GOST 6130-71

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  ГОСТ 6130-71

GOST 6130−71 Metals. Methods for the determination of heat resistance (Change No. 1)

GOST 6130−71

Group B09

STATE STANDARD OF THE USSR

METALS

Methods of determination heat resistance

Metals. Methods of determining
heat resistance

AXTU 0909

Valid from 01.01.72
until 01.01.2000*
______________________________
* Expiration removed
Protocol N 7−95 Interstate Council
for standardization, Metrology and certification
(IUS N 11, 1995). — Note the CODE.

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Ministry of heavy power and transport machine building of the USSR

The DEVELOPERS Cranin I. R., A. I. Maximov, P. V. Sorokin

2. APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from 12.02.71 N 225

3. Replace GOST 6130−52

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

5. Validity extended up to 01.01.2000 by Decree of Gosstandart of the USSR from 05.12.88 N 3945

6. REPRINT (September 1990) with amendment No. 1, approved in December 1988 (IUS 2−89)


This standard specifies methods for the determination of heat resistance in conditions of exposure to gaseous media and air at high temperatures of steel, alloys and products from them.

The standard does not apply to steel, alloys and products made of them, subjected to erosiona the influence of gaseous media.

(Changed edition, Rev. N 1).

1. TEST METHODS

1.1. Heat resistance was determined after keeping the samples in a furnace with an installed environment or in air for a predetermined time at a constant temperature by the following methods:

direct measurement of corrosion depth — to clarify;

combined with combination weighting method or any method of direct measurement of the sample with thickness podokonnogo layer, depleted in alloying elements or the depth of local corrosion.

1.2. Heat resistance is determined during the test, allowing to set the pattern of the corrosion process. By further extrapolation, determine the depth of corrosion over a given period of time.

1.1, 1.2. (Changed edition, Rev. N 1).

1.3. Weight method to reduce the mass of the sample is to determine the thickness of the metal layer, subjected to corrosion in the testing process, the mass difference of sample before and after testing and removal of corrosion products from its surface.

1.4. Gravimetric method for increasing sample mass is to determine the thickness of the metal layer, subjected to corrosion in the testing process, to increase the mass of the sample determined directly in the testing process. Thus, to calculate pre-determine the correlation coefficient of the increase in mass of the sample to reduce its weight:

.

The value of the coefficient determined for studied steel grade, temperature and gas environment once. By multiplying the magnitude of the increase in mass of the sample by a coefficient get the value of the conditional reduction of the mass of the sample, which is determined by the thickness of the metal layer, subjected to corrosion.

Note. Allowed determination of the heat resistance of the gain, without taking into account the coefficient .

1.5. The method of direct measurement of corrosion depth on the refinement is to measure the reduction of the linear dimensions of a sample subjected to corrosion.

1.5. The combined method is to determine the mass of the sample weighting methods for PP.1.3 and 1.4 or direct measurement of depth of corrosion on refining samples subjected to oxidation with the maximum thickness podokonnogo layer, depleted in alloying elements or depth the maximum local corrosion.

(Added, Rev. N 1).

1.6. Recommendations for application methods, see the Appendix.

2. SAMPLING

2.1. For testing of metals and alloys should be used flat samples cut from metal in a state of delivery or of products. For testing of semi-finished products are allowed to use cylindrical specimens. The dimensions of the flat and cylindrical specimens shall be as specified in table.1.

Table 1

Note. Sample faces shall be rounded at a radius of 1.5 mm.

2.2. When tested by the method of direct measurement of corrosion depth are applied only to flat samples. The thickness variation of a flat sample should not exceed 0.01 mm.

2.3. To evaluate the heat resistance of products and samples at full-scale and rig tests use samples of different shapes and sizes depending on the purpose and type of test materials.

2.4. In the manufacture of samples of rolled and other products that have a directional texture deformation, the samples cut along the direction of the fibers.

3. EQUIPMENT

3.1. Installation for testing the heat resistance must meet the following requirements:

a) have automatic temperature control with an accuracy of ±5 °C;

b) the temperature deviation at specific points of the furnace in the area of samples should be not more than 0.5% at temperatures up to 850 °C and 1% at temperatures above 850 °C;

C) to ensure uniform washing of the surface of the test samples of the gas environment.

(Changed edition, Rev. N 1).

3.2. Gaseous environment on the chemical composition should match or be close to the environment in which the work will be the test material.

3.3. The flow rate of the gaseous medium during the test shall not be less than 0.025 m/s, but not more than the flow rates that cause erosion.

Note. When simultaneously testing a large number of samples, the total surface of which is large, therefore, possible depletion of the gaseous medium aggressive individual components, the flow rate set on the basis of the constancy of the composition of the medium in the area of the samples.

3.4. In determining the heat resistance of the samples placed in the ovens on heat-resistant ceramic base, ceramic crucibles or hung on a wire of heat-resistant materials.

(Changed edition, Rev. N 1).

3.5. In determining the heat resistance of the gravimetric method for increasing sample mass should be used special ceramic crucibles, not preventing the penetration of gaseous environment and ensure the preservation of the crumbling dirt. The crucible with sample is placed in a furnace on a ceramic stand or hung on lodowych rods.

3.5.1. Before the test, the crucibles must be calcined to constant weight.

3.5.2. The installation must provide continuous or batch weighing of test specimens directly in a furnace at test temperature. It is recommended to use an installation equipped with analytical balance, one arm of the rocker arm which hung the crucible with the sample in the furnace.

3.5.3. Allowed periodic weighing of the cooled samples outside the furnace.

3.5.4. If in the process of interaction of metal with the environment are formed compounds, sublimes at the temperature of test, you must apply the methods and devices enabling to take into account the number of volatile compounds.

3.6. Contact of the samples with a stand or crucible should be only at specific points.

4. PREPARING FOR THE TEST

4.1. The sample surface is polished with a low flow, intense cooling. Allowance for grinding shall be not less than 0.3 mm on a side. Surface roughness — according to GOST 2789−73.

4.2. In determining the heat resistance of the weight by counting the surface produced by the total area.

4.3. The measurement of the sample in the determination of the surface area produced with an accuracy of ±0.1 mm.

4.4. Before the test samples should be degreased with ethyl alcohol, ether or other organic volatile solvents.

4.5. In determining the heat resistance of the weight methods fat samples must be dried and weighed with an accuracy of ±0.1 mg.

4.6. When determining the heat resistance by a direct measurement of corrosion depth thickness measurement of a flat sample is made in at least three points with an accuracy of ±0.003 mm.

5. TESTING

5.1. General requirements

5.1.1. Samples are loaded into the furnace having a predetermined temperature. You may load the samples in the cold furnace. The beginning of the test think the time of reaching the working zone of the furnace set temperature. By the end of the test, consider the moment of switching off the furnace or unloading samples on expiry of the period of the test.

5.1.2. A time of testing, depending on the service life of the material shall be those specified in table.2.

Table 2

To assess the quality of the material when the sample testing is allowed to set the testing time is less than the specified.

5.1.3. In tests lasting no longer than 100 h, the samples are loaded into the furnace having a predetermined temperature. The end of the test is the time of discharge samples from the hot oven.

5.1.4. If the selected test time, it is impossible to establish regularities of the oxidation, the test duration should be increased.

5.1.5. To determine the regularities of oxidation of the periodic sampling should be performed via: 5, 10, 20, 50, 100, 200, 500, 1000, 2000, 5000, 10000 h. the Maximum duration of the test may not match the time given in tab.2. The number of experimental points should not be less than five.

For example:

5.1.6. When test time less than 100 hours to apply the method of determining the heat resistance to increase the mass of the sample. Must use units equipped analytical balance.

5.1.7. Each point is defined as the arithmetic mean of the results of the test at least three samples.

5.1.8. Test for heat resistance conducted periodic samples are cooled together with the furnace or on the tranquil air.

Cooling loops are chosen depending on the destination of the investigated metal.

For industrial plants operating continuously (for weeks), samples should be cooled in 100, 200, 500 hours and then every 200 hours

For the units periodically, and at full-scale and rig tests, the samples should be cooled in accordance with the planned mode of operation of the plants.

5.1.9. The temperature of the test set depending on the operating conditions of the investigated material.

5.2. The weight method of determining the heat resistance by reducing the mass of the sample

5.2.1. When determining the heat resistance by reducing the mass of the sample with its surface completely remove the formed oxidation products, so that when the sample inspection through a magnifying glass with 10x magnification it was not revealed traces of oxidation.

5.2.2. Depending on the composition of steels and alloys removal of corrosion products from the samples after the test shall be one of the following ways:

a) for carbon and low alloy steels it is recommended to use cathodic electrochemical treatment in 10% strength sulfuric acid solution with additive of acid corrosion inhibitor (hexamine, Unicode, etc. catamin the rate of 1 g of inhibitor per 1 liter of solution); as the anode is used lead plates. The current density of 10−15 a/DM, the solution temperature is 20 °C, the duration of treatment until complete removal of corrosion products. To determine the completeness of removal of corrosion products samples every 10−15 min is removed from the bath, washed with water and scan, as specified in clause 5.2.1;

b) for carbon, low-alloyed, medium-alloyed and high-alloyed steels, it is recommended to apply the electrochemical treatment in the melt mixture consisting of 40−60% soda ash and 60−40% sodium hydroxide. Treatment should be maintained at 450−500 °C, a current density of 25 to 50 a/DM, duration of treatment 1−5 minutes depending on the thickness and composition of the oxide film;

b) for all steels and alloys in addition to the above methods it is recommended that the method, based on reduction of oxides by atomic hydrogen. In this case, the samples after the test are immersed in a bath of molten metallic sodium, which is continuously purged through the ammonia. The melt temperature of 350−420 °C, process duration 1−2 hours

Ammonia should be thoroughly drained. The flow rate of ammonia should not exceed 0.5 l/min per 1 cm ofthe surface of the treated samples.

(Changed edition, Rev. N 1).

5.2.3. The selected processing mode, you must check on the non-oxidized sample. The non-oxidized control sample should not change its weight during the time corresponding to the selected mode of removal of oxidation products.

5.2.4. After descaling in accordance with the requirements of section 5.2.2 samples shall be thoroughly washed in running water, hair brush, dried with filter paper, cleaned with an ink eraser and washed with ethanol.

Cleaned from scale samples should be placed in a desiccator for 1 h, and then weighed with an accuracy of ±0.1 mg.

(Changed edition, Rev. N 1).

5.3. Gravimetric method for the determination of heat resistance to increase the mass of the sample

5.3.1. Before the test, the crucibles with the samples are weighed with an accuracy of ±0.1 mg and then placed into an oven for testing.

5.3.2. The increase in mass of the sample is determined by difference weighing results to the cold sample before the test and direct weighing during the test or after cooling the samples in crucibles, pre-closed lids made of heat-resistant material.

5.3.3. For the determination of the experience, at least three samples. In the test process record the increase in mass of the sample, and the decrease of mass is determined in accordance with the requirements of paragraphs.5.2.1−5.2.4. Recommended time of testing for 200−500 h

The value of the coefficient - variable is at the set temperature and can vary by 25−30%, depending on the time of testing. This change of magnitude in the calculation of the underlying rate of corrosion is not considered.

5.3.4. The change in mass of the sample during the test register periodically (after a specified time interval) or continuously.

5.4. The method of direct measurement of corrosion depth

5.4.1. The depth of uniform corrosion should be determined by direct measurement of sample thickness before and after testing to an accuracy of ±0.003 mm.

5.4.2. The depth of uniform corrosion under corrosion bilateral flat sample is defined as half the difference between the thickness of the initial sample and the thickness of the sample after the test .

The thickness of the sample is determined by measuring the distance between the maximum bulges on opposite sides.

5.4.1, 5.4.2. (Changed edition, Rev. N 1).

5.4.3, 5.4.4. 5.4.5. (Deleted, Rev. N 1).

5.4.6. Maximum depth of localized corrosion is determined by measuring the distance between the maximum protrusions and depressions on the specimen after the test.

The rate is measured at a length of 5 mm.

(Changed edition, Rev. N 1).

5.5. Combined method of determining depth of corrosion

5.5.1. The depth of uniform corrosion is defined as the sum of the depths of uniform corrosion, as measured by the decrease in the sample thickness or calculated change in mass of the sample before and after the test with the maximum thickness of podokonnogo sdoa depleted in alloying elements, or maximum local corrosion.

5.5.2. The depth of uniform corrosion, as measured by the reduction of the thickness of the sample, determined in accordance with the requirements of section 5.4.2.

5.5.3. The depth of uniform corrosion is determined by recalculating the weight increased in depth and expressed in millimeters for a given period of time.

5.5.4. The depth of local corrosion (intergranular internal oxidation, pitting, ulcers) and podokonnogo layer, depleted in alloying elements, determined on etched metallographic sections or by x-ray diffraction microanalysis.

Metallographic determination of the depth of local corrosion (, ) is carried out using optical microscope with magnification 100, 200(500 allowed) with an accuracy of ±0.003 mm. the Determination is carried out in at least three sections and takes the maximum value.

Electron microprobe determination of the depth podokonnogo layer, depleted in alloying elements (,), is carried out using x-ray micro-analysers by means of fixation of boundaries of a layer having a modified content of alloying elements compared to the original at the place of the highest for this sample depth. Held at least three measurements taken and average value

.

5.5−5.5.4. (Added, Rev. N 1);

6. PROCESSING OF THE RESULTS

6.1. Quantitative evaluation of the heat resistance is determined by the depth of penetration of corrosion, expressed in mm over a given period of time (the underlying index). Allowed a quantitative assessment on the weight indicator, expressed in mg/cm.

6.1.1. The depth of penetration of corrosion according to the method of reducing the mass of the sample () are in millimeters calculated by the formula

where the reduction in mass of the sample for a preset time obtained by direct testing or by extrapolation of experimental data, graphically processed in the coordinates: logarithm of mass loss of a sample is the logarithm of the time mg/cm;

 — density of metal, g/cm.

6.1.2. The depth of penetration of corrosion at a given time according to the method of increasing the mass of the sample () are in millimeters calculated by the formula

where  — weight of the sample in a given time obtained by direct testing or extrapolation of test data is graphically processed in the coordinates; the logarithm of the increase in mass of the sample is the logarithm of the time mg/cm;

 — the correlation coefficient of the increase in mass of the sample to reduce its mass.

In this case

where is the experimental data, obtained when tested in accordance with the requirements of the PP.1.4 and 5.3.3.

6.1.3. The depth of penetration of corrosion combined methods determined by the formula

or

where - thickness of specimen before test, mm.

 — thickness of specimen after test, mm.

,- maximum thickness of podokonnogo layer, depleted in alloying elements, determined in accordance with clause 5.5.4, mm;

, — maximum depth of localized corrosion as determined in accordance with clause 5.5.4, mm;

 — the depth of uniform corrosion is calculated on weighted indicators in accordance with the PP.6.1.1, 6.1.2, mm.

(Changed edition, Rev. N 1)

.

6.2. The quantitative characteristic of heat resistance depending on temperature is determined according to the long-term test not less than at three temperatures: working, working below and above 50 °C. the Test is carried out in accordance with the requirements of sec. 5.

6.3. The results of the measurements carried out in accordance with the requirements of sec. 5, graphically treated in logarithmic coordinates: the time — depth of penetration of corrosion.

6.4. The standards and technical documentation approved in the established order, for metals and products made of them must specify the method of determining heat resistance, the type of sample or its size (in the case of deviations from the standard), place cuttings in full-scale tests, temperature, time period and gas environment.

For example. Heat resistance according to GOST 6130−71 according to the method of increasing the weight of the samples K15 at 1000 °C, 5000 h, in the environment .

APPLICATION (recommended). THE SCOPE OF THE METHODS OF DETERMINATION HEAT RESISTANCE

APP
Recommended

1. The weight method of determining the heat resistance by reducing the mass of the sample is recommended for carbon and low alloy steels in the whole range of temperatures; for all steels and alloys at relatively low temperatures, when the oxidation is evenly distributed, without education potokina the layer of internal oxidation, sulfides, nitrides and other compounds.

2. Gravimetric method for the determination of heat resistance to increase the mass of the sample is recommended in those cases that the weighting method to reduce the mass of the sample when tests are widespread, or required the determination of the kinetics of the oxidation process.

The method is not recommended for use during field tests.

3. The method of direct measurement of the corrosion depth is used for all steels at relatively high temperatures, as well as in cases when it is impossible to apply the weight method.

(Changed edition, Rev. N 1).

4. Combined method of determining heat resistance is used when the corrosion process occurs unevenly, accompanied by various types of localized corrosion (intergranular internal oxidation, pitting, ulcers) and is characterized by processes in which the growth podokonnyh layers, depleted in alloying elements, is comparable or significantly exceeds the formation of surface layers of oxidation products.

(Added, Rev. N 1).