Its best that you do not weld AR500 plate because you'll mess with the material hardness. The welded areas will get annealed.
Its better that you get whoever is cutting the plate to do holes so that you can assemble with screws. Trust me its hard to drill AR500 plate if you don't have the right equipment. We actually found it was easier to drill with a carbide end mill than with a carbide drill.
You can get hardened screws or just replace them if they get hit too many times.
Flame cutting or plasma cutting also heats the plate and anneals the areas near the cut, which has the same effect as welding. You'll get divots in these areas.
The best way to cut AR500 plate is with water jet because there is no heat involved. That's how I did mine.
To keep the weight down, I have one that consists of 4 pieces that are 2 feet square and 1/4 inch thick each, that I assemble on a frame to create a 4 foot square target for long range. Then we hang smaller targets in front and use the 4 footer as the back stop. It works well and the bullets barely scratch the AR500 steel.
Oh, how I love the "because that's what I do" stories..... Should we let Big Dog Steel know that they shouldn't be welding on their targets?
BadAsMo, while I agree that it is preferable to water jet the profile and the holes of AR500 targets, you most certainly can weld it and it is done extremely commonly in abrasion and impact resistant applications such as conveyor hoppers, truck boxes, gravel crushers, etc. ad nauseum. As with most things, you just have to know what you're doing. The key is to not approach the phase change temperature of the steel, so you don't "anneal" it. Of much bigger concern is hydrogen embrittlement due to inadequate cleaning of the weld zones and use of inappropriate or 'wet' filler metals. Cracking can also occur due to inadequate heat input (will essentially shock the crystalline structure of the base metal).
I previously stated that one should preheat to 400F and I would like to retract somewhat. One should not
exceed 400F interpass temperature (heat input while welding). Preheat to 200F to 300F. Post heat of a larger area after welding to get a more even heat distribution across a larger area. Cool slowly - preheat helps to reduce hydrogen and post heat helps to prevent hydrogen migration into the heat affected zone, which is what can initiate cracking. Have you ever noticed that most of the cracks you see are in the base metal beside a weld and not in the weld? That is the result of this effect.
The incredibly common 7018 GMAW rod and ER70S solid wire filler metals are more than adequate for this job (low hydrogen fillers). I would stay away from rod such as 6010, 6011, 6013, 7014, 7024, etc.
Simple, right? It actually is if you have a few of the right tools and some know how.
OP; apologies for the tangent.
Rooster
