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Welding of X80 Pipe
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Welding of X80.NF.12.1
Welding of X80 base material
Nordic Welding Conference, Oct. 2012
Harm MeelkerLincoln Smitweld B.V.
Welding of X80.NF.12.2
Overview
� Introduction
� Material properties
� Challenges
• Yield overmatching, hydrogen
� Welding processes
� Conclusions
Welding of X80.NF.12.3
Saving of material as function of Yield strength
Welding of X80.NF.12.4
Motivation & drivers for X80
Ensure performance demanded by
modern pipeline design is delivered
reliably & economically with large scale
high strength steel field implementation
� Modern pipeline design drives higher
performance expectations
� Reliability means hitting smaller
targets
� Higher strength & performance
targets; means fewer options
Welding of X80.NF.12.5
Development history linepipe steels
Welding of X80.NF.12.6
Requirements acc. API 5L code X80
%C %Mn %P %S %Ti CEV
API 0.24 1.40 0.025 0.015 0.060 0.43
Yield (Mpa) Tensile (Mpa) Elongation (%) Impact (J) 0°C
552 - 690 621 - 827 - 41
Chemical
Mechanical
Welding of X80.NF.12.7
Requirements acc. EN 10208-2 (L550MB)
% C Mn P S Si Cr Ni Mo Cu V Ti N Al Nb
EN 0.16 1.80 .025 .020 .45 .30 .30 .10 .25 .10 .06 .012 .06 .06
Chemical
V+Nb+Ti max.0.15
Al min. 0.015
CEV by agreement
Mechanical
Yield (Mpa) Tensile (Mpa) Elongation (%) Impact (J) 0°C
555 625 18.0 -
Welding of X80.NF.12.8
Influence of Boron on Yield Strength
Welding of X80.NF.12.9
Max. permitted Ceq. acc. EN 10208-2 and DNV
Welding of X80.NF.12.10
Challenges
� Weldability
� Yield requirements per country
(overmatching)
� Impact requirements (overmatching)
� Hydrogen
� Preheat
� NACE?
� Heat Input (true energy)
Welding of X80.NF.12.11
Welding challenge for High Strength Pipe
� X80• Minimum specified pipe Yield – 552 MPa acc. API 5L
• Design requires weld metal even or over match actual pipe properties�Even match pipe in Yield or Tensile Strength
�Over match 10% pipe
• Design demands higher toughness & ductility with strength�Weld capacity to deliver diminishes with strength
� Implications• Tighter limits on upper bound pipe properties
• Balanced considerations for weld properties
• Limit the welding options – consumables & processes
Welding of X80.NF.12.12
Overmatching
� Over-matching approach in the weld
metal selection is a general practice
Aspects to define:
� What is the min. WM YS needed to
have an actual overmatching?
� What is the impact property required
to the weld metal (WM)?
Welding of X80.NF.12.13
Overmatching
Actual or theoretical overmatching ?
� Codes require a min. YS value for the base material
� The actual YS of the base material should be very close to the min. or much more than the min.
� The weld metal YS, depending on the actual base material YS, could satisfy the over or the mis-matching requirement
� As practical approach is usually required: min WM YS = min BM YS + 10% = max. BM YS
Welding of X80.NF.12.14
Overmatching
� If owner can accept this narrow range of YS
(YS min + 10%) the YS WM and the YS BM
could be of the same order of magnitude
� But if we want an actual OM and the owner
does not accept YS min+10% we have to
consider an higher WM YS min (+15,+20,+30%)
� The highest YS for X80 acc. API 5L (552 – 690
MPa) can make it very difficult or almost
impossible to meet all the mechanical req.
Welding of X80.NF.12.15
Weld metal Overmatching
� Welding consumables are an industrial
product, this means an acceptable range
for the chemical elements is required
� The Standards (EN/ISO – AWS) require an
acceptable range of mechanical properties
� To compare the Code requirements we can
consider the following example based on
API 5L min./max. Yield for X80:
BM YS 552 552+10%= 607 MPa - min WM
BM YS 690 690+10%= 759 MPa - min WM
Welding of X80.NF.12.16
OvermatchingChemical composition welded joint
� Dilution with base material
• Dilution will effect the final weld joint chemistry
• This results in other mechanical properties than
for all weld metal
• Other aspects are of course the used welding
technique
�Process
�Preheating and Interpass temperature
�Heat Input, bead sequence, etc.
� This all influences the final mechanical
properties of the welded joint
Welding of X80.NF.12.17
Welding processes
� Manual or (semi-) automatic
• SMAW (cellulosic or basic)
• GMAW
• FCAW (gas shielded or gasless)
• (SAW)
• Advanced!
2007
2004
2002
Welding of X80.NF.12.18
Welding Process Parameters
� Define Essential Welding Variables:
• Process type, Transfer Mode
• Position and Direction
• Wire Feed Speed (WFS), Travel Speed (TS)
• Voltage, Amperage, and Heat Input
� Influence on Thermal Cycles
• Deposition Volume (WFS/TS)
• Heat Input (Joules/mm)
• ∆∆∆∆t8-5
Welding of X80.NF.12.19
Key welding process variables
� Combined welding & material
variables
• Preheat/interpass temperatures
(RT-180°C)
• Consumable composition (Pcm)
• Pipe composition (Pcm / CEIIW or CEN)
• (True) Heat Input
True Heat Input adopted by ASME
Welding of X80.NF.12.20
Does pre-heating make sense?
� Lowering cooling rate of weld- and base material, softens the metal and gives a micro structures with less hardness
� A lower cooling rate, allows hydrogen diffusion from the welding joint
� It reduces shrinkage stresses in weld- and base material (important for high restraint)
� Depending on type of steel, reducing risk for brittle fracture
� Preheating may improve mechanical properties
Welding of X80.NF.12.21
Considerations for preheating
� Type of steel ���� chemical composition
� Material thickness
� Internal stresses (restraint)
� Ambient temperature during welding
� Welding process
� Hydrogen content welding consumable
� Fabricator’s practice and experience
with cracking phenomena
� Code or standard requirements
Welding of X80.NF.12.22
Graphical representation of Ceq.
Welding of X80.NF.12.23
Welding fundamentals
� Functional understanding of welding
process control
• New approach transcends power source
& wave form design
• Methodology for using welding process
as tool in delivering performance
• Practical means of achieving the
necessary weld process control
� Basis for new codes and standards
Welding of X80.NF.12.24
Calculation of average Heat Input
� Assumptions with average Heat Input calculation:
• Voltage and Amperage are constant …
“Constant DC” Process
• Travel speed is constant
• Deposition volume is constant
(WFS/TS)
� Cooling Rate can be correlated to average Heat Input
� Accurate calculation for “Constant DC” processes that
produces repeatable results
� Must be carefully considered with other welding
process variables and changing conditions
TSTSTSTSIIIIVVVVHIHIHIHI 60**
=
Welding of X80.NF.12.25
� Welding Power Supplies of today:
• Output can be simple DC with natural (exponential)
responses
• Output can be complex for additional control
and better transfer modes
�Waveform Controlled Welding (i.e. Pulse Welding)
� What is Waveform Controlled Welding?
• A Waveform is the output response of an arc welding
machine to the actions of the electric arc itself
• Every arc welding machine has a waveform characteristic
� In traditional machines, the waveform characteristic is
based on the design of the transformer and choke
�More complex machines combine hardware design with
electronics to give optimized control of the waveform
Waveform Controlled Welding Processes
Welding of X80.NF.12.26
� Assumptions with average Heat Input calculation:
• Voltage and Amperage are constant … “Constant
DC” Process
• Travel speed is constant
• Deposition Volume is
constant (WFS/TS)
Waveform controlled welding waveforms are not constant. Therefor, ave. Heat Input calculation is not accurate
Waveform Controlled Welding Processes
Welding of X80.NF.12.27
Comparisons of calculation methods
True Heat Input
V A Power (kW) TS (ipm) HI (kJ/in) Error
DCAvg 28.43 371.5 10.56
2228.8 none
True 10.56 28.8
Pulse #1
Avg 22.17 113.8 2.5210
15.1 -16.6%
True 3.02 18.8
Pulse #2
Avg 19.18 119.1 2.2810
13.7 -14.6%
True 2.67 16.0
#1 #2DC
Welding of X80.NF.12.28
Summary True Energy
� Traditional approach• Limit variation of individual
variables• Heat input using average or rms
� Adequate for soundness� Poor estimate of energy &
thermal cycle TODAY
� New approach• True Energy based on
measurement at 10kHz
� Traditional approach
• Pipe based on performance standards beyond minimum specification
• Weld consumables
� conformance with set PQR
� New approach
• Characterize materials during development / qualification
• Balance tradeoffs between material and process selection
THERMAL HISTORYControlled by
Welding Processes & Practices
MATERIAL PROPERTIESControlled by
Chemistry & Microstructure
As a result of this ASME code changed the requirements for Heat Input calculation in section IX QW-409.1(c)(1) in energy in Joules per weld bead length
Welding of X80.NF.12.29
Consumables for X80 pipe
� For root welding:
• SMAW: E8010-P1, E9018-G H4 till E12018-G H4
• GMAW: ER80S-G till ER120S-G
� For fill and cap layers:
• SMAW: E8010-P1, E9018-G H4 till E12018-G H4
• GMAW: ER80S-G till ER120S-G
• FCAW-G: E91T1-GM H4 till E111T1-GM H4
Welding of X80.NF.12.30
Summary
� X80 Line pipe is good weldable,
however, be aware of special
requirements and take care of all
thermal influences
� Today codes are and will be updated
Welding of X80.NF.12.31
Questions, Comments, Discussion