A method for testing the uniformity of hot bimetallic strips for disc-shaped components

Abstract

The present invention provides a method for testing the uniformity of a hot bimetallic strip for a disc-shaped element, comprising the following steps: (1) Sampling and slitting: continuously cutting samples of a certain length at the head and tail of the hot bimetallic strip, and slitting the samples, and sorting the slitting samples into two transverse edges on the human side and the machine side, and a strip in the middle; (2) Stamping and forming: placing the strip obtained by slitting in step (1) in a stamping die to stamp out a concave active layer spherical crown-shaped sample; (3) Measuring the temperature / force of the sample: testing the temperature or force of the sudden jump / recovery of the spherical crown-shaped sample in step (3), recording the corresponding test values, and calculating the range as an indicator for evaluating the transverse and longitudinal non-uniformity of the sample. Compared with the prior art, the testing method provided by the present invention is more suitable for practical use, simple and reliable, and can achieve the characteristics of quantifying the overall uniformity of the material.

Description

Technical Field

[0001] The invention relates to the technical field of quality evaluation of thermal bimetallic materials, and in particular to a method for testing the uniformity of a thermal bimetallic thin strip for a disc-shaped element. Background Art

[0002] Thermo bimetal is a composite material formed by two or more layers of metal or alloy with different expansion coefficients firmly bonded to each other along the entire contact surface. Its structure includes an active layer and a passive layer with different linear expansion coefficients, or an active layer and a passive layer and an intermediate layer between the active and passive layers as a guide layer. Because the linear expansion coefficients of the active and passive materials are inconsistent, the thermo bimetal can change its shape under temperature changes and convert thermal energy into mechanical energy. Its temperature characteristics make it widely used in low-voltage electrical appliances, household appliances and other fields. The property of thermo bimetal to bend due to temperature changes is called thermal sensitivity. In 1951, WHWITTRICK conducted theoretical calculations on snap-action thermo bimetal discs in "Stability of a bimetallic disk". Thermo bimetal discs are used as core components in snap-action protectors and circuit breakers.

[0003] In the domestic and international standards such as GB / T 8364 and ASTM B106, when testing the thermal sensitivity of thermal bimetallic strips, the sample length is more than 100mm, but the actual disc diameter is less than 30mm, which is not close to the actual usage.

[0004] The testing methods for thermal performance of materials at home and abroad can only be tested by making standard samples with thickness specifications ≥0.30mm and length specifications ≥40mm. Sampling tests are often performed on semi-finished products, and finally the test data is quoted to measure the overall thermal performance of the finished material. However, in actual applications, thermal bimetallic materials are often processed to less than 0.30mm, and punched and stamped into discs with a size of less than 30mm. The current testing methods cannot directly measure the thermal performance of materials with thickness specifications ≥0.30mm and length specifications ≥40mm, and it is even more difficult to achieve a "higher resolution" evaluation of the uniformity of the material. Summary of the invention

[0005] In view of this, the present invention provides a testing method for the uniformity of thermal bimetallic strips for disc-shaped elements, which involves the field of uniformity evaluation of thermal bimetallic strips with a thickness specification of less than 0.30 mm. The method is more suitable for practical use, simple and reliable, and can realize the quantification of the overall uniformity of the material.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for testing the uniformity of a hot bimetallic strip for a disc-shaped element comprises the following steps:

[0008] (1) Sampling and slitting: Samples of a certain length are continuously cut from the head and tail of the hot bimetallic thin strip, and the samples are slit. The slit samples are sorted into two horizontal edges on the human side and the machine side, and a strip in the middle, which are marked as 1A, 1B, 2A, 2B, 3A, and 3B respectively; the sampling position is based on the characteristic position of "edge-middle-edge" to evaluate the uniformity in the width direction.

[0009] (2) Stamping: The strips 1A, 1B, 2A, 2B, 3A, and 3B obtained by cutting in step (1) are placed in a stamping die for forming into spherical crown-shaped samples (spherical crown diameter is D, chord height is A0, thickness is S) concave toward the active layer, and are marked as 1A-1, 1A-2 ... 1A-16 ... 3B-1, 3B-2 ... 3B-16 respectively; stamping is performed to form an initial arc so that the thermometal has the conditions for forming an action under temperature changes.

[0010] (3) Temperature / force measurement of the sample: The spherical crown-shaped samples 1A-1, 1A-2...1A-16...3B-1, 3B-2...3B-16 in step (3) are tested for the temperature or force of the sudden jump / recovery, and the corresponding test values ​​are recorded, and the extreme value is calculated as an index for evaluating the transverse and longitudinal non-uniformity of the sample, that is, the present invention statistically analyzes the temperature / force test values, takes the extreme value as a quantitative index of the uniformity of the thin strip material, and takes 16 samples, mainly considering the efficiency and effectiveness of the test. The force / temperature test is used to obtain the test value of the force / temperature of each numbered disc sample, and the difference between the maximum force / temperature of the disc test and the minimum force / temperature of the disc test is used as a measure of uniformity.

[0011] Preferably, the sampling and slitting method in step (1) is to sample a strip of a certain thickness (S) with a head-to-tail length of 1-10 meters and a width of 2-50 mm in the longitudinal direction, and sample the side close to people, the side close to the machine and one in the middle in the transverse direction, a total of 6 representative strips, which are marked as "1, 2, 3..." in sequence from the side close to people to the side close to the machine, with the head section sampled with the letter A and the tail section sampled with the letter B, and the sampling sections are respectively marked as 1A, 1B, 2A, 2B, 3A, 3B (as shown in the attached figure). Figure 1 ).

[0012] Preferably, in step (2), the strip material is formed by stamping to complete the forming of 16 spherical crown-shaped discs on each sampling strip.

[0013] Preferably, the tension-free section should be cut off before sampling in step (1) to ensure the representativeness of the head and tail sampling of the thermal bimetallic material.

[0014] Preferably, the stamping die in step (2) has multiple cores corresponding to materials of different thicknesses and widths.

[0015] Preferably, the certain length in step (1) is 1 m.

[0016] Preferably, the width W of the strip in step (2) is 5-30 mm.

[0017] Preferably, the arc diameter of the spherical crown-shaped sample in step (3) is D<W, that is, D≤50mm, and the chord height is A0.

[0018] The formula is as follows:

[0019]

[0020]

[0021] In the above formula, L≈the diameter of the disc, and Rr is the diameter of the arc. Through preliminary estimation, the diameter D will be around 4 to 50 mm, so it is necessary to set the D value ≤50 mm.

[0022] Preferably, the ratio of the chord height (A0) / thickness (s) of the spherical cap-shaped sample in step (3), i.e., A0 / s=2-7 (as shown in the attached figure). Figure 3 ).

[0023] The ratio of chord height (A0) / thickness (s) mainly affects the difference between the jump and recovery temperatures. The larger the ratio of chord height (A0) / thickness (s), the larger the difference. Selecting this ratio range can achieve a certain degree of widening the difference between the jump / recovery temperature test, which is beneficial to reduce the test error. Thermo bimetal can achieve a stable temperature curvature within the linear temperature range of -20~+150 / +370 (depending on the brand), and the deflection caused by temperature change changes linearly. If the ratio is too small, the difference between the recovery temperature and the jump temperature is low, and the range of each sample after the test is too small. However, when the ratio exceeds 7, the actual temperature of the thermo bimetal will exceed the linear temperature range, and the material will be stretched to a large extent, which is prone to cracking. This range is selected based on the comprehensive consideration of the ratio (3-4) corresponding to the temperature range used by the actual thermostat in the market, and an enlargement of the range is made.

[0024] Preferably, in step (3), the disc-shaped element is tested by directly testing the sudden jump / recovery temperature, or by using a spring or other sensor to test the force required for sudden jump, and the test data is recorded and the range is calculated.

[0025] Preferably, the temperature / force measurement method in step (3) comprises the following steps:

[0026] (1) The formed disc is placed in a silicone oil tank with a heating device and slowly heated to a set temperature. There is a temperature measuring device in the silicone oil tank to detect the temperature to observe the flipping temperature of the formed sample. After flipping occurs, the flipping temperature is recorded as the "jump temperature". Then the power is turned off and the silicone oil tank is allowed to slowly cool down to room temperature. During the process, the recovery flipping process is observed and the temperature at that time is recorded as the "recovery temperature";

[0027] (2) The formed disc is fixed in position on two feature tools each with a circular hole, and placed in a container or silicone oil tank with a heating and constant temperature device. A pin with a spring or sensor is used to press down on the center of the disc to obtain the pressure value required to flip the disc, and record it as the "jump force". After flipping, the direction is changed and the test is performed again. The pressure value for flipping again is recorded and recorded as the "return force".

[0028] Compared with the prior art, the present invention has the following beneficial effects: the method provided by the present invention for testing the uniformity of a hot bimetallic strip for a disc-shaped element is more suitable for practical use, simple and reliable, and can quantify the overall uniformity of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a sampling and identification schematic diagram of the method of the present invention;

[0030] Figure 2 Schematic diagram of a stamping die head for forming a spherical crown in the method of the present invention;

[0031] Figure 3 It is a schematic diagram of forming a spherical crown and testing according to the method of the present invention;

[0032] Figure 4 It is a schematic diagram of the test device in the national standard GB / T 8364;

[0033] Figure 5 It is a schematic diagram of the test process in the national standard GB / T 8364. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0035] The experimental methods or test methods described in the following examples are conventional methods unless otherwise specified; the raw materials and auxiliary agents are obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0036] Example 1

[0037] (1) Cut a 420kg roll of 0.10mm x 100mm 5J39110 (national standard grade) strip into 10 strips of 0.10mm x 9.5mm. Take 1m long samples from the side close to the person, the side close to the machine, and the middle, and mark them as 1A, 1B, 2A, 2B, 3A, and 3B;

[0038] (2) Six 1-meter-long specimens were punched into a spherical cap shape, the diameter of the spherical cap was 8.0 mm, the chord height / thickness value of the spherical cap was 2.0, and 16 spherical cap samples were punched successively (a total of 96 samples), which were marked as 1A-1, 1A-2, 1A-3...1A-16, 1B-1, 1B-2, 1B-3...1B-16...3B-1, 3B-2, 3B-3...3B-16;

[0039] (3) The marked samples were tested for sudden jump temperature and recovery temperature respectively to obtain the sudden jump / recovery temperature of each sample, and the maximum difference of sudden jump temperature was 10.5°C and the maximum difference of recovery temperature was 15.2°C respectively.

[0040] Example 2

[0041] (1) Cut 380kg of 5J39110 strip with a size of 0.12mm x 105mm into 9 strips with a size of 0.10mm x 10.3mm. Take 1m long samples from the side close to the person, the side close to the machine, and the middle, and mark them as 1A, 1B, 2A, 2B, 3A, and 3B;

[0042] (2) Six 1-meter-long specimens were punched into a spherical cap shape, the diameter of the spherical cap was 8.0 mm, the chord height / thickness value of the spherical cap was 3.0, and 16 spherical cap samples (a total of 96) were punched out successively and marked as 1A-1, 1A-2, 1A-3 ... 1A-16, 1B-1, 1B-2, 1B-3 ... 1B-16 ... 3B-1, 3B-2, 3B-3 ... 3B-16;

[0043] (3) The marked samples were tested for sudden jump temperature and recovery temperature respectively to obtain the sudden jump / recovery temperature of each sample. The maximum difference of sudden jump temperature was 8.4°C and the maximum difference of recovery temperature was 16.2°C respectively.

[0044] Example 3

[0045] (1) Cut 410kg of 0.18mm x 100mm 5J2780 strip into 6 strips of 0.18mm x 15.0mm. Take 1m long samples from the side close to the person, the side close to the machine, and the middle, and mark them as 1A, 1B, 2A, 2B, 3A, and 3B.

[0046] (2) Six 1-meter-long specimens were stamped into a spherical cap shape, the diameter of the spherical cap was 8.0 mm, the chord height / thickness value of the spherical cap was 5.0, and 16 spherical cap samples (a total of 96) were stamped out successively and marked as 1A-1, 1A-2, 1A-3 ... 1A-16, 1B-1, 1B-2, 1B-3 ... 1B-16 ... 3B-1, 3B-2, 3B-3 ... 3B-16;

[0047] (3) The marked samples were tested for sudden jump force and recovery force respectively to obtain the sudden jump / recovery force of each sample, and the maximum difference in sudden jump force of 4.7N and the maximum difference in recovery force of 10.5N were calculated respectively.

[0048] Example 4

[0049] (1) Cut 544 kg of 0.15 mm x 110 mm 5J2370 strip into 8 strips of 0.15 mm x 14 mm. Take 1 m long sample from the side close to the person, the side close to the machine, and the middle, and mark them as 1A, 1B, 2A, 2B, 3A, and 3B.

[0050] (2) Six 1-meter-long specimens were stamped into a spherical cap shape, the diameter of the spherical cap was 13.0 mm, the chord height / thickness value of the spherical cap was 6.0, and 16 spherical cap samples (a total of 96) were stamped continuously and marked as 1A-1, 1A-2, 1A-3...1A-16, 1B-1, 1B-2, 1B-3...1B-16...3B-1, 3B-2, 3B-3...3B-16;

[0051] (3) The marked samples were tested for sudden jump force and recovery force respectively to obtain the sudden jump / recovery force of each sample, and the maximum difference in sudden jump force of 13.5N and the maximum difference in recovery force of 18.9N were calculated respectively.

[0052] Example 5

[0053] (1) Cut 485kg of FPA721-95 strip with a size of 0.20mm x 105mm into 8 strips with a size of 0.20mm x 12mm. Take 1m long samples from the side close to the person, the side close to the machine, and the middle, and mark them as 1A, 1B, 2A, 2B, 3A, and 3B;

[0054] (2) Six 1-meter-long specimens were stamped into a spherical cap shape, the diameter of the spherical cap was 8.0 mm, the chord height / thickness value of the spherical cap was 4.0, and 16 spherical cap samples (a total of 96) were stamped continuously and marked as 1A-1, 1A-2, 1A-3...1A-16, 1B-1, 1B-2, 1B-3...1B-16...3B-1, 3B-2, 3B-3...3B-16;

[0055] (3) The marked samples were tested for sudden jump force and recovery force respectively to obtain the sudden jump / recovery force of each sample, and the maximum difference in sudden jump force of 15.6N and the maximum difference in recovery force of 13.1N were calculated respectively.

[0056] Example 6

[0057] (1) Cut 443kg of 0.25mm x 100mm 5J2880 strip into three strips of 0.25mm x 30.0mm. Take 1m long samples from the side close to the person, the side close to the machine, and the middle, and mark them as 1A, 1B, 2A, 2B, 3A, and 3B.

[0058] (2) Six 1-meter-long specimens were stamped into a spherical cap shape, the diameter of the spherical cap was 8.0 mm, the chord height / thickness value of the spherical cap was 2.4, and 16 spherical cap samples (a total of 96) were stamped continuously and marked as 1A-1, 1A-2, 1A-3...1A-16, 1B-1, 1B-2, 1B-3...1B-16...3B-1, 3B-2, 3B-3...3B-16;

[0059] (3) The marked samples were tested for sudden jump temperature and recovery temperature respectively to obtain the sudden jump / recovery temperature of each sample. The maximum difference of sudden jump temperature was 3.4°C and the maximum difference of recovery temperature was 8.2°C.

[0060] Example 7

[0061] (1) Cut 487kg of 0.30mm x 100mm 5J2780 strip into 5 strips of 0.30mm x 19.0mm. Take 1m long samples from the side close to the person, the side close to the machine, and the middle, and mark them as 1A, 1B, 2A, 2B, 3A, and 3B.

[0062] (2) Six 1-meter-long specimens were stamped into a spherical cap shape. The diameter of the spherical cap was 17.0 mm, and the chord height / thickness value of the spherical cap was 4.1. 16 spherical cap samples (a total of 96) were stamped continuously and marked as 1A-1, 1A-2, 1A-3...1A-16, 1B-1, 1B-2, 1B-3...1B-16...3B-1, 3B-2, 3B-3...3B-16;

[0063] (3) The marked samples were tested for sudden jump temperature and recovery temperature respectively to obtain the sudden jump / recovery temperature of each sample, and the maximum difference of sudden jump temperature was 5.2°C and the maximum difference of recovery temperature was 9.5°C respectively.

[0064] Comparative Example 1

[0065] (1) Sampling: Take a 50 mm long sample from the head and tail of the coiled 5J39110 strip with a size of 0.80 mm x 120 mm along the rolling direction;

[0066] (2) Sample preparation: According to the sample preparation method and test method of the medium-temperature curvature test in GB / T 8364, the samples were cut into straight strips with a width of 12 mm and a length of 120 mm. One standard sample was selected from the head and tail samples, and the burrs and surface oxide scale were polished off. The samples were then placed in a heat treatment furnace for stabilization heat treatment at 260°C for 2 hours.

[0067] (3) Test: Figure 4 , use the support and the press holder to clamp and fix one of the straight strip samples, first use the screw micrometer fixed on the support to test its original position at room temperature, and record it. Place the clamped material together with the entire support and the press holder in a constant temperature silicone oil bath at 20°C (temperature T1), and after the temperature stabilizes, use the screw micrometer to measure the deflection and record it (deflection value D1). Then place the entire device in a constant temperature silicone oil bath at 130°C (temperature T2), perform the same operation, test the deflection and record it (deflection value D2);

[0068] (4) Calculation: Figure 5 , substitute the test data into the formula to calculate and obtain the temperature curvature F.

[0069] The formula in step (4) is as follows:

[0070]

[0071] Difference: This test method can only test the thermo-bimetallic materials with a thickness of ≥0.30 and a test sample length of ≥40mm. It cannot directly measure the thermo-bimetallic materials with a specification below 0.30mm. It can only measure the semi-finished products with a thickness that meets the test sample specification range. The test results are quoted as the thermal curvature of the whole roll of finished material, and the uniformity evaluation test of the material cannot be realized.

[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for testing the uniformity of a hot bimetallic strip for a disc-shaped element, characterized in that: The following steps are involved: (1) Sampling and cutting: Cut a certain length of samples from the head and tail of the hot bimetallic thin strip continuously, and cut the samples into two horizontal edges on the human side and the machine side, and a strip in the middle; (2) Stamping: placing the strip obtained by slitting in step (1) in a stamping die to stamp out a spherical cap-shaped sample concave toward the active layer; (3) Measuring the temperature / force of the sample: Testing the temperature or force of the sudden jump / recovery of the spherical crown shape sample in step (2), recording the corresponding test values, and calculating the range as an indicator for evaluating the transverse and longitudinal non-uniformity of the sample; The length of the strip in step (1) is 1-10 meters and the width is 2-50 millimeters. The arc diameter D of the spherical crown-shaped sample in step (2) is ≤50 mm; The ratio of the chord height to the thickness of the spherical cap shaped sample in step (2) is 2-7; The temperature / force measurement method in step (3) comprises the following steps: Place the formed disc in a silicone oil tank with a heating device and slowly heat it to the set temperature. There is a temperature measuring device in the silicone oil tank to detect the temperature to observe the flipping temperature of the sample after forming. After flipping, record the flipping temperature as the "jump temperature". Then turn off the power and let the silicone oil tank slowly cool down to room temperature. Observe the recovery flipping process during the process and record the temperature at that time as the "recovery temperature"; The formed disc is fixed in position on two feature tools with round holes, placed in a container or silicone oil tank with a heating and constant temperature device, and the center of the disc is pressed down with a top pin with a spring or sensor to obtain the pressure value when the disc is flipped, and recorded as the "jump force". After flipping, change the direction and test again, record the pressure value of the second flip, and record it as the "return force".

2. The method for testing uniformity of hot bimetallic thin strips for disc-shaped elements according to claim 1, characterized in that: The certain length in step (1) is 1 m.

3. The method for testing uniformity of hot bimetallic thin strips for disc-shaped elements according to claim 1, characterized in that: The width W of the strip in step (2) is 5 to 30 mm.

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