[Ultralow787]

I just watched a you tube video by Miller Welding where they had Detroit Speed and Engineering doing a promo video for their welding equipment.
In the video, one of the guys said they prefer to TIG weld their body panels on cars because the weld is softer and easier to sand and shape. I asked them to clarify this because he also said he was using ER70S-2 filler rod .045". I also asked if the difference in hardness for the weld metal deposited would be because of the difference in shielding gases. Typically Argon for TIG and Argon/CO2 for MIG. In my opinion, ER70S-2 is going to deposit the same hardness of deposit regardless of what process was used to melt it? They replied to my first question, but the answer was rather vague. They eluded to the thickness of the deposit (weld reinforcement) being greater with MIG. I see their point in this regard, but can't see it being any harder to sand or grind.

The second fellow in the video talked about "welding" with Silicon Bronze rod and the TIG process. My question on this was with regard to this being more of a "Brazing" application than a "welding" application. I have never used this filler with TIG so I'm asking for clarification as to whether the base metal is actually melted while using Silicon Bronze. Everything I can find tells me that Silicon Bronze rods melt at between 1800 and 1900 deg.F which is below the melting point of most steels.

I realize that I might be considered "anal" about these points, but I'm just trying to learn and I am fussy about details!

Anyone have any opinions? Thanks

[Oscar]

You are correct on all accounts. Carry on.

The only thing I can think of is that the guy who replied to you couldn't really express what he was trying to say. Perhaps he was saying that grinding down a 1/32" tall TIG bead is a hell of a lot "easier" (read: faster) than a 1/8" tall MIG bead. This I could see being true, but of course it all depends on lots of factors that ultimately lead to how much metal is actually being deposited and how tall the bead stands.

[weldin mike 27]

Hey,

Ill weigh in on the mig/tig hardness question....

I am lead to beleive that the overall heat v time is higher with tig leading to a more annealed "softer" weld bead. Mig is simply zap zap zap. Allowing for very little annealing of the weld deposit.

Old school panel shops wont touch either, opting for oxy welding, which allows for a beautifully annealed weld area, which in some cases doesnt need grinding at all, moving straight to planishing with dollies and tools.

Mick

[tradetek]

I think I saw the same video and assumed that "harder" was referring to effort not physical hardness of the metal itself.

The annealing point is interesting though because I've started doing (trying) some metal art and annealing is part of the process and I don't get the feeling that my primitive TIG welds are "soft" in any way and it sounds a bit odd to me that a critical weld application like TIG would leave you with an annealed weld which would lead to a weak weld since annealed metal is relatively easy to damage/form.

???

Bill

[Ultralow787]

Thanks guys for your input. The annealing aspect is interesting. I always thought that oxy-fuel put way too much heat into the metal and caused more warping and distortion. It would definitely be a broader heat. I think I have heard the same argument before concerning chrome moly tubular fuselage piping on small aircraft. Old timers prefer the oxy-fuel welding over the localized heating that TIG welding offers. I guess it is a trade off?

Definitely with oxy-fuel, the added heat would slow the cooling of the parts and therefore cause the annealing to increase.

Interesting stuff!

[Ultralow787]

Any additional thoughts on the difference in shielding gases affecting the hardness of the weld deposit?

Anyone with experience with Silicon Bronze? I have see "Restolad" do some cool stuff on cars with it using a TIG torch in his You Tube videos. He sure seems to know his trade!

[Oscar]

Any additional thoughts on the difference in shielding gases affecting the hardness of the weld deposit?

Anyone with experience with Silicon Bronze? I have see "Restolad" do some cool stuff on cars with it using a TIG torch in his You Tube videos. He sure seems to know his trade!

It works great for what it is intended. You can braze parts up with very little heat so long as you use the appropriate size filler rod. Don't go using 3/32" SilBr on 16ga sheet metal. Use as thin as possible to minimize the required heat input while not having the rod ball up from it being too thin.

Thanks guys for your input. The annealing aspect is interesting. I always thought that oxy-fuel put way too much heat into the metal and caused more warping and distortion. It would definitely be a broader heat. I think I have heard the same argument before concerning chrome moly tubular fuselage piping on small aircraft. Old timers prefer the oxy-fuel welding over the localized heating that TIG welding offers. I guess it is a trade off?

Definitely with oxy-fuel, the added heat would slow the cooling of the parts and therefore cause the annealing to increase.

Interesting stuff!

Chromoly in thick parts needs preheat because if allowed to cool too rapidly, you get areas that become brittle. Less than about 11ga (~1/4") doesn't need preheat because the whole piece will get warm and thus cool slowly (for the most part, individual circumstances vary). Even then, a little preheat never hurt, and if anything it will "guarantee" that the cooling process is at a minimal rate.