A Cu-Mg-Ni alloy fuse wire for initiating explosive and a preparation method thereof

Abstract

This invention discloses a Cu-Mg-Ni alloy fuse for pyrotechnics and its preparation method, belonging to the technical field of pyrotechnics manufacturing and special functional materials. The fuse, by weight percentage, consists of 3.0%-9.0% Mg, 1.0%-2.0% Ni, and the balance Cu. It exhibits a solid-liquid two-phase region at 20°C, a tensile strength of 400-500 MPa, and an elongation of 5%-15%. The preparation method includes batching, vacuum melting, casting, hot working, cold drawing and intermediate annealing, and finished product treatment. The fuse of this invention has a melting response time ≤1ms under pulsed current triggering, a molten droplet spatter range ≤2mm, and a performance retention rate ≥96% after 90 days of accelerated aging at 100°C. It possesses advantages such as narrow melting range, high load-bearing capacity, fast response, low spatter, and long-term storage stability, making it suitable for low-impact separation and unlocking mechanisms in pyrotechnics and millisecond-level cutting actuators.

Description

Technical Field

[0001] This invention belongs to the technical field of pyrotechnics manufacturing and special functional materials, specifically relating to a Cu-Mg-Ni alloy fuse for pyrotechnics and its preparation method, which is particularly suitable for core triggering elements of pyrotechnics such as low-impact separation and unlocking mechanisms and millisecond-level cutting execution devices. Background Technology

[0002] Pyrotechnic separation devices are key components in defense equipment and aerospace systems. Traditional pyrotechnic separation devices are primarily propelled by gunpowder, which suffers from drawbacks such as high impact overload, severe environmental pollution, low safety, and non-reusability. Low-impact non-pyrotechnic separation technology has become the core development direction for the next generation of pyrotechnic devices. As the core triggering element of such devices, the fuse wire must simultaneously meet five performance requirements: narrow melting range, high load capacity, fast response, low splash, and long-term storage stability.

[0003] In existing technologies, the fuse materials used for such triggering devices mostly use conventional pure copper and ordinary Cu-Mg binary alloys, which have the following technical defects: 1. Excessively wide melting range, insufficient melting consistency and response speed: Pure copper fuse wires have excessively high conductivity and a wide melting range. Under pulse current triggering, uneven local overheating leads to dispersed melting time and severely delayed response (≥5ms), failing to meet the millisecond-level fast response requirements of pyrotechnics. Although ordinary Cu-Mg binary alloys have narrow melting range characteristics, they have poor high-temperature stability and insufficient melting consistency, making it difficult to achieve precise and controllable trigger separation. 2. Poor mechanical property matching, insufficient load-bearing and deformation adaptability: Pure copper fuse wires have extremely low tensile strength (≤250MPa), making them prone to plastic deformation or even fracture during assembly and use, failing to meet the load-bearing requirements of pyrotechnics; some alternative materials have excessively high strength but insufficient elongation, making them prone to brittle fracture during bending and winding, resulting in poor process adaptability. Existing materials cannot simultaneously achieve both load-bearing capacity and deformation adaptability. III. Poor process adaptability and difficulty in preserving narrow melting range characteristics: Existing fusing material preparation processes have not been systematically optimized for narrow melting range characteristics. Inappropriate hot working temperature windows and mismatched cold drawing and annealing process parameters lead to phase transformations or grain coarsening in the alloy during processing, destroying the narrow melting range characteristics. This makes it difficult to obtain fine wires with high dimensional accuracy and uniform performance, resulting in low efficiency in mass production. IV. Severe molten bead spatter and substandard low-impact performance: Existing fusing materials generate a large number of high-temperature molten beads (≥8mm for pure copper, ≥4mm for ordinary Cu-Mg alloys) at the moment of melting. This easily contaminates the internal sensitive structures of pyrotechnic devices or causes secondary faults such as short circuits. The device's trigger impact acceleration is too high, failing to meet the stringent requirements of low-impact and pollution-free operation.

[0004] V. Insufficient long-term storage stability and poor adaptability to operating conditions: In ordinary Cu-Mg binary alloys, the Mg element is easily oxidized during long-term storage, leading to a decrease in melting performance and failing to meet the requirement of reliable operation of pyrotechnics after long-term storage. In addition, some existing melting materials contain volatile elements, which can easily cause internal contamination in vacuum or closed pyrotechnic environments, affecting the overall reliability of the device.

[0005] Therefore, based on the characteristics of the Cu-Mg binary phase diagram, developing a special Cu-Mg-Ni alloy fuse with a solid-liquid two-phase region of 20℃, a strength of 400-500MPa, an elongation of 5%-15%, and suitable for low-impact separation devices of pyrotechnics, along with its supporting preparation process, is of great significance for solving the above-mentioned technical problems and improving the overall performance, reliability, and service life of new pyrotechnics. Summary of the Invention

[0006] This invention aims to provide a Cu-Mg-Ni alloy fuse wire for pyrotechnic applications and its preparation method, addressing the technical problems of existing pyrotechnic fuse materials, such as excessively wide melting range, poor strength matching, slow response, large molten droplet splash, and insufficient long-term storage stability. Based on the characteristics of the Cu-Mg binary phase diagram, this invention optimizes the process through Ni microalloying to achieve a fuse wire with narrow melting range, high load-bearing capacity, fast response, low splash, and high reliability, meeting the requirements of next-generation low-impact pyrotechnic separation devices.

[0007] A Cu-Mg-Ni alloy fuse for pyrotechnics, by weight percentage, has the following chemical composition: Mg 3.0%-9.0%, Ni 1.0%-2.0%, with the balance being Cu and unavoidable impurities.

[0008] Furthermore, the solid-liquid two-phase region of the alloy is 20°C, with a narrow melting range and excellent melting consistency.

[0009] Furthermore, the tensile strength of the fuse wire is 400-500MPa, and the elongation is 5%-15%, with mechanical properties matching the load-bearing and deformation requirements of pyrotechnics.

[0010] Furthermore, the fuse wire is in the form of a fine filament with a nominal diameter of φ0.2-φ0.5mm. Under pulse current triggering conditions, the fuse response time is ≤1ms, and the molten bead spatter range is ≤2mm.

[0011] This invention also provides a method for preparing the above-mentioned Cu-Mg-Ni alloy fused wire, which includes the following steps: S1 Ingredients Select electrolytic copper, pure magnesium, and electrolytic nickel with a purity ≥99.95% according to the above chemical composition ratio, and mix them evenly to obtain a mixture; S2 Melting Protection The mixture is placed in a vacuum induction melting furnace with a vacuum degree ≤ 5 × 10⁻⁶. -3 Pa, heat to 1150-1250℃ for melting, and refine for 5-15 minutes after complete melting; S3 casting The molten alloy is poured into a water-cooled copper mold to obtain an ingot; S4 Hot Working The ingot is heated to 450-550℃ and held for 4-6 hours, then hot forging and hot drawing are carried out. The final processing temperature is not lower than 350℃ to produce wire blanks with a diameter of φ2.0mm. S5 Cold Drawing and Intermediate Annealing The wire blank is cold-drawn in multiple passes, with a total deformation of ≥95%. The deformation of each cold drawing pass is controlled at 15%-25%. After every 2-3 cold drawing passes, intermediate annealing is carried out at 500-600℃ for 1-2 hours, using an argon protective atmosphere. S6 Finished Product Processing The cold-drawn wire to the target diameter is straightened and finished, and then stress-relief annealed at 300-400℃ for 0.5-1h to obtain the finished Cu-Mg-Ni alloy fusing wire.

[0012] Compared with the prior art, this patent application has the following advantages: 1. Narrow melting range design combined with Ni microalloying comprehensively improves melting consistency, response speed, and stability. This invention strictly designs the alloy composition based on the Cu-Mg binary phase diagram, controlling the Mg content between 3.0% and 9.0%, thus precisely controlling the solid-liquid two-phase region of the alloy within an extremely narrow range of 20°C. The melting response time can be controlled within 1ms, avoiding problems such as uneven local overheating and dispersed melting times caused by excessively wide melting range. Simultaneously, 1.0%-2.0% Ni is added to the Cu-Mg binary alloy, exerting a triple synergistic effect of solid solution strengthening, grain boundary purification, and oxidation resistance: solid solution strengthening achieves tensile strength of 400-500MPa and elongation of 5%-15%, balancing load-bearing capacity and plasticity requirements; grain boundary purification controls the molten droplet spatter range within 2mm, achieving low-impact, contamination-free triggering; and oxidation resistance ensures a long-term storage performance retention rate of over 96%, comprehensively solving the technical problems of poor high-temperature stability, insufficient melting consistency, and easy oxidation during long-term storage in existing Cu-Mg alloys.

[0013] 2. Precise matching of mechanical properties, synergistic improvement in load-bearing capacity and deformation adaptability. The tensile strength of the fuse wire in this invention is controlled within a preferred range of 400-500 MPa and elongation within a range of 5%-15%. This strength range ensures that the fuse wire can withstand certain tensile loads during assembly and use, while avoiding the risk of brittle fracture due to excessive strength. This elongation range provides sufficient plastic deformation capacity, making the fuse wire less prone to breakage during the assembly, bending, and winding of pyrotechnic devices. It has good process adaptability and achieves a synergistic improvement in load-bearing capacity and deformation adaptability.

[0014] 3. Synergistic optimization of the entire preparation process effectively preserves and leverages the narrow melting range characteristic. This invention systematically optimizes the entire process parameters from smelting to finished product: using a vacuum degree ≤5×10 -3 High-vacuum melting at Pa effectively prevents Mg oxidation and burn-off, ensuring precise and controllable composition. The ingot is heated to 450-550℃ and held for 4-6 hours, with the final processing temperature controlled to be no lower than 350℃ for hot working, avoiding phase transformation or grain coarsening and preserving the narrow melting range. Multi-pass cold drawing with a total deformation of ≥95% is employed, with each pass involving 15%-25% deformation. After every 2-3 passes, intermediate annealing is performed at 500-600℃ to prevent wire breakage and eliminate work hardening. Finally, stress-relief annealing at 300-400℃ eliminates residual stress and stabilizes dimensions. The synergistic effect of all process parameters ensures the final product is a fine wire with a diameter of φ0.2-0.5mm, high dimensional accuracy, and uniform performance.

[0015] 4. Millisecond-level fuse response and low-splash control, achieving full compliance with low-impact performance standards. The fuse of this invention, under pulse current triggering conditions, has a fuse-breaking response time of no more than 1ms and a molten bead splash range of no more than 2mm. The millisecond-level response time ensures that the pyrotechnic separation device can complete triggering and unlocking in an extremely short time, meeting the stringent requirements of aerospace and defense equipment for rapid response; the low splash characteristic effectively suppresses the risk of contamination or short circuit to sensitive internal structures of the pyrotechnic by molten bead splashing at the moment of fuse breaking; the device's triggering impact acceleration is controllable, which is a key indicator for achieving low-impact design.

[0016] 5. It has strong adaptability to working conditions and good economic efficiency for large-scale production. This invention's alloy contains no volatile elements, preventing internal contamination due to volatilization in vacuum or sealed pyrotechnic environments, thus ensuring device cleanliness. The dense oxide film formed by Ni microalloying effectively inhibits Mg oxidation, ensuring no performance degradation after long-term storage. Furthermore, the vacuum melting, hot forging, hot drawing, and cold drawing annealing processes employed in this invention are all mature metal processing technologies. The equipment is highly versatile, enabling continuous mass production. Manufacturing costs are significantly lower than for special materials such as nickel-titanium alloys, demonstrating excellent economic viability and industrialization prospects. Attached Figure Description

[0017] Figure 1 This is a microstructure diagram of the Cu-Mg-Ni alloy fused wire prepared in Example 1 of the present invention.

[0018] Figure 2 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto. Appropriate adjustments to the component ratios and process parameters without departing from the technical concept of the present invention are all within the scope of protection of the present invention.

[0020] Example 1 This embodiment provides a method for preparing Cu-Mg-Ni alloy fuse wire for pyrotechnic devices, comprising the following steps: S1 Ingredients Electrolytic copper, pure magnesium, and electrolytic nickel with a purity ≥99.95% were selected by weight percentage. Their chemical composition was: Mg 5.0%, Ni 1.5%, and the balance Cu. The materials were calculated and weighed according to the above proportions, and mechanically mixed evenly to obtain a mixture.

[0021] S2 Melting Protection The mixture is placed into a graphite crucible inside a vacuum induction melting furnace, and a vacuum is drawn until the vacuum degree is ≤5×10⁻⁶. -3 Pa, slowly heat to 1200℃ for melting. After all the material has melted, refine for 10 minutes, then let stand for 10 minutes to complete the melting process.

[0022] S3 casting The molten alloy was poured into a water-cooled copper mold and cooled to room temperature in air to obtain an ingot with a diameter of φ30 mm.

[0023] S4 Hot Working The ingot is milled, then heated to 500℃ and held for 5 hours, and then hot forged and hot drawn. The final processing temperature is not lower than 350℃ to produce wire blanks with a diameter of φ2.0 mm.

[0024] S5 Cold Drawing and Intermediate Annealing The φ2.0 mm wire blank is subjected to multiple cold drawing passes, with a total deformation of ≥95%. The deformation of each cold drawing pass is controlled at 15%-25%. After every 2-3 cold drawing passes, intermediate annealing is carried out at 550℃ for 1.5 h, using an argon protective atmosphere.

[0025] S6 Finished Product Processing The wire, cold-drawn to the target diameter (φ0.3 mm), is straightened and finished, and then stress-relief annealed at 350℃ for 1 h to obtain the finished Cu-Mg-Ni alloy fusing wire.

[0026] Performance testing and application verification The prepared fusible wire was applied to a low-impact separation and unlocking device for pyrotechnics, and its performance was tested. The test results are as follows: At 20℃ in the solid-liquid two-phase region, the tensile strength is 450 MPa, the elongation is 10%, the fusing response time is 0.8 ms, the molten droplet splash range is 1.5 mm, the performance retention rate after 90 days of accelerated aging at 100℃ is 96%, and the device triggering impact acceleration is ≤300g. The test results indicate that the Cu-Mg-Ni alloy fusible wire prepared in this embodiment exhibits excellent performance in terms of fusing range, mechanical properties, fusing response speed, splash control, and long-term storage stability, meeting the requirements for use in low-impact separation devices for pyrotechnics.

[0027] Example 2 This embodiment provides a method for preparing Cu-Mg-Ni alloy fuse wire for pyrotechnic devices, comprising the following steps: S1 Ingredients Electrolytic copper, pure magnesium, and electrolytic nickel with a purity ≥99.95% were selected by weight percentage. Their chemical composition was: Mg 8.0%, Ni 2.0%, and the balance Cu. The samples were calculated and weighed according to the above proportions, and then mixed thoroughly to obtain a mixture.

[0028] S2 Melting Protection The mixture is placed in a vacuum induction melting furnace with a vacuum degree ≤ 5 × 10⁻⁶. -3 Pa, heat to 1230℃ for melting, refine for 12 min, then let stand for an appropriate time to complete the melting.

[0029] S3 casting The molten alloy is rapidly poured into a circulating water-cooled copper mold and cooled to room temperature in air to obtain a φ30 mm ingot.

[0030] S4 Hot Working The ingot is milled, heated to 520℃ and held for 4.5 h, and then hot forged and hot drawn. The final processing temperature is not lower than 350℃ to produce wire blanks with a diameter of φ2.0 mm.

[0031] S5 Cold Drawing and Intermediate Annealing The φ2.0 mm wire blank is subjected to multiple cold drawing passes, with a total deformation of ≥95%. The deformation of each cold drawing pass is controlled at 15%-25%. After every two cold drawing passes, intermediate annealing is carried out at 580℃ for 1.2 h, using an argon protective atmosphere.

[0032] S6 Finished Product Processing The cold-drawn wire to the target diameter (φ0.5 mm) is straightened and finished, and then stress-relief annealing is carried out at 380℃ for 0.5 h to obtain the finished Cu-Mg-Ni alloy fusing wire.

[0033] Performance testing and application verification The prepared fusible wire was applied to a high-load-bearing pyrotechnic separation mechanism, and its performance was tested. The test results are as follows: in the solid-liquid two-phase region at 20℃, the tensile strength is 490 MPa, the elongation is 6%, the melting response time is 0.9 ms, the molten droplet spatter range is 1.8 mm, and the long-term storage stability is excellent. The test results show that the Cu-Mg-Ni alloy fusible wire prepared in this example exhibits excellent performance in terms of melting range, mechanical properties, melting response speed, spatter control, and long-term storage stability, meeting the requirements of pyrotechnic separation mechanisms under harsh operating conditions.

[0034] Comparative Example 1 This comparative example provides a method for preparing a pure copper fuse wire, comprising the following steps: S1 Ingredients Select electrolytic copper with a purity ≥ 99.95% by weight, whose chemical composition is Cu 100%. Calculate and weigh according to the above proportions, mix evenly, and obtain the mixture.

[0035] S2 Melting Protection The mixture is placed in a vacuum induction melting furnace with a vacuum degree ≤ 5 × 10⁻⁶. -3 Pa, heat to 1200℃ for melting, refine for 10 min, then let stand for an appropriate time to complete the melting.

[0036] S3 casting The molten alloy is poured into a water-cooled copper mold and cooled to room temperature in air to obtain an ingot with a diameter of 30 mm.

[0037] S4 Hot Working The ingot is milled, heated to 500℃ and held for 5 hours, and then hot forged and hot drawn. The final processing temperature is not lower than 350℃ to produce wire blanks with a diameter of φ2.0 mm.

[0038] S5 Cold Drawing and Intermediate Annealing The φ2.0 mm wire blank is subjected to multiple cold drawing passes, with a total deformation of ≥95%. The deformation of each cold drawing pass is controlled at 15%-25%. After every 2-3 cold drawing passes, intermediate annealing is carried out at 550℃ for 1.5 h, using an argon protective atmosphere.

[0039] S6 Finished Product Processing The cold-drawn wire to the target diameter (φ0.3 mm) is straightened and finished, and then stress-relief annealing is carried out at 350℃ for 1 h to obtain the finished pure copper fusing wire.

[0040] Performance testing and application verification The prepared fuse wire was applied to a low-impact separation and unlocking device for pyrotechnics, and performance tests were conducted. The results are as follows: tensile strength 210 MPa, fusing response time ≥ 5 ms, and molten droplet splash range ≥ 8 mm. The results indicate that pure copper fuse wire cannot meet the requirements for high load-bearing capacity and low impact in pyrotechnic applications.

[0041] Comparative Example 2 This comparative example provides a method for preparing a common Cu-Mg binary alloy fusible wire, including the following steps: S1 Ingredients Electrolytic copper and pure magnesium with a purity ≥99.95% were selected by weight percentage. Their chemical composition was: Mg 5.0%, with the balance being Cu. The samples were calculated and weighed according to the above proportions, and then mixed evenly to obtain a mixture.

[0042] S2 Melting Protection The mixture is placed in a vacuum induction melting furnace with a vacuum degree ≤ 5 × 10⁻⁶. -3 Pa, heat to 1200℃ for melting, refine for 10 min, then let stand for an appropriate time to complete the melting.

[0043] S3 casting The molten alloy is poured into a water-cooled copper mold and cooled to room temperature in air to obtain a φ30 mm ingot.

[0044] S4 Hot Working The ingot is milled, heated to 500℃ and held for 5 hours, and then hot forged and hot drawn. The final processing temperature is not lower than 350℃ to produce wire blanks with a diameter of φ2.0 mm.

[0045] S5 Cold Drawing and Intermediate Annealing The φ2.0 mm wire blank is subjected to multiple cold drawing passes, with a total deformation of ≥95%. The deformation of each cold drawing pass is controlled at 15%-25%. After every 2-3 cold drawing passes, intermediate annealing is carried out at 550℃ for 1.5 h, using an argon protective atmosphere.

[0046] S6 Finished Product Processing The wire, cold-drawn to the target diameter (φ0.3 mm), is straightened and finished, and then stress-relief annealed at 350℃ for 1 h to obtain the finished Cu-Mg binary alloy fusing wire.

[0047] Performance testing and application verification The prepared fusible wire was applied to a low-impact separation and unlocking device for pyrotechnics, and its performance was tested. The results are as follows: in the solid-liquid two-phase region at 20℃, the tensile strength was 420 MPa, the elongation was 12%, the melting response time was 1.5 ms, and the molten droplet spatter range was ≥4 mm. Significant oxidation and rapid performance degradation were observed after long-term storage. The results indicate that the ordinary Cu-Mg binary alloy without Ni is inferior to the Cu-Mg-Ni alloy of this invention in terms of melting response speed, spatter control, and long-term storage stability.

[0048] The above embodiments and comparative examples fully demonstrate that the Cu-Mg-Ni alloy fuse wire designed based on the Cu-Mg binary phase diagram of the present invention has a scientific composition and stable process. It has excellent mechanical properties such as a narrow melting range of 20°C in the solid-liquid two-phase region, tensile strength of 400-500MPa, and elongation of 5%-15%. At the same time, it is significantly superior to existing materials in terms of millisecond-level melting response, low spatter, and long-term storage reliability, and fully meets the stringent requirements of the core triggering element for the new generation of low-impact pyrotechnic separation devices.

Claims

1. A Cu-Mg-Ni alloy fuse for pyrotechnic devices, characterized in that, Its chemical composition by weight percentage is: Mg 3.0%-9.0%, Ni 1.0%-2.0%, with the balance being Cu and unavoidable impurities.

2. The Cu-Mg-Ni alloy fuse for pyrotechnics according to claim 1, characterized in that, The solid-liquid two-phase region width of the alloy is 20°C.

3. The Cu-Mg-Ni alloy fuse for pyrotechnics according to claim 1, characterized in that, The tensile strength of the fuse wire is 400-500 MPa, and the elongation is 5%-15%.

4. The Cu-Mg-Ni alloy fuse for pyrotechnics according to claim 1, characterized in that, The fuse wire is in the form of a fine wire with a nominal diameter of φ0.2-φ0.5mm; under pulse current triggering conditions, the fuse response time is ≤1ms and the molten bead splash range is ≤2mm.

5. A method for preparing a Cu-Mg-Ni alloy fuse wire for pyrotechnics as described in any one of claims 1 to 4, characterized in that, The steps are as follows: S1 Ingredients: Select electrolytic copper, pure magnesium and electrolytic nickel with a purity ≥99.95% according to the chemical composition ratio described in claim 1, and mix them evenly to obtain a mixture; S2 Melting Protection: Place the mixture in a vacuum induction melting furnace with a vacuum degree ≤5×10 -3 Pa, heat to 1150-1250℃ for melting, and refine for 5-15 minutes after complete melting; S3 casting: The molten alloy is poured into a water-cooled copper mold to obtain an ingot; S4 Hot Working: Heat the ingot to 450-550℃ and hold for 4-6 hours, then perform hot forging and hot drawing. The final processing temperature is not lower than 350℃ to produce wire blanks with a diameter of φ2.0mm. S5 Cold Drawing and Intermediate Annealing: The wire blank is cold drawn in multiple passes, with a total deformation of ≥95%. The deformation of each cold drawing pass is controlled at 15%-25%. After every 2-3 cold drawing passes, intermediate annealing is carried out at 500-600℃ for 1-2 hours, using an argon protective atmosphere. S6 Finished Product Processing: The cold-drawn wire to the target diameter is straightened and finished, and then stress-relief annealed at 300-400℃ for 0.5-1h to obtain the finished Cu-Mg-Ni alloy fusing wire.

6. The preparation method according to claim 5, characterized in that, In the S2 smelting protection, the smelting temperature is 1200-1230℃ and the refining time is 10-12min.

7. The preparation method according to claim 5, characterized in that, In the S4 hot processing, the heating temperature is 500-520℃ and the holding time is 4.5-5h.

8. The preparation method according to claim 5, characterized in that, In the S5 cold drawing and intermediate annealing process, the intermediate annealing temperature is 550-580℃, and the holding time is 1.2-1.5h.

9. The preparation method according to claim 5, characterized in that, In the S6 finished product processing, the stress-relief annealing temperature is 350-380℃, and the holding time is 0.5-1h.

10. The application of a Cu-Mg-Ni alloy fusion wire for pyrotechnics as described in any one of claims 1 to 4 in a low-impact separation and unlocking mechanism or a millisecond-level cutting actuator for pyrotechnics.

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