A piezoelectric ceramic shock wave generating element

Abstract

This invention discloses a piezoelectric crystal ceramic shock wave generating element, comprising a cable trough fixedly connected to the side wall of a container, with its inner end extending into the container to install a concave spherical body. Multiple piezoelectric crystal blocks are installed inside the concave spherical body. Wires are arranged within the cable trough, and the piezoelectric crystal blocks are connected to a high-energy capacitor via these wires. The high-energy capacitor is located at the outer end of the cable trough and connected to a power source. The piezoelectric crystal blocks focus energy to a single focal point. A protective membrane covers the outer side of the cable trough and the outer side of the concave spherical body. This invention introduces a shock wave that acts on the melt, performing a series of purification operations including degassing, impurity removal, and slag removal, cleaning and repairing defects in the melt's mesoscopic to microscopic structure.

Description

Technical Field

[0001] This invention belongs to the technical field of shock wave generation devices, specifically relating to a piezoelectric crystal ceramic shock wave generating element for casting applications. Background Technology

[0002] Shock waves are mechanical waves that combine acoustic, optical, and mechanical properties. They can expand and concentrate in a medium, thereby changing the density of the medium. Currently, they are mainly used in medical diagnosis and treatment.

[0003] In practical engineering applications, the preparation and processing of metals almost always involves a solidification process, including metal ingots and castings. This process involves the composition, morphology, and distribution of precipitated phases, crystal nucleation and selective growth, as well as the quantity of segregation, cracks, pores, shrinkage cavities, looseness, and inclusions. These are thermodynamic processes of the growth of material structural particles from the microscopic (atomic size, approximately 0.1 nm and below) to the mesoscopic (material structural unit size, approximately 0.1 nm to 1 mm). This process and its accompanying defects have a decisive influence on the properties of the resulting solid materials. Since the particle combination and defect structure of solid materials are difficult to change once solidified, although heat treatment and external deformation processing can adjust the particle combination and defect structure of solid materials to a certain extent, these defects cannot be eliminated from the perspective of the phase structure system or statistical significance. If we consider the control of defects from the perspective of "eradication," we must trace back to the processing of melts with fluid particle structures.

[0004] Gas phases, inclusions, and slag contained in the melt can exacerbate the tendency for casting defects during crystallization and solidification. Therefore, in industrial production, a "three-removal" process must be carried out before casting to purify the melt. These processes are also known as "refining" or "purification" of the melt.

[0005] Existing technologies for the "three removals" of molten aluminum alloys generally involve a "refining-purification" process. This process involves first introducing reactants to be removed, then directly discharging the reaction products from the melt via gaseous discharge, or discharging solid particles after adsorption and filtration. However, most of the introduced reactants are toxic (such as halides, chlorine, Freon, and chlorofluorocarbons). Whether gaseous or solid, the reaction products have adverse environmental impacts. Gaseous emissions not only pollute the air but also damage the ozone layer, while the treatment and degradation of solid waste have become increasingly serious environmental challenges.

[0006] To minimize defects such as melt crystallization stratification and segregation during casting, researchers and engineers have conducted extensive studies and developed and applied technologies such as mechanical stirring, electromagnetic stirring, current pulse, electromagnetic oscillation, and mechanical oscillation. These technologies have alleviated the formation of defects to some extent, but they cannot fundamentally solve the problem. The problems of internal and external stratification during water-cooled crystallization of large billets and the overlapping distribution of macroscopic stress still exist. Problems caused by uneven cooling in castings with complex shapes have not yet been properly resolved.

[0007] In summary, the "three eliminations and four transformations" technology for the melt solidification process has not yet achieved primary control in theory or practice. That is, by applying macroscopic techniques to directly control the synchronous phase transformation of a large number of particles at the crystallization interface, allowing their crystallization behavior to be arbitrarily intervened as needed, and being able to distinguish between the melt and impurities (gas, impurities, and slag) and effectively separate them—there is still no top-level design scheme that can achieve these goals.

[0008] Therefore, the applicant, combining the characteristics of shock waves, "treats" the defects of the molten casting and purifies the molten casting without introducing other substances, and has therefore designed a shock wave generating device for casting. Summary of the Invention

[0009] The purpose of this invention is to provide a piezoelectric crystal ceramic shock wave generating element that provides high-energy energy for melt solidification and crystallization, thereby achieving the goals of melt purification, solidification process optimization, solidified phase homogenization, and crystal grain refinement.

[0010] The technical solution adopted in this invention is a piezoelectric crystal ceramic shock wave generating element, comprising a concave spherical body installed in the melt and a plurality of piezoelectric crystal blocks arranged inside the concave spherical body. The plurality of piezoelectric crystal blocks are all connected to a high-energy capacitor, which is connected to a power supply, and the piezoelectric crystal blocks converge energy to a focal point.

[0011] Furthermore, it also includes a cable trough, which is fixedly connected to the side wall of the container and has its inner end extending into the container to install a concave spherical body. Wires are arranged in the cable trough, and the piezoelectric crystal block is connected to a high-energy capacitor through the wires. The high-energy capacitor is arranged at the outer end of the cable trough, and a protective membrane is wrapped around the outer side of the cable trough to the outer side of the concave spherical body.

[0012] Furthermore, the piezoelectric crystal block is a shock wave generator made of a ceramic crystal material that can withstand the temperature of the melt environment and maintain its piezoelectric properties.

[0013] Furthermore, the protective membrane is made of a thin film resistant to high-temperature melt corrosion and is prepared from an elastic material with a single-layer thickness of less than 0.02 mm.

[0014] Furthermore, the piezoelectric crystal block is rotatably connected to the concave spherical body via a connecting rod and a universal bearing in the middle. Electric telescopic rods are provided on both sides of the connecting rod to connect the piezoelectric crystal block, and the electric telescopic rods are connected to the controller.

[0015] The principle behind the generation of shock waves by piezoelectric shock wave generators is the piezoelectric effect. A series of piezoelectric crystal blocks are placed on the inner surface of a spherical disk, forming a series of piezoelectric transmitters. When a high-frequency pulse voltage is input to the piezoelectric crystal blocks, the piezoelectric crystals expand and deform. The piezoelectric ceramic material can convert the high-voltage pulse signal into nano- to micrometer-level displacement through simple volume changes. The synchronous deformation of thousands of piezoelectric crystal blocks causes a tiny compression deformation of the liquid medium inside the spherical container and a huge focused pressure pulse, forming a shock wave.

[0016] The high energy of the shock wave can form a "high-energy homomorphic aggregate surface of particle oscillators" in the liquid state, making the surface a singular surface with unequal density at the front and back (high density at the front and low density at the back) that propagates rapidly forward. For an ideal Newtonian fluid, this singular surface acts like a "comb" to regulate each particle oscillator that passes through it through a "homomorphic, synchronous compression deformation and deconstruction". For a real melt containing a large number of voids and impurities, this "comb effect" is decomposed into a variety of physical effects, which can be used to "divide and transform" the melt.

[0017] The beneficial effects of this invention are that the high-energy laser plasma shock wave generating element designed in this invention acts inside the container. The advantage of the built-in shock wave source is that it generates shock waves from inside the melt, with energy cascading as its basic characteristic. It breaks through the composite grid structure of fluid viscosity and surface tension, creating a local instantaneous high-pressure, high-energy wavefront that is rapidly transmitted and deconstructed. This induces the homogenization of the wavefront particle oscillators, thereby achieving strong disturbances that penetrate the molecular and lattice levels, forming a pressure rheological field with a time scale of microseconds. Through a series of physical effects of this pressure rheological field (PRF), it performs a series of purification operations on the melt, including degassing, impurity removal, and slag removal; it cleans and repairs defects in the melt's structure at the mesoscopic to microscopic (millimeters to nanometer scale); and it effectively suppresses or deconstructs energy fluctuations, concentration fluctuations, and structural fluctuations between different regions of the "liquid-solid system," thereby compensating for macroscopic solidification defects in the melt and optimizing the control of the solidification process.

[0018] Built-in shock wave generating elements do not suffer from energy loss during the introduction process and can be positioned at any spatial location within the melt. This makes them more flexible than externally introduced shock waves. They can not only flexibly remove gas and impurities, but are also particularly effective for remelting or homogenizing the crystallization interface. They can make the solidified liquid cavity morphology flat and easy to control, allowing the fine grains that solidify preferentially at the boundary to mix fully with the interior of the melt. This results in uniform grain size stratification and integral growth across the entire crystallization surface, forming a cast billet with uniform internal and external grain size. This essentially solves most of the solidification defects that existing casting technologies cannot avoid or eliminate.

[0019] The piezoelectric crystal block is movably connected to the concave spherical body. The controller controls the electric telescopic rod to perform matching telescopic movements, causing the piezoelectric crystal block to swing around the universal bearing, thereby changing the energy convergence focus and expanding the purification area of ​​the shock wave. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention;

[0021] Figure 2 This is a schematic diagram of the installation of the piezoelectric crystal block;

[0022] The diagram is labeled as follows: 1. Cable trough, 2. Protective membrane, 3. Wire, 4. High-energy capacitor, 5. Concave spherical body, 6. Piezoelectric crystal block, 7. Connecting rod, 8. Universal bearing, 9. Electric telescopic rod. Detailed Implementation

[0023] The present invention will be further explained and described below with reference to the accompanying drawings to enable those skilled in the art to better understand it. Example

[0024] like Figure 1 As shown, a piezoelectric crystal ceramic shock wave generating element includes a cable trough 1, which is fixedly connected to the side wall of a container and has its inner end extending into the container to install a concave spherical body 5. Multiple piezoelectric crystal blocks 6 are installed inside the concave spherical body 5. Wires 3 are arranged inside the cable trough 1, and the piezoelectric crystal blocks 6 are connected to a high-energy capacitor 4 through the wires 3. The high-energy capacitor 4 is arranged at the outer end of the cable trough 1 and is connected to a power source. The piezoelectric crystal blocks 6 focus energy to a focal point. A protective membrane 2 covers the outer side of the cable trough 1 to the outer side of the concave spherical body 5.

[0025] Furthermore, the piezoelectric crystal block 6 is rotatably connected to the concave spherical body 5 via a connecting rod 7 and a universal bearing 8. Electric telescopic rods 9 are respectively provided on both sides of the connecting rod 7, connecting the piezoelectric crystal block 6 and a controller. The controller controls the electric telescopic rods 9 to perform matching telescopic movements, causing the piezoelectric crystal block 6 to swing around the universal bearing 8, thereby changing the energy focusing point and expanding the purification area of ​​the shock wave.

[0026] Among them, the piezoelectric crystal ceramic element in the melt is a shock wave generator made of a ceramic crystal material that can withstand the temperature of the melt environment and maintain its piezoelectric properties (for aluminum and aluminum alloy melts, a bismuth layered structure piezoelectric calcium bismuth niobium ceramic crystal with a Curie temperature of over 940℃ can be used, molecular formula: CaBi2Nb2O9). The structural feature of this generator is that piezoelectric crystal blocks 6 of the same specification are densely embedded on a spherical surface. Through the discharge of the high-energy capacitor 4, each piezoelectric crystal block 6 expands and contracts synchronously, generating a focused shock wave pulse on the melt covered by the spherical surface.

[0027] The protective membrane 2 is made of a thin film resistant to high-temperature melt corrosion and is prepared from an elastic material with a single-layer thickness of less than 0.02 mm. On the one hand, the thinner the membrane, the lower the acoustic impedance and energy loss. On the other hand, existing manufacturing technologies, such as "hand-tearable steel" foil, have achieved a thickness of only 0.015 mm and have realized industrialized mass production. Using it as a substrate for plasma coating, high-temperature, high-corrosion-resistant metals such as Be, Co, Cr, Mo, Nb, Ni, Ti, W, and RE can be deposited on the steel foil surface to form a robust nano-coating, thereby producing a high-entropy alloy foil with a melting point above 2200℃, thus meeting the requirements of the inner wall of the membrane in high-temperature melt containers. Furthermore, when a single-layer membrane is insufficient in strength, it can be laminated, i.e., double, triple, or more layers can be stacked to form the membrane. Example

[0028] A method for processing melts by introducing shock wave energy is described. The method involves transmitting artificially generated, controllable shock wave pulses to the melt. Using energy cascading (EC effect) as a fundamental characteristic, this pulse breaks through the composite network structure of fluid viscosity and surface tension, creating a localized, instantaneous high-pressure, high-energy wavefront that is rapidly transmitted and deconstructed. This induces the homogenization of wavefront particle oscillators, resulting in strong disturbances penetrating the molecular and lattice levels, forming a pressure rheological field (PRF) with a duration on the microsecond scale. Through a series of physical effects of this PRF, a sequential purification process is performed on the melt, including degassing, impurity removal, and slag removal. Defects in the melt's mesoscopic to microscopic (millimeters to nanometers in scale) structure are cleaned and structurally repaired. Furthermore, by suppressing or deconstructing energy fluctuations, concentration fluctuations, and structural fluctuations between different regions of the liquid-solid system, macroscopic solidification defects in the melt are compensated for, and the solidification process is optimized and controlled.

[0029] The energy φ of the shock wave introduced into the melt must meet certain conditions. The corresponding physical and mathematical model is as follows: the action field of the shock wave in the melt, i.e., the impact surface S, is divided into infinitely many parts, and the area of ​​each part is denoted as d. SThen the impact energy passes through each small portion of the flow rate d φ As a measure of the divergence of φ, it can be derived from the energy flux density E. D Its corresponding area element d S The product representation, i.e., d φ =E D d S The energy level intensity of the shock wave can be obtained by integrating the divergence. Under this model framework, the energy scale of the shock wave in the melt can be controlled by adjusting the lower limit from the following aspects, and satisfying any one of them is sufficient.

[0030] (1) When the energy flux density E of the wave on an equivalent cross section in the melt is... D When expressing this, the inequality E must be satisfied. D >σ af In the formula σ af The surface tension or interfacial energy (unit: Newtons / m N / m or Joules / m² J / m) represents the surface tension or interfacial energy within an area element at any location in the melt. 2 The two units are equivalent, E D The dimension is mJ / mm 2 , equivalent to 10 3 J / m 2 That is, 1mJ / mm 2 =1000J / m 2 ).

[0031] (2) When the wave propagation phase velocity C P When expressing this, inequality C must be satisfied. P >σ If / ηm, where σ If Interfacial tension or interfacial energy of a melt (unit: Newtons / meter N / m or Joules / square meter J / m) 2 (The two units are equivalent), ηm represents the dynamic viscosity of the melt (unit: Newton-second / square meter N·s / m). 2 Or Pascal-second (Pa·s), the two units are equivalent.

[0032] (3) When the pseudo-velocity C of the particles caused by the wave in the melt is taken as N When expressing this, inequality C must be satisfied. N >(R et ηm) / (D ρm ), where R et The Reynolds number represents the turbulent or turbulent state of the melt, ηm represents the dynamic viscosity of the melt, D represents the diameter of the focal spot formed by the focused shock wave (in meters), and ρ m Represents melt density (unit: kg / m³) 3The aforementioned particle pseudo-velocities refer to the initial instantaneous velocities that can be obtained from the differential perspective when observing fluid volume element particles in the context of considering the melt as a Newtonian fluid and the shock wave pressure as the fluid driving force. They do not represent the velocity of the fluid medium on a macroscopic scale.

[0033] (4) When the radius of action of the shock wave field in the melt is R (unit: m) and the pressure P at the interface of the field is... f When expressing this, the inequality R must be satisfied. Pf >σ If In the formula, the radius of action R represents the distance from the shock wave source or focus to the boundary of the melt shock wave field, and σ If It represents the interfacial tension or interfacial energy of the melt.

[0034] (5) When shock waves are required to remelt the solidification interface, restore the fluidization characteristics of the crystallized particles, or make the melt exhibit a near-superfluid state, the selection of the energy level scale of the introduced shock wave should first consider the latent heat of fusion L of the melt alloy. m . Example

[0035] A method for processing the melting and solidification process of a melt by introducing shock wave energy, which differs from Example 2 in that the method is in the solidification stage. The specific difference is that by adjusting the shock wave energy, a high-energy pulse is used to remelt the already solidified interface, and it can be combined with cooling methods. By using a repeated "melt-solidify-melt-solidify...-melt-solidify" control mode, the occurrence rate of various solidification defects can be reduced.

[0036] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection of the claims.

Claims

1. A piezoelectric crystal ceramic shock wave generating element, characterized in that, The device includes a concave spherical body (5) installed in the melt and multiple piezoelectric crystal blocks (6) arranged inside the concave spherical body (5). The multiple piezoelectric crystal blocks (6) are all connected to a high-energy capacitor (4), which is connected to a power source. The piezoelectric crystal blocks (6) concentrate energy to a focal point. The piezoelectric crystal blocks (6) are shock wave generators made of ceramic crystal materials that can withstand the ambient temperature of the melt and maintain piezoelectric properties. The middle part of the piezoelectric crystal block (6) is rotatably connected to the concave spherical body (5) by a universal bearing (8) through a connecting rod (7). Electric telescopic rods (9) are provided on both sides of the connecting rod (7) to connect the piezoelectric crystal blocks (6). The electric telescopic rods (9) are connected to the controller.

2. The piezoelectric crystal ceramic shock wave generating element according to claim 1, characterized in that, It also includes a cable trough (1), which is fixedly connected to the side wall of the container and has its inner end extended into the container to install a concave spherical body (5). A wire (3) is arranged in the cable trough (1), and a piezoelectric crystal block (6) is connected to a high-energy capacitor (4) through a wire. The high-energy capacitor (4) is arranged at the outer end of the cable trough (1), and a protective membrane (2) is wrapped around the outer side of the cable trough (1) to the outer side of the concave spherical body.

3. The piezoelectric crystal ceramic shock wave generating element according to claim 2, characterized in that, The protective membrane is made of a thin film resistant to high-temperature melt corrosion and is prepared from an elastic material with a single layer thickness of less than 0.02 mm.

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