A high-temperature alloy with oxidation resistance under high temperature and high pressure and its preparation method

Abstract

This invention discloses a high-temperature alloy with oxidation resistance under high temperature and high pressure and its preparation method. The alloy comprises, by weight percentage, C≦0.12%, Si≦1.0%, Mn≦1.00%, P≦0.04%, S≦0.04%, Cr 20-35%, Ni≧65%, Cu 0.5-2.5%, Fe≦8%, and Y≦0.25%. By adjusting the content of each element and employing a vacuum induction + electroslag remelting smelting process, the high-temperature alloy prepared exhibits excellent oxidation resistance and excellent resistance to corrosion from solutions containing nitric acid, hydrofluoric acid, sulfuric acid, hydrochloric acid, moist chlorine, hypochlorite, chlorine dioxide, ferric chloride, and copper chloride.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials technology, specifically relating to a high-temperature alloy with oxidation resistance under high temperature and high pressure and its preparation method. Background Technology

[0002] Coal gasification units, sulfuric acid burners, furnace tubes, petrochemical furnaces, heat exchangers, incinerators, and vitrification equipment for radioactive waste disposal are all located in harsh, corrosive environments with high temperatures (600-800 degrees Celsius) and media containing chlorine, including nitric acid, hydrofluoric acid, moist chlorine, hypochlorite, chlorine dioxide, ferric chloride, and copper chloride. Currently, my country uses high-temperature alloys Inconel 601 and Inconel 600 to manufacture these coal gasification units and vitrification equipment.

[0003] Inconel 601 has acceptable high-temperature oxidation resistance, but it has two problems: first, it contains a high amount of Al, which worsens its corrosion resistance; second, Al is easily oxidized during the smelting process and is difficult to control precisely. In addition, the steel ingot surface generally has defects such as slag grooves and slag skin, resulting in a low yield (generally less than 80%). Furthermore, the precipitation phases formed by Al, such as Ni3Al, greatly improve the alloy's resistance to deformation, increasing the number of forging processes and forging costs.

[0004] While Inconel 600 exhibits acceptable corrosion resistance, its low Cr content of 14-17% results in a thin and insufficiently dense oxide film forming on the steel surface at high temperatures. This leads to inadequate oxidation resistance in components such as coal gasification plants and glass curing equipment, resulting in a significantly shorter service life and failing to meet the long-life requirements of critical equipment. Furthermore, Inconel 600 has a nickel content of ≥72.0%, which is very high. Nickel is a scarce and expensive metal in my country, hindering the domestic application of Inconel 600.

[0005] Therefore, the currently used high-temperature alloys Inconel 601 and Inconel 600 cannot meet the requirements of existing technologies for alloys to simultaneously possess high-temperature oxidation resistance and corrosion resistance. Summary of the Invention

[0006] The purpose of this invention is to provide a high-temperature alloy with oxidation resistance under high temperature and high pressure and its preparation method, so as to solve the problem that high-temperature alloys Inconel 601 and Inconel 600 cannot meet the requirements of the prior art for alloys to simultaneously have high-temperature oxidation resistance and corrosion resistance.

[0007] To achieve the above objectives, the first aspect of the present invention provides a high-temperature alloy with oxidation resistance under high temperature and high pressure, comprising, by weight percentage: C≦0.12%, Si≦1.0%, Mn≦1.00%, P≦0.04%, S≦0.04%, Cr 20-35%, Ni≧65%, Cu 0.5-2.5%, Fe≦8%, and Y≦0.25%.

[0008] Preferably, by weight percentage, it includes C 0.02%, Si 0.32%, Mn 0.30%, P 0.02%, S 0.001%, Cr 28.70%, Ni 66.1%, Cu 1.0%, Fe 3.5%, and Y 0.05%.

[0009] A second aspect of this invention provides a method for preparing a high-temperature alloy with oxidation resistance under high temperature and high pressure, comprising the following steps: (1) Raw material preparation; (2) Vacuum melting Various raw materials are weighed according to weight percentage, and alloy ingots are obtained by loading, melting, refining and casting in a vacuum induction furnace. (3) Electroslag remelting Alloy ingot electrode rods are remelted using an electroslag remelting equipment under a protective atmosphere to obtain alloy electroslag remelted ingots; (4) Forging Forged alloys are obtained by forging alloy electroslag remelting ingots using a hydraulic air hammer or a fast forging hydraulic press. (5) Heat treatment The forging alloy is placed in a heating furnace, heated, held at a certain temperature, and then cooled to obtain a high-temperature alloy.

[0010] Preferably, the raw materials in step (1) include pure iron, Jinchuan nickel, electrolytic copper, metallic chromium, silicon calcium powder, lime, fluorite, Ni-Mg, rare earth Y, and deoxidizer. The deoxidizer includes silicon calcium blocks and aluminum blocks. The deoxidizer is baked and dried in an oven at 450-550℃.

[0011] Preferably, the charging step in step (2) is as follows: first, a layer of fine light material is laid at the bottom of the furnace to make it loose at the top and tight at the bottom, while the high melting point furnace material is loaded in the middle and lower high temperature zone of the crucible; The melting step in step (2) is as follows: After the material is loaded, start to draw a vacuum. When the pressure in the vacuum chamber reaches 0.03 mbar, turn on the power to heat. In the early stage of melting, maintain a high vacuum and a slow melting speed. The melting time is greater than 120 minutes. After melting, take a sample for full analysis.

[0012] Preferably, the refining step in step (2) is as follows: the refining temperature is 1540-1560℃, the vacuum degree is increased to 0.013mba, the refining time is greater than 30 minutes, and Ni-Mg and rare earth Y are added 3-5 minutes before tapping to further deoxidize and desulfurize. The amount of Ni-Mg added is controlled at 0.05-0.25% of the steel volume, and the amount of rare earth Y added is controlled at 0.01-0.25% of the steel volume.

[0013] Preferably, the casting step in step (2) is as follows: stirring at high power for 3-5 minutes before tapping, controlling the tapping temperature at 1560-1590℃, and casting ingots of Φ220-Φ290.

[0014] Preferably, the parameters of the electroslag remelting equipment in step (3) are: The electrode size is Φ220-Φ290. Electrode finishing: the shrinkage cavities at the head of the induction electrode are removed, and the electrode surface is ground clean to remove defects such as cold steel, cracks, slag inclusions, and impurities. Electroslag system: low-melting-point, high-flowability quaternary slag CaF2:Al2O3:MgO:CaO=70:20:5:5 is used. The voltage is 60-65V, the current is 8000-8500A, the feeding time is greater than 10 minutes, and the feeding current is gradually reduced from 5000A to 2000A.

[0015] Preferably, the specific parameters for forging in step (4) are: forging ratio of 8-10, soaking temperature of 1100-1200℃, heating rate of ≤120℃ / hour, soaking time of 4-6 hours, initial forging temperature of 1130-1150℃, final forging temperature of ≥900℃, and upsetting times of 2-3 times.

[0016] Preferably, the specific parameters for heat treatment in step (5) are: the heat treatment temperature is 1000-1200℃, the heat treatment time is 1-2 minutes / mm, and the heat treatment is followed by rapid water cooling to reduce the temperature to less than 100℃ within 3 minutes.

[0017] Preferably, the heat preservation time in step (5) is 5-10 hours.

[0018] Therefore, the present invention provides a high-temperature alloy with oxidation resistance under high temperature and high pressure and a preparation method thereof using the above-described structure, which has the following beneficial effects: (1) By adjusting the content of each element, this invention prepares an alloy with excellent antioxidant properties and excellent resistance to corrosion by solutions such as nitric acid, hydrofluoric acid, sulfuric acid, hydrochloric acid, moist chlorine, hypochlorite, chlorine dioxide, ferric chloride and copper chloride. It can be used in coal gasification devices, burners and furnace tubes for treating sulfuric acid, petrochemical furnaces, heat exchangers, incinerators and glass curing equipment for disposing of radioactive waste. It has a higher yield, lower cost and better corrosion resistance.

[0019] (2) The smelting process of vacuum induction + electroslag remelting is adopted, which makes full use of vacuum induction technology to effectively deoxidize and degas. Ni-Mg and rare earth Y are further used for refining, which fully utilizes the deoxidation, desulfurization and degassing effects of Ni-Mg and rare earth Y. The [O] content is reduced from 20-25ppm to 10-15ppm, the [S] content is reduced from 6-8ppm to 1-3ppm, and the [N] content is reduced from 35-45ppm to less than 10ppm. At the same time, the metallic and non-metallic inclusions are greatly reduced. Therefore, the oxidation resistance of the alloy of the present invention at high temperature and its resistance to corrosion by solutions such as nitric acid, hydrofluoric acid, sulfuric acid, hydrochloric acid, moist chlorine, hypochlorite, chlorine dioxide, ferric chloride and copper chloride are improved.

[0020] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0021] The present invention will be further described below. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the present invention is not limited to this embodiment.

[0022] Comparative Example The chemical compositions of high-temperature alloys Inconel 601 and Inconel 600 are shown in Table 1.

[0023]

[0024] Example The chemical composition design of each embodiment is shown in Table 2.

[0025]

[0026] A method for preparing a high-temperature alloy with oxidation resistance under high temperature and high pressure includes the following steps: (1) Raw material preparation The raw materials include pure iron, Jinchuan nickel, electrolytic copper, metallic chromium, silicon-calcium powder, lime, fluorite, Ni-Mg, rare earth element Y, and deoxidizers. The deoxidizers include silicon-calcium blocks and aluminum blocks, which are dried in a 500℃ oven. The raw materials are not limited to those listed above; the raw material preparation process mainly involves preparing all the raw materials used in the preparation process.

[0027] (2) Vacuum melting Various raw materials are weighed according to weight percentage, and alloy ingots are obtained by loading, melting, refining and casting in a vacuum induction furnace. The specific charging steps are as follows: First, lay a layer of fine, light material at the bottom of the furnace, making it loose at the top and tight at the bottom, while high-melting-point furnace material is loaded into the middle and lower high-temperature zones of the crucible; The specific melting steps are as follows: After the material is loaded, vacuuming begins. When the pressure in the vacuum chamber reaches 0.03 mbar, power is supplied for heating. In the initial stage of melting, a high vacuum and a slow melting rate must be maintained. The melting time is greater than 120 minutes. After melting, a sample is taken for full analysis. The refining process is as follows: the refining temperature is 1550℃, the vacuum degree is increased to 0.013mba, the refining time is 60 minutes, and Ni-Mg and rare earth Y are added 5 minutes before tapping for further deoxidation and desulfurization. The amount of Ni-Mg added is controlled at 0.15% of the steel volume, and the amount of rare earth Y added is controlled at 0.1% of the steel volume. The specific casting steps are as follows: stir at high power for 3-5 minutes before tapping, control the tapping temperature at 1580℃, and cast ingots with a diameter of Φ220-Φ290.

[0028] (3) Electroslag remelting Alloy ingot electrode rods are remelted using an electroslag remelting equipment under a protective atmosphere to obtain alloy electroslag remelted ingots; The parameters of the electroslag remelting equipment are as follows: The electrode size is Φ220-Φ290. Electrode finishing: the shrinkage cavities at the head of the induction electrode are removed, and the electrode surface is ground clean to remove defects such as cold steel, cracks, slag inclusions, and impurities. Electroslag system: a low-melting-point, highly fluid quaternary slag CaF2:Al2O3:MgO:CaO=70:20:5:5 is used. The voltage is 62V, the current is 8200A, the feeding time is greater than 10 minutes, and the feeding current is gradually reduced from 5000A to 2000A.

[0029] (4) Forging Forged alloys are obtained by forging alloy electroslag remelting ingots using a hydraulic air hammer or a fast forging hydraulic press. The specific forging parameters are as follows: forging ratio of 9, soaking temperature of 1150℃, heating rate of 120℃ / hour, soaking time of 5 hours, initial forging temperature of 1150℃, final forging temperature of 900℃, and upsetting times of 2-3.

[0030] (5) Heat treatment The forging alloy is placed in a heating furnace, heated, held at that temperature, and then cooled to obtain a high-temperature alloy. The specific parameters for heat treatment are: a soaking temperature of 1500℃, a soaking time of 1.5 minutes / mm, a holding time of 8 hours, and rapid water cooling after heat treatment to reduce the temperature to less than 100℃ within 3 minutes.

[0031] Test case (1) The high-temperature alloy prepared in Example 3 has better corrosion resistance in HNO3+HF solution than Inconel 601 and Inconel 600.

[0032] According to GB / T 4334.4 "Test Method for Corrosion of Stainless Steel by Nitric Acid and Hydrofluoric Acid", the corrosion resistance of the high-temperature alloy prepared in Example 3, Inconel 601 and Inconel 600 were tested. The specific test data are shown in Tables 3 and 4.

[0033]

[0034]

[0035] (2) The high-temperature alloy of Example 3 has better resistance to metal dust formation than Inconel 601 and Inconel 600 under the conditions of 621°C and CO-20%H2 atmosphere.

[0036] The resistance to metal dust formation of the alloy in Example 3, Inconel 601 alloy, and Inconel 600 alloy was tested under the conditions of 621℃ and CO-20%H2 atmosphere. The maximum pitting depth (Mills) of each alloy was obtained. The specific data are shown in Tables 5 and 6.

[0037]

[0038]

[0039] (3) Compared with Inconel 601 alloy and Inconel 600 alloy, the alloy prepared in Example 3 has a significantly improved overall yield due to the improved hot and cold working properties. The results are shown in Table 7.

[0040]

[0041] (4) The alloy prepared in Example 3 has better high-temperature oxidation resistance than Inconel 601 alloy and Inconel 600 alloy.

[0042] According to HB5258-2000 "Test Method for Determination of Oxidation Resistance of Steel and High Temperature Alloys", the test temperatures were 600℃, 700℃ and 800℃, and the test time was 100h. The specific average oxidation rate is shown in Table 8.

[0043]

[0044] (5) The alloy prepared in Example 3 has a higher critical crevice corrosion temperature compared with Inconel 601 alloy and Inconel 600 alloy.

[0045] According to ASTM G48 B method, the critical crevice corrosion temperature (CCT, °C) was tested under three chloride ion environments: 10% FeCl3•6H2O, 11% H2SO4+1.2%HCl+1%FeCl3+1%CuCl2, and 4% NaCl+0.1%FeCl3+0.1M HCl. The critical crevice corrosion temperature of the alloy prepared in Example 3 was higher than that of Inconel 601 alloy and Inconel 600 alloy. The specific test results are shown in 9.

[0046]

[0047] Therefore, the present invention provides a high-temperature alloy with oxidation resistance under high temperature and high pressure and a preparation method thereof, which adopts the above-mentioned structure. By adjusting the content of each element and adopting a smelting process of vacuum induction + electroslag remelting, the prepared high-temperature alloy has excellent oxidation resistance and excellent resistance to corrosion by solutions such as nitric acid, hydrofluoric acid, sulfuric acid, hydrochloric acid, moist chlorine, hypochlorite, chlorine dioxide, ferric chloride and copper chloride.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a high-temperature alloy with oxidation resistance under high temperature and high pressure, characterized in that, Includes the following steps: (1) Raw material preparation; By weight percentage, including: C≦0.12%, Si≦1.0%, Mn≦1.00%, P≦0.04%, S≦0.04%, Cr 20-35%, Cu 1.0%, Fe 3.2-8%, Y≦0.25%, balance Ni, total 100%; (2) Vacuum melting: Weigh various raw materials according to weight percentage, and then charge, melt, refine and cast them in a vacuum induction furnace to obtain alloy ingots; The refining process includes: refining temperature at 1540-1560℃, increasing the vacuum to 0.013 mba, refining time greater than 30 minutes, and adding Ni-Mg and rare earth Y 3-5 minutes before tapping for further deoxidation and desulfurization. The amount of Ni-Mg added is controlled at 0.05-0.25% of the molten steel, and the amount of rare earth Y added is controlled at 0.01-0.25% of the molten steel. (3) Electroslag remelting; using an electroslag remelting device to remelt the alloy ingot electrode rod under a protective atmosphere to obtain an alloy electroslag remelted ingot; (4) Forging; Forging alloys are obtained by forging alloy electroslag remelting ingots using a hydraulic air hammer or a fast forging hydraulic press; (5) Heat treatment; the forging alloy is placed in a heating furnace, heated, held, and cooled to obtain a high-temperature alloy; The prepared high-temperature alloy is used in coal gasification devices, burners and furnace tubes for treating sulfuric acid, petrochemical furnaces, heat exchangers, incinerators, and vitrification equipment for disposing of radioactive waste. The above preparation method uses Ni-Mg and rare earth Y for refining, giving full play to the deoxidation, desulfurization and degassing effects of Ni-Mg and rare earth Y, which significantly reduces the [O] content from the original 20-25ppm to 10-15ppm, the [S] content from the original 6-8ppm to 1-3ppm, and the [N] content from the original 35-45ppm to less than 10ppm.

2. The method for preparing a high-temperature alloy with oxidation resistance under high temperature and high pressure according to claim 1, characterized in that, The raw materials in step (1) include pure iron, Jinchuan nickel, electrolytic copper, metallic chromium, silicon calcium powder, lime, fluorite, Ni-Mg, rare earth Y, and deoxidizer. The deoxidizer includes silicon calcium blocks and aluminum blocks. The deoxidizer is baked and dried in an oven at 450-550℃.

3. The method for preparing a high-temperature alloy with oxidation resistance under high temperature and high pressure according to claim 1, characterized in that, The specific steps of the charging process in step (2) are as follows: First, lay a layer of fine light material at the bottom of the furnace, making it loose at the top and tight at the bottom, while the high melting point furnace material is loaded in the middle and lower high temperature zone of the crucible; The melting step in step (2) is as follows: After the material is loaded, start to draw a vacuum. When the pressure in the vacuum chamber reaches 0.03 mbar, turn on the power to heat. In the early stage of melting, maintain a high vacuum and a slow melting speed. The melting time is greater than 120 minutes. After melting, take a sample for full analysis.

4. The method for preparing a high-temperature alloy with oxidation resistance under high temperature and high pressure according to claim 1, characterized in that, The casting steps in step (2) are as follows: stir at high power for 3-5 minutes before tapping, control the tapping temperature at 1560-1590℃, and cast ingots of Φ220-Φ290.

5. The method for preparing a high-temperature alloy with oxidation resistance under high temperature and high pressure according to claim 4, characterized in that, The parameters of the electroslag remelting equipment in step (3) are as follows: The electrode size is Φ220-Φ290. Electrode finishing: the shrinkage cavities at the head of the induction electrode are removed, and the electrode surface is ground clean to remove defects such as cold steel, cracks, slag inclusions, and impurities. Electroslag system: low-melting-point, high-flowability quaternary slag CaF2:Al2O3:MgO:CaO=70:20:5:5 is used. The voltage is 60-65V, the current is 8000-8500A, the feeding time is greater than 10 minutes, and the feeding current is gradually reduced from 5000A to 2000A.

6. The method for preparing a high-temperature alloy with oxidation resistance under high temperature and high pressure according to claim 5, characterized in that, The specific parameters for forging in step (4) are as follows: forging ratio is 8-10, soaking temperature is 1100-1200℃, heating rate is ≤120℃ / hour, soaking time is 4-6 hours, initial forging temperature is 1130-1150℃, final forging temperature is ≥900℃, and upsetting times are 2-3 times.

7. The method for preparing a high-temperature alloy with oxidation resistance under high temperature and high pressure according to claim 6, characterized in that, The specific parameters for heat treatment in step (5) are: the soaking temperature is 1000-1200℃, the soaking time is 1-2 minutes / mm, and the heat treatment is followed by rapid water cooling to reduce the temperature to less than 100℃ within 3 minutes.

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