Ladle and types

In metallurgy, a ladle is a barrel or vessel used for transporting and pouring molten metal.Ladles are commonly used in foundries and range in size from small hand-held containers similar to kitchen ladles, which can hold 20 kg (44 lbs),to large steel mill ladles,which can hold up to 300 tons (295 long tons; 331 short tons).Many non-ferrous foundries also use ceramic crucibles for transporting and pouring molten metal, also known as ladles.

Types 

Basic terms are often prefixed to define the actual use of the ladle.Therefore,the basic ladle design can include many variations that improve the use of the ladle for a particular task.For example:

Ladle:A ladle used to pour molten metal into molds to produce castings.

Transfer Ladle:A ladle used to transfer large quantities of molten metal from one process to another.Typically,transfer ladles are used to transfer molten metal from primary melting furnaces to holding furnaces or automatic pouring units.

Processing Ladle:A ladle in which processes that alter some aspect of the molten metal take place.A typical example is the conversion of cast iron to ductile iron by adding various elements in the ladle.Unless the ladle is used with alloys with very low melting points, the ladle is also fitted with a refractory lining.When ladles are used to transport metals with high melting temperatures,refractory linings protect the steel vessel from damage,and if the molten metal comes into direct contact with the ladle shell, it will melt rapidly through the shell.Refractory lining materials come in many forms and the correct choice depends largely on the working practices of each foundry.Ladles have traditionally been lined with prefabricated refractory bricks, but in many countries refractory concrete tends to replace these linings.Casting ladles are usually rated for their working capabilities rather than physical size.Hand held ladles are often called handle ladles and feature a long handle to keep the heat of the metal away from the person holding it.Their abilities are limited to what a single person can safely handle.Larger ladles are often referred to as geared crane ladles.

Their capacity is usually determined by the ladle function. Small hand-held ladles may also be crucibles fitted with carrying devices.However, in most foundries, a foundry ladle is a steel container fitted with lifting rings so that the container can be handled by an overhead crane or a monorail system, and also fitted with a mechanism for rotating the container, usually in the form of a gearbox.The gearbox can be manually or power operated.For the transport of large quantities of molten metal, such as in steel mills, ladles can be run on wheels, dedicated ladle transfer vehicles or hoisted from an overhead crane and tilted using a second overhead lifting device.The most common shape of the ladle is a vertical cone,but other shapes are possible.Having a tapered shell as the shell increases the strength and rigidity of the shell.Having a taper also helps when the refractory lining needs to be removed.However, straight-sided shells can also be made like other shapes.The most common of these other shapes is the drum ladle,which is shaped as a horizontal cylinder suspended between two bogies.Steel mills typically use larger versions with capacities in excess of 100 tons (98 long tons; 110 short tons), often called torpedo ladles.Torpedo ladles are commonly used to transport molten iron from a blast furnace to another part of a steelworks. Some versions have even been modified to sit on special bogies that can be transported by road or rail.

Pour designs

Ladles can be of "lip pour" design, "teapot spout" design, "lip shaft design" or "bottom pour" design:For lip pour designs, the ladle is tilted and the molten metal is poured from the ladle like water from a jug.Teapot spout design, like a teapot, draws liquid from the bottom of the spoon and pours it out through the lipped spout.Any impurities in the molten metal form on top of the metal, so by taking the metal from the bottom of the ladle,the impurities do not pour into the mold.The same idea is behind the bottom pouring process.

The vessel pivot point of the lip shaft ladle is as close as possible to the tip of the gate.As a result, the actual pouring point barely moves as the ladle rotates.Lip shaft pouring is typically used in molten metal pouring systems where it is desirable to automate the process as much as possible and for the operator to remotely control the pouring operation.For bottom pouring ladles, insert the stopper rod into the tapping hole in the bottom of the ladle. When pouring metal,the plug is lifted vertically to allow the metal to flow from the bottom of the ladle.To stop pouring, insert the stopper stem back into the weep hole. Large ladles in the steelmaking industry may use sliding doors below the taphole.Ladles can be open at the top or covered.Covered ladles have a (sometimes removable) dome-shaped cover to contain radiant heat; they dissipate heat more slowly than open ladles.Ladles usually don't have lids, but ceramic blankets can be used instead (if available).Medium and large ladles suspended from cranes have an eye, called a trunnion, that holds the ladle to the shaft.For tilting the ladle, a gearbox is used, which is usually a worm gear.The gear mechanism can be operated manually with large wheels, or with electric or air motors.Powered rotation allows the ladle operator to move to a safe distance and control the rotation of the ladle from a pendant or radio remote.Powered rotation also allows for multiple rotational speeds of the ladle, which may benefit the entire casting process.The powered rotation also obviously reduces the workload required of the ladle operator and allows for the transfer and pouring of large quantities of molten metal for extended periods of time without operator fatigue.If the ladle has a manual transmission, the most common type of transmission is the worm gear design, as in most practical cases it can be considered "self-locking" if properly maintained and does not require internal friction brakes to adjust ladle tilt speed.Other types of gear systems can also be used, but they must be equipped with an additional braking system to hold the ladle in place when the operator removes his hand from the hand wheel.

Lip shaft ladles can also use hydraulic cylinders to tilt the ladle.The largest ladles have no gears and are usually poured using special twin-winch cranes, where the main winch carries the ladle while the second winch engages with lifting lugs at the bottom of the ladle. Raise the second winch and spin the ladle on the trunnion.Ladles are usually designed for special purposes, such as adding alloys to molten metal.Ladles may also have porous plugs inserted into the bottom so inert gas can be bubbled through the ladle to enhance alloying or metal treatment practices.