Heat Input Calculation for Multiple Electrode SAW

[bmoorthy]

How does one calculate the Heat Input for SAW when Multiple Electrodes are used.

For Example
3 electrodes are used to weld a joint.
All the 3 has different Voltage and Current Parametere.

Should we calculate the Heat Input for all the 3 separately and add it up.
Or should we check whether they are connected in series or parallel and then calculate?

If the Job has Impact test, is it necessary that heat Input in individual electrode is restricted to Max heat input (Sex IX) or is it the net Heat Input that should be accounted for?

 

[metengr]

bmoorthy;
How was the original WPS for submerged arc welding (SAW) qualified for impact testing - using a max electrode size or all three sizes?

In accordance with Section IX, QW-409.1, if the original WPS was qualified for a max heat input per pass under Supplementary Essential Welding variable listed under QW-254 for the SAW process, any increase in heat input above this maximum heat input per pass requires re-qualification.

QW-409.1 lists two methods where heat input would be increased per pass - using the standard heat input formula or by increasing the volume of deposited weld metal per unit length of weld.

From what you have stated, if your original WPS was not qualified with 3 different electrode sizes to account for the max range of heat input OR you decided to add two additional electrode sizes to increase the volume of weld deposited, you need to re-qualify the SAW WPS.

An increase in heat input by either using a larger electrode size or by increasing the volume of weld deposited per pass will adversely affect the toughness of the base metal and this is the reason for this supplementary essential welding variable for SAW.

 

[weldtek]

Adding further to metengr's comments, assuming the wires are spaced closely together, < 3" or so, you would add the three together and divide by travel speed. Eg. If you had 550 A, 32 V on the first, 450 A 30 V on the second and 400 A 30 V on the third, and your travel was 31 ipm, your heat input would be calculated as [(550*32*60)+(450*30*60)+(400*30*60)] / 31 = 83,419 j/in. For impact tested applications, in your terms, net heat input would be critical.