Method for producing 4J36 steel ingot by adopting VODC refining furnace

Abstract

The invention discloses a method for producing a 4J36 steel ingot by adopting a VODC refining furnace, which comprises the following steps of: smelting alloy scrap steel according to chemical components of the 4J36 steel ingot to obtain alloy steel liquid; the alloy steel liquid and the first slag charge are mixed, argon-oxygen mixed blowing decarburization under vacuum is conducted through a VODC refining furnace, and first molten steel is obtained; the first molten steel is subjected to deep carbon deoxidation in a VODC refining furnace, and second molten steel is obtained; the second molten steel and the second slag are mixed, dehydrogenation and denitrification are conducted in a VODC refining furnace, and third molten steel is obtained; the third molten steel is subjected to steel ladle weak argon stirring treatment, inclusions in the molten steel are removed, and fourth molten steel is obtained through standing; the sedation time is 15-25 minutes; and the fourth molten steel is subjected to protective atmosphere pouring, and the iron-nickel alloy 4J36 steel ingot is obtained. The vacuum argon-oxygen combined blowing technology, the vacuum carbon deoxidation technology, the vacuum aluminothermic reduction technology and the closed pouring technology are adopted, and the low manufacturing cost is achieved on the premise that the steel ingot quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of alloy material preparation, and in particular to a method for preparing a low expansion iron-nickel alloy 4J36 steel ingot for the OLED industry by using a VODC refining furnace. Background Art

[0002] The main components of the iron-nickel alloy 4J36 are 63% Fe and 37% Ni, with a face-centered cubic structure. The thermal expansion coefficient decreases significantly near the Curie point, and is called Invar alloy. Due to its special expansion properties, Invar alloy is widely used in precision instrument parts, membrane-type LNG carrier inner wall, carbon fiber reinforced plastic (CFP) production molds, aerospace molds, new OLED display molding tooling molds and other industries.

[0003] Invar alloy 4J36 has high performance index requirements and is difficult to produce. It is mainly imported from abroad. In order to prevent restrictions on imported materials, various industries are actively promoting the localization of Invar alloy. At present, the domestic production of 4J36 steel ingots usually adopts the non-vacuum induction furnace + AOD + LF + VD + die casting production process.

[0004] For example, the patent document with patent number 201410652793.5 discloses a process method for vacuum induction melting of 4J36 low expansion alloy, using a thermodynamically stable yttria-stabilized zirconia crucible to induction melt the 4J36 low expansion alloy under a positive pressure argon atmosphere, wherein the preparation method of the yttria-stabilized zirconia crucible is as follows: 8% by mass of yttria powder and 92% by mass of zirconia powder are mixed and ball-milled, sintered at high temperature and then spheroidized and granulated, and zirconium diacetate is used as a binder to form a blank by cold isostatic pressing, and finally sintered to obtain a yttria-stabilized zirconia crucible.

[0005] The above process method can effectively reduce the reaction between the alloy liquid and the crucible wall, and greatly reduce the content of oxide slag inclusions; and filling argon gas during the smelting process can effectively reduce the splashing of the alloy liquid, ensuring that the alloy liquid is pure and meets the use requirements.

[0006] However, this process method has low production efficiency, long smelting time, difficulty in controlling the oxygen, nitrogen and carbon contents in the steel, and high manufacturing costs.

[0007] Therefore, it is necessary to improve the existing technical solutions to overcome the above-mentioned defects. Summary of the invention

[0008] The purpose of the present invention is to provide a method for preparing a low expansion iron-nickel alloy 4J36 steel ingot for the OLED industry, a VODC refining furnace is used for the production of 4J36 steel ingots, and a new process flow of non-vacuum induction furnace + VODC + mold casting is developed. Due to the shortening of the steel ingot production cycle, the control levels of oxygen content, nitrogen content and carbon content in the steel are improved. A single furnace can produce 20 tons, the cost is low and the product quality can meet the requirements.

[0009] The above technical objectives of the present invention are achieved through the following technical solutions: A method for producing 4J36 steel ingots using a VODC refining furnace comprises the following steps: According to the chemical composition of 4J36 steel ingot, alloy scrap steel is smelted to obtain alloy steel liquid; The alloy steel liquid is mixed with a first slag material, and subjected to argon-oxygen mixed blowing and decarburization under vacuum in a VODC refining furnace to obtain a first steel liquid; the first slag material comprises metallurgical lime, secondary fluorite blocks and aluminum ingots; The first molten steel is subjected to deep carbon deoxidation in a VODC refining furnace to obtain a second molten steel; The second molten steel and the second slag are mixed, and dehydrogenated and denitrified in a VODC refining furnace to obtain a third molten steel; the second slag comprises low-carbon metallurgical lime, secondary fluorite block, a VODC furnace-specific reducing agent and an aluminum ingot; the third molten steel is subjected to a ladle weak argon stirring treatment to remove inclusions in the molten steel, and is calmed to obtain a fourth molten steel; the calming time is 15-25 minutes; The fourth molten steel is cast in a protective atmosphere to obtain an iron-nickel alloy 4J36 steel ingot.

[0010] Furthermore, the pouring temperature of the protective atmosphere pouring is 1520±10°C; special ultra-low carbon mold casting protective slag and special silicon high-efficiency heating agent are added in the protective atmosphere pouring; the amount of the protective slag is 1.0-1.5kg / t; The dosage of the special silicon high-efficiency heat-generating agent is 2.5-3.0kg / t; the method for adding the special silicon high-efficiency heat-generating agent includes: after the cap mouth is filled with the fourth steel liquid to more than two-thirds of the height, 40-60% of the special silicon high-efficiency heat-generating agent is added, and the remaining special silicon high-efficiency heat-generating agent is added before the pouring is finished.

[0011] Furthermore, the addition amount of the first slag in the alloy steel liquid is: 10-16 kg / t of metallurgical lime, 1.0-2.5 kg / t of secondary fluorite block, and 1-1.5 kg / t of aluminum ingot.

[0012] Furthermore, the bottom blowing gas for decarburization in the VODC refining furnace under vacuum with argon-oxygen mixed blowing is argon, and the argon flow rate is controlled at 5-8m 3 / h, the vacuum degree of VODC refining furnace is maintained at 70-110 mbar.

[0013] Furthermore, the total amount of oxygen used in the argon-oxygen mixed blowing decarburization process of the VODC refining furnace under vacuum is obtained according to Formula I: O used =O total ×M w , Formula I; In the formula I, O used It is the total amount of oxygen used in the argon-oxygen mixed blowing decarburization process of the VODC refining furnace under vacuum, in Nm 3 ;O total Oxygen consumption per ton of steel, in Nm 3 / t, calculated by formula II; M w is the weight of molten steel, in t; O total =1 / eta×[9.31×(C1-C2)+7.98×Si1+6.22×A1]+3.22×(Cr1-Cr2), formula II; In the formula II, eta is oxygen release, and its value is 0.75; C1 is the initial carbon content by mass percentage; C2 is the final carbon content by mass percentage; Si1 is the initial silicon content by mass percentage; A1 is the initial aluminum content by mass percentage; Cr1 is the initial chromium content by mass percentage; and Cr2 is the expected chromium content by mass percentage.

[0014] Furthermore, the VODC refining furnace directly performs vacuum carbon deoxidation after decarburization by argon-oxygen mixed blowing under vacuum; the vacuum degree of the vacuum carbon deoxidation is less than 5 mbar, the bottom blowing gas of the vacuum carbon deoxidation is argon, and the argon flow rate is controlled at 5-8 m 3 / h, and the control time of the vacuum carbon deoxidation is 7-10min.

[0015] Furthermore, when the temperature of the second molten steel is ≥1650°C, the temperature is not increased; when the temperature of the second molten steel is <1650°C, the temperature is increased.

[0016] Furthermore, the temperature of the second molten steel is raised by a vacuum aluminothermic method, the vacuum degree of the vacuum aluminothermic method is 300-400 mbar, the bottom blowing gas of the vacuum aluminothermic method is argon, and the flow rate of the argon is controlled at 5-8m 3 / h; The amount of oxygen used to burn aluminum during the vacuum aluminothermic method is calculated by formula III; O' total =0.62×m Al , Formula III; In the formula III, O' totalThe amount of oxygen used to burn aluminum during the vacuum aluminothermic process, in Nm 3 ;m Al is the mass of aluminum added, in kg; 0.62 is the coefficient, in Nm 3 / kg.

[0017] Furthermore, the addition amount of the second slag in the second molten steel is: 20-28 kg / t of low-carbon metallurgical lime, 2.0-3.5 kg / t of secondary fluorite block, 6-8 kg / t of VODC furnace special reducing agent, and 2.5-4.5 kg / t of aluminum ingot.

[0018] Furthermore, when the fourth molten steel is cast in a protective atmosphere, the amount of nitrogen introduced into the molten steel during the mold casting process is ≤9ppm; The amount of the special ultra-low carbon mold casting protection slag added in the protective atmosphere casting is 1.2kg / t, and the carbon content of the molten steel in the mold casting process is ≤50ppm; The special high-efficiency heating agent added in the protective atmosphere pouring is a silicon high-efficiency heating agent, and the dosage is 3.0-3.5 kg / ton; The prepared iron-nickel alloy 4J36 steel ingot has an oxygen content of ≤45ppm, a nitrogen content of ≤70ppm, and a carbon content of ≤250ppm.

[0019] In summary, the present invention has the following beneficial effects: By optimizing the smelting process route, the efficient metallurgical function of the VODC refining furnace was fully utilized, and the vacuum argon-oxygen composite blowing technology, vacuum carbon deoxidation technology, vacuum aluminum thermal reduction technology, and closed pouring technology were adopted. The quality of auxiliary materials used in the die casting system was improved, achieving low manufacturing costs while improving the quality of steel ingots. DETAILED DESCRIPTION

[0020] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0021] The present invention provides a method for producing a low expansion iron-nickel alloy 4J36 steel ingot for the OLED industry, comprising the following steps: According to the chemical composition required by 4J36 technical standard, alloy scrap steel is used as raw material for melting to obtain alloy steel liquid; The molten steel and the first slag are mixed, and argon-oxygen composite blowing and decarburization are performed under vacuum in a VODC refining furnace to obtain a first molten steel; the first slag comprises metallurgical lime, secondary fluorite blocks and aluminum ingots; The first molten steel is subjected to deep carbon deoxidation in a VODC refining furnace to obtain a second molten steel; The second molten steel and the second slag are mixed, and dehydrogenation and denitrification operations are performed in a VODC refining furnace to obtain a third molten steel; the second slag comprises low-carbon metallurgical lime, secondary fluorite blocks, a VODC furnace-specific reducing agent, and aluminum ingots; The third molten steel is subjected to ladle weak argon stirring treatment to remove inclusions in the molten steel, thereby obtaining a fourth molten steel; the sedation time is 15-25 minutes; The fourth molten steel is poured in a protective atmosphere to obtain an iron-nickel alloy 4J36 steel ingot; The pouring start temperature is 1520±10°C; special ultra-low carbon mold casting protection slag and special silicon high-efficiency heating agent are added during the pouring process; the amount of the protection slag is 1.0-1.5kg / t; The dosage of the silicon-specific high-efficiency heat-generating agent is 2.5-3.0 kg / t; the method for adding the heat-generating agent includes: after the cap mouth is filled with the fourth molten steel to more than two-thirds of the height, adding 40-60% of the heat-generating agent, and adding the remaining heat-generating agent before the end of pouring.

[0022] The 4J36 technical standard of the present invention requires chemical composition, and alloy scrap steel is used as a raw material for melting to obtain alloy steel liquid. In the present invention, the scrap steel raw material preferably includes high-nickel scrap steel and / or high-chromium scrap steel. In the present invention, the smelting temperature is preferably 1650-1660°C; the smelting time is preferably 80-100 minutes. In the present invention, the tapping temperature of the smelting is preferably above 1640°C, more preferably 1650-1660°C. In the present invention, the smelting is preferably carried out in a non-vacuum induction furnace.

[0023] In the present invention, after the smelting, the obtained crude molten steel is preferably subjected to slag removal. In the present invention, the slag removal is preferably carried out in a tundish. In the present invention, the amount of residue in the molten steel is preferably <2.5kg / t, more preferably <2.0kg / t.

[0024] After obtaining the molten steel, the present invention mixes the molten steel with a first slag, performs vacuum oxygen blowing decarburization, and obtains a first molten steel. In the present invention, the first slag comprises metallurgical lime, secondary fluorite blocks, and aluminum ingots. In the present invention, according to the proportion of the first slag to the molten steel, the addition amount of the first slag comprises: 10-16 kg / t of metallurgical lime, 1.0-2.5 kg / t of secondary fluorite blocks, and 1-1.5 kg / t of aluminum ingots.

[0025] In the present invention, the bottom blowing gas of the VODC furnace vacuum oxygen blowing decarburization is argon; the flow rate of the argon gas at the bottom of the VODC furnace is controlled at 5-8m 3 / h, the vacuum degree of VODC furnace is maintained at 70-110 mbar.

[0026] The present invention closely observes the changes in vacuum degree, exhaust gas temperature, cooling water temperature and oxygen pressure during the vacuum oxygen blowing decarburization process, and ensures a stable reaction in the furnace by adjusting the vacuum degree, oxygen gun height, oxygen blowing flow rate, bottom blowing argon flow rate and oxygen pressure.

[0027] In the present invention, the total amount of oxygen used in the vacuum oxygen blowing decarburization process is preferably obtained according to Formula I: O used =O total ×M w , Formula I; In the formula I, O used It is the total amount of oxygen used in the argon-oxygen mixed blowing decarburization process of the VODC refining furnace under vacuum, in Nm 3 ;O total Oxygen consumption per ton of steel, in Nm 3 / t, calculated by formula II; M w is the weight of molten steel, in t; O total =1 / eta×[9.31×(C1-C2)+7.98×Si1+6.22×A1]+3.22×(Cr1-Cr2), formula II; In the formula II, eta is oxygen release, and its value is 0.75; C1 is the initial carbon content by mass percentage; C2 is the final carbon content by mass percentage; Si1 is the initial silicon content by mass percentage; A1 is the initial aluminum content by mass percentage; Cr1 is the initial chromium content by mass percentage; and Cr2 is the expected chromium content by mass percentage.

[0028] After obtaining the first molten steel, the present invention performs vacuum carbon deoxidation on the first molten steel to obtain the second molten steel. In the present invention, the VODC refining furnace process is used for production, and the vacuum carbon deoxidation stage can be directly performed without breaking the air after vacuum oxygen blowing decarburization, thereby improving the degassing efficiency of the molten steel and shortening the smelting cycle.

[0029] In the present invention, the vacuum degree of the vacuum carbon deoxidation is less than 5 mbar, the bottom blowing gas of the vacuum carbon deoxidation is argon, and the bottom blowing argon flow rate is controlled at 5-8m 3 / h, and the control time of the vacuum carbon deoxidation is 7-10min, more preferably 9-10min.

[0030] The present invention closely observes the parameter changes of vacuum degree, cooling water temperature, exhaust gas temperature and argon gas flow rate during the vacuum carbon deoxidation process to ensure the temperature of molten steel and the reduction effect of molten steel.

[0031] After obtaining the second molten steel, the present invention mixes the second molten steel with the second slag and performs vacuum degassing to obtain the third molten steel. In the present invention, the second molten steel is preferably degassed before mixing with the second slag.

[0032] In the present invention, after obtaining the second molten steel, it is preferred to first measure the temperature of the second molten steel. When the temperature of the second molten steel is ≥1650°C, the temperature is not raised; when the temperature of the second molten steel is <1650°C, the temperature is raised. In the present invention, the heating is preferably performed by vacuum aluminothermic heating. In the present invention, the vacuum degree of the vacuum aluminothermic heating is 300-400 mbar, the bottom blowing gas of the vacuum aluminothermic heating must be argon, and nitrogen must not be used. The bottom blowing argon flow rate of the VODC refining furnace is controlled at 5-8m 3 / h;

[0033] In the present invention, the amount of oxygen used to burn aluminum during the vacuum aluminothermic method is preferably calculated by formula III; O' total =0.62×m Al , Formula III; In the formula III, O' total The amount of oxygen used to burn aluminum during the vacuum aluminothermic process, in Nm 3 ;m Al is the mass of aluminum added, in kg; 0.62 is the coefficient, in Nm 3 / kg.

[0034] In the present invention, after the second molten steel is heated, it is preferred that vacuum degassing is directly performed without breaking the vacuum.

[0035] In the present invention, the second slag includes lime, fluorite, a reducing agent and aluminum. In the present invention, according to the proportion of the second molten steel, the addition amount of the second slag preferably includes: 20-28 kg / t of low-carbon metallurgical lime, 2.0-3.5 kg / t of secondary fluorite block, 6-8 kg / t of VODC furnace-specific reducing agent, and 2.5-4.5 kg / t of aluminum ingot; more preferably includes: 25-28 kg / t of low-carbon metallurgical lime, 3.0-3.5 kg / t of secondary fluorite block, 7-8 kg / t of VODC furnace-specific reducing agent, and 4-4.5 kg / t of aluminum ingot. In the present invention, the VODC furnace-specific reducing agent preferably includes low-aluminum ferrosilicon.

[0036] In the present invention, after adding the second slag, alloy is preferably added according to the sampling result to meet the chemical composition requirements of the 4J36 steel ingot.

[0037] In the present invention, the vacuum degree of the vacuum degassing is preferably <5 mbar, more preferably 2-3 mbar; the bottom blowing gas of the vacuum degassing is preferably argon, and the bottom blowing argon gas flow rate is preferably controlled at 5-8 mbar. 3 / h, more preferably 6-8m 3 / h.

[0038] After obtaining the third molten steel, the present invention performs a ladle weak argon stirring treatment on the third molten steel to obtain a fourth molten steel. In the present invention, the ladle weak argon stirring treatment time is 15 to 25 minutes, preferably 22 to 25 minutes. In the present invention, the argon flow rate during the ladle weak argon stirring treatment is preferably adjusted to 1 to 2.5 Nm 3 / h, more preferably 1.0-1.5Nm 3 / h. The present invention is conducive to the floating of inclusions in the steel through the calming, and can further reduce the total oxygen content of the molten steel.

[0039] After obtaining the fourth molten steel, the present invention pours the fourth molten steel to obtain a 4J36 steel ingot. In the present invention, the pouring preferably uses a fully enclosed argon protection device. In the present invention, the argon pressure of the mold casting argon closed system is preferably controlled at above 0.7MPa, and more preferably above 0.9MPa. In the present invention, the pouring start temperature is 1520±10℃, preferably 1510~1520℃. In the present invention, the pouring speed is preferably 0.8-2.0 tons / minute, and more preferably 1.2-1.4 tons / minute.

[0040] In the present invention, protective slag and exothermic agent are added during the pouring process. In the present invention, the amount of protective slag used is 1.0-1.5kg / t, preferably 1.0-1.2kg / t. In the present invention, the protective slag is preferably a special ultra-low carbon mold casting protective slag; in terms of mass percentage, the main components of the special ultra-low carbon mold casting protective slag preferably include Al2O3 (13.7%), C (0.2%), CaO (26.6%), SiO2 (45.2%), H2O (0.25%). By using special ultra-low carbon mold casting protective slag, the present invention can control the carbon intake of molten steel during the pouring process to ≤25ppm.

[0041] In a specific embodiment of the present invention, the composition and performance of the special silicon high-efficiency heat-generating agent are shown in Table 1. In the present invention, the dosage of the special silicon high-efficiency heat-generating agent is 2.5-3.0kg / t; the method of adding the heat-generating agent includes: after the cap mouth is filled with the fourth molten steel to a height greater than two-thirds, 40-60% of the heat-generating agent is added, and the remaining heat-generating agent is added before the end of pouring. More preferably, after the cap mouth is filled with the fourth molten steel to a height greater than two-thirds, 50% of the heat-generating agent is added, and the remaining heat-generating agent is added before the end of pouring. The present invention controls the dosage of the heat-generating agent within the above range, advances the actual control point of addition, can improve the heating effect, reduce the shrinkage compensation of the ingot riser, and reduce the riser shrinkage holes.

[0042] Table 1 Main components and properties of silicon-based high-efficiency heating agent Inspection items Test results Inspection items Test results Inspection items Test results Si 68.25wt% Calorific value kJ / kg 13500 <![CDATA[Body density g / cm 3 > 1.95 <![CDATA[Na2O]]> 9.11wt% Moisture 0.5wt% Maximum combustion temperature ℃ 1920 <![CDATA[Fe2O3]]> 20.23wt% other 1.91wt% 38 minutes of holding temperature 1250 In the present invention, the chemical composition of the 4J36 steel ingot is preferably as shown in Table 2.

[0043] Table 2 Chemical composition of 4J36 steel ingot, mass percentage C% Si% Mn% S% P% Cr% Ni% Cu% Al% Fe% 0.018-0.03 0.40~0.70 1.10~1.50 ≤0.005 ≤0.02 ≤0.2 35~37 ≤0.50 0.35~0..50 margin As% Sn% Sb% Bi% Pb% Mo% Co% N H O ≤0.01 ≤0.01 ≤0.0025 ≤0.001 ≤0.001 ≤0.3 ≤0.08 <70ppm <1.5ppm <45ppm The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example 1 1. Non-vacuum induction furnace melting scrap steel process The non-vacuum induction furnace uses all-scrap steel smelting. High-nickel scrap steel and high-chromium scrap steel are heated by induction coils. The scrap steel is dissolved and allowed to be tapped after reaching 1655°C. The molten steel is then poured into the tundish.

[0045] 2.VODC molten steel refining process 2.1. Pulling slag After the crude molten steel comes out of the furnace, the slag removal operation is carried out in the tundish, and the slag amount of the molten steel is <2.0kg / t.

[0046] 2.2. Steel After the molten steel is poured into the VODC furnace, samples are taken to measure the temperature, and slag is added: 11kg / t of metallurgical lime, 1.2kg / t of secondary fluorite blocks, and 1.3kg / t of aluminum ingots.

[0047] 2.3.VOD (Vacuum Oxygen Decarburization) The vacuum degree is 100mbar, and the bottom blowing argon flow rate is controlled at 5~6m 3 / h. After the oxygen blowing is completed, VCD (vacuum carbon deoxidation) operation is carried out directly without breaking the air.

[0048] The total oxygen consumption in the VOD stage is obtained according to Formula I: O used =O total ×M w , Formula I; In the formula I, O used It is the total amount of oxygen used in the argon-oxygen mixed blowing decarburization process of the VODC refining furnace under vacuum, in Nm 3 ;O total Oxygen consumption per ton of steel, in Nm 3 / t, calculated by formula II; M w is the weight of molten steel, in t; O total=1 / eta×[9.31×(C1-C2)+7.98×Si1+6.22×A1]+3.22×(Cr1-Cr2), formula II; In the formula II, eta is oxygen release, and its value is 0.75; C1 is the initial carbon content by mass percentage; C2 is the final carbon content by mass percentage; Si1 is the initial silicon content by mass percentage; A1 is the initial aluminum content by mass percentage; Cr1 is the initial chromium content by mass percentage; and Cr2 is the expected chromium content by mass percentage.

[0049] 2.4.VCD (Vacuum Carbon Deoxidation) Vacuum degree <4 mbar, bottom blowing argon flow rate controlled at 5~6m 3 / h.

[0050] VCD processing time is 10 minutes.

[0051] 2.5.VOH (vacuum aluminum thermal heating) After VCD, the vacuum was broken and the temperature was measured. The temperature of the molten steel was 1660℃ and no VOH operation was required.

[0052] 2.6.VD (vacuum degassing) After VCD is completed, the vacuum is broken and slag is added: 22kg / t low-carbon metallurgical lime, 3.0kg / t secondary fluorite block, 7.5kg / t reducing agent low-aluminum ferrosilicon, 4.0kg / t aluminum ingot, and the alloy is supplemented according to the sampling results to adjust the steel liquid composition.

[0053] After VOH, the vacuum is not broken and VD operation is performed directly.

[0054] VD stage parameters: vacuum degree is 2mbar, bottom blowing argon flow rate is controlled at 5.0m 3 / h.

[0055] 2.7. Steel placement After VD is completed, temperature measurement and sampling are carried out. When the composition enters the control range and the temperature is ≥ the pouring temperature + 70℃, a steel release signal is issued; The ladle should be fully baked before lifting, and the slide device should be installed and adjusted to ensure it is well installed.

[0056] After the ladle is in place, it is connected to argon gas, checked to make sure there are no leaks in the pipeline, and then hoisted into the pit.

[0057] Turn on the argon gas before placing the steel. Pay attention to the surface of the molten steel during the placing process and adjust the argon gas flow rate to prevent the molten steel from being exposed.

[0058] 3. Pouring process: 3.1. Adjust the argon flow rate to 1.4Nm before pouring 3 / h, and conduct weak argon stirring treatment in the ladle for 22 minutes to make the inclusions float fully; 3.2. After the quenching is completed, the ladle outlet is aligned with the bell mouth of the center pouring pipe for pouring. A fully enclosed argon protection device is used during pouring. The argon pressure is controlled at 0.9MPa and the molten steel temperature is 1510℃, and the pouring operation is carried out; 3.3. When pouring, start pouring fully, start to collect the protective slag when it falls, control the pouring speed of the main body at 1.3 tons / minute, and the riser shrinkage time (time for pouring the riser) should be greater than 2 / 3 of the time for pouring the ingot body to ensure good shrinkage compensation.

[0059] 3.4. The protective slag adopts special ultra-low carbon mold casting protective slag, which is added in a hanging manner at a rate of 1.2kg / t to ensure that the slag surface does not show redness or crust; 3.5. After the steel liquid is filled to more than two-thirds of the cap mouth, add 2.5kg / t of special high-efficiency heat-generating agent of silicon. When the pouring is almost finished, add another 2 kg / t of heat-generating agent to obtain 4J36 steel ingot.

[0060] Example 2 The preparation method is basically the same as that in Example 1, the only difference is that the mold casting start temperature is adjusted from 1510°C to 1520°C, the pouring process is smooth, and there is no leakage or flashing during the pouring rising process. The calibrated pouring nitrogen addition amount is 6ppm, and the control level is good.

[0061] Test Case (1) The 4J36 steel ingot products prepared in Example 1 and Example 2 have good surface quality and are free of defects such as slag pits, pinholes, and cracks.

[0062] (2) The chemical composition of the 4J36 steel ingots prepared in Example 1 and Example 2 both meet the technical marking requirements, with an average carbon content of 180 ppm.

[0063] (3) The gas content control level of the 4J36 steel ingots prepared in Example 1 and Example 2 is good, with an average oxygen content of 27 ppm, an average nitrogen content of 65 ppm, and an average hydrogen content of 1.2 ppm.

[0064] In this document, terms such as "up", "down", "front", "back", "left", "right", "top", "bottom", "inside", "outside", "vertical", and "horizontal" indicate directions or positional relationships, which are only used to express the technical solution clearly and for the convenience of description, and therefore should not be understood as limitations of the present invention.

[0065] In this document, the terms "comprises," "comprising," or any other variations thereof, are intended to cover a non-exclusive inclusion of elements other than those listed and may also include additional elements not expressly listed.

[0066] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for producing 4J36 steel ingots using a VODC refining furnace, characterized in that: The steps include: According to the chemical composition of 4J36 steel ingot, alloy scrap steel is smelted to obtain alloy steel liquid; The alloy steel liquid is mixed with a first slag material, and subjected to argon-oxygen mixed blowing and decarburization under vacuum in a VODC refining furnace to obtain a first steel liquid; the first slag material comprises metallurgical lime, secondary fluorite blocks and aluminum ingots; The first molten steel is subjected to deep carbon deoxidation in a VODC refining furnace to obtain a second molten steel; The second molten steel and the second slag are mixed and dehydrogenated and denitrified in a VODC refining furnace to obtain a third molten steel; the second slag comprises low-carbon metallurgical lime, secondary fluorite blocks, a VODC furnace-specific reducing agent and aluminum ingots; The third molten steel is subjected to ladle weak argon stirring treatment to remove inclusions in the molten steel, and then calmed to obtain a fourth molten steel; the calming time is 15-25 minutes; The fourth molten steel is cast in a protective atmosphere to obtain an iron-nickel alloy 4J36 steel ingot.

2. The method for producing 4J36 steel ingots using a VODC refining furnace according to claim 1, characterized in that: The pouring temperature of the protective atmosphere pouring is 1520±10°C; special ultra-low carbon mold casting protection slag and special silicon high-efficiency heating agent are added in the protective atmosphere pouring; the amount of the protection slag is 1.0-1.5kg / t; the main chemical composition of the special ultra-low carbon mold casting protection slag is Al2O 3： 13.7%, C: 0.2%, CaO: 26.6%, SiO2: 5.2%; the main chemical components of the special high-efficiency heating agent for silicon are Si: 68%, Na2O: 9%, Fe2O3: 20%.

3. The dosage of the special silicon high-efficiency heating agent is 2.5-3.0 kg / t; the method for adding the special silicon high-efficiency heating agent includes: After the fourth molten steel is added to the cap mouth to a height greater than two-thirds, add 40-60% of the special silicon high-efficiency heating agent, and add the remaining special silicon high-efficiency heating agent before the end of pouring.

4. The method for producing 4J36 steel ingots using a VODC refining furnace according to claim 1, characterized in that: The addition amount of the first slag material in the alloy steel liquid is: 10-16 kg / t of metallurgical lime, 1.0-2.5 kg / t of secondary fluorite block, and 1-1.5 kg / t of aluminum ingot.

5. The method for producing 4J36 steel ingots using a VODC refining furnace according to claim 1, characterized in that: The bottom blowing gas for decarburization in the VODC refining furnace under vacuum is argon, and the argon flow rate is controlled at 5-8m 3 / h, the vacuum degree of VODC refining furnace is maintained at 70-110 mbar.

6. The method for producing 4J36 steel ingots using a VODC refining furnace according to claim 1, characterized in that: The total amount of oxygen used in the argon-oxygen mixed blowing decarburization process of the VODC refining furnace under vacuum is obtained according to Formula I: O used =O total ×M w , formula I; In the formula I, O used It is the total amount of oxygen used in the argon-oxygen mixed blowing decarburization process of the VODC refining furnace under vacuum, in Nm 3 ;O total Oxygen consumption per ton of steel, in Nm 3 / t, calculated by formula II; M w is the weight of molten steel, in t; O total =1 / eta×[9.31×(C1-C2)+7.98×Si1+6.22×A1]+3.22×(Cr1-Cr2), formula II; In the formula II, eta is oxygen release, and its value is 0.75; C1 is the initial carbon content by mass percentage; C2 is the final carbon content by mass percentage; Si1 is the initial silicon content by mass percentage; A1 is the initial aluminum content by mass percentage; Cr1 is the initial chromium content by mass percentage; and Cr2 is the expected chromium content by mass percentage.

7. The method for producing 4J36 steel ingots using a VODC refining furnace according to claim 1, characterized in that: After the VODC refining furnace carries out decarburization by argon-oxygen mixed blowing under vacuum, vacuum carbon deoxidation is directly carried out; the vacuum degree of the vacuum carbon deoxidation is less than 5 mbar, the bottom blowing gas of the vacuum carbon deoxidation is argon, and the argon flow rate is controlled at 5-8m 3 / h, and the control time of the vacuum carbon deoxidation is 7-10min.

8. The method for producing 4J36 steel ingots using a VODC refining furnace according to claim 1, characterized in that: When the temperature of the second molten steel is ≥1650° C., the temperature is not increased; when the temperature of the second molten steel is <1650° C., the temperature is increased.

9. The method for producing 4J36 steel ingots using a VODC refining furnace according to claim 7, characterized in that: The second molten steel is heated by vacuum aluminothermic method, the vacuum degree of vacuum aluminothermic method is 300-400 mbar, the bottom blowing gas of vacuum aluminothermic method is argon, and the flow rate of argon is controlled at 5-8m 3 / h; The amount of oxygen used to burn aluminum during the vacuum aluminothermic method is calculated by formula III; O' total =0.62×m Al , Formula III; In the formula III, O' total The amount of oxygen used to burn aluminum during the vacuum aluminothermic process, in Nm 3 ;m Al is the mass of aluminum added, in kg; 0.62 is the coefficient, in Nm 3 / kg.

10. The method for producing 4J36 steel ingots using a VODC refining furnace according to claim 1, characterized in that: The addition amount of the second slag in the second molten steel is: 20-28 kg / t of low-carbon metallurgical lime, 2.0-3.5 kg / t of secondary fluorite block, 6-8 kg / t of VODC furnace special reducing agent, and 2.5-4.5 kg / t of aluminum ingot.

11. The method for producing 4J36 steel ingots using a VODC refining furnace according to claim 1, characterized in that: When the fourth molten steel is cast in a protective atmosphere, the amount of nitrogen introduced into the molten steel during the mold casting process is ≤9ppm; The amount of the special ultra-low carbon mold casting protection slag added in the protective atmosphere casting is 1.2kg / t, and the carbon content of the molten steel in the mold casting process is ≤50ppm; The special high-efficiency heating agent added in the protective atmosphere pouring is a silicon high-efficiency heating agent, and the dosage is 3.0-3.5 kg / ton; The prepared iron-nickel alloy 4J36 steel ingot has an oxygen content of ≤45ppm, a nitrogen content of ≤70ppm, and a carbon content of ≤250ppm.