Heat treatment method for cyclic regeneration supporting roller with ultrasonic flaw detection defects in roller body

Abstract

The invention discloses a heat treatment method of a cyclic regeneration supporting roller with ultrasonic flaw detection defects in a roller body. The heat treatment method comprises the steps of roller body induction heating annealing and roller body surface quenching. The roller body induction heating annealing comprises oven preheating, transferring into an integral induction heating coil to perform induction heating annealing on the roller body, transferring into an oven, performing heat preservation, and then performing furnace cooling; the roller body surface quenching comprises the steps of preheating in an oven, transferring into an integral induction heating coil to perform surface quenching on the roller body, hoisting out for air cooling, spraying for cooling and finally tempering. According to the method, roller body induction heating annealing is conducted before roller body surface quenching, so that the defect of the near-surface structure of the roller body can be overcome, the risk of breakage during quenching cooling is avoided, and when roller body surface quenching is conducted, the roller body surface is quenched by reducing the quenching heating temperature, prolonging the air cooling time, improving the quenching cooling final cooling temperature and prolonging the tempering heat preservation time. Therefore, the risk of breakage during quenching cooling can be further avoided, and meanwhile the residual stress of the roller body is further reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of recycled regeneration support rollers, and in particular relates to a heat treatment method for a recycled regeneration support roller with ultrasonic flaw detection defects inside the roller body. Background Art

[0002] Large forged steel support rollers are the key core components of rolling mills. Their performance directly determines the stability of rolling mills, production line operation, production consumption and product quality. Steel mills consume a large number of large forged steel support rollers every year. The manufacturing process of large forged steel support rollers is complex, the manufacturing cycle is long, and the price is expensive. The quality of large forged steel support rollers not only directly affects their service life, but also has a great impact on the quality of steel, production efficiency and production cost.

[0003] The effective working layer of large forged steel support rollers only accounts for 10%-25% of the overall weight of the rollers. When the rollers are used until they are scrapped normally, they still have a large weight and large size. If they are directly disposed of as scrap steel, it will cause a huge waste of resources. Recycling can realize the recycling and value maximization of old support rollers. The more mature recycling method for waste rollers used at home and abroad is roller modification, including large to small and partial small to large.

[0004] During the ultrasonic flaw detection during the recycling of large forged steel support rollers, it was found that some recycled support rollers had defects near the surface of the roller body. For the recycled support rollers with ultrasonic flaw detection defects inside the roller body, conventional heat treatment methods and surface quenching processes were used for heat treatment. There would be a greater risk of cracking during the quenching and cooling process. Summary of the invention

[0005] The object of the present invention is to solve the above-mentioned problem and to provide a heat treatment method for a recycled support roller having ultrasonic flaw detection defects inside the roller body.

[0006] The technical solution to achieve the purpose of the present invention is: a heat treatment method for a recycled support roller with ultrasonic flaw detection defects inside the roller body, including roller body induction heating annealing + roller body surface quenching.

[0007] The roller body induction heating annealing is specifically as follows: First, place the recycled support roller in an oven at 450-550°C and keep it warm for 40-60 hours.

[0008] Then the recycled support roller is transferred into the integral induction heating coil, and the temperature is raised to 830-900° C. by induction heating for 0.5-2 hours, and the temperature is kept for 2-5 hours, so as to perform induction heating annealing on the roller body of the recycled support roller.

[0009] Finally, the recycled support roller is transferred into a drying oven at 550-650°C, kept warm for 30-50 hours, and then cooled to 50-200°C at a rate of 10-70°C / h.

[0010] The roller surface quenching is specifically as follows: First, place the recycled support roller in an oven at 350-450°C and keep it warm for 20-40 hours.

[0011] Then the recycled support roller is transferred into the integral induction heating coil, firstly induction heated to 850-920°C for 0.5-2h, kept warm for 0.5-2h, then induction heated to quenching temperature for 20-40min, kept warm for 0.5-2h.

[0012] The recycled support roller is then lifted out of the integral induction heating coil, first air-cooled, and then spray-cooled.

[0013] Finally, the recycled support roller is tempered.

[0014] The quenching temperature is 15-20° C. lower than that of conventional new support rollers.

[0015] The air cooling time is extended by 1 to 5 minutes compared with that of a conventional newly manufactured support roll, so as to reduce the cracking tendency and deformation amount of the roll body during spray cooling.

[0016] The spray cooling time is shortened by 20 to 30 minutes compared with that of a conventional new support roller, and the air jet cooling time after the spray cooling is prolonged by 40 to 60 minutes compared with that of a conventional new support roller, thereby increasing the final cooling temperature of the quenching cooling.

[0017] The tempering temperature is 5-20°C lower than that of a conventional new support roller, and the tempering time coefficient is extended by 0.5-1.5 min / mm compared with that of a conventional new support roller, thereby making the near-surface structure of the roller body transform more fully and further reducing the residual stress of the roller body.

[0018] The present invention has the positive effects: (1) The method of the present invention performs induction heating annealing on the roller body before quenching the roller body surface, which can improve the microstructural defects near the surface of the roller body, thereby avoiding the risk of fracture during quenching cooling.

[0019] (2) When quenching the roller surface, the method of the present invention can further avoid the risk of fracture during quenching and cooling by lowering the quenching heating temperature, extending the air cooling time, increasing the quenching cooling final cooling temperature, and extending the tempering holding time, while further reducing the residual stress of the roller body. DETAILED DESCRIPTION

[0020] (Example 1) The recycled support roller with ultrasonic flaw detection defects inside the roller body of this embodiment is a Cr5 support roller with a roller body diameter of Ф1200mm, and its technical requirements are: the roller body surface hardness is 58-63HSD, the hardened layer depth is ≥70mm, and the scrap hardness is ≥54HSD.

[0021] The heat treatment method of the recycled support roller with ultrasonic flaw detection defects inside the roller body of this embodiment comprises the following steps: S1. Induction heating annealing of the roller body.

[0022] S11. Place the recycled support roller in an oven at 500±10°C and keep it warm for 50 hours.

[0023] S12, placing the recycled support roller into the integral induction heating coil, induction heating the roller to 880° C. for 1 hour, keeping the temperature for 3 hours, and performing induction heating annealing on the roller body of the recycled support roller.

[0024] S13, transfer the recycled support roller into a 600±10℃ oven, keep it warm for 40h, and then cool it to 150℃ at 40℃ / h.

[0025] The hardness of the recycled support roller after induction heating annealing in step S1 is shown in Table 1.

[0026] Table 1 Short roll neck 42~43HSD Roller end (short roll neck) 33~35HSD Middle of roller 34~36HSD Roller end (long roll neck) 34~35HSD Long roll neck 42~43HSD

[0027] S2, semi-finishing.

[0028] The semi-finishing machining and grinding of the roller body are carried out according to the semi-finishing drawings. After grinding, the surface roughness of the roller body is controlled at 0.8-1.6μm. At the same time, the chamfering of both sides of the roller body is processed to R50-R80, and the roughness of the end faces of the roller body on both sides is polished to 1.6-3.2μm.

[0029] S3. Roller surface quenching.

[0030] S31. Place the recycled support roller in an oven at 400±10°C and keep it warm for 30 hours.

[0031] S32, transfer the recycled support roller into the integral induction heating coil, first induction heat it to 900°C for 1 hour, keep it warm for 1 hour, then induction heat it to 950-955°C [normally 970°C] for 30 minutes, keep it warm for 1 hour.

[0032] S33, the recycled support roller is lifted out from the integral induction heating coil, air-cooled for 9 to 10 minutes [conventionally 5 to 8 minutes], and then spray-cooled, the spray cooling time is 90 to 95 minutes [conventionally 115 to 120 minutes], and the air jet cooling time after spray cooling is 140 to 150 minutes [conventionally 90 to 100 minutes].

[0033] S34, the recycled support roller is tempered, the tempering temperature is 480°C [conventionally 500°C], and the tempering time is 130-140h [conventionally 110-120h].

[0034] The hardness of the recycled support roller after the roller surface quenching in step S3 is shown in Table 2. It can be seen from Table 2 that the roller surface hardness meets the technical requirements.

[0035] The roller surface hardness in Table 2 is tested on 4 generatrixes on the roller surface, with 3 points on each generatrix (end of roller / middle of roller / end of roller).

[0036] Table 2 Roller end Middle of roller Roller end Bus 1 60-62 61-62 60-61 Bus 2 61-62 62-63 60-62 Bus 3 61-62 61-62 60-61 Bus 4 61-62 62-63 61-62

[0037] S4. Finish to finished size according to drawing requirements.

[0038] The surface hardness (unit: HSD) of the finished roller and the end hardness (i.e., the hardness of the hardened layer) of the roller were tested respectively. The results are shown in Table 3 and Table 4 respectively, where: The roller surface hardness in Table 3 is measured by testing 4 generatrixes on the roller surface, with 3 points on each generatrix (end of roller body / middle between the middle of roller body and both ends of roller body / middle of roller body / middle between the middle of roller body and both ends of roller body / end of roller body).

[0039] Table 3 Roller end Roller end / middle Middle of roller Roller end / middle Roller end Bus 1 61.1 62.5 62.4 62.9 61.9 Bus 2 61.7 62.5 62.6 63.1 62.3 Bus 3 61.4 62.1 62.8 62.5 62.1 Bus 4 61.6 62.8 63.1 62.8 61.9

[0040] Table 4 Distance from roller surface Roller end surface hardness 10mm 61.6HSD 20mm 61.1HSD 30mm 60.5HSD 40mm 60.1HSD 50mm 59.2HSD 60mm 58.3HSD 70mm 57.5HSD 80mm 56.1HSD 90mm 54.5HSD 100mm 51.5HSD

Claims

1. A heat treatment method for a recycled support roller with ultrasonic flaw detection defects inside the roller body, comprising roller body induction heating annealing + roller body surface quenching.

2. The heat treatment method for a recycled backup roller having ultrasonic flaw detection defects inside the roller body according to claim 1, characterized in that The roller body induction heating annealing is specifically as follows: First, place the recycled support roller in an oven at 450-550°C and keep it warm for 40-60 hours; Then the recycled support roller is transferred into the integral induction heating coil, and the temperature is raised to 830-900°C by induction heating for 0.5-2h, and the temperature is kept for 2-5h, so as to perform induction heating annealing on the roller body of the recycled support roller; Finally, the recycled support roller is transferred into a drying oven at 550-650°C, kept warm for 30-50 hours, and then cooled to 50-200°C at a rate of 10-70°C / h.

3. The heat treatment method for a recycled backup roller having ultrasonic flaw detection defects inside the roller body according to claim 1, characterized in that The roller surface quenching is specifically as follows: First, place the recycled support roller in an oven at 350-450°C and keep it warm for 20-40 hours; Then the recycled support roller is transferred to the integral induction heating coil, firstly induction heated to 850-920°C for 0.5-2h, kept warm for 0.5-2h, then induction heated to quenching temperature for 20-40min, kept warm for 0.5-2h; Then the recycled support roller is lifted out from the integral induction heating coil, first air-cooled and then spray-cooled; Finally, the recycled support roller is tempered.

4. The heat treatment method of a recycled backup roller having ultrasonic flaw detection defects inside the roller body according to claim 3, characterized in that: The quenching temperature is 950-955°C.

5. The heat treatment method of a recycled backup roller having ultrasonic flaw detection defects inside the roller body according to claim 3, characterized in that: The air cooling time is 9 to 10 minutes.

6. The heat treatment method of a recycled backup roller having ultrasonic flaw detection defects inside the roller body according to claim 3, characterized in that: The spray cooling time is 90 to 95 minutes; the air jet cooling time after the spray cooling is 140 to 150 minutes.

7. The heat treatment method of a recycled backup roller having ultrasonic flaw detection defects inside the roller body according to claim 3, characterized in that: The tempering treatment temperature is 480° C., and the tempering treatment time is 130 to 140 hours.