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...

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...

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...

Understanding the Process of Continuous Casting of Steel Jun07

Understanding the Process of Continuous Casting of Steel...

Understanding the Process of Continuous Casting of Steel Continuous casting (CC) of steel is a process whereby liquid steel is solidified into a semi-finished steel product (billet, bloom, beam- blank, round or slab) for subsequent rolling in the rolling mills. The basic operation of a CC machine is to convert liquid steel of a given composition into a strand of desired shape and size through a group of operations like mould operation, spray cooling zone, straightener operation, etc. For successful continuous casting, it is necessary to understand the process behaviour under different conditions for these operations. The process of continuous casting basically comprised of the following sections. A tundish, located above the mould, to receive the liquid steel from steel teeming ladle and to feed it to the mould at a regulated rate. A primary cooling zone consisting of water cooled copper mould through which the liquid steel is fed from the tundish for generating a solidified outer steel shell sufficiently strong enough to maintain the strand shape as it passes into the secondary cooling zone. A secondary cooling zone in association with a containment section positioned below the mould, through which the steel strand (still mostly liquid) passes and is sprayed with water or a mix of water and air (air mist) for further solidifying of the steel strand. A section for the unbending and straightening of steel strand. This section is not there in the straight vertical casting machines. A cutting section consisting of cutting torches or mechanical shears for the cutting of the solidified steel strands into desired lengths for removal. A run out table to cooling beds or directly to a product transfer area. In the CC process, liquid steel flows from the steel teeming ladle, through a tundish into...

Refractory Lining of a Continuous Casting Tundish Dec23

Refractory Lining of a Continuous Casting Tundish...

Refractory Lining of a Continuous Casting Tundish In the continuous casting (CC) of steels, tundish is a buffer refractory lined vessel which is located between the ladle and the CC mould. The tundish serves the purpose of a reservoir  and a distribution vessel. Over the years, there have been dramatic changes in CC tundish. From a mere reservoir and distribution vessel, the tundish today  is viewed as a steel refining vessel and a totally new field in the process of steel making technology has emerged which is known as tundish metallurgy. Tundish today also fulfills certain metallurgical functions such as feeding of the liquid steel to the mould at a controlled rate, and thermal and chemical homogenization etc. It also focus on the continuous improvement of many quality related parameters such as fluid dynamics, thermal insulation, inclusion floatation and removal, and hydrogen pickup etc. Different refractories associated with tundish include tundish lining materials (both permanent and working lining), dams and weirs, impact pad, flow control system (monoblock stopper or slide gate), pouring stream protection between tundish and mould (shroud or submerged entry nozzle,SEN), tundish nozzle, and seating block. Dams and weirs are made of magnesite (MgO) boards or alumina (Al2O3) bricks. Liquid steel from tundish to mould is fed by nozzle submerged into molten steel in mould. SEN are to be resistant to corrosion and spalling, Nozzle clogging is also important. Isostatic pressed SEN with alumina graphite-fused silica are commonly used. Fig 1 shows typical tundish along with its refractories. Fig 1 Typical tundish along with its refractories The refractory lining design and quality of refractories used for lining have major influence on the operational parameters of CC machines such as super heat requirements, speed of the machine, the phenomenon like initial cold running stopper,...