Search Results for thermite reaction

This article provides a discussion on the process descriptions, processing conditions, and processing variables of the most common chemical methods for metal powder production. These methods include oxide reduction, precipitation from solution, and thermal decomposition. Methods such as precipitation from salt solution and gas, chemical embrittlement, hydride decomposition, and thermite reactions are also discussed. The article also discusses the methods used to produce powders electrolytically and the types of metal powders produced. The physical and chemical characteristics of these powders are also reviewed.

Thermite welding (TW) is a fusion welding process in which two metals become bonded after being heated by superheated metal that has experienced an aluminothermic reaction. This article describes the thermite welding principles by presenting equations of the aluminothermic reaction that occurs in thermite welding. It provides information on the applications of thermite welding: rail welding, electrical connections, and railroad applications. The article concludes with a discussion on the associated safety aspects.

Dross, which is the oxide-rich surface that forms on melts due to exposure to air, is a term that is usually applied to nonferrous melts, specifically the lighter alloys such as aluminum or magnesium. This article describes dross formation and ways to reduce it, the economic implications of dross, and in-plant enhancement or recovery of dross. It discusses the influence of the melter type on dross generation and the influence of charge materials and operating practices on melt loss. Fluxing is a word applied in a broad sense to a number of melt-treating methods. The article also discusses the in-furnace treatment with chemical fluxes.

Exothermic brazing is a process that utilizes the heat produced in a solid-state chemical reaction to melt a conventional filler metal or to produce molten filler metal as a product of the reaction. This article provides the pros and cons of exothermic brazing, describes procedure of the process, and illustrates a typical arrangement for the exothermic brazing of tube. It provides information on the exothermic compounds used for brazing refractory metals and aluminum alloys.

This article discusses the principles of operation, equipment needed, applications, and advantages and disadvantages of various fusion welding processes, namely, oxyfuel gas welding, electron beam welding, stud welding, laser beam welding, percussion welding, high-frequency welding, and thermite welding.

Atomic absorption spectrometry (AAS) is generally used for measuring relatively low concentrations of approximately 70 metallic or semimetallic elements in solution samples. This article describes several features that are common to three techniques, namely, AAS, atomic emission spectrometry (AES), and atomic fluorescence spectrometry (AFS). It discusses the reasons for the extreme differences in AAS sensitivities that affect AFS and AES. The article provides information on the advantages and disadvantages of the Smith/Hieftje system and two types of background correction systems, namely, the continuum-source background correction and Zeeman background correction. It also provides a list of applications of conventional AAS equipment, which includes most of the types of samples brought to laboratories for elemental analyses.

This article is a compilation of definitions for terms related to welding fundamentals and all welding processes. The processes include arc and resistance welding, friction stir welding, laser beam welding, explosive welding, and ultrasonic welding.

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.

The role of an engineer in designing risers is to make sure that risers provide the feed metal in the right amount, at the right place, and at the right time. This article addresses feed metal volume, riser location, and duration of liquid feed metal. It discusses the three types of feeding systems used in riser design: riser sleeves, topping compounds, and breaker cores.

Fluxes are added to the welding environment to improve arc stability, provide a slag, add alloying elements, and refine the weld pool. This article discusses the effect of oxygen, which is an important chemical reagent to control the weld metal composition, microstructure, and properties. It provides information on the inclusions that form as a result of reactions between metallic alloy elements and nonmetallic tramp elements, or by mechanical entrapment of nonmetallic slag or refractory particles. The article reviews the considerations of flux formulation during shielded metal arc welding and flux cored arc welding (FCAW). It describes the types of fluxes used for submerged arc welding and FCAW as well as five essential groups of flux ingredients and their interactions.

This article discusses the production of aluminum and aluminum alloy powders with emphasis on the gas atomization method and the atomizing nozzle. It illustrates the particle formation mechanism and details the requisites for particle size distribution, control, and morphology. The article presents information on the mean oxide thickness formed on atomized powders. It also describes the mechanical and physical properties of aluminum and aluminum alloy powders, as well as their applications.

Thermal spray coatings (TSCs) are surface coatings engineered to provide wear-, erosion-, abrasion-, and corrosion-resistant coatings for original equipment manufacture and for the repair and upgrading of in-service equipment. This article presents an overview of five thermal spray processes and the specific flame and arc spray processes used to preserve large steel components and structures. It describes the TSC selection guide and an industrial process procedure guide for applying aluminum and zinc TSCs onto steel.

This article discusses the metallurgical aspects of underwater welds. It describes the microstructural development, which mainly includes three types of ferrite associated with low carbon steel weld metal: grain-boundary ferrite, sideplate ferrite, and acicular ferrite. The article explains the factors that affect heat-affected zone (HAZ) cracking. These include hydrogen from the weld pool, microstructures that develop in the HAZ, and stress levels that develop in the weld joint. The article describes the welding practices that can reduce residual stresses. It explains the effect of water pressure on the formation of porosity in underwater gravity welding. The article concludes with a discussion on the practical applications of underwater welding.

Because of the tough engineering environment of the railroad industry, fatigue is a primary mode of failure. The increased competitiveness in the industry has led to increased loads, reducing the safety factor with respect to fatigue life. Therefore, the existence of corrosion pitting and manufacturing defects has become more important. This article presents case histories that are intended as an overview of the unique types of failures encountered in the freight railroad industry. The discussion covers failures of axle journals, bearings, wheels, couplers, rails and rail welds, and track equipment.

This article presents an overview of the rules, regulations, and techniques implemented to minimize the safety hazards associated with welding, cutting, and allied processes. Safety management, protection of the work area, process-specific safety considerations, and robotic and electrical safety are discussed. The article explains the use of personal protective equipment and provides information on protection against fumes, gases, and electromagnetic radiation. It concludes with a discussion on safe handling of compressed gases as well as the prevention and protection of fire and explosion.

This article provides an overview of the corrosion theory relating to refractories on the basis of acid/base reactions, thermodynamics, and kinetic considerations. The tests to evaluate refractory corrosive wear are reviewed. The article describes the specific refractories used in steel, glass, aluminum, and chemical-resistant applications. Specific material issues that should be considered or evaluated when choosing or using refractory materials are discussed.

Safety is an important consideration in all welding, cutting, and related work. This article discusses the basic elements of safety general to all welding, cutting, and related processes. It includes safety procedures common to a variety of applications. The most important component of an effective safety and health program is management support and direction. The article reviews the role of management, training, housekeeping, and public demonstrations in welding safety to minimize personal injury and property damage. It provides information on the safety measures for eye and face protection in various welding and cutting operations. Injuries and fatalities from electric shock in welding and cutting operations can occur if proper precautionary measures are not followed. The article discusses the electrical safety aspects to be considered for various welding and cutting operations.