Search Results for iron-iron carbide-silicon system

This chapter discusses the crystal structures of steel and cast iron, the iron-iron carbide equilibrium diagram, microconstituents or phases in the iron-iron carbide phase diagram, the iron-carbon carbide-silicon equilibrium diagram of cast irons, and the influence on microstructure by base elements and alloying elements. Graphitization, cooling rates, and heat treatment effects are covered. There also is discussion on inoculation benefits, flake graphite types and typical applications, evolution of cast iron types, ASTM specification A247 for graphite shapes, and selection of the best molding process. A large table lists typical material choices for various applications.

This chapter introduces the metallographer to the various types of steels and cast irons and explains how they are classified and defined. Classification and designation details are provided for plain carbon steels, alloy steels, and gray, white, ductile, and malleable cast irons.

Ductile iron has far superior mechanical properties compared to gray iron as well as significantly improved castability and attractive cost savings compared to cast steel. This chapter begins with information on graphite morphology and matrix type. It then discusses the advantages and applications of ductile iron. Next, the effects of various factors on the grades, chemistry, matrix, and mechanical properties of ductile iron are covered. This is followed by a section detailing the ductile iron treatment methods and the quality control methods used. Guidelines for gating and feeder design are then provided. Further, the chapter addresses the technology of ductile iron castings, including the performance and geometric attributes, molding and core-making processes used, material grades, mechanical properties, and chemical compositions of a few applications. Finally, it describes ductile iron casting defects and presents practical cases of problem-solving.

This article discusses the metallurgy and properties of ductile cast iron. It begins with an overview of ductile or spheroidal-graphite iron, describing the specifications, applications, and compositions. It then discusses the importance of composition control and explains how various alloying elements affect the properties, behaviors, and processing characteristics of ductile iron. The article describes the benefits of nickel and silicon additions in particular detail, explaining how they make ductile iron more resistant to corrosion, heat, and wear.

The properties of cast iron are determined primarily by the form of carbon they contain, which in turn, is controlled by modifying compositions and cooling rates during casting. Certain alloys (such as Si, Al, Ni, Co, and Cu) promote graphite formation, while others (such as S, V, Cr, Sn, Mo, and Mn) promote the formation of cementite. This chapter examines the relative potencies of these alloys and their effect on microstructure. It covers the five most common commercial cast irons, including white, gray, ductile, malleable, and compacted graphite, describing their compositional ranges, distinguishing features, advantages, limitations, and applications.

The commercial relevance of cast irons is best understood in the context of the iron-carbon phase diagram, where their composition places them near the eutectic point, which sheds light on why they melt at lower temperatures than steel and why they can be cast into more intricate shapes. This chapter examines these unique properties and how they are derived. It begins by describing the basic metallurgy of cast iron, focusing on the eutectic reaction. It explains how to control the reaction and thus properties of cast iron by overcooling and inoculation. The chapter also discusses composition, microstructure, heat treatments, and the classification and casting characteristics of white, gray, ductile, malleable, compacted graphite, and special cast irons.

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.

This chapter provides guidelines and insights on the selection of materials, coatings, and treatments for friction and wear applications. It begins with a review of the system nature of tribological effects, the subtleties of friction, and the selection idiosyncrasies of the material systems and lubricants covered in prior chapters. It then presents a systematic approach for selecting tribomaterials, using an automotive fan motor as an example.

This chapter discusses the effect of composition and cooling rate on the microstructure and properties of cast irons and explains how they differ from steel. It describes the conditions under which white, gray, mottled (chilled), and nodular (ductile) cast irons are produced, and examines the growth mechanisms and structural details that set them apart. It also discusses the formation of compacted (vermicular) graphite and malleable iron, and compares and contrasts the composition, properties, and heat treatment of whiteheart and blackheart malleable types.

Malleable iron has unique properties that justify its application in the metal working industry. This chapter discusses the advantages, limitations, and mechanical properties of malleable iron; provides a description of the malleabilization process; and presents manufacturing guidelines for malleable iron castings.

This chapter covers mechanical properties, microstructures, chemical compositions, manufacturing processes, and engineering of gating practices for several applications of gray, white, and alloyed cast irons. It begins with a description of material standards, followed by a section providing information on the practice of stress relieving. Next, the chapter details various ways of eliminating slag entrainment while designing gating and venting systems. Several factors related to the establishment of the optimum pouring rate and time are then covered. Further, the chapter discusses the technology of unalloyed or low-alloyed gray iron castings and white iron and high-alloyed cast irons. Finally, it describes the casting defects that are associated with cast iron and the processes involved in solving these defects. The article includes a number of figures illustrating the topics discussed.

Metallurgy, as discussed in this chapter, focuses on phases normally encountered in stainless steels and their characteristics. This chapter describes the thermodynamics and the three basic phases of stainless steels: ferrite, austenite, and martensite. Formation of the principal intermetallic phases is also covered. In addition, the chapter provides information on carbides, nitrides, precipitation hardening, and inclusions.

Unlike conventional quench and temper heat treatment, austempering is an iron and steel heat-treatment process that enhances mechanical properties through the isothermal transformation of austenite with a minimum amount of quenching stresses. This chapter begins with a discussion of austemperability requirements. Then outlines of austenitizing and austempering cycles and resultant microstructures are presented. This is followed by sections discussing the mechanical properties, advantages, limitations, machinability, process variants, and applications of austempered ductile iron (ADI). Information on the growth of premachined ADI components is also provided. Further, the chapter describes two slightly different systems for austempering: atmospheric-salt and salt-salt systems. Finally, it presents general guidelines for component designers, casting manufacturers, and heat treaters to apply ADI more widely and with improved success.

This article covers the metallurgy and properties of gray irons. It describes the classes or grades of gray iron, the types of applications for which they are suited, and the corresponding compositional ranges. It discusses the role of major, minor, and trace elements, how they are added, and how they affect various properties, behaviors, and processing characteristics. It explains how silicon, chromium, and nickel, in particular, improve high-temperature, corrosion, and wear performance.

This article examines the role of alloying in the production and use of nickel and its alloys. It explains how nickel-base alloys are categorized and lists the most common grades along with their compositional ranges and corresponding UNS numbers. It describes the role of nearly 20 alloying elements and how they influence strength, ductility, hardness, and corrosion resistance. It also addresses processing issues, explaining how alloying and intermetallic phases affect forming, welding, and machining operations.

Compacted graphite iron (GCI) is a cast iron grade that is engineered through graphite morphology modifications to achieve a combination of thermal and mechanical properties that are in between those of flake graphite iron and ductile iron. This chapter discusses the advantages of compacted graphite iron over gray iron and ductile iron. It presents examples of low- and high-frequency thermal cycling, both of which affect the thermal stresses that castings are exposed to during temperature fluctations. Information on optimum carbon and silicon ranges as well as mechanical property standards for CGI are provided. The chapter describes the critical factors that control CGI and discusses methods of CGI manufacturing.

This chapter describes the various phases that form in tool steels, starting from the base of the Fe-C system to the effects of the major alloying elements. The emphasis is on the phases themselves: their chemical compositions, crystal structures, and properties. The chapter also provides general considerations of phases and phase diagrams and the determination of equilibrium phase diagrams. It describes the formation of martensite, characteristics of alloy carbides, and the design of tool steels.