A process for smelting invar alloys
By using the medium-frequency furnace → AOD → LF process route, iron-nickel alloy raw materials are used to replace pure nickel resources, which solves the problem of high production cost of Invar alloys and realizes low-cost mass production and full utilization of resources.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANXI TAIGANG STAINLESS STEEL CO LTD
- Filing Date
- 2023-06-15
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies for Invar alloy production are characterized by high production costs, low efficiency, and heavy reliance on high-grade nickel-iron resources, making mass production difficult.
The process route of medium frequency furnace → AOD → LF is adopted, and economical iron-nickel alloy raw materials are used to replace pure nickel resources. Through specific gas ratios and process flow, dephosphorization and composition adjustment are carried out to achieve low-cost smelting of Invar alloy.
This enabled low-cost mass production of Invar alloys, reduced reliance on high-grade nickel-iron resources, ensured product quality, and improved production efficiency.
Abstract
Description
Technical Field
[0001] This invention relates to the field of Invar alloy smelting technology, and in particular to a process method for smelting Invar alloy. Background Technology
[0002] Invar alloys are binary austenitic iron-nickel alloys that, compared to other metallic materials, exhibit a very small coefficient of thermal expansion in the temperature range of -250℃ to 200℃. Typically, the coefficient of thermal expansion in this range is less than 2 × 10⁻⁶. -6 / ℃, the coefficient of thermal expansion in the range of -100℃ to 100℃ is less than 1.5×10. -6 / ℃. This alloy is used in fields where a very low coefficient of thermal expansion is required, such as liquefied gas production and storage containers, color TV cathode covers, bimetallic thermostats, cryogenic instruments, and aerospace components.
[0003] For a long time, Invar alloy production has mostly used induction furnaces with pure nickel, which has disadvantages such as high cost, low output and low efficiency.
[0004] This invention employs a "medium-frequency furnace → AOD → LF" process route, representing a pioneering low-cost smelting process for Invar alloys in China. This process fully utilizes iron-nickel alloy resources and reduces reliance on high-grade nickel-iron and pure nickel resources during Invar alloy production. Simultaneously, it enables mass production of Invar alloys, resolving the bottleneck issues of high production costs and demanding equipment requirements. Summary of the Invention
[0005] The purpose of this invention is to address the above-mentioned problems by providing a process for smelting Invar alloys.
[0006] The objective of this invention is achieved as follows: a process for smelting Invar alloy, comprising the following steps: Step 1: charging an iron-nickel alloy raw material into a medium-frequency furnace, with a tapping temperature of 1590±20℃ and a power consumption of 520±30 kWh / t per ton of steel; Step 2: after melting in the medium-frequency furnace, adding AOD for smelting; Step 3: after oxygen blowing and dephosphorization in the AOD, slag removal is carried out, with an iron-nickel alloy raw material added to the medium-frequency furnace at a rate of 30±3t, an AOD gas flow ratio of O2:Ar=8:1, and adding 24±2t of nickel-iron alloy in batches during the AOD oxygen blowing process, and an oxygen consumption of 2500±200 Nm³ during the dephosphorization process. 3 The lime consumption is 3.5±1t, and the fluorite consumption is 0.5±0.2t. The process temperature is controlled at ≤1620℃. Step 4: After AOD slag discharge, the composition is adjusted and the molten steel is deoxidized; 4±2t of scrap steel, 3±1t of lime, and 0.3±0.1t of fluorite are added, and oxygen is blown at 600±100Nm. 3After heating, deoxidation is carried out using aluminum shot as the deoxidizer, with an addition amount of 1.4±0.2t. After reduction for 8 minutes, slag is discharged and samples are taken. Step 5: The composition and temperature of the LF are adjusted. Molten steel is processed at the LF station with an inlet temperature of 1560±20℃. After 25 minutes of power supply, the temperature is measured at 1630±10℃. Lime 1.5±0.2t and fluorite 0.5±0.2t are added in batches to form slag. After slag formation, argon blowing and stirring are performed. The LF outlet temperature is 1540±5℃, and then casting is carried out.
[0007] The chemical composition and mass percentage of the iron-nickel alloy raw material in step one are as follows: C: 1.5±0.3%, Si: 0.3±0.2%, Mn: 0.04±0.02%, P: 0.04±0.02%, S: 0.15±0.03%, Cr: 1±0.6%, Ni: 20±6%; the remainder is iron and unavoidable impurities; the loading weight is 30±3t.
[0008] The chemical composition and mass percentage of the nickel-iron alloy in step three are as follows: C: 0.05±0.02%, Si: 0.10±0.05%, P: 0.015±0.005%, S: 0.06±0.015%, Cr: 0.05±0.03%, Ni 40±5%, with the remainder being iron and unavoidable impurities.
[0009] The chemical composition and mass percentage of the scrap steel in step four are C: 0.4±0.05%, Si: 0.5±0.05%, P: 0.015±0.005%, with the remainder being iron and unavoidable impurities.
[0010] The beneficial effects of this invention are as follows: This invention uses a medium-frequency furnace to melt nickel-iron alloy to provide pre-melted liquid for AOD (Alternating Oxide). During the AOD smelting process, dephosphorization is performed by using a specific gas ratio. After dephosphorization, the slag is discharged, and the composition is adjusted and the molten steel is deoxidized. After tapping, the composition and temperature are adjusted in an LF (Alternating Current Furnace) before casting. This invention is the first domestically developed low-cost process for smelting Invar alloys. Under the premise of ensuring product quality, it can produce Invar alloys with the required composition without using pure nickel resources, but using more economical iron-nickel alloy raw materials, thus realizing the full utilization of iron-nickel alloy resources and significantly reducing the production cost of Invar alloys. Implementation
[0011] The concept of this invention is to develop a low-cost process for smelting Invar alloys. It employs a technology that uses economical raw materials to replace precious metals, and the process route is: medium-frequency furnace → AOD → LF. Through this unique process route, mass production of Invar alloys is achieved, significantly reducing production costs.
[0012] The method described in this invention includes the following key steps: Ⅰ. Induction furnace is used to charge iron-nickel alloy raw materials; Ⅱ. After melting induction furnace, AOD is added for smelting; Ⅲ. After oxygen blowing and deoxidation of P by AOD, slag is discharged; Ⅳ. After slag discharge by AOD, composition adjustment and deoxidation of molten steel are performed; Ⅴ. LF is used to adjust composition and temperature.
[0013] Specifically: Ⅰ. The medium-frequency furnace is loaded with relatively economical iron-nickel alloy raw materials for melting, and the tapping temperature is 1590±20℃. The power consumption per ton of steel in the medium-frequency furnace is 500±30Kwh / t.
[0014] II. After tapping steel from the medium-frequency furnace, AOD is added for dephosphorization. The AOD gas flow ratio is O2:Ar=8:1. The temperature is controlled at ≤1620℃ throughout the process. After AOD dephosphorization and slag discharge, samples are taken for composition analysis.
[0015] Ⅲ. After AOD removal of P is completed, the composition and temperature of the molten steel are adjusted, and deoxidation treatment is carried out.
[0016] IV. The "medium frequency furnace → AOD → LF" process flow design makes the production process more efficient.
[0017] V. Using this process, Invar alloys with the required composition can be produced using more economical iron-nickel alloy raw materials without the use of pure nickel resources.
[0018] The specific implementation of the method of the present invention will be described in detail below with reference to the embodiments, but the specific implementation of the present invention is not limited to the following embodiments. Example 1
[0019] The specific composition of the Invar alloy in the finished product is shown in the table below.
[0020]
[0021] This example was implemented using a 30t medium-frequency furnace + 45t AOD + 45t LF furnace, and the specific implementation details are as follows.
[0022] The production of high-grade nickel-iron alloys involves the following process route: 30t medium-frequency furnace → 45t AOD → 45t LF furnace (30t and 45t are the nominal capacities of each metallurgical furnace).
[0023] The operation steps in this embodiment are as follows.
[0024] I. The raw material composition for the medium-frequency furnace is: C 1.39%; Si 0.37%; Mn 0.043%; P 0.021%; S 0.162%; Cr 0.470%; Ni 23.968%; the remainder is iron and unavoidable impurities; the charge weight is 32t; the tapping temperature of the medium-frequency furnace is 1609℃; the power consumption per ton of steel in the medium-frequency furnace is 525 kWh / t.
[0025] II. The composition of the pre-melted liquid for AOD in the furnace is C 1.32%; Si 0.37%; Mn 0.045%; P 0.021%; S 0.157%; Cr 0.625%; Ni 24.092%; the remainder is iron and unavoidable impurities.
[0026] III. After tapping from the intermediate frequency furnace, AOD (Alternating Current) is added for dephosphorization, with an addition amount of 31.5t. The AOD gas flow ratio is O2:Ar = 8:1. During the AOD oxygen blowing process, 24t of nickel-iron alloy (composition: C 0.05%, Si 0.11%, P 0.016%, S 0.068%, Cr 0.02%, Ni 43.07%, with the remainder being iron and unavoidable impurities) is added in batches. The oxygen consumption of AOD during the dephosphorization process is 2400 Nm³. 3 The process consumes 4 tons of lime and 0.5 tons of fluorite. The process temperature is controlled at ≤1620℃. After dephosphorization, slag is discharged and samples are taken for composition analysis.
[0027] The sample analysis results are as follows: C 0.0033%; Si 0.005%; Mn 0.023%; P 0.001%; S 0.069%; Cr 0.019%; Ni 38.086%; the remainder is iron and unavoidable impurities.
[0028] After AOD dephosphorization and slag removal, the composition was adjusted by adding 4t of scrap steel (composed of 0.4% C, 0.5% Si, 0.015% P, with the remainder being iron and unavoidable impurities), 3t of lime, and 0.3t of fluorite, followed by oxygen blowing at 600 Nm³. 3 After heating, deoxidation is carried out using aluminum pellets at a rate of 1.4t. After 8 minutes of reduction, slag is discharged and samples are taken.
[0029] The sample analysis results are as follows: C 0.0022%; Si 0.107%; Mn 0.07%; P 0.0024%; S 0.007%; Cr 0.15%; Ni 35.52%; N 0.0012%; the remainder is iron and unavoidable impurities.
[0030] After AOD slag removal, 0.15t of electrolytic manganese (composition: C 0.01%, Si 0.006%, Mn 99.9%, the remainder being iron and unavoidable impurities) was added before tapping the steel. The tapped steel weighed 46.2t and the steel temperature was 1576℃. Samples were taken for composition analysis.
[0031] The final sample composition analysis results of the AOD in the example were as follows: C 0.0028%; Si 0.123%; Mn 0.376%; P 0.0023%; S 0.005%; Cr 0.180%; Ni 35.463%; N 0.0015%; the remainder was iron and unavoidable impurities.
[0032] IV. After the steel is tapped from the AOD station, the molten steel enters the LF station for processing. The temperature at the station entrance is 1545℃. After 25 minutes of power supply, the temperature is measured at 1638℃. 1.5t of lime and 0.6t of fluorite are added in batches to form slag. After slag formation, argon blowing and stirring are performed. The temperature at the LF station exit is 1540℃, and then the casting operation is carried out.
[0033] V. The final product sample analysis results of the example are as follows: C 0.0044%; Si 0.120%; Mn 0.375%; P 0.0027%; S 0.001%; Cr 0.185%; Ni 35.478%; N 0.0016%; the remainder is iron and unavoidable impurities. Example 2
[0034] The specific composition of the Invar alloy in the finished product is shown in the table below.
[0035]
[0036] This example was implemented using a 30t medium-frequency furnace + 45t AOD + 45t LF furnace, and the specific implementation details are as follows.
[0037] The production of high-grade nickel-iron alloys involves the following process route: 30t medium-frequency furnace → 45t AOD → 45t LF furnace (30t and 45t are the nominal capacities of each metallurgical furnace).
[0038] The operation steps in this embodiment are as follows.
[0039] I. The raw material composition for the medium-frequency furnace is: C 1.49%; Si 0.17%; Mn 0.045%; P 0.028%; S 0.171%; Cr 0.450%; Ni 24.921%; the remainder is iron and unavoidable impurities; the charge weight is 31t; the tapping temperature of the medium-frequency furnace is 1595℃; the power consumption per ton of steel in the medium-frequency furnace is 510 kWh / t.
[0040] II. The composition of the pre-melted liquid for AOD in the furnace is C 1.51%; Si 0.2%; Mn 0.045%; P 0.026%; S 0.167%; Cr 0.52%; Ni 24.952%; the remainder is iron and unavoidable impurities.
[0041] III. After tapping from the intermediate frequency furnace, AOD (Alternating Current) is added for dephosphorization, with an addition amount of 30.6t. The AOD gas flow ratio is O2:Ar = 8:1. During the AOD oxygen blowing process, 22.2t of nickel-iron alloy (composition: C 0.04%, Si 0.10%, P 0.015%, S 0.063%, Cr 0.03%, Ni 40.1%, the remainder being iron and unavoidable impurities) is added in batches. The oxygen consumption of AOD during the dephosphorization process is 2450 Nm³. 3 The lime consumption was 4.2t and the fluorite consumption was 0.5t. The process temperature was controlled at ≤1620℃. After the dephosphorization was completed, the slag was discharged and samples were taken for composition analysis.
[0042] The sample analysis results are as follows: C 0.003%; Si 0.006%; Mn 0.021%; P 0.001%; S 0.071%; Cr 0.020%; Ni 38.952%; the remainder is iron and unavoidable impurities.
[0043] After AOD dephosphorization and slag removal, the composition was adjusted by adding 4t of scrap steel (composed of 0.4% C, 0.5% Si, 0.015% P, with the remainder being iron and unavoidable impurities), 3t of lime, and 0.3t of fluorite, followed by oxygen blowing at 600 Nm³. 3 After heating, deoxidation is carried out using aluminum pellets at a rate of 1.4t. After 8 minutes of reduction, slag is discharged and samples are taken.
[0044] The sample analysis results are as follows: C 0.0060%; Si 0.033%; Mn 0.069%; P 0.0041%; S 0.014%; Cr 0.078%; Ni 35.55%; N 0.0023%; the remainder is iron and unavoidable impurities.
[0045] After AOD slag removal, 0.17t of electrolytic manganese (composition: C 0.01%, Si 0.006%, Mn 99.9%, the remainder being iron and unavoidable impurities) was added before tapping the steel. The tapped steel weighed 46.8t at a temperature of 1588℃, and samples were taken for composition analysis.
[0046] The final sample composition analysis results of the AOD in the example were as follows: C 0.0081%; Si 0.02%; Mn 0.45%; P 0.0042%; S 0.0066%; Cr 0.093%; Ni 35.423%; N 0.0015%; the remainder was iron and unavoidable impurities.
[0047] IV. After the steel is tapped from the AOD station, the molten steel enters the LF station for processing. The temperature at the station entrance is 1556℃. After 23 minutes of power supply, the temperature is measured at 1640℃. 1.5t of lime and 0.6t of fluorite are added in batches to form slag. After slag formation, argon blowing and stirring are performed. The temperature at the LF station exit is 1540℃, and then the casting operation is carried out.
[0048] V. The final product sample analysis results of the example are as follows: C 0.0108%; Si 0.1432%; Mn 0.463%; P 0.0049%; S 0.001%; Cr 0.1207%; Ni 35.600%; N 0.0020%; the remainder is iron and unavoidable impurities.
[0049] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.
Claims
1. A process for smelting Invar alloy, characterized in that: Includes the following steps: Step 1: Load the iron-nickel alloy raw material into the medium frequency furnace. The tapping temperature of the medium frequency furnace is 1590±20℃. The power consumption per ton of steel in the medium frequency furnace is 520±30 kWh / t. Step 2: After melting in an intermediate frequency furnace, AOD is added for smelting; Step 3: After oxygen blowing and P removal are completed in the AOD (Alternating Current Oxygen Desulfurization) process, slag is discharged. The amount of molten iron added to the medium-frequency furnace is 30±3t, and the AOD gas flow ratio is O2:Ar=8:
1. During the AOD oxygen blowing process, 24±2t of nickel-iron alloy is added in batches. The oxygen consumption of the AOD during the P removal process is 2500±200 Nm³. 3 The lime consumption was 3.5±1t, the fluorite consumption was 0.5±0.2t, and the process temperature was controlled at ≤1620℃. Step 4: After AOD slag removal, adjust the composition and deoxidize the molten steel; add 4±2t of scrap steel, 3±1t of lime, and 0.3±0.1t of fluorite, and blow oxygen at 600±100Nm. 3 After heating, deoxidation is carried out using aluminum shot as the deoxidizer, with an addition amount of 1.4±0.2t. After reduction for 8 minutes, slag is discharged and samples are taken. Step 5: The composition and temperature of the LF are adjusted. The molten steel is processed at the LF station with an inlet temperature of 1560±20℃. After 25 minutes of power supply, the temperature is measured at 1630±10℃. Lime 1.5±0.2t and fluorite 0.5±0.2t are added in batches to form slag. After slag formation, argon blowing and stirring are performed. The LF outlet temperature is 1540±5℃, and then the casting operation is carried out. The chemical composition and mass percentage of the iron-nickel alloy raw material in step one are as follows: C: 1.5±0.3%, Si: 0.3±0.2%, Mn: 0.04±0.02%, P: 0.04±0.02%, S: 0.15±0.03%, Cr: 1±0.6%, Ni: 20±6%; the remainder is iron and unavoidable impurities; the loading weight is 30±3t. The chemical composition and mass percentage of the nickel-iron alloy in step three are as follows: C: 0.05±0.02%, Si: 0.10±0.05%, P: 0.015±0.005%, S: 0.06±0.015%, Cr: 0.05±0.03%, Ni 40±5%, with the remainder being iron and unavoidable impurities.
2. The process for smelting Invar alloy according to claim 1, characterized in that: The chemical composition and mass percentage of the scrap steel in step four are C: 0.4±0.05%, Si: 0.5±0.05%, P: 0.015±0.005%, with the remainder being iron and unavoidable impurities.