GOST 25698-98

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  ГОСТ 25698-98

GOST 25698−98 (ISO 4498−1-90) sintered metal Materials, excluding hardmetals. Determination of apparent hardness of the material mainly with uniform hardness over the cross section

GOST 25698−98
(ISO 4498−1-90)

Group B59

INTERSTATE STANDARD

SINTERED METAL MATERIALS,
EXCLUDING HARD ALLOYS

Determination of apparent hardness materials
mostly with uniform hardness over the cross section

Sintered metal materials, excluding hardmetals. Determination of apparent hardness.
Materials of essentially uniform section hardness

ISS 77.160
GST 17 0030

Date of introduction 2001−07−01

Preface

1 DEVELOPED by the Interstate Technical Committee for standardization MTK 150; Institute for problems of materials science im. I. N. Frantsevich of NAS of Ukraine

SUBMITTED to the State Committee of Ukraine for standardization, Metrology and certification

2 ADOPTED by the Interstate Council for standardization, Metrology and certification (minutes N 13 dated 28.05.98)

The adoption voted:

3 this standard is a full authentic text of international standard ISO 4498−1-90 «sintered metal Materials, excluding hardmetals. Determination of apparent hardness. Part 1. The materials are mostly with uniform hardness over the cross section» and contains additional requirements that reflect the needs of the economy of Commonwealth countries, the text of which is shown in italics.

4 Resolution of the State Committee of the Russian Federation for standardization and Metrology dated December 19, 2000 N 384-St inter-state standard GOST 25698−98 (ISO 4498−1-90) introduced directly as a state standard of the Russian Federation from July 1, 2001

5 REPLACE GOST 25698−83

Introduction

The hardness obtained in the study of sintered (powder) metal materials using a test instrument according to the methods of Brinell, Rockwell and Vickers, called the apparent hardness. Because the sintered powder material consists of a thick metallic substance and then, its hardness is usually less than the hardness of the dense material of the same composition and condition. But this does not mean that the functional characteristics (e.g., abrasion resistance) sintered materials worse characteristics of dense materials with equivalent (equal) densities of the metal substance.

1 Scope

This standard specifies methods of hardness testing of sintered metal materials.

Standard applies to:

a) sintered materials not subjected to heat treatment;

b) sintered materials subjected to a heat treatment so that their hardness is mainly uniform from the surface to a depth of not less than 5 mm.

Note — Sintered metal materials due to surface processing (for example, surface hardening) does not meet the requirements of listing b), this standard will not be considered.

2 Normative references

The present standard features references to the following standards:

GOST 2999−75 Metals and alloys. Method of measurement of hardness by Vickers

GOST 9012−59 Metals. Method of measuring hardness Brinell hardness

GOST 9013−59 Metals. Method of measuring Rockwell hardness

3 Equipment

Equipment for carrying out tests according to GOST 2999, GOST 9012, GOST 9013.

4 Selection and preparation of samples for testing

4.1 as the apparent hardness of the sintered material depends on the density, which can vary across items, the position of the field indentation hardness must be agreed between the parties concerned.

4.2 the surface of the sintered metal must be clean, smooth and flat to obtain accurate hardness values on the indentation. This condition is important in determining the hardness Vickers and Brinell. This is enough to clean the surface with a suitable solvent. In some cases, the surface may be slightly polished on the condition that according to laboratory measurements (or regulation), the effect of this polishing is negligible.

Note — Polishing may be performed, for example, by the use of metallographic emery paper or diamond paste with a particle size of not more than 6 µm.

5 testing

5.1 Tests shall be performed in accordance with the requirements of GOST 2999, GOST 9012, GOST 9013 and 5.2−5.5 of this standard.

The hardness measurement is carried out at a temperature from 10 °C to 35 °C.

5.2 the Class of hardness to which the sample to be tested must be identified using tests on the Vickers hardness (HV) at a load of 49,03 N (5 kgf). Then, you should select according to table 1 test conditions for hardness corresponding to a specific (derived) class of hardness and of HG on the production of the material.

Conditions of test for Rockwell hardness given in Appendix A.

The method of determining the hardness Vickers is a control (arbitration) method and is used in cases of dispute.

Note — In case of impossibility of determination of hardness by Vickers method hardness test Rockwell used as a control (arbitration).


If after initial testing there are any doubts regarding the selection of the grade of hardness should be selected lower class.

If the hardness value for the sample cover more than one class of hardness, tests should be conducted under conditions corresponding to lower stiffness.


Table 1

Examples of temper designation:

150 HBS 2,5/62,5/10 — Brinell hardness number 150 that is defined by the use of a steel ball with a diameter of 2.5 mm at a load of 62.5 kgf (612.9 N) and the duration of exposure of 10 seconds.

300 HBW 2,5/187,5/10 — Brinell hardness number 300, as defined when applying a bead of hard alloy with a diameter of 2.5 mm at a load of 187,5 kgf (1839 M) and length of exposure 10.

5.3 For some of the samples should be (allowed) to use a load smaller than indicated in table 1, but the conditions of testing meet the requirements of GOST 2999, GOST 9012, GOST 9013.

In particular, this applies:

a) thin test samples;

b) to test samples with low surface intended to test;

V) to samples with very low surface intended to test;

g) to samples with a mount or without it, which can be deformed or distorted during the test.

If it is necessary to conduct such tests, the conditions must be agreed by the interested parties.

When the distance from the center of the print to the edge of the product less than required by GOST 9012 allowed the hardness measurement Brinell hardness to hold a ball with a diameter of 1 mm. the number of fingerprints in the determination of hardness, measurement conditions and processing set in the normative document for the product.

It should be noted that under the above test conditions, the variability will be greater than with ordinary test, and the result will be less accurate to characterize the condition of the material due to the very small indentation impact (reduce the clarity of the prints).

5.4 If in the determination of hardness by Vickers imprint of the indenter does not have the clear corners, the result of the test should be considered invalid.

5.5 you Must obtain five acceptable definition prints and calculate the corresponding values of hardness (in determining the Rockwell hardness to produce a simple reading of the result). The lowest value of the hardness is not taken into account (cast).

6 processing of the results

Determine the arithmetic average of the remaining four hardness values (5.5) and round it to the nearest whole number.

Another method of processing results (for example, when all five acceptable definition prints hardness are characteristic of the material) apply by agreement between the parties concerned and indicated in the normative document on the specific material.

Not allowed the transfer of hardness values in Vickers, Brinell or Rockwell from one scale to another.

7 test report

The test report must contain:

a) reference to this standard;

b) data necessary to identify the test sample;

C) the results obtained in accordance with the symbols and test conditions according to GOST 2999, GOST 9012, GOST 9013;

d) actions not covered by this standard, or conduct that would be considered as optional;

d) any accidental phenomena that could affect the test results.

Annex a (mandatory). The conditions for determining Rockwell hardness

APPENDIX A
(required)

The type of indenter and the test load of sintered (powder) metal materials Rockwell hardness shall be as given in table A. 1.


Table A. 1