GOST 22762-77

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  ГОСТ 22762-77

GOST 22762−77 Metals and alloys. A method of measuring the hardness at the yield point indentation of the ball

GOST 22762−77
Group B09

STATE STANDARD OF THE USSR

METALS AND ALLOYS

A method of measuring the hardness at the yield point indentation of the ball

Metals and alloys.
Yield point hardness test by ball indentation

Valid from 01.01.1979
to 01.01.1984*
________________
* Expiration removed
Protocol N 3−93 Interstate Council
for standardization, Metrology and certification.
(IUS No. 5/6, 1993). — Note the CODE.

DEVELOPED by the Moscow order of Lenin energy Institute

Vice-Rector G. M. Utkin

The Head Of The M. P. Markovets

The By V. I. Yakovlev

INTRODUCED by the Ministry of higher and secondary special education of the USSR

Member Of The Board Of D. I. Ryzhonkov

The draft all-Union scientific research Institute of standardization (VNIIS)

Director A. V. Gichev

APPROVED AND promulgated by the Decree of the State Committee of standards of the Council of Ministers of the USSR dated 31 Oct 1977 N 2555


This standard applies to ferrous and nonferrous metals and alloys, and specifies a method of measuring the hardness at the yield point from about 78.5 to 3285 MPa (8−335 kgf/mm) by pressing the globe at temperatures from 0 to plus 40 °C.

The hardness at the yield point characterized by the mean stress in the hole during indentation of a ball when it appears the average residual deformation, which is close to 0.2%, occurs when the ratio of the diameter of the hole to the diameter of the ball is equal to 0.09.

1. EQUIPMENT

1.1. As a test apparatus used static effect devices or test equipment, enabling:

a smooth increase of the load;

ensure continuity of the applied load for the required time;

suspension of loading up to one smallest division of the scale siloizmeritelya. The price of division of the scale siloizmeritelya should be no more than 1% of the value of the load at the yield point. Permissible relative error of load shall not exceed ±1%;

application of the current efforts perpendicular to the surface of the test items (sample).

1.2. Used in the hardness measurement on the yield strength of the balls shall meet the following requirements:

material for balls, heat treated steel with hardness not less than 850 units by Vickers;

the diameter of used balls — 10, 20, 30, 40 and 50 mm;

limit deviations of the diameter of the balloon should correspond to GOST 3722−60 in the group;

the roughness parameter Ra of the surface of the ball should be no more than 0,040 µm according to GOST 2789−73.

1.3. Ball showed after measuring the hardness, the residual deformation exceeding the specified tolerance in size in accordance with the group In GOST 3722−60 or any surface defect, must be replaced by another, and the corresponding measurement should be considered invalid.

1.4. To measure the diameter of the imprint is to be applied to microscopes, providing measurement with an error not exceeding:

1.5. Periodic checking of the instrument to determine the hardness at the yield point is made according to GOST 8.043−72.

2. PREPARATION FOR CONTROL

2.1. The roughness parameter Ra of the surface of the item (sample) in the test area should not exceed 0,32 µm according to GOST 2789−73.

2.2. In preparing the surface of the test products (sample), you should take precautions to prevent change in hardness of the test items (sample) due to heating or cold working of the surface when machined.

2.3. Tested product (sample) should not shift in the measurement of hardness.

2.4. The minimum thickness of the product (specimen) shall be not less than 8 times the depth of the imprint.

2.5. The distance from the center of the print to the edge of the sample should be not less than 1.5 times the diameter of the imprint, and the distance between the centers of two adjacent prints must be at least two diameters of the print.

2.6. When measuring hardness on the products (samples) with a convex cylindrical surface, the minimum radius of curvature of the product (the sample) must be at least five diameters of the ball. In this case, the test shall be carried out without preparation a flat surface.

When measuring hardness on the products (samples) with a cylindrical surface whose radius of curvature less than five times the diameter of the ball, width and length prepared flat surface must be at least five times the diameter of the imprint, respectively. The distance from the center of the print to the border between the flat and cylindrical surfaces should not be less than 1.5 the diameter of the print.

3. CONTROL

3.1. When the hardness at the yield point the ball pressed into the surface of the test sample of the product load so that the measured indentation diameter was less than 0.09 to not more than 5%, with a shutter speed under load 1.

3.2. After relieving the load, measure indentation diameter, which should be measured in two mutually perpendicular directions and determine the arithmetic average of results of two measurements.

The difference between the measurements of the diameters of the imprint must not exceed 2% of the smaller of them. For anisotropic materials and products with convex cylindrical surfaces, the difference between the measurements of the diameters of the imprint must be specified in normative and technical documentation for metal products.

3.3. Produce subsequent indentation load so that the measured indentation diameter was more than 0.09 to not more than 5%.

By values and by interpolation determine the load at yield point .

4. PROCESSING OF THE RESULTS

4.1. The hardness at the yield stress () MPa (kgf/mm) is determined according to table.1 and 2, are shown in mandatory Appendix, or calculated by the formula

,

where is the load in N corresponding to the diameter of the print ;

 — diameter of ball, mm;

 — indentation diameter, mm.

4.2. When referring to the hardness to the yield stress calculated value is supplemented by a symbol indicating the dimension, for example: 250 , MPa.

4.3. During indentation of a sphere with diameter 20, 30, 40, 50 mm load should be divided respectively by 4; 9; 16; 25 and received by the division result to determine the desired hardness value .

For example: during indentation of a ball with a diameter of 40 mm to the diameter of the imprint 3.6 mm load at yield point was equal 3200 N. Then for determining the hardness values must load at 3200 N divided by and at the table.1 for the values of load of 200 N. find the corresponding value of the hardness at the yield point equal to 314 MPa.

4.4. The hardness values for the yield stress to determine the yield stress in tension at the test site. The ratio between the load at the yield point , hardness at the yield point and yield strength for alloy steels when tested ball with a diameter of 10 mm are shown in the table.

The determination error for is ±7%.

APP (mandatory)

APP
Mandatory

Table 1

A hardness yield strength (MPa) during indentation of a sphere with a diameter of 10 mm under a load (N) corresponding to the indentation diameter of 0.9 mm

Extension table 1

Extension table 1

Extension table 1

Table 2

The hardness at the yield point (kgf/mm) during indentation of a sphere with a diameter of 10 mm under load (kgf) corresponding to the indentation diameter of 0.9 mm

Extension table 2

Extension table 2

Extension table 2

The text of the document is verified by:
the official publication of the
M.: Publishing house of standards, 1978