Showing papers on "Butt welding published in 2006"

Effects of pulse level of Nd-YAG laser on tensile properties and formability of laser weldments in automotive aluminum alloys

Abstract: Tensile properties and formability are important parameters in many applications. Being a lightweight material, aluminum is increasingly employed in the fabrication of automotive body panels. This study performs butt welding without filler metal on two frequently used automotive body panel aluminum alloys, 5754-O and 6022-T4E29. Welding is conducted using a Nd-YAG laser with a rectangular wave form having various pulse levels (ΔP) but a constant mean power of 1.5 kW. For both alloys, the results indicate that the travel speed required to achieve a successful butt joint increases as ΔP decreases. For a constant pulse level, the travel speed required for the higher Mg content 5754-O alloy (2.9 wt.% Mg) is approximately 2.5 times that of the lower Mg content 6022-T4E29 alloy (0.61 wt.% Mg). Additionally, it is shown that the tensile strength, percentage elongation and formability of both alloy weldments increase with decreasing ΔP level. In the 5754-O alloy, these trends are attributed primarily to the occurrence of magnesium evaporation during the welding process, microstructure refining, and porosity reduction in the resultant welds. However, for 6022-T4E29, the evaporation of Mg is not significant, and consequently, the variation in porosity is not great. These results are caused by a lower Mg content in the base metal. Therefore, the enhancement of the mechanical properties observed in the weldments is a result of a refinement of the weld microstructure.

A study of structure and mechanical properties of welded joints in polyethylene pipes

Abstract: The structure and the mechanical properties of a butt weld in a polyethylene pipe were examined and contrasted to non-welded PE pipe. X-ray diffraction, differential scanning calorimeter and fourier transform infra red spectrometer measurements revealed details of axial amorphous and crystal orientation in the original pipe. Contrary to expectations considering the squeeze flow nature of butt-welding, formation of randomly oriented crystal structure was determined in the weld region. Tensile and notched impact tests at ambient and sub-ambient temperatures and varying rates of impact showed that welding consistently reduced resistance to failure. Microscopic evaluation of the brittle fracture surfaces revealed the surface morphology of the welded zone to be coarser than the non-welded PE material.

Multi sensor data fusion for improving performance and reliability of fully automatic welding system

Abstract: This paper presents a new generation of system for pressure vessel and shipbuilding. Typical pressure vessel and ship building weld joint preparations are either traditional V, butt, fillet grooves or have narrow or semi narrow gap profiles. The fillet and U groove are prevalently used in heavy industries and shipbuilding to melt and join the parts. Since the wall thickness can be up to 6 in. or greater, welds must be made in many layers, each layer containing several passes. However, the welding time for the conventional processes such as submerged arc welding (SAW) and flux cored arc welding (FCAW) can be many hours.

Shimmed laser beam welding process for joining superalloys for gas turbine applications

Abstract: A method of laser beam welding at least two adjacent superalloy components (12, 14) includes (a) aligning the components along a pair of faying surfaces (18, 20) but without a backing plate; (b) placing a superalloy shim (16) between the faying surfaces; (c) welding the components together using a laser beam causing portions of the superalloy components along the faying surfaces to mix with the superalloy shim; and cooling the components to yield a butt weld (22) between the components.

Determination of C2 Stress Index of Back-to-Back Welded Piping Bends Using Finite Element Method

Abstract: In current ASME Boiler and Pressure Vessel Code, the C2 stress index for back-to-back elbows welded together is taken as the product of the C2 index of the elbow and the C2 index of the girth butt weld. In recent years, many finite element analyses studies have been conducted on the elbow C2 index itself which have found that the code C2 value is conservative. The girth butt weld C2 given in the code resulted from analytical studies on transition joint between two straight pipes. While the code considers that the secondary stress due to the weld reinforcement including the effect from the mismatch to be small and practically negligible for a thick pipe, it recommends a formula to calculate C2 for weld in a thin pipe of thickness less than 0.237”. The purpose of this paper is to present an approach that C2 caused by weld mismatch can be determined by finite element analysis. Back-to-back bends are modeled with 2 typical configurations: in-plane and out-of-plane. Parametric studies of linear elastic secondary stresses are carried out to determine the “worst possible” two bend central line mismatch. The stress indices at elbows and weld location are established. It is found that the C2 index based on the code formula is overly conservative for back-to-back welded pipe bends and the multiplication by the C2 index of the weld is not needed.Copyright © 2006 by ASME

Verification of residual stresses in flash-butt-weld rails using neutron diffraction

Abstract: Residual stresses developed during flash-butt welding may play a crucial role in prolonging the fatigue life of the welded tracks under service loading conditions. The finished welds typically exhibit high levels of tensile residual stresses in the web region of the weld. Moreover, the surface condition of the web may contain shear drag or other defects resulting from the shearing process which may lead to the initiation and propagation of fatigue cracks in a horizontal split web failure mode under high axle loads. However, a comprehensive understanding into the residual stress behaviour throughout the complex weld geometry remains unclear and is considered necessary to establish the correct localised post-weld heat treatment modifications intended to lower tensile residual stresses. This investigation used the neutron diffraction technique to analyse residual stresses in an AS60 flash-butt-welded rail cooled under normal operating conditions. The findings will ultimately contribute to developing modifications to the flash-butt-welding procedure to lower tensile residual stresses which may then improve rail performance under high axle load.

Practical welding techniques to minimize distortion in lightweight ship structures

Abstract: The trend in both military and commercial shipbuilding is the increased use of thin steel to reduce weight and improve performance. Complex panel structures have thickness transitions for weight and structural optimization with multiple inserts ranging from 5 to 45 mm. Welding practices developed for thicker plate can result in significant out-of-plane distortion when applied to thin-plate structures. Buckling distortion of complex lightweight panels has resulted in a significant negative effect on manufacturing cost and production throughput, limiting the shipbuilders' ability to produce innovative ship designs. High fitting and welding costs are the consequence of this large welding distortion. This problem is exacerbated as the fairness requirements are tightened. New methods are needed to control distortion when welding thinner materials. To tackle the distortion problems, in 2002 Northrop Grumman Ship Systems initiated a multiyear program to develop distortion-control technology for complex panels. This paper reports the results of a study to develop "best practices" for welding of lightweight structures. Control of welding distortion for thin structures requires control of each welding operation from butt welding of plates through to unit assembly. A general philosophy was applied to minimize welding heat input while maximizing restraint during unit construction. To achieve this, the following techniques were evaluated: increasing restraint during each welding operation, improving fitting practice, weld sequencing, and minimizing welding heat input. Additionally, an active distortion mitigation approach, known as transient thermal tensioning, was investigated for reduction of buckling distortion during thin-panel longitudinal stiffener welding. A series of tests were performed to evaluate various distortion control approaches and to optimize production processes. The culmination of the project will involve demonstrating best practices in the production of thin-steel structures. A plan is also being developed for implementing the most advantageous approaches into production.

Hybrid laser and resistance welding system and method

Abstract: An improved fusion welding system having a heating unit and welding device is adapted for increasing the efficiency of welding a plurality of workpieces. The system preferably presents a single-sided process, and includes first and second electrode wheels operable to heat a portion of the workpieces to a minimum temperature, and a translatable laser cooperatively configured to form a continuous weld within the heated portion. The preferred system provides the advantages of laser welding, such as precision, while enabling weld production at lower laser power outputs or faster welding speeds than conventional laser welding systems.

Grounding assembly for welding wire feeder

Abstract: A portable wire feeder for providing welding wire and welding current to a welding operation includes an input electrically connected to a power source. An output is electrically connected to the input to receive welding current delivered to the input from the power source and to provide the welding current and welding wire to the welding operation through a guide hose. A motorized wire feeding system includes a motor and a feed roll driven by the motor to direct the wire from a wire supply to the output for provision of the welding wire to the welding operation through the guide hose. Power for the motorized wire feeding system is drawn from the welding current passed from the input to the output. A grounding assembly nonattachably contacts a work piece of the welding operation to electrically ground the power drawn from the welding current directly to the work piece.

Robust sensing and control of the weld pool surface

Abstract: Gas tungsten arc welding is the primary process for precision joining. To develop a control system for this process, a novel sensor is proposed to measure the depth of the weld pool surface using a non-transferred arc. A flat surface is periodically established to provide a real-time reference. The main-arc-on period is selected as the system's input. Because of possible large variations/ranges in manufacturing conditions, an interval model control algorithm with updated intervals is adopted. To demonstrate the use of the proposed sensor and control algorithm, closed-loop experiments under different variations have been conducted. Circumferential butt welding of steel pipe has also been included as an application example.

Allowance of Deviation and Gap in Butt Joint on Friction Stir Welding

Abstract: Friction Stir Welding (FSW) has special properties for its low distortion, low residual stress of the joints and needless skilled worker. Application of three-dimensional FSW can apply many industry, etc automobile industry or airplane industry. However, FSW is only applicable to use linier welding at present. To realize three-dimensional FSW, it is most important to improve operation accuracy. On the other hand, it is also important to clarify \"the allowance of operation\" for application. In this work (A) the influence of deviation; the mismatching between the butt line and the center of tool traveling line, and (B) the influence of gap; the spacing between two plates at butt line, on tensile properties of FSW joints are investigated. A5083-O alloy plates with 3 mm thickness were welded in various deviation or gap spacing conditions by a gate type FSW machine with sufficient rigidity and accuracy. It was found that the allowance of deviation is a half of probe diameter of FSW tool in the case of the butt line was set on the advancing side of tool rotation. So we have the one-fourth of probe diameter allowance in both sides by setting the butt line from the probe center in a quarter of the probe diameter to advancing side. Beyond this allowance range, tensile properties rapidly decreased. Contrary to this, the gap spacing within 2 mm did not affect the tensile properties in this experiment, and the joint strength and ductility over 2 mm gap showed a gradual decrease.

Argon gas filling protection device for biphase stainless steel pipe line welding

Abstract: The utility model relates to an argon gas filling protection device for biphase stainless steel pipeline welding The device is used for welding a biphase stainless steel pipeline in which argon gas is filled, and belongs to the technical field of the manufacture of argon gas filling equipment for biphase stainless steel pipeline butt welding for delivering gas The utility model is provided with two end pipe inner end plugs and a flexible corrugated pipe for filling argon gas The device can realize the local argon gas substitution for a butt-welding area The utility model comprises a front end plug, a rear end plug, the corrugated pipe and a gas filling pipe The device solves the problems when a biphase stainless pipe in the prior art is welded, one of the biphase stainless pipe is plugged, and the other end is open, and the whole journey argon filling of the whole pipe can not satisfy technological requirements After a welded elbow and a three-way are arranged, the device can also be taken out Welded seams welded by the device can keep in proportion that austenite and ferrite respectively occupy 50% The consumption of the argon gas is only 1/20 of the whole pipe argon gas filling of the prior art

Study of keyhole closure and analysis of microstructure and mechanical performance of weld joints for variable polarity vertical up plasma arc welding process

Abstract: Two technical approaches for keyhole closure were conducted. Workpieces of aluminium alloy 2219 were welded using variable polarity vertical up plasma arc welding technology. Effects of welding process parameters on keyhole closure were analysed. Appropriate technical criteria for keyhole closure in the welding of aluminium alloys (3 or 6 mm in thickness) via the variable polarity vertical up plasma arc welding technique were obtained. Experimental simulation of girth welding (overlap welding) was conducted using the appropriate process parameters for the keyhole closure stage of plate butt welding, and the feasibility of circumferential welding was verified. Accordingly, girth welding of the external tank of a carrier rocket was achieved using the appropriate parameters for the keyhole closure technique. In addition, the metallurgical process and mechanical performance for the single pass and overlap welds were analysed and compared.

Butt Welding System of Steel Plate and Butt Welding Method of Steel Plate

Abstract: A butt welding system and a butt welding method of steel plate by which the quality of a product can be ensured. Butting portions of blank members (1, 2) to be joined together are butted and a predetermined butting load is applied to the butting portion. Under that state, the blank members (1, 2) are moved relatively in the direction of the welding line thus matching the butting portions. Consequently, protrusions and recesses formed on each butting portion of each blank member (1, 2) are flattened, and linear precision at each butting portion of each blank member (1, 2) is enhanced as compared with a case where the butting portions are not matched. Since the gap is reduced extremely at the butting portion, welding is facilitated at the butting portion. Good welding beads are thereby obtained at the butting portion and the quality of a product is ensured.

Distortion behaviour of Fillet T-Joint during In-Process Control Welding by Additional Cooling

Abstract: It is desirable to control welding distortion and to apply this procedure during welding, rather than before or after welding in order to reduce the cost. The method suggested in this paper is to cool the hot section of weld metal during the welding of a fillet T-joint, in order to control rotational distortion in the web. Using this method, increasing the gap distance between web and flange is avoided so that it is possible to continue the welding procedure. Distortion behaviour of a fillet T-joint during in-process control welding by additional cooling is numerically analysed by the three-dimensional thermal elastic-plastic analysis considering a moving heat source with weld metal deposition. It is confirmed that the additional cooling method is effective to reduce the rotational distortion, which makes welding process impossible. Under the proper condition of cooling, it is possible to weld a T-joint without any tacking or restraint.

Numerical analysis of single sided spot welding process used in sheet to tube joining

Abstract: As a new kind of lightweight structure, hydroformed tubes are now widely used in vehicle bodies. The single sided spot welding (SSSW) is a variation of resistance welding used in joining hydroformed closed tubular parts and vehicle structures. During the process of SSSW, large deformation and complex contact status of the workpieces occur because there is no inside support. The time variation of the contact region and pressure distribution changes the flow paths for electric current timely and brings a fierce shunting at the position far away from the axis line, which prevents the heat concentration at the faying surface of workpieces. The characteristics of SSSW different from those of classical resistance welding mentioned above make it difficult to determine rational welding processing parameters for SSSW. In the present paper, a comprehensive structural–thermoelectric model is established. Using the incrementally coupled analysis of finite element analysis, the electrical, thermal and mechanic...

Effects of Shielding Gas Flow Rate and Power Waveform on Nd:YAG Laser Welding of A5754-O Aluminum Alloy

Abstract: results show that reducing the value ofP increases the welding speed required for full-penetration, and therefore increases the penetration depth to bead width ratio and the micro-hardness of the weld bead. The butt welding results show that the tensile strength and total elongation properties of the highF (� FH) specimens are approximately three times higher than those of the lowF (� FL) specimens. This is primarily due to the absence of hot cracking in theFH specimens, together with a finer microstructure and a lower level of porosity. This study demonstrates that the effect ofF on the weld bead geometry, microstructure, hot crack susceptibility and mechanical properties is far higher than that ofP. However, the effect ofP on the change of welding speed is higher than that ofF. (doi:10.2320/matertrans.47.1365)

Structural integrity of diffusion bonds in Ti-6Al-4V processed via low cost route

Abstract: Low cost resistance butt welds between a similar Ti–6Al–4V alloy couple have been fabricated using a Gleeble thermomechanical simulator. The optimisation of the key bonding parameters (pressure, time, temperature and environment) required to produce high quality joints with near parent properties is discussed. Metallographic sections, chemical composition and microhardness traverses across the bond line are presented. The mechanical response of the bonds was assessed under monotonic tensile loading conditions. The suitability of this solid state diffusion technique for the fabrication of engineering components is discussed.

Steam turbine welded rotor and method of manufacturing it, and steam turbine and power generating plant using it

Abstract: PROBLEM TO BE SOLVED: To provide a steam turbine welded rotor having high fatigue strength since stress concentration is not applied to its heat-affected part formed by a final welding in a laminated welding and a method of manufacturing it, and a steam turbine and a power generating plant using it SOLUTION: In this steam turbine welded rotor, a turbine rotor divided into at least two pieces is connected to each other by butt welding The abutted part of these pieces of the turbine rotor comprises a hollow part formed at its center part and an outer peripheral raised part radially raised more than the base part surface of the turbine rotor formed on the outer peripheral side Groove parts formed at the abutted part are butt-welded by the laminated welding COPYRIGHT: (C)2008,JPO&INPIT

Joining of lightweight components by sticking for use in an automotive industry, a machine- and an aircraft construction, comprises applying inorganic and/or organic adhesives on surfaces to be joined and joining the surfaces

Abstract: The joining of lightweight components by sticking for use in an automotive industry, a machine- and an aircraft construction, comprises applying inorganic and/or organic adhesives on surfaces to be joined and joining the surfaces. Immediately or after the application of the adhesives and the joining of the components, the sticking/joining surface is fixed through individual welding point and/or welded joint produced by means of laser welding, or is spot welded through several welding points and/or welded joints produced by means of remote laser. The joining of lightweight components by sticking for use in an automotive industry, a machine- and an aircraft construction, comprises applying inorganic and/or organic adhesives on surfaces to be joined and joining the surfaces. Immediately or after the application of the adhesives and the joining of the components, the sticking/joining surface is fixed through individual welding point and/or welded joint produced by means of laser welding, or is spot welded through several welding points and/or welded joints produced by means of remote laser. The hardening of the adhesive is continued and completed during the procedure of the cathode-dip lacquering or similar processes. The hardening of the adhesive takes place during the welding process or after the fusing via the heat entry of the laser. A fiber laser with a power of 100 watts to 10 kilowatts is used for the laser welding/laser point welding. For fixing of the lightweight components, the laser spotwelds are statistically or regularly distributed over the adhesive surfaces or attached at the places of the largest load. Load-adapted welding seam geometry is produced by means of remote welding.

The influence of joint gap on the strength of hybrid Nd:yttrium-aluminum-garnet laser-metal inert gas welds

Abstract: This article presents the results of an experimental and theoretical analysis of the effect of joint gap on the strength of hybrid laser-metal inert gas welds. The welds were of the partial penetration butt type with various joint gaps but identical weld penetration. Impact testing established that a zero gap gave a weak weld because the weld geometry contained the equivalent of a sharp crack where the unwelded parts met each other. A small gap between the workpieces improved the weld impact strength as the sharp crack effect became dissipated. Further increases in gap width resulted in a weakening of the joint and this is the subject of a discussion on joint gap optimization.