High-alloy steel straightening centrifugal roller ring and production method thereof

Abstract

This invention belongs to the field of metallurgical technology and relates to a high-alloy steel straightening centrifugal roller ring and its production method. The outer layer of the roller ring is made of high-alloy cast steel, and the inner layer is made of graphite steel. A centrifugal composite casting process is employed, including centrifugal cold-casting coating application, molten metal smelting and modification treatment, centrifugal casting, pit insulation, and heat treatment. The working outer layer of this invention fully utilizes the characteristics of chromium, tungsten, niobium, and cobalt alloy carbides, giving it high hardness and high wear resistance. Through specific centrifugal process technology, while ensuring good bonding between the working outer and inner layers, the content of high-alloy elements penetrating from the centrifugal outer layer into the inner layer is strictly limited to avoid quality defects such as cracks. A quenching + four-stage tempering process ensures that the roller ring has high quenching hardness and effectively eliminates internal stress, preventing cracks or even explosions caused by high stress from alloy elements. The steel throughput of this roller ring can be increased by 1 to 2 times.

Description

Technical Field

[0001] This invention relates to a high-alloy steel straightening centrifugal roller ring and its production method, belonging to the technical field of high-alloy steel straightening centrifugal roller ring production process in the metallurgical industry. Background Technology

[0002] Against the backdrop of cost reduction and efficiency improvement in the steel industry, the steel throughput requirements put forward by section steel rolling enterprises are gradually increasing. Commonly used materials can no longer meet the ever-increasing steel throughput requirements of section steel production lines. It is necessary to re-optimize the chemical composition of the outer working layer of the straightening centrifugal roller ring to improve its hardness and wear resistance.

[0003] Chromium in steel can form hexagonal Cr7C3 eutectic compounds with carbon, which are mostly distributed in isolated blocks or chrysanthemum-like patterns. These carbides have high microhardness and form a wear-resistant structure with martensite, exhibiting good wear resistance and toughness. To fully utilize the high hardness of Cr7C3 eutectic compounds, a reasonable chromium-to-carbon ratio should be determined in the composition design of straightening centrifugal roller rings to ensure a sufficient content of Cr7C3 eutectic compounds in the matrix.

[0004] Tungsten dissolves in the matrix to form high-hardness carbides, which can effectively prevent precipitation during tempering. Due to the large atomic radius and high elastic modulus of tungsten, it interacts with dislocations, segregates on dislocation lines, locks the dislocations, making them difficult to move, and has a significant solid solution strengthening effect.

[0005] Niobium is characterized by refining primary grains, thereby refining eutectic carbides and improving the distribution of primary carbides. It can also increase the recrystallization temperature of austenite, thus achieving the purpose of refining austenite grains and acting as an inoculant.

[0006] Cobalt, as an alloying element with significant high-temperature hardness and improved secondary hardness, can increase the nucleation rate of secondary carbides and reduce their growth rate during tempering, promote the precipitation of secondary carbides in martensite, refine its grains, and thus increase secondary hardness.

[0007] By fully utilizing the properties of chromium, tungsten, niobium, and cobalt alloying elements and through reasonable composition design, a high-alloy steel straightening centrifugal roller ring has been developed. This gives the outer layer high hardness and high wear resistance, further increasing the steel throughput of the straightening centrifugal roller ring. On the other hand, due to the high hardness requirements and significant post-production stress of the straightening centrifugal roller ring, a high-strength and high-toughness material must be added internally using a centrifugal composite method to resist the stress of the working outer layer. Since the outer layer needs to be fused with the inner layer, an appropriate centrifugation time must be determined. If the centrifugation time is too long, poor bonding between the outer and inner layers will occur, resulting in severe quality defects such as slag inclusions in the centrifuged layer, leading to the scrapping of the roller ring. However, if the centrifugation time is too short, the erosion of the outer layer will increase. The high-alloying elements in the outer layer will penetrate into the inner layer and combine with the carbon elements in the inner layer, easily forming highly brittle alloy carbides. This will cause the inner layer to fail in strength and toughness, unable to withstand the stress of the outer layer, and cracks will appear during solidification, heat treatment, and even machining of the inner hole keyway, resulting in scrapping.

[0008] In summary, due to the high requirements and difficulty in producing straightening rollers, it is necessary to develop a new type of high-alloy centrifugal straightening roller ring to improve its hardness and wear resistance, and to reduce the amount of high-alloy material penetrating from the outer layer into the inner layer and eliminate internal stress through centrifugal processing technology while ensuring good bonding between the outer and inner layers. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a high-alloy steel straightening centrifugal roller ring with high hardness and high wear resistance, and also to provide a method for producing the high-alloy steel straightening centrifugal roller ring.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0011] A high-alloy steel straightening centrifugal roller ring is composed of a two-layer centrifugal composite structure, with the outer layer of the roller ring made of high-alloy cast steel and the inner layer of the roller ring made of graphite steel.

[0012] The high-alloy steel straightening centrifugal roller ring described above has the following chemical composition and mass percentage of its outer high-alloy cast steel material: C: 0.70–0.80%, Si: 0.60–0.80%, Mn: ≤0.6%, P ≤0.030%, S ≤0.020%, Ni: 1.10–1.30%, Cr: 19.7–19.9%, W: 4.50–4.70%, Nb: 30%W–40%W, Co: 5.20–5%. 40%, with the balance being iron and unavoidable impurities; the chemical composition and mass percentage of the graphite steel material in the inner layer of the roller ring are as follows: C: 1.30~1.50%, Si: 1.80~2.00%, Mn: 0.40~0.60%, P≤0.030%, S≤0.020%, Ni: 0.20~0.40%, Cr≤0.02%, W≤0.02%, Nb≤0.02%, Co≤0.02%, with the balance being iron and unavoidable impurities.

[0013] As described above, for the high-alloy steel straightening centrifugal roller ring, after the roller ring cools and solidifies, the composition and mass percentage of the alloy chemical composition that penetrates from the outer layer into the inner layer must meet the following requirements: Cr≤0.30%, W≤0.15%, Nb≤0.10%, Co≤0.20%, and Cr+W+Nb+Co≤0.40%. The purpose is to prevent the high-alloy elements from forming alloy carbides with the carbon elements in the inner layer, which would increase the brittleness of the inner layer, reduce its strength, and easily cause cracks in the roller ring.

[0014] The high-alloy steel straightening centrifugal roller ring described above requires the inner layer thickness to meet the following formula to prevent the inner layer thickness from being too thin and resulting in insufficient strength.

[0015] δ≥0.09*(ab)

[0016] In the formula:

[0017] δ – Finished inner layer thickness of the roller ring, in mm;

[0018] a – Finished outer diameter of the roller ring, in mm;

[0019] b – Finished inner diameter of the roller ring, in mm;

[0020] A method for producing high-alloy steel straightening centrifugal roller rings, employing a centrifugal composite casting process, and controlled according to the following requirements:

[0021] A. Roller coating of centrifugal cooling coatings

[0022] During roller coating, the cold temperature is controlled at 300-340℃, the centrifuge speed is initially 200r / min, and after the coating is completely poured into the roller mold, the speed is quickly increased to 480r / min, and the coating layer thickness is 3.5-4.5mm.

[0023] The coating formula is as follows: quartz powder dry material, sodium bentonite at 8% by weight of quartz powder dry material, aluminum dihydrogen phosphate at 8% by weight of quartz powder dry material, and water at 30% by weight of quartz powder dry material.

[0024] B. Metal molten smelting

[0025] According to the composition of the roller ring, the outer layer of high alloy cast steel molten steel and the inner layer of graphite steel molten steel are smelted in a medium frequency induction furnace.

[0026] C. Metal molten metal smelting and alteration treatment

[0027] The outer and inner layers are smelted in two separate medium-frequency furnaces. First, steel is added and smelted, then alloy components are added. When adding the materials, two-thirds of the niobium alloy needs to be placed at the bottom of the medium-frequency furnace, with a particle size of 10mm to 30mm. The remaining one-third is added when the liquid temperature in the medium-frequency furnace reaches above 1580℃, with a particle size of 2mm to 5mm. After the outer layer of metal and alloy materials in the medium-frequency furnace are completely melted, crushed glass is added to the surface of the molten iron to prevent oxidation, at a rate of 6kg to 8kg per ton of molten metal.

[0028] Before the outer layer of molten steel is tapped, 0.1% to 0.3% silicon-zirconium alloy, 0.1% to 0.3% ferromanganese, and 0.3% to 0.5% cerium are added to the ladle.

[0029] After the inner metal material is completely melted, broken glass is added to the surface of the molten steel to prevent oxidation. The amount added is 6-8 kg per ton of molten steel. Before tapping, 0.4%-0.6% silicon-zirconium alloy, 0.1%-0.3% silicon-calcium alloy, and 0.7%-0.9% cerium are added to the bottom of the ladle according to the amount of molten steel.

[0030] D. Centrifugal casting

[0031] ①After the chemical composition of the molten steel in each of the medium-frequency furnaces for melting the outer and inner layers is qualified, centrifugal casting is carried out;

[0032] ② When centrifugally casting, the cold mold temperature requirement is 180~200℃. The first pour of the outer layer of molten steel should be 1520~1540℃ when exiting the furnace and 1450~1470℃ when pouring. After pouring, an interface protectant should be added to the inner cavity of the cold mold immediately.

[0033] ③ When the centrifugation time of the outer layer reaches the interval, pour the inner layer of molten steel. The furnace exit temperature is 1580~1600℃, and the pouring temperature is 1500~1520℃. After the molten steel is poured, immediately add an interface protectant to the inner cavity of the cold mold.

[0034] ④ When the centrifugation time reaches the total operating time, stop the centrifuge from rotating;

[0035] E. Pit insulation

[0036] After the centrifuge stops, the cold mold is hoisted into the pit and covered with an insulation cover. When the inner surface temperature of the inner layer reaches 600-700℃, the insulation cover is removed. When the inner surface temperature of the inner layer reaches 500-550℃, it is placed in an annealing furnace for annealing heat treatment.

[0037] F. Heat Treatment

[0038] The blank is first fully annealed, then rough-machined according to the rough turning drawings, and then subjected to a quenching + four-time tempering heat treatment process.

[0039] G. Processing: After heat treatment, the rolls are processed according to the precision machining drawings, and then put into storage after passing inspection.

[0040] As described above, in the production method of high alloy steel straightening centrifugal roller ring, the interface protective agent is "O" type glass slag, borax, and sodium carbonate. The amount of "O" type glass slag added is 7kg to 8kg per square meter of cold-formed inner surface. The amount of borax added accounts for 40% of the amount of "O" type glass slag used, and the amount of sodium carbonate added accounts for 15% of the amount of "O" type glass slag used.

[0041] As described above, in the production method of high alloy steel straightening centrifugal roller rings, the casting interval T between the outer and inner layers... i Calculate using the following formula:

[0042]

[0043] In the formula: T i - The time interval between the completion of the outer layer pouring and the start of the inner layer pouring, in minutes;

[0044] D – Outer diameter of the blank, in meters;

[0045] d – Outer layer design casting diameter, in meters;

[0046] L – Width of blank, in meters.

[0047] As described above, in the production method of high alloy steel straightening centrifugal roller rings, the total centrifugal operation time T c Calculate using the following formula:

[0048]

[0049] In the formula: T c - Total centrifugal operation time, in minutes;

[0050] D – Outer diameter of the blank, in meters;

[0051] q – Inner diameter of the blank, in meters;

[0052] L – Width of blank, in meters.

[0053] When the centrifugation time reaches T c Stop the centrifuge when the time comes.

[0054] As described above, the production method of high alloy steel straightening centrifugal roller rings includes the following process: the heat treatment furnace is preheated to 495-505℃ before the roller rings are placed into the furnace. After the roller rings are hot-removed and placed into the annealing furnace, they are held at this temperature for 4-4.2 hours. Then, the temperature is increased to 640-650℃ at a rate of 10-20℃ / h and held for 8-8.2 hours. Next, the temperature is increased to 885-895℃ at a rate of 15-25℃ / h and held for 24-24.5 hours. Then, the temperature is controlled to cool to 670-680℃ at a rate of 10-15℃ / h and held for 20-20.5 hours. Finally, the temperature is cooled with the furnace at a rate of 5-20℃ / h to 80-100℃, and the furnace door is opened to a depth of 0.6 meters. The roller rings are removed from the furnace when their surface temperature is 30-50℃.

[0055] As described above, the production method of high-alloy steel straightening centrifugal roller rings includes a quenching and four-times tempering process after rough machining. The rough-machined roller ring is first heated at 5–8℃ / h to 200–210℃ and held for 5–5.2 hours. Then, it is heated at 8–12℃ / h to 340–350℃ and held for 6–6.2 hours. Next, it is heated at 10–15℃ / h to 650–660℃ and held for 10–10.2 hours. Then, it is heated at 20–25℃ / h to 980–990℃ and held for 15–15.5 hours. Afterward, it is mist-cooled to 540–550℃ for 10–15 minutes, then air-cooled to 450–460℃ for approximately 15–25 minutes and held for 2–2.2 hours. Finally, it undergoes four tempering processes. The first tempering involves heating at 10–15℃ / h to 505–515℃ and holding for 15–10 minutes. 5.5h, cool in the furnace at 5-15℃ / h to 120-130℃, hold for 1-1.2h, second tempering, heat up to 505-515℃ at 10-15℃ / h, hold for 20-20.5h, cool in the furnace at 5-15℃ / h to 120-130℃, hold for 2-2.2h, third tempering, heat up to 525-535℃ at 10-15℃ / h, hold... The furnace is heated to 35–35.5 h, then cooled in the furnace at 5–15 h to 80–90 h, and held for 2–2.2 h. In the fourth tempering, the temperature is increased to 500–510 h at 10–15 h, and held for 30–30.5 h. Finally, the temperature is increased to 70–80 h at 5–15 h, and held for 10–10.2 h. The furnace door is then opened 0.4 meters, and the roll ring is removed from the furnace when its surface temperature is 20–40 h. The purpose of this four-stage tempering process is to eliminate the significant internal stress caused by the high alloy content in the roll ring.

[0056] The beneficial effects of this invention are as follows: This invention fully utilizes the characteristics of chromium, tungsten, niobium, and cobalt alloy carbides, giving them high hardness and high wear resistance. Compared to ordinary Cr12MoV centrifugal straightening roller rings, its steel throughput can be increased by 1 to 2 times, meeting the high steel throughput requirements of section steel production lines. This invention adopts centrifugal composite casting production. The working layer is made of high-alloy cast steel, and the inner layer is made of graphite steel. Through specific centrifugal process technology, while ensuring good bonding quality between the outer and inner working layers, the high alloy element content penetrating from the outer layer into the inner layer is strictly limited, avoiding quality defects such as cracks and improving the yield. The quenching + four-stage tempering process ensures that the roller ring has high quenching hardness and effectively eliminates internal stress, preventing cracks or even explosions caused by high stress from alloy elements. Attached Figure Description

[0057] Figure 1 This is a process diagram for full annealing heat treatment;

[0058] Figure 2 This is a process diagram for quenching followed by four tempering processes. Detailed Implementation

[0059] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0060] Example 1

[0061] In this embodiment, the finished product specifications (outer circle / inner circle) of the high alloy steel straightening centrifugal roller ring are Φ795 / Φ330, and the blank specifications are Φ840*1080. The structure is a two-layer centrifugal composite structure. The outer layer is made of high alloy cast steel, and the inner layer is made of graphite steel. The chemical composition and mass percentage of each layer are shown in Table 1 and Table 2.

[0062] The production process of high-alloy steel straightening centrifugal roller rings in this embodiment also includes the following process steps:

[0063] (1) Iron and steel molten metal transformation process: 7t and 3t medium frequency induction furnaces are used to melt the outer layer of iron and the inner layer of steel respectively.

[0064] Before the outer layer of molten steel is tapped, 0.2% silicon-zirconium alloy, 0.1% ferromanganese, and 0.3% cerium are added to the ladle.

[0065] Before the inner layer of molten steel is tapped, 0.6% silicon-zirconium alloy, 0.3% silicon-calcium alloy, and 0.8% cerium are added to the bottom of the ladle.

[0066] (2) Centrifugal casting process: The temperature of the cold mold is controlled at 193℃ during the centrifugal casting of the outer layer. The first casting of the outer layer of molten steel is at a casting temperature of 1464℃. When the centrifugal time of the outer layer reaches the interval time of 55 minutes, the inner layer of molten steel is cast at a casting temperature of 1505℃. When the centrifugal time reaches the total running time of 178 minutes, the centrifuge is stopped.

[0067] (3) Heat treatment process:

[0068] After the centrifuge stops, the cooled roll is hoisted into the pit and covered with an insulation cover. When the inner surface temperature reaches 625℃, the insulation cover is removed. When the inner surface temperature reaches 542℃, the roll is placed in an annealing furnace for annealing heat treatment. Before the roll ring enters the furnace, the heat treatment furnace is preheated to 500℃. After the roll ring is hot-removed and placed in the annealing furnace, it is held at that temperature for 4 hours. Then, the temperature is increased to 644℃ at a rate of 15℃ / h and held for 8.2 hours. Then, the temperature is increased to 888℃ at a rate of 15℃ / h and held for 24.2 hours. Then, the temperature is controlled to cool to 680℃ at a rate of 13℃ / h and held for 20.3 hours. Finally, the temperature is cooled to 100℃ with the furnace at a rate of 15℃ / h, and the furnace door is opened 0.6 meters. The roll ring is removed from the furnace when its surface temperature reaches 44℃.

[0069] After annealing, rough machining is performed according to the drawings. Following this, quenching and four tempering heat treatments are applied. The rough-machined roller ring is first heated to 200℃ at 7℃ / h and held for 5.1h, then heated to 340℃ at 8℃ / h and held for 6h, then heated to 654℃ at 11℃ / h and held for 10.2h, then heated to 980℃ at 22℃ / h and held for 15.2h. It is then mist-cooled to 543℃ for 12 minutes, followed by air-cooling to 455℃ for approximately 15 minutes and held for 2.1h. Finally, four tempering treatments are performed. The first tempering is heated to 507℃ at 12℃ / h and held for... The heat treatment process involves several steps: 15.2 hours of initial heating, followed by furnace cooling at 7℃ / h to 125℃ and holding for 1.1 hours; a second tempering process with the temperature increased to 508℃ at 13℃ / h and held for 20.4 hours; a third tempering process with the temperature increased to 528℃ at 13℃ / h and held for 35.3 hours; a fourth tempering process with the temperature increased to 85℃ at 8℃ / h and held for 2.1 hours; a fifth tempering process with the temperature increased to 505℃ at 10℃ / h and held for 30.2 hours; and finally, a final tempering process with the temperature increased to 75℃ at 8℃ / h and held for 10 hours. The furnace door is then opened 0.4 meters, and the roller ring is removed from the furnace when its surface temperature reaches 25℃. After heat treatment, the roller ring undergoes precision machining and is then inspected and stored.

[0070] The hardness of the alloy roller ring in this embodiment is shown in Table 3, the ultrasonic test results of the bonding layer are shown in Table 4, and the chemical composition and mass percentage of the inner layer material after the roller ring cools and solidifies are shown in Table 5.

[0071] Example 2

[0072] In this embodiment, the finished product specifications (outer circle / inner circle) of the high alloy steel straightening centrifugal roller ring are Φ800 / Φ360, and the blank specifications are Φ840*950. The structure is a two-layer centrifugal composite structure. The outer layer is made of high alloy cast steel, and the inner layer is made of graphite steel. The chemical composition and mass percentage of each layer are shown in Table 1 and Table 2.

[0073] The production process of high-alloy steel straightening centrifugal roller rings in this embodiment also includes the following process steps:

[0074] (1) Iron and steel molten metal transformation process: 7t and 3t medium frequency induction furnaces are used to melt the outer layer of iron and the inner layer of steel respectively.

[0075] Before the outer layer of molten steel is tapped, 0.3% silicon-zirconium alloy, 0.2% ferromanganese, and 0.5% cerium are added to the ladle.

[0076] Before the inner layer of molten steel is tapped, 0.5% silicon-zirconium alloy, 0.2% silicon-calcium alloy, and 0.7% cerium are added to the bottom of the ladle.

[0077] (2) Centrifugal casting process: The cold mold temperature is controlled at 190℃ during the centrifugal casting of the outer layer. The first casting of the outer layer of molten steel is at a casting temperature of 1453℃. When the centrifugal time of the outer layer reaches the interval time of 52 minutes, the inner layer of molten steel is cast at a casting temperature of 1510℃. When the centrifugal time reaches the total running time of 170 minutes, the centrifuge is stopped.

[0078] (3) Heat treatment process:

[0079] After the centrifuge stops, the cooled roll is lowered into the pit and covered with an insulation cover. When the inner surface temperature reaches 644℃, the insulation cover is removed. When the inner surface temperature reaches 500℃, the roll is placed in an annealing furnace for annealing heat treatment. Before the roll ring enters the furnace, the heat treatment furnace is preheated to 498℃. After the roll ring is hot-removed and placed in the annealing furnace, it is held at that temperature for 4.2 hours. Then, the temperature is increased to 640℃ at a rate of 18℃ / hour and held for 8.1 hours. Then, the temperature is increased to 895℃ at a rate of 25℃ / hour and held for 24.3 hours. Then, the temperature is controlled to cool to 674℃ at a rate of 10℃ / hour and held for 20.1 hours. Finally, the temperature is cooled to 88℃ with the furnace at a rate of 18℃ / hour. The furnace door is then opened 0.6 meters. The roll ring is removed from the furnace when its surface temperature reaches 48℃.

[0080] After annealing, rough machining is performed according to the drawings. Following this, quenching and four tempering heat treatments are applied. The rough-machined roller ring is first heated to 204℃ at 5℃ / h and held for 5.2h, then heated to 348℃ at 10℃ / h and held for 6.2h, then heated to 658℃ at 13℃ / h and held for 10h, then heated to 985℃ at 20℃ / h and held for 15h. It is then mist-cooled to 540℃ for 10 minutes, followed by air-cooling to 460℃ for approximately 21 minutes and held for 2.2h. Finally, four tempering treatments are performed. The first tempering is heated to 509℃ at 10℃ / h and held for 1 hour. The heat treatment process involves several steps: First, the temperature is increased to 128°C at a rate of 14°C / h and held for 1.2 hours. Second, the temperature is increased to 506°C at a rate of 11°C / h and held for 20.2 hours. Then, the temperature is reduced to 128°C at a rate of 15°C / h and held for 2.1 hours. Third, the temperature is increased to 526°C at a rate of 10°C / h and held for 35 hours. Then, the temperature is reduced to 90°C at a rate of 9°C / h and held for 2 hours. Fourth, the temperature is increased to 510°C at a rate of 15°C / h and held for 30 hours. Finally, the temperature is increased to 76°C at a rate of 5°C / h and held for 10.2 hours. The furnace door is then opened 0.4 meters, and the roller ring is removed from the furnace when its surface temperature reaches 29°C. After heat treatment, the roller ring undergoes precision machining and is then inspected and stored.

[0081] The hardness of the alloy roller ring in this embodiment is shown in Table 3, the ultrasonic test results of the bonding layer are shown in Table 4, and the chemical composition and mass percentage of the inner layer material after the roller ring cools and solidifies are shown in Table 5.

[0082] Example 3

[0083] In this embodiment, the finished product specifications (outer circle / inner circle) of the high alloy steel straightening centrifugal roller ring are Φ890 / Φ400, and the blank specifications are Φ945*650. The structure is a two-layer centrifugal composite structure. The outer layer is made of high alloy cast steel, and the inner layer is made of graphite steel. The chemical composition and mass percentage of each layer are shown in Table 1 and Table 2.

[0084] The production process of high-alloy steel straightening centrifugal roller rings in this embodiment also includes the following process steps:

[0085] (1) Iron and steel molten metal transformation process: 7t and 3t medium frequency induction furnaces are used to melt the outer layer of iron and the inner layer of steel respectively.

[0086] Before the outer layer of molten steel is tapped, 0.1% silicon-zirconium alloy, 0.3% ferromanganese, and 0.4% cerium are added to the ladle.

[0087] Before the inner layer of molten steel is tapped, 0.4% silicon-zirconium alloy, 0.3% silicon-calcium alloy, and 0.9% cerium are added to the bottom of the ladle.

[0088] (2) Centrifugal casting process: The cold mold temperature is controlled at 195℃ during the centrifugal casting of the outer layer. The first pour of the outer layer of molten steel is at a pouring temperature of 1450℃. When the centrifugal time of the outer layer reaches the interval time of 46 minutes, the inner layer of molten steel is poured at a pouring temperature of 1518℃. When the centrifugal time reaches the total running time of 157 minutes, the centrifuge is stopped.

[0089] (3) Heat treatment process:

[0090] After the centrifuge stops, the cooled roll is lowered into the pit and covered with an insulation cover. When the inner surface temperature reaches 600℃, the insulation cover is removed. When the inner surface temperature reaches 534℃, the roll is placed in an annealing furnace for annealing heat treatment. Before the roll ring enters the furnace, the heat treatment furnace is preheated to 503℃. After the roll ring is hot-removed and placed in the annealing furnace, it is held at that temperature for 4.1 hours. Then, the temperature is increased to 650℃ at a rate of 13℃ / h and held for 8 hours. Then, the temperature is increased to 890℃ at a rate of 22℃ / h and held for 24 hours. Then, the temperature is controlled to cool to 670℃ at a rate of 12℃ / h and held for 20 hours. Finally, the temperature is cooled to 93℃ with the furnace at a rate of 9℃ / h. The furnace door is then opened 0.6 meters. The roll ring is removed from the furnace when its surface temperature reaches 30℃.

[0091] After annealing, rough machining is performed according to the drawings. Following this, quenching and four tempering heat treatments are applied. The rough-machined roller ring is first heated to 205℃ at 6℃ / h and held for 5 hours, then heated to 342℃ at 12℃ / h and held for 6.1 hours, then heated to 650℃ at 15℃ / h and held for 10.1 hours, then heated to 990℃ at 23℃ / h and held for 15.3 hours. It is then mist-cooled to 548℃ for 15 minutes, followed by air cooling to 453℃ for approximately 25 minutes and held for 2.1 hours. Finally, it undergoes four tempering treatments. The first tempering involves heating to 513℃ at 15℃ / h and holding for 1 hour. The heat treatment process involves several steps: First, the temperature is increased to 130℃ at a rate of 15℃ / h and held for 1 hour. Second, the temperature is increased to 511℃ at a rate of 10℃ / h and held for 20 hours. Then, the temperature is reduced to 120℃ at a rate of 8℃ / h and held for 2.2 hours. Third, the temperature is increased to 530℃ at a rate of 11℃ / h and held for 35.4 hours. Then, the temperature is reduced to 88℃ at a rate of 5℃ / h and held for 2.2 hours. Fourth, the temperature is increased to 508℃ at a rate of 13℃ / h and held for 30.5 hours. Finally, the temperature is increased to 70℃ at a rate of 12℃ / h and held for 10.1 hours. The furnace door is then opened 0.4 meters, and the roller ring is removed from the furnace when its surface temperature reaches 30℃. After heat treatment, the roller ring undergoes precision machining and is stored after passing inspection.

[0092] The hardness of the alloy roller ring in this embodiment is shown in Table 3, the ultrasonic test results of the bonding layer are shown in Table 4, and the chemical composition and mass percentage of the inner layer material after the roller ring cools and solidifies are shown in Table 5.

[0093] Example 4

[0094] In this embodiment, the finished product specifications (outer circle / inner circle) of the high alloy steel straightening centrifugal roller ring are Φ980 / Φ490, and the blank specifications are Φ1030*750. The structure is a two-layer centrifugal composite structure. The outer layer is made of high alloy cast steel, and the inner layer is made of graphite steel. The chemical composition and mass percentage of each layer are shown in Table 1 and Table 2.

[0095] The production process of high-alloy steel straightening centrifugal roller rings in this embodiment also includes the following process steps:

[0096] (1) Iron and steel molten metal transformation process: 7t and 3t medium frequency induction furnaces are used to melt the outer layer of iron and the inner layer of steel respectively.

[0097] Before the outer layer of molten steel is tapped, 0.3% silicon-zirconium alloy, 0.2% ferromanganese, and 0.5% cerium are added to the ladle.

[0098] Before the inner layer of molten steel is tapped, 0.5% silicon-zirconium alloy, 0.1% silicon-calcium alloy, and 0.8% cerium are added to the bottom of the ladle.

[0099] (2) Centrifugal casting process: The temperature of the cold mold is controlled at 180℃ during the centrifugal casting of the outer layer. The first pour of the outer layer of molten steel is at a pouring temperature of 1467℃. When the centrifugal time of the outer layer reaches the interval time of 52 minutes, the inner layer of molten steel is poured at a pouring temperature of 1500℃. When the centrifugal time reaches the total running time of 155 minutes, the centrifuge is stopped.

[0100] (3) Heat treatment process:

[0101] After the centrifuge stops, the cooled roll is hoisted into the pit and insulated with a heat-insulating cover. When the inner surface temperature reaches 638℃, the heat-insulating cover is removed, and when the inner surface temperature reaches 512℃, it is placed in an annealing furnace for annealing heat treatment. Before the roll ring enters the furnace, the heat treatment furnace is preheated to 501℃. After the roll ring is hot-removed and placed in the annealing furnace, it is held at that temperature for 4.2 hours. Then, the temperature is increased at 20℃ / h to 648℃ and held for 8.2 hours. Then, the temperature is increased at 20℃ / h to 887℃ and held for 24.5 hours. Then, the temperature is controlled to cool down to 672℃ at 15℃ / h and held for 20.4 hours. Finally, the temperature is cooled down to 90℃ with the furnace at 11℃ / h, and the furnace door is opened 0.6 meters. The roll ring is removed from the furnace when its surface temperature reaches 36℃.

[0102] After annealing, rough machining was performed according to the drawings. Following this, a quenching and four-stage tempering heat treatment was conducted. The rough-machined roller ring was first heated to 207℃ at a rate of 7℃ / h and held for 5.2 hours, then heated to 347℃ at a rate of 11℃ / h and held for 6.2 hours, then heated to 660℃ at a rate of 10℃ / h and held for 10 hours, then heated to 982℃ at a rate of 25℃ / h and held for 15.5 hours. It was then mist-cooled to 545℃ for 11 minutes, followed by air cooling to 459℃ for approximately 23 minutes and held for 2 hours. Finally, four tempering treatments were performed. The first tempering was carried out by heating to 515℃ at a rate of 13℃ / h and holding for 15.1 hours. The first tempering involves heating at 5℃ / h to 122℃ and holding for 1.2h. The second tempering involves heating at 12℃ / h to 515℃ and holding for 20.3h, followed by cooling at 9℃ / h to 124℃ and holding for 2.1h. The third tempering involves heating at 12℃ / h to 529℃ and holding for 35.5h, followed by cooling at 12℃ / h to 80℃ and holding for 2.1h. The fourth tempering involves heating at 11℃ / h to 500℃ and holding for 30.1h. Finally, the temperature is increased to 10℃ / h to 77℃ and held for 10.2h. The furnace door is then opened 0.4 meters, and the roll ring is removed from the furnace when its surface temperature reaches 22℃. After heat treatment, the roll ring undergoes precision machining and is stored after passing inspection.

[0103] The hardness of the alloy roller ring in this embodiment is shown in Table 3, the ultrasonic test results of the bonding layer are shown in Table 4, and the chemical composition and mass percentage of the inner layer material after the roller ring cools and solidifies are shown in Table 5.

[0104] Example 5

[0105] In this embodiment, the finished product specifications (outer circle / inner circle) of the high alloy steel straightening centrifugal roller ring are Φ1071 / Φ550, and the blank specifications are Φ1120*820. The structure is a two-layer centrifugal composite structure. The outer layer is made of high alloy cast steel, and the inner layer is made of graphite steel. The chemical composition and mass percentage of each layer are shown in Table 1 and Table 2.

[0106] The production process of high-alloy steel straightening centrifugal roller rings in this embodiment also includes the following process steps:

[0107] (1) Iron and steel molten metal transformation process: 7t and 3t medium frequency induction furnaces are used to melt the outer layer of iron and the inner layer of steel respectively.

[0108] Before the outer layer of molten steel is tapped, 0.2% silicon-zirconium alloy, 0.1% ferromanganese, and 0.3% cerium are added to the ladle.

[0109] Before the inner layer of molten steel is tapped, 0.6% silicon-zirconium alloy, 0.3% silicon-calcium alloy, and 0.9% cerium are added to the bottom of the ladle.

[0110] (2) Centrifugal casting process: The cold mold temperature is controlled at 186℃ during the centrifugal casting of the outer layer. The first casting of the outer layer of molten steel is at a casting temperature of 1460℃. When the centrifugal time of the outer layer reaches the interval time of 57 minutes, the inner layer of molten steel is cast at a casting temperature of 1514℃. When the centrifugal time reaches the total running time of 154 minutes, the centrifuge is stopped.

[0111] (3) Heat treatment process:

[0112] After the centrifuge stops, the cooled roll is hoisted into the pit and insulated with a heat-insulating cover. When the inner surface temperature reaches 700℃, the heat-insulating cover is removed. When the inner surface temperature reaches 550℃, the roll is placed in an annealing furnace for annealing heat treatment. Before the roll ring enters the furnace, the heat treatment furnace is preheated to 495℃. After the roll ring is hot-removed and placed in the annealing furnace, it is held at that temperature for 4.1 hours. Then, the temperature is increased to 645℃ at a rate of 10℃ / hour and held for 8.1 hours. Then, the temperature is increased to 893℃ at a rate of 23℃ / hour and held for 24.1 hours. Then, the temperature is controlled to cool to 678℃ at a rate of 13℃ / hour and held for 20.5 hours. Finally, the temperature is cooled to 95℃ with the furnace at a rate of 13℃ / hour. The furnace door is then opened 0.6 meters. The roll ring is removed from the furnace when its surface temperature reaches 40℃.

[0113] After annealing, rough machining is performed according to the drawings. Following this, quenching and four tempering heat treatments are applied. The rough-machined roller ring is first heated to 210℃ at 8℃ / h and held for 5 hours, then heated to 345℃ at 9℃ / h and held for 6.2 hours, then heated to 655℃ at 12℃ / h and held for 10.2 hours, then heated to 983℃ at 20℃ / h and held for 15.1 hours. It is then mist-cooled to 550℃ for 15 minutes, followed by air cooling to 457℃ for approximately 17 minutes and held for 2.2 hours. Finally, four tempering treatments are performed. The first tempering is heated to 505℃ at 14℃ / h and held for... The heat treatment process involves several steps: 15.3 hours of initial heating; 2. Cooling at 11℃ / h in the furnace to 120℃, holding for 1 hour; 3. Tempering at 14℃ / h to 505℃, holding for 20.5 hours; 4. Cooling at 5℃ / h in the furnace to 125℃, holding for 2 hours; 5. Tempering at 13℃ / h to 535℃, holding for 35.1 hours; 6. Cooling at 10℃ / h in the furnace to 84℃, holding for 2 hours; 7. Tempering at 15℃ / h to 503℃, holding for 30.4 hours; 8. Finally, heating at 7℃ / h to 79℃, holding for 10.1 hours; 9. Opening the furnace door 0.4 meters; 10. Remove the roller ring from the furnace when the surface temperature reaches 20℃. After heat treatment, the roller ring undergoes precision machining and is stored after passing inspection.

[0114] The hardness of the alloy roller ring in this embodiment is shown in Table 3, the ultrasonic test results of the bonding layer are shown in Table 4, and the chemical composition and mass percentage of the inner layer material after the roller ring cools and solidifies are shown in Table 5.

[0115] Example 6

[0116] In this embodiment, the finished product specifications (outer circle / inner circle) of the high alloy steel straightening centrifugal roller ring are Φ1157 / Φ620, and the blank specifications are Φ1210*880. The structure is a two-layer centrifugal composite structure. The outer layer is made of high alloy cast steel, and the inner layer is made of graphite steel. The chemical composition and mass percentage of each layer are shown in Table 1 and Table 2.

[0117] The production process of high-alloy steel straightening centrifugal roller rings in this embodiment also includes the following process steps:

[0118] (1) Iron and steel molten metal transformation process: 7t and 3t medium frequency induction furnaces are used to melt the outer layer of iron and the inner layer of steel respectively.

[0119] Before the outer layer of molten steel is tapped, 0.3% silicon-zirconium alloy, 0.2% ferromanganese, and 0.4% cerium are added to the ladle.

[0120] Before the inner layer of molten steel is tapped, 0.5% silicon-zirconium alloy, 0.2% silicon-calcium alloy, and 0.7% cerium are added to the bottom of the ladle.

[0121] (2) Centrifugal casting process: The cold mold temperature is controlled at 191℃ during the centrifugal casting of the outer layer. The first casting of the outer layer of molten steel is at a casting temperature of 1461℃. When the centrifugal time of the outer layer reaches the interval time of 63 minutes, the inner layer of molten steel is cast at a casting temperature of 1520℃. When the centrifugal time reaches the total running time of 153 minutes, the centrifuge is stopped.

[0122] (3) Heat treatment process:

[0123] After the centrifuge stops, the cooled roll is hoisted into the pit and insulated with a heat-insulating cover. When the inner surface temperature reaches 687℃, the heat-insulating cover is removed. When the inner surface temperature reaches 521℃, the roll is placed in an annealing furnace for annealing heat treatment. Before the roll ring enters the furnace, the heat treatment furnace is preheated to 499℃. After the roll ring is hot-removed and placed in the annealing furnace, it is held at that temperature for 4 hours. Then, the temperature is increased to 642℃ at a rate of 14℃ / h and held for 8 hours. Then, the temperature is increased to 892℃ at a rate of 21℃ / h and held for 24.4 hours. Then, the temperature is controlled to cool to 675℃ at a rate of 11℃ / h and held for 20.2 hours. Finally, the temperature is cooled to 80℃ with the furnace at a rate of 14℃ / h. The furnace door is then opened 0.6 meters. The roll ring is removed from the furnace when its surface temperature reaches 48℃.

[0124] After annealing, rough machining is performed according to the drawings. Following this, quenching and four tempering heat treatments are applied. The rough-machined roller ring is first heated to 203℃ at 6℃ / h and held for 5.1h, then heated to 346℃ at 10℃ / h and held for 6.1h, then heated to 652℃ at 11℃ / h and held for 10.1h, then heated to 985℃ at 23℃ / h and held for 15h. It is then mist-cooled to 546℃ for 10 minutes, followed by air-cooling to 452℃ for approximately 19 minutes and held for 2.1h. Finally, it undergoes four tempering treatments. The first tempering is performed by heating to 510℃ at 11℃ / h and holding for 15 hours. The first tempering involves heating at 10℃ / h to 125℃ and holding for 1.1h. The second tempering involves heating at 15℃ / h to 513℃ and holding for 20.4h, followed by cooling at 8℃ / h to 130℃ and holding for 2.2h. The third tempering involves heating at 14℃ / h to 525℃ and holding for 35.2h, followed by cooling at 15℃ / h to 81℃ and holding for 2.2h. The fourth tempering involves heating at 12℃ / h to 508℃ and holding for 30.5h. Finally, the temperature is increased to 9℃ / h to 80℃ and held for 10h. The furnace door is then opened 0.4 meters, and the roll ring is removed from the furnace when its surface temperature reaches 40℃. After heat treatment, the roll ring undergoes precision machining and is stored after passing inspection.

[0125] The hardness of the alloy roller ring in this embodiment is shown in Table 3, the ultrasonic test results of the bonding layer are shown in Table 4, and the chemical composition and mass percentage of the inner layer material after the roller ring cools and solidifies are shown in Table 5.

[0126] Example 7

[0127] In this embodiment, the finished product specifications (outer circle / inner circle) of the high alloy steel straightening centrifugal roller ring are Φ1244 / Φ650, and the blank specifications are Φ1290*1150. The structure is a two-layer centrifugal composite structure. The outer layer is made of high alloy cast steel, and the inner layer is made of graphite steel. The chemical composition and mass percentage of each layer are shown in Table 1 and Table 2.

[0128] The production process of high-alloy steel straightening centrifugal roller rings in this embodiment also includes the following process steps:

[0129] (1) Iron and steel molten metal transformation process: 7t and 3t medium frequency induction furnaces are used to melt the outer layer of iron and the inner layer of steel respectively.

[0130] Before the outer layer of molten steel is tapped, 0.1% silicon-zirconium alloy, 0.1% ferromanganese, and 0.5% cerium are added to the ladle.

[0131] Before the inner layer of molten steel is tapped, 0.4% silicon-zirconium alloy, 0.3% silicon-calcium alloy, and 0.8% cerium are added to the bottom of the ladle.

[0132] (2) Centrifugal casting process: The temperature of the cold mold is controlled at 200℃ during the centrifugal casting of the outer layer. The first casting of the outer layer of molten steel is at a casting temperature of 1470℃. When the centrifugal time of the outer layer reaches the interval time of 74 minutes, the inner layer of molten steel is cast at a casting temperature of 1504℃. When the centrifugal time reaches the total running time of 157 minutes, the centrifuge is stopped.

[0133] (3) Heat treatment process:

[0134] After the centrifuge stops, the cooled roll is hoisted into the pit and covered with an insulation cover. When the inner surface temperature reaches 650℃, the insulation cover is removed. When the inner surface temperature reaches 542℃, the roll is placed in an annealing furnace for annealing heat treatment. Before the roll ring enters the furnace, the heat treatment furnace is preheated to 504℃. After the roll ring is hot-removed and placed in the annealing furnace, it is held at that temperature for 4.2 hours. Then, the temperature is increased to 647℃ at a rate of 19℃ / hour and held for 8.1 hours. Then, the temperature is increased to 891℃ at a rate of 20℃ / hour and held for 24.2 hours. Then, the temperature is controlled to cool to 671℃ at a rate of 12℃ / hour and held for 20.3 hours. Finally, the temperature is cooled to 84℃ with the furnace at a rate of 18℃ / hour. The furnace door is then opened 0.6 meters. The roll ring is removed from the furnace when its surface temperature reaches 50℃.

[0135] After annealing, rough machining was performed according to the drawings. Following this, quenching and four tempering heat treatments were conducted. The rough-machined roller ring was first heated to 209℃ at a rate of 5℃ / h and held for 5.2h, then heated to 350℃ at a rate of 9℃ / h and held for 6h, then heated to 658℃ at a rate of 10℃ / h and held for 10.2h, then heated to 984℃ at a rate of 24℃ / h and held for 15.3h. It was then mist-cooled to 547℃ for 13 minutes, followed by air cooling to 454℃ for approximately 20 minutes and held for 2h. Finally, four tempering treatments were performed. The first tempering was carried out by heating to 511℃ at a rate of 13℃ / h and holding for 15h. The roller rings are cooled to 128°C at a rate of 13°C / h and held for 1.2 hours. In the second tempering, the temperature is increased to 510°C at a rate of 13°C / h and held for 20.1 hours. Then, they are cooled to 128°C at a rate of 9°C / h and held for 2.1 hours. In the third tempering, the temperature is increased to 531°C at a rate of 15°C / h and held for 35.4 hours. Then, they are cooled to 82°C at a rate of 14°C / h and held for 2.1 hours. In the fourth tempering, the temperature is increased to 509°C at a rate of 13°C / h and held for 30.2 hours. Finally, the temperature is increased to 72°C at a rate of 13°C / h and held for 10.1 hours. The furnace door is then opened 0.4 meters, and the roller rings are removed from the furnace when the surface temperature reaches 38°C. After heat treatment, the roller rings undergo precision machining and are stored after passing inspection.

[0136] The hardness of the alloy roller ring in this embodiment is shown in Table 3, the ultrasonic test results of the bonding layer are shown in Table 4, and the chemical composition and mass percentage of the inner layer material after the roller ring cools and solidifies are shown in Table 5.

[0137] Example 8

[0138] In this embodiment, the finished product specifications (outer circle / inner circle) of the high alloy steel straightening centrifugal roller ring are Φ1300 / Φ700, and the blank specifications are Φ1340*1000. The structure is a two-layer centrifugal composite structure. The outer layer is made of high alloy cast steel, and the inner layer is made of graphite steel. The chemical composition and mass percentage of each layer are shown in Table 1 and Table 2.

[0139] The production process of high-alloy steel straightening centrifugal roller rings in this embodiment also includes the following process steps:

[0140] (1) Iron and steel molten metal transformation process: 7t and 3t medium frequency induction furnaces are used to melt the outer layer of iron and the inner layer of steel respectively.

[0141] Before the outer layer of molten steel is tapped, 0.2% silicon-zirconium alloy, 0.3% ferromanganese, and 0.4% cerium are added to the ladle.

[0142] Before the inner layer of molten steel is tapped, 0.5% silicon-zirconium alloy, 0.2% silicon-calcium alloy, and 0.7% cerium are added to the bottom of the ladle.

[0143] (2) Centrifugal casting process: The cold mold temperature is controlled at 198℃ during the centrifugal casting of the outer layer. The first casting of the outer layer of molten steel is at a casting temperature of 1456℃. When the centrifugal time of the outer layer reaches the interval time of 71 minutes, the inner layer of molten steel is cast at a casting temperature of 1508℃. When the centrifugal time reaches the total running time of 152 minutes, the centrifuge is stopped.

[0144] (3) Heat treatment process:

[0145] After the centrifuge stops, the cooled roll is hoisted into the pit and covered with an insulation cover. When the inner surface temperature reaches 664℃, the insulation cover is removed, and when the inner surface temperature reaches 525℃, it is placed in an annealing furnace for annealing heat treatment. Before the roll ring enters the furnace, the heat treatment furnace is preheated to 505℃. After the roll ring is hot-removed and placed in the annealing furnace, it is held at that temperature for 4 hours. Then, the temperature is increased to 641℃ at a rate of 17℃ / h and held for 8.2 hours. Then, the temperature is increased to 885℃ at a rate of 24℃ / h and held for 24.4 hours. Then, the temperature is controlled to cool to 679℃ at a rate of 14℃ / h and held for 20.4 hours. Finally, the temperature is cooled to 82℃ with the furnace at a rate of 12℃ / h. The furnace door is then opened 0.6 meters, and the roll ring is removed from the furnace when the surface temperature reaches 41℃.

[0146] After annealing, rough machining was performed according to the drawings. Following this, quenching and four tempering heat treatments were applied. The rough-machined roller ring was first heated to 206℃ at a rate of 6℃ / h and held for 5.1h, then heated to 341℃ at a rate of 10℃ / h and held for 6.2h, then heated to 659℃ at a rate of 12℃ / h and held for 10.1h, then heated to 988℃ at a rate of 20℃ / h and held for 15.4h. It was then mist-cooled to 542℃ for 14 minutes, followed by air-cooling to 459℃ for approximately 22 minutes and held for 2.2h. Finally, four tempering treatments were performed. The first tempering was carried out by heating to 512℃ at a rate of 14℃ / h and holding for... The heat treatment process involves several steps: 15.5 hours of initial heating, followed by furnace cooling at 9℃ / h to 123℃, holding for 1 hour; a second tempering process, heating at 10℃ / h to 514℃, holding for 20.5 hours; a third tempering process, heating at 12℃ / h to 126℃, holding for 2.2 hours; a fourth tempering process, heating at 11℃ / h to 527℃, holding for 35.2 hours; a fifth tempering process, heating at 7℃ / h to 83℃, holding for 2 hours; a sixth tempering process, heating at 14℃ / h to 510℃, holding for 30.1 hours; and finally, heating at 15℃ / h to 74℃, holding for 10.2 hours. The furnace door is then opened 0.4 meters, and the roller ring is removed from the furnace when its surface temperature reaches 34℃. After heat treatment, the roller ring undergoes precision machining and is then inspected and stored.

[0147] The hardness of the alloy roller ring in this embodiment is shown in Table 3, the ultrasonic test results of the bonding layer are shown in Table 4, and the chemical composition and mass percentage of the inner layer material after the roller ring cools and solidifies are shown in Table 5.

[0148] Table 1. Chemical composition (%) of the outer layer of the centrifugal roller ring for straightening steel types 1-8 in Examples 1-8

[0149]

[0150]

[0151] Table 2 Chemical composition (%) of the inner layer of the centrifugal roller ring for straightening steel types 1-8 in Examples

[0152] Φ795 / Φ330 1.36 1.80 0.60 0.028 0.018 0.40 0.018 0.019 0.016 0.018 Φ800 / Φ360 1.30 1.88 0.59 0.030 0.017 0.38 0.019 0.017 0.015 0.017 Φ890 / Φ400 1.42 1.83 0.40 0.026 0.019 0.37 0.020 0.018 0.013 0.019 Φ980 / Φ490 1.50 2.00 0.48 0.027 0.020 0.36 0.017 0.019 0.020 0.015 Φ1071 / Φ550 1.49 1.92 0.46 0.029 0.018 0.20 0.018 0.016 0.019 0.018 Φ1157 / Φ620 1.40 1.95 0.50 0.024 0.019 0.30 0.015 0.020 0.017 0.015 Φ1244 / Φ650 1.41 1.90 0.44 0.028 0.017 0.32 0.016 0.018 0.011 0.014 Φ1300 / Φ700 1.47 1.98 0.53 0.022 0.016 0.29 0.019 0.017 0.014 0.020

[0153] Table 3 Hardness of the straightening centrifugal roller rings for steel types 1-8 in Examples 3

[0154]

[0155] Table 4. Ultrasonic testing results of the bonding layer of the centrifugal roller ring for straightening steel in Examples 1-8 (based on GB / T 1503-2008)

[0156]

[0157] Table 5. Chemical composition and mass percentage of the inner layer material of the straightening centrifugal roller rings of steel types 1-8 after cooling and solidification.

[0158] Φ795 / Φ330 0.16 0.07 0.08 0.09 0.4 Φ800 / Φ360 0.15 0.08 0.06 0.08 0.37 Φ890 / Φ400 0.20 0.05 0.05 0.09 0.39 Φ980 / Φ490 0.17 0.07 0.08 0.07 0.39 Φ1071 / Φ550 0.18 0.06 0.07 0.08 0.4 Φ1157 / Φ620 0.16 0.07 0.05 0.07 0.35 Φ1244 / Φ650 0.17 0.09 0.07 0.06 0.39 Φ1300 / Φ700 0.18 0.06 0.07 0.07 0.38

[0159] As shown in Tables 3, 4, and 5, the high-alloy steel straightening centrifugal roller rings cast by this invention have advantages such as high hardness and good wear resistance. At the same time, the centrifugal casting process provided by this invention can ensure a good bonding layer that meets national standards, and the amount of alloy infiltrated into the inner layer can be controlled, which can ensure good accident resistance in practical applications.

Claims

1. A high-alloy steel straightening centrifugal roller ring, composed of an outer layer and an inner layer of centrifugal composite structure, characterized in that: The outer layer of the roller ring is made of high-alloy cast steel, and the inner layer of the roller ring is made of graphite steel. The chemical composition and mass percentage of the high-alloy cast steel material of the outer layer of the roller ring are as follows: C: 0.70-0.80%, Si: 0.60-0.80%, Mn: ≤0.6%, P≤0.030%, S≤0.020%, Ni: 1.10-1.30%, Cr: 19.7-19.9%, W: 4.50-4.70%, Nb: 30%W-40%W, Co: 5.20-5.40%, with the balance being iron. The chemical composition and mass percentage of the graphite steel material in the inner layer of the roller ring are as follows: C: 1.30~1.50%, Si: 1.80~2.00%, Mn: 0.40~0.60%, P≤0.030%, S≤0.020%, Ni: 0.20~0.40%, Cr≤0.02%, W≤0.02%, Nb≤0.02%, Co≤0.02%, with the balance being iron and unavoidable impurities. After the roller ring cools and solidifies, the chemical composition and mass percentage of the alloy that penetrates from the outer layer into the inner layer must meet the following requirements: Cr≤0.30%, W≤0.15%, Nb≤0.10%, Co≤0.20%, and Cr+W+Nb+Co≤0.40%.

2. The high-alloy steel straightening centrifugal roller ring according to claim 1, characterized in that: The thickness of the inner layer of the roller ring is: δ≥0.09*(ab) In the formula: δ – Finished thickness of the inner layer of the roller ring, in mm; a – Finished outer diameter of the roller ring, in mm; b – Finished inner diameter of the roller ring, in mm.

3. The method for producing a high-alloy steel straightening centrifugal roller ring according to claim 1, employing a centrifugal composite casting process, is characterized in that: Control should be implemented according to the following requirements: A. Roller coating of centrifugal cooling coatings During roller coating, the cold temperature is controlled at 300-340℃, the centrifuge speed is initially 200r / min, and after the coating is completely poured into the roller mold, the speed is quickly increased to 480r / min, and the coating layer thickness is 3.5-4.5mm. Coating formulation: quartz powder dry material, sodium bentonite (8% by weight of quartz powder dry material), aluminum dihydrogen phosphate (8% by weight of quartz powder dry material), and water (30% by weight of quartz powder dry material). B. Metal molten smelting According to the material composition of the roller ring, the outer layer of high alloy cast steel molten steel and the inner layer of graphite steel molten steel are smelted in a medium frequency induction furnace. C. Metal molten metal smelting and alteration treatment The outer and inner layers are smelted in two separate medium-frequency furnaces. First, steel is added and smelted, then alloy components are added. When adding the materials, two-thirds of the niobium alloy needs to be placed at the bottom of the medium-frequency furnace, with a particle size of 10mm to 30mm. The remaining one-third is added when the liquid temperature in the medium-frequency furnace reaches 1580℃, with a particle size of 2mm to 5mm. After the outer layer of metal and alloy materials in the medium-frequency furnace are completely melted, crushed glass is added to the surface of the molten iron to prevent oxidation, at a rate of 6kg to 8kg per ton of molten metal. Before the outer layer of molten steel is tapped, 0.1% to 0.3% of silicon-zirconium alloy, 0.1% to 0.3% of ferromanganese, and 0.3% to 0.5% of cerium are added to the ladle. After the inner metal material is completely melted, broken glass is added to the surface of the molten steel to prevent oxidation. The amount added is 6-8 kg per ton of molten steel. Before tapping, 0.4%-0.6% silicon-zirconium alloy, 0.1%-0.3% silicon-calcium alloy, and 0.7%-0.9% cerium are added to the bottom of the ladle according to the amount of molten steel. D. Centrifugal casting ①After the chemical composition of the molten steel in each of the medium-frequency furnaces for melting the outer and inner layers is qualified, centrifugal casting is carried out; ② When centrifugally casting, the cold mold temperature requirement is 180~200℃. The first pour of the outer layer of molten steel should be 1520~1540℃ when exiting the furnace and 1450~1470℃ when pouring. After pouring, an interface protectant should be added to the inner cavity of the cold mold immediately. ③ When the centrifugation time of the outer layer reaches the interval, pour the inner layer of molten steel. The furnace exit temperature is 1580~1600℃, and the pouring temperature is 1500~1520℃. After the molten steel is poured, immediately add an interface protectant to the inner cavity of the cold mold. ④ When the centrifugation time reaches the total operating time, stop the centrifuge from rotating; E. Pit insulation After the centrifuge stops, the cold mold is hoisted into the pit and covered with an insulation cover. When the inner surface temperature of the inner layer reaches 600-700℃, the insulation cover is removed. When the inner surface temperature of the inner layer reaches 500-550℃, it is placed in an annealing furnace for annealing heat treatment. F. Heat Treatment The blank is first fully annealed, then rough-machined according to the rough turning drawings, and then subjected to a quenching + four-time tempering heat treatment process. G. Processing: After heat treatment, the rolls are processed according to the precision machining drawings, and then put into storage after passing inspection.

4. The method for producing a high-alloy steel straightening centrifugal roller ring according to claim 3, characterized in that: The interface protectant consists of "O" type glass slag, borax, and sodium carbonate. The amount of "O" type glass slag added is 7 kg to 8 kg per square meter of the cold-formed inner surface. The amount of borax added accounts for 40% of the amount of "O" type glass slag, and the amount of sodium carbonate added accounts for 15% of the amount of "O" type glass slag.

5. The method for producing a high-alloy steel straightening centrifugal roller ring according to claim 3, characterized in that: The complete annealing process for the blank is as follows: the heat treatment furnace is preheated to 495-505℃ before the roller ring enters the furnace. After the roller ring is hot-removed and placed into the annealing furnace, it is held at this temperature for 4-4.2 hours. Then, the temperature is increased to 640-650℃ at a rate of 10-20℃ / hour and held for 8-8.2 hours. Then, the temperature is increased to 885-895℃ at a rate of 15-25℃ / hour and held for 24-24.5 hours. Then, the temperature is controlled to cool to 670-680℃ at a rate of 10-15℃ / hour and held for 20-20.5 hours. Finally, the temperature is cooled to 80-100℃ with the furnace at a rate of 5-20℃ / hour. The furnace door is then opened, and the roller ring is removed from the furnace when the surface temperature is 30-50℃.

6. The method for producing a high-alloy steel straightening centrifugal roller ring according to claim 3, characterized in that: The quenching + four-times tempering process is as follows: The rough-machined roller ring is first heated to 200-210℃ at a rate of 5-8℃ / h and held for 5-5.2 hours; then heated to 340-350℃ at a rate of 8-12℃ / h and held for 6-6.2 hours; then heated to 650-660℃ at a rate of 10-15℃ / h and held for 10-10.2 hours; then heated to 980-990℃ at a rate of 20-25℃ / h and held for 15-15.5 hours; then mist-cooled to 540-550℃ for 10-15 minutes; then air-cooled to 450-460℃ for 15-25 minutes and held for 2-2.2 hours; finally, it undergoes four tempering processes. The first tempering is performed by heating to 505-515℃ at a rate of 10-15℃ / h and holding for 15-15.5 hours; then quenching at a rate of 5-15℃ / h... The furnace is cooled to 120–130°C and held for 1–1.2 hours. The second tempering involves raising the temperature at 10–15°C / hour to 505–515°C and holding for 20–20.5 hours. The furnace is then cooled to 120–130°C at 5–15°C / hour and held for 2–2.2 hours. The third tempering involves raising the temperature at 10–15°C / hour to 525–535°C and holding for 35–35.5 hours. The furnace is then cooled to 80–90°C at 5–15°C / hour and held for 2–2.2 hours. The fourth tempering involves raising the temperature at 10–15°C / hour to 500–510°C and holding for 30–30.5 hours. Finally, the temperature is raised to 70–80°C at 5–15°C / hour and held for 10–10.2 hours. The furnace door is then opened, and the roll rings are removed from the furnace when their surface temperature is 20–40°C.

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