[dynasty200sd]

In one of my texts it mentioned as a general rule for every 10 amps of welding current, there should be 1 second of post-flow (i.e., 200 amps needs 20 seconds of post-flow). Is this so the weld bead/area reaches a certain temperature before it is no longer shielded? Other than this general rule, what are good post-flow settings?

[weldin mike 27]

Hey,

Some of the older machines have a setting for post flow based on the diameter of the tungsten electrode. Im not sure of the time/ diam ratio, but its a start.

Mick

[Otto Nobedder]

Unless you're welding very slowly, 10 seconds of post-flow will give coverage to the previous part of the weld. Especially considering most of us have "some" push angle on the torch, and if you're walking the cup, you have a high "push" angle. See it in most of Jody's videos. There is some flow-out behind the weld, for reasons that take that "PhD" to fully understand.

Tungsten cooling doesnt't take all that long, either. Even HFAC on 1/8" pure at 310A, I don't carry more than 20 seconds post-flow, and I'm not buying the gas.

If you're welding a sensitive alloy, you'll want more measures than post-flow, anyway. Like a trailing purge, or a purge-box to weld in.

Your mileage may vary...

Steve S

[CaveMechanic]

Post flow is important to a degree, I buy my own gas so being thrifty is as important as the weld, remember after the weld you only need to post flow long enough to solidify the weld and cool the tungsten, NOT to completely cool the weld. if you run a 20 sec post @ 15cfm, keep in mind you only needed 4-6 sec then you just wasted about 15 sec of gas so 15 sec @ 15cfm that's about 3.75cuft. you only need to post shield the weld until it solidifies from then on no contaminates can get into the weld. So keep this in mind, thin material 4-6 sec, thicker material 7-10 sec, doing this extends the life of my gas by upto 40%, and as some one who welds pretty much all day, everyday, it saves me probably a 100lb. cylinder a month, and that is still enough to get good certified welds, and save a couple of hundred dollars a year. guidelines below, hope this helps.

up to 18guage 4-6 sec
18gauge - 1/4" 7-10 sec
over 1/4" 11+ sec

I also use a heat sink spray gel on the back side of the material, to help solidify the weld quicker if needed.

[Braehill]

CaveMechanic,
Your times are about right but the gas flow is measured in cubic feet per hour not cubic feet per minute so this makes your math off. other than that you've offered sound advice.

Len

[AKweldshop]

I like about 7 seconds of post flow.

On 1/16 or 3/32 tungsten, from 50-200amps.

My preference.

~John

[CaveMechanic]

sorry my bad .... brain fart .... cfh not cfm knew that , duh LOL