Twin Wire Technique using TIG

[Soldador]

Anybody Knows about this technique?
Basically, One use two wires. So that, One can reach different chemical composition in the weld metal using different wires.
I need to know what wire configuration is the best. I guess to put both wires in front of the torch, but I am not sure about that. Could anybody help me?

thank you.

 

[kenvlach]

What exactly are you trying to do?
1) you may be describing co-deposition of 2 filler metals to get the desired weld composition (better to buy the correct filler). Or,
2) you are describing the welding of a thermocouple. Specific alloy/element combinations are used. For Type K, you use one Chromel and one Alumel wire, twist together a few turns at one end, heat to redness, dip in borax flux, then heat until you get a good weld.

Read all about thermocouple basics at

http://www.omega.com/temperature/Z/pdf/z021-032.pdf

Omega has a very good handbook/catalog on Temperature which they will mail you for free.

 

[Soldador]

Basically, I am going on with the project that have mentioned before in this forum: Dissimilar Welding between 304L and Monel (as a Filler Metal). Because of the corrosion behavior changes (galvanic corrosion), We are traiting to change the chemical composition of the weld pool using monel and other material as filler metals.
Obviusly, we do not have the correct filler metal to using just one filler, because we do not know which compotition bring the best corrosion behavior yet. This is the objective.

 

[Koz]

Hola Soldador,

This should be an easy welding problem. Monel welds very nicely to 300 series stainless. Inco Alloys (800) 334-INCO should get you on the right track for a welding rod.

Your configuration may be the difficult part. We are blind to your application and job specifications. No help to you there.

Twin wire GTAW is generally used to increase deposition rates. The welder can greatly increase the amount of weld laid down with a specialty GTAW wire feeder or electrically charging the wire with the "hot-wire" TIG process. We've laid down more wire per foot of overlay with a hot-wire TIG than with SAW!!! This process is generally automated to get the most benefit. Big Bucks in savings and less thermal distortion.

I would be reluctant to achieve my chemistries by combining filler metals in the weld arc, however I'm largely self taught. It just seems to me that there would be too many variables to coordinate to effectively control the dilution rates of four different chemical inputs. It might work with ultra-automated systems and even then I would want to control the rate of input for each filler metal.

I build my chemistries one weld pass at a time or I get a "trick" filler metal from a good supplier. INCO and SANDVIK are two valuable resources I have used to figure out what was best for my particular dissimilar metal weldment. Correct filler metals are the key to effective welding of dissimilar materials. The Welding Handbook by American Welding Society is also a proven resource.

But you still must factor in experience. Weld chemistries largly depend upon weld dilution. There are a lot of variables that go into controlling the weld dilution. I position my weldments, change processes, weld cold, weld hot, all to develop the chemistries I am looking for. I've also run a fair share of welding chemistries, so I know a little bit about where these "tweaks" will take me. They're fairly cheap, so run some as you develop your welding procedure.

Your material designers should tell you what material chemistries and other attributes you must achieve. Do you match the monel? Do you match the SS? What dimensional zones must meet the specified requirements? Are you permitted to overlay to achieve corrosion resistance? Is there a suitable comprise between design and material availabity? Hey this is fun!

Weld dilution is where the where it's at for me as a welder. I'm jealous. Enjoy yourself.

Koz