question about armor construction/assembly

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chugwater shale
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question about armor construction/assembly

Postby chugwater shale » Sat Jan 05, 2013 6:34 pm

Hi all, I am new here, so forgive me if this has been covered and I've just missed it; how are armored belts (or decks) actually assembled? I find it hard to believe that a given belt could be one giant slab--if for no other reason than the material handling capability of the time could'nt move such large or heavy pieces! So I am assuming they were built with many plates joined together, how was this done in such a way as to avoid zones of weakness at plate boundaries?

Byron Angel
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Re: question about armor construction/assembly

Postby Byron Angel » Sun Jan 06, 2013 2:43 am

chugwater shale wrote:Hi all, I am new here, so forgive me if this has been covered and I've just missed it; how are armored belts (or decks) actually assembled? I find it hard to believe that a given belt could be one giant slab--if for no other reason than the material handling capability of the time could'nt move such large or heavy pieces! So I am assuming they were built with many plates joined together, how was this done in such a way as to avoid zones of weakness at plate boundaries?



Welcome aboard, sir.

Armored belts and decks were formed from multiple plates, as you have no doubt suspected. All sorts of jointing arrangements between the plates were tried over time, from reinforced butts to tongue and groove to lapping. None, to the best of my knowledge, ever really succeeded in eliminating relative weakness near the plate edges.

B

chugwater shale
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Re: question about armor construction/assembly

Postby chugwater shale » Sun Jan 06, 2013 5:37 pm

Thanks Byron, that's close to what I suspected, but had never really seen spelled out.

I suppose now would be as good a time as any to warn you that I'll have a lot more questions like this to come in the days ahead! :)

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RNfanDan
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Re: question about armor construction/assembly

Postby RNfanDan » Sun Jan 06, 2013 9:24 pm

I'd like to point out that "multiple plates" doesn't necessarily mean a LAMINATE of plates stacked like a sandwich. Although this is ONE type of armor plating that was used, it should not be misconstrued as applying to the large, deep side belt armor , such as found on big battleships. These were HOMOGENOUS in their makeup, and might be better described as "blocks" than as "plates". for illustrative purposes.

I mention this only for clarification.
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Dave Saxton
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Re: question about armor construction/assembly

Postby Dave Saxton » Mon Jan 07, 2013 2:36 pm

Homogenous armour could be and usually was successfully welded by the late 1930s. This formed a continuous peice. There was still the heat effected zone, which could be of lesser ductility but higher strength, and the weld metal was usually undermatched in terms of tensile strength and hardness. However most of the weakness at plate boundries was eliminated. Face hardened armour can not be welded.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

MikeBrough
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Re: question about armor construction/assembly

Postby MikeBrough » Tue Jan 15, 2013 8:51 pm

Dave Saxton wrote:Homogenous armour could be and usually was successfully welded by the late 1930s. This formed a continuous peice. There was still the heat effected zone, which could be of lesser ductility but higher strength, and the weld metal was usually undermatched in terms of tensile strength and hardness. However most of the weakness at plate boundries was eliminated. Face hardened armour can not be welded.


Dave, my understanding was that armour plate wasn't welded 'all the way through', i.e. the welder would join the top couple of inches (and I suppose the bottom couple of inches if you did that second weld from the back) but not for the full 12 or 13 inches of plate depth.

This must have created a weakness at the joins wth the welding basically holding the adjacent plates together to stop them flapping apart :D but not turning them into a single homogenous super-plate.

My grandfather was a blacksmith/welder (late 1940s - 80s) but I never got a chance to ask him about this kind of thing.

Happy to be educated.

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Dave Saxton
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Re: question about armor construction/assembly

Postby Dave Saxton » Tue Jan 15, 2013 10:00 pm

In most cases armour that thick would be face hardened armour and therefore not weldable. Face hardened armour such as used for belt armour on battleships is too hard and of too high of carbon and nickel content to be welded (The only use of homogenous, and therefore weldable, armour of such thickness was the American substitution of Class B for Class A for turrets. The Class A as originally called for, was of such poor quality that it was unacceptable, and so Class B was used instead.)

In the case of welding weldable homoguous armour the thickest the plates would likely be was 18cm, but preferably less than 15cm thick. For welding such heavy plates they would normally have used submerged arc welding whenever they could. SA is done by a machine, or is a type of automatic welding. (Yes even during the 30's and 40's) With SA the arc is protected from the atmosphere by pooring a protective powder over the arc. The machine makes several passes over and over until the bevel is finally filled. The cap may then be done manually to avoid undercutting the top of the parent metal. The root is sometimes done manually first and then the back of root is welded or "back -welded". Submerged arc until recently always has a higher rate of defects (all welds have defects but there's a tolerance to what is allowed- boiler tube welding has virtually no defects allowable though) than manual welds, but manually welding such wide and deep bevels over such distances are unpractical. Generally, submerged arc can make for amply acceptable welds-Unless the engineers get greedy and try too heavy of passes to make more time.

Welding armour plate during the 30's and 40's was usually done using stainless steel weld metals. For example, the German welding rod for armour plate was the Fox A7 which is a type of 307 stainless steel. The tensile strength is only about 90,000 psi compared to the tensile strength of about 130,000 psi for Wh. But SS is more ductile, than using a matching or over matching weld metal. Furthermore, austenic SS excludes hyrdogen from the weld metal and the fusion boundry (hydrogen enbrittlement being the lead cause of weld failure).The USN found a similar solution. The USN specified type 310 (25/20) SS for welding STS, and Type 309 SS for welding STS to carbon high tensile or mild steel.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.


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