CN102489677A - Block-type amorphous alloy plate continuous casting device and method thereof - Google Patents

Abstract

The invention discloses a continuous casting device and method for bulk amorphous alloy plates, belonging to the technical field of metal material preparation. It is characterized in that it combines the characteristics of continuous casting cooling roll cooling and mold cooling of bulk amorphous alloy plates, and the solidification and forming of the alloy are completed between two cooling belts that are parallel to each other and move synchronously. The smelted master alloy is melted and kept warm in the crucible, and is poured at a set temperature through a nozzle with a rectangular cross section to cool and solidify between two parallel water-cooled cooling zones to form an amorphous plate. Under the action of driving roller and positioning roller, the solidified amorphous plate moves at a certain speed to complete the continuous casting process. The structure of the device is simple, the cooling speed is high, the metal solidification and casting are completed in the cooling zone, the process stability is good, and the ingot size adjustment is convenient. The device and method of the invention can efficiently and continuously prepare large-thick bulk amorphous alloy plates.

Description

Device and method for continuous casting of bulk amorphous alloy sheet

technical field

The invention belongs to the technical field of metal material preparation, and in particular relates to the continuous preparation technology of amorphous alloy and non-equilibrium solidified material plate.

Background technique

Amorphous alloys, also known as metallic glasses, are a class of solid materials with unique atomic composition and properties of both metal and glass. The constituent atoms of amorphous alloys are long-range disordered and short-range ordered; there are no crystal defects such as grain boundaries, dislocations, and stacking faults inside; the physical, chemical, and mechanical properties remain isotropic; thermodynamically, they are in a metastable state , above the crystallization temperature, the crystal structure phase transition will occur, but below the crystallization temperature, it can exist stably for a long time. The bulk amorphous alloy has high thermal stability and large glass forming ability. The alloy melt can form an amorphous phase even at a slow cooling rate of 0.1 to hundreds of K/s. The method of metal mold casting can Amorphous single-phase bulk materials with a three-dimensional size of more than millimeters are obtained.

Compared with traditional metal materials, bulk amorphous alloys have excellent mechanical, physical and chemical properties. Such as high strength and high specific strength, large elastic limit, low elastic modulus, excellent corrosion resistance, wear resistance and excellent soft magnetic properties that are difficult to obtain in crystalline alloys. Bulk amorphous alloys have an obvious glass transition temperature and a wide supercooled liquid phase region before crystallization. When the temperature is in the supercooled liquid phase region, due to structural relaxation and free volume changes, similar to oxide glass Softening phenomenon, the viscosity decreases sharply, exhibits viscous flow characteristics, and can perform high-precision superplastic deformation and near-net-shape processing. Therefore, bulk amorphous alloys have broad application prospects in aerospace, micro-electromechanical, defense industry, information technology, biomaterials, and sporting goods.

For ordinary amorphous alloys, the formation of amorphous phase requires a cooling rate above 10 ⁶ K/s. Such a large cooling rate makes amorphous alloys only made into low-dimensional materials such as thin strips, filaments, and powders, with an effective thickness of 100 μm. the following. In 1988, Inoue et al. discovered the supercooled liquid stabilization phenomenon in the multi-element alloy system. These alloys have a wide supercooled liquid phase region and a large glass-forming ability. Amorphous single-phase can be obtained by copper mold casting bulk material. Since then, researchers have done a lot of work in developing new alloy components with large amorphous formation ability, and prepared bulk amorphous alloys in many alloy systems, among which the critical size of amorphous formation reaches centimeter level. 20, while Zr-based, Pd-based, Cu-based, Mg-based, Ni-based, La-based and other alloys have an amorphous formation size of more than 2 cm, and a critical cooling rate of less than 5K/s. The development of bulk amorphous alloys with the ability to form large amorphous crystals not only makes it possible for large-scale industrial applications of bulk amorphous alloys as high-tech materials, but also enables the use of some high-efficiency, low-cost common metal material forming technologies for mass production. Bulk amorphous alloys provide a viable prerequisite.

Methods for preparing bulk amorphous alloys, including melt water quenching, copper mold casting, arc melting casting, high pressure casting, precision casting and powder solidification, are all single-piece or small-batch discontinuous processes , low production efficiency and high cost limit the large-scale industrial application of bulk amorphous alloys. Bulk amorphous alloy sheets can be used for high-performance structural and functional components, and are also convenient for manufacturing various precision devices by hot pressing, hot extrusion, hot rolling and blow molding. Using continuous forming technology to prepare a large number of amorphous alloy strips with unlimited length, especially bulk amorphous alloy sheets with a thickness exceeding millimeters, has always been the goal pursued by researchers.

The single-roll melt quenching method is referred to as the single-roll method, which has a large cooling rate, which can reach 10 ⁶ K/s. By changing the structure of the nozzle and the cooling roll, the preparation of a wide-width amorphous ribbon is realized, and the width can reach hundreds of mm. However, the flow velocity of the molten metal in the single-roll method is mainly controlled by the aperture of the nozzle, the pressure difference inside and outside, and the viscous flow between the solidification front. In order to obtain a sufficient cooling rate to ensure that the molten metal solidifies into an amorphous state, the surface of the cooling roll The rotation speed is generally above 30m/s, and the high rotation speed limits the thickness of the amorphous ribbon to below 20μm. Reducing the speed of the cooling roll can increase the thickness of the amorphous strip. For alloys with a large amorphous forming ability, a thick amorphous strip with a thickness of 50-75 μm can be obtained by the single roll method, but the low speed of the cooling roll is not conducive to forming a stable molten pool and continuous cooling process. At present, the thickness of the bulk amorphous alloy ribbon prepared by the single-roll method is less than 100 μm.

The twin-roll melt quenching method, referred to as the twin-roll method, is also one of the important methods for preparing amorphous thin strips. Based on the twin-roll method, a variety of methods for continuously preparing bulk amorphous alloy sheets have been developed. Patent CN 1486800A discloses a continuous casting and rolling technology of bulk amorphous alloys. The alloy is melted in a crucible, and then the molten metal is injected into two relatively rotating water-cooled rolls, and the bulk amorphous plate is prepared by roll casting and rolling. Rods and special-shaped profiles. U.S. Patent US2006/0260782A1 discloses a continuous casting device and method for bulk amorphous alloy sheets. s, but the cooling rate is less than 10 °C/s, which is limited to the formation of Be-containing Zr-based bulk metallic glasses with large glass-forming ability. Theoretically speaking, the double-roller method cools the metal melt on both sides, and the cooling capacity is greater than that of the single-roller method. However, due to the short effective distance between the metal melt and the cooling roller in the double-roller method, the actual cooling rate is much smaller; The casting and rolling method increases the contact distance between the molten metal and the roll, but controlling the thickness of the solidified layer in contact with the roll and the stability of the process have always been difficult problems to be solved.

According to the solidification characteristics of bulk amorphous alloys, our research group invented a graphite/water-cooled copper mold composite mold (ZL200920013438.8). The composite mold has a large cooling rate and a large temperature gradient at the solidification front. A device and method for horizontal continuous casting of bulk metallic glass (ZL 200910011405.4) was developed using graphite/water-cooled copper mold composite molds. Continuous molding of rods and wires, billets, plates, pipes and special-shaped materials with different cross-sectional sizes. The cooling of the alloy mainly depends on the water-cooled copper mold, and the solidified billet is pulled continuously by the motor-driven drawbar.

For the continuous forming process of bulk amorphous alloys, a large cooling rate of the device is necessary and beneficial. The greater the cooling rate, the larger the size of the formed amorphous ingot. The present invention combines the features of bulk amorphous alloy continuous casting plate, strip cooling roll cooling and mold cooling, and its principle, structure and method have not been published yet.

Principle of the present invention is:

1. The metal melt is cooled and solidified on the double cooling belt (or crystallizer), and the cooling capacity is strong. After the metal melt enters the cooling zone (or crystallizer) through the nozzle, it contacts the surface of the cooling zone and cools rapidly. The cooling zone has good heat conduction and heat storage capabilities, so that the alloy melt can obtain a maximum cooling rate; the formed alloy leaves the cooling zone The belt has been cooled before, and the contact time between the alloy and the cooling belt is long, which can efficiently dissipate the heat inside the plate, and has a strong cooling capacity, especially suitable for cooling large-thickness plates.

2. There is no relative movement between the alloy and the cooling zone. When the alloy undergoes amorphous phase transition, the solidification shrinkage is small, and the interface thermal resistance between the alloy and the cooling zone is small, and a large cooling rate can be obtained.

3. The cooling zone is cooled by medium, and the heat released by the solidification of the plate is continuously exported through the cooling zone to realize continuous cooling.

4. The alloy is clamped by the cooling belt and moves at a certain speed along the casting direction. The cooling belt not only cools and solidifies the alloy melt, but also drives the solidified plate to move and play the role of casting. The structure of the device is simple and solves the problem at the same time. It solves the problem that the amorphous alloy has small solidification shrinkage and is easy to "freeze" in the crystallizer.

5. The alloy entering the cooling zone is cooled and solidified while moving with the cooling zone. The front end of the cooling zone is continuously poured with molten alloy, and the casting slab with the same cross-sectional shape and size can be continuously pulled out from the other end of the cooling zone. Realize continuous casting process and obtain castings of any or specific length.

Contents of the invention

The invention provides a continuous casting device and method for bulk amorphous alloy plates and strips.

Technical scheme of the present invention is as follows:

A continuous casting device for bulk amorphous alloy plate and strip, including crucible, thermocouple, nozzle, cooling belt or crystallizer, driving roller, positioning roller, dummy head, speed regulating motor and cutting machine, inside the crucible Melt the master alloy, adjust the pouring temperature and pressure; the molten metal is poured through the rectangular cross-section nozzle and the crystallizer into the cooling zone to cool and solidify to form amorphous alloy plates and strips; the speed-regulating motor drives the drive roller to rotate to make the cooling The belt and the solidified amorphous plate and belt move synchronously at a certain speed, the positioning roller keeps the cooling belt parallel to each other, and the inside of the cooling belt is cooled by water; after the plate and strip reach the required length, they are cut by a cutting machine to obtain a bulk amorphous alloy Continuous casting of plates and strips.

The cooling belt is made of heat-conducting metal materials, such as stainless steel, aluminum alloy, copper alloy, etc. The more suitable materials are chromium copper, beryllium copper, dispersion-strengthened copper alloy, and oxygen-free copper alloy; the cooling belt is cooled by water inside, and the outer surface is cooled. Polished or chrome-plated; the gap between the cooling zone is 0.05-10cm, and the contact length between the cooling zone and the plate or strip is 5-500cm.

There are driving rollers and positioning rollers in the cooling belt. The driving rollers keep rotating synchronously to make the cooling belt move along the casting direction. The moving speed of the cooling belt is 0.01-50m/min; at least one set of positioning rollers keeps the cooling belts parallel to each other.

The crucible and nozzle are made of high-temperature-resistant materials that do not chemically react with the bulk amorphous alloy, such as high-purity graphite; the crucible is heated by induction or resistance, and the operating temperature is greater than 500 ° C; the crucible is placed in a vacuum environment or with gas and Flux protection; the outlet section of the nozzle can be rectangular or other special-shaped, and when rectangular, the width is 0.05-100cm, and the length is greater than 0.1cm.

The device can adopt horizontal or vertical continuous casting, and the height of the device is required to be greater than the length of the required block amorphous alloy continuous casting plate during vertical continuous casting.

The method for using the above-mentioned continuous casting device for bulk amorphous alloy plates comprises the following steps:

a. Alloy melting and heat preservation: put the dummy head into the nozzle, and seal between the dummy head and the nozzle (or crystallizer); put the melted master alloy into the crucible, and quickly heat the crucible to melt the master alloy. Measure the temperature of the metal melt with a thermocouple, control the temperature of the metal melt to be 5°C higher than the liquidus temperature of the alloy, and keep it warm for a period of time to make the temperature of the metal melt uniform; when the alloy is melted under vacuum, the crucible is vacuumed before heating to the required vacuum;

b. Alloy melt pouring: adjust the temperature of the metal melt to be 5-200°C higher than the alloy liquidus temperature, pull the dummy head to gradually separate from the nozzle, and the metal melt passes through under the action of static pressure or gas pressure The nozzle and the crystallizer flow into the cooling zone;

c. Continuous casting: Start the speed regulating motor to rotate the driving roller, drive the cooling belt to move at a certain speed along the casting direction, and fix the roller to keep the cooling belts parallel to each other; the metal melt entering the cooling belt moves together with the cooling belt. Cool and solidify to form amorphous alloy plates and strips; when the required length is reached, start the cutting machine to cut off the amorphous alloy plates and strips to complete the continuous casting process.

The present invention adopts the above-mentioned technical scheme, and has the following advantages and positive effects: 1. The contact time between the cooling zone and the forming alloy is long, the cooling capacity is large, and it is suitable for forming bulk amorphous alloy plates and strips; 2. The cooling zone and forming alloy There is no relative movement between the alloys, the thermal resistance of the interface is small, and the ingot has a large cooling rate; 3. The solidification and output of the alloy are completed in the cooling zone, and the device structure is simple; 4. The alloy melt is cooled and solidified in the cooling zone At the same time, it moves along the casting direction to form a continuous casting process and obtain continuous casting plates and strips of amorphous alloys.

Description of drawings

The accompanying drawing is a schematic structural diagram of the continuous casting principle of the bulk amorphous alloy plate of the present invention.

In the figure: 1 crucible, 2 thermocouple, 3 nozzle, 4 crystallizer, 5 cooling belt, 6 driving roller, 7 positioning roller, 8 dummy head,

9 adjustable speed motors, 10 cutting machines.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

The Cu-Zr based bulk amorphous alloy continuous casting plate with a thickness of 10 mm and a width of 50 mm is prepared by using the device and method for continuous casting of bulk amorphous alloy plates proposed by the present invention.

a. Alloy melting and heat preservation: select a bulk amorphous alloy whose nominal composition is Cu ₃₆ Zr ₄₈ Al ₈ Ag ₈ , configure the alloy raw materials according to the atomic ratio, smelt the master alloy in a vacuum electric arc furnace, and measure the liquid phase of the alloy with DTA The line temperature is 870°C, and the heating rate during the test is 20K/min; crucible 1, nozzle 3 and crystallizer 4 are made of high-purity graphite and placed in a vacuum chamber. The cross-sectional size of the nozzle is 10×50mm ² , The wall thickness is 15mm, put the dummy head 8 into the nozzle, and seal between the dummy head and the nozzle; put the master alloy into the crucible, vacuumize to 10 ^-3 Pa, heat the crucible rapidly to melt the master alloy, and heat the Couple 2 measures and controls the temperature of the metal melt at 920°C and keeps it warm for 30 minutes to make the temperature of the alloy melt uniform;

b. Alloy melt pouring: adjust the temperature of the alloy melt in the crucible 1 to 970°C, the cooling water flow in the cooling zone 5 to 5L/min, and the pressure difference between the inside and outside of the vacuum chamber to be 0.2Mpa, and pull the dummy head 8 to make it Gradually detached from the nozzle 3, the molten metal flows into the cooling zone through the nozzle and the crystallizer under the action of static pressure and gas pressure;

c, continuous casting: start the speed regulating motor 9, make the driving roller 6 rotate, drive the cooling zone to move along the casting direction with a speed of 20cm/min, the fixed roller 7 keeps the cooling zone parallel to each other; The cooling belt moves synchronously and cools and solidifies to form a plate; after being cut by the cutting machine 10, a continuously cast plate with a length of 500mm and a cross-section of 10×50mm2 is obtained; the two ends and the middle ^part of the plate are cut off, and the cross-section of the sample is After grinding, polishing, and corrosion, observe the microstructure with an optical microscope, and measure the phase structure of the sample with an X-ray diffractometer. The microstructure of the sample is uniform, and no different phase structures with light and dark deviations are found; the X-ray diffraction spectrum shows the large and wide slow peaks of typical amorphous alloys, and there is no obvious sharp diffraction peak corresponding to the crystal structure. It has an amorphous single-phase structure.

Claims (7)

1. a block amorphous alloy sheet material continuous casting apparatus comprises crucible (1), thermocouple (2); Stem bar (3), crystallizer (4), salband (5); Driven roller (6), registration roller (7), dummy bar head (8); Buncher (9) is characterized in that: crucible (1) and stem bar (3) with not with the high temperature resistant nonmetallic materials of block amorphous alloy generation chemical reaction; Crucible is with eddy-current heating or resistance heated, and serviceability temperature is greater than 500 ℃; Salband (5) is used the heat conductive metal material; Inner water flowing of salband or the cooling of other medium, outer surface polishes or chromium plating is handled; The gap of salband is 0.05～10cm, and the contact length of salband and forming metal is 5～500cm; Be provided with driven roller (6) and registration roller (7) in the salband, buncher (9) drives driven roller and rotates synchronously, makes the outer salband motion of driven roller; At least one group of registration roller keeps salband to be parallel to each other.

2. block amorphous alloy sheet material continuous casting apparatus according to claim 1 is characterized in that the cross section of stem bar and crystallizer (4) is a rectangle, and width is 0.05～10cm, and length is greater than 0.1cm.

3. block amorphous alloy sheet material continuous casting apparatus according to claim 1 is characterized in that, crucible (1) and stem bar (3) adopt high purity graphite.

4. block amorphous alloy sheet material continuous casting apparatus according to claim 1 is characterized in that, salband adopts stainless steel, aluminium alloy, copper alloy.

5. block amorphous alloy sheet material continuous casting apparatus according to claim 3 is characterized in that, salband adopts chromium-copper, beryllium copper, dispersion strengthening copper alloy, oxygenless copper alloy.

6. use the method for claim 1,2,3,4 or 5 said block amorphous alloy sheet material continuous casting apparatus, its characteristic may further comprise the steps:

A, alloy melting and insulation: dummy bar head (8) put between stem bar (3), dummy bar head and stem bar seal; Melted foundry alloy is put into crucible (1), and the Fast Heating crucible makes the foundry alloy fusing, measures the metal bath temperature through thermocouple (2), and the temperature of control metal bath is higher than alloy liquid phase line temperature more than 5 ℃, and insulation makes the metal bath temperature even; Under vacuum, during melted alloy, before beginning to heat, crucible is evacuated to required vacuum;

B, alloy melt cast: the temperature of adjustment metal bath is higher than 5～200 ℃ of alloy liquid phase line temperature; Pulling dummy bar head (8) breaks away from it gradually in stem bar (3), metal bath is getting between crystallizer (4) and the salband (5) through stem bar under static pressure or the gas pressure effect; When crystallizer was made with nonmetallic materials, alloy melt cooled off in salband, solidifies; When crystallizer was made with metal material, alloy melt is moulding in crystallizer, in salband, cooled off;

C, continuous casting: start buncher (9), driven roller (6) is rotated synchronously, drive salband and move along casting direction with the speed of 0.01～50m/min, stationary roll (7) makes salband keep being parallel to each other; The alloy that gets into salband is cooled and cools off, solidifies formation block amorphous alloy sheet material when strap clamp is held motion; When sheet material reaches Len req, start cutting machine (10), cut off sheet material, accomplish the continuous casting process.

7. a kind of block amorphous alloy sheet material continuous casting apparatus according to claim 6; It is characterized in that: employing level or continuous vertical casting mode, the height of claimed apparatus is greater than the length of desired blocks non-crystaline amorphous metal continuous casting sheet material during continuous vertical casting.

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