Smelting process of nickel-chromium-iron-based alloy

Abstract

The invention discloses a smelting process of a nickel-chromium-iron-based alloy, which comprises the following steps of: smelting and pouring a cast ingot by adopting an EAF (Electric Arc Furnace)-LF (Ladle Furnace)-VOD (Vacuum Oxygen Decarburization) furnace-LF (Ladle Furnace)-die casting process route, carrying out VOD vacuum oxygen decarburization by utilizing coarse smelting molten steel obtained by full scrap steel smelting in the electric arc furnace, and using nitrogen in the LF furnace to replace nitrided chromium iron to increase nitrogen. The desulfurization and deoxidation control parameters of each furnace are optimized, and finally the yield of Cr is controlled to be 99% or above and the yield of C is controlled to be 0.025% or below through a VOD oxygen blowing decarburization model; according to an LF furnace nitrogen increasing model, the nitrogen content of molten steel is accurately controlled, meanwhile, oxygen in the molten steel is controlled to be 0.003% or below, other chemical components meet the standard requirements, and the problem that the nickel-chromium-iron-based alloy is smelted through an electric arc furnace, and key elements cannot be accurately controlled is solved.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a smelting process of a nickel-chromium-iron based alloy. Background Art

[0002] Nickel-chromium-iron corrosion-resistant high-temperature alloy has good resistance to stress corrosion and pitting corrosion due to its high Ni and Cr content. It is widely used in photovoltaics, energy storage, power generation, petrochemicals and other fields. The medium and thick plates with a thickness of more than 40 mm used for the core cylinder plates of photovoltaic storage equipment have long relied on imports from Japan and the United States.

[0003] At present, the main process used in smelting high-chromium-nickel corrosion-resistant high-temperature alloys is vacuum induction furnace smelting. Vacuum induction furnace smelting has high requirements on furnace charge and requires pure materials, which is costly. The present invention adopts a smelting method of scrap steel → electric furnace smelting → LF furnace → VOD furnace → LF furnace → die casting to produce flat ingots, which provides convenience for the subsequent flat ingots to be directly rolled into plates. On the one hand, it provides raw materials with high purity, and on the other hand, it can effectively utilize existing equipment, reduce production costs, and improve production efficiency. Summary of the invention

[0004] The purpose of the present invention is to provide a smelting process of nickel-chromium-iron-based alloy, which removes gas and decarburizes raw materials through vacuum refining in the early stage; in the later stage, nitrogen content in steel is accurately controlled by nitrogen addition through nitrogen blowing from the bottom of the ladle, and the refining slag system is configured to ensure the deoxidation and desulfurization effect of the deinclusion agent, so as to obtain a flat ingot with high purity and meet the high quality requirements of raw materials for medium and thick plate rolling.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: A nickel-chromium-iron based alloy, the chemical composition of which is optimized based on the requirements of SB-409 in ASME SecII PartB: the change of chemical composition directly affects the comprehensive performance of the material. For this alloy, the alloy content is high, the amount of alloy added is large, and the material is required to have good purity, good plasticity and toughness, so the requirements for harmful elements such as S, P, H, O and gas elements are relatively strict. The optimized chemical composition is composed of the following components in mass percentage: C: 0.04-0.10; Si: ≤1.0; Mn: 0.40-0.90; P: ≤0.025; S: ≤0.005; Ni: 35.5-39.0; Cr: 24.0-27.0; Co: 0.38-0.47; Al: ≤0.15; Nb: 0.50-0.70; gas elements [H]: ≤0.0003; [O]: ≤0.0030; [N]: 0.16-0.25; the remainder is Fe and unavoidable impurities.

[0006] The smelting process route of the nickel-chromium-iron-based alloy is: EAF electric arc furnace smelting → LF furnace adjustment → VOD furnace vacuum oxygen blowing decarburization → LF furnace nitrogen blowing nitrogen addition, deoxidation, desulfurization → die casting. The specific steps are as follows: 1) EAF electric arc furnace smelting EAF electric arc furnace scrap steel smelting, the scrap steel is 2535NB return material accounting for 60% (mass fraction) + N08810 return material accounting for 20% (mass fraction), the remaining furnace charges are metallic chromium and electrolytic nickel, electrolytic cobalt alloy for adjusting the composition, 15-20kg / t of lime and 3-5kg / t of fluorite are added to the furnace bottom before adding materials, argon is used to stir the molten pool composition and temperature after the charge is melted, 1-2kg of ferrosilicon powder is added to reduce the Cr in the slag according to the amount of 1 ton of molten steel, the composition of molten steel, mass proportion: C0.40-0.60%, P≤0.025%, Si≤0.30%, Mn≤0.8%, Cr22.0-25.0%, Ni35.0-37.0%, the remaining elements do not exceed the control range, the temperature is 1640-1660℃, and the steel is tapped (the slag is tapped at the same time).

[0007] 2) LF furnace adjustment The molten steel from the EAF arc furnace in the previous step enters the LF furnace for heating, and electrolytic nickel, metallic chromium and electrolytic cobalt are added in sequence to adjust the composition; at the same time, 1.0-1.5kg / t of C powder and 0.5kg / t of aluminum particles are used for diffusion deoxidation, and lime and fluorite are added appropriately according to the slag conditions to adjust the composition of the molten steel, by mass: C0.40-0.65%, P≤0.025%, Si≤0.30%, Mn≤0.80%, Cr25.0-26.0%, Ni36.5-37.2%, Co0.38-0.45%, and the remaining elements do not exceed the control range. The temperature is 1640-1670℃, and the ladle is hoisted to the slag removal area for slag removal, and the slag removal requirement is more than 90%.

[0008] 3) VOD vacuum oxygen decarburization The ladle is hoisted to the VOD vacuum tank with a temperature of 1590-1610℃ and a free space of 800-1200mm. The vacuum tank cover is closed and vacuum is drawn. Pre-oxygen blowing: When the vacuum degree reaches 25kPa, the oxygen gun is set 1200m away from the steel liquid surface and oxygen blowing is started. The oxygen flow rate is 350Nm 3 / h~450Nm 3 / h, argon flow rate 60NL / min~80NL / min, vacuum degree stabilized to 25-20kPa; main oxygen blowing: when the oxygen blowing amount reaches the theoretical calculation to blow out silicon and aluminum in the molten steel and blow carbon to 0.25%, the oxygen gun is lowered to 1100m from the steel liquid surface, the vacuum degree is reduced to 15kPa, and the oxygen flow rate is 450Nm 3 / h~550Nm 3 / h, argon flow rate 60NL / min~80NL / min, vacuum degree stabilized to 15-10kPa; slow oxygen blowing: lower the oxygen gun to 1050m from the steel liquid surface, reduce the vacuum degree to 8kPa, oxygen flow rate 550Nm 3 / h~450Nm 3 / h, argon flow rate 70NL / min~90NL / min, vacuum degree stabilized to 8-2kPa; when oxygen concentration potential E→0, and the tail gas temperature dropped significantly from the highest value (inflection point), CO, CO 2 After the concentration reaches the intersection point, stop blowing oxygen; continue to evacuate to less than 67Pa, maintain pressure for 15 minutes for vacuum carbon deoxidation, and the argon flow rate in this stage is 70-80NL / min; reduction: after breaking the air, the Ar flow rate is 60-80L / min, and the reduction slag is added: pre-melted slag 5kg / t, high-quality lime 17kg / t, fluorite 5kg / t, deoxidizer Al cake 6kg / t, CaSi block 2kg / t, industrial silicon 1kg / t, and niobium iron alloy is added according to the Nb content requirements to adjust the Nb content in the molten steel to the specified range of the component weight percentage. The vacuum tank cover is evacuated to less than 67Pa and the pressure is maintained for 20 minutes. After the whole process is completed, the C element content of the molten steel is less than 0.025%, and the ladle is hoisted to the slag removal area to remove the slag and enter the LF furnace.

[0009] 4) LF nitrogen blowing to increase nitrogen, deoxidize and desulfurize The ladle enters the LF furnace, nitrogen is blown from the bottom of the ladle, 10kg / t of pre-melted slag, 6kg / t of lime, 3kg / t of fluorite are added to make slag, 1kg / t of aluminum particles and 1kg / t of calcium silicon powder are added in batches for diffusion deoxidation, nitrogen addition: nitrogen flow rate 50Nm 3 / h, nitrogen addition rate 0.0030% / min, temperature control range 1580-1620℃, nitrogen is added to the specified range of component weight percentage in combination with the initial nitrogen content of molten steel, nitrogen blowing is stopped and switched to argon; after the slag forms grayish white or white, it is kept for more than 30 minutes, and calcium treatment is carried out by feeding silicon calcium wire at 2m / t; ferroboron is added according to the mass ratio of 0.005% of the molten steel, argon flow rate 30-40NL / min, soft blowing ≥20min, all element compositions meet the weight percentage of each component, temperature 1480-1500℃; 5) Mold casting: lift the ladle to the pouring station and use the ladle car for pouring.

[0010] In the vacuum oxygen blowing decarburization step of the VOD furnace, when the carbon blowing of the main oxygen is up to 0.25%, the oxygen amount is 50% of the total theoretical oxygen blowing amount.

[0011] In the LF nitrogen blowing, deoxidation and desulfurization steps, the added ferroboron is wrapped with iron sheets and inserted into the molten steel.

[0012] In the vacuum oxygen decarburization step of the VOD furnace, the process of evacuating the vacuum to less than 67Pa and maintaining the pressure for 20 minutes is divided into two stages: the argon flow rate is 70-90L / min in the first 10 minutes and the argon flow rate is 20-40L / min in the second 10 minutes.

[0013] Beneficial effects of the invention: The purpose of the invention is to provide a preferred composition and smelting process of a nickel-chromium-iron-based alloy, wherein the nickel-chromium-iron-based corrosion-resistant high-temperature alloy is smelted by using an EAF furnace + LF furnace + VOD furnace + LF furnace. During the smelting process, each element can be precisely controlled and in place, and the smelting qualified rate reaches more than 98%; the temperature of the molten steel is controlled at 1590-1610°C before entering the VOD furnace, and heat is released by the chemical reaction of the VOD furnace. The temperature of the molten steel after the VOD furnace can reach 1680°C. After the VOD furnace, reducing slag can be added to the molten steel at high temperature for reduction and deoxidation, thereby effectively controlling the C content not to exceed the standard; the VOD furnace is pre-oxygenated , main oxygen blowing, slow oxygen blowing. By adjusting the oxygen lance height, oxygen flow, argon flow and vacuum degree, the C element can reach a minimum of 0.008% after smelting in the VOD furnace, and the oxidation of Cr element is small. Through vacuum reduction, the Cr recovery rate reaches more than 98%, not only the C element meets the standard requirements, but also reduces the oxidation of Cr element. The nitrogen blowing method at the bottom of the ladle is used to increase nitrogen instead of adding ferrochrome nitride, which can not only reduce the addition of ferrochrome nitride and avoid too fast cooling of molten steel, but also solve the problem of excessive carbon content caused by electrode power supply and carbon increase, and nitrogen instead of ferrochrome nitride can significantly reduce the smelting cost. Through the nitrogen increase model, the nitrogen increase accuracy is high. DETAILED DESCRIPTION

[0014] The present invention is further described in detail below.

[0015] A nickel-chromium-iron-based alloy contains the following components in weight percentage: C: 0.04-0.10; Si: ≤1.0; Mn: 0.40-0.90; P: ≤0.025; S: ≤0.005; Ni: 35.5-39.0; Cr: 24.0-27.0; Co: 0.38-0.47; Al: ≤0.15; Nb: 0.50-0.70; gas elements [H]: ≤0.0003; [O]: ≤0.0030; [N]: 0.16-0.25; the balance is Fe and unavoidable impurities.

[0016] A smelting process of a nickel-chromium-iron-based alloy, wherein the chemical composition of the alloy steel meets the above requirements, and the nickel-chromium-iron-based alloy is prepared by adopting an EAF electric arc furnace smelting → LF furnace adjustment → VOD furnace vacuum oxygen blowing decarburization → LF furnace nitrogen blowing nitrogen addition, deoxidation, desulfurization → die casting process route to smelt and pour flat steel ingots to form square billets; the specific steps are as follows: 1) EAF electric arc furnace smelting The charge is calculated based on the amount of 30t of molten steel in one furnace. The EAF electric arc furnace is used for scrap steel smelting. The scrap steel is 2535NB return material accounting for 60% + N08810 return material accounting for 20%. The remaining charges are metal chromium and electrolytic nickel and electrolytic cobalt alloys for adjusting the composition. Before adding the charge, 450kg of lime and 90kg of fluorite are added to the bottom of the furnace. After the charge is melted, argon is used to stir the molten pool composition and temperature. 30kg of ferrosilicon powder is added to reduce the Cr in the slag to increase the alloy recovery rate. The composition of molten steel is C0.48%, P0.019%, Si0.25%, Mn0.47%, Cr24.0%, Ni36.9%, and the remaining elements do not exceed the control range. The temperature is 16658℃, and the steel is tapped (the slag is tapped at the same time).

[0017] 2) LF furnace adjustment The molten steel from the EAF electric arc furnace enters the LF furnace mainly for temperature increase and composition adjustment; at the same time, 30kg of C powder and 15kg of aluminum particles are added in three batches for diffusion deoxidation, and 100kg of lime and 20kg of fluorite are added appropriately according to the slag conditions. The order of alloy addition is electrolytic nickel, metallic chromium, and electrolytic cobalt; the composition of molten steel is C0.54%, P0.020%, Si0.28%, Mn≤0.80%, Cr25.0-26.0%, Ni36.5-37.2%, Co0.38-0.45%, and the remaining elements do not exceed the control range. The temperature is 1668℃, and the ladle is hoisted to the slag removal area to remove the slag, and the slag removal is more than 90%.

[0018] 4) VOD vacuum oxygen decarburization The ladle is hoisted to the VOD vacuum tank with a temperature of 1610℃ and a free space of 1050mm. The vacuum tank cover is closed to evacuate the air. Pre-oxygen blowing: When the vacuum degree reaches 25kPa, the oxygen gun is set 1200m away from the steel liquid surface and oxygen blowing is started. The oxygen flow rate is 350Nm 3 / h~450Nm 3 / h, argon flow rate 70NL / min, vacuum degree stabilized to 25-20kPa; main oxygen blowing: when the oxygen blowing amount reaches the theoretical calculation to blow out silicon, aluminum and carbon to 0.25% in the molten steel (50% of the total theoretical oxygen blowing amount), the oxygen gun is lowered to 1100m from the steel liquid surface, the vacuum degree is reduced to 15kPa, and the oxygen flow rate is 450Nm 3 / h~550Nm 3 / h, argon flow rate 70NL / min, vacuum degree stabilized to 15-10kPa; slow oxygen blowing: lower the oxygen gun to 1050m from the steel liquid surface, reduce the vacuum degree to 8kPa, oxygen flow rate 550Nm 3 / h~450Nm 3 / h, argon flow rate 80NL / min, vacuum degree stabilized to 8-2kPa; when oxygen concentration potential E→0, and the tail gas temperature dropped significantly from the highest value (inflection point), CO, CO 2After the concentration reaches the intersection point, stop blowing oxygen; continue to evacuate to 11Pa, maintain pressure for 15 minutes for vacuum carbon deoxidation, and the argon flow rate in this stage is 70NL / min; reduction: after breaking the air, the Ar flow rate is 80L / min, and the reduction slag is added: 150kg of pre-melted slag, 510kg of high-quality lime, 150kg of fluorite, 180kg of deoxidizer Al cake, 60kg of CaSi block, 30kg of industrial silicon, and 150kg of niobium iron alloy is added according to the Nb content requirements to adjust the Nb content in the molten steel to 0.62%. Close the vacuum tank cover and evacuate to 11Pa, and maintain pressure for 20 minutes (argon flow rate is 80L / min for the first 10 minutes, and 20L / min for the last 10 minutes). After the whole process is completed, the C element content of the molten steel is 0.013%, and the ladle is hoisted to the slag removal area to remove the slag and enter the LF furnace.

[0019] 4) LF nitrogen blowing to increase nitrogen, deoxidize and desulfurize Molten steel enters the LF furnace ladle bottom and nitrogen is blown. 300kg of pre-melted slag, 180kg of lime, and 90kg of fluorite are added to make slag. 30kg of aluminum particles and 30kg of calcium silicon powder are added in batches for diffusion deoxidation. Nitrogen increase: nitrogen flow rate 50Nm 3 / h, nitrogen addition rate 0.0030% / min, temperature control range 1580-1620℃, combined with the initial nitrogen content of molten steel of 0.0512% to increase nitrogen to 0.2327%, nitrogen consumption 58Nm 3 , nitrogen utilization rate 72%, stop blowing nitrogen and switch to argon. After the slag forms grayish white or white, keep it for more than 30 minutes, and feed silicon calcium wire at 60m for calcium treatment. Add ferroboron (wrapped in iron sheet, inserted into molten steel) 6kg. Argon flow rate 30-40NL / min, soft blowing ≥20min. All element composition C0.056%; Si0.39%; Mn0.58%; P0.016; S0.0009; Ni37.2%; Cr24.8%; Co0.42%; Al0.042%; Nb0.61%; gas elements [H] 0.0003%; [O] 0.0027%; [N] 0.2098%, temperature 1492℃, hang the ladle to the pouring station and pour the ladle car.

[0020] By adopting the above smelting method, the C content of the material obtained after VOD is 0.013%, Cr: 25.0%, and the other elements also meet the requirements. Not only does C meet the requirements but also leaves space for the subsequent LF electrode carbon increase. Moreover, the Cr recovery rate is 99.2%, which meets the expected requirements. By blowing nitrogen through the nitrogen increase model, the nitrogen content of the molten steel can be accurately controlled, and there is no need to add nitrided chromium iron. The final steel composition is C0.056%; Si0.39%; Mn0.58%; P0.016; S0.0009; Ni37.2%; Cr24.8%; Co0.42%; Al0.042%; Nb0.61%; gas elements [H]0.0003%; [O]0.0027%; [N]0.2105%, and all the components meet the standard requirements.

[0021] After the alloy ingot obtained by the method of the present invention is subjected to hot working and forming heat treatment, two groups of samples are taken for performance testing, including room temperature yield strength (Rp0.2), tensile strength (Rm) and elongation (A), 590℃ high temperature yield strength (Rp0.2), hardness (HBW), grain size, intergranular corrosion test, and the performance meets and exceeds the standard requirements. The test results are as follows: The first group of samples: room temperature yield strength (Rp0.2) is 365MPa, tensile strength (Rm) is 720MPa and elongation (A) is 51%, 590℃ high temperature yield strength (Rp0.2) is 182MPa, hardness (HBW) is 170, grain size is 3.5, intergranular corrosion is carried out by ferrous sulfate-sulfuric acid solution method, and the average corrosion rate is 0.083mm / a; The second group of samples: room temperature yield strength (Rp0.2) is 360MPa, tensile strength (Rm) is 722MPa and elongation (A) is 51%, 590℃ high temperature yield strength (Rp0.2) is 185MPa, hardness (HBW) is 171, grain size is 3.5, intergranular corrosion is carried out by ferrous sulfate-sulfuric acid solution method, and the average corrosion rate is 0.086mm / a.

[0022] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A smelting process for a nickel-chromium-iron-based alloy, containing the following components by weight percentage: C: 0.04-0.10; Si: ≤1.0; Mn: 0.40-0.90; P: ≤0.025; S: ≤0.005; Ni: 35.5-39.0; Cr: 24.0-27.0; Co: 0.38-0.47; Al: ≤0.15; Nb: 0.50-0.70; gas elements [H]: ≤0.0003; [O]: ≤0.0030; [N]: 0.16-0.25; the balance is Fe and unavoidable impurities, characterized in that: The process route of the N08120 corrosion-resistant high-temperature alloy is: EAF electric arc furnace smelting→LF furnace adjustment→VOD furnace vacuum oxygen blowing decarburization→LF furnace nitrogen blowing nitrogen addition, deoxidation, desulfurization→die casting.

2. The smelting process of a nickel-chromium-iron-based alloy according to claim 1, characterized in that: The specific steps of the process route are as follows: 1) EAF electric arc furnace smelting EAF electric arc furnace scrap steel smelting, scrap steel is 2535NB return material accounting for 60% + N08810 return material accounting for 20%, the rest of the charge is metal chromium and electrolytic nickel, electrolytic cobalt for adjusting the composition, before adding lime 15-20kg / t, fluorite 3-5kg / t added to the bottom of the furnace, after the charge is melted, argon is used to stir the molten pool composition and temperature, according to the amount of 1-2kg per ton of molten steel, ferrosilicon powder is added to reduce the Cr in the slag, the composition of the molten steel, the mass proportion is: C0.40-0.60%, P≤0.025%, Si≤0.30%, Mn≤0.8%, Cr22.0-25.0%, Ni35.0-37.0%, the other elements do not exceed the control range, the temperature is 1640-1660℃, and the slag is discharged together; 2) LF furnace adjustment The molten steel from the EAF arc furnace in the previous step enters the LF furnace for heating, and electrolytic nickel, metallic chromium, and electrolytic cobalt are added in sequence to adjust the composition; at the same time, C powder 1.0-1.5kg / t and aluminum particles 0.5kg / t are used for diffusion deoxidation, and lime and fluorite are added appropriately according to the slag conditions to adjust the composition of the molten steel, by mass: C0.40-0.65%, P≤0.025%, Si≤0.30%, Mn≤0.80%, Cr25.0-26.0%, Ni36.5-37.2%, Co0.38-0.45%, and the remaining elements do not exceed the control range. The temperature is 1640-1670℃, and the ladle is hoisted to the slag removal area to remove the slag, and the slag removal requirement is more than 90%; VOD furnace vacuum oxygen decarburization The ladle is hoisted to VOD, the vacuum tank temperature is 1590-1610℃, the free space of the ladle is 800-1200mm, and the vacuum tank cover is closed to evacuate; pre-oxygen blowing: when the vacuum degree reaches 25kPa, the oxygen gun is set 1200m away from the steel liquid surface, and oxygen blowing begins, with an oxygen flow rate of 350Nm 3 / h~450Nm 3 / h, argon flow rate 60NL / min~80NL / min, vacuum degree stabilized to 25-20kPa; main oxygen blowing: when the oxygen blowing amount reaches the theoretical calculation to blow out silicon and aluminum in the molten steel and blow carbon to 0.25%, the oxygen gun is lowered to 1100m from the steel liquid surface, the vacuum degree is reduced to 15kPa, and the oxygen flow rate is 450Nm 3 / h~550Nm 3 / h, argon flow rate 60NL / min~80NL / min, vacuum degree stabilized to 15-10kPa; slow oxygen blowing: lower the oxygen gun to 1050m from the steel liquid surface, reduce the vacuum degree to 8kPa, oxygen flow rate 550Nm 3 / h~450Nm 3 / h, argon flow rate 70NL / min~90NL / min, vacuum degree stable to 8-2kPa; When the oxygen concentration difference potential E→0, and the tail gas temperature drops significantly from the highest value (an inflection point appears), and the CO and CO2 concentrations intersect, stop blowing oxygen; continue to evacuate to less than 67Pa, maintain the pressure for 15 minutes for vacuum carbon deoxidation, and the argon flow rate in this stage is 70-80NL / min; Reduction: after breaking the air, the Ar flow rate is 60-80L / min, and the reducing slag is added: pre-melted slag 5kg / t, lime 17kg / t, fluorite 5kg / t, deoxidizer Al cake 6kg / t, CaSi block 2kg / t, industrial silicon 1kg / t, and niobium iron alloy is added according to the Nb content requirements to adjust the Nb in the molten steel to the specified range of the weight percentage of the component in claim 1. The vacuum tank cover is closed and the vacuum is less than 67Pa, and the pressure is maintained for 20 minutes. After the whole process is completed, the C element content in the molten steel is less than 0.025%, and the ladle is lifted to the slag removal area to remove the slag; 4) LF furnace nitrogen blowing to increase nitrogen, deoxidize and desulfurize The ladle enters the LF furnace, nitrogen is blown from the bottom of the ladle, 10kg / t of pre-melted slag, 6kg / t of lime, 3kg / t of fluorite are added to make slag, 1kg / t of aluminum particles and 1kg / t of calcium silicon powder are added in batches for diffusion deoxidation, nitrogen addition: nitrogen flow rate 50Nm 3 / h, nitrogen addition rate 0.0030% / min, temperature control range 1580-1620℃, nitrogen addition to the initial nitrogen content of molten steel to the specified range of component weight percentage in claim 1, stop blowing nitrogen and switch to argon; keep the slag in gray or white color for more than 30 minutes, feed calcium silicon wire at 2m / t for calcium treatment; Add ferroboron at a mass ratio of 0.005% to the molten steel, with an argon flow rate of 30-40NL / min, soft blowing for ≥20min, and all element compositions meet the weight percentage of each component in claim 1, and the temperature is 1480-1500℃; 5) Mold casting: lift the ladle to the pouring station and use the ladle car for pouring.

3. A smelting process for a nickel-chromium-iron-based alloy according to claim 2, characterized in that: In the vacuum oxygen blowing decarburization step of the VOD furnace, when the carbon blowing of the main oxygen is up to 0.25%, the oxygen amount is 50% of the total theoretical oxygen blowing amount.

4. A smelting process for a nickel-chromium-iron-based alloy according to claim 2, characterized in that: In the LF nitrogen blowing, deoxidation and desulfurization steps, the added ferroboron is wrapped with iron sheets and inserted into the molten steel.

5. The smelting process of a nickel-chromium-iron-based alloy according to claim 2, characterized in that: In the vacuum oxygen decarburization step of the VOD furnace, the process of evacuating the vacuum to less than 67Pa and maintaining the pressure for 20 minutes is divided into two stages: the argon flow rate is 70-90L / min in the first 10 minutes and the argon flow rate is 20-40L / min in the second 10 minutes.