Application of Ultrasonic Technology in Steel Bucket Process (1)
Sinopec Sales Company Baoji Company Bucket Factory Wang Chengxian
First, the basic concept of ultrasound
1. Acoustics, sound waves, sound spectrum, audio
The science that studies the generation, propagation, and absorption of mechanical waves in matter is called acoustics. The materials (in a narrow sense) for acoustic studies are solids, liquids, gases, plasmas, and the like. Their state can be homogeneous isotropic, it can also be non-uniform anisotropic; it can be static or flowing.
The fluctuation of the medium generated during the propagation of mechanical vibrations in the medium is called sound waves. Sound waves, electromagnetic waves, and light waves are three major techniques for exploring the nature of matter today.
Acoustic vibration frequency (audio frequency) can be divided into infrasound, audible sound, ultrasound and ultrasonography. According to their frequency arrangement for the sound spectrum, see Figure 1.
Figure 1 Sound spectrum
2. Application of sound waves
Infrasound (104 to 20 Hz) is below the human hearing range. It is used to detect meteorological changes, nuclear explosions, earthquake predictions, storms, auroraes and tsunamis. It monitors the launch of rockets, missiles, and spacecraft. Foreignly developed infrasound bombs and infrasound guns have been used to eliminate enemy resistance.
Acoustic sound waves (20 to 2×104 HZ) are the main means of communicating information between people and some higher animals. They can also be used to detect climate distribution and changes.
Ultrasound (above 2 x 10.4 Hz) - The audio frequency is higher than the human hearing range and cannot be heard. Its use is quite extensive, and some applications even reach a magical point. Ultrasonic technology and computer technology combine to make brilliant achievements in ultrasound science. They are widely used in machinery, electronics, optoelectronics, metallurgy, surface treatment, heat treatment, corpse agriculture, medicine, life, Geophysical, measurement, chemical, cold and hot processing and other disciplines and fields.
Second, the ultrasonic effect
In addition to the general properties of sonic waves such as reflection, refraction, interference, standing wave, diffraction, attenuation, absorption, holography, and Doppler effect (this article does not describe these properties), there are some unique effects. Ultrasonic technology is Applying these effects makes it widely used.
1, mechanical effect. When the ultrasonic wave propagates in the medium, it will cause the vibration of the media particle, and the effect caused by the mechanical quantity such as displacement, velocity, acceleration, sound pressure, and sound intensity is called ultrasonic mechanical effect.
The mechanical effect of ultrasound is very strong. Sound intensity up to several hundred W/cm2, up to tens of thousands of W/cm2 after focusing. When the frequency is 106 Hz and the displacement amplitude is several micrometers, the sound pressure amplitude can reach several hundred atmospheres, and the acceleration amplitude can be tens of millions of times of the gravity acceleration, thereby causing strong ultrasonic effects.
The strong mechanical effect produced by high-intensity ultrasound will change the nature and state of the material and apply it to the processing of materials in various fields such as metallurgy, cleaning, drilling, nesting, cutting, grinding, crushing and so on. Ultrasonic processing can process hard, brittle materials, regardless of whether the material is conductive or not.
2, thermal effects. During the propagation of ultrasonic waves in the medium, part of the acoustic energy absorbed by the medium causes the temperature of the medium to rise. When the ultrasonic wave encounters the interface between the liquid and the solid, temperature gradients and velocity gradients are generated at the interface, and this part of the ultrasonic energy is also converted into heat energy. If there are suspended particles inside the medium, the ultrasonic energy at the interface between the medium and the suspended particles also transforms into thermal energy (the boundary friction of the ultrasonic wave). These are the thermal effects of ultrasonic waves that are converted into ultrasonic energy.
The application of thermal effects to high-frequency ultrasound makes the absorption phenomenon more pronounced, and the friction at the interface is more intense (the absorption coefficient is proportional to the square of the frequency). Ultrasonic welding machines and ultrasonic dryers are very effective. The steel drum industry uses ultrasonic spot welding machines and seam welding machines to save energy and no pollution. The chemical industry and food industry use its drying, which is non-toxic, fast, and energy-saving. It can be widely used for all thin plate welding and plastic welding.
3, chemical effects. When the ultrasonic wave passes through the medium, the phenomenon of strong molecular collisions in the medium causing molecular ionization and other chemical reactions is called the chemical effect of ultrasonic waves.
Certain chemical reactions that can be performed under high temperature and high pressure conditions can be carried out under the action of ultrasonic waves at normal temperature and pressure. When some of the chemical reactions are introduced into the ultrasound, the reaction is rapid and sufficient (such as electroplating and electrolytic etching).
4. Cavitation effect. When ultrasonic waves are radiated into a liquid, at a certain sound intensity and frequency, the liquid generates a large number of small bubbles. The bubbles grow strongly and close more strongly as the sound pressure vibrates. Finally, the small bubbles collapse, which is called the cavitation effect of the ultrasonic wave. .
When cavitation occurs, the liquid undergoes localized high temperature and high pressure, ionization and luminescence. Cavitation bubbles are generated when the ultrasonic negative pressure occurs, and then they close and collapse when the ultrasonic pressure is positive. At this time, shock waves are generated, and the pressure thereof reaches several thousand atmospheres. With this effect, dirt and oxides on the solid surface can be removed, making it an ideal method for industrial cleaning of oxides, greases, and dirt on parts and materials. Widely used in the electronics industry, and recently extended to the automotive, tractor, petrochemical industry, the prospects are very broad.
Third, the basic principle of ultrasonic devices
Due to the different uses of ultrasound devices, the structure is also different. The power level, frequency, and modulation method are also different, but the basic principle is that the oscillation pulse number generated by the electric energy can be converted into ultrasonic vibration, and the processed object can be processed or assisted in processing or detection.
The ultrasonic device consists of an ultrasonic generator (also called an ultrasonic power supply), a transducer, a horn, an acoustic focusing device, and a corresponding body. Different uses, The size of the devices varies greatly.
1, ultrasonic generator. Ultrasonic generators convert electrical energy into electrical pulses that are converted into ultrasonic waves by the transducer. It is equivalent to the electric motor in the machining equipment. The ultrasonic generator is composed of a power supply, an oscillator (a trigger), a power amplifying unit, an output transformer, a transducer, and the like. Among them, electronic circuits include electron tube type, transistor type, electronic tube and transistor hybrid type, and integrated circuit type. According to the power points can be divided into small power, medium power and high power ultrasonic generator. Their delineation and views vary.
2, transducer. A device that converts electrical oscillations (pulses) into mechanical vibrations. There are two major categories of transducers, namely piezoelectric transducers and magnetostrictive transducers. The former has a lower power and is used to detect many of the latter's power detectors and is used in the processing field.
Piezoelectric transducers use piezoelectric materials to produce an electric field: productivity and strain (converse piezoelectric effect. The positive piezoelectric effect produces an electric field when a piezoelectric material is stressed, and electric sparks use this effect). Use this effect to convert electrical energy into sound energy. Piezoelectric materials include quartz, potassium sodium tartrate, and the like.
Magnetostrictive transducers are placed in a magnetic field using certain materials and the linear dimension of the material changes (Joule effect). When an alternating magnetic field of a certain frequency is applied, the material will extend and contract at the same frequency along the direction of the magnetic field, thereby causing ultrasonic vibration. Magnetostrictive materials include annealed nickel, aluminum-iron alloys, iron drill alloys, and nickel ferrites.
3, horn.
The horn is a variable crossbar. When resonating with the transducer, one end of the large section is used as the ultrasonic input end, and when the end of the small section is used as the ultrasonic output end, a large vibration displacement can be obtained at the output end, that is, the amplitude of the mechanical vibration of the ultrasonic wave is amplified to concentrate the energy. Builds a concentric effect on a smaller area. With the horn, ultrasonic waves can be introduced into the load more efficiently and the conversion rate of energy can be increased.
The horn has conical, stepped, exponential, catenary, Gaussian, Fourier, etc. It can also be composed of different curves with different cross-section variations to meet special functional requirements.
4, sound focusing equipment. The sound energy is concentrated in the focal area to obtain strong acoustic radiation, similar to the case of light focusing. Used to study the role of physical, chemical, and biological processes in strong ultrasonic fields.
Fourth, ultrasonic applications
Since the fifties and sixties of this century, ultrasonic technology has been applied in many fields such as industry, agriculture, national defense, scientific research, medicine, and people's lives. Ultrasound technology is "an efficient, energy-saving technology without pollution." According to the current popular words, it is a kind of "green" processing technology.
During the Great Leap Forward of our country, we launched the "ultrasonication" of the mass movement, leaving nothing to be desired. Since then, China has stepped up its research, first using the defense and electronics industry (mainly ultrasonic cleaning and grinding technology, and later expanded to processing, welding, testing, metallurgy, and chemical industries. With the introduction of ultrasonic medical instruments, it has also expanded into medicine. At present, there are backbone ultrasonic instrument manufacturers in Shanghai, Jining, Guilin, and Shenzhen, and many township and village enterprises are also involved in this technology.
1, ultrasonic applications in the machinery industry. Ultrasonic technology in China has been used for drilling, nesting, turning, cutting, deburring, polishing, grinding, welding (spot welding, multi-spot welding, seam welding, ring welding, brazing and wave soldering, etc.), engraving, metallization (metal materials are welded on non-metallic materials), coated (non-metallic materials such as ceramics, glass, ferrites, and polymers are coated with metal materials), powder metallurgy, electroplating, emulsification, atomization (use this Principle made of civilian humidifier), broken (crushed ore, glass, fiber) and so on. Ultrasonic turning, powerful milling, powerful grinding, and super-finishing are all introduced into the machining process.
2. Preparation of emulsified oil. Ultrasonic waves are used to make two mutually incompatible liquids such as water and gasoline to form a uniform, highly stable, highly disperse liquid, that is, an emulsified liquid. Using this principle, 10 to 15% of self-contained water in gasoline is emulsified by phacoemulsification to make emulsified gasoline, which increases the burning rate, saves energy by about 10%, reduces exhaust emissions, and improves the environment.
3, ultrasonic applications in medicine. Ultrasound diagnosis has become one of the main methods for doctors to diagnose diseases. Especially in the diagnosis of visceral organ diseases in humans, it provides a reliable means for the diagnosis of diseases.
Currently widely used A-type ultrasonic tester, B-type ultrasonic tester, Doppler ultrasonic heart tester, combined with the computer to make the internal lesions of the human body clearly visible, and can geometrically measure the size of the lesion, the nature of distortion, human biochemical parameters and pregnant women Fetal status, found deformity. Stop pregnancy, prenatal and postnatal care. Ultrasonic fracture of gallstones, kidney stones have been widely used. Ultrasound medicine has developed into an independent science. It is believed that a perfect human ultrasonic tomography instrument (ultrasonic CT) will be developed in the near future to eliminate X-ray damage to the human body.
4, ultrasonic applications in industrial testing. Reflections, refractions, and diffraction occur when ultrasound is used to propagate solids and liquids. Scattering, attenuation, penetration, absorption, Doppler, and other effects detect internal defects in materials and parts such as cracks, bubbles, sand holes, impurities, and Weld quality, but also can measure a variety of coatings, coating thickness, to achieve no damage detection, widely used in various processing areas.
Ultrasonic technology can also be used to determine the material's elastic modulus, material hardness, fluid viscosity, liquid level flow rate and flow, temperature, and physical parameters of electronic components.
5, the application of ultrasound in agriculture. Use ultrasound to treat the seeds of agricultural crops, accelerate seed germination, stimulate farming, and crop growth. In cold regions, we can effectively use short crops to grow time and increase grain yield.
6, the use of ultrasonic modulation can produce acousto-optic devices. Using ultrasonic surface wave technology, interference technology can broaden the electronic processing.
7, ultrasonic cleaning technology. This technology was applied earlier and has been applied to the cleaning of electronic components in the 1950s. In the seventies to eighties, cleaning of electronic components took up the majority of them, and IC circuit components had all been cleaned using ultrasonic technology. At present, ultrasonic cleaning technology has developed into an independent ultrasound science. The following focuses on the principle of ultrasonic cleaning and its application in industry.
V. Ultrasonic cleaning technology
1, ultrasonic cleaning principle. Ultrasonic cleaning device consists of high-frequency ultrasonic generator, transducer, sound energy amplifier, voltage regulator, liquid tank, pump, conveyor frame and body. The higher frequency ultrasonic wave is introduced into the cleaning liquid, and under the action of the ultrasonic wave, the cleaning liquid and the cleaned workpiece contact interface generate strong friction and increase in temperature. The liquid particle point produces a mechanical effect and the sound pressure reaches thousands of atmospheric pressures. As the ultrasonic intensity increases beyond the cavitation threshold (the cavitation effect produces the lowest required sound intensity at a certain frequency), liquid cavitation occurs, resulting in localized high pressure during cavitation bubble generation and collapse. And ionization. If the natural frequencies of the body and the workpiece resonate with the applied ultrasonic frequencies, a strong cavitation effect will occur, and the scale, grease, and dirt on the surface of the workpiece will be peeled off.
2, ultrasonic cleaning applications. Ultrasonic cleaning technology can be used to remove metal, non-metallic materials and parts surface oxide skin, grease, dirt, can also be used to accelerate the phosphating, passivation process, improve quality, but also for non-metallic materials, metallization.
Medium and high power high frequency ultrasonic cleaning machines and phosphating and passivation equipment are particularly suitable for surface treatment processes in automobiles, tractors, motorcycles, water tanks, air conditioners, bicycles, steel doors and windows, filing cabinets, and packaging drums. At present, the Beijing Venus Institute of Ultrasound has successfully produced high-power automotive ultrasonic cleaning and phosphating equipment for degreasing, rust removal, and phosphating.
Ultrasonic cleaning external heating source can also be added, surfactants can be used, additives can also be used, depending on the status of the workpiece and ultrasonic power, so energy saving, no pollution.
3, ultrasonic cleaning technology requirements are as follows:
