Carbon Steel TIG Rod vs Gas Welding Rod

Chemically, they are close, but not exactly the same. Most important differences are in the amounts of deoxidizers like Si and Mn. You risk porosity using a gas rod doing TIG.

Tensile stength also differs. Gas rods RG45 and RG60 have 45 ksi and 60 ksi minimum tensile stength respectively. ER70S-2 has minimum tensile strength of 70 ksi, and is typically well over that.

If you are welding to procedure under the requirements of one of the welding codes, you have to use what the procedure calls for.

Now you have made me curious. What about using TIG rod when gas welding?

Dan

Randy Zimmerman wrote:

Yes there is a reason(s). But first: the copper coating is very light and only meant to add some protection against rust.

Are you sure you mean 'carbon steel.' Most stuff like a truck bumper etc. is made from mild steel which is different from high carbon steel.

My first try at TIG was with RG45, a oxy/acet filler rod. The weld was not very good, my poor TIG technique notwithstanding--porous and looked rough. On advice from lamentations here, I got and used ER-70-S2. The general difference is that a TIG rod has more oxidizers and in most situations eliminates the little pinholes that a gas rod will leave.

I believe ER-70-S2 is considered the general purpose mild steel TIG rod.

I am not sure why TIG rod needs oxidizers. I am also not sure if a TIG rod would work with gas welding. I'd like to read some answers here on these questions.

Ciao, David Todtman

My mistake it should say ER instead of ES on my OEM post.

My other question is that if I needed to stock one rod for general purpose mild steel (carbon steel) TIG, do I purchase the ER70S-2 or

-6?

I've got some stainless rod either 308 or 316 that works great on mild steel, but not sure if that would be cost effective or as strong? B.G.

General purpose is ER70-S2.

I have used 316 for MS. It flows well. It is the appropriate choice when joining SS to MS. As you note, when comparing cost, it is more dear than the ER70S-n series.

My betters will correct me if I am wrong, but I believe you want to use ER70S-2. I tried ER70S-6 and it leaves a noticably rougher bead. But maybe something in my technique...

See below for information taken directly from the AWS specifications for both the gas welding rods (R45 and R60) and the TIG welding rods (ER70-S2 and ER70S-6).

Note the following items regarding the differences in the chemical compositions:

1) Both Mn and Si are deoxidiers but ER70S-2 requires the addition of small amounts of other powerful deoxidizers. 2) Increasing the Si level generally also provides increasing fluidity to the molten weld puddle (i.e. it should flow easier). Therefore, the ER70S-6 should provide a smoother weld bead than ER70S-2. This is indicated in the usage information listed below. Also note how low the Si levels are for the gas rods compared to the GTAW rods.

Chemical composition requirements from AWS A5.2 (gas rods) and A5.18 (GTAW rods) [I hope the table layout is readable after posting]

rod carbon Manganese Silicon

R45 0.08 % max 0.50 % max 0.10 % max

R60 0.15 % max 0.90 - 1.4 % 0.10 - 0.35 %

ER70S-2 0.07 % max 0.90 - 1.40 % 0.40 - 0.70 % plus required small amounts of additional deoxidizers Ti, Zr, and Al

ER70S-6 0.06 - 0.15 % 1.40 - 1.85 % 0.80 - 1.15 %

Useage information from AWS A5.18 (GTAW rods)

ER70S-2: "...primarily used for single-pass welding of...steels...Because of the added deoxidants, these filler metals can be used for welding steels that have a rusty or dirty surface, with a possible sacrifice of weld quality depending on the condition of the surface. ...[U]sed extensively to produce high quality, high toughness welds with the GTAW process."

ER70S-6: "...intended for both single- and multiple-pass welding. They are especially suited for sheet metal applications, where smooth weld beads are desired, and structural and plate steels that have moderate amounts of rust of mill scale.

It melts at a slightly higher temp than gas rod, so it tends to stick to the puddle. At school students always get the 2 mixed up on the tables.