Hi all

With more welding experience repairing the hull of a seagoing vessel,
the meaning of the wise words of a late mentor who used to contribute
a lot on here came to me.

I've appended my calculations.

To get a 6mm fillet, you could have
* a 3.2mm-dia (1/8th-inch) 7018 rod at about 125A
* a 5.0mm-dia 6013 (~3/16-inch) at about 200A

If productivity is proportional to Amps, productivity of 6013 is 160%
of the productivity of 7018.

Yes 7018 is massively tough compared to 6013.
But sometimes you can tear-out the plate-surface with a good 6013
fillet, so there is no call for vastly more toughness and ductility.

This dawned on me when I was wondering why people were bothering
weaving 3.2mm 6013 building up a big bead.
For eg. lap joints overplating a steel hull, that 200A is not a
problem because the run-rate is fast - twice that of 7018 - and the
polarity is Direct Current Electrode Negative (DCEN) - smooth and
consistent but not very penetrative, so at 200A you'd be absolutely
fine "striping" a 6013 fillet.

I've just "seen it".
If I've got this right...
Have I got this right?

Regards,
Rich Smith

================================================================

A_rod=pi.d^2/4
A_fillet=z^2/2

6013
----

run-out-length = rod length
A_fillet=A_rod

z=sqrt(pi.d^2/2)

(defun z-6013 (roddia) (sqrt (/ (* pi (expt roddia 2)) 2e0)))

(sqrt (* (my-circle-area-dia 3.2) 2)) ;; 4.010605239409601
(z-6013 3.2) ;; 4.010605239409601

7018
----

run-out-length = half of rod length
A_fillet=2.A_rod
z=sqrt(pi.d^2/4)

(defun z-7018 (roddia) (sqrt (* pi (expt roddia 2))))

(z-7018 3.2) ;; 5.671852322897651
(sqrt (* (my-circle-area-dia 3.2) 4)) ;; 5.671852322897651

================================================================

(z-7018 3.2) ;; 5.671852322897651 ;; that would be at about 125A
(z-6013 4.0) ;; 5.0132565492620005 ;; that would be at about 160A?
(z-6013 5.0) ;; 6.266570686577501 ;; that would be at about 200A?

For given fillet size, productivity would be much increased with 6013 vs 7018. Compensating for all factors and using 5mm 6013 for 3.2mm 7018,
(/f 200 125) ;; 1.6
more than half as fast again.

Remember 5mm 6013 for 6mm fillet...

--------------------------------

(z-6013 6) ;; 7.519884823893001
(z-7018 4) ;; 7.0898154036220635

--------------------------------

Also think with 6013, are on DCEN and running fast, so can weld
material of thickness about the rod dia?
Fits with all I have seen. eg. my "short arc training T-fillet"
(Newham College, etc.)

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