Processes for Casting of Metals Dec07

Processes for Casting of Metals...

Processes for Casting of Metals Casting of metals is a process of manufacturing materials made of metals. It is a forming process for the forming of hot liquid metals. It is the simplest, most direct route to a near net shape product, and often the least expensive.  It is a process, in which liquid metal is poured into a mould, which contains a hollow cavity of the desired shape, and then allowed to cool and solidify. The solidified part is also known as a casting, which is ejected or removed out of the mould to complete the process. Casting is very often used for making complex shapes which are difficult or uneconomical to make by other methods. The processes for the casting of metals (Fig 1) have two distinct subdivisions namely (i) non-expendable mould casting, and (ii) expendable mould casting. It is further broken down by the mould material, such as sand or metal, and pouring method, such as gravity, vacuum, or low pressure. Fig 1 Processes for the casting of metals Non-expendable mould casting processes Non-expendable mould casting is a casting process in which the mould need not be reformed after each production cycle. Non-expendable mould casting is a casting technique which has at least 4 distinct casting processes. These are (i) continuous casting, (ii) centrifugal casting, (iii) die casting, and (iv) permanent mould casting. This form of casting also results in improved repeatability in parts produced and delivers near net shape casting. Continuous casting process Continuous casting of metals can be defined as a refined process of casting for continuous production in high volume of metal shapes with constant cross-section. During the process, the pouring of liquid metal takes place into a water-cooled, open-ended copper mould. This allows a skin of solid metal being formed...

Important Aspects of Continuous Casting of Billets Mar31

Important Aspects of Continuous Casting of Billets...

Important Aspects of Continuous Casting of Billets Continuous casting of steel billets is an operation which is sensitive to a number of factors. It is to be performed with adequate controls and with steadiness and in such a way so as to produce safe casting product with sound steel mechanical properties, and to ensure a continuous process with limited delays. The process requires good control of operating parameters in order to produce sound and continuous billets. Important aspects of the continuous casting of billets are (i) quality of the billets, (ii) productivity of the machine, and (iii) cost of production. There is necessity to optimize the performance parameters to achieve high productivity and required billet quality with decreasing operating costs. The machine availability and the process reliability are the important factors during the continuous casting of the billets. The continuous casting of billet is a highly flexible process in which the operator is to react to changing requirements extremely quickly. The steel qualities needed from a billet continuous casting machine range from simple construction steel (rebar) to state-of-the-art ‘special bar quality’ (SBQ) for the automotive industry and other engineering applications, as well as high grade wire products such as soft-steel wires, pre-stressed concrete reinforcing wire, and tire cord. During the continuous casting, the quality of cast steel billets, thermal stress, surface defects and cracks formation are highly dependent on the temperature distribution along the entire continuously cast billet. The main attention is usually paid to the surface temperatures and particularly to the corner temperature distributions. However, from the technological point of view the temperature distribution in the core of cast billet, which is highly related to the metallurgical length and to the unbending process, is very important as well. Therefore, monitoring of temperature field...

Continuous casting of steel billets Mar19

Continuous casting of steel billets...

Continuous casting of steel billets Continuous casting of steel is a process in which liquid steel is continuously solidified into a strand of metal. Depending on the dimensions of the strand, these semi-finished products are called slabs, blooms or billets. Steel billet has a square cross section with one side normally 150 mm or less. It is a feed material for rolling of steel in light section mills, bar mills, and wire rod mills. Steel billets are also used in forging of certain products. The process of continuous casting was invented in the 1950s in an attempt to increase the productivity of steel production. Previously only ingot casting was available which still has its benefits and advantages but does not always meet the productivity demands. Since then, continuous casting has been developed further to improve on yield, quality and cost efficiency. Continuous casting of steel is now the method of choice by all steel producers replacing the old method of ingot casting. Distinguished by its many advantages, this process has gone through many improvements and was and still is the subject of wide range of studies both empirically and mathematically. Continuous casting of steel billets is one of the type of continuous casting adopted in steel industry, by which, steel billets are produced continuously and simultaneously. This type of process requires great control of operating parameters in order to produce sound and continuous billets. The process can be divided into a number of steps starting by pouring the hot liquid steel from the steelmaking furnace into the ladle, where the steel chemistry is being adjusted in secondary steelmaking, then pouring into the distributor (tundish), and from the distributor into the casting mould. Solidification of steel begins in the copper casting mould by indirect cooling,...

Historical aspects of the Continuous Casting and related Technologies for Steel Mar06

Historical aspects of the Continuous Casting and related Technologies for Steel...

Historical aspects of the Continuous Casting and related Technologies for Steel Continuous casting (CC) technology of steel, as a method of solidification processing of liquid steel has a relatively short history —not much longer than oxygen steelmaking. Different to other processes in steel production, continuous casting is the vital link between the liquid and the solid phase and has to live with metallurgical effects as well as mechanical challenges at the same time. Continuous casting transforms liquid steel into solid on a continuous basis and includes a variety of important commercial processes. These processes are the most efficient way to solidify large volumes of liquid steel into simple shapes for subsequent processing. The CC ratio for the world steel industry is now around 96 % of crude steel output which was a mere 4 % in 1970. Continuous casting is distinguished from other solidification processes by its steady state nature. The liquid steel solidifies against the mould walls while it is simultaneously withdrawn from the bottom of the mould at a rate which maintains the solid / liquid interface at a constant position with time. The process works best when all of its aspects operate in this steady-state manner. Relative to other casting processes, continuous casting generally has a higher capital cost, but lower operating cost. It is the most cost- and energy- efficient method to mass-produce semi-finished steel products with consistent quality in a variety of sizes and shapes. Cross-sections can be rectangular, for subsequent rolling into plate or sheet, square or circular for long products and seamless pipes, and even dog-bone shapes, for rolling into I or H beams. Today continuous casting machines consist of modularized technological/mechatronic packages to allow fast design and short project execution time as well as rapid production ramp-up...

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...