GOST 9.019-74
GOST 9.019−74 (ISO 9591−89) a unified system of corrosion protection and ageing (ESSEX). Alloys of aluminum and magnesium. Methods of accelerated tests for stress corrosion cracking (with Amendments No. 1, 2)
GOST 9.019−74
(ISO 9591−89)*
____________
* Changed the wording, Rev. N 2
Group Т99
STATE STANDARD СОЮ3А SSR
Unified system of protection against corrosion and aging
ALLOYS ALUMINUM AND MAGNESIUM
Methods of accelerated tests for stress corrosion cracking
Unified system of corrosion and ageing protection. Alluminium and magnesium alloys.
Accelerated test methods for corrosion cracking
AXTU 0009*
____________
* Changed the wording, Rev. N 2.
Valid from 01.01.75
to 01.01.83*
_______________________________
* Expiration removed
By the decree of Gosstandart of the USSR N 1859 from 22.06.89
(IUS N 10, 1989). — Note the CODE.
Promulgated by decree of the State Committee of standards of the USSR Council of Ministers dated March 19, 1974, N 627
REPRINT (November 1981) with amendment No. 1, approved in November 1979 (IUS N 1 1980)
The Change N 2 approved and put into effect by the decree of the USSR State Committee for standards from
Change 2 N entered the law office of «Code» in the text ICS N 10, 1989
This standard applies to aluminum and magnesium alloys without protective coatings and establishes methods of accelerated tests for stress corrosion cracking.
1. GENERAL PROVISIONS
1.1. The standard specifies two test methods:
at a given deformation;
at a constant axial tensile load.
1.2. Assessment criteria corrosion cracking of alloys are:
the level of safe voltage — maximum voltage at which there is destruction of samples for the specified test period;
the time of appearance of the first crack detected visually (or by increasing 30), when tested at a single stress level;
the character of the corrosion destruction.
(Changed edition, Rev. N 2).
2. SAMPLING
2.1. Set the direction of cut of samples of semi-finished products and products. The scheme of cutting out of samples is given in Appendix 1.
Samples of cast alloys is cut in the directions defined by the test program.
2:2. To obtain the characteristics, which are referred to the documents on alloy, test at least 10 samples of each option*. In other cases, it is possible to test at least 5 samples.
____________________
* Under option understand the group of samples with identical parameters.
2.3. When tested by the method specified strain used sample size 110х15х2,5 mm.
If you want to keep the original size of the part or semi-finished product allowed to apply samples of any thickness, but not more than 5.0 mm.
2.3.1. In those cases when it is impossible to produce samples of size 110х15 mm, it is possible to use samples with size about 40 x 10 mm and thickness up to 3.0 mm, and circular samples of 20 mm height, with a diameter of 10 mm and a wall thickness of not more than 0.1 of the outer diameter (Fig.2). If the wall thickness exceeds 0.1
, then the sample is drown from the inner side to the wall thickness, equal to 0.1
(see Annex 1).
2.3.2. From tubes and bars with diameter less than 10 mm cut samples in the form of segments with a length of 110 mm.
2.4. At a constant axial tensile load applied to the cylindrical samples with the diameter of the working part is not less than 3 mm and flat samples with width of the working part is not less than 4 mm.
(Changed edition, Rev. N 2).
2.5. In the manufacture of samples of welded joints of a seam in the middle of the sample perpendicular to the direction of tensile stresses.
2.6. The roughness parameter of the surface of samples is machined, must meet the standard for prefabricated.
The roughness parameter of the machined surface Ra of the samples according to GOST 2789−73 should be:
for aluminum alloys not more than 1 µm;
for magnesium alloys of more than 2.5 µm (circular pattern) or not more than 1.25 µm (flat samples).
For aluminum alloys it is possible to use the parameter of surface roughness specified for magnesium alloys, if it does not affect the test results.
(Changed edition, Rev. N 1, 2).
2.7. Samples with surface defects (mechanical or metallurgical origin) are rejected.
2.8. On one end of the sample labeling, which indicates the variant number and the sequence number of the sample. The marking are entered into the inventory, which should be reflected:
the chemical composition or grade;
production technology;
heat treatment;
cutting direction samples;
the dimensions of the samples;
surface condition;
the beginning and the end of the test.
2.9. The markings should be protected with varnish (for example, AK-20).
3. PREPARATION FOR TESTING
3.1. Prepare the surface of samples of aluminum alloys
3.1.1. Samples of aluminum alloy is degreased with an organic solvent (e.g. petrol), and then etched in 5−10% strength sodium hydroxide solution GOST 4328−77при a temperature of 50−60 °C for 0.5−2 min, Then samples were washed in running water, clarified in 30% strength solution of nitric acid GOST 4461−77 for 2−6 min, again washed in running, and then in distilled water at a temperature of 70−90 °C and dried.
3.1.2. Samples with a machined surface is allowed to dry etching.
3.2. Surface preparation of the samples of magnesium alloys
3.2.1. The samples with rough surface mechanical cleaning of a glass cloth 8 N or 10 N according to GOST 6456−82. After cleaning the sample surface is wiped with a swab moistened with ethyl alcohol.
(Changed edition, Rev. N 2).
3.2.2. Samples with machined surface additional not be machined.
3.2.3. Instead of Stripping the glass cloth mechanically untreated samples, and also for machined samples allowed etching in a 5−7% solution of nitric acid GOST 4461−77 for 0.5−2 minutes After washing in water samples clarified within 2−5 minutes in chromonemata solution at room temperature containing:
chromic anhydride according to GOST 3776−78; 80−100 g/DM;
sodium nitrate according to GOST 4168−79 or potassium nitrate according to GOST 4217−77; 5−8, g/DM.
The samples were then washed in running water and then in distilled water at a temperature of 70−90 °C.
(Changed edition, Rev. N 2).
3.3. Before the test samples wiped with a swab moistened with ethyl alcohol.
3.4. Calculation of deflection of when tested by the method given strain in a uniaxial stress state
3.4.1. Tensile stress in flat or cylindrical samples are generated in special appliances — brackets for four-point bending scheme (Fig.1).
Damn.1
The deflection is determined with an accuracy of ±0,02 mm. for Example, using the indicator of type IC 0−10 mm according to GOST 577−68 or other device.
The deflection in millimeters is calculated by the formula
where is the calculated stress, PA;
— modulus of elasticity, PA;
— distance between the supports in the brace, mm.
— thickness for flat specimen or the outer diameter of the cylindrical specimen, mm.
(Changed edition, Rev. N 2).
3.4.2. Tensile stress in ring samples to create a compression ring diameter (Fig.2).
Damn.2
Compression ring design is made in the clamp or coupling stud (see Annex 2).
The strain value in millimeters is calculated by the formula
where — the average ring diameter, mm;
— the wall thickness of the ring, mm;
— correction factor.
The value of the coefficient is determined according to the schedule (Annex 8) depending on the relationship
.
(Changed edition, Rev. N 2).
3.5. When tested by the method given deformation in complex stress state (bending and torsion) stress of bending and torsion creates a diagram in hell.3, special fixtures (brackets).
Damn.3
Design of brackets are given in Appendix 3.
The deflection in bending () in millimeters is calculated by the formula
The twist angle () in radians is calculated by the formula
where is the torsion, kgf/mm
;
— the shear modulus, kgf/mm
.
Since the deformation of the sample to measure the torsional angle constraint, is determined by the vertical displacement of the boundary points of the sample point (see Annex 3).
Vertical displacement () are in millimeters calculated by the formula
where the width of sample, mm.
3.6. Determination of design stress when tested by the method given deformation
3.6.1. Tests of the basic material is carried out at rated voltage () that make up a certain proportion (
) of the yield strength in tension (
).
3.6.2. For aluminum alloys, taken as equal to 1,0; 0,9; 0,75; 0,5 and 0,25; magnesium alloys — 0,9; 0,75; 0,5 and 0,25.
3.6.3. (Deleted, Rev. N 2).
3.6.4. Voltage for aluminum alloys with 0.25, 0.5 and 0.75 and magnesium alloys during
equal to 0.25 and 0.5, calculated by the formula
(Changed edition, Rev. N 2).
3.6.5. Stresses in specimens of aluminum alloys during equal to 0.9 and 1.0, determined by the table of Appendix 4 or calculated by the formula
when
when 
3.6.6. Stresses in samples made of magnesium alloys with 0.75 and 0.9, determined according to table 5 or calculated by the formula
where
3.6.7. The torsional stress () is taken equal to 0.5
3.6.8. Samples of welded joints is tested on several or a single voltage level. For aluminum and magnesium alloys, the following values of the calculated stresses , MPa:
140, (100), (120), (160) — for alloys of the system Al-Mg-Si, Al-Mg;
220, (180), (200), (240) — for alloys of the systems Al-Cu, Al-Cu-Mg, Al-Cu-Mg-Si;
240, (200), (220), (260) — for alloys of the system Al-Zn-Mg, Al-Zn-Mg-Cu.
For magnesium alloys the design stress take is equal to 0,6; (0,4); (0,5); (0,75) of the tensile strength of the welded joint. When welding dissimilar metals stress value is determined by less durable material.
(Changed edition, Rev. N 2)
.
3.6.9. With the aim of reducing the time of test or simulation of operation of the parts is allowed to test samples of aluminum alloys at voltages in excess (
>1) — for the basic material according to the formulas (7) and (8), or the maximum value in row reduced stress for welded joints.
3.7. Determination of design stress when tested by the method specified axial tensile load
3.7.1. The tensile stress created in the installations of the «Signal» according to GOST 9.909−86 (see Annex 6) or other devices that maintain constant load during the entire test time. The tensile stress (), N, is calculated by the formula
where is the cross — sectional area of sample (for weldments — base metal), mm
.
(Changed edition, Rev. N 2).
3.7.2. When tested on a single voltage level is taken equal to 0.75for aluminum alloys and 0.5
for magnesium alloys. When tested on several levels these stresses take over primary. The following values of voltages sequentially change to 20 MPa.
(Changed edition, Rev. N 2).
3.7.3. Welded joints of aluminum alloys tested under the stresses, MPa:
120, (80); (100), (140) — for alloys of the system Al-Mg-Si, Al-Mg;
180, (160), (200), (220) — for alloys of the systems Al-Cu, Al-Cu-Mg, Al-Cu-Mg-Si;
200, (160), (180), (220), (240) — for alloys of the system Al-Zn-Mg, Al-Zn-Mg-Cu.
(Changed edition, Rev. N 2).
3.7.4. Welded joints of magnesium alloys tested at a stress of 0.5; (0,4); (0,6) of the tensile strength of the welded joint.
4. TESTING
4.1. Tests of aluminum alloys is carried out at periodic immersion of the samples in 3% solution of sodium chloride according to GOST 4233−77 cycle: 10 min. in solution and 50 min in the air. The ambient temperature of 18−25 °C.
4.2. Testing of magnesium alloys is carried out at periodic immersion in 0.001% solution of sodium chloride cycle: 10 min. in solution and 50 min. in air (ambient temperature 18 to 25 °C) and in a humid atmosphere (chamber), two-stage cycle:
1st stage — the humidity of 95−98% and a temperature of 50±2 °C, exposure time 16 h;
Level 2 — the humidity of 95−98%, temperature 18−25 °C, exposure time 8 h
4.2.1. The samples in the chamber are placed so that the convex (stretched) side of the sample facing upwards.
4.3. Allowed to test the alloys by the method specified uniaxial tensile load at a constant immersion of samples in solutions, as indicated in the claims.4.1. 4.2.
4.4. The solutions were prepared in distilled water by the GOST 6709−72.
4.5. The volume of the solution is at least 10 cmby 1 cm
sample surface.
(Changed edition, Rev. N 2).
4.6. The change of the solution is made after every 15 days of testing. The solution as it evaporates, top up with distilled water.
4.7. Tests with periodic immersion is carried out without a break or regular break lasting no more than 9 hours are Allowed occasional breaks lasting no more than 3 days.
When calculating the duration of the tests take into account calendar time.
During the breaks, the samples should be air.
(Changed edition, Rev. N 2).
4.8. The test duration is:
according to the method given strain — 90 day — periodic and full immersion, 180 days — when testing in the chamber;
according to the method given load — 45 days.
Allowed to increase the test duration to 90, 180, 270 and 360 days or reduce to 10, 20 or 30 days.
(Changed edition, Rev. N 2).
4.9. When tested by the method given deformation periodically make the recovery of the deformation. For this the sample is completely unloaded and re-deform the initial deflection. The recovery of deformation of the samples is carried out after 15 and 45 days since the beginning of the test, and then every 45 days. Allowed deviation to 2 days.
If the duration of the test less than 30 days, the restoration of deformation is not carried out.
(Changed edition, Rev. N 2).
5. PROCESSING OF TEST RESULTS
5.1. When the number of samples is 10 or more in the embodiment, the received data are subject to mathematical processing building probability curves in the coordinates «the cumulative probability of failure — time to failure».
5.1.1. Calculate the arithmetic mean time to failure () in days by the formula
where is the time to failure a single sample, day;
— the number of samples in the embodiment.
If samples are not destroyed during the selected time trials, counting take into account the duration of the test nerazrushaushsii samples.
(Changed edition, Rev. N 2).
5.1.2. The variance () is calculated by the formula
5.1.3. The standard deviation () is calculated by the formula
5.1.4. The coefficient of variation () in percent is calculated by the formula
The variance, standard deviation and coefficient of variation is calculated only based on the value of the collapsed samples.
(Changed edition, Rev. N 2).
5.1.5. The probability of destruction of the sample (
) in percent is calculated by the formula
where is the ordinal number of the tested sample in the row sequence of the destruction of the samples.
5.1.6. Next, build a probabilistic curves, where the vertical axis lay the accumulated probability of failure and the abscissa shows the time to failure. A straight line that characterize the empirical distribution function is carried out through two points with coordinates (
5.2. To determine the level of safe stress, build a graph of «time to failure-stress». The time to failure is determined by the accumulated probability of () 5 and 50%.
5.3. When the number of samples is 10 determine only the arithmetic mean time to failure () with the time before the destruction of the first and last samples.
5.4. An additional criterion for the evaluation of the test results is the nature of the corrosion cracks determined by microscopic examination of thin sections.
The plane of the sections, made according to GOST 1778−70, must be perpendicular to the working surface of the sample and parallel to the direction of tensile stresses.
ANNEX 1 (recommended). The scheme of cutting out of samples
ANNEX 1
Recommended
list;
— extruded profile;
— extruded strip;
— forging.
Cutting direction: D — share; P — transverse; high-rise; R — radial; X — chordal.
ANNEX 2 (informative)
ANNEX 2
Reference
Deformation of the ring sample tie pin
1 — coupling pin of titanium alloy steel grades 12X18H9T; 2 — a nut of titanium alloy or steel 12X18H9T;
3 — textolite gasket; 4 — specimen ring.
Deformation of ring specimen in the clamp
Deformation of ring specimen in the clamp
1 — pressure screw made of titanium alloy or steel 12X18H9T; 2 — the upper bar of titanium alloy or steel 12X18H9T; 3 — rail, made of titanium or steel 12X18H9T; 4 — movable crossbar textolite;
5 — a sample ring; 6 — the bottom rung textolite.
APPENDIX 3 (reference). Fixture for testing flat specimens at a given strain in the complex stress condition (bending and torsion)
APPENDIX 3
Reference
1 — bracket; 2 — stud; 3 — earring; 4 — sample; 5, 6 — strip. Material: POS.1, 3, 5, 6 — PCB;
POS.2 - titanium alloy or steel 12X18H9T.
ANNEX 4 (reference). Determination of design stress, in MPa, in the samples of aluminum alloys for values K, equal to 0.9 and 1.0
ANNEX 4
Reference
| 100,0 |
: 142.0 cm |
120,0 |
: 270.0 cm |
348,0 |
295,0 |
440,0 |
535,0 |
467,0 |
| 105,0 |
148,0 |
125,0 |
275,0 |
354,0 |
300,0 |
445,0 |
541,0 |
471,0 |
| 110,0 |
155,0 |
131,0 |
280,0 |
359,0 |
305,0 |
450,0 |
546,0 |
477,0 |
| 115,0 |
160,0 |
136,0 |
285,0 |
365,0 |
310,0 |
455,0 |
551,0 |
481,0 |
| 120,0 |
167,0 |
141,0 |
290,0 |
370,0 |
315,0 |
460,0 |
556,0 |
486,0 |
| 125,0 |
173,0 |
146,0 |
295,0 |
376,0 |
320,0 |
465,0 |
562,0 |
492,0 |
| 130,0 |
180,0 |
152,0 |
300,0 |
382,0 |
325,0 |
470,0 |
567,0 |
496,0 |
| Of 135.0 |
Of 186.0 |
157,0 |
305,0 |
387,0 |
330,0 |
475,0 |
572,0 |
502,0 |
| 140,0 |
Of 193.0 |
162,0 |
310,0 |
392,0 |
335,0 |
480,0 |
577,0 |
506,0 |
| 145,0 |
199,0 |
167,0 |
315,0 |
398,0 |
341,0 |
485,0 |
583,0 |
511,0 |
| 150,0 |
205,0 |
172,0 |
320,0 |
404,0 |
346,0 |
Of 490.0 |
588,0 |
517,0 |
| 155,0 |
211,0 |
177,0 |
325,0 |
409,0 |
351,0 |
495,0 |
593,0 |
521,0 |
| 160,0 |
218,0 |
183,0 |
330,0 |
414,0 |
355,0 |
500,0 |
599,0 |
527,0 |
| 165,0 |
223,0 |
188,0 |
335,0 |
420,0 |
360,0 |
505,0 |
605,0 |
532,0 |
| 170,0 |
230,0 |
Of 193.0 |
340,0 |
426,0 |
366,0 |
510,0 |
610,0 |
536,0 |
| 175,0 |
236,0 |
198,0 |
Of 345.0 |
431,0 |
371,0 |
515,0 |
615,0 |
542,0 |
| 180,0 |
242,0 |
203,0 |
To 350.0 |
436,0 |
376,0 |
520,0 |
620,0 |
547,0 |
| 185,0 |
248,0 |
208,0 |
355,0 |
442,0 |
381,0 |
525,0 |
625,0 |
552,0 |
| 190,0 |
254,0 |
213,0 |
360,0 |
448,0 |
386,0 |
530,0 |
631,0 |
557,0 |
| 195,0 |
260,0 |
218,0 |
365,0 |
453,0 |
391,0 |
535,0 |
637,0 |
562,0 |
| 200,0 |
266,0 |
224,0 |
370,0 |
458,0 |
396,0 |
540,0 |
642,0 |
567,0 |
| 205,0 |
272,0 |
228,0 |
375,0 |
464,0 |
401,0 |
545,0 |
647,0 |
571,0 |
| Of 210.0 |
278,0 |
234,0 |
380,0 |
470,0 |
406,0 |
550,0 |
652,0 |
577,0 |
| 215,0 |
283,0 |
239,0 |
385,0 |
475,0 |
411,0 |
555,0 |
657,0 |
582,0 |
| 220,0 |
289,0 |
244,0 |
390,0 |
481,0 |
416,0 |
560,0 |
662,0 |
587,0 |
| 225,0 |
295,0 |
249,0 |
395,0 |
486,0 |
421,0 |
565,0 |
667,0 |
592,0 |
| 230,0 |
300,0 |
254,0 |
400,0 |
492,0 |
426,0 |
570,0 |
673,0 |
597,0 |
| 235,0 |
307,0 |
259,0 |
405,0 |
497,0 |
431,0 |
575,0 |
679,0 |
602,0 |
| 240,0 |
313,0 |
264,0 |
410,0 |
502,0 |
436,0 |
580,0 |
684,0 |
607,0 |
| 245,0 |
318,0 |
269,0 |
415,0 |
508,0 |
441,0 |
585,0 |
689,0 |
612,0 |
| 250,0 |
324,0 |
275,0 |
420,0 |
513,0 |
446,0 |
590,0 |
694,0 |
617,0 |
| 255,0 |
330,0 |
280,0 |
425,0 |
518,0 |
451,0 |
595,0 |
699,0 |
622,0 |
| 260,0 |
336,0 |
284,0 |
430,0 |
524,0 |
456,0 |
600,0 |
704,0 |
627,0 |
| 265,0 |
342,0 |
290,0 |
435,0 |
529,0 |
461,0 |
|||
Annex 4. (Changed edition, Rev. N 2).
ANNEX 5 (reference). Determination of design stress, in MPa, in the samples of magnesium alloys for values of K equal to 0.75 and 0.9
ANNEX 5
Reference
| 100,0 | 125,0 |
205,0 | 237,0 | 310,0 | Of 345.0 |
| 105,0 |
131,0 | Of 210.0 | 242,0 | 315,0 | To 350.0 |
| 110,0 |
136,0 | 215,0 | 247,0 | 320,0 | 355,0 |
| 115,0 |
: 142.0 cm | 220,0 | Of 252.0 | 325,0 | 360,0 |
| 120,0 |
147,0 | 225,0 | 258,0 | 330,0 | 365,0 |
| 125,0 |
153,0 | 230,0 | 263,0 | 335,0 | 370,0 |
| 130,0 |
To 158.0 | 235,0 | 268,0 | 340,0 | 375,0 |
| Of 135.0 |
163,0 | 240,0 | 273,0 | Of 345.0 | 380,0 |
| 140,0 |
169,0 | 245,0 | 278,0 | To 350.0 | 386,0 |
| 145,0 |
174,0 | 250,0 | 283,0 | 355,0 | 391,0 |
| 150,0 |
179,0 | 255,0 | 289,0 | 360,0 | 396,0 |
| 155,0 |
185,0 | 260,0 | 294,0 | 365,0 | 401,0 |
| 160,0 |
190,0 | 265,0 | 299,0 | 370,0 | 406,0 |
| 165,0 |
195,0 | : 270.0 cm | 304,0 | 375,0 | 411,0 |
| 170,0 |
201,0 | 275,0 | 309,0 | 380,0 | 416,0 |
| 175,0 |
206,0 | 280,0 | 314,0 | 385,0 | 421,0 |
| 180,0 |
211,0 | 285,0 | 319,0 | 390,0 | 426,0 |
| 185,0 |
216,0 | 290,0 | 324,0 | 395,0 | 431,0 |
| 190,0 |
221,0 | 295,0 | 329,0 | 400,0 | 436,0 |
| 195,0 |
U.S. $ 227.0 | 300,0 | 335,0 | ||
| 200,0 |
232,0 | 305,0 | 340,0 |
Appendix 5. (Changed edition, Rev. N 2).
APPENDIX 6 (reference). Diagram of the setup Signal for test of samples for stress corrosion cracking under constant axial tensile load
APPENDIX 6
Reference
- the scheme of installation «Signal»;
— the connection of samples in the chain by means of couplings; 1 — sample;
2 — clutch; 3 — corrosion environment; 4 — lever; 5 — fitting for the feed solution;
6 moving load, 7 — loading screw.
APPENDIX 7 (reference). An example of a full mathematical treatment of test data, stress corrosion cracking
ANNEX 7
Reference
1. Obtained the following values of time until the cracks (time to failure) — day:
8, 13, 16, 19, 21, 28, 35, 37, 42, 45.
2. The calculated arithmetic mean () of time to failure:
p. 1, 2. (Changed edition, Rev. N 2).
3. The computed variance ():
4. The computed mean square ():
5. The computed coefficient of variation ():
6. Data mathematical handling are given in the table and depicted on the chart.
| Sample number |
|
| ||||||
| day |
||||||||
| 1 |
5 |
8 |
18 | 324 |
||||
| 2 |
15 |
13 |
13 |
169 |
||||
| 3 |
25 | 15 |
11 |
121 |
||||
| 4 |
35 |
19 |
7 |
49 |
||||
| 5 |
45 |
21 |
5 |
25 |
||||
| 6 |
55 |
28 |
26 |
2 |
4 |
167,9 |
12,9 |
49,6 |
| 7 |
65 | 35 | 9 | 81 | ||||
| 8 |
75 |
37 |
11 |
121 |
||||
| 9 |
85 | 42 | 16 | 256 | ||||
| 10 |
95 | 45 | 19 | 361 | ||||
(Changed edition, Rev. N 2).
ANNEX 8 (obligatory). The dependence of the correction factor from the ratio of the outer diameter of the ring specimen to the thickness of its walls
ANNEX 8
Mandatory
The dependence of the correction factor from the ratio of external
the diameter of the circular sample to the thickness of its walls
Appendix 8. (Introduced doplnitelno, Rev. N 2).
