Welding Tips and Tricks

A friend and I are thinking about building a couple of bullet traps. We're considering using AR500 for the angled plate and mild steel for the rest of the trap. Neither one of us have welded AR plate before. Been doing a bit of research and found some conflicting information regarding preheat and postheat. All tips and tricks appreciated.

Larry

My quick research show regular old 7018 will work....

AKweldshop wrote:My quick research show regular old 7018 will work....

That's about the only thing all my meager research agreed on, John. Lot of mention made of the need for a low-hydrogen electrode.

Some folks said "never MIG", others were "MIG's OK". Some said no preheat necessary, others said preheat mandatory. Some were slow cool, some were fast cool. Found a WPS that called for 300 ° F preheat, interpass temp between 250° F and 500° F, and wrap in welding blankets and slow cool.

Everything I've heard about it over the years talking to guys who have welded it involves preheat and some guys mentioned a post heat to stress relieve it. We're gonna be thumping these things fairly firmly and we'd like to have 'em stay together. I remember a friend telling me years ago about a shop he worked in where a couple of guys tacked up a big hopper (AR500) without preheat. Said everybody was on break and they heard this godawful clatter and ran out to the shop to find that the thing had just fallen apart. We want our bullet traps to hold up way longer than that

AR plate is seldom used in a "structural" application and in many cases is only there for its hardness/Abrasion resistance. The hardness is achieved by quenching during manufacture . Any subsequent heating process can have a tempering/annealing effect on the base metal so should be done with caution. The manufacturers of most AR plate have suggestions for fabrication.

In my hands on experience with AR400, joints that are free to move/contract are one of the best methods for reducing cracking during welding. Crush wires can also help on tee joints. Slight preheat can help but does contribute to the peak temperature achieved during welding.

The mfg of the plate y o have would be the best place to start. Hardox has a guide at http://www.ssab.com/-/media/Files/EN/St ... 5-2015.pdf

I used AR400 for teeth on a compact diesel tractor backhoe. The operator was digging through decomposed granite, so they would wear out any other teeth. At the time I only had access to a stick welder and very few other tools.

The teeth were made out of 1/4"x2" bar and they were 5" long. All I did was weld them to the bucket with about 2-1/2" of 7018 weld on each side of the tooth. I did no preheat or post heat. I did a total of 10 teeth this way and I had no problems with cracking or any failures.

I had many questions when I was looking to do my project as well. I didn't have many options at the time, and it worked fine. I don't know that it is correct, I just wanted to let you know what I did and how it worked.

Good Luck with the project.

R.J.

If you can spring mount the impact surface, that will help quite a bit. S/F.....Ken M

echosixmike wrote:If you can spring mount the impact surface, that will help quite a bit. S/F.....Ken M

I hadn't thought of that. I like it.

Fairly early 1st/2nd generation technique for increasing armour resistance on tanks, mounting the outer steel on springs, over the cast or welded turret. Works up to about 5000fps or so, then penetration is more along the lines of fluid dynamics. Still used for armour intended to resist small arms, like 50cal and the like, saves weight. Good luck. S/F....Ken M

I have had to put together a fair bit of AR 234, its the lite version of ar500... its "weldable" or so they say...
I also did a batch of ar400 (I think) steel targets. I used 12018 and quite a bit of preheat. The preheat was as much for the metal as it was to get rid of the arc blow from being magnetized...
I mainly use tig on the ar234 due to the shape of the parts and how they go together, not conducive for mig or stick.
309ss or 312ss as a stick and very minimum preheat on the AR might work. Or more preheat and a 7018 or whichever xx18 rod you so desire.
If you were going to mig then use the 309/312 unless you have a machine with enough oomph to spray transfer...
good luck
Clif

Unfortunately I know the pain of welding on magnetized plate . You couldn't pay the steel to take your weld haha spits it back at you , I weld ar500 on a daily basis with 11018 rod and if I don't preheat the plate I'm guaranteed to have arc blow, if it still happens I put a mag square under the material I'll still see the puddle pulling them it just take skill to keep it nice , I preheat everything really it just puddles so much better you won't under cut and penetration is great , though I weld material larger then 1" thick we also hard face the ar500 with mg765 rod and if you don't preheat haha have fun that rod doesn't like to apply if it's not clean and hot , I'll only post heat thing with flex like with out padding buckets the torque tube I'll preheat and post , I also will spray arc with superarc L-56 .045 no need for pre heat that shit will penetrate no problem and comes out really nice , but like I side I weld thick materials just remember to always route pass to help deflect the mag I always 1/8 11018 rod route the 3/16 cover