Welding 101

[Mach1]

So, I always have this fear about a weld that lets go costing me my life. I feel that I can weld pretty well, at least they look pretty decent. Time to tackle what really matters, the strength of the weld.
What are some keys to making sure you have a good full pentration weld with TIG and Mig?
With tig, I feel like I turn the heat up too high, good penetration but the color seems like it's too hot, if I get the color right, I don't feel like the penetration is good.

Also, another scenario, I wanted to beef up a OE control arm on my Miata, is welding on the control arm a bad idea because I don't know what kind of heat treating, etc it went through.

I have been welding intake and exhaust piping mostly, and other non critical components, I'd like to feel confident in doing some suspension.

[junior]

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[HickamHatch]

What do you mean it seems too hot? Do you have a pic?

[Mach1]

What do you mean it seems too hot? Do you have a pic?

No pic, just loses it's color, turns gray and looks too hot, maybe I am way off.

[Mach1]

Check the bottom center weld, kind of like this.

http://www.streetchopperweb.com/tech/1009_stcp_tig_welding_steel_101/photo_13.html

[projectPONY]

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X2

[HickamHatch]

What size cup are you using? How many amps for the thickness of material? Are you using a gas lens?

[turbostang]

Check the bottom center weld, kind of like this.
http://www.streetchopperweb.com/tech.../photo_13.html

The bottom center weld is WAY too hot - the tale tell signs are the undercutting near the edges and the overall saggy-ness of the weld.

You can disguise a hot weld by moving fast, but it's not necessarily right. Keys here would be over-oxidation (grey flakes on and under the parent material)

A cold weld is obviously opposite - it will stack easily and appear to lay on top of the material. Some visible signs are the edges of the weld are clearly not joined - they look almost as if you could pry them up..

Starting and stopping are VERY important to weld integrity. Keyholes are a GREAT place for a weld to start failing. Your example weld in the linked pic is a prime example of a keyhole. Those can generally be prevented by backing off the pedal and piling the rod in as you stop.

[Matt]

The corner to corner welds heat up much faster and use less heat than a fillet weld.

[Mach1]

Also, another scenario, I wanted to beef up a OE control arm on my Miata, is welding on the control arm a bad idea because I don't know what kind of heat treating, etc it went through.

Any input on this?

[Matt]

I don't think you will hurt anything. I have taken the new GTOs and notched and boxed them in on 1000hp setups so they could clear the slicks with the mini tubs. I just boxed it in to help retain strength.

[NoClassic]

Ideally you want to build a fixture for the control arm that uses at least the factory mounting locations. The concern is those points moving when the part is heated during welding, not so much weakening the material.

If you want to learn more about the process itself I would check out some of the welding specific message boards. The guys building stuff here know their shit, but you will be overwhelmed with the amount of existing information out there.

[034V]

Do a 1g plate to plate with a backing and start from there. Some of the welds would pass visually under asme and aws but may fail the bend.

The middle one would be rejected under visual for sure.