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zx9
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Sounds like 'I need help with my Phd. '
rikrobson
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mig-welding.co.uk mut be high up on the google search list 
when I was doing my degree with the OU one of the modules was on about how the internet started and ARPAnet. THere was some research to be done, so one bright spark emailed Vint Cerf (one of the fathers of the internet). She got a reply, I think he was quite flattered, but the teaching staff Posted outsaying please dont email Vint any more.
Whether he complained or they just didn't want several thousand students emailing him, I'm affraid I cant remember. Was quite funny at the time.
when I was doing my degree with the OU one of the modules was on about how the internet started and ARPAnet. THere was some research to be done, so one bright spark emailed Vint Cerf (one of the fathers of the internet). She got a reply, I think he was quite flattered, but the teaching staff Posted outsaying please dont email Vint any more.
Whether he complained or they just didn't want several thousand students emailing him, I'm affraid I cant remember. Was quite funny at the time.
cumbriasteve
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Was your first post a true introduction? mine wasn't because I had never been on a forum.
The OP is not from this country, may not be used to forums and may not be writing in his own language.
His request was polite and hopefully he will find members who can help once he clarifies his post a bit more.
Thanks For Your Feedback Sir,100amps ,6lpm, try a 3mm fillet joint.
It's more useful if you give a clue as to what your doing.
Basically I need information about theoretical calculation for welding parameter of TIG welding.
& then I have to conduct trial with respect to present parameter we are using & compare.
I need this for welding of M.S sheet having thickness ranges from 0.8 mm to 2mm.
Regards
Vishnu
I apologize for the mistake. I should introduce my self prior asking any help.
I am mechanical engineer, working with automobile firm.
I am working on TIG welding analysis & I need guidance from basic calulation of TIG welding.
Sorry again for Mistake.
Regards
Vishnu
roofman
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Go to your local BOC stockist as they have these small circular charts on the counters for free
EDIT...just seen your location,so you may have a job finding the above...sorry
Richard.
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Ok. I think I've got an idea of what your looking for Vishnu.
First you need to calculate heat input from a given procedure. Amps x volts(Ocv)/travel speed x .8(tig process correction factor)
This will give you a figure in j.
The limitation with all manners of welding is heat input. There is only so much the parent material can take before either the mechanicals drop off or in your case with the thin metals you end up through it. Now you also need enough heat to ensure adequate fusion and penetration levels. Regarding
Your joints, material thickness with regard to current levels are usually worked out in two ways.
1) what works in a practical sense
2) how far can it be pushed before the weld strength/toughness drop below acceptable.
Wps is produced on the distructive test results based on what is needed from a weld. It could be purely penetration/fusion levels in which a simple macro test is sufficient. Strength and ductility are tested with face,root and side bend tests. Charpys can be taken anywhere on a weld sample for notch toughness results. So you see the calculations are minimal really as all you need to know is heat input. Then carry out weld samples for testing. The tests that provide the results you want are the ones you record your heat input for because overall it's that heat input level that needs to remain the same for your results to remain the same.
I hope somewhere amongst that post there is some useful info to take away. It's been a while but I remember some stuff from my inspection days.
K18 NOB
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Richard.
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Im going to put this reply to your pm on open forum in the hope @TechnicAl or like can add to it better than I as I'm struggling to directly answer your Q
Richard.
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Dear Sir,
Thanks for your valuable feedback & time.
I need your guidance in following area.
Basically I am working with automotive Firm & we are into fabrication.
Where we use MIG,TIG welding.
I have to do analysis on TIG welding both theoretical & Practical Way.
For this I need to know how to calculate each parameter for welding.
Like Welding Current, Voltage, Gas Flow required, Arc Length, Type of Electorde & Diameter.
Welding Speed.
Basic Things which I have seen on Welding Rod Manufacture manual for current selection.
But I have to tabulate all above parameter theoretically.
For example,
If have to weld 1.2 mm thick round sheet having square butt weld with no gap.
How to calculate above parameter theoretically.
Please suggest.
I would like to say sorry if i am disturbing you.
Thanks & have a great day.
Regards
Vishnu
Vishnu, Today at 9:59 AMReport
Reply
Richard.Forum Supporter
Well first off your arc length and gas flow don't really change much at all. These are not calculated variables they are fixed to ensure adequate weld quality. Arc length should always be short and tight. No exceptions. Gas flow should be set on what's needed to shield the pool and based purely on practical experience. Cup sizes and lens type and joint configuration make a difference mind but it's not a calculated thing it's a practical test . Post flow can be calculated based on current. As the hotter you run the more post flow needed to protect the finished run and tungsten from oxides while it cools. The longer it cools for the more post needed. 5 seconds is minimum and add 2 seconds per every MM after 2mm of metal thickness. It's based on solidification time and cooling.
I'm sure you could work out that formulae with the figures above using material solidification times.
Current settings nowadays are done based on what we know,what we are shown and what we read. You'll come across charts showing figures like 30 amps per MM for steel, 25mm for stainless and 40 for (cold) aluminium . Rough starting guides . While this doesn't answer your question as you want to know why via formula they are these numbers per MM. The distructive tests results and practical weld ability under those figures are the things what have proved they are good guidelines over the years. Everything can be formulated but is it always needed. In this case no. For example 20 amps produced a cold lap and a bend test showed low yield strength before it snapped. A macro showed lack of root pen.
40 amps produced undercut and lack of cap reinforcement excessive root pen. Bend test failed again due to huge haz created in the parent.
I believe more theory's have been created on test results. I can't help with a current selection formula as I don't know of one. Toughness is measured in pascals at service temperature. And is based on grain refinement. Heat input is the result driver here and travel speed is the biggest control measure. If you use the heat input formula I posted you'll see that the division over the travel has the biggest effect over A and V.
Sorry I don't have a long list of calcs for you but it's not something I've done to that in depth. I would of thought they are available but in the practical world we test and wps on our results. The real clever part is understanding why we got the results we did and making the correct changes to suit.
slim_boy_fat
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Welcome, Vishnu 
Dimitri De Spiegeleer
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You don't need weld calculation, it appears you need a set of WPS'ses for different thicknesses.
I suggest you spend a day or two in the welding department of your company, and observe what the weldors there are doing.
When you mention M.S., do you mean martensitic steel? Can you elaborate what kind exactly, as there are new inventions quite regularly in tailored blanks.
As for joint calculation, there are several standards that deal with this. In Europe it's the Eurocodes (EN 1993-1-8). In most local building codes, you'll find this as well. I suggest looking for a copy of the relevant eurocodes, as everything is quite well explained in there. For automotive applications, you'll need to explain further what exactly you are trying to accomplish.
I suggest you spend a day or two in the welding department of your company, and observe what the weldors there are doing.
When you mention M.S., do you mean martensitic steel? Can you elaborate what kind exactly, as there are new inventions quite regularly in tailored blanks.
As for joint calculation, there are several standards that deal with this. In Europe it's the Eurocodes (EN 1993-1-8). In most local building codes, you'll find this as well. I suggest looking for a copy of the relevant eurocodes, as everything is quite well explained in there. For automotive applications, you'll need to explain further what exactly you are trying to accomplish.
