GOST R ISO 7438-2013
GOST R ISO 7438−2013 Materials metal. The bend test
GOST R ISO 7438−2013
NATIONAL STANDARD OF THE RUSSIAN FEDERATION
MATERIALS METAL
The bend test
Mettallic materials — Bend test
OKS 77.040.10
Date of introduction 2014−10−01
Preface
1 PREPARED by FSUE «tsniichermet im.And.P.Bardin," on the basis of their own authentic translation into Russian language specified in paragraph 4 of the standard.
2 APPROVED AND put INTO EFFECT by the Federal Agency for technical regulation and Metrology, dated 22 November 2013 No. 2052-St
3 this standard is identical with ISO 7438:2005* metal Materials. The bend test (ISO 7438:2005 Metallic materials — Bend test)
4 INTRODUCED FOR THE FIRST TIME
Application rules of this standard are established in GOST R 1.0−2012 (section 8). Information about the changes to this standard is published in the annual (as of January 1 of the current year) reference index «National standards» and the official text changes and amendments — in monthly information index «National standards». In case of revision (replacement) or cancellation of this standard a notification will be published in a future issue of information index «National standards». Relevant information, notification and lyrics are also posted in the information system of General use — on the official website of the Federal Agency for technical regulation and Metrology on the Internet (gost.ru)
1 Scope
This standard specifies a method for determining the ability of metallic materials to undergo plastic deformation in bending.
The standard applies to samples taken from metallic products in accordance with the normative documentation on the product. The standard does not apply to certain materials or products, such as pipe full section or welded joints, which are subject to the requirements of other standards.
2 Notation and definitions
Designation and name of the parameters used in the bending test, are given in table 1 and figures 1 and 2.
Table 1 — Symbols and designations
| Marking |
The name of the parameter | Ed. izm. |
| The thickness or diameter of the specimen (or the inscribed circle diameter for samples with multi-faceted cross-section) |
mm | |
| Sample width |
mm | |
| The length of the sample |
mm | |
|
The distance between supports |
mm |
| The diameter of the punch |
mm | |
| The bending angle |
C | |
| The inner radius of the bent portion after bending | ||
| The movement of the punch |
mm | |
| The distance between the plane in which lie the horizontal axis of the cylindrical supports, and the axis of the cylindrical part of the punch before the test |
mm | |
| The distance between the vertical planes in which lie the major axis and the vertical axis in each foot, and the vertical plane containing the horizontal axis of the punch, after the test |
mm |
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* The text of the document matches the original. — Note the manufacturer’s database.
3 the essence of the method
The test is that the sample round, square, rectangular or polygonal cross-section is subjected to plastic deformation by bending, without changing the direction of the load to achieve a given bending angle.
The axis of the two halves of the sample remain in the plane perpendicular to the axis of the bend. Depending on the requirements of the normative documentation for the product after bending 180° two side surfaces can touch each other, or remain parallel to each other at a predetermined distance controlled by using a liner.
4 testing Equipment
4.1 General provisions
Tests are carried out on testing machine or press, equipped with the following:
a) a bending device with two supports and a punch (figure 1);
b) a bending device with a V-shaped notch and a punch (figure 2);
c) a bending device with a vise (figure 3).
Figure 1. The bending device with two supports and the punch
Figure 1
Figure 2. Bending device with a V-shaped notch and punch
Figure 2
Figure 3. The bending device grip
1 Clip
2 Punch
Figure 3
4.2 bending device with supports and a punch
4.2.1 the anchorage Length and the width of the punch must be larger than the width or diameter of the specimen. The diameter of the punch is established by the normative documentation on products. Support and the plug needs to have a sufficiently high hardness (figure 1).
4.2.2 Unless otherwise specified, the distance between supports shall be
and should not be changed during the test.
4.3 bending device with a V-shaped notch
The inclined surface of the slot excavation should form an angle of 180°-(figure 2). The angle
is established by the normative documentation on products.
The edges of the V-shaped socket needs to be rounded with a radius ranging from 1 to 10 thicknesses of the sample, and to have a sufficiently high hardness.
4.4 bending device with a clamp
The fixture consists of a clamp and a punch having a sufficiently high hardness. It may also be equipped with a lever for application of a bending force to the sample (figure 3).
Since the position of the left side of the clamp can influence the result of the test, the party must not protrude beyond a vertical line passing through the center of curvature of the punch, as shown in figure 3.
5 preparing for the test
5.1 General provisions
For tests used samples of round, square, rectangular or polygonal cross-section. Portions of the sample, the structure of which is violated when cutting with scissors or a sharp fiery during sampling should be removed. Allowed testing of the sample without removal of areas with the damaged structure, provided that the test results are to comply with regulations for steel products.
5.2 Edge samples with a rectangular cross section
The edge samples with a rectangular cross section shall be rounded with a radius not exceeding the following values:
3 mm sample thickness of 50 mm and more;
1.5 mm at thickness less than 50 mm but greater than or equal to 10 mm, inclusive;
1 mm thickness of less than 10 mm.
Rounding must be performed in such a way as to avoid burrs, scratches or marks, which could have a negative impact on the result of the test. Allowed sample test without rounding of the edges subject to obtaining satisfactory results.
5.3 sample Width
If the regulations for metal products is not specified, the sample width should be equal to:
a) the width of the product, if the width is 20 mm or less;
b) when the width of the product more than 20 mm:
— (20±5) mm thickness less than 3 mm;
— from 20 to 50 mm with a thickness of 3 mm or more.
5.4 the Thickness of the sample
5.4.1 the thickness of the samples taken from sheets, strips and profiles must be equal to the thickness of the test items. If its thickness exceeds 25 mm, it is possible to reduce machining to a thickness of not less than 25 mm When the bending of the raw surface should be on the stretch side of the specimen.
5.4.2 Specimens with a round or polygonal cross section have the same cross section as the test product, if the diameter of the circular cross-section or diameter of inscribed circle of a polygonal cross-section does not exceed 30 mm. If the diameter of the circular cross-section or diameter of inscribed circle of the polygonal cross section of more than 30 mm but less than 50 mm, it may be reduced to not less than 25 mm. If the diameter of the circular cross-section or diameter of inscribed circle of the polygonal cross section of more than 50 mm, it must be reduced to not less than 25 mm (figure 4). Bending the raw surface should be on the stretch side of the specimen.
Figure 4. The diameter of the circular cross-section
Figure 4
5.5 Samples taken from forgings, castings and semi-finished products
When testing forgings, castings and semi-finished dimensions of samples and location sampling should be established by agreement between the consumer and the manufacturer.
5.6 the Test specimens of greater thickness and width
By agreement between the consumer and the manufacturer of the bend test may be subjected to samples with a thickness and a width that exceed those listed in 5.3 and 5.4.
5.7 Length samples
The length of the specimen depends on its thickness and used test equipment.
6 testing
ATTENTION! During the test, you must take appropriate security measures and use protective equipment.
6.1 As a rule, tests shall be performed at room temperature from 10 °C to 35 °C. the differences in the assessment of the quality of steel products tests shall be carried out at a temperature of (23±5) °C.
6.2 the bend Test is carried out in accordance with the requirements of one of the following methods specified in the normative documents for the products:
a) to achieve a given bending angle at an appropriate force and under specified conditions (figures 1, 2 and 3);
b) to the parallel sides of the specimen at a given distance between them and an appropriate force (figure 6);
C) to contact the sample when an appropriate force (figure 7).
Figure 5
Figure 6
Figure 7
6.3 When tested in bending until the required bending angle is mounted on the sample support (figure 1) or V-shaped notch (figure 2) and Flex, applying force in the middle between the supports. The bending angle can be calculated by measuring the movement of the punch, as indicated in Appendix A.
In any method according to figures 1, 2 and 3, the bending force shall be applied slowly to permit free plastic flow of the material. In case of disagreement, the travel speed should be (1±0,2) mm/s.
If it is impossible to bend the sample to a predetermined angle as described above, the test is produced by direct compression of the ends of the specimen (figure 5).
If you want the bend to the parallel sides, the first Flex sample, as shown in figure 5 and then placed between the plates of the press (figure 6), and continue the bend to the parallel sides. The test can be carried out with the liner or without. Liner thickness shall be specified by the regulations for metal products or be established by agreement of the parties.
An alternative method of testing is bending around the punch (4.4).
6.4 When tested in bending to the contact side of the specimen (figure 7), the sample is then pre-bend is subjected to further bending between parallel plates press with ever-increasing force.
7 Processing of test results
7.1 Evaluation of test results produced according to the requirements of the normative documentation for the products. If there are no such requirements, the sample shall be deemed satisfactory if no cracks visible to the naked eye.
7.2 the bending Angle specified by the regulations for steel products is always considered to be minimal. If you specify the inner radius of the bend, it is considered maximum.
8 test report
The test report should be given the following information:
a) reference to this standard;
b) identification of the sample (type of material, number of melt, the direction of the axis of the sample relative products, etc.);
c) the shape and size of the sample;
d) test method;
e) any deviations from the requirements of this standard;
f) the result of the test.
Annex a (informative). Determination of the bending angle on the movement of the punch
Appendix A
(reference)
This standard requires the determination of the bending angle of the sample under load. Direct measurement of this angle is difficult. For this reason, we propose a method for computing the angle
by measuring the displacement
of the punch. The bending angle of the sample
under load can be determined by the displacement of the punch with respect to the dimensions specified in figure A1, as follows:
where:
Dimensions are in millimeters
Figure A. 1 Dimensions for calculating the bending angle alpha
Figure A. 1 Dimensions for calculating the bending angle
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UDC 669.01:620.174:006.354 OKS 77.040.10
Key words: metallic materials, bending
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The electronic text of the document
prepared by JSC «Code» and checked by:
the official publication of the
M.: STANDARTINFORM, 2014
