Arc stability indexes evaluation of ultrasonic wave-assisted underwater FCAW using electrical signal analysis

2021

Materials

The paper presents the effects of waterproof coatings use to cover electrodes on the weldability of high-strength, low-alloy (HSLA) steel in water. With the aim of improving the weldability of S460N HSLA steel in water, modifications of welding filler material were chosen. The surfaces of electrodes were covered by different hydrophobic substances. The aim of the controlled thermal severity (CTS) test was to check the influence of these substances on the HSLA steel weldability in the wet welding conditions. The visual test, metallographic tests, and hardness Vickers HV10 measurements were performed during investigations. The results proved that hydrophobic coatings can reduce the hardness of welded joints in the heat-affected zone by 40–50 HV10. Additionally, the number of cold cracks can be significantly reduced by application of waterproof coatings on the filler material. The obtained results showed that electrode hydrophobic coatings can be used to improve the weldability of HSLA steel in underwater conditions.

Section: Introductionmentioning

confidence: 99%

Weldability of Underwater Wet-Welded HSLA Steel: Effects of Electrode Hydrophobic Coatings

2021

Materials

“…During wet welding, the welder and the welding area are in direct contact with the surrounding environment throughout the process. The most popular wet welding processes are flux-cored arc welding (FCAW) [22][23][24][25][26] and welding with the use of covered electrodes (MMA) [27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Dissimilar underwater wet welding of HSLA steels

Int J Adv Manuf Technol

Fydrych

2020

The high-strength low-alloy S460ML and S460N steels were chosen for underwater wet welding of dissimilar T-joints using covered electrodes. For improving the quality of joints, the temper bead welding (TBW) method was used. The application of TBW in pad welding conditions has been investigated earlier but the possibility of usage of this technique in welded joints was not analyzed. The main aim of the study was to check the influence of TBW on the hardness and structures of the heat-affected zone (HAZ) of dissimilar T-joints made in the underwater conditions. The experiments conducted showed that the technique used can reduce the susceptibility to cold cracking by decreasing the hardness in HAZ, which is a result of changes in its structure. The TBW technique reduced the hardness in the HAZ of the S460N steel by 40-50 HV10 and in S460ML by 80-100 HV10. It was also found that the changes in S460ML and S460N were much different, and therefore, the investigated technique can provide better results in the steel characterized by lower carbon equivalent Ce IIW .

“…These changes result from the instability of the welding arc in the water, which is the other problem in this environment. Wang et al stated that ultrasonic wave-assisted during underwater FCAW welding has the potential to control the dynamic bubble and then improve arc stability [32]. Xu et al [33] proved, that droplet has significant influence on the stability of underwater welding process.…”

Section: Introductionmentioning

confidence: 99%

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

Janeczek

2020

Applied Sciences

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.