GOST 26849-86
GOST 26849−86 (ST SEV 4657−84, ISO 4003−77) Materials powder. The method of determining the size of the pores (Change No. 1)
GOST 26849−86
(ST CMEA 4657−84,
ISO 4003−77)*
______________________
* The designation of the standard.
Changed the wording, Rev. N 1.
Group B59
STATE STANDARD OF THE USSR
MATERIALS POWDER
The method of determining the size of the pores
Powder materials.
Method of pore size determination
AXTU 1790
Valid from 01.01.87
before 01.01.92*
________________________________
* Expiration removed
by the decree of Gosstandart of the USSR
from
Note the manufacturer’s database.
DEVELOPED by the Academy of Sciences of the Ukrainian SSR
PERFORMERS
V. N. Klimenko, A. G. Kostornov, L. E. Lunin, A. E. Kushchevsky, M. Simonovic
INTRODUCED by the Academy of Sciences of the Ukrainian SSR
Vice-President I. K. pokhodnya
APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on standards of 26 March 1986 No. 625
The Change N 1, approved and put into effect by the Decree of the USSR State Committee for standards from
Change No. 1 made by the manufacturer of the database in the text ICS N 7, 1989
This standard specifies a method for determining the size of the pores of permeable powder materials and products from them.
The essence of the method consists in measuring the pressure required to discharge on surfaces are completely saturated with sample liquid of the first bubble of air, when determining the maximum size of the pores; measuring the pressure corresponding to the beginning of the selection to the entire surface of the sample air bubbles in the determination of the average size of the pores.
The standard fully complies ST SEV 4657−84.
The standard introduced by the international standard ISO 4003−77.
(Changed edition, Rev. N 1).
1. SAMPLING METHOD
1.1. Sampling is carried out according to GOST 18321−73 with the following additions:
the number of samples for testing shall not be less than three.
Samples for trials are and the finished product.
It is possible to produce samples of the finished products by machining.
Machining of working surfaces of products are not allowed.
1.2. The place of cutting samples from products and requirements for their machining needs to be given in the normative-technical documentation on the product.
If you cannot sample the products they produce in terms of the finished product.
Samples must be in the form of a disk with a diameter of from 25 to 100 mm or of a hollow cylinder (bushing) with a working surface from 5 to 100 cm. The thickness of the samples should correspond to the thickness of the products.
1.3. Samples for testing of materials shall be in the form of a disk with a diameter of from 25 to 100 mm and a thickness of not less than 0.25 mm. the thickness of the samples should be different and chosen experimentally. The range of variation of the sample thickness should be 2 mm.
The number of samples for testing must ensure that plotting the variation of the maximum value of the pore to the thickness of the sample.
1.4. To ensure when testing the fit of the product or sample to the holder of the allowed machining of surfaces fit.
2. EQUIPMENT AND MATERIALS
Installation whose schema is shown in hell.1.
1 — the source of compressed air; 2 — valve; 3 — oil separator; 4 — dehumidifier;
5 — filter; 6 — valve of fine adjustment; 7 — drain pipe installation liquid level above the sample;
8 — the test sample; 9 — holder for fixing samples; 10 — valve; 11 — pressure gauge Mo 0.4 MPa
according to GOST 6521−72; 12 — gauge Mo 0,16 MPa according to GOST 6521−72; 13 — U-shaped manometer,
filled with water; 14 — micromanometer MMN-2400 (5)-0,6 GOST 11161 — 84.
Damn.1
Holder, the design of which should provide a working surface that meets the requirements of samples for testing.
To saturate the samples used ethyl alcohol GOST 18300−87 with a mass fraction of alcohol of not less than 96.2% of the density 0,807 g/cmand the surface tension 0,0228 N/m at 20 °C.
Allowed to use other liquids, to ensure a complete wetting of the surface of the material in the absence of chemical interaction with it.
Thermometer type t-62А1−8 according to GOST 215−73 with an error of not more than 0.5 °C.
(Changed edition, Rev. N 1).
3. PREPARING FOR THE TEST
3.1. Before testing, the samples were subjected to the examination without the use of magnifying tools. On the surface of the samples shall be free of scratches, chips, cracks, delamination, foreign inclusions, protrusions and mechanical damage.
3.2. Samples for test shall be dried to constant weight at temperature 105−110 °C.
3.3. The samples before the test, saturate in boiling liquid for at least 1 h. Then the samples together with the liquid cooled to the test temperature.
3.4. In the case that the samples saturate in boiling liquid is not recommended, the saturation produced under vacuum in the vessel to vacuum.
The air from the vessel in which samples are located, is evacuated to a residual pressure of not more than 13.3 PA (0.1 mm Hg.St.), after that, the vessel serves the fluid to fully cover the samples. Further, the vacuum in the vessel is carried out at a pressure below the vapor pressure of the impregnating liquid until, until you no longer stand out gas bubbles on the surface of the specimens, and then the evacuation process continues for at least 1 h. After depressurization of the vessel, the samples are removed from the liquid and subjected to tests.
3.5. The sample for test should be mounted in a holder so that its working surface was open. The holder must provide the ability to monitor the release of air bubbles. The rest of the surface seal of the rubber gaskets, and if that is not possible with a mixture of 60% paraffin and 40% of rosin, synthetic resin or clay.
The material for the seal should not chemically react with the liquid to saturate the sample.
3.6. Holder for cylindrical samples (plugs) must provide the possibility of immersion of the sleeve in the fluid in the horizontal position and its rotation around the axis of symmetry. The deviation from horizontality of the sample — no more than 1 mm in the greatest linear dimension of the working surface of the sample.
4. TESTING
4.1. The sample is saturated with liquid, fixed in the holder. A cylindrical sample (sleeve) placed in the liquid and on the surface of a flat sample, pour a layer of the same fluid, which it is saturated. Then measure over the sample surface (Fig.2) the height of the liquid column , which must be not less than 5 mm. the temperature of the liquid is recorded using a thermometer with an error of not more than 0.5 °C and shall be (20±5) °C.
1 — sample holder; 2 — test sample; 3 — a tube for draining liquid; 4 — liquid;
5 — a liquid vessel; — the height of a column of liquid above the test sample.
Damn.2
4.2. The pressure of the supplied air should increase at a rate of 20 to 100 PA/s. Speed of pressure rise is determined experimentally. It should be less for materials with large pore sizes and larger for materials with smaller pore sizes.
4.3. In the case of testing cylindrical samples (bushings) pressure rise speed periodically interrupted in the range of 50 PA (for materials with pore size 20−30 µm) to 500 PA (for materials with pore size less than 20 microns). Exposure at the steady state pressure after each interval should be sufficient for observation through the mirror liquid over the entire working surface of the sample while rotating it around the axis of symmetry of revolution.
4.4. Pressure extrusion of the first bottle is fixed when the flow of bubbles rising simultaneously from one or several points on the sample surface. Then increase the pressure and lock it in the allocation of air bubbles on the entire surface of the sample.
The appearance of the first bubbles in the fixing piece is allowed.
4.5. When re-tested, re-saturate the liquid.
5. PROCESSING OF THE RESULTS
5.1. The maximum size of the pores or the average pore size (a) in micrometers is calculated by the formula
where — surface tension, N/m;
— the pressure at which stands out like a bubble of air in the case of determining the maximum value of the pore size (
) or allocated air bubbles from the entire surface of the sample in determining the average value of time (
), PA;
is the fluid density, g/cm
;
— acceleration of free fall, m/s
;
— the height of the liquid column above the sample under test or when the test samples in the form of hollow cylinders (sleeves) — the shortest distance from the side wall of the sleeve to the liquid mirror, M.
The values of surface tension and density of ethanol with a mass fraction of alcohol at least 96%, depending on the temperature in the reference application.
(Changed edition, Rev. N
1).
5.2. In determining the material characteristics and
the minimum and the sample thickness at which they can be obtained, after calculation by the formula for samples with different thickness proceed to the construction on the graph paper, graph the dependence
from the sample thickness (Fig.3).
Damn.3
5.2.1. Schedule build at scale:
y-axis is the distance on the paper 5 mm should correspond to the amount equal to 10−15% of the lesser of the received values in micrometers;
the abscissa shows the distance on paper not less than 10 mm should correspond to the magnitude of the adopted interval of changes of the sample thickness.
On the chart, conduct the dotted lines of the confidence interval determine the maximum value of the pore, providing the absolute discrepancy between the results of parallel measurements and is equal to 10%.
5.2.2. Through point of the curve, for example , which corresponds to the lowest value
determined in the most thick of the tested samples is carried out straight and parallel to the x-axis lines
and
. Measured on the drawing segments
and
calculated the ratio of
and
, i.e. the tangent of the slope of the tangent line to the x-axis. Absolute error of measurement of segments
and
not more than 0.5
mm.
5.2.3. If the tangent of the slope of the tangent line to the x-axis of 0.2 or more, the tests by definition must be continued on the samples with increased thickness.
If the tangent of the angle of inclination of less than 0.2, the abscissa of the point of intersection of the tangent line to the dotted line, confidence interval (period
) corresponds to the smallest thickness of the specimen that must be tested to determine
how the characteristics of the powder material.
5.2.4. The value determined by the measurement (Fig.3) the ordinates
with the subsequent multiplication of the result of measurements, the scale on the y-axis; the measurement error ordinate
is not more than 0.5 mm.
5.3. For an average pore size of the powder material take any of the calculated according to the formula test results of samples which have a thickness that satisfies the requirement of section 5.2.1, and more.
5.4. The result of the test products and materials be the arithmetic mean of the results of the test at least three samples.
The results of calculations are rounded to the nearest whole number for values of then, more than 100 µm, to the first decimal place for values of from 10 to 100 µm to the second decimal place for values less then 10 microns.
5.5. The absolute discrepancy between the results of the parallel determinations should not exceed 10% of the value of the arithmetic mean of the test results.
5.6. The test results are entered into the Protocol, comprising:
the name (brand) of the product (material);
batch number;
the dimensions of the samples;
the liquid employed in the test;
the conditions of increasing pressure;
the pressure allocation of the first bubble;
the pressure of bubbles from the entire surface;
the maximum amount of pores and the average pore size for each of the tested samples;
the arithmetic average of the results of tests to determine the maximum size of pores and the average size of the pores of the powder material or the finished product;
the minimum thickness of the sample required to determine the maximum value of the pore and the average size of the pores of a powder material;
the designation of this standard;
the testing date.
APPLICATION (reference). The values of surface tension and density of ethanol depending on temperature
APP
Reference
Temperature |
0 |
10 | 20 | 30 |
Surface tension |
0,0244 |
0,0236 | 0,0228 | 0,0219 |
Density |
824 |
816 | 807 | 800 |
(Changed edition, Rev. N 1).
