What does the construction industry know about hot rolled structural steel? Difference between hot rolled and cold rolled steel Hot rolled steel graphics.

With unedged edge should not exceed +20 mm.

Maximum deviations along the length of rolled sheets:

Rolled sheet by sheet, must not exceed:

On continuous mills and cut into sheets, must not exceed:

At the request of the consumer, rolled sheets are manufactured with the following maximum deviations in length:

Rolled products supplied in sheets with cut edges must be cut at right angles. The oblique cut and crescent shape should not take the sheets beyond the nominal size.

Weight per square meter of sheet (GOST 19903-74 and 19904-90)

Rolled thick sheets of carbon steel of ordinary quality.

Rolled products are produced in the form of sheets and rolls from steel grades St0, St2kp, St2ps, St2sp, St3kp, St3ps, St3sp, St3Gps, St3Gsp, St4ps, St4sp, St5ps, St5sp, St5Gps in accordance with GOST 380.

Depending on the standardized characteristics, rental products are divided into categories: 1, 2, 3, 4, 5, 6.

Rolled products of categories 1 - 5 are produced in a hot-rolled state, category 6 - in a hardened state. To ensure the required properties of rolled products of all categories, heat treatment can be used. It is allowed to produce rolled products of categories 1 - 5 in a state strengthened by rolling heating or after controlled rolling.

Rolled thin sheets of carbon steel of high quality and ordinary quality for general purposes.

Thin-sheet hot-rolled and cold-rolled carbon steel of high-quality and ordinary quality for general purpose, manufactured with a width of 500 mm or more, thickness up to 3.9 mm inclusive. Rentals are divided into:

1. by production method: hot-rolled, cold-rolled;

2. by type of product: sheets, rolls;

3. according to the minimum value of tensile strength (B) for strength groups: K260V, K270V, OK300V, K310V, K330V, K350V, OK360V, OK370V (for the production of welded cylinders for liquefied hydrocarbon gases at pressures up to 1.6 MPa), K390V, OK400V, K490V ;

4. according to standardized characteristics into categories: 1, 2, 3, 4, 5, 6;

5. by quality of surface finishing into groups:

cold rolled:

hot rolled:

6. by drawing ability (cold-rolled steel up to 2 mm thick, strength groups: K260V, K270V, K310V, K330V, K350V):

In terms of assortment, rolled products must comply with the requirements of GOST 19903 (hot-rolled), GOST 19904 (cold-rolled).

Hot-rolled thick sheet of carbon steel of ordinary quality. GOST 14637

Hot-rolled thin-sheet carbon steel of high-quality and ordinary quality for general purpose. GOST 16523

GOST 380-50

Group B20

STATE UNION STANDARD

HOT-ROLLED CARBON STEEL OF ORDINARY QUALITY

Classification and general technical conditions

Date of introduction 1950-10-01

INTRODUCED by the Ministry of Metallurgical Industry

APPROVED by the All-Union Committee of Standards 17/V 1950

Date of introduction 1/X 1950

INSTEAD GOST 380-41

A typo has been inserted, published in the collection of standards “Ordinary quality carbon steel (long and shaped rolled products)”, (M.: Standartgiz, 1952)

Typo introduced by database manufacturer

This standard is general for all types of hot-rolled carbon steel of ordinary quality. Certain types of this steel are supplied according to special standards established on the basis of this standard.

I. Classification

I. Classification

II. Specifications

3. Steel is produced by open-hearth or Bessemer methods.

Note. The method of smelting steel supplied under group A is selected by the manufacturer, unless this method is specifically specified in the order.

4. In mild and semi-mild steel, the shrinkage cavity and harmful shrinkage looseness must be completely removed.

Group A steel

5. The guaranteed characteristics of mechanical properties for steel group A are:

a) tensile strength;

b) relative elongation.

Note. The chemical composition of steel supplied under group A is indicated in the certificate, but is not a rejection sign, except for the cases specified in paragraphs 6 and 7 of this standard, as well as in special standards.

6. At the request of the consumer, specified in the order, the following must also be guaranteed:

a) yield strength;

b) satisfactory results of the cold bend test;

c) maximum content of sulfur and phosphorus (according to the norms of clause 14 of this standard);

d) impact strength of steel intended for critical structures.

For steel grade St.3 with a thickness of 12 to 25 mm, the impact strength of each sample should be:

Impact strength standards for steel grade St.3 with a thickness of over 25 mm, as well as for steel of other grades, are established in the relevant standards or departmental technical specifications.

7. In steel for welded structures, at the request of the consumer, specified in the order, the following must be guaranteed:

a) the maximum content of carbon, sulfur and phosphorus in accordance with the norms of clause 14 of this standard;

c) the maximum content of chromium, nickel and copper in accordance with clause 15 of this standard.

Steel for welded structures must also be tested for weldability. The testing methodology and standards are established by a special standard.

8. The norms of mechanical properties of steel of group A are indicated in Table 1.

Table 1

9. The cold bend test should be carried out:

Note. Steel grades St.6 and St.7 are not tested for cold bending.

10. With values ​​of relative elongation corresponding to the standards of Table 1, it is allowed to increase the tensile strength by 3 kg/mm ​​against the upper limit of the standards specified in this table, and with the consent of the customer - without limiting the upper value of the tensile strength, and in these cases A cold bend test is required according to the standards specified in clause 9.

11. The test standards specified in clauses 6, 8 and 9 of this standard apply to samples taken from the metal as delivered. Tensile testing is carried out on section, wide and sheet steel with a diameter or thickness of 4 mm or more, as well as shaped steel with a wall or flange thickness of 4 mm or more. With a thickness of less than 4 mm, section, shaped, wide and sheet steel, as a rule, is subjected to cold bending tests only.

The standards for tensile strength, relative elongation and yield strength indicated in the table apply to round, square, strip and shaped rolled products with a thickness of 8 to 40 mm, as well as to flat and wide rolled products with a thickness of 8 to 20 mm. For other thicknesses of rolled products, these standards are established in the relevant standards or departmental technical specifications for individual types and sizes of rolled products.

12. The cold bend test conditions apply to all types of rolled products with a thickness from 2 to 25 mm. For other thicknesses, the conditions are specified in the relevant standards or departmental technical specifications.

13. When supplying hot-rolled steel of group A with guaranteed limits for the content of carbon, sulfur and phosphorus, these limits must satisfy the standards of clause 14 of this standard for the corresponding grade of steel and for a given production method.

Group B steel

14. For group B steel, the guaranteed quality characteristic is the chemical composition. The chemical composition standards are indicated in Table 2.

table 2

Notes:

1. At the request of the consumer, specified in the order, in steel grades MSt.1, MSt.2, MSt.3, MSt.4, MSt.5, MSt.6 and MSt.7, the sulfur content should be no more than 0.05% , phosphorus content - not less than 0.045%.

2. In boiling steel grades MSt.1, MSt.2 and MSt.3, the manganese content can be in the range of 0.30-0.50%.

15. At the request of the consumer, specified in the order, the content of chromium, nickel and copper in steel should not exceed 0.30% (of each element).

Note. Analysis for chromium, nickel and copper may not be carried out at the manufacturer, but the latter must ensure that their content does not exceed the specified norm.

16. Sampling to determine the average chemical composition of the melt and for control chemical analysis of finished rolled products is carried out in accordance with clauses 22, 23 and 24 of this standard.

17. During control chemical analysis of finished rolled products, the following deviations from the standards established in Table 2* are allowed:

________________

* The table number corresponds to the original. - Database manufacturer's note.

Table 3

III. Acceptance rules

18. Product quality checks during manufacturing and acceptance of finished products are carried out by the technical control department (QC) of the manufacturer. The quality control department checks the compliance of the dimensions, appearance, mechanical properties and chemical composition of steel with the standards specified in the relevant standards and departmental technical specifications.

Control and acceptance of products are carried out by the quality control department based on observations of the steel production process, records of test results carried out during its manufacture, and tests of finished products.

19. Steel of groups A and B is supplied either as whole heats or parts of heats, depending on the batch sizes and order conditions. For steel grades St.0, MSt.0 and BSt.0, float delivery is not required.

20. Lot sizes and the number of samples for testing are established in special standards or departmental technical specifications for individual types of rolled products.

21. In case of an unsatisfactory result of any test, this test may be repeated, for which a double number of samples are taken. If the results of re-testing the steel are unsatisfactory, the manufacturer is given the right to subject the delivered batch to normalization or annealing and re-sorting and present it for delivery again.

IV. Sampling and sampling, test methods

22. To determine the average chemical composition of the smelting metal, samples are taken as follows.

Two samples are taken from under each bucket. Sampling is carried out after half the metal has been poured from the ladle. A second sample is taken in case of repeat testing.

The metal for the sample is poured into cast iron conical cups - molds. Recommended cup sizes: cup diameter at the bottom 50 mm, at the top 80 mm, height 120 mm. Cups are not filled approximately 20 mm.

Sample weight - at least 2 kg. Filling into cups should be done in an even stream; splashing and splashing of metal is not allowed. Aluminum is added to the sample.

After pouring, a tag with the heat number and sample number and with the QC stamp is immersed in each of the cups. The height of the numbers on the tag is 10-12 mm. Samples are released from the cups after the head of the sample has completely darkened.

It is recommended to forge the sample on four sides in order to compact the metal.

In the case of emergency casting of the melt, for example, when casting without a stopper when covering the cup with a stopper, samples for chemical analysis are taken from the sprues of two ingots, the middle ones for the casting or the middle siphon.

23. If, for some reason, during steel casting, samples for chemical analysis were not taken or if additional verification of the chemical analysis is required, then samples are taken during the process of cutting the rolled product with scissors or from the finished rolled product, preferably from the middle strip of the average casting ingot.

(Typo. Collection of standards "Carbon steel").

24. Chips for analysis are taken from the sample by gouging the entire cross-sectional surface of the sample or by drilling in the middle part of the sample to a depth of about half its thickness. Selection of chips for analysis is carried out only after complete removal of scale from the surface intended for selection of chips.

For control analysis of finished rolled products, chips are selected in one of the following ways: a) by gouging the entire cross-section of the rolled product or a fraction of the cross-section (not less than it); b) by drilling a cross section along the rolling with a uniform distribution of drill bits over the cross section and with the same drilling depth at different points; c) drilling along the center line (along the generatrix) of any face of the profile to a depth of the longitudinal axis.

25. For tensile and bend testing of I-beams, channels and z-beams, flat samples are made, blanks for which are taken along the rolling direction from a vertical stand, closer to the flange, and if this is not possible, from the flange itself.

To test angles and tees, flat samples are made, the workpiece for which is taken along the rolling line from one of the flanges, closer to the edge of the flange.

Other shaped profiles are tested in their entirety or samples are made from them in accordance with the instructions of the relevant standards or technical specifications.

To test strip steel, flat or round samples are made, depending on the thickness of the strips. Blanks for samples are taken along the rolling line, closer to one of the edges of the strip.

Round, square and strip steel with dimensions (diameter or width and thickness) within the sample dimensions recommended by GOST 1497-42 are tensile tested without treatment, preserving the outer surfaces of the metal. If the power of the testing machine is insufficient, turning the samples or cutting out part of the profile is allowed.

If the standards for individual types and sizes of rolled products do not specify the dimensions of the samples and their location, then their dimensions and the location of the axis of the samples in relation to the axis of the material being tested should be as follows:

Table 4

Dimensions in mm

26. Blanks for making samples from longitudinally rolled sheets (rolled from both ingots and slabs) are cut across the rolling from the middle third of the sheet width from the head of the sheet.

From boiling cross-rolled steel sheets (rolled from slabs), blanks for making samples are cut transverse to the rolling direction, anywhere along the width of the sheet. In this case, if the roll is cut into several sheets, then the workpiece is cut between the sheets; if the roll produces one sheet, then the blank is cut from the end of the sheet.

From sheets of cross-rolled quiet steel, blanks for making samples are cut transverse to the rolling direction from the end of the sheet, anywhere along the width of the sheet.

For sheet thicknesses up to 25 mm inclusive, flat samples are made while preserving the surface layers of the sheet; For larger sheet thicknesses, cylindrical samples are made.

27. To determine impact toughness, samples are taken in such a way that one of the faces of the sample coincides with the surface of the metal, and the axis of the cut is perpendicular to this surface. Impact strength is determined according to GOST 1524-42.

28. Chemical analysis of steel is carried out according to GOST 2331-43 or another method that provides the necessary accuracy of determination. For arbitration tests, GOST 2331-43 is mandatory.

29. The mechanical properties of steel are determined by tensile testing according to GOST 1497-42.

30. The bend test is carried out according to OST 1683.

V. Marking and documentation

31. Steel of all grades must be marked by painting the ends or ends of the rods, or packs (packages) with indelible paint of the appropriate color (clause 33); in addition, the steel must be branded in accordance with paragraphs 34 and 35 of this standard.

32. Paint marking of steel weighing up to 20 kg per linear meter is carried out by applying a stripe of color corresponding to the given steel grade on each pack; marking of larger steel - by painting the ends or ends.

33. For marking steel with paint, the following colors are established:

34. On each piece of rolled steel, except for those packed in bundles, at a distance of 50-100 mm from the end or at the end, the following must be clearly stamped: the mark of the technical control department, certifying the suitability of the product, as well as the manufacturer’s trademark, steel grade and number swimming trunks If the consumer has his own acceptor at the manufacturing plant, then the acceptor’s stamp is also stamped. The place where the signs are knocked out is outlined with paint. The manufacturer's trademark is not knocked out in cases where it is rolled out in a hot state during rolling.

The heat number can be indicated by a symbol or code, which must be indicated in the certificate.

For steel packaged in bundles and bags, these marks are applied on steel plates (tags) of about 50x50 mm in size, in an amount of at least 2 pieces, attached to them. In this case, each piece of rental product is not branded.

The weight of the bound steel should not exceed 5 tons.

Sheets with a thickness of 4 mm and more are branded and marked individually, and the stamps and markings are applied to the end of the sheet corresponding to the head of the ingot.

Sheets thinner than 4 mm are supplied in bags weighing up to 5 tons.

Notes:

1. With the consent of the customer, it is allowed to supply steel in packs of more than 5 tons, provided that the binding is sufficiently strong to allow safe loading and unloading.

2. With the consent of the customer, it is allowed to supply steel with a weight of 1 linear meter less than 20 kg without packaging, subject to branding and marking of each piece of rolled product.

35. Marks on rolled products should be located as follows (see sketch): in the first column - the manufacturer’s trademark, if it is not hot rolled (for example, “DGZ”); steel grade (for example, "St. 3"); OTK stamp; in the second column, at a distance of about 30 mm from the first, is the heat number (for example, “1452”) and above it the acceptance mark, if any (for example, “P”).

The numbers and letters of the brands should be 8-10 mm high and 5-6 mm wide. When stamping steel weighing 1 linear meter less than 20 kg, the height of numbers and letters can be 4-5 mm, width 2-3 mm.

36. The supplied steel must be accompanied by a certificate or a document replacing it (certificate of technical suitability).

37. Certificate - a document issued by the manufacturer to certify that the supplied metal meets the order and all the requirements of the relevant standards regarding the shape, size, outer surface and quality of the metal, must be signed by the head of the quality control department or his deputy.

38. The manufacturer is obliged to issue a certificate or certificate of technical suitability for each batch of steel. If a batch of steel is loaded into several wagons, a certificate is issued for each wagon separately.

Notes:

1. When loading steel from different batches into a wagon, one common certificate is issued.

2. When steel is shipped from the warehouse, an extract from the factory certificates is issued.

39. The certificate for the supply of steel of all grades in groups A and B must indicate:

a) name of the customer;

b) date and order number;

c) steel grade;

d) profile;

e) dimensions;

f) the number of rolled pieces or packs;

g) numbers of standards or technical conditions according to which the metal is supplied.

In addition to these general data, the certificate must indicate:

a) when supplying steel of group A of all grades, except for grade St.0, - the results of mechanical and technological tests, the method of steel smelting, the heat number and the guaranteed content of harmful impurities; in addition, a complete chemical analysis (for information), and for steel grade St.0 - guaranteed content of carbon, sulfur and phosphorus (if such a requirement is specified in the order);

b) when supplying steel of group B of all grades, except MSt.0 and BSt.0, - heat number and full chemical analysis, and for steel grades MSt.0 and BSt.0 - only the maximum content of carbon and harmful impurities; It is not necessary to indicate the melt numbers.

Electronic document text
prepared by Kodeks JSC and verified against:
official publication
Ordinary carbon steel
quality (long and shaped steel):
Collection of standards. - M.: Standardgiz, 1952

As noted in an earlier post, different types of steel undergo a wide range of processes to achieve proper physical properties. Many people have heard that there is a difference between hot and cold rolled steel, but do not understand how and what is the difference between the production of hot rolled and cold rolled steel, what are the applications, what industries do hot and cold rolled products serve and for what applications is hot or cold rolled steel best for a particular application, machining or other needs. As the name suggests, all types of rolled products pass through two or four rolls. The coils compress the steel and apply pressure to flatten or shape it into the desired shape, which changes the physical properties of the steel. The steel is almost always passed through the rollers more than once until the exact shape or approximate desired shape of the steel is achieved.

Hot rolled steel

Difference

The hot rolling process processes rolled steel at temperatures above the steel's recrystallization temperature, which occurs at more than 1,700 degrees Fahrenheit. Steel that is above its recrystallization temperature can be formed into the desired shape much more easily than colder steel, and such steel can start at significantly larger sizes. It is also usually cheaper to produce than cold rolled steel and is often produced without pauses or delays in the process, so hot rolled steel does not need to be reheated. During the cooling process, hot rolled steel will shrink and the size and shape of the steel will be less predictable than cold rolled steel.

Appearance

Hot rolled products will have a flaky gray color and rounder, less precise corners than cold rolled steel. This makes hot rolled steel more ideal for applications where extremely precise dimensions are not needed and there is no strong competition for appearance. Sometimes a flake finish is preferred for the final product in machining or metalworking applications.

Mechanical properties

The mechanical properties of steel often depend on its grade or chemical composition. For this reason, assumptions should never be made about the mechanical properties of hot and cold rolled products unless they are in the same class. Using the very common example of 1018, the chemical properties of 1018 steel will be the same.

However, we see that there are key differences between cold rolled and hot rolled:

Hot rolled / Cold rolled

Tensile strength 67,000 psi / 85,000 psi

Yield strength 45,000 psi / 70,000 psi

Area reduction 58 / 55

Extension 2 "36 / 28

Brinell hardness 137 / 167

Where is it used?

You will find hot rolled products such as hot rolled steel bars in welding and construction applications, making railroad tracks, I-beams and other steel building materials that do not require ultra-precise shapes. For all these products, you can buy hot-rolled sheets in specialized stores.

Cold rolled steel

Difference

Cold rolled steel is produced at temperatures below its recrystallization temperature, typically at room temperature. Because the steel is made at a much lower temperature, there is no need to worry about the steel abrading or changing its shape.

Appearance

Cold rolled steel products, such as cold rolled steel bar, have a smoother appearance and can have square corners that are more accurate in size and cleanliness.

Mechanical properties

The yield strength and tensile strength of a cold-rolled specimen will be higher than a hot-rolled specimen, making the cold-rolled specimen less likely to fail under pressure.

Where is it used?

Cold rolled steel is much more preferred in the world of processing, where the quality of the steel is an important factor in the quality of the final product, and the appearance of the steel is also a very important factor. For these purposes, you can buy cold-rolled steel from a supplier.

Summary

Below are some of the main differences between hot rolled and cold rolled:

• Hot rolled steel is rolled or formed at a high temperature, while cold rolled steel is rolled at room temperature.
• Cold rolled has a smooth and shiny surface, while hot rolled has a gray and scaly finish.
• Cold rolled steel has sharper corners and more accurate dimensions than hot rolled steel.
• In general, cold rolled products have better mechanical properties than hot rolled products.
• Cold rolled is more expensive than hot rolled.