>the effects of rapid cooling you can simply prepare a piece of plain A36 in the shape of a bend strap and apply an arc strike
I can help with that....I have a few pics of arc strikes on A36 flatbar, and bent in my coupon bender.
As a control piece, the A36 flatbar bent "without" any arc strikes is to the far left in the picture. The other 4 were laid on a table side by side and a welder took a E7018 and drug it quickly across the four pieces, then ground them down to his satisfaction, the samples were bent in a coupon bender set up for A36/V50 using the correct bend radius and bent. As shown in the pic, every where there was a droplet of weld metal that melted and rapidly cooled....initiated a crack.