PRODUCTION OF HELICAL TWO STEP PIPE – USE OF MICROALLOYING ELEMENTS TO IMPROVE STRENGTH FOR GRADES UP TO X70 WITH SOUR SERVICE RESISTANCE Franz Martin Knoop Salzgitter Mannesmann Grossrohr GmbH Djordje Mirkovic, Volker Flaxa Djordje Mirkovic, Volker Flaxa Salzgitter Mannesmann Forschung GmbH
Introduction Contents Contents • Introduction • History • Development programme • Manufacturing issues relevant for sour service resistance • steel production • steel production • hot rolling • pipe production • Mechanical and corrosion test results • Summary and outlook 2. Dr. Knoop July 2013, London
Introduction Salzgitter's research and development activities for HSAW-pipe 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 • 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 3. Dr. Knoop July 2013, London
History Failures of helical welded pipe p p 4. Dr. Knoop July 2013, London
History Cooking recipe for sour service material g p Malcolm Gray „Full Scale Testing of Linepipe for Severe H 2 S Service“; NACE Canadian Regional Western Conference, A Anchorage, Alaska, February 19—22. 1996 h Al k F b 19 22 1996 5. Dr. Knoop July 2013, London
Development programme Targeted pipe properties R&D and commercial projects g p p p p p j SSC HIC (base + weld) NACE DWTT DWTT Grade / Grade / YS YS TS TS CVN CVN w.th. w th Quantity Quantity OD OD (base+weld) (base+weld) TM248 TM248 Project (% shear (t) (mm) (4 point (J/cm 2 ) Standard (mm) (MPa) (MPa) area) bend.) CAR CLR CTR CSR X60MS X60MS ≥ 250; 0 ° C ≥ 250; 0 ° C 85 @ at 85 @ at 80% SMYS 80% SMYS SZ X60 200 API 5L/ISO3183 14.0 1067 ≥ 420 ≥ 520 ≤ 5 - (base) -40 ° C No crack X65MS ≥ 300; 0 ° C 85 @ at 80% SMYS SZ X65 SZ X65 200 200 API 5L/ISO3183 14.1 14 1 813 813 ≥ 450 ≥ 450 ≥ 535 ≥ 535 ≤ 5 ≤ 5 - (base) -40 ° C No crack X70MS ≥ 300; 0 ° C 85 @ at 80% SMYS SZ X70 200 API 5L/ISO3183 16.0 1016 ≥ 485 ≥ 570 ≤ 5 - (base) ( ) -40 ° C No crack 762 Grade GR241 ≥ 50; not 80% AYS 1000 1000 CSA_Z245.1-07 15.9 15 9 and and ≥ 241 ≥ 241 ≥ 414 ≥ 414 - ≤ 15 ≤ 15 ≤ 5 ≤ 5 ≤ 2 ≤ 2 0 ° C required No crack 241 914 Grade GR448 ≥ 50; 60 @ at not 800 CSA Z245.1-07 13.7 1372 ≥ 448 ≥ 531 - ≤ 15 ≤ 5 ≤ 2 CSA_Z245.1 07 -18 ° C 18 C -18 ° C 18 C required required 448 448 (mechanical properties in hoop direction) 6. Dr. Knoop July 2013, London
Development programme Chemical composition for R&D and commercial projects p p j C Si Mn P S Al Cu + Cr + Ni Mo Nb CEV (IIW) CEV (Pcm) Project Purpose wt % wt.% wt.% wt % wt % wt.% ppmw ppmw ppmw ppmw wt % wt.% wt.% wt % wt % wt.% 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 Grade Grade Commercial 0.041 0.23 1.14 95 4 0.04 0.23 0.004 0.02 0.25 0.11 241 Grade Commercial 0.060 0.32 1.55 150 8 0.04 0.36 0.005 0.05 0.35 0.16 448 7. Dr. Knoop July 2013, London
Manufacturing issues relevant for sour service resistance Production: Metallurgical process up to slab casting Production: Metallurgical process up to slab casting 1 2 1. Blast furnace 1. Blast furnace 3 3 2. Hot-metal mixer 4 3. Desulphurization facility p y 4. BOF shop 5. Secondary metallurgy facilities y gy 5 6. Continuous slab caster High automatization level including close integration of steel plant control and supervision system with technical planning 6 6 slab thickness: 250 mm 8. Dr. Knoop July 2013, London
Manufacturing issues relevant for sour service resistance Steel plant: quality issues and measures Steel plant: quality issues and measures Consistently applied Salzgitter’s measures to attain them Desired quality issues Continuous composition control and adjustment Narrow steel composition tolerances Secondary metallurgy and appropriate casting procedure High steel cleanliness • lowering non-metal inclusions • lowering non-metal inclusions • gas stirring + caster with vertical section ti i t ith ti l ti ( low [O] total ) • Ca – treatment for inclusion shape control • inclusion shape and size control • vacuum degassing vacuum degassing • low tramp element steel contents ( especially P and S ) • low H content High slab centerline quality Soft reduction at continuous slab caster • avoiding centerline segregation (C, Mn, P) 9. Dr. Knoop July 2013, London
Manufacturing issues relevant for sour service resistance Steel cleanliness: non-metallic inclusions as HIC initiating sites Steel cleanliness: non-metallic inclusions as HIC initiating sites Example: insufficient ladle rinsing and unsuitable degassing top view of US scan top view of US scan Rolling direction side view of US scan HIC fracture surface consistent application of LM refining measures to remove inclusions from the steel melt, such as: Al � bottom stirring with N 2 and Ar � use of tap hole slide gates for minimized slag carry over f t h l lid t f i i i d l O � optimized Ca-treatment with Ca-wire injection; high Ca recovery � optimized ladle rinsing procedure � use of argon shielded tundish for optimized flow pattern / inclusion removal � use of argon shielded tundish for optimized flow pattern / inclusion removal HIC cracks primarily initiated at Al- � application of caster with 2.6 m long vertical section instead of bow casters O inclusions and are traced back to slab upper half 10. Dr. Knoop July 2013, London
Manufacturing issues relevant for sour service resistance Slab centerline quality: segregation effects Slab centerline quality: segregation effects Example: casting without dynamic soft reduction top view of US scan HIC crack at strip mid thickness Martensite side view of US scan consistent slab centerline quality optimization by application of Dynamic Soft Reduction consistent slab centerline quality optimization by application of Dynamic Soft Reduction � dynamic segment regulation (soft reduction), particularly at the point of final solidification 11. Dr. Knoop July 2013, London
Manufacturing issues relevant for sour service resistance Production: layout of Salzgitter’s hot strip mill Production: layout of Salzgitter s hot strip mill Reheating furnaces (4) Slab sizing Slab sizing press press Roughing mill R Roughing mill R hi hi ill ill Descaler Finishing train Crop shear Crop shear C C h h descaler Run-out table: Laminar cooling unit Slab thickness = 250 mm St i Strip thickness thi k = 1.5 - 25 mm 1 5 25 Strip width = 900 - 2.000 mm Strip length = 100 - 2.000 m 3 Down coilers One of the world’s most modern high performance hot strip mills 12. Dr. Knoop July 2013, London
Manufacturing issues relevant for sour service resistance Hot strip mill: quality issues and measures Hot strip mill: quality issues and measures Desired quality issues Consistently applied Salzgitter’s measures to attain them Narrow strip dimension tolerances Continuous control and adjustment of rolling parameters • highly planar • lowering of residual stresses in the ness µm] strip profile strip profile pipe bodies and welds pipe bodies and welds Strip thickn variation [µ Thickness ± 60 µm High strip surface quality • prevention of surface defects e.g. slivers, roll-ins Strip width [mm] Homogeneous strip temperature Precise temperature monitoring from furnace to coiler distribution distribution • highly desirable acicular ferrite microstructure along the • prevention of γ→α transformation strip length and across the strip width during the finishing • Precise strip temperature prediction and control p p p • strip microstructure adjustment based on run-out table simulation without undesirable phases 13. Dr. Knoop July 2013, London
Manufacturing issues relevant for sour service resistance Hot strip mill: strip profile and temperature distribution Hot strip mill: strip profile and temperature distribution Example: two-phase finish rolling / undesirable phases at strip edge area Temperature scan after finishing train Temperature scan after finishing train Rolling direction iation Temp. dev undercooled strip edges strongly elongated α - grains, Martensite also observed precise temperature monitoring and control in every process phase and section � to obtain fine-grain structure across the strip width to obtain fine grain structure across the strip width � indispensable to prevent γ→α transformation already during the finishing � to prevent undesirable phases, such as martensite Rolling direction properly cooled strip edges NO HIC cracks observed ! 14. Dr. Knoop July 2013, London
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