What is metal rolling

Metal rolling process

The process of shaping metals into semi-finished or finished shapes by passing them between rollers is called rolling. Rolling is the most widely used metal forming process. It is used to convert metal ingots into simple elements such as billets, slabs, sheets, plates, gaskets and others.

When rolling, metal is plastically deformed by passing it between rollers rotating in the opposite direction. The main purpose of rolling is to reduce the thickness of the metal. There is usually a slight increase in width, so that a decrease in thickness results in an increase in length.

Rolling operation

Rolling is carried out both hot and cold. It performs in rolling mills. A rolling mill is a complex machine that has two or more working rollers, support rollers, roll stands, a drive motor, a gearbox, a flywheel, a coupling device, etc.

Rollers can be simple or corrugated depending on the shape of the rental. The metal gradually changes its shape during the period in which it is in contact with the two rollers.

The range of products that can be produced by rolling is very large. Rolling is a more economical forming method than forging when metal is required in long lengths of uniform cross-section.

It is one of the most widely used among all metalworking processes due to its higher productivity and lower cost. Typically rolled materials are steel, copper, magnesium, aluminum and their alloys.

 Sequence of operations associated with the production of rolled products

1) primary rolling:

Basic rolling is used for converting ingot metal into simple elements such as plates. This process refines the structure of the cast ingot, improves its mechanical properties and eliminates hidden internal defects.

2) hot rolling:

Slabs obtained from primary rolling are again converted into slabs, sheets, rods and structural forms by the hot rolling process.

3) cold rolling:

Cold rolling is generally a finishing process in which hot rolled products are given their final shape. These processes provide a good surface finish, closer dimensional tolerances and increase the mechanical strength of the material.

The steel we receive from the smelter or steel mills is primarily in the form of ingots. The ingots have an approximately square cross-section of 1.5m x 1.5m and weigh in tonnes.

These ingots are first heated to temperatures of around 1200°C in heating pits and then passed through rollers to produce intermediate shapes. The above element has approximately the following dimensions:

Cast ingots - 1.5 m x 1.5 m (rectangular cross section)

Slabs-width: 500 to 1800 mm (rectangular cross-section) thickness: 50 to 300 mm

Blanks - from 30 mm to 150 mm square.

Plates are 6 mm or more thick, 1200-1400 mm wide, 6000 mm long.

Sheets - thickness from 0.5 mm to 5.0 mm

Strip width: 750mm or less. (Narrow slab or sheet).

Sequence of operations when rolling timber

Rolling is a process that involves passing metal through a gap between rollers rotating in the opposite direction. This gap is less than the thickness of the workpiece. Therefore, the rollers compress the metal while simultaneously carrying it forward due to friction at the roller-metal interfaces.

When the workpiece passes completely through the gap between the rollers, it is considered fully processed. As a result, the thickness of the workpiece decreases, and its length and width increase.

However, the increase in width is minor and is usually ignored. A decrease in thickness is called slope, while an increase in length is called absolute elongation. Increasing width is known as absolute spread.

Lubricant is used in the rolling process to reduce friction between the rolls and the metal to be rolled. Friction plays a very important and beneficial role in the rolling process. In fact, it is responsible for moving the work forward between the rolls and therefore should not be eliminated or reduced below an appropriate level. This is an important consideration when selecting a lubricant for the rolling process.

When cold rolling steel, liquid lubricants with low viscosity are used, paraffin is suitable for non-ferrous materials such as aluminum, copper and its alloys to avoid coloration during subsequent heat treatment. While hot rolling is often carried out without lubricants, but with a stream of water to generate steam and destroy the formed flakes. Sometimes a graphite grease emulsion is used as a lubricant.

Source: https://znatprovse.ru/polezno-znat/process-prokatki-metalla.html

Corrugated sheeting, a universal material for fencing and roofing

For the manufacture of fences and enclosures, various materials are used - wood, OSB boards, mesh, metal, brick and various stones.

One of the universal, reliable, aesthetic, durable and quickly erected materials is corrugated sheeting.

The scope of application of corrugated sheets in construction and everyday life is enormous.

A fence made of turnkey corrugated sheets, roofing, walls, partitions, fences, this is only a small part of the application of profiled sheets.

Advantages of a fence made of corrugated sheets:

1. Quick and easy installation;
2. Does not require special skills;
3. No expensive or complex tools required;
4. Easily combined with concrete and brick, which allows you to build artistic compositions in an individual style;
5. The cost of a fence made of corrugated board is lower in comparison with fences made of stone, brick or concrete;
6. Long service life, unlike fences made of wood or OSB boards;
7. Good noise absorption (sound insulation);
8. Possibility of installing fences more than 3 meters high;
9. Large selection of profiles and colors. For example, you can make a fence from corrugated board to look like wood;
10. Does not require seasonal painting or repairs.

To preserve the aesthetic appearance, it is recommended to wash with water.

Types of corrugated sheets

Profile sheets made from steel 0.35-1 mm, by cold rolling, through special machines.

When rolling, ribs (profiles) of various shapes and heights are formed, from 8 mm to 114 mm.

To make a fence from corrugated sheets, a profile from 8 mm to 35 mm is usually used.

The metal is coated with various types of protective coating to protect it from moisture, sun, ultraviolet radiation and temperature changes.

Types of protective coating for corrugated sheets:

• Galvanized coating - metal is coated with a thin layer of zinc, up to 30 microns, used for ceilings inside outbuildings or simple fences. This material is cheaper in cost, but no less durable.
• Aluzinc coating (zinc + aluminum) - like the previous option, comparable in appearance, the protective layer is more reliable, but somewhat more expensive than its predecessor.
• Polymer coating is a mixture of synthetic resins and plastic, applied over a galvanized layer, as a result - the sheet is perfectly protected, plus it has an aesthetic appearance. This coating is resistant to ultraviolet radiation and fading. Maintains a presentable appearance for a long time. It costs more, but here the price is justified by the quality.
• The coating with pural or plastisol has a protective layer of about 200 microns; it is not afraid of harsh conditions of use, loads of various kinds (strong gusty wind, rain, snow, hail, various temperatures). The cost is high - the aesthetic and performance characteristics are as high as possible.
• The best option is a profile sheet coated with polymer. Large selection of colors. Harmoniously combines both price and quality.
• The best quality is PVDF (polyvinidine fluoride) coating with a protective layer of up to 40 microns.

Marking

When buying corrugated board for a fence, you need to carefully study the markings to avoid unnecessary costs:

1. H - means “load-bearing product”, a reinforced heavy product reinforced with stiffening ribs. The best application is in the roofs of large industrial workshops and large buildings. Application in a fence is not economically feasible (to put it simply, it is expensive).
2. C – means “wall”, this is used in the construction of fences or walls of structures (sheds) for economic purposes.
3. NS - means that the profile is “universal”, suitable for roofs, walls or fences.

Source: https://materialyinfo.ru/profnastil-universalnyj-material-dlya-zabora-i-krovli/

Metal rolling

There are volumetric rolling of metals and sheet rolling. Volumetric rolling is a metal forming process in which the deformation is naturally three-dimensional. This term, volumetric rolling or more generally volumetric forming, is used primarily to distinguish it from sheet metal processing processes.

Volumetric and plane deformation

In sheet production, the stresses that shape the metal are in the plane of the sheet, whereas in volumetric deformation, the stresses have components in all three coordinate directions.

Volumetric deformation, generally speaking, includes metal forming methods such as forging, pressing (extrusion), rolling and drawing. It is used for many metals, primarily, of course, steel, aluminum and copper.

Metal rolling temperature

The rolling temperature of metals - steel, aluminum, copper - is usually divided into two main intervals:

• cold processing;
• hot processing.

Cold rolling occurs at relatively low temperatures relative to the melting point of the metal. Hot rolling is carried out at temperatures above the recrystallization temperature of the metal. There is also a third temperature range - warm rolling, which is caused by the need to save energy and in some cases is used in industry.

Cold rolling

Cold rolling usually refers to the plastic deformation of metal at room temperature.

The phenomena that are associated with cold working occur when a metal is deformed at temperatures around 30% and below its melting point on an absolute scale of measurement. During cold working, an increasing number of dislocations appear in the metal.

The entanglement of these dislocations causes hardening of the metal - cold hardening or strain hardening. During strain hardening, the strength of the metal increases with increasing deformation.

Annealing of deformed metal

To recrystallize the metal, a special heat treatment is often necessary - tempering. During annealing, the strength of the metal can sharply decrease with a significant increase in ductility. This increase in ductility often allows further deformation of the metal without breaking it.

Cold working generally allows for greater control over the dimensional tolerances of the final product, as well as the quality of its surface, than does hot rolling.

Hot rolling

Hot rolling occurs at temperatures 60% or more of the melting temperature of the metal on an absolute scale. At elevated temperatures, the metal reduces its strength, which makes it possible to reduce the forces required for its plastic deformation.

Directly during the deformation of the metal, its recrystallization occurs with the constant formation of new grains. The constant formation of new grains ensures the preservation of high ductility of the metal. This makes it possible to achieve large values ​​of deformation without destroying the metal.

Control of final dimensions during hot working is more difficult due to the formation of scale and volumetric changes during subsequent cooling.

Warm rolling

Warm rolling of metals is between hot rolling and cold rolling. It occurs in the temperature range of 30-60% of the melting temperature of the metal on an absolute scale. The forces required to deform the metal during warm rolling are higher than during hot rolling.

The final surface quality and dimensional tolerances are higher than with hot rolling, but not as good as with cold rolling. Although warm rolling has disadvantages, the main incentive for its use is economics. Heating metal for hot working is very, very expensive.

By lowering the rolling temperature, significant funds are released, which can be used to improve product quality.

Source: https://steel-guide.ru/prokatka-metallov

What is rental and where is it used?

Humanity has long learned to process metals and alloys based on them. For this, different technologies are used. Rolling is a popular technological operation used to produce various metal parts.

What is rental?

Rolling is a metal processing process in which increased pressure is applied to the material. Before it gets under the rollers, it undergoes heat treatment. Under the influence of high temperature, the metal becomes more pliable, which makes it possible to manufacture products of different sizes and shapes from it. Using this technological operation, pipes, sheets, beams, fittings, rods, channels, and angles are produced.

Types of rental

Factories use different types of rolled products. Technologies differ in the equipment used and the stages of work. To produce steel parts, machines of different designs are used.

Sheet

This is a popular type of metal processing in which the part is first heated and then passed through rotating rolls. The technology can be carried out in two ways:

1. Hot rolled - the method involves heating the material to 1700 degrees Fahrenheit. After heating, the metal becomes more ductile and less hard. However, rolling at high temperatures does not allow accurately calculating the size of finished products after cooling. In addition, strong heating promotes the formation of scale, which must be removed.
2. Cold-rolled technology involves slightly heating the workpieces before further work. The surfaces of the parts are cleaned of scale. After this, they are subjected to other technological operations.

The first rolling option is more economical. With its help you can work with sheets of large thickness. The second method allows you to create parts that are more accurate in size, but is not suitable for working with metal sheets thicker than 5 mm.

Varietal

This type of technology can be divided into hot and cold methods. With its help it is produced:

1. wire, fittings;
2. hexagons, squares;
3. circles, semicircular details.

Shaped

Small rental group. The technology received its name because of the complex shape of the finished products. The output is large parts. They are made on industrial machines. Shaped products can be divided into two groups:

1. For mass use. This includes channels and corner profiles.
2. For special purposes. These include rails for railway or tram tracks, floors, beams, industrial stops.

This method of rolling is used in construction.

Equipment

To understand how different parts are made, you need to know what equipment is used during technological processes. Rolling is carried out on the following machines:

1. Wire mechanisms. With their help, wire with a diameter of up to 10 mm is produced.
2. Slabs - designed for processing long rectangular products.
3. Bloomings - used in the manufacture of large square products. In addition to square sections, mechanisms can make blanks of various shapes.
4. Pipe rolling are industrial machines that are used to create metal pipes of different diameters.

Before rolling begins, the metal is heated using industrial furnaces and fed through cutting shears to rotating shafts.
Production of galvanized rolled products from A to Z. How it is done.

Execution technique

Experts distinguish two methods of rolling:

1. Metal ingots are heated and fed to special clamping mechanisms. The surface of the workpiece is cleaned of formed defects. The workpieces are heated again and fed through the rotating shafts again.
2. An industrial method that involves continuous casting without interruption. Molten metal is fed under rotating rollers. This method is suitable for processing non-ferrous metals.

Next, the products are subjected to turning, grinding, milling, boring, drilling, and cutting. Stages of rolling aluminum alloys:

1. The sheet passes through movable rollers to create smooth surfaces.
2. The metal is milled.
3. Aluminum sheets are placed on the workpiece on both sides.
4. The part is heating up.

The last stages are annealing and cold rolling.

Rolling is a technological operation by which metal parts of different sizes and shapes are produced. There are several processing methods. Products made using this processing method are popular in various industries.

What is rental and where is it used? Link to main publication

Source: https://metalloy.ru/obrabotka/termo/prokat

Volumetric and plane deformation

In sheet production, the stresses that shape the metal are in the plane of the sheet, whereas in volumetric deformation, the stresses have components in all three coordinate directions.

Volumetric deformation, generally speaking, includes metal forming methods such as forging, pressing (extrusion), rolling and drawing. It is used for many metals, primarily, of course, steel, aluminum and copper.

Metal rolling temperature

The rolling temperature of metals - steel, aluminum, copper - is usually divided into two main intervals:

• cold processing;
• hot processing.

Cold rolling occurs at relatively low temperatures relative to the melting point of the metal. Hot rolling is carried out at temperatures above the recrystallization temperature of the metal. There is also a third temperature range - warm rolling, which is caused by the need to save energy and in some cases is used in industry.

Cold rolling

Cold rolling usually refers to the plastic deformation of metal at room temperature.

The phenomena that are associated with cold working occur when a metal is deformed at temperatures around 30% and below its melting point on an absolute scale of measurement. During cold working, an increasing number of dislocations appear in the metal.

The entanglement of these dislocations causes hardening of the metal - cold hardening or strain hardening. During strain hardening, the strength of the metal increases with increasing deformation.

Annealing of deformed metal

To recrystallize the metal, a special heat treatment is often necessary - tempering. During annealing, the strength of the metal can sharply decrease with a significant increase in ductility. This increase in ductility often allows further deformation of the metal without breaking it.

Cold working generally allows for greater control over the dimensional tolerances of the final product, as well as the quality of its surface, than does hot rolling.

Hot rolling

Hot rolling occurs at temperatures 60% or more of the melting temperature of the metal on an absolute scale. At elevated temperatures, the metal reduces its strength, which makes it possible to reduce the forces required for its plastic deformation.

Directly during the deformation of the metal, its recrystallization occurs with the constant formation of new grains. The constant formation of new grains ensures the preservation of high ductility of the metal. This makes it possible to achieve large values ​​of deformation without destroying the metal.

Control of final dimensions during hot working is more difficult due to the formation of scale and volumetric changes during subsequent cooling.

Warm rolling

Warm rolling of metals is between hot rolling and cold rolling. It occurs in the temperature range of 30-60% of the melting temperature of the metal on an absolute scale. The forces required to deform the metal during warm rolling are higher than during hot rolling.

The final surface quality and dimensional tolerances are higher than with hot rolling, but not as good as with cold rolling. Although warm rolling has disadvantages, the main incentive for its use is economics. Heating metal for hot working is very, very expensive.

By lowering the rolling temperature, significant funds are released, which can be used to improve product quality.

Source: http://otlivka.info/articles/%D0%BF%D1%80%D0%BE%D0%BA%D0%B0%D1%82%D0%BA%D0%B0-%D0%BC% D0%B5%D1%82%D0%B0%D0%BB%D0%BB%D0%BE%D0%B2/

I-beam 70 B2 in simple words about the main thing

I-beam 70 B2 – black, shaped metal with a profile section in the shape of the letter “H”. Two shelves, a wall (neck) between them. This is a hot-rolled I-section (the abbreviated name I-beam is used). It is widely used in various sectors of the national economy.

Products with parallel edges of equal-width shelves. According to their ratio and working conditions, it belongs to normal type B. The height of the profile is greater than the width of the shelves. The wall thickness is the minimum. I-beam 70 B2 belongs to the beam category, which determines its scope of use. This type of beam in metal structures primarily works in bending.

Products in the Russian Federation are manufactured on the basis of the national standard GOST R 57837-2017. It replaced STO ASChM 20-93, GOST 26020-83 and GOST 8239-89. When I-beam 70 B2 is sold, reference is made to these documents. They are still operating in a number of CIS countries. Rolled height 70 mm, profile size 2 (2). Read on for other characteristics and important parameters.

I-beam 70 B2 – main characteristics

I-beam 70 B2 in the Russian Federation is produced on the basis of GOST R 57837-2017. It predetermines all dimensions of the specified type of rental in tabular form. Main characteristics of the designated type of rolled products according to GOST R 57837-2017:

• total height (h), mm – 697.0;
• shelf width (equal-flange rolled, b), mm – 260.0;
• wall thickness (neck, s), mm – 12.5;
• shelf thickness (both shelves have the same t), mm – 18.5;
• radius of conjugation (internal rounding, rounding of the transition from the flange to the neck, r), mm – 24.0;
• weight of 1 half-beam I-beam, kg – 144.2;
• moment of inertia relative to the x axis (Ix)/y (Iy), cm4 – 145913.0/5436.7;
• moment of resistance relative to the x axis (Wx)/y (Wy), cm³ – 4186.9/418.2;
• static half-section moment relative to the x axis (Sx), cm³ – 2392.8;
• radius of gyration relative to the x (ix)/y (iy) axis, cm – 291.9/54.4.

Two important points

Moment one. The indicated parameters are specified in the amendment to GOST R 57837-2017 dated May 15, 2018. In the document itself, the values ​​​​for some positions differ. Second moment. Please note that the indicated characteristics will differ when using GOST 26020-83 and STO ASChM 20-93. But the application of these regulatory documents in Russia is not relevant.

Products are available in a variety of lengths, including:

• measured (marked MD), ranging from 6 to 24 m, in increments of 0.100 m;
• unmeasured (ND), in the range from 4 to 24 m;
• measured with unmeasured (MD1);
• limited within the unmeasured (OD).

I-beam 70 B2 should be selected for load-bearing structures based on the calculations performed. The basis is taken from the main characteristics of the rental and the structural features of the object, its functional purpose. The material of manufacture plays an important role. More on this later.

Recommended reading:

What is a metal beam in construction? 7 main areas of application

Types of beams, secrets of selection and application

Calculation of the load on an I-beam - relevance of implementation and basic methods

Production technology and materials

I-beam 70 B2 is made of steel using hot rolling technology of a metal billet. This is either a bloom or, most often, a blank obtained by continuous casting. It heats up to a certain temperature.

The metal becomes ductile and lends itself well to molding. Forming is performed on rolling mills using rolls. Hot plastic deformation occurs. As a result, the cross-section of the workpiece decreases, its shape changes and its length increases.

After rolling is completed, finishing and cooling are carried out, sometimes accelerated.

According to GOST R 57837-2017, I-beam 70 B2 is made of unalloyed, less often alloyed, steel grades. In particular, this type of shaped black metal products, made from carbon grades, steel St3sp and St3Gsp, is widely used.

An I-beam 70 B2 made of low-alloy steel grade 09G2S and a number of others is also offered. The operational and structural characteristics of the products and their cost depend on the selected grade of steel.

It is especially critical when determining the size of the spans between planes or support columns.

Directions for use

Hot-rolled steel profile 70 B2 is actively used in various building structures that work primarily in bending. These are floor beams, roofs, and other structural elements. Especially those structures where the use of welded and bolted connections is allowed. Other areas of use include the arrangement of horizontal and vertical connections, truss elements, and foundations.

To put it simply, I-beam 70 B2 is actively used in industrial and civil construction. This type of rolled product is also used in the construction of loaded, load-bearing, supporting and non-loaded metal structures. Moreover, they can be erected both at the construction site and delivered in the form of ready-to-assemble segments.

This type of shaped steel is also used in the construction of infrastructure facilities. For example, let's note transport construction (roads, overpasses, bridges, interchanges, overpasses, platforms for access roads). Other areas include heavy engineering.

The areas of application of I-beam 70 B2 are not limited to this. The main technical, engineering and economic justification for the use of this type of I-beam. After all, it can be used both as an independent structural element and in a composite engineering structure.

I-beam 70 B2 advantages of use

I-beam 70 B2 has several undeniable advantages of use. Among the main advantages we highlight:

• ability to withstand various multidirectional loads;
• lighter weight compared to beams of solid rectangular or square cross-section with similar strength characteristics;
• ease of delivery, storage and installation in metal structures;
• efficiency, less metal is used, which means the cost is lower compared to solid beams;
• wide variability of installation technologies, using welding, including electric arc, gas, bolted connections;
• high degree of structural rigidity;
• low degree of fluidity, linear dimensions do not change under the influence of constant, long-term static loads.

There are other advantages too. They are largely determined by the grade and steel used, as well as the disadvantages. That is, when choosing an I-beam 70 B2, you need to take into account what grade of steel it is made of. In other words, I-beams 70 B2 made of St3sp and 09G2S steel are significantly different. They have their advantages and disadvantages, directions for use.

Purchase and additional services

When purchasing an I-beam 70 B2, you need to check the availability of accompanying documentation (certificates and other documents). There must be marking in accordance with GOST 7566. It indicates the grade of beam and steel, manufacturer and a number of other parameters. Form of sale – individually or in packs.

Among the main additional services provided by metal warehouses:

• loading and unloading operations;
• delivery to the customer’s site;
• cutting into fragments of a certain length;
• galvanizing or painting (depending on the steel grade and direction of use).

There are other support services. Among them are the production of metal structures according to customer drawings from I-beam 70 B2 and others.

Do you need an I-beam 70 B2? Still have questions and need help choosing? Contact us! We will definitely help.

Source: http://blog.kpmtrade.ru/harakteristiki-tovarov/harakteristiki-balki-dvutavrovoj/balka-dvutavrovaya-70-b2/

What is rolling

Rolling - 1. Action according to value.
verb: to roll (2*1), to roll. 2. Compression and stretching of something.
pressure of the rotating rolls. 3. Metal processing by compression between rotating rollers of special machines.
4. decompression Rolling shop.

The meaning of the word Rolling along Ozhegov:

Rolling - Hot processing of metal by pressure, squeezing it between rotating rolls in special mills to give it the desired shape and profile

Rolling in the Encyclopedic Dictionary:

Rolling - metals - a method of processing metals by pressure - compression between rotating rolls of rolling mills. There are longitudinal, transverse and helical (oblique) rolling, as well as transverse helical and longitudinal helical rolling. depending on the degree of heating of the metal being processed - hot, cold and warm rolling. A variety is non-ingot rolling.

The meaning of the word Rolling according to Ushakov’s dictionary:

ROLLING
rolling, pl. no, w. (those.). Passing a piece of metal between two rotating shafts to give it the desired shape. rolling . Rolling iron. Rolling shop.

Definition of the word “Rolling” according to TSB:

Rolling - metals, a method of processing metals and metal alloys by pressure, consisting of compressing them between rotating rolls of rolling mills.
The rolls are mostly in the shape of cylinders, smooth or with grooves (streams) cut into them, which, when two rolls are combined, form the so-called. gauges (see Rolling rolls, Calibration of rolling rolls, Profiling of rolls). Thanks to the characteristic P.

continuity of the work process, it is the most productive method of giving products the required shape. During casting, the metal, as a rule, is subjected to significant plastic compressive deformation, due to which its primary cast structure is destroyed and a structure that is more dense and fine-grained is formed in its place, which leads to an increase in the quality of the metal. T. o., P.

serves not only to change the shape of the metal being processed, but also to improve its structure and properties.
Like other methods of metal forming, P. is based on the use of the plasticity of metals. There are hot, cold and warm steel. The main part of the rolled products (blanks, long and sheet metal, pipes, balls, etc.) is produced by hot steel.

at initial temperatures: steel 1000-1300 °C, copper 750-850 °C, brass 600-800 °C, aluminum and its alloys 350-400 °C, titanium and its alloys 950-1100 °C, zinc about 150 °C . Cold P. is used mainly for the production of sheets and tape with a thickness of less than 1.5-6 mm, precision high-quality profiles and pipes. in addition, cold P.

subjected to hot-rolled metal to obtain a smoother surface and better mechanical properties, as well as due to the difficulty of heating and rapid cooling of small thickness products.
Warm deformation, in contrast to cold deformation, occurs at a slightly elevated temperature in order to reduce the hardening (hardening) of the metal during its deformation. In special cases, to protect the surface of the rolled product from oxidation, plating is used in a vacuum or in a neutral atmosphere.

There are 3 main methods of P.: longitudinal, transverse and helical (or oblique). In longitudinal processing (Fig. 1, a), the deformation of the workpiece occurs between rollers rotating in opposite directions and located in most cases parallel to one another. By frictional forces arising between the surface of the rolls and the rolled metal, it is drawn into the space between the rolls, thereby undergoing plastic deformation. Longitudinal P.

is much more widespread than the other 2 methods. Transverse P. (Fig. 1, b) and screw (oblique) P. (Fig. 1, c) serve only for processing bodies of rotation. In transverse processing, the metal is given a rotational movement relative to its axis and, therefore, it is processed in the transverse direction. In screw rolling, due to the oblique arrangement of the rolls, the metal, in addition to rotational motion, is also given translational motion in the direction of its axis.

If the translational speed of the rolled metal is less than the peripheral speed due to its rotation, the process is also called transverse helical, and if it is greater, longitudinal helical.
Transverse cutting is used for processing gear teeth and some other parts; cross-helical is used in the production of solid-rolled pipes, balls, axles, and other bodies of rotation (Fig. 2). Longitudinal helical P. is used in the production of drills. With longitudinal P.

, when metal passes between the rolls, the height of its cross-section decreases, and its length and width increase (Fig. 3).
The difference in height of the metal section before and after the passage between the rolls is called. linear (absolute) compression: &Delta.h = h0 - h1.
The ratio of this value to the initial height h0, expressed as a percentage 21/210160.tif, is called relative compression. for 1 pass it is usually 10-60%, and sometimes more (up to 90%).

The increase in the length of the rolled metal is characterized by the elongation coefficient &lambda.
(the ratio of the length of the metal after it exits the rolls to the original length). The deformation of the rolled metal in the direction of the width of its section is called broadening (the difference between the width of the section before and after rolling). Broadening increases with increasing reduction, roll diameter and coefficient of friction between the metal and the roll surface.

The area (volume) between the rolls, in which the rolled metal is in direct contact with them, is called the deformation zone. This is where the metal is compressed. Small areas adjacent on both sides to the deformation zone are called non-contact deformation zones. in them the metal is deformed only to a small extent.

The deformation zone consists of two main sections: a lagging zone, in which the average metal speed is less than the horizontal component of the peripheral speed of the rolls, and a leading zone, in which the metal speed is relatively higher. Therefore, the exit speed of the rolled metal from the rolls is slightly higher (by 2-6%) than their peripheral speed. The boundary between these zones is called the neutral section.

The friction forces acting on the rolled material from the rolls are directed along its movement in the lagging zone, and against it in the leading zone.
The capture of metal by rolls and the stability of the process are determined by the friction forces that arise on the contact surface of the metal with the rolls. For gripping, it is necessary that the tangent of the gripping angle α, i.e., the angle between the radii drawn from the axis of the rolls to points A and B (see Fig. 3), does not exceed the friction coefficient: tg&alpha. &le. &mu.. In cases where high demands are not placed on the cleanliness of the product surface, to increase the gripping angle (and, consequently, compression), the surface of the rolls is roughened by notching. Practically, the gripping angles are within the following limits: with hot P. in smooth rolls 20-26°, in notched ones - 27-34°. with cold P. with lubricant - 3-6°.

Force on rolls at P.

is defined as the product of the contact surface and the average specific force P = F·pcp (the specific force is distributed unevenly over the contact surfaces: its maximum is located near the neutral section, and towards the entrance and exit of the metal from the rolls the specific force decreases).

When rolling strips of rectangular cross-section, the contact surface is calculated using the formula 21/210161.tif, where r is the radius of the roll. During cold rolling of strips, the actual contact surface is larger due to the elastic compression of the rolls at the points of contact with the rolled metal.

The average specific force, also called normal contact stress, depends on a large number of factors and can be expressed by the formula pcp = n1 n2 n3 &sigma., where n1 is the stress coefficient of the metal, depending mainly on the ratio of the gripping arc length, i.e. that is, the arc between points A and B on the circumference of the roll section (see Fig. 3), to the average thickness of the rolled strip and its width, to the coefficient of friction and to the tension of the rolled metal (tension is widely used in cold rolling).
n2 is a coefficient that takes into account the influence of the metal speed: n3 is a coefficient that takes into account the influence of the amount of hardening of the metal. &sigma. — yield strength (resistance to deformation) of the metal being processed at rolling temperature. The coefficient n1 is of greatest importance, varying depending on the above factors within a wide range (0.8-8).
the greater the friction force on the contact surfaces and the smaller the thickness of the rolled metal, the higher this coefficient. In practical calculations, it is assumed that at hot P. n3 = 1, and at cold P. n2 = 1. For carbon steels at hot P. the average specific force is in the range of 100-300 n/m² (10-30 kgf/mmI), at cold P. 800-1500 n/m² (80-150 kgf/mm²). The resultant forces on the rolls under the most common conditions of rolling are directed parallel to the line connecting the axes of the rolls, that is, vertically (Fig. 4). The relationship between the force P and the moment M required to rotate each roll is determined by the formula M = P (a + &rho.), where a is the arm of the force P, located in the range (0.35-0.5)21/210162.tif , and
&rho. — the radius of the friction circle of the roll bearings, equal to the product of the friction coefficient of the bearing and the radius of its trunnion. The force on the roll when cutting steel wire, narrow steel strips is about 200-1000 kn (20-100 tf), and when cutting sheets 2-2.5 m wide it reaches 30-60 mn (3000-6000 tf). The torque required to rotate both rolls when cutting steel wire and small sections is 40-80 kn m (4-8 tf m), and when turning slabs and wide sheets it reaches 6000-9000 kn m (600 -900 tf m). About P. various steel profiles and profiles made of non-ferrous metals and alloys, see Art. Rolling production.

Lit.: Tselikov A.I., Fundamentals of the theory of rolling, M., 1965. Smirnov V.S., Theory of rolling, M., 1967. Tselikov A.I., Grishkov A.I., Theory of rolling, M., 1970. Teterin P.K., Theory of cross-helical rolling, M., 1971. Tretyakov A.V., Zyuzin V.I., Mechanical properties of metals and alloys during pressure treatment, M., 1973. Lugovskoy V.M. , Algorithms for automation systems for sheet mills, M., 1974.

A. I. Tselikov.

Rice. 1. Scheme of longitudinal (a), transverse (b) and helical (c) rolling: 1 - rolled metal. 2 and 3 - rollers.

Rice. 2. Scheme of screw rolling of round periodic profiles. Fig. 3. Scheme of metal deformation during longitudinal rolling.

Rice. 4. Direction of the resultant forces on the rolls during a simple rolling process, taking into account the influence of friction in the bearings.

Source: https://xn----7sbbh7akdldfh0ai3n.xn--p1ai/prokatka.html

Main types of metal forming based on mechanical properties

12Nov

articles

Everyone knows that even a child can bend an aluminum spoon, and a blacksmith can make a sword from a piece of steel using a hammer and a hot furnace. But not everyone understands that these processes are related from the point of view of knowledge about metalworking. In this article we will tell you about the basics of metal forming (MDM): what it is, the essence of the method and its application in practice with various materials.

Physical basis of the process

Iron, tin and other alloys and rocks have an elastic limit. This is the maximum load, after removal of which no residual (plastic) deformation occurs.

If the workpiece is exposed to an impact that exceeds this value, then changes will occur at the atomic level. The atoms will leave their stable compounds and bond into other, deformed ones, forming a new crystal lattice.

And now the product will remain in the state in which it was under mechanical load.

Let's take the same aluminum spoon as an example. Aluminum has a very low elastic limit. Therefore, you need to apply minimal external force to bend the cutlery. And evidence that plastic deformation has occurred is that the object does not return to its former shape. To summarize: metal forming is based on the mechanical property of the smallest atomic particles to occupy a new position under the influence of a load.

There is a hot and cold procedure

Which of these varieties to use depends on the material and their plasticity properties. A number of substances (for example, low-carbon steels, as well as ferritic and austenitic steels) have very high flexibility. Their recrystallization rate is very low. This means the following: crystalline grains of a polycrystal grow in a new place (where deformation occurs) due to the destruction of the lattice in the previous place. This process usually goes much faster if you increase the temperature.

Let's give an example not related to metalworking. If you bend a cold block of plasticine in half, it will break into two parts, and if you preheat it in your hands, it will melt - its plasticity will increase.

This is how the second method works - hot metal forming technology. Resistance decreases when heated, and the part is subject to mechanical stress.

But you need to be careful, because if you turn up the heat too much, you can simply burn the steel, that is, lose all its physical and chemical properties.

Cold OMD is less harmful to the atmosphere and the environment, but is not suitable for all materials. When heated, oxidation processes occur, an oxide layer appears on the surface, and the metal part itself acquires greater strength. Without heating, oxides will not be released, which is often more preferable, and strength can be ensured by other methods, for example, pressing. In both cases, strengthening occurs at the molecular level.

Main types of metal forming

There are 6 of them in total, but each of them can be divided into many subspecies depending on many factors. When choosing a metalworking method, you should focus on a number of the following indicators:

• physical and chemical characteristics of the workpiece;
• subsequent goals during operation;
• additional stages of exposure - paint coating, electric shock, etc.;
• workshop capabilities.

The proposed options have different prices and many differences; let’s look at them in more detail below. And if you want to purchase high-quality professional equipment for sawing, band sawing even the most durable metal sheets, we recommend you the Rosta company, which cooperates both with individuals and with representatives of manufacturing companies and metallurgical shops.

Metal forming: rolling

It happens as follows: there is a machine, rolling rolls are attached to it. When a part passes through them, it is subject to widespread impact from the tools. The result is a reduction in the cross-sectional diameter and giving an exclusive shape. There are three types of process:

• Longitudinal. The axes of the rotating rolls and the workpiece are co-directed or located at a slight angle. In this case, at least two rotation elements are used, and they move in one direction, while the product moves in the opposite direction. The crimping occurs so efficiently that as a result, the metal parts acquire a radius equal to the gap between the body being processed and the machine. The result is elongated, long cylinders.
• Transverse. The workpiece itself does not make translational movements, but the rollers work at full power; they process the body of rotation along the diameter, clamping it in place from all sides. Gears, balls and axles are made this way.
• Transverse helical, also known as oblique. The axis shifts slightly, the working tools also continue to be aligned with the workpiece, but no longer strictly parallel, but at a slight angle. This tilt leads to the fact that two multidirectional force vectors begin to act actively at once. They help to obtain a hollow pipe.

Rolled products have their own standardized names; all of its elements differ in cross-sectional diameter and size. The totality of all varieties, types and dimensional transformations is called assortment. But despite its diversity, it can still be divided into four groups:

• Varietal. It contains simple and shaped profiles. These are channels, hexagons, angles, as well as straight parts, for example, railway rails. Most often used.
• Sheet. It is represented by the production of metal sheets of various thicknesses.
• Special types are those that require special conditions that have a difficult configuration.
• Pipes (seamless and welded are distinguished). This refers to all cavities that are created in a cross-helical manner, for example, weapon cartridges.

Metal forming: forging

If the previous process could occur both with cold and hot material, now we are dealing with high-temperature work. Before applying mechanical impact to the workpiece, it is necessary to heat it, and the temperature must correspond to an indicator that exceeds the elastic limit in order to achieve plastic deformation.

Previously, this technology was used by blacksmiths; this is a very labor-intensive craft that requires precise and painstaking work, as well as a large amount of knowledge about the physical characteristics of each alloy. Now there is also a niche for hand forging, but it happens in a more mechanized way, for example, there is no need to inflate the bellows to maintain a living fire. A handmade product is usually considered high quality and expensive, as it is exclusive. In addition to this ancient look, forging is now used:

• On pneumatic, steam or hydraulic hammers - all movements are preset and predetermined by the program.
• All types of stamping, and there are many of them - from types of cutting to ways to bend the workpiece in the desired way.

The result of any process is forging. If the material is in a die, then the final part will follow its contour.

Metal forming: pressing process

Allows you to make holes, as well as apply stiffening ribs to any internal or external side. The cavity is literally punched out with knives on the press. In this case, you can choose either a hot or cold option. The second is suitable for fairly plastic materials, and if it is a brittle alloy, it has nickel or titanium added, then it should be heated in advance.

The matrices (pressing tools) are designed so that they have holes. It is through them that the metal layer is literally squeezed out - this is the result, it goes to finishing metal processing. And what was directly compressed remains for the repeated process. Again, we can give an example with soft plasticine tightly clenched in a fist. Some of it will seep between the fingers - pressing also works.

Drawing

A die, also known as a die, is the main tool for this type of processing. It has a hole and guides. The workpiece should be carried, or wired, through this space. It changes shape and acquires the required profile section.

This is how wire and steel strands and fittings are made. Initially, a product of a wider diameter is cast, and then, gradually passing through a number of machines with various dies, that is, nozzles, it is gradually narrowed to the desired size.

Source: http://rocta.ru/info/obrabotka-metallov-davleniem-omd-vidy-sposoby-i-osobennosti-tekhnologii/

Classification of types of rolled metal and its features

Rolled metal is part of complex structures. They are widely used in mechanical engineering, construction, shipbuilding and other sectors of the national economy. The process of processing iron ore into finished metal products occurs in several stages:

1. Smelting of iron and steel.
2. Production of rolled products.

The material for manufacturing is low-carbon or alloy steel with a high carbon content http://www.rostov.spk.ru/metalloprokat/.

 Long products

The composition includes profiles manufactured on section longitudinal rolling machines. Depending on the purpose and area of ​​application, it is divided into hot-rolled round, which is used for the manufacture of various:

• shafts;
• axes;
• bushings;
• gears, as well as other parts widely used in mechanical engineering.

In the construction industry, various reinforced concrete structures are used, in which round smooth or special rolled steel is used for reinforcement. Profile types of rolled metal include:

• hexagonal;
• square;
• rectangular.

They are often used in various sectors of the national economy.

Shaped types of rolled metal include:

These structures are widely used in mechanical engineering for the manufacture of all kinds of metal structures, construction of buildings and industrial facilities.

A special type of shaped steel is rails used for the construction and repair of railways, as well as for laying crane tracks on construction sites and in production workshops.

Sheet metal

According to the manufacturing method, it is divided into hot-rolled and cold-drawn. It is used for the manufacture of various prefabricated and welded metal structures used in industrial production and construction.

Carbon and low-alloy steels are used to produce both cold-drawn and hot-rolled sheets.

Certain types of sheet metal include:

• metal tape;
• tin;
• corrugated and expanded metal sheets (PVL), used for special purposes. For example, PVL sheets are used for the manufacture of various floorings and fences http://www.rostov.spk.ru/listovoy-prokat/.

The importance of waterproofing in roof construction

Pipes

One of the types of rolled metal, according to the method of application, is divided into:

• water and gas pipelines;
• seamless;
• electric welded;
• square and rectangular, which are used for the manufacture of frames for various products and metal structures;
• casing

Water and gas pipes are used in almost all sectors of the national economy, from the laying of water pipelines and industrial gas mains to the construction of various billboards and temporary structures http://www.rostov.spk.ru/trubnyy-prokat/.

Channel

A channel is one of the existing types of profiles obtained in the production of metal products. Steel (SS) have a U-shape; their composition includes 2 walls with shelves located at an angle of 90 degrees to the wall. The design specificity of the device gives it increased resistance to loads.

SS are used when it is necessary to produce a load-bearing metal structure; their use is widespread in various industrial sectors.

Types of steel channel

Hot-rolled channel is one of the existing types of production of shaped metal products. It is possible to arrange the edges of the shelves of this device both parallel and with a slight slope.

It is worth noting that the slope should not exceed 10%. The range of shelf widths for such a device varies from 35-120 mm, and as for the height: 45-400 mm.

Rolling accuracy parameter (TP):

1. Conventional TP - marked with the symbol (B).
2. Increased TP - marked with symbol (B).

A bent channel can be made using machines, the material is often hot-rolled or cold-rolled steel, but other types of this metal are also used. Bent channels differ from hot-rolled ones in that they have a rounded corner. The digital recording of a channel device indicates the length of the device in millimeters.

The most purchased and valuable types of channels

TypeDescription

Channels number 10	A similar device is used throughout the construction industry when creating machine tools and machines. Industry is the main area of ​​application of this device. They have the best characteristics for the buyer. Their use is widespread for supports and metal structures.
Channels number 14	These channels can have either a normal accuracy parameter or an increased one. Their main area of ​​operation is construction work
Channels number 20	These are equal-flange channels, since there is an interval of 210 mm between the edges of such a device. They are used if the structure is subject to increased loads of various types. Such channels are also used to improve the strength of bridges. Complex reinforcement is another area where they are used

Quick construction of a private house: technology review

It should be noted that the sale of rolled metal products is currently thriving, and the following are especially in demand:

• round pipes;
• sheet metals;
• beams;
• corners;
• circles and many other positions.

Both black and stainless steel are quite popular among buyers. Hot compression is performed at different temperature values ​​specified by the technologists.

It would not be amiss to remind you of technological discipline: it is required to strictly maintain the temperature regime according to technology. Only in this case can you get a quality product.

To roll steel (to condition), that is, to the required GOST thickness, it is necessary to perform not one, but several rollings between rolls.

Sales of rolled metal products are especially growing in the stainless steel category, since everyone is satisfied with the resistance of this type of material to corrosion. There are a lot of people interested in this species both in Russia and in the CIS countries, as well as in the near and far abroad.

A consumer, choosing between products from Russian manufacturers and, for example, Chinese or Turkish ones, always chooses our product. This is always a traditionally high-quality product, the structure and chemical composition of which, as well as strength indicators, are almost ideal in comparison with competitors.

Buyers come from everywhere, since products of this type are used in a variety of industries. The cost mainly depends on the raw materials used and the availability of cheap energy. You will see high prices for metals such as AISI 316 steel. The structure of this metal contains a lot of molybdenum. The presence of this effective component gives the AISI 316 material new properties to withstand when working in aggressive environments.

Repair and finishing of ceilings

If, at a low cost of advertising, you inform with an announcement that you are selling a round pipe made of AISI 304 steel, then a lot of buyers will be recruited. They buy everything that can be offered. Popular, expensive rolled metal products are in great demand, which lags behind supply.

The client always has a lot of doubts when receiving cheap Chinese supplies. The price indicator, which is below the market price, speaks for itself. This material can only be taken after laboratory testing of the entire proposed batch. In 90 percent of cases, a discrepancy with the declared structure and chemical composition can be detected.

Source: https://domik-derevne.ru/stroitelstvo/klassifikaciya-vidov-metalloprokata-i-ego-osobennosti.html

Types, characteristics and application of rolled metal

Rolled metal products are used in all spheres of the national economy. It is produced by hot rolling from cast and forged billets at temperatures exceeding the recrystallization temperature of the metal. As a result of hot deformation, metal products with low surface quality and dimensional accuracy are obtained. To improve these characteristics, cold deformation methods are used (cold rolling, drawing, calibration).

Types of rolled metal according to production material – steel and non-ferrous

Rolled steel is the most in demand in all industries and construction.
It is made from unalloyed, low-alloyed and alloyed (corrosion-resistant, heat-resistant, heat-resistant) steels. Unalloyed grades are usually called “black”. These include carbon steels of ordinary quality and high-quality ones containing varying amounts of carbon. The percentage of other elements (except iron and carbon) does not exceed 1%.

In the production of non-ferrous rolled products, non-ferrous metals are used - aluminum, copper, titanium and others, and alloys based on them.

Rolled metal is divided according to many criteria, each of which is regulated by relevant regulatory documents. According to the cross-sectional shape, rolled products are divided into sections, shapes, sheets, and pipes.

What applies to long products?

In accordance with GOST 535-2005, long products include metal products in which any tangent drawn to a cross section does not intersect this section.

Classification of types of long products:

• Circle. Hot-rolled wheels are manufactured in accordance with GOST 2590-2006, diameter range - 5-270 mm. Metal products may have a larger diameter, but such products are produced only on an individual order. Hot-rolled circles are used in the production of fasteners, construction, mechanical engineering parts, and as a blank for cold deformation. Surface quality and dimensional accuracy are improved by cold deformation. Cold-rolled and cold-drawn circles are produced in accordance with GOST 7417-75 in the diameter range of 3-100 mm. Such products are used without heat treatment or after heat treatment in the mechanical and automotive industries, in the production of household appliances, and production equipment.
• Square. Hot-rolled products with a square cross section are produced in accordance with GOST 2591-88. The side sizes are in the range of 8-200 mm. Hot-rolled square is used in the production of fasteners or other hardware, and also as a blank for cold-formed products. Calibrated rolled products have precise dimensional parameters and a high-quality surface. Manufactured according to GOST 8559-75. The purpose of this type of rental is the production of parts for automotive and mechanical engineering, industrial equipment and household appliances, application in architecture and interior design (after appropriate surface treatment. The range of side sizes is 3-100 mm.
• Hexagon. Hot-rolled metal with a hexagonal cross-section is produced in accordance with GOST 2879-2006. The hexagon number is equal to the diameter of the inscribed circle, taken in millimeters. Range – 8-103 mm. The products are widely in demand in the production of fasteners - bolts, nuts. Cold-rolled hexagon is manufactured according to GOST 8560-78. The main area of ​​application of hexagonal rolled products is the production of high-precision fasteners on automatic machines.
• Band. The characteristics of hot-rolled metal products are regulated by GOST 103-2006. Strip products are used to produce various types of hardware by cold and hot stamping, bent profiles, and in construction. Strip width – 10-200 mm, strip thickness – 4-80 mm.

What is included in the concept of “shaped rolled products”?

According to GOST 535-2005, shaped metal products include metal products in which some tangents to the section contours intersect this section.

• I-beam is a hot-rolled product with a cross section in the shape of the letter “H”. It is manufactured with the internal edges of the shelves - parallel (GOST 26020-83 and STO ASChM 20-93) or located at an angle (GOST 8239-89). These metal products are used mainly in mass housing construction; they are rarely used for the construction of private houses.
• Channel is a hot-rolled product with a cross section in the shape of the letter “P”. It is manufactured with the inner edges of the shelves - parallel or inclined - in accordance with GOST 8240-89. The areas of application of rolled metal are individual and mass construction, the construction of various frame structures, small forms - canopies, greenhouses, gazebos.
• Corner. Hot rolled equal flange angles are regulated by GOST 85009-83, unequal flange angles are regulated by GOST 8510-86. The side size of an equal angle angle is in the range of 2-25 cm. The angle is intended for construction, mechanical engineering, manufacturing of production equipment, and household appliances.

Rolled pipes: types and characteristics

Pipes have a round or profile (different from round) cross-section, are made seamless or with a welded seam (straight - one or more, spiral.

• Round pipes. Seamless hot-rolled products are used in areas that require high resistance to various types of influences, for example, for the transmission of media under pressure. Cheaper and more common products are welded pipes. One of the varieties of welded pipe products - VGP pipes (water and gas pipes) - is widely in demand in housing and communal services for organizing pipeline systems for water, heat and gas supply.
• Profile pipes – rectangular and square. These metal products are not used for transmitting gaseous and liquid media. Profile pipe products are in demand in frame construction, for the manufacture of canopies, greenhouses, and gazebos.

Table of main rental characteristics

Rental name	Basic GOSTs	Size range	Main Applications
Hot rolled circle	2590-2006	Diameters – 5-300 mm	Production of fasteners, blanks for cold deformation
Cold-deformed circle	7417-75	Diameters – 3-100 mm	Manufacturing of fasteners and other parts on automatic machines
Hot rolled square	2591-88	Side size – 8-200 mm	Fastener production, construction
Cold-deformed square	8559-75	Side size – 3-100 mm	Manufacturing of parts for automobile and mechanical engineering
Hot rolled hexagon	2879-2006	Diameter of inscribed circle – 8-103 mm	Production of fasteners, machine parts and mechanisms
Band	103-2006	Thickness – 4-80, width – 10-200 mm	Production of bent profiles, pipes, construction, ground loop installation, decorative, finishing work
Corner	85009-83	Side size of equal angle angle – 20-250 mm	Construction (production of various metal structures, reinforcement of reinforced concrete elements), production of machines, mechanisms, industrial equipment, pipeline racks
Channel	8240-89	Channel wall height – 5-40 cm	Construction, installation of span structures, production of frames for finishing materials, production of advertising media
I-beam	8239-89	Wall height – 10-60 cm	Civil, industrial, infrastructure construction
Hot rolled sheet	19903-2015	Thickness – 0.5-160.0 mm	Production of pipes, bent profiles, production of decking, continuous fencing, rolling for cold-rolled sheets, boiler building
Cold rolled sheet	19904-90	Thickness – 0.35-5.0 mm	Automotive and mechanical engineering
Round seamless	8732-78	Outer diameter – 20-550 mm	Transfer of liquid and gas media at high temperatures and pressure, creation of metal structures
Round electric-welded straight-seam	10704-91	Outer diameter – 10-245 mm	Organization of water, gas, heat supply systems
Profile welded	8645-68	Length – 15-230 mm, height – 10-150 mm	Frame construction, production of stairs, fences

Source: https://www.navigator-beton.ru/articles/metalloprokat-vidy-harakteristiki.html