Process for improving the service life of hafnium materials and use thereof

Abstract

The application belongs to the technical field of metal surface treatment process, and particularly discloses a process method for prolonging the service life of hafnium material. The process method is based on the relationship between the service life of hafnium material and its performance. The process method provided by the application refines the grains of hafnium in microcosm through cryogenic treatment, so that the hafnium exhibits excellent oxidation resistance in macrocosm, thereby ensuring that the service life of the treated hafnium material is greatly prolonged when the treated hafnium material is applied. The application also discloses the application of the process method in electrodes for plasma cutting, that is, the process is applied to the production of electrodes for plasma cutting, and the hafnium particles treated by the process method are used as emitters, so that the service life of the electrodes can be significantly improved, and the service life of the electrodes can be increased to close to the service life of imported electrodes, and the electrodes have lower cost than the imported electrodes, thereby obviously accelerating the development of plasma cutting technology.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology. Specifically, it relates to a process method for improving the service life of hafnium materials and the application of this process method in plasma cutting electrodes. Background Technology

[0002] Hafnium metal has a wide range of applications due to its good oxidation resistance, good thermal and electrical conductivity and low electron work function, such as being used as a plasma emitter in plasma cutting electrodes.

[0003] Plasma cutting is mainly used for cutting metal materials. The plasma electrode head is a major consumable in a plasma cutting machine, and its quality significantly affects the cutting quality, efficiency, and cost. The electrode's lifespan is a crucial parameter for evaluating its quality.

[0004] Currently, the main ways to improve electrode lifespan are to improve the internal and external quality of the plasma emitter material, as well as the connection method between the plasma emitter and the copper electrode body. Internal quality is reflected in the purity of the emitter material and the presence of defects or inclusions, while external quality is reflected in the surface quality of the emitter wire.

[0005] my country began producing air plasma cutting machines in 1984, and the development has been very rapid, with significant progress in cutting capacity, cutting quality, and cutting cost. However, even when the purity, surface quality, and connection method of the plasma emitter material are similar, the service life of domestically produced plasma cutting electrode heads is only about 70% to 80% of that of imported electrodes, which seriously limits the development of plasma cutting technology. Summary of the Invention

[0006] The inventors of this invention discovered during long-term research on electrodes for plasma cutting that the reason for the sudden drop in the lifespan of the electrode head for plasma cutting is that the hafnium particles embedded in the copper electrode body as emitters are easily oxidized at high temperatures during plasma cutting, forming a thick oxide film. Although the oxide film itself has a relatively dense structure, it is easy to fall off due to its thickness, which causes the hafnium particles to gradually burn out until they are completely consumed.

[0007] To address this, the inventors improved the oxidation resistance of hafnium particles, thereby slowing down the formation of an excessively thick oxide film during plasma cutting and thus extending the lifespan of the emitter.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] A process for improving the service life of hafnium materials includes the following steps: subjecting the hafnium material to cryogenic treatment for 2 to 72 hours.

[0010] When performing cryogenic treatment on hafnium materials, to avoid the adverse effects of thermal stress caused by a sudden drop in temperature on the performance of the hafnium materials, a stepped, slow cooling method is preferred. Preferably, the hafnium materials are cooled to the cryogenic treatment temperature by controlling 2 to 3 temperature steps at a cooling rate of 1℃ / min to 60℃ / min, with each temperature step held for 20 to 30 minutes, for a total cooling time of 2 hours to 5 hours.

[0011] Cryogenic treatment generally includes two methods: liquid method (treatment temperature around -150℃) and gas method (treatment temperature around -196℃). All treatment temperatures refer to one standard atmosphere and are related to the inherent properties of liquid nitrogen as the refrigerant. Preferably, the gas method is used for cryogenic treatment of hafnium materials to prevent cracking caused by significant thermal shock.

[0012] The aforementioned cryogenic treatment of hafnium materials refines the grain size at the microscopic level, thereby improving the oxidation resistance of hafnium materials at high temperatures and preventing the formation of excessively thick oxide films that would cause frequent peeling during high-temperature applications. Higher oxidation resistance prevents the formation of excessively thick oxide films on the surface of hafnium materials. Conversely, the thinner oxide film covering the surface of hafnium materials is not only less prone to peeling and burn-off, but its dense structure also protects the surface, thus extending the service life of hafnium materials.

[0013] Another object of the present invention is to provide an application of the above-described process method, namely, using hafnium particles obtained by the above-described process method in a plasma cutting electrode as an emitter.

[0014] The plasma cutting electrode includes a copper electrode body and hafnium particles obtained by the above-described process embedded in the copper electrode body.

[0015] Specifically, in this plasma cutting electrode, the hafnium particles have a purity of at least 99.95%, a smooth surface, and no traces of drawing.

[0016] Preferably, hafnium particles are embedded in the copper electrode body by interference fit and brazing.

[0017] This invention refines the hafnium grains at the microscopic level through cryogenic treatment, resulting in superior oxidation resistance at the macroscopic level. This significantly extends the service life of the treated hafnium material. Applying this process to electrodes for plasma cutting can significantly improve electrode lifespan, reaching levels approaching those of imported electrodes, while also offering lower costs. Attached Figure Description

[0018] Figure 1 These are metallographic photographs of hafnium products subjected to cryogenic treatment according to Embodiment 3 of the present invention;

[0019] Figure 2 These are metallographic photographs of hafnium products without cryogenic treatment according to Embodiment 3 of the present invention;

[0020] Figure 3 This is a comparison diagram of the high-temperature oxidation resistance of hafnium products before and after cryogenic treatment according to Embodiment 3 of the present invention. Detailed Implementation

[0021] The above-mentioned technical solutions of the present invention will be illustrated by specific embodiments below. However, it should be understood that the following embodiments are only specific examples of the above-mentioned technical solutions and are not intended to limit all of them. Those skilled in the art can make appropriate adjustments and changes based on their understanding of the spirit of the invention.

[0022] The following embodiments 1 to 4 of the present invention provide a process method for improving the service life of hafnium materials, specifically: hafnium wire with a diameter of 5.1 mm is formed by stamping Φ2.21 mm hafnium wire, and then the hafnium particles are cooled to the cryogenic treatment temperature by a stepped cooling method for cryogenic treatment for 2 h to 72 h.

[0023] The stepped cooling method specifically refers to the method of cooling hafnium particles down to the cryogenic treatment temperature by controlling 2 to 3 temperature steps at a cooling rate of 1℃ / min to 60℃ / min, and holding each temperature step for 20 min to 30 min, maintaining a total cooling time of 5 h to 7 h.

[0024] It is worth noting that the cooling rate is not constant during the cooling period. Therefore, the cooling rate refers to the range of the maximum and minimum rates distributed throughout the entire cooling process, and does not refer to the average rate during a specific cooling period.

[0025] The specific process parameters for Examples 1 to 4 are shown in Table 1 below.

[0026] Table 1. Specific process parameters for Examples 1 to 4

[0027]

[0028]

[0029] That is, in the above embodiments, in the stepped cooling process, Embodiment 1 uses 2 temperature steps, while Embodiments 2 to 4 all use 3 temperature steps.

[0030] Microscopic observation was performed on the hafnium particles before and after cryogenic treatment in Example 3 above. The metallographic images before and after cryogenic treatment are shown below. Figure 1 and Figure 2 As shown. Figure 2 The untreated hafnium particles were rated as having a grain size of 8.5, while Figure 1 The grain size of hafnium particles that underwent cryogenic treatment for 48 hours was rated as 9.5. This shows that cryogenic treatment has a significant effect on refining the grain size of hafnium particles, which can improve their high-temperature oxidation resistance on a macroscopic scale and thus increase their service life.

[0031] Meanwhile, isothermal oxidation experiments were conducted on hafnium particles before and after cryogenic treatment in Example 3. The experimental temperature was set at 800℃, and the isothermal oxidation time was 10 hours. The changes in oxidative weight gain of both particles over time are as follows: Figure 3 As shown. From Figure 3 As can be seen, the oxidative weight gain of hafnium particles after cryogenic treatment for 48 hours was significantly lower than that of hafnium particles without cryogenic treatment. This indicates that the cryogenically treated hafnium particles formed a thinner oxide film layer than the untreated hafnium particles, which also confirms that cryogenic treatment can improve the high-temperature oxidation resistance of hafnium particles.

[0032] Hafnium material that has undergone cryogenic treatment can be used in the fabrication of electrodes for plasma cutting, where it is embedded in a copper electrode body as an emitter.

[0033] The hafnium particles that underwent cryogenic treatment in Examples 1 to 4 were respectively made into electrodes for plasma cutting, and the first electrode to the fourth electrode were obtained respectively.

[0034] In each electrode, the hafnium particles have a purity of at least 99.95%, a smooth surface, and no obvious drawing marks.

[0035] The purity and surface condition of the hafnium particles are comparable to those of hafnium particles in general imported electrodes.

[0036] To verify the lifespan performance of the plasma cutting electrodes obtained above, the first to fourth electrodes were applied to cut a 20mm thick steel plate. Simultaneously, untreated hafnium particles of the same quality and imported hafnium particles were used as emitters, respectively, as the first and second control electrodes, and the same performance tests were conducted for comparison.

[0037] The comparison of the one-time cutting lengths of each electrode is shown in Table 2.

[0038] Table 2 Comparison of one-time cutting lengths for each electrode and the comparison electrode

[0039]

[0040] As can be seen from Table 2, the service life of ion cutting electrodes made from hafnium material processed by the process method of the present invention is far greater than that of conventional electrodes without antioxidant treatment, with a service life increase of 11% to 16%, and the service life can reach almost the same as that of imported electrodes, but at a lower cost.

Claims

1. A process for improving the antioxidant properties of hafnium particles, characterized in that, The hafnium particles are cryogenically treated for 2 h to 72 h to improve the grain size of the hafnium particles at the microscopic level, thereby enhancing the oxidation resistance of the hafnium particles; and the cryogenically treated hafnium particles are used in the fabrication of electrodes for plasma cutting.

2. The process method according to claim 1, characterized in that, A stepped cooling method is used to lower the hafnium material to the cryogenic treatment temperature.

3. The process method according to claim 2, characterized in that, The specific steps of the stepped cooling method are as follows: control 2 to 3 temperature steps according to the cooling rate of 1℃ / min to 60℃ / min, and hold each temperature step for 20 min to 30 min, and maintain the total cooling time of 2 h to 5 h to reduce the hafnium material to the cryogenic treatment temperature.

4. The process method according to any one of claims 1 to 3, characterized in that, The cryogenic treatment is a gas method.

5. An electrode for plasma cutting, comprising a copper electrode body and an emitter embedded in the copper electrode body; characterized in that, The emitter is hafnium particles obtained by the process method described in any one of claims 1 to 4.

6. The plasma cutting electrode according to claim 5, characterized in that, The hafnium particles have a purity of at least 99.95%, a smooth surface, and no traces of drawing.

7. The plasma cutting electrode according to claim 5 or 6, characterized in that, The hafnium particles are embedded in the copper electrode body by interference fit and brazing.

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