In situ micro gas tungsten constricted arc welding of ultra-thin walled 2.275 mm outer diameter grade 2 commercially pure titanium tubing

• Published in: Journal of instrumentation 2020-06, Vol.15 (6), p.P06022-P06022
• Main Authors: Cooper, L., Crouvizier, M., Edwards, S., French, R., Gannaway, F., Kemp-Russell, P., Marin-Reyes, H., Mercer, I., Rendell-Read, A., Viehhauser, G., Yeadon, W.
• Format: Article
• Language: English
• Subjects: Arc welding; Automatic welding; Buttresses; Circuits; Condenser tubes; Cooling; Diameters; Gas pressure; Heat exchangers; Joinery; Liquid metals; Mass flow; Radiation counters; Service life; Sleeves; Stainless steels; Tensile strength; Titanium; Tungsten; Wall thickness; Welded joints
• ISSN: 1748-0221; 1748-0221
• DOI: 10.1088/1748-0221/15/06/P06022

Ultra-thin walled cooling tubes for heat exchangers and condenser units have applications in multiple high-value manufacturing industries. Grade 2 commercially pure titanium (CP-2 Ti) requires far less mass to achieve the same mass flow handling abilities as stainless steel tubing yet it is more challenging to join, particularly at wall thicknesses less than 500 μm (termed ultra-thin walled tube). This paper presents a single-pass joinery method that produces reliable welds on 2.275 mm outer diameter (OD), 160 ± 10 μm wall thickness tubing with a service life of 20 of more years. This is achieved through an automated orbital gas tungsten constricted arc welding (GTCAW) process incorporating enveloping low-mass sleeves used in tandem with a buttressing internal gas pressure to support the molten metal and maintain consistent internal diameter inside the tube. The industrial applicability is demonstrated through the production of a 1:1 scale mock-up of a fixed geometry CO 2 cooling circuit for a next-generation particle detector. The tensile strengths of the joints, 403.8 ± 4.2 MPa, exceed the tensile strength of the parent CP-2 Ti.