Test method for simulating generation of oxide scale on surface of hot-rolled steel plate

Abstract

The invention discloses a test method for simulating generation of scale on the surface of a hot-rolled steel plate. The test method comprises the following steps: 1) preparing a primary oxidation sample, a secondary oxidation sample, a tertiary oxidation sample and a quartic oxidation sample; 2) respectively carrying out a primary oxide scale generation test, a secondary oxide scale generation test and a third oxide scale generation test on the primary oxidation sample, the secondary oxidation sample and the third oxidation sample by adopting a thermal simulation testing machine; and (3) stacking three quartic oxidation samples in a muffle furnace in a sandwich manner, carrying out quartic scale generation test, and taking the quartic oxidation sample in the middle as a result sample of the quartic scale generation test. The method is high in operability of process and atmosphere control and convenient to implement; the scale generation test can be simulated in a segmented manner, so that the hot rolling process can be adjusted in a targeted manner; not only can the generation of the oxide scale be simulated, but also the binding force of the primary and secondary oxide scales can be judged.

Description

Technical Field

[0001] The present invention relates to the field of physical simulation of metal materials, and particularly to a test method for simulating the formation of scale on the surface of hot-rolled steel plates. Background Art

[0002] During the hot rolling process of strip steel, its surface is always at a high temperature, resulting in the formation of an oxide layer on the strip steel surface, commonly known as "scale". Usually, the oxide layer formed during the hot rolling process can be effectively removed through the arranged high-pressure water descaling process. However, for some steel grades with high silicon content, more complex oxidation behaviors occur at high temperatures, and many problems will appear during the production process. Since substances such as fayalite (Fe2SiO4) are easily formed on its surface, the viscosity of the oxide layer is high and the bonding force with the substrate is strong, which will reduce the effect of high-pressure water descaling. During the subsequent rolling process, defects such as scale pressing-in will occur. In addition, compared with plain carbon steel, alloy steel with a higher Si content will have relatively serious oxidation and burning loss in the heating furnace. Therefore, simulating the formation of scale on hot-rolled steel strips and conducting observational research on scale based on this can provide a theoretical basis and technical reference for formulating the slab heating process system and optimizing the hot rolling and pickling processes.

[0003] In addition to on-site large-scale production trial research, the existing technical research methods generally use heat treatment furnaces and thermal simulation devices to conduct static controlled oxidation simulation tests on steel plate specimens, which is quite different from the actual situation in real production where the scale is deformed, broken, removed, and regenerated several times, resulting in a large difference in the structural characteristics of the scale formed on the test steel plate and the scale on the on-site steel plate.

[0004] The patent document with the publication number CN108097726A discloses a test method for simulating the post-rolling cooling process of hot-rolled steel plates. This method only provides a control method for the post-rolling cooling process of hot-rolled steel plates and does not provide an effective simulation method for the deformation and cooling process before rolling. Therefore, it is impossible to simulate the scale on the surface of steel plates during the entire production process of hot-rolled steel plates.

[0005] The patent document with the publication number CN112782208A discloses a test method for simulating the surface oxidation of hot-rolled steel plates. It uses a Gleeble thermal simulation test machine to perform compression and tensile deformation on the high-temperature oxidized steel plate specimen to break the high-temperature scale on the surface of the steel plate specimen, and cooperates with high-pressure air purging to achieve dynamic simulation of the high-temperature descaling process in the hot rolling process. At the same time, with the precise temperature control function of the thermal simulation test machine, it achieves the simulation of the scale on the surface of the steel plate under approximate hot rolling process conditions. However, this method has the following problems: 1) It can only simulate the entire process and cannot simulate the formation of primary, secondary, tertiary, and quaternary scale in segments. 2) By subjecting the high-temperature strip sample to tensile and compressive deformation, internal stress is generated on the surface of the strip sample. When the internal stress is greater than the stress for breaking the scale, the scale on the surface of the strip sample will break and fall off, which can achieve the elimination of the influence of primary scale or part of the secondary scale on the oxidation process of the strip in subsequent processes, but the elimination effect cannot be guaranteed; 3) Only the formation of the final scale is simulated, and the bonding strength of the scale in each stage cannot be judged. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a test method for simulating the formation of scale on the surface of hot-rolled steel sheets.

[0007] To solve the above technical problem, the technical solution adopted by the present invention includes the following steps: 1) Prepare primary oxidation specimens, secondary oxidation specimens, tertiary oxidation specimens, and quaternary oxidation specimens; 2) Use a thermal simulation testing machine to conduct primary scale formation tests, secondary scale formation tests, and tertiary scale formation tests on the primary oxidation specimens, secondary oxidation specimens, and tertiary oxidation specimens respectively; 3) There are three quaternary oxidation specimens, which are stacked in a sandwich manner in a muffle furnace for quaternary scale formation tests, and the middle quaternary oxidation specimen is taken as the result specimen of the quaternary scale formation test.

[0008] Further, in the primary scale formation test in step 2): First, heat the primary oxidation specimen to 580°C at a heating rate of 10 - 20°C / s and hold for 0.5 - 1 minute; then heat to 1100 - 1300°C at a heating rate of 10 - 20°C / s and hold for 0.5 - 1 minute; then cool slowly to 600°C at a rate of 0.2 - 0.4°C / s, and finally cool at a cooling rate of 20 - 30°C / s.

[0009] Further, in the secondary scale formation test in step 2): First, heat the secondary oxidation specimen to 580°C at a heating rate of 10 - 20°C / s and hold for 0.5 - 1 minute; Then simulate each rough rolling and high-pressure water descaling pass: First, heat to the starting temperature of this rough rolling pass at a heating rate of 10 - 20°C / s and hold for 0.5 - 1 minute; then cool at a cooling rate of 20 - 30°C / s and stretch the specimen, with a tensile deformation of 5 - 30% and a strain rate of 0.05 - 0.15 / s, and stop cooling after the stretching ends; Then heat to the starting temperature of finish rolling at a heating rate of 10 - 20°C / s and hold for 0.5 - 1 minute; then cool slowly to 600°C at a rate of 0.2 - 0.4°C / s, and finally cool at a cooling rate of 20 - 30°C / s.

[0010] Further, in the three - time scale oxide scale formation test in step 2): First, heat the three - time scale oxide sample from room temperature to the finish rolling start temperature at a heating rate of 10 - 20 °C / s, then cool it to the finish rolling end temperature, and the cooling rate = (finish rolling start temperature - finish rolling end temperature) / finish rolling time; then cool it to the coiling temperature at the actual laminar cooling rate, and finally cool it at a cooling rate of 20 - 30 °C / s.

[0011] Further, in the four - time scale oxide scale formation test in step 3): First, heat the four - time scale oxide sample from room temperature to the coiling temperature at a heating rate of 10 - 20 °C / s, hold it for 300 - 600 s, and then close the furnace door and cool it naturally.

[0012] Further, step 2) also simulates the adhesion test between the primary scale and the substrate and the adhesion test between the secondary scale and the substrate.

[0013] Furthermore, for the adhesion test between the primary scale and the substrate: First, heat the primary scale sample from room temperature to 580 °C at a heating rate of 10 - 20 °C / s and hold it for 0.5 - 1 minute; then heat it to 1100 - 1300 °C at a heating rate of 10 - 20 °C / s and hold it for 0.5 - 1 minute; cool it to room temperature at a cooling rate of 20 - 30 °C / s, and stretch the sample by 5 - 30% when starting to cool, with a strain rate of 0.05 - 0.15 / s.

[0014] Furthermore, for the adhesion test between the secondary scale and the substrate: First, heat the secondary scale sample from room temperature to 580 °C at a heating rate of 10 - 20 °C / s and hold it for 0.5 - 1 minute; Then simulate each rough rolling pass and high - pressure water descaling: First, heat it to the rough rolling start temperature of this pass at a heating rate of 10 - 20 °C / s and hold it for 0.5 - 1 minute; then cool it at a cooling rate of 20 - 30 °C / s and stretch the sample, with a stretching deformation of 5 - 30% and a strain rate of 0.05 - 0.15 / s, and stop cooling when the stretching ends; Then heat it to the finish rolling start temperature at a heating rate of 10 - 20 °C / s and hold it for 0.5 - 1 minute; then cool it to room temperature at a cooling rate of 20 - 30 °C / s, and stretch the sample by 5 - 30% when starting to cool, with a strain rate of 0.05 - 0.15 / s.

[0015] The technical idea of the present invention is to use a Gleeble thermal simulation testing machine to generate primary, secondary, and tertiary scale on the steel plate, and use the thermo-mechanical coupling effect of rapid cooling and tensile deformation to break the high-temperature scale on the surface of the steel plate specimen. This can not only evaluate the bonding strength of the scale, but also effectively remove the primary scale by combining specific specimens, realizing the dynamic simulation of the high-temperature descaling process in the hot rolling process. At the same time, with the precise temperature control function of the thermal simulation testing machine, the simulation of sectional scale on the steel plate surface under approximate hot rolling process conditions is achieved. The experiment to simulate the generation of the fourth scale on the steel plate is completed in a muffle furnace, and a sandwich-type specimen is used to achieve the oxygen-deficient effect of the middle specimen.

[0016] The beneficial effects of adopting the above technical solutions are as follows: 1) The method of the present invention can approximately simulate the primary, secondary, tertiary, and fourth oxidation processes on the surface of hot-rolled steel plates in sections, so as to obtain the scale on the surface of hot-rolled steel plates under the corresponding hot rolling processes, and can specifically optimize the heating and rolling processes, ultimately achieving the purpose of effectively controlling the scale on the surface of hot-rolled steel plates.

[0017] 2) Through specific specimens, when simulating the generation of secondary scale, the primary scale can be effectively removed; through specific specimens, the generation of scale in the oxygen-deficient area at the core of the steel coil can be effectively simulated.

[0018] 3) The method of the present invention can not only simulate the generation of scale, but also evaluate the bonding strength of the primary and secondary scale.

[0019] 4) The process and atmosphere control of the method of the present invention are highly operable and easy to implement; the generation test of scale can be simulated in sections, which is convenient for specifically adjusting the hot rolling process; the high-pressure water descaling process is simulated by using the thermo-mechanical coupling mode, and with the use of a necked specimen, the effect is obvious; the method of the present invention can not only simulate the generation of scale, but also evaluate the bonding strength of the primary and secondary scale. Description of the Drawings

[0020] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0021] Figure 1 It is a schematic structural diagram of the primary oxidation specimen, secondary oxidation specimen, and tertiary oxidation specimen of the present invention; Figure 2 It is a schematic structural diagram after stacking the fourth oxidation specimens of the present invention; Figure 3 It is a control process diagram of the primary scale generation test in the embodiment; Figure 4 It is a control process diagram of the bonding strength test between the primary scale and the substrate in the embodiment; Figure 5It is the control process diagram of the secondary scale generation test in the embodiment; Figure 6 It is the control process diagram of the bonding strength test between the secondary scale and the substrate in the embodiment; Figure 7 It is the control process diagram of the tertiary scale generation test in the embodiment; Figure 8 It is the control process diagram of the quaternary scale generation test in the embodiment; Figure 9 It is the specimen assembly diagram of the Gleeble thermal simulation test in the embodiment; Figure 10 It is the schematic diagram (2000 times) of observing the characteristics of the primary scale by scanning electron microscope in the embodiment; Figure 11 It is the schematic diagram (200 times) of observing the scale characteristics of the specimen for the bonding strength between the primary scale and the substrate by scanning electron microscope in the embodiment; Figure 12 It is the schematic diagram (2000 times) of observing the characteristics of the secondary scale by scanning electron microscope in the embodiment; Figure 13 It is the schematic diagram (200 times) of observing the scale characteristics of the specimen for the bonding strength between the secondary scale and the substrate by scanning electron microscope in the embodiment; Figure 14 It is the schematic diagram (5000 times) of observing the characteristics of the tertiary scale by scanning electron microscope in the embodiment; Figure 15 It is the schematic diagram (1000 times) of observing the characteristics of the quaternary scale by scanning electron microscope in the embodiment.

[0022] In the figure: Specimen 1, fixing bolt 2, fixture 3, cooling nozzle 4. Specific implementation method

[0023] The test method for simulating the formation of scale on the surface of hot-rolled steel plates includes the following steps: 1) Prepare primary oxidation specimens, secondary oxidation specimens, tertiary oxidation specimens and quaternary oxidation specimens. For each scale generation test and bonding strength test, new specimens are used.

[0024] Figure 1As shown, the primary oxidation specimen, secondary oxidation specimen, and tertiary oxidation specimen are all long rectangular specimens with a thin neck in the middle. Holes are drilled at both ends of the specimen to facilitate the matching installation of the positioning pins. Among them, the thin neck position in the middle is the area for the formation and testing of the mill scale on the specimen. The length of the specimen is 150 - 180 mm, the width is 20 - 30 mm; the length of the thin neck position of the specimen is 16 mm, and the width is 10 mm; there is an arc transition between the specimen clamping section and the thin neck position, and the radius of the arc is 2 - 4 mm; the thickness of the specimen is 3 - 5 mm. The specimen is made of hot-rolled steel plate by wire cutting. Before the test, the mill scale on the surface is removed cleanly with 280-mesh sandpaper, and then polished smoothly with 600-mesh, 800-mesh, and 1000-mesh sandpapers in sequence. Then, the surface of the specimen is cleaned with alcohol and air-dried naturally. After welding the temperature-measuring thermocouple wire at the center position of the specimen, it is ready for use.

[0025] Figure 2 As shown, the quaternary oxidation specimen is a long rectangular specimen with a length of 150 - 180 mm, a width of 20 - 30 mm, and a thickness of 3 - 5 mm. At least three specimens are required, with consistent dimensions and straightness.

[0026] 2) Use a Gleeble thermal simulation testing machine. Take two primary oxidation specimens to conduct the primary mill scale formation test and the primary mill scale and matrix bonding strength test respectively; take two secondary oxidation specimens to conduct the secondary mill scale formation test and the secondary mill scale and matrix bonding strength test respectively; take one tertiary oxidation specimen to conduct the tertiary mill scale formation test. Figure 9 As shown, during the test, the specimen 1 is fixed on the fixture 3 of the thermal simulation testing machine through the fixing bolt 2, and the blowing direction of the cooling nozzle 4 of the thermal simulation testing machine is directly opposite to the thin neck position of the specimen.

[0027] 2.1) Primary mill scale formation test: The primary mill scale is formed in the heating furnace. This test is used for the subsequent observation of the morphological characteristics of the mill scale.

[0028] Figure 3 As shown, the test process is as follows: First, heat the primary oxidation specimen from room temperature to 580 °C at a heating rate of 10 - 20 °C / s and hold for 0.5 - 1 minute; then heat it to 1100 - 1300 °C at a heating rate of 10 - 20 °C / s and hold for 0.5 - 1 minute; then cool it slowly to 600 °C at a rate of 0.2 - 0.4 °C / s; finally, cool it to room temperature at a cooling rate of 20 - 30 °C / s.

[0029] 2.2) Primary mill scale and matrix bonding strength test: The primary mill scale is formed in the heating furnace. This test is used for the subsequent determination of the bonding strength between the mill scale and the matrix.

[0030] Figure 4As shown, the test process is as follows: First, heat the primary oxidized sample at a heating rate of 10 - 20 °C / s to 580 °C and hold for 0.5 - 1 minute; then heat it to 1100 - 1300 °C at a heating rate of 10 - 20 °C / s and hold for 0.5 - 1 minute; cool it to room temperature at a cooling rate of 20 - 30 °C / s. When starting to cool, stretch the sample with a deformation of 5 - 30% and a strain rate of 0.05 - 0.15 / s.

[0031] 2.3) Secondary scale formation test: The secondary scale is formed during rough rolling. This test is used for subsequent observation of the scale morphology characteristics. Figure 5 As shown, the test process is as follows: 2.3.1) First, heat the secondary oxidized sample at a heating rate of 10 - 20 °C / s to 580 °C and hold for 0.5 - 1 minute; 2.3.2) Simulate one - pass rough rolling and primary high - pressure water descaling: First, heat it to 1100 - 1300 °C at a heating rate of 10 - 20 °C / s and hold for 0.5 - 1 minute; then cool it at a cooling rate of 20 - 30 °C / s. When starting to cool, stretch the sample with a tensile deformation of 5 - 30% and a strain rate of 0.05 - 0.15 / s. Stop cooling after the stretching ends. The end - point temperature T of the cooling 终点 is: T 终点 = T 起始 - S 拉伸 × V 冷速 , where T 终点 is the end - point temperature of cooling, °C, T 起始 is the starting temperature of cooling, °C, S 拉伸 is the stretching time, s, and V 冷速 is the cooling rate, °C / s; The above process simulates one - pass rough rolling and primary high - pressure water descaling; 2.3.3) Simulate two - pass and subsequent passes of rough rolling and secondary and subsequent high - pressure water descaling: Conduct simulations of two - pass, three - pass,... in sequence; The process for each pass is: First, heat it to the starting temperature of rough rolling for this pass at a heating rate of 10 - 20 °C / s and hold for 0.5 - 1 minute; then cool it at a cooling rate of 20 - 30 °C / s. When starting to cool, stretch the sample with a tensile deformation of 5 - 30% and a strain rate of 0.05 - 0.15 / s. Stop cooling after the stretching ends. The end - point temperature T of the cooling 终点 is: T 终点 = T 起始 - S 拉伸 × V 冷速 , where T 终点 is the end - point temperature of cooling, °C, T 起始 is the starting temperature of cooling, °C, S 拉伸 is the stretching time, s, and V 冷速 is the cooling rate, °C / s; 2.3.4) Simulated finish rolling: Heat at a heating rate of 10 - 20 °C / s to the finish rolling start temperature and hold for 0.5 - 1 minute; then cool slowly at a rate of 0.2 - 0.4 °C / s to 600 °C, and finally cool to room temperature at a cooling rate of 20 - 30 °C / s.

[0032] 2.4) Test on the bonding strength between secondary scale and substrate: The secondary scale is generated during rough rolling, and this test is used for subsequent determination of the bonding strength between scale and substrate. Figure 6 As shown, the test process is as follows: 2.4.1) First, heat the secondary oxidation specimen at a heating rate of 10 - 20 °C / s to 580 °C and hold for 0.5 - 1 minute; 2.4.2) Simulate one - pass rough rolling and primary high - pressure water descaling: First, heat at a heating rate of 10 - 20 °C / s to 1100 - 1300 °C and hold for 0.5 - 1 minute; then cool at a cooling rate of 20 - 30 °C / s. Tensile the specimen at the start of cooling, with a tensile deformation of 5 - 30% and a strain rate of 0.05 - 0.15 / s. Stop cooling after the tensile test. The end temperature T of the cooling is: T = T - S×V, where T is the end temperature of cooling, °C, T is the start temperature of cooling, °C, S is the tensile time, s, and V is the cooling rate, °C / s. The above process simulates one - pass rough rolling and primary high - pressure water descaling; 终点 is: T 终点 = T 起始 - S 拉伸 ×V 冷速 where, T 终点 is the end temperature of cooling, °C, T 起始 is the start temperature of cooling, °C, S 拉伸 is the tensile time, s, V 冷速 is the cooling rate, °C / s; The above process simulates one - pass rough rolling and primary high - pressure water descaling; 2.4.3) Simulate two - pass and subsequent passes of rough rolling and secondary and subsequent high - pressure water descaling: Conduct simulations for two - pass, three - pass,... in sequence. The process for each pass is: First, heat at a heating rate of 10 - 20 °C / s to the start temperature of rough rolling for this pass and hold for 0.5 - 1 minute; then cool at a cooling rate of 20 - 30 °C / s. Tensile the specimen at the start of cooling, with a tensile deformation of 5 - 30% and a strain rate of 0.05 - 0.15 / s. Stop cooling after the tensile test. The end temperature T of the cooling is: T = T - S×V, where T is the end temperature of cooling, °C, T is the start temperature of cooling, °C, S is the tensile time, s, and V is the cooling rate, °C / s; 终点 is: T 终点 = T 起始 - S 拉伸 ×V 冷速 where, T 终点 is the end temperature of cooling, °C, T 起始 is the start temperature of cooling, °C, S 拉伸 is the tensile time, s, V 冷速 is the cooling rate, °C / s; 2.4.4) Simulated finish rolling: Heat at a heating rate of 10 - 20 °C / s to the finish rolling start temperature and hold for 0.5 - 1 minute; then cool to room temperature at a cooling rate of 20 - 30 °C / s. When starting to cool, stretch the specimen by 5 - 30% at a strain rate of 0.05 - 0.15 / s.

[0033] 2.5) Tertiary scale formation test: The tertiary scale is formed during finish rolling. This test is used for subsequent observation of the scale morphology characteristics and determination of the bonding strength between the scale and the substrate; since there is no high-pressure water descaling process during finish rolling, the tertiary scale formation test and the test for the bonding strength between the tertiary scale and the substrate are the same test.

[0034] Figure 7 As shown, the test process is as follows: First, heat the tertiary oxidized specimen at a heating rate of 10 - 20 °C / s to the finish rolling start temperature, and then cool to the finish rolling end temperature. The cooling rate V 冷速 is: V 冷速 =(T 精始 -T 精束 ) / S 精轧 , where V 冷速 is the cooling rate, °C / s, T 精始 is the finish rolling start temperature, °C, T 精束 is the finish rolling end temperature, °C, and S 精轧 is the finish rolling time, s; then cool to the coiling temperature at the actual laminar cooling rate, and finally cool to room temperature at a cooling rate of 20 - 30 °C / s.

[0035] 2.6) Quaternary scale formation test: The quaternary scale is formed during coiling and cooling. This test is used for the formation and morphology observation of the scale in the oxygen-depleted area at the core of the steel coil. The test is completed in a muffle furnace. Stack three quaternary oxidized specimens neatly in a sandwich style, and place the stacked quaternary oxidized specimens in the muffle furnace for the quaternary scale formation test. Take the middle quaternary oxidized specimen as the result sample of the quaternary scale formation test.

[0036] Figure 8 As shown, the test process is as follows: First, heat the stacked quaternary oxidized specimens at a heating rate of 10 - 20 °C / s to the coiling temperature, hold for 300 - 600 s, and then close the furnace door and let it cool naturally to room temperature.

[0037] 3) After the above-mentioned first, second, and third thermal simulation tests are completed, samples are cut at the necking position of the specimen, and the scale characteristics are observed with the help of equipment such as a scanning electron microscope. After the above-mentioned first and second scale adhesion tests with the substrate are completed, samples are cut at the necking position of the specimen, and the scale characteristics are observed with the help of equipment such as a scanning electron microscope to check the scale residue degree. After the above-mentioned fourth scale formation test is completed, the middle result sample is cut at the center position, and the scale characteristics are observed with the help of equipment such as a scanning electron microscope. Example

[0038] 1) HC550 / 980QP hot-rolled steel plate is used as the test material. The specimen is processed by wire cutting from the hot-rolled steel plate, with dimensions of 150 mm × 30 mm × 3.5 mm. Before the test, the surface scale is removed cleanly with 280-mesh sandpaper, and then polished smoothly with 600-mesh, 800-mesh, and 1000-mesh sandpapers in sequence. Then the surface of the specimen is cleaned with alcohol and air-dried naturally for standby.

[0039] Refer to Figure 9 , a pair of V-shaped thermal simulation fixtures 3 are selected. At the same time, the cooling nozzle 4 of the thermal simulation testing machine is connected and fixed inside the working box of the thermal simulation testing machine. The platinum-rhodium high-temperature thermocouple wire is welded at the center point of the necking of the specimen 1 with dimensions of 150 mm × 30 mm × 3.5 mm. The specimen 1 is fastened to the fixture 3 with the fixing bolt 2, and the direction of the cooling nozzle 4 is adjusted to ensure that the air jet holes are aligned with the middle of the specimen necking.

[0040] Configure the equipment conditions of the thermal simulation testing machine. After evacuating the vacuum degree inside the working box of the thermal simulation testing machine to 0.08 MPa, the vacuum pump is closed, and then argon gas is filled into the working box. When the vacuum degree of the working box reaches 5 MPa, the argon gas filling is stopped.

[0041] 2) Use QuikSim software to compile the test control program, set process parameters such as heating, holding, cooling, and stretching according to the predetermined process requirements, and use the thermocouple temperature control mode throughout the test process.

[0042] 2.1) First scale formation test: First, the specimen is quickly heated to 580 °C at a heating rate of 20 °C / s and held for 1 minute; then quickly heated to 1300 °C at a heating rate of 10 °C / s and held for another 0.5 minute; then slowly cooled to 600 °C at a rate of 0.2 °C / s, and then cooled to room temperature at a cooling rate of 20 °C / s. The specific process diagram is as Figure 3 shown. After the thermal simulation test is completed, samples are cut at the necking position of the specimen, and the scale characteristics are observed with the help of equipment such as a scanning electron microscope. The observation results are as Figure 10 shown.

[0043] 2.2) Adhesion test of primary scale and substrate: The previous steps of this test are the same as those of 2.1) Primary scale formation test. After holding at 1300 °C in the high-temperature zone and finishing, it is cooled to room temperature at a cooling rate of 20 °C / s. When starting to cool, the specimen is stretched by 5%, and the strain rate is 0.05 / s. The specific process diagram is as shown in Figure 4 shown. After the thermo-simulation test, the specimen is cut at the necking position, and the characteristics of the scale are observed with the help of equipment such as a scanning electron microscope. The observation results are as shown in Figure 11 shown.

[0044] 2.3) Secondary scale formation test: First, the specimen is quickly heated to 580 °C at a heating rate of 10 °C / s and held for 0.5 minutes; then it is quickly heated to 1100 °C at a heating rate of 20 °C / s and held for 1 minute; then it is cooled at a cooling rate of 30 °C / s. When starting to cool, the specimen is stretched by 30%, the strain rate is 0.15 / s, and it is stretched for 2 s. The cooling end temperature is 1040 °C. The above process simulates the first rough rolling and the first high-pressure water descaling. The actual rough rolling production is in three passes. After the first high-pressure water descaling, it is quickly heated to the starting temperature of the second rough rolling, 1060 °C, at a heating rate of 20 °C / s and held for 1 minute; then it is cooled at a cooling rate of 30 °C / s. When starting to cool, the specimen is stretched by 30%, the strain rate is 0.15 / s, and it is stretched for 2 s. The cooling end temperature is 1000 °C. The above process simulates the second rough rolling and the second high-pressure water descaling. After the second high-pressure water descaling, it is quickly heated to the starting temperature of the third rough rolling, 1020 °C, at a heating rate of 20 °C / s and held for 1 minute; then it is cooled at a cooling rate of 30 °C / s. When starting to cool, the specimen is stretched by 30%, the strain rate is 0.15 / s, and it is stretched for 2 s. The cooling end temperature is 960 °C. After the rough rolling is completed, it is quickly heated to the starting temperature of the finish rolling, 1000 °C, at a heating rate of 10 °C / s and held for 0.8 minutes; then it is slowly cooled to 600 °C at a rate of 0.3 °C / s; then it is cooled to room temperature at a cooling rate of 25 °C / s. The specific process diagram is as shown in Figure 5 shown. After the thermo-simulation test, the specimen is cut at the necking position, and the characteristics of the scale are observed with the help of equipment such as a scanning electron microscope. The observation results are as shown in Figure 12 shown.

[0045] 2.4) Adhesion test of secondary scale and substrate: The previous steps of this test are the same as those of the secondary scale formation test. After holding at 1000 °C at the start of finish rolling and finishing, it is cooled to room temperature at a cooling rate of 30 °C / s. When starting to cool, the specimen is stretched by 20%, and the strain rate is 0.10 / s. The specific process diagram is as shown in Figure 6 shown. After the thermo-simulation test, the specimen is cut at the necking position, and the characteristics of the scale are observed with the help of equipment such as a scanning electron microscope. The observation results are as shown in Figure 13 shown.

[0046] 2.5) Generation test of the third scale: First, quickly heat the specimen to the finishing rolling start temperature of 1000 °C at a heating rate of 15 °C / s; then cool it to the finishing rolling end temperature of 880 °C. The finishing rolling time is 5 min, and the calculated cooling rate is 24 °C / s; then cool it to the coiling temperature of 600 °C at a cooling rate of 30 °C / s; then cool it to room temperature at a cooling rate of 28 °C / s. The specific process diagram is as shown in Figure 7 shown. After the thermo-simulation test, cut the specimen at the necking position and observe the scale characteristics with the help of equipment such as a scanning electron microscope. The observation results are as shown in Figure 14 shown.

[0047] 2.6) Generation test of the fourth scale at the core of the coil: Use long rectangular specimens with a length of 180 mm, a width of 20 mm, and a thickness of 5 mm. The three specimens have the same size, are straight, and are neatly stacked in a sandwich style. First, quickly heat the stacked three specimens to the coiling temperature of 570 °C at a heating rate of 12 °C / s and hold for 300 s; then close the furnace door and cool naturally to room temperature. The specific process diagram is as shown in Figure 8 shown. After the thermo-simulation test, cut the center position of the middle specimen of the sandwich-style stacked specimens and observe the scale characteristics with the help of equipment such as a scanning electron microscope. The observation results are as shown in Figure 15 shown.

[0048] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be modified or equivalently replaced, and any modification or partial replacement without departing from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims

1. A test method for simulating the formation of iron oxide scale on the surface of hot-rolled steel plates, characterized in that: The method comprises the following steps: 1) preparing a primary oxidation sample, a secondary oxidation sample, a tertiary oxidation sample and a quaternary oxidation sample; 2) A thermal simulation test machine is used to conduct a primary scale formation test, a secondary scale formation test and a tertiary scale formation test on the primary oxidation sample, the secondary oxidation sample and the tertiary oxidation sample respectively; 3) There are three four oxidation samples, which are stacked in a sandwich style in a muffle furnace to carry out four iron oxide scale formation tests, and the middle four oxidation samples are taken as the result sample of the four iron oxide scale formation tests.

2. A test method for simulating the formation of iron oxide scale on the surface of hot-rolled steel plates according to claim 1, characterized in that: The primary iron scale formation test in step 2) is as follows: first, the primary oxidation sample is heated to 580°C at a heating rate of 10-20°C / s, and kept warm for 0.5-1 minute; then, it is heated to 1100-1300°C at a heating rate of 10-20°C / s, and kept warm for 0.5-1 minute; then, it is slowly cooled to 600°C at a rate of 0.2-0.4°C / s, and finally, it is cooled at a cooling rate of 20-30°C / s.

3. A test method for simulating the formation of iron oxide scale on the surface of hot-rolled steel plate according to claim 1, characterized in that: In the step 2), the secondary oxidation scale generation test is as follows: first, the secondary oxidation sample is heated to 580° C. at a heating rate of 10 to 20° C. / s, and kept at this temperature for 0.5 to 1 minute; Then simulate each rough rolling and high-pressure water descaling: first heat to the starting temperature of the rough rolling at a heating rate of 10-20℃ / s, and keep warm for 0.5-1 minute; then cool at a cooling rate of 20-30℃ / s and stretch the sample, with a stretching deformation of 5-30% and a strain rate of 0.05-0.15 / s, and stop cooling after stretching; Then heat to the start temperature of finishing rolling at a heating rate of 10-20°C / s and keep warm for 0.5-1 minute; then slowly cool to 600°C at a rate of 0.2-0.4°C / s, and finally cool at a cooling rate of 20-30°C / s.

4. A test method for simulating the formation of iron oxide scale on the surface of hot-rolled steel plate according to claim 1, characterized in that: In the step 2), the three-times scale formation test is as follows: first, the three-times oxidized sample is heated to the finishing start temperature at a heating rate of 10-20°C / s, and then cooled to the finishing end temperature, where the cooling rate = (finishing start temperature - finishing end temperature) / finishing time; then, it is cooled to the coiling temperature at an actual laminar cooling rate, and finally, it is cooled at a cooling rate of 20-30°C / s.

5. The test method for simulating the formation of iron oxide scale on the surface of hot-rolled steel plate according to claim 1, characterized in that: In the four-time iron oxide scale generation test in step 3), the four-time oxidation sample is first heated to the coiling temperature at a heating rate of 10-20° C. / s, kept at this temperature for 300-600s, and then the furnace door is closed and cooled naturally.

6. A test method for simulating the formation of iron oxide scale on the surface of a hot-rolled steel plate according to any one of claims 1 to 5, characterized in that: The step 2) also simulates a primary test of the bonding strength between the iron oxide scale and the substrate and a secondary test of the bonding strength between the iron oxide scale and the substrate.

7. A test method for simulating the formation of iron oxide scale on the surface of hot-rolled steel plates according to claim 6, characterized in that: The primary iron oxide scale and substrate bonding strength test is as follows: first, the primary oxidation sample is heated to 580°C at a heating rate of 10-20°C / s, and kept warm for 0.5-1 minute; then, it is heated to 1100-1300°C at a heating rate of 10-20°C / s, and kept warm for 0.5-1 minute; it is cooled to room temperature at a cooling rate of 20-30°C / s, and the sample is stretched by 5-30% at the beginning of cooling, and the strain rate is 0.05-0.15 / s.

8. A test method for simulating the formation of iron oxide scale on the surface of hot-rolled steel plates according to claim 6, characterized in that: The secondary oxidation iron scale and substrate bonding test: firstly, the secondary oxidation sample is heated to 580°C at a heating rate of 10-20°C / s and kept at this temperature for 0.5-1 minute; Then simulate each rough rolling and high-pressure water descaling: first heat to the starting temperature of the rough rolling at a heating rate of 10-20℃ / s, and keep warm for 0.5-1 minute; then cool at a cooling rate of 20-30℃ / s and stretch the sample, with a stretching deformation of 5-30% and a strain rate of 0.05-0.15 / s, and stop cooling after stretching; Then heat to the start temperature of finishing rolling at a heating rate of 10-20°C / s and keep warm for 0.5-1 minute; then cool to room temperature at a cooling rate of 20-30°C / s. When starting to cool, stretch the sample by 5-30% and the strain rate by 0.05-0.15 / s.

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