Pulse TIG Welding Of 21%Cr Ferritic Stainless Steel

The demand of steel increases gradually with the high-speed development of the automotive industry. Nickel is a kind of important adding elements in stainless steel, but with the reduction of Ni resource, developing the ferritic stainless steel without Ni or with a small amount has become an important topic. However, the development and application of ferritic stainless steel has been limited because of their welding problem. The microstructural features, mechanical properties have been investigated during pulse TIG welding of 21%Cr ferritic stainless steel in this paper.At first, with 8mm/s welding speed, 55% duty cycle ratio, 10Hz pulse frequency, the peak current changed from 95A to135A. Studies have shown that the weld penetration changed from 0.32mm to 1.2mm with the peak current increased from 95A to 115A. The weld was epitaxial crystallization model, and few equiaxed grains have been found in the weld center. The grain size increased when the peak current increased from 115A to 125A, but the grain size decreased when the peak current was 135A. The average hardness values of the weld center decreased with the peak current from 115A to 135A. The weld joint was excellent with the peak current of 115A.Secondly, with 115A peak current, 55% duty cycle ratio, 10Hz pulse frequency, the welding speed alterd from 4mm/s to 10mm/s.The results show that the amount equiaxed grains was the most with the welding speed of 4mm/s, the tensile property was best with the welding speed of 8mm/s.Thirdly, with 115A peak current, 8mm/s welding speed, 10Hz pulse frequency the duty cycle ratio verified from 15% to 90%, the weld penetration depth increased from 0.09mm to 1.2mm, the deformation increased. The recrystallized grains have been observed in HAZ. The tensile strength of weld joints were higher then base metal in condition of different duty cycle ratio.The pulse frequency changed from 1Hz to 50Hz with 115A peak current, 8mm/s welding speed, 55% duty cycle ratio. The continuous weld could not form with the frequency of 1Hz. The grain size in heat affected zone increased with the pulse frequency increased from 10Hz to 40Hz. In this experimental condition, the pulse frequency of 10Hz reflected the characteristics of pulse TIG welding most.