Offshore Structural Steel Plates for Extreme Low Temperature Service With Excellent HAZ Toughness

2014 ◽  
Author(s):  
Katsuyuki Ichimiya ◽  
Kazukuni Hase ◽  
Shigeru Endo ◽  
Yusuke Terazawa ◽  
Takaki Fujiwara ◽  
...  
Keyword(s):  
Low Temperature ◽  
Main Property ◽  
Offshore Structures ◽  
Nucleation Site ◽  
Steel Plates ◽  
Crack Tip Opening Displacement ◽  
Offshore Structure ◽  
Opening Displacement ◽  
Low Temperature Toughness ◽  
Haz Toughness

The strength and the toughness required for steel plates used for offshore structures became higher as the installation areas move into arctic areas. The main property of offshore structure steel is the crack tip opening displacement (CTOD) property of weld joint, and CTOD testing is performed at the minimum design temperature of the structure. Thus, the demand for satisfying −40°C of CTOD test temperature specification has increased. For the improvement of HAZ toughness, coarse austenite grain is suppressed by TiN, and low-C, Ceq, Si, P, Nb design is adopted to decrease the formation of M-A constituents. Furthermore, by using Ca inclusion, which works as a pinning particle and a bainite nucleation site, very fine bainite microstructure are formed in HAZ and excellent low temperature toughness are achieved. The YP420 class plate with excellent low temperature toughness has been developed using these technology.

Development of YS 500MPa Class Thick Steel Plate With Weld Joint CTOD Property for Offshore Structures

2019 ◽  
Author(s):  
Yusuke Terazawa ◽  
Katsuyuki Ichimiya ◽  
Keiji Ueda ◽  
Satoshi Igi ◽  
Minoru Suwa ◽  
...  
Keyword(s):  
Weld Joint ◽  
Steel Plate ◽  
Plate Thickness ◽  
Offshore Structures ◽  
Nucleation Site ◽  
Crack Tip Opening Displacement ◽  
Offshore Structure ◽  
Opening Displacement ◽  
Thick Steel ◽  
Haz Toughness

Abstract Recently, the installation areas of offshore structures has expanded into deep sea areas, and as a result, strength and plate thickness of the steel plate required for the offshore structures have become higher. And the main property of offshore structure steel is the crack tip opening displacement (CTOD) property of multi-pass weld joint. Thus, the developed steel was designed to improve HAZ toughness of multi-pass weld joint. Firstly, in order to achieve both high strength of the base metal and good HAZ toughness, the TMCP technology was applied, and Ceq. was minimized. And to obtain fine HAZ microstructure, fine TiN and Ca(O,S) particles having pinning effect and nucleation site effect were used. Finally, to decrease the formation of brittle martensite-austenite constituent (M-A) in HAZ of multi-pass weld joint, Si content was decreased. By using above technologies, the YS 500MPa class thick steel plate with good weld joint CTOD property have been developed.

CTOD Evaluation for HAZ Toughness of Offshore Structure Steels with Heavy Thickness Based on API RP 2Z

2013 ◽  
Vol 634-638 ◽  
pp. 2916-2922
Author(s):  
Ting Miao ◽  
Zhang Mu Miao ◽  
Ling Hu ◽  
Xiang Kui Zhang ◽  
Wei Fang Qian
Keyword(s):  
Steel Structures ◽  
American Petroleum Institute ◽  
International Standards ◽  
Steel Plates ◽  
Crack Tip Opening Displacement ◽  
Offshore Structure ◽  
Opening Displacement ◽  
And Control ◽  
Crack Tip Opening ◽  
Haz Toughness

The CTOD (Crack Tip Opening Displacement) evaluation and control for HAZ (Heat Affected Zone) toughness of welded joints are the most effective measures to the security of steel structures. This paper address the problem of the newly developed offshore structure steel API 2W 50Z with heavy thickness of 100mm. In accordance with the American Petroleum Institute standard Recommended Practice 2Z (API PR 2Z), the CTOD tests of two critical positions of HAZ in three kinds of heat inputs were carried out in low temperature (-10°C). All of these CTOD testing and assessments are finished under the witness of American Bureau of Shipping (ABS). The result shows that all of the CTOD values are greater than the required value (0.38mm) in API RP 2Z. This indicates that the newly developed offshore structure steel (API 2W 50Z) meet the requirement of the toughness. Further, the CTOD testing and assessments in several international standards about weld joints of steel plates are also compared and discussed in this paper.

Steel Plates With Excellent HAZ Toughness for Offshore Structure

2013 ◽  
Author(s):  
Katsuyuki Ichimiya ◽  
Kazukuni Hase ◽  
Shigeru Endo ◽  
Masao Yuga ◽  
Kenji Hirata ◽  
...  
Keyword(s):  
Yield Stress ◽  
High Strength ◽  
Offshore Structures ◽  
Controlled Rolling ◽  
Steel Plates ◽  
Accelerated Cooling ◽  
Crack Tip Opening Displacement ◽  
Offshore Structure ◽  
Opening Displacement ◽  
The Matrix

In the field of offshore structure, the strength and the toughness required for steel plates used for oil resource development become higher as the installation areas of the structures move into arctic and deep water areas. High strength steel plates for offshore structures, which meet the low temperature specification, have been developed. Excellent properties of the steel plates have been achieved by micro-alloying, the latest controlled rolling and accelerated cooling technology. Excellent properties of weld joints have been also achieved by advanced metallurgical techniques, which are grain-refinement of the coarse grain heat affected zone (CGHAZ), reduction of Martensite-Austenite (M-A) constituent in inter-critically CGHAZ (ICCGHAZ), and improvement of the matrix toughness. These steels are designed for excellent weldability due to low weld cracking parameter (PCM) value up to 550 MPa class in yield stress, and also up to 101.6 mm in thickness with 420 MPa class in yield stress, and satisfying −40°C of crack tip opening displacement (CTOD) temperature specification for offshore structure.

Production of High-Strength and High-Toughness Steel for Offshore Structures

2003 ◽  
Author(s):  
Yoshihide Nagai ◽  
Hidenori Fukami ◽  
Hajime Inoue ◽  
Takao Nakashima ◽  
Akihiko Kojima ◽  
...  
Keyword(s):  
Welded Joints ◽  
Mass Production ◽  
Fine Particles ◽  
High Strength ◽  
Offshore Structures ◽  
Bearing Steel ◽  
Steel Plates ◽  
Carbon Equivalent ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement

By the utilization of new fine particles, steels refining the heat affected zone (HAZ) structure have been developed. This has made possible the mass-production of offshore structural steels which have high-strength of 460–500N/mm2 in yield strength (YS) and excellent crack-tip opening displacement (CTOD) properties. These newly developed steels for offshore structures have been mass-production to over 45,000 tons. The new particles are dispersed finely in the developed steels and show a strong pinning effect. The newly developed steels also use the intragranular ferrite (IGF) like titanium oxide bearing steel (TiO steel). In mass-production heats, γ grain size is restricted below 200 μm under conditions of 1400°C for 60 seconds. The improvement of HAZ toughness and the utilization of the thermo-mechanical control process (TMCP) has restrained the increase in carbon equivalent (Ceq,PCM) far as possible. By application of these technologies, it has been possible to mass-produce steels with high-strength, excellent CTOD properties and good weldability. As for steel plates of YS500N/mm2, the production of steel plates up to 70mm in thickness was carried out. The properties of welded joints for the 70mm-thick plates of YS500N/mm2 steel have been evaluated under heat input in 0.7kJ/mm of flux-cored are welding (FCAW) and 3.5kJ/mm of sub-merged arc welding (SAW). They have shown excellent CTOD and Charpy impact properties at welded joints; and have moreover indicated good weldability when PCM has been restricted to 0.22% or lower.

Dynamic Structural Integrity Assessment for Offshore Structures

2004 ◽  
Vol 126 (4) ◽  
pp. 358-363 ◽  
Author(s):  
W. Zhao ◽  
F. M. Burdekin
Keyword(s):  
Structural Integrity ◽  
Global Analysis ◽  
Offshore Structures ◽  
Crack Tip Opening Displacement ◽  
Offshore Structure ◽  
Opening Displacement ◽  
Structural Dynamic ◽  
Integrity Assessment ◽  
Crack Tip Opening ◽  
Cracked Members

The paper initially presents the results of a dynamic structural integrity assessment for fracture of cracked plate and tubular members under sinusoidal loading at different frequencies. The behavior of cracked members and joints in an offshore structure under wave loading (Stokes 5th order or gridded wave) is then examined. Global structural dynamic analyses of a whole offshore jacket were carried out as the first step, then, a set of sub-models of joints was selected from chosen locations and modeled with through thickness cracks under the loading extracted from the global analysis. The sub-model dynamic results were analyzed to obtain the fracture response in terms of variation of crack tip opening displacement (CTOD). Related values of K, J and their rates were also calculated. These results are used to give guidance on methods for design and assessment of structural integrity under dynamic loading.

Experimental Study on Fracture Toughness of Q460C the High-Strength Construction Steel at Low Temperature

2011 ◽  
Vol 71-78 ◽  
pp. 890-897 ◽  
Author(s):  
Yuan Qing Wang ◽  
Yun Lin ◽  
Yan Nian Zhang ◽  
Yong Jiu Shi
Keyword(s):  
Low Temperature ◽  
High Strength ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Three Point Bending ◽  
Function Fitting ◽  
Ductile Brittle Transition Temperature ◽  
Boltzmann Function ◽  
Fracture Appearance ◽  
Crack Tip Opening

Three point bending tests were carried out on 14mm-thick Q460C the high-strength structural steel at low temperature, and scanning electronic microscope of the fracture appearance was analyzed. The results showed that the obvious feature of brittle mechanism was shown on the three point bending specimen fracture whose testing took place at -40°C. And the crack tip opening displacement value of Q460C steel, which was less than that of Q235 steel, Q345 steel and Q390 steel at low temperature, tended to decrease with respect to the temperature reduction. Moreover, a Boltzmann function fitting analysis was applied to the experimental data, and the ductile-brittle transition temperature and the changing regularity were obtained.

Experimental Study on CTOD Fracture Toughness of Welded Joints of Low Temperature Steel

2011 ◽  
Vol 328-330 ◽  
pp. 1272-1276 ◽  
Author(s):  
Zong Tao Fang ◽  
Bo Sun ◽  
Chun Run Li
Keyword(s):  
Fracture Toughness ◽  
Low Temperature ◽  
Welded Joints ◽  
Welding Process ◽  
Offshore Platform ◽  
Fracture Toughness Test ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Welding Procedure ◽  
Crack Tip Opening

According to BS7448 fracture toughness test standard, crack tip opening displacement (CTOD) for ASTM A333 Gr.6 low temperature steel which is used in offshore platform were carried out in low temperature (0°C, -29°C). Three point bending tests were conducted on the specimens, the dimension of which is B×2B (B is the thickness) and notch direction is NP. The final value of CTOD was calculated by P-V curves of both the welds and HAZ (heat affected zone). And the experimental results were analyzed and discussed in the paper. The low temperature steel welded joints show good low temperature toughness, the selected welding procedure is applied to construction of pipelines.The CTOD value of HAZ is larger than weld metal and weld is the weakest position in the whole structure. The experiment results provide an important basis for the choice of welding method and welding process parameters, ECA assessment and construction of offshore platform.

Development of 550 MPa Yield Strength Steel Plate for Offshore Structures

2004 ◽  
Author(s):  
Takahiro Kamo ◽  
Takeshi Urabe ◽  
Kazushi Ohnishi ◽  
Hirofumi Nakamura ◽  
Shuji Okaguchi ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Yield Strength ◽  
Base Metal ◽  
Steel Plate ◽  
High Strength ◽  
Offshore Structures ◽  
Steel Plates ◽  
Offshore Structure ◽  
Copper Precipitation ◽  
High Toughness

Offshore structure steel with high strength of YS550MPa has been investigated. As for offshore structure steel, high toughness in welded joints is required in addition to that in base metal. TMCP type steel of up to YS420MPa grade is used widely, and up to YS500MPa grade is reported in some papers. However, steel of higher strength grade with good toughness and weldability will be beneficial to structures in strict conditions. To reach the YS550MPa requirement, hardening effect by Cu precipitation was utilized. Steel plates were designed with micro-alloyed low C-Mn-Cu-Ni-Cr-Mo system. The combination of the copper precipitation and TMCP technology can increase strength without deteriorating toughness and weldability. Heat treatment for Cu precipitation was carried out to optimize the balance of strength and toughness of the base metal. The developed steel also shows good HAZ CTOD toughness up to 76.2mm thickness in several welding conditions including after PWHT. The newly developed steel has the possibility to increase the flexibility to design large-sized structures.

scholarly journals The Effect of Notch Depth on CTOD Values in Fracture Tests of Structural Steel Elements

2018 ◽  
Vol 25 (2) ◽  
pp. 85-91
Author(s):  
Jakub Kowalski ◽  
Janusz Kozak
Keyword(s):  
Brittle Fracture ◽  
Test Procedure ◽  
Charpy Impact ◽  
Steel Structures ◽  
Charpy Impact Test ◽  
Offshore Structures ◽  
The Arctic ◽  
Notch Depth ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement

Abstract In elements of steel structures working at low temperatures, there is a risk of appearance of brittle fracture. This risk is reduced through the use of certified materials having guaranteed strength at a given temperature. A method which is most frequently used to determine brittle fracture toughness is the Charpy impact test, preformed for a given temperature. For offshore structures intended to work in the arctic climate, the certifying institutions more and more often require Crack Tip Opening Displacement (CTOD) tests instead of conventional impact tests, especially for steel and welded joints of more than 40 mm in thickness in the case of high-strength steel, and more than 50 mm for the remaining steels. The geometry of specimens and the test procedure are standardised; however, these standards provide some margin for specimen notch depth. The paper analyses the effect of notch depth difference, within the range permitted by the standards, on the recorded CTOD values of a given material. The analysis was performed via numerical modelling of destruction of specimens with different notch geometries and further verification of the obtained numerical results in laboratory tests. The calculations were carried out at the Academic Computer Centre in Gdansk.

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