Special high-nickel-chromium working roll for medium plate and preparation method of special high-nickel-chromium working roll

Abstract

The invention discloses a high-nickel-chromium special working roll for a medium plate, which belongs to the technical field of roll collar manufacturing, and comprises an outer layer and a core part, the outer layer molten iron alloy comprises the following components in percentage by weight: 2.80-4.00% of C, 0.50-1.50% of Si, 0.30-1.50% of Mn and less than or equal to 0.03% of P; the steel comprises the following components in percentage by weight: less than or equal to 0.03% of S, 1.00-4.00% of Cr, 4.00-6.00% of Ni, 0.20-3.00% of Mo, 0.20-3.00% of V, 0.2-2.0% of Nb and the balance of Fe and inevitable impurities. The core molten iron is made of nodular cast iron; and in the outer-layer molten iron, the addition amounts of C, Cr, Ni and V are limited to meet the conditions that Cr / C is larger than or equal to 0.5 and smaller than or equal to 1.0, Ni / Cr is larger than or equal to 2.0, and V / Mo is larger than or equal to 2.0. The comprehensive performance of the high-nickel-chromium special working roll for the medium-thickness plate can meet the rolling requirements of the medium-thickness plate under special working conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of roller ring manufacturing, and in particular relates to a high-nickel-chromium special working roller for medium and thick plates and a preparation method thereof. Background Art

[0002] The steel products rolled in the medium and thick plate rolling line are widely used in offshore engineering platforms, dock construction, shipbuilding, oil and natural gas transportation (pipeline steel), storage (pressure vessel plate), urban transportation construction and large public buildings. At present, the working rolls of the domestic double-stand medium and wide plate rolling line mills are mostly made of traditional high-nickel-chromium materials. The main characteristics of high-nickel-chromium materials are good plate surface quality and plate shape control capabilities. With the improvement of steel mill rolling technology, the increase in the variety of rolled products, and the improvement of the strength level of rolled products, higher requirements are placed on the quality of the rolls. Conventional high-nickel-chromium performance can no longer meet the on-site rolling needs, especially the pits and pitting on the roll surface, which greatly affect the quality of the rolled products.

[0003] With the improvement of rolling technology, higher requirements are put forward for the quality of rolls. For example, when rolling composite plates, stainless steel and other plates, frequent roll replacement, low roll hardness and surface peeling are prone to occur during the rolling process, which cannot meet the rolling requirements at all. During the use of high nickel-chromium rolls, there are problems such as excessive soft point values, roll surface pits and roll marks after leaving the machine.

[0004] In view of the problems arising during the rolling of medium and thick plates, it is necessary to improve the comprehensive performance of the rolling rollers to meet the rolling of the plates and to improve and solve the roller surface problems that users are currently focusing on. Summary of the invention

[0005] The purpose of the present invention is to provide a high-nickel-chromium special working roll for medium and thick plates and a preparation method thereof, so as to solve the problems of pits and pitting on the working rolls during the existing special rolling method for medium and thick plates and the rolling process of special plates, and achieve relatively high wear resistance, pressure resistance, accident resistance and relatively good organizational uniformity.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A special working roll for medium and thick plates with high nickel and chromium content, the working roll is a centrifugal composite casting roll, comprising an outer layer and a core, the outer layer molten iron alloy composition and content range are: C: 2.80-4.00%, Si: 0.50-1.50%, Mn: 0.30-1.50%, P≤0.03%; S≤0.03%, Cr: 1.00-4.00%, Ni: 4.00-6.00%, Mo: 0.20-3.00%, V: 0.20-3.00%, Nb: 0.2-2.0%, and the rest is Fe and inevitable impurities; the core molten iron is made of ductile iron; the addition amounts of C, Cr, Ni and V in the outer layer molten iron are limited to meet 0.5≤Cr / C≤1.0, Ni / Cr≥2.0, and V / Mo≥2.0.

[0008] A further improvement of the technical solution of the present invention is that the composition and content range of the molten iron alloy of the outer layer of the working roller are: C: 2.80-4.00%, Si: 0.50-1.50%, Mn: 0.30-1.50%, P≤0.03%; S≤0.03%, Cr: 1.00-3.00%, Ni: 4.00-6.00%, Mo: 0.20-1.50%, V: 0.30-3.00%, Nb: 0.2-2.0%.

[0009] A method for preparing a high nickel-chromium special working roll for medium and thick plates comprises the following steps:

[0010] Step S1, placing the selected outer layer raw material and core raw material into an electric furnace for smelting respectively, and adjusting the alloy composition;

[0011] Step S2, after the above raw materials are smelted, the molten iron is calmed for a period of time, and argon is blown from the bottom when the molten iron is transferred to the casting ladle to make the composition and temperature uniform to prevent the oxidation of the molten iron; when the outer layer of molten iron reaches the casting temperature, casting is carried out; using ladle inoculation, adding a certain amount of inoculant during the casting process, and after the outer layer of molten iron solidifies, a temperature measuring device is used to detect the cavity temperature, and the core molten iron is cast after reaching a certain temperature;

[0012] Step S3, after pouring is completed, heat preservation treatment is performed, and the box is opened when the temperature of the outer wall of the casting mold drops to 80°C. After opening the box, three-stage annealing heat treatment is performed, and the cooling method is air cooling;

[0013] Step S4, when the temperature is cooled to 150°C, the roll is taken out of the furnace, and when the roll is cooled to room temperature by cold air, mechanical processing is performed to obtain a special working roll for medium and thick plates with high nickel and chromium content.

[0014] The further improvement of the technical solution of the present invention is that the smelting temperature in step S1 is 1450-1550°C, the cooling time of the molten iron in step S2 is 10-15 minutes, and the temperature of the molten iron during pouring is the melting point of the molten iron plus 60-80°C.

[0015] A further improvement of the technical solution of the present invention is that the inoculant in step S2 is Fe-Si particles, Si-Ba and ZL80 particles, and the added amount is 5 to 10 kg.

[0016] The further improvement of the technical solution of the present invention is that the heat treatment method in step S3 is specifically as follows: three-stage annealing is performed after unpacking, the first stage annealing temperature is 350-420°C, the annealing time is 20-40h, after air cooling to a temperature of ≤120°C, the second stage annealing is performed within 20 hours; the second stage annealing temperature is 400-460°C, the annealing time is 20-40h, after air cooling to a temperature of ≤120°C, the third stage annealing is performed within 20 hours; the third stage annealing temperature is 440-500°C, the annealing time is 20-40h.

[0017] The further improvement of the technical solution of the present invention is that the graphite content in the structure of the high nickel-chromium special working roll for medium and thick plates is 1.0-2.0%, the carbide content is 26-34%, and the microhardness of the matrix is ​​greater than 510HV.

[0018] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0019] The present invention adjusts the composition of the high nickel-chromium special working roll for medium and thick plates, and limits 0.5≤Cr / C≤1.0, Ni / Cr≥2.0, and V / Mo≥2.0. By designing reasonable Cr, C element content ratio, Ni, Cr element content ratio, and V, Mo element content ratio, it is ensured that the organization contains a high content of carbides, and the carbides have a high matrix microhardness, which ensures that the high nickel-chromium special working roll for medium and thick plates has higher wear resistance and pressure resistance than conventional high nickel-chromium; the organization contains a certain amount of graphite, which improves the heat cracking resistance of the rolling roll, and at the same time has a matrix toughness higher than that of conventional materials, which improves the accident resistance during the rolling process; the matrix is ​​strengthened, and the high matrix microhardness ensures the high wear resistance of the high nickel-chromium special working roll for medium and thick plates;

[0020] The present invention ensures that the amount of graphite in the structure is 1.0-2.0%, the amount of carbide is 26-34%, and the matrix microhardness is greater than 510HV by limiting the above-mentioned components. At the same time, by adding a certain amount of Nb element and coordinating the heat treatment process, the purpose of grain refinement is achieved, and ultimately the comprehensive performance of the rolling roller can meet the rolling requirements of medium and thick plates under special working conditions, solving the problem of roller pits and pitting in conventional high-nickel-chromium working rollers with high nickel-chromium during the rolling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a metallographic structure photo of the high nickel-chromium special working roll for medium and thick plates of the present invention;

[0022] Figure 2This is a metallographic structure photograph of a high nickel-chromium special working roll for medium and thick plates of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with embodiments:

[0024] The invention discloses a high nickel-chromium special working roll for medium and thick plates and a preparation method thereof. The manufacturing method includes the chemical composition range, casting and heat treatment parameters, control of the microstructure and performance indexes of the special working roll, and flow inoculation during the molten iron pouring process. Through the study of the material and the preparation process, a high nickel-chromium special working roll for medium and thick plates is prepared, which ensures that the microstructure and performance indexes meet the set expected goals, and effectively solves the problem of pits and pitting on the roll during the rolling process of medium and thick plates.

[0025] The following are specific embodiments of the present invention:

[0026] Embodiment 1:

[0027] a) Put the selected outer layer raw materials and core raw materials into an electric furnace for smelting. The outer layer alloy composition and the weight percentage of each alloy component are C: 2.80%, Si: 1.30%, Mn: 0.80%, Cr: 1.40%, Ni: 4.00%, Mo: 0.20%, V: 0.40%, Nb: 0.30, with incidental P≤0.03%; S≤0.03%, and the rest are Fe and unavoidable impurities; the core molten iron is made of ductile cast iron.

[0028] b) After the smelting in step a) is completed, the molten iron is calmed for 10 minutes. When the melting point of the molten iron is reached + 60°C, pouring begins. The outer layer of molten iron is poured on a centrifuge by a centrifugal composite pouring method. 6 kg of Fe-Si particles, Si-Ba particles and ZL80 particles (1:1:1) are added and inoculated as the pouring proceeds.

[0029] c) After the pouring in step b) is completed, insulation treatment is performed: when the outer wall temperature of the cold mold drops to 100°C, the box is opened and heat treatment is performed, and three-stage annealing is performed. The first stage annealing temperature is 360°C and the annealing time is 30h; the second stage annealing temperature is 410°C and the annealing time is 20h; the third stage annealing temperature is 450°C and the annealing time is 22h, and then cooling is performed.

[0030] d) Step c) When the steel is cooled to 60°C, it is taken out of the furnace and mechanically processed when cooled to room temperature by cold air to obtain a high nickel-chromium special working roll for medium and thick plates.

[0031] The graphite content of the high nickel-chromium special work roll for medium and thick plates is 1.0-2.0%, the carbide content is 26-34%, and the matrix microhardness is greater than 510HV. The metallographic structure of the prepared work roll is shown in the figure. Figure 1 and Figure 2As shown. The high nickel-chromium working roll structure made by the present invention is graphite + bainite + carbide. The structure contains a certain amount of graphite to play the role of lubrication and heat conduction. Graphite is a soft phase structure and should not be too high. It is best to keep it at 1.0-2.0%. The outer layer of molten iron is limited to the addition ratio of C, Cr, Ni, and V to 0.5≤Cr / C≤1.0, Ni / Cr≥2.0, and V / Mo≥2.0 to ensure that the structure contains a certain amount of eutectic carbide. At the same time, the addition of Ni content in the present invention eliminates the soft phase pearlite in the process of organizational transformation and improves the hardenability of the outer layer of the roller. The addition of V and Mo reinforcement forming elements ensures the matrix strength and high microhardness (matrix hardness>510HV), so that the roller has high wear resistance and foreign body resistance.

[0032] Embodiment 2:

[0033] a) Put the selected outer layer raw materials and core raw materials into an electric furnace for smelting. The outer layer alloy composition and the weight percentage of each alloy component are C: 2.90%, Si: 1.20%, Mn: 0.80%, Cr: 1.50%, Ni: 4.10%, Mo: 0.30%, V: 0.60%, Nb: 0.40, with incidental P≤0.03%; S≤0.03%, and the rest are Fe and unavoidable impurities; the core molten iron is made of ductile cast iron.

[0034] b) After the smelting in step a) is completed, the molten iron is calmed for 11 minutes. When the melting point of the molten iron is reached +65°C, pouring begins. The outer layer of molten iron is poured on a centrifuge by a centrifugal composite pouring method. 5 kg of Fe-Si particles, Si-Ba particles and ZL80 particles (1:1:1) are added and inoculated as the pouring proceeds.

[0035] c) After the pouring in step b) is completed, insulation treatment is performed: when the outer wall temperature of the cold mold drops to 100°C, the box is opened and heat treatment is performed, and three-stage annealing is performed. The first stage annealing temperature is 370°C and the annealing time is 32h; the second stage annealing temperature is 420°C and the annealing time is 22h; the third stage annealing temperature is 450°C and the annealing time is 22h, and then cooling is performed.

[0036] d) Step c) When the steel is cooled to 60°C, it is taken out of the furnace and mechanically processed when cooled to room temperature by cold air to obtain a high nickel-chromium special working roll for medium and thick plates.

[0037] Embodiment 3:

[0038] a) Put the selected outer layer raw materials and core raw materials into an electric furnace for smelting. The outer layer alloy composition and the weight percentage of each alloy component are C: 3.00%, Si: 1.10%, Mn: 0.85%, Cr: 1.70%, Ni: 4.20%, Mo: 0.40%, V: 0.80%, Nb: 0.30, with incidental P≤0.03%; S≤0.03%, and the rest are Fe and unavoidable impurities; the core molten iron is made of ductile cast iron.

[0039] b) After the smelting in step a), the molten iron is calmed for 12 minutes. When the melting point of the molten iron is reached +70°C, pouring begins. The outer layer of molten iron is poured on a centrifuge by centrifugal composite pouring. 5 kg of Fe-Si particles, Si-Ba particles and ZL80 particles (1:1:1) are added. Ladle inoculation is adopted, and a certain amount of inoculant is added during the pouring process.

[0040] c) After the pouring in step b) is completed, insulation treatment is performed: when the temperature of the outer wall of the cold mold drops to 100°C, the box is opened and heat treatment is performed, and three-stage annealing is performed. The first stage annealing temperature is 380°C and the annealing time is 32h; the second stage annealing temperature is 420°C and the annealing time is 24h; the third stage annealing temperature is 450°C and the annealing time is 24h, and then cooling is performed.

[0041] d) Step c) When the steel is cooled to 60°C, it is taken out of the furnace and mechanically processed when cooled to room temperature by cold air to obtain a high nickel-chromium special working roll for medium and thick plates.

[0042] Embodiment 4:

[0043] a) Put the selected outer layer raw materials and core raw materials into an electric furnace for smelting. The outer layer alloy composition and the weight percentage of each alloy component are C: 3.30%, Si: 0.75%, Mn: 0.70%, Cr: 1.90%, Ni: 4.30%, Mo: 0.60%, V: 1.40%, Nb: 0.70, with incidental P≤0.03%; S≤0.03%, and the rest are Fe and unavoidable impurities; the core molten iron is made of ductile cast iron.

[0044] b) After the smelting in step a), the molten iron is calmed for 13 minutes. When the melting point of the molten iron is reached +80°C, pouring begins. The outer layer of molten iron is poured on a centrifuge by a centrifugal composite pouring method. 5 kg of Fe-Si particles, Si-Ba particles and ZL80 particles (1:1:1) are added and inoculated as the pouring proceeds.

[0045] c) After the pouring in step b) is completed, insulation treatment is performed: when the temperature of the outer wall of the cold mold drops to 100°C, the box is opened and heat treatment is performed, and three-stage annealing is performed. The first stage annealing temperature is 400°C and the annealing time is 32h; the second stage annealing temperature is 430°C and the annealing time is 24h; the third stage annealing temperature is 460°C and the annealing time is 26h, and then cooling is performed.

[0046] d) Step c) When the steel is cooled to 60°C, it is taken out of the furnace and mechanically processed when cooled to room temperature by cold air to obtain a high nickel-chromium special working roll for medium and thick plates.

[0047] Embodiment 5:

[0048] a) Put the selected outer layer raw materials and core raw materials into an electric furnace for smelting. The outer layer alloy composition and the weight percentage of each alloy component are C: 3.40%, Si: 0.70%, Mn: 0.70%, Cr: 2.00%, Ni: 4.50%, Mo: 0.80%, V: 1.60%, Nb: 0.40, with incidental P≤0.03%; S≤0.03%, and the rest are Fe and unavoidable impurities; the core molten iron is made of ductile cast iron.

[0049] b) After the smelting in step a), the molten iron is calmed for 13 minutes. When the melting point of the molten iron is reached +80°C, pouring begins. The outer layer of molten iron is poured on a centrifuge by a centrifugal composite pouring method. 7kg of Fe-Si particles, Si-Ba particles and ZL80 particles (1:1:1) are added and inoculated as the pouring proceeds.

[0050] c) After the pouring in step b) is completed, insulation treatment is performed: when the outer wall temperature of the cold mold drops to 100°C, the box is opened and heat treatment is performed, and three-stage annealing is performed. The first stage annealing temperature is 410°C and the annealing time is 32h; the second stage annealing temperature is 440°C and the annealing time is 25h; the third stage annealing temperature is 470°C and the annealing time is 28h, and then cooling is performed.

[0051] d) Step c) When the steel is cooled to 60°C, it is taken out of the furnace and mechanically processed when cooled to room temperature by cold air to obtain a high nickel-chromium special working roll for medium and thick plates.

[0052] Embodiment 6:

[0053] a) Put the selected outer layer raw materials and core raw materials into an electric furnace for smelting. The outer layer alloy composition and the weight percentage of each alloy component are C: 3.50%, Si: 0.70%, Mn: 0.70%, Cr: 2.20%, Ni: 4.80%, Mo: 0.50%, V: 1.50%, Nb: 1.00, with incidental P≤0.03%; S≤0.03%, and the rest are Fe and unavoidable impurities; the core molten iron is made of ductile cast iron.

[0054] b) After the smelting in step a) is completed, the molten iron is calmed for 14 minutes. When the melting point of the molten iron is reached + 90°C, pouring begins. The outer layer of molten iron is poured on a centrifuge by a centrifugal composite pouring method. 7 kg of Fe-Si particles, Si-Ba particles and ZL80 particles (1:1:1) are added and inoculated as the pouring proceeds.

[0055] c) After the pouring in step b) is completed, insulation treatment is performed: when the outer wall temperature of the cold mold drops to 100°C, the box is opened and heat treatment is performed, and three-stage annealing is performed. The first stage annealing temperature is 420°C and the annealing time is 32h; the second stage annealing temperature is 450°C and the annealing time is 28h; the third stage annealing temperature is 480°C and the annealing time is 30h, and then cooling is performed.

[0056] d) Step c) When the steel is cooled to 60°C, it is taken out of the furnace and mechanically processed when cooled to room temperature by cold air to obtain a high nickel-chromium special working roll for medium and thick plates.

[0057] Embodiment 7:

[0058] a) Put the selected outer layer raw materials and core raw materials into an electric furnace for smelting. The outer layer alloy composition and the weight percentage of each alloy component are C: 3.45%, Si: 0.75%, Mn: 0.88%, Cr: 2.35%, Ni: 5.80%, Mo: 0.60%, V: 1.80%, Nb: 0.45, with incidental P≤0.03%; S≤0.03%, and the rest are Fe and unavoidable impurities; the core molten iron is made of ductile cast iron.

[0059] b) After the smelting in step a) is completed, the molten iron is calmed for 14 minutes. When the melting point of the molten iron is reached + 90°C, pouring begins. The outer layer of molten iron is poured on a centrifuge by a centrifugal composite pouring method. 7 kg of Fe-Si particles, Si-Ba particles and ZL80 particles (1:1:1) are added and inoculated as the pouring proceeds.

[0060] c) After the pouring in step b) is completed, insulation treatment is performed: when the outer wall temperature of the cold mold drops to 100°C, the box is opened and heat treatment is performed, and three-stage annealing is performed. The first stage annealing temperature is 420°C and the annealing time is 34h; the second stage annealing temperature is 475°C and the annealing time is 30h; the third stage annealing temperature is 480°C and the annealing time is 36h, and then cooling is performed.

[0061] d) Step c) is taken out of the furnace when cooled to 60°C, and mechanical processing is performed when cooled to room temperature by cold air.

[0062] Comparative Example 1:

[0063] a) Put the selected outer layer raw materials and core raw materials into an electric furnace for smelting. The outer layer alloy composition and the weight percentage of each alloy component are C: 3.00%, Si: 0.70%, Mn: 0.70%, Cr: 1.2%, Ni: 4.00%, Mo: 0.50%, V: 0.50%, Nb: 1.00, with incidental P≤0.03%; S≤0.03%, and the rest are Fe and unavoidable impurities; the core molten iron is made of ductile cast iron.

[0064] b) After the smelting in step a) is completed, the molten iron is calmed for 14 minutes. When the melting point of the molten iron is reached + 90°C, pouring begins. The outer layer of molten iron is poured on a centrifuge by a centrifugal composite pouring method. 7 kg of Fe-Si particles, Si-Ba particles and ZL80 particles (1:1:1) are added and inoculated as the pouring proceeds.

[0065] c) After the pouring in step b) is completed, insulation treatment is performed: when the outer wall temperature of the cold mold drops to 100°C, the box is opened and heat treatment is performed, and three-stage annealing is performed. The first stage annealing temperature is 420°C and the annealing time is 32h; the second stage annealing temperature is 450°C and the annealing time is 28h; the third stage annealing temperature is 480°C and the annealing time is 30h, and then cooling is performed.

[0066] d) Step c) is taken out of the furnace when cooled to 60°C, and mechanical processing is performed when cooled to room temperature by cold air.

[0067] Comparative Example 2:

[0068] a) Put the selected outer layer raw materials and core raw materials into an electric furnace for smelting. The outer layer alloy composition and the weight percentage of each alloy component are C: 3.20%, Si: 1.30%, Mn: 0.80%, Cr: 3.30%, Ni: 5.00%, Mo: 0.50%, V: 0.80%, Nb: 0.30, with incidental P≤0.03%; S≤0.03%, and the rest are Fe and unavoidable impurities; the core molten iron is made of ductile cast iron.

[0069] b) After the smelting in step a) is completed, the molten iron is calmed for 10 minutes. When the melting point of the molten iron is reached + 60°C, pouring begins. The outer layer of molten iron is poured on a centrifuge by a centrifugal composite pouring method. 6 kg of Fe-Si particles, Si-Ba particles and ZL80 particles (1:1:1) are added and inoculated as the pouring proceeds.

[0070] c) After the pouring in step b) is completed, insulation treatment is performed: when the outer wall temperature of the cold mold drops to 100°C, the box is opened and heat treatment is performed, and three-stage annealing is performed. The first stage annealing temperature is 360°C and the annealing time is 30h; the second stage annealing temperature is 410°C and the annealing time is 20h; the third stage annealing temperature is 450°C and the annealing time is 22h, and then cooling is performed.

[0071] d) Step c) is taken out of the furnace when cooled to 60°C, and mechanical processing is performed when cooled to room temperature by cold air.

[0072] The experimental results are shown in Table 1.

[0073] Table 1 Experimental results

[0074]

[0075]

[0076] According to the data, the high nickel-chromium special work roll for medium and thick plates produced by the present invention has higher matrix microhardness than conventional high nickel-chromium work rolls, and the relative wear resistance tested under the same test conditions is significantly improved, the thermal shock crack length is shorter, and the percentage of cold and hot fatigue crack area is smaller. The test data comprehensively show that the high nickel-chromium special roll of the present invention has high wear resistance, better impact resistance and thermal crack resistance.

[0077] The optional materials of various components are listed in the description of the present invention, but those skilled in the art should understand that the above-mentioned list of component materials is not limiting and not exhaustive, and various components can be replaced by other equivalent materials not mentioned in the description of the present invention, while still achieving the purpose of the present invention. The specific embodiments mentioned in the description are also only for the purpose of explanation, and are not used as examples to limit the scope of the present invention.

Claims

1. A high nickel-chromium special working roll for medium and thick plates, characterized by: The working roll is a centrifugal composite casting roll, including an outer layer and a core. The alloy composition and content range of the outer layer molten iron are: C: 2.80-4.00%, Si: 0.50-1.50%, Mn: 0.30-1.50%, P≤0.03%; S≤0.03%, Cr: 1.00-4.00%, Ni: 4.00-6.00%, Mo: 0.20-3.00%, V: 0.20-3.00%, Nb: 0.2-2.0%, and the rest are Fe and unavoidable impurities; the core molten iron is made of ductile iron; the addition amounts of C, Cr, Ni, and V in the outer layer molten iron are limited to satisfy 0.5≤Cr / C≤1.0, Ni / Cr≥2.0, and V / Mo≥2.

0.

2. The high nickel-chromium special working roll for medium and thick plates according to claim 1 is characterized in that: The composition and content range of the molten iron alloy of the outer layer of the working roller are: C: 2.80-4.00%, Si: 0.50-1.50%, Mn: 0.30-1.50%, P≤0.03%; S≤0.03%, Cr: 1.00-3.00%, Ni: 4.00-6.00%, Mo: 0.20-1.50%, V: 0.30-3.00%, Nb: 0.2-2.0%.

3. A method for preparing a high nickel-chromium special working roll for medium and thick plates, characterized in that The steps include: Step S1, placing the selected outer layer raw material and core raw material into an electric furnace for smelting respectively, and adjusting the alloy composition; Step S2, after the above raw materials are smelted, the molten iron is calmed for a period of time, and argon is blown from the bottom when the molten iron is transferred to the casting ladle to make the composition and temperature uniform and prevent the oxidation of the molten iron; when the outer layer of molten iron reaches the casting temperature, a centrifugal composite casting method is adopted to cast the outer layer of molten iron on a centrifuge; a ladle inoculation is adopted, a certain amount of inoculant is added during the casting process, and after the outer layer of molten iron solidifies, a temperature measuring device is used to detect the cavity temperature, and the core molten iron is cast after reaching a certain temperature; Step S3, after pouring is completed, heat preservation treatment is performed, and the box is opened when the temperature of the outer wall of the casting mold drops to 80°C. After opening the box, three-stage annealing heat treatment is performed, and the cooling method is air cooling; Step S4, when the temperature is cooled to 150°C, the roll is taken out of the furnace, and when the roll is cooled to room temperature by cold air, mechanical processing is performed to obtain a special working roll for medium and thick plates with high nickel and chromium content.

4. The method for preparing a high nickel-chromium special working roll for medium and thick plates according to claim 3, characterized in that: The smelting temperature in step S1 is 1450-1550° C., the cooling time of the molten iron in step S2 is 10-15 minutes, and the temperature of the molten iron during pouring is the melting point of the molten iron plus 60-80° C.

5. The method for preparing a high nickel-chromium special working roll for medium and thick plates according to claim 3, characterized in that: In step S2, the inoculant is Fe-Si particles, Si-Ba and ZL80 particles, the ratio of Fe-Si particles, Si-Ba and ZL80 particles is 1:1:1, and the added amount is 5-10 kg.

6. The high nickel-chromium special working roll for medium and thick plates and the method for preparing the same according to claim 3, characterized in that: The heat treatment method in step S3 is specifically as follows: three-stage annealing is performed after unpacking, wherein the first stage annealing temperature is 350-420°C, the annealing time is 20-40h, and after air cooling to a temperature of ≤120°C, the second stage annealing is performed within 20 hours; the second stage annealing temperature is 400-460°C, the annealing time is 20-40h, and after air cooling to a temperature of ≤120°C, the third stage annealing is performed within 20 hours; the third stage annealing temperature is 440-500°C, and the annealing time is 20-40h.

7. The high nickel-chromium special working roll for medium and thick plates according to claim 1 is characterized in that: The graphite content in the structure of the high nickel-chromium special working roll for medium and thick plates is 1.0-2.0%, the carbide content is 26-34%, and the microhardness of the matrix is ​​greater than 510HV.

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