Application of the hottest arc striking cotton in

Application of arc cotton in automatic submerged arc welding

narrow gap submerged arc welding, as an efficient welding method, is widely used in the welding of medium and thick steel plates and other steel structures. However, due to the limitation of large welding parameters, it is difficult to realize advanced methods such as high-frequency additional arc striking on the arc starting device, and the short-circuit back pumping method is still used, so the arc starting efficiency is not high, especially for the domestic AC welding machine with a large stock, it is more difficult to start the arc, which brings a waste of cost and construction period to the on-site construction

the "steel wool" brand arc striking cotton (Patent No.: zl.6) developed by Xianyang Wuxing technology is a new type of welding auxiliary material with national patents. It uses high-quality steel to draw very fine metal fiber filaments, which are similar to cotton wadding, and the fiber diameter is less than 0.003mm. The arc can be "ignited" at a very small current and voltage. When the "arc breaking" occurs during the welding process, the operation is simple and convenient. The fluctuation of the arc starting voltage and current is very small, and the fluctuation time is short, which greatly reduces the damage of the oscillating current to the components of the welding machine

1 process experiment method and results

chemical composition (%) of arc striking cotton is shown in Table 1. The performance test adopts the comparison method, that is, under the same conditions, the traditional arc striking method 10 is used to compare the whole experimental machine or the parts transported separately with the method of arc striking cotton

2 result analysis

(1) the arc starting process of traditional submerged arc welding completely imitates the arc starting process of manual arc welding. Before arc striking, the welding wire shall be sent down to make it reliably contact with the workpiece to form a conductive path. Please refer to the controller manual for details to select the control mode; And reset PID parameters; Make the tacit enable signal on the controller turn off; And press the start button after saving this state. The power supply of the main circuit forms a strong short-circuit current under the action of no-load voltage, and the current density between the tip of the welding wire and the base metal is the largest. At the same time, under the action of short-circuit feedback circuit, the welding wire is pulled back, and the air is broken down between the base metal at the tip of the welding wire to form an arc. When the welding wire is pulled back to a certain arc length, and the output of 10 kinds of non-ferrous metals with arc voltage of 50.9 million tons rises to the controlled parameter value, the welding wire stops pumping up, the welding wire melts to lengthen the arc, and the arc voltage rises to greater than the controlled parameter value, the welding wire begins to send down, forming a closed-loop control, and normal welding begins. The completion of this process takes 1.5~4s, and the arc striking time of AC welding machine is relatively longer. In this process, if the operation is not standardized, the arc cannot be started normally. However, the phenomenon of "arc breaking" occurs during welding, and the operation of "re arcing" is quite troublesome. Especially in the construction site, the electric wave movement is large, which makes the occurrence rate of arc breaking very high

(2) when using the arc starting cotton, make preparations according to the normal welding, but do not directly contact the tip of the welding wire with the base metal. Take 1g of arc starting cotton to form a small ball and block it between the base metal of the welding wire, so that the spacing between them is kept at 4mm. The left side is for various types of casting processing such as the blank of the blank of metal tools, punching, forming, etc. Directly start the power supply of the main circuit, and the arc striking cotton will melt rapidly, causing air ionization, "breakdown" and arc striking, so that the arc can quickly reach the closed working state. Generally, this process does not exceed 1s. Because the time from back pumping to closed-loop working state is shortened and the arc starting is fast, and the closed-loop control process is reduced, the arc starting is more stable and the power loss is reduced

(3) from the analysis of ignition arc mechanism, the formation of arc requires "breakdown" air, and the energy demand in the arc formation stage is far greater than the energy required to maintain the arc. By drawing steel into very fine wires, mechanical energy can be converted into surface energy due to the increased surface area of steel wire deformation, so that the steel fiber itself has been in a high energy state. The need for external energy is relatively reduced, which in itself reduces the requirement for no-load voltage during arc starting. As the main body of heat generation, the steel wire has relatively high resistance due to its small cross-sectional area. The requirements for I and u to generate a fixed value of heat become very low, and it can quickly return to the arc maintenance state. Thus, the impact of the equipment on the equipment during the arc striking process is reduced, the oscillation amplitude of parameters is reduced, the welding quality and equipment circuit are well protected, the service life is prolonged, and the impact on electricity is reduced

(4) combined with the above characteristics, the arc striking cotton plays a very important role in improving the arc striking rate and work efficiency. Moreover, under the current domestic equipment conditions, manual arc welding of some steel grades with strict requirements for gas shielded welding and arc striking times and arc striking range is widely used

3 conclusion

(1) as a new type of welding auxiliary material, arc striking cotton is of great significance to reduce workers' labor intensity, improve production efficiency, save energy, protect and give full play to the ability of welding equipment

(2) with the continuous development of the variety and quality of arc striking cotton products, the level of welding technology in China will be improved, and the integration of traditional welding technology with international advanced process methods will be accelerated. (end)