Wear-resistant hypereutectic high-chromium cast iron composite roller and preparation method thereof

Abstract

The invention discloses a wear-resistant hypereutectic high-chromium cast iron composite roller and a preparation method thereof, and belongs to the field of rollers. Firstly, waste steel, a carburant, high-carbon ferrochrome, ferromanganese and ferrosilicon are mixed, heated and melted in a medium-frequency induction furnace, when the temperature of molten iron reaches 1523-1547 DEG C, the molten iron is discharged out of the furnace and placed into a casting ladle, aluminum-magnesium alloy is put into the bottom of the casting ladle in advance, and the adding amount of the aluminum-magnesium alloy accounts for 0.25-0.30% of the mass fraction of the molten iron entering the casting ladle. The wear-resistant hypereutectic high-chromium cast iron roller sleeve is produced by adopting a centrifugal casting method, the wear-resistant hypereutectic high-chromium cast iron roller sleeve and the medium-carbon low-alloy forged steel roller shaft are subjected to hot charging and compounding into a whole, the wear-resistant hypereutectic high-chromium cast iron composite roller is obtained, and the wear-resistant hypereutectic high-chromium cast iron composite roller has the characteristics of simple and convenient process, high production efficiency, and the service life is prolonged by 40% or above compared with that of a high-nickel-chromium infinite cooling cast iron roller, and good economic and social benefits are achieved in application and popularization.

Description

Technical Field

[0001] The invention discloses a wear-resistant high-chromium cast iron roll and a preparation method thereof, in particular to a wear-resistant hypereutectic high-chromium cast iron composite roll and a preparation method thereof, belonging to the technical field of steel rolling. Background Art

[0002] Rollers are parts of the rolling mill that cause the rolled metal to undergo plastic deformation. The shape, size and material of the rolls must be adapted to the rolling mill and the rolled product. Rollers mainly include a roll body, a roll neck and a joint. The roll body is the working part of the roll, and the roll neck is the part in contact with the bearing, which is connected to the transmission device by a joint. With the development of steel rolling technology, the speed of the rolling mill is constantly increasing, and higher requirements are placed on the performance of the rolls. Rollers are subjected to various cyclic stresses during use, including bending, torsion, shear, contact stress and thermal stress, etc. The distribution of these stresses along the roll body is uneven and constantly changing. The rolls currently used have poor wear resistance, short service life, and need to be replaced frequently. The maintenance and replacement costs are high, and frequent maintenance and replacement lead to frequent production shutdowns, which seriously affects production efficiency and reduces production economic benefits.

[0003] In order to improve the performance of the rolling mill, Chinese invention patent CN116065082A discloses a method for manufacturing a high-tungsten vanadium high-speed steel wear-resistant rolling mill roll, which uses an electric furnace to apply a purifier with a preset formula, puts the pure molten steel into the electric furnace for smelting, and smelts until foam appears in the electric furnace, then adds alloy powder steel into the electric furnace, and waits to obtain smelted molten steel; the unprocessed rolling mill roll is refined for a preset time period in the refining furnace to obtain a refined rolling mill roll; the refined rolling mill roll is placed in a vacuum heat treatment furnace for quenching treatment to obtain a treated rolling mill roll; the electroslag is remelted for a preset time period to prepare an electrode ingot; the treated rolling mill roll is ground for a preset time period to remove the fatigue layer attached to the rolling mill roll to obtain a forged rolling mill roll; the smelted molten steel is used, in combination with the electrode ingot, to cast the forged rolling mill roll for a preset time period to obtain a manufactured high-tungsten vanadium high-speed steel wear-resistant rolling mill roll. Chinese invention patent CN113020273A also discloses a highly wear-resistant rolling roller, comprising a first mounting shaft end, a roller body, a second mounting shaft end, a storage support plate and a screw mounting assembly, wherein the second mounting shaft end is arranged in the middle of the side of the roller body, the first mounting shaft end is arranged on the side of the second mounting shaft end, a threaded hole is arranged on the inner side of the first mounting shaft end, a mounting hole is arranged next to the threaded hole, the screw mounting assembly is arranged on the other side of the roller body, a screw hole is arranged on the inner side of the screw mounting assembly, the side of the screw mounting assembly is externally connected to the roller body, a reinforcement layer is arranged on the inner side of the roller body, and the storage support plate is arranged inside the reinforcement layer. The invention has solved the problems in the prior art that the roller has no reinforcement function, resulting in a short service life of the roller, and the cooling method cannot achieve rapid cooling of the roller, resulting in extremely low working efficiency. Chinese invention patent CN110760665A also discloses a production process of a high-wear-resistant roller, and its production process includes the following steps: Step 1, smelting: (1) select high-strength alloy steel and put it into a high-temperature furnace to melt it into molten metal for standby use; (2) select wear-resistant zinc alloy material and put it into a high-temperature furnace to melt it into molten metal, keep it warm for standby use; Step 2, casting: (1) the inner cavity of the roller mold is coated with 2-3mm thick wear-resistant alloy powder, let it stand for 10-15min, and put it into standby use; (2) pour the high-strength alloy steel melted into molten metal into the inner cavity of the roller mold. This invention can increase the wear resistance of the roller by coating the inner cavity of the mold with wear-resistant alloy powder in the casting process, and after the roller is obtained, it is hot-dip coated with wear-resistant zinc alloy, so that the produced roller can have high-strength hardness and toughness. The above-mentioned roller still has a small amount of wear-resistant hard phase, and the wear resistance needs to be further improved.

[0004] Chinese invention patent CN110000362A discloses a high-tungsten-vanadium high-speed steel wear-resistant roller and a manufacturing method thereof, wherein an electric furnace is used to melt the outer layer high-speed steel molten steel and the roller core molten iron respectively, the outer layer high-speed steel of the roller is firstly melted in the electric furnace, and the chemical composition and mass fraction of the molten steel in the furnace are controlled within 10.23-10.67% W, 1.76-1.94% Mo, 2.81-2.97% C, <<0.035% P, <0.030% S, 6.15-6 .42% Cr, 2.27-2.46% Nb, 2.24-2.41% Si, 0.64-0.83% Mn, the balance is Fe and other inevitable impurities, and then the molten steel is heated to 1653-1677℃, aluminum and ferrovanadium are added in turn, and then multi-element alloy particles are added into the ladle, and cast into rollers on a vertical centrifuge. After heat treatment, it has good strength and toughness and excellent wear resistance, and is used for rolling low-alloy hot-rolled rebar with excellent use effect. Chinese invention patent CN107350456A also discloses a preparation process for a highly wear-resistant roller, which specifically includes the following steps: selecting ZG35SiMn as a matrix, and putting it into a high-temperature furnace to melt it into a molten metal, the melting temperature of which is 1560-1600°C; then coating the side wall inside the mold with a 1-2 mm thick wear-resistant alloy powder, and then rapidly pouring the above-mentioned molten metal into the mold so that the molten metal covers the wear-resistant alloy powder on the side wall of the mold; using a cooling air gun to air-cool the mold surface, thereby driving the cooling of the molten metal inside the mold, thereby cooling and forming, and integrating the wear-resistant alloy powder on the side wall of the mold into the product surface, and finally obtaining a highly wear-resistant roller. Through the above method, the invention can make the prepared roller have extremely high wear resistance. Chinese invention patent CN107185965A also discloses a high wear-resistant roller, comprising: a high chromium cast iron roller body, a high strength wear-resistant layer plated on the outer surface of the high chromium cast iron roller body, the high strength wear-resistant layer having at least one layer, the chemical composition and mass ratio of each component thereof being: carbon 0.21%-0.28%, silicon 0.1%-0.2%, manganese 0.5%-1.2%, nickel 0.02%-0.08%, chromium 0.8%-1.8%, zinc 0.5%-1.1%, and the rest being iron and inevitable impurities. In the above manner, the invention makes the roller have excellent wear resistance by plating at least one layer of high strength wear-resistant layer on the outer surface of the high chromium cast iron roller body, and at the same time, by optimizing the composition and ratio of the high strength wear-resistant layer, the roller has excellent resistance to high temperature oxidation and thermal fatigue crack growth.Chinese invention patent CN107164694A also discloses a processing technology for a highly wear-resistant roller, the roller comprising a roller body and a wear-resistant zinc alloy layer formed on the surface of the roller body by hot-dip plating, the processing technology for the roller comprising the following steps: 1) smelting and casting alloy steel; 2) low-pressure casting; 3) heat treatment: placing the roller casting obtained in step 2) into a normalizing furnace, normalizing and heating to 650-700°C, keeping the temperature for 1-2 hours, and then cooling with the furnace to below 300°C and taking it out of the furnace; 4) hot-dip plating of a wear-resistant coating. In the above manner, the invention adopts low-pressure casting, heat treatment and surface hot-dip galvanizing wear-resistant coating to obtain a roller, which can effectively improve the intrinsic and surface quality of the roller, avoid cracking, and at the same time make the roller have excellent strength and wear resistance, which can improve its service life to a limited extent. Chinese invention patent CN107034411A also discloses a method for preparing a wear-resistant roll, which is characterized by using an induction furnace for smelting. The specific preparation process steps are: (1) using scrap steel, pig iron, ferrochrome, nickel plate, ferrotungsten, ferroniobium, ferrosilicon, ferromanganese and metallic aluminum ingredients, first mixing ferrotungsten, ferroniobium, scrap steel, pig iron and nickel plate in a furnace for heating and melting, adding ferrochrome after all the above materials are melted, and after the ferrochrome is melted, heating the molten iron to 1532-1555°C, and then adding ferrosilicon, ferromanganese and Metal aluminum, and slag the molten iron at 1563-1587℃ and test the composition. When the chemical composition and mass fraction of the molten iron are 3.28-3.63% C, 2.15-2.44% Cr, 0.064-0.095% Nb, 3.95-4.38% Ni, 2.19-2.56% W, 0.69-0.88% Al, 0.72-0.99% Si, 0.25-0.51% Mn, <0.035% S, <0.040% P, the balance Fe and When the inevitable impurities are removed, the molten iron is taken out of the furnace and poured into a ladle. The bottom of the ladle is pre-placed with copper-magnesium alloy, ferrovanadium, ferromanganese nitride, rare earth ferrosilicon and ferroboron which have been preheated at 200-250°C for 90-150 minutes. The size of the above alloys is (8-15mm)×(8-15mm)×(8-15mm). The amount of copper-magnesium alloy, ferrovanadium, ferromanganese nitride, rare earth ferrosilicon and ferroboron added accounts for 0.25-0.35%, 0.35-0.45%, 0.35-0. 45%, 0.55-0.70% and 0.15-0.25%, and then the molten iron in the ladle is stirred, slag-stripped and allowed to stand; (2) when the temperature of the molten iron in the ladle in step (1) drops to 1437-1470°C, the molten iron is poured into a casting mold to obtain a roll blank product. After rough machining, the roll blank is heated to 375-425°C in a furnace, kept warm for 10-15 hours, cooled to a temperature below 180°C, taken out of the furnace and air-cooled to room temperature, and finally fine-machined to a specified size and accuracy to obtain a wear-resistant roll product.Chinese Patent for Invention CN101412096A also discloses a preparation method of a composite wear-resistant roll with primary columns / ribbon-shaped hard particles. The composite wear-resistant roll prepared by this method consists of a core part and a surface wear-resistant layer. The core part is made of a steel material with high toughness, and the surface wear-resistant layer is composed of high-hardness columns / ribbon-shaped hard particles and a high-toughness metal material. First, the roll core is machined, and then a wire / ribbon-shaped material skeleton with a certain thickness is woven on the surface support frame of the roll core using a high-alloy powder-cored wire / ribbon (note: the ribbon can be pressed from the wire), and is fixed by binding or welding. The woven preform is placed into a casting cavity, and is cast using high-temperature molten steel. The high-alloy powder-cored wire / ribbon is infiltrated, sintered or melted. Within a certain temperature range, alloy elements perform short-range diffusion, and metallurgical bonding between the two parts of high-hardness columns / ribbon-shaped hard particles and high-toughness matrix metal is achieved on the roll surface, forming a surface hard-particle wear-resistant composite layer containing a certain proportion of columns / ribbon-shaped hard particles. Chinese Patent for Invention CN1557579A also discloses a bionic non-smooth wear-resistant roll, which is composed of a wear-resistant material roll skin and a core material with good toughness. Its characteristic lies in that the roll skin has a micron-level corrugated non-smooth surface, and the corrugation pattern on the roll skin surface is: the wave width b is 50 - 200 microns, the height d between the wave peak and the wave valley is 25 - 100 microns, and the distribution direction of the corrugations can be radial or axial. However, when manufacturing wear-resistant rolls by the above methods, there are generally deficiencies such as complex production processes and high production costs. Summary of the Invention

[0005] In view of the series of problems existing in the production of wear-resistant rolls, the present invention uses a centrifugal casting method to produce a wear-resistant hypereutectic high-chromium cast iron roll sleeve, and then thermally assembles it with a medium-carbon low-alloy forged steel roll shaft into one body, obtaining a wear-resistant composite roll with a high-hardness roll surface, good wear resistance, and good strength and toughness of the roll shaft.

[0006] A preparation method of a wear-resistant hypereutectic high-chromium cast iron composite roll, and the specific preparation process steps are as follows:

[0007] ① Melting hypereutectic high-chromium cast iron using an intermediate frequency induction furnace; first, scrap steel, carburizer, high-carbon ferrochromium, ferromanganese and ferrosilicon are mixed and heated for melting in the intermediate frequency induction furnace. After the molten iron is melted and clarified, a sample is taken for analysis, and the chemical composition and mass fraction of the molten iron in the furnace are controlled at 4.16 - 4.33% C, 25.58 - 25.97% Cr, 1.25 - 1.38% Si, 0.64 - 0.79% Mn, <0.04% S, <0.06% P, 5.90 < Cr / C < 6.25, and the balance is Fe and inevitable impurities; when the temperature of the molten iron reaches 1523 - 1547 °C, the molten iron is poured out into a ladle; an aluminum-magnesium alloy is pre-placed at the bottom of the ladle, and the addition amount of the aluminum-magnesium alloy accounts for 0.25 - 0.30% of the mass fraction of the molten iron entering the ladle;

[0008] ② After all the molten iron has entered the ladle for 4-7 minutes, the slag is removed and the molten iron is allowed to stand. When the temperature of the molten iron drops to 1442-1459° C., the molten iron is poured into a casting mold on a high-speed rotating horizontal centrifuge at a casting speed of 920-980 rpm. During the molten iron pouring process, multi-element alloy additive particles are added along with the molten iron flow. The amount of the multi-element alloy additive added accounts for 0.8-1.0% of the mass fraction of the molten iron entering the casting mold. The particle size of the multi-element alloy additive is 0.3-0.7 mm. The chemical composition and mass fraction of the multi-element alloy additive are 12.47-13.15% Ti, 6.02-6.48% Al, 3.37-3.66% Zn, 5.50-5.87% Ca, 10.13-10.82% Si, 3.38-3.70% K, 2.17-2.49% N, and the remainder is Fe and unavoidable impurities.

[0009] ③ After the molten iron is completely solidified, the casting is taken out of the mold, and after grinding and sand removal, it is roughly processed to obtain a hypereutectic high chromium cast iron roller sleeve; the hypereutectic high chromium cast iron roller sleeve after rough processing is heated to 1025-1045℃ with the furnace, kept warm for 50-60 minutes, furnace cooled to a temperature of 975-990℃, kept warm for 60-80 minutes, and air-cooled to a roller surface temperature of 380-430℃ after being taken out of the furnace; it is re-entered into the furnace and heated to 520-550℃, kept warm for 8-10 hours, furnace cooled to a temperature of 350-380℃, taken out of the furnace, and composited with the roller shaft, which is a medium-carbon low-alloy forged steel; the interference is controlled at 0.13-0.18mm; finally, it is finely processed to the specified size and accuracy to obtain a wear-resistant hypereutectic high chromium cast iron composite rolling roller.

[0010] As mentioned above, the chemical composition and mass fraction of the aluminum-magnesium alloy are 85-87% Al, 13-15% Mg, and the sum of the two is 100%.

[0011] The wear-resistant working layer of the composite roll of the present invention is made of high chromium cast iron containing hypereutectic carbide, mainly because the hypereutectic carbide can increase the wear resistance of the roll. The wear-resistant hypereutectic high chromium cast iron roll sleeve is produced by centrifugal casting, and then hot-fitted and composited with a medium-carbon low-alloy forged steel roll shaft to obtain a wear-resistant composite roll with high roll surface hardness, good wear resistance, and good roll shaft toughness. The specific preparation process steps are:

[0012] First, hypereutectic high chromium cast iron is melted in an intermediate frequency induction furnace. The molten iron melting process is simple, and the composition is easy to control. In this invention, scrap steel, carburizer, high-carbon ferrochrome, ferromanganese, and ferrosilicon are first mixed and heated to melt in the intermediate frequency induction furnace. After the molten iron is melted and clarified, a sample is taken for analysis, and the chemical composition and mass fraction of the molten iron in the furnace are controlled at 4.16 - 4.33% C, 25.58 - 25.97% Cr, 1.25 - 1.38% Si, 0.64 - 0.79% Mn, <0.04% S, <0.06% P, 5.90 < Cr / C < 6.25, and the balance is Fe and unavoidable impurities. In this invention, the carbon content is controlled at 4.16 - 4.33%, the chromium content is controlled at 25.58 - 25.97%, and 5.90 < chromium to carbon ratio (Cr / C) < 6.25, ensuring that the carbide obtained in the solidification structure of hypereutectic high chromium cast iron is the high-hardness Cr7C3, and the volume fraction of carbide is as high as 50 - 53%, thus significantly improving the wear resistance of the hypereutectic high chromium cast iron roll. If the chromium to carbon ratio (Cr / C) is too high, low-hardness Cr 23 C6 carbide is likely to precipitate during solidification; if the chromium to carbon ratio (Cr / C) is too low, a small amount of low-hardness (Cr,Fe)3C carbide will precipitate, both of which will reduce the wear resistance of the roll. When 5.90 < chromium to carbon ratio (Cr / C) < 6.25, the obtained carbides are all high-hardness Cr7C3 carbides, making the hypereutectic high chromium cast iron composite roll have excellent wear resistance. The furnace charge smelted in this invention is scrap steel, carburizer, high-carbon ferrochrome, ferromanganese, and ferrosilicon. The above raw materials are convenient to obtain and low in price, ensuring that the roll has a low production cost.

[0013] When the temperature of the molten iron reaches 1523-1547℃, the molten iron is taken out of the furnace and poured into a ladle; an aluminum-magnesium alloy is placed in the bottom of the ladle in advance, and the amount of aluminum-magnesium alloy added accounts for 0.25-0.30% of the mass fraction of the molten iron entering the ladle. The chemical composition and mass fraction of the aluminum-magnesium alloy are 85-87% Al, 13-15% Mg. During the solidification process of hypereutectic high-chromium cast iron, Cr7C3 type carbide is a primary phase, which first solidifies and grows from the molten steel, grows into coarse block carbides, increases the brittleness of hypereutectic high-chromium cast iron, and is very easy to produce brittle fracture during casting and use. After adding the aluminum-magnesium alloy, the aluminum element is enriched on the surface of the primary carbide. During the solidification process of the hypereutectic high-chromium cast iron, the aluminum element enriched on the surface of the primary carbide can also play a role in hindering the diffusion of atoms of carbide-forming elements such as C and Cr in the melt to the carbide crystals, thereby slowing down the growth rate of the carbide and refining the hypereutectic carbide. And aluminum can also be preferentially adsorbed on the crystal plane with larger growth, thereby reducing the growth rate of carbides in the preferred growth direction, and also improving the morphology of carbides. In addition, aluminum can deoxidize, degas, purify molten iron and reduce the resistance to nucleation of primary austenite. Aluminum oxide, as the core of heterogeneous nucleation, accelerates the solidification of austenite and refines the grains. In addition, aluminum is a non-carbide forming element, which limits the number of eutectic carbides and the coarsening of eutectic carbides, thereby significantly reducing the brittleness of hypereutectic high chromium cast iron. When hypereutectic high chromium cast iron is in liquid state, it is not a single uniform melt of Fe, C, Cr and other element atoms, but also contains a large amount of impurities such as S, P and their compounds, and will absorb a large amount of oxygen, nitrogen and other gases at high temperature. The addition of magnesium can effectively remove impurities such as P, S, O, N, so after adding magnesium, the number of shrinkages is significantly reduced, the microstructure is more compact, and it is beneficial to improve the wear resistance of hypereutectic high chromium cast iron. In addition, the primary carbides of hypereutectic high chromium white cast iron grow in the hexagonal system. Due to the obvious anisotropy of hexagonal crystals, the main growth direction is

[0001] , forming long rod-shaped crystals with a hexagonal cross-section. Magnesium is easily adsorbed on the surface of carbide crystals that grow preferentially, that is, it selectively adsorbs on the surface

[0001] in the preferential growth direction of carbides during crystallization to form an adsorption film. The formation of this film plays a barrier role, which can effectively repel or hinder the diffusion of Fe, C, Cr and other atoms in molten iron, reduce the growth rate of carbides in the preferential direction, and curb the anisotropy of carbide growth. To a certain extent, the lamellar growth tendency of primary carbides is suppressed, which plays a role in improving the morphology of carbides. The improvement of carbide morphology is conducive to improving the impact toughness of hypereutectic high chromium cast iron, ensuring that the wear-resistant hypereutectic high chromium cast iron composite roller does not crack or peel off during use.

[0014] In the present invention, after all the molten iron enters the ladle for 4-7 minutes, the slag is removed and the ladle is left to stand. When the temperature of the molten iron drops to 1442-1459°C, the molten iron is poured into a casting mold on a high-speed rotating horizontal centrifuge, and the casting speed is 920-980rpm. The centrifugal casting method is used to cast the hypereutectic high chromium cast iron roll, which has high production efficiency and dense solidification structure, ensuring that the roll has excellent wear resistance. However, due to the centrifugal force in the centrifugal casting process, the number of carbides in the hypereutectic high chromium cast iron is too large, and the roll sleeve is prone to cracking, resulting in a high roll scrap rate. In order to solve the cracking problem of hypereutectic high chromium cast iron during centrifugal pouring, the present invention adds a multi-element alloy additive along with the molten iron flow during the molten iron pouring process; the amount of the multi-element alloy additive added accounts for 0.8-1.0% of the mass fraction of the molten iron entering the casting mold; the particle size of the multi-element alloy additive is 0.3-0.7mm; the chemical composition and mass fraction of the multi-element alloy additive are 12.47-13.15% Ti, 6.02-6.48% Al, 3.37-3.66% Zn, 5.50-5.87% Ca, 10.13-10.82% Si, 3.38-3.70% K, 2.17-2.49% N, and the balance is Fe and inevitable impurities. The addition of the above-mentioned multi-element alloy additives, because the multi-element alloy additives contain 3.37-3.66% Zn, 3.38-3.70% K, 2.17-2.49% N and 12.47-13.15% Ti, can further refine the carbides, and the multi-element alloy additives contain 5.50-5.87% Ca and 3.38-3.70% K, which can reduce inclusions and improve the morphology and distribution of inclusions, completely solve the cracking problem in the centrifugal pouring process of hypereutectic high chromium cast iron, and significantly improve the qualified rate of roll casting.

[0015] After the molten iron of the present invention is completely solidified, the casting is taken out from the mold, and after grinding and sand removal, rough processing is performed to obtain a hypereutectic high chromium cast iron roller sleeve. The hypereutectic high chromium cast iron roller sleeve after rough processing is heated to 1025-1045°C with the furnace and kept warm for 50-60 minutes. Heating and keeping warm at high temperature can promote the carbide to further dissolve into the high-temperature austenite, thereby improving the strength and toughness of the roller sleeve. However, the quenching temperature of the roller sleeve cannot be too high, otherwise there will be too much residual austenite in the quenching structure, and the wear resistance of the roller sleeve will be reduced. The present invention is heated to 1025-1045°C at high temperature, kept warm for 50-60 minutes, and then needs to be furnace cooled to a temperature of 975-990°C, kept warm for 60-80 minutes, and then taken out of the furnace and air-cooled to a roller surface temperature of 380-430°C. When the hypereutectic high chromium cast iron roller sleeve is furnace cooled from 1025-1045℃ to 975-990℃, fine secondary carbides are precipitated in the matrix structure and evenly distributed in the matrix structure, which improves the wear resistance of the matrix structure, is conducive to improving the wear resistance of the hypereutectic high chromium cast iron roller sleeve, and can also ensure that a high-hardness martensitic matrix is ​​obtained after quenching, thereby improving the wear resistance of the roller sleeve. At this time, the internal stress of the roller sleeve is large, and it needs to be reheated to 520-550℃ in the furnace, kept warm for 8-10 hours, and furnace cooled to a temperature of 350-380℃ before being taken out of the furnace. Then it is combined with the roller shaft to obtain a hypereutectic high chromium cast iron composite roll. The roller shaft is a common medium-carbon low-alloy forged steel, and the interference is controlled at 0.13-0.18mm to ensure that the roller sleeve and the roller shaft are firmly combined, and the roller sleeve will not fall off during the use of the composite roll. Finally, it is finely processed to the specified size and accuracy to obtain a wear-resistant hypereutectic high chromium cast iron composite roll.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The charge for smelting the hypereutectic high chromium cast iron roll sleeve of the composite roll working layer of the present invention is scrap steel, carburizer, high carbon ferrochrome, ferromanganese and ferrosilicon, and does not contain expensive molybdenum and nickel elements. The above raw materials are easy to source and low in price, ensuring that the roll has a lower production cost.

[0018] 2. The composite roller of the present invention combines the hypereutectic high chromium cast iron roller sleeve and the medium carbon low alloy forged steel roller shaft into one by hot-assembly, which has simple process, high production efficiency, and the roller shaft can be reused, which is green and environmentally friendly.

[0019] 3. The present invention controls the carbon content of the hypereutectic high chromium cast iron roller sleeve to 4.16-4.33%, the chromium content to 25.58-25.97%, and the chromium-carbon ratio (Cr / C) of 5.90<6.25, ensuring that the carbide obtained in the solidification structure of the hypereutectic high chromium cast iron is high-hardness Cr7C3, and the volume fraction of the carbide is as high as 50-53%, thereby significantly improving the wear resistance of the hypereutectic high chromium cast iron roller.

[0020] 4. The hardness of the hypereutectic high chromium cast iron roller sleeve of the present invention is greater than 83HSD, the roller surface hardness is uniform, the hardness difference is less than 2.5HSD, and the impact toughness is greater than 6.0J / cm 2 The invention has excellent wear resistance when used in hot rolling bar and wire mills and plate and strip mills, and its service life is increased by more than 40% compared with high nickel-chromium infinite cooling cast iron rolls, and the production cost is reduced by 12-15%. The popularization and application of the rolls of the invention can improve the surface quality of rolled materials and reduce the production cost of rolled materials, and the popularization and application has good economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of wear-resistant hypereutectic high chromium cast iron composite roll.

[0022] 1-Eutectic high chromium cast iron roller sleeve, 2-Medium carbon low alloy forged steel roller shaft. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to the examples, but the present invention is not limited to the following examples.

[0024] Embodiment 1:

[0025] A wear-resistant hypereutectic high-chromium cast iron composite roll and a preparation method thereof, wherein a wear-resistant hypereutectic high-chromium cast iron roll sleeve 1 is produced by a centrifugal casting method, and then hot-fitted and composited with a medium-carbon low-alloy forged steel roll shaft 2. The specific preparation process steps are:

[0026] ① A medium frequency induction furnace is used to melt hypereutectic high chromium cast iron; scrap steel, carburizer, high carbon ferrochrome, ferromanganese and ferrosilicon are first mixed and heated in a medium frequency induction furnace for melting, and the molten iron is sampled and analyzed after being melted, and the chemical composition and mass fraction of the molten iron in the furnace are controlled at 4.28% C, 25.82% Cr, 1.34% Si, 0.75% Mn, 0.039% S, 0.048% P, Cr / C=6.03, and the remainder is Fe and unavoidable impurities; when the temperature of the molten iron reaches 1538°C, the molten iron is taken out of the furnace and poured into a ladle; an aluminum-magnesium alloy (the chemical composition and mass fraction of the aluminum-magnesium alloy are 86.5% Al, 13.5% Mg) is pre-placed at the bottom of the ladle, and the amount of the aluminum-magnesium alloy added accounts for 0.28% of the mass fraction of the molten iron entering the ladle;

[0027] ② After all the molten iron has entered the ladle for 5 minutes, the slag is removed and the molten iron is allowed to stand. When the temperature of the molten iron drops to 1455°C, the molten iron is poured into a casting mold on a high-speed rotating horizontal centrifuge at a casting speed of 950rpm; and during the molten iron pouring process, a multi-element alloy additive is added along with the molten iron flow; the amount of the multi-element alloy additive added accounts for 0.9% of the mass fraction of the molten iron entering the casting mold; the particle size of the multi-element alloy additive is 0.3-0.7mm; the chemical composition and mass fraction of the multi-element alloy additive are 12.80% Ti, 6.36% Al, 3.51% Zn, 5.64% Ca, 10.73% Si, 3.57% K, 2.39% N, and the remainder is Fe and unavoidable impurities;

[0028] ③ After the molten iron is completely solidified, the casting is taken out of the mold, and after grinding and sand removal, it is roughly processed to obtain a hypereutectic high chromium cast iron roller sleeve 1; the hypereutectic high chromium cast iron roller sleeve 1 after rough processing is heated to 1030℃ with the furnace, kept warm for 55 minutes, cooled to 980℃ in the furnace, kept warm for 70 minutes, and air-cooled to the roller surface temperature of 390-420℃ after being taken out of the furnace; it is re-entered into the furnace and heated to 540℃, kept warm for 9 hours, cooled to 370℃ in the furnace, and taken out of the furnace; it is composited with the roller shaft 2, which is 40Cr medium carbon low alloy forged steel; the interference is controlled at 0.16mm; finally, it is finely processed to the specified size and accuracy to obtain a wear-resistant hypereutectic high chromium cast iron composite roller. The mechanical properties of the roller are shown in Table 1.

[0029] Embodiment 2:

[0030] A wear-resistant hypereutectic high-chromium cast iron composite roll and a preparation method thereof, wherein a wear-resistant hypereutectic high-chromium cast iron roll sleeve 1 is produced by a centrifugal casting method, and then hot-fitted and composited with a medium-carbon low-alloy forged steel roll shaft 2. The specific preparation process steps are:

[0031] ① A medium frequency induction furnace is used to melt hypereutectic high chromium cast iron; scrap steel, carburizer, high carbon ferrochrome, ferromanganese and ferrosilicon are first mixed and heated in a medium frequency induction furnace for melting, and the molten iron is sampled and analyzed after being melted, and the chemical composition and mass fraction of the molten iron in the furnace are controlled at 4.16% C, 25.97% Cr, 1.25% Si, 0.79% Mn, 0.037% S, 0.054% P, Cr / C=6.24, and the remainder is Fe and unavoidable impurities; when the temperature of the molten iron reaches 1523°C, the molten iron is taken out of the furnace into a ladle; an aluminum-magnesium alloy (the chemical composition and mass fraction of the aluminum-magnesium alloy are 85% Al, 15% Mg) is pre-placed at the bottom of the ladle, and the amount of the aluminum-magnesium alloy added accounts for 0.25% of the mass fraction of the molten iron entering the ladle;

[0032] ② After all the molten iron has entered the ladle for 4 minutes, the slag is removed and the molten iron is allowed to stand. When the temperature of the molten iron drops to 1459°C, the molten iron is poured into a casting mold on a high-speed rotating horizontal centrifuge at a casting speed of 920rpm; and during the molten iron pouring process, a multi-element alloy additive is added along with the molten iron flow; the amount of the multi-element alloy additive added accounts for 0.8% of the mass fraction of the molten iron entering the casting mold; the particle size of the multi-element alloy additive is 0.3-0.7mm; the chemical composition and mass fraction of the multi-element alloy additive are 12.47% Ti, 6.48% Al, 3.37% Zn, 5.87% Ca, 10.13% Si, 3.70% K, 2.17% N, and the remainder is Fe and unavoidable impurities;

[0033] ③ After the molten iron is completely solidified, the casting is taken out of the mold, and after grinding and sand removal, it is roughly processed to obtain a hypereutectic high chromium cast iron roller sleeve 1; the hypereutectic high chromium cast iron roller sleeve 1 after rough processing is heated to 1025℃ with the furnace, kept warm for 60 minutes, cooled to 975℃ in the furnace, kept warm for 80 minutes, and air-cooled to a roller surface temperature of 380-410℃ after being taken out of the furnace; it is re-entered into the furnace and heated to 520℃, kept warm for 10 hours, cooled to 350℃ in the furnace, and taken out of the furnace; it is composited with the roller shaft 2, which is 35CrMo medium carbon low alloy forged steel; the interference is controlled at 0.13mm; finally, it is finely processed to the specified size and accuracy to obtain a wear-resistant hypereutectic high chromium cast iron composite roller. The mechanical properties of the roller are shown in Table 1.

[0034] Embodiment 3:

[0035] A wear-resistant hypereutectic high-chromium cast iron composite roll and a preparation method thereof, wherein a wear-resistant hypereutectic high-chromium cast iron roll sleeve 1 is produced by a centrifugal casting method, and then hot-fitted and composited with a medium-carbon low-alloy forged steel roll shaft 2. The specific preparation process steps are:

[0036] ① A medium frequency induction furnace is used to melt hypereutectic high chromium cast iron; scrap steel, carburizer, high carbon ferrochrome, ferromanganese and ferrosilicon are first mixed and heated in a medium frequency induction furnace to melt, and the molten iron is sampled and analyzed after being melted, and the chemical composition and mass fraction of the molten iron in the furnace are controlled at 4.33% C, 25.58% Cr, 1.38% Si, 0.64% Mn, 0.031% S, 0.055% P, Cr / C=5.91, and the remainder is Fe and unavoidable impurities; when the temperature of the molten iron reaches 1547°C, the molten iron is taken out of the furnace into a ladle; an aluminum-magnesium alloy (the chemical composition and mass fraction of the aluminum-magnesium alloy are 87% Al, 13% Mg) is pre-placed at the bottom of the ladle, and the amount of the aluminum-magnesium alloy added accounts for 0.30% of the mass fraction of the molten iron entering the ladle;

[0037] ② After all the molten iron has entered the ladle for 7 minutes, the slag is removed and the molten iron is allowed to stand. When the temperature of the molten iron drops to 1442°C, the molten iron is poured into a mold on a high-speed rotating horizontal centrifuge at a mold speed of 980rpm; and during the molten iron pouring process, a multi-element alloy additive is added along with the molten iron flow; the amount of the multi-element alloy additive added accounts for 1.0% of the mass fraction of the molten iron entering the mold; the particle size of the multi-element alloy additive is 0.3-0.7mm; the chemical composition and mass fraction of the multi-element alloy additive are 13.15% Ti, 6.02% Al, 3.66% Zn, 5.50% Ca, 10.82% Si, 3.38% K, 2.49% N, and the remainder is Fe and unavoidable impurities;

[0038] ③ After the molten iron is completely solidified, the casting is taken out of the mold, and after grinding and sand removal, rough processing is performed to obtain a hypereutectic high chromium cast iron roller sleeve 1; the hypereutectic high chromium cast iron roller sleeve 1 after rough processing is heated to 1045℃ with the furnace, kept warm for 50 minutes, cooled to 990℃ in the furnace, kept warm for 60 minutes, and air-cooled to a roller surface temperature of 400-430℃ after being taken out of the furnace; re-entered the furnace and heated to 550℃, kept warm for 8 hours, cooled to 380℃ in the furnace, and taken out of the furnace; combined with the roller shaft 2, which is 42CrMo medium carbon low alloy forged steel; the interference is controlled at 0.18mm; finally, fine processing is performed to the specified size and accuracy to obtain a wear-resistant hypereutectic high chromium cast iron composite roller. The mechanical properties of the roller are shown in Table 1.

[0039] Table 1 Mechanical properties of wear-resistant hypereutectic high chromium cast iron composite roll

[0040]

[0041] The composite roller working layer hypereutectic high chromium cast iron roller sleeve of the present invention is made of scrap steel, carburizer, high carbon ferrochrome, ferromanganese and ferrosilicon, and does not contain expensive molybdenum and nickel elements. The above raw materials are convenient to source and low in price, ensuring that the composite roller has a low production cost. The composite roller of the present invention combines the hypereutectic high chromium cast iron roller sleeve with the medium carbon low alloy forged steel roller shaft by hot assembly, with simple process, high production efficiency, and the roller shaft can be reused, which is green and environmentally friendly. The present invention controls the carbon content of the hypereutectic high chromium cast iron roller sleeve to 4.16-4.33%, the chromium content to 25.58-25.97%, and the chromium carbon ratio (Cr / C) of 5.90<6.25, ensuring that the carbide obtained in the solidification structure of the hypereutectic high chromium cast iron is Cr7C3 with high hardness, and the carbide volume fraction is as high as 50-53%, thereby significantly improving the wear resistance of the hypereutectic high chromium cast iron roller. The hardness of the hypereutectic high chromium cast iron roller sleeve of the present invention is greater than 83HSD, the roller surface hardness is uniform, the hardness difference is less than 2.5HSD, and the impact toughness is greater than 6.0J / cm 2The invention has excellent wear resistance when used in hot rolling bar and wire mills and plate and strip mills, and its service life is more than 40% longer than that of high nickel-chromium infinite cooling cast iron rolls, and its production cost is reduced by 12-15%. The popularization and application of the rolls of the invention can improve the surface quality of rolled materials, reduce the labor intensity of workers, significantly save nickel, and reduce the production cost of rolled materials. The popularization and application of the rolls of the invention has good economic and social benefits.

Claims

1. A method for preparing a wear-resistant hypereutectic high chromium cast iron composite roll, characterized in that: The specific preparation process steps are as follows: ① Melting hypereutectic high chromium cast iron in an intermediate frequency induction furnace; first, mixing and heating scrap steel, carburant, high-carbon ferrochrome, ferromanganese, and ferrosilicon in the intermediate frequency induction furnace to melt. After the molten iron is melted and clarified, a sample is taken for analysis, and the chemical composition and mass fraction of the molten iron in the furnace are controlled at 4.16 - 4.33% C, 25.58 - 25.97% Cr, 1.25 - 1.38% Si, 0.64 - 0.79% Mn, <0.04% S, <0.06% P, 5.90 < Cr / C < 6.25, and the balance is Fe and unavoidable impurities; when the temperature of the molten iron reaches 1523 - 1547 °C, the molten iron is poured out into a ladle; an aluminum-magnesium alloy is pre-placed at the bottom of the ladle, and the addition amount of the aluminum-magnesium alloy accounts for 0.25 - 0.30% of the mass fraction of the molten iron entering the ladle; ② 4 - 7 minutes after all the molten iron enters the ladle, skim the slag and let it stand. When the temperature of the molten iron drops to 1442 - 1459 °C, pour the molten iron into the mold on a horizontally rotating centrifugal casting machine with a casting speed of 920 - 980 rpm; and during the pouring process of the molten iron, add a multi-element alloy additive along with the flow of the molten iron; the addition amount of the multi-element alloy additive accounts for 0.8 - 1.0% of the mass fraction of the molten iron entering the mold; the particle size of the multi-element alloy additive is 0.3 - 0.7 mm; the chemical composition and its mass fraction of the multi-element alloy additive are 12.47 - 13.15% Ti, 6.02 - 6.48% Al, 3.37 - 3.66% Zn, 5.50 - 5.87% Ca, 10.13 - 10.82% Si, 3.38 - 3.70% K, 2.17 - 2.49% N, and the balance is Fe and unavoidable impurities; ③ After the molten iron is completely solidified, take out the casting from the mold, and after grinding and sand cleaning, perform rough machining to obtain a hypereutectic high chromium cast iron roll sleeve; the rough machined hypereutectic high chromium cast iron roll sleeve is heated in the furnace to 1025 - 1045 °C, held for 50 - 60 minutes, cooled in the furnace to a temperature of 975 - 990 °C, held for 60 - 80 minutes, taken out of the furnace and air-cooled to a roll surface temperature of 380 - 430 °C; re-enter the furnace and heat to 520 - 550 °C, hold for 8 - 10 hours, cool in the furnace to a temperature of 350 - 380 °C, take out of the furnace, and compound it with the roll shaft into one body. The roll shaft is medium carbon low alloy forged steel; the interference amount is controlled at 0.13 - 0.18 mm; finally, finish machine it to the specified size and precision to obtain a wear-resistant hypereutectic high chromium cast iron composite roll.

2. The method according to claim 1, characterized in that The chemical composition and its mass fraction of the aluminum-magnesium alloy are 85 - 87% Al, 13 - 15% Mg, and the sum of the two is 100%.

3. A wear-resistant hypereutectic high chromium cast iron composite roll prepared by the method according to claim 1 or 2.

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