PAW(plasma arc welding) VS GMAW(gas metal arc welding)

Date 11-28-2013 14:04

Both processes have their pro's and con's. Especially as related to tight areas.

GMAW is difficult because of the size of the gun and the way a corner can disturb gas shielding, especially if the flow rate is too high.

The main question to me would be if they have approved PQR's or still need to do testing as it is not a pre-approved process. At least to D1.1.

You should let us know which code in particular you are dealing with.

Have a Great Day, Brent

By pyman4407 Date 11-29-2013 09:14

The applicable standard is AWS D1.1. and to my knowledge there is no PQR for PAW process UP TO NOW.

By Metarinka (****)

Date 12-06-2013 18:43

as what most have said, PAW is most likely the wrong process for this application. PAW is generally not used for inside corners, it's used in keyhole type modes in semiautomated or mechanized welders for full thickness groove welds. PAW is also notriously tricky to dial in due to the number of variables.

By 803056

Date 11-28-2013 19:58

Brent makes a good point regarding the need for qualified WPSs regardless of the of the process selected. Depending on the welding standard, there may be the possibility one or both processes may be considered to be prequalified, but the chances are pretty slim. If the contractor can provide a qualified WPS for the process he wants to use, I know of no standard that would prohibit the use of either GMAW or PAW.

One thing to consider is that PAW utilizes the keyhole technique. That is, the plasma stream must be capable of penetrating ("blasting") through the full thickness of the joint being welded. In essence, the weld is a CJP groove weld. Most PAW I have seen has been mechanized. I'm not saying it cannot be performed manually, it just not something I've seen used very often.

Most welding standards give the responsibility of determining the ways and means of manufacturing the product. If the contractor can produce the required results, does it really matter what welding process he elects to use?

Best regards - Al

By 46.00

Date 11-28-2013 21:00 Edited 11-28-2013 21:25

I would like to know what joint configuration was being welded here? PAW's main advantage is seen in high volume repetitive production welds. Mainly on cylindrical products. pyman4407 states that his contractors wish to use the process because GMAW is hard in corners? :confused:

Both processes have quite bulky end torches and the PAW end set up require's quite a large diameter orifice and maybe a separate wire feeding nozzle as well, so I feel that the use of PAW process over GMAW would have limited or no benefits if access was the major concern. Depending on joint and material thickness, I would not immediately see any speed advantage over a properly utilised and set up'ed GMAW machine either, other than as Al stated, PAW is nearly always automated to some extent, so if PAW was to replace a manual welder for instance, maybe with time and enough production weld's completed , some saving in time could be seen. But with the high initial cost and setup time, it wouldn't be quick.

Either way, I would also reiterate both Brent and Al's thoughts regarding acceptance of a qualified WPSs

Al, modern PAW machines can use 'Keyhole' technique and also what we in the UK call 'Melt Mode' where additional filler wire is added as well. This is used for thicknesses beyond what can be keyholed.

http://www.youtube.com/watch?v=jo376zPns8I

By 803056

Date 11-28-2013 21:17

Nice video. It looks like a keyhole w/ filer metal technique to me.

There are always new developments in the field of welding. There are many variants for the common processes and if there is enough money, the sky is the limit. "Ya gotta love it!"

Best regards - Al

By ssbn727 (*****)

Date 12-01-2013 09:54 Edited 12-02-2013 04:41

That's a

http://www.airliquidewelding.com/file/otherelement/pj/soudage%20tig%20plasma14602.pdf

http://www.plasmatechnik.com/english/schweissbrenner/schweissbrenner.htm

http://www.oemeyer.com/Media/Default/Industrial/Plasma%20Cutting/Automated/plasmawelding.pdf

http://www.twi.co.uk/technical-knowledge/job-knowledge/equipment-for-plasma-welding-018/

http://victortechnologies.com/IM_Uploads/DocLib_7037_Thermal%20Arc%20Plasma%20Welding%20Handbook_%280-2090%29_May2006.pdf

This is TIG welding with an attitude:

http://www.k-tig.com/

http://www.k-tig.com/wp-content/uploads/2013/03/K-TIG-Brochure.pdf

You know, I could go on and on but, if we don't have on hand sufficient information regarding your application this could end up becoming a lesson in futility...
So, we would appreciate it very much that you supply us with more details of your project in order to assist you.

The bottom line is this; The plasma welding with keyhole process variant is used in applications that require a certain amount of automation or even mechanization and would not be useful in narrow corners due to the size of the plasma torch... However, there is another process variant that may suit your need but, it is totally dependent on the thickness of the material and the current range that the power source is capable of providing and your willingness to reduce your production level substantially...

Why not consider this GTAW(TIG) process variant known as Tip-TIG... Here's the link:

http://www.tiptig-international.com/

http://www.youtube.com/watch?v=tZyntkRFXto

And if that doesn't work for you then how about this?

http://www.youtube.com/watch?v=Lvi8nyXEsCU

Respectfully,
Henry