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Presentation on
LINEPIPE STEEL USED IN PETROLEUM INDUSTRIES
SUBMITTED BY-
B. TECH. IVTH YEARMETALLURGY AND MATERIALS ENGINEERINGNIFFT, RANCHI
UNDER GUIDANCE OF-
DR. GHANSHYAM DASASSOCIATE PROFESSORMATERIALS AND METALLURGICAL DEPT.NIFFT, RANCHI
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CONTENTS
INTRODUCTION
CHEMICAL COMPOSITION
ROLE OF ALLOYING ELEMENTS
MICROSTRUCTURE AND MECHANICAL PROPERTIES
PRODUCTION ROUTES
CONCLUSIONS
REFERENCES
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HISTORY OF LINEPIPE STEEL
REQUISITES A LINEPIPE STEEL SHOULD FOLLOW
The birth of the linepipe started from requirement of energy and fuel transportation across distant miles.
Linepipe steel manufacturing started from steelmaking, continuous casting and hot rolling in the form of coil or plate and further down to pipe rolling and welding
The linepipe steel should have larger diameter and high pressure withstanding capabilities.
For efficient transportation the linepipe steel must possess higher strength and toughness, good corrosion resistance, good weldability, as well as good resistance to HIC.
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CHEMICAL COMPOSITION OF LINEPIPE STEELS The chemical composition of High strength Linepipe steels may
vary for different product thicknesses to meet particular mechanical property requirements.
Usually, they have a manganese (Mn) content up to 2.0 wt% in combination with very low carbon content (< 0.10 wt% C) and also minor additions of alloying elements such as niobium (Nb), vanadium (V), titanium (Ti), molybdenum (Mo) and boron (B).
The main function of the alloying additions is strengthening of ferrite through the following mechanisms: grain refinement, solid solution and precipitation hardening.
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Grade C Si Mn P S Nb Ti Others Ceq
X80 0.06 0.26 1.81 0.005 0.002 0.04 0.01 Ni, Mo, Mg 0.41
X100 0.03 0.18 1.84 0.005 0.001 0.04 0.01 Ni, Cu, Cr, Mo 0.60
Typical chemical composition of Pipeline materials (mass%).
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ROLE OF ALLOYING ELEMENTS
C – Matrix strengthening
Mo – Increases hardenability
Mn – Decreases DBTT
Ti – Fixes the free Ni
V – Precipitation hardening
Nb – Improves strength and toughness by grain refinement
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MICROSTRUCTURE – 1. accicular ferrite matrix (ϒ – phase rolling)
2. Ferrite, Bainite and Pearlite (ϒ+α–phase rolling)
Yield strength – 550-600 MPa
Good low temperature toughness
MICROSTRUCTURE AND MECHANICAL PROPERTIES OF X80
ϒ+α – Phase rolled microstructure
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MICROSTRUCTURE AND MECHANICAL PROPERTIES OF X100
MICROSTRUCTURE – Very fine Bainitic ferrite as matrix
M/A (Martensite/Austenite) as second phase
Yield strength – 740MPa (achieved only
at pipe forming stage)
TEM image of X100 steel
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CONVENTIONAL WAY FOR PRODUCTION OF LINEPIPE STEEL PLATE
STEEL MELT
(From oxygen converters)
CONTINUOUS SLAB CASTING (200mm thickness)
PLATE ROLLING
(ϒ+α or ϒ phase rolling) (15mm thickness)
ACCELERATED COOLING
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NEED FOR ENERGY AND COSTEFFICIENT PRODUCTION TECHNIQUE
1. Ever increasing demand of energy world-wide.
2. Cost of gas and oil minimisation.
3. Larger distance transportation requirement.
4. For more diversified applications.
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MODIFICATIONS DURING PRODUCTION FOR ENERGY AND COST EFFICIENCY
1. Change of Microstructure
2. Thin Slab Casting and Rolling
3. Continuous Strip Production(CSP)
4. Thermomechanical Controlled Processing(TMCP)
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THIN SLAB CASTING AND ROLLING
Schematic of Compact Steel Production process
To reduce number of process steps.To get faster production( 6m/min. for 50-55 mm thickness)
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Replaced continuous slab casting because of
improvements in1. Design of mould
2. Mould oscillations
3. Electromagnetic breakers
4. Use of high pressure and edger
5. Water spray cooling
Advantages
1. Reduction in capital cost, manpower, floor space, fuelconsumption
2. Improvement in Yield value
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METALLURGICAL ADVANTAGES OF Thin Slab Casting and Rolling
No dendritic structure and greater homogeneity
Isotropic properties(toughness and Bendability)
Premature precipitation is eliminated
Heavy deformation helps in refining coarse Austenite grains
Accelerated cooling further refines Ferritic grains
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CONTINUOUS STRIP PRODUCTION(CSP)
Replaced continuous slab casting
Even more energy and cost efficient
High casting speeds are required
ADVANTAGES OF CSP1. Less capital expenditure(40% lower than TSCR)
2. Energy cost decrease
3. Can be used in small firms
4. Possibility for development of new technology
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CONCLUSIONS
For efficient transportation, the linepipe steel must possess high yield strength,high toughness, high corrosion resistance and good weldability as well as highresistance to HYDROGEN INDUCED CRACKING (HIC).
Chemical composition of linepipe steel is designed so as to produce highstrength, toughness, good weldability, low DBTT.
The main strengthening effect in linepipe steel (X80-X100) is coming fromprecipitation hardening and grain refinement.
ϒ single phase and ϒ+α rolling is found as an effective way for increasingstrength in X80 steel plate. Now-a-days Bainite, Martensite matrix is replacingthe conventional ferrite matrix.
Continuous strip production (CSP) technology has emerged as a newadvancement in manufacture of linepipe steel(x80-x100). It is also energy andcost efficient.
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REFERENCES[1] Kalwa, G., Kaup, K., "Steels for Linepipe", Steel A Handbook for Material Research and Engineering, Volume 2, Springer-Verlag, Verlag Staheisen mbH.993
[2] Llewllyn, D.T., Hudd, R.C.,1992, "Steels: Metallurgy & Applications", p 187, Butterworth - Heinemann.
[3] K. Hulka, J.M. Gray and F. Heisterkamp, “High Temperature Thermomechanical
Processing of Pipe Steel – Technical Basis Production Experience”, Pipeline Technology, Vol.2 (2000), pp. 291-396.
[4] Williams, J. G., Advances in Steels for High Strength ERW Pipeline Application in Australia, Materials Forum Volume 31, 1–10, 2007.
[5] Y. Terada, A. Kiyose, A. Doi and H. Morimoto, “High-strength Linepipes with Excellent HAZ Toughness”, Nippon Steel Technical Report No. 90, JULY 2004.
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CONTINUED…
[6] API RP 1111 (1999), Design, Construction, Operation, and Maintenance of Offshore Hydrocarbon Pipelines (Limit State Design), Third Edition, American Petroleum Institute.
[7] S.H. Hashemi, I.C. Howard, J.R. Yates and R.M. Andrews, “Micro-mechanical Damage Modelling of Notched Bar Testing on Modern Pipeline Steel”, Proceedings of the 15th European Conference of Fracture, August 11-13 (2004), Stockholm, Sweden.
[8] Alberto Moreira Jorge Junior, Luiz Henrique Guedes, Oscar Balancing, Journal of Materials Research and Technology 1 (2012) p. 141.
[9] R. D. K. Misra, G. C. Weatherly, J. E. Hartmann and A. Boucek, Material Science and Technology, 17 (2001) p. 1119.
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THANK YOU
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