The Relationship Between Continuous Cooling Rate and Microstructure in the Heat Affected Zone (Haz) of the Dissimilar Weld Between Carbon Steel and Austenitic Stainless Steel

Abstract

This paper investigates the changed in the microstructure in HAZ of the dissimilar weld between carbon steel and 304 austenitic stainless steel. Continuous cooling transformation diagrams (CCT), peak temperature profiles and cooling rates can be used to predict the change in the microstructure of the HAZ during the welding process. Optical microscopy, X -ray, SEM and TEM were used to determine the phases which formed in HAZ of carbon steel and austenitic stainless steel. The results of this study indicate that grain size in HAZ depended on the temperature at that point could be reached during the welding. Fully Martensitic layer observed at the interface in carbon side due to the combination of the rapid cooling subsequent to weld and local chemical composition. Cooling rate played the rule on forming Widmanstatten ferrite, Bainite and Pearlite. On the other hand, microstructures and grain size in HAZ of austenitic stainless steel were not affected by temperature and cooling rate. Carbides precipitation (M23C6, M7C3), however, were found in the boundary of grains.

Ageing Effects on Room-Temperature Tensile Properties and Fracture Behavior of Quenched and Tempered T92/TP316H Dissimilar Welded Joints with Ni-Based Weld Metal

“…In accordance with our previous studies about the effects of various PWHT regimes on a very similar type of dissimilar T92/TP316H weldments with Nirod 600 Ni WM [18][19][20], the microstructures of all material regions of the presently investigated weldment are clearly coarse-grained and homogenized without the presence of traditionally heterogeneous T92 HAZ microstructural gradient, as a result of performed re-austenitization; i.e., the solutionizing stage of performed two-step QT PWHT. This means that the T92 steel region next to the Ni WM ( Figure 4a) does not consist of several microstructural sub-regions such as coarse-grained HAZ (CGHAZ), fine-grained HAZ (FGHAZ), intercritical HAZ (ICHAZ), and subcritical HAZ (SCHAZ), which are commonly present within the HAZ regions of ferritic steels' welded joints subjected to conventional single-step "T PWHT" [17][18][19][20][21][22]. Figure 4b shows the general view on QT microstructures of NiWM and TP316H austenitic regions exhibiting polygonal grains with secondary phase precipitates.…”

Observation of inclusions and intra-granular ferrite evolutions at the HAZ of low-carbon steel with different thermal histories

“…These sectors demand high safety standards, necessitating materials with high strength and excellent welding properties, particularly strong welding joints. [1][2][3][4][5][6][7]. Welding technology with high temperatures makes the heat-affected zone (HAZ) around the welding bead heated to 1400 °C causing coarse austenite grains are formed.…”

Study of the influence of wire metals on dissimilar welds

“…Thus, several researches have been pursued to improve DWJ performance. One is to remove welding defects by the evaluation of welding parameters like current and gas flow [8]; the other is improve metallurgical behavior of DWJ by cooling rate and Post Weld Heat Treatment [9][10]. Despite these proposals, DWJ between HSLA and ASS constitutes a major challenge of researchers [7], especially for solving metallurgical problems of fusion zone (FZ) and heat affected zone (HAZ).…”

“…Despite these proposals, DWJ between HSLA and ASS constitutes a major challenge of researchers [7], especially for solving metallurgical problems of fusion zone (FZ) and heat affected zone (HAZ). These problems are concentrated around the fusion line, due to coarsening of microstructures, hardening precipitates and the formation of brittle phases during welding process [9][10]. In view of welding process application, thermal welding cycles provokes the diffusion of some alloying elements like C, Fe, Cr and Ni [10][11].…”

“…It is also observed that Cr and Ni diffuse towards Carbone steel from austenitic steel; however, the diffusion Fe followed an inverse direction [12][13]. This phenomenon is accompanied by the presence of chromium carbides precipitation, intermetallic phases and grain coarsening in HAZ [9][10][11][12]. It is important to note that the formation of intermetallic phase precipitation is dominated mainly by sigma phase (σ) in ASS welds [13].…”