GOST 25280-90
GOST 25280−90 (ST SEV 6741−89, ISO 3927−77) Powder metal. Method of determining the compactibility
GOST 25280−90
(ST CMEA 6741−89,
ISO 3927−77)
Group B59
STATE STANDARD OF THE USSR
POWDER METAL
Method of determining the compactibility
Metal powders. Method for determination of compressibility
AXTU 1709
Date of introduction 1991−07−01
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Academy of Sciences of the Ukrainian SSR
DEVELOPERS
V. N. Klimenko, A. E. Kushchevsky, G. G. Serdyuk, And S. V. Mironets, V. A. Reytor, T. F. Mozol
2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on management of quality and standards from
3. REPLACE GOST 25280−82
4. The term of the first verification the third quarter of 1996.
5. The application is prepared by the direct application of international standard ISO 3927−85 «metal Powders (except powders of hard alloys). Determination of compressibility in uniaxial compression"
6. The standard fully complies ST SEV 6741−89, in addition to the app
7. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the reference document referenced |
Item number |
| GOST 2768−84 |
2 |
| GOST 6507−90 |
2 |
| GOST 23148−78* |
1.1 |
______________
* On the territory of the Russian Federation GOST 23148−98, here and hereafter. — Note the manufacturer’s database.
This standard specifies the method of determining the compactibility of metal powders, powdered alloys and powder mixtures.
The method consists in determining the density of pressovac made at specified pressures bilateral compression in a cylindrical or rectangular molds.
You can define the compactibility of metal powders of MS ISO 3927−77 given in the Appendix.
The standard does not apply to powders of solid alloys.
1. SAMPLING AND SAMPLE PREPARATION
1.1. Sampling and sample preparation — according to GOST 23148.
1.2. Mass selected samples should be sufficient for manufacturing the required quantity of pressovac cylindrical or rectangular shape and specified in the normative-technical documentation (NTD) for a specific powder.
2. EQUIPMENT AND MATERIALS
Mold to obtain a cylindrical (Fig.1) and rectangular (Fig.2) pressovac. Cylindrical mold needs to ensure the production of pressovac diameter (25) mm and a ratio of height and diameter from 0.8 to 1.0. Rectangular mould need to ensure the production of pressovac size 30х12 mm and a thickness of from 5 to 7 mm. of the Matrix and the two punch each mold should be made of hard metal or tool steel with a hardness of at least 55 HRC
. Use press tooling of a different design, allowing manufacturing of pressing of the same size. The accuracy of determining the compactibility of powders is controlled by using the base of the mold. On demand of the consumer is allowed to apply the press-the form given on features.3, to obtain a cylindrical pressovac with a diameter of 11.3 mm.
Damn.1. The mold to obtain cylindrical samples with a diameter of 25 mm
The mold to obtain cylindrical samples with a diameter of 25 mm
1 — matrix; 2 — yoke; 3 — punch the upper (=110 mm) and lower (
=65 mm)
Damn.1
Damn.2. The mold for pressing the rectangular samples
The mold for pressing the rectangular samples
1 — matrix; 2 — yoke; 3 — punch the upper (=25 mm) and lower (
=70 mm)
Damn.2
Damn.3. Die mould to obtain cylindrical samples with a diameter of 11.3 mm
Die mould to obtain cylindrical samples with a diameter of 11.3 mm
1 — matrix; 2 — yoke; 3 — the punch top (=40 mm) and lower (
=70 mm)
Damn.3
Press, providing the force up to 500 kN and accuracy of force measurement is not more than 2%. The press should provide a constant rate of increase of effort is not more than 50 kN/s.
Scales with a weighing error of no more than 0.01 g.
MICS types MK MK 25−1 and 50−1 GOST 6507 or other measuring device to measure sizes of pressovac with an accuracy of at least 0,01 mm.
Zinc stearinovokisly for NTD.
Acetone GOST 2768.
3. TESTING
3.1. The weight of the powder (a) in grams, providing the cylindrical or rectangular pressovac, calculated by the formula
where is the proposed level of compression, cm
;
— the density of the powder material, g/cm
.
The volume of the cylindrical pressovac () is calculated by the formula
where is the diameter of the holes of the matrix, see
3.2. Before the powder filling, the surfaces of the walls forming a cylindrical or rectangular strips of the matrix of the mold, smeared with a solution stearinovokisly zinc volatile organic liquid (100 g stearinovokisly of zinc per 1000 cmof acetone or other liquid, which must be specified in the normative-technical documentation for the particular powder. After removal of excess liquid, allow the solution to evaporate, leaving on the walls of a thin layer of grease. It is allowed to apply a layer of grease on the surface of the walls of the matrix of the mold in the presence of it in the pressed powder.
In coordination with the consumer the grease is from 0.5 to 1.5% can be introduced into the powder before pressing.
3.3. The lower punch is introduced into the matrix and establish it on supports. A portion of powder poured into the cavity of the matrix, providing a uniform filling. Enter into the matrix of the upper punch and a mold together with the supports between the plates of the press.
3.4. Apply a pre-load of 20 kN with a diameter of 25 mm and pressovac rectangular pressovyj or 4 kN — with a diameter of 11,3 mm. pressovac Remove the supports, a mold, and compressed at a constant rate of increasing force, not exceeding 50 kN/s. Push the pressing out of the die using the lower punch with support. The sequence of operations during compaction and the ejection of pressovac given on features.4.
Damn.4. The sequence of operations during compaction and the ejection of pressovac
Damn.4
Get pressing at pressures of 200, 400, 500, 600 and 800 MPa or when one of the pressures. Other compacting pressure is installed in the NTD on a particular brand of powder.
At each pressure, the three pressing.
4. PROCESSING OF THE RESULTS
4.1. Compaction () in g/cm
is calculated by the formula
where is the mass of the compression, Mr;
— the amount of compression, cm
.
The results of calculations are rounded to the second decimal place.
4.2. The measurement result should be the arithmetic mean of the results of the three tests, rounded to the second decimal place.
4.3. The compactibility of the powder are in the form of tables or charts based on the density of pressovac from the pressure of compaction, unless otherwise indicated in the reference document on the specific powder.
4.4. The test results recorded in the Protocol, which must include:
the name (brand) of powder;
batch number;
the name of the manufacturer (consumer);
the presence in the powder of the plasticizer and its content;
the test results in a table or chart;
the designation of this standard;
date of the test.
APPLICATION (recommended). INTERNATIONAL STANDARD ISO 3927−85 METAL POWDERS (EXCEPT POWDERS OF HARD ALLOYS). DETERMINATION OF COMPRESSIBILITY IN UNIAXIAL COMPRESSION
APP
Recommended
METAL POWDERS (EXCEPT POWDERS OF HARD ALLOYS). DETERMINATION OF COMPRESSIBILITY IN UNIAXIAL COMPRESSION
1. Purpose and scope
This international standard specifies a method for the determination of compressibility of metal powder in uniaxial compression in the mold. The standard does not apply to powders of solid alloys.
2. The essence of the method
The method consists in the bilateral pressing of the powder in the mold. Powder samples can be subjected to pressing under single or multiple pressure. After ejection of the compact from the mold, determine its density.
The obtained value of the density in the first case represents the compressibility of the powder at the specified pressure. The obtained density values in the second case you can use to draw the curve of the compressibility of the powder, i.e., graph density as a function of compacting pressure.
3. Symbols
| Symbol |
Marking |
Unit |
| Compressibility |
g/cm | |
| Mass pressing |
g | |
| The amount of compression |
cm |
If the compressibility is measured after reports of a single pressure, e.g. 400 N/mm, then use the symbol
(400).
4. Equipment
4.1. The mold of a sintered hard alloy or tool steel and two of the punch for receiving the cylindrical and rectangular pressovac.
4.1.1. Cylindrical mold needs to ensure the production of pressovac with a diameter of 20−25 mm and a ratio of height and diameter from 0.8 to 1.0 (Fig.1).
Damn.1. The mold to obtain cylindrical samples with a diameter of 25 mm
The mold to obtain cylindrical samples with a diameter of 25 mm
1 — clamping ring, 2 — sintered hard alloy, 3 — upper punch and the lower
Damn.1
4.1.2. Rectangular mould need to ensure the production of pressovac size 30х12 mm and a thickness of from 5 to 7 mm (Fig.2).
Damn.2. The mold for pressing the rectangular samples
The mold for pressing the rectangular samples
1 — coupling ring; 2 — cemented carbide alloy; 3 — upper punch and the lower
Damn.2
4.2. Press force up to 500 kN with uncertainty of the registration efforts are not more than ±2% adjustable on a straight-line increase in effort at a speed of not more than 50 kN/s.
4.3. Scales, allowing to weigh at least 100 g with an accuracy of ±0.01 g.
4.4. A micrometer or other measuring device to measure sizes of pressovac with an accuracy of ±0.01 mm.
5. Sampling
Samples are taken in amounts sufficient to obtain the required number of samples for testing (sect.7), the dimensions of which must conform to the PP.4.1.1 and
If necessary, conduct a preliminary test to determine the amount of powder to perform the specified requirements.
6. Testing
6.1. Cleaning molds and punches
The cavity of the mold, wipe with soft and clean paper towel soaked in an appropriate solvent, e.g., acetone. The solvent give the opportunity to evaporate.
6.2. Test conditions powder
6.2.1. Powders that do not contain grease, can be put to the test:
a) dry press shape (it should be borne in mind that the result of the high pressing pressures can cause excessive wear of the mold);
b) in the mold with greased walls (p. 6.3.1);
C) after adding grease (item 6.3.2) and dry the mold.
6.2.2. The powder containing the lubricant, can be put to the test:
a) to dry a mold;
b) after adding additional lubricant (p. 6.3.2) and dry the mold.
6.3. Grease
Use one of the following two ways lubrication.
6.3.1. Lubrication of the walls of the mold
The walls of the mold is lubricated with a mixture or solution of lubricant and volatile liquid, for example, 100 g of zinc stearate in 1000 cmof acetone. After removal of excess liquid, allow the solution adhering to the walls, to evaporate, while leaving them on a thin layer of grease.
6.3.2. Lubricant powder
Designed to test powder mixed with a certain amount of (0,5−1,5%) of the appropriate grease (zinc stearate or stearic acid).
6.4. Pressing and pushing
The lower punch inserted into the mold cavity. Set the mold to the desired fill level is reached using support constraints between the mold and support the bottom of the punch. The sample is poured into the cavity of the mold, making sure the powder is evenly distributed in the cavity. Install the upper punch and a mold with a punch between the plates of the press. Pre-load force approximately 20 kN, and then it is removed. Removed the limiters that support the mold. If the mold is supported by springs or similar devices, to make a preliminary effort is not required.
Loading to the final pressing force is carried out at a constant speed not exceeding 50 kN/s.
Eject the compact from the die with lower punch.
The sequence of pressing and pushing presents on the devil.3.
Damn.3. The sequence of pressing and pushing
Damn.3
After popping and deburring pressing is weighed with an accuracy of 0,01 g. measurements carried out with an accuracy of 0.01 mm.
6.5. The pressing pressure of
To determine the compressibility curve of the powder by repeated pressure efforts should be 200, 400, 500, 600 and 800 N/mm. If you want to determine the compressibility at a single pressure, it should be measured in one of the above pressures.
7. Processing of the results
7.1. The density is determined in g/cmaccording to the formula
The density value is recorded with an accuracy of 0.01 g/cm.
7.2. For the result of the determination of extrudability be the arithmetic mean of the three values of the density calculated with an accuracy of 0.01 g/cmand obtained at the specified pressing pressure.
7.3. The compressibility curve of the powder is drawn through points that represent a single determination () for these values of the pressing pressure.
8. Test report
The test report should include:
a) reference to this international standard;
b) all details necessary for identification of the sample;
C) the shape of the sample for testing;
g) the name, type and amount of lubricant, if it is added to the powder; in some cases it is desirable to provide a method of adding a lubricant;
d) compacting pressure;
e) the result obtained;
g) all operations not specified in this standard or which are considered optional;
h) all random factors that could affect the outcome.
