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