Search Results for gas purity

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.

Laser has found its applications in cutting, drilling, and shock-peening operations of manufacturing industry because of its accurate, safe, and rapid cutting property. This article provides an account on the fundamental principles of laser cutting (thermal), drilling, and shock-peening processes of which emphasis is placed on thermal laser cutting. It details the principal set-up parameters, such as the laser beam output, nozzle design, focusing optic position and characteristics, assist gases, surface conditions, and cutting speed. A discussion on the types of gas, supply system, purity level, and flow rates of lasing and assist gases is also provided. The article also describes the metallurgies and other key material considerations that impact laser-cutting performances and includes examples of laser cutting of nonmetal materials.

This article discusses various control processes carried out in powder feeding, thermal spraying, and gas flow of the thermal spray process to standardize the coating quality. Quality of the entire powder feeding process can be achieved by controlling the processing of feeding equipment as well as the characteristics of the powder being fed. Gas flow control can be achieved by using rotameters, critical orifices, and thermal mass flowmeters, whose ability to provide useful information is defined by their resolution, accuracy, linearity, and repeatability. The commercial thermal spray controls discussed here include the open-loop input-based, open-loop output-based, closed-loop input-based, and closed-loop output-based or adaptive controls. The article discusses the common causes and practical solutions for arc starting problems. It also outlines certain important developments in measuring individual and collective particle velocities, temperature, and trajectories as well as other plume characteristics for the plasma spray process.

This article describes the classification of ferritic stainless steels. It reviews the metallurgical characteristics of various ferritic grades as well as the factors that influence their weldability. The article provides a discussion on various arc welding processes. These processes include gas-tungsten arc welding (GTAW), gas-metal arc welding (GMAW), flux-cored arc welding (FCAW), shielded metal arc welding (SMAW), and plasma arc welding (PAW). The selection criteria for welding consumables are discussed. The article also explains the welding procedures associated with the ferritic stainless steels. It concludes with information on weld properties.

Plasma melting is a material-processing technique in which the heat of thermal plasma is used to melt a material. This article discusses two typical design principles of plasma torches in the transferred mode: the tungsten tip design and the hollow copper electrode design. It describes the sources of atmospheric contamination in plasma melting furnaces and their control measures. The equipment used in plasma melting furnaces are also discussed. The article provides a detailed discussion on various plasma melting processes, such as plasma consolidation, plasma arc remelting, plasma cold hearth melting, and plasma casting.

Controlled atmosphere chambers are used to control the surface chemistry of the metals that are being processed. This article focuses on the various types of controlled atmospheres used in induction heat treating and brazing, namely, inert gas atmospheres based on argon and helium; prepared and commercial nitrogen-base atmospheres; and brazing atmospheres. It provides detailed information on two types of controlled atmosphere chambers: atmosphere and vacuum. The article also describes the selection factors, advantages, and disadvantages of these chambers.

The melting temperature necessary to weld materials in the gas-tungsten arc welding (GTAW) process is obtained by maintaining an arc between a tungsten alloy electrode and a workpiece. This article discusses the advantages and limitations and applications of the GTAW process. It schematically illustrates the key components of a GTAW manual torch. The article describes the process parameters, such as welding current, shielding gases, and filler metal. It discusses the GTAW process variations in terms of manual welding, mechanized welding, narrow groove welding, and automatic welding.

The gas tungsten arc welding (GTAW) process derives the heat for welding from an electric arc established between a tungsten electrode and the part to be welded. This article provides a discussion on the basic operation principles, advantages, disadvantages, limitations, and applications of the process. It describes the equipment used for GTAW, namely, power supplies, torch construction and electrodes, shielding gases, and filler metals as well as the GTAW welding procedures. The article concludes with a review of the safety precautions to avoid possible hazards during the GTAW process: electrical shock, fumes and gases, arc radiation, and fire and explosion.

This article briefly describes the capabilities of gas chromatography/mass spectrometry, which is used to qualitatively and quantitatively determine organic (and some inorganic) compound purity and stability and to identify components in a mixture. The discussion covers in more detail gas chromatography/mass spectrometry (GC/MS) instrumentation, interpreting mass spectra, GC/MS methodology, and GC/MS advances. Sample preparation, which is very important in GC/MS to avoid erroneous data and to minimize maintenance and troubleshooting of the instrument, is also discussed. Further, the article highlights the state of the art in the MS detector technology.

The electronic microcircuit industry has placed severe demands on metal suppliers to provide metals of the highest reproducible purity attainable as a result of the constant quest for the true values of physical and chemical properties of metals. This article describes the commonly used methods for ultrapurification of metals produced by electrolytic processes, including fractional crystallization, zone refining, vacuum melting, distillation, chemical vapor deposition, and solid state refining techniques. In addition, it describes the trace element analysis and resistance-ratio test methods used to characterize purity. Tables list the values for resistance ratios of zone-refined metals and their corresponding chemical compositions, and provide an example of the detection of impurities to concentrations in the parts per billion range, utilizing a combination of the glow discharge mass spectroscopy method and Leco combustion methods.

Gas analysis by mass spectrometry, or gas mass spectrometry, is a general technique using a family of instrumentation that creates a charged ion from a gas phase chemical species and measures the mass-to-charge ratio. This article covers gas analysis applications that do not use chromatographic separation to physically isolate components of the sample prior to analysis. It is intended to provide an understanding of gas analysis instrumentation and terminology that will help make informed decisions in choosing an instrument and methodology appropriate for the data needed. Mass-analyzer technologies for gas mass spectrometry, namely quadrupole mass filters, magnetic sector mass filters, and time-of-flight mass analyzers are covered. Common factors to consider in choosing an analyzer for static or continuous gas measurement are also described. In addition, the article presents some examples of applications of gas mass spectrometry.

This article provides members of the thermal spray community with practical recommendations for the safe installation, operation, and maintenance of gas equipment used in the thermal spray process. It focuses on safety issues concerning gas equipment used in conjunction with thermal spray equipment at consumer sites. The article covers the gas sources (bulk or gaseous), the piping (hard and soft) leading to the gas console or the torch, and the specific safety devices used to help ensure safe operation. It discusses the characteristics and safety hazards of gases such as oxygen, compressed air, nitrogen, helium, argon, carbon dioxide, hydrogen, acetylene, kerosene, propylene, propane, and natural gas. The article also provides information on the maintenance and safety practices involved in the plumbing configurations of cylinder gas supply units and bulk gas supply units.

This article provides a brief account of glow discharge mass spectrometry (GDMS) for direct determination of trace elements in solid samples and for fast depth profiling in a great variety of innovative materials. It begins by describing the general principles of GDMS. This is followed by a discussion on the various components of a GDMS system as well as commercial GDMS instruments. A description of processes involved in specimen preparation and cleaning in GDMS is then presented. Various problems pertinent to multielemental calibrations in GDMS are discussed along with measures to overcome them. The article further provides information on the processes involved in the analytical setup of parameters in GDMS, covering the steps involved in the analysis of GDMS data. It ends with a section on the application and interpretation of GDMS in the metals industry.

This article discusses the methods for producing powder metallurgy (PM) nickel powders, including carbonyl process, hydrometallurgical process, hydrogen reduction process, and atomization process, as well as their applications. It describes three processes for producing nickel alloy powders: water atomization, high-pressure water atomization, and gas atomization. The article also provides information on the applications of PM hot isostatic pressing in the oil and gas industry.

The purity of aluminum is generally characterized in one of two ways, by terminology or by the Aluminum Association designation system. This article reviews the properties of pure aluminum in purities from 99.99 percent through commercial purity, 99.00 percent. The mechanical properties of aluminum are discussed in terms of tensile properties, stress-strain relationships, and creep. The article also reviews the physical properties of aluminum, such as atomic structure and nuclear properties, atomic spectrum, crystal structure, density, thermal expansion, and thermal conductivity. It discusses the chemical properties of aluminum and presents a summary tabulation of the mechanical strength, ductility, and hardness of pure aluminum.