What steel is used to make reinforcement

Reinforcement class: table and technological characteristics of metal rods – Machine

Today, the construction of any building or technical structure cannot be completed without the use of concrete mortar.

The reinforced frame of the structure greatly increases the strength of the structure, preventing cracking and destruction of concrete buildings.

Modern rolled metal products offer various types of steel construction reinforcement for the formation of reinforced concrete structures for various purposes.

Main characteristics of steel reinforcement

To absorb tension and strengthen compressed zones of concrete structures is the main purpose of construction reinforcement. To implement this function, reinforcing bars are manufactured with the highest possible strength and ductility. To obtain a high-quality product, metal rolling enterprises increase the strength properties of raw materials:

• regulate the chemical composition of steel, increasing the content of carbon and chemical additives;
• in a cold state, steel is strengthened by twisting, drawing, stretching, flattening and other methods;
• heat treatment is applied;
• several methods are combined.

Durable and ductile, not susceptible to corrosion under a layer of concrete, withstanding temperature changes, time-tested steel building reinforcement is used both in the construction of low-rise residential buildings and in the construction of complex industrial and technical structures.

Types of reinforcement products

According to their purpose, fittings are divided into 4 types:

• Working. It absorbs tensile forces that arise in reinforced concrete structures under the pressure of external loads and its own weight.
• Distribution. It is a reinforcement mesh or frame connected by wire or welding. By tying the rods together, it prevents the working base from shifting during concreting and is intended to distribute a uniform load between the elements of the working reinforcement.
• Clamps. They are used when assembling the frame, protecting against the appearance of cracks near the supports in the beams.
• Assembly room. Used when concreting or assembling a frame to ensure the correct position of clamps and working reinforcement. It does not take any loads and is usually removed upon completion of work.

Types of building reinforcement

According to the orientation in the structure, it is divided into transverse and longitudinal. Transverse reinforcement binds concrete in the compressed and tensile zones of the structure to prevent the formation of inclined cracks near the supports. Longitudinal reinforcement, perceiving compressive and tensile stress, prevents vertical cracking in the tensile zone of the structure.

According to the conditions of use, it is divided into prestressed and non-prestressed reinforcement. Only working reinforcement that has been pre-tensioned to increase the strength of a reinforced concrete structure can be prestressed. Tensioning the reinforcing bars, reducing deflections and reducing the weight of the structure, prevents the formation of cracks and reduces the amount of steel reinforcement.

Reinforcement manufacturing methods

According to production technology, reinforcement for reinforced concrete buildings is of two types:

• Hot rolled rod. Reinforcement with any diameter, supplied in steel rods up to 13 meters long or in coils weighing up to 1.3 tons.
• Cold drawn wire. In the process of pulling (drawing) steel through the holes of drawing mills, the wire or rods change their cross-sectional shape and dimensions. A longer and more expensive production process, which results in high-quality reinforcement with a thickness of no more than 5 mm.

Hot-rolled steel reinforcement is significantly less expensive than cold-drawn steel reinforcement and has a higher level of corrosion resistance. Hot-rolled reinforcement bars are used more often and to increase strength they undergo subsequent thermal and mechanical treatment. This type of reinforcement is divided into 2 types according to the shape of the surface:

1. Smooth – metal rods with a smooth surface. Used for mounting the frame.
2. Periodic profile (corrugated) - rods with transverse protrusions and longitudinal ribs on the surface, twisted along a helix.

When casting reinforced concrete products or buildings, recesses and surface protrusions provide better adhesion of concrete to the reinforcement frame.

Classification of fittings

The strength of reinforcing bars depends on the steel alloy from which they are made. Reinforcement is classified according to its mechanical properties. Today there are several types of marking of steel construction reinforcement by class:

• A240 A-I.
• A300 A-II.
• A400 A-III.
• A600 A-IV.
• A800 AV.
• A1000 A-VI.

Class A240 (A-I) produces smooth fittings, other classes are produced with periodic corrugated profiles. Special properties, production method or purpose of fittings are indicated in the marking of finished products with additional indices.

Thermo-mechanical treatment is designated “At”, hardening by drawing is designated “Ab”. For regions of the Far North, frost-resistant reinforcement is marked “c”. Increased resistance to corrosion is designated “K”, and rods for welding are marked “C”.

Requirements for the strength of steel reinforcement are determined by GOSTs, which set yield limits for each class. For hot-rolled rod reinforcement GOST 5781, rod reinforcement strengthened by thermomechanical method is produced in accordance with GOST 10884. In accordance with the requirements of GOST, steel reinforcement cannot have holes, membranes, cracks or sunsets on its surface. Steel reinforcement bars are produced with a diameter from 6 mm to 80 mm.

Marking of finished products in production includes a class, an additional index and painting of the ends of the rods with a color corresponding to the brand. The class designation looks like this: At400S or At800KS.

Steel for the production of reinforcing bars

Low-alloy and carbon steel grades are used in the production of reinforcing bars. By changing the amount of chemicals, the alloy is given certain properties. Aluminum, silicon, manganese, nitrogen, chromium, boron, titanium, and zirconium are used as alloying additives.

Adding, for example, manganese to the alloy increases the rigidity of the material without reducing its elasticity. By changing the crystal lattice, silicon increases the density of steel rods, which improves the performance properties of the reinforcement, but makes it difficult to weld the elements. The strength of steel increases significantly when carbon is added to the alloy.

But an overdose of this substance impairs the ductility of building reinforcement.

The steel grade of the reinforcement is specified by the customer. If there are no brand requirements in the order, the manufacturer agrees it with the recipient, or the plant determines it at its own discretion.

Frequency of use

12 mm reinforcement made of steel class A3500C is in wide demand. Welding can be used to fasten plastic ribbed rods of this type. 12 mm reinforcement bars give the frame higher strength.

Application of construction reinforcement

Flat or three-dimensional structures made of steel rods are connected to each other by electric welding, knitting wire or special reinforcement clamps.

The high-quality adhesion of flat reinforcing meshes (grids) and volumetric frames to concrete depends on its strength and shrinkage amount, as well as on the type of surface and cross-sectional shape of the reinforcing bars.

Reliable adhesion of concrete and reinforcement is ensured by three factors:

1. Mechanical engagement of protrusions and surface irregularities of reinforcement with concrete.
2. Frictional forces arising on the surface of reinforcing bars when they are compressed by concrete during the shrinkage process.
3. Adhesion (gluing) of a reinforcing surface to concrete due to the viscosity of the cement mortar.

Currently, any concrete structure has a strong, reliable steel reinforced “skeleton”. Modern office or commercial buildings, residential or technical buildings, power plant dams or bridges are constructed using cast-in-place concreting technology.

Source: https://regionvtormet.ru/instrumenty/klass-armatury-tablitsa-i-tehnologicheskie-harakteristiki-metallicheskih-prutev.html

Production of fittings

Reinforcement is a type of rolled steel, which, unlike other products in this group, has a clear purpose - the production of reinforced concrete structures. The fittings are produced in the form of round rods and wires with a smooth or corrugated periodic profile. For the manufacture of these products, clearly defined grades of structural steel are used.

The manufacture of fittings is carried out in accordance with two regulatory documents: GOST 5781-82 and GOST 10884-94

The manufacture of fittings is carried out in accordance with two regulatory documents: GOST 5781-82 and GOST 10884-94. The first of them applies to conventional reinforcement, and the second to reinforcement reinforced by thermal and mechanical stress. According to these documents, fittings are divided into classes.

A fairly convenient way to indicate the class of reinforcement using the letters A or At and the yield strength of the material, which is expressed in N/mm2 (MPa). An example of such a designation: A300. Strengthened reinforcement may also have the letter C, which indicates increased weldability, or K, which indicates resistance to corrosion.

In addition, there is a class of special fittings Ac300.

Methods of production of fittings

Like many other metallurgical products, rod reinforcement is made by hot rolling. The workpiece is heated to a high temperature and driven through numerous rotating rolls. If you need to get corrugations on the surface, then they are also made using rollers, only of a special shape, with a corresponding profile on the surface.

Since high surface quality for reinforcement is not required, but rather productivity is primarily important, hot rolling is ideal for the production of these products. To ensure strength properties, reinforcement of class A800 and higher is subjected to low-temperature tempering.

Wire reinforcement is made by drawing. This method involves pulling the workpiece through a hole slightly smaller in diameter than the diameter of the workpiece.

In this way, it is impossible to greatly change the diameter of the product at one time, so this operation is performed repeatedly, using for each subsequent matrix with a smaller hole.

In general, drawing is a fairly effective production method, but it cannot produce products with a diameter of more than 25 mm due to significant loads on the tool.

Rebar of class A300 and below with a diameter of up to 12 mm and A400 with a diameter of up to 10 mm is wound into skeins. Higher-class fittings are produced only in the form of rods; production in the form of coils is carried out exclusively in agreement with the customer. Heat-treated reinforcement can be rolled into coils with a diameter of up to 8 and product class up to At600C.

Materials for the production of fittings

Most reinforcement cages are produced by welding, so the material is required to have good weldability. Another important parameter is tensile strength.

Reinforcement of different classes is made from different grades of steel. For the least durable class A240, the simplest structural steels are used - StZkp, StZps, StZsp. The price of such material is also minimal.

For products of class A300, both conventional steels St5sp, St5ps, and alloy steel 18G2S, to which manganese and silicon impart increased performance properties, can be used. Products of higher classes are produced only from alloy steel.

As alloying elements, in addition to those mentioned above, chromium, titanium, aluminum, etc. are used. The choice of alloying elements was largely made so as not to reduce the weldability of products.

Most rebar has low carbon content. It is limited to 0.32 – 0.35%. This is true for conventional and thermomechanically strengthened reinforcement, with the exception of products with a diameter of up to 18 mm class A600, which are made of 80C steel with a carbon content of 0.8%.

Among the substances that negatively affect the properties of the material, sulfur and phosphorus are primarily distinguished. Their content in reinforcing steel should not exceed 0.045%, maximum deviation +0.005%.

Use of fittings

Reinforcement is used to create reinforced concrete elements of buildings. When reinforcing, the specifics of materials should be taken into account. Concrete has a fairly high compressive strength, but when working in tension it quickly fails. Concrete tolerates bending loads moderately. Therefore, reinforcement is primarily intended to withstand tensile loads. It also protects concrete elements from surface crumbling.

Most of the reinforcement has a corrugated surface, due to which its adhesion to concrete is significantly improved. In the rubble of destroyed buildings, you can often see that the concrete partially remained on the reinforcement, which is an excellent indication of the strength of the connection.

Prestressed reinforced concrete structures have very high strength. To create them, the ends of the reinforcing bars are clamped and stretched. After this, concrete is poured into the mold. Relieving stress from the rods is carried out only after the concrete has completely hardened. The rods exert a compressive effect on concrete, due to which the strength of such a reinforced concrete element increases significantly.

The article is for informational purposes only.
Don't forget to consult with experts.

Source: https://samara-metall.ru/articles/armatura

Reinforcing products (reinforcement): types and application

And reinforcing products are structures assembled from reinforcing components, both finished and semi-finished. With the help of reinforcement, the frame of reinforced concrete elements is assembled.

And a ready-made reinforcing structure allows you to minimize labor costs in the manufacture of reinforced concrete products.

:
1. Reinforcement products: classification and types.
2. Knitted reinforcement mesh.
4. Reinforcement frames.
5.

Prestressed reinforcement products.
6. Other reinforcement products.

Reinforcement products: classification and types

A wide variety of products requires their classification, so → building reinforcement (you can order it using the link) is classified according to various characteristics and applications, here are the main ones:

By profile:

• periodic profile fittings. The rods have corrugations - transverse protrusions located on the surface of the metal base at an angle to its longitudinal axis;
• fittings with a smooth profile. The surface of the rods is smooth, they have a round cross-section.

Periodic reinforcement profile and smooth

According to the nature of the loads, the reinforcement can be:

• transverse. Such rods prevent the formation of inclined cracks, the appearance of which is caused by oblique shear stress near the supports;
• longitudinal The products absorb tensile stresses, preventing the appearance of vertical cracks in the material. In reinforced concrete products operating in compression, the loads are distributed between the longitudinal reinforcement and concrete.

Transverse and longitudinal reinforcement

According to the principle of operation, reinforcing products can be:

• non-stressed. They are used for the manufacture of reinforced concrete products during the construction of small structures where the frame does not experience high loads;
• tense. Such reinforcement is pre-tensioned , which makes it more resistant to high loads. Resists the appearance of cracks and deflections. Used for the construction of reinforced concrete structures of increased strength. The diameter of the rod ranges from 5 to 35 mm.

According to their purpose, the fittings are divided into:

• working Fittings that are installed according to calculations. Takes on external loads, as well as stresses arising under the influence of the structure’s own weight.
• assembly - used for assembling the reinforced concrete frame. Due to this, during concreting, the position of the working reinforcement rods remains unchanged. Installed for technological reasons for ease of frame assembly;
• constructive (distributive). To install such reinforcement, preliminary calculations are not required. It is installed for practical purposes where random force impacts may occur. These are corrugated products that ensure precise load distribution, so that the position of the working rods does not change during operation;
• anchor - embedded parts;

Example of reinforcement cage

There are the following types of reinforcing products :

• reinforcing mesh. They can be welded and knitted;
• frames. They are divided into spatial and flat;
• prestressed reinforcement products (ropes and bundles with and without anchors);
• piece products (clamps, mounting loops, embedded elements).

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Let's look at all these types in more detail.

Welded reinforcement mesh

The most common products are welded reinforcement mesh. They are made of rods (wires), cross-shapedly connected to each other at the intersection points using spot welding.

Welded mesh is made from rods with a cross-section of more than 3 mm or from reinforcing wire. They can be:

• flat (if the diameter of the transverse rods is 10 mm or more, and the longitudinal rods are 5 mm or more)
• or rolled, if the cross-section of the rods is less than the specified values.

Cells can be rectangular or square.

Flat reinforcement mesh

Conventionally, grids are divided into:

If the diameter of each element does not exceed 10 mm, the design is considered lightweight . If the cross-section of the elements in at least one direction exceeds this indicator, the product is included in the heavy .

Rods (wire) going in the same direction must always have the same cross-section.

The designs also differ in the location of the working fittings . It can be used in one direction or in both. In the first case, distribution fittings are installed in a perpendicular direction.

Rolled mesh with rectangular cells

The length of the nets can be up to 9 m. The width depends on the type of product: for light ones - 0.65-3.8 m, for heavy ones - 0.65-3.05 m.

Welded mesh is used to reinforce reinforced concrete elements, road surfaces and brickwork; arrange → screeding of cement floors (the link describes the construction of cement-sand screeds). It is used when laying the foundation of buildings and structures, in the manufacture of frames for greenhouses in crop production and cages in animal husbandry. Decorative and functional fences are made from it.

Knitted reinforcement mesh

If the volume of construction work is small, then reinforcing mesh is sometimes knitted by hand from soft wire after annealing, the cross-section of which is 0.8-1.0 mm. For knitting, special reinforcement cutters are used, the teeth of which are slightly blunted so as not to bite the wire during work.

Knitted reinforcement mesh

The meshes are tied manually in the following cases:

• when the rods cannot be connected by welding (for example, in the manufacture of non-standard structures);
• for the purpose of enlarging the product on the construction site;
• when performing urgent work, when finished reinforcing products cannot be delivered to the site within the required time frame;
• for small volumes of reinforcement, when there is no point in using → a welding machine (how to work with a welding inverter is described in the link);
• when the reinforcement is made from non-weldable steel rods or waste wire.

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To speed up the process of manual knitting and increase its productivity, the joints of the rods are fastened not with wire, but with clamps made on an automatic machine.

Reinforcement frames

There are 2 types of such structures:

In frames of the first type, the transverse rods are located in the same plane. The number of longitudinal rods can be different, and according to this indicator, frame structures can be 2-, 3-, or 4-branch.

They are used to produce spatial reinforcement cages for reinforcing reinforced concrete elements that are tensile or bending and have a narrow cross-section of reinforcement.

The joints of the rods are fastened by resistance welding using high-performance multi-electrode welding equipment.

Flat reinforcement cage

A feature of spatial reinforcement frames is the arrangement of transverse rods in different planes. Structures are assembled from various reinforcing products and elements - rods, meshes, flat frames, embedded elements, etc. The joints are connected to each other by welding or knitting.

To give the products additional rigidity, steel strips, angles or square rods are used instead of rods.

Volumetric reinforcement frame

Advantages of using ready-made frames:

• saving time. Ready-made structures allow you to complete work faster without wasting time on soldering and knitting reinforcement;
• complete absence of reinforcement waste;
• reliability of the design. Frames manufactured using specialized equipment in a factory are stronger and more stable than structures assembled on a construction site;
• the ability to select the necessary parameters. The frames are manufactured taking into account the required dimensions for a specific object and do not require modification on site.

In addition, the number of people involved at a construction site is reduced, since when delivering finished structures, specialists in the production of reinforcement cages are not needed.

Prestressed reinforcement products

Non-tensioned reinforced concrete structures are reinforced with meshes and frames. Prestressed products are strengthened with ropes and reinforcement bundles. The elements are tensioned in the following ways:

• on the stops. The products are concreted after stretching them onto special forms and fixed with clamps. After the mixture has hardened, the clamps are removed;
• on concrete. Channel formers (pipes, rods) are installed in the formwork, the cross-section of which is 10-15 mm larger than the diameter of the product. 2-3 hours after concreting they are removed, reinforcement is inserted into the hole and tensioned;
• electromechanically. An alternating current of the required frequency is passed through the fittings. Due to thermal expansion, the product lengthens, and after cooling it shortens, transferring the compressive force to the concrete.

Prestressed concrete products are durable and effectively withstand dynamic loads.

Source: https://chonemuzhik.ru/armiruyushhie-izdeliya-armatura-vidy-i-primenenie.html

What steel are the fittings made from? — Machine tools, welding, metalworking

Reinforcement is a set of elements that improve the performance of reinforced concrete structures by increasing strength and compensating for various stresses. Due to the active use of reinforced concrete in modern construction, reinforcement of various categories is used very widely.

Reinforcing elements can be flexible (individual rods of various profiles, knitted and welded mesh, frames) and rigid (angles, I-beams, channels and other rolled products). The material for rods is usually steel (in accordance with GOST 10884-94), although there are composite (basalt-plastic, fiberglass, carbon-fiber), wood (bamboo) and other options.

Most often, the fittings are made of low-alloy or carbon steel. In general, the production of steel rod reinforcement is regulated by GOST 5781-82.

Depending on the processing method, steel reinforcement can be cold-drawn or hot-rolled.

Steel grades used for the manufacture of reinforcing elements: AI - St3kp, 18G2S, AII - St5sp, 25G2S, AIII - 35GS, A400S, A500S, 32G2RPS.

The choice of a particular steel grade determines the manufacturing technology, as well as the characteristics and operational features of the manufactured fittings:

• construction with reinforcement by hood (category “B”);
• construction reinforced, in accordance with GOST 10884-81 (category “T”);
• fittings with the possibility of welding (category “C”, for example, fittings A500C);
• reinforcement with increased resistance to corrosion cracking (category “K”).

The most popular brand of fittings in Russia is A500C; such a high level of demand is largely explained by the selected steel grade (ZPS), which is characterized by a lower content of alloying components. This ensures good ductility, strength, as well as high-quality weldability (A500C welded joints are not subject to brittle fractures).

What grade of steel is construction reinforcement made from?

Construction reinforcement plays the role of a reinforcing frame, increasing the strength and durability of concrete buildings. In the modern construction industry, standard reinforced concrete slabs and special castings of various shapes and purposes are widely used.

Construction reinforcement is required to have high tensile and shear strength; in addition, it should not be hardened and weld well with all types of welding.

This is achieved due to the low carbon content with a sufficient degree of purification from harmful non-metallic impurities.

The cheapest and most common reinforcing steel are steels St.2 and St.3, since they are the most widely used in the construction industry and have sufficient strength. In addition, a number of special reinforcing steels are used.

There are a number of classes of reinforcing steels, depending on their mechanical properties: A-I (A240), A-II (A300), A-III (A400); A-IV (A600), A-V (A800), A-VI (A1000).

The higher the class, the higher the strength of the reinforcing steel, which is determined by the carbon content, degree of steel purification, and the presence of alloying additives. Reinforcement is produced by hot rolling, both round and periodic (corrugated) profiles.

Round reinforcement has greater strength, while corrugated reinforcement has better adhesion to concrete.

Round reinforcement is more often used for structures operating in tension and shear; in addition, round reinforcement is used when thin reinforcement is used in a large product, then due to the large surface area of ​​the entire set of reinforcing wire in one slab, high strength of the structure as a whole is achieved. Reinforcement with a diameter of more than 32 mm is almost never produced round.

The table shows the steel grades used for the manufacture of reinforcement of a given diameter.

For the production of class A-V (A800) fittings, it is allowed to use steel grades 22Kh2G2AYU, 22Kh2G2P and 20Kh2G2SR. The diameters of the fittings indicated in brackets can be produced by agreement with the consumer.

In practice, there are no clear requirements for the diameter of the reinforcement; for example, instead of 6 mm reinforcement, 8 mm can be used, but such deviations are allowed only for large-sized products.

When using reinforcement of a different diameter, it is always necessary to specify the amount of reinforcing wire, mainly through the cross-sectional area of ​​the reinforcement per unit area of ​​the concrete casting.

In addition to the composition and properties of carbon steels, which must comply with GOST 380-88, the content of all main components in alloyed reinforcing steels is standardized. The composition of the most common alloy reinforcing steels is given in the table.

sulfur and phosphorus are given according to the upper ceiling, the content of copper and, especially nickel, as a rule, does not need to be limited, since copper is too expensive a component for metallurgists to allow its high content, and nickel at a content of up to 1.5%, in the case carbon content is not more than 0.35%, does not have a negative effect in the form of too high hardness, or the formation of hardening structures during welding.

It should be noted that steel with the lowest carbon content is used mainly to make small-diameter reinforcement; steel with a higher carbon content is used to produce more massive reinforcement for the construction of high-rise buildings.

Reinforcing steels with additions of aluminum (the letter “Y” in the index) and chromium (the letter “X”) have significant resistance to corrosion, and can be used for the production of reinforcement, the operation of which involves high humidity (dams, bridges, pier supports, hydraulic buildings, etc.).

Most often, alloying additives are added to reinforcing steels in order to improve their weldability and reduce the coefficient of thermal expansion. Since the weakest points in a frame made of reinforcement are the welding points of large rods, and the durability of a reinforced concrete structure is determined, among other things, by thermal distortions of the reinforcement during temperature changes.

Depending on the ferroalloys used in the deoxidation of steels, other alloying elements, such as nickel, titanium, vanadium, etc., may also enter the steel. Their content should not exceed 0.3% (each). Unlike rolled steel, from which load-bearing structural elements are produced (I-beams, channels, profile pipes, etc.)

), reinforcing steels never contain large amounts of manganese or nickel, as in steels with a zero coefficient of thermal expansion, used to assemble huge welded structures (bridges, railway tracks, gas pipelines, etc.).

Since this solution is too expensive and the calculation is made on the heat-insulating properties of concrete, which will not allow the metal reinforcement to cool or heat up sharply when the weather changes.

The use of certain steels for the production of reinforcement is determined by the requirements for structural strength (for example, seismic activity in the region), and the available resources for its production (for example, deposits of alloying metal ores).

Technology of alloys and steels. Part 2.

According to the classification of reinforcing steel

Please tell me where I can get a clear explanation about the classification of fittings (A-III, A-500 35GS)

Dmitry Vershinin Sage (11621) 6 years ago

reinforcement Steel reinforcement (rod, GOST 5781-82, GOST R 52544-2006) for reinforcement according to the nature of the profile is divided into: smooth; periodic profile (corrugated). Depending on the mechanical characteristics, rod reinforcement is divided into classes: AI (A240), AII(A300), AIII(A400), AIV(A600), AV(A800), AVI(A1000). Reinforcing steel bars of class: AI - smooth; AII, AIII, AIV - periodic profile.

The following is added to the index: t - for thermally strengthened reinforcing steel; c - for reinforced hood. Periodic profile reinforcement is a round profile with two longitudinal and transverse projections. For each class of hot-rolled reinforcement, certain steel grades are established: AI (A240) - St3kp (ps, sp); AII(A300) - St5sp (ps).

18G2S; AIII(A400) - 35GS, 25G2S, A500S, A400S, 32G2RPS; AIV(A600) - 80C, 20ХГ2С; AV(A800) - 23Х2Г2Т; AVI(A1000) - 22Х2Г2АУ, 22Х2Г2Р, 20Х2Г2СР. Thermo-mechanically strengthened reinforcing steel grades A400S and A500S are produced by the West Siberian Metallurgical Plant (ZSMK) on the basis of St3 and are a substitute for steels 35GS, 25G2S.

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For the construction of critical reinforced concrete structures, thermomechanical and thermally strengthened steel rods of periodic profile with a diameter of 6-40 mm are used - the so-called thermal, GOST 10884-81.

Reinforcement according to this standard is made from the following grades of steel: AtIII - St5(sp, ps); AtIV, AtIVS, AtIVK - 20GS, 25G2S, 35GS, 28S, 10GS2, 08G2S, 25S2R; AtV(K and SK) - 20GS, 20GS2, 08G2S, 10GS2, 28S, 25G2S, 35GS, 25S2R, 20HGS2; AtVII - 30ХС2. In the designation of classes of this reinforcement, the letters mean the following: k - increased resistance to stress corrosion cracking; c - weldable.

The minimum size of reinforcement of any class is 6 (mm). maximum - 80 (mm). everything lower or higher is only on special. order to manufacturing plants The size of the periodic profile reinforcement (corrugated) corresponds to the diameter of the smooth part of the reinforcement. Wire rod. Wire rod made of carbon steel of ordinary quality, intended for tensioning onto wire and other purposes, is manufactured in accordance with GOST 535-88.

The range of wire rod corresponds to GOST 30136-95. The wire rod is made from carbon steel of ordinary quality, grades St0, St1, St2, St3 of all degrees of deoxidation in accordance with GOST 380-94 (chemical composition). According to the cooling method, the wire rod can be: cooled in air - VO; subjected to one-U01 and two-stage U02 accelerated cooling. According to rolling accuracy, wire rod is manufactured: B - increased accuracy; B - normal accuracy.

Wire rod is produced with a diameter of 5.0, 5.5, 6.0, 6.3, 6.5, 7.0, 8.0 and 9.0 in coils consisting of one continuous piece. By agreement with the consumer, it is allowed to produce wire rod with a diameter of more than 9.0 mm in coils. The diameters of the wire rod, maximum deviations in diameter, cross-sectional area and weight of one meter must comply with TU 14-15-212-89.

Source: https://stanki-info.com/iz-kakoy-stali-delayut-armaturu/

What kind of steel are the fittings made from?

Reinforcement is a type of rolled steel, which, unlike other products in this group, has a clear purpose - the production of reinforced concrete structures. The fittings are produced in the form of round rods and wires with a smooth or corrugated periodic profile. For the manufacture of these products, clearly defined grades of structural steel are used.

The manufacture of fittings is carried out in accordance with two regulatory documents: GOST 5781-82 and GOST 10884-94

The manufacture of fittings is carried out in accordance with two regulatory documents: GOST 5781-82 and GOST 10884-94. The first of them applies to conventional reinforcement, and the second to reinforcement reinforced by thermal and mechanical stress. According to these documents, fittings are divided into classes.

A fairly convenient way to indicate the class of reinforcement using the letters A or At and the yield strength of the material, which is expressed in N/mm2 (MPa). An example of such a designation: A300. Strengthened reinforcement may also have the letter C, which indicates increased weldability, or K, which indicates resistance to corrosion.

In addition, there is a class of special fittings Ac300.

Steel reinforcement: GOST, size, purpose:

Today, the construction of any building or technical structure cannot be completed without the use of concrete mortar. The reinforced frame of the structure greatly increases the strength of the structure, preventing cracking and destruction of concrete buildings. Modern rolled metal products offer various types of steel construction reinforcement for the formation of reinforced concrete structures for various purposes.

Types of steel reinforcement

By production method:

• Hot rolled - obtained from a preheated billet by rolling. This reinforcement is characterized by increased flexibility and large rod diameters (from 3 to 80 mm). It is produced in accordance with GOST 5781-82. The tensile strength class is designated here by the letter “A”, for example, A300 (A-II) and A400 (A-III).

• Cold-formed - made with a diameter of 3 to 5 mm by drawing rolled rods through a system of successively smaller holes. The peculiarity of such reinforcement is that it has increased tensile strength and reduced flexibility. The main standard here is GOST 6727-80. It is designated in the same way as the previous fittings, only instead of the letter “A” the letter B is placed. Example: B500 (Вр-I) or B500С.

• Thermomechanically strengthened - reinforcement obtained by plastic deformation and heat treatment. In terms of its properties, it is something between hot-rolled and cold-deformed reinforcement. In other words, such reinforcement has increased flexibility and at the same time quite high strength. The main standard for it is GOST 10884-94, according to which the diameter of the rods here can be 6-40 mm. As for the strength class, it is designated by the letters “At”, which are placed before the numbers indicating the yield strength in MPa. It is also not uncommon to see the indices “C” and “K” after the number, which “speak” of good weldability of elements or resistance to corrosion cracking, respectively. Designation examples: At400S, At600K.

By profile:

• Smooth - reinforcement that has a constant cross-section along its entire length.

• Periodic profile - reinforcement with uniform corrugation for better adhesion to concrete.

By method of secondary exposure:

• Tensile reinforcement is reinforcement that is stretched before being concreted. Usually uses jacks or electric current for this. It is produced only as part of finished reinforced concrete products that require increased load-bearing capacity.

• Non-tensioned - reinforcement that is sold in separate rods. It is from this that monolithic structures are erected on the construction site.

Scope and price

The table shows the most commonly used reinforcement bars for private construction.

Mode of production	Strength class	Profile view	Scope and price for 2016
Hot rolled	A240	Smooth	Clamps that protect the working reinforcement from compression. As an anchor element in an embedded part, but only in case of bending the end of the reinforcing bar. Price - from 19,000 rubles/t.
A400, A500, A600	Grooved	Working reinforcement for mesh foundation slabs, floor slabs, as well as longitudinal and transverse reinforcement for frames in reinforced concrete beams and monolithic strip foundations. Price - from 19,000 rubles/t.
Cold-formed	B500	Smooth and grooved	Mesh for reinforcing masonry made of bricks and blocks. Price - from 25,000 rubles/t.
Thermomechanically hardened	At800	Smooth	Elements of embedded parts where increased strength is required. Price - from 29,000 rubles/t.
At400, At500, At600	Grooved	Working reinforcement in meshes and frames, where the use of a certain diameter of reinforcement is required, and it is not possible to use class “A” reinforcement. As working reinforcement in heavily loaded reinforced concrete products. Price - from 25,000 rubles/t.

Advantages and disadvantages

Pros (+):

• time-tested - standards for steel reinforcement have long been developed according to which they are produced. Also, the regulatory documents (SP and SNiP for reinforced concrete structures) indicate steel reinforcement, i.e. all formulas and calculations are made specifically for such reinforcement;

• large range of diameters - this fittings can be produced with diameters from 3 to 80 mm;

• predictable and relatively long service life - steel reinforcement under normal conditions (in the absence of an aggressive environment and contact with water) can last 50 years or more;

• works well in bending - steel reinforcement has a modulus of elasticity 4 times greater than fiberglass reinforcement. This means that it can withstand bending load so many times more;

• accessibility - this building material is very easy to find and buy;

• the ability to choose the installation method - reinforcing bars can be either welded together or tied with wire;

• environmental friendliness - zero impact of the material on the human body;

• simplicity of the anchoring device - steel reinforcement can be bent by 90° in any place when heated with a burner. This circumstance makes it possible to produce bent elements required for anchoring reinforcement directly on the construction site;

• good adhesion to concrete - the “tandem” of steel and concrete works well throughout the entire life of the structure. This is largely facilitated by the almost equal coefficients of linear expansion of both materials (according to the reference book of the designer V. Blasi, for concrete it is equal to 0.000010 m/m°C, and for reinforcement - 0.000012 m/m°C);

• frost resistance - steel reinforcement does not change its properties at subzero temperatures.

Minuses (-):

• limited length - steel reinforcement is produced with a maximum length of 11.7 m (in very rare cases 12 m);

• heavy weight - to transport the material to the construction site, you need to hire special transport;

• poor corrosion resistance - steel, when exposed to oxygen, water and (or) an aggressive environment, corrodes at a rate of 0.1-0.5 mm/year;

• special storage requirements - such material is not recommended to be stored for a long time in the open air and without pallets, as the material will quickly become covered with rust.

Related calculators:

• calculation of reinforcement along the length;
• calculation of reinforcement mesh.

Other types of fittings:

article with friends:

Source: https://steelfactoryrus.com/iz-kakoy-stali-delayut-armaturu/

What steel is the fittings made of?

Reinforcement is a set of elements that improve the performance of reinforced concrete structures by increasing strength and compensating for various stresses. Due to the active use of reinforced concrete in modern construction, reinforcement of various categories is used very widely.

Reinforcing elements can be flexible (individual rods of various profiles, knitted and welded mesh, frames) and rigid (angles, I-beams, channels and other rolled products). The material for rods is usually steel (in accordance with GOST 10884-94), although there are composite (basalt-plastic, fiberglass, carbon-fiber), wood (bamboo) and other options.

Most often, the fittings are made of low-alloy or carbon steel. In general, the production of steel rod reinforcement is regulated by GOST 5781-82.

Depending on the processing method, steel reinforcement can be cold-drawn or hot-rolled.

Steel grades used for the manufacture of reinforcing elements: AI - St3kp, 18G2S, AII - St5sp, 25G2S, AIII - 35GS, A400S, A500S, 32G2RPS.

The choice of a particular steel grade determines the manufacturing technology, as well as the characteristics and operational features of the manufactured fittings:

• construction with reinforcement by hood (category “B”);
• construction reinforced, in accordance with GOST 10884-81 (category “T”);
• fittings with the possibility of welding (category “C”, for example, fittings A500C);
• reinforcement with increased resistance to corrosion cracking (category “K”).

The most popular brand of fittings in Russia is A500C; such a high level of demand is largely explained by the selected steel grade (ZPS), which is characterized by a lower content of alloying components. This ensures good ductility, strength, as well as high-quality weldability (A500C welded joints are not subject to brittle fractures).

Steel reinforcement - classification, production method, scope of application, advantages

The production of reinforced concrete products and monolithic construction technology involves the use of reinforcing materials from various grades of steel.

Steel reinforcement has become the most widely used in this area, making it possible to significantly increase the load-bearing capacity of individual structural elements and achieve uniform distribution of created loads.

You can always check on our website the current prices for fittings, including classes A1, A2, A3, A500C, A500SP and AT800.

Purpose and scope of application

In reinforced concrete products, longitudinal and transverse steel reinforcement, connected into meshes or volumetric structures, is designed to prevent the formation of vertical and oblique cracks in the concrete mass under the influence of various types of loads arising during the operation of the structure.

The main purpose of reinforcement is considered to be to work together with concrete in terms of absorbing tensile and compressive loads, strengthening and improving strength characteristics in areas with increased compression. The use of such a technical solution makes it possible to achieve an increase in the mechanical strength of the structure, which can significantly increase its service life.

The main area of ​​application of steel reinforcement is various areas in civil and industrial construction. At the same time, for certain operating conditions, fittings of the appropriate class must be used.

Product benefits

Despite the emergence of new generation materials, in particular reinforcement made of composite materials, steel reinforcing bars have not lost their relevance for the following reasons:

• Higher modulus of elasticity (4 times higher than that of composite products), ensuring minimal deflections even with a large span of the structure.
• Significant thermal stability. When heated to 600 degrees, fiberglass reinforcement loses its elasticity and softens, which leads to a decrease in the load-bearing capacity of the structure. Steel reinforcement does not have this disadvantage.
• Possibility of bending steel rods to obtain different configurations. It will not be possible to perform such an operation with composite materials.
• Easier installation, ensuring high speed of work. 

Production Features

In practice, two main technologies are used for the production of steel reinforcement intended for reinforcing conventional and prestressed reinforced concrete structures (reinforced concrete structures).

1. Hot rolled reinforcement, production is carried out from a continuous cast steel billet, the temperature of which is in the range of 1150/12000C. The use of this technology makes it possible to produce reinforcement with a cross-section of up to 80 mm.  
    
2. A cheaper technology is the production of reinforcement using the cold-rolled method, which makes it possible to obtain products with a cross-section of up to 12 mm. The share of products of this type in the domestic market is relatively small, but there is a tendency to increase the consumption of materials of this class.

In the production of fittings of various classes, different grades of steel are used that can provide the required technical characteristics of the material.

Classification

The main regulatory document in force in the production of steel reinforcement is considered to be GOST 5781-82, which regulates the main parameters of products.

Based on their cross-section, they distinguish between reinforcement with a smooth and periodic (corrugated) profile, which differs in its strength characteristics.

According to the conditions of use in reinforced concrete structures, a distinction is made between non-prestressed and prestressed reinforcement; the use of the latter involves pre-tensioning a steel rod, which can significantly improve the strength characteristics of the structure.

All manufactured reinforcement is divided into 7 main classes, differing in the value of relative elongation, yield strength and tensile strength. The main technical characteristics of all existing classes of fittings are given in the table.

Taking into account the different characteristics of different classes of bar reinforcement, the scope of its application also differs accordingly.

• Classes A-1 and A-2 are used in the manufacture of meshes and frames for conventional (non-prestressed) reinforced concrete products.
• Reinforcing steel of class A-3 is used as working reinforcement in the same structures.
• In prestressed structures, class A-4 reinforcement is used.
• For the construction of prestressed structures with a span length of more than 12 meters, reinforcement of higher classes with more advanced technical characteristics is used.

The production of fittings of various classes requires the use of certain grades of steel, data on which are given in the following table:

Delivery features

Manufacturers offer steel reinforcement in coils and rods, and it is possible to supply material in measured lengths.

• Reinforcement with a diameter of no more than 10 mm is usually offered in coils. By agreement, supplies of class A-1 material with a diameter of up to 12 mm are possible.
• Large diameter fittings, as well as material of class A-4 and higher, are supplied only in separate rods, the length of which is 6-12 meters.

To simplify the calculation of requirements, you can use the table of the ratio of weight and diameter of reinforcement.

Source: https://stroitel.promindex.ru/stati/stalnaya_armatura_oblast_primeneniya_i_klassifikaciya.html

Steel for GOST fittings

Steel rod reinforcement is widely used in construction. This is an integral element of reinforced concrete structures, increasing the flexural and compressive strength of cement stone. We will tell you what metal fittings are, what they are made from, what classes they are divided into and the features of their use.

Rebar manufacturing technologies

According to the production method, the fittings are:

• Hot rolled rod;
• Cold drawn wire.

In both cases, low-alloy or carbon steel of different grades is used, depending on this, it is divided into 6 classes A-IA-VI.

The hot production method involves forming a softened steel rod blank using rollers. As the temperature increases, the bonds of the metal structure are strengthened; accordingly, reinforcement made from it is able to withstand greater loads compared to cold-drawn products, and the tensile strength increases.

Cold drawn reinforcement is obtained from an unheated workpiece passing through crimping rollers.

To increase the strength of the reinforcement, it is subjected to heat treatment or galvanizing - the procedure ensures the resistance of the metal to moisture and aggressive environments.

Rod reinforcement with a cross-section of 8 mm or more is produced in individual rods, thin wire reinforcement is produced in coils.

Classification and marking of fittings

The classification of reinforcement involves dividing products according to the class of steel used for the production of rods. The division is regulated by GOST 5781-82 “Hot-rolled steel for reinforcement of reinforced concrete structures”:

*by agreement with the customer, A-IIA-V steel can be manufactured with a smooth profile.

Classes, in turn, are divided into subclasses, which are designated by additional indices:

• “C” is a rod steel that is suitable for welding;
• “T” - heat-treated product;
• “K” - corrosion-resistant steel, i.e. treated with zinc;
• "SK" is a corrosion-resistant steel that can be welded.

Metal fittings of different classes are made from various steel alloys, which determine its technical properties. In this case, the diameter of the rods is taken into account:

The table is compiled according to GOST 5781-82.

Mechanical properties of reinforcing steel

Bar reinforcement of different brands has individual mechanical properties, which are taken into account when choosing a product for reinforcing concrete structures. The main ones are given in table No. 8 GOST 5781-82:

The properties of the reinforcement bars are determined by laboratory tests, based on the results of which a protocol is drawn up. Deviation from GOST rules is allowed in agreement with the customer.

Reinforcement cross-sectional area table

When calculating reinforcing rods, in addition to the diameter, the mass of the products is also taken into account. It is given in the assortment GOST 5781-82:

*weight is given as an average value - a more accurate parameter depends on the specific grade used for the production of rolled steel bars.

Areas of application of steel reinforcement

The characteristics of steel reinforcement determine the scope of its application. Smooth profile rods are used:

• For dressing the working rods of the frame;
• Knitting of decorative items for design;
• Installation of individual elements of complex mechanisms.

Periodic profile bars are more in demand:

• Strengthening concrete structures in areas of greatest tension and compression;
• Installation of supporting elements and structures;
• Reinforcement of plaster layers, floor screeds;
• Construction of road surfaces and sidewalk areas;
• Installation of reinforcing belts for laying blocks and bricks.

The main purpose of bar reinforcement with a periodic profile is to strengthen concrete structures. Their rods are knitted into flat or spatial frames. The fittings in them perform different functions:

• Compensation for concrete fracture by creating tensile stress on the rod. Maximum loads are concentrated in the lower part of beam-type structures on two supports or with rigid pinching;
• Compensation for compression that is concentrated in the upper part of the same beam.

Flaws

Bar reinforcement has several disadvantages that need to be taken into account:

• In the absence of an anti-corrosion coating, the rods are subject to oxidation upon contact with water. Processes can even begin from exposure to water in the cement during its hardening.
• Inability to perform functions with rod products if the rod class and its diameter are incorrectly selected.
• Excessively stressed reinforcement can have the opposite effect and form cracks in the concrete structure.
• A protective layer of concrete is required - at least 2 diameters of the section size to prevent water from entering the rods.

Packaging, transportation and storage

For convenience, steel rods are painted in different colors:

• A-IV – red;
• A-V – red and green;
• A-VI – red and blue.

It is allowed to apply paint to the ends of 0.5 meters.

The rod reinforcement is assembled in batches of 15 tons and tied with wire and cordage. Thin wire is also packaged in coils. If necessary, dressings of a different weight are made for the customer - 3 or 5 tons, as well as individual tonnage. Complete bundles must be marked with a class of rods.

Transportation of metal products is allowed only in a horizontal position to avoid kinks and deformations.

It is recommended to store rod reinforcement in closed, dry rooms, excluding contact with water.

Nuances and features of fittings according to GOST

Reinforcement is one of the most popular categories of rolled products in construction. It is used as a base for all categories of reinforced concrete structures without exception, for the construction of lightweight plasterboard or other similar partitions, as well as for improving the characteristics of concrete. It is also used for the construction of light small structures (for example, such as greenhouses).

For the correct use of these products, it is very important to understand what types of products exist according to the regulatory standard, how they are marked, and also for what purposes they are used according to the same marking.

1 Technical features of fittings

Under the reinforcement, a fairly wide group of products is combined, combining rods with notches, as well as various types of profiles.

For its production, hot-rolled steel is used, in which the carbon content must be below 0.22%.

Source: https://moy-instrument.ru/masteru/stal-dlya-armatury-gost.html