The Research On Welding Process Of Pulsed GMAW In Dry High Pressure Enbironment

With the continuous development of offshore oil and gas resources,marine metal structure and maintenance of submarine pipeline is becoming more and more important, The underwater dry type high pressure welding method is used to eliminate the harmful effect of water on the welding quality,which has the advantages of good welding quality, and the advantages of adapting to the deep water construction. At present, China’s large offshore structures and pipelines life nearly, the failure probability of offshore structures will be greatly improved. Therefore, the study of high pressure pulse melting polar gas shielded arc welding(GMAW-P) welding process is very necessary.Firstly, the influence of environmental pressure, process parameters(arc voltage, peak current, pulse frequency, base current) and gas composition on the formation of pulse GMAW welding seam were studied. Test was carried out in the hyperbaric chamber, and the Q345 steel plate was used for surfacing test.The Research shows that: the more pressure on the environment, weld width becomes larger, weld penetration decreases; high pressure environment change gas ratio, the average welding voltage, pulse peak current, pulse base values of current and pulse frequency can affect the weld quality.The groove welding research environment pressure, welding process parameters and protective gas ratio of Q345 steel pulsed GMAW metallographic, microstructure and mechanical properties of welded joints.Under the condition that the other process parameters are constant, the single parameter adjustment is adopted, and the influence of the welding joint quality inspection is analyzed and studied.Hyperbaric pulsed GMAW tensile specimens fractured in base material,the tensile strength of the welded joint is greater than that of the parent material; The higher the ambient pressure, weld zone Vickers hardness is higher; optimization of the microstructure of the weld zone after optimization of the arc voltage, the Vickers hardness becomes small, the metal enhanced flexibility; welding joint Vickers hardness and impact toughness of little change in the pulse peak current and pulse basis value currents were enhanced;increasing pulse frequency welding joint strength, hardness and impact toughness of raise.Finally, we use orthogonal test method to optimize the combination of arc voltage, peak current, pulse frequency and basic value current four factors, to get the optimal combination of process parameters with the typical environmental pressure.