Author ORCID Identifier

0000-0002-4262-4861

Date of Award

21-7-2025

Document Type

Thesis

School

School of Mechanical Engineering

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Dr.S.Ramesh Kumar

Keywords

MIAB, STBW, Hardness, Tensile Strength, Microstructure

Abstract

Boiler-graded tubes of T11, T12, T91, and T92 materials with a thickness of 4.5 mm thick and 44.5 mm outer diameter were selected for the Straight Tube Butt Welding process using Hot Wire (STBW-HW) and Cold Wire (STBW-CW) conditions. Moreover, the research investigates and compares the welding characteristics of dissimilar T11 and T91 boiler-graded tubes using STBW - HW & Magnetically Impelled Arc Butt (MIAB) welding techniques. Similar and dissimilar welding was performed in STBW – HW & CW conditions.

In dissimilar welding, the tensile strength was higher in the T11-T91 STBWHW joints of 663 MPa than in the T12-T92 STBW-HW joints of 569 MPa. Regarding hardness and tensile properties, the STBW-HW welding process exhibits better weld properties than the STBW-CW welding process. In the MIAB welding phase, the experimental trials were conducted by varying the magnet positions (parallel and perpendicular directions) to achieve better magnetic flux density.

An increase in magnets (2,4,6,8 nos) led to a corresponding enhancement in magnetic flux density, resulting in improved uniform arc rotation. From the identified results, 8 magnets that faced parallel to the tubes produced the uniform arc rotation and sound weld of dissimilar T11-T91 joints. The straight tube butt-welded with hot wire conditions of T11- T91 joints were compared with the MIAB-welded T11-T91 joints. MIAB weld joints are formed with shorter weld time and without filler material. It had a more stable microstructure, and overall, it exhibited a uniform WI.

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