The Study Of TIG-MIG Alternating Compound Arc's Welding Mechanism

Since the concept of "Made in China 2025" was put forward,the manufacture in China has promoted the rapid development of modern manufacturing industry.In the field of welding manufacturing,it has become one of the hottest issues to meet the requirements of high quality and high efficiency welding process,and the competition in this field is very fierce.With the advantages of good welding quality,less weld defects and high production efficiency,the composite welding process has won the primary attention,and has been regarded as the key direction to realize the high efficiency of welding.In the traditional Gas Metal Arc Welding,the heat input of welding is approximately proportional to the amount of deposited metal,so it is difficult to increase the amount of deposited metal under the condition of the same heat input.The traditional welding process is mostly a single point heat source,that is,the energy distribution of the heat input in the space can not be adjusted,so the temperature gradient at the welding toe can not be reduced.To a certain extent,these two problems affect the speed of welding greatly.In the welding direction,the heat distribution can be prolonged,and the temperature field of low heat input can be obtained under the condition of high current and high speed welding,and the main power of liquid metal flow can be obtained by increasing the temperature gradient.It can achieve high efficiency,improve welding speed and improve welding quality.In this paper,a new composite arc welding process is proposed,which consists of a DC reverse MIG welding and a variable polarity TIG welding.The MIG arc is used as the main arc to melt the welding wire and to promote the droplet transfer,and the pulsating arc form is formed between the wire and the base metal.By polarity transformation,a periodically switched arc form can be formed between the tungsten electrode and the welding wire and between the tungsten electrode and the base metal.When the auxiliary arc burns between the tungsten electrode and the welding wire,the arc heat of the auxiliary arc acts mostly on the wire,so the amount of deposited metal can be increased,and the heat input of the base metal is affected very little.When the auxiliary arc burns between the tungsten electrode and the base metal,the heat input and the energy distribution can be changed,and the temperature gradient can be reduced.At the same time,the alternating auxiliary arc can not only promote droplet drop,but also have periodic force on the molten pool,thus stirring the base metal melting pool regularly.At the same time,the time ratio and strength of the auxiliary arc transformation can be adjusted reasonably,the relative independent control of the amount of deposited metal and heat input can be realized,and the grain size of weld can be refined,so the welding quality is optimized.The TIG-MIG alternating arc composite welding platform is optimized and improved.The space position mechanism of the two welding torch is designed,which can adjust the relative height,the whole height and the distance of the TIG-MIG welding torch accurately.The experiment of MIG single wire short transfer welding is carried out and the PI parameter is adjusted,so the following characteristic of power supply is optimized.What's more,the core control circuit is modified and the control method of stable peak current mode PWM is realized,and the software and hardware system of welding power source is optimized,too.Finally,we set a corresponding experimental platform and a high-speed camera system.In this paper,the characteristics of alternating hybrid welding TIG auxiliary arc are summarized by using high speed camera technology and electrical signal data acquisition system,and the arc test of DC TIG composite welding process is carried out.This paper describes the shape of the arc under the condition of the top circuit sustained conduction and the bottom circuit sustained conduction of the TIG power supply,and briefly analyzes the conductive mechanism of the arc,and carries out the experiments in the stable alternating composite welding process to analyze the movement of the auxiliary arc in the TIG.The conversion process of TIG power supply under variable polarity state is described.By means of high speed camera technique,we explored that the distance between the end of tungsten electrode and the center of welding wire is 3mm / 4mm / 5mm respectively,and the relative distance between the end of tungsten electrode and the electrode conductive nozzle is 10 mm / 11 mm / 12 mm respectively and the dry elongation L of MIG is 15 mm / 16 mm / 17 mm,respectively,under the condition that the distance between the end of tungsten electrode and the center of welding wire is 3mm / 4mm / 5mm,respectively.The welding code of alternating composite welding experiment in different combination space position is used to find out the droplet transfer interval with one pulse and one drop.The effects of the distance between the tungsten terminal and the wire center,the relative distance between the tungsten terminal and the wire conductive nozzle H and the dry elongation L of MIG on the droplet transfer were analyzed.