GOST 22662-77

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  ГОСТ 22662-77

GOST 22662−77 Powder metal. Methods of sedimentation analysis (with Amendments No. 1, 2)

GOST 22622−77

Group B59

INTERSTATE STANDARD

POWDER METAL

Methods of sedimentation analysis

Metal powders. Methods of sedimentation analysis of powders

AXTU 1790

Date of introduction 1979−01−01

INFORMATION DATA

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

2. APPROVED AND promulgated by the Decree of the State Committee of the Council of Ministers of the USSR from 1950 11.08.77 N

3. INTRODUCED FOR THE FIRST TIME

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

5. Limitation of actions taken by Protocol No. 3−93 Interstate Council for standardization, Metrology and certification (ICS 5−6-93)

6. EDITION (may 2001) with Amendments No. 1, 2 approved in August 1983, June 1988 (IUS 12−83, 9−88)


This standard specifies the gravimetric method of sedimentation and the method of photosedimentation to determine particle size distribution of metal powders with spherical and polyhedral form of the particles size from 0.5 to 40 microns. For the size of the particles of polyhedral shape take the diameter of the sphere with volume equal to the volume of the particles (Stokes diameter). Methods based on determining the mass fraction of particle sizes of this powder over the speed of their sedimentation in a viscous liquid in laminar motion of particles.

The standard does not specify methods for determining the granulometric composition of the powder mixtures of different metals.

(Changed edition, Rev. N 1).

1. SAMPLING AND SAMPLE PREPARATION

1.1. The sample for test weight not less than 50 g are selected according to GOST 23148 and dried in conditions that do not allow oxidation.

1.2. For removal of large particles of the dried sample for testing sieved N 0040 mesh according to GOST 6613.

1.3. A sample for sediment analysis are taken in the quantity necessary for the preparation of suspensions with a volume fraction of powder less than 0.4%.

The sample is weighed with an error of not more than 0.0005 g.

2. THE METHOD OF WEIGHT SEDIMENTATION

2.1. The essence of the method

When the weight of sedimentation determine the settling velocity of particles on the rate of accumulation of sediment of powder deposited from suspension. For this throughout the analysis continuously or at certain intervals of time weighing the residue and get the dependence of the mass of sediment from the time of sedimentation. The obtained dependence is the basis for the calculation of the mass fraction of particles of different sizes.

2.2. Equipment and reagents

Libra sedimentation, registered ultimate sludge mass with an error of no more than 3% (Fig.1).

Damn.1. Libra sedimentation, registered ultimate sludge mass with an error of no more than 3%

1 — glass cell; 2 — a rod with a Cup of scales; 3 — suspension of powder; 4 — rocker scales; 5 — block and sludge;  — the height of the sedimentation of powder particles

Damn.1

A sieve with mesh N 0040 according to GOST 6613.

Scales according to GOST 24104.

Pycnometer ПЖМ2 according to GOST 22524.

Water jet or vacuum pump.

Porcelain Cup according to GOST 9147.

Glass wand.

Thermometer according to GOST 28498.

Stopwatch.

The dispersion liquid.

Dispersion liquid to form a powder stable stable suspension and to meet the following requirements:

should be well to wet the powder;

should not chemically interact with the material of the powder;

must not be poisonous;

density and viscosity should be such as to ensure conditions of laminar motion of the large particles of powder and the time of analysis did not exceed 6 h.

Composition dispersion liquids are shown in the Appendix.

To ensure laminar motion of the large particles of the powder shall conform to the following inequality:

, (1)

where is the maximum particle size of the analyzed powder, cm;

 — free fall acceleration, cm/s;

 — micrometrically the particle density of powder, g/cm;

is the fluid density, g/cm;

 — viscosity of fluid, PA·s, the estimated value of which is calculated by the formula

. (2)

(Changed edition, Rev. N 1).

2.3. Preparation for assay

2.3.1. Determination of the relationship between particle size and time of sedimentation in liquid

The time of sedimentation of the particles in the fluid (), in seconds, calculated from the Stokes equations by the formula

, (3)

where is the liquid viscosity, PA·s;

 — sedimentation height, cm;

 — free fall acceleration, cm/s;

 — micrometrically density of powder, g/cm;

is the fluid density, g/cm;

 — particle diameter, cm

(Changed edition, Rev. N 1).

2.3.2. Determination of the density of the dispersion liquid and micrometrically density of powder

Weighed clean dried pycnometer with a capacity of 25 cm, then fill it one third with the powder and re-weighed. Gradually poured into the pycnometer dispersion liquid, stirred vigorously, shaking the resulting suspension.

With the help of a water jet or vacuum pump removes remaining air from the suspension. Topped up with fluid to the mark on the pycnometer and the pycnometer is weighed with the suspension. Empty the pycnometer, fill it to the mark of the dispersion liquid and weigh the pycnometer with the liquid.

At the time of weighing the temperature of the liquid in the pycnometer must be equal to the temperature at which it will be carried out sedimentation analysis.

The density of the dispersion liquid (a) in g/cmis calculated by the formula

, (4)

where  — weight of empty pycnometer, g;

 — the mass of the pycnometer with the liquid g;

 — the volume of the pycnometer, cm.

Micrometrically density of powder particles () g/cmcalculated by the formula

, (5)

where  — weight of empty pycnometer, g;

 — the mass of the pycnometer with the liquid g;

 — weight of pycnometer with powder, g;

 — weight of pycnometer with powder and liquid, g;

 — the density of the dispersion liquid, g/cm.

Weighing is carried out with accuracy up to 0.001 g.

The difference between the results of two parallel definitions for the density of the liquid should not be more than 0.005 g/cmfor density of powder — 0.05 g/cm.

The calculation of the density of the liquid is carried out with an accuracy of at least 0.001 g/cmand density of powder — accuracy up to 0.01 g/cm.

The result of taking the arithmetic mean of two parallel definitions.

2.3.3. The viscosity of the dispersion liquid must be expressed with an uncertainty of less than 0.1 MPa·s.

(Changed edition, Rev. N 1).

2.3.4. The height of the subsidence is defined as the distance from the top edge of the suspension to the plane measurement accuracy up to 0.5 cm (see the devil.1). If during the analysis of the height changes by more than 1 cm, it is necessary to take into account in calculations by formula (3).

2.4. Analysis

2.4.1. Preparation of a suspension of powder

A sample for sediment analysis was placed in a porcelain Cup. Pour the dispersion liquid to the consistency of thick paste. The resulting paste was triturated with a glass rod for at least 2 min, to prevent any crushing of the individual particles of the powder, and then dilute the dispersion liquid and transferred to a cuvette. Bring the suspension volume to the required values, and stirred with a mixer for 1 to 5 min, avoiding the formation of bubbles. After mixing the powder should be evenly distributed over the height of the cell.

2.4.2. After mixing, the stirrer is removed from the cuvette and the cuvette is immersed in a Cup of scales. The time of installation of the cuvette in the slot of the device should not exceed 15 seconds.

2.4.3. The time of sedimentation of particles has to be recorded automatically or visually.

If the time of the sedimentation of particles is recorded opt-in, then measure the mass of precipitate should be carried out through 0,5; 1,0; 2,0; 3,0; 5,0; 7,0; 10,0; 15,0; 20,0; 25,0; 30,0; 45,0; 60,0; 70,0; 90,0; 120 min.

2.4.4.Build the graph of the sludge from the sedimentation time . Excesses on the sedimentation curve is not allowed to testify about errors in the analysis.

2.5. Processing of the results

2.5.1. The graph

According to the formula (3) timing () the sedimentation of powder particles with diameters , , , where , , is the particle size, limiting the selected classes. Classes of particle size is set to medium diameter classes, starting from the minimum, submitted to geometrical progression. Allowed uniform breakdown into classes. The number of classes must be at least 5.

The calculated values of time () lay on the x-axis. Of these points restore the perpendiculars to the x-axis to the intersection of the sedimentation curve. At the crossing points is carried out tangent to the sedimentation curve to the intersection with the y-axis. If the initial straight-line portion of the curve, then it is renewed and from a point of separation lower perpendicular on the x-axis. To get the value calculate the value of the diameter . Horizontal portion of the curve extends to the left to the intersection with the ordinate axis (point ). The scheme of these actions is presented on the devil.2.

Damn.2. The graph

Damn.2

The length of the segment on the y-axis is a measure of the fraction of the fraction of the powder. The length of the segment 0is proportional to the mass of all particles deposited on the Cup, and corresponds to 100%.

(Changed edition, Rev. N 1).

2.5.2. The results of the graphical analysis are recorded in a table.1.

Table 1

2.5.3. Analysis of the powder is carried out at least two times. The deviation of the results of the parallel determinations should not exceed 10% of the average. For the final result take the arithmetic mean of parallel definitions.

2.5.4. The results of the analysis are issued in the form of a Protocol, which must contain the following information:

the name of the powder;

the name of the dispersion liquid;

the density of the dispersion fluid;

micrometrically the density of the powder;

temperature analysis;

the viscosity of the dispersion liquid;

the height of the subsidence;

the results of the analysis.

2.5.5. The weight method is used when the differences in assessing the quality of metal powders.

(Added, Rev. N 1).

3. PHOTOSEDIMENTATION METHOD

3.1. The essence of the method

When photosedimentation analysis of the settling velocity of particles is determined by the rate of change of optical density of a suspension of the powder. The optical density is fixed continuously or at certain intervals of time photoelectrode force or the photocurrent arising in the solar cell from the light flux transmitted through the suspension. The resulting analysis of the dependence fotoelectronica power (photocurrent) from the time of sedimentation is the basis for the calculation of the mass fraction of particles of different sizes.

3.2. Equipment and reagents

Instrument and reagent according to claim 2.2 with the exception of sedimentation scales with the following addition:

Photosedimentometer, recording changes in optical density of the suspension with the error not exceeding 3%.

Scheme photosedimentometer presented on hell.3.

Damn.3. Scheme photosedimentometer

1 — light source; 2 — diaphragm; 3 — suspension of powder; 4 — glass cuvette; 5 — photodetector; 6 — the block and fotoelectronica power (photocurrent);  — the height of the sedimentation of powder particles

Damn.3

3.3. Preparation for assay

3.3.1. Selection of the dispersion liquid and a preparation for the analysis carried out on PP.2.2 and 2.3.

3.4. Analysis

3.4.1. Preparation of a suspension of the powder is carried out according to claim 2.4.1.

3.4.2. After stirring the slurry mixer remove and install the cuvette in the slot of photosedimentometer. The first reference optical density should be carried out after calming suspension after 15−20 sec after the start of sedimentation.

3.4.3. The time of sedimentation of particles of a register as in claim 2.4.3.

3.4.4. Build a graph of fotoelectronica power (photocurrent) from the time of sedimentation. The kinks in the curve are not allowed.

3.5. Processing of the results

3.5.1. The graph

Timing of the sedimentation of powder particles with diameters that , in accordance with paragraph 2.5.1. The obtained values of time () lay on the x-axis according to fotoelectronica power (photocurrent) from the time of sedimentation. The number of calculated values should not be less than 5. Of these points restore the perpendiculars to the x-axis to the intersection of the sedimentation curve and find the ordinates of the intersection points. The scheme of these actions is presented on the devil.4.

Damn.4. The graph

Damn.4

3.5.2. The results of determinations recorded in the table.2.

3.5.3. Evaluation of the results of the analysis carried out according to claim 2.5.3.

3.5.4. The results of the analysis draw up a Protocol according to claim 2.5.4.

(Changed edition, Rev. N 1).

Table 2

APPLICATION (recommended) 1. THE COMPOSITION AND PROPERTIES OF THE DISPERSION LIQUIDS

APP
Recommended

1.1. Metal powders for better dispersion liquids are organic liquids.

1.2. Some liquids are given in table.1.

Table 1

1.3. Properties of some dispersion liquids are shown in table.2.

Table 2

1.4. The density and viscosity of aqueous solutions of glycerol are given in table.3.

Table 3

APP. (Changed edition, Rev. N 1, 2).