Challenges and developments in pipeline weldability and mechanical properties.pdf

7/25/2019 Challenges and developments in pipeline weldability and mechanical properties.pdf

1/13

REVIEW

Challenges and developments in pipelineweldability and mechanical properties

C. Liu*1 and S. D. Bhole2

Recent economic and political events have further highlighted the need for new and strategically

accessible sources of oil and gas. With the continually increasing demand for oil and gas, the

requirement for pipeline steels with higher strength, toughness and weldability has been one of

the most important factors driving the development of high strength pipeline steels, particularly

with the oil exploration proceeding into arctic and deep sea regions, enhancing the weldability

and mechanical properties of the new pipeline steels and weld consumables. Developments in

the welding processes for manufacture and field welding are described in terms of process

principles, equipment, consumables, weld quality, process economics and further developments.

The increasing and changing requirement for weldability and mechanical properties in the heat

affected zone and weld metal of pipeline welds are presented along with the reported solutions to

the problems.

Keywords: Pipeline, Weldability, Mechanical properties, Welding process

Introduction

Pipelines used for the transportation of crude oil or

natural gas over long distance and under high pressure

primarily require a combination of high strength and

toughness, and good weldability for lowering transpor-

tation cost.13 Particularly during the late two decades,the exploration of energy has expanded to cold regions

such as northern Canada, the North Sea and Siberia.4

The higher grade steel pipes and enhanced weldability

are being proposed for the purpose of enhancing the

transport efficiency of pipelines. Thus, the investigation

and development of improved and innovative welding

techniques to face the new technical challenges is a

major consideration in the pipeline industry.

This paper presents an overview of challenges and

developments in the weldability of pipeline steels in

grades from X70 to X120. The various welding processes

for both the manufacturing of pipes and the construc-

tion of pipelines are evaluated. The mechanical proper-ties of the base metal (BM), heat affected zone (HAZ)

and weld metal (WM) in pipeline welds and the

approaches to improve the toughness of the HAZ and

WM are summarised.

Developments of high grade pipelinesteels

The development and the changes in production

techniques of high strength pipeline steels from 1990 to

2010 are shown in Fig. 1.

513

The chemical compositionand mechanical properties of pipeline steel from X70 to

X120 are given in Tables 1 and 2 respectively.8,14,15

It is seen that X80 steels instead of X60 and X65 are

microalloyed with molybdenum, niobium and titanium,

and the reduced carbon content has been developed and

utilised for gas pipelines. A 163 mile, 48 in gas pipeline

installed in 19921993 in Germany was the first to use

X80 steel in the world. It thus has a higher design

potential than the more widely used X70 because it

allows system design with either thinner wall thicknesses

at constant operating pressure or a corresponding in-

crease in operating pressure.16 From the 1990s, the higher

strength of X100 pipeline steels, having a further reduced

carbon and a good combination of higher strength andbetter toughness (see Tables 1 and 2), compared with

either X80 or X70 steels has been developed by an

improved processing method, consisting of thermome-

chanically controlled process (TMCP) plus subsequent

accelerated cooling (ACC). The aim of the TMCP process

is to create an extremely fine grain microstructure by a

skilled combination of rolling steps at particular tem-

perature control. The grain in strength obtained by the

grain refinement can reduce effectively the contents of

both carbon and alloys in TMCP steel compared with

normalised steel of the same grade. Thus, the weldability

can be improved due to the leaner steel composition. For

thick plates, an ACC after final rolling pass is beneficialfor the achievement of the most suitable microstructure as

it forces the transformation of elongated austenite grains

1College of Mechanical Engineering, Yangzhou University, Yangzhou225009, China2

Department of Mechanical and Industrial Engineering, RyersonUniversity, 350 Victoria Street, Toronto, Ont. M5B 2K3 Canada

*Corresponding author, email [email protected]

2013 Institute of Materials, Minerals and MiningPublished by Maney on behalf of the InstituteReceived 22 August 2012; accepted 4 November 2012DOI 10.1179/1362171812Y.0000000090 Science and Technology of Welding and Joining 2013 VOL 1 8 NO 2 16 9


2/13

before recrystallisation.3 The characterisation of proto-

types of X100 pipes has been extensively studied by pipemanufacturers.7,1719 Further additions of Mo, Ni and B

enable the strength level to be raised to that of grade X120

by the same processing method.9 To enable the develop-

ment of remote gas sources in the future, higher strength

pipelines such as X100 and X120 will play very important

roles in the pipe industry.20,21 It is also seen from Fig. 1

that the grain refinement is the key method by which both

strength and toughness can simultaneously be improved.

Generally, the ferrite grain of X70 steels (ASTM 10-11) is

finer than that of X60 (ASTM 7-8).18 Changing the

microstructure of the steel matrix from ferritepearlite to

ferritebainite can attain further increases in strength and

toughness, which leads to the development of X80 steel. It

has been observed that the ferritebainite microstructure

in X80 steel is more uniform and extremely fine with a

mean grain size of,1 mm.22 However, this is still not the

end. In order to significantly increase the strength above

the X80 level, a fully bainitic microstructure with a very

fine grain size has been aimed for X100 and X120 steels.

As applying the high strength steels, the materials

used for pipeline can be saved greatly. The use of grade

X80 pipeline in the construction leads to a materials

saving of,20 000 t, compared with X70 pipes, througha reduction in the wall thickness from 20?8 mm for X70

to 18?3 mm for X80.23 The use of higher strength, such

as grade X100 or grade X120, can result in further

savings. For example, the X100 pipeline could give

investment cost savings of ,7% compared with grade

X80 pipeline. This study claims cost savings of up to

30% when X70 and X100 are compared.24

Developments in weldability in X70 andX80 pipelines

In the early 1970s, grade X70 was introduced in the

world for use as a pipe in the construction of gastransmission.25 Since then, there are satisfactory experi-

ences to show that it can be welded trouble free with

Table 1 Chemical composition of pipeline steel fromgrade X70 to X120*/wt-%8,14,15

Grade X70 X80 X100 X120

C 0?095 0?075 0?06 0?030?06Si 0?32 0?31 0?35 0?36Mn 1?55 1?59 1?90 1?95P 0?015 0?018 NS NSS 0?001 0?001 NS NSNb 0?040 0?057 0?05 0?04Ti 0?013 0?013 0?018 0?02Al 0?030 0?026 NS NSV 0?06 NS NS NSMo NS 0?22 0?28 0?20Ni NS NS 0?25 NSCu NS NS NS NSCr NS NS NS NSB/ppm 2 NS NS 1020N/ppm 52 60 40 40Ca/ppm 8 11 NS NS

*NS: not specified.

1 Development of pipeline steel grades and production techniques from 1990 to 2010

Liu and Bhole Pipeline weldability and mechanical properties

Science and Technology of Welding and Joining 2013 VOL 1 8 NO 2 17 0


3/13

cellulosic electrodes providing care taken to avoid

hydrogen induced cold crack.13,25,26 In summer 1994, a

33 km of NGTs Eastern Alberta system main line along

the gas pipeline system operated in Alberta was the firstNorth America long distance, large diameter pipeline to

use X80 steel.27 Up to 2001, X80 pipeline was used

widely in the world. Now, it becomes the basis of astandard platform for design and construction of large

diameter pipeline projects in the network.

Achieving the balance between strength and weld-

ability in the development of X70 and X80 has been amajor consideration in respect of alloy design as

indicated schematically in Fig. 2.14 The higher carbon

equivalent (CE) values are obtained in the commercial

X70 grade steels (Nb/V steel A and Nb/V steel B).

Particularly, the Nb/V steel B provides little margin forpipe yield strength at a specified maximum CE per cent

level of 0?39. An increase in CE to 0?40 allows for more

comfortable achievement of strength but can be a

questionable approach if heavier wall thicknesses arerequired from a weldability viewpoint. The applicationof Mo/Nb steel C in a subsequent X70/X80 provides for

a good wide excellent strength at a considerably lower

CE. The trend of X80 and X70 development is also

indicated on the diagram, suggesting that the balance of

strength/weldability also requires appropriate weldingprocedures for higher strength X80 pipelines for either

metallurgical or economic reasons because of the

changing of the alloying elements and the strength.

Welding process developments for X70 and X80pipelinesThe pipeline welding can be divided into the following:

manufacture welding and field welding. Good weld-

ability of the steel used for the manufacture of pipeline is

a prerequisite for trouble free welding in pipe laying. The

field welding to be used has to meet requirements formaximum productivity and reliability.28,29

The manufacture of large diameter pipeline involvesthe forming of plate to pipe, followed by seam welding

and finally expansion of pipe to final shape. The seamwelding operation is generally carried out using the highproductivity submerged arc welding (SAW) process.30

Manual shielded metal arc welding (SMAW) process

and mechanised gas metal arc welding (GMAW) processare two principal welding methods for field welding.15,27,31

These welding methods are well established now and

regarded as sufficiently validated for large scale use. Themethod adopted depends on economic considerations: themost cost effective use of mechanised GMAW and manualSMAW depends on the type of mechanised weldingsystem, the length of each individual construction and thetopography of the land to be traversed.32

Submerged arc welding process

During longitudinal SAW seam process, the welded pipeis usually formed by a double SAW method, whoselongitudinal butt joint is welded in at least two passes,

one of which is on the inside of the pipe; the welds aremade by heating with an electric arc between the baremetal electrodes. Pressure is not used. Filler metal forthe welds is obtained from the electrodes. This processcan penetrate the full thickness of the pipe because theheat input during the SAW is 2 kJ cm21 per milli-metre of thickness and gives a high productivity withgood mechanical properties and a low repair rate.3335

The SAW welds in X70 pipeline are generally madewith wire electrodes alloyed with Mn and Mo or with Mn,Mo and Ni.3439 The chemical composition of the wires isadjusted in such a way that the WMs, which contain 6070%BM by dilution, exhibit maximum toughness. Aproper balance between C, Mn and Mo contents as well

as microalloying with Ti and B has a beneficial effect onWM toughness.6 Welding of X80 is carried out similarlyusing the same slightly basic agglomerated fluxes thathave been well established for welding X70 line pipe steel.There are no needs of developing welding wires specifi-

cally for this material.38 Owing to reduced carboncontent, X80 exhibits a slightly improved toughness inthe HAZ compared with X70.29,38

Since the high strength pipelines are welded by highheat input SAW process, the high heat input results inan increased grain size in the HAZ, and often leads tosoftening and a detrimental effect on the properties ofthe welded joint.2,11 Jansenet al.35 pointed out that thisproblem became even worse for the thin wall pipe due tothe deep penetration of the second weld pass. Thus, pipemanufacturers have to take care of this by adjusting thechemical compositions of both BM and WM.

Table 2 Mechanical properties of pipeline steel from grade X70 to X120*8,14,15

Grade X70 X80 X100 X120

Pipe size Thickness/mm 5?2 3 16 1518Mechanical properties Yield strength/MPa 580 685 752 843

Tensile strength/MPa 630 718 816 1128Elongation/% 35 28 18 14?3

Charpy V-notch toughness Test temperature/uC 10 215 20 240Energy/J 70 32 270 22750% FATT{/uC 2100 ,2125 NS NS

*NS: not specified.{The 50% ductile to brittle appearance fracture transition temperature measured in the Charpy impact test.

2 Influence of strength and weldability considerations on

alloy design for X70 and X8014




4/13

Manual SMAW process

Because of the high tensile strength of X80 pipe steel, it

is not possible for the WM deposited by the cellulosic

electrode used in X70 welding procedure to fulfil therequirement for the minimum tensile strength and to

have simultaneously satisfactory toughness and resis-

tance to cold cracking.25 Considerable changes have to

be made to the manual SMAW method required in the

construction of large diameter in high strength pipes. A

combined electrode manual welding procedure has been

proposed for use in X80 welding. This consists of

making the root and hot pass welding with soft (lower

strength grade) cellulosic electrodes, as in the case of

X70, and the filler and cap passes with high strength

vertical down basic electrodes (such as MAW type

E55010 or AWS type E 10018-G) are used for both the

root and hot passes. It is thus possible to ensure uniformprogress during pipe laying.26,39

Mechanised GMAW process

Besides manual SMAW, the mechanised GMAW be-

comes increasingly important as an economic process.

For example, the SMAW process traditionally has been

used to make the field girth welds; however, increasing

use is being made of mechanised GMAW systems and for

large diameter pipeline construction.40 The different steps

in pipe welding with mechanised GMAW are shown in

Fig. 3. It has several advantages over manual processes as

follows: high metal deposition rates, a reduced gap, low

hydrogen, consistency in both strength and toughness,very narrow welds, relatively low heat input with a variety

of wires and gas shielding, and reduced welding time.25,27

Unlike the 100%CO2 shielding gas used in GMAW for

X70, the mechanised GMAW process for X80 requires

the use of a principally inert gas shield, which greatly

increases the notch and fracture toughness of the WM

and virtually eliminates defects according to Prices

investigation.40

Even with the developments in mechanised GMAW,

manual SMAW remains important in pipeline construc-

tion for repairing and future maintaining depending on

the flexibility of this process. It should be carefully

considered also in the case of frequent interruptions(road or rivers) where it may be more economical to

apply manual SMAW welding.

Investigation of HAZ and WM in X70 and X80weldsThe mechanical properties of both HAZ and WM play

very important roles for the use of pipeline welds.Generally, the joint is constituted of three differentregions: WM, HAZ and BM. If the failure occurs in the

WM, the material will not be approved since it isdesigned to have higher strength than BM; if failureoccurs at the HAZ, it is said to be embrittled. Therefore,the best result for a joint is when the failure occurs in theBM rather than either WM or HAZ.41 In such highstrength pipeline, excellent toughness in the HAZ andWM is required to arrest a running shear fracture and toprevent brittle fracture for improving the installationefficiency. Thus, the possibilities of improving the tough-ness of HAZ and WM with increasing strength of

pipeline have received extensive investigations.4247

Heat affected zone

For a typical X80 pipeline, the resulting microstructure ofthe commercial alloy is one containing ferrite and bainite

(seeFig. 1). This microstructure can increase the strengthwithout significant losses of toughness. However, theexcellent combination of strength and toughness can be

greatly degraded by the thermal cycles imposed duringthe fabrication of the final pipeline product and its onsiteassembly for service. On one hand, welding processesimpose cycles that can lead to intercritical coarse grainregions to form local brittle zones in the HAZ.5,41 On theother hand, the microstructure of the HAZ changes frommartensite to lower bainite, upper bainite and then toferrite and pearlite, as the heat input at welding increases,or the rate of cooling decreases.41,48,49 Especially, the lowtemperature toughness will deteriorate when the micro-structure consists of hard martensiteaustenite (MA)islands. Figure 4 shows that the reduction in toughness isdependent on the volume fraction of MA present.50 Thecrack tip open distance (CTOD) value decreases with theincreasing volume fraction of MA. Thus, the initialbalance between strength and toughness in the BM can belost in the HAZ of the weld.

High or ultrahigh heat input (about 3001300 kJ cm21)in highly efficient welding technologies to reduce the

fabrication cost has recently been widely applied inpipeline industry.2,11,28,44 It is easy to form coarse grainmicrostructure and MA constituent in HAZ after such

3 Diagram of mechanised GMAW process steps40




5/13

ultrahigh heat input welding. Since grain coarsening and

the MA constituent present in HAZ structure are the mainreasons for toughness deterioration in the weld area, a finemicrostructure and reduced formation of MA will lead toimprove the HAZ toughness in X70 and X80 pipes.35,41,48

Three main methods have been advanced to increase theHAZ toughness, which are summarised in Table 3. Thefirst method used titanium as TiN has been utilised inpipeline steels to improve the HAZ toughness. It is alsoclear from Fig. 5 that the hardness of the HAZ can bereduced by austenite (c) grain size refinement from 95 to63 mm, which is controlled by the adjustment of Ti/N ratio.This result cannot be obtained in the predicted Ti freesteels (also shown in Fig. 5).14,51 However, this method isnot always satisfactory in the refinement of c grain size

because the TiN particles coarsen or disappear near thefusion line (FL) where the weld is heated to 1400uC orhigher, and, as a result, their effect to inhibit the coarsening

ofc grain is lost (seeFig. 6a).3,35,48

Under these circumstances, a new technology hasbeen developed where fine TiO particles dispersed insteel are utilised (TiO steel).3,5254 In a TiO steel, TiOparticles existing inside a c grain serve as nuclei ofintragranular ferrite (IGF). The IGF forms around theTiO particles, and as a result, coarse c grains are dividedinto fine ferrite grains to give excellent HAZ toughness(seeFig. 6b). On the basis of this, an innovative HTUFFtechnology has been developed by Terada et al.48 In thesteel based on HTUFF, the coarsening of c grains nearthe FL is suppressed by pinning particles of oxides, andthe IGF forms inside them. As a consequence, themicrostructure of the HAZ is made remarkably fine (seeFig. 6c). The average size of c grain in HTUFF pipesteel is much finer (200 mm) than that in TiO pipe steel

(500 mm). The HAZ of toughness of the HTUFF steel

under X80 is superior to that in the conventional TiN

steel.

The MA volume fraction is related to the carbon

content.30 It was shown from the research result of Bott

et al.41 that the volume fraction of MA in HAZ of X80(NbCrMo) pipeline steel was increased from 7?3 to

8?3% as the carbon content increased from 0?04 to

0?07 wt-%. It was also observed that the volume fraction

of MA increased with increasing CE. For the same level

of carbon content of 0?04 wt-%, the volume fraction of

MA in NbCrMo X80 pipeline steel was 1?4 times as high

as that in NbCr X80 pipeline steel because the formal

steel has a higher CE. For pipeline steels, there is a

general shift of toughness values depending on the

extent to which the microalloying additions contribute

to grain size refinement of the HAZ. Fracture appear-

ance transition temperature (FATT) is the temperature

for which the fracture surface of the broken Charpyspecimen exhibits 50% brittle and 50% ductile morphol-

ogies. Various microstructures and different chemical

compositions influence the FATT values. This effect is

particularly noticeable in the HAZ of weldments.18,22,46

It was shown from Fig. 7 that the FATT value in HAZ

decreased with increasing Ni content from 1 to 5 wt-%.

Ni additions in excess of ,3% would shift the upper

bainitic transformation range to longer cooling times, as

a result of which favourable transformation conditions

would be achieved in the cooling time range.40

It was apparent from Fig. 8athat the most susceptible

region to cracking was not the HAZ but the WM in X70

grade, no doubt reflecting the enhanced weldability of

the pipe.14,55 These steel characteristics also provided the

added benefits of the high fracture toughness in the

HAZ of field welded X70 pipeline. The higher CTOD

value in HAZ was also obtained as in field welded X80

line pipe (seeFig. 8b). However, it was evident that WM

toughness was inferior to that recorded in the X70 field

Table 3 Methods of improving HAZ toughness of pipeline

I Refinement of grain size TiN methodSuppression of austenite grain coarsening by fine particles such as TiN14,52

TiO methodUtilisation of intragranular ferrite nucleated from precipitates such as Ti oxide4,14,5254

HTUFF method

Suppression of austenite grain coarsening near FL and formation of intragranular ferrite

3,48

II Decrease in MA constituent Reductions in C content and CE value30,41

III Modification of matrix alloy Addition of Ni30,43

5 Relationship between Ti/N ratio, microhardness in HAZ

and austenite grain size beside fusion boundary (0?14C/

1?15Mn/0?025Nb structural steel)14,51

4 Dependence of reheated HAZ toughness on volume

fraction of MA50




6/13

welding. This can be attributed to the increased WM

strength (E9010) employed in the X80 trials. From the

above results, it can be seen that the low toughness

problem is displaced from the HAZ to the WM with the

increasing strength of pipeline steel. Thus, the improve-

ment of the WM toughness is becoming more important

for the higher strength pipeline steels.

Weld metal

The relationships between the WM microstructure,

composition and welding conditions are even more

complex than in the HAZ. This is because, while all the

factors discussed above come into play, the chemical

composition of the WM and its macrodistribution in the

solidified weld pool are functions of the BM and

consumable compositions, the flux activity and the

welding process variables.

Specified minimum strength requirements for pipelines

and currently available cellulosic consumables are shown

in Fig. 9.55 It is seen that with the introduction of X80

pipeline, the maximum available cellulosic consumable

strength level is now marginal with respect to strength

matching for the pipe. Studies have shown that over-

matching the WM strength causes gross section yielding

in the pipe; undermatching the WM strength will cause

straining of the weld.40 Generally practice in industry is

that the welding WM overmatches the pipe yield

strength.23 However, this can lead to some undesirable

results when applied to higher strength pipe, such as X80.

First, with SMAW with cellulosic consumables, the

weldability decreases as strength increases, which will

result in the potential for more defects. Since the higher

strength electrode will be more susceptible to cracking, it

will certainly promote WM cracking. Second, the defects

could be of the more deleterious planar type, including

hydrogen cracks. Third, toughness usually decreases with

increasing strength.27,40,56 Therefore, the development of

SMAW procedure for X80 pipelines is a greater challenge

than for GMAW because of the difficulty in selecting

consumables to match strength and toughness while

maintaining good productivity and acceptable weld

quality.

Two major approaches have been pursued to improvethe toughness of the WM in SAW process. One is to use

different types of fluxes/wires.57,58 The other of great

interest is to alter WM composition either through the use

of newer filler metals or by metal powder additions in the

WM.5963 Many of the basic microstructural principles

that apply to the HAZ are also valid with respect to the

WM. However, an additional important microstructure

is acicular ferrite (AF), consisting of fine interlocking

grains, which is associated with good toughness. The for-

mation of AF depends not only on a suitable combination

of alloying elements and cooling rate but also on the

existence of an appropriate distribution of inclusions.6466

It is well known that Ni and Mo in the WM playimportant roles in microstructural control.67,68 However,

there is no general agreement regarding the optimum

6 Schematic of HAZ microstructure control in three kind steels

3,48

7 Correlation between FATT and cooling time for coarsegrained HAZ microstructures of pipeline steels40 [CEIIW5

CzMn/6z(MozCrzV)/5z(CuzNi)/15]




7/13

amount and combinations of Ni and Mo in the WM. Ni

can be either detrimental or beneficial to impact tough-

ness. It has been reported that the WM toughness can be

increased markedly by an increase in Ni content.69

However, some investigations have shown that the benefit

from Ni is conditional. Keehan et al.found that once Ni

exceeded a critical point, which depends on Mn concen-

tration, the Charpy toughness at 240uC decreases.70,71

Shankar and Devletian61 found the toughness decreased

due to Ni increasing in FeNi alloys but could be better in

FeCNi ternary alloys related to composition in terms of

a variable coefficient for C in the Ni equivalent. It was

reported by Evans72 that the best impact toughness

occurred at ,0?5 wt-%Mo in a controlled manner with

respect to Mn. Thuvander et al.73 showed that significant

amounts of Mo offered excellent properties in WMs in a

highly alloyed steel. The addition of Mo and Ni together

has been reported to harden the WM and therefore

decrease the impact toughness.74 On the contrary, Snyder

and Pense75 found an improvement in impact toughness

by introducing 0?42 wt-%Mo and 0?84 wt-%Ni in WMs.

It was shown by Bholeet al.37 that the addition of Mo in

the range 0?8170?881 wt-% resulted in a decrease in

FATT and an increase in impact toughness in X70 pipe

steel. It was also found that the combined presence of

2?032?91 wt-%Ni and 0?750?995 wt-%Mo in the WM

led to a high volume fraction of fine AF with good

toughness (seeFig. 10).

Figure 11 shows the chemical composition of the

longitudinal seam WM deposited by the two pass SAW

method in X80 grade pipe plate with the thickness of

18?3 mm [the chemical composition of X80 steel is

0?09C1?9Mn0?02Nb0?02Ti (wt-%)]. Also shown in

the figure are the impact energy values measured at

0uC.26 The WM has a high Mn content and is addi-

tionally alloyed with Mo. This MnMo WM represents

a good compromise with respect to toughness and

mechanical strength. The average impact energy value

measured varied between 100 and 200 J, which is higher

than that (,95 J) of the BM. Therefore, the weldment

breaks in the BM, which is outside the weld region. It is

said that the beneficial effect of Mo is due to the

8 Girth weld CTOD test results for a

X70 (wall thickness 7?

5 mm) and b

X80 pipeline (wall thickness 9?

0 mm)(E9010 WM)14,55

9 Specified minimum strength requirements for pipe and

currently available cellulosic consumables55

10 Grain size of AF of weld samples37

[LWMo1 (0?75 wt-%Mo); LWMo2 (0?90 wt-%Mo); LWMoNi1 (2?03 wt-%Ni,

0?995 wt-%Mo); LWMoNi2 (2?99 wt-%Ni, 0?75 wt-%Mo]




8/13

formation of predominant AF and granular bainite, atthe expense of ferrite with second phase and grain

boundary ferrite in the WM.37

Careful control of the flux is beneficial controlling the

WM toughness. In welding high strength pipe steel usingthe SAW process, neutral Al basic or fluoride basicfluxes are the only options. With higher strength, thelowest diffusible hydrogen content level is preferred.

Usually, the use of a certain flux is necessary to controlthe oxygen content of the weld deposit in relation toaluminium (Al) content of the BM (dilution).35,76

As proposed by Peng et al.,65 the chemical composi-

tions of wire for the SAW of higher strength pipeline steelare designed according to the following requirements:

(i) the WM mainly consists of AF

(ii) microalloying elements are added to increasethe strength and toughness of the WM, and toproduce particles of high temperature stability

(iii) the wire is purified to decrease the content of S,

P, H, O and N

(iv) low carbon content is adopted.

Typically, solid wires are used when the SAW process isapplied. The chemical composition of these solid wiresalso includes Mn, Ni, Mo and Cr in some cases. Today,cored wires (metal core) are more often used for

increasing the deposition rate.39 The most importantissue from a manufacturer point of view is the possibility

of making any desired alloy and choosing flux/wirecombination in order to obtain a satisfactory weld.35

In summary, X80 is becoming more popular pipelinethan X70 in the pipe industry, since it is more economical.With the development of welding processing methods and

further optimisation of the TMCP treatment, consistentlypredictable and reproducible mechanical properties and

good field weldability can be achieved without difficulty.

Developments and challenges ofweldability in X100 and X120 pipelines

The natural environment of resource development sites

has become more severe with the increasing demand foroil and gas. As a consequence, increasingly sophisticatedand diversified properties are required for pipelines, such

as shown in Fig. 12.4

Hence, the development of higherstrength steels has intensified worldwide. As the devel-opment of grade X80 matures, this grade is now state ofthe art application for high pressure gas pipelines. Grade

X100 has currently reached the stage of full scale testing.Some pipe manufacturers have produced large diameterpipes in grade X100 on a commercial scale for extensive

research.28,58 In the case of X120 grade steel, somecompanies8,9,77 have developed a basic concept formanufacturing and using the steel for high pressuregas pipelines. In February 2004, a pipeline was laid inCanada under frigid conditions using X120. Since highergrades like X100 and X120 are not yet specified in thecurrent line pipe standards such as API 5L, a lot ofinvestigations have to be established by correlation withthe minimum specified yield strength and tensile strengthof X70 and X80.8 Welding procedure specificationsusing existing welding technologies for producingwelded joints with good toughness and strength havebeen designed and studied extensively.79,12,15,20,21,24,31,78

Welding processes challenges for X100 andX120 pipelinesA significant challenge in the deployment of higher

strength pipeline such as X100 and X120 is the develop-ment of welding technology that is compatible withexisting pipeline manufacture and construction methods.

Successful welding of high strength pipeline requiressufficient hydrogen cracking resistance, good weldingproductivity and ease of welder use, while maintaining theproper balance between strength and toughness.20

Longitudinal seam welding technology

In order that as many existing production facilities aspossible can be used for the production of X100 andX120 pipelines, the multiwire SAW welding process witha high heat input used to deposit the two-pass long-itudinal seam weld in pipe has been adopted for thelongitudinal seam welding of X100 and X120 pipes.9

However, there are two problems emphasised by Grafet al.15 First is the softening of the BM beside the

longitudinal seam weld. This problem also exists ingrade X80 but can be easily managed. Productionexperience available today is not sufficient to permit an

11 Mean chemical composition and distribution of impact energy values for SAW longitudinal seam WM for X80 pipe26




9/13

assessment of the softening that occurs in the BM beside

the weld. To advice this aspect, the X120 pipe steelcontains some amount of V for its precipitationhardening effect.8 Second is continuing the use of theproven SAW and achieving adequate strength andtoughness for the WM of two-pass longitudinal seamweld in the higher strength X100 and X120. The newhigh strength and high toughness WMs for SAW have tobe developed. Any conventional consumable cannot beused for either X100 or X120 pipe because the strengthequal to or higher than that of the BM is required in theWM of the seam weld. This problem cannot be resolvedby simply electing a matching chemical composition forthe consumable alone. It would be rather necessary toreduce the heat input per pass. From the view of

production safety, it is impossible to reduce the heatinput with two-pass SAW to the extent necessary.

Field girth welding technology

Manual SMAW and mechanised GMAW field weldingof high strength pipeline in grades X100 and X120 donot pose any severe problems.7,15 From the results ofBarsantiet al.given from Tables 4 and 5,79 it can be seenthat the WM of SMAW weld deposited in the verticaldown position, in combination with softer root passwelds, has sufficient strength to achieve the strength

specified for the BM of X100. The GMAW weld also

shows enough tensile and yield strengths compared withthe BM. Both WMs of SMAW and GMAW weldsexhibit sufficiently high Charpy V-notch impact energyat 230uC. It is also clear that besides the manual vertical

down SMAW methods, the mechanised GMAW tech-niques are very promising considering the fact that thistechnique will be much more involved in the applica-

tions suitable for X100 steel grade and above under thesituation of long distance natural gas transportationover large diameter and high pressure. It is also said thatthe X100 and X120 pipes produced respond favourably

to manual SMAW and mechanised GMAW fieldwelding due to their reduced carbon contents.

It should be noted that cold cracking is a typical pro-

blem associated to high strength pipeline welding.7,8,15

Table 6 shows that it is not the BM but the filler WM(with the highest maximum hardness) deposited withultrahigh strength electrodes that is more sensitive and,therefore, plays the major role with regard to avoid-ing cold cracking in grade X100. The preheat tempera-ture must be appropriate to the WM chemistry andthe hydrogen input during welding. Barsanti et al.79

suggested that using a preheat temperature of 100120uC would be sufficient for hydrogen to adequatelydiffuse from the ultrahigh strength basic WM in the

12 New requirements for pipeline for oil exploration4

Table 4 Welding process of SMAW and mechanised GMAW X100 girth welds79

Weldingprocess

Root pass(AWS type)

Hot pass(AWS)

Filler and cappasses (AWS) Note

SMAW E6010 E9010 E11018-G First and second cellulosic vertical down,rest basic vertical down welded

GMAW ER 100 S-G On a quarter of circumference followingpasses have been executed from the root to cap

Table 5 Strength properties of SMAW and mechanised GMAW X100 girth welds79

Weldingprocess

All WM test (two samples) Transverse weld tensile test (two samples) Charpy V-notch

Yield strength/MPa Tensile strength/MPa Tensile strength/MPaFractureposition

Absorbed energyat 230uC/J

SMAW 865865 885895 803808 HAZ-BM 69GMAW 851886 921941 813816 BM-BM 58




10/13

filling and cap passes before the weld cooled down toroom temperature. This is also the case for X120 fieldgirth welding. This is because, in girth welds, which arecharacterised by cooling times of t8/5526 s, the peakhardness of the root pass HAZ is due to a 100%

martensitic microstructure and dependent on the carboncontent rather than the CE. Thus, it is seen from Fig. 13that there is no difference in the HAZ cold crackingbehaviour in the range of girth welding between X100and X120 pipe steel.15

Investigation of HAZ and WM in X100 and X120weldsHeat affected zone

The possibilities to improve the HAZ toughness of

longitudinal seam weld have been widely discussed.38,48,80

It is difficult to improve the HAZ toughness of a X100and above pipeline steel by conventional microstructure

refining technologies because of the presence of thedetrimental MA in the HAZ of such steels. It has beenreported by Teradaet al.48 that the most effective method

for improving the HAZ toughness of either X100 or X120pipeline would lower the carbon content. Figure 14shows that under the single cycle condition as well asthe double cycle condition, the simulated HAZ Charpy V-

notch value tended to increase when C content decreasedto 0?04 wt-% or less. Under the double cycle condition,the MA formed in great amounts at the boundaries ofprior austenite grains when the C content was high, butthe amount of the MA decreased drastically when Ccontent was #0?04 wt-%. The improvement of HAZtoughness is attributed to the decrease in the formation of

the MA.It was mentioned by Bottet al.41, Ouchi81 and Liet al.82

that the deleterious effect of MA on HAZ toughness wasnot only associated with MA volume fraction but alsowith its morphology, size and distribution in the matrix.They also found that the MA particles with small average

size resulted in not very low HAZ toughness in SAW X80

welds.

The preexisting welding technology is modified and

optimised by reducing the heat input of each pass asmentioned in this paper. A low heat input welding

process leads to a minimisation of the softening of the

HAZ in combination with an improvement in its

toughness.8 However, the potential for rapid cooling

of the weldment increases its susceptibility to formation

of hard, brittle microstructures in the grain coarsened

HAZ of the weld, microstructures that increase the risk

of hydrogen assisted cold cracking.46 Wu et al .47

attempted to overcome this problem by controlling the

fast cooling process with holding time above Ac3 and

the cooling time from 800 to 500uC. They found that the

shorten holding time led to thinner HAZ width and finer

austenite grains in the FL and coarse grained HAZ,

while the decreased cooling time from 800 to 500uC

resulted in finer bainitic ferrite in the HAZ.

The low carbon content in conjunction with a

relatively high CE has been found to be optimum with

respect to reducing the softening of the HAZ, which

gains in significance as the pipeline steel grade increases

to X100 and X120.48,79

Weld metal

Okaguchi et al.21 suggested that WM toughness and

hydrogen cracking were expected to be the primary

challenges for grades X100 and X120 welds. Particularly

for X120 application, since the AF is likely to be too

weak, the martensite, bainite and/or their derivativesshould be the primary WM components.9,21 Therefore,

the design of the chemical composition of the WM to

obtain the desired microstructure for adequate strength

and toughness to match BM is a major consideration.

The WM properties reported by Hillenbrand et al.83,84

for X100 pipelines show that both the conventional C

MnMo and CMnMoTiB WMs result in adequate

toughness and strength of the X100 weld. The almost

fully AF with an ultrafine grain size (12 mm) leads to

the optimum strength and toughness obtained in MoB

Ti alloyed WMs.1 Some experimental work has been

carried out to develop a new WM for the longitudinal

seam weld of X120, given in Table 7.8,9

It is possible toobtain a WM that yields a combination of strength of

roughly 1000 MPa and a high toughness by appropriate

13 Hardenability of pipeline steel X100 and X12015

[CEIIW5CzMn/6z(MozCrzV)/5z(CuzNi)/15] 14 Effect of carbon content on simulated HAZ toughness

of X100 pipe steel48

Table 6 Peak values of hardness of SMAW andmechanised GMAW X100 girth welds79

Welding process

Maximum HV10 (average

values at three positions)

HAZ WM BM

SMAW 287 332 281GMAW 298 323 281




11/13

design of the chemistry (MnNiMoCr) of WM ingrade X120.

X100 pipeline has been developed, and the character-isation of prototype pipes has been extensively studied

by pipe manufacturers and major oil companies. Furtherdevelopment is required to extend grade X100 to higherpipe diameters and lower design temperatures. Duringthe current development, the heavy plate rolling and

pipe production as well as processes for longitudinalseam welding are modified or even completely newlydeveloped with respect to the new high strength grade

X120. Furthermore, new welding consumables and lowheat input welding technology have to be developed toavoid typical problems associated to X120 microstruc-tures and chemical compositions, namely, cold cracking,weld joint toughness and hydrogen susceptibility.

After extensive developments, the X100 and X120options appear to be mature from the technologicalpoint of view. Although the welding processes have to bemodified or even developed with respect to them, it is tobe expected that both X100 and X120 pipelines will beincreasingly used in the incoming years.

Latest developments and challenges ofnon-conventional welding technologyThe arc welding processes have been applied for pipelinewelding of oil and gas for many years. However, with anincreasing demand for high strength steels for pipelineapplications, some novel welding techniques have beeninvestigated to achieve higher quality welds and moreefficiency operations compared to conventional SMAWand GMAW.28,44,58,8588

Electron beam welding (EBW) and laser processes havebeen introduced into pipeline industry recently. Theadvantages of both processes are an extremely high power

density and thus a low heat input. The EBW is a maturewelding process, in which the gun can rotate along thehorizontal direction and move inside. It offers manyadvantages in terms of weld productivity, avoidance ofdistortion and minimal metallurgical disturbance. How-ever, the necessity to weld in a high vacuum atmospherehas restricted the application of the process to com-ponents and structures that can be entirely containedwithin a vacuum chamber.28,44 Hybrid laser arc welding

(HLAW) is a combined process of GMAW and laserbeam welding, which improves the absorption of laserenergy in GMAW weld pool as well as the arc stabilitydue to laser induced ionisation. Hybrid laser arc welding

allows welding to be performed at higher travel speeds,with greater penetration and reduced distortion thanconventional arc welding processes. It has been demon-

strated that the improvements in weld microstructuresand WM toughness are possible using the HLAWprocess.85,86 Although HLAW is a productive and

advantageous welding process, there are certain limita-tions that restrict its use such as expensive laserequipment.

Recently, FRIEX, a new variant of the well knownfriction welding process, has been developed for use inpipeline welding. A welding ring is placed in between the

pipes, and rotating the ring under an axial pressuregenerates the required friction heat during welding. Itgreatly reduces distortion and eliminates solidificationdefects.28,58 Because the joining takes place below themelting temperature, the better quality weld can becreated with low heat input, minimal distortion, no fillermaterial and no fumes. Despite extensive developmentefforts on pipe grads from X70 to X120, this process hasso far failed to archive widespread benefits for pipelineconstruction due to the need for a better understandingon the role of process parameters on microstructuralevolution and weld quality.87,88

The main advantages of using these welding techniquesinstead of conventional arc welding processes are toreduce the number of passes at constant and to improveweld quality. Although they have shown promise for field

pipeline construction, more research and development isstill being required to optimise the processes and to

balance cost for a practical industrial application.

ConclusionsDuring more than two decades of developments, X80 isbecoming a more popular pipeline than X70 in the pipeindustry. The use of X80 causes no problems with respectto mechanical properties and welding. Recent marketrequirements for enhanced pipelines with higher strength,larger diameter, greater operating pressure and reduced

cost have led to new high grade pipes, such as X100 andX120. With regard to the arc welding of X80 pipelines,

the challenge for welding X100 and X120 is even moresignificant. The following main challenges need to be

addressed for the high strength steels including X100 andX120.

First is to develop appropriate welding procedures.The strength softening in the HAZ and the low HAZ

toughness at the FL boundary are two weakest links forthe SAW of high strength pipe steels, which are attributedto the high heat input between BM and WM in SAWprocess. The major challenge during girth welding ofX100 and X120 is how to avoid cold cracking thatresulted from WM deposited with ultrahigh strengthelectrodes. Therefore, the existing welding techniques

have to be optimised and a low heat input welding processhas to be developed.Second is to produce WM with suitable mechanical

properties.

The WM should overmatch the minimum yieldstrength of the BM of either X100 or X120 and provide

Table 7 Chemical composition of WM for X120 longitudinal seam welds/wt-%8,9

Grade WM C Si Mn Cr Ni Mo Pcm*

X120 (A) Outside 0?05 0?23 1?63 1 2?2 0?92 0?31Inside 0?05 0?18 1?69 1?1 2?6 0?98 0?32

X120 (B) Outside 0?06 0?29 1?88 0?9 1?3 0?82 0?32

Inside 0?06 0?30 1?87 0?8 1?3 0?75 0?32

*Pcm5CzSi/30z(MnzCuzCr)/20zNi/60zMo/15zV/10z5B.




12/13

the considerable satisfactory levels of toughness even atlow temperatures simultaneously. However, based oncurrent technology, it is difficult for WM to fulfill theexisting requirements at the same time. Commercially,such WMs are not yet available and need to be designedand developed.

The novel welding techniques including EBW, HLAWand FRIEX have now been developed to a stage wherethey present opportunities for cost savings, which arise

from reductions in labour content. However, a widerange of implementation of these new processes has beenlimited for its popular applications for different reasons.

References1. G. Thewlis: Weldability of X100 linepipe, Sci. Technol. Weld.

Join., 2000, 5 , 365377.

2. A. K. Pathak and G. L. Datta: Study of grain size and

microhardness of submerged arc welded joint of AISI 1060 steel,

Sci. Technol. Weld. Join., 2005, 10, 139141.

3. K. Nishioka and K. Ichikawa: Progress in the thermomechanical

control of steel plates and their commercialization, Sci. Technol.

Adv. Mater., 2012, 13, 120.

4. H. Akasaki: Progress in pipe and tube technology and its future

prospect application and manufacturing, Nippon Steel Tech.

Rep., 2004, 90, 7581.

5. Hrivnak: Weldability of modern steel materials, ISIJ Int., 1995,

35, 11481156.

6. M. Sireesha, S. K. Albert and S. Sundaresan: Importance of filler

material chemistry for optimising weld metal mechanical properties

in modified 9Cr1Mo steel, Sci. Technol. Weld. Join., 2001, 6, 247

254.

7. G. Demofonti, G. Mannucci, H. G. Hillenbrand and D. Harris:

Suitability evaluation of X100 steel pipes for high pressure gas

transportation pipelines by full scale tests, Proc. 14th Joint

Technical Meet. on Pipeline research, Berlin, Germany, May

2003, EPRG-PRCI-APIA, 118.

8. H. G. Hillenbrand, A. Liessem, K. Biermann, C. J. Heckmann and

V. Schwinn: Development of grade X120 pipe materials for high

pressure gas transportation lines, Proc. 4th Int. Conf. on Pipeline

technology, Ostend, Belgium, May 2004, Scientific Surveys Ltd.,110.

9. H. Asahi, E. Tsuru, S. Ohkita, N. Maruyama, K. Koyama,

H. Akasaki, M. Murata, H. Miyazaki, T. Hara, H. Morimoto,

M. Sugiyama, K. Shinada, Y. Terada, N. Ayukawa, N. Doi and

T. Yoshida: Development of ultra-high-strength linepipe X120,

Nippon Steel Tech. Rep., 2004, 90, 8297.

10. B. Beidokhti, A. Dolati and A. H. Koukabi: Effects of alloying

elements and microstructure on the susceptibility of the welded

HSLA steel to hydrogen-induced cracking and sulfide stress

cracking, Mater. Sci. Eng. A, 2009, A507, 167173.

11. L. Y. Lan, C. L. Qiu, D. W. Zhao, X. H. Gao and L. X. Du: Effect

of single pass welding heat input on microstructure and hardness of

submerged arc welded high strength low carbon bainitic steel,Sci.

Technol. Weld. Join., 2012, 17, 564570.

12. F. Huang, J. Liu, Z. J. Deng, J. H. Cheng, Z. H. Cheng, Z. H. Lu

and X. G. Li: Effect of microstructure and inclusions on hydrogeninduced cracking susceptibility and hydrogen trapping efficiency of

X120 pipeline steel, Mater. Sci. Eng. A, 2010, A527, 69977001.

13. J. Ni, Z. Li, J. Huang and Y. Wu: Strengthening behavior analysis

of weld metal of laser hybrid welding for microalloyed steel,

Mater. Des., 2010, 31, 48764880.

14. J. G. Williams, C. R. Killmore, F. J. Barbaro, J. Piper and

L. Fletcher: High strength ERW linepipe manufacture in

Australia, Mater. Forum, 1996, 20, 1328.

15. M. K. Graf, H. G. Hillenbrand, C. J. Heckman and K. A.

Niederhoff: High-strength large pipe for long-distance high

pressure gas pipelines, Int. J. Offshore Polar Eng., 2004, 14, 6974.

16. V. Chaudhari, H. P. Ritzmann, G. Wellnitz, H. G. Hillenbrand and

V. Willings: German gas pipeline first to use new generation line

pipe, Oil Gas J., 1995, 93, 4047.

17. W. Deng, X. Gao, X. Qin, D. Zhao and L. Du: Microstructure

and properties of an X80 pipeline steel manufactured by untradi-

tional TMCP, Adv. Sci. Lett., 2011, 4, 10881092.

18. H. G. Hillenbrand, M. Graf and K. Christoph: Development and

production of high strength pipeline steels, Proc. Int. Symp.

Niobium 2001, Orlando, FL, USA, May 2001, Minerals, Metals

and Materials Society, 543569.

19. N. Bannenberg, A. Streielberger and V. Schwinn: New steel plates

for the oil and gas industry,Steel Res. Int., 2007, 78, 185188.

20. D. P. Fairchild, M. L. Macia, N. V. Bangaru and J. Y. Koo: Girth

welding development for X120 linepipe, Int. J. Offshore Polar

Eng., 2004, 14, 1828.

21. S. Okaguchi, H. Makino, M. Hamada, A. Yamamoto, T. Iked,

I. Takeuchi, D. P. Fairchild, M. L. Macia, S. D. Papka, J. H.

Stevens, C. W. Patersen, J. K. Koo, N. V. Bangaru and M. J.

Luton: Development and mechanical properties of X120 linepipe,

Int. J. Offshore Polar Eng., 2004, 14, 2932.

22. H. G. Hillenbrand and P. Schwaab: Determination of the

microstructure of high strength structural steels for correlation

with their mechanical properties, Mater. Sci. Eng. A, 1987, A94,

7178.

23. D. Yapp and S. A. Blackman: Recent developments in high

productivity pipeline welding, J. Braz. Soc. Mech. Sci. Eng., 2004,

26, 8997.

24. L. Barsanti, H. G. Hillenbrand, G. Mannucci, G. Demofonti and

D. Harris: Possible use of new materials for high pressure linepipe

construction: an opening on X100 grade steel, Proc. 4th Int.

Pipeline Conf., Calgary, Alta, Canada, September 2002, ASME,

287298.

25. H. G. Hillenbrand, K. A. Niederhoff, G. Hauck, E. Perteneder and

G. Wellnitz: Procedures, considerations for welding X-80 line pipe

established, Oil Gas J., 1997, 95, 4756.

26. H. G. Hillenbrand, C. J. Heckmann and K. A. Niederhoff: X80line pipe for large-diameter high strength pipelines, Proc. APIA

2002 Annual Conf., X80 Pipeline Workshop, Hobart, Tas.,

Australia, October 2002, Australian Pipeline Industry

Association, 3549.

27. A. G. Glover, D. J. Horsley and D. Dorling: High-strength steel

becomes standard on Alberta gas system,Oil Gas J., 1999, 97, 44

49.

28. Y. Komizo: Overview of recent welding technology relating to

pipeline construction, Trans. JWRI, 2008, 37, 15.

29. D. Ren, F. Xiao, P. Tian, X. Wang and B. Liao: Effects of welding

wire composition and welding process on the weld metal toughness

of submerged arc welded pipeline steel, Int. J. Miner., Metall.

Mater., 2009, 16, 6570.

30. G. E. Ridings, R. C. Thomson and G. Thewlis: Prediction of

multiwire submerged arc weld bead shape using network model-

ing, Sci. Technol. Weld. Join., 2002, 7, 265279.

31. S. Jindal, R. Chhibber and N. P. Mehta: Issues in welding of

HSLA steels, Adv. Mater. Res., 2012, 365, 4449.

32. D. J. Widgrey: Welding high strength pipelines: from laboratory to

field, Svetsaren, 2002, 57, 2225.

33. Rautaruukki, your partner in steel, gas and oil pipes,

Rautaruukki, Helsinki, Finland, 18.

34. J. C. Coiffier, J. P. Jansen, G. Peru and J. Clays: Combination of

laser beam and submerged arc process for the longitudinal welding

of large-diameter welded pipes, Proc. Int. Symp. on Safety in

application of high strength steel, Trondheim, Norway, July 1997,

Statoil Research Centre, 235252.

35. J. P. Jansen, J. C. Coiffier and V. Thillou: How to improve the

toughness at low temperature of the longitudinal weld seam of pipes

with w.t. , 12?7 mm, Proc. 3rd Int. Pipeline Technology Conf.,

Bruges, Belgium, May 2000, Technologisch Instituut, 527543.

36. V. Schwinn, W. Schuetz, P. Fluess and J. Bauer: Prospect and state

of the art of TMPC steel plate for structural and linepipeapplication, Mater. Sci. Forum, 2007, 539, 47264731.

37. S. D. Bhole, J. B. Nemade, L. Collins and C. Liu: Effect of nickel

and molybdenum additions on weld metal toughness in a

submerged arc welded HSLA line-pipe steel, J. Mater. Process.

Technol., 2006, 173, 92100.

38. D. Hejazi, A. J. Haq, N. Yazdipour, D. P. Dunne, A. Calka,

F. Barbaro and E. V. Pereloma: Effect of manganese content and

microstructure on the susceptibility of X70 pipeline steel to

hydrogen cracking, Mater. Sci. Eng. A, 2012, A551, 4049.

39. V. V. D. Mee and F. Neessen: Development of high strength

consumables form project to products. www.pdfio.com/k-739934.

html#

40. J. C. Price: Welding needs specified for X80 offshore line pipe,Oil

Gas J., 1993, 91, 95100.

41. S. Bott, L. F. G. D. Souza, J. C. G. Teixeira and P. R. Rios: High-

strength steel development for pipelines: a Brazilian perspective,

Metall. Mater. Trans. A, 2005, 36A, 443454.

42. N. Coniglio, V. Linton and E. Gamboa: Coating composition,

weld parameter and consumable conditioning effects on weld metal




13/13

composition in shielded metal arc welding, Sci. Technol. Weld.

Join., 2010, 15, 361368.

43. M. R. Krishnadev, W. L. Zhang and J. T. Bowker: Influence of

alloying and progress on the HAZ and base plate properties of

experimental HSLA-80 steels, Proc. 3rd Int. Conf. on Trends in

welding research, Gatlinburg, TN, USA, June 1992, ASM, 599603.

44. S. Y. Shin, K. Oh, K. B. Kang and S. Lee: Effects of complex

oxides on Charpy impact properties of heat affected zones of two

API X70 linepipe steels, ISIJ Int., 2009, 49, 48764880.

45. P. K. Ghosh, P. K. Singh, K. K. Vaze and H. S. Kushwaha:

Characterisation of pipe welds and HAZ in primary heat transport

system piping of pressurised heavy water reactors, Sci. Technol.

Weld. Join., 2004, 9, 200208.

46. D. Nolan, Z. Sterjovski and D. Dunner: Hardness prediction

models based on HAZ simulation for in-service welded pipeline

steels, Sci. Technol. Weld. Join., 2005, 10, 681694.

47. H. H. Wu, K. M. Wu, X. W. Lei and Y. Qian: Effect of fast

cooling process on microstructure and toughness of heat affected

zone in high strength pipeline steel X120, Sci. Technol. Weld. Join.,

2012, 17, 309313.

48. Y. Terada, A. Kiyose, N. Dol, H. Morimoto, A. Kojima,

T. Nakashima, T. Hara and M. Sugiyama: High-strength linepipes

with excellent HAZ toughness, Nippon Steel Tech. Rep., 2004, 90,

8893.

49. C. Liu, Z. B. Zhao and D. O. Northwood: Mechanical properties

of the heat-affected zone in a bainitic high strength low alloy steel,

Mater. Sci. Technol., 2002, 18, 13251328.

50. S. Aihara and K. Okamoto: Influence of local brittle zones onHAZ toughness of TMCP steels, Proc. AWS Int. Conf. on

Metallurgy, welding and qualification of microalloyed (HSLA)

steel weldments, Houston, TX, USA, November 1990, AWS, 402

426, IITT Internat, 125131.

51. K. A. Belyaev, V. A. Polyanskiy and Y. A. Yakovlev: Stresses in a

pipeline affected by hydrogen,J. Mater. Sci., 2011, 46, 715722.

52. H. Nakaugi, H. Tamehiro, K. Nishioka, Y. Ogata and Y. Kawada:

Recent development of X80 grade line pipe, Proc. Int. Conf. on

Welding technology, materials and fracture, Geesthacht,

Germany, October 1990.

53. NSC patent on Ti-oxide treated structural steels, EP 0177851.

54. Y. Terada, H. Ishikawa, R. Chijiiwa, K. Tomioka, T. Takamoto,

G. Itsubo and H. Tamehiro: High-strength titanium-oxide bearing

tether pipe for tension leg platform, Proc. 8th Int. Offshore and

Polar Engineering Conf., Montreal, Que., Canada, May 1998,

International Society of Offshore and Polar Engineers, 131137.

55. J. G. Williams, C. R. Killmore, P. D. Edwards and P. G. Kelly:Thermomechanical processing of MoNb high strength steels for

application to X70 and X80 ERW linepipe, THERMEC 97: Proc.

Int. Conf. on Thermomechanical processing of steels and other

materials, Wollongong, NSW, Australia, July 1997, TMS, 475482.

56. L. Fletcher and N. Yurioka: A holistic model of hydrogen

cracking in pipeline girth welding, Proc. Conf. on Weld metal

hydrogen cracking in pipeline girth welds, Lidcombe, NSW,

Australia, April 2000, WTIA, 12-112-14.

57. D. Nolan, D. Dunne and J. Norrish: Root pass solidification

cracking in low carbon pipeline girth welds deposited via cellulosic

manual metal arc welding,Sci. Technol. Weld. Join., 2003,8, 102112.

58. P. Kah and J. Martikainen: Current trends in welding processes

and materials: improve in effectiveness, Rev. Adv. Mater. Sci.,

2012, 30, 189200.

59. M. Krishnadev and W. Zhang: Extra low carbon welding

consumables for HSLA80 and HSLA100 steels and improvingHAZ toughness at high heat inputs, in, Montreal, , Metal welding

and applications, (ed. J. P. Boillotet al.), 5570; 1999, Metallurgy

and Materials Society of CIM Montreal.

60. A. Barbangelo: Influence of alloying elements and heat treatment

on impact toughness of chromium steel surface deposits, J. Mater.

Sci., 1990, 25, 29752984.

61. V. Shankar and J. H. Devletian: Solidification cracking in low

alloy steel welds, Sci. Technol. Weld. Join., 2005, 10, 236243.

62. J.-G. Jung, J. Kim, K.-M. Noh, K. K. Park and Y.-K. Lee: Effects

of B on microstructure and hardenability of resistance seam welded

HSLA linepipe steel, Sci. Technol. Weld. Join., 2012, 17, 7784.

63. B. Dixon: Submerged arc welding with alloy powder additions for

high strength steels, Int. J. Join. Mater., 1996, 8 , 1421.

64. M. C. Zhao, Y. Y. Shan, E. R. Xiao and K. Yang: Acicular ferrite

formation during hot plate rolling for pipeline steels, Mater. Sci.

Technol., 2003, 19, 355359.

65. Y. Peng, W. Chen and Z. Xu: Study of high toughness ferrite wirefor submerged arc welding of pipeline steel,Mater. Charact., 2001,

47, 6773.

66. B. Hwang, S. Lee, Y. M. Kim, N. J. Kim and J. Y. Yoo:

Correlation of rolling condition, microstructure and low-tempera-

ture toughness of X70 pipeline steels, Metall. Mater. Trans. A,

2005, 36A, 17931805.

67. G. M Evans and N. Bailey: Metallurgy of basic weld metal, 161

185; 1997, Cambridge, Woodhead Publishing Limited.

68. W. Wang and S. Liu: Alloying and microstructural management in

developing SMAW electrodes for HSLA-100 steels,Weld. J., 2002,

81, 132s145s.

69. S. H. Kim, C. Y. Bang and K. S. Bang: Welding metal impact

toughness of electron beam welded 9% Ni steel, J. Mater. Sci.,2001, 36, 11972000.

70. D. S. Taylor and G. M. Evans: Development of MMA electrodes

for offshore fabrication, Met. Constr., 1983, 15, 438443.

71. E. Keehan, H. O. Andren, L. Karlsson, M. Murugananth and H.

K. D. H. Bhadeshia: Microstructural and mechanical effects of

nickel and manganese on high strength steel weld metals, Proc. 6th

Int. Conf. on Trend in welding research, Pine Mountain, GA,

USA, April 2003, ASM, 695700.

72. G. M. Evans: Effect of molybdenum on microstructure and

properties of CMn all-weld metal deposits, Join. Mater., 1988, 1,

239246.

73. M. Thuvander, L. Karisson and B. Munir: Controlling segregation

in Nickel-base weld metals by balanced alloying, Stainless Steel

World, 2004, 16, 5257.

74. D. D. Crockett, J. A Rhone, R. F. Young and D. C. Noernberg:

Design considerations for submerged arc consumables intended for

the manufacture of line pipe, Pipeline Technol., 1995, 1, 151162.

75. J. P. Snyder and A. W. Pense: Effects of titanium on submerged

arc weld metal, Weld. J., 1982, 61, 201-s211-s.

76. J. F. Dos Santos, V. R. Dos Santos and J. C. Jorge: Properties of a

ferritic metal cored wire weld metal deposited in the pressure range

from 51 bar to 110 bar, Proc. 6th Int. Offshore and Polar

Engineering Conf., Los Angeles, CA, USA, May 1996, ASM, 141

146.

77. N. Pradhan, N. Banerjee, B. B. Reddy, S. K. Sahay, D. S. Basu, P.

K. Bhor, S. Das and S. Bhattyacharya: Control of defects during

continuous casting of line pipe (API) quality steels, Scand. J.

Metall., 2005, 34, 23322340.

78. B. Tanguy, T. T. Luu, G. Perrin, A. Pineau and J. Besson: Plastic

and damage behavior of a high strength X100 pipeline steel:

experiments and modeling, Int. J. Press. Vessels Pip., 2008, 85,

322335.

79. L. Barsanti, G. Pozzoli and H. G. Hillendbrand: Production and

field weldability evaluation of X100 line pipe, Proc. 13th Joint

Meet. PRCI-EPRG, New Orleans, LA, USA, May 2001, PRCI-

EPRG, 7.

80. H. K. D. H. Bhadeshia, L.-E. Svensson and B. Gretoft: Prediction

of the microstructure of submerged-arc linepipe weld, Proc. 3rd

Int. Conf. on Welding and performance of pipeline, Abington,

UK, November 1986, The Welding Institute, 17-117-10.

81. C. Ouchi: Development of steel plates by intensive use of TMCP

and direct quenching processes, ISIJ Int., 2001, 41, 542553.

82. Y. Li, D. N. Crowther, M. J. W. Green, P. S. Mitchell and T. N.

Baker: Effect of vanadium and niobium on the properties and

microstructure of the intercritically reheated coarse grained heat

affected zone in low carbon microalloyed steels, ISIJ Int., 2001, 41,

4655.

83. H. G. Hillenbrand, E. Amoris, K. A. Niederhoff, C. Perdrix,

A. Streisselberger and U. Zeislmair: Manufacturability of linepipein grades up to X100 from TM processed plate, Proc. Pipeline

Technology Conf., Oostende, Belgium, September 1995. TI-K VIV,

273-286.

84. H. G. Hillenbrand, K. A. Niederhoff, E. Amoris, C. Perdrix, A.

Streisselberger and U. Zeislmair: Development of linepipe in grades

up to X100, Proc. Biennial Joint Technical Meet. on Linepipe

research, Washington, DC, USA, April 1997, EPRG/PRC, 6.

85. J. Ni, Z. Li, J. Huang and Y. Wu: Strengthening behavior analysis

of weld metal of laser hybrid welding for microalloyed steel,

Mater. Des., 2010, 31, 48764880.

86. L. Quintino, R. M. Miranda, S. Williams and C. J. Kong: Gas

shielding in fiber laser welding of high strength pipeline steel, Sci.

Technol. Weld. Join., 2011, 6, 399404.

87. K. Faes, A. Dhooge, P. Baets and P. Afschrift: Influence of

deceleration phase on properties of friction welded pipelines using

intermediate ring, Sci. Technol. Weld. Join., 2008, 10, 136145.88. H. K. D. Bhadeshia and T. DebRoy: Critical assessment: friction

stir welding of steels,Sci. Technol. Weld. Join., 2009, 14, 193196.


Documents

Challenges and developments in pipeline weldability and mechanical properties.pdf