A chromium-aluminum hardening alloy and a method for producing the same

Abstract

The application provides a chromium-aluminum intermediate alloy and a preparation method thereof, and the chromium-aluminum intermediate alloy has the following mass percentage: Al 30%~35%, and the balance is Cr. The application adopts a vacuum induction furnace to produce the chromium-aluminum intermediate alloy, and the production process specifically comprises the following steps: material distribution: placing chromium metal into a crucible in the vacuum induction furnace; melting period: after the furnace material is red-hot, adding aluminum ingots until the furnace material is completely melted; refining period: starting refining when the temperature reaches the refining temperature; pouring: pouring the alloy. The application sets a reasonable feeding sequence, and reasonably controls the melting process and the pouring process, so that the chromium-aluminum intermediate alloy with good component consistency, low inclusion content and high product yield is prepared.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of vacuum smelting, in particular to a chromium-aluminum intermediate alloy and a preparation method thereof. BACKGROUND

[0002] In the fields of modern energy industry and aerospace industry, high-temperature protective coating is an indispensable important part. MCrAlY coating has excellent oxidation resistance, corrosion resistance, high-temperature strength, low density, low cost and other advantages, and is widely used as a high-temperature protective coating or thermal barrier bonding layer in the fields of aerospace, gas turbine, automobile and energy. Chromium-aluminum intermediate alloy is a key process material for preparing MCrAlY coating.

[0003] CN 102965527A discloses a method for preparing aluminum-chromium intermediate alloy from chromium scrap. In the method, aluminum ingots are first added to a smelting furnace, and then covering agents are added after melting. Then, chromium scrap is added twice after heating. The chromium-aluminum alloy produced by the method has a high risk of high impurity element content due to the addition of covering agents. Moreover, the Cr content of the produced aluminum-chromium intermediate alloy is only up to 20%, which is not suitable for the Cr content of 65% to 70%.

[0004] CN 114734048A discloses a method for preparing high-chromium aluminum alloy powder. In the method, chromium powder and aluminum powder are mixed and then hot isostatic pressing is performed to form an electrode rod. Then, PREP powdering is performed. However, the method has problems such as uneven mixing, easy breaking of the powdering electrode rod, and the like, which may result in uneven composition of the prepared chromium-aluminum alloy powder. CN 114101677A also uses the above-mentioned similar process to prepare high-chromium aluminum alloy powder, and then forms a target material, which also has similar problems.

[0005] CN 102212723A discloses a method for preparing chromium-aluminum intermediate alloy. The method uses aluminum-chromium intermediate alloy produced by aluminum thermal reduction reaction. The aluminum thermal reduction reaction has problems such as high inclusion content and alloy element segregation, which greatly affect the quality of the subsequent product. CN 116179917A discloses an aluminum-chromium intermediate alloy powder for 3D printing and a preparation method thereof. The chromium-aluminum intermediate alloy is produced by aluminum thermal reduction reaction, and then powdering is performed. However, the chromium-aluminum intermediate alloy produced by aluminum thermal reduction reaction also has problems such as high inclusion content and alloy element segregation. SUMMARY

[0006] The present application aims to solve the problems in the prior art. The present application discloses a chromium-aluminum intermediate alloy and a preparation method thereof. The chromium-aluminum intermediate alloy has an atomic percentage close to 1:1 and can be directly applied to prepare MCrAlY material.

[0007] Technical solution: The application discloses a chromium-aluminum intermediate alloy, and the mass percentage of the chromium-aluminum intermediate alloy is as follows: Al 30%-35%, and the balance is Cr. The atomic percentage is close to 1:1.

[0008] Figure 1 is an Al-Cr binary phase diagram, and through Figure 1 It can be seen that the melting point of Al is 660 DEG C, the melting point of Cr is 1863 DEG C, and the density of Cr is larger, and the density of Al is lower. It can be known from the Al-Cr binary phase diagram that the Al-Cr reaction is a continuous peritectic reaction, which needs to absorb a large amount of heat, and therefore the dissolution speed of high-melting-point Cr is slow. The application designs a reasonable melting process of the alloy, ensures that the refractory Cr element is completely melted, and further ensures the consistency of the alloy composition.

[0009] The preparation method of the chromium-aluminum intermediate alloy disclosed by the application has the mass percentage of the chromium-aluminum intermediate alloy as follows: Al: 30%-35%, and the balance is Cr, and the method comprises the following steps:

[0010] Step 1, material distribution: high-purity metal chromium is placed in a vacuum induction furnace crucible, and aluminum ingots are added from the upper charging chamber;

[0011] Step 2, melting period: the furnace is vacuumized, high-purity metal chromium is heated by power transmission, the aluminum ingots are added from the upper charging chamber of the vacuum induction furnace after the high-purity metal chromium is in a red-hot state, then argon gas is filled, the argon gas pressure is 10000Pa-20000Pa, high power is transmitted to the furnace charge to melt and clean, and overheating is performed to 1650 DEG C ± 10 DEG C, and then power is stopped to cool to 1550 DEG C ± 10 DEG C;

[0012] Step 3, refining period: the temperature is raised to 1600 DEG C ± 10 DEG C, and the temperature is kept for 10min-20min, and the argon gas pressure is 10000Pa-20000Pa;

[0013] Step 4, pouring period: power is stopped to cool to 1580 DEG C ± 10 DEG C, uninterrupted pouring is performed, and the alloy ingot is cooled to break the space and take the ingot.

[0014] Specifically, in step 1, the mass percentage of Cr in the high-purity metal chromium is ≥99.80%.

[0015] Specifically, in step 2, the vacuumization is performed to be lower than 1.33Pa.

[0016] Specifically, in step 2, the temperature for heating the high-purity metal chromium is 1550 DEG C-1600 DEG C.

[0017] Specifically, in step 2, the argon gas filled is high-purity argon, and the purity of the argon gas is ≥99.999%.

[0018] Specifically, in step 2, the temperature is superheated to 1650℃±10℃, and then power-off cooling is performed to 1550℃±10℃, and the process is repeated for 3 times to ensure that the furnace charge is completely melted.

[0019] Specifically, in step 4, the chromium-aluminum intermediate alloy should be cooled to below 500℃ before breaking the vacuum.

[0020] Specifically, the chromium-aluminum intermediate alloy has an atomic percentage of chromium and aluminum close to 1:1.

[0021] Beneficial effects: Compared with the prior art, the chromium-aluminum intermediate alloy preparation method has the following beneficial advantages:

[0022] 1. The chromium-aluminum intermediate alloy is produced by vacuum induction melting, which has the advantages of good consistency of alloy composition, low inclusion content, and high product yield compared with hot isostatic pressing and aluminum thermal reduction reaction processes.

[0023] 2. The chromium-aluminum intermediate alloy produced by the present application has an Al element mass percentage of 30%~35%, and the balance is Cr, and the atomic percentage is close to 1:1, which can be directly applied to the preparation of CrAl materials.

[0024] 3. The present application designs a reasonable melting process of the alloy, which ensures that the refractory Cr element is completely melted and ensures the consistency of the alloy composition.

[0025] 4. The present application reduces the volatilization loss of Cr and Al elements in the vacuum induction melting process by injecting high-purity argon during the melting process, thereby greatly improving the yield of chromium-aluminum intermediate alloy.

[0026] 5. The method is simple and easy to operate, and can realize stable industrial production and popularization. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is an Al-Cr binary alloy phase diagram.

[0028] Figure 2 is a chromium-aluminum intermediate alloy produced by a vacuum induction furnace.

[0029] Figure 3 is a chromium-aluminum intermediate alloy produced by an aluminum thermal reduction method.

[0030] Figure 4 is the un-melted chromium produced by the method of comparative example 1. DETAILED DESCRIPTION

[0031] The technical solutions of the present application will be described in detail below through examples, but the protection scope of the present application is not limited to the examples.

[0032] The composition of the chromium-aluminum hardening alloy is as follows (mass percentage): the mass percentage of Al element is 30% to 35%, and the balance is Cr. The examples are all prepared by using a 25 Kg vacuum induction furnace to smelt the chromium-aluminum hardening alloy. Example 1

[0033] The target composition of the alloy in this example is (wt%): 33% Al, and the balance is Cr. The total amount of alloy ingredients is 100 Kg, that is, 33 Kg of aluminum ingot and 67 Kg of high-purity metal chromium. The mass percentage of Cr in the high-purity metal chromium is greater than or equal to 99.80%.

[0034] 1. Material distribution: The high-purity metal chromium is placed in the crucible of the vacuum induction furnace, and the aluminum ingot is added from the upper charging chamber.

[0035] 2. Melting period: The furnace is vacuumized to less than 1.33 Pa, the high-purity metal chromium is heated by power supply, and the aluminum ingot is added from the upper charging chamber after the high-purity metal chromium is red-hot. Then, high-purity argon is filled, the argon pressure is 10,000 Pa to 20,000 Pa, the argon purity is greater than or equal to 99.999%, the high power is supplied to melt the furnace charge completely, and the temperature is overheated to 1650℃±10℃. Then, the power is stopped to cool down to 1550℃±10℃. The overheating and power-off cooling process needs to be repeated for 3 times to ensure that the furnace charge is completely melted.

[0036] 3. Refining period: The temperature is raised to 1600℃±10℃, and the argon pressure is 10,000 Pa to 20,000 Pa.

[0037] 4. Pouring period: The power is stopped to cool down to 1580℃±10℃, and the alloy ingot is poured without interruption. After the alloy ingot is cooled to below 500℃, the space is broken to take the ingot.

[0038] After the alloy ingot is cooled to room temperature, samples are taken from the upper, middle and lower parts of the alloy ingot for alloy composition analysis. The specific results are shown in Table 1. It can be seen that the consistency of Al element is good, and there is no obvious segregation.

[0039] Table 1 Chemical composition (wt%) of chromium-aluminum hardening alloy produced by the process of Example 1

[0040] Element Al Cr Standard 30~35 Surplus Example 1 - Upper 33.02 Surplus Example 1 - Middle 33.01 Surplus Example 1 - Lower 32.99 Surplus

[0041] After the chromium-aluminum hardening alloy ingot is demolded, it is weighed, and the weight is 99.43 Kg. The product yield = 99.43 Kg / 100 Kg = 99.43% > 99.0%. The product yield is relatively high. Example 2

[0042] The target composition of the alloy of the embodiment is (wt%): 34% Al, and the balance is Cr, and the total amount of alloy ingredients is 100 Kg, that is, the amount of aluminum ingot ingredients is 34 Kg, and the amount of high-purity metal chromium ingredients is 66 Kg, and the mass percentage of Cr in the high-purity metal chromium is greater than or equal to 99.80%.

[0043] 1. Material distribution: all high-purity metal chromium is placed in the crucible of the vacuum induction furnace, and aluminum ingots are added from the upper charging chamber.

[0044] 2. Melting period: the furnace is vacuumized to less than 1.33 Pa, high-purity metal chromium is heated by power transmission, and after the high-purity metal chromium is red-hot, the power is turned off, aluminum ingots are added from the upper charging chamber of the vacuum induction furnace, then high-purity argon is filled, the argon pressure is 10,000 Pa to 20,000 Pa, the argon purity is greater than or equal to 99.999%, high power is transmitted to melt the furnace charge completely, and then overheating is performed to 1,650 ℃±10 ℃, and then power is turned off to cool to 1,550 ℃±10 ℃, and the overheating and power-off cooling process needs to be repeated for three times to ensure that the furnace charge is completely melted.

[0045] 3. Refining period: the temperature is raised to 1,600 ℃±10 ℃, and the temperature is maintained for 10 min to 20 min, and the argon pressure is 10,000 Pa to 20,000 Pa.

[0046] 4. Pouring period: the power is turned off to cool to 1,580 ℃±10 ℃, and uninterrupted pouring is performed, and after the alloy ingot is cooled to below 500 ℃, the space is broken to take the ingot.

[0047] After the alloy ingot is cooled to room temperature, samples are taken from the upper, middle and lower parts of the alloy ingot for analysis of the alloy composition, and the specific results are shown in Table 2. It can be seen that the consistency of the Al element is good, and there is no obvious segregation.

[0048] Table 2 Chemical composition of chromium-aluminum intermediate alloy produced by the process of Example 2 (wt%)

[0049] Element Al Cr Standard 30~35 Surplus Example 2 - Upper 34.05 Surplus Example 2 - Middle 34.02 Surplus Example 2 - Lower 33.98 Surplus

[0050] After the chromium-aluminum intermediate alloy ingot is demolded, it is weighed, and the weight is 99.68 Kg, and the product yield is 99.68 Kg / 100 Kg=99.68%>99.0%, and the product yield is relatively high.

[0051] Comparative Example 1

[0052] The target composition of the alloy of the embodiment is (wt%): 34% Al, and the balance is Cr, and the total amount of alloy ingredients is 100 Kg, that is, the amount of aluminum ingot ingredients is 34 Kg, and the amount of high-purity metal chromium ingredients is 66 Kg, and the mass percentage of Cr in the high-purity metal chromium is greater than or equal to 99.80%.

[0053] 1. Material distribution: all high-purity metal chromium and aluminum ingots are placed in the crucible of the vacuum induction furnace.

[0054] 2. Melting period: the furnace is vacuumed to below 1.33 Pa, and the furnace charge is heated by power supply. Since the melting point of the aluminum ingot is low, the aluminum ingot is melted first, and then reacts with high-purity metallic chromium. High-purity argon is filled when the aluminum ingot is melted, the argon pressure is 10,000 Pa to 20,000 Pa, the argon purity is greater than or equal to 99.999%, high power is supplied until the furnace charge is melted and cleaned, and overheating is performed to 1650℃±10℃, then power is cut off to cool to 1550℃±10℃, and the overheating and power cut-off cooling process needs to be repeated for 3 times.

[0055] 3. Refining period: heated to 1600℃±10℃, and kept for 10 min to 20 min, the argon pressure is 10,000 Pa to 20,000 Pa.

[0056] 4. Pouring period: power is cut off to cool to 1580℃±10℃, and uninterrupted pouring is performed, and the alloy ingot is broken after cooling to below 500℃.

[0057] After pouring is completed, it is found that a large amount of metallic chromium is bonded together at the bottom of the crucible and is not melted and cleaned. The alloy composition is analyzed by sampling from the upper, middle and lower positions of the alloy ingot, and the specific results are shown in Table 3. It can be seen that the Al element exceeds the standard due to the uncleaned part of the Cr raw material.

[0058] Table 3 Chemical composition of chromium-aluminum intermediate alloy produced by the process of Comparative Example 1 (wt%)

[0059] Element Al Cr Standard 30~35 Surplus Comparative Example 1 - Upper 39.82 Surplus Comparative Example 1 - Middle 39.78 Surplus Comparative Example 1 - Lower 39.92 Surplus

[0060] After the chromium-aluminum intermediate alloy ingot is demolded, it is weighed, and the weight is 8.46 Kg, the product yield = 8.46 Kg / 10 Kg = 84.6%, and the product yield is low.

[0061] Comparative Example 2:

[0062] The target composition of the comparative example alloy is (wt%): 30-35% Al, and the balance is Cr. The CrAl alloy is produced by the aluminothermic reduction method. The raw materials used are chromium trioxide powder, aluminum powder, sodium nitrate, and aluminum rod. The chromium-aluminum intermediate alloy ingot is prepared according to the steps of the patent with the application publication number CN102212723A, and the alloy composition is analyzed by sampling from the upper, middle and lower positions of the alloy ingot, and the specific results are shown in Table 3. It can be seen that there is obvious segregation of the Al element.

[0063] Table 4 Chemical composition of chromium-aluminum intermediate alloy produced by the process of Comparative Example 2 (wt%)

[0064] Element Al Cr Standard 30~35 Surplus Comparative Example 2 - Upper 34.81 Surplus Comparative Example 2 - Middle 32.12 Surplus Comparative Example 2 - Lower 31.28 Surplus

[0065] The results of example 1, example 2 and comparative example 1, comparative example 2 are analyzed. As shown in Tables 1, 2, 3 and 4, the Al element control of example 1 and example 2 both reach the target value, and there is no obvious segregation, while part of the metal chromium of the alloy produced in comparative example 1 is not melted clean, resulting in that the Al element exceeds the standard, and the Al element of the alloy produced in comparative example 2 has obvious segregation phenomenon; the product yield of the alloy of example 1 and example 2 is greater than 99.0%, and the product yield is relatively high.

[0066] Meanwhile, the chromium-aluminum intermediate alloy produced in the example of the present application and the chromium-aluminum intermediate alloy produced in comparative example 2 by the aluminothermic reduction method are compared, and metallographic structure observation is performed, as shown in Figure 2 , Figure 3 , it can be known that the chromium-aluminum intermediate alloy produced in the present application has basically no inclusions; while the chromium-aluminum intermediate alloy produced in comparative example 2 by the aluminothermic reduction method has more inclusions.

[0067] In summary, the chromium-aluminum intermediate alloy produced by the method of the present application has the advantages of good composition consistency, low inclusion content, high product yield and the like, and solves the problems of the chromium-aluminum intermediate alloy produced by other processes.

[0068] The above only describes the preferred embodiments of the present application and is not used to limit the present application.

Claims

1. A method for preparing a chromium-aluminum master alloy, characterized in that, The chromium-aluminum master alloy has the following mass percentage composition: Al: 30%~35%, with the balance being Cr. The method includes the following steps: Step 1, Fabrication: Place high-purity chromium metal in the crucible of the vacuum induction furnace, and add aluminum ingots from the upper feeding chamber; Step 2, Melting Period: The furnace is closed and a vacuum is drawn until it is below 1.33 Pa. High-purity chromium metal is heated to 1550℃~1600℃. Once the high-purity chromium metal is red-hot, the power is cut off. Aluminum ingots are added through the charging chamber on the vacuum induction furnace, and then argon gas is introduced at a pressure of 10000Pa~20000Pa. High power is supplied to melt the furnace charge and superheat it to 1650℃±10℃. Then the power is cut off and the temperature is lowered to 1550℃±10℃. This process needs to be repeated 3 times to ensure that the furnace charge is completely melted. Step 3, refining period: heat to 1600℃±10℃, hold for 10min~20min, argon pressure 10000Pa~20000Pa; Step 4, casting period: Power off and cool down to 1580℃±10℃, cast continuously, and remove the ingot after it has cooled down; before removing the ingot, the chromium-aluminum master alloy should be cooled to below 500℃.

2. The method for preparing the chromium-aluminum master alloy according to claim 1, characterized in that, In step 1, the Cr content in the high-purity metallic chromium is ≥99.80% by mass.

3. The method for preparing the chromium-aluminum master alloy according to claim 1, characterized in that, In step 2, the argon gas introduced is high-purity argon with a purity ≥ 99.999%.

4. The method for preparing the chromium-aluminum master alloy according to claim 1, characterized in that, The chromium-aluminum master alloy has an atomic percentage of chromium to aluminum of 1:

1.

5. The product obtained by the preparation method according to any one of claims 1 to 4, characterized in that, It can be directly used for the preparation of MCrAlY coatings.

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