Search Results for heat treatment

This chapter provides an overview of the alloy and temper designations adopted for aluminum cast and wrought products. It explains the naming system and how to identify the main alloying elements and basic strengthening mechanism from any given alloy and temper designation. The chapter provides additional detail on the strengthening and softening mechanisms that allow aluminum alloys to attain a range of engineering properties. The strength of aluminum alloys can be controlled by three methods: solid-solution hardening by alloying, work hardening by plastic deformation, and precipitation hardening with appropriate alloying and heat treatment.

The existence of austenite and ferrite, along with carbon alloying, is fundamental in the heat treatment of steel. In view of the importance of structure and its formation to heat treatment, this chapter describes the various microstructures that form in steels, the various factors that determine the formation of microstructures during heat treatment processing of steel, and some of the characteristic properties of each of the microstructures. The discussion also covers the constitution of iron during heat treatment and the phases of heat-treated steel with elaborated information on iron phase transformation, hysteresis in heating and cooling, ferrite and austenite as two crystal structures of solid iron, and the diffusion coefficient of carbon.

Heat treatment of steel involves a number of processes to condition the microstructure and obtain desired properties. This includes various methods namely, annealing, normalizing, and hardening by quenching and tempering. This chapter focuses on general heat treatment procedures and the applications of particular types or grades of carbon and low-alloy steels. The discussion covers carbon steel classification for heat treating, tempering of quenched carbon steels, and austempering of steel. In addition, the chapter discusses the effects of alloying and hardenability on steel and provides information on martempering of steel.

This chapter discusses the composition and classification of stainless steels and focuses on the processes involved in heat treatment and applications of these steels. The wrought and the cast stainless steels covered are ferritic, austenitic, duplex (ferritic-austenitic), martensitic, and precipitation-hardening. In addition, information on special considerations for stainless steel castings is also provided. The heat treatment processes explained in the chapter are preheating, annealing, stress relieving, hardening, tempering, austenite conditioning, heat aging, and nitride surface hardening. Finally, some special considerations for stainless steel castings are discussed.

The possible classification for tool steels is their division into four groups according to their final application: hot-worked, cold-worked, plastic mold, and high-speed tool steels. This chapter mainly follows such division by application, but the grade nomenclatures used here are primarily from AISI. It presents the classification of tool steels and discusses the principles and processes of tool steel heat treating, namely normalizing, annealing, hardening, and tempering. Various factors associated with distortion in several tool steels are also covered. The chapter discusses the composition, classification, and properties of unalloyed and low-alloy cold-worked tool steels; medium and high-alloy cold-worked tool steels; and 18% nickel maraging steels.

Cast irons, like steels, are iron-carbon alloys but with higher carbon levels than steels to take advantage of eutectic solidification in the binary iron-carbon system. Like steel, heat treatment of cast iron includes stress relieving, annealing, normalizing, through hardening, and surface hardening. This chapter introduces solid-state heat treatment of iron castings, covering general considerations for heat treatment and discussing the processes, advantages, and disadvantages of heat treatment of cast iron.

The term heat treatable alloys is used in reference to alloys that can be hardened by heat treatment, and this chapter briefly describes the major types of heat treatable nonferrous alloys. The discussion provides a general description of annealing cold-worked metals and describes some of the common nonferrous alloys that can be hardened through heat treatment. The nonferrous alloys covered include aluminum alloys, cobalt alloys, copper alloys, magnesium alloys, nickel alloys, and titanium alloys.

This chapter is a collection of tables listing: cast alloy designations of Aluminum Association, along with their general applications; the chemical compositions of the frequently used alloys for gravity permanent molds, low-pressure permanent molds, squeeze castings, and die castings; the typical tensile properties of die cast alloys; and the designations of different heat treatments and their description. The tables also list the temperatures and times of typical heat treatment cycles for different permanent mold cast alloys; typical components in sand, gravity, and low-pressure permanent mold castings and die castings, the functional requirements of each process, and the corresponding suitable alloys and heat treatments; and alloys that are high vacuum die cast for structural castings. The chapter also presents examples of photomicrographs of some alloys cast by different processes.

This chapter provides a practical understanding of heat treatments and how to employ them to optimize the properties and structures of cast irons and steels. It discusses annealing, normalizing, quenching, tempering, patenting, carburizing, nitriding, carbonitriding, and nitrocarburizing. It describes the primary objectives of each treatment along with processing sequences, process parameters, and related phase transformations. The chapter contains more than 100 images, including time-temperature diagrams, transformation curves, data plots, and detailed micro- and macrographs. It also discusses the concepts of hardenability, critical diameter, quench severity, and Jominy testing.

Induction heat treating is used in a wide range of applications. Typical uses, as described in this chapter, include the surface hardening of many types of shafts as well as gears and sprockets and the through-hardening of gripping teeth, cutting edges, and impact zones incorporated into various types of tools and track pins manufactured for off-highway equipment.

Temperature and deformation gradients developed in the course of manufacturing can have undesired effects on the microstructures along their path; the two most common being residual stress and distortion. This chapter discusses these manufacturing-related problems and how they can be minimized by heat treatments. It also provides information on residual stress evaluation and prediction techniques.

Titanium alloys respond well to heat treatment be it to increase strength (age hardening), reduce residual stresses, or minimize tradeoffs in ductility, machinability, and dimensional and structural stability (annealing). This chapter describes the phase transformations associated with these processes, explaining how and why they occur and how they are typically controlled. It makes extensive use of phase diagrams and cooling curves to illustrate the effects of alloying and quenching on beta-to-alpha transformations and the conditions that produce metastable phases. It also examines several time-temperature-transformation diagrams, which account for the effect of cooling rate.

This chapter discusses the processes used in manufacturing to thermally alter the properties of metals and alloys. It begins with a review of the iron-carbon system, the factors that affect hardenability, and the use of continuous cooling transformation diagrams. It then explains how various steels respond to heat treatments, such as annealing, normalizing, spheroidizing, tempering, and direct and interrupted quenching, and surface-hardening processes, such as flame and induction hardening, carburizing, nitriding, and carbonitriding. It also addresses the issue of temper embrittlement and discusses the effect of precipitation hardening on aluminum and other alloys.

This chapter discusses the types, methods, and advantages of heat treating procedures, including annealing, normalizing, tempering, and case hardening. It describes the iron-carbon system, the formation of equilibrium and metastable phases, and the effect of alloy elements on hardenability and tempering response. It discusses the significance of critical temperatures, the use of transformation diagrams, and types of annealing treatments. It also provides information on heat treating furnaces, the effect of heating rate on transformation temperatures, quench and temper procedures, and the use of cold treating.

Nonferrous alloys are heat treated for a variety of reasons. Heat treating can reduce internal stresses, redistribute alloying elements, promote grain formation and growth, produce new phases, and alter surface chemistry. This chapter describes heat treatment processes and how nonferrous alloys respond to them. It provides information on aluminum, cobalt, copper, magnesium, nickel, and titanium alloys and their composition, microstructure, properties, and processing characteristics.

This chapter provides an overview of the fundamental material- and process-related parameters of quenching on residual stress, distortion control, and cracking. It begins with a description of phase transformations during heating and quenching of steel. This is followed by a section on the effects of materials and quench process design on distortion of steel during heat treating. Details on stress raisers and their role in quench cracking are then presented. The chapter ends with various selected case histories of failures attributed to the quenching process.

This chapter reviews the causes and cases associated with the problems originated by tempering of steels. To provide background on this phenomenon, a brief description of the martensite reactions and the steel heat treatment of tempering is given to review the different stages of microstructural transformation. A section describing the types of embrittlement from tempering, along with mechanical tests for the determination of temper embrittlement (TE), is presented. Various factors involved in the interaction of the TE phenomenon with hydrogen embrittlement and liquid-metal embrittlement are also provided. The cases covered are grinding cracks on steel cam shaft and transgranular and intergranular crack path in commercial steels.

One of the primary advantages of steels is their ability to attain high strengths through heat treatment while still retaining some degree of ductility. Heat treatments can be used to not only harden steels but also to provide other useful combinations of properties, such as ductility, formability, and machinability. This chapter discusses various heat treatment processes, namely annealing, stress relieving, normalizing, spheroidizing, and hardening by austenitizing, quenching and tempering. It also discusses two types of interrupted quenching processes: martempering and austempering. The chapter concludes with a brief section on temper embrittlement.

Grain size has a determining effect on the mechanical properties of steel and responds favorably to forging and heat treating. This chapter explains how to measure and quantify grain size and how to control it through thermal cycling and forging operations. It describes how surface tension acting on grain-boundary segments contributes to grain growth and how the formation of new grains, driven by phase transformations and recrystallization, lead to a reduction in average grain size. It also discusses the effect of alloying elements on grain growth rates, particularly the curbing effect of particle and solute drag.

The metallurgy of aluminum and its alloys offers a range of opportunities for employing heat treatments to obtain desirable combinations of mechanical and physical properties such that castings meet defined temper requirements. This chapter discusses the processes involved in solution heat treatment, quenching, precipitation hardening, and annealing of aluminum alloys. The effects of these processes on dimensional stability and residual stresses are also discussed. Troubleshooting and diagnosis of heat treating problems are covered in the concluding section of the chapter.