Search Results for Heat treating-related failures

This article provides an overview of the effects of various material- and process-related parameters on residual stress, distortion control, cracking, and microstructure/property relationships as they relate to various types of failure. It discusses phase transformations that occur during heat treating and describes the metallurgical sources of stress and distortion during heating and cooling. The article summarizes the effect of materials and the quench-process design on distortion and cracking and details the effect of cooling characteristics on residual stress and distortion. It also provides information on the methods of minimizing distortion and tempering. The article concludes with a discussion on the effect of heat treatment processes on microstructure/property-related failures.

This article focuses on the frequently encountered causes of induction coil failures and typical failure modes in fabrication of hardening inductors, tooth-by-tooth gear-hardening inductors, clamshell inductors, contactless inductors, split-return inductors, butterfly inductors, and inductors for heating internal surfaces. It discusses the current density distribution and the skin effect, the proximity effect, and crack-propagation specifics. The article also describes selected properties of copper alloys, the electromagnetic edge effect of coil copper turn, and the effect of magnetic flux concentrators on coil life. It also reviews the importance of having appropriate and reliable electrical contacts.

Distortion often is observed in the analysis of other types of failures, and consideration of the distortion can be an important part of the analysis. This article first considers that true distortion occurs when it was unexpected and in which the distortion is associated with a functional failure. Then, a more general consideration of distortion in failure analysis is introduced. Several common aspects of failure by distortion are discussed and suitable examples of distortion failures are presented for illustration. The article provides information on methods to compute load limits, errors in the specification of the material, and faulty process and their corrective measures to meet specifications. It discusses the general process of material failure analysis and special types of distortion and deformation failure.

Distortion failure occurs when a structure or component is deformed so that it can no longer support the load it was intended to carry. Every structure has a load limit beyond which it is considered unsafe or unreliable. Estimation of load limits is an important aspect of design and is commonly computed by classical design or limit analysis. This article discusses the common aspects of failure by distortion with suitable examples. Analysis of a distortion failure often must be thorough and rigorous to determine the root cause of failure and to specify proper corrective action. The article summarizes the general process of distortion failure analysis. It also discusses three types of distortion failures that provide useful insights into the problems of analyzing unusual mechanisms of distortion. These include elastic distortion, ratcheting, and inelastic cyclic buckling.

This article describes the corrosion mechanisms, challenges, and control methods in service water distribution systems. It provides a discussion on typical designs and water qualities for distribution systems used in fossil-fueled and nuclear power plants. The article also explains the techniques for controlling corrosion in service water systems.

This article is a compilation of definitions for terms related to engineering materials.

This article reviews the failure analysis process with specific reference to the considerations that should be addressed when a casting has failed. It describes the failure analysis methodology for three failed cast components: an aluminum bracket, a bronze suction roll, and a steel automotive spindle. The article discusses failure analysis investigation by obtaining casting background information, planning the evaluation and selecting the appropriate casting for analysis, conducting a preliminary examination, conducting the proper material evaluations, and thoroughly evaluating the test data. It concludes with information on case studies that show how the methodology is adapted for differing materials, failure mechanisms, and failure circumstances.

This article introduces some of the general sources of heat treating problems with particular emphasis on problems caused by the actual heat treating process and the significant thermal and transformation stresses within a heat treated part. It addresses the design and material factors that cause a part to fail during heat treatment. The article discusses the problems associated with heating and furnaces, quenching media, quenching stresses, hardenability, tempering, carburizing, carbonitriding, and nitriding as well as potential stainless steel problems and problems associated with nonferrous heat treatments. The processes involved in cold working of certain ferrous and nonferrous alloys are also covered.

The information provided in this article is intended for those individuals who want to determine why a casting component failed to perform its intended purpose. It is also intended to provide insights for potential casting applications so that the likelihood of failure to perform the intended function is decreased. The article addresses factors that may cause failures in castings for each metal type, starting with gray iron and progressing to ductile iron, steel, aluminum, and copper-base alloys. It describes the general root causes of failure attributed to the casting material, production method, and/or design. The article also addresses conditions related to the casting process but not specific to any metal group, including misruns, pour shorts, broken cores, and foundry expertise. The discussion in each casting metal group includes factors concerning defects that can occur specific to the metal group and progress from melting to solidification, casting processing, and finally how the removal of the mold material can affect performance.

Quenching is one of the most important heat treating processes, because it is so closely related to dimensional control requirements and control of residual stresses. This article provides an overview of the fundamental material- and process-related parameters of quenching on residual stress, distortion control, and cracking. This overview is followed by various selected case histories of failures attributed to the quenching process.

This article focuses on the fractography features of the conventional powdered metal (PM) process for ferrous powders. It discusses porosity, which is one of the inherent features present in components produced by conventional press-and-sinter processes, and green cracks, which are the most common fracture issue in conventional PM processes. It explains the effect of post-sintering operations. The article also presents the common ferrous powder metallurgy materials.

Induction hardening is a prominent method in the gear manufacturing industry due to its ability of selectively hardening portions of a gear such as the flanks, roots, and/or tips of teeth with desired hardness, wearing resistance, and contact fatigue strength without affecting the metallurgy of the core. This article provides an overview of gear technology and materials selection. It describes different gear-hardening patterns, namely, tooth-by-tooth hardening, tip-by-tip hardening, gap-by-gap hardening, spin hardening, single-frequency gear hardening, dual-frequency gear hardening, simultaneous dual-frequency gear hardening, and through heating for surface hardening. It provides information on the different inspection methods based on the American Gear Manufacturers Association, revealing metallurgical data, hardness, and dimensions of gears. In addition, the article presents a comparative study on the mechanical properties of contour-hardened and carburized gears. It concludes by describing typical failures of induction-hardened steels and the corresponding prevention methods.

This article provides information on single-shot and scanning, the two types of induction heat treating processes that are based on whether the induction coil is moving relative to the part during the heating process. It describes the effect of the frequency of induction heating current on the induction coil and process design, and the control of heating in different areas of the inductor part. The article reviews three main tools for adjustment of coil design and fabrication: coupling gap, coil copper profile, and magnetic flux controllers. It examines the method of holding a part and presenting it to the inductor during the initial inductor design. The article provides information on coil leads/busswork and contacts that mechanically and electrically connect the induction coil head to the power supply. It concludes with a discussion on flux and oxide removal, leak and flow checking, silver plating, and electrical parameter measurement.

This article describes the sectioning process, some general practices, common tools, and guidelines on how to select a cutting tool for a given metallographic sectioning operation. It provides a discussion on the consumable-abrasive cutting and nonconsumable-abrasive cutting methods for metallographic sectioning. Other methods, including the use of hacksaws, shears, burning torches, wire saws, and electrical discharge machining, are also reviewed. The article reviews the issues related to the specimen test location for certification work as well as process troubleshooting and component failure analysis.

This article discusses the properties of threaded fasteners made from carbon and low-alloy steels containing a maximum of 0.55% carbon. It provides guidelines for the selection of steels for bolts, studs, and nuts intended for use at temperatures between -50 and 370 deg C. The article also discusses steels rated for service above 370 deg C and describes internationally recognized grade designations. The specifications provided can be used to outline fastener requirements, control manufacturing processes, and establish functional or performance standards. The most commonly used protective metal coatings for ferrous metal fasteners; zinc, cadmium, and aluminum; are described as well.

This article describes the characteristics of tools and dies and the causes of their failures. It discusses the failure mechanisms in tool and die materials that are important to nearly all manufacturing processes, but is primarily devoted to failures of tool steels used in cold-working and hot-working applications. It reviews problems introduced during mechanical design, materials selection, machining, heat treating, finish grinding, and tool and die operation. The brittle fracture of rehardened high-speed steels is also considered. Finally, failures due to seams or laps, unconsolidated interiors, and carbide segregation and poor carbide morphology are reviewed with illustrations.

Of the various thermal processing methods for steel, heat treating has the greatest overall impact on control of residual stress and on dimensional control. This article provides an overview of the effects of material- and process-related parameters on the various types of failures observed during and after heat treating of quenched and tempered steels. It describes phase transformations of steels during heating, cooling of steel with and without metallurgical transformation, and the formation of high-temperature transformation products on the surface of a carburized part. The article illustrates the use of carbon restoration on decarburized spring steels. Different geometric models for carbide formation are shown schematically. The article also describes the different microstructural features such as grain size, microcracks, microsegregation, and banding.

This article focuses on heat treating of the most important H-series and low-alloy hot-work tool steels, namely, normalizing, annealing, stress relieving, preheating, austenitizing, quenching, tempering, and surface hardening. It describes the heat-treating procedure for hot-work tools using examples. The article provides information on the North American Die-Casting Association's requirements for steel grades and heat treatment of dies made of hot-work tool steels. It also describes the chemical compositions and mechanical and metallurgical properties of hot-work tool steels.

Quench cracking is a brittle fracture phenomenon, and its occurrence depends not only on the stress changes but also on the mechanical characteristics of metals. Simulation of quenching processes has become possible in the analysis of quench cracking. This article commences with a discussion on the studies conducted to determine the origin of quench cracks, and then describes various test procedures for determining the susceptibility of quench cracking. It provides a description of the brittle fracture in terms of fracture mechanics and fracture toughness of quenched metals, and discusses the effects of impurities, hydrogen, and surface roughness on cracking. The article exemplifies simulation works applied to several successful cracking tests on cylindrical and complex-shaped steel parts.

This article provides information on fracture toughness and fatigue crack growth of structural steels. It describes fatigue life behavior in terms of unnotched fatigue limits, notch effects, axial strain-life fatigue, and mean stress effects. The article analyzes the mechanisms of corrosion fatigue crack initiation and prevention of corrosion fatigue. It presents case histories of fatigue failure of various steel components. The article reviews the failure of coiled tubing in a drilling application and the failure of coiled tubing due to hydrogen sulfide exposure, with examples.