A high-performance forging and heat treatment process for backing bearing outer rings

Abstract

The present application relates to the technical field of backing bearing outer ring, and particularly relates to a forging heat treatment process of high-performance backing bearing outer ring, at least comprising the following steps: S1, pouring after melting the raw material of the high-performance backing bearing outer ring, the pouring temperature is controlled at 1500-1530 DEG C, and the cooling temperature is 500-560 DEG C to form a blank; S2, the blank is heated to 1150-1250 DEG C to carry out initial forging deformation by upsetting and elongation; S3, final forging deformation is carried out at a final forging temperature of 1050-1150 DEG C to obtain a forged piece; S4, the forged piece is annealed after secondary forging. The present application adopts a specific forging heat treatment process, improves the uniformity of the matrix grain and structure, increases the strength and toughness of the matrix, meets the rolling requirements of ultra-high strength and ultra-thin silicon steel of the silicon steel production line, improves the production efficiency, reduces the production cost, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to the field of backing bearing outer ring technology, and more specifically to a forging heat treatment process for a high-performance backing bearing outer ring. Background Technology

[0002] The process of manufacturing bearing steel backing bearings encompasses smelting, casting, billet forging, heat treatment of the forged billet, outer ring forging, heat treatment of the forged outer ring, final heat treatment, and finishing. Among these, the forging of the billet and its subsequent heat treatment steps have a significant impact on the grain size and microstructure of the outer ring billet, thus fundamentally determining the final strength, toughness, oxidation resistance, and resistance to hot cracking of the outer ring.

[0003] However, the outer rings of currently imported bearing backers are mainly made of high-carbon chromium bearing steel. This material has revealed a series of problems during use, such as high price, long procurement cycle, relatively high failure rate, frequent cracking and peeling of the outer ring, and severe indentation on the roller surface. In contrast, domestically produced high-carbon chromium bearing steel backers have not yet reached the performance level of imported products.

[0004] Chinese patent CN203412957U provides a backing bearing for a Sendzimir rolling mill, solving technical problems such as poor sealing performance of existing backing bearings. CN201908950U provides a backing bearing for a multi-roll rolling mill, improving the end face structure of the inner retaining ring, reducing the contact area between the inner retaining ring and the inner ring, and simultaneously improving lubrication of the contact end faces. However, the outer ring material in the above-mentioned prior art is high-carbon chromium bearing steel. In practical applications, this material is prone to cracking and peeling, failing to meet the rolling requirements of ultra-thin, ultra-high-strength silicon steel sheets in Sendzimir rolling mills.

[0005] Therefore, it is of great significance to explore the failure mechanism of the outer ring of domestically produced high-carbon chromium bearing steel backing bearings and to develop improved technical solutions and processes to enhance the performance of its blanks. Summary of the Invention

[0006] To address the problems in the prior art, the present invention provides a forging heat treatment process for the outer ring of a high-performance backing bearing, comprising at least the following steps:

[0007] S1. The high-performance backing bearing outer ring material is melted and then cast. The casting temperature is controlled at 1500-1530℃, and the cooling temperature is reduced to 500-560℃ to form a billet.

[0008] S2. The billet is heated to 1150-1250℃ and undergoes initial forging deformation through upsetting and drawing.

[0009] S3. Perform final forging deformation at a final forging temperature of 1050-1150℃ to obtain the forging;

[0010] S4. Perform secondary forging followed by annealing heat treatment on the forgings.

[0011] In one embodiment, the chemical composition and weight percentage of the raw material for the outer ring of the high-performance backing bearing include:

[0012] C: 0.98-1.5wt%, Si: 0.65-0.95wt%, Mn: 0.45-0.75wt%, P: <0.005wt%, S: <0. 003wt%, Cr: 2.5-4.5wt%, Mo: 0.5-0.85wt%, W: 0.3-0.5wt%, N: 0.12-0.25wt%.

[0013] In a preferred embodiment, the content of element C is any one of 0.99wt%, 1.1wt%, 1.2wt%, 1.3wt%, and 1.5wt%.

[0014] In a preferred embodiment, the Si element content is any one of 0.69wt%, 0.75wt%, 0.8wt%, 0.9wt%, and 0.95wt%.

[0015] In a preferred embodiment, the content of the Mn element is any one of 0.48wt%, 0.55wt%, 0.6wt%, 0.65wt%, and 0.75wt%.

[0016] In a preferred embodiment, the content of the P element is 0.015 wt%.

[0017] In a preferred embodiment, the content of the sulfur element is 0.008 wt%.

[0018] In a preferred embodiment, the Cr content is any one of 2.6wt%, 3wt%, 3.5wt%, 4.3wt%, and 4.5wt%.

[0019] In a preferred embodiment, the content of the Mo element is any one of 0.58wt%, 0.65wt%, 0.7wt%, 0.07wt%, 0.8wt%, and 0.85wt%.

[0020] In a preferred embodiment, the content of the W element is any one of 0.32wt%, 0.4wt%, 0.45wt%, 0.48wt%, and 0.5wt%.

[0021] In a preferred embodiment, the content of the N element is any one of 0.12wt%, 0.15wt%, 0.18wt%, 0.03wt%, 0.2wt%, and 0.25wt%.

[0022] In one embodiment, the outer ring of the high-performance backing bearing is made of GCr18Mo.

[0023] In a preferred embodiment, the pouring temperature in step S1 is any one of 1500°C, 1510°C, 1520°C, 1525°C, and 1530°C.

[0024] In a preferred embodiment, the cooling temperature in step S1 is any one of 500°C, 520°C, 540°C, 550°C, and 560°C.

[0025] In one embodiment, the billet heating process in step S2 is as follows: heating to 850°C at a heating rate of <80°C / h, holding at that temperature for 1 hour, and then heating to 1150-1250°C at a heating rate of 180-200°C / h.

[0026] In a preferred embodiment, the heating rate is any one of 180℃ / h, 185℃ / h, 190℃ / h, and 200℃ / h.

[0027] In a preferred embodiment, the initial forging temperature in step S2 is any one of 1150°C, 1180°C, 1200°C, 1220°C, and 1250°C.

[0028] In one embodiment, the upsetting is performed 2-3 times, and the elongation is performed 2-3 times.

[0029] In one embodiment, the forging ratio of the initial forging deformation is >5.

[0030] In a preferred embodiment, the forging ratio of the initial forging deformation is any one of 5, 5.5, 6, 6.2, and 6.5.

[0031] During the forging production of the outer ring blank of the backing bearing, the forging ratio is controlled above 5. After cooling, the forging can obtain fine and uniform grains, which provides a good original grain structure for the heat treatment process and lays the foundation for the forging to obtain qualified mechanical properties.

[0032] In one embodiment, the upsetting deformation is controlled between 35 and 55.

[0033] In a preferred embodiment, the upsetting deformation is any one of 35%, 40%, 50%, 52%, and 55%.

[0034] In one embodiment, the lengthening is performed using a wide anvil strong pressure method, with the amount of pressure applied to each anvil controlled at 20-30%.

[0035] In a preferred embodiment, the pressing amount per anvil is any one of 20%, 22%, 26%, 28%, or 30%.

[0036] In one embodiment, the final forging temperature in step S3 is any one of 1050°C, 1080°C, 1100°C, 1120°C, and 1150°C.

[0037] In one embodiment, the final forging deformation in step S3 is 15-20%.

[0038] In a preferred embodiment, the final forging deformation in step S3 is any one of 15%, 16%, 17%, 18%, or 20%.

[0039] In one implementation, step S4 includes:

[0040] a. After step S3, the forgings are air-cooled until the surface temperature of the forging shaft drops to 860-980℃. Then, they are normalized and placed in the furnace for 4-8 hours.

[0041] b. After the heat preservation is completed, the furnace is cooled to 620-640℃ for tempering, and the heat preservation is carried out for 8-12 hours;

[0042] c. Cool the forging after step b to obtain the final product.

[0043] In one embodiment, step c specifically involves: holding the forging treated in step b at a temperature of ≤20℃ / h, and then cooling it to room temperature when the furnace temperature is ≤200℃.

[0044] In one embodiment, the grain size of the forging after step S4 is 6.5-7.0.

[0045] After undergoing the forging heat treatment process described in this application, the forgings exhibit fine and uniform grains, providing a favorable microstructure for the final heat treatment. This is because the fine grains after forging heat treatment result in more grain boundaries within a given volume, increasing the resistance to dislocation movement, raising the yield strength, and thus playing a role in grain boundary strengthening. Secondly, the interfaces hinder the movement of microcracks, limiting their propagation rate. Simultaneously, the increased grain boundary area relatively reduces inclusions caused by segregation at the grain boundaries, improving grain boundary bonding and increasing plasticity. The finer the grains, the more grain boundaries per unit volume, the greater the number of grains participating in deformation, and the more uniform the deformation, leading to greater plastic deformation before fracture. With both strength and plasticity increasing simultaneously, the metal consumes more energy before fracture, thus improving its toughness.

[0046] Beneficial effects

[0047] 1. Based on the system of the present invention, when forging the outer ring blank of the backing bearing, the forging ratio is controlled above 5. After cooling, the forging obtains fine and uniform grains, which provides a good original grain structure for the heat treatment process and lays the foundation for the forging to obtain qualified mechanical properties.

[0048] 2. Based on the system of this invention, an innovative two-stage forging and annealing heat treatment process is adopted to eliminate internal stress and mixed grain phenomena caused by uneven grain size in the forging. The first annealing improves the microstructure of the forging billet, and the second annealing improves the mechanical properties of the forging billet, ensuring the mechanical property requirements of the backing bearing billet. This can further solve problems such as through cracking, short service life, and frequent spalling of the outer ring of high-carbon chromium bearing steel backing bearings during use, thereby improving production efficiency and reducing production costs.

[0049] 3. In this invention, by increasing the forging ratio, increasing the number of upsetting and drawing operations, and appropriately optimizing and controlling the final forging temperature, the rolling performance stability of the designed backing bearing outer ring during its service life on the mill is improved, meeting the rolling requirements of ultra-high strength and ultra-thin silicon steel products. At the same time, the rolling mileage per single mill operation is increased by 20% compared to the original material.

[0050] 4. The microstructure of the outer ring working layer of the backing bearing developed by the present invention using a specific forging heat treatment process is stable and consistent, with a small hardness difference. The hardness difference within a single working layer is only about 1 HSD.

[0051] 5. This invention adopts a specific forging and post-forging heat treatment process design. After forging, the outer ring of the backing bearing has a tensile strength of 1260-1320MPa at room temperature, an impact energy of 40-50J (AKV2), and a hardness of 45-50 HRC. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0053] Example 1

[0054] This embodiment provides a forging heat treatment process for the outer ring of a high-performance backed bearing, which includes at least the following steps:

[0055] S1. The high-performance backing bearing outer ring material is melted and then cast. The casting temperature is controlled at 1500℃ and the cooling temperature is reduced to 500℃ to form a billet.

[0056] S2. The billet is heated to 850℃ at a heating rate of 75℃ / h, held for 1 hour, and then heated to 1150℃ at a heating rate of 180℃ / h for initial forging deformation.

[0057] S3. Perform final forging deformation at a final forging temperature of 1050℃ to obtain the forging;

[0058] S4. Perform secondary forging followed by annealing heat treatment on the forgings.

[0059] The chemical composition and weight percentage of the raw material for the outer ring of the high-performance backing bearing include:

[0060] C: 0.99wt%, Si: 0.69wt%, Mn: 0.48wt%, P: 0.015wt%, S: 0.008wt%, Cr: 2.6wt%, Mo: 0.58wt%, W: 0.32wt%, N: 0.12wt%, balance Fe.

[0061] The upsetting process is repeated twice, and the elongation process is repeated twice.

[0062] The forging ratio of the initial forging deformation is 5.

[0063] The upsetting deformation is 35%.

[0064] The lengthening process employs a wide anvil strong pressure method, with the pressure applied to each anvil controlled at 20%.

[0065] The final forging deformation in step S3 is 15%.

[0066] The S4 step includes:

[0067] a. After step S3, the forgings are air-cooled and the surface temperature of the forging shaft is reduced to 860℃ for normalizing. The forgings are then placed in the furnace and held for 6 hours.

[0068] b. After the heat preservation is completed, the furnace is cooled to 630℃ for tempering, and the heat preservation is carried out for 10 hours.

[0069] c. After holding the forgings treated in step b at a constant temperature, cool them at a rate of 20℃ / h until the furnace temperature reaches 200℃. Then remove them from the furnace and cool them to room temperature to obtain the final product.

[0070] Example 2

[0071] This embodiment provides a forging heat treatment process for the outer ring of a high-performance backed bearing, which includes at least the following steps:

[0072] S1. The high-performance backing bearing outer ring material is melted and then cast. The casting temperature is controlled at 1510℃ and the cooling temperature is reduced to 520℃ to form a billet.

[0073] S2. The billet is heated to 850℃ at a heating rate of 75℃ / h, held for 1 hour, and then heated to 1180℃ at a heating rate of 185℃ / h for initial forging deformation.

[0074] S3. Perform final forging deformation at a final forging temperature of 1080℃ to obtain the forging;

[0075] S4. Perform secondary forging followed by annealing heat treatment on the forgings.

[0076] The chemical composition and weight percentage of the raw material for the outer ring of the high-performance backing bearing include:

[0077] C: 1.1 wt%, Si: 0.75 wt%, Mn: 0.55 wt%, P: 0.015 wt%, S: 0.008 wt%, Cr: 3 wt%, Mo: 0.65 wt%, W: 0.4 wt%, N: 0.15 wt%, balance Fe.

[0078] The upsetting process is repeated twice, and the elongation process is repeated twice.

[0079] The forging ratio of the initial forging deformation is 5.5.

[0080] The upsetting deformation is 40%.

[0081] The lengthening process employs a wide anvil strong pressure method, with the pressure applied to each anvil controlled at 22%.

[0082] The final forging deformation in step S3 is 16%.

[0083] The S4 step includes:

[0084] a. After step S3, the forgings are air-cooled and the surface temperature of the forging shaft is reduced to 860℃ for normalizing. The forgings are then placed in the furnace and held for 6 hours.

[0085] b. After the heat preservation is completed, the furnace is cooled to 630℃ for tempering, and the heat preservation is carried out for 10 hours.

[0086] c. After holding the forgings treated in step b at a constant temperature, cool them at a rate of 20℃ / h until the furnace temperature reaches 200℃. Then remove them from the furnace and cool them to room temperature to obtain the final product.

[0087] Example 3

[0088] This embodiment provides a forging heat treatment process for the outer ring of a high-performance backed bearing, which includes at least the following steps:

[0089] S1. The high-performance backing bearing outer ring material is melted and then cast. The casting temperature is controlled at 1520℃ and the cooling temperature is reduced to 540℃ to form a billet.

[0090] S2. The billet is heated to 850℃ at a heating rate of 75℃ / h, held for 1 hour, and then heated to 1200℃ at a heating rate of 190℃ / h for initial forging deformation.

[0091] S3. Perform final forging deformation at a final forging temperature of 1100℃ to obtain the forging;

[0092] S4. Perform secondary forging followed by annealing heat treatment on the forgings.

[0093] The chemical composition and weight percentage of the raw material for the outer ring of the high-performance backing bearing include:

[0094] C: 1.2wt%, Si: 0.8wt%, Mn: 0.6wt%, P: 0.015wt%, S: 0.008wt%, Cr: 3.5wt%, Mo: 0.7wt%, W: 0.45wt%, N: 0.18wt%, balance Fe.

[0095] The upsetting process is repeated 3 times, and the elongation process is repeated 3 times.

[0096] The forging ratio of the initial forging deformation is 6.

[0097] The upsetting deformation is 50%.

[0098] The lengthening process employs a wide anvil strong pressure method, with the pressure applied to each anvil controlled at 26%.

[0099] The final forging deformation in step S3 is 17%.

[0100] The S4 step includes:

[0101] a. After step S3, the forgings are air-cooled and the surface temperature of the forging shaft is reduced to 860℃ for normalizing. The forgings are then placed in the furnace and held for 6 hours.

[0102] b. After the heat preservation is completed, the furnace is cooled to 630℃ for tempering, and the heat preservation is carried out for 10 hours.

[0103] c. After holding the forgings treated in step b at a constant temperature, cool them at a rate of 20℃ / h until the furnace temperature reaches 200℃. Then remove them from the furnace and cool them to room temperature to obtain the final product.

[0104] Example 4

[0105] This embodiment provides a forging heat treatment process for the outer ring of a high-performance backed bearing, which includes at least the following steps:

[0106] S1. The high-performance backing bearing outer ring material is melted and then cast. The casting temperature is controlled at 1525℃ and the cooling temperature is reduced to 550℃ to form a billet.

[0107] S2. The billet is heated to 850℃ at a heating rate of 75℃ / h, held for 1 hour, and then heated to 1220℃ at a heating rate of 185℃ / h for initial forging deformation.

[0108] S3. Perform final forging deformation at a final forging temperature of 1120℃ to obtain the forging;

[0109] S4. Perform secondary forging followed by annealing heat treatment on the forgings.

[0110] The chemical composition and weight percentage of the raw material for the outer ring of the high-performance backing bearing include:

[0111] C: 1.3wt%, Si: 0.9wt%, Mn: 0.65wt%, P: 0.015wt%, S: 0.008wt%, Cr: 4.3wt%, Mo: 0.8wt%, W: 0.48wt%, N: 0.2wt%, balance Fe.

[0112] The upsetting process is repeated 3 times, and the elongation process is repeated 3 times.

[0113] The forging ratio of the initial forging deformation is 6.2.

[0114] The upsetting deformation is 52%.

[0115] The lengthening process employs a wide anvil strong pressure method, with the pressure applied to each anvil controlled at 28%.

[0116] The final forging deformation in step S3 is 18%.

[0117] The S4 step includes:

[0118] a. After step S3, the forgings are air-cooled and the surface temperature of the forging shaft is reduced to 860℃ for normalizing. The forgings are then placed in the furnace and held for 6 hours.

[0119] b. After the heat preservation is completed, the furnace is cooled to 630℃ for tempering, and the heat preservation is carried out for 10 hours.

[0120] c. After holding the forgings treated in step b at a constant temperature, cool them at a rate of 20℃ / h until the furnace temperature reaches 200℃. Then remove them from the furnace and cool them to room temperature to obtain the final product.

[0121] Example 5

[0122] This embodiment provides a forging heat treatment process for the outer ring of a high-performance backed bearing, which includes at least the following steps:

[0123] S1. The high-performance backing bearing outer ring material is melted and then cast. The casting temperature is controlled at 1530℃ and the cooling temperature is reduced to 560℃ to form a billet.

[0124] S2. The billet is heated to 850℃ at a heating rate of 75℃ / h, held for 1 hour, and then heated to 1250℃ at a heating rate of 200℃ / h for initial forging deformation.

[0125] S3. Perform final forging deformation at a final forging temperature of 1150℃ to obtain the forging;

[0126] S4. Perform secondary forging followed by annealing heat treatment on the forgings.

[0127] The chemical composition and weight percentage of the raw material for the outer ring of the high-performance backing bearing include:

[0128] C: 1.5wt%, Si: 0.95wt%, Mn: 0.75wt%, P: 0.015wt%, S: 0.008wt%, Cr: 4.5wt%, Mo: 0.85wt%, W: 0.5wt%, N: 0.25wt%, balance Fe.

[0129] The upsetting process is repeated 3 times, and the elongation process is repeated 3 times.

[0130] The forging ratio of the initial forging deformation is 6.5.

[0131] The upsetting deformation is 55%.

[0132] The lengthening process employs a wide anvil strong pressure method, with the pressure applied to each anvil controlled at 30%.

[0133] The final forging deformation in step S3 is 20%.

[0134] The S4 step includes:

[0135] a. After step S3, the forgings are air-cooled and the surface temperature of the forging shaft is reduced to 860℃ for normalizing. The forgings are then placed in the furnace and held for 6 hours.

[0136] b. After the heat preservation is completed, the furnace is cooled to 630℃ for tempering, and the heat preservation is carried out for 10 hours.

[0137] c. After holding the forgings treated in step b at a constant temperature, cool them at a rate of 20℃ / h until the furnace temperature reaches 200℃. Then remove them from the furnace and cool them to room temperature to obtain the final product.

[0138] Performance testing

[0139] 1. Room temperature mechanical property test: The high-performance backed bearing outer rings prepared in Examples 1-5 and the original backed bearing outer rings (KOYO bearings) were tested for room temperature mechanical properties in accordance with GB / T 13313 Shore and Leeb hardness test method for rolls and GB / T228.1-2010 tensile testing of metallic materials - Part 1: tensile testing at room temperature. The test results are shown in Table 1.

[0140] 2. Average rolling mileage per run: The high-performance backed bearing outer ring prepared in Example 5 and the original backed bearing outer ring were tested. The test results are shown in Table 2.

[0141] Table 1

[0142] <![CDATA[R m / MPa]]> <![CDATA[A KU2 / J]]> HRC Example 1 1260 40 45.0 Example 2 1280 42 43.5 Example 3 1290 45 45.0 Example 4 1300 47 48.5 Example 5 1320 50 50.0 Original backing bearing outer ring 1180-1230 30-40 40-46

[0143] Table 2

[0144] sample Average rolling kilometers per slot per run / km Example 5 10800 Original backing bearing outer ring 9000

[0145] As shown in Tables 1-2, the outer ring of the backed bearing in Examples 1-5 has a tensile strength of 1260-1320 MPa at room temperature and an impact energy of A. KV2 Its strength is 40-50 J, and its hardness HRC is 45-50.

[0146] The outer ring of the backing bearing prepared by this invention, after undergoing the same final heat treatment process, has an average rolling mileage of 10,800 km per run, which is 20% higher than the average rolling mileage of 9,000 km per run of the original backing bearing outer ring.

Claims

1. A forging heat treatment process for the outer ring of a high-performance backed bearing, characterized in that, At least the following steps are included: S1. The high-performance backing bearing outer ring material is melted and then cast. The casting temperature is controlled at 1500-1530℃, and the cooling temperature is reduced to 500-560℃ to form a billet. S2. The billet is heated to 1150-1250℃ and undergoes initial forging deformation through upsetting and drawing. S3. Perform final forging deformation at a final forging temperature of 1050-1150℃ to obtain the forging; S4. Perform secondary forging followed by annealing heat treatment on the forgings; The chemical composition and weight percentage of the raw material for the outer ring of the high-performance backing bearing include: C: 1.1-1.5wt%, Si: 0.65-0.95wt%, Mn: 0.45-0.75wt%, P: <0.005wt%, S: <0.0 03wt%, Cr: 2.5-4.5wt%, Mo: 0.5-0.85wt%, W: 0.3-0.5wt%, N: 0.12-0.25wt%; The S4 step includes: a. After step S3, the forgings are air-cooled until the surface temperature of the forging shaft drops to 860-980℃. Then, they are normalized and placed in the furnace for 4-8 hours. b. After the heat preservation is completed, the furnace is cooled to 620-640℃ for tempering, and the heat preservation is carried out for 8-12 hours; c. After holding the forgings treated in step b at a temperature of ≤ 20℃ / h, cool them out of the furnace when the furnace temperature is ≤ 200℃ and then cool them to room temperature to obtain the final product. The billet heating process in step S2 is as follows: heating to 850℃ at a heating rate of <80℃ / h, holding for 1h, and then heating to 1150-1250℃ at a heating rate of 180-200℃ / h. The upsetting process is repeated 2-3 times, and the drawing process is repeated 2-3 times; the forging ratio of the initial forging deformation is >5. The upsetting deformation is controlled between 35% and 55%. The lengthening process employs a wide-anvil, high-pressure method, with each anvil pressing down by 20-30%. The final forging deformation in step S3 is 15-20%.