Search Results for stoichiometric carbon content

This article describes the effects of undissolved carbides formed by segregation of alloying elements on the hardness of the powder-metallurgical (PM) high-alloy tool steels (HATS). It explains the calculation of exact stoichiometric carbon content that depends on the required martensite hardness, amount of carbon forming alloying elements, types of undissolved carbides during austenitizing, and the densities of the carbides. Microhardness values for carbides in HATS are also listed.

This article focuses on the production methods, properties, and applications of two main types of commercially available continuous-length ceramic fibers, namely, oxide fibers based on the alumina-silica system and on alpha-alumina, and nonoxide fibers based primarily on beta-phase silicon carbide. It provides a discussion on factors that are considered in understanding thermostructural capability of ceramic fiber for high-temperature ceramic-matrix composites (CMC) applications. The article tabulates other commercial oxide and nonoxide fiber types for CMC reinforcement.

Ferritic stainless steels are essentially chromium containing steel alloys with at least 10.5% Cr. They can be grouped based on their chromium content: low chromium (10.5 to 12.0%), medium chromium (16 to 19%), and high chromium (greater than 25%). This article provides general information on the metallurgy of ferritic stainless steels. It describes two types of heat treatments to avoid sensitization and embrittlement. They are annealing and stress relieving. The article also provides information on casting and stabilization of ferritic stainless steels to avoid precipitation of grain boundary carbides.

Heat treating involves the use of fuel gases for heating and gases in the furnace atmosphere. This article describes the hazards associated with furnace atmospheres and the related safety considerations. It discusses the effect of fuel on combustion efficiency. The article also contains tables that provide information on the physical, thermal and combustion properties of common gases and liquids, and the heat content of various gases.

This article discusses the classification schemes for cast irons and describes the characteristics of major categories, including gray iron, white iron, ductile iron, compacted graphite iron, mottled iron, malleable iron, and austempered ductile iron. It also discusses some of the basic principles of cast iron metallurgy. When discussing the metallurgy of cast iron, the main factors of influence on the structure include chemical composition, cooling rate, liquid treatment, and heat treatment. In terms of commercial status, cast irons can be classified as common cast irons and special cast irons. Special cast irons differ from the common cast irons mainly in the higher content of alloying elements. Alloying elements can be added in common cast iron to enhance some mechanical properties. They influence both the graphitization potential and the structure and properties of the matrix.

This article discusses the methods and procedures used to extract, purify, and synthesize tungsten carbide powder, metal, and other refractory carbide/nitride powders used in hard metal production. Selection of powders, additives, equipment, and processes for making ready-to-press hard metal powders is also discussed. The article also provides information on the emerging technologies for tungsten carbide synthesis and binders in hard metal production, such as cobalt, iron, and nickel.

This article discusses criteria that can be used for the classification of cast iron: fracture aspect, graphite shape, microstructure of the matrix, commercial designation, and mechanical properties. It addresses the main factors of influence on the structure of cast iron, including chemical composition, cooling rate, and heat treatment. The article describes some basic principles of cast iron metallurgy. It discusses the main effects of the chemical composition of ductile iron and compacted graphite (CG) iron. The composition of malleable irons must be selected in such a way as to produce a white as-cast structure and to allow for fast annealing times. Some typical compositions of malleable irons are presented in a table. The article concludes with information on special cast irons.

This article discusses the most common methods of melting steels, namely, electric arc and induction melting. It describes the classification of refractories by an index of the “basicity” of the slag formed on the steel surface. The article provides a discussion on the converter metallurgy, which includes melt refinement in argon oxygen decarburization (AOD) vessels and vacuum oxygen decarburization (VODC) in a converter vessel. It also discusses ladle metallurgy, which includes vacuum induction degassing, vacuum oxygen decarburization, and vacuum ladle degassing.

The process of case hardening of steel includes three consecutive steps of heat treatment: heating; the thermochemical process with the enrichment of the surface area during the carburizing or carbonitriding stage with carbon and nitrogen; and the subsequent quenching process for hardening. This article provides a model-based description of the development of residual stresses during case hardening. It also describes the influence and effects of residual stresses and distortion in hardening, carburizing, and nitriding processes of the steel.

Sintering atmosphere protects metal parts from the effects of contact with air and provides sufficient conduction and convection for uniform heat transfer to ensure even heating or cooling within various furnace sections, such as preparation, sintering, initial cooling, and final cooling sections. This article provides information on the different zones of these furnace sections. It describes the types of atmospheres used in sintering, namely, endothermic gas, exothermic gas, dissociated ammonia, hydrogen, and vacuum. The article concludes with a discussion on the furnace zoning concept and the problems that arise when these atmospheres are not controlled.

Fluxes are added to the welding environment to improve arc stability, to provide a slag, to add alloying elements, and to refine the weld pool. This article describes the effect of oxygen that directly reacts with alloying elements to alter their effective role by reducing hardenability, promoting porosity, and producing inclusions. It proposes basicity index for welding as a measure of expected weld metal cleanliness and mechanical properties. The article discusses alloy modification in terms of slipping and binding agents, slag formation, and slag detachability. It reviews the types of fluxes for different arc welding processes, such as shielded metal arc welding (SMAW), flux-cored arc welding (FCAW), and submerged arc welding (SAW).

Electrodeposition of tin alloys is used to protect steel against corrosion or wear, to impart resistance to etching, and to facilitate soldering. This article focuses on the compositions, operating conditions, advantages, and limitations of methane sulfonic acid plating solutions and fluoborate plating solutions for tin-lead. It briefly describes the solution compositions and operating conditions of tin-bismuth, tin-nickel, and tin-zinc.

The term cast iron designates a group of materials that contain more than one constituent in their microstructure due to excess carbon that result in unique characteristics such as the fracture appearance and graphite morphology. This article discusses the classification of cast iron and the various metallurgical aspects, such as the composition, alloying element, solidification, and graphite morphologies, of different types of cast iron. It describes the physical properties for various cast irons and the influence of microstructure and chemical composition on each property. The article provides a detailed account on thermal properties, conductive properties, magnetic properties, and acoustic properties of cast iron. It also examines heat treatment, namely, stress relieving, annealing, normalizing, through hardening, and surface hardening. The article presents a discussion on the welding, machining and grinding, and coating of the types of cast iron.

Hardfacing refers to the deposition of a specially selected material onto a component in order to reduce wear in service as a preventative measure or return a worn component to its original dimensions as a repair procedure. This article provides information on various hardfacing materials, namely, iron-base overlays, chromium carbide-based overlays, nickel- and cobalt-base alloys, and tungsten carbide-based metal-matrix composite overlays. It discusses the types of hardfacing processes, such as arc welding processes, and laser cladded, oxyacetylene brazing and vacuum brazing processes. The arc welding processes include shielding metal arc welding, gas metal arc welding/flux cored arc welding, gas tungsten arc welding, submerged arc welding, and plasma transferred arc welding. The article also reviews various factors influencing the selection of the appropriate hardfacing for specific applications.

The heat treatment of steel is based on the physical metallurgical principles that relate to its processing, properties, and structure. The microstructures that result from the heat treatment of steel are composed of one or more phases in which the atoms of iron, carbon, and other elements in steel are associated. This article describes the phases of heat treated steel, and provides information on effect of temperature change and the size of carbon atoms relative to that of iron atoms during the heat treatment.

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.