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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