A Novel Alloying Concept for Thermo-Mechanical Hot-Rolled Strip for Large Diameter HTS (Helical Two Step) Line Pipe

2008 ◽  
Author(s):  
Sandrine Bremer ◽  
Volker Flaxa ◽  
Franz M. Knoop
Keyword(s):  
Acicular Ferrite ◽  
Large Diameter ◽  
High Strength ◽  
Carbon Equivalent ◽  
Material Strength ◽  
Rolled Strip ◽  
Low Carbon ◽  
Line Pipe ◽  
Processing Strategies ◽  
Product And Process

One of the major priorities of the research and development department of the Salzgitter Group is placed on the product and process optimisation of both approved conventional steel grades for line pipe application and novel high strength alloying concepts. With respect to reduced wall-thicknesses and higher operating pressures for gas transportation pipelines, the requirements for hot wide strip material are steadily increasing. Material strength can be increased either by grain refinement of the ferritic-pearlitic phase in combination with precipitation hardening or by replacing the ferrite-pearlite by an intermediate microstructure, so-called acicular ferrite. A low carbon content supports the formation of the microstructure desired and results in an improvement of the carbon equivalent. This acicular ferrite does not only raise the material strength but also improve low temperature toughness, weldability and workability. New processing routes based on the demands of novel alloying concepts have been developed in order to achieve the intermediate microstructure. In the following paper, two different alloying and processing strategies and the resulting mechanical properties and microstructures are described and illustrated.

Rosenhain Centenary Conference - 3. Materials development present and future 3.3 Development of line pipe steels

1976 ◽  
Vol 282 (1307) ◽  
pp. 305-318 ◽  
Keyword(s):  
Large Diameter ◽  
High Strength ◽  
High Yield ◽  
Low Alloy Steels ◽  
Low Carbon ◽  
High Yield Strength ◽  
Line Pipe ◽  
Materials Development ◽  
Alloy Steels ◽  
Low Carbon Bainite

The demand for large diameter gas line pipe with high yield strength and high notch toughness has led to increased research in high strength low alloy steels. Physical metallurgists have developed both a fundamental and an empirical understanding of the properties and microstructures of ferrite pearlite steels. As specifications become more rigorous, alternative microstructures (low carbon bainite or tempered bainite and martensite) are being used in line pipe. There is a definite need for metallurgists to develop a clearer understanding of the interrelationships between their properties, microstructures, and processing before these alternatives are completely accepted for use in line pipe.

Development of the SAW Wire for High Strength TMCP Steel

2005 ◽  
Vol 475-479 ◽  
pp. 269-272
Author(s):  
Xiao Huai Xue ◽  
Song Nian Lou ◽  
Bainian Qian ◽  
Shaofei Yu
Keyword(s):  
Acicular Ferrite ◽  
High Strength ◽  
Alloy System ◽  
Carbon Equivalent ◽  
Low Carbon ◽  
Key Factors ◽  
Mixture Ratio ◽  
Mn Content ◽  
Nitrogen Contents ◽  
Submerged Arc

The wire for high strength and toughness TMCP steels of submerged arc welding was developed. The low carbon and micro-alloying with Ti-B system was adopted to obtain the acicular ferrite dominated deposited metals. Experimental results show that the carbon equivalent (Pcm) should be higher than 0.17, which can ensure the high strength and high toughness of the deposited metals. In the alloy system, Oxygen and Nitrogen contents, micro-alloyed elements (C, Mn) and its mixture ratio are the key factors that affect the deposited metals toughness. With increasing C, Mn content, the acicular ferrite is increased and toughness is improved. Oxygen and Nitrogen are deleterious to the toughness of deposited metals.

The Thermomechanical Controlled Processing of High-Strength Steel Plate: A New View of Toughness Based on Modern Metallography

2013 ◽  
Vol 762 ◽  
pp. 38-46 ◽  
Author(s):  
Xiao Jun Liang ◽  
Ming Jian Hua ◽  
C. Isaac Garcia ◽  
Anthony J. DeArdo
Keyword(s):  
Mechanical Properties ◽  
Large Diameter ◽  
High Strength ◽  
Rolled Plate ◽  
Processing Route ◽  
Carbon Equivalent ◽  
Low Carbon ◽  
Structure Property ◽  
Engineering Structures ◽  
Controlled Processing

Modern thermomechanical controlled processing (TMCP) of advanced steels is now an important processing route in the production of engineering structures and products that are of value to society. The principles of TMCP are now practiced in the hot mill, cold mill and press forming shops around the world. Successful TMCP means that the proper metallurgical microstructure has been obtained in the required areas of the steel. The ideal microstructure is often defined by the correct phase balance and dimensions either of the parent austenite or final ferritic phase. Technological and economic demands have led to ever increasing levels of strength, especially for applications such as large diameter linepipe. The operative yield strengths in 18mm hot rolled plate have increased from X52(ferrite pearlite) in 1970 to X80(ferrite-bainite) today. The next frontier is the X100-X120 strength range, where bainitic or martensitic microstructures are required. It is clear that achieving a high-strength bainitic microstructure in heavy plate requires a high Carbon Equivalent value (C. E. II or Pcm), a rapid cooling rate, and a low water-end temperature. The requirement of high toughness and good weldability also means a low carbon content. This paper will describe the results of a research program where a steel of C. E. 0.56 and Pcm 0.23 was reheated, rough rolled for grain refinement, finish rolled for austenite pancaking, and direct quenched to below the Bs temperature. It was found that the strength and especially the toughness of the fully processed plates could not be explained using conventional metallographic techniques in conjunction with known structure-property relationships. However, the application of modern metallographic techniques based on FEG-SEM incorporating OIM led to microstructural characterization that more fully explained the observed mechanical properties. Of particular importance were the amount of MA micro-constituent, the crystallographic packet size of the bainite, and the high angle boundary character, especially the CSL boundaries, found in the microstructure. In the future, improved modeling of microstructural evolution and attendant mechanical properties will incorporate these important features.

Expulsion Intensity Monitoring and Modeling in Resistance Spot Welding Based on Electrode Displacement Signals

2020 ◽  
Author(s):  
Yu-Jun Xia ◽  
Yan Shen ◽  
Lang Zhou ◽  
Yong-Bing Li
Keyword(s):  
Resistance Spot Welding ◽  
Spot Welding ◽  
Low Carbon Steel ◽  
Sheet Thickness ◽  
High Strength Steels ◽  
High Strength ◽  
Material Strength ◽  
Low Carbon ◽  
Resistance Spot ◽  
Electrode Displacement

Abstract Weld expulsion is one of the most common welding defects during resistance spot welding (RSW) process especially for high strength steels (HSS). In order to control and eventually eliminate weld expulsion in production, accurate assessment of the expulsion severity should be the first step and is urgently required. Among the existing methods, real-time monitoring of RSW-related process signals has become a promising approach to actualize the online evaluation of weld expulsion. However, the inherent correlation between the process signals and the expulsion intensity is still unclear. In this work, a commonly used process signal, namely the electrode displacement and its instantaneous behavior when expulsion occurs are systematically studied. Based upon experiments with various electrodes and workpieces, a nonlinear relation between the weight of expelled metal and the sudden displacement drop accompanied by the occurrence of weld expulsion is observed, which is mainly influenced by electrode tip geometry but not by material strength or sheet thickness. The intrinsic relationship between this specific signal feature and the magnitude of expulsion is further explored through geometrical analysis, and a modified analytical model for online expulsion evaluation is finally proposed. It is shown that the improved model could be applied to domed electrodes with different tip geometries and varying workpieces ranging from low carbon steel to HSS. The error of expulsion estimation could be limited within ±20.4 mg (±2σ) at a 95% confidence level. This study may contribute to the online control of weld expulsion to the minimum level.

Development of High Strength Material and Pipe Production Technology for Grade X120 Line Pipe

2004 ◽  
Author(s):  
Hans-Georg Hillenbrand ◽  
Andreas Liessem ◽  
Karin Biermann ◽  
Carl Justus Heckmann ◽  
Volker Schwinn
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Point Of View ◽  
Accelerated Cooling ◽  
Pipe Production ◽  
Production Test ◽  
Low Carbon ◽  
Long Distance ◽  
Line Pipe ◽  
Economic Point

The increasing demand for natural gas will further influence the type of its transportation in the future, both from the strategic and economic point of view. Long-distance pipelines are a safe and economic means to transport the gas from production sites to end users. High-strength steels in grade X80 are nowadays state of the art. Grade X100 was recently developed but not yet utilised. The present-day technical limitations on the production of X120 line pipe namely the steel composition, the pipe forming and the welding are addressed in this paper. Production test results on X120 pipes are presented to describe the materials properties. A low carbon and low PCM steel with VNbTiB microalloying concept is used. In the plate rolling the main attention is turned to the heavy accelerated cooling. The large spring back that occurs during the U-forming step of the UOE process is one of the most complex aspects in forming X120. To handle this aspect FEM calculations were used to modify the forming parameters and to optimise the shape of the U-press tool. For optimising the existing welding procedure with respect to an avoidance of HAZ softening, a low heat input welding technology and new welding consumables were developed.

Alloying Concept for High-Strength Seamless Heavy-Wall Line Pipe Suitable for Sour Service Applications

2004 ◽  
Author(s):  
K. Biermann ◽  
C. Kaucke ◽  
M. Probst-Hein ◽  
B. Koschlig
Keyword(s):  
Heat Treatment ◽  
Wall Thickness ◽  
Oil And Gas ◽  
High Strength ◽  
Gas Production ◽  
Pipe Material ◽  
Low Carbon ◽  
Line Pipe ◽  
Oil And Gas Production ◽  
Sour Service

Offshore oil and gas production worldwide is conducted in increasingly deep waters, leading to more and more stringent demands on line pipes. Higher grades and heavier wall thicknesses in combination with deep temperature toughness properties, good weldability and suitability for sour service applications are among the characteristics called for. It is necessary that pipe manufacturers develop materials to meet these at times conflicting requirements. An alloying concept based on steel with very low carbon content is presented. This type of material provides excellent toughness properties at deep temperatures in line pipe with a wall thickness of up to 70 mm, produced by hot rolling followed by QT heat treatment. Pipes from industrial production of identical chemical composition and heat treatment achieved grades X65 to X80, depending on wall thickness. The properties of the steel used in pipes are presented. The resistance of the pipe material to the influence of sour gas was assessed by standard tests. To demonstrate weldability, test welds were performed and examined.

Expulsion Intensity Monitoring and Modeling in Resistance Spot Welding Based on Electrode Displacement Signals

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Yu-Jun Xia ◽  
Yan Shen ◽  
Lang Zhou ◽  
Yong-Bing Li
Keyword(s):  
Resistance Spot Welding ◽  
Spot Welding ◽  
Low Carbon Steel ◽  
Sheet Thickness ◽  
High Strength Steels ◽  
High Strength ◽  
Material Strength ◽  
Low Carbon ◽  
Resistance Spot ◽  
Electrode Displacement

Abstract Weld expulsion is one of the most common welding defects during the resistance spot welding (RSW) process, especially for high strength steels (HSS). In order to control and eventually eliminate weld expulsion in production, accurate assessment of the expulsion severity should be the first step and is urgently required. Among the existing methods, real-time monitoring of RSW-related process signals has become a promising approach to actualize the online evaluation of weld expulsion. However, the inherent correlation between the process signals and the expulsion intensity is still unclear. In this work, a commonly used process signal, namely, the electrode displacement and its instantaneous behavior when expulsion occurs are systematically studied. Based upon experiments with various electrodes and workpieces, a nonlinear correlation between the weight of expelled metal and the sudden displacement drop accompanied by the occurrence of weld expulsion is observed, which is mainly influenced by electrode tip geometry but not by material strength or sheet thickness. The intrinsic relationship between this specific signal feature and the magnitude of expulsion is further explored through geometrical analysis, and a modified analytical model for online expulsion evaluation is finally proposed. It is shown that the improved model could be applied to domed electrodes with different tip geometries and varying workpieces ranging from low carbon steel to HSS. The error of expulsion estimation could be limited within ±20.4 mg (±2σ) at a 95% confidence level. This study may contribute to the online control of weld expulsion to the minimum level.

Evolution of Carbides during Prestrain and Tempering

2021 ◽  
Vol 1016 ◽  
pp. 82-87
Author(s):  
Wen Hong Ding ◽  
Bo Jiang ◽  
Chao Lei Zhang ◽  
Ya Zheng Liu ◽  
Li Sun ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Dynamic Equilibrium ◽  
Energy State ◽  
High Strength ◽  
High Energy ◽  
Material Strength ◽  
Low Carbon ◽  
The Matrix ◽  
High Energy State ◽  
Two Stages

The effect of thermo-mechanical treatment on the microstructural evolution of low carbon micro-alloyed high strength steel was studied by combining prestrain with tempering (PST) in this paper. It was found that the prestrain causes the dislocation to plug up around the grain boundary and carbide, resulting in carbide boundary fragmentation. Moreover, it breaks the thermo-dynamic equilibrium between the matrix and carbide, induces the dissolution of carbon in the high energy state, and then changes the distribution of carbon in the matrix. In the subsequent tempering process, the precipitation regularity of carbide was changed, which promoted the precipitation carbide at low temperature. The influence of carbide precipitation on dislocation can be divided into two stages: the first stage was precipitation induced creep, which promoted stress relaxation; the second stage was precipitation pinning dislocation, which improved material strength and inhibited stress relaxation.

Microstructural Features of a Ultra Low Carbon High Strength Acicular Ferrite Steel Thick Plate

2007 ◽  
pp. 57-60
Author(s):  
Zhi Qiang Cao ◽  
Ai Bing Zhang ◽  
Deng Luo ◽  
Zheng Hai Xia ◽  
Yong Dong Zhang ◽  
...  
Keyword(s):  
Acicular Ferrite ◽  
Thick Plate ◽  
High Strength ◽  
Low Carbon ◽  
Ferrite Steel

Development of low carbon Nb–Ti–B microalloyed steels for high strength large diameter linepipe

2005 ◽  
Vol 32 (4) ◽  
pp. 337-341 ◽  
Author(s):  
C. J. Heckmann ◽  
D. Ormston ◽  
F. Grimpe ◽  
H.-G. Hillenbrand ◽  
J.-P. Jansen
Keyword(s):  
Large Diameter ◽  
High Strength ◽  
Microalloyed Steels ◽  
Low Carbon
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