Search Results for ingot-related defects

This appendix provides detailed information on design deficiencies, material and manufacturing defects, and service-life anomalies. It covers ingot-related defects, forging and sheet forming imperfections, casting defects, heat treating defects, and weld discontinuities. It shows how application life is affected by the severity of service conditions and discusses the consequences of using inappropriate materials.

This chapter discusses the melting and conversion of superalloys and the solidification challenges they present. Superalloys have high solute content which can lead to untreatable defects if they solidify too slowly. These defects, called freckles, are highly detrimental to fatigue life. The chapter explains how and why freckles form as well as how they can be prevented. It describes the criteria for selecting the proper melting method for specific alloys based on melt segregation and chemistry requirements. It compares standard processes, including electric arc furnace/argon oxygen decarburization melting, vacuum induction melting, vacuum arc remelting, and electroslag remelting. It also addresses related issues such as consumable remelt quality, control anomalies, melt pool characteristics, and melt-related defects, and includes a section that discusses the processes involved in converting cast ingots into mill products.

In forgings of both ferrous and nonferrous metals, the flaws that most often occur are caused by conditions that exist in the ingot, by subsequent hot working of the ingot or the billet, and by hot or cold working during forging. The inspection methods most commonly used to detect these flaws include visual, magnetic particle, liquid penetrant, ultrasonic, eddy current, and radiographic inspection. This chapter provides a detailed discussion on the characteristics, process steps, applications, advantages, and limitations of these methods. It also describes the flaws caused by the forging operation and the principal factors that influence the selection of a nondestructive inspection method for forgings.

This chapter describes the basic steps in the production of titanium ingots and their subsequent conversion to standards product forms. It explains how titanium ore is reduced to a spongy residue, then granularized, compacted, and melted (along with alloying additions) to form an ingot, which may be remelted several times to achieve the necessary properties. It also discusses the cause of defects and ingot imperfections and the benefits of billet reduction and grain-refinement processes.

This chapter provides an overview of beryllium casting practices and the challenges involved. It discusses the stages of solidification, the effect of cooling rate, the difficulty of heat removal, and the potential for hot cracking. It describes common melting techniques, including vacuum induction melting, vacuum arc melting, and electron beam melting, and some of the ways they have been used to cast beryllium alloys. The chapter also includes information on metal purification and grain refinement procedures.

This article discusses the steps in the primary processing of stainless steels: melting, refining, remelting, casting, and hot rolling. It provides information of the major categories of defects in hot rolled stainless steels, namely hot mill defects, inclusion-related defects, and hot ductility-related defects.

This chapter discusses the effects of hot working on the structure and properties of steel. It explains how working steels at high temperatures promotes diffusion, which helps close cavities and pores, and how it changes the shape and distribution of segregates, offsetting their effect. It describes the effect of hot working on nonmetallic inclusions and the many properties influenced by them. It discusses the recrystallization mechanism by which hot working produces microstructural changes and explains how to control it by adjusting temperature, degree of reduction, and cooling rates. It describes special cases of segregation, including banding and why it occurs, and the application of closed die forging. The chapter also presents several examples of hot working defects, including forging laps, cracks, and overheated or burned steel.

This chapter provides an overview of the rolling and finishing processes required to create a sheet, plate, or foil product from a direct chill (DC) cast ingot. The flow paths, equipment, and operations are described with a view to the basic evolution of the microstructure, surface characteristics, and dimensions.

Casting is the most economical processing route for producing titanium parts, and unlike most metals, the properties of cast titanium are on par with those of wrought. This chapter covers titanium melting and casting practices -- including vacuum arc remelting, consumable electrode arc melting, electron beam hearth melting, rammed graphite mold casting, sand casting, investment casting, hot isostatic pressing, weld repair, and heat treatment -- along with related equipment, process challenges, and achievable properties and microstructures. It also explains how titanium parts are produced from powders and how the different methods compare with each other and with conventional production techniques. The methods covered include powder injection molding, spray forming, additive manufacturing, blended elemental processing, and rapid solidification.

Gas turbine disks made from nickel-base superalloys are often produced using powder metallurgy (P/M) techniques because the alloy compositions normally used are difficult or impractical to forge by conventional methods. This chapter discusses the P/M process and its application to superalloys. It describes the gas, vacuum, and centrifugal atomization processes used to make commercial superalloy powders. It explains how the powders are consolidated into preforms or billets using hot isostatic pressing, extrusion, or a combination of the two. It also provides information on spray forming and consolidation by atmospheric pressure, and includes a section on powder-based disk components, where it discusses the general advantages of P/M as well as the effects of inclusions, carbon contamination, and the formation of oxide and carbide films due to prior particle boundary conditions. The chapter concludes with a detailed discussion on mechanically alloyed superalloy compositions, the product forms into which they are made, and some of the applications where they are used.

This chapter focuses on the inspection of steel bars for the detection and evaluation of flaws. The principles involved also apply, for the most part, to the inspection of steel wire. The nondestructive inspection methods discussed include magnetic particle inspection, liquid penetrant inspection, ultrasonic inspection, and electromagnetic inspection. Eddy current and magnetic permeability are also covered.

Many of the structural characteristics of steel products are a result of changes that occur during solidification, particularly volume contractions and solute redistribution. This chapter discusses the solidification process and how it affects the quality and behaviors of steel. It explains how steel shrinks as it solidifies, causing issues such as pipe and voids, and how differences in the solubility of solid and liquid steel lead to compositional heterogeneities or segregation. It describes the dendritic nature of solidification, peritectic and eutectic reactions, microporosity, macro- and microsegregation, and hot cracking, as well as the effects of solidification and remelting on castings, ingots, and continuous cast products. It explains how to determine where defects originate in continuous casters and how to control alumina, sulfide, and nitride inclusions.

Most integrated titanium mills have primary working equipment designed specifically for titanium. This chapter describes the forging, rolling, and extruding equipment used to produce titanium mill products and sheds light on the corresponding process, structure, property relationships.

This chapter discusses the extrusion characteristics of hard aluminum alloys, particularly those in the 5000 and 7000 series. It begins with a review of two studies, one showing how the extrudability of 7 xxx alloys varies with the presence and amount of different alloying elements, the other relating minimum wall thickness with circumscribing circle diameter. It then explains how oxides on either the billet or container complicate the control of extrusion as well as auxiliary processes and how material flow and the movement of trapped gasses in different regions of the extrusion can lead to defects and variations in strength. It also discusses the extrusion of aluminum matrix composites and explains how composite billets are made.

This chapter describes the processes involved in alloy production, including melting, casting, solidification, and fabrication. It discusses the effects of alloying on solidification, the formation of solidification structures, supercooling, nucleation, and grain growth. It describes the design and operation of melting furnaces as well as melting practices and the role of fluxing. It also discusses casting methods, nonferrous casting alloys, and atomization processes used to make metal powders.

This chapter discusses the extrusion technology of hard alloys. The chapter provides an overview of hollow extrusion for aerospace application. It presents extrusion defects related to hard alloys. The chapter describes the extrusion quality requirements for aerospace applications. It also discusses extrusion of aluminum-matrix composites. The chapter outlines the powder metallurgy process for making billets for extrusion.

Porosity in aluminum is caused by the precipitation of hydrogen from liquid solution or by shrinkage during solidification, and more usually by a combination of these effects. Nonmetallic inclusions entrained before solidification influence porosity formation and mechanical properties. This chapter describes the causes and control of porosity and inclusions in aluminum castings as well as the combined effects of hydrogen, shrinkage, and inclusions on the properties of aluminum alloys. In addition, it discusses the applications of radiography to reveal internal discontinuities in aluminum.

This chapter describes various aspects of the billet making process and how they affect the quality of aluminum extrusions. It begins with an overview of the direct-chill continuous casting technique and its advantages over other methods, particularly for hard aluminum alloys. It then discusses the influence of casting variables, including pouring temperature and cooling rate, and operating considerations such as the make-up of charge materials, fluxing and degassing procedures, and grain refining. The chapter also provides information on vertical and horizontal casting systems, billet homogenization, and the cause of casting defects, including cracking and splitting, segregation, porosity, and grain growth.

This chapter describes the processes involved in the fabrication of wrought and cast metal products. It discusses deformation processes including bending and forming, material removal processes such as milling, cutting, and grinding, and joining methods including welding, soldering, and brazing. It also discusses powder consolidation, rolling, drawing and extrusion, and common forging methods.

This chapter discusses the progress that has been made in the development of superalloy operating temperatures, properties, and performance. It also provides forward-looking projections based on advances in process modeling, alloying, and production techniques.