Mechanical Properties and Microstructure of GTAW Welded Joints Between A335 P11 and A312 TP304

Abstract

This study aimed to determine the mechanical properties and metallurgical structure of welded joints of A335 P11 and A312 TP304 steel for pipe size 3 inches, length 13 cm., thickness 5.54 mm. by gas tungsten arc GTAW method using filler metals SMT-625 (ER NiCrMo-3), RILON TIG 200S argon welding machine, welding current 120 A, welding speed 13.7 mm/min, shielding gas flow volume 16 liters/min. Perform mechanical property tests and metallurgical structures. The results of the experiment found that characteristics of deep penetration and melting between the weld metal and consistent fusion and there is sound metallurgical bonding and the work metal. The width of the thermal influence zone of the welding process is similar and there are no defects in the welding line. The gas tungsten arc welding process will produce an average maximum tensile strength of 675 MPa and an average maximum hardness of 230.4 HV. Impact tests have found that the average energy absorbed in the HAZ (A312 TP304) has better toughness than the HAZ (A335 P11) and the weld metal. Bending test results when bending to an angle of 180° and visual inspection did not reveal surface cracks in all specimens. It can be concluded that the welding processes in all these workpieces were of satisfactory quality and will serve as a guideline for selecting welding processes for applications to achieve optimum performance.