scholarly journals Research for the Optimal Flux-Cored Arc Welding Process of 9% Nickel Steel Using Multi Object Optimization with Solidification Crack Susceptibility

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1659
Author(s):  
Minho Park ◽  
Jisun Kim ◽  
Changmin Pyo ◽  
Joonsik Son ◽  
Jaewoong Kim
Keyword(s):  
Coastal Region ◽  
Welding Process ◽  
Oxide Content ◽  
Sulfur Oxide ◽  
Nickel Steel ◽  
Quality Deterioration ◽  
Flux Cored Arc Welding ◽  
Lng Fuel ◽  
Crack Susceptibility ◽  
Solidification Crack

The environment of the global shipbuilding market is changing rapidly. Recently, the International Maritime Organization (IMO) has tightened regulations on sulfur oxide content standards for marine fuels and tightened sulfur oxide emission standards for the entire coastal region of China to consider the environment globally and use LNG as a fuel. There is a tendency for the number of vessels to operate to increase significantly. To use cryogenic LNG fuel, various pieces of equipment, such as storage tanks or valves, are required, and equipment using steel, which has excellent impact toughness in cryogenic environments, is required. Four steel types are specified in the IGG Code, and 9% Ni steel is mostly used for LNG fuel equipment. However, to secure safety at cryogenic temperatures, a systematic study investigating the causes of quality deterioration occurring in the 9% Ni steel welding process is required and a discrimination function capable of quality evaluation is urgent. Therefore, this study proposes a plan where the uniform quality of 9% Nickel steel is secured by reviewing the tendency of the solidification crack susceptibility among the quality problems of cryogenic steel to establish the criteria for quality deterioration and to develop a system capable of quality discrimination and defect avoidance.

scholarly journals A Study on the Algorithm of Quality Evaluation for Fiber Laser Welding Process of ASTM A553-1 (9% Nickel Steel) Using Determination of Solidification Crack Susceptibility

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5617
Author(s):  
Minho Park ◽  
Jisun Kim ◽  
Changmin Pyo ◽  
JoonSik Son ◽  
Jaewoong Kim
Keyword(s):  
Welding Process ◽  
Optimization Procedure ◽  
Nickel Steel ◽  
Cryogenic Temperatures ◽  
Fiber Laser Welding ◽  
Materials Used ◽  
Lng Fuel ◽  
Crack Susceptibility ◽  
Cryogenic Tanks ◽  
Solidification Crack

To prevent the contamination of the marine environment caused by ship exhaust gas, the demand for LNG (liquefied natural gas) fueled ships is increasing worldwide. A tank to store LNG at cryogenic temperatures is indispensable to such LNG-fueled ships. Since the materials used for LNG fuel propulsion tanks must have excellent mechanical properties such as impact toughness at cryogenic temperatures, the International Maritime Organization limits the IGC Code only to four types. Most of the tank materials for LNG-fueled ships ordered recently are adopting ASTM A553-1 material, but a systematic study to analyze the problem of quality degradation that may occur when welding A553-1 steel is required to secure the safety of cryogenic tanks. Therefore, in this study, among various quality problems, the tendency of weld solidification crack vulnerability is identified, and a decision system and optimization procedure are developed. In addition, a method of securing the welding quality of A553-1 steel was proposed by setting quality deterioration standards.

scholarly journals Laser Welding of ASTM A553-1 (9% Nickel Steel) (PART I: Penetration Shape by Bead on Plate)

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 484 ◽  
Author(s):  
Jaewoong Kim ◽  
Jisun Kim ◽  
Sungwook Kang ◽  
Kwangsan Chun
Keyword(s):  
Laser Welding ◽  
Steel Part ◽  
Total Production ◽  
Nickel Steel ◽  
Basic Study ◽  
Steel Material ◽  
Flux Cored Arc Welding ◽  
Lng Fuel ◽  
Welding Electrode ◽  
Main Factor

The International Maritime Organization (IMO) is tightening regulations, in order to reduce greenhouse gas emissions from ship operations. As a result, the number of vessels using Liquefied Natural Gas (LNG) as fuel has increased rapidly. At this time, ASTM A553-1 (9% nickel steel) is being used as a tank material for storing LNG as fuel, because it has higher strength than other cryogenic materials. Currently, shipyards are manufacturing LNG fuel tanks by using the Flux Cored Arc Welding (FCAW) method, using 9% nickel steel material. However, fabrication through FCAW welding has two drawbacks. The first is to use a welding electrode that is 20 times higher in cost than the base metal, and the second is that the total production cost increases because the thickness of the tank increases due to the strength drop near the Heat Affected Zone (HAZ) after welding. Laser welding, which does not require additional welding rods and has no strength reduction in the HAZ, can overcome the drawbacks of FCAW welding and ensure price competitiveness. In this study, it is confirmed the characteristics of the penetration shape of Bead on Plate (BOP) after various laser welding conditions as a basic study to apply laser welding to A553-1 welding. For this, penetration characteristics of A553-1, according to laser welding speed and power, which is a main factor of laser welding, are confirmed.

scholarly journals A Study on the Weldment Hardening Discrimination Procedure and Improvement of Flux Cored Arc Welding Process of ASTM A553-1 (9% Nickel Steel) Material Using Bead Geometry Distribution

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1282
Author(s):  
Minho Park ◽  
Jisun Kim ◽  
Changmin Pyo ◽  
Jaewoong Kim ◽  
Kwangsan Chun
Keyword(s):  
Base Metal ◽  
Arc Welding ◽  
Welding Process ◽  
Fuel Oil ◽  
Bead Geometry ◽  
Nickel Steel ◽  
Welding Quality ◽  
Dilution Ratio ◽  
Flux Cored Arc Welding ◽  
Arc Welding Process

As a result of strengthened sulfur content standards for ship fuel oil in IMO regulations, major domestic and foreign carriers have a high and growing demand for liquefied natural gas (LNG) powered ships and related equipment. For LNG operation in a cryogenic environment, a storage tank and fuel supply system that uses steel with excellent brittleness and fatigue strength is required. Ships that use LNG have a high vulnerability to explosion and fire. For this reason, 9% Ni is typically used, since a ship requires high quality products with special materials and structural technologies that guarantee operability at cryogenic temperatures. However, there is an urgent need for research to derive a uniform welding quality, since high process difficulty and differences in welding quality related to a welder’s skills can cause a deterioration of the weld quality in the 9% Ni steel welding process. For 9% Ni steel, the higher the dilution ratio of the base metal, the lower the strength. In order to secure the required strength, excessive dilution of the base metal should be avoided, and the relationship between dilution ratio and strength should be investigated. According to previous research, if it exceeds 25% it may be lower than the API standard of 363 MPa for hardening welds. Therefore, in this study, the flux cored arc welding process is performed by establishing criteria that can be evaluated based on the SVM method in order to determine the structure of the weld to be cured according to the dilution rate of the base metal. We would like to propose a multipurpose optimization algorithm to ensure uniform quality of 9% Ni steel.

Correlation between wire feed speed and external mechanical constraint for enhanced process stability in underwater wet flux-cored arc welding

2018 ◽  
Vol 233 (10) ◽  
pp. 2061-2073 ◽  
Author(s):  
Jianfeng Wang ◽  
Qingjie Sun ◽  
Jiangkun Ma ◽  
Peng Jin ◽  
Tianzhu Sun ◽  
...  
Keyword(s):  
Welding Process ◽  
Electrical Signal ◽  
Feed Speed ◽  
Process Stability ◽  
Underwater Wet Welding ◽  
Extinction Process ◽  
Flux Cored Arc Welding ◽  
Wire Feed Speed ◽  
Wire Feed ◽  
Mechanical Constraint

It is a great challenge to improve the process stability in conventional underwater wet welding due to the formation of unstable bubble. In this study, mechanical constraint method was employed to interfere the bubble generated by underwater wet welding, and the new method was named as mechanical constraint assisted underwater wet welding. The aim of the study was to quantify the combined effect of wire feed speed and condition of mechanical constraint on the process stability in mechanical constraint assisted underwater wet welding. Experimental results demonstrated that the introduction of mechanical constraint not only suppressed the bubble without floating but also stabilized the arc burning process. The degree of influence of mechanical constraint, which changed with wire feed speed, played an important role during the mechanical constraint assisted underwater wet welding process. For all wire feed speeds, the fluctuations of welding electrical signal were decreased through introduction of mechanical constraint. The difference in the proportion of arc extinction process between underwater wet welding and mechanical constraint assisted underwater wet welding became less with increasing wire feed speed. At wire feed speed lower than 7.5 m/min, the improvement of process stability was very significant by mechanical constraint. However, the further improvement produced limited effect when the wire feed speed was greater than 7.5 m/min. The observation results showed that a better weld appearance was afforded at a large wire feed speed, corresponding to a lower variation coefficient.

Recent Development of HFW Linepipe With a High-Quality Weld Seam Suitable for Sour Service Environments

2014 ◽  
Author(s):  
Shunsuke Toyoda ◽  
Sota Goto ◽  
Yasushi Kato ◽  
Satoru Yabumoto ◽  
Akio Sato
Keyword(s):  
Crack Propagation ◽  
Chemical Reactions ◽  
Weld Seam ◽  
Welding Process ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Oxide Content ◽  
Electric Resistance ◽  
Diffusible Hydrogen ◽  
High Quality

Based on the appreciable progress being made in quality control and assurance technology for the electric resistance welding process, the number of applications for high-frequency electric resistance welded (HFW) linepipe in highly demanding, severe environments, such as offshore and sour environments, has gradually increased. Resistance to hydrogen-induced cracking (HIC) is the most important property for a linepipe to possess for use in sour environments. However, resistance to HIC, especially along the longitudinal weld seam, has not yet been fully related to metallurgical factors. In this study, to clarify the effects of inclusions on the sour resistance properties of X60- to X70-grade steels, their resistances to HIC were numerically simulated. For the simulation, the steels were assumed to have a yield strength of 562 MPa and a tensile strength of 644 MPa. To estimate the effect of nonmetallic inclusions, a virtual inclusion was situated at the center of a 10-mm-thick HIC test specimen. Tests were performed using NACE test solution A. The crack propagation rate was calculated as a function of the content of diffusible hydrogen, the diameter of the inclusion, and the fracture toughness of the matrix after hydrogen absorption. In the propagation calculation, the resistance to chemical reactions at the interface of the inclusion matrix was also considered to be a delaying factor. By assuming a resistance to chemical reactions at the interface, the crack propagation rate could be fitted to the actual HIC propagation rate. Based on the numerical simulation results, HFW linepipe with a high-quality weld seam was developed. Controlling the morphologies and distributions of oxides generated during the welding process is the key factor for improving the resistance to HIC. Using a combination of optimized chemical composition, microstructure and oxide content, the weld seam of the developed X70-grade HFW steel pipe showed excellent resistance to HIC.

scholarly journals Multivariate Stochastic Optimization Approach Applied in a Flux-Cored Arc Welding Process

IEEE Access ◽  
2020 ◽  
Vol 8 ◽  
pp. 61267-61276 ◽  
Author(s):  
Alexandre F. Torres ◽  
Franco B. Rocha ◽  
Fabricio A. Almeida ◽  
Jose H. F. Gomes ◽  
Anderson P. Paiva ◽  
...  
Keyword(s):  
Stochastic Optimization ◽  
Arc Welding ◽  
Welding Process ◽  
Optimization Approach ◽  
Flux Cored Arc Welding ◽  
Arc Welding Process
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