A method for purifying and recovering high-temperature alloy return material

Abstract

The purification recovery method described in the present invention comprehensively utilizes vacuum refining, air blowing refining, slag washing treatment, overheating treatment, filtration treatment, and decompression purification, and synergistic purification treatment, which fully and effectively guarantees the cleanliness of the returned alloy after treatment, and smelting under pressure atmosphere reduces the volatilization loss of useful elements and the crucible reaction of active elements such as hafnium, aluminum, and titanium, thereby ensuring the accuracy of the alloy composition. Overheating treatment and gas stirring also further promote the homogenization of alloy composition and organizational refinement, and reduce the generation of harmful aggregates. The quality of the returned material is significantly improved, and the quality risk of the returned material is reduced, especially for the treatment of alloys containing hafnium, high aluminum, high chromium, etc., the advantages are obvious.

Description

Technical Field

[0001] The present application relates to the technical field of alloy smelting, and in particular to a method for purifying and recovering high-temperature alloy return materials. Background Art

[0002] Superalloys (high-temperature alloys) are used in the hot end components of aircraft engines or gas engines and are key core materials. The components with the highest operating temperatures are generally made by precision casting.

[0003] The precision casting process produces a large amount of casting waste such as runners and risers, defective unqualified parts, etc. Generally, this part of the alloy material is remelted in vacuum and mixed with new materials in a certain proportion before use. In practice, it is found that adding return materials will cause the performance of parts to deteriorate, especially the durability and plasticity.

[0004] The main reason is the non-metallic inclusions brought into the mold shell during the precision casting process, especially the incomplete removal of non-metallic inclusions generated by the core in the cavity parts, the enrichment of inclusions in the solidification process of the runner and riser, and the high-temperature surface oxidized (nitrided) film. These inclusions are not well removed during ordinary vacuum remelting, which affects the performance of the material and causes quality risks of the cast parts. Summary of the invention

[0005] Purpose of the invention: In view of the shortcomings of the prior art, the present application proposes a method for purifying and recovering returned materials to improve the utilization rate and quality stability of returned materials.

[0006] Ordinary high-temperature alloys are melted at high temperatures for many times, and during the process, oxidation, nitridation, and contamination of refractory materials occur, forming inclusions, which seriously damage the performance of the alloy and cause quality defects. For example, hafnium-containing alloys are very active and can easily combine with oxygen and nitrogen in refractory materials and the environment to form oxy(nitrided) hafnium inclusions. Moreover, the density of hafnium oxide is close to that of the alloy melt, so it is difficult to remove it by density difference. These inclusions are distributed in the alloy and seriously affect the performance of the alloy.

[0007] Therefore, the core of solving the utilization of returned materials is to solve the "inclusion problem". The process method of this patent is characterized by adopting a multi-faceted composite method to reduce refractory pollution and reduce the volatilization loss of low-melting-point or volatile useful elements (for example, basic elements aluminum and chromium commonly contained in high-temperature alloys). At the same time, it adopts the principle of bubble flotation and the principle of slag adsorption and dissolution to remove existing inclusions in the returned materials, purify the alloy melt, and increase the number of times the returned materials are reused.

[0008] The method proposed in this patent does not increase the cost of additional pre-treatment procedures, has a high metal element recovery rate, and has a significant purification treatment effect. The loss of aluminum and chromium, which are easily burned, is small, and the treatment effect of oxide (nitrogen) compound inclusions of elements such as hafnium and titanium is obvious. In particular, the purification recovery of high-value hafnium, rhenium, high aluminum, and high chromium alloys has obvious advantages.

[0009] Technical solution: The method for purifying and recovering high-temperature alloy return material of the present invention is carried out according to the following steps:

[0010] After pre-treatment of the returned material, it is loaded into the crucible, the furnace is closed and vacuumed, and the electric melting is carried out, and vacuum refining is carried out;

[0011] After vacuum refining, the melting chamber is filled with argon gas to 0.07MPa~1.0MPa and then heated to 1600℃~1700℃ for superheat treatment;

[0012] Cool down to 1400℃~1500℃ and keep warm, add homemade refining agent and carry out slag washing treatment;

[0013] Keeping the crucible warm and using a bottom gas diffuser to fill the crucible with hydrogen mixed gas for blowing refining;

[0014] Keep warm, stop blowing, release air, evacuate, and perform decompression purification;

[0015] The casting temperature is adjusted, the alloy is poured into a chute for physical filtration, and then poured into an ingot mold to obtain an alloy ingot.

[0016] Specifically, the pretreatment includes: classification, cutting, and shot blasting.

[0017] Specifically, the vacuum refining is as follows: temperature 1440±20° C., vacuum degree ≤1 Pa, and heat preservation for 10 to 20 minutes.

[0018] Specifically, the overheating treatment lasts for 1 to 5 minutes.

[0019] Specifically, the self-made refining agent mainly comprises and has the following proportions: 10 to 30 parts by weight of nickel-calcium alloy, 30 to 60 parts by weight of fluorite, and 10 to 30 parts by weight of calcium chloride. The self-made refining agent can be prepared by uniformly mixing nickel-calcium alloy with a particle size of 2 to 4 mm, fluorite powder, and calcium chloride according to the above proportions.

[0020] Specifically, in the nickel-calcium alloy, Ca accounts for 6% and the balance is nickel.

[0021] Specifically, the main composition and content of the hydrogen mixed gas are: 10% to 30% hydrogen and 70% to 90% argon by volume.

[0022] Specifically, the physical filtration is carried out through the slag pool, slag dam, gate plate and filter screen in the chute.

[0023] The method described in the present invention can effectively remove vacuum volatiles, aggregates, floating materials, and adsorbed inclusions through vacuum refining, overheating treatment, physical filtration treatment and other processes. On the basis of these purification processes, the overheating treatment proposed in this patent is special in that it adopts a 0.07MPa to 1.0MPa positive pressure argon environment, which effectively reduces the pollution brought in by the crucible reaction at high temperature of the alloy melt and the vacuum burning of useful elements at high temperature.

[0024] The present invention also adds a homemade refining agent to absorb and dissolve non-metallic inclusions floating to the melt surface, avoiding the floating refractory inclusions caused by electromagnetic stirring and air blowing refining from returning to the melt, and at the same time achieving purification effects such as replacement and deterioration.

[0025] The present invention blows reducing mixed gas into the melt in the crucible through the bottom blowing device to deoxidize and promote the floating of inclusions, thereby purifying the alloy melt. After the blowing refining is completed, the hydrogen dissolved in the alloy melt is preferentially precipitated at the sharp corners of the inclusions during the fifth step of decompression purification, thereby driving the inclusions to float, and further purifying the alloy melt.

[0026] Beneficial effects: The purification recovery method described in the present invention comprehensively utilizes the coordinated purification treatment of "vacuum refining", "air blowing refining", "slag washing treatment", "superheating treatment", "filtration treatment" and "decompression purification", which fully and effectively guarantees the cleanliness of the returned alloy after treatment. In addition, smelting under pressure atmosphere reduces the volatilization loss of useful elements and the crucible reaction of active elements such as hafnium, aluminum, and titanium, thereby ensuring the accuracy of the alloy composition. Superheating and gas stirring also further promote the homogenization of the alloy composition and the refinement of the structure, reducing the generation of harmful aggregates. The quality of the returned material is significantly improved, reducing the quality risk of the returned material, especially for the treatment of alloys containing hafnium, high aluminum, high chromium, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a photo of the HB5406 scum test in Example 1.

[0028] Figure 2 This is a photo of the HB5406 scum sample of Comparative Example 1.

[0029] Figure 3 This is a microscope photo of the dross of the remelted sample using ordinary technology.

[0030] Figure 4 Microscope dross photograph of the remelted sample using the refining agent pressure process. DETAILED DESCRIPTION

[0031] The technical solution of the present application is described in detail below through embodiments, but the protection scope of the present application is not limited to the embodiments.

[0032] Example 1

[0033] This embodiment recovers the returned material according to the following method:

[0034] 1. Pre-treat the casting runner, riser, and unqualified parts according to conventional methods and weigh them before loading them into the crucible.

[0035] 2. Close the furnace, evacuate the vacuum, and when the vacuum degree is ≤1Pa, supply 70kW of electricity for heating for 10 minutes, increase the power to 140KW and continue to supply electricity for melting for 30 minutes until the temperature reaches 1440℃.

[0036] 3. Adjust the power to keep warm, vacuum refining for 10 minutes, vacuum degree ≤1Pa, stop the pump.

[0037] 4. Fill with argon to 0.3MPa, adjust the power to 140KW and continue to heat up to 1600℃, reduce the power and keep warm for 1min, and cut off the power to cool down.

[0038] 5. Cool down to 1440℃, add the prepared refining agent (main components: 20 parts of nickel-calcium alloy;

[0039] 60 parts of fluorite; 20 parts of calcium chloride), adjust the power to keep warm, and blow hydrogen mixed gas into the crucible through the gas diffuser for 5 minutes.

[0040] 6. After stopping the air blowing, open the pressure relief valve to 0MPa in the smelting chamber, then evacuate to ≤1Pa, load the preheated chute with a filter device, increase the power to 140KW and raise the temperature to 1480℃, and adjust the power to 40KW for casting.

[0041] 7. After the alloy is cooled to ≤300℃, it is removed from the furnace and demoulded. The riser and bottom plug are cut, and component samples and oxygen and nitrogen samples are taken from both ends. The bar blank is sent for surface processing and the slag test material is taken.

[0042] Example 2

[0043] This embodiment recovers the returned material according to the following method:

[0044] 1. Pre-treat the casting runner, riser, and unqualified parts according to conventional methods and weigh them before loading them into the crucible.

[0045] 2. Close the furnace, evacuate the vacuum, and when the vacuum degree is ≤1Pa, supply 80KW of power for heating for 20 minutes, increase the power to 160KW and continue to supply power for melting for 40 minutes until the temperature reaches 1440℃.

[0046] 3. Adjust the power to keep warm, vacuum refining for 20 minutes, vacuum degree ≤1Pa, stop the pump.

[0047] 4. Fill with argon to 0.3MPa, adjust the power to 160KW and continue to heat up to 1600℃, reduce the power and keep warm for 5 minutes, and cut off the power to cool down.

[0048] 5. Cool down to 1440℃, add the prepared refining agent (main components: 20 parts of nickel-calcium alloy;

[0049] 60 parts of fluorite; 20 parts of calcium chloride), adjust the power to keep warm, and blow hydrogen into the crucible through the gas diffuser for 10 minutes.

[0050] 6. After stopping the air blowing, open the pressure relief valve to 0MPa in the smelting chamber, then evacuate to ≤1Pa, load the preheated chute with a filter device, increase the power to 160KW and raise the temperature to 1480℃, and adjust the power to 60KW for casting.

[0051] 7. After the alloy is cooled to ≤300℃, it is removed from the furnace and demoulded. The riser and bottom plug are cut, and component samples and oxygen and nitrogen samples are taken from both ends. The bar blank is sent for surface processing and the slag test material is taken.

[0052] Example 3 (Comparative Example 1)

[0053] This comparative example recovers the returned material according to the following conventional vacuum remelting method:

[0054] 1. Pre-treat the casting runner, riser, and unqualified parts according to conventional methods and weigh them before loading them into the crucible.

[0055] 2. After the furnace is closed and vacuumed, the vacuum degree is ≤1Pa, supply 70KW of power for heating for 10 minutes, increase the power to 140KW and continue to supply power for melting for 30-40 minutes, and continue to heat up and melt to a temperature of 1440℃.

[0056] 3. Adjust the power to keep warm, vacuum refining for 10 minutes with vacuum degree ≤1Pa, and cool down to conjunctival temperature.

[0057] 4. Load the preheated chute with filtering device, heat it to 1480℃ with high power of 140KW, and adjust the power to 40KW for casting.

[0058] 5. After the alloy is cooled to ≤300℃, it is removed from the furnace and demoulded. The riser and bottom plug are cut, and component samples and oxygen and nitrogen samples are taken from both ends. After the surface of the bar blank is processed, the slag test material is taken.

[0059] Component analysis results: Unit: WT%

[0060]

[0061] From the composition analysis results, it can be seen that the oxygen (nitrogen) content of Example 1 and Example 2 is significantly reduced compared with the representative value of the returned material before remelting and Comparative Example 1.

[0062] The photos of HB5406 scum test of Example 1 and Example 3 (Comparative Example 1) are shown in Figure 1 and Figure 2 The slag test also confirmed that the removal effect of the oxide (nitride) inclusions in Example 1 was obvious, and the argon atmosphere protection under pressure reduced the volatilization and burning loss of aluminum, a volatile element.

[0063] Example 4 (Comparative Example 2)

[0064] The basic steps of this comparative example are the same as those of Example 1, except that the homemade refining agent described in the present invention is not added.

[0065] Laser confocal microscopy showed that large flake inclusions floated on the surface of the ordinary remelted recycled material sample after melting. Figure 3 After the remelting of the reclaimed material sample with the addition of refining agent, only a few and fine spherical inclusions were found on the surface. Figure 4 .

[0066] The above description is only a preferred embodiment of the present application and is not intended to limit the present application.

Claims

1. A method for purifying and recovering high-temperature alloy return material, characterized in that: Proceed as follows: After pre-treatment of the returned material, it is loaded into the crucible, the furnace is closed and vacuumed, and the electric melting is carried out, and vacuum refining is carried out; After vacuum refining, the melting chamber is filled with argon gas to 0.07MPa~1.0MPa and then heated to 1600℃~1700℃ for superheat treatment; Cool down to 1400℃~1500℃ and keep warm, add homemade refining agent and carry out slag washing; Keeping the crucible warm and using a bottom gas diffuser to fill the crucible with hydrogen mixed gas for blowing refining; Keep warm, stop blowing, release air, evacuate, and perform decompression purification; Adjusting to the casting temperature, injecting the alloy into the chute for physical filtration, and then injecting into the ingot mold to obtain the alloy ingot; The vacuum refining is as follows: temperature 1440±20°C, vacuum degree ≤1Pa, heat preservation 10~20min; The self-made refining agent has the following main components and proportions: by weight: 10-30 parts of nickel-calcium alloy; 30-60 parts of fluorite; 10-30 parts of calcium chloride; The nickel-calcium alloy comprises 6% Ca and the remainder nickel; The main composition and content of the hydrogen mixed gas are: 10% to 30% hydrogen and 70% to 90% argon by volume.

2. The method for purifying and recovering high-temperature alloy return material according to claim 1, characterized in that: The pretreatment includes: classification, cutting and shot blasting.

3. The method for purifying and recovering high-temperature alloy return material according to claim 1, characterized in that: The overheating treatment lasts for 1 to 5 minutes.

4. The method for purifying and recovering high-temperature alloy return material according to claim 1, characterized in that: The physical filtration is through the slag pool, slag dam, gate plate and filter screen in the chute.

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