CN1265915C - Method and apparatus for making metal alloy castings - Google Patents

Abstract

A method and apparatus are provided for fabricating of continuous castings with fine and uniform microstructure, which can be used as feedstock for secondary processing routes, such as thixoforming, forging and machining or direct application in industry. An overheated liquid alloy is fed into a high shear device (for example, a twin-screw extruder) and sheared intensively to produce a sheared liquid alloy or a semisolid slurry, wherein the sheared liquid alloy is at a temperature close to its liquidus and the semisolid slurry is then transferred to a shaping device for production of continuous castings with fine and uniform microstructures through a solidification process. The shaping device is any device capable of forming continuous (i.e. infinite length) products, such as a direct chill (DC) caster (DC rheocasting) for production of continuous billets, an extrusion die (rheo-extrusion) for production of continuous bars or wires, or a twin-roll caster (twin-roll rheocasting) for producing of continuous strips. In all those cases, the cross-section of the continuous castings exhibits a microstructure in which a controlled volume fraction of fine and spherical primary particles are uniformly distributed in a fine structured matrix.

Description

Method and apparatus for making metal alloy castings

technical field

This application relates to a method and apparatus for forming continuous products from liquid metal alloys, in particular for the manufacture of continuous castings which can be used as raw materials for secondary process processes such as thixoforming, forging and machining and have a fine and uniform microstructure . The present application also relates to articles such as billets, rods, wires, pipes or strips produced by these methods.

Background technique

In the metal forming industry, continuously cast billets are usually made by the direct chill (DC) casting process. In this process, superheated liquid alloy is continuously charged into a water-cooled cylindrical mold, and then the solidified alloy is continuously produced to form continuous casting strands. The final cross-section of the slab has three distinct zones, a chill zone at the surface, a columnar zone and a coarse equiaxed zone at the center. This microstructural inhomogeneity has limited the direct application of DC slabs.

Many secondary processing methods such as rolling, extrusion and recrystallization are commonly used to refine and homogenize the microstructure. Such secondary treatment processes are energy-intensive, time-consuming and costly. Therefore, there is an urgent need to develop a continuous casting process that can directly produce continuous casting slabs with fine and uniform microstructure without using these secondary treatment processes.

A known process using DC strands as raw material is the extrusion process to produce bars of simple or complex cross-section. Metal extrusion can be divided into two categories: cold extrusion and hot extrusion. In cold extrusion, cold metal is loaded into an open die at a temperature near room temperature. During metal cold extrusion, some pressure is necessary to force the metal through the die, which results in high cost of capital equipment, shortened die life and reduced energy utilization. In hot extrusion, the alloy billet is heated below its solidus line and thus extruded like a cold extrusion process. In hot extrusion, the life of the die can be increased but the utilization of energy is still limited. At the same time, it is very difficult to precisely extrude products (such as thin wires) with hot extrusion process. Therefore, it would be advantageous to develop an extrusion process that can directly form rods and wires from liquid alloys.

Another process using DC slab as raw material is the rolling process, which produces strip by continuously rolling the slab to the required thickness. The rolling process is more costly than the extrusion process because it is very energy intensive, has high capital equipment costs and low material yield.

Another technique for producing strip is the twin roll casting process, which is effective for a limited range of different metals. In the twin-roll casting process, a pair of rollers with transverse axes and rotating in opposite directions are positioned parallel to each other with a certain gap between them, and a liquid alloy molten pool is formed on the upper annular surface of the roller above the gap, and then the liquid alloy continues Cast into alloy strip.

Problems involved in the conventional twin roll casting process include leakage of liquid alloy near side dams, damage to side dams, formation of cracks in the side of the cast strip, short roll life, difficult process control and chemical segregation in the solid product.

There is another process using DC billet as raw material is the recently developed thixoforming process. It is basically a two-step method. In the first step, a modified DC casting process was used to produce thixotropic raw materials to produce cast strands with a non-dendritic microstructure. In the second step, the thixotropic billet/raw material is reheated to its semi-solid state (temperature between its solidus and liquidus) and then cast (thixocasting) or forged (thixoforging) to It forms pores. Ideally, the raw material for thixoforming should contain a certain amount of fine spherical solid particles in the matrix. The main current limitations of thixoforming are the low quality and high cost of raw materials. The processes used for the production of thixoforming raw materials include simple mechanical stirring, electromagnetic stirring, coarsening of the initial dendritic microstructure, adding a large amount of grain refiner during continuous casting, and using ultrasonic oscillation. However, these processes have certain disadvantages. An important disadvantage of the known method is the inhomogeneity of the microstructure in the cross-section, which makes the reheating process difficult and the mechanical properties of the final component relatively poor. Another disadvantage is due to the non-spherical particle morphology, since it requires long reheating times to spheroidize the solid particles, which reduces the potential advantage of the semi-solid process. Another disadvantage is the high cost of raw materials, which account for as much as 50% of the cost of the final component.

Numerous references disclose thixotropic molding processes in which a solid or semi-solid is first charged (eg, liquefied by heating the charge while shearing) and sprayed into a mold to form a component. These references include: EP 0867246 A1 (Mazda Motor Corporation); WO 90/09251 (The Dow Chemical Company); US 5,711,366 (Thixomat, Inc.); US 5,735,333 (The Japan Steel Works, Limited); US 5,685,357 (The Japan Steel Works, Limited); Steel Works, Limited); US4,694,882 (The Dow Chemical Company); and CA 2,164,759 (Inventronics Limited).

However, the disadvantage of converting solid particles into a thixotropic state by heating them (thixomoulding) rather than cooling liquid metal into a thixotropic state (rheomoulding) is the particle size and substructure in the thixotropic slurry. Particle size distribution is difficult to control. In particular, the particle size of thixomolded slurries tends to be an order of magnitude larger than that of rheologically molded slurries, and has a broader size distribution. This has the potential to adversely affect the structural properties of the cast article.

Furthermore, the above references use a standard single screw extruder to shear the thixotropic pulp, resulting in a lower quality product.

Many references do disclose rheological molding processes. For example WO97/21509 (Thixomat, Inc.) refers to a process for forming metal articles in which the alloy is heated above its liquidus temperature and then extruded using a single screw as the liquid metal cools to the region of two-phase equilibrium The machine shears the liquid metal.

US4,694,881 (The Dow Chemical Company) relates to a process in which a material with a non-thixotropic type of structure is loaded in solid form into a single screw extruder. The feedstock is heated above its liquidus temperature and then cooled under shear to below its liquidus temperature and above its solidus temperature.

WO95/34393 (Cornell Research Foundation, Inc.) also discloses a rheological molding process in which superheated liquid metal is cooled to a semi-solid state in the barrel of a single-screw extruder before being injected into a casting, and Simultaneously cut.

WO 01/21343 (Brunel University) is a co-pending application published after the priority date of the present invention. It discloses a process for forming liquid metal alloys into shaped products by cooling the alloy below its liquidus line while shearing in order to transform the alloy into a thixotropic state. The alloy is then fed into a discrete casting mold to make shaped products. The formation of continuously cast products is not disclosed therein.

WO 01/23124 (Brunel University) is another co-pending patent published after the priority date of the present invention. In particular it relates to a method of producing castings from metal alloys (with at least two immiscible components) in which the product is sheared to transform it into a semi-solid state slurry which can then be fed into a casting mold or a preheated in the metal belt.

No references to thixotropic or rheological molding describe processes capable of forming continuously cast products with sufficiently high structural integrity.

Contents of the invention

According to a first aspect of the invention there is provided a method of making a continuous product from a liquid metal alloy comprising cooling the alloy to approximately the liquidus or from the solidus of the alloy to the liquidus of the alloy, cooling the alloy Shearing at a high enough shear rate and turbulence intensity to convert the alloy to the thixotropic state and conveying the sheared liquid metal or sheared semi-solid slurry to a forming device capable of forming a continuous product.

Since "continuous product" refers to a product that is formed continuously, any length of product can be formed as long as sufficient raw material is provided. This is in contrast to a discontinuous (eg formed in a mould) product.

The forming device can be a DC caster (DC rheocasting), or an extrusion die (rheological extrusion), or a twin roll caster (twin roll rheocasting). The materials processed according to the invention may be miscible alloys or immiscible alloys, and in the case of immiscible alloys, the process is called rheological mixing.

It has been found that prior art thixotropic deformation occurs if the temperature of the loaded liquid alloy is lower and the viscosity is greater (which can be obtained by shearing the liquid alloy near the liquidus temperature or between liquidus and solidus). (Traditional DC casting and twin roll casting process and extrusion process) most of the disadvantages can be overcome. The high viscosity of fully sheared liquid alloy or semi-solid slurry can shorten the solidification time, prevent leakage in twin-roll casters, reduce chemical segregation in continuous casting solidification and extrusion and increase productivity. Low pour/load temperatures also increase mold life, energy efficiency and product quality.

A second aspect of the present invention is to provide a method of making a continuous cast product from a liquid metal alloy, the steps of which include cooling the alloy to near the liquidus line or from the solidus line to the liquidus line of the alloy, cooling the alloy at a sufficiently high The shear rate and turbulence intensity are sheared to transform it into a thixotropic state, and the sheared liquid alloy or sheared semi-solid slurry is transported to a forming device to form a solid product, wherein the forming device can form a continuous product, Wherein the alloy is formed by miscible components.

According to a third aspect of the present invention, there is provided a method of making a continuous cast product from a liquid metal alloy, the steps comprising cooling the alloy to near the liquidus line, shearing the alloy at a sufficiently high shear rate and turbulence intensity It is transformed into a thixotropic state by shearing, and the sheared liquid alloy is transported to the forming equipment to form a solid product. Preferably, the forming apparatus is capable of forming a continuous product wherein the alloy can be formed from miscible or immiscible components.

Another aspect of the present invention is to provide a method of making a continuous cast product from a liquid metal alloy having immiscible components, the steps comprising cooling the alloy below the immiscible gap, subjecting the alloy to a sufficiently high shear rate and The intensity of turbulent flow shears it into a thixotropic state and conveys the sheared liquid alloy or sheared semi-solid slurry to the forming equipment to form a solid product, where the forming equipment can form a continuous product, but where the forming equipment is not A preheated metal strip.

Typically, the shearing device is a high-shear extruder, the steps of which include placing the liquid alloy in a temperature-controlled barrel and operating a screw fixed in the barrel at a shear rate high enough to convert the liquid alloy into Its high shear state and/or thixotropic state. The shape of the screw should be specially designed to provide high shear rate and high turbulence intensity to obtain forced suction during the process of transporting the liquid alloy from one end of the barrel to the other. The extruder can be any kind of extruder as long as at least one screw is positioned in the barrel.

Preferably, the extruder is a twin-screw extruder having at least two screws which are at least partially intermeshed, more preferably which are substantially fully intermeshed.

Forming equipment can be various molds or molds with auxiliary equipment (depending on the needs of the final product manufactured). (a) In the DC rheocasting process, the mold/mold can be a simple cylinder with an optional starting base, where the cylinder has a cooling system. The solidified alloy is continuously drawn from the mold/mold by the starting substrate, thereby continuously forming the casting. (b) In the twin-roll rheocasting process, the mold/mold consists of a pair of rotating rolls and a pair of side dams arranged at the opposite ends of the roll shaft so that a shear liquid alloy or Semi-solid slurry pool. The two rolls rotate in opposite directions so that the sheared liquid alloy or semi-solid slurry subsequently solidifies to form solid shells which are extruded against each other as they pass through the nip between the rolls to form a continuous strip. (c) In the rheological extrusion process the die/mold can be a simple opening on the end of the shear. The forced suction of the shearer forces the sheared liquid alloy or semi-solid slurry through a preheated open die to form rod or wire or any other suitable cross-sectional shape.

When the sheared liquid alloy or semi-solid slurry passes through the mold, the mold can be heated to or maintained at a predetermined temperature. The relationship between the mold temperature and the metal shear temperature is determined by individual technical requirements.

The continuous casting method and equipment of the present invention preferably use a shearer having an inlet at one end and an outlet at the other end, a temperature-controlled barrel connecting said inlet with said outlet and at least one screw positioned in said barrel.

Said screw in said shearer preferably includes a shaft having at least one blade thereon, said blade forming a helix at least partially around the shaft to push metal through said barrel, wherein said The screw is capable of shearing said liquid alloy, while said metal is in a semi-solid state, at a rate sufficient to inhibit complete formation of a dendritic structure therein, and the rotation of said screw is also capable of transporting said metal through said barrel from said inlet to said outlet .

In one embodiment, temperature control methods are used to adjust the temperature of the extruder barrel, screw and alloy to maintain the temperature of the alloy near its liquidus or between its liquidus and solidus. The exit of the extruder may have a control valve to allow the alloy in the extruder to be delivered to the forming equipment. The amount of liquid alloy or semi-solid slurry from the extruder to the forming equipment can be controlled with the above valve to maintain the continuity of the semi-solid slurry in the forming equipment.

In a preferred embodiment, the extrusion die is directly attached to the extruder to produce continuous strands of different cross-sections. This process is called rheological extrusion.

As an alternative, in addition to the high-shear equipment, a single-screw extruder can also be used, wherein the sheared liquid alloy or semi-solid slurry is poured out from the above-mentioned high-shear equipment and extruded through the above-mentioned single-screw extruder. Continuous rotation of the discharge screw to produce continuously cast billets such as bars or fine wire or billets.

The continuous product produced according to the method of the present invention can also be further deformed by conventional extrusion processes.

Generally, the material that can be processed according to the present invention can be any metal alloy, such as Al, Mg, Zn, Cu, Fe-based alloys, etc. An important group of metal materials that can be processed according to the present invention are those containing Mixed gap materials such as Al-Pb, Al-Bi, Al-In and Cu-Pb based alloys.

An important advantage of the method according to the invention is that the obtained cast strand has a fine and homogeneous microstructure throughout its cross-section, wherein a controlled amount of fine round particles is evenly distributed in the matrix. Therefore, the cast slab has high thixotropy, and is especially suitable as a raw material for thixoforming.

Another advantage of the process of the present invention lies in the fact that it does not require secondary processing processes for microstructure control, such as extrusion and recrystallization, since the resulting cast strand already contains a fine and uniform microstructure. Therefore, they can be directly used for solid-state processing, such as machining and forging.

Cylindrical molds/molds for DC rheocasting can be made of any material, but the molds are preferably made of graphite or copper based alloys. Cylindrical moulds/casting molds can be equipped with a cooling system to solidify the sheared liquid alloy or semi-solid slurry at a suitable cooling rate. The starting base can be used at the beginning of casting.

The rotating rolls of a twin roll caster can have any profile that will provide the narrowest gap while rotating, preferably the roll profile is flat.

The section of the extrusion die in the rheological extrusion process can be in any shape, including simple shapes, such as circles, triangles, rectangles, or polygons or any other suitable complex shapes, and the size of the section can vary in a large range, which This means that the product can be a thin wire or a larger rod.

The method described above can be used with a sheared liquid alloy at a temperature close to its liquidus, or with a sheared liquid alloy at a temperature between the liquidus and solidus with varying solid volume fractions (0% to 750%). A sheared semi-solid slurry of fine, uniform microstructure. When shearing is performed near its liquidus, a fine and uniform microstructure is generated in the final solidified product due to the effective enhancement of the nucleation rate of highly sheared liquid alloys with uniform temperature and chemical composition . When shearing is carried out between the liquidus line and the solidus line, under strong shearing, a semi-solid slurry with fine spherical particles can be produced, which can be used to directly form components or as a thixotropic process Raw materials are formed into billets. The above-described apparatus and methods can also improve the mechanical properties of metal parts due to effective modification of the microstructure, especially for alloys of near-eutectic composition.

The above-mentioned apparatus and method preferably include the following steps:

* providing the liquid alloy in a liquid state and feeding said liquid alloy into a temperature-controlled extruder through an inlet at one end of the extruder;

* using an extruder comprising at least one screw, shearing said liquid alloy at a shear rate sufficiently high to form a sheared liquid alloy or a semi-solid slurry;

*The above-mentioned sheared liquid alloy or semi-solid slurry in the extruder is sent to the forming equipment, which can be a cylindrical mold for DC rheocasting or a twin-roll press for a two-roll rheocasting process Or open an open die for rheological extrusion by opening a control valve fixed at the other end of the extruder.

* Solidify the sheared liquid alloy or semi-solid slurry in the forming equipment to form continuous castings with different cross-sections. The above-mentioned forming equipment can be a DC casting machine or an extrusion die or a twin-roll casting machine.

Typically, an extruder consists of a barrel, one or more screws and a drive system that accepts liquid alloy through an inlet at one end of the extruder. Once the liquid alloy enters the channel of the extruder, it is cooled or maintained at a predetermined temperature. In another case, the treatment temperature may be a temperature near the liquidus or a temperature between the solidus and the liquidus.

The treatment temperature depends on the liquidus and solidus of the alloy, which varies with the alloy. What is a suitable temperature will be apparent to those skilled in the art.

Shearing of the liquid alloy is also performed in the extruder. The shear rate is sufficient to obtain spherical particles and a fine, uniform microstructure in the final product. The shear action is initiated by the screw in the barrel and intensified by the helical screw flights formed on the screw body. The enhanced shear is created by the barrel and the annular space between the screw flight and the screw flight. Positive movement in the extruder moves the sheared liquid alloy or semi-solid slurry from the inlet to the outlet of the extruder, from where it is discharged.

In the twin-roll rheocasting process, a nip consisting of a pair of rolls, a pair of side dams and a drive system is best used to receive shear through the upper molten pool formed by the inner surfaces of the two side dams and the upper surface of the twin rolls. Cut liquid alloy or semi-solid pulp. Once the sheared liquid alloy or semi-solid slurry enters the molten pool in a twin-roll caster, it cools and forms a crust on the roll surfaces. Roller temperatures vary from alloy to alloy. A suitable temperature will be apparent to those skilled in the art, but generally it should be below the solidus of the alloy. Also in the twin-roll casting process, shearing the liquid alloy or semi-solid slurry also undergoes solidification, deformation, connection of solidified shells and continuous pulling of solid strips. The withdrawal speed should be sufficient to maintain the continuity of the process. Deformation and connection shall be sufficient to maintain effective connection of the deck sections.

In the rheological extrusion process, the extrusion pressure used to shear the liquid alloy or semi-solid slurry is controlled by the temperature and the shear rate of known composition. The temperature difference between the extruder barrel and the open die will greatly reduce the external friction between the shear liquid alloy or semi-solid pulp and the open die during extrusion. The balance of external friction, shear liquid alloy or viscosity of semi-solid pulp and extruder forced suction pressure determines the extrusion speed through the open die. Extrusion dies with different cross-sectional shapes are used for continuous castings with different cross-sectional shapes.

When using rheological mixing, either a homogeneous liquid alloy at temperature above its mixing gap or a pre-blended liquid mixture in the temperature mixing gap can be loaded into an extruder for high-intensity mixing to produce a fine, uniform liquid mixture . In the extruder, the liquid alloy undergoes cooling and high-intensity shearing, and the extruder can operate at temperatures above or below the metaeutectic temperature. The forming equipment can be an extrusion die or a twin roll caster.

Description of drawings

Preferred embodiments of the present invention are described in detail below with reference to the figures, wherein:

Figure 1 is a schematic diagram of an embodiment of an apparatus for converting a liquid alloy into a high-strength shear liquid alloy or semi-solid slurry according to the principles of the present invention.

Fig. 2 is a schematic diagram of an embodiment of equipment for converting liquid alloy into high-strength shear liquid alloy or semi-solid slurry according to the principle of the present invention, and then using DC rheological casting process to produce metal slabs.

Figure 3 is a schematic diagram of another embodiment of an apparatus for converting liquid alloys into high-strength shear liquid alloys or semi-solid slurries according to the principles of the present invention, and then using extrusion dies to produce metal rods/wires through a rheological casting process.

Figure 4 is a schematic diagram of an extrusion die set-up used in a rheological extrusion extrusion process in another embodiment.

Figure 5 is a schematic diagram of another embodiment of an apparatus for converting liquid alloys into high strength shear liquid alloys or semi-solid slurries according to the principles of the present invention and then using a single screw extruder to produce metal rods/wires through a rheological casting process picture.

Figure 6 is a schematic diagram of an embodiment of an apparatus for converting liquid alloys into high strength shear liquid alloys or semi-solid slurries and then producing metal strips using a twin-roll rheocasting process in accordance with the principles of the present invention.

Detailed ways

In the preferred embodiment described subsequently, castings are made by an extruder and forming equipment made of AZ91D liquid alloy. The invention is not limited to AZ91D manganese alloys, but is applicable to other types of metals including aluminum alloys, manganese alloys, zinc alloys, copper alloys, iron alloys and others that may be suitable for shear-induced metal processing and/or semi-solid metal processing alloy. Moreover, the specific temperature and temperature range described in the preferred embodiment can only be used for AZ91D manganese alloy, but those skilled in the art can adapt this to other alloys such as Al, Mg, Zn according to the principles of the present invention. and Cu-based alloys.

Figure 1 shows an extruder system according to an embodiment of the present invention. The liquid alloy is loaded into the feeder 10 . The periphery of the feeder 10 is provided with a series of heating elements 11, which may be of any conventional type. The heating elements are operated to maintain the temperature of the hopper 10 high enough to keep the metal supplied through the hopper 10 in a liquid state. For the AZ91D alloy, this temperature can be above 600°C (the liquidus of the alloy). The extruder has a plurality of cooling channels 12 and heating elements 13 distributed along its length. Matching cooling channels 12 and heating elements 13 can form a series of heating and cooling zones, respectively. Heating and cooling zones enable a complex temperature profile to be maintained along the extruder axis, which meets the special requirements of semi-solid processes. The temperature control of each zone is achieved by balancing heating and cooling power (this power is input through the central control system of thermocouples 20). The heating method can be resistance heating, reduction heating or any other heating method. The cooling medium can be water or air or any other medium, depending on the process requirements. Although Figure 1 shows only one heating/cooling zone, the extruder can be equipped with between 1 and 10 respectively controllable heating/cooling zones.

Extruders also have physical ramps or inclines. The inclination is generally 0 to 90° with respect to the metal plate-moving plane. Ramps are designed to help transport the sheared liquid alloy or semi-solid slurry from the extruder to the next step of the different process.

The extruder also has two screws 14 driven by electric or hydraulic motors 16 through a transmission 17 . Two screws 14 are located inside the barrel 15 in line with the end caps 18,19. Two screws 14 are designed to provide high shear rates, which are necessary to obtain fine and uniform solid particles. Of course, the shape of the screw used can be different. Alternatively, any equipment that can provide high shear rates can be substituted for a twin-screw extruder.

The sheared liquid alloy or semi-solid slurry in the extruder is delivered to the forming device through a valve 21 connected to the end cover 19 . The valve 21 operates according to a signal from the central control system. Valve 21 is used to continuously provide a regulated runoff of semi-solid slurry to provide an appropriate bath for the next step in the process. The optional opening of valve 21 should be matched to the needs of the process. The valve 21 can be opened continuously with a limited flow rate or opened discontinuously without flow rate limitation.

Figure 2 is a DC rheological casting system. The system has two functional devices: a twin-screw extruder 1 and a DC caster 2. The extruder 1 has been described in FIG. 1 . The DC casting machine 2 mainly includes a cylindrical mold 31 and a cooling medium 33 . The mold is placed on a support 36 having a predetermined gap with the extruder 1. Load the starting base for continuous movement. The unloaded sheared liquid alloy or semi-solid slurry is loaded into the DC caster. The direct chiller 31 is filled with a cooling medium 33 entering through an inlet 32 and flowing out through an outlet 34 . The sheared liquid alloy or semi-solid slurry in the molten pool 30 can thus solidify to continuously form a strand 34 which is supported by the base 35 at the start of the process and then continuously produces a strand.

Figure 3 is a rheological extrusion system. This system is modified from the extruder shown in Figure 1. A temperature-controlled extrusion die 8 is mounted directly on the outlet valve 21. The extrusion die 8 has an independent thermocouple 9 to maintain the required temperature of the die and an outlet 7 to extrude the alloy. Larger temperature variations around the open die may reduce resistance to shearing liquid alloy or semi-solid slurry flow. Shear liquid alloy or semi-solid slurry is extruded from extrusion die to form rod or wire.

Fig. 4 is another extrusion die, wherein the extrusion die 8 adopts another cross-sectional shape 7 to produce products with different cross-sectional shapes. In general, the cross-section of the extrusion die can be any simple or complex shape, or any other shape suitable for extrusion.

Figure 5 is another rheological extrusion system. This system has two functional units: a twin-screw extruder and a single-screw extruder. The twin-screw extruder has been described in Figure 1. Single-screw extruders are used as forming equipment to produce sheared liquid alloy or semi-solid pulp into rod/wire. The single screw extruder consists of a barrel 42, a screw 43, a nozzle 41 and a heating element 45 for the barrel 42 with thermocouples 46 for temperature requirements. The sheared liquid alloy or semi-solid slurry is discharged through valve 22 into the single screw extruder. Continuous rotation of the screw 43 moves the sheared liquid alloy or semi-solid slurry to the nozzle 41 to form a continuous product. A barrel 42 temperature controlled by a heating element 45 may greatly reduce the resistance to outflow of shear liquid alloy or semi-solid pulp. The cross-sectional shape of the nozzle 41 determines the shape of the extruded portion. The nozzle can be a simple small circle forming a wire or any other possible shape. This prior art extruder can be modified by employing an alternative embodiment of the present invention in which at least one of the opening dies is modified to a different shape.

Figure 6 is a twin roll rheocasting system. This system includes two functional devices: a twin-screw extruder 1 and a twin-roll caster 2. The extruder is depicted in Figure 1. The twin roll casting machine 2 mainly includes a pair of rolls 22 and a pair of side dams 23 . The two rollers are placed parallel to each other horizontally and at a certain interval, and one or both rollers are supported so that they can be selectively moved in the radial direction of the rollers. The direction of rotation of the rollers 22 is indicated by the arrows. The interior of each roller 22 can constitute a cooling sleeve or a heating sleeve. The side dam 23 is connected to the roller in the axial direction of the roller 22 . A molten pool 24 for storing semi-solid slurry is formed between the upper surface of the opposite end of the roller 22 and the inner surfaces of the dams 23 on both sides. Under this condition, the rollers 22 rotate in the direction indicated by the arrows so that the solid shell 25 formed on the surface of the rollers 22 is pulled down and bonded together by pressure to form a continuous cast belt 26 .

As shown in Figure 6, the outer surface of the roller is generally flat, such as a smooth cylindrical roller. Such prior art casting machines may be modified by employing another embodiment of the present invention wherein at least a portion of the surface of the rollers is a convex or concave surface or any other suitable surface.

Typically, the system also has a control unit for all functions. The control means is preferably programmed to obtain the desired properties of the metal. The control means (not shown) may include, for example, a microprocessor which can be easily and quickly reprogrammed to change relevant parameters depending on the type of final product.

Embodiments may also contain a device connected to the extruder for increasing the pressure in the barrel. Embodiments may also contain a device connected to the extruder and associated components for providing a shielding gas to prevent oxidation. Such gases may be argon, nitrogen or other suitable gases.

While particular embodiments of the invention have been illustrated and described in the foregoing, it is obvious that the invention can also be embodied in other different forms within the scope of the appended claims. For example the barrel and screw can be of modular design.

Claims (13)

1. method by the continuous product of liquid metal alloy manufacturing may further comprise the steps:

Alloy is cooled to such temperature, and this temperature is the temperature from the solidus of alloy to liquidus curve;

Alloy is sheared so that alloy changes its thixotroping attitude into sufficiently high shear rate and turbulence intensity; With

Liquid alloy of shearing or the semisolid ore pulp of shearing are transported in the former to form solid product;

Described former wherein can be made continuous product,

Wherein shearing is applied to alloy by having at least two double screw extruders to the screw rod of small part interlock.

2. method as claimed in claim 1, at least have a blade on wherein said at least two at least one screw rods to the screw rod of small part interlock, described blade defines spiral at least in part and passes through extruder to advance alloy around screw rod, wherein, when alloy was semi-solid state, described at least one screw rod can rotate enough to be suppressed at the speed that wherein is completed into dendritic structure sheared above-mentioned liquid alloy.

3. as the method for claim 1 or 2, wherein, screw rod is interlock fully basically.

4. as the method for above-mentioned claim 1 or 2, wherein, described former is direct chill casting machine, extrusion die or dual roll casting machine.

5. as above-mentioned the process of claim 1 wherein, described alloy comprises at least two kinds of unmixing compositions and wherein, and described composition provides with liquid condition separately, and carries out premix before shearing.

6. method as claimed in claim 5, wherein, described alloy is fully sheared to be transformed into liquid suspension, and wherein, less important unmixing composition is dispersed in the main unmixing composition mutually with liquid.

7. as the method in the claim 6, wherein, when described liquid suspension is sheared, should be cooled to below its monotectic temperature or the monotectic temperature to form semi-solid ore pulp.

8. method as claimed in claim 7, wherein, it is enough big to prevent the thick segregation of unmixing system that ore pulp viscosity is wanted.

9. as each method in the claim 1 to 2, wherein, alloy does not comprise any immiscible composition.

10. goods of being made by metal alloy, wherein, goods can be required that each method obtains among the 1-2 by aforesaid right.

11. device of liquid metal alloy being made continuous product, comprise: can give enough shearings of semi-solid metal alloy and turbulence intensity, it is transformed into the temperature controlled shear of its thixotropic state, with the building mortion that links to each other with shear with liquid form, wherein, this building mortion can be made continuous product, and wherein said shear is to have at least two double screw extruders to the screw rod of small part interlock.

12. device as claim 11, at least have a blade on wherein said at least two at least one screw rods to the screw rod of small part interlock, this blade passes through extruder at peripheral part definition spiral of screw rod to advance alloy at least, wherein, when alloy was semi-solid state, this at least one screw rod can wherein be completed into dendritic structure to be suppressed at enough above-mentioned liquid alloys of speed rotational shear.

13. as the device of claim 11 or 12, wherein, described screw rod is interlock fully basically.

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