How to weld 1/2"armour plate?

[Darrin Wright]

After info and advice on how to weld 1/2" mild steel plate into the existing front armour of the BGC (Australian).

Over the years I have heard of reverse polarity when using welding rods, also to pre-heat the armour with oxy and then to mig weld it or just weld away like normal.

What are peoples experiances when conducting welding repairs on this type of steel? In the next couple of weeks I want to get this repair work done to my hull.

Thanks

[Richard Farrant]

Originally Posted by Darrin Wright

After info and advice on how to weld 1/2" mild steel plate into the existing front armour of the BGC (Australian).

Over the years I have heard of reverse polarity when using welding rods, also to pre-heat the armour with oxy and then to mig weld it or just weld away like normal.

What are peoples experiances when conducting welding repairs on this type of steel? In the next couple of weeks I want to get this repair work done to my hull.

Thanks

Hi Darrin,
I don't know about Australian armour plate, but British armour was welded with Nickel Chrome electric rods, hence the shiny welds. I do have a copy of a War Office booklet on armour plate welding. One thing for sure the edges of all plates to be butt welded have to be vee-ed out in order to get penetration. If armour plate is welded with normal rods, it can crack down the side of the weld, so best to use the correct procedures. I would think Colin Jones from Adelaide will be your local man on the subject.

regards,
Richard

[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