Recent Developments of Oil and Gas Transmission Pipeline Steels: Microstructure, Mechanical Properties and Sour Gas Resistance

2008 ◽  
Author(s):  
Navid Pourkia ◽  
Morteza Abedini
Keyword(s):  
Mechanical Properties ◽  
Acicular Ferrite ◽  
Oil And Gas ◽  
High Strength ◽  
Accelerated Cooling ◽  
Low Carbon ◽  
Pipeline Steels ◽  
Bainitic Microstructure ◽  
Transmission Pipeline ◽  
Sour Gas

In modern oil and gas transmission pipeline steels technology, a suitable microstructure is an important factor for improvement of strength, toughness and sour gas resistance. Therefore, thermo-mechanically controlled rolling processes have been developed and their microstructures have been changed from ferrite-pearlite to acicular ferrite. Moreover in the recent years extensive attempts have been made to improve pipeline steels properties, which include: i) Ultra fine-grained steels, which are produced by optimized usage of dynamic recrystallization and strain-induced transformation with about 1μm equiaxed ferrite grain size. ii) Ultra low carbon steels with less than 0.025 wt% carbon and significant amount of Mo and Nb microalloying elements. iii) Ultra fine acicular ferrite steels, which are produced by application of more accurate controlled thermo mechanical processes and accelerated cooling. iv) Ultra high strength X100 and X120 grade steels, which are produced by thermo-mechanically controlled processes and heavy accelerated cooling. The former is without special technological changes and mainly consist of low carbon upper bainitic microstructure while the latter needs more technological developments with very little amount of boron and mainly consists of lower bainitic microstructure. This paper gives an overview of these new pipeline steels in viewpoint of microstructure, mechanical properties and sour gas resistance. The studies show that ultra fine acicular ferrite is the best alternative microstructure for nowadays ordinary pipeline steels, but because of numerous advantages of ultra high strength pipelines steels which finally reduce the cost of pipeline projects, the trend of the investigations is focused on further development of these steels. Moreover, acicular ferrite microstructure which is generally accepted by pipeline engineers and it is just in doubt because of its differences with acicular ferrite microstructure of weld metal and numerous offered definitions, is completely described.

Recent Development in High Strength Linepipe for Sour Environment

2003 ◽  
Author(s):  
Nobuyuki Ishikawa ◽  
Toyohisa Shinmiya ◽  
Shigeru Endo ◽  
Tsunemi Wada ◽  
Joe Kondo
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Controlled Rolling ◽  
Accelerated Cooling ◽  
Optimum Conditions ◽  
Microstructural Characteristics ◽  
Design Concepts ◽  
Bainitic Microstructure ◽  
Linepipe Steels ◽  
Sour Gas

This paper firstly summarizes the design concepts for controlling crack resistant property and mechanical properties of high strength linepipe steels for sour gas service. Optimum conditions of controlled rolling and accelerated cooling that balances crack resistant property and toughness were investigated. It was demonstrated that higher cooling rate in accelerated cooling process brings tremendous advantages for balancing toughness and strength by fine bainitic microstructure even for heavy wall thick pipes. Production results of high strength sour resistant linepipes were introduced. In order to increase strength grade of sour linepipes, further investigation was made using the steels with different microstructures. It was found that precipitation hardened ferrite-bainite steels have extremely high resistance against HIC even for Grade X80. Mechanical properties and microstructural characteristics of this newly developed steel were introduced in this paper.

scholarly journals Evolution of Microstructure and Precipitation State During Thermomechanical Processing of a Low Carbon Microalloyed Steel

2012 ◽  
Vol 18 (S5) ◽  
pp. 119-120
Author(s):  
P. Valles ◽  
M. Gómez ◽  
S. F. Medina ◽  
A. Pastor ◽  
O. Vilanova
Keyword(s):  
Mechanical Properties ◽  
Acicular Ferrite ◽  
Thermomechanical Processing ◽  
Transformation Products ◽  
Microalloyed Steels ◽  
Accelerated Cooling ◽  
Low Carbon ◽  
Fine Grained ◽  
Increasing Demand ◽  
Carbon Microalloyed

The increasing demand of sources of energy such as oil and natural gas induces at the steel industry a development on low carbon microalloyed steels for pipeline applications in order to achieve excellent mechanical properties of strength and toughness at a reduced cost. To obtain an adequate fine-grained final structure, the strict control of thermomechanical processing and accelerated cooling is crucial. Depending on the thermomechanical processing conditions and chemical composition, pipeline steels can present different microstructures. Several authors have found that the microstructure of acicular ferrite usually provides an optimum combination of mechanical properties. Higher levels of austenite strengthening before cooling promote a refinement of final microstructure but can also restrict the fraction of low temperature transformation products such as acicular ferrite.

The Formation of Acicular Ferrite and Mechanical Properties Behaviors in a Low Welding Crack Susceptibility Steel

2010 ◽  
Vol 163-167 ◽  
pp. 337-341 ◽  
Author(s):  
Liang Yun Lan ◽  
Chun Lin Qiu ◽  
De Wen Zhao
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Acicular Ferrite ◽  
Electron Backscatter Diffraction ◽  
High Strength ◽  
Accelerated Cooling ◽  
Transmission Electron ◽  
Crystallographic Characteristics ◽  
Backscatter Diffraction ◽  
Crack Susceptibility

The nucleation and crystallographic characteristics of acicular ferrite in the as-rolled and tempered steel were investigated by using an optical microscopy (OM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD). The results showed that acicular ferrite forms at nucleation sites such as dislocations within austenite grains under the heavy reduction in the austensite non-recrystallization region and accelerated cooling conditions, and the inclusions such as Al2O3•MnS may have promotion effect for the formation of acicular ferrite. Acicular ferrite has high misorientation angle boundaries and a number of sub-boundaries or high density of dislocations inside, which contributes to an excellent combination of high strength and toughness. And the morphology of acicular ferrite does not show obvious change in tempering microstructure due to high temperature thermal stability, which plays an important part in keeping good mechanical properties for tempered specimens.

Modern High Strength Steels for Oil and Gas Transmission Pipelines

2008 ◽  
Author(s):  
Fulvio Siciliano ◽  
Douglas G. Stalheim ◽  
J. Malcolm Gray
Keyword(s):  
Acicular Ferrite ◽  
Oil And Gas ◽  
High Strength Steels ◽  
High Strength ◽  
Alloy System ◽  
Alloy Design ◽  
Nb Content ◽  
Transmission Pipeline ◽  
Rolling Temperatures ◽  
Transmission Pipelines

Increasing world demand for energy has resulted in plans to expand the oil and gas transmission pipeline infrastructure in many countries utilizing higher strength steels of API grade X70 and X80. Traditional transmission pipeline steels, up to grade X70, relied on a ferrite/pearlite microstructural design generated through traditional TMCP rolling of a niobium microalloyed C-Mn steel design. Increasing strengths up to X70 and X80 for transmission pipelines has resulted in a shift toward a ferrite/acicular ferrite microstructure designs. Traditionally, to generate the ferrite/acicular ferrite microstructure design for X70 or X80, TMCP rolling is applied to a C-Mn-Si-Mo-Nb alloy system. The Nb content is typically less than 0.070% in this alloy system. With the rising cost of alloys over the past three years, steel and pipe producers have been working with different alloy designs to reduce total costs to produce the ferrite/acicular ferrite microstructure. In recent developments it has been determined that an optimized low-C-Mn-Si-Cr-Nb alloy design (usually referred as NbCr steel), utilizing an Nb content between 0.080 – 0.11% can produce the same ferrite/acicular ferrite microstructure with either no, or minimal, use of molybdenum. This approach has been successfully used in several transmission pipeline projects such as the Cantarell, Cheyenne Plains and Rockies Express. Recognizing the success of previous projects around the world, the large ∼ 4500 Km 2nd West-East Pipeline Project specification in China has been modified to allow for the use of this NbCr design for both plate and coil for conversion to long seam or spiral pipe. The NbCr design allows the steel producer to utilize niobium’s unique ability to retard recrystallization at higher than normal TMCP rolling temperatures, hence the term for the alloy design High Temperature Processing (HTP), producing the desired ferrite/acicular ferrite microstructure with excellent strength, toughness and weldability. This paper will discuss the technical background, rolling strategy, mechanical properties, welding, specific projects, and specification modifications with practical examples.

scholarly journals Comprehensive Analysis of the Microstructure and Mechanical Properties of Friction-Stir-Welded Low-Carbon High-Strength Steels with Tensile Strengths Ranging from 590 MPa to 1.5 GPa

2021 ◽  
Vol 11 (12) ◽  
pp. 5728
Author(s):  
HyeonJeong You ◽  
Minjung Kang ◽  
Sung Yi ◽  
Soongkeun Hyun ◽  
Cheolhee Kim
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Joint Strength ◽  
Solid Phase ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Friction Stir ◽  
Welding Processes

High-strength steels are being increasingly employed in the automotive industry, requiring efficient welding processes. This study analyzed the materials and mechanical properties of high-strength automotive steels with strengths ranging from 590 MPa to 1500 MPa, subjected to friction stir welding (FSW), which is a solid-phase welding process. The high-strength steels were hardened by a high fraction of martensite, and the welds were composed of a recrystallized zone (RZ), a partially recrystallized zone (PRZ), a tempered zone (TZ), and an unaffected base metal (BM). The RZ exhibited a higher hardness than the BM and was fully martensitic when the BM strength was 980 MPa or higher. When the BM strength was 780 MPa or higher, the PRZ and TZ softened owing to tempered martensitic formation and were the fracture locations in the tensile test, whereas BM fracture occurred in the tensile test of the 590 MPa steel weld. The joint strength, determined by the hardness and width of the softened zone, increased and then saturated with an increase in the BM strength. From the results, we can conclude that the thermal history and size of the PRZ and TZ should be controlled to enhance the joint strength of automotive steels.

Development of NbTiB Microalloyed HSLA Steels for High-Strength Heavy Plate

2005 ◽  
Vol 500-501 ◽  
pp. 565-572 ◽  
Author(s):  
H. Meuser ◽  
F. Grimpe ◽  
S. Meimeth ◽  
C.J. Heckmann ◽  
C. Träger
Keyword(s):  
High Strength ◽  
Optimum Process ◽  
Low Carbon ◽  
Low Alloy Steel ◽  
Alloying Element ◽  
Heavy Plate ◽  
Hsla Steels ◽  
Bainitic Microstructure ◽  
Bainitic Structure ◽  
Low Temperature Toughness

This paper deals with the development of low carbon NbTiB micro-alloyed high strength low alloy steel for heavy plates with high wall thickness. In the production of heavy plate it is remarkably difficult to achieve a combination of high strength and good low-temperature toughness. Bainitic microstructures have shown the capability to attain such requirements. To achieve a bainitic microstructure even for heavy wall products the formation of bainite can be promoted and supported by the use of small amounts of boron as a micro-alloying element. This industrial research project is based on the addition of small amounts of boron to promote the desired bainitic structure. Mill rolling trials were carried out to determine the optimum process parameters. The results of experimental mill rolling trials on 35 mm plates will be presented in this paper.

The Influence of Oxide Inclusion on the Refinement of Bainite and Toughness in HAZ for Low Carbon Steels

2013 ◽  
Vol 651 ◽  
pp. 163-167
Author(s):  
Shu Rui Li ◽  
Xue Min Wang ◽  
Xin Lai He
Keyword(s):  
Mechanical Properties ◽  
Acicular Ferrite ◽  
Oxide Inclusion ◽  
Optical Microscope ◽  
Carbon Steels ◽  
Low Carbon ◽  
Low Carbon Steels ◽  
The Core ◽  
Ti Oxides ◽  
Bainitic Steels

The influence of Ti oxide on the toughness of heat affected zone for low carbon bainitic steels has been investigated. The optical microscope, SEM and TEM were used to analyze the composition, size and distribution of the inclusions, and the microstructure and mechanical properties after welding thermal simulation were also investigated. The effect of Ti oxide inclusion on the transformation of acicular ferrite has also been studied. The results show that after the melting with Ti dioxide technique the inclusion is complex, in the core is Ti oxides about 1-3 micron and around it is MnS. It has been found the acicular ferrite can nucleate at the inclusions and the Ti oxide inclusion will promote the nucleation of acicular ferrite, and the acicular ferrite will block the growth of bainite. Therefore by introducing the Ti oxide in the steels the microstructure of HAZ could be refined markedly therefore the toughness of HAZ can be improved evidently.

Development of Low Carbon High Strength H-Beam Steel

2010 ◽  
Vol 168-170 ◽  
pp. 969-972
Author(s):  
Jian Qing Qian ◽  
Ji Ping Chen ◽  
Bao Qiao Wu ◽  
Jie Ca Wu
Keyword(s):  
Mechanical Properties ◽  
Laboratory Experiments ◽  
Theoretical Study ◽  
High Strength ◽  
Rolling Process ◽  
Low Carbon ◽  
Study Product ◽  
H Beam ◽  
Nitrogen Alloy

The application of vanadium-nitrogen alloy to develop a certain low carbon high strength H-beam steel was determined through the combination of theoretical study, product requirements and existing practical conditions. The specific rolling process was further defined through laboratory experiments. The developed low carbon high strength H-beam steel was trial produced and its properties were also analyzed. The results showed that the newly developed low carbon high strength H-beam steel had excellent mechanical properties and good weldability.

Effect of the Time between Last Deformation Pass and Accelerated Cooling on the Mechanical Properties in Nb and Nb-Mo Microalloyed Steels

2016 ◽  
Vol 716 ◽  
pp. 281-290
Author(s):  
Gorka Larzabal ◽  
Nerea Isasti ◽  
J.M. Rodriguez-Ibabe ◽  
Isabel Gutiérrez ◽  
P. Uranga
Keyword(s):  
Mechanical Properties ◽  
Charpy Impact ◽  
Holding Time ◽  
Microalloyed Steels ◽  
Accelerated Cooling ◽  
Low Carbon ◽  
Compression Tests ◽  
Electron Backscattered Diffraction ◽  
Microstructural Refinement ◽  
Deformation Pass

The microstructural refinement induced when the holding time between last deformation pass and accelerated cooling is reduced, affects the mechanical properties in low carbon Nb and Nb-Mo microalloyed steels. Plane strain compression tests were performed and mechanical property samples machined in order to quantify this effect using tensile and Charpy impact tests. A complete microstructural characterization was carried out using electron backscattered diffraction (EBSD) measuring unit size distributions and homogeneity of complex microstructures. The synergetic combination of Nb and Mo elements modifies the final microstructures and, therefore, affects the contribution of different strengthening mechanisms, such as substructure, precipitation hardening and dislocation density. Even though strength is not clearly affected by the reduction of the holding time after the last deformation pass, Charpy properties are considerably improved in the case of the Nb steel. The presence of MA islands in the Nb-Mo steel limits the beneficial effect of the microstructural refinement and toughness remains unmodified.

Microstructure and Mechanical Properties of High Strength Low Alloy Steel Q550D

2021 ◽  
Vol 1035 ◽  
pp. 424-429
Author(s):  
Fang Po Li ◽  
Ning Li ◽  
Xian Lin Wang ◽  
Ming Hua Liang
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Oil And Gas ◽  
High Strength ◽  
Service Performance ◽  
Low Alloy Steel ◽  
Micro Structure ◽  
Gas Drilling ◽  
Drilling Equipment ◽  
Equipment Manufacture

Drilling equipment is the key of oil and gas drilling development. Its manufacturing quality and service performance have important influence on oil and gas drilling development safety. The application of high strength grade steel plays an important role in improving drilling equipment manufacturing level and service performance. In this paper, the chemical composition, microstructure, tensile properties, impact properties and hardness of TMCP Q550D and Q-T Q550D high-strength low-alloy steel were tested and compared, and the application feasibility for drilling equipment manufacture was analyzed comprehensively. The experimental results show that the mechanical properties of Q550D by two different methods were obviously higher than the requirement of national standard. Q550D steel had excellent plasticity and toughness, which meets the requirement of drilling equipment manufacture. The main difference between different steel lied in their chemical composition and micro-structure. Carbon content of TMCP Q550D steel plate was lower than that of QT Q550D, and TMCP Q550 was mainly depend on TMCP technology and micro-alloy elements, whose micro-structure was mainly granular bainite. Q-T Q550D was mainly depend on Q-T technology, and its microstructure was tempered sorbite with obvious banded structure and slightly low toughness.

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