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Assessment of Structural Integrity of Titanium Weldments for U.S. Navy ApplicationsREC2010
William [email protected]
Weldments for ApplicationsU.S. Navy applicationsStructural integrity for long-term serviceTitanium
Weld Strength
Indirect requirements set strength- Matching weld chemistry of Ti alloy- Some range to what is “matching”
Sometimes welds are below base metal in strength
AWS D1.9 assumes weld strength 90% of base metal requirement- Conservative for low strength base metals
Different from Steel and Aluminum- Steel weld usually “over-match”- Al welds almost always greatly “under-match”
Weld FatigueAvailable standard methods for fatigue assessment for steel and aluminumSlope change to 1/3.5, based on crack growth rate data
Design Cycles to Failure
103 104 105 106 107
Stre
ss R
ange
(MP
a)
10
100
1000
Stre
ss R
ange
(ksi
)
10
100
FAT Classes Scaled from IIW RecommendationFAT 3.5 Classes
100908071635650454036322825
112125 140160
22
Butt Welds
Tests in bending with differing heat treatment
Other tests showing PWHT advantage not confirmed
Cycles
103 104 105 106
Cal
ibra
ted
Nom
inal
Stre
ss R
ange
(ksi
)
40
50
60
70
80
90
150
100
Cal
ibra
ted
Nom
inal
Stre
ss R
ange
(MP
a)
300
400
500
600
700
800
900
1000
No PWHTNo PWHT- Runout or Base MetalAir PWHTAir PWHT - Base MetalVacuum PWHTNo PWHT AverageAir PWHT AverageVacuum PWHT Average
Span Range 0.92-in.
Runout
Tension on Root Surface
Butt Welds
4-Point BendingMinor effect of weld defects
Cycles
103 104 105 106
Cal
ibra
ted
Nom
inal
Stre
ss R
ange
(ksi
)
20
30
40
50
60
708090
100
Cal
ibra
ted
Nom
inal
Stre
ss R
ange
(MP
a)200
300
400
500
600
BaselineBaseline - Base MetalHeavily Contam. GasHeavily Contam. Gas - Base MetalLinear DefectLinear Defect - Base MetalRound Pores - Base Metal
Corner Joints
4-Point Bending Stronger effect of root linear defects
Cycles
102 103 104 105 106
Cal
ibra
ted
Nom
inal
Stre
ss R
ange
(ksi
)
20
30
40
50
60
708090
10
100
Cal
ibra
ted
Nom
inal
Stre
ss R
ange
(MP
a)
708090
200
300
400
500
600
100
BaselineContam. GasHeavily Contam. GasLinear DefectLinear Defect - Runout
Tang and Slot Models
Attachment weld modelsMinor effect of imperfections
Cycles
103 104 105 106 107
Cal
ibra
ted
Nom
inal
Stre
ss R
ange
(ksi
)
20
30
40
50
60
708090
100
Cal
ibra
ted
Nom
inal
Stre
ss R
ange
(MPa
)200
300
400
500
600
7008009001000
BaselineContam. GasContam. Gas - RONo FilletLinear DefectRound PoresRound Pores - Base MetalCantilever Bending
Butt Welds
Tension testing2 programs, 2 alloys, 3 thicknessesBig effect of sharp weld toe
Cycles
103 104 105 106 107
Nom
inal
Stre
ss R
ange
(ksi
)
20
30
40
50
60
708090
200
100
Nom
inal
Stre
ss R
ange
(MPa
)
200
300
400
500
600
7008009001000
Baseline Ti-6Al-4VBase Metal Ti-6Al-4VRound Pores Ti-6Al4VContam. GasSharp Toe2 mm CP2 mm CP - RO10 mm CP10 mm CP - ROFAT3.5 Class 80
Corner Joints
Overall tension, but local bendingPerformance similar to 4-point bending
Cycles
102 103 104 105 106
Cal
ibra
ted
Nom
inal
Stre
ss R
ange
(ksi
)
20
30
40
50
60
708090
10
100
Cal
ibra
ted
Nom
inal
Stre
ss R
ange
(MP
a)
708090
200
300
400
500
600
100
BaselineContam. GasHeavily Contam. GasLinear Defect
Attachments
Tension tests2 programs, 2 alloys, 3 materials
Cycles
103 104 105 106 107
Nom
inal
Stre
ss R
ange
(ksi
)
20
30
40
5060708090
200
10
100
Nom
inal
Stre
ss R
ange
(MPa
)
708090
200
300
400
500600700800900
100
1000Baseline Ti-6Al-4VLinear Defects Ti-6Al-4VRound Pores Ti-6Al-4VContam. Gas Ti-6Al-4VNo Root Fillet Ti-6Al-4V2mm CP2 mm CP - RO10 mm CP10 mm CP - ROFAT3.5 Class 71
Longitudinal Attachments
Iwata data on CP titaniumLower performance than correlated for steel and aluminum
Cycles
105 106 107
Nom
inal
Stre
ss R
ange
(MP
a)
60
70
80
90
150
100
Nom
inal
Stre
ss R
ange
(ksi
)
9
15
20
10
2 mm thick2 mm thick - RO10 mm thick10 mm thick - ROFAT 3.5 Class 71FAT Class 71
Application to Howitzer
AWS Standard developed for welding acceptability along with howitzer developmentAdditional areas of study- Inserts for reducing total weld metal- Welding on cast material
Application to Thin Structure
Mock-up with gas shielding demonstrationAWS Code does not cover minimum thickness, so use NAVSEA 248Pulse welding (GMAW) with 100% helium
Application to Large Door
GMAW design mock-upSpatter indicates need for improved weld procedures and shieldingNeed for Navy application ballistic testing
Knowing Enough
Transferability from steel and aluminum to titaniumTransferability from one alloy to anotherTransferability from one weld geometry to anotherTransferability of weld acceptance criteriaTransferability from GTAW to GMAWTransferability from one thickness to another
