Shot peening is a method of cold working in which compressive stresses are induced in the exposed surface layers of metallic parts by the impingement of a stream of shot, directed at the metal surface at high velocity under controlled conditions. This article focuses on the major variables, applications, and limitations of shot peening and provides information on peening action, surface coverage, and peening intensity. It discusses the equipment used for shot recycling and shot propelling as well as the types and sizes of media used for peening. The article describes the problems in shot peening of production parts. It concludes with information on the SAE standard J442 that describes the test strips, strip holder, and gage used in measuring shot peening intensity.

Mechanical cleaning systems are used to remove contaminants of work surface by propelling abrasive materials through any of these three principal methods: airless centrifugal blast blade- or vane-type wheels; compressed air, direct-pressure dry blast nozzle systems; or compressed-air, indirect-suction (induction) wet or dry blast nozzle systems. This article focuses on the abrasive media, equipment, applications, and limitations of dry and wet blast cleaning. It discusses the health and safety precautions to be taken during mechanical cleaning.

Thixomolding is a method of molding thixotropic semisolid magnesium alloy pellets in a machine that resembles an injection molding machine in physical appearance and operation. This article describes the process of thixomolding. The use of hot sprues and hot runners in the thixomolding is discussed. The article provides information on thixoblending and summarizes results from two independent studies of the mechanical properties of recycled AZ91D. It also describes the factors on which the mechanical properties depend and illustrates microstructures of semisolid thixomolded AZ91D.

Finishing refers to a wide variety of processes that generally involve material removal in one form or another to generate surfaces with specific geometries, tolerances, and functional or decorative characteristics. This article discusses four major finishing methods, namely, abrasive machining, electropolishing, mass finishing, and shot peening. In each case, it describes subtypes, process variations, and the associated equipment.

This article illustrates various rheocasting processes. These include new rheocasting, semisolid rheocasting, subliquidus casting, rheo-diecasting, swirled enthalpy equilibration device process, slurry-on-demand process, and continuous rheoconversion processes.

This article focuses on the techniques used in recycling of aluminum metal matrix composites (MMCs) such as discontinuous SiC reinforced aluminum MMCs and continuous reinforced aluminum MMCs. It provides a discussion on the properties of recycled aluminum MMCs and disposal of aluminum MMCs.

A significant amount of the worldwide demand for metals is met with recycled materials acquired by metal producers in the form of purchased scrap. This article focuses primarily on the methods and technology used to process and repurpose the vast amounts of purchased scrap that recirculate in the industrial supply chain. It describes the U.S. market for iron and steel scrap, providing information on scrap use by industry, factors influencing demand, and the purchased scrap supply. Iron and steel recycling is discussed separately from stainless steel and superalloy recycling in this article, as the scrap industry treats them differently. The scrap processing of iron involves collection, separation and sorting, size reduction and compaction, detinning, blending, and incineration. The recycling of stainless steels and superalloys follows the same process, but requires several additional steps, including secondary nickel refining, degreasing, and separation of metallurgical wastes.

This article describes the melting process of casting metals used in hot chamber die casting. It discusses the design and capabilities of injection components, such as gooseneck, plunger, and cylinder. The article reviews the distinctions between hot and cold chamber processes. An example of a typical runner, gate and overflow configuration for faucet fixture casting is shown. Temperature control for die casting is also discussed. The article explains some ejection and post-processing techniques used for the hot chamber die casting: robotics, recycling, and fluxing.

This article focuses on the recycling of metals including iron and steel, stainless steel, superalloys, nickel, aluminum, copper, precious metals, lead, magnesium, tin, titanium, and zinc. It provides information on the identification and sorting of scrap metals and discusses the equipment and procedures used for small-scale and large-scale scrapping operations.

This article provides information on the factors influencing the selection of the proper corrosion-resistant coating system. It focuses on the proper execution of surface preparation and the available surface preparation methods. The preparation process includes the removal of visible contaminants, removal of invisible contaminants, and roughening of the surface. Solvent or chemical washing, steam cleaning, hand tool cleaning, power tool cleaning, water blasting, and abrasive blast cleaning, are some preparation methods discussed. The article describes the most common application techniques of coating as well as the equipment used. An overview of some of the most common coating inspection points and inspection equipment is also provided.

This article focuses on the variety of alloys, furnaces, and associated melting equipment as well as the casting methods available for manufacturing magnesium castings. These methods include sand casting, permanent mold casting, die casting, thixomolding, and direct chill casting. The article discusses the flux process and fluxless process for the melting and pouring of magnesium alloys. It describes the advantages and disadvantages of green sand molding and tabulates typical compositions and properties of magnesium molding sands. The article provides information on the machining characteristics of magnesium and the applications of magnesium alloys.

This article reviews the steps involved in presurface-preparation inspection: substrate replacement; removal of weld spatter, rounding of sharp edges, and grinding of slivers/laminations; and removal of rust scale, grease, oil, and chemical (soluble salt) contamination. It focuses on surface preparation methods that range from simple solvent cleaning to hand and power tool cleaning, dry and wet abrasive blast cleaning, centrifugal wheel blast cleaning, chemical stripping, and waterjetting for the application of the coating system. In addition, the article provides a description of the Society for Protective Coatings' (SSPC) standards and NACE International standards as well as the International Organization for Standardization (ISO) standards and International Concrete Repair Institute (ICRI) guidelines for surface cleanliness.

This article describes the control of alloy composition and impurity levels in die casting of zinc alloys based on agitation, use of foundry scrap, and melt temperature and fluxing. It reviews the process considerations for the melt processing of the zinc alloys. The process considerations include the usage of furnaces and launder system, scrap return, inclusions in zinc alloys, fluxing of zinc alloys, and galvanizing fluxes. The article discusses the materials and lubricant selection, casting and die temperature control, and trimming process used in hot chamber die casting for zinc alloys. It also reviews other casting processes for zinc alloys, such as sand casting, permanent mold casting, plaster mold casting, squeeze casting, and semisolid casting.

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.

Nearly two-thirds of the aluminum castings made in North America are produced using high-pressure die casting techniques. This article compares and contrasts traditional high-pressure die casting with an improved version that uses a vacuum to pull air out of the die in order to reduce porosity in as-cast parts. It begins by describing a typical cycle for a traditional cold-chamber die casting machine, using detailed illustrations to show how gas can become trapped in the liquid metal. It then presents various remedies, ultimately focusing on vacuum die casting for the production of high-integrity parts. In addition to vacuum technology, the article discusses casting alloys, dies, and cells, and describes some of the benefits of structural die castings.

Aluminum possesses many characteristics that make it highly compatible with recycling. Production of aluminum from scrap has a number of advantages. This article discusses the technology for the recovery, sorting, and remelting of aluminum. It describes the collection and acquisition of aluminum scrap in transportation, packaging, electrical and electronic, and building and construction sectors. The article reviews the technologies used to accomplish comminution for aluminum: shearing, knife shredding, and swing-hammer shredding. It provides a description of the devices used in scrap sorting, such as hand sorting, air classification, magnetic separation, eddy-current separation, heavy-media separation, and sensor-based sorting. The article also describes thermal processing, refining and casting, and dross processing of aluminum. It provides information on reverberatory and electric furnaces used for melting aluminum.

This article discusses classification of foundry processes based on the molding medium, such as sand molds, ceramic molds, and metallic molds. Sand molds can be briefly classified into two types: bonded sand molds, and unbonded sand molds. Bonded sand molds include green sand molds, dry sand molds, resin-bonded sand molds, and sodium silicate bonded sand. The article describes the casting processes that use these molds, including the no-bake process, cold box process, hot box process, the CO2 process, lost foam casting process and vacuum molding process. The casting processes that use ceramic molds include investment casting, and plaster casting. Metallic molds are used in permanent mold casting, die casting, semisolid casting, and centrifugal casting.

This article discusses the properties, primary and secondary production, product forms and applications of various grades of lead and lead-base alloys with the aid of several tables and illustrations. It lists the Unified Numbering System (UNS) designations for various pure lead grades and lead-base alloys grouped according to nominal chemical composition. The properties of lead that make it useful in a wide variety of applications are also discussed. The largest use of lead is in lead-acid storage batteries. Other applications include ammunition, cable sheathing, cast products such as type metals, terneplate, foils, and building construction materials. Lead is also used as an alloying element in steel and in copper alloys to improve machinability. The article concludes with information on the principles of lead corrosion, corrosion resistance of lead in water, atmospheres, underground ducts, soil and chemicals.

Zinc and zinc alloys require surface engineering prior to coating or use to improve adhesion and corrosion resistance. Die-cast zinc parts, in addition, must be trimmed and finished to remove flash and parting lines. This article covers zinc cleaning procedures as well as coating and finishing processes. It explains how to remove parting lines and presents several mechanical finishing methods, including surface polishing, brushing, controlled shot peening, and buffing. It also provides information on solvent cleaning, emulsion cleaning, aqueous detergent or alkaline cleaning), electrocleaning, acid dipping, and zinc conversion coating treatments.

Injection molding is a process of forcing or injecting a fluid plastic material into a closed mold. The process generally has the advantages of being more readily automated and of permitting finer part details. Injection-molding compounds are thermoplastic or thermosetting materials and their composites that are specifically formulated for the injection-molding process. This article discusses the injection molding process, which includes the two basic categories of thermoplastic and thermoset injection molding, and lists the common thermoplastic and thermoset molding compounds and applications. It also describes the operation of the different types of injection molding machines as well as mold design and process controls. The article also describes the selection of injection-moldable thermosets, and provides an overview of part performance, properties, blowing agents, and aesthetic concerns related to thermoplastic structural-foam injection molding.