Stamping casting forging. Methods for processing metals by pressure for industrial purposes. Types of rims

Before proceeding with the manufacture of a part, the material from which it should be made is turned into blanks. They try to get blanks so that their shape and dimensions are as close as possible to the shapes and dimensions of the finished part. This allows you to reduce the consumption of materials and electricity, increase labor productivity.

Depending on the nature of the material, the purpose of the part, the required accuracy of its manufacture, etc., blanks are obtained by casting, forging, stamping, upsetting, rolling, drawing, and other methods.

Casting. Molten liquid metal is poured into special molds, after the metal cools down and the molds are split (or destroyed), a billet (casting) of a given configuration and size is obtained.

Blanks are cast from cast iron, steel, non-ferrous metals and alloys in various ways: in sand, metal and shell molds, under pressure, according to investment patterns, centrifugal.

Sand casting quite common, since the cost of such molds is much less than with other casting methods. Sand molds are made from molding sand, which includes sand, clay and special additives.

Metal it is possible to pour into such a mold only once, since after receiving the casting, the mold is destroyed. Therefore, this casting method is inefficient and, in addition, gives less accuracy compared to other casting methods.

Casting in metal molds (molds) is more productive, since it allows multiple pouring of metal into one mold. This provides a higher surface roughness parameter and more accurate workpiece dimensions.

Shell casting- comparatively new way casting blanks and parts from ferrous and non-ferrous metals, in which the mold is made from mixtures containing thermosetting resins. The molding mixture is applied to the surface of a heated metal model, as a result of which the thermosetting resin is melted and a pre-hardened mold (crust) 5-7 mm thick is formed on the model. Then the model with a slightly hardened shell is placed in an electric furnace, where the final hardening of the mold takes place. After that, the mold is removed from the model and sent for pouring with metal.

Ease of manufacturing shell molds, a significant reduction in machining allowances, and high dimensional accuracy of castings of complex configuration (±0.2 mm per 100 mm length) are the main advantages of this method.

Injection molding especially common in the production of electrical and radio equipment and other similar products. The essence of this method lies in the fact that liquid metal is fed into a metal mold under pressure in special injection molding machines, due to which it fills all its cavities well. Injection molding is used to obtain cast billets of complex shape from non-ferrous alloys with various protrusions, tides and holes.

Investment casting based on the use of models that are made in metal molds by filling them with a paraffin-stearin mixture. The models obtained in this way are covered with a thin layer of a special liquid mass and fine quartz sand, dried and calcined in an electric furnace. In this case, the paraffin stearin mixture flows out of the mold, which is then used to produce precision metal parts.

In this way, very accurate and clean castings are obtained. A feature of this casting method is that it allows you to get not only blanks, but also finished parts of complex shape without further machining.

With centrifugal casting liquid metal is poured into a mold that rapidly rotates around a vertical or horizontal axis. This method is most effective in obtaining ring-shaped blanks, pipes, gears, etc.

Forging and hot stamping. In these processes, the heated metal is treated by impact or pressure, using hammers and forging machines. If the heated metal is processed without special forms (dies), then the process is called free forging, if in stamps - hot stamping.

With hot stamping, much less time is spent on the manufacture of blanks than with free forging. In this case, the blanks are obtained more accurate in shape and size, with smaller allowances for further machining.

Cold stamping. This is the process of obtaining blanks and parts from sheet, strip and strip material by cutting, bending, drawing, flanging in dies on presses.

The cold stamping method is very productive and is widely used in various types of production. With different methods of obtaining blanks, the allowance for their processing will be different.

How to buy products?

1. Open the required section on the site and select products according to standard sizes.

2. When you click on the size, the calculator is activated, where you can calculate the required product and completeness.

3. If you need a calculation according to your sizes - enter your sizes

4. After calculations in the calculator, put the product in the basket.

5. Place an order by entering information about yourself and the delivery address.

6. Receive an invoice and an offer contract for the manufacture of goods.

7. Delivery to the object of the goods is carried out by the transport of our logistics network.

8. Installation of products at the facility by prior arrangement.

For individuals and organizations 1

Attention at a great distance we do not make measurements! All measurements are the responsibility of the customer or contractor. It is required to take into account the clearances for counterparts, hinges, etc. The sizes are given executive on the edges of a cloth.

1. Decide on the model of gates, fences, railings, etc.

2. Decide on the size. If you are satisfied with the standard sizes, choose them. If additional accessories are required, also determine what exactly is required. If you need to manufacture according to your size, recalculate in the calculator.

3. Make a calculation in the calculator for each product. To calculate, you need to click on the required size or select according to your size. In the calculator, select the required components. If you cannot decide what you need, read the instructions on the website or call the office for advice.

4. After the calculations, put the goods in the basket and fill in your data to place an order.

For individuals and organizations 2

5. After the formation of the order, we create an invoice and an agreement for you in electronic form.

6. Payment can be within the framework of the invoice from 60% of the initial payment or immediately 100%. Second payment on completion. Attention! The goods will be sent to the customer subject to 100% payment on the invoice.

7. The goods are brought to your site by transport companies from our logistics network. It is required to accept the goods and carry out unloading by the customer. Driver alone. Delivery on schedule transport company. There is no office pickup.

8. If the installation is ordered, the team leaves on the day of the preliminary agreement. The amount for installation on the site is preliminary. Not included in invoice payment. Calculation for the installation separately, at the installation site with the foreman. The minimum cost of the brigade's departure for installation is 8000 rubles.

General order and conditions

1. We work on low prices. The minimum order amount is 12000r. The order amount to receive the red price is from 130,000 rubles. Delivery time 2-3 weeks, depending on the workload of production.

2. Delivery of goods to your site throughout Russia. The amount of delivery depends on the volume of the order and the distance from the production.

3. Installation of products. The amount is calculated depending on the volume of the order, the complexity of installation and the distance from the Moscow Ring Road. Installation of products by our company is carried out only in Moscow and the Moscow region. There is no office pickup.

4. Before ordering, you must determine the size of the products. Before ordering, you need to calculate the required dimensions and gaps yourself or get advice from the office on your opening dimensions.

5. Departure of the manager-measurer for the conclusion of the contract is possible. Departure is paid depending on the distance from the office. We do not go to the budget gates.

For construction organizations

We work with construction organizations, contracts and private teams.

If you need advice on installation or sizing, call us, we will advise.

The site contains instructions for assembling various products, as well as for altering standard sizes of gates and fences to fit your opening.

See instructions on the next page.

Having the desire to change appearance car, or simply faced with the need to replace wheels, the car owner is faced with a dilemma of which type of wheels to give preference to. And since modern market literally overflowing with a variety of models of eminent and completely unknown manufacturers, we will try to help in resolving this issue. So, which discs are better, and what is their difference?

Types of rims

Let's start by looking at various kinds car rims, the reliability and strength of which directly depends on the material used in their manufacture, as well as the production method.

stamped discs

Budget cars in the initial configurations are most often equipped with stamped rims made of steel. Such models are made from metal rolled sheets of a certain thickness. In this case, the blanks for the hub and the rim are separately subjected to press processing in the hot state, after which the finished product is formed by welding.
In this case, the use of rolled steel guarantees the disks high strength and ductility, which are the main advantage of such models. With a strong impact, they do not crack, but bend, which allows for restoration or repair, even without the use of specialized tools and equipment.
However, it is impossible to unequivocally state that stamped discs are certainly better than their expensive counterparts, since their low cost and maintainability are opposed by a significant mass, which increases suspension wear, reduces efficiency and ride comfort. It is for this reason that almost all stamped models have special holes to reduce their weight. But even in this case, steel wheels are 2-3 times heavier than alloy wheels.

You also need to remember that steel is subject to corrosion, which can render the disc unusable in just a couple of years of operation. To avoid this, steel wheels are coated with a special varnish or primer, which, however, are not able to create an ideal protective layer.
Well, another drawback is the outdated design, which rarely harmonizes with the exterior of a modern vehicle.

Alloy wheels

When buying a new car, you should decide which wheels to give preference to. At the same time, most experts recommend choosing, of course, if you have finances.
Alloy models are made using classic casting, when the alloy is poured into a mold prepared in advance. When produced by this method, the boundary between the disc and the rim is completely leveled, which increases the durability and reliability of the entire structure.

The material for alloy wheels in most cases is an aluminum alloy, which may include titanium or magnesium. Cast models are significantly superior in strength to stamped counterparts, since their deformation limit is significantly higher. In other words, to damage such a wheel, the required impact energy must be increased by a factor of 3–5.
On the other hand, the ductility of non-ferrous alloys is lower than that of steel. And this aspect provokes great difficulties, if necessary. In this case, improvised means are not enough. Requires a whole set professional work including hot rolling, argon welding, drawing, etc. Necessary equipment it is expensive, and therefore repairs will not be cheap. In addition, when heated, the alloy of alloy wheels changes the molecular structure. As a result, the wheel loses strength, and often becomes unsuitable for further use.

Alloy wheels, due to their low weight, provide high level reliability, safety, comfort and economy, not to mention the fact that they look great. In addition, they are not afraid of corrosion, with the exception of magnesium alloy models, which are gradually destroyed by moisture if the multi-layer coating is missing or damaged.
The advantages of the considered models can also be attributed to the geometric accuracy of manufacturing, which improves the handling of the car.

Forged wheels

Immediately, we note that mechanical forging, through which these products are made, has nothing to do with manual forging. In fact, this is the same stamping, in which light-alloy blanks are used instead of sheet iron. The main difference from the creation of steel discs is the use of high temperature and the use of other forms.

Forged wheels are made from non-ferrous alloys, which, compared to cast models, contain a much higher proportion of high-strength components (titanium or magnesium). While casting implies a violation of the molecular structure of the metal, due to its complete melting, this does not happen when forging a heated billet. As a result, discs become stronger, more durable and more reliable. Practice has shown that a strong blow received while driving is more likely to harm the suspension of the car than the integrity of the forged disk.

You can notice the difference between forged and cast products in their mass. The former will be lighter by 10-25%, which allows them to demonstrate the best fuel efficiency and comfort, as well as provide less wear on the chassis.
Experts believe that forged wheels have only one drawback, which is expressed in the high cost of the product, which is determined by the peculiarities of the manufacturing process.

What to choose?

In the case when you live in a city and move exclusively along good roads, but do not want to spend extra money - the best option become alloy wheels. Moreover, the car market today offers many quality models at an affordable price, the best of which are products of European, Russian and South Korean production, and the worst, respectively, of Chinese and Turkish.

Those who love speed and are not able to ride otherwise should take a closer look at forged wheels, which have more strength and less weight. In addition, connoisseurs of tuning and people with high incomes adore these products.

As for stamped steel wheels, they are often chosen for driving on roads with poor coverage, they are used as a replacement for cast models in winter time years, and also used to equip cars a la "workhorse". These discs are inexpensive and allow for unaided repairs even in the field.

Methods for processing metals by pressure for industrial purposes are divided into two types.

1. Metallurgical, designed to obtain blanks of constant cross-section (rods, wire, sheets, etc.) used for the manufacture of parts using preliminary plastic forming and cutting. The main metallurgical pressure treatment methods are rolling, drawing and pressing.

2. Engineering, designed to obtain parts or blanks having a shape and size close to the shape and size of the parts; in mechanical engineering, the main methods for obtaining workpieces by pressure treatment are forging and stamping.

Rolling(Fig. 3.10, a) is to compress the workpiece 2 between rotating rolls 1 .

Pressing(Fig. 3.10, 6) consists in pushing the pusher 4 blanks 2, located in the sleeve 3, through the matrix hole 1.

Drawing(Fig. 3.10, c, d) consists in pulling the workpiece 2 through the tapering cavity of the matrix 1; in this case, the cross section of the workpiece takes the form of a cross section of the die hole.

stamping(Fig. 3.10, e) change the shape and size of the workpiece using a special tool - a stamp.

sheet metal stamping get flat and spatial parts from workpieces, in which the thickness is much less than the dimensions in the plan (sheet, tape, strip). When sheet stamping (Fig. 3.10, d) blank 3 deformed with a punch 1 and matrices 2.

Forging(Fig. 3.10, e) change the shape and dimensions of the workpiece 2 by sequential exposure to universal tools 1 to individual sections of the workpiece.

At forging(Fig. 3.10, e) the workpiece, which is a segment of the rod 2, is affected by a stamp 1, moreover, the metal of the workpiece fills the cavity of the stamp, acquiring its shape and dimensions.

Rice. 3.10. The main types of metal pressure treatment: a - rolling; b - pressing; c, d - drawing; e - sheet stamping (one of the processes); e - forging; P is the pressing force of the rolling rolls; P tr - friction force; P p - pressing force;

P pr - pulling force; P to - forging force; R w - stamping force.

Forging — a method of processing metals by pressure, carried out using a forging tool or dies, in which the tool has a repeated, intermittent effect on a heated workpiece, as a result of which it is deformed and gradually acquires a given shape and size. Forging is the only way production of large forgings (weighing up to 250 tons): hydro generator shafts, ship engine crankshafts, rolls rolling mills etc. Forging is usually used in small-scale or single production, as well as for the manufacture of large forgings.

Forging can be free or in backing dies, manual or machine, carried out on steam-air hammers or on forging hydraulic presses. At hand forged they use anvils, large and small hammers (sledgehammers and handbrakes), tongs to capture and maintain the workpiece, barbs, chisels, chisels, crimps (Fig. 3.11, a-h), at machine forging - strikers, crimps, rolls, clamps, cartridges (Fig. 3.11, i-p).

Rice. 3.11. Tool for manual and machine forging: a - anvil; b - sledgehammer;

c - handbrake; g - mites; d - beard; e - chisel; g - podboynik; h - crimp;

and - flat strikers; to - cut-out strikers; l - rounded strikers; m - crimps;

n - rolling; o - clamps; p - cartridges.

The main forging operations are upsetting, upsetting, broaching, flashing, cutting off, and bending. draft called such a technological operation of pressure treatment, in which the height of the original workpiece decreases while increasing its cross-sectional area (Fig. 3.12).

In this case, the sediment of a cylindrical sample can be considered without taking into account friction at the ends (Fig. 3.12, a)(ideal) or in the presence of friction at the ends (Fig. 3.12, b)(real version). For stability during upsetting of cylindrical workpieces, the height of the workpiece h 0 should be no more 2,5 diameters:

Rice. 3.12. Schemes of upsetting a cylindrical sample without friction at the ends (a - ideal option) and with friction at the ends (b - real option):

h o and h1- initial and final dimensions of the workpiece; d- workpiece diameter; d1- part diameter; ∆h- amount of draft; P- draft force.

disembarkation is a type of sediment. In this case, the metal is deposited only on part of the length of the workpiece (Fig. 3.13, a). Firmware - the operation of obtaining cavities due to the displacement of metal (Fig. 3.13, b) using the firmware tool. To obtain the required shape of the part, backing dies are used (Fig. 3.14).

Rice. 3.13. Disembarkation schemes (a) and double-sided firmware (b).

Rice. 3.14. Scheme of stamping in backing stamps.

Hot forging- this is a type of metal forming by pressure, in which the shaping of a forging from a heated billet is carried out using a special tool called stamp. During stamping, the flow of metal is limited by the surfaces of cavities or protrusions in certain parts of the stamp. At the final moment of stamping, the metal occupies the entire closed cavity of the stamp (stream) in accordance with the configuration of the forging. Due to this, hot forging can be used to obtain forgings of complex configuration with minimal overlaps (or without them) and with smaller tolerances than with forging (Fig. 3.15).

Rice. 3.15. Stamping schemes in open (a) and closed (b) dies: h zaz- gap.

By the presence or absence of a burr, open dies are distinguished (Fig. 3.15, a) and closed (Fig. 3.15, b).

Forging is divided into cold and hot (depending on the heating temperature of the workpieces), forming, upsetting, piercing, etc. (by type of operations), hammer and press (by type of equipment used).

The main parts of the stamp are the punch and the matrix. Dies designed for hammer and crank hot forging presses consist of upper and lower parts, on the contact surfaces of which there are streams for consistent shaping of the product. Stamps are made from carbon and alloyed (mainly chromium) die steels.

Stamping in open dies characterized by a variable gap between the movable and fixed parts of the stamp. A burr (flash) flows into the gap. As the gap decreases, the metal in it is intensively cooled, the yield strength of the metal increases and the resistance to movement of the burr increases. Due to this, the entire die cavity is filled, and only excess metal is forced out into the burrs. Burrs are subsequently removed in special trimming dies.

When stamping in closed dies, the gap between the movable and stationary parts of the die is sufficient for the relative movement of the parts of the die, but not for the formation of a burr. Therefore, in order to avoid not filling the corners of the die cavity or increasing the height of the forging, it is necessary to strictly observe the equality of the volumes of the metal blank and the forging.

Stamping in closed dies can be attributed to stamping by extrusion. Hot forging is used in large-scale or mass production, makes it possible to obtain forgings of complex configuration with minimal overlaps and smaller (compared to standard methods) tolerances.

The productivity of stamping is much higher than that of forging. At the same time, a stamp is an expensive tool designed for the manufacture of only one particular forging. Forging forces are greater than forging identical forgings. Therefore, the mass of forgings produced by forging rarely exceeds 20 kg.

The main equipment for forging and stamping are forging and stamping hammers and presses. forging hammer serves to process metal blanks by impacts of falling parts. According to the type of drive, hammers are steam-air (Fig. 3.16, a), pneumatic (Fig. 3.16, b) mechanical, hydraulic.

Rice. 3.16. Schematic diagrams of hammers: a - steam-air: 1 - woman; 2 - guides; 3 - piston; 4 - cylinder for supplying steam; 5 - lower striker; b - pneumatic: 1 - working cylinder; 2 - compressor cylinder; 3 - piston of the compressor cylinder; 4 - connecting rod; 5 - shaft; 6.7 - upper and lower spools, respectively;

8 - piston of the working cylinder; 9 - a woman of a hammer; 10 - upper striker; 11 - lower striker.

Steam-air hammers(see fig. 3.16, a) are driven by steam or compressed air at a pressure of 0.7 ... 0.9 MPa. Moving a woman 1 regarding guides 2 occurs when the piston moves 3 under the influence of compressed steam or air. When steam (or air) is supplied to the upper cavity of the cylinder, the falling parts move down and strike the workpiece laid on the lower striker 5. When steam (or compressed air) is supplied to the lower cavity of the cylinder, the falling parts rise to the upper position.

Pneumatic hammers(see fig. 3.16, b) contain two cylinders: working 1 and compressor 2. Piston 3 compressor cylinder is moved by a connecting rod 4 from crankshaft 5. At the same time, the air is compressed (p = 0.3 MPa) in the upper or lower cavities of the cylinder and when you press the pedal or the handle that opens the spools 6 and 7 enters the working cylinder 1. The working cylinder acts on the piston 8. Piston together with a massive rod 9 at the same time it is a woman of the hammer, in which the upper striker is attached 10, When moving the falling parts down, the upper striker hits the workpiece laid on the fixed lower striker 11.

The base of the forging hammer (shabot) has a mass 8-15 times greater than the mass of the falling parts. The shafts of stamping hammers are even more massive - 20-30 times the mass of the falling parts. This provides a high impact efficiency (η= 0.8...0.9) and high impact precision of the die parts. In addition, for the same purpose, the hammers have reinforced adjustable guides for the movement of the woman.

Distinguish according to the way they work simple hammers and double action. In single-action hammers, the falling part (baba) falls freely under the action of its own gravity, and in double-action hammers, it is additionally accelerated. The speed of the woman of high-speed hammers can reach 25 m / s, and for conventional hammers 3 ... 6 m / s.

Steam-air forging hammers have a mass of falling parts of 500 ... 5,000 kg, and stamping - 500 ... 30,000 kg. On forging hammers, forgings weighing 20 ... 2,000 kg are made, as a rule, from rolled billets or from ingots. The maximum mass of stamped forgings is 1,000 kg.

In non-chamber steam-air hammers, the chabot is replaced by a lower movable woman connected to the upper woman by a mechanical or hydraulic connection.

The required hammer is selected on the basis of calculation or reference tables.

Crank punch presses have a constant stroke equal to twice the radius of the crank (Fig. 3.17). Stamping on crank presses is characterized by high productivity and accuracy of workpieces in height. The workpiece is removed from the die during the reverse stroke of its upper part with the help of ejectors. Thanks to this, it is convenient to stamp in closed dies by extrusion and stitching.

Rice. 3.17. Scheme of a crank punching press: 1 - punch; 2 - emphasis; 3 - drive;

4 - electric motor; 5 - movable matrix; 6 - drive shaft; 7 - main slider;

8 - cover; 9 - crank shaft; 10 - wings; 11.12 - upper and lower strikers.

Crank stamping presses with a force of 6.3 ... 100 MN successfully replace stamping hammers with a mass of falling parts of 630 ... 10,000 kg. However, the cost of a crank hot forging press is 3–4 times higher than the cost of an equivalent hammer in terms of technological capabilities.

Horizontal forging machines(GKM) (Fig. 3.18) have stamps consisting of three parts: a fixed matrix 3, movable die 5 and punch 1, opening in two mutually perpendicular planes.

Rice. 3.18. GCM scheme

rod 4 with a heated area facing the punch, laid in a fixed matrix 3. The position of the bar is fixed with a stop 2. When the GCM is turned on, the movable die 5 presses the bar against the fixed die, the stop 2 retracted to the side, and the punch 1 strikes the protruding part of the bar, deforming it. The operation of the GCM is illustrated by the kinematic diagram shown in fig. 3.19.

Rice. 3.19. Kinematic diagram of a horizontal forging machine: 1 - movable

cheek; 2 - system of levers; 3 - slider; 4 - movable cams; 5 - connecting rod;

6 - crank shaft; 7 - main slider.

The main slider 7, carrying the punch, is driven by the crank shaft 6 with connecting rod 5. Movable jaw 1 driven by side slider 3 lever system 2. Side slider driven by cams 4, mounted on the end of the crankshaft 6. Horizontal forging machines are usually built with a force of up to 30 MN. The main operations performed at the gas condensate field are upsetting, piercing and punching.

Forging on GCM can be performed in several passes in separate streams, the axes of which are located horizontally one above the other. Each transition is performed in one working stroke of the machine.

Action hydraulic press is based on Pascal's law of hydrostatic pressure, who in 1698 pointed out that "a vessel filled with water is a new machine for increasing forces to the desired degree" (Fig. 3.20). The force of modern hydraulic stamping presses (Fig. 3.21) reaches 750 MN.

Rice. 3.20. Scheme to explain Pascal's law.

Rice. 3.21. Schematic diagram of a hydraulic press.

sheet stamping It is designed to produce a variety of flat and spatial products such as facing automotive parts, aircraft parts, rockets and other products of complex shape. Sheet stamping is used in the automotive, aviation, electrical industries, in tractor construction, instrument making, etc.

Sheet stamping reduces the amount of machining, provides high dimensional accuracy and productivity (up to 40 thousand parts per shift from one machine). As blanks, a sheet, strip or tape is used. The thickness of the blanks usually does not exceed S≤ 10 mm.

As a rule, in sheet stamping, plastic deformation, which provides the necessary shape and dimensions, is obtained only by a part of the workpiece. The wall thickness of stamped parts differs slightly from the thickness of blanks. Operations in which only the shape and dimensions of the workpiece are changed without destroying it during the deformation process are called form-changing. O Operations that cause the destruction of the material of the workpiece are called separating.

The form-changing operations of sheet stamping include bending, drawing, flanging, crimping, distribution, etc. (Fig. 3.22).

Rice. 3.22. Sheet punching operations: a - bending; b - hood; in - flanging;

g - crimp; d - distribution.

bending(Fig. 3.22, a) It is used to change the curvature of the workpiece with virtually no change in its linear dimensions. AT As a result of such deformation, part of the workpiece is rotated relative to the other by a certain angle. Plastic deformation during bending is concentrated on a narrow area in contact with the punch.

When bending, the destruction of the material, the formation of cracks, folds is not allowed. The weakest point is the zone of tensile deformations in the outer layer of the part in the area of ​​the rounding of the punch. With a decrease in the ratio of the radius of curvature R to workpiece thickness S deformation increases. Therefore, to prevent the appearance of cracks, folds or destruction of the workpiece, the minimum dimensions of the radius of curvature of the punch are limited: R min =(0,1 ...2) S.

Hood(see fig. 3.22, b) consists in pulling the workpiece through the hole of the matrix, and the flat workpiece turns into a hollow product, and the transverse dimensions of the spatial workpiece decrease (Fig. 3.23). The drawing can be carried out without thinning or with thinning of the workpiece wall.

Rice. 3.23. Drawing scheme: 1- matrix with a working diameter D m and radius of curvature R m; 2 - semi-finished product; 3 - clamp; 4 - punch with a working diameter D p and radius of curvature R p; 5-blank for drawing diameter D and thickness S.

The shape change during drawing (Fig. 3.23) is estimated by the ratio of the diameter D3 workpiece (disc type, flange) to diameter d of the resulting part of the cylinder type, which is called the elongation ratio:

K p \u003d D 3 / d

When drawing without measuring the wall thickness, the gap z between the punch and the matrix must be more than the thickness s blanks: z= (1,1 ... 1,3)S. When drawing with a change in wall thickness, the latter can be reduced by 1.5-2 times in one transition, while the gap between the punch and the matrix should be less than the wall thickness, and the specific forces will be large. Thinning hood is used to eliminate the risk of wrinkling, as well as to obtain parts with walls whose thickness is less than the thickness of the bottom.

The pulling force at the moment when the workpiece completely covers the rounded edge of the die can be determined by the formula:

P vyt \u003d 2πR m SQ p max,

where Q p max is the true strength of the workpiece material at full hardening.

At flanging part of the workpiece bordering the pre-punched hole is pressed into the matrix, while the size of the hole increases, and this section of the workpiece acquires a cylindrical shape (see Fig. 3.22, in). The permissible increase in the diameter of the hole without destruction during flanging depends on the mechanical properties of the material of the workpiece and its relative thickness s/d Q and is d/d Q= 1,2.,. 1.8, where dQ — original workpiece diameter.

At crimping(see fig. 3.22, G) a hollow thin-walled cylindrical workpiece is fed into the die hole, resulting in a decrease in transverse dimensions.

When distributing(see fig. 3.22, e) the punch is introduced into a hollow thin-walled cylindrical billet, and its transverse dimensions in the deformation zone increase. When considering the stressed and deformed states in the deformation zone, when analyzing sheet stamping operations, they usually use a polar coordinate system with a pole coinciding with the center of curvature of the middle surface of the workpiece at the given moment of deformation (Fig. 3.24).

Rice. 3.24. The scheme of stresses during sheet stamping: R n - the outer radius of the workpiece before deformation; R n - variable radius in the polar coordinate system; r ext - inner diameter details; σ - stresses; ε - deformations; indices ρ, θ and z relate

to radial, tangential and axial parameters, respectively.

In the form-changing operations of sheet stamping, shear stresses are relatively small and, therefore, it is assumed that the directions of normal stresses σ p and σ θ coincide with the main directions of the stress tensor, i.e., they are the main stresses. At rBH/s > 5 accept ρ p ≈ r BH + s/2.

Deformations in sheet stamping operations are carried out when stresses σ p and σ θ correspond to the limiting state (plasticity condition). Depending on the loading conditions of the workpiece in various sheet forging operations, the stress state schemes and stress signs σ p and σ θ in the deformation zone can be different. In the operations of drawing and flanging, the stresses a p are tensile, and in the operations of crimping and expansion, they are compressive. The stresses σ θ are tensile in expansion and flanging operations, and in drawing and crimping operations they are compressive (Fig. 3.25).

Rice. 3.25. Limit state conditions for flat

tense state

On fig. 3.25 graphically presents the conditions of the limiting state in a plane stress state (in the form of an ellipse and a hexagon in the coordinates σ s - σ θ) and shows the schemes of operations in which the deformation of the workpiece is carried out with stress signs corresponding to certain quadrants.

Forging called the processing of metal in a plastic state, static or dynamic pressure. During forging, both the external shape and the structure of the metal change. The product obtained by forging is called forging. There are two types of forging: free and in stamps.

Forging is performed either by impact (dynamic) action on the metal, where the energy of the falling parts of the hammer is used (mechanical forging), or by slow (static) action, where press pressure is used.

free forging

Free forging is used in serial and small-scale production. Forging operations include drawing, upsetting, bending, punching, piercing, cutting, etc.

When drawing the length of the forging is increased by reducing its cross section. A variation of the hood is a broach, in which the workpiece is turned over after each blow.

Draft- operation, the reverse of the hood. During upsetting, the cross section of the forging increases due to the height.

Holes are pierced using a punch, called a piercing. A through hole or recess is obtained by firmware - (blind firmware). On fig.3 7 diagrams of some free forging operations are given.

Forging is carried out on forging hammers or hydraulic presses.

Hammers- machines of dynamic, shock impact. The duration of deformation on them is thousandths of a second. The metal is deformed due to the energy accumulated by the moving (falling) parts of the hammer by the time they collide with the workpiece. One of the main types of forging hammers are steam hammers.

Hydraulic presses - machines of static action; the duration of the deformation is a few seconds. The metal is deformed by the application of a force generated by the fluid supplied to the working cylinder of the press.

Fig.38. Schemes of forging operations: a - two-sided firmware, b-through

stitching, v-stitching, g-cutting, d-axes, e-bending,

w-stamping in backing dies, h-broach

Stamping

Forging is called forging in steel molds-stamps. The performance of stamping is ten times greater than free forging. In addition, stamping achieves significantly greater dimensional accuracy and surface finish than free forging. However, stamping is beneficial only in mass and serial production, because the cost of manufacturing a stamping tool is justified only when a large batch of parts is manufactured. Stamping is hot and cold, bulk and sheet.

Hot forging(forging in stamps). If, during free forging, the metal pressed by the strikers from above and below can freely flow to the sides, then during stamping, the flow of metal is limited by the surfaces of the stamp, and the workpiece takes the form of its shaped cavity (stream).

The machining allowance for hot die forging is about half that for free forging. Hot stamping is carried out on hammers and forging machines.

Hammer stamping- the most common method of hot stamping. Stamp ( rice.39 ,a) consists of two parts: upper 1 and lower 2. The lower part is mounted on a stamp holder installed on the shabot, and the upper part is in the woman; fastening of each part of the stamp is carried out by a wedge and a key. Attachment points are made in the form of a dovetail. Both parts have cavities constituting a groove that matches the shape of the forging.

Rice.3 9. Stamping of gear blanks in a single-strand die

For stamping, the workpiece is heated to the forging temperature and placed in the lower cavity 2 of the stamp. Under the impact of the upper part of the die, the metal flows and fills the stream. Excess metal is squeezed out of the stream into the annular cavity and forms the so-called flash (burr) 3 ( rice.39 ,b), which contributes to a better filling of the die cavity, preventing further metal flow in the cavity of the die connector. Burrs are cut on a press in a special cutting die in a hot or cold state. According to the number of strands, the stamps are divided into single-strand and multi-strand.

Single Strand Dies used for the manufacture of simple products and for stamping blanks previously prepared by free forging. This preparation consists in bringing the billet shape closer to that of the finished forging.

Multi-strand dies have blanking, stamping and cutting strands. In the procurement streams, the operations of drawing and bending are performed, in the stamping streams - giving the final shape to the workpiece, in the cutting sections of the stamping from the bar (rolled workpiece).

Procurement streams are located along the edges of the stamp, and stamping in the middle. On the rice.40 a multi-strand die is shown, as well as sketches of the original workpiece, its deformation during successive stamping transitions and the finished forging. The workpiece first enters the broaching stream 4, where it is pulled. Then it is deformed in the rolling strand 3 for thickening at the ends, then it is transferred to the bending strand 1, after which it is stamped first in the preliminary strand 2, and then in the final strand 5.

Rice.4 0. Multi-stranded stamp

In recent years, it has been spreading flashless stamping in closed stamps. At the same time, significant metal savings are achieved, there is no need for trimming presses and dies, as well as flash trimming, and the mechanical properties of forgings increase. For hot stamping, crank presses, friction and steam-air hammers are used.

Stamping on horizontal forging machines ( GCM). Unlike hammers, forging machines have a slider that moves horizontally, which is why these machines are called horizontal forging machines. Such machines are used for the manufacture of forgings in the form of hollow or solid rods with a thickening (bolts, rivets, etc.), as well as for the manufacture of ring-shaped forgings (bushings, nuts, rings).

These machines are highly productive, provide greater precision than hammer stamping, and produce almost no waste.

Rice.4 1. The scheme of stamping the ring on the GCM

Stamping on the GCM is usually reduced to the operation of upsetting a heated rolled billet. The stamp has two streams. In the first stream, landing is carried out to obtain the outer contour of the ring ( rice.4 1,a), in the second stream ( rice.4 1b) punch P stitches and ejects the workpiece. The pressure developed by the GCM ranges from 500 to 3000 kN.

Rice.4 2. Scheme of cutting sheet material

Cold stamping it is used for products made of sheet steel, aluminum and its alloys, copper, brass, etc. Simple stamping is reduced to cutting, drawing and bending. Complex stamping is a combination of the above operations.

felling used for the manufacture of flat parts from a sheet; the shape of the contour can be any: circle, square, etc. Holes can also be punched with this method. The die for punching has two main parts ( fig.42): die 4 and punch 1.

When moving down, the punch 1 cuts off part of the workpiece with the sharp edges of the working contour. During the reverse movement, the rest of the workpiece 3 rests against the puller 2 and is removed from the punch.

Hood get hollow products from sheet blanks. The workpiece with a diameter D is placed in the groove of the matrix ( rice.4 3a) and pulled out with a punch into a glass ( fig.43,b). In order not to cut the workpiece, the edges of the punch are rounded.

Rice.4 3. Scheme of drawing from a sheet blank

If the gap a between the matrix and the punch is equal to the thickness of the workpiece, then the wall thickness of the product remains the same; if this gap is smaller, then the walls become thinner. To locally change the shape, for example, to obtain stiffeners, the workpiece is additionally molded in dies.

Cold stamping is done by mechanical crank, hydraulic or friction presses.

To remove hardening, some products are annealed. If they are stamped in several transitions with a large deformation, then they are annealed repeatedly.