Shielding gas

About: Shielding gas is a research topic. Over the lifetime, 6697 publications have been published within this topic receiving 58668 citations.

Determination of enthalpy, temperature, surface tension and geometry of the material transfer in PGMAW for the system argon-iron

Abstract: The metal transfer is a fundamental process in gas metal arc welding, which substantially determines the shape of the weld seam and strongly influences arc formation and stability. In this investigation the material transfer from the wire electrode (anode) to the workpiece (cathode) is analysed experimentally with high accuracy using various innovative diagnostic techniques for a pulsed gas metal arc welding (PGMAW) process. A high-speed two-colour pyrometer, a calorimeter, thermocouples, a stereo optical setup and a droplet oscillation technique are used to analyse a precisely defined PGMAW process. Thus, results obtained are verified by different measurement techniques and enable a comprehensive description of the material transfer procedure.The surface temperature of both electrodes as well as the droplet temperature, enthalpy and surface tension were determined. Furthermore, the geometry of the arc, wire, droplets and weld pool were extracted in three dimensions in order to describe the interaction between the material transfer and the formation of the weld seam. The experiments are performed using argon as shielding gas and pure iron as filler and base material to reduce complex chemical processes. It turned out that the wire feed rate has the biggest influence on droplet temperature and detachment. A correlation between weld pool formation and weld pool surface temperature gradient was observed, which is mainly a function of welding speed and wire feed rate. The experimental results obtained provide a detailed data pool for use in modelling.

Plasma properties of helium gas tungsten arc with metal vapour

Abstract: The energy source characteristics of gas tungsten arc (GTA) strongly depend on the physical property of arc plasma. In welding processes, it has been experimentally confirmed that metal vapour evaporated from a high temperature weld pool drastically changes the property of arc plasma and decreases its temperature. However, the effect of metal vapour on the characteristics of heat flux into a base metal is still not clear owing to the difficulty in experimental studies of arc plasma. In the present paper, the energy source property of helium GTA mixed with metal vapour was numerically analysed. It was found that the intense radiation generated from dense metal vapour decreases heat flux into a base metal and contracts the current density distribution especially near the arc axis.

Weld microstructure and shape of laser–arc hybrid welding

Abstract: A series of CO2 laser–metal inert gas arc hybrid welding experiment was carried out to investigate the effects of laser/arc energy ratio and groove parameters on the shape and microstructure of hybrid weld The results showed that increasing arc current and groove cross-section area can reduce dimension difference of laser zone and arc zone by enhancing the uniform of energy distribution in molten pool The arc current can speed the melted metal flow to the pool root and drive more heat to the pool below by the arc pressure, and groove area can reduce the resistance of melted metal flowing to the pool root The microstructure of hybrid weld is simultaneously determined by the total line energy of hybrid welding and energy ratio of laser/arc (ER LA), and only under the proper or relatively smaller total line energy ER LA has obvious effects on microstructure Increasing the ER LA can increase the tendency of hybrid weld to obtain structure with higher hardness Furthermore, the mechanical performan

Formation mechanism and reduction method of porosity in laser welding of stainless steel

Abstract: It is generally acknowledged in any steels or alloys that porosity is liable to be formed in a keyhole type of deeply penetrated fusion zones made with a high power laser. Therefore, this investigation was carried out with the objectives of elucidating the formation mechanism of porosity and developing preventive procedure of pores in high power laser welding.The formation behavior of keyhole, bubbles and porosity was observed during butt-joint or bead-on-plate CO2 laser welding of stainless steel by microfocused X-ray transmission insitu imaging system with high speed video camera. The influence of various laser welding conditions on porosity formation was investigated. As a result, it was observed that many bubbles were predominantly frequently formed at the bottom of a molten pool from the tip part of a deep keyhole in consequence of its dynamic motion due to intense evaporation, and some bubbles were formed from the middle part of the keyhole in the case of focal point under the plate surface or high power laser irradiation. It was also seen that most of the bubbles were soon captured or trapped into pores by the solidifying solid-liquid interface during floating up in a stainless steel. SEM observation result of a fractured surface demonstrated traces that liquid was penetrated and solidified inside pores, probably because evaporated materials trapped in the bubble solidified and/or the temperature dropped to render their inside pressure lower. According to Q mass-spectroscopic analysis of gas content of porosity, it was revealed that He shielding gas and H2 gas were included inside a pore near the bottom of the weld fusion zone. It was observed to be feasible to produce a sound full-penetration weld bead without porosity in steel plates of 10 mm thickness, since no bubbles were formed from the bottom part of the fully penetrated keyhole. Bubbles, porosity or pores were confirmed to be reduced by utilizing N2 shielding gas and forward keyhole-inclination welding in He shielding gas even in the case of partially penetrated weld.It is generally acknowledged in any steels or alloys that porosity is liable to be formed in a keyhole type of deeply penetrated fusion zones made with a high power laser. Therefore, this investigation was carried out with the objectives of elucidating the formation mechanism of porosity and developing preventive procedure of pores in high power laser welding.The formation behavior of keyhole, bubbles and porosity was observed during butt-joint or bead-on-plate CO2 laser welding of stainless steel by microfocused X-ray transmission insitu imaging system with high speed video camera. The influence of various laser welding conditions on porosity formation was investigated. As a result, it was observed that many bubbles were predominantly frequently formed at the bottom of a molten pool from the tip part of a deep keyhole in consequence of its dynamic motion due to intense evaporation, and some bubbles were formed from the middle part of the keyhole in the case of focal point under the plate surface or high ...

Flux cored wire for welding Ni-Cr-Fe alloys

Abstract: A self-shielding, flux cored arc welding electrode for joining Ni-Cr-Fe alloys and overlaying dissimilar metals. The wire has a nickel-chromium containing alloy sheath and a flux core containing special proportions of carbonates, fluorides, metal oxides, and powdered metals. Sound welds can be prepared without the use of a supplemental inert shielding gas. Welded joints provide essentially the same properties as those of the Ni-Cr-Fe base alloy.