The microstructure effect on the fracture toughness of ferritic Ni-alloyed steels

Scheid, Adriano; Félix, Lorenzo Marzari; Martinazzi, Douglas; Renck, Tiago; Kwietniewski, Carlos Eduardo Fortis

doi:10.1016/j.msea.2016.03.019

Cited by 23 publications

(3 citation statements)

References 14 publications

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“…Thus, LNG transporting ships and storage tanks are under construction all around the world [1,2]. The heat-treated 9%Ni steel is the material of choice for manufacturing large-scale LNG storage tanks and vessels where high tensile strength ( ≥ 700 MPa) and high charpy impact energy ( ≥ 34J at −196°C/77 K) are required [3][4][5]. Since welding is widely used in the fabrication of LNG transportation and storage facilities, a good understanding of factors affecting the quality of welded joints is critical.…”

Section: Introductionmentioning

confidence: 99%

Shielded metal arc welding of 9%Ni steel using matching ferritic filler metal

El-Batahgy

Saiyah

Khafagi

et al. 2020

Science and Technology of Welding and Joining

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Motivated by the tensile strength loss of 9%Ni steel arc welded joints made using Ni-based austenitic filler metals, the feasibility of maintaining the tensile strength using matching ferritic filler metal has been demonstrated. In comparison with shielded metal arc welded joint made using Ni-based austenitic electrode ENiCrMo-6, higher tensile strength comparable to that of the base metal was obtained using matching ferritic electrode. Besides, sufficient impact toughness energies with much lower mismatch were obtained for weld metal and heat-affected zone. Welded joint with a lower mechanical mismatching is of considerable importance for achieving acceptable combination of tensile strength and impact toughness. A better combination of these mechanical properties is ensured by applying a post weld heat treatment.

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Section: Introductionmentioning

confidence: 99%

Shielded metal arc welding of 9%Ni steel using matching ferritic filler metal

El-Batahgy

Saiyah

Khafagi

et al. 2020

Science and Technology of Welding and Joining

View full text Add to dashboard Cite

show abstract

“…Transport ships and storage tanks for liquefied natural gas (LNG) are being built around the world [ 1 , 2 ]. Heat-treated ferritic steel alloyed with 9%Ni is widely accepted as the most important material for the fabrication of large LNG storage tanks and vessels where high strength (≥700 MPa) and pronounced notch impact energy (≥34 J at −196 °C/−320 °F) are required [ 3 , 4 , 5 ]. Welding is commonly used in the manufacturing of LNG transportation and storage equipment; therefore, understanding the factors that affect the quality of welded joints is crucial to maintaining its mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

Retaining Mechanical Properties of GMA-Welded Joints of 9%Ni Steel Using Experimentally Produced Matching Ferritic Filler Metal

et al. 2022

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Motivated by the loss of tensile strength in 9%Ni steel arc-welded joints performed using commercially available Ni-based austenitic filler metals, the viability of retaining tensile strength using an experimentally produced matching ferritic filler metal was confirmed. Compared to the austenitic Ni-based filler metal (685 MPa), higher tensile strength in gas metal arc (GMA) welded joints was achieved using a ferritic filler metal (749 MPa) due to its microstructure being similar to the base metal (645 MPa). The microstructure of hard martensite resulted in an impact energy of 71 J (−196 °C), which was two times higher than the specified minimum value of ≥34 J. The tensile and impact strength of the welded joint is affected not only by its microstructure, but also by the degree of its mechanical mismatch depending on the type of filler metal. Welds with a harder microstructure and less mechanical mismatch are important for achieving an adequate combination of tensile strength and notched impact strength. This is achievable with the cost-effective ferritic filler metal. A more desirable combination of mechanical properties is guaranteed by applying low preheating temperature (200 °C), which is a more practicable and economical solution compared to the high post-weld heat treatment (PWHT) temperature (580 °C) suggested by other research.

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“…The welding consumable with TIG welding has the highest nickel content among welding consumables. It is known that a high nickel content has been used extensively to improve fracture toughness [19]. Therefore, the weldment of TIG has the highest CTOD value at cryogenic temperature.…”

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confidence: 99%

An Investigation of the Mechanical Properties of a Weldment of 7% Nickel Alloy Steels

Lee

Kim

2016

Metals

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During the last decade, the demand for natural gas has steadily increased for the prevention of environmental pollution. For this reason, many liquefied natural gas (LNG) carriers have been manufactured. Since one of the most important issues in the design of LNG carriers is to guarantee structural safety, the use of low-temperature materials is increasing. Among commonly employed low-temperature materials, nickel steel has many benefits such as good strength and outstanding corrosion resistance. Accordingly, nickel steels are one of the most commonly used low-temperature steels for LNG storage tanks. However, the study of fracture toughness with various welding consumables of 7% nickel alloy steel is insufficient for ensuring the structural safety of LNG storage tanks. Therefore, the aim of this study was to evaluate fracture toughness of several different weldments for 7% nickel alloy steels. The weldment of 7% nickel alloy steel was fabricated by tungsten inert gas (TIG), flux cored arc welding (FCAW), and gas metal arc welding (GMAW). In order to assess the material performance of the weldments at low temperature, fracture toughness such as crack tip opening displacement (CTOD) and the absorbed impact energy of weldments were compared with those of 9% nickel steel weldments.

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The microstructure effect on the fracture toughness of ferritic Ni-alloyed steels

Cited by 23 publications

References 14 publications

Shielded metal arc welding of 9%Ni steel using matching ferritic filler metal

Shielded metal arc welding of 9%Ni steel using matching ferritic filler metal

Retaining Mechanical Properties of GMA-Welded Joints of 9%Ni Steel Using Experimentally Produced Matching Ferritic Filler Metal

An Investigation of the Mechanical Properties of a Weldment of 7% Nickel Alloy Steels

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