Bonded Al and MS bar

[BobL]

Over Xmas my boat building BIL cave me an interesting piece of metal.

It's cut from a 35 mm thick by 100 mm wide bar and consists of a 19mm thick layer of MS bonded to a 16 mm thick layer of Al.
They also use a similar bar that is 150 mm wide bar as well
It's used quite often to join (weld) structure is steel to Al structures on boats as there is no galvanic corrosion involved
IMG_4280p.jpeg

When I polish it up I can see a secondary layer at the interface of Al and MS.

If it was a result of the manufacturing process one might think it would not be a clearly distinct layer but more of a graded affect.
I wonder if they have used a separate layer of Al or Al alloy as a transition material.
Here you can clearly see that layer marked as "?"
I will polish it up a bit more so I can see if I can get a clearer picture.
IMG_4281p.jpeg

[J.C.]

Apparently you can do it explosively - have a look at the "bonded metals" section here:

High Energy Metals, Inc. - Explosive Metalworking Experts

[elanjacobs]

I wonder if ultrasonic or friction welding might also work?

[Chief Tiff]

It is done explosively. Back in the late 1980’s the Royal Navy started constructing the Type 23 frigates which utilised aluminium in a fair bit of the upper deck superstructure. Previously this was done by riveting the aluminium sections onto the steel hull but with a electrical insulating layer between them to try to prevent galvanic corrosion. It caused problems at the joint because you had to ensure that the two different paint schemes didn’t react with each other or allow any saltwater to get in. This type of bar removed much of the problems and was extremely easy to install, you just weld the bar onto the hull then weld the superstructure sections onto the bar.

During the hull construction phase of my apprenticeship this (then) new technology was fascinating; the instructor explained it’s manufacture as having a thin layer of almost pure aluminium forced onto the the steel bar using plastic high explosive, the upper layer could then be formed by pouring molten ally onto it in a mould.

[lamestllama]

The car manufacturers have started using friction stir welding for this https://newatlas.com/honda-steel-alu...welding/24096/

But yours looks much older.

[Ted Hobson]

Ain't technology wonderful.

GE us a process of friction welding to join to straight-cut gears together mounting one small gear in essentially a tailstock and the other element in a 12 rotating assembly - then jamming them together until the 'flywheel' rotating chuck literally grinds to a halt - voila - items joined. It would be practically impossible to machine the two elements because of their proximity to each other - sorry no photo.

Another modern material is called Glare, and it's a fibre metal laminate based on aluminium sheets bonded together with a glass reinforced epoxy layer and used as skin material for a large part of the Airbus A380 fuselage. As a consequence the Glare part of the A380 fuselage is certified to need no inspection at all in 20,000 flights conicidentally Glare is almost impossible to recycle.

[azzrock]

When i was an apprentice they had some of that metal bar on display in the war ship construction class rooms. it had been milled and had a clear wave pattern.
Like others have said it was used in ships construction. from memory. The hull and deck steel the super structure made of aluminum. The joiner piece would be just above deck level. It was common. Ship built with this technology might get a uncomplamentry nic name.