GOST 22975-78

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  ГОСТ 22975-78

GOST 22975−78 Metals and alloys. Method of measuring Rockwell hardness at low loads (for Super-Rockwell) (with Amendments No. 1, 2)

GOST 22975−78

Group B09

STATE STANDARD OF THE USSR
METALS AND ALLOYS

Method of measuring Rockwell hardness
at low loads (for Super-Rockwell)

Metals and alloys. Rockwell hardness test under low loads
(using Super-Rockwell test)

AXTU 1909

Valid from 01.01.79
before 01.01.99*
________________________________
* Expiration removed
Protocol N 7−95 Interstate Council
for standardization, Metrology and certification
(IUS N 11 1995). — Note the CODE.

INFORMATION DATA

1. DESIGNED AND MADE by MISI USSR

DEVELOPERS

N. P. Liakishev, A. A. Gudkov, N. A. Birun, V. I. Chebotarev, I. Slavske

2. APPROVED AND put INTO EFFECT by decision of the USSR State Committee for standards from 16.02.78 No. 467

3. INTRODUCED FOR THE FIRST TIME

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

5. Validity extended till 01.01.99 by the Resolution of Gosstandart of the USSR from 14.01.88 No. 45

6. REPRINT (July 1992) with Amendments No. 1, 2, approved in June 1982, January 1988 (IUS 10−82, 4−88)


This standard applies to ferrous and nonferrous metals and alloys, and establishes a method of measuring Rockwell hardness during indentation of a diamond cone (N scale) or steel ball (scale T) with loads of 147 N (15 kgf) to 441 N (45 kgf).

(Changed edition, Rev. N 1).

1. EQUIPMENT

A device for measuring the hardness according to GOST 23677−79, ensuring the application of loads: pre = 29.42 N (3.0 kgs); total =147.1 N (15 kgf); 294.2 N (30 kgf); 441,3 N (45 kgf),

where is the main load.

Tips 23677−79 GOST for GOST 9377−81.

Hardness of exemplary GOST 9031−75.

Periodic checking of the devices according to GOST 8.398−80.

(Changed edition, Rev. No. 2).

2. PREPARING FOR THE TEST

2.1. Before measuring the hardness of the produce inspection samples (products).

2.2. In preparing the surface of the test sample it is necessary to take measures to prevent a possible change in the hardness of the specimen due to heating or cold working of the surface.

2.3. The sample surface must have a roughness of not more than 1.25 µm according to GOST 2789−73 or to meet the requirements of normative-technical documentation on the roughness of the surface of metal products to be free from any foreign material (grease etc.).

2.4. After changing the tip, the working table (stand) are checking the readings on exemplary measures the hardness.

2.3, 2.4. (Changed edition, Rev. No. 2).

2.5. Scale for testing is chosen depending on the thickness of the sample, and the expected hardness so that on the reverse side it was not noticeable deformation traces from the print. The dependence of the choice of the scale from the thickness of the sample, and the expected hardness are given in table. 1 and 2, mandatory Appendix 1.

When the hardness on the scale of T on the sample thickness or hardness less than shown in table. 2 mandatory application 1, the measurement of hardness we recommend the use of coasters with a diamond grain with a diameter of 4.5 mm in the center. This should be reflected in the test report.

(Changed edition, Rev. No. 1).

2.6. The reference surface of the working table (stand) and the sample should be cleaned from extraneous substances. The sample must be mounted on the work table (stand) firmly, steadily, to avoid bending and displacement during hardness measurement. Hardness of contact surfaces work tables and stands shall be not less than 60 HRC. Samples of cylindrical shape have to be installed on V-shaped supports.

(Changed edition, Rev. No. 2).

3. TESTING

3.1. When measuring Rockwell hardness scales are N and T the tip of a standard type is pressed into the test sample (the product) under the action of successively attached and the loads and after removal of the base load measured residual increase (Fig. 1 and 2) depths of penetration of the tip.

Damn. 1

1 — the surface of the test sample; 2 — the source surface during the measurement;
3 — the scale of hardness

Damn. 1

Damn. 2

1 — the surface of the test sample; 2 — the source surface during the measurement;
3 — the scale of hardness

Damn. 2

Refer to traits. 1−2:

the depth of penetration of the tip under the action of pre-load , mm;  — depth of penetration of the tip under the action of the main load , mm; - the residual increase in the penetration depth of the tip, measured after removing the base load, while maintaining pre-load , expressed in arbitrary units of the scale indicator with a scale division of 0.001 mm; HRN — Rockwell hardness at low loads on a scale equal to 100 N-e; HRT — Rockwell hardness at low loads on the scale T equals 100.

3.2. When measuring the hardness of a diamond cone (N scale) or a steel ball (T scales) hardness is indicated by: 75 HRN 15 (hardness 75, scale N, the load of 147 N (15 kgf) or 49 HRT30 (hardness 49, scale T, load 294 N (30кгс).

3.3. The test is carried out at a temperature of 20°C.

If there is disagreement in the assessment of product quality testing should be carried out at temperatures of 20 ± 2 °C in temperate climates and at 27 ± 2 °C in tropical climates.

3.4. When measuring hardness must be complied with the following conditions:

perpendicular to the axis of the tip to the test surface of the sample or prepared section of the product;

a smooth application of the preload ;

smooth application within 2−8 with the main load ;

gradual withdrawal of 1−3 with a base load after the sharp slowdown of the movement of the indicator arrows and 10−15 s (if the movement arrow of the indicator continues) for the materials to plastic deformation.

(Changed edition, Rev. No. 2).

3.5. Readout of the results of measurement of hardness scale indicator with their rounded to the 0.5 division of the scale is produced by the continued action of the preload .

3.6. In determining hardness on a cylindrical convex surface with a diameter equal to or less than 25 mm, the hardness value added of the amendments listed in the table. 3 and 4, mandatory Appendix 1.

Amendments to the hardness values for the samples with curved surfaces, different from the convex cylindrical given in recommended Appendix 2.

3.7. The minimum distance between the centers of two adjacent prints must be not less than three diameters of the print. The distance from the center of the print to the edge of the sample shall be not less than 2.5 diameters of the print.

3.8. The number of fingerprints in the determination of the hardness indicated in the normative-technical documentation for metal products.

3.9. The first three measurements after the change of the tip or the working table (stand) trial and are not recorded in the test report.

3.10. During the test the device must be protected from exposure to bumps and vibrations.

3.11. The number of hardness on the scale of Super-Rockwell do not have an exact translation of hardness, certain other scales or methods of determining hardness.

(Changed edition, Rev. No. 2).

3.12. The test results are entered into the record, which indicate:

coded sample;

the results of measurements;

kind of used table.

(Added, Rev. No. 1).

ANNEX 1 (mandatory). THE CHOICE OF SCALES FOR TESTING DEPENDING ON THE THICKNESS OF THE TEST SAMPLE, AND THE EXPECTED HARDNESS AND AMENDMENTS TO THE HARDNESS VALUES FOR CYLINDRICAL SAMPLES

ANNEX 1
Mandatory

Table 1

The choice of scales depending on the sample thickness and expected hardness (measured on the scale of N)

____________________

* Approximate hardness values in the scale given only to select the appropriate scale when measuring hardness on a scale N and may not apply for transfer to other hardness scales.

Note. Hardness measurement can be performed on the scales shown in the table, on any sample, the thickness and hardness of which is equal to or greater than the specified.

Table 2

The choice of scales for testing a ball tip

______________________

* Approximate values of hardness In given only to select the appropriate scale when measuring on scales T and may not apply for transfer to other hardness scales.

Note. Hardness measurement can be performed on the scales shown in the table, on any sample, the thickness and hardness of which is equal to or greater than the specified.

Table 3

Amendments to the hardness values determined on scales 15 N, 30 N, 45 N for cylindrical samples

Table 4

Amendments to the hardness values determined on scales T15, T30, T45 for cylindrical samples

Notes to the table. 3 and 4:

1. Amendments, shown in brackets, entered by agreement of the parties.

2. For cylindrical samples with diameters intermediate values of corrections can be determined by linear interpolation.

APPENDIX 2 (recommended). AMENDMENTS TO THE HARDNESS VALUES FOR ROCKWELL SCALES N AND T FOR SAMPLES WITH CONVEX AND CONCAVE SURFACES

ANNEX 2
Recommended

When determining the hardness of specimens with curved surfaces, different from the convex cylindrical nomograms are given on features. 1 and 2, which

, the values of corrections to hardness values for Rockwell scales N and T curved surfaces;

 — the equivalent radius of curvature of the test surface. The magnitude and the sign is calculated by the formula

where and are the main radii of curvature of the test surface, taken with the sign «plus» for convex and «minus» for concave surfaces.

Hell 1.

Hell 1.

Hell 2.

Hell 2.

For example. For cylindrical surfaces of the cylinder, for spherical spheres.

Amendments to surfaces with >0 is added to HRN (T), if <0 — is subtracted from the HRN(T). For samples with intermediate radii values of corrections determined by linear interpolation.


The text of the document is verified by:
the official publication of the
M.: Publishing house of standards, 1992