Preparation method of high-manganese-based brazing filler metal

Abstract

The invention discloses a preparation method of high-manganese-based brazing filler metal, and belongs to the technical field of high-temperature brazing material preparation. The method comprises the following steps: (1) pretreating a nickel-chromium intermediate alloy and a manganese raw material; (2) in an inert atmosphere environment, the pretreated nickel-chromium intermediate alloy is added into a smelting furnace to be subjected to stepped heating smelting, and a nickel-chromium alloy melt is obtained; (3) the inert atmosphere is kept to be introduced, the pretreated manganese raw material is added into the nickel-chromium alloy melt in batches, smelting continues to be conducted, and a brazing filler metal melt is obtained; (4) casting the brazing filler metal melt to obtain a cast ingot; and (5) the cast ingot is subjected to annealing treatment, and the high-manganese-based brazing filler metal is obtained. According to the method, the smelting process of the high-manganese-based brazing filler metal and the smelting furnace body are optimized, the comprehensive preparation cost of the high-manganese-based brazing filler metal is effectively reduced, the deviation range between the actual component content and theoretical design of the high-manganese-based brazing filler metal is reduced, and the stable service life of the smelting furnace is prolonged; and an excellent comprehensive solution is provided for low-cost and long-term stable production of high-quality high-manganese-based brazing filler metal.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature brazing material preparation technology, and relates to a method for preparing a high-manganese-based brazing filler metal. Background Technology

[0002] High-manganese-based brazing filler metals possess excellent high-temperature strength and brazing performance, making them valuable for connecting hot-end components in aerospace engines. However, two main problems currently exist in the preparation of high-manganese-based brazing filler metals: 1. Manganese volatilization is difficult to control: High-manganese brazing filler metals contain a relatively high level of manganese. Due to manganese's relatively low boiling point, its vapor pressure rises rapidly at high temperatures, making it highly susceptible to escaping from the liquid filler metal. This is especially true under vacuum melting conditions, where the system pressure decreases, causing manganese to exist more predominantly in a gaseous state, leading to intensified volatilization. Furthermore, the volatilization rate increases exponentially with the increase in manganese content in the melt. For example, when brazing filler metals with 2% and 25% manganese content are melted at 1600℃ and 67Pa respectively, the volatilization rate jumps from 1% to over 24%. This is because, with increasing manganese content, the volatilization mechanism shifts from melt boundary layer mass transfer to a more complex gas-phase mass transfer and diffusion process. This phenomenon not only wastes raw materials and increases costs but also causes the filler metal composition to deviate significantly from the designed ratio, severely impacting joint performance and reliability.

[0003] 2. The smelting furnace is severely corroded from use: To ensure high-temperature resistance, fused magnesia linings are typically installed inside the smelting furnace cavity. These magnesia linings have a melting point as high as 2800℃, meeting the requirements for high-temperature smelting. However, during the high-temperature smelting process of high-manganese-based brazing filler metals, the alloy melt containing Mn, Ni, and Cr reacts with impurities such as SiO2 and FeO in the magnesia lining, generating low-melting-point compounds (such as MnO·SiO2, with a melting point of approximately 1300℃). These low-melting-point compounds rapidly liquefy at high temperatures and penetrate along the interparticle gaps, causing chemical erosion of the lining and weakening its overall structural stability. Simultaneously, the magnesia lining itself has high thermal conductivity and a large coefficient of thermal expansion; frequent heating and cooling operations easily lead to thermal stress concentration, resulting in through-cracks. Consequently, the lining life is generally short, and the scrap rate is high, which is detrimental to the low-cost and stable production of high-manganese-based brazing filler metals.

[0004] Therefore, it is necessary to provide a method for preparing high-manganese-based brazing filler metals, which combines process optimization with furnace cavity protection optimization to synergistically improve the long-term stability of the high-manganese-based brazing filler metal preparation process. This will help to prepare high-manganese-based brazing filler metals with high quality qualification rate at a lower cost and with higher raw material utilization. Summary of the Invention

[0005] To overcome the problems in the prior art, this invention optimizes the high-manganese-based brazing filler metal smelting process and adopts a three-layer furnace cavity inner surface protection design, which effectively reduces the overall cost of high-manganese-based brazing filler metal preparation, reduces manganese volatilization, and improves the stable working life of the smelting furnace, providing an excellent comprehensive solution for low-cost, long-term stable production of high-quality high-manganese-based brazing filler metal.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention proposes a method for preparing a high-manganese-based solder, the method comprising the following steps: (1) Pretreatment of nickel-chromium master alloy and manganese raw materials; (2) In an inert atmosphere, the pretreated nickel-chromium master alloy from step (1) is added to a melting furnace for step heating and melting to obtain a nickel-chromium alloy melt. (3) Maintain an inert atmosphere and add the pretreated manganese raw material from step (1) to the nickel-chromium alloy melt from step (2) in batches, and continue to smelt to obtain the brazing filler melt; (4) Cast the brazing filler metal from step (3) to obtain an ingot; (5) Anneal the ingot in step (4) to obtain high manganese-based brazing filler metal.

[0007] Preferably, in step (1), the manganese raw material is electrolytic manganese flakes. The pretreatment process of the electrolytic manganese flakes is as follows: under vacuum, the electrolytic manganese flakes are heated to 450~500℃ and held for 2~3 hours. The vacuum degree of the vacuum environment is <10Pa. The purity of the electrolytic manganese flakes is usually around 99.7%, which contains H2 impurities, with an H2 content of approximately 250 cm³. 3 / 100g, through pretreatment, can remove more than 96% of H2 from electrolytic manganese sheets, avoiding defects such as porosity caused by H2 escaping during the smelting process, which is beneficial to improving the quality of high manganese-based brazing filler metal. At the same time, it can also remove the MnO oxide film on the surface of electrolytic manganese sheets.

[0008] Preferably, in step (1), the pretreatment process of the nickel-chromium master alloy is as follows: under vacuum or inert atmosphere protection, the nickel-chromium master alloy is heated to 150~200℃ and held for 3~4 hours. The pretreatment removes moisture and trace dissolved gases from the nickel-chromium master alloy, reduces cold working stress, and alleviates component segregation during the smelting process.

[0009] Preferably, the sidewalls and bottom surfaces of the smelting furnace cavity are provided with a magnesia lining and an alumina fiber buffer layer from the outside to the inside, and a corundum mullite crucible is nested on the inner wall of the alumina fiber buffer layer.

[0010] When setting the magnesia furnace lining and alumina fiber buffer layer on the side wall and bottom of the smelting furnace cavity, firstly, fused magnesia with a particle size of no more than 5mm is mixed with a mixed binder of water glass and boric acid. The mass ratio of fused magnesia to mixed binder is fused magnesia:mixed binder = 50:1, and the mass percentage of boric acid in the mixed binder is 2%. After thorough mixing, the magnesia furnace lining material is applied to the inner wall and bottom of the smelting furnace cavity by tamping or pouring to form a preliminary magnesia furnace lining blank. Then, alumina fiber felt is cut to a suitable size, and a layer of water glass is evenly coated onto the inner wall of the preliminary magnesia furnace lining blank (the amount of coating should be sufficient to allow the alumina fiber felt to adhere tightly without significant liquid accumulation). The cut alumina fiber felt is then smoothly attached to the inner wall of the magnesia furnace lining, gently pressed to ensure full contact with the water glass, completing the initial bonding. Finally, a layer of water glass is evenly coated onto the outer surface of the corundum-mullite crucible, and then the coated water glass is... The corundum mullite crucible is embedded into the furnace cavity with alumina fiber felt attached, ensuring accurate positioning and tight fit of each part. Finally, the temperature inside the furnace cavity is raised to 1000℃ at a rate of 5℃ / min and held for 2 hours to allow the water glass to fully react. On the one hand, this allows the magnesia furnace lining to complete sintering and solidification, obtaining good strength and stability; on the other hand, the adhesive effect of the water glass allows the magnesia furnace lining, alumina fiber layer, and corundum mullite crucible to be tightly bonded together, forming a structure with good fit and integrity, reducing gaps and ensuring the stability and safety of the subsequent melting process.

[0011] Preferably, in step (2), the smelting process is as follows: first, the nickel-chromium master alloy is heated to 1200°C and held for 3 minutes, then the temperature is raised to 1300°C and held for 3 minutes, then the temperature is raised to 1350°C and held for 3 minutes, and finally the temperature is raised to 1450°C and held for 10 minutes.

[0012] Preferably, in step (2), the inert atmosphere is argon. Before starting the melting process, argon is first introduced, and then argon is introduced again to expel the previously introduced argon. This process of introducing and expelling argon is repeated twice. After the last introduction of argon, the argon pressure in the furnace cavity is not less than 3 × 10⁻⁶. 3 Pa.

[0013] In steps (2) and (3), the argon flow rate is not less than 5 L / min.

[0014] Preferably, in step (3), the manganese raw material is divided into three equal parts and added to the nickel-chromium alloy melt in three batches, with a 5-minute interval between adjacent batches. Before adding the manganese raw material, the temperature of the nickel-chromium alloy melt is reduced to 1380~1420℃. After the last batch of manganese raw material is added, it is kept at the temperature for 20 minutes.

[0015] Preferably, in step (4), the melt temperature is controlled at 1350°C during casting, the casting mold is preheated to 200°C, and the melt is water-cooled after casting.

[0016] Preferably, in step (5), the annealing is carried out in an inert atmosphere, the annealing temperature is 850°C, the holding time is 2 hours, and after annealing, the ingot is cooled with the furnace.

[0017] Preferably, the high-manganese-based brazing filler metal comprises, by mass fraction: Ni: 24.0%~26.0%, Cr: 4.5%~5.5%, with the balance being Mn.

[0018] The beneficial effects of this invention are: 1. The present invention first melts the nickel-chromium master alloy to establish a nickel-rich molten pool, which provides an excellent melting environment for the subsequent addition of Mn, allowing the manganese to melt in rapidly and shortening its exposure time on the liquid surface, thereby helping to inhibit its volatilization and oxidation.

[0019] 2. This invention uses a stepped heating method to melt nickel-chromium master alloys, which reduces the probability of furnace lining cracking caused by sudden temperature rises, while also enhancing melt convection, which is beneficial for homogenizing the composition field at different temperatures and resulting in better melt quality.

[0020] 3. By adding Mn in batches, this invention can further accelerate the melting rate of Mn, avoid instantaneous supersaturation and surface floating, reduce the formation of oxide films and inclusions, reduce the risk of porosity caused by bubbles failing to rise in time, and at the same time ensure sufficient convection and diffusion of the melt, effectively controlling the fluctuation of Mn content within 0.5%, thereby improving the compositional uniformity and structural stability of the melt and laying a good foundation for subsequent casting.

[0021] 4. This invention, by setting a magnesia furnace lining, an alumina fiber buffer layer, and a nested corundum mullite crucible on the inner wall and lower surface of the furnace cavity, ensures the load-bearing capacity of the corundum mullite crucible and the heat insulation capacity of the furnace cavity, significantly reducing the thermal stress concentration caused by the thermal expansion difference between the corundum mullite crucible and the magnesia furnace lining. The cracking rate of the magnesia furnace lining caused by thermal stress is reduced from 15% to about 1%, while effectively inhibiting melt penetration, reducing the melt penetration range by more than 60%, thereby effectively extending the service life and operational stability of the smelting furnace. The smelting furnace of this invention can still maintain excellent service performance after more than 50 heats.

[0022] 5. By precisely controlling the pressure and flow rate of inert gas during the smelting process and optimizing the preparation process, this invention can effectively control the Mn volatilization rate to within 1%, thereby controlling the cost deviation of the final high-manganese-based solder to within 0.5%.

[0023] 6. This invention uses a relatively inexpensive corundum-mullite crucible to hold the melt, which effectively reduces the probability of the melt being contaminated. The oxygen content of the high-manganese-based brazing filler metal can be controlled within 0.006%, and the non-metallic inclusion level can be controlled above 1.5 (GB / T10561-2023).

[0024] 7. The present invention achieves a single-furnace 10kg-level smelting qualification rate of over 95%. Compared with vacuum smelting equipment, the investment cost is reduced by about 70%, and the energy consumption per furnace is reduced by 40%, making it suitable for industrial promotion and application.

[0025] 8. This invention pours molten material at 1350°C into a mold preheated to 200°C, which enables rapid molding of the molten material and effectively reduces thermal stress concentration caused by excessive temperature difference. Water cooling achieves a high cooling rate, effectively refining the ingot grains and improving the uniformity of the microstructure.

[0026] 9. This invention eliminates casting stress, promotes the uniform diffusion of alloying elements, and reduces dendrite segregation through medium-temperature annealing, thereby improving the plastic processing performance of the ingot and laying a good foundation for subsequent processing. Attached Figure Description

[0027] Figure 1 This is a structural diagram of the furnace cavity of the smelting furnace of the present invention; In the figure, 1-smelting furnace, 2-furnace cavity, 3-magnesia furnace lining, 4-alumina fiber buffer layer, 5-corundum mullite crucible; Figure 2 The images show actual photos of the smelting furnace nested with the corundum mullite crucible in the embodiment of the present invention and the corundum mullite crucible in Comparative Example 4 after 30 repeated smelting cycles. The left image shows the smelting furnace nested with the corundum mullite crucible in the embodiment of the present invention, and the right image shows the corundum mullite crucible in Comparative Example 4. Figure 3 This is a physical image of the melt from Comparative Example 3 of the present invention; Figure 4 This is a physical diagram of the furnace cavity of Comparative Example 8 of the present invention. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0029] Example 1 This embodiment describes the preparation of high-manganese-based solder through the following steps: (1) Weigh electrolytic manganese sheets and nickel-chromium master alloy according to the following mass fractions of Mn (70%), Ni (25%), and Cr (5%) in the high-manganese-based brazing filler metal. Then, pretreat the electrolytic manganese sheets and nickel-chromium master alloy respectively. Place the electrolytic manganese sheets in a vacuum furnace and evacuate the furnace cavity to 5 Pa (or introduce argon into the furnace cavity to form an inert atmosphere). Then, turn on the vacuum furnace and heat the electrolytic manganese sheets to 480°C and hold for 2.5 h for annealing to allow H2 to escape fully and remove the oxide film on the surface of the electrolytic manganese sheets. Place the nickel-chromium master alloy in a vacuum drying oven and heat to 180°C and hold for 3.5 h in a vacuum environment (or introduce argon into the oven to form an inert atmosphere) for annealing to remove moisture and trace dissolved gases from the nickel-chromium master alloy.

[0030] (2) Place the pretreated nickel-chromium master alloy in a corundum-mullite crucible inside the furnace chamber of the smelting furnace, and fill the furnace chamber with argon gas. Repeat the argon gas filling process three times, and then discharge the previously filled argon gas. After the last argon gas filling, make the argon gas pressure inside the furnace chamber 3×10⁻⁶. 3 Pa, then start the melting furnace, first heat the nickel-chromium master alloy to 1200℃ and hold for 3 minutes, then raise the heating temperature to 1300℃ and hold for 3 minutes, then raise the heating temperature to 1350℃ and hold for 3 minutes, and finally raise the heating temperature to 1450℃ and hold for 10 minutes to obtain the nickel-chromium alloy melt.

[0031] (3) After the nickel-chromium master alloy melt is held at 1450℃ for 10 min, the holding temperature of the nickel-chromium master alloy melt is adjusted to 1400℃, so that the temperature of the nickel-chromium master alloy melt drops to 1400℃. Then, the manganese raw material is divided into three equal parts and added to the nickel-chromium alloy melt in three batches, with an interval of 5 min between adjacent batches. After the last batch of manganese raw material is added, it is held for 20 min to obtain the brazing filler metal melt. Argon gas is kept flowing throughout the smelting process, and the argon gas flow rate is 5 L / min.

[0032] (4) Set the heating temperature to 1350℃, reduce the temperature of the brazing filler metal to 1350℃, then pour the brazing filler metal into a copper mold preheated to 200℃, and water cool the brazing filler metal to obtain an ingot.

[0033] (5) Place the ingot in a box furnace and introduce argon gas to form an argon atmosphere for protection. Then heat the ingot to 850°C, keep it at that temperature for 2 hours, and then let the ingot cool with the furnace to obtain high manganese-based brazing filler metal.

[0034] Example 2 This embodiment describes the preparation of high-manganese-based solder through the following steps: (1) Weigh electrolytic manganese sheets and nickel-chromium master alloy according to the following mass fractions of Mn (71.5%), Ni (24%), and Cr (4.5%) in the high-manganese-based brazing filler metal. Then, pretreat the electrolytic manganese sheets and nickel-chromium master alloy respectively. Place the electrolytic manganese sheets in a vacuum furnace and evacuate the furnace cavity to 5 Pa (or introduce argon into the furnace cavity to form an inert atmosphere). Then turn on the vacuum furnace and heat the electrolytic manganese sheets to 450°C and hold for 3 hours for annealing to allow H2 to escape fully and remove the oxide film on the surface of the electrolytic manganese sheets. Place the nickel-chromium master alloy in a vacuum drying oven and heat to 150°C and hold for 4 hours in a vacuum environment (or introduce argon into the oven to form an inert atmosphere) for annealing to remove moisture and trace dissolved gases from the nickel-chromium master alloy.

[0035] (2) Place the pretreated nickel-chromium master alloy in a corundum-mullite crucible inside the furnace chamber of the smelting furnace, and fill the furnace chamber with argon gas. Repeat the argon gas filling process three times, and then discharge the previously filled argon gas. After the last argon gas filling, make the argon gas pressure inside the furnace chamber 4×10⁻⁶. 3 Pa, then start the melting furnace, first heat the nickel-chromium master alloy to 1200℃ and hold for 3 minutes, then raise the heating temperature to 1300℃ and hold for 3 minutes, then raise the heating temperature to 1350℃ and hold for 3 minutes, and finally raise the heating temperature to 1450℃ and hold for 10 minutes to obtain the nickel-chromium alloy melt.

[0036] (3) After the nickel-chromium master alloy melt is held at 1450℃ for 10 min, the holding temperature of the nickel-chromium master alloy melt is adjusted to 1380℃, so that the temperature of the nickel-chromium master alloy melt drops to 1380℃. Then, the manganese raw material is divided into three equal parts and added to the nickel-chromium alloy melt in three batches, with an interval of 5 min between adjacent batches. After the last batch of manganese raw material is added, it is held for 20 min to obtain the brazing filler metal melt. Argon gas is kept flowing throughout the smelting process, and the argon gas flow rate is 6 L / min.

[0037] (4) Set the heating temperature to 1350℃, reduce the temperature of the brazing filler metal to 1350℃, then pour the brazing filler metal into a copper mold preheated to 200℃, and water cool the brazing filler metal to obtain an ingot.

[0038] (5) Place the ingot in a box furnace and introduce argon gas to form an argon atmosphere for protection. Then heat the ingot to 850°C, keep it at that temperature for 2 hours, and then let the ingot cool with the furnace to obtain high manganese-based brazing filler metal.

[0039] The high-manganese-based brazing filler metal prepared in this embodiment has similar properties to that in Example 1.

[0040] Example 3 This embodiment describes the preparation of high-manganese-based solder through the following steps: (1) Weigh electrolytic manganese sheets and nickel-chromium master alloy according to the following mass fractions of Mn (68.5%), Ni (26%), and Cr (5.5%) in the high-manganese-based brazing filler metal. Then, pretreat the electrolytic manganese sheets and nickel-chromium master alloy respectively. Place the electrolytic manganese sheets in a vacuum furnace and evacuate the furnace cavity to 5 Pa (or introduce argon into the furnace cavity to form an inert atmosphere). Then turn on the vacuum furnace and heat the electrolytic manganese sheets to 500°C and hold for 2 hours for annealing to allow H2 to escape fully and remove the oxide film on the surface of the electrolytic manganese sheets. Place the nickel-chromium master alloy in a vacuum drying oven and heat to 200°C and hold for 3 hours in a vacuum environment (or introduce argon into the oven to form an inert atmosphere) for annealing to remove moisture and trace dissolved gases from the nickel-chromium master alloy.

[0041] (2) Place the pretreated nickel-chromium master alloy in a corundum-mullite crucible inside the furnace chamber of the smelting furnace, and fill the furnace chamber with argon gas. Repeat the argon gas filling process three times, and then expel the previously filled argon gas. After the last argon gas filling, make the argon gas pressure inside the furnace chamber 5×10⁻⁶. 3 Pa, then start the melting furnace, first heat the nickel-chromium master alloy to 1200℃ and hold for 3 minutes, then raise the heating temperature to 1300℃ and hold for 3 minutes, then raise the heating temperature to 1350℃ and hold for 3 minutes, and finally raise the heating temperature to 1450℃ and hold for 10 minutes to obtain the nickel-chromium alloy melt.

[0042] (3) After the nickel-chromium master alloy melt is held at 1450℃ for 10 min, the holding temperature of the nickel-chromium master alloy melt is adjusted to 1420℃, so that the temperature of the nickel-chromium master alloy melt drops to 1420℃. Then, the manganese raw material is divided into three equal parts and added to the nickel-chromium alloy melt in three batches, with an interval of 5 min between adjacent batches. After the last batch of manganese raw material is added, it is held for 20 min to obtain the brazing filler metal melt. Argon gas is kept flowing throughout the smelting process, and the argon gas flow rate is 7 L / min.

[0043] (4) Set the heating temperature to 1350℃, reduce the temperature of the brazing filler metal to 1350℃, then pour the brazing filler metal into a copper mold preheated to 200℃, and water cool the brazing filler metal to obtain an ingot.

[0044] (5) Place the ingot in a box furnace and introduce argon gas to form an argon atmosphere for protection. Then heat the ingot to 850°C, keep it at that temperature for 2 hours, and then let the ingot cool with the furnace to obtain high manganese-based brazing filler metal.

[0045] The high-manganese-based brazing filler metal prepared in this embodiment has similar properties to that in Example 1.

[0046] Comparative Example 1 This comparative example uses the same method as Example 1 to prepare high-manganese-based brazing filler metal, the difference being that: in this comparative example, nickel-chromium master alloy and electrolytic manganese sheet are directly mixed and smelted.

[0047] The oxygen content in the high-manganese-based solders prepared in this comparative example and Example 1 was detected, and the results are shown in Table 1.

[0048] Table 1 As shown in Table 1, the oxygen content of the high-manganese-based brazing filler metal in Comparative Example 1 was significantly higher than that in Example 1, exceeding the control target. The reason for this result is that in Comparative Example 1, the nickel-chromium master alloy and electrolytic manganese sheet were mixed and smelted, making it impossible to establish a molten pool in advance. This caused the manganese to be exposed to a high-temperature atmosphere for a long time during the entire melting stage, resulting in continuous volatilization / oxidation. Furthermore, the oxygen carried by the electrolytic manganese was concentrated and difficult to remove completely in a short time. Therefore, the oxygen content of the resulting high-manganese-based brazing filler metal was significantly increased, exceeding the industry limit and resulting in a non-compliance. In contrast, in Example 1, a nickel-chromium molten pool could be established first, allowing the manganese to melt quickly and shortening its floating and exposure time on the liquid surface, thereby inhibiting volatilization and oxidation.

[0049] Comparative Example 2 This comparative example uses the same method as Example 1 to prepare high-manganese-based brazing filler metal, the difference being that: in this comparative example, the nickel-chromium master alloy is directly heated to 1450°C and held for 10 minutes for melting.

[0050] The comparative example involved a single heating and melting of the nickel-chromium master alloy, resulting in significant thermal stress, which caused thermal shock and cracking of the furnace lining. Furthermore, the convection and liquid surface in the melt were uncontrollable, and the initial inclusions and oxide films were disturbed and unable to float. Consequently, it was impossible to effectively remove the initial inclusions and oxide films, ultimately resulting in poor cleanliness, uniformity, and stability of the nickel-chromium molten pool, which could not provide a high-performance molten pool for the subsequent addition of Mn.

[0051] Comparative Example 3 This comparative example uses the same method as Example 1 to prepare high-manganese-based brazing filler metal, the difference being that: in this comparative example, all electrolytic manganese sheets are added to the nickel-chromium intermediate alloy melt at once.

[0052] pass Figure 3 It can be seen that, due to the addition of all electrolytic manganese sheets at once, the manganese floats and is exposed to a high-temperature atmosphere for a long time during the melting stage, resulting in continuous volatilization and oxidation. This leads to the formation of MnO inclusions, which are then carried into the molten pool. Consequently, the oxygen content and inclusion levels in the high-manganese-based brazing filler metal prepared in this comparative example are significantly increased, the manganese yield is significantly reduced, and the composition of the high-manganese-based brazing filler metal deviates significantly from the theoretical value, resulting in a significant decrease in the performance of the high-manganese-based brazing filler metal.

[0053] Comparative Example 4 This comparative example uses the same method as Example 1 to prepare high-manganese-based brazing filler metal, the difference being that: in this comparative example, the corundum mullite crucible is not nested with the alumina fiber buffer layer, but is placed directly into the furnace cavity.

[0054] pass Figure 2 As can be seen, compared with Example 1, the bottom of the corundum mullite crucible in this comparative example cracked. Directly placing the corundum mullite crucible into the furnace cavity easily leads to uneven heating during the melting process, causing the crucible to crack easily and reducing its service life.

[0055] Comparative Example 5 This comparative example uses the same method as Example 1 to prepare high-manganese-based brazing filler metal, the difference being that: in this comparative example, corundum mullite raw material is coated on the surface of the alumina fiber buffer layer to form a corundum mullite coating.

[0056] The high-manganese-based brazing filler metal prepared in this comparative example has a high oxygen content and contains many impurities, resulting in a significant decrease in its performance. While this comparative example uses a coating to contain the melt, compared to a pre-formed corundum-mullite crucible, the coating lacks sufficient density. Furthermore, the binders used in the coating process are prone to failure and deterioration at higher temperatures, leading to side reactions. Under the combined effects of strong convection and liquid surface turbulence caused by electromagnetic stirring in the medium-frequency furnace, as well as thermal cycling and mechanical erosion, pinholes, cracks, and localized spalling are easily generated. This negates the protective function of the coating, and the melt can penetrate through these defects into the alumina fiber buffer layer and magnesia furnace lining, generating non-metallic inclusions that are difficult to remove. Consequently, the impurity content in the high-manganese-based brazing filler metal increases, and its performance deteriorates.

[0057] Comparative Example 6 This comparative example uses the same method as Example 1 to prepare high-manganese-based brazing filler metal, except that the argon flow rate during the melting process is controlled at 3L / min.

[0058] Compared to the high-manganese-based brazing filler metal prepared in Example 1, this comparative example showed severe oxidation. Due to insufficient argon flow, air intrusion occurred during the melting process, leading to high-temperature oxidation of the melt and consequently, severe oxidation of the final high-manganese-based brazing filler metal.

[0059] Comparative Example 7 This comparative example uses the same method as Example 1 to prepare high-manganese-based brazing filler metal, the difference being that: in this comparative example, the argon pressure in the furnace cavity is 2 × 10⁻⁶ after the final argon purging. 3 Pa.

[0060] The Mn content was monitored during the smelting process of Example 1 and Comparative Example 7, and the results are shown in Table 2.

[0061] Table 2 As shown in Table 2, during the smelting process, the Mn loss in Comparative Example 7 reached 1%, while the Mn loss in Example 1 was only 0.2%. This means that in Comparative Example 7, the deviation of Mn from the designed ratio in the final high-manganese-based brazing filler metal could not be less than 1%, a larger deviation compared to Example 1. To further demonstrate that the present invention can stably control the Mn content deviation within a small range for a long period, the smelting time was extended to 2 hours. It can be seen that the Mn content in the melt of Comparative Example 7 decreased by another 1%, while the Mn content in Example 1 decreased by only 0.1%.

[0062] Comparative Example 8 This comparative example uses the same method as Example 1 to prepare high-manganese-based brazing filler metal, the difference being that this comparative example uses a smelting furnace with only magnesia sand lining for smelting.

[0063] The service life of the smelting furnaces in Example 1 and this comparative example was tested, and the results are shown in Table 3.

[0064] Table 3 As can be seen from Table 3, after 15 heats, the furnace lining of the smelting furnace with only magnesia lining showed erosion and collapse, while the bottom and side walls of the furnace cavity of the present invention remained uneroded after 50 heats. This proves that the present invention, by setting a three-layer structure of magnesia lining-alumina fiber buffer layer-corundum mullite crucible nesting, effectively extends the service life of the smelting furnace and reduces the overall preparation cost of high manganese-based brazing filler metal.

[0065] Comparative Example 9 This comparative example uses the same method as Example 1 to prepare high-manganese-based brazing filler metal, the difference being that the electrolytic manganese sheet was not pretreated in this comparative example.

[0066] The cracking rate of the high-manganese-based brazing filler metals of Example 1 and this comparative example was tested, and the results are shown in Table 4.

[0067] Table 4 As can be seen from Table 4, the lack of pretreatment of electrolytic manganese sheets resulted in a high gas content, leading to a high porosity in the ingots and ultimately causing the ingots to crack easily.

[0068] In summary, this invention effectively reduces the overall cost of high-manganese-based brazing filler metal preparation, narrows the deviation between the actual composition of high-manganese-based brazing filler metal and the theoretical design by optimizing the high-manganese-based brazing filler metal smelting process and the smelting furnace, and improves the stable working life of the smelting furnace. It provides an excellent comprehensive solution for low-cost, long-term stable production of high-quality high-manganese-based brazing filler metal.

[0069] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a high-manganese-based solder, characterized in that: The preparation method includes the following steps: (1) Pretreatment of nickel-chromium master alloy and manganese raw materials; (2) In an inert atmosphere, the pretreated nickel-chromium master alloy from step (1) is added to a melting furnace for step heating and melting to obtain a nickel-chromium alloy melt. (3) Maintain an inert atmosphere and add the pretreated manganese raw material from step (1) to the nickel-chromium alloy melt from step (2) in batches, and continue to smelt to obtain the brazing filler melt; (4) Cast the brazing filler metal from step (3) to obtain an ingot; (5) Anneal the ingot in step (4) to obtain high manganese-based brazing filler metal.

2. The preparation method according to claim 1, characterized in that: In step (1), the manganese raw material is electrolytic manganese sheet. The pretreatment process of the electrolytic manganese sheet is as follows: under vacuum environment, the electrolytic manganese sheet is heated to 450~500℃ and kept at the temperature for 2~3h. The vacuum degree of the vacuum environment is <10Pa.

3. The preparation method according to claim 1, characterized in that: In step (1), the pretreatment process of the nickel-chromium master alloy is as follows: under vacuum or inert atmosphere protection, the nickel-chromium master alloy is heated to 150~200℃ and held for 3~4 hours.

4. The preparation method according to claim 1, characterized in that: The sidewalls and bottom surfaces of the smelting furnace cavity are provided with a magnesia lining and an alumina fiber buffer layer from the outside to the inside, and a corundum mullite crucible is nested on the inner wall of the alumina fiber buffer layer.

5. The preparation method according to claim 1, characterized in that: In step (2), the smelting process is as follows: first, the nickel-chromium master alloy is heated to 1200°C and held for 3 minutes, then the temperature is raised to 1300°C and held for 3 minutes, then the temperature is raised to 1350°C and held for 3 minutes, and finally the temperature is raised to 1450°C and held for 10 minutes.

6. The preparation method according to claim 1, characterized in that: In step (2), the inert atmosphere is argon. Before starting the melting process, argon is first introduced, and then argon is introduced again to expel the previously introduced argon. This process of introducing and expelling argon is repeated twice. After the last introduction of argon, the argon pressure in the furnace cavity is not less than 3 × 10⁻⁶. 3 Pa; In steps (2) and (3), the argon flow rate is not less than 5 L / min.

7. The preparation method according to claim 1, characterized in that: In step (3), the manganese raw material is divided into three equal parts and added to the nickel-chromium alloy melt in three batches, with a 5-minute interval between adjacent batches. Before adding the manganese raw material, the temperature of the nickel-chromium alloy melt is reduced to 1380~1420℃. After the last batch of manganese raw material is added, it is kept at the temperature for 20 minutes.

8. The preparation method according to claim 1, characterized in that: In step (4), the melt temperature is controlled at 1350°C during casting, the casting mold is preheated to 200°C, and the melt is water-cooled after casting.

9. The preparation method according to claim 1, characterized in that: In step (5), annealing is carried out in an inert atmosphere, the annealing temperature is 850℃, the holding time is 2h, and after annealing, the ingot is cooled with the furnace.

10. The preparation method according to claim 1, characterized in that: The high-manganese-based brazing filler metal comprises, by mass fraction: Ni: 24.0%~26.0%, Cr: 4.5%~5.5%, with the balance being Mn.

Images