Showing papers on "Welding published in 1988"

Welding Metallurgy of Stainless Steels

Abstract: Contents: Significance of Constitution Diagrams for the Understanding of Welding Phenomena * Metallurgical Processes During Solidification and Cooling in Stainless Steel Weld Metal * Metallurgical Phenomena in Secondary Crystallization of Stainless Steels and Weld Metals * Precipitation Phenomena in Stainless Steel and Weld Metals * Hot Cracking Resistance During the Welding of Austenitic Stainless Steels * Welding Metallurgy of Ferritic Stainless Chromium Steels with Carbon Contents Below 0.15 per cent * Welding Metallurgy of Low Carbon Chromium-Nickel Martensitic Stainless Steels (Soft Martensitic Steels) * Welding Metallurgy of Duplex Austenitic-Ferritic Stainless Steels * Welding Metallurgy of Austenitic Stainless Steels * General Instructions for the Welding and Post-Weld Surface Treatments of Fabrications and Welded Components Made from Austenitic Stainless Steel * Welding Metallurgy of Heat Resisting Steels * Welding Metallurgy of Austenitic-Ferritic Dissimilar Joints * Appendix: Abbreviations and Short Designations * References * Author Index * Subject Index.

Low emissivity film for high temperature processing

Abstract: A multiple-layer, high transmittance, low emissivity coated article which can be subjected to high temperature processing such as bending, annealing, tempering, laminating or glass welding as a result of primer layers comprising metal and metal oxide is disclosed.

Free surface flow and heat transfer in conduction mode laser welding

Abstract: Temperature profiles and fluid flow fields in a weld pool are simulated through numerical solutions of Navier-Stokes equation and the equation of conservation of energy for low power laser welding in conduction mode. Experimentally determined weld pool surface topography, peak temperature, and the secondary dendrite arm spacings are found to be in fair agreement with the corresponding theoretically calculated values.

Laser welding of titanium in dentistry

Abstract: Unalloyed titanium of the quality used for osseointegrated implants by the method of Branemark is also sometimes used for the metallic part of the prosthetic superstructure placed on the fixtures and for crowns and bridges of conventional type. Forty bars of titanium, 8 of ASTM B 348 grade-1 quality and 32 of ASTM B 348 grade-2 quality, were laser-welded, using dissimilar laser joint variables. Tensile strength, 0.2% proof stress, and percentage elongation of the welded bars were measured and compared with the corresponding values for the titanium bars as delivered and with those of brazed type-3 gold alloy bars of similar dimensions. The type of fracture was evaluated from fractographs. The results showed that the use of certain defined laser joint variables during welding produced values for the mechanical properties studied which were more favorable than those obtained from the brazed gold bars. The fracture of the titanium specimens was ductile, with dimples occurring at the fracture surfaces.

Tubular tissue welding device without moving parts

Abstract: Exoscopes for joining tubular like objects has a housing made in two sections which clamp around the objects to be welded together. The end of the objects are held in place by an internal stent which claps the ends of the object together. Optic fibers or the like connected to a laser source terminate in the housing in such a way that the conducted laser beam is directed simultaneously circumferentially around the abutting ends to be welded. There are no moving parts during the welding.

On the weldability, composition, and hardness of pulsed and continuous Nd:YAG laser welds in aluminum alloys 6061,5456, and 5086

Abstract: The effect of Nd:YAG laser welding aluminum alloys 6061, 5456, and 5086 was studied from a perspective of alloying element vaporization, hot cracking susceptibility, and resultant mechanical properties. Both continuous wave and pulsed Nd.YAG laser welds were investigated. It was found that Mg was vaporized during welding, the extent of which was a function of the weld travel speed. Calculations based upon evaporation theory, and assuming a regular solution model, resulted in an estimation of weld pool surface temperatures from 1080 to 1970 K for the continuous wave welds. Pulsed Nd:YAG laser welds were observed to be extremely susceptible to weld metal hot cracking whereas continuous wave Nd:YAG laser welds were crack-free. The hardness of 6061 welds was affected by the Mg vaporization such that base metal strengths could not be achieved by subsequent re-heat treatment to the T6 condition. This loss in hardness was attributed to a reduced ability of the alloy to precipitation harden due to a lower Mg concentration. In the cases of 5456 and 5086, when samples containing welds were processed to the O condition, the weld metal had reduced hardness relative to the base metal. This loss of hardness was also attributed to the loss of Mg in these welds, resulting in reduced solid solution strengthening.

A point and line source model of laser keyhole welding

Abstract: The keyhole formed during penetration welding with a laser is modelled so far as its thermal absorption characteristics are concerned by the combination of a point and a line source. In this way a representation of the broader surface section of the weld is obtained in addition to the lower section. A simple analytical form for the temperature distribution is obtained and possible weld profiles are found numerically from this. These are compared with examples of actual welds; it is possible in this way to estimate the proportion of the laser power absorbed in each section of the weld. Graphs and some simple approximations are given which allow it to be done easily for a given weld.

Vibration welding of thermoplastics. Part I: Phenomenology of the welding process

Abstract: In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters in vibration welding are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time. How these parameters affect weld quality, the conditions that result in the best welds, the weldability of dissimilar plastics, and the effect of fillers such as glass are of interest. To address these issues, a research vibration welding machine in which all the parameters can be independently and accurately controlled and monitored was designed and fabricated. The phenomenology of welding, as determined by experiments on the four thermoplastics polycarbonate, poly (butylene terephthalate), polyetherimide, and modified poly (phenylene oxide), is described.

Vibration welding of thermoplastics. Part II: Analysis of the welding process

Abstract: The vibration welding process for thermoplastics is known to consist of four phases: (1) initial heating of the interface to the melting temperature by Coulomb friction; (2) unsteady melting and flow in the lateral direction; (3) steady-state flow; and (4) unsteady flow and solidification of the film after the vibratory motion is stopped. Simple analytical models are developed for the first three phases. These models are used for estimating the molten film thickness, the size of the heat affected zone, and the weld time as functions of the weld parameters: the amplitude and frequency of the weld motion, and the weld pressure. The steady-state film thickness and the heat-affected zone are shown to be very small.

Deformations and stresses in welding of shell structures

Abstract: The simulation of welding of shell structures is investigated in this paper. In order to verify the implementation of the shell element adopted, two different problems were studied. In the first problem the butt-welding of two plates was simulated. In the second problem the butt-welding of a thin-walled pipe was simulated. It is concluded from the analysis of the plate problem that the shell element is quite effective in the membrane state. The comparison between calculated values and experimental values for the residual stress field in the pipe shows that the shell element performs quite well in the analysis of a realistic problem.

Polymer welding relations investigated by a lap shear joint method

Abstract: A lap shear joint method was used to study strength development during welding of polystyrene surfaces- The surfaces previously had not been in contact and care was taken to insure rapid wetting of the interface. The shear stress at failure, τf was measured at room temperature as a function of contact time, t, at constant welding temperatures up no 20°C above the glass transition temperature, Tg. The time dependence of welding could be well described by τfαt1/4. This result is in agreement with predictions of the reptation molecular dynamics model applied to inter-diffusion at a symmetric amorphous polymer-polymer interface. The activation energy for the thermally activated increase in strength development was determined as E = 96 kcal/mol at T = 113.5°C, which compares with E = 93,2 kcal/mole as predicted by the W-L-F theory using C1 = 13.7, C2 = 50 and Tg = 100°C. The polystyrene samples had molecular weights, Mn = 143,000 and Mw = 262.000. The time to achieve complete healing, t∞ ≈ 256 min at 118°C, was found to be of the same order of magnitude as the viscoelastic relaxation time and also with the time required for a polymer chain to diffuse a distance equal to its root mean square end-to-end vector.

Welding parameters and the grain structure of weld metal — A thermodynamic consideration

Abstract: The grain structure of the weld metal can significantly affect its resistance to solidification cracking during welding and its mechanical properties after welding. An experimental study was conducted to investigate the effect of two basic welding parameters,i.e., the heat input and the welding speed, on the grain structure of aluminum-alloy welds. Gas-tungsten arc welding was performed under various heat inputs and welding speeds, with thermal measurements in the weld pool being carried out during welding and the amounts and nuclei of equiaxed grains in the resultant welds being examined using optical and electron microscopy. The experimentally measuredG/R ratios and the clearly revealed heterogeneous nuclei together demonstrated the thermodynamic effect of the heat input and welding speed on the weld metal grain structure.

Ultrasonic sensing of weld pool penetration

Abstract: This paper reports how the geometry of the sidewall as it is penetrated by the weld pool during gas metal arc welding (GMAW) can be detected by high-frequency sound waves. The penetration geometry is detected using a piezoelectric transducer, operating in the pulse-echo mode, to generate shear sound waves that travel through the base metal to the weld region. The received echoes contain information that can be related to the sidewall penetration and thus to the quality of the weld. Different geometries can be discriminated using expert system methods, thus providing the potential of sending information on sidewall penetration to a closed-loop welding system for real-time feedback control to assure adequate sidewall penetration.

Finite element analysis of three-dimensional transient heat transfer in gma welding. .

Abstract: The thermal history of a weld joint produced by the gas metal arc (GMA) welding process is analyzed by using a three-dimensional finite element model. The problem consists of one in which the finite element mesh is growing continuously in time in order to accommodate metal transfer in CMA welding. The procedure of how to incorporate the growth of the mesh in the analysis has been described. The finite element program ABAQUS, along with a few user subroutines, was employed to obtain the numerical results. Temperature-dependent thermal properties, effect of latent heat, and the convective and radiative boundary conditions are included in the model. Numerically predicted sizes of the heat-affected zone and the melt-pool zone are compared with the experimentally observed val-

Resistance Welding of Graphite Polyetheretherketone Composites: An Experimental Investigation

Abstract: Resistance welding of preconsolidated unidirectional graphite (AS4) rein forced polyetheretherketone (PEEK) composite laminates (I.C.I. APC-2) is investigated experimentally. An apparatus is developed to conduct experiments to identify important process variables governing the efficiency of the welding process. Experiments were con ducted under displacement control and prescribed initial consolidation pressure. Heating elements consisted of a single ply of APC-2 with adjacent layers of neat film to minimize current leakage into the laminates to be welded. Temperature at the weld interface and consolidation pressure versus time were monitored and provided insight into the welding process. A strong correlation between the extent of welded surface area and process parameters such as power, energy and time in the melt were demonstrated. The quality and extent of the welded surface is quantified using ultrasonic nondestructive evaluation techniques. Experimental results indicate that superior welds exhibiting ...

CO2 and argon laser vascular welding: acute histologic and thermodynamic comparison

Abstract: CO2 and argon lasers have been used successfully for vascular welding in both experimental and clinical settings. This study compared the thermodynamics during CO2 and argon laser welding of 1-cm longitudinal arteriotomies in a canine model. Continuous recordings using an AGA 782 digital thermographic system with spatial and thermal resolution of ±0.2 mm and ±0.2°C, respectively, were analyzed. A HGM argon laser using a 300-μm optic fiber held at 1 cm from the vessel edges (spot diameter = 2.8 mm) with concomitant room temperature saline irrigation (1 drop/sec) was used for argon welds. Total exposure time was 150 sec/cm. CO2 welds were performed with a Sharplan CO2 laser (spot diameter = 0.22 mm) with no irrigation for total exposure time of 10 sec/cm. Thermodynamic results and laser parameters are summarized as follows: Argon–n = 20; power = 500 mW; energy fluence = 1,400 J/cm2; Tmax = 48.8°C; T mean ± S.D. = 45.1 ± 2.7°C; CO2–n = 20; power = 150 mW; energy fluence = 3,000 J/cm2; Tmax 84.0°C; T mean ± S.D. = 60.7 ± 9.8°C. There was a significant difference (P < .05) in thermal measurements between successful CO2 and argon vascular welds. Temperature rise during the argon welds was limited by saline irrigation. In contrast, during CO2 laser welding, the temperature rose quickly to its maximum and was maintained at a relatively high level as the laser progressed (0.1 cm/sec) along the anastomosis. Histologic examination revealed charring at the CO2 weld site but absence of thermal damage at the argon laser weld. These thermodynamic differences may account for the different welding mechanisms currently described.

Vibration welding of thermoplastics. Part III: Strength of polycarbonate butt welds

Abstract: In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time or weld penetration; The effects of these parameters on weld quality were systematically studied by first butt-welding polycarbonate specimens under controlled conditions over a wide range of process parameters, and by then determining the strengths and ductilities of these welds by tensile tests, A significant result is the apparent existence of a weld-penetration threshold above which high weld strengths are attained, but below which the strength drops off. Under the right conditions, the strengths of polycarbonate butt welds are shown to equal the strength of the virgin polymer.

Vibration welding of thermoplastics. Part IV: Strengths of poly(butylene terephthalate), polyetherimide, and modified polyphenylene oxide butt welds

Abstract: In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time or weld penetration.; The effects of these parameters on weld quality were systematically studied by first butt welding thermoplastic specimens under controlled conditions, over a wide range of process parameters, and by then determining the strengths and ductilities of these welds by tensile tests. The three thermoplastics investigated are poly (butylene terephthalate), polyetherimide, and modified polyphenylene oxide. Changes in the weld pressure are shown to have opposite effects on the strengths of polyetherimide and modified polyphenylene oxide welds; Also, the weld frequency is shown to have a significant effect on the weldability of polyetherimide. The weldability data for these three thermoplastics are compared with data for polycarbonate. Under the right conditions, the strengths of butt welds in these materials are shown to equal the strength of the virgin polymer.

Retinal burns caused by exposure to MIG-welding arcs: report of two cases.

Abstract: A new generation of arc welder has recently become widely available at a price which is within reach of most amateurs and part-time mechanics, known as the MIG welder (metal-arc inert gas welder). In MIG welding the arc is ensheathed in a stream of inert gas which prevents the molten metal from oxidising. The stream of gas changes the character of the emitted radiation, and it is possible that this type of welder poses a greater threat to sight than previously recognised. Radiation in the ultraviolet range emitted by arc welders is absorbed by the unprotected cornea and lens, giving rise to a keratoconjunctivitis, or 'arc-eye,' which, though intensely painful, is not considered a threat to sight. Radiation in the visible and near infrared spectrum, however, penetrates the eye to be absorbed by the retina and may cause thermal or photochemical damage which may be permanent and sight-threatening. Retinal injuries resulting from exposure to ordinary electric welding arcs have been reported, but such injuries are uncommon. Two cases of retinal burns resulting from exposure to MIG welder emissions which presented on consecutive days to the Leicester Royal Infirmary are presented. This is the first report of such injuries relating specifically to MIG welding.

High-Speed Laser Welding Discontinuities

Abstract: AN ATTRACTIVE way to increase the productivity of many welding processes is to increase the speed of travel of the process. Unfortunately, unique discontinuities are encountered at high travel speeds. These discontinuities limit the acceptable range of travel speed.AN ATTRACTIVE way to increase the productivity of many welding processes is to increase the speed of travel of the process. Unfortunately, unique discontinuities are encountered at high travel speeds. These discontinuities limit the acceptable range of travel speed.

Process for the remote-controlled semi-automatic welding of two rotationally symmetrical components

Abstract: Welding is controlled from a control station (14) located at some distance from the welding zone. Before the start of a welding pass, the welding parameters are set by an operator, to whom the values to be given to the parameters as a function of the type of pass are supplied by a memory in which the information relating to the welding is stored. The welding operation is started, after the parameters have been checked as a function of the content of the memory. The welding operation is monitored continuously by the operator by means of a remote screen display of the welding zone. If appropriate, the operator changes some of the welding parameters according to the screen image of the welding zone. These changes are checked by comparison with the content of the memory.

Apparatus for welding components together with the use of ultrasound

Abstract: An apparatus for receiving components having overlapping surfaces and welding the components together with the use of ultrasound. An ultrasound emitter receives a high frequency current and converts it into mechanical ultrasonic vibrations having the same frequency. A transmitter transmits the ultrasonic vibrations to a sonotrode which focuses the ultrasonic vibrations on the components to be welded together. The sonotrode is provided with a circumferential collar and means are provided for lowering the collar during the welding process so that a part of the collar tangentially contacts the overlapping surface of one of the components. The part of the collar which tangentially contacts the overlapping surface introduces ultrasonic energy into the components. The ultrasonic emitter, transmitter and sonotrode are rotatably mounted via a vibration node of the transmitter. Means are provided for rotation of the sonotrode and movement of the sonotrode relative to the components such that the collar rolls over the components during the welding process.

Apparatus for the televisual monitoring of an arc welding operation

Abstract: The televisual monitoring apparatus incorporates at least one camera (10) fastened to the support of the welding machine. The camera (10) incorporates, interposed on the path of the light rays coming from the welding zone and upstream of a device (22) for conversion of the light rays into video signals, a filter (24) composed of a plate of ceramic material having light rotatory properties and electrodes disposed in contact with each of the two faces of the plate in accordance with a determined network. The monitoring device also incorporates, associated with the camera 10, an electronic video signal analysis and electrode potential control arrangement.

Sheet metal laser welding

Abstract: A method for the thermal welding of contiguous sheet metal elements comprising the steps of directing a defocussed laser beam at the joint formed therebetween so as to plasticize the areas thereof proximate thereto with a substantial portion of the energy thereof, and simultaneously feeding a powdered filler material into and about the joint so as to fully encompass the area of laser beam impingement thereupon, with a portion of the filler material being heated to a plastic state by the remaining portion of the beam's energy. The powdered filler material thus partially shields the sheets from the direct impingement of the beam's full energy thereupon, whereby the likelihood of sheet burn-through and/or excessive heat distortion is greatly reduced. The plasticized filler material thereafter attaches to the plasticized area proximate with the joint and builds thereupon a homogeneous weld seam characterized by excellent weld fusion and a high joint efficiency.

Apparatus and method for ultrasonic welding of wires

Abstract: An apparatus and method for ultrasonically welding wires includes an ultrasonic horn tip and associated structure for allowing adjustment to accommodate different diameters of wires to be welded while maintaining a tight grip around the wires during the welding process to avoid spreading or splaying of the wires. The tip is rotable to provide several alternative and interchangeable work surfaces on a standard-shaped readily machineable cross section, thereby allowing for a longer total worklife and a reduced cost of manufacture.

A predicting method of welding residual stress using source of residual stress.

Abstract: In this paper, a predicting method of welding residual stress by using the source of residual stress (inherent strain) is proposed. And the validity of the method is demonstrated by numerical experiments with the aid of the finite element method.Welding residual stress is produced as a result of thermal elasto-plastic behavior. Their source is composed of the thermal strain and/or plastic strain, etc., which is called here inherent strain.Taking a butt welding joint as an example, the sources of residual stress are estimated in different sizes manufactured on the same welding condition. It is found that the distributions of the source of residual stress are almost the same if the sizes of the joint are larger than that of a specific one, which is named a standard size.It is demonstrated that the residual stress produced in the joint of any different sizes can be predicted accurately by elastic analysis using the inherent strain in a standard size of the joint, unless the sizes are too small.

New applied technology of plasma heat sources

Abstract: (1990). New applied technology of plasma heat sources. Welding International: Vol. 4, No. 4, pp. 276-282.