Method for evaluating hydrogen resistance of material
阅读说明：本技术 材料抗氢性能的评价方法 (Method for evaluating hydrogen resistance of material ) 是由 许述剑 刘小辉 屈定荣 单广斌 于 2018-09-03 设计创作，主要内容包括：本发明涉及一种材料抗氢性能的评价方法,主要解决现有技术中尚无材料抗氢性能的评价方法的问题。本发明通过采用一种材料抗氢性能的评价方法,通过确定实验工艺条件、测量充氢前后材料的塑性损失和强度损失、分析充氢前后材料的组织与断口形貌、计算材料扩散系数,对临氢设备材料抗氢性能进行综合评价,从而指导装置正确开展停工过程设备恒温脱氢处理操作的技术方案较好地解决了上述问题,可用于材料抗氢性能的评价中。(The invention relates to a method for evaluating the hydrogen resistance of a material, which mainly solves the problem that no method for evaluating the hydrogen resistance of the material exists in the prior art. The invention adopts an evaluation method of the hydrogen resistance of the material, comprehensively evaluates the hydrogen resistance of the material of the hydrogen-contacting equipment by determining experimental process conditions, measuring the plasticity loss and the strength loss of the material before and after hydrogen charging, analyzing the morphology of the tissue and the fracture of the material before and after hydrogen charging and calculating the diffusion coefficient of the material, thereby guiding a device to correctly carry out the technical scheme of constant-temperature dehydrogenation treatment operation of the equipment in the shutdown process, better solving the problems and being applicable to the evaluation of the hydrogen resistance of the material.)
1. A method for evaluating the hydrogen resistance of a material comprises the following steps:
(1) determining experimental process conditions for simulating the operation environment of the hydrogen equipment, and carrying out hydrogen charging and dehydrogenation experiments of the material at different temperatures and pressures;
(2) measuring the plasticity loss and the strength loss of the material before and after hydrogen charging, carrying out an experiment of charging the material at the temperature and the pressure for a specific period of time, carrying out a slow material stretching experiment, and measuring the plasticity loss and the strength loss of the material before and after hydrogen charging, standing at room temperature and heating at different temperatures for a certain period of time;
(3) analyzing the structure and fracture morphology of the material before and after hydrogen charging;
(4) calculating H diffusion coefficient of material, measuring I-T curve by electrochemical workstation, and using formula
(5) And (4) comprehensively evaluating, and comprehensively analyzing the plasticity loss and strength loss of the material, the morphology of the tissue and the fracture and the H diffusion coefficient under different temperatures and pressures to obtain the hydrogen resistance of the material.
2. The method for evaluating the hydrogen resistance of a material according to claim 1, wherein in the step (1), the experiments of charging hydrogen and dehydrogenating hydrogen at 200 ℃, 300 ℃, 400 ℃ and 20MPa, respectively, are performed on the material.
3. The method for evaluating the hydrogen resistance of the material according to claim 1, wherein in the step (2), experiments of charging the material with hydrogen for 100 hours at 200 ℃, 300 ℃, 400 ℃ and 20MPa are respectively carried out, an electrohydraulic servo fatigue test system is adopted to carry out a slow tensile experiment of the material, and the plastic loss and the strength loss of the material are measured before charging, after placing for 100 hours at room temperature, heating for 10 hours at 200 ℃, heating for 10 hours at 300 ℃ and heating for 10 hours at 400 ℃.
4. The method for evaluating the hydrogen resistance of the material according to claim 1, wherein in the step (3), the changes of the texture morphology and the fracture morphology of the material before and after hydrogen charging are observed by using an optical microscope and a scanning electron microscope.
5. The method for evaluating the hydrogen resistance of a material according to claim 1, wherein in the step (4), the solubility of hydrogen and the residual hydrogen content are measured by a hydrogen meter.
6. The method for evaluating the hydrogen resistance of a material according to claim 1, wherein an I-T curve is measured using an electrochemical workstation, and the time at which It/Imax is 0.63, i.e., T, is obtained from the I-T curve0.63Using the formula
7. The method for evaluating the hydrogen resistance of the material according to claim 1, wherein in the step (2), an electro-hydraulic servo fatigue test system is adopted to perform a slow tensile test on the material.
8. The method for evaluating hydrogen resistance of a material according to claim 1, wherein the material is a metallic material.
Technical Field
The invention relates to a method for evaluating hydrogen resistance of a material, and belongs to the technical field of petroleum and natural gas engineering.
Background
Equipment operated under high temperature, high pressure and hydrogen environment faces the harm of hydrogen damage caused by hydrogen permeating into steel, so that the strength of the steel is reduced, and even the equipment is damaged. Hydrogen damage includes two forms, the first of which is "hydrogen corrosion," i.e., the chemical reaction of carbon and hydrogen in steel at high temperature to form methane, resulting in decarburization and internal cracking of the steel. Another form is "hydrogen embrittlement" which is characterized by a decrease in ductility and an increase in notch sensitivity in steel below 149 ℃ after hydrogen diffusion into the steel. At (maximum supersaturated hydrogen concentration allowed for the walls of the equipment enclosure that does not cause crack propagation below 149 ℃ is defined as the safe hydrogen concentration Cs. if the initial hydrogen concentration CR at the end of an operating cycle, at the beginning of shutdown of a hydrocracking reactor, exceeds the safe hydrogen concentration Cs, then special measures are taken during the shutdown sequence of the reactor to remove as much supersaturated hydrogen from the enclosure walls as possible so that the reactor enclosure walls contain hydrogen at a concentration below 149 ℃ that will lower the safe hydrogen concentration Cs.
At present, the unplanned shutdown times and shutdown days of a hydrogenation device of an oil refining enterprise are obviously increased, and hydrogen damage of equipment operated under high-temperature, high-pressure and hydrogen-contacting environments is a main reason. Apart from the choice of high-quality steel and the strict control of the quality of manufacture, rational operation is also an important aspect, in particular the dehydrogenation process. Therefore, establishing a method for evaluating the hydrogen resistance of the material and developing the research on constant-temperature dehydrogenation of a hydrogenation device are fundamental methods for solving the problems.
In 2015, the petrochemical refining unit is unplanned to be shut down 21 times, the number of shut-down days is 159 days, and the unplanned shut-down time of the hydrogenation unit is 9 times, and is 42.8%. Compared with the year 2012 and 2014, the unplanned shutdown times of the hydrogenation unit in the year 2014 and 2016 are increased by 100%, and the shutdown days are increased by 100%, wherein the units with the unplanned shutdown times being increased more are hydrocracking and diesel hydrogenation. The equipment problem is the main factor causing the unplanned shutdown of the hydrogenation unit, and is concentrated on the corrosion of the high-pressure heat exchanger, air cooling, units, pumps and equipment pipelines. Since hydrogen damage occurs mainly in critical equipment and pipelines at high temperature parts, such as reactors, high-pressure heat exchangers, reaction effluent pipelines and the like, the result is often unplanned shutdown and even fire explosion accidents. Therefore, establishing a material hydrogen resistance performance evaluation method, researching the necessity of constant temperature dehydrogenation of the hydrogenation device is an important process for identifying large risks, and has positive significance for preventing and controlling the large risks of the Chinese petrochemical hydrogenation device.
Disclosure of Invention
The invention aims to solve the technical problem that no method for evaluating the hydrogen resistance of the material exists in the prior art, provides a novel method for evaluating the hydrogen resistance of the material, and has the advantage of accurate evaluation result.
In order to solve the problems, the technical scheme adopted by the invention is as follows: a method for evaluating the hydrogen resistance of a material comprises the following steps:
(1) determining experimental process conditions for simulating the operation environment of the hydrogen equipment, and carrying out hydrogen charging and dehydrogenation experiments of the material at different temperatures and pressures;
(2) measuring the plasticity loss and the strength loss of the material before and after hydrogen charging, carrying out an experiment of charging the material at the temperature and the pressure for a specific period of time, carrying out a slow material stretching experiment, and measuring the plasticity loss and the strength loss of the material before and after hydrogen charging, standing at room temperature and heating at different temperatures for a certain period of time;
(3) analyzing the structure and fracture morphology of the material before and after hydrogen charging;
(4) calculating H diffusion coefficient of material, measuring I-T curve by electrochemical workstation, and using formula
(5) And (4) comprehensively evaluating, and comprehensively analyzing the plasticity loss and strength loss of the material, the morphology of the tissue and the fracture and the H diffusion coefficient under different temperatures and pressures to obtain the hydrogen resistance of the material.
In the above technical solution, preferably, in the step (1), the experiment of hydrogen charging and dehydrogenation of the material at 200 ℃, 300 ℃, 400 ℃ and 20MPa is performed.
In the above technical solution, preferably, in the step (2), the experiments of charging hydrogen for 100 hours at 200 ℃, 300 ℃, 400 ℃ and 20MPa are respectively carried out, the slow tensile experiment of the material is carried out by adopting an electrohydraulic servo fatigue test system, and the plasticity loss and strength loss of the material are measured before charging hydrogen, after placing for 100 hours at room temperature, heating for 10 hours at 200 ℃, heating for 10 hours at 300 ℃ and heating for 10 hours at 400 ℃.
In the above technical solution, preferably, in the step (3), an optical microscope and a scanning electron microscope are used to observe changes of the material texture morphology and the fracture morphology before and after hydrogen charging.
In the above technical solution, preferably, in the step (4), the solubility of hydrogen and the residual hydrogen content are measured by a hydrogen meter.
In the above technical solution, preferably, the electrochemical workstation is used to measure the I-T curve, and It/Imax is 0.63 time, i.e. T0.63Using the formula
In the above technical scheme, preferably, in the step (2), an electro-hydraulic servo fatigue test system is adopted to perform a material slow-stretching experiment.
In the above technical solution, preferably, the material is a metal material.
The invention comprehensively evaluates the hydrogen resistance of the material of the equipment in process of shutdown by determining experimental process conditions, measuring the plasticity loss and the strength loss of the material before and after hydrogen charging, analyzing the tissue and the fracture morphology of the material before and after hydrogen charging and calculating the H diffusion coefficient of the material, thereby guiding the device to correctly carry out the operation of constant-temperature dehydrogenation treatment of the equipment in the process of shutdown, avoiding the unplanned shutdown of the equipment caused by hydrogen damage of the equipment in process of shutdown and obtaining better technical effect.
The present invention will be further illustrated by the following examples, but is not limited to these examples.
Detailed Description
[ example 1 ]
A method for evaluating the hydrogen resistance of a material comprises the following steps:
1. determining experimental process conditions (temperature, pressure) for simulating the operation environment of the hydrogen equipment
According to the actual working environment of the equipment, the hydrogen charging and dehydrogenation experiments of the material are generally carried out under the conditions which can be achieved by the test equipment, namely 200 ℃, 300 ℃, 400 ℃ and 20MPa respectively.
2. Measurement of plasticity and strength loss of material before and after hydrogen charging
The method comprises the following steps of respectively carrying out experiments of charging hydrogen for 100 hours at 200 ℃, 300 ℃, 400 ℃ and 20MPa, carrying out slow tensile experiments on the materials by adopting an electro-hydraulic servo fatigue test system (MTS), and measuring the plastic loss and strength loss of the materials which are placed at room temperature for 100 hours before and after charging hydrogen, heated at 200 ℃ for 10 hours, heated at 300 ℃ for 10 hours and heated at 400 ℃ for 10 hours.
3. Analyzing the structure and fracture morphology of the material before and after hydrogen charging
And observing the change of the material texture morphology and the fracture morphology before and after hydrogen charging by adopting an optical microscope and a scanning electron microscope (zeiss auriga).
4. Calculation of the H diffusion coefficient of a Material
Measuring the I-T curve by using an electrochemical workstation, wherein It/Imax is 0.63 time, i.e. T0.63Using the formulaSolving the diffusion coefficient D of the material H; wherein I is the current density in units of A (amperes); t is time, unit S (seconds); l is the thickness of the test material in m (meters); t is t0.63To achieve a time at which It/Imax is 0.63, the unit is S (seconds); d is the diffusion coefficient of material H, unit m2S; the solubility of hydrogen and the residual hydrogen content were measured with a hydrogen meter (G4 PHOENIX).
5. Comprehensive evaluation
And comprehensively analyzing the plasticity loss and the strength loss of the material, the morphology of the tissue and the fracture and the H diffusion coefficient under different temperatures and pressures to obtain the hydrogen resistance of the material.
[ example 2 ]
Evaluation of hydrogen resistance of 15CrMoR was carried out according to the conditions and procedure described in example 1.
1. Hydrogen charging for 100h at the pressure of between 200 and 20MPa of 15CrMoR and different heating dehydrogenation treatment
The 15CrMoR is ideal medium-temperature hydrogen-resistant steel because the low-carbon steel is added with alloy elements such as Cr, Mo and the like. The yield strength in the delivered state was 503MPa, and the elongation was 15%. The mechanical property of the 15CrMoR material in the experiment is higher than that given in the general material handbook, the tensile strength Rm of the 15CrMoR with the general specification is generally 515-550MPa, and is about 770MPa in the experiment, because the material in the delivery state is not subjected to annealing heat treatment. The strength and the elongation of the material are obviously reduced after the material is charged with hydrogen for 100 hours under the condition of 200-20 MPa. After the heat-insulation board is placed at room temperature, the heat-insulation board recovers to a certain extent, but the recovery amplitude is small, and the heat-insulation board recovers again under the heating condition of 200 ℃. But the material performance can not be recovered after being heated at 400 ℃, and the material performance is not obviously different from that of being heated at 200 ℃. This may result from experimental error and may be the effect of 400 ℃ heating on material properties. The hydrogen diffusion coefficient of the 15CrMoR material at room temperature is slightly lower than that of Q345R, the performance of the material cannot be completely recovered after the material is placed at room temperature, the material cannot be completely recovered after the material is heated at 200 ℃ and at 400 ℃ for dehydrogenation, and irreversible hydrogen damage caused by long-time hydrogen charging at 200 ℃ is about 12-17%. Compared with Q345, the 15CrMoR can cause irreversible hydrogen damage after being charged with hydrogen for a long time at 200 ℃ under 20MPa, and the Q345 is superior to the 15CrMoR in terms of hydrogen damage resistance. This is because the higher the strength, the more the second phase in the material is, and hydrogen damage is also likely to occur. The hydrogen charging at 200-20 MPa for 100h causes the unrecoverable hydrogen induced plasticity loss to be about 12-18%, which is higher than the unrecoverable hydrogen induced plasticity loss of Q345 under the same conditions. The results are shown in Table 1.
TABLE 115 CrMoR tensile data after 200 ℃ Hydrogen Charge and dehydrogenation
2. 15CrMoR 300-20 MPa hydrogen charging 100h and different heating dehydrogenation treatment
Under the condition of charging hydrogen at 300 ℃, the performance reduction and recovery rule of the 15CrMoR material are similar to those of the 15CrMoR material under the condition of charging hydrogen at 200 ℃. The stress of the material is reduced by 4.6 percent and the elongation is reduced by 30 percent when the material is charged with hydrogen at 300 ℃ and 20MPa for 100 hours. The strength recovery is obvious after the steel is heated at 200 ℃ for 2 hours, the plastic damage is recovered to 28 percent from 30 percent, 26 percent from 400 ℃ for 2 hours, and 22 percent from 400 ℃ for 10 hours, but the strength is basically kept unchanged. The irreversible hydrogen damage caused by the hydrogen charging at 300 ℃ and 20MPa is 22-28 percent, which is obviously increased compared with 11.8 percent when the hydrogen charging is carried out at 200 ℃. A somewhat similar situation compared to Q345R, namely that hydrogen damage is worse at 300 c than at 200 c. The results are shown in Table 2.
TABLE 215 CrMoR tensile data after 300 ℃ Hydrogen Charge and dehydrogenation
3. Performance of 15CrMoR material in hydrogen charging-constant temperature-cooling mode
After the hydrogen charging at 300 ℃, the reheating constant temperature dehydrogenation treatment is carried out to test the recovery condition of the material. And (3) filling hydrogen for 100h for each material at the temperature of 300 ℃ and the pressure of 20MPa, then discharging the hydrogen in the autoclave, and cooling after heat preservation for 24 h. The performance of the experimental material in this hydrogen charging-constant temperature-cooling mode was compared with the performance of the material in each case after the hydrogen charging and constant temperature dehydrogenation process at 300 ℃. The results are shown in Table 3.
TABLE 315 comparison of Material Properties after different treatments of CrMoR
The plastic loss of the material after the 15CrMoR hydrogen charging-constant temperature-cooling mode is 10-18 percent, which is much smaller than the hydrogen damage caused by immediately cooling and then discharging hydrogen after charging hydrogen at 300 ℃. Moreover, the hydrogen damage of the 15CrMoR material after being charged with hydrogen at 300 ℃ is irreversible, the plastic loss can not be well recovered even being heated at 400 ℃ for 10 hours, and the plastic loss at the lowest time is still about 22 percent. The effect of all the hydrogen firstly released after the cooling mode is far better than the effect of reheating to remove the hydrogen.
4. Morphology observation of 15CrMoR tissues and fractures before and after hydrogen charging
SEM microscopic analysis of the fracture of the sample after 15CrMoR is charged with hydrogen shows that the microstructure of the sample before 15CrMoR is charged with hydrogen consists of ferrite and lamellar pearlite, and the pearlite accounts for a very high ratio; the microstructure of the sample is not changed obviously after being charged with hydrogen. The SEM microscopic fracture image shows that the fracture of the dimple is mainly combined with the quasi-cleavage fracture before the hydrogen charging, and after the hydrogen charging, the morphology proportion of the quasi-cleavage fracture is increased, the size of the fracture of the dimple is reduced, and secondary cracks are increased.
5. 15CrMoR material hydrogen permeation experimental result
In the experiment, the charging was started at 9190s, the curve was measured, and the charging rising curve was considered to have reached a plateau at 10970 s. Using formulas
D＝3.03×10-6cm2/s
The 15CrMoR material has better hydrogen resistance. The strength loss of the material under the hydrogen charging condition is small. The H diffusion coefficient of the 15CrMoR material is calculated to be about 3 multiplied by 10-6Is slightly lower than Q345, but there is no significant difference. H in the material also overflows relatively easily. In the dehydrogenation process, the material needs to be heated at 400 ℃ for 10 hours, so that the performance of the material can be well recovered. The material structure is a large-area pearlite structure and a small amount of ferrite structure, the microstructure is converted into a large-area pearlite structure after hydrogen charging, and the ferrite exists in a small part in gaps of the pearlite structure. The appearance ratio of the quasi-cleavage fracture is larger, the fracture size of the dimple is reduced, and secondary cracks are increased. The irreversible hydroplastic loss is between 22 and 28%.
[ example 3 ]
Evaluation of hydrogen resistance of 14Cr1MoR was carried out under the conditions and procedures described in example 1.
1. Hydrogen charging for 100h at the pressure of 200-20 MPa of 14Cr1MoR and different heating dehydrogenation treatments
The 14Cr1MoR is novel Cr-Mo hydrogen-resistant steel, the yield strength of the steel in a delivery state is about 380MPa, the tensile strength is about 680MPa, the elongation is 23%, and the steel has high strength and good ductility. The performance of the material is obviously reduced after 100 hours of hydrogen charging under the condition of 200-20 MPa, and the strength and the elongation rate are greatly reduced. The material property is greatly recovered after being heated at 200 ℃. The material performance is continuously recovered after the heating at 400 ℃, and the material performance is not obviously recovered after the heating at 400 ℃ for 10 hours. Under the heating condition of 400 ℃, the plastic damage of the material after 2 hours and 10 hours is respectively 11.6 percent and 11.2 percent, and the results are similar. Therefore, the irreversible hydrogen damage of the 14Cr1MoR steel material is 11-12% under the condition of hydrogen charging at 200 ℃. The hydrogen removal effect is better after the addition of 2 hours at 400 ℃. The results are shown in Table 4.
TABLE 414 tensile data of Cr1MoR after 200 ℃ Hydrogen charging and dehydrogenation
2. Hydrogen charging for 100h at the pressure of 300-20 MPa of 14Cr1MoR and different heating dehydrogenation treatments
The ductility of the 14Cr1MoR material is reduced seriously after the material is charged with hydrogen at 300 ℃, and the plasticity loss is 24.2 percent and is higher than 14.3 percent when the material is charged with hydrogen at 200 ℃. The material performance is better recovered under the heating condition of 200 ℃, the elongation of the material is obviously recovered after heating and dehydrogenation, and the material performance is not obviously recovered under the conditions of continuing heating for 2h and 10h at 400 ℃. After the material is heated for 2 hours at 400 ℃, the strength damage of the material reaches a small value of 3.5 percent, the elongation rate is also recovered to a good degree, and the plasticity loss is 16.9 percent. Therefore, the irreversible hydrogen damage of the 14Cr1MoR material under the condition of charging hydrogen at 300 ℃ is 12.6-16.9%, which is basically the same as the irreversible hydrogen damage of 11-12% under the condition of charging hydrogen at 200 ℃. The better dehydrogenation effect can be achieved under the condition of heating for 2h at 400 ℃. The results are shown in Table 5.
TABLE 514 tensile data of Cr1MoR after 300 ℃ Hydrogen charging and dehydrogenation
3. Performance of material in 14Cr1MoR hydrogen charging-constant temperature-cooling mode
After the hydrogen charging at 300 ℃, the reheating constant temperature dehydrogenation treatment is carried out to test the recovery condition of the material. And (3) filling hydrogen for 100h for each material at the temperature of 300 ℃ and the pressure of 20MPa, then discharging the hydrogen in the autoclave, and cooling after heat preservation for 24 h. The performance of the experimental material in this hydrogen charging-constant temperature-cooling mode was compared with the performance of the material in each case after the hydrogen charging and constant temperature dehydrogenation process at 300 ℃. The results are shown in Table 6.
TABLE 614 comparison of Material Properties after different treatments of Cr1MoR
The plastic loss of the material after the 14Cr1MoR hydrogen charging-constant temperature-cooling mode is 10-14%, which is much less than the hydrogen damage caused by immediately cooling and then discharging hydrogen after charging hydrogen at 300 ℃. The hydrogen damage of the 14Cr1MoR material after being charged with hydrogen at 300 ℃ is higher, but the plastic loss is well recovered when the material is heated at 400 ℃ for 10 hours, and the plastic loss at the lowest temperature is still about 13 percent. Therefore, for 14Cr1MoR, the effects of firstly releasing hydrogen, preserving heat for 24 hours and then cooling are similar to the effects of removing hydrogen by heating after charging hydrogen.
4. Morphology observation of structure and fracture before and after hydrogen charging of 14Cr1MoR
SEM microscopic analysis of the fracture of the sample after the 14Cr1MoR is charged with hydrogen shows that the microstructure of the sample before and after the 14Cr1MoR is charged with hydrogen consists of ferrite and lamellar pearlite. The microscopic fracture images of the pearlite-containing sheet mainly show the shapes of dimple fractures and partial cleavage fractures before hydrogen charging, and the crystal fracture shapes of partial pearlite-containing sheet lamellar tissues can be observed through amplification. The appearance of the fracture can be observed after the hydrogen is filled, the appearance of a large-area river-shaped cleavage fracture and a small-area dimple can be seen, and the material becomes brittle obviously.
5. 14Cr1MoR material hydrogen permeation experiment result
In the experiment, the hydrogen charge was started at 5700s, the curve was measured, and the hydrogen charge rising curve was considered to have reached a plateau at 12200 s. Using formulas
D＝2.08×10-6cm2/s。
14Cr1MoR is novel Cr-Mo hydrogen-resistant steel, the H diffusion coefficient is higher at room temperature, the elongation percentage can be reduced to 24.2% after the steel is charged with hydrogen at 300 ℃ and 20MPa, the material performance can be obviously recovered after heating, a better recovery effect can be achieved after the steel is heated for 2H-10H at 200 ℃ to 400 ℃, and the irreversible hydrogen induced plasticity loss can be recovered to 13%. The microstructure consists of ferrite and lamellar pearlite, and the fracture morphology mainly refers to the fracture morphology of a dimple and a partial cleavage fracture morphology. The appearance of the fracture can be observed after the hydrogen is filled, and the appearance of a large-area river-shaped cleavage fracture and a small-area dimple can be seen.
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