Triplate transition joints The ultimate solution to weld

Triplate transition joints The ultimate solution to weld aluminium to steel By Ko Buijs Metallurgical engineer SMT-Metals b. v.

Production route of Triplate • • • Choice of right materials and study of features Grinding of the surfaces Preparing of special grade explosives Preparing vacuum chamber Explosion welding Flattening of the plates Cutting into bars and special shapes Inspection by QA-manager and independent surveyor Transport to customer After sales and all kind of recommendations

What happens during welding? Explosives Aluminium plate Steel plate S = collision point high pressure will locally cause super plastic behavior of metals

Metallic bond between Al and Fe

Applications in the marine sector • Cruise vessels and mega • • • yachts Offshore platforms Fishing vessels Ferries Tenders and supply boats Special ships such as navy vessels

Some examples

Differences with open air cladding • Triplate is manufactured in a • • • vacuum environment Therefore we need less explosives This will lead to a smooth interface The result is no oxide conglomerations in the interface Better bending properties Less risk of corrosion Easy to machine

Three different interfaces

Open air cladding versus vacuum Oxide conglomerations are visible Small holes will initiate corrosion in due course especially when bend Disadvantage during bending and cutting Limited fatigue strength Source: http: //www. fme-cwm. nl/Download/Publicaties/vm_115. pdf

Atmospheric cladded transition joints

Side bend test Vacuum clad generates no oxide holes

Hammer bend test MIL-J-24445 A Combination hammer bend and side bend test Oxide holes can initiate cracks after bending

The result of crevices

The strength of the interface Tensile test Even at bending radius 2 x width Triplate shows no cracks.

Summary of differences • • Open air cladding Oxides with porosity Oxides initiate fractures Holes initiate corrosion Side bend radius 10 x width of the strip Variable weather conditions Harder to machine (sawing and bending) • • Vacuum cladding 100% dense Does not apply Side bend radius 5 x width or even less Does not apply since it is inside Easy sawing and forming thanks to high ductility

The right set-up of Triplate

Transit zone shear strength in N/mm 2 Relationship between temperature and shear strength aluminium/steel transition joints after 200 hours heat input.

Temperature gradient during welding Subjected to normal circumstances. It’s relevant to first weld the aluminium plate to the transition joint

Unacceptable configurations The interface will overheat during welding. That will cause an hard brittle interlayer.

What happens when the temperature is too high during processing of Triplate? Aluminium 99, 5% 23 Hv Brittle aluminium iron crystals 760 Hv Steel 127 Hv

Tensile test asymmetric set-up Triplate is not the weakest link in the chain

Special shapes by means of water cutting Full freedom of design and digitally controlled

Triplate butt welds • Butt welds are labour intensive • Butt welds are expensive • Difficult to seal it in a right way • Avoid butt welds as much as possible • Therefore longer lengths available (5. 8 m)

Various approvals such as Lloyd’s, Veritas, RINA, Germanische Lloyd, Det Norske Veritas and American Bureau of Shipping

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