A method for measuring the elongation of high temperature tensile specimens

Abstract

The present invention relates to a method for determining the mechanical properties of metal materials in a high-temperature tensile test, and in particular to a method for determining the elongation of a high-temperature tensile test specimen. The test specimen is placed in a solution, and each time it is lowered by the same distance d, mm; a relationship curve between the total volume V of the solution and the sample immersed therein and the sample lowering distance d is drawn, if point A corresponds to a sample lowering distance d1, mm, and point B corresponds to a sample lowering distance d2, mm, then L=d2-d1; the original length of the sample is measured to be l0, mm, and the length of the two sections of the sample connected to form a sample is l1, mm, then the deformation amount of high-temperature tensile ΔL mm is ΔL=l1-l0; the original length L0 of the actual deformed part of the sample is L0=L-ΔL; then the elongation λ, %, can be obtained according to the elongation calculation formula, which is #imgabs0# The present invention can effectively and accurately determine the elongation of a high-temperature tensile test specimen.

Description

Technical Field

[0001] The invention relates to a method for measuring the mechanical properties of metal materials in a high-temperature tensile test, and in particular to a method for measuring the elongation of a high-temperature tensile test specimen. Background Art

[0002] Thermal simulation test machine is a physical property testing instrument used in the field of materials science. Thermal simulation test is an important means of conducting metallurgical material research using small specimens and thermal simulation test machine, and plays an important role in new product development and process optimization. The main function of thermal simulation test machine is to reproduce the physical process of materials (especially steel materials) being heated during preparation or hot processing, or being heated and stressed at the same time, to study the change law of the organization or performance of materials, to evaluate or predict the problems that arise in the preparation or heating process of materials, and to provide theoretical guidance and technical basis for formulating reasonable processing technology and developing new materials.

[0003] At present, in order to study the plastic properties of the ingot during the continuous casting process, a thermal simulation testing machine is generally used to heat the sample to a higher temperature range, keep it in the high temperature zone for a period of time, then lower it to a certain temperature, and finally stretch it at a certain stretching rate until the sample is broken. The cross-sectional area of ​​the sample after breaking is analyzed to obtain the cross-sectional shrinkage rate.

[0004] However, in addition to the cross-sectional shrinkage, the parameters that reflect the mechanical property of plasticity also include the elongation after fracture. The measurement of elongation is generally focused on the measurement of the elongation of tensile specimens at room temperature. Since the material has a certain fluidity under high temperature conditions, and when the specimen is heated by a thermal simulation test machine, the temperature distribution of the specimen has a certain gradient. Therefore, when the specimen is stretched and deformed, not the entire specimen participates in the deformation, which is more obvious on a resistance-type thermal simulation test machine. If the original length of the entire specimen is still used when calculating the elongation, a large error will inevitably occur.

[0005] Therefore, there is no effective method for calculating the elongation of high temperature tensile specimens. Since high temperature tensile specimens have the characteristics of uneven temperature and uneven deformation under high temperature conditions, the elongation of the specimen cannot be simply calculated by dividing the difference between the length of the specimen after breaking and the original length by the original length. A more effective and accurate method is needed to determine the elongation of high temperature tensile specimens. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the present invention provides a method for measuring the elongation of a high-temperature tensile specimen, which can effectively and accurately measure the elongation of a high-temperature tensile specimen.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for measuring the elongation of a high temperature tensile specimen, the method specifically comprising the following steps:

[0009] Step 1) Obtain samples through simulation experiments.

[0010] A rod-shaped cylinder is selected as a simulation specimen, and the simulation specimen is heated, kept warm, cooled, and then stretched according to a predetermined experimental plan using a thermal simulation testing machine until the specimen is broken to obtain a specimen broken into two sections.

[0011] The two sections of the sample are butted together to form a coaxial whole, and the two sections of the sample are joined by magnetization or adhesion to the state at the moment the sample is stretched and broken.

[0012] Step 2) Use a solution that does not react with the sample, take a container filled with a sufficient amount of solution, and place it on a horizontal surface. Place the axis of the two sections of the sample that have been docked in step 1 perpendicular to the liquid surface of the solution, and slowly place it into the solution in a direction perpendicular to the liquid surface of the solution.

[0013] During the insertion process, two methods can be used: one is to descend the same distance d, mm each time; the other is to descend the sample at a constant speed, with a descent speed of v, mm / s.

[0014] When the sample descends, record the rise of the solution level H, mm; the total volume of the solution and the sample immersed therein V, ml.

[0015] Step 3) Draw a relationship curve between the total volume V of the solution and the sample immersed therein and the sample falling distance d, or draw a relationship curve between the total volume V of the solution and the sample immersed therein and the sample falling time t in step 2.

[0016] When the sample is just immersed in the solution, the curve rises straightly. When the table-shaped part of the sample is immersed in the solution, the slope of the curve decreases. When the sample continues to descend to another section, the slope of the curve increases. Finally, the curve rises straightly again.

[0017] Step 4) Based on the curve analysis drawn in step 3, the curve is first differentiated to obtain a curve showing the relationship between the slope of the curve and the sample falling distance d or the slope of the curve and the sample falling time.

[0018] The cross-sectional area of ​​the sample immersed in the solution begins to decrease, that is, the sample enters the deformation zone, and this point is recorded as A. The point when the volume increment returns to a constant value is recorded as B.

[0019] It can be seen from the curve in the figure that the part between points A and B corresponds to the part of the sample where elongation and deformation occur. From this, the length of the actual deformed part of the sample can be determined, that is, the length L of the deformed part of the sample after stretching corresponds to the distance L, mm, that the sample enters into the solution during the process from A to B.

[0020] If point A corresponds to a sample drop distance of d1, mm, and point B corresponds to a sample drop distance of d2, mm, then

[0021] L=d2-d1 (1)

[0022] If point A corresponds to the sample falling time t1,s, and point B corresponds to the sample falling time t2,s, then

[0023] L = (t2 - t1) × v (2)

[0024] Step 5) Calculate the elongation of the sample after high-temperature stretching. Measure the original length of the sample l0, mm, and measure the length of the sample l1, mm after the two sections of the sample are joined together in step 1. Then the deformation ΔL mm after high-temperature stretching is

[0025] ΔL=l1-l0 (3)

[0026] Step 6) Calculation of the elongation of the high temperature tensile specimen. Based on the L and ΔL determined in steps 4 and 5, the original length L0 of the actual deformed portion of the specimen can be determined as

[0027] L0=L-ΔL (4)

[0028] According to the elongation calculation formula, the elongation λ, %, can be obtained as

[0029]

[0030] The elongation of the sample after high temperature stretching can be obtained by formula (5).

[0031] Compared with the existing method, the beneficial effects of the present invention are:

[0032] The present invention establishes a relationship curve between the volume increment caused by the sample being immersed in a solution and the sample descent distance or the sample uniform descent time, and accurately finds the point corresponding to the actual deformation of the sample, thereby accurately determining the actual deformation length of the high-temperature tensile sample, rather than taking the length of the entire sample as the original length to calculate the elongation. Under the condition of fully considering the uneven deformation of the high-temperature tensile sample, the elongation of the high-temperature tensile sample can be determined more reasonably and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1Schematic diagram of the relationship between the total volume V of the solution of the present invention and the sample immersed therein and the distance d from which the sample descends;

[0034] Figure 2 It is a schematic diagram of the relationship between the total volume V of the solution of the present invention and the sample immersed therein and the sample falling time t;

[0035] Figure 3 Schematic diagram of the relationship between the total volume increment ΔV of the solution of the present invention and the sample immersed therein and the descending distance d of the sample;

[0036] Figure 4 It is a schematic diagram of a curve showing the relationship between the total volume increment ΔV of the solution of the present invention and the sample immersed therein and the sample falling time t;

[0037] Figure 5 is a graph showing the relationship between the total volume V of the solution and the sample immersed therein and the descending distance d of the sample measured in Examples 1, 3 and 5 of the present invention;

[0038] Figure 6 is a graph showing the relationship between the total volume increment ΔV of the solution and the sample immersed therein and the descending distance d of the sample measured in Examples 1, 3 and 5 of the present invention;

[0039] Figure 7 is a graph showing the relationship between the total volume V of the solution and the sample immersed therein and the sample falling time t measured in Examples 2, 4 and 6 of the present invention;

[0040] Figure 8 It is a relationship curve between the total volume increment ΔV of the solution and the sample immersed therein and the sample falling time t measured in Examples 2, 4 and 6 of the present invention. DETAILED DESCRIPTION

[0041] The present invention discloses a method for determining the elongation of a high-temperature tensile specimen. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0042] A method for measuring the elongation of a high temperature tensile specimen, the method specifically comprising the following steps:

[0043] Step 1. Obtain the sample through simulation experiment. The simulation sample is a rod-shaped cylinder, and the simulation sample is heated, kept warm, and cooled according to the predetermined experimental plan by a thermal simulation test machine, and then stretched at 600-1400°C until the sample is broken, thereby obtaining a sample broken into two sections.

[0044] Based on the deformation behavior of the sample at high temperature, the sample is broken into two sections, one end of each section near the fracture is in a table shape, and the rest is in a cylindrical shape. The two sections of the sample are butted together to form a whole, and the two sections of the sample can be joined to the state of the sample at the moment of stretching and breaking by magnetization or adhesion.

[0045] Step 2. Take a container with enough solution and place it on a horizontal surface. The solution does not react with the sample. Place the axis of the two connected sample sections in step 1 perpendicular to the liquid surface of the solution and slowly place it in the solution in a direction perpendicular to the liquid surface of the solution. During the placement process, two methods can be used: one is to drop the same distance d, mm each time; the other is to drop the sample at a uniform speed, with a drop speed of v, mm / s.

[0046] When the sample descends, record the rise of the solution level H, mm; the total volume of the solution and the sample immersed in it, ml.

[0047] Step 3. Draw a curve of the relationship between the total volume of the solution and the sample immersed therein and the sample falling distance d, or the relationship between the total volume of the solution and the sample immersed therein and the sample falling time t in step 2, such as Figure 1 and Figure 2 shown.

[0048] When the sample is just immersed in the solution, the sample raises the liquid level, causing the solution volume to increase. The increase is the volume of the cylinder immersed in the solution. Since the cross section of the cylinder is equal everywhere, the curve rises in a straight line. When the table-shaped part of the sample is immersed in the solution, the cross section at this time gradually decreases as the sample descends, so the slope of the curve also decreases. When the sample continues to descend to another section, the cross section at this time gradually increases as the sample descends, so the slope of the curve also increases. Finally, the table-shaped part of the sample is completely immersed in the solution, and the increase in the solution volume is only affected by the volume of the cylinder immersed in the solution, and the curve rises in a straight line again.

[0049] Step 4. Based on the curve analysis drawn in step 3, the first-order differential of the curve is performed to obtain the relationship curve between the slope of the curve and the sample falling distance d or the slope of the curve and the sample falling time, such as Figure 3 and Figure 4 shown.

[0050] As can be seen from the figure, the curve value is constant at the beginning because the part of the sample immersed in the solution is a cylinder. When the part of the sample immersed in the solution is a cylinder, the total volume increment (volume increment) of the solution and the sample immersed therein is only related to the cross-section of the cylinder. Therefore, when the sample begins to be immersed in the solution, the volume increment is a constant value, but as the sample descends, the volume increment decreases, indicating that the cross-sectional area of ​​the sample immersed in the solution begins to decrease, that is, the sample enters the deformation zone, and this point is recorded as A. As the sample continues to be immersed in the solution, the volume increment gradually decreases and then gradually increases, and finally tends to a constant value, which corresponds to the change in the cross-sectional area of ​​the sample immersed in the solution. The point when the volume increment returns to a constant value is recorded as B.

[0051] It can be seen from the curve in the figure that the part between points A and B corresponds to the part of the sample where elongation and deformation occur. From this, the length of the actual deformed part of the sample can be determined, that is, the length L of the deformed part of the sample after stretching corresponds to the distance L, mm, that the sample enters into the solution during the process from A to B.

[0052] If point A corresponds to a sample drop distance of d1, mm, and point B corresponds to a sample drop distance of d2, mm, then

[0053] L=d2-d1 Formula (1)

[0054] If point A corresponds to the sample falling time t1,s, and point B corresponds to the sample falling time t2,s, then

[0055] L=(t2-t1)×v Formula (2)

[0056] Step 5. Calculate the elongation of the sample after high-temperature stretching. Measure the original length of the sample l0, mm, and measure the length of the sample l1, mm after the two sections of the sample are joined together in step 1. The deformation of the high-temperature stretching ΔLmm is

[0057] ΔL=l1-l0 Formula (3)

[0058] Step 6. Calculation of the elongation of the high temperature tensile specimen. Based on the L and ΔL determined in steps 4 and 5, the original length L0 of the actual deformed portion of the specimen can be determined as

[0059] L0=L-ΔL Formula (4)

[0060] According to the elongation calculation formula, the elongation λ, %, can be obtained as

[0061]

[0062] The elongation of the sample after high temperature stretching can be obtained by formula (5).

[0063] The present invention adopts the sample-displaced solution method to determine the elongation after fracture of the high-temperature tensile sample. The change in the cross-sectional area of ​​the deformed part of the high-temperature tensile sample on its axis reflects the change law of the volume increment generated by the sample displacing the solution, and can accurately find out the actual length of the deformed part of the sample after high-temperature stretching. Then, according to the actual elongation of the sample, the length of the actual deformed part of the sample is obtained, and then the elongation of the high-temperature tensile sample can be accurately determined.

[0064] [Example]

[0065] Embodiment 1:

[0066] Step 1: Obtain a sample through a simulation experiment. The selected material is a low-carbon steel, which is processed into a simulation sample with a size of Φ10×120mm cylinder.

[0067] The film was heated to 1300°C by a thermal simulation test machine, kept at this temperature for 5 minutes, then cooled to 1000°C at a rate of 3°C / s, and then kept at this temperature for 1 minute for stretching. The stretching rate was set to 1×10 -3 s -1 , until the sample is broken to obtain a sample broken into two pieces.

[0068] Based on the deformation behavior of the sample at high temperature, the sample is broken into two sections, one end of each section near the fracture is in a table shape, and the rest is in a cylindrical shape. The two sections of the sample are magnetized and butted together to form a whole.

[0069] Step 2: Take a container filled with sufficient water and place it on a horizontal surface. Place the axis of the two sections of the sample connected in step 1 perpendicular to the water surface and slowly place them in the solution. During the placement process, lower them by the same distance of 0.5m each time.

[0070] Step 3: Draw a curve of the relationship between the total volume of water and the part of the sample immersed in water and the distance the sample falls in step 2, such as Figure 5 shown.

[0071] Step 4: Based on the curve analysis drawn in step 3, perform first-order differentiation to obtain the relationship curve of the slope of the curve as the sample descends the distance d, such as Figure 6 shown.

[0072] From the curve, we can see that the coordinates of point A are (5.1, 78.5), and the coordinates of point B are (21.5, 78.5). Point A corresponds to a sample drop distance of 5.1 mm, and point B corresponds to a sample drop distance of 21.5 mm. According to formula (1), L = 16.4 mm.

[0073] Step 5: The original length of the sample is l0=120 mm, and the length of the sample formed by joining the two sections is l1=125 mm. The high-temperature tensile deformation ΔL=5 mm is obtained from formula (3), and the original length of the actual deformed part L0=11.4 mm is obtained from formula (4). According to formula (5), the elongation λ of the high-temperature tensile sample is 43.86%.

[0074] Embodiment 2:

[0075] Step 1: Obtain the sample through simulation experiment. The material is a low-carbon steel, which is processed into a simulation sample with a size of Φ10×120mm. It is heated to 1300℃ by a thermal simulation test machine, kept warm for 5 minutes, then cooled to 1000℃ at a rate of 3℃ / s, and then kept warm for 1 minute for stretching. The stretching rate is set to 1×10 -3 s -1 , until the sample is broken to obtain a sample broken into two pieces.

[0076] Based on the deformation behavior of the sample at high temperature, the sample is broken into two sections, one end of each section near the fracture is in a table shape, and the rest is in a cylindrical shape. The two sections of the sample are magnetized and butted together to form a whole.

[0077] Step 2: Take a container with sufficient water and place it on a horizontal surface. Place the two sections of the sample connected in step 1 with their axes perpendicular to the water surface and slowly place them in the solution. During the placement process, the sample descends at a constant speed, with a speed of v = 1 mm / s.

[0078] Step 3: Draw a curve of the relationship between the total volume of water and the part of the sample immersed in water and the sample descent time in step 2, such as Figure 7 shown.

[0079] Step 4: Based on the curve analysis drawn in step 3, perform first-order differentiation to obtain the relationship curve between the slope of the curve and the sample drop time t, such as Figure 8 shown.

[0080] From the curve, we can see that the coordinates of point A are (5.1, 78.5), and the coordinates of point B are (21.5, 78.5). Point A corresponds to a sample drop time of 5.1s, and point B corresponds to a sample drop time of 21.5s. According to formula (2), L = 16.4mm

[0081] Step 5: The original length of the sample is l0=120 mm, and the length of the sample formed by joining the two sections is l1=125 mm. The high-temperature tensile deformation ΔL=5 mm is obtained from formula (3), and the original length of the actual deformed part L0=11.4 mm is obtained from formula (4). According to formula (5), the elongation λ of the high-temperature tensile sample is 43.86%.

[0082] Embodiment 3:

[0083] Step 1: Obtain the sample through simulation experiment. The material is a low-carbon steel, which is processed into a simulation sample with a size of Φ10×120mm. It is heated to 1300℃ by a thermal simulation test machine, kept warm for 5 minutes, then cooled to 700℃ at a rate of 3℃ / s, and then kept warm for 1 minute for stretching. The stretching rate is set to 1×10 -3 s -1 , until the sample is broken, and a sample is obtained that is broken into two sections. Based on the deformation behavior of the sample at high temperature, the sample is broken into two sections, one end of each section near the fracture is in a table shape, and the rest is in a cylindrical shape. The two sections of the sample are magnetized and butted together to form a whole.

[0084] Step 2: Take a container filled with sufficient water and place it on a horizontal surface. Place the axis of the two sections of the sample that have been connected in step 1 perpendicular to the water surface and slowly place them in the solution. During the placement process, lower them by the same distance of 0.5 mm each time;

[0085] Step 3: Draw a curve of the relationship between the total volume of water and the part of the sample immersed in water and the distance the sample falls in step 2, such as Figure 5 shown.

[0086] Step 4: Based on the curve analysis drawn in step 3, perform first-order differentiation to obtain the relationship curve of the slope of the curve as the sample descends the distance d, such as Figure 6 As shown in the figure, the coordinates of point A are (3.5, 78.5), and the coordinates of point B are (15.5, 78.5). Point A corresponds to a sample drop distance of 3.5 mm, and point B corresponds to a sample drop distance of 15.5 mm. According to formula (1), L = 12.0 mm.

[0087] Step 5: The original length of the sample is l0=120 mm, and the length of the sample formed by joining the two sections is l1=123.2 mm. The high-temperature tensile deformation ΔL=3.2 mm is obtained from formula (3), and the original length of the actual deformed part L0=8.8 mm is obtained from formula (4). According to formula (5), the elongation λ of the high-temperature tensile sample is 36.4%.

[0088] Embodiment 4:

[0089] Step 1: Obtain the sample through simulation experiment. The material is a low-carbon steel, which is processed into a simulation sample with a size of Φ10×120mm. It is heated to 1300℃ by a thermal simulation test machine, kept warm for 5 minutes, then cooled to 700℃ at a rate of 3℃ / s, and then kept warm for 1 minute for stretching. The stretching rate is set to 1×10 -3 s -1, until the sample is broken, and a sample is obtained that is broken into two sections. Based on the deformation behavior of the sample at high temperature, the sample is broken into two sections, one end of each section near the fracture is in a table shape, and the rest is in a cylindrical shape. The two sections of the sample are magnetized and butted together to form a whole.

[0090] Step 2: Take a container with sufficient water and place it on a horizontal surface. Place the two sections of the sample connected in step 1 with their axes perpendicular to the water surface and slowly place them in the solution. During the placement process, the sample descends at a constant speed, with a speed of v = 1 mm / s.

[0091] Step 3: Draw a curve of the relationship between the total volume of water and the part of the sample immersed in water and the sample descent time in step 2, such as Figure 7 shown.

[0092] Step 4: Based on the curve analysis drawn in step 3, perform first-order differentiation to obtain the relationship curve between the slope of the curve and the sample drop time t, such as Figure 8 As shown. From the curve, the coordinates of point A are (3.5, 78.5), and the coordinates of point B are (15.5, 78.5). The falling time of point A is 3.5s, and the falling time of point B is 15.5s. According to formula (2), L = 12.0mm

[0093] Step 5: The original length of the sample is l0 = 120 mm, and the length of the sample formed by joining the two sections is l1 = 123.2 mm. The high-temperature tensile deformation ΔL = 3.2 mm is obtained by formula (3). The original length of the actual deformed part L0 = 8.8 mm is obtained by formula (4). The elongation λ of the high-temperature tensile sample is obtained by formula (5): 36.4%

[0094] Embodiment 5:

[0095] Step 1: Obtain the sample through simulation experiment. The material is a low-carbon steel, which is processed into a simulation sample with a size of Φ10×120mm. It is heated to 1300℃ by a thermal simulation test machine, kept warm for 5 minutes, then cooled to 1200℃ at a rate of 3℃ / s, and then kept warm for 1 minute for stretching. The stretching rate is set to 1×10 -3 s -1 , until the sample is broken, and a sample is obtained that is broken into two sections. Based on the deformation behavior of the sample at high temperature, the sample is broken into two sections, one end of each section near the fracture is in a table shape, and the rest is in a cylindrical shape. The two sections of the sample are magnetized and butted together to form a whole.

[0096] Step 2: Take a container filled with sufficient water and place it on a horizontal surface. Place the axis of the two sections of the sample that have been connected in step 1 perpendicular to the water surface and slowly place them in the solution. During the placement process, lower them by the same distance of 0.5 mm each time.

[0097] Step 3: Draw a curve of the relationship between the total volume of water and the part of the sample immersed in water and the distance the sample falls in step 2, such as Figure 5 shown.

[0098] Step 4: Based on the curve analysis drawn in step 3, perform first-order differentiation to obtain the relationship curve of the slope of the curve as the sample descends the distance d, such as Figure 6 The coordinates of point A are (6.3, 78.5), and the coordinates of point B are (16.5, 78.5). The distance of sample drop corresponding to point A is 6.3 mm, and the distance of sample drop corresponding to point B is 16.5 mm. According to formula (1), L = 10.2 mm

[0099] Step 5: The original length of the sample is l0=120 mm, and the length of the sample formed by joining the two sections is l1=122.5 mm. The high-temperature tensile deformation ΔL=2.5 mm is obtained from formula (3), and the original length of the actual deformed part L0=7.7 mm is obtained from formula (4). According to formula (5), the elongation λ of the high-temperature tensile sample is 32.5%.

[0100] Embodiment 6:

[0101] Step 1: Obtain the sample through simulation experiment. The material is a low-carbon steel, which is processed into a simulation sample with a size of Φ10×120mm. It is heated to 1300℃ by a thermal simulation test machine, kept warm for 5 minutes, then cooled to 1200℃ at a rate of 3℃ / s, and then kept warm for 1 minute for stretching. The stretching rate is set to 1×10 -3 s -1 , until the sample is broken, and a sample is obtained that is broken into two sections. Based on the deformation behavior of the sample at high temperature, the sample is broken into two sections, one end of each section near the fracture is in a table shape, and the rest is in a cylindrical shape. The two sections of the sample are magnetized and butted together to form a whole.

[0102] Step 2: Take a container with sufficient water and place it on a horizontal surface. Place the two sections of the sample connected in step 1 with their axes perpendicular to the water surface and slowly place them in the solution. During the placement process, the sample descends at a constant speed, with a speed of v = 1 mm / s.

[0103] Step 3: Draw a curve of the relationship between the total volume of water and the part of the sample immersed in water and the sample descent time in step 2, such as Figure 7 shown.

[0104] Step 4: Based on the curve analysis drawn in step 3, perform first-order differentiation to obtain the relationship curve between the slope of the curve and the sample drop time t, such as Figure 8As shown. From the curve, the coordinates of point A are (6.3, 78.5), and the coordinates of point B are (16.5, 78.5). Point A corresponds to a sample drop distance of 6.3s, and point B corresponds to a sample drop distance of 16.5s. According to formula (2), L = 10.2mm

[0105] Step 5: The original length of the sample is l0=120 mm, and the length of the sample formed by joining the two sections is l1=122.5 mm. The high-temperature tensile deformation ΔL=2.5 mm is obtained from formula (3), and the original length of the actual deformed part L0=7.7 mm is obtained from formula (4). According to formula (5), the elongation λ of the high-temperature tensile sample is 32.5%.

[0106] The present invention adopts the liquid displacement method, fully considering the characteristics of high-temperature tensile specimens under high temperature conditions, such as uneven temperature and uneven deformation. By establishing a relationship curve between the volume increment caused by the specimen being immersed in the solution and the specimen descending distance or the uniform descending time of the specimen, the actual deformation point of the specimen can be accurately found, and the actual deformation length of the high-temperature tensile specimen can be accurately determined. While fully considering the uneven deformation of the high-temperature tensile specimen, the elongation of the high-temperature tensile specimen can be more accurately determined.

[0107] The present invention establishes a relationship curve between the volume increment caused by the sample being immersed in a solution and the sample descent distance or the sample uniform descent time, and accurately finds the point corresponding to the actual deformation of the sample, thereby accurately determining the actual deformation length of the high-temperature tensile sample, rather than taking the length of the entire sample as the original length to calculate the elongation. Under the condition of fully considering the uneven deformation of the high-temperature tensile sample, the elongation of the high-temperature tensile sample can be determined more reasonably and accurately.

[0108] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for determining the elongation of a high temperature tensile specimen, the method specifically comprising the following steps: Step 1) A rod-shaped cylindrical specimen is selected, and the simulated specimen is heated, kept warm, cooled, and then stretched according to a predetermined experimental plan using a thermal simulation test machine until the specimen is broken to obtain a specimen broken into two sections; The two sections of the specimen are butt-joined to form a coaxial whole, and the two sections of the specimen are joined to the state at the moment of the specimen being stretched and broken; Step 2) using a solution that does not react with the sample, injecting the solution into a container, and placing the container on a horizontal surface; placing the axis of the docked sample perpendicular to the liquid surface of the solution, and placing the sample in the solution along a direction perpendicular to the liquid surface of the solution; During the insertion process, the same distance d, mm, is dropped each time; When the sample descends, record the rise of the solution level H, mm; the total volume of the solution and the sample immersed therein V, ml; Step 3) drawing a curve of the relationship between the total volume V of the solution and the sample immersed therein and the descending distance d of the sample in step 2); When the sample is just immersed in the solution, the curve rises in a straight line; when the table-shaped part of the sample is immersed in the solution, the slope of the curve decreases; when the sample continues to descend to another section, the slope of the curve increases; finally, the table-shaped part of the sample is completely immersed in the solution, and the curve rises in a straight line again; Step 4) Based on the curve analysis drawn in step 3), the curve is first differentiated to obtain the relationship curve of the slope of the curve as the sample descends the distance d; The cross-sectional area of ​​the sample immersed in the solution begins to decrease, that is, the sample enters the deformation zone, and this point is marked as A; The point when the volume increment returns to a constant value is recorded as B; From the curve in the figure, it can be seen that the part between points A and B corresponds to the part where the specimen undergoes elongation deformation; If point A corresponds to a sample drop distance of d1, mm, and point B corresponds to a sample drop distance of d2, mm, then (1) Step 5) Calculate the elongation of the sample after high temperature stretching; measure the original length of the sample , mm, measure the length of the two specimens joined together in step 1) , mm, then the deformation of high temperature stretching , mm, is （3） Step 6) Calculation of the elongation of the high temperature tensile specimen; Based on the elongation determined in steps 4) and 5) and , determine the original length of the actual deformed part of the specimen for （4） According to the elongation calculation formula, the elongation is obtained ,%,for （5） The elongation of the sample after high temperature stretching is obtained from formula (5).

2. The method for determining the elongation of a high temperature tensile specimen according to claim 1, characterized in that: Step 1) The two sections of the sample are joined by magnetization or bonding to the state at the moment when the sample is stretched and broken.

3. The method for determining the elongation of a high temperature tensile specimen according to claim 1, characterized in that: Step 2) During the placement process, the sample descends at a constant speed, with a descending speed of v, mm / s; Step 3) drawing a relationship curve between the total volume V of the solution and the sample immersed therein and the sample falling time t; Step 4) Perform the first-order differentiation of the curve to obtain the relationship between the slope of the curve and the sample drop time; if point A corresponds to the sample drop time t1,s, and point B corresponds to the sample drop time t2,s, then （2）。

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