GOST 29012-91

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  ГОСТ 29012-91

GOST 29012−91 (ISO 4492−85) Powder metallurgy. Method of determining change in the dimensions of pressovac after removal of the compacting pressure and sintering time

GOST 29012−91
(ISO 4492−85)

Group B59

INTERSTATE STANDARD

POWDER METALLURGY

Method of determining change in the dimensions of pressovac after removal of the compacting pressure and sintering time

Powder metallurgy. Method for determination of compacts dimensional changes after compacting pressure relief and at the time of sintering

MKC 77.160
AXTU 1790

Date of introduction 1992−07−01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Academy of Sciences of the Ukrainian SSR

2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on management of quality and standards from 17.05.91 N 703

3. The standard fully complies ST SEV 6745−89, in addition to the app

4. The application is prepared by the direct application of international standard ISO 4492−85* «Powder metal (except carbide). The definition of change of size during compaction and sintering"
_______________
* Access to international and foreign documents mentioned here, you can get a link on the website shop.cntd.ru.- Note the manufacturer’s database.

5. INTRODUCED FOR THE FIRST TIME

6. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

7. REPRINTING. September 2004


This standard specifies a method for determining changes in sizes of pressovac made from metal powders, powdered alloys and powder mixtures, in the direction perpendicular to the pressing force and the pressing direction after the removal of pressure during sintering.

The method consists in determining the size of the forming cavity of the mold, and sintered respecing pressovac made in it, and compute their algebraic difference.

This standard does not apply to powders of hard alloys.

Terms used in the standard correspond to GOST 17359.

You can define resize pressovac after removal of the compacting pressure and the sintering time according to MS ISO 4492−85 given in the Appendix.

1. SAMPLING METHOD

1.1. Sampling and sample preparation — according to GOST 23148.

1.2. The density of pressovac needs to be set or selected based on the density of the pressed products.

1.3. Compaction shall have a height of from 5 to 20 mm, cylindrical shape with 25 mm in diameter or rectangular sizes 30х12 mm.

1.4. The weight () grams for the manufacture of compression is calculated by the formula

, (1)

where is the specified compaction, g/cm;

 — the amount of compression, cm.

1.5. Weight of sample for test shall be not less than four times the mass of the compact.

1.6. Produce at least three pressovac the same density.

2. EQUIPMENT AND MATERIALS

Press, providing the force to 500 n and the measurement error not more than 2%.

Mold given on features.1, 2, for the manufacture of pressovac cylindrical and rectangular shape. The matrix and the punches to the mold should be made of hard metal or tool steel with a hardness of at least 55 HRC.

Damn.1. The scheme of the mold for the manufacture of pressovac cylindrical shape

The scheme of the mold for the manufacture of pressovac cylindrical shape

1 — ferrule; 2 — matrix; 3 — punches the top (110 mm) and bottom (65 mm)

Damn.1

Damn.2. The scheme of the mold for the manufacture of pressovac rectangular shape

The scheme of the mold for the manufacture of pressovac rectangular shape

1 — ferrule; 2 — matrix; 3 — upper punch (25 mm) and lower (70 mm)

Damn.2

Scales, providing weighing up to 100 g with error of at most 0.01 g

Oven, providing the conditions of sintering (temperature, time and gaseous environment) of products (pressovac) from different types of metal powders and their mixtures.

Indicators multi-turn 1 MOMENT or 1 PSYCHOLOGY GOST 9696.

Tripod sh-1N-8 according to GOST 10197.

Allowed to use other measuring tools with a measuring error of size pressovac not more than 0.005 mm.

Measures end with a length of from 2.5 to 25 mm, accuracy class 2 according to GOST 9038.

System for measuring deformation which measure the compressibility of punches of the mold and the pressing force with an error of not more than 2%, of type SID-1 or SID-2 according to normative-technical documentation.

3. PREPARING FOR THE TEST

Get pressing in accordance with the requirements of paragraph 1.2.

3.1. Method of filling powder into the cavity of the matrix of the mold pressure, pressing speed and the use of lubricants during compaction should be stated specifically. Each mode of compression, get at least three pressovac. The sequence of clamping operations shown in hell.3.

Damn.3. The sequence of clamping operations

The sequence of clamping operations

Damn.3

Pressure support 2 (Fig.4) must be less than the pressing pressure is not less than 100 times.

3.2. The pressure of pressing is determined using strain gages mounted on the elastic base plate and connected to the measurement system of deformation registered by the instrument, the scale of which needs to be calibrated in units of the measured value.

Damn. 4. The scheme of the mold

The scheme of the mold

1 — pressure plate press; 2 — support; 3 — elastic supporting plate; 4 — strain gages

Damn. 4

The pressing is sintered for a given regime or in conditions of technological process of production of particular products. Pressing at sintering should be located in close proximity to ensure equal conditions for temperature, duration of sintering and gas environment.

Allowed to compact, to match the shape and size of specific products.

4. TESTING

4.1. Determine the size of the cavity of the mold in the direction perpendicular to the pressing force.

4.2. The height of the die () are in millimeters, limited supports 2 (see the devil.4) in the direction of pressing in the absence of pressure on the punches, is calculated by the formula

, (2)

where  — height of the piers to provide the intended height of compact, mm;

 — the length of the upper punch, mm;

 — length of the lower punch, mm;

 — the height of the elastic support plate, mm.

Allowed to more accurately determine the height of the die () by precipitation in the mold (see the devil.4) sample of powder of lead, previously produced by pressing in a cylindrical mold with a diameter of (15±5) mm, force on supports not more than 5 kN, and then measure its height. The density of the sample from the powder of lead shall be not less than 9.5 g/cm. The height of precipitation must be greater than the proposed height of the pressing is not more than 1 mm.

4.3. The height of pressovac located in the mold at the time of the maximum pressing force, is determined from the deformation (compressibility) of punches and an elastic deflection of the base plate. These data are in the form of graphs with the axes: pressing force — deformation (or punch plate).

The height of the compact () in millimeters is calculated by the formula

, (3)

where the height of the die calculated by the formula (2), mm.

 — the compressibility of the upper punch, mm;

 — compressibility of the lower punch, mm;

 — the deflection of the elastic base plate, mm.

4.4. Determine the size of pressovac made before and after sintering. However, the methods and technical means of measurement must be the same.

4.5. The sizes of molds and pressovac before and after sintering to determine with an accuracy of 0.005 mm.

5. PROCESSING OF THE RESULTS

5.1. Resize the compression (elastic after-effect) in percent, determined in the direction perpendicular to the pressing force or in the direction of the pressing force after removing the pressure, calculated by the formulas:

, (4)

, (5)

where is the diameter of the pressing to sintering in a direction perpendicular to the pressing force, mm;

the diameter of the die cavity of the mold in the direction perpendicular to the pressing force, mm;

the diameter of compacts before sintering in the direction of the pressing force, mm;

height of pressing in the mold at the time of the maximum pressing force.

5.2. Resizing (linear increase or linear shrinkage) compaction in percent, defined in the direction perpendicular to the pressing force () or in the direction of the pressing force () during the sintering is calculated by the formula:

, (6)

, (7)

where is the diameter of the pressing after sintering in a direction perpendicular to the pressing force, mm;

the diameter of the pressing to sintering in a direction perpendicular to the pressing force, mm;

the diameter of the pressing after sintering in the direction of the pressing force, mm;

the diameter of compacts before sintering in the direction of the pressing force.

5.3. The total change of the size of the compression percentage, as defined in the direction perpendicular to the pressing force () or in the direction of the pressing force (), after removal of the compacting pressure during the sintering is calculated by the formula:

, (8)

, (9)

where is the diameter of the pressing after sintering in a direction perpendicular to the pressing force, mm;

the diameter of the die cavity of the mold in the direction perpendicular to the pressing force, mm;

the diameter of the pressing after sintering in the direction of the pressing force, mm;

height of pressing in the mold at the time of the maximum pressing force.

5.4. For resizing pressovac take the arithmetic mean of at least three test results, rounded to the second decimal place.

5.5. The test results recorded in a Protocol containing:

the name (brand) of powder or the composition of the mixture;

information about the shape, size, compaction and density of pressovac before sintering;

the conditions of sintering and the size of pressovac after sintering;

the average of the test results;

the designation of this standard;

the testing date.

APPLICATION (recommended). POWDER METAL (EXCEPT CARBIDE). THE DEFINITION OF CHANGE OF SIZE DURING COMPACTION AND SINTERING. ISO 4492−85

APP
Recommended

INTERNATIONAL STANDARD

1. Purpose and scope

This international standard specifies a method for the comparison of changes in dimensions during the pressing and sintering metal powders with changes in the dimensions of the reference powder when processed under the same conditions (see sect.4).

The method is used to determine three types of measurements of the dimensions associated with the processing of metallic powders, excluding powders of hard alloys.

2. Links

ISO 2740 sintered metal Materials, excluding hard metals. Samples for tensile tests.

ISO 3927 metallic Powders, excluding powders of hard alloys. Determination of compressibility (compactibility) under uniaxial compression.

3. The essence of the method

The pressing of metal powder or powder mixture with the addition of a lubricant to obtain a sample for testing, followed by sintering under controlled conditions. Depending on the specific sizing measurement size unfilled die cavity, respectnot pressing and (or) sintered sample for test. The computation of the algebraic difference between these different dimensions in the form of a percentage of the size of the die cavity or respectnot pressing (see sect.9).

Standard samples for test are made from the inspection lot and processed together with the sample under test, with cheat measurement of the sizes of the two powders.

4. Test parameters

Control powder should be chosen by agreement between the supplier and the consumer. The composition and properties it should be closer to the investigated powder.

In this international standard to consider three types of changes of the amounts specified in the PP.4.1−4.3.

4.1. The size of the matrix to the size respectnot pressing (elastic after-effect) — increase in the size of the compacts, measured at right angles to the direction of compression after vypressovyvaniem from the matrix.

4.2. Size NISPAcee pressing to the size of the sintered sample (size changes in sintering) — change products in size that occurs as a result of sintering.

4.3. The size of the matrix to a size of a sintered sample, the total change size.

5. Symbols

6. Equipment

6.1. A set of stamps, which are used for the manufacture of cylindrical samples is given in hell.1, rectangular samples are given in hell. Or 2 samples to test, analogous to the specific details, which requires this powder.

Damn.1. The scheme of the mold for the manufacture of pressovac cylindrical shape

The scheme of the mold for the manufacture of pressovac cylindrical shape

1 — ferrule; 2 — cemented carbide alloy; 3 — punch the upper () and lower ()

Note. Mated parts must be fitted and lapped.

Damn.1

Damn.2. The scheme of the mold for the manufacture of pressovac rectangular shape

The scheme of the mold for the manufacture of pressovac rectangular shape

1 — ferrule; 2 — cemented carbide alloy; 3 — punches (steel HRC 60−62) upper (25) and lower (70)

Damn.2

6.2. Press allowing to obtain pressure needed to achieve the required density.

6.3. Scales with a weighing capacity of 100 g and an accuracy of ±0.01 g.

6.4. Micrometer or other suitable measuring device for measuring the pressing and matrix with an accuracy of ±0,005 mm.

6.5. Furnace for sintering, allowing to create the conditions of sintering (curve time — temperature and gas environment) are as similar as possible to industrial conditions for the investigated type of material.

7. Sampling

For the test must be taken the appropriate amount of the test and control powders, sufficient to obtain at least three pressovac.

8. The test procedure

8.1. Test and control powders must be mixed under the same conditions with the same mass of additives, including lubricant, each of which is taken from a single batch to the composition of sintered parts, which require the powder.

The investigated powder, supplied ready for pressing, should be tested in the delivery condition.

To avoid deformation during sintering, it is recommended to take samples for testing with a minimum thickness of 5 mm.

8.2. Measured with an accuracy of 0.005 mm investigated the size (diameter or length) of the matrix in the unfilled condition and writes the obtained value .

8.3. Produce compression at a matched density of not less than three pressovac as from the study and control of powders, prepared as described in step 8.1.

8.4. Measured with an accuracy of 0.005 mm investigated the size respectnot pressing and record the value obtained .

8.5. Conduct sintering study and control of pressovac, placing them close to each other under conditions of temperature, time and gaseous environment that reproduce the industrial conditions used for sintered parts, which needed of the investigated powder.

Note. Stand used to the samples to prevent deformation (i.e., the ceramic plate or tape furnace), heating rate, gas atmosphere and cooling rate can affect the measured size changes and needs to be permanent.

8.6. After cooling to room temperature is measured with an accuracy of 0.005 mm investigated the size of the sintered test and control of pressovac and record the resulting amount , after making sure that the dimensions measured before and after sintering are taken from the same position pressovyj.

9. Processing of the results

9.1. The sizing, expressed in percentage of

9.1.1. Resize respectnot pressing (elastic effect)

.

9.1.2. Changing the size of the sintered compact (positive or negative)

.

9.1.3. The total change in size (positive or negative)

.

9.2. Record the resize as for the studied and the control powders as the average of at least three definitions, rounded to the nearest 0,01%.

10. Test report

The test report shall include the following information:

a) reference to this international standard;

b) all details necessary for identification of the test sample;

C) all details necessary to identify a test powder;

g) type of sample for test and its dimensions before sintering;

d) density respectnot pressing;

e) details of modes of sintering;

g) the result obtained;

h) all operations, not stipulated in this international standard, or operation regarded as optional;

s) details of any phenomenon, which could affect the result.