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.

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.

Analysis on Critical CTOD of Long-Term Used Penstock

2017 ◽  
Vol 741 ◽  
pp. 57-62
Author(s):  
Fumito Kawamura ◽  
Masazumi Miura ◽  
Ryuichiro Ebara ◽  
Keiji Yanase
Keyword(s):  
Fracture Toughness ◽  
Structural Integrity ◽  
Steel Structures ◽  
Chemical Compositions ◽  
Structural Components ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Crack Tip Opening

Many studies have been conducted to characterize the fracture toughness of structural steels and their welded joints. However, most studies focus on newly developed steels, and the number of studies on the fracture toughness of long-term used steels in structural components is rather limited. Furthermore, a lack of data on the fracture toughness causes difficulties in evaluating the structural integrity of existing steel structures. In this study, CTOD tests were performed to characterize the fracture toughness of penstock that has been in service for 50 years. By measuring the critical crack tip opening displacement in conjunction with analysis for chemical compositions, the characteristics of fracture toughness were investigated.

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.

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.

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.

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.

Investigation of metal cored arc welded FCA (fatigue crack arrester) steel in terms of microstructure, toughness and tensile properties

2018 ◽  
Author(s):  
Εμμανουήλ-Μάριος Καζασίδης
Keyword(s):  
Fatigue Crack ◽  
Tensile Properties ◽  
Arc Welding ◽  
Crack Tip ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Arrester ◽  
Crack Tip Opening ◽  
Welding Technique

Η παρούσα διδακτορική διατριβή αποσκοπεί στη μελέτη συγκολλήσεων ελασμάτων χάλυβα τύπου ΑΗ-40 FCA (Fatigue Crack Arrester), πάχους 13 mm, οι οποίες πραγματοποιήθηκαν με τη μέθοδο τόξου κοίλου ηλεκτροδίου με πυρήνα μεταλλικής σκόνης (Μetal Cored Arc Welding technique-MCAW). Η συγκεκριμένη μέθοδος συγκόλλησης επιλέχθηκε επειδή συνίσταται σε αυτοματοποιημένες διαδικασίες συγκόλλησης και ιδιαίτερα με πολλαπλά περάσματα καθώς δεν απαιτεί ενδιάμεσο καθαρισμό σκωρίας (σε αντίθεση με την FCAW). Κατά συνέπεια, οι συγκολλήσεις πραγματοποιήθηκαν με χρήση ρομποτικού μηχανισμού προκειμένου να εξασφαλιστεί η επαναληψιμότητα και η ακρίβεια των πειραματικών δοκιμών.Η διαδικασία που ακολουθήθηκε για τη μελέτη των συγκολλήσεων του χάλυβα AH-40 FCA περιλαμβάνει την εκτέλεση προπαρασκευαστικών-διερευνητικών πειραμάτων, τη διαδικασία βελτιστοποίησης ως προς τη μικροδομή και των ιδιοτήτων ένταντι εφελκυστικής φόρτισης, τη μελέτη της δυσθραυστότητας καθώς και την κατασκευή αναλυτικού μοντέλου. Πιο συγκεκριμένα: Aρχικά καθορίστηκε το εύρος των συνθηκών συγκόλλησης. Η σχετική μελέτη πραγματοποιήθηκε μέσω της διεξαγωγής μεμονωμένων στρώσεων μετάλλου στην επιφάνεια των χαλύβδινων ελασμάτων. Τα πειραματικά αποτελέσματα σε συνδυασμό με τη βιβλιογραφική ανασκόπηση, καθόρισαν το εύρος των εντέλει χρησιμοποιηθησών ρυθμών εισαγωγής θερμότητας (0.5-2.5 kJ/mm με βήμα 0.5 kJ/mm). Στη συνέχεια, η βελτιστοποίηση της συγκόλλησης πραγματοποιήθηκε βάσει των αποτελεσμάτων του μικροδομικού χαρακτηρισμού και των δοκιμών εφελκυσμού εγκαρσίως της διεύθυνσης συγκόλλησης. Σε αυτό το στάδιο τα παρακάτω κριτήρια καθορίστηκαν ως κρίσιμα για την επίτευξη της βέλτιστης συγκολλητής δομής:- Έκταση θερμικά επηρεασμένης ζώνης (η ελαχιστοποίηση του πλάτους της είναι επιθυμητή). Χρήση στερεοσκοπίου.- Ομοιογένεια των μικροδομικών συστατικών μεταξύ της θερμικά επηρεασμένης ζώνης, της ζώνης τήξης και του μετάλλου βάσης (η μέγιστη ομοιογένεια είναι επιθυμητή). Χρήση οπτικής μικροσκοπίας, ηλεκτρονικής μικροσκοπίας σάρωσης.- Κατανομή μικροσκληρομετρήσεων (ομαλή κατανομή είναι επιθυμητή, πλησιέστερη στη τιμή αναφοράς, δηλαδή στη μικροσκληρότητα του μετάλλου βάσης). Χρήση της μεθόδου Vickers.- Όριο διαρροής της συγκόλλησης (επιθυμητή η μεγιστοποίηση του ορίου διαρροής). Δοκιμή εφελκυσμού εγκαρσίως της διεύθυνσης συγκόλλησης- Αντοχή σε εφελκυσμό (επιθυμητή η μεγιστοποίηση της αντοχής). Δοκιμή εφελκυσμού εγκαρσίως της διεύθυνσης συγκόλλησης.-Επιμήκυνση θραύσης ως δείκτης της ολκιμότητας (επιθυμητή η μεγιστοποίησης της επιμήκυνσης). Δοκιμή εφελκυσμού εγκαρσίως της διεύθυνσης συγκόλλησης. Έπειτα, η μελέτη επικεντρώθηκε στη διερεύνηση της βέλτιστης συγκόλλησης και πιο συγκεκριμένα στην περιοχή που παρουσιάζει τη μέγιστη υποβάθμιση των μηχανικών ιδιοτήτων. Σε αυτήν πραγματοποιήθηκαν δοκιμές με χρήση προρωγματωμένων δοκιμίων για τη μέτρηση της δυσθραυστότητας με τις μεθόδους Charpy V-notch και CTOD (Crack tip opening displacement).Παράλληλα με την πειραματική διαδικασία πραγματοποιήθηκε η ανάπτυξη ενός αιτιοκρατικού αναλυτικού μοντέλου το οποίο χρησιμοποιεί ρητές-μαθηματικές εξισώσεις με διττό στόχο: την πρόβλεψη του εμβαδού της περιοχής ενίσχυσης ενός κορδονιού ευθείας ραφής, καθώς και του απαιτούμενου αριθμού κορδονιών σε μία συγκόλληση με πολλαπλά περάσματα. Η αξιοπιστία των προβλεπόμενων αποτελεσμάτων και η επαναληψιμότητα του μοντέλου επιβεβαιώθηκαν πειραματικά.

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