A bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance and a preparation method thereof

Abstract

The present invention discloses a bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance and a preparation method thereof, belonging to the technical field of bimetallic composite sheets. 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, 59-60 wt% iron, 28 wt% nickel, 11.5 wt% aluminum, and 0.5-1.5 wt% tantalum; the passive layer comprises, by mass fraction, 53.81-55.94 wt% titanium, 41.43-43.07 wt% nickel, and 1-5 wt% copper; the bimetallic composite sheet prepared by the present invention has good elasticity and a long service life.

Description

Technical Field

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

[0002] In the field of low-voltage electrical appliances, miniature circuit breakers (MCBs), as key protection components in terminal power distribution systems, are widely used in household, industrial, and commercial power distribution systems. Their primary function is to automatically cut off power in the event of an overload or short-circuit fault, thereby ensuring the safety of electrical equipment and circuits. In the thermal trip mechanism of a MCB, a bimetallic strip is the core component for overload protection. Its operating principle is based on a composite structure consisting of two metal layers with different thermal expansion coefficients. When current passes through the bimetallic strip, the Joule heating effect causes the temperature to rise, and the difference in thermal expansion between the active layer (high-expansion coefficient material) and the passive layer (low-expansion coefficient material) bends and deforms, triggering the trip mechanism to automatically disconnect the circuit.

[0003] Traditional bimetallic strips are typically made of two metal layers: an active layer and a passive layer, welded or rolled together. For example, the active layer often uses materials with high thermal expansion coefficients, such as copper-nickel or iron-nickel alloys, while the passive layer is often made of materials with lower thermal expansion coefficients, such as iron-chromium alloys or nickel-based alloys. This structural design effectively utilizes the difference in thermal expansion between the materials to achieve the desired mechanical displacement response. However, in practical applications, bimetallic strips face technical challenges such as elastic fatigue and limited service life.

[0004] Research has shown that bimetallic strips are susceptible to a decrease in elastic properties when subjected to long-term, cyclical thermal stress, particularly under conditions of frequent overloads or large temperature fluctuations. This can lead to a decrease in the bimetallic strip's operating accuracy or even failure, compromising the reliability and safety of the circuit breaker.

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

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

[0007] The technical solution for achieving the purpose of the present invention is:

[0008] In a first aspect, the present invention provides a bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance, comprising an active layer and a passive layer fixedly arranged on one side of the active layer, wherein the active layer comprises, by mass fraction, 59-60 wt% iron, 28 wt% nickel, 11.5 wt% aluminum, and 0.5-1.5 wt% tantalum.

[0009] Furthermore, the passive layer comprises, by mass fraction, 53.81-55.94 wt % titanium, 41.43-43.07 wt % nickel, and 1-5 wt % copper.

[0010] In a second aspect, the present invention provides a method for preparing a bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance as described in the first aspect, wherein the bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance is a sheet in which an active layer and a passive layer having the same length, width and thickness are composited together by cold rolling.

[0011] Furthermore, the preparation steps of the active layer are as follows:

[0012] (1) Electrolytic iron, electrolytic nickel, electrolytic aluminum and tantalum powder are weighed and mixed according to the mass percentage of each element of iron, nickel, aluminum and tantalum;

[0013] (2) Under argon protection, the electrolytic iron, electrolytic nickel, electrolytic aluminum and tantalum powder weighed in step (1) are mixed and smelted into button-shaped ingots in a water-cooled copper crucible and a vacuum non-consumable arc furnace. After repeated smelting 3 to 4 times, the ingots are hot-rolled at 1000±10°C into thin plates with a thickness of 1.2 to 2 mm, and then solution-treated at 1200±10°C for 25 to 35 minutes. After water quenching, the ingots are cold-rolled to 0.6 to 1 mm, and then solution-treated at 1200±10°C for 25 to 35 minutes. The ingots are then aged at 600±10°C for 60 hours, and air-cooled. An active layer with a length*width of (30 to 40) mm*(4 to 8) mm is cut along the rolling direction.

[0014] Furthermore, the preparation steps of the passive layer are as follows:

[0015] S1. The nickel powder, titanium powder, copper powder according to the mass percentage of nickel, titanium, copper, each element were weighed ingredients;

[0016] S2. First, the nickel powder and titanium powder weighed in step S1 are mixed in a V-type powder mixer for 23-25 ​​hours, then copper powder is added and mixing is continued for 7-9 hours. Then, the mixture is poured into a mold and pressed into a 15-30 mm thick green body. Then, the green body is placed in a quartz tube sintering furnace and gradient sintered under argon protection. The green body is then kept at 930-980°C for 10-12 hours. The green body is then heated to 880-900°C and hot-rolled to 9-18 mm. The green body is annealed at 600-800°C for 25-35 minutes. The green body is then rolled to 0.6-1 mm at 850-880°C and annealed at 600-800°C for 25-35 minutes. After air cooling, a passive layer with a length*width of (30-40) mm*(4-8) mm is cut along the rolling direction.

[0017] Furthermore, the steps of the gradient sintering are: first heating to 250±5°C, keeping warm for 30~40 minutes, then heating to 680±5°C, keeping warm for 12~18 minutes, continuing to heat to 800±5°C, keeping warm for 15~25 minutes, then heating to 1000±5°C, keeping warm for 350~370 minutes, cooling to 460±5°C, and keeping warm for 20~40 minutes.

[0018] Furthermore, the heating rates are 18~22℃ / min, 14~16℃ / min, 8~12℃ / min, and 6~10℃ / min, respectively.

[0019] Furthermore, the cooling rate is 4-6°C / min.

[0020] By adopting the above technical solution, the present invention has the following beneficial effects:

[0021] (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, 59-60 wt% iron, 28 wt% nickel, 11.5 wt% aluminum, and 0.5-1.5 wt% tantalum; the passive layer comprises, by mass fraction, 53.81-55.94 wt% titanium, 41.43-43.07 wt% nickel, and 1-5 wt% copper. The sheet has good elasticity and a long service life.

[0022] (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 bimetallic material, which fundamentally solves the fatigue life bottleneck problem. The shape memory metal realizes the back-and-forth shape transformation between hot and cold states through the thermoelastic phase transition between 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 slip of the microstructure in long-term cycles will cause irreversible damage, and the service life is relatively short.

[0023] (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 is (-7~-4)*10 between 103~145℃. -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.

[0024] (4) The addition of metallic copper to the passive layer of the present invention can effectively improve the conductivity of the passive layer.

[0025] (5) The addition of tantalum alloy to the active layer of the present invention causes the alloy to gradually precipitate a large number of dispersed small point-like γ' phases. At this time, the compressive strength and recoverable strain of the alloy reach the maximum, and the residual strain is relatively minimum, reflecting better elastic properties. DETAILED DESCRIPTION

[0026] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with specific implementation methods.

[0027] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0028] The following examples are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0029] (Example 1)

[0030] A method for preparing a bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance: the bimetallic composite sheet is prepared by cold-rolling an active layer and a passive layer having the same length, width and thickness.

[0031] The preparation steps of the active layer are as follows:

[0032] (1) Electrolytic iron, electrolytic nickel, electrolytic aluminum, and tantalum powder are weighed and mixed according to the mass percentage of each element:

[0033] 60wt% iron, 28wt% nickel, 11.5wt% aluminum, 0.5wt% tantalum;

[0034] (2) Under argon protection, the electrolytic iron, electrolytic nickel, electrolytic aluminum and tantalum powder weighed in step (1) are mixed and melted into button-shaped ingots in a water-cooled copper crucible and a vacuum non-consumable arc furnace. After repeated melting for 3 times, the ingots are hot-rolled at 1000°C into a thin plate with a thickness of 1.6 mm, and then solution-treated at 1200°C for 25 minutes. After water quenching, the ingots are cold-rolled to 0.6 mm, solution-treated at 1200°C for 25 minutes, and then aged at 600°C for 60 hours. After air cooling, the active layer with a length and width of 35 mm and 6 mm is cut along the rolling direction. The thermal expansion coefficient at 125°C is 9*10 -6 K -1 .

[0035] The preparation steps of the passive layer are as follows:

[0036] S1. Weigh nickel powder, titanium powder, and copper powder according to the mass percentage of nickel, titanium, copper, and each element:

[0037] 53.81wt% titanium, 41.43wt% nickel, 4.76wt% copper;

[0038] S2. The nickel powder and titanium powder weighed in step S1 were mixed in a V-type powder mixer for 23 hours, and then copper powder was added and mixed for 7 hours. The mixture was then poured into a mold and pressed into a 15 mm thick green body. The green body was then placed in a quartz tube sintering furnace and gradient sintered under argon protection. The green body was then kept at 930°C for 10 hours, then heated to 880°C and hot-rolled to 9 mm. The green body was annealed at 600°C for 25 minutes, and then rolled to 0.6 mm at 850°C. The green body was annealed at 600°C for 25 minutes. After air cooling, a passive layer with a length and width of 35 mm and 6 mm was cut along the rolling direction. The negative thermal expansion range of the passive layer under 100 MPa cold pressing pressure was 116.5~145.4°C, and the thermal expansion coefficient was -7.56*10 -6 K -1 .

[0039] The gradient sintering steps are: first heating to 250°C, keeping warm for 30 minutes, then heating to 680°C, keeping warm for 12 minutes, continuing to heat to 800°C, keeping warm for 15 minutes, then heating to 1000°C, keeping warm for 350 minutes, cooling to 460°C, and keeping warm for 20 minutes.

[0040] The heating rates are 20°C / min, 15°C / min, 10°C / min and 8°C / min respectively.

[0041] The cooling rate is 5°C / min.

[0042] (Example 2)

[0043] A method for preparing a bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance: the bimetallic composite sheet is prepared by cold-rolling an active layer and a passive layer having the same length, width and thickness.

[0044] The preparation steps of the active layer are as follows:

[0045] (1) Electrolytic iron, electrolytic nickel, electrolytic aluminum, and tantalum powder are weighed and mixed according to the mass percentage of each element:

[0046] 59.5wt% iron, 28wt% nickel, 11.5wt% aluminum, 1wt% tantalum;

[0047] (2) Under argon protection, the electrolytic iron, electrolytic nickel, electrolytic aluminum and tantalum powder weighed in step (1) are mixed and melted into button-shaped ingots in a water-cooled copper crucible and a vacuum non-consumable arc furnace. After repeated melting for 3 times, the ingots are hot-rolled at 1000°C into a thin plate with a thickness of 1.6 mm, and then solution-treated at 1200°C for 25 minutes. After water quenching, the ingots are cold-rolled to 0.6 mm, solution-treated at 1200°C for 25 minutes, and then aged at 600°C for 60 hours. After air cooling, the active layer with a length and width of 35 mm and 6 mm is cut along the rolling direction. The thermal expansion coefficient is 8.8*10 at 125°C. -6 K -1 .

[0048] The preparation steps of the passive layer are as follows:

[0049] S1. Weigh nickel powder, titanium powder, and copper powder according to the mass percentage of nickel, titanium, copper, and each element:

[0050] 54.875wt% titanium, 42.25wt% nickel, 2.875wt% copper;

[0051] S2. The nickel powder and titanium powder weighed in step S1 were mixed in a V-type powder mixer for 23 hours, and then copper powder was added and mixed for 7 hours. The green body was then poured into a mold and pressed into a 15 mm thick green body. The green body was then placed in a quartz tube sintering furnace and gradient sintered under argon protection. The green body was then kept at 930°C for 10 hours, then heated to 880°C and hot-rolled to 9 mm. The green body was annealed at 600°C for 25 minutes, and then rolled to 0.6 mm at 850°C. The green body was annealed at 600°C for 25 minutes. After air cooling, a passive layer with a length and width of 35 mm and 6 mm was cut out along the rolling direction. The negative thermal expansion range of the passive layer under 100 MPa cold pressing pressure was 103~126.7°C, and the thermal expansion coefficient was -6.05*10 - 6 K -1 .

[0052] The gradient sintering steps are: first heating to 250°C, keeping warm for 30 minutes, then heating to 680°C, keeping warm for 12 minutes, continuing to heat to 800°C, keeping warm for 15 minutes, then heating to 1000°C, keeping warm for 350 minutes, cooling to 460°C, and keeping warm for 20 minutes.

[0053] The heating rates are 20°C / min, 15°C / min, 10°C / min and 8°C / min respectively.

[0054] The cooling rate is 5°C / min.

[0055] (Example 3)

[0056] A method for preparing a bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance: the bimetallic composite sheet is prepared by cold-rolling an active layer and a passive layer having the same length, width and thickness.

[0057] The preparation steps of the active layer are as follows:

[0058] (1) Electrolytic iron, electrolytic nickel, electrolytic aluminum, and tantalum powder are weighed and mixed according to the mass percentage of each element:

[0059] 59wt% iron, 28wt% nickel, 11.5wt% aluminum, 1.5wt% tantalum;

[0060] (2) Under argon protection, the electrolytic iron, electrolytic nickel, electrolytic aluminum and tantalum powder weighed in step (1) are mixed and melted into button-shaped ingots in a water-cooled copper crucible and a vacuum non-consumable arc furnace. After repeated melting for 3 times, the ingots are hot-rolled at 1000°C into thin plates with a thickness of 1.6 mm, and then solution-treated at 1200°C for 25 minutes. After water quenching, the ingots are cold-rolled to 0.6 mm, and then solution-treated at 1200°C for 25 minutes. The ingots are then aged at 600°C for 60 hours, and air-cooled. The active layer is cut into a length*width of 35 mm*6 mm along the rolling direction. The thermal expansion coefficient is 9.1*10 at 125°C. -6 K -1 .

[0061] The preparation steps of the passive layer are as follows:

[0062] S1. Weigh nickel powder, titanium powder, and copper powder according to the mass percentage of nickel, titanium, copper, and each element:

[0063] 55.94wt% titanium, 43.07wt% nickel, 0.97wt% copper;

[0064] S2. The nickel powder and titanium powder weighed in step S1 were mixed in a V-type powder mixer for 23 hours, and then copper powder was added and mixed for 7 hours. The mixture was then poured into a mold and pressed into a 15 mm thick green body. The green body was then placed in a quartz tube sintering furnace and gradient sintered under argon protection. The green body was then kept at 930°C for 10 hours, then heated to 880°C and hot-rolled to 9 mm. The green body was annealed at 600°C for 25 minutes, and then rolled to 0.6 mm at 850°C. The green body was annealed at 600°C for 25 minutes. After air cooling, a passive layer with a length and width of 35 mm and 6 mm was cut along the rolling direction. The negative thermal expansion range of the passive layer under 100 MPa cold pressing pressure was 112.8~125.7°C, and the thermal expansion coefficient was -4.21*10 -6 K -1 .

[0065] The gradient sintering steps are: first heating to 250°C, keeping warm for 30 minutes, then heating to 680°C, keeping warm for 12 minutes, continuing to heat to 800°C, keeping warm for 15 minutes, then heating to 1000°C, keeping warm for 350 minutes, cooling to 460°C, and keeping warm for 20 minutes.

[0066] The heating rates are 20°C / min, 15°C / min, 10°C / min and 8°C / min respectively.

[0067] The cooling rate is 5°C / min.

[0068] (Comparative Example)

[0069] The bimetallic strip of the comparative example adopts the commercially available bimetallic strip 5J1580.

[0070] (Effect example)

[0071] The bimetallic strips prepared in the examples and comparative examples were heated at 125°C to deform, then cooled to room temperature and allowed to recover. The above steps were repeated, and the number of cycles until the bimetallic strips broke was calculated. The test results are shown in Table 1 below:

[0072]

[0073] It can be seen from Table 1 that the bimetallic strips prepared in the embodiment have a longer service life.

[0074] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a bimetallic composite sheet for a low-voltage electrical miniature circuit breaker, characterized in that: The bimetallic composite sheet for a low-voltage electrical miniature circuit breaker is a composite sheet of an active layer and a passive layer having the same length, width, and thickness, which are cold-rolled together; the active layer comprises, by mass fraction, 59-60 wt% iron, 28 wt% nickel, 11.5 wt% aluminum, and 0.5-1.5 wt% tantalum; the passive layer comprises, by mass fraction, 53.81-55.94 wt% titanium, 41.43-43.07 wt% nickel, and 1-5 wt% copper; The preparation steps of the active layer are as follows: (1) Electrolytic iron, electrolytic nickel, electrolytic aluminum and tantalum powder are weighed and mixed according to the mass percentage of each element of iron, nickel, aluminum and tantalum; (2) Under argon protection, the electrolytic iron, electrolytic nickel, electrolytic aluminum and tantalum powder weighed in step (1) are mixed and placed in a water-cooled copper crucible of a vacuum non-consumable arc furnace to be smelted into a button-shaped ingot. After repeated smelting 3 to 4 times, the ingot is hot-rolled at 1000±10°C into a thin plate with a thickness of 1.2 to 2 mm, and then solution-treated at 1200±10°C for 25 to 35 minutes. After water quenching, the ingot is cold-rolled to 0.6 to 1 mm, and then solution-treated at 1200±10°C for 25 to 35 minutes. The ingot is then aged at 600±10°C for 60 hours. After air cooling, an active layer with a length × width of 30 to 40 mm × 4 to 8 mm is cut along the rolling direction.

2. The method for preparing a bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance according to claim 1, characterized in that: The preparation steps of the passive layer are as follows: S1. The nickel powder, titanium powder, and copper powder are weighed according to the mass percentage of each element of nickel, titanium, and copper; S2. First, the nickel powder and titanium powder weighed in step S1 are mixed in a V-type powder mixer for 23-25 ​​hours, then copper powder is added and mixing is continued for 7-9 hours. Then, the mixture is poured into a mold and pressed into a 15-30 mm thick green body. The green body is then placed in a quartz tube sintering furnace and gradient sintered under argon protection. The green body is then kept at 930-980°C for 10-12 hours, then heated to 880-900°C and hot-rolled to 9-18 mm. The green body is annealed at 600-800°C for 25-35 minutes, then rolled to 0.6-1 mm at 850-880°C, annealed at 600-800°C for 25-35 minutes, and air-cooled. A passive layer with a length and width of 30-40 mm and a width of 4-8 mm is cut along the rolling direction.

3. The method for preparing a bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance according to claim 2, characterized in that: The gradient sintering steps are: first heating to 250±5°C, keeping warm for 30-40 minutes, then heating to 680±5°C, keeping warm for 12-18 minutes, continuing heating to 800±5°C, keeping warm for 15-25 minutes, then heating to 1000±5°C, keeping warm for 350-370 minutes, cooling to 460±5°C, and keeping warm for 20-40 minutes.

4. The method for preparing a bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance according to claim 3, characterized in that: The heating rates are 18-22°C / min, 14-16°C / min, 8-12°C / min, and 6-10°C / min, respectively.

5. The method for preparing a bimetallic composite sheet for a small circuit breaker of a low-voltage electrical appliance according to claim 3, characterized in that: The cooling rate is 4-6°C / min.

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