Method for correcting the melting section of high temperature tensile specimens in resistance type thermal simulation testing machine

Abstract

The present invention relates to a method for correcting the cross section of a metal sample during a high-temperature tensile test when the cross section melts, and in particular to a method for correcting the cross section of a high-temperature tensile sample of a resistance-type thermal simulation test machine; the sample axis is made perpendicular to the liquid surface of a solution and placed in the solution; the sample is lowered by the same distance d, mm each time during the placement process; when the sample is lowered, the rise H, mm of the liquid surface of the solution is recorded; the total volume V, ml of the solution and the sample immersed therein; a relationship curve between the total volume V, ml of the solution and the sample part immersed in the solution and the distance d of the sample lowering is drawn; the curve is first-order differentiated to obtain a curve of the relationship between the slope of the curve and the distance d of the sample lowering; according to the law of the unchanged volume before and after the deformation of the sample, the corrected elongation Δl is calculated by the following formula, Δl=2(L1+L2-L0). In view of the situation where the fracture is destroyed due to melting, the fracture is corrected to achieve accurate measurement and calculation of the fracture elongation and cross-sectional shrinkage.

Description

Technical Field

[0001] The invention relates to a cross-section correction method when the cross-section of a metal sample in a high-temperature tensile test melts, and in particular to a cross-section correction method for a high-temperature tensile sample of a resistance-type thermal simulation test machine. Background Art

[0002] The resistance type thermal simulation test machine uses the principle of resistance heating to conduct thermal / mechanical simulation tests. This test machine is a material thermodynamic processing performance analysis system with the functions of rapid (slow) heating and cooling, rapid (slow) tension and compression deformation, and simultaneous recording of temperature, force, stress, strain and other parameter change curves. This equipment can accurately simulate the relationship between the process and material performance changes in each preparation stage of metal materials such as smelting, casting, forging, forming, heat treatment and welding.

[0003] At present, a thermal simulation test machine is generally used to heat the sample to a high temperature zone, 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, simulating the bending and straightening process of the continuous casting billet. The cross-sectional area of ​​the sample after breaking is analyzed or the tensile length of the sample after breaking is analyzed, so as to obtain the section shrinkage rate or elongation rate, so as to study the plastic properties of the billet during the continuous casting process. The plasticity of the continuous casting billet is closely related to whether the billet has cracks after the continuous casting to bending and straightening process. Therefore, it is very important to accurately calculate the section shrinkage rate of the broken sample.

[0004] However, the specimen is regarded as a resistor in a closed circuit in a resistance-type thermal simulation testing machine. At the moment the specimen is broken under high temperature, the current passing through the specimen is extremely unstable. The heat input of the current causes the temperature of the specimen to rise instantly, which can easily exceed the melting point of the specimen, causing the fracture of the specimen to melt, ultimately making it difficult to measure the cross-sectional area and elongation of the specimen, making it difficult to accurately calculate the cross-sectional shrinkage or elongation of the specimen.

[0005] The existing technology is only applicable to tensile fracture specimens with regular shapes and sizes. 201110081820.4 discloses a "clamping device for measuring the elongation and cross-sectional shrinkage of cylindrical tensile specimens", and CN200620045221.1 discloses a "quick measurement device for the elongation and cross-sectional shrinkage of circular specimens". The adopted cross-sectional shrinkage calculation method is only applicable to regular cross-sections with circular fractures. The diameter or major and minor axis lengths of fractures with regular circular or elliptical cross-sectional shapes can be measured by a vernier caliper, and then the area can be calculated according to the circular or elliptical area calculation formula; however, if the fracture is destroyed due to melting when the specimen is pulled apart at high temperature, effective measurement and calculation cannot be performed.

[0006] Therefore, in view of the situation that the fracture surface is destroyed due to melting when the sample is pulled apart at high temperature, an effective fracture correction method is urgently needed to achieve effective measurement and calculation of cross-sectional shrinkage or elongation. Summary of the invention

[0007] In order to overcome the shortcomings of the prior art, the present invention provides a method for correcting the melting section of a high-temperature tensile specimen of a resistance-type thermal simulation test machine. In view of the situation where the fracture is destroyed due to melting when the specimen is pulled apart at high temperature, the fracture is corrected to achieve accurate measurement and calculation of the fracture elongation and section shrinkage.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for correcting the melting section of a high-temperature tensile specimen of a resistance-type thermal simulation testing machine, the method specifically comprising the following steps:

[0010] Step 1: Select a rod-shaped cylindrical specimen, and use a resistance-type thermal simulation testing machine to heat, keep warm, and cool the simulated specimen according to a predetermined experimental plan, and then stretch it until the specimen is broken to obtain a specimen broken into two sections, and take one of the sections.

[0011] Step 2: Place a container on a horizontal surface and inject a solution that does not react with the sample into the container. Place a section of the sample taken out in step 1 slowly into the solution in a direction perpendicular to the surface of the solution, with its axis perpendicular to the surface of the solution.

[0012] 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.

[0013] When the sample descends, record the rise of the solution level H, mm, and the total volume of the solution and the sample immersed therein v, ml.

[0014] Step 3, draw a relationship curve between the total volume V, ml of the solution and the sample immersed therein and the sample falling distance d, or draw a relationship curve between the total volume V, ml of the solution and the sample immersed therein and the sample falling time t, s.

[0015] 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 cross section gradually decreases as the sample descends, and the slope of the curve also decreases until the sample descends to the molten part of the fracture.

[0016] Step 4: Based on the curve analysis drawn in step 3, the curve is differentiated in first order 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 t.

[0017] The maximum volume increment ΔV1 corresponds to the maximum cross-sectional area S1 of the sample, and the minimum volume increment ΔV2 corresponds to the minimum cross-sectional area S2 of the sample. Based on the fact that the volume increment is proportional to the cross-sectional area, the following formula is obtained:

[0018] K=ΔV1 / S1=ΔV2 / S2 (1)

[0019] Where: K is a constant;

[0020] ΔV1 is the maximum volume increment, ml;

[0021] S1 is the maximum cross-sectional area, mm 2 ;

[0022] ΔV2 is the minimum volume increment, ml;

[0023] S2 minimum cross-sectional area, mm 2 ;

[0024] For the volume increment ΔV between the maximum volume increment ΔV1 and the minimum volume increment ΔV2, ml, the cross-sectional area S of the sample corresponding to the volume increment ΔV, mm 2 , which is expressed by the following formula:

[0025] K=ΔV / S (2)

[0026] Step 5: Select a descending section of the curve in step 4 and perform polynomial fitting to obtain the following formula:

[0027] ΔV=f(l) (3)

[0028] ΔV=f(t) (4)

[0029] Combining formula (3), formula (4) and formula (2) to obtain

[0030]

[0031]

[0032] Step 6: The original length of the sample is 2L0, mm; the cross-sectional area is S0, mm 2 , then half of its volume before deformation is L0S0, and the volume of the specimen after tensile deformation and fracture consists of two parts, one is the undeformed cylinder with a length of L1, mm, and the other is the deformed table with a height of L2, mm.

[0033] According to the law that the volume of the sample remains unchanged before and after deformation,

[0034]

[0035]

[0036] L2=vt0 (9)

[0037] From formula (7) or formula (8), L2 or t0 is obtained. Then, l = L2 is substituted into formula (5) or t = t0 is substituted into formula (6) to obtain the corrected cross-sectional area S. The corrected elongation Δl is calculated by the following formula:

[0038] Δl=2(L1+L2-L0) (10)

[0039] Compared with the existing method, the beneficial effects of the present invention are:

[0040] The present invention establishes a relationship curve between the volume increment caused by immersion in a solution and the sample descent distance or the uniform descent time of the sample, finds the variation law of the sample cross-sectional area along the axial direction, and combines the unchanged volume of the sample before and after deformation to correct the influence of the sample's fused fracture on the cross-sectional area or elongation, thereby avoiding the human error caused by direct measurement, and the cross-sectional shrinkage rate or elongation obtained based on this is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic 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;

[0042] 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;

[0043] 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;

[0044] 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;

[0045] 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 and 3 of the present invention;

[0046] 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 and 3 of the present invention;

[0047] 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 and 4 of the present invention;

[0048] 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 and 4 of the present invention. DETAILED DESCRIPTION

[0049] The present invention discloses a method for correcting the melting section of a high-temperature tensile specimen of a resistance-type thermal simulation testing machine. 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 deemed 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.

[0050] A method for correcting the melting section of a high-temperature tensile specimen of a resistance-type thermal simulation testing machine, the method specifically comprising the following steps:

[0051] Step 1: Obtain a sample through a simulation experiment. The simulation sample is a rod-shaped cylinder, and the simulation sample is heated, kept warm, and cooled according to a predetermined experimental plan using a resistance-type thermal simulation test machine, and then stretched at 600 to 1400°C until the sample is broken, obtaining a sample broken into two sections, and taking one section.

[0052] Step 2: Take a container with sufficient solution and place it on a horizontal surface. The solution does not react with the sample. Place a section of the sample taken out in step 1 slowly into the solution along a direction perpendicular to the solution surface, with its axis perpendicular to the solution surface.

[0053] 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.

[0054] When descending, record the rise of the solution level and the total volume v, ml, of the solution and the sample immersed therein.

[0055] 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 in step 2, or a relationship curve between the total volume v of the solution and the sample immersed therein and the sample falling time t, s, such as Figure 1 and 2 shown.

[0056] 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 gradually decreases as the sample descends. Therefore, the slope of the curve also decreases until the sample descends to the molten part of the fracture.

[0057] 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 drop distance d or the slope of the curve and the sample drop time t. The slope of the curve corresponds to the volume increment, such as Figure 3 and 4 shown.

[0058] The maximum volume increment ΔV1 corresponds to the maximum cross-sectional area S1 of the sample, and the minimum volume increment ΔV2 corresponds to the minimum cross-sectional area S2 of the sample. Based on the fact that the volume increment is proportional to the cross-sectional area, the following formula is obtained:

[0059] K=ΔV1 / S1=ΔV2 / S2 (1)

[0060] Where: K is a constant;

[0061] ΔV1 is the maximum volume increment, ml;

[0062] S1 is the maximum cross-sectional area, mm 2 ;

[0063] ΔV2 is the minimum volume increment, ml;

[0064] S2 minimum cross-sectional area, mm 2 ;

[0065] For the volume increment ΔV between the maximum volume increment ΔV1 and the minimum volume increment ΔV2, ml, the cross-sectional area S of the sample corresponding to the volume increment ΔV, mm 2 , which is expressed by the following formula:

[0066] K=ΔV S (2)

[0067] Step 5: Figure 3 or Figure 4 The curve in the figure is selected, and a descending section of the curve is selected for polynomial fitting to obtain the following formula

[0068] ΔV=f(l) (3)

[0069] ΔV=f(t) (4)

[0070] Combining formula (3), formula (4) and formula (2) to obtain

[0071]

[0072]

[0073] Step 6: The original length of the sample is 2L0, mm; the cross-sectional area is S0, mm 2 , then half of its volume before deformation is L0S0, and the volume of the specimen after tensile deformation and fracture consists of two parts, one is the undeformed cylinder with a length of L1, mm, and the other is the deformed table with a height of L2, mm.

[0074] According to the law that the volume of the sample remains unchanged before and after deformation,

[0075]

[0076]

[0077] L2=vt0 (9)

[0078] From formula (7) or formula (8), L2 or t0 is obtained. Then, l = L2 is substituted into formula (5) or t = t0 is substituted into formula (6) to obtain the corrected cross-sectional area S. The corrected elongation Δl is calculated by the following formula:

[0079] Δl=2(L1+L2-L0) (10)

[0080] [Example]

[0081] Embodiment 1: A method for correcting the melting section of a high-temperature tensile specimen of a resistance-type thermal simulation test machine, the method specifically comprising the following steps:

[0082] 1. Obtain samples through simulation experiments.

[0083] The material selected was a kind of low carbon steel, which was processed into a simulated specimen with a size of Φ10×125mm cylinder. It was heated to 1300℃ by a Gleeble-3800 resistance 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 was set to 1×10 -3 s -1 , until the sample is broken to obtain a sample broken into two pieces.

[0084] Based on the deformation behavior of the sample at high temperature, the sample was broken into two sections, one end of each section near the fracture was in a table shape, and the rest was in a cylindrical shape;

[0085] 2. Take a container filled with sufficient water and place it on a horizontal surface. Take a section of the sample from step 1, place its axis perpendicular to the water surface, and slowly place it in the water. During the placement process, lower it by the same distance of 0.5 mm each time.

[0086] 3. Draw the relationship curve 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 As shown;

[0087] 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 drop distance l of the sample, such as Figure 6 shown.

[0088] The slope of the curve corresponds to the volume increment, the maximum volume increment ΔV1 corresponds to the maximum cross-sectional area S1 of the sample, and the minimum volume increment ΔV2 corresponds to the minimum cross-sectional area S2 of the sample. According to formula (1), the K value is 1, and from formula (2), ΔV=S.

[0089] 5. Yes Figure 6 The descending section of the curve in is obtained by fitting the third-order polynomial

[0090] ΔV=-3687+244.6l-4.99l 2 +0.03l 3 (11)

[0091] S=-3687+244.6l-4.99l 2 +0.03l 3 (12)

[0092] 6. The original length of the specimen is 125 mm and the cross-sectional area is 78.5 mm 2 , then half of its volume before deformation is 4906.25mm 3 , the length of the undeformed cylinder is 52.5 mm, substituting it into formula (7) yields L2 as 13.5 mm, and substituting l = 13.5 mm into formula (5) yields a cross-sectional area of ​​21.7 mm 2 The elongation is calculated by formula (10) to be 3.5 mm.

[0093] Embodiment 2: A method for correcting the melting section of a high-temperature tensile specimen of a resistance-type thermal simulation test machine, the method specifically comprising the following steps:

[0094] 1. Obtain samples through simulation experiments.

[0095] The material selected was a kind of low carbon steel, which was processed into a simulated specimen with a size of Φ10×125 mm. It was heated to 1300°C by a Gleeble-3800 resistance thermal simulation test machine, kept warm for 5 minutes, then cooled to 1000°C at a rate of 3°C / s, and then kept warm 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.

[0096] Based on the deformation behavior characteristics of the sample at high temperature, the sample was broken into two sections, one end of each section near the fracture was terrace-shaped, and the rest was cylindrical.

[0097] 2. Take a container filled with sufficient water and place it on a horizontal surface. Take a section of the sample from step 1, place it slowly in the water with its axis perpendicular to the water surface. During the placement process, the sample descends at a constant speed, with a descending speed of v = 1 mm / s.

[0098] 3. Draw the relationship curve 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.

[0099] 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 drop time t, such as Figure 8 shown.

[0100] The slope of the curve corresponds to the volume increment, the maximum volume increment ΔV1 corresponds to the maximum cross-sectional area S1 of the sample, and the minimum volume increment ΔV2 corresponds to the minimum cross-sectional area S2 of the sample. According to formula (1), the K value is 1, and from formula (2), ΔV = S;

[0101] right Figure 6 The descending section of the curve in is obtained by fitting the third-order polynomial

[0102] ΔV=-3467.5+228.5t-4.63t 2 +0.03t 3 (13)

[0103] S=-3467.5+228.5t-4.63t 2 +0.03t 3 (14)

[0104] 6. The original length of the specimen is 125 mm and the cross-sectional area is 78.5 mm 2 , then half of its volume before deformation is 4906.25mm 3, the length of the undeformed cylinder is 52.5 mm, substituting it into formula (8) yields t0 = 13.5 s, and substituting t0 = 13.5 s into formula (6) yields a cross-sectional area of ​​21.7 mm 2 .

[0105] Substituting t0=13.5s into formula (9), we get L2=13.5mm, and then using formula (10) to calculate the elongation to be 3.5mm.

[0106] Embodiment 3: A method for correcting the melting section of a high-temperature tensile specimen of a resistance-type thermal simulation test machine, the method specifically comprising the following steps:

[0107] 1. Obtain the sample through simulation experiment. The material selected is a kind of low carbon steel, and it is processed into a simulation sample with a size of Φ10×125mm cylinder. It is heated to 1300℃ by Gleeble-3800 resistance 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 characteristics of the sample at high temperature, the sample is broken into two sections, and one end of each section near the fracture is in a table shape, and the rest is in a cylindrical shape.

[0108] 2. Take a container filled with sufficient water and place it on a horizontal surface. Take a section of the sample from step 1, place its axis perpendicular to the water surface, and slowly place it in the water. During the placement process, lower it by the same distance of 0.5 mm each time.

[0109] 3. Draw the relationship curve 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.

[0110] 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 drop distance l of the sample, such as Figure 6 As shown. The slope of the curve corresponds to the volume increment, the maximum volume increment ΔV1 corresponds to the maximum cross-sectional area S1 of the sample, and the minimum volume increment ΔV2 corresponds to the minimum cross-sectional area S2 of the sample. According to formula (1), the K value is 1, and from formula (2), ΔV = S;

[0111] 5. For the descending section of the curve in the figure, a third-order polynomial fitting is used to obtain

[0112] ΔV=-3016+193.1l-5.2l 2 +0.028l 3 (11)

[0113] S=-3016+193.1l-5.2l 2 +0.028l 3 (12)

[0114] 6. The original length of the specimen is 125 mm and the cross-sectional area is 78.5 mm 2 , then half of its volume before deformation is 4906.25mm 3 , the length of the undeformed cylinder is 53.1 mm, substituting it into formula (7) yields L2 as 11.9 mm, and substituting l = 11.9 mm into formula (5) yields a cross-sectional area of ​​68.6 mm 2 The elongation is calculated to be 2.5 mm using formula (10).

[0115] Embodiment 4: A method for correcting the fused section of a high-temperature tensile specimen of a resistance-type thermal simulation test machine, the method specifically comprising the following steps:

[0116] 1. Obtain the sample through simulation experiment. The material selected is a kind of low carbon steel, and it is processed into a simulation sample with a size of Φ10×125mm cylinder. It is heated to 1300℃ by Gleeble-3800 resistance 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 characteristics of the sample at high temperature, the sample is broken into two sections, and one end of each section near the fracture is in a table shape, and the rest is in a cylindrical shape.

[0117] 2. Take a container filled with sufficient water and place it on a horizontal surface. Take a section of the sample from step 1, place it slowly in the water with its axis perpendicular to the water surface. During the placement process, the sample descends at a constant speed, with a descending speed of v = 1 mm / s.

[0118] 3. Draw the relationship curve 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.

[0119] 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 drop time t, such as Figure 8 As shown. The slope of the curve corresponds to the volume increment, the maximum volume increment ΔV1 corresponds to the maximum cross-sectional area S1 of the sample, and the minimum volume increment ΔV2 corresponds to the minimum cross-sectional area S2 of the sample. According to formula (1), the K value is 1, and from formula (2), ΔV = S;

[0120] For the descending section of the curve in the figure, a third-order polynomial fitting is used to obtain

[0121] ΔV=-3966.3+198.5t-5.01t 2 +0.028t 3 (13)

[0122] S=-3966.3+198.5t-5.01t 2 +0.028t 3 (14)

[0123] The original length of the specimen is 125 mm and the cross-sectional area is 78.5 mm 2 , then half of its volume before deformation is 4906.25mm 3 , the length of the undeformed cylinder is 53.1 mm, substituting it into formula (8) yields t0 = 11.9 s, and substituting t0 = 11.9 s into formula (6) yields a cross-sectional area of ​​68.6 mm 2 .

[0124] Substituting t0=11.9s into formula (9), we get L2=11.9mm, and then using formula (10) to calculate the elongation to be 2.5mm.

[0125] The present invention establishes a relationship curve between the volume increment caused by immersion in a solution and the sample descent distance or the uniform descent time of the sample, finds the variation law of the sample cross-sectional area along the axial direction, and combines the unchanged volume of the sample before and after deformation to correct the influence of the sample's fused fracture on the cross-sectional area or elongation, thereby avoiding the human error caused by direct measurement, and the cross-sectional shrinkage rate or elongation obtained based on this is more accurate.

[0126] The present invention corrects the fracture surface in view of the situation that the fracture surface is destroyed due to melting when the sample is pulled apart at high temperature, thereby realizing accurate measurement and calculation of the fracture elongation and cross-sectional shrinkage.

[0127] 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 correcting the melting section of a high-temperature tensile specimen of a resistance-type thermal simulation testing machine, the method specifically comprising the following steps: Step 1) using a rod-shaped cylindrical sample, heating, keeping warm, cooling the sample, and then stretching the sample until the sample is broken to obtain a sample broken into two sections; taking one of the sections; Step 2) Place a container on a horizontal surface, inject a solution that does not react with the sample into the container; place the table-shaped sample in the solution in a direction perpendicular to the liquid surface of the solution with its axis perpendicular to the liquid surface of the solution; During the placement process, the sample descends at a constant speed, with a descending speed of v, mm / s; 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 relationship curve between the total volume V, ml, of the solution and the sample immersed therein and the distance d from which the sample descends; Step 4) performing first-order differentiation on the curve to obtain a curve showing the relationship between the slope of the curve and the descending distance d of the sample; The maximum volume increment ΔV1 corresponds to the maximum cross-sectional area S1 of the sample, and the minimum volume increment ΔV2 corresponds to the minimum cross-sectional area S2 of the sample; based on the fact that the volume increment is proportional to the cross-sectional area, the following formula is obtained: K=ΔV1S1=ΔV2S2 (1) Where: K is a constant; ΔV1 is the maximum volume increment, ml; S1 is the maximum cross-sectional area, mm 2 ; ΔV2 is the minimum volume increment, ml; S2 minimum cross-sectional area, mm 2 ; For the volume increment ΔV between the maximum volume increment ΔV1 and the minimum volume increment ΔV2, ml, the cross-sectional area S of the sample corresponding to the volume increment ΔV, mm 2 , which is expressed by the following formula: K=ΔVS (2) Step 5) Select a descending section of the curve in step 4) and perform polynomial fitting to obtain the following formula ΔV=f(l) (3) Combining formula (3) with formula (2), we can get Step 6) The original length of the sample is 2L0, mm; the cross-sectional area is S0, mm 2 , then half of its volume before deformation is L0S0, and the volume of the specimen after tensile deformation and fracture consists of two parts, one is the undeformed cylinder with a length of L1, mm, and the other is the deformed table with a length of L2, mm; According to the law that the volume of the sample remains unchanged before and after deformation, L2=vt0 (9) From formula (7), we can get L2. Then, we can substitute l=L2 into formula (5) to get the corrected cross-sectional area S, mm. 2 , and the corrected elongation Δl is calculated by the following formula Δl=2(L1+L2-L0) (10).

2. The method for correcting the melting section of a high-temperature tensile specimen of a resistance-type thermal simulation test machine according to claim 1, characterized in that: The step 3) draws a relationship curve between the total volume V, ml, of the solution and the sample descent time t, s, of the sample.

3. The method for correcting the melting section of a high-temperature tensile specimen of a resistance-type thermal simulation test machine according to claim 2, characterized in that: The step 4) performs first-order differentiation on the curve to obtain a curve showing the relationship between the slope of the curve and the falling time t of the sample.

4. The method for correcting the melting section of a high-temperature tensile specimen of a resistance-type thermal simulation test machine according to claim 3 is characterized in that: In step 5), a descending section of the curve in step 4) is selected for polynomial fitting to obtain the following formula: ΔV=f(t) (4) Combining formula (4) with formula (2), we can get 5. The method for correcting the melting section of a high-temperature tensile specimen of a resistance-type thermal simulation test machine according to claim 4, characterized in that: In step 6), according to the law that the volume of the sample remains unchanged before and after deformation, L2=vt0 (9) From formula (8), we can get t0. Then, by substituting t=t0 into formula (6), we can get the corrected cross-sectional area S, mm 2 The corrected elongation Δl is calculated by the following formula: Δl=2(L1+L2-L0) (10).

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