Rare earth electroslag steel containing alloyed rare earth elements and its manufacturing method
By preparing a mixed electroslag agent of rare earth penetrant and matrix powder, the problem of rare earth element utilization was solved, and efficient and low-energy-consumption electroslag steel production was realized. This improved the purity and fatigue performance of the steel and solved the problems of high energy consumption and environmental pollution in traditional methods.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YINGKOU SPECIAL STEEL FORGING
- Filing Date
- 2025-11-06
- Publication Date
- 2026-06-30
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of electroslag metallurgy, specifically to a rare earth electroslag steel containing alloyed rare earth elements and its manufacturing method. Background Technology
[0002] As the core functional material in the electroslag remelting (ESR) process, the electroslag agent melts under the action of electric current to form a slag pool with specific physicochemical properties. Through full contact with the molten metal droplets and the molten metal pool, the slag efficiently removes harmful elements such as sulfur and phosphorus from the steel by means of physical adsorption, dissolution and complex slag-metal interface chemical reactions, and captures and removes non-metallic inclusions such as oxides and sulfides, thereby obtaining high-purity steel ingots.
[0003] However, existing electroslag remelting technology faces significant drawbacks in utilizing rare earth elements when addressing the demands of producing ultra-pure, high-performance special steels, particularly due to the limitations of traditional addition methods. While rare earth elements are excellent purifiers and modifiers for molten steel, their chemical reactivity is extremely high. If traditional methods of directly adding rare earth alloys are used, the rare earth elements react violently with oxygen and sulfur in the molten steel, readily generating large, irregularly shaped rare earth oxides and other hard, brittle inclusions. These inclusions are not only difficult to remove but also become crack initiation points within the material, severely impairing the steel's fatigue performance, impact toughness, and isotropy.
[0004] Furthermore, under the backdrop of green manufacturing and the circular economy, the preparation of electroslag agents from metallurgical solid waste has become a trend. However, these solid waste slags often contain a certain amount of P2O5, FeO, and harmful heavy metals such as Pb and Zn. Existing treatment processes mostly employ high-temperature melting for pretreatment, which is energy-intensive. At high temperatures, volatile elements such as Pb and Zn can form harmful fumes, causing secondary environmental pollution. P2O5 and FeO in the slag are difficult to completely remove. If they are used directly in electroslag agents, under the strong reducing atmosphere of electroslag remelting, P2O5 will be reduced to phosphorus, and FeO will be reduced to iron, adding oxygen to the molten steel, resulting in secondary pollution of the high-purity molten steel. Summary of the Invention
[0005] In view of the shortcomings of the prior art, the present invention provides a method for manufacturing rare earth electroslag steel containing alloyed rare earth elements, specifically including the following:
[0006] This invention discloses a method for manufacturing rare earth electroslag steel containing alloying rare earth elements, including the preparation of an electroslag agent, electroslag remelting, and post-remelting heat treatment. The preparation of the electroslag agent includes:
[0007] The matrix powder is prepared by mixing slag waste, calcium thermal reducing agent and carbothermic reducing agent and reacting at 1450-1550℃ for 1-2 hours.
[0008] The oxides of rare earth elements and nano-carbon materials are dispersed in deionized water, spray-dried, and then heat-treated at a low temperature of 500~700℃ for 1 hour to obtain rare earth permeable material.
[0009] Electroslag agent is obtained by mixing matrix powder, rare earth penetrant and flux.
[0010] The slag waste originates from iron and steel metallurgy or other high-temperature industrial processes, and its main chemical components are calcium oxide and aluminum oxide.
[0011] Preferably, the slag waste is derived from waste slag produced by converters or ladle refining furnaces.
[0012] Preferably, the mass ratio of the slag waste, calcic reducing agent, and carbic reducing agent is 100:5~10:2~5.
[0013] Preferably, the mass ratio of the rare earth element oxide, nano-carbon material, and deionized water is 10:1.5~2:100~200.
[0014] Preferably, the oxide of the rare earth element is selected from one or any combination of scandium oxide, yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide.
[0015] Preferably, the calcothermic reducing agent comprises, but is not limited to, one or more strong reducing agents selected from calcium carbide, metallic calcium, and calcium-silicon alloys.
[0016] Preferably, the carbothermic reducing agent comprises, but is not limited to, one or more carbonaceous reducing agents selected from graphite powder, coke powder, carbon nanotubes, and graphene.
[0017] Preferably, the nano-carbon material is selected from one or more of graphene oxide, reduced graphene oxide, carbon nanotubes, graphene nanosheets, and highly active carbon black.
[0018] Preferably, the mass ratio of the matrix powder, rare earth penetrant, and flux is 60~95:1~25:0.5~15.
[0019] Preferably, the flux is selected from one or more glassy substances or pre-melted slags prepared by pre-melting, including fluorides, borides, boron-containing oxides, alkali metal oxides, alkaline earth metal oxides, and transition metal oxides.
[0020] Preferably, the spray dryer has an inlet temperature of 180-220°C and an outlet temperature of 100-120°C.
[0021] The present invention has the following beneficial effects:
[0022] (1) This invention utilizes the slag waste generated during the iron and steel smelting process, transforming the low-value slag waste into matrix powder with low P, low FeO content and high basicity (high CaO content). The high basicity ensures efficient desulfurization during the electroslag remelting process, while the low P and low FeO content prevents these impurities from re-polluting the molten steel during electroslag remelting. The waste slag that originally needed to be landfilled is transformed into the core component of the electroslag agent, reducing the cost of raw materials.
[0023] (2) This invention obtains rare earth permeated material by spray drying and low-temperature heat treatment of rare earth element oxides and nano carbon materials, so that the reducing carbon and rare earth oxides are uniformly and tightly mixed. Compared with simple physical mixing, the kinetic energy barrier of the subsequent carbothermic reduction reaction is reduced, so that the reaction can be carried out at a lower temperature, faster and more completely in the slag. This solves the problems of carbon powder being easily burned off and floating, or uneven mixing with rare earth oxides leading to low reaction efficiency in traditional methods.
[0024] (3) In the process of electroslag remelting, the matrix powder in the electroslag agent component performs efficient desulfurization of the molten steel. The low P and low FeO content avoids these impurities from re-contaminating the molten steel during electroslag remelting. The rare earth penetrant undergoes a reduction reaction, generating a high concentration of Ce atoms, which will create an oxygen potential trap to absorb oxygen in the molten steel. At the same time, Ce atoms diffuse and dissolve into the molten steel, forming regular rare earth oxygen sulfides with oxygen and sulfur elements in the molten steel. This changes the way rare earth is added, avoiding the technical problem of forming large-sized, irregular rare earth oxygen sulfides and other brittle inclusions in the molten steel when rare earth alloys are directly added. The synergistic effect of the two significantly reduces the oxygen and sulfur content of the molten steel during electroslag remelting, resulting in high purity electroslag steel. Detailed Implementation
[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0026] Example 1
[0027] This embodiment prepares an alloyed rare earth electroslag steel, and the manufacturing method includes the following steps:
[0028] S1. Preparation of electroslag agent:
[0029] By weight, 100 parts of waste slag from the ladle refining furnace were ball-milled into powder with a particle size of less than 1 mm. After removing metallic iron particles by magnetic separation, the powder was mixed with 8 parts of calcium carbide and 3 parts of graphite powder. The mixture was reacted at 1500℃ for 2 hours, cooled to 25℃, and subjected to secondary magnetic separation. After grinding, the matrix powder was obtained. The matrix powder was found to have a P2O5 content of less than 0.1%, an FeO content of less than 0.5%, an Al2O3 content of 15% to 30%, and a CaO to SiO2 mass ratio of greater than 3.
[0030] In the above process, the phosphate in the slag is reduced by graphite powder at high temperature:
[0031] (CaO)3·P2O5(solid) + 5C(solid) → 3CaO(solid) + 2P(g)↑ + 5CO(g)↑, phosphorus oxides are reduced to gaseous elemental phosphorus, which escapes from the slag, thus achieving the removal of harmful phosphorus; at the same time, calcium carbide, as a stronger reducing agent, more effectively reduces phosphorus and iron oxides.
[0032] (CaO)3·P2O5 (solid) + 5CaC2 (solid) → 8CaO (solid) + 2P (gas)↑ + 10C (solid).
[0033] FeO (solid) + CaC2 (solid) → Fe (liquid) + CaO (solid) + 2C (solid); the resulting matrix powder has high purity and high basicity (high CaO content). High basicity is the basis for efficient desulfurization in the electroslag remelting process. Low P and low FeO content avoid these impurities from contaminating the molten steel in the subsequent electroslag remelting process, ensuring the high cleanliness of the electroslag steel.
[0034] Ten parts of cerium dioxide powder and two parts of graphene oxide were ultrasonically dispersed evenly in 200 parts of deionized water, then spray-dried, and then kept at 600℃ for 1 hour under an inert atmosphere to obtain rare earth permeable material.
[0035] During the spray drying process described above, the droplets rapidly dehydrate, and the surface tension drives the sheet-like graphene oxide to shrink and wrap around the denser cerium dioxide powder. After heat treatment, the oxygen-containing functional groups of the graphene oxide are removed, achieving a close and uniform mixture of graphene and cerium dioxide powder. Compared with simple physical mixing, this reduces the kinetic energy barrier of the subsequent carbothermic reduction reaction, solving the problems of easy carbon powder burn-off and floating, or uneven mixing with rare earth oxides leading to low reaction efficiency in traditional methods. This allows the subsequent carbothermic reduction reaction to proceed more quickly and completely in the molten slag at a lower temperature.
[0036] 80 parts of matrix powder, 10 parts of rare earth penetrant and 5 parts of B2O3-Na2O pre-melted glass powder were mixed evenly and dried at 200℃ for 5 hours to obtain electroslag agent.
[0037] S2. Electroslag remelting: Add 50 parts of electroslag agent to a water-cooled copper crystallizer, heat to 1800℃, add 100 parts of 40CrNiMoA as a consumable electrode, perform electroslag remelting, and obtain rare earth steel ingots after solidification.
[0038] In the above process, after the electroslag agent melts, the rare earth infiltrated material inside undergoes a reduction reaction, and the graphene reacts with the cerium dioxide powder:
[0039] CeO2 (solid) + 2C (solid) → [Ce] (liquid) + 2CO (gas)↑. This reaction occurs inside the molten electroslag agent, generating highly chemically active Ce atoms. These Ce atoms briefly dissolve in the slag-gold interface layer, forming a region with extremely high Ce chemical potential. According to thermodynamic principles, an oxygen potential trap forms here. When a steel droplet passes through, the oxygen in the steel droplet is strongly attracted out due to the huge chemical potential gradient, reacting with the active Ce in the slag to generate Ce2O3, which remains in the slag. Simultaneously... High concentrations of Ce atoms will also diffuse and dissolve into the molten steel along the concentration gradient. When Ce atoms combine with O and S in the molten steel, they preferentially form regular, small, spherical or ellipsoidal rare earth oxysulfide inclusions. These inclusions have lower hardness and better mechanical compatibility with the steel matrix. Under cyclic loading, they can buffer stress through plastic deformation and inhibit crack initiation, thereby increasing the impact toughness of the steel. This avoids the technical problem of forming large, irregular rare earth oxysulfide and other brittle inclusions in the molten steel by directly adding rare earth alloys.
[0040] S3. Heat treatment after remelting: After heating the rare earth steel ingot to 1200℃ and holding it for 15 hours, it is forged in multiple directions until the total forging ratio is >3 to obtain alloyed rare earth electroslag steel.
[0041] The final alloyed rare earth electroslag steel is composed of the following elements by weight percentage:
[0042] C: 0.38%~0.43%;
[0043] Si: 0.15%~0.35%;
[0044] Mn: 0.60%~0.80%;
[0045] Cr: 0.70%~0.90%;
[0046] Ni: 1.65%~2.00%;
[0047] Mo: 0.20%~0.30%;
[0048] Ce: 0.005%~0.030%;
[0049] The balance consists of iron and unavoidable impurities, of which:
[0050] P: ≤0.015%;
[0051] S: ≤0.005%;
[0052] O: ≤0.0015%.
[0053] Example 2
[0054] This embodiment prepares an alloyed rare earth electroslag steel, and the manufacturing method includes the following steps:
[0055] S1. Preparation of electroslag agent:
[0056] By weight, 100 parts of waste slag from the converter were crushed and ball-milled to make the particle size less than 1 mm. The metallic iron particles were removed by magnetic separation. The mixture was then thoroughly mixed with 5 parts of metallic calcium powder and 2 parts of coke powder, placed in a reactor, and reacted at 1450°C for 1.5 hours. After cooling to room temperature, a second magnetic separation was performed, and the mixture was ground to obtain the matrix powder.
[0057] Ten parts of lanthanum oxide (La2O3) powder and 1.5 parts of carbon nanotubes were ultrasonically dispersed in 150 parts of deionized water, spray-dried, and then subjected to low-temperature heat treatment at 600℃ for 1 hour under a nitrogen protective atmosphere to obtain rare earth permeable material.
[0058] Mix 85 parts of matrix powder, 5 parts of rare earth permeate and 3 parts of calcium fluoride evenly, and dry them in an oven at 200°C for 5 hours to obtain electroslag agent.
[0059] S2, Electroslag Remelting:
[0060] In a water-cooled copper crystallizer, 45 parts of the prepared electroslag agent were added as bottom slag. An electric arc was initiated to melt the electroslag agent and form a molten pool. Then, 100 parts of 40CrNiMoA steel were used as consumable electrodes, and electroslag remelting was performed at a slag temperature of 1750℃. The remelting process proceeded smoothly, and after the consumable electrodes were completely melted, the mixture was slowly cooled and solidified to obtain rare earth steel ingots.
[0061] S3. Heat treatment after remelting:
[0062] The obtained rare earth steel ingots are heated to 1200℃ and held for 12 hours before being subjected to multi-directional forging. The total forging ratio is greater than 3, resulting in alloyed rare earth electroslag steel.
[0063] The final alloyed rare earth electroslag steel is composed of the following elements by weight percentage:
[0064] C: 0.38%~0.43%;
[0065] Si: 0.15%~0.35%;
[0066] Mn: 0.60%~0.80%;
[0067] Cr: 0.70%~0.90%;
[0068] Ni: 1.65%~2.00%;
[0069] Mo: 0.20%~0.30%;
[0070] La: 0.008%~0.025%;
[0071] The balance consists of iron and unavoidable impurities.
[0072] Example 3
[0073] This embodiment prepares an alloyed rare earth electroslag steel, and the manufacturing method includes the following steps:
[0074] S1. Preparation of electroslag agent:
[0075] By weight, 100 parts of steel ladle refining furnace waste slag were ball-milled to a particle size of less than 1 mm, and after magnetic separation to remove iron, it was mixed with 10 parts of calcium silicon alloy powder and 5 parts of graphene powder. The mixture was reacted at 1550℃ for 1 hour, cooled, and then subjected to a second magnetic separation and grinding to obtain matrix powder.
[0076] A mixture of 5 parts yttrium oxide (Y2O3) and 5 parts neodymium oxide (Nd2O3) powders was ultrasonically dispersed with 2 parts highly active carbon black in 100 parts deionized water. After spray drying, the mixture was heat-treated at 700°C for 1 hour under an argon atmosphere to obtain rare earth permeable material.
[0077] 75 parts of matrix powder, 15 parts of rare earth penetrant and 6 parts of CaO-Al2O3-B2O3 pre-melted glass powder flux were mixed evenly and dried at 200℃ for 5 hours to obtain electroslag agent.
[0078] S2, Electroslag Remelting:
[0079] Add 50 parts of electroslag agent to a water-cooled copper crystallizer, heat to 1800℃ to form a molten pool, use 100 parts of 40CrNiMoA steel as a consumable electrode for electroslag remelting, and allow it to cool and solidify naturally to obtain rare earth steel ingots containing yttrium and neodymium.
[0080] S3. Heat treatment after remelting:
[0081] Rare earth steel ingots are held at 1180℃ for 20 hours and then subjected to multi-directional forging with a total forging ratio greater than 3 to obtain alloyed rare earth electroslag steel.
[0082] The final alloyed rare earth electroslag steel is composed of the following elements by weight percentage:
[0083] C: 0.38%~0.43%;
[0084] Si: 0.15%~0.35%;
[0085] Mn: 0.60%~0.80%;
[0086] Cr: 0.70%~0.90%;
[0087] Ni: 1.65%~2.00%;
[0088] Mo: 0.20%~0.30%;
[0089] Y: 0.005%~0.015%;
[0090] Nd: 0.005%~0.015%;
[0091] The balance consists of iron and unavoidable impurities.
[0092] Example 4
[0093] This embodiment prepares an alloyed rare earth electroslag steel, and the manufacturing method includes the following steps:
[0094] S1. Preparation of electroslag agent:
[0095] By weight, 100 parts of converter waste slag were ball-milled, mixed with 6 parts of calcium carbide and 4 parts of graphite powder, reacted at 1520℃ for 2 hours, cooled to room temperature, and then magnetically separated and ground to obtain matrix powder.
[0096] 10 parts of praseodymium oxide (Pr6O) 11 The powder and 1.8 parts of reduced graphene oxide were evenly dispersed in 180 parts of deionized water, spray-dried, and then heat-treated at 550℃ for 1 hour under vacuum to obtain rare earth infiltrated material.
[0097] 70 parts of matrix powder, 12 parts of rare earth permeate and 8 parts of boride MgB2 were mixed evenly and dried at 200℃ for 5 hours to obtain electroslag agent.
[0098] S2, Electroslag Remelting:
[0099] 60 parts of electroslag agent were added to a water-cooled copper crystallizer and heated to 1900℃ to form a molten pool. Electroslag remelting was performed using 100 parts of 40CrNiMoA steel as a consumable electrode. After solidification, a steel ingot containing praseodymium rare earth was obtained.
[0100] S3. Heat treatment after remelting:
[0101] The steel ingot is held at 1250℃ for 8 hours and then subjected to multi-directional forging with a total forging ratio greater than 3 to obtain alloyed rare earth electroslag steel.
[0102] The final alloyed rare earth electroslag steel is composed of the following elements by weight percentage:
[0103] C: 0.38%~0.43%;
[0104] Si: 0.15%~0.35%;
[0105] Mn: 0.60%~0.80%;
[0106] Cr: 0.70%~0.90%;
[0107] Ni: 1.65%~2.00%;
[0108] Mo: 0.20%~0.30%;
[0109] Pr: 0.010%~0.030%;
[0110] The balance consists of iron and unavoidable impurities.
[0111] Example 5
[0112] This embodiment prepares an alloyed rare earth electroslag steel, and the manufacturing method includes the following steps:
[0113] S1. Preparation of electroslag agent:
[0114] By weight, 100 parts of steel ladle refining furnace waste slag were ball-milled and then mixed with 9 parts of a mixture of metallic calcium and calcium-silicon alloy in a mass ratio of 1:1 and 3.5 parts of a mixture of coke powder and carbon nanotubes in a mass ratio of 3:1. The mixture was reacted at 1480℃ for 1.8 hours, cooled to room temperature, and then magnetically separated and ground to obtain matrix powder.
[0115] Ten parts of gadolinium oxide (Gd2O3) powder and 1.9 parts of graphene nanosheets were dispersed in 120 parts of deionized water, spray-dried, and then heat-treated at 650°C for 1 hour under an inert atmosphere to obtain rare earth infiltrated material.
[0116] 82 parts of matrix powder, 10 parts of rare earth permeate and 4 parts of a mixture of sodium oxide (Na2O) and magnesium oxide (MgO) in a mass ratio of 1:1 were mixed evenly and dried at 200℃ for 5 hours to obtain electroslag agent.
[0117] S2, Electroslag Remelting:
[0118] 55 parts of electroslag agent were added to a water-cooled copper crystallizer and heated to 1850℃ to form a molten pool. Electroslag remelting was performed using 100 parts of 40CrNiMoA steel as a consumable electrode. After solidification, gadolinium-containing rare earth steel ingots were obtained.
[0119] S3. Heat treatment after remelting:
[0120] The steel ingot is held at 1220℃ for 15 hours and then subjected to multi-directional forging with a total forging ratio greater than 3 to obtain alloyed rare earth electroslag steel.
[0121] The final alloyed rare earth electroslag steel is composed of the following elements by weight percentage:
[0122] C: 0.38%~0.43%;
[0123] Si: 0.15%~0.35%;
[0124] Mn: 0.60%~0.80%;
[0125] Cr: 0.70%~0.90%;
[0126] Ni: 1.65%~2.00%;
[0127] Mo: 0.20%~0.30%;
[0128] Gd: 0.005%~0.020%;
[0129] The balance consists of iron and unavoidable impurities.
[0130] Example 6
[0131] This embodiment prepares an alloyed rare earth electroslag steel, the manufacturing method of which includes the following steps:
[0132] S1. Preparation of electroslag agent:
[0133] By weight, 100 parts of converter waste slag were ball-milled, then mixed with 7 parts of calcium-silicon alloy and 4.5 parts of coke powder. The mixture was reacted at 1470℃ for 1.7 hours, cooled to room temperature, and then magnetically separated and ground to obtain matrix powder.
[0134] Ten parts of dysprosium oxide (Dy2O3) powder and 1.7 parts of highly active carbon black were ultrasonically dispersed in 160 parts of deionized water. After spray drying, the mixture was heat-treated at 680°C for 1 hour under an argon atmosphere to obtain heavy rare earth permeable material.
[0135] 78 parts of matrix powder, 13 parts of rare earth permeate and 7 parts of magnesium fluoride MgF2 were mixed evenly and dried at 200℃ for 5 hours to obtain electroslag agent.
[0136] S2, Electroslag Remelting:
[0137] Add 50 parts of electroslag agent to a water-cooled copper crystallizer, heat to 1880℃ to form a molten pool, and use 100 parts of 40CrNiMoA steel as a consumable electrode for electroslag remelting. After solidification, dysprosium-containing rare earth steel ingots are obtained.
[0138] S3. Heat treatment after remelting:
[0139] The steel ingot is held at 1230℃ for 10 hours and then subjected to multi-directional forging with a total forging ratio greater than 3 to obtain alloyed rare earth electroslag steel.
[0140] The final alloyed rare earth electroslag steel is composed of the following elements by weight percentage:
[0141] C: 0.38%~0.43%;
[0142] Si: 0.15%~0.35%;
[0143] Mn: 0.60%~0.80%;
[0144] Cr: 0.70%~0.90%;
[0145] Ni: 1.65%~2.00%;
[0146] Mo: 0.20%~0.30%;
[0147] Dy: 0.010%~0.035%;
[0148] The balance consists of iron and unavoidable impurities.
[0149] Example 7
[0150] This embodiment prepares an alloyed rare earth electroslag steel, and the manufacturing method includes the following steps:
[0151] S1. Preparation of electroslag agent:
[0152] By weight, 100 parts of treated ladle refining furnace slag were thoroughly mixed with a mixed calcium thermal reducing agent consisting of 5 parts calcium carbide and 5 parts metallic calcium, and a mixed carbothermic reducing agent consisting of 2.5 parts graphite powder and 2.5 parts graphene. The mixture was reacted at 1530℃ for 1.2 hours. After cooling, magnetic separation, and grinding, the matrix powder was obtained.
[0153] A mixture of rare earth oxides consisting of 5 parts cerium dioxide (CeO2) and 5 parts erbium oxide (Er2O3) was dispersed with 1.6 parts reduced graphene oxide in 140 parts deionized water. After spray drying, the mixture was heat-treated at 620°C for 1 hour under a nitrogen atmosphere to obtain a rare earth infiltrated material.
[0154] 72 parts of matrix powder, 14 parts of rare earth penetrant and 6 parts of glassy flux made from calcium fluoride and boron oxide were mixed evenly and dried at 200°C for 5 hours to obtain electroslag agent.
[0155] S2, Electroslag Remelting:
[0156] 58 parts of electroslag agent were added to a water-cooled copper crystallizer, and the temperature was raised to 1920℃ to form a molten pool. Electroslag remelting was performed using 100 parts of 40CrNiMoA steel as a consumable electrode, and steel ingots were obtained after solidification.
[0157] S3. Heat treatment after remelting:
[0158] The steel ingot is held at 1190℃ for 18 hours and then subjected to multi-directional forging with a total forging ratio greater than 3 to obtain alloyed rare earth electroslag steel.
[0159] The final alloyed rare earth electroslag steel is composed of the following elements by weight percentage:
[0160] C: 0.38%~0.43%;
[0161] Si: 0.15%~0.35%;
[0162] Mn: 0.60%~0.80%;
[0163] Cr: 0.70%~0.90%;
[0164] Ni: 1.65%~2.00%;
[0165] Mo: 0.20%~0.30%;
[0166] Ce: 0.003%~0.015%;
[0167] Er: 0.004%~0.018%;
[0168] The balance consists of iron and unavoidable impurities.
[0169] Comparative Example 1
[0170] This embodiment prepares an alloyed rare earth electroslag steel, and the manufacturing method includes the following steps:
[0171] S1. Preparation of electroslag agent:
[0172] By weight, 80 parts of commercially available electroslag agent (CaO:Al2O3:CaF2 mixed in a weight ratio of 55:30:15), 10 parts of cerium dioxide powder, and 5 parts of B2O3-Na2O pre-melted glass powder were directly physically mixed and dried at 200℃ for 5 hours to obtain the traditional electroslag agent.
[0173] S2, Electroslag Remelting:
[0174] Add 40-60 parts of traditional electroslag agent to a water-cooled copper crystallizer, heat to 1700-1950℃, add 100 parts of 40CrNiMoA consumable electrode, and when the electrode is 50% melted, directly add 2 parts of rare earth ferrosilicon alloy containing 20% Ce to the surface of the molten pool, and continue to remelt until solidification to obtain rare earth steel ingots.
[0175] S3. Heat treatment after remelting:
[0176] By holding at 1150-1250℃ for 8-24 hours and then multi-directionally forging until the total forging ratio is >3, alloyed rare earth electroslag steel is obtained.
[0177] The final alloyed rare earth electroslag steel is composed of the following elements by weight percentage:
[0178] C: 0.38%~0.43%;
[0179] Si: 0.15%~0.35%;
[0180] Mn: 0.60%~0.80%;
[0181] Cr: 0.70%~0.90%;
[0182] Ni: 1.65%~2.00%;
[0183] Mo: 0.20%~0.30%;
[0184] Ce: 0.001%~0.008%;
[0185] The balance consists of iron and unavoidable impurities, of which:
[0186] P: ≥0.025%;
[0187] S: ≥0.010%;
[0188] O: ≥0.0030%.
[0189] Comparative Example 2
[0190] This embodiment prepares an alloyed rare earth electroslag steel, and the manufacturing method includes the following steps:
[0191] S1. Preparation of electroslag agent:
[0192] Matrix powder preparation: 100 parts by weight of steel ladle refining furnace waste slag were ball-milled and magnetically separated to obtain matrix powder. The matrix powder was tested and found to contain 0.3% to 0.5% P2O5 and 1.2% to 1.5% FeO.
[0193] Ten parts of cerium dioxide powder and two parts of carbon powder were directly mixed to obtain rare earth permeation material.
[0194] 80 parts of matrix powder, 10 parts of rare earth permeate and 5 parts of B2O3-Na2O pre-melted glass powder were mixed and dried at 200℃ for 5 hours to obtain electroslag agent.
[0195] S2, Electroslag Remelting: Same as Example 1.
[0196] S3. Heat treatment after remelting: Same as in Example 1.
[0197] The final alloyed rare earth electroslag steel is composed of the following elements by weight percentage:
[0198] C: 0.38%~0.43%;
[0199] Si: 0.15%~0.35%;
[0200] Mn: 0.60%~0.80%;
[0201] Cr: 0.70%~0.90%;
[0202] Ni: 1.65%~2.00%;
[0203] Mo: 0.20%~0.30%;
[0204] Ce: 0.002%~0.010%;
[0205] The balance consists of iron and unavoidable impurities, of which:
[0206] P: ≥0.030%;
[0207] S: ≥0.012%;
[0208] O: ≥0.0040%.
[0209] Comparative Example 3
[0210] This embodiment prepares an alloyed rare earth electroslag steel, and the manufacturing method includes the following steps:
[0211] S1. Preparation of electroslag agent
[0212] The matrix powder used was the matrix powder prepared in Example 1.
[0213] Ten parts of cerium dioxide powder and two parts of graphene oxide were mixed evenly to obtain rare earth permeable material.
[0214] 80 parts of matrix powder, 10 parts of rare earth permeate and 5 parts of B2O3-Na2O pre-melted glass powder were mixed and dried at 200℃ for 5 hours to obtain electroslag agent.
[0215] S2, Electroslag Remelting: Same as Example 1.
[0216] S3. Heat treatment after remelting: Same as in Example 1.
[0217] The final alloyed rare earth electroslag steel is composed of the following elements by weight percentage:
[0218] C: 0.38%~0.43%;
[0219] Si: 0.15%~0.35%;
[0220] Mn: 0.60%~0.80%;
[0221] Cr: 0.70%~0.90%;
[0222] Ni: 1.65%~2.00%;
[0223] Mo: 0.20%~0.30%;
[0224] Ce: 0.003%~0.015%;
[0225] The balance consists of iron and unavoidable impurities, of which:
[0226] P: ≤0.015%;
[0227] S: ≤0.005%;
[0228] O: 0.0018%~0.0025%.
[0229] Elemental content analysis: Comparative Example 1 uses a traditional electroslag agent, which has limited dephosphorization capacity and poor desulfurization effect. Direct addition of rare earth alloys leads to severe rare earth burn-off, insufficient deoxidation, and low and unstable recovery rate. In Comparative Example 2, the matrix powder was not dephosphorized, resulting in phosphorus recontamination of the molten steel. The rare earth oxides did not undergo a reduction reaction, resulting in high oxygen content in the molten steel. In the rare earth permeate of Comparative Example 3, the rare earth oxides only underwent simple physical mixing with the reduced carbon. Uneven mixing led to incomplete local reactions, and the recovery rate was lower than that of Example 1. In summary, only by adopting the technical solution of Example 1 of this invention can the efficient and stable recovery of rare earth elements and the deep purification of impurity elements such as P, S, and O be achieved simultaneously.
[0230] Performance testing was conducted on the impact toughness and fatigue resistance of the alloyed rare earth electroslag steels prepared in Example 1 and Comparative Examples 1-3:
[0231] 1. Impact Toughness Test: Sample blanks were longitudinally cut along the forging direction from the alloyed rare-earth electroslag steels prepared in Example 1 and Comparative Examples 1-3 at a radius 1 / 2 from the center. The blanks were machined into standard specimens with dimensions of 10mm × 10mm × 55mm. A V-shaped notch with a depth of 2mm and a bottom curvature radius of R = 0.25mm was machined at the center of the specimen's length. Five parallel specimens were prepared for each group. The specimens were placed in alcohol at -40℃ for 20 minutes. They were then quickly removed from the low temperature and placed on the support of a pendulum impact testing machine within 5 seconds, ensuring the notch faced away from the impact direction of the pendulum. The pendulum was immediately released to impact the specimen, causing it to fracture. The work consumed by the pendulum to break the specimen, i.e., the impact absorbed work (AkV), was recorded in joules (J). The arithmetic mean of the five valid data points for each group was taken as the final impact toughness value for that group of samples.
[0232] 2. Fatigue resistance test: Blanks were cut longitudinally from the alloyed rare earth electroslag steels prepared in Examples 1 and 1-3 at half the radius. The blanks were machined into smooth hourglass-shaped round bar specimens, ensuring a surface roughness Ra ≤ 0.2 μm at the minimum diameter. The specimens were finely polished to eliminate surface tool marks. 10-15 specimens were prepared for each group of samples. The specimens were precisely mounted in the clamps of a rotary bending fatigue testing machine. A preset bending load was applied using weights, causing the specimens to experience alternating tensile and compressive stresses during rotation. The testing machine was started, and the specimens rotated at a constant frequency until fracture occurred or a preset number of cycles (10) were reached. 7 (Times), record the number of cycles (Nf) for each specimen at a specific stress level. If the specimen is at 10 7 If the specimen does not fracture after several cycles, it is considered to have an infinite lifespan at that stress level. A step-down method is used for data processing. Starting from an estimated stress level, if the specimen fractures, the next specimen is subjected to a lower stress level; if it does not fracture, the stress level is increased. The fatigue limit (σ) of the material is statistically calculated based on the test results. -1 ).
[0233] The test results are shown in Table 1 below:
[0234] Table 1. Test results of impact toughness and fatigue resistance of alloyed rare earth electroslag steel
[0235]
[0236] Results Analysis
[0237] As can be seen from Table 1, the alloyed rare earth electroslag steel prepared in Example 1 has an impact absorption energy of 115J at -40℃, and good low-temperature toughness. Example 1 prepared a high-purity, high-alkalinity electroslag agent by pretreating the slag waste with carbothermic reduction, thus avoiding the pollution of molten steel by harmful elements such as P and O at the source. Secondly, by coating cerium dioxide with graphene oxide, the in-situ and efficient reduction and penetration of rare earth elements at the slag-metal interface were achieved. This not only deeply purified the molten steel, but also transformed the unavoidable sulfide and oxide inclusions in the steel into dispersed, fine spherical rare earth oxysulfides. These inclusions have good bonding with the steel matrix interface, high deformation coordination, and can effectively passivate crack tips and prevent crack propagation under impact, thereby significantly improving the toughness of the material. Comparative Examples 1 and 2, due to high impurity content and improper rare earth addition methods, formed a large number of coarse, irregular, brittle inclusions, which became crack sources, resulting in extremely poor toughness. Although Comparative Example 3 used clean slag, the traditional rare earth addition method resulted in low rare earth utilization and incomplete modification of inclusions. Therefore, although its toughness was improved, it was far inferior to that of Example 1.
[0238] Table 1 also shows that the rotational bending fatigue limit of Example 1 is as high as 554 MPa, significantly better than all comparative examples. The essence of fatigue failure is the initiation and propagation of microcracks under cyclic loading, and crack initiation usually occurs in stress concentration areas, such as hard and brittle inclusions inside the material. This invention, through deep deoxidation and desulfurization of electroslag steel and modification of inclusions using rare earth elements, greatly reduces the number of large, angular hard inclusions such as Al2O3 and TiN in the steel, replacing them with small, spherical rare earth inclusions with better plasticity. These spherical inclusions are less likely to cause stress concentration, effectively inhibiting the initiation of fatigue cracks. At the same time, the ultra-high purity of the molten steel itself also reduces the number of defects that can serve as fatigue sources, thereby improving the fatigue resistance and service life of electroslag steel.
[0239] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.
Claims
1. A method for manufacturing rare earth electroslag steel containing alloyed rare earth elements, comprising the preparation of an electroslag agent, electroslag remelting, and post-remelting heat treatment, characterized in that, The preparation of the electroslag agent includes: The matrix powder is prepared by mixing slag waste, calcium-thermal reducing agent and carbothermal reducing agent and reacting at 1450~1550℃ for 1~2h, wherein the mass ratio of the slag waste, calcium-thermal reducing agent and carbothermal reducing agent is 100:5~10:2~5. Oxides of rare earth elements and nano-carbon materials are dispersed in deionized water, wherein the mass ratio of the oxides of rare earth elements, nano-carbon materials and deionized water is 10:1.5~2:100~200. After spray drying, the mixture is heat-treated at a low temperature of 500~700℃ for 1 hour to obtain rare earth permeable material. Electroslag agent is obtained by mixing matrix powder, rare earth penetrant and flux. The mass ratio of matrix powder, rare earth penetrant and flux is 70~85:5~15:2~8. The flux is selected from one or more glassy substances or pre-melted slags made from fluorides, borides, boron oxides, alkali metal oxides, alkaline earth metal oxides and transition metal oxides. The slag waste originates from iron and steel metallurgy or other high-temperature industrial processes, and its main chemical components are calcium oxide and aluminum oxide.
2. The method for manufacturing rare earth electroslag steel containing alloyed rare earth elements according to claim 1, characterized in that, The slag waste comes from waste residue generated by converters or ladle refining furnaces.
3. The method for manufacturing rare earth electroslag steel containing alloyed rare earth elements according to claim 1, characterized in that, The oxides of the rare earth elements are selected from one or any combination of scandium oxide, yttrium oxide, lanthanum oxide, cerium dioxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide.
4. The method for manufacturing rare earth electroslag steel containing alloyed rare earth elements according to claim 1, characterized in that, The calcothermic reducing agent includes, but is not limited to, one or more strong reducing agents selected from calcium carbide, metallic calcium, and calcium-silicon alloys.
5. The method for manufacturing rare earth electroslag steel containing alloyed rare earth elements according to claim 1, characterized in that, The carbothermic reducing agent includes, but is not limited to, one or more carbonaceous reducing agents selected from graphite powder, coke powder, carbon nanotubes, and graphene.
6. The method for manufacturing rare earth electroslag steel containing alloyed rare earth elements according to claim 1, characterized in that, The nano-carbon material is selected from one or more of graphene oxide, reduced graphene oxide, carbon nanotubes, graphene nanosheets, and highly active carbon black.