GOST 10145-81

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  ГОСТ 10145-81

GOST 10145−81 Metals. Test method for long-term strength

GOST 10145−81

Group B09

STATE STANDARD OF THE USSR

METALS

Test method for long-term strength

Metals. Stressorupture test method

Valid from 01.07.1982
before 01.07.1987*
______________________________
* Expiration removed
according to the Protocol of the Intergovernmental Council
for standardization, Metrology and certification.
(IUS N 2, 1993). — Note the CODE.

APPROVED AND put INTO EFFECT by decision of the USSR State Committee for standards from 02.09.1981 G. N 4138

This standard specifies the test method for long-term strength of ferrous and nonferrous metals and alloys at temperatures up to 1200 °C.

The essence of the method consists in bringing the sample to failure under a constant tensile load at a constant temperature.

The tests determine the long-term strength, i.e. the voltage that causes the destruction of metal for some time trials at a constant temperature, or (if the acceptance and other control tests) establish a control characteristic in which the time to failure at a specified voltage that is equal to or exceeds the time specified in the standards or technical conditions of steel products.

Application of the method provided for in the standards and technical conditions for steel.

Standard corresponds to RS 63−64*.
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* In accordance with the Change in N 1 the link changes to ISO/R-206**.
** Access to international and foreign documents can be obtained by clicking on the link — note the manufacturer’s database.

1. THE SHAPE AND DIMENSIONS OF SAMPLES

1.1. Set basic samples:

a cylindrical sample with a diameter of 5 mm with an initial estimated length of 25 mm;

a cylindrical sample with a diameter of 10 mm with an initial estimated length of 50 mm;

a cylindrical sample with a diameter of 10 mm with an initial estimated length of 100 mm;

a cylindrical sample with a diameter of 7 mm with an initial estimated length of 70 mm;

flat samples with the initial design length mm, where the initial cross-sectional area of the working part of the specimen in mm. The thickness of the flat sample is determined by the thickness of the rental.

Allowed if there is technical justification to apply a proportional samples of other sizes and shapes. The diameter of the cylindrical specimen should not be less than 3 mm. the Shape and size of test specimen set standards or specifications for the products.

When using samples of different sizes it is necessary to consider the possible influence of scale factor on the test results.

1.2. Permissible deviations on dimensions and surface roughness parameter RA of the processed surfaces of the samples shall conform to the requirements specified in table.1.

Table 1

1.2.1. The runout of the cylindrical sample at check in centers must not exceed 0,02 mm.

1.2.2. Allowable deviation of the largest cross-sectional area should not exceed ±0,5%.

1.3. Samples shape and dimensions of the heads of sample and the transition from the head to its working length is determined by the adopted method of mounting the specimen in the grips of the testing machine and method of fastening of the gauge elongation, if the test is accompanied by measuring the deformation of the sample. The mate of the head of the sample with its working parts must be smooth.

1.4. Samples can be applied in two types: surface-treated or preservation of the surface layer (for example, the samples of rolled steel plates or samples fabricated by precision casting method) in accordance with the standards and technical conditions for steel.

1.5. Samples with warpage, mechanical damage, surface defects such as foreign inclusions, delaminations, pores, cavities, cracks (caused by mechanical or thermal treatment), the test is not exposed. Straightening or straightening workpieces or test specimens is not allowed.

1.6. If the metal to be tested in heat-treated, then heat treatment of the workpiece exposed to the samples. If after heat treatment the metal has poor cutting, the workpiece must first be brought to the dimensions, including allowance for final processing and possible warping. Requirements for metal and size of workpiece are established by standards or specifications for steel.

In the manufacture of samples should not occur changes in the structure and properties of the test of metal (for example, due to heating or cold working).

1.7. Accuracy requirements for the measurement of samples before testing should sootvetstvovat 9651−73, if not imposed more stringent requirements.

2. EQUIPMENT

Technical requirements to machines for testing metals for long-term strength should correspond to GOST 15533−80*.
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* On the territory of the Russian Federation the document is not valid. Standards 28845−90. — Note the manufacturer’s database.

3. TESTING

3.1. The sample mounted in the grips of the testing machine and placed in an oven and heated to a predetermined temperature (the heating time should be no more than 8 hours) and kept at this temperature for at least 1 h. If necessary, the duration of exposure is regulated in the standards or technical conditions of steel products.

Notes:

1. In special cases, if the test material has a stable structure and designed for long service life, the heating time can be more than 8 hours, and a material having an unstable structure and is intended for small deployments, pre-exposure less than 1 h.

2. The heating device can be used with or other protective atmosphere, if required by the test conditions.

3.2. To measure the temperature of the samples at the ends of their working parts must be installed at least two thermocouples, and samples with an estimated length of over 100 mm of at least three, evenly distributed throughout the estimated length. The thermocouple is mounted so that the hot junctions are firmly in contact with the surface of the sample. The hot end needs to be protected from exposure to the hot walls of the furnace.

3.3. Thermocouples must be tested out according to GOST 8.338−78*. Time to calibrate thermocouples from base metal shall be as specified in table.2.
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* On the territory of the Russian Federation the document is not valid. Valid GOST 8.338−2002. — Note the manufacturer’s database

Table 2

If the test duration exceeds specified time to calibrate thermocouples, the latter must be tested out between tests. In case of change of the readings of the thermocouples used are different thermocouples, preserves stability until the end of the test.

The cold junction of the thermocouple during the test must have a constant temperature.

In the case of emergency failure of the second thermocouple is allowed when the test is complete with one thermocouple, provided her work is not less than 70% of the time of the test specified in standards or technical specifications for products.

3.4. Deviations from the set temperature at any time during the duration of the test and at any point the calculated length of the sample must not exceed:

3.5. Periodically, not less than 2 h, to measure the test temperature. It is recommended that automatic recording of the temperature throughout the test.

Note. Arbitration test automatic recording of temperature is required.

3.6. Test temperature is chosen a multiple of 25, if a study does not require a special temperature.

3.7. After heating of the sample and exposure at a given temperature to the sample gradually applied load.

The time to failure at a given voltage, i.e., load, referred to the initial cross sectional area of the sample is the main indicator of this type of test.

3.8. After the destruction of the sample is determined relative elongation and relative narrowing of the sample .

Note. In the case of the acceptance tests to bring the sample to failure is not necessary if the specimen has withstood the time required by the standards or specifications for steel, and it does not require the definition of elongation and contraction of the sample.

3.9. The test duration is set for each material depending on its purpose.

In determining the limits of long-term strength it is recommended to test the duration 50, 100, 500, 1000, 3000, 5000, 10000 h if you do not want the other tests.

3.10. In the case of a forced interruption during the testing, the load can be removed completely or partially. If unloading a sample is not performed, it is necessary to ensure the absence of additional stresses in the sample during its cooling.

Results acceptance and other control tests with breaks are considered valid if the total duration of the sample under load at a specified temperature below the prescribed standards or specifications for the products.

3.11. The test is considered invalid:

at break of the sample the markers of risk or cores, as well as beyond its estimated length or area of the fillets, with the exception of tests in which the total test duration or total elongation not below the established standards or specifications for the products;

at rupture of a sample for defects of metallurgical production (rassai, blisters, slivers, etc.).

3.12. The room temperature during testing should be ongoing, to ensure that the temperature of the sample in accordance with the requirements of section 3.3.

3.13. The method is applicable to long-term strength testing of several samples simultaneously on a single machine (test «chain») and a cylindrical notched specimen. Conduct these tests is not fundamentally different from testing of a smooth specimen.

3.13.1. If test «chain» the temperature of each sample allowed to measure one thermocouple installed in the middle part, provided that the temperature gradient in the test samples does not exceed the standards of this standard. The temperature of the notched specimen is measured with one thermocouple inserted in the incision.

3.13.2. Settings incision (shape, angle, radius at the base) are specified in the standards or technical conditions of steel products. If these parameters are not specified, they are set based on the configuration of the part or test purposes. The diameter of the specimen in the notch must be equal to the diameter of the smooth sample.

Cut samples shall be applied after heat treatment in accordance with the requirements of paragraph 1.4.

3.14. Testing of smooth specimens for long-term strength it is recommended to measure the elongation of the sample prior to destruction.

4. TEST RESULTS

4.1. As a result of tests establish the relationship between stress and time to failure at a given constant temperature. The number of voltage levels should not be less than three. Each voltage should roughly correspond to the time to failure of a series described in paragraph 3.8.

The results of the test series of samples for each voltage is determined by the average time to failure. The number of samples in a series should provide the necessary accuracy of determining the long-term strength. Graphically, the relationship between the voltage and the average time to failure is represented in a logarithmic or semi-logarithmic coordinates. The graphs by interpolation or extrapolation determine average values of a long-term strength of the material, recording the value accurate to 5 MPa, this indicates the method of determining these quantities.

It is recommended to determine the values of the limits of long-term strength for the time to failure of a series described in paragraph 3.8.

If necessary, the statistical evaluation of values the limits of long-term strength using standard methods of mathematical statistics.

In extrapolating the experimental interval of the average values of time to failure shall be not less than 1.3 per order.

Not recommended for extrapolation to service life, exceeding the maximum average value of time to failure of more than one-half of the order.

Example of symbolic designation of long-term strength for 1000 h test at a temperature of 700 °C:

or .

4.2. Elongation of cylindrical, smooth and flat samples after rupture (a) percentage calculated by the formula

where is the initial gauge length, measured at room temperature before testing of the specimen, mm;

 — the gauge length after rupture, mm.

The initial estimated length  — the length of the area of the working part of the specimen on which the elongation is measured before the start of the test to limit risk or cores with an accuracy of ±1%.

Allowed for the initial estimated length make the distance between the heads of the sample or the distance between the cores deposited on the fillets last.

4.3. For measuring the estimated length after rupture of the destroyed part of the specimen tightly formed so that their axes form a straight line.

If after the test sample in place of the gap forms a partial gap, due to the chipping of metal or other causes, it is included in the length calculation of the sample after rupture.

Gauge length of the specimen before and after testing is measured with an accuracy of up to 0.05 mm.

4.4. The relative constriction after rupture of cylindrical smooth specimens and notched specimens in percent calculated by the formula

where is the initial cross-sectional area of the working part of the sample, measured at room temperature before testing, mm;

the cross — sectional area of specimen after fracture calculated according to the arithmetic mean of measurements minimum diameter at the break in two mutually perpendicular directions, mm.

The measurement of specimens after test is done with an accuracy up to 0.01 mm.

Note. Allowed to measure the diameter of the specimen at the place of fracture after the test, with accuracy up to 0.05 mm.

4.5. The test report must include: test temperature, voltage, material, and dimensions of the test piece, the parameters of the incision, where the sample is cut, the time to failure or the duration of the test, the elongation of the sample and narrowing the cross sectional area of the specimen after fracture.

If during the test there were breaks, you should specify their number and the conditions which held the sample during the break.

The results of the tests on long durability record in the form set out in the recommended application.

APPLICATION (recommended). FORM RECORDING THE RESULTS OF THE TESTS OF METALS AND ALLOYS FOR LONG-TERM STRENGTH

APP
Recommended

1. Material

1. Mark.

2. Chemical composition.

3. View of the semi-finished product (bars, sheets, pipe, forging, casting, etc.) and its size.

4. The types and modes of thermal treatment.

5. Microstructure, grain size and fracture.

2. Samples

1. From what place of the workpiece or product sample taken.

2. The cut direction of the sample (longitudinal, transverse sample).

3. The shape of the sample.

3. Equipment

1. Installation type for the test.

2. The accuracy of temperature measurement.

3. The accuracy of the applied load.

4. The conditions and test results

The text of the document is verified by:
the official publication of the
M.: Publishing house of standards, 1981