Case study efficiency arc welding

Hi,
As a student (european welding engineer), I'm doing a case study on
determining the efficiency of some arc welding processes (Gas Metal
Arc Welding =MIG/MAG; Gas Tungsten Arc Welding =TIG) in various
positions (PA=1G; PC=2G; PF=3G; PG=3G).
As can be found in NEN-EN 1011-1 (european standard) the efficiency
suggests to be 80% for GMAW and 60% for GTAW. These values don't vary
for different welding positions neither for base-metal (and
fillermetals) used.
We think these effiencies have to be different when different base
metals are used (Since heat transfer also depends on radiation and the
radiation coefficient is characterized by the blackness degree. In
such, there should be a difference in efficiency between e.g
construction steel and Aluminium).
I have developed a Thermocouple-harpoon which shoots a thermocouple
into a weld when the electrode has just passed the harpoon. With this
thermocouple (which measures the temperature in the weld) I can
determine the cooling time from 800 to 500 degrees (550 and 300 used
when welding on Aluminium).
Using the formula for the cooling time I can determine the heat-input
in the weld.
Formula for cooling time:
delta t8/5 = (4300-4,3*T0)*10E5 * [ (500-T0)E(-2) - (800-T0)E(-2) ] *
QE2 / dE2
Comparing the heat-input Q from this formula with the heat input
(measured at the machine) I can calculate the efficiency of all arc
welding processes.
Of course, if it would be that simple I wouldn't post it over here...
I've made a copper head surrounding the thermocouple so it can't melt
when passing the arc (and creating multiple thermocouples when
melting). The thermocouple itself is chosen as small as possible.
I have done some tests and only became efficiencies between 40 and 50%
for the GMAW process. I guess the copper surrounding is responsible
for this heat loss.
(I'll soon be trying a method only using a ceramic surrounding for the
thermocouple.)
I was wondering whether there is somebody who knows how these
effiencies have been measured before. Shouldn't there have been a
procedure when they were determined for the European standard?
I also have a book (heat effects of welding by Dieter Dadaj) in which
I found values going from 0,65-0,90 for GMAW and 0,20-0,50 for GTAW.
He got these data out of different books. I would like to make a
table which concludes all these data so it can be seen that nobody
really has found 1 value for the effiency. Unfortunately I'm just a
student with a low budget and can't afford to buy all these books...
It would be really helpfull if anyone could give me these data (with
its reference)
Kind regards,
Dries Vandezande
Belgium
Reply to
Dries VDZ
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am i understanding you correctly to indicate the MIG process is more efficient at putting heat into the metal than the TIG process?
Reply to
dogalone
My guess that previously experimenters would have done the process in an enclosed chamber then measured the increase in ambient air temp and the increase in temperature of a previously weighed sample. Knowing the mass of the the sample and the air in the chamber one could calculate the total calories produced and the relationship between the two. I can't figure out they would have calculated radiant energy other than insulate the interior of the chamber and line wiht reflective material? Randy
Reply to
Randy Zimmerman
The low efficiency with the Tig process can be found in the losses by heating up your non-melting electrode. And as an answer to you question: yes. When looking at your energy-cost (electricity) , it's cheaper to use a MIG. (But of course one can find so many reasons for using the TIG instead of a Mig. For instance the torch is more flexibel...)
Reply to
Dries VDZ
i was sure MIG process to be the winner as far as depositing metal (power out of the wall vs amount of metal deposited), but was not so sure about pure heat transfer: you may be on to something there, as almost all foundries melt the incoming ore(s) with arc only
Reply to
dogalone
You can talk power cost and radiant energy all day long. The cost to repair welds that should have been TIG welded eats up the savings. It all looks good on paper, but in the field it can cost you a lot of money. Mig & Tig can both save money with the right application.
Reply to
Lance

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