The Effect of Tempering on Low-Temperature Toughness of the Direct Quenched High-Strength Offshore Steel

2017 ◽  
Vol 735 ◽  
pp. 49-53
Author(s):  
Ta Hung Tseng ◽  
Chieh Yu ◽  
Ren Kae Shiue ◽  
Tze Ching Yang ◽  
Ching Yuan Huang
Keyword(s):  
Low Temperature ◽  
High Strength ◽  
Tempering Temperature ◽  
Depth Profiles ◽  
Toughness Test ◽  
Tempering Treatment ◽  
Quenched Steel ◽  
Low Temperature Toughness

Microstructures, Vickers depth profiles and low-temperature toughness of the tempered direct water quenched steels have been evaluated in the experiment. Martensite dominates the direct quenched specimen, and it is brittle at low-temperature toughness test. The toughness of direct quenched steel is improved when it is tempered at 500 °C for 1800 s. However, increasing the tempering temperature from 500 °C to 660 °C has little effect on low-temperature toughness of the steel. The application of offshore steel must avoid bainite formation. Tempering treatment is very effective to improve low-temperature toughness of the martensite dominated structure.

Hydrogen Assisted Tempered Martensite Embrittlement of Ultra High Strength Martensitic Steel

2016 ◽  
Vol 880 ◽  
pp. 29-32
Author(s):  
T.C. Chen ◽  
Wen Hao Chien ◽  
Yuan Tsung Wang ◽  
Ching Yuan Huang ◽  
Hung Wei Yen ◽  
...  
Keyword(s):  
Hydrogen Charge ◽  
High Strength Steels ◽  
High Strength ◽  
Tempered Martensite ◽  
Tempering Temperature ◽  
High Strength Level ◽  
Tempering Treatment ◽  
Ultra High Strength Steels ◽  
Mechanical Strengths ◽  
Tempering Process

The demand for new materials that provide excellent structural performance while reducing weight and being cost-effectively manufactured is increasing. For applications with high strength requirements, ultra-high strength steels (UHSS) have been widely used. However, with such a high strength level, UHSS are very sensitive to the hydrogen that could be ease by the tempering process. In this research, the correlation of hydrogen and tempering process on commercial UHSS 15B30 has been studied. Results show that the tensile strength (TS) of as-quenched 15B30 is about 1900MPa. After tempering treatment of the quenched 15B30, the TS decreases from 1600MPa to 1200MPa with tempering temperature increased from 200°C to 400°C. The 15B30 specimens, being subjected to hydrogen charge, exhibit the dramatic reduction of mechanical strengths.

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.

Microstructural Observations of the Direct Quenched Offshore Steel

2017 ◽  
Vol 732 ◽  
pp. 55-58
Author(s):  
Chieh Yu ◽  
Ta Chien Cheng ◽  
Ren Kae Shiue ◽  
Tze Ching Yang ◽  
Ching Yuan Huang
Keyword(s):  
Retained Austenite ◽  
Vickers Microhardness ◽  
Iron Carbide ◽  
High Strength ◽  
Heat Treating ◽  
Carbide Formation ◽  
Tempered Martensite ◽  
Depth Profiles ◽  
Quenched Steel ◽  
Direct Quench

The purpose of this investigation is focused on the direct quench and temper mechanisms of the high strength offshore steel. Microstructural analyses of martensite and retained austenite in the direct quenched steel, simulations of martensitic transformation temperatures, Ms/Mf, and morphologies of bainite and ferrite have been evaluated in the experiment. Additionally, carbide formation after temped at various temperatures and microhardness depth profiles after heat treating are also included in the study. The direct quenched steel is primarily comprised of martensite, bainite and a few retained austenite with Vickers microhardness above 300. Tempered martensite, iron carbide and bainite are widely observed from all tempered specimens.

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.

The Role of Niobium in High Strength Oil and Gas Transmission Linepipe Steels

2006 ◽  
Author(s):  
Douglas G. Stalheim ◽  
Steven G. Jansto
Keyword(s):  
Low Temperature ◽  
Oil And Gas ◽  
Elevated Temperatures ◽  
Operating Cost ◽  
High Strength ◽  
Processing Technique ◽  
Alloy Design ◽  
Transmission Pipeline ◽  
Low Temperature Toughness ◽  
Transmission Pipelines

Niobium’s role in the production of oil and gas transmission pipelines steels has gained significant importance in recent years. The economical movement of gas and oil to the marketplace from remote and rugged locations requires transmission pipelines to be designed to operate at higher pressures with improved toughness over a variety of temperature ranges. With the increased demand for energy resources continuing to grow, traditional plate mills, hot strip mills along with Steckel mills around the world are processing skelp for API pipe. The capabilities of these mills can be quite varied. Consequently, a variety of operational considerations and practices have put additional focus on Nb for its ability to retard recrystallization at elevated temperatures. This ability has added a new form of processing skelp for API pipe called High Temperature Processing or HTP. This new use of Nb in higher strength API oil and gas transmission pipeline steels allows a producer to create a ferrite/acicular ferrite microstructure without the traditional molybdenum alloy based design. The HTP Nb microalloy approach has benefits including reduced operating cost per ton, ease of rolling and welding, excellent low temperature toughness properties and high strength. This processing technique for API X70 and X80 is gaining acceptance as major pipeline projects are now applying this technology. In addition, X100 properties have been achieved with a combination of the traditional X80 alloy design and the newer employed HTP alloy design. This paper will discuss Nb’s role in meeting the increased strength requirements related to operating at higher pressures, improved low temperature toughness (TCVN > 200 J@−40 °C), microstructural demands and processing capability improvements for traditional plate, strip, and Steckel mill technology. The use of the new HTP concept in high strength API production will also be introduced.

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