I once happened to work on a project where simple and easy carbon steel furnishings were designed everyday. They were regularly tig welded with the help of super missile weld rods by the welder. (A coined promotion term used for either 309 or the 312 stainless tog rods)

Why so? In spite of these supports being much more costly than the simple and earlier 70s2, it was preferred more by the welder as they could weld combined steel more easily without developing porosity. Moreover, it was a blessing  when doors were opened to the welding place which triggered plenty of effervescent unless the above mentioned super missile rods were used.

Then, when do we not make use of the 309 tig rods for tig welding carbon steel?

What about keyed welds where er70 rods are prescribed?

A firestorm over this problem is on in several platforms.

Then, what will be the answer?

Where  and when is it permitted to utilize 309 tig rod on carbon steel?

All said and done, the 309 tig rod is developed specifically for welding carbon into stainless.

The weld that results is a combination of carbon and stainless steel but with the power to hold up against pressure as well as heat periods.

But having said that, 309 stainless steel tig rod should not be used on on tube welds or pipes for high pressure unless particularly mentioned in the rules.

But then again, there are several instances where utilizing 309 stainless steel tig rod does work extremely well.

These are some that come immediately to mind:

Where it cannot absolutely eliminate the water or wetness causing porosity when the carbon steel tig rod is utilized.

When the areas being welded have carbon that is sufficient to cause the solidifying of weld … particularly in cases when the deposit of the weld will have to be machined later.

topping-up a threaded opening which has pollutants that cannot be washed out.

In cases where we aren’t sure about the type of steel like when a wrench is being modified.

Welding fairly any type of stainless steel into any carbon steel.

Hot combined light steel racks.

Injection pattern fixes for places where firmness is not needed.

There is a chance of hot breaking when the stainless steel rig rod is utilized for carbon steel. To my knowledge, this mostly  happens in complete transmission butt welds …or extremely controlled welds.

And remember this fact:

Carbon steel joint areas that are welded with 309 tig rod could be unreliable.

The welded steel relies on the heat and other techniques used.  It is a case where one welder blends more basic metal since he welds very hot whereas  another welder uses lesser warmth and the weld steel can be totally different.

To ensure the safety of the welds, they have to be reliable and in cases where reliability cannot be acquired, it will not be possible for the welds cannot be as foreseeable as when the carbon tig rod is utilized for carbon  steel welding.