A New Approach to Simulate HSLA Steel Multipass Welding through Distributed Point Heat Sources Model

Abstract

Mechanical properties of welded joints depend on the way heat flows through the welding passes. In multipass welding the reheating of the heat affected zone (HAZ) can form local brittle zones that need to be delimited for evaluation. The difficulty lies in the choice of a model that can simulate multipass welding. This study evaluated Rosenthal’s Medium Thick Plate (MTP) and the Distributed heat Sources (DHS) of Mhyr and Gröng models. Two assumptions were considered for both models: constant and temperature-dependent physical properties. It was carried out on a multipass welding of an API 5L X80 tube, with 1016 mm (42″) external diameter, 16 mm thick and half V-groove bevel, in the 3G up position. The root pass was welded with Gas Metal Arc Welding (GMAW) process with controlled short-circuit transfer. The Flux Cored Arc Welding (FCAW) process was used in the filling and finishing passes, using filler metal E111T1-K3M-JH4. The evaluation criteria used were overlapping the simulated isotherms on the marks revealed in the macrographs and the comparison between the experimental thermal cycle and those simulated by the proposed models. The DHS model with the temperature-dependent properties presented the best results and simulated with accuracy the HAZ of root and second welding passes. In this way, it was possible to delimit the HAZ heated sub-regions.

Effect of the t8/5 Cooling Time on the Properties of S960MC Steel in the HAZ of Welded Joints Evaluated by Thermal Physical Simulation

“…Detailed microstructures of typical subzones of the HAZ that are formed in In the HAZ prepared by our physical simulation, except for the coarse-grained microstructure located in the central part of the specimen, additional HAZ areas with different microstructures were visible. Similar observations in real welded joints have also been reported in works published by Jambor et al [25,26], Guo [11], Ferreira [29], and Bayock [4]. Next to the central coarse-grained area of the HAZ, a fine-grained area of the heat-affected zone (FGHAZ) occurs.…”

Effect of Post-Weld Heat Treatment Conditions on Mechanical Properties, Microstructures and Nonductile Fracture Behavior of SA508 Gr.1a Thick Weldments

“…4a-e, the IPF map results, the grain size decreases as the distance from the top surface increases, as seen in the microstructural analysis by optical microscope. The average grain size for the samples decreases to 28.7, 18.3, 11.5, 10.2, 6.6 µm from sample A (top) to sample E (bottom), as shown in Table 5 because of the recrystallization by reheating from the upper welding passes [22]. Figure 4f-j show a GOS map analyzing the area fraction of ferrite microstructure using grain of 5° and an orientation difference condition of 2°.…”

“…Figure 3 shows the microstructure of the HAZ about 500 µm away from the fusion line toward the base metal, through the coupon thickness at 25-mm intervals. The average grain size decreases with increasing distance from the top surface, because the lower-pass regions are reheated to a temperature above the recrystallization temperature by upper welding passes [22]. Therefore, the transformed microstructure in the upper-pass region is coarser than in the lower-pass region.…”

Adaptive thermal model for real-time peak temperature and cooling rate prediction in laser material processing

“…To analyze the difference in thermal diffusivity between carbon steel and stainless steel with respect to the temperature, A comparison of the thermal diffusivity between those two materials is shown in figure 6.1. In this figure, the thermal diffusivity values are adapted from literature [47,48]. As can be observed from Figure 6.1, the thermal diffusivity of stainless steel between 300 • C and 1427 • C increases linearly with temperature.…”