A method for controlling chromium element in high temperature alloy

Abstract

The present invention belongs to the technical field of alloy manufacturing, and discloses a method for controlling chromium elements in high-temperature alloys, aiming to solve the problem that the chromium element yield and distribution uniformity cannot be taken into account at the same time. By not adding chromium and carbon raw materials to the base material, adding chromium elements and matching carbon content in batches, and adopting a "carbon control" refining process and a "double" stirring alloying process, the chromium element loss is effectively reduced and the chromium distribution uniformity is improved. The method described in the present invention has achieved good results in the production of high-temperature alloys with different chromium contents. Compared with the prior art, it significantly improves the chromium element yield and improves its distribution uniformity in the alloy, thereby reducing the tendency of harmful phase precipitation and improving the quality of the alloy.

Description

Technical Field

[0001] The present application relates to the technical field of nonferrous alloy manufacturing, and in particular to a method for controlling chromium elements in high-temperature alloys. Background Art

[0002] The metallic element chromium is an indispensable alloying element in nickel-, iron- and cobalt-based superalloys. Almost all superalloys contain the metallic element chromium. The chromium content varies in different superalloys. The chromium content in nickel- and iron-based superalloys is generally 3% to 20%, while in cobalt-based alloys, the chromium content is generally 10% to 30%. Chromium not only plays a role in solid solution strengthening in superalloys, but also forms carbides with carbon elements to play a precipitation strengthening role. On the other hand, chromium can also form a dense oxide film on the surface of the alloy, blocking the material matrix from the environment, and effectively improving the anti-oxidation corrosion performance. However, if the chromium content is not properly controlled, it is easy to form harmful phases such as σ phase and μ phase with W, Mo, Co, Ni and Mo, reducing the comprehensive performance of the alloy. Therefore, while improving the stability of chromium content control, improving its distribution uniformity is one of the important criteria for evaluating the technical level of superalloy production process.

[0003] The metallic element chromium is easy to burn when the vacuum is low (high oxygen content), and it is easy to volatilize when the vacuum is high (low oxygen content). Therefore, how to reduce the loss of metallic element chromium during vacuum induction melting and improve its distribution uniformity is an important direction for the development of vacuum melting process technology suitable for high-temperature alloy production.

[0004] At present, when vacuum induction melting is used to produce high-temperature alloys, the technical solution of "low temperature and short time vacuum refining" is usually used, which reduces the loss of chromium and controls its recovery rate at about 93%. However, due to the reduction of refining temperature and the shortening of refining time, the uniformity of chromium in the melt is affected, resulting in a deviation of chromium content of up to 0.15% at the beginning and end of the high-temperature alloy ingot, which increases the tendency of harmful phase precipitation and reduces the quality of the alloy.

[0005] In order to improve the uniformity of chromium distribution, reduce the tendency of harmful phase precipitation, and improve the quality of the alloy, a vacuum induction melting process with "increasing the amount of chromium, increasing the refining temperature, and extending the refining time" as the core was derived. Although this process technology can control the deviation of chromium content at the beginning and end of the high-temperature alloy ingot within 0.12%, due to the high refining temperature and long refining time, the loss of chromium elements is significantly increased, which seriously reduces its recovery rate (≤91%) and increases the alloy cost.

[0006] Therefore, in the vacuum induction melting process of chromium-containing high-temperature alloys, the bottleneck of the existing technology is that the chromium element yield and the chromium element distribution uniformity cannot be taken into account at the same time. Summary of the invention

[0007] Purpose of the invention: In view of the deficiencies in the prior art, the present application provides a method for controlling the chromium element, which can solve the technical bottleneck of the inability to balance the chromium element yield and the chromium element distribution uniformity in the existing vacuum induction melting process of chromium-containing high-temperature alloys.

[0008] Technical solution: The method for controlling chromium in a high-temperature alloy provided by the present invention mainly comprises the following steps:

[0009] Step 1, raw material loading: In the reaction equipment (crucible), place the materials from bottom to top in the following order: nickel, other elements, nickel. The raw materials placed are called base materials.

[0010] Step 2, melting of raw materials: when the vacuum degree is less than 5Pa, start to supply power; when the vacuum degree is less than 1.3Pa, gradually increase the power supply and adjust the power to prevent large amounts of exhaust and "sputtering". The time is usually 20 to 30 minutes. After the base material is melted, add cobalt and nickel; after the above raw materials are melted, add chromium raw materials and carbon for the first time; after the first added chromium raw materials and carbon are melted and the alloy melt does not completely cover the chromium raw materials, add chromium raw materials and carbon for the second time; in the above manner, add all the chromium raw materials, and do not add carbon when adding the chromium raw materials for the last time.

[0011] Step 3, "carbon control" refining: After the above raw materials are melted, add the remaining carbon, adjust the refining temperature to 1520℃~1600℃, perform vacuum refining, and continue for 15~50min before ending the refining. During the refining process, adjust the electromagnetic frequency to 60~130Hz, and perform the first electromagnetic stirring, which lasts for 2~10min.

[0012] Step 4, "double" stirring alloying: after refining, turn off the power and cool to almost conjunctival film, add Ti and Al according to the smelting composition to melt; adjust the melt temperature to 1500-1550°C, perform alloying once, last for 10-30 minutes, during which a second electromagnetic stirring is performed, the stirring frequency is 70-100 Hz, and the time is 1-4 minutes; after completing the first alloying, turn off the power and cool to 1440-1490°C, add trace components in the target alloy, melt clearly, perform secondary alloying, and at the same time perform a third electromagnetic stirring, the stirring frequency is 50-80 Hz, and the time is 1-5 minutes.

[0013] Step 5, pouring: adjust the temperature and then pour, thus completing the alloy smelting.

[0014] Specifically, in step 1, the other elements are: one or more of cobalt, molybdenum, niobium, tantalum, and vanadium.

[0015] More specifically, when the target product alloy is K452 alloy, the material order is Ni, Co, Mo, Nb, W, Ni; when the target product alloy is K438 alloy, the material order is Ni, Co, Mo, Nb, W, Ta, Ni; when the target product alloy is DZ22B alloy, the material order is Ni, Co, Nb, W, Ni.

[0016] Specifically, in step 2, the time is usually 20 to 30 minutes. A further improvement is to observe the melting of the raw materials, and when small particles or flake carbon remain, reduce the power supply and extend the melting time to more than 40 minutes.

[0017] Specifically, in step 3, when the Cr content in the target product alloy exceeds 20% (for example, K452), the added carbon content is 20-40% of the total carbon content; when the Cr content in the target product alloy is 10-20% (for example, K438), the added carbon content is 60-70% of the total carbon content; when the Cr content in the target product alloy is less than 10% (for example, DZ22B), the added carbon content is 70-90% of the total carbon content.

[0018] The "carbon control" refining process described in step 3 of the present invention is the core part of this technology. Refining is a stage in the vacuum induction melting process where the melt temperature is high and the vacuum degree is high (low partial pressure). It is a key core stage for controlling element volatilization and burn-off, as well as reducing element segregation. During the refining stage, the volatilization and burn-off of elements are closely related to the physicochemical properties of the melt / vacuum interface. Among the influencing factors, the diffusion of elements in the melt is mainly dominated by the alloy composition system itself, and is also affected by the smelting process (temperature and time). On the other hand, the volatilization of elements at the melt / vacuum interface is not only affected by the alloy composition system, but also by the characteristics of the melt / vacuum interface. The characteristics of the melt / vacuum interface, such as the interface area, are affected by the refining process.

[0019] Specifically, during the "carbon control" refining process, first, by adjusting the melt temperature (controlling the diffusion kinetics of the Cr element from the melt to the melt / vacuum interface), the melt / vacuum interface is controlled by controlling the size of the melt "hump", laying the core control foundation for controlling the burning and volatilization of the Cr element. Secondly, by adding carbon content (scientifically matching the Cr content in the melt), since the radius and density of the carbon element are much smaller than those of the Cr element, and its saturated vapor pressure is greater than that of the Cr element. Therefore, under the same conditions (vacuum refining), carbon will preferentially diffuse to the melt / vacuum interface and occupy the diffusion channel (when no carbon is added, this channel is occupied by the Cr element, causing the Cr element to burn and volatilize), thereby inhibiting the volatilization of the Cr element. On the other hand, by controlling the matching relationship between the carbon content and the Cr element, the total time that carbon occupies the diffusion channel can also be effectively regulated (during this time, the loss of the Cr element can be suppressed), thereby in turn determining and controlling the "carbon control" refining time. Therefore, in the "carbon control" refining stage, it is necessary to calculate the kinetic characteristics of the diffusion of Cr to the melt / vacuum interface based on the Cr content in the melt, to determine the required carbon content (matching the Cr content) and the refining temperature, to ensure that the kinetic characteristics of the diffusion of carbon to the melt / vacuum interface are greater than the kinetic characteristics of Cr. Afterwards, the total time that the carbon element can effectively occupy the diffusion channel is calculated based on the refining temperature, and then the refining time is determined in turn.

[0020] Therefore, the "carbon control" refining process described in step 3 requires precise control of the residual carbon content (that is, controlling the proportion of the added residual carbon content to the total carbon content). If the added carbon content is not controlled or improperly controlled at this stage, the diffusion of carbon at the melt / vacuum interface cannot effectively occupy all diffusion channels, or the time occupied in the diffusion channel is insufficient, and the diffusion and volatilization of the Cr element at the melt interface cannot be effectively inhibited, thereby increasing the loss of the Cr element and then reducing the yield of the Cr element.

[0021] More specifically, in step 3, when the Cr content in the target alloy is greater than 20%, the process conditions are: the refining temperature is adjusted to 1520-1540°C; the refining time is 30-50min; the electromagnetic stirring frequency is adjusted to 100-130Hz; and the stirring time is adjusted to 5-10min. When the Cr content in the target alloy is between 10% and 20%, the process conditions are: the refining temperature is adjusted to 1540-1560°C; the refining time is 20-40min; the electromagnetic stirring frequency is adjusted to 80-100Hz; and the stirring time is adjusted to 4-8min. When the Cr content in the target alloy is less than 10%, the process conditions are: the refining temperature is adjusted to 1560-1600°C; the refining time is 15-25min; the electromagnetic stirring frequency is adjusted to 60-80Hz; and the stirring time is adjusted to 2-6min.

[0022] Furthermore, in step 3, in the "carbon control" refining stage, after adding the remaining carbon, the smelting equipment is tilted 3 to 5 degrees, and other parameters and operations remain unchanged. It was unexpectedly found that this operation can effectively reduce the slag content of the product (HB5406, the slag area is reduced from 1% to 0.5%), and reduce the oxygen content in the product (the oxygen content is less than 4ppm, originally 5 to 7ppm), improve the purity of the product, and further improve the product quality.

[0023] Specifically, in step 4, when the Cr content in the target alloy is greater than 20%, the process conditions are: the first alloying temperature is 1530-1550°C, the duration is 10-15min; the second electromagnetic stirring frequency is 70-80Hz, the duration is 1-3min; the second alloying temperature is 1440-1460°C; the third electromagnetic stirring frequency is 70-80Hz, the duration is 1-3min. When the Cr content in the target alloy is between 10 and 20%, the process conditions are: the first alloying temperature is 1520-1540°C, the duration is 15-25min; the second electromagnetic stirring frequency is 80-90Hz, the duration is 2-4min; the second alloying temperature is 1450-1470°C; the third electromagnetic stirring frequency is 60-70Hz, the duration is 2-4min. When the Cr content in the target alloy is less than 10%, the process conditions are: the first alloying temperature is 1500-1520°C, the duration is 20-30 minutes; the second electromagnetic stirring frequency is 90-100Hz, the duration is 2-4 minutes; the secondary alloying temperature is 1470-1490°C; the third electromagnetic stirring frequency is 50-60Hz, the duration is 3-5 minutes.

[0024] Specifically, in step 4, when the target product alloy is K452 alloy, the trace components are La, Y, B and Zr; when the target product alloy is K438 alloy, the trace components are La, Y, B and Zr; when the target product alloy is DZ22B alloy, the trace components are Hf, B and Zr. The content of the trace components is less than 2% of the total mass of the alloy.

[0025] Beneficial effects: Compared with the prior art, the method of the present invention can effectively improve the recovery rate of chromium element: 1) The scheme of not adding Cr element to the base material can avoid the loss of Cr element caused by Cr oxidation due to low vacuum degree (high oxygen content) in the initial stage; 2) Compared with the traditional one-time addition of Cr element, the scheme of adding Cr element in batches can effectively reduce the volatilization of Cr element; 3) By adding carbon element while adding Cr element in batches, the volatilization of Cr element can be further suppressed and the recovery rate of Cr element can be improved; 4) In the refining stage, on the basis of adjusting the added carbon content, the refining temperature and refining time are optimized to effectively inhibit the volatilization of Cr element in the refining stage and improve the recovery rate of Cr element; 5) The scheme of controlling the electromagnetic stirring frequency and adjusting the "hump" area of ​​the melt is selected to control the melt / vacuum interface area (that is, the channel for the volatilization of Cr element); at the same time, the electromagnetic stirring time is adjusted to adjust the existence time of the "hump", thereby reducing the volatilization of Cr element. The above technical solution can effectively reduce the loss of Cr element in the alloy during the melting stage and the refining stage, thereby improving the recovery rate of Cr element.

[0026] On the other hand, the method of the present invention not only improves the yield of Cr element, but also develops a "three-step" uniformization method: 1) in the melting stage, by adding Cr element in batches, controlling the melt temperature and extending the melting time, the uniformity of Cr element is initially improved; 2) in the refining and alloying stages, the scheme of regulating the frequency and stirring time of electric pulse magnetic stirring is selected to further improve the uniformity of Cr element and other elements; 3) by regulating the "double" matching relationship between refining temperature and time, and alloying temperature and time, the uniformity of Cr and other elements is further improved.

[0027] The high-temperature alloys with different Cr contents melted by the technology of the present invention have achieved good results. Compared with other technical methods, the recovery rate of Cr element is significantly improved, and the distribution uniformity of Cr element is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the SEM image of the K452 alloy product of Example 1

[0029] Figure 2 This is the EDS scan of the K452 alloy product of Example 1

[0030] Figure 3 This is the SEM image of the K452 alloy product of Example 2

[0031] Figure 4 This is the EDS scan of the K452 alloy product of Example 2

[0032] Figure 5 This is the SEM image of the K452 alloy of comparative example 1

[0033] Figure 6 EDS scan of K452 alloy, product of comparative example 1 DETAILED DESCRIPTION

[0034] 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.

[0035] Example 1

[0036] This example produces a nickel-based K452 high-temperature alloy according to the following steps:

[0037] Step 1: According to the composition of K452 alloy, place the raw materials in the crucible in the order of Ni, Co, Mo, Nb, W, and Ni from bottom to top.

[0038] Step 2: When the vacuum degree is less than 2Pa, start to supply power, and when the vacuum degree is less than 1.3Pa, gradually increase the power supply. After the base material is melted, gradually add the remaining Co and Ni; when the above raw materials are nearly melted, add 40% chromium raw materials and 30% carbon at the same time for the first time; when they are nearly melted, add 40% chromium raw materials and 30% carbon at the same time for the second time; when they are nearly melted, add the remaining chromium raw materials to melt.

[0039] Step 3: After the raw materials are melted, add the remaining 40% carbon, adjust the melt temperature to 1540℃, and perform vacuum refining. During this period, the frequency is selected to be 100Hz, and the first electromagnetic stirring is performed for 5 minutes. After the refining process lasts for 30 minutes, the refining is completed.

[0040] Step 4: After refining, turn off the power and cool down to almost conjunctivae, add Ti and Al according to the composition of K452 alloy, and perform alloying for 15 minutes. During this period, the frequency is 75Hz, and the second electromagnetic stirring is performed for 1 minute. After the first alloying is completed, turn off the power and cool down to 1450℃, add La, Y, B and Zr, and then perform the third electromagnetic stirring for 1 minute at a frequency of 70Hz to complete the secondary alloying.

[0041] Step 5: Adjust the temperature to 1550℃ and then pour. The alloy melting is completed.

[0042] The SEM image and EDS scan of the product obtained in Example 1 are as follows: Figure 1 and Figure 2 It can be seen that the Cr content in the alloy product has a small deviation, good distribution uniformity and stable structure.

[0043] Example 2

[0044] This example produces a nickel-based K452 high-temperature alloy according to the following steps:

[0045] Step 1: According to the composition of K452 alloy, place the raw materials in the crucible in the order of Ni, Co, Mo, Nb, W, and Ni from bottom to top.

[0046] Step 2: When the vacuum degree is less than 1.4Pa, start to supply power, and when the vacuum degree is less than 1.3Pa, gradually increase the power supply. After the base material is melted, gradually add the remaining Co and Ni; when the above raw materials are nearly melted, add 25% chromium raw materials and 25% carbon at the same time for the first time; when they are nearly melted, add 25% chromium raw materials and 25% carbon at the same time for the second time; when they are nearly melted, add 25% chromium raw materials and 25% carbon at the same time for the third time; when they are nearly melted, add the remaining chromium raw materials to melt.

[0047] Step 3: After the raw materials are melted, add the remaining 25% carbon, adjust the melt temperature to 1530℃, and perform vacuum refining. During this period, the frequency is selected to be 120Hz, and the first electromagnetic stirring is performed for 8 minutes. After the refining process lasts for 40 minutes, the refining is completed.

[0048] Step 4: After refining, turn off the power and cool down to almost conjunctivae, add Ti and Al according to the composition of K452 alloy, adjust the melt temperature to 1540℃, and carry out the first alloying for 12 minutes. During this period, the frequency is selected to be 70Hz, and the second electromagnetic stirring is carried out for 2 minutes; after the first alloying is completed, turn off the power and cool down to 1440℃, add La, Y, B and Zr, etc., and then the frequency is selected to be 75Hz, and the third electromagnetic stirring is carried out for 3 minutes to complete the second alloying.

[0049] Step 5: Adjust the temperature to 1550℃ and then pour. The alloy melting is completed.

[0050] The SEM image and EDS scan of the product obtained in Example 2 are as follows: Figure 3 and Figure 4 As shown, it can be seen that the Cr content in the product has a small deviation, good distribution uniformity, and stable structure.

[0051] Example 3

[0052] This example produces a nickel-based K452 high-temperature alloy according to the following steps:

[0053] Step 1: According to the composition of K452 alloy, place the raw materials in the crucible in the order of Ni, Co, Mo, Nb, W, and Ni from bottom to top.

[0054] Step 2: When the vacuum degree is less than 3Pa, start to supply power, and when the vacuum degree is less than 1.3Pa, gradually increase the power supply. After the base material is melted, gradually add the remaining Co and Ni; when the above raw materials are nearly melted, add 30% chromium raw materials and 20% carbon at the same time for the first time; when they are nearly melted, add 30% chromium raw materials and 20% carbon at the same time for the second time; when they are nearly melted, add 30% chromium raw materials and 20% carbon at the same time for the third time; when they are nearly melted, add the remaining chromium raw materials to melt.

[0055] Step 3: After the raw materials are melted, add the remaining 40% carbon, adjust the melt temperature to 1520℃, and perform vacuum refining. During this period, the frequency is selected to be 130Hz, and the first electromagnetic stirring is performed for 10 minutes. After the refining process lasts for 50 minutes, the refining is completed.

[0056] Step 4: After refining, turn off the power and cool down to almost conjunctivae, add Ti and Al according to the composition of K452 alloy, and adjust the melt temperature to 1550℃, and carry out the first alloying for 10 minutes. During this period, the frequency is 85Hz, and the second electromagnetic stirring is carried out for 3 minutes; after the first alloying is completed, turn off the power and cool down to 1460℃, add La, Y, B and Zr, and then the frequency is 80Hz, and the third electromagnetic stirring is carried out for 2 minutes to complete the second alloying.

[0057] Step 5: Adjust the temperature to 1550℃ and then pour. The alloy melting is completed.

[0058] Comparative Example 1

[0059] This example produces a nickel-based K452 high-temperature alloy according to the following steps:

[0060] Step 1: According to the composition of K452 alloy, place the raw materials in the crucible in the order of 30-40% C, Ni, Co, Cr, Mo, Nb, W, and Ni from bottom to top.

[0061] Step 2: When the vacuum degree is less than 20Pa, start to supply power, and when the vacuum degree is less than 5Pa, gradually increase the power supply. After the base material is melted, add the remaining Co and Ni in a distributed manner; when the above raw materials are nearly melted, continue to add the remaining Co and Ni. When the remaining Co and Ni are added for the last time, add all the remaining carbon to melt the raw materials.

[0062] Step 3: After the raw materials are melted, adjust the melt temperature to 1580℃ and perform vacuum refining. During this period, the frequency is selected to be 60Hz, and the first electromagnetic stirring is performed for 3 minutes. After the refining process lasts for 40 minutes, the refining is completed.

[0063] Step 4: After refining, turn off the power and cool down to almost conjunctivae, add Ti and Al according to the K452 alloy composition to melt; adjust the melt temperature to 1550℃, perform the first alloying, and the whole alloying lasts for 10 minutes. During this period, the frequency is selected to be 60Hz, and the second electromagnetic stirring is carried out for 3 minutes; after the first alloying is completed, turn off the power and cool down to 1450℃, add La, Y, B and Zr to melt, select the frequency of 50Hz, and perform the third electromagnetic stirring for 3 minutes to complete the second alloying.

[0064] Step 5: Adjust the temperature to 1550℃ and then pour. The alloy melting is completed.

[0065] The SEM image and EDS scan image of the product obtained in Comparative Example 1 are as follows: Figure 5 and Figure 6 It can be seen that the Cr content in the product has a large deviation, the uniformity of element distribution is poor, and large-sized Cr-containing precipitates appear in the organization.

[0066] Example 4

[0067] This example produces a nickel-based K438 high-temperature alloy according to the following steps:

[0068] Step 1: According to the composition of K438 alloy, place the raw materials in the crucible in the order of Ni, Co, Mo, Nb, W, Ta, and Ni from bottom to top.

[0069] Step 2: When the vacuum degree is less than 5Pa, start to supply power, and when the vacuum degree is less than 1.3Pa, gradually increase the power supply. After the base material is melted, gradually add the remaining Co and Ni; when the above raw materials are nearly melted, add 50% chromium raw materials and 30% carbon at the same time for the first time; when they are nearly melted, add the remaining chromium raw materials to melt.

[0070] Step 3: After the raw materials are melted, add the remaining 70% carbon, adjust the melt temperature to 1560℃, and perform vacuum refining. During this period, the frequency is selected to be 100Hz, and the first electromagnetic stirring is performed for 8 minutes. After the refining process lasts for 40 minutes, the refining is completed.

[0071] Step 4: After refining, turn off the power and cool down to almost conjunctivae, add Ti and Al according to the K438 alloy composition, and adjust the melt temperature to 1540℃ for alloying for 15 minutes. During this period, the frequency is 90Hz, and the second electromagnetic stirring is carried out for 4 minutes; after the first alloying is completed, turn off the power and cool down to 1450℃, add La, Y, B and Zr, and then the frequency is 60Hz, and the third electromagnetic stirring is carried out for 2 minutes to complete the second alloying.

[0072] Step 5: Adjust the temperature to 1550℃ and then pour. The alloy melting is completed.

[0073] Example 5

[0074] This example produces a nickel-based K438 high-temperature alloy according to the following steps:

[0075] Step 1: According to the composition of K438 alloy, place the raw materials in the crucible in the order of Ni, Co, Mo, Nb, W, Ta, and Ni from bottom to top.

[0076] Step 2: When the vacuum degree is less than 3Pa, start to supply power, and when the vacuum degree is less than 1.3Pa, gradually increase the power supply. After the base material is melted, gradually add the remaining Co and Ni; when the above raw materials are nearly melted, add 40% chromium raw materials and 20% carbon at the same time for the first time; when they are nearly melted, add 40% chromium raw materials and 20% carbon at the same time for the second time; when they are nearly melted, add the remaining chromium raw materials to melt.

[0077] Step 3: After the raw materials are melted, add the remaining 60% carbon, adjust the melt temperature to 1550℃, and perform vacuum refining. During this period, the frequency is selected to be 90Hz, and the first electromagnetic stirring is performed for 6 minutes. After the refining process lasts for 30 minutes, the refining is completed.

[0078] Step 4: After refining, turn off the power and cool down to almost conjunctivae, add Ti and Al according to the K438 alloy composition, and adjust the melt temperature to 1520℃ for alloying for 18 minutes. During this period, the frequency is 80Hz, and the second electromagnetic stirring is carried out for 2 minutes; after the first alloying is completed, turn off the power and cool down to 1460℃, add La, Y, B and Zr, and then select the frequency of 70Hz for the third electromagnetic stirring, which lasts for 3 minutes to complete the second alloying.

[0079] Step 5: Adjust the temperature to 1550℃ and then pour. The alloy melting is completed.

[0080] Example 6

[0081] This example produces a nickel-based K438 high-temperature alloy according to the following steps:

[0082] Step 1: According to the composition of K438 alloy, place the raw materials in the crucible in the order of Ni, Co, Mo, Nb, W, Ta, and Ni from bottom to top.

[0083] Step 2: When the vacuum degree is less than 2Pa, start to supply power, and when the vacuum degree is less than 1.3Pa, gradually increase the power supply. After the base material is melted, gradually add the remaining Co and Ni; when the above raw materials are nearly melted, add 25% chromium raw materials and 10% carbon at the same time for the first time; when they are nearly melted, add 25% chromium raw materials and 10% carbon at the same time for the second time; when they are nearly melted, add 25% chromium raw materials and 10% carbon at the same time for the third time; when they are nearly melted, add the remaining chromium raw materials to melt.

[0084] Step 3: After the raw materials are melted, add the remaining 70% carbon, adjust the melt temperature to 1540℃, and perform vacuum refining. During this period, the frequency is selected to be 80Hz, and the first electromagnetic stirring is performed for 4 minutes. After the refining process lasts for 20 minutes, the refining is completed.

[0085] Step 4: After refining, turn off the power and cool down to almost conjunctivae, add Ti and Al according to the K438 alloy composition, and adjust the melt temperature to 1530℃ for alloying for 20min. During this period, the frequency is 85Hz, and the second electromagnetic stirring is carried out for 3min; after the first alloying is completed, turn off the power and cool down to 1470℃, add La, Y, B and Zr, and then the frequency is 65Hz, and the third electromagnetic stirring is carried out for 4min to complete the second alloying.

[0086] Step 5: Adjust the temperature to 1550℃ and then pour. The alloy melting is completed.

[0087] Comparative Example 2

[0088] This example produces a nickel-based K438 high-temperature alloy according to the following steps:

[0089] Step 1: According to the composition of K438 alloy, place the raw materials in the crucible in the order of 30-40% C, Ni, Co, Cr, Mo, Nb, W, Ta, and Ni from bottom to top.

[0090] Step 2: When the vacuum degree is less than 20Pa, start to supply power, and when the vacuum degree is less than 5Pa, gradually increase the power supply. After the base material is melted, add the remaining Co and Ni in a distributed manner; when the above raw materials are nearly melted, continue to add the remaining Co and Ni. When the remaining Co and Ni are added for the last time, add all the remaining carbon to melt the raw materials.

[0091] Step 3: After the raw materials are melted, adjust the melt temperature to 1580℃ and perform vacuum refining. During this period, select a frequency of 60Hz and perform the first electromagnetic stirring for 5 minutes. After the refining process lasts for 40 minutes, the refining is completed.

[0092] Step 4: After refining, turn off the power and cool down to almost conjunctivae, add Ti and Al according to the K438 alloy composition; adjust the melt temperature to 1550℃, perform the first alloying, and the whole alloying lasts for 10 minutes. During this period, the frequency is selected to be 60Hz, and the second electromagnetic stirring is carried out for 2 minutes; after the first alloying is completed, turn off the power and cool down to 1450℃, add La, Y, B and Zr, etc., and then select the frequency of 50Hz for the third electromagnetic stirring, which lasts for 3 minutes to complete the second alloying.

[0093] Step 5: Adjust the temperature to 1550℃ and then pour. The alloy melting is completed.

[0094] Example 7

[0095] This example produces a nickel-based DZ22B high-temperature alloy according to the following steps:

[0096] Step 1: According to the composition of DZ22B alloy, place the raw materials in the crucible in the order of Ni, Co, Nb, W, and Ni from bottom to top.

[0097] Step 2: When the vacuum degree is less than 3Pa, start to supply power, and when the vacuum degree is less than 1.3Pa, gradually increase the power supply. After the base material is melted, gradually add the remaining Co and Ni; when the above raw materials are nearly melted, add 50% chromium raw materials and 10% carbon at the same time for the first time; when they are nearly melted, add the remaining chromium raw materials to melt.

[0098] Step 3: After the raw materials are melted, add the remaining 90% carbon, adjust the melt temperature to 1600℃, and perform vacuum refining. During this period, the frequency is selected to be 60Hz, and the first electromagnetic stirring is performed for 6 minutes. After the refining process lasts for 15 minutes, the refining is completed.

[0099] Step 4: After refining, turn off the power and cool down to almost conjunctivae, add Ti and Al according to the composition of DZ22B alloy, adjust the melt temperature to 1520℃, and carry out the first alloying for 20min. During this period, the frequency is selected at 90Hz, and the second electromagnetic stirring is carried out for 2min; after the first alloying is completed, turn off the power and cool down to 1470℃, add Hf, B and Zr, etc., and carry out the third electromagnetic stirring for 5min to complete the second alloying.

[0100] Step 5: Adjust the temperature to 1550℃ and then pour. The alloy melting is completed.

[0101] Example 8

[0102] This example produces a nickel-based DZ22B high-temperature alloy according to the following steps:

[0103] Step 1: According to the composition of DZ22B alloy, place the raw materials in the crucible in the order of Ni, Co, Nb, W, and Ni from bottom to top.

[0104] Step 2: When the vacuum degree is less than 2Pa, start to supply power, and when the vacuum degree is less than 1.3Pa, gradually increase the power supply. After the base material is melted, gradually add the remaining Co and Ni; when the above raw materials are nearly melted, add 30% chromium raw materials and 8% carbon at the same time for the first time; when they are nearly melted, add 30% chromium raw materials and 8% carbon at the same time for the second time; when they are nearly melted, add 30% chromium raw materials and 8% carbon at the same time for the third time; when they are nearly melted, add the remaining chromium raw materials to melt.

[0105] Step 3: After the raw materials are melted, add the remaining 76% carbon, adjust the melt temperature to 1560℃, and perform vacuum refining. During this period, the frequency is selected to be 80Hz, and the first electromagnetic stirring is performed for 4 minutes. After the refining process lasts for 20 minutes, the refining is completed.

[0106] Step 4: After refining, turn off the power and cool down to almost conjunctivae, add Ti and Al according to the composition of DZ22B alloy, adjust the melt temperature to 1510℃, and carry out the first alloying for 25min. During this period, the frequency is selected at 95Hz, and the second electromagnetic stirring is carried out for 3min; after the first alloying is completed, turn off the power and cool down to 1490℃, add Hf, B and Zr, etc., and carry out the third electromagnetic stirring for 4min, and then the second alloying is completed.

[0107] Step 5: Adjust the temperature to 1550℃ and then pour. The alloy melting is completed.

[0108] Example 9

[0109] This example produces a nickel-based DZ22B high-temperature alloy according to the following steps:

[0110] Step 1: According to the composition of DZ22B alloy, place the raw materials in the crucible in the order of Ni, Co, Nb, W, and Ni from bottom to top.

[0111] Step 2: When the vacuum degree is less than 5Pa, start to supply power, and when the vacuum degree is less than 1.3Pa, gradually increase the power supply. After the base material is melted, gradually add the remaining Co and Ni; when the above raw materials are nearly melted, add 40% chromium raw materials and 5% carbon at the same time for the first time; when they are nearly melted, add 40% chromium raw materials and 5% carbon at the same time for the second time, and when they are nearly melted, add the remaining chromium raw materials to melt.

[0112] Step 3: After the raw materials are melted, add the remaining 90% carbon, adjust the melt temperature to 1580℃, and perform vacuum refining. During this period, the frequency is selected to be 70Hz, and the first electromagnetic stirring is performed for 2 minutes. After the refining process lasts for 25 minutes, the refining is completed.

[0113] Step 4: After refining, turn off the power and cool down to almost conjunctivae, add Ti and Al according to the composition of DZ22B alloy, adjust the melt temperature to 1500℃, and carry out the first alloying for 30 minutes. During this period, the frequency is 100Hz, and the second electromagnetic stirring is carried out for 4 minutes; after the first alloying is completed, turn off the power and cool down to 1480℃, add Hf, B and Zr, and then the frequency is 50Hz, and the third electromagnetic stirring is carried out for 3 minutes to complete the second alloying.

[0114] Step 5: Adjust the temperature to 1550℃ and then pour. The alloy melting is completed.

[0115] Comparative Example 3

[0116] This example produces a nickel-based DZ22B high-temperature alloy according to the following steps:

[0117] Step 1: According to the composition of DZ22B alloy, place the raw materials in the crucible in the order of 30-40% C, Ni, Co, Cr, Nb, W, and Ni from bottom to top.

[0118] Step 2: When the vacuum degree is less than 20Pa, start to supply power, and when the vacuum degree is less than 5Pa, gradually increase the power supply. After the base material is melted, add the remaining Co and Ni in a distributed manner; when the above raw materials are nearly melted, continue to add the remaining Co and Ni. When the remaining Co and Ni are added for the last time, add all the remaining carbon to melt the raw materials.

[0119] Step 3: After the raw materials are melted, adjust the melt temperature to 1600℃ and perform vacuum refining. During this period, the frequency is selected to be 60Hz, and the first electromagnetic stirring is performed for 3 minutes. After the refining process lasts for 20 minutes, the refining is completed.

[0120] Step 4: After refining, turn off the power and cool down to almost conjunctivae, add Ti and Al according to the composition of DZ22B alloy, adjust the melt temperature to 1580℃, perform the first alloying, and the whole alloying lasts for 10 minutes. During this period, the frequency is selected to be 60Hz, and the second electromagnetic stirring is carried out for 2min; after the first alloying is completed, turn off the power and cool down to 1460℃, add Hf, B and Zr, etc., and then select the frequency of 50Hz for the third electromagnetic stirring, which lasts for 3min to complete the second alloying.

[0121] Step 5: Adjust the temperature to 1550℃ and then pour. The alloy melting is completed.

[0122] The alloys obtained in Examples 1-9 and Comparative Examples 1-3 were tested, as shown in the following table. The Cr yield rate was obtained by measuring the Cr content (Cr%) of the product, then measuring the total mass W of the product, and then calculating (Cr%*W / Cr addition amount)*100%. The Cr content deviation was obtained by measuring the upper end content Cr% of the product. UP , and the lower end content Cr% Uown , then calculate │Cr% UP -Cr% Uown │Get.

[0123]

[0124]

[0125] It can be seen from the test data that in alloys with a Cr content of more than 20%, the Cr element yield of the present invention is ≥96%, and the maximum deviation of the Cr element content at the beginning and end of the ingot is ≤0.11%, which is better than the prior art. In alloys with a Cr content of 10-20%, the Cr element yield of the present invention is ≥97%, and the maximum deviation of the Cr element content at the beginning and end of the ingot is ≤0.10%, which is better than the prior art. In alloys with a Cr content of less than 10%, the Cr element yield is ≥98%, and the maximum deviation of the Cr element content at the beginning and end of the ingot is ≤0.09%, which is better than the prior art.

[0126] 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 controlling chromium in a high-temperature alloy, characterized in that: The steps include: Step 1, raw material charging: In the smelting equipment, the raw materials are laid from bottom to top in the following order: when the target product alloy is K452 alloy, the laying order is Ni, Co, Mo, Nb, W, Ni; when the target product alloy is K438 alloy, the laying order is Ni, Co, Mo, Nb, W, Ta, Ni; when the target product alloy is DZ22B alloy, the laying order is Ni, Co, Nb, W, Ni; Step 2, melting the raw materials: when the vacuum degree is less than 5Pa, start to supply power, when the vacuum degree is less than 1.3Pa, gradually increase the power supply for 20 to 30 minutes, after the base material is melted, add the remaining cobalt and nickel; after the above raw materials are melted, add the chromium raw material and carbon for the first time; after the first added chromium raw material and carbon are melted, and when the alloy melt does not completely cover the chromium raw material, add the chromium raw material and carbon for the second time; in the above manner, add all the chromium raw materials, and do not add carbon when adding the chromium raw material for the last time; Step 3, "carbon control" refining: after the above raw materials are melted, add the remaining carbon, adjust the refining temperature to 1520℃~1600℃, perform vacuum refining, and continue for 15~50min before ending the refining; during the refining process, adjust the electromagnetic frequency to 60~130Hz, and perform the first electromagnetic stirring, which lasts for 2~10min; Step 4, "double" stirring alloying: after refining, turn off the power and cool to almost conjunctival film, add Ti and Al according to the smelting composition to melt; adjust the melt temperature to 1500~1550℃, perform alloying once, last for 10~30min, during which, perform the second electromagnetic stirring, the stirring frequency is 70~100Hz, and the time is 1~4min; after completing the first alloying, turn off the power and cool to 1440~1490℃, add the trace components in the target alloy, melt and perform the second alloying, and perform the third electromagnetic stirring at the same time, the stirring frequency is 50~80Hz, and the time is 1~5min; Step 5, pouring: adjust the temperature and then pour, thus completing the alloy smelting.

2. The method for controlling chromium in a high temperature alloy according to claim 1, characterized in that: In step 2, when small particles or flake carbon still remain, the power supply is reduced and the melting time is extended to more than 40 minutes.

3. The method for controlling chromium in a high temperature alloy according to claim 1, characterized in that: In step 3, when the Cr content in the target product alloy exceeds 20%, the added carbon content is 20-40% of the total carbon content; when the Cr content in the target product alloy is 10-20%, the added carbon content is 60-70% of the total carbon content; when the Cr content in the target product alloy is less than 10%, the added carbon content is 70-90% of the total carbon content.

4. The method for controlling chromium in a high temperature alloy according to claim 1, characterized in that: In step 3, when the Cr content in the target alloy is greater than 20%, the process conditions are: the refining temperature is adjusted to 1520~1540℃; the refining time is 30~50min; the electromagnetic stirring frequency is adjusted to 100~130Hz; the electromagnetic stirring time is adjusted to 5~10min; When the Cr content in the target alloy is between 10 and 20%, the process conditions are: the refining temperature is adjusted to 1540-1560°C; the refining time is 20-40 min; the electromagnetic stirring frequency is adjusted to 80-100 Hz; the electromagnetic stirring time is adjusted to 4-8 min; When the Cr content in the target alloy is less than 10%, the process conditions are: the refining temperature is adjusted to 1560~1600℃; the refining time is 15~25min; the electromagnetic stirring frequency is adjusted to 60~80Hz; and the electromagnetic stirring time is adjusted to 2~6min.

5. The method for controlling chromium in a high temperature alloy according to claim 1, characterized in that: In step 3, after adding the remaining carbon, the smelting equipment is tilted 3-5 degrees.

6. The method for controlling chromium in a high temperature alloy according to claim 1, characterized in that: In step 4, when the Cr content in the target alloy is greater than 20%, the primary alloying temperature is 1530-1550°C, and the duration is 10-15 minutes; at the same time, the second electromagnetic stirring frequency is 70-80 Hz, and the duration is 1-3 minutes; When the Cr content in the target alloy is between 10 and 20%, the primary alloying temperature is 1520-1540°C and the duration is 15-25 min; at the same time, the second electromagnetic stirring frequency is 80-90 Hz and the duration is 2-4 min. When the Cr content in the target alloy is less than 10%, the primary alloying temperature is 1500~1520℃, and the duration is 20~30min; at the same time, the second electromagnetic stirring frequency is 90~100Hz, and the duration is 2~4min.

7. The method for controlling chromium in a high temperature alloy according to claim 1, characterized in that: In step 4, when the Cr content in the target alloy is greater than 20%, the secondary alloying temperature is 1440-1460°C; at the same time, the third electromagnetic stirring frequency is 70-80 Hz, and the duration is 1-3 min; When the Cr content in the target alloy is between 10 and 20%, the secondary alloying temperature is 1450-1470°C; at the same time, the third electromagnetic stirring frequency is 60-70 Hz, and the duration is 2-4 min; When the Cr content in the target alloy is less than 10%, the secondary alloying temperature is 1470~1490℃; at the same time, the third electromagnetic stirring frequency is 50~60Hz, and the duration is 3~5min.

8. The method for controlling chromium in a high temperature alloy according to claim 1, characterized in that: In step 4, when the target product alloy is K452 alloy, the trace components are La, Y, B and Zr; when the target product alloy is K438 alloy, the trace components are La, Y, B and Zr; when the target product alloy is DZ22B alloy, the trace components are Hf, B and Zr.

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