An investigation on girth friction welding of duplex stainless steel pipes

Abstract

Girth friction welding is a novel technique to join co-axial linepipes with an external ring (girth) in solid state and without melting of materials. The ring or the girth is rotated between two pipes under an axial force resulting in frictional heat generation and plastic deformation along the pipe-girth interfaces. The rotation of the girth is stopped after a preset displacement of the pipes while the force is maintained to consolidate the deformed material and form the joint along the girth-pipe interfaces. Since the girth is only rotated and the pipeline sections remain stationary, the process simplifies the in situ assembly operations and enables the joining of complex configurations. As the melting of pipes and girth is avoided, the formation of harmful intermetallic compounds and deterioration of toughness in the heat affected zone are minimized. A comprehensive numerical model is reported in the present work to analyse the influence of key process variables on the rate of heat generation, resulting temperature field and thermal cycles, and the nature of material flow along the pipe-girth interfaces in girth friction welding of duplex stainless steel pipes. The computed results of thermal cycles and joint shapes are validated with the corresponding experimentally measured results. The results showed a favorable balance of the ferrite and austenite phases, and very little presence of the harmful sigma phases in the recrystallized weld-zone, which is difficult in fusion welding processes of similar materials.

Surface morphology and experimental investigation on joint characteristics of solid-state welded duplex stainless steel tubes

“…This is because the higher upset time resulted in a predominant austenite phase with coarser grains. 11 For the optimized parameter, the hardness value is even low at PDZ due to higher upset time. 14 It has been observed by Chan et al 19 in their work that the microhardness was high for higher heat input.…”

“…Supplementary Figure 3 shows the survey of microhardness throughout the sample. Milton et al 11 reported that the DSS welds were softer than the base metal owing to their low ferrite proportion. In supplementary Figure 3 it is observed that the hardness values were lower in the weld zone for all three experiments compared to other zones PM and PDZ.…”

“…10 Because no filler material is utilized in the solid-state welding process, the risk of an intermetallic compound forming is very low. 11 Solid-state welding methods such as rotary friction welding (RFW) and friction stir welding (FSW) have proven that intermetallic phase production is minimal since the base metal is only heated to a temperature below that of melting. RFW uses less heat and provides defect-free welds when compared to classic fusion techniques.…”

Friction taper stitch welding of a duplex stainless steel

“…3 d. The model showed a peak temperature of ~ 1537 K near the insert bottom, which is around ~ 93% of the solidus temperature of the DSS 2205. Kanan et al 26 and van Zyl et al 27 reported peak temperatures of around 91% and 90% of the substrate materials during FHPP. Higher peak temperature of the interface region aids towards the solid-state coalescence between the substrate and deformed material.…”

Effect of groove angle on residual stress and deformation of super duplex stainless steel SAF 2507 and austenitic stainless steel 316L dissimilar plasma arc welding

“…With the development of computer technology, the numerical simulation of welding process provides a new way for the analysis of welding process and the optimization of welding process [16,17]. At the same time, many research institutions and researchers have done a lot of research on the shape of molten pool, residual stress, thermal cycle and deformation in the welding process of duplex stainless steel by numerical simulation technology [18][19][20][21]. At present, most studies mainly focus on the simulation of welding process between the same material of duplex stainless steel, while the simulation of welding between duplex stainless steel and dissimilar metal materials is rarely reported [22,23].…”