How to weld 1/2"armour plate?

[Lynn Eades]

My British built (welded hull) carrier, was welded with stainless steel rods. (I couldn't tell the difference between stainless and nickel chromium)
I was given some free old stainless rods which I found very forgiving (of my very average welding ability). Under normal circumstances, stainless would be a more expensive option.
Back in the day, arc welding rods were cumbersome and fragile, with the flux contained around the rod with a paper wrapping. They needed a high amperage to get them started. Hence the seemingly large amounts of spatter around some of the original welds.
I think back then, rods were "non contact", Now days, they are "contact"
(easier to use)

BTW, stainless welds wont gas cut, but arc-air gouging works well on it.

I too am waiting for Colin to chime in. I expect him to make it sound very easy.

[Richard Farrant]

Just found the booklet, Welding Technique - the Repair of Armour Plate in the Field, dated 1943.

The rods they describe are Austenitic, but it does state;
"if armour plate electrodes are not available welding may be attempted with ordinary 'stainless steel' electrodes of 18% Cr and 8% Ni type"

"All austeniitc armour plate electrodes should be operated on reverse polarity (ie. electrode positive = work negative) at approx the following values;
6 SWG rod size ; 120-180 amps
8 SWG ; 100-140 amps
10 SWG ; 80-100 amps "

Hope this is of help.

[cletrac (RIP)]

I would think a low hydrogen 7018 would be a good modern choice. They don't cause hydrogen embrittlement like most rods do.

[Mike K]

Hi Darrin

I'm not one to give welding advice , but

For steel that thick , you would be best to use a 3 phase welder , or a big DC welder driven by a petrol/deisel generator , you need big amps , single phase welding is not powerful enough .

If you have a TAFE near you, you may be able to enroll in a course and use their welding gear, they usually have big WIA 3 phase welders .

Try to study the original welds on the hull .

Also, they developed a substitute hardener for the local armour plate as they could not use Tungsten or Nickel as it wasn't available in Australia at the time ?

At a guess, the Aust. armour plate would have been made by BHP ?

Mike

[The Bedford Boys]

If you can, get the use of a decent MIG welder. Vee the edges of the material and then weld away.

I have welded up cracks in a carrier hull with a small Arc welder, using rods that weren't anything special and it came up pretty good. No cracking around the weld at all. Wouldn't want to do a whole carrier hull with it though, MIG is the way to go. Easier to tack things in place with a MIG too.

The welding on LP hulls can be pretty damn shocking from factory if you look at it closely. The factory welds on the bottom of the floor of my hull are spectaculary crappy, highly peaked and bugger all penetration. So don't run your welder too cold.

Keen to hear what Mr Jones thinks.

[Joe Lorenzino]

I have been working in a welding repair shop for a few years, so this is what I would suggest.

Although I haven't welded armour plate, we do have to repair cutting edges on loader buckets and such. The normal procedure is to "V" it out properly, then fill it in with narrow "stringer" beads using 1/8" dia. low hydrogen ( _ _18 series, i.e.: 7018, 8018, 11018 ) electrodes at around 125 amps.. If you have a DC machine, they are always run DC Reverse. If you have an AC machine, and it has sufficient open circuit voltage to start and run an _ _18 series rod (many of the lighter ones do NOT) then use a 7018AC rod which has ionisers in the flux to allow it to run properly on an AC machine. On plate that thin, preheat is not essential, but would help prevent possible cracking. A preheat of 200°-250°F is ample, and mostly used to dry out any moisture that my contribute to hydrogen embrittlement.

A better choice is a more "forgiving" low hydrogen rod (higher percentage-of-elongation) such as an ArcTec 223 from ArcTec Alloys. This allows the weld to stretch more than an _ _18 series rod, and so puts less stress in the base metal. We use this rod for the long welds when attaching cutting edges to buckets as it causes less warpage and has higher impact resistance.

Stainless rods ARE nickel/chromium, and the 18-8 they speak of would be a standard 304 grade. All of the "300" grades of stainless are "austenitic" meaning nonmagnetic and nonhardenable. Higher nickel (first number) makes it tougher, higher chromium makes it harder. If using this type of rod, a 304L, or 309L would be good choices as the "L" signifies "Low Carbon", and it will not pick up as much hardness from the base material. The drawback is the price, and that they do not weld very well out of position. A better choice in this category would be ArcTec 265 Unichrome, which has a much higher strength rating, and welds some what better out of position.

If wanting to use a MIG, I would lean towards a Flux core, Dual Shield, or Metal core type of wire, for added weld ductility. If using solid wire, a type ending with S2 or S3 would be preferable to an S6 wire because of a higher elongation value. If Mig welding, I would definitely use a preheat to prevent the weld from cooling to fast and causing hardness/brittleness problems.

A high nickel rod designed for use on cast iron, like an ArcTec Supercast 90, would likely give very good results as well.

[cletrac (RIP)]

Well, there we have it from an expert on the subject! Joe, I was by your shop the other day but you weren't around.

[colin jones]

Hey guy's! Darrin, quite simply, prepare, as in grind clean, V out about least half the thickness you're welding to both pieces and leave a little gap for penetration, High amps on your welder, set gas to 18-20. Solid wire welding with mig is already low hydrogen. If you're going to war then preheat if you're not "don't bother" inert mig gas prevents hydrogen from affecting your welds. watch your welding while you're doing it, you can see if it's flowing or sitting on top. if it's not a flowing a flatish weld then you need more heat or you're dragging instead of pushing. If you welder is on high amps it will put plenty of heat into the material anyway. Don't try and weld an oxy cut that still has slagg on it as it won't work.
"My 2 bobs worth""
Colin.