A cr5 alloy cast steel backup roll and a method of manufacturing the same

Abstract

The application relates to the technical field of a supporting roller preparation method, and discloses a Cr5 alloy cast steel supporting roller and a preparation method thereof, which comprises the following steps: smelting and purifying forged stamping waste steel, Cr4 waste roller rings, steel scrap and waste rollers, using glass slag to deoxidize after smelting and purifying, using silicon-calcium alloy to precipitate and deoxidize, and finally deoxidizing in the furnace by inserting aluminum to obtain molten steel; pouring the molten steel into a supporting roller mold, adding molten steel twice after pouring to obtain a casting blank; placing the casting blank obtained in the step S2 in a heat treatment furnace for heat treatment, using an iron sheet protective cover to seal and shield the roll neck conical surface after austenitizing, and using fiber cotton to coat the small roll neck; taking off the protective cover and the fiber cotton after the casting blank obtained in the step S3 is taken out of the furnace and is subjected to spray quenching treatment, opening the air blowing and water spraying devices, taking off the protective cover and the fiber cotton after the spray quenching is completed, and cooling to obtain the Cr5 alloy cast steel supporting roller; and the supporting roller obtained by the method has the advantages of roll body wear resistance and roll neck toughness.

Description

Technical Field

[0001] This application relates to the field of support roller manufacturing technology, and in particular to a Cr5 alloy cast steel support roller and its manufacturing method. Background Technology

[0002] In the manufacturing of large support rollers, the current mainstream technology still relies on forging to produce support roller forgings. Although this process can achieve a uniform and dense microstructure and good overall performance, the production process requires ultra-large presses, resulting in huge equipment investment, long manufacturing cycles, and high production costs. To reduce manufacturing costs and improve production flexibility, the industry has long explored the technical path of "casting instead of forging," that is, using casting to produce large support rollers.

[0003] When producing large support rollers using casting, it is difficult to achieve the required hardness gradient on a single workpiece in a conventional heat treatment furnace. In particular, when using highly permeable Cr5 alloy steel, the roller neck is prone to becoming brittle due to excessive hardness during overall quenching, leading to brittle fracture during use. This makes it impossible to achieve both wear resistance of the roller body and strength and toughness of the roller neck. Summary of the Invention

[0004] To address the challenge of achieving both wear resistance of the roll body and strength and toughness of the roll neck when Cr5 alloy cast steel support rolls are manufactured using casting, a Cr5 alloy cast steel support roll and its manufacturing method are provided.

[0005] The first inventive objective of this invention is achieved through the following technical solution:

[0006] A method for preparing a Cr5 alloy cast steel support roller includes the following steps:

[0007] S1: Forging and stamping scrap steel, Cr4 scrap roll ring, steel chips and scrap roll are melted and cleaned. After melting and cleaning, glass slag is used for deoxidation, silicon-calcium alloy precipitation is used for deoxidation, and aluminum is inserted in the furnace for final deoxidation to obtain molten steel.

[0008] S2: Pour molten steel into the support roller mold. After pouring, add molten steel for the first time 4-8 minutes later, and add molten steel for the second time 55-65 minutes later to obtain the billet.

[0009] S3: Place the billet obtained in step S2 into a heat treatment furnace for heat treatment. After austenitization, seal and shield the tapered surface of the roll neck with a sheet metal protective cover, and cover the small roll neck with fiber cotton.

[0010] S4: After the billet obtained in step S3 is taken out of the furnace for 1-3 minutes, the billet is placed in a spray quenching machine for spray quenching treatment. The blowing and water spraying devices are turned on. After 4-6 minutes, the water spraying is stopped. The blowing is maintained for 0.4-0.6 hours. The protective cover is then removed and the blowing is stopped. After 3-4 hours, the fiber cotton is removed and cooled to obtain the Cr5 alloy cast steel support roller.

[0011] By adopting the above technical solutions, the glass slag deoxidation process utilizes molten glass slag to cover the surface of molten steel, isolating it from air and preventing secondary oxidation. At the same time, it adsorbs non-metallic inclusions such as floating deoxidation products. The calcium-silicon alloy has a strong affinity for both oxygen and sulfur in the molten steel, generating low-melting-point composite inclusions that float to the slag, thereby further purifying the molten steel. The final deoxidation of aluminum can effectively fix the residual oxygen in the steel, forming fine Al2O3 particles, and can also serve as a heterogeneous nucleation core to refine the grains. Through multi-stage deoxidation, high-purity molten steel is obtained, which helps to obtain dense billets with fewer defects.

[0012] The two additions of molten steel are for shrinkage compensation. The first addition is made 4-8 minutes after casting, when the surface of the casting has formed a solidified shell but the interior is still liquid. This is to compensate for liquid shrinkage and prevent shrinkage cavities from forming in the near-surface area of ​​the roll body or roll neck. The second addition is made 55-65 minutes later to compensate for solid shrinkage in the center area of ​​the casting. This can effectively reduce central shrinkage defects. The two additions help to compensate for the shrinkage of the casting during solidification, improve the overall density of the billet, reduce internal micro-shrinkage, and thus improve the overall load-bearing capacity, fatigue strength and toughness of the support roll.

[0013] The heat treatment austenitization process allows carbon and alloying elements to fully dissolve in austenite, preparing for subsequent phase transformation. The tapered surface of the roll neck is sealed and shielded with a sheet metal protective cover, and the small roll neck is covered with fiber cotton. Utilizing the heat insulation properties of the protective cover and fiber cotton, the cooling rate of these protected areas is reduced during the subsequent spray quenching process. This prevents the roll neck from undergoing a violent martensitic phase transformation during cooling, and tends to form bainite or pearlite-like structures. Thus, while obtaining a certain strength, it also maintains higher plasticity and toughness to adapt to the working conditions where the roll neck is subjected to alternating bending stress. Meanwhile, the surface of the roll body is exposed to the cooling medium, forming a high-hardness martensitic structure. The differentiated heat treatment of the roll body and the roll neck makes the roll body wear-resistant and the roll neck strong and tough.

[0014] After the billet exits the furnace, it is quickly placed in a quenching machine to reduce temperature fluctuations and stabilize the initial quenching temperature. The air blowing and water spraying devices are then activated. The water spray causes intense cooling of the roll surface, rapidly passing through the unstable austenite region, inhibiting the transformation of ferrite and pearlite, and promoting the transformation of supercooled austenite into high-carbon martensite and retained austenite. Fine, dispersed alloy carbides precipitate in the matrix, resulting in high hardness and wear resistance for the roll. Water spraying is stopped after 4-6 minutes, at which point the martensitic transformation of the roll surface is essentially complete. Air blowing is maintained at 0.4- For 0.6 hours, cooling continues through forced convection heat transfer, but the cooling intensity is much lower than that of water spraying. This ensures that the heat in the core continues to dissipate outward, promoting the full transformation of the core structure, and also allows the formed martensite to undergo a certain degree of self-tempering. At the same time, slow cooling helps to reduce thermal stress and structural stress, preventing cracking. The iron sheet protective cover is removed first, followed by the fiber cotton to achieve a step-by-step adjustment of the cooling rate, so that the roll neck can complete the final cooling under relatively gentler conditions, obtaining a strong and tough structure mainly composed of bainite or tempered sorbite.

[0015] In summary, smelting deoxidation improves the cleanliness of molten steel, and sequential solidification characteristics are used for a time-sequential feeding process to ensure the internal density of the billet. Furthermore, through differential protection of the roll neck area during heat treatment and subsequent staged controlled spray quenching process, a gradient distribution between the wear-resistant structure dominated by high-hardness martensite on the roll body surface and the structure dominated by tough bainite / sorbite in the roll neck and transition zone is successfully achieved on the same component. This results in an overall roll body with wear resistance and a tough roll neck.

[0016] Preferably, the mass ratio of forging and stamping scrap steel, Cr4 scrap roll rings, steel chips, and scrap rolls is 45:35:10:10.

[0017] By adopting the above technical solution, 45% of the forging and stamping scrap steel is used as the main component. Its dense texture and small compositional segregation can provide a pure matrix iron source. 35% of the Cr4 scrap roll rings are the main and stable source of chromium, which helps to stabilize the chromium content of the finished rolls at around the Cr5 level. 10% of steel chips help to adjust the carbon content of the molten pool. 10% of the self-produced scrap rolls can realize the recycling of materials within the plant. This specific ratio makes the final steel composition meet the design range and controls the total amount of residual elements and impurities, thus obtaining a stable and consistent original as-cast structure.

[0018] Preferably, in step S1, the amount of silicon-calcium alloy used is 0.48-0.52 kg / t of molten steel, and the amount of aluminum used is 0.58-0.62 kg / t of molten steel.

[0019] By adopting the above technical solution, the dosage range of this silicon-calcium alloy enables it to effectively perform diffusion deoxidation and precipitation deoxidation, while reducing the excessive silicon addition in the molten steel or the formation of large-sized calcium aluminate inclusions due to excessive calcium addition. Within this range, aluminum can effectively fix free oxygen and nitrogen in the steel, forming fine AlN and Al2O3, which plays a role in refining austenite grains. It also helps to reduce the problem of toughness damage caused by the formation of coarse clusters of Al2O3 inclusions due to excessive aluminum, achieving the effect of deep deoxidation and grain refinement, and improving the purity and toughness of the material.

[0020] Preferably, the amount of glass slag used is 1.5-2 kg / t of molten steel, and the silica content in the glass slag is 70wt-80wt%.

[0021] By adopting the above technical solution, a slag layer of sufficient thickness and fluidity can be formed with a dosage range of 1.5-2 kg / t of molten steel, effectively covering the molten steel. The high silica content of 70-80 wt% gives the glass slag high viscosity and acidity, which can better adsorb the alkaline deoxidation products floating in the molten steel, improve deoxidation and desulfurization efficiency, and purify the molten steel.

[0022] Preferably, the quenching air pressure is 0.5-0.7 MPa and the water pressure is 0.25-0.4 MPa.

[0023] By adopting the above technical solution, this pressure range enables the quenching medium (gas, liquid) to have sufficient impact force and uniform coverage on the high-temperature roller surface. The higher air pressure helps to form a stable and uniform airflow layer on the roller surface, which can not only assist in atomizing droplets and enhance heat transfer, but also continue to remove heat after the water spraying stops, thus achieving controllable cooling. This water pressure ensures that there is enough cooling water per unit area to contact the high-temperature surface and quickly vaporize and absorb heat, achieving a rapid transformation from austenite to martensite, thereby obtaining a high-hardness hardened layer on the roller surface. The coordinated control of air pressure and water pressure balances cooling intensity, uniformity and reduces quenching stress, reduces the risk of cracking, and increases the depth of the hardened layer.

[0024] Preferably, the gas medium for the spray quenching treatment is nitrogen.

[0025] By adopting the above technical solution, nitrogen, as an inert protective gas, covers the surface of the workpiece during the spray quenching process, which can effectively reduce the oxidation and decarburization of the roller surface at high temperature. Surface decarburization will directly lead to a decrease in surface hardness and damage to wear resistance after quenching. Using nitrogen protection maintains the integrity of the chemical composition of the roller surface before quenching and maintains the strength of the support roller surface.

[0026] Preferably, the liquid medium for the spray quenching treatment is a polyethylene glycol solution, which includes polyethylene glycol with an average molecular weight of 120,000 and polyethylene glycol with an average molecular weight of 8,000, and the mass concentration of polyethylene glycol in the polyethylene glycol solution is 8-12 wt%.

[0027] By adopting the above technical solution, the reverse solubility of poly(ethylene glycol) allows the polymer to precipitate and form a thin film on the workpiece surface at high temperatures. By using poly(ethylene glycol) with different average molecular weights in a compound, in the high-temperature region, the lower average molecular weight poly(ethylene glycol) molecules have shorter chains and faster movement speeds, resulting in faster and thinner film formation. This helps to break down the vapor film more quickly at high temperatures, increasing the cooling rate in the high-temperature region, allowing austenite to rapidly cross the pearlite transformation zone, reducing the formation of non-martensitic structures, and ensuring hardenability. Furthermore, in the high-temperature region, the higher average molecular weight poly(ethylene glycol)... The film formed by glycols is less stable and more easily broken down. In the medium temperature stage, the polymer film formed by high average molecular weight polyalkylene glycol on the workpiece surface is more stable and thicker than that formed by low molecular weight polyalkylene glycol. This can suppress the cooling rate in this stage, reduce the structural stress and thermal stress generated by the martensitic transformation, and help prevent quenching cracks. By compounding polyalkylene glycols with different average molecular weights, different cooling rates can be achieved in different cooling stages, realizing fast cooling at high temperature and slow cooling at medium temperature, so that the support roller has low quenching internal stress and high surface hardness.

[0028] The second objective of this invention is achieved through the following technical solution:

[0029] A Cr5 alloy cast steel support roller prepared by the above method is composed of the following components by mass percentage:

[0030] C: 0.42%-0.46%,

[0031] Si: 0.5%-0.7%,

[0032] Mn: 0.4%-0.6%,

[0033] Cr: 4.8%-5.5%,

[0034] Ni: 0.5%-0.55%,

[0035] Mo: 0.4%-0.45%,

[0036] The balance consists of iron and unavoidable impurities.

[0037] By adopting the above technical solution, the carbon content is in the medium carbon range, which combines with chromium to form 3C type and more complex alloy carbides, providing a wear-resistant phase. Silicon is dissolved in ferrite to improve strength. Manganese expands the austenite region, improves hardenability, and strengthens through solid solution. Chromium improves hardenability, strengthens the matrix through solid solution, and forms carbides to improve wear resistance and corrosion resistance. Nickel is dissolved in austenite / ferrite, which significantly improves toughness while improving strength. Molybdenum further improves hardenability, reduces high-temperature tempering brittleness, refines grains, and enhances toughness. The overall synergistic effect of this composition system gives the support roller high wear resistance and good toughness.

[0038] In summary, this application has at least the following beneficial effects:

[0039] (1) In the deoxidation process, molten glass slag is used to cover the surface of the molten steel to isolate the air and adsorb non-metallic inclusions. The composite deoxidation effect of silicon-calcium alloy and aluminum generates low-melting-point composite oxides that float to the surface, thereby effectively purifying the molten steel and providing a basis for obtaining high-purity molten steel.

[0040] (2) Based on the sequential solidification characteristics, a two-stage time-sequential steel replenishment process is implemented. The first time, liquid shrinkage is compensated 4-8 minutes after pouring to prevent near-surface shrinkage cavities. The second time, solid shrinkage is compensated for in the central area after 55-65 minutes to reduce shrinkage defects and improve the overall density of the billet.

[0041] (3) During the heat treatment process, the roll neck is insulated to reduce the cooling rate and form a strong and tough structure mainly composed of bainite or sorbite. The roll body is rapidly cooled by spray quenching to obtain high-hardness martensite. The cooling is controlled in stages to achieve a gradient distribution of the structure, so that the parts have both wear resistance and toughness. Detailed Implementation

[0042] raw material

[0043] Polyethylene glycol with average molecular weights of 8,000 and 120,000 was purchased from Guangzhou Bitao Trading Co., Ltd.

[0044] The riser insulation agent, type I, was purchased from Wuxi Ji'ao Foundry Materials Co., Ltd.

[0045] The silicon-calcium alloy, grade Ca31Si60, is sourced from commercially available products.

[0046] Ferrosilicon particles, grade FeSi75A, particle size 12mm, sourced from commercially available sources;

[0047] Ferromanganese granules, grade FeMn84C0.4, particle size 12mm, sourced from commercially available sources.

[0048] Example 1

[0049] A Cr5 alloy cast steel support roller, the preparation method of which is as follows:

[0050] S1: 27.9t of forging and stamping scrap steel (composition: C: 0.46wt%, Si: 0.48wt%, Mn: 0.98wt%, Cr: 0.76wt%, Ni: 0.22wt%, Mo: 0.14wt%, with the remainder being Fe and unavoidable impurities), and 21.7t of Cr4 scrap roll rings (composition: C: 0.45wt%, Si: 0.53wt%, Mn: 0.18wt%, Cr: 4.12wt%, Ni: 0.3wt%). 2 wt%, Mo: 0.37%, the remainder being Fe and unavoidable impurities), 6.2 t of steel scrap (composition: C: 0.38 wt%, Si: 0.35 wt%, Mn: 0.20 wt%, Cr: 5.56 wt%, Ni: 0.38 wt%, Mo: 0.23%, the remainder being Fe and unavoidable impurities), and 6.2 t of waste rolls (composition: C: 0.42 wt%, Si: 0.53 wt%, Mn: 0.21 wt%, Cr: 2 wt%, Mo: 0.37%, the remainder being Fe and unavoidable impurities) ... (3.06wt%, Ni: 1.22wt%, Mo: 0.43%, the remainder being Fe and unavoidable impurities) is added to a converter for melting and cleaning at a melting temperature of 1570℃. After melting and cleaning, the slag in the furnace is removed, and 60kg of glass slag (75wt% silica content) is added for slag formation and deoxidation. 31kg of silicon-calcium alloy precipitate is added for further deoxidation, and 37.2kg of aluminum is inserted into the furnace for final deoxidation. Ferrosilicon and ferromanganese particles are added to adjust the composition. After deoxidation is completed, the formed slag is removed, and molten steel is tapped. The tapping temperature was 1605℃. During the tapping process, argon gas was blown into the ladle for 13 minutes at a pressure of 0.3 MPa. Chemical composition analysis of the molten steel showed that it met the requirements: C: 0.42wt%-0.46wt%, Si: 0.5wt%-0.7wt%, Mn: 0.4wt%-0.6wt%, Cr: 4.8wt%-5.5wt%, Ni: 0.5wt%-0.6wt%, Mo: 0.40wt%-0.45wt%.

[0051] S2: 35t of molten steel is poured into a preheated support roll mold at a pouring temperature of 1510℃ and a support roll mold temperature of 100℃. The pouring time is 140min. 15kg of heat preservation agent is added. 6min after pouring, the first molten steel replenishment is carried out, adding 2.5t of molten steel and 50kg of heat preservation agent. 60min after that, the second molten steel replenishment is carried out, adding 1t of molten steel and 15kg of heat preservation agent. The temperature of the molten steel replenishment is 1550℃ after both additions, resulting in a cast billet.

[0052] S3: Place the billet obtained in step S2 in a heat treatment furnace, raise the temperature to 150°C at 5°C / h, raise the temperature to 260°C at 8°C / h, hold for 5 hours, raise the temperature to 425°C at 10°C / h, hold for 10 hours, raise the temperature to 665°C at 15°C / h, hold for 26 hours, raise the temperature to 980°C at 35°C / h, and hold for 23 hours to perform heat treatment austenitization. Use a sheet metal protective cover to cover the tapered surface of the roll neck. The sheet metal protective cover is made of 310S material and is fixed with pins for sealing and shielding. The small roll neck is covered with ceramic fiber cotton with a thickness of 50mm.

[0053] S4: Two minutes after the billet obtained in step S3 is removed from the furnace, it is placed in a spray quenching machine for spray quenching treatment. The blowing and water spraying devices are turned on, with a spray quenching air pressure of 0.6 MPa and a water pressure of 0.3 MPa. The spray quenching gas medium is nitrogen, and the liquid medium is a polyethylene glycol solution containing polyethylene glycol with an average molecular weight of 120,000, polyethylene glycol with an average molecular weight of 8,000, and deionized water. The mass ratio of the 120,000 average molecular weight polyethylene glycol to the 8,000 average molecular weight polyethylene glycol is 7:3, and the polyethylene glycol concentration is 10 wt%. After 5 minutes, the water spraying is stopped, the roller body temperature is 357℃, and the blowing is maintained for 0.5 hours before removal. The protective cover was used, and the roller neck temperature was 685℃. After stopping the blowing, the fiber cotton was removed after 3.5 hours. The roller body and roller neck were air-cooled to 335℃ and held for 14 hours. The temperature was then furnace-cooled to 100℃. The temperature was increased to 150℃ at 6℃ / h, to 260℃ at 8℃ / h, to 425℃ at 10℃ / h, and to 540℃ at 15℃. The temperature was held for 45 hours and then cooled to ≤50℃ at 25℃ / h. In this embodiment, the temperature was cooled to 48℃. The roller was then removed from the furnace to obtain a Cr5 alloy cast steel support roller. The support roller has the following contents: C content 0.45wt%, Si content 0.6wt%, Mn content 0.5wt%, Cr content 4.85wt%, Ni content 0.55wt%, and Mo content 0.42wt%.

[0054] Comparative Example 1

[0055] A Cr5 alloy cast steel support roller, which differs from Example 1 in that: no shielding is performed; S3: the cast billet obtained in step S2 is placed in a heat treatment furnace, heated to 150°C at 5°C / h, heated to 260°C at 8°C / h and held for 5h, heated to 425°C at 10°C / h and held for 10h, heated to 665°C at 15°C / h and held for 26h, heated to 980°C at 35°C / h and held for 23h, to perform heat treatment austenitization;

[0056] S4: Two minutes after the billet obtained in step S3 is removed from the furnace, it is placed in a spray quenching machine for spray quenching treatment. The blowing and water spraying devices are turned on, the spray quenching air pressure is 0.6 MPa, the water pressure is 0.3 MPa, the spray quenching gas medium is nitrogen, and the liquid medium is polyethylene glycol solution. The polyethylene glycol solution contains polyethylene glycol with an average molecular weight of 120,000, polyethylene glycol with an average molecular weight of 8,000, and deionized water. The mass ratio of ethylene glycol to poly(ethylene glycol) with an average molecular weight of 8000 is 7:3. After 5 minutes, water spraying is stopped, the roller body temperature is 357℃, and it is air-cooled until the roller body and roller neck are both 335℃. It is kept at this temperature for 14 hours, then furnace-cooled to 100℃. The temperature is then increased to 150℃ at 6℃ / h, to 260℃ at 8℃ / h, to 425℃ at 10℃ / h, and to 540℃ at 15℃. It is kept at this temperature for 45 hours, and then cooled to ≤50℃ at 25℃ / h.

[0057] The rest is the same as in Example 1.

[0058] Comparative Example 2

[0059] A Cr5 alloy cast steel support roller differs from Example 1 in that: S4 involves quenching the cast billet obtained in step S3 2 minutes after it exits the furnace, with a flow rate of 200 L / min·m² per unit area. 2 The quenching medium was a polyethylene glycol solution, which consisted of polyethylene glycol with an average molecular weight of 120,000, polyethylene glycol with an average molecular weight of 8,000, and deionized water. The mass ratio of the polyethylene glycol with an average molecular weight of 120,000 to that with an average molecular weight of 8,000 was 7:3. After 5 minutes, the water spraying was stopped, and the rollers were air-cooled to 335°C for both the roller body and the roller neck. The temperature was held for 14 hours, then furnace-cooled to 100°C. The temperature was then increased to 150°C at a rate of 6°C / h, to 260°C at a rate of 8°C / h, to 425°C at a rate of 10°C / h, and to 540°C at a rate of 15°C. The temperature was held for 45 hours, and then cooled to ≤50°C at a rate of 25°C / h. The rest of the process was the same as in Example 1.

[0060] Example 2

[0061] A Cr5 alloy cast steel support roll differs from Example 1 in that: in step S1, 26.04 kg of silicon-calcium alloy is added, which means the amount of silicon-calcium alloy used is 0.42 kg / t of molten steel; the rest is the same as in Example 1.

[0062] Example 3

[0063] A Cr5 alloy cast steel support roll differs from Example 1 in that: in step S1, 29.76 kg of silicon-calcium alloy is added, which is 0.48 kg / t of molten steel; the rest is the same as in Example 1.

[0064] Example 4

[0065] A Cr5 alloy cast steel support roll differs from Example 1 in that: in step S1, 32.24 kg of silicon-calcium alloy is added, which is 0.52 kg / t of molten steel; the rest is the same as in Example 1.

[0066] Example 5

[0067] A Cr5 alloy cast steel support roll differs from Example 1 in that: in step S1, 35.96 kg of silicon-calcium alloy is added, which is 0.58 kg / t of molten steel; the rest is the same as in Example 1.

[0068] Example 6

[0069] A Cr5 alloy cast steel support roller differs from Example 1 in that: in step S1, 32.24 kg of aluminum is added, which is 0.52 kg / t of molten steel; the rest is the same as in Example 1.

[0070] Example 7

[0071] A Cr5 alloy cast steel support roller differs from Example 1 in that: 35.96 kg of aluminum is added in step S1, which is 0.58 kg / t of molten steel; the rest is the same as in Example 1.

[0072] Example 8

[0073] A Cr5 alloy cast steel support roller differs from Example 1 in that: in step S1, 38.44 kg of aluminum is added, which is 0.62 kg / t of molten steel; the rest is the same as in Example 1.

[0074] Example 9

[0075] A Cr5 alloy cast steel support roller differs from Example 1 in that: in step S1, 42.16 kg of aluminum is added, which is 0.68 kg / t of molten steel; the rest is the same as in Example 1.

[0076] Example 10

[0077] A Cr5 alloy cast steel support roller differs from Example 1 in that: the amount of glass slag added in step S1 is 49.6 kg, that is, the amount of glass slag used is 0.8 kg / t of molten steel; the rest is the same as in Example 1.

[0078] Example 11

[0079] A Cr5 alloy cast steel support roller differs from Example 1 in that: the amount of glass slag added in step S1 is 55.8 kg, that is, the amount of glass slag used is 0.9 kg / t of molten steel; the rest is the same as in Example 1.

[0080] Example 12

[0081] A Cr5 alloy cast steel support roller differs from Example 1 in that: 62 kg of glass slag is added in step S1, i.e., the amount of glass slag used is 1.0 kg / t of molten steel; the rest is the same as in Example 1.

[0082] Example 13

[0083] A Cr5 alloy cast steel support roller differs from Example 1 in that: the amount of glass slag added in step S1 is 74.4 kg, that is, the amount of glass slag used is 1.2 kg / t of molten steel; the rest is the same as in Example 1.

[0084] Example 14

[0085] A Cr5 alloy cast steel support roller differs from Example 1 in that the silica content in the glass slag is 65wt%; the rest is the same as in Example 1.

[0086] Example 15

[0087] A Cr5 alloy cast steel support roller differs from Example 1 in that the silica content in the glass slag is 70 wt%; the rest is the same as in Example 1.

[0088] Example 16

[0089] A Cr5 alloy cast steel support roller differs from Example 1 in that the silica content in the glass slag is 80wt%; the rest is the same as in Example 1.

[0090] Example 17

[0091] A Cr5 alloy cast steel support roller differs from Example 1 in that the silica content in the glass slag is 85wt%; the rest is the same as in Example 1.

[0092] Example 18

[0093] A Cr5 alloy cast steel support roller differs from Example 1 in that the quenching air pressure in step S4 is 0.45 MPa; the rest is the same as Example 1.

[0094] Example 19

[0095] A Cr5 alloy cast steel support roller differs from Example 1 in that the quenching air pressure in step S4 is 0.5 MPa; the rest is the same as Example 1.

[0096] Example 20

[0097] A Cr5 alloy cast steel support roller differs from Example 1 in that the quenching air pressure in step S4 is 0.7 MPa; the rest is the same as Example 1.

[0098] Example 21

[0099] A Cr5 alloy cast steel support roller differs from Example 1 in that the quenching air pressure in step S4 is 0.75 MPa; the rest is the same as Example 1.

[0100] Example 22

[0101] A Cr5 alloy cast steel support roller differs from Example 1 in that the quenching air pressure in step S4 is 0.2 MPa; the rest is the same as Example 1.

[0102] Example 23

[0103] A Cr5 alloy cast steel support roller differs from Example 1 in that the quenching air pressure in step S4 is 0.25 MPa; the rest is the same as Example 1.

[0104] Example 24

[0105] A Cr5 alloy cast steel support roller differs from Example 1 in that the quenching air pressure in step S4 is 0.4 MPa; the rest is the same as Example 1.

[0106] Example 25

[0107] A Cr5 alloy cast steel support roller differs from Example 1 in that the quenching air pressure in step S4 is 0.45 MPa; the rest is the same as Example 1.

[0108] Example 26

[0109] A Cr5 alloy cast steel support roller differs from Example 1 in that the quenching gas medium in step S4 is oxygen; the rest is the same as Example 1.

[0110] Example 27

[0111] A Cr5 alloy cast steel support roller differs from Example 1 in that the quenching gas medium in step S4 is air; the rest is the same as Example 1.

[0112] Example 28

[0113] A Cr5 alloy cast steel support roller differs from Example 1 in that the quenching liquid medium in step S4 is deionized water; the rest is the same as in Example 1.

[0114] Example 29

[0115] A Cr5 alloy cast steel support roller differs from Example 1 in that the polyalkylene glycol solution consists of polyalkylene glycol with an average molecular weight of 120,000 and deionized water; the rest is the same as in Example 1.

[0116] Example 30

[0117] A Cr5 alloy cast steel support roller differs from Example 1 in that the polyalkylene glycol solution consists of polyalkylene glycol with an average molecular weight of 8000 and deionized water; the rest is the same as in Example 1.

[0118] Example 31

[0119] A Cr5 alloy cast steel support roller differs from Example 1 in that the polyalkylene glycol concentration in the polyalkylene glycol solution is 6 wt%; the rest is the same as in Example 1.

[0120] Example 32

[0121] A Cr5 alloy cast steel support roller differs from Example 1 in that the polyalkylene glycol concentration in the polyalkylene glycol solution is 8 wt%; the rest is the same as in Example 1.

[0122] Example 33

[0123] A Cr5 alloy cast steel support roller differs from Example 1 in that the polyalkylene glycol concentration in the polyalkylene glycol solution is 12 wt%; the rest is the same as in Example 1.

[0124] Example 34

[0125] A Cr5 alloy cast steel support roller differs from Example 1 in that the polyalkylene glycol concentration in the polyalkylene glycol solution is 15wt%; the rest is the same as in Example 1.

[0126] Example 35

[0127] A Cr5 alloy cast steel support roller differs from Example 1 in that: in step S2, the first molten steel is added 4 minutes after casting, and the second molten steel is added 55 minutes later; in step S4, the billet is placed in a spray quenching machine for spray quenching 1 minute after exiting the furnace; after turning on the blowing and water spraying devices, water is sprayed for 4 minutes and then stopped; after blowing for 0.4 hours, the protective cover is removed; after stopping blowing for 3 hours, the fiber cotton is removed; the rest is the same as in Example 1.

[0128] Example 36

[0129] A Cr5 alloy cast steel support roller differs from Example 1 in that: in step S2, the first molten steel is added 8 minutes after casting, and the second molten steel is added 65 minutes later; in step S4, the billet is placed in a spray quenching machine for spray quenching 3 minutes after exiting the furnace; after turning on the blowing and water spraying devices, water spraying is performed for 6 minutes and then stopped; after blowing for 0.6 hours, the protective cover is removed; after stopping blowing for 4 hours, the fiber cotton is removed; the rest is the same as in Example 1.

[0130] The following tests were conducted on Examples 1-36 and Comparative Examples 1-2:

[0131] According to GB / T 4341-2014, the Shore hardness of the roller body was tested, and the test results are shown in Table 1. According to GB / T 229-2020, the standard Charpy V-notch impact specimen was subjected to impact test at room temperature (20±2℃), and the impact absorbed energy (Akv, unit: J) was recorded. The higher the Akv value, the better the toughness. The test results are shown in Table 1.

[0132] Table 1. Detection results of Examples 1-36 and Comparative Examples 1-2

[0133] Based on Table 1, the test results are analyzed as follows:

[0134] Comparing Example 1 and Comparative Example 1, the neck toughness of Example 1 is superior to that of Comparative Example 1. The difference between Example 1 and Comparative Example 1 is that the neck of the support roller in Example 1 was shielded during its fabrication. A sheet metal protective cover and fiber cotton were used to cover the neck, reducing its cooling rate during the spray quenching process, thereby inhibiting the martensitic transformation and promoting the formation of bainite or pearlite structures. This allows the neck to maintain a certain strength while possessing higher toughness to adapt to alternating bending stress. The roller body, after cooling, forms high-hardness martensite, achieving differentiated performance of wear resistance in the roller body and strength and toughness in the neck. Therefore, shielding the neck during the fabrication of the support roller is beneficial for achieving both wear resistance in the roller body and strength and toughness in the neck.

[0135] Comparing Example 1 and Comparative Example 2, the roll neck toughness and roll body wear resistance of Example 1 are superior to those of Comparative Example 2. The difference between Example 1 and Comparative Example 2 is that Example 1 uses a spray quenching treatment during the preparation of the support roll. After the billet exits the furnace, it is rapidly sprayed to form a high-hardness martensite structure on the surface of the roll body. During the blowing stage, slow cooling is achieved to promote the transformation of the core structure and reduce stress. Finally, the roll neck is subjected to step cooling to obtain a strong and tough structure mainly composed of bainite or tempered sorbite. Therefore, the spray quenching treatment during the preparation of the support roll is beneficial to enable the support roll to achieve both roll body wear resistance and roll neck strength and toughness.

[0136] Comparing Examples 1 and 26-27, the wear resistance of the roller body in Example 1 is superior to that in Examples 26-27. The difference between Examples 1 and 26-27 is that the gas medium for the spray quenching treatment in Example 1 is nitrogen. Using nitrogen as a protective atmosphere during the spray quenching process can effectively suppress the oxidation and decarburization tendency of the roller surface at high temperatures, thereby maintaining the stability of the surface chemical composition. This helps to ensure that the roller body surface obtains the expected hardness and wear resistance after quenching. Therefore, using nitrogen as the gas medium for spray quenching treatment is beneficial for enabling the support roller to achieve both roller body wear resistance and roller neck strength.

[0137] Comparing Example 1 and Example 28, the wear resistance of the roller body in Example 1 is better than that in Example 28. The difference between Example 1 and Example 28 is that the liquid medium for spray quenching in Example 1 is a polyalkylene glycol solution. Polyalkylene glycol forms a reversible heat insulation film on the surface of the workpiece, making the cooling more uniform and reducing thermal stress and structural stress. Therefore, using a polyalkylene glycol solution as the liquid medium for spray quenching is beneficial for the support roller to achieve both wear resistance of the roller body and toughness of the roller neck.

[0138] Comparing Examples 1 and 29-30, the wear resistance of the roller body in Example 1 is superior to that in Examples 29-30. The difference between Examples 1 and 29-30 is that the polyethylene glycol solution for spray quenching in Example 1 includes polyethylene glycol with a molecular weight of 120,000 and polyethylene glycol with an average molecular weight of 8,000. By compounding polyethylene glycol polymers with different average molecular weights, the cooling process can be controlled in stages. In the high-temperature zone, cooling is promoted to ensure hardenability, while in the medium-temperature zone, cooling is slowed down to reduce structural stress, thereby effectively controlling the quenching internal stress while obtaining high surface hardness. Therefore, the inclusion of polyethylene glycol with a molecular weight of 120,000 and polyethylene glycol with an average molecular weight of 8,000 in the spray quenching solution is beneficial for enabling the support roller to achieve both wear resistance of the roller body and toughness of the roller neck.

[0139] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of protection claimed in this application.

Claims

1. A method for preparing a Cr5 alloy cast steel support roller, characterized in that, Includes the following steps: S1: Forging and stamping scrap steel, Cr4 scrap roll ring, steel chips and scrap roll are melted and cleaned. After melting and cleaning, glass slag is used for deoxidation, silicon-calcium alloy precipitation is used for deoxidation, and aluminum is inserted in the furnace for final deoxidation to obtain molten steel. S2: Pour molten steel into the support roller mold. After pouring, add molten steel for the first time 4-8 minutes later, and add molten steel for the second time 55-65 minutes later to obtain the billet. S3: The billet obtained in step S2 is placed in a heat treatment furnace for heat treatment. After austenitization, the tapered surface of the roll neck is sealed and shielded with a sheet metal protective cover, and the small roll neck is covered with fiber cotton. S4: After the billet obtained in step S3 is taken out of the furnace for 1-3 minutes, the billet is placed in a spray quenching machine for spray quenching treatment. The blowing and water spraying devices are turned on. After 4-6 minutes, the water spraying is stopped. The blowing is maintained for 0.4-0.6 hours. The protective cover is then removed and the blowing is stopped. After 3-4 hours, the fiber cotton is removed and cooled to obtain the Cr5 alloy cast steel support roller.

2. The method for preparing a Cr5 alloy cast steel support roller according to claim 1, characterized in that, The mass ratio of the forging and stamping scrap steel, Cr4 scrap roll rings, steel chips, and scrap rolls is 45:35:10:

10.

3. The method for preparing a Cr5 alloy cast steel support roller according to claim 1, characterized in that, In step S1, the amount of silicon-calcium alloy used is 0.48-0.52 kg / t of molten steel, and the amount of aluminum used is 0.58-0.62 kg / t of molten steel.

4. The method for preparing a Cr5 alloy cast steel support roller according to claim 1, characterized in that, The amount of glass slag used is 0.9-1 kg / t of molten steel, and the silica content in the glass slag is 70wt-80wt%.

5. The method for preparing a Cr5 alloy cast steel support roller according to claim 1, characterized in that, The spray quenching air pressure is 0.5-0.7MPa, and the water pressure is 0.25-0.4MPa.

6. The method for preparing a Cr5 alloy cast steel support roller according to claim 1, characterized in that, The gas medium used in the spray quenching process is nitrogen.

7. The method for preparing a Cr5 alloy cast steel support roller according to claim 1, characterized in that, The liquid medium for the spray quenching treatment is a polyethylene glycol solution, which includes polyethylene glycol with an average molecular weight of 120,000 and polyethylene glycol with an average molecular weight of 8,000. The mass concentration of polyethylene glycol in the polyethylene glycol solution is 8-12 wt%.

8. A Cr5 alloy cast steel support roller obtained by the preparation method according to any one of claims 1-7, characterized in that, It consists of the following components by mass percentage: C: 0.42%-0.46%， Si: 0.5%-0.7%, Mn: 0.4%-0.6%, Cr: 4.8%-5.5%， Ni: 0.5%-0.55%, Mo: 0.4%-0.45%, The balance consists of iron and unavoidable impurities.

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