CN107817165A - Device for measuring stress corrosion behavior of steel in corrosion environment - Google Patents

Abstract

The invention relates to the field of oil and gas field material testing, and discloses a device for measuring stress corrosion behavior of steel in a corrosion environment, which comprises an inner shell, a sample clamping device and a corrosion medium introducing system, wherein the inner shell is provided with a sample inlet; the inner shell is a sealed shell; the sample clamping device comprises a lower nickel-based alloy sample rack arranged at the bottom of the inner shell and an upper nickel-based alloy sample rack arranged in the middle of the inner shell, a stainless steel magnetized medium is fixed above the upper nickel-based alloy sample rack, and a pressure sensor and an electromagnet are sequentially arranged above the inner shell; the inner shell is filled with corrosive medium. The device provided by the invention provides an effective device for testing the sample in a multi-element environment, and ensures the stability and accuracy of the concentration of the volatile medium in the corrosive solution in the experimental process, so that the tested experimental result has high accuracy.

Description

A device for measuring stress corrosion behavior of steel in corrosive environments

technical field

The invention specifically relates to the field of oil and gas field material testing, and more specifically relates to a device for measuring the stress corrosion behavior of steel in a corrosive environment.

Background technique

In the oil and gas field industry, the service environment of materials becomes more and more complex, which leads to the failure and brittle fracture of materials during use, and stress corrosion cracking is one of many corrosion failure behaviors, because the reason is that the material is corroded. In the environment, under certain tensile stress conditions, material brittle fracture often occurs suddenly without obvious warning, which is extremely harmful, and relevant experimental tests need to be carried out for evaluation.

As a stress corrosion test and evaluation method, slow strain tension is widely recognized by scholars. However, due to the reason of the test device, the corrosive medium cannot be sealed during the test, which makes the use of the test device limited. Only some corrosive media can be tested. Volatile substances, and the test results are not ideal, such as testing the stress corrosion behavior of chloride ions, for volatile corrosive media, stress corrosion test evaluation cannot be carried out.

Contents of the invention

In order to solve the problem that the stress corrosion evaluation of materials under the corrosion system in the prior art cannot be evaluated due to the volatile gas in the corrosion medium, the present invention provides a method for measuring the stress corrosion of steel in a corrosion environment. device of behavior.

The present invention adopts the following technical scheme: a device for measuring the stress corrosion behavior of steel in a corrosive environment, the device includes an inner shell, a sample holding device, and a corrosive medium feeding system; the inner shell is a sealed shell The sample clamping device includes a lower nickel-based alloy sample rack arranged at the bottom of the inner shell, an upper nickel-based alloy sample rack arranged at the middle of the inner shell, and a stainless steel magnetizing medium is fixed above the upper nickel-based alloy sample rack; A pressure sensor and an electromagnet are sequentially arranged above the inner shell; the inner shell is filled with a corrosive medium.

A foamed aluminum interlayer is set between the upper nickel-based alloy sample holder and the stainless steel magnetized medium.

The device includes a temperature testing system, the system includes an electric heating wire, a galvanic couple chamber, and a thermocouple, and the electric heating wire is arranged on the outside of the inner wall for heating the corrosive medium in the area where the tensile sample is located; the galvanic couple chamber extends into the housing; the thermocouple is inserted into the couple chamber.

A cooling pipe is arranged outside the inner shell, and the cooling pipe is arranged between the stainless steel magnetized medium and the top of the inner shell.

Aluminum foam is arranged on the outside of the heating wire and the cooling pipe.

A shell is arranged on the outside of the foamed aluminum.

The invention utilizes the magnetic force of the electromagnet to carry out the tensile stress of the slow-strain stretching, so that the test of the stress corrosion behavior of the steel in the corrosive environment can be completed, and especially can ensure the sealing performance of the highly volatile corrosive medium in the slow-strain stretching process, fully It ensures the safety of the experimenters during the experiment, and at the same time ensures the stability and accuracy of the concentration of the volatile medium in the corrosion solution during the experiment, so that the accuracy of the experimental results is high.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the device of the present invention.

Symbol Description

1. Electromagnet; 2. Shell; 3. Cooling water pipe; 4. Pressure sensor; 5. Aluminum foam 6. Inner shell; 7. Top of the inner shell; 8. Corrosion medium solution; 9. Upper nickel-based alloy sample holder; 10 1. Foamed aluminum interlayer; 11. Stainless steel magnetized medium; 12. Fixing bolts of the upper sample rack; 13. Hydrogen sulfide inlet pipe; 14. Hydrogen sulfide inlet control valve; 15. Thermocouple chamber; 16. Thermocouple; 17. Waste liquid Discharge channel; 18. Waste liquid discharge control valve; 19. Carbon dioxide inlet pipe; 20. Carbon dioxide inlet control valve; 21. Sodium carbonate solution inlet hole; 22. Sodium carbonate solution inlet control valve; 23. Lower nickel base alloy Sample rack; 24. Lower sample rack fixing bolts; 25. Sample fixing clamp; 26. Heating wire; 27. Tensile sample; 28. Fixing bolts at the top of the inner shell.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

A device for measuring the stress corrosion behavior of steel in a corrosive environment, the device includes an inner shell 6, a sample holding device, and a corrosive medium feeding system; the inner shell is a sealed shell; the sample holder The holding device includes a lower nickel-based alloy sample rack 23 arranged at the bottom of the inner shell 6, an upper nickel-based alloy sample rack 9 arranged at the middle of the inner shell 6, and a stainless steel magnetizing medium 11 is fixed above the upper nickel-based alloy sample rack 9, said A pressure sensor 4 and an electromagnet 1 are sequentially arranged above the inner shell 6; the inner shell is filled with a corrosive medium.

In the traditional test of the sample, because the corrosive gas is difficult to control during the test process, leakage problems often occur, endangering the health of the staff, and the sample cannot be tested in this environment. Based on this, the present invention innovatively uses the electromagnet 1 , the pressure sensor 4 and the stainless steel magnetized medium 11 to be used together, so that the test of the sample in a corrosive environment can be realized.

A foamed aluminum interlayer 10 is arranged between the upper nickel-based alloy sample rack 9 and the stainless steel magnetized medium 11 . The upper and lower nickel-based alloy sample racks 9, 23 fix the bottom of the sample, and further preferably, sample holders 25 are set on the upper and lower nickel-based alloy sample holders 23, and the two sample holders 25 are respectively used to fix the samples. The sample is fixed on the upper nickel-based alloy sample holder 9 and the lower nickel-based alloy sample holder 23, the foamed aluminum interlayer 10 is placed in the upper nickel-based alloy sample holder 9, the stainless steel magnetization medium 11 is placed on it, and the upper sample holder is used to fix the bolts 12 Connect the upper nickel base alloy sample holder 9, the aluminum foam interlayer 10 and the stainless steel magnetized medium 11. The foamed aluminum interlayer 10 is located between the stainless steel outer shell 2 and the nickel-based alloy inner shell 6, which plays the role of heat preservation and magnetic isolation, and the entire sealing system plays the role of sealing the corrosive medium.

Described device comprises temperature test system, and this system comprises heating wire 26, galvanic couple chamber 15, thermocouple 16, and described heating wire 26 is arranged on the outside of inner wall and is used for heating the corrosive medium in the area where tensile sample is located; The chamber 15 protrudes into the inner shell; the thermocouple 16 is inserted into the thermocouple chamber 15, and the heating wire 26 is controlled through temperature feedback to make the test temperature equalize.

A cooling pipe 3 is arranged on the outside of the inner shell, and the cooling pipe 3 is arranged between the stainless steel magnetized medium 11 and the top 7 of the inner shell, and the cooling water pipe 3 keeps the temperature of the upper part of the inner shell at room temperature. Keeping the temperature of the upper part of the inner shell at room temperature is to ensure that the magnetic field and electromagnetic force between the upper electromagnet and the stainless steel magnetic conductor are affected by temperature. If the temperature is too high, the electromagnetic force will decrease and the tensile force will be insufficient.

Aluminum foam 5 is provided on the outside of the heating wire 26 and the cooling pipe 3 . Utilizing the magnetic isolation and thermal insulation properties of foamed aluminum, it can ensure the electromagnetic radiation of the experimenters, and can ensure the stability of the temperature of the environment where the sample is located.

The shell 2 is arranged on the outside of the foamed aluminum 5 .

Working process: open the top 7 of the inner shell, fix the tensile sample 27 on the lower nickel-based alloy sample holder with the sample fixing clip 25, pour the solution containing sodium chloride into the nickel-based alloy inner shell 6, and then use The sample fixing clamp 25 fixes the tensile sample 27 on the upper nickel-based alloy sample holder 9, puts the foamed aluminum interlayer 10 in the upper nickel-based alloy sample holder 9, puts the stainless steel magnetizing medium 11 on it, and fixes it with the upper sample holder The bolt 12 connects the upper nickel-based alloy sample holder 9, the foamed aluminum interlayer 10 and the stainless steel magnetized medium 11; then pour the solution containing sodium chloride, cover the top 7 of the inner shell, and seal it tightly with the fixing bolts on the top 7 of the inner shell; A pressure sensor 4 is placed on the top 7 of the inner shell, and a magnet 1 is placed on the pressure sensor 4 .

Open the sodium carbonate solution and feed the control valve 22, feed nitrogen at the sodium carbonate solution feed hole 21, remove the oxygen in the corrosive medium; close the control valve 22 and open the hydrogen sulfide feed control valve 14, and feed the hydrogen sulfide into the inlet 13 Pass into hydrogen sulfide; Open the carbon dioxide feed control valve 20, feed carbon dioxide on the carbon dioxide feed hole 19. Maintain the pressure of hydrogen sulfide and carbon dioxide to form a ternary corrosion system.

Insert a thermocouple 16 into the thermocouple chamber 15, heat the heating wire 26 with current, control the heating wire 26 through temperature feedback, so that the test temperature meets the experimental requirements, and at the same time open the cooling water pipe 3 to keep the upper temperature at room temperature.

The electromagnet 1 is energized to magnetize the stainless steel magnetized medium 11, attract the stainless steel magnetized medium 11, and then drive the upper nickel-based alloy sample holder 9 to pull the tensile sample 27, so that it is subjected to tensile stress and subjected to stress corrosion in the corrosive medium, through the force sensor 4 Feedback to adjust the current of the electromagnet 1 to control the suction force of the electromagnet; and set and record the force value.

After the tensile sample 27 is broken, close the hydrogen sulfide feed control valve 14 and the carbon dioxide feed control valve 20, open the waste liquid discharge control valve 18, and use the waste liquid discharge hole 17 to discharge the corrosion waste liquid into the sodium carbonate solution or hydrogen In the sodium oxide solution; when the corrosive medium in the container is almost exhausted, open the sodium carbonate solution and feed the control valve 22, feed a small amount of sodium carbonate solution into the device, and then get rid of the waste liquid through the waste liquid discharge hole 17, so that 5 After -6 times, the device can be opened to remove the tensile sample 27 for fracture analysis.

Due to the complex corrosion environment of oil and gas fields, often accompanied by multiple types of corrosion media, which interact with each other, higher requirements are put forward for the evaluation of stress corrosion of materials, and H ₂ S, CO ₂ , Cl ^- corrosion are the main corrosion environments , the stress corrosion evaluation of materials under the corrosive medium system H ₂ S-CO ₂ -Cl ^- ternary corrosion system. Because there are volatile H ₂ S and CO ₂ gases in the corrosive medium, they cannot be sealed, so the current experiment The device cannot be evaluated, which makes it difficult to select materials under the H ₂ S-CO ₂ -Cl ^- ternary corrosion system. The present invention is especially suitable for the H ₂ S-CO ₂ -Cl ^- ternary corrosion system.

When the corrosive medium is H ₂ S—CO ₂ —Cl ^— ternary corrosion system, the corrosive medium enters the inner shell 6 through the corrosive medium feeding system. The corrosive medium feeding system includes a carbon dioxide feeding pipe 20, a waste liquid discharge channel 17, a hydrogen sulfide feeding pipe 13, and a sodium carbonate solution feeding pipe 21. The corrosive medium feeding system is arranged on the upper nickel base alloy sample rack 9 and the lower Between nickel-based alloy sample racks 23; carbon dioxide inlet control valve 20 is set on the carbon dioxide inlet pipe 20; hydrogen sulfide inlet control valve 14 is arranged on the hydrogen sulfide inlet pipe 13; sodium carbonate solution is arranged on the sodium carbonate solution inlet pipe 21 Lead into the control valve 22; the waste liquid discharge control valve 18 is set on the waste liquid discharge channel 17.

The invention utilizes the magnetic force of the electromagnet to carry out the tensile stress of the slow-strain stretching, which can ensure the sealing performance of the highly volatile corrosive medium during the slow-strain stretching process, fully guarantee the safety of the experimenters during the experiment, and at the same time ensure the corrosion during the experiment process The stability and accuracy of the concentration of the volatile medium in the solution makes the experimental results accurate; the use of the foamed aluminum's magnetic isolation and thermal insulation can ensure the electromagnetic radiation of the experimenters and the temperature of the environment where the sample is located. stable; the present invention can carry out the stress corrosion test and evaluation of the H ₂ S-CO ₂ -Cl ^- ternary corrosion system of materials under different temperature and different concentration conditions, which overcomes the complicated conditions of different temperatures and different concentrations that cannot be performed by other equipment The multi-component hydrogen sulfide-containing stress corrosion test has wide adaptability.

Claims (6)

1. A device for measuring the stress corrosion behavior of steel in a corrosive environment, characterized in that the device includes an inner shell (6), a sample holding device, and a corrosive medium feeding system; the inner shell (6) ) is a sealed shell; the sample holding device includes a lower nickel-based alloy sample holder (23) arranged at the bottom of the inner casing (6), an upper nickel-based alloy sample holder (9) arranged in the middle of the inner casing (6) ), a stainless steel magnetized medium (11) is fixed above the upper nickel-based alloy sample holder (9); a pressure sensor (4) and an electromagnet (1) are sequentially arranged above the inner shell (6); the inner shell (6) Filled with corrosive media. 2. The device for measuring the stress corrosion behavior of steel in a corrosive environment according to claim 1, characterized in that aluminum foam is arranged between the upper nickel-based alloy sample holder (9) and the stainless steel magnetization medium (11) Mezzanine (10). 3. The device for measuring the stress corrosion behavior of steel in a corrosive environment according to claim 1, characterized in that the device includes a temperature testing system, which includes a heating wire (26), a galvanic chamber (15) . Thermocouple (16), the heating wire (26) is arranged on the outside of the inner wall to heat the corrosive medium in the area where the tensile sample is located; the thermocouple chamber (15) extends into the inner shell; the thermocouple (16) ) into the galvanic chamber (15). 4. The device for measuring the stress corrosion behavior of steel in a corrosive environment according to claim 1, characterized in that a cooling pipe (3) is arranged outside the inner shell, and the cooling pipe (3) is arranged on a stainless steel magnetized medium (11) and the top of the inner shell (7). 5. The device for measuring the stress corrosion behavior of steel in a corrosive environment according to claim 1, characterized in that aluminum foam (5) is arranged outside the heating wire (26) and the cooling pipe (3). 6 . The device for measuring the stress corrosion behavior of steel in a corrosive environment according to claim 1 , characterized in that a shell ( 2 ) is arranged outside the foamed aluminum ( 5 ).