CN112649278A - Method for testing metal creep property - Google Patents
Method for testing metal creep property Download PDFInfo
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- CN112649278A CN112649278A CN202011355106.5A CN202011355106A CN112649278A CN 112649278 A CN112649278 A CN 112649278A CN 202011355106 A CN202011355106 A CN 202011355106A CN 112649278 A CN112649278 A CN 112649278A
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- 238000012360 testing method Methods 0.000 title claims abstract description 143
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 41
- 239000002184 metal Substances 0.000 title claims abstract description 41
- 238000000034 method Methods 0.000 title claims description 42
- 238000012545 processing Methods 0.000 claims abstract description 8
- 238000005303 weighing Methods 0.000 claims abstract description 6
- 238000010586 diagram Methods 0.000 claims abstract description 5
- 238000010438 heat treatment Methods 0.000 claims description 25
- 238000010998 test method Methods 0.000 claims description 4
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- 229910000838 Al alloy Inorganic materials 0.000 description 8
- 238000005259 measurement Methods 0.000 description 7
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- 239000007769 metal material Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 2
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- 238000007796 conventional method Methods 0.000 description 1
- 230000004069 differentiation Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/0003—Steady
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/006—Crack, flaws, fracture or rupture
- G01N2203/0067—Fracture or rupture
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0071—Creep
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
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Abstract
The application provides a metal creep property testing method, which comprises the steps of sequentially increasing axial stress which is the same as initial axial stress at the same time interval after loading the initial axial stress on a test sample until the test sample is broken; then, acquiring stress and strain data in real time by using a weighing sensor and a linear variable differential transformer, transmitting the data to a computer, processing the data by using software, and drawing a creep curve of the sample; and obtaining the minimum creep rate by using the obtained creep curve, and then drawing a logarithm diagram of the minimum creep rate and creep stress according to a power law formula to obtain a creep index. The testing method provided by the application can solve the problems of more used samples and long testing time in the metal creep performance test.
Description
Technical Field
The application relates to the technical field of metal performance testing, in particular to a method for testing metal creep performance.
Background
"creep" refers to the ability of a material to resist deformation or failure under prolonged loading at relatively high temperatures. In practical production applications, some metal materials need to be used for a long time at room temperature or relatively high temperature under fixed or non-fixed load, and the creep behavior is crucial to the long-time stable operation of the metal material, so that it is clear that the working life of the metal material under different pressures and temperatures can be avoided from excessive creep or creep damage.
At present, for the test of the creep property of metal, the creep index of the metal under different pressures and temperatures is mainly determined. The traditional method needs to use a plurality of samples to carry out the creep index test, and the measurement of the plurality of samples often causes the accuracy difference of the measurement result due to the difference between the samples and has long creep measurement time. Therefore, it is an urgent problem for those skilled in the art to develop a method for rapidly testing the creep property of metal.
Disclosure of Invention
The embodiment of the application aims to provide a metal creep performance testing method, which is used for solving the problems of more samples and long testing time in the creep performance testing.
The application provides a metal creep property testing method, which comprises the following steps:
(1) fixing a metal sample to be tested in a sample chamber of creep deformation quantity testing equipment, and aligning a temperature sensor to the upper position, the middle position and the lower position of the sample in sequence;
(2) adjusting the height of the creep deformation quantity testing equipment, and selecting a creep deformation quantity measuring testing rod to continuously measure creep deformation;
(3) heating the sample to a preset test temperature;
(4) after loading initial axial stress on the sample, sequentially increasing the axial stress which is the same as the initial axial stress at the same time interval until the sample is broken;
acquiring stress and strain data in real time by using a weighing sensor and a linear variable differential transformer, transmitting the data to a computer, processing the data by using software, and drawing a creep curve of the sample;
(5) and (4) obtaining the minimum creep rate by using the creep curve obtained in the step (4), and then drawing a logarithm diagram of the minimum creep rate and creep stress according to a power law formula to obtain a creep index.
In some embodiments of the present application, the time interval is 0.5-5 h.
In some embodiments of the present application, the initial axial stress is 2% to 8% of the yield stress of the metal coupon to be tested.
In some embodiments of the present application, the test temperature ranges from 25 to 1500 ℃.
In some embodiments of the present application, the sample has dimensions of (2-20) mm x (20-200) mm.
In some embodiments of the present application, prior to securing the specimen to the specimen chamber of the creep deformation amount testing apparatus, the method further comprises:
debugging the accuracy of the creep deformation quantity testing equipment to enable the resolution of the creep deformation quantity testing equipment to be less than 0.0001 mm;
debugging the heating equipment to ensure that the temperature difference between the test temperature and the display temperature is less than 5 ℃;
and detecting stress loading to ensure that the error between the experimental stress value and the loading stress value is less than 1 percent.
In some embodiments of the present application, after the specimen is secured to the specimen chamber of the creep deformation amount testing apparatus, the method further comprises:
and detecting the parallelism of the creep deformation quantity testing equipment and the heating equipment in the axial direction.
The method for testing the metal creep property provided by the application adopts a step-type testing method, obtains a series of creep curves of the metal to be tested at the same testing temperature and the same time interval and under the same stress applying change step by the same sample, and further obtains the creep index of the metal to be tested. The test method only uses one sample, and the problem of different accuracy of the measurement result caused by the difference among the samples when a plurality of samples are measured is avoided; moreover, the testing method is short in testing time and simple and convenient in testing process, and the method is more efficient in testing the metal creep property.
Of course, not all advantages described above need to be achieved at the same time in the practice of any one product or method of the present application.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and other embodiments can be obtained by those skilled in the art according to the drawings.
FIG. 1 is a creep curve of example 1;
FIG. 2 is a creep curve of example 2;
FIG. 3 is a graph of the minimum creep rate versus the logarithm of creep stress for examples 1-2;
FIG. 4 is a creep curve of example 3;
FIG. 5 is a creep curve of example 4;
FIG. 6 is a creep curve of example 5;
FIG. 7 is a creep curve of example 6;
FIG. 8 is a creep curve of example 7;
FIG. 9 is a creep curve of example 8;
FIG. 10 is a plot of the minimum creep rate versus the logarithm of creep stress for examples 3-8;
FIG. 11 is a creep curve of example 9;
FIG. 12 is a creep curve of example 10;
FIG. 13 is a plot of the minimum creep rate versus the log of creep stress for examples 9-10.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments obtained based on the embodiments in the present application belong to the protection scope of the present application.
The application provides a metal creep property testing method, which comprises the following steps:
(1) fixing a metal sample to be tested in a sample chamber of creep deformation quantity testing equipment, and aligning a temperature sensor to the upper position, the middle position and the lower position of the sample in sequence;
in some embodiments of the present application, the size of the sample is not particularly limited, and may be selected by those skilled in the art according to actual needs as long as the purpose of the present application is satisfied, and for example, the size of the sample may be (2-20) mm × (2-20) mm × 20-200 mm.
In some embodiments of the present application, a metal sample to be tested is fixed in a sample chamber of a creep deformation amount testing device through a clamp, and the clamp is used for ensuring the fixation of the sample in a creep testing process. In the present application, the size and type of the jig are not particularly limited, and those skilled in the art can select the jig according to the size of the sample as long as the object of the present application is satisfied. In the present application, the creep deformation amount testing apparatus is not particularly limited, and those skilled in the art can select the creep deformation amount testing apparatus according to actual needs as long as the purpose of the present application is satisfied.
In some embodiments of the present application, the temperature sensor is sequentially aligned with the upper, middle and lower three positions of the sample to monitor the temperature of the sample at different positions, when the upper, middle and lower three positions of the sample all reach the preset test temperature, the thermal equilibrium of the sample is reached, and after the thermal equilibrium, the axial stress can be loaded on the sample. In the present application, the type of the temperature sensor is not particularly limited, and those skilled in the art can select the temperature sensor according to actual needs as long as the purpose of the present application is satisfied.
In some embodiments of the present application, the accuracy of the creep deformation amount testing apparatus may be adjusted to a resolution of less than 0.0001mm before the specimen is fixed to the specimen chamber of the creep deformation amount testing apparatus, so as to more accurately measure the strain data of the creep process; heating equipment can be debugged, so that the temperature difference between the test temperature and the display temperature of three temperature sensors connected with the upper, middle and lower positions of the sample is less than 5 ℃, the temperature deviation in the heating process is smaller, and the heating temperature of the sample can be controlled more accurately; stress loading can also be detected, so that the error between the experimental stress value and the loading stress value is less than 1 percent, and more accurate stress data can be obtained in the creep test process. Through the operation steps, the data error values of strain, stress and heating temperature in the metal creep performance test process can be smaller, so that more real and accurate creep performance indexes of the metal to be tested can be obtained.
In some embodiments of the present application, after the specimen is fixed in the specimen chamber of the creep deformation amount testing device, the parallelism of the creep deformation amount testing device and the heating device in the axial direction can also be detected, so that the specimen is uniformly heated in the heating process and uniformly stressed in the stretching process, and a reasonable creep curve is obtained.
(2) Adjusting the height of the creep deformation quantity testing equipment, and selecting a creep deformation quantity measuring testing rod to continuously measure creep deformation;
in some embodiments of the present application, the height of the creep deformation amount testing apparatus and the length of the creep deformation amount measuring and testing rod are not particularly limited, and those skilled in the art can select the height according to actual needs as long as the purpose of the present application is satisfied, and creep deformation can be continuously measured, so as to ensure smooth proceeding of the creep test. For example, the height of the creep deformation amount testing apparatus may be 50mm to 1050 mm; the length of the creep deformation measurement test rod can be 0.01-1000 mm.
(3) Heating the sample to a preset test temperature;
in some embodiments of the present application, the test temperature range is not particularly limited, and those skilled in the art can select the test temperature range according to actual needs as long as the purpose of the present application can be achieved, for example, the test temperature range may be 25 to 1500 ℃.
In the present application, the heating time of the sample is not particularly limited as long as the entire sample reaches the preset test temperature, and may be, for example, 10min to 2 h.
(4) After loading initial axial stress on the sample, sequentially increasing the axial stress which is the same as the initial axial stress at the same time interval until the sample is broken;
acquiring stress and strain data in real time by using a weighing sensor and a linear variable differential transformer, drawing a creep curve of the sample, for example, transmitting the data to a computer, processing the data by using software, and drawing the creep curve of the sample; in some embodiments of the present application, the time interval is not particularly limited, and can be selected by those skilled in the art according to actual needs as long as the purpose of the present application can be achieved, for example, the time interval is 0.5 to 5 h.
In some embodiments of the present application, the initial axial stress is not particularly limited, and can be selected by those skilled in the art according to actual needs as long as the purpose of the present application can be achieved, for example, the initial axial stress is 2% to 8% of the yield stress of the metal sample to be tested. In the present application, the yield stress of the metal sample to be tested is known before creep test, and the method for obtaining the yield stress of the sample is not particularly limited in the present application, and can be selected by those skilled in the art according to actual needs as long as the purpose of the present application is satisfied.
In some embodiments of the present application, a stress value at each interval time in a creep test process is obtained by using a load cell, a strain value at each interval time in the creep test process is obtained by using a linear variable differential transformer, different stress and strain data corresponding to different time intervals are transmitted to a computer, and then the data are processed by using software, and a stress increase change creep curve of a sample at the same time interval is obtained by drawing.
In the present application, the types of the symmetrical load sensors and the linear variable differential transformer are not particularly limited, and those skilled in the art may select them according to actual needs as long as the purpose of the present application is satisfied. For example, the load cell may be a tension sensor.
(5) And (4) obtaining the minimum creep rate by using the creep curve obtained in the step (4), and then drawing a logarithm diagram of the minimum creep rate and creep stress according to a power law formula to obtain a creep index.
In some embodiments of the present application, by using the obtained stress increase change creep curve, in Origin, performing differentiation processing on each section of creep curve corresponding to different stress values at each same time interval, obtaining a differential value of strain in each section of creep curve with respect to time, and screening out a minimum value, that is, a minimum creep rate of each section of creep curve, thereby sequentially obtaining the minimum creep rates corresponding to different stress values; then, according to the power law formula:
stress, n is the creep index, B' is a constant related to the material and microstructure, QCFor activation energy of creep, the effect of temperature is usually integrated into a constant B, representing a constant related to the material microstructure and temperature, when the temperature is constant.
The above curves can be made using software. In the present application, the software is not particularly limited, and those skilled in the art can select the software according to actual needs as long as the purpose of the present application is satisfied, and for example, at least one of Origin, Excel, Mathlab, and the like can be included.
According to the method for testing the metal creep property, only one sample is needed to be used in the testing process, the creep experiment is carried out at the same interval time under the same stress applying change step, stress and strain data are obtained, a creep curve is made, the corresponding minimum creep rate under different stress values is obtained, then a logarithm diagram of the minimum creep rate and the creep stress is made according to a power law formula, and the creep index of the metal to be tested is obtained. The test method only uses one sample, thereby avoiding the problem of different accuracy of the measurement result caused by the difference among the samples when a plurality of samples are measured; moreover, the testing method has short time and simple and convenient testing process, thereby enabling the metal creep property testing to be more efficient.
Terms used in the art are generally terms commonly used by those skilled in the art, and if they are inconsistent with commonly used terms, the terms in this application control.
Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples. Various tests and evaluations were carried out according to the following methods.
Example 1
< creep test >
(1) Fixing a semi-solid cast A365(SSM-A365-T6) aluminum alloy sample subjected to heat treatment of T6 and having the size of 4mm multiplied by 25mm in a sample chamber of a creep deformation quantity testing device through a clamp, and aligning temperature sensors at the upper, middle and lower positions of the sample in sequence;
(2) adjusting the height of the creep deformation quantity testing equipment to be 500mm, and selecting a creep deformation quantity measuring testing rod with the length of 200 mm;
(3) heating the sample to 25 ℃;
(4) loading the sample with 5% yield stress (360MPa), namely 18MPa, and then increasing the yield stress by 18MPa every 1h until the sample is broken;
in the stress loading process, stress values corresponding to different time intervals are transmitted to a computer by using a weighing sensor; transmitting strain values generated under different stresses and at the same time interval to a computer by using a linear variable differential transformer, processing data by using Origin software, and drawing to obtain a creep curve as shown in figure 1;
(5) in the creep curve shown in FIG. 1, differentiating different creep curve segments obtained every 1h through Origin respectively to obtain corresponding minimum creep rates in sequence;
then, according to the power law formula:
the minimum creep rate is plotted against the log of creep stress by Origin, as shown in FIG. 3, with a slope creep index n.
Example 2
< creep test >
(1) The method is the same as the embodiment 1 except that the sample to be tested is the A365(A365-T6) aluminum alloy after T6 heat treatment;
(2) - (3) same as in example 1;
(4) the same procedure as in example 1 was repeated, except that the test piece was subjected to a 5% yield stress (350MPa), i.e., 17.5MPa, and then increased by 17.5MPa every 1 hour;
(5) same as in example 1.
Wherein the obtained creep curve is shown in FIG. 2; the log plot of minimum creep rate versus creep stress is shown in FIG. 3.
Example 3
< creep test >
(1) - (2) same as in example 1;
(3) heating the sample to 220 ℃;
(4) the same procedure as in example 1 was repeated, except that the test piece was subjected to a yield stress of 5% (290MPa), i.e., 14.5MPa, and then increased by 14.5MPa every 1 hour;
(5) same as in example 1.
Wherein the obtained creep curve is shown in FIG. 4; the log plot of minimum creep rate versus creep stress is shown in FIG. 10.
Example 4
< creep test >
(1) - (2) same as in example 1;
(3) same as in example 3;
(4) the same procedure as in example 1 was repeated, except that the test piece was subjected to a 5% yield stress (280MPa), namely 14MPa, and then, the yield stress was increased by 14MPa every 1 hour;
(5) same as in example 1.
Wherein the obtained creep curve is shown in fig. 5; the log plot of minimum creep rate versus creep stress is shown in FIG. 10.
Example 5
< creep test >
(1) - (2) same as in example 1;
(3) heating the sample to 250 ℃;
(4) the same procedure as in example 1 was repeated, except that the test piece was subjected to a yield stress of 5% (255MPa), i.e., 12.75MPa, and then increased by 12.75MPa every 1 hour;
(5) same as in example 1.
Wherein the obtained creep curve is shown in fig. 6; the log plot of minimum creep rate versus creep stress is shown in FIG. 10.
Example 6
< creep test >
(1) - (2) same as in example 1;
(3) same as example 5;
(4) the same procedure as in example 1 was repeated, except that the test piece was subjected to a 5% yield stress (250MPa), namely 12.5MPa, and then increased by 12.5MPa every 1 hour;
(5) same as in example 1.
Wherein the obtained creep curve is shown in FIG. 7; the log plot of minimum creep rate versus creep stress is shown in FIG. 10.
Example 7
< creep test >
(1) - (2) same as in example 1;
(3) heating the sample to 280 ℃;
(4) the same procedure as in example 1 was repeated, except that the test piece was subjected to a yield stress of 5% (260MPa), namely 13MPa, and then 13MPa was added every 1 hour;
(5) same as in example 1.
Wherein the obtained creep curve is shown in fig. 8; the log plot of minimum creep rate versus creep stress is shown in FIG. 10.
Example 8
< creep test >
(1) - (2) same as in example 1;
(3) same as example 7;
(4) the same procedure as in example 1 was repeated, except that the test piece was subjected to a yield stress of 5% (235MPa), i.e., 11.75MPa, and then increased by 11.75MPa every 1 hour;
(5) same as in example 1.
Wherein the obtained creep curve is shown in fig. 9; the log plot of minimum creep rate versus creep stress is shown in FIG. 10.
Example 9
< creep test >
(1) - (2) same as in example 1;
(3) heating the sample to 300 ℃;
(4) the same procedure as in example 1 was repeated, except that the test piece was subjected to a 5% yield stress (245MPa), namely 12.25MPa, and then increased by 12.25MPa every 1 hour;
(5) same as in example 1.
Wherein the obtained creep curve is shown in FIG. 11; the log plot of minimum creep rate versus creep stress is shown in FIG. 13.
Example 10
< creep test >
(1) - (2) same as in example 1;
(3) same as in example 9;
(4) the same procedure as in example 1 was repeated, except that the test piece was subjected to a yield stress of 5% (220MPa), i.e., 11MPa, and then, the yield stress was increased by 11MPa every 1 hour;
(5) same as in example 1.
Wherein the obtained creep curve is shown in fig. 12; the log plot of minimum creep rate versus creep stress is shown in FIG. 13.
The data and test results for examples 1-10 are shown in Table 1.
Comparative example 1
< creep test >
(1) 5 identical 4mm by 25mm SSM-A365-T6 aluminum alloy test specimens were prepared;
(2) fixing the 1 st sample in a sample chamber of creep deformation quantity testing equipment through a clamp, and aligning a temperature sensor to the upper position, the middle position and the lower position of the sample in sequence;
(3) adjusting the height of the creep deformation quantity testing equipment to be 500mm, and selecting a creep deformation quantity measuring testing rod with the length of 200 mm;
(4) heating the sample to 25 ℃;
(5) the sample is loaded with a 5% yield stress (360MPa), i.e. a constant axial stress of 18MPa, over time until the sample breaks;
transmitting the stress value to a computer by using a weighing sensor, transmitting the strain value to the computer by using a linear variable differential transformer, processing data by using Origin software, and drawing to obtain a creep curve;
obtaining a corresponding creep rate-normalization time curve graph by Origin processing of the obtained creep curve to obtain a minimum creep rate;
(6) repeating the steps (1) to (5) on the remaining 4 samples respectively, correspondingly, changing the constant axial stress in the step (5) into yield stresses of 25%, 45%, 65% and 85% in sequence to act on the 4 samples respectively, and obtaining creep curves and minimum creep rates of the remaining 4 samples;
(7) then, according to the power law formula:
and drawing a minimum creep rate-stress relation curve graph on the log-log coordinate paper to obtain a creep index n.
Comparative example 2
< creep test >
(1) The method is the same as the comparative example 1 except that the sample to be tested is A365-T6 aluminum alloy;
(2) - (4) same as in comparative example 1;
(5) the test piece was the same as comparative example 1 except that the test piece was loaded with 5% yield stress (350MPa), i.e., a constant axial stress of 17.5 MPa;
(6) - (7) same as in comparative example 1.
Comparative example 3
< creep test >
(1) 10 identical 4mm by 25mm SSM-A365-T6 aluminum alloy test specimens were prepared;
(2) - (3) same as in comparative example 1;
(4) heating the sample to 220 ℃;
(5) the test piece was the same as comparative example 1 except that the test piece was loaded with 5% yield stress (290MPa), i.e., a constant axial stress of 14.5 MPa;
(6) repeating the steps (1) to (5) on the remaining 9 samples respectively, and correspondingly, changing the constant axial stress in the step (5) into yield stresses of 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% and 50% in sequence to act on the 9 samples respectively to obtain creep curves and minimum creep rates of the remaining 9 samples;
(7) same as in comparative example 1.
Comparative example 4
< creep test >
(1) The method is the same as the comparative example 3 except that the sample to be tested is A365-T6 aluminum alloy;
(2) - (4) same as in comparative example 3;
(5) the same as in comparative example 3, except that the sample was loaded with 5% yield stress (280MPa), i.e., a constant axial stress of 14 MPa;
(6) - (7) same as in comparative example 3.
Comparative example 5
< creep test >
(1) - (3) same as in comparative example 3;
(4) heating the sample to 280 ℃;
(5) the test piece was identical to comparative example 3, except that the test piece was loaded with a 5% yield stress (260MPa), i.e., a constant axial stress of 13 MPa;
(6) - (7) same as in comparative example 3.
Comparative example 6
< creep test >
(1) - (3) same as in comparative example 4;
(4) same as comparative example 5;
(5) the test piece was the same as comparative example 4 except that the test piece was loaded with 5% yield stress (235MPa), i.e., a constant axial stress of 11.75 MPa;
(6) - (7) same as in comparative example 4.
Comparative example 7
< creep test >
(1) 20 identical 4mm by 25mm T6 heat treated semi-solid cast A365(SSM-A365-T6) aluminum alloy coupons were prepared;
(2) - (3) same as in comparative example 1;
(4) heating the sample to 300 ℃;
(5) the test piece was the same as comparative example 1 except that the test piece was loaded with 5% yield stress (245MPa), i.e., a constant axial stress of 12.25 MPa;
(6) repeating the steps (1) to (5) on the remaining 19 samples, respectively, correspondingly, changing the constant axial stress in the step (5) into yield stresses of 8%, 11%, 14%, 17%, 20%, 23%, 26%, 29%, 32%, 35%, 38%, 41%, 44%, 47%, 50%, 53%, 56%, 59% and 62%, respectively, and acting on the 19 samples to obtain creep curves and minimum creep rates of the remaining 19 samples;
(7) same as in comparative example 1.
Comparative example 8
< creep test >
(1) The method is the same as the comparative example 7 except that the sample to be tested is A365-T6 aluminum alloy;
(2) - (4) same as in comparative example 7;
(5) the same as in comparative example 7, except that the sample was loaded with 5% yield stress (220MPa), i.e., a constant axial stress of 11 MPa;
(6) - (7) same as in comparative example 7.
The data and test results for comparative examples 1-8 are shown in Table 1.
TABLE 1 preparation parameters and test results for the examples and comparative examples
As can be seen from examples 1-10 and comparative examples 1-8 of the present application, the method for testing the creep property of the step-type metal used in the present application uses a smaller number of test samples, has a shorter test time, and is simpler than the conventional method, and the obtained creep index is very close to the creep index in comparative examples 1-8.
Therefore, according to the metal creep property testing method provided by the application, a series of creep curves of the metal to be tested are obtained through the same sample at the same testing temperature and at the same time interval and in the same stress applying change step, and then the creep index of the metal to be tested is further obtained. The test method only uses one sample, and the problem of different accuracy of the measurement result caused by the difference among the samples when a plurality of samples are measured is avoided; in addition, the testing method is short in testing time and simple and convenient in testing process, and the creep index can be obtained without complex mathematical calculation, so that the method is more efficient when used for testing the metal creep index.
The above description is only for the preferred embodiment of the present application and is not intended to limit the scope of the present application. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application are included in the protection scope of the present application.
Claims (7)
1. A metal creep property testing method comprises the following steps:
(1) fixing a metal sample to be tested in a sample chamber of creep deformation quantity testing equipment, and aligning a temperature sensor to the upper position, the middle position and the lower position of the sample in sequence;
(2) adjusting the height of the creep deformation quantity testing equipment, and selecting a creep deformation quantity measuring testing rod to continuously measure creep deformation;
(3) heating the sample to a preset test temperature;
(4) after loading initial axial stress on the sample, sequentially increasing the axial stress which is the same as the initial axial stress at the same time interval until the sample is broken;
acquiring stress and strain data in real time by using a weighing sensor and a linear variable differential transformer, transmitting the data to a computer, processing the data by using software, and drawing a creep curve of the sample;
(5) and (4) obtaining the minimum creep rate by using the creep curve obtained in the step (4), and then drawing a logarithm diagram of the minimum creep rate and creep stress according to a power law formula to obtain a creep index.
2. The metal creep property testing method according to claim 1, wherein the time interval is 0.5-5 h.
3. The metal creep property testing method according to claim 1, wherein the initial axial stress is 2% -8% of the yield stress of the metal specimen to be tested.
4. The metal creep property testing method according to claim 1, wherein the testing temperature is in the range of 25 to 1500 ℃.
5. The metal creep property test method according to claim 1, wherein the size of the test specimen is (2-20) mm x (20-200) mm.
6. The metal creep performance testing method of claim 1, wherein prior to fixing the specimen in a specimen chamber of a creep deformation amount testing apparatus, the method further comprises:
debugging the accuracy of the creep deformation quantity testing equipment to enable the resolution of the creep deformation quantity testing equipment to be less than 0.0001 mm;
debugging the heating equipment to ensure that the temperature difference between the test temperature and the display temperature is less than 5 ℃;
and detecting stress loading to ensure that the error between the experimental stress value and the loading stress value is less than 1 percent.
7. The metal creep performance testing method of claim 1, wherein after the specimen is fixed to a specimen chamber of a creep deformation amount testing apparatus, the method further comprises:
and detecting the parallelism of the creep deformation quantity testing equipment and the heating equipment in the axial direction.
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