1 Introduction to results At present, successful broadband high-power arc ultrasonic excitation devices (including continuous wave and pulse wave excitation methods) have been developed to study the excitation and control characteristics of arc ultrasonic, and this technology has been successfully applied to welding, spraying, surface modification. In the field of material processing such as sex, applied for the national invention patent "a method of exciting ultrasonic waves with an electric arc", which will soon be authorized. 2 Application Notes In the welding, the coarse grain in the weld zone, the growth of the heat-affected zone, the large residual stress of the weld, the stress concentration phenomenon, and the drop of the impact toughness of the weld are common phenomena that are easy to occur in the welding process, and not only Limited to one or several materials and welding methods. The generation of arc ultrasound is independent of the solder material and the soldering method, and is only affected by the characteristics of the applied excitation source and the high frequency characteristics of the arc plasma. Through arc ultrasonic welding experiments on various materials (A3, 45, 16MnDR, 09MnNiDR, 1Cr18NiTi, TC4, etc.) and various welding methods (manual arc welding, CO2 gas shielded welding, submerged arc automatic welding, TIG, MIG, etc.) It is proved that arc ultrasonic is a general method, which is not limited by welding materials and welding methods. It has obvious effect on improving the comprehensive performance of welded joint structure, and provides a new and effective way to improve the performance of welded joint structure. method. (1) Carbon steel welding Experiments on various steels show that the introduction of arc ultrasonic has obvious effects on refining the microstructure of welded joints, improving the microstructure of heat affected zone, and improving the stress distribution in the weld zone, greatly improving the synthesis of welded joints. Performance; at the same time, many new phenomena that are difficult to achieve under conventional welding conditions have been discovered. For the A3 steel AC submerged arc automatic welding, under the action of arc ultrasonic, the heat affected zone of the welded joint structure changes significantly. The frequency of the excitation ultrasound increases, the width of the "heat affected zone" increases, and is distributed in a finger shape. The microscopic metallographic analysis shows that under the action of arc ultrasonic, the structure of the "heat affected zone" is no longer a weak link of excessive grain growth, but a small equiaxed crystal, showing the excellent characteristics of normalized structure. For manual arc welding of 45 steel, after adding 50 kHz arc ultrasonic, the microstructure of the weld zone is remarkably refined. Arc ultrasonication has an inhibitory effect on the growth of columnar crystals in the weld and causes significant changes in the microstructure of the welded joint. In the conventional welding, the weld microstructure is more pro-eutectoid ferrite and side-plate ferrite; when the center frequency of the excitation source is about 50 kHz, the coarse intercalation crystal structure is obviously refined, and the weld metal is More acicular ferrite is formed. (2) Low temperature steel welding For the submerged arc automatic welding of low temperature steel 09MnNiDR, the morphology of the weld zone and the heat affected zone were analyzed. It was observed that the growth of columnar crystals in the weld was suppressed, the microstructure was refined and the distribution was uniform. The low temperature impact toughness test of the specimens confirmed that the impact toughness of the weld zone and the heat affected zone was improved to some extent. Especially at the excitation frequency of 50 kHz, the impact toughness of the 09MnNiDR weld zone increased by nearly 50%, and the heat affected zone increased by 80. %the above. (3) Stainless steel welding The austenitic stainless steel 1Cr18Ni9Ti was tested by manual arc welding and surfacing. The results show that the introduction of arc ultrasonic has a great influence on the microstructure of the weld zone of stainless steel. The original strip structure becomes a network structure. The particle size is reduced, and as the frequency increases, the tissue mass is more uniform. It can be seen that arc ultrasonic welding has a significant effect on the grain refinement of stainless steel weld zone. (4) Titanium alloy welding A series of tests were carried out on AC/DC/pulse TIG welding of the most widely used α+β dual phase titanium alloy Ti-6Al-4V (TC4) in the aerospace industry. After the addition of arc ultrasound, the columnar crystals in the weld zone were refined to some extent. At the excitation frequency of 50 kHz, the morphology of the grain in the weld zone has changed significantly. The weld zone is almost entirely composed of fine equiaxed grains, and the boundaries between the regions are not obvious. This will greatly improve the performance of titanium alloy welded joints. (5) Improve weld stress distribution Using the welding specification of the A3 steel oblique Y groove, the ultrasonic energy was directly introduced into the welding process through the arc, and the comparative experiment was carried out. The stress distribution of the weld and the surrounding area was measured by the small hole method and the magnetic memory method. When no arc ultrasonic is applied, the stress distribution around the weld is extremely uneven, and the maximum stress is also relatively high. After the addition of arc ultrasonic, the stress distribution is obviously improved. When the excitation frequency is 50 kHz, the average value of the stress is reduced by about 40%, and the fluctuation range of the stress value is also small. At the same time, the introduction of arc ultrasonic can add compressive stress to the weld. , thereby improving the performance of the weld joint. â—Application of arc ultrasonic technology in arc spraying Under the action of arc ultrasonic, pure zinc was used for spraying, and the metallographic test, micro Vickers hardness test and corrosion resistance test were carried out on the sample, which proved that the effect of arc ultrasonication reduced the particle size and porosity of the coating. The reduction of oxides, the reduction of micro Vickers hardness, and the corrosion resistance in an alkaline environment and a saline environment are remarkably improved, and in particular, the 50 kHz arc ultrasonic has the best effect of improving corrosion resistance. Through the tensile test of the chrome coating sprayed under different ultrasonic frequencies and ultrasonic excitation voltage, the bond strength of the coating is obviously improved, and the bond strength of the sample coating is generally increased by more than 12%, which proves the introduction of ultrasound. It has a significant effect on improving the bonding strength of the coating. As the ultrasonic frequency and the ultrasonic excitation voltage increase, the bond strength also increases, which fully reflects the corresponding relationship between frequency and energy. 3 Benefit Analysis Introducing the arc ultrasonic into the welding process can refine the grain of the welded joint structure, improve the stress distribution of the joint structure, improve the strength and toughness of the joint, and provide a new and effective welding method for comprehensively improving the microstructure of the welded joint. Introducing arc ultrasonic into the arc spraying process can reduce the particle size and porosity of the coating, reduce oxides, improve the bonding strength and corrosion resistance of the coating, and provide a new and effective arc spraying method for improving coating performance. .
The innovation of arc ultrasound is to realize the idea that "the arc is not only used as a heat generating mechanism, but also as an ultrasonic transmitting mechanism". Its basic principle is to use the varistor load characteristics of the arc to excite the arc ultrasound. This method overcomes the shortcomings of the conventional ultrasonic generation method and the difficulty of adjusting the parameters. The application of power ultrasound in engineering practice is to the direction of self-coupling, frequency and energy real-time adjustment, using ultrasonic sound flow and cavitation. The effect has an effect on the quality of the process.
â—Application of arc ultrasonic technology in welding
As a general external field method, arc ultrasonic has the characteristics of real-time controllable parameters such as frequency and power, self-coupling to the workpiece through arc, and high coupling efficiency.