orch
Industrial
- Feb 19, 2003
- 17
When welding thin st/st (generally 304/316) tube we have traditionally TIG welded outside using a purge gas on the inside of the tube, but have previously tacked the assembly for trial fits without purge gasses.
A client has suggested that we should purge all tack welds as the oxide layer formed on the internal surface at that time must corrupt the chemical make up of the st/st when fully welded.
The oxide layer "dissappears" when welded and has never caused any issues in the past (food processing) so we have not previously considered it. There is an obvious cost in time and gas to undertake this "tack purging".
Does anyone know what oxides are involved, and if they are sufficient to contaminate the weld that follows, or if they disperse into the atmosphere. If they are included into the weld are they likely to affect the weld quality in any recognisable way?
A client has suggested that we should purge all tack welds as the oxide layer formed on the internal surface at that time must corrupt the chemical make up of the st/st when fully welded.
The oxide layer "dissappears" when welded and has never caused any issues in the past (food processing) so we have not previously considered it. There is an obvious cost in time and gas to undertake this "tack purging".
Does anyone know what oxides are involved, and if they are sufficient to contaminate the weld that follows, or if they disperse into the atmosphere. If they are included into the weld are they likely to affect the weld quality in any recognisable way?
