Repair treatment method after hardening and tempering of supporting roller

Abstract

The invention discloses a method for repairing a quenched and tempered supporting roller, belongs to the technical field of supporting roller preparation, and solves the problems of long repairing process time and low production efficiency of the existing quenched and tempered supporting roller with unqualified hardness. The repair treatment method after hardening and tempering comprises the steps of preheating, differential temperature heating-quenching and tempering. The preheating comprises the following steps of: loading the supporting roller forge piece into a furnace at 280-320 DEG C for heating and heat preservation; quickly heating to T3, and preserving heat, wherein T3 is 575-630 DEG C; then, the furnace temperature is adjusted to 480-530 DEG C, and heat preservation continues; the differential temperature heating-quenching comprises the following steps: transferring the supporting roller into a differential temperature furnace, only heating a roller body, rapidly raising the furnace temperature to 1021-1070 DEG C, and carrying out air cooling on a roller neck; the temperature is kept at 1021-1070 DEG C; the furnace temperature is adjusted to 980-1000 DEG C for heat preservation; and then the roller body is sprayed and cooled. The surface hardness of the roller body and the hardness of the roller neck of the supporting roller obtained through the repairing method meet the technical requirements, and the residual stress is small.

Description

Technical Field

[0001] This invention relates to the field of support roller manufacturing technology, and in particular to a method for reworking support rollers after tempering. Background Technology

[0002] Support rolls are generally used to support intermediate rolls or work rolls. During the rolling process, support rolls are subjected to significant bending stress, thus requiring the roll neck to possess certain strength and toughness. The roll body endures prolonged friction and wear, contact stress, and fatigue caused by rapid cooling and heating, requiring the working layer of the roll body to have high hardness, wear resistance, and high contact fatigue strength. To meet the differentiated performance requirements of different parts of the support roll, a combination of pre-treatment heat treatment and differential temperature heat treatment is typically used in production. The pre-treatment heat treatment employs overall quenching and tempering to ensure the internal properties of the roll neck and roll body, while the differential temperature heat treatment specifically performs surface quenching on the roll body.

[0003] Hardness is a key technical and acceptance indicator for evaluating the performance of the support roll body and neck. Different users and rolling mills have significantly different requirements for the surface hardness of support rolls. During the support roll manufacturing process, issues such as ineffective tempering furnace air circulation equipment, phase loss in the heating resistor, and intermittent malfunctions in the furnace temperature monitoring system directly affect the accurate control of the furnace temperature, thus impacting the hardness of the support roll and ultimately leading to product defects. Existing processes for reworking support rolls with substandard hardness are time-consuming and costly. Summary of the Invention

[0004] In view of the above, the present invention aims to provide a method for rework of support rollers after tempering, which can at least solve one of the following technical problems: the existing rework process for support rollers with unqualified hardness after tempering is time-consuming, has low production efficiency, and high cost.

[0005] The objective of this invention is mainly achieved through the following technical solutions: This invention provides a method for reworking support rollers after tempering, comprising the following steps: Preheating, differential heating - quenching, tempering; The preheating process includes the following steps: The support roll forging is placed in a furnace at 280~320℃ and heated and held at that temperature; the temperature is rapidly increased to T3 and then held at that temperature, which is 575~630℃; then the furnace temperature is adjusted to 480~530℃ and held at that temperature for a longer period. Differential temperature heating-quenching includes the following steps: The support roller is transferred into the differential temperature furnace, and only the roller body is heated to rapidly raise the furnace temperature to 1021~1070℃, while the roller neck is air-cooled. The temperature is then maintained at 1021~1070℃ until the roller surface temperature reaches the predetermined quenching temperature. The furnace temperature is then adjusted to 980~1000℃ and maintained. Finally, the roller body is spray-cooled.

[0006] Furthermore, the maximum hardness of the neck of the tempered support roll is higher than the technical requirement of 1~6 HSD.

[0007] Furthermore, during the preheating process, after the T3 heat preservation, the internal temperature of the roller body is below 530℃.

[0008] Furthermore, during the preheating process, after the T3 heat preservation, the neck temperature of the roll reaches 575~630℃.

[0009] Furthermore, during the preheating process, the holding time in the 280~320℃ stage is t2, t2=1.2~1.5×D1 / 100, where D1 is the roller diameter in millimeters, and the holding time t2 is in hours.

[0010] Furthermore, during the rapid heating of the furnace to 1021~1070℃, the heating time is controlled to be less than 90 minutes.

[0011] Furthermore, the holding time t5 at 1021~1070℃ ranges from D1 / 10-5 to D1 / 10+5, where D1 is the roller diameter in mm and the holding time t5 is in min.

[0012] Furthermore, the holding time t6 at 980~1000℃ ranges from D1 / 20-5 to D1 / 20+5, where D1 is the roller diameter in mm and the holding time t6 is in min.

[0013] Furthermore, during the roller spray cooling process, the workpiece surface is cooled to 220~240℃, at which point the cooling is complete.

[0014] Furthermore, the components of the support roller, by mass percentage, include: C: 0.38%~0.48%, Si: 0.3%~0.5%, Mn: 0.4%~0.6%, Cr: 2.5%~3.5%, Mo: 0.5%~0.8%, Ni: 0.1%~0.3%, with the balance being Fe and unavoidable impurities; The present invention also provides a support roller, which is prepared by the above method.

[0015] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: In the rework process of the support roller after tempering of the present invention, by precisely controlling the process parameters such as heating rate, holding temperature, holding time, and cooling rate at each stage, the hardness of the support roller after tempering is higher than the technical requirements, which can reduce the hardness of the roller neck while ensuring the quenching process requirements of the roller body, the surface hardness of the roller body and the hardness of the roller neck meet the technical requirements, and the residual stress is small, which meets the technical requirements.

[0016] In the rework process of the support roller after tempering of the present invention, the time is greatly reduced, the cost is reduced, and the production efficiency is improved by precisely controlling each process step and the key process parameters.

[0017] The support roller of this invention achieves the required hardness for both the roller body and the roller neck. The roller body exhibits high surface hardness and strength, while the roller neck possesses high strength and toughness. For example, the surface hardness of the roller body can reach 52 HSD or higher, such as 52-62 HSD; the roller neck hardness is 37-48 HSD. Furthermore, the support roller of this invention exhibits good hardness uniformity between the roller body and the roller neck. For instance, the maximum hardness difference between different parts of the roller body surface of the same workpiece is less than 3 HSD, and the maximum hardness difference between different parts of the roller neck is also less than 3 HSD. The support roller of this invention has low residual stress, for example, less than 450 MPa.

[0018] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of what is particularly pointed out in the written description. Detailed Implementation

[0019] Preferred embodiments of the present invention are described in detail below.

[0020] The present invention provides a support roller, which includes a roller body and a roller neck, wherein the diameter D1 of the roller body is greater than the diameter D2 at the maximum diameter of the roller neck.

[0021] Specifically, the components of the support roller of the present invention, by mass percentage, include: C: 0.38%~0.48%, Si: 0.3%~0.5%, Mn: 0.4%~0.6%, Cr: 2.5%~3.5%, Mo: 0.5%~0.8%, Ni: 0.1%~0.3%, with the balance being Fe and unavoidable impurities.

[0022] The research revealed that determining whether the neck hardness of the support roller meets the technical requirements only requires a hardness test after the tempering heat treatment. If the hardness is qualified, the roller can be transferred to another machining process; if the hardness is unqualified, it needs to be reworked. Existing processes for reworking support rollers with excessively high hardness are time-consuming and costly.

[0023] This invention provides a method for rework of support rollers after tempering, comprising the following steps: preheating, differential temperature heating-quenching, and tempering; The preheating process includes the following steps: Step 1: The support roll forging is subjected to quenching and tempering treatment. After quenching and tempering treatment, the hardness of the roll neck is higher than the technical requirements. Step 2: Place the support roll forging into a furnace at 280~320℃ for heating and heat preservation; Step 3: Rapidly raise the temperature to T3, which is 575~630℃; Step 4: Incubate at T3; Step 5: Adjust the furnace temperature to 480~530℃ and continue to maintain the temperature.

[0024] Differential temperature heating-quenching includes the following steps: Step 6: Transfer the support roller into the differential temperature furnace and heat only the roller body to rapidly raise the furnace temperature to 1021~1070℃, then air cool the roller neck. Step 7: Hold at 1021~1070℃ until the roller surface temperature reaches the predetermined quenching temperature; adjust the furnace temperature to 980~1000℃ and hold. Step 8: Spray cooling of the roller body.

[0025] Tempering includes the following steps: Step 9: After spray cooling, transfer to a tempering furnace, heat to the tempering temperature of 500~565℃, and hold at that temperature; Step 10: Cool down to below 220℃ at a cooling rate of less than 20℃ / h, remove from the furnace, and obtain the support roller.

[0026] Specifically, in step 1 above, the tempering parameters for the quenching and tempering treatment are set as follows: the tempering holding temperature is T1 and the holding time is t1. During the holding of the support roll forging, due to equipment failure, the furnace temperature is too low, resulting in a higher hardness of the roll neck after quenching and tempering treatment.

[0027] Specifically, step 2 above also includes machining the roller body to prepare for spray quenching of the roller body.

[0028] Specifically, in step 2 above, a thermocouple can be applied to the surface of the roller body before loading it into the furnace.

[0029] Specifically, in step 2 above, considering that 250~350℃ is the blue brittle temperature range of steel, and the risk of cracking caused by internal stress is high, it is necessary to reduce the temperature difference between 250~350℃. In order to enable the roll neck to quickly reach the tempering temperature (575~630℃) in the future, it can be kept warm in the furnace at 280~320℃ first.

[0030] Specifically, in step 2 above, considering that the temperature difference between the inside and outside of the workpiece should be ≤50℃ during the heat preservation time, if the heat preservation time is too short, the temperature difference will be too large, which may easily cause blue brittleness; if the heat preservation time is too long, resources will be wasted. Therefore, the heat preservation time is controlled as t2, t2 = (1.2~1.5) × D1 / 100, where D1 is the diameter of the roller body, and the unit of D1 is millimeters (mm). The unit of the heat preservation time t2 is hours (h). For example, t2 is 1.2D1 / 100, 1.25D1 / 100, 1.30D1 / 100, 1.35D1 / 100, 1.4D1 / 100, or 1.5D1 / 100.

[0031] Specifically, in step 3 above, because the heating rate is too slow, the internal temperature of the workpiece rises too much, failing to create a sufficient temperature difference between the inside and outside. Therefore, the heating rate should be controlled at 40~50℃ / h to reach 575~630℃, for example, heating rates of 40℃ / h, 45℃ / h, and 50℃ / h.

[0032] Specifically, the purpose of step 4 above is to further soften the fabric to reduce the hardness of the roll neck and meet the technical requirements, while also preheating the roll body. The holding time in this stage should meet the following conditions: ① The internal temperature of the roll body is below 530℃; ② The roll neck temperature reaches the set furnace temperature (575~630℃) and is maintained for a certain period of time to adjust the roll neck hardness.

[0033] Specifically, the heat preservation temperature T3, heat preservation time t3, the difference d between the maximum value of the roll neck hardness and the upper limit of the technical requirement for hardness, the tempering heat preservation temperature T1 set for the quenching and tempering treatment, and the tempering heat preservation time t1 set for the quenching and tempering treatment in step 4 above conform to the following relationship: If d is 1~2HSD, then T3=T1+8, t3=3t1 / 5±1; it should be noted that t3=3t1 / 5±1 means that the range of t3 is 3t1 / 5-1~3t1 / 5+1; the ± in the following text has a similar meaning; If d is 3HSD, then T3 = T1 + 12, t3 = 3t1 / 5 ± 1; If d is 4HSD, then T3 = T1 + 20, t3 = 5t1 / 8 ± 1; If d is 5~6HSD, then T3=T1+25, t3=5t1 / 8±1.

[0034] The units for T1 and T3 are °C, and the units for t1 and t3 are h.

[0035] Specifically, step 5 above aims to bring the temperature inside and outside the roller body to a uniform level, allowing the entire roller body cross-section to enter a plastic state to withstand subsequent intense and rapid heating, and to reduce the thermal stress caused by heating. Therefore, the holding time t4 should be controlled to be ≥1.5×D1 / 100, where D1 is the roller body diameter in mm, and t4 is in hours.

[0036] Preferably, in step 5 above, the heat preservation time t4 is (1.5~2.0)×D1 / 100.

[0037] Specifically, in step 6 above, if the heating rate is too low, the internal temperature of the roller body will be too high, resulting in excessive residual stress in the workpiece after the final heat treatment. Therefore, the heating time should be controlled to be below 90 minutes, for example, 60 to 90 minutes, such as 60 minutes, 70 minutes, 80 minutes, or 90 minutes.

[0038] Specifically, in step 7 above, the holding time t5 at 1021~1070℃ is D1 / 10±5, and the holding time t6 at 980~1000℃ is D1 / 20±5, where D1 is the roller diameter in mm, the holding time is in min, and the holding time is rounded to the nearest integer.

[0039] Specifically, in step 8 above, the cooling intensity is adjusted by regulating the air pressure and water pressure. When the workpiece surface is cooled to 230±10℃, the cooling is complete. If the surface temperature is too high after cooling, the amount of bainite transformation will be too small; if the surface temperature is too low, quenching cracks are likely to occur.

[0040] Specifically, in step 9 above, if the tempering temperature is too high, the surface hardness of the roll body will be too low; if the tempering temperature is too low, the surface hardness of the roll body will be too high. Therefore, the tempering temperature should be controlled at 500~565℃, for example, 500℃, 520℃, 530℃, 550℃, or 560℃.

[0041] Specifically, in step 9 above, if the heating rate is too high, it exceeds the capacity of the resistance furnace; if the heating rate is too low, resources are wasted. Therefore, the heating rate should be controlled at 40~50℃ / h, for example, 40℃ / h, 42℃ / h, 45℃ / h, 47℃ / h, or 50℃ / h.

[0042] Specifically, in step 10 above, if the cooling rate is too high, it can easily cause excessive residual stress in the workpiece; if it is too low, the process cycle will be too long. Therefore, the cooling rate should be controlled to be below 20℃ / h, preferably 15~20℃ / h, such as 15℃ / h, 18℃ / h, or 20℃ / h, to minimize the residual stress in the forging during the cooling process.

[0043] Compared with the prior art, the rework process of the support roller after tempering in this invention precisely controls the process parameters such as heating rate, holding temperature, holding time, and cooling rate at each stage; for support rollers whose hardness after tempering is higher than the technical requirements, it can reduce the hardness of the roller neck while ensuring the quenching process requirements of the roller body; ultimately ensuring that the surface hardness of the roller body and the hardness of the roller neck meet the technical requirements, and ensuring that the residual stress is small and meets the technical requirements.

[0044] In the rework process of the support roller after tempering of the present invention, the time is greatly reduced, the cost is reduced, and the production efficiency is improved by precisely controlling each process step and the key process parameters.

[0045] The present invention also provides a support roller, which is prepared by the above method.

[0046] The support roller of this invention achieves the required hardness for both the roller body and the roller neck. The roller body exhibits high surface hardness and strength, while the roller neck possesses high strength and toughness. For example, the surface hardness of the roller body can reach 52 HSD or higher, such as 52-62 HSD; the roller neck hardness is 37-48 HSD. Furthermore, the support roller of this invention exhibits good hardness uniformity between the roller body and the roller neck. For instance, the maximum hardness difference between different parts of the roller body surface of the same workpiece is less than 3 HSD, and the maximum hardness difference between different parts of the roller neck is also less than 3 HSD. The support roller of this invention has low residual stress, for example, less than 450 MPa.

[0047] The advantages of precise control of process parameters of the present invention will be demonstrated below with specific embodiments and comparative examples.

[0048] Example 1 This embodiment provides a method for rework of a support roller after tempering. The diameter of the support roller body in this embodiment is 2110mm, and the diameter D2 at the maximum diameter of the roller neck is 1580mm. The hardness requirements are: 37~42HSD for the roller neck and 52~58HSD for the roller body. The residual compressive stress on the roller body surface is <450MPa.

[0049] After quenching and tempering, the hardness of the roll neck in this embodiment is 42~47HSD, and the maximum hardness exceeds the upper limit of 5HSD required by the technical specifications.

[0050] The support roller composition of this embodiment includes 0.40% C, 0.35% Si, 0.55% Mn, 3.1% Cr, 0.50% Mo, 0.20% Ni, with the balance being Fe and unavoidable impurities.

[0051] The process and execution of the tempering treatment for this support roller were investigated: Tempering parameters: tempering temperature 595±5℃, holding time 80h. When the support roller was held at 595±5℃ for 45h, a short circuit occurred in one of the resistance bands at the rear end of the electric furnace, resulting in a lower furnace temperature and consequently, higher roller neck hardness. Therefore, the preparation method of this invention was adopted, with the following steps: Step 1: First, the roller body is machined to achieve a surface roughness of 1.6, in preparation for subsequent roller body processing; Step 2: Place the support roll forging into a 320℃ furnace and keep it at that temperature for 30 hours; before placing it into the heating furnace, apply thermocouples to the surface of the roll body. Step 3: Increase the temperature to 620±5℃ at a rate of 40℃ / h, taking 7.5h; Step 4: Keep warm at 620±5℃ for 50 hours; Step 5: Reduce the furnace temperature to 480℃ and keep it at that temperature for 38 hours. The temperature of the thermocouple on the surface of the support roller is 515℃. Step 6: Transfer the support roller into the differential temperature furnace, heat only the roller body and air cool the roller neck; rapidly raise the furnace temperature to 1040℃ at maximum power for 70 minutes. Step 7: Hold at 1040℃ for 211 min, then lower the furnace temperature to 990℃ and hold at 990℃ for 106 min to complete the differential heating. Step 8: Spray cooling on the roll body until the surface temperature of the roll body reaches 220℃, cooling is complete; air cooling on the roll neck; Step 9: Transfer the spray-quenched workpiece into a tempering furnace and temper it at a rate of 40℃ / h to 545℃ for 95h. Step 10: When the temperature drops to 220℃ at a rate of 20℃ / h, the product is removed from the furnace. The process takes 16 hours.

[0052] Excluding machining processes, the total production cycle is approximately 11 days.

[0053] After the above treatment, the surface hardness and residual stress of the support roller were tested, as shown in Tables 1 and 2 below, and fully meet the technical requirements.

[0054] Table 1 Surface hardness (HSD) of the support roller in Example 1

[0055] Table 2. Surface residual compressive stress (MPa) of the support roller in Example 1

[0056] Example 2 This embodiment provides a method for rework of a support roller after tempering. The diameter of the support roller body in this embodiment is 2310mm, and the diameter D2 at the maximum diameter of the roller neck is 1620mm. The hardness requirements are: 40~46HSD for the roller neck and 55~60HSD for the roller body. The residual compressive stress on the roller body surface is <450MPa.

[0057] After quenching and tempering, the hardness of the roll neck in this embodiment is 45~48HSD, and the maximum hardness exceeds the upper limit of the technical requirement of 2HSD.

[0058] The support roller in this embodiment comprises 0.45% C, 0.40% Si, 0.45% Mn, 2.8% Cr, 0.52% Mo, 0.15% Ni, with the balance being Fe and unavoidable impurities.

[0059] The process and execution of the tempering treatment for this support roller were investigated: Tempering parameters: tempering holding temperature 580±5℃, holding time 100h. This support roller weighs over 230 tons and can only be tempered in a non-air-circulating electric furnace. The furnace top temperature is too high. To avoid uneven hardness between the upper and lower parts of the support roller, a flipping measure is taken during the holding process (the flipping time is approximately halfway through the holding time). During the tempering process, the overhead crane broke down when the roller was to be flipped, preventing the flipping. This resulted in the portion of the roller with the neck facing down having higher hardness. Therefore, the preparation method of this invention is adopted, with the following steps: Step 1: First, the roller body is machined to achieve a surface roughness of 1.6, in preparation for subsequent roller body processing; Step 2: Place the support roll forging into a 300℃ furnace and keep it at that temperature for 33 hours; before placing it into the heating furnace, apply thermocouples to the surface of the roll body. Step 3: Increase the temperature to 588±5℃ at a rate of 45℃ / h, taking 6.4h; Step 4: Incubate at 588±5℃ for 60 hours; Step 5: Reduce the furnace temperature to 490℃ and keep it at that temperature for 40 hours. The temperature of the thermocouple on the surface of the support roller is 525℃. Step 6: Transfer the support roller into the differential temperature furnace, heat only the roller body and air cool the roller neck; rapidly raise the furnace temperature to 1050℃ at maximum power for 90 minutes. Step 7: Hold at 1050℃ for 231 minutes, then lower the furnace temperature to 1000℃ and hold at 1000℃ for 115 minutes to complete the differential heating. Step 8: Spray cooling on the roll body until the surface temperature of the roll body reaches 225℃, cooling is complete; air cooling on the roll neck; Step 9: Transfer the spray-quenched workpiece into a tempering furnace and temper it at a rate of 50℃ / h to 540℃ for 105h. Step 10: When the temperature drops to 220℃ at a rate of 16℃ / h, the product is removed from the furnace. The process takes 20 hours.

[0060] Excluding machining processes, the total production cycle is approximately 12 days, which is short.

[0061] After the above treatment, the surface hardness and residual stress of the support roller were tested, as shown in Tables 3 and 4 below, and they fully meet the technical requirements.

[0062] Table 3 Surface hardness (HSD) of the support roller in Example 2

[0063] Table 4. Surface residual compressive stress (MPa) of the support roller in Example 2

[0064] Example 3 This embodiment provides a method for rework of a support roller after tempering. The diameter of the support roller body in this embodiment is 1950mm, and the diameter D2 at the maximum diameter of the roller neck is 1400mm. The hardness requirements are: 43~48HSD for the roller neck and 56~62HSD for the roller body. The residual compressive stress on the roller body surface is <480MPa.

[0065] After quenching and tempering, the hardness of the roll neck in this embodiment is 48~52HSD, and the maximum hardness exceeds the upper limit of 4HSD required by the technical specifications.

[0066] The support roller in this embodiment comprises 0.43% C, 0.42% Si, 0.48% Mn, 3.4% Cr, 0.60% Mo, 0.14% Ni, with the balance being Fe and unavoidable impurities.

[0067] The tempering process and execution procedure for the support roller were reviewed. The tempering parameters were: tempering holding temperature 570±5℃, holding time 70 h. The three furnace temperature monitoring couplers temporarily malfunctioned, causing the furnace temperature to be lower than normal. Therefore, the preparation method of this invention was adopted, with the following steps: Step 1: First, the roller body is machined to achieve a surface roughness of 1.6, in preparation for subsequent roller body processing; Step 2: Place the support roll forging into a 290℃ furnace and hold it for 24 hours; before placing it into the heating furnace, apply thermocouples to the surface of the roll body; Step 3: Increase the temperature to 590±5℃ at a rate of 40℃ / h, taking 7.5h; Step 4: Keep warm at 590±5℃ for 44 hours; Step 5: Reduce the furnace temperature to 500℃ and keep it at that temperature for 30 hours. The temperature of the thermocouple on the surface of the support roller is 510℃. Step 6: Transfer the support roller into the differential temperature furnace, heat only the roller body and air cool the roller neck; rapidly raise the furnace temperature to 1060℃ at maximum power for 60 minutes. Step 7: Hold at 1060℃ for 195 minutes, then lower the furnace temperature to 1010℃ and hold at 1010℃ for 100 minutes to complete the differential heating. Step 8: Spray cooling of the roller body until the surface temperature reaches 220°C, cooling complete; air cooling of the roller neck; Step 9: Transfer the spray-quenched workpiece into a tempering furnace and temper it at a rate of 45℃ / h to 530℃ for 80h. Step 10: When the temperature drops to 220℃ at a rate of 20℃ / h, the product is removed from the furnace. The process takes 15.5 hours.

[0068] Excluding machining processes, the total production cycle is approximately 9 days, which is short.

[0069] After the above treatment, the surface hardness and residual stress of the support roller were tested, as shown in Tables 5 and 6 below, and fully meet the technical requirements.

[0070] Table 5 Surface hardness (HSD) of the support roller in Example 3

[0071] Table 6. Surface residual compressive stress (MPa) of the support roller in Example 3

[0072] Comparative Example 1 The components, technical requirements, heat treatment process, and execution process of the support roller in this comparative example are the same as those in Example 1, and will not be repeated here.

[0073] After quenching and tempering, the hardness of the roll neck in this comparative example is 42~47HSD, and the maximum hardness exceeds the upper limit of 5HSD required by the technical specifications.

[0074] The rework method for this comparative example includes the following steps: Step 1: Keep warm at 285℃ for approximately 30 hours; Step 2: Increase the temperature to 595℃ at a rate of 30℃ / h, which takes about 11 hours; Step 3: Incubate at 595℃ for 80 hours; Step 4: The furnace temperature is reduced to 400℃, and the process takes about 11 hours; Step 5: Cool down to 200℃ at a rate of 10℃ / h, the process takes about 20 hours; Step 6: After the workpiece is taken out of the furnace, it is air-cooled to room temperature, which takes about 8 days; Step 7: Test the hardness of the roll neck; 41~44 HSD, which meets the technical requirements. Step 8: Machining the roller body to achieve a surface roughness of 1.6, in preparation for differential temperature heating and spray quenching of the roller body; Step 9: Incubate at 280℃ for 30 hours; Step 10: Increase the temperature to 500℃ at a rate of 30℃ / h; Step 11: Incubate at 500℃ for 48 hours; Step 12: Transfer the support roller into the differential temperature furnace, heat only the roller body and air cool the roller neck; rapidly raise the furnace temperature to 1050℃ at maximum power for 90 minutes. Step 13: Hold at 1050℃ for 231 minutes, then lower the furnace temperature to 1000℃ and hold at 1000℃ for 115 minutes to complete the differential heating. Step 14: Spray cooling on the roller body until the surface temperature of the roller body reaches 225°C, then air-cool the roller neck; Step 15: Transfer the spray-quenched workpiece into a tempering furnace and temper it at a rate of 50℃ / h to 540℃ for 105h. Step 16: Remove from the furnace when the temperature drops to 240℃ at a rate of 16℃ / h.

[0075] Excluding machining processes, the total production cycle is approximately 24 days. This is about 13 days longer than the process cycle in Example 1.

[0076] Comparative Example 2 The components, technical requirements, heat treatment process, and execution process of the support roller in this comparative example are the same as those in Example 2, and will not be repeated here.

[0077] The steps of the repair method in this comparative example are generally the same as those in Example 2, except that: Step 4: Incubate at 588±5℃ for 80 hours; After final heat treatment, the support rollers in this comparative example had a neck hardness of 40-42 HSD, which met the technical requirements. However, the residual compressive stress of the support rollers all exceeded 450 MPa, exceeding the technical requirements. Analysis revealed that the total process time in step 4 was too long, resulting in a roller body temperature exceeding 530℃ and excessive overall heat storage in the workpiece. The increased austenitization layer depth on the roller body surface during differential heating further contributed to the residual stress exceeding the technical requirements. Therefore, the support rollers in this comparative example did not meet the technical requirements.

[0078] Comparative Example 3 The components, technical requirements, heat treatment process, and execution process of the support roller in this comparative example are the same as those in Example 3, and will not be repeated here.

[0079] The steps of the repair method in this comparative example are generally the same as those in Example 3, except that: Step 4: Keep warm at 570±5℃ for 38 hours; After treatment, the neck hardness of the support roller in this comparative example is 46~50HSD, which is still higher than the technical requirements. After research and analysis, it was found that the heat preservation temperature and heat preservation time in step 4 were too low, and the neck hardness was not reduced enough, still exceeding the technical requirements.

[0080] 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 method for reworking a support roller after tempering, characterized in that, The rework process after tempering includes the following steps: preheating, differential temperature heating - quenching, and tempering; The preheating process includes the following steps: The support roll forging is placed in a furnace at 280~320℃ and heated and held at that temperature; the temperature is rapidly increased to T3 and then held at that temperature, which is 575~630℃; then the furnace temperature is adjusted to 480~530℃ and held at that temperature for a longer period. Differential temperature heating-quenching includes the following steps: The support roller is transferred into the differential temperature furnace, and only the roller body is heated to rapidly raise the furnace temperature to 1021~1070℃, while the roller neck is air-cooled. The temperature is then maintained at 1021~1070℃ until the roller surface temperature reaches the predetermined quenching temperature. The furnace temperature is then adjusted to 980~1000℃ and maintained. Finally, the roller body is spray-cooled.

2. The rework process after tempering according to claim 1, characterized in that, The maximum hardness of the neck of the tempered support roll is 1~6 HSD higher than the technical requirement.

3. The rework process after tempering according to claim 1, characterized in that, During the preheating process, after the T3 heat preservation, the internal temperature of the roller body is below 530°C.

4. The rework process after tempering according to claim 3, characterized in that, During the preheating process, after the T3 heat preservation, the neck temperature of the roll reaches 575~630℃.

5. The rework process after tempering according to claim 1, characterized in that, During the preheating process, the holding time in the 280~320℃ stage is t2, where t2 = 1.2~1.5×D1 / 100, D1 is the roller diameter in millimeters, and the holding time t2 is in hours.

6. The rework process after tempering according to claim 1, characterized in that, During the rapid heating of the furnace to 1021~1070℃, the heating time should be controlled to be less than 90 minutes.

7. The rework process after tempering according to claim 1, characterized in that, During the roller spray cooling process, the workpiece surface is cooled to 220~240℃, at which point the cooling is complete.

8. The rework process after tempering according to any one of claims 1 to 7, characterized in that, The tempering process includes the following steps: after spray cooling, the material is transferred to a tempering furnace, heated to a tempering temperature of 500~565℃ and held at that temperature; then cooled to below 220℃ and removed from the furnace to obtain the support roller.

9. The rework process after tempering according to any one of claims 1 to 7, characterized in that, The components of the support roller, by mass percentage, include: C: 0.38%~0.48%, Si: 0.3%~0.5%, Mn: 0.4%~0.6%, Cr: 2.5%~3.5%, Mo: 0.5%~0.8%, Ni: 0.1%~0.3%, with the balance being Fe and unavoidable impurities.

10. A support roller, characterized in that, It is prepared by the method according to any one of claims 1 to 9.

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