Universal mill vertical roll ring and method of manufacturing the same

Abstract

This invention relates to the field of rolling mill technology, and more particularly to a universal rolling mill vertical roll ring and its preparation method. The outer layer comprises alloy ductile iron, the chemical composition of which, by weight percentage, is: C: 2.7-3.2%, Si: 1.3-2.0%, Mn: 0.7-1.0%, Cr: 1.5-2.5%, Mo: 1.5-2.5%, V: 0.3-0.6%, Ti: 0.1-0.3%, Ni: 2.0-3.0%, Mg: 0.07-0.12%, with the remainder being Fe and unavoidable impurities. The inner layer is high-strength ductile iron. By adding appropriate amounts of wear-resistant metals to the ductile iron, dispersed wear-resistant phases such as Mo2C, VC, and TiC are obtained. Through high-temperature quenching and tempering treatment, uniformly distributed Fe3C-type carbides, dispersed wear-resistant alloy carbides, spheroidal graphite, and martensitic structure are obtained. Compared to semi-steel, the wear-resistant phase structure is significantly increased, greatly improving wear resistance. It also has self-cooling capabilities, effectively reducing steel adhesion and improving the surface quality of the rolled material. Compared to high-speed steel, it has a lower alloy content, lower casting and heat treatment stress, and does not require the formation of a surface oxide film, reducing cooling requirements during use.

Description

Technical Field

[0001] This invention relates to the field of rolling mill technology, and in particular to a universal rolling mill vertical roll ring and its preparation method. Background Technology

[0002] Currently, most vertical roll rings used in universal rolling mills both domestically and internationally are made of high-carbon semi-steel centrifugal roll rings. However, their wear resistance is insufficient for operational requirements, leading to frequent roll changes and a tendency for steel to stick to the surface, affecting the surface quality of the rolled product. Some manufacturers have introduced high-speed steel vertical roll rings, whose wear resistance can reach 3-4 times that of high-carbon semi-steel. However, these rings have high operational requirements, necessitating a good cooling environment and the formation of a wear-resistant oxygen film on the surface to achieve good wear resistance. The complex structure of universal rolling mills makes it difficult to fully meet cooling needs, introducing instability into the use of high-speed steel vertical roll rings. Furthermore, the high production cost, long production cycle, and low yield of high-speed steel also hinder product development. Therefore, the market urgently needs a low-cost, high-quality vertical roll ring. Summary of the Invention

[0003] To address the technical problems in the prior art, this invention provides a universal rolling mill vertical roll ring and its preparation method.

[0004] The technical solution adopted by this invention to solve its technical problem is: a universal rolling mill vertical roll ring, comprising an outer layer, wherein the outer layer comprises alloy ductile iron, and the chemical composition and weight percentage of the alloy ductile iron are: C: 2.7-3.2%, Si: 1.3-2.0%, Mn: 0.7-1.0%, Cr: 1.5-2.5%, Mo: 1.5-2.5%, V: 0.3-0.6%, Ti: 0.1-0.3%, Ni: 2.0-3.0%, Mg: 0.07-0.12%, with the remainder being Fe and unavoidable impurities; and an inner layer, wherein the inner layer is high-strength ductile iron; the alloy ductile iron is subjected to high-temperature quenching and tempering treatment to obtain uniformly distributed Fe3C type carbides and dispersed wear-resistant alloy carbides, spheroidal graphite, and martensitic structure.

[0005] The universal mill vertical roll ring of this invention obtains dispersed wear-resistant phases such as Mo2C, VC, and TiC by adding appropriate amounts of wear-resistant metals Cr, Mo, V, and Ti to ductile iron. Through high-temperature quenching and tempering, it yields uniformly distributed island-like or blocky Fe3C-type carbides, dispersed wear-resistant alloy carbides, spheroidal graphite, and martensitic structure. Compared to semi-steel materials, the wear-resistant phase structure is significantly increased, significantly improving wear resistance. The presence of spheroidal graphite provides self-cooling capability during use, effectively reducing steel adhesion and improving the surface quality of the rolled material. Compared to high-speed steel materials, it has a lower alloy content, lower casting and heat treatment stress, and lower production costs. It does not require the formation of a surface oxide film during use, reducing cooling requirements.

[0006] Furthermore, the surface hardness of the universal rolling mill vertical roller ring is HSD65-75, the hardness difference within a radial 80mm is less than HSD3, and its wear resistance is 2-3 times that of the centrifugal semi-steel roller ring.

[0007] A preparation method based on the above-mentioned universal mill vertical roll ring includes the following steps:

[0008] S1, casting centrifugal roller;

[0009] S2. Cut the centrifugal roller into roller rings according to the length requirements;

[0010] S3. Heat the cut roller ring to 900-950 degrees Celsius and keep it at that temperature for 6-10 hours.

[0011] S4. Cool the roller ring to 400-480 degrees Celsius;

[0012] S5. The roller ring undergoes a tempering and slow cooling heat treatment process at 450-550 degrees Celsius, and then is cooled to room temperature.

[0013] S6. Processing completed.

[0014] Furthermore, in step S1, when casting the centrifugal rollers, two medium-frequency furnaces are used to melt the outer and inner layers of molten iron respectively. When the chemical composition in each furnace meets the requirements, spheroidizing inoculation treatment is carried out. The outer and inner layers of centrifugal rollers are cast at a specified temperature and time, and then the outer and inner layers are metallurgically bonded.

[0015] Furthermore, in step S3, during heating, the cut roller ring is placed in an electric resistance furnace and heated to 380-400℃. After averaging for 3-5 hours, the temperature is raised to 700-750℃ and averaged for 3-5 hours. Then, the temperature is raised to 900-950℃ and averaged for 6-10 hours.

[0016] Furthermore, in step S3, the temperature is increased at a uniform rate of 10°C per hour to 380-400°C, at a rate of 20°C per hour to 700-750°C, and at a rate of 40°C per hour to 900-950°C.

[0017] Furthermore, in step S4, during the cooling of the roller ring, it is first air-cooled to 720-770°C, and then spray-cooled to 400-480°C using water as the medium.

[0018] Furthermore, in step S5, during the tempering and slow cooling heat treatment, the roller ring is first heated at 400-480℃ for 3-5 hours, then heated to 450-500℃ at a rate of 10℃ per hour, and heated for 30-40 hours, before being cooled to room temperature in the furnace.

[0019] Furthermore, in step S5, after tempering and slow cooling heat treatment, the roller ring is heated to 350-400°C at a rate of 25°C per hour, and the temperature is uniformly maintained for 10-15 hours before being cooled to room temperature in the furnace.

[0020] Furthermore, in step S1, after both the inner and outer layers have completely solidified, the centrifugal roller is placed inside an insulation cover to cool to room temperature. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Figure 1 This is a schematic diagram illustrating the structure of the inner and outer layers of the vertical roll ring of the universal rolling mill in this invention.

[0023] In the diagram: 1. Outer layer; 2. Inner layer. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0025] In a first aspect, the present invention discloses a universal rolling mill vertical roll ring.

[0026] A universal rolling mill vertical roll ring includes an outer layer 1 and an inner layer 2, which are metallurgically bonded together. The outer layer 1 is made of alloy ductile iron, with the following chemical composition and weight percentages: C: 2.7-3.2%, Si: 1.3-2.0%, Mn: 0.7-1.0%, Cr: 1.5-2.5%, Mo: 1.5-2.5%, V: 0.3-0.6%, Ti: 0.1-0.3%, Ni: 2.0-3.0%, Mg: 0.07-0.12%, with the remainder being Fe and unavoidable impurities. The inner layer 2 is made of high-strength ductile iron. The alloy ductile iron is subjected to high-temperature quenching and tempering treatment to obtain a uniformly distributed Fe3C type carbide and a dispersed distribution of wear-resistant alloy carbides, spheroidal graphite, and martensitic structure. By adding appropriate amounts of wear-resistant metals Cr, Mo, V, and Ti to the outer layer 1, dispersed wear-resistant phases such as Mo2C, VC, and TiC are obtained. Through high-temperature quenching and tempering, uniformly distributed island-like or blocky Fe3C-type carbides, dispersed wear-resistant alloy carbides, spheroidal graphite, and martensitic structure are obtained, thus giving the outer layer 1 high hardness and wear resistance. The inner layer 2, on the other hand, uses high-strength ductile iron, ensuring basic strength and hardness while saving costs.

[0027] The surface hardness of the universal rolling mill vertical roller ring obtained by the above formula through quenching and tempering is HSD65-75, the hardness difference within a radial 80mm is less than HSD3, and the wear resistance is 2-3 times that of the centrifugal semi-steel roller ring. The wear resistance is the ratio of the steel throughput of the vertical roller ring of this application to that of the example semi-steel roller ring in a single groove, and the steel throughput is derived from production data.

[0028] Working Principle: By adding appropriate amounts of wear-resistant metals such as Cr, Mo, V, and Ti to ductile iron, dispersed wear-resistant phases such as Mo2C, VC, and TiC are obtained. Through high-temperature quenching and tempering, uniformly distributed island-like or blocky Fe3C-type carbides, dispersed wear-resistant alloy carbides, spheroidal graphite, and martensitic structure are obtained. Compared with semi-steel materials, the wear-resistant phase structure is significantly increased, significantly improving wear resistance. The presence of spheroidal graphite provides self-cooling capability during use, effectively reducing steel adhesion and improving the surface quality of the rolled material. Compared with high-speed steel materials, the alloy content is lower, casting and heat treatment stress is smaller, and production costs are lower. No surface oxide film formation is required during use, reducing cooling requirements.

[0029] Secondly, this application discloses a preparation method.

[0030] One preparation method includes the following steps:

[0031] S1. Use two medium-frequency furnaces to melt the molten iron of outer layer 1 and inner layer 2 respectively. When the chemical composition in each furnace meets the requirements, perform spheroidizing inoculation treatment. Cast the centrifugal rollers of outer layer 1 and inner layer 2 at the specified temperature and time. Outer layer 1 and inner layer 2 are metallurgically bonded. After the centrifugal rollers are completely solidified, place them in a heat preservation cover to cool slowly to room temperature.

[0032] S2. According to the length requirements and external dimensions of the vertical roller ring, the centrifugal roller is cut on a lathe to obtain the roller ring.

[0033] S3. Quenching: The cut roll ring is placed in an electric resistance furnace and heated to 380-400℃ at a uniform rate of 10℃ per hour. After averaging for 3-5 hours, the temperature is increased to 700-750℃ at a rate of 20℃ per hour and averaged for 3-5 hours. Finally, the temperature is increased to 900-950℃ at a rate of 40℃ per hour and averaged for 6-10 hours to obtain austenite. By heating slowly and uniformly, the roll ring is heated evenly. Then, through staged heat preservation, the overall temperature of the roll ring rises evenly.

[0034] S4. Remove the roller ring and air-cool it to 720-770℃. During the slow cooling process, stress concentration is reduced. Then, use water as a medium for spray cooling to 400-480℃. This spray cooling achieves rapid cooling and yields a martensitic structure.

[0035] S5. Tempering: Immerse at 400-480℃ for 3-5 hours, then increase the temperature to 450-500℃ at a rate of 10℃ per hour, immerse for 30-40 hours, and cool to room temperature in the furnace. Then increase the temperature to 350-400℃ at a rate of 25℃ per hour, immerse for 10-15 hours, and cool to room temperature in the furnace. Through two tempering processes and prolonged holding, the martensitic structure is fully transformed.

[0036] S6. Processing and shaping.

[0037] Example 1

[0038] A vertical roller ring with a diameter of Ф550 / 305×220 was prepared, where 550 is the outer diameter of the outer layer 1, 305 is the inner diameter of the inner layer 2, and 220 is the length of the vertical roller ring. The chemical composition (weight percentage) of the outer layer 1 is as follows: C: 3.15%, Si: 1.32%, Mn: 0.73%, Cr: 1.62%, Mo: 1.73%, V: 0.44%, Ti: 0.22%, Ni: 2.42%, Mg: 0.07%, with the remainder being Fe and unavoidable impurities. The inner layer 2 is made of high-strength ductile iron.

[0039] S1. Use two medium-frequency furnaces to melt the molten iron of outer layer 1 and inner layer 2 respectively. When the chemical composition in each furnace meets the requirements (i.e., when the chemical composition in outer layer 1 reaches the corresponding percentage), perform spheroidizing inoculation treatment, and then cast centrifugal rollers of outer layer 1 and inner layer 2. Outer layer 1 and inner layer 2 are metallurgically bonded. After the centrifugal rollers are completely solidified, they are placed in a heat preservation cover to cool slowly to room temperature.

[0040] S2. According to the length requirements and external dimensions of the vertical roller ring, the centrifugal roller is cut on a lathe to obtain the roller ring.

[0041] S3. Quenching: The cut roller ring is placed in a resistance furnace and heated to 390°C at a uniform rate of 10°C per hour. After averaging for 3.5 hours, it is heated to 720°C at a rate of 20°C per hour and averaged for 4 hours. Finally, it is heated to 925°C at a rate of 40°C per hour and averaged for 8 hours.

[0042] S4. Remove the roller ring, rotate and air cool to 745℃, then spray with water as the medium to cool to 460℃.

[0043] S5. Tempering: Isostatically heat at 460℃ for 4 hours, then increase the temperature to 477℃ at a rate of 10℃ per hour, oscillate at the same temperature for 36 hours, and then cool to room temperature in the furnace. Alternatively, increase the temperature to 380℃ at a rate of 25℃ per hour, oscillate at the same temperature for 14 hours, and then cool to room temperature in the furnace.

[0044] S6. Processing and shaping.

[0045] Example 2

[0046] A vertical roller ring with a diameter of Ф740 / 456×285 was prepared, where 740 is the outer diameter of the outer layer 1, 456 is the inner diameter of the inner layer 2, and 285 is the length of the vertical roller ring. The chemical composition percentage of the outer layer 1 is: C: 2.95%, Si: 1.35%, Mn: 0.77%, Cr: 1.66%, Mo: 1.75%, V: 0.47%, Ti: 0.25%, Ni: 2.41%, Mg: 0.08%, with the remainder being Fe and unavoidable impurities. The inner layer 2 is made of high-strength ductile iron.

[0047] S1. Use two medium-frequency furnaces to melt the molten iron of outer layer 1 and inner layer 2 respectively. When the chemical composition in each furnace meets the requirements, perform spheroidizing inoculation treatment. Cast the centrifugal rollers of outer layer 1 and inner layer 2 at the specified temperature and time. Outer layer 1 and inner layer 2 are metallurgically bonded. After the centrifugal rollers are completely solidified, place them in a heat preservation cover to cool slowly to room temperature.

[0048] S2. According to the length requirements and external dimensions of the vertical roller ring, the centrifugal roller is cut on a lathe to obtain the roller ring.

[0049] S3. Quenching: The cut roller ring is placed in a resistance furnace and heated to 395°C at a uniform rate of 10°C per hour. After averaging for 3.5 hours, it is heated to 725°C at a rate of 20°C per hour and averaged for 4 hours. Finally, it is heated to 935°C at a rate of 40°C per hour and averaged for 8 hours.

[0050] S4. Remove the roller ring, rotate and air cool to 755℃, then spray with water as the medium to cool to 465℃.

[0051] S5. Tempering: Isostatically heat at 465℃ for 5 hours, then increase the temperature to 479℃ at a rate of 10℃ per hour, oscillate at the same temperature for 38 hours, and cool to room temperature in the furnace. Then increase the temperature to 385℃ at a rate of 25℃ per hour, oscillate at the same temperature for 14 hours, and cool to room temperature in the furnace.

[0052] S6. Processing and shaping.

[0053] A vertical roller ring with a diameter of Ф925 / 535×390 was prepared, where 925 is the outer diameter of the outer layer 1, 535 is the inner diameter of the inner layer 2, and 390 is the length of the vertical roller ring. The chemical composition percentage of the outer layer 1 is: C: 3.17%, Si: 1.34%, Mn: 0.79%, Cr: 1.67%, Mo: 1.73%, V: 0.45%, Ti: 0.23%, Ni: 2.46%, Mg: 0.07%, with the remainder being Fe and unavoidable impurities. The inner layer 2 is made of high-strength ductile iron.

[0054] S1. Use two medium-frequency furnaces to melt the molten iron of outer layer 1 and inner layer 2 respectively. When the chemical composition in each furnace meets the requirements, perform spheroidizing inoculation treatment. Cast the centrifugal rollers of outer layer 1 and inner layer 2 at the specified temperature and time. Outer layer 1 and inner layer 2 are metallurgically bonded. After the centrifugal rollers are completely solidified, place them in a heat preservation cover to cool slowly to room temperature.

[0055] S2. According to the length requirements and external dimensions of the vertical roller ring, the centrifugal roller is cut on a lathe to obtain the roller ring.

[0056] S3. Quenching: The cut roller ring is placed in a resistance furnace and heated to 395°C at a uniform rate of 10°C per hour. After averaging for 4.3 hours, it is heated to 730°C at a rate of 20°C per hour and averaged for 4.5 hours. Then, it is heated to 930°C at a rate of 40°C per hour and averaged for 7 hours.

[0057] S4. Remove the roller ring, rotate and air cool to 730°C, then spray with water as the medium to cool to 455°C.

[0058] S5. Tempering: Isostatically heat at 455℃ for 4.5 hours, then increase the temperature to 479℃ at a rate of 10℃ per hour, oscillate at the same temperature for 36 hours, and cool to room temperature in the furnace. Then increase the temperature to 385℃ at a rate of 25℃ per hour, oscillate at the same temperature for 13 hours, and cool to room temperature in the furnace.

[0059] S6. Processing and shaping.

[0060] The data from the experiment are summarized in Table 1.

[0061]

[0062] Table 1

[0063] Through experiments and actual production, it was found that the vertical roller ring of this application has a larger single-slot steel throughput compared to the centrifugal semi-steel roller ring when the size is larger, which means that it has better wear resistance and is more suitable for the production of large-size products.

[0064] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a vertical roll ring for a universal rolling mill, characterized in that, include The outer layer (1) comprises alloy ductile iron, the chemical composition and weight percentage of which are: C: 2.7-3.2%, Si: 1.3-2.0%, Mn: 0.7-1.0%, Cr: 1.5-2.5%, Mo: 1.5-2.5%, V: 0.3-0.6%, Ti: 0.1-0.3%, Ni: 2.0-3.0%, Mg: 0.07-0.12%, with the remainder being Fe and unavoidable impurities; Inner layer (2), wherein the inner layer (2) is high-strength ductile iron; The alloy ductile iron is subjected to high-temperature quenching and tempering treatment to obtain uniformly distributed Fe3C type carbides and dispersed wear-resistant alloy carbides, spheroidal graphite, and martensitic structure. Includes the following steps: S1, casting centrifugal roller; S2. Cut the centrifugal roller into roller rings according to the length requirements; S3. Quench the cut roller ring. During quenching, heat the roller ring to 900-950 degrees Celsius and hold for 6-10 hours. S4. Then the roller ring is cooled to 400-480 degrees Celsius; S5. Then, the roller ring is tempered. During the tempering process, the roller ring is heated to 450-550 degrees Celsius and then cooled to room temperature. S6. Processing completed; In step S3, during heating, the cut roller ring is placed in an electric resistance furnace and heated to 380-400℃. After averaging for 3-5 hours, the temperature is raised to 700-750℃ and averaged for 3-5 hours. Then, the temperature is raised to 900-950℃ and averaged for 6-10 hours. In step S4, when the roller ring is cooled, it is first air-cooled to 720-770℃, and then spray-cooled to 400-480℃ using water as the medium. In step S5, during the tempering process, the roller ring is first heated at 400-480℃ for 3-5 hours, then heated to 450-500℃ at a rate of 10℃ per hour, and heated for 30-40 hours, before being cooled to room temperature in the furnace.

2. The method for preparing the vertical roll ring of a universal rolling mill as described in claim 1, characterized in that, The surface hardness of the universal mill vertical roll ring is HSD65-75, the hardness difference within 80mm radially is less than HSD3, and its wear resistance is 2-3 times that of the centrifugal semi-steel roll ring.

3. The method for preparing the vertical roll ring of a universal rolling mill according to claim 1, characterized in that, In step S1, when casting the centrifugal rollers, two medium-frequency furnaces are used to melt the molten iron of the outer layer (1) and the inner layer (2) respectively. When the chemical composition in each furnace meets the requirements, spheroidization inoculation treatment is carried out. The centrifugal rollers of the outer layer (1) and the inner layer (2) are cast at the specified temperature and time. Then the outer layer (1) and the inner layer (2) are metallurgically bonded.

4. The method for preparing the vertical roll ring of a universal rolling mill as described in claim 1, characterized in that, In step S3, the temperature is increased at a constant rate of 10°C per hour to 380-400°C, at a rate of 20°C per hour to 700-750°C, and at a rate of 40°C per hour to 900-950°C.

5. The method for preparing the vertical roll ring of a universal rolling mill as described in claim 1, characterized in that, In step S5, after tempering and slow cooling heat treatment, the roller ring is heated to 350-400°C at a rate of 25°C per hour, and the temperature is uniform for 10-15 hours before being cooled to room temperature in the furnace.

6. The method for preparing the vertical roll ring of a universal rolling mill as described in claim 4, characterized in that, In step S1, after both the inner layer (2) and the outer layer (1) have completely solidified, the centrifugal roller is placed in the heat insulation cover and cooled to room temperature.

7. A universal rolling mill vertical roll ring, characterized in that, The universal mill vertical roll ring is prepared according to the preparation method of any one of claims 1-6.

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