Welding Tips and Tricks

Good Afternoon,
I offered to help out my gun range with repairing some AR Plates used for handguns. IPSC and Steel Challenge type shooting or pistol calibers.
The plates have a mounting tab located on the back that are breaking off. Does anyone have experience with TIG welding on AR plate steel?
I understand pre heating to 250-300 would be ideal but any other "Tips or Tricks"? lol
Best filler rod to use, best practice etc,
Thanking you all in advance,
Shawn

Post up a picture of the break. There may be a better way to weld it or to prep it.

Yup post a pic of the break, that would be the best way for us to tell you the ideal method of repair, that being said, While getting them even briefly to 400f shouldn't compromise their heat treatment as pistol targets, because hell unless you're shooting magnum calibers you could easily use mild steel for pistol targets. I'd still use a heat pen or IR gun to monitor both the preheat and the temperature while welding, I'd highly suggest welding in short little runs allowing time to cool in between as welding the entire bracket in one pass you're liable to heat the immediate area or backside upwards of 700-800 degrees, especially if you're already starting off at 300f+

Welding AR400 both to itself and to mild is something I actually have a decent bit of experience with, and I'd highly suggest ER312 as it's meant for welding armor and dissimilar steels though ER309L seems to work about as well in a pinch.