A preparation method of a composite casting wear-resistant rolling roll

Abstract

The present invention relates to the technical field of roll manufacturing, and specifically discloses a preparation method for a composite-cast wear-resistant roll. In the present invention, two medium-frequency induction furnaces are respectively used to smelt the molten metal for the outer layer of the roll, the intermediate layer and the core iron of the roll. The outer layer material of the roll includes high-speed steel, high-chromium cast iron or high-nickel chromium molybdenum cast iron, the intermediate layer is cast iron, and the core is ductile iron. The outer layer and the intermediate layer of the roll are formed by centrifugal composite molding, and the core is formed by static casting. There is a firm metallurgical bond between the three layers of metal. The composite roll prepared by the present invention has high hardness, good strength, toughness and wear resistance. Under the same working conditions, the wear resistance of the roll of the present invention is increased by more than 30% compared with that of ordinary centrifugal composite rolls, which can effectively reduce the production cost of rolled materials and has good economic and social benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of roll manufacturing, and particularly relates to a method for preparing a composite-cast wear-resistant roll. Background Art

[0002] Rolls are important consumable spare parts in steel rolling production. With the development of steel rolling technology and the continuous improvement of the automation level of rolling mills, higher requirements are put forward for the strength, toughness and wear resistance of rolls. In order to improve the performance of rolls to meet the needs of rolling mills, roll workers have developed process technologies such as electroslag remelting, spray forming, forging and dual-frequency quenching.

[0003] Chinese invention patent CN103146978A discloses a method for producing high-chromium and low-phosphorus electroslag steel for rolls. The technical solution is: including top and bottom combined blowing converter smelting, LF refining, RH vacuum degassing, billet continuous casting, and bipolar series ingot extraction electroslag remelting process to produce high-chromium and low-phosphorus roll steel. Compared with the traditional electric furnace combined with fixed electroslag remelting process to produce roll steel, the comprehensive yield rate of this invention is increased by 10%. The chromium content in the finished electroslag steel ingot with a diameter of 600mm and a length of 6m is controlled to be above 3.00% and the phosphorus content is below 0.012%. Other chemical elements are also stabilized and optimized, and the surface quality and internal structure are good. This method meets the needs of downstream users very well and achieves good economic benefits. Chinese invention patent CN118080785A also discloses a method for manufacturing a roll neck reinforced roller, which belongs to the field of roll casting, including step 1: casting a cast steel roll according to the chemical composition ratio of the roll neck reinforced roller; step 2: sawing the cast steel roll at the roll neck position to obtain a broken neck roll; step 3: leveling and polishing the sawn surface of the broken neck roll after sawing to ensure that the sawn surface is free of oxidation, impurities, and metallic luster; step 4: preheating the broken neck roll to eliminate stress; step 5: standing the broken neck roll in an electroslag furnace after preheating, with the sawn surface facing up, adding slag, and using electrode ingots of the same material or higher material to electroslag remelt the roll neck to obtain a roll neck reinforced roll; step 6: air cooling the remelted roll neck reinforced roll for 4 to 6 hours to demold; step 7: annealing according to the tempering temperature after demolding, and machining after annealing. The invention can manufacture rolls with high roll neck strength to meet rolling requirements. Chinese invention patent CN112410673A also discloses a method for manufacturing a high-speed steel roll for rolling ultra-high strength steel plates, including smelting and forging roll blanks, preliminary heat treatment and final heat treatment according to chemical composition and weight percentage; the chemical composition and weight percentage are as follows: carbon 0.80~1.20%, silicon 0.20~1.45%, manganese 0.15~0.40%, chromium 7.70~8.30%, molybdenum 1.20~3.00%, vanadium 1.50~2.50%, tungsten 0.80~2.00%, niobium 0.40~0.60%, phosphorus ≤0.020%, sulfur ≤0.015%, the rest is iron and Inevitable impurities; the smelting includes electric furnace smelting, refining outside the furnace, vacuum degassing and spray forming to obtain the steel ingot; the process parameters of the spray forming are as follows: the atomizing gas is nitrogen, the atomizing pressure is 0.3~0.6MPa, the spray distance is 400~500mm, the spray angle is 25~30°, the guide nozzle diameter is 3.5~4.5mm, and the spray temperature is 1450~1550℃; the final heat treatment includes high-temperature overall quenching and high-temperature tempering; the high-temperature overall quenching temperature is 1100~1150℃, and the time is 2~3h; the high-temperature tempering temperature is 520~580℃, and the time is 10~15h.Chinese invention patent CN111270122A also discloses a manufacturing method of a niobium microalloyed cold rolling roll and a niobium microalloyed cold rolling roll. The manufacturing method of the niobium microalloyed cold rolling roll includes: S1, smelting: Electric furnace smelting is carried out to prepare molten steel containing C, Si, Mn, Cr, Mo, V, Ni, P and S. When the molten steel comes out of the electric furnace, ferroniobium powder is added to the molten steel along with the flow to prepare molten steel for the cold rolling roll; S2, refining; S3, vacuum treatment; S4, pouring electrode rods and annealing the electrode rods; S5, electroslag remelting ingot casting; S6, forging: First upsetting and then drawing out the electrode ingot to prepare the cold rolling roll, and spray cooling treatment is carried out on the cold rolling roll; S7, heat treatment of the cold rolling roll; S8, rough and finish machining of the cold rolling roll. The manufacturing method of the niobium microalloyed cold rolling roll described in this invention can overcome the problem that Nb is easily burned out and difficult to control, so that a cold rolling roll containing niobium elements can be manufactured; and the prepared cold rolling roll has high hardness, wear resistance and long service life. Chinese invention patent CN109807554A also discloses a manufacturing process of a cold rolling roll, which successively includes ingot casting, forging, post-forging heat treatment, rough turning, quenching and tempering, finish turning, surface hardening, cold treatment, low-temperature tempering, finish grinding, surface texturing, and electrochemical passivation processes; among them, in the surface hardening process, a dual-frequency quenching machine tool is used to perform dual-frequency quenching treatment on the working surface of the cold rolling roll; in the surface texturing process, an EDT electro-discharge texturing machine tool is used to texture the working surface of the cold rolling roll; in the electrochemical passivation process, a pulsed electrochemical deburring device is used to perform deburring and passivation treatment on the microscopic peak parts on the working surface of the cold rolling roll. This invention improves the service life of the EDT-textured cold rolling roll and the quality of the rolled parts, and reduces the roll change frequency. Chinese invention patent CN114032364A also discloses a surface heat treatment process for a roll made of EN~9. Before quenching, the hardness of the roll reaches 35~45HSD after quenching and tempering heat treatment. The preheating temperature is selected at 350~450°C, and the holding time is 12~16h. After the preheating and holding stage is completed, a 50 / 250Hz dual-frequency quenching machine tool is used for surface heating and quenching. When quenching, the heating temperature is selected at 860~870°C, the 50Hz quenching power is maintained at 510±10KW, the 250Hz quenching power is maintained at 210±10KW, the descending speed is 0.8~1.0mm / s, the rotation speed is selected at 35~40r / min, the quenching water pressure is maintained at 0.8~0.9MPa, and the total quenching time is 50±5min; after quenching, continuous cooling is carried out in the water tank, and the quenching process is completed after 80±10min of continuous cooling; after quenching, the hardness of the roll body is 75~80HSD, and the tempering temperature is selected at 300±10°C to complete the surface heat treatment process; after heat treatment, the hardness of the roll body reaches 45~50HSD, the quality of the roll is good, the hardness uniformity is within 1.5HSD, which is higher than 3HSD of the overall quenching and tempering, and the accident resistance is good.The roll is produced by using process technologies such as electroslag remelting, spray forming, forging, and dual-frequency quenching. Although it can improve the roll performance, there are deficiencies such as low production efficiency, high energy consumption, and high costs.

[0004] In view of the requirement that the roll body (roll surface) should have high hardness and excellent wear resistance during the use of the roll, while the roll neck must have high strength and high toughness to ensure that no roll breakage accident occurs during the use of the roll, the use of the composite casting method to produce the roll is expected to significantly improve the comprehensive performance of the roll. Chinese invention patent CN118531318A discloses a high-boron low-alloy high-speed steel roll and its processing and forming method. Its chemical composition is (by weight percentage): C: 1.2 - 1.8%, Cr: 4.5 - 6.5%, W: 1.0 - 3.0%, Mo: 1.0 - 3.0%, V: 3.0 - 5.0%, Al: 0.6 - 1.2%, Si: 0.8 - 1.2%, N: 0.05 - 0.15%, B: 0.04 - 0.12%, Nb: 0.05 - 0.20%, Ti: 0.06 - 0.18%, Y: 0.04 - 0.15%, Mn < 0.5%, P < 0.04%, S < 0.04%, with the balance being Fe. In this invention, the centrifugal composite casting process is adopted for one-time forming, and the production efficiency is increased by more than 50% compared with the forging process, effectively improving the production efficiency. At the same time, the centrifugal composite casting process can obtain a uniform organizational structure, reduce defects, improve the quality of the roll, and thus reduce the processing procedures and production costs. Chinese invention patent CN114737107A also discloses an infinitely chilled centrifugally composite cast roll and process for the finishing stand of bright steel. The roll includes a roll outer layer and a roll core. The chemical components and mass percentage contents of the roll outer layer are as follows: C 3.00 - 3.50%, Si 0.60 - 1.20%, Mn 0.60 - 1.20%, Cr 1.20 - 1.80%, Ni 3.50 - 4.50%, Mo 0.40 - 0.80%, niobium + vanadium 1.00 - 2.00%, P ≤ 0.03%, S ≤ 0.025%, Re ≥ 0.02%, with the balance being Fe and unavoidable impurities; the chemical components and mass percentage contents of the roll core are as follows: C 3.00 - 3.40%, Si 2.00 - 2.50%, Mn 0.40 - 0.60%, Cr 0.10 - 0.20%, Mg ≥ 0.04%, with the balance being Fe and unavoidable impurities; the process includes the following steps: furnace charge selection; addition of alloys during melting; casting process; special heat treatment process for the roll; roll performance detection. This invention adds carbide-forming vanadium element and strong grain-refining element niobium, improving the physical and chemical properties of the roll, with a high hardness of the working layer, good wear resistance, and not prone to generating oxidative hot cracks during rolling.Chinese invention patent CN113369462A also discloses a Cr5 alloy cast steel roll and its production method. The outer layer material of the roll body is Cr5 alloy steel, and its chemical composition and weight percentage are as follows: C 0.3 - 0.9%, Si 0.3 - 0.8%, Mn 0.5 - 0.8%, P ≤ 0.04%, S ≤ 0.02%, Cr 4.5 - 5.5%, N 0.5 - 1.0%, Mo 0.3 - 0.9%, V 0.04 - 0.2%; the core material is low alloy steel, and its chemical composition and weight percentage are as follows: C 0.5 - 2.0%, Si 1.1 - 1.8%, Mn 0.4 - 1.0%, P ≤ 0.04%, S ≤ 0.02%, Cr ≤ 0.30%, Ni 0 - 0.5%, Mo 0 - 0.2%; this roll is obtained by centrifugal composite casting. Selecting low alloy steel material for the roll core to match its outer layer material can effectively improve the mechanical properties of the roll core. Without reducing the tensile strength of the roll neck and core, it can significantly improve the plasticity and toughness of the roll neck and core, and improve the accident resistance performance of the roll; using a chill bottom box can achieve sequential solidification after the molten steel of the roll bottom neck and core is poured, reducing the porosity generation in the bottom neck and core, and avoiding serious accidents such as roll breakage. Chinese invention patent CN106636877A also discloses a high chromium cast iron composite cast steel product roll. The chemical composition of this high chromium cast iron composite cast steel product roll is configured in two parts: the outer layer and the core. Among them, the outer layer chemical composition is: C 2.80 - 3.30%; Si 0.50 - 1.00%; Mn 0.50 - 1.20%; Cr 10.00 - 15.00%; Ni 1.50 - 2.50%; Mo 1.00 - 1.50%; V 0.20 - 0.60%; Nb 0.10 - 0.30%; P ≤ 0.03%; S ≤ 0.025%; the core chemical composition is: C 3.00 - 3.40%; Si 1.80 - 2.50%; Mn 0.30 - 0.70%; Nb ≥ 0.10%; Ni ≥ 0.30%; P ≤ 0.03%; S ≤ 0.025%; Mg 0.04 - 0.07%; the balance is Fe and a small amount of residual elements. Compared with ordinary rolls, this invention improves the surface quality of the section steel roll, extends the service life of the roll, reduces the production cost of the section steel roll, and enhances the market competitiveness of the product through optimized configuration.Chinese invention patent CN106350730A also discloses a high wear-resistant alloy tool steel roll and its manufacturing method, which is applied to the front section of finish rolling of a hot strip mill and a medium and heavy plate mill. The alloy components and their weight percentages in the working layer are C 1.50 - 2.00%, Si 0.30 - 1.00%, Mn 0.50 - 1.20%, P ≤ 0.10%; S ≤ 0.05%, Cr 10.0 - 15.0%, Ni 0.50 - 2.00%, Mo 0.20 - 1.50%, V 0.20 - 2.00%, and the rest are Fe and inevitable impurities. This invention is produced by means of centrifugal composite casting process and through quenching heat treatment process of spray cooling at 1020 - 1100 °C × 40 - 80 min and three-stage tempering at 450 - 550 °C × 10 - 20 h, and it is a roll with high wear resistance, low oxide film growth rate, and excellent thermal crack resistance. Chinese invention patent CN105618715A also discloses a wear-resistant high-speed steel composite roll and its preparation method. The composite roll is integrally formed by centrifugal composite casting of a roll body high-speed steel and a roll core ductile iron. The chemical composition and its mass fraction of the molten steel of the roll body are controlled at 1.5 - 2.4% C, 3.5 - 6.0% Cr, 3.5 - 6.0% Mo, 3.5 - 6.0% V, 1.5 - 3.5% W, 0.6 - 1.2% Nb, 0.5 - 1.2% Ni, 0.3 - 0.8% Si, 0.3 - 0.8% Mn, S ≤ 0.04%, P ≤ 0.04%, and the balance is Fe. The molten steel of the roll body is deoxidized and subjected to out-of-furnace modification treatment of the molten steel with a multi-element micro-alloy steel, and then poured into a roll on a centrifuge. The roll core uses ductile iron. The roll is subjected to quenching and then tempering treatment, and has characteristics such as high hardness, good strength, toughness, and wear resistance, and has excellent use effects. However, for a composite roll produced by an ordinary centrifugal composite casting method, the bonding strength between the outer layer and the roll core of the roll is low, and the alloy elements in the outer layer of the roll are easily infiltrated into the roll core, resulting in an increase in the hardness of the roll core part and a decrease in toughness and plasticity. A composite roll produced by an ordinary centrifugal composite casting method is prone to peeling, cracking, and roll breakage accidents during use, seriously affecting the normal operation of the steel rolling production line. Summary of the Invention

[0005] In view of the above problems existing in the existing composite-cast wear-resistant rolls, the present invention provides a preparation method for a composite-cast wear-resistant roll.

[0006] To solve the above technical problems, the technical solution provided by the embodiment of the present invention is:

[0007] A preparation method for a composite-cast wear-resistant roll, the composite-cast wear-resistant roll includes a roll outer layer, an intermediate layer, and a roll core, and its preparation method specifically includes the following steps:

[0008] S1. Heat and melt the raw materials on the outer layer of the roll to obtain molten metal for the outer layer; raise the temperature of the molten metal for the outer layer to 1595°C - 1630°C, add ferrosilicon-calcium alloy, adjust the composition to be qualified, then tap the molten metal into a ladle, and then feed a multi-alloy wire into the ladle, skim the slag, and pour. After pouring, add a low-melting-point protective slag; wherein, the raw materials of the multi-alloy wire include boron iron powder, ferrosilicon-calcium-barium alloy powder, aluminum-magnesium alloy particles, and nano-TiC powder;

[0009] S2. Heat and melt the raw materials of the middle layer of the roll and metallic copper, and then add ferrosilicon alloy, ferromanganese alloy, and metallic tin in sequence to obtain molten metal for the middle layer; raise the temperature of the molten metal for the middle layer to 1495°C - 1530°C, tap a part of the molten metal for the middle layer into the first ladle, and add ferrosilicon particles during tapping. When the inner surface temperature of the outer layer of the roll is 1290°C - 1360°C, pour the part of the molten metal for the middle layer, and add protective slag after pouring;

[0010] S3. Place rare earth ferrosilicon-magnesium alloy particles and ferrosilicon-calcium-barium alloy powder at the bottom of the second ladle, then tap the remaining molten metal for the middle layer into the second ladle, skim the slag to obtain nodular cast iron molten metal for the roll core; when the inner surface temperature of the middle layer of the roll is 1242°C - 1295°C, pour the nodular cast iron molten metal for the roll core, and add multi-alloy particles during pouring. After pouring, take it out for slow cooling, rough machining, and heat treatment to obtain a composite-cast wear-resistant roll; wherein, the multi-alloy particles include metallic antimony, metallic bismuth, and rare earth ferrosilicon alloy.

[0011] Compared with the prior art, in the method for preparing a composite-cast wear-resistant roll provided by the present invention, ferrosilicon-calcium alloy is added to the molten metal for the outer layer to fully deoxidize the molten metal. The addition of calcium element helps the inclusions to change from rod-shaped and block-shaped to spherical, promotes the discharge of inclusions from the molten metal, improves the purity of the molten metal for the outer layer, and improves the anti-fatigue performance of the roll. At the same time, boron iron powder, ferrosilicon-calcium-barium alloy powder, aluminum-magnesium alloy particles, and nano-TiC powder are fed into the molten metal for the outer layer of the ladle in the form of a multi-alloy wire. Among them, aluminum and magnesium elements have excellent deoxidation and desulfurization effects, and magnesium element has an excellent effect of refining the outer layer of the roll (i.e., the working layer of the roll), which can significantly improve the toughness and anti-fatigue performance of the roll, ensuring that the roll does not crack and spall during use. The added boron is dissolved in the roll matrix, which can significantly improve the hardenability of the roll. The addition of nano-TiC can not only refine the solidification structure of the roll, but also significantly improve the wear resistance of the roll. In addition, the combined action of nano-TiC with calcium and barium can promote the network-distributed carbides in the working layer of the roll to become isolated carbides, thereby significantly improving the impact toughness of the roll, ensuring that the roll does not crack and spall during use, and significantly extending the service life of the roll.

[0012] Copper element is added to the intermediate layer, which can not only refine the solidification structure of cast iron, but also increase the amount of pearlite in cast iron, improving the strength and toughness of cast iron; tin element can gather at the graphite-austenite interface, hinder the diffusion of carbon into graphite, promote the solid solution of carbon in austenite, contribute to the formation of pearlite, and thus improve the strength of cast iron. At the same time, ferrosilicon particles are added with the flow during the tapping process of the intermediate layer molten metal, which can increase the number of graphite solidification nuclei, refine the graphite structure, prevent the appearance of white cast iron structure in the intermediate layer, and at the same time, can significantly reduce the brittleness of the intermediate layer.

[0013] The roll has a large size, and the molten iron in the roll core is poured statically with a long solidification time. Ordinary ductile iron is prone to spheroidization decay, significantly reducing the strength and toughness of ductile iron. In the pouring process of the molten iron in the roll core of the present invention, multi-element alloy particles mixed with antimony, bismuth and rare earth ferrosilicon are added with the flow, which can significantly increase the number of graphite nuclei, prevent the occurrence of graphite decay, ensure good spheroidization effect in the roll core, and thus ensure excellent strength and toughness of the composite roll core.

[0014] As a specific embodiment of the present invention, in S1, the raw materials of the outer layer of the roll include scrap steel, carburizer and ferroalloy. The scrap steel includes Q235 scrap steel, used high-speed steel, used high-chromium cast iron or used high-nickel chromium molybdenum cast iron. The addition amounts of the carburizer and ferroalloy can be obtained by conventional adjustment according to the requirements of the composition of the outer layer of the roll, and no special limitation is made in the present invention.

[0015] As a specific embodiment of the present invention, if in S1, the scrap steel is selected as used high-speed steel and Q235 scrap steel, then the mass fraction of the components of the outer layer molten metal is: C 1.50% - 2.20%, Si 0.30% - 1.20%, Mn 0.40% - 1.20%, P ≤0.030%, S≤0.025%, Cr 3.00% - 8.00%, Ni 0.00% - 1.50%, Mo 2.00% - 8.00%, V 2.00% - 9.00%, W 0.30% - 2.00%, Nb 0.30% - 2.00%, and the balance is Fe and inevitable impurities.

[0016] Using used high-speed steel and Q235 as raw materials and controlling the composition of the outer layer molten metal within the above range, the roll can have the advantages of high hardness, good red hardness and wear resistance.

[0017] As a specific embodiment of the present invention, in S1, if the scrap steel selects Q235 scrap steel and used high-chromium cast iron, the component mass fractions of the outer layer metal melt are as follows: C 2.30% - 3.30%, Si 0.30% - 1.00%, Mn 0.50% - 1.20%, P ≤ 0.10%, S ≤ 0.05%, Cr 18.01% - 22.00%, Ni 0.50% - 1.70%, Mo 1.01% - 3.00%, V 0.20% - 0.60%, and the balance is Fe and unavoidable impurities.

[0018] Using used high-chromium cast iron and Q235 as raw materials and controlling the component of the outer layer metal melt of the roll within the above range can make the roll contain more M7C3 type carbides and improve the wear resistance of the roll.

[0019] As another specific embodiment of the present invention, in S1, if the scrap steel selects Q235 scrap steel and used high-nickel-chromium-molybdenum cast iron, the component mass fractions of the outer layer metal melt are as follows: C 2.90% - 3.60%, Si 0.60% - 2.00%, Mn 0.40% - 1.20%, P ≤ 0.10%, S ≤ 0.05%, Cr 1.00% - 3.00%, Ni 3.01% - 5.00%, Mo 0.20% - 2.00%, V 0.50% - 2.50%, W 0.00% - 8.00%, Nb 0.00% - 1.00%, and the balance is Fe and unavoidable impurities.

[0020] Using used high-nickel-chromium-molybdenum cast iron and Q235 as raw materials and controlling the component of the outer layer metal melt of the roll within the above range can endow the roll with excellent hardenability and wear resistance, and a martensite matrix can be obtained in the as-cast state without subsequent high-temperature quenching treatment.

[0021] As a specific embodiment of the present invention, two intermediate frequency induction furnaces are used to smelt the outer layer metal liquid of the roll, the intermediate layer of the roll and the core metal liquid respectively. Using one electric furnace to smelt the intermediate layer and the core molten iron simultaneously can not only reduce equipment investment, simplify smelting operations, but also effectively reduce production energy consumption and improve production efficiency.

[0022] Further, in S1, the addition amount of the calcium-silicon alloy is 0.20% - 0.25% of the mass of the metal melt.

[0023] Further, in S1, the chemical composition and mass fractions of the calcium-silicon alloy are as follows: Ca 31.27% - 33.50%, Si 58.06% - 62.75%, C ≤ 1.0%, Al ≤ 2.4%, and the balance is Fe and unavoidable impurities.

[0024] Further, in S1, the feeding amount of the multi - element alloy wire is 7.5 m / t - 8.0 m / t of the molten metal, and the feeding speed is 10 m / min - 12 m / min.

[0025] Further, in S1, the mass fractions of the raw materials in the multi - element alloy wire are as follows: ferroboron powder 15% - 16%, calcium - silicon - barium alloy powder 46% - 48%, aluminum - magnesium alloy particles 32% - 34%, nano - TiC powder 4.0% - 4.5%, and the sum of each component is 100%.

[0026] The boron element in the ferroboron powder forms hard phases such as iron boride with iron, improving the surface hardness and wear resistance of the roll, and can also refine the grains and enhance the comprehensive mechanical properties. The calcium - silicon - barium alloy powder removes oxygen in the molten metal through deoxidation, reduces the surface tension to improve the casting performance, and its alloying effect can also enhance the roll performance. The aluminum - magnesium alloy particles can not only further deoxidize and refine, but also improve the strength and toughness of the roll through solid - solution strengthening, while improving the surface quality. The nano - TiC powder, with its high hardness, high wear resistance and good high - temperature stability, improves the surface hardness and high - temperature dimensional stability of the roll. Its good interfacial bonding force with the metal matrix can effectively transfer the load and prevent crack propagation. These components act together to comprehensively improve the performance and service life of the roll.

[0027] Further, in S1, the particle size of the ferroboron powder is 15 mesh - 25 mesh, the particle size of the calcium - silicon - barium alloy powder is 20 mesh - 30 mesh, and the particle size of the aluminum - magnesium alloy particles is 0.5 mm - 3.5 mm.

[0028] Further, in S1, the preparation method of the multi - element alloy wire includes the following steps:

[0029] Mix the ferroboron powder, calcium - silicon - barium alloy powder, aluminum - magnesium alloy particles and nano - TiC powder evenly to obtain a mixed powder; coat the mixed powder with a low - carbon steel strip and roll it to obtain a multi - element alloy wire with a diameter of 13 mm - 14 mm.

[0030] Combined with the above, as a specific implementation method, the chemical composition of the low - carbon steel strip is: C 0.08% - 0.19%, Si 0.40% - 0.49%, Mn 3.67% - 3.95%, Al 2.08% - 2.55%, S≤0.030%, P≤0.035%, and the balance is Fe and unavoidable impurities. The thickness of the low - carbon steel strip is 0.55 mm - 0.65 mm. The chemical composition of the low - carbon steel strip is: C 0.08% - 0.19%, Si 0.40% - 0.49%, Mn 3.67% - 3.95%, Al 2.08% - 2.55%, S≤0.030%, P≤0.035%, and the balance is Fe and unavoidable impurities; the thickness of the low - carbon steel strip is 0.55 mm - 0.65 mm.

[0031] It should be noted that in S1, slag skimming is carried out after feeding the multi - element alloy wire for 8 min to 10 min.

[0032] Further, in S1, the chemical composition of the boron iron powder is: B 19.09% - 20.84%, C ≤ 0.5%, Si ≤ 2%, Al ≤ 0.5%, S ≤ 0.01%, P ≤ 0.1%, and the balance is Fe and inevitable impurities;

[0033] The chemical composition of the calcium - silicon - barium alloy powder is: Si 42.16% - 44.38%, Ca 10.26% - 11.85%, Ba 10.40% - 11.86%, C ≤ 0.8%, P ≤ 0.04%, S ≤ 0.06%, and the balance is Fe and inevitable impurities;

[0034] The chemical composition of the aluminum - magnesium alloy powder is: Al 72% - 75%, Mg 25% - 28%.

[0035] Further, in S1, the rotational speed of the casting mold for pouring is 900 r / min to 1100 r / min, and the pouring temperature is 1430 °C to 1460 °C.

[0036] Further, in S1, the low - melting - point protective slag is an anti - oxidation O type glass slag, and its addition amount is 0.8 kg / m 2 ~1.0 kg / m 2 .

[0037] It should be noted that the low - melting - point protective slag needs to be added immediately after the outer layer pouring is completed to prevent the oxidation of the outer - layer metal, improve the metallurgical bonding effect between the outer - layer metal and the middle - layer metal, and ensure that the roll does not crack and fall off during use.

[0038] As a specific embodiment of the present invention, the raw materials of the middle layer include scrap steel and a carbon - increasing agent. The scrap steel is Q235 scrap steel. The addition amount of each raw material can be adjusted conventionally according to the composition requirements of the middle - layer metal melt, and the present invention does not make special limitations. The carbon - increasing agent for the outer layer and the middle layer can be a conventional carbon - increasing agent in the art, such as petroleum coke powder, and the present invention does not make special limitations.

[0039] As a specific embodiment of the present invention, the metallic copper is in the form of copper plates.

[0040] Further, in S2, the composition of the intermediate layer metal melt is: C 3.22% - 3.45%, Si 1.35% - 1.58%, Mn 0.59 - 0.76%, Cu 0.52% - 0.65%, Sn 0.05% - 0.08%, P ≤ 0.080%, S ≤ 0.040%, and the balance is Fe and inevitable impurities.

[0041] Further, in S2, the chemical composition of the ferrosilicon particles is: Si 74.80% - 76.17%, Al ≤ 1.0%, Ca ≤ 1.0%, Mn ≤ 0.4%, Cr ≤ 0.3%, P ≤ 0.035%, S ≤ 0.020%, C ≤ 0.10%, and the balance is Fe and inevitable impurities.

[0042] Further, in S2, the particle size of the ferrosilicon particles is 5 mm - 12 mm.

[0043] Further, in S2, the addition amount of the ferrosilicon particles is 0.7% - 0.9% of the mass of the partial intermediate layer metal melt.

[0044] Further, in S2, the pouring temperature of the partial intermediate layer metal melt is 1355°C - 1385°C, and the pouring thickness of the intermediate layer is 16 mm - 22 mm.

[0045] Controlling the pouring temperature of the intermediate layer metal melt at 1355°C - 1385°C and pouring the intermediate layer metal melt when the inner surface temperature of the outer layer of the roll is 1290°C - 1360°C can prevent the outer layer of the roll from being mixed with the intermediate layer metal melt, enabling the intermediate layer to play a good isolation role, avoiding the alloy elements in the outer layer of the roll from entering the roll core layer, and ensuring that the roll core layer has a good spheroidization effect and excellent strength and toughness.

[0046] The present invention overcomes the problem that the outer layer metal of a common bimetallic centrifugal composite roll is easily mixed into the nodular iron of the roll core, resulting in poor spheroidization effect of the roll core and insufficient strength and toughness of the nodular iron of the roll core.

[0047] Further, in S2, the protective slag is anhydrous sodium tetraborate, and its addition amount is 0.40 kg / m 2 ~0.45 kg / m 2 .

[0048] Further, in S3, the particle size of the rare earth ferrosilicon alloy particles is 7 mm - 12 mm; the particle size of the calcium silicate barium alloy powder is 20 mesh - 30 mesh.

[0049] Further, in S3, the addition amount of the rare earth ferrosiliconmagnesium alloy particles is 1.2% - 1.4% of the mass of the remaining intermediate layer molten metal, and the addition amount of the calcium silicobarium alloy powder is 0.5% - 0.6% of the mass of the remaining intermediate layer molten metal.

[0050] Further, in S3, the chemical composition of the rare earth ferrosiliconmagnesium alloy particles is as follows: Mg 11.15% - 11.82%, RE 2.21% - 2.68%, Si 40.16% - 41.96%, Ca 2.08% - 2.66%, and the balance is Fe and inevitable impurities.

[0051] Further, in S3, the chemical composition of the rare earth ferrosilicon alloy is as follows: RE 27.42% - 29.27%, Si 38.66% - 41.51%, Mn < 3.0%, Ca < 5.0%, Ti < 3.0%, and the balance is Fe and inevitable impurities.

[0052] Further, in S3, the pouring temperature of the roll core molten metal is 1325°C - 1350°C.

[0053] Further, in S3, the mass percentage content of each raw material in the multi - element alloy particles is as follows: antimony 9% - 10%, bismuth 3% - 4%, rare earth ferrosilicon 86% - 88%, and the sum of each component is 100%.

[0054] Further, in S3, the particle size of the multi - element alloy particles is 0.8 mm - 3.5 mm.

[0055] Further, in S3, the addition amount of the multi - element alloy particles is 0.25% - 0.30% of the mass of the roll core molten metal entering the mold.

[0056] It should be noted that in S3, after 8 h - 12 h from the end of pouring, the roll is taken out of the mold and placed in a slow - cooling pit for slow cooling.

[0057] Further, in S3, the heat treatment includes quenching and tempering. Among them, the temperature of quenching is 1020°C - 1080°C, and the time of quenching is 3 h - 5 h; the temperature of tempering is 520°C - 580°C, and the time of tempering is 18 h - 22 h.

[0058] It should be noted that if the outer layer is high - speed steel, the heat treatment selects the quenching + tempering treatment method; high - nickel chromium molybdenum cast iron directly adopts the tempering treatment; high - chromium cast iron can adopt the quenching + tempering treatment method or the direct tempering heat treatment method.

[0059] Further, in S3, the heat treatment is tempering treatment, the temperature of tempering is 350°C - 400°C, and the treatment time is 22 h - 28 h.

[0060] It should be noted that in the present invention, the outer layer and the intermediate layer of the roll are centrifugally cast, and the roll core is statically top-cast.

[0061] The present invention has the following advantages compared with the prior art:

[0062] (1) The present invention realizes the smelting of three metal melts by two electric furnaces, with high production efficiency and low energy consumption.

[0063] (2) Due to the addition of the intermediate layer and the in-stream inoculation of the roll core in the composite cast wear-resistant roll of the present invention, the nodularization effect of the roll core and the roll neck ductile iron is good, the nodularization rate exceeds 95%, the tensile strength of the roll core and the roll neck ductile iron exceeds 550 MPa, and the elongation rate exceeds 12%, ensuring that no roll breakage accident occurs during the use of the composite cast wear-resistant roll.

[0064] (3) The outer layer and the intermediate layer of the composite cast wear-resistant roll of the present invention are centrifugally compound-cast, with high bonding strength. The intermediate layer and the roll core are both molten iron smelted in the same furnace, and the compounding effect between the intermediate layer and the roll core is good, realizing a firm metallurgical bond and ensuring that no spalling and sleeve-off accidents occur during the use of the roll.

[0065] (4) The solidification structure of the outer layer of the composite cast wear-resistant roll of the present invention is fine, the carbides are isolatedly distributed, and the strength, toughness and wear resistance are good. Under the same working conditions, the wear resistance of the roll of the present invention is improved by more than 30% compared with that of the ordinary centrifugal composite roll. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic structural diagram of the composite roll prepared in Example 1 of the present invention; wherein, 11 - roll neck; 12 - outer layer (roll body working layer); 13 - intermediate layer; 14 - roll core;

[0067] Figure 2 It is a schematic diagram of core filling after the composite cast wear-resistant roll used in the embodiment of the present invention is closed; wherein, 1 - riser box; 2 - end cover; 3 - mold; 4 - outer layer metal; 5 - intermediate layer cast iron; 6 - base box; 7 - refractory brick; 8 - bottom plate. DETAILED DESCRIPTION OF THE INVENTION

[0068] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0069] In order to better illustrate the present invention, further examples will be given below through embodiments.

[0070] In the following examples, the particle size of the ferrophosphorus powder used is 15 - 25 mesh, the particle size of the calcium-silicon alloy powder is 20 - 30 mesh, the particle size of the aluminum-magnesium alloy particles is 0.5 - 3.5 mm, the particle size of the ferrosilicon particles is 5 - 12 mm, and the particle size of the rare earth ferrosilicon magnesium alloy particles is 7 - 12 mm.

[0071] In the following examples, the impact toughness is determined according to GB / T 229-2020 Metallic materials - Charpy pendulum impact test method; the elongation and tensile strength are determined according to GB / T228.1-2020 Metallic materials - Tensile testing - Part 1: Method of test at room temperature; the hardness is determined according to GB / T 13313-2008 Roller Shore and Leeb hardness test method.

[0072] Example 1

[0073] This example provides a preparation method of a composite cast wear-resistant roll. Refer to Figure 1 , the composite cast wear-resistant roll is composed of three parts: the roll outer layer 12, the intermediate layer 13 and the roll core 14. The specific preparation process includes the following steps:

[0074] S1, use two medium-frequency induction furnaces to smelt the molten metal of the roll outer layer 12, the intermediate layer 13 and the molten iron of the roll core 14 respectively; the roll outer layer 12 is high-speed steel.

[0075] The smelting process of the outer layer 12 material is as follows: Mix waste high-speed steel, Q235 scrap steel, petroleum coke carburizer and ferroalloy and heat them to melt to obtain the outer layer molten metal (chemical composition: C 1.93%, Si 0.77%, Mn 0.64%, P 0.028%, S 0.020%, Cr 5.28%, Ni 0.61%, Mo 3.76%, V 4.09%, W 0.84%, Nb 0.52%, the balance is Fe and inevitable impurities); when the temperature of the outer layer molten metal rises to 1630 °C, add calcium-silicon alloy (the chemical composition and mass fraction of the calcium-silicon alloy are: Ca 31.27%, Si 62.75%, C 0.55%, Al 1.63%, the balance is Fe and inevitable impurities), and the addition amount of the calcium-silicon alloy accounts for 0.20% of the mass of the outer layer molten metal in the furnace. After adjusting the composition to be qualified in front of the furnace, tap the molten metal into the ladle; after all the outer layer molten metal enters the ladle, use a wire feeder to feed the multi-element alloy wire into the outer layer molten metal in the ladle, and the addition amount of the multi-element alloy wire is 8.0 m / t of molten metal; control the wire feeding speed of the multi-element alloy wire in the ladle at 10 m / min; 8 minutes after adding the multi-element alloy wire to the molten metal, skim the slag and let it stand for the molten metal in the ladle. When the temperature drops to 1460 °C, pour it into the mold 3 on the horizontal centrifuge, and the rotation speed of the mold 3 is 900 r / min; after pouring the molten metal of the outer layer 12, immediately add an anti-oxidation flux OType of glass cullet, with the addition amount calculated based on the inner surface of the outer layer 12 of the roll being 0.8 kg / m 2 ;

[0076] Among them, the multi - element alloy wire includes: 15% boron iron powder, 48% calcium - silicon - barium alloy powder, 33% aluminum - magnesium alloy particles and 4% nano - TiC powder. The chemical composition of the boron iron powder is: B 19.09%, C 0.37%, Si 0.84%, Al 0.26%, S 0.008%, P 0.056%, and the balance is Fe and inevitable impurities; the chemical composition of the calcium - silicon - barium alloy powder is: Si 42.16%, Ca 11.85%, Ba 10.40%, C 0.48%, P 0.033%, S 0.047%, and the balance is Fe and inevitable impurities; the chemical composition of the aluminum - magnesium alloy particles is: Al 72%, Mg 28%;

[0077] The preparation method of the multi - element alloy wire includes the following steps: Mix the boron iron powder, calcium - silicon - barium alloy powder, aluminum - magnesium alloy particles and nano - TiC powder evenly, and then pack the evenly - mixed above - mentioned powders with a low - carbon soft steel strip with a thickness of 0.55 - 0.65 mm, and roll them into a multi - element alloy wire with a diameter of φ13 mm on an alloy cored - wire machine; the chemical composition of the low - carbon soft steel strip is: C 0.08%, Si 0.49%, Mn 3.67%, Al 2.55%, S 0.021%, P 0.032%, and the balance is Fe and inevitable impurities;

[0078] S2. The smelting process of the molten iron in the intermediate layer 13 and the roll core 14 is as follows: Scrap steel, petroleum coke carburizer, and copper plates are mixed and heated to melting in another medium-frequency induction furnace. After the molten iron is melted and clarified, ferrosilicon, ferromanganese, and metallic tin are added in sequence, and the chemical composition and mass fraction of the molten iron in the furnace are controlled as follows: C 3.22%, Si 1.58%, Mn 0.59%, Cu 0.65%, Sn 0.08%, S 0.037%, P 0.061%, and the balance is Fe and unavoidable impurities; When the temperature of the molten iron rises to 1495 °C, first, part of the molten iron in the intermediate layer 13 is tapped into the ladle I. When the molten iron is tapped, ferrosilicon particles (chemical composition: Si 74.80%, Al 0.64%, Ca 0.39%, Mn 0.11%, Cr 0.17%, P 0.032%, S 0.013%, C 0.05%, and the balance is Fe and unavoidable impurities) are added along with the flowing molten iron. The addition amount of ferrosilicon particles accounts for 0.7% of the mass of the molten iron entering the ladle I; The molten iron in the ladle I is poured into the mold 3 on the centrifuge in step S1; Before pouring, the inner surface temperature of the outer layer 12 of the roll in the mold 3 is measured with a non-contact thermometer. When the temperature is 1290 - 1317 °C, the cast iron molten iron of the intermediate layer 13 is poured on the centrifuge. The pouring temperature of the cast iron molten iron of the intermediate layer 13 is 1355 °C, and the pouring thickness of the intermediate layer 13 is 16 mm. Immediately after the pouring of the intermediate layer 13 is completed, the protective agent anhydrous sodium tetraborate is added. The addition amount of anhydrous sodium tetraborate is 0.40 kg / m based on the inner surface of the cast iron of the intermediate layer 13 of the roll. 2 ;

[0079] S3. All the remaining molten iron in the furnace in step S2 is tapped into the ladle II. Rare earth ferrosilicon magnesium alloy particles (chemical composition: Mg 11.15%, Ce 2.68%, Si 40.16%, Ca 2.66%, and the balance is Fe and unavoidable impurities) and calcium silicate barium alloy powder are pre-placed at the bottom of the ladle II. The addition amounts of the rare earth ferrosilicon magnesium alloy and the calcium silicate barium alloy powder respectively account for 1.2% and 0.5% of the mass fraction of the molten iron entering the ladle II. After spheroidizing and inoculation treatment, ductile iron molten iron is obtained, and then slag skimming and standing are carried out; 2 minutes after the pouring of the cast iron of the intermediate layer 13 of the roll is completed, the inner surface temperature of the cast iron of the intermediate layer 13 of the roll is measured with a non-contact thermometer. When the temperature is 1242 - 1276 °C, the ductile iron molten iron of the roll core 14 is top-poured statically, and the pouring temperature of the molten iron is 1325 °C; During the pouring process of the ductile iron molten iron of the roll core 14, multi-element alloy particles composed of antimony, bismuth, and rare earth ferrosilicon are added along with the flowing molten iron. The addition amount of the multi-element alloy particles accounts for 0.25% of the mass fraction of the ductile iron molten iron entering the mold; 8 hours after the pouring of the ductile iron of the roll core 14 is completed, the roll is taken out and put into a slow cooling pit, and then rough machining is carried out;

[0080] Among them, the multi - element alloy particles are composed of 9% antimony, 4% bismuth and 87% rare - earth ferrosilicon by mass fraction; the size of the multi - element alloy particles is 0.8 - 3.5 mm; the chemical composition and mass fraction of the rare - earth ferrosilicon are: Ce 27.42%, Si 41.51%, Mn 1.07%, Ca 2.84%, Ti 0.95%, and the balance is Fe and inevitable impurities;

[0081] S4. Quench + temper the rough - processed roll (high - speed steel roll). The quenching heating temperature is 1050 °C, the holding time is 4 h, air cooling is used. The tempering heating temperature is 550 °C, the holding time is 20 h, and furnace cooling is used. Finally, finish - machine it to the specified size and accuracy to obtain the composite - cast wear - resistant high - speed steel roll.

[0082] The hardness of the outer layer 12 of the roll is 84.3 HSD, and the room - temperature impact toughness of the outer layer 12 is 14.8 J / cm 2 ; the tensile strength of the roll neck 14 (roll core 14) is 575 MPa, and the elongation exceeds 12.7%.

[0083] After detection, the volume fraction of inclusions in the outer layer is 0.11%, and the volume fraction of inclusions in the roll core is 0.13%.

[0084] Example 2

[0085] This example provides a preparation method for a composite - cast wear - resistant roll. Refer to Figure 1 , the composite - cast wear - resistant roll is composed of three parts: the outer layer 12 of the roll, the intermediate layer 13, and the roll core 14. The specific preparation process includes the following steps:

[0086] S1. Use two intermediate - frequency induction furnaces to smelt the metal melt of the outer layer 12 of the roll and the molten iron of the intermediate layer 13 and the roll core 14 respectively; the outer layer 12 of the roll is high - chromium cast iron;

[0087] The smelting process of the outer layer 12 material is as follows: Mix Q235 scrap steel, waste high-chromium cast iron, petroleum coke carburizer, and ferroalloy and heat them to melt to obtain the outer layer metal melt (chemical composition: C 2.97%, Si 0.85%, Mn 0.82%, P 0.062%, S 0.041%, Cr 18.87%, Ni 0.91%, Mo 2.05%, V 0.38%, and the balance is Fe and unavoidable impurities); when the temperature of the outer layer metal melt rises to 1595 °C, add calcium-silicon alloy (chemical composition: Ca 33.50%, Si 58.06%, C 0.27%, Al 1.03%, and the balance is Fe and unavoidable impurities), and the addition amount of calcium-silicon alloy accounts for 0.25% of the mass fraction of the outer layer metal melt in the furnace. After adjusting the composition to be qualified in front of the furnace, tap the molten metal into the ladle; after all the outer layer metal melt enters the ladle, use a wire feeder to feed the multi-alloy wire into the outer layer metal melt in the ladle, and the addition amount of the multi-alloy wire is 7.5 m / t of the metal melt; the wire feeding speed of the multi-alloy wire in the ladle is controlled at 12 m / min; 10 minutes after the multi-alloy wire is added to the metal melt, skim the slag and let it stand in the ladle. When the temperature drops to 1430 °C, pour it into the mold 3 on the horizontal centrifuge, and the rotation speed of the mold 3 is 1100 r / min; after the outer layer 12 metal melt is poured, immediately add an anti-oxidation flux O type glass slag, and its addition amount is 1.0 kg / m based on the inner surface of the outer layer 12 of the roll 2 ;

[0088] The multi-alloy wire includes: 16% boron iron powder, 46% calcium-silicon-barium alloy powder, 33.5% aluminum-magnesium alloy particles, and 4.5% nano-TiC powder. The chemical composition and mass fraction of the boron iron are: B 20.84%, C 0.26%, Si 1.05%, Al 0.41%, S 0.009%, P 0.048%, and the balance is Fe and unavoidable impurities. The chemical composition and mass fraction of the calcium-silicon-barium alloy are: Si 44.38%, Ca 10.26%, Ba 11.86%, C 0.51%, P 0.030%, S 0.044%, and the balance is Fe and unavoidable impurities. The chemical composition and mass fraction of the aluminum-magnesium alloy are: Al 75%, Mg 25%.

[0089] The preparation method of the multi - element alloy wire includes the following steps: Mix boron iron powder, calcium - silicon - barium alloy powder, aluminum - magnesium alloy particles and nano - TiC powder evenly, and then wrap the evenly - mixed above - mentioned powder with a low - carbon mild steel strip with a thickness of 0.55 - 0.65 mm, and roll it into a multi - element alloy wire with a diameter of φ14 mm on an alloy cored - wire unit; The chemical composition of the low - carbon mild steel strip is: C 0.19%, Si 0.40%, Mn 3.95%, Al 2.08%, S 0.029%, P 0.034%, and the balance is Fe and unavoidable impurities;

[0090] S2. The smelting process of the molten iron of the intermediate layer 13 and the roll core 14 is as follows: Mix scrap steel, petroleum coke carburizer and copper plates in another intermediate - frequency induction furnace and heat - melt them. After the molten iron is melted completely, add ferrosilicon, ferromanganese and metallic tin in sequence, and control the chemical composition and mass fraction of the molten iron in the furnace at: C 3.45%, Si 1.35%, Mn 0.76%, Cu 0.52%, Sn 0.05%, S 0.036%, P 0.069%, and the balance is Fe and unavoidable impurities; When the temperature of the molten iron rises to 1530 °C, first tap part of the molten iron of the intermediate layer 13 into the ladle Ⅰ, and when tapping the molten iron, add ferrosilicon particles (chemical composition: Si 76.17%, Al 0.76%, Ca 0.52%, Mn 0.33%, Cr 0.19%, P 0.032%, S 0.010%, C 0.08%, and the balance is Fe and unavoidable impurities) along with the flowing molten iron. The addition amount of ferrosilicon particles accounts for 0.9% of the mass fraction of the molten iron entering the ladle Ⅰ; Pour the molten iron in the ladle Ⅰ into the mold 3 on the centrifuge in step S1; Before pouring, measure the inner - surface temperature of the outer layer 12 of the roll in the mold 3 with a non - contact thermometer. When the temperature is 1330 - 1360 °C, continue to pour the cast iron molten iron of the intermediate layer 13 on the centrifuge. The pouring temperature of the cast iron molten iron of the intermediate layer 13 is 1385 °C, the pouring thickness of the intermediate layer 13 is 22 mm. Immediately after pouring the intermediate layer 13, add the protective agent anhydrous sodium tetraborate. The addition amount of anhydrous sodium tetraborate is 0.45 kg / m based on the inner - surface of the cast iron of the roll intermediate layer 13 2 ;

[0091] S3. Pour all the remaining molten iron in the furnace in step S2 into ladle II. Rare earth ferrosilicon magnesium alloy (chemical composition: Mg 11.82%, Ce 2.21%, Si 41.96%, Ca 2.08%, with the balance being Fe and inevitable impurities) and calcium silicobarium alloy powder are pre-placed at the bottom of ladle II. The addition amounts of rare earth ferrosilicon magnesium alloy and calcium silicobarium alloy powder respectively account for 1.4% and 0.6% of the mass fraction of the molten iron entering ladle II. After the molten iron undergoes spheroidizing and inoculation treatment, ductile iron molten iron is obtained, and then slag skimming and static setting are carried out. 4 minutes after the casting of the cast iron in the middle layer 13 of the roll is completed, use a non-contact thermometer to measure the inner surface temperature of the cast iron in the middle layer 13 of the roll. When the temperature is 1261 - 1295 °C, top-cast the ductile iron molten iron of the roll core 14 under static conditions, and the molten iron pouring temperature is 1350 °C. During the pouring process of the ductile iron molten iron of the roll core 14, add multi-element alloy particles composed of antimony, bismuth, and rare earth ferrosilicon along with the molten iron flow. The addition amount of the multi-element alloy particles accounts for 0.30% of the mass fraction of the ductile iron molten iron entering the mold. 10 hours after the pouring of the ductile iron of the roll core 14 is completed, take out the roll and put it into a slow cooling pit, and then carry out rough machining;

[0092] The multi-element alloy particles include: 10% antimony, 4% bismuth, and 86% rare earth ferrosilicon; the size of the multi-element alloy particles is 0.8 - 3.5 mm. The chemical composition and mass fraction of the rare earth ferrosilicon are: 29.27% Ce, Si 41.51%, Mn 2.07%, Ca 3.80%, Ti 0.95%, with the balance being Fe and inevitable impurities.

[0093] S4. Quench + temper the rough-machined roll (high-chromium cast iron roll). The quenching heating temperature is 1025 °C, the holding time is 4 h, air cooling is used, the tempering heating temperature is 525 °C, the holding time is 22 h, furnace cooling is used, and finally finish machining to the specified size and precision to obtain a composite-cast wear-resistant high-chromium cast iron roll.

[0094] The hardness of the outer layer 12 of the roll is 81.7 HSD, and the room-temperature impact toughness of the outer layer 12 is 10.8 J / cm 2 ; the tensile strength of the roll neck 14 (roll core 14) is 565 MPa, and the elongation exceeds 13.2%.

[0095] After testing, the volume fraction of inclusions in the outer layer of the composite roll is 0.08%, and the volume fraction of inclusions in the roll core is 0.11%.

[0096] Example 3

[0097] This example provides a method for preparing a composite-cast wear-resistant roll. Refer to Figure 1 , the composite-cast wear-resistant roll is composed of three parts: the outer layer 12 of the roll, the middle layer 13, and the roll core 14. The specific preparation process includes the following steps:

[0098] S1. Two medium-frequency induction furnaces are respectively used to smelt the molten metal of the outer layer 12 of the roll, the intermediate layer 13 and the molten iron of the roll core 14; the outer layer 12 of the roll is high-nickel chromium molybdenum cast iron;

[0099] The smelting process of the material for the outer layer 12 is as follows: Q235 scrap steel, waste high-nickel chromium molybdenum cast iron, petroleum coke carburizer and ferroalloy are mixed and heated to melt to obtain the molten metal for the outer layer (chemical composition: C 3.27%, Si 1.17%, Mn 0.88%, P 0.073%, S 0.040%, Cr 2.15%, Ni 3.84%, Mo 0.95%, V 0.87%, Nb 0.28%, the balance is Fe and inevitable impurities); when the temperature of the molten metal for the outer layer rises to 1613 °C, calcium-silicon alloy (chemical composition: Ca 32.35%, Si 60.80%, C 0.46%, Al 2.13%, the balance is Fe and inevitable impurities) is added, and the addition amount of calcium-silicon alloy accounts for 0.22% of the mass of the molten metal for the outer layer in the furnace. After the composition is adjusted to be qualified in front of the furnace, it is discharged into the ladle; after all the molten metal for the outer layer enters the ladle, a multi-element alloy wire is fed into the molten metal for the outer layer in the ladle by a wire feeding machine. The addition amount of the multi-element alloy wire is 7.8 m / t of molten metal, and the wire feeding speed of the multi-element alloy wire in the ladle is controlled at 11 m / min; 9 minutes after the multi-element alloy wire is added to the molten metal, the slag on the molten metal in the ladle is skimmed and allowed to stand. When the temperature drops to 1446 °C, it is poured into the mold 3 on the horizontal centrifuge, and the rotation speed of the mold 3 is 1000 r / min; after the pouring of the molten metal for the outer layer 12 is completed, an anti-oxidation flux O type glass slag is immediately added, and its addition amount is 0.9 kg / m based on the inner surface of the outer layer 12 of the roll 2 ;

[0100] The multi-element alloy wire includes: 15.5% boron iron powder, 47% calcium-silicon-barium alloy powder, 33.3% aluminum-magnesium alloy particles and 4.2% nano-TiC powder. The chemical composition and mass fraction of the boron iron are: B 19.94%, C 0.28%, Si 1.26%, Al 0.19%, S 0.005%, P 0.041%, the balance is Fe and inevitable impurities. The chemical composition and mass fraction of the calcium-silicon-barium alloy are: Si 42.82%, Ca 10.95%, Ba 10.81%, C 0.48%, P 0.039%, S 0.028%, the balance is Fe and inevitable impurities. The chemical composition and mass fraction of the aluminum-magnesium alloy are: Al 74%, Mg 26%.

[0101] The preparation method of the multi-element alloy wire comprises the following steps: mixing boron iron powder, calcium silicon barium alloy powder, aluminum magnesium alloy particles and nano-TiC powder evenly, and then packaging the evenly mixed powder with a low-carbon mild steel strip with a thickness of 0.55 - 0.65 mm, and rolling it into a multi-element alloy wire with a diameter of φ13.5 mm on an alloy cored wire unit; the chemical composition and mass fraction of the low-carbon mild steel are: C 0.13%, Si 0.46%, Mn 3.80%, Al 2.26%, S 0.027%, P 0.034%, and the balance is Fe and inevitable impurities;

[0102] S2. The smelting process of the molten iron of the intermediate layer 13 and the roll core 14 is as follows: mixing scrap steel, petroleum coke carburizer and copper plate in another intermediate frequency induction furnace and heating and melting them. After the molten iron is melted and clarified, ferrosilicon, ferromanganese and metallic tin are added in sequence, and the chemical composition and mass fraction of the molten iron in the furnace are controlled to be: C 3.36%, Si 1.42%, Mn 0.69%, Cu 0.58%, Sn 0.06%, S 0.031%, P 0.047%, and the balance is Fe and inevitable impurities; when the temperature of the molten iron rises to 1516 °C, first tap part of the molten iron of the intermediate layer 13 into the ladle I, and when tapping the molten iron, add ferrosilicon particles (chemical composition: Si 75.38%, Al 0.66%, Ca 0.47%, Mn 0.15%, Cr 0.21%, P 0.031%, S 0.014%, C 0.08%, and the balance is Fe and inevitable impurities) along with the flowing molten iron. The addition amount of the ferrosilicon particles accounts for 0.8% of the mass of the molten iron entering the ladle I; pour the molten iron in the ladle I into the mold 3 on the centrifuge in step S1; before pouring, measure the inner surface temperature of the outer layer 12 of the roll in the mold 3 with a non-contact thermometer. When the temperature is 1310 - 1348 °C, pour the cast iron molten iron of the intermediate layer 13 on the centrifuge. The pouring temperature of the cast iron molten iron of the intermediate layer 13 is 1372 °C, and the pouring thickness of the intermediate layer 13 is 20 mm. Immediately after pouring the intermediate layer 13, add the protective agent anhydrous sodium tetraborate. The addition amount of anhydrous sodium tetraborate is 0.42 kg / m based on the inner surface of the cast iron of the roll intermediate layer 13 2 ;

[0103] S3. Pour all the remaining molten iron in the furnace in step S2 into ladle II. Rare earth ferrosiliconmagnesium alloy particles (chemical composition: Mg 11.73%, Ce 2.54%, Si 40.92%, Ca 2.57%, with the balance being Fe and inevitable impurities) and calcium silicobarium alloy powder are pre-placed at the bottom of ladle II. The addition amounts of the rare earth ferrosiliconmagnesium alloy particles and the calcium silicobarium alloy powder respectively account for 1.3% and 0.55% of the mass fraction of the molten iron entering ladle II. After the molten iron is spheroidized and inoculated, ductile iron molten iron is obtained, and then slag skimming and static setting are carried out. 3 minutes after the casting of the cast iron in the middle layer 13 of the roll is completed, use a non-contact thermometer to measure the inner surface temperature of the cast iron in the middle layer 13 of the roll. When the temperature is 1257 - 1288 °C, under static conditions, top-cast the ductile iron molten iron of the roll core 14, and the molten iron pouring temperature is 1343 °C. During the pouring process of the ductile iron molten iron of the roll core 14, add multi-element alloy particles mixed with antimony, bismuth and rare earth ferrosilicon along with the molten iron flow. The addition amount of the multi-element alloy particles accounts for 0.28% of the mass of the ductile iron molten iron entering the mold. 9 hours after the pouring of the ductile iron of the roll core 14 is completed, take out the roll and put it into the slow cooling pit, and then carry out rough machining;

[0104] The multi-element alloy particles include: 9% antimony, 3% bismuth and 88% rare earth ferrosilicon; the size of the multi-element alloy particles is 0.8 - 3.5 mm; the chemical composition and mass fraction of the rare earth ferrosilicon are: Ce 28.63%, Si 39.75%, Mn 2.05%, Ca 4.27%, Ti 1.84%, with the balance being Fe and inevitable impurities;

[0105] S4. Carry out tempering treatment on the rough-machined roll (high nickel chromium molybdenum cast iron roll), with the tempering heating temperature of 385 °C, the holding time of 25 h, and furnace cooling. Finally, finish machine it to the specified size and accuracy to obtain a composite-cast wear-resistant high nickel chromium molybdenum cast iron roll.

[0106] The hardness of the outer layer 12 of the roll is 83.6 HSD, and the room temperature impact toughness of the outer layer 12 is 7.3 J / cm 2 ; the tensile strength of the roll neck 14 (roll core 14) is 580 MPa, and the elongation rate exceeds 12.5%.

[0107] After detection, the volume fraction of inclusions in the outer layer of the composite roll is 0.09%, and the volume fraction of inclusions in the roll core is 0.13%.

[0108] The roll cores and roll necks prepared in Examples 1 - 3 have good spheroidization effects. After detection, the spheroidization rate exceeds 95%.

[0109] For a hot-rolled strip mill, under the same working conditions, the steel passing capacity per millimeter of the composite wear-resistant roll (high-speed steel roll) prepared in Example 1 of the present invention reaches 22,000 tons, while that of the ordinary centrifugally composite-cast high-speed steel roll is only 16,500 tons, and its wear resistance is improved by more than 30% compared with the ordinary centrifugally composite-cast high-speed steel roll.

[0110] For a hot-rolled strip mill, under the same working conditions, the steel passing capacity per millimeter of the composite wear-resistant roll (high-chromium cast iron roll) prepared in Example 2 of the present invention reaches 10,000 tons, while that of the ordinary centrifugally composite-cast high-chromium cast iron roll is only 7,200 tons, and its wear resistance is improved by more than 38% compared with the ordinary centrifugally composite-cast high-chromium cast iron roll.

[0111] For a hot-rolled bar mill, under the same working conditions, the steel passing capacity per millimeter of the composite wear-resistant roll (high-nickel chromium molybdenum cast iron roll) prepared in Example 3 of the present invention reaches 3,400 tons, while that of the ordinary centrifugally composite-cast high-nickel chromium molybdenum cast iron roll reaches 2,510 tons, and its wear resistance is improved by more than 35% compared with the ordinary centrifugally composite-cast high-nickel chromium molybdenum cast iron roll.

[0112] The present invention realizes the smelting of three metal melts in two electric furnaces, with high production efficiency and low energy consumption. By controlling the smelting and pouring processes of the outer layer, intermediate layer and roll core, the nodularization effect of the roll core and roll neck is good, the nodularization rate exceeds 95%, the tensile strength of the roll core and roll neck exceeds 550 MPa, the elongation rate exceeds 12%, the hardness of the outer layer of the roll body exceeds 80 HSD, and the room temperature impact toughness exceeds 7 J / cm 2 , and the bonding strength of each layer is high. The intermediate layer and the roll core are cast from the molten iron smelted in the same furnace, with good composite effect, realizing a firm metallurgical bond, ensuring that no spalling and sleeve-off accidents occur during the use of the roll, significantly extending the service life of the roll, improving the operation efficiency of the rolling mill, and having good economic and social benefits.

[0113] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements or improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a composite cast wear-resistant roller, characterized in that: The composite cast wear-resistant roller comprises a roller outer layer, an intermediate layer and a roller core, and the preparation method thereof specifically comprises the following steps: S1, heating and melting the raw materials of the outer layer of the roller to obtain an outer layer of molten metal; raising the temperature of the outer layer of molten metal to 1595°C~1630°C, adding silicon-calcium alloy, adjusting the composition to meet the requirements and then taking it out of the furnace and placing it in a casting ladle, then feeding multi-element alloy wire into the casting ladle, slagging, pouring, and adding low-melting-point protective slag after the pouring is completed; wherein the raw materials of the multi-element alloy wire include ferroboron powder, silicon-calcium-barium alloy powder, aluminum-magnesium alloy particles and nano-TiC powder; S2, after heating and melting the raw materials of the middle layer of the roller and the metal copper, sequentially adding ferrosilicon alloy, ferromanganese alloy and metal tin to obtain a middle layer molten metal; heating the middle layer molten metal to 1495°C-1530°C, tapping part of the middle layer molten metal into the first iron ladle, adding ferrosilicon particles along with the tapping process, pouring part of the middle layer molten metal when the inner surface temperature of the outer layer of the roller is 1290°C-1360°C, and adding protective slag after the pouring is completed; S3, placing rare earth magnesium ferrosilicon alloy particles and silicon calcium barium alloy powder at the bottom of the second molten iron ladle, and then tapping the remaining middle layer of molten metal into the second molten iron ladle, skimming off the slag, and obtaining the roller core ductile iron molten iron; when the inner surface temperature of the roller middle layer is 1242°C~1295°C, pouring the roller core ductile iron molten iron, adding multi-element alloy particles along with the pouring process, after the pouring is completed, taking out and slowly cooling, rough processing, and heat treatment to obtain a composite cast wear-resistant roller; wherein the multi-element alloy particles include metal antimony, metal bismuth and rare earth ferrosilicon alloy.

2. The method for preparing a composite cast wear-resistant roller according to claim 1, characterized in that: In S1, the composition mass fraction of the outer layer metal melt is: C 1.50%~2.20%, Si 0.30%~1.20%, Mn 0.40%~1.20%, P ≤0.030%, S≤0.025%, Cr 3.00%~8.00%, Ni 0.00%~1.50%, Mo 2.00%~8.00%, V 2.00%~9.00%, W 0.30%~2.00%, Nb 0.30%~2.00%, and the balance is Fe and unavoidable impurities; or In S1, the composition mass fraction of the outer layer metal melt is: C 2.30%~3.30%, Si 0.30%~1.00%, Mn0.50%~1.20%, P≤0.10%, S≤0.05%, Cr 18.01%~22.00%, Ni 0.50%~1.70%, Mo 1.01%~3.00%, V 0.20%~0.60%, and the balance is Fe and unavoidable impurities; or In S1, the composition mass fractions of the outer layer metal melt are: C 2.90%~3.60%, Si 0.60%~2.00%, Mn0.40%~1.20%, P≤0.10%, S≤0.05%, Cr 1.00%~3.00%, Ni 3.01%~5.00%, Mo 0.20%~2.00%, V0.50%~2.50%, W 0.00%~8.00%, Nb 0.00%~1.00%, and the balance is Fe and unavoidable impurities.

3. The method for preparing a composite cast wear-resistant roller according to claim 1, characterized in that: In S1, the amount of the silicon-calcium alloy added is 0.20% to 0.25% of the mass of the molten metal; and / or In S1, the chemical composition and mass fraction of the silicon-calcium alloy are: Ca 31.27%~33.50%, Si 58.06%~62.75%, C≤1.0%, Al≤2.4%, and the balance is Fe and unavoidable impurities; and / or In S1, the feeding amount of the multi-element alloy wire is 7.5m / t~8.0m / t of molten metal, and the feeding speed is 10m / min~12m / min.

4. The method for preparing a composite cast wear-resistant roller according to claim 1, characterized in that: In S1, the mass fraction of each raw material in the multi-element alloy wire is: 15% to 16% of ferroboron powder, 46% to 48% of silicon-calcium-barium alloy powder, 32% to 34% of aluminum-magnesium alloy particles, and 4.0% to 4.5% of nano-TiC powder, and the sum of each component is 100%; and / or In S1, the particle size of the ferroboron powder is 15-25 mesh, the particle size of the silicon-calcium-barium alloy powder is 20-30 mesh, and the particle size of the aluminum-magnesium alloy particles is 0.5 mm-3.5 mm; and / or In S1, the preparation method of the multi-element alloy wire comprises the following steps: mixing ferroboron powder, silicon-calcium-barium alloy powder, aluminum-magnesium alloy particles and nano-TiC powder uniformly to obtain a mixed powder; coating the mixed powder with a low-carbon steel strip, rolling, and obtaining a multi-element alloy wire with a diameter of 13 mm to 14 mm; the chemical composition of the low-carbon steel strip is: C 0.08% to 0.19%, Si 0.40% to 0.49%, Mn 3.67% to 3.95%, Al 2.08% to 2.55%, S≤0.030%, P≤0.035%, and the remainder is Fe and unavoidable impurities; the thickness of the low-carbon steel strip is 0.55 mm to 0.65 mm; and / or In S1, the chemical composition of the ferroboron powder is: B 19.09%~20.84%, C≤0.5%, Si≤2%, Al≤0.5%, S≤0.01%, P≤0.1%, and the balance is Fe and unavoidable impurities; The chemical composition of the silicon-calcium-barium alloy powder is: Si 42.16%-44.38%, Ca 10.26%-11.85%, Ba 10.40%-11.86%, C≤0.8%, P≤0.04%, S≤0.06%, and the balance is Fe and unavoidable impurities; The chemical composition of the aluminum-magnesium alloy powder is: Al 72%-75%, Mg 25%-28%.

5. The method for preparing a composite cast wear-resistant roller according to claim 1, characterized in that: In S1, the casting speed is 900r / min~1100r / min, and the casting temperature is 1430℃~1460℃; and / or In S1, the low melting point protective slag is anti-oxidation O The amount of glass slag added is 0.8kg / m 2 ~1.0kg / m 2 .

6. The method for preparing a composite cast wear-resistant roller according to claim 1, characterized in that: In S2, the composition of the intermediate layer metal melt is: C 3.22%~3.45%, Si 1.35%~1.58%, Mn 0.59%~0.76%, Cu 0.52%~0.65%, Sn0.05%~0.08%, P≤0.080%, S≤0.040%, and the balance is Fe and unavoidable impurities.

7. The method for preparing a composite cast wear-resistant roller according to claim 1, characterized in that: In S2, the chemical composition of the ferrosilicon particles is: Si 74.80% to 76.17%, Al≤1.0%, Ca≤1.0%, Mn≤0.4%, Cr≤0.3%, P≤0.035%, S≤0.020%, C≤0.10%, and the balance is Fe and unavoidable impurities; and / or In S2, the particle size of the ferrosilicon particles is 5 mm to 12 mm; and / or In S2, the amount of ferrosilicon particles added is 0.7% to 0.9% of the mass of the molten metal in the intermediate layer; and / or In S2, the pouring temperature of the molten metal of the intermediate layer is 1355°C to 1385°C, and the pouring thickness of the intermediate layer is 16mm to 22mm; and / or In S2, the protective slag is anhydrous sodium tetraborate, and the amount added is 0.40 kg / m 2 ~0.45kg / m 2 .

8. The method for preparing a composite cast wear-resistant roller according to claim 1, characterized in that: In S3, the particle size of the rare earth magnesium ferrosilicon alloy particles is 7 mm to 12 mm; and / or In S3, the amount of the rare earth magnesium ferrosilicon alloy particles added is 1.2% to 1.4% of the mass of the remaining intermediate layer metal melt, and the amount of the silicon calcium barium alloy powder added is 0.5% to 0.6% of the mass of the remaining intermediate layer metal melt; and / or In S3, the chemical composition of the rare earth magnesium ferrosilicon alloy particles is: Mg 11.15%~11.82%, RE 2.21%~2.68%, Si 40.16%~41.96%, Ca 2.08%~2.66%, and the balance is Fe and unavoidable impurities; In S3, the chemical composition of the rare earth ferrosilicon alloy is: RE 27.42%~29.27%, Si 38.66%~41.51%, Mn<3.0%, Ca<5.0%, Ti<3.0%, and the balance is Fe and unavoidable impurities.

9. The method for preparing a composite cast wear-resistant roller according to claim 1, characterized in that: In S3, the pouring temperature of the ductile iron molten iron of the roller core is 1325° C. to 1350° C.; and / or In S3, the mass fraction of each raw material in the multi-element alloy particles is: metal antimony 9%-10%, metal bismuth 3%-4%, rare earth ferrosilicon 86%-88%, and the sum of each component is 100%; and / or In S3, the particle size of the multi-element alloy particles is 0.8 mm to 3.5 mm; and / or In S3, the amount of the multi-element alloy particles added is 0.25% to 0.30% of the mass of the ductile iron liquid entering the inner roller core of the casting mold.

10. The method for preparing a composite cast wear-resistant roller according to claim 1, characterized in that: In S3, the heat treatment includes quenching and tempering, wherein the quenching temperature is 1020°C to 1080°C, and the quenching time is 3h to 5h; the tempering temperature is 520°C to 580°C, and the tempering time is 18h to 22h; or In S3, the heat treatment is tempering treatment, the tempering temperature is 350°C to 400°C, and the treatment time is 22h to 28h.

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