Search Results for reactive metals

This article provides a discussion on filler metal selection, brazing procedures, and brazing equipment for brazing refractory metals. These include molybdenum, tungsten, niobium, and tantalum, and reactive metals. Commercially pure and alpha titanium alloys, alpha-beta alloys, zirconium alloys, and beryllium alloys are some reactive metals discussed in the article.

This article focuses on the machining of reactive metals which refer collectively to the elements titanium, hafnium, and zirconium. It provides guidelines for machining titanium and titanium alloys and describes machining operations, such as turning, milling, drilling, tapping, reaming, grinding, and sawing, performed on titanium and its alloys. The article also provides information on electrochemical machining (ECM), chemical milling (CHM), and laser beam machining (LBM) for titanium and titanium alloys. Guidelines for machining zirconium alloys and hafnium are also provided. The article provides a short description of turning, milling, and drilling operations performed on zirconium alloys and hafnium. It also discusses health and safety considerations related to zirconium and hafnium.

Zirconium, hafnium, and their alloys are reactive metals used in a variety of nuclear and chemical processing applications. This article describes various specimen preparation procedures for these materials, including sectioning, mounting, grinding, polishing, and etching. It reviews some examples of the microstructure and examination for zircaloy alloys, hafnium, zirconium, and bimetallic forms.

This article reviews the basic types of mold aggregates and bonding methods for expendable molds and coremaking. It provides an overview of mold media and the basic types of sands and their properties. The most significant clays used in green sand operations, such as bentonites, are discussed. The article describes the methods of sand bonding with inorganic compounds. It provides a description of resin-bonded sand systems: no-bake binder systems, heat-cured binder systems, and cold box binder systems. The article concludes with a discussion on the media used for expendable molds, namely, ceramic shells and rammed graphite, for casting reactive metals such as titanium or zirconium.

Electron beam melting includes melting, refining, and conversion processes for metals and alloys. This article describes the electron beam melting process, as well as the principles, equipment, and process considerations of drip melting and cold hearth melting process.

This article describes typical foundry practices used to commercially produce zirconium castings. The foundry practices are divided into two sections, namely, melting and casting. The article discusses various melting processes, such as vacuum arc skull melting, induction skull melting, and vacuum induction melting. Various casting processes, such as rammed graphite casting, static and centrifugal casting, and investment casting are reviewed. The article also provides information on the mechanical and chemical properties of zirconium castings.

Skull melting refers to the use of furnaces with water-cooled crucibles that freeze a solid “skull” of material on the crucible wall. This article describes the basic components, operating pressure, advantages, and applications of vacuum arc and induction skull melting furnaces.

The primary market for metal powder is the production of powder metallurgy (PM) parts, which are dominated primarily by iron and copper powders. This article reviews the chemical and pyrotechnics applications of ferrous and nonferrous powders. It describes the characteristics of iron powder used in oxygen scavengers and chemical reactive warmers and heaters. Metal powders used as fuels in solid propellants, pyrotechnic devices, explosives, and similar applications are reviewed. Atomized aluminum, magnesium, tungsten, and zirconium powders are also discussed.

Coextrusion welding (CEW) is a solid-state process that produces a weld by heating two or more workpieces to the welding temperature and forcing them through an extrusion die. This article describes cold and hot CEW for common metals such as low-carbon steel, aluminum, aluminum alloys, copper, and copper alloys. Additional applicable materials include nickel, nickel-base alloys, zirconium, titanium, tantalum, and niobium.

This article describes the processes involved in the production of hafnium and its alloys. It discusses the physical, mechanical and chemical properties of hafnium. The aqueous corrosion testing of hafnium and its alloys is detailed. The article reviews the corrosion resistance of hafnium in specific media, namely, water, steam, hydrochloric acid, nitric acid, sulfuric acid, alkalis, organics, molten metals, and gases. Forms of corrosion, namely, galvanic corrosion, crevice corrosion, and pitting corrosion are included. The article explains the corrosion of hafnium alloys such as hafnium-zirconium alloys and hafnium-tantalum alloys. It also deals with the applications of hafnium and its alloys in the nuclear and chemical industries.

The shielding gas used in an arc welding process has a significant influence on the overall performance of the welding system. These gases are argon, helium, oxygen, hydrogen, nitrogen, and carbon dioxide. This article discusses the shielding gas selection criteria for plasma arc welding, gas metal arc welding, and flux cored arc welding. It describes the basic properties of shielding gases, namely, dissociation, recombination, reactivity potential, oxidation potential, and gas purity. The article also provides information on the influence of the shielding gas on weld mechanical properties and self-shielded flux cored arc welding.

The shielding gas used in a welding process has a significant influence on the overall performance of the welding system. This article discusses the basic properties of a shielding gas in terms of ionization potential, thermal conductivity, dissociation and recombination, reactivity/oxidation potential, surface tension, gas purity, and gas density. It describes the characteristics of the components of a shielding gas blend. The article discusses the selection of shielding gas for gas-metal arc welding (GMAW), gas-tungsten arc welding (GTAW), and plasma arc welding (PAW), as well as the influence of shielding gas on weld mechanical properties. It concludes with a discussion on flux-cored arc welding.

Nonferrous metals and alloys are widely used to resist corrosion. This article describes the corrosion behavior of the most widely used nonferrous metals, such as aluminum, copper, nickel, and titanium. It also provides information on several specialty nonferrous products that cannot easily be categorized by elemental base.

High-frequency (HF) welding is a welding process in which the heat source used to melt the joining surfaces is obtained from HF alternating current (ac) resistance heating. This article discusses the advantages and disadvantages and applications of HF welding. It describes the equipment used for HF welding and the safety aspects to be considered during welding. The article concludes with a discussion on inspection and quality control.

Zirconium and its alloys are available in two general categories: commercial grade and reactor grade. This article discusses the welding processes that can be used for welding any of the zirconium alloys. These include gas-tungsten arc welding (GTAW), gas-metal arc welding (GMAW), plasma arc welding (PAW), electron-beam welding (EBW), laser-beam welding (LBW), friction welding (FRW), resistance welding (RW), resistance spot welding (RSW), and resistance seam welding (RSEW). The article reviews the selection of shielding gases and filler metals for welding zirconium alloys. It concludes with a discussion on process procedures for welding zirconium alloys.

The measurement of thermophysical properties of metal alloys, especially at high temperatures, is difficult because of the reactivity of some alloys. This article reviews the methods available for measurement of thermal and other physical properties for liquid, semi-solid, and solid commercial alloys, including adiabatic calorimetry, modulated calorimetry, Calvet calorimetry, single-pan calorimetry, and drop calorimetry. It describes differential scanning calorimetry and differential temperature analysis for measuring transition temperatures such as phase transformation or glass transition temperatures. The article schematically illustrates the laser flash apparatus for measuring the thermal diffusivity of solids and oscillation viscometer for measurements of the viscosity of metals. A summary of the measurement methods is presented in tables.