Gating system, its purpose and device. Elements of gating systems Structure of the gating system

Gating system - a system of channels and casting mold elements that provide the supply of molten metal to the mold cavity, its high-quality filling and feeding of the casting during solidification. Its main elements are (Fig. 3.45): gating bowl 7, riser 2, slag trap 3, feeders 4 , extrusion 5, profit, zoom 6.

Gating bowl - an element of the gating system for receiving molten metal from a ladle and feeding it into a mold. In addition, a filled gating cup during pouring prevents slag from penetrating into the mold, which is lighter than metal, and therefore floats up and remains on the surface of the gating cup. When pouring from large ladles, a wide jet of metal can destroy the bottom of the bowl and the washed-out pieces of the mixture will fall into the mold. To avoid erosion of the gating bowl, its walls are made of a more durable facing mixture, and ceramic tiles are molded into the bottom.

The type of sprue bowl depends on the required volume of metal in it. It is convenient to make small sprue bowls recessed on the mold surface (Fig. 3.45, A), if between the bottom of the bowl and the mold cavity 8 a sufficient layer of the mixture remains. If the bottom of the bowl is located close to the mold cavity, then the metal poured into the bowl can push through a small layer of the mixture and destroy the top of the mold. In such cases, the sprue bowl is made not in the form, but in a separate small frame 7, placed on the surface of the mold above the riser (Fig. 3.45, b).

Riser - an element of the gate system in the form of a vertical or inclined channel, which serves to supply molten metal from the gate bowl to other elements of the system or directly into the working cavity of the mold. For the convenience of removing the model from the mold, the risers are made conical, expanding upwards. In small forms, the upper part of the riser ends with a small funnel that acts as a bowl (Fig. 3.45, V). When pouring large molds, in order to avoid erosion by the metal of the bottom of the riser under it (on the surface of the mold connector, in the lower flask), a recess is made, called a sump (Fig. 3.45, a, b).

Rice. 3.45. Gating system elements: 1 - sprue bowl; 2 - riser; 3 - slag trap; 4 - feeders; 5 - exudate; 6 - sumpf; 7 - frame; 8 - mold cavity

Slag trap - an element of the gating system for retaining slag, pieces of molding sand and supplying molten metal from the riser to the feeders. There are several designs of slag traps: trapezoidal, zigzag, spherical, stepped. In raw forms for artistic castings, slag traps with a trapezoidal section are most often used. Slag particles, falling with metal into the slag trap located above the feeders, float up and remain in it without penetrating into the mold cavity. In lumpy forms, the device of a slag trap that supplies molten metal from the riser to the feeders is not always possible. In these cases, to supply metal from the riser to the feeders, a channel is cut out on the surface of the mold connector, called the gate.

Feeder - an element of the gating system for supplying molten metal to the mold cavity. Feeders are most often located in the lower mold half under the slag trap. They should not be made in the place under the slag trap, where the riser enters it, since slag may enter the mold. In the forms of thick-walled castings, feeders are cut in the form of channels with a triangular section, in thin-walled castings - in the form of wide trapezoidal channels (Fig. 3.45, V). The thickness of such feeders should not exceed the wall thickness of the casting; otherwise, when the sprue is cut off, the wall of the casting will break out.

Upstream - an element of the gating system for removing gases from the mold during pouring, controlling the filling of the mold with molten metal, feeding the casting at the time of its solidification, softening the impact of the metal jet on the upper wall of the mold cavity at the end of pouring, draining cold metal from the upper part of the mold cavity.

Pouring, in which part of the cold metal is drained from the mold cavity through the uplift, is called bypass pouring. When pouring a mold with bypass, the level of metal in the bowl should be slightly higher than the level of metal in the riser. In casting molds, the cavity of which is located in the lower flask, the riser is made in the form of a riser at the end of the mold opposite from the gating system (Fig. 3.46, A). Such an extrusion is called a diversion. In addition, it can be power and signal.

Rice. 3.46. Ejection and profit device: A- discharge outlet; b - extrusion in the upper part of the form; V - casting without profit; g - casting with a profit

In molds whose cavities are located in the upper flask, the bulge is placed in that part of the mold cavity that is located above all the others (Fig. 3.46, b). If the vent is placed in a part of the mold that is located below the others, gases and slag, which always accumulate in the upper part of the mold, may not get into it, and therefore remain in the mold, forming gas or slag shells.

Profit. During the shrinkage of the metal in the mold, shrinkage cavities can form in the walls of the casting. Most often they occur where the metal remains in a liquid state for a long time, i.e. in thick sections of the casting (Fig. 3.46, V). In thin sections, shells cannot form, because the shrinkage that occurs during solidification is compensated by metal from adjacent, thicker sections of the casting, which are still in a liquid state.

Thus, shrinkage cavities are located in the thickest parts of the casting, which are the last to harden. If, during the solidification of the casting, liquid metal is added in a timely manner to the place where the shrinkage cavity is formed - to feed the casting, then there will be no shrinkage cavity in it. This technique in the production of castings is used as a means of combating shrinkage cavities.

The feed of the casting at the moment of its shrinkage is carried out due to the liquid metal of the gating system element arranged in the mold above that part of the casting where the formation of a shell is possible. Such a cavity in the form is called a profit (Fig. 3.46, G). But such a profit can feed the casting only if the metal in it is still liquid at the time of the formation of the shell in the casting and solidifies after the solidification of the fed node. Therefore, in order to keep the metal in the liquid state in the profit, its cross section and dimensions must be greater than the dimensions of the part of the casting that it feeds. Under this condition, shrinkage cavities will not form in the casting, but in the profit, which will subsequently be removed. Profits can be closed and open. On fig. 3.46, d shows a part of a pipe casting with a flange and an open profit.

The method described above for the arrangement of heads as a means of combating shrinkage cavities in castings is uneconomical due to the high consumption of metal and the complexity of the operation of cutting off the heads. There are more profitable ways to supply castings with the help of heads with atmospheric and gas pressure, which can significantly reduce the size of the heads. The principle of operation of a profit operating under atmospheric pressure is that a sand rod is inserted into its cavity before pouring, through which atmospheric pressure is transferred inside, which contributes to the supply of liquid metal to the fed node.

A cartridge with chalk is inserted into the profit operating under gas pressure. Decomposing during filling, it releases gas and creates increased pressure in the profit. The wall thickness of the cartridge is made such that it melts after a crust of solidified metal has formed on the surface of the nose.

Used in the casting of large products, open profits are heated to reduce their size by adding metal, backfilling with heat-releasing materials (ground slag, charcoal, lunkerite). Open profits are heated by lining them with exothermic mixtures, which include aluminum powder, ferrosilicon, iron scale, fireclay powder and refractory clay. During a chemical reaction between the components of the mixture, heat is released, which heats the profit. Exothermic heating of the profit allows to reduce its size by 8-9%.

Profits are made direct and diversion. Diverting profits are used to power local thermal units and several small castings. Unlike straight lines, they are located on the side of the fed node and connected to it with a massive neck.

Each of the elements of the gating system has its own purpose, and therefore improper manufacture of it can cause marriage in the casting. Therefore, in the mass production of castings, it is more profitable to use pre-made models of the gating system, which have a calculated cross-sectional area and the correct profile.

The production of castings can significantly reduce labor costs for processing parts, removing excess material. The gating system is used to transport the melt from the ladle to the mold. It evenly fills the voids, guarantees the crystallization of the metal without the formation of stresses. The gating system is a complex structure of channels that regulate the speed and pressure of the melt. With its configuration, it contributes to the floating of slag into the profit.

When the casting is removed from the sand, the LS looks rough. It gives the impression of excess metal around the part. In fact, air is removed through the details of the gating supply system during the pouring process and slag is separated, and shrinkage during cooling is fed by metal. LPS regulates the pressure to fill all elements of the workpiece. As a result of correct calculation, the structure of the resulting casting is dense and uniform throughout the entire section.

Purpose of the system

Transportation of the liquid melt without destroying the walls, uniform filling of the mold cavity at a constant speed is considered the purpose of the gating system. At the same time, a labyrinth of passages from risers, feeders and profits:

• separates slag from metal;
• does not pass and separate air;
• removes accumulated gases;
• regulates crystallization;
• nourishes the form when cooled.

The shape of the parts of the gating system prevents the surface of the cooling casting from contacting with air, ensures uniform cooling without transition zones and places of rapid crystallization.

Foundry production includes the creation of contours of manufactured parts with the necessary technological biases and machining tolerances. After that, a power system is made in the molds - LPS. It is calculated taking into account the uniform filling of the entire void based on the shape of the future part and the thickness of its walls.

The location and type of the gating system is selected based on the configuration of the workpiece, its dimensions. The metal must fill the entire space evenly, at the same speed, without destroying the inner walls of the mold.

Essential elements

The gating system is a complex structure with several elements. Every detail plays its role and it is impossible to remove it.

The elements of the gating system include:

• outer cone;
• vertical conical riser;
• feeder;
• gate.

Liquid metal falls from the ladle into the bowl - a cone-shaped inverted funnel. It is easier to get into the wide outer part of the cone with a jet of liquid metal than into a narrow channel. At the same time, the air accompanying the jet is squeezed upwards and does not get inside. The gating bowl is used in all designs of filling systems. The size of the cone is selected according to the size of the casting, its weight. The outer cone regulates the speed of movement of the melt through the gating system and the pouring time.

Heavy liquid rushes down the narrow riser, reducing the speed of movement. Regardless of the direction of the cone, the section of the riser is much smaller than the funnel.

Under the riser there is a small conical expansion and a recess - a sump that prevents splashing. It collects liquid metal and extinguishes the energy of the jet by analogy with a reservoir under a waterfall. If the jet falls on a solid surface of the mold, it will break it. Small splashes will quickly solidify, forming shells and discontinuities in the total mass of the material.

From the sump, the liquid flows from the bottom up, flowing into the gate passage and pushing the slag to the surface. This allows you to reduce the length of the moves, rationally use the metal.

Sprue runs are always made in the parting plane. They have a trapezoidal section and divide the total flow into several, distributing it evenly over the feeders, along the entire length.

The LPS feeders are the last of its elements. They are distributed over the entire area of ​​the connector and evenly fill the void of the future casting.

In addition to the nutritional system, the following are installed in the upper part of the part: profit and uplift. The first serves to accumulate slag and replenish shrinkage. When cooled, the part decreases in size, sags, and the metal replenishes the level from the profit. The number of profits depends on the configuration and area of ​​the casting. For example, the flywheel is poured. Its axis is vertical. One profit is installed above the hub if the part is up to 0.5 tons. For larger sizes, slag cones are also made along the rim.

Through the vent located in the upper part of the mold, gases escape outside, which nevertheless got inside the mold and rose up. It is allowed to combine the uplift with the central profit.

After complete cooling, the part is knocked out of the mold, and chopping is performed - all feeders and profits are cut off with an autogenous or jackhammer. The length of the remaining section depends on the steel grade. For high-alloy steels, it is 80–150 mm and is finally removed by machining after annealing. High-alloy steels and cast iron are annealed together with the gating system or only the risers, only after that the chipping is performed. Heat treatment is done immediately after removing the casting from the mixture, to relieve stress and reduce hardness.

Methods for calculating the gating system are based on the speed of complete filling of the mold. They determine, first of all, the cross-section of feeders, their number. The calculations are based on hydraulic formulas and the height of the risers that create pressure. For cast iron and steels of different grades, the ratio of the areas of feeders, risers and risers is different, based on the fluidity of the material, wall thickness. In addition, a correction factor is introduced into the formula, the value of which depends on the weight of the casting.

System types

The type of LPS is defined as the best option between fast and uniform filling of the mold and minimal metal loss in the channels. Various types of systems are used.

In many ways, the design depends on the brand of material. For small parts made of non-ferrous metals and cast iron up to 20 kg, injection molding is performed. Its principle is to fill the first part of the mold with liquid metal, then quickly, under high pressure, press the melt into the second half, which is directly the shape of the part. Rapid crystallization by means of a cooling system and after a few seconds the casting is removed.

The high cost of a mold, up to $100,000, and the production time of 2–3 months make single castings fabulously expensive. It is cost-effective to use pressure molds with their capacity of 10-50 castings per hour, in mass production.

The destructive method - casting aluminum in sand according to investment patterns, allows you to melt products with complex configurations.

The peculiarity is to create an exact copy of the part from wax or other low-melting material and place it in sand with one feed channel. Pouring is carried out vertically, without loss of metal in LPS. It is distinguished by a large number of vents through which gas escapes from the burnt model.

For steel and cast iron products weighing more than 50kg, the horizontal gating system is mainly used, more convenient design to match with connectors. The vertical design of the feeders is suitable for non-ferrous alloys and high melting point metals that are cast. Gating system types and calculations are influenced by part characteristics:

• weight;
• the ratio of length and width;
• Wall thickness;
• configuration complexity.

Types of gating structures are distinguished by the direction of pouring: vertical for low parts with a large area, and horizontal, if the height of the casting is greater than the width.

By way of supply

Melts can be supplied to LPS at different levels:

• above;
• side;
• bottom;
• vertically in height;
• combined in several lines.

According to the way the feeders are located, types of LPS are distinguished.

Upper

With the top system, the feeders are on the same level with the sprues. This method is most often used to obtain thin-walled cast iron castings. The metal is poured from above. With a complex configuration, it flows along the lower jumpers to the other side of the form from the bowl and riser. In order to fill quickly, with thin jumpers on the side of the riser, a thickening is made in the form. When processed on the machine, it is removed.

The top sprue system is the simplest in execution, characterized by fast direct filling of the mold with metal. It leads to uniform crystallization and minimal material consumption for filling the supply channels. When knocked out, the casting is easily released from the molding sand.

A characteristic disadvantage is the cascade discharge of liquid metal. This leads to air entrapment and mixing of the metal with the slag. As a result of active flow, foam is formed. The slag lingers in the collector without leaving the sprue. The melt falls into the mold from a great height and the sump does not prevent the destruction of the walls, the bottom of the mold and the cores by the hot jet. Splashes are formed.

Disadvantages of the upper gating system are eliminated by canting or tilting the mold. Top pouring is used for parts with a height of less than 100 mm.

For thin-walled hollow parts, a rain system is used - a kind of upper one. Feeders are installed along the perimeter from above and evenly fill the casting. Crystallization occurs from the bottom up, the shrinkage of the material is compensated directly from the feeders. When pouring massive parts, the rain system is combined with sprues.

Lower

The molten metal is fed by feeders to the bottom of the mold. The pressure is created by a high-placed bowl and long risers with a reverse cone - narrowed towards the bottom. Filling the form from below occurs evenly, without oxidation and foaming. Non-metallic inclusions are retained without getting into the base metal. Entering from below, along the gating channels, the melt displaces air, gases, and slag into the profit.

The disadvantage of the gating structure is overheating of the lower part of the mold and large shrinkage during crystallization. This is especially noticeable on non-ferrous metals, their alloys, cast iron. Shrinkage cavities can descend into the main body of the part. in high-alloy steels, transitional stress zones are formed when the lower part is overheated and the upper part is rapidly cooled.

The calculation of the gate system for aluminum with its high thermal conductivity includes a cooling system and additional metal to compensate for shrinkage, increased height of the gates and feeders.

Lateral

Easy-to-use gating system. Its parts are mostly located in the plane of the connector. The melt fills the upper part of the casting from below and flows down from above. The walls are not destroyed, foam is not formed. Filling occurs smoothly, calmly across the entire width of the void.

A variation of side pouring is a vertical slotted gating system used for the manufacture of parts of great height. In it, the feeders are located on the side, vertically along the axis of the part. The system is suitable for castings with variable section, thin walls and sharp transitions. The melt is introduced calmly, fills the mold well. Slags and particles of the sand mixture are separated in the collector. The crystallization process proceeds evenly, from bottom to top.

The weak point of the vertical slot design is the foaming of hot liquid at the initial moment of pouring. In places near the feeders, overheating and shrinkage of the metal may occur. The vertical slotted gating system is difficult to make, knock out of the mold and remove.

Longline

Large parts are filled simultaneously by two or more feeder lines. They are placed horizontally or vertically in the plane of the connector, increasing the number of mold sections. The metal flows into the mold from above and below, evenly filling a large volume. The crystallization process occurs throughout the volume.

If a tiered system is located horizontally, the calculation is made with correction factors that take into account faster filling of the void through the lower gating feeders with high pressure. Alignment of the speed of movement of the melt is carried out by reducing the cross section of the lower feeders.

With a tiered casting system, a uniform flow of metal occurs in different planes. The risk of creating transition zones during crystallization is reduced. Shrinkage occurs slowly, with the filling of voids with melt.

For tall parts, the feeders are arranged vertically in 2 lines. The metal is fed through risers from below. The filling is uniform and quiet, without air entrapment. Gases and slag rise along with the base metal upwards, filling the profit.

Combined

The combination of several types of gate structures into one design allows you to compensate for the shortcomings of some with the advantages of others. Such systems are created when parts with a large mass and complex configuration are cast into sand molds. If the part has a cross-section at the edges larger than in the middle, the feeders are brought to the lines of the largest dimensions. As a result, the largest by mass elements are filled. Then the middle is poured. Crystallization begins along the perimeter simultaneously in all parts of the casting.

Complex configurations require the simultaneous flow of the melt into all elements connected by thin partitions. The combination of sprue structures allows metal to flow simultaneously to all places.

The smaller the part by weight, the simpler the gating system. For large castings with a large number of transitions, tiered and combined runner systems are installed. The design is simplified by combining its elements. For example, uplift and profit, pouring through slag collectors.

You may also be interested in articles:

Types of casting metals and alloys

One of the most important conditions for obtaining a high-quality casting is the correct arrangement of the gating system. Gating system serves for a smooth supply of liquid alloy into the cavity of the casting mold and for feeding castings during crystallization. The location of the alloy supply to the casting largely determines its density, appearance and the formation of various casting defects. Choosing a gating system that produces good quality castings is the most difficult part of foundry technology. Therefore, the molder, foreman and technologist, when choosing a gating system, must take into account the features of the foundry technology.

A properly constructed gating system must meet the following requirements: 1) ensure good filling of the mold with metal and feed the casting during its solidification; 2) contribute to the production of a casting with accurate dimensions, without surface defects (blockages, uzhimin, slag inclusions, etc.); 3) promote directional solidification of the casting; 4) metal consumption for the gating system should be minimal.

Gating funnel for small castings and gating bowl-reservoir for large castings, they are designed to receive a jet of metal flowing out of the ladle, and to retain slag that enters the bowl along with the metal. When the bowl is full to the brim, pure metal enters the riser, and light slag is at the top. In addition, a continuous supply of metal into the mold at the same pressure is ensured. To retain slag, the openings of the risers are sometimes closed with cast-iron plugs, thin tin plates. Corks are opened after the entire bowl is filled with metal, while the plates are melted with hot metal. The mold must be filled with metal as quickly as possible, while the metal must have a sufficient temperature.

During the pouring of metal, the gating cup must be full. If the depth of the metal is not deep enough, a funnel is formed in the bowl, through which air and slag floating on the surface of the metal can enter the riser and then into the casting. For small castings, especially in conditions of mass production, the slag in the bowl is retained by filter grids, which are made from the core mixture.

Riser- a vertical channel that transfers the metal of their funnel to other elements of the gating system. It is performed somewhat tapering downwards for ease of molding and providing hydraulic pressure in the gating system. The taper of the riser is 2-4%. In the manufacture of large castings, the riser and other elements of the gating system are often made from standard fireclay tubes-bricks.

Slag trap serves to retain slag and transfer metal free of slag from the riser to feeders; is located in the horizontal plane. Usually, the slag trap is made in the upper half of the mold, and the feeders - in the lower one. The cross section of the slag traps is made trapezoidal. In the process of filling the mold with metal, for better retention of slag, the slag trap must be filled with metal. This is ensured by the appropriate ratio of the sections of the riser, slag trap and feeder. If the flow of metal through the riser is greater than the flow through the feeders, then the slag trap is filled with metal and the slag, floating up, lingers in it. If the flow through the riser is less than the flow through the feeders, then the slag trap will be empty and the slag will enter the casting. Thus, in order to retain slag, the cross section of the riser must be greater than the cross section of the slag trap, and the cross section of the slag trap must be greater than the total cross section of the feeders. Such a gating system is called locked.

Feeders(gates) are channels for supplying liquid metal directly into the mold cavity. The cross section of the feeders should be of such a configuration that the metal enters the mold cavity smoothly, cools a little on the way from the slag trap to the casting, and after hardening, its feeders easily break off from the casting. It has been established by practice that the best cross-sectional configuration of feeders is a trapezoid with a transition to a wide rectangle at the point of conjugation with the casting. For better separation of feeders from castings, if the thickness of its body is less than one and a half height of the feeder at the place of its supply to the casting, a pinch is made on the feeders at a distance of 2-2.5 mm from the casting.

vypory serve to remove gases from the mold cavity and to feed the casting. They also reduce the dynamic pressure of the metal on the mold and signal the end of pouring. Depending on the size of the form, one or more bulges are placed. The section of the bulge at the base is usually 1/2 -1/4 of the section of the wall of the casting. Above the base, the section of the bulge increases.

Among the elements of the gating system that supply the casting with liquid metal in the process of its solidification, are feeding upstreams and risers.

Gains and nourishing outbursts used for castings from white low-carbon, high-strength cast iron, as well as for thick-walled castings from gray cast iron. They serve to feed the thickened places of the casting, which are the last to solidify. Profits are arranged so that the metal in them freezes last. The thickness of the profit must be greater than the thickness of the place of the casting over which it is placed. Profits of large sizes are economically unprofitable, since the consumption of metal for profits and the cost of castings increase.

When constructing profits, the following rules must be followed:

Profit should solidify later than the fed casting unit.

The dimensions of the profit must be sufficient to compensate for the shrinkage of the castings.

The height of the profit must be such that the entire shrinkage cavity is located above the neck of the profit - the junction with the casting. The neck should be as short as possible and, just like the profit, harden after casting. If the casting has several thickened places separated by thin walls, then a separate profit must be placed for each thickening.

Most often profits are used in the manufacture of castings from steel and non-ferrous alloys.

casting mold bushing core

Types of gating systems

TO Category:

Foundry

Types of gating systems

Gating system is a set of channels and reservoirs through which liquid metal from the ladle enters the mold cavity. The gating system has a significant impact on the quality of castings; incorrectly designed or incorrectly calculated, it can be the reason for the rejection of castings.

The main elements of the gating system are as follows.

Gating funnel or bowl - a reservoir designed to receive liquid metal from a ladle, partially retain slag (in a bowl) and transfer metal to a riser.

Riser - a vertical (sometimes inclined) channel of a round, oval or other section, designed to transfer metal from a bowl (funnel) to other elements of the gating system (slag trap, feeders).

Rice. 1. Elements of the gating system

The runner, called a "slag trap" for iron castings and a collector for non-ferrous castings, is a horizontal channel designed to hold slag and transfer riser metal to feeders.

Feeders (sprues) - channels designed to transfer metal directly into the mold cavity.

Rice. 2. Types of gate systems: 1 - bowl (funnel); 2 - riser; 3 - sprue; 4 - feeder; 5 - extrusion; 6 - casting

Gating systems are divided into five main types:
1. Upper gating system (Fig. 2, a). Feeders are brought either to the upper part of the casting, or to the head or under the head.
2. Lower or siphon gating system (Fig. 2, b). Feeders are fed into the lower part of the casting.
3. Lateral gating system (Fig. 2, c). The feeders are brought along the form connector.
4. Tiered (storey) gating system (Fig. 2, d). The feeders lead to the casting at several levels. A variation of the tiered gating system is the vertical slotted system (Fig. 2, e).
5. Rain gating system.

The gating system is chosen depending on the type of metal, the design of the casting, its position during pouring, etc.

We always strive to ensure that, while ensuring the required quality of the casting, the metal consumption for the gating system is the lowest. If this condition is met, the yield of a suitable casting increases (the ratio of metal consumption for casting to the total metal consumption, taking into account the gating system and profits).

The top gating system is the simplest in design, easy to implement, and requires little metal consumption. It creates the most favorable conditions for feeding the casting, i.e. creates the temperature distribution necessary for directional crystallization - an increase in temperature from the bottom of the casting to the top.

However, the upper gating system has a significant drawback, namely, when a metal jet falls from a great height, the mold is washed out and blockages form; the metal oxidizes, splashes, and the number of non-metallic inclusions increases in it. In addition, the top gating system does not provide slag retention. Therefore, it is used for low castings of small mass, simple configuration, with small and medium wall thicknesses.

The lower (siphon) gating system ensures smooth filling of the mold, eliminates the risk of wall erosion and clogging. However, the lower metal supply creates an unfavorable temperature distribution over the volume of the casting metal (since the hot metal enters from below), contributes to the development of local heating and internal stresses.

The siphon gating system is difficult to manufacture and requires an increased consumption of metal; it is usually used for castings of medium and large mass of considerable height, with a large wall thickness.

The supply of metal along the parting is one of the most common ways of pouring molds of various castings, especially castings whose symmetry plane coincides with the parting plane of the mold.

The side gating system, by reducing (compared to the top) the height of the fall of the metal and the possibility of mold destruction, at the same time worsens the conditions of crystallization and increases the consumption of metal. It is used for castings of small height, medium weight, large sizes; widely used in machine mold making.

The tiered gating system is used for large, heavy castings. It provides better casting feed than a siphon gating system. The tiers of the system must feed the metal into the mold cavity sequentially, from bottom to top. The tiered gating system is the most difficult to implement and requires the highest metal consumption. The vertical slot gate system, which ensures smooth filling of the mold while maintaining the direction of solidification, is used for casting non-ferrous alloys.

The rain gating system is mainly used for cylindrical castings. The metal from the riser enters the annular collector, from which, through the feeders located along the circumference at an equal distance from each other, it evenly fills the mold cavity located below in thin streams. In this case, the metal should not be splashed, since the metal drops quickly harden, oxidize and do not weld with the base metal, forming defects in the castings, called queens,

In addition to the choice of the type of gating system, the choice of the location for supplying feeders to the casting is of great importance. Depending on the properties of the alloy, the design of the casting (overall dimensions, wall thickness), when metal is supplied, they strive to ensure either directional solidification or simultaneous uniform cooling of various parts of the casting.

For castings with thick walls, massive knots, prone to the formation of shrinkage cavities, it is necessary to create conditions for directional crystallization. This is achieved not only by the appropriate location of the casting in the mold, when the more massive parts are located above the thin ones, but also by the appropriate supply of metal to the most massive parts of the casting. Such a supply of metal enhances the effect of directional solidification. Therefore, steel, which has a large shrinkage and low fluidity, is brought into the thick section under the head in order to heat up the mold near the head and improve the nutrition of the hardening casting. They are also used in the manufacture of castings from special bronzes, brasses, and some aluminum alloys. Sometimes steel is poured directly through the profits.

However, if, due to an excessively large difference in the cooling rates of the individual parts of the casting, there is a danger of stresses and cracks, then to reduce the difference in cooling rates, the metal is brought into the less massive parts of the casting.

Simultaneous and uniform solidification and cooling of the casting is achieved by supplying metal to the thin parts of the casting and the appropriate arrangement of feeders, which ensures symmetrical and uniform filling of the mold. This reduces the risk of internal stresses, warpage and cracks. A similar supply of metal is used in the manufacture of castings of great length with walls of various thicknesses.

Tapering gating systems better trap slag, reduce air injection, and increase the linear velocity of metal passing through the channels of the gating system. They are used in casting alloys that are not prone to oxidation, forming fragile oxide films.

Expanding gating systems reduce the speed of metal movement, ensure smooth filling of the mold cavity without metal oxidation. They are used in casting alloys prone to oxidation, forming strong oxide films.

Gating system is a system of channels through which molten metal is fed into the mold cavity. The gating system must ensure that the casting mold is filled at the required speed, retaining slag and other non-metallic inclusions, escaping vapors and gases from the mold cavity, and continuously supplying molten metal to the hardening casting.

According to the hydrodynamic feature, narrowing and expanding gating systems are distinguished.

Tapering gating systems are characterized by a consistent decrease in the cross-sectional areas of the riser, slag trap and feeders F st >F sl >F pit. This gating system ensures rapid filling of the entire system with melt and better slag capture. However, the melt enters the mold cavity at a high linear velocity, which can lead to splashing and oxidation of the melt, air entrapment and mold erosion. Such gating systems are used in the manufacture of cast iron castings.

In expanding gating systems, the bottleneck is the lower section of the riser: F st

Depending on the configuration and wall thickness of castings 5, the composition of the poured alloy and the direction of its flow into the mold cavity, it is divided into side (Fig. 4, a), lower (Fig. 4, b) and upper (Fig. 4, c).

Rice. 4. Methods for supplying molten metal to the mold cavity

For the side gating system (Fig. 4, a), it is characteristic that the feeders and slag traps are located in the horizontal plane of the mold parting, which is convenient in terms of molding.

In the lower gating systems (Fig. 4b), the melt enters from below under the flooded level without splashing, oxidation and foaming, which is very important in the manufacture of castings from easily oxidized film-forming alloys (aluminum, magnesium and others).

In the upper gating systems (Fig. 4c), a hot melt mirror is provided throughout the pouring, which contributes to upward solidification. Such gating systems are used in the manufacture of iron and steel castings.

The main elements of gating systems are as follows (Fig. 4).

Gating bowl (funnel) 4 is designed to receive a jet of melt flowing from the pouring ladle, and to retain slag that enters the bowl with the melt.

Riser 3 - a vertical channel that transfers the melt from the gating bowl to other elements of the gating system.

The slag trap 2, located horizontally and, as a rule, in the upper half of the mold, serves to retain the slag and transfer the melt from the riser to the feeders.

Feeders 1 - channels designed to supply the melt directly into the mold cavity. Feeders must ensure a smooth flow of the melt into the mold cavity. Usually the feeders are located in the lower mold half.

Upstream 6 serves to remove gases from the mold cavity, signals the completion of pouring, reduces the dynamic pressure of the melt on the mold, and contributes to feeding the casting with melt during solidification.

The collector 7 is a distribution channel for directing the melt to various parts of the casting. It is placed horizontally along the mold connector. It must always be filled with molten metal.

The sections of the elements of the gating system are selected on the basis of an approximate calculation, which allows you to establish the relationship between them (usually between the riser, slag trap and feeders).