Residual stress evaluation in small diameter pipes welded using the orbital TIG process

Abstract

The objective of this work is to evaluate the effect of orbital TIG welding on the level of residual stresses in the joint, on the resultant microstructure and on the surface appearance of the weld bead, considering the effects of the welding energy, of the number of passes and of the pulse type (current and rotation) in tubes of small diameter and to contribute to the analysis of decisions of whether or not to apply hydrostatic tests or thermal treatment post welding. The test pieces, welded with different levels of energy, pulses and number of passes, were submitted to measurement of residual stresses in an X-ray diffractometer. The samples were also submitted to metallographic analyses. It was concluded that the residual stresses on the external surface of the tubes are compressive in nature. The level of residual stresses in the tubes falls with the increase in welding energy and is lower for tubes welded using pulsing than for those welded without pulsing and, for this work, was not influenced substantially by the number of passes. The samples analysed presented conventional microstructures for the steel employed.

Keywords:

• residual stresses
• orbital TIG welding
• X-ray diffraction

Acknowledgements

The authors of this work would like to thank Engesolda – UFC and Lacam – for all the infrastructure to carry out this work. They would also like to thank ANP-PRH31 and CNPq for their financial support.

Notes

^1. [email protected]

^2. [email protected]

^3. [email protected]

Additional information

Notes on contributors

George Luiz Gomes de Oliveira

1 1. [email protected]

Hélio Cordeiro de Miranda

2 2. [email protected]

Jesualdo Pereira Farias

3 3. [email protected]