A nickel-based alloy containing strontium and preparation method thereof

Abstract

The invention discloses a strontium-containing nickel-based alloy and a preparation method thereof. The nickel-based alloy comprises, by mass percentage, 0.01% to 0.06% carbon, 14% to 15% chromium, 26% to 27% cobalt, 1.5% to 2.0% niobium, 3% to 4% molybdenum, 2.3% to 2.8% aluminum, 4.9% to 5.5% titanium, 4.0% to 4.5% manganese, 0.03% to 0.06% strontium, and 2.0% to 3.5% magnesium. The balance is nickel and unavoidable impurity elements. The production process includes the following steps: 1) weighing metallurgical raw materials capable of producing carbon, chromium, cobalt, niobium, molybdenum, aluminum, titanium, manganese, strontium, and magnesium according to the element ratio principle of the strontium-containing alloy; 2) adding the raw materials smelted in step 1) to a vacuum induction furnace for treatment, followed by tapping and casting to form an alloy ingot; 3) using the alloy ingot in step 2) as a base material through an electroslag remelting process to obtain a nickel-based alloy electroslag ingot; and 4) performing a vacuum consumable operation on the basis of step 3) to obtain a strontium-containing nickel-based alloy product. The present invention improves the hot working properties of the nickel-based alloy and prevents cracking.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, and in particular to a strontium-containing nickel-based alloy and a preparation method thereof. Background Art

[0002] Nickel-based alloys in steel metallurgy are widely used in hot-end components of aircraft engines and gas turbines because of their high strength under high-temperature corrosion conditions. As engine thrust continues to increase, higher operating temperatures are required. However, the current operating temperature of nickel-based alloys is generally around 650°C. Excessively high temperatures cause the precipitate phase in the nickel-based alloy to coarsen, leading to poor performance. By increasing the aluminum-titanium content in the nickel-based alloy, the composition of the precipitate phase can be stabilized and the operating temperature of the nickel-based alloy can be increased. However, increasing the aluminum-titanium content will cause the presence of coarse (r+r`) eutectic precipitates during solidification, which will cause cracks to form between the (r+r`) eutectic phase and the matrix of the nickel-based alloy during forging, thus rendering it scrapped. In addition, the large size of nickel-based alloys is also a cause of poor high-temperature plasticity and forging cracking. Therefore, in response to this situation, there is an urgent need to improve the components produced by existing nickel-based alloys. Summary of the Invention

[0003] (1) Technical issues that need to be resolved

[0004] In response to the deficiencies in the prior art, the present invention provides a strontium-containing nickel-based alloy and a preparation method thereof. By adding an appropriate amount of strontium element to the nickel-based alloy, the hot working performance of the nickel-based alloy is improved, and high quality effects are achieved through process control to prevent the occurrence of cracks.

[0005] (2) Technical issues that need to be resolved

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A nickel-based alloy containing strontium, comprising the following components by mass percentage:

[0008] Carbon: 0.01-0.06%;

[0009] Chromium: 14% to 15%;

[0010] Cobalt: 26% to 27%;

[0011] Niobium: 1.5% to 2.0%;

[0012] Molybdenum: 3% to 4%;

[0013] Aluminum: 2.3% to 2.8%;

[0014] Titanium: 4.9% to 5.5%;

[0015] Manganese: 4.0% to 4.5%;

[0016] Strontium: 0.03% to 0.06%;

[0017] Magnesium: 2.0% to 3.5%;

[0018] The balance is nickel and unavoidable impurity elements.

[0019] In addition, the present invention also provides a method for preparing a nickel-based alloy containing strontium, the production process comprising the following contents:

[0020] Step 1) weighing metallurgical raw materials capable of obtaining carbon, chromium (metallic chromium), cobalt, niobium, molybdenum, aluminum, titanium, manganese, strontium, and magnesium according to the element ratio principle of the strontium-containing alloy;

[0021] Step 2) adding the smelted raw materials in step 1) into a vacuum induction furnace, performing full melting and refining treatment in the vacuum induction furnace under vacuum conditions, and then casting to form an alloy ingot;

[0022] Step 3) using the alloy ingot prepared in step 2) as a base material to obtain a nickel-based alloy electroslag ingot through an electroslag remelting process;

[0023] Step 4) Based on step 3), a vacuum self-consumable operation is performed, followed by forging, rolling and heat treatment to obtain a strontium-containing nickel-based alloy product.

[0024] Preferably, in step 2), the oxygen content in the vacuum induction furnace under vacuum conditions is less than 20 ppm.

[0025] Preferably, the alloy ingot smelted in step 2) has the following composition: carbon: 0.01% to 0.06%, chromium: 14% to 15%, cobalt: 26% to 27%, niobium: 1.5% to 2.0%, molybdenum: 3% to 4%; aluminum: 2.3% to 2.8%, titanium: 4.9% to 5.5%, manganese: 4.0% to 4.5%, and strontium: 0.03% to 0.06%.

[0026] Preferably, in step 3), the smelting slag system CaF2-CaO-MgO-Al2O3-TiO2-SrO in the electroslag remelting is combined with the alloy ingot for electroslag remelting to obtain a nickel-based alloy electroslag ingot, wherein the basic slag system components in the electroslag remelting are as follows, in percentage by weight:

[0027]

[0028] Preferably, for a nickel-based alloy containing 0.41% strontium and 3.52% aluminum, the base slag composition is determined to be: CaF2:Al2O3:CaO:MgO:TiO2:SrO=53:17:13:3:3:10 according to the composition characteristics of the consumable electrode.

[0029] Preferably, in step 4), the nickel-based alloy electroslag ingot is polished and then subjected to a first vacuum consumable long arc operation to obtain ingot 1#, and ingot 1# is polished again and then subjected to a second vacuum consumable short arc operation to obtain ingot 2#.

[0030] Preferably, the first vacuum consumable needs to control the arc to be long arc and high melting rate, the arc length is controlled at 8-12mm, and the melting rate is controlled at 3.5-3.7.KG / Min; the arc needs to be controlled to be short arc and low melting rate, and the arc length is controlled at 4-8mm, and the melting rate is controlled at 3.0-3.3KG / Min.

[0031] Preferably, in the step 4), after the ingot 2# is kept at 1100°C for 10 hours, the temperature is further increased to 1150°C and kept for 15 hours, and then the temperature is further increased to 1190°C and kept for 48 hours, followed by air cooling. The air-cooled ingot 2# is then isothermally forged at 1000°C to 1100°C, with a forging ratio greater than 5. Finally, after the forged ingot 2# is kept at 960°C for 1 hour, the temperature is cooled to 780°C at a cooling rate of 55°C to 60°C, kept for 20 hours, and then air-cooled to obtain a strontium-containing nickel-based alloy product.

[0032] (3) Technical effects to be achieved

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] Firstly, the strontium-containing nickel-based alloy of the present invention adds an appropriate amount of strontium element to improve high-temperature thermoplasticity, which helps to improve the forging cracking problem of the ingot.

[0035] Secondly, the present invention develops a slag system for electroslag remelting of strontium-containing alloys, and determines the SrO content in the slag system from the perspective of thermodynamic equilibrium, which is beneficial to improving the forging cracking problem of ingots.

[0036] Thirdly, the present invention adds strontium to the nickel-based high-temperature alloy to solve the problem of coarse r+r' eutectic phase.

[0037] Fourthly, the present invention proposes a high-temperature diffusion annealing process for strontium-containing nickel-based alloy ingots, which can eliminate the adverse factors of strontium, give full play to the beneficial effects of strontium, and reduce the cracking phenomenon of nickel-based alloys during the forging process. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a forging cracking diagram of the prior art nickel-based alloy without adding strontium.

[0039] Figure 2 The present invention is a flow chart of a method for preparing a nickel-based alloy containing strontium. DETAILED DESCRIPTION

[0040] Example 1: See Figure 1 , a nickel-based alloy containing strontium, comprising the following components by mass percentage:

[0041] Carbon: 0.01-0.06%;

[0042] Chromium: 14% to 15%;

[0043] Cobalt: 26% to 27%;

[0044] Niobium: 1.5% to 2.0%;

[0045] Molybdenum: 3% to 4%;

[0046] Aluminum: 2.3% to 2.8%;

[0047] Titanium: 4.9% to 5.5%;

[0048] Manganese: 4.0% to 4.5%;

[0049] Strontium: 0.03% to 0.06%;

[0050] Magnesium: 2.0% to 3.5%;

[0051] The balance is nickel and unavoidable impurity elements.

[0052] Because strontium is considered a cleansing element in some alloys, it not only deoxidizes but also transforms clustered Al₂O₃ inclusions into fine, dispersed SrAl₂O₄ oxide particles, which can serve as nucleation particles for NbC, improving the size and distribution of NbC in nickel-based alloys and mitigating NbC forging cracking. Strontium in solution can also enhance purification and strengthen grain boundaries, improving the (r+r′) eutectic. However, excessive amounts can have the opposite effect, resulting in the formation of a low-melting-point SrNi phase, deteriorating the alloy's hot workability and increasing its tendency to crack. Therefore, controlling the optimal strontium composition range to improve the hot workability of nickel-based alloys is the best approach.

[0053] A method for preparing a nickel-based alloy containing strontium, the production process comprising the following:

[0054] Step 1) weighing smelting raw materials capable of obtaining carbon, chromium (metallic chromium), cobalt, niobium, molybdenum, aluminum, titanium, manganese, strontium, and magnesium according to the element ratio principle of the strontium-containing alloy;

[0055] Among them, the following components are included in percentage by mass:

[0056] Carbon: 0.01-0.06%;

[0057] Chromium: 14% to 15%;

[0058] Cobalt: 26% to 27%;

[0059] Niobium: 1.5% to 2.0%;

[0060] Molybdenum: 3% to 4%;

[0061] Aluminum: 2.3% to 2.8%;

[0062] Titanium: 4.9% to 5.5%;

[0063] Manganese: 4.0% to 4.5%;

[0064] Strontium: 0.03% to 0.06%;

[0065] Magnesium: 2.0% to 3.5%;

[0066] The balance is nickel and unavoidable impurity elements.

[0067] Step 2) adding the smelted raw materials in step 1) into a vacuum induction furnace, and performing full melting and refining treatment in the vacuum induction furnace, followed by casting to form alloy ingots. This step is also called vacuum induction melting;

[0068] The oxygen content in the vacuum induction furnace is less than 20 ppm under vacuum conditions.

[0069] Smelting raw materials (including industrial pure iron, metallic chromium, graphite, aluminum ingot, strontium iron, sponge titanium, and nickel-magnesium alloy) are added to a vacuum induction furnace, and industrial pure iron and metallic chromium are placed in a crucible of the vacuum induction furnace, graphite, aluminum ingot, strontium iron, and sponge titanium are placed in a charging bin of the vacuum induction furnace, and finally the nickel-magnesium alloy is added. The vacuum induction furnace is then evacuated to below 15 Pa, powered on and heated to melt the smelting raw materials in the crucible. After all the raw materials in the crucible are melted, graphite, aluminum ingot, strontium, and sponge titanium are sequentially added to the crucible (graphite is added sequentially according to the alloy content requirement in the steel grade). After the alloy is fully melted, it is refined at a temperature of 1530° C. to 1590° C. for half an hour, and then argon is filled into the induction furnace to a slightly positive pressure (50-200 Pa higher than atmospheric pressure), the nickel-magnesium alloy is added, and the temperature in the crucible is maintained at a temperature of 1530° C. to 1590° C. for 10 to 15 minutes, and then steel is tapped and cast to form an alloy ingot.

[0070] The composition of the smelted alloy ingot is: carbon: 0.01%~0.06%, chromium: 14%~15%, cobalt: 26%~27%, niobium: 1.5%~2.0%, molybdenum: 3%~4%; aluminum: 2.3%~2.8%, titanium: 4.9%~5.5%, manganese: 4.0%~4.5%, strontium: 0.03%~0.06%.

[0071] Step 3) The alloy ingot prepared in step 2) is used as a base material, and the smelting slag system CaF2-CaO-MgO-Al2O3-TiO2-SrO in the electroslag remelting is combined with the alloy ingot for electroslag remelting to obtain a nickel-based alloy electroslag ingot, wherein the basic slag system components in the electroslag remelting are as follows, in percentage by weight:

[0072]

[0073] For a nickel-based alloy containing 0.41% strontium and 3.52% aluminum, the method established by the present invention is used to determine the base slag composition as follows: CaF2:Al2O3:CaO:MgO:TiO2:SrO=53:17:13:3:3:10 according to the composition characteristics of the consumable electrode.

[0074] This slag was used in an electroslag furnace with a capacity of 100 kg and a mold inner diameter of 36 cm. The current and voltage were 8000 A and 67 V, respectively. The electrode diameter was 26 cm, and 40 kg of slag was used. At the start of electroslag remelting, 20 g of aluminum powder was added to the slag. After remelting 2000 kg of electroslag ingots, the remelting process was completed. The ingots were demolded and then placed in a slow cooling pit for slow cooling. The electroslag ingot composition was tested. The axial Al, Ti, Sr, and Si compositions of the electroslag ingots from a typical heat are shown in the table below. The axial Sr content of the resulting alloy ingots showed minimal deviation, ranging from 0.036% to 0.041%. While the aluminum, strontium, and titanium contents fluctuated, they were all within acceptable ranges. The oxygen content was reduced to less than 5 ppm by electroslag remelting.

[0075] The content of aluminum, strontium and titanium in electroslag ingot along the height of electroslag ingot

[0076]

[0077] Step 4) After polishing the nickel-based alloy electroslag ingot in step 3), a first vacuum consumable long arc operation is performed to obtain ingot 1#, wherein the first vacuum consumable operation needs to control the arc to be long arc and high melting rate to achieve the purpose of removing inclusions, and the arc length is controlled at 8-12 mm, and the melting rate is controlled at 3.5-3.7.KG / Min, which is more conducive to the purpose of removing inclusions; after polishing ingot 1# again, a second vacuum consumable short arc operation is performed again to obtain ingot 2#, wherein the arc is controlled to be short arc and low melting rate, and the second vacuum consumable operation is performed again to reduce the problem of solidification structure segregation and (r+r`) coarse eutectic precipitation phase, and the arc length is controlled at 4-8 mm, and the melting rate is controlled at 3.0-3.3KG / Min, which is more conducive to reducing solidification structure segregation;

[0078] The nickel-based alloy electroslag ingot is polished and then subjected to the first vacuum consumable long arc operation to obtain vacuum consumable ingot 1#. The vacuum consumable ingot 1# is then polished and subjected to the second vacuum consumable short arc operation, during which manganese is volatilized in the vacuum consumable process, resulting in a manganese content of 1.2% in the final ingot. The vacuum consumable process reduces the oxygen content to less than 5ppm.

[0079] Step 5) The ingot 2# obtained in step 4) is subjected to forging, rolling and heat treatment, wherein multiple heating and holding operations are required, followed by air cooling (a process of cooling in the atmosphere);

[0080] Among them, after ingot 2# is kept at 1100℃ for 10 hours, this is conducive to melting the low-melting-point SrNi precipitate phase back into the matrix, thereby avoiding cracking defects during forging. After continuing to heat up to 1150℃ and keeping it for 15 hours, this can melt the low-melting-point Laves phase back into the matrix, thereby avoiding cracking defects during forging. After continuing to heat up to 1190℃ and keeping it for 48 hours, this can evenly distribute the original segregation of Nb in the matrix, and then air-cooling.

[0081] Step 6) isothermally forging the ingot 2# after air cooling in step 5) at 1000° C. to 1100° C., with a forging ratio greater than 5;

[0082] Step 7) The ingot 2# forged in step 6) was kept at 960°C for 1 hour, cooled to 780°C at a cooling rate of 55°C to 60°C, kept for 20 hours, and then air-cooled to obtain a strontium-containing nickel-based alloy product. No cracking problem occurred during the forging process of the product.

[0083] Comparative Example 1:

[0084] This comparative example provides a nickel-based alloy, which, by mass percentage, includes: carbon: 0.01% to 0.06%, chromium: 14% to 15%, cobalt: 26% to 27%, niobium: 1.5% to 2.0%, molybdenum: 3% to 4%; aluminum: 2.3% to 2.8%, titanium: 4.9% to 5.5%, manganese: 1.0% to 1.5%, and the balance is nickel. The rest is the same as above, the difference being whether strontium is added. Cracking problems occurred during forging, such as Figure 1 shown.

[0085] Comparative Example 2:

[0086] The strontium-containing nickel-based alloy in this comparative example is the same as that in the application example, except that ingot 2# was not kept at 1100°C for 10 hours. Instead, the ingot was directly heated to 1150°C and kept warm for 15 hours, then heated to 1190°C and kept warm for 48 hours, and then air-cooled. Since the melting point of the SrNi precipitate phase is 1120°C, the temperature was directly raised to 1150°C during the heating process, and the SrNi precipitate phase melted, causing the area to melt into a liquid state, making it a source of cracks during forging. Therefore, the ingot of comparative example 2 cracked during the forging process.

[0087] Due to the irrational design of the remelting slag system in the electroslag remelting of strontium-containing alloys in the current prior art, the unstable oxides in the slag, and the constant changes in the reaction temperature between the metal and the slag, the strontium element can be unevenly distributed along the axial direction of the ingot, which in severe cases exceeds the required range of the alloy and reduces the yield rate. At present, the problem of controlling the uniformity of the strontium element added to the nickel-based alloy along the axial direction of the electroslag ingot has become a bottleneck problem for the electroslag remelting production of high-quality strontium-containing alloys. In addition, the vacuum and high temperature environment in the long arc vacuum consumable and short arc vacuum consumable will cause the burning of the manganese element. Therefore, the existing technology cannot control the manganese element in the parent material and achieve the manganese element within the control range after vacuum consumable. Therefore, the present invention can reduce the cracking phenomenon of the nickel-based alloy during the forging process, which can better meet the use requirements.

[0088] The nickel-based alloy provided by the present invention adds an appropriate amount of strontium to improve high-temperature thermoplasticity, which helps to improve the forging cracking problem of the ingot. The present invention develops a slag system for electroslag remelting of strontium-containing alloys, and determines the SrO content in the slag system from the perspective of thermodynamic equilibrium; the present invention first adds strontium to the nickel-based high-temperature alloy to solve the problem of coarse r+r` eutectic phase; the present invention proposes a high-temperature diffusion annealing process for strontium-containing nickel-based alloy ingots, which can eliminate the adverse factors of strontium, give full play to the beneficial effects of strontium, and improve the problem of hot working cracking. The heat treatment and forging method of the strontium-containing nickel-based alloy proposed by the present invention can reduce the cracking phenomenon of the nickel-based alloy during the forging process.

[0089] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection of the present invention. Therefore, based on the innovative concept of the present invention, changes and modifications to the embodiments described herein, or equivalent structural or equivalent process transformations made using the contents of the present invention's description and drawings, and direct or indirect application of the above technical solutions to other related technical fields, are all included in the scope of protection of the present invention's patent.

Claims

1. A nickel-based alloy containing strontium, characterized in that: Calculated by mass percentage, it includes the following components: Carbon: 0.01-0.06%; Chromium: 14% to 15%; Cobalt: 26% to 27%; Niobium: 1.5% to 2.0%; Molybdenum: 3% to 4%; Aluminum: 2.3% to 2.8%; Titanium: 4.9% to 5.5%; Manganese: 4.0% to 4.5%; Strontium: 0.03% to 0.06%; Magnesium: 2.0% to 3.5%; The balance is nickel and unavoidable impurity elements; The preparation process of the nickel-based alloy containing strontium comprises the following steps: Step 1) weighing metallurgical raw materials capable of obtaining carbon, chromium, cobalt, niobium, molybdenum, aluminum, titanium, manganese, strontium, and magnesium according to the element ratio principle of the strontium-containing alloy; Step 2) adding the smelted raw materials in step 1) into a vacuum induction furnace, performing full melting and refining treatment in the vacuum induction furnace under vacuum conditions, and then casting to form an alloy ingot; Step 3) using the alloy ingot prepared in step 2) as a base material to obtain a nickel-based alloy electroslag ingot through an electroslag remelting process; Step 4) performing a vacuum consumable operation on the basis of step 3), followed by forging, rolling and heat treatment to obtain a strontium-containing nickel-based alloy product, wherein the forging step comprises: keeping the ingot at 1100° C. for 10 hours, then heating it to 1150° C. and keeping it for 15 hours, then heating it to 1190° C. and keeping it for 48 hours, followed by air cooling, and then isothermally forging the air-cooled ingot at 1000° C. to 1100° C., with a forging ratio greater than 5, and the heat treatment step comprises: after the forged ingot is kept at 960° C. for 1 hour, cooling it to 780° C. at a cooling rate of 55° C. to 60° C. and keeping it for 20 hours, and then air cooling it to obtain the strontium-containing nickel-based alloy product.

2. The method for preparing a nickel-based alloy containing strontium according to claim 1, wherein: The metallurgical raw materials of carbon, chromium, cobalt, niobium, molybdenum, aluminum, titanium, manganese, strontium, magnesium and nickel in step 1) include the following components by mass percentage: Carbon: 0.01-0.06%; Chromium: 14% to 15%; Cobalt: 26% to 27%; Niobium: 1.5% to 2.0%; Molybdenum: 3% to 4%; Aluminum: 2.3% to 2.8%; Titanium: 4.9% to 5.5%; Manganese: 4.0% to 4.5%; Strontium: 0.03% to 0.06%; Magnesium: 2.0% to 3.5%; The balance is nickel and unavoidable impurity elements.

3. The method for preparing a strontium-containing nickel-based alloy according to claim 1, wherein: In the step 2), oxygen is less than 20 ppm under vacuum conditions in the vacuum induction furnace.

4. The method for preparing a nickel-based alloy containing strontium according to claim 1, wherein: In the step 3), the smelting slag system CaF2-CaO-MgO-Al2O3-TiO2-SrO in the electroslag remelting is combined with the alloy ingot to perform electroslag remelting to obtain a nickel-based alloy electroslag ingot, wherein the basic slag system components in the electroslag remelting are as follows, in percentage by weight:

5. The method for preparing a nickel-based alloy containing strontium according to claim 1, wherein: In the step 4), the nickel-based alloy electroslag ingot is polished and then subjected to a first vacuum consumable long arc operation to obtain ingot 1#, and ingot 1# is polished again and then subjected to a second vacuum consumable short arc operation to obtain ingot 2#.

6. The method for preparing a nickel-based alloy containing strontium according to claim 5, wherein: The first vacuum consumable requires controlling the arc to be long and high melting speed, with the arc length controlled at 8-12 mm and the melting speed controlled at 3.5-3.7 kg / min; controlling the arc to be short and low melting speed, with the arc length controlled at 4-8 mm and the melting speed controlled at 3.0-3.3 kg / min.

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