triplate transition joints the ultimate solution to weld aluminium to steel by ko buijs...
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Triplate transition jointsTriplate transition joints
The ultimate solution to weld The ultimate solution to weld aluminium to steelaluminium to steel
By Ko Buijs
Metallurgical engineer SMT-Metals b.v.
Vacuum cladding
Production route of TriplateProduction route of Triplate
• Choice of right materials and study of featuresChoice of right materials and study of features• Grinding of the surfacesGrinding of the surfaces• Preparing of special grade explosivesPreparing of special grade explosives• Preparing vacuum chamberPreparing vacuum chamber• Explosion weldingExplosion welding• Flattening of the platesFlattening of the plates• Cutting into bars and special shapesCutting into bars and special shapes• Inspection by QA-manager and independent Inspection by QA-manager and independent
surveyorsurveyor• Transport to customerTransport to customer• After sales and all kind of recommendations After sales and all kind of recommendations
What happens during What happens during weldingwelding??
Steel plate
Aluminium plate
Explosives
S = collision point high pressure will locally cause super plastic behavior of metals
Vd
B
B1
Vp
ß
Vp
Cladding Jet
Steel plate
Explosives
Collision point
S
Metallic bond between Al Metallic bond between Al and Feand Fe
Metal bond
Ironatoms
Aluminiumatoms
Electronclouds
Nucleus
Applications in the marine Applications in the marine sectorsector• Cruise vessels and Cruise vessels and
mega yachtsmega yachts
• Offshore platformsOffshore platforms
• Fishing vesselsFishing vessels
• FerriesFerries
• Tenders and supply Tenders and supply boatsboats
• Special ships such as Special ships such as navy vesselsnavy vessels
Vacuum cladding
Some examplesSome examples
Differences with open air Differences with open air claddingcladding
• Triplate is manufactured in a Triplate is manufactured in a vacuum environmentvacuum environment
• Therefore we need less explosivesTherefore we need less explosives• This will lead to a smooth interfaceThis will lead to a smooth interface• The result is no oxide The result is no oxide
conglomerations in the interfaceconglomerations in the interface• Better bending properties Better bending properties • Less risk of corrosionLess risk of corrosion• Easy to machineEasy to machine
Three different interfacesThree different interfaces
Smooth wave interface
Undulating wave interface
Turbulent wave interface
Oxide concentrations are visible
Open air cladding versus Open air cladding versus vacuumvacuum
Open air cladding
Source: http://www.fme-cwm.nl/Download/Publicaties/vm_115.pdf
Vacuum cladding
Oxide conglomerations are visible
Small holes will initiate corrosion in due course especially when bend
Disadvantage during bending and cutting
Limited fatigue strength
Atmospheric cladded transition Atmospheric cladded transition jointsjoints
Atmosferic clad transition jointsaluminium/steel
Concentrations of oxides are visible
Open air cladding
Side bend testSide bend test
Top: Atmospheric claddedBottom: Vacuum cladded Triplate
Side Bend Test 90°
Open air cladding
Vacuum clad generates no oxide holes
Hammer bend test MIL-J-Hammer bend test MIL-J-24445A24445A
Left: Atmospheric claddedRight: Vacuum cladded Triplate
Oxide holes can initiate cracks after bending
Combination hammer bend and side bend test
The result of crevices The result of crevices
Oxide conglomerations are dangeroussince they could initiate serious corrosionin the interface steel/aluminium. This is a result of an open air cladding.
Result of vacuum cladding. No oxideconglomerations are visible. No creviceor galvanic corrosion.
The strength of the The strength of the interfaceinterface
Even at bending radius 2x width Triplate shows no cracks.
Tensile test
Summary of differencesSummary of differences• Open air claddingOpen air cladding
• Oxides with porosityOxides with porosity
• Oxides initiate fracturesOxides initiate fractures
• Holes initiate corrosionHoles initiate corrosion
• Side bend radius 10x Side bend radius 10x width of the stripwidth of the strip
• Variable weather Variable weather conditionsconditions
• Harder to machine Harder to machine (sawing and bending)(sawing and bending)
• Vacuum claddingVacuum cladding
• 100% dense100% dense
• Does not applyDoes not apply
• Does not applyDoes not apply
• Side bend radius 5x width Side bend radius 5x width or even lessor even less
• Does not apply since it is Does not apply since it is insideinside
• Easy sawing and forming Easy sawing and forming thanks to high ductility thanks to high ductility
The right set-up of TriplateThe right set-up of Triplate
Steel plate
Triplate transition joint
Steel plate
Aluminium superstructure
Acceptable set upGood set upSteel plate
Optimum set up
Transit zone shear strength in Transit zone shear strength in N/mmN/mm22
Relationship between temperature and shear strength aluminium/steel transition joints after 200 hours heat input.
110
96
83
69
55
41
28
14
0 40 90 100 200 260 315 370 425
Temperature °C
Temperature gradient during Temperature gradient during weldingwelding
240°C 670°C
1550°C
Aluminium
Steel
Al/Mg
Temperature
Subjected to normal circumstances. It’s relevant to first weld the aluminium plate to the transition joint
Unacceptable configurationsUnacceptable configurations
Unacceptable set up
Steel plate
Worst possible set up
The interface will overheat during welding. That will cause an hard brittle interlayer.
What happens when the What happens when the temperature is too high during temperature is too high during processing of Triplate?processing of Triplate?
Brittle aluminium iron crystals 760Hv
Aluminium 99,5% 23Hv
Steel 127Hv V= 500x
6,5x
Torque = F x a
aF
F
FF
F
F
Ideal situationTensile strenght min. 275 Mpa100%
Tensile strength min. 205 Mpa75%
Tensile strength min. 165 Mpa60%
Sensitive location for notch effects
Steel plate
1
2
3
Width transition joint must be fourtimes the thickness of thealuminium plate.
Aluminium plate
Tensile test asymmetric set-Tensile test asymmetric set-upup
Triplate is not the weakest link in the chain
Special shapes by means of Special shapes by means of water cuttingwater cutting
Full freedom of design and digitally controlled
Triplate butt weldsTriplate butt welds
• Butt welds are labour intensiveButt welds are labour intensive
• Butt welds are expensiveButt welds are expensive
• Difficult to seal it in a right wayDifficult to seal it in a right way
• Avoid butt welds as much as possibleAvoid butt welds as much as possible
• Therefore longer lengths available (5.8 Therefore longer lengths available (5.8 m)m)
Various approvals such as Lloyd’s, Various approvals such as Lloyd’s, Veritas, RINA, Germanische Lloyd, Det Veritas, RINA, Germanische Lloyd, Det Norske Veritas and American Bureau Norske Veritas and American Bureau of Shippingof Shipping
Many thanks for your Many thanks for your attentionattention
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