Recent developments in repair welding technologies in Japan

Yurioka, Nobutaka; Horii, Yukihiko

doi:10.1179/174329306x101382

Cited by 43 publications

(22 citation statements)

References 19 publications

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“…At the same time, compared with air, the thermal conductivity of water is relatively high. The water environment will greatly increase the cooling rate of the weld zone and the cooling speed can reach 6–8 times that of land welding [11]. Currently, the problem of cold cracking in underwater wet welding can be controlled from the two aspects of welding material and process.…”

Section: Introductionmentioning

confidence: 99%

Control of Droplet Transition in Underwater Welding Using Pulsating Wire Feeding

Guo

Huang

et al. 2019

Materials

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Underwater wet welding technology is widely used. Because the stability of droplet transfer in underwater wet welding is poor, the feasibility of improving the droplet transfer mode has been discussed from various technical directions. In this work, the characteristics of pulsating wire feeding were studied in the pulsating wire feeding mode by investigating the effects of changing the pulsating frequency, the wire withdrawal speed, and the wire withdrawal quantity on the droplet transfer process and the welding quality. With the aim of improving weld forming and welding stability, the authors selected the coefficient of variation and the ratio of unstable droplet transfer as the indexes to evaluate the effect of droplet transfer control. The pulsating wire feeding process of underwater wet flux-cored wire was analyzed in depth, and the following conclusions were drawn: using the pulsating wire feeding mode and after comparing and analyzing the pulsed wire feeding process under the same frequency condition, the authors found that the forming and stability were better under the conditions of slower withdrawal speed and smaller withdrawal quantity. The short-circuit transition ratio decreased steadily with the increase of pulsating wire feeding frequency, the rejection transition ratio first rose and then decreased, and the splash ratio first decreased and then rose.

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Section: Introductionmentioning

confidence: 99%

Control of Droplet Transition in Underwater Welding Using Pulsating Wire Feeding

Guo

Huang

et al. 2019

Materials

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“…Helium gas is insoluble in metals, so it precipitates and forms bubbles (at the nanoscale), nucleating at dislocations, point defects, and grain boundaries [4]. When conventional fusion welding is used for weld repair, the high temperatures and thermal stresses inherent in the process enhance the growth of helium bubbles, causing intergranular cracking in the heataffected zone (HAZ) [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

“…In both cases the issue of helium embrittlement, accelerated by the temperatures and stresses of fusion welding, presents a serious difficulty that must be overcome. While low heat input laser welding can be a partial solution to the problem [7], reactors with 30-40 years of service may have irradiated components which cannot be repaired by any of the conventional methods [11]. It is anticipated that many nuclear reactors will function for up to 80 years [12], so the repairability of irradiated stainless steel is of great importance to this industry.…”

Section: Introductionmentioning

confidence: 99%

Simulation of Friction Stir Processing in 304L Stainless Steel

et al. 2016

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Abstract.A major dilemma facing the nuclear industry is repair or replacement of stainless steel reactor components that have been exposed to neutron irradiation. When conventional fusion welding is used for weld repair, the high temperatures and thermal stresses inherent in the process enhance the growth of helium bubbles, causing intergranular cracking in the heat-affected zone (HAZ). Friction stir processing (FSP) has potential as a weld repair technique for irradiated stainless steel, because it operates at much lower temperatures than fusion welding, and is therefore less likely to cause cracking in the HAZ. Numerical simulation of the FSP process in 304L stainless steel was performed using an Eulerian finite element approach. Model input required flow stresses for the large range of strain rates and temperatures inherent in the FSP process. Temperature predictions in three locations adjacent to the stir zone were accurate to within 4% of experimentally measure values. Prediction of recrystallized grain size at a location about 6mm behind the tool center was less accurate, because the empirical model employed for the prediction did not account for grain growth that occurred after deformation in the experiment was halted.

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“…7 The residual stresses and transverse contraction can be reduced successfully by the vibratory weld conditioning in multipass welding, 8 the preheating and controlling an optimum interpass temperatures, 9 and the local postweld heat treatment. 10 Furthermore, the residual stress can also be alleviated by the microscale interaction of phase transformation with local stresses. 2,11 For example, the carbon fibre/SiC composite was brazed to Ti alloy using interlayer of Ag-Cu-Ti-W mixed powder.…”

Section: Introductionmentioning

confidence: 99%

Relaxing welding residual stresses by diamond like carbon coating on duplex titanium alloys

Lee¹,

Wang²,

Shih³

et al. 2008

Science and Technology of Welding and Joining

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The distribution of welding residual stresses in titanium alloy plates composed of Ti-6Al-4V (Ti-64) and Ti-4?5Al-3V-2Mo-2Fe (SP700) alloys was measured and calculated under the same heat input. Ti-64 alloy exhibited a higher residual tensile stress than the SP700 alloy due to the low thermal conductivity and thermal diffusivity of the former alloy, in addition to its high thermal expansion coefficient. Diamond like carbon (DLC) thin film deposited on the as welded titanium alloy plates reduced the magnitude of the welding residual stress caused by the cathodic arc physical vapour deposition (PVD) process. The distribution of the measured welding residual stresses agreed with the finite element method (FEM) simulated results very well.

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Recent developments in repair welding technologies in Japan

Cited by 43 publications

References 19 publications

Control of Droplet Transition in Underwater Welding Using Pulsating Wire Feeding

Control of Droplet Transition in Underwater Welding Using Pulsating Wire Feeding

Simulation of Friction Stir Processing in 304L Stainless Steel

Relaxing welding residual stresses by diamond like carbon coating on duplex titanium alloys

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