Welding current effect on diffusible hydrogen content in flux cored arc weld metal

Abstract

The application of flux cored arc welding (FCAW) has increased in manufacturing and fabrication. Even though FCAW is well known for its good capability in producing quality welds, few reports have been published on the cause of the relatively high diffusible hydrogen content in the weld metal and its relation with the ingredients used in the wire production and with the welding parameters (mainly welding current). This paper describes experiments where data obtained from weld metal diffusible hydrogen analysis, metal droplet collection, and high-speed recording of metal droplet transfer were used to evaluate the effect of welding current on diffusible hydrogen content in the weld metal. The results from gas chromatography analysis showed that weld metal hydrogen content indeed increased with welding current. A polynomial regressional analysis concluded that hydrogen increase with current was better described by a linear function with proportional constant of approximately 0.7 or 70%. Different from the GMA welding transfer behavior, statistical analysis showed only a small increase in metal droplet size with increasing current. The metal transfer mode remained in the globular range for currents between 100 and 150 A. The most surprising findings were with the high-speed cinematography recording. Observing the high speed movies, it was possible to see that at low current, "unmelted" flux sporadically touched the weld pool but at higher current, the flux remained touching the weld pool during the whole time of droplet formation and transfer. It is believed that since the flux has ingredients that contain hydrogen, hydrogen passes through the arc undisturbed, going to the weld bead intact and increasing the hydrogen content in the weld metal. Another important observation is regarding to droplet size. Droplet size increased with increasing current because forces from decomposed gases from the flux could sustain the droplets, retarding their transfer and allowing them to grow

Operational behavior assesment of coated tubular electrodes for SMAW hardfacing

“…7, left side), as already referenced in the literature (Haidar and Lowke, 1996;Haidar, 1998;Choi et al, 2001;Wang et al, 2003), augmenting the detaching critical droplet diameter. This droplet growing behavior with current increases had been observed experimentally by other researchers, so much as for continuous tubular wires (flux cored arc welding) (Bracarence et al, 2002), as for coating electrode (shield metal arc welding) (Brandi et al, 1991).…”

Effect of Storage Conditions of Rutile Flux Cored Welding Wires on Properties of Welds

“…1 . The differences in temperature and relative humidity changes from 15 February to 15 March in Gdańsk and Katowice were small and constitute only one of the factors affecting the degradation of the surface of wires and the change in the properties of padding welds made using them. Other factors, such as nitrogen, sulfur and carbon oxides could also have had a significant impact on the destruction of wires.…”

“…Consumables for welding by this process include: basic cored wires, rutile cored wires, self-shielded wires and shielding gases such as CO2 and Ar + CO2 mixture. Appropriate selection of process parameters and filler materials enables the creation of a continuous, metallic weld without welding defects disqualifying the welded joint from operation [12][13][14][15][16][17]. For the proper quality of the process, it is necessary to maintain a technological regime in the scope of storage of welding consumables.…”

Możliwości sterowania ilością wodoru dyfundującego w złączach spawanych

“…W przypadku wszystkich opisanych metod spawania ilość wodoru dyfundującego w stopiwie jest silnie uzależniona od parametrów spawania wpływających na wymiary jeziorka spawalniczego, od których zależy intensywność wymiany gazowej między otoczeniem a ciekłym metalem. Przedstawione wyniki potwierdzają również w ogólności pogląd, że parametry elektryczne spawania wpływają na ilość wodoru dyfundującego w stopiwie pośrednio: zmieniając charakter przenoszenia metalu w łuku [30,43]. Zmiany wartości parametrów spawania wpływają na rozmiar kropli metalu w łuku, co poprzez stosunek pola powierzchni do objętości metalu wpływa na kinetykę reakcji utleniania stopiwa.…”