GOST 18661-73

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  ГОСТ 18661-73

GOST 18661−73 Steel. Hardness measurement by shock imprint

GOST 18661−73

Group B09

STATE STANDARD OF THE USSR


STEEL

Hardness measurement by shock imprint

Steel. Method for measurement of hardness by shock indentation

Date of introduction 1974−01−01

APPROVED AND promulgated by the Decree of the State Committee of standards of the USSR Council of Ministers dated 27 April 1973, N 1062

By the decree of Gosstandart of the USSR from 22.06.88 N 2096 validity period extended*
______________
* Expiration removed by Protocol No. 3−93 Interstate Council for standardization, Metrology and certification (I & C N 5−6, 1993). — Note the CODE.

REPRINTING. March 1991


This standard applies to steel and sets the comparative measurement of the hardness at temperatures from minus 10 to plus 50 °C by shock imprint. The method is based on embedding in the surface of the control bar and the test sample (object) carbide conical indenter (for testing steel with a hardness of HV 850) or steel ball (for testing steel with a hardness of HB 350).

1. EQUIPMENT

1.1. The measurement of the comparative steel hardness Vickers, the Brinell hardness and plastic hardness is carried out by means of portable hardness testers impact with impact energy of from 0.03 to 2.5 KGM (for the conical indenter) and from 0.03 to 0.7 KGM (ball indenter) and at an initial speed of impact (the speed of meeting the drummer of the device with striker) from 1 to 5 m/s.

1.2. Measurement of diameters of drum prints of the conical indenter in a tested surface and a surface of the control block should be implemented using readout optical microscope, the error of which should not exceed ±0.01 mm one of the smallest scale division.

1.3. Measurement of the diameters of the shock of the footprint of the bead on the test surface and the surface of the control block should be implemented using readout optical microscope, the error of which should not exceed ±0.05 mm at one smallest division of the scale.

1.4. The depth dimension of the footprint of the bead on the test surface and the surface of the control bar should be indicator depth gauge with a scale division of 0.01 mm.

1.5. Used to measure comparative hardness Brinell plastic hardness of steel balls shall meet the following requirements:

a) material for balls, heat treated steel with hardness not less than HV of 850;

b) the diameters of the balls 5 and 10 mm;

C) the maximum deviation in the diameter of the ball — GOST 3722−81;

g) the roughness parameter of the ball should be µm according to GOST 2789−73 and have no defects that are visible with a magnifying glass with 5-fold magnification.

1.6. Used to measure comparative hardness Vickers bilateral or unilateral cone hard alloy must have forming the corners at the tops and rounded tops with the radius of the sphere is not more than 0.2 mm.

1.7. The surface of the cones over 0.3 mm from the top, counting on its axis, must be carefully polished and free from cracks and other defects that are visible with a magnifying glass at a 30-fold increase.

2. PREPARING FOR THE TEST

2.1. When measuring hardness on curved surfaces a radius of curvature of them in the application of the prints must be at least 5 mm.

2.2. The minimum thickness of the test sample or layer must be greater than the diameter of the print 1.2 times.

2.3. When testing devices with double-sided cone used steel controlling the cross-bar 4,5x4,5 mm of any hardness HV in the range of 100−320.

2.4. The distance between the center of the print and the edge of the specimen (object) and control block or the neighboring edge of the print must be at least 2.5 of the diameter of the print.

2.5. The roughness parameter of the surface of the test sample (object) and the control bar should be in the range of µm — µm (when testing instruments with a conical indenter) and the µm — µm (when testing devices with ball indenter) according to GOST 2789−73 and free from scale and other foreign substances.

2.6. In preparing the surface of the test specimen (product) and the control bar is necessary to take measures to prevent a possible change in the hardness of these surfaces due to heating or work hardening when machining.

2.7. The minimum thickness of the test sample should be at least 10 times the depth of the imprint.

2.8. When testing devices with a spherical indenter applied to steel test bars with cross section 10 x 10 mm in any hardness HB in the range of120−200.

3. TESTING

3.1. When measuring comparative hardness of steel Vickers carbide tip in the form of bilateral or unilateral cone angles at the vertices embedded in the surface of the control bar and the test sample (object) under the action of short-term dynamic loads generated by the impact mechanism. After removal of the indenter with the test surface to measure the diameters of the prints of the cone on the surface of a steel control bar and the test sample (object) (damn. 1).

Note. For static tests of hardness cone (HK) with angle at the vertex equal to the Vickers hardness HV measured by a four-sided pyramid with angles between opposite faces equal to 136°.

Damn.1

Damn.1

3.2. When measuring comparative hardness Brinell plastic hardness steel ball with a diameter of simultaneously implanted into the surface of steel control bar and the test sample (object) under the action of short-term dynamic loads generated by the impact mechanism. After removal of the indenter with the test surface to measure the diameters of the imprints of the ball on surfaces of the control bar and the test sample (object) or the depth of restored prints on the surfaces of the sample (object) and steel control bar (Fig. 2).

Damn.2

Damn.2

4. CALCULATION OF RESULTS

4.1. The number of comparative hardness of the test sample (object) Vickers (HV) is calculated using the formula

where  — the average value of hardness of a test block Vickers, measured by static stationary device according to the GOST 2999−75 kg/mm;

and the diameter of the shock cone prints on the surface of a steel control bar and the test sample (object), mm;

and dynamic coefficients of hardness of materials of steel control bar and the test sample (object) to impact implementation of the cone (with the speed of implementation 1−5 m/s).

Note. Hardness values calculated by these formulas, depending on the size of the diameters of dynamic prints and and hardness control of the steel bars , given in table. 1.

niya.

4.2. The number of comparative hardness of the test sample (object) on the Brinell hardness and the plastic is calculated by the formula:

where and  — average values of Brinell hardness and plastic hardness control of the steel bar measured by means of static devices TS or TC according to GOST and GOST 9012−59 9013−59 kg/mm;

 — diameter of ball, mm;

and the diameter and depth of the restored drums of the print on the surface of the control bar, mm;

and the diameter and depth of the restored drums of the print on the surface of the test specimen, mm;

and ; and dynamic coefficients of hardness of steel control bar and the test sample (object) under shock introduction of the ball at a speed of m/s.

Note. Hardness numbers defined by the formulas depending on the size and or depths and as well as hardness Brinell (HB) and plastic hardness (HG) steel control bar, are given in table. 2−4

app.

4.3. The diameters of the prints measured in two perpendicular directions and is defined as the arithmetic mean of the results of the two measurements.

The difference between the measurements of the diameters of the single print must not exceed 2% of the smaller of them.

For anisotropic materials we obtain the difference between the measurements of the diameters of the prints may not meet the specified tolerance. The standards and technical conditions for the supply of such materials should be specified the permissible limits of the difference between the measurements of two perpendicular diameters of the prints.

4.4. The ball, which showed after measuring the hardness, the residual deformation exceeding the specified tolerance for size, or any surface defect, must be replaced by another, and the corresponding measurement should be considered invalid.

APP. Comparative hardness of the test steel sample

APP

Comparative hardness of the test steel sample
depending on the relationship of the diameters of the prints on the control
the bar on the sample and the hardness of the steel control
block by Vickers

Table 1

Comparative hardness of the test steel sample NVdepending on the relationship of the diameters of the prints on the control bar on the sample and hardness control of the steel bar of NVkg/mm, mm

Table 2

Comparative hardness of the test steel sample NVdepending on the relationship of the diameters of the prints on the control bar on the sample and hardness control of the steel bar of NVkg/mm, mm

Table 3

Comparative ND plastic hardnessof the test steel sample depending on the relationship of the depths of the footprint of the ball on the control bar and the specimen and plastic hardness steel control bar NDkg/mm

Table 4