Method for smelting high-temperature alloy metal chromium through vacuum cooling process
The vacuum cooling process addresses the purity issues in high-temperature alloy chromium production by minimizing oxygen and nitrogen content, ensuring the chromium meets the stringent requirements for high-temperature applications, thereby enhancing the material's properties and performance.
Patent Information
- Application Number
- CN202411815835.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-11
- Publication Date
- 2025-03-25
AI Technical Summary
Current methods for producing high-temperature alloy chromium using aluminum reduction furnaces fail to meet the stringent purity requirements for high-temperature applications due to high oxygen and nitrogen content, which negatively impact the material's properties, particularly at elevated temperatures.
A vacuum cooling process is employed to refine chromium, ensuring minimal exposure to air and maintaining a controlled vacuum environment to significantly reduce oxygen and nitrogen levels, achieving purities below 0.05% oxygen and 0.006% nitrogen, thereby meeting the requirements for high-temperature alloys.
The vacuum cooling process effectively prevents oxidation and removes impurities, enhancing the uniformity and purity of chromium, significantly improving the quality and performance of high-temperature alloys by reducing harmful elements to acceptable levels.
Smart Images
Figure CN119685628A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for smelting metallic chromium, in particular to a method for smelting metallic chromium of high-temperature alloy using a vacuum cooling process. Background Art
[0002] High temperature alloy, also known as super alloy, is a kind of metal material that can maintain its strength and corrosion resistance in high temperature environment. It belongs to functional materials and has many excellent properties, which makes it play an important role in specific functional fields.
[0003] Usually, high-temperature alloy refers to a type of metal material that is made of iron, cobalt, and nickel as the base elements and fused with other metal or non-metal elements. It can work for a long time at ultra-high temperatures above 600°C and under certain stress. These alloys are widely used in various industrial fields due to their excellent properties at high temperatures, such as creep resistance, oxidation resistance, corrosion resistance, and fatigue resistance. Therefore, they are also called heat-resistant alloys, heat-resistant alloys, or superalloys. They are core application materials in the fields of aerospace, gas turbines, automobiles, nuclear power, and petrochemicals. Regardless of whether it is an iron-based, nickel-based, or cobalt-based high-temperature alloy, chromium is an important component, and its content accounts for about 18% in various alloys.
[0004] High-temperature alloys have high requirements on raw material indicators. At present, the metal chromium indicators smelted by the aluminothermic furnace method cannot meet the requirements, especially the gas content, which cannot meet the requirements of high-temperature alloys.
[0005] The composition of metallic chromium smelted by the existing aluminothermic furnace method is: chromium content ﹥ 99%, iron content < 0.3%, aluminum < 0.3%, silicon < 0.25%, sulfur < 0.01%, phosphorus < 0.005%, carbon < 0.01%, oxygen < 0.3%, nitrogen < 0.02%.
[0006] The metal chromium composition required for high-temperature alloys is: chromium content ﹥99.5%, iron content <0.15%, aluminum <0.1%, silicon <0.15%, sulfur <0.003%, phosphorus <0.005%, carbon <0.05%, oxygen <0.05%, and nitrogen <0.006%.
[0007] Oxygen is a harmful element in special alloy steel. During the solidification of molten steel, oxygen in the solution reacts with carbon to produce carbon monoxide, which can cause bubbles in the steel. Oxygen mainly exists in steel in the form of oxides, such as chromium oxide, ferrous oxide, manganese monoxide, silicon dioxide, aluminum oxide, etc., which reduce the strength and plasticity of the steel. In particular, it has a serious impact on fatigue strength and impact toughness.
[0008] Nitrogen significantly reduces the plasticity of steel, especially its toughness, and deteriorates its weldability. It also increases its aging tendency and hot brittleness, and damages its welding and cold bending properties. Therefore, the nitrogen content in steel should be reduced and limited as much as possible.
[0009] It can be seen that the high oxygen and nitrogen content in metallic chromium will directly affect the performance of high-temperature alloys. Vacuum metallurgy is mainly used in the processes of metal smelting, refining, casting and heat treatment, especially in the smelting of rare metals and special alloys. Vacuum metallurgy technology originated in the mid-19th century. With the development of vacuum technology, vacuum metallurgy began to be widely used in the 1950s. With the rapid development of cutting-edge science and technology, vacuum metallurgy has been increasingly widely used in the smelting of rare metals, steel and special alloys. The chromium content in nickel-based, cobalt-based, iron-based and other high-temperature alloys is about 18%. Chromium can greatly improve the hardness and oxidation resistance of the alloy, especially under high temperature conditions. The purity of chromium has a direct impact on the performance of the alloy. High oxygen and nitrogen will cause an increase in oxides and nitrides in the alloy, especially seriously affecting the high-temperature strength of the high-temperature alloy. In order to further improve the performance of the alloy, especially the high-temperature resistance, the oxygen and nitrogen content in metallic chromium must be reduced.
[0010] Therefore, it is very necessary to use vacuum metallurgy combined with appropriate process conditions to smelt metallic chromium so as to effectively remove gases and impurities in the chromium metal and improve the purity of metallic chromium. Summary of the invention
[0011] The object of the present invention is to provide a method for smelting high-temperature alloy metal chromium by a vacuum cooling process. The present invention cools the smelted metal chromium ingot under vacuum conditions to avoid the chromium ingot absorbing oxygen and nitrogen in the air under a high-temperature environment during cooling, thereby reducing the oxygen and nitrogen content in the metal chromium. The present invention adopts a vacuum cooling method, wherein the oxygen content ranges from 0.04% to 0.05%, and the nitrogen content ranges from 0.004% to 0.006%, which is significantly lower than the oxygen content of 0.1% to 0.3% and the nitrogen content of 0.01% to 0.02% in the current production process, and meets the requirements of high-temperature alloys for oxygen and nitrogen content.
[0012] The objective of the present invention is achieved through the following technical solutions: A method for smelting high-temperature alloy metal chromium by vacuum cooling process, the method comprising the following process: (1) Place the smelting furnace in a vacuum-sealed device and carry out the first step of normal smelting; (2) The second step is cooling in air for 4 hours (the cooling time of this stage is adjusted according to the number of smelting batches); (3) Seal the vacuum sealing device to isolate the entire smelting furnace from the air; (4) Open the vacuum pump in order and start pumping air; (5) Control the vacuum degree according to the specific situation; (6) Cooling the chromium ingot to below 150° C. in a vacuum; (7) Sand blasting, crushing, weighing and packaging are then performed.
[0013] The method for smelting high-temperature alloy metal chromium by a vacuum cooling process comprises the following process steps: mixing chrome green, aluminum powder and sodium chlorate with a mixer for 30 minutes, mixing the materials evenly and placing them in a cast iron furnace shell; placing the furnace shell in a vacuum chamber, paving the bottom of the furnace shell with magnesium bricks, and making a sand nest with fine magnesium sand; after the mixed material is loaded, the middle of the top material surface is convex, and then the top of the middle convex part is made into a nest shape, and a thin (thin) magnesium strip and a small amount of sodium chlorate are placed in the nest, and the thin (thin) magnesium strip is ignited to ignite the reaction. After the reaction is completed, the vacuum chamber is cooled for 4 hours, the vacuum chamber is sealed, and vacuuming is started to reach a vacuum degree of less than 50 Pa, and the vacuuming is performed for 72 hours, and the sealing device is opened to lift the furnace shell. After the furnace shell is lifted, slag chromium separation is performed. After the slag chromium separation, the chromium ingot is taken out of the vacuum chamber, sandblasted, and the composition of the metal chromium ingot is sampled and analyzed.
[0014] The method for smelting high-temperature alloy metal chromium by a vacuum cooling process, the smelting ratio is: 100 kg of metallurgical chrome green (Cr2O3 content 99.1%, particle size <3 mm), 35.6 kg of aluminum powder (AL content 99.2%, particle size <1 mm), and 8.5 kg of sodium chlorate (NaCLO3 content 99.5%, particle size <0.12 mm).
[0015] The method for smelting high-temperature alloy metal chromium by vacuum cooling process has a vacuum degree of 0 to 0.2 atm (0.2 atmospheric pressure).
[0016] The vacuum cooling process for smelting high-temperature alloy metal chromium is described, wherein the vacuum cooling time is 0 to 120 hours. The advantages and effects of the present invention are: 1. The method of the present invention prevents metal oxidation. Smelting is carried out in a vacuum environment, which can effectively prevent the metal from contacting with oxygen in the air, thereby preventing oxidation.
[0017] 2. The method of the present invention separates substances with different boiling points. By controlling the pressure in a vacuum environment, substances with different boiling points can be separated.
[0018] 3. The method of the present invention removes impurities: in a vacuum environment, gases and impurities in metals can be effectively removed to improve the purity of the metal.
[0019] 4. The method of the present invention enhances the deoxidation ability of carbon. In a vacuum environment, the deoxidation ability of carbon is enhanced, which helps to improve the quality of metals and alloys, significantly improve the uniformity and purity of alloys, and reduce segregation and inclusion content.
[0020] 5. The present invention reduces the oxygen and nitrogen contents in the metal chromium from <0.3% to <0.05% and the nitrogen from <0.02% to <0.006%, which meets the requirements of high-temperature alloys for the oxygen and nitrogen contents in metal chromium. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 The figure is a process flow chart of vacuum smelting of metallic chromium according to the present invention. DETAILED DESCRIPTION
[0022] The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.
[0023] The implementation steps of the present invention are as follows: 1 Place the smelting furnace in a vacuum-sealed device and carry out the first step of normal smelting.
[0024] 2 The second step is cooling in the air for 4 hours (the cooling time of this stage is adjusted according to the number of smelting batches).
[0025] 3. Seal the vacuum sealing device to isolate the entire smelting furnace from the air.
[0026] 4 Open the vacuum pump in order and start pumping air.
[0027] 5Control the vacuum degree according to the specific situation.
[0028] 6 Cool the chromium ingot to below 150°C in vacuum.
[0029] 7. Carry out sandblasting finishing, crushing, weighing and packaging.
[0030] The process is as follows: chrome green, aluminum powder, and sodium chlorate are mixed with a mixer for 30 minutes, the materials are mixed evenly, and then placed in a cast iron furnace shell. First, the furnace shell is placed in a vacuum chamber, the furnace shell is paved with magnesium bricks, and a sand nest is made with fine magnesium sand. After the mixture is loaded, the middle of the top material surface is convex, and then the top of the middle convex part is made into a nest shape, and a thin (thin) magnesium strip and a small amount of sodium chlorate are placed in the nest, and the thin (thin) magnesium strip is ignited to ignite the reaction. After the reaction is completed, it is cooled for 4 hours, the vacuum chamber is sealed, and vacuuming is started to reach a vacuum degree of <50 Pa. After vacuuming for 72 hours, the sealing device is opened to lift the furnace shell. After the furnace shell is lifted, slag chromium separation is carried out. After the slag chromium separation, the chromium ingot is taken out of the vacuum chamber, sandblasted, and the composition of the metal chromium ingot is sampled and analyzed.
[0031] The smelting ratio of the present invention is: 100 kg of metallurgical chrome green (Cr2O3 content 99.1%, particle size <3 mm), 35.6 kg of aluminum powder (AL content 99.2%, particle size <1 mm), and 8.5 kg of sodium chlorate (NaCLO3 content 99.5%, particle size <0.12 mm). Example 1
[0032] The smelting ratio is: 100 kg of metallurgical chrome green (Cr2O3 content 99.1%, particle size <3 mm), 35.6 kg of aluminum powder (AL content 99.2%, particle size <1 mm), 8.5 kg of sodium chlorate (NaCLO3 content 99.5%, particle size <0.12 mm), The process is as follows: 500 kg of chrome green, 178 kg of aluminum powder, and 42.5 kg of sodium chlorate are mixed in a mixer for 30 minutes, and the materials are mixed and placed in a cast iron furnace shell. First, the furnace shell is placed in a vacuum chamber, the furnace shell is paved with magnesium bricks, and a sand nest is made with fine magnesium sand. After the mixture is loaded, the middle of the top material surface is convex, and then the top of the middle convex part is made into a nest shape, and a thin (thin) magnesium strip and a small amount of sodium chlorate are placed in the nest, and the thin (thin) magnesium strip is ignited to ignite the reaction. After the reaction is completed, it is cooled for 4 hours, the vacuum chamber is sealed, and vacuuming is started to reach a vacuum degree of <50 Pa. After vacuuming for 72 hours, the sealing device is opened to lift the furnace shell. After the furnace shell is lifted, slag chromium separation is carried out. After the slag chromium separation, the chromium ingot is taken out of the vacuum chamber, sandblasted, and the composition of the metal chromium ingot is sampled and analyzed. Example 2
[0033] The smelting ratio is: 100 kg of metallurgical chrome green (Cr2O3 content 99.1%, particle size <3 mm), 35.6 kg of aluminum powder (AL content 99.2%, particle size <1 mm), 8.5 kg of sodium chlorate (NaCLO3 content 99.5%, particle size <0.12 mm), The process is as follows: 500 kg of chrome green, 178 kg of aluminum powder, and 42.5 kg of sodium chlorate are mixed in a mixer for 30 minutes, and the materials are mixed and placed in a cast iron furnace shell. First, the furnace shell is placed in a vacuum chamber, the furnace shell is paved with magnesium bricks, and a sand nest is made with fine magnesium sand. After the mixture is loaded, the middle of the top material surface is convex, and then the top of the middle convex part is made into a nest shape, and a thin (thin) magnesium strip and a small amount of sodium chlorate are placed in the nest, and the thin (thin) magnesium strip is ignited to ignite the reaction. After the reaction is completed, it is cooled for 4 hours, the vacuum chamber is sealed, and vacuuming is started to reach a vacuum degree of <40 Pa. After vacuuming for 72 hours, the sealing device is opened to lift the furnace shell. After the furnace shell is lifted, slag chromium separation is carried out. After the slag chromium separation, the chromium ingot is taken out of the vacuum chamber, sandblasted, and the composition of the metal chromium ingot is sampled and analyzed. Example 3
[0034] The smelting ratio is: 100 kg of metallurgical chrome green (Cr2O3 content 99.1%, particle size <3 mm), 35.6 kg of aluminum powder (AL content 99.2%, particle size <1 mm), 8.5 kg of sodium chlorate (NaCLO3 content 99.5%, particle size <0.12 mm), The process is as follows: 500 kg of chrome green, 178 kg of aluminum powder, and 42.5 kg of sodium chlorate are mixed in a mixer for 30 minutes, and the materials are mixed and placed in a cast iron furnace shell. First, the furnace shell is placed in a vacuum chamber, the furnace shell is paved with magnesium bricks, and a sand nest is made with fine magnesium sand. After the mixture is loaded, the middle of the top material surface is convex, and then the top of the middle convex part is made into a nest shape, and a thin (thin) magnesium strip and a small amount of sodium chlorate are placed in the nest, and the thin (thin) magnesium strip is ignited to ignite the reaction. After the reaction is completed, it is cooled for 4 hours, the vacuum chamber is sealed, and vacuuming is started to reach a vacuum degree of <20 Pa. After vacuuming for 80 hours, the sealing device is opened to lift the furnace shell. After the furnace shell is lifted, slag chromium separation is carried out. After the slag chromium separation, the chromium ingot is taken out of the vacuum chamber, sandblasted, and the composition of the metal chromium ingot is sampled and analyzed.
Claims
1. A method for smelting high-temperature alloy metal chromium by vacuum cooling process, characterized in that: The method comprises the following process: (1) Place the smelting furnace in a vacuum-sealed device and carry out the first step of normal smelting; (2) The second step is cooling in air for 4 hours (the cooling time of this stage is adjusted according to the number of smelting batches); (3) Seal the vacuum sealing device to isolate the entire smelting furnace from the air; (4) Open the vacuum pump in order and start pumping air; (5) Control the vacuum degree according to the specific situation; (6) Cooling the chromium ingot to below 150° C. in a vacuum; (7) Sand blasting, crushing, weighing and packaging are then performed.
2. The method for smelting high-temperature alloy chromium by vacuum cooling process according to claim 1, characterized in that: The process of the method is as follows: chrome green, aluminum powder and sodium chlorate are mixed with a mixer for 30 minutes, the materials are mixed evenly and placed in a cast iron furnace shell; the furnace shell is placed in a vacuum chamber, the furnace shell is paved with magnesium bricks at the bottom, and a sand nest is made with fine magnesium sand. After the mixed material is loaded, the middle of the top material surface is convex, and then the top of the middle convex part is made into a nest shape, a thin (thin) magnesium strip and a small amount of sodium chlorate are placed in the nest, the thin (thin) magnesium strip is ignited, and the reaction is ignited. After the reaction is completed, the vacuum chamber is cooled for 4 hours, the vacuum chamber is sealed, and vacuuming is started to reach a vacuum degree of less than 50 Pa. The vacuuming is performed for 72 hours, and the sealing device is opened to lift the furnace shell. After the furnace shell is lifted, slag chromium separation is performed. After the slag chromium separation, the chromium ingot is taken out of the vacuum chamber, sandblasted, and the composition of the metal chromium ingot is sampled and analyzed.
3. The method for smelting high-temperature alloy metal chromium by vacuum cooling process according to claim 1, characterized in that: The smelting ratio is: 100 kg of metallurgical chrome green (Cr2O3 content 99.1%, particle size <3 mm), 35.6 kg of aluminum powder (AL content 99.2%, particle size <1 mm), and 8.5 kg of sodium chlorate (NaCLO3 content 99.5%, particle size <0.12 mm).
4. The method for smelting high-temperature alloy chromium by vacuum cooling process according to claim 1, characterized in that: The vacuum degree is 0 to 0.2 atm (0.2 atmospheres).
5. The method for smelting high-temperature alloy metal chromium by vacuum cooling process according to claim 1, characterized in that: The vacuum cooling time is 0 to 120 hours.