 230 directs thevaporous gas 500C downward, toward the metal surface, inhibiting the expansion of the expandinggas 600, maintaining the reinforced vapor near the surface of themetal 300. - Conventional processes use either already expanded inert gas or an inert cryogenic liquid as a protective barrier for the molten metal and/or charge material in the container. The vapor reinforced expanding gas approach to inert blanketing is distinguished from such conventional processes in that it offers a higher level of safety for the furnace operator, an increased consistency and effect of the inert blanket, and an increase in inert gas efficiency or lower application cost. It delivers the entire inert product from the
source 400 through thedelivery system 200 to the internal atmosphere of thecontainer 100 at a point above the melt interface. - This above-describe system is effective to guide the
vaporous cryogen 500B into thecontainer 100, providing for the complete utilization of the vaporous cryogen, using it to reinforce the expandinggas 600. In conventional systems, a 3-15% of the inert cryogen is wasted of the tip of a lance due to flash losses. The present system avoids these losses by completely utilizing thevaporous cryogen 500B, directing it into thecontainer 100 in a manner (at a speed and in an amount) effective to minimize and/or avoid flash losses. - While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. For example, the
hood 230 may possess any dimensions and shape suitable for its described purpose (directing a biphasic flow into the container), and may be modified based on factors such as manufacturing cost, manufacturing method, and application site parameters. In addition, while the flow rate is dependent primarily upon the surface area of themetal 300 in thecontainer 100 requiring protection by the expandinggas 600, secondary factors may be used to determine the flow rate of the liquid cryogen, such as the reactivity of the alloy or metal being protected, the existence and strength of the ventilation system, and the quality requirements of the end user for the metal being produced. Furthermore, while asingle source 400 of inert cryogen is illustrated, it is understood thatmultiple sources 400 may be connected to lance 210 to provide multiple types of inert cryogen to the container, including mixtures. - In addition, the systems and methods described can include any one or more suitable controllers and/or sensors to facilitate monitoring and control of various operational parameters during heating of the load in the furnace. One or more suitable sensors and related equipment can also be provided to measure and monitor the concentration of the gaseous species within the furnace, preferably at locations in the immediate vicinity of the load surface. In addition, with regard to each embodiment of the present invention, there may be either one or more than one injection site depending upon the particular container utilized with the number typically depending upon such factors as the size and shape of the container. More specifically, there may be multiple streams dispersed throughout the container with the number being from one stream to six streams. Also, when the
container 100 is an induction furnace, the induction furnace can include any suitable number and different types of sensors to monitor one or more of the temperature, pressure, flow rate and concentration of nitrogen and/or any other gaseous species within the furnace. - It is to be understood that terms such as “top”, “bottom”, “front”, “rear”, “side”, “height”, “length”, “width”, “upper”, “lower”, “interior”, “exterior”, and the like as may be used herein, merely describe points of reference and do not limit the present invention to any particular orientation or configuration. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
Claims (19)
1. A method for reducing the oxidation of molten metal, the method comprising:
(a) forming molten metal within a container, the molten metal having an exposed surface defining a surface area and possessing a generally meniscoid shape with a lowered center meniscus portion and a upper edge meniscus portion;
(b) generating a biphasic inert cryogen comprising a liquid flow component and a vaporous flow component;
(c) directing the liquid flow component into contact with the upper edge meniscoid portion of the molten metal to generate an expanding gaseous volume having a rate of expansion; and
(d) directing the vaporous flow component into the container to inhibit the rate of expansion of the gaseous volume.
2. The method of claim 1 , wherein (b) comprises (b.1) directing a flow of biphasic inert cryogen at a flow rate effective to generate the expanding gaseous volume that is substantially coextensive with the exposed surface of the molten metal.
3. The method of claim 2 , wherein the flow rate is dependent upon the surface area of the molten metal.
4. The method of claim 2 , wherein the flow rate is in the range of about 0.001 lb/in2/min. to about 0.005 lb/in2/min., based upon the surface area of the molten metal.
5. The method of claim 1 , further comprising (e) maintaining the flow rate to localize the liquid flow component within a portion of the molten metal exposed surface.
6. The method of claim 1 , wherein:
the container comprises:
a bottom wall,
a side wall, and
an opening; and
(c) further comprises directing the liquid flow component proximate the side wall such that the liquid flow component contacts the molten metal at a point proximate the side wall.
7. The method of claim 6 , wherein the flow rate of the inert cryogen is maintained such that liquid flow is localized within an area smaller than the total surface area of the molten metal exposed surface.
8. The method of claim 7 , wherein the flow rate is in the range of about 0.001 lb/in2/min. to about 0.005 lb/in2 min., based upon the surface area of the molten metal.
9. The method of claim 1 , wherein:
(a) the container comprises a side wall;
(b) generating the biphasic inert cryogen comprises (b.1) directing a liquid inert cryogen from a source through a diffuser to separate the liquid flow component from the vaporous flow component; and
(c) directing the liquid flow component comprises (c.1) directing the liquid flow component along the side wall such that it contacts the upper edge meniscoid portion to form a volume of vaporizing liquid cryogen localized within the upper edge meniscus edge portion.
10. The method of claim 1 , wherein (b) generating the biphasic inert cryogen comprises (b.1) directing a liquid inert cryogen from a source through a diffuser to separate the liquid flow component from the vaporous flow component.
11. The method of claim 1 , wherein:
(a) the container comprises a side wall;
(b) generating the biphasic inert cryogen comprises (b.1) directing a liquid inert cryogen from a source through a diffuser to separate the liquid flow component from the vaporous flow component; and
(c) directing the liquid flow component comprises (c.1) directing the liquid flow component along the side wall such that it contacts the lower centered meniscoid portion to form a volume of vaporizing liquid cryogen localized within the lower meniscus edge portion.
12. A method for reducing the oxidation of molten metal, the method comprising:
(a) forming molten metal within a container, the molten metal having an exposed surface defining a surface area and possessing a generally flattened surface shape;
(b) generating a biphasic inert cryogen comprising a liquid flow component and a vaporous flow component;
(c) directing the liquid flow component into contact with a confined area on the surface of the molten metal to generate an expanding gaseous volume having a rate of expansion; and
(d) directing the vaporous flow component into the container to inhibit the rate of expansion of the gaseous volume.
13. The method of claim 12 , wherein (b) comprises (b.1) directing a flow of biphasic inert cryogen at a flow rate effective to generate the expanding gaseous volume that is substantially coextensive with the exposed surface of the molten metal.
14. The method of claim 13 , wherein the flow rate is dependent upon the surface area of the molten metal.
15. The method of claim 13 , wherein the flow rate is in the range of about 0.001 lb/in2/min. to about 0.005 lb/in2/min., based upon the surface area of the molten metal.
16. The method of claim 15 , further comprising (e) maintaining the flow rate to localize the liquid flow component within a portion of the molten metal exposed surface.
17. The method of claim 12 , wherein:
the container comprises:
a bottom wall,
a side wall, and
an opening; and
(c) further comprises directing the liquid flow component proximate the side wall such that the liquid flow component contacts the molten metal at a point proximate the side wall.
18. The method of claim 17 , wherein the flow rate of the inert cryogen is maintained such that liquid flow is localized within an area smaller than the total surface area of the molten metal exposed surface.
19. The method of claim 18 , wherein the flow rate is in the range of about 0.001 lb/in2/min. to about 0.005 lb/in2 min., based upon the surface area of the molten metal.
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US13/632,923 US20130025415A1 (en) | 2006-08-23 | 2012-10-01 | Vapor-reinforced expanding volume of gas to minimize the contamination of products treated in a melting furnace |
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US12/271,994 US20090064821A1 (en) | 2006-08-23 | 2008-11-17 | Vapor-Reinforced Expanding Volume of Gas to Minimize the Contamination of Products Treated in a Melting Furnace |
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Cited By (1)
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US20130125839A1 (en) * | 2010-08-02 | 2013-05-23 | L'air Liquide Societe Anonyme Pour L'etude Et L' Exploitation Des Procedes Georges Claude | U-tube vaporizer |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20130125839A1 (en) * | 2010-08-02 | 2013-05-23 | L'air Liquide Societe Anonyme Pour L'etude Et L' Exploitation Des Procedes Georges Claude | U-tube vaporizer |
US9109795B2 (en) * | 2010-08-02 | 2015-08-18 | L'Air Liquide Société Anonyme Pour L'Étude Et L'Exploitation Des Procedes Georges Claude | U-tube vaporizer |
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Legal Events
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Owner name: AIR LIQUIDE INDUSTRIAL US LP, TEXAS Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:LASORDA, TERENCE D.;JEPSON, STEWART C.;REEL/FRAME:021938/0063;SIGNING DATES FROM 20081114 TO 20081117 |
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STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |