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...

Heat Transfer during Continuous Casting of Steel Jun19

Heat Transfer during Continuous Casting of Steel...

Heat Transfer during Continuous Casting of Steel During continuous casting (CC) of steel, careful control of the strand cooling and growth of the shell along the CC machine is of great importance. These factors play an important role on the formation of cracks and other defects which can be formed in the cast steel product. To ensure defect free cast steel products, the strand is to be cooled down according to a pattern which depends on steel grade, steel product dimensions, casting speed, and CC machine design. On the other hand, the control of the liquid pool length is a key element in optimizing the casting speed with respect to good productivity. So, the heat transfer plays a very important role in the operation of the CC machines, especially when casting crack sensitive steel grades. In fact, many diverse phenomena simultaneously control the complex sequence of events which govern heat transfer in the CC process. The temperature of liquid steel in the tundish is typically 30 deg C to 50 deg C higher than the liquidus temperature. At the beginning of the continuous casting process, the liquid steel is cooled in a water cooled mould to form a solidified shell which can support the liquid pool at the mould exit. Typical temperature at the end of the mould is1100 deg C and that in the center of the strand is 1550 deg C. Since steel does not solidify at a fixed temperature, but over a range of temperature, there is a mushy region where the steel is neither completely solid nor completely liquid. Steel grades used in continuous casting are completely solid below a temperature ranging from 1350 deg C to 1500 deg C, and the solidification starts at a temperature ranging from 1450...

Continuous Casting Machine and its Equipment Jun13

Continuous Casting Machine and its Equipment...

Continuous Casting Machine and its Equipment Continuous casting (CC) is a method of producing an infinite solid strand from liquid steel by continuously solidifying it as it moves through a CC machine. It is the predominant process route in a modern steel plant which links steelmaking and hot rolling. A typical section and plan view of a CC machine is shown in Fig 1. Fig 1 Typical section and plan view of a CC machine Types of continuous casting machines CC machines have evolved from the strictly vertical type of machine to curved machines in order to limit the installation height while still using high casting speeds. In recent years, CC machines of more sophisticated mechanical design are being constructed. These machines apply several techniques for achieving higher casting speeds and higher outputs and are with progressive straightening or progressive bending over a liquid core. The main types of the CC machines which are in operation these days are given below. Simple vertical CC machine with a straight mould and cutoff in the vertical position Vertical CC machine with a straight mould along with single point bending and straightening Vertical CC machine with a straight mould along with progressive bending and straightening Bow type machine with curved mould and straightening Bow type machine with curved mould and progressive straightening In all cases, the bending and straightening is usually carried out in one or several steps. Multistep bending and straightening reduces the mechanical stresses and reduces the risk of strand cracking. The first CC machine which was built up for CC of liquid steel was a simple vertical CC machine. Then later the development led to many kinds of CC machines with various ways of bending and straightening. The main objective for these developments have...