Method for testing physical and chemical results of steel sample blank after heat treatment

Abstract

The invention discloses a method for testing physical and chemical results of a steel sample blank after heat treatment. The method comprises the following steps: step 1, preparing the steel sample blank; 2, the steel sample blank is pretreated; 3, the steel sample blank is subjected to heat treatment, then the steel sample blank is tested, and a test result is recorded; step 4, optimizing process parameters of heat treatment according to a test result; according to the method, the physical and chemical property change rules of steel sample blanks with different sizes under the fixed heat treatment condition are verified, the influence of different heat treatment schemes on the properties of the steel sample blanks with the fixed sizes is evaluated, finally test data are analyzed, heat treatment process parameters are optimized, and the heat treatment efficiency is improved. A technological method capable of accurately judging the influence rule of the size of the steel sample blank on the physicochemical result after heat treatment is formed.

Description

Technical Field

[0001] The invention belongs to the technical field of material heat treatment, and particularly relates to a method for testing physical and chemical results of a steel sample after heat treatment. Background Art

[0002] In the field of material heat treatment, the size of steel samples has a significant impact on the heat treatment effect. Studies have shown that changes in the size of steel samples will directly affect key parameters such as heat conduction and heat radiation, which in turn profoundly affect the microstructure and physical and chemical properties of the material. Usually, in order to improve the consistency of product quality, it is necessary to optimize the process parameters by adjusting the size of steel samples and repeating the heat treatment experiments. However, in traditional methods, since the mechanism by which the heat treatment effect is affected by the size of steel samples is unclear, it is impossible to accurately judge the influence of the size of steel samples on the heat treatment performance, and there is a lack of corresponding process solutions. Therefore, it is very necessary to design a process method that has wide promotion value and can accurately judge the influence of the size of steel samples on the physical and chemical results after heat treatment. Summary of the Invention

[0003] The purpose of the present invention is to provide a testing method for the physical and chemical results of steel samples after heat treatment, which solves the problems in the prior art of being unable to accurately judge the influence of the size of steel samples on the physical and chemical results after heat treatment and lacking corresponding process solutions.

[0004] The technical solution adopted by the present invention is a method for testing the physical and chemical results of steel samples after heat treatment, comprising the following steps: Step 1: Prepare steel sample; Step 2: pre-treating the steel sample in step 1; Step 3: heat-treating the steel sample in step 2, then testing the steel sample and recording the test results; Step 4: Optimize the process parameters of the heat treatment according to the test results in step 3.

[0005] The present invention is also characterized in that: The specific process of step 1 is as follows: Select steel samples of the same model, and divide the steel samples into several groups of steel samples of different sizes and several groups of steel samples of the same size, with each group having several steel samples.

[0006] The specific process of step 2 is as follows: The surface of each steel sample in step 1 is cleaned to remove the surface oxide scale of the steel sample. The surface cleaning is specifically carried out by ultrasonic cleaning.

[0007] The specific process of step 3 is as follows: Step 3.1: Perform a uniform heat treatment on several groups of steel samples of different sizes after pretreatment in step 2, then test each steel sample and record the test parameters of each steel sample. The specific process is as follows: Step 3.1.1: Quenching treatment. The specific process is as follows: Step 3.1.1.1. Raise the heating furnace temperature to 815°C at a rate of less than 10°C / min. When the furnace temperature fluctuation range is less than 5°C, load steel samples of the same size. Step 3.1.1.2: Perform thermal insulation control at a constant temperature of 815°C for 1 hour. Use a thermocouple to monitor the temperature fluctuation in real time. The temperature fluctuation range should be less than 5°C. Step 3.1.1.3: Perform oil cooling. After the end of the heat preservation in step 3.1.1.2, transfer the sample to a quenching oil tank at a temperature of 40℃-80℃ and force-circulate and cool it to below 50℃ within 10 seconds. The flow rate of the quenching oil tank should be no less than 2.5m / s. Step 3.1.2, tempering treatment, the specific process is as follows: Step 3.1.2.1: Perform a rapid converter treatment to transfer the steel sample quenched in step 3.1.1 to an independent tempering furnace that has been preheated to 150°C. Step 3.1.2.2: Perform low-temperature tempering treatment in a constant temperature environment of 150°C for 3 to 4 hours, with the furnace temperature fluctuation range less than 3°C; Step 3.1.2.3: Perform air cooling. After the tempering and heat preservation in step 3.1.2.2 is completed, place the steel sample on a ventilation rack to cool naturally. At the same time, monitor the surface temperature until it drops to 22°C-28°C before taking it out of the furnace. The cooling rate should be less than 2°C / min. Step 3.1.3, hardness test, the specific process is as follows: Hardness is measured using the Rockwell HRC method. Test the Rockwell hardness of the steel sample according to GB / T 230.1-2018. Select three test points evenly on the same cross-section of the tempered steel sample in step 3.1.2. Measure each point three times, and take the average value as the hardness value of the steel sample. Step 3.1.4, tensile test, the specific process is as follows: Tensile tests were performed using an electronic universal testing machine in accordance with GB / T 228.1-2021. The room temperature tensile tests were performed using the tempered steel specimens from step 3.1.2. Each steel specimen was stretched to fracture, and the force-displacement curve of the steel specimen was recorded. The tensile strength, yield strength, elongation after fracture, and reduction of area of the tensile specimen were calculated and measured based on the curve.

[0008] Step 3.1.5. Record the test results of steps 3.1.3 and 3.1.4. Step 3.2: Heat treat several groups of steel samples of the same size after pretreatment in step 2 under different insulation conditions. Then, test each steel sample and record the test parameters of each steel sample. The specific process is as follows: Step 3.2.1, quenching treatment, the specific process is as follows: Step 3.2.1.1. Raise the heating furnace temperature to 815°C at a rate of less than 10°C / min. When the furnace temperature fluctuation range is less than 5°C, load steel samples of the same size. Step 3.2.1.2: Perform thermal insulation control at a constant temperature of 815°C for 1 hour. Use a thermocouple to monitor the temperature fluctuation in real time. The temperature fluctuation range is less than 5°C. Step 3.2.1.3: Perform oil cooling. After the end of the heat preservation in step 3.1.1.2, transfer the sample to a quenching oil tank at a temperature of 40℃-80℃ within 10 seconds and force circulation cool it to below 50℃. The flow rate of the quenching oil tank should be no less than 2.5m / s. Step 3.2.2, tempering treatment, the specific process is as follows: Step 3.2.2.1, perform rapid converter treatment, transfer the steel sample quenched in step 3.2.1 to an independent tempering furnace, which has been preheated to 150°C; Step 3.2.2.2, perform low-temperature tempering treatment in a constant temperature environment of 150°C with different holding times, the holding time range is 3 to 4 hours, and the furnace temperature fluctuation range is less than 3°C; Step 3.2.2.3: Perform air cooling. After the different tempering holding times in step 3.2.2.2 are completed, take out the steel samples and place them on ventilation racks for natural cooling. At the same time, monitor the surface temperature until it drops to 22°C-28°C before taking them out of the furnace. The cooling rate should be less than 2°C / min. Step 3.2.3, hardness test, the specific process is as follows: Hardness was measured using the Rockwell HRC method. Test the Rockwell hardness of the steel sample according to GB / T 230.1-2018. Select the tempered steel sample from step 3.2.2.3. Three test points were evenly selected on the same cross-section of the steel sample. Each point was measured three times, and the average value was taken as the hardness value of the steel sample. Step 3.2.4, tensile test, the specific process is as follows: Perform tensile tests using an electronic universal testing machine in accordance with GB / T 228.1-2021. Perform room temperature tensile tests on the tempered steel specimens from step 3.2.2.3. Stretch each steel specimen until it breaks. Record the force-displacement curve for the specimen. Calculate and measure the tensile strength, yield strength, elongation after fracture, and reduction of area of the tensile specimen based on the curve.

[0009] Step 3.2.5. Record the test results of steps 3.2.3 and 3.2.4. The beneficial effects of the present invention are: The present invention provides a method for testing the physical and chemical results of steel samples after heat treatment. By verifying the changing patterns of the physical and chemical properties of steel samples of different sizes under fixed heat treatment conditions and evaluating the effects of different heat treatment schemes on the performance of steel samples of fixed sizes, and finally analyzing the test data and optimizing the process parameters of the heat treatment, a set of process methods is formed that can accurately determine the effects of the size of the steel sample on the physical and chemical results after heat treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The present invention is a flow chart of a method for testing the physical and chemical results of a steel sample after heat treatment. DETAILED DESCRIPTION

[0011] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0012] The present invention provides a method for testing the physical and chemical results of steel sample after heat treatment, such as Figure 1 The specific steps are as follows: Step 1: Prepare steel sample. The specific process is as follows: The same type of steel samples are selected and made into several groups of steel samples with different sizes and several groups of steel samples with the same size, with each group having several steel samples.

[0013] Step 2: Pre-treat the steel sample in step 1. The specific process is as follows: The surface of each steel sample in step 1 is cleaned to remove the surface oxide scale of the steel sample. The surface cleaning is specifically carried out by ultrasonic cleaning.

[0014] Step 3: Heat treat the sample in step 2, then test the steel sample and record the test results. The specific process is as follows: Step 3.1: Perform a uniform heat treatment on several groups of steel samples of different sizes that have been pre-treated in step 2. Then, test each steel sample and record the test parameters of each steel sample. By verifying the change pattern of the physical and chemical properties of steel samples of different sizes under fixed heat treatment conditions, analyze the relationship between the change pattern and material properties. The specific process is as follows: Step 3.1.1: Quenching treatment. The specific process is as follows: Step 3.1.1.1. Raise the heating furnace temperature to 815°C at a rate of less than 10°C / min. When the furnace temperature fluctuation range is less than 5°C, load steel samples of the same size. Step 3.1.1.2: Perform thermal insulation control at a constant temperature of 815°C for 1 hour. Use a thermocouple to monitor the temperature fluctuation in real time. The temperature fluctuation range should be less than 5°C. Step 3.1.1.3: Perform oil cooling. After the end of the heat preservation in step 3.1.1.2, transfer the sample to a quenching oil tank at a temperature of 40℃-80℃ and force-circulate and cool it to below 50℃ within 10 seconds. The flow rate of the quenching oil tank should be no less than 2.5m / s. Step 3.1.2, tempering treatment, the specific process is as follows: Step 3.1.2.1: Perform a rapid converter treatment to transfer the steel sample quenched in step 3.1.1 to an independent tempering furnace that has been preheated to 150°C. Step 3.1.2.2, perform low-temperature tempering treatment, keep the temperature at 150℃ for 3 hours, and the furnace temperature fluctuation range is less than 3℃; Step 3.1.2.3: Perform air cooling. After the tempering and heat preservation in step 3.1.2.2 is completed, place the steel sample on a ventilation rack to cool naturally. At the same time, monitor the surface temperature until it drops to 22°C-28°C before taking it out of the furnace. The cooling rate should be less than 2°C / min. Step 3.1.3, hardness test, the specific process is as follows: Hardness is measured using the Rockwell hardness HRC method. According to GB / T 230.1-2018, "Rockwell hardness test for metallic materials - Part 1: Test method," the Rockwell hardness value of the test specimen is measured. At least three test points are evenly selected on the same cross-section of the tempered steel specimen in step 3.1.2. Each point is measured at least three times, and the average value is taken as the hardness value of the steel specimen. Step 3.1.4, tensile test, the specific process is as follows: In accordance with GB / T 228.1-2021 "Room Temperature Tensile Tests on Metallic Materials - Part 1: Room Temperature Test Methods", an electronic universal testing machine is used to conduct tensile tests. The room temperature tensile tests are conducted using the tempered steel specimens from step 3.1.2. Each steel specimen is stretched to fracture, and the force-displacement curve of the steel specimen is recorded. The tensile strength, yield strength, elongation after fracture, and reduction of area of the tensile specimen are calculated and measured based on the curve.

[0015] Step 3.1.5. Record the test results of steps 3.1.3 and 3.1.4. Step 3.2: Heat treat several groups of steel samples of the same size after pretreatment in step 2 under different insulation conditions. Then test each steel sample and record the test parameters of each steel sample. Use the test parameters to evaluate the impact of different heat treatment schemes on the performance of fixed-size samples, and summarize the best heat treatment scheme based on the test results. The specific process is as follows: Step 3.2.1, quenching treatment, the specific process is as follows: Step 3.2.1.1. Raise the heating furnace temperature to 815°C at a rate of less than 10°C / min. When the furnace temperature fluctuation range is less than 5°C, load steel samples of the same size. Step 3.2.1.2: Perform thermal insulation control at a constant temperature of 815°C for 1 hour. Use a thermocouple to monitor the temperature fluctuation in real time. The temperature fluctuation range is less than 5°C. Step 3.2.1.3: Perform oil cooling. After the end of the heat preservation in step 3.1.1.2, transfer the sample to a quenching oil tank at a temperature of 40℃-80℃ within 10 seconds and force circulation cool it to below 50℃. The flow rate of the quenching oil tank should be no less than 2.5m / s. Step 3.2.2, tempering treatment, the specific process is as follows: Step 3.2.2.1, perform rapid converter treatment, transfer the steel sample quenched in step 3.2.1 to an independent tempering furnace, which has been preheated to 150°C; Step 3.2.2.2, perform low-temperature tempering treatment in a constant temperature environment of 150°C with different holding times, the holding time range is 3 to 4 hours, and the furnace temperature fluctuation range is less than 3°C; Step 3.2.2.3: Perform air cooling. After the different tempering holding times in step 3.2.2.2 are completed, take out the steel samples and place them on ventilation racks for natural cooling. At the same time, monitor the surface temperature until it drops to 22°C-28°C before taking them out of the furnace. The cooling rate should be less than 2°C / min. Step 3.2.3, hardness test, the specific process is as follows: Hardness is measured using the Rockwell hardness HRC method. According to GB / T 230.1-2018, "Rockwell hardness test for metallic materials - Part 1: Test method," the Rockwell hardness value of the test specimen is measured. Select the tempered steel specimen from step 3.2.2.3. Select three test points evenly on the same cross-section of the steel specimen. Measure each point three times, and take the average value as the hardness value of the steel specimen. Step 3.2.4, tensile test, the specific process is as follows: In accordance with GB / T 228.1-2021 "Room Temperature Tensile Tests on Metallic Materials - Part 1: Room Temperature Test Methods", an electronic universal testing machine was used to conduct tensile tests at room temperature. The tempered steel specimens from step 3.2.2.3 were selected and each steel specimen was stretched to fracture. The force-displacement curve of the specimen was recorded. The tensile strength, yield strength, elongation after fracture, and reduction of area of the tensile specimen were calculated and measured based on the curve.

[0016] Step 3.2.5. Record the test results of steps 3.2.3 and 3.2.4. Step 4: Based on the test results in step 3, the process parameters of the heat treatment are optimized. By analyzing the test data, the process parameters of the heat treatment are optimized, and a set of process methods are formed that can accurately determine the influence of the size of the steel sample on the physical and chemical results after heat treatment.

[0017] The present invention provides a method for testing the physical and chemical properties of steel samples after heat treatment. By verifying the patterns of physical and chemical property changes in steel samples of different sizes under fixed heat treatment conditions, the method completes performance testing of at least three different sizes of samples under a unified heat treatment regime, records detailed data, and analyzes its relationship with material properties. Furthermore, the method evaluates the impact of different heat treatment regimes on the performance of fixed-size steel samples. Finally, the method analyzes the test data and optimizes heat treatment process parameters, resulting in a process method that can accurately determine the patterns of influence of steel sample size on physical and chemical properties after heat treatment.

[0018] The present invention provides a method for testing the physical and chemical results of steel samples after heat treatment, and a specific embodiment is as follows: Example 1 Step 1: Select the same batch of 9310 steel with a specification of 220 and an average grain size of 7. Its main chemical composition is shown in the following table: Table 19310 Steel Chemical Composition

[0019] Select 4 groups of 9310 steel samples of different sizes, 3 9310 steel samples in each group, as shown in the following table: Table 2 9310 steel samples of different sizes in Example 1

[0020] Select 4 groups of 9310 steel samples with the same size, 2 in each group. The specific sizes are shown in the following table: Table 3 9310 steel sample with the same size as Example 1

[0021] Step 2: pre-treat the steel samples in step 1 by using ultrasonic cleaning to clean the surface of each steel sample and remove the surface oxide scale of the steel sample.

[0022] Step 3: Perform uniform heat treatment on the two groups of steel samples of different sizes pre-treated in step 2, specifically: Quenching treatment: Heat the heating furnace to 815°C at a rate of less than 10°C / min. When the furnace temperature fluctuation range is less than 5°C, load the steel samples of the same size. Perform insulation control and keep the temperature at 815°C for 1 hour. Use a thermocouple to monitor the furnace temperature fluctuation in real time. The furnace temperature fluctuation range is less than 5°C. Perform oil cooling. Within 10 seconds after the end of the insulation in step 3.1.1.2, transfer the samples to a quenching oil tank at a temperature of 40°C-80°C and force-circulate and cool them to below 50°C. The flow rate of the quenching oil tank should be no less than 2.5 m / s. Tempering treatment: Perform a rapid converter treatment, transferring the steel sample quenched in step 3.1.1 to an independent tempering furnace that has been preheated to 150°C; perform a low-temperature tempering treatment, maintaining the temperature at 150°C for 3 hours, with a temperature fluctuation range of less than 3°C; perform an air cooling treatment, after the tempering and holding in step 3.1.2.2 is completed, place the steel sample on a ventilation rack to cool naturally, and monitor the surface temperature until it drops to 22°C-28°C before removing it from the furnace, with a cooling rate of less than 2°C / min; Hardness test: The hardness was measured using the Rockwell hardness HRC method. The Rockwell hardness value of the test sample was measured in accordance with GB / T 230.1-2018 "Rockwell hardness test for metallic materials - Part 1: Test method". Three test points were evenly selected on the same cross section of the tempered steel sample. Each point was measured three times, and the average value was taken as the hardness value of the steel sample.

[0023] Tensile test: In accordance with GB / T 228.1-2021 "Room Temperature Tensile Tests on Metallic Materials Part 1: Room Temperature Test Methods", an electronic universal testing machine was used to conduct tensile tests. Tempered steel specimens were used for room temperature tensile tests. Each steel specimen was stretched to fracture, and the force-displacement curve of the steel specimen was recorded. The tensile strength, yield strength, elongation after fracture, and reduction of area of the tensile specimen were calculated and measured based on the curve. The test results are shown in the following table: Table 4 Test results of 9310 steel samples of different sizes in Example 1

[0024] A group of steel samples of the same size after pretreatment in step 2 are uniformly heat treated as follows: Quenching treatment: Heat the heating furnace to 815°C at a rate of less than 10°C / min. When the furnace temperature fluctuation range is less than 5°C, load the steel samples of the same size. Perform insulation control and keep the temperature at 815°C for 1 hour. Use a thermocouple to monitor the furnace temperature fluctuation in real time. The furnace temperature fluctuation range is less than 5°C. Perform oil cooling. Within 10 seconds after the end of the insulation in step 3.1.1.2, transfer the samples to a quenching oil tank at a temperature of 40°C-80°C and force-circulate and cool them to below 50°C. The flow rate of the quenching oil tank should be no less than 2.5 m / s. Tempering treatment: Perform a rapid converter treatment, transferring the steel samples quenched in step 3.1.1 to an independent tempering furnace, which has been preheated to 150°C in advance; perform a low-temperature tempering treatment, in a constant temperature environment of 150°C, holding 1-4 groups of steel samples of the same size for different time periods, wherein group 1 of the same size samples is held for 3 hours, group 2 of the same size samples is held for 3.5 hours, group 3 of the same size samples is held for 3.8 hours, and group 4 of the same size samples is held for 4 hours, with the furnace temperature fluctuation range being less than 3°C; perform an air cooling treatment, placing the steel samples on a ventilation rack for natural cooling after the tempering and holding period, while monitoring the surface temperature until it drops to 22°C-28°C before being removed from the furnace, with a cooling rate of less than 2°C / min; Hardness test: The hardness was measured using the Rockwell hardness HRC method. The Rockwell hardness value of the test sample was measured in accordance with GB / T 230.1-2018 "Rockwell hardness test for metallic materials - Part 1: Test method". Three test points were evenly selected on the same cross section of the tempered steel sample. Each point was measured three times, and the average value was taken as the hardness value of the steel sample.

[0025] Tensile test: In accordance with GB / T 228.1-2021 "Room Temperature Tensile Tests on Metallic Materials Part 1: Room Temperature Test Methods", an electronic universal testing machine was used to conduct tensile tests. Tempered steel specimens were used for room temperature tensile tests. Each steel specimen was stretched to fracture, and the force-displacement curve of the steel specimen was recorded. The tensile strength, yield strength, elongation after fracture, and reduction of area of the tensile specimen were calculated and measured based on the curve. The test results are shown in the following table: Table 5 Test results of 9310 steel samples of the same size as in Example 1

[0026] Step 4: Optimize the process parameters of the heat treatment according to the test results in step 3.

[0027] The test results of Example 1 above show that the size of the heat-treated 9310 steel sample with a gauge of 220 has a significant effect on the test results. Sample size is a key factor influencing the test results. As sample size increases, its Rockwell hardness shows a downward trend. At the same time, large samples are significantly affected by the heat treatment, with a significant reduction in tensile strength and yield strength. This is more pronounced for square billets than for round billets. Similarly, tempering time also significantly affects the tensile strength and yield strength of the drawn samples. Extended tempering time reduces tensile strength and yield strength. Therefore, to ensure a first-pass yield, smaller test samples should be used and the tempering time should be shortened.

[0028] Example 2 This example uses the same batch of 9310 steel with a specification of 400, and selects three groups of 9310 steel samples of different sizes, with two steel samples in each group, as shown in the following table: Table 6 9310 steel samples of different sizes in Example 2

[0029] Select 2 groups of steel samples of the same size, with 2 steel samples in each group, as shown in the following table: Table 7 9310 steel sample with the same size as Example 2

[0030] The method for testing the physical and chemical properties of heat-treated steel samples of the present invention was used to test steel samples of different sizes and steel samples of the same size in this embodiment, and the test results were recorded. The tempering and holding times for each group of steel samples of the same size were 3 hours and 3.5 hours, respectively. The specific results are shown in the following table: Table 8 Test results of 9310 steel samples of different sizes in Example 2

[0031] Table 9 Test results of 9310 steel samples of the same size as in Example 2

[0032] Example 3 This example uses the same batch of 9310 steel with a specification of 300, and selects three groups of 9310 steel samples of different sizes, with two steel samples in each group, as shown in the following table: Table 10 9310 steel samples of different sizes in Example 3

[0033] Select 2 groups of steel samples of the same size, with 2 steel samples in each group, as shown in the following table: Table 11 9310 steel sample with the same size as Example 3

[0034] The method for testing the physical and chemical properties of heat-treated steel samples of the present invention was used to test steel samples of different sizes and steel samples of the same size in this embodiment, and the test results were recorded. The tempering and holding times for the steel samples of the same size were 3.5 hours and 3.8 hours, respectively. The specific results are shown in the following table: Table 12 Test results of 9310 steel samples of different sizes in Example 3

[0035] Table 13 Test results of 9310 steel samples of the same size as in Example 3

[0036] Example 4 This example uses the same batch of 9310 steel with a specification of 250, and selects three groups of 9310 steel samples of different sizes, with two steel samples in each group, as shown in the following table: Table 14 9310 steel samples of different sizes in Example 4

[0037] Select 2 groups of steel samples of the same size, with 2 steel samples in each group, as shown in the following table: Table 15 9310 steel sample with the same size as Example 4

[0038] The method for testing the physical and chemical properties of heat-treated steel samples of the present invention was used to test steel samples of different sizes and steel samples of the same size in this embodiment, and the test results were recorded. The tempering and holding times for each group of steel samples of the same size were 3.5 hours and 4 hours, respectively. The specific results are shown in the following table: Table 16 Test results of 9310 steel samples of different sizes in Example 4

[0039] Table 17 Test results of 9310 steel samples of the same size as in Example 4

[0040] Example 5 This example uses the same batch of 9310 steel with a specification of 300, and selects three groups of 9310 steel samples of different sizes, with two steel samples in each group, as shown in the following table: Table 18 9310 steel samples of different sizes in Example 5

[0041] Select 2 groups of steel samples of the same size, with 2 steel samples in each group, as shown in the following table: Table 19 9310 steel sample with the same size as Example 5

[0042] The method for testing the physical and chemical properties of heat-treated steel samples of the present invention was used to test steel samples of different sizes and steel samples of the same size in this embodiment, and the test results were recorded. The tempering and holding times for the steel samples of the same size were 3 hours and 3.8 hours, respectively. The specific results are shown in the following table: Table 20 Test results of 9310 steel samples of different sizes in Example 5

[0043] Table 21 Test results of 9310 steel samples of the same size as in Example 5

[0044] Example 6 This embodiment uses the same batch of 9310 steel with a specification of 350, and selects three groups of 9310 steel samples of different sizes, with two steel samples in each group, as shown in the following table: Table 22 9310 steel samples of different sizes in Example 6

[0045] Select 2 groups of steel samples of the same size, with 2 steel samples in each group, as shown in the following table: Table 23 9310 steel sample with the same size as Example 6

[0046] The method for testing the physical and chemical properties of heat-treated steel samples of the present invention was used to test steel samples of different sizes and steel samples of the same size in this embodiment, and the test results were recorded. The tempering and holding times for each group of steel samples of the same size were 3.8 hours and 4 hours, respectively. The specific results are shown in the following table: Table 24 Test results of 9310 steel samples of different sizes in Example 6

[0047] Table 25 Test results of 9310 steel samples of the same size as Example 6

[0048] As can be seen from Examples 1-6 above, by verifying the changes in the physical and chemical properties of steel samples of different sizes under fixed heat treatment conditions, completing performance tests on at least three different-sized samples under a unified heat treatment regime, recording detailed data, and analyzing its relationship with material properties, the effects of different heat treatment regimes on the performance of fixed-size steel samples were evaluated. Finally, the test data was analyzed and heat treatment process parameters were optimized, resulting in a process method that can accurately determine the effect of steel sample size on the physical and chemical results after heat treatment. This effectively solves the problem of the existing art that cannot accurately determine the effect of steel sample size on the physical and chemical results after heat treatment and lacks a corresponding process solution.

Claims

1. A method for testing the physical and chemical results of steel samples after heat treatment, characterized in that: The following steps are involved: Step 1: Prepare steel sample; Step 2: pre-treating the steel sample in step 1; Step 3: heat-treating the steel sample in step 2, then testing the steel sample and recording the test results; Step 4: Optimize the process parameters of the heat treatment according to the test results in step 3.

2. The method for testing the physical and chemical results of steel samples after heat treatment according to claim 1, characterized in that: The specific process of step 1 is as follows: Select steel samples of the same model, and divide the steel samples into several groups of steel samples of different sizes and several groups of steel samples of the same size, with each group having several steel samples.

3. The method for testing the physical and chemical results of steel samples after heat treatment according to claim 1, characterized in that: The specific process of step 2 is as follows: The surface of each steel sample in step 1 is cleaned to remove the surface oxide scale of the steel sample. The surface cleaning is specifically carried out by ultrasonic cleaning.

4. The method for testing the physical and chemical results of steel samples after heat treatment according to claim 1, characterized in that: The specific process of step 3 is as follows: Step 3.1, subjecting several groups of steel samples of different sizes pretreated in step 2 to a uniform heat treatment, then testing each steel sample, and recording the test parameters of each steel sample; Step 3.2: Heat treat several groups of steel samples of the same size after pretreatment in step 2 under different insulation conditions, then test each steel sample and record the test parameters of each steel sample.

5. The method for testing the physical and chemical results of steel samples after heat treatment according to claim 4, characterized in that: The specific process of step 3.1 is as follows: Step 3.1.1, quenching treatment; Step 3.1.2, tempering treatment; Step 3.1.3, hardness test; Step 3.1.4, tensile test; Step 3.1.

5. Record the test results of steps 3.1.3 and 3.1.

4.

6. The method for testing the physical and chemical results of steel samples after heat treatment according to claim 5, characterized in that: The specific process of the quenching treatment in step 3.1.1 is as follows: Step 3.1.1.

1. Raise the heating furnace temperature to 815°C at a rate of less than 10°C / min. When the furnace temperature fluctuation range is less than 5°C, load steel samples of the same size. Step 3.1.1.2: Perform thermal insulation control at a constant temperature of 815°C for 1 hour. Use a thermocouple to monitor the temperature fluctuation in real time. The temperature fluctuation range should be less than 5°C. Step 3.1.1.3: Perform oil cooling. After the end of the heat preservation in step 3.1.1.2, transfer the sample to a quenching oil tank at a temperature of 40°C-80°C and circulate and cool it to below 50°C within 10 seconds. The flow rate of the quenching oil tank should be no less than 2.5m / s. The specific process of the tempering treatment in step 3.1.2 is as follows: Step 3.1.2.1: Perform a rapid converter treatment to transfer the steel sample quenched in step 3.1.1 to an independent tempering furnace that has been preheated to 150°C. Step 3.1.2.2, perform low-temperature tempering treatment, keep the temperature at 150℃ for 3 hours, and the furnace temperature fluctuation range is less than 3℃; Step 3.1.2.3: Perform air cooling. After the tempering and heat preservation in step 3.1.2.2 is completed, place the steel sample on a ventilation rack to cool naturally. At the same time, monitor the surface temperature until it drops to 22°C-28°C before taking it out of the furnace. The cooling rate should be less than 2°C / min. The specific process of the hardness test in step 3.1.3 is as follows: Hardness is measured using the Rockwell HRC method. Test the Rockwell hardness of the steel sample according to GB / T 230.1-2018. Select three test points evenly on the same cross-section of the tempered steel sample in step 3.1.

2. Measure each point three times, and take the average value as the hardness value of the steel sample. The specific process of the tensile test in step 3.1.4 is as follows: Tensile tests were performed using an electronic universal testing machine in accordance with GB / T 228.1-2021. The room temperature tensile tests were performed using the tempered steel specimens from step 3.1.

2. Each steel specimen was stretched to fracture, and the force-displacement curve of the steel specimen was recorded. The tensile strength, yield strength, elongation after fracture, and reduction of area of the tensile specimen were calculated and measured based on the curve.

7. The method for testing the physical and chemical results of steel samples after heat treatment according to claim 4, characterized in that: The specific process of step 3.2 is as follows: Step 3.2.1, quenching treatment; Step 3.2.2, tempering treatment; Step 3.2.3, hardness test; Step 3.2.4, tensile test; Step 3.2.

5. Record the test results of steps 3.2.3 and 3.2.

4.

8. The method for testing the physical and chemical results of steel samples after heat treatment according to claim 7, characterized in that: The specific process of quenching treatment in step 3.2.1 is as follows: Step 3.2.1.

1. Raise the heating furnace temperature to 815°C at a rate of less than 10°C / min. When the furnace temperature fluctuation range is less than 5°C, load steel samples of the same size. Step 3.2.1.2: Perform thermal insulation control at a constant temperature of 815°C for 1 hour. Use a thermocouple to monitor the temperature fluctuation in real time. The temperature fluctuation range is less than 5°C. Step 3.2.1.3: Perform oil cooling. After the end of the heat preservation in step 3.1.1.2, transfer the sample to a quenching oil tank at a temperature of 40°C-80°C and circulate and cool it to below 50°C within 10 seconds. The flow rate of the quenching oil tank should be no less than 2.5m / s. The specific process of the tempering treatment in step 3.2.2 is as follows: Step 3.2.2.1, perform rapid converter treatment, transfer the steel sample quenched in step 3.2.1 to an independent tempering furnace, which has been preheated to 150°C; Step 3.2.2.2, perform low-temperature tempering treatment in a constant temperature environment of 150°C with different holding times, the holding time range is 3 to 4 hours, and the furnace temperature fluctuation range is less than 3°C; Step 3.2.2.3: Perform air cooling. After the different tempering holding times in step 3.2.2.2 are completed, take out the steel samples and place them on ventilation racks for natural cooling. At the same time, monitor the surface temperature until it drops to 22°C-28°C before taking them out of the furnace. The cooling rate should be less than 2°C / min. The specific process of the hardness test in step 3.2.3 is as follows: Hardness was measured using the Rockwell HRC method. Test the Rockwell hardness of the steel sample according to GB / T 230.1-2018. Select the tempered steel sample from step 3.2.2.

3. Three test points were evenly selected on the same cross-section of the steel sample. Each point was measured three times, and the average value was taken as the hardness value of the steel sample. The specific process of the tensile test in step 3.2.4 is as follows: Perform tensile tests using an electronic universal testing machine in accordance with GB / T 228.1-2021. Perform room temperature tensile tests on the tempered steel specimens from step 3.2.2.

3. Stretch each steel specimen until it breaks. Record the force-displacement curve for the specimen. Calculate and measure the tensile strength, yield strength, elongation after fracture, and reduction of area of the tensile specimen based on the curve.

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