| With the development of modern industry,the demand for metal components in many industries is developing towards high strength and thick plate.In the welding process of medium and heavy plates,ultra-narrow gap welding method has many advantages over traditional welding methods,such as high production efficiency,low line energy,less consumption of welding wire filling,small deformation of welded joints,etc.However,the groove width of ultra-narrow gap welding usually varies between 4-5mm,the welding arc becomes very sensitive,the arc stability decreases,and the welding process is greatly affected by random interference factors and is prone to arc climbing,thus greatly affecting the quality of welded joints.If not limited by the bevel width,the arc welding power source with flat characteristics makes the arc have self-regulating function to ensure the stability of the arc.However,in ultra-narrow gap welding,the arc static characteristic curve is in the horizontal slightly rising section of the whole arc static characteristic curve under the constraint of flux sheet.Under the action of flat characteristic power supply,the arc self-regulation effect is small or even unable to play a role and the stability of the arc is reduced.The static characteristics of the arc with a certain shape need to be matched with the appropriate external characteristics of the power supply,so as to meet the stable conditions of the power supply-arc system.At present,the power supply used in the ultra-narrow gap welding test is flat and does not have the function of adjusting the external characteristics,that is,the matching mode between the external characteristics of the arc welding power supply and the ultra-narrow gap welding arc is not the best,which cannot meet the requirements of the ultra-narrow gap welding arc.In order to improve the stability of the arc and seek the best matching effect between the external characteristics of the welding power supply and the arc,this paper proposes to adjust the external characteristics of the arc welding power supply by increasing the feedback of welding current,and studies the arc welding power supply suitable for ultra-narrow gap welding.According to the demand of ultra-narrow gap welding method for arc welding power supply,the main circuit and control circuit of the power supply are designed.The external characteristics of the power supply are adjusted by increasing the form of welding current feedback.In addition,according to the high requirement of the welding method on the precision of welding process parameters,the digital input design of the preset voltage and current of the welding power supply is carried out to improve the automation degree of the welding device.According to the design requirements,the external characteristic adjustment circuit and digital input circuit are built.In the part of external characteristic adjustment circuit,the adjustment function of external characteristics of arc welding power supply is mainly realized by adjusting the feedback intensity of welding current,which can be adjusted according to the external characteristics of different groove widths to enhance the arc stability in the welding process and improve the welding quality.In the digital input circuit part,PLC and DA module can realize the digital input of preset voltage and current values to improve the accuracy of input values,meet the setting requirements of welding voltage and current in different stages of ultra-narrow gap welding method,and stabilize the welding process and improve the welding quality.At the same time,a matching test platform is built,and on this basis,the influence of different strength external characteristics of power supply on welding arc stability under different groove widths is studied.To sum up,it can be concluded that the ultra-narrow gap welding power supply can enhance the arc stability through external characteristic adjustment,which is helpful to the stability of the welding process. |
