Industrial production method for smelting low-aluminum cobalt-based high-temperature alloy and increasing nitrogen in induction vacuum furnace

Abstract

The invention relates to the technical field of metallurgical industry, in particular to an industrial production method for increasing nitrogen in smelting low-aluminum cobalt-based high-temperature alloy by an induction vacuum furnace, which comprises the following steps: putting a metal raw material into a magnesium oxide crucible of a vacuum induction furnace for pretreatment; power is supplied to the vacuum induction furnace subjected to pretreatment, and metal raw materials start to be smelted; after melting the metal raw materials, measuring the temperature, and controlling the temperature of the molten steel for high-temperature refining; according to the method, a magnesium crucible in a vacuum induction furnace is used for smelting, blocky vacuum chromium nitride with the nitrogen content being 12.35% is used as a raw material for increasing nitrogen of the cobalt-based high-temperature alloy, molten steel is frozen before chromium nitride is added, so that a layer of conjunctiva is formed on the surface of the molten steel, the chromium nitride can enter the molten steel to the maximum extent, and the cobalt-based high-temperature alloy is obtained. The high-nitrogen low-aluminum cobalt-based high-temperature alloy with the nitrogen content ranging from 0.15% to 0.20% is obtained, the operation method is simple, the production cost is low, and the nitrogen increasing effect is good.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgical industry, and in particular to an industrial production method for adding nitrogen to a low-aluminum cobalt-based high-temperature alloy by smelting it in an induction vacuum furnace. Background Art

[0002] Vacuum induction melting (VIM) involves melting metals under confined vacuum conditions using electromagnetic induction, generating eddy currents. This process is used to melt high-purity metals and alloys, as well as to produce high-temperature alloys. Because vacuum melting facilitates the removal of nitrogen, hydrogen, oxygen, and carbon from steel and alloys to levels far lower than those achieved under atmospheric pressure, impurity elements (such as copper, zinc, lead, antimony, bismuth, tin, and arsenic) with higher vapor pressures than the base metal at melting temperatures can be removed through volatilization. The addition of active elements such as aluminum, titanium, boron, and zirconium to the alloy can also be easily controlled. Consequently, VIM-melted metals can exhibit significant improvements in various properties, including toughness, fatigue strength, corrosion resistance, high-temperature creep properties, and, in the case of magnetic alloys, magnetic permeability.

[0003] Cobalt-based superalloys are a class of materials with excellent properties, including high-temperature strength, oxidation resistance, corrosion resistance, and wear resistance. They are widely used in aerospace, aeroengines, medical, marine, and automotive applications. Nitrogen, a common alloying element, also has a significant impact on the properties of cobalt-based superalloys. Nitrogen can form effective strengthening phases with other elements in cobalt-based superalloys, such as M23C6, MC, and M6C, thereby improving the material's high-temperature strength and tensile strength. Nitrogen can form cobalt nitride with cobalt, stabilizing the material's lattice structure and providing excellent corrosion resistance under high temperatures and high pressures, especially in complex corrosive media. Adding an appropriate amount of nitrogen can prevent the formation of voids and excessive undesirable grain boundaries in cobalt-based superalloys, thereby optimizing the microstructure and enhancing material properties. The processing properties of cobalt-based superalloys directly affect their preparation cost and performance. Adding a certain amount of nitrogen can reduce the material's hot work hardening, improve its processing properties, and facilitate its forming and processing. In summary, nitrogen has a significant impact on the properties of cobalt-based superalloys, improving their high-temperature strength and tensile strength, enhancing corrosion resistance, optimizing their microstructure, and improving their processing properties. Therefore, when preparing cobalt-based high-temperature alloys, factors such as nitrogen content and processing technology need to be considered to achieve optimal mechanical properties and corrosion resistance.

[0004] A major factor limiting the application of nitrogen-containing alloys is their smelting. Nitrogen, a gaseous element, has a low solubility in steel, which decreases with increasing temperature. Currently, high-nitrogen alloys are typically smelted using processes such as pressurized electroslag remelting and reverse pressure casting. Other methods include hot isostatic pressing, pressurized induction melting, and powder metallurgy. These processes require specialized equipment and are costly.

[0005] When using a vacuum induction furnace to smelt high-nitrogen cobalt-based high-temperature alloys, nitrogen can be increased by adding nitrides or filling with nitrogen. Since the solubility of nitrogen in molten steel is limited, and chromium nitride decomposes into nitrogen at 700-1200°C, if a higher nitrogen content is to be achieved, splashing will occur during the smelting process, resulting in a large amount of metal loss. At the same time, the splashed high-temperature steel droplets will cause damage to the seals of the vacuum induction furnace, affecting the sealing of the vacuum induction furnace. Summary of the Invention

[0006] The present invention provides an industrial production method for nitrogen addition of low-aluminum cobalt-based high-temperature alloys smelted in an induction vacuum furnace, which overcomes the shortcomings of the above-mentioned existing technologies and can effectively solve the problem of high cost caused by the use of special equipment in the existing smelting of high-nitrogen alloys using processes such as pressurized electroslag remelting.

[0007] To solve the above problems, the present invention provides an industrial production method for nitrogen addition in an induction vacuum furnace for smelting low-aluminum cobalt-based high-temperature alloy, comprising the following steps: The metal raw materials are placed in a magnesium oxide crucible in a vacuum induction furnace for pretreatment; Power is supplied to the vacuum induction furnace which has completed the pretreatment to start melting the metal raw materials; After the metal raw materials are melted, the temperature is measured and the temperature of the molten steel is controlled for high-temperature refining; Fill the vacuum induction furnace with nitrogen or argon to make the pressure of the vacuum induction furnace reach zero pressure; The vacuum induction furnace is powered off to perform freezing and conjunctival treatment on the high-temperature molten steel; The bulk vacuum chromium nitride is processed into granular chromium nitride. After the steel liquid forms a film on the surface, the granular chromium nitride is added in small amounts and multiple times. The nitrogen content of the bulk vacuum chromium nitride is 12.35%. After adding chromium nitride, the temperature is measured and the alloy is poured out of the furnace to form a low-aluminum, high-nitrogen cobalt-based high-temperature alloy.

[0008] The metal raw material is placed in a magnesium oxide crucible in a vacuum induction furnace for pretreatment, including: Put the metal raw materials into a crucible made of magnesium oxide; Close the cover of the vacuum induction furnace after charging; Use the vacuum unit to evacuate the vacuum induction furnace to 5Pa, then stop the unit; Fill the vacuum induction furnace with nitrogen or argon to make the pressure of the vacuum induction furnace reach zero pressure, and then use the vacuum unit to evacuate the furnace to 5Pa again.

[0009] The above-mentioned magnesium oxide crucible contains 66-70% magnesium oxide, 26-30% aluminum oxide, and 3.3% silicon dioxide.

[0010] The above-mentioned high-temperature refining by controlling the temperature of the molten steel includes controlling the temperature of the molten steel at 1550-1600° C. and performing high-temperature refining for 10 minutes.

[0011] The processing of the granular chromium nitride includes: The bulk vacuum chromium nitride was baked at 200°C for 1 h; The baked bulk chromium nitride is crushed into granules.

[0012] The above-mentioned small amount of multiple additions of processed granular chromium nitride includes: After the steel liquid forms a film on the surface, add the first chromium nitride; The vacuum induction furnace with the primary addition of chromium nitride was powered off for freezing and conjunctiva- tion; After the steel liquid forms a film on the surface, add chromium nitride for the second time; The vacuum induction furnace with secondary addition of chromium nitride was powered off for freezing and conjunctiva; After the steel liquid forms a film on the surface, chromium nitride is added for the third time.

[0013] The present invention uses a magnesium crucible in a vacuum induction furnace for smelting, uses block vacuum chromium nitride with a nitrogen content of 12.35% as a raw material for nitrogen-enhancing a cobalt-based high-temperature alloy, fills the vacuum induction furnace with argon gas for smelting, and makes the pressure of the vacuum induction furnace reach zero pressure. Before adding the chromium nitride, the molten steel is frozen to form a conjunctiva on the surface of the molten steel, so that the chromium nitride can enter the molten steel to the greatest extent, avoiding the problem of splashing caused by a large amount of gas escaping due to a violent reaction at high temperature. Thus, a high-nitrogen, low-aluminum cobalt-based high-temperature alloy with a nitrogen content of 0.15-0.20% is obtained. The present invention has a simple operation method, low production cost, and good nitrogen-enhancing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0015] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0016] The present invention is not limited to the following embodiments, and specific implementation methods can be determined based on the technical solutions of the present invention and actual conditions.

[0017] like Figure 1 As shown, an industrial production method for adding nitrogen to a low-aluminum cobalt-based high-temperature alloy by smelting in an induction vacuum furnace is characterized by comprising the following steps: The metal raw materials are placed in a magnesium oxide crucible in a vacuum induction furnace for pretreatment; Power is supplied to the vacuum induction furnace which has completed the pretreatment to start melting the metal raw materials; After the metal raw materials are melted, the temperature is measured and the temperature of the molten steel is controlled for high-temperature refining. Therefore, chromium nitride is added after the high-temperature refining is completed. Before adding chromium nitride, the vacuum induction furnace needs to be filled with nitrogen or argon to make the pressure of the vacuum induction furnace reach zero pressure (gauge pressure 0MPa) to reduce the amount of nitrogen escaping from the molten steel after the addition of chromium nitride.

[0018] Fill the vacuum induction furnace with nitrogen or argon to make the pressure of the vacuum induction furnace reach zero pressure (gauge pressure 0MPa); therefore, before adding vacuum chromium nitride, it is necessary to fill the vacuum induction furnace with nitrogen or argon to make the pressure of the vacuum induction furnace reach zero pressure (gauge pressure 0MPa). Because the higher the temperature of the molten steel, the easier it is for nitrogen to escape from the molten steel. Therefore, reduce the power of the induction vacuum furnace to form a conjunctiva on the surface of the molten steel. At this time, add chromium nitride so that chromium nitride can enter the molten steel to the greatest extent, avoiding splashing caused by a large amount of gas escaping due to the intense reaction when the temperature is high.

[0019] The vacuum induction furnace is powered off to perform freezing and conjunctival treatment on the high-temperature molten steel; The bulk vacuum chromium nitride is processed into granular chromium nitride. After the surface of the molten steel forms a film, the granular chromium nitride is added in small amounts and multiple times. The bulk vacuum chromium nitride is a nitrogen-increasing raw material. The nitrogen content of chromium nitride is 12.35%. The chromium nitride is added at 0.35%. The target nitrogen content of the produced cobalt-based high-temperature alloy is 0.15-0.20%. The chromium nitride is added after the surface of the molten steel forms a film, so that the vacuum chromium nitride can enter the molten steel to the greatest extent, avoiding splashing caused by a large amount of gas escaping due to the intense reaction when adding at high temperature, resulting in loss of metal or chromium nitride. The granular chromium nitride is added in small amounts and multiple times to avoid large splashing caused by adding a large amount.

[0020] After adding chromium nitride, the temperature is measured and the product is poured out of the furnace to form a low-aluminum, high-nitrogen cobalt-based high-temperature alloy. The addition of chromium nitride and the temperature is measured before the product is poured out of the furnace to avoid nitrogen escape caused by long smelting, which may result in the product failing to meet the target nitrogen content requirements.

[0021] The metal raw materials are placed in a magnesium oxide crucible in a vacuum induction furnace for pretreatment, including: Put the metal raw materials into a crucible made of magnesium oxide; Close the cover of the vacuum induction furnace after charging; Use the vacuum unit to evacuate the vacuum induction furnace to 5Pa, then stop the unit; Fill the vacuum induction furnace with nitrogen or argon until the pressure reaches zero (gauge pressure 0 MPa), and then use the vacuum unit to evacuate the furnace to 5 Pa. This replaces the furnace with nitrogen, achieving the purpose of reducing oxygen and increasing nitrogen.

[0022] The magnesium oxide crucible contains 66-70% magnesium oxide, 26-30% aluminum oxide, and 3.3% silicon dioxide. This allows the aluminum content of the cobalt-based high-temperature alloy to be controlled below 0.005%, while also providing the crucible with high thermal shock resistance and a crucible life of more than six furnaces, significantly reducing production costs.

[0023] The high-temperature refining is performed by controlling the temperature of the molten steel, including controlling the temperature of the molten steel at 1550-1600° C. for high-temperature refining for 10 minutes.

[0024] The processing of granular chromium nitride includes: The bulk vacuum chromium nitride is baked at 200°C for 1 hour to remove moisture and avoid splashing caused by direct addition of moisture. Crush the baked chromium nitride blocks into granules to avoid adding the blocks directly into the hot molten steel, which will cause the chromium nitride to decompose rapidly and produce a lot of gas.

[0025] Among them, the processed granular chromium nitride is added in small amounts and multiple times, including: After the steel liquid forms a film on the surface, add the first chromium nitride; The vacuum induction furnace with the primary addition of chromium nitride was powered off for freezing and conjunctiva- tion; After the steel liquid forms a film on the surface, add chromium nitride for the second time; The vacuum induction furnace with secondary addition of chromium nitride was powered off for freezing and conjunctiva; After the steel liquid forms a film on the surface, chromium nitride is added for the third time.

[0026] Before each addition of chromium nitride, the vacuum induction furnace is powered off to freeze the hot molten steel. Once the molten steel forms a film, chromium nitride is added. The frozen film slows down the violent reaction between the chromium nitride and the hot molten steel. Once added to the molten steel, the chromium nitride melts quickly and is stirred evenly. Due to the short stirring time, the large amount of supersaturated nitrogen dissolved in the molten steel does not have time to escape before being cast into ingots and remains in the molten steel, resulting in a higher nitrogen content. After adding chromium nitride, the power is adjusted to the tapping temperature for casting.

[0027] In summary, the embodiment of the present invention discloses an industrial production method for nitrogen enhancement of low-aluminum cobalt-based high-temperature alloy by induction vacuum smelting, which is carried out by using a magnesium crucible in a vacuum induction furnace for smelting, using block vacuum chromium nitride with a nitrogen content of 12.35% as a raw material for nitrogen enhancement of cobalt-based high-temperature alloy, filling the vacuum induction furnace with argon gas for smelting, so that the pressure of the vacuum induction furnace reaches zero pressure, and freezing the molten steel before adding chromium nitride to form a conjunctiva on the surface of the molten steel, so that the chromium nitride can enter the molten steel to the greatest extent, avoiding the problem of splashing caused by a large amount of gas escaping due to the intense reaction at high temperature, and adding an appropriate amount of nitrogen can prevent the generation of voids and excessive bad grain boundaries in the cobalt-based high-temperature alloy, thereby obtaining a high-nitrogen, low-aluminum cobalt-based high-temperature alloy with a nitrogen content of 0.15-0.20%, optimizing the organizational structure, and improving the performance of the material; the operation method of the present invention is simple, the production cost is low, and the nitrogen enhancement effect is good.

Claims

1. An industrial production method for smelting low-aluminum cobalt-based high-temperature alloy with nitrogen addition in an induction vacuum furnace, characterized in that: The following steps are involved: The metal raw material is placed in a magnesium oxide crucible in a vacuum induction furnace for pretreatment; Power is supplied to the vacuum induction furnace that has completed the pretreatment to start smelting the metal raw materials; After the metal raw materials are melted, the temperature is measured and the temperature of the molten steel is controlled for high-temperature refining; Fill the vacuum induction furnace with nitrogen or argon to make the pressure of the vacuum induction furnace reach zero pressure; The vacuum induction furnace is powered off to perform freezing and filming treatment on the high-temperature molten steel; The bulk vacuum chromium nitride is processed into granular chromium nitride, and after the steel liquid surface forms a film, the granular chromium nitride is added in small amounts and multiple times; wherein the nitrogen content of the bulk vacuum chromium nitride is 12.35%; After adding chromium nitride, the temperature is measured and the alloy is poured out of the furnace to form a low-aluminum, high-nitrogen cobalt-based high-temperature alloy.

2. The industrial production method for smelting low-aluminum cobalt-based high-temperature alloy and increasing nitrogen by induction vacuum furnace according to claim 1, characterized in that: The metal raw material is placed in a magnesium oxide crucible of a vacuum induction furnace for pretreatment, including: Put the metal raw material into a crucible made of magnesium oxide; Close the cover of the vacuum induction furnace after charging; After the vacuum induction furnace is evacuated to 5Pa using a vacuum unit, the unit is shut down; Fill the vacuum induction furnace with nitrogen or argon to make the pressure of the vacuum induction furnace reach zero pressure, and then use the vacuum unit to evacuate the furnace to 5Pa again.

3. The industrial production method for smelting low-aluminum cobalt-based high-temperature alloy and increasing nitrogen by induction vacuum furnace according to claim 1, characterized in that: The magnesium oxide crucible contains 66-70% magnesium oxide, 26-30% aluminum oxide and 3.3% silicon dioxide.

4. The industrial production method for smelting low-aluminum cobalt-based high-temperature alloy and increasing nitrogen by induction vacuum furnace according to claim 1, characterized in that: The controlling the temperature of the molten steel for high temperature refining includes controlling the temperature of the molten steel at 1550-1600° C. for high temperature refining for 10 minutes.

5. The industrial production method for smelting low-aluminum cobalt-based high-temperature alloy and increasing nitrogen by induction vacuum furnace according to claim 1, characterized in that: The processing of the granular chromium nitride comprises: The block vacuum chromium nitride was baked at 200°C for 1h; The baked block chromium nitride is crushed into particles.

6. The industrial production method for smelting low-aluminum cobalt-based high-temperature alloy and increasing nitrogen by induction vacuum furnace according to claim 1, characterized in that: The step of adding a small amount of processed granular chromium nitride multiple times comprises: After the steel liquid forms a film on its surface, add the first chromium nitride; The vacuum induction furnace with primary chromium nitride added was powered off for freezing and concretion; After the steel liquid forms a film on its surface, add chromium nitride for the second time; The vacuum induction furnace with secondary addition of chromium nitride was powered off for freezing and concretion; After the steel liquid forms a film on its surface, chromium nitride is added for the third time.

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