Shielded metal arc welding

About: Shielded metal arc welding is a research topic. Over the lifetime, 4462 publications have been published within this topic receiving 40560 citations. The topic is also known as: manual metal arc welding & flux shielded arc welding.

Aluminium to steel resistance spot welding with cold sprayed interlayer

Abstract: Studies on bonding of aluminium alloys to steels are popular because these are structural materials widely used in a variety of industries. However, joining these dissimilar materials is difficult mainly because of the formation of brittle intermetallic compounds. This paper presents a study on welding aluminium to steel by resistance spot welding. Before the welding, steel surface was covered by cold spraying with the layer of aluminium, nickel and nickel–aluminium. This way, instead of the welding of dissimilar materials, the welding of aluminium to aluminium (or nickel) layer pre-deposited on the steel sample was performed. The feasibility of using interlayers for improving the welding of dissimilar materials was tested using SEM, EDX and XRD. Mechanical properties of welds were investigated by microhardness and shear strength tests. The results showed that the coating allowed to decrease hardness in the welding zone and to increase the shear strength of the weld.

Heat treatment of welded 13%Cr-4%Ni martensitic stainless steels for sour service

Abstract: For many years, the petroleum industry has employed martensitic stainless steels for wellhead and valve applications, and increasing use has been made of 13%Cr-4%Ni alloys. This material type was originally developed as a cast alloy (e.g., ASTM A487/A487M-89a Grade CA6NM). The combination of a low-carbon content and the addition of 3.5 to 4.5% nickel produces a fine, lath martensite structure which, after a tempering heat treatment, can exhibit superior mechanical properties. Thus, CA6NM and its forged variant ASTM A182/A182M-91 F6NM find application for production fluids containing CO{sub 2} and H{sub 2}S environments, particularly when hardening occurs, as is the case with fusion welds. Sensitivity to sulfide SCC increases at high material hardness levels, and the NACE MR0175 standard limits 13%Cr-4%Ni alloys to HRC 23 maximum for sour service. Attainment of such a hardness level requires careful consideration of tempering procedure. In this paper, the roles of welding procedure, material composition and postweld heat treatment are examined in relation to producing the minimum hardness levels in the weld zone.

Weldability and Microstructural Aspects of Shielded Metal Arc Welded HSLA-100 Steel Plates

Abstract: HSLA-100 steel with 14 mm thickness in quenched and tempered condition was shielded metal arc welded (SMAW) with 2 kJ/mm heat input using basic flux coated filler rods without any pre or post welding heat treatments. The steel was found to be welded satisfactorily in this condition without developing any defect. Optical microscopy studies revealed typical cast dendritic structure in the weld metal and coarse bainite in grain-coarsened area of the heat-affected zone (HAZ). Transmission electron microscopy (TEM) study confirmed incidence of mixed structure of martensite laths and bainite in weld metal, while, it was mainly of bainite laths in HAZ with evidence of martensite–austenite (M–A) constituent and massive ferrite. The yield strength (YS), ultimate tensile strength (UTS) and Charpy V-notch (CVN) impact energy of the weld metal (YS-695 MPa, UTS-842 MPa and CVN-105 J at –50°C) and HAZ (YS-790 MPa, UTS-891 MPa and CVN-130 J at –50°C) were found satisfactory although HAZ properties were inferior to the base metal properties. The hardening of HAZ was not very significant in this steel under the present welding condition.

Variable AC polarity GTAW fusion behavior in 5083 aluminum

Abstract: Aluminum alloys are typically welded on AC with the gas tungsten arc welding (GTAW) process. Many power sources have "max penetration" indicated when more than 50% of the AC cycle is spent on electrode negative polarity and "max cleaning" when more than 50% of the cycle is on electrode positive polarity. In the work reported here, weld bead dimensions, notably penetration and bead width, increase with the percentage of electrode positive polarity during the unbalanced square wave AC welding of aluminum alloys with the GTAW process. This is in direct contradiction of conventional assumptions about the role of electrode positive and electrode negative contributions to surface cleaning and fusion behavior during AC welding. The primary source of the extra base metal melting during electrode positive operation is in the nature of cold cathode field emission of electrons from the base metal. The dielectric breakdown of surface oxide as electrons are emitted also contributes to the increased fusion, but this is not a contributory factor once the weld metal surface is completely clean. Both phenomena require extra energy to be supplied to the cathode, which results in the increased fusion. Earlier works on the gas metal arc welding (GMAW) process confirm this behavior of enhanced melting at the cathode. Positive ion bombardment, thermal convection from the plasma jet, and radiation from the plasma complete the thermal input to the cathode for metal fusion.