This article overviews the classification of welding processes and the key process embodiments for joining by various fusion welding processes: fusion welding with chemical sources for heating; fusion welding with electrical energy sources, such as arc welding or resistance welding; and fusion welding with directed energy sources, such as laser welding, electron beam welding. The article reviews the different types of nonfusion welding processes, regardless of the particular energy source, which is usually mechanical but can be chemical, and related subprocesses of brazing and soldering.

Dissimilar metal welding applications require careful control over the welding parameters and corresponding dilution level in order to produce welds with proper microstructure and properties for the intended service. This article reviews the relation between the dilution and bulk fusion-zone compositions and describes the effect of fusion welding parameters on dilution. It also provides typical examples of the microstructure and property control in dissimilar weld applications.

This article discusses the classifications, specifications, applications and methods for producing welded and seamless steel tubular products, including pipes and tubes. Common types of pipes include standard pipe, conduit pipe, piling pipe, pipe for nipples, transmission or line pipe, water main pipe, oil country tubular goods, water well pipe, and pressure pipe. Pipes in suitable sizes, and most of the products classified as tubing, both seamless and welded, may be cold finished. Pressure tubes are given a separate classification by both the American Society for Testing and Materials (ASTM) and producers. The term tube covers three groups, including pressure tubes, structural tubing, and mechanical tubing.

Microjoining with high energy density beams is a new subject in the sense that the progress of miniaturization in industry has made the desire to make microjoints rapidly and reliably a current and exciting topic. This article summarizes the current state of microjoining with both electron and laser beams. It considers the elementary physical processes such as heat and fluid flow to introduce the reader to the phenomena that affect melting, coalescence, and solidification needed for a successful microweld. The various forces driving (and resisting) fluid flow are analyzed. The article discusses the equipment suitable for microjoining and the metallurgical consequences and postweld metrology of the process. It also provides examples of developmental welds employing laser and electron beam microwelding techniques.

This article aims to survey the factors controlling the weldability of carbon and low-alloy steels in arc welding. It discusses the influence of operational parameters, thermal cycles, and metallurgical factors on weld metal transformations and the susceptibility to hot and cold cracking. The article addresses the basic principles that affect the weldability of carbon and low-alloy steels. It outlines the characteristic features of welds and the metallurgical factors that affect weldability. It describes the common tests to determine steel weldability. There are various types of tests for determining the susceptibility of the weld joint to different types of cracking during fabrication, including restraint tests, externally loaded tests, underbead cracking tests, and lamellar tearing tests. Weldability tests are conducted to provide information on the service and performance of welds. The major tests that are discussed in this article are weld tension test, bend test, the drop-weight test, the Charpy V-notch test, the crack tip opening displacement test, and stress-corrosion cracking test.

This article discusses two categories of stainless steel casting alloys and their nomenclature. It provides information on two situations in which welding of stainless steel castings is required. These situations are based on casting defects and selection of welding processes. The article presents compositions and typical microstructures of corrosion-resistant stainless steel casting alloys in tabular form. It presents special considerations for the welding of martensitic stainless steel castings. The article reviews the two most serious problems encountered in the welding of stainless steel castings, namely, solidification hot cracking and heat-affected zone hot cracking. It concludes with a discussion on the some useful considerations for welding corrosion-resistant alloys to avoid defects.

Flash welding, also called flash butt welding, is a resistance welding process in which a butt joint weld is produced by a flashing action and by the application of pressure. The flash welding process consists of preweld preparation, flashing, upsetting (forging), and postweld heat treatment. This article provides an overview of both flash welding and upset welding and describes the various process and failure origins of flash welding as well as the equipment used. It also explains the characteristics and advantages of solid-state upset welding.

Fusion welding processes involve four phase changes, namely, solid-solid state, solid-liquid, liquid-vapor, and vapor-plasma. Each has its own thermal, momentum, and stress history. This article discusses some important techniques to validate temperature, momentum, stress, and residual strain history observed in the heat-affected zone of fusion welded materials.

This article discusses four types of defects in materials that have been fusion welded and that have been the focus of much attention because of the magnitude of their impact on product quality. These include hot cracks, heat-affected zone (HAZ) microfissures, cold cracks, and lamellar tearing. These defects, all of which manifest themselves as cracks, are characteristic of phenomena that occur at certain temperature intervals specific to a given alloy. The article presents selected alloy 625 compositions used in weldability study.

Joining is key to the manufacture of large or complex devices or assemblies; construction of large and complex structures; and repair of parts, assemblies, or structures in service. This article describes the three forces for joining: physical, chemical, and mechanical. It provides an overview of the joining processes, namely, mechanical fastening, integral attachment, adhesive bonding, welding, brazing, and soldering. The article concludes with information on the various aspects of joint design and location that determine the selection of a suitable joining method.

This article describes the coating materials, surface-preparation requirements, and application techniques used to protect underground pipelines. It provides a valuable insight into the types of polymer-based coatings that are both cost-effective and widely accepted in the pipeline industry.

This article describes some of the welding discontinuities and flaws characterized by nondestructive examinations. It focuses on nondestructive inspection methods used in the welding industry. The sources of weld discontinuities and defects as they relate to service failures or rejection in new construction inspection are also discussed. The article discusses the types of base metal cracks and metallurgical weld cracking. The article discusses the processes involved in the analysis of in-service weld failures. It briefly reviews the general types of process-related discontinuities of arc welds. Mechanical and environmental failure origins related to other types of welding processes are also described. The article explains the cause and effects of process-related discontinuities including weld porosity, inclusions, incomplete fusion, and incomplete penetration. Different fitness-for-service assessment methodologies for calculating allowable or critical flaw sizes are also discussed.

Fluid flow is important because it affects weld shape and is related to the formation of a variety of weld defects in gas tungsten arc (GTA) welds. This article describes the surface-tension-driven fluid flow model and its experimental observations. The effects of mass transport on arc plasma and weld pool are discussed. The article reviews the strategies for controlling poor and variable penetration and describes the formation of keyhole and fluid flow in electron beam and laser welds. It also explains the fluid flow in gas metal arc welding and submerged arc welding, presenting its transport equations.

This article discusses the applications and tensile properties of selected copper tube alloys, as well as the methods for producing copper tubular products, namely extrusion and rotary piercing. It explains the methods available for the finishing of copper tubular products, such as tube welding, cold drawing, and tube reducing. The article lists the standard dimensions and tolerances for several kinds of copper tubes and pipes in the ASTM specifications, along with other requirements for the tubular products.

This article describes some examples of the different welding processes for gray, ductile, and malleable irons. These processes include fusion welding, repair welding, shielded metal arc welding, gas metal arc welding, flux cored arc welding, gas tungsten arc welding, submerged arc welding, oxyfuel welding, and braze welding. The article discusses various special techniques, such as groove-face grooving, studding, joint design modifications, and peening, for improving the strength of a weld or its fitness for service. The article describes other fusion welding methods such as electrical resistance welding and thermite welding. It reviews thermal spraying processes, such as flame spraying, arc spraying, and plasma spraying, of a cast iron.

This article discusses the failure analysis of several steel transmission pipeline failures, describes the causes and characteristics of specific pipeline failure modes, and introduces pipeline failure prevention and integrity management practices and methodologies. In addition, it covers the use of transmission pipeline in North America, discusses the procedures in pipeline failure analysis investigation, and provides a brief background on the most commonly observed pipeline flaws and degradation mechanisms. A case study related to hydrogen cracking and a hard spot is also presented.

Manufacturing processes typically involve the reshaping of materials from one form to another under a set of processing conditions. This article discusses the two classification schemes of modeling for manufacturing processes, namely, on-line or off-line models and empirical, mechanistic, or deterministic models along with their important considerations. It describes the various aspects of modeling of deformation processes, casting operations, and fusion welding processes, with examples.

This article discusses tubular products made from wrought carbon or alloy constructional steels, particularly pipe, specialty tubing, and oil country tubular goods. The article covers product classifications, available specifications, chemical compositions, sizes, and other dimensional attributes. Some of the common types of pipe are standard pipe, conduit pipe, piling pipe, pipe for nipples, transmission or line pipe, water main and water well pipe, and pressure pipe. Pipe in suitable sizes and most products classified as tubing, both seamless and welded, may be cold finished. Pressure tubes, a separate classification, include double-wall brazed tubing, structural tubing, welded mechanical tubing, continuous-welded cold-finished mechanical tubing, and seamless mechanical tubing.

This article provides an overview of fractography as it applies to metal weldments and presents examples of various fracture surface morphologies to demonstrate how fractographic analysis can be used to determine the cause of weld failures. It identifies weld fractography principles and details several weldment-specific geometric and metallurgical considerations. The role of the weld-cracking mechanisms on the resultant fracture surfaces is described, along with example micrographs and fractographs of weldments. Common discontinuities related to welding processes and their impact on the resulting fracture behavior and surfaces are covered, as well as the common fractographic features related to fatigue failures of welds.