Porosity C. INDICATES USED FOR ROLLING BARS BELOW got A ot B PI -Bar rolled from ingot A-Bar rolled from ingot B- Fig. 1 Longitudinal sections of two types of ingots showing typical pipe and porosity. When the ingots are rolled into bars, these flaws become elongated throughout the center of the bars Metalforming and fabrication of wrought forms also involve other manufacturing operations, such as electroplating, heat treatment, machining, or welding. These operations may also introduce possible defects (Table 1)that may be considered in conjunction with possible defects from metal working. Failures can also occur from a complex series of manufacturing factors. For example, the level of residual hoop and bending stresses can occur in a tube produced by drawing, heat treating, and straightening operations. By varying the severity of these operations, it is possible to produce tubes with very low residual stresses or with very high residual stresses that are near the yield strength of the metal. In other words, parts are made by a rather complex series of operations, which thus requires a broad understanding not only in the context of failure analysis but also in the organizational traditions for failure prevention Table 1 Defects that may result from postforming processes rocess Possible defects Electroplatin Hydrogen embrittlement galvanic corrosion Heat treatment Excessive grain growth, burning of grain boundaries, brittle structure, carburization, decarburization, quench crack Surface hardening, nitriding, Excessive case thickness microcracks. embrittled material at stress carburizing anodic hard coating raisers Machining Tool marks grinding cracks Welding Weld-metal defects, hydrogen-induced cracking, inclusions, improper tructure The primary purpose of this article is to describe general root causes of failure that are associated with wrought metals and metalworking. This includes a brief review of the discontinuities or imperfections that may beFig. 1 Longitudinal sections of two types of ingots showing typical pipe and porosity. When the ingots are rolled into bars, these flaws become elongated throughout the center of the bars. Metalforming and fabrication of wrought forms also involve other manufacturing operations, such as electroplating, heat treatment, machining, or welding. These operations may also introduce possible defects (Table 1) that may be considered in conjunction with possible defects from metalworking. Failures can also occur from a complex series of manufacturing factors. For example, the level of residual hoop and bending stresses can occur in a tube produced by drawing, heat treating, and straightening operations. By varying the severity of these operations, it is possible to produce tubes with very low residual stresses or with very high residual stresses that are near the yield strength of the metal. In other words, parts are made by a rather complex series of operations, which thus requires a broad understanding not only in the context of failure analysis but also in the organizational traditions for failure prevention. Table 1 Defects that may result from postforming processes Process Possible defects Electroplating Hydrogen embrittlement, galvanic corrosion Heat treatment Excessive grain growth, burning of grain boundaries, brittle structure, carburization, decarburization, quench cracks Electrolytic cleaning Pitting Surface hardening, nitriding, carburizing, anodic hard coating Excessive case thickness, microcracks, embrittled material at stress raisers Machining Tool marks, grinding cracks Welding Weld-metal defects, hydrogen-induced cracking, inclusions, improper structure The primary purpose of this article is to describe general root causes of failure that are associated with wrought metals and metalworking. This includes a brief review of the discontinuities or imperfections that may be