A method for designing parameters of a vacuum system of a vacuum melting furnace for powder recovery

Abstract

The present application relates to the field of metal powder smelting and casting, and particularly relates to a vacuum system parameter design method for a vacuum melting furnace used for powder recovery. The method comprises a vacuum induction furnace vacuum system parameter design and process control technology used for powder recovery. The critical maximum pumping capacity of the vacuum induction furnace vacuum system is calculated through a formula and relevant parameters of the powder and the induction furnace, and the vacuum induction furnace vacuum system parameters are controlled during the vacuumizing process. The present application can ensure that the powder is not pumped up into the equipment pumping pipeline and the vacuum pump body during the pumping process according to the actual situation, thereby ensuring that the vacuum system of the equipment is not "polluted" by the powder, achieving the effects of protecting the smelting equipment and reducing the loss in the powder smelting process. The present application realizes the purpose of powder recovery by using the vacuum induction melting furnace, is conducive to ensuring the normal use of the smelting equipment, and has significant economic benefits.

Description

Technical fields:

[0001] This invention relates to the fields of metal powder smelting and casting, and specifically to a method for designing vacuum system parameters for a vacuum smelting furnace used for powder recovery. Background technology:

[0002] As a critical component in aero-engines, turbine disks require materials with excellent strength, toughness, fatigue performance, reliability, and durability. High-temperature alloys, with their high alloying degree and increased strengthening elements in the matrix, are prone to severe segregation, leading to uneven alloy microstructure and deteriorated thermal processing properties. Conventional casting and forging processes cannot meet the requirements of new engines for these disks. With the rapid development of advanced technologies such as rapid atomization alloy powder preparation and hot isostatic pressing, the emergence of powder metallurgy for turbine disks has effectively overcome these problems and is widely used as a hot-end component in aero-engines. Powder metallurgy exhibits uniform microstructure, fine grains, high yield strength, and good fatigue performance, making it the preferred material for turbine disks in high thrust-to-weight ratio, high-performance engines. Powder metallurgy materials are generally manufactured into disks using powder metallurgy methods such as pre-alloyed powders, hot isostatic pressing, and appropriate hot working and heat treatment processes. Currently, in actual production, high-temperature alloy powders are generally produced using argon atomization, plasma rotating electrode, and hydrogen atomization processes. However, due to limitations such as particle size requirements, the overall powder utilization rate is generally less than 50%, resulting in significant resource waste. Traditional hot pressing sintering can press high-temperature alloy powders into ingots for recycling, but its production efficiency is relatively low. Vacuum induction melting technology offers advantages such as a vacuum atmosphere and high production efficiency, but the powder can easily be extracted during the vacuuming process in the melting chamber, contaminating the vacuum system. Therefore, optimizing the design of vacuum system parameters in vacuum induction melting furnaces is a pressing issue for improving powder recycling efficiency when applying vacuum induction melting technology to high-temperature alloy powder recovery. Summary of the Invention:

[0003] To address the shortcomings and deficiencies of existing technologies, this invention provides a method for designing vacuum system parameters for a vacuum smelting furnace used for powder recycling. This method achieves the recycling of waste powder through vacuum induction melting process by rationally designing the parameters of the vacuum system in the vacuum smelting process, which has extremely high economic benefits in improving the recycling efficiency of waste powder and reducing the cost of powder production.

[0004] The technical solution adopted in this invention is:

[0005] A method for designing parameters of a vacuum system for a vacuum smelting furnace used for powder recovery, comprising the following steps:

[0006] (1) Calculate the critical pumping capacity of the vacuum system according to formulas (1) to (4) based on the parameters of the powder to be smelted and recovered and the relevant dimensional parameters of the smelting equipment.

[0007] First, based on Bernoulli's equation and the gravity formula, the critical condition for preventing powder from being extracted during the vacuuming process is calculated according to formula (1):

[0008]

[0009] In the formula, ρ f True density of the powder, in kg / m³ 3 ;R f The minimum particle size of the powder is expressed in meters (m); g is the acceleration due to gravity, taken as 9.81 m / s². 2 ;ρ q The density of air at room temperature is taken as 1.29 kg / m³. 3 ;v q The pumping speed is expressed in m / s.

[0010] R f The minimum particle size of the powder is approximated using empirical formula (2):

[0011] R f =aD 10 (2)

[0012] In the formula, D 10 The minimum critical particle size is the particle size at which the powder volume content accounts for 10% of the total powder content, in meters; a is an empirical coefficient, ranging from 0.2 to 0.5.

[0013] The critical extraction rate inside the furnace is calculated according to formulas (3) and (4):

[0014] Q L =1000v q S (3)

[0015] In the formula, Q L The theoretical critical extraction rate is expressed in L / s; S is the maximum cross-sectional area of ​​the vertical extraction duct inside the furnace, expressed in m². 2 ;

[0016]

[0017] In the formula, Q1 is the critical maximum pumping capacity of the vacuum system of the induction furnace, in L / s; b is an empirical coefficient, ranging from 2 to 10.

[0018] (2) Place the powder to be smelted and recovered and the melting initiator into the smelting crucible as required, and close the furnace door;

[0019] (3) Turn on the vacuum system to evacuate the melting chamber. At this time, the vacuum system pumping volume should not exceed the vacuum system pumping volume calculated according to formulas (1) to (4). After the vacuum degree of the melting chamber drops to below 1000 Pa, adjust the vacuum system pumping volume to the maximum and continue to evacuate.

[0020] (4) After the vacuum level is evacuated to meet the requirements, power is supplied to start smelting; after melting, it is refined at high temperature and low temperature and then cast to obtain a remelted master alloy ingot.

[0021] In the vacuum system parameter design method for the vacuum smelting furnace used for powder recovery, in step (2), the total mass of the melting initiator is 0.05 to 0.25 times the total mass of the powder recovered by smelting.

[0022] The design concept of this invention is:

[0023] With the rapid development of my country's aerospace industry, the application scope of powder metallurgy will become increasingly wider, and its demand will gradually increase, resulting in a larger and larger amount of waste high-temperature alloy powder. Compared with traditional powder metallurgy methods, vacuum induction melting technology is more efficient in recycling waste powder. At the same time, the vacuum atmosphere and refining process during melting are conducive to powder degassing, which is very beneficial for the removal of gaseous elements from remelted alloy ingots and is of great significance for the secondary powder production of remelted alloy ingots.

[0024] Because scrap metal powder has a small particle size and a relatively large specific surface area, the lift force generated by the pressure change inside the furnace during vacuum induction melting can easily cause the powder to be lifted from the crucible and enter the vacuum pipeline. This invention calculates the critical maximum pumping capacity of the vacuum induction furnace system using formulas and relevant parameters of the powder and the induction furnace. During the vacuuming process, the parameters of the induction furnace vacuum system are controlled, and the lift force on the powder during pumping is adjusted according to the actual situation. This ensures that the powder is not lifted during pumping and enters the equipment's pumping pipeline and vacuum pump body, thus preventing the equipment's vacuum system from being "contaminated" by the powder. This achieves the effect of protecting the smelting equipment and reducing losses during powder smelting.

[0025] The advantages and beneficial effects of this invention are:

[0026] This invention solves the problem of powder being extracted during the vacuuming process when using a vacuum induction melting furnace for waste powder recycling due to the small size and mass of the powder. By designing reasonable vacuum system parameters, this invention avoids contamination of the vacuum system, extends the service life of the equipment's vacuum system, ensures normal operation of the equipment, and results in significant economic benefits. Detailed Implementation

[0027] In practical implementation, this invention proposes a method for designing vacuum system parameters for a vacuum smelting furnace used for powder recovery, comprising the following steps:

[0028] (1) Calculate the critical pumping capacity of the vacuum system according to formulas (1) to (4) based on the parameters of the powder to be smelted and recovered and the relevant dimensional parameters of the smelting equipment.

[0029] (2) Place the powder to be smelted and recovered and the melting initiator into the smelting crucible as required, and close the furnace door;

[0030] (3) Turn on the vacuum system to evacuate the melting chamber. At this time, the vacuum system pumping volume should not exceed the vacuum system pumping volume calculated according to formulas (1) to (4). After the vacuum degree of the melting chamber drops to below 1000Pa, the vacuum system pumping volume can be adjusted to the maximum and the vacuuming can continue.

[0031] (4) Once the vacuum level meets the requirements, power can be supplied to begin smelting. After melting, the alloy is refined at high temperature and low temperature before being cast to obtain a remelted master alloy ingot.

[0032] The vacuum system parameters are calculated based on the parameters of the powder to be smelted and recovered and the relevant dimensional parameters of the smelting equipment. First, according to Bernoulli's equation and gravity formula, the critical condition for the powder not to be extracted during the vacuuming process is calculated according to formula (1):

[0033]

[0034] In the formula, ρ f True density of the powder, in kg / m³ 3 ;R f The minimum particle size of the powder is expressed in meters (m); g is the acceleration due to gravity, typically taken as 9.81 m / s². 2 ;ρ q The density of air at room temperature is generally taken as 1.29 kg / m³. 3 ;v q The pumping speed is expressed in m / s.

[0035] Considering that it is difficult to calculate the minimum particle size R of powder in actual production f Generally, the approximate value can be obtained according to the empirical formula (2):

[0036] R f =aD 10 (2)

[0037] In the formula, D 10 The critical particle size is the percentage of powder volume content that is 10% of the total powder, expressed in meters (m); a is an empirical coefficient, typically taken as 0.2 to 0.5.

[0038] The critical extraction rate inside the furnace is calculated according to formulas (3) and (4):

[0039] Q L =1000v qS (3)

[0040] In the formula, Q L The theoretical critical extraction rate is expressed in L / s; S is the maximum cross-sectional area of ​​the vertical extraction duct inside the furnace, expressed in m². 2 .

[0041]

[0042] In the formula, Q1 is the critical maximum pumping capacity of the vacuum system of the induction furnace, in L / s; b is an empirical coefficient, which can be taken as 2 to 10 depending on the complexity of the vacuum pipeline.

[0043] After loading the waste powder and melting initiator into the furnace, the vacuum system is turned on. At this time, the actual pumping volume of the vacuum system should not exceed the maximum pumping volume Q1 of the induction furnace vacuum system calculated by formulas (1) to (4). When the vacuum degree in the melting chamber reaches below 1000 Pa, the vacuum system can be fully turned on and the vacuum system can be evacuated according to the maximum pumping volume. After the vacuum degree meets the requirements, the power can be supplied to start smelting. By adding the melting initiator, the high-temperature alloy powder can be melted smoothly by using vacuum induction melting technology. The material distribution and composition can be adjusted according to the element burn-off situation during the production process to realize the remelting and recycling of waste powder and the adjustment of composition.

[0044] The present invention will now be described in further detail through embodiments.

[0045] Example 1

[0046] The remelted powder used for recovery is grade GH4169, weighing 3.1 kg. The selected melting initiator is a base alloy block, with an added melting initiator weight of 0.25 kg. A 10 kg vacuum induction melting furnace is selected for powder recovery. This equipment's vacuum system is equipped with a two-stage vacuum pump. The first-stage pump has a maximum pumping capacity of 70 L / s. When the first-stage pump is activated and the vacuum inside the furnace is evacuated to approximately 600 Pa, the second-stage pump automatically starts, with a maximum pumping capacity of 300 L / s. The maximum cross-sectional area of ​​the vertical exhaust pipe in the melting chamber is approximately 0.32 m². 2 .

[0047] The critical particle size D for powders with a volume content of less than 10% of the total powder was determined. 10 The particle size is 16.82 μm, and the true density of the powder (i.e., the density of the GH4169 alloy ingot) is 8.24 g / cm³. 3 According to formulas (1) to (4), the maximum pumping capacity Q1 of the induction furnace vacuum system when the powder is not pumped out is 95.97 L / s.

[0048] The remelted recovery powder and melting initiator are loaded into the crucible, with the melting initiator placed near the center line of the crucible and covered with powder. After closing the furnace door, the vacuum system is turned on with an initial pumping rate of 70 L / s. When the vacuum level in the melting chamber drops below 1 Pa, power is supplied for smelting.

[0049] The powder remelting process is as follows:

[0050] (1) High-temperature refining: 1650℃, 8min;

[0051] (2) Low-temperature refining: 1400℃, 8 min;

[0052] (3) Pouring temperature: 1430℃.

[0053] During the powder remelting process in this embodiment, no powder extraction occurred. The gas content of the alloy ingot and the original powder obtained from the smelting is shown in Table 1.

[0054] Table 1 Gas content of remelted alloy ingots and original powder

[0055] gaseous elements Remelted recycled powder This invention prepares alloy ingots O 210ppm 6ppm N 91ppm 20ppm

[0056] The results show that using this invention for powder recovery in a vacuum induction melting furnace helps ensure the normal operation of the smelting equipment.

Claims

1. A method for designing vacuum system parameters for a vacuum smelting furnace used for powder recovery, characterized in that, Includes the following steps: (1) Calculate the critical pumping capacity of the vacuum system according to formulas (1) to (4) based on the parameters of the powder to be smelted and recovered and the relevant dimensional parameters of the smelting equipment. First, based on Bernoulli's equation and the gravity formula, the critical condition for preventing powder from being extracted during the vacuuming process is calculated according to formula (1): In the formula, ρ f True density of the powder, in kg / m³ 3 ;R f The minimum particle size of the powder is expressed in meters (m); g is the acceleration due to gravity, taken as 9.81 m / s². 2 ; ρ q The density of air at room temperature is taken as 1.29 kg / m³. 3 ;v q The pumping speed is expressed in m / s. R f The minimum particle size of the powder is approximated using empirical formula (2): In the formula, D 10 The minimum critical particle size is the particle size at which the powder volume content accounts for 10% of the total powder content, in meters; a is an empirical coefficient, ranging from 0.2 to 0.

5. The critical extraction rate inside the furnace is calculated according to formulas (3) and (4): In the formula, Q L This is the theoretical critical pumping capacity, in L / s. S represents the maximum cross-sectional area of ​​the vertical exhaust pipe inside the furnace, in meters. 2 ; In the formula, Q1 is the critical maximum pumping capacity of the vacuum system of the induction furnace, in L / s; b is an empirical coefficient, ranging from 2 to 10. (2) Place the powder to be smelted and recovered and the melting initiator into the smelting crucible as required, and close the furnace door; (3) Turn on the vacuum system to evacuate the melting chamber. At this time, the vacuum system pumping volume should not exceed the vacuum system pumping volume calculated according to formulas (1) to (4). After the vacuum degree of the melting chamber drops to below 1000 Pa, adjust the vacuum system pumping volume to the maximum and continue to evacuate. (4) After the vacuum level is evacuated to meet the requirements, power is supplied to start smelting; after melting, it is refined at high temperature and low temperature and then cast to obtain a remelted master alloy ingot.

2. The method for designing vacuum system parameters for a vacuum smelting furnace for powder recovery according to claim 1, characterized in that, In step (2), the total mass of the melting initiator is 0.05 to 0.25 times the total mass of the powder recovered from smelting.

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