Showing papers on "Submerged arc welding published in 2015"
TL;DR: In this article, the authors showed that dissimilar currents at lead and trail wires induce stability in the welding arcs, resulting in a considerable influence on weld microstructures, hardness, heat affected zone, and weld penetration-width ratio.
48 citations
TL;DR: In this article, the metal transfer process of underwater flux-cored wire wet welding was successfully observed by an X-ray transmission method and the relatively large retention forces acting on the droplet induced by the electromagnetic force, vaporization force, surface tension resultant force and gas flow drag force made the transfer mode as a combination of globular repelled transfer mode and short circuit transfer mode.
43 citations
TL;DR: In this paper, the formation mechanism of weld cross section was studied using a high-speed camera and X-ray imaging system to study the formation of weld seam during high-power deep-penetration laser welding.
Abstract: During high-power deep-penetration laser welding of thick plate, the geometrical characteristics of weld cross section were investigated under different welding conditions. The molten metal behaviors were observed by using the high-speed camera and X-ray imaging system to study the formation mechanism of weld cross section. With the increase of welding speed, the width and depth of weld seam decreased, and the geometry of weld cross section changed from big-head shape to needle-like shape. The change of focal position of laser beam led to the variation of molten metal behavior which thus resulted in different geometries of weld cross sections during laser welding. The accumulation of high-temperature molten metal at both the top surface of molten pool and the middle depth of molten pool could lead to a higher heat-transferring efficiency of the molten metal which could lead to a wider weld width. The stable molten metal behavior on the molten pool surface resulted in a low heat-transferring efficiency, and the sound appearance of weld seam could be obtained when the focal position was inside the metal.
41 citations
TL;DR: In this article, the effects of arc voltage on the stability of the underwater wet flux-cored arc welding (FCAW-S 114) process are explained based on studying the droplet transfer process using the X-ray transmission method.
39 citations
TL;DR: In this paper, the welding process using 100% CO2 gas was characterized by a large number of spatters, while the penetration depth of a weld was increased and porosity was reduced.
38 citations
TL;DR: In this paper, a unified arc model for gas metal arc welding, including metal transfer, is presented, which does not account for heat transfer in the metal, but the wire melting rate is determined by the arc current.
Abstract: The gas metal arc welding (GMAW) process combines aspects of arc plasma, droplet transfer, and weld pool phenomena. In the GMAW process, an electrode wire is melted by heat from an arc plasma, and molten metal at the wire tip is deformed by various driving forces such as electromagnetic force, surface tension, and arc pressure. Subsequently, the molten droplet detaches from the tip of the wire and is transferred to the base metal. The arc plasma shape changes together with the metal transfer behavior, so the interaction between the arc plasma and the metal droplet changes from moment to moment. In this paper, we describe a unified arc model for GMAW, including metal transfer. In the model, we do not account for heat transfer in the metal, but the wire melting rate is determined by the arc current. The developed model can show transition from globular transfer at low currents to spray transfer at higher currents. It was found that electromagnetic force is the most important factor at high currents, but surface tension is more important than electromagnetic force at low currents in determining the transfer mode.
36 citations
25 Jun 2015-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the fracture toughness and related microstructure characteristics of dissimilarly welded joint manufactured by advanced 9Cr and CrMoV steels were systematically investigated for different regions including weld metal (WM), heat affected zone (HAZ) of 9Cr side (9Cr-HAZ), and 9Cr base metal (BM).
Abstract: In this paper, the fracture toughness and the related microstructure characteristics of dissimilarly welded joint manufactured by advanced 9Cr and CrMoV steels were systematically investigated. The dissimilarly welded joint was fabricated by narrow gap submerged arc welding (NG-SAW) applying multi-layer and multi-pass technique. Fracture toughness, as one of the most important property to assess the reliability of welded joint, was studied for different regions including CrMoV base metal (CrMoV-BM), heat affected zone (HAZ) of CrMoV side (CrMoV-HAZ), weld metal (WM), heat affected zone of 9Cr side (9Cr-HAZ) and 9Cr base metal (9Cr-BM). It was found that the fracture toughness of CrMoV-BM, CrMoV-HAZ and WM was better than that of 9Cr-HAZ and 9Cr-BM. In order to illustrate these results, the microstructure of the whole welded joint was observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM) detailedly. It was found that the fine high-temperature tempered martensite and bainite in WM, CrMoV-BM and CrMoV-HAZ contribute to the higher fracture toughness, while lower fracture toughness for 9Cr-BM and HAZ was caused by coarse tempered lath-martensite. Furthermore, the fracture morphology showed that ductile fracture occurred in WM and CrMoV side, while brittle fracture appeared in BM and HAZ of 9Cr side.
35 citations
TL;DR: In this paper, the hybrid laser/arc welding (HLAW) was applied to join aluminum alloy (AA6061) to an advanced high strength steel (AHSS) where an explosively welded transition joint, TRICLAD®, was used as an intermediate structural insert between the thick plates of the aluminum alloy and AHSS.
34 citations
TL;DR: In this paper, carbon migration in the welds between 9% Cr steel and CrMoV steel during high-cycle fatigue (HCF) test at various temperatures was studied.
34 citations
TL;DR: In this article, the welding process is represented in the form of mathematical models developed using response surface methodology and the models were then used to predict the weld bead characteristics with reasonable accuracy.
33 citations
TL;DR: In this paper, the microstructure of the as-welded and machined steel plate was characterized by optical and scanning electron microscopy and the residual stresses determined by X-ray diffraction and incremental hole drilling method.
TL;DR: In this paper, a three-dimensional numerical heat transfer and fluid flow model is developed to understand the temperature distribution and molten pool behavior in a three wire submerged arc welding process, where the model solves the equations of the conservation of mass, momentum, and energy along with the volume of fluid method.
TL;DR: In this paper, a method of reducing welding fumes at source towards green welding process has been worked out after nano coating of conventional electrodes, which involves the dipping of a core welding wire, prior to its flux coating, in a sol containing aluminium iso-propoxide, to obtain a thin film of nano alumina coating.
TL;DR: In this paper, a high speed tandem gas tungsten arc welding process involving an assistant arc following the main arc to suppress the formation of undercut and humping defects is proposed.
TL;DR: In this article, a finite element model was developed to investigate the thermal process of large spot laser + MIG arc brazing-fusion welding, where the laser was treated as a Gaussian plane heat source, the arc distortion was taken into consideration and the overheated droplet was treated by a uniform body heat source.
TL;DR: In this paper, the effect of the amount of one flux of one component (Cr2O3) placed on the surface of the work piece, and the additions of KClO4 and Al 2O3, on the shape of the weld bead was evaluated.
Abstract: Active flux TIG (ATIG) welding is a simple variant of the conventional TIG process that allows increased penetration of the weld and enables welding in one pass, with total penetration and without chamfer opening, for joints with thicknesses of 5 mm or more. Different mechanisms have been proposed to explain this effect, with emphasis on contraction of the arc due to the presence of negative ions and alteration in the movement of liquid metal in the weld pool, associated with variations of surface tension as a function of temperature. This study evaluates the effect of the amount of one flux of one component (Cr2O3) placed on the surface of the work piece, and the additions of KClO4 and Al2O3, on the shape of the weld bead. Three sets of bead-on-plate weld tests were performed on 5-mm-thick ABNT 304 stainless steel plates. In the first set, the amount of flux used varied; in the second set, the effect of the additions of KClO4 was studied; and in the third, Al2O3. Electric current and voltage were measure...
TL;DR: Based on Fuzzy logic and NSGA-II (Non-dominated Sorting Genetic Algorithm-II) algorithm, a new approach was proposed for weld bead geometry prediction and for process parameters optimization.
Abstract: Submerged arc welding (SAW) is one of the main welding processes with high deposition rate and high welding quality. This welding method is extensively used in welding large-diameter gas transmission pipelines and high-pressure vessels. In welding of such structures, the selection process parameters has great influence on the weld bead geometry and consequently affects the weld quality. Based on Fuzzy logic and NSGA-II (Non-dominated Sorting Genetic Algorithm-II) algorithm, a new approach was proposed for weld bead geometry prediction and for process parameters optimization. First, different welding parameters including welding voltage, current and speed were set to perform SAW under different conditions on API X65 steel plates. Next, the designed Fuzzy model was used for predicting the weld bead geometry and modeling of the process. The obtained mean percentage error of penetration depth, weld bead width and height from the proposed Fuzzy model was 6. 06%, 6. 40% and 5. 82%, respectively. The process parameters were then optimized to achieve the desired values of convexity and penetration indexes simultaneously using NSGA-ll algorithm. As a result, a set of optimum vectors (each vector contains current, voltage and speed within their selected experimental domains) was presented for desirable values of convexity and penetration indexes in the ranges of (0. 106, 0. 168) and (0. 354, 0. 561) respectively, which was more applicable in real conditions.
Patent•
03 Jun 2015
TL;DR: In this paper, a submerged arc welding flux for low-alloy-steel narrow-gap welding and a preparation method of the submerged-arc welding flux is described. But the welding flux has a high alkalinity, ranging from 2.0 to 3.0.
Abstract: The invention relates to a submerged-arc welding flux for low-alloy-steel narrow-gap welding and a preparation method thereof. A high-alkalinity MgO-CaO-Al2O3-CaF slag system is adopted, and the submerged-arc welding flux is mainly made from raw materials including calcium fluoride, aluminum oxide, wollastonite, marbles, silicon iron and ferromanganese iron. The preparation method of the submerged-arc welding flux mainly comprises the steps of 1 dry mixing in proportion, 2 impurity removal, 3 bonding agent adding for wet mixing and 4 baking and high-temperature sintering. The alkalinity of the welding flux ranges from 2.0 to 3.0, low-hydrogen and low-oxygen deposited metal containing ultra low P and S impurity contents can be obtained through welding, and accordingly it can be ensured that the deposited metal has excellent comprehensive mechanical property. When the submerged-arc welding flux is matched and welded with a low-purity low-alloy steel welding wire, S and P are not added into the deposited metal by adopting the welding flux. The submerged-arc welding flux has excellent alloy transition capacity.
TL;DR: A Fuzzy Logic model is proposed and optimal levels of NiO,MnO and MgO were obtained using a single multi-response performance index (MRPI) in submerged arc welding.
TL;DR: Bypass Current Double Sided Arc Welding (BC-DSAW) for high-speed welding of thin plates has been investigated in this paper, where the bypass current increased melting efficiency of the filler wire and reduced the heat input of the base metal.
TL;DR: In this paper, a model of a tungsten inert gas (TIG) welding arc is presented, which provides a consistent description of the free burning arc, the arc attachment and the electrodes.
Abstract: This work presents modelling results concerning a tungsten inert gas (TIG) welding arc. The model provides a consistent description of the free burning arc, the arc attachment and the electrodes. Thermal and chemical non-equilibrium is considered in the whole arc area, and a detailed model of the cathode space-charge sheath is included. The mechanisms in the cathode pre-sheath are treated in the framework of a non-equilibrium approach which is based on a two-fluid description of electrons and heavy particles and a simplified plasma chemistry of argon. A consistent determination of the electrode fall voltages and temperature distributions is achieved. The model is applied to arcs in pure argon at currents up to 250 A, whereby welding of a workpiece made of mild steel with a fixed burner is considered. Arc voltages in the range from 12 to 17 V are obtained at 50 at 250 A, respectively. The space-charge sheath voltage is found to be about 7 V and almost independent of the current. The corresponding temperatures of the cathode tip are in the range from 3,000 K to about 3,800 K. The results obtained are in a good agreement with measurements.
TL;DR: In this article, the effect of CO2 mixture in a shielding gas on a metal transfer process was investigated through the observation of the plasma characteristics and dynamic behaviour at the droplet's growth-separation-transfer by the temperature measurement methods which were suitable, respectively, to the argon plasma region and the metal plasma region.
Abstract: For gas metal arc welding, the effect of CO2 mixture in a shielding gas on a metal transfer process was investigated through the observation of the plasma characteristics and dynamic behaviour at the droplet’s growth-separation-transfer by the temperature measurement methods which were suitable, respectively, to the argon plasma region and the metal plasma region. At the present experimental conditions, the metal transfer process was a spray transfer type with 100%Ar shielding gas. On the other hand, with 85%Ar + 15%CO2 shielding gas, the metal transfer process was a globular transfer type in which the arc length was shorter, the width was narrower and the time interval of the droplet separation was longer. For both shielding gases, the metal plasma region near the arc central axis exhibited 6500–7500 K, which was lower than the argon plasma region. With 85%Ar + 15%CO2 shielding gas, when the metal droplet grew below the electrode wire, the region below the droplet has a high plasma temperature an...
TL;DR: In this paper, the authors investigated the effect of Ce on inclusions, microstructure and mechanical properties of the weld metal in flux copper backing submerged arc welding and found that the inclusions are mainly composed of Al2O3, MnO, SiO2, TiO, Ce2S3, CeS and Ce2O2S compound.
Abstract: This paper investigates the effect of Ce on inclusions, microstructure and mechanical properties of the weld metal in flux copper backing submerged arc welding. The results show, with the addition of Ce in weld metal, the inclusions are mainly composed of Al2O3, MnO, SiO2, TiO, Ce2S3, CeS and Ce2O2S compound, and the proportion of the inclusions of < 1.0 μm in size increased. In competitive nucleation, acicular ferrite nucleates on the oxysulphides of Ce and inhibits the formation of proentectoid ferrite and ferrite side plate. This led to a high proportion of acicular ferrite, good mechanical properties of weld metal. A small lattice disregistry between CeS, Ce3S4, Ce2O2S and acicular ferrite contributed to low energy for nucleation of acicular ferrite.
Patent•
20 May 2015
TL;DR: In this article, an H-steel or T-steel full-penetration back-gouging-free welding method was proposed, in which a K-shaped groove was formed in a web of H- steel or T steel, a truncated edge with the width ranging from 3 mm to 4 mm was reserved, and the web was arranged on a ship-form assembly jig.
Abstract: The invention discloses an H-steel or T-steel full-penetration back-gouging-free welding method. According to the method, a K-shaped groove ranging from 45 degrees to 60 degrees is formed in a web of H-steel or T-steel, a truncated edge with the width ranging from 3 mm to 4 mm is reserved, the H-steel or the T-steel is arranged on a ship-form assembly jig, the web and a flange plate are assembled in a gapless mode, the top end of the web of the T-steel is provided with a locating plate, the included angle between the bottom edge of the ship-form assembly jig and the ground ranges from 20 degrees to 50 degrees, and the web is parallel to the bottom edge of the ship-form assembly jig; the web and the reverse side and the obverse side of a K-shaped groove of the flange plate are subjected to backing welding, single-wire submerged arc welding and double-wire submerged arc welding are adopted, the included angle between a welding wire and the web ranges from 60 degrees to 70 degrees, and welding parameters are set respectively; after backing welding is completed, filling welding and cosmetic welding are conducted, single-wire submerged arc welding and double-wire submerged arc welding are adopted, and welding parameters are set. By means of the H-steel or T-steel full-penetration back-gouging-free welding method, the defects of a traditional back-gouging-free welding method are overcome, the complex back-gouging-free procedure in the welding process is omitted, the welding efficiency is improved, environmental pollution on a working site is avoided, and the full-penetration welding quality is guaranteed.
Patent•
16 Dec 2015
TL;DR: In this paper, a sintering flux for submerged-arc welding of X100 pipeline steel and a preparation method for the Sintering Fluid was proposed, and the technical problem that many toxic substances and acid or corrosive gas produced due to incomplete combustion, which can easily occur during welding of the X100 pipe steel, have potential threats to human health and the environment is solved.
Abstract: The invention aims at providing sintering flux for submerged-arc welding of X100 pipeline steel and a preparation method for the sintering flux. By means of the sintering flux, the technical problem that many toxic substances and acid or corrosive gas produced due to incomplete combustion, which can easily occur during welding of the X100 pipeline steel, of the sintering flux containing halogen elements have potential threats to human health and the environment is solved. Meanwhile, the alkalinity is improved, so that the low-temperature impact toughness of weld metal is improved. Besides, the electrical conductivity during welding is enhanced, and the electrochemical corrosion resistant performance of welded joints is improved. The sintering flux comprises chemical components of, 45-55 wt.% of MgO, 3-5 wt.% of Al2O3, 5-10 wt.% of CaO, 5-8 wt.% of SiO2, 2-3 wt.% of MnO, 8-10 wt.% of TiO2, 3-5 wt.% of FeO, 2-3 wt.% of ZrO2, 5-10 wt.% of Na2O and 3-4 wt.% of K2O.
Patent•
01 Apr 2015
TL;DR: In this paper, a multiple-wire submerged arc welding process suitable for thick-wall straight-seam steel pipes X70 is presented. But the welded joint of the X70, manufactured by the process, has good low-temperature toughness and fracture toughness and good crack resistance and void resistance, and meets the special requirements on multiple comprehensive performances.
Abstract: The invention discloses a multiple-wire submerged arc welding process suitable for thick-wall straight-seam steel pipes X70. According to the process, by means of the JCOE forming process, a steel pate is made into a steel pipe, and a pipe seam is closed the steel pipe; the steel pipe is pre-welded by high-power mixed gas shielded welding to obtain a continuous, standard and stable-quality pre-weld; internal and external welds of the steel pipe are welded by automatic submerged arc welding with four wires for internal welding and five wires for external welding; the internal welding wires and the external welding wires are all H08C wires 4.0mm in diameter; flux 998N is used. The problem that a heat affected zone of a welded joint is softened and embrittled under the condition of multiple-wire common-path High heat input welding is solved; the welded joint of the thick-wall straight-seam steel pipe X70, manufacture by the process, has good low-temperature toughness and fracture toughness and good crack resistance and void resistance, and meets the special requirements on multiple comprehensive performances of the welded joints of deep-sea oil and gas transmission pipelines for deep-sea services, such as high toughness, high plasticity, fatigue resistance and corrosion resistance.
01 May 2015
TL;DR: The transfer of elements C, Si, Mn, P and S from slag into the weld metal or from weld metal into the slag and microhardness has been studied using formulated fluxes.
Abstract: The transfer of elements C, Si, Mn, P and S from slag into the weld metal or from weld metal into the slag and microhardness has been studied using formulated fluxes. The fluxes have been formulate...
12 Jan 2015-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: The role of micro-alloying in the submerged arc welding (SAW) of high strength low alloy steel linepipe is paramount in facilitating the high strength properties of the linepipe as mentioned in this paper.
Abstract: The role of micro-alloying in the submerged arc welding (SAW) of high strength low alloy steel linepipe is paramount in facilitating the high strength properties of the linepipe. In this study, transmission electron microscopy analysis revealed the presence of large (0.85 µm) Ti (C,N) precipitates within the predominantly acicular ferrite SAW joint. Cross-weld Vickers hardness and Charpy impact tests revealed that the fusion zone has high hardness and low toughness properties in relation to the base metal and heat affected zone. Fractography observations made on the ductile fracture surface of the fusion zone revealed a high number of the large Ti (C,N) precipitates to be located within the microvoids – suggesting their role in nucleating microvoids. Finally, fracture micro-mechanics are used to evaluate the relationship between the coarse precipitates and reduced strength-toughness properties in the SAW weld of the API-5L grade X65 linepipe steel.
Patent•
04 Mar 2015
TL;DR: In this paper, a super-thick steel plate welding method was proposed for domestic single wire submerged arc welding machines and was shown to improve the fabrication weldability of the super-thin steel plate.
Abstract: The invention relates to a super-thick steel plate welding method. According to the method, the fabrication weldability of super-thick steel can be effectively improved, and the construction efficiency and the weld inspection first-pass yield can be improved. The method comprises the following steps of 1, processing a welding groove; 2, preparing before welding; 3, preheating before welding; 4, welding. The method is simple; the improved design of the welding groove is reasonable and reliable, and the method is suitable for common domestic single wire submerged arc welding machines and is high in practicability; a combined welding process of taking super low hydrogen electrode arc welding as backing weld and adopting submerged arc welding for filling and cosmetic welding is adopted, and the welding advantages of the two processes are integrated; the fabrication weldability of the super-thick steel plate is greatly improved, the welding quality of the super-thick steel plate is controlled, the first-pass yield of super-thick steel plate butt weld inspection is improved, and the method can be widely applied to welding construction of low-alloy high-strength structural steel super-thick steel plates which are 60-300mm in thickness and has good technical, economic and social benefits.
14 Sep 2015
TL;DR: In this paper, the authors have completed thermodynamic calculations of oxidation-reduction processes under submerged arc welding with application of carbon containing additive, and they have shown that carbon, due to its high reducing properties under T = 1950 - 2200 K, introduced into the system can significantly decrease the amount of non-metallic inclusions in the weld metal and so improve its mechanical properties.
Abstract: The authors have completed thermodynamic calculations of oxidation-reduction processes under submerged arc welding with application of carbon containing additive. The calculations have shown that carbon, due to its high reducing properties under T = 1950 - 2200 K, introduced into the system can significantly decrease the amount of non-metallic inclusions in the weld metal and so improve its mechanical properties.