A molybdenum alloy electrode resistant to hot corrosion by molten metal and a preparation method thereof

Abstract

The present invention discloses a molybdenum alloy electrode resistant to hot corrosion of liquid metal and a preparation method thereof. The preparation method mainly includes the following steps: mixing TiB2 powder and Mo powder in proportion by using a method combining sieving and mixing with a mixer, drying and screening the mixture after mixing, and then obtaining the molybdenum alloy electrode through hot pressing sintering, deformation treatment, and machining. After adding TiB2, it remains in the grain boundaries. Because it has characteristics such as a stable oxide film, chemical inertness, and low solubility when facing liquid metal, the molybdenum alloy has excellent resistance to liquid metal erosion. The forging process reforms the clamping part at the front end of the robotic arm, adding a hydraulic cylinder that can freely and automatically adjust the clamping part to float slightly within the range of [-10, +10] mm along the Z-axis, ensuring the flatness of the contact part between the clamped part of the bar and the mold during forging and avoiding the occurrence of shear failure. Using the method of the present invention, a high-performance molybdenum alloy electrode with high density, good liquid metal corrosion resistance, and high yield is obtained.

Description

Technical Field

[0001] The present invention relates to the field of preparation of high-performance molybdenum electrode rods, and specifically to a molybdenum alloy electrode resistant to hot corrosion of molten metal and a preparation method thereof. Background Art

[0002] Due to the characteristics of low resistivity and high conductivity of molybdenum material, molybdenum electrode rods are widely used in the glass processing industry and other low-melting-point metal processing industries. However, after glass or low-melting-point metal becomes liquid at high temperature, it is easy to erode the molybdenum electrode rods, thereby affecting the service life of the molybdenum electrode rods. Therefore, how to improve the erosion resistance of molybdenum electrode rods has become the top priority of research in the entire industry. Currently, in the industry, the method of adding zirconia to molybdenum electrode rods is generally used to improve the performance of molybdenum electrode rods against glass liquid erosion, while there is less research on how to resist the erosion of low-melting-point molten metal.

[0003] Therefore, how to improve the erosion resistance of molybdenum electrode rods to molten metal has become the main obstacle to promoting the application of molybdenum electrode rods in the low-melting-point metal heating industry. Summary of the Invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a molybdenum alloy electrode resistant to hot corrosion of molten metal and a preparation method thereof. This preparation method can improve the erosion resistance of the molybdenum alloy electrode in molten metal and ensure the service life of the molybdenum alloy electrode in molten metal.

[0005] In order to achieve the above object, the specific solution adopted by the present invention is as follows:

[0006] A preparation method of a molybdenum alloy electrode resistant to hot corrosion of molten metal mainly includes the following steps:

[0007] Step 1: Select Mo powder and TiB2 powder, and perform sieving and ball milling mixing on the Mo powder and TiB2 powder to obtain a first mixed powder;

[0008] Step 2: Perform drying and sieving on the first mixed powder to obtain a second mixed powder with uniform particle size;

[0009] Step 3: Place the second mixed powder in a mold and perform hot pressing and sintering to obtain a sintered blank;

[0010] Step 4: Clamp the sintered blank with a robotic arm and place it on a forging platform for forging to obtain a forged part; wherein, during forging, it is necessary to ensure that the levelness of the sintered blank and the forging platform is the same;

[0011] Step 5: Perform turning and post-treatment on the forged part in sequence to obtain the molybdenum alloy electrode.

[0012] As a preferred solution, in step one, the mass fraction of Mo powder in the first mixed powder is 98.8% - 99.9%, and the mass fraction of TiB2 powder is 0.1% - 1.2%.

[0013] As a preferred solution, in step one, the average particle size of Mo powder is 2.0 - 3.0 μm, and the purity is 99.95%; the average particle size of TiB2 powder is 1.0 - 3.0 μm, and the purity is 99.9%.

[0014] As a preferred solution, in step two, the first mixed powder is placed in a drying furnace and dried at a temperature of 100 ± 20 °C for 2 - 4 h, and then sieved through a 200 - mesh sieve.

[0015] As a preferred solution, in step three, the temperature of hot - press sintering is 1450 °C - 1800 °C, the pressure is 15 - 50 MPa, and the heat - preservation time is 10 - 30 min.

[0016] As a preferred solution, in step four, after each forging, it needs to be reheated in the furnace. The first forging temperature is 1500 °C - 1700 °C, the single - time heating time is 0.5 - 2 h, and the temperature of each reheating in the furnace decreases by 50 - 100 °C.

[0017] As a preferred solution, in step four, there are two hydraulic cylinders oppositely arranged at the front end of the robotic arm, which can adjust the clamping part along the Z - axis direction. The piston rods of the two hydraulic cylinders act on the two opposite side walls of the clamping part respectively. Under the action of the hydraulic cylinders, the clamping part at the front end of the robotic arm can freely adjust slightly within the range of [-10 mm, +10 mm] along the Z - axis, thereby ensuring the same levelness of the sintered blank and the forging platform during forging.

[0018] A molybdenum alloy electrode resistant to hot corrosion by molten metal is prepared by the above - mentioned method.

[0019] As a preferred solution, the density ρ of the molybdenum alloy electrode satisfies: 10.01 g / cm 3 ≤ ρ ≤ 10.19 g / cm 3 .

[0020] Beneficial effects:

[0021] 1), In the present invention, the TiB2 powder and Mo powder are mixed in proportion by using the method of sieving and mixing + ball - milling mixing, and after mixing, a series of subsequent processes such as hot - press sintering and forging in a hot - press furnace are carried out to obtain a molybdenum alloy with a certain degree of alloying. The alloy density ∈ [10.01 g / cm 3 , 10.19 g / cm 3], when used as a heating electrode for low-melting-point metals such as Al and Mg, it has a longer service life than other molybdenum and molybdenum alloys, that is, it has excellent resistance to liquid metal corrosion, in order to lay a theoretical and practical foundation for the preparation of high-performance electrode material products for molten low-melting-point metals.

[0022] 2) The present invention uses hot pressing to increase the sintering density of the sintered blank. Conventional pressing and medium-frequency sintering produces molybdenum alloys with large intergranular defects and numerous pores. Adding TiB2 to enhance the grain boundary properties makes high-temperature deformation processing of Mo-TiB2 extremely difficult, hindering the preparation of high-performance molybdenum alloys. However, the hot pressing process improves the high-temperature deformation properties of the molybdenum alloy by increasing the density of Mo-TiB2, ultimately achieving the goal of improving the performance of molybdenum alloy electrodes.

[0023] 3) The present invention improves the alloy's resistance to liquid metal corrosion by adding TiB2. Since TiB2 will mainly remain on the grain boundaries after being added, and the corrosion of the alloy after encountering liquid metal often starts from the grain boundaries, the TiB2 in the grain boundaries will rely on its own characteristics to enhance the corrosion resistance of the molybdenum alloy. The principles are as follows: 1. Stable oxide film. When TiB2 comes into contact with liquid metal, an oxide film, usually titanium oxide (TiO2), will form on its surface. This oxide film can provide a certain degree of protection and prevent the liquid metal from further corroding TiB2; 2. Chemical inertness. TiB2 is chemically inert in common liquid metals, which means that it has almost no reaction with these metals. This is because the titanium carbide and boride units in the TiB2 crystal structure are tightly combined, making it difficult to be corroded by liquid metal; 3. Low solubility. TiB2 has a low solubility, so when in contact with liquid metal, TiB2 will hardly dissolve into the metal, which also helps to maintain its corrosion resistance.

[0024] 4) During the forging process, the rods, especially the molybdenum alloy rods doped with TiB2 ceramics, are prone to brittle fracture, cracks and other problems due to the existence of forging shear force. Considering that the rods are clamped by a robotic arm and placed on a forging platform for forging, the horizontal height of the robotic arm and the forging platform is determined by the flatness of the ground, the flatness of the forging platform and the height adjustment button of the robotic arm. Once the flatness of the ground is insufficient or the forging platform is deformed due to long-term thermal processing, it will affect the consistency of the horizontal height of the robotic arm and the forging platform, thereby causing the rod to form a certain angle with the forging die during processing, thereby causing the rod to shear and fracture during the thermal processing. The present invention has two hydraulic cylinders relatively arranged along the Z-axis direction at the front clamping part of the robotic arm to ensure that the two ends of the rod are level during forging, avoid the occurrence of shear fracture or shear crack problems during the forging process, and help to improve the thermal processing yield of molybdenum alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic structural diagram of the front end of the robotic arm in the present invention.

[0026] Markings in the figure: 1. Control console, 2. Robotic arm, 3. First hydraulic cylinder, 4. Clamping part, 5. Second hydraulic cylinder. Specific embodiments

[0027] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] A preparation method of a molybdenum alloy electrode resistant to hot corrosion of molten metal, the method comprising the following preparation steps:

[0029] Step 1: Powder selection: The average particle size of Mo powder is 2.0 - 3.0 μm, and the purity is 99.95%; the average particle size of TiB2 powder is 1.0 - 3.0 μm, and the purity is 99.9%.

[0030] Step 2: Powder mixing: The TiB2 powder and Mo powder are mixed in proportion by using the method of sieving + ball milling, and the mixing time is: 12h - 24h, so as to obtain the first mixed powder; in the first mixed powder, the TiB2 content is by mass fraction: 0.1% - 1.2%, and the Mo content is by mass fraction: 98.8% - 99.9%.

[0031] Step 3: Drying and sieving: The first mixed powder is placed in a dryer and dried at 100 ± 20 °C for a time of: 2 - 4h; the dried powder is sieved, and after passing through a 200-mesh sieve, a second mixed powder with uniform particle size is obtained.

[0032] Step 4: Hot pressing and sintering molding: Using a hot press furnace and matching corresponding molds, a sintered blank is prepared for standby. The temperature of the hot press furnace: 1450 °C - 1800 °C, the pressure: 15 - 50 Mpa, and the hot pressing and heat preservation time: 10 - 30 min.

[0033] Step 5. Deformation treatment: The sintered blank is forged in multiple heat treatments. The initial forging temperature is 1500°C - 1700°C, and the final forging temperature is 1200°C. The deformation amount per heat treatment is ≥20%. The reheating temperature for each return to the furnace decreases by 50 - 100°C successively. The single heating time is 0.5 - 2h. There are two hydraulic cylinders (the first hydraulic cylinder 3 and the second hydraulic cylinder 5 respectively) oppositely arranged at the front end of the robotic arm 2, which can adjust the clamping part 4 in the Z-axis direction. The piston rods of the two hydraulic cylinders 3 and 5 act on the two opposite side walls of the clamping part 4 respectively. During the treatment process, the clamping part 4 at the front end of the robotic arm 2 is freely adjusted along the Z-axis according to the needs of the deformation treatment to ensure that during the deformation treatment process, the levelness of the bar, the clamping part, and the forging platform should always be maintained to ensure that the bar is not affected by the forging shear stress during the forging process;

[0034] Step 6. Turning processing: The Mo-TiB2 after the deformation treatment is subjected to turning processing to obtain the finished product;

[0035] Step 7. Post-treatment: The product after the previous machining treatment is cleaned, inspected, and packaged to obtain a molybdenum alloy electrode with high resistance to hot corrosion by molten metal.

[0036] The following combines specific examples and comparative examples to illustrate that the molybdenum alloy electrode prepared by the present invention has excellent resistance to molten metal erosion.

[0037] Example 1

[0038] A preparation method of a molybdenum alloy electrode with high resistance to hot corrosion by molten metal includes the following preparation steps:

[0039] Step 1. Powder selection: The average particle size of Mo powder is 2.0μm, the average particle size of TiB2 powder is 1.0μm, the purity of Mo powder is 99.95%, and the purity of TiB2 powder is 99.9%;

[0040] Step 2. Powder mixing: The TiB2 powder and Mo powder are mixed in proportion by using the method of sieving + ball milling. The mixing time is 12h to obtain the first mixed powder. In the first mixed powder, the content of TiB2 is 0.1% by mass fraction, and the content of Mo is 99.9% by mass fraction;

[0041] Step 3. Drying and screening: The first mixed powder is placed in a vacuum furnace and dried at 100°C for 2h; the dried powder is ground and screened. After passing through a 200-mesh sieve, a second mixed powder with uniform particle size is obtained;

[0042] Step 4. Hot pressing and sintering forming: Using a hot press furnace and matching molds, a sintered blank is prepared for standby. The temperature of the hot press furnace is 1450°C, the pressure is 15Mpa, and the hot pressing and heat preservation time is 10min;

[0043] Step Five, Deformation Treatment: The sintered billet is forged in three heating cycles. Forging temperature: 1500 °C, single heating time: 0.5 h, the reheating temperature for each time is gradually reduced by 50 °C, and the single forging deformation amount is 20%. During the forging process, the clamping part at the front end of the robotic arm is freely adjusted along the Z-axis according to the forging requirements to ensure the flatness of the bar during the forging process;

[0044] Step Seven, Turning Process: The forged Mo-TiB2 is subjected to turning to obtain the finished product;

[0045] Step Eight, Post-treatment: The product after the previous machining process is cleaned, inspected, and packaged to obtain a molybdenum alloy electrode with high resistance to liquid metal corrosion.

[0046] After inspection and testing, the molybdenum alloy electrode has a dense structure, good coating performance, and the density of the molybdenum alloy is 10.01 g / cm 3 (The theoretical density of the molybdenum alloy is 10.05 g / cm 3 , that is, the density of the molybdenum alloy > 95% of the theoretical density). Inspection of the yield rate during the high-temperature deformation processing found that for the molybdenum alloy electrode prepared by this method, the probability of brittle fracture and cracking of the bar is significantly reduced, the yield rate > 98%, and the obtained molybdenum alloy has excellent resistance to liquid metal corrosion.

[0047] Example 2

[0048] A preparation method of a molybdenum alloy electrode resistant to liquid metal heat erosion, comprising the following preparation steps:

[0049] Step One, Powder Selection: The average particle size of Mo powder is 3.0 μm, the average particle size of TiB2 powder is 2.0 μm, the purity of Mo powder is: 99.95%, and the purity of TiB2 powder is: 99.9%;

[0050] Step Two, Powder Mixing: The TiB2 powder and Mo powder are mixed in proportion by using the method of sieving + ball milling. The mixing time is: 12 h, and the first mixed powder can be obtained. In the first mixed powder, the TiB2 content is 1.2% by mass fraction, and the Mo content is 98.8% by mass fraction;

[0051] Step Three, Drying and Sieving: The first mixed powder is placed in a vacuum furnace and dried at 80 °C for a time of: 4 h; the dried powder is ground and sieved. After sieving through a 200-mesh sieve, a second mixed powder with uniform particle size is obtained;

[0052] Step Four, Hot Pressing and Sintering Molding: Using a hot press furnace and matching molds, a sintered billet is prepared for standby. Hot press furnace temperature: 1800 °C, pressure: 20 Mpa, hot press holding time: 20 min;

[0053] Step 5. Deformation treatment: The sintered billet is forged in four heating cycles. Forging temperature: 1700 °C, single heating time: 2 h, and the reheating temperature decreases by 100 °C each time. The single forging deformation is 25%. During the forging process, the clamping part at the front end of the robotic arm can be freely adjusted along the Z-axis according to forging requirements to ensure the flatness of the bar during the forging process;

[0054] Step 6. Turning process: The forged Mo-TiB2 is subjected to a turning process to obtain the finished molybdenum alloy electrode.

[0055] Step 7. Post-treatment: The products after the previous machining process are cleaned, inspected, and packaged to obtain molybdenum alloy electrodes with high resistance to liquid metal corrosion.

[0056] After inspection and testing, the molybdenum alloy has a dense structure and good coating performance. Molybdenum alloy density: 10.15 g / cm 3 (The theoretical density of the molybdenum alloy is 10.19 g / cm 3 , that is, the molybdenum alloy density > 95% of the theoretical density). Inspection of the finished product rate during the forging process found that for the molybdenum alloy electrodes prepared by this method, the probability of brittle fracture and cracking of the bars was significantly reduced, the finished product rate > 98%, and the obtained molybdenum alloy has excellent resistance to liquid metal corrosion.

[0057] Comparative Example 1

[0058] The difference between Comparative Example 1 and Example 1 is only that: after the height of the clamping part of the robotic arm is determined in Step 6, it is no longer adjusted during the subsequent forging process.

[0059] After inspection and testing, the molybdenum alloy electrode has a dense structure and good coating performance. Density: 10.0 g / cm 3 (The theoretical density of the molybdenum alloy is 10.05 g / cm 3 , that is, the molybdenum alloy density > 95% of the theoretical density). The obtained molybdenum alloy has excellent resistance to liquid metal corrosion. Inspection of the finished product rate during the forging process found that the bars are prone to brittle fracture and cracking, and the finished product rate is only 93%, indicating that when the flatness of the two ends of the molybdenum alloy electrode is insufficient, defects such as fracture or cracking are likely to occur.

[0060] Comparative Example 2

[0061] The difference between Comparative Example 2 and Example 1 is only that: only Mo powder is used as the raw material, without adding TiB2 powder; the mass fraction of Mo powder in the first mixed powder is 100%.

[0062] Comparative Example 3

[0063] The difference between Comparative Example 3 and Example 1 is only that: the raw materials used are Mo powder and ZrO2 powder. In the first mixed powder, the ZrO2 content is 0.5% by mass fraction, and the Mo content is 99.5% by mass fraction;

[0064] The electrodes of Φ63.2*800 were prepared by the methods of Example 1 and Comparative Examples 2-3 respectively, and the electrodes were placed in the molten Al bath and molten Mg bath for 500 h respectively for metal production. The weight loss results of the electrodes due to the erosion of the molten metal are shown in Table 1.

[0065] Table 1 Weight loss results of molten metal erosion of electrodes prepared by the methods of Example 1 and Comparative Examples 2-3

[0066]

[0067] As can be seen from Table 1, the molybdenum alloy electrode has obvious advantages in resisting the erosion of low melting point metals (such as Al, Mg) compared with the pure Mo rod and Mo-ZrO2 rod (excellent performance in resisting molten glass).

[0068] For those not specified in the above examples and comparative examples, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained by purchasing in the market.

[0069] The above is only a preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. Any equivalent transformation or modification made according to the essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A preparation method of a molybdenum alloy electrode resistant to hot corrosion by molten metal, characterized in that: It mainly includes the following steps: Step 1: Select Mo powder and TiB2 powder, and process them by a combination of sieving and mixing and ball milling to obtain a first mixed powder; Step 2: Perform drying and sieving on the first mixed powder to obtain a second mixed powder with uniform particle size; Step 3: Place the second mixed powder in a mold and perform hot press sintering to obtain a sintered blank; Step 4: Clamp the sintered blank with a robotic arm, place it on a forging platform for forging, and obtain a forged part; among them, during forging, it is necessary to ensure that the levelness of the sintered blank and the forging platform is consistent; Step 5: Perform turning and post-treatment on the forged part in sequence to obtain a molybdenum alloy electrode; Among them, in Step 4, two hydraulic cylinders capable of adjusting the clamping part along the Z-axis are oppositely arranged at the front end of the robotic arm, and the piston rods of the two hydraulic cylinders act on the two opposite side walls of the clamping part respectively. Under the action of the hydraulic cylinders, the clamping part at the front end of the robotic arm can freely and slightly adjust within the range of [-10mm, +10mm] along the Z-axis, thereby achieving the same levelness of the sintered blank and the forging platform.

2. The preparation method of a molybdenum alloy electrode resistant to hot corrosion of molten metal according to claim 1, characterized in that: In Step 1, the mass fraction of Mo powder in the first mixed powder is 98.8% - 99.9%, and the mass fraction of TiB2 powder is 0.1% - 1.2%.

3. The preparation method of a molybdenum alloy electrode resistant to hot corrosion of molten metal according to claim 1, characterized in that: In Step 1, the average particle size of Mo powder is 2.0 - 3.0μm, and the purity is 99.95%; the average particle size of TiB2 powder is 1.0 - 3.0μm, and the purity is 99.9%.

4. The preparation method of a molybdenum alloy electrode resistant to hot corrosion by molten metal as claimed in claim 1, wherein: In Step 2, place the first mixed powder in a drying furnace, dry it at a temperature of 100 ± 20°C for 2 - 4h, and then sieve it through a 200-mesh sieve.

5. The preparation method of a molybdenum alloy electrode resistant to hot corrosion of molten metal according to claim 1, characterized in that: In Step 3, the temperature of hot press sintering is 1450°C - 1800°C, the pressure is 15 - 50MPa, and the heat preservation time is 10 - 30min.

6. The preparation method of a molybdenum alloy electrode resistant to hot corrosion of molten metal according to claim 1, characterized in that: In Step 4, it is necessary to heat back to the furnace after each forging. The first forging temperature is 1500°C - 1700°C, the single heating time is 0.5 - 2h, and the temperature of each heat back to the furnace decreases by 50 - 100°C.

7. A molybdenum alloy electrode resistant to hot corrosion by molten metal, characterized in that, It is prepared by the method described in any one of claims 1 - 6.

8. A molybdenum alloy electrode resistant to hot corrosion by molten metal, as claimed in claim 7, wherein The density ρ of the molybdenum alloy electrode satisfies: 10.01 g / cm 3 ≤ ρ ≤ 10.19 g / cm 3 .

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