Showing papers on "Welding published in 1982"

Process for plastic LCD fill hole sealing

Abstract: The access hole for filling the liquid crystal cavity in an LCD having plastic front and rear members is sealed by welding the two members together Pressure is applied during the weld to insure a good joint The welding process avoids problems of non-adhesion or poor adhesion associated with the use of epoxy, especially the type of epoxy used for sealing glass LCDs

Numerical analysis of thermal stresses during welding including phase transformation effects

Abstract: The problem of determining temperature distributions, transient thermal strains, and residual stresses during butt welding thick plates with the multipass GMAW process is solved using the finite element method. First, a nonlinear heat transfer analysis is performed taking into account the temperature dependence of the material properties, and convection and radiation surface heat losses. This is followed by a thermo-elastic-plastic stress analysis that incorporates phase transformation strains. Finally, the theoretical predictions are compared with experimentally obtained data showing good correlation.

Austenitic stainless steel-ferritic steel weld joint failures

Abstract: The cause of failures of dissimilar-alloy (austenitic or ferritic) joints in superheater and reheater tubes of fossil-fired steam plants was investigated. In the failures of interest, cracks form and propagate in the ferritic steel (usually 2 1/4 Cr-1 Mo steel) about 5 to 15 ..mu..m from the fusion lines. The complex microstructure developed at the interface between weld metal and 2 1/4 Cr-1 Mo steel during welding and elevated-temperature service was examined in (1) the as-welded and as-welded-and-tempered conditions, and (2) failed and unfailed joints having more than 100,000 h of service in a fossil-fired boiler. Metallographic observations on failed and unfailed joints were combined with literature observations to explain the interface microstructure and subsequent failure mode. On the basis of the proposed failure model, recommendations are presented for improving joint reliability.

The effect of quenching on the solidification structure and transformation behavior of stainless steel welds

Abstract: Weld solidification structure of three different types of stainless steel,i.e., 310 austenitic, 309 and 304 semiaustenitic, and 430 ferritic, was investigated. Welds of each material were made without any quenching, with water quenching, and with liquid-tin quenching during welding. The weld micro-structure obtained was explained with the help of the pseudobinary phase diagrams for Fe-Cr-Ni and Fe-Cr-C systems. It was found that, due to the postsolidification 5 → γ phase transformation in 309 and 304 stainless steels and the rapid homogenization of microsegregation in 430 stainless steel, their weld solidification structure could not be observed unless quenched from the solidification range with liquid tin. Moreover, the formation of acicular austenite, and hence, martensite, at the grain boundaries of 430 stainless steel welds was eliminated completely when quenched with liquid tin. The weld solidification structure of 310 stainless steel, on the other hand, was essentially unaffected by quenching. Based upon the observations made, the weld microstructure of these stainless steels was summarized. The effect of cooling rate on the formation of primary austenite in 309 stainless steel welds was discussed. Finally, a simple method for determining the relationship between the secondary dendrite arm spacing and the solidification time, based on welding speeds and weld pool configurations, was suggested.

Heat generation and heat flow in the filler metal in GMA welding

Abstract: The physical processes governing the generation and the flow of heat in a consumable mild steel wire were investigated to determine the influence of the welding parameters on melting rate and drop temperature. The work is limited to processes where the wire is at positive polarity. The analysis of the heat balance is based on measurements of the melting rate as a function of the electric current and the extension length, at a given wire diameter. The ohmic power developed in the wire was calculated from the measured data. It was found that it is, in general, not sufficient to account for the observed melting rate. Consequently, there must be a flow of heat from the anode surface on the molten tip, through the liquid metal, to the solid part of the wire. The corresponding heat flow rate was derived from the experimental data; it was found to depend on current and melting rate. Simple physical models are presented that describe the transport of heat through the liquid and account for the experimental results. In the model for globular drop transfer, the dominant mechanism is fluid flow, which is caused by the Lorentz force. In the case of spray transfer, the heat flow is ascribed to thermal conduction through the liquid metal that is flowing down the pointed wire tip. The models yield expressions for melting rate and drop temperature as functions of current, extension length, and wire diameter. An analysis was made of data reported by Lesnewich on the critical current for the transition from globular to spray transfer. This transition occurs in a current range where the downward force on a drop is mainly due to the impact of the incoming liquid, and to electromagnetic effects. It was found that the total downward force is roughly equal to the sustaining force by the surface tension, at the critical current. Introduction This paper describes an investigation of the flow of heat and mass from a consumable wire to the weld pool. This subject is of interest, because the influx of drops of hot metal supplies a major part of the total power supplied to the weld pool (Ref. 1, 2). The work is limited to gas metal arc (GMA) and to stationary processes where the electric current I, the electrode or wire velocity, vw , and the length of the electrode or wire extension, L, are constant in time. We define the extension length as the distance between the melting front and the point, where the current enters the wire within the contact tube —Fig. 1. The flow processes mentioned above are described by the melting rate rh, and the drop temperature, Tdr. The latter two quantities are determined by the heat generated in the wire, and the heat flow through it. The work presented here deals with these processes. It leads to expressions for rh and T^r as functions of I, L, and the wire diameter, d w . Furthermore, an analysis is given of the mechanism which governs the transition from globular to spray transfer. The work presented here is limited to processes where the wire is positive with respect to the workpiece. A power I ip is then generated at the surface of the liquid tip by electron absorption, where

Resistance spot welder adaptive control

Abstract: The adaptive controller for a resistance spot welder is implemented with a microcomputer and peripherals to handle the monitoring of several process variable inputs and control the welding machine in real time. Before welding power is applied, electrode load, workpiece thickness and dynamic resistance are measured and must fall within predefined limits in order to continue. The workpiece, if necessary, is conditioned to correct fit-up and surface contamination problems by applying power pulses to lower its resistance. The welding power in each half cycle is dynamically adjusted as a function of workpiece thermal expansion and its first derivative to control formation of the weld nugget, and to control the cooling rate and temper the workpiece. During welding the power limits are adjusted in real time to compensate for electrode flattening and shunt effects. The quality of each weld is diagnosed and machine diagnostics are performed.

Friction welded fastener system

Abstract: A thermoplastic fastener having a slight taper, is friction welded to a thermoplastic workpiece. A system for friction welding the fastener includes a way of automatically stopping rotation of the fastener while contact pressure between the fastener and the workpiece is maintained.

Advanced processing methods for titanium

Abstract: Among the topics discussed are recent advancements in Ti near-net shape technology, vacuum hot pressing of large, near-net shape spar fittings, Ti alloy sheet forming, superplastic forming/diffusion bonding of Ti alloys, the influence of H additions on the high temperature superplasticity of Ti alloys, the effects of processing on the fatigue life of Ti-6Al-4V castings, and the laser welding of a Ti alloy. Also considered are aspects of speed machining of Ti, the microstructures and mechanical properties of laser-welded Ti alloys, and the failure characteristics of cutting tools for Ti alloy machining at high speeds.

Nondestructive real-time method for monitoring the quality of a weld

Abstract: Herein disclosed is a noncontact, nondestructive method for monitoring the quality of a high energy weld, e.g., laser beam weld. In accordance with the proposed method, an acoustic sensor (32) is positioned at a distance from the welding zone (34) and picks up airborne acoustic emission signals (33) associated with the laser welding process. These acoustic signals, propagating through the air space between the welding zone (34) and the sensor (32), are detected and analyzed (36,37) to determine the quality of the weld (FIG. 3).

Lap welding method for textile fabrics

Abstract: Textile fabrics are firmly lap welded to each other by superposing two end portions of one or two fabrics on each other while interposing a piece of a synthetic polymeric bonding tape between the superposed two end portions and by applying a high frequency wave treatment and/or heat treatment to the interposed portion of the bonding tape through at least one of the superposed end portions while pressing them, to melt the interposed portion of the bonding tape thereby lap welding the end portions of the fabric or fabrics to each other.

Process for the production of a composite metal part and products thus obtained

Abstract: The present invention relates to the production of metal parts whose core and surface must have different characteristics. Its subject comprises firstly a process for the production of a composite metal part by coating or hard-surfacing a metal core of low-alloy structural steel with a harder metal layer composed of a high-speed chromium-tungsten or chromium-molybdenum steel or a high-speed steel containing chromium associated at the same time with a plurality of elements such as tungsten, molybdenum, vanadium, and cobalt, this process being at the same time characterized in that this high-speed steel has a hardness higher than 57 Rockwell C, in that the low-alloy steel which constitutes the metal core is selected to be compatible with the said high-speed steel, in that the said high-speed steel is applied exclusively in the form of a prealloyed powder, and in that the coating or hard-surfacing of the core with this powder is effected with the aid of one of the welding processes of the follow-group: welding by means of a transferred or semi-transferred arc plasma torch, or welding by means of a laser torch, the operation of coating or hard-surfacing by welding being followed by heat treatment. Another subject of the invention comprises the products obtained by the abovedescribed process. It is particularly applicable to the production of rolls for cold rolling mills, rolling or forming rollers, shear blades, wear plates, and armor plates.

Laser welding: state of the art review

Abstract: Since its initial development, the laser has been hailed as a potentially useful welding tool for a variety of applications. The scope for technical and commercial laser welding applications has increased greatly since the development of multikilowatt CW CO2 lasers around 1970. The laser’s capability of generating a power density greater than 106 watts/cm2 is a primary factor in establishing its potential for welding. Numerous experiments have shown that the laser permits high-quality precision weld joints rivaled only by electron beam. This article will present the state of the art of laser welding by reviewing recent work in the field.

Apparatus for welding a joint between plastic pipes

Abstract: A welded joint for plastic pipe is formed by apparatus including a sleeve (6) which is placed over the place where the pipes are joined and a heating mat (3) which is inserted between the sleeve and the pipes. The heating mat (3) and the sleeve (6) are provided with gear-tooth system (4, 5, 114, 115) which engage each other in the assembled condition of the device. Consequently, the surfaces of the ends of the heating mat (3) and the sleeve (6) which are in contact are circumferentially extended, resulting in a satisfactory welded joint, even where large pipe tolerances are involved.

Spark plug for internal combustion engines having an alloy layer between the electrodes and tip ends

Abstract: A spark plug for an internal combustion engine including a center electrode, an earth electrode, a metal tip joined by welding to an ignition section of at least one of the center electrode and the earth electrode, and an alloy layer located at a welding portion between the metal tip and the at least one electrode. The metal tip is formed of material highly resistant to heat and wear which is distinct in the coefficient of thermal expansion from the material of the electrodes. The alloy layer is formed to have a thickness of at least about 10μ, so as to avoid the rupture of the metal tip along the surface thereof adjacent to the welding portion.

Arc welding guide tube with non-adhesive tip

Abstract: A guide tube for guiding a wire (23) of filler metal in an arc welding machine and for applying arc current thereto comprises a metal body (80) having a longitudinal bore (82) through which the wire passes. Near the front end of the tube there are two transverse passages (95) housing respective ball (96) which are urged to project into the bore by respective spiral compression springs (97). These serve to keep the wire pressed against the opposite side of the bore to maintain good electrical contact. The springs are held in by a sheath (100) fitted over the end of the tube. The sheath also serves to keep an end piece (50) in place. Both the sheath and the end piece are made of refractory material which is electrically insulating and which is non-adhesive to spattering metal from the weld melt. This helps to prevent the front of the tube getting clogged up in operation.

Method of making wrought high tension steel having superior low temperature toughness

Abstract: OF THE DISCLOSURE Due to increasing demands for steel to be used for construction such as buildings, pressure vessels, pipe lines or the like, various kinds of high tension steels, particularly steels suitable for welding have increasingly been developed. Heretofore, proposed methods of making such high tension steel have relied on so-called cold rolling and/or rolling followed by quenching and tempering, however, these conventional steels have suffered from drawbacks such as a tempering step indispensable after quenching, softening of welded zone and lack of uniformity in the metal structure in the direction of plate thickness. A compositional feature of the new method resides in addition of minor amounts of Ti and B along with Nb as contributing to grain refining or precipitation hardening elements in addition to limited amounts of other ingredients such as C, Si, Mn, S, Al and N. Further addition of at least one of V, Ni, Cu, Cr, Mo, Ca and REM also acts to improve the properties of the steel. The steel prepared to have the aforesaid composition is subjected to controlled heating, subse-quent rolling under prescribed rolling reduction ratio, temperature for terminating rolling and to a specified cooling rate. The steel plate thus processed has a structure having fine bainite grains alone or a duplex grain

Sidewall-matching adaptive control system for welding

Abstract: An adaptive control system for welding which senses the lateral profile of a weld joint while the welding electrode moves laterally across the joint, compares a first portion of the sensed lateral profile to a second portion of the sensed lateral profile, and then adjusts a welding parameter, such as the center of oscillation for tracking, the width of oscillation, and constant fill control, in response to the results of the comparison. One disclosed signal processing technique matches an average of data samples for the left portion of the weld seam to an average of data samples for the right portion. Another disclosed technique involves comparing an integrated signal corresponding to the leftward portion of the sensed lateral profile to an integrated signal corresponding to the rightward portion. Another disclosed technique involves comparing an integrated sensed profile signal to a predetermined reference value which is based upon a reference signal. The reference signal comprises data representative of the prior history of the weld joint. The disclosed embodiments employ programmed microprocessors to provide horizontal cross-seam control and process the arc signal to remove undesirable noise. The system can adapt to changes in direction of the weld seam as well as changes in the width and shape of the profile of the weld seam.

Residual Stresses and Their Redistribution During Annealing of a Girth-Butt Welded Thin-Walled Pipe

Abstract: The redistribution of calculated welding stresses during different post weld heat treatments (PWHT) is numerically investigated for a girth-butt welded thin-walled pipe made of a micro-alloyed carbon manganese steel. A finite element analysis with assumed rotational symmetry is performed. The influence of creep, relaxation and phase transformations is included. The amount of stress reduction is found to be mainly controlled by the holding temperature. Most of this reduction was observed to occur during the end of the heating period where the transient stresses followed the fall of the yield stress with temperature.

Z-bar guide apparatus and method of butt welding

Abstract: A method and apparatus for guiding the opposed edges of sheet metal (16) into substantially abutting edge-to-edge relationship with one another and thereafter welding said edges by a high energy welding source (17) to form a seam. The invention enables the continuous high speed butt welding of the sheet metal to form cylindrical bodies. The apparatus includes three elements (24, 25, 26) which are cooperatively secured in assembled relationship and thereby form opposed and converging guide channels (46, 47) which ' converge into open relationship with one another along the length of the apparatus so that the opposing edges of sheet metal (16) are guided into intimate abutting edge-to-edge relationship with one another. The elements (24 - 26) extend to a point adjacent the weld zone (W) in order to maintain the sheet metal edges in abutting relationship as they enter the weld zone. In another embodiment, two of the elements (25, 26) may include portions (65) which extend into and beyond the weld zone (W). Such portions are provided with a tapered opening (68) through which the high energy welding source (17) may be continuously focused relative to the point of the weld.

Laser pipe welding system for nonstationary pipe

Abstract: A laser pipe welding system for welding 360° around a pipe includes a pair of focusing heads each welding half the pipe circumference, a seam tracker to keep the focal spot on the seam to compensate for axial and radial variations, an active beam alignment system for real-time compensation of angular misalignment, and both passive and active-feedback beam transport systems that flexibly follow the focus head.

Adaptive welding system

Abstract: The performance of prior automated welding systems has been limited by their inability to independently track and weld and by their inability to accurately determine the groove profile. The adaptive welding system disclosed herein includes a weld torch (20) adapted to be controllably positioned in at least two dimensions, and means (28,38) for tracking a workpiece seam (12) to be welded. The tracking means (28,38) is pivotably connected to the weld torch (20). Means (19,40) for pivoting the tracking means (28,38) relative to the weld torch (20) is included to permit both the tracking means (28,38) and the weld torch (20) to be independently maintained over the seam (12). The tracking means (28,38) monitors the seam (12) by optical triangulation of a rotating laser beam (60) projected against the workpieces. This rotating laser beam (60) crosses the seam twice during each cycle of the beam (60).

Microstructure and Mechanical Properties of Laser Welded Titanium 6Al-4V

Abstract: Laser butt welds were fabricated in a titanium alloy (Ti-6A1-4V, AMS 4911-Tal0 BSS, annealed) using a Control Laser 2 kW CW CO2 laser. The relationships between the weld microstructure and mechanical properties are described and compared to the theoretical thermal history of the weld zone as calculated from a three-dimensional heat transfer model of the process. The structure of the weld zone was examined by radiography to detect any gross porosity as well as by both optical and electron microscopy in order to identify the microstructure. The oxygen pick-up during gas shielded laser welding was analyzed to correlate further with the observed mechanical properties. It was found that optimally fabricated laser welds have a very good combination of weld microstructure and mechanical properties, ranking this process as one which can produce high quality welds.

Electric heating element for sterilely cutting and welding together thermoplastic tubes

Abstract: An electric heating element for sterilely cutting and welding together a pair of thermoplastic tubes transversely of the axis of each tube includes as an outer layer a folded sheet of a metal, such as copper, aluminum, silver or gold, having a thermal conductivity of at least about 173 watts/m°K at a thickness of 0.10 mm and a tensile yield strength of at least 34×104 kPa at a 0.10 mm thickness. A resistance heating element, preferably having a positive thermal coefficient of resistance (PTC), in the form of a resistor of stainless steel or the like is disposed inside the fold of the metal sheet and a layer of dielectric adhesive, such as an epoxy or acrylic adhesive, stable to about 260° C., is disposed between the inner surfaces of the metal sheet and the resistor to insulate the resistor from the folded sheet and bond the resulting structure together. The folded edge of the metal sheet forms the melting edge of the heating element. The heating element has a thickness of from about 0.13 mm. to about 0.76 mm.

Experimental Investigation of Buckling of Hydrostatically Loaded, Conical Shells and Practical Evaluation of the Buckling Load

Abstract: An extensive experimental investigation of buckling of conical shells that are supported only along their lower edge and that are loaded by the weight of a liquid leads to diagrams and formulas which can be used directly in the design of such shells. The margin of safety to be applied, the influence of welding stresses and the limitations on the validity of the formulas for structures with different boundary conditions are discussed.

Microprocessor control of welding apparatus

Abstract: Stick and stud welding apparatus which utilizes a microprocessor and related RAMs, ROMs and peripheral interface devices to control the welding parameters. The ideal desired weld current and weld cycles in the case of stud welding can be selected depending upon the mode of operation and/or stud conditions. The program for the microprocessor instructs the microprocessor to periodically compare the actual welding current to the ideal current, compute the difference and alter the phase firing time of an SCR bridge to compensate or adjust the welding current to the ideal current. In the case of stud welding mode, the program further instructs the microprocessor to reference the selected number of cycles, compute the total energy delivered across the stud and workpiece gap from actual current, welding terminal voltage and time and enlarge the number of actual weld cycles to a given percentage of that initially selected to provide a total energy input to the stud as selected. In the stud mode, the pilot arc current and cycles may likewise be selected and controlled. Such parameters as pilot arc current, pilot arc cycles, main welding current, main welding current cycles, total energy, welding terminal voltage and error occurrence are displayed visually by means of lights and/or written printout.

Article comprising an elastic gathered strip, method and device for its manufacture.

Abstract: This article comprises an elastic element 31 interposed between two sheets of support material 30, 32. This elastic element held in tension is attached to the support sheets by producing, by means of heat welding, weld zones 33 between these two sheets. Application particularly to the making of protective garments, babies' nappies, packagings, etc.