Pouring method of high aluminum nickel-based alloy castings

Abstract

The invention discloses a pouring method for high-aluminum nickel-based alloy castings, and relates to the field of casting technology. The technical scheme is as follows: comprising the following steps: shell baking, melting, refining and pouring; wherein, after the refining is completed, the temperature is reduced to the surface of the high-aluminum nickel-based alloy, and the film is solidified, and then the temperature is kept for 1 to 2 minutes, and then the temperature is raised to the pouring temperature, and the heating process is divided into two stages, the heating power of the first heating stage is 35 to 45 kW, the heating time is 12 to 15 seconds, and the heating power of the second heating stage is 20 to 25 kW, and the heating time is 40 to 80 seconds; the high-aluminum nickel-based alloy is K424 alloy. The invention controls the power and time of the power transmission in the pouring heating process without changing the overall scheme of the pouring process, thereby achieving the purpose of changing the mechanical properties of the casting, and improving the mechanical properties of the casting such as the elongation after fracture and the section shrinkage rate.

Description

Technical Field

[0001] The invention relates to the technical field of casting, in particular to a pouring method for high-aluminum nickel-based alloy castings. Background Art

[0002] High aluminum nickel-based alloys have good high temperature performance, thermal corrosion resistance and oxidation resistance, and are widely used in aerospace engines, ship gas turbines, internal combustion engines and other fields.

[0003] At present, domestic OEMs mainly use vacuum induction melting furnaces to cast high-quality castings for aerospace and gas turbines. The casting process is mainly divided into the master alloy ingot melting period, refining period and pouring period. Major domestic manufacturers mainly use the following two casting methods in the casting process: 1) After the master alloy ingot is refined at high temperature, it is cooled to the pouring temperature, the power is adjusted to keep the temperature of the molten steel unchanged, and then pouring is carried out; 2) After the master alloy ingot is refined at high temperature, it is cooled to the conjunctival solidification on the surface of the molten steel, and then the power is adjusted to quickly heat it to the pouring temperature, and then the power is adjusted to keep the temperature of the molten steel unchanged before pouring. However, in the process of casting high-aluminum nickel-based alloy castings, it was found that when the above two casting methods were used, the elongation and cross-sectional shrinkage of the castings were poor.

[0004] Therefore, how to improve the mechanical properties of cast castings by optimizing the casting process is a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art, to provide a casting method for high-aluminum-nickel-based alloy castings, to control the power and time of the casting temperature rise process without changing the overall scheme of the casting process, thereby achieving the purpose of changing the mechanical properties of the casting and improving the mechanical properties of the casting such as the elongation after fracture and the cross-sectional shrinkage rate.

[0006] The technical solution of the present invention is:

[0007] The invention provides a casting method for a high-aluminum nickel-based alloy casting, comprising the following steps: shell baking, melting, refining and casting; wherein, during casting, after the refining is completed, the temperature is lowered to a surface of the high-aluminum nickel-based alloy so that the film solidifies, the temperature is kept for 1-2 minutes, and then the temperature is raised to the casting temperature, and the heating process is divided into two stages, the heating power of the first heating stage is 35-45 kW, and the heating time is 12-15 seconds, and the heating power of the second heating stage is 20-25 kW, and the heating time is 40-80 seconds; the high-aluminum nickel-based alloy is K424 alloy.

[0008] The present invention first lowers the temperature to the conjunctival solidification temperature of the high-aluminum nickel-based alloy surface during pouring because: the high-aluminum nickel-based alloy contains 5.1-5.7% of aluminum elements, and the aluminum element mainly forms a γ' (Ni3AlTi) phase in the high-aluminum nickel-based alloy; in high-temperature molten steel, the aluminum element can form Ni2Al3 clusters, which can act as a refiner during the solidification process, change the grain size, and improve the plasticity of the casting; Ni2Al3 clusters exist in large quantities during the process from the solidification state of the alloy to the melting of the molten steel surface, so if the temperature is directly lowered to above the conjunctival solidification temperature of the high-aluminum nickel-based alloy surface, Ni2Al3 clusters may not be formed or the number of clusters formed is too small.

[0009] Since Ni2Al3 clusters are extremely unstable, during the casting process, the vacuum induction melting furnace will destroy the aggregation of Ni2Al3 clusters under high-power heating conditions, and cannot play the role of Ni2Al3 clusters in refining grains. Therefore, in the process of heating the temperature to the pouring temperature, the present invention adopts a staged heating method, firstly adopting high-power rapid heating to promote the rapid melting of the solidified alloy. If low-power heating is always adopted, it is difficult to melt it, resulting in a long heating time, which is not conducive to production; then low-power slow heating is adopted to allow Ni2Al3 clusters to form in large quantities and maintain the existence of Ni2Al3 clusters in the low-power heating stage.

[0010] Preferably, the shell is baked at a temperature of 800-850° C. for 5-7 hours.

[0011] Preferably, the refining temperature is 1580-1620° C. and the refining time is 3-5 min.

[0012] Preferably, during the melting, refining and pouring processes, the vacuum degree is ≤5Pa.

[0013] Preferably, the pouring temperature is the conjunctival solidification temperature of the high aluminum nickel-based alloy surface + (210-250)°C.

[0014] Preferably, the melting and refining are carried out in a vacuum induction melting furnace. The film solidification on the surface of the high aluminum nickel-based alloy in the present invention refers to the film solidification phenomenon on the surface of the high aluminum nickel-based alloy, which can be observed through the visual mirror of the vacuum induction melting furnace.

[0015] Preferably, the method specifically comprises the following steps:

[0016] S1 Mold baking: Place the mold shell of the casting into the sand box and keep it at 800~850℃ for 5~7h;

[0017] S2 melting: put the high aluminum nickel-based alloy material into the vacuum induction melting furnace, close the furnace cover, evacuate the furnace to a vacuum degree of ≤5Pa, supply power, and adjust the power to 35~40kW;

[0018] S3 refining: After the high aluminum nickel-based alloy material is melted, keep the power unchanged and measure the temperature. When the temperature of the molten steel is 1580~1620℃, adjust the power to 15~20kW and keep warm for 3~5 minutes;

[0019] S4 pouring: After refining is completed, adjust the power to 0kW, cool down, and make the temperature of the molten steel drop from 1580~1620℃ to solidify the surface film. Keep warm for 1~2min, adjust the power to 35~45kW, heat up for 12~15s, and melt the solidified molten steel on the surface; then adjust the power to 20~25kW, heat up for 40~80s to the pouring temperature, then adjust the power to 15~20kW, keep the temperature of the molten steel unchanged, and then pour.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The casting method of the high aluminum nickel-based alloy casting of the present invention achieves the purpose of changing the mechanical properties of the casting by changing the heating strategy after refining and controlling the power supply power and time during the casting heating process without changing the overall scheme of the casting process, thereby improving the mechanical properties of the casting such as the elongation after fracture and the cross-sectional shrinkage rate. DETAILED DESCRIPTION

[0022] In order to enable persons skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0023] The melting point of K424 high aluminum nickel-based alloy is 1280℃.

[0024] Example 1

[0025] The pouring method of the K424 high aluminum nickel-based alloy casting of the present embodiment comprises the following steps:

[0026] S1 Mold baking: Place the casting mold into the sand box and keep it at 825℃ for 6.5h;

[0027] S2 melting: 7kg of K424 high aluminum nickel-based alloy material is placed in a 20kg vacuum induction melting furnace, the furnace cover is closed, and the vacuum is evacuated to a vacuum degree of 5Pa, and then power is supplied and the power is adjusted to 38kW;

[0028] S3 refining: After the K424 high aluminum nickel-based alloy material is melted, keep the power unchanged, measure the temperature, and when the temperature of the molten steel reaches 1600℃, adjust the power to 18kW and keep warm for 4 minutes;

[0029] S4 pouring: After refining is completed, adjust the power to 0kW, cool down, and make the temperature of the molten steel drop from 1600℃ until the film on the surface of the molten steel solidifies. Keep warm for 1.5 minutes, adjust the power to 40kW, heat up for 14s, and melt the solidified molten steel on the surface; then adjust the power to 22kW, heat up for 60s to the pouring temperature of 1510℃, adjust the power to 18kW, keep the temperature of the molten steel unchanged, and then pour.

[0030] Example 2

[0031] The pouring method of the K424 high aluminum nickel-based alloy casting of the present embodiment comprises the following steps:

[0032] S1 Mold baking: Place the casting mold into the sand box and keep it at 850℃ for 5h;

[0033] S2 melting: 7kg of K424 high aluminum nickel-based alloy material is placed in a 20kg vacuum induction melting furnace, the furnace cover is closed, and the vacuum is evacuated to a vacuum degree of 4Pa, and then power is supplied and the power is adjusted to 35kW;

[0034] S3 refining: After the K424 high aluminum nickel-based alloy material is melted, keep the power unchanged, measure the temperature, and when the temperature of the molten steel reaches 1580℃, adjust the power to 15kW and keep warm for 5 minutes;

[0035] S4 pouring: After refining is completed, adjust the power to 0kW, cool down, and make the temperature of the molten steel drop from 1580℃ to solidify the film on the surface of the molten steel. Keep warm for 1min, adjust the power to 35kW, heat up for 15s, and melt the solidified molten steel on the surface; then adjust the power to 20kW, heat up for 80s to the pouring temperature of 1490℃, adjust the power to 15kW, keep the temperature of the molten steel unchanged, and then pour.

[0036] Example 3

[0037] The pouring method of the K424 high aluminum nickel-based alloy casting of the present embodiment comprises the following steps:

[0038] S1 Mold baking: Place the mold shell of the casting into the sand box and keep it at 800℃ for 7h;

[0039] S2 melting: 7kg of K424 high aluminum nickel-based alloy material is placed in a 20kg vacuum induction melting furnace, the furnace cover is closed, and the vacuum is evacuated to a vacuum degree of 4Pa, and then power is supplied and the power is adjusted to 40kW;

[0040] S3 refining: After the K424 high aluminum nickel-based alloy material is melted, keep the power unchanged, measure the temperature, and when the temperature of the molten steel reaches 1620℃, adjust the power to 20kW and keep warm for 3 minutes;

[0041] S4 pouring: After refining is completed, adjust the power to 0kW, cool down, and make the temperature of the molten steel drop from 1620℃ to solidify the film on the surface of the molten steel. Keep warm for 2 minutes, adjust the power to 45kW, heat up for 12s, and melt the solidified molten steel on the surface; then adjust the power to 25kW, heat up for 40s to the pouring temperature of 1530℃, adjust the power to 20kW, keep the temperature of the molten steel unchanged, and then pour.

[0042] Comparative Example 1

[0043] The pouring method of the K424 high aluminum nickel-based alloy casting of Comparative Example 1 comprises the following steps:

[0044] S1 Mold baking: Place the casting mold into the sand box and keep it at 825℃ for 6.5h;

[0045] S2 melting: 7kg of K424 high aluminum nickel-based alloy material is placed in a 20kg vacuum induction melting furnace, the furnace cover is closed, and the vacuum is evacuated to a vacuum degree of 5Pa, and then power is supplied and the power is adjusted to 38kW;

[0046] S3 refining: After the K424 high aluminum nickel-based alloy material is melted, keep the power unchanged, measure the temperature, and when the temperature of the molten steel reaches 1600℃, adjust the power to 18kW and keep warm for 4 minutes;

[0047] S4 pouring: After refining is completed, adjust the power to 0kW, cool down, and make the temperature of the molten steel drop from 1600℃ until the film on the surface of the molten steel solidifies. Keep warm for 1.5 minutes, adjust the power to 40kW, and when the temperature rises to the pouring temperature of 1510℃, adjust the power to 18kW, keep the temperature of the molten steel unchanged, and then pour.

[0048] Comparative Example 2

[0049] The pouring method of the K424 high aluminum nickel-based alloy casting of Comparative Example 2 comprises the following steps:

[0050] S1 Mold baking: Place the casting mold into the sand box and keep it at 825℃ for 6.5h;

[0051] S2 melting: 7kg of K424 high aluminum nickel-based alloy material is placed in a 20kg vacuum induction melting furnace, the furnace cover is closed, and the vacuum is evacuated to a vacuum degree of 5Pa, and then power is supplied and the power is adjusted to 38kW;

[0052] S3 refining: After the K424 high aluminum nickel-based alloy material is melted, keep the power unchanged, measure the temperature, and when the temperature of the molten steel reaches 1600℃, adjust the power to 18kW and keep warm for 4 minutes;

[0053] S4 pouring: After refining is completed, adjust the power to 0kW, cool down the temperature of the molten steel from 1600℃ until the film on the surface of the molten steel solidifies, adjust the power to 22kW, and when the temperature rises to the pouring temperature of 1510℃, adjust the power to 18kW, keep the temperature of the molten steel unchanged, and then pour.

[0054] Comparative Example 3

[0055] The pouring method of the K424 high aluminum nickel-based alloy casting of Comparative Example 3 comprises the following steps:

[0056] S1 Mold baking: Place the casting mold into the sand box and keep it at 825℃ for 6.5h;

[0057] S2 melting: 7kg of K424 high aluminum nickel-based alloy material is placed in a 20kg vacuum induction melting furnace, the furnace cover is closed, and the vacuum is evacuated to a vacuum degree of 5Pa, and then power is supplied and the power is adjusted to 38kW;

[0058] S3 refining: After the K424 high aluminum nickel-based alloy material is melted, keep the power unchanged, measure the temperature, and when the temperature of the molten steel reaches 1600℃, adjust the power to 18kW and keep warm for 4 minutes;

[0059] S4 pouring: After refining is completed, adjust the power to 0kW, cool down, and when the temperature of the molten steel drops from 1600℃ to the pouring temperature of 1510℃, adjust the power to 18kW, keep the temperature of the molten steel unchanged, and then pour.

[0060] Comparative Example 4

[0061] The pouring method of the K424 high aluminum nickel-based alloy casting of Comparative Example 4 comprises the following steps:

[0062] S1 Mold baking: Place the casting mold into the sand box and keep it at 825℃ for 6.5h;

[0063] S2 melting: 7kg of K424 high aluminum nickel-based alloy material is placed in a 20kg vacuum induction melting furnace, the furnace cover is closed, and the vacuum is evacuated to a vacuum degree of 5Pa, and then power is supplied and the power is adjusted to 38kW;

[0064] S3 refining: After the K424 high aluminum nickel-based alloy material is melted, keep the power unchanged, measure the temperature, and when the temperature of the molten steel reaches 1600℃, adjust the power to 18kW and keep warm for 4 minutes;

[0065] S4 pouring: After refining is completed, adjust the power to 0kW, cool down the temperature of the molten steel from 1600℃ to 1320℃, adjust the power to 18kW, keep the temperature of the molten steel unchanged for 1.5min; adjust the power to 23kW, raise the temperature from 1320℃ to 1510℃, then adjust the power to 18kW, keep the temperature unchanged, and pour.

[0066] Comparative Example 5

[0067] The pouring method of the K424 high aluminum nickel-based alloy casting of Comparative Example 5 comprises the following steps:

[0068] S1 Mold baking: Place the casting mold into the sand box and keep it at 825℃ for 6.5h;

[0069] S2 melting: 7kg of K424 high aluminum nickel-based alloy material is placed in a 20kg vacuum induction melting furnace, the furnace cover is closed, and the vacuum is evacuated to a vacuum degree of 5Pa, and then power is supplied and the power is adjusted to 38kW;

[0070] S3 refining: After the K424 high aluminum nickel-based alloy material is melted, keep the power unchanged, measure the temperature, and when the temperature of the molten steel reaches 1600℃, adjust the power to 18kW and keep warm for 4 minutes;

[0071] S4 pouring: After refining is completed, adjust the power to 0kW, cool down, and make the temperature of the molten steel drop from 1600℃ until the film on the surface of the molten steel solidifies. Adjust the power to 22kW, increase the temperature for 13s, and melt the solidified molten steel on the surface; then adjust the power to 40kW, increase the temperature for 60s to the pouring temperature of 1510℃, adjust the power to 18kW, keep the temperature of the molten steel unchanged, and then pour.

[0072] Comparative Example 6

[0073] The pouring method of the K424 high aluminum nickel-based alloy casting of Comparative Example 6 comprises the following steps:

[0074] S1 Mold baking: Place the casting mold into the sand box and keep it at 825℃ for 6.5h;

[0075] S2 melting: 7kg of K424 high aluminum nickel-based alloy material is placed in a 20kg vacuum induction melting furnace, the furnace cover is closed, and the vacuum is evacuated to a vacuum degree of 5Pa, and then power is supplied and the power is adjusted to 38kW;

[0076] S3 refining: After the K424 high aluminum nickel-based alloy material is melted, keep the power unchanged, measure the temperature, and when the temperature of the molten steel reaches 1600℃, adjust the power to 18kW and keep warm for 4 minutes;

[0077] S4 pouring: After refining is completed, adjust the power to 0kW, cool down the temperature of the molten steel from 1600℃ to 1320℃, adjust the power to 40kW, and heat up for 14s; then adjust the power to 22kW, heat up for 60s to the pouring temperature of 1510℃, adjust the power to 18kW, keep the temperature of the molten steel unchanged, and then pour.

[0078] In Examples 1-3 and Comparative Examples 1-6, the capacity of the vacuum induction melting furnace is 20 kg, and the power range is 0-50 kW. During the melting process, when the power supply is between 15 and 20 kW, the temperature of the molten steel can remain unchanged. When the power supply is greater than 20 kW, the greater the power, the faster the heating rate of the molten steel.

[0079] The mechanical properties of the K424 high aluminum nickel-based alloy castings cast in Examples 1-3 and Comparative Examples 1-6 were tested using a room temperature tensile testing machine of model CMT-5105 and a high temperature endurance testing machine of model RD-50. The room temperature tensile performance test was conducted in accordance with the "HB 5143-1996 Metal Room Temperature Tensile Test Method", and the high temperature endurance performance test was conducted in accordance with the "HB5150-1996 Metal High Temperature Tensile Endurance Test Method". Each casting was tested 3 times, and the test results are shown in Table 1:

[0080] Table 1 Mechanical properties test results of K424 high aluminum nickel-based alloy castings of Examples 1-3 and Comparative Examples 1-6

[0081]

[0082] As can be seen from Table 1, after the refining is completed, the present invention cools down until the film on the surface of the molten steel solidifies, and then adopts a heating strategy of first quickly heating up and then slowly heating up to the pouring temperature, which helps to improve the mechanical properties of the casting, especially its elongation after fracture and cross-sectional shrinkage.

[0083] At the same time, after the refining is completed, the temperature of comparative examples 1-2 is cooled to the conjunctival solidification of the steel liquid surface, and the strategies of rapid heating to the pouring temperature and slow heating to the pouring temperature are respectively adopted. After the refining is completed, the strategy of direct cooling to the pouring temperature is adopted in comparative example 3, which is not conducive to the mechanical properties of the casting. The reason is that: comparative example 1 adopts a high-power rapid heating method, and high-power heating leads to aggravated atomic diffusion, which is not conducive to the formation of Ni2Al3 clusters in the steel liquid and affects the performance of the alloy casting; comparative example 2 adopts a low-power slow heating method, although it is conducive to the formation of Ni2Al3 clusters and plays a role in refining grains. Under room temperature stretching, the elongation and cross-sectional shrinkage of the casting are improved, but it is not conducive to the high-temperature endurance performance of the casting; comparative example 3 adopts a direct cooling method, which is not conducive to the formation of Ni2Al3 clusters and does not play a role in refining grains, so the room temperature tensile properties of the casting are reduced.

[0084] Comparative Example 4 directly cooled the temperature to a temperature higher than the melting point of K424 high aluminum nickel-based alloy, and then slowly heated the temperature to the pouring temperature using a low-power method. Since the Ni2Al3 clusters are formed during the solidification process, Comparative Example 4 was cooled to 40°C above the solidification temperature. Due to the small amount of Ni2Al3 clusters formed, Ni2Al3 clusters could not even be formed, resulting in poor elongation and cross-sectional shrinkage of the casting.

[0085] Comparative Example 5 adopts a method of first slowly heating up with low power and then rapidly heating up with high power, which is not conducive to the formation of Ni2Al3 clusters, because the subsequent rapid heating process is not conducive to the existence of a large number of Ni2Al3 clusters formed during the slow heating process, thus resulting in poor elongation and cross-sectional shrinkage of the casting.

[0086] In Comparative Example 6, after refining, the temperature is lowered to a temperature higher than the melting point of the K424 high aluminum nickel-based alloy, and then the temperature is quickly increased and then slowly increased. Since the Ni2Al3 clusters are formed during the solidification process, cooling to 40°C above the solidification temperature will result in poor room temperature tensile properties of the casting due to the small amount of Ni2Al3 clusters formed, or even the failure to form Ni2Al3 clusters.

Claims

1. A casting method for high aluminum nickel-based alloy castings, characterized in that: The following steps are involved: The mold shell is baked, melted, refined and poured; wherein, the pouring is after the refining is completed, the temperature drops to the surface of the high aluminum nickel-based alloy and the film solidifies, and then the temperature is kept for 1-2 minutes, and then the temperature is raised to the pouring temperature, and the heating process is divided into two stages. The heating power of the first heating stage is 35-45kW, and the heating time is 12-15s. The heating power of the second heating stage is 20-25kW, and the heating time is 40-80s. The pouring temperature is the high aluminum nickel-based alloy surface film solidification temperature + (210-250) ° C; the high aluminum nickel-based alloy is K424 alloy, containing 5.1-5.7% aluminum.

2. The pouring method of high aluminum nickel-based alloy casting according to claim 1, characterized in that: The mold shell is baked at a temperature of 800-850° C. for 5-7 hours.

3. The pouring method of high aluminum nickel-based alloy casting according to claim 1, characterized in that: The refining temperature is 1580-1620° C. and the refining time is 3-5 minutes.

4. The pouring method of high aluminum nickel-based alloy casting according to claim 1, characterized in that: During the melting, refining and pouring process, the vacuum degree is ≤5Pa.

5. The pouring method of high aluminum nickel-based alloy casting according to claim 1, characterized in that: The melting and refining are carried out in a vacuum induction melting furnace.

6. The pouring method of high aluminum nickel-based alloy casting according to claim 1, characterized in that: The specific steps include: S1 Mold baking: Place the mold shell of the casting into the sand box and keep it at 800~850℃ for 5~7h; S2 melting: put the high aluminum nickel-based alloy material into the vacuum induction melting furnace, close the furnace cover, evacuate the furnace to a vacuum degree of ≤5Pa, supply power, and adjust the power to 35~40kW; S3 refining: After the high aluminum nickel-based alloy material is melted, keep the power unchanged and measure the temperature. When the temperature of the molten steel is 1580~1620℃, adjust the power to 15~20kW and keep warm for 3~5 minutes; S4 pouring: After refining is completed, adjust the power to 0kW, cool down, and make the temperature of the molten steel drop from 1580~1620℃ to solidify the surface film. Keep warm for 1~2min, adjust the power to 35~45kW, heat up for 12~15s, and melt the solidified molten steel on the surface; then adjust the power to 20~25kW, heat up for 40~80s to the pouring temperature, then adjust the power to 15~20kW, keep the temperature of the molten steel unchanged, and then pour.

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