Sendzimir supporting roller backing bearing outer ring and preparation method thereof

Abstract

The invention discloses a Sendzimir supporting roll backing bearing outer ring and a preparation method thereof. The Sendzimir supporting roll backing bearing outer ring is prepared from the following components in percentage by weight: 0.8 to 1.25 percent of C, 0.60 to 0.90 percent of Si, 0.25 to 0.45 percent of Mn, less than 0.008 percent of P, less than 0.005 percent of S, 1.6 to 2.8 percent of Cr, 0.30 to 0.55 percent of Mo, 0.20 to 0.5 percent of W, 0.10 to 0.30 percent of V, 0.15 to 0.58 percent of Re and the balance of Fe and inevitable impurities. By improving the ratio of the components of the backing bearing outer ring and adjusting the heat treatment process, the normal-temperature and high-temperature mechanical properties of the backing bearing outer ring are comprehensively improved, the service life is effectively prolonged, the problems that the backing bearing outer ring is fractured and short in service life and the roller surface is often peeled off in use are solved, the production efficiency is improved, and the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technology of rolling mills, and more particularly to a back-up bearing outer ring of Sendzimir support rolls and a preparation method thereof. Background Art

[0002] The back-up bearing is a key component for load-bearing and transmission in a 20-high rolling mill. To directly ensure the high precision of rolled thin sheets under high-speed and heavy-load working conditions, its service precision and lifespan directly affect the performance of the rolling mill. The back-up bearing is a rolling bearing with a particularly thick outer ring. When in use, it is installed on a stationary shaft in a grouped form to become a support roll. The pressure on the work roll is transmitted to the support roll through the intermediate roll and then to the rack through the saddle system. This design ensures the support of the work roll in the entire length direction, with extremely small deformation of the roll system, and very precise thickness deviation can be obtained in the entire width direction of rolling. There are multiple back-up bearings on the mandrel of a support roll device, and the outer ring of the back-up bearing directly contacts the roll surface of the intermediate roll.

[0003] The outer ring of the back-up bearing directly contacts the intermediate roll. While the outer ring rotates, it bears the rolling component force. Therefore, the outer ring of the back-up bearing is the working surface of the support roll in a 20-high rolling mill. The main failure forms are as follows: (1) Crack: The main damage feature is that there are long-strip scars and cracks on the outer diameter surface of the bearing outer ring along the axial direction; (2) Spalling: The main feature is that cracks appear on the outer diameter surface, accompanied by local spalling of uneven sizes at the crack; (3) When the damage is severe, there will be a serious situation of through-type direct fracture in the axial direction; (4) Burn of the outer diameter surface of the outer ring, and the main damage feature is that the outer diameter surface of the outer ring shows long and thin traces in the axial direction, and there is an obvious burn discoloration phenomenon.

[0004] The structural characteristics and working conditions of the bearing require that the bearing parts must have high hardness, wear resistance, contact fatigue strength, good toughness, dimensional stability, corrosion resistance, and hot and cold processing performance. The working environment of the back-up bearing is harsh, and it is subject to high-load impact forces, etc. The commonly used material abroad is high-carbon chromium bearing steel, and the common material in China is carburized bearing steel. High-carbon chromium bearing steel is a bearing steel with a carbon content of 0.95 - 1.05% and different chromium contents (0.5 - 1.65%). Using high-carbon chromium bearing steel to manufacture the raceway and rolling elements, the parts have high hardness. According to the current on-site use situation, the single-time rolling kilometers of the back-up bearings produced abroad can reach 12,000 km, while the single-time rolling kilometers of the back-up bearings produced in China are generally 10,000 km, slightly inferior to the imported back-up bearings.

[0005] Since the 20-high rolling mill has a particularly large usage and turnover volume of back-up bearings, and the equipment investment cost is high, it is of great significance and extremely urgent to study the material and heat treatment process for improving the single-time on-machine service life of domestic back-up bearings to lay a foundation for formulating a domestic substitution technology plan.

[0006] The technology of bearing support rolls is gradually becoming popular in industrial fields at home and abroad, which has become an important measure to reduce the operating cost of production equipment. Among them, domestic companies mainly focus on the use and maintenance of large bearings, while there is relatively less technology in the material and preparation of support rolls. For example, Chinese Patent 201720969120.1 discloses a device capable of realizing reliable detection of the sealing performance of a backing bearing, including a sealing fixture, a gas flow regulation structure, and a gas pressure measurement structure; this technology mainly aims at the problem of the lack of reliable sealing performance detection technology and means in the prior art. Chinese Patent CN201410490498.4 discloses a backing bearing, in which one of the outer surface of the inner ring and the inner surface of the outer ring has a first arc surface and at least one second arc surface. The second arc surface, as the bearing area of the inner ring for bearing radial loads, can make the load distribution on each part of the inner ring more uniform, and extend the service life of the inner ring under the same working conditions; the purpose of this technology is to solve the problem of the low service life of the backing bearing under high radial loads. Chinese Patent CN200910013158.1 discloses a backing bearing, especially a high-service-life backing bearing assembled by a double-row and a single-row cage, so that the axes of the rolling elements in the same row are all on the same axis. Through reasonable structural design, the inner ring is uniformly stressed, the fatigue life of the inner ring is improved, the damage of the friction shims is reduced, the maintenance workload is reduced, and the service life of the bearing and the production efficiency of the rolling mill are improved. Chinese Patent 201811011804.6 discloses a processing technology for backing bearings. On the basis of the existing technology, grinding the outer diameter of the bearing outer ring is changed to grinding the outer diameter of the whole bearing by using a fixture, and the H value of the bearing is ground, with good processing accuracy and high efficiency. Chinese Patent CN201911393638.5 discloses a method for deep carburizing of large backing bearing rings, which can meet the different carburizing index requirements of different parts of the same ring bearing and meet the hardness and carbon layer index requirements of large backing bearings. Chinese Patent CN201721188681.4 discloses a grinding tool for the grinding operation of the backing bearing outer ring, which has the advantages of simple structure and convenient operation. Chinese Patent CN202220802416.5 discloses a grinding tool for backing bearings, which can perform outer circle grinding operations on backing bearings by using an ordinary external cylindrical grinder, reducing labor costs and processing costs. Most of these above-mentioned technologies are improvements in structure, while there is relatively less research on materials and preparation methods.

[0007] Since the RCM unit was put into production, the back-up bearings have basically been supplied exclusively by Koyo of Japan. Their prices are high, the procurement cycle is long, and the accident rate is relatively high. At present, the following problems mainly exist with the back-up bearings of the RCM unit: there are many rolling accidents, cracking and spalling of the inner and outer rings occur from time to time, the roll surface has serious indentations, after-sales service cannot meet on-site requirements, and technical improvements cannot be carried out. Therefore, the service performance of the back-up bearings has become one of the key factors restricting the improvement of the efficiency and product quality of the RCM unit. It can be seen that the existing domestic back-up bearing materials and their mechanical properties can no longer meet the rolling requirements of silicon steel products with increasingly improved mechanical properties. It is urgent to further study the materials of the back-up bearings and their preparation methods to solve the problems of fracture, short service life, and roll surface spalling that occur during the use of the back-up bearings. Summary of the Invention

[0008] Aiming at the defects existing in the prior art, the purpose of the present invention is to provide an outer ring of a Sendzimir support roll back-up bearing and its preparation method. By improving the proportion of the components of the outer ring of the back-up bearing and adjusting the heat treatment process, the comprehensive improvement of the mechanical properties of the outer ring of the back-up bearing at normal temperature and high temperature is realized, the service life is effectively extended, the problems of fracture, short service life, and frequent roll surface spalling during its use are solved, the production efficiency is improved, and the production cost is reduced.

[0009] To achieve the above purpose, the present invention adopts the following technical solutions:

[0010] The first aspect of the present invention provides an outer ring of a Sendzimir support roll back-up bearing, which includes the following components by weight percentage: C: 0.8 - 1.25%, Si: 0.60 - 0.90%, Mn: 0.25 - 0.45%, P ≤ 0.008%, S ≤ 0.005%, Cr: 1.6 - 2.8%, Mo: 0.30 - 0.55%, W: 0.20 - 0.5%, V: 0.10 - 0.30%, Re: 0.15 - 0.58%, and the balance is Fe and other inevitable impurities.

[0011] Preferably, the hardness HRC of the outer ring of the Sendzimir support roll back-up bearing at normal temperature is 60 - 62, the tensile strength ≥ 950 Mpa, the hardness HRC ≥ 55 at 600 °C, and the tensile strength ≥ 610 MPa.

[0012] Preferably, the tensile strength of the outer ring of the Sendzimir support roll back-up bearing at normal temperature is 980 - 1200 MPa, and the impact energy A KV2 is 4.5 - 5.2 J; at 600 °C, the tensile strength ≥ 610 MPa.

[0013] The second aspect of the present invention provides a method for preparing the outer ring of the back-up bearing of Sendzimir support rolls as described in the first aspect of the present invention, including melting, continuous casting, forging, heat treatment, and cold working processes;

[0014] The heat treatment process includes the following steps:

[0015] S1, quenching and tempering heat treatment. The outer ring blank obtained by forging is heated to 980 - 1020 °C after two equalizing treatments, held in the furnace for 2.5 - 3.5 h, then slowly cooled in the furnace to 280 - 380 °C, and then taken out of the furnace and air-cooled to room temperature;

[0016] S2, quenching treatment. The outer ring blank after quenching and tempering heat treatment is continuously heated to 1080 - 1180 °C for quenching and held for 80 - 90 min, then cooled in the furnace, and tempering treatment is carried out within 2 - 3 h;

[0017] S3, tempering treatment. The outer ring blank is heated to 480 - 550 °C, held for 120 - 180 min, cooled in the furnace to 190 - 210 °C, and taken out of the furnace and air-cooled to room temperature; the tempering treatment is repeated 2 - 3 times.

[0018] Preferably, in step S1, the two equalizing treatment processes are as follows:

[0019] S11, primary equalizing heat preservation. The outer ring blank is heated to 600 ± 10 °C at a heating rate of 200 - 230 °C / h for 8 - 10 min of primary equalizing heat preservation treatment;

[0020] S12, secondary equalizing heat preservation. It is continuously heated to 800 ± 10 °C at a heating rate of 200 - 230 °C / h for 8 - 10 min of secondary equalizing heat preservation treatment.

[0021] Preferably, in step S2, during the process of cooling in the furnace, the outer ring blank after quenching heat preservation is cooled in the furnace to 850 - 980 °C and held for 20 - 30 min, then cooled by blowing nitrogen, and the cooling rate is controlled at 4.5 - 5.5 °C / s. After cooling to below 300 °C, it is taken out of the furnace and air-cooled to room temperature.

[0022] Preferably, in step S3, the heating rate during the tempering treatment process is 200 - 230 °C / h.

[0023] Preferably, the cold working process adopts a grinding process, with the grinding wheel speed of 450 - 580 r / min, the workpiece speed of 40 - 68 r / min, the feed rate of 0.03 - 0.07 mm, the number of grinding passes of 4 - 8 times, and the carriage moving speed of 38 - 86 mm / s.

[0024] Preferably, magnetic particle flaw detection is used to detect the outer ring of the backing bearing of the support roll before and after the cold working process.

[0025] The functions of each element in the outer ring of the Sendzimir support roll backing bearing of the present invention in the alloy are as follows:

[0026] C: The C element is an important carbide-forming element in the outer ring of the backing bearing. The C content needs to match the alloy content. With a suitable C content, an appropriate amount of primary and secondary carbides can be formed in the matrix, ensuring the strength and hardness of the outer ring of the backing bearing, and increasing wear resistance and fatigue resistance. The test results show that in the outer ring of the backing bearing, when C < 0.8 wt.%, the alloying elements in the matrix cannot fully play their roles, and fewer carbides are difficult to ensure the mechanical properties of the outer ring of the support roll backing bearing; when C > 1.25 wt.%, M3C-type carbides will precipitate in the matrix, resulting in an increased overheating tendency of the matrix and a decrease in toughness; therefore, the C content satisfies 0.8 - 1.25 wt.%.

[0027] Si: Si is an indispensable reducing agent and deoxidizing element in the melting process. The research results show that Si can dissolve into austenite to improve the tensile strength and elastic limit of the matrix, improve the oxidation resistance of the matrix, and reduce the appearance of annular marks on the roll surface of the support roll after use. However, when the Si content is excessive, it will reduce the hardenability of the matrix. Therefore, the content of the Si element is controlled at 0.6 - 0.9 wt.%.

[0028] Mn: To control costs, in the present invention, low-cost Mn is used to replace the precious metal Ni, which is a rare resource in our country; at the same time, the Mn element can improve the strength and toughness of the matrix, help to form a uniform structure, and is easy to combine with harmful elements such as S and O to form MnS, reducing the harmful effects of S and O. The test results show that when Mn > 0.25 wt.%, the Mn element is infinitely soluble in Fe, which can not only dissolve into the matrix but also exist in the form of carbides, improving the strength of the matrix and reducing the risk of fracture and spalling of the outer ring of the support roll backing bearing during cold rolling; however, when Mn > 0.45 wt.%, it will significantly lower the Ms point, increase the content of retained austenite in the outer ring of the support roll backing bearing after quenching, and increase the risk of roll breakage; therefore, the content of Mn is controlled at 0.25 - 0.45 wt.%.

[0029] Cr: The Cr element is a strong carbide - forming element. Part of it can be dissolved in the carbide, and most of it is dissolved in the matrix, playing a role in solid - solution strengthening. At the same time, it can improve the hardenability, tempering hardness and oxidation resistance of the outer ring of the back - up roll bearing. It can also improve the corrosion resistance and wear resistance of the bearing steel. However, when the Cr content is too large, it affects the hot plasticity of the matrix. Experimental studies have shown that when Cr > 1.6 wt.%, the corrosion resistance and wear resistance continuously increase with the increase of the content; when Cr > 2.8 wt.%, the excessive Cr content will significantly increase the brittle - transition temperature of the outer ring of the back - up roll bearing and promote the temper brittleness of the outer ring of the back - up roll bearing. Therefore, the Cr content is controlled at 1.6 - 2.8 wt.%.

[0030] Mo: Mo is also a strong carbide - forming element. It can improve the stability of austenite and the hardenability of the matrix, and prevent the second - type temper brittleness. The experimental results show that in the present invention, when the Mo content is controlled at 0.30 - 0.55 wt.%, better results can be obtained. The formed M6C - type carbide can improve the stability of MC - type carbide and the temper - resistance stability of the matrix, and can inhibit the generation of thermal cracks during the use of the back - up roll bearing; in the formed M7C3 - type carbide, it plays a role in dispersion strengthening for others. The ratio of Mo element used to form M6C - type carbide and M7C3 - type carbide is 1:(1.2 - 1.5), which can effectively improve the hardness, wear resistance and service life. In addition, about 15 - 25% is dissolved in the matrix, significantly improving the hardenability of the material.

[0031] W: Compared with the working layer of the traditional back - up roll, the W element is added in the present invention. The purpose is to increase the wear resistance and service life of the working layer through W. Because W is a typical solid - solution strengthening element, it can reduce the stacking - fault energy and diffusion coefficient of the alloy, slow down the high - temperature diffusion rate of Cr, etc., strengthen the atomic binding force in the solid solution and slow down the softening rate. The operating temperature of Sendzimir back - up roll is 900 - 1200 °C. Utilizing the combined effect of W and Mo, when the operating temperature < 1000 °C, the influence of Mo on the thermal crack resistance and plasticity of the back - up roll is better than that of W; but when the operating temperature > 1000 °C, the solid - solution strengthening effect of W is better; but when W > 0.5%, more precipitation phases will reduce the thermal crack resistance of the matrix;

[0032] V: Compared with the working layer of the back - up roll, the V element is added in the present invention, increasing the V element which is a stable - type carbide - forming element MC; V can strengthen the matrix through precipitation strengthening and carbide dispersion strengthening, obtaining higher high - temperature strength and toughness; a large number of experimental research results show that the mass percentage of V needs to be controlled between 0.1 - 0.3%.

[0033] Re: During the smelting stage, to reduce the contents of O and S and the inclusion content, a small amount of rare earth elements is added. The research results show that when the content is 0.15 - 0.58%, the contents of O and S are low, and at the same time, the distribution of rare earth elements can be detected at the grain boundaries, which plays a role in pinning and preventing grain boundary migration. Therefore, adding rare earth elements can play a role in refining grains.

[0034] Advantages of the present invention:

[0035] By improving the comprehensive ingredient ratio and adjusting the heat treatment process, the present invention has achieved an overall improvement in the mechanical properties of the outer ring of the backup roll backing bearing at normal temperature and high temperature. In particular, the high-temperature strength and toughness and the thermal crack resistance have been greatly improved, the service life has been effectively extended, the problems of fracture during use, short service life, and frequent roll surface spalling have been solved, the production efficiency has been improved, and the production cost has been reduced. Specific embodiments

[0036] To better understand the above technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with embodiments.

[0037] The present invention researches and develops an outer ring of a Sendzimir backup roll backing bearing. Based on high-carbon bearing steel, according to the types and mechanical properties of currently rolled ultra-thin high-strength silicon steel, the mechanical property indexes of the backing bearing are reset, and its composition and structure are optimized. At the same time, from the perspective of saving manufacturing costs, the preparation process of the backing bearing is formulated. First, analyze the failure mechanism of the existing backing bearing, including a detailed analysis of the currently used material, microstructure, and mechanical properties of the failed outer ring of the backing bearing, and master the mechanical property level of the existing material; at the same time, analyze the failure mechanism of the backing bearing, master the failure principle, and formulate targeted improvement measures; the original material of the outer ring of the backup roll backing bearing is high-carbon bearing steel GCr18Mo (its chemical composition is C: 0.95 - 1.05 wt.%, Si: 0.15 - 0.35 wt.%, Mn: 0.25 - 0.45 wt.%, Cr: 1.40 - 1.65 wt.%, Mo: 0.08 - 0.15 wt.%), and the hardness is 58 - 60 HRC. On the basis of GCr18Mo, the present invention designs and optimizes its chemical composition and heat treatment process to further improve its wear resistance and fatigue resistance, and determines that the hardness requirement of the outer ring of the backup roll is HRC60 - 62 according to the service conditions and mechanical property requirements of the backing bearing.

[0038] A back-up bearing outer ring for Sendzimir support rolls provided by the present invention comprises the following components by weight percentage: C: 0.8 - 1.25%, Si: 0.60 - 0.90%, Mn: 0.25 - 0.45%, P < 0.008%, S < 0.005%, Cr: 1.6 - 2.8%, Mo: 0.30 - 0.55%, W: 0.20 - 0.5%, V: 0.10 - 0.30%, Re: 0.15 - 0.58%, and the balance is Fe and unavoidable impurities.

[0039] Among them, the hardness of the back-up bearing outer ring for Sendzimir support rolls at room temperature is HRC 60 - 62, and the hardness at 600 °C is HRC ≥ 55.

[0040] The tensile strength of the back-up bearing outer ring for Sendzimir support rolls at room temperature is 980 - 1200 MPa, and the impact energy A KV2 is 4.5 - 5.2 J; at 600 °C, the tensile strength ≥ 610 MPa.

[0041] The preparation method of the above-mentioned back-up bearing outer ring for Sendzimir support rolls specifically includes melting, continuous casting, forging, heat treatment, and cold working processes; that is, after the composition ratio of the back-up bearing outer ring for Sendzimir support rolls, the outer ring blank is obtained through melting, continuous casting, and forging, then heat treatment is carried out, and finally the back-up bearing outer ring for Sendzimir support rolls is obtained through cold working processes.

[0042] Among them, the heat treatment process includes the following steps:

[0043] S1, quenching and tempering heat treatment, the outer ring blank obtained by forging is heated to 980 - 1020 °C after two soaking treatments, held in the furnace for 2.5 - 3.5 h, then slowly cooled in the furnace to 280 - 380 °C, and then taken out of the furnace and air-cooled to room temperature;

[0044] Specifically, the outer ring blank obtained by forging is heated to 980 - 1020 °C after two soaking treatments and held in the furnace for 2.5 - 3.5 h. This process also has the effect of high-temperature diffusion treatment, reducing the banded distribution of carbides in the blank; then slowly cooled in the furnace to 280 - 380 °C, and then taken out of the furnace and air-cooled to room temperature.

[0045] Among them, the two soaking treatment processes are as follows:

[0046] S11, the first soaking heat preservation, the outer ring blank is heated to 600 ± 10 °C at a heating rate of 200 - 230 °C / h, and the first soaking heat preservation treatment is carried out at 600 ± 10 °C for 8 - 10 min;

[0047] S12. Secondary temperature equalization and heat preservation: The outer ring blank is continuously heated at a heating rate of 200 - 230 °C / h to 800 ± 10 °C, and a secondary temperature equalization and heat preservation treatment is carried out at 800 ± 10 °C for 8 - 10 min.

[0048] S2. Quenching treatment: The outer ring blank after quenching and tempering heat treatment is continuously heated to 1080 - 1180 °C for quenching and held for 80 - 90 min, then cooled in the furnace, and tempering treatment is carried out within 2 - 3 h;

[0049] Specifically, the outer ring blank after quenching and tempering heat treatment is continuously heated to 1080 - 1180 °C for quenching and held for 80 - 90 min, then cooled in the furnace. During the furnace cooling process, the outer ring blank after quenching and heat preservation is cooled in the furnace to 850 - 980 °C and held for 20 - 30 min, then cooled by blowing nitrogen, the cooling rate is controlled at 4.5 - 5.5 °C / s. After cooling to below 300 °C, it is taken out of the furnace and air-cooled to room temperature. Tempering treatment is carried out within 2 - 3 h after the quenching treatment.

[0050] S3. Tempering treatment: The outer ring blank is heated at a heating rate of 200 - 230 °C / h to 480 - 550 °C, held for 120 - 180 min, cooled in the furnace to 190 - 210 °C, and taken out of the furnace and air-cooled to room temperature; the tempering treatment is repeated 2 - 3 times.

[0051] After heat treatment, the tensile strength R of the outer ring of the backup roll bearing at room temperature m is 980 - 1200 MPa, the impact energy is A KV2 is 4.5 - 5.2 J, and the hardness HRC is 60 - 62.

[0052] Cold processing technology: The present invention optimizes the cold processing technology and adopts a special grinding processing technology to ensure the accuracy stability of the outer ring of the back-up bearing. By adjusting grinding process parameters such as the grinding wheel speed, workpiece speed, feed rate, number of grinding passes, and carriage moving speed, the relationship between the roll surface roughness and each parameter is studied, and the rationality of the matching of grinding parameters is explored. After processing, inspection is carried out to verify the rationality of the parameters, and no burns on the surface of the backup roll back-up bearing are achieved.

[0053] Cold processing process parameters: The cold processing grinding wheel speed is 450 - 580 r / min, the workpiece speed is 40 - 68 r / min, the feed rate is 0.03 - 0.07 mm, the number of grinding passes is 4 - 8 times, and the carriage moving speed is 38 - 86 mm / s.

[0054] Magnetic particle flaw detection is used before and after the cold processing technology to ensure that no microcracks appear on the outer ring of the Sendzimir backup roll back-up bearing; dimensional accuracy is detected to ensure that each dimension of the backup roll meets the use requirements.

[0055] The outer ring of the back-up bearing of Sendzimir support roll of the present invention has a hardness of HRC 60 - 62 at room temperature, a tensile strength R m of 980 - 1200 MPa, and an impact energy A KV2 of 4.5 - 5.2 J; at 600 °C, the hardness HRC ≥ 55, and the tensile strength R m ≥ 610 MPa.

[0056] Example 1

[0057] This example provides an outer ring of a back-up bearing of Sendzimir support roll and its preparation method:

[0058] (1) The outer ring of the back-up bearing of Sendzimir support roll comprises the following components by weight percentage: C: 1.20%, Si: 0.80%, Mn: 0.3%, P: 0.007%, S: 0.005%, Cr: 2.5%, Mo: 0.45%, W: 0.35%, V: 0.20%, Re: 0.23%, and the balance is Fe and inevitable impurities.

[0059] (2) According to the component ratio of the outer ring of the back-up bearing of Sendzimir support roll, the outer ring blank is obtained through melting, continuous casting billet and forging;

[0060] (3) Heat treatment

[0061] Quenching and tempering heat treatment: The outer ring blank is heated to 1000 °C after two equalizing treatments and subjected to soaking treatment for 3 h. This step also has the function of high-temperature diffusion treatment to reduce the banded distribution of carbides in the blank; then it is slowly cooled in the furnace to 280 °C, and then taken out of the furnace and air-cooled to room temperature. Two equalizing treatments: For the first equalizing treatment, the outer ring blank is heated at a heating rate of 200 °C / h and subjected to equalizing soaking treatment for 10 min at 610 °C; for the second equalizing treatment, the outer ring blank is continuously heated at a heating rate of 200 °C / h and subjected to equalizing soaking treatment for 10 min at 810 °C.

[0062] Quenching treatment: The outer ring blank after quenching and tempering heat treatment is continuously heated to 1100 °C for quenching and soaked for 90 min, then cooled in the furnace to 900 °C, soaked for 30 min, and then cooled by blowing nitrogen, controlling the cooling rate at 5.5 °C / s. After cooling to below 300 °C, it is taken out of the furnace and air-cooled to room temperature, and then tempered within 2.5 h.

[0063] Tempering treatment: The outer ring blank after quenching treatment is heated at a heating rate of 200 °C / h, then soaked at a tempering temperature of 550 °C for 150 min, cooled in the furnace to 210 °C, and taken out of the furnace and air-cooled to room temperature; the tempering treatment is repeated 3 times.

[0064] Through the design of the material and heat treatment process of the backup roll, the tensile strength R of the outer ring of the backup roll bearing in this embodiment at room temperature m is 1080 MPa, and the impact energy is A KV2 is 4.8 J, and the hardness HRC is 61.

[0065] (4) Cold working process: A special grinding process is used to ensure the accuracy stability of the outer ring of the backing bearing. Adjust the grinding process parameters such as the grinding wheel speed, workpiece speed, feed rate, number of grinding passes, and carriage movement speed: the grinding wheel speed is 560 r / min, the workpiece speed is 68 r / min, the feed rate is 0.07 mm, the number of grinding passes is 6 times, and the carriage movement speed is 75 mm / s; after processing, check to ensure that the surface of the outer ring of the backup roll bearing is not burned.

[0066] (5) Detection of the outer ring of the backup roll backing bearing: Magnetic particle flaw detection is used before and after cold working to ensure that no microcracks appear; the dimensional accuracy is detected to ensure that each dimension of the backup roll meets the usage requirements.

[0067] The mechanical properties at room temperature and high temperature of the outer ring of the backup roll backing bearing prepared in this embodiment are shown in Table 1. That is, at room temperature, the tensile strength R m is 1180 MPa, the impact energy A KV2 is 4.52 J, the hardness HBC is 60. At a high temperature of 600 °C, the tensile strength R m is 780 MPa, and the hardness HBC is 56;

[0068] The single rolling kilometer number of the backup roll using the outer ring of the backup roll backing bearing in this embodiment is 12800 km.

[0069] Example 2

[0070] This embodiment provides a Sendzimir backup roll backing bearing outer ring and a preparation method thereof:

[0071] (1) The Sendzimir backup roll backing bearing outer ring includes the following components by weight percentage: C: 1.25%, Si: 0.90%, Mn: 0.35%, P: 0.004%, S: 0.003%, Cr: 2.8%, Mo: 0.55%, W: 0.5%, V: 0.30%, Re: 0.58%, and the balance is Fe and other inevitable impurities.

[0072] (2) According to the component ratio of the Sendzimir backup roll backing bearing outer ring, the outer ring blank is obtained through melting, continuous casting billet, and forging;

[0073] (3) Heat treatment

[0074] Quenching and tempering heat treatment: The outer ring blank is heated to 1020 °C after two equalizing treatments, and is kept in the furnace for 2.5 h. This step also has the effect of high-temperature diffusion treatment, reducing the banded distribution of carbides in the blank; then it is slowly cooled in the furnace to 380 °C, and then taken out of the furnace and air-cooled to room temperature. Two equalizing treatments: The first equalizing treatment, the outer ring blank is heated at a heating rate of 230 °C / h, and is kept at 590 °C for 8 min for equalizing heat preservation; the second equalizing treatment, the outer ring blank is continuously heated at a heating rate of 230 °C / h, and is kept at 790 °C for 8 min for equalizing heat preservation.

[0075] Quenching treatment: The outer ring blank after quenching and tempering heat treatment is continuously heated to 1180 °C for quenching and kept for 80 min, then cooled in the furnace to 980 °C, kept for 30 min, and then cooled by blowing nitrogen, controlling the cooling rate at 4.5 °C / s. After cooling to below 300 °C, it is taken out of the furnace and air-cooled to room temperature, and then tempered within 3 h.

[0076] Tempering treatment: The outer ring blank after quenching treatment is heated at a heating rate of 230 °C / h, then kept at a tempering temperature of 480 °C for 180 min, cooled in the furnace to 190 °C, and taken out of the furnace and air-cooled to room temperature; the tempering treatment is repeated 2 times.

[0077] Through the design of the material and heat treatment process of the backup roll, the tensile strength R of the outer ring of the backup roll bearing in this embodiment at room temperature m is 1132 MPa, the impact energy is A KV2 is 4.8 J, and the hardness HRC is 61.5.

[0078] (4) Cold working process: Adopt a special grinding process to ensure the accuracy stability of the outer ring of the backup bearing. Adjust the grinding process parameters such as the grinding wheel speed, workpiece speed, feed rate, number of grinding passes, and carriage moving speed: the grinding wheel speed is 580 r / min, the workpiece speed is 50 r / min, the feed rate is 0.05 mm, the number of grinding passes is 4 times, and the carriage moving speed is 86 mm / s; after processing, check to ensure that the surface of the outer ring of the backup roll bearing is not burned.

[0079] (5) Detection of the outer ring of the backup roll bearing: Use magnetic particle inspection before and after cold working to ensure that there are no microcracks; detect the dimensional accuracy to ensure that each dimension of the backup roll meets the use requirements.

[0080] The mechanical properties at room temperature and high temperature of the outer ring of the backup roll bearing prepared in this embodiment are shown in Table 1, that is, at room temperature, the tensile strength R m is 1132 MPa, the impact energy A KV2 is 4.8 J, the hardness HBC is 61.5, and at 600 °C high temperature, the tensile strength R m is 57 MPa, and the hardness HBC is 796;

[0081] The single-rolling kilometer number of the backup roll with the backup roll back-up bearing outer ring of this embodiment is 15,000 km.

[0082] Embodiment 3

[0083] This embodiment provides a Sendzimir backup roll back-up bearing outer ring and a preparation method thereof:

[0084] (1) The Sendzimir backup roll back-up bearing outer ring comprises the following components by weight percentage: C: 1.25%, Si: 0.90%, Mn: 0.25%, P: 0.005%, S: 0.004%, Cr: 1.6%, Mo: 0.30%, W: 0.2%, V: 0.10%, Re: 0.15%, and the balance is Fe and other inevitable impurities.

[0085] (2) According to the component ratio of the Sendzimir backup roll back-up bearing outer ring, an outer ring blank is obtained through melting, continuous casting billet, and forging;

[0086] (3) Heat treatment

[0087] Quenching and tempering heat treatment: The outer ring blank is heated to 980 °C after two equalizing treatments and subjected to furnace holding treatment for 3.5 h. This step also has the effect of high-temperature diffusion treatment to reduce the banded distribution of carbides in the blank; then it is slowly cooled in the furnace to 280 °C, and then taken out of the furnace and air-cooled to room temperature. Two equalizing treatments: The first equalizing treatment, the outer ring blank is heated at a heating rate of 200 °C / h and subjected to equalizing holding treatment for 9 min at 600 °C; the second equalizing treatment, the outer ring blank is continuously heated at a heating rate of 200 °C / h and subjected to equalizing holding treatment for 8 min at 800 °C.

[0088] Quenching treatment: The outer ring blank after quenching and tempering heat treatment is continuously heated to 1080 °C for quenching and held for 90 min, then cooled in the furnace to 850 °C, held for 20 min, and then cooled by blowing nitrogen, controlling the cooling rate at 4.0 °C / s. After cooling to below 300 °C, it is taken out of the furnace and air-cooled to room temperature, and then tempered within 2 h.

[0089] Tempering treatment: The outer ring blank after quenching treatment is heated at a heating rate of 200 °C / h, then held at a tempering temperature of 500 °C for 120 min, cooled in the furnace to 210 °C, and taken out of the furnace and air-cooled to room temperature; the tempering treatment is repeated 2 times.

[0090] Through the design of the backup roll material and heat treatment process, the tensile strength R of the backup roll bearing outer ring in this embodiment at room temperature m is 1125 MPa, and the impact energy A KV2 is 5.2 J, and the hardness HBC is 61.

[0091] (4) Cold working process: A special grinding process is adopted to ensure the precision stability of the outer ring of the backup roll bearing. Adjust the grinding process parameters such as the grinding wheel speed, workpiece speed, feed rate, number of grinding passes, and carriage moving speed: the grinding wheel speed is 450 r / min, the workpiece speed is 40 r / min, the feed rate is 0.03 mm, the number of grinding passes is 8 times, and the carriage moving speed is 38 mm / s; After processing, check to ensure that the surface of the outer ring of the backup roll bearing is not burned.

[0092] (5) Detection of the outer ring of the backup roll bearing: Magnetic particle flaw detection is carried out before and after cold working to ensure that no microcracks appear; Detect the dimensional accuracy to ensure that each dimension of the backup roll meets the usage requirements.

[0093] The mechanical properties at room temperature and high temperature of the outer ring of the backup roll bearing prepared in this embodiment are shown in Table 1, that is, at room temperature, the tensile strength R m is 1125 MPa, and the impact energy A KV2 is 5.2 J, and the hardness HBC is 61. At a high temperature of 600 °C, the tensile strength R m is 793 MPa, and the hardness HBC is 58;

[0094] The single rolling mileage of the backup roll using the outer ring of the backup roll bearing in this embodiment is 13,600 km.

[0095] Table 1 Performance of the outer ring of the backup roll bearing prepared in Examples 1-3

[0096]

[0097] Combined with Table 1, compared with the original material GCr18Mo, the mechanical properties at room temperature and high temperature of the Sendzimir backup roll bearing outer ring prepared in the embodiments of the present invention have been comprehensively improved. In particular, its high-temperature strength and toughness and thermal crack resistance have been greatly improved, and the service life has been effectively extended; The tensile strength at room temperature of the Sendzimir backup roll bearing outer ring prepared in the embodiments of the present invention is 1125-1200 MPa, and the impact energy A KV2 is 4.5-5.2 J, and the hardness HRC is 60-62; At 600 °C, the hardness HRC ≥ 55, and the tensile strength ≥ 780 MPa. When used on the backup roll, the single rolling mileage far exceeds that of the original material GCr18Mo.

[0098] In summary, through the analysis of the quality and failure mechanism of the existing failed outer ring of the backing bearing, and on the basis of GCr18Mo, the present invention optimizes the composition and preparation process of the outer ring of the backing bearing, further improves its wear resistance and fatigue resistance, accelerates the pace of improving the green manufacturing of the outer ring of the backing bearing for supporting rolls used by various steel enterprises, achieves the purpose of further reducing costs and increasing the rolling tonnage, supports the cost transformation and high-quality product strategy of steel enterprises, and has good prospects for popularization and application.

[0099] Those of ordinary skill in the art in this technical field should recognize that the above embodiments are only used to illustrate the present invention, rather than to limit the present invention. As long as within the scope of the substantial spirit of the present invention, changes and modifications to the above-described embodiments will fall within the scope of the claims of the present invention.

Claims

1. A back-up bearing outer ring for Sendzimir support roll, characterized in that: It includes the following components by weight percentage: C: 0.8 - 1.25%, Si: 0.60 - 0.90%, Mn: 0.25 - 0.45%, P ≤ 0.008%, S ≤ 0.005%, Cr: 1.6 - 2.8%, Mo: 0.30 - 0.55%, W: 0.20 - 0.5%, V: 0.10 - 0.30%, Re: 0.15 - 0.58%, and the balance is Fe and other inevitable impurities.

2. The back-up bearing outer ring for Sendzimir support roll according to claim 1, characterized in that: The hardness HRC of the outer ring of the Sendzimir backup roll backing bearing at room temperature is 60 - 62, the tensile strength ≥ 950 Mpa, the hardness HRC ≥ 55 at 600 °C, and the tensile strength ≥ 610 MPa.

3. The back-up bearing outer ring for Sendzimir support roll according to claim 1, characterized in that: The tensile strength of the outer ring of the Sendzimir backup roll's backing bearing at room temperature is 980 - 1200 MPa, and the impact energy A KV2 is 4.5 - 5.2 J.

4. A preparation method for the back-up bearing outer ring for Sendzimir support roll according to any one of claims 1-3, characterized in that: It includes smelting, continuous casting billet, forging, heat treatment, and cold working processes; The heat treatment process includes the following steps: S1, quenching and tempering heat treatment. Heat the outer ring blank obtained by forging to 980 - 1020 °C after two equalizing treatments, keep it warm in the furnace for 2.5 - 3.5 h, then slowly cool it in the furnace to 280 - 380 °C, and then take it out of the furnace and air cool it to room temperature; S2, quenching treatment. Continuously heat the outer ring blank after quenching and tempering heat treatment to 1080 - 1180 °C for quenching and keep it warm for 80 - 90 min, then cool it in the furnace, and carry out tempering treatment within 2 - 3 h; S3, tempering treatment. Heat the outer ring blank to 480 - 550 °C, keep it warm for 120 - 180 min, cool it in the furnace to 190 - 210 °C, take it out of the furnace and air cool it to room temperature; the tempering treatment is repeated 2 - 3 times.

5. The preparation method for the back-up bearing outer ring for Sendzimir support roll according to claim 4, characterized in that: In the step S1, the process of the two equalizing treatments is as follows: S11, primary equalizing heat preservation. Heat the outer ring blank at a heating rate of 200 - 230 °C / h to 600 ± 10 °C for 8 - 10 min of primary equalizing heat preservation treatment; S12, secondary equalizing heat preservation. Continue to heat it at a heating rate of 200 - 230 °C / h to 800 ± 10 °C for 8 - 10 min of secondary equalizing heat preservation treatment.

6. The preparation method for the back-up bearing outer ring for Sendzimir support roll according to claim 4, characterized in that: In the step S2, during the process of cooling in the furnace, after quenching and heat preservation, the outer ring blank is cooled in the furnace to 850 - 980 °C and kept warm for 20 - 30 min, then cooled by blowing nitrogen, and the cooling rate is controlled at 4.5 - 5.5 °C / s. After cooling to below 300 °C, take it out of the furnace and air cool it to room temperature.

7. The preparation method for the back-up bearing outer ring for Sendzimir support roll according to claim 4, characterized in that: In the step S3, the heating rate during the tempering treatment process is 200 - 230 °C / h.

8. The preparation method for the back-up bearing outer ring for Sendzimir support roll according to claim 4, characterized in that: The cold working process adopts a grinding process, with the grinding wheel speed of 450 - 580 r / min, the workpiece speed of 40 - 68 r / min, the feed rate of 0.03 - 0.07 mm, the number of grinding passes of 4 - 8 times, and the carriage moving speed of 38 - 86 mm / s.

9. The preparation method for the back-up bearing outer ring for Sendzimir support roll according to claim 4, characterized in that: Before and after the cold working process, the outer ring of the backup roll backing bearing is detected by magnetic particle flaw detection.

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