Showing papers on "Welding published in 1994"

A model of deep penetration laser welding based on calculation of the keyhole profile

Abstract: A model describing the process of deep-penetration laser welding has been developed by calculating the keyhole profile using a point-by-point determination of the energy balance at the keyhole wall. A formula for heat conduction was derived from the model of a moving line source of heat. The various absorption mechanisms were modelled. The corresponding absorbed power transferred to the keyhole wall balances the conduction losses, which yields the local inclination of the wall. The thermodynamics and the flow of metal vapour inside the keyhole have been calculated. Accordingly, beam damping due to the plasma plume above the workpiece and the mean plasma absorption coefficient in the keyhole could be estimated. The keyhole profile tends to a geometry that distributes the major part of the beam to the front wall owing to higher conduction losses at the upstream side. The reasons for decreasing energy absorption with increasing welding speed are discussed.

Electron Beam Welding

Abstract: Generation of the electron beam The behaviour of the electron beam on penetrating metal Welding parameters and advice on welding practice The weldability of metallic materials Preparation of the workpiece Beam and machine control Electron beam welding machines and equipment Quality levels and acceptable variations in electron beam welds Examples of electron beam welded components Personnel qualifications and machine testing Standards and regulations Other methods of working materials with electron beams A comparison of electron beam and laser welding

System and method for controlling a welding process for an arc welder

Abstract: A method and system for controlling a welding cycle of an arc welder comprising: a number of digital programs stored in a digital memory device, with each of the programs including a plurality of digitally coded welding parameters indicative of selected functions of a specific welding cycle; a weld controller for converting the selected functions of a digital program into welding parameters at the output of the welder; a display panel having a group of switches located in a given pattern and a decoder network at a selected position for creating a decoded signal indicative of the activation pattern of the decoder network; means responsive to the decoded signal for activating said switches in either a first condition where the switches activate means for modifying a selected one of said digital programs or a second condition where said switches activate means for creating a program select signal corresponding to a given digital program; means responsive to a program select signal for selecting one of the programs corresponding to the program select signal; and, loading means for loading a selected one of the programs into the weld controller for controlling the welding parameters of the welder in accordance with the selected one of the programs.

Improvement in HAZ Toughness of Steel by TiN-MnS Addition

Abstract: High-strength steel of the 490-MPa class strength for offshore structures was developed by making the most of a TiN-MnS complex precipitate effective that is over a wide welding heat input range. At the same time, its HAZ toughness improvement mechanism was clarified. The TiN-MnS system provided superior HAZ toughness with a medium heat input in -60°C Charpy test and -50°C CTOD test and with a high heat input in -60°C Charpy test. This is probably attributable to the TiN compound that pins austenite grains and to the TiN-MnS complex precipitate that produces fine intragranular ferrite (IGF) and reduce the fracture facet unit after welding. IGF may be formed either by increase in driving energy for nucleation in the region where manganese is depleted by the MnS precipitation or decrease in interfacial energy with nucleation by the crystal coherency of TiN and ferrite. The presence of manganese-depleted zone is an indispensable mechanism and is complemented by the crystal coherency of TiN and ferrite.

A process model for friction welding of AlMgSi alloys and AlSiC metal matrix composites—I. Haz temperature and strain rate distribution

Abstract: The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of AlMgSi alloys and AlSiC metal matrix composites. In Part I the different components of the model are outlined and analytical solutions presented which provide quantitative information about the HAZ temperature distribution for a wide range of operational conditions. Moreover, a general procedure for modelling the HAZ strain rate distribution has been developed by introducing a series of kinematically admissible velocity equations which describe the material flow fields in the radial, the rotational, and the axial direction, respectively. Calculations performed for both types of materials show that the effective strain rate may exceed 1000 s −1 in positions close to the contact section due to the high rotational velocities involved. Application of the model for evaluation of the response of AlMgSi alloys and AlSiC metal matrix composites to the imposed heating and plastic deformation is described in an accompanying paper (Part II).

Oscillations of the keyhole in penetration laser beam welding

Abstract: Free oscillations of the keyhole in penetration laser beam welding are studied theoretically with regard to characteristic frequencies, damping rates and stability at large amplitudes. The normal modes form a discrete set which may be characterized by axial and azimuthal numbers. Due to viscous damping, only the lowest modes survive many oscillation periods, which yields a limited range of frequencies for the dynamic response of the keyhole to fluctuations of external welding parameters.

Interactive laser welding at elevated temperatures of superalloy articles

Abstract: A process is provided for laser welding a superalloy article (20) by pre-heating the entire weld area and region adjacent to the weld area of the article to a ductile temperature within the range of 1400-2100 degrees F with an induction heat coil (14) and maintaining such tem-perature during welding and solidification of the weld; and welding the preheated ar-ticle using a laser (11) with a powder al-loy feed (12), with a control system which controls the laser powder feed (12) and a motion system on which the article is fix-tured, wherein the control system includes a vision system which digitizes the weld area of the article (20) providing a path for the laser to follow.

Exposure to stainless steel welding fumes and lung cancer: a meta-analysis.

Abstract: Stainless steel welding is associated with exposure to metals including hexavalent chromium and nickel. This study is a meta-analysis of five studies of stainless steel welders and the occurrence of lung cancer. Asbestos exposure and smoking habits have been taken into account. The calculated pooled relative risk estimate was 1.94 with a 95% confidence interval of 1.28-2.93. This result suggests a causal relation between exposure to stainless steel welding and lung cancer.

Control of Microstructures and Properties in Steel Arc Welds

Abstract: Control of Microstructures and Properties in Steel Arc Welds provides an overview of the most recent developments in welding metallurgy. Topics discussed include common welding processes, the thermal cycle during welding, defects that may occur during the welding process, the metallurgy of the material, metallurgical processes in the heat-affected zone and the fused metal, and the relationship between microstructures and mechanical properties. The book's final chapter presents examples of welded joints, illustrating how modern theories are capable of predicting the microstructure and properties of these joints. This book is an excellent resource for welding engineers, metallurgists, materials scientists, and others interested in the subject.

Solidification behavior and cracking susceptibility of pulsed-laser welds in austenitic stainless steels

Abstract: The solidification cracking susceptibility of several commercial heats of Types 304L, 316L and 321Mo stainless steels was evaluated under pulsed-laser welding conditions. Both the Suutala weldability diagram and the WRC constitution diagram predicted that all the heats tested in this investigation would be resistant to weld solidification cracking based on the individual values of their Cr[sub eq]/Ni[sub eq] ratio. Under the rapid solidification conditions imposed by pulsed-laser welding, however, a number of these resistant heats were found to be extremely susceptible to weld solidification cracking. As a result, a modified weldability diagram is proposed for austenitic stainless steels welded under conditions producing rapid solidification. The variation from predicted cracking susceptibility resulted from a shift in solidification behavior under rapid solidification growth conditions. Alloys susceptible to cracking exhibited a primary austenite solidification mode with a fully austenitic microstructure. Crack-resistant alloys were also fully austenitic, but this microstructure resulted from a massive transformation to austenite following primary solidification as ferrite. Several alloys exhibited mixed solidification modes, resulting in variable cracking susceptibility. The solidification conditions under which this shift in the primary solidifying phase occurs is reviewed in the context of the current results and previous observations.

Device for spot welding of structures formed of pressed sheet metal elements.

Abstract: In a welding station, particularly for motor-vehicle bodies, the elements to be welded are locked in a precise position by locking devices carried by locating gates. There are provided a number of pairs of locating gates, corresponding to the number of different types of structures to be welded on which the station must operate. The gates are mounted on powered carriages which are guided longitudinally on both sides of the conveyor line to allow the pair of gates which are in the operative position to be rapidly interchanged. The elements of the structure to be welded reach the work area suspended to a hook, without being preliminarly connected to each other.

Porous coated implant and method of making same

Abstract: The method forms a thin layer of metal mesh (14) on the surface (12) of the implant (10) for the bonding with a porous surface layer (16) to prevent the formation of notches within the body of the implant (10) The layer of metal mesh (14) can be formed by a number of known methods including conventional welding processes such as arc welding, resistance welding, electron beam welding, laser beam welding, friction welding, ultrasonic welding, cladding The porous metal surface layer (16) is preferably formed from titanium wire or titanium beads in a known process The porous surface layer (16) is bonded by a known process such as diffusion bonding, sintering, welding, or cladding By bonding the porous surface layer (16) to the thin layer of metal mesh (14), notches normally formed in the body of the implant (10) are substantially eliminated Therefore, the designer of the implant (10) is not limited as to the location and amount of porous surface layer (16) to be placed on the implants (10)

A simple model for multipass steel welds

Abstract: A model has been developed which is capable of describing the thermal cycles occurring in multipass welds. The method involves a calculation of the size and shape of the single bead-on-plate weld. The isotherms beneath the weld centre-line are estimated using an analytical solution for the problem of heat-flow into a thick plate. The volume of metal deposited per unit length of weld, i.e. the reinforcement, is then assumed to adopt the shape of a spherical cap on the surface of the plate. For multipass welds, the model applies the heat-flow equations as each bead is deposited. The model has been calibrated for a 214Cr1Mo multipass weld of a type commonly used for joining steam-pipes in a modern steam-generating power plant. The method has been used to investigate theoretically the effect of interpass temperature, welding current and Ac3 temperature on the fraction of weld microstructure which becomes reaustenitised during fabrication of the weldment. Where possible, the results are rationalised by comparison with experimental observations.

Wheel for a motor vehicle and method of making same

Abstract: A rim for a motor vehicle has several radial hollow spokes in a wheel disk which is manufactured in a die tool and is connected with a rim well. The cast wheel disk is connected with a deformed rim well by friction welding in the area of a rim flange. On an interior side, the wheel disk has at least one flat welding surface which extends around as an annulus and which is arranged so that it corresponds with another opposite flat welding surface of the rim well. In at least one of the hollow spokes, one reinforcing rib is arranged which extends radially from the wheel center axis toward the outside and connects two opposite walls of the spoke with one another.

Weldability of Ferritic Steels

Abstract: Factors influencing weldability Potential welding problem areas Solidification cracking Lamellar tearing Hydrogen cracking Reheat cracking Faults of welding Inspection for defects Joint integrity Service problems Repair.

Lead-acid battery

Abstract: PURPOSE:To provide a lead-acid battery small in size and excellent in characteristics in the lead-acid battery having a metallic terminal board by simplifying bonding of an upper end part of a battery jar to a fitting part of a battery middle cover and a bonding process of an adhesive agent to be charged in a recessed part of the battery middle cover for housing a joint part of an end of the terminal board to an electrode plate group welding shelf. CONSTITUTION:The battery is provided with a battery middle cover 2 equipped with a recessed part 9a wherein a connection part of an electrode plate group welding shelf 4, composed of lead or lead alloy, to an end of a terminal board 1 is housed; a fitting part 3a to an upper end part of a battery jar 3; and a through-hole 2a penetrating the other end of the metallic terminal board 1; and the terminal board 1 whose one end is connected to the electrode group welding shelf 4 by means of welding or soldering. Adhesive agents 9 and 7 are filled respectively into the recessed part 9a housing the connection part of the electrode plate group welding shelf 4 to the one end of the terminal board 1 and the fitting part 3a to the upper end part of the battery jar 3 for bonding.

A Study on the Three-Dimensional Analysis of Heat and Fluid Flow in Gas Metal Arc Welding Using Boundary-Fitted Coordinates

Abstract: Computer simulation of three-dimensional heat transfer and fluid flow in gas metal arc (GMA) welding has been studied by considering the three driving forces for weld pool convection, that is the electromagnetic force, the buoyancy force, and the surface tension force at the weld pool surface. Molten surface deformation, particularly in the case of GMA welding, plays a significant part in the actual weld size and should be considered in order to accurately evaluate the weld pool convection. The size and profile of the weld pool are strongly influenced by the volume of molten electrode wire, impinging force of the arc plasma, and surface tension of molten metal. In the numerical simulation, difficulties associated with the irregular shape of the weld bead have been successfully overcome by adopting a boundary-fitted coordinate system that eliminates the analytical complexity at the weld pool and bead surface boundary. The method used in this paper has the capacity to determine the weld bead and penetration profile by solving the surface equation and convection equations simultaneously.

Spectroscopic measurements of laser induced plasma during welding with CO2 laser

Abstract: Results of spectroscopic measurements of laser‐induced plasma under welding conditions are presented. Welding was performed with the use of a continuous‐wave CO2 laser operating at a power of 2 kW. Argon or helium was used as a shielding gas. The welding metal was stainless steel or titanium. Emission spectra from plasma were measured with a spectrograph and 1254 Silicon Intensified Target detector connected to the optical multichannel analyzer. The plasma electron temperatures were determined from the relative intensities of spectral lines and the electron densities were determined either from Stark broadening of atomic line or the absolute intensity of ionic line. The distributions of the electron temperature and density over the metal surface are presented and the influence of a shielding gas on plasma parameters is demonstrated. The plasma parameters obtained were used to calculate the absorption of a laser beam in the plasma over the metal surface. No significant absorption was found in our experimen...

Phenomenological Modeling of Fusion Welding Processes

Abstract: Welding is utilized in 50% of the industrial, commercial, and consumer products that make up the U.S. gross national product. In the construction of buildings, bridges, ships, and submarines, and in the aerospace, automotive, and electronic industries, welding is an essential activity. In the last few decades, welding has evolved from an empirical art to a more scientifically based activity requiring synthesis of knowledge from various disciplines. Defects in welds, or poor performance of welds, can lead to catastrophic failures with costly consequences, including loss of property and life.Figure 1 is a schematic diagram of the welding process showing the interaction between the heat source and the base metal. During the interaction of the heat source with the material, several critical events occur: melting, vaporization, solidification, and solid-state transformations. The weldment is divided into three distinct regions: the fusion zone (FZ), which undergoes melting and solidification; the heat-affected zone (HAZ) adjacent to the FZ, that may experience solid-state phase changes but no melting; and the unaffected base metal (BM).Creating the extensive experimental data base required to adequately characterize the highly complex fusion welding process is expensive and time consuming, if not impractical. One recourse is to simulate welding processes either mathematically or physically in order to develop a phenomenological understanding of the process. In mathematical modeling, a set of algebraic or differential equations are solved to obtain detailed insight of the process. In physical modeling, understanding of a component of the welding process is achieved through experiments designed to avoid complexities that are unrelated to the component investigated.In recent years, process modeling has grown to be a powerful tool for understanding the welding process. Using computational modeling, significant progress has been made in evaluating how the physical processes in the weld pool influence the development of the weld pool and the macrostructures and microstructures of the weld.

Organic electrolyte secondary battery

Abstract: PURPOSE:To lower current collecting resistance by joining the U shape bottom section of a plate in an U shape to a side conductive current collector. CONSTITUTION:A negative plate 6 mainly composed of carbon, and a positive plate 8 mainly composed of lithium cobalt oxide are separately formed into an U shape. These plates 6 and 8 are combined with each other while a microporous separator 9 made of polypropylene is being held in between, the U shape bottom section of the plate 8 is welded to the welding section 81 of a positive electrode side conductive current collector 5, and the U shape bottom section of the plate 6 is also welded to the welding section 61 of a negative electrode side conductive current collector 9. The current collector 5 is insulated by an insulating plate 4, and is welded to the positive electrode 21 at a positive electrode welding section 52. The current collector 9 is welded so as to be fixed to a battery jar 1 concurrently acting as the terminal of the negative electrode at a welding section 10. By this constitution, internal resistance can be reduced, so that the battery capable of being charged/discharged under large current, can thereby be obtained.

Portable AC/DC wire feed welder

Abstract: In a preferred embodiment, a portable wire feed electric arc welder, including a cabinet, a welding gun connected to the cabinet through a flexible conduit, and a supply mechanism to continuously feed the wire to the welding gun. There is a mechanism to receive either AC or DC power into the welder and a selector mechanism to selectively switch between a first mode of operation in which welding is performed with an external DC source, a second mode of operation in which welding is performed with an external AC source, and a third mode of operation in which welding is performed with an internal AC source. The internal AC source includes a step-down transformer connected to a conventional 115 VAC power source.

Tips for welding and their manufacturing process

Abstract: An excellent welding tip in the feed stability of a wire, in the release capacity of foreign matter, and in the stability of current control, and a process for manufacturing such a tip economically, is achieved in accordance with a sectional shape of a guide hole opened and provided to a welding tip. The sectional shape is derived by forming a wire in a passable non-circular shape. The sectional shape of the guide hole may be a polygonal or elliptic shape, or approximately so. In the case of making the sectional shape of the guide hole polygonal, it is more preferable to make it a polygon circumscribing on a circle, for example, such a polygon circumscribing on a larger circle than the outer diameter of the wire to be inserted into the guide hole by 0.02-0.20 mm in diameter. Specifically, it is preferable to arrange the sectional shape as a triangle.

Dynamic stresses in weld metal hot cracking

Abstract: This paper presents the results of a study aimed at understanding the influence of dynamic stresses, induced by thermal and mechanical loading, on weld metal hot cracking. The study attempts to resolve the relationship between the dynamic stress distribution in the specimen, particularly near the trailing edge of the pool, and the observed cracking behavior in a Sigmajig test specimen. The transient stress distribution in the specimen resulting from mechanical and thermal loading was calculated for a Type 316 stainless steel specimen. The initiation and propagation of the crack during welding was visually monitored using a stroboscopic vision system. The numerical results were used to understand the initiation and propagation of weld metal hot cracks during controlled welding of a specimen subjected to external restraint. The results of this study indicate that for hot cracking to occur, there exists a dynamic relationship between the metallurgical and mechanical factors, which can be influenced by the welding conditions and mechanical restraint.

A method for manufacturing packages for liquid products, especially liquid foodstuffs, a package obtained through this method

Abstract: A method for manufacturing packages (1) for liquid products, especially liquid foodstuffs, includes a step in which longitudinal strips (6) of a flexible sheet material member (2), that is folded into a tubular shape so that the abovementioned longitudinal strips (6) extends outwardly, are joined to each other. Along the longitudinal strips (6) already joined suitable welding lines (7, 8) are made so as to form a portion (9) in form of a channel compartment (10) that is closed at one end, and having the other end in communication with the inside of the package. Also a longitudinal breaking line (12) is made in the strips with the aim of allowing the portion (9) to be partially detached from the package. In the strips (6) there is also made a notch (13) aimed at allowing the detachable portion (9) to be opened at the end opposite to the one in communication with the inside of the package (1).

The effect of surface condition on acoustic emission during welding of aluminium with CO2 laser radiation

Abstract: The fast Fourier transform spectrum of acoustic emission during CO2 laser welding of Al 1100 shows frequency components in the 3-9 kHz range that can be identified with the presence of a keyhole and correlate with penetration. In addition, a study of the effect of anodization and surface pretreatment of Al 1100 with excimer laser radiation has shown that acoustic emission at 9-10 kHz arises from burning off of surface oxide. A comparison of these results with those predicted from simple thermal and fluid dynamical models yields good agreement with theory. These results indicates that acoustic emission over specific frequency ranges may be highly diagnostic of laser processing conditions.

Explosive welding of a near-equiatomic nickel-titanium alloy to low-carbon steel

Abstract: Equiatomic and near-equiatomic NiTi alloys are very resistant to cavitation erosion compared with the alloys commonly used to construct pumps and hydroturbines. Thin layers (0.4-1.0 mm) of a near-equiatomic NiTi alloy were explosively welded to low-carbon steel substrates to fabricate high-strength, bimetallic tandems in which the NiTi provided resistance to cavitation damage and the low-carbon steel provided structural strength. Tensile lap-shear tests on the welded material revealed bond strength of up to 387 MPa. As-welded NiTi/steel tandems were less resistant to cavitation erosion than annealed, unwelded samples; however, a post-weld heat treatment at 500 °C recovered most of the lost resistance.