Arc welding technology is an important part of modern welding technology, and its application scope covers almost all welding production fields. As a basic metal treatment method, arc welding is widely used in all sectors of the national economy, and the arc welding power supply that provides energy for arc welding has made great development since its birth.
Development course of 1 arc welding power supply
Arc, as a physical phenomenon of gas conduction, was discovered at the beginning of19th century, until 1885, when Russian Benado invented carbon electrode arc, which can be regarded as the foundation of the application of arc as heat source, and the real application of arc in industry was after 1892 discovered metal electrode arc. Submerged arc welding was successfully studied in 1940s, but argon arc welding appeared with the development of aerospace and atomic energy. In 1950s, CO2 shielded welding of various gases appeared, and plasma arc welding was developed. In 1970s and 1980s, the development of arc welding power supply was more rapid: various types of arc welding rectifiers appeared and improved one after another, and various types of pulse arc welding power supply were successfully developed, which provided excellent arc welding power supply for further improving welding quality and adapting to all-position welding automation. In addition, thyristors, transistors, field effect transistors and IGBT arc welding inverters with high efficiency, energy saving and good performance have also been successfully developed. With the development of new arc welding technology, arc welding power supply has also made great progress.
Classification, characteristics and application of 2 arc welding power supply
2. 1 Classification of arc welding power supply
The classification methods of arc welding power sources at home and abroad are different, so the results are different. This paper adopts Chen Zhunian's classification method.
2.2 Characteristics and application of various arc welding power sources
Arc welding transformer is to convert alternating current of grid voltage into low-voltage alternating current suitable for arc welding, which consists of main transformer, required regulating part and indicating device.
It has the advantages of simple structure, convenient manufacture and maintenance, low cost and high efficiency, but its current waveform is sine wave and its output is AC voltage drop, so the arc stability is poor and the power factor is low, but the phenomenon of magnetic bias blowing is rare and the no-load loss is small. Generally used for manual arc welding, arc welding and argon tungsten arc welding.
Square-wave AC arc welding power supply adopts semiconductor control technology to obtain square-wave AC current, which has good arc stability, many adjustable parameters and high power factor. It can be used not only for AC TIG welding, but also for submerged arc welding, and even for alkaline covered electrode manual arc welding instead of DC arc welding power supply.
DC arc welding generator is generally composed of special DC generator and regulating device to obtain the required external characteristics. Its disadvantages are large no-load loss, obvious magnetic bias, low efficiency, high noise, high cost and difficult maintenance. It has the advantages of strong overload capacity and small output pulsation, and can be used as power supply for various arc welding methods or driven by diesel engine for field construction without power supply. Arc welding rectifier, which obtains direct current by step-down rectification of alternating current, has flat or falling external characteristics, and is composed of main transformer, semiconductor rectifier element and regulating device to obtain the required external characteristics. Compared with DC arc welding generator, it has the advantages of convenient manufacture, low price, low no-load loss and low noise, and most of them can be adjusted remotely, which can automatically compensate the influence of grid voltage fluctuation on output voltage and current, but there is magnetic bias. It can be used as power supply for various arc welding methods.
Arc welding inverter converts single-phase (or three-phase) alternating current into intermediate frequency alternating current of hundreds to tens of thousands of hertz after rectification, and outputs alternating current or direct current after step-down. The whole process is controlled by electronic circuit, so that the power supply has the required external characteristics and dynamic characteristics. It has the unique advantages of high efficiency, energy saving, light weight, small volume, high power factor, good control performance, fast dynamic response, easy real-time control of welding process and good welding performance. It can be used in various arc welding methods and is a popular and most promising arc welding power supply. Pulse arc welding power supply, welding current is fed by low-frequency modulation pulse, which is generally composed of ordinary arc welding power supply and pulse generating circuit, and there are other structural forms. It has the advantages of high efficiency, low input line energy and controllable line energy in a wide range. This kind of arc welding power supply has unique advantages for high alloy sheet and all-position welding which is sensitive to heat input.
Present situation and development of 3 arc welding power supply technology
3. 1 current situation of arc welding power supply technology
Traditional arc welding power sources, such as hand arc welding machine, which accounts for 90% of the total welding output, are mainly rectangular moving iron welding machine with backward technology and moving coil AC arc welding machine with more consumables. In China DC arc welding power supply, although the production of rotary DC arc welding generators driven by electricity has been gradually reduced, it has not been completely banned. The rectifier arc welding power supply is also difficult to popularize, because the performance of the old silicon rectifier arc welding power supply is difficult to compare with the rotary DC arc welding power supply, and the initial performance of the thyristor rectifier power supplies ZX5 -250 and ZX5-400 promoted by the state is unstable, which makes users at a loss. This situation did not change until the mid-1990s.
Digital arc welding technology is a new technology. Digital arc welding power supply means that the traditional analog control technology is replaced by digital control technology in the main control circuit of welding machine, and the control signal in the control circuit is also transformed from analog signal to 0/1 coded digital signal. Compared with analog system, digital system has obvious advantages. Digital system has the characteristics of good system flexibility, high control precision, good stability and product consistency, good interface compatibility, convenient system function upgrade and so on. In 1994, La Steiner. Robert of Fronius Company pointed out that modern GMAW welding power supply should meet different requirements in many aspects, such as: it is suitable for welding processes such as short-circuit transition welding, pulse welding, spray transition welding, high deposition rate welding, etc. The reasonable external characteristics of welding power supply can be realized by inverter power supply whose primary side works in switch state; The design of a large number of welding specification parameters must realize collaborative control (centralized control) to make the welding power supply easy to operate; In order to meet the new quality control requirements, welding power supply must record welding specification parameters and identify deviations in real time. Based on the above ideas, along with the appearance of a new powerful digital information processor DSP, Fronius Company launched a fully digital welding power supply, and then companies such as Panosonic also launched their own digital welding power supply products, and entered the China market one after another. The invention realizes flexible control and multifunctional integration, and has the advantages of high control precision, good system stability, good product consistency and convenient function upgrade. For example, the Trans Plus Synergic 2700/4000/5000 series products of Fronius Company have realized various welding methods such as MIG/MAG, TIG and manual arc welding on one welder, which can store nearly 80 welding programs and display welding specification parameters in real time. By giving welding specification parameters and current waveform parameters with a single knob, droplet transfer and arc length change can be accurately controlled. At the same time, this welding power supply can also be managed and controlled through the network.
3.2 Development of arc welding power supply technology
Arc welding power supply has experienced more than one hundred years since its birth, and it always develops with the progress of science and technology. It is predicted that the arc welding power supply will develop in the following aspects in the future:
First, digital arc welding power supply. From the point of view of hardware circuit, the digital power supply realizes the digitalization of PID controller and PWM signal generation circuit with the help of DSP technology. With the emergence of mixed-mode circuits that combine analog circuits and digital circuits organically, it is expected that in the near future, discrete analog circuits will be gradually replaced by highly integrated digital mixed-mode circuits. The design and manufacture of welding power supply and power module can also be completed in a digital way as needed. The energy control of welding power supply is completed through the cooperation of current, voltage and time, which is embodied in the digitization of output waveform.
Second, the green arc welding power supply. As early as 2000, the concept of green welding machine was put forward. Green welding is put forward under the situation that global resources and energy are increasingly scarce and people's awareness of environmental protection is gradually enhanced. Energy-saving and environment-friendly green electric welding machine will be the development direction of arc welding power supply for electric welding machine in the future.
4 conclusion
In recent years, with the increasingly fierce market competition, people pay more and more attention to improving the productivity of welding production, ensuring product quality and realizing automation and intelligence of welding production. The combination of artificial intelligence technology, computer vision technology, digital information processing technology, robotics and other modern high-tech technologies has also promoted the development of arc welding technology in the direction of high efficiency of welding process, digitalization of welding power supply control, intelligence of welding quality control and robot of welding production process, and the development of arc welding equipment in the direction of intelligence and robot. The content summarized in this paper is only a small part of it, hoping to promote communication and perfection.