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Ferrous and non-ferrous metals
Published in Arthur Lyons, Materials for Architects and Builders, 2019
Stainless steel is manufactured by a three-stage process. Scrap is melted in an electric arc furnace, then refined in an argon-oxygen decarburiser and alloyed to the required composition in a ladle furnace by the addition of the minor constituents. Most molten metal is continuously cast into billets or slabs for subsequent forming. Stainless steel is hot-rolled into plate, bar and sheet, while thin sections may be cold-rolled. Heavy universal sections are made up from plates. Stainless steel may be cast or welded and is readily formed into small components such as fixings and architectural ironmongery. Polished, brushed, matt, patterned and profiled finishes are available (Fig. 5.20); additionally, the natural oxide film may be permanently coloured by chemical and cathodic treatment to bronze, blue, gold, red, purple or green according to its final thickness. The physical vapour deposition process done under vacuum can produce a range of colour finishes, as illustrated in Figure 5.21. Approximately 50% of stainless steel derives from recycled scrap steel.
Iron and steel
Published in Peter Domone, John Illston, Construction Materials, 2018
All structural concrete contains steel reinforcement in the form of bars or welded mesh to compensate for the low tensile strength of the concrete. Bars with nominal diameters from 4 to 50 mm diameter are available. The steel is produced in either the basic oxygen process, in which up 30% scrap steel can be added to the pig iron from the converter, or in the electric arc furnace process, in which 100% scrap steel can be used for the charge. Billets are produced from continuous casting, which are then reheated to 1100–1200°C and hot rolled to the required bar diameter, which increases strength and closes any defects in the billets. A pattern of ribs is rolled onto the steel in the last part of the rolling process to improve the bond between the steel and the concrete in service.
Use of Ultrasonics in the Nondestructive Testing and Evaluation of Metals
Published in Dale Ensminger, Leonard J. Bond, Ultrasonics, 2011
Dale Ensminger, Leonard J. Bond
Typical types of defects that can be located in castings and billets, but only if the conditions are favorable, are shrinkage defects, hot tears, cracks, gas pockets and porosity, pipe, and coarse nonmetallic inclusions such as slag and sand. Typical castings that have been inspected successfully ultrasonically include cast-iron brake drums, cast-iron rolls (as mentioned previously), cast-iron crankshafts containing globoidal graphite, cast-aluminum and aluminum alloys, cast piston rings, and ductile-iron parts.
Achievement of forging without canning for β-solidifying γ-TiAl alloy containing high content of niobium
Published in Materials and Manufacturing Processes, 2021
Gengwu Ge, Zeming Wang, Siyuan Liang, Laiqi Zhang
Casting and forging are the two main traditional processing technologies. Of the two, forging is important for molding. For TiAl-based alloys, the main processes of billet forming include isothermal forging, canned forging and hot extrusion. Considering the relatively poor plasticity of TiAl alloys, most need to be canned in the hot forming processes to keep the temperature and prevent formation of cracks. However, canned forging is a high cost and complex process, and is especially difficult to implement with the requirements of the complex components. Many researchers have studied the forging of TiAl-based alloys. Xiao et al.[15] studied the effect of multisteps forging on the microstructure and tensile properties of β-solidify TiAl alloy without high content of Nb. Li et al.[16] obtained pancakes by canned forging and studied microstructure and high temperature mechanical properties of TiAl alloy containing less β phase. However, these researches mainly focused on canned forging. Tetsui et al.[17] developed a new β-solidified TiAl alloy without high Nb content, and carried out ordinary hot forging. Forging and machining tests showed that the β phase containing alloy possesses superior hot forgeability compared to the conventional TiAl alloy.[18]