Showing papers on "Submerged arc welding published in 2012"

Microstructure and type IV cracking behavior of HAZ in P92 steel weldment

Abstract: The creep rupture behavior and microstructure changes of W strengthened P92 steel weld joints have been investigated at 873 K, 898 K and 923 K. The joints were prepared by submerged arc welding (SAW). The results showed that low ductility type IV fracture took place more easily at higher temperature and lower stress. There would be a critical Larson–Miller parameter (LMP) of 35.5 and a critical applied stress of 120 MPa for type IV fracture. The critical stress was independent of creep temperature. Type IV cracks occurred in the fine grained heat affected zone (FGHAZ), corresponding to the maximum heating temperature just above A c3 , which showed the fine equiaxed microstructure without lath structure and the lowest hardness due to the instability of microstructure. An increased number density of Laves phases precipitated on grain boundaries in FGHAZ compared with other zones of weldment during creep, while the coarsening of M 23 C 6 carbides was not very significant in W strengthened P92 steel. The fracture location in FGHAZ exhibited the most severe creep damage among the various zones of weldment and many cavities formed at the grain boundaries during creep. It was considered that the coarse Laves phase at the grain boundaries acted as the preferential cavity nucleation sites. We believe that the degradation of lath substructure and fast formation of Laves phase may be the main metallurgical factors for the type IV cracking.

TIG and A-TIG welding experimental investigations and comparison with simulation

Abstract: In this part II, the comparison of physical mechanisms between tungsten inert gas (TIG) and active TIG (A-TIG) welding is shown. The plasma was monitored by a high speed camera to present the arc constriction phenomena while passing from TIG to A-TIG. The elemental analysis and the arc temperature measured by optical emission spectroscopy were performed according to the type of welding and the different fluxes in A-TIG welding. The two-dimensional axial symmetric model presented in part I was used to simulate the flow behaviour in the melting pool realised on a stainless steel disc (304L) melted by a stationary heat source and to study the influence of energy density.

Method for welding specially-thick high-strength bridge steel plate

Abstract: The invention provides a method for welding a specially-thick high-strength bridge steel plate and belongs to the technical field of specially-thick plate welding. The test plate of the method adopts a symmetric narrow gap U-shaped groove form, is combinedly welded by using two efficient welding methods, namely gas shielded welding for priming and bottom filling, and double-wire submerged arc welding for continuous filling and finishing, so as to achieve the purposes of reducing filling level and giving full play to the efficient double-wire submerged arc welding and high automation degree. The method has strong operability, greatly improves the welding efficiency of the specially-thick bridge steel plate, and significantly reduces manpower cost. Furthermore, by selecting a proper welding sequence, the method solves the problem that the welding deformation of the specially-thick steel plate is hard to control.

Modified series arc welding and improved control of one sided series arc welding

Abstract: An electric arc welding system for depositing weld metal along a groove between two edges of a metal workpiece where the system contains a first power supply and a second power supply, each providing a welding waveform to respective welding electrodes. The positive output terminals of both power supplies are coupled to the same contact tip and the negative output terminal of one of the power supplies is not coupled to the workpiece.

Prediction of weld bead parameters, transient temperature distribution & haz width of submerged arc welded structural steel plates

Abstract: In submerged arc welding process, concept on temperature distribution is essential in order to control HAZ dimensions and get the required bead size and quality. In this paper, an analytical solution for moving heat source with Gaussian distribution of inside volume of central conicoidal shape is derived. Heat transfer in welded plates during welding is assumed to be conductive heat transfer of a semi infinite body. With the help of this analytical solution, transient temperature distribution, HAZ width, weld bead dimensions are estimated. Good agreements between predicted and experimental values are achieved.

Measurement of arc pressure and shield gas pressure effect on surface of molten pool in TIG welding

Abstract: Tungsten inert gas (TIG) welding is most frequently used for arc study because it is clean and easy to control welding factor. Many researchers have been focused on the plasma stream to find out the relationship between vertex angle and penetration of the tungsten electrode in TIG welding. Moreover, researchers studied the characteristics of vertex angle and arc pressure and heat flux distribution of the tungsten electrode. In addition, they have carried out factors that have influence on the behaviour of the molten pool. Previous studies assumed that arc pressure was dominant for the force that physically works on the surface of the molten pool, neglecting the shield gas pressure. In addition, they have been focused on the protection of molten weld pool from exposure to the atmosphere. The object of this study is to investigate the effect of shield gas pressure on the surface of the molten pool by measuring the distribution of arc pressure and shield gas pressure compared with arc physical result...

Numerical Simulation of heat source property with metal vapor behavior in GMA Welding

Abstract: We study about effects of metal vapor on arc plasma and heat source properties in a gas metal arc (GMA) welding by a GMA model considering behavior of metal vapor.The metal vapor from a weld pool is swept away towards surrounding of arc plasma. On the other hand, the metal vapor from a wire is mixed into arc plasma, and then, arc center is dominated by metal vapor. The highest temperatures occur at the edge of the arc center. Because metal vapor have strong radiation, energy loss of radiation becomes large. In GMAW process, temperature of arc plasma is low because energy loss of radiation is large at the arc center.

Method of submerged-arc welding of thick sheet S355NL for low-temperature wind tower

Abstract: The invention discloses a method of submerged-arc welding of a thick sheet S355NL for a low-temperature wind tower, which comprises the following steps: adopting an S355NL thick sheet satisfying requirements for chemical composition, weight percentage and technical conditions, wherein the carbon equivalent Ceq of steel is less than or equal to 0.42 percent; using welding wires satisfying requirements for chemical composition and weight percentage; adopting symmetric double-sided X type grooves as submerged-arc welding groove, wherein the groove angle is 60 degrees, the groove gap is 0.5mm, and when the thickness of the sheet is less than or equal to 50mm and the ambient temperature is no lower than 10 DEG C, no preheating is needed for welding; and selecting welding parameters, wherein the welding heat input is less than or equal to 50KJ/cm. The invention realizes the welding process that no preheating is needed prior to welding and no heat treatment is needed after welding during manufacture of the thick sheet structure of the butt joint of the steel plate S355NL for the low-temperature wind tower in marine and cold regions. Due to the multi-layer multi-channel continuous welding, the welded joint has excellent comprehensive mechanical properties, and weld joints and weld heat-affected zones has large impact toughness reserves and safety margins. Therefore, the invention is suitable for promotion and application in the manufacture of the low-temperature wind tower in the factory.

Using a new general-purpose ceramic flux SFM-101 in welding of beams

Abstract: The composition of a new general-purpose ceramic flux for welding of carbon steels is described. The flux is not susceptible to hydration, has low chemical activity in relation to deposited metal ensuring minimum oxidation of the alloying elements, with easy separation of the slag layer immediately after welding. Consequently, no labour-consuming operations are required for the removal of the slag from the surface of the welded joint. The flux ensures efficient melting with the edges of the welded components and prevents the formation of unacceptable defects in the weld metal.

Vacuum milling method for metal compound plate

Abstract: The invention provides a vacuum milling method for a metal compound plate, which relates to a compound plate production method and comprises the following steps that: 1, circumference lead angle beveled edges are processed on the circumference of the single side of a base plate, and the circumference dimension of a stainless steel plate is smaller than the dimension of the circumference lead angle beveled edges; 2, a right-angle hole is drilled between the lead angle beveled edges; 3, the stainless steel plate is flatly paved on the lead angle beveled edges side of the base plate, in addition, a soldering flux layer is flatly paved between the stainless steel plate and the base plate, and the circumference sealing welding is carried out on a pressure platform; 4, the vacuum pumping is carried out through the right-angle hole of the base plate, and the sealing and plugging is carried out after the vacuum pumping; 5, the two prepositive blank stainless steel surfaces are combined, in addition, a high-temperature adhesion-prevention agent layer is flatly paved between the two prepositive blank stainless steel surfaces, then, separation plates with the same circumference lengths are in dot welding on the circumference, and next, submerged arc welding sealing welding is carried out between the two lead angle beveled edges and the separation plates; 6, a plurality of vent holes are drilled on a sealing and welding ring frame and the separation plates, 7, the hot milling is carried out; and 8, the edge milling separation is carried out. The vacuum milling method has the advantages that the prepositive blank processing and the vacuum pumping are firstly carried out, then, air holes are drilled, excessive air can be exhausted during the milling, and the plate material quality is ensured.

Modelling and predicting the effects of submerged arc weldment process parameters on weldment characteristics and shape profiles

Abstract: The submerged arc weldment cross section shape profiles indicate the macrostructure zones’ boundaries of both the base metal and weld that are affected by the weld thermal cycle. These macrostructu...

Behaviour of the iron vapour core in the arc of a controlled short-arc GMAW process with different shielding gases

Abstract: The controlled metal transfer process (CMT) is a variation of the gas metal arc welding (GMAW) process which periodically varies wire feeding speed. Using a short-arc burning phase to melt the wire tip before the short circuit, heat input to the workpiece is reduced. Using a steel wire and a steel workpiece, iron vapour is produced in the arc, its maximum concentration lying centrally. The interaction of metal vapour and welding gas considerably impacts the arc profile and, consequently, the heat transfer to the weldpool. Optical emission spectroscopy has been applied to determine the radial profiles of the plasma temperature and iron vapour concentration, as well as their temporal behaviour in the arc period for different mixtures of Ar, O2 and CO2 as shielding gases. Both the absolute iron vapour density and the temporal expansion of the iron core differ considerably for the gases Ar + 8%O2, Ar + 18% CO2 and 100% CO2 respectively. Pronounced minimum in the radial temperature profile is found in the arc centre in gas mixtures with high Ar content under the presence of metal vapour. This minimum disappears in pure CO2 gas. Consequently, the temperature and electrical and thermal conductivity in the arc when CO2 is used as a shielding gas are considerably lower.

Submerged-arc welding root welding and back chipping process of thick plate with K-type groove

Abstract: The invention discloses a submerged-arc welding root welding and back chipping process of a thick plate with a K-type groove. The K-type groove is an asymmetric K-type groove, an upper open angle and a lower open angle of the groove are both 45 degrees to 50 degrees, and truncated edges are not reserved at the root. During assembly, groove clearance of 2mm to 3mm is reserved. During welding, solid gas protection welding wires under pulse current are adopted for backing welding of a root pass of the front side of a K-type groove test piece, and after the root pass is thoroughly fused, a part of weld metal penetrates through the reverse side of the groove to achieve backing welding. After welding, back chipping of the reverse side is performed. Finally, gas shielded welding under large current is adopted for fusion welding of the roof of the reverse side groove, and gas rich in argon is used as protective gas. The submerged-arc welding root welding and back chipping process reduces time for slag removal of root pass of submerged-arc welding and polishing and finishing of the reverse side groove of the welding test piece, improves welding efficiency by more than 30%, removes a carbon arc gouging process, decreases welding noises and dust emission, lowers labor intensity of welders and reduces time for damaging workers under high-decibel noises.

Nuclear island primary device connection tube safe end dissimilar metal welding technology

Abstract: The invention relates to a nuclear island primary device connection tube safe end dissimilar metal welding technology which comprises the following steps: selection of form of a welding groove: selecting a single groove form as the groove form of a primary device connection tube; overlay welding of stainless steel: overlay-welding a stainless steel anti-corrosion layer on the inner wall of the primary device connection tube; overlay welding of isolating layer: overlay-welding an isolating layer on the end face of the primary device connection tube by carrying out TIG overlay welding with hot wire to obtain a transition layer and carrying out submerged arc overlay welding to obtain a surface layer; butt welding: butting the safe end with the surface layer at the end face of the primary device connection tube in a submerged arc welding mode; and postweld heat treatment. The invention reduces the welding cost and the labor intensity of welders, and ensures the successful welding of the safe end structure, thereby laying foundation for reliable welding of the safe end and the primary device connection tube.

Methods and apparatuses for heavy plate joining with hybrid laser and submerged-arc welding process

Abstract: A welding system (400) and method is provided for welding heavy plate (W), where the method and system (400) include using a laser (201) which directs a beam (203) to a first weld puddle (209A) to weld at least a portion of a work piece (W). A welding torch (205) having a first welding electrode (207) may be directed to the first weld puddle (209A) while the laser beam (203) is being directed to the same weld puddle (209A). Thus, the welding torch (205) may deposit the first welding electrode (207) to create a first weld bead (209). A flux nozzle (211) is employed to deposit a welding flux (F) onto the weld bead (209), and at least one submerged arc welding torch (213; 215) is used to direct a sub" merged arc filler metal (214; 216) to the weld bead (209) to create a second weld bead (217) through a submerged arc welding process, where the submerged arc welding process melts a portion of the first weld bead (209) to consume the melted portion into the second weld bead (217).

Hybrid welding system and method of welding

Abstract: A hybrid welding system including a hybrid welding apparatus and method of welding are provided. The hybrid welding apparatus includes a laser, an electric arc welder with a non-consumable electrode and a wire feeding device. The electric arc welder provides an electric arc without feeding a welding wire. The wire feeding device is arranged and disposed to feed a wire to a treatment area, which is located between the projections of laser beam and the electric arc. The laser and the electric arc welder are arranged and disposed to direct energy toward at least two adjacent components to form a common molten pool. The wire is fed by the wire feeding device into the common molten pool created by the laser and the electric arc.

Method for welding steel substrate layers of zirconium steel compound slabs

Abstract: The invention discloses a method for welding steel substrate layers of zirconium steel compound slabs, which realizes fusion welding between steel substrate layers of the zirconium steel compound slabs by adopting automatic plasma welding for bottoming and welding the covered surfaces by automatic submerged arc welding under atmospheric environment. The method is convenient in operation, has highefficiency and low cost, and is free of limitation by surrounding environments and weld joint lengths; the welding efficiency in the method is improved by over 30% as compared with the traditional welding method; and the weld joint has beautiful appearance, and obviously reduced defects such as cracks, pores, included slag, incomplete fusion, lack of penetration and the like, excellent weld jointperformance, and respectively conforms to the requirements at the levels of JB/T4730.2-2005II, JB/T4730.5-2005I and JB/T4730.3-2005I by detection of 100% RT, 100% PT and 100% UT.

Dilution Control by Advanced Submerged Arc Welding

Abstract: Dilution is a vital element in surfacing and depends on the difference in chemical composition between the weld and the parent metal, the welding process and the technique used. Metal surfacing is becoming the natural choice for reducing the consumption of expensive raw materials, processing cost and proper resource utilization. Mechanical as well as the metallurgical properties are greatly influenced by the degree of dilution. The advanced submerged arc welding (ASAW) process controls the response parameters independently and breaks the fixed relationship between the wire feed rate (W) and the welding current (I). A study was conducted to investigate the effect of process variables on the dilution during the process. The preheating of the electrode wire used in Submerged Arc Welding process (SAW) for surfacing application was done with the modification in the existing setup. Stainless steel 308L electrode wire was used on mild steel substrate to study the effect of preheating on the dilution. The results show that ASAW process controls and significantly reduces the percent dilution as compared with the conventional SAW process. ASAW process reduces the heat input, use of consumables and increased productivity, is the added advantages over the conventional process.

Hybrid heat source model designing and parameter prediction on tandem submerged arc welding

Abstract: In submerged arc welding simulation, the heat source parameters are always decided by experience, and it usually leads to a high simulation error. This work is aimed to develop a methodology for the estimation of the heat source in submerged arc welding. A hybrid heat source model was applied on submerged arc welding simulation. The new heat source model was combined by a surface heat source model and the double ellipsoid heat source model. The surface heat source model was designed based on the Gaussian heat source model. The width and penetration of the weld pool were simulated and compared with the measurement results, and the width at 2 mm depth from the top surface was also considered to describe the shape of the weld pool more accurately. In order to reduce the simulation complexity, the sensitivity of heat source parameters was discussed. The heat source parameter corresponding to different experimental processes was obtained by modified pattern search method. The artificial neural network algorithm and the support vector machine algorithm were applied to predict the relationship between all possible process and the heat source parameters. The validation experiment showed that the prediction model was accurate.

Development of Residual Stress during Manufacturing of Spiral Welded Pipes

Abstract: Spiral welded pipes (SWPs) are produced from forming and welding of plate or strip material with seam running its entire length in a spiral form. The relative structural weakness of these pipes is due to high residual stress developed during welding, which depends on various parameters and their interaction. Finite element method (FEM) was used to predict the temperature and stress fields in a 56-inch spirally welded steel pipe. Temperature-dependent thermal and mechanical properties of steel were incorporated in the model. Arc welding was modelled as a three-dimensional (3D) volumetric moving heat source. The residual stresses produced after the completion of the welding process were investigated. For validation, the numerically predicted residual stress was compared with measured values using split-ring and hole-drilling methods. It was found that von Mises stress attained high values in the cooling cycle after the solidification of the molten zones. Moreover, the effect of welding speed on the level of...

Submerged arc welding system with pressurized flux delivery and welding torch

Abstract: A submerged arc welding system includes a robot having a first arm connected to a second arm, and at least one wire supply. A welding torch is connected to a first end of the second arm of the robot. A wire motor is mounted to a second end of the second arm of the robot. The wire motor moves wire from the wire supply along a wire path to the welding torch. The system further includes a flux supply and a flux delivery system configured to move flux from the flux supply along a flux path to the welding torch.