A low expansion soft magnetic alloy and preparation method thereof

Abstract

The present invention relates to the technical field of soft magnetic alloy material preparation, and in particular to a low expansion soft magnetic alloy and a preparation method thereof. The chemical composition of the alloy is C 0.001-0.2, Ni 30-34, Co 2-6, Nb 0.05-0.5, Mo 0.1-0.5, Cu 0.05-0.5, Si<0.2, Mn<0.2, P<0.020, S<0.015, and the remainder is Fe and unavoidable impurities in terms of mass percentage; the soft magnetic alloy is prepared by the following steps: batching → vacuum induction melting electrode rod → vacuum consumable remelting → blanking, forging, machining → graded heat treatment; the expansion coefficient of the soft magnetic alloy is α≤1.0ppm / ℃ at ‑50-100℃. The alloy has a combination of high maximum magnetic permeability and low expansion coefficient, and is suitable for making parts with low expansion performance and high soft magnetic performance requirements, especially quartz accelerometer yoke iron.

Description

Technical Field

[0001] The invention relates to the technical field of soft magnetic alloy material preparation, and in particular to a low expansion soft magnetic alloy and a preparation method thereof. Background Art

[0002] Quartz accelerometers have the advantages of simple structure, small size, low cost and high precision. Yoke iron material is one of the key materials for quartz accelerometer torquer components, and its performance determines the accuracy of the quartz accelerometer.

[0003] Super Invar alloy has low expansion coefficient, α 20～100℃ The minimum can be less than 0.1ppm / ℃, but the soft magnetic properties are poor.

[0004] The Chinese invention patent application No. 2018116234727 previously filed by the applicant of the present application discloses "a high-strength, low-density, low-expansion iron-nickel alloy and a preparation method thereof". The chemical composition of the soft magnetic alloy is Ni28.0-40.0%, Co 3.0-5.0%, Ti 2.0-4.0%, Cu 0.4-1.4%, Mn 0.1-0.7%, C 0.15-0.40%, P≤0.010%, S≤0.010%, and the rest is Fe; the density of the expansion alloy is 7.8g / cm3; the expansion performance α 20～100℃ ≤0.5×10 -6 / ℃, can be used as ultra-low expansion alloy; the preparation method of the alloy is vacuum induction melting alloy → gas atomization powder making → SLM printing → preheating treatment → water quenching → finished product heat treatment; the preparation process is complicated. When the low expansion alloy prepared by this process is used as the yoke material of the accelerometer, due to its poor magnetic properties, it has an adverse effect on the accuracy and long-term stability of the accelerometer. Summary of the invention

[0005] The purpose of the present invention is to provide a low expansion soft magnetic alloy and a preparation method thereof, which improves the alloy composition on the basis of the prior art, simplifies the preparation method, and enables the alloy to have both excellent expansion performance and soft magnetic properties.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A low expansion soft magnetic alloy, the chemical composition of the alloy is C0.001-0.2, Ni 30-34, Co 2-6, Nb 0.05-0.5, Mo 0.1-0.5, Cu 0.05-0.5, Si<0.2, Mn<0.2, P<0.020, S<0.015, the rest is Fe and unavoidable impurities;

[0008] The soft magnetic alloy is prepared by the following steps: batching → vacuum induction melting electrode rod → vacuum consumable remelting → blanking, forging, machining → graded heat treatment;

[0009] The expansion coefficient α of the soft magnetic alloy is ≤1.0ppm / °C at -50 to 100°C.

[0010] The chemical composition of the alloy is C 0.001-0.02, Ni 30.0-34.0, Co 2.0-6.0, Nb 0.05-0.5, Mo 0.1-0.5, Cu 0.05-0.5, Si<0.2, Mn<0.2, P<0.020, S<0.015, and the rest is Fe and inevitable impurities.

[0011] The alloy has the following combination of expansion coefficient and magnetic properties: expansion coefficient α≤1.0ppm / ℃ at -50~100℃, maximum magnetic permeability μ m ≥20mH / m, coercive force Hc≤15A / m.

[0012] The alloy has the following combination of expansion coefficient, maximum magnetic permeability and coercive force: expansion coefficient α0.5~1.0ppm / ℃ at -50~100℃, maximum magnetic permeability μ m 20~40mH / m, coercive force Hc 4~10A / m.

[0013] The soft magnetic alloy is used for preparing yoke iron of quartz accelerometer.

[0014] A method for preparing the low expansion soft magnetic alloy as described above, the method comprising the following steps:

[0015] a) Ingredients: Ingredients are prepared according to the following raw material ratios (wt.%): C 0.001-0.2, Ni 30-34, Co 2-6, Nb 0.05-0.5, Mo 0.1-0.5, Cu 0.05-0.5, Si < 0.2, Mn < 0.2, P < 0.020, S < 0.015, and the rest is Fe;

[0016] b) Vacuum induction melting electrode rod: The alloy is melted in a vacuum induction furnace and cast into electrode rods. The vacuum degree of the melting process is ≤1Pa. Fe, Ni, Co, Nb, and Mo are directly put into the crucible as primary feeds; C and Cu are put into the hopper of the vacuum induction furnace as secondary feeds. After all the raw materials are cleared, they are refined for 20 to 30 minutes, and then the molten steel is cast into electrode rods in the vacuum chamber of the vacuum induction furnace;

[0017] c) Vacuum consumable remelting: After the electrode rod component analysis meets the requirements, the electrode rod surface is polished and vacuum consumable remelting is performed. During the melting process, constant drop control technology is used, and the vacuum degree is ≤0.1Pa;

[0018] d) Opening the blank, forging into bars, and processing the obtained forged bars into finished products;

[0019] e) Graded heat treatment: The finished product obtained in step d) is subjected to vacuum heat treatment, kept at 1170±10°C for 2-3 hours, then cooled to 870±10°C at a cooling rate of 100±10°C / hour and kept at this temperature for 1-2 hours, and then air-cooled out of the furnace.

[0020] In step c), the steel ingot is charged into a furnace at a temperature lower than 700°C, with a heating rate of ≤200°C / h, and after being kept at 1140±10°C for a suitable period of time, the ingot is opened and forged into bars of required specifications.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The alloy has a high maximum magnetic permeability and a low expansion coefficient, and is suitable for making parts with low expansion performance and high soft magnetic properties requirements (such as quartz accelerometer yoke).

[0023] By adding trace elements of Nb, Mo and Cu and then undergoing graded heat treatment, the alloy obtains better soft magnetic properties while maintaining a lower expansion coefficient.

[0024] The Fe-Ni-Co system is adopted, a certain amount of Nb is added to fix free carbon atoms, and the alloy expansion coefficient is reduced; a small amount of Mo and Cu are added to improve the stability of the alloy magnetic properties. The present invention aims to optimize the alloy element ratio, and through the optimized heat treatment process, the alloy has both excellent expansion performance and soft magnetic properties. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below in conjunction with the embodiments of the present invention.

[0026] A low expansion soft magnetic alloy, the chemical composition (wt.%) of the alloy is C≤0.2, Ni30-34, Co2-6, Nb0.05-0.5, Mo0.1-0.5, Cu0.05-0.5, Si<0.2, Mn<0.2, P<0.020, S<0.015, and the rest is Fe.

[0027] The role of the above alloying elements and the basis for alloy design are as follows:

[0028] Nb: fixes free C elements and reduces the expansion coefficient;

[0029] Mo: Improves the stability of alloy softness;

[0030] Cu: Similar to Mo;

[0031] Fe: matrix;

[0032] Si, Mn: control their content below 0.3%;

[0033] P, S: impurity elements, the lower the content, the better.

[0034] The soft magnetic alloy is prepared by the following steps: vacuum induction melting of alloy→blank opening, forging→heat treatment.

[0035] The preparation method of the soft magnetic alloy comprises the following steps:

[0036] a) The raw materials are proportioned, and the raw material proportion (wt.%) is C≤0.2, Ni30-34, Co2-6, Nb0.05-0.5, Mo0.1-0.5, Cu0.05-0.5, Si<0.2, Mn<0.2, P<0.020, S<0.015, and the rest is Fe.

[0037] b) Melting: A vacuum induction furnace is used to melt the alloy and cast it into electrode rods. The vacuum degree of the melting process is ≤1Pa. The burnout of alloy elements is strictly controlled to control the composition of the alloy within the design range. Among them, Fe, Ni, Co, Nb, and Mo are directly placed in the crucible as primary feeds; C and Cu are placed in the hopper of the vacuum induction furnace as secondary feeds. After all the raw materials are cleared, they are refined for 20 to 30 minutes, and then the molten steel is cast into electrode rods in the vacuum chamber of the vacuum induction furnace. After the electrode rod component analysis meets the requirements, the surface of the electrode rod is polished and vacuum consumable remelting is performed. Constant droplet control technology is used during the melting process, and the vacuum degree is ≤0.1Pa.

[0038] c) Billeting and forging

[0039] The steel ingot is charged into the furnace at a temperature lower than 700℃, with a heating rate of ≤200℃ / h. After being kept at 1140±10℃ for a suitable period of time, it is opened and forged into bars of required specifications.

[0040] d) Heat treatment

[0041] After the forged bars are directly processed into finished products, they are vacuum heat treated, kept at 1170±10℃ for 2-3 hours, then cooled to 870℃ at a cooling rate of 100℃ / hour and kept at that temperature for 1 hour, and then air-cooled out of the furnace.

[0042] Example 1

[0043] The chemical analysis results of the four alloy components smelted by vacuum induction furnace + vacuum consumable furnace are shown in Table 2:

[0044] Table 2 Chemical composition of molten alloy (mass percentage %)

[0045]

[0046] The processing technology used for the above alloy components is the same: vacuum induction melting electrode rod → vacuum consumable remelting → peeling and forging at 1140℃ → Φ42mm rod. Samples are taken from the rod and processed into test rings of φ40×φ32×5mm. The test rings are vacuum heat treated, kept at 1170±10℃ for 3 hours, then cooled to 870℃ at a cooling rate of 100℃ / hour and kept at this temperature for 1 hour, and then air-cooled out of the furnace.

[0047] The expansion performance and soft magnetic properties of the soft magnetic alloy with low expansion coefficient prepared by the above process are shown in Table 3. The expansion coefficient of the alloy is α≤1.0ppm / ℃ at -50~100℃, the maximum magnetic permeability μm≥20mH / m, and the coercive force Hc≤15A / m; the alloy material has good expansion and soft magnetic properties and has broad application prospects.

[0048] Table 3 Alloy expansion and soft magnetic properties

[0049]

[0050]

Claims

1. A low expansion soft magnetic alloy, characterized in that: The soft magnetic alloy is used for preparing a quartz accelerometer yoke, and the chemical composition of the soft magnetic alloy is C 0.001-0.2, Ni 30-34, Co 2-6, Nb 0.05-0.5, Mo0.1-0.5, Cu 0.05-0.5, Si<0.2, Mn<0.2, P<0.020, S<0.015, and the rest is Fe and unavoidable impurities; The soft magnetic alloy is prepared by the following steps: batching → vacuum induction melting electrode rod → vacuum consumable remelting → blanking, forging, machining → graded heat treatment; The soft magnetic alloy has the following combination of expansion coefficient, maximum magnetic permeability and coercive force: expansion coefficient α 0.5-1.0 ppm / °C at -50-100°C, maximum magnetic permeability μ m 20~40mH / m, coercive force Hc 4~10A / m.

2. The soft magnetic alloy according to claim 1, characterized in that: The chemical composition of the soft magnetic alloy is C 0.012, Ni 30.2-33.8, Co 2.18-5.91, Nb 0.07-0.48, Mo 0.12-0.48, Cu 0.08-0.46, Si 0.04-0.06, Mn 0.06-0.07, P 0.006-0.007, S 0.002-0.003, and the rest is Fe and inevitable impurities.

3. The soft magnetic alloy according to claim 2, characterized in that: The soft magnetic alloy has the following combination of expansion coefficient, maximum magnetic permeability and coercive force: expansion coefficient α 0.65-0.91 ppm / °C at -50-100°C, maximum magnetic permeability μ m 26~33mH / m, coercive force Hc 5.6~7.1A / m.

4. A method for preparing a low expansion soft magnetic alloy as claimed in claim 1, characterized in that: The method comprises the following steps: a) Ingredients: Ingredients are prepared according to the following raw material ratios (wt.%): C 0.001-0.2, Ni 30-34, Co 2-6, Nb 0.05-0.5, Mo 0.1-0.5, Cu 0.05-0.5, Si<0.2, Mn<0.2, P<0.020, S<0.015, and the rest is Fe; b) Vacuum induction melting electrode rod: The alloy is melted in a vacuum induction furnace and cast into electrode rods. The vacuum degree of the melting process is ≤1Pa. Fe, Ni, Co, Nb, and Mo are directly put into the crucible as primary feeds; C and Cu are put into the hopper of the vacuum induction furnace as secondary feeds. After all the raw materials are cleared, they are refined for 20 to 30 minutes, and then the molten steel is cast into electrode rods in the vacuum chamber of the vacuum induction furnace; c) Vacuum consumable remelting: After the electrode rod component analysis meets the requirements, the electrode rod surface is polished and vacuum consumable remelting is performed. During the melting process, constant drop control technology is used, and the vacuum degree is ≤0.1Pa; In step c), the steel ingot is charged into a furnace at a temperature lower than 700°C, the heating rate is ≤200°C / h, and after being kept at 1140±10°C for a suitable period of time, the ingot is opened and forged into bars of required specifications; d) Opening the blank, forging into bars, and processing the obtained forged bars into finished products; e) Graded heat treatment: The finished product obtained in step d) is subjected to vacuum heat treatment, kept at 1170±10°C for 2-3 hours, then cooled to 870±10°C at a cooling rate of 100±10°C / hour and kept at this temperature for 1-2 hours, and then air-cooled out of the furnace.

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