GOST 5781-82 Hot-rolled steel for reinforcement of reinforced concrete structures. Specifications

GOST 5781-82

INTERSTATE STANDARD

HOT-ROLLED STEEL FOR REINFORCEMENT OF REINFORCED CONCRETE STRUCTURES

TECHNICAL CONDITIONS

INTERSTATE STANDARD

Date of introduction 07/01/83

This standard applies to hot-rolled round steel of smooth and periodic profiles intended for the reinforcement of ordinary and prestressed reinforced concrete structures (reinforcing steel).

Regarding the standards for the chemical composition of low-alloy steels, the standard also applies to ingots, blooms and billets.

(Changed edition, Amendment No. 4).

CLASSIFICATION AND ASSORTMENT

1.1. Depending on the mechanical properties, reinforcing steel is divided into classes AI (A240), A-II (A300), A-III (A400), A-IV (A600), AV (A800), A-VI (A1000).

1.2. Reinforcing steel is manufactured in bars or coils. Reinforcing steel of class AI (A240) is made smooth, classes A-II (A300), A-III (A400), A-IV (A600), AV (A800) and A-VI (A1000) - periodic profile.

At the request of the consumer, steel of classes A-II (A300), A-III (A400), A-IV (A600) and AV (A1000) is made smooth.

1.1, 1.2. (Changed edition, Amendment No. 5).

1.3. Profile numbers, cross-sectional areas, weight of 1 m length of reinforcing steel of smooth and periodic profiles, as well as maximum mass deviations for periodic profiles must correspond to those indicated in the table. 1.

1.4. The nominal diameters of periodic profiles must correspond to the nominal diameters of smooth profiles of equal cross-sectional area.

Table 1

Table 1

(Changed edition, Amendment No. 3).

1.5. The weight of 1 m of profile is calculated based on the nominal dimensions with a steel density of 7.85 × 103 kg/m3. The probability of providing a mass of 1 m must be at least 0.9.

(Changed edition, Amendment No. 3).

1.6. The maximum deviations of the diameter of smooth profiles must comply with GOST 2590-88 for normal rolling accuracy.

1.7. Periodic profile reinforcing steel is a round profile with two longitudinal ribs and transverse projections running along a three-lead helix. For profiles with a diameter of 6 mm, protrusions running along a single-start helical line are allowed, with a diameter of 8 mm - along a double-start helical line.

1.8. Reinforcing steel of class A-II (A300), manufactured in a conventional design, with a profile shown in Fig. 1a, and special purpose Ac-II (Ac300) profile shown in Fig. 2a, must have protrusions running along helical lines with the same approach on both sides of the profile.

Steel class A-III (A400), manufactured with the profile shown in Fig. 1b, and classes A-IV (A600), AV (A800), A-VI (A1000) with the profile shown in Fig. 1b, 2b, must have protrusions along helical lines that have right entries on one side of the profile and left entries on the other

Crap. 1

Crap. 2

Reinforcing steel for special purposes of class Ac-II (Ac300) is made with profiles shown in Fig. 1a or 2a.

The profile shown in Fig. 2a, for special purposes is manufactured by agreement between the manufacturer and the consumer. The shape and dimensions of the profiles shown in Fig. 2a and b may be specified.

1.9. Dimensions and maximum deviations in dimensions of reinforcing steel of periodic profile, manufactured according to drawing. 1a and b must correspond to those given in table. 2, but damn. 2a and b - given in table. 3.

table 2

Dimensions, mm

Note. At the request of the consumer, maximum deviations of size d 1

should not exceed maximum deviations
d
plus double maximum deviations
h .
Table 3

Dimensions, mm

1.10. Relative displacements of helical protrusions on the sides of the profile, separated by longitudinal ribs, are not standardized.

Dimensions for which maximum deviations are not established are given for caliber construction and are not checked on the finished profile.

1.11. The ovality of smooth profiles (the difference between the largest and smallest diameters in one section) should not exceed the sum of the plus and minus maximum deviations in diameter.

1.9-1.11. (Changed edition, Amendment No. 3).

1.12. Reinforcing steel of classes A-I (A240) and A-II (A300) with a diameter of up to 12 mm and class A-III (A-400) with a diameter of up to 10 mm inclusive is produced in coils or rods, large diameters - in rods. Reinforcing steel of classes A-IV (A600), AV (A800) and A-VI (A1000) of all sizes is produced in rods, with a diameter of 6 and 8 mm, manufactured in coils by agreement between the manufacturer and the consumer.

1.13. The rods are made from 6 to 12 m long:

measured length;

measured length with unmeasured segments of at least 2 m in length, not more than 15% of the lot weight;

of unmeasured length.

In a batch of rods of unmeasured length, the presence of rods from 3 to 6 in length and no more than 7% of the mass of the batch is allowed.

By agreement between the manufacturer and the consumer, it is possible to manufacture rods from 5 to 25 m.

1.14. Maximum deviations along the length of measuring rods must correspond to those given in table. 4.

Table 4

High-precision rods are manufactured according to customer requirements.

1.15. The curvature of the rods should not exceed 0.6% of the measured length.

Examples of symbols

Reinforcing steel with a diameter of 20 mm, class A-II (A300):

20-A-II (A300) GOST 5781-82

Reinforcing steel with a diameter of 18 mm, class AI (A240):

18- A - I (A240) GOST 5781-82

In the designation of class A-II rods for special purposes, the index c is added: Ac-II.

(Changed edition, Amendment No. 4).

TECHNICAL REQUIREMENTS

2.1. Reinforcing steel is manufactured in accordance with the requirements of this standard according to technological regulations approved in the prescribed manner.

2.2. Reinforcing steel is made from carbon and low-alloy steel of the grades indicated in table. 5. The steel grade is indicated by the consumer in the order. If there is no indication, the steel grade is determined by the manufacturer. For class A-VI (A-1000) rods, steel grades are established by agreement between the manufacturer and the consumer.

Table 5

Notes:

1. Production of reinforcing steel class AV (A800) is allowed. Made from steel grades 22Kh2G2AYU, 22Kh2G2R and 20Kh2G2SR.

2. The dimensions indicated in brackets are manufactured by agreement between the manufacturer and the consumer.

(Changed edition, Amendment No. 3, 4).

2.3. The chemical composition of reinforcing carbon steel must comply with GOST 380-88, low-alloy steel - with the standards given in table. 6.

Table 6

Continuation of the table. 6

2.3.1. In steel grade 20KhG2Ts, it is allowed to increase the mass fraction of chromium to 1.7% and replace zirconium with 0.02-0.08% titanium. In steel grade 23Х2Г2Т it is allowed to replace titanium with 0.05-0.10% zirconium. In this case, in the designation of steel grade 20KhG2Ts, the letter T is used instead of the letter C; steel grade 23Kh2G2T is marked with the letter T instead of the letter T.

In steel grade 32G2Rps, aluminum can be replaced with titanium or zirconium in equal units.

2.3.2. The mass fraction of nitrogen in steel grade 22Х2Г2А10 should be 0.015-0.030%, the mass fraction of residual nitrogen in steel grade 10GT should be no more than 0.008%.

2.3.3. The mass fraction of boron in steel grades 22Kh2G2R, 20Kh2G2SR and 32G2Rps should be 0.001-0.007%. In steel grade 22Х2Г2АУ, the addition of 0.001-0.008% boron is allowed.

2.3.4. It is allowed to add titanium to steel grades 18G2S, 25G2S, 35GS based on its mass fraction in finished rolled products of 0.01-0.03%, to steel grade 35GS based on its mass fraction in finished rolled products produced in coils of 0.01-0 .06%.

2.4. Deviations in the chemical composition in finished rolled products from carbon steels - according to GOST 380-88, from low-alloy steels, subject to compliance with the standards of mechanical properties - according to table. 7. Minus deviations in the content of elements (except for titanium and zirconium, and for the steel grade 20Kh2G2SR silicon) are not limited.

Table 7

Note. By agreement between the manufacturer and the consumer, steel can be manufactured with other deviations in the content of chromium, silicon and manganese.

(Changed edition, Amendment No. 3).

2.5. Reinforcing steel of classes A-I (A240), A-II (A300), A-III (A400), A-IV (A600) is made hot-rolled, class AV (A800) - with low-temperature tempering, class A-VI (A1000) — with low-temperature tempering or thermomechanical treatment in the flow of a rolling mill.

It is allowed not to carry out low-temperature tempering of steel classes AV (A800) and A-VI (A1000) provided that a relative elongation of at least 9% and a uniform elongation of at least 2% are obtained when tested within 12 hours after rolling.

2.6. The mechanical properties of reinforcing steel must comply with the standards specified in table. 8.

Table 8

Notes:

1. By agreement between the manufacturer and the consumer, it is allowed not to test the impact strength of reinforcing steel of class Ac-II (Ac300).

2. (Deleted, Amendment No. 3).

3. For reinforcing steel of class A-IV (A600) with a diameter of 18 mm, grade 80C steel, the cold bending rate is set to at least 30°.

4. For reinforcing steel class AI (A240) with a diameter of over 20 mm when cold bending 180° with

= 2
d
, class A-II (A300) with a diameter over 20 mm
c
= 4
d.
5. Symbols for the yield strength are indicated in parentheses.

(Changed edition, Amendment No. 1, 3).

For class A-II (A300) steel with a diameter of over 40 mm, a reduction in elongation of 0.25% is allowed for each millimeter increase in diameter, but not more than 3%.

For steel class Ac-II (Ac300), a reduction in tensile strength to 426 MPa (43.5 kgf/mm2) is allowed with relative elongation: d 5

30% or more.

For steel grade 25G2S class A-III (A400), a reduction in tensile strength to 560 MPa (57 kgf/mm2) is allowed with a yield strength of at least 405 MPa (41 kgf/mm2), relative elongation: d 5

at least 20%.

2.7. Statistical indicators of the mechanical properties of periodic reinforcing steel must comply with Appendix 1, with increased uniformity of mechanical properties - mandatory Appendix 1 and Table. 9.

Table 9

Notes:

1. S

— standard deviation in the general population of tests;

S about

— standard deviation in the melting batch;

— average value in the population of tests;

— the minimum average value in a batch-smelting.

2. For reinforcing steel in coils with a diameter of 6 and 8 mm, it is allowed to increase the standards for S

and
S o
by 4.9 MPa (0.5 kgf/mm2).

3. (Deleted, Amendment No. 5).

The probability of achieving the mechanical properties indicated in table. 8, must be at least 0.95.

(Changed edition, Amendment No. 3, 5).

2.8. On the surface of the profile, including the surface of the ribs and protrusions, there should be no rolled cracks, stress cracks, flaws, rolled films or sunsets.

Minor damage to the ribs and protrusions is allowed, in the amount of no more than three per 1 m of length, as well as minor rust, individual rolled out stains, prints, sagging, traces of rolled out bubbles, rippling and scaliness within the permissible deviations in size.

(Changed edition, Amendment No. 2).

2.9. The weldability of reinforcing steel of all grades, except 80C, is ensured by the chemical composition and manufacturing technology.

2.10. The carbon equivalent for welded rod reinforcement made of low-alloy steel of class A-III (A400) should be no more than 0.62.

Features of marking construction reinforcement

Reinforcing bars are in demand in many areas, therefore they are produced in a wide range. Each manufacturer is required to apply certain markings to their products, which reflect the physical and mechanical properties and performance qualities of the products.

What is fittings needed for?

Concrete is not in vain considered one of the strongest and most durable building materials. It can withstand compressive loads well, but weakly resists tensile or shear loads. Because of this, the structure can quickly crack or break.

To improve quality characteristics, reinforced concrete has been used for many years. This is a kind of alloy of metal and artificial stone. First, a frame of steel rods - reinforcement - is formed in the formwork. And then the concrete is poured. The resulting structure has all the necessary set of properties: strong, yet quite plastic, and can withstand almost all types of deformation loads, including vibration, bending, and the like.

The description of construction reinforcement will be incomplete if we do not list the areas of use of steel products. This:

1. Construction of residential low- and multi-storey buildings (foundations, monolithic walls, ceilings), industrial buildings, complex special-purpose structures (berths, hydroelectric power stations, subways).

2. Construction of various supporting and protective structures (greenhouses, pipeline supports, columns).

3. Installation of screed, strengthening of plaster.

4. Production of shaped reinforced concrete products (rings, pipes, floor slabs, beams, foundation blocks).

5. Formation of road surfaces, sidewalks, airfield runways, etc.

For each of the above areas, fittings of a certain grade, type and diameter are produced. These parameters are indicated as an alphanumeric character set on each rod.

Reading the marking symbols

The symbolic code for reinforcing bars begins with the letter:

• A – hot-rolled or cold-rolled (heat-strengthened) products;
• B – cold-deformed;
• K - ropes.

Next comes an indication of the class of reinforcement in the form of a digital set from A240 to A1000, which indicates the fluidity index of steel in MPa. The higher the indicator, the stronger and more reliable the product.

The following series of reinforcing bars are distinguished:

1. A240 or A1 – made from steel grades St3SP, St3PS, St3KP, classified as mounting rods with a smooth profile with a diameter of 4 to 40 mm.

2. A300 or A2 – made of metal of the ST5SP(ps) or ST18G2S series, refers to work products with a corrugated surface with a cross-section of 10-80 mm. Depending on the diameter, it is produced in the form of wire, rolled into coils or rods 6-12 m long.

3. A400/A500 or A3 – produced from steel grades 35GS, 25G2S, 32G2R. This is a working reinforcement of a periodic profile with a cross section of 6-40 mm. Also produced in the “B” series from metal using the cold drawing method. This is the most popular reinforcement for slab, strip or pile type foundations.

4. A600 or At4 - made from low-alloy heat-strengthened (cold-rolled) steel of class 80C, 20ХГ2Ц, intended for welded structures. The length of the rods is classified as measured (rods of 6, 9 and 11.7 m) or unmeasured (rods and coils up to 12 m). The diameter varies from 10 to 32 mm. The surface is periodic, crescent-shaped.

5. A800 or At5 - made from low-alloy metal raw materials of grade 23Х2Г2Т. The products are produced in diameters of 6-40 mm and are intended for the formation of welded frames in conventional and prestressed concrete products.

6. A1000 or A6 - made of low-alloy steel of classes 22Х2Г2АУ, 22Х2Г2Р and 20Х2Г2СС. A distinctive feature is the use of any type of welding work without restrictions. The diameter of the rods varies from 6 to 32 mm.

The marking also includes an indication of the special properties of the product:

• K – corrosion resistance. Products undergo galvanizing, galvanizing and other processes, as a result of which a protective film is formed on the surface to prevent oxidation.
• C – connection by welding.
• T – thermomechanically hardened steel.

After the main parameters, the diameter is indicated. For example, the marking A500C Ø12 stands for hot-rolled reinforcement with a fluidity index of 500 MPa and a periodic profile, intended for welding work, the diameter of the product is 12 mm.

For certain types of products, GOST standards require painting the ends of the rods. The following colors are used for different classes:

1. For low-alloy steel fittings:

• A4 – red;
• A5 – red and green;
• A6 – red and blue.

2. For rolled heat-strengthened metal:

• At3 – white and blue;
• At4 – white and yellow;
• At4K – green;
• At5 – blue;
• At5SK – white and green;
• At5K – yellow and green;
• At6 – yellow;
• At6K – green and black.

Color marking complements the alphanumeric marking and provides additional information about the product.

ACCEPTANCE RULES

3.1. Reinforcing steel is accepted in batches consisting of profiles of the same diameter, one class, one melt-ladle and issued with one quality document.

The batch weight should be up to 70 tons.

It is allowed to increase the mass of the batch to the mass of the melting ladle.

3.2. Each batch is accompanied by a quality document in accordance with GOST 7566-81 with additional data:

profile number;

Class;

minimum average value and standard deviations S o

in the batch of values
​​s t
(
s 0.2
) and
s in
;

results of cold bending tests;

values ​​of uniform elongation for steel classes A-IV (A600), AV (A800), A-VI (A1000).

3.3. To check the size and quality of the surface, select:

in the manufacture of reinforcing steel in rods - at least 5% of the batch;

when making and skeins - two skeins from each batch.

(Changed edition, Amendment No. 3).

3.4. To check the chemical composition, samples are taken according to GOST 7565-81.

The manufacturer determines the mass fraction of aluminum periodically, but at least once a quarter.

3.5. To test for tensile, bending and impact strength, two rods are selected from the batch.

For the manufacturer, the interval for selecting rods must be at least half the time spent on rolling one profile size of one batch.

(Changed edition, Amendment No. 3).

3.6. If unsatisfactory test results are obtained for at least one of the indicators, repeated tests are carried out in accordance with GOST 7566-81.

TEST METHODS

4.1 Chemical analysis of steel is carried out according to GOST 12344-88, GOST 12348-78, GOST 12350-78, GOST 12352-81, GOST 12355-78, GOST 12356-81, GOST 18895-81 or other methods that provide the required accuracy.

4.2. The diameter and ovality of the profiles are measured at a distance of at least 150 mm from the end of the rod or at a distance of at least 1500 mm from the end of the skein with a skein weight of up to 250 kg and at least 3000 mm with a skein weight of more than 250 kg.

4.3. Dimensions are checked with a measuring tool of the required accuracy.

4.4. One sample is cut from each selected rod for tensile, bending and impact strength testing.

4.5. Sampling for tensile, bending and impact strength testing is carried out in accordance with GOST 7564-73.

4.6. The tensile test is carried out according to GOST 12004-81.

4.7. The bending test is carried out according to GOST 14019-80 on samples with a cross-section equal to the cross-section of the rod.

For rods with a diameter over 40 mm, it is allowed to test samples cut along the axis of the rod on a mandrel with a diameter reduced by half compared to that indicated in the table. 4, with bending force applied from the side of the cut.

4.8. Determination of impact strength is carried out according to GOST 9454-78 on samples with a concentrator type U type 3 for rods with a diameter of 12-14 mm and samples of type 1 for rods with a diameter of 16 mm or more. Samples are manufactured in accordance with the requirements of GOST 9454-78.

4.9. It is allowed to use statistical and non-destructive methods for monitoring the mechanical properties and mass of profiles.

4.10. The curvature of the rods is measured along the length of the supplied profile, but not shorter than 1 m.

4.11. Determination of statistical indicators of mechanical properties in accordance with mandatory Appendix 2.

4.12. The quality of the surface is checked without the use of magnifying devices.

4.10-4.12. (Introduced additionally, Amendment No. 3).

4.13. The height of the transverse projections of a periodic profile should be measured along the vertical axis of the cross-section of the reinforcing bars.

(Introduced additionally, Amendment No. 4).

Application area

The widespread use of A3 in the construction of residential and industrial buildings and structures is due to the high level of ductility, excellent weldability and high resistance to mechanical/fatigue loads of this class of reinforcing steel. The economic factor is also important: when using A3 in conventional, non-prestressed structures, steel savings reach almost 30%.

The most popular diameters on the rolled metal market are the following: 6, 8, 10, 12, 14, 16, 18, 20. A3 reinforcement is used for the construction of load-bearing reinforcement frames for structures of any responsibility class, and thanks to the alloying additive of manganese, A3 is frost-resistant and is successfully used in regions with low temperatures.

You can also:

• “Hot-rolled steel for reinforcement of reinforced concrete structures”;
• “Rolling of periodic profiles from reinforcing steel”;
• find out prices and buy A3 fittings

PACKAGING, LABELING, TRANSPORTATION AND STORAGE

5.1. Packaging, labeling, transportation and storage - in accordance with GOST 7500-81 with additions:

the ends of rods made of low-alloy steels of class A-IV (A600) must be painted with red paint, class AV (A800) - red and green, class A-VI (A1000) - red and blue. It is allowed to paint the ligaments at a distance of 0.5 m from the ends;

the rods are packaged in bundles weighing up to 15 tons, tied with wire or wire rod. At the consumer's request, the rods are packaged in bundles weighing up to 3 and 5 tons;

on the label attached to each bundle of rods, the accepted designation of the reinforcing steel class (for example, A-III) or the symbol of the yield strength class (A400) is applied.

On ties, paint is applied in strips no less than 20 mm wide on the side surface around the circumference (at least 1/2 the length of the circumference) at a distance of no more than 500 mm from the end.

Paint is applied to skeins in strips no less than 20 mm wide across the turns on the outside of the skein.

For unpackaged products, paint is applied to the end or side surface at a distance of no more than 500 mm from the end.

(Changed edition, Amendment No. 3, 5).

REQUIREMENTS FOR STATISTICAL INDICATORS OF MECHANICAL PROPERTIES

1. The manufacturer guarantees the consumer the average values ​​of tensile strength s in

and yield strength (physical
s t
and conditional
s 0.2
) in the general population -
i
and the minimum average values ​​of these same indicators in each batch-melting -
i
; the values ​​of which are set from the conditions:

i

³
x i b p
+
t × S
i

> 0.9
x i b p
+ 3
S o
i

³
x i b p
,

where x i b p

— rejection values ​​of values
​​s in
,
s 0.2
, indicated in table. 8 of this standard;

t

— quantile value taken equal to 2 for classes A-II (A300) and A-III (A400) and 1.64 for rods of classes A-IV (A600), AV (A800) and A-VI (A 1000).

2. Quality control of indicators of mechanical properties of products at the manufacturer.

2.1. The required quality indicators of profiles are ensured by compliance with production technology and are controlled by testing in accordance with the requirements of clause 3.5, clauses. 4.4-4.8.

2.2. Quantities , , S

and
S o
are established in accordance with the test results and the provisions of Appendix 2.

3. Quality control of indicators of mechanical properties of products at the consumer enterprise.

3.1. The consumer, if he has a quality document for products of the highest quality category, may not test the mechanical properties.

3.2. If it is necessary to check the mechanical properties of each batch, six samples taken from different bags or skeins and from different profiles are tested, and based on the results, the fulfillment of the conditions is checked

xmin

³
i
— 1.64
So
in

³
i
³
i br
,

where in

— average value of mechanical properties based on test results of six samples;

tmin

— the minimum value of the test results of six samples.

3.3. Minimum elongation values ​​d 5

and uniform elongation
d r
must be no less than the values ​​given in table. 8.

(Changed edition, Amendment No. 3).

METHODOLOGY for determining statistical indicators of the strength characteristics of the mechanical properties of hot-rolled products for reinforcing reinforced concrete structures

This technique applies to hot-rolled, accelerated-cooled, thermomechanically and thermally strengthened rolled periodic profiles made in coils or rods.

The technique is used to assess the reliability of mechanical properties in each batch of smelting and steel as a whole, and to control the stability of the technological process.

1. To determine statistical indicators of mechanical properties (yield strength of physical s t

or conditional
s 0.2
, tensile strength
s in
) control test results are used, starting with general populations.

2. Compliance of the mechanical properties of rolled products with the requirements of regulatory and technical documentation is determined on the basis of statistical processing of test results forming a sample from the general population. All findings, results and conclusions drawn from the sample apply to the entire population.

3. Sampling - a set of control test results that form an information array to be processed.

The sample includes the results of acceptance tests of rolled products of the same class, one grade and smelting method, rolled into one or a group of similar profile sizes.

4. The sample on the basis of which statistical indicators are calculated must be representative and cover a sufficiently long period of time, but not less than three months, during which the technological process does not change. If necessary, the time period for sampling can be increased. Checking the homogeneity of the sample according to regulatory and technical documentation.

5. The number of heat batches in each sample must be at least 50.

6. When forming a sample, the condition of random sampling from the smelting batch must be observed. The assessment of abnormality of test results is carried out according to regulatory and technical documentation.

7. During statistical processing, the average value, standard deviation S

each sample (general population), the standard deviation within the heat batch
S o
, as well as the standard deviation of the heat averages
S 1
.
The value of S 1
is determined by the formula

.

Quantities, S

are determined according to regulatory and technical documentation.

8. Checking the stability of characteristics and S

carried out in accordance with OST 14-34-78.

9. Quantity So

is determined for accelerated-cooled, thermomechanically and thermally strengthened reinforcing steel only by the experimental method, for hot-rolled steel - by the experimental method and the span method according to the formula , where and
S v
are, respectively, the average value and standard deviation of the span distribution for two tests from the batch.
The minimum value of S o
is 1.

10. Determination of the value of S o

the experimental method is carried out on at least two heats for each steel grade, class and profile size of rolled products by randomly selecting at least 100 samples from each heat.

11. The value of the minimum average value of strength characteristics s t

(
s 0.2
),
s in
) in each heat batch
2
is determined from the condition
i
= -
t
×
S 1
, where
t
is the quantile value of 1.64 for a probability of 0.95.

12. Minimum value of tensile test results for two samples ( n

= 2) each batch subject to control must have at least
xmin
, determined by the formula

xmin

³
i
-

1.64 So.

13. To provide a guarantee to the consumer of mechanical properties, the following conditions must be satisfied:

i

³
xi br
+ 1.64
S
;

i

³
xi br
;

i

³ 0.9
xi br
+ 3
So
,

where xi br

— rejection value
s t
(
s 0.2
) and
s b
specified in the relevant regulatory and technical documentation.

(Introduced additionally, Amendment No. 3).

Technical characteristics and areas of application of A3 fittings

The products are made from low-alloy steel grades 35GS, 25G2S, 32G2Rps. Due to the increased manganese content, the material is resistant to low temperatures. This type of rolled product is capable of withstanding high operational static and dynamic loads. To increase the service life of fittings, galvanizing or aluminum galvanizing is usually used by hot, electrochemical or thermal diffusion methods.

Main physical characteristics:

• yield strength – 390 N/mm2;
• temporary tensile strength – 590 N/mm2;
• relative elongation – no less than 14%.

Thermo-mechanically strengthened reinforcement with similar tensile strength - 550-600 N/mm2 - is manufactured in accordance with GOST 10884-94.

Product performance properties:

• strength;
• the ability to give the required shape;
• good weldability (without restrictions) of products made from steels with low carbon content, high strength of welded joints.

Due to their technical characteristics, A3 class reinforcing bars are used:

• in monolithic construction and production of reinforced concrete products for the production of flat and spatial reinforcement frames;
• for creating metal structures for various purposes;
• for reinforcing floor screeds, paths, blind areas;
• to strengthen road surfaces;
• for the manufacture of gratings, fences, nets;