A method for determining the maximum service temperature of high-aluminum ethylene cracking furnace tubes

Abstract

The present invention belongs to the field of ethylene cracking furnace tube detection, and particularly relates to a method for determining the maximum service temperature of high-aluminum ethylene cracking furnace tubes. The present invention determines the area fraction influence factor A of the total inter-dendritic precipitates (M 23 C6, M7C3, Ni3Al), the area fraction influence factor B of the total precipitates on the dendrite stem (M 23 C6, Ni3Al), and the area fraction influence factor C of M7C3 in the total inter-dendritic precipitates accounting for the area of the total inter-dendritic precipitates; it also determines the Vickers hardness influence factor D, and finally obtains the influence function for judging the maximum service temperature of the ethylene cracking furnace tubes. The present invention first proposes a method for determining the maximum service temperature of high-aluminum ethylene cracking furnace tubes. The present invention provides a method for determining the maximum service temperature of furnace tubes for the detection, evaluation and analysis of in-service ethylene cracking furnace tubes, determines the maximum service temperature of the furnace tubes, and provides a basis for evaluating the service state of the furnace tubes and finding the causes of furnace tube failures.

Description

Technical Field

[0001] The invention belongs to the field of ethylene cracking furnace tube detection, and in particular relates to a method for determining the maximum service temperature of a high-aluminum ethylene cracking furnace tube. Background Art

[0002] Ethylene cracking furnace is the core equipment of petrochemical ethylene plant. Centrifugal casting furnace tube is the key component of ethylene cracking furnace. It serves in high temperature and carburizing environment for a long time. Determining the maximum service temperature of furnace tube is an important technical means to analyze the cause of furnace tube failure.

[0003] High-aluminum ethylene cracking furnace tubes are new centrifugal casting furnace tubes developed by furnace tube manufacturers in recent years. Compared with traditional 25Cr35NiNb+MA alloy and 35Cr45NiNb+MA alloy centrifugal furnace tubes, they have higher anti-coking and anti-carburization performance. At present, the determination of the maximum service temperature of the new high-aluminum ethylene cracking furnace tubes is mainly based on the installation of temperature measuring thermocouples on the outer wall of the furnace tube. This method is costly, has poor operability, and cannot achieve measurement of each furnace tube. Summary of the invention

[0004] One of the purposes of the present invention is to provide a method for determining the maximum service temperature of a high-aluminum ethylene cracking furnace tube. The determination method can determine the maximum service temperature of an in-service ethylene cracking furnace tube, providing a basis for evaluating the service status of the furnace tube and finding the cause of furnace tube failure.

[0005] To achieve the above object, the present invention adopts the following technical scheme: A method for determining the maximum service temperature of a high-aluminum ethylene cracking furnace tube comprises the following steps:

[0006] S1. Microstructure analysis of high-aluminum ethylene cracking furnace tubes

[0007] An optical metallographic microscope is used to cut a high-aluminum ethylene cracking furnace tube along the tube diameter direction to obtain a cross section, and a sample is taken at a thickness position of 1 / 4 to 3 / 4 of the tube wall surface in the cross section. The cross section is used as the observation surface for microstructure analysis, and the magnification is 500 to 1000 times. Each sample has at least 5 measuring points, and the average value is taken to measure the area S1 of the total precipitates between dendrites of the furnace tube material within the field of view per unit area S0. The total precipitates between dendrites specifically include thick strips and blocky precipitates M at the edge of the dendrite. 23 C6, coarse strip and block precipitates Ni3Al at the edge of dendrites, fine fishbone and worm-like precipitates M7C3 inside dendrites, calculate the total area fraction of precipitates between dendrites A = (S1 / S0) × 100%, the unit is 1;

[0008] S2. Determine the maximum service temperature range of the high-aluminum ethylene cracking furnace tube: when A>7%, the maximum service temperature of the furnace tube is less than 1100°C; when A≤7%, the maximum service temperature of the furnace tube is ≥1100°C.

[0009] As a further improvement of the method for determining the maximum service temperature of high-aluminum ethylene cracking furnace tubes:

[0010] 5. When the area S1 is measured in step S1, the area S2 of the total precipitate of the dendrite of the furnace tube material in the field of view per unit area S0 is measured, wherein the total precipitate of the dendrite of the furnace tube material includes the M in the dendrite in the form of thin strips and particles. 23 C6, for thin strips and granular Ni3Al, calculate the total area fraction of dendrite stem precipitates B = (S2 / S0) × 100%, the unit is 1;

[0011] While measuring the area S1 in step S1, the area S3 of the fine fishbone-shaped and worm-shaped precipitates M7C3 inside the dendrites in the total precipitates between the dendrites of the furnace tube material in the field of view of the unit area S0 is measured, and the percentage of S3 to the total precipitate area between the dendrites is calculated as C=(S3 / S1)×100%, where the unit is 1;

[0012] The Vickers hardness test was carried out on the high aluminum ethylene cracking furnace tube, and the Vickers hardness D of the furnace tube material was measured, and the unit was HV10;

[0013] Then the maximum service temperature of ethylene cracking furnace tubes is divided according to the following procedure:

[0014] 1) When A>7%, the influence function of the maximum service temperature of the high aluminum ethylene cracking furnace tube is determined according to the total area fraction A of the interdendritic precipitates, the total area fraction B of the dendrite stem precipitates and the Vickers hardness D of the furnace tube material:

[0015] f(A, B, D) = aA + bB + dD

[0016] Where A is the total area fraction of the interdendritic precipitates of the furnace tube, the unit is 1; B is the area fraction of the dendrite stem precipitates, the unit is 1; D is the Vickers hardness of the furnace tube material, the unit is HV10; where a is 10, b is 150, and d is 0.003;

[0017] The range of the maximum service temperature T of high-aluminum ethylene cracking furnace tubes is divided as follows:

[0018] If f(A, B, D)≥4.2, determine T≤900℃;

[0019] If 3.4≤f(A, B, D)≥4.2, it is determined that 900℃<T≤950℃;

[0020] If 2.9≤f(A, B, D)<3.4, it is determined that 950<T≤1000℃;

[0021] If 2.5≤f(A, B, D)<2.9, it is determined that 1000<T≤1050℃;

[0022] If 1.9≤f(A, B, D)<2.5, it is determined that 1050<T≤1100℃;

[0023] 2) When A≤7%, and the maximum service temperature of the furnace tube is ≥1100°C, the influence function of the maximum service temperature of the high aluminum ethylene cracking furnace tube is determined according to the area fraction C and the Vickers hardness D of the fine fishbone-shaped and worm-shaped M7C3 precipitates inside the dendrites of the furnace tube material obtained in step 3 and step 4:

[0024] f(C, D)=cC+dD

[0025] C is the area fraction of the fine fishbone-shaped and worm-shaped M7C3 precipitates inside the dendrites, and the unit is 1; where D is the Vickers hardness of the furnace tube material, and the unit is HV10; c is 10, and d is 0.003;

[0026] The range of the maximum service temperature T of high-aluminum ethylene cracking furnace tubes is divided as follows:

[0027] If 6.1≤f(C, D)<6.9, it is determined that 1100<T≤1150℃;

[0028] If 5.2≤f(C, D)<6.1, it is determined that 1150<T≤1200℃;

[0029] If 4.8≤f(C, D)<5.2, it is determined that 1200<T≤1250℃.

[0030] Preferably, a GX53 Olympus optical metallographic microscope is used for microstructural analysis.

[0031] Preferably, a DVK-1S Vickers hardness tester is used to measure the Vickers hardness D of the furnace tube material according to GB / T 4340.1-2009 "Vickers hardness test for metallic materials - Part 1: Test method".

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The present invention provides a method for quickly judging the maximum service temperature of a new type of high-aluminum ethylene cracking furnace tube by microstructure observation and Vickers hardness test. 23 C6, M7C3, Ni3Al) area fraction influence factor A, dendrite trunk total precipitate (M 23The influence factor B of the area fraction of C6, Ni3Al) and the influence factor C of the area fraction of M7C3 in the dendrites and the total precipitation in the dendrites are determined; the influence factor D of the Vickers hardness is also determined, and finally the influence function for judging the maximum service temperature of the ethylene cracking furnace tube is obtained. The present invention starts from the perspective of the microstructure and hardness change of the furnace tube, and realizes the judgment of the maximum service temperature of the furnace tube by quantitative analysis of the microstructure between the dendrites and the dendrite trunk of the furnace tube and the Vickers hardness measurement.

[0034] Where S1 represents the area of ​​total precipitates between dendrites of furnace tube material within the field of view of unit area S0, specifically including coarse strips and blocks of precipitates M at the edge of dendrites. 23 C6, thick strip and block precipitates Ni3Al at the edge of the dendrite, and fine fishbone and worm-like precipitates M7C3 inside the dendrite; S2 represents the area of ​​the total precipitates of the dendrite trunk of the furnace tube material within the field of view of the unit area S0, specifically including the thin strip and granular M7C3 in the dendrite trunk. 23 C6, thin strips and granular Ni3Al; S3 represents the area of ​​fine fishbone and worm-like precipitates M7C3 inside the dendrite of the furnace tube material within the field of view per unit area S0, which is a part of the total precipitates between dendrites. The dendrites and dendrite trunks belong to different parts. The dendrites are mainly composed of primary precipitated carbides, mainly located near the austenite grain boundary; the dendrite trunks are mainly located in the austenite grains, and the precipitates are mainly secondary precipitated carbides. For details, see Figure 1 and Figure 2 .

[0035] The technical principle of the determination method of the present invention is as follows:

[0036] With the increase of service temperature (below 1100℃), the fishbone-shaped and worm-shaped precipitates M7C3 inside the dendrites of high-aluminum ethylene cracking furnace tubes will gradually turn into blocky M7C3. 23 C6 transformation, interdendritic edge precipitate M 23 C6 will gradually aggregate and grow, and the massive Ni3Al will gradually dissolve, corresponding to the dendrite M7C3, M 23 The volume fraction of C6 and Ni3Al will decrease; the dendrite trunk will disperse and precipitate granular M 23 C6 and Ni3Al will also gradually dissolve with the increase of service temperature, so the dendrite dry precipitate M 23 The area fractions of C6 and Ni3Al will also gradually decrease. In addition, since the hardness of carbides is higher than that of the austenite matrix, the reduction in the number of carbides is accompanied by a decrease in Vickers hardness.

[0037] As the service temperature continues to increase (above 1100℃), the fishbone-shaped and worm-shaped precipitates M7C3 in the dendrites of the high-aluminum ethylene cracking furnace tube continue to turn into blocky M 23C6 transformation, at this time, the interdendritic Ni3Al has dissolved, so the number of fishbone and worm-like M7C3 between dendrites decreases, while the interdendritic block M 23 As the size of C6 increases, the area fraction of fishbone-shaped and worm-shaped M7C3 in the total interdendritic precipitates decreases; due to the decrease in the total number of carbides in the interdendritic crystals, the Vickers hardness decreases. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a photo of a typical microstructure of the dendrites of the high-aluminum ethylene cracking furnace tube of the present invention;

[0039] Figure 2 This is a photo of a typical microstructure of a dendrite of a high-aluminum ethylene cracking furnace tube of the present invention;

[0040] Figure 3 This is a photograph of the microstructure of furnace tube No. 1 in Example 1 of the present invention;

[0041] Figure 4 is a photograph of the microstructure of furnace tube No. 2 in Example 2 of the present invention;

[0042] Figure 5 is a photograph of the microstructure of furnace tube No. 3 in Example 3 of the present invention;

[0043] Figure 6 This is a photograph of the microstructure of the 4# furnace tube in Example 4 of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] This embodiment provides a method for determining the maximum service temperature of a high-aluminum ethylene cracking furnace tube, specifically comprising the following steps:

[0047] 1) Take the high-aluminum ethylene cracking furnace tube (1#) after high-temperature heat treatment at 900°C in the heating furnace, take a sample at the 1 / 2 wall thickness of the cross section of the high-aluminum ethylene cracking furnace tube, take the cross section as the observation surface, and use GX53 Olympus optical metallographic microscope to analyze the microstructure of the sample, with a magnification of 1000 times. The microstructure photos are shown in Figure 3 The area S1 of the total precipitates between dendrites of the furnace tube material in the field of view per unit area S0 is measured, and the total precipitates between dendrites specifically include thick strips and blocks of precipitates M at the edge of the dendrite. 23C6, thick strip and block precipitates Ni3Al at the edge of the dendrite, and fine fishbone and worm-like precipitates M7C3 inside the dendrite. The total precipitate area fraction A between the dendrites is calculated as A=(S1 / S0)×100%, with the unit being 1; at the same time, the area S2 of the total precipitates of the dendrite stem of the furnace tube material within the field of view within the unit area S0 is measured. The total precipitates of the dendrite stem of the furnace tube material include thin strips and granular precipitates M7C3 in the dendrite stem. 23 C6, for thin strips and granular Ni3Al, calculate the total area fraction of dendrite stem precipitates B = (S2 / S0) × 100%, the unit is 1;

[0048] Switch the test interface, repeat the above operation 4 times, calculate the average value A of the total area fraction of the interdendritic precipitates of the 1# furnace tube in the 5 tests to be 13.8%; calculate the average value B of the total area fraction of the dendrite stem precipitates in the 5 tests to be 1.1%;

[0049] 2) According to GB / T 4340.1-2009 "Vickers hardness test for metallic materials Part 1: Test method", a DVK-1S Vickers hardness tester was used to measure the Vickers hardness D of the furnace tube material, and the test result was 392HV10.

[0050] 3) Determine the maximum service temperature of ethylene cracking furnace tubes:

[0051] Since A = 13.8%, which is greater than 7%, a is 10, b is 150, and d is 0.003, the influence function is calculated as follows:

[0052] f(A, B, D) = aA + bB + dD

[0053] =10×0.138+150×0.011+0.003×392

[0054] =4.206

[0055] It is determined that the maximum service temperature of the No. 1 furnace tube is about 900℃, which is consistent with the actual heat treatment temperature of the furnace tube of 900℃.

[0056] Example 2

[0057] This embodiment provides a method for determining the maximum service temperature of a high-aluminum ethylene cracking furnace tube, specifically comprising the following steps:

[0058] 1) Take the high-aluminum ethylene cracking furnace tube (2#) after high-temperature heat treatment at 1020°C in the heating furnace, take a sample at the 1 / 2 wall thickness of the cross section of the high-aluminum ethylene cracking furnace tube, take the cross section as the observation surface, and use GX53 Olympus optical metallographic microscope to analyze the microstructure of the sample, with a magnification of 1000 times. The microstructure photos are shown in Figure 4The area S1 of the total precipitates between dendrites of the furnace tube material in the field of view per unit area S0 is measured, and the total precipitates between dendrites specifically include thick strips and blocks of precipitates M at the edge of the dendrite. 23 C6, thick strip and block precipitates Ni3Al at the edge of the dendrite, and fine fishbone and worm-like precipitates M7C3 inside the dendrite. The total precipitate area fraction A between the dendrites is calculated as A=(S1 / S0)×100%, with the unit being 1; at the same time, the area S2 of the total precipitates of the dendrite stem of the furnace tube material within the field of view within the unit area S0 is measured. The total precipitates of the dendrite stem of the furnace tube material include thin strips and granular precipitates M7C3 in the dendrite stem. 23 C6, for thin strips and granular Ni3Al, calculate the total area fraction of dendrite stem precipitates B = (S2 / S0) × 100%, the unit is 1;

[0059] Switch the test interface, repeat the above operation 4 times, calculate the average value A of the total area fraction of the interdendritic precipitates of the 1# furnace tube in the 5 tests to be 12.1%, and calculate the average value B of the total area fraction of the dendrite stem precipitates in the 5 tests to be 0.27%;

[0060] 2) According to GB / T 4340.1-2009 "Vickers hardness test for metallic materials Part 1: Test method", a DVK-1S Vickers hardness tester was used to measure the Vickers hardness D of the furnace tube material, and the test result was 380HV10.

[0061] 3) Determine the maximum service temperature of ethylene cracking furnace tubes:

[0062] Since A = 12.1%, which is greater than 7%, a is 10, b is 150, and d is 0.003, the influence function is calculated as follows:

[0063] f(A, B, D) = aA + bB + dD

[0064] =10×0.121+150×0.0027+0.003×380

[0065] =2.775

[0066] It is determined that the maximum service temperature of the 2# furnace tube is between 1000 and 1050°C, which is consistent with the actual heat treatment temperature of the furnace tube of 1020°C.

[0067] Example 3

[0068] This embodiment provides a method for determining the maximum service temperature of a high-aluminum ethylene cracking furnace tube, specifically comprising the following steps:

[0069] 1) Take the high-aluminum ethylene cracking furnace tube (3#) after high-temperature heat treatment at 1150°C in the heating furnace, take a sample at the 1 / 2 wall thickness of the cross section of the high-aluminum ethylene cracking furnace tube, take the cross section as the observation surface, and use the GX53 Olympus optical metallographic microscope to analyze the microstructure of the sample, with a magnification of 1000 times. The microstructure photos are shown in Figure 5 The area S1 of the total precipitates between dendrites of the furnace tube material in the field of view per unit area S0 is measured, and the total precipitates between dendrites specifically include thick strips and blocks of precipitates M at the edge of the dendrite. 23 C6, thick strip and block precipitates Ni3Al at the edge of the dendrite, and fine fishbone and worm-like precipitates M7C3 inside the dendrite, calculate the total precipitate area fraction A between the dendrites = (S1 / S0) × 100%, the unit is 1; at the same time, measure the area S3 of the fine fishbone and worm-like precipitates M7C3 inside the dendrite in the total precipitates between the dendrites of the furnace tube material in the field of view per unit area S0, and calculate the percentage of S3 in the total precipitate area between the dendrites C = (S3 / S1) × 100%, the unit is 1;

[0070] Switch the test interface, repeat the above operation 4 times, calculate the average value A of the total area fraction of the interdendritic precipitates of the 1# furnace tube in the 5 tests to be 6.1%, A≤7%; calculate the average value C of the area fraction of the total area fraction of the interdendritic precipitates of the M7C3 inside the interdendritic precipitates in the 5 tests to be 51%;

[0071] 2) According to GB / T 4340.1-2009 "Vickers hardness test for metallic materials Part 1: Test method", a DVK-1S Vickers hardness tester was used to measure the Vickers hardness D of the furnace tube material, and the test result was 343HV10.

[0072] 3) Determine the maximum service temperature of ethylene cracking furnace tubes:

[0073] Since A = 6.1%, which is less than 7%, c is 10, and d is 0.003, the influence function is calculated as follows:

[0074] f(C, D)=cC+dD

[0075] =10×0.51+0.003×343

[0076] =6.1

[0077] It is determined that the maximum service temperature of the 3# furnace tube is about 1150℃, which is consistent with the actual heat treatment temperature of the furnace tube of 1150℃.

[0078] Example 4

[0079] This embodiment provides a method for determining the maximum service temperature of a high-aluminum ethylene cracking furnace tube, specifically comprising the following steps:

[0080] 1) Take the high-aluminum ethylene cracking furnace tube (4#) after high-temperature heat treatment at 1190°C in the heating furnace, take a sample at the 1 / 2 wall thickness of the cross section of the high-aluminum ethylene cracking furnace tube, take the cross section as the observation surface, and use GX53 Olympus optical metallographic microscope to analyze the microstructure of the sample, with a magnification of 1000 times. The microstructure photos are shown in Figure 6 The area S1 of the total precipitates between dendrites of the furnace tube material in the field of view per unit area S0 is measured, and the total precipitates between dendrites specifically include thick strips and blocks of precipitates M at the edge of the dendrite. 23 C6, thick strip and block precipitates Ni3Al at the edge of the dendrite, and fine fishbone and worm-like precipitates M7C3 inside the dendrite, calculate the total precipitate area fraction A between the dendrites = (S1 / S0) × 100%, the unit is 1; at the same time, measure the area S3 of the fine fishbone and worm-like precipitates M7C3 inside the dendrite in the total precipitates between the dendrites of the furnace tube material in the field of view per unit area S0, and calculate the percentage of S3 in the total precipitate area between the dendrites C = (S3 / S1) × 100%, the unit is 1;

[0081] Switch the test interface, repeat the above operation 4 times, calculate the average value A of the total area fraction of the interdendritic precipitates of the 1# furnace tube in the 5 tests to be 6.0%, A≤7%; calculate the average value C of the area fraction of the total area fraction of the interdendritic precipitates of the M7C3 inside the interdendritic precipitates in the 5 tests to be 44%;

[0082] 2) According to GB / T 4340.1-2009 "Vickers hardness test for metallic materials Part 1: Test method", a DVK-1S Vickers hardness tester was used to measure the Vickers hardness D of the furnace tube material, and the test result was 340HV10.

[0083] 3) Determine the maximum service temperature of ethylene cracking furnace tubes:

[0084] Since A = 6.0%, which is less than 7%, c is 10, and d is 0.003, the influence function is calculated as follows:

[0085] f(C, D)=cC+dD

[0086] =10×0.44+0.003×340

[0087] =5.4

[0088] It is determined that the maximum service temperature of the 4# furnace tube is in the range of 1150-1200℃, which is consistent with the actual heat treatment temperature of the furnace tube of 1190℃.

[0089] Those skilled in the art should understand that the above are only some specific embodiments of the present invention, rather than all embodiments. It should be noted that for those of ordinary skill in the art, many modifications and improvements can be made, and all modifications or improvements that do not exceed the scope of protection of the present invention should be regarded as the scope of protection of the present invention.

Claims

1. A method for determining the maximum service temperature of a high-aluminum ethylene cracking furnace tube, characterized in that: The steps include: S1. Microstructure analysis of high-aluminum ethylene cracking furnace tubes An optical metallographic microscope is used to cut a high-aluminum ethylene cracking furnace tube along the tube diameter direction to obtain a cross section, and a sample is taken at a thickness position of 1 / 4 to 3 / 4 of the tube wall surface in the cross section. The cross section is used as the observation surface for microstructure analysis, and the magnification is 500 to 1000 times. Each sample has at least 5 measuring points, and the average value is taken to measure the area S1 of the total precipitates between dendrites of the furnace tube material within the field of view per unit area S0. The total precipitates between dendrites specifically include thick strips and blocky precipitates M at the edge of the dendrite. 23 C6, coarse strip and block precipitates Ni3Al at the edge of dendrites, fine fishbone and worm-like precipitates M7C3 inside dendrites, calculate the total area fraction of precipitates between dendrites A = (S1 / S0) × 100%, the unit is 1; S2. Determine the maximum service temperature range of the high-aluminum ethylene cracking furnace tube: when A>7%, the maximum service temperature of the furnace tube is less than 1100°C; when A≤7%, the maximum service temperature of the furnace tube is ≥1100°C; When the area S1 is measured in step S1, the area S2 of the total precipitate of the dendrite of the furnace tube material in the field of view per unit area S0 is measured, and the total precipitate of the dendrite of the furnace tube material includes the M in the dendrite in the form of thin strips and particles. 23 C6, for thin strips and granular Ni3Al, calculate the total area fraction of dendrite stem precipitates B = (S2 / S0) × 100%, the unit is 1; While measuring the area S1 in step S1, the area S3 of the fine fishbone-shaped and worm-shaped precipitates M7C3 inside the dendrites in the total precipitates between the dendrites of the furnace tube material in the field of view of the unit area S0 is measured, and the percentage of S3 to the total precipitate area between the dendrites is calculated as C=(S3 / S1)×100%, where the unit is 1; The Vickers hardness test was carried out on the high aluminum ethylene cracking furnace tube, and the Vickers hardness D of the furnace tube material was measured, and the unit was HV10; Then the maximum service temperature of ethylene cracking furnace tubes is divided according to the following procedure: 1) When A>7%, the influence function of the maximum service temperature of the high aluminum ethylene cracking furnace tube is determined according to the total area fraction A of the interdendritic precipitates, the total area fraction B of the dendrite stem precipitates and the Vickers hardness D of the furnace tube material: f(A, B, D) = aA + bB + dD Where A is the total area fraction of the interdendritic precipitates of the furnace tube, the unit is 1; B is the area fraction of the dendrite stem precipitates, the unit is 1; D is the Vickers hardness of the furnace tube material, the unit is HV10; where a is 10, b is 150, and d is 0.003; The range of the maximum service temperature T of high-aluminum ethylene cracking furnace tubes is divided as follows: If f(A, B, D)≥4.2, determine T≤900℃; If 3.4≤f(A, B, D)≥4.2, it is determined that 900℃<T≤950℃; If 2.9≤f(A, B, D)<3.4, it is determined that 950<T≤1000℃; If 2.5≤f(A, B, D)<2.9, it is determined that 1000<T≤1050℃; If 1.9≤f(A, B, D)<2.5, it is determined that 1050<T≤1100℃; 2) When A≤7%, and the maximum service temperature of the furnace tube is ≥1100°C, the influence function of the maximum service temperature of the high aluminum ethylene cracking furnace tube is determined according to the area fraction C and the Vickers hardness D of the fine fishbone-shaped and worm-shaped M7C3 precipitates inside the dendrites of the furnace tube material obtained in step 3 and step 4: f(C, D)=cC+dD C is the area fraction of the fine fishbone-shaped and worm-shaped M7C3 precipitates inside the dendrites, and the unit is 1; where D is the Vickers hardness of the furnace tube material, and the unit is HV10; c is 10, and d is 0.003; The range of the maximum service temperature T of high-aluminum ethylene cracking furnace tubes is divided as follows: If 6.1≤f(C, D)<6.9, it is determined that 1100<T≤1150℃; If 5.2≤f(C, D)<6.1, it is determined that 1150<T≤1200℃; If 4.8≤f(C, D)<5.2, it is determined that 1200<T≤1250℃.

2. The method for determining the maximum service temperature of a high-aluminum ethylene cracking furnace tube according to claim 1, characterized in that: The microstructure was analyzed using an Olympus GX53 optical metallographic microscope.

3. The method for determining the maximum service temperature of a high-aluminum ethylene cracking furnace tube according to claim 1, characterized in that: The DVK-1S Vickers hardness tester was used to measure the Vickers hardness D of the furnace tube material in accordance with GB / T 4340.1-2009 “Vickers hardness test for metallic materials Part 1: Test method”.

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