The Effect of Hot Strip Mill Processing Parameters and Alloy Addition on Low Temperature Toughness of API-X70 Steel

2010 ◽  
Author(s):  
Kwang Seop Ro ◽  
Saad Al-Shammary ◽  
Adel A. Al-Butairi ◽  
Khaled F. Al-Hajeri
Keyword(s):  
Low Temperature ◽  
High Strength ◽  
Processing Parameters ◽  
Prediction Equation ◽  
Hot Strip Mill ◽  
Hot Strip ◽  
Statistical Equation ◽  
Alloy Addition ◽  
Low Temperature Toughness ◽  
Shear Area

Correlation of rolling conditions, microstructure, and low-temperature toughness of X70 pipeline steels was investigated in this study through statistical analysis. High strength API X70 steel grade with excellent DWTT toughness can be designed by the developed statistical equation. The predicted equation is as follows; ‘Pct Shear area of DWTT (−10°C) = 954 − 0.3*SRT + 0.5*TBT − 0.4*FRT + 0.04*CT − 306*C −60*(Mn+Ni+Cu) + 38*(Mo+Cr) − 791*(Ti+Nb+V) − 4*MA’ and the predicted equation showed very good relationship. M/A constituent showed high relationship with DWTT toughness. By inserting this effect into the equation, the reliability of the equation has been improved. By using the prediction equation, new chemical composition and relevant processing variables could be optimized and newly designed steel shows proper tensile properties with the excellent DWTT toughness at −10°C.

Development of Offshore X65/70 Steels for Deep Water Application

2012 ◽  
Author(s):  
Yun-Jo Ro ◽  
Seung-Hwan Chon ◽  
Jang-Yong Yoo ◽  
Ki-Bong Kang
Keyword(s):  
Low Temperature ◽  
Deep Water ◽  
Processing Parameters ◽  
Alloying Elements ◽  
Accelerated Cooling ◽  
Dual Phase ◽  
Effective Grain Size ◽  
Low Temperature Toughness ◽  
Shear Area ◽  
Linepipe Steels

Heavy gauge X65/70 steels have been developed for deep-water offshore application. As the thickness of linepipe steels is increased, Mo, Ni, V alloying elements are generally employed to improve the low temperature toughness and strength balance. However, the price of such alloying element has been rapidly increased. Hence, in the present work, a lean composition is designed to achieve thick X65/70 grade steels with better strength and toughness balance. To prevent the degradation of toughness or strength due to a lean alloying composition, the authors optimize processing parameters, such as a rolling stop temperature or accelerated cooling patterns. By in large, two strategies have been applied to develop linepipe steels; i) cooling starts in γ + α region, and iii) rolling stops in γ + α region. These strategies promote ferrite+bainite dual phase microstructures exhibiting a good low temperature toughness and strength balance. Such dual phase microstructures are characterized by using EBSD (electron back scattered diffraction) technique. The result shows a percentage of DWTT shear area is strongly correlated with effective grain size (misorientation ≥ 15°). As a result, the present work demonstrates that heavy gauge API steels grade X65/70 can be achieved with Mo+V free or small addition of Mo alloying elements.

Effect of Rolling Parameters on the Low-Temperature Toughness and Microstructure of High-Strength Linepipe Steel

2016 ◽  
Author(s):  
C. Stallybrass ◽  
A. Völling ◽  
H. Meuser ◽  
F. Grimpe
Keyword(s):  
Electron Microscopy ◽  
Low Temperature ◽  
Electron Backscatter Diffraction ◽  
High Strength ◽  
Processing Parameters ◽  
Small Scale ◽  
Electron Backscatter ◽  
Low Temperature Toughness ◽  
Backscatter Diffraction ◽  
Scanning Electron

In recent years, large-diameter pipe producers around the world have witnessed a growing interest to develop gas fields in arctic environments in order to fulfill the energy demand. High-strength linepipe grades are attractive for economic reasons, because they offer the benefit of a reduced wall thickness at a given operating pressure. Excellent low-temperature toughness of the material is essential under these conditions. Modern high-strength heavy plates used in the production of UOE pipes are produced by thermomechanical rolling followed by accelerated cooling (TMCP). The combination of high strength and high toughness of these steels is a result of the bainitic microstructure and is strongly influenced by the processing parameters. For this reason, the relationship between rolling and cooling parameters of heavy plate production, the low-temperature toughness and the microstructure is at the center of attention of the development efforts at Salzgitter Mannesmann Forschung (SZMF) in collaboration Salzgitter Mannesmann Grobblech (SMGB). It has been shown previously that a variation of the processing parameters has a direct influence on the microstructure and correlates with mechanical properties that are accessible via small-scale tests. Modern characterization methods such as scanning electron microscopy in combination with electron backscatter diffraction have broadened our understanding of the underlying mechanisms and have helped to define processing conditions for the production of heavy plates with optimized low-temperature toughness in small scale tests. Within the present paper, the results of a recent laboratory investigation of the effect of a systematic variation of rolling parameters on the microstructure and low-temperature toughness of as-rolled and pre-strained Charpy specimens are discussed. In these trials, final rolling temperatures above the onset of the ferrite-austenite transformation and cooling stop temperatures above the martensite start temperature were selected. The microstructure of the plates was investigated by scanning electron microscopy and electron backscatter diffraction. In a series of Charpy tests in a specific temperature range, it was found that plate material in the as-rolled condition is not strongly sensitive to variations of the selected processing parameters, whereas pre-straining the Charpy specimens made it possible to assess the potential of individual processing concepts particularly with regard to low-temperature toughness. In addition to Charpy testing, the toughness was also quantified via instrumented drop-weight tear (DWT) testing. By comparing total energy values from regular pressed-notch DWT-test specimens to J-integral values determined in drop-weight testing of pre-fatigued DWT-test specimens, the impact of variations of specimen type on material tearing resistance is shown.

Development of Economic-Type X70 Linepipe Steel Hot Strip

2013 ◽  
Vol 750-752 ◽  
pp. 446-449
Author(s):  
Hong Mei Yang
Keyword(s):  
Low Temperature ◽  
Acicular Ferrite ◽  
Production Cost ◽  
Pipeline Steel ◽  
High Strength ◽  
Alloy System ◽  
Hot Strip ◽  
Low Temperature Toughness ◽  
Linepipe Steel ◽  
Cost Economic

In order to reduce the production cost, economic-type X70 pipeline steels with the thickness of 14.6 and 15.9mm were redesigned . The latest alloy system of pipeline steel designed by non-molybdenum C-Mn-Cr-Nb alloy system, which replaces the high-molybdenum C-Mn-Mo-Nb alloy system, was adopted along with acicular ferrite microstructure. The microstructure of X70 strip is homogeneous and ferrite grains are fine, resulting in high strength, excellent low-temperature toughness and weldability.

Application of Deformation to Improve Hot Ductility in the Peritectic Steel

2005 ◽  
Vol 500-501 ◽  
pp. 203-210 ◽  
Author(s):  
Ahmad Rezaeian ◽  
Faramarz Zarandi ◽  
D.Q. Bai ◽  
Steve Yue
Keyword(s):  
Flow Stress ◽  
High Strength ◽  
Microalloyed Steels ◽  
Hot Strip Mill ◽  
Mean Flow ◽  
Hot Strip Rolling ◽  
Strip Rolling ◽  
Slip Ratio ◽  
Hot Strip ◽  
Mean Flow Stress

The hot strip rolling of advanced microalloyed high strength steels still represents a new task to many mills due to the lack of data on the hot deformation resistance. With the aid of processing data from the Ispat-Inland hot strip mill, the “measured mean flow stresses” are calculated from the mill force using the Sims analysis and taking into account roll flattening, slip ratio and the redundant strain. A modification of the Misaka mean flow stress equation is proposed for C – Mn – Si – Al steels microalloyed with up to 0.02 % Nb. The effects of alloying and microalloying are then estimated. A new fitting parameter shows excellent agreement with the mean flow stress data from industrial processing of advanced high strength microalloyed steels. However, during the second half of the rolling schedule (lower temperature region), indications of austeniteto- ferrite transformation were found.

Research and Development of High Strength Architectural Heavy Plates

2012 ◽  
Vol 190-191 ◽  
pp. 590-594
Author(s):  
Ming Wei Tong ◽  
Ze Xi Yuan ◽  
Kai Guang Zhang
Keyword(s):  
Low Temperature ◽  
Large Scale ◽  
High Strength ◽  
Technical Requirement ◽  
Good Match ◽  
Iron And Steel ◽  
Fracture Transition ◽  
Fine Microstructure ◽  
Low Temperature Toughness ◽  
Base Plates

This paper provides a detailed description of high strength architectural heavy plates with 80mm in thickness developed at Wuhan Iron and Steel（Group）Corporation(WISCO). The chemical composition of plates contains mainly C-Mn-Nb-V-Ti with proper content of other alloys, and the thermal-mechanical controlled process and normalizing treatment were applied. The results show that the base plates manufactured at WISCO have a good match of high strength, good through-thickness characteristic, low yield ratio and low temperature toughness with fine microstructure, and the fracture transition temperature is about -40°C. The welding plate also has high strength and good low temperature toughness which comprehensively meet the technical requirement of large-scale architectural buildings.

IN-787

Alloy Digest ◽  
1973 ◽  
Vol 22 (3) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
Low Temperature ◽  
Atmospheric Corrosion ◽  
High Strength ◽  
Heat Treating ◽  
Line Pipe ◽  
International Nickel Company ◽  
Pipe Welding ◽  
Low Temperature Toughness

Abstract IN-787 is an age-hardenable, high-strength structural steel. It is characterized by low-temperature toughness, good atmospheric corrosion resistance and excellent weldability, even under adverse field conditions such as line-pipe welding. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SA-286. Producer or source: International Nickel Company Inc..

Metallurgical Design and Development of High-Grade Line Pipe

2012 ◽  
Author(s):  
Takuya Hara ◽  
Taishi Fujishiro ◽  
Yasuhiro Shinohara ◽  
Eiji Tsuru ◽  
Naoki Doi ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Low Temperature ◽  
Cost Savings ◽  
High Strength ◽  
Design And Development ◽  
Line Pipe ◽  
Good Balance ◽  
Low Temperature Toughness ◽  
And Control ◽  
High Deformability

The application of high-strength line pipes has enabled pipelines to operate at high pressure, generating cost savings for both gas transportation and construction. In general, high-strength line pipes require crack initiation resistance and crack arrestability at low temperatures, as well as field weldability. High strength and deformability for strain-based design and excellent sour resistance are also required. Moreover, composite properties are often required for high-strength line pipes. This paper describes our progress in this field with regard to metallurgical design and development. Metallurgical design aimed at achieving a good balance between strength, low temperature toughness and deformability for strain-based design is also described from the perspectives of grain refinement, microstructure and chemical composition. Metallurgical design focused on a good balance between strength and sour resistance in limited low chemical composition is described from the perspectives of microstructure and control to chemical composition and center segregation. These efforts have led to the development of high-strength heavy wall line pipes of API X60 to X100 grades offering excellent low temperature toughness and high deformability for stain-based design, while API grades X65 to X70 with good sour resistance have also been developed.

Research and Development of Deep-Sea Pipeline Steel

2010 ◽  
Vol 152-153 ◽  
pp. 1492-1498
Author(s):  
Jin Qiao Xu ◽  
Bin Guo ◽  
Lin Zheng ◽  
Yin Hua Li ◽  
Le Yu
Keyword(s):  
Low Temperature ◽  
Deep Sea ◽  
Pipeline Steel ◽  
High Strength ◽  
Steel Company ◽  
Line Pipe ◽  
Iron And Steel ◽  
Company Group ◽  
Pipeline Project ◽  
Low Temperature Toughness

This paper provides a detailed description of deep-sea pipeline steel developed at Wuhan Iron and Steel Company(Group), WISCO for short. The thickness of the trial produced plates is 28mm. The chemical composition of low C-high Mn-Nb-Ti with proper content of other alloys and thermo-mechanical controlled process were applied. The results show that the deep-sea pipeline steel developed at Wuhan Iron and Steel Company has a good match of high strength, low temperature toughness and excellent deformability with fine uniform microstructure. The LSAW line pipe manufactured by JCOE method has high strength, good low temperature toughness and low yield ratio which comprehensively meet the requirements of the South China Sea Liwan pipeline project.

Development of Heavy Gauge X70 Helical Line Pipe

2018 ◽  
Author(s):  
L. E. Collins ◽  
K. Dunnett ◽  
T. Hylton ◽  
A. Ray
Keyword(s):  
Low Temperature ◽  
Large Diameter ◽  
High Strength ◽  
Helical Line ◽  
Slab Thickness ◽  
Long Distance ◽  
Austenite Grain Size ◽  
Line Pipe ◽  
Nitrogen Levels ◽  
Low Temperature Toughness

A decade ago, the pipeline industry was actively exploring the use of high strength steels (X80 and greater) for long distance, large diameter pipelines operating at high pressures. However in recent years the industry has adopted a more conservative approach preferring to utilize well established X70 grade pipe in heavier wall thicknesses to accommodate the demand for increased operating pressures. In order to meet this demand, EVRAZ has undertaken a substantial upgrade of both its steelmaking and helical pipemaking facilities. The EVRAZ process is relatively unique employing electric arc furnace (EAF) steelmaking to melt scrap, coupled with Steckel mill rolling for the production of coil which is fed into helical DSAW pipe mills for the production of large diameter line pipe in lengths up to 80 feet. Prior to the upgrade production had been limited to a maximum finished wall thickness of ∼17 mm. The upgrades have included installation of vacuum de-gassing to reduce hydrogen and nitrogen levels, upgrading the caster to improve cast steel quality and allow production of thicker (250 mm) slabs, upgrades to the power trains on the mill stands to achieve greater rolling reductions, replacement of the laminar flow cooling system after rolling and installation of a downcoiler capable of coiling 25.4 mm X70 material. As well a new helical DSAW mill has been installed which is capable of producing large diameter pipe in thicknesses up to 25.4 mm. The installation of the equipment has provided both opportunities and challenges. Specific initiatives have sought to produce X70 line pipe in thicknesses up to 25.4 mm, improve low temperature toughness and expand the range of sour service grades available. This paper will focus on alloy design and rolling strategies to achieve high strength coupled with low temperature toughness. The role of improved centerline segregation control will be examined. The use of scrap as a feedstock to the EAF process results in relatively high nitrogen contents compared to blast furnace (BOF) operations. While nitrogen can be reduced to some extent by vacuum de-gassing, rolling practices must be designed to accommodate nitrogen levels of 60 ppm. Greater slab thickness allows greater total reduction, but heat removal considerations must be addressed in optimization of rolling schedules to achieve suitable microstructures to achieve both strength and toughness. This optimization requires definition of the reductions to be accomplished during roughing (recrystallization rolling to achieve a fine uniform austenite grain size) and finishing (pancaking to produce heavily deformed austenite) and specification of cooling rates and coiling temperatures subsequent to rolling to obtain suitable transformation microstructures. The successful process development will be discussed.

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