Category: Blog

Welding and assembly production

Welding is considered one of the most efficient methods of production on rolled metal products. It is used to create both large-sized complex structures and small items where high precision manipulation is required. Welding works are used quite widely. They are used in such areas as mechanical engineering, transport and construction. This fact is due to significant savings in material (compared to riveted or bolted connections), as well as the high strength of welded structures, their affordable cost.

Types of welding work 

It is customary to classify welding according to the condition of the metal in the welded area. The first class – by the way the welded parts of the structure are joined (here the welding can be performed by one of two methods: by pressure or fusion). The second class – by the type of energy used (here we distinguish thermal, thermomechanical and mechanical welding).

Pressure welding has a number of advantages (compared to fusion). Less thermal effect on the metal (lower heating temperature). Accordingly, the material is not exposed to harmful effects that change its properties. Also, the operation requires much less energy.

There are also certain “disadvantages” of this method that limit its application. These include the necessity of using sophisticated equipment, which provides high compression forces on the parts to be welded. Furthermore, at the time of welding, it is important to ensure that the surfaces are as clean as possible. Otherwise, the strength of the joint cannot be guaranteed.

Pressure welding includes the following types: 

-Diffusion;

-Contact;

-Explosion;

-Friction;

-Electrosound.

Fusion welding is considered the more versatile method. It is important to have a powerful heat source that provides local heating until the parts to be welded melt. Sophisticated welding machines are not needed here. Unlike the first option, the heat source is brought to the product (rather than the other way around), which expands the possibilities, allowing for large-scale construction.

Fusion welding includes:

 -Electroslag;

-Beam;

-Laser;

-Thermite;

-Electron-beam;

-Gas.

Assembly work

Assembly is also a technological process that is part of the final stage of part processing. It includes the work of joining the elements into a single structure.

Assembly is performed before the welding work. Although they are so closely related to each other that they are usually performed in the same shop. During assembly, the following types of tools are used: marking, measuring, assembly and inventory tools.

Welded structures are divided into two types: lattice and spatial. The first include radio masts, radio towers. The latter are transmission line supports, light poles, towers, masts and so on. For each of the above-mentioned types of structures, the stages of assembly, docking and welding directly apply.

Deep drilling

Drilling is a mechanical process whose purpose is to create holes using rotating tools. Holes are usually divided into regular holes (10 cm or less in depth) and deep holes (10 cm or more in depth). In deep drilling, the depth of the hole can be 150 times its diameter. Normal drilling implies a depth of no more than 5 hole diameters.

A hole with a depth of ten or more diameters is machined using deep hole drilling technology with specialized equipment. This technology is used in various production areas: steel, nuclear power, oil and gas, aerospace, and so on. Always the most important parameters of the final result are the highest quality of machining, geometric accuracy and the specified dimensions of the hole.

Another important factor that determines the quality of hole machining is the formation of easily evacuated chips and their direct removal from the finished hole. To obtain quality results when drilling deep holes, it is important to ensure that the chips are crushed. In this way, chip buildup and the resulting damage to the machined surface can be avoided.

Deep hole drilling belongs to the category of continuous processes. It is therefore considered to be more productive and of higher quality than other processes.

Used tools

Special tools are used to produce deep holes. It is customary to distinguish between three types of machining systems:

-Ejector (double rod).

-STS (single rod).

-Joule (tube and lobe) drills.

The ejector system uses two tubes, which are a one-in-one design. They are connected to the drill head. The cutting fluid (coolant) flows inside the drill, into the gap between the rods. The chips are flushed out through the inner cavity. The advantage of this method is that no high pressure is required for lubrication (compared to the single rod method). It is usually used for medium batches.

The second STS system consists of a single boom, and the fluid is fed through a special device that is placed on the end face of the workpiece. The coolant is fed at high pressure, flushing the chips, similar to an ejector system, through the boom. This ensures that the chips come out quickly without lingering, leaving no destructive marks on the walls of the hole. The single-bar system itself is considered more reliable.

STS drilling is used for low-carbon and stainless steels, that is, with materials that have strong chip formation. But since this method requires special equipment, it is most profitable and effective for large-scale production.

The use of gun drills (another name) or shot drills differs in the way the chips are washed out. Its exit is provided through an external V-shaped groove, which is equipped with a drill bit. Tubular drills are equipped with machining centers. The main condition for high quality machining is to provide the necessary coolant pressure. This method eliminates the need for countersinking and reaming.

Machine equipment

There are different types of machines for which deep hole drilling is the primary process. Most of them are machines for producing holes in metal rotating cylinders. The tool itself (the drill bit) is simply moved at a certain feed rate. This operating principle is similar to a lathe. This equipment allows you to perform machining with a high level of accuracy, while at the same time it is characterized by the productivity of a medium level. However, this method is only suitable for holes centered on the axis of the workpiece.

However, for maximum holemaking accuracy and productivity, machines in which the drill bit and workpiece rotate simultaneously, but in the opposite direction to each other, can be used. If eccentric holes and heavy workpieces need to be machined, machines with rotating tools are used.

Deep Hole Drilling Machines come in different types: horizontal or vertical, rotary and multi-spindle. Some of them can perform additional manipulations, such as boring.

Since in deep hole drilling the supply of coolant under pressure at a certain flow rate is considered mandatory, the system must be equipped with pumping equipment: an oil pump or a pump for pumping viscous fluids. The flow and the required pressure of the coolant have a direct influence on the performance of the equipment.

METAL PROCESSING (BORING, HEAT TREATMENT)

Coordinate-boring work

A wide variety of technologies are used for machining metals. Coordinate-boring is one of their varieties, which is the final stage of this type of machining of workpieces. For quality results, boring, drilling and milling techniques are used with different degrees of accuracy.

A wide variety of technologies are used for machining metals. Coordinate-boring is one of their varieties, which is the final stage of this type of machining of workpieces. For quality results, boring, drilling and milling techniques are used with different degrees of accuracy.

Classified by two types of this plan of work: machining horizontal-boring, vertical-boring. They are performed on holes obtained by casting. The purpose of boring operations is to enlarge a given hole, increase its size and achieve a certain diameter. This also eliminates the surface roughness of the workpiece.

The performance of work on specialized boring machines operating at low speeds makes it possible to obtain high-precision, down to tenths of a millimeter in the result.

Despite the similarity of coordinate boring processes with drilling and milling, their main feature is the ability to perform unique operations.

Such as:

– High-precision machining in grooves;

– Obtaining tapered holes;

– Milling at different angles. 

And as related work are: drilling holes, finish milling the ends, marking, checking intercenter and countersinking holes.

And as related work are: drilling holes, finish milling the ends, marking, checking intercenter and countersinking holes.

Special machine equipment used in coordinate boring operations has a number of advantages. As a rule, machines are equipped with rotary tables, which allow performing operations with high accuracy:

  • Machining of holes specified in a polar coordinate system;
  • Operations in inclined surfaces;
  • Perpendicular holes;
  • Countersinking of end holes.

Additional digital indications on the machines help to clearly and accurately set the coordinates for certain operations.

Center-to-center distances can be set to an accuracy of 0.004 mm in the coordinate system, and the accuracy between axes is 0.006 mm.

Thermal metalworking

Heat treatment of metals is a technological process that is an essential step in the manufacture of parts made of carbon and alloy steels. It always has a positive effect on the performance qualities of the metal, respectively the finished product. It is used to obtain higher parameters of strength, hardness, wear resistance, elasticity, or on the contrary, softness, malleability.

There are three main types of heat treatment:

–  Annealing

– Normalization .

– Tempering.

The first is a high-temperature metalworking technique. First the alloy is heated to a certain high temperature, then it is kept for some time and subjected to a slow gradual cooling. The purpose of annealing is to level the structure of the metal, improving its ductility and relieving stress.

Annealing is divided into several types: first type, diffuse, second type, complete and incomplete, spheroidizing, isometric, recrystallization, light. Each of them makes it possible to achieve certain structural changes in the metal, bringing it to the desired state.

Normalization is a high-temperature treatment of the metal. The steel is heated 30-50 degrees above the temperature of the upper critical points of AC3 or ACm. Then the product is subjected to cooling, which takes place slowly outdoors. The normalization process has two purposes: the first is the elimination of hardening and the second is the removal of internal stress. Normalization is mainly carried out on carbon and low carbon steels. The result of the process is a fine-grained structure of the metal.

Quenching is necessary when you want to give the metal hardness and strength. Unlike normalization, the cooling stage takes place at high speed, in water, oil or other liquids. The process results in a hardened material with a nonequilibrium structure.

The heat treatment of metals has a number of positive characteristics. Among the main ones: increasing the wear resistance of products, reducing rejects in the manufacture of parts, tools, saving on new products by increasing the strength of the alloy used to make parts.

Part I

METAL PROCESSING (MACHINING, TURNING, MILLING, ETC.)

Metalworking is a technological process that involves the impact on metal products, alloys. The main purpose of different types of impacts is to change the size, shape, physical and mechanical characteristics, properties of products. In modern industry there is a wide variety of methods and technologies for processing metals. All of them are used in production.

Mechanical processing 

This type of machining is carried out to change the external shape, configuration and size of the product. It is used in cases where it is necessary to adjust the finished part to a given size. Cutting tools, metal-cutting machines and welding are used in this process.

The finished part has a perfect shape, smooth surface, correct dimensions with millimeter accuracy in accordance with the drawings.

Turning

Metal machining includes several different types of technology. One of them is the technology of turning or screw-turning. It is performed using a special tool – a cutter on a lathe. Turning is used for parts with cylindrical, spiral and helical shapes. The workpiece is clamped on the lathe, then a rotational impulse is given to it, while the pick is given a translational impulse. In this way, the cutter grinds the workpiece in the desired direction (lengthwise or crosswise).

Machining with a milling cutter

Milling is also a method of cutting metal, but with it the workpiece is given a translational impulse, and the cutting tool – milling cutter – a rotational impulse. This technology is used when it is necessary to process a horizontal, shaped, inclined or vertical surface, gears, to make a groove, groove.

The peculiarity of the process is that each “tooth” of the cutter interrupts the cutting process.

Stamping

Punching is another method in the category of metal machining. It is carried out with the help of special, so-called chiseling equipment. A special cutter makes a reciprocating movement in the vertical plane. In the horizontal plane the feed movement of the workpiece takes place.

This method is used to obtain grooves, shaped surfaces of low height with large cross-sectional dimensions.

Drilling

Drilling technology makes it possible to get through or blind holes in workpieces. This method also requires the use of machines. The countersinking method is used to increase the diameter of the hole. To obtain a hole with a quality surface and precise dimensions, the reaming method is used. The last method in this section, countersinking, is used to produce holes for semi countersunk or countersunk rivet and bolt heads.

Grinding

Grinding is a finishing process which belongs to the final stage of machining. Its purpose: to obtain the most accurate dimensions of the workpiece. Grinding wheels or abrasive belts (coarse and fine grit) are used. The surface of the part is improved, the smallest defects are removed, and the texture becomes even and smooth.

Laser cutting

The method of laser cutting metal is the most advanced among other methods of mechanical processing. This technology makes it possible to achieve jewel-like precision of part dimensions, high speed of processing, minimization of waste, and excludes possible defects in finished products. Finished products (elbows, pipes, fittings, channels) after laser processing are of high quality and have flawless external surface.

In addition, since during laser cutting metal is heated much less, the result is a part that is more durable, with high rates of resistance to deformation. Accordingly, the resulting product will serve many times longer. It is laser technology that is considered ideal for machining metal workpieces and structures.

Continued Part II

Fildes of aplplication and production process of forgings

So, steel forgings are special metal billets for the production of which technologies of forging or stamping are used. At the same time, they get the shape and dimensions of the required part.

The main market for steel forgings is the automotive industry, which involves the production of various gears and bearing shapes. Forgings are also in demand in the mining, power and nuclear industries.

Metal forgings, as a rule, serve as a basis in the process of conveyor machine tool production, where requirements to blanks are extremely high, because their exact size will ensure production efficiency.

The process of making forgings consists of three main steps:

  • Cutting blanks according to the desired dimensions of the future product;
  • Forging and stamping begins;
  • Acceptance by the TCD.

The technological process of preparation that precedes the direct production of forgings is a whole complex of works:

  • A drawing (sketch) of the future billet is made;
  • Calculations are made: mass, dimensions, melting methods;
  • The type of equipment for this or that kind of forging (press, hammer) is selected, the technological scheme is determined;
  • Forging operations are determined, the required number of modes, transitions are calculated, and tools are selected;
  • Calculation of modes: heating, cooling, temperature intervals is made;
  • The rules for marking, acceptance, sample sizes, cutting schemes, methods that are needed for testing, to remove defects from the surface of the finished forgings are determined.

Varieties of tools 

A set of tools used in forging or stamping of forgings make up a fairly large range. It is even customary to classify them according to the technological type of application. The basic tools include cut-out beats, flat or shaped, as well as various application tools: sledgehammers, hammers and multi-ton presses. The manual method of forging increases the plasticity of metal, but the accuracy of the dimensions and shapes of ingots is much inferior to stamped products.

Universal tools are used in small batch or single forging production. A certain tooling set makes it possible to produce metal blanks of different configurations and dimensions. Universal forging machines are also used: driven pneumatic hammers, forging steam and air hammers, and forging hydraulic presses. The latter type of equipment is needed for making large-size heavy ingots. Hammers, on the other hand, are used in the production of small parts, blanks, and bars. There is also a class of supporting tools for forging on hammers and presses. These include various types of tongs, stands and chucks.

Any set of forging tools is needed to move, hold, grip, measure blanks in the current work process. The efficiency of the entire manufacturing equipment and the quality of the blanks produced depends on the production equipment.

Forgings type

There are various ways of working metals. One of them is the so-called free forging. The fundamental process of forging is pressure. The method itself is a complex of certain operations alternating with each other. During these operations, the original workpiece is modified. This occurs as a result of the free flow of metal on the sides perpendicular to the movement of the tool, which subjects the workpiece to deformation. Therefore, it is not uncommon to hear this process referred to as free forging. The workpieces resulting from the forging process are called forgings.

Forgings types

Forgings are classified into types depending on the type of steel used to make them.

Carbon steel – has high strength, used for construction reinforcement structures in construction, petrochemical, metallurgical industries.  Pressed – produced by punching, used in mechanical engineering, mining and other industries.

Hammer – made with sledgehammers, hammers, such forgings are characterized by improved flexibility and hardness. Stainless – they are characterized by a homogeneous structure, used in the electrical industry, shipbuilding, for turbines, shafts, their weight is counted in tons.

Alloyed – products are supplemented with substances: chromium, nickel, manganese, cobalt, silicon, and so on, respectively, have an increased level of hardness, resistance to corrosion changes. Tooling – here alloyed or carbon steel is used, forgings are used in agriculture, as components for machinery and agricultural tools.

Pros and cons of forging 

This process of manufacturing metal blanks has a number of advantageous features. These include the following factors:

  • Metal of forgings is endowed with better quality properties, indicators, in comparison with casting.
  • Forging makes it possible to obtain dimensional blanks, which is impossible or impractical with other methods.
  • Since forging of forgings is carried out in parts, it is enough to use machine equipment (presses, hammers) of relatively small capacity for their production.
  • Using universal tools and equipment, it is possible to obtain quality forgings at minimum costs. This is a cost-effective enterprise for single and small-scale production.

Among the significant disadvantages of this method of obtaining blanks are a fairly low productivity, as well as high metal consumption, a particularly time-consuming machining required due to large overlaps and allowances on the forgings.

Casting in sand models

This casting method consists of a series of working steps. To understand them, it is first necessary to understand the terminology, without which it is impossible to do without in production.

So, regardless of the casting method chosen in this or that case, in order to obtain castings you need special casting molds, the cavity of which will correspond to the configuration of the required part or, as it is also called – the model.

A model is – a metal or wooden part that has the configuration of the outer surface of the casting. And a casting rod is used to form the inner surface. It is installed inside the mold. It is an integral part of the mold. It is made from a special core mixture, which includes sand, bonding substances.

The space formed between the rod and the cavity of the mold is filled with liquid metal. After the metal hardens, you get a casting with holes, cavities, or other complex contours inside.

Shapes: the technology of manufacturing 

A casting mold – is a production tool whose working cavity, when poured into it with liquid metal, forms a casting of a given configuration. Special molding mixtures are used to make such molds. Their components are sand, clay, water and binding materials.

The molds are made in several stages. A flask is placed on the pattern plate, and a filled frame, the height of which is equal to the degree of compaction of the molding sand in the mold. Then the flask and the frame are filled with the molding sand from the hopper. There it is compacted (different methods are used for this: manual, machine: pressing, shaking, sand molding machine) and the model is extracted from it. The result of these manipulations is the casting mold. 

Mixtures: molding and core mixes 

A molding compound is a multi-component molding material that meets all the conditions and requirements of the non-metal mold making process. This material is poured into so-called casting flasks. They are used as a result of model casts.

The casting flask is also a production tool that helps hold the molding compound in place while the molten metal is being made, transported and poured into the mold.

As mentioned above, molding and core sands consist of a number of components (sand, clay, binders) that have certain properties. Their extraction is carried out in pre-explored quarries. The main requirements to be met by the finished mixtures are good plasticity, flowability, gas permeability, high strength, non-stick coverage.

The last property for the production of steel castings must meet the highest indices. Therefore, to improve non-stick properties, ordinary clay is replaced by refractory clay. In order to obtain large-sized ingots, chromium ironstone is added to the molding mixture.

Rods: application, manufacturing

Casting cores are needed to form the inner surface of the casting. Special mixtures are used to make them. The mixture is compacted in the core box (manually or with special equipment). Volumetric cores with complex configuration are produced in separate parts, which are subsequently glued, assembled into blocks and installed in the mold.

To strengthen the strength and gas permeability indicators, rods are dried in special continuous dryers. At certain temperatures (from 150 to 300 degrees) during the drying process, the binder materials in the mixture are sintered, oxidized or, due to internal chemical reactions, the sand particles are glued together.

 Sand casting process

This type of casting is a multi-step process. First the molds and cores are made, then they are assembled and poured with an alloy. In the last step, the castings are knocked out of the molds, cleaned and trimmed.

Splitting is done with pneumatic hammers and chisels, and air-arc cutting is used to remove castings. The purpose of the subsequent cleaning is to remove burrs (consisting of compound residues) from the surface of the casting. This step is performed in a blast chamber.

Burrs can occur on the surface of the ingot due to the penetration of liquid metal into the pores of the mold. To eliminate this defect, the mold cavity is coated with a special non-stick paint. To avoid gas pockets, which are a consequence of intense gas formation, so-called ventilation channels are made on the upper and lower half molds.

After cleaning, ingots go to the workshop for mechanical processing and to the warehouse in a clean condition.

Ways stell casting

Steel casting is a complex, critical process that directly affects the quality of the metal. It directly affects the following steel characteristics: the number of foreign inclusions, chemical heterogeneity, gas saturation, structure, and surface quality of the billets. The fact is that during casting, various physical and chemical reactions occur in the metal. They, in fact, determine its final quality.

Casting can be carried out by one of three existing methods:

– So-called “raining,” or pouring into molds from above;

– “Siphonic” or from below into bottomless molds;

– Continuous casting in water-cooled molds.

The continuous casting method (the latter), due to a number of advantages over pot casting, is used more frequently in steelmaking.

The “rain” casting method 

This method uses conventional carbon steels. The molten metal in rain pouring is fed directly from the ladle into the mold. The advantages of this method include easy preparation of equipment for the process, lower steel temperature than the bottom pouring method, and elimination of material consumption for sprues.

The method also has one, but significant disadvantage. During casting, the steel is poured into the mold from a great height. This creates a splash film which hits the mold walls and hardens quickly. These spatters make the subsequent machining of the castings very difficult, deteriorating their surface due to the formation of oxide films on it. Even rolling does not drain these films from the “body” of the casting, so special surface cleaning is required, which is a very time-consuming operation. 

Casting from below

Alloy and high-alloy steels are used for casting from below. Siphon casting involves filling several molds with liquid steel simultaneously. The number ranges from four to sixty. This method is based on the principle of communicating vessels. All the molds are positioned on a special pallet with a central riser, where the molten metal flows in. The molds are filled through channels from below. This ensures smooth, splash-free filling of the molds and gives the castings a clean surface.

In addition, a clear advantage of this method is a significant reduction in casting time, since several small mold cavities can be filled simultaneously with a large quantity of metal.

However, it also has its disadvantages. The siphon feeding of steel increases the labor intensity of the preparation process, increases the consumption of refractories and metal for sprues, and necessitates heating the metal to higher temperatures, since the steel cools quickly while flowing through the channels.

Continuous casting

This is a more advanced method. The process looks like this: molten steel flows continuously into the water-cooled crystallizer, which has no bottom. The ingot, with its solidified periphery and liquid core, is pulled out of the lower opening of the mold. It then passes through the secondary cooling zone, where it solidifies completely and is fed for cutting with a gas cutter that divides it into blanks of the desired length.

The process continues until the pouring ladle is empty. A dovetail-shaped seed is introduced into the mold before casting begins. It is pulled out of the mold together with the casting.

This method produces ingots with a dense, fine-grained structure, without shrinkage shells, and with a high-quality surface. These properties are given to the castings through a directed solidification process and continuous feeding during shrinkage. There are practically no rejects at the output. The number of good products reaches 98% of the weight of the cast metal.

The continuous casting machines are equipped with two to eight casting molds. This makes it possible to make several ingots simultaneously, which also has a positive effect on the speed of obtaining high-quality results.

Castings: production features

Foundries are engaged in the production of castings or cast parts. These products are in great demand in modern society, and in absolutely different spheres of human activity. Casting is the cheapest and easiest way to produce billets or finished parts with complex geometric shapes. It is used to produce castings weighing from a few grams to 300 tons and measuring from a few centimeters to two dozen meters.

The technological process itself takes place in stages: 

  • First, a mold is made for casting according to the model;
  • Then cores are made (round clay cores to form inner holes in the casting);
  • Metal is melted and poured into the mold cavity;After crystalliza
  • ion, the ingot is knocked out of the mold;
  • Cleaning of risers and gating system;
  • At the end of the process, if necessary, the part is transferred for processing (mechanical, laser, thermal, etc.).

The main task of any foundry is to obtain castings that are as close in shape and size as possible to the parameters of the required product or part. At the same time, the last technological stage (machining) should not go beyond cleaning and grinding processes.

Castings materials

The majority of all castings for mechanical engineering and large-scale equipment are made of steel. The challenge for the molder is to choose an alloy based on its properties and cost.

Steel (which is an iron-carbon alloy) is ideal for making complex-shaped parts that are subsequently subject to stringent performance requirements – strength, impact toughness, and so on. Three types of foundry steel can be used here:

-constructional,

-instrumental,

-with special properties.

The first type goes to the production of parts designed for mechanical loads (static, dynamic or vibration). These steels are classified according to their composition (carbon steel class and alloy steel class) and structural features (ferritic-pearlitic steel class and pearlitic steel class).

The second type is ideal for casting various cutting, stamping and measuring tools. Metals are classified according to their chemical composition. There are three classes: medium-carbon, high-carbon and alloy steels of the pearlitic, martensitic and carbide types.

Steels of the third type, having increased properties of resistance to corrosion, heat resistance, acid resistance, wear resistance, are used for products used in conditions of exposure to various environments, loads, temperature regimes. These steels are divided into two classes – ferritic and austenitic.

Processes and equipment

Steel is melted in special melting furnaces. From there it is liquid and transferred to the so-called pouring ladle, from which the metal is poured into molds or crystallizers in the plant. There the metal solidifies and takes the desired shape of the part, which is then sent for machining.

The pouring ladle has a refractory body lined with refractory bricks and a ceramic bowl-shaped bottom with a hole for pouring metal through it. The opening is closed and opened manually or with a remote-controlled hydraulic actuator.

The ladle is chosen according to its capacity (from 5 to 260 tons), taking into account the volume of the furnace and the slag layer, which usually reaches 100-200 mm. Large units assume the use of large-capacity buckets – from 350-480 tons.

Ladle molds are cast iron molds for casting. Their configuration depends directly on the type of steel used for casting, and their size depends on the weight of the ingot. Boiling steel is poured into molds with an enlarged bottom, and low-carbon steel with an enlarged top.

It is economically advantageous for production to get solid castings, as it significantly reduces labor costs, metal losses, casting time and the cost of refractory materials.

Литейное производство: задачи и технологии

Литейное производство занимается выпуском так называемых фасонных заготовок и относится к такой промышленной отрасти как машиностроение. Литейный процесс – это заливание жидкого (расплавленного) металла в формовочную полость, повторяющую полностью контуры требуемой для получения детали. В процессе остывания металл затвердевает. После освобождения его из формы выходит готовое изделие, подлежащее дальнейшей несложной механической обработке. Такие заготовки получили название отливки.

Сегодня большинство всех деталей, предназначенных для промышленных оборудующих устройств, агрегатов, машин, сложных механизмов, изготавливаются именно путем литья. Таким образом получают блоки, цилиндры, поршни для двигателей внутреннего сгорания, рабочие колеса насосов, лопасти газовых турбин, станочные станины, прочие комплектующие.

Производственные задачи

Главной целью производственного литейного процесса является изготовление отливок, которые будут полностью совпадать по габаритам, конфигурации конечного изделия. Для этого применяется специальное литейное оснащение – формы. От конструктивных особенностей таких форм, в целом их качества напрямую зависит как результат, так и трудозатраты на производство деталей.

К литейным формам предъявляется целый ряд достаточно жестких требований. Например, они должны быть максимально прочными, чтобы выдерживать высокие нагрузки, пластичные, огнеупорные, непригораемые, газопроницаемые.

Литейные формы классифицируются в зависимости от материала их изготовления, кратности использования, степени участия в производственном процессе. Так согласно первой классификации, формы бывают песчаными, металлическими, и так далее. Второй – одноразовые и многократные (могут выдерживать до тысячи заливок). Третьей – основные (формообразующие) и вспомогательные (универсальные).

Для достижения поставленных перед производством целей именно качество каждой литейной формы играет наиважнейшую роль.

Технология производства

Для получения литейных форм, отвечающим всем вышеперечисленным требованиям, как правило, берутся такие металлы, как ковкий или серый чугун, углеродистая и легированная сталь. Бронза, латунь, силумин также используются для изготовления форм, но гораздо реже.

Применяемая на производстве технология состоит из нескольких этапов:

  • Изготовление литейной формы;
  • Плавка металла и заполнение им полученной формы;
  • Затвердевание в форме металла, охлаждение отливки;
  • Извлечение ее из формы, путем разрушения (при использовании одноразовой формы) или раскрытия (многоразовой);
  • Снятие прибылей (массивных приливов, которые затвердевают самыми последними, предотвращают образование в отливке усадочных раковин), удаление литниковой системы с отливки;
  • Очистка поверхности детали (если требуется).

Затем полученную отливку предают термической обработке (при наличии таковых требований в чертежах, техзадании) и отправляют на механическую обработку, где конечной детали задают необходимые размеры, доводят поверхность до нужной чистоты.

Данная технология позволяет получать металлические изделия самых сложных форм. При этом детали отвечают всем установленным стандартам качества, обладают высокими эксплуатационными показателями, характеристиками, не требуют дальнейшей сложной механической обработки.

Существует несколько способов заполнения литейной формы горячим сплавом: под воздействием высокого или низкого избыточного давления, гравитационных или центробежных сил, прочие. Сфера их применения напрямую зависит от типа самого производства: серийное, массовое, единичное.

Области применения литых деталей

Литейное производство предполагает выпуск изделий из тугоплавких металлов. Именно такие требуются для применения в следующих промышленных сферах: авиастроении, ракетостроении, приборостроении, машиностроении, судостроении, радиоэлектроники, атомной энергетики. Химическая же промышленность использует исключительно детали из жаропрочных и стойких в отношении коррозии сплавов.