Couple of questions please

[andy82]

Hi, not posted in here for a while

My work has just ordered me a new tig
Fusion PHF

First one with a pulse function, having never used pulse mode on a tig could anyone tell me what the best setting for doing 2 inch exhaust tubing (stainless) would be, the wall thickness is 1.5mm - 2mm.

Just an average setting is needed to try it out until i get used to the machine and play about with the settings.

Another question is there a bigger advantage using pulse on this kind of tubing.

I am doing this sort of thing

 

[hotrodder]

There aren't really any average or standard settings for pulse, each parameter has (at least) a small effect on some of the others. All are effected by travel speed. More info and some links in this thread

Starting point would the amperage you use for welding without pulse. With pulse on you need to increase the 'peak' current to compensate for the lower 'background' current. There's a link in that thread to a pulse calculator that makes it easier to see the effects that changes to peak and/or background make to the 'average' (or without pulse) current.

Pulse frequency is related to travel speed (for a slow on-off pulse), cranking the frequency way up tightens the arc cone resulting in a better depth to width ratio for the weld. High frequency pulse is like welding normally in many respects (eye can't see the pulse) but the weld pool is much more controlled (best way i can describe it) and you can go faster because of it

Advantages... lower average heat input (can help distortion), potentially faster travel speeds and supposidly can result in a better weld microstructure. For the sort of work you're talking about... if you have daylight tight fit up then once dialled in i would weld autogenously (exhausts not manifolds/headers) with a frequency around 2.6 - 3Hz i.e. about twice the travel speed i can manage without pulse

Many people simply use pulse more for weld appearence, makes it easier to get 'the look'...

Edit. When using a slow pulse with filler you need enough 'on time' to add filler. Not going to be enough time with the more radical pulse settings so i guess one standard setting would be an on time of 50% when using filler

 

[andy82]

Thats great advice, and thanks for the links

I think its just a case of trying different settings that suit.

Its still a little confusing, i will need to keep reading up on it

 

[hotrodder]

Yep, have a play and it'll make more sense more quickly.

From the pro-fusion pulse calculator link sort yourself out with some peak and background settings (based on the amperage you'd normally weld at) for pulse widths of 50%, 40% and 30%. They'll only be starting points. Sorting pulse frequency is easier and quicker with a piece of scrap, looking for an overlap (peak pulse freeze lines) of around 70%

Cut some coupons and have a play

 

[andy82]

lol thanks, it does sound confusing I am Sorry to be a pain, the calculator looks confusing as i am still trying to get to terms with the variations like the peak and background frequency etc

if possible Could you explain the settings for me and what i would expect from the setting that the calculator is showing.

 

[hotrodder]

OK with pulse on the arc switches between a 'peak' (high) and 'background' (low) current. With many machines the peak and background amperages can be set indepentantly. That site (and Miller machines IIRC) work with a peak to background ratio.

Pulse width is the time spent in each. Most machines this parameter is set as a percentage i.e. 50% peak time (or duty cycle or pulse width) means the arc spends the same amount of time at peak as it does background.

In that example the peak amperage is 3 times higher than the background and the pulse width is 35% i.e. arc spends 35% of it's time at 21A, 65% at 7A. The actual time is dependant on pulse frequency, typically Hz or pps (pulses per scond) and doesn't really matter (it's fractions of a sec). Say you had a frequency of 1Hz with those settings... arc will spend 0.35s at 21A, drop to 7A for 0.65s and repeat.

HTH

 

[andy82]

Ah great i get it now

Thanks, i am due the machine this week and will start trying the settings and post some pics. No doubt i will be asking for more advice

Many thanks hotrodder for taking the time to explain this.


Regards

Andy.

 

[hotrodder]

No worries. Remember they'll only be starting points. Based on weld appearence (cap and root profiles) i'll usually tweak background and/or peak amperages. Although frequency is a function of travel speed a small tweak can improve things

Say the weld cap is looking good (nice profile, good overlap with no fisheyes between pulses) but the roots not so good- say a series of voids between spots of good fusion. Increasing the background amps alone may well improve/fix it but it'll also increase total heat input and could, just maybe spoil the cap so more usual for me to drop the peak a little at the same time. Sometimes increasing the frequency a little instead may do a better job of fixing it

 

[slim_boy_fat]

..... and you can go faster because of it

Looks like your bosses'll be demanding increased productivity.....

 

[andy82]

yes and the good benefits of pulse like this.

http://www.millerwelds.com/resources/articles/Dynasty-200-Pulsed-TIG-GTAW-welding-exhaust/