CN107478566B - Method for obtaining reoxidation analysis sample in steam service environment - Google Patents
Method for obtaining reoxidation analysis sample in steam service environment Download PDFInfo
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- CN107478566B CN107478566B CN201710574840.2A CN201710574840A CN107478566B CN 107478566 B CN107478566 B CN 107478566B CN 201710574840 A CN201710574840 A CN 201710574840A CN 107478566 B CN107478566 B CN 107478566B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/18—Performing tests at high or low temperatures
Abstract
The invention discloses a method for obtaining a sample for reoxidation analysis in a steam service environment, which comprises the following steps: 1) carrying out steam oxidation on the material through water steam to obtain a primary oxidation sample; 2) according to the requirements of simulation analysis, mechanical cutting, grinding or electric spark cutting is adopted to remove part or all of the surface oxide layer, and the peeling conditions of different oxide layers are simulated; 3) carrying out high-temperature creep loading on the material treated in the step 2) in a protective gas environment; 4) carrying out steam oxidation on the material treated in the step 3) again to obtain a reoxidation analysis sample in a simulated steam service environment; wherein, H is adopted in the step 1)2O steam, using heavy oxygen water (H) in step 4)2 18O) steam to distinguish the two oxidation products.
Description
Technical Field
The invention belongs to the technical field of material oxidation resistance evaluation, and particularly relates to a method for obtaining a sample for reoxidation analysis in a steam service environment.
Background
In parts in the high-temperature high-pressure steam oxidation service environment of nuclear power and thermal power equipment, the oxidation resistance evaluation of the material is essential. Conventional laboratory analysis typically employs a single oxidation process for the starting material. However, in the practical process, the periodic process of 'oxide scale growth-peeling-secondary oxide scale regrowth' is a common phenomenon in the service process of the high-temperature parts. The single scale analysis result is only suitable for primary scale growth. Therefore, it is necessary to study the secondary scale regrowth law to reveal the oxidation mechanism throughout the life of the part.
The difference between the growth of the secondary oxide skin and the primary oxide skin lies in that: in the service process of a high-temperature high-pressure steam environment, the material undergoes high-temperature and mechanical interaction, and the influence of creep damage caused by a creep process on steam oxidation exists. And creep and steam oxidation are carried out simultaneously under the actual service environment, and the experimental acquisition of such analysis samples is difficult. Analysis of the actual service process reveals that the creep damage development process takes much longer than an oxidation process of "scale growth-spalling".
At present, the combination of chemical environment and mechanical effect can be realized on a slow tensile test system with a high-temperature high-pressure closed container, but the combination of the chemical environment and different creep deformation cannot be realized, and the equipment system is expensive. Theoretically, the method for acquiring the secondary oxide skin in the high-temperature high-pressure steam service environment is to directly add a test pipeline on production equipment, such as: a test pipeline is additionally arranged on a power station boiler in Europe, and the practicability of a new material is verified; the method comprises the steps of obtaining the simulation test result on a test bed of simulation service equipment meeting temperature and pressure conditions. The realization difficulty of the two is very big, and the cost is high.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for obtaining a sample for reoxidation analysis in a steam service environment.
The method for obtaining the sample for reoxidation analysis in the steam service environment comprises the following steps:
1) carrying out steam oxidation on the material through water steam to obtain a primary oxidation sample;
2) according to the requirements of simulation analysis, mechanical cutting, grinding or electric spark cutting is adopted to remove part or all of the surface oxide layer, and the peeling conditions of different oxide layers are simulated;
3) carrying out high-temperature creep loading on the material treated in the step 2) in a protective gas environment;
4) carrying out steam oxidation on the material treated in the step 3) again to obtain a reoxidation analysis sample in a simulated steam service environment;
wherein, H is adopted in the step 1)2O steam, using heavy oxygen water (H) in step 4)2 18O) steam to distinguish the two oxidation products.
Further, the steam oxidation in the step 1) and the step 4) is suitable for steam oxidation under any temperature and pressure combination.
Further, the high-temperature creep loading in the step 3) is suitable for creep loading under any combination of temperature, load and loading time.
The invention regards the process of 'oxide layer growth-spalling' as the oxidation process under the condition of constant creep damage, so that the steam oxidation process of creep-oxidation interaction can be decomposed into the oxidation process after creep. On the basis, the invention provides a method for obtaining a sample for reoxidation analysis under a steam service environment, which comprises the steps of steam oxidation, stripping of part or all of primary oxide skin, high-temperature creep and steam reoxidation.
The invention has the beneficial effects that:
the method of the invention decomposes the complex process which is difficult to realize into the process of combined action of chemistry and high-temperature creep, and can realize the work which can be finished by the original complex experiment through two simple experimental works.
By analyzing the sample obtained by the method, the oxidation resistance of the material can be evaluated more scientifically and reasonably, and reliable basis is provided for development and evaluation of the oxidation resistant material and optimization design of the oxidation resistant part.
Drawings
FIG. 1 is a schematic structural diagram of a high-temperature high-pressure reaction kettle, wherein a is a sectional view and b is a top view.
FIG. 2 is a schematic diagram of a high temperature creep machine.
FIG. 3 is a schematic view of a high temperature creep machine furnace.
FIG. 4 is a schematic view of high temperature creep machine specimen loading.
FIG. 5 is a schematic view of a sample.
FIG. 6 is a 600 ℃ creep rupture stress-life time curve for a standard specimen.
Description of reference numerals: 1-upper pull rod, 2-screw-pin joint, 3-taper sleeve, 4-sample, 5-quartz glass tube, 6-lower pull rod, 7-upper chuck, 8-lower chuck, 9-extension plate, 10-furnace plug, 11-heating furnace, 12-gasket, 13-displacement meter, 14-through hole, 15-upright column, 16-lower spherical connecting seat, 17-hand wheel, 18-control console, 19-pressure gauge, 20-safety valve, 21-main bolt, 22-kettle body flange, 23-kettle body, 24-silicon carbide electric heating furnace, 25-sampling tube, 26-heating power socket, 27-temperature measuring element, 28-kettle cover, 29-needle valve, 30-temperature measuring sleeve, 31-cooling coil, 32-a discharge valve, 33-a discharge port, 34-an air inlet (air outlet), 35-a cooling water inlet, 36-a sampling port, 37-a handle and 38-a cooling water outlet.
Detailed Description
The invention is further described with reference to the following figures and specific embodiments. It should be emphasized that the following description is merely exemplary in nature and is not intended to limit the scope of the invention or its application.
Example 1
The research problem is as follows: material super304H, an oxidation mechanism associated with steam reoxidation after initial scale crust spalling at 600 c, 20MPa steam environment, creep stress level of 105MPa, and 50% creep damage (corresponding to about 5 ten thousand hours of run time).
The method for obtaining the sample for reoxidation analysis in the steam service environment comprises the following steps:
1) as shown in FIG. 1 a-FIG. 1b, the autoclave is first oxidized with oxygen at high temperature H2The O vapor steam oxidizes sample 4. Oxygenation-simulated oxidation is a widely used method for simulating steam oxidation by accelerated oxidation. The oxygen addition is determined according to an oxidation time-weight gain curve of Super304H at 600 ℃ and 20MPa, the oxidation degree is about 1500h under the oxygen addition of 800ppb, and a single oxidation scale phase obtained by running for 5 ten thousand hours in a steam environment at 600 ℃ and 20MPaWhen the temperature is higher than the set temperature. The creep damage of the oxidized sample can be ignored, namely the initial oxidized sample without the creep damage effect is obtained.
The working process of the high-temperature high-pressure reaction kettle for steam oxidation is as follows:
① A control sample (for determining the thickness of the surface scale) and sample 4 of the same shape were first fixed in the vessel 23, the vessel lid 28 was closed, and the main bolt 21 was tightened.
② connecting the metal pipes corresponding to the interfaces.
③ closing the discharge valve 32 at the bottom of the reaction kettle, opening the needle valve 29 on the reaction kettle, connecting the needle valve 29 with a vacuum pump, opening the vacuum pump to pump out the gas in the reaction kettle, closing the needle valve 29 to make the kettle in vacuum state with vacuum degree of 10-3～10-4Pa。
④ 200ml of oxygen-containing 800ppb H2O is injected into the reaction vessel through the gas inlet (outlet) port 34, and the gas inlet (outlet) port 34 is closed.
⑤ the circulating cooling water pump is started, then the main control heating switch is turned on, the heating temperature is set at 600 ℃ to heat the reaction kettle, the steam is kept at 600 ℃ and the pressure is kept at 20MPa through the safety valve 20.
⑥ the test was stopped after 1500h, the heating switch was turned off to lower the temperature of the autoclave to room temperature, and then the circulating cooling water pump was turned off.
⑦ the gas inlet (outlet) 34 on the reactor is opened to communicate the inside of the reactor with the outside, the discharge valve 32 at the bottom of the reactor is unscrewed to discharge the water in the reactor.
⑧ break the metal tubes corresponding to each interface.
⑨ when the water no longer flows out, a nitrogen bottle is connected with the air inlet (air outlet) 34 on the reaction kettle, then nitrogen is introduced to completely dry the water in the reaction kettle, purging is carried out for about 2min, and the nitrogen is closed.
⑩ the main bolt 21 is unscrewed and the kettle cover 28 is removed and fixed.
2) Cutting the comparison sample along the symmetrical plane by adopting electric spark cutting, grinding the cut plane to be flat, measuring the thickness of the surface oxidation layer under an optical microscope or a scanning electron microscope, and removing the oxidation layer on the surface of the sample 4 according to the measured value.
3) Carrying out creep loading on the sample 4 treated in the step 2) under a protective gas environment, wherein a high-temperature creep machine is shown in figures 2-4: the heating furnace 11 of the creep machine is a hollow tube furnace, protective gas such as helium, argon and the like is filled in the hollow tube furnace, the upper end of a sample 4 is connected with an upper pull rod 1 through a thread-pin joint 2 at the upper side, and the lower end of the sample is connected with a lower pull rod 6 through a thread-pin joint 2 at the lower side, so that the sample is installed in the heating furnace 11 and is covered by a quartz glass tube 5; the upper screw-pin joint 2 is connected with the upper end of an extension plate 9 through an upper taper sleeve 3 and an upper chuck 7, the lower screw-pin joint 2 is connected with the extension plate 9 through a lower taper sleeve 3 and a lower chuck 8, and the lower end of the extension plate 9 is connected with a displacement meter 13; the upper end and the lower end of the heating furnace 2 are respectively provided with a furnace plug 10, and a gasket 12 is arranged to reduce the leakage of protective gas and keep the sealing performance in the furnace; the protective gas can be introduced through the through-hole 14 in the lower tie rod 6. The lower end of the lower pull rod 6 is connected with a lower spherical connecting seat 16, and the lower end of the lower spherical connecting seat 16 is connected with a hand wheel 17.
The temperature in the heating furnace 11 is 600 ℃ of steam oxidation temperature, the protective gas is argon (normal pressure), and the creep deformation machine transfers the loaded load to the sample 4 through the upper pull rod 1, the lower pull rod 6 and the upper and lower screw-pin joints 2. In the test process, due to the influence of high-temperature creep, the test sample 4 can be elongated, the elongation of the test sample 4 is transmitted to a displacement meter 13 fixed at the lower end of the extension plate 9 through the extension plate 9, and the displacement meter 13 transmits the measured elongation to a computer for recording. And a thallium balancer is arranged at the top of the high-temperature creep machine and connected with the leveling machine, and the leveling machine is controlled by the control console 18 to level.
The use and the working process of the high-temperature creep machine are as follows:
① the sample 4 is connected by the upper pull rod 1, the lower pull rod 6, the upper and lower screw-pin joints 2.
② the upper and lower screw-pin joints 2 are connected with the extension plate 9 through the upper and lower taper sleeves 3, the upper chuck 7 and the lower chuck 8.
③ binding the thermocouple on the upper and lower screw-pin joints 2 (or the corresponding positions connected with the upper and lower pull rods 1 and 6).
④ the heating furnace 11 is put down slowly, the furnace stopper 10 is blocked, argon gas as protective gas is introduced, the protective gas is always injected when the sample 4 is taken out in the whole creep process, and the sample 4 is ensured not to be oxidized by air.
⑤ test parameters are set by a computer, the test temperature is 600 ℃, the temperature rise rate is 3 ℃/min, the heat preservation time is 120min (the heat preservation aims at eliminating the temperature difference inside the sample) and the applied stress is 130MPa, the creep stress is determined by increasing the stress and accelerating the creep according to the creep rupture stress-service life time at 600 ℃ determined by a standard sample and the creep loading load is determined according to the actual section of the sample according to the creep isothermal extrapolation method, the accelerated creep stress is equivalent to the creep damage of 105MPa and 50000h in the test of about 4000h, and the stress value is about 130 MPa.
⑥ the switch of the heating furnace 11 is turned on to start heating.
⑦ when the incubation is finished, the loading is started.
⑧, removing load, turning off power supply of the heating furnace, and cooling the temperature of the heating furnace to room temperature in protective gas environment.
⑨ the protective gas was turned off and sample 4 was removed.
4) Finally, the sample 4 after high-temperature creep deformation is put into a high-temperature high-pressure reaction kettle and is treated with heavy oxygen water (H) at the high temperature of 800ppb2 18And O) carrying out steam oxidation again in a steam environment, wherein the operation process and conditions are the same as those of the primary steam oxidation in the step 1), so that a steam reoxidation analysis sample after the primary oxidation layer is stripped in a simulated steam service environment is obtained. By using a container containing18H with O of 800ppb2 18O is utilization of18O2-Distinguishing H2O in O2-The oxidized products can thus be easily identified by means of the relevant spectral analysis tools.
Claims (3)
1. The method for obtaining the sample for reoxidation analysis in the steam service environment is characterized by comprising the following steps of:
1) carrying out steam oxidation on the material through water steam to obtain a primary oxidation sample;
2) according to the requirements of simulation analysis, mechanical cutting, grinding or electric spark cutting is adopted to remove part or all of the surface oxide layer, and the peeling conditions of different oxide layers are simulated;
3) carrying out high-temperature creep loading on the material treated in the step 2) in a protective gas environment;
4) carrying out steam oxidation on the material treated in the step 3) again to obtain a reoxidation analysis sample in a simulated steam service environment;
wherein, H is adopted in the step 1)2O steam, using heavy oxygen water (H) in step 4)2 18O) steam to distinguish the two oxidation products.
2. The method of claim 1, wherein the steam oxidation in step 1) and step 4) is suitable for steam oxidation at any combination of temperature and pressure.
3. The method of claim 1, wherein the high temperature creep loading in step 3) is applied to creep loading at any combination of temperature, load and loading time.
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Citations (5)
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| JPH08201253A (en) * | 1995-01-23 | 1996-08-09 | Toshin Kogyo Kk | High-temperature testing device |
| CN1174893A (en) * | 1996-04-16 | 1998-03-04 | 欧洲塞扎斯“锆”公司 | Zirconium-based alloy which is resistant to creep and to corrosion by water and steam, manufacturing process and use in nuclear reactor |
| KR20010086816A (en) * | 2000-03-03 | 2001-09-15 | 이종훈 | Small punch creep test device with small specimen |
| CN103234835A (en) * | 2013-04-28 | 2013-08-07 | 华北电力大学 | Method and system for realizing interaction of high-temperature steam oxidation and high-temperature creep |
| CN105372146A (en) * | 2015-12-22 | 2016-03-02 | 上海锅炉厂有限公司 | Testing device and method for high temperature oxidation properties of material under stress action |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH08201253A (en) * | 1995-01-23 | 1996-08-09 | Toshin Kogyo Kk | High-temperature testing device |
| CN1174893A (en) * | 1996-04-16 | 1998-03-04 | 欧洲塞扎斯“锆”公司 | Zirconium-based alloy which is resistant to creep and to corrosion by water and steam, manufacturing process and use in nuclear reactor |
| KR20010086816A (en) * | 2000-03-03 | 2001-09-15 | 이종훈 | Small punch creep test device with small specimen |
| CN103234835A (en) * | 2013-04-28 | 2013-08-07 | 华北电力大学 | Method and system for realizing interaction of high-temperature steam oxidation and high-temperature creep |
| CN105372146A (en) * | 2015-12-22 | 2016-03-02 | 上海锅炉厂有限公司 | Testing device and method for high temperature oxidation properties of material under stress action |
Non-Patent Citations (2)
| Title |
|---|
| Effect of exposure in steam or argon on the creep properties of Ni-based alloys;S. Dryepondt*等;《Materials and Corrosion》;20121015;第63卷(第10期);全文 * |
| 耐热钢高温蒸汽氧化行为及控制技术的研究进展;夏铁锋等;《腐蚀科学与防护技术》;20150315;第27卷(第2期);全文 * |
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