High-purity high-temperature alloy and preparation method thereof

Abstract

The invention relates to a high-purity high-temperature alloy and a preparation method thereof, and belongs to the technical field of high-temperature alloys. The preparation method comprises the following steps: proportioning and melting: proportioning by using a Ni-Cr-Nb intermediate alloy; wherein the oxygen content and the nitrogen content are both smaller than 100 ppm; the melting point is below 1250 DEG C; in the refining stage, after the raw materials are completely melted, the temperature is gradually increased to the refining temperature of 1490-1510 DEG C, and then the refining stage is started; in the refining process, the vacuum degree is kept to be smaller than or equal to 1 Pa; the tapping temperature is adjusted to 1440 DEG C to 1460 DEG C, electrified pouring is carried out under the power of 200 Kw to 300 Kw and the vacuum condition, demolding is carried out after cooling, and the high-temperature alloy is prepared. The content of oxygen and the content of nitrogen are both smaller than 100 ppm; according to the Ni-Cr-Nb intermediate alloy with the melting point being 1250 DEG C or below, the smelting time is shortened, the power consumption needed by smelting is reduced, and the purity of the obtained high-temperature alloy is high.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature alloys, and in particular to a high-purity high-temperature alloy and a preparation method thereof. Background Art

[0002] High-temperature alloys are an important type of alloys, and they are mainly used at higher temperatures, such as above 650°C. With the rapid growth of demand for high-temperature alloys and the increasingly harsh service environment of high-temperature alloy structural parts, higher requirements are placed on the performance and quality stability of high-temperature alloy products.

[0003] In order to ensure the performance of high-temperature alloys, various types of high-temperature alloys have been continuously introduced, and high-niobium high-temperature alloy is one of them. However, niobium is easy to combine with oxygen and nitrogen, thereby reducing the purity level of high-temperature alloys, which will lead to a decrease in the performance of high-temperature alloys.

[0004] In the process of preparing high-temperature alloys, single-element materials were initially used for preparation, but the smelting time was long and the consumption was high. With the development, Ni-Cr-Nb master alloys were used to replace single-element materials for preparation. However, the existing Ni-Cr-Nb master alloy is prepared in one step by aluminothermic reduction reaction. This preparation process can reduce the oxygen content in the alloy, but it introduces new aluminum oxide impurities, which affects the subsequent preparation of high-temperature alloys. Summary of the invention

[0005] In view of the above analysis, the present invention aims to provide a high-purity high-temperature alloy and a preparation method thereof, so as to shorten the smelting time, reduce consumption, and improve purity.

[0006] In one aspect, the present invention provides a method for preparing a high-purity high-temperature alloy, comprising the following steps:

[0007] (1) Batching and melting: Ni-Cr-Nb master alloy is used for batching; the oxygen and nitrogen contents in the Ni-Cr-Nb master alloy are both less than 100 ppm; and the melting point is below 1250°C;

[0008] (2) Refining stage: After the raw materials are completely melted, the temperature is gradually raised to the refining temperature of 1490-1510°C, and then the refining stage begins; during the refining process, the vacuum degree is maintained at ≤1Pa;

[0009] (3) Composition adjustment: sampling, analysis, adjustment of alloy composition, addition of aluminum, titanium, ferrophosphorus and ferroboron, continued melting and stirring, and steelmaking after the composition is qualified;

[0010] (4) Steel tapping and pouring: The steel tapping temperature is adjusted to 1440-1460°C, and the casting is performed under vacuum conditions with a power of 200Kw-300Kw. After cooling, the steel is demolded to obtain a high-temperature alloy.

[0011] Furthermore, the niobium content in the high-temperature alloy is 4.75%-5.7%.

[0012] Furthermore, the grade of the high-temperature alloy is GH4169, GH4169D, Inconel 718 or Inconel718Plus.

[0013] Furthermore, the oxygen content in the high-temperature alloy is below 5 ppm, and the nitrogen content is below 15 ppm.

[0014] Furthermore, the volume proportion of inclusions in the high-temperature alloy is ≤0.1%.

[0015] Furthermore, the total time of the smelting process is reduced by more than 21%, and the power consumption is reduced by more than 15%.

[0016] Furthermore, the raw materials for preparing the Ni-Cr-Nb master alloy include 17%-35% of elemental chromium, 8%-16% of elemental niobium, 50%-75% of elemental nickel and 0.04-0.11% of graphite, and the weight ratio of elemental chromium to elemental niobium is 2-4.

[0017] Furthermore, the Ni—Cr—Nb master alloy is prepared through steps including melting, refining and pouring.

[0018] Furthermore, during the refining process, the alloy liquid is stirred, the stirring power is 180Kw-250Kw, and the stirring time is more than 20 minutes.

[0019] On the other hand, the present invention provides a high-purity high-temperature alloy obtained by the preparation method of the present invention.

[0020] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0021] 1. The present invention utilizes the Ni-Cr-Nb master alloy provided by the present invention when preparing the high-temperature alloy, and the oxygen and nitrogen contents thereof are both less than 100 ppm; the melting point is below 1250°C, the oxygen content in the high-temperature alloy is below 5 ppm, the nitrogen content is below 15 ppm, and the volume proportion of inclusions can be stabilized below 0.1%; and according to statistical calculations, the time taken for the smelting process is reduced by more than 21%, and the power consumption is reduced by more than 15%;

[0022] 2. The present invention prepares Ni-Cr-Nb master alloy by combining vacuum induction and refining, adjusts the composition and controls the smelting process, and reduces the oxygen and nitrogen content in the master alloy. The preparation method of the present invention is completely different from the existing aluminothermic reaction reduction method and two-step method. The present invention directly synthesizes Ni-Cr-Nb master alloy in one step, which not only has the characteristics of high purity and low melting point, but also can be directly used to prepare high-temperature alloys, reducing production costs.

[0023] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are only used for the purpose of illustrating specific preparation examples and are not to be considered as limiting the present invention. The same reference symbols denote the same components throughout the accompanying drawings.

[0025] Figure 1 The metallographic structure of the GH4169 alloy prepared in Example 1;

[0026] Figure 2 The metallographic structure of the GH4169 alloy prepared in Example 1;

[0027] Figure 3 The metallographic structure of the GH4169 alloy prepared in Comparative Example 1;

[0028] Figure 4 This is the metallographic structure of the GH4169 alloy prepared in Comparative Example 1. DETAILED DESCRIPTION

[0029] The preferred preparation examples of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the preparation examples of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0030] With the rapid growth of demand for high-temperature alloys and the increasingly harsh service environment of high-temperature alloy structural parts, higher requirements are placed on the product performance and quality stability of high-temperature alloys. In order to ensure the performance of high-temperature alloys, various types of high-temperature alloys have been continuously introduced, and high-niobium high-temperature alloys are one of them. However, niobium is easily combined with oxygen and nitrogen, thereby reducing the purity level of high-temperature alloys, which will lead to a decrease in the performance of high-temperature alloys.

[0031] In the process of preparing high-temperature alloys, single-element materials were initially used for preparation, but the smelting time was long and the consumption was high. With the development, Ni-Cr-Nb master alloys were used to replace single-element alloys. However, the existing Ni-Cr-Nb master alloys are mainly prepared by a one-step aluminothermic reaction reduction. This preparation process can reduce the oxygen content in the alloy, but it introduces new aluminum oxide impurities, which affects the subsequent preparation of high-temperature alloys.

[0032] Therefore, the present invention provides a method for preparing a high-purity high-temperature alloy, comprising the following steps:

[0033] (1) Batching and melting: Ni-Cr-Nb master alloy is used for batching; the oxygen and nitrogen contents in the Ni-Cr-Nb master alloy are both less than 100 ppm; and the melting point is below 1250°C;

[0034] (2) Refining stage: After the raw materials are completely melted, the temperature is gradually raised to the refining temperature of 1490-1510°C, and then the refining stage begins; during the refining process, the vacuum degree is maintained at ≤1Pa;

[0035] (3) Composition adjustment: sampling, analysis, adjustment of alloy composition, addition of aluminum, titanium, ferrophosphorus and ferroboron, continued melting and stirring, and steelmaking after the composition is qualified;

[0036] (4) Steel tapping and pouring: The steel tapping temperature is adjusted to 1440-1460°C, and the casting is performed under vacuum conditions with a power of 200Kw-300Kw. After cooling, the steel is demolded to obtain a high-temperature alloy.

[0037] Compared with the prior art, the present invention uses Ni-Cr-Nb master alloy to prepare high-temperature alloy, and the master alloy is prepared by combining vacuum induction and refining. The oxygen and nitrogen contents of Ni-Cr-Nb master alloy are both less than 100ppm; the melting point is below 1250℃. The master alloy used in the present invention is completely different from the existing aluminothermic reaction reduction method and two-step method, and has the characteristics of high purity and low melting point. Therefore, in the melting or refining process of the high-temperature alloy, the power consumption is small and the time is short. According to statistical calculations, the total time of the melting process is reduced by more than 21%, and the power consumption is reduced by more than 15%; the obtained high-temperature alloy has high purity, the oxygen content is below 5ppm, and the nitrogen content is below 15ppm.

[0038] Specifically, the niobium content in the high-temperature alloy is 4.75%-5.7%.

[0039] It should be noted that, in the present invention, the obtained Ni-Cr-Nb master alloy is used to prepare a high-temperature alloy with a high niobium content, which effectively reduces the melting point of the raw material from about 1400°C (single-element raw material) to below 1250°C. The reduction in melting point will shorten the time required for smelting and reduce the power consumption required for smelting. In addition, the use of Ni-Cr-Nb master alloy can also reduce the gas element content of the raw material, especially the oxygen, nitrogen and sulfur content, avoid excessive impurity precipitation, and improve the purity of the high-temperature alloy.

[0040] It should be noted that in the preparation process of the high-temperature alloy of the present invention, the raw materials need to be added in three times. In the early stage of melting, other metals except metal aluminum (Al), metal titanium (Ti), ferrophosphorus, ferroboron and intermediate alloy are added first. Metal aluminum, metal titanium, ferroboron and ferrophosphorus are easy to combine with oxygen and nitrogen elements to form impurities, so the main raw materials are melted and degassed before adding. Metal niobium in the intermediate alloy is easy to combine with oxygen and nitrogen elements, and needs to be added in the later stage of melting. Metal aluminum, metal titanium, ferroboron and ferrophosphorus are added in the composition adjustment stage.

[0041] It should be noted that when the intermediate alloy is used to prepare the high-temperature alloy, the refining temperature is controlled at 1490-1510°C, which is lower than the existing refining temperature of 1520-1550°C.

[0042] It should be noted that the power is controlled at 200Kw-300Kw in order to maintain the temperature of the alloy liquid and prevent the alloy liquid from cooling down during the pouring process.

[0043] Specifically, the grade of the high temperature alloy is GH4169, GH4169D, Inconel 718 or Inconel718Plus.

[0044] Specifically, the melting temperature in the later stage of melting is 1330° C.-1380° C.; the vacuum is quickly evacuated to 0.1 Pa-0.3 Pa.

[0045] It should be noted that in the present invention, metallic nickel and metallic iron are first added at the initial stage of melting, and the temperature is gradually raised to melt the alloy liquid, at which time the temperature of the alloy liquid is controlled at 1450±5°C. In the later stage of melting, an intermediate alloy (Ni-Cr-Nb ternary alloy) is added to complete the composition blending, and the temperature is gradually lowered from 1450°C to 1330°C-1380°C, such as 1340°C, 1350°C, 1360°C or 1370°C. In the above temperature range, the alloy liquid can be prevented from re-solidifying, and the removal effect of gas impurities such as oxygen and nitrogen can be effectively improved.

[0046] In addition, while the temperature is lowered, it is necessary to quickly evacuate to 0.1Pa-0.3Pa. The purpose of rapid evacuation in the present invention is to significantly reduce the oxygen content in the smelting environment, inhibit metal oxidation on the surface and inside the melt, and reduce the residual nitrogen and water vapor in the environment to prevent the generation of nitrides and hydrogen. The vacuum environment can accelerate the release of dissolved gases (such as hydrogen, oxygen and nitrogen) in the melt in the form of bubbles, thereby significantly improving the degassing efficiency and impurity removal effect.

[0047] In the present invention, in order to ensure the stability of the rapid vacuuming process, a step-by-step decompression method is used to gradually reduce the vacuum degree, ensure that the gasification process on the surface of the melt proceeds smoothly, and avoid the phenomenon of inclusions being mixed back due to excessive boiling. The actual operation is: start a pump at the beginning, start the second pump when the vacuum degree is lower than 200Pa, and start the third pump when the vacuum degree is lower than 10Pa until the target vacuum degree is reached. This operation can balance the pressure changes in the smelting environment, optimize the degassing and refining effects, and ensure the final purity and quality of the alloy.

[0048] It should be noted that in the prior art, when preparing high-temperature alloys, single materials are used instead of intermediate alloys. During the melting process, the melting temperature needs to be controlled to be always above 1450°C. When the temperature is lower than this, the alloy liquid will re-solidify. Therefore, the temperature control during melting in the present invention is completely different from the prior art.

[0049] Specifically, the oxygen content in the high-temperature alloy is 2-5ppm, the nitrogen content is ≤15ppm, and the volume proportion of inclusions can be stabilized at less than 0.1%.

[0050] It should be noted that the raw materials used in the preparation of existing high-temperature alloys have too high a gas element content, resulting in incomplete removal of oxygen and nitrogen gases during the smelting process. The oxygen element in the high-temperature alloy fluctuates around 10ppm, and the nitrogen element is ≥25ppm, resulting in a large amount of precipitated oxides and nitrides, with the volume proportion of inclusions being 0.2%-0.5%. The intermediate alloy produced by the aluminothermic reduction reaction contains 5-10ppm of oxygen and 18-25ppm of nitrogen in the prepared high-temperature alloy, and the amount of precipitated inclusions is reduced, and the volume proportion of inclusions can be stabilized within the range of 0.1%-0.2%.

[0051] By using the intermediate alloy provided by the present invention for preparation, the amount of gas elements introduced can be reduced to 70-110ppm, and the amount of nitrogen can be reduced to 50-100ppm. The oxygen element in the prepared finished alloy is 2-5ppm, and the nitrogen element is ≤15ppm, the gas element is the lowest, and the amount of precipitated inclusions is small, and the volume proportion of inclusions can be stabilized at less than 0.1%.

[0052] Specifically, the raw materials for preparing the Ni-Cr-Nb master alloy include 17%-35% of elemental chromium, 8%-16% of elemental niobium, 50%-75% of elemental nickel and 0.04-0.11% of graphite, and the weight ratio of elemental chromium to elemental niobium is 2-4.

[0053] Compared with the prior art, the present invention synthesizes a high-purity, low-melting-point Ni-Cr-Nb master alloy by compounding elemental chromium, elemental niobium, elemental nickel and graphite at one time, which is completely different from the existing Ni-Cr-Nb master alloy obtained by thermite reduction or two-step method. The present invention does not introduce aluminum oxide impurities, and the oxygen and nitrogen content is less than 100ppm, which greatly reduces the difficulty of removing gas elements in the subsequent preparation of high-temperature alloys.

[0054] It should be noted that in the present invention, the graphite is deoxidized to improve the purity of the master alloy, and the amount of graphite added is controlled between 0.04% and 0.11%. When using the Ni-Cr-Nb master alloy to prepare a high-temperature alloy, the carbon content of the high-temperature alloy needs to be met. In addition, since the single chromium and single niobium contain a large amount of oxygen, the C element will be consumed. Therefore, the amount of graphite added is controlled to be between 0.04% and 0.11%.

[0055] Specifically, the weight ratio of the elemental chromium to the elemental niobium is 2-4, such as 2.24, 2.5, 2.77, 3.0, 3.35 or 3.88.

[0056] It should be noted that the addition ratio of elemental chromium to elemental niobium needs to be strictly controlled in the present invention, mainly from the following three aspects: (1) From the aspect of the preparation of the intermediate alloy, controlling the ratio can reduce the fluctuation of the composition of the intermediate alloy and improve the controllability and stability of the smelting process. Controlling the weight ratio of elemental chromium to elemental niobium between 2-4 can also help improve the uniformity of the intermediate alloy and reduce the uncertainty in the smelting process. (2) From the aspect of the application of the intermediate alloy, the intermediate alloy prepared by the present invention is mainly used in high-temperature alloys with a high niobium content. The intermediate alloy is used to directly replace elemental chromium, elemental niobium and elemental nickel. Therefore, it is necessary to ensure that the composition of the target high-temperature alloy meets the requirements. (3) From the aspect of production cost, niobium is a rare metal and its price is relatively high. By adjusting the ratio of chromium to niobium, the use of niobium can be reduced while ensuring the performance of the intermediate alloy, thereby controlling the cost.

[0057] Specifically, the Ni-Cr-Nb master alloy is prepared by melting, refining, pouring and the like, and specifically comprises the following steps:

[0058] S1: batching, weighing the raw materials according to the ratio of the target alloy;

[0059] S2: Loading the furnace, placing the prepared raw materials in the crucible of the vacuum induction furnace, and starting heating when the vacuum degree in the furnace drops to 5Pa;

[0060] S3: refining, during which the alloy liquid is stirred;

[0061] S4: pouring, under vacuum conditions, the pouring temperature is 1290-1310°C, and high-purity Ni-Cr-Nb intermediate alloy is obtained after solidification.

[0062] Compared with the prior art, the present invention prepares Ni-Cr-Nb master alloy by combining vacuum induction and refining, adjusts the composition and controls the smelting process, and reduces the oxygen and nitrogen content in the master alloy. The preparation method of the present invention is completely different from the existing aluminothermic reaction reduction method and two-step method. The present invention directly synthesizes Ni-Cr-Nb master alloy in one step, which not only has the characteristics of high purity and low melting point, but also can be directly used to prepare high-temperature alloys, reducing production costs.

[0063] It should be noted that in step S1, 17%-35% of elemental chromium (Cr), 8%-16% of elemental niobium (Nb), 50%-75% of elemental nickel (Ni) and 0.04%-0.11% of graphite (C) are weighed by weight to ensure that the raw materials used have no obvious impurities to avoid affecting the final quality of the alloy.

[0064] Specifically, in step S2, the power is gradually increased until all the raw materials are completely melted, and the final power is controlled at 2 / 3 of the rated power.

[0065] It should be noted that during the vacuum induction melting process, the raw materials are melted by controlling the power of the induction furnace, and the power is increased in a gradient of 25%, 40%, 45%, and 60% (for example, if the rated power is 750Kw, the power is controlled at 200Kw, 300Kw, 350Kw, and 450Kw, respectively). In the initial stage of melting, the raw materials are solid and need to be heated at a lower power. Excessive power can easily lead to bridging accidents. As the raw materials are gradually melted, the power of the induction furnace is also increased, thereby ensuring the final melting quality.

[0066] Specifically, during the vacuum induction melting process, the metal is heated to 1450-1460° C. for melting.

[0067] It should be noted that during the heating process, when the temperature reaches 1450-1460°C, part of the elemental nickel first melts to form a liquid metal molten pool, and at this time, the elemental chromium and elemental niobium enter the liquid molten pool in the form of dissolution. However, part of the elemental nickel is still not melted, so the molten pool temperature is still maintained at 1450-1460°C until all the raw materials are melted.

[0068] Specifically, in step S3, the refining temperature is controlled at 1540-1560°C.

[0069] It should be noted that controlling the temperature at 1540-1560℃ during the refining process can better remove oxygen and nitrogen in the alloy liquid and ensure the purity of the master alloy. When the refining temperature is too high, although the removal rate of oxygen and nitrogen is faster, the alloy liquid will react with the crucible, increasing the oxygen content in the alloy liquid.

[0070] Specifically, in step S3, the stirring power is controlled at 180Kw-250Kw, such as 180Kw, 200Kw, 220Kw, 230Kw or 250Kw, and the stirring time is more than 20 minutes.

[0071] It should be noted that after the raw materials are completely melted, the stirring device is turned on to stir the alloy liquid to promote the full mixing of the elements in the alloy and improve the homogenization of the alloy liquid. The stirring time is not less than 20 minutes. After the stirring is completed, keep warm for 30 minutes to ensure that the gas elements (such as oxygen, nitrogen, etc.) are fully released, and at the same time promote the collision and floating of inclusions, which helps to remove impurities in the alloy.

[0072] The stirring power of the stirring device in the present invention is controlled at 180Kw-250Kw to better remove gases such as oxygen and nitrogen. When the stirring power is too low, the alloy liquid will cool down, affecting the gas removal effect; when the stirring power is too high, the alloy liquid will flush the crucible, introduce new impurities, and affect the purity. The stirring device of the present invention can be used in the existing way, and will not be described in detail here.

[0073] Specifically, in step S4, the vacuum degree is ≤5 Pa, and the pouring temperature is 1290-1310°C.

[0074] It should be noted that the vacuum degree is controlled below 5Pa or filled with inert gas (argon) protection, and the filling amount is 20-100Torr. The pouring temperature is controlled at 1290-1310℃, which not only prevents the alloy liquid from solidifying during the pouring process due to the pouring temperature being too low, but also prevents the alloy ingot from being too dense due to the pouring temperature being too high. In addition, the cooling rate of the alloy liquid at different positions in the mold is inconsistent, which will produce stress. The higher the superheat, the greater the stress. When the pouring temperature is too high (above 1350℃), it is very easy to cause the alloy ingot to crack.

[0075] Specifically, the melting point of the master alloy is lower than 1250°C.

[0076] Specifically, the oxygen and nitrogen contents of the master alloy are both lower than 100 ppm.

[0077] It should be noted that the present invention first controls the proportion of each raw material added through the ratio of the components, and then controls the parameters of the smelting, refining and pouring processes, such as the smelting temperature, refining temperature, stirring power and pouring temperature, etc. The obtained master alloy has a lower melting point and oxygen and nitrogen content, the melting point is lower than 1250°C, and the oxygen and nitrogen content are both lower than 100ppm.

[0078] Specifically, the crucible is an alumina crucible or a magnesia crucible.

[0079] It should be noted that in the present invention, when preparing Ni-Cr-Nb master alloy and high temperature alloy, an alumina crucible or a magnesia crucible is used, and there is no need to replace the crucible, which saves preparation cost and improves efficiency.

[0080] The present invention provides a high-purity high-temperature alloy obtained by the preparation method of the present invention, wherein the oxygen content is below 5 ppm, the nitrogen content is below 15 ppm, and the volume proportion of inclusions can be stably kept below 0.1%.

[0081] In order to more clearly describe the present invention, it is further illustrated by the following preparation examples and comparative preparation examples.

[0082] Preparation Example 1

[0083] The preparation of Ni-Cr-Nb master alloy comprises the following steps:

[0084] S1: Ingredients: according to the ratio of the target alloy, the raw materials are weighed by weight, 34.5% of elemental chromium, 15.4% of elemental niobium and 50.1% of elemental nickel, and 0.1% of graphite is additionally added;

[0085] S2: Loading the furnace, placing the prepared raw materials in the crucible of the vacuum induction furnace, melting the prepared raw materials by controlling the power of the induction furnace, increasing the power by a gradient of 25%, 40%, 45%, and 60%, and starting heating when the vacuum degree in the furnace drops to 5 Pa, heating to 1455°C for melting;

[0086] The crucible is a magnesium oxide crucible.

[0087] S3: Refining, during the refining process, the refining temperature is controlled at 1550°C, and the alloy liquid is stirred, the stirring power is controlled at 200Kw, and the stirring time is more than 20min;

[0088] S4: pouring, under vacuum conditions, the vacuum degree is controlled below 5Pa, the pouring temperature is 1300°C, and a high-purity Ni-Cr-Nb intermediate alloy is obtained after solidification.

[0089] Preparation Example 2-5, Comparative Preparation Example 1-2

[0090] Preparation Examples 2-5, Comparative Preparation Example 1 The difference between Preparation Example 1 and Preparation Example 1 is the different ratios of the preparation raw materials, as shown in Table 1.

[0091] Table 1 Preparation Examples 1-5, Comparison of different ratios of Preparation Example 1

[0092] Group Wt(Ni) Wt(Cr) Wt(Nb) Wt(Cr) / Wt(Nb) Preparation Example 1 50.1％ 34.5％ 15.4％ 2.240 Preparation Example 2 60.4％ 31.5％ 8.1％ 3.889 Preparation Example 3 65.2％ 26.8％ 8.0％ 3.358 Preparation Example 4 69.8％ 22.2％ 8.0％ 2.775 Preparation Example 5 74.5％ 17.6％ 7.9％ 2.239 Comparative Preparation Example 1 47.7％ 29.6％ 22.7％ 1.304

[0093] Comparative Preparation Example 2

[0094] The preparation process of Comparative Preparation Example 2 is substantially the same as that of Preparation Example 1, except that Comparative Preparation Example 2 uses a two-step aluminothermic reaction to prepare the Ni-Cr-Nb master alloy. The specific preparation steps are:

[0095] (1) First, niobium pentoxide, chromium trioxide and aluminum powder are dried at 118° C. for 12 h, then 90.33 kg of niobium pentoxide, 53.84 kg of chromium trioxide and 49.69 kg of aluminum powder are weighed and loaded into a V-type mixer for full mixing, and then the mixed raw materials are loaded into a sintered corundum crucible for ignition reaction. The temperature of the aluminothermic reaction is 1950° C. and the time is 45 s. After cooling for 12 h, the crucible is removed, the alloy ingot is taken out, the slag layer and oxide film on the surface of the alloy ingot are removed, and the alloy ingot is crushed and sized to 5-50 mm. After magnetic separation and manual selection, a niobium-chromium alloy is obtained;

[0096] (2) First, the niobium-chromium alloy and the electrolytic nickel were dried at 120°C for 12 hours respectively, then 57.00 kg of the niobium-chromium alloy and 43.00 kg of the electrolytic nickel were weighed and mixed evenly, and then loaded into a knotted and dried corundum crucible, and the medium frequency vacuum induction melting furnace was evacuated to below 10 Pa to remove the gas in the furnace, and the initial power was set to 20 kW, and the power was adjusted to 30 kW after 10 minutes, and the power was adjusted to 80 kW after 20 minutes until the alloy was completely melted; finally, the power was adjusted to 100 kW, and the refining was carried out at 100 kW power and 1900°C for 5 minutes, and the medium frequency vacuum induction melting furnace was evacuated to below 10 Pa again to remove the oxygen element in the melt, and the nickel-niobium-chromium alloy liquid was obtained;

[0097] (3) The power of the medium frequency vacuum induction melting furnace is adjusted to 80 kW, the crucible is tilted, and the nickel-niobium-chromium alloy liquid is slowly and steadily poured into the water-cooled crucible, and vacuum cooling is maintained for 12 hours to obtain the nickel-niobium-chromium intermediate alloy.

[0098] Performance Testing

[0099] The above-mentioned Preparation Examples 1-5 and Comparative Preparation Examples 1-2 were subjected to performance tests, mainly including oxygen and nitrogen content tests and melting point tests. The test results are shown in Table 2.

[0100] Table 2 Test results

[0101]

[0102]

[0103] Examples and Comparative Examples

[0104] Example 1

[0105] The master alloy obtained in Preparation Example 3 was used to prepare the GH4169 alloy components, and a 3t grade GH4169 alloy ingot was prepared. The preparation steps are as follows:

[0106] (1) Weigh the raw materials for preparation according to Table 3.

[0107] (2) Mix 311 kg of metallic nickel, 87 kg of metallic molybdenum, 517 kg of metallic iron, and 6.4 kg of metallic cobalt and put them into a furnace.

[0108] (3) After evacuating to a vacuum degree of ≤1Pa, the raw materials are sent to electric smelting with an initial power of 50Kw. The power is increased step by step to melt the raw materials.

[0109] (4) After the raw materials are prepared and melted, the intermediate alloy is added in batches, with the weight of each batch being 425kg, 400kg, 400kg, 400kg, and 400kg respectively; after each batch is added, the power is increased to 350Kw to melt the raw materials.

[0110] (5) After the master alloy is melted, turn off the power to cool down until the alloy liquid temperature reaches 1350℃, then keep warm at low power, with the heat preservation power set at 130Kw. Turn on the high vacuum pump step by step according to the liquid level until the vacuum degree stabilizes at 0.2Pa. Stir at 150Kw for 15 minutes, then continue to keep warm until the alloy liquid surface is calm and no obvious bubbles escape.

[0111] (6) Raise the alloy liquid temperature at a power of 400 kW to 1500°C (i.e., refining temperature).

[0112] (7) After the temperature is reached, the refining phase begins. 0.61 kg of graphite is added and stirring is started (power 200 kW, duration not less than 20 minutes) to further remove gas elements in the alloy liquid while maintaining a vacuum degree of ≤1 Pa to improve gas removal efficiency.

[0113] (8) After the molten pool surface returns to calm, take two samples for full element analysis. The main elements include: Ni, Co, Cr, Mo, Nb, Al, Ti, Ta, Fe, Cu, Mn, Si, B, S, P, C, O, N, etc. According to the analysis results, make necessary adjustments to the alloy composition and add the corresponding metal or alloy.

[0114] (9) After the raw materials are completely melted again, 18 kg of metallic aluminum, 29 kg of metallic titanium, 1.2 kg of ferrophosphorus and 0.66 kg of ferroboron are added, and the mixture is further melted and stirred at 200 kW for not less than 20 minutes, and then samples are taken for analysis again.

[0115] (10) After all element contents are qualified, the steel tapping temperature is adjusted to 1450℃, and the launder is hoisted and prepared for pouring.

[0116] (11) Casting was carried out under vacuum conditions with a power of 280KW. After the casting was completed, the electrode was cooled in the furnace for 1 hour and then demolded to obtain a high-temperature alloy.

[0117] Table 3 Preparation of raw material ratio

[0118]

[0119] Example 2

[0120] The preparation process of Example 2 is substantially the same as that of Example 1, except that the intermediate alloy obtained in Preparation Example 2 is used in Example 2, and the raw material ratio is as shown in Table 4.

[0121] Table 4 Preparation of raw material ratio

[0122]

[0123] Example 3

[0124] The preparation process of Example 3 is substantially the same as that of Example 1, except that in Example 3:

[0125] In step (5), firstly, the intermediate alloy is added into the furnace for melting, and then metal nickel, metal iron, metal molybdenum, etc. are added in sequence; after melting, the power is turned off to cool down until the alloy liquid temperature reaches 1330°C, and then low-power insulation is performed, and the insulation power is set at 130Kw. According to the liquid level, the high vacuum pump is turned on step by step until the vacuum degree is stabilized at 0.2Pa;

[0126] Step (6) The temperature of the alloy liquid is raised to 1490°C (i.e., the refining temperature) at a power of 400Kw.

[0127] Step (10) After all the elements are qualified, the tapping temperature is adjusted to 1440°C, and the launder is hoisted to prepare for pouring;

[0128] Step (11) Casting is carried out under vacuum conditions with electricity at a power of 220 Kw; other operations are the same as in Example 1.

[0129] Comparative Example 1

[0130] The GH4169 alloy components are prepared using single raw materials and a 3t grade GH4169 alloy ingot is prepared. The preparation steps are as follows:

[0131] (1) Weigh the raw materials for preparation according to Table 5 below and set aside.

[0132] (2) First, weigh 200 kg of nickel and place it at the bottom of a crucible. Then, mix 1431 kg of nickel, 543 kg of chromium, 87 kg of molybdenum, 517 kg of iron, and 6.4 kg of cobalt into a furnace.

[0133] (3) After evacuating to a vacuum degree of ≤1Pa, the raw materials are sent to electric smelting with an initial power of 50Kw. The power is increased step by step to melt the prepared raw materials.

[0134] (4) After the raw materials are prepared and melted, the temperature of the alloy liquid is increased at a power of 350 kW to 1530°C (i.e., the refining temperature).

[0135] (5) After the temperature is reached, the refining phase begins. 0.61 kg of graphite is added and stirring is started (power 200 kW, duration not less than 20 minutes) to further remove gas elements in the alloy liquid while maintaining a vacuum degree of ≤1 Pa to improve gas removal efficiency.

[0136] (6) After the molten pool surface returns to calm, take two samples for full element analysis. The main elements include: Ni, Co, Cr, Mo, Nb, Al, Ti, Ta, Fe, Cu, Mn, Si, B, S, P, C, O, N, etc.

[0137] (7) According to the analysis results, make necessary adjustments to the alloy composition and add the corresponding metal or alloy. Then add 162kg of niobium metal and stir at 200KW for no less than 20 minutes after it is completely melted.

[0138] (8) After the stirring is completed, the power is turned off and the film is formed. Then 18 kg of aluminum, 29 kg of titanium, 1.2 kg of ferrophosphorus and 0.66 kg of ferroboron are added, and the mixture is melted and stirred at 200 KW for not less than 20 minutes. Samples are taken again for analysis.

[0139] (9) After all element contents are qualified, the steel tapping temperature is adjusted to 1450℃, and the launder is hoisted at the same time to prepare for pouring.

[0140] (10) Casting is carried out under vacuum conditions with power of 260Kw.

[0141] (11) After the pouring is completed, the electrode is cooled in the furnace for 1 hour and then demolded to prepare a high-temperature alloy.

[0142] Table 5 Preparation raw material ratio

[0143]

[0144] Comparative Example 2

[0145] The preparation process of Comparative Example 2 is substantially the same as that of Example 1, except that the intermediate alloy obtained in Comparative Preparation Example 3 is used in Example 2, and the raw material ratio is as shown in Table 6.

[0146] Table 6 Preparation of raw material ratio

[0147]

[0148]

[0149] Performance Testing

[0150] The above-mentioned Examples 1-2 and Comparative Examples 1-2 were subjected to component detection, inclusion detection, total time statistics and power consumption statistics, and the specific detection results are shown in Table 7. In the present invention, component detection mainly includes detection of oxygen, nitrogen and sulfur elements, and other contents meet the requirements and are not listed in Table 7. The total time and power consumption are records from the beginning to the end of smelting.

[0151] Table 7 Test results

[0152]

[0153] Combining Examples 1-3 and Comparative Examples 1-2 and Table 7, it can be seen that the smelting method described in the embodiments of the present invention and the use of the intermediate alloy provided by the present invention not only shortens the smelting process time, reduces energy consumption, but also has high purity. According to statistics and testing, when the intermediate alloy of the present invention is used to prepare a high-temperature alloy, the total time is less than 6.7 hours, which is more than 21% shorter than that of Comparative Example 1, and the power consumption is less than 11257 Kwh, which is more than 15% lower than that of Comparative Example 1. The oxygen content is less than 3ppm, the nitrogen content is less than 13ppm, the sulfur content is more than 8ppm, and the volume proportion of inclusion impurities is less than 0.1%.

[0154] Reference Figure 1-4 ,in Figure 1 and Figure 2 All are metallographic structures of the GH4169 alloy prepared in Example 1, but at different locations; Figure 3 and Figure 4 All are metallographic structures of the GH4169 alloy prepared in Comparative Example 1, but at different locations.

[0155] As can be seen from the figure, the high-temperature alloy is prepared by using the intermediate alloy. The contents of elements such as O, N, and S in the high-temperature alloy are relatively low, which effectively improves the purity of the alloy and no inclusion clusters are detected.

[0156] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a high-purity high-temperature alloy, characterized in that: The following steps are involved: (1) Batching and melting: Ni-Cr-Nb master alloy is used for batching; the oxygen and nitrogen contents in the Ni-Cr-Nb master alloy are both less than 100 ppm; and the melting point is below 1250°C; (2) Refining stage: After the raw materials are completely melted, the temperature is gradually raised to the refining temperature of 1490-1510°C, and then the refining stage begins; during the refining process, the vacuum degree is maintained at ≤1Pa; (3) Composition adjustment: sampling, analysis, adjustment of alloy composition, addition of aluminum, titanium, ferrophosphorus and ferroboron, continued melting and stirring, and steelmaking after the composition is qualified; (4) Steel tapping and pouring: The steel tapping temperature is adjusted to 1440-1460°C, and the casting is performed under vacuum conditions with a power of 200Kw-300Kw. After cooling, the steel is demolded to obtain a high-temperature alloy.

2. The method for preparing a high-purity high-temperature alloy according to claim 1, characterized in that: The niobium content in the high-temperature alloy is 4.75%-5.7%.

3. The method for preparing a high-purity high-temperature alloy according to claim 2, characterized in that: The grade of the high temperature alloy is GH4169, GH4169D, Inconel 718 or Inconel 718Plus.

4. The method for preparing a high-purity high-temperature alloy according to claim 1, characterized in that: The oxygen content in the high temperature alloy is below 5 ppm, and the nitrogen content is below 15 ppm.

5. The method for preparing a high purity high temperature alloy according to claim 1, characterized in that: The volume proportion of inclusions in the high temperature alloy is ≤0.1%.

6. The method for preparing a high-purity high-temperature alloy according to claim 1, characterized in that: The total time of the smelting process is reduced by more than 21%, and the power consumption is reduced by more than 15%.

7. The method for preparing a high purity high temperature alloy according to any one of claims 1 to 6, characterized in that: The raw materials for preparing the Ni-Cr-Nb master alloy include 17%-35% of elemental chromium, 8%-16% of elemental niobium, 50%-75% of elemental nickel and 0.04-0.11% of graphite, and the weight ratio of elemental chromium to elemental niobium is 2-4.

8. The method for preparing a high-purity high-temperature alloy according to claim 1, characterized in that: The Ni-Cr-Nb master alloy is prepared through the steps of melting, refining and pouring.

9. The method for preparing a high-purity high-temperature alloy according to claim 8, characterized in that: During the refining process, the alloy liquid is stirred, the stirring power is 180Kw-250Kw, and the stirring time is more than 20 minutes.

10. A high purity high temperature alloy, characterized in that: The method is obtained by the preparation method according to any one of claims 1 to 9.

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