In-situ observations of melt degassing and hydrogen removal enhanced by ultrasonics in underwater wet welding

Chen, Hao; Guo, Ning; Xu, Kexin; Xu, Cheng; Zhou, Li; Wang, Guodong

doi:10.1016/j.matdes.2020.108482

Cited by 28 publications

(14 citation statements)

References 55 publications

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“…The same factor was responsible for higher abrasive wear resistance of layers welded inthe air. The water, as a welding environment, increased the cooling rate, which generated brittle structures [27][28][29][30][31]35,38] with lower wear resistance.…”

Section: Hardness Hv10 Measurementsmentioning

confidence: 99%

“…This process is carried out in direct contact with water and can be performedusing different methods, e.g., by the self-shielded flux-cored arc welding (FCAW-S) method [27][28][29]. The FCAW-S process does not require the use of shielding gas, and it is easy to automate and train welders [23,[27][28][29][30]. However, manual metal arc (MMA) welding is still the most commonly used as an underwater welding process [31,32].…”

Section: Introductionmentioning

confidence: 99%

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The Abrasive Wear Resistance of Coatings Manufactured on High-Strength Low-Alloy (HSLA) Offshore Steel in Wet Welding Conditions

2020

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Some marine and offshore structure elements exploited in the water cannot be brought to the surface of the water as this will generate high costs, and for this reason, they require in-situ repairs. One of the repair techniques used in underwater pad welding conditions is a wet welding method. This paper presents an investigation of the abrasive wear resistance of coatings made in wet welding conditions with the use of two grades of covered electrodes—an electrode for underwater welding and a commercial general use electrode. Both electrodes were also used for manufacturing coatings in the air, which has been also tested. The Vickers HV10 hardness measurements are performed to demonstrate the correlation in abrasive wear resistance and the hardness of each specimen. The microscopic testing was performed. For both filler materials, the coatings prepared in a water environment are characterized by higher resistance to metal–mineral abrasion than coatings prepared in an air environment—0.61 vs. 0.44 for commercial usage electrode and 0.67 vs. 0.60 for underwater welding. We also proved that in the water, the abrasive wear was greater for specimens welded by the general use electrode, which results in a higher hardness of the layer surface. In the air welding conditions, the layer welded by the electrode for use in the water was characterized by a lower hardness and higher resistance to metal–mineral abrasion. The microstructure of the prepared layers is different for both the environment and both electrodes, which results in abrasive wear resistance.

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Section: Hardness Hv10 Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Abrasive Wear Resistance of Coatings Manufactured on High-Strength Low-Alloy (HSLA) Offshore Steel in Wet Welding Conditions

2020

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“…Xu et al [33] proved, that droplet has significant influence on the stability of underwater welding process. Chen et al [34] stated also that ultrasonic energy decreases the porosity and diffusible hydrogen content, which can improve the quality of underwater welded joints.…”

Section: Introductionmentioning

confidence: 99%

Underwater In Situ Local Heat Treatment by Additional Stitches for Improving the Weldability of Steel

Tomków

Janeczek

2020

Applied Sciences

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In this paper the influence of in situ local heat treatment performed by additional stitches on the weldability of high-strength low-alloy (HSLA) S355J2C+N steel was tested. The investigated steel is characterized by high susceptibility to cold cracking. It is necessary to find a method to improve the quality of welded joints. The local heat treatment was applied as an effect of bead-on plate welding made on the face of a Tekken test joint. The specimens were made by the use of covered electrodes in the water environment. For testing weldability, Tekken test specimens were made. Then, the different number of the pad welds with different overlapping were laid on the face of the tested welds. Non-destructive (NDT) visual and penetrant tests were undertaken. During the NDT, imperfections like shape mistakes and spatters were found. Then, metallographic macro- and microscopic testing were performed. The macroscopic observations proved that water environment can generate imperfections like cracking and pores. However, for specimens with additional stitches the number of imperfections decreased. Microscopic tests proved that the proposed technique affected the structure of the heat-affected zone (HAZ). The specimens without the application of additional stitches are characterized by brittle bainitic and martensitic structure. Specimens, in which the additional stitches were applied, contain tempered martensite, fine ferrite and fine pearlite in their HAZ. It was also observed that the number of cracks decreased for in situ local heat-treatment specimens. The final step was Vickers HV10 hardness measurement. These measurements confirmed previous results. The heat from additional stitches affected the steel by significantly decreasing the hardness by 80–100 HV10. The results of experiments showed that the heat from pad welds provided microstructural changes in heat-affected zones and a decrease in the susceptibility to cold cracking, which results in improvement in the weldability of HSLA steel in wet welding conditions.

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“…The value of Re was proportional to the values of L and v. The melt flow improved by ultrasonic vibration increased the weld width and melt flow velocity. In previous studies, the calculated value of Re increased from 5614 to 11389, with the ultrasonic power increased from 0 to 60% [33]. Ultrasonic vibration accelerated the melt flow, which broke the stable status of grain growth.…”

Section: Microstructures and Microhardnessmentioning

confidence: 81%

“…The value of the v e could be calculated by dividing weld penetration depth (P) by solidification time (t) of the weld pool. In the ordinary welding without ultrasonic (P and t were 2.36 mm and 6.7 s, respectively), the minimal escaping diameter for the cavitation bubble was approximately 22 µm [33]. It meant that cavitation bubbles would be left in the weld pool and became pores in the case of that the cavitation bubble was smaller than the critical value of 22 µm.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Investigating the Advantages of Ultrasonic-assisted Welding Technique Applied in Underwater Wet Welding by in-situ X-ray Imaging Method

Chen

Guo

et al. 2020

Materials

Self Cite

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In this study, the effects of ultrasonic on melt pool dynamic, microstructure, and properties of underwater wet flux-cored arc welding (FCAW) joints were investigated. Ultrasonic vibration enhanced melt flow and weld pool oscillation. Grain fragmentation caused by cavitation changed microstructure morphology and decreased microstructure size. The proportion of polygonal ferrite (PF) reduced or even disappeared. The width of grain boundary ferrite (GBF) decreased from 34 to 10 μm, and the hardness increased from 204 to 276 HV. The tensile strength of the joint increased from 545 to 610 MPa, and the impact toughness increased from 65 to 71 J/mm2 due to the microstructure refinement at the optimum ultrasonic power.

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In-situ observations of melt degassing and hydrogen removal enhanced by ultrasonics in underwater wet welding

Cited by 28 publications

References 55 publications

The Abrasive Wear Resistance of Coatings Manufactured on High-Strength Low-Alloy (HSLA) Offshore Steel in Wet Welding Conditions

The Abrasive Wear Resistance of Coatings Manufactured on High-Strength Low-Alloy (HSLA) Offshore Steel in Wet Welding Conditions

Underwater In Situ Local Heat Treatment by Additional Stitches for Improving the Weldability of Steel

Investigating the Advantages of Ultrasonic-assisted Welding Technique Applied in Underwater Wet Welding by in-situ X-ray Imaging Method

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