CN115824799A - Method for evaluating processability of oriented silicon steel based on strain energy - Google Patents
Method for evaluating processability of oriented silicon steel based on strain energy Download PDFInfo
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Abstract
The invention relates to a method for evaluating the processability of oriented silicon steel based on strain energy, which comprises the following steps of 1) carrying out a tensile test on a detection sample, collecting stress sigma and strain epsilon data of the sample in the test process, and obtaining a corresponding stress-strain curve; 2) Differentiating the stress-strain data to obtain a differential curve of sigma with respect to strain epsilon, 3) epsilon a The strain is the corresponding strain at the end of elastic deformation; after the elastic deformation phase is finished, necking starts when d σ =0, and epsilon b Is the corresponding strain at the beginning of necking; when d sigma is less than 0, the material enters a necking and breaking stage; 4) Selecting strain quantity epsilon in [ epsilon a, ε b ]Test sample tensile curve data, polynomial fit curves within the range; 5) And (3) integral processing is carried out on the section with the tensile deformation higher than the critical strain value, and the area of a real plastic deformation curve is calculated: the size of S characterizes the ability of the material to withstand cracking during plastic deformation to the necking stage. The cold rolling workability of the material was evaluated more accurately.
Description
Technical Field
The invention relates to the field of ferrous metallurgy, and relates to a method for evaluating the processability of oriented silicon steel based on strain energy.
Background
The processing performance of the metal material refers to the requirements of various cold and hot processing technologies on the material performance in the manufacturing process of parts, and comprises casting performance, welding performance, cutting performance, heat treatment performance, surface treatment performance and the like. The processing performance of the metal material plays an important role in ensuring the product quality, reducing the cost and improving the productivity. In the subsequent cold rolling process of oriented silicon steel production, because of large plastic deformation, the silicon steel has higher requirements on the mechanical properties of materials in the processing process. Due to different use environments of metals, requirements on metal materials are greatly different, and requirements on mechanical properties are different. Mechanical properties are classified into strength, plasticity, hardness, impact toughness, and the like according to the properties of applied loads, such as tensile, compression, torsion, impact, cyclic load, and the like. The tensile test is the most common test method in the mechanical property test of the metal material, and is widely applied to the research, production and acceptance of the metal material. The yield strength has important significance in engineering and is an indispensable important index in material performance. The larger the difference between the yield point and the tensile strength is, the larger the deformation processing of the material before fracture can be performed, that is, the plastic deformation stage is long, and the better the formability and the shape stability of the material are, which is beneficial to the forming processing.
At present, the existing material processability evaluation method adopts mechanical index evaluation, and judges the cold rolling difficulty degree of the oriented silicon steel through parameters such as yield point, tensile point and the like. However, it is known that the workability of the material is also closely related to the ductility of the material, and the simple yield point and tensile point cannot fully explain the workability of the oriented silicon steel. The cold rolling process of the oriented silicon steel is a large plastic deformation process, so the data of the elastic deformation stage in the tensile test process of the oriented silicon steel is not suitable for evaluating the processability. Meanwhile, the oriented silicon steel material and the cold rolling characteristics show that the cold rolling edge crack is easy to cause strip breakage, so that the necking breakage process in the testing process can interfere with the overall processability evaluation of the material.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for evaluating the processability of oriented silicon steel based on strain energy, wherein the strain energy of a sample is obtained by calculating the area of a tensile curve so as to evaluate the processability of the oriented silicon steel.
In order to realize the purpose, the invention adopts the following technical scheme:
a method for evaluating the processability of oriented silicon steel based on strain energy is characterized in that a tensile test is adopted to determine the corresponding strain epsilon at the end of elastic deformation a Strain epsilon corresponding to the onset of necking b Selecting the strain amount to be [. Epsilon. ] a ,ε b ]And (3) performing integral treatment on the tensile curve data of the test sample in the range according to a fitting formula, calculating the area of a real plastic deformation curve, and representing the capability of the material capable of bearing cracks in the stage from plastic deformation to necking, namely representing the cold rolling processability of the oriented silicon steel.
The method comprises the following specific steps:
1) Carrying out a tensile test on a detection sample, collecting stress sigma and strain epsilon data of the test sample in the test process, and obtaining a corresponding stress-strain curve;
2) The obtained stress-strain data is subjected to differential processing according to formula (1) to obtain a differential curve of sigma with respect to strain epsilon,
wherein, sigma is stress, epsilon is strain, and n is the number of the collected data points;
3) The linear and steep drop of the stress change d sigma curve indicates that the test is in an elastic deformation stage, the stress change d sigma curve begins to rise after reaching the 1 st inflection point, and the epsilon indicates that the elastic deformation is finished a The strain is the corresponding strain at the end of elastic deformation; after the elastic deformation phase, the stress change d σ curve starts to gradually decrease, necking starts when d σ =0, and ∈ b Is the corresponding strain at the beginning of necking; when d sigma is less than 0, the material enters a necking and breaking stage;
4) Selecting strain quantity epsilon in [ epsilon a ,ε b ]Test sample tensile curve data within the range, fitting a curve according to a polynomial of formula (2);
σ＝A+Bε+Cε 2 +Dε 3 +... (2)
wherein, A, B, C, D \8230isa constant obtained by fitting a test sample tensile curve by a least square method;
5) And (3) performing integral processing on the section with the tensile deformation higher than the critical strain value in the formula (2), and calculating the area of a real plastic deformation curve according to a formula (3):
wherein S is strain energy representing strain from ε a Increase to epsilon b The true value of the strain energy consumed in the process, the size of S represents the capability of the material for bearing cracks in the stage from plastic deformation to necking, namely the cold rolling processability of the oriented silicon steel is represented; the larger the S, the better the processability, and conversely, the worse the processability.
Compared with the prior art, the invention has the beneficial effects that:
according to the method, the strain energy of the sample is obtained by calculating the actual stress-strain curve area of the oriented silicon steel so as to evaluate the processability of the oriented silicon steel. The method integrates the interaction of yield strength, tensile strength and elongation on the processability, calculates the area of a plastic deformation zone according to the stress-strain curve of the oriented silicon steel, takes the area as the characteristic index of the processability of the material, eliminates the interference of data of an elastic deformation section and a necking fracture section in the process of a sample tensile test, and more accurately evaluates the cold rolling processability of the material.
Drawings
In fig. 1, a is a stress-strain curve of the test sample 1 of the example.
In fig. 1, b is a stress-strain curve of the test sample 2 of the example.
In FIG. 1, c is a stress-strain curve of the test sample 3 of the example.
In FIG. 1, d is a stress-strain curve of the test sample 4 of the example.
In FIG. 1, e is a stress-strain curve of the test sample 5 of the example.
In FIG. 1, f is a stress-strain curve of the test sample 6 of the example.
In fig. 2, a is a first order differential curve of stress-strain of the test sample 1 of the example.
In fig. 2, b is a first order differential plot of stress-strain of the test sample 2 of the example.
In fig. 2, c is a first order differential plot of stress-strain of the test sample 3 of the example.
In fig. 2 d is a first order differential plot of stress-strain for the test sample 4 of the example.
In FIG. 2, e is a first order differential plot of stress versus strain for the test sample 5 of the example.
In fig. 2, f is a first order differential plot of stress-strain of the test sample 6 of the example.
In fig. 3, a is a stress-strain fitting curve of the plastic deformation process of the test sample 1 of the example.
In fig. 3 b is a stress-strain fitting graph of the plastic deformation process of the test sample 2 of the example.
In fig. 3, c is a stress-strain fitting curve of the plastic deformation process of the test sample 3 of the example.
In fig. 3 d is the stress-strain fit curve of the plastic deformation process of the test sample 4 of the example.
In fig. 3, e is a stress-strain fitting curve of the plastic deformation process of the test sample 5 of the example.
In fig. 3, f is a stress-strain fitting graph of the plastic deformation process of the test sample 6 of the example.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A method for evaluating the processability of oriented silicon steel based on strain energy comprises the following specific steps:
1) Carrying out a tensile test on a detection sample, collecting stress sigma and strain epsilon data of the test sample in the test process, and obtaining a corresponding stress-strain curve;
2) The obtained stress-strain data is subjected to differential processing according to the formula (1) to obtain a differential curve of sigma with respect to strain epsilon,
wherein, sigma is stress, epsilon is strain, and n is the number of the collected data points;
3) The linear and steep drop of the stress change d sigma curve indicates that the test is in an elastic deformation stage, the stress change d sigma curve begins to rise after reaching the 1 st inflection point, and the epsilon indicates that the elastic deformation is finished a The strain is the corresponding strain at the end of elastic deformation; after the elastic deformation phase, the stress change d σ curve starts to gradually decrease, necking starts when d σ =0, and ∈ b Is the corresponding strain at the onset of necking; when d sigma is less than 0, the material enters a necking and breaking stage;
4) Selecting strain quantity epsilon in [ epsilon a ,ε b ]Test sample tensile curve data within the range, fitting a curve according to a polynomial of formula (2);
σ＝A+Bε+Cε 2 +Dε 3 +... (2)
wherein, A, B, C, D \8230isa constant obtained by fitting a test sample tensile curve by a least square method;
5) And (3) performing integral processing on the section with the tensile deformation higher than the critical strain value in the formula (2), and calculating the area of a real plastic deformation curve according to a formula (3):
wherein S is strain energy representing strain from ε a Increase to epsilon b The true value of the strain energy consumed in the process, the size of S represents the capability of the material for bearing cracks in the stage from plastic deformation to necking, namely the cold rolling processability of the oriented silicon steel is represented; the larger the S, the better the processability, and conversely, the worse the processability.
In the plastic deformation process of the oriented silicon steel, when the strain reaches the necking critical value, cracks are generated, and the processability is deteriorated, so that the section of the formula (2) in which the tensile deformation is higher than the critical strain value is subjected to integral treatment to obtain an integral result: the area represents the capability of the material to bear cracks in the stage from plastic deformation to necking, and the integral result is used as an index for evaluating the cold rolling workability of the oriented silicon steel; the method is used for characterizing the cold rolling processability of the oriented silicon steel;
taking the strain energy obtained by the formula (3) as a parameter for evaluating the cold rolling processability of the oriented silicon steel, wherein the higher the strain energy is, the better the processability is; and evaluating the processability in the cold rolling process according to strain energy S obtained by calculation of the oriented silicon steel tensile curve, wherein the larger the S is, the better the processability is, and on the contrary, the poorer the processability is.
Examples
1. 3 oriented silicon steel raw materials with the same annealing process before rolling and different cold rolling yield are selected as samples to be tested for processability test and evaluation, the materials to be tested adopt the same annealing process before rolling and cold rolling process, and the specific process information is shown in table 1.
Table 1: annealing before rolling and cold rolling process information of material to be tested for cold rolling processability
2. A group of tensile experiments are carried out by applying a tensile testing machine, the environmental temperature of the test sample is 30 ℃, and the test speed is 0.5s -1 . The mechanical property indexes of the samples obtained by the test are shown in table 2. On this basis, a stress-strain curve obtained from stress and strain data collected during the experiment is shown in fig. 1.
TABLE 2 mechanical Properties of the test specimens
| Sample numbering | Yield strength/MPa | Tensile strength/MPa | Elongation rate/%) | Reduction of area/%) |
| 1 | 506.67 | 645.53 | 22.82 | 4.76 |
| 2 | 501.90 | 655.67 | 22.72 | 4.68 |
| 3 | 506.03 | 659.86 | 22.75 | 4.62 |
| 4 | 512.57 | 627.14 | 22.86 | 4.33 |
| 5 | 501.63 | 625.38 | 22.72 | 4.22 |
| 6 | 509.65 | 613.45 | 22.58 | 4.20 |
3. Differentiating the stress strain data of the obtained test sample according to the formula (1) to obtain a differential curve (shown as figure 2) of sigma relative to strain epsilon, wherein the change d sigma of the curve stress in the test process is linearly and steeply reduced to indicate that the test is in an elastic deformation stage, and then the d sigma begins to rise after reaching the 1 st inflection point to indicate that the elastic deformation is finished, and the strain epsilon is reached at the moment a (ii) a After the elastic deformation stage is finished, d sigma begins to gradually decrease, and when d sigma =0, the corresponding critical strain amount is epsilon b (ii) a When d sigma is less than 0, the material enters a necking and breaking stage. Accordingly, the critical strain amounts of the test samples obtained are shown in table 3.
TABLE 3 Critical strain for test sample processability evaluation
| Sample numbering | ε a | |
| 1 | 0.43 | 16.15 |
| 2 | 0.72 | 13.92 |
| 3 | 0.59 | 12.94 |
| 4 | 0.83 | 15.23 |
| 5 | 0.78 | 15.02 |
| 6 | 0.70 | 15.12 |
4. Selecting strain value epsilon in [ epsilon a, ε b ]The test sample tensile curve data within the range is subjected to a polynomial fitting process according to equation (2):
σ 1 ＝448.15+31.26×ε-1.29×ε 2 -0.15×ε 3 +0.12×ε 4 -0.00041×ε 5 (4)
σ 2 ＝481.72-48.94×ε-7.57×ε 2 +0.79×ε 3 -0.05×ε 4 -0.0015×ε 5 (5)
σ 3 ＝493.98+55.11×ε-10.18×ε 2 +1.26×ε 3 -0.09×ε 4 -0.002×ε 5 (6)
σ 4 ＝446.58+101.28×ε-28.69×ε 2 +4.29×ε 3 -0.03×ε 4 -0.007×ε 5 (7)
σ 5 ＝474.97+58.74×ε-10.80×ε 2 +1.23×ε 3 -0.07×ε 4 -0.002×ε 5 (8)
σ 6 ＝483.84+63.72×ε-13.97×ε 2 +1.95×ε 3 -0.14×ε 4 -0.004×ε 5 (9)
wherein the expressions (4) to (9) are 1 respectively # ～6 # Fitting results of the corresponding curves of the samples; FIG. 3 shows example 1 # ～6 # And (3) fitting a stress-strain fitting curve of the sample in the plastic deformation process.
5. Integrating the critical strain values determined in the step 3 into the equations (4) to (9) of (10) to (15) respectively corresponding to 1 # ～6 # The sample is strained.
5. The results of evaluating the processability of the oriented silicon steel by the method of the invention and the conventional method obtained by calculation in the step 4 are shown in Table 4.
TABLE 4 Cold-ROLLING WORKABILITY ESTIMATION METHOD AND COMPARISON OF THE STEEL RATES OF TEST SAMPLES
From the analysis of table 4, the result obtained by adopting the method for determining the cold rolling workability of the oriented silicon steel characterized by the strain energy provided by the invention is consistent with the actual yield rate change trend of the product after comprehensively considering the mechanical performance indexes such as yield strength, tensile strength, elongation percentage and the like of the sample.
In contrast, the mechanical property indexes obtained by the traditional stretching method have small difference, and the cold rolling processability of the oriented silicon steel cannot be directly evaluated intuitively and accurately. Compared with the conventional method, the method can accurately and stably measure the cold rolling processability of the oriented silicon steel and is used as an important basis for setting the cold rolling process.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (2)
1. Method for evaluating processability of oriented silicon steel based on strain energyCharacterized in that the strain epsilon corresponding to the end of the elastic deformation is determined by means of a tensile test a Strain epsilon corresponding to the onset of necking b Selecting the strain amount to be [. Epsilon. ] a ,ε b ]And (3) performing integral treatment on the tensile curve data of the test sample in the range according to a fitting formula, calculating the area of a real plastic deformation curve, and representing the capability of the material capable of bearing cracks in the stage from plastic deformation to necking, namely representing the cold rolling processability of the oriented silicon steel.
2. The method for evaluating the processability of the oriented silicon steel based on the strain energy as claimed in claim 1, is characterized by comprising the following specific steps:
1) Carrying out a tensile test on a detection sample, collecting stress sigma and strain epsilon data of the test sample in the test process, and obtaining a corresponding stress-strain curve;
2) The obtained stress-strain data is subjected to differential processing according to the formula (1) to obtain a differential curve of sigma with respect to strain epsilon,
wherein, sigma is stress, epsilon is strain, and n is the number of the collected data points;
3) The linear and steep drop of the stress change d sigma curve indicates that the test is in an elastic deformation stage, the stress change d sigma curve begins to rise after reaching the 1 st inflection point, and the epsilon indicates that the elastic deformation is finished a The strain is the corresponding strain at the end of elastic deformation; after the elastic deformation phase, the stress change d σ curve starts to gradually decrease, necking starts when d σ =0, and ∈ b Is the corresponding strain at the beginning of necking; when d sigma is less than 0, the material enters a necking and breaking stage;
4) Selecting strain quantity epsilon in [ epsilon a ,ε b ]Test sample tensile curve data within the range, fitting a curve according to a polynomial of formula (2);
σ＝A+Bε+Cε 2 +Dε 3 +... (2)
wherein, A, B, C, D \8230isa constant obtained by fitting a test sample tensile curve by a least square method;
5) And (3) performing integral processing on the section with the tensile deformation higher than the critical strain value in the formula (2), and calculating the area of a real plastic deformation curve according to a formula (3):
wherein S is strain energy representing strain from ε a Increase to epsilon b The true value of the strain energy consumed in the process, the size of S represents the capability of the material for bearing cracks in the stage from plastic deformation to necking, namely the cold rolling processability of the oriented silicon steel is represented; the larger the S, the better the processability, and conversely, the worse the processability.
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