CN101117698A - Process and apparatus for preparing a metal alloy - Google Patents
Process and apparatus for preparing a metal alloy Download PDFInfo
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- CN101117698A CN101117698A CNA2007101482904A CN200710148290A CN101117698A CN 101117698 A CN101117698 A CN 101117698A CN A2007101482904 A CNA2007101482904 A CN A2007101482904A CN 200710148290 A CN200710148290 A CN 200710148290A CN 101117698 A CN101117698 A CN 101117698A
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Abstract
A method and apparatus for producing a metal component from a non-dendritic, semi-solid metal alloy slurry involves the use of a graphite agitator that is functionally equivalent to conventional metal rod agitators, and has the additional advantage of having a very low surface wettability, whereby labor and expenses associated with removing a metal alloy skin formed after withdrawal of the agitator from a metal slurry is eliminated or at least substantially reduced. The invention also provides an improved process and apparatus for producing a metal component from a non-dendritic semi-solid metal slurry by transferring the slurry to a cooling vessel for subsequent cooling and raising of the solids content without agitation after the slurry has been formed with agitation in a first vessel, whereby more rapid cooling of the slurry and increased production rates are achievable.
Description
The divisional application is based on the Chinese patent application with the application number of 200480008420.9 (the international application number is PCT/US 2004/006224), the application date of 3/1/2004 and the invented name of "method and device for preparing metal alloy".
According to article 35 of the U.S. code, article 119 (e), which claims James A Yurko equal to the priority of "PROCESS AND APPARATUS FOR PREPARING METAL ALLOY" filed on 3, 4, 2003 with the application serial number 60/451,748, the entire disclosure of which is incorporated herein by reference, AND according to article 35 (e) of the U.S. code, which claims James A Yurko equal to 6, 2003 with the application serial number 60/476,438, the entire disclosure of which is incorporated herein by reference.
Technical Field
The present invention relates to the field of industrial metal forming, and more particularly to an apparatus and method for forming a metal part from a non-dendritic, semi-solid metal slurry.
Background
It is well known that most metal alloy compositions are dendritic. As the alloy composition cools below the liquidus temperature, it gradually forms dendritic or tree-like particles starting from the crystal nuclei. It is also well known that there are certain advantages to segmenting dendritic particles or to preventing dendritic growth during consolidation to form generally spherical or ellipsoidal non-dendritic or degenerate dendritic particles. In particular, it has been discovered that various process and physical property advantages can be obtained by forming metal components from a non-dendritic, semi-solid metal slurry by casting or other methods. The non-dendritic metal particles in the semi-solid metal slurry substantially reduce the viscosity of the particular solid portion as compared to the semi-solid metal alloy composition containing dendritic particles. The difference in viscosity is typically several orders of magnitude.
Advantages of non-dendritic semi-solid metal forming include: higher speed part forming, high speed continuous casting, lower mold erosion, less energy consumption, improved mold filling, reduced oxides (which improve the processability of the final metal part), less entrapped gas (thereby reducing its porosity). Other advantages of casting or otherwise forming a metal component from a semi-solid slurry include less shrinkage during formation of the metal component, less porosity and less porosity in the formed metal component, lower and macrosegregation, and more uniform mechanical properties (e.g., strength). It is also possible to form more complex components using non-dendritic, semi-solid alloy compositions in casting or other forming processes. For example, a component having a thinner outer wall and improved strength characteristics may be formed.
Non-dendritic, semi-solid slurries for industrial casting and other metal forming processes have been prepared by the use of mechanical mixing during the cooling of liquid metal alloy compositions below the liquidus temperature of the alloy composition. Other techniques that have been used include electromagnetic stirring during cooling (typically used in continuous casting processes), cooling of the liquid metal composition as it passes through tortuous passages, prolonged heat treatment in the semi-solid temperature region, and the like. These processes are well known and have been well adapted for use in a variety of industrially important applications.
More recently, non-dendritic semi-solid slurries have been produced by pouring superheated molten alloy into a relatively cool vessel, such as a furnace or the cooling chamber of a die-casting machine. These processes rely on cooling the alloy composition from above the liquidus temperature to below the liquidus temperature as the alloy contacts the vessel wall during the pouring process. This process is effective in forming a non-dendritic, semi-solid metal slurry; however, it has process limitations. First, the process relies on the removal of heat from the vessel wall. Controlling heat removal using this technique is difficult due to the varying container wall temperatures and the discontinuous cylinder surface area. Second, convection can occur through decantation; thus, if the alloy is injected at too high a temperature, the convective forces will dissipate before the alloy cools through the liquid phase, preventing the formation of a non-dendritic slurry.
The industry includes a variety of aluminum magnesium alloy parts used in automotive applications, such as main brake cylinders, and various parts used in steering and suspension systems. Other practical or potential applications include rocker arms, engine pistons, wheels, transmission components, fuel system components, and air conditioning components.
One problem with known processes that use mechanical agitation to form a non-dendritic, semi-solid metal slurry is that the surfaces of the agitator become wetted by the liquid metal in the metal slurry. Therefore, when the stirrer is removed from the metal paste, some of the liquid metal in the metal paste sticks to the surface of the stirrer. Some of the liquid metal that wets or sticks to the surface of the stirrer and/or vessel quickly solidifies and forms a metal coating that must be removed before the stirrer and/or vessel can be used again to make more non-dendritic semi-solid metal slurry. Removal of metal deposits from the surfaces of the stirrer is often difficult, time consuming and costly, and results in lower yields. Materials with lower wettability are generally not suitable for processing liquid metal alloy compositions (e.g., because they lack sufficient mechanical properties associated with the production of the non-dendritic semi-solid metal slurry at high temperatures) and/or do not have sufficiently high thermal conductivity suitable for rapid heat removal from the non-dendritic semi-solid metal slurry. Lower wettability can be achieved by applying a coating with low wettability to the surface of the metal stirrer. Boron nitride coatings have been used on stirrer and/or container surfaces to successfully reduce wettability without reducing thermal conductivity. However, boron nitride coatings lack structural strength and need to be replaced periodically.
Another problem with conventional processes for preparing non-dendritic, semi-solid metal alloy compositions having relatively high solids contents (e.g., greater than about 10%) is that a significant amount of time is often required to cool the metal slurry to achieve the desired solids content. The alloy composition is typically agitated in a ceramic vessel or a preheated vessel to prevent the formation of nuclei and solids on the walls of the vessel (where agitation is accomplished). Therefore, the cooling is performed relatively slowly, resulting in longer processing time and lower throughput. Rapid cooling can be achieved by using a cool container with sufficient mass, thermal conductivity and thermal capacity. However, this can create unacceptably high temperature gradients that are detrimental to the formation of the non-dendritic, semi-solid metal slurry, and/or cool the alloy composition to temperatures that are not suitable for configuring the alloy composition into the desired component.
U.S. Pat. No. 6,645,323 discloses a skinless metal alloy composition that is free of occluded gas and includes discrete degenerate dendrites of a primary phase solid uniformly distributed in a secondary phase. The disclosed alloys are formed by a process that heats a metal alloy in a vessel until it becomes liquid. Thereafter, the liquid is rapidly cooled while stirring is being attempted under conditions that avoid enclosing the gas therein when solid crystal nuclei uniformly distributed in the liquid are formed. The cooling and agitation can be accomplished by a cooled rotary probe that extends into the liquid. When the liquid contains a small amount of solid or the liquid-solid alloy is removed from the stirring source, the stirring is stopped while cooling is continued to form discontinuous degenerate dendrites of the primary phase solid in the secondary phase of the liquid. The solid-liquid mixture is then formed, for example by casting. One problem with the process disclosed in US6,645,323 is that the cooled rotating probe used for cooling and stirring tends to be coated with liquid metal which adheres to the surfaces of the stirrer. Thus, the agitator described in this patent requires frequent cleaning and/or replacement. In addition, there is a need for improved control of the amount of heat rejected by the aluminum alloy composition. In certain aspects of the present invention, methods and apparatus are provided that address these deficiencies.
Disclosure of Invention
The present invention provides an improved method for producing a non-dendritic, semi-solid alloy slurry for forming a metal component. In particular, the present invention provides an apparatus and method that facilitates rapid cooling of a non-dendritic semi-solid metal slurry and/or eliminates or reduces problems associated with the accumulation and removal of metal on the surfaces of the apparatus that contact the metal slurry.
According to one aspect of the present invention, there is provided a method and apparatus for producing a non-dendritic, semi-solid metal alloy slurry using a graphite agitator. The graphite stirrer has suitable high temperature strength properties and thermal conductivity which facilitates rapid cooling of the liquid alloy constituents and which also exhibits low wettability, thus eliminating or greatly reducing the need to remove metal from the stirrer surface after the stirrer is removed from the metal slurry and any metal that has accumulated on the stirrer can be easily removed. Thus, the graphite stirrer can be used to simultaneously remove heat from the alloy composition and can also promote the generation of convection currents that contribute to the formation of the non-dendritic, semi-solid alloy composition and can also avoid the freezing or deposition of metal slurry on the stirrer.
According to another aspect of the invention, the amount of heat removed from the aluminum alloy composition can be controlled by contacting the aluminum alloy composition with the stirrer for a predetermined period of time, depending on the initial temperature of the aluminum alloy composition prior to contact with the stirrer and the rate at which the stirrer removes heat.
In yet another aspect, a method and apparatus for rapidly cooling a non-dendritic, semi-solid metallic alloy slurry is provided that cools a temperature at which the metallic alloy slurry contains a relatively low solids content (e.g., from about 1 to about 10 weight percent) to a temperature at which the metallic alloy slurry contains a relatively high solids content (e.g., from about 10 to about 65 weight percent). The method and apparatus described involve the use of a vessel having walls made of a material with high thermal conductivity that facilitates rapid cooling of the metal alloy slurry. Fans or blowers may be used to direct cool air around the vessel walls.
These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.
Drawings
FIG. 1 is a schematic diagram of an apparatus according to an embodiment of the present invention.
Fig. 2 is a schematic diagram according to another embodiment of the present invention.
Detailed Description
As shown in fig. 1, an apparatus 10 for producing a non-dendritic, semi-solid metal alloy composition in accordance with an embodiment of the present invention is illustrated. A non-dendritic semi-solid metal component is a component containing a liquid metal and discrete solid non-dendritic alloy particles distributed in the liquid metal. A non-dendritic particle is a particle that is generally spherical or ellipsoidal and that is produced by convection in the liquid phase at a temperature below the liquid phase temperature of the alloy composition during liquid nucleation and cooling. One accepted theory holds that non-dendritic particles are generated by convection currents which break the growing dendritic arms, with subsequent ripening helping to smooth the particles into characteristic spherical and/or ellipsoidal shapes. For this reason, non-dendritic particles are sometimes referred to as degenerate dendritic particles.
The apparatus includes a first holding vessel 12 for containing and holding a liquid alloy composition into which a stirrer 14 is inserted and rotated to generate convection currents in the liquid alloy composition. The stirrer also conducts heat from the alloy components and forms nuclei. As the liquid metal alloy is cooled from a temperature just above the liquidus temperature to a temperature below the liquidus temperature, the non-dendritic solid particles 16 gradually precipitate from the liquid as the composition is agitated, forming a semi-solid metal slurry 18. Ideally, the stirrer is made of a material and has a mass that rapidly removes heat from the alloy composition as the alloy composition decreases from a temperature slightly above the liquidus temperature to a temperature a few degrees below the liquidus temperature. That is, the agitator 14 is designed to rapidly remove the heat required to form the non-dendritic, semi-solid metal alloy constituent, which typically contains about 1% to about 20% by weight solids content. The duration of stirring with the stirrer controls the amount of heat removed from the aluminum alloy composition. Thus, if there is a change in the initial metal temperature, the duration of the stirring is controlled to produce a product at the same temperature. The temperature of the metal may be controlled using any of a variety of devices, such as optical pyrometers, thermocouples, and the like.
For example, the agitator 14 may be cylindrical. Thus, the agitator 14 can be significantly different from conventional agitators that physically break the dendrites as they form. However, the cylindrical stirrer which enables rapid cooling generates crystalline nuclei or degraded dendrites distributed by convection generated by the stirring motion. Thus, the formation of a non-dendritic metal paste using conventional mechanical agitation, which physically breaks up the dendritic arms, is not necessary.
According to a preferred embodiment of the invention, the stirrer is made of a material having a relatively high thermal conductivity (preferably comparable to that of copper) and a relatively low wettability in the presence of aluminum (preferably comparable to boron nitride). One recognized stirrer may be a copper stirrer coated with boron nitride. It would be further desirable to provide an uncoated stirrer having the required thermal diffusivity to rapidly remove heat, which is important to prevent the stirrer surfaces from approaching the liquidus temperature of the alloy composition, and also having the required low wettability to prevent metal buildup or build up on the stirrer surfaces as they are removed from the metal slurry. It has been found that a very useful material for making the agitator 14 is graphite. Graphite has a relatively high thermal diffusivity (e.g., comparable to copper) and a relatively low wettability (e.g., comparable to boron nitride coatings). It has been found that graphite stirrers have strength and thermal properties that are functionally equivalent to stirrers commonly used to form non-dendritic, semi-solid metal alloy slurries, and also add the advantage of being substantially non-wetting to the liquid metal alloy. Thus, it is possible to reuse the graphite stirrer in a plurality of separate cycles without removing the metal alloy from the stirrer surface. However, the rod surface must be at a temperature below the liquidus temperature of the alloy to quickly remove heat from the molten alloy. In addition, any accumulated metal can be easily removed, for example by passing the surface of the graphite stirrer against the sleeve.
The method of the present invention includes a first step of forming a metal alloy liquid composition. The liquid alloy composition is located in vessel 12 and allowed to cool while attempting to stir the alloy to be cooled, such as by stirring under conditions to form solid, nucleated particles, while avoiding the entrapment of gases within the stirred alloy composition. Efforts are made to stir the alloy while it is cooling in a manner such that the solid nuclei are substantially uniformly distributed throughout the metal liquid alloy composition. The stirring can be carried out for a short period of time, such as between about 1 second and about 1 minute, preferably between about 1 second and 30 seconds, using a speed range of rapid cooling within a temperature range corresponding to a percent solidification of the alloy of between about 1% and about 20% by weight solids, preferably between about 3% and about 7% by weight solids. The stirring can be achieved in any way using a cold stirrer, which avoids creating too many cavities in the liquid surface and thus avoids enclosing the gas in the liquid. The stirrer may be cooled by passing a heat exchange fluid, such as water. Representative suitable stirring means include one or more cylindrical rods provided with internal cooling means, helical stirrers or the like, which preferably extend through the depth of the liquid. The stirrer extends into the liquid to a depth of substantially 100% of the liquid depth to assist in the uniform distribution of the crystal nuclei. Then, the stirring is stopped in one batch production, or the liquid-solid alloy is removed from the stirring source in a continuous production. Thereafter, the formed liquid-solid metal alloy composition is cooled in a vessel to cause the formation and concentration of spherical solid particles around the solid nucleation particles, wherein the non-dendritic spherical and/or ellipsoidal solid particles increase the viscosity of the entire liquid-solid composition, wherein the liquid-solid composition can be moved to a forming step, such as a casting step. Typically, the upper weight percentage of non-dendritic primary phase solids is between about 40% and about 65%, and preferably contains 10% to 50% of the total weight of the liquid-solid content. Without stirring, the formation of spherical and/or ellipsoidal solid particles can be achieved by coarsening without forming an inter-crosslinked dendritic network. Since the stirring is effected only for a short time, the confinement of the gas within the alloy composition is avoided. Furthermore, it has been found that by operating in this manner, macro-segregation of elements is eliminated or minimized throughout the entire batch of metal alloy products produced. Thereafter, the liquid-solid component is shaped, for example by casting.
The metal alloy composition comprising the non-dendritic solid metal alloy particles and the liquid phase may be comprised of a variety of metals or alloys that form a dendritic network when frozen from the liquid state without agitation. The non-dendritic particles may consist of a primary phase having an average composition which is different from the average composition of the surrounding secondary phase (temperature dependent liquid or solid), which itself may comprise both primary and secondary phases upon further solidification.
The non-dendritic solid (degenerate dendrite) is characterized by having a smooth surface and few branch structures, which are closer to a spherical structure than a general dendrite and have no dendritic structure in which the interconnection of primary phase particles is affected to form a dendritic network structure. Furthermore, the primary phase solids are not substantially co-crystals. The term "secondary phase solid" as used herein means a phase state formed by the solidification of a liquid present in a metal slurry at a temperature lower than the temperature at which non-dendritic solid particles are formed. Typically, the solidified alloy has dendrites that separate from each other at an early stage of solidification, i.e., a weight percentage of solids that reaches 15 to 20, and which forms an interconnected network as the temperature decreases and the weight percentage of solids increases. On the other hand, the components of the invention containing a primary phase, non-dendritic solid, prevent the formation of interconnected network structures by maintaining the discrete non-dendritic particles separated from each other by the liquid phase even at a fraction of solids of up to 65% by weight.
After the formation of the non-dendritic solid, during the formation of the liquid phase by solidification, the formed secondary phase solid contains one or more types of phase states, which can be obtained during solidification by conventional forming methods. That is, the secondary phase comprises a solid solution, or a mixture of dendrites, compounds and/or solid solutions.
The size of the non-dendritic particles depends on the alloy or metal component used, the temperature of the solid-liquid mixture, and the time it takes for the alloy to be in the solid-liquid temperature range. In general, the size of the primary phase particles depends on the composition and heat engine history of the metal slurry, the number of nuclei formed, the cooling rate, and is in the range of about 1 micron to about 10,000 microns and uniform in size throughout the metal alloy composition. Preferably, because these ingredients have a viscosity that facilitates ease of casting or forming, the ingredients comprise 10 to 50 weight percent primary phase solids.
The composition of the present invention may be formed from any metal alloy system that forms a dendritic structure when formed by freezing from a liquid state. Even if pure metals and eutectics melt at a certain temperature, they can be used to form the compositions of the present invention because they have a liquid-solid equilibrium at the melting point by controlling the net heat input or output to the melt so that the metal or eutectic contains enough heat at the melting point to melt only a portion of the metal or eutectic liquid. This occurs because complete removal of the heat of fusion within the metal slurry used in the casting process of the present invention cannot be achieved by equalizing the heat supplied to the heat removed by the ambient cooling means. Typical suitable alloys include, but are not limited to, lead alloys, magnesium alloys, zinc alloys, aluminum alloys, copper alloys, iron alloys, cobalt alloys. Examples of such alloys are lead-tin alloys, zinc-aluminum alloys, zinc-copper alloys, magnesium-aluminum-zinc alloys, magnesium-silicon alloys, aluminum-copper-zinc-magnesium alloys, copper-tin-bronze, brass, aluminum bronze, steel, cast iron, tool steel, stainless steel, super heat resistant stainless steel, and cobalt-chromium alloys, or pure metals such as iron, copper, or aluminum.
Fig. 2 shows an alternative embodiment of the invention which includes apparatus 10 which is substantially similar to the embodiment shown in fig. 1, but which includes a cooling vessel 20 into which the metal slurry 18 is poured 20 after stirring is complete in holding vessel 12 and the solids content reaches about 1% to about 20%. The cooling vessel 20 has a wall 22 made of a material with high thermal conductivity. The vessel wall 22 has a total thermal capacity (wall specific heat capacity multiplied by wall mass) that allows the wall 22 to quickly reach temperature equilibrium with a given amount of metal slurry 18 to enable rapid cooling of the metal slurry while maintaining a relatively low preset temperature before the vessel wall 22 is in contact with the metal slurry, thereby achieving the desired solids content. A fan or blower 24 may be used to generate a high velocity that removes heat from the metal slurry passing through the wall 22 and from the wall 22 to the surrounding air, thereby causing the metal slurry 18 to cool rapidly. This allows for higher production speeds.
Suitable materials having high thermal conductivity, including steel, stainless steel, and graphite, may be used to fabricate the walls of vessel 20. Graphite is well suited for high volume production at low cost because it has a high thermal conductivity compared to metals, and its surface exhibits low wettability for various metal alloys of interest, such as alloys of aluminum and magnesium. Thus, relatively rapid cooling of the alloy slurry from a relatively low solids content (e.g., from about 1% to about 20%) to a relatively high solids content (e.g., from about 10% to about 65%) is possible, while the surfaces of the vessel 20 can be reused without subsequent cleaning to remove metal deposits and/or can be relatively easily removed, so high speed production is possible at low cost. When container 20 is made of a metal or other material having a wettable surface relative to the metal slurry, the interior walls of the container in contact with the alloy slurry are preferably coated with a low wettability coating, such as a boron nitride coating.
The cooling vessel 20 may be cooled by passing a heat transfer fluid through cooling passages formed or disposed within the walls of the cooling vessel. Also, the cooling vessel may have a suitable surface area, mass and heat capacity to rapidly cool the metal slurry from a lower solids content to a desired higher solids content at rest without cooling the metal slurry to a temperature suitable for forming the desired metal part.
After the metal slurry 18 is cooled to the desired higher solids content without agitation (i.e., at rest), the metal slurry can be formed into the desired metal part, such as by casting.
First example of graphite stirrer
A batch of molten aluminum alloy is held in a vessel. The aluminum alloy has the following properties:
temperature (T) I )＝640℃
Latent heat of fusion (H) f ) =400,000j/kg (where J is joule, energy unit)
Heat capacity (C) of aluminum p )≈1,000J/(kg℃)
The aluminum alloy amount (m) is approximately equal to 4kg
In order to cool the partially solidified aluminum alloy to 610 ℃ and a percent solids of 0.10, the following amounts of heat must be removed:
solids content (. DELTA.f) s )＝0.10
Temperature (T) f )＝610℃
To remove 280,000 joules of energy, the rod must have sufficient mass and thermal capacity to absorb this amount of energy. The rod must also have a sufficiently high thermal diffusivity, α, to allow heat to be removed from the rod from the surface, keeping the surface temperature below the liquid temperature of the alloy.
Graphite cylindrical stirrer:
outer diameter (R) o )＝0.025m
Cylinder height (H) =0.25m
The density of the graphite is approximately equal to 1,800kg/m 3
Graphite mass =0.88kg
If the initial temperature of the rod is 100 ℃ and is raised to 500 ℃, the rod can remove the following amount of heat:
bar temperature =100 deg.c
Mass of graphite container =0.88kg
The heat capacity of the graphite is approximately equal to 800J/(kg DEG C)
The rod has sufficient mass and heat capacity to absorb the heat of the aluminum to cool the alloy from above its liquidus temperature to below its liquidus temperature.
Coefficient of thermal diffusion
The bar extracts heat from the molten aluminum alloy through its surface according to the following heat transfer formula:
q(W)＝hAΔT
heat transfer coefficient (h) approximately equal to 1,500W (m) 2 W is Watt (J/s).
Surface area of bar =0.0393m 2
Mean temperature difference =250 deg.c
The bar must remove 280,000j of heat and the heat transfer rate is 15,000w, so the time required to remove the heat transfer is about 19 seconds. This duration will vary depending on the thermophysical properties of the alloy, the initial temperature of the alloy, and the rod and mass and thermophysical properties.
The thermal diffusivity (α) is defined as the thermal conductivity (k) divided by the density (ρ) and heat capacity (C) of the material P ) Product:
for materials with lower thermal conductivity and high density, such as ceramic materials, the thermal diffusivity is lower. The material cannot transfer heat from its surface to its interior, and therefore, the surface temperature is in equilibrium with the alloy, and it cannot further lower the temperature of the alloy.
In addition to having a mass large enough to absorb energy from the alloy, the material of the rod must also have a suitable thermal diffusivity to transfer heat from the surface of the rod to its interior.
If a heat transfer fluid is used to remove heat from the rod with agitation and heat removal, a rod with a high thermal diffusivity may have a smaller mass than would normally be required to absorb sufficient energy in the alloy to initiate solidification.
Second example of graphite stirrer
A continuous batch of molten aluminum alloy is held in a container. The aluminum alloy has the following processes:
temperature of the first batch (T) I )＝640℃
Temperature of the second batch (T) I )＝657℃
Latent heat of fusion (H) f ) =400,000j/kg (where J is joule, energy unit)
Heat capacity (C) of aluminum p )≈1,000J/(kg℃)
The amount of aluminum alloy (m) is approximately equal to 4kg
In order to cool the partially solidified aluminium alloy to 610 ℃ and a solids content of 0.10, the following amounts of heat must be removed:
solids content (. DELTA.f) s )＝0.10
Temperature (T) f )＝610℃
First batch:
and (2) second batch:
the wand in this example can be removed 15000W. In the first batch the stick must be removed 280,000j, while in the second batch the stick must be removed 348,000j. The time required to remove heat from the first and second batches was 19 seconds and 23 seconds, respectively.
By measuring the temperature of the melt prior to cooling and stirring with the stirrer, the variation in temperature within the semi-solid slurry can be eliminated. The duration of stirring can be determined by a calculation method based on the temperature of the metal added, the temperature of the rod, the time delay (loss of energy to the surroundings), and the like.
Examples of cylindrical containers (cooling cups)
A batch of partially solidified aluminum alloy is stored in a container. The aluminum alloy has the following properties:
temperature (T) I )＝610℃
Solids content (f) s )＝0.10
Latent heat of fusion (H) f ) =400,000j/kg (where J is joule, energy unit)
Heat capacity (C) of aluminum p )≈1,000J/(kg℃)
The amount of aluminum alloy (m) is approximately equal to 4kg
In order to cool the partially solidified aluminium alloy to 590 ℃ and a solids content of 0.30, the following amounts of heat must be removed:
difference in solid content (. DELTA.f) s )＝0.20
Temperature (T) f )＝590℃
To remove 400,000 joules of energy, the vessel was designed to absorb this amount of heat. A thin-walled graphite container with the following properties can remove this heat.
A graphite cylindrical container:
inner diameter (R) i )＝0.0508m
Outer diameter (R) o )＝0.0568m
Height of cylinder (H) =0.2346m
Wall thickness (t) =0.006m
The density of the graphite is approximately equal to 1,800kg/m 3
Graphite mass =0.97kg
If the initial temperature is 90 ℃ and is in equilibrium with aluminum at 590 ℃, the graphite can remove the following amounts of heat:
the temperature of the graphite =90 deg.C
Mass of graphite container =0.97kg
The heat capacity of the graphite is approximately equal to 800J/(kg DEG C)
The graphite container required the same amount of heat to reach a temperature of 590 c. Thus, the graphite container is designed to rapidly remove a predetermined amount of heat to rapidly increase the solids content from a first value in the range of about 1% to about 10% by weight to a second value in the range of about 10% to 65% by weight.
The foregoing is considered as the preferred embodiment only. Many modifications may be made to the invention by one skilled in the art and to make or use the invention. Therefore, it is to be understood that the above-described embodiments are illustrative only and are not limiting upon the scope of the invention, which is to be given the full breadth of the appended claims when interpreted in accordance with the principles of patent law including the doctrine of equivalents.
Claims (7)
1. An apparatus for directly producing a non-dendritic, semi-solid metal alloy slurry from a liquid state for forming a metal part, comprising:
a container for holding a metal alloy composition; and
a graphite stirrer for generating convection currents when rapidly cooling the metal component to initiate solidification thereof and form non-dendritic solid particles in the metal alloy component.
2. The apparatus of claim 1, further comprising a separate cooling vessel.
3. An apparatus for producing a non-dendritic, semi-solid metal alloy slurry from a liquid state for forming a metal component, comprising:
a container for holding a metal alloy composition;
an agitator for creating convection currents upon rapid cooling of the metal component to initiate solidification thereof and formation of non-dendritic solid particles in the metal alloy component; and
a cooling vessel to further cool the slurry and increase its solids content.
4. The apparatus of claim 2 or 3, wherein: the cooling vessel has a wall made of one material selected from steel and stainless steel.
5. The apparatus of claim 2 or 3, wherein: the cooling vessel has walls made of graphite.
6. The apparatus of claim 4, wherein: the inner wall of the cooling container has a non-wetting or low-wetting coating.
7. The apparatus of claim 6, wherein: the coating is a boron nitride coating.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US45174803P | 2003-03-04 | 2003-03-04 | |
| US60/451,748 | 2003-03-04 | ||
| US60/476,438 | 2003-06-06 | ||
| US10/761,911 | 2004-01-21 |
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| CN102732951A (en) * | 2012-06-25 | 2012-10-17 | 中国科学院上海技术物理研究所 | Method for solidifying gallium-rich gallium arsenide melt used for liquid phase epitaxy |
| CN103147120B (en) * | 2013-04-01 | 2016-04-20 | 东方电气集团东方汽轮机有限公司 | A kind of device for directionally solidifying of superalloy |
| EP3142812B1 (en) * | 2014-05-16 | 2020-11-11 | Gissco Company Limited | Process for preparing molten metals for casting at a low to zero superheat temperature |
| CN105855498A (en) * | 2015-01-21 | 2016-08-17 | 中兴通讯股份有限公司 | Semisolid metal slurry preparation device and method |
| CN104907527A (en) * | 2015-06-17 | 2015-09-16 | 深圳领威科技有限公司 | Semi-solid pulping equipment, semi-solid pulping system and semi-solid pulping method |
| CN109226700B (en) * | 2018-10-25 | 2020-06-23 | 上海应用技术大学 | Device and method for preparing semi-solid metal slurry by U-shaped water-cooling stirring |
| CN111001778A (en) * | 2019-12-31 | 2020-04-14 | 北京科技大学 | Method for efficiently preparing large-volume semi-solid slurry by composite process |
| JP7247917B2 (en) * | 2020-02-19 | 2023-03-29 | トヨタ自動車株式会社 | Method for producing semi-solidified molten metal |
Family Cites Families (7)
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|---|---|---|---|---|
| US3902544A (en) * | 1974-07-10 | 1975-09-02 | Massachusetts Inst Technology | Continuous process for forming an alloy containing non-dendritic primary solids |
| JP3473214B2 (en) * | 1995-09-26 | 2003-12-02 | 宇部興産株式会社 | Forming method of semi-molten metal |
| CA2177455C (en) * | 1995-05-29 | 2007-07-03 | Mitsuru Adachi | Method and apparatus for shaping semisolid metals |
| JPH0987768A (en) * | 1995-09-22 | 1997-03-31 | Ube Ind Ltd | Production of half-melted hypereutectic al-si alloy |
| JP2849708B2 (en) * | 1996-04-05 | 1999-01-27 | 工業技術院長 | Appropriate condition automatic selection type continuous rheocasting method and apparatus |
| US5881796A (en) * | 1996-10-04 | 1999-03-16 | Semi-Solid Technologies Inc. | Apparatus and method for integrated semi-solid material production and casting |
| AU5121999A (en) * | 1998-07-24 | 2000-02-14 | Gibbs Die Casting Aluminum Corporation | Semi-solid casting apparatus and method |
-
2004
- 2004-03-01 CN CNB2004800084209A patent/CN100346904C/en not_active Expired - Lifetime
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103658608A (en) * | 2013-12-11 | 2014-03-26 | 昆明理工大学 | Device and application for preparing metal semi-solid slurry |
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| CN1767915A (en) | 2006-05-03 |
| CN100346904C (en) | 2007-11-07 |
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