Abstract
The importance of the additional growth and/or transformation of the austenite phase that occurs in weld metals of super duplex stainless steel upon reheating is known. However, the effects have not been fully investigated, especially with respect to reheating induced by weaving during single-pass welding. In this work, bead-on-pipe gas tungsten arc welding (GTAW) was conducted on super duplex stainless steel to understand the effect of weaving on the microstructure of weld metal. Microstructural analysis, electron backscatter diffraction (EBSD), and focused ion beam transmission electron microscopy (FIB-TEM) were carried out to investigate the relationship between weaving and microstructural change. The weaving of GTAW produced a dynamic reheated area just before the weld bead during welding. It was revealed that extensive reheated weld existed even after one welding pass, and that the content of the austenite phase in the reheated area was higher than that in the non-reheated area, indicating the existence of a large quantity of intragranular austenite phase. In addition, the Cr2N content in the reheated area was lower than that in the non-reheated area. This reduction of Cr2N was closely related to the reheating resulting from weaving. TEM analysis revealed that Cr2N in the non-reheated area was dispersed following heating and transformed to secondary austenite.
Highlights
Super duplex stainless steel (SDSS) has been widely used in various fields, including process piping in offshore top-side structures and the chemical industry
The weaving action was started from one side of the weld edge through the weld centerline and completed to the other side of the weld edge, melting and mixing both base metal and filler metal
GTA welding with an ER2594 welding rod was conducted using weaving, in order to investigate the effects of weaving on the microstructure of weld metal of 25Cr SDSS
Summary
Super duplex stainless steel (SDSS) has been widely used in various fields, including process piping in offshore top-side structures and the chemical industry. SDSS has been shown to have excellent mechanical properties and chemical immunity toward several environments, especially chloride-bearing atmospheres [1,2,3,4,5,6] It has exhibited unexpected behaviors when treated thermally, such as during welding or heat treatment. Many researchers have studied the material from the time-temperature-transformation (TTT) or continuous cooling transformation (CCT) viewpoint, using simulation programs and isothermal heat treatments [7,8,9,10,11] They emphasized the importance of precipitate and secondary austenite on the properties of SDSS. The secondary austenite contains lower levels of major chemical elements involved in resistance against pitting
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
