API 5L X65+Inconel 625镍基合金复合管GTAW+FCAW-G焊接工艺研究及应用OA

Aiming at the problems of low efficiency of traditional welding process and easy micro-cracks in submerged arc welding,an efficient and reliable welding method combining GTAW and FCAW-G was proposed for API 5L X65+Inconel 625 bimetallic composite pipe.Through optimization of groove design,welding parameters,selection of appropriate protec-tive gas and strict welding process control,combined with macro analysis,mechanical properties analysis(tensile test,bend-ing test,hardness test,low temperature impact test),root chemical composition analysis and corrosion resistance analysis,the feasibility of the process is fully verified.Macroscopic metallography shows that the welding quality is good,no defects;The tensile strength is 629 MPa and the fracture is in the base metal area.The maximum hardness value is 288 HV10,much lower than the project limit of 350 HV10;Weld and heat affected zone meet the impact requirements of-196℃and-46℃respectively.The chemical composition analysis of the root position met the standards and project requirements,the Fe con-tent was 0.83％,far lower than the project limit of 10％and the dilution rate of the weld was low,the PREN value was 52.26,meeting the minimum requirement of 45;ASTM G28 Method A intergranular corrosion test result is 0.738 mm/y,which meets the project acceptance standard≤0.914 mm/y and has good corrosion resistance.At present,the process has been suc-cessfully applied to a Middle East oil and gas project,and the pass rate of welding is 100％.This study provides theoretical and practical basis for the large-scale application of GTAW+FCAW-G welding process for nickel-based composite pipes,and has high engineering application and popularization value.