A method for smelting Inconel 625 alloy steel ingot using VODC refining furnace

Abstract

This invention discloses a method for smelting Inconel 625 alloy steel ingots using a VODC refining furnace, comprising the following steps: melting pure alloy scrap steel as raw material according to the chemical composition of the Inconel 625 alloy steel ingot to obtain molten alloy steel; mixing the molten alloy steel with a first slag and performing argon-oxygen mixed blowing decarburization in a VODC refining furnace to obtain a first molten steel; subjecting the first molten steel to continuous vacuum carbon deoxidation in a VODC refining furnace to obtain a second molten steel; mixing the second molten steel with the second slag and performing reduction and degassing in a VODC refining furnace to obtain a third molten steel; subjecting the third molten steel to weak argon gas stirring in a ladle to remove inclusions to obtain a fourth molten steel; and casting the fourth molten steel under a protective atmosphere to obtain an Inconel 625 alloy steel ingot. This invention employs vacuum argon-oxygen combined blowing technology, vacuum carbon deoxidation technology, vacuum aluminothermic reduction technology, and closed casting technology, achieving low manufacturing costs while improving ingot quality.

Description

Technical Field

[0001] The invention relates to the technical field of alloy material preparation, and in particular to a method for smelting Inconel 625 alloy steel ingots by using a VODC refining furnace. Background Art

[0002] Inconel 625 alloy is a solid solution strengthened nickel-based deformable high-temperature alloy with molybdenum and niobium as the main strengthening elements. It has excellent corrosion resistance and oxidation resistance, good tensile and fatigue properties from low temperature to 980°C, and is resistant to stress corrosion in salt spray atmosphere. It can be widely used in the manufacture of aviation engine parts, aerospace structural components and chemical equipment, and is an indispensable material for high-end manufacturing.

[0003] The commonly used smelting processes for Inconel 625 alloy steel ingots are vacuum induction furnace + electroslag furnace, or medium frequency induction furnace + ladle refining furnace VOD, among which the vacuum induction furnace + electroslag furnace process route is used for production.

[0004] For example, the patent document with patent number 202211039544.X discloses a method for preparing Inconel 625 forgings, comprising the following steps: vacuum induction melting: adding photoelectric carbon, molybdenum bars, electrolytic nickel and metallic chromium to the furnace for smelting in sequence, controlling the vacuum exhaust valve in the furnace to exhaust the vacuum degree in the furnace to ≤50Pa, and stirring, and adding metallic niobium before the raw materials in the furnace are melted; refining: further adding aluminum blocks, titanium plates and metallic chromium to the furnace after the treatment in step S11, continuing to stir the raw materials in the furnace, measuring the temperature after the molten steel surface is calm, and controlling the temperature of the molten steel at 1590±10℃, controlling the vacuum exhaust valve in the furnace to exhaust the vacuum degree in the furnace to ≤ 10Pa, start refining, control the refining time to be 30-60min, and end refining; alloying: close the vacuum exhaust valve, add aluminum blocks and metallic titanium into the refined furnace, stir the molten steel, rush argon into the molten steel in the furnace to more than 30000Pa, add nickel-magnesium alloy, and obtain mixed molten steel; casting: adjust the treated molten steel to a temperature of 1530±10℃ and then tap the steel, and maintain vacuum after casting the electrode; cooling: demould the cast electrode after cooling; electroslag remelting: grind the electrode obtained after demoulding and then energize it for electroslag remelting to obtain electroslag ingot.

[0005] Inconel 625 alloy steel ingots require expensive metal resources, high manufacturing costs, and a long production cycle; when using the medium frequency induction furnace + ladle refining furnace VOD process route to produce Inconel 625 alloy steel ingots, although relatively cheap metal resources can be used, this process route is limited by the VOD (ladle vacuum argon oxygen composite blowing refining furnace) furnace type. The production efficiency is low, the gas content in the steel is difficult to control, and the quality stability is relatively poor.

[0006] Therefore, it is necessary to improve the above prior art to overcome the above defects. Summary of the invention

[0007] The purpose of the present invention is to provide a method for smelting Inconel 625 alloy steel ingots by using a VODC refining furnace. The VODC refining furnace is used for the production of Inconel 625 steel ingots, and a new process flow of non-vacuum induction furnace + VODC + die casting is developed. Due to the shortening of the steel ingot production cycle, the control levels of oxygen content, nitrogen content and hydrogen 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.

[0008] The above technical objectives of the present invention are achieved through the following technical solutions: A method for smelting Inconel 625 alloy steel ingot using a VODC refining furnace comprises the following steps: According to the chemical composition of Inconel 625 alloy steel ingot, pure alloy scrap steel is used as raw material for melting to obtain alloy steel liquid; The alloy steel liquid is mixed with a first slag material, and subjected to an argon-oxygen mixed blowing and decarburization operation in a VODC refining furnace to obtain a first steel liquid; the first slag material includes an alkaline slag material and a heating agent; The first molten steel is subjected to continuous vacuum carbon deoxidation in a VODC refining furnace to obtain a second molten steel; The second molten steel and the second slag are mixed, and reduced and degassed in a VODC refining furnace to obtain a third molten steel; the second slag comprises a low-carbon alkaline slag and a reducing agent; The third molten steel is subjected to a ladle weak argon stirring treatment to remove inclusions in the third molten steel, thereby obtaining a fourth molten steel; The fourth molten steel is cast in a protective atmosphere to obtain an Inconel 625 alloy steel ingot.

[0009] Furthermore, the ladle weak argon stirring treatment time is 10-18 minutes; The pouring temperature of the protective atmosphere pouring is 1500±10°C; the protective atmosphere pouring adopts a fully enclosed protective atmosphere control system; During the protective atmosphere pouring process, a special dual-phase steel mold casting protective slag is added in an amount of 1.5-2.0 kg / ton; during the protective atmosphere pouring process, a special silicon-based special high-efficiency heating agent is added in an amount of 3.0-3.5 kg / ton; After the protective atmosphere pouring is completed, a heat-insulating agent is added to the cap end, with the amount being 2.0-2.5 kg / ton.

[0010] Furthermore, the second slag material includes alkaline slag material and a temperature raising agent; The addition amount of alkaline slag in the first slag is: 10-16 kg / ton of secondary metallurgical lime and 1.0-2.5 kg / ton of secondary fluorite block; the heating agent in the first slag is: 1-1.5 kg / ton of aluminum ingot.

[0011] Furthermore, when the VODC refining furnace performs vacuum oxygen blowing decarburization, the bottom blowing gas is argon; the argon flow rate is controlled at 8-10m 3 / h, the vacuum degree of VODC refining furnace is maintained at 60-100 mbar.

[0012] Furthermore, the total amount of oxygen used in the vacuum oxygen decarburization is obtained according to Formula I: O used =O total ×M w , Formula I; In the formula I, O used is the total amount of oxygen used in the vacuum oxygen decarburization process, 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; Al is the initial aluminum content by mass percentage; Cr1 is the initial chromium content by mass percentage; Cr2 is the expected chromium content by mass percentage.

[0013] Furthermore, the VODC refining furnace directly performs vacuum carbon deoxidation after argon-oxygen mixed blowing decarburization; the vacuum degree of the vacuum carbon deoxidation is less than 6 mbar, the bottom blowing gas of the vacuum carbon deoxidation is argon, and the argon flow rate is controlled at 7-10m 3 / h, the control time of vacuum carbon deoxidation is 5-8min.

[0014] 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.

[0015] Furthermore, the heating method adopts vacuum aluminothermic method, and the heating agent adopts aluminum ingot; the vacuum degree of vacuum aluminothermic method is 320-420 mbar, the bottom blowing gas of vacuum aluminothermic method is argon, and the flow rate of bottom blowing argon in VODC refining furnace 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.

[0016] Furthermore, the second slag material includes low-carbon alkaline slag material and a reducing agent; The addition amount of the low-carbon alkaline slag is 20-28 kg / ton of low-carbon metallurgical lime, 2.0-3.5 kg / ton of secondary fluorite block, and the addition amount of the reducing agent is 2.5-4.5 kg / ton of aluminum ingot.

[0017] Furthermore, the nitrogen intake of the molten steel during the die casting process of the fully enclosed protective atmosphere control system is ≤10ppm; The dosage of the special dual-phase steel mold casting protection slag is 1.5-2.0 kg / ton; The dosage of the special silicon-based high-efficiency heating agent is 3.0-3.5 kg / ton; The dosage of the heat preservation agent is 2.0-2.5 kg / ton; The protective atmosphere casting obtains an Inconel 625 alloy steel ingot having an oxygen element of ≤60ppm, a carbon element of ≤500ppm, and a nitrogen element of ≤200ppm.

[0018] 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

[0019] 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.

[0020] The present invention proposes a production method for smelting Inconel 625 alloy steel ingots using a VODC refining furnace, comprising the following steps: According to the chemical composition requirements of the Inconel 625 alloy steel ingot 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 a ladle weak argon stirring treatment to remove inclusions in the molten steel, thereby obtaining a fourth molten steel; the ladle weak argon stirring treatment time is 10-18 minutes; The fourth molten steel is cast in a protective atmosphere to obtain an Inconel 625 alloy steel ingot; The pouring start temperature is 1435±10°C; duplex stainless steel mold casting protection slag and high-efficiency heating agent are added during the pouring process; the amount of the protection slag is 1.5-2.0 kg / ton; The dosage of the special high-efficiency heating agent is 2.5-3.0 kg / ton; the method for adding the heating 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 heating agent, and adding the remaining heating agent before the pouring is completed.

[0021] The present invention adopts alloy scrap steel as raw material for melting to obtain alloy steel liquid according to the chemical composition required by the technical standard of Inconel 625 steel ingot. 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 1635-1650°C; the smelting time is preferably 80-100 minutes. In the present invention, the tapping temperature of the smelting is preferably above 1630°C, more preferably 1635-1640°C. In the present invention, the smelting is preferably carried out in a non-vacuum induction furnace.

[0022] 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 <2.5 kg / ton, more preferably <2.0 kg / ton.

[0023] After obtaining the molten steel, the present invention mixes the molten steel with the first slag, performs vacuum oxygen blowing decarburization, and obtains the first molten steel. In the present invention, the addition amount of the first slag includes alkaline slag and a heating agent, wherein the alkaline slag includes: in proportion to the molten steel, preferably, 10-16 kg / ton of secondary metallurgical lime and 1.0-2.5 kg / ton of secondary fluorite blocks; the heating agent includes: 1-1.5 kg / ton of aluminum ingots. More preferably: 14-16 kg / ton of secondary metallurgical lime, 2.0-2.5 kg / ton of secondary fluorite blocks, and 1.5 kg / ton of aluminum ingots.

[0024] In the present invention, the bottom blowing gas for vacuum oxygen decarburization in the VODC furnace is argon; the flow rate of the bottom blowing argon in the VODC furnace is controlled to be preferably 5-8 cubic meters / hour, more preferably 7-8 cubic meters / hour, and the vacuum degree of the VODC furnace is maintained at 70-110 millibars.

[0025] 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.

[0026] 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 is the total amount of oxygen used in the vacuum oxygen decarburization process, 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; Al is the initial aluminum content by mass percentage; Cr1 is the initial chromium content by mass percentage; Cr2 is the expected chromium content by mass percentage.

[0027] 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.

[0028] In the present invention, the vacuum degree of the vacuum carbon deoxidation is <6 mbar, the bottom blowing gas of the vacuum carbon deoxidation is argon, the bottom blowing argon flow rate is controlled at 7-10 cubic meters / hour, more preferably controlled at 9-10m³ / h, and the control time of the vacuum carbon deoxidation is 5-8 minutes, more preferably controlled at 7-8 minutes.

[0029] 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.

[0030] 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.

[0031] 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 increased; when the temperature of the second molten steel is <1650°C, the temperature is increased.

[0032] In the present invention, vacuum aluminothermic method is used for heating; aluminum ingot is used as heating agent; the vacuum degree of vacuum aluminothermic method for heating is 320-420 mbar, the bottom blowing gas for heating in vacuum aluminothermic method must be argon, and nitrogen must not be used, and the bottom blowing argon flow rate of VODC refining furnace is controlled at 5-8m³ / h; 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.

[0033] In the present invention, after the second molten steel is heated, it is preferred that vacuum degassing is directly performed without breaking the vacuum.

[0034] In the present invention, the second slag includes low-carbon alkaline slag and a reducing agent. In the present invention, according to the proportion of the second molten steel, the addition amount of the second slag is as follows: the low-carbon alkaline slag includes: low-carbon metallurgical lime 20-28 kg / ton, secondary fluorite block 2.0-3.5 kg / ton, and the reducing agent includes: aluminum ingot 2.5-4.5 kg / ton. More preferably: low-carbon metallurgical lime 26-28 kg / ton, secondary fluorite block 3.0-3.5 kg / ton, aluminum ingot 3.5-4.0 kg / ton.

[0035] 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 Inconel 625 steel ingot.

[0036] 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 flow rate is preferably controlled at 5-8m³ / h, more preferably 6-8m³ / h.

[0037] After obtaining the third molten steel, the present invention subjects the third molten steel to a ladle weak argon stirring treatment to obtain a fourth molten steel. In the present invention, the time for the ladle weak argon stirring treatment is 10-18 minutes, preferably 15-18 minutes. In the present invention, the argon flow rate during the ladle weak argon stirring treatment is preferably adjusted to 1-2.5N cubic meters / hour, more preferably 1.0-1.5N cubic meters / hour. The present invention facilitates the floating of inclusions in the steel through the ladle weak argon stirring treatment, and can further reduce the total oxygen content of the molten steel.

[0038] After obtaining the fourth molten steel, the present invention pours the fourth molten steel to obtain an Inconel 625 steel ingot. In the present invention, the pouring preferably adopts 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 of the pouring is 1430±10°C, preferably 1435-1440°C. In the present invention, the pouring speed is preferably 0.2-0.26 tons / minute, and more preferably 0.2-0.23 tons / minute.

[0039] 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 1.5-2.0 kg / ton, preferably 2.0 kg / ton. In the present invention, the protective slag is preferably a special mold casting protective slag for duplex stainless steel; in terms of mass percentage, the main components of the special mold casting protective slag for duplex stainless steel preferably include Al2O3 (15.7%), C (4.5%), CaO (35.6%), SiO2 (47.5%), H2O (0.25%). In the present invention, by using the special mold casting protective slag for duplex stainless steel, the surface quality of Inconel 625 alloy steel ingot is good, without cracks, slag pits, and pore defects.

[0040] In a specific embodiment of the present invention, the composition and performance of the high-efficiency heat-generating agent are shown in Table 1. In the present invention, the preferred dosage of the high-efficiency heat-generating agent is 2.5-3.0 kg / ton, and more preferably 3.0 kg / ton; the method of adding the heat-generating agent comprises: 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 cavity.

[0041] 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 42.15wt% Calorific value kJ / kg 11000 <![CDATA[Body density g / cm 3 > 1.76 <![CDATA[Na2O]]> 13.72wt% Moisture 1wt% Maximum combustion temperature ℃ 1830 <![CDATA[Fe2O3]]> 25.98wt% other 15wt% 38 minutes of holding temperature 1200 In the present invention, the chemical composition of the Inconel 625 steel ingot is preferably as shown in Table 2.

[0042] Table 2 Chemical composition of Inconel 625 steel ingot, mass percentage C% Si% Mn% S% P% Cr% Ni% Mo% 0.035~0.055 ≤0.50 ≤0.50 ≤0.015 ≤0.015 21.5-23 ≥58 8.1~9.9 Ti Al% Cu% Fe% Nb+Ta N O ≤0.40 ≤0.40 ≤0.75 ≤5 3.2~4.1 ≤200ppm ≤60ppm 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.

[0043] Example 1 1. Non-vacuum induction furnace melting alloy scrap process The non-vacuum induction furnace uses alloy scrap steel for smelting. The high-nickel scrap steel and high-chromium scrap steel are heated by induction coils, the alloy scrap steel is dissolved and made to reach 1640℃ for steelmaking, and then the molten steel is poured into the tundish.

[0044] 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 <2.0 kg / ton.

[0045] 2.2. Steel After the molten steel is poured into the VODC furnace, samples are taken to measure the temperature, and slag is added: 15 kg / ton of secondary metallurgical lime, 2.5 kg / ton of secondary fluorite blocks, and 1.5 kg / ton of aluminum ingots.

[0046] 2.3.VOD (Vacuum Oxygen Decarburization) The vacuum degree is 100mbar, and the bottom blowing argon flow rate is controlled at 5~6 cubic meters / hour. After the oxygen blowing is completed, VCD operation is carried out directly without breaking the air.

[0047] 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 is the total amount of oxygen used in the vacuum oxygen decarburization process, 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; Al is the initial aluminum content by mass percentage; Cr1 is the initial chromium content by mass percentage; Cr2 is the expected chromium content by mass percentage.

[0048] 2.4.VCD (Vacuum Carbon Deoxidation) The vacuum degree is <4 mbar, the bottom blowing argon flow rate is controlled at 7-9 cubic meters per hour, and the vacuum carbon deoxidation treatment time is 8 minutes.

[0049] 2.5.VOH (vacuum aluminum thermite heating) After VCD, the vacuum was broken and the temperature was measured. The temperature of the molten steel was 1665℃ and no VOH operation was required.

[0050] 2.6.VD (vacuum degassing) After VCD is completed, the vacuum is broken and slag is added: 27 kg / ton of low-carbon metallurgical lime, 3.5 kg / ton of secondary fluorite block, and 3.5 kg / ton of aluminum ingot. The alloy is added according to the sampling results to adjust the composition of the molten steel.

[0051] After VOH, the vacuum is not broken and VD operation is performed directly.

[0052] VD stage parameters: vacuum degree is 2 mbar, bottom blowing argon flow rate is controlled at 5.0 cubic meters per hour.

[0053] 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.

[0054] 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.

[0055] The ladle was subjected to weak argon stirring treatment for 16 minutes, with an argon flow rate of 1.0-1.3 N m3 / h.

[0056] 3. Pouring process: 3.1. After the weak argon stirring treatment of the ladle 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 1.0MPa, the molten steel temperature is 1435℃, and the pouring operation is carried out; 3.2. When pouring, start pouring fully and let the protective slag fall and start to shrink. The pouring time of the main body is 7 minutes and the shrinkage time of the riser (the time for pouring the riser) is 5 minutes.

[0057] 3.3. The protective slag is made of duplex stainless steel die casting protective slag, which is added in a hanging manner at a dosage of 1.5 kg / ton to ensure that the slag surface does not show redness or crust; 3.4. After the molten steel is filled to more than two-thirds of the cap mouth, 3.0 kg / ton of high-efficiency heat-generating agent is added to obtain Inconel 625 steel ingot.

[0058] Example 2 The preparation method is basically the same as that of Example 1, except that the vacuum is broken after VCD and the temperature is measured, and the temperature of the molten steel is 1625°C; During VOH operation, aluminum ingots are added with heating agent to heat up by vacuum thermite method. The heat released by oxidation of 1 kg / ton of aluminum is calculated to increase by 20°C (temperature loss during oxygen blowing is not considered).

[0059] VOH stage parameters: vacuum degree 400mbar, bottom blowing argon flow rate 5.5m 3 / h.

[0060] The amount of oxygen used to burn aluminum 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.

[0061] Test Case (1) The surface quality of the Inconel 625 steel ingot products prepared in Example 1 and Example 2 is good, without cracks, slag pits, or pore defects, and the end of the cap mouth is shrunk and flat.

[0062] (2) The chemical compositions of the Inconel 625 steel ingots prepared in Example 1 and Example 2 are shown in Table 3.

[0063] Table 3 Chemical composition of Inconel 625 steel ingot, mass percentage C% Si% Mn% S% P% Cr% Ni% 0.042 0.18 0.23 0.005 0.003 21.64 60.96 Mo% Ti Al% Cu% Nb+Ta N O 8.45 0.26 0.27 0.02 3.41 195ppm 25ppm (3) The non-metallic inclusion requirements of the Inconel 625 steel ingots prepared in Example 1 and Example 2 are as follows: A+CS 1.0 grade, B+D+DsS 1.0 grade, A+B+C+D+Ds 2.0 grade according to ASTM E45A method.

[0064] 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.

[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 smelting Inconel 625 alloy steel ingot using a VODC refining furnace, characterized in that: The steps include: According to the chemical composition of Inconel 625 alloy steel ingot, pure alloy scrap steel is used as raw material for melting to obtain alloy steel liquid; The alloy steel liquid is mixed with a first slag material, and subjected to an argon-oxygen mixed blowing and decarburization operation in a VODC refining furnace to obtain a first steel liquid; the first slag material includes an alkaline slag material and a heating agent; The first molten steel is subjected to continuous vacuum carbon deoxidation in a VODC refining furnace to obtain a second molten steel; The second molten steel and the second slag are mixed, and reduced and degassed in a VODC refining furnace to obtain a third molten steel; the second slag comprises a low-carbon alkaline slag and a reducing agent; The third molten steel is subjected to a ladle weak argon stirring treatment to remove inclusions in the third molten steel, thereby obtaining a fourth molten steel; The fourth molten steel is cast in a protective atmosphere to obtain an Inconel 625 alloy steel ingot.

2. The method for smelting Inconel 625 alloy steel ingot using a VODC refining furnace according to claim 1, characterized in that: The ladle weak argon stirring treatment time is 10-18 minutes; The pouring temperature of the protective atmosphere pouring is 1500±10°C; the protective atmosphere pouring adopts a fully enclosed protective atmosphere control system; During the protective atmosphere pouring process, special dual-phase steel mold casting protection slag is added in an amount of 1.5-2.0 kg / ton; the main chemical components of the special dual-phase steel mold casting protection slag are Al2O3: 15.7%, C: 4.5%, CaO: 35.6%, and SiO2: 47.5%.

3. During the protective atmosphere pouring process, a special silicon-based high-efficiency heating agent is added in an amount of 3.0-3.5 kg / ton; the main chemical components of the special silicon-based high-efficiency heating agent are Si: 68%, Na2O: 9%, and Fe2O3: 20%.

4. After the protective atmosphere pouring is completed, add a heat-insulating agent at the cap end, with a dosage of 2.0-2.5 kg / ton.

5. The method for smelting Inconel 625 alloy steel ingot using a VODC refining furnace according to claim 1, characterized in that: The second slag material includes alkaline slag material and a temperature raising agent; The addition amount of alkaline slag in the first slag is: 10-16 kg / ton of secondary metallurgical lime and 1.0-2.5 kg / ton of secondary fluorite block; the heating agent in the first slag is: 1-1.5 kg / ton of aluminum ingot.

6. The method for smelting Inconel 625 alloy steel ingot using a VODC refining furnace according to claim 1, characterized in that: When the VODC refining furnace performs vacuum oxygen blowing decarburization, the bottom blowing gas is argon; the argon flow rate is controlled at 8-10m 3 / h, the vacuum degree of VODC refining furnace is maintained at 60-100 mbar.

7. The method for smelting Inconel 625 alloy steel ingot using a VODC refining furnace according to claim 1 or 4, characterized in that: The total amount of oxygen used in the vacuum oxygen decarburization is obtained according to Formula I: O used =O total ×M w , formula I; In the formula I, O used is the total amount of oxygen used in the vacuum oxygen decarburization process, 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; Al is the initial aluminum content by mass percentage; Cr1 is the initial chromium content by mass percentage; Cr2 is the expected chromium content by mass percentage.

8. The method for smelting Inconel 625 alloy steel ingot using a VODC refining furnace according to claim 1, characterized in that: The VODC refining furnace directly performs vacuum carbon deoxidation after argon-oxygen mixed blowing decarburization; the vacuum degree of the vacuum carbon deoxidation is less than 6 mbar, the bottom blowing gas of the vacuum carbon deoxidation is argon, and the argon flow rate is controlled at 7-10m 3 / h, the control time of vacuum carbon deoxidation is 5-8min.

9. The method for smelting Inconel 625 alloy steel ingot 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.

10. The method for smelting Inconel 625 alloy steel ingot using a VODC refining furnace according to claim 1, characterized in that: The heating method adopts vacuum aluminothermic method, and the heating agent adopts aluminum ingot; the vacuum degree of vacuum aluminothermic method is 320-420 mbar, the bottom blowing gas of vacuum aluminothermic method is argon, and the flow rate of argon gas at the bottom of VODC refining furnace 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.

11. The method for smelting Inconel 625 alloy steel ingot using a VODC refining furnace according to claim 1, characterized in that: The second slag material includes low-carbon alkaline slag material and a reducing agent; The addition amount of the low-carbon alkaline slag is 20-28 kg / ton of low-carbon metallurgical lime, 2.0-3.5 kg / ton of secondary fluorite block, and the addition amount of the reducing agent is 2.5-4.5 kg / ton of aluminum ingot.

12. The method for smelting Inconel 625 alloy steel ingot using a VODC refining furnace according to claim 2, characterized in that: The nitrogen intake of molten steel during the die casting process of the fully enclosed protective atmosphere control system is ≤10 ppm; The dosage of the special dual-phase steel mold casting protection slag is 1.5-2.0 kg / ton; The dosage of the special silicon-based high-efficiency heating agent is 3.0-3.5 kg / ton; The dosage of the heat preservation agent is 2.0-2.5 kg / ton; The protective atmosphere casting obtains an Inconel 625 alloy steel ingot having an oxygen element of ≤60ppm, a carbon element of ≤500ppm, and a nitrogen element of ≤200ppm.