Smelting method for reducing gas content in Ti and Al-containing iron-nickel base alloy

Abstract

The present invention relates to a smelting method for reducing the gas content in an iron-nickel-based alloy containing Ti and Al. The present invention reasonably selects the order of adding materials and metallurgical process parameters, increases the slag making in the furnace and the solidification control under the vacuum state after the ingot is poured, and optimizes the vacuum induction melting (VIM) process, effectively deoxidizes and denitrifies, reduces the O, N, and H gas content in the steel ingot, and combines the selection of vacuum consumable remelting (VAR) or protective atmosphere electroslag remelting (PESR) and other remelting and refining processes to make the oxygen content in the alloy 20ppm, the nitrogen content ≤50ppm, the hydrogen content ≤1ppm, and the total non-metallic inclusion content not more than 1.5 levels. The alloy has low gas content and high purity, can be used to manufacture high-end equipment parts in the fields of nuclear power, petroleum, chemical industry, aviation, aerospace, etc., and can realize large-scale engineering production.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of iron-nickel based alloy materials, and in particular relates to a smelting method for reducing gas content in an iron-nickel based alloy containing Ti and Al. Background Art

[0002] The gas elements in metals were originally defined as three interstitial phase elements: oxygen (O), nitrogen (N), and hydrogen (H), which exist in solid and molten metal systems in the form of solutions and residual phase inclusions.

[0003] Age-hardened iron-nickel alloys usually contain strengthening elements such as titanium (Ti) and aluminum (Al). These active elements have a strong affinity with O and N, and are prone to generate non-metallic inclusions such as TiN, AlN, Ti(CN) and Al2O3. Among them, nitride inclusions are difficult to remove even after subsequent remelting due to their high hardness, high melting point and irregular shape. While reducing the metallurgical quality of the alloy, it will cause a decrease in the overall performance of the material, and the alloy may fail in advance when used in special application environments after being formed into parts, affecting the operating energy efficiency and safety of the device and complete set of equipment. Therefore, reducing the content of O, N and H elements in iron-nickel alloys as much as possible through advanced metallurgical equipment, reasonable composition design and smelting methods has become an important and long-term research direction for improving the overall performance of materials.

[0004] At present, iron-nickel alloys usually choose to use one or more combinations of smelting equipment such as electric furnace (EAF) + external refining (argon oxygen decarburization refining AOD, air oxygen decarburization VOD), vacuum induction melting (VIM), electroslag remelting (ESR), vacuum consumable remelting (VAR) to obtain the ingots required for subsequent processing based on performance requirements and comprehensive consideration of factors such as cost.

[0005] Among them, VIM+PSER, VIM+VAR and VIM+VAR+PESR are the main smelting methods for low gas content and high purity steel.

[0006] VIM can prevent the melt from contacting with O, N, and H in the atmosphere. Electromagnetic stirring can not only make the melt uniform, but also continuously bring the reactants to the melt and vacuum interface, so that the subsequent refining reaction can proceed smoothly. However, due to a certain degree of component segregation, the metal yield is low. Therefore, it is often used in combination with ESR, PESR or VAR.

[0007] VAR uses the heat energy of a DC arc to remelt the metal consumable electrode layer by layer in a low-pressure atmosphere and cool and solidify the molten steel in turn. The smelting process removes relatively stable non-metallic inclusions such as Al2O3 and Ti(C,N) by flotation, and the remaining non-metallic inclusions are broken and evenly distributed on the cross-section of the solidified ingot, reducing the dissolved gases such as hydrogen, nitrogen and carbon dioxide in the alloy.

[0008] PESR relies on the resistance heat generated by the slag to form a slag pool. The consumable electrode is inserted into the slag and gradually melts. It gathers into molten droplets and falls through the slag pool into the metal molten pool. Due to the forced cooling of the crystallizer, the liquid metal gradually solidifies into an electroslag ingot. Since the gas has different solubility in solid metal and liquid metal, the supersaturated gas is discharged from the solid phase to the liquid phase during the solidification process, and bubbles are formed along the crystallization front. The gas solubility in the slag pool is higher than that in the molten steel, so it can absorb the floating bubbles, which is conducive to the removal of gas. Compared with ESR, this process can effectively reduce the entry of O and N elements in the atmosphere into the metal molten pool because the smelting process is carried out in a protective atmosphere and combined with constant melting rate control.

[0009] The combination of the above three methods can reduce the O, N, and H contents in the ingot to varying degrees. However, due to the unreasonable reasons such as the feeding elements, the discharge method, the feeding sequence, the process flow, the selection of the remelting slag material, and the unreasonable metallurgical parameters, the O content in the smelted Ti and Al iron-nickel-based alloy is as high as 40ppm, the N content is as high as 80ppm, and the H content is as high as 2ppm, which is significantly different from similar products at home and abroad. Although there have been many process attempts in the deoxidation and denitrification smelting methods of nickel-based alloys in China, compared with the present invention, there is a need to select raw materials with low gas content or multiple smelting + refining to increase the process links and manufacturing costs, long-term ultra-high temperature refining and standing lead to aggravated erosion of the refractory lining, increased oxide inclusions and slag inclusions, and the transformation of the furnace body or crucible equipment does not have universality and other disadvantages, resulting in the current market. There is no large-scale engineering production that can meet the special environment O≤20ppm, N≤50ppm, H≤1ppm, and the total content of non-metallic inclusions is not greater than 1.5. The alloy material. Summary of the invention

[0010] In view of the problems described in the background technology, the present invention proposes a smelting method for reducing the gas content in Ti- and Al-containing iron-nickel-based alloys. The method can make the oxygen content in the alloy 20ppm, the nitrogen content ≤50ppm, the hydrogen content ≤1ppm, and the total content of non-metallic inclusions not greater than level 1.5. The alloy has low gas content and high purity, and can be used to manufacture bellows, wave springs, grids, instrument valves, sensors or other parts with requirements for strength, elasticity, and corrosion resistance for high-end equipment in the fields of nuclear power, petroleum, chemical industry, aviation, aerospace, etc. The method of the present invention can realize large-scale engineering production.

[0011] The technical solution described in the present invention is:

[0012] When the gas O content in the product is required to be ≤15ppm, the N content is ≤40ppm, and the H content is ≤1ppm, a smelting method (VIM+VAR) for reducing the gas content in the Ti and Al-containing iron-nickel base alloy comprises the following steps:

[0013] 1) Vacuum Induction Melting (VIM)

[0014] Take various smelting raw materials according to the alloy composition, take slag material, the smelting raw materials are baked at 300℃ for more than 12h, and the slag material is baked at 800℃ for more than 6h;

[0015] Take the baked Ni, Cr, (Mo), 1 / 3 of C and Fe, slowly heat and melt them under vacuum, after all are melted, heat to 1580-1620℃ for refining, time ≥30min, film formation for 30-60min, stir for 5min, add a small Al and the remaining 2 / 3 of C, heat to 1520-1550℃, evacuate to vacuum degree>2Pa, film formation for 30-60min, stir for 30min;

[0016] Take the second type of small materials Si, Mn, Ti, Nb and slag making materials, heat to 1520-1550℃, vacuum degree>2Pa, time≥30min, film formation for 30-60min, stir for 45min;

[0017] Take three kinds of small materials FeB20 and FeV50, vacuum degree>2Pa, adjust the molten steel temperature to 1480℃~1500℃, pour ingots with a diameter of φ200mm~400mm, vacuum degree of the mold chamber ≤20MPa, ingot cooling time>4h, and obtain the cast billet;

[0018] 2) Vacuum consumable remelting (VAR)

[0019] Step 1) After the ingot is sanded and surface-finished, it is arc-heated and melted in a vacuum environment to form a molten pool; then the arc-starting current is gradually reduced to the working current (stable smelting current), and the melting rate is maintained constant, and the average rate is controlled at 2.5-5.0 kg / min; before remelting is completed, it is switched to current control, and the current is gradually reduced to 40% of the working current for shrinkage compensation, and cooled and allowed to stand to obtain a φ270mm-350mm consumable remelting ingot.

[0020] The finished vacuum consumable remelting steel ingot obtained by the VIM+VAR method has an O content of ≤10ppm, a nitrogen content of ≤40ppm, and a hydrogen content of ≤1ppm.

[0021] When the product requires that the gas O content is ≤20ppm, the N content is ≤50ppm, and the H content is ≤1ppm, the smelting method for reducing the gas content in the Ti and Al-containing iron-nickel base alloy adopts VIM+PESR, which includes the following steps:

[0022] 1) Vacuum Induction Melting (VIM)

[0023] Take slag material for slag making, and take various smelting raw materials according to the alloy composition. The smelting raw materials are baked at 300℃ for more than 12h, and the slag material is baked at 800℃ for more than 6h;

[0024] Take Ni, Cr, (Mo), 1 / 3 of C and Fe, slowly melt them under vacuum, after all are melted, heat up to 1580-1620℃ for refining, time ≥30min, film formation for 30-60min, stir for 5min, add a small material of Al and the remaining 2 / 3 of C, heat up to 1520-1550℃, evacuate to vacuum degree>2Pa, film formation for 30-60min, stir for 30min;

[0025] Take the second type of small materials Si, Mn, Ti, Nb and slag making materials, heat to 1520-1550℃, vacuum degree>2Pa, time≥30min, film formation for 30-60min, stir for 45min;

[0026] Take three kinds of small materials FeB20 and FeV50, vacuum degree>2Pa, adjust the molten steel temperature to 1480℃~1500℃, pour ingots with a diameter of φ200mm~400mm, vacuum degree of the mold chamber ≤20MPa, ingot cooling time>4h, and obtain the cast billet;

[0027] 2) Protective atmosphere electroslag furnace (PESR)

[0028] Step 1) The surface of the cast blank is sanded and polished to obtain the consumable electrode rod required for PESR; the consumable electrode rod is welded to the dummy electrode, and a circular plate of the same material as the consumable electrode is used as an arc starting plate, CaF2, Al2O 3、 CaO and MgO are used as pre-melted slag, arcing and slag formation are carried out in the crystallizer, and the remelting speed is controlled at 2.5-4.0 kg / min. Heat shrinkage is performed before the end, and the shrinkage current decrease rate is 0.0007-0.0015 KA / S. After cooling and standing, an electroslag remelting ingot is obtained.

[0029] The finished electroslag remelting steel ingot obtained by the VIM+PESR method has an O content of ≤15ppm, a nitrogen content of ≤50ppm, and a hydrogen content of ≤1ppm.

[0030] The weight percentage of each component in the alloy is C≤0.08%, Si≤1.0%, Mn≤0.8%, Ni40.0%-55.0%, Cr 4.8%-22.0%, Mo≤3.3%, Nb≤5.5%, Ti 0.5%-3.0%, Al 0.2%-1.0%, FeB20≤0.08%, FeV50≤0.015%, impurity element O≤0.05%, N≤0.02%, S≤0.002%, P≤0.003%, Co≤0.1%, Cu≤0.20%; Ta≤0.04%, Fe balance.

[0031] Step 1) The slag-making material is composed of CaO, SiO2, Fe2O3, and MgO, and the mass ratio of each component is: CaO: SiO2: Fe2O3: MgO = 50-70: 10-20: 10-25: 5-10;

[0032] A better technical solution is that the CaO:SiO2:Fe2O3:MgO=50:20:20:10.

[0033] The slow melting in step 1) is as follows: the heating power is increased from 450 kW to 550 kW by 50 kW every half an hour.

[0034] The stirring in step 1) is performed for 5 minutes every 5 minutes.

[0035] Step 2) The heating and melting method is to obtain the consumable electrode rod required for VAR by finishing and concentrically welding it with the dummy electrode, set the working current to 18 to 22 times the diameter of the crystallizer (in millimeters), start the arc with a vacuum degree of ≤0.5Pa, and the arc starting current is 30% of the working current; 1 to 2 minutes after arc starting, increase the current to 1.1 times the working current to form a molten pool, and gradually reduce the current to the working current; then keep the melting speed constant, and control the average rate at 2.5 to 5.0 kg / min; switch to current control before remelting is completed, and gradually reduce the current to 40% of the working current for shrinkage compensation.

[0036] When the gas content O in the product is required to be ≤10ppm, the N content is ≤30ppm, and the H content is ≤1ppm, a smelting method (VIM+VAR+PESR) for reducing the gas content in the Ti and Al-containing iron-nickel-based alloy comprises the following steps:

[0037] 1) VIM

[0038] Take various smelting raw materials according to the alloy composition, take slag material, the smelting raw materials are baked at 300℃ for more than 12h, and the slag material is baked at 800℃ for more than 6h;

[0039] Take the baked Ni, Cr, (Mo), 1 / 3 of C and Fe, slowly heat and melt them under vacuum, after all are melted, heat to 1580-1620℃ for refining, time ≥30min, film formation for 30-60min, stir for 5min, add a small Al and the remaining 2 / 3 of C, heat to 1520-1550℃, evacuate to vacuum degree>2Pa, film formation for 30-60min, stir for 30min;

[0040] Take the second type of small materials Si, Mn, Ti, Nb and slag making materials, heat to 1520-1550℃, vacuum degree>2Pa, time≥30min, film formation for 30-60min, stir for 45min;

[0041] Take three kinds of small materials FeB20 and FeV50, vacuum degree>2Pa, adjust the molten steel temperature to 1480℃~1500℃, pour ingots with a diameter of φ200mm~400mm, vacuum degree of the mold chamber ≤20MPa, ingot cooling time>4h, and obtain the cast billet;

[0042] 2) VAR

[0043] Step 1) After the ingot is sanded and finished, it is heated and melted in a vacuum environment to form a molten pool; then the arc starting current is gradually reduced to the working current (stable smelting current), the melting rate is maintained constant, and the average rate is controlled at 2.5-5.0 kg / min; before the remelting is completed, it is switched to current control, and the current is gradually reduced to 40% of the working current for shrinkage compensation, cooled and allowed to stand, to obtain a φ270mm-350mm consumable remelting steel ingot. It is necessary to adopt (PESR preparation, that is, adding PESR on the basis of VIM+VAR, specific method: Step 2) The consumable remelting steel ingot is finished to obtain the consumable electrode rod required for PESR; the consumable electrode rod is welded to the dummy electrode, and a circular plate of the same material as the consumable electrode is used as the arc starting plate, CaF2, Al2O 3、 CaO and MgO are used as pre-melted slag (the purity of each component of the slag is greater than 98.5%, the total content of unstable oxide impurities such as manganese oxide, ferrous oxide and silicon dioxide is less than 0.5%, and the particle size is less than 50 mesh), arcing slag is started in the crystallizer, the remelting speed is 2.5-4.0 kg / min, smelting is performed, hot shrinkage is performed before the end, the shrinkage current decrease rate is 0.0007-0.0015 KA / S, and the electroslag remelting ingot is obtained after cooling and standing.

[0044] The finished electroslag remelting steel ingot obtained by VIM+VAR+PESR has an O content of ≤6ppm, a nitrogen content of ≤30ppm, and a hydrogen content of ≤1ppm.

[0045] The method of the present invention is used to produce Ti and Al-containing iron-nickel-based alloy ingots. Compared with conventional VIM smelting, denitrification and deoxidation are carried out by reasonably selecting the feeding sequence (timing of adding small materials) and metallurgical process parameters (control of solution temperature, refining and stirring time, etc.), and processes such as solidification control under vacuum state after slag making in the furnace and ingot pouring (the process of the ingot changing from liquid to solid, by slowly solidifying under vacuum state, oxygen and nitrogen absorption during the solidification process is prevented) are added to prevent the ingot from secondary oxygen and nitrogen absorption during the solidification process, so as to ensure that the method of the present invention can effectively deoxidize and denitrify, significantly reduce the O, N, H gas content in the ingot, reduce the number of non-metallic inclusions such as TiN, AlN, Ti(CN) and Al2O3, and lay a good foundation for subsequent VAR and PESR further purification. The method described in the present application is a process of secondary remelting and refining in a vacuum atmosphere for VAR and an inert atmosphere for PESR, which uses automation to accurately and stably control the melting rate, which can further reduce the content of harmful gas elements in the steel ingot, making the remelting process more stable and controllable, and controlling the gas element content within the range of O≤20ppm, N≤50ppm, H≤1ppm, and the total content of non-metallic inclusions within the range of no more than 1.5. The fluctuation value of the gas element content at the head and tail of the steel ingot in the same furnace is

[0046] ±0.0002%, and the fluctuation value between furnaces is ≤0.0005%. The method of the present invention can reasonably and flexibly select the smelting method according to the needs of product performance, such as VIM+VAR, VIM+PESR, VIM+VAR+

[0047] PESR and other combinations can effectively control the content of O, N, and H elements in the alloy without adding proprietary equipment to the existing production equipment, and obtain alloys that meet the composition requirements and have a small number of non-metallic inclusions, small size, and uniform distribution (see Figures 1-2 ), fine and dense structure, good surface quality, less segregation (see Figures 3-4 ) ingots ensure the efficiency and economy of engineering mass production, which is conducive to industrial promotion.

[0048] The method of the present invention can be widely applied to the production of nickel-based high-temperature alloys, heat-resistant steels, precision alloys and other similar materials. The prepared alloy steel ingots with low gas content and high purity can be used to manufacture key components of high-end equipment in many fields such as nuclear power, automobiles, aerospace, etc., which is of great significance to improving the service life, operating accuracy and reliability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is the non-metallic inclusion morphology of the product produced by the method of Example 1 of the iron-nickel-based alloy containing Ti and Al (specification is φ170mm×L=2500mm); -100X;

[0050] Figure 2 It is the non-metallic inclusion morphology of the product produced by the method of Example 2 of the iron-nickel-based alloy containing Ti and Al (specification is φ130mm×L=1800mm); -100X;

[0051] Figure 3 Non-metallic inclusion morphology of the product produced by the method of Example 3 in the iron-nickel-based alloy containing Ti and Al (specifications are φ48mm×L=1000mm); -100X;

[0052] Figure 4 The non-metallic inclusion morphology of the product produced by the method of Example 4 in the iron-nickel-based alloy containing Ti and Al (specification: φ140mm×L=1500mm); -100X;

[0053] Figure 5 This is a macrostructure of a product produced by the method of Example 1 using an iron-nickel-based alloy containing Ti and Al (specifications are φ170mm×L=2500mm);

[0054] Figure 6 This is the macrostructure of the product produced by the method of Example 2 of the iron-nickel-based alloy containing Ti and Al (specification is φ130mm×L=1800mm);

[0055] Figure 7 This is the macrostructure of the product produced by the method of Example 3 containing Ti and Al iron-nickel base alloy (specification is φ48mm×L=1000mm)

[0056] Figure 8 This is a macrostructure of a product produced by the method of Example 4 using an iron-nickel-based alloy containing Ti and Al (specifications are φ140mm×L=1500mm); DETAILED DESCRIPTION

[0057] The present invention will be further described below, but the present invention is not limited to the scope of the embodiments described.

[0058] According to the ratio described in Table 1, take the components described in the present invention and prepare the material described in the present invention according to the following method:

[0059] Table 1 Chemical composition of each element (wt%)

[0060] Element Name scope Alloy component 1 Alloy component 2 C ≤0.08％ 0.03 0.03 Si ≤1.0％ / 0.4 Mn ≤0.8％ / 0.4 Ni 40.0％～55.0％ 52.5 42.6 Cr 4.8％～22.0％ 19.0 5.4 Mo ≤3.3％ 3.0 / Nb ≤5.5％ 5.1 / Ti 0.5％～3.0％ 0.95 2.6 Al 0.2％～1.0％ 0.55 0.7 FeB20 ≤0.08％ 0.08 0.015 FeV50 ≤0.015％ 0.01 / Fe margin margin margin

[0061] Example 1

[0062] Take the above components according to the ratio of alloy component 1 in Table 1, bake at 300℃ for 12 hours, mix 60kg of slag material in the ratio of CaO:SiO2:Fe2O3:MgO=50:20:20:10, and bake at 800℃ for 6 hours; put Ni, Cr, Mo, 1 / 3 of C and Fe as bulk materials into the crucible of the furnace in sequence, evacuate to ensure that the vacuum degree is better than 20Pa, and then slowly melt from 450kw to 550kw in a step-by-step power supply mode of increasing 50kw every half an hour. After all the raw materials are melted, power is supplied to 1580~1620℃, and evacuate to a vacuum degree better than 5Pa for ≥30min, then the power is turned off for 30~60min, and the film is stirred for 5min every 5min with 200kw power frequency. After filling with argon at 3KPa, add the first type of small material Al and the remaining 2 / 3 of C in sequence, raise the temperature to 1520-1550℃, evacuate until the vacuum degree is better than 2Pa, then turn off the power and congeal for 30-60min, during which time, stir for 5min with 200kw power frequency every 5min, and the total time is 30min. After filling with argon at 3KPa, add the second type of small material Ti, Nb and slag-making material in sequence, raise the temperature to 1520-1550℃, evacuate until the vacuum degree is better than 2Pa, the time is ≥30min, then turn off the power and congeal for 30-60min, during which time, stir for 5min with 200kw power frequency every 5min, and the total time is 45min. After filling with argon at 3KPa, three types of small materials, FeB20 and FeV50, are added. The composition and content of the alloy are adjusted by testing and analysis. During the period, the vacuum degree is kept better than 2Pa, and then stirred for 5 minutes at an industrial frequency every 5 minutes. When the composition is qualified, O≤15ppm, N content≤50ppm, and the molten steel temperature is adjusted to 1480℃~1500℃, an ingot with a diameter of φ210mm is cast under electric casting. At the same time, the vacuum degree of the mold chamber is kept less than or equal to 20MPa. The ingot is cooled in the mold chamber for 6 hours and then lifted out of the mold to obtain a vacuum consumable electrode rod.

[0063] The obtained φ210mm consumable electrode rod is sanded to remove the oxide scale and defects on the surface of the steel ingot. After sanding, the diameter of the steel ingot is φ200mm; the bottom of the consumable electrode rod is connected to the dummy electrode, and the concentricity is ensured during welding. The arc is started with a crystallizer diameter of φ270mm and a vacuum degree of ≤0.5Pa, and the arc starting current is 1500A; 1 minute after arc starting, the current is increased to 5500A, and after the molten pool is formed (the molten steel covers the bottom of the crystallizer), the current is gradually reduced to a working current of 5000A; then the melting rate is constant, with an average rate of about 3.0kg / min; the shrinkage and remelting ingot are fed when there is 200kg left, and the current control is switched to current control before the remelting is completed, and the current is gradually reduced to 2000A of the working current for shrinkage feeding; after the shrinkage is completed, the circulating cold water in the crystallizer is placed for cooling for 45 minutes, and the VAR consumable remelting ingot is taken out from the crystallizer.

[0064] Example 2

[0065] The following differences are the same as those in Example 1:

[0066] The φ270 mm consumable electrode rod obtained in Example 1 was sanded to remove the oxide scale and defects on the surface of the steel ingot. After sanding, the diameter of the steel ingot was φ255 mm. The bottom of the consumable electrode rod was connected to the dummy electrode to ensure concentricity during welding. A circular plate of the same material as the consumable electrode with a crystallizer diameter of φ380 mm, a thickness of 30 mm and a diameter of φ350 mm was used as an arc starting plate. 40 kg of quaternary pre-melted slag uniformly mixed in the ratio of CaF2:Al2O3:CaO:MgO=55:17:15:8 was baked at 800°C for 12 hours. h is evenly spread on the arc starting plate, the crystallizer is in a sealed argon state, the steady-state melting rate is controlled to be 3.5kg / min, the cooling water inlet temperature of the crystallizer is 20℃, the outlet temperature is 30℃, and the power reduction method is used for thermal shrinkage before the end of smelting. The shrinkage current reduction rate is 0.0015KA / S. When remelting is finished, the electrode is stopped from descending and its end is allowed to melt by itself until the electrode is exposed from the slag surface and the power is cut off when an arc occurs; after the shrinkage is finished, the circulating cold water in the crystallizer is placed for cooling for 45 minutes, and the electroslag remelted ingot is taken out from the crystallizer.

[0067] Example 3

[0068] Take the above components according to the ratio of alloy component 2 in Table 1, bake at 300℃ for 12 hours, mix 60kg of slag material in the ratio of CaO:SiO2:Fe2O3:MgO=50:20:20:10, and bake at 800℃ for 6 hours; put Ni, Cr, 1 / 3 of C and Fe as bulk materials into the crucible of the furnace in sequence, evacuate to ensure that the vacuum degree is better than 20Pa, and then slowly melt from 450kw to 550kw in a step-by-step power supply mode of increasing 50kw every half an hour. After all the raw materials are melted, power is supplied to 1580~1620℃, and evacuate to a vacuum degree better than 5Pa for ≥30min, then the power is turned off for 30~60min, and the film is stirred for 5min every 5min with 200kw power frequency. After filling with argon at 3KPa, add the first type of small material Al and the remaining 2 / 3 of C in sequence, raise the temperature to 1520-1550℃, evacuate until the vacuum degree is better than 2Pa, then turn off the power and congeal for 30-60min, during which time, stir for 5min with 200kw power frequency every 5min, and the total time is 30min. After filling with argon at 3KPa, add the second type of small materials Si, Mn, Ti and slag-making materials in sequence, raise the temperature to 1520-1550℃, evacuate until the vacuum degree is better than 2Pa, the time is ≥30min, then turn off the power and congeal for 30-60min, during which time, stir for 5min with 200kw power frequency every 5min, and the total time is 45min. After filling with argon at 3KPa, add three types of small materials FeB20, test and analyze to adjust the composition and content of the alloy, keep the vacuum better than 2Pa during the period, stir for 5 minutes at an industrial frequency every 5 minutes, and when the composition is qualified, O≤15ppm, N content≤30ppm, adjust the molten steel temperature to 1480℃~1500℃, cast an ingot with a diameter of φ220mm under electric casting, and keep the vacuum degree of the mold chamber less than or equal to 20MPa. After the ingot is cooled in the mold chamber for 6 hours, it is lifted out of the mold to obtain a vacuum consumable electrode rod.

[0069] The obtained φ220mm consumable electrode rod was sanded to remove the oxide scale and defects on the surface of the ingot. After sanding, the diameter of the ingot was φ205mm. The bottom of the consumable electrode rod was connected to the dummy electrode to ensure concentricity during welding. A circular plate of the same material as the consumable electrode with a crystallizer diameter of φ300mm, a thickness of 30mm and a diameter of φ270mm was used as the arc starting plate. 30kg of quaternary pre-melted slag well mixed in the ratio of CaF2:Al2O3:CaO:MgO=55:17:15:8 was baked at 800℃ for 12h. Evenly spread it on the arc starting plate, the crystallizer is in a sealed argon state, the steady-state melting rate is controlled at 2.8kg / min, the cooling water inlet temperature of the crystallizer is 20℃, and the outlet temperature is 30℃. Before the end of smelting, the power reduction method is used for thermal shrinkage, and the shrinkage current reduction rate is 0.001KA / S. When remelting is completed, stop lowering the electrode and let its end melt by itself until the electrode exposes the slag surface and an arc occurs, then the power is cut off; after the shrinkage is completed, place it in the circulating cold water in the crystallizer for cooling for 40 minutes, and take it out from the crystallizer to obtain the electroslag remelting ingot.

[0070] Example 4

[0071] The following differences are the same as those in Example 3:

[0072] The φ220 mm consumable electrode rod obtained in Example 3 was sanded to remove the oxide scale and defects on the surface of the steel ingot. After sanding, the diameter of the steel ingot was φ200 mm. The bottom of the consumable electrode rod was connected to the dummy electrode. Concentricity was ensured during welding. Arcing was started with a mold diameter of φ270 mm and a vacuum degree of ≤0.5 Pa. The arcing current was 1500 A. One minute after arcing, the current was increased to 5500 A. After the molten pool was formed (the molten steel covered the bottom of the crystallizer), the current was gradually reduced to a working current of 5000 A. Then the melting rate was constant, with an average rate of about 3.0 kg / min. When the remaining amount of the ingot was 200 kg, the feeding and remelting were carried out. Before the remelting was completed, the current control was switched to current control, and the current was gradually reduced to 2000 A of the working current for feeding. After the feeding was completed, the circulating cold water in the crystallizer was cooled for 45 minutes, and the VAR consumable remelting ingot was taken out from the crystallizer.

[0073] Table 2 shows the gas elements (wt%) in the alloy materials of Example 1 and Example 2

[0074] Examples O N H Example 1 0.0008 0.0036 0.00010 Example 2 0.0005 0.0028 0.00010 Example 3 0.0006 0.0018 0.00010 Example 4 0.0005 0.0013 0.00005

[0075] Table 3 shows the content of non-metallic inclusions in the alloy materials of Example 1 and Example 2 (wt%)

[0076]

[0077] The steel ingots obtained in Example 1 and Example 2 were produced into bar products according to the national standard GB / T 14999.2. After acid etching, no macroscopic defects such as cracks, shrinkage cavities, bubbles, slag inclusions, and white spots were found. Figures 3-4 shown.

[0078] From Table 2-3 and Figure 1-8 The experimental verification results shown show that the steel ingot obtained by this method has low gas content, high purity, few non-metallic inclusions, uniform and dense crystallization, and meets the requirements of O≤20ppm, N≤50ppm, H≤1ppm for special environment use, and the total content of non-metallic inclusions is not more than level 1.5.

[0079] The present invention is not limited by the above embodiments. The above embodiments and descriptions in the specification are only for illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which all fall within the scope of protection claimed by the present invention.

Claims

1. A smelting method for reducing the gas content in Ti and Al-containing iron-nickel-based alloys, characterized in that: The following steps are involved: 1) Vacuum induction melting Take slag material for slag making, and take various smelting raw materials according to the alloy composition. The smelting raw materials are baked at 300℃ for more than 12h, and the slag material is baked at 800℃ for more than 6h; Take Ni, Cr, Mo, 1 / 3 of C and Fe, slowly melt them under vacuum, after all are melted, heat up to 1580~1620℃ for refining, time ≥30min, film formation for 30~60min, stir for 5min, add a small material of Al and the remaining 2 / 3 of C, heat up to 1520~1550℃, evacuate to vacuum degree>2Pa, film formation for 30~60min, stir for 30min; Take the second type of small materials Si, Mn, Ti, Nb and slag making materials, heat to 1520~1550℃, vacuum degree>2Pa, time≥30min, film formation for 30~60min, stir for 45min; Take three kinds of small materials FeB20 and FeV50, vacuum degree>2Pa, adjust the molten steel temperature to 1480℃~1500℃, pour ingots with a diameter of φ200mm~400mm, vacuum degree of the mold chamber ≤20MPa, ingot cooling time>4h, and obtain the cast billet; 2) Vacuum consumable remelting Step 1) After the ingot is sanded and surface-finished, arc heating is started in a vacuum environment to melt and form a molten pool; then the arc starting current is gradually reduced to the working current, and the melting rate is maintained constant, and the average rate is controlled at 2.5~5.0kg / min; before remelting is completed, it is switched to current control, and the current is gradually reduced to 40% of the working current for shrinkage compensation, and cooled and allowed to stand to obtain a φ270mm~350mm consumable remelting ingot.

2. A smelting method for reducing the gas content in Ti and Al-containing iron-nickel-based alloys, characterized in that: The following steps are involved: 1) Vacuum induction melting Take slag material for slag making, and take various smelting raw materials according to the alloy composition. The smelting raw materials are baked at 300℃ for more than 12h, and the slag material is baked at 800℃ for more than 6h; Take Ni, Cr, Mo, 1 / 3 of C and Fe, slowly melt them under vacuum, after all are melted, heat up to 1580~1620℃ for refining, time ≥30min, film formation for 30~60min, stir for 5min, add a small material of Al and the remaining 2 / 3 of C, heat up to 1520~1550℃, evacuate to vacuum degree>2Pa, film formation for 30~60min, stir for 30min; Take the second type of small materials Si, Mn, Ti, Nb and slag making materials, heat to 1520~1550℃, vacuum degree>2Pa, time≥30min, film formation for 30~60min, stir for 45min; Take three kinds of small materials FeB20 and FeV50, vacuum degree>2Pa, adjust the molten steel temperature to 1480℃~1500℃, pour ingots with a diameter of φ200mm~400mm, vacuum degree of the mold chamber ≤20MPa, ingot cooling time>4h, and obtain the cast billet; 2) Protective atmosphere electroslag furnace (PESR) Step 1) The surface of the cast blank is sanded and polished to obtain the consumable electrode rod required for PESR; the consumable electrode rod is welded to the dummy electrode, and a circular plate of the same material as the consumable electrode is used as an arc starting plate, CaF2, Al2O 3、 CaO and MgO are used as pre-melted slag, arcing and slag formation are carried out in the crystallizer, and the remelting speed is controlled at 2.5~4.0kg / min. Heat shrinkage is performed before the end, and the shrinkage current decrease rate is 0.0007~0.0015KA / S. After cooling and standing, the electroslag remelting ingot is obtained.

3. The method according to claim 1 or 2, characterized in that: Step 1) The slag-making material consists of CaO, SiO2, Fe2O3, and MgO, and the mass ratio of each component is: CaO:SiO2:Fe2O3:MgO=50~70:10~20:10~25:5~10.

4. The method according to claim 3, characterized in that: The CaO:SiO2:Fe2O3:MgO=50:20:20:

10.

5. The method according to claim 1 or 2, characterized in that: Step 1) The slow melting is: the heating power starts from 450kw and increases by 50kw every half an hour to 550kw.

6. The method according to claim 1 or 2, characterized in that: The stirring in step 1) is performed for 5 minutes every 5 minutes.

7. The method according to claim 1, characterized in that: Step 2) The consumable remelting steel ingot has an O content of ≤15ppm, a nitrogen content of ≤40ppm, and a hydrogen content of ≤1ppm.

8. The method according to claim 2, characterized in that: Step 2) The O content in the protective atmosphere electroslag remelting steel ingot is ≤20ppm, the nitrogen content is ≤50ppm, and the hydrogen content is ≤1ppm.

9. The method according to claim 1, characterized in that: Step 2) The heating and melting method is to obtain the consumable electrode rod required for VAR by finishing and concentrically welding with the dummy electrode, set the working current to 18 to 22 times the diameter of the crystallizer, the unit of the crystallizer diameter is millimeter, the vacuum degree is ≤0.5Pa for arc starting, and the arc starting current is 30% of the working current; 1 to 2 minutes after arc starting, increase the current to 1.1 times the working current to form a molten pool, and gradually reduce the current to the working current; then keep the melting speed constant, with an average rate of about 3.0 kg / min; switch to current control before remelting is completed, and gradually reduce the current to 40% of the working current for shrinkage compensation.

10. The method according to claim 1, characterized in that: The method further comprises, 3) Protective atmosphere electroslag furnace (PESR) Step 2) After the consumable remelted steel ingot is surface finished, the consumable electrode rod required for PESR is obtained; the consumable electrode rod is welded to the dummy electrode, and a circular plate of the same material as the consumable electrode is used as an arc starting plate, CaF2, Al2O 3、 CaO and MgO are used as pre-melted slag, arcing slag is started in the crystallizer, the remelting speed is 2.5~4.0kg / min, smelting is performed, hot shrinkage is performed before the end, and the shrinkage current decrease rate is 0.0007~0.0015KA / S. After cooling and standing, the electroslag remelting ingot is obtained.

11. The method according to claim 10, characterized in that: The electroslag remelting steel ingot has an O content of ≤10ppm, a nitrogen content of ≤30ppm, and a hydrogen content of ≤1ppm.

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