GOST 27208-87
Castings of cast iron. Methods of mechanical testing
GOST 27208−87
Group B89
INTERSTATE STANDARD
Cast Iron Castings
Methods of mechanical testing
Cast iron castings. Methods of mechanical testing
OKP 41 1100
Date of introduction 1988−01−01
INFORMATION DATA
1. DEVELOPED AND IMPLEMENTED by the Ministry of Power Engineering of the USSR
2. APPROVED AND ENTRY INTO ACTION By the Resolution of the USSR State Committee on Standards dated
3. The period of the first audit of 1992
4. The standard corresponds to ST SEV 2860−81 (in the part of tensile testing of cast iron castings with lamellar graphite); ST SEV 2841−81 (in the part of tests on the bending of castings from cast iron)
5. The replacement of GOST 2055−81, GOST 24804−81, GOST 24805−81, GOST 24806−81
6. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the normative document for which reference is made |
Number of the item, subparagraph |
| GOST 577−68 |
3.2.1 |
| GOST 1215−79 |
1.1.2 |
| GOST 1497−84 |
1.4.3, 1.4.4, 1.5.1 |
| GOST 2789−73 |
1.3.1, 2.3.2, 3.3.1, 4.3.1 |
| GOST 7293−85 |
1.1.3 |
| GOST 7769−82 |
3.1.1 |
| GOST 9012−59 |
4.2.1 |
| GOST 18661−73 |
4.4.1 |
| GOST 22761−77 |
4.4.1 |
| GOST 23677−79 |
4.2.1 |
| GOST 24648−90 | 1.1.1, 2.1.1, 3.1.1 |
| GOST 28840−90 |
1.2.1, 2.2.1, 3.2.1 |
| TU 25−06−325−78 |
4.4.1 |
| TU 25−06−845−76 | 4.4.1 |
7. The limitation of the term of validity is withdrawn according to the protocol No. 7−95 of the Interstate Council for Standardization, Metrology and Certification (ISC 11−95)
8. REVISION
This standard establishes methods for the mechanical testing of castings from cast iron at a temperature of (20 ) ° C to determine:
time resistance and elongation after tensile break;
time compression resistance;
temporal resistance and maximum flexural bend;
hardness for Brinell.
1. TESTING FOR STRETCHING
1.1. Method of sampling
1.1.1. The method of obtaining blanks for making samples from cast iron with lamellar graphite — according to GOST 24648 .
The shape and dimensions of the samples should correspond to those shown in Figures 1−3.
Devil.1
Devil.2
Damn.3
The total length of the specimen and the method of fixing it are determined depending on the design of the grippers or the size of the working space of the testing machine.
1.1.2. The method of obtaining the billet, the shape and dimensions of the sample for testing castings of malleable cast iron — according to GOST 1215 .
1.1.3. The method of obtaining the billet, the shape and dimensions of the specimen for testing castings of cast iron with nodular graphite — according to GOST 7293 .
1.1.4. Tests should be carried out on three samples, if there are no other requirements for castings in the normative technical documentation (NTD).
1.2. Test facilities
1.2.1. Tensile tests of castings from cast iron are carried out on rupturing machines provided they meet the requirements of GOST 28840 .
1.3. Preparation for testing
1.3.1. After machining, there should be no shells, non-metallic inclusions, cracks, scratches and mechanical damages on the working surface of the sample.
Roughness the treated surfaces of the working part of the sample should not be more than 0.63 μm, and the roughness of the heads of the sample
— no more than 20 microns according to GOST 2789 .
1.3.2. The diameter of the working part of the sample according to Figures 1 and 2 is measured before the test in the smallest section in two mutually perpendicular directions, and by the features in Fig. 3 — in three places: in the middle part and at the boundaries of the working length. The difference between the smallest and largest diameter of the sample should not be more than 0.05 mm.
The result is their average arithmetic value. The cross-sectional area of the sample is calculated by rounding up to 1.0 mm .
1.4. Testing
1.4.1. The sample is smoothly loaded with an axial tensile force until fracture to determine the mechanical characteristics.
1.4.2. A sample of cast iron castings with lamellar graphite (Fig. 2) is screwed into the gripper so that the thread on the entire length of the sample head engages with the thread of the gripper.
1.4.3. Tests of samples from malleable cast iron are carried out in accordance with GOST 1497 .
1.4.4. Tests of samples made of cast iron with nodular graphite are carried out in accordance with GOST 1497 .
1.4.5. The loading speed of the specimen under tension should not exceed 10 MPa / s [1 kgf / (mm ·from)].
1.5. Processing Results
1.5.1. Temporary resistance is the voltage corresponding to the greatest load preceding the destruction of the sample () in megapascals (kilogram-force per square millimeter) is calculated by the formula
Where — maximum load, preceding the destruction of the sample, H (kgf);
— the cross-sectional area of the working part of the specimen before the test, mm
.
The relative elongation after the break is determined in accordance with GOST 1497 .
For gray cast iron, only temporary resistance is determined.
1.5.2. The results are rounded to 5.0 MPa (0.5 kgf / mm ).
1.5.3. The results of the tests are not taken into account if the destruction occurred outside the working part of the sample or in the fracture after the destruction shells, various inclusions or other defects were found.
In this case, the tests are repeated on another sample from the same batch.
1.5.4. The form of the test report is given in Appendix 1.
2. COMPRESSION TESTS
2.1. Method of sampling
2.1.1. The method of obtaining blanks for the manufacture of samples — according to GOST 24648 or should be specified in the NTD on castings.
2.1.2. For the tests, cylindrical samples with a nominal diameter of 10, 15, 20, 25 mm are manufactured. It is allowed to produce a sample of a different diameter in the range from 10 to 25 mm. The diameter of the workpiece must not be less than 5 mm greater than the diameter of the sample.
2.1.3. The height of the sample is set equal to the diameter.
2.1.4. Tests should be carried out on three samples, if there are no other requirements for casting in the NTD.
2.2. Test facilities
2.2.1. Tests of compression specimens are carried out on machines of any type provided they meet the requirements of GOST 28840 .
2.3. Preparation for testing
2.3.1. After machining, there should be no risks, corrosion, shells and pores on the surface of the sample.
2.3.2. Roughness of the working surface of the cylindrical and end part of the sample in accordance with GOST 2789 should not exceed 1.25 microns.
2.3.3. The diameter of the sample is measured before testing in two mutually perpendicular directions. The result is the arithmetic mean of the two measurements. The difference between the smallest and largest diameter of the sample should not be more than 0.05 mm.
The cross-sectional area of the sample is rounded to 1.0 mm .
2.3.4. The ends of the sample must be plane-parallel and perpendicular to the axis. The deviation from perpendicularity is not more than ± 1 °.
The measurement of the height of the specimen before the test is carried out in two mutually perpendicular cross sections. The result is the arithmetic mean of the two measurements. The measurement difference should not be more than 0.1 mm.
2.3.5. Permissible deviations from the nominal diameter of the sample ± 0.1 mm, height ± 0.2 mm.
2.4. Testing
2.4.1. The sample is loaded with an axial compressive force before failure.
2.4.2. During the tests, a reliable centering of the specimen on the supports must be ensured (Fig. 4).
1 and 3 — supports; 2 — sample
Dam 4
2.4.3. The ends of the specimen shall be supported on the supports with polished flat planes of hardened steel with a hardness of at least 60 NRС and roughness
not more than 1.25 microns. Parallelism of the reference planes should be provided by a sphere made on one of the supports. The center of the spherical surface must coincide with the center of the end surface of the sample.
2.4.4. Moving of the movable traverse should ensure the loading speed of the sample no more than 20 MPa / s [2 kgf / (mm) ·from)].
2.5. Processing Results
2.5.1. Temporary resistance is the voltage corresponding to the greatest load preceding the destruction of the sample, () in megapascals (kilogram-force per square millimeter) is calculated by the formula
Where — maximum load, preceding the destruction of the sample, H (kgf);
— initial cross-sectional area of the sample, mm
.
2.5.2. The results are rounded to 5.0 MPa (0.5 kgf / mm ).
2.5.3. The test results are not taken into account if shells, cracks, nonmetallic inclusions and other defects are found in the fracture after fracture.
In this case, the tests should be repeated on another sample from the same lot.
2.5.4. The form of the test report is given in Appendix 2.
3. BENDING TEST
3.1. Method of sampling
3.1.1. The method of obtaining blanks for the manufacture of samples — according to GOST 24648, GOST 7769 .
3.1.2. The bending tests are subjected to cylindrical specimens with a diameter = 30 mm and long
= 650 mm with the distance between the centers of the supports
= 600 mm or long
= 340 mm with the distance between the centers of the supports
= 300 mm (Fig. 5).
Devil.5
When making samples directly from castings, in agreement with the consumer, the use of samples of a different size is permitted.
3.1.3. The permissible deviation of the diameter in the middle third of the working part of the sample should not exceed +2 mm.
3.1.4. The ovality of the sample (the difference between the largest and smallest diameter of the same section) should not be more than 5% of the nominal diameter.
3.1.5. Tests should be carried out on three samples, if there are no other requirements for casting in the NTD.
3.2. Test facilities
3.2.1. Tests of bending samples are carried out on machines of any type provided they meet the requirements of GOST 28840 .
To measure the deflection boom, use a deflectometer with a mechanical indicator of the type IH 10 cl. 1 GOST 577 or a recording device with a scale of at least 10: 1 deformation.
3.3. Preparation for testing
3.3.1. Samples before testing should be cleaned from the residue. Burrs and roughness of the surface of the samples are removed by stripping.
Roughness of the sample in accordance with GOST 2789 should not exceed 100 microns.
3.3.2. Surfaces of samples should not have cracks, and also prints of lines of a socket of the form in depth more than 1 mm.
The surface on the middle third of the length of the sample should be free of defects.
3.4. Testing
3.4.1. The sample before the test is freely installed on two supports so that the traces from the form-fitting lines are located in the neutral plane and load it in the middle with a concentrated load until failure (Fig. 5). The axis of the specimen must be perpendicular to the axis of the supports and mandrel. Radius of rounding of supports and mandrel should be within 20−30 mm.
3.4.2. The loading speed of the specimen during bending should not exceed 10 MPa (1 kgf / (mm ·from)).
3.4.3. The diameter of the sample after the tests is measured to the point of fracture in two mutually perpendicular directions with an error of not more than 0.1 mm.
The result is the arithmetic mean of the two measurements.
3.5. Processing Results
3.5.1. Temporary resistance () in megapascals (kilogram-force per square millimeter) is calculated by the formula
or
Where — Bending moment, N · mm (kgf · mm);
— moment of resistance, mm
;
— maximum load at the moment of fracture of the sample, N (kgf);
— Distance between supports, mm;
— diameter of the sample after the test, mm.
Denoting 
Values of the coefficient are given in the table.
Diameter of the sample |
Coefficient value | |
at |
at | |
| 30.0 |
0.0283 |
0.0566 |
| 30.1 |
0.0280 |
0.0560 |
| 30.2 |
0.0277 |
0,0555 |
| 30.3 |
0.0275 |
0.0549 |
| 30.4 |
0,0272 |
0.0544 |
| 30.5 |
0,0269 |
0.0539 |
| 30.6 |
0,0267 |
0.0533 |
| 30.7 |
0.0264 |
0.0526 |
| 30.8 |
0.0261 |
0.0523 |
| 30.9 |
0.0259 |
0.0518 |
| 31.0 |
0.0256 | 0.0513 |
| 31.1 |
0.0254 |
0.0508 |
| 31.2 |
0.0251 |
0.0503 |
| 31.3 |
0.0249 |
0.0498 |
| 31.4 |
0.0247 |
0.0494 |
| 31.5 |
0.0244 |
0.0489 |
| 31.6 |
0.0242 |
0.0484 |
| 31.7 |
0.0240 |
0.0480 |
| 31.8 |
0.0237 |
0.0475 |
| 31.9 |
0.0235 | 0.0471 |
| 32.0 |
0.0233 |
0.0466 |
3.5.2. The results are rounded to 5.0 MPa (0.5 kgf / mm ).
3.5.3. Traction arrow — the maximum bending preceding the beginning of the destruction of the sample, is measured in the direction of the load at the point where the specimen breaks.
In order to eliminate the measurement error, it is necessary to apply an initial load of 300−400 N (30−40 kgf) to the sample and establish a zero position on the deformation measuring device.
3.5.4. The test results are not taken into account if shells, various inclusions or other defects are found in the fracture after the destruction of the sample.
In this case, the tests are repeated on another sample from the same batch or melting.
3.5.5. The form of the test report is given in Appendix 3.
4. MEASURING HARDNESS BY BRINELL
4.1. Method of sampling
4.1.1. Measurement of hardness on castings is carried out in places provided for in NTD on castings.
It is allowed to determine the hardness on the specimen after the bend test or on the tensile test billets. Samples should be of the same melting as the casting to be tested.
It is allowed to measure hardness on special samples in the form of tides to castings. In this case, their locations and dimensions, as well as the test sites should be installed in the NTD on castings.
4.2. Measuring
4.2.1. The hardness is measured by the Brinell method in accordance with GOST 9012 and GOST 23677 .
4.3. Preparation for measurement
4.3.1. The place for carrying out the measurement must be pre-stripped to a depth of at least 2.0 mm, if there are no other requirements for casting in the NTD.
Surface roughness in accordance with GOST 2789 should not exceed 2.5 microns.
4.3.2. The installation surface of the casting must be cleaned of any residue, scales and other coatings.
4.4. Carrying out measurements
4.4.1. On large-sized castings, in the case of impossibility of measuring Brinell hardness by a stationary device, it is allowed to measure hardness by a portable hardness tester of static action in accordance with GOST 22761 or TU 25−06−325 *, TU 25−06−845 or with a dynamical action instrument using Brinell hardness reference standard, or the normalized impact force in accordance with GOST 18661 .
________________
* The specifications mentioned here and below are author’s work. For more information, please click here. — Note of the database manufacturer.
4.4.2. Brinell hardness is defined as the arithmetic mean of the results of the three hardness measurements, if there are no other indications in the NTD for castings.
ANNEX 1 (recommended). TEST PROTOCOL FOR STRETCHING
ANNEX 1
Recommended
The grade of pig iron _______________________________
Number of samples ________________________
Type of testing machine ___________________
| Number or stamp of the sample |
Melting Number |
Batch number |
Initial estimated length |
Diameter of the sample |
Final design length after rupture |
Maximum breaking force, N (kgf) |
Temporary resistance |
Elongation after break |
APPENDIX 2 (recommended). TEST PROTOCOL FOR COMPRESSION
ANNEX 2
Recommended
The grade of pig iron _______________________________
Number of samples ________________________
Type of testing machine __________________
| Number or stamp of the sample |
Melting Number |
Batch number |
Diameter of the sample |
Cross-sectional area |
Load |
Temporary resistance |
ANNEX 3 (recommended). BENDING TEST PROTOCOL
ANNEX 3
Recommended
The grade of pig iron ______________________________________
Number of samples _______________________________
Type of testing machine _________________________
| Number or stamp of the sample |
Melting Number |
Batch number |
Sample Diameter |
Distance between supports |
Breaking load |
Temporary resistance |
The maximum deflection arrow, |
Diameter of the ball, mm _________ Load P, N (kgf) ___________ Brinell hardness, (HB) ______________________ | |||
| Imprint |
Average | ||||||||||
| 1st | 2 nd | 3rd |
|||||||||
Electronic text of the document
prepared by JSC «Codex» and reconciled by:
official publication
Casting from metals and alloys: Sat. GOST. -
Moscow: IPK Publishing House of Standards, 2002
