In this paper, efficient MIG / MAG welding the melting efficiency of the melting rate of the concepts were analyzed, and made a impact on MIG / MAG Welding Electrode Suppliers melting efficiency, and finally proposed to improve the efficient and effective fusion welding methods.
MIG welding gas for its high efficiency, simple operation, easy to implement mechanization and automation, etc., in the actual production is widely used and has become an alternative to arc welding process. Currently, Western Europe, the United States and Japan and other industrialized countries of the MIG / MAG welding process the workload of all welded 60% to 80%. Since the 1990s, along with the development of industrial production, high-parametric, thick, thick plate welded metal structure of the application was more widely, the manufacturers in order to enhance market competitiveness, more and more intense demands improve welding productivity and reduce production costs. Current survey results show that, if the wire deposition rate of less than 20% / min or more, then that is difficult to meet the efficiency requirements of welding products, we can not achieve the expected economic benefits. Therefore, raising the MIG / MAG welding process efficiency, improve the market competitiveness of welding products in an effective way.
Improve welding productivity mainly include two aspects: First, to increase the welding speed for the purpose of high-speed welding, and its basic starting point is to increase welding speed and improve the welding current, welding heat input to maintain the largely unchanged, mainly used in sheet metal welding; second is to enhance the melting rate of welding materials for the purpose of high deposition rate welding, which requires more in the melt per unit time of welding materials, this study aimed to discuss the second aspect.
1 the melting efficiency of welding materials
To improve the efficiency of fusion welding materials, welding specifications should be in a certain context to improve the melting rate of welding materials, welding materials, so those who can raise the melting rate of the methods and measures can improve the deposition efficiency of welding.
Melting rate per unit time is defined as the molten weld material (filler metal and base metal) weight, which is the efficient method of welding the most important factor. Gas for MIG welding, welding materials, melting the energy consists of two parts, part of the arc energy generated C1; the other is part of the wire elongation produced by dry heat resistance of C1, shown in Figure 1. (2) melting of solder material factors affecting the efficiency of
(1) To increase the welding current melting rate, increasing the welding current is necessary, along with the increase of welding current, welding materials, the melting rate will be significantly improved. But for a certain diameter of the wire in terms of its current capacity there is a certain limit. When the welding current increases to a certain extent, the welding arc and metal transfer patterns will change significantly the form. The use of filaments, the welding current increases to a certain degree of instability of the rotation will jet into the transition, this time horizontal droplet often throw a splash, welding process is very unstable. The use of thick wire high current welding as SAW, with the increasing welding current, welding wire melting rate increase, but at the same heat input to the workpiece also will increase the amount of increased heat input welding, which uses high-strength steel and special materials welding is inappropriate. In this case, in order to ensure the welding quality of the premise of improving welding productivity must improve the welding current process while supporting other measures.
(2) dry stretch the length of wire in the same welding current circumstances, increase the wire stem elongation can also increase the wire melting rate. C2 in Figure 1 indicates the ohm wire to generate heat and current proportional to the square, which is to improve the wire melting rate is very important. Because the wire with the wire resistivity will increase the temperature rises, with the welding current increases, the wire resistivity will increase. Figure 2 shows three different lengths of wire extended dry deposition efficiency and the current relationship between the curves. As can be seen from Figure 2, in the same welding current circumstances, with the increase in dry elongation, wire the deposition efficiency improved significantly. Therefore, in high-current welding, the wire on the ohmic heat generated by the melting rate of the wire plays a vital role. (3) The polarity of the deposition efficiency of different polarity for welding, welding wire and base metal deposition efficiency is different. Typically, melting polar gas shielded arc welding using DCEP (DC reverse), as DCEP can achieve greater penetration and to prevent the lack of penetration defects. Figure 3 and Figure 4 shows the polarity of the wire with the penetration depth and the relationship between the deposition efficiency. It can be seen, the DC reverse can get a larger penetration depth, but the smaller wire of the deposition efficiency; DCEN (DC is connected) wire can be very high deposition efficiency, but a smaller base metal penetration. From Figure 3 and Figure 4 can be seen, can be adjusted by changing the polarity of the base metal and wire melting rate of deposition efficiency, to meet the requirements of different welding processes. If the requirements of increased penetration of base metal, you can use DCEP; if welding sheet metal, can be used DCEN, thereby reducing the base metal penetration, and increasing the wire melting efficiency, high-end high-speed welding. (4) wire diameter of the Figure 5 illustrates the different diameters of wire welding specification parameters at different deposition efficiency. It can be seen, in the same welding current circumstances, with the wire diameter decreases, the welding current density increased, the wire of the deposition efficiency has increased; the contrary, if the deposition efficiency must be maintained, with the reduction in wire diameter small, welding current decreases, corresponding to the workpiece also reduces the heat input, ie deposition efficiency in the same context, can reduce the heat input to the base metal, which uses high-strength steel and special steel welding is very favorable of. Therefore, workers in the study of efficient welding MIG / MAG welding process, the most high-current welding using filaments, is the use of these advantages. TIME welding process, such as the wire of 1.2mm, the maximum wire speed up to 50m/min. LINFAST and dual wire welding processes are used such as TANDEM 1.2mm filaments. Using filaments welding additional advantage is the low current arc welding improve the stability, the impact of the pool decreases, thereby maintaining the uniform penetration. (5) the impact of shielding gas for MIG / MAG inert gas studies have been carried out for many years, the gas in the welding process to protect the role mainly in the following aspects: ① improve arc stability. ② improving the metal transfer. ③ improve the mechanical properties of weld metal. ④ improve welding productivity. ⑤ to reduce the possibility of welding defects, such as porosity, not fusion, etc. In addition, due to different gas physical and chemical properties different from that in the welding process is not the same role, so the choice of shielding gas should be for different process conditions, different applications and different.
Figure 6 shows the conductivity of different gases with temperature variation. It can be seen from Figure 6 as the temperature increased, the decomposition and ionization of the gas more easily, so the conductivity of the gas increase as the temperature increased. Figure 7 shows the thermal conductivity of the gas and the relationship between the temperature curve. Gas thermal conductivity is a very important protective gas properties, which directly affects the temperature and shape of the welding arc and weld. It can be seen from Figure 7, hydrogen, oxygen, CO2 gas at low temperature (about 3000K) when high thermal conductivity, while helium and argon at high temperatures (about 9000K) when high thermal conductivity. MIG / MAG welding is often used in pure tritium gas, CO2 and Ar-He mixed the basis of the oxygen or CO2 gas, to increase the oxidation potential of the gas. Currently, workers welding on MIG / AG welding shielding gas made a lot of research results, especially in the high (high deposition rate) welding shielding gas. Such as the TIME gas (Ar / 8% CO2/0.5% O2/26.5% He), LINFAST gas Corgon He30 (10% CO2/30% He / Ar) and so on.
Although differences in composition of these gases, but they are to achieve a high deposition efficiency welding process. Then, the shielding gas for welding deposition efficiency has been affected? To illustrate this problem W. Lucas and M. Suban and J. Tusek protection of different media in case of wire deposition efficiency changes were studied, Figure 8a for the W. Lucas 5 different types of shielding gas to protect the wire to get the case of changes in deposition efficiency. Figure 8b for the M. Suban and J. Tusek protection gas for different circumstances where the wire melting rate changes. Studies have shown that different components of the gas on the arc characteristics and metal transfer in the form and characteristics of weld pool have a greater impact, while the wire melting rate impact is very limited. Based on these results, the choice of shielding gas should be based on different technical requirements (welding material composition, material thickness and welding position, etc.) choose a different shielding gas. 3 Conclusion
(1) increasing the welding current can significantly improve the efficiency of Low Alloy Steel Electrodes, melting, but at the same time increasing the welding current process should complement other measures, to ensure good welding process.
(2) increasing the welding wire to stretch the length of wire to improve the deposition efficiency plays a vital role.
(3) selection of high-current filaments welding process, welding can improve the deposition efficiency while reducing the heat input to the base metal, is conducive to high-strength steel and special purpose welding.
(4) Select DCEP can get a larger penetration depth, the use of wire DCEN can improve the deposition efficiency, suitable for high speed welding sheet metal.
(5) the composition of the gas column to protect the deposition efficiency of the wire has little effect, however, the protective gas can improve the arc stability, improving droplet transfer and expand the use of welding specifications. Use less helium or helium-free gas mixture of low-cost, instead of three yuan or quaternary helium-rich body, and then assisted the other process measures (field control), high-current filaments can be realized in the case of the stability of the metal transfer, which MAG welding of low-cost and efficient new technology is of great practical significance.