Bimetal clad sheet for small circuit breaker of low-voltage electric appliance and preparation method of bimetal clad sheet

Abstract

The invention discloses a bimetal clad sheet for a miniature circuit breaker of a low-voltage electric appliance and a preparation method of the bimetal clad sheet, and belongs to the technical field of bimetal clad sheets. The invention discloses a bimetal clad sheet for a miniature circuit breaker of a low-voltage electric appliance. The bimetal clad sheet comprises an active layer and a passive layer fixedly arranged on one side of the active layer, the active layer comprises the following element components in percentage by mass: 59 to 60 weight percent of iron, 28 weight percent of nickel, 11.5 weight percent of aluminum and 0.5 to 1.5 weight percent of tantalum; the passive layer is prepared from the following element components in percentage by mass: 53.81 to 55.94 weight percent of titanium, 41.43 to 43.07 weight percent of nickel and 1 to 5 weight percent of copper; the bimetal clad sheet prepared by the method is relatively good in elasticity and relatively long in service life.

Description

Technical Field

[0001] The present invention relates to a bimetallic composite sheet for a low-voltage electrical appliance miniature circuit breaker and a preparation method thereof. Background Art

[0002] In the field of low-voltage electrical appliances, as a key protection component in the terminal power distribution system, the miniature circuit breaker is widely used in household, industrial, and commercial power distribution systems. Its main function is to automatically cut off the power supply when an overload or short-circuit fault occurs in the circuit to ensure the safety of electrical equipment and lines. In the thermal tripping mechanism of the miniature circuit breaker, the bimetallic sheet is the core component to achieve overload protection, and its working principle is based on the composite structure of two metal layers with different thermal expansion coefficients. When current passes through the bimetallic sheet, due to the Joule heat effect, the temperature rises, and the active layer (material with a high thermal expansion coefficient) and the passive layer (material with a low thermal expansion coefficient) generate bending deformation due to the thermal expansion difference, thereby pushing the tripping mechanism to act and realizing the automatic disconnection of the circuit.

[0003] Traditional bimetallic sheets are usually composed of two metal materials, an active layer and a passive layer, which are compounded by welding or rolling. For example, the active layer often uses materials with a relatively high thermal expansion coefficient such as copper-nickel alloy or iron-nickel alloy, while the passive layer often selects materials with a relatively low thermal expansion coefficient such as iron-chromium alloy and nickel-based alloy. This structural design can effectively utilize the thermal expansion difference between materials to achieve the required mechanical displacement response. However, in practical applications, the bimetallic sheet faces technical problems of elastic fatigue and limited service life.

[0004] Research shows that under the long-term action of periodic thermal stress, the bimetallic sheet is prone to attenuation of elastic properties, especially more obvious under working conditions of frequent overload or large ambient temperature fluctuations. This will lead to a decrease in the action accuracy of the bimetallic sheet and even failure, thus affecting the reliability and safety of the circuit breaker.

[0005] Therefore, the applicant has prepared a bimetallic composite sheet for a low-voltage electrical appliance miniature circuit breaker. Summary of the Invention

[0006] The purpose of the present invention is to provide a bimetallic composite sheet for a low-voltage electrical appliance miniature circuit breaker and a preparation method thereof to solve the technical problems mentioned in the above background art.

[0007] The technical solution to achieve the purpose of the present invention is as follows: In a first aspect, the present invention provides a bimetallic composite sheet for a low-voltage electrical appliance miniature circuit breaker, including an active layer and a passive layer fixedly arranged on one side of the active layer. By mass fraction, the elemental components of the active layer include: 59 - 60 wt% iron, 28 wt% nickel, 11.5 wt% aluminum, and 0.5 - 1.5 wt% tantalum.

[0008] Further, by mass fraction, the elemental components of the passive layer include: 53.81 - 55.94 wt% titanium, 41.43 - 43.07 wt% nickel, and 1 - 5 wt% copper.

[0009] In a second aspect, the present invention provides a method for preparing a bimetallic composite sheet for a low-voltage electrical appliance miniature circuit breaker as described in the first aspect. The bimetallic composite sheet for the low-voltage electrical appliance miniature circuit breaker is formed by cold rolling together an active layer and a passive layer with the same length, width, and thickness.

[0010] Further, the preparation steps of the active layer are as follows: (1) Weigh and proportion electrolytic iron, electrolytic nickel, electrolytic aluminum, and tantalum powder according to the mass percentages of the elements iron, nickel, aluminum, and tantalum. (2) Under argon protection, mix the electrolytic iron, electrolytic nickel, electrolytic aluminum, and tantalum powder weighed in step (1), and then melt them into a button-shaped ingot using a water-cooled copper crucible and a vacuum non-consumable arc furnace. After melting repeatedly 3 - 4 times, hot roll it into a thin sheet with a thickness of 1.2 - 2 mm at 1000 ± 10 °C, then perform solution treatment at 1200 ± 10 °C for 25 - 35 min, water quench it, cold roll it to 0.6 - 1 mm, then perform solution treatment at 1200 ± 10 °C for 25 - 35 min again, and then perform aging treatment at 600 ± 10 °C for 60 h. After air cooling, cut out an active layer with a length * width of (30 - 40) mm * (4 - 8) mm along the rolling direction.

[0011] Further, the preparation steps of the passive layer are as follows: S1. Weigh and proportion nickel powder, titanium powder, and copper powder according to the mass percentages of the elements nickel, titanium, and copper. S2. First, mix the nickel powder and titanium powder weighed in step S1 in a V-type powder mixer for 23 - 25 h, then add copper powder and continue to mix for 7 - 9 h. Subsequently, pour it into a mold and press it into a green compact with a thickness of 15 - 30 mm. Then put it into a quartz tube sintering furnace and perform gradient sintering under argon protection. Then keep it at 930 - 980 °C for 10 - 12 h, then heat it to 880 - 900 °C and hot roll it to 9 - 18 mm, perform annealing at 600 - 800 °C for 25 - 35 min, then continue to roll it to 0.6 - 1 mm at 850 - 880 °C, perform annealing at 600 - 800 °C for 25 - 35 min, and after air cooling, cut out a passive layer with a length * width of (30 - 40) mm * (4 - 8) mm along the rolling direction.

[0012] Furthermore, the steps of gradient sintering are: first heat up to 250±5℃, keep warm for 30~40min, then heat up to 680±5℃, keep warm for 12~18min, continue to heat up to 800±5℃, keep warm for 15~25min, then heat up to 1000±5℃, keep warm for 350~370min, cool down to 460±5℃, keep warm for 20~40min.

[0013] Furthermore, the heating rates are 18-22°C / min, 14-16°C / min, 8-12°C / min, and 6-10°C / min, respectively.

[0014] Furthermore, the cooling rate is 4-6°C / min.

[0015] By adopting the above technical solution, the present invention has the following beneficial effects: (1) The bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance of the present invention comprises an active layer and a passive layer fixedly arranged on one side of the active layer. The active layer comprises, by mass fraction, 59-60wt% iron, 28wt% nickel, 11.5wt% aluminum, and 0.5-1.5wt% tantalum; the passive layer comprises, by mass fraction, 53.81-55.94wt% titanium, 41.43-43.07wt% nickel, and 1-5wt% copper. The sheet has good elasticity and a long service life.

[0016] (2) The iron-nickel-aluminum-tantalum alloy used in the active layer and the titanium-nickel-copper alloy used in the passive layer of the present invention are both shape memory alloys. The reversibility of the crystal phase transition of the shape memory alloy replaces the mechanical stress accumulation mechanism of the traditional bimetal, which fundamentally solves the bottleneck problem of fatigue life. The shape memory metal realizes the back-and-forth shape transformation between hot and cold states through the thermoelastic phase transition of austenite and martensite; while the traditional bimetallic strip generates bending deformation through the difference in thermal expansion coefficients of the two metals and relies on macroscopic mechanical stress accumulation. The dislocation and grain boundary sliding of the microstructure in long-term cycles will cause irreversible damage, and the service life is relatively short.

[0017] (3) The thermal expansion coefficient of the iron-nickel-aluminum-tantalum alloy used in the active layer of the present invention is at least 8*10 -6 *K -1 The thermal expansion coefficient of the passive layer between 103 and 145°C is (-7 to -4)*10 -6 *K -1 When the temperature reaches 103~145℃, the bimetallic strips of the active layer and the passive layer bend and deform due to the difference in thermal expansion coefficients, giving the bimetallic strips an initial deformed shape.

[0018] (4) The addition of metallic copper to the passive layer of the present invention can effectively improve the conductivity of the passive layer.

[0019] (5) The addition of tantalum alloy in the active layer of the present invention causes the alloy to gradually precipitate more and finely dispersed dot-like γ' phases. At this time, the compressive strength and recoverable strain of the alloy reach the maximum, and the residual strain is relatively the smallest, showing good elastic properties. Specific Embodiments

[0020] In order to better understand the above technical solutions, the following will describe the above technical solutions in detail in conjunction with specific embodiments.

[0021] 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 scope of protection of the present invention.

[0022] The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be used to limit the scope of protection of the present invention.

[0023] (Example 1) A preparation method of a bimetallic composite sheet for a low-voltage electrical miniature circuit breaker: The bimetallic composite sheet is obtained by cold rolling and laminating an active layer and a passive layer with the same length, width, and thickness.

[0024] The preparation steps of the active layer are as follows: (1) Weigh and proportion electrolytic iron, electrolytic nickel, electrolytic aluminum, and tantalum powder according to the mass percentages of iron, nickel, aluminum, and tantalum elements: 60wt% iron, 28wt% nickel, 11.5wt% aluminum, 0.5wt% tantalum; (2) Under argon protection, mix the electrolytic iron, electrolytic nickel, electrolytic aluminum, and tantalum powder weighed in step (1), and melt them into a button-shaped ingot using a water-cooled copper crucible and a vacuum non-consumable arc furnace. After melting three times repeatedly, hot roll it into a thin sheet with a thickness of 1.6 mm at 1000 °C, then solutionize it at 1200 °C for 25 min, water quench it and cold roll it to 0.6 mm, then solutionize it at 1200 °C for 25 min again, then perform aging treatment at 600 °C for 60 h, air cool it, and cut out an active layer with a length * width of 35 mm * 6 mm along the rolling direction. The coefficient of thermal expansion at 125 °C is 9*10 -6 K -1 .

[0025] The preparation steps of the passive layer are as follows: S1. Weigh and proportion nickel powder, titanium powder, and copper powder according to the mass percentages of nickel, titanium, and copper elements: 53.81wt% titanium, 41.43wt% nickel, 4.76wt% copper; S2. First, mix the nickel powder and titanium powder weighed in step S1 in a V-type powder mixer for 23 hours, then add copper powder and continue mixing for 7 hours. Subsequently, pour the mixture into a mold and press it into a green compact with a thickness of 15 mm. Then, place the green compact into a quartz tube sintering furnace. Under argon protection, perform gradient sintering. First, heat it to 930 °C and hold for 10 hours, then heat it to 880 °C and hot roll it to 9 mm. Anneal it at 600 °C for 25 minutes, then continue to roll it to 0.6 mm at 850 °C, anneal it at 600 °C for 25 minutes, and after air cooling, cut out a passive layer with a length * width of 35 mm * 6 mm along the rolling direction. Under a cold pressing force of 100 MPa, the negative thermal expansion range of the passive layer is 116.5 - 145.4 °C, and the thermal expansion coefficient is -7.56 * 10 -6 K -1 。

[0026] The steps of the gradient sintering are as follows: First, heat up to 250 °C and hold for 30 minutes, then heat up to 680 °C and hold for 12 minutes, continue to heat up to 800 °C and hold for 15 minutes, then heat up to 1000 °C and hold for 350 minutes, and then cool down to 460 °C and hold for 20 minutes.

[0027] The heating rates are 20 °C / min, 15 °C / min, 10 °C / min, and 8 °C / min respectively.

[0028] The cooling rate is 5 °C / min.

[0029] (Example 2) A preparation method of a bimetallic composite sheet for a low-voltage electrical miniature circuit breaker: The bimetallic composite sheet is formed by cold rolling and combining an active layer and a passive layer with the same length, width, and thickness.

[0030] The preparation steps of the active layer are as follows: (1) Weigh and proportion electrolytic iron, electrolytic nickel, electrolytic aluminum, and tantalum powder according to the mass percentages of iron, nickel, aluminum, and tantalum elements: 59.5 wt% iron, 28 wt% nickel, 11.5 wt% aluminum, 1 wt% tantalum; (2) Under argon protection, mix the electrolytic iron, electrolytic nickel, electrolytic aluminum, and tantalum powder weighed in step (1), and then melt them into a button-shaped ingot using a water-cooled copper crucible and a vacuum non-consumable arc furnace. After melting repeatedly for 3 times, hot roll it into a thin sheet with a thickness of 1.6 mm at 1000 °C, then perform solution treatment at 1200 °C for 25 minutes, water quench it and then cold roll it to 0.6 mm, perform solution treatment at 1200 °C for 25 minutes again, then perform aging treatment at 600 °C for 60 hours, and after air cooling, cut out an active layer with a length * width of 35 mm * 6 mm along the rolling direction. The thermal expansion coefficient at 125 °C is 8.8 * 10 -6 K -1 。

[0031] The preparation steps of the passive layer are as follows: S1. Weigh and proportion nickel powder, titanium powder, and copper powder according to the mass percentages of nickel, titanium, and copper elements: 54.875wt% titanium, 42.25wt% nickel, 2.875wt% copper; S2. First, mix the nickel powder and titanium powder weighed in step S1 in a V-type powder mixer for 23 hours, then add the copper powder and continue to mix for 7 hours. Subsequently, pour it into a mold and press it into a green compact with a thickness of 15 mm. Then, place it in a quartz tube sintering furnace. Under argon protection, perform gradient sintering. Then, hold it at 930 °C for 10 hours, then heat it to 880 °C and hot roll it to 9 mm, anneal it at 600 °C for 25 minutes, then continue to roll it to 0.6 mm at 850 °C, anneal it at 600 °C for 25 minutes, and after air cooling, cut out a passive layer with a length * width of 35 mm * 6 mm along the rolling direction. The passive layer has a negative thermal expansion range of 103 - 126.7 °C under a cold pressing force of 100 MPa, and the thermal expansion coefficient is -6.05×10 - 6 K -1 。

[0032] The steps of the gradient sintering are as follows: First, heat up to 250 °C and hold for 30 minutes, then heat up to 680 °C and hold for 12 minutes, continue to heat up to 800 °C and hold for 15 minutes, then heat up to 1000 °C and hold for 350 minutes, cool down to 460 °C, and hold for 20 minutes.

[0033] The heating rates are 20 °C / min, 15 °C / min, 10 °C / min, and 8 °C / min respectively.

[0034] The cooling rate is 5 °C / min respectively.

[0035] (Example 3) A preparation method of a bimetallic composite sheet for a low-voltage electrical miniature circuit breaker: The bimetallic composite sheet is obtained by cold rolling and combining an active layer and a passive layer with the same length, width, and thickness.

[0036] The preparation steps of the active layer are as follows: (1) Weigh and proportion electrolytic iron, electrolytic nickel, electrolytic aluminum, and tantalum powder according to the mass percentages of iron, nickel, aluminum, and tantalum elements: 59wt% iron, 28wt% nickel, 11.5wt% aluminum, 1.5wt% tantalum; (2) Under argon protection, the electrolytic iron, electrolytic nickel, electrolytic aluminum, and tantalum powder weighed in step (1) are mixed and then melted into a button-shaped ingot using a water-cooled copper crucible and a vacuum non-consumable arc furnace. After melting three times repeatedly, it is hot-rolled into a thin plate with a thickness of 1.6 mm at 1000 °C, then solution-treated at 1200 °C for 25 min, water-quenched, cold-rolled to 0.6 mm, solution-treated at 1200 °C for 25 min again, then aged at 600 °C for 60 h, air-cooled, and an active layer with a length * width of 35 mm * 6 mm is cut out along the rolling direction. The coefficient of thermal expansion at 125 °C is 9.1×10 -6 K -1 。

[0037] The preparation steps of the passive layer are as follows: S1. Weigh and mix nickel powder, titanium powder, and copper powder according to the mass percentages of nickel, titanium, and copper for each element: 55.94 wt% titanium, 43.07 wt% nickel, 0.97 wt% copper; S2. First, mix the nickel powder and titanium powder weighed in step S1 in a V-type powder mixer for 23 h, then add the copper powder and continue to mix for 7 h. Subsequently, pour it into a mold and press it into a green compact with a thickness of 15 mm. Then, put it into a quartz tube sintering furnace. Under argon protection, perform gradient sintering, then hold at 930 °C for 10 h, then heat to 880 °C and hot-roll to 9 mm, anneal at 600 °C for 25 min, then continue to roll to 0.6 mm at 850 °C, anneal at 600 °C for 25 min, air-cool, and cut out a passive layer with a length * width of 35 mm * 6 mm along the rolling direction. In the passive layer, in the negative thermal expansion range of 112.8 - 125.7 °C under a cold pressing force of 100 MPa, the coefficient of thermal expansion is -4.21×10 -6 K -1 。

[0038] The steps of the gradient sintering are as follows: First, heat up to 250 °C and hold for 30 min, then heat up to 680 °C and hold for 12 min, continue to heat up to 800 °C and hold for 15 min, then heat up to 1000 °C and hold for 350 min, cool down to 460 °C and hold for 20 min.

[0039] The heating rates are 20 °C / min, 15 °C / min, 10 °C / min, and 8 °C / min respectively.

[0040] The cooling rate is 5 °C / min respectively.

[0041] (Comparative example) The bimetallic strip of the comparative example uses a commercially available bimetallic strip 5J1580.

[0042] (Effect example) The bimetallic strips prepared in the examples and comparative examples were heated at 125 °C to cause deformation, then cooled to room temperature to recover the deformation, and the above steps were repeated cyclically. The number of cycles until the bimetallic strips broke was calculated, and the test results are shown in Table 1 below:

[0043] As can be seen from Table 1, the bimetallic strips prepared in the examples have a longer service life.

[0044] The specific embodiments described above have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A bimetallic composite sheet for a miniature circuit breaker of low-voltage electrical appliances, comprising an active layer and a passive layer fixedly arranged on one side of the active layer, characterized in that, In the active layer by mass fraction, the elemental components include: 59 - 60 wt% iron, 28 wt% nickel, 11.5 wt% aluminum, 0.5 - 1.5 wt% tantalum.

2. The bimetallic composite sheet for miniature circuit breakers of low-voltage electrical appliances according to claim 1, wherein In the passive layer by mass fraction, the elemental components include: 53.81 - 55.94 wt% titanium, 41.43 - 43.07 wt% nickel, 1 - 5 wt% copper.

3. A preparation method of a bimetallic composite sheet for a miniature circuit breaker of low-voltage electrical appliances according to any one of claims 1 to 2, characterized in that, The bimetallic composite sheet for the low - voltage electrical miniature circuit breaker is obtained by cold - rolling and combining an active layer and a passive layer with the same length, width and thickness.

4. The preparation method of the bimetallic composite sheet for the low-voltage electrical appliance miniature circuit breaker according to claim 3, characterized in that, The preparation steps of the active layer are as follows: (1) Weigh and proportion electrolytic iron, electrolytic nickel, electrolytic aluminum and tantalum powder according to the mass percentages of iron, nickel, aluminum and tantalum elements. (2) Under argon protection, mix the electrolytic iron, electrolytic nickel, electrolytic aluminum and tantalum powder weighed in step (1), and then melt them into a button - shaped ingot using a water - cooled copper crucible and a vacuum non - consumable arc furnace. After remelting 3 - 4 times, hot - roll them into a thin sheet with a thickness of 1.2 - 2 mm at 1000 ± 10 °C, then solutionize at 1200 ± 10 °C for 25 - 35 min, water - quench and then cold - roll to 0.6 - 1 mm, then solutionize at 1200 ± 10 °C for 25 - 35 min again, then perform aging treatment at 600 ± 10 °C for 60 h, air - cool and cut out an active layer with a length * width of (30 - 40) mm * (4 - 8) mm along the rolling direction.

5. The preparation method of the bimetallic composite sheet for the miniature circuit breaker of low-voltage electrical appliances according to claim 3, characterized in that, The preparation steps of the passive layer are as follows: S1. Weigh and proportion nickel powder, titanium powder and copper powder according to the mass percentages of nickel, titanium and copper elements. S2. First, mix the nickel powder and titanium powder weighed in step S1 in a V - type powder mixer for 23 - 25 h, then add copper powder and continue to mix for 7 - 9 h. Then pour it into a mold and press it into a green compact with a thickness of 15 - 30 mm. Then put it into a quartz tube sintering furnace, under argon protection, perform gradient sintering, then keep it at 930 - 980 °C for 10 - 12 h, then heat it to 880 - 900 °C and hot - roll it to 9 - 18 mm, anneal it at 600 - 800 °C for 25 - 35 min, then continue to roll it to 0.6 - 1 mm at 850 - 880 °C, anneal it at 600 - 800 °C for 25 - 35 min, air - cool and cut out a passive layer with a length * width of (30 - 40) mm * (4 - 8) mm along the rolling direction.

6. The preparation method of the bimetal composite sheet for a miniature circuit breaker of low-voltage electrical appliances according to claim 5, characterized in that, The steps of the gradient sintering are: first heat up to 250 ± 5 °C, keep it warm for 30 - 40 min, then heat up to 680 ± 5 °C, keep it warm for 12 - 18 min, continue to heat up to 800 ± 5 °C, keep it warm for 15 - 25 min, then heat up to 1000 ± 5 °C, keep it warm for 350 - 370 min, cool down to 460 ± 5 °C, keep it warm for 20 - 40 min.

7. The preparation method of the bimetallic composite sheet for the miniature circuit breaker of low-voltage electrical appliances according to claim 6, characterized in that, The heating rates are 18 - 22 °C / min, 14 - 16 °C / min, 8 - 12 °C / min, 6 - 10 °C / min respectively.

8. The preparation method of the bimetallic composite sheet for the low-voltage electrical appliance miniature circuit breaker according to claim 6, wherein, The cooling rate is 4 - 6 °C / min respectively.

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