Manganese copper alloy with negative temperature coefficient of resistance, manufacturing method and applications

Abstract

The present invention relates to a manganese copper alloy with a negative temperature coefficient of resistance, a manufacturing method thereof, and its applications. The alloy components are 10% to 15% Mn, 2% to 5% Ni, 1% to 5% additional element X, and the remainder Cu; Mn, Ni, and X are all dissolved in a copper-based solid solution with a face-centered cubic structure. The resistivity of this alloy is 0.4 to 0.5 μΩ·m, and the average temperature coefficient of resistance is -60 to -100×10. -6 / ℃ (-20 to 120℃) and the thermoelectric power against copper is ≦0.5μV / ℃, making it suitable for high-precision shunt resistors fabricated using joining and welding technology.

Description

[Technical Field]

[0001] The present invention relates to the field of metallic materials, and more particularly to a manganese-copper alloy with a negative temperature coefficient of resistance, its manufacturing method and application. [Background technology]

[0002] Since its invention in 1888, manganese copper alloys have been widely used in current sensing resistors due to their excellent electrical properties. Among them, manganin (12% Mn, 2-4% Ni, the remainder Cu) is the classic manganese copper alloy that is still in use today. It corresponds to two types of the national standard, 6J12 and 6J13, and has become the first choice for precision resistors due to its relatively low temperature coefficient of resistance, thermoelectric power relative to copper, relatively good long-term resistance stability, and excellent processability. Its temperature coefficient of resistance is generally -20~20×10 in the range of 10~60℃. -6 / ℃.

[0003] In recent years, shunt resistors have been used in electronic current detection for new energy vehicles, such as power battery packs and charging stations, and the operating temperature range of the galvanometer resistors is required to reach -20 to 120°C. The operating current is generally between 1 and 100A, and the short-term load requires 2 to 300A. The vehicle startup current can reach 1500A. In the power battery pack BMS system, and in extreme situations: when the vehicle is running, the sustained current requires 100 to 300A, and when stationary, the current is only a few milliamperes, and accurate detection is required.

[0004] Therefore, in order to suppress the temperature rise of shunt resistors and reduce power consumption under such application conditions of large currents and wide temperature ranges, precision resistance alloys have become the first choice for such shunt resistors due to their good thermal conductivity, low power consumption, low temperature coefficient of resistance, and low thermoelectric power relative to copper.

[0005] Considering issues such as detection accuracy, heat generation, and power consumption, shunt resistor resistance values ​​are generally designed to be less than 1 milliohm, such as 0.1 or 0.25 milliohms. Lowering resistance values ​​in galvanic circuits places higher requirements on the temperature coefficient of resistance of resistors and resistor alloys, such as thicker resistors (typically around 2 mm). Due to the increased resistor thickness, it is difficult to fabricate shunt resistors using traditional processes such as plating, riveting, and etching. Therefore, the mainstream process for manufacturing shunt resistors in high-current circuits is welding, using electron beam or laser welding. However, this welding process requires a large amount of energy, and inevitably forms a molten zone and a heat-affected zone at the joint interface, resulting in changes in the alloy composition and metallographic structure on both sides of the resistor layer, significantly increasing the temperature coefficient of resistance of the resistor.

[0006] This welding technique is used to manufacture shunt resistors, with copper electrodes on both sides, and resistors 6J12 and 6J13 are selected and joined. However, the temperature coefficient of resistance of pure copper used for the copper electrodes is 4000 × 10 -6 / ℃, and the temperature coefficient of resistance of the welded joint is usually 500×10 -6 / ℃, and the absolute value of the resistor temperature coefficient is small, but due to the presence of copper electrodes and welds, the overall temperature coefficient of the shunt resistor is 100×10 -6 / ℃ or more, it is difficult to meet the demand for high-precision current detection.

[0007] An improved manganese copper alloy with a negative temperature coefficient of resistance over a wide temperature range is used, and the shunt resistance is offset and compensated for during design by the resistance of the copper with a positive temperature coefficient of resistance at the electrode site and the improved manganese copper alloy with a negative temperature coefficient of resistance in the resistor, forming a temperature coefficient of resistance close to zero for the entire shunt resistance, which greatly improves the accuracy of current detection in the shunt circuit.

[0008] The design concept of conventional precision resistance alloys is based on the idea that the smaller the absolute value of the temperature coefficient of resistance, the better. The ΔR / RT curve of conventional manganese copper alloys (such as 6J12) shows a typical parabolic curve as shown in Figure 3, and the lowest TCR appears near the apex of the parabola, generally between 10 and 60°C.

[0009] As a well-known technique, the electrical properties of metal materials all follow the energy band theory, and their average temperature coefficient of resistance generally exhibits a positive temperature coefficient. Among them, pure metals with good conductivity have a temperature coefficient of several thousand × 10 -6 / ℃, for example, the temperature coefficient of resistance of copper is 4000×10 -6 / ℃, and the temperature coefficient of resistance of Ni is 6000×10 -6 / ℃ or more, and the resistance alloy can be designed with additive elements to reduce the temperature coefficient of resistance to about 0, but this requires a temperature coefficient of resistance of -50×10 -6 No alloy number has yet been found that can reduce the temperature coefficient of resistance below ±20×10 / °C. The lowest temperature coefficient of resistance between 20 and 60°C for some typical manganese copper alloys (e.g., 6J8, 6J12, and 6J13) is ±20×10 -6 / ℃.

[0010] Another manufacturing method for precision resistors is the film resistor process. Film resistors made using electronic slurry can be formed into NCR resistors by adjusting the slurry formula. However, the internal structure of resistors made using slurry cannot be dense, and there are many holes and cavities. Under high current conditions, heat dissipation is poor, heat generation is large, power consumption is high, and noise is loud, which cannot meet the application needs of this field.

[0011] The design of shunt resistors is similar to that of series circuits. To reduce the temperature coefficient of resistance of the entire shunt resistor, the precision resistor alloy selected for the resistor must have a large negative temperature coefficient of resistance over a wide temperature range. This necessitates the development of an improved manganese-copper alloy with a wide temperature range negative temperature coefficient of resistance. Summary of the Invention [Problem to be solved by the invention]

[0012] The objective of the present invention is to provide a manganese-copper alloy with a negative temperature coefficient of resistance, a manufacturing method thereof, and its use. The resistivity of this alloy is 0.4 to 0.5 μΩ m, and the average temperature coefficient of resistance is -60 to -100 × 10 -6 / ℃ (-20 to 120℃), and thermoelectric power against copper ≦0.5μV / ℃. It is suitable for producing shunt resistors with a negative temperature coefficient of resistance over a wide temperature range, and is particularly suitable for precision shunt resistors produced by bonding and welding technology. [Means for solving the problem]

[0013] Technical solution of the present invention:

[0014] The manganese copper alloy with a negative temperature coefficient of resistance has a mass percent content of 10% to 15% Mn, 2% to 5% Ni, 1% to 5% additional element X, and the balance Cu; Mn, Ni, and X are all dissolved in a copper-based solid solution with a face-centered cubic structure.

[0015] The additional element X is a combination of two or more of V, Sn, Si, Fe, Ce, La, Ge, and Ga.

[0016] The combined mass percent contents of the additional elements X are 0.6% to 2% V, 0.6% to 2% Sn, 0.7% to 4% Si, 0.5% to 1% Fe, 0.6% to 1% Ce, 0.6% to 1% La, 0.5% to 1% Ga, and 0.5% to 1% Ge, and the total mass percent content of the additional elements X is 1% to 5%.

[0017] In a preferred technical solution, the additive element X is Sn, Si, Fe, Ce, or Ge.

[0018] In a preferred technical solution, the additive element X is V, Si, Fe, La, or Ga.

[0019] The method for producing the alloy includes the following steps:

[0020] 1) Vacuum melting

[0021] 1. The alloy of any one of claims 1 to 5 is prepared by melting and casting the alloy in a suitable ratio under vacuum or other inert protective conditions to obtain an ingot;

[0022] 2) Homogenizing annealing

[0023] The ingot is forged into a slab blank, which is then heat treated at 800-950°C for 30 minutes to 4 hours, and then immediately water-cooled;

[0024] 3) Slab blank processing

[0025] The slab blank treated by homogenizing annealing is cold rolled to obtain a slab;

[0026] 4) Intermediate recrystallization annealing

[0027] Slab vacuum <10 -2 ·Pa, temperature 750℃~850℃, time 30 minutes~4 hours, cooling rate ≧30℃ / sec, the first recrystallization annealing condition;

[0028] 5) Cold rolling and recrystallization annealing of the finished product

[0029] After cold rolling the recrystallization annealed slab, a vacuum of <10 -2 The second recrystallization annealing is carried out under the conditions of Pa, temperature 650°C to 800°C, time 30 minutes to 3 hours, and cooling rate ≥ 50°C / sec.

[0030] Step 5) is rapidly cooled using liquid nitrogen.

[0031] The above alloys are used to make shunt resistors.

[0032] The present invention uses the composition of (6J12, 6J13) and adds elements to adjust the temperature coefficient of resistance (ΔR / RT) curve, changing its parabolic characteristics to a ΔR / RT curve that is close to a straight line with a negative slope within a relatively large temperature range, significantly expanding the temperature range of the resistance temperature coefficient of the alloy and increasing the resistance temperature coefficient to -60~-100×10 -6 / ℃, which is of great practical significance to the accuracy of automotive electronic current detection.

[0033] The main effects of each element in the added element X on the ΔR / RT curve are as follows:

[0034] By adding elements such as Fe, Si, Al, Sn, and V, and then using appropriate processing techniques to fully dissolve these elements in a copper-based face-centered cubic solid solution, the crystal structure and lattice constant of the ordered solid solution can be altered, thereby affecting the number of free electrons, electron scattering, and lattice vibration characteristics of the alloy, resulting in an extraordinary decrease in resistance as the alloy temperature increases.

[0035] The addition of rare earth elements such as Ce and La can not only purify the alloy, but also form rare earth oxides during the alloying process, which further reduces the temperature coefficient of resistance of the entire alloy. The addition of Ce and La, which have large atomic radii, can also make the alloy solid solution more stable, thereby improving the long-term resistance stability of the alloy.

[0036] The addition of elements such as Ge and Ga can improve the resistance stability of the alloy, while avoiding the tendency for the addition of large amounts of elements such as Fe, Si, Sn, and V to significantly increase the thermoelectric power of the alloy to copper. This allows the alloy to maintain a thermoelectric power of copper of ≦0.5μV / ℃, thereby meeting the requirements for high-precision measurement.

[0037] The component contents and combinations of the additive element X in the present invention are 0.6%-2% V or Sn, 0.7%-4% Si, 0.5%-1% Fe, 0.6%-1% Ce or La, 0.5%-1% Ga or Ge, and the total mass percentage is 1%-5%; where only one of the three element groups V or Sn, Ce or La, Ga or Ge is selected.

[0038] The manufacturing process of the alloy in the present invention is carried out according to the conventional process, and the typical process is as follows:

[0039] Because the alloy contains many additive elements, the most important feature of the alloy manufacturing method in the present invention is the temperature and cooling rate during heat treatment, so as to ensure a sufficient temperature to fully dissolve the solid solution and to freeze the solid solution into the alloy matrix by rapid cooling, thereby ensuring the beneficial effects of the additive elements. Otherwise, the improved manganese copper alloy in this patent will have poor plasticity, be difficult to process, and the electrical properties after the alloy has precipitated in large amounts will not meet the electrical property requirements set forth in the claims, making it difficult to achieve its beneficial effects.

[0040] (1) Uniform heat treatment process: The alloy ingot is heat treated at 800°C to 950°C for 30 minutes to 4 hours, and then immediately water-cooled;

[0041] (2) Intermediate recrystallization annealing process: Recrystallization annealing is performed using a vacuum annealing furnace, and the vacuum degree is 10 -2 Pa or less, the heat treatment temperature is 750℃ or more and 850℃ or less, the time is 30 minutes or more and 4 hours or less, and the cooling rate is ≥ 30℃ / s;

[0042] (3) Final recrystallization annealing process: Recrystallization annealing is performed using a vacuum annealing furnace, and the vacuum degree is 10 -2 Pa or less, the heat treatment temperature is 650℃ or more and 800℃ or less, the time is 30 minutes or more and 3 hours or less, and the cooling rate is ≥ 50℃ / s; [Brief explanation of the drawings]

[0043] [Figure 1]FIG. 1 shows the ΔR / RT curve of the modified manganese copper alloy with a negative temperature coefficient of resistance according to the present invention.

[0044] [Figure 2] FIG. 2 is a process map for producing the alloy of the present invention.

[0045] [Figure 3] Figure 3 shows the ΔR / RT curve for the 6J12 manganese copper alloy. DETAILED DESCRIPTION OF THE INVENTION

[0046] Hereinafter, embodiments of the present invention will be described in detail.

[0047] Example 1: The mass percentages of the alloy components were 11% to 13% manganese, 3% to 5% nickel, 1.5% Sn, 1.5% Si, 0.7% Fe, 0.7% Ce, 0.5% Ge, and the balance Cu.

[0048] Example 2: The mass percentages of the alloy components were 13% to 15% manganese, 1% to 3% nickel, 1.8% V, 0.8% Si, 1.0% Fe, 0.6% La, 0.5% Ga, and the balance Cu.

[0049] Example 3: The mass percentages of the alloy components were 12% to 14% manganese, 2% to 4% nickel, 1.0% Sn, 1.0% Si, 0.5% Fe, 1.0% Ce, 0.7% Ge, and the balance Cu.

[0050] Each component is collected in the blending ratio described in any of Examples 1 to 3 above, and produced by the following method (see Figure 2):

[0051] The melting was carried out using a vacuum induction melting furnace. -2 ~10 -3After evacuating to 100 Pa, electricity is applied, and after the alloy is melted, it is thoroughly stirred to remove gas, and then an inert protective gas such as argon gas is passed through it, and after it has settled, it is finally cast into a water-cooled copper mold to form an ingot; the ingot is forged into a 40 mm thick slab blank, which is then subjected to the following processes;

[0052] 1) The thick slab blank obtained in Example 1 of the above step is placed in a cart furnace and subjected to homogenization annealing at an annealing temperature of 920°C for 3.5 hours. After leaving the furnace, it is immediately water-cooled. After that, the blank is surface-treated, and then placed in a blank rolling mill for cold rolling to a thickness of 4 mm. Then, it is subjected to recrystallization annealing in a vacuum annealing furnace at a vacuum degree of 10°C. -2 Pa or less, heating temperature 850 ° C, heating time 3 hours, then use liquid nitrogen to rapidly cool, cooling rate ≥ 30 ° C / sec, after leaving the furnace, enter into a four-roll cold rolling mill to roll the finished product, and after rolling to 2.0 mm, enter into a vacuum annealing furnace again to perform recrystallization annealing, vacuum degree of vacuum annealing furnace 10 -2 The heating temperature is 800°C or less, and after 2 hours of heating, liquid nitrogen is used for rapid cooling at a cooling rate of 50°C / s or more. The finished product is obtained after annealing. The electrical property parameters of the finished product sampling test are shown in the table below.

[0053] 2) The thick slab blank obtained in Example 2 of the above step is placed in a cart furnace and subjected to homogenization annealing at an annealing temperature of 900°C for 3.5 hours. After leaving the furnace, it is immediately water-cooled. After that, the blank is surface-treated, and then placed in a blank rolling mill for cold rolling to a thickness of 4 mm. Then, it is subjected to recrystallization annealing in a vacuum annealing furnace at a vacuum degree of 10°C. -2 Pa or less, heating temperature 800 ° C, heating time 3 hours, then use liquid nitrogen to rapidly cool, cooling rate ≥ 30 ° C / sec, after leaving the furnace, enter into a four-roll cold rolling mill to roll the finished product, and after rolling to 2.0 mm, enter into a vacuum annealing furnace again to perform recrystallization annealing, vacuum degree of vacuum annealing furnace 10 -2 The heating temperature is 750°C or less, and after 2 hours of heating, liquid nitrogen is used for rapid cooling at a cooling rate of 50°C / s or more. The finished product is obtained after annealing. The electrical property parameters of the finished product sampling test are shown in the table below.

[0054] Comparative example: Referring to the national standard "GB / T 6145-2010 Manganin or Constantan wire, sheet, and rolled wire for precision electrical resistance," strips of 6J12 and 6J13 are manufactured using conventional techniques, and electrical performance tests are conducted on samples of the finished products, as shown in the table below.

[0055] Electrical performance testing:

[0056] The resistivity test is based on the national standard "GB / T 6146 Test Method for Resistivity of Precision Resistor Alloys", the temperature coefficient of resistance test is based on "GB / T 6148 Test Method for Temperature Coefficient of Resistance of Precision Resistor Alloys", and the thermoelectric power test against copper is based on "GB / T 6147 Test Method for Thermoelectric Power of Precision Resistor Alloys". The electrical property test results of the above-mentioned Examples 1-3 and Comparative Examples 6J12 and 6J13 are as shown in the table below:

[0057] [Table 1]

[0058] According to the applicant's experimental verification, the temperature range of the average temperature coefficient of resistance of the alloy of the present invention is -20 to 120°C, and the temperature coefficient of resistance curve (ΔR / RT curve) in this temperature range is close to a negative line (see Figure 1), the resistivity is 0.4 to 0.5 μΩ m, and the average temperature coefficient of resistance is -60 to -100 × 10 -6 / ℃ (-20~120℃), thermoelectric power against copper ≦0.5μV / ℃. Using conventional alloy melting and pressure processing techniques, it can be easily processed into wire or strip and then used with joining and welding techniques to produce shunt resistors.

Claims

1. A manganese copper alloy having a negative temperature coefficient of resistance, characterized in that the alloy components have a mass percent content of 10% to 15% Mn, 2% to 5% Ni, 1% to 5% of an additional element X, and the balance Cu, and that Mn, Ni, and X are all dissolved in a copper-based solid solution having a face-centered cubic structure.

2. 2. The alloy according to claim 1, wherein the additional element X is a combination of two or more of V, Sn, Si, Fe, Ce, La, Ge, and Ga.

3. 3. The alloy of claim 2, wherein the combined mass percent content of each of the additional elements X is 0.6%-2% V, 0.6%-2% Sn, 0.7%-4% Si, 0.5%-1% Fe, 0.6%-1% Ce, 0.6%-1% La, 0.5%-1% Ga, and 0.5%-1% Ge, with the total mass percent content of the additional elements X being 1%-5%.

4. 3. The alloy of claim 2, wherein the additional element X is Sn, Si, Fe, Ce, or Ge.

5. 3. The alloy according to claim 2, wherein the additional element X is V, Si, Fe, La, or Ga.

6. A method for producing an alloy according to any one of claims 1 to 5, characterized in that it comprises the following steps: 1) Vacuum melting 1. Taking the alloy components according to any one of claims 1 to 5 in the blending ratio, melting and casting them under vacuum or other inert protective conditions to obtain an ingot; 2) Homogenizing annealing The ingot is forged into a slab blank, and heat treated at 800°C to 950°C for 30 minutes to 4 hours, followed by immediate water quenching; 3) Slab blank processing The slab blank treated by homogenizing annealing is cold rolled to obtain a slab; 4) Intermediate recrystallization annealing Slab vacuum <10 －２ Pa, a temperature of 750°C to 850°C, a time of 30 minutes to 4 hours, and a cooling rate of 30°C / sec or more; 5) Cold rolling and recrystallization annealing of the finished product After cold rolling the recrystallization annealed slab, a vacuum of <10 －２ The second recrystallization annealing is carried out under the conditions of Pa, temperature 650° C. to 800° C., time 30 minutes to 3 hours, and cooling rate ≧50° C. / sec.

7. 7. The method according to claim 6, wherein the cooling in step 5) is performed using liquid nitrogen for rapid cooling.

8. Use of an alloy according to any one of claims 1 to 5 for making a shunt resistor.

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