Heat treatment method of sector plate for hot rolling coiler

Abstract

The invention discloses a heat treatment method of a sector plate for a hot rolling coiler, and belongs to the technical field of hot rolling sector plates, the heat treatment method comprises the steps of graded heating solution treatment, water-air alternate quenching, tempering and the like, and by specifically setting the steps and specific setting modes and parameters of the steps, the specific setting of the sector plate workpiece to be treated is matched, so that the heat treatment efficiency is improved. Existing quenching medium oil is changed into medium water, and on the basis that it is guaranteed that the good performance that the tensile strength Rm ranges from 850 MPa to 900 MPa, the plastic extension strength Rp0.2 is larger than or equal to 650 MPa, the percentage elongation after fracture A is larger than or equal to 15%, and the room-temperature impact energy DVM is larger than or equal to 38 J can be obtained, the production cost is reduced, and environmental protection is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment of specific workpieces, and in particular to a heat treatment method for a fan-shaped plate of a hot rolling coiler. Background Art

[0002] As the amount of steel required for industrial production continues to increase, steel production equipment has also increased. Coilers are important equipment for strip steel production lines in various steel mills, especially hot-rolled strip steel production lines. Coilers can roll steel into rolls, effectively improving the production efficiency of the steel industry. The components of the coiler include a roll, a reducer, a box, a base, etc. Among them, the fan plate is one of the important parts of the coiler roll, and its quality directly affects the service life of the coiler.

[0003] During the use of the coiler, the temperature of the steel plate processed can be as high as 600-800℃, and the coiler has to withstand the alternating cycle of high temperature and cooling medium. Therefore, the fan plate, as an important component, requires higher plasticity and toughness indicators to ensure the normal working state of the coiler. Therefore, it is necessary to select a suitable heat treatment method to ensure the excellent mechanical properties of the fan plate and extend the service life of the coiler.

[0004] Quenching and tempering is a traditional heat treatment method, which generally involves heating the alloy steel to a critical temperature (Ac3 or above Ac1), keeping it warm for a certain period of time to austenitize it, and then cooling it at a cooling rate greater than the critical cooling rate to obtain a martensite or bainite structure, and then tempering it at a suitable temperature to obtain tempered martensite or tempered bainite. During the quenching process of martensitic stainless steel, in order to avoid cracking of the workpiece, oil is generally used instead of water as the quenching medium. However, oil quenching not only has the problem of high cost, but also has the risk of oil fume pollution and fire. Therefore, how to reasonably set the fan-shaped plate steel so that it can be cooled with medium water while ensuring that the workpiece does not crack, and can obtain excellent comprehensive mechanical properties has become a research difficulty for this type of steel.

[0005] Chinese invention patent publication CN107755490B discloses a 3D free bending forming method for martensitic steel, and discloses a technical solution for quenching martensitic steel by spraying water through an annular water nozzle. However, the purpose of water spray quenching is to achieve rapid bending and forming, and it cannot solve the adverse effects of water spray quenching on plasticity and toughness indicators and the possibility of cracking.

[0006] Chinese invention patent publication CN110157984B discloses a highly uniform and highly polished plastic mold steel and a preparation method, and discloses a quenching treatment using a water-air alternating method. However, since it is aimed at mold steel and the purpose of such a setting is to reduce the difference in internal and external structures of the module, its specific setting method cannot be used to solve the technical problem of ensuring that the martensitic stainless steel of the fan-shaped plate for the hot rolling coiler of the present invention does not crack under the premise of ensuring plasticity and toughness indicators. Summary of the invention

[0007] The purpose of the present invention is to provide a heat treatment method for a fan-shaped plate for a hot rolling coiler, which uses water with the lowest cost to perform quenching and cooling by reasonably setting the water-air alternation method, and achieves excellent comprehensive mechanical properties without cracking the workpiece.

[0008] The hot rolling coiler fan-shaped plate described in the present invention is martensitic stainless steel and has been subjected to forging, annealing and other treatments before heat treatment.

[0009] This is achieved through the following technical means:

[0010] A heat treatment method for a fan-shaped plate for a hot rolling coiler comprises the following steps:

[0011] S1, solution treatment: the fan-shaped plate is heated to the solution temperature by graded heating, the solution temperature is 1030-1060°C, the graded heating is to place the fan-shaped plate in a heating furnace at 250-300°C and keep it warm for 2-4h; then the temperature is increased to 550-650°C at a heating rate of 30-40°C / h, and it is kept warm at this temperature for 2.5-3.5h, and then the temperature is increased to 750-850°C at a heating rate of 50-60°C / h, and it is kept warm at this temperature for 2.6-3.5h, and then the temperature is increased to the solution temperature at a heating rate of 70-80°C / h, and it is kept warm at the solution temperature for 6-9h to obtain a fully austenitized fan-shaped plate, and the solution treatment is completed.

[0012] S2, water-air alternating quenching: Place the fully austenitized sector plate obtained in step S1 into a quenching tank filled with water, and cool the sector plate to a core temperature of 155-185°C by water-air alternating time-controlled quenching. Then, lift the workpiece out of the quenching tank and air-cool it in air for 30-50 minutes to obtain a quenched sector plate.

[0013] S3, tempering: placing the quenched sector plate obtained in step S2 into a tempering furnace at 250-300°C, keeping it at this temperature for 3-4 hours, then heating it to 685-695°C at a heating rate of 40-60°C / h, then keeping it at this temperature for 10-15 hours, then taking it out of the furnace and air-cooling it to room temperature to obtain a heat-treated sector plate product.

[0014] Preferably, the water-air alternating controlled quenching method in step S2 is as follows: adding an air cooling pass during the water cooling process, first water-cooling the fan-shaped plate in the quenching tank to a core temperature of 853-866°C, then hanging out the fan-shaped plate, cooling it in the air for 145-155s, then re-placing the fan-shaped plate in the water body of the quenching tank, continuing to water-cool it in the water body to a core temperature of 565-578°C, then hanging out the fan-shaped plate, cooling it in the air for 155-165s, and then re-placing the fan-shaped plate in the water body of the quenching tank. The fan-shaped plate is placed in the water body of the quenching tank, and continues to be water-cooled in the water body until the core temperature is 306-316°C. Then the fan-shaped plate is lifted out and cooled in the air for 195-205s. Then the fan-shaped plate is placed in the water body of the quenching tank again, and continues to be water-cooled in the water body until the core temperature is 189-198°C. Then the fan-shaped plate is lifted out and cooled in the air for 195-205s. Then the fan-shaped plate is placed in the water body of the quenching tank again, and continues to be water-cooled in the water body until the core temperature is 155-185°C. The cooling speed of the core of the workpiece is close to that of the conventional oil cooling method.

[0015] Preferably, in step S2, the water temperature in the quenching tank is set to 30-35°C.

[0016] Preferably, in step S2, the air cooling is performed in air for 30 to 50 minutes, and the maximum temperature of the surface of the sector plate is set to 150 to 180°C.

[0017] Preferably, in step S1, the heating furnace is a gas furnace.

[0018] Preferably, in step S3, the surface temperature of the quenched sector plate obtained in step S2 placed in the tempering furnace is 100-120°C.

[0019] Preferably, the sector plate is made of martensitic stainless steel, and its chemical composition is as follows by mass percentage: C: 0.16-0.25wt.%, Si: 0.21-0.41wt.%, Mn: 0.28-0.80wt.%, P<0.030wt.%, S<0.020wt.%, Cr: 10.0-12.5wt.%, Ni: 0.28-0.80wt.%, Mo: 0.76-1.18wt.%, V: 0.25-0.35wt.%, and the remainder is Fe and unavoidable impurities.

[0020] Preferably, the microstructure of the heat-treated fan-shaped plate product obtained in step S3 is tempered troostite, and the martensite lath is tempered at high temperature to form a complex structure with ferrite as the matrix and fine and uniform carbide particles distributed inside. In its microstructure, M23C6 carbides are dispersed on the ferrite matrix, and the shape of the M23C6 carbides is an irregular sphere with an equivalent diameter of 100 to 350 nm or a long rod-shaped structure with a length of 100 to 350 nm.

[0021] Preferably, the heat-treated fan-shaped plate product obtained in step S3 has a hardness of 245-270 HB, a tensile strength Rm of 850-900 MPa, and a plastic extension strength Rp of 0.2 ≥650MPa, elongation after fracture A≥15%, room temperature impact energy DVM≥38J.

[0022] A fan-shaped plate for a hot-rolled coiler, the fan-shaped plate for a hot-rolled coiler is obtained by the above-mentioned heat treatment method after forming, and the microstructure of the fan-shaped plate is tempered troostite, and the martensite lath is tempered at high temperature to form a complex phase structure with ferrite as the matrix and fine and uniform carbide particles distributed inside. In its microstructure, M23C6 carbides are dispersed on the ferrite matrix, and the shape of the M23C6 carbides is an irregular sphere with an equivalent diameter of 100 to 350nm or a long rod-shaped structure with a length of 100 to 350nm; the hardness of the fan-shaped plate is 245 to 270HB, the tensile strength Rm is 850 to 900MPa, and the plastic extension strength Rp is 100 to 1000MPa. 0.2 ≥650MPa, elongation after fracture A≥15%, room temperature impact energy DVM≥38J.

[0023] Beneficial effects of the present invention:

[0024] 1. The present invention provides a heat treatment method for martensitic stainless steel of fan-shaped plates for hot rolling coilers. By heating in stages to a specific preferred solution treatment temperature, the risk of cracking caused by residual stress due to the different heating rates of the surface and core of the workpiece and the temperature difference between the inside and outside is reduced. The solid solution effect is ensured by selecting the specific temperature and insulation time of each section; by setting the specific quenching cooling rate (i.e., the specific water-air alternating quenching setting), it is ensured that the workpiece does not crack and obtains a deeper hardened layer, and combined with the subsequent specific step-by-step heating and insulation tempering method setting, a microstructure in which fine carbides are dispersed and precipitated in the matrix is ​​achieved, so that the final workpiece can achieve excellent comprehensive mechanical properties, with a hardness of 245-270HB, a tensile strength Rm of 850-900MPa, a plastic extension strength Rp of 0.2≥650MPa, an elongation after fracture A≥15%, and a room temperature impact energy DVM≥38J, achieving high performance at a low cost.

[0025] 2. Since martensitic stainless steel is sensitive to cooling speed and is prone to cracking during the production process, traditional production uses oil cooling for cooling. The present invention sets a specific water-air alternating time-controlled quenching method, and uses different specific core temperatures as the alternating intervals of water cooling and air cooling to achieve a cooling trend that is basically the same as oil cooling under the same conditions. The quenching method is evaluated by numerical simulation, and specific air cooling passes are added at each stage of specific core temperature during the water cooling process, so that the cooling rate of the workpiece core is close to that of the oil cooling method. Thereby, the same quenching effect as oil cooling is achieved by using medium water cooling, thereby reducing production costs, reducing environmental pollution, and avoiding quenching cracking.

[0026] 3. The present invention achieves a technical effect of low cost and high performance for a specific fan-shaped plate and a specific martensitic stainless steel material by performing specific graded heating solution treatment, water-air alternating quenching and step-by-step heating and heat preservation tempering treatment on a specific martensitic stainless steel fan-shaped plate workpiece, and the two are closely coordinated and arranged. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a curve diagram of the solution treatment and tempering treatment of the present invention.

[0028] Figure 2 This is a core temperature drop curve of a sector plate in a numerical simulation of a water-air alternating process and an oil cooling process in an embodiment of the present invention.

[0029] Figure 3 This is a tempered microstructure diagram of a fan-shaped plate according to an embodiment of the present invention.

[0030] Figure 4 This is the microstructure diagram of the tempered stainless steel of comparative example 4 of the present invention. DETAILED DESCRIPTION

[0031] The method and technical solution of the present invention are further illustrated below by combining embodiments and drawings. The orientations involved in this specification are based on the orientations of the present invention during normal operation, and do not limit the orientations during storage and transportation. They only represent relative positional relationships, not absolute positional relationships. Specific implementation methods Unless otherwise described, each feature is only an example of a series of equivalent or similar features. Just to help understand the present invention, those skilled in the art should understand that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0032] Example 1

[0033] The hot rolling coiler fan plate described in this embodiment is martensitic stainless steel (X22CrMoV12-1 martensitic stainless steel), and the specific chemical composition is calculated by mass percentage: C: 0.18wt.%, Si: 0.31wt.%, Mn: 0.52wt.%, P: 0.012wt.%, S: 0.005wt.%, Cr: 11.3wt.%, Ni: 0.61wt.%, Mo: 0.98wt.%, V: 0.31wt.%, and the balance is Fe and unavoidable impurities. After forging and annealing, it is subjected to the following heat treatment method:

[0034] S1, heating the sector plate in a gas furnace in stages to a solution temperature, wherein the specific conditions of the solution treatment are as follows: Figure 1 The temperature is then increased to 600°C at a rate of 35°C / h and kept at that temperature for 3 hours; the temperature is then increased to 800°C at a rate of 55°C / h and kept at that temperature for 3 hours; the temperature is then increased to the solution temperature of 1050°C at a rate of 75°C / h and kept at that temperature for 8 hours.

[0035] S2, quenching cooling, the fully austenitized workpiece is quickly cooled to a core temperature of 160°C by alternating water and air. The water temperature of the quenching tank is controlled at 32°C. Specifically: add air cooling passes during the water cooling process, first water cool the fan plate in the quenching tank to a core temperature of 860°C, then lift the fan plate out, cool it in the air for 150s, then put the fan plate back into the water body of the quenching tank, continue to water cool it in the water body to a core temperature of 570°C, then lift the fan plate out, cool it in the air for 156s, then put the fan plate back into the water body of the quenching tank, continue to water cool it in the water body to a core temperature of 310°C, then lift the fan plate out, cool it in the air for 198s, then put the fan plate back into the water body of the quenching tank, continue to water cool it in the water body to a core temperature of 194°C, then lift the fan plate out, cool it in the air for 197s, then put the fan plate back into the water body of the quenching tank, continue to water cool it in the water body to a core temperature of 160°C. The workpiece was lifted out of the quenching tank and air-cooled for 45 minutes. After the workpiece was air-cooled for 45 minutes, the maximum temperature of the workpiece surface was 155°C.

[0036] S3, tempering, when the surface temperature of the workpiece drops to 115℃, put it into the furnace for tempering. Figure 1 The staged tempering on the right side is carried out, specifically, after loading the furnace, it is kept in a 250°C furnace for 3.5 hours, then heated to 685°C at a heating rate of 60°C / h and kept for 12 hours for tempering, and then air-cooled to room temperature.

[0037] The quenched and tempered microstructure of the fan-shaped plate product is as follows: Figure 3 As shown, from Figure 3 It can be seen from the figure that the microstructure of the product of this embodiment is tempered troostite. The martensite lath is tempered at high temperature to form a complex phase structure with ferrite as the matrix and fine and uniform carbide particles distributed inside. And the M23C6 type carbide is dispersed on the ferrite matrix, and as shown in FIG. Figure 3 As shown, the shape of the M23C6 carbide is an irregular sphere with an equivalent diameter of 100 to 350 nm or a long rod-like structure with a length of 100 to 350 nm.

[0038] Example 2

[0039] The hot-rolled coiler fan plate described in the present invention is a martensitic stainless steel having the same composition as that of Example 1, which is subjected to the following heat treatment method after forging and annealing:

[0040] S1, heating the sector plate in a gas furnace in stages to the solution temperature. The specific conditions of the solution treatment are: keeping it in a 300°C furnace for 2.5 hours, then heating it to 630°C at a heating rate of 30°C / h and keeping it at a uniform temperature for 3 hours, then heating it to 810°C at a heating rate of 50°C / h and keeping it at a uniform temperature for 3 hours, then heating it to the solution temperature of 1045°C at a heating rate of 75°C / h and keeping it at a uniform temperature for 8 hours.

[0041] S2, quenching cooling, the fully austenitized workpiece is quickly cooled to a core temperature of 155°C using a water-air alternating method. Specifically, add air cooling during the water cooling process, first water cool the fan plate in the quenching tank to a core temperature of 858°C, then lift the fan plate out, cool it in the air for 150s, then put the fan plate back into the water body of the quenching tank, continue to water cool it in the water body to a core temperature of 575°C, then lift the fan plate out, cool it in the air for 155s, then put the fan plate back into the water body of the quenching tank, continue to water cool it in the water body to a core temperature of 308°C, then lift the fan plate out, cool it in the air for 198s, then put the fan plate back into the water body of the quenching tank, continue to water cool it in the water body to a core temperature of 196°C, then lift the fan plate out, cool it in the air for 198s, then put the fan plate back into the water body of the quenching tank, continue to water cool it in the water body to a core temperature of 155°C. Lift the workpiece out of the quenching tank and air cool it for 40min. The maximum temperature of the workpiece surface is 150°C. The water temperature of the quenching tank needs to be controlled at 33°C.

[0042] S3, tempering, when the workpiece surface temperature drops to 118℃, put it into the furnace for tempering. Keep it in the furnace at 280℃ for 3.8h, then heat it to 685℃ at a heating rate of 60℃ / h and keep it for 12h for tempering, and then air cool it to room temperature.

[0043] Example 3

[0044] The hot rolling coiler fan plate described in this embodiment is martensitic stainless steel, and its specific chemical components are as follows by mass percentage: C: 0.21wt.%, Si: 0.28wt.%, Mn: 0.61wt.%, P: 0.010wt.%, S: 0.005wt.%, Cr: 10.8wt.%, Ni: 0.65wt.%, Mo: 1.08wt.%, V: 0.30wt.%, and the remainder is Fe and unavoidable impurities.

[0045] After forging and annealing, it undergoes the following heat treatment methods:

[0046] S1, heating the sector plate in a gas furnace in stages to the solution temperature. The specific conditions of the solution treatment are: keeping the temperature in a 280°C furnace for 4 hours, then heating to 650°C at a heating rate of 35°C / h and keeping it at a constant temperature for 3 hours, then heating to 850°C at a heating rate of 60°C / h and keeping it at a constant temperature for 3 hours, then heating to the solution temperature of 1055°C at a heating rate of 70-80°C / h and keeping it at a constant temperature for 8 hours.

[0047] S2, quenching cooling, the fully austenitized workpiece is quickly cooled to a core temperature of 165°C using a water-air alternating method. Specifically, add air cooling during the water cooling process, first water cool the fan plate in the quenching tank to a core temperature of 860°C, then lift the fan plate out, cool it in the air for 148s, then put the fan plate back into the water body in the quenching tank, continue to water cool it in the water body to a core temperature of 569°C, then lift the fan plate out, cool it in the air for 156s, then put the fan plate back into the water body in the quenching tank, continue to water cool it in the water body to a core temperature of 311°C, then lift the fan plate out, cool it in the air for 201s, then put the fan plate back into the water body in the quenching tank, continue to water cool it in the water body to a core temperature of 190°C, then lift the fan plate out, cool it in the air for 202s, then put the fan plate back into the water body in the quenching tank, continue to water cool it in the water body to a core temperature of 165°C. Lift the workpiece out of the quenching tank and air cool it for 35min. The maximum temperature of the workpiece surface is 160℃; the water temperature of the quenching tank needs to be controlled at 35℃.

[0048] S3, tempering, when the workpiece surface temperature drops to 120℃, put it into the furnace for tempering. After keeping it in the furnace at 300℃ for 4 hours, heat it to 690℃ at a heating rate of 60℃ / h and keep it for 12 hours for a tempering treatment, and then air cool it to room temperature.

[0049] The mechanical property test results of the above embodiments are shown in Table 1. Table 1 is the mechanical property test results of Embodiments 1 to 3.

[0050] Table 1

[0051]

[0052] Comparative Example 1

[0053] The other settings of this comparative example are the same as those of Example 1, except that: in step S2, quenching oil is provided in the quenching tank, the fully austenitized sector plate obtained in step S1 is placed in the quenching tank filled with quenching oil, and is cooled by immersion in the quenching oil. The cooling time is consistent with the quenching time of water-air alternating time control, and then the workpiece is lifted out of the quenching tank to obtain the quenched sector plate. The other settings are the same as those of Example 1.

[0054] The quenching process of Example 1 and the quenching process of this comparative example were monitored and plotted, and the following results were obtained: Figure 2 The cooling curve shown in the figure shows that the horizontal axis is the time in seconds, the vertical axis is the temperature of the fan-shaped plate workpiece, the solid points in the figure are the oil quenching temperature points, and the hollow points are the water-air alternating temperature points. Figure 2 It can be seen that the cooling curves of the water-air alternating controlled quenching method of Example 1 and the oil quenching cooling method of Comparative Example 1 are basically overlapped, especially in the initial cooling stage, and basically overlapped in the middle stage with very small difference, and further overlapped in the later stage. This shows that the specific water-air alternating timing and number and the setting of parameters and ranges set by the present invention can completely replace the existing oil quenching method, and can achieve basically the same cooling trend, thereby achieving the prevention of cracking while ensuring the high plasticity and toughness indicators of the fan-shaped plate workpiece.

[0055] Comparative Example 2

[0056] The other settings of this comparative example are the same as those of Example 1, except that step S2 directly adopts water quenching by immersing in water instead of the water-air alternating controlled time quenching method of Example 1. The other settings are the same as those of Example 1. The obtained product is tested and 3 cracks are found on the surface, which proves that it is not a simple replacement of oil quenching with water quenching. The specific temperature points, alternating timings and specific parameters set in the present invention cannot be simply replaced.

[0057] Comparative Example 3

[0058] The other settings of this comparative example are the same as those of Example 1, except that step S1 is performed by directly heating to the solution temperature of 1050°C at 75°C / h and keeping the temperature for 8 hours. The other settings are the same as those of Example 1. The fan-shaped plate product obtained is monitored and it is found that the core is cracked, and its impact is 30J. This is because the thermal conductivity of stainless steel is low below 800°C, and a higher heating rate is used to heat it to 1050°C, resulting in excessive thermal stress in the blank and cracking; and the solid solution treatment is performed by direct heating once, resulting in the carbide of the original internal structure not being fully integrated into the austenite, so that the toughness cannot be guaranteed after the subsequent specific quenching and tempering treatment, resulting in cracking of the workpiece and a reduction in toughness relative to the present invention. This shows that the graded heating method set by the present invention is closely coordinated with the subsequent water-air alternating quenching and specific tempering method.

[0059] Comparative Example 4

[0060] The other configurations of this comparative example are the same as those of Example 1, except that the martensitic stainless steel of Example 1 is not used, but 2Cr12NiMoWV stainless steel is used. The other configurations are the same as those of Example 1. The obtained product is tested and found to have a hardness of 290 HB and an impact strength of 30 J. This is because the alloying elements Mn, Cr, Ni, and Mo in 2Cr12NiMoWV are higher than those in Example 1, and 2Cr12NiMoWV has an additional alloying element W, so the tempering resistance of 2Cr12NiMoWV is higher than that of Example 1. Figure 4 The microstructure diagram of the comparative example is shown, and it can be seen that the size of the carbides precipitated by tempering is 560-1000nm, which is larger than that of Example 1. It can be found that when 2Cr12NiMoWV adopts the same heat treatment process as Example 1, the hardness is higher and the impact is lower than that of the present invention. This shows that the specific heat treatment setting of the present invention is carried out for X22CrMoV12-1 martensitic stainless steel, and the two have a coordinated correlation.

[0061] Comparative Example 5

[0062] The other settings of this comparative example are the same as those of Example 1, except that in step S3, the tempering treatment is directly carried out at 685°C for 12 hours without adopting the tempering treatment process of the segmented heating and heat preservation of Example 1. The other settings are the same as those of Example 1. The obtained fan-shaped plate product is monitored and found to have a hardness of 239HB. This is because the low-temperature section of 250-300°C is not heat-insulated, and the supercooled austenite is not fully transformed, resulting in a lower hardness than the present invention. This shows that even after the specific step-by-step heating solution and water-air alternating quenching of the present invention, the specific segmented heating and heat preservation tempering treatment is also a creative setting. Such a setting is coordinated with the previous specific solution and quenching treatment. The single modification of the tempering treatment will also result in the production of defective products, and the production of such products is not the adverse consequence of poor tempering in the conventional sense, thus proving the coordinated creativity of each step.

[0063] The technical principles and examples of the present invention are described above in conjunction with specific embodiments. The above embodiments and comparative examples of the present invention are all examples and do not have a limiting effect on the protection scope of the technical solution. The technical effects that are not compared can be clearly described through the textual description of the technical effects, and do not mean that the invention is low in height. These descriptions are only for explaining the principles and examples of the present invention and cannot be interpreted as limiting the protection scope of the present invention in any way. Based on the explanations herein, those skilled in the art can think of other specific implementations of the present invention without creative labor, and these methods will fall within the protection scope of the present invention.

Claims

1. A method for heat treatment of a fan-shaped plate for a hot rolling coiler, characterized in that: The following steps are involved: S1, solution treatment: the fan-shaped plate is heated to the solution temperature by graded heating, the solution temperature is 1030-1060°C, the graded heating is to place the fan-shaped plate in a heating furnace at 250-300°C, and keep it warm for 2-4h; then the temperature is increased to 550-650°C at a heating rate of 30-40°C / h, and the temperature is kept at this temperature for 2.5-3.5h, and then the temperature is increased to 750-850°C at a heating rate of 50-60°C / h, and the temperature is kept at this temperature for 2.6-3.5h, and then the temperature is increased to the solution temperature at a heating rate of 70-80°C / h, and the temperature is kept at the solution temperature for 6-9h, so as to obtain a fully austenitized fan-shaped plate, and complete the solution treatment; S2, water-air alternating quenching: placing the fully austenitized sector plate obtained in step S1 into a quenching tank filled with water, and cooling the sector plate to a core temperature of 155-185° C. by water-air alternating time-controlled quenching, then lifting the workpiece out of the quenching tank, and air cooling in air for 30-50 minutes to obtain a quenched sector plate; S3, tempering: placing the quenched sector plate obtained in step S2 into a tempering furnace at 250-300°C, keeping it at this temperature for 3-4 hours, then heating it to 685-695°C at a heating rate of 40-60°C / h, then keeping it at this temperature for 10-15 hours, then taking it out of the furnace and air cooling it to room temperature to obtain a heat-treated sector plate product.

2. The heat treatment method for the fan-shaped plate for the hot rolling coiler according to claim 1, characterized in that: The water-air alternating controlled quenching method described in step S2 is specifically as follows: adding air cooling passes during the water cooling process, first water cooling the fan-shaped plate in the quenching tank to a core temperature of 853-866°C, then hanging out the fan-shaped plate, cooling it in the air for 145-155s, then placing the fan-shaped plate back into the water body of the quenching tank, continuing to water cool it in the water body to a core temperature of 565-578°C, then hanging out the fan-shaped plate, cooling it in the air for 155-165s, and then placing the fan-shaped plate back into the water body of the quenching tank. In the water body of the quenching tank, continue to water-cool in the water body until the core temperature is 306-316°C, then lift out the fan-shaped plate, cool it in the air for 195-205s, and then put the fan-shaped plate back into the water body of the quenching tank, continue to water-cool it in the water body until the core temperature is 189-198°C, then lift out the fan-shaped plate, cool it in the air for 195-205s, and then put the fan-shaped plate back into the water body of the quenching tank, and continue to water-cool it in the water body until the core temperature is 155-185°C.

3. The heat treatment method for the fan-shaped plate for the hot rolling coiler according to claim 1 or 2, characterized in that: In step S2, the water temperature in the quenching tank is set to 30-35°C.

4. The heat treatment method for a fan-shaped plate for a hot rolling coiler according to claim 1 or 2, characterized in that: In step S2, air cooling is performed in air for 30 to 50 minutes, and the maximum temperature of the fan-shaped plate surface is set to 150 to 180°C.

5. The heat treatment method for a fan-shaped plate for a hot rolling coiler according to claim 1 or 2, characterized in that: In step S1, the heating furnace is a gas furnace.

6. The heat treatment method for a fan-shaped plate for a hot rolling coiler according to claim 1 or 2, characterized in that: In step S3, the surface temperature of the quenched sector plate obtained in step S2 placed in the tempering furnace is 100 to 120°C.

7. The heat treatment method for the fan-shaped plate for hot rolling coiler according to claim 1 or 2, characterized in that: The fan-shaped plate is martensitic stainless steel, and its chemical composition is as follows by mass percentage: The fan-shaped plate is martensitic stainless steel, and its chemical composition is as follows by mass percentage: C: 0.16-0.25wt.%, Si: 0.21-0.41wt.%, Mn: 0.28-0.80wt.%, P<0.030wt.%, S<0.020wt.%, Cr: 10.0-12.5wt.%, Ni: 0.28-0.80wt.%, Mo: 0.76-1.18wt.%, V: 0.25-0.35wt.%, and the remainder is Fe and unavoidable impurities.

8. The heat treatment method for a fan-shaped plate for a hot rolling coiler according to claim 1 or 2, characterized in that: The microstructure of the heat-treated fan-shaped plate product obtained in step S3 is tempered troostite, and the martensite laths are tempered at high temperature to form a complex phase structure with ferrite as the matrix and fine and uniform carbide particles distributed inside; in its microstructure, M23C6 carbides are dispersed on the ferrite matrix, and the shape of the M23C6 carbides is an irregular sphere with an equivalent diameter of 100 to 350 nm or a long rod-shaped structure with a length of 100 to 350 nm.

9. The heat treatment method for a fan-shaped plate for a hot rolling coiler according to claim 1 or 2, characterized in that: The heat-treated fan-shaped plate product obtained in step S3 has a hardness of 245-270 HB, a tensile strength Rm of 850-900 MPa, and a plastic extension strength Rp of 0.2 ≥650MPa, elongation after fracture A≥15%, room temperature impact energy DVM≥38J.

10. A fan-shaped plate for a hot rolling coiler, characterized in that: The fan-shaped plate for hot rolling coiler is obtained by the heat treatment method according to any one of claims 1 to 7 after forming, and the microstructure of the fan-shaped plate is tempered troostite, and the martensite lath is tempered at high temperature to form a complex phase structure with ferrite as the matrix and fine and uniform carbide particles distributed inside; in its microstructure, M23C6 carbides are dispersed on the ferrite matrix, and the shape of the M23C6 carbides is an irregular sphere with an equivalent diameter of 100 to 350 nm or a long rod-shaped structure with a length of 100 to 350 nm; the hardness of the fan-shaped plate is 245 to 270 HB, the tensile strength Rm is 850 to 900 MPa, and the plastic extension strength Rp is 100 to 150 MPa. 0.2 ≥650MPa, elongation after fracture A≥15%, room temperature impact energy DVM≥38J.

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