Search Results for internal treatment

The corrosion process that occurs in industrial systems is often difficult to discern until extensive deterioration has occurred. For boilers to function properly, the incoming water must be processed to meet the water quality required for the boiler. This article discusses pretreatment methods of the incoming water and preboiler corrosion protection methods. It analyzes internal treatment and condensate treatment of boilers. The article discusses three types of cooling systems: once-through systems, open recirculating systems, and closed recirculating systems. The corrosion processes which occur in water-recirculating systems and the effect of dissolved gases, temperature, pH, suspended solids, dissolved salts, and scale deposition on corrosivity of water, are also reviewed. The article also considers anodic and cathodic inhibitors and the control of corrosion in municipal water systems.

Thermal spray coatings are often modified or treated by a variety of post-coating operations to transform the as-coated material into a final product based on coating composition and application. This article provides a detailed description of the post-coating operations that fall under two basic categories: surface treatments, such as dimensional, non-dimensional, and geometric finishing; and internal treatments, such as sealing, heat treating, and peening. It also describes various inspection and testing methods, including destructive and non-destructive inspections, often employed after post-coating operations.

Ductile cast irons are heat treated primarily to create matrix microstructures and associated mechanical properties not readily obtained in the as-cast condition. This article discusses the most important heat treatments of ductile irons and their purposes. International standards of ductile iron provided by ASTM International, the International Organization for Standardization (ISO), and SAE International are presented in a table. The article explains basic structural differences between the ferritic, pearlitic, martensitic, and ausferritic classes. It presents recommended practices for annealing ductile iron castings for different alloy contents and for castings with and without eutectic carbides. The article discusses the induction surface hardening and remelt hardening of ductile iron. It concludes with information on the effect of heat treatment on fatigue strength of ductile iron.

This article discusses the important characteristics of fluidized beds. The total space occupied by a fluidized bed can be divided into three zones: grid zone, main zone, and above-bed zone. The article discusses the various types of atmospheres of fluidized beds, such as oxidizing and decarburizing atmosphere; nitrocarburizing and nitriding atmosphere; carburizing and carbonitriding atmosphere; and chemical vapor deposition atmosphere. External resistance heating, external combustion heating, internal resistance heating, direct resistance heating, submerged combustion heating, and internal combustion heating can be used to achieve the heat input for a fluidized bed. The article also describes the operations, design considerations, and applications of fluidized-bed furnaces in heat treating. Thermochemical surface treatments, such as carburizing, carbonitriding, nitriding, and nitrocarburizing, are also discussed. Finally, the article reviews the principles and applications of fluidized-bed heat treatment.

This article focuses on the general internal state variable method, and its simplification, for single-parameter models, in which the microstructure evolution may be treated as an isokinetic reaction. It explains that isokinetic microstructure models are applied to diffusional transformations in fusion welding, covering particle dissolution, growth, and coarsening of precipitates in the heat-affected zone. The article discusses the versatility of the internal state variable approach in modeling of nonisothermal transformations for various materials and processes. It describes the process models applied to predict the microstructure evolution in Al-Mg-Si alloys during multistage thermal processing involving heat treatment and welding. The article also provides information on the microstructure models exploited in engineering design to optimize the load-bearing capacity of welded aluminum components.

Copper steels are precipitation-strengthened steels that are designed to have a unique combination of physical and mechanical properties. This article provides an overview of copper precipitate-strengthened steels and their applications, and discusses appropriate ASTM International standards. It describes the common phases and alloying elements present in copper precipitate-strengthened steels, and reviews the influences of alloying elements on processing, phase diagrams, microstructures, and mechanical properties. The article also discusses the thermomechanical process, solutionizing heat treatment, and isothermal aging in detail. It concludes with a review of the interrelationships between heat treatments, microstructures, and mechanical properties.

Induction heat treatment is a common method for hardening and tempering of crankshafts, which are necessary components in almost every internal combustion engine for cars, trucks, and machinery, as well as pumps, compressors, and other devices. Similar to crankshafts, camshafts also belong to the same group of the critical engine/powertrain components. This article focuses on induction technologies used for surface hardening and tempering of automotive crankshafts, and provides general information on U-shaped inductors with crankshaft rotation and clamshell or split inductors without crankshaft rotation and their pros and cons. It also describes the effect of post-heat-treatment processes in crankshafts. The article concludes with a discussion on induction hardening of camshafts that focuses on those used in automobiles and truck engines.

Cold-finished steel bars are carbon and alloy steel bar products (round, square, hexagonal, flat, or special shapes) that are produced by cold finishing previous hot-wrought bars. by means of cold drawing, cold forming, turning, grinding, or polishing (singly or in combination) to yield straight lengths or coils that are uniform throughout their length. Cold-finished bars fall into five classifications: cold-drawn bars; turned and polished bars; cold-drawn, ground, and polished bars; turned, ground, and polished bars; cold-drawn, turned, ground, and polished bars. Different size tolerances are applicable to cold-finished products, depending on shape, carbon content, and heat treatment. When used to identify cold-finished steel bars, the various quality descriptors are indicative of many characteristics, such as degree of internal soundness, relative uniformity of chemical composition, and relative freedom from detrimental surface imperfections. Cold drawing significantly increases machinability, tensile and yield strengths of steel bars. Two special die-drawing processes have been developed to give improved properties over those offered by standard drawing practices. These processes are cold drawing using heavier-than-normal drafts, followed by stress relieving; and drawing at elevated temperatures.

This article discusses the compositions, properties, and typical applications for ductile irons that are defined by U.S. and international standards . It describes the various methods used to test and inspect the metallurgical control processes in ductile iron production. The article discusses the effect of composition, graphite shape, and section size on the properties of ductile iron. The article also describes the mechanical properties of ductile iron at elevated temperatures. The heat treatment of ductile iron castings produces a significant difference in mechanical properties from as-cast ductile iron. A ductile iron generally has higher hardenability than a eutectoid steel with comparable alloy content. The article also discusses the physical properties of ductile iron, including density, thermal conductivity, electrical conductivity, electrical resistivity, and magnetic properties. Ductile iron has been chosen in many instances on the basis of significantly lower machining costs, which resulted in lower overall cost of the part.

This article addresses classifications and designations for carbon steels and low-alloy steels, particularly high-strength low-alloy (HSLA) steels, based on chemical composition, manufacturing methods, finishing method, product form, deoxidation practice, microstructure, required strength level, heat treatment and quality descriptors. It describes the effects of alloying elements on the properties and characteristics of steels. The article provides extensive tabular data pertaining to domestic and international designations of steels.

Low-expansion alloys are materials with dimensions that do not change appreciably with temperature. Alloys included in this category are various binary iron-nickel alloys and several ternary alloys of iron combined with nickel-chromium, nickel-cobalt, or cobalt-chromium alloying. Low-expansion alloys are used in various applications such as rods and tapes for geodetic surveying, moving parts that require control of expansion (such as pistons for some internal-combustion engines), bimetal strip, components for electronic devices etc. This article discusses the properties, composition, and applications of iron-nickel low-expansion alloys (Invar), as well as other special alloys, including iron-nickel-chromium alloys, iron-nickel-cobalt alloys, iron-cobalt-chromium alloys, and high-strength, controlled-expansion alloys. It covers the factors affecting coefficient of thermal expansion of iron-nickel alloys, including heat treatment and cold drawing. Magnetic, physical, thermal, electrical and mechanical properties of iron-nickel alloys are also covered.

Tapping is a machining process for producing internal threads. This article provides a discussion on machines and accessories of tapping. It reviews the seven categories of taps, namely, solid, shell, sectional, expansion, inserted-chaser, adjustable, and collapsible taps, as well as their design and functions. It explains the influences of various factors on the selection of tap design features and discusses the principal factors that influence the selection of equipment and procedure for tapping. The article reviews the factors that determine torque demand. It also provides an overview of tap materials and surface treatment and concludes with a discussion on tapping of taper pipe threads.

The mechanical properties of ductile cast irons are determined largely by the microstructure of the steel matrix in combination with the shape, size, and distribution of the graphite nodules. This article describes the designation of ductile cast irons according to the ASTM International designation system and reviews standard-grade ductile cast irons. An overview of the most commonly used standards related to designation and specification of ductile cast iron is presented in a table. This article discusses the use of low-alloy ductile cast irons at elevated temperatures and the chemical compositions and some mechanical properties of austenitic ductile cast irons. The article concludes with a discussion on heat treatment of austempered ductile iron.

This article is a general introduction to surface engineering of engineering components, providing an overview of the applications of surface treatments and the environmental protection regulations directly or indirectly related to surface engineering processes.

This article presents an overview of the techniques used in the design for heat treatment and discusses the primary criteria for design: minimization of distortion and undesirable residual stresses. It provides theoretical and empirical guidelines to understand the sources of common heat treat defects. A simple example is presented to demonstrate how thermal and phase-transformation-induced strains cause dimensional changes and residual stresses. The article concludes with a discussion on the heat treatment process modeling technology.

This article describes the fundamental concepts of heat treatment simulation, including the physical events and their interactions, the heat treatment simulation software, and the commonly used simulation strategies. It summarizes material data needed for heat treatment simulations and discusses reliable data sources as well as experimental and computational methods for material data acquisition. The article provides information on the process data needed for accurate heat treatment simulation and the methods for their determination. Methods for validating heat treatment simulations are also discussed with an emphasis on the underlying philosophy for the selection and design of validation tests. The article also discusses the applications, capabilities, and limitations of heat treatment simulations via selected industrial case studies for a better understanding of the effect of microstructure, distortion, residual stress, and cracking in gears, shafts, and bearing rings.

This article discusses factors that influence the effect of alloying, metallurgical treatments, and mechanical treatments on the corrosion resistance of metallic materials, with schematic illustrations.