A heat treatment method for improving the toughness of the core of a wide and thick plate backup roll body

Abstract

This invention discloses a heat treatment method for improving the internal toughness of a heavy plate support roller, belonging to the technical field of heavy plate support rollers; it solves the technical problems of poor internal toughness and weak accident resistance of existing heavy plate support rollers. The heat treatment method includes: S1, performing post-forging heat treatment on the heavy plate support roller; S2, performing quenching and tempering heat treatment on the heavy plate support roller; specifically including: S21, holding the post-forging heat-treated heavy plate support roller at 250-300℃ for the first time; S22, raising the temperature to 650-670℃ after the first holding; S23, performing a second holding at 650-670℃; S24, raising the temperature to 900-940℃ after the second holding; S25, performing a third holding at 900-940℃; S26, quenching after the third holding, followed by tempering to complete the quenching and tempering heat treatment; step 3, performing differential temperature heat treatment to obtain the heavy plate support roller product. This invention improves the impact toughness of the roll body while ensuring the mechanical properties of the roll neck.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for support rollers, and in particular to a heat treatment method for improving the internal toughness of support rollers for wide and thick plates. Background Technology

[0002] Heavy plates are widely used in large ships, large-diameter oil and gas straight seam welded pipes, boilers, large oil and gas storage tanks, and machinery manufacturing. Support rolls are a crucial core component of heavy plate rolling mills, serving to support and stabilize the work rolls. They require high performance: high fatigue resistance and wear resistance in the working layer; high strength and toughness in the roll neck; and good plasticity and toughness in the roll body itself. Heavy plate support rolls undergo three heat treatments: post-forging heat treatment, pre-heat treatment (quenching and tempering), and differential temperature heat treatment. Post-forging heat treatment primarily refines the grain size and microstructure, removes hydrogen to prevent white spots, and facilitates machining. The performance of the roll neck is ensured by the pre-heat treatment (quenching and tempering). The microstructure of the roll body surface (working layer) is achieved through the differential temperature heat treatment process. Large heavy plate support rolls with a roll body length of over 3 meters and a roll body diameter of over 2 meters are among the largest and most difficult-to-manufacture roll products, characterized by high technology content and high added value.

[0003] Due to the large size and weight of heavy plate support rollers, the following drawbacks are unavoidable during production: segregation of internal and external components, uneven forging deformation, and asynchronous microstructural transformation during heat treatment, resulting in uneven internal structure and poor performance. After final heat treatment, the workpiece exhibits high residual stress, placing it in a dangerous tensile stress state. Occasionally, heavy plate support rollers experience breakage (i.e., cracking) during placement or use. The main factors contributing to these cracking accidents are: ① hydrogen content in the steel; ② internal stress in the steel; ③ weak points in the area of ​​maximum internal stress in the steel, such as micropores and segregation. Reducing the internal hydrogen content and residual stress of forgings, eliminating weak points in the core, and thus improving the safety of heavy plate support rollers has been a persistent research focus for manufacturers. However, the inherent drawbacks of heavy plate support rollers are difficult to completely eliminate. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a heat treatment method for improving the toughness of the body and core of a heavy plate support roll, in order to solve the technical problems of poor toughness and weak accident resistance of existing heavy plate support rolls.

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] This invention provides a heat treatment method for improving the internal toughness of a support roll body for thick plates, the heat treatment method comprising the following steps:

[0007] S1. Perform heat treatment on the forging of the thick plate support roller;

[0008] S2. The support rolls after forging and heat treatment are subjected to quenching and tempering heat treatment; the quenching and tempering heat treatment process includes the following sub-steps:

[0009] S21. The forged and heat-treated wide and thick plate support rolls are kept at 250-300℃ for the first time.

[0010] S22. After the first heat preservation, raise the temperature to 650-670℃;

[0011] S23. The support rollers of the thick plate are subjected to a second heat preservation at 650-670℃.

[0012] S24. The support rollers for wide and thick plates are heated to 900-940℃ after the second heat preservation.

[0013] S25. The support rollers of the thick plate are subjected to a third heat preservation at 900-940℃.

[0014] S26. After the third heat treatment, quenching is performed, followed by tempering to complete the heat treatment.

[0015] Step 3: Perform differential temperature heat treatment on the support roller after tempering and heat treatment to obtain the wide and thick plate support roller product.

[0016] Furthermore, in S21, the initial heat preservation time is 15-30 hours.

[0017] Furthermore, in S22, after the first heat preservation, the thick plate support roller is heated to 650-670℃ at a rate of ≤30℃ / h.

[0018] Furthermore, in S23, the second heat preservation time is 10-50 hours.

[0019] Furthermore, in S24, after the second heat treatment, the temperature is increased to 900-940℃ at a rate of ≤50℃ / h.

[0020] Furthermore, in S25, the third heat preservation time is 20-50 hours.

[0021] Furthermore, in S26, the tempering temperature is 550-650℃.

[0022] Furthermore, in S1, the post-forging heat treatment includes two normalizing processes, spheroidizing annealing, and high-temperature tempering.

[0023] Furthermore, in step S3, the differential temperature heat treatment process includes the following sub-steps:

[0024] S31. The support roller needs to be preheated before differential temperature heating. The preheating temperature is 500-600℃.

[0025] S32. Transfer the support roller into the furnace, heat only the roller body and air cool the roller neck, and use the maximum power to quickly raise the furnace temperature to 1000-1050℃.

[0026] S33. Maintain at 1000-1050℃ until the roller surface temperature reaches the predetermined quenching temperature, thus completing heating stage I;

[0027] S34. Adjust the furnace temperature to 950-1000℃ and maintain it; complete heating stage II;

[0028] S35, roller body spray cooling, the cooling intensity is adjusted by regulating the air pressure and water pressure;

[0029] S36. After spray quenching, transfer to a tempering furnace and maintain at 250-300℃ for a period of time.

[0030] S37. Heat to the tempering temperature of 450-550℃ at a rate of less than or equal to 30℃ / h;

[0031] S38. Maintain at 450-550℃ for a period of time;

[0032] S39. Cool down to 400℃ at a rate of less than or equal to 20℃ / h.

[0033] Furthermore, S3 also includes S310, cooling to 150°C at a rate of less than or equal to 10°C / h to complete the differential temperature heat treatment.

[0034] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0035] (1) The present invention uses the diameter of the root of the large roller neck of the thick plate support roller as the effective section for setting the quenching and heating parameters, rather than the roller body diameter. On the one hand, the roller neck achieves the purpose of quenching and heating and ensures mechanical properties; on the other hand, the roller body is still in the temperature range of "easily forming granular pearlite" when quenching and heating at high temperature.

[0036] (2) After the first heat preservation, the present invention heats up to 650-670℃ at a rate of ≤30℃ / h. At this stage, the core of the forging is still in an elastic state. Excessive temperature difference can easily cause excessive thermal stress and increase the risk of cracking of the forging. In addition, the size of the forging is large. Therefore, the heating rate is controlled to be ≤30℃ / h.

[0037] (3) In step S23 of the present invention, the temperature is kept at 650-670℃ for 10-50h; the intermediate temperature is controlled below the phase transformation point (Ac1): 650-670℃. On the one hand, this reduces the temperature difference between the inside and outside of the forging, and on the other hand, it prepares for the phase transformation, so that the phase transformation is as uniform as possible on the entire cross section of the forging, and avoids generating large structural stress.

[0038] (4) Compared with the prior art, the present invention, while ensuring the mechanical properties of the neck of the support roller of the thick plate, processes the core of the support roller into a granular (or spheroidized) pearlite structure, improves the core toughness of the support roller of the thick plate, prevents crack propagation, and improves the resistance of the support roller to accidents.

[0039] (5) The present invention improves the microstructure near the crack source to weaken the harm caused by the weak link, thereby improving the safety of the support roller.

[0040] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0041] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0042] Figure 1 (a) and Figure 1 (b) are all microstructure diagrams of existing thick plate support rollers;

[0043] Figure 2 Simulation curves were generated during the research process of quenching and tempering heat treatment parameters;

[0044] Figure 3 Quenching hardness curves during the research process of tempering heat treatment parameters;

[0045] Figure 4 The dissolution of carbides at high temperature (860℃) during the study of tempering heat treatment parameters;

[0046] Figure 5 The dissolution of carbides at high temperature (940℃) during the study of tempering heat treatment parameters;

[0047] Figure 6 Microstructure of the core after tempering (860℃) during the study of tempering heat treatment parameters;

[0048] Figure 7 The image shows the microstructure of the core after tempering (940℃) during the study of tempering heat treatment parameters.

[0049] Figure 8 When studying the parameters of tempering heat treatment, the core impact toughness after tempering was considered.

[0050] Figure 9Specifications for support roller test pieces;

[0051] Figure 10 Temperature variation curves at various locations during the study of quenching and tempering heat treatment parameters;

[0052] Figure 11 The metallographic structure (tempered sorbite) on the neck surface of the thick plate support roller prepared in Example 1;

[0053] Figure 12 The metallographic structure (mainly granular pearlite) of the roll body of the thick plate support roll prepared in Example 1;

[0054] Figure 13 The heat treatment curve after forging;

[0055] Figure 14 Differential temperature heat treatment curve. Detailed Implementation

[0056] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0057] This invention relates to a support roller for thick plates, wherein the roller body length is greater than 3m, the roller body diameter is greater than 2m, and the support roller weight is greater than 100t.

[0058] Existing case studies of fractured support rolls show that brittle fracture often originates near the center of the roll body, where the microstructure is lamellar pearlite with poor toughness. Figure 1 The microstructure (lamellar pearlite) at the fracture origin (core) is shown in Table 1. The impact toughness test results at the same location are shown in Table 1.

[0059] Table 1 Impact toughness at the fracture origin

[0060]

[0061] When microcracks are generated in weak links such as micropores under stress, lamellar pearlite with poor toughness will accelerate the propagation of microcracks, while granular (or spheroidized) pearlite has much higher toughness than lamellar pearlite.

[0062] The problem is that in the existing technology, the high temperature during the tempering process can easily destroy the spheroidized structure (spheroidized pearlite) of the roll body after forging. The re-austenitic roll body undergoes a near-equilibrium transformation during the slow cooling process, forming lamellar pearlite. Lamellar pearlite has poor toughness, which leads to poor toughness of the roll body of the thick plate support roll.

[0063] To address the aforementioned technical problems, this invention studies the tempering heat treatment stage of thick plate support rolls: 1. This invention characterizes the mechanical properties of the roll neck using hardness, and studies the relationship between quenching hardness and heating temperature to ensure the mechanical properties of the roll neck; 2. Taking the body and core of the thick plate support roll as the research object, this invention studies the tempering heat treatment process, and investigates the influence of tempering heat treatment heating process parameters on microstructure and impact toughness. Experiments are conducted from the above two aspects to formulate reasonable heating parameters in the tempering heat treatment process.

[0064] This invention provides a heat treatment method for improving the internal toughness of a support roll body for thick plates, comprising the following steps:

[0065] S1. Perform heat treatment on the forging of the thick plate support roller;

[0066] S2. The support rolls after forging and heat treatment are subjected to quenching and tempering heat treatment; the quenching and tempering heat treatment process includes the following sub-steps:

[0067] S21. The forged and heat-treated wide and thick plate support rolls are kept at 250-300℃ for the first time, and the first time is kept for 15-30 hours.

[0068] S22. After the first heat preservation, heat the wide and thick plate support roller to 650-670℃ at a rate of ≤30℃ / h.

[0069] S23. The support rollers of the thick plate are subjected to a second heat preservation at 650-670℃ for 10-50 hours.

[0070] S24. After the second heat preservation, heat the wide and thick plate support roller to 900-940℃ at a rate of ≤50℃ / h.

[0071] S25. The support rollers of the thick plate are subjected to a third heat preservation at 900-940℃.

[0072] S26. After the third heat treatment, quenching is performed, followed by tempering at a temperature of 550-650℃ to complete the heat treatment.

[0073] Step 3: Perform differential temperature heat treatment on the support roller after tempering and heat treatment to obtain the wide and thick plate support roller product.

[0074] In the above S21, the first heat preservation is carried out at 250-300℃ for 15-30 hours. The purpose is to reduce the temperature difference between the inside and outside of the workpiece, especially the temperature difference at 250-300℃, because 250-300℃ is the blue brittle temperature range of steel, and the risk of internal stress causing cracks is very high.

[0075] In S22 above, the temperature is increased to 650-670℃ at a rate of ≤30℃ / h. At this stage, the core of the forging is still in an elastic state. Excessive temperature difference can easily cause excessive thermal stress and increase the risk of cracking of the forging. In addition, the forging is large in size, so the heating rate is controlled to be ≤30℃ / h.

[0076] In the above S23, the temperature is held at 650-670℃ for 10-50 hours; the intermediate holding temperature is controlled below the phase transformation point (Ac1): 650-670℃. This reduces the temperature difference between the inside and outside of the forging and prepares for the phase transformation, making the phase transformation as uniform as possible across the entire cross section of the forging and avoiding the generation of large structural stress.

[0077] In S24 above, the temperature is raised to 900-940℃ at a rate of ≤50℃ / h; after being held at 650-670℃, the temperature difference between the inside and outside of the forging basically disappears. At this time, the core temperature of the forging is relatively high and it is in a plastic state. Therefore, a higher heating rate can be adopted, namely ≤50℃ / h.

[0078] In step S25 above, the temperature is held at 900-940℃ for 20-50 hours. The purpose of this holding is to ensure that the core of the support roll neck reaches the heating temperature and completes the austenitization transformation; it is not necessary to reach the heating temperature of the roll body itself, thus preserving a good granular pearlite structure. In step S26 above, after high-temperature heating and quenching, the roll neck is tempered at 550-650℃ to complete the quenching and tempering heat treatment. This reduces the internal stress generated during quenching and cooling, and also obtains a stable tempered structure, achieving the required mechanical properties of the roll neck.

[0079] Compared with existing technologies, this invention, through mechanistic research on materials and adjustment of tempering heat treatment process parameters, ensures the mechanical properties of the roll neck while rationally improving the internal microstructure of the roll body, increasing the core toughness, weakening the effect of weak links in the core, preventing crack propagation, and reducing the risk of support roll breakage.

[0080] For the support rolls of extra-large and thick plate rolling mills, two recrystallization processes are required to refine the core grains. Therefore, in S1 above, the post-forging heat treatment method is two normalizing processes, spheroidizing annealing, and high-temperature tempering, specifically including the following sub-steps:

[0081] S11: Waiting and holding at 600-650℃ to eliminate forging stress.

[0082] S12: Cool the furnace to 300-400℃.

[0083] S13: Hold at 300-400℃; This stage allows the core of the forging to fully transform from austenite to ferrite-carbide structure, which is beneficial for adjusting and refining the grain structure of the steel through subsequent phase transformation recrystallization.

[0084] S14: Heat to 650-670℃ at a rate of less than or equal to 30℃ / h; this stage is a rate-limited heating stage in an effort to reduce the internal and external temperature difference and instantaneous internal stress in large support roll forgings.

[0085] S15: 650-670℃ heat preservation; minimize the internal and external temperature difference and non-simultaneous transformation of the forging during heating transformation, and further reduce stress and deformation in the workpiece.

[0086] S16: Heat to 920-960℃ at a rate of less than or equal to 50℃ / h.

[0087] S17: Hold at 920-960℃, then heat to the austenitizing temperature for recrystallization to refine the coarse austenite grains in the original forged state.

[0088] S18: Remove from the air-cooler and put into the furnace when the roller body is cooled to 400-500℃.

[0089] S19: Cool the furnace to 300-400℃.

[0090] S110: Hold at 300-400℃; this stage allows the austenite in the core of the forging to fully transform into a ferrite-carbide structure.

[0091] S111: Heat to 650-670℃ at a rate of less than or equal to 30℃ / h; this stage is a rate-limited heating stage in an effort to reduce the internal and external temperature difference and instantaneous internal stress in large support roll forgings.

[0092] S112: 650-670℃ heat preservation; minimize the internal and external temperature difference and non-simultaneous transformation of the forging during heating transformation, and further reduce stress and deformation in the workpiece.

[0093] S113: Heat to 890-930℃ at a rate of less than or equal to 50℃ / h.

[0094] S114: Hold at 890-930℃, then heat to the austenitizing temperature for recrystallization to refine the coarse austenite grains in the original forged state.

[0095] S115: Remove from the air-cooler and put into the furnace when the roller body is cooled to 400-500℃.

[0096] S116: Furnace cooling to 300-400℃.

[0097] S117: Hold at 300-400℃; this stage allows the austenite in the core of the forging to fully transform into a ferrite-carbide structure.

[0098] S118: Heat to 650-670℃ at a rate of less than or equal to 30℃ / h.

[0099] S119: 650-670℃ heat preservation; minimize the internal and external temperature difference and non-simultaneous transformation of the forging during heating transformation, and further reduce stress and deformation in the workpiece.

[0100] S120: Heat to 780-810℃ at a rate of less than or equal to 50℃ / h.

[0101] S121: Hold at 780-810℃; This stage is spheroidizing annealing. The temperature is maintained near Ac1, which allows some of the (Fe,Cr)3C type carbides to dissolve, and the remaining undissolved carbides to aggregate and spheroidize. After cooling, the fine spheroids are evenly distributed to obtain a granular pearlite (spheroidized body) structure with good plasticity and toughness.

[0102] S122: Cool the furnace to a furnace temperature of 300-400℃.

[0103] S123: Heat treatment at 300-400℃; this stage allows the austenite in the core of the forging to fully transform into a ferrite-carbide structure.

[0104] S124: Increase the temperature to 640-660℃ at a rate of 30℃ / h or less.

[0105] S125: Maintained at 640-660℃; also considers hydrogen expansion, effectively preventing white spots and hydrogen embrittlement, further reducing forging stress, and facilitating machining.

[0106] S126: Cool to 400℃ at a rate of less than or equal to 20℃ / h; minimize residual stress in the forging during the cooling process.

[0107] S127: Cool to 150℃ at a rate of less than or equal to 10℃ / h; below 400℃, since the steel has entered a range of greater cold hardening and brittleness, a slower cooling rate is adopted to avoid cracking and reduce instantaneous stress.

[0108] like Figure 13 As shown in the post-forging heat treatment curve, the internal structure of the thick plate support roll after post-forging heat treatment is spheroidized pearlite.

[0109] In the above-mentioned S3, when the thick plate support roller undergoes differential temperature heat treatment, only the surface layer is austenitized, while the core region is equivalent to high-temperature tempering in this process. Therefore, the microstructure and performance of the core of the support roller still mainly depend on the quenching and tempering heat treatment.

[0110] Differential temperature heat treatment involves placing the support roller body in a specialized differential temperature furnace and rapidly heating the roller body surface using high-speed burners. This creates a temperature difference between the inside and outside of the roller body, resulting in a certain depth of austenite layer on the surface while the core remains below the phase transformation point. This is followed by quenching. Differential temperature heat treatment is a crucial process that determines the microstructure, hardness distribution, stress distribution, and performance of the support roller's working layer. The specific process of differential temperature heat treatment in this invention is as follows: Figure 14 As shown in the differential temperature heat treatment curve, the differential temperature heat treatment process specifically includes the following sub-steps:

[0111] S31. The support roller needs to be preheated before differential heating. The preheating temperature is 500-600℃. This allows the entire roller body cross section to enter a plastic state so that it can withstand the subsequent intense heating and reduce the thermal stress caused by heating.

[0112] S32. Transfer the support roller into the furnace, heat only the roller body, and air-cool the roller neck. Use maximum power to rapidly raise the furnace temperature to 1000-1050℃.

[0113] S33. Maintain a temperature of 1000-1050℃ and use strong radiation and convection heat transfer to rapidly heat the surface of the support roller until the roller surface temperature reaches the predetermined quenching temperature. This completes the first stage of heating.

[0114] S34. Adjust the furnace temperature to 950-1000℃ and maintain it; the heat from the roller surface is transferred to the interior by thermal conduction to obtain the required austenitization layer depth, so that the required hardened layer and a sufficiently smooth transition layer distribution are obtained after quenching, thus completing the heating stage II.

[0115] S35, roller body spray cooling, the cooling intensity can be flexibly adjusted by adjusting the air pressure and water pressure.

[0116] S36. After spray quenching, immediately transfer to a tempering furnace and maintain at a low temperature of 250-300℃ for a period of time to make the internal and external temperatures tend to be balanced, and allow the residual austenite to continue to transform.

[0117] S37. Heat to the tempering temperature of 450-550℃ at a rate of 30℃ / h or less. This stage is a rate-limited heating process to minimize the internal and external temperature difference and instantaneous internal stress in large support roll forgings.

[0118] S38, 450-550℃, to eliminate quenching stress and meet the hardness requirements of the support roller.

[0119] S39. Cool the forging to 400℃ at a rate of 20℃ / h or less; minimize residual stress in the forging during the cooling process.

[0120] S310 should be cooled to 150℃ at a rate of 10℃ / h or less; steel below 400℃ has entered a range of greater cold hardening and brittleness, so a slower cooling rate should be adopted to avoid cracking and reduce instantaneous stress.

[0121] It should be noted that the large support roll forgings involved in this invention refer to thick plate support rolls.

[0122] It should be emphasized that the research and determination process of the quenching and tempering heat treatment parameters in step 2 above is as follows:

[0123] The thick plate support rolls with a spheroidized pearlite microstructure after S1 forging and heat treatment were heated to different quenching temperatures and held for different times (see specific heat treatment curves). Figure 2 ), specifically as Figure 2 As shown, for the surface of the heavy plate support roll: quenching was performed, and the quenching hardness and microstructure were tested; for the interior of the heavy plate support roll: rate-limited cooling + high-temperature tempering was performed, and the impact toughness and microstructure were tested. See the research results for [link to research]. Figures 3 to 8 Specifically:

[0124] (1) The hardness of the quenched part increases with increasing temperature; when the quenching temperature is ≥910℃, the hardness tends to stabilize. (2) The carbide content gradually decreases with increasing quenching temperature; when the quenching temperature is ≥870℃, the amount of carbide decreases significantly with increasing quenching temperature, and when the quenching temperature is ≥930℃, all carbides dissolve. (3) The microstructure of the core after tempering: granular pearlite when the quenching temperature is <870℃; lamellar pearlite when the quenching temperature is >920℃. (4) The impact toughness of the core after tempering decreases significantly with increasing quenching temperature. The impact value at 870℃ is more than twice that at 930℃, and the values ​​are 60J at 870℃ and 13J at 930℃.

[0125] To ensure the mechanical properties of the roll neck, a quenching temperature ≥910℃ is preferable; while to improve the impact toughness of the roll body, a quenching temperature ≤870℃ is preferable. In order to balance the mechanical properties of the roll neck and the toughness of the roll body, this invention designs the above-mentioned quenching temperature and holding time parameters during the tempering and high-temperature heating process, so as to improve the impact toughness of the roll body while ensuring the mechanical properties of the roll neck.

[0126] It should also be emphasized that the effective section for setting the tempering and heating parameters is the diameter of the large neck root of the thick plate support roll, rather than the roll body diameter. This ensures that the roll neck achieves the purpose of tempering and guarantees mechanical properties, and also keeps the roll body within the temperature range where "granular pearlite is easily formed" during the high-temperature tempering and heating process.

[0127] Example 1

[0128] This embodiment provides a roller body diameter made of Cr3 material. Production trials were conducted on the wide and thick plate support roll forgings (see specifications and dimensions). Figure 9 ).

[0129] The heat treatment process for this thick plate support roller includes:

[0130] S1. Perform heat treatment on the forging of the thick plate support roller;

[0131] S2. The support rolls after forging and heat treatment are subjected to quenching and tempering heat treatment; the quenching and tempering heat treatment process includes the following sub-steps:

[0132] S21: Hold at 260℃ for 18 hours;

[0133] S22: Heat to 670℃ at a rate of 25℃ / h;

[0134] S23: Keep warm at 670℃ for 45 hours;

[0135] S24: Heat to 920℃ at a rate of 45℃ / h;

[0136] S25: Keep warm at 920℃ for 40 hours;

[0137] S26. After high-temperature heating and quenching, tempering is performed at 580℃ to complete the heat treatment.

[0138] S3. Perform differential temperature heat treatment.

[0139] After the tempering heat treatment is completed in step S2, the internal and external microstructure and properties of the support roll are dissected and tested. The specific process is as follows: the temperature of five locations is recorded: T1 on the surface of the roll body, T2 near the center of the roll body, T3 inside the roll body, T4 on the surface of the large roll neck root, and T5 at the center of the large roll neck root.

[0140] Target temperatures at five locations: ≥910℃ at the roll neck (T4 / T5), and ≤870℃ at the roll body (T2 / T3). The high-temperature heating temperature and holding time during the tempering heat treatment process were adjusted. Numerical simulation of the heat treatment was performed to calculate the temperature field at various locations on the thick plate support roll. The results are shown below. Figure 10 As shown.

[0141] Based on the temperature field calculation of the tempering and heating process of the support roller test piece, the process for the tempering and heating section is formulated, and the steps are as follows:

[0142] After the quenching and tempering heat treatment was completed, holes were drilled at the neck end and the central axis of the test piece, and performance test bars were inserted to test the microstructure and mechanical properties of the roll surface and roll body. The results are as follows:

[0143] (1) Microstructure

[0144] Figure 11 , 12 These are the microstructures of the roll neck surface and the roll body, respectively. Figure 11 In the middle, the metallographic structure of the roll neck surface is tempered sorbite. Figure 12 In the middle, the metallographic structure of the roller body is mainly composed of granular pearlite.

[0145] (2) Mechanical properties

[0146] Table 2 Mechanical Properties of Rolls

[0147]

[0148] Generally, the mechanical properties required for the surface of the neck of a heavy plate support roll up to a certain depth are: tensile strength ≥ 760 MPa and yield strength ≥ 450 MPa. As can be seen from Table 2, the mechanical properties of the core of the large roll neck and the surface of the roll of the test piece fully meet the requirements for heavy plate support rolls; the impact energy of the roll body is 54 J, which is nearly 3 times higher than the toughness of the core of the accident roll (13 J).

[0149] Test results show that the heat treatment of the wide and thick plate support rolls is carried out with the diameter of the large roll neck root as the effective section for setting the quenching and heating parameters. This not only ensures the mechanical properties of the roll neck, but also makes the core of the support roll have better impact toughness, thereby improving the support roll's resistance to accidents.

[0150] Currently, for wide and thick plate support rollers with a roller body diameter ≥ 2m, the above-mentioned quenching and tempering heat treatment process ensures stable quality.

[0151] Example 2

[0152] This invention provides a heat treatment method for improving the internal toughness of a support roll body for thick plates, comprising the following steps:

[0153] S1. Perform heat treatment on the forging of the thick plate support roller;

[0154] S11: 610℃ for material preparation and heat preservation to eliminate forging stress.

[0155] S12: Cool the furnace to 320℃.

[0156] S13: Hold at 320℃; This stage allows the core of the forging to fully transform from austenite to ferrite-carbide structure, which is beneficial for adjusting and refining the grain structure of the steel through subsequent phase transformation recrystallization.

[0157] S14: Heat to 655°C at a rate of 28°C / h; this stage is a rate-limited heating stage in an effort to reduce the internal and external temperature difference and instantaneous internal stress in large support roll forgings.

[0158] S15: 655℃ heat preservation; minimize the internal and external temperature difference and non-simultaneous transformation of the forging during heating transformation, and further reduce stress and deformation in the workpiece.

[0159] S16: Heat to 930℃ at a rate of 48℃ / h.

[0160] S17: Hold at 930℃ and heat to the austenitizing temperature for recrystallization to refine the coarse austenite grains in the original forged state.

[0161] S18: Remove from the air-cooler and put into the furnace when the roller body is cooled to 410℃.

[0162] S19: Cool the furnace to 340℃.

[0163] S110: Hold at 340℃; this stage allows the austenite in the core of the forging to fully transform into a ferrite-carbide structure.

[0164] S111: Heating to 655°C at a rate of 28°C / h; this stage is a rate-limited heating process in an effort to reduce the internal and external temperature difference and instantaneous internal stress in large support roll forgings.

[0165] S112: 655℃ heat preservation; minimize the internal and external temperature difference and non-simultaneous transformation of the forging during heating transformation, and further reduce stress and deformation in the workpiece.

[0166] S113: Heat to 900℃ at a rate of 48℃ / h.

[0167] S114: Hold at 900℃, then heat to the austenitizing temperature for recrystallization to refine the coarse austenite grains in the original forged state.

[0168] S115: Remove from the air-cooler and put into the furnace when the roller body is cooled to 410℃.

[0169] S116: Furnace cooling to 320℃.

[0170] S117: Hold at 320℃; this stage allows the austenite in the core of the forging to fully transform into a ferrite-carbide structure.

[0171] S118: Heat to 655℃ at a rate of 28℃ / h.

[0172] S119: 655℃ heat preservation; minimize the internal and external temperature difference and non-simultaneous transformation of the forging during heating transformation, and further reduce stress and deformation in the workpiece.

[0173] S120: Heat to 790℃ at a rate of 48℃ / h.

[0174] S121: Hold at 790℃; This stage is spheroidizing annealing. The temperature is maintained near Ac1, which allows some of the (Fe,Cr)3C type carbides to dissolve, and the remaining undissolved carbides to aggregate and spheroidize. After cooling, the fine spheroids are evenly distributed to obtain a granular pearlite (spheroidized body) structure with good plasticity and toughness.

[0175] S122: The furnace is cooled to a furnace temperature of 310℃.

[0176] S123: Hold at 310℃; this stage allows the austenite in the core of the forging to fully transform into a ferrite-carbide structure.

[0177] S124: Increase the temperature to 640℃ at a rate of 28℃ / h.

[0178] S125: Holds at 640℃; also absorbs hydrogen, effectively prevents white spots and hydrogen embrittlement, further reduces forging stress, and facilitates machining.

[0179] S126: Cool to 400℃ at a rate of 18℃ / h; minimize residual stress in the forging during the cooling process.

[0180] S127: Cool to 150℃ at a rate of 9℃ / h; below 400℃, because the steel has entered a range of greater cold hardening and brittleness, a slower cooling rate is adopted to avoid cracking and reduce instantaneous stress.

[0181] S2. The support rolls after forging and heat treatment are subjected to quenching and tempering heat treatment; the quenching and tempering heat treatment process includes the following sub-steps:

[0182] S21. The forged and heat-treated wide and thick plate support rolls are kept at 255℃ for the first time for 20 hours.

[0183] S22. After the first heat preservation, the temperature of the wide and thick plate support roller is increased to 655℃ at a speed of 28℃ / h.

[0184] S23. The thick plate support roller is subjected to a second heat preservation at 655℃ for 20 hours.

[0185] S24. After the second heat preservation, the temperature of the wide and thick plate support roller is increased to 910℃ at a rate of 48℃ / h.

[0186] S25. The thick plate support roller is subjected to a third heat preservation at 910℃.

[0187] S26, 910℃ heat preservation, holding time 45h;

[0188] S27. After the third heat treatment, quenching is performed, followed by tempering at 570℃ to complete the heat treatment.

[0189] Step 3: Perform differential temperature heat treatment on the support roller after tempering and heat treatment to obtain the wide and thick plate support roller product.

[0190] S31. The support roller needs to be preheated before differential heating. The preheating temperature is 510℃. This allows the entire roller body cross section to enter a plastic state so that it can withstand the subsequent intense heating and reduce the thermal stress caused by heating.

[0191] S32. Transfer the support roller into the furnace, heat only the roller body, and air-cool the roller neck. Use maximum power to rapidly raise the furnace temperature to 1040℃.

[0192] S33. Maintain at 1040℃, using intense radiation and convection heat transfer to rapidly heat the surface of the support roller until the roller surface temperature reaches the predetermined quenching temperature. This completes heating stage I.

[0193] S34. Adjust the furnace temperature to 990℃ and maintain it; the heat from the roller surface is transferred to the interior by thermal conduction to obtain the required austenitization layer depth, so that the required hardened layer and a sufficiently smooth transition layer distribution are obtained after quenching, thus completing the heating stage II.

[0194] S35, roller body spray cooling, the cooling intensity can be flexibly adjusted by adjusting the air pressure and water pressure.

[0195] S36. After spray quenching, immediately transfer to a tempering furnace and maintain at a low temperature of 260℃ for a period of time to make the internal and external temperatures tend to be balanced, and allow the residual austenite to continue to transform.

[0196] S37. Heat to the tempering temperature of 520°C at a rate of 28°C / h. This stage is a rate-limited heating process to minimize the internal and external temperature difference and instantaneous internal stress in large support roll forgings.

[0197] S38, 520℃ is maintained to eliminate quenching stress and meet the hardness requirements of the support roller.

[0198] S39. Cool the forging to 400℃ at a rate of 18℃ / h; minimize residual stress in the forging during the cooling process.

[0199] S310 is cooled to 150℃ at a rate of 8℃ / h; steel below 400℃ has entered a range of greater cold hardening and brittleness, so a slower cooling rate is adopted to avoid cracking and reduce instantaneous stress.

[0200] In this embodiment, the core of the support roller is treated to have a granular (or spheroidized) pearlite structure, which improves the core toughness of the support roller for thick plates, prevents crack propagation, and improves the support roller's resistance to accidents.

[0201] Example 3

[0202] This invention provides a heat treatment method for improving the internal toughness of a support roll body for thick plates, comprising the following steps:

[0203] S1. Perform heat treatment on the forging of the thick plate support roller;

[0204] S11: Waiting and holding at 630℃ to eliminate forging stress.

[0205] S12: Cool the furnace to 350℃.

[0206] S13: Hold at 350℃; This stage allows the core of the forging to fully transform from austenite to ferrite-carbide structure, which is beneficial for adjusting and refining the grain structure of the steel through subsequent phase transformation recrystallization.

[0207] S14: Heat to 660°C at a rate of 25°C / h; this stage is a rate-limited heating stage in an effort to reduce the internal and external temperature difference and instantaneous internal stress in large support roll forgings.

[0208] S15: 660℃ heat preservation; minimize the internal and external temperature difference and non-simultaneous transformation of the forging during heating transformation, and further reduce stress and deformation in the workpiece.

[0209] S16: Heat to 940℃ at a rate of 45℃ / h.

[0210] S17: Hold at 940℃, then heat to the austenitizing temperature for recrystallization to refine the coarse austenite grains in the original forged state.

[0211] S18: Remove from the air-cooler and put into the furnace when the roller body is cooled to 450℃.

[0212] S19: Cool the furnace to 350℃.

[0213] S110: Hold at 350℃; this stage allows the austenite in the core of the forging to fully transform into a ferrite-carbide structure.

[0214] S111: Heating to 660°C at a rate of 25°C / h; this stage is a rate-limited heating stage in an effort to reduce the internal and external temperature difference and instantaneous internal stress in large support roll forgings.

[0215] S112: 660℃ heat preservation; minimize the internal and external temperature difference and non-simultaneous transformation of the forging during heating transformation, and further reduce stress and deformation in the workpiece.

[0216] S113: Heat to 910℃ at a rate of 45℃ / h.

[0217] S114: Hold at 910℃, then heat to the austenitizing temperature for recrystallization to refine the coarse austenite grains in the original forged state.

[0218] S115: Remove from the air-cooler and put into the furnace when the roller body is cooled to 450℃.

[0219] S116: Furnace cooling to 350℃.

[0220] S117: Hold at 350℃; this stage allows the austenite in the core of the forging to fully transform into a ferrite-carbide structure.

[0221] S118: Heat to 660℃ at a rate of 25℃ / h.

[0222] S119: 660℃ heat preservation; minimize the internal and external temperature difference and non-simultaneous transformation of the forging during heating transformation, and further reduce stress and deformation in the workpiece.

[0223] S120: Heat to 800℃ at a rate of 45℃ / h.

[0224] S121: Hold at 800℃; This stage is spheroidizing annealing. The temperature is maintained near Ac1, which allows some of the (Fe,Cr)3C type carbides to dissolve, and the remaining undissolved carbides to aggregate and spheroidize. After cooling, the fine spheroids are evenly distributed to obtain a granular pearlite (spheroidized body) structure with good plasticity and toughness.

[0225] S122: The furnace is cooled to a furnace temperature of 360℃.

[0226] S123: 360℃ heat preservation; this stage allows the austenite in the core of the forging to fully transform into a ferrite-carbide structure.

[0227] S124: Increase the temperature to 655℃ at a rate of 25℃ / h.

[0228] S125: Holds at 655℃; also considers hydrogen expansion, effectively preventing white spots and hydrogen embrittlement, further reducing forging stress, and facilitating machining.

[0229] S126: Cool to 400℃ at a rate of 15℃ / h; minimize residual stress in the forging during the cooling process.

[0230] S127: Cool down to 150℃ at a rate of 7℃ / h; below 400℃, since the steel has entered a range of high cold hardness and brittleness, a slower cooling rate is adopted to avoid cracking and reduce instantaneous stress.

[0231] S2. The support rolls after forging and heat treatment are subjected to quenching and tempering heat treatment; the quenching and tempering heat treatment process includes the following sub-steps:

[0232] S21. The forged and heat-treated wide and thick plate support rolls are kept at 280℃ for the first time for 18 hours.

[0233] S22. After the first heat preservation, heat the wide and thick plate support roller to 660℃ at a rate of 25℃ / h.

[0234] S23. The thick plate support roller is subjected to a second heat preservation at 660℃ for 30 hours.

[0235] S24. After the second heat preservation, the temperature of the wide and thick plate support roller is increased to 930℃ at a rate of 45℃ / h.

[0236] S25. The thick plate support roller is subjected to a third heat preservation at 930℃.

[0237] S26, 930℃ heat preservation, holding time 38h;

[0238] S27. After the third heat treatment, quenching is performed, followed by tempering at 610℃ to complete the heat treatment.

[0239] Step 3: Perform differential temperature heat treatment on the support roller after tempering and heat treatment to obtain the wide and thick plate support roller product.

[0240] S31. The support roller needs to be preheated before differential heating. The preheating temperature is 530℃. This allows the entire roller body cross section to enter a plastic state so that it can withstand the subsequent intense heating and reduce the thermal stress caused by heating.

[0241] S32. Transfer the support roller into the furnace, heat only the roller body, and air-cool the roller neck. Use maximum power to rapidly raise the furnace temperature to 1030℃.

[0242] S33. Maintain at 1030℃, using strong radiation and convection heat transfer to rapidly heat the surface of the support roller until the roller surface temperature reaches the predetermined quenching temperature. This completes heating stage I.

[0243] S34. Adjust the furnace temperature to 980℃ and maintain it; the heat from the roller surface is transferred to the interior by thermal conduction to obtain the required austenitization layer depth, so that the required hardened layer and a sufficiently smooth transition layer distribution are obtained after quenching, thus completing the heating stage II.

[0244] S35, roller body spray cooling, the cooling intensity can be flexibly adjusted by adjusting the air pressure and water pressure.

[0245] S36. After spray quenching, immediately transfer to a tempering furnace and maintain at a low temperature of 280℃ for a period of time to make the internal and external temperatures tend to be balanced, and allow the residual austenite to continue to transform.

[0246] S37. Heat to the tempering temperature of 510°C at a rate of 25°C / h. This stage is a rate-limited heating process to minimize the internal and external temperature difference and instantaneous internal stress in large support roll forgings.

[0247] S38, 510℃ is maintained to eliminate quenching stress and meet the hardness requirements of the support roller.

[0248] S39. Cool the forging to 400℃ at a rate of 15℃ / h; minimize residual stress in the forging during the cooling process.

[0249] S310 is cooled to 150℃ at a rate of 7℃ / h; steel below 400℃ has entered a range of greater cold hardening and brittleness, so a slower cooling rate is adopted to avoid cracking and reduce instantaneous stress.

[0250] In this embodiment, the core of the support roller is treated to have a granular (or spheroidized) pearlite structure, which improves the core toughness of the support roller for thick plates, prevents crack propagation, and improves the support roller's resistance to accidents.

[0251] Example 4

[0252] This invention provides a heat treatment method for improving the internal toughness of a support roll body for thick plates, comprising the following steps:

[0253] S1. Perform heat treatment on the forging of the thick plate support roller;

[0254] S11: Waiting and holding at 645℃ to eliminate forging stress.

[0255] S12: Cool the furnace to 380℃.

[0256] S13: Hold at 380℃; This stage allows the core of the forging to fully transform from austenite to ferrite-carbide structure, which is beneficial for adjusting and refining the grain structure of the steel through subsequent phase transformation recrystallization.

[0257] S14: Heating to 665°C at a rate of 24°C / h; this stage is a rate-limited heating stage in an effort to reduce the internal and external temperature difference and instantaneous internal stress in large support roll forgings.

[0258] S15: 665℃ heat preservation; minimize the internal and external temperature difference and non-simultaneous transformation of the forging during heating transformation, and further reduce stress and deformation in the workpiece.

[0259] S16: Heat to 960℃ at a rate of 43℃ / h.

[0260] S17: Hold at 960℃, then heat to the austenitizing temperature for recrystallization to refine the coarse austenite grains in the original forged state.

[0261] S18: Remove from the air-cooler and put into the furnace when the roller body is cooled to 500℃.

[0262] S19: Cool the furnace to 400℃.

[0263] S110: Hold at 400℃; this stage allows the austenite in the core of the forging to fully transform into a ferrite-carbide structure.

[0264] S111: Heating to 670°C at a rate of 28°C / h; this stage is a rate-limited heating stage in an effort to reduce the internal and external temperature difference and instantaneous internal stress in large support roll forgings.

[0265] S112: 670℃ heat preservation; minimize the internal and external temperature difference and non-simultaneous transformation of the forging during heating transformation, and further reduce stress and deformation in the workpiece.

[0266] S113: Heat to 930℃ at a rate of 44℃ / h.

[0267] S114: Hold at 930℃, then heat to the austenitizing temperature for recrystallization to refine the coarse austenite grains in the original forged state.

[0268] S115: Remove from the air-cooler and put into the furnace when the roller body is cooled to 500℃.

[0269] S116: Furnace cooling to 400℃.

[0270] S117: Hold at 400℃; this stage allows the austenite in the core of the forging to fully transform into a ferrite-carbide structure.

[0271] S118: Heat to 670℃ at a rate of 24℃ / h.

[0272] S119: 670℃ heat preservation; minimize the internal and external temperature difference and non-simultaneous transformation of the forging during heating transformation, and further reduce stress and deformation in the workpiece.

[0273] S120: Heat to 810℃ at a rate of 45℃ / h.

[0274] S121: Hold at 810℃; This stage is spheroidizing annealing. The temperature is maintained near Ac1, which allows some of the (Fe,Cr)3C type carbides to dissolve, and the remaining undissolved carbides to aggregate and spheroidize. After cooling, the fine spheroids are evenly distributed to obtain a granular pearlite (spheroidized body) structure with good plasticity and toughness.

[0275] S122: The furnace is cooled to a temperature of 400℃.

[0276] S123: Hold at 400℃; this stage allows the austenite in the core of the forging to fully transform into a ferrite-carbide structure.

[0277] S124: Increase the temperature to 655℃ at a rate of 27℃ / h.

[0278] S125: Holds at 655℃; also considers hydrogen expansion, effectively preventing white spots and hydrogen embrittlement, further reducing forging stress, and facilitating machining.

[0279] S126: Cool to 400℃ at a rate of 15℃ / h; minimize residual stress in the forging during the cooling process.

[0280] S127: Cool to 150℃ at a rate of 6℃ / h; below 400℃, because the steel has entered a range of greater cold hardening and brittleness, a slower cooling rate is adopted to avoid cracking and reduce instantaneous stress.

[0281] S2. The support rolls after forging and heat treatment are subjected to quenching and tempering heat treatment; the quenching and tempering heat treatment process includes the following sub-steps:

[0282] S21. The forged and heat-treated wide and thick plate support rolls are kept at 300℃ for the first time for 28 hours.

[0283] S22. After the first heat preservation, the temperature of the wide and thick plate support roller is increased to 670℃ at a rate of 27℃ / h.

[0284] S23. The thick plate support roller is subjected to a second heat preservation at 670℃ for 50 hours.

[0285] S24. After the second heat preservation, the temperature of the wide and thick plate support roller is increased to 940℃ at a rate of 45℃ / h.

[0286] S25. The thick plate support roller is subjected to a third heat preservation at 940℃.

[0287] S26. After the third heat treatment, quenching is performed, followed by tempering at 650℃ to complete the heat treatment.

[0288] Step 3: Perform differential temperature heat treatment on the support roller after tempering and heat treatment to obtain the wide and thick plate support roller product.

[0289] S31. The support roller needs to be preheated before differential heating. The preheating temperature is 600℃. This allows the entire roller body cross section to enter a plastic state so that it can withstand the subsequent intense heating and reduce the thermal stress caused by heating.

[0290] S32. Transfer the support roller into the furnace, heat only the roller body, and air-cool the roller neck. Use maximum power to rapidly raise the furnace temperature to 1050℃.

[0291] S33. Maintain at 1050℃, using intense radiation and convection heat transfer to rapidly heat the surface of the support roller until the roller surface temperature reaches the predetermined quenching temperature. This completes heating stage I.

[0292] S34. Adjust the furnace temperature to 1000℃ and maintain it; the heat from the roller surface is transferred to the interior by thermal conduction to obtain the required austenitization layer depth, so that the required hardened layer and a sufficiently smooth transition layer distribution are obtained after quenching, thus completing the heating stage II.

[0293] S35, roller body spray cooling, the cooling intensity can be flexibly adjusted by adjusting the air pressure and water pressure.

[0294] S36. After spray quenching, immediately transfer to a tempering furnace and maintain at a low temperature of 300℃ for a period of time to make the internal and external temperatures tend to be balanced, and allow the residual austenite to continue to transform.

[0295] S37. Heat to the tempering temperature of 550°C at a rate of 24°C / h. This stage is a rate-limited heating process to minimize the internal and external temperature difference and instantaneous internal stress in large support roll forgings.

[0296] S38, 550℃, to eliminate quenching stress and meet the hardness requirements of the support roller.

[0297] S39. Cool the forging to 400℃ at a rate of 15℃ / h; minimize residual stress in the forging during the cooling process.

[0298] S310 is cooled to 150℃ at a rate of 6℃ / h; steel below 400℃ has entered a range of greater cold hardening and brittleness, so a slower cooling rate is adopted to avoid cracking and reduce instantaneous stress.

[0299] In this embodiment, the core of the support roller is treated to have a granular (or spheroidized) pearlite structure, which improves the core toughness of the support roller for thick plates, prevents crack propagation, and improves the support roller's resistance to accidents.

[0300] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A heat treatment method for improving the internal toughness of a support roll body for a thick plate, characterized in that, The length of the support roller of the thick plate is greater than 3m, the diameter of the roller body is greater than 2m, and the weight of the support roller is greater than 100t. The diameter of the root of the large roller neck of the support roller of the thick plate is used as the effective section for formulating the quenching and heating parameters, so that the body of the roller body is still in the temperature range that is easy to form granular pearlite when the quenching and heating is carried out at high temperature. Includes the following steps: S1. Perform heat treatment on the forging of the thick plate support roller; The post-forging heat treatment includes two normalizing processes, spheroidizing annealing, and high-temperature tempering. The post-forging heat treatment includes the following sub-steps: S11: 600-650℃ for material preparation and heat preservation to eliminate forging stress; S12: Cool the furnace to 300-400℃; S13: Insulation temperature 300-400℃; S14: Heat to 650-670℃ at a rate of less than or equal to 30℃ / h; S15: Insulation temperature 650-670℃; S16: Heat to 920-960℃ at a rate of less than or equal to 50℃ / h; S17: Maintain at 920-960℃; S18: Remove from the air and air cool. When the roller body is cooled to 400-500℃, put it into the furnace. S19: Cool the furnace to 300-400℃; S110: Insulation temperature 300-400℃; S111: Heat to 650-670℃ at a rate of less than or equal to 30℃ / h; S112: Insulation temperature 650-670℃; S113: Heat to 890-930℃ at a rate of less than or equal to 50℃ / h; S114: Maintain at 890-930℃; S115: Remove from the air and air cool. When the roller body is cooled to 400-500℃, put it into the furnace. S116: Furnace cooling to 300-400℃; S117: Insulation temperature 300-400℃; S118: Heat to 650-670℃ at a rate of less than or equal to 30℃ / h; S119: Insulation temperature 650-670℃; S120: Heat to 780-810℃ at a rate of less than or equal to 50℃ / h; S121: Insulation temperature 780-810℃; S122: Cool the furnace to a furnace temperature of 300-400℃; S123: Insulation temperature 300-400℃; S124: Increase the temperature to 640-660℃ at a rate of 30℃ / h or less; S125: Maintain at 640-660℃; S126: Cool to 400℃ at a rate of less than or equal to 20℃ / h; S127: Cool to 150℃ at a rate of less than or equal to 10℃ / h; S2. The support rolls after forging and heat treatment are subjected to quenching and tempering heat treatment. The quenching and tempering heat treatment process includes the following sub-steps: S21. The forged and heat-treated wide and thick plate support rolls are subjected to a first heat treatment at 250-280℃; the first heat treatment time is 15-30 h; S22. After the first heat preservation, heat the wide and thick plate support roller to 670℃ at a rate of ≤30℃ / h. S23. The support rollers for the thick plate are subjected to a second heat preservation at 670℃; the second heat preservation time is 10-50 h. S24. After the second heat preservation, the support rollers for wide and thick plates are heated to 930-940℃ at a rate of ≤50℃ / h. S25. The support rollers of the thick plate are subjected to a third heat preservation at 930-940℃; the third heat preservation time is 20-50 hours. S26. After the third heat treatment, quenching is performed, followed by tempering to complete the heat treatment. In step S26, the tempering temperature is 610-650℃; S3. The support roller after heat treatment is subjected to differential temperature heat treatment to obtain the wide and thick plate support roller product; the internal structure of the wide and thick plate support roller after treatment is granular or spheroidized pearlite structure.

2. The heat treatment method for improving the internal toughness of the support roll body of a thick plate according to claim 1, characterized in that, In S21, the first heat preservation time is 18-30 h.

3. The heat treatment method for improving the internal toughness of the support roll body of a thick plate according to claim 1, characterized in that, In S23, the second heat preservation time is 30-50 h.

4. The heat treatment method for improving the internal toughness of the support roll body of a thick plate according to claim 1, characterized in that, In S24, the temperature is raised to 940°C after the second heat preservation.

5. The heat treatment method for improving the internal toughness of the support roll body of a thick plate according to claim 1, characterized in that, In S25, the third heat preservation time is 38-50 hours.

6. The heat treatment method for improving the internal toughness of the support roll body of a thick plate according to any one of claims 1 to 5, characterized in that, In step S3, the differential temperature heat treatment process includes the following sub-steps: S31. The support roller needs to be preheated before differential temperature heating. The preheating temperature is 500-600℃. S32. Transfer the support roller into the furnace, heat only the roller body and air cool the roller neck, and use the maximum power to quickly raise the furnace temperature to 1000-1050℃. S33. Maintain at 1000-1050℃ until the roller surface temperature reaches the predetermined quenching temperature, thus completing heating stage I; S34. Adjust the furnace temperature to 950-1000℃ and maintain it; complete heating stage II; S35, roller body spray cooling, the cooling intensity is adjusted by regulating the air pressure and water pressure; S36. After spray quenching, transfer to a tempering furnace and maintain at 250-300℃ for a period of time. S37. Heat to the tempering temperature of 450-550℃ at a rate of less than or equal to 30℃ / h; S38. Maintain at 450-550℃ for a period of time; S39. Cool down to 400℃ at a rate of less than or equal to 20℃ / h.

7. The heat treatment method for improving the internal toughness of the support roll body of a thick plate according to claim 6, characterized in that, S3 also includes S310, cooling to 150°C at a rate of less than or equal to 10°C / h to complete the differential temperature heat treatment.

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