Search Results for metal removal operations

Both surface finish and surface integrity must be defined, measured, and maintained within specified limits in the processing of any product. Surface texture is defined in terms of roughness, waviness, lay, and flaws. This article illustrates some of the designations of surface roughness and the symbols for defining lay and its direction. In addition, it describes the applications of surface integrity, typical surface integrity problems created in metal removal operations, and principal causes of surface alterations produced by machining processes. The article tabulates the effect of some machining methods on fatigue strength, and low-stress grinding procedures for steels, nickel-base high-temperature alloys, and titanium alloys.

This article describes the principles of operation, operating techniques, equipment selection, and important process variables of air-carbon arc cutting. It also provides information on the safety practices to be followed during the air-carbon arc cutting process.

Electric arc cutting is used on ferrous and nonferrous metals for rough severing, such as removing risers or scrap cutting, as well as for more closely controlled operations. This article describes the operating principles, equipment selection, process variables, and safety measures recommended for plasma arc cutting and air carbon arc cutting. Special applications of electric arc cutting, including shape cutting, gouging, and underwater cutting, are also discussed. The article provides information on other electric arc cutting methods, namely, the exo-process and oxygen arc cutting. It concludes with information on the seldom-used electric arc cutting methods, such as shielded metal arc cutting, gas metal arc cutting, and gas tungsten arc cutting.

This article distinguishes between a surface finish and a surface texture. It provides information on the surface integrity technology that describes and controls the many possible alterations produced in a surface layer during manufacture, including their effects on material properties and the performance of the surface in service. The types of surface alterations associated with metal removal practices are described. The article discusses the surface roughness, surface integrity, and produced in manufacturing processes, and mechanical property effects. Surface alterations associated with metal removal practices of traditional and nontraditional machining operations, as well as their effect on the static mechanical properties of materials, are reviewed. Finally, the article provides guidelines for material removal, postprocessing, and inspection.

Aluminum fluxing is a step in obtaining clean molten metal by preventing excessive oxide formation, removing nonmetallic inclusions from the melt, and preventing and/or removing oxide buildup on furnace walls. This article discusses the solid fluxes and gas fluxes used in foundries. It reviews the classification of solid fluxes depending on their use and function at the foundry operation. These include cover fluxes, drossing fluxes, cleaning fluxes, and furnace wall cleaner fluxes. The article also examines the operational practices and applications of the flux injection in the foundries. It describes the applications of the aluminum fluxing such as crucible furnaces, transfer ladles, reverberatory furnaces, and holding/casting furnaces.

Field ion microscopy (FIM) can be used to study the three-dimensional structure of materials, such as metals and semiconductors, because successive atom layers can be ionized and removed from the surface by field evaporation. The ions removed from the surface by field evaporation can be analyzed chemically by coupling to the microscope a time-of-flight mass spectrometer of single-particle sensitivity, known as the atom probe (AP). This article describes the principles, sample preparation, and quantitative analysis of FIM. It also provides information on the principles, instrument design and operation, mass spectra and their interpretation, and applications of AP microanalysis.

This article provides an overview of the interfacial interactions with a lubricant film between a die and a metal, lubricant mechanisms, chemistry, qualification testing, application methods, and property test methods. It focuses on sheet metal-forming operations, although the discussions are relevant to metal-forming operations in general. The article also deals with lubricant selection as influenced by the metal to be formed and particular sheet-metal forming operations. The article also discusses some aspects of microbiology and toxicity in lubricants.

Oxyfuel gas cutting (OFC) includes a group of cutting processes that use controlled chemical reactions to remove preheated metal by rapid oxidation in a stream of pure oxygen. This article discusses the operation principles and process capabilities of the OFC. It reviews the properties and compositions of fuel types such as acetylene, natural gas, propane, propylene, and methyl-acetylene-propadiene-stabilized gas. The article describes the effects of OFC on base metal, including carbon and low-alloy steels, cast irons, and stainless steels. It provides information on light cutting, medium cutting, heavy cutting, and stack cutting. The article informs that the basic oxyfuel method can be modified to allow gas cutting of metals, such as stainless steel and most nonferrous alloys, that resist continuous oxidation.

Laser beam machining removes, melts, or thermally modifies a material by focusing a coherent beam of monochromatic light on the workpiece. This article describes the principal lasers used in metal processing: neodymium-glass, carbon dioxide, and neodymium-doped yttrium aluminum garnet lasers. It discusses the operating parameters of concern in percussion drilling and trepanning. The process variables in surface treatment and laser cutting, as well as the operating parameters of concern in laser welding are reviewed. The article also explains the various categories of surface treatment: heat treating, cladding, surfacing, glazing, and marking.

Trimming is the removal of excess metal from a stamped part to allow the part to reach the finished stage or to prepare it for subsequent operations. This article presents an analysis of parts to be trimmed and describes the selection criteria for the different types of trimming dies such as conventional trimming dies and cam trimming dies. It provides information on rough and finish trimming and construction details of trimming dies. The article reviews the selection criteria of presses for a trimming operation. It provides a discussion on the scrap and material handling processes in trimming.

Alkaline cleaning is a commonly used method for removing a wide variety of soils from the surface of metals. This article focuses on the composition, operating conditions, and test and control of alkaline cleaners, as well as equipment used and their application methods. It describes the mechanisms of alkaline cleaning, such as saponification, displacement, emulsification and dispersion, and metal oxide dissolution. The article concludes with information of the safety and environmental considerations in the usage of alkaline cleaners.

Oxyfuel gas cutting (OFC) includes a group of cutting processes that use controlled chemical reactions to remove preheated metal by rapid oxidation in a stream of pure oxygen. This article provides a detailed discussion on the principles of operation and the process capabilities of OFC. In addition to providing information on the equipment used, the article describes the properties of fuel gases (acetylene, natural gas). It also presents an overview of the effect of OFC on base metal and explains the application of OFC in cutting thin, medium, and thick sections, bars, and structural and close-tolerance shapes.

Selecting the proper cutting tool material for a specific machining application can provide substantial advantages, including increased productivity, improved quality, and reduced costs. This article begins with a description of the factors affecting the selection of a cutting tool material. This is followed by a schematic representation of their relative application ranges in terms of machining speeds and feed rates. The article provides a detailed account of chemical compositions of various tool materials, including high-speed tool steels, cobalt-base alloys, cemented carbides, cermets, ceramics, cubic boron nitride, and polycrystalline diamond. It compares the toughness, and wear resistance for these cutting tool materials. Finally, the article explains the steps for selecting tool material grades for specific application.

In terms of the design of a forging, flash is an excess or surplus of metal that is trimmed or otherwise removed after forging operations are completed. This article discusses flash components and the functions of flash. It describes a series of conventional and unconventional flash designs and design adjustments, covering several forging processes and configurations. The article concludes with information on the checklists for the convenience of both designers of forgings and designers of forging dies and contiguous flash.

Metal is removed from the workpiece by the mechanical action of irregularly shaped abrasive grains in all grinding operations. This article discusses three primary components of grinding wheels, namely, abrasive (the cutting tool), bond (the tool holder), and porosity or air for chip clearance and/or the introduction of coolant. It describes the compositions and applications of coated abrasives and types of grinding fluids, such as petroleum-base and mineral-base cutting oils, water-soluble oils, synthetic fluids, semisynthetic fluids, and water plus additives. The article concludes with information on different types of grinding processes, namely, rough grinding, precision grinding, surface grinding, cylindrical grinding, centerless grinding, internal grinding, and tool grinding.

Planing is a machining process for removing metal from surfaces in horizontal, vertical, or angular planes. This article discusses the process capabilities of planing and the operations of double-housing and open-side planers. It reviews workpiece setup procedures, including platelike workpieces, irregularly shaped workpieces, and workpieces used for tandem planning. The article provides information on the applications of high-speed steels and carbides in planer tools. It analyzes the tools available in a variety of configurations suited to the undercutting, slotting, and straight planing of either horizontal or vertical surfaces. These include carbide roughing, finishing, gooseneck-holder finishing, and double-cutting tools. The article lists recommended speeds and feeds for planing with high-speed steel or carbide tools. It concludes with a comparison of planing with sawing and milling.

This article describes the methods for removing metallic contaminants, tarnish, and scale resulting from hot-working or heat-treating operations on nickel-, cobalt-, and iron-base heat-resistant alloys. It provides a brief description of applicable finishing and coating processes, including polishing, electroplating, ceramic coatings, diffusion coatings, and shot-peening. The article presents numerous examples that identify cleaning and finishing problems and the procedures used to solve them.

Electroforming is the process by which articles or shapes can be exactly reproduced by electrodeposition on a mandrel or form that is later removed, leaving a precise duplicate of the original. This article discusses electroforming applications, and explains electroforming of nickel, cobalt, iron, and copper, providing information on mandrel design and selection, electroforming solutions and operating variables. It discusses the significant aspects of electroforming that demand special considerations, such as metal distribution, internal deposit stress, roughness, and treeing. The article concludes with an overview of alloy electroforming.

Metal surfaces must often be cleaned before subsequent operations to remove unwanted substances such as pigmented drawing compounds, unpigmented oil and grease, chips and cutting fluids, polishing and buffing compounds, rust and scale, and miscellaneous contaminants. The article describes common cleaning processes, including alkaline, electrolytic, solvent, emulsion, molten salt bath, ultrasonic and acid cleaning as well as pickling and abrasive blasting. It also explains how to select the appropriate process for a given soil type and surface composition.

Machining is a term that covers a large collection of manufacturing processes designed to remove unwanted material, usually in the form of chips, from a workpiece. This article discusses the basic classes of machining operations, including conventional, abrasive, and nontraditional, and outlines the type of costs incurred by the process. It describes the types of machining equipment, including general-purpose machine tools, production machining systems, and computer numerically controlled machining systems. The article lists the common classes of metallic work materials, in order of decreasing machinability. It also shows the range of dimensional and surface finish tolerances in graphical form that can be achieved using various machining processes under general machining conditions.