Large-size high-precision torsion sensor elastomer and preparation method thereof

Abstract

The application discloses a large-size high-precision torque sensor elastomer, which comprises C, Si, Mn, P, S, Cr, Ni, Mo and Fe. The preparation method comprises a vacuum arc furnace smelting process, a forging and post-forging normalizing and high-temperature tempering process, a rough machining process, a quenching and tempering heat treatment process, a cold treatment process and a finishing process, wherein the finishing process is performed according to the size requirement of the sensor elastomer parts, and a vibration aging stress relief process. The application removes residual stress and strengthens and stabilizes the sensor material structure through three aging processes of heat treatment aging, cold treatment aging and external field vibration aging. The elastomer prepared by the method combines good structure stability, a small thermal expansion coefficient and excellent comprehensive performance, can meet the use requirements of large-size high-precision torque sensor elastomers of different specifications, can work in different atmospheric environments, and can be used for mass production of elastomer materials.

Description

Technical Field

[0001] This invention relates to a torque sensor, and more specifically to an elastomer for the torque sensor and its preparation method. Background Technology

[0002] A torque sensor is a precision, high-accuracy thermal measurement instrument that converts torsional torque signals into electrical signals. It is primarily used to measure various torques, speeds, and power. Widely used in weaponry, shipbuilding, aviation, aerospace, and other industries, it can be applied in various complex environments. The elastomer is the core component of a torque sensor, and the primary factor affecting the technical indicators of the elastomer material is its microstructure stability and overall performance. Material selection and heat treatment methods are the most important factors influencing the torque sensor elastomer. The fine and stable structure of these microstructures, including the content of retained austenite, the morphology of martensite transformation, and the distribution of carbide morphology, are all affected by heat treatment technology. This is especially true for torque sensors of different sizes, significantly impacting accuracy, sensitivity, and stability. Internationally, the materials for large-size torque sensor elastomers are strictly regulated due to commercial secrets and vested interests, and there are few domestic reports on the research and manufacturing technology of stainless steel elastomer materials. In particular, basic research on elastomers is limited, and their composition, smelting processes, and heat treatment processes are largely unknown.

[0003] In recent years, with the development of torque sensor technology, the microstructural stability and overall performance of materials at the microscale have gradually become a hot topic in scientific research. Due to the scale effect, the long-term stability of materials at the microscale is closely related to their macroscopic overall performance. Further research is needed on methods to regulate material stability and optimize overall performance through a series of thermal treatment techniques to reveal the essential mechanism of its stability.

[0004] Chinese invention patent document CN 104451423A discloses a stainless steel elastomer material for a weighing sensor and its heat treatment method. The stainless steel elastomer material for the weighing sensor has the following composition and mass percentages: C≤0.06%, Si≤1.35%, P≤0.035%, S≤0.03%, Mn≤1.0%, Cr 15.0~17.0%, Ni 4.50~8.0%, Cu 3.50~5.50%, Nb 0.15~0.45%, with the balance being Fe. The heat treatment method includes: cleaning; solution treatment; cryogenic treatment; and aging treatment. After heat treatment, this stainless steel exhibits excellent mechanical properties, with a hardness reaching HRC40~45 and a tensile strength reaching 135 kg / mm². 2 The coefficient of linear expansion is 11.0 × 10⁻⁶. -6 / ℃, comparable to alloy steel 40CrNiMoA.

[0005] Chinese invention patent document CN 10143048B discloses a method for reducing the hysteresis error of precipitated martensitic stainless steel elastomers. The method includes: solution treatment: heating the bar stock to 1040℃±10℃ at a rate of 5℃ / min to 30℃ / min, holding for 1 to 4 hours, and then forcibly cooling to room temperature; cryogenic treatment: immersing the forcibly cooled bar stock in liquid nitrogen at a temperature of -70℃ to -90℃ for 2.5 to 6 hours; deformation processing: stretching or compressing the cryogenically cooled bar stock at room temperature at a rate of ≤5mm / s, controlling the elongation or compression rate along the stretching or compressing direction to 1.0% to 5.0%; and aging treatment: placing the deformed bar stock in a furnace at a temperature not exceeding 200℃, heating to 480℃±5℃ at a rate of 5℃ / min to 30℃ / min, and holding for 2.5 to 5 hours.

[0006] The stainless steel elastomer materials and heat treatment methods disclosed above are only applicable to weighing sensors. Therefore, there is a need to develop an elastomer material and preparation method suitable for large-size torque sensors. Summary of the Invention

[0007] The technical problem to be solved by this invention is: how to improve the resistance of precipitated martensitic stainless steel to micro-region plastic deformation and reduce the hysteresis error of the weighing sensor.

[0008] To address the aforementioned problems, this invention provides a large-size, high-precision torque sensor elastomer, the composition of which comprises, by mass percentage: C 0.3%-0.35%, Si≤0.8%, Mn≤1.0%, P≤0.02%, S≤0.02%, Cr 12%-14%, Ni≤0.6%, Mo 1.0%-1.2%, and the balance Fe.

[0009] The present invention also provides a method for preparing the above-mentioned large-size, high-precision torque sensor elastomer, comprising the following steps:

[0010] Step 1) Vacuum arc furnace melting process: The raw materials are melted in a vacuum arc furnace to make elastic materials that meet the composition and forging requirements;

[0011] Step 2) Forging and post-forging normalizing and high-temperature tempering process: Forging hot working is used to change the shape of the billet and eliminate defects generated in the metal during the smelting process. Post-forging normalizing and high-temperature tempering optimize the microstructure and homogenize the grain size.

[0012] Step 3) Rough machining process: The blank is rough machined according to the size requirements of the sensor elastomer to obtain the rough elastomer product;

[0013] Step 4) Quenching and tempering heat treatment process: The crude elastomer is placed in a vacuum gas quenching furnace for heating and heat preservation, and then subjected to high-pressure gas quenching to room temperature.

[0014] Step 5) Cold treatment process: Place the quenched and tempered elastomer into the effective area of ​​the cold treatment chamber for cold treatment, and after the cold treatment is completed, warm it to room temperature in the air.

[0015] Step 6) Finishing process: The elastomer is finished according to the part size requirements of the sensor elastomer;

[0016] Step 7) Vibration aging stress relief process: Use a residual stress analyzer to monitor residual stress in each direction, and use vibration aging stress relief equipment to relieve stress.

[0017] Preferably, the defects in step 2) include as-cast porosity.

[0018] Preferably, in step 2), the normalizing temperature is 850-900℃ and the tempering temperature is 550-620℃.

[0019] Preferably, in step 4), the temperature uniformity of the vacuum air quenching furnace is less than ±5℃. After placing the billet in the effective area of ​​the vacuum air quenching furnace, the staged heating involves raising the temperature to 650℃ and holding it at 850℃ before raising it to 1020℃.

[0020] Preferably, in step 4), the high-pressure gas quenching is performed by tempering at 250°C for a holding time of not less than 300 minutes, followed by water cooling to room temperature.

[0021] More preferably, the cooling medium for the high-pressure gas quenching is an inert gas, and the gas cooling pressure is not greater than 15 Pa.

[0022] More preferably, the water cooling temperature is controlled at 25-60℃, and the water cooling time is no more than 10 minutes.

[0023] Preferably, in step 5, the temperature uniformity of the effective area of ​​the cold treatment chamber is no greater than ±2℃; the cold treatment involves lowering the temperature to -80℃ within 10 to 30 minutes, and then maintaining the temperature for 60 minutes.

[0024] Preferably, the Rockwell hardness of the elastomer of the large-size high-precision torque sensor is: HRC 55±1.5, impact energy 10±0.5J, yield strength 1600MPa, ultimate tensile strength 1990MPa, elongation 12%~16%, and coefficient of thermal expansion 7.8×10⁻⁶. -6 K -1～ 9.8×10 -6 K -1 .

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] This invention utilizes martensitic reinforced stainless steel and a three-stage thermal processing technique—heat treatment aging, cryogenic aging, and external vibration aging—to successfully fabricate elastomers suitable for large-size, high-precision torque sensors of various specifications. The resulting material exhibits a stable microstructure with low residual stress; high precision; good strength-toughness matching; low coefficient of thermal expansion; and excellent overall performance. The core steps include heat treatment, cryogenic treatment, and stress relief techniques. The elastomers prepared using this method possess excellent overall performance and can meet the requirements for torque sensors of different sizes and specifications in certain special applications. Detailed Implementation

[0027] To make the present invention more apparent and understandable, preferred embodiments are described in detail below.

[0028] Example 1

[0029] A high-precision torque sensor elastomer with a diameter of 540mm has the following components and their mass percentages: C 0.35%, Si 0.8%, Mn 1.0%, P≤0.01%, S≤0.01%, Cr 12%, Ni 0.5%, Mo 1.0%, with the balance being Fe.

[0030] The preparation method is as follows:

[0031] Step 1: Use a vacuum electric arc furnace melting method to process the raw materials into elastic materials that meet the composition and forging requirements;

[0032] Step 2: Use forging hot working to change the shape of the billet, and then normalize and temper at high temperature after forging to optimize the microstructure and homogenize the grains; normalize at 860℃ and temper at 620℃.

[0033] Step 3: Perform rough machining based on the dimensions of the sensor elastomer;

[0034] Step 4: Place the forged elastomer in a vacuum quenching furnace and heat it in stages to 1020℃ for 70 minutes; then quench it with liquid nitrogen at high pressure to room temperature; then temper it at 260℃ for at least 300 minutes, and water cool it to room temperature, with the water temperature controlled at 25-60℃.

[0035] Step 5: Place the quenched elastomer into a cold treatment chamber for cold treatment. After the cold treatment is completed, allow it to warm up to room temperature in the air. During the cold treatment, lower the temperature to -80℃ within 30 minutes. The holding time for the cold treatment is 60 minutes.

[0036] Step 6: Perform precision machining according to the dimensional requirements of the sensor elastomer parts;

[0037] Step 7: Use a residual stress analyzer to monitor residual stress in each direction, and use a directional vibration aging stress relief device to relieve stress.

[0038] After treatment, the resulting elastomer has the following Rockwell hardness: HRC 55.5, impact energy: 10.5 J, yield strength: 1600 MPa, ultimate tensile strength: 1970 MPa, elongation: 16%, and coefficient of thermal expansion: 7.8 × 10⁻⁶. -6 K -1 .

[0039] Example 2

[0040] A high-precision torque sensor elastomer with a diameter of 450mm has the following components and their mass percentages: C 0.32%, Si 0.6%, Mn 0.8%, P≤0.01%, S≤0.01%, Cr 14%, Ni 0.4%, Mo 1.2%, with the balance being Fe.

[0041] The preparation method is as follows:

[0042] Step 1: Use a vacuum electric arc furnace melting method to process the raw materials into elastic materials that meet the composition and forging requirements;

[0043] Step 2: Use forging hot working to change the shape of the billet, and then normalize and temper at high temperature after forging to optimize the microstructure and homogenize the grain size; normalize at 880℃ and temper at 600℃.

[0044] Step 3: Based on the dimensions of the sensor elastomer, and with an allowance, perform rough machining;

[0045] Step 4: Place the forged elastomer in a vacuum quenching furnace and heat it in stages to 1020℃ for 80 minutes; then quench it with liquid nitrogen at high pressure to room temperature; then temper it at 250℃ for at least 300 minutes, and water cool it to room temperature, with the water temperature controlled at 25-60℃.

[0046] Step 5: Place the quenched elastomer into the effective area of ​​the cold treatment chamber for cold treatment. After the cold treatment is completed, allow it to warm up to room temperature in the air. The temperature uniformity of the effective area of ​​the cold treatment chamber should be less than or equal to ±2℃. During the cold treatment, the temperature should be lowered to -80℃ within 10-30 minutes. The holding time for the cold treatment is 60 minutes.

[0047] Step 6: Perform precision machining according to the dimensional requirements of the sensor elastomer parts;

[0048] Step 7: Use a residual stress analyzer to monitor residual stress in each direction, and use a directional vibration aging stress relief device to relieve stress.

[0049] After treatment, the resulting elastomer has the following Rockwell hardness: HRC 56.5, impact energy: 11.5 J, yield strength: 1580 MPa, ultimate tensile strength: 1990 MPa, elongation: 15%, and coefficient of thermal expansion: 7.8 × 10⁻⁶. -6 K -1 .

Claims

1. A large-size, high-precision torque sensor elastomer, characterized in that, The composition includes, by mass percentage, 0.3%-0.35% C, ≤0.8% Si, ≤1.0% Mn, ≤0.02% P, ≤0.02% S, 12%-14% Cr, ≤0.6% Ni, 1.0%-1.2% Mo, and the balance Fe.

2. A method for preparing a large-size, high-precision torque sensor elastomer as described in claim 1, characterized in that, Includes the following steps: Step 1) Vacuum arc furnace melting process: The raw materials are melted in a vacuum arc furnace to make elastic materials that meet the composition and forging requirements; Step 2) Forging and post-forging normalizing and high-temperature tempering process: Forging hot working is used to change the shape of the billet and eliminate defects generated in the metal during the smelting process. Post-forging normalizing and high-temperature tempering optimize the microstructure and homogenize the grain size. Step 3) Rough machining process: The blank is rough machined according to the size requirements of the sensor elastomer to obtain the rough elastomer product; Step 4) Quenching and tempering heat treatment process: The crude elastomer is placed in a vacuum gas quenching furnace for heating and heat preservation, and then subjected to high-pressure gas quenching to room temperature. Step 5) Cold treatment process: The elastomer after quenching and tempering heat treatment is placed in the effective area of ​​the cold treatment chamber for cold treatment. After the cold treatment is completed, it is warmed to room temperature in the air. Step 6) Finishing process: The elastomer is finished according to the part size requirements of the sensor elastomer; Step 7) Vibration aging stress relief process: Use a residual stress analyzer to monitor residual stress in each direction, and use vibration aging stress relief equipment to relieve stress.

3. The preparation method according to claim 2, characterized in that, Defects in step 2) include as-cast porosity.

4. The preparation method according to claim 2, characterized in that, In step 2), the normalizing temperature is 850-900℃ and the tempering temperature is 550-620℃.

5. The preparation method according to claim 2, characterized in that, In step 4), the temperature uniformity of the vacuum air quenching furnace is less than ±5℃. After placing the billet in the effective area of ​​the vacuum air quenching furnace, the staged heating involves raising the temperature to 650℃ and 850℃ in sequence, holding it at that temperature, and then raising it to 1020℃.

6. The preparation method according to claim 2, characterized in that, In step 4), the high-pressure gas quenching is performed by tempering at 250°C for a holding time of not less than 300 minutes, followed by water cooling to room temperature.

7. The preparation method according to claim 6, characterized in that, The cooling medium for the high-pressure gas quenching is an inert gas, and the gas cooling pressure is no more than 15 Pa.

8. The preparation method according to claim 6, characterized in that, The water cooling temperature is controlled between 25-60℃, and the water cooling time is no more than 10 minutes.

9. The preparation method according to claim 2, characterized in that, In step 5, the temperature uniformity of the effective area of ​​the cold treatment chamber is no greater than ±2℃; the cold treatment involves lowering the temperature to -80℃ within 10 to 30 minutes, and then maintaining the temperature for 60 minutes.

10. The preparation method according to claim 2, characterized in that, The Rockwell hardness of the elastomer in the large-size, high-precision torque sensor is: HRC 55±1.5, impact energy 10±0.5J, yield strength 1600MPa, ultimate tensile strength 1990MPa, elongation 12%~16%, and coefficient of thermal expansion 7.8×10⁻⁶. -6 K -1～ 9.8×10 -6 K -1 .