Method for spheroidizing alloy ductile iron roll and manufacturing ductile iron roll

Abstract

The invention discloses an alloy ductile iron roll spheroidizing and ductile iron roll manufacturing method, and belongs to the technical field of roll manufacturing. The method is realized by adopting out-of-furnace wire feeding spheroidizing, wire feeding inoculation and stream pouring inoculation. The method comprises the following steps: firstly, mixing, heating and melting waste steel and a carburant, sequentially adding ferrochrome, ferromolybdenum, a nickel plate, ferrosilicon and ferromanganese after furnace charge is molten, slagging off after molten iron is melted down, finely adjusting components, slagging off after the temperature reaches 1455-1491 DEG C, discharging the molten iron in a furnace into a ladle, sequentially adding a spheroidizing alloy wire and an inoculation alloy wire into the molten iron by adopting a wire feeder, and when the temperature of the molten iron is reduced to 1330-1360 DEG C, carrying out heat preservation for 2-3 hours; the method comprises the following steps of: directly pouring the molten iron into a roller, and adding a multi-element alloy particle inoculant formed by mixing bismuth, antimony and rare earth silicon iron along with molten iron flow in the molten iron pouring process, so that the obtained alloy ductile iron roller is fine, round and uniform in graphite nodule distribution, good in toughness and wear resistance, and safe and reliable to use.

Description

Technical Field

[0001] The invention discloses a method for manufacturing a ductile iron roll, in particular to a spheroidizing treatment of an alloy ductile iron roll and a method for manufacturing the ductile iron roll, belonging to the technical field of roll manufacturing. Background Art

[0002] Rollers are essential and important parts of rolling mills. They are usually required to have high hardness and strength on the roll surface, and good plasticity and toughness inside the roll core. Traditional rolls are usually produced using chilled cast iron, high chromium cast iron or ductile iron. However, with the development of the metallurgical industry towards large-scale, high-speed and automated production, rolls produced by traditional methods can no longer meet the specific requirements of modern production. Austenitic ductile iron has excellent comprehensive mechanical properties of high strength, hardness, good plasticity and toughness, but the current production of Austenitic ductile iron mostly adopts austempering process, which has the disadvantages of high energy consumption and environmental pollution. In order to overcome the unfavorable conditions of austempering, reduce energy consumption, improve working conditions and further improve the comprehensive mechanical properties of rolls, it is urgent to study how to improve the performance of ductile iron rolls by improving the spheroidizing process in the cast state.

[0003] In order to improve the performance of ductile iron rolls, Chinese invention patent CN117778672A discloses a method for preparing alloy ductile iron rolls. The preparation method comprises the following steps: optimizing the alloy ratio of alloy ductile iron rolls, and increasing the mass percentage of nickel on the basis of conventional products; pre-processing the alloy ductile iron roll blank; moving the pre-processed alloy ductile iron roll into a high-temperature resistance furnace, heating it to 900-930°C, and keeping it warm for a period of time; after the end of the insulation, the alloy ductile iron roll is subjected to overall water cooling; after the end of the water cooling, the alloy ductile iron roll is subjected to air blowing; after the end of the air blowing, the alloy ductile iron roll is air-cooled out of the furnace; after the end of the air cooling, the alloy ductile iron roll is tempered; after the end of the tempering insulation, the alloy ductile iron roll is cooled to room temperature and unloaded from the furnace. The invention improves the hardness of the internal groove bottom and side wall of the alloy ductile iron roll hole, and improves the performance of the product. Chinese invention patent CN113481353A also discloses a quenching method for alloy ductile iron rolls. The alloy ductile iron rolls are made of alloy ductile iron, the surface hardness of the rolls is 48-56HSD, the heat treatment quenching temperature is 920℃-1000℃, a two-stage quenching method is adopted, the tempering temperature is 450-600℃, the holding time is 24-40h, and the spray quenching equipment is used. This invention solves the problem of oil quenching pollution, effectively avoids quenching cracks, and improves the hardness, uniformity and organizational properties of the produced products. Chinese invention patent CN103962526A also discloses a method for casting a ductile iron roll with grooves, including: the first step, shaping; the second step, assembling the chill ring and the cold mold; hanging the equally divided chill ring on the platform, grinding the surface of the chill ring to a metallic luster; then placing the equally divided chill rings in a circular shape, connecting the adjacent equally divided chill rings with bolts to form a circular integral chill ring, adjusting the integral chill ring so that its inner circle and outer circle are at the same center, tightening the connecting bolts, and loading the integral chill ring into the cold mold; the third step, baking the mold; the fourth step, cold mold spraying; the fifth step, buckling the box; the sixth step, melting; the seventh step, pouring; the eighth step, removing the positioning pin; after pouring, cooling for 20-30 minutes, and taking the positioning pin out of the cold mold; the ninth step, unpacking, and obtaining a semi-finished product. The groove shape is directly cast at the original chill ring to avoid the influence of the processing and grooving on the wear resistance of the roll, while reducing the processing amount; the production cost of the entire processing process is low, and the blank groove shape is smooth and flat. Chinese invention patent CN102728794A also discloses a combination of a special spheroidizing agent and an inoculant for large-section ductile iron rolls, characterized in that the composition range (weight percentage) of the spheroidizing agent is: 2-3% RE, 8-10% Mg, 2-3% Ca, 3-4% Ba, 38-41% Si, and the balance is Fe; the composition range (weight percentage) of the inoculant is: 0.5-1.0% RE, 1-2% Mg, 2-3% Ca, 3-5% Ba, 1-3% Mn, 1-3% Cr, 0.05-0.2% Sb, 38-40% Si, and the balance is Fe. Its advantage is that it can prolong the spheroidizing and inoculation decay time.It can reduce the scrap rate of rolls that do not meet the requirements due to serious spheroidization and inoculation decay in the core of the roll. Chinese invention patent CN102234734A also discloses an improved alloy ductile iron roll production process, the main feature of which is that V, Nb, and Mo alloys are added to the molten iron to improve the microhardness and core toughness of the roll. Nickel-magnesium alloy + copper-magnesium alloy + magnesium-silicon rare earth composite spheroidizer is used, with a total addition amount of 1.0-2.0%; pure cerium rare earth + silicon-calcium alloy + silicon-zirconium alloy + 75 ferrosilicon + strontium silicon composite inoculant is used, with a total addition amount of 5-10%, both of which improve the spheroidization quality of thick and large sections. A large-scale spray quenching machine is used to spray quench and force cool the roll to improve the surface hardness of the roll body. However, the production of ductile iron rolls using the above method still has the disadvantages of complex production process and poor roll performance stability.

[0004] In order to further improve the performance of ductile iron rolls, Chinese invention patent CN1068149A discloses vanadium-titanium infinitely chilled ductile iron rolls and casting methods, which are characterized by the chemical composition not containing precious alloy elements such as Ni, Cr, Mo, and Cu, and the roll body working layer to the core is all ductile iron. During casting, a mixed spheroidizing agent composed of rare earth magnesium and iron-magnesium mechanism spheroidizing agents was used, and a small dose of inoculant method and in-mold annealing process were adopted. The rolls produced by this invention have low cost, high hardness, good wear resistance, and high strength. When rolling steel, the rolls are not easy to break, and the roll groove edges are not easy to fall off. They can be used on the first and second stands of small and medium-sized rolling mills to replace cast steel rolls, and their service life is increased by more than 20% compared with cast steel rolls. Chinese invention patent CN112813339A also discloses a method for preparing ductile iron vertical rollers for tropical vertical rolling mills, comprising the following steps: A. Using scrap steel, nickel iron, ferrovanadium iron, ferromolybdenum iron and electrode powder as raw materials, smelting molten iron in an electric arc furnace at a smelting temperature of 1400-1600°C, and obtaining a ladle after melting; B. Adding a spheroidizing agent to the ladle obtained in step A, casting a ductile iron vertical roller blank for tropical vertical rolling mill, and cold unpacking for 120-160 hours; C. Using an overall heating heat treatment method to treat the ductile iron vertical roller blank for tropical vertical rolling mill prepared in step B. The ductile iron vertical roller for tropical vertical rolling mill prepared by the invention has good wear resistance and hot and cold fatigue performance, good thermal conductivity and lubrication performance, good toughness, and is well adapted to the good high temperature thermal shock and thermal cracking resistance, adhesion resistance and relatively good wear resistance required for tropical vertical rollers to contact high temperature steel billets, and meets the requirements of hot rolled strip edge rolling. Chinese invention patent CN111926239A also discloses a high-strength and high-hardness troostite ductile iron steel roll and a manufacturing method thereof, and the manufacturing method of the high-strength and high-hardness troostite ductile iron steel roll comprises the following steps: S1, adding scrap steel, ferromolybdenum, ferrochrome, and pure nickel into a medium frequency furnace for smelting;

[0005] S2, composite spheroidization and multiple inoculation treatment: first, add the first spheroidizer and the second spheroidizer into the molten iron ladle and cover the first inoculant thereon, so that the weight percentage of the total Si increase is controlled below 0.8%, then quickly pour the original molten iron into the molten iron ladle for spheroidization treatment, and the residual magnesium content of the molten iron after spheroidization treatment is controlled within 0.045-0.075%. After the spheroidization treatment is completed, add the second inoculant and the third inoculant into the molten iron ladle for inoculation treatment; S3, static casting; S4, rough processing and heat treatment; S5, inspection and finishing. The roll manufactured by this manufacturing method has the advantages of higher hardness and steel content, better wear resistance, lower stress, and less prone to roll breakage. Chinese invention patent CN118341834A also discloses a pearlite ductile iron roll for a rolling mill, comprising two rolls, the outer surfaces of the two roll bodies are respectively rotatably sleeved with two collars near the two ends, the two sides of the two collars are fixedly connected by a fixing frame, an anti-collision mechanism is arranged between the two fixing frames, the anti-collision mechanism comprises four plug-in rods, the outer surfaces of the two plug-in rods are respectively slidably sleeved with two spring seats near the bottom ends, and an anti-wear mechanism is arranged between the two spring seats. In this invention, the anti-collision mechanism and the anti-wear mechanism are effectively combined, which not only effectively prevents the two ribbed rolls from touching each other, but also the vibrating spring seat can drive the spray head to spray lubricant to the friction contact position between the steel bar and the two rolls in a wider range, effectively reducing the wear of the rolling groove in the roll, and the steel brush cleaning mechanism can effectively clean the debris inside the rolling groove in the roll. Chinese invention patent CN118345301A also discloses a full-base ductile iron roll material and roll manufacturing method, which includes the following components by mass percentage: C: 3.15% to 3.5%, Mn: 0.4% to 0.65%, Si: 1.35% to 1.6%, S≤0.03%, P≤0.05%, Cr≤0.15, Ni: 1.8% to 2.8%, Mo: 0.75% to 1.0%, the rest is Fe element, impurity elements ≤0.1%; the microstructure is 100% upper bainite structure in terms of area ratio. The advantages are: the composition of the roll body working layer is reasonable, which greatly reduces the content of Cr component, ensures that no carbide is formed in the working layer, meets the performance requirements of the long rough rolling work roll, the roll body working layer has uniform hardness and wear, the roll body tensile strength reaches 700 to 900 MPa, has high toughness and good thermal crack resistance. Chinese invention patent CN114807732A also discloses a method for preventing the core of ductile iron roll from becoming loose. The production process includes smelting, molten iron modification, pouring, insulation, and heat treatment processes; the heat treatment process adopts a high-temperature normalizing + two-stage stress relief annealing heat treatment process, with a normalizing temperature of 970-990°C and a normalizing time of 15-17 hours; the first stage annealing temperature is 515-535°C and the insulation time is 11-13 hours; the second stage annealing temperature is 550-570°C and the insulation time is 11-13 hours.The invention solves the problem of shrinkage cavities and porosity in the core of centrifugal composite ductile iron rolls, and realizes ultrasonic flaw detection without attenuation. Chinese invention patent CN113523201A also discloses a method for preparing a high wear-resistant ductile iron roll for hot rolling and furnace coil rolling mills, comprising the following steps: step A, using scrap steel, nickel iron, vanadium iron, chromium iron, molybdenum iron, tungsten iron, and electrode powder as raw materials, using a power frequency furnace to smelt the outer layer molten iron and the core molten iron; step B, after the smelting components meet the standards, the outer layer molten iron and the core molten iron are heated separately and then taken out of the furnace and poured; step C, after pouring, the box is opened cold, and rough processing is performed after cold opening; step D, after the addition is completed, the roll body is normalized and heated and tempered as a whole; step E, after normalization and tempering, fine processing and testing are performed until the finished product. The working rolls manufactured by the invention are more suitable for rollers for the rough rolling stand of hot rolling and furnace coil rolling mills, and can also be used for working rolls of medium and thick plate mills. Chinese invention patent CN111922320A also discloses a method for preparing a ductile iron roll and a roll, the method comprising the following steps: S1, molding by means of a composite sand box, and presetting a pouring position in the upper roll neck molding process; S2, putting the pre-proportioned raw materials into a medium frequency furnace for smelting, setting the smelting temperature to 1440-1540°C, adopting the in-laundering method for spheroidization and multiple inoculation and metamorphism treatment. S3, setting the pouring temperature to 1300-1360°C, pouring molten iron from the ladle into the mold cavity, when the molten iron is poured to the preset pouring position, after judging that the molten iron stops rotating and the liquid level stops rising and falling, the molten iron is poured from the riser for a second time, after the pouring is completed, the slag in the riser is removed, and a heat preservation agent is added; S4, cooling at room temperature, unpacking when the temperature is less than 100°C, and heat treating the roll after the roll is cooled to room temperature. According to the method of the embodiment of the invention, the overall strength of the roll is effectively increased. Chinese invention patent CN111349843A also discloses a high-strength alloy ductile iron roughing roll and its production process, wherein the chemical composition of the high-strength alloy ductile iron roughing roll is expressed in mass percentage as follows: C is 3.0-3.5, Si is 1.2-1.8, Mn is 0.7-1.0, P≤0.03, S≤0.015, Ni is 1.2-2.2, Mo is 0.3-0.8, V is 0.1-0.5, Cr is 0.2-1.0, Mg is 0.045-0.075, Re is 0.01-0.016, and the rest is Fe and unavoidable impurities. The invention increases the formation amount of different types of carbides in the material and the wear resistance of the material by the reasonable addition of alloy elements such as Cr, Mo and V, improves the strength of the material by dissolving in the matrix in an appropriate amount, and the combined action of Mg and Re reduces the separation effect of graphite on the matrix and further improves the toughness of the material.Chinese invention patent CN111036859A also discloses a spheroidizing inoculation method for high-strength ductile iron rolls, the method and process are as follows: (1) adding a spheroidizing agent, an inoculant, iron filings and steel plates to the backwater side of the bottom of the spheroidizing treatment ladle in sequence; when the roll body diameter D of the ductile iron roll is less than or equal to 400 mm, a light rare earth magnesium ferrosilicon composite spheroidizing agent is used; a composite rare earth ferrosilicon inoculant is used; when the roll body diameter D of the ductile iron roll is greater than or equal to 400 mm, a nickel-magnesium composite spheroidizing agent and a heavy rare earth magnesium ferrosilicon spheroidizing agent are used; a silicon-zirconium composite inoculant is used; (2) when tapping molten iron, the molten iron is mixed with the inoculant on the backwater side of the bottom of the ladle for primary inoculation in the ladle; during the process of tapping 1 / 3 to 2 / 3 of the molten iron, the inoculant is added in the process of floating silicon inoculation on the surface of the molten iron; (3) after spheroidizing and inoculation, pouring is carried out, and during the pouring process, a silicon-zirconium composite inoculant is added in the process of inoculation. The method realizes the spheroidization and inoculation treatment tasks, and finally obtains a ductile iron roll with higher strength. Chinese invention patent CN102618779A also discloses a cast bainite ductile iron composite roll, wherein the working layer is composed of 2.9-3.6% C, 1.0-2.0% Si, 0.5-1.0% Mn, ≤0.1% P, ≤0.03% S, 2.5-3.5% Ni, 0.5-1.0% Cr, 0.5-1.2% Mo, 0.03-0.15% Ti, 0.005-0.06% RE, ≤0.4% Cu, 0.05-0.1% Nb+V, 0.04-0.1% Mg, other inevitable impurities, and the balance is Fe; in terms of weight percentage, the inner layer is composed of 3.0-3.6% C, 1.6-2.8% Si, 0.3-0.9% Mn, ≤0.1% P, ≤0.03% S, ≤3.0% Ni, ≤0.3% Cr, ≤0.8% Mo, a trace amount of Re, and the balance is Fe. The ductile iron roller manufactured by the above method may need to undergo complex heat treatment, resulting in high energy consumption and long production cycle of the ductile iron roller, or there are problems such as large graphite ball size, uneven distribution of graphite balls, low toughness of the roller, fatigue peeling during use of the roller, and short service life of the roller. Summary of the invention

[0006] The present invention aims at the problems that the existing ductile iron roller production needs to perform complex high-temperature quenching heat treatment, resulting in high energy consumption and long production cycle of the ductile iron roller, or the existence of coarse graphite ball size, low graphite spheroidization rate, uneven graphite ball distribution and low roll toughness, which lead to fatigue peeling of the roll during use and shorten the roll life. The present invention proposes to adopt wire feeding spheroidization + wire feeding inoculation and flow casting inoculation outside the furnace to achieve a significant reduction in the size of the graphite balls of the ductile iron roller and a significant improvement in the spheroidization rate, thereby promoting a significant increase in the strength and toughness of the ductile iron roller.

[0007] A spheroidizing treatment of an alloy ductile iron roll and a method for preparing a ductile iron roll, wherein the specific preparation process steps include the following:

[0008] ① Using scrap steel and carburizer as main charge, adopt medium frequency induction furnace to melt molten iron; firstly, mix scrap steel and carburizer and heat to melt; after the charge is melted, add ferrochrome, ferromolybdenum and nickel plate in turn; after the ferrochrome, ferromolybdenum and nickel plate are melted, heat the molten iron to 1440-1470℃, add ferrosilicon and ferromanganese in turn, and heat the molten iron to 1500-1520℃, then add metal aluminum, the amount of metal aluminum added accounts for 0.05-0.12% of the mass fraction of the molten iron in the furnace; after the molten iron is melted, slag is removed, the composition is fine-tuned, and the chemical composition and mass fraction of the molten iron in the furnace are controlled within the required range; keep warm for 5-8 minutes; then naturally cool down to 1455-1491℃ in the furnace, remove slag, and discharge the molten iron in the furnace into the ladle;

[0009] ② After all the molten iron in the furnace enters the ladle, a wire feeder is used to add the multi-element alloy wire I to the molten iron in the ladle, and the amount of the multi-element alloy wire I added is 17-19 meters / ton of molten iron; the method for making the multi-element alloy wire I is to firstly mix 7-15 mesh passivation magnesium powder, 25-35 mesh rare earth ferrosilicon powder and nano-TiC powder uniformly, the mass compositions of the passivation magnesium powder, the rare earth ferrosilicon powder and the nano-TiC powder are 58-60%, 38-40% and 1.8-2.0% respectively, and the total mass composition of the passivation magnesium powder, the rare earth ferrosilicon powder and the nano-TiC powder is 100%, and then the uniformly mixed powder is packaged with a low-carbon soft steel strip with a thickness of 0.35-0.50mm, and rolled on the alloy cored wire unit into a multi-element alloy wire I with a diameter of φ9-12mm; after the multi-element alloy wire I is added to the molten iron for 4-7 minutes, the wire feeder is continued to be used. The multi-element alloy wire II is added to the molten iron in the ladle, and the addition amount of the multi-element alloy wire II is 8-10 meters / ton of molten iron. The preparation method of the multi-element alloy wire II is: firstly, 15-30 mesh silicon-barium-calcium alloy powder, 15-30 mesh silicon-zirconium alloy powder and 15-30 mesh silicon-strontium alloy powder are uniformly mixed, the mass compositions of the silicon-barium-calcium alloy powder, the silicon-zirconium alloy powder and the silicon-strontium alloy powder are 48-50%, 30-32% and 18-20% respectively, and the total mass composition of the silicon-barium-calcium alloy powder, the silicon-zirconium alloy powder and the silicon-strontium alloy powder is 100%, and then the uniformly mixed alloy powder is packaged with a low-carbon soft steel strip with a thickness of 0.35-0.50mm, and rolled on the alloy cored wire unit into the multi-element alloy wire II with a diameter of φ9-12mm; the wire feeding speeds of the multi-element alloy wire I and the multi-element alloy wire II are both controlled at 15-18m / minute;

[0010] ③ Step ② After the molten iron in the ladle is skimmed and allowed to stand, when the temperature drops to 1330-1360° C., it is directly poured into a casting mold to form a roll; and during the molten iron pouring process, multi-component alloy particles mixed with bismuth, antimony and rare earth ferrosilicon are added along with the molten iron flow, the multi-component alloy particles have a size of 0.8-3.5 mm, and the amount of the multi-component alloy particles added accounts for 0.15-0.20% of the mass fraction of the molten iron entering the casting mold; the multi-component alloy particles are composed of 8-9% of bismuth, 5-6% of antimony and 85-86% of rare earth ferrosilicon by mass fraction, and the total mass composition of bismuth, antimony and rare earth ferrosilicon is 100%;

[0011] ④ After the molten iron in the mold solidifies and cools, the roller blank is taken out of the box and rough-processed after sand cleaning and grinding; the rough-processed roller is put into the furnace and heated to 260-350℃. After keeping warm for 12-16 hours, the furnace is cooled to a temperature below 180℃, taken out of the furnace and air-cooled to room temperature, and finally fine-processed to the specified size and accuracy to obtain the alloy ductile iron roller.

[0012] Wherein the chemical composition and mass fraction of the molten iron in the furnace described in step ① are controlled within the required range, and the final composition of the molten iron in the furnace is selected from one of chromium-molybdenum ductile infinitely chilled molten iron, nickel-chromium-molybdenum ductile infinitely chilled molten iron I, nickel-chromium-molybdenum ductile infinitely chilled molten iron II, pearlite ductile I molten iron, pearlite ductile II molten iron, pearlite ductile III molten iron, bainite ductile I molten iron, and bainite ductile II molten iron;

[0013] As mentioned above, the chemical composition and mass fraction of the infinitely cold hardened chromium-molybdenum ductile iron in the furnace molten iron are: 2.90-3.60% C, 0.80-2.50% Si, 0.40-1.20% Mn, ≤0.25% P, ≤0.03% S, 0.30-1.00% Cr, 0.20-0.60% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities;

[0014] As mentioned above, the chemical composition and mass fraction of nickel-chromium-molybdenum ductile iron infinitely chilled I in the molten iron in the furnace are: 2.90-3.60% C, 0.80-2.50% Si, 0.40-1.20% Mn, ≤0.25% P, ≤0.03% S, 0.40-1.00% Cr, 0.50-1.00% Ni, 0.20-0.80% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities;

[0015] As mentioned above, the chemical composition and mass fraction of nickel-chromium-molybdenum ductile infinitely cold hardened II in the molten iron in the furnace are: 2.90-3.60% C, 0.80-2.50% Si, 0.40-1.20% Mn, ≤0.20% P, ≤0.03% S, 0.50-1.50% Cr, 1.01-1.50% Ni, 0.20-0.80% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities;

[0016] As mentioned above, the chemical composition and mass fraction of pearlite ductile iron I in the molten iron in the furnace are: 2.90-3.60% C, 1.40-2.20% Si, 0.40-1.00% Mn, ≤0.15% P, ≤0.03% S, 0.40-1.50% Cr, 1.51-2.00% Ni, 0.20-0.80% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities;

[0017] As mentioned above, the chemical composition and mass fraction of pearlite ductile iron II in the molten iron in the furnace are: 2.90-3.60% C, 1.20-2.00% Si, 0.40-1.00% Mn, ≤0.15% P, ≤0.03% S, 0.50-1.60% Cr, 2.01-2.50% Ni, 0.20-0.80% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities;

[0018] As mentioned above, the chemical composition and mass fraction of pearlite ductile iron III in the hot metal in the furnace are: 2.90-3.60% C, 1.00-2.00% Si, 0.40-1.00% Mn, ≤0.15% P, ≤0.03% S, 0.60-1.80% Cr, 2.51-3.00% Ni, 0.20-0.80% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities;

[0019] As mentioned above, the chemical composition and mass fraction of bainite ductile iron I in the molten iron in the furnace are: 2.90-3.60% C, 1.20-2.20% Si, 0.20-0.80% Mn, ≤0.10% P, ≤0.03% S, 0.50-1.60% Cr, 3.01-3.50% Ni, 0.50-1.00% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities;

[0020] As mentioned above, the chemical composition and mass fraction of bainite ductile iron II in the hot metal in the furnace are: 2.90-3.60% C, 1.00-2.00% Si, 0.20-0.80% Mn, ≤0.10% P, ≤0.03% S, 0.80-1.80% Cr, 3.51-4.50% Ni, 0.50-1.00% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities;

[0021] As mentioned above, the chemical composition and mass fraction of rare earth ferrosilicon are: 27.0-30.0% RE, 38.0-42.0% Si, <3.0% Mn, <5.0% Ca, <3.0% Ti, and the remainder is Fe and unavoidable impurities.

[0022] As mentioned above, the thickness of the passivation layer of the passivated magnesium powder is 0.05-0.08 mm, and the passivation layer of the passivated magnesium powder is composed of the following raw materials in proportion by mass: potassium chloride: 15-18%, magnesium chloride: 35-38%, barium chloride: 15-18% and calcium oxide: 30-32%.

[0023] As mentioned above, the chemical composition and mass fraction of the silicon-barium-calcium alloy powder are: 55.14-59.87% Si, 5.18-6.75% Ca, 4.55-5.91% Ba, <2.0% Mn, <3% Al, and the remainder is Fe and unavoidable impurities.

[0024] As mentioned above, the chemical composition and mass fraction of the silicon-zirconium alloy powder are: 48-58% Si, <2.0% Ca, 22.0-28.0% Zr, <5.0% Al, and the remainder is Fe and unavoidable impurities.

[0025] As mentioned above, the chemical composition and mass fraction of the silicon strontium alloy powder are: 62.33-69.76% Si, 8.08-8.91% Sr, <0.5% Al, <0.5% Ca, and the remainder is Fe and unavoidable impurities.

[0026] As mentioned above, the chemical composition and mass fraction of the low carbon mild steel strip are 0.08-0.25% C, <0.30% Si, 0.30-0.80% Mn, <0.040% P, <0.035% S, and the balance is Fe.

[0027] Some of the chemical compositions and mass fractions of nickel-chromium-molybdenum ductile iron infinitely chilled I, nickel-chromium-molybdenum ductile iron infinitely chilled II, pearlite ductile iron I, pearlite ductile iron II, pearlite ductile iron III, bainite ductile iron I and bainite ductile iron II overlap. If they overlap, they can be classified into any group of the overlapping pairs.

[0028] The present invention is mainly to solve the problems in the existing ductile iron roll production, such as the need for complex high-temperature quenching heat treatment, resulting in high energy consumption and long production cycle of ductile iron rolls, or the existence of coarse graphite ball size, low graphite spheroidization rate, uneven distribution of graphite balls and low roll toughness, which leads to fatigue peeling during use of the rolls and shortens the service life of the rolls. In order to solve the above problems, the present invention proposes to adopt out-of-furnace wire feeding spheroidization + wire feeding inoculation and flow casting inoculation to achieve a significant reduction in the size of graphite balls of ductile iron rolls and a significant increase in the spheroidization rate, thereby promoting a significant increase in the strength and toughness of ductile iron rolls.

[0029] A spheroidizing treatment of alloy ductile iron roll and a manufacturing method of ductile iron roll, the specific preparation process steps are: using scrap steel and carburizer as the main furnace charge, and using a medium frequency induction furnace to melt molten iron. Using scrap steel and carburizer as the main furnace charge to smelt molten iron has a simple process and a wide source of raw materials, ensuring that the roll has a low production cost. First, the scrap steel and carburizer are mixed and heated to melt, and ferrochrome, ferromolybdenum and nickel plates are added in sequence after the furnace charge is melted. After the furnace charge is melted, ferrochrome, ferromolybdenum and nickel plates are added in sequence, which can promote the rapid melting of ferrochrome, ferromolybdenum and nickel plates and significantly reduce the burning loss of alloy elements. After the ferrochrome, ferromolybdenum and nickel plates are melted, the molten iron is heated to 1440-1470°C, ferrosilicon and ferromanganese are added in sequence for deoxidation and alloying, and the molten iron is heated to 1500-1520°C, and then metal aluminum is added, and the amount of metal aluminum added accounts for 0.05-0.12% of the mass fraction of the molten iron in the furnace. Adding 0.05-0.12% aluminum to the molten iron in the furnace, in addition to deoxidation, the small amount of aluminum remaining in the molten iron has an important influence on the spheroidization of ductile iron. It can change the organizational structure and mechanical properties of ductile iron, making it more conducive to processing, with better wear resistance and tensile strength. In addition, aluminum can also reduce the adverse factors caused by the interaction between carbon and iron metals, thereby improving the spheroidization effect of ductile iron.

[0030] After the molten iron is melted, the slag is removed and the composition is finely adjusted, and the chemical composition and mass fraction of the molten iron in the furnace are controlled within the required range. The final molten iron composition in the furnace is selected from one of chromium-molybdenum ductile infinitely chilled molten iron, nickel-chromium-molybdenum ductile infinitely chilled molten iron I, nickel-chromium-molybdenum ductile infinitely chilled molten iron II, pearlite ductile I molten iron, pearlite ductile II molten iron, pearlite ductile III molten iron, bainite ductile I molten iron, and bainite ductile II molten iron, wherein the chemical composition and mass fraction of the chromium-molybdenum ductile infinitely chilled ductile iron are controlled within the range of: 2.90-3.60% C, 0.80-2.50% Si, 0.40-1.20% Mn, ≤0.25% P, ≤0.03% S, 0.30-1.00% Cr, 0.20-0.60% Mo, 0.005-0.030% Al, and the balance is Fe and unavoidable impurities; The chemical composition and mass fraction of nickel-chromium-molybdenum ductile infinitely chilled ductile iron I are controlled at: 2.90-3.60% C, 0.80-2.50% Si, 0.40-1.20% Mn, ≤0.25% P, ≤0.03% S, 0.40-1.00% Cr, 0.50-1.00% Ni, 0.20-0.80% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities; the chemical composition and mass fraction of nickel-chromium-molybdenum ductile infinitely chilled ductile iron II are controlled at: 2.90-3.60% C, 0.80-2.50% Si, 0.40-1.20% Mn, ≤0.25% P, ≤0.03% S, 0.50-1.5 0%Cr,1.01-1.50%Ni,0.20-0.80%Mo,0.005-0.030%Al,the balance is Fe and inevitable impurities;The chemical composition and mass fraction of pearlite ductile iron I are controlled at:2.90-3.60%C,1.40-2.20%Si,0.40-1.00%Mn,≤0.15%P,≤0.03%S,0.40-1.50%Cr,1.51-2.00%Ni,0.20-0.80%Mo,0.005-0.030%Al,the balance is Fe and inevitable impurities;The chemical composition and mass fraction of pearlite ductile iron II are controlled at:2.90-3.60 %C,1.20-2.00%Si,0.40-1.00%Mn,≤0.15%P,≤0.03%S,0.50-1.60%Cr,2.01-2.50%Ni,0.20-0.80%Mo,0.005-0.030%Al,the balance is Fe and unavoidable impurities;The chemical composition and mass fraction of pearlite ductile iron III are controlled at: 2.90-3.60%C,1.00-2.00%Si,0.40-1.00%Mn,≤0.15%P,≤0.03%S,0.60-1.80%Cr,2.51-3.00%Ni,0.20-0.80%Mo,0.005-0.030%Al, the balance is Fe and inevitable impurities; the chemical composition and mass fraction of bainitic ductile iron I are controlled at: 2.90-3.60%C, 1.20-2.20%Si, 0.20-0.80%Mn, ≤0.10%P, ≤0.03%S, 0.50-1.60%Cr, 3.01-3.50%Ni, 0.50-1.00%Mo, 0.005-0.030%Al, the balance is Fe and inevitable impurities; the chemical composition and mass fraction of bainite ductile iron II are controlled at: 2.90-3.60% C, 1.00-2.00% Si, 0.20-0.80% Mn, ≤0.10% P, ≤0.03% S, 0.80-1.80% Cr, 3.51-4.50% Ni, 0.50-1.00% Mo, 0.005-0.030% Al, the balance is Fe and inevitable impurities. In particular, the molten iron of the present invention is kept warm for 5-8 minutes, then naturally cooled to 1455-1491°C in the furnace, and then slag is removed, and the molten iron in the furnace is discharged into the ladle. The high-temperature smelting of molten iron of the present invention is mainly to promote the full melting and uniform distribution of alloy elements; the natural cooling to 1455-1491°C and discharged can promote the removal of gas in the furnace and the floating of inclusions, thereby improving the quality of molten iron. .

[0031] After all the molten iron in the furnace enters the ladle, a wire feeder is used to add the multi-element alloy wire I into the molten iron in the ladle, and the added amount of the multi-element alloy wire I is 17-19 meters per ton of molten iron. The preparation method of the multi-element alloy wire I is to firstly mix 7-15 mesh passivation magnesium powder, 25-35 mesh rare earth ferrosilicon powder and nano TiC powder uniformly; the passivation magnesium powder, rare earth ferrosilicon (the chemical composition and mass fraction of the rare earth ferrosilicon are: 27.0-30.0% RE, 38.0-42.0% Si, <3.0% Mn, <5.0% Ca, <3.0% Ti, the balance is Fe and inevitable impurities) powder and The mass compositions of nano-TiC powder are 58-60%, 38-40% and 1.8-2.0% respectively, and the total mass composition of passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder is 100%. The uniformly mixed powders are then packaged with a low-carbon mild steel strip with a thickness of 0.35-0.50 mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.08-0.25% C, <0.30% Si, 0.30-0.80% Mn, <0.040% P, <0.035% S, and the balance is Fe), and rolled on an alloy cored wire unit into a multi-element alloy wire I with a diameter of φ9-12 mm.

[0032] At present, there are two most widely used molten iron spheroidization treatments, one is the flushing method commonly used at home and abroad, and the other is the wire feeding method with good development prospects. Compared with the flushing method, the wire feeding method has the advantages of improved magnesium absorption rate, less secondary oxidation slag, and better working conditions. However, the content of magnesium in the spheroidizing wire is generally 25% to 30%, which is higher than the flushing method. The reaction during the spheroidization process is more intense, the deoxidation is intense, the graphite core is reduced, and the tendency of white cast iron is increased. In order to solve the above-mentioned shortcomings of spheroidization, the present invention uses passivated magnesium powder to replace metallic magnesium. The thickness of the passivation layer of the passivation magnesium powder is 0.05 to 0.08 mm, and the passivation layer of the passivation magnesium powder is composed of the following raw materials in mass percentage: potassium chloride: 15-18%, magnesium chloride: 35-38%, barium chloride: 15-18% and calcium oxide: 30-32%. After using passivated magnesium powder, due to the effect of the passivation layer, the reaction of magnesium can be delayed and the absorption rate of magnesium can be increased. The absorption rate of magnesium is increased from the common 30% to 40% to 70-75%. In addition, multi-element alloy wire I also contains 1.8-2.0% nano-TiC. The addition of nano-TiC can significantly increase the spheroidization rate of ductile iron, reduce the diameter difference of graphite balls, and make the distribution of graphite balls and pearlite more uniform. Due to the increase in spheroidization rate and the hindering effect of intergranular nano-TiC particles on crack propagation, the plastic toughness of ductile iron can be significantly improved without reducing tensile strength. Nano-TiC particles in the matrix can also reduce the friction coefficient and improve the wear resistance of the roll. At the same time, due to the thermal mismatch effect of nano-TiC particles, the high temperature deformation resistance of ductile iron rolls is improved.

[0033] After the multi-element alloy wire I of the present invention is added to the molten iron for 4 to 7 minutes, the multi-element alloy wire II is continuously added to the molten iron in the molten iron ladle by a wire feeder, and the addition amount of the multi-element alloy wire II is 8 to 10 meters per ton of molten iron; the preparation method of the multi-element alloy wire II is to firstly add 15-30 mesh silicon-barium-calcium alloy powder (the chemical composition and mass fraction of the silicon-barium-calcium alloy powder are: 55.14-59.87% Si, 5.18-6.75% Ca, 4.55-5.9 1%Ba, <2.0%Mn, <3%Al, the balance is Fe and inevitable impurities), 15-30 mesh silicon zirconium alloy powder (the chemical composition and mass fraction of the silicon zirconium alloy powder are: 48-58%Si, <2.0%Ca, 22.0-28.0%Zr, <5.0%Al, the balance is Fe and inevitable impurities) and 15-30 mesh silicon strontium alloy powder (the chemical composition and mass fraction of the silicon strontium alloy powder are: 6 2.33-69.76% Si, 8.08-8.91% Sr, <0.5% Al, <0.5% Ca, the balance being Fe and unavoidable impurities) are mixed evenly; the mass compositions of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder are 48-50%, 30-32% and 18-20% respectively, and the total mass composition of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder is 100%; and the above alloy powders are mixed evenly. The invention adopts a low-carbon mild steel strip with a thickness of 0.35-0.50 mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.08-0.25% C, <0.30% Si, 0.30-0.80% Mn, <0.040% P, <0.035% S, and the balance is Fe) for packaging, and rolls it into a multi-element alloy wire II with a diameter of φ9-12 mm on an alloy cored wire unit; the wire feeding speed of the multi-element alloy wire is controlled at 15-18 m / min. The invention adopts a wire feeding method for inoculation, which is convenient to operate and has a high yield of inoculating elements. Barium and calcium are added to the inoculant, and the melting point of barium is 710°C, and the boiling point is as high as 1637°C. It will not turn into gas in molten iron, so adding barium into the molten iron will not cause smoke, light and splashing. Compared with magnesium, it can reduce the intensity of the reaction, improve process performance and working conditions. Ca and Ba have stronger deoxidation and desulfurization capabilities than Mg. When added to molten iron together with Mg, they mainly combine with oxygen and sulfur, which creates good metamorphic conditions for Mg and increases the residual amount of Mg. In addition, when a certain amount of Ba and Ca is added to molten iron, in addition to BaO and CaO, BaS and CaS will also be formed. The lattice mismatch between the generated CaS and BaS and graphite is 4.1% and 7.5%, respectively. The substrate with a lattice mismatch of less than 6% is an efficient core for heterogeneous nucleation, and the substrate with a lattice mismatch between 6% and 12% is a moderately effective heterogeneous nucleation core. Therefore, CaS is an efficient substrate for graphite nucleation, and BaS is an effective substrate. The (Mn,Ca)S that CaS can form with MnS has a smaller lattice mismatch with graphite than CaS, and is also an efficient substrate for graphite nucleation.The addition of barium and calcium can significantly promote the nucleation of graphite and make the graphite nodules small. In addition, strontium is very active and can easily form high-melting-point oxygen and sulfide with sulfur oxide. Strontium has a similar effect to barium and calcium, that is, it forms ionic bond carbides ((SrC), and SrC is insoluble in Fe-C-Si melt, which plays an effective inoculating role in the nucleation of graphite. Since strontium can form high-melting-point oxides, sulfides, and carbides in high-temperature molten iron, these refractory particles can all serve as the core of heterogeneous nucleation of graphite, thus strongly promoting graphitization, making the graphite more rounded, and the number of graphite nodules is large and small. Adding less strontium can achieve a good inoculation effect. Zirconium is a very good inoculant in cast iron, with strong anti-decay ability. The combined effect of barium, calcium, strontium and zirconium has a stronger inoculation effect and anti-decay ability, ensuring the refinement of graphite nodule size, which is beneficial to improving the toughness of ductile iron. The wire feeding speed in the wire feeding spheroidization process determines the absorption rate of magnesium in the cored wire. The appropriate wire feeding speed should ensure that the spheroidized wire is detonated when it extends to 100-200mm from the bottom of the liquid surface, so as to ensure that the molten iron in the ladle is fully desulfurized. If the wire feeding speed is too low, it cannot ensure that the spheroidized cored wire penetrates into the bottom of the molten iron ladle to detonate, so that the molten iron at the bottom of the spheroidization ladle cannot fully contact the spheroidized powder in the cored wire for desulfurization; if the wire feeding speed is too fast, the spheroidized cored wire cannot be detonated when it reaches the bottom, so that the spheroidized cored wire floats to the upper part of the molten iron or burns on the surface under the action of buoyancy, and the desulfurization and deoxidation effect cannot be achieved. The present invention controls the wire feeding speed at 15-18m / min, has a good spheroidization effect, and a high magnesium recovery rate.

[0034] The molten iron in the ladle of the present invention is directly cast into a roll when the temperature drops to 1330-1360°C after slagging and standing. In the process of pouring the molten iron, multi-component alloy particles mixed with bismuth, antimony and rare earth ferrosilicon are added with the molten iron flow, the multi-component alloy particles have a size of 0.8-3.5 mm, and the amount of the multi-component alloy particles added accounts for 0.15-0.20% of the mass fraction of the molten iron entering the casting mold. The multi-component alloy particles are composed of 8-9% of bismuth, 5-6% of antimony and 85-86% of rare earth ferrosilicon, and the total mass composition of bismuth, antimony and rare earth ferrosilicon is 100%. The roll size is large, the solidification and cooling are slow, the solidification time is long, the segregation phenomenon is serious, and the spheroidization and inoculation decline phenomenon are very likely to occur, so that the variability graphite in the form of flakes, worms and fragments appears in the ductile iron organization, resulting in the decrease of the mechanical properties of the ductile iron roll. Adding an appropriate amount of bismuth can reduce the diameter of the graphite balls, increase the number of graphite balls, and improve the impact toughness of the ductile iron. Adding trace amounts of bismuth and antimony to ductile iron containing rare earths can significantly increase the number of graphite nodules, making the graphite nodules smaller and rounder, and improving performance. In large-section ductile iron rolls, the addition of bismuth, antimony and rare earth elements can effectively improve the graphite morphology, increase the number of graphite nodules, reduce or eliminate the variant graphite in the center of the large section, and after adding antimony, the pearlite content in the ductile iron matrix increases dramatically, the strength and hardness are greatly improved, and the wear resistance is significantly improved.

[0035] After the molten iron in the casting mold solidifies and cools, the roller blank is taken out of the box, and rough processing is performed after sand removal and grinding. The rough-processed roller is heated to 260-350°C in the furnace and kept warm for 12-16 hours, so that the internal stress of the roller can be eliminated, the roller structure can be stabilized, and the safe use of the roller can be ensured. The furnace is cooled to a temperature below 180°C, and the roller is air-cooled to room temperature after being taken out of the furnace. Finally, it is finely processed to the specified size and accuracy, and an alloy ductile iron roller with excellent toughness and wear resistance can be obtained.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] (1) The present invention adopts the wire feeding method to spheroidize and inoculate cast iron, and the spheroidizing and inoculating element yields are significantly improved. Compared with the ordinary punching method, the spheroidizing element yield is increased by more than 30%, and the inoculating element yield is increased by more than 15%.

[0038] (2) The alloy ductile iron spheroidizing method of the present invention is safe, simple and environmentally friendly to operate.

[0039] (3) The ductile iron roller manufactured by the method of the present invention has graphite balls of small size and uniform distribution, and the graphite spheroidization rate is as high as over 95%. The ductile iron roller has the advantages of good toughness, high hardness and steel passing capacity, good wear resistance, low stress, and continuous rolling.

[0040] (4) Compared with ordinary ductile iron rolls, the wear resistance of the rolls of the present invention is improved by more than 20% under the same rolling conditions. Compared with the traditional spheroidizing treatment method using rare earth magnesium alloy, nickel-magnesium alloy, and copper-magnesium alloy, the spheroidizing cost is reduced by more than 30%, and the graphite spheroidizing rate reaches the national standard level 1 or above. The rolls have good toughness and wear resistance, and have both the high wear resistance of alloy infinitely chilled rolls and the high toughness of alloy ductile iron rolls. The promotion and application of the present invention has good economic and social benefits. DETAILED DESCRIPTION

[0041] 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.

[0042] Embodiment 1:

[0043] A spheroidizing treatment of alloy ductile iron roll and a method for manufacturing ductile iron roll, which is achieved by using wire feeding spheroidizing + wire feeding inoculation and flow casting inoculation outside the furnace, and the specific preparation process steps are:

[0044] ① Take scrap steel and carburizer as the main charge, and use medium frequency induction furnace to melt molten iron; first, mix scrap steel and carburizer and heat to melt; after the charge is melted, add ferrochrome and ferromolybdenum in sequence; after ferrochrome and ferromolybdenum are melted, heat the molten iron to 1440℃, add ferrosilicon and ferromanganese in sequence, and heat the molten iron to 1500℃, then add metal aluminum, the amount of metal aluminum added accounts for 0.05% of the mass fraction of the molten iron in the furnace; after the molten iron is melted, remove the slag and fine-tune the composition. The chemical composition and mass fraction of the infinitely cold and hardened molten iron of chromium-molybdenum ductile iron in the furnace are controlled to be: 3.37% C, 1.88% Si, 0.73% Mn, 0.16% P, 0.028% S, 0.71% Cr, 0.37% Mo, 0.009% Al, and the balance is Fe and inevitable impurities; keep warm for 5 minutes; then naturally cool down to 1455℃ in the furnace, remove the slag, and discharge the molten iron in the furnace into the ladle;

[0045] ② After all the molten iron in the furnace enters the ladle, a wire feeder is used to add the multi-element alloy wire I to the molten iron in the ladle, and the amount of the multi-element alloy wire I added is 17 meters / ton of molten iron; the method for making the multi-element alloy wire I is to first add 7-15 mesh passivation magnesium powder (the passivation layer thickness of the passivation magnesium powder is 0.05-0.08 mm, and the passivation layer of the passivation magnesium powder is composed of the following raw materials in mass percentage, potassium chloride: 15%, magnesium chloride: 38%, barium chloride: 17% and calcium oxide: 30%), 25-35 mesh rare earth ferrosilicon (the chemical composition and mass fraction of the rare earth ferrosilicon are: 28.07% RE, 39.65% Si, 1.28% Mn, 2.69% Ca, 1.08% Ti, and the balance is Fe and unavoidable impurities The passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder are uniformly mixed; the mass compositions of the passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder are 60%, 38% and 2.0% respectively, and the total mass composition of the passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder is 100%; the uniformly mixed powders are then packed with a low-carbon mild steel strip with a thickness of 0.35-0.50 mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.08% C, 0.21% Si, 0.57% Mn, 0.038% P, 0.031% S, and the balance is Fe), and rolled on an alloy cored wire unit into a multi-element alloy wire I with a diameter of φ9 mm; after the multi-element alloy wire I is added to the molten iron for 4 minutes, the multi-element alloy wire II is continuously added to the molten iron in the molten iron ladle using a wire feeder, and the multi-element alloy wire II is rolled into a multi-element alloy wire I with a diameter of φ9 mm on an alloy cored wire unit ... The addition amount of alloy wire II is 8 meters / ton of molten iron; the preparation method of multi-element alloy wire II is to firstly mix 15-30 mesh silicon-barium-calcium alloy powder (the chemical composition and mass fraction of the silicon-barium-calcium alloy powder are: 55.14% Si, 6.75% Ca, 4.55% Ba, 1.26% Mn, 1.84% Al, the balance is Fe and inevitable impurities), 15-30 mesh silicon-zirconium alloy powder (the chemical composition and mass fraction of the silicon-zirconium alloy powder are: 52.66% Si, 1.05% Ca, 25.80% Zr, 2.53% Al, the balance is Fe and inevitable impurities) and 15-30 mesh silicon-strontium alloy powder (the chemical composition and mass fraction of the silicon-strontium alloy powder are: 62.33% Si, 8.91% Sr , 0.17% Al, 0.38% Ca, the balance is Fe and inevitable impurities) are mixed evenly; the mass compositions of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder are 48%, 32% and 20% respectively, and the total mass composition of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder is 100%; the above alloy powders mixed evenly are packaged with a low-carbon mild steel strip with a thickness of 0.35-0.50mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.08% C, 0.21% Si, 0.57% Mn, 0.038% P, 0.031% S, the balance is Fe), and rolled into a multi-element alloy wire II with a diameter of φ9mm on an alloy cored wire unit; the wire feeding speed of the multi-element alloy wire is controlled at 15m / min;

[0046] ③ Step ② After the molten iron in the ladle is skimmed and allowed to stand, when the temperature drops to 1330° C., it is directly cast into a roll; and during the molten iron pouring process, multi-component alloy particles mixed with bismuth, antimony and rare earth ferrosilicon are added along with the molten iron flow, the multi-component alloy particles have a size of 0.8 to 3.5 mm, and the amount of the multi-component alloy particles added accounts for 0.15% of the mass fraction of the molten iron entering the casting mold; the multi-component alloy particles are composed of 8% by mass of bismuth, 6% by mass of antimony and 86% by mass of rare earth ferrosilicon, and the total mass composition of bismuth, antimony and rare earth ferrosilicon is 100%;

[0047] ④ After the molten iron in the mold solidifies and cools, the roll blank is taken out of the box, and rough processing is performed after sand removal and grinding; the rough-processed roll is heated to 260°C in the furnace, kept warm for 16 hours, cooled to a temperature below 180°C in the furnace, air-cooled to room temperature, and finally fine-processed to the specified size and accuracy to obtain the alloy ductile iron roll. The roll has a tensile strength of 855MPa, a hardness of 68.3HSD, and an impact toughness of 36.7J / cm 2 .

[0048] Embodiment 2:

[0049] A spheroidizing treatment of alloy ductile iron roll and a method for manufacturing ductile iron roll, which is achieved by using wire feeding spheroidizing + wire feeding inoculation and flow casting inoculation outside the furnace, and the specific preparation process steps are:

[0050] ① Use scrap steel and carburizer as the main charge, and use medium frequency induction furnace to melt molten iron; first, mix scrap steel and carburizer and heat to melt; after the charge is melted, add ferrochrome, ferromolybdenum and nickel plate in turn; after the ferrochrome, ferromolybdenum and nickel plate are melted, heat the molten iron to 1470℃, add ferrosilicon and ferromanganese in turn, and heat the molten iron to 1520℃, then add metal aluminum, the amount of metal aluminum added accounts for 0.12% of the mass fraction of the molten iron in the furnace; after the molten iron is melted, remove the slag, fine-tune the composition, and The chemical composition and mass fraction of the nickel-chromium-molybdenum ductile iron infinitely chilled I in the furnace are controlled to be: 3.08% C, 1.61% Si, 0.97% Mn, 0.20% P, 0.026% S, 0.85% Cr, 0.66% Ni, 0.43% Mo, 0.013% Al, and the balance is Fe and unavoidable impurities; keep warm for 5 minutes; then naturally cool down to 1491°C in the furnace, then slag off, and discharge the molten iron in the furnace into a ladle;

[0051] ② After all the molten iron in the furnace enters the ladle, a wire feeder is used to add the multi-element alloy wire I to the molten iron in the ladle, and the amount of the multi-element alloy wire I added is 19 meters / ton of molten iron; the method for making the multi-element alloy wire I is to first add 7-15 mesh passivation magnesium powder (the passivation layer thickness of the passivation magnesium powder is 0.05-0.08 mm, and the passivation layer of the passivation magnesium powder is composed of the following raw materials in mass percentage ratio, potassium chloride: 15%, magnesium chloride: 38%, barium chloride: 15% and calcium oxide: 32%), 25-35 mesh rare earth ferrosilicon (the chemical composition and mass fraction of the rare earth ferrosilicon are: 28.08% RE, 40.55% Si, 1.86% Mn, 3.29% Ca, 1.25% T i, the balance is Fe and inevitable impurities) powder and nano-TiC powder are mixed evenly; the mass compositions of passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder are 60%, 38.2% and 1.8% respectively, and the total mass composition of passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder is 100%; the evenly mixed powders are packaged with a low-carbon mild steel strip with a thickness of 0.35-0.50 mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.25% C, 0.18% Si, 0.71% Mn, 0.027% P, 0.009% S, and the balance is Fe), and rolled into a multi-element alloy wire I with a diameter of φ12 mm on an alloy cored wire unit; the multi-element alloy wire I is added with molten iron for 7 minutes After 10 minutes, the multi-element alloy wire II is added to the molten iron in the ladle by a wire feeder, and the amount of multi-element alloy wire II added is 10 meters / ton of molten iron; the preparation method of multi-element alloy wire II is to first add 15-30 mesh silicon-barium-calcium alloy powder (the chemical composition and mass fraction of the silicon-barium-calcium alloy powder are: 59.87% Si, 5.18% Ca, 5.91% Ba, 1.67% Mn, 1.08% Al, and the balance is Fe and inevitable impurities), 15-30 mesh silicon-zirconium alloy powder (the chemical composition and mass fraction of the silicon-zirconium alloy powder are: 50.60% Si, 0.51% Ca, 23.75% Zr, 2.63% Al, and the balance is Fe and inevitable impurities) and 15 -30 mesh silicon strontium alloy powder (the chemical composition and mass fraction of the silicon strontium alloy powder are: 69.76% Si, 8.08% Sr, 0.15% Al, 0.26% Ca, the balance is Fe and inevitable impurities) is mixed evenly; the mass compositions of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder are 50%, 30% and 20% respectively, and the total mass composition of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder is 100%; then the above alloy powders are mixed evenly with a low-carbon mild steel strip with a thickness of 0.35-0.50mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.25% C, 0.18% Si, 0.71% Mn, 0.027% P, 0.009% S, balance Fe) packaging, rolled into φ12mm diameter multi-element alloy wire II on the alloy cored wire unit; the wire feeding speed of the multi-element alloy wire is controlled at 18m / min;.

[0052] ③ Step ② After the molten iron in the ladle is skimmed and allowed to stand, when the temperature drops to 1360° C., it is directly cast into a roll; and during the molten iron pouring process, multi-component alloy particles mixed with bismuth, antimony and rare earth ferrosilicon are added along with the molten iron flow, the multi-component alloy particles have a size of 0.8 to 3.5 mm, and the amount of the multi-component alloy particles added accounts for 0.20% of the mass fraction of the molten iron entering the casting mold; the multi-component alloy particles are composed of 9% by mass of bismuth, 5% by mass of antimony and 86% by mass of rare earth ferrosilicon, and the total mass composition of bismuth, antimony and rare earth ferrosilicon is 100%;

[0053] ④ After the molten iron in the mold solidifies and cools, the roll blank is taken out of the box, and rough processing is performed after sand removal and grinding; the rough-processed roll is heated to 350℃ in the furnace, kept warm for 12 hours, cooled to a temperature below 180℃, air-cooled to room temperature, and finally fine-processed to the specified size and accuracy to obtain the alloy ductile iron roll. The roll has a tensile strength of 750MPa, a hardness of 63.7HSD, and an impact toughness of 40.6J / cm 2 .

[0054] Embodiment 3:

[0055] A spheroidizing treatment of alloy ductile iron roll and a method for manufacturing ductile iron roll, which is achieved by using wire feeding spheroidizing + wire feeding inoculation and flow casting inoculation outside the furnace, and the specific preparation process steps are:

[0056] ① Use scrap steel and carburizer as the main charge, and use medium frequency induction furnace to melt molten iron; first, mix scrap steel and carburizer and heat to melt; after the charge is melted, add ferrochrome, ferromolybdenum and nickel plate in turn; after the ferrochrome, ferromolybdenum and nickel plate are melted, heat the molten iron to 1457℃, add ferrosilicon and ferromanganese in turn, and heat the molten iron to 1516℃, then add metal aluminum, the amount of metal aluminum added accounts for 0.09% of the mass fraction of the molten iron in the furnace; after the molten iron is melted, remove the slag, fine-tune the composition, and The chemical composition and mass fraction of the nickel-chromium-molybdenum ductile iron infinitely chilled II in the furnace are controlled to be: 3.38% C, 1.81% Si, 0.66% Mn, 0.12% P, 0.025% S, 1.16% Cr, 1.27% Ni, 0.62% Mo, 0.012% Al, and the balance is Fe and unavoidable impurities; keep warm for 7 minutes; then naturally cool down to 1472°C in the furnace, then slag off, and discharge the molten iron in the furnace into a ladle;

[0057] ② After all the molten iron in the furnace enters the ladle, a wire feeder is used to add the multi-element alloy wire I to the molten iron in the ladle, and the amount of the multi-element alloy wire I added is 18 meters / ton of molten iron; the method for making the multi-element alloy wire I is to first add 7-15 mesh passivation magnesium powder (the passivation layer thickness of the passivation magnesium powder is 0.05-0.08 mm, and the passivation layer of the passivation magnesium powder is composed of the following raw materials in proportion by mass percentage, potassium chloride: 17%, magnesium chloride: 37%, barium chloride: 16% and calcium oxide: 30%), 25-35 mesh rare earth ferrosilicon (the chemical composition and mass fraction of the rare earth ferrosilicon are: 28.15% RE, 39.24% Si, 1.48% Mn, 2.35% Ca, 0.51% Ti, and the balance is Fe and unavoidable impurities The passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder are uniformly mixed; the mass compositions of the passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder are 59%, 39% and 2.0% respectively, and the total mass composition of the passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder is 100%; the uniformly mixed powders are then packed with a low-carbon mild steel strip with a thickness of 0.35-0.50 mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.15% C, 0.28% Si, 0.43% Mn, 0.036% P, 0.030% S, and the balance is Fe), and rolled on an alloy cored wire unit into a multi-element alloy wire I with a diameter of φ10 mm; after the multi-element alloy wire I is added to the molten iron for 5 minutes, the multi-element alloy wire II is continuously added to the molten iron in the molten iron ladle using a wire feeder, and the multi-element alloy wire II is rolled into a multi-element alloy wire I with a diameter of φ10 mm on an alloy cored wire unit ..., and the multi-element alloy wire II is rolled into a multi The addition amount of alloy wire II is 9 meters / ton of molten iron; the preparation method of multi-element alloy wire II is to firstly mix 15-30 mesh silicon-barium-calcium alloy powder (the chemical composition and mass fraction of the silicon-barium-calcium alloy powder are: 57.37% Si, 5.90% Ca, 4.96% Ba, 0.61% Mn, 1.27% Al, the balance is Fe and inevitable impurities), 15-30 mesh silicon-zirconium alloy powder (the chemical composition and mass fraction of the silicon-zirconium alloy powder are: 52.66% Si, 0.57% Ca, 26.85% Zr, 2.06% Al, the balance is Fe and inevitable impurities) and 15-30 mesh silicon-strontium alloy powder (the chemical composition and mass fraction of the silicon-strontium alloy powder are: 68.20% Si, 8.52% Sr , 0.16% Al, 0.25% Ca, the balance is Fe and inevitable impurities) are mixed evenly; the mass compositions of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder are 49%, 31% and 20% respectively, and the total mass composition of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder is 100%; the above alloy powders mixed evenly are packaged with a low-carbon mild steel strip with a thickness of 0.35-0.50mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.15% C, 0.28% Si, 0.43% Mn, 0.036% P, 0.030% S, the balance is Fe), and rolled into a multi-element alloy wire II with a diameter of φ10mm on an alloy cored wire unit; the wire feeding speed of the multi-element alloy wire is controlled at 16m / min;

[0058] ③ Step ② After the molten iron in the ladle is skimmed and allowed to stand, when the temperature drops to 1340° C., it is directly cast into a roll; and during the molten iron pouring process, multi-component alloy particles mixed with bismuth, antimony and rare earth ferrosilicon are added along with the molten iron flow, the multi-component alloy particles have a size of 0.8 to 3.5 mm, and the amount of the multi-component alloy particles added accounts for 0.18% of the mass fraction of the molten iron entering the casting mold; the multi-component alloy particles are composed of 8.5% by mass of bismuth, 5.5% by mass of antimony and 86% by mass of rare earth ferrosilicon, and the total mass composition of bismuth, antimony and rare earth ferrosilicon is 100%;

[0059] ④ After the molten iron in the mold solidifies and cools, the roll blank is taken out of the box, and rough processing is performed after sand removal and grinding; the rough-processed roll is heated to 290°C in the furnace, kept warm for 13 hours, cooled to a temperature below 180°C in the furnace, air-cooled to room temperature, and finally fine-processed to the specified size and accuracy to obtain the alloy ductile iron roll. The roll has a tensile strength of 820MPa, a hardness of 67.6HSD, and an impact toughness of 38.2J / cm 2 .

[0060] Embodiment 4:

[0061] A spheroidizing treatment of alloy ductile iron roll and a method for manufacturing ductile iron roll, which is achieved by using wire feeding spheroidizing + wire feeding inoculation and flow casting inoculation outside the furnace, and the specific preparation process steps are:

[0062] ① Use scrap steel and carburizer as the main charge, and use medium frequency induction furnace to melt molten iron; first, mix scrap steel and carburizer and heat to melt; after the charge is melted, add ferrochrome, ferromolybdenum and nickel plate in turn; after the ferrochrome, ferromolybdenum and nickel plate are melted, heat the molten iron to 1460℃, add ferrosilicon and ferromanganese in turn, and heat the molten iron to 1515℃, then add metal aluminum, the amount of metal aluminum added accounts for 0.10% of the mass fraction of the molten iron in the furnace; after the molten iron is melted, remove the slag and fine-tune the composition The chemical composition and mass fraction of pearlite ductile iron Ⅰ in the furnace are controlled to be: 3.27% C, 1.69% Si, 0.76% Mn, 0.11% P, 0.028% S, 1.35% Cr, 1.93% Ni, 0.62% Mo, 0.014% Al, and the balance is Fe and unavoidable impurities; keep warm for 7 minutes; then naturally cool down to 1487℃ in the furnace, then slag off, and discharge the molten iron in the furnace into the ladle;

[0063] ② After all the molten iron in the furnace enters the ladle, a wire feeder is used to add the multi-element alloy wire I to the molten iron in the ladle, and the amount of the multi-element alloy wire I added is 18.5 meters / ton of molten iron; the preparation method of the multi-element alloy wire I is to first add 7-15 mesh passivation magnesium powder (the passivation layer thickness of the passivation magnesium powder is 0.05-0.08 mm, and the passivation layer of the passivation magnesium powder is composed of the following raw materials in mass percentage, potassium chloride: 17%, magnesium chloride: 37%, barium chloride: 15% and calcium oxide: 31%), 25-35 mesh rare earth ferrosilicon (the chemical composition and mass fraction of the rare earth ferrosilicon are: 29.70% RE, 41.33% Si, 1.38% Mn, 2.61% Ca, 1.05 %Ti, the balance is Fe and inevitable impurities) powder and nano-TiC powder are evenly mixed; the mass compositions of passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder are 59%, 39% and 2.0% respectively, and the total mass composition of passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder is 100%; the evenly mixed powders are packaged with a low-carbon mild steel strip with a thickness of 0.35-0.50mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.22%C, 0.24%Si, 0.66%Mn, 0.031%P, 0.027%S, the balance is Fe), and rolled into a multi-element alloy wire I with a diameter of φ11mm on an alloy cored wire unit; the multi-element alloy wire I is added with molten iron for 6 minutes After that, the multi-element alloy wire II is added to the molten iron in the ladle by a wire feeder, and the addition amount of the multi-element alloy wire II is 9.5 meters / ton of molten iron; the preparation method of the multi-element alloy wire II is firstly to add 15-30 mesh silicon-barium-calcium alloy powder (the chemical composition and mass fraction of the silicon-barium-calcium alloy powder are: 58.04% Si, 6.24% Ca, 5.60% Ba, 0.81% Mn, 1.26% Al, and the balance is Fe and inevitable impurities), 15-30 mesh silicon-zirconium alloy powder (the chemical composition and mass fraction of the silicon-zirconium alloy powder are: 51.38% Si, 0.63% Ca, 27.42% Zr, 2.69% Al, and the balance is Fe and inevitable impurities) and 15 -30 mesh silicon strontium alloy powder (the chemical composition and mass fraction of the silicon strontium alloy powder are: 67.37% Si, 8.75% Sr, 0.19% Al, 0.25% Ca, the balance is Fe and inevitable impurities) is mixed evenly; the mass compositions of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder are 49%, 32% and 19% respectively, and the total mass composition of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder is 100%; then the above alloy powders are mixed evenly with a low-carbon mild steel strip with a thickness of 0.35-0.50mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.22% C, 0.24% Si, 0.66% Mn, 0.031% P, 0.027% S, balance Fe) packaging, rolled into φ11mm diameter multi-element alloy wire II on the alloy cored wire unit; the wire feeding speed of the multi-element alloy wire is controlled at 17m / min;.

[0064] ③ Step ② After the molten iron in the ladle is skimmed and allowed to stand, when the temperature drops to 1350° C., it is directly cast into a roll; and during the molten iron pouring process, multi-component alloy particles mixed with bismuth, antimony and rare earth ferrosilicon are added along with the molten iron flow, the multi-component alloy particles have a size of 0.8 to 3.5 mm, and the amount of the multi-component alloy particles added accounts for 0.16% of the mass fraction of the molten iron entering the casting mold; the multi-component alloy particles are composed of 9% by mass of bismuth, 6% by mass of antimony and 85% by mass of rare earth ferrosilicon, and the total mass composition of bismuth, antimony and rare earth ferrosilicon is 100%;

[0065] ④ After the molten iron in the mold solidifies and cools, the roll blank is taken out of the box, and rough processing is performed after sand removal and grinding; the rough-processed roll is heated to 300℃ in the furnace, kept warm for 15 hours, cooled to a temperature below 180℃, air-cooled to room temperature, and finally fine-processed to the specified size and accuracy to obtain the alloy ductile iron roll. The roll has a tensile strength of 695MPa, a hardness of 53.4HSD, and an impact toughness of 52.7J / cm 2 .

[0066] Embodiment 5:

[0067] A spheroidizing treatment of alloy ductile iron roll and a method for manufacturing ductile iron roll, which is achieved by using wire feeding spheroidizing + wire feeding inoculation and flow casting inoculation outside the furnace, and the specific preparation process steps are:

[0068] ① Take scrap steel and carburizer as the main charge, and use medium frequency induction furnace to melt molten iron; first, mix scrap steel and carburizer and heat to melt; after the charge is melted, add ferrochrome, ferromolybdenum and nickel plate in turn; after the ferrochrome, ferromolybdenum and nickel plate are melted, heat the molten iron to 1465℃, add ferrosilicon and ferromanganese in turn, and heat the molten iron to 1508℃, then add metal aluminum, the amount of metal aluminum added accounts for 0.08% of the mass fraction of the molten iron in the furnace; after the molten iron is melted, remove the slag and fine-tune the composition. The chemical composition and mass fraction of pearlite ductile iron II in the furnace are controlled to be: 3.47% C, 1.57% Si, 0.69% Mn, 0.08% P, 0.020% S, 1.17% Cr, 2.28% Ni, 0.71% Mo, 0.006% Al, and the balance is Fe and unavoidable impurities; the temperature is kept for 7.5 minutes; the temperature is naturally reduced to 1476℃ in the furnace, and then the slag is removed, and the molten iron in the furnace is discharged into the ladle;

[0069] ② After all the molten iron in the furnace enters the ladle, a wire feeder is used to add the multi-element alloy wire I to the molten iron in the ladle, and the amount of the multi-element alloy wire I added is 17.5 meters / ton of molten iron; the method for making the multi-element alloy wire I is to first add 7-15 mesh passivation magnesium powder (the passivation layer thickness of the passivation magnesium powder is 0.05-0.08mm, and the passivation layer of the passivation magnesium powder is composed of the following raw materials in proportion by mass percentage, potassium chloride: 17%, magnesium chloride: 36%, barium chloride: 17% and calcium oxide: 30%), 25-35 mesh rare earth ferrosilicon (the chemical composition and mass fraction of the rare earth ferrosilicon are: 27.81% RE, 38.75% Si, 1.16% Mn, 2.44% Ca, 0.82% The uniformly mixed powder is made of a low-carbon mild steel strip with a thickness of 0.35 to 0.50 mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.14% C, 0.26% Si, 0.39% Mn, 0.038% P, 0.032% S, and the balance is Fe), and is rolled into a multi-element alloy wire I with a diameter of φ10 mm on an alloy cored wire unit; the multi-element alloy wire I is added with molten iron 6.5 After 15 minutes, the wire feeder is continued to add the multi-element alloy wire II to the molten iron in the ladle, and the addition amount of the multi-element alloy wire II is 9.5 meters / ton of molten iron; the preparation method of the multi-element alloy wire II is firstly to add 15-30 mesh silicon-barium-calcium alloy powder (the chemical composition and mass fraction of the silicon-barium-calcium alloy powder are: 55.14% Si, 6.75% Ca, 4.55% Ba, 0.58% Mn, 1.14% Al, and the balance is Fe and inevitable impurities), 15-30 mesh silicon-zirconium alloy powder (the chemical composition and mass fraction of the silicon-zirconium alloy powder are: 53.74% Si, 0.65% Ca, 25.71% Zr, 2.68% Al, and the balance is Fe and inevitable impurities) and 1 5-30 mesh silicon strontium alloy powder (the chemical composition and mass fraction of the silicon strontium alloy powder are: 69.76% Si, 8.08% Sr, 0.11% Al, 0.37% Ca, the balance is Fe and inevitable impurities) is mixed evenly; the mass compositions of silicon barium calcium alloy powder, silicon zirconium alloy powder and silicon strontium alloy powder are 50%, 30% and 20% respectively, and the total mass composition of silicon barium calcium alloy powder, silicon zirconium alloy powder and silicon strontium alloy powder is 100%; then the above alloy powders are mixed evenly with a low carbon mild steel strip with a thickness of 0.35-0.50 mm (the chemical composition and mass fraction of the low carbon mild steel strip are 0.14% C, 0.26% Si, 0.39% Mn, 0.038% P, 0.032% S, balance Fe) packaging, rolled into φ11mm diameter multi-element alloy wire II on the alloy cored wire unit; the wire feeding speed of the multi-element alloy wire is controlled at 16m / min;.

[0070] ③ Step ② After the molten iron in the ladle is skimmed and allowed to stand, when the temperature drops to 1338° C., it is directly cast into a roll; and during the molten iron pouring process, multi-component alloy particles mixed with bismuth, antimony and rare earth ferrosilicon are added along with the molten iron flow, the multi-component alloy particles have a size of 0.8 to 3.5 mm, and the amount of the multi-component alloy particles added accounts for 0.19% of the mass fraction of the molten iron entering the casting mold; the multi-component alloy particles are composed of 9% by mass of bismuth, 5% by mass of antimony and 86% by mass of rare earth ferrosilicon, and the total mass composition of bismuth, antimony and rare earth ferrosilicon is 100%;

[0071] ④ After the molten iron in the mold solidifies and cools, the roll blank is taken out of the box and rough-processed after sand removal and grinding; the rough-processed roll is heated to 330℃ in the furnace, kept warm for 13 hours, cooled to a temperature below 180℃, air-cooled to room temperature, and finally fine-processed to the specified size and precision to obtain the alloy ductile iron roll. The roll has a tensile strength of 740MPa, a hardness of 62.6HSD, and an impact toughness of 47.4J / cm 2 .

[0072] Embodiment 6:

[0073] A spheroidizing treatment of alloy ductile iron roll and a method for manufacturing ductile iron roll, which is achieved by using wire feeding spheroidizing + wire feeding inoculation and flow casting inoculation outside the furnace, and the specific preparation process steps are:

[0074] ① Take scrap steel and carburizer as the main charge, and use medium frequency induction furnace to melt molten iron; first, mix scrap steel and carburizer and heat to melt; after the charge is melted, add ferrochrome, ferromolybdenum and nickel plate in turn; after the ferrochrome, ferromolybdenum and nickel plate are melted, heat the molten iron to 1462℃, add ferrosilicon and ferromanganese in turn, and heat the molten iron to 1513℃, then add metal aluminum, the amount of metal aluminum added accounts for 0.08% of the mass fraction of the molten iron in the furnace; after the molten iron is melted, remove the slag and fine-tune the composition. The chemical composition and mass fraction of pearlite ductile iron III in the furnace are controlled to be: 3.52% C, 1.36% Si, 0.75% Mn, 0.090% P, 0.024% S, 1.13% Cr, 2.84% Ni, 0.48% Mo, 0.011% Al, and the balance is Fe and unavoidable impurities; the temperature is kept for 7 minutes; after that, the temperature is naturally reduced to 1473℃ in the furnace, the slag is removed, and the molten iron in the furnace is discharged into the ladle;

[0075] ② After all the molten iron in the furnace enters the ladle, a wire feeder is used to add the multi-element alloy wire I to the molten iron in the ladle, and the amount of the multi-element alloy wire I added is 18 meters / ton of molten iron; the method for making the multi-element alloy wire I is to first add 7-15 mesh passivation magnesium powder (the passivation layer thickness of the passivation magnesium powder is 0.05-0.08mm, and the passivation layer of the passivation magnesium powder is composed of the following raw materials in mass percentage, potassium chloride: 16%, magnesium chloride: 36%, barium chloride: 18% and calcium oxide: 30%), 25-35 mesh rare earth ferrosilicon (the chemical composition and mass fraction of the rare earth ferrosilicon are: 29.14% RE, 38.86% Si, 1.35% Mn, 2.61% Ca, 1.18% Ti, the remainder is Fe and inevitable impurities The passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder are uniformly mixed; the mass compositions of the passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder are 60%, 38% and 2.0% respectively, and the total mass composition of the passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder is 100%; the uniformly mixed powders are then packed with a low-carbon mild steel strip with a thickness of 0.35-0.50 mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.19% C, 0.23% Si, 0.67% Mn, 0.028% P, 0.015% S, and the balance is Fe), and rolled on an alloy cored wire unit into a multi-element alloy wire I with a diameter of φ11 mm; after the multi-element alloy wire I is added to the molten iron for 6 minutes, the multi-element alloy wire II is continuously added to the molten iron in the molten iron ladle using a wire feeder, and the multi-element alloy wire II is rolled into a multi-element alloy wire I with a diameter of φ11 mm on an alloy cored wire unit ...10 minutes, the multi-element alloy wire II is rolled into the molten iron in the molten iron ladle using a wire feeder, and the multi-element alloy wire II is rolled into the molten iron in the molten iron ladle, and the multi-element alloy wire II is rolled into the molten iron in the molten iron ladle The addition amount of alloy wire II is 10 meters / ton of molten iron; the preparation method of multi-element alloy wire II is to firstly mix 15-30 mesh silicon-barium-calcium alloy powder (the chemical composition and mass fraction of the silicon-barium-calcium alloy powder are: 57.02% Si, 5.97% Ca, 4.80% Ba, 1.67% Mn, 2.85% Al, the balance is Fe and inevitable impurities), 15-30 mesh silicon-zirconium alloy powder (the chemical composition and mass fraction of the silicon-zirconium alloy powder are: 56.16% Si, 0.83% Ca, 23.97% Zr, 2.08% Al, the balance is Fe and inevitable impurities) and 15-30 mesh silicon-strontium alloy powder (the chemical composition and mass fraction of the silicon-strontium alloy powder are: 65.31% Si, 8.85% Sr , 0.40% Al, 0.28% Ca, the balance is Fe and inevitable impurities) are mixed evenly; the mass compositions of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder are 50%, 30% and 20% respectively, and the total mass composition of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder is 100%; the above alloy powders mixed evenly are packaged with a low-carbon mild steel strip with a thickness of 0.35-0.50mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.19% C, 0.23% Si, 0.67% Mn, 0.028% P, 0.015% S, the balance is Fe), and rolled into a multi-element alloy wire II with a diameter of φ11mm on an alloy cored wire unit; the wire feeding speed of the multi-element alloy wire is controlled at 16m / min;

[0076] ③ Step ② After the molten iron in the ladle is skimmed and allowed to stand, when the temperature drops to 1351° C., it is directly cast into a roll; and during the molten iron pouring process, multi-component alloy particles mixed with bismuth, antimony and rare earth ferrosilicon are added along with the molten iron flow, the multi-component alloy particles have a size of 0.8 to 3.5 mm, and the amount of the multi-component alloy particles added accounts for 0.19% of the mass fraction of the molten iron entering the casting mold; the multi-component alloy particles are composed of 9% by mass of bismuth, 6% by mass of antimony and 85% by mass of rare earth ferrosilicon, and the total mass composition of bismuth, antimony and rare earth ferrosilicon is 100%;

[0077] ④ After the molten iron in the mold solidifies and cools, the roll blank is taken out of the box, and rough processing is performed after sand removal and grinding; the rough-processed roll is heated to 310℃ in the furnace, kept warm for 14 hours, cooled to a temperature below 180℃, air-cooled to room temperature, and finally fine-processed to the specified size and accuracy to obtain the alloy ductile iron roll. The roll has a tensile strength of 815MPa, a hardness of 70.8HSD, and an impact toughness of 41.9J / cm 2 .

[0078] Embodiment 7:

[0079] A spheroidizing treatment of alloy ductile iron roll and a method for manufacturing ductile iron roll, which is achieved by using wire feeding spheroidizing + wire feeding inoculation and flow casting inoculation outside the furnace, and the specific preparation process steps are:

[0080] ① Take scrap steel and carburizer as the main charge, and use medium frequency induction furnace to melt molten iron; first, mix scrap steel and carburizer and heat to melt; after the charge is melted, add ferrochrome, ferromolybdenum and nickel plate in turn; after the ferrochrome, ferromolybdenum and nickel plate are melted, heat the molten iron to 1463℃, add ferrosilicon and ferromanganese in turn, and heat the molten iron to 1508℃, then add metal aluminum, the amount of metal aluminum added accounts for 0.10% of the mass fraction of the molten iron in the furnace; after the molten iron is melted, remove the slag and fine-tune the composition. The chemical composition and mass fraction of the bainite ductile iron Ⅰ in the furnace are controlled to be: 3.37% C, 1.73% Si, 0.66% Mn, 0.070% P, 0.021% S, 1.38% Cr, 3.39% Ni, 0.64% Mo, 0.019% Al, and the balance is Fe and unavoidable impurities; the temperature is kept for 7 minutes; then the temperature is naturally reduced to 1485℃ in the furnace, and then the slag is removed, and the molten iron in the furnace is discharged into the ladle;

[0081] ② After all the molten iron in the furnace enters the ladle, a wire feeder is used to add the multi-element alloy wire I to the molten iron in the ladle, and the amount of the multi-element alloy wire I added is 18 meters / ton of molten iron; the method for making the multi-element alloy wire I is to first add 7-15 mesh passivation magnesium powder (the passivation layer thickness of the passivation magnesium powder is 0.05-0.08 mm, and the passivation layer of the passivation magnesium powder is composed of the following raw materials in proportion by mass percentage, potassium chloride: 17%, magnesium chloride: 37%, barium chloride: 15% and calcium oxide: 31%), 25-35 mesh rare earth ferrosilicon (the chemical composition and mass fraction of the rare earth ferrosilicon are: 29.15% RE, 40.06% Si, 2.12% Mn, 2.69% Ca, 0.53% Ti, and the balance is Fe and unavoidable impurities The passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder are uniformly mixed; the mass compositions of the passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder are 59%, 39% and 2.0% respectively, and the total mass composition of the passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder is 100%; the uniformly mixed powders are then packed with a low-carbon mild steel strip with a thickness of 0.35-0.50 mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.19% C, 0.18% Si, 0.57% Mn, 0.035% P, 0.029% S, and the balance is Fe), and rolled on an alloy cored wire unit into a multi-element alloy wire I with a diameter of φ10 mm; after the multi-element alloy wire I is added to the molten iron for 6 minutes, the multi-element alloy wire II is continuously added to the molten iron in the molten iron ladle using a wire feeder, and the multi-element alloy wire II is rolled into a multi-element alloy wire I with a diameter of φ10 mm on an alloy cored wire unit ...10 minutes, the multi-element alloy wire II is rolled into the molten iron in the molten iron ladle using a wire feeder, and the multi-element alloy wire II is rolled into the molten iron in the molten iron ladle, and the multi-element alloy wire II is rolled into the molten iron in the molten iron ladle The addition amount of alloy wire II is 9 meters / ton of molten iron; the preparation method of multi-element alloy wire II is to firstly mix 15-30 mesh silicon-barium-calcium alloy powder (the chemical composition and mass fraction of the silicon-barium-calcium alloy powder are: 59.87% Si, 5.18% Ca, 5.91% Ba, 1.27% Mn, 0.82% Al, the balance is Fe and inevitable impurities), 15-30 mesh silicon-zirconium alloy powder (the chemical composition and mass fraction of the silicon-zirconium alloy powder are: 53.64% Si, 1.16% Ca, 27.15% Zr, 2.38% Al, the balance is Fe and inevitable impurities) and 15-30 mesh silicon-strontium alloy powder (the chemical composition and mass fraction of the silicon-strontium alloy powder are: 67.13% Si, 8.52% Sr , 0.42% Al, 0.17% Ca, the balance is Fe and inevitable impurities) are mixed evenly; the mass compositions of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder are 49%, 32% and 19% respectively, and the total mass composition of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder is 100%; the above alloy powders mixed evenly are packaged with a low-carbon mild steel strip with a thickness of 0.35-0.50mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.19% C, 0.18% Si, 0.57% Mn, 0.035% P, 0.029% S, the balance is Fe), and rolled into a multi-element alloy wire II with a diameter of φ11mm on an alloy cored wire unit; the wire feeding speed of the multi-element alloy wire is controlled at 17m / min;

[0082] ③ Step ② After the molten iron in the ladle is skimmed and allowed to stand, when the temperature drops to 1349° C., it is directly cast into a roll; and during the molten iron pouring process, multi-component alloy particles mixed with bismuth, antimony and rare earth ferrosilicon are added along with the molten iron flow, the multi-component alloy particles have a size of 0.8 to 3.5 mm, and the amount of the multi-component alloy particles added accounts for 0.16% of the mass fraction of the molten iron entering the casting mold; the multi-component alloy particles are composed of 8.5% by mass of bismuth, 5.5% by mass of antimony and 86% by mass of rare earth ferrosilicon, and the total mass composition of bismuth, antimony and rare earth ferrosilicon is 100%;

[0083] ④ After the molten iron in the mold solidifies and cools, the roll blank is taken out of the box, and rough processing is performed after sand removal and grinding; the rough-processed roll is heated to 295°C in the furnace, kept warm for 15 hours, cooled to a temperature below 180°C in the furnace, air-cooled to room temperature, and finally fine-processed to the specified size and accuracy to obtain the alloy ductile iron roll. The roll has a tensile strength of 945MPa, a hardness of 74.3HSD, and an impact toughness of 28.7J / cm 2 .

[0084] Embodiment 8:

[0085] A spheroidizing treatment of alloy ductile iron roll and a method for manufacturing ductile iron roll, which is achieved by using wire feeding spheroidizing + wire feeding inoculation and flow casting inoculation outside the furnace, and the specific preparation process steps are:

[0086] ① Take scrap steel and carburizer as the main charge, and use medium frequency induction furnace to melt molten iron; first, mix scrap steel and carburizer and heat to melt; after the charge is melted, add ferrochrome, ferromolybdenum and nickel plate in turn; after the ferrochrome, ferromolybdenum and nickel plate are melted, heat the molten iron to 1462℃, add ferrosilicon and ferromanganese in turn, and heat the molten iron to 1514℃, then add metal aluminum, the amount of metal aluminum added accounts for 0.11% of the mass fraction of the molten iron in the furnace; after the molten iron is melted, remove the slag and fine-tune the composition. The chemical composition and mass fraction of the bainite ductile iron II in the furnace are controlled to be: 3.55% C, 1.41% Si, 0.70% Mn, 0.062% P, 0.019% S, 1.48% Cr, 4.07% Ni, 0.83% Mo, 0.025% Al, and the balance is Fe and unavoidable impurities; the temperature is kept for 7 minutes; then the temperature is naturally reduced to 1483°C in the furnace, and then the slag is removed, and the molten iron in the furnace is discharged into the ladle;

[0087] ② After all the molten iron in the furnace enters the ladle, a wire feeder is used to add the multi-element alloy wire I to the molten iron in the ladle, and the amount of the multi-element alloy wire I added is 18 meters / ton of molten iron; the method for making the multi-element alloy wire I is to first add 7-15 mesh passivation magnesium powder (the passivation layer thickness of the passivation magnesium powder is 0.05-0.08 mm, and the passivation layer of the passivation magnesium powder is composed of the following raw materials in mass percentage, potassium chloride: 17%, magnesium chloride: 35%, barium chloride: 17% and calcium oxide: 31%), 25-35 mesh rare earth ferrosilicon (the chemical composition and mass fraction of the rare earth ferrosilicon are: 28.62% RE, 40.57% Si, 1.63% Mn, 2.77% Ca, 1.39% Ti, and the balance is Fe and unavoidable impurities The passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder are uniformly mixed; the mass compositions of the passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder are 60%, 38% and 2.0% respectively, and the total mass composition of the passivated magnesium powder, rare earth ferrosilicon powder and nano-TiC powder is 100%; the uniformly mixed powders are then packed with a low-carbon mild steel strip with a thickness of 0.35-0.50 mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.13% C, 0.22% Si, 0.77% Mn, 0.029% P, 0.018% S, and the balance is Fe), and rolled on an alloy cored wire unit into a multi-element alloy wire I with a diameter of φ11 mm; after the multi-element alloy wire I is added to the molten iron for 6 minutes, the multi-element alloy wire II is continuously added to the molten iron in the molten iron ladle using a wire feeder, and the multi-element alloy wire II is rolled into a multi-element alloy wire I with a diameter of φ11 mm on an alloy cored wire unit ...10 minutes, the multi-element alloy wire II is rolled into the molten iron in the molten iron ladle using a wire feeder, and the multi-element alloy wire II is rolled into the molten iron in the molten iron ladle, and the multi-element alloy wire II is rolled into the molten iron in the molten iron ladle The addition amount of alloy wire II is 9 meters / ton of molten iron; the preparation method of multi-element alloy wire II is to firstly mix 15-30 mesh silicon-barium-calcium alloy powder (the chemical composition and mass fraction of the silicon-barium-calcium alloy powder are: 58.10% Si, 5.94% Ca, 5.27% Ba, 1.15% Mn, 1.82% Al, the balance is Fe and inevitable impurities), 15-30 mesh silicon-zirconium alloy powder (the chemical composition and mass fraction of the silicon-zirconium alloy powder are: 54.07% Si, 1.14% Ca, 27.19% Zr, 2.88% Al, the balance is Fe and inevitable impurities) and 15-30 mesh silicon-strontium alloy powder (the chemical composition and mass fraction of the silicon-strontium alloy powder are: 65.26% Si, 8.47% Sr , 0.33% Al, 0.41% Ca, the balance is Fe and inevitable impurities) are mixed evenly; the mass compositions of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder are 49%, 32% and 19% respectively, and the total mass composition of silicon-barium-calcium alloy powder, silicon-zirconium alloy powder and silicon-strontium alloy powder is 100%; the above alloy powders mixed evenly are packaged with a low-carbon mild steel strip with a thickness of 0.35-0.50mm (the chemical composition and mass fraction of the low-carbon mild steel strip are 0.13% C, 0.22% Si, 0.77% Mn, 0.029% P, 0.018% S, the balance is Fe), and rolled into a multi-element alloy wire II with a diameter of φ10mm on an alloy cored wire unit; the wire feeding speed of the multi-element alloy wire is controlled at 16m / min;

[0088] ③ Step ② After the molten iron in the ladle is skimmed and allowed to stand, when the temperature drops to 1348° C., it is directly cast into a roll; and during the molten iron pouring process, multi-component alloy particles mixed with bismuth, antimony and rare earth ferrosilicon are added along with the molten iron flow, the multi-component alloy particles have a size of 0.8 to 3.5 mm, and the amount of the multi-component alloy particles added accounts for 0.18% of the mass fraction of the molten iron entering the casting mold; the multi-component alloy particles are composed of 9% by mass of bismuth, 5% by mass of antimony and 86% by mass of rare earth ferrosilicon, and the total mass composition of bismuth, antimony and rare earth ferrosilicon is 100%;

[0089] ④ After the molten iron in the mold solidifies and cools, the roll blank is taken out of the box, and rough processing is performed after sand removal and grinding; the rough-processed roll is heated to 340℃ in the furnace, kept warm for 14 hours, cooled to a temperature below 180℃ in the furnace, air-cooled to room temperature, and finally fine-processed to the specified size and accuracy to obtain the alloy ductile iron roll. The roll has a tensile strength of 920MPa, a hardness of 78.6HSD, and an impact toughness of 23.6J / cm 2 .

[0090] The present invention adopts the wire feeding method to spheroidize and inoculate cast iron, and the spheroidization and inoculation element yields are significantly improved. Compared with the ordinary punching method, the spheroidization element yield is increased by more than 30%, and the inoculation element yield is increased by more than 15%. The alloy ductile iron roller spheroidization method of the present invention is safe, simple, environmentally friendly, efficient and low in cost. The ductile iron roller manufactured by the method of the present invention has fine graphite balls and uniform distribution, and the graphite spheroidization rate is as high as more than 95%. Compared with the ordinary ductile iron roller in GB / T1504-2024, under the same rolling conditions, the wear resistance of the roller of the present invention is improved by more than 20%, and compared with the traditional spheroidization treatment method using rare earth magnesium alloy, nickel-magnesium alloy, and copper-magnesium alloy, the spheroidization cost is reduced by more than 30%, and the graphite spheroidization rate reaches the national standard level or above. The roller has good toughness and wear resistance, and has both the high wear resistance of the alloy infinite cold hardening roller and the high toughness of the alloy ductile iron roller. The popularization and application of the present invention can improve the operation rate of the rolling mill, improve the surface quality of the rolled material, improve the dimensional accuracy of the rolled material, reduce the labor intensity of the workers, and has good economic and social benefits.

Claims

1. A method for spheroidizing alloy ductile iron rolls and preparing ductile iron rolls, characterized in that: The specific preparation process steps include the following: ① Using scrap steel and carburizer as main charge, adopt medium frequency induction furnace to melt molten iron; firstly, mix scrap steel and carburizer and heat to melt; after the charge is melted, add ferrochrome, ferromolybdenum and nickel plate in turn; after the ferrochrome, ferromolybdenum and nickel plate are melted, heat the molten iron to 1440-1470℃, add ferrosilicon and ferromanganese in turn, and heat the molten iron to 1500-1520℃, then add metal aluminum, the amount of metal aluminum added accounts for 0.05-0.12% of the mass fraction of the molten iron in the furnace; after the molten iron is melted, slag is removed, the composition is fine-tuned, and the chemical composition and mass fraction of the molten iron in the furnace are controlled within the required range; keep warm for 5-8 minutes; then naturally cool down to 1455-1491℃ in the furnace, remove slag, and discharge the molten iron in the furnace into the ladle; ② After all the molten iron in the furnace enters the ladle, a wire feeder is used to add the multi-element alloy wire I to the molten iron in the ladle, and the amount of the multi-element alloy wire I added is 17-19 meters / ton of molten iron; the method for making the multi-element alloy wire I is to firstly mix 7-15 mesh passivation magnesium powder, 25-35 mesh rare earth ferrosilicon powder and nano-TiC powder uniformly, the mass compositions of the passivation magnesium powder, the rare earth ferrosilicon powder and the nano-TiC powder are 58-60%, 38-40% and 1.8-2.0% respectively, and the total mass composition of the passivation magnesium powder, the rare earth ferrosilicon powder and the nano-TiC powder is 100%, and then the uniformly mixed powder is packaged with a low-carbon soft steel strip with a thickness of 0.35-0.50mm, and rolled on the alloy cored wire unit into a multi-element alloy wire I with a diameter of φ9-12mm; after the multi-element alloy wire I is added to the molten iron for 4-7 minutes, the wire feeder is continued to be used. The multi-element alloy wire II is added to the molten iron in the ladle, and the addition amount of the multi-element alloy wire II is 8-10 meters / ton of molten iron. The preparation method of the multi-element alloy wire II is: firstly, 15-30 mesh silicon-barium-calcium alloy powder, 15-30 mesh silicon-zirconium alloy powder and 15-30 mesh silicon-strontium alloy powder are uniformly mixed, the mass compositions of the silicon-barium-calcium alloy powder, the silicon-zirconium alloy powder and the silicon-strontium alloy powder are 48-50%, 30-32% and 18-20% respectively, and the total mass composition of the silicon-barium-calcium alloy powder, the silicon-zirconium alloy powder and the silicon-strontium alloy powder is 100%, and then the uniformly mixed alloy powder is packaged with a low-carbon soft steel strip with a thickness of 0.35-0.50mm, and rolled on the alloy cored wire unit into the multi-element alloy wire II with a diameter of φ9-12mm; the wire feeding speeds of the multi-element alloy wire I and the multi-element alloy wire II are both controlled at 15-18m / minute; ③ Step ② After the molten iron in the ladle is skimmed and allowed to stand, when the temperature drops to 1330-1360° C., it is directly poured into a casting mold to form a roll; and during the molten iron pouring process, multi-component alloy particles mixed with bismuth, antimony and rare earth ferrosilicon are added along with the molten iron flow, the multi-component alloy particles have a size of 0.8-3.5 mm, and the amount of the multi-component alloy particles added accounts for 0.15-0.20% of the mass fraction of the molten iron entering the casting mold; the multi-component alloy particles are composed of 8-9% of bismuth, 5-6% of antimony and 85-86% of rare earth ferrosilicon by mass fraction, and the total mass composition of bismuth, antimony and rare earth ferrosilicon is 100%; ④ After the molten iron in the mold solidifies and cools, the roller blank is taken out of the box and rough-processed after sand cleaning and grinding; the rough-processed roller is put into the furnace and heated to 260-350℃. After keeping warm for 12-16 hours, the furnace is cooled to a temperature below 180℃, taken out of the furnace and air-cooled to room temperature, and finally fine-processed to the specified size and accuracy to obtain the alloy ductile iron roller.

2. The method according to claim 1, characterized in that Wherein the chemical composition and mass fraction of the molten iron in the furnace described in step ① are controlled within the required range, and the final composition of the molten iron in the furnace is selected from one of chromium-molybdenum ductile infinitely chilled molten iron, nickel-chromium-molybdenum ductile infinitely chilled molten iron I, nickel-chromium-molybdenum ductile infinitely chilled molten iron II, pearlite ductile I molten iron, pearlite ductile II molten iron, pearlite ductile III molten iron, bainite ductile I molten iron, and bainite ductile II molten iron; As mentioned above, the chemical composition and mass fraction of the infinitely cold hardened chromium-molybdenum ductile iron in the furnace molten iron are: 2.90-3.60% C, 0.80-2.50% Si, 0.40-1.20% Mn, ≤0.25% P, ≤0.03% S, 0.30-1.00% Cr, 0.20-0.60% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities; As mentioned above, the chemical composition and mass fraction of nickel-chromium-molybdenum ductile iron infinitely chilled I in the molten iron in the furnace are: 2.90-3.60% C, 0.80-2.50% Si, 0.40-1.20% Mn, ≤0.25% P, ≤0.03% S, 0.40-1.00% Cr, 0.50-1.00% Ni, 0.20-0.80% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities; As mentioned above, the chemical composition and mass fraction of nickel-chromium-molybdenum ductile infinitely cold hardened II in the molten iron in the furnace are: 2.90-3.60% C, 0.80-2.50% Si, 0.40-1.20% Mn, ≤0.20% P, ≤0.03% S, 0.50-1.50% Cr, 1.01-1.50% Ni, 0.20-0.80% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities; As mentioned above, the chemical composition and mass fraction of pearlite ductile iron I in the molten iron in the furnace are: 2.90-3.60% C, 1.40-2.20% Si, 0.40-1.00% Mn, ≤0.15% P, ≤0.03% S, 0.40-1.50% Cr, 1.51-2.00% Ni, 0.20-0.80% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities; As mentioned above, the chemical composition and mass fraction of pearlite ductile iron II in the molten iron in the furnace are: 2.90-3.60% C, 1.20-2.00% Si, 0.40-1.00% Mn, ≤0.15% P, ≤0.03% S, 0.50-1.60% Cr, 2.01-2.50% Ni, 0.20-0.80% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities; As mentioned above, the chemical composition and mass fraction of pearlite ductile iron III in the hot metal in the furnace are: 2.90-3.60% C, 1.00-2.00% Si, 0.40-1.00% Mn, ≤0.15% P, ≤0.03% S, 0.60-1.80% Cr, 2.51-3.00% Ni, 0.20-0.80% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities; As mentioned above, the chemical composition and mass fraction of bainite ductile iron I in the molten iron in the furnace are: 2.90-3.60% C, 1.20-2.20% Si, 0.20-0.80% Mn, ≤0.10% P, ≤0.03% S, 0.50-1.60% Cr, 3.01-3.50% Ni, 0.50-1.00% Mo, 0.005-0.030% Al, the balance is Fe and unavoidable impurities; As mentioned above, in the molten iron in the furnace, the chemical composition and mass fraction of bainite ductile iron II are: 2.90-3.60% C, 1.00-2.00% Si, 0.20-0.80% Mn, ≤0.10% P, ≤0.03% S, 0.80-1.80% Cr, 3.51-4.50% Ni, 0.50-1.00% Mo, 0.005-0.030% Al, and the balance is Fe and unavoidable impurities.

3. The method according to claim 1, characterized in that As mentioned above, the chemical composition and mass fraction of rare earth ferrosilicon are: 27.0-30.0% RE, 38.0-42.0% Si, <3.0% Mn, <5.0% Ca, <3.0% Ti, and the remainder is Fe and unavoidable impurities.

4. The method according to claim 1, characterized in that As mentioned above, the thickness of the passivation layer of the passivated magnesium powder is 0.05-0.08 mm, and the passivation layer of the passivated magnesium powder is composed of the following raw materials in proportion by mass: potassium chloride: 15-18%, magnesium chloride: 35-38%, barium chloride: 15-18% and calcium oxide: 30-32%.

5. The method according to claim 1, characterized in that As mentioned above, the chemical composition and mass fraction of the silicon-barium-calcium alloy powder are: 55.14-59.87% Si, 5.18-6.75% Ca, 4.55-5.91% Ba, <2.0% Mn, <3% Al, and the remainder is Fe and unavoidable impurities.

6. The method according to claim 1, characterized in that As mentioned above, the chemical composition and mass fraction of the silicon-zirconium alloy powder are: 48-58% Si, <2.0% Ca, 22.0-28.0% Zr, <5.0% Al, and the remainder is Fe and unavoidable impurities.

7. The method according to claim 1, characterized in that As mentioned above, the chemical composition and mass fraction of the silicon strontium alloy powder are: 62.33-69.76% Si, 8.08-8.91% Sr, <0.5% Al, <0.5% Ca, and the remainder is Fe and unavoidable impurities.

8. The method according to claim 1, characterized in that As mentioned above, the chemical composition and mass fraction of the low carbon mild steel strip are 0.08-0.25% C, <0.30% Si, 0.30-0.80% Mn, <0.040% P, <0.035% S, and the balance is Fe.

9. A ductile iron roll prepared according to the method of any one of claims 1 to 8.