Steel ingots and their Casting during Steelmaking...

Steel ingots and their Casting during Steelmaking Ingot casting is a conventional casting process for liquid steel. Production of crude steel through the ingot casting route constitutes a very small percentage of global crude steel production. However, the method of casting of the liquid steel in ingot moulds is still fundamental for specific low-alloy steel grades and for special forging applications, where products of large dimension, high quality or small lot size are needed. Typical application for conventional ingot casting includes the power engineering industry (e.g. shafts for power generation plants, turbine blades), the oil and gas industry (conveying equipment, seamless tubes), the aerospace industry (shafts, turbines, engine parts), ship building (shafts for engines and drives), tool making and mechanical engineering (heavy forgings, cold, hot and high-speed steels, bearing, drive gears) as well as automotive engineering (shafts, axes). As the demand of heavy ingot increases nowadays, especially from the power engineering industry and ship industry, there is a tendency of producing extreme large ingots over 600 t and continuous cast strands with thickness over 450 mm and rounds with diameter up to 800 mm, which are mainly applied for pressure retaining components such as reaction vessels for nuclear power plant and rotating components like drive shafts of gas turbines and generator rotors. The moulds used for casting of ingots are made of cast iron. Cast iron is used for the production of the mould since the thermal coefficient of cast iron is lower than that of steel. Because of this property of cast iron, liquid steel on solidification contracts more than cast iron which makes detachment of ingot easier from the mould. Inner walls of the mould are coated by either tar or fine carbon. The coated material decomposes during solidification and this prevents sticking...

Defects in Continuous Cast Steels Dec11

Defects in Continuous Cast Steels...

Defects in Continuous Cast Steels Continuous casting (CC) is the process which converts liquid steel into a solid product mainly in the form of slab (either thick or thin), bloom or billets. It is one of progressive steel making technologies which produces a cast product of a desired cross section in indefinite length. The CC process requires strict observance of operating procedures,  technological norms, and advanced production and control techniques. Despite these measures, the occurrence of defects in the CC product cannot be fully ruled out. The formation and the type of defects depends on the status of CC machine equipment, the cast product shape and size, the steel grade, the technological conditions of casting such as casting temperature and speed, the mould oscillation and cooling, the quality and properties of the casting powder etc. A defect in a CC product can be defined as a deviation in the appearance, shape, dimension, macrostructure, and/or chemical properties when compared with the specifications given in the technical standards or any other normative documents in force. Defects are detected after casting in the CC product through visual inspection of their surface at the cooling beds, by checking the surface quality again by visual inspection on the inspection beds, or by checking the chemical analysis and the macrostructure of the test samples in the laboratories. The defects in CC products generated during the solidification and cooling process lead to loss or diversion of prime material for further processing or sale. To prevent these losses, it is necessary to analyze the causes of the occurrence of defects for taking preventive action by adopting preventive metallurgical technologies and constructive solutions. Also it is necessary to segregate and remove defective product from the prime material. A defect is not always the...