In metallurgy, a ladle is a bucket-shaped container or vessel used to transport and pour out molten metals. Ladles are often used in foundries and range in size from small hand-carried vessels that resemble a kitchen ladle and hold 20 kilograms (44 lb) to large steelmill ladles that hold up to 300 tonnes (295 long tons; 331 short tons). Many non-ferrous foundries also use ceramic crucibles for transporting and pouring molten metal and will also refer to these as ladles.
Types The basic term is often prefixed to define the actual purpose of the ladle. The basic ladle design can therefore include many variations that improve the usage of the ladle for specific tasks. For example:
Casting ladle: a ladle used to pour molten metal into moulds to produce the casting. Transfer ladle: a ladle used to transfer a large amount of molten metal from one process to another. Typically a transfer ladle will be used to transfer molten metal from a primary melting furnace to either a holding furnace or an auto-pour unit. Treatment ladle: a ladle used for a process to take place within the ladle to change some aspect of the molten metal. A typical example being to convert cast iron to ductile iron by the addition of various elements into the ladle. Unless the ladle is to be used with alloys that have very low temperature melting point, the ladle is also fitted with a refractory lining. It is the refractory lining that stops the steel vessel from suffering damage when the ladle is used to transport metals with high melting temperatures that, if the molten metal came in direct contact with the ladle shell, would rapidly melt through the shell. Refractory lining materials come in many forms and the right choice very much depends on each foundry's working practices. Traditionally ladles used to be lined using pre-cast firebricks however refractory concretes have tended to supersede these in many countries. Foundry ladles are normally rated by their working capacity rather than by their physical size. Hand-held ladles are typically known as handshank ladles and are fitted with a long handle to keep the heat of the metal away from the person holding it. Their capacity is limited to what a worker can safely handle. Larger ladles are usually referred to as geared crane ladles. Their capacity is usually determined by the ladle function. Small hand-held ladles might also be crucibles that are fitted with carrying devices. However, in most foundries, the foundry ladle refers to a steel vessel that has a lifting bail fitted so that the vessel can be carried by an overhead crane or monorail system and is also fitted with a mechanical means for rotating the vessel, usually in the form of a gearbox. The gearbox can either be manually operated or powered operation. (See the paragraph below for further details). For the transportation of very large volumes of molten metal, such as in steel mills, the ladle can run on wheels, a purpose-built ladle transfer car or be slung from an overhead crane and will be tilted using a second overhead lifting device. The most common shape for a ladle is a vertical cone, but other shapes are possible. Having a tapered cone as the shell adds strength and rigidity to the shell. Having the taper also helps when it comes time to remove the refractory lining. However straight sided shells are also fabricated as are other shapes. The most common of these other shapes is known as a drum ladle and is shaped as a horizontal cylinder suspended between two bogies. Large versions, often having capacities in excess of 100 tonnes (98 long tons; 110 short tons) are used in steel mills are often referred to as torpedo ladles. Torpedo ladles are commonly used to transport liquid iron from a blast furnace to another part of the steel mill. Some versions are even adapted so that they can be carried on special bogies that can be transported by either road or rail.
Pour designs Ladles can be "lip pour" design, "teapot spout" design, "lip-axis design" or "bottom pour" design:
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