Ironing out the pouring options.Inside This Story: * Selecting the proper iron pouring technique has tremendous effects on all areas of a foundry. * This article breaks down the complete issue of choosing an iron pouring technique by detailing the various options. ********** While pouring is often seen as simply the method of moving molten iron from the furnace to the mold, its influence on iron casting production cost and quality can be great. Affecting such diverse areas as casting yield and safety and labor requirements, the selection of pouring technique and technology requires foundries to consider numerous factors, including type and grade of iron, casting weights to be poured and the scale of casting production. Beyond these factors, iron pouring is a complicated process for metalcasters because of the high sensitivity to holding time. Excessive holding may cause temperature losses, chemistry changes and fading of inoculation inoculation, in medicine, introduction of a preparation into the tissues or fluids of the body for the purpose of preventing or curing certain diseases. The preparation is usually a weakened culture of the agent causing the disease, as in vaccination against and nodulizing effects. In addition, molten iron must be poured at a rate equal to the consumption of the gating system in order to ensure adequate metalostatic head pressure in the mold. The variety of different pouring methods currently used in iron foundries can be broken down into two groups--ladle and ladleless systems. The first group includes hand-held and manually-operated pouring ladies suitable for low-volume production. Ladleless systems are made up of more advanced pouring systems, with reduced levels of human involvement, ranging from mechanical to fully automated. Automated ladles and ladleless pouring systems allow stabilization of the pouring process parameters and improve casting production, economics, safety and working conditions. How ever, the installation and handling costs of such equipment poses a problem for a majority of small foundries, making it common to see a variety of manual, mechanical and automatic pouring devices and equipment. Pouring Ladles Ladles ranging from hand-held to large and mechanically-operated are the most common pieces of molten melt pouring and transfer equipment used in iron casting production. Ladles can be broken into two major groups--conical and drum-shaped. Conical conical /con·i·cal/ (kon´i-k'l) cone-shaped. con·i·cal or con·ic adj. Of, relating to, or shaped like a cone. ladles are steel receptacles with capacities varying from 220 lb to upwards of 44,000 lb (100-20,000 kg). They are lined with refractory refractory Material that is not deformed or damaged by high temperatures, used to make crucibles, incinerators, insulation, and furnaces, particularly metallurgical furnaces. and usually have an open top and a pouring lip or nozzle for convenience. Typically, such ladles are secured in a steel ring with two trunnions and are equipped with pawls that prevent overturning during transferring. The downside of these ladles is that they have relatively high temperature losses, considerable rates of emissions during transfer and pouring and a higher possibility of producing castings contaminated contaminated, v 1. made radioactive by the addition of small quantities of radioactive material. 2. made contaminated by adding infective or radiographic materials. 3. an infective surface or object. with slag inclusions because of excess exposure to the atmosphere and oxidation. With dram-shaped ladles, temperature losses are significantly lower, but they have a capacity up to 7500 lb (3400 kg). The molten iron is poured into the mold through the nozzle by tilting the ladle. The drawback to using these ladles is their difficulty to clean and reline reline /re·line/ (re-lin´) to resurface the tissue side of a denture with new base material in order to achieve a more accurate fit. . To ease these problems, conical and drum-shaped ladles can be equipped with a teapot device, which restrains slag inside the ladle. But even the teapot creates a constant need to reline the ladle because of slag build-up build·up also build-up n. 1. The act or process of amassing or increasing: a military buildup; a buildup of tension during the strike. 2. in the nozzle. For some conical ladles, shanks
The shanks and tattlers are wading bird species in a number of genera characterised by a medium length bill and long, often brightly coloured legs. (one-piece, teapot-shaped liners) with a ceramic web for slag separation may be used. Mechanically-Operated Ladles Pouring ladies with a motorized mo·tor·ize tr.v. mo·tor·ized, mo·tor·iz·ing, mo·tor·iz·es 1. To equip with a motor. 2. To supply with motor-driven vehicles. 3. To provide with automobiles. , gear-tilting option and mechanical transfer system are typically used for medium- and high-volume production. Depending on the type of iron, molding equipment and production rate, ladies may be transported and teamed by a monorail monorail, railway system that uses cars that run on a single rail. Typically the rail is run overhead and the cars are either suspended from it or run above it. or overhead crane An overhead crane is a type of crane where the hook-and-line mechanism runs along a horizontal beam that runs along two widely separated rails. Often it is in a long factory building and runs along rails along the building's two long walls. . Ladles carried by roller tracks are usually used as transfers and are teamed with other devices. Iron pouring is often done b a more complicated combination of several mechanized mech·a·nize tr.v. mech·a·nized, mech·a·niz·ing, mech·a·niz·es 1. To equip with machinery: mechanize a factory. 2. systems that transport position and tilt the ladle. One effective system is a manipulator (Fig. 1)--a manually-controlled machine that helps an operator move the ladle and pour molds. Manipulators let an operator pour molten metal quickly, precisely and safely because of simple movements of the manipulating arms that carry the ladle. The traveling pouring stallion stallion 1. an entire male horse aged 4 years and over. 2. in UK, applied to a male donkey (jack). stallion ring see stallion ring. teaser stallion stallion used to detect those mares which are in estrus. , used for iron pouring on straight molding lines with different rates of production, is a typical design of a mechanically-operated pouring station. The ladle is transferred and teamed by two different mechanized systems. One system combines a traveling gear and a hydraulic ladle tilting device to move a standard conical ladle or a drum-shaped ladle along the molding line. The other system uses a set of powered roller tracks to exchange an empty ladle for a full one. Automatically-Operated Ladles The use of automatically-controlled devices for the transporting and teaming of ladles provides a correctly-performed pour and almost entirely eliminates human involvement in all stages of the pouring process, ultimately increasing productivity and reducing cost. The automatically-controlled ladle also may be coupled with automatic molding lines and associated machines, stabilizing the pouring process and improving quality control and working conditions. A typical example of these pouring machines is an automatically-operated, specially-designed tundish tun·dish n. 1. A funnel. 2. A container for pouring molten metal into a mold, having holes in the bottom to prevent splashing. ladle with a controlled stopper rod. This device is placed on the support frame and a hydraulically-activated position system. It has a tundish ladle, which is lined with refractory and equipped with a thermal insulation The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer. Heat is transferred from one material to another by conduction, convection and/or radiation. cover. The tundish is divided into intake and pouring chambers by a removable refractory dam that separates slag from the poured iron. The size of the ladies may vary form 2200 lb-6600 lb (1000 kg-3000 kg)' depending on the weight of castings. The controlled stopper rod, located in the tundish's pouring chamber, regulates the molten iron flow by opening and closing the hole in the pouring sleeve. The level of molten iron in the pouring cup is controlled by intelligent sensors, either visual cameras or laser sensors. Automatic ladling systems (Fig. 2) utilize small ceramic pouring ladles (cups) for moving across short distances and pouring small amounts of iron. The ceramic pouring cup picks up enough molten iron to pour an entire mold from a holding furnace, and a servomotor ser·vo·mo·tor n. A motor that controls the action of the mechanical device in a servomechanism. [French servomoteur : Latin servus, slave + French moteur, motor drive system allows smooth movement of the arm by simultaneously rotating the ladle. The pouring process parameters are controlled by a computer with pre-installed programs for arm manipulation, allowing the pouring sys tern to work without control sensors. The ladling pouring system supplies precisely-dosed molten iron at a constant temperature into the mold without operator involvement. Removable ladies can be changed without special tools, but the unit's use is limited because it is designed for only low-weight castings. Another limitation of this system is a break in the pouring process while the holding furnace is recharging. Ladleless Pouring Systems The increased productivity of automatic molding lines has pushed precisely dosing automatic ladleless pouring systems to equal the consumption achievable with high production. Ladleless pouring systems are electric holding/pouring furnaces that require no ladles. They are equipped with additional devices that create special forces to move molten metal up to the mold. Pressurized pres·sur·ize tr.v. pres·sur·ized, pres·sur·iz·ing, pres·sur·iz·es 1. To maintain normal air pressure in (an enclosure, as an aircraft or submarine). 2. pouring furnaces with a controlled stopper rod (Fig. 3) are one of the most widely used ladleless pouring systems in the foundry. It utilizes an induction channel pouring furnace, and has a lined vessel with one intake and one pouring channel and a water-cooled inductor inductor, electric device consisting of one or more turns of wire and typically having two terminals. An inductor is usually connected into a circuit in order to raise the inductance to a desired value. that is positioned vertically or horizontally at the bottom of the vessel to serve as a heating element Noun 1. heating element - the component of a heater or range that transforms fuel or electricity into heat bar - a heating element in an electric fire; "an electric fire with three bars" . As the pressurizing gas (nitrogen or dry air) flows into the chamber above the melt, molten iron is forced into the pouring channel. During the pouring process, a float regulates the pressure of gas inside the vessel so molten iron in the pouring channel stays at a constant level. A laser sensor or video camera then measures the level of molten iron in the pouring cup and sends a command to close the pouring sleeve and start moving the molding line. It also controls the automated inoculation process. The tilt-pour furnace also provides foundries accuracy in pouring. The tilt-pour furnace is a vertical induction channel-type furnace with a bottom in the shape of a dish-head. The body of the furnace is designed as a pressure vessel Pressure vessel A cylindrical or spherical metal container capable of withstanding pressures exerted by the material enclosed. Pressure vessels are important because many liquids and gases must be stored under high pressure. with built-in teapot fill and pour spouts and a conventional throat-type inductor attached to the bottom of the furnace via a water--cooled throat extension. The cover is gasketed and bolted to the top plate of the furnace and has a small hatch for deslagging as well as two ports for checking inductor condition. Computer-controlled hydraulic cylinders tilt the furnace up and down, maintaining metal levels with an accuracy of [+-] 0.8 in. (20 mm). The tilt-pour furnace taps iron into an unheated tundish ladle equipped with a stopper rod that pours iron into the molds. There also has been a recent trend to use an electromagnetic field electromagnetic field Property of space caused by the motion of an electric charge. A stationary charge produces an electric field in the surrounding space. If the charge is moving, a magnetic field is also produced. A changing magnetic field also produces an electric field. for transferring and precise dosing of molten metal. This modification of the automatic pouring system also uses the channel induction furnace An induction furnace is an electrical furnace in which the heat is applied by induction heating of a conductive medium (usually a metal) in a crucible around which water-cooled magnetic coils are wound. , but it is combined with an electromagnetic unit electromagnetic unit n. Abbr. EMU Any of various systems of units for electricity and magnetism based on a system of equations in which the permeability of free space is taken as unity and by means of which the abampere is defined as the that produces a force capable of moving molten metal. The pouring furnace (Fig. 4) consists of a steel vessel lined with refractory bricks. In this system, molten iron is charged through the intake hole at the top of the vessel. When the furnace is charged, the intake hole is covered with a thermal insulating cover to prevent temperature losses and the contact of metal with air. An electromagnetic induction electromagnetic induction: see induction. electromagnetic induction Induction of an electromotive force in a circuit by varying the magnetic flux linked with the circuit. unit is attached to the bottom of the furnace and can be operated in two different modes--preheating or pouring. While in the pouring mode, molten iron is electromagnetically forced into the pouring pipe, up to the pouring channel of the furnace and dispensed into the mold. The level of molten iron in the mold's pouring cup is assessed by sensors that also command the unit to change the mode of operation. This system provides a non-contact influence on the molten iron and is flexible for a wide range of casting weights. However, the practical applications of this or similar furnace designs have shown frequent clogging in the pouring pipe or channel. Some attempts to use this system to pour ductile iron Ductile iron, also called ductile cast iron or nodular cast iron, is a type of cast iron invented in 1943 by Keith Millis[1]. While most varieties of cast iron are brittle, ductile iron is much more ductile, as the name implies. without a protective atmosphere have failed because of considerable slag build-up in the channel. Automatic Pouring Control Systems Since repeatability of pouring weight for each individual mold is one of the major requirements for automatically-operated molding lines and machines, precise computerized systems have been designed to control this parameter. Depending on the type of operations, two major systems may be used--laser sensors or video cameras. A laser sensor is typically used in straight sand molding lines. The major elements of this sensor are an optocator, which shines a beam of infra [Latin, Below, under, beneath, underneath.] A term employed in legal writing to indicate that the matter designated will appear beneath or in the pages following the reference. infra prep. red light on the metal surface. and a linear light sensor, which picks up the reflection of this beam. Using a triangulation triangulation: see geodesy. The use of two known coordinates to determine the location of a third. Used by ship captains for centuries to navigate on the high seas, triangulation is employed in GPS receivers to pinpoint their current location on earth. technique, the distance between the sensor and the metal level is computed. As the molten metal in the pouring cup reaches a certain level, the laser sensor gives a command to stop pouring and to start moving the pouring conveyor. Video cameras monitor the molten metal in the pouring cup and can be used with any type of pouring equipment and molding line. The camera is inserted into an air-cooled protection container and works with an electronic shutter (1) An opaque window that is moved in one direction to let light in and in another to close off the light. In fixed-lens cameras, one shutter often suffices for aperture and speed. that operates at speeds of 1/8000 sec. Because the molten iron emits bright light, the contrast between the metal in the pouring cup and the dark mold surface is clear. A computer digitizes information from the pouring cup and processes it, establishing the metal level in relation to the mold surface. As the computer receives information that the pouring cup has reached a certain level, it gives the command to stop pouring. Complicated Decision Pays Off The basic process of pouring poses complex issues for foundries. A properly-selected pouring method is essential because it significantly influences the quality and cost of castings, the casting yield and safety and labor intensity Labor intensity is the relative proportion of labor (compared to capital) used in a process. The term "labor intensive" can be used when proposing the amount of work that is assigned to each worker/employee (labor), emphasizing on the skill involved in the respective line of work. of production. A variety of factors go into the decision, but just as many benefits can come out of making the right choice. For More Information Powell W.L., Duca W.J., "Pouring Concept Extends Hold Times for Treated Ductile Iron," MODERN CASTING, May 2001, pp.48-49 Lerner, Y.S., Laukhin, N.U.., "Development Trends in Pouring Technology," Foundry Trade Journal, November 2000. pp. 16-21 Yury S. Lerner is a professor in the Department of Industrial Technology and the faculty advisor to the Metalcasting Center at the University of Northern Iowa The University of Northern Iowa, in Cedar Falls, Iowa, was founded in 1876, as the Iowa State Normal School. It has colleges of Business Administration, Education, Humanities and Fine Arts, Natural Sciences, and Social and Behavioral Sciences, and a graduate school. . |
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