question Restoring Armour. Help appreciated

[Mark Pearson]

Gentlemen,

 

Im now in a position to start patching some armour on a Bren Carrier. I do have some spare 7mm armour to patch it with. Can anyone advise me the best way to weld once grinded and ready to fit ? as ive heard it can crack or split being armoured steel and not mild steel ????????

 

Guessing once its in place it can be grinded, sandblasted and maybe a little filler to make flush prior to painting.

 

 

Thanks......

 

[Caddy]

If just for display purposes (ie no live fire), then what about bronze welding? Good vibration resistance, shouldn't warp the metal, isn't going to melt the parent metal either.

[Mark Pearson]

I was just going to Mig weld it, grind, sandblast and then finish and imperfections, but then Im used to doing cars.

[attleej]

Mark,

 

If it is only 7 mm I would have thought a suitably powerful mig welder (ie not a mini mig) would be fine. If poss try a test weld of the type that you want to do (ie a butt weld) on a scrap bit and then test it for strength. Grind most of the rust off from the weld area. You need to be careful about distortion but I think that it would be less of a problem than sheet metal on a car.

 

John

[ruxy]

7mm - stick weld , armour plate - without the benefit of a carbon analysis then a educated guess can be made , this would enable a most suitable rod to be selected. Standard weld procedure , prep- plate edges (grind for vee ) tack-up , lay weld beads so as not to distort, grind weld penetration that has blown through reverse side / clean vee , lay weld beads , finish dress with grinder.

[dgrev]

It all depends on the type of armour.

 

With US homogenous the secret is to pre-heat like you would not believe.

 

Face hardened, such as most early British stuff is a real issue

as you are dealing with essentially 2 different materials.

 

You will need to play with samples of the Bren armour, but you

may find that the secret is either stitch welding say 1", let

cool and do another 1" or pre-heat. However, I have been

told face hardened will warp like there is no tomorrow when

heated.

Also, many armours can only be welded using stainless electrodes

or low hydrogen electrodes, depending on what the armour is

that you have.

 

Which is why you don't normally find butt joints. But do find

doubler plates riveted to join the plates.

 

Regards

Doug

[ruxy]

https://en.wikipedia.org/wiki/Rolled_homogeneous_armour

 

I doubt if a Bren carrier was made of RHA ?

 

When you are half exposed (unless crouched in the bilges) - why bother ? Qty. and cost , not a gun-tank as such.

 

7mm I would check on that too , I would expect a inch fraction. Material - I would guess on a common boiler-plate ?

[Adrian Barrell]

British armour was metric, we used to buy a lot of it from Austria and continued with metric thicknesses.

You will probably need a nickel wire but a test weld is the only way to be sure, trying different techniques to see which works best.

[Mark Pearson]

Well, not being an expert or any where close on that. Ill do a test with the mig welder and see what happens. Other than that I may have to get someone to stick weld if necessary. Thanks for the info chaps...much appreciated

[Lauren Child]

I'm not a welder (it's a skill I need to learn), but I do have a copy of "Notes on Welding Technique for the use of Welders, Part 2, The repair of armour plate in the field" from 1943.

 

http://www.iwm.org.uk/collections/item/publication/80002761

 

It notes that there were four types of armour in use at the time (Machinable quality rolled armour plate, Cast armour, Homo-hard rolled armour plate, Face hardened armour plate), which have different properties.

 

The advice on pre-heating is echoed as armour plate is prone to cracking through different expansion. Similarly you should avoid stitching or wide beads due to local heating, and avoid any sharp corners to spread the stresses.

 

It also notes that it is not possible to weld the hardened surface of face hardened armour, but you can weld the back of it. At the time it was rare on allied kit, so it's probably not an issue for you.

Edited July 27, 2015 by Lauren Child

[eddy8men]

just use normal mig wire and lots of amps, the more heat you put in the better. I did the t16 resto using that technique without any issues. although some of the wading plates on the side cracked which I put down to it being short inch long welds that didn't get the surrounding steel hot. try it and you will see.

just make sure the new plates are straight when you get them back from the profiler as this caught me out on one side and was an arse to cut and reweld !