Metallurgical Aspects in the Welding of Clad Pipelines—A Global Outlook

Bunaziv, Ivan; Olden, Vigdis; Akselsen, Odd M.

doi:10.3390/app9153118

Cited by 20 publications

(15 citation statements)

References 80 publications

(99 reference statements)

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“…The austenitic steels, when the ratio Cr eq /Ni eq is in the range 1.5-2.0, solidify as ferrite-δ. Then, if the cooling rate is sufficiently low, it is transformed into austenite (FA mode), according to the following sequence of transformations [34]:…”

Section: Discussionmentioning

confidence: 99%

Weld Metal Microstructure Prediction in Laser Beam Welding of Austenitic Stainless Steel

Giudice

Sili

2021

Applied Sciences

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In the present work an approach to weld metal microstructure prediction is proposed, based on an analytical method that allows the evaluation of the thermal fields generated during the laser beam travel on thick plates. Reference is made to AISI 304L austenitic steel as a base material, with the aim to predict the molten zone microstructure and verify the best condition to avoid hot cracking formation, which is a typical issue in austenitic steel welding. The “keyhole” full penetration welding mode, characteristic of high-power laser beam, was simulated considering the phenomenological laws of conduction by the superimposition of a line thermal source along the whole thickness and two point sources located, respectively, on the surface and at the position of the beam focus inside the joint. This model was fitted on the basis of the fusion zone profile, which was experimentally detected on a weld seam obtained by means of a CO2 laser beam, in a single pass on two squared edged AISI 304L plates, that were butt-positioned. Then the model was applied to evaluate the thermal fields and cooling rates, the fusion zone composition and the solidification mode.

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Section: Discussionmentioning

confidence: 99%

Weld Metal Microstructure Prediction in Laser Beam Welding of Austenitic Stainless Steel

Giudice

Sili

2021

Applied Sciences

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“…The weld metal solidifies as a Ni-rich austenite phase with equiaxed dendrites, as shown in Figure 12 a. For the ERNiCrMo-3 filler, the mode of solidification is given by Equation (1) [ 46 ], where filler solidifies first as a final microstructure of Ni-enriched austenite with precipitation of the Nb-enriched NbC and Laves phase in the inter-dendritic areas, as depicted in Figure 12 b.

…”

Section: Resultsmentioning

confidence: 99%

Study on Microstructural Characterization, Mechanical Properties and Residual Stress of GTAW Dissimilar Joints of P91 and P22 Steels

et al. 2021

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This article deals with the dissimilar joining of two different grade Cr-Mo steel (2.25Cr-1Mo: P22 and modified 9Cr-1Mo: P91) for power plant application. The dissimilar butt-welded joint was produced for conventional V groove design by using the gas tungsten arc welding (GTAW) process with the application of an ERNiCrMo-3 Ni-based super alloy filler. A microstructure characterization was performed to measure the inhomogeneity in the microstructure and element diffusion across the interface in a welded joint. The experiments were also performed to evaluate the mechanical properties of the dissimilar welded joint in as-welded (AW) and post-weld heat treatment (PWHT) conditions. An acceptable level of the mechanical properties was obtained for the AW joint. After PWHT, a significant level of the element diffusion across the interface of the weld metal and P22 steel was observed, resulting in heterogeneity in microstructure near the interface, which was also supported by the hardness variation. Inhomogeneity in mechanical properties (impact strength and hardness) was measured across the weldments for the AW joint and was reduced after the PWHT. The tensile test results indicate an acceptable level of tensile properties for the welded joint in both AW and PWHT conditions and failure was noticed in the weak region of the P22 steel instead of the weld metal.

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“…In the case of AWS 309 L inserts, the weld composition is strongly affected by dilution and thus by the welding speed values; the representative points are characterized by high FN values and solidification as ferrite (F mode), which subsequently transforms partially into austenite during cooling [31]. Conversely, the simulations with the AWS 308 L inserts gives lower values of FN and representative points placed across the boundary between FA and F mode.…”

Section: Fused Zone Composition and Propertiesmentioning

confidence: 98%

Investigation on Laser Beam Weldability of AISI 304L Plates Based on Thermal Field Simulation by Experimentally-Fitted Analytical Modeling

Giudice

Sili

2021

Lasers Manuf. Mater. Process.

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The objective of the work is to present a new approach to the simulation of the thermal field in laser beam welding, based on an experimentally-fitted analytical model, applied to investigate the weldability of AISI 304L austenitic steel. Reference is made to the welding trial in a single pass of two 10 mm thick butt-positioned plates. Welding was performed under the keyhole full penetration mode, which is characteristic of high-power laser beam, and simulated by an analytical model based on a multipoint-line thermal source system and fitted on the experimental fusion zone profile. The model was applied to simulate the effects of welding speed changes on thermal fields and cooling rates, in order to determine how they can affect the weld composition, the solidification mode and the possible formation of a sensitized zone in the heat affected zone. A limit value of welding speed, which allows the weld formation without lack of fusion, was identified. For all the welding speeds considered, the formation of a sensitized zone can be excluded. The contribution of welding speed on cooling rate, not significant near the welding axis, results to be determinant at the boundary of the fused zone with base metal. The combined choice of the filler material and the welding speed, which in all cases gives rise to primary ferrite solidification modes, affects the content of residual ferrite, which must be balanced to enhance the resistance to solidification cracking, avoiding the adverse effects due to too high contents. As a conclusion, the model proves to be a valid support in investigating the thermal effects, which result from the setup of welding parameters, on the weldability of the base metal-filler system. Graphic Abstract

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Metallurgical Aspects in the Welding of Clad Pipelines—A Global Outlook

Cited by 20 publications

References 80 publications

Weld Metal Microstructure Prediction in Laser Beam Welding of Austenitic Stainless Steel

Weld Metal Microstructure Prediction in Laser Beam Welding of Austenitic Stainless Steel

Study on Microstructural Characterization, Mechanical Properties and Residual Stress of GTAW Dissimilar Joints of P91 and P22 Steels

Investigation on Laser Beam Weldability of AISI 304L Plates Based on Thermal Field Simulation by Experimentally-Fitted Analytical Modeling

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