Investigation of Correlation Between Fracture Toughness and Charpy Impact Energy of Cryogenic Steel Welds

The high manganese steel was developed to improve the fracture toughness and safety at cryogenic temperatures, the austenite structure was formed by increasing the manganese (Mn) content. The developed weld high manganese steel was alloyed with austenite stabilizing elements (e.g., C, Mn, and Ni) for cryogenic toughness and fluxes contained less than 10% of acidic slag formers such as rutile (TiO2) and silica (SiO2). This paper describes the work carried out to enhance the fracture toughness of Mn contents in an economical way by means of increase of manganese up to 23% instead of using nickel (Ni) which has unique element to improve fracture toughness especially at cryogenic steel. The new cryogenic steels should be carefully evaluated in terms of safety for application in real structures including LNG ships. In this study, the fracture toughness performance was evaluated for recently developed cryogenic steels (high-Mn steels), especially the crack tip opening displacement (CTOD) parameter was evaluated using the prediction formula proposed by conventional equation. The CTOD value was investigated the effect of microstructure and mechanical properties of Fe–C–Mn and Fe–C–Mn–Ni high manganese steel, it was revealed that the e-martesnsite phase formed in high manganese steel of 0.2C–20Mn and 0.4C–20Mn as a result of a low stability of austenite upon strain-induced phase transformation.

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Study on the Mechanical Behavior and Microscopic Mechanism of Explosive Working of High-Manganese Steel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.239-242.506 ◽

2011 ◽

Vol 239-242 ◽

pp. 506-512

Author(s):

Cheng Gang Ding

Keyword(s):

Surface Hardness ◽

Residual Deformation ◽

Charpy Impact ◽

Charpy Impact Test ◽

Manganese Steel ◽

High Manganese ◽

High Manganese Steel ◽

Microscopic Mechanism ◽

Abrasive Resistance ◽

Metallographic Structure

This paper has examined the hardening effect and mechanism of explosive working on high-manganese steel. According to the experiment result, the surface hardness of high-manganese steel is improved greatly after explosive working and the hardened depth exceeds 40mm. The surface hardness and hardened depth increase slightly, the tensile strength is improved and ductility is reduced after three times of explosion. Charpy impact test demonstrates that it has still high ductility, the fatigue performance isn’t inferior to that before the explosion, the abrasive resistance is higher than that before the explosion and macroscopic residual deformation is extremely small. Such changes are related with the internal stress and changes of metallographic structure after explosion. After explosion, the surface is at stress state and the metallographic structure still retains the single-phase austenite matrix; and it produces high-density dislocation, stacking fault, cross-slip, lattice torsion, twin-crystal and refinement of austenite crystal grains.

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Interpretation of significant decrease in cryogenic-temperature Charpy impact toughness in a high manganese steel

Materials Science and Engineering A ◽

10.1016/j.msea.2018.09.043 ◽

2018 ◽

Vol 737 ◽

pp. 158-165 ◽

Cited By ~ 1

Author(s):

Jun Chen ◽

Jia-kuan Ren ◽

Zhen-yu Liu ◽

Guo-dong Wang

Keyword(s):

Impact Toughness ◽

Cryogenic Temperature ◽

Charpy Impact ◽

Manganese Steel ◽

High Manganese ◽

High Manganese Steel ◽

Charpy Impact Toughness

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A Comparison of Fracture Toughness and Fatigue Crack Propagation Characteristics of High Manganese and Nickel Steels

Volume 4: Materials Technology ◽

10.1115/omae2018-77247 ◽

2018 ◽

Author(s):

Jeong-Yeol Park ◽

Myung-Hyun Kim

Keyword(s):

Fracture Toughness ◽

Fatigue Crack ◽

Low Temperature ◽

Natural Gas ◽

Structural Integrity ◽

Liquefied Natural Gas ◽

Manganese Steel ◽

Nickel Steel ◽

High Manganese ◽

High Manganese Steel

Recently, demands for liquefied natural gas (LNG) are increased by developing countries such as China, India and Middle East area. In addition, the International Maritime Organization (IMO) reinforced regulations to avoid the serious environmental pollution. This trend has led to manufacturing and operating various LNG vessels such as liquefied natural gas carrier (LNGC), floating liquefied natural gas (FLNG) and very large gas carrier (VLGC). In the design of LNG vessels, the structural integrity of LNG storage tank is of significant importance to satisfy the service conditions. In order to secure structural integrity, LNG storage tank is fabricated with low temperature materials. In general, low temperature materials such as SUS304L, Invar alloy, Al 5083-O, nickel alloy steel and high manganese steel exhibit excellent fatigue and fracture performances at cryogenic temperature. In particular, high manganese steel has attracted interest because they are potentially less expensive than the competing other low temperature materials. This study compares the fracture toughness and fatigue crack growth characteristics of high manganese steel with those of nickel steels. In addition, fracture toughness and fatigue crack growth rate tests for various nickel steels are conducted according to BS 7448 and ASTM E647, respectively. In order to obtain less conservative design values, the results of high manganese steel and various nickel steels were compared to those of BS7910. As a result, the CTOD value of high manganese steel is higher than that of 9% nickel steel at cryogenic temperature. In case of FCGR, the high manganese steel and 9% nickel steel are found to be similar to each other.

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Structural Integrity Evaluation of API 5L X65 Pipe Subjected to Pre-Strain up to Tensile Strain Using the API 579 Procedure

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.345-346.1353 ◽

2007 ◽

Vol 345-346 ◽

pp. 1353-1356

Author(s):

Jong Hyun Baek ◽

Cheol Man Kim ◽

Young Pyo Kim ◽

Chang Sung Seok

Keyword(s):

Mechanical Properties ◽

Fracture Toughness ◽

Tensile Test ◽

Structural Integrity ◽

Mechanical Damage ◽

Charpy Impact ◽

Charpy Impact Test ◽

Ground Subsidence ◽

Crack Tip Opening Displacement ◽

Opening Displacement

Mechanical properties of the pre-strained material are different with those of virgin material without pre-strain. Buried pipelines for natural gas transmission may be deformed by outside force such as ground subsidence, ground liquefaction, cold bending and mechanical damage. Plastic deformation affects the tensile properties and fracture toughness. The effects of prestrain on the mechanical properties of API 5L X65 pipe were diversely investigated through the tensile test, crack tip opening displacement test and Charpy impact test. Axial tensile pre-strain of 1.5, 5 and 10% was applied to plate-type tensile specimens cut from the pipe body prior to mechanical testing. Tensile test revealed that yield strength and tensile strength were increased with increasing tensile pre-strain. However, Fracture toughness for crack initiation decreased with increasing tensile pre-strain. Structural integrity evaluation of the API 5L X65 pipe with crack-like flaws was assessed by using the level 2 in the API 579 code.

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