PRODUCTION OF HELICAL TWO STEP PIPE – USE OF ...

PRODUCTION OF HELICAL TWO STEP PIPE – USE OF MICROALLOYINGELEMENTS TO IMPROVE STRENGTH FOR GRADES UP TO X70 WITH

SOUR SERVICE RESISTANCE

Franz Martin Knoop Salzgitter Mannesmann Grossrohr GmbH

Djordje Mirkovic, Volker FlaxaDjordje Mirkovic, Volker FlaxaSalzgitter Mannesmann Forschung GmbH

Introduction

Contents

• Introduction• History

Contents

• Development programme• Manufacturing issues relevant for sour service resistance

• steel production• steel production• hot rolling• pipe production

Dr. Knoop July 2013, London 2.

• Mechanical and corrosion test results• Summary and outlook

Introduction

Salzgitter's research and development activities for HSAW-pipe

• extending pipe/coil wall thickness up to 25.4 mm for grades X70 and X80• steel grades with high strength and excellent low temperature toughness

Salzgitter s research and development activities for HSAW pipe

• sour service resistant steel and pipe• enhancement of collapse resistance for shallow water off-shore applications• use of FEM for simulation of pipe forming and welding• use of FEM for simulation of pipe forming and welding• reducing residual stresses in pipe and weld seam• improving the strain capacity of pipes for strain based design requirements


• reduction of geometrical tolerances on steel and pipe

History

Failures of helical welded pipe p p


History

Cooking recipe for sour service material g p

Malcolm Gray „Full Scale Testing of Linepipe for Severe H2S Service“; NACE Canadian Regional Western Conference, A h Al k F b 19 22 1996Anchorage, Alaska, February 19—22. 1996


Development programme

Targeted pipe properties R&D and commercial projects

Quantity Grade / w th OD YS TS CVN DWTTHIC (base + weld) NACE

TM248SSC

(base+weld)

g p p p p p j

Project Quantity(t)

Grade /

Standardw.th.(mm)

OD(mm)

YS

(MPa)

TS

(MPa)

CVN(J/cm2)

DWTT(% shear

area)TM248 (base+weld)

(4 point bend.)CAR CLR CTR CSR

X60MS ≥ 250; 0°C 85 @ at 80% SMYSSZ X60 200 X60MSAPI 5L/ISO3183 14.0 1067 ≥ 420 ≥ 520 ≥ 250; 0°C

(base)85 @ at -40°C ≤ 5 - 80% SMYS

No crack

SZ X65 200 X65MS 14 1 813 ≥ 450 ≥ 535 ≥ 300; 0°C 85 @ at ≤ 5 - 80% SMYSSZ X65 200 API 5L/ISO3183 14.1 813 ≥ 450 ≥ 535 (base) -40°C ≤ 5 No crack

SZ X70 200 X70MSAPI 5L/ISO3183 16.0 1016 ≥ 485 ≥ 570 ≥ 300; 0°C

(base)85 @ at -40°C ≤ 5 - 80% SMYS

No crack( )

Grade1000 GR241 15 9

762 and ≥ 241 ≥ 414 ≥ 50; not ≤ 15 ≤ 5 ≤ 2 80% AYS

2411000 CSA_Z245.1-07 15.9 and

914≥ 241 ≥ 414 0°C required - ≤ 15 ≤ 5 ≤ 2 No crack

Grade

448800 GR448

CSA Z245.1-07 13.7 1372 ≥ 448 ≥ 531 ≥ 50; -18°C

60 @ at -18°C - ≤ 15 ≤ 5 ≤ 2 not

required


448 CSA_Z245.1 07 18 C 18 C required

(mechanical properties in hoop direction)

Development programme

Chemical composition for R&D and commercial projects

Project Purpose Cwt %

Siwt %

Mnwt %

Pppmw

Sppmw

Alwt %

Cu + Cr + Niwt %

Mowt %

Nbwt %

CEV (IIW)wt %

CEV (Pcm)wt %

p p j

wt.% wt.% wt.% ppmw ppmw wt.% wt.% wt.% wt.% wt.% wt.%

SZ X60 R&D 0.035 0.30 1.46 70 5 0.04 0.44 0.07 0.05 0.33 0.14

SZ X65 R&D 0.038 0.28 1.37 80 7 0.04 0.86 0.04 0.05 0.36 0.14

SZ X70 R&D 0.038 0.33 1.33 90 6 0.04 0.84 0.32 0.05 0.43 0.15

GradeGrade 241 Commercial 0.041 0.23 1.14 95 4 0.04 0.23 0.004 0.02 0.25 0.11

Grade448 Commercial 0.060 0.32 1.55 150 8 0.04 0.36 0.005 0.05 0.35 0.16


Production: Metallurgical process up to slab casting

Manufacturing issues relevant for sour service resistance

Production: Metallurgical process up to slab casting

12

31. Blast furnace 34

1. Blast furnace

2. Hot-metal mixer

3. Desulphurization facility

5

p y

4. BOF shop

5. Secondary metallurgy facilities y gy

6. Continuous slab caster

6

High automatization level including close integration of steel plant control and supervision systemwith technical planning 6


slab thickness: 250 mm

Steel plant: quality issues and measures


Steel plant: quality issues and measures

Desired quality issues Consistently applied Salzgitter’s measures to attain them

Narrow steel composition tolerances

High steel cleanliness

• lowering non-metal inclusions

Continuous composition control and adjustment

Secondary metallurgy and appropriate casting procedure

ti i t ith ti l ti• lowering non-metal inclusions

( low [O] total)

• inclusion shape and size control

• gas stirring + caster with vertical section

• Ca – treatment for inclusion shape control

• vacuum degassing• low tramp element steel contents

( especially P and S )

• low H content

vacuum degassing

High slab centerline quality

• avoiding centerline segregation

Soft reduction at continuous slab caster

(C, Mn, P)


Steel cleanliness: non-metallic inclusions as HIC initiating sites


Example: insufficient ladle rinsing and unsuitable degassing

Steel cleanliness: non-metallic inclusions as HIC initiating sites

top view of US scan

Rolling direction

top view of US scan

side view of US scan

HIC fracturesurface

Al

consistent application of LM refining measures to remove inclusionsfrom the steel melt, such as:

bottom stirring with N2 and Arf t h l lid t f i i i d l

Ouse of tap hole slide gates for minimized slag carry overoptimized Ca-treatment with Ca-wire injection; high Ca recoveryoptimized ladle rinsing procedureuse of argon shielded tundish for optimized flow pattern / inclusion removal


HIC cracks primarily initiated at Al-O inclusions and are traced back to slab upper half

use of argon shielded tundish for optimized flow pattern / inclusion removalapplication of caster with 2.6 m long vertical section instead of bow casters

Slab centerline quality: segregation effects


Slab centerline quality: segregation effects

Example: casting without dynamic soft reduction

MartensiteHIC crack at strip mid thickness

top view of US scan

side view of US scan

consistent slab centerline quality optimization by application of Dynamic Soft Reductionconsistent slab centerline quality optimization by application of Dynamic Soft Reductiondynamic segment regulation (soft reduction), particularly at the point of final solidification


Production: layout of Salzgitter’s hot strip mill


Production: layout of Salzgitter s hot strip mill

Reheating furnaces (4)

Slab sizingpressSlab sizingpress

R hi illR hi illDescaler

Roughing millRoughing mill

C hC h

Finishing train

Crop shearCrop shearRun-out table:Laminar cooling unit

descaler

Slab thickness = 250 mmSt i thi k 1 5 25Strip thickness = 1.5 - 25 mmStrip width = 900 - 2.000 mmStrip length = 100 - 2.000 m

3 Down coilers


One of the world’s most modern high performance hot strip mills

Hot strip mill: quality issues and measures


Consistently applied Salzgitter’s measures to attain them

Hot strip mill: quality issues and measures

Desired quality issues

Continuous control and adjustment of rolling parameters

• highly planar

strip profile ness

µm]

Narrow strip dimension tolerances

• lowering of residual stresses in the

pipe bodies and welds strip profile

Stri

p th

ickn

vari

atio

n[µpipe bodies and welds

High strip surface quality

• prevention of surface defects e.g.

Thickness ± 60 µm

Precise temperature monitoring from furnace to coiler

Strip width [mm]slivers, roll-ins

Homogeneous strip temperature

distribution• highly desirable acicular ferrite microstructure along the

strip length and across the strip width

• Precise strip temperature prediction and control

distribution

• prevention of γ→α transformation

during the finishing p p p

based on run-out table simulation• strip microstructure adjustment

without undesirable phases


Hot strip mill: strip profile and temperature distribution


Hot strip mill: strip profile and temperature distribution

Temperature scan after finishing train

Example: two-phase finish rolling / undesirable phases at strip edge area

Rolling direction

Temperature scan after finishing train

iatio

n

undercooled strip edges

Tem

p. d

ev

strongly elongated α-grains,Martensite also observed

precise temperature monitoring and control in every process phase and sectionto obtain fine-grain structure across the strip widthto obtain fine grain structure across the strip widthindispensable to prevent γ→α transformation already during the finishingto prevent undesirable phases, such as martensite

Rolling direction


properly cooled strip edgesNO HIC cracks observed !

Pipe production: Helical seam Two Step (HTS) technology


Pipe production: Helical seam Two Step (HTS) technology

B = 1200 - 1500 mmα = 20 - 40°D = f (B, α) ( , α)D = 610 - 1676 mm

Second step: inside and outside

Fi i f i i h i k ldi

Second step: inside and outside submerged arc welding


First step: pipe forming with continuous tack welding

Pipe mill: quality issues and measures


Consistently applied SZ’ measures to attain them

Pipe mill: quality issues and measures

Desired quality issues

Quality controls and R&D

• use of FEM simulation methods

• consistent quality controls and recording of forming

controlled cold working

• during coil straightening and pipe

forming consistent quality controls and recording of forming

parameters

• continuous control of pipe geometry using a patented in-situ

l di t t l

forming

• minimized springback

• optimized pre-bending of coil edges to

id ki d d i l l laser diameter control

• peaking below 0.8mm

avoid peaking and reducing local

stress which might affect sour gas

resistivity at weld area (SOHIC)

separating forming and welding by using the HTS –processno forming stresses during welding

Material selection and welding process controls

• qualification and careful selection of coil material and

welding consumables

maximum hardness of 248 HV


g

• continuous recording and documentation of all essential

welding parameters

Pipe mill: reduction of residual stresses


Pipe mill: reduction of residual stresses

640

720

800

240

320

400

480

560

Stre

ss

, MPa

0°

0

80

160

240

0 2,5 5 7,5 10 12,5 15 17,5 20

Strain %

030°45°60°90°

Strain , %

2 0

2.5

3.0

[-]

Maximum value over wall thicknessInner surfaceOuter surface

Stress strain curves at different angles Simulation of different forming strategies

0.0

0.5

1.0

1.5

2.0

oop

stre

ss h

/ h

(NF)

2 5

-2.0

-1.5

-1.0

-0.5

Rel

ativ

e re

sidu

al h

o

negative spring-backpositive spring-back


-3.0

-2.5

1.8E-03 1.9E-03 2.0E-03 2.1E-03 2.2E-03 2.3E-03 2.4E-03 2.5E-03 2.6E-03 2.7E-03

Curvature under load [1/mm]

Relative residual hoop stress as function of the curvature under load

R&D sour service trials: SZ X65Mechanical and corrosion test results

Coil

Pipe

Type ofsamples & direction

Rt0.5

[MPa]

Rm

[MPa]Rt0.5/Rm

ADIN[%]

AAPI[%]

DWTT @ [% shear area];

- 60°C

CVN @[J/cm2]- 80°Cp direction [ ] [ ] - 60 C - 80 C

Strip 30° [rect.] 528 581 0.91 24 39 93 382

Pipe hoop [rect.] 483 575 0.84 24 38 75 379

HIC 24 HIC i t t d

Targeted API X65 grade reached reliably; excellent low temperature toughness

HIC: 24 HIC specimens were tested

Result: mean CAR value ~0.1 %

SSC (4-point-bending test): 9 specimens were tested at 85% of SMYS (383 MPa)

R lt SSC k b dResult: no SSC cracks were observed

Full ring test: 72% of SMYS (323 MPa) for 720h in


NACE TM0177 solution A Result: No indications above threshold were found by ultrasonic examinations prior to and after the test

Very good sour gas resistivity

R&D sour service trials: SZ X70Mechanical and corrosion test results

680

700

720

Rm

90

100

%]

580

600

620

640

660

API Samples DIN Samples

Rt0.5, Rm [

MP

a]

70

80

90

DWTT transition

Coil 686056actu

re a

rea

[%

500

520

540

560

580

Coil centerRectangular samplesHoop direction

Rt0

.5

40

50

60Coil 686056 Coil 686057 Coil 686059

She

ar fr

a

Test temperature: -50°C100% shear area

6860

56

6860

57

6860

58

6860

59

6860

60

500

Coil

-60 -50 -40 -30 -2040

Test temperature [°C]

Targeted API X70 grade reached reliably; excellent low temperature toughness

HIC: 112 HIC specimens (base and weld) tested

Result: mean CAR value of 2.82 % (max. 13.1 %);mean average CAR value base material: 3.62%, mean CAR value for weld specimens: 1.16%

V d i ti it f API X70 d


Very good sour gas resistivity, even for API X70 grade

Commercial projects: GR448Mechanical and corrosion test results

p j

620

640

660 Rt0.5

Rm

A

38

39

40 400

540

560

580

600

620

A [%

]

5 , R

m [

MP

a]

34

35

36

37

38

350

375

VN

aK [J

/cm

2 ]

209

188

198

203

460

480

500

520

DIN rect. sample; hoop direction

Coil

Rt0

.

30

31

32

3341

88

4198

4203

4209

300

325

Mean valueTest temperature -18°C

CV

360 357 383 344

CoilLOM Microstructure ¼ thick ½ width

Targeted GR448 grade reached reliably

9574

/ 984

20

9571

/ 984

18

9572

/ 984

19

9573

/ 984

20Coil

Heat 9571

/ 984

18

9572

/ 984

19

9573

/ 984

20

9574

/ 984

20

Heat

CoilLOM Microstructure ¼ thick., ½ width50 % Ferrite; 40 % Bainite; 10 % Pearlite

HIC: 1 set for both base material and weld per heat were tested. Result: mean CLR and CSR values of all samples 3.5 , 0.7 and 0.3 %, respectively

G d i ti it ! (d it f l ti l hi h C d M t t )

PipeDWTT [% shear area]; average of 2 specimens

0°C °C 10°C 20°C 40°C 60°C E ll l DWTT l

Good sour gas resistivity! (despite of relatively high C and Mn contents)


0°C -5°C -10°C -20°C -40°C -60°C

100 100 100 100 100 93100 100 100 100 95 83

Excellent low temperature DWTT results

SummarySummary and outlook

y

Large diameter helical line pipe for sour service up to X70 has been successfully d l d d d ddeveloped and produced

Critical parameters in steel production and hot rolling have been shown and their influence has been explained by means of examples.

Well balanced microalloying and steel cleanness has been achieved in industrial trials and commercial projects

All relevant process parameters during continuous casting and hot rolling wereAll relevant process parameters during continuous casting and hot rolling were effectively controlled and adjusted to the used chemistry an microalloying

All necessary measures for the improvement of HIC and SSC resistance have been optimized and managed during spiral pipe forming and weldingoptimized and managed during spiral pipe forming and welding

Excellent mechanical properties (incl. low temperature toughness) and corrosion resistance have been achieved


OutlookSummary and outlook

Next milestones are defined on basis of actual and future market needs

Growing interest for sour service resistant line pipe with heavy wall thickness up to 1’’ and grades up to X70 is expected

Technical solutions require further developmentq p

- on chemical composition of the base material,

- on welding consumables

- on further production parameters at each stage of production

- and on suitable equipment at each stage of production

Pi ith ll di t i th f 26’’ d hi h ll thi k (hi h ldPipes with smaller diameters in the range of 26’’ and higher wall thickness (high cold forming degree) need further development


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PRODUCTION OF HELICAL TWO STEP PIPE – USE OF ...

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