Technical PaperJoining of mild steel pipes using microwave hybrid heating at 2.45Â GHz and joint characterization

- Mild steel pipes were joined using microwave hybrid heating at 2.45 GHz.
- Principles and physics involved in the microwave pipe joining are discussed.
- Significance of interface powder size in heating of the surfaces illustrated.
- Microstructure and mechanical properties of the joint are presented.

The present experimental study was carried out to explore the possibility of joining mild steel (MS) pipes using microwave hybrid heating (MHH) technique. Candidate MS pipes, with a thin sandwich layer of Ni powder in between, were exposed to microwaves inside a multimode applicator at 2.45 GHz and 900 W. The principles of microwave joining and the role of MHH in context to the pipe joining have been discussed. Microwave absorption in the material system and mechanism of heating the candidate layers of the MS pipes are presented. Effect of the interface powder particle size on heating of the faying surfaces has been analyzed. Experimental results imply a dense joint zone in scanning electron micrographs due to good metallurgical bonding between the MS pipes and Ni powder. The elemental study reveals that joint zone is nickel and iron rich. Average micro indentation hardness of the joint zone, interface and base metal were observed to be 572 HV, 519 HV and 397 HV, respectively. It was found that joint efficiency mainly depends upon the microwave exposure time. The joints developed through microwave exposure upto 480 s were observed more efficient (65%) than the joints obtained at 420 s (40%) and 510 s (57%).

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