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

Abstract

The invention discloses a large-size high-precision torque sensor elastomer which comprises the following components: 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 finish machining process, wherein the finish machining process and the vibration aging destressing process are carried out according to the size requirement of the sensor elastomer part. According to the method, residual stress is removed and a sensor material structure is strengthened and stabilized through a three-stage aging process of heat treatment aging, cold treatment aging and external field vibration aging; the elastomer prepared by the method combines good structure stability, relatively small thermal expansion coefficient and excellent comprehensive performance, can meet the use requirements of different specifications, large sizes and high-precision torque sensor elastomers, can work in atmospheric environments of different atmospheres, and can be used for mass production of elastomer materials.

Description

Technical Field

[0001] The invention relates to a torque sensor, and in particular to an elastomer of the torque sensor and a preparation method thereof. Background Art

[0002] Torque sensor is a high-precision thermal precision detection instrument that converts torsional torque signal into electrical signal. It is mainly used to measure various torques, speeds and powers. It is widely used in weapons, ships, aviation, aerospace and various industries. It can be used in various complex environments. The torque sensor elastomer is the core component of the torque sensor. The primary factor affecting the various technical indicators of the elastomer material is the material organization stability and comprehensive performance. The material selection and heat treatment method are the most important factors affecting the torque sensor elastomer. The fine and stable structure of these microstructures, including the residual austenite content, martensite transformation organization morphology, and carbide morphology distribution, are all affected by the thermal processing technology. In particular, it has an important impact on the accuracy, low sensitivity and stability of torque sensors of different specifications and sizes. The international large-size torque sensor elastomer materials may be strictly sealed due to commercial secrets and interest relations, and there are few reports on the research and development and manufacturing technology of stainless steel elastomer materials in China. In particular, there is little basic research on elastomers, and their composition, smelting process, and thermal processing technology are all unknown.

[0003] Especially in recent years, with the development of torque sensor technology, the organization stability and comprehensive performance of materials at the microscopic scale have gradually become a hot topic in scientific research. Due to the influence of scale effect, the long-term stability of materials at the microscopic scale is closely related to the macroscopic comprehensive performance. The method of regulating the stability of materials and optimizing the comprehensive performance through a series of cold and hot treatment technologies urgently needs further research to reveal the essential mechanism of its stability.

[0004] The Chinese invention patent document with patent announcement number CN 104451423A discloses a stainless steel elastomer material for a weighing sensor and a heat treatment method thereof. The stainless steel elastomer material for the weighing sensor has the following components and their mass percentages: C≤0.06%, Si≤1.35%, P≤0.035%, S≤0.03%, Mn≤1.0%, Cr 15.0-17.0%, Ni4.50-8.0%, Cu 3.50-5.50%, Nb 0.15-0.45%, and the remainder is Fe. The heat treatment method includes: cleaning; solution treatment; cryogenic treatment; aging treatment. After heat treatment, the stainless steel has excellent mechanical properties, with a hardness of up to HRC40-45 and a strength limit of up to 135kg / mm 2 , linear expansion coefficient 11.0×10 -6 / ℃, equivalent to alloy steel 40CrNiMoA.

[0005] The Chinese invention patent document with patent announcement number CN 10143048B discloses a method for reducing the hysteresis error of a precipitated martensitic stainless steel elastomer, comprising the following steps: solution treatment: heating the bar material to 1040°C±10°C at a rate of 5°C / min to 30°C / min with the furnace, keeping the temperature for 1 to 4 hours, and forced cooling to room temperature; deep cooling: cooling the forced cooled bar material in liquid nitrogen at a temperature of -70°C to -90°C for 2.5 to 6 hours; deformation processing: stretching or compressing the deep cooled bar material at a rate of ≤5mm / sec at room temperature, and controlling the elongation or compression rate of the bar material in the tensile and compressive directions to 1.0% to 5.0%; aging treatment: placing the deformed bar material in a heating furnace at a temperature not higher than 200°C and heating the temperature to 480°C±5°C at a rate of 5°C / min to 30°C / min with the furnace, and keeping the temperature for 2.5 to 5 hours.

[0006] The stainless steel elastic material and heat treatment method disclosed above are only applicable to weighing sensors. Therefore, it is necessary to develop an elastic material and preparation method applicable to large-size torque sensors. Summary of the invention

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

[0008] In order to solve the above problems, the present invention provides a large-size high-precision torque sensor elastomer, whose components include, by mass percentage, C 0.3%-0.35%, Si≤0.8%, Mn≤1.0%, P≤0.02%, S≤0.02%, Cr12%-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: using a vacuum arc furnace melting method to make the raw material into an elastic material that meets the composition requirements and forging requirements;

[0011] Step 2), forging and post-forging normalizing and high-temperature tempering process: forging hot processing is used to change the shape of the billet, eliminate the defects of the metal produced during the smelting process, and post-forging normalizing and high-temperature tempering are used to optimize the microstructure and homogenize the grains;

[0012] Step 3), rough processing process: rough processing the blank according to the size requirements of the sensor elastic body to obtain a rough elastic body;

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

[0014] Step 5), cold treatment process: put the elastomer after quenching and tempering heat treatment into the effective area of ​​the cold treatment box for cold treatment, and return the temperature to room temperature in the air after the cold treatment;

[0015] Step 6), finishing process: finishing the elastic body according to the part size requirements of the sensor elastic body;

[0016] Step 7), vibration aging stress relief process: use a residual stress analyzer to monitor the residual stress in all directions, 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°C, and the tempering temperature is 550-620°C.

[0019] Preferably, in step 4), the temperature uniformity of the vacuum air quenching heating furnace is less than ±5°C, and after the billet is placed in the effective zone of the vacuum air quenching heating furnace, the temperature is sequentially increased to 650°C and 850°C for insulation and then increased to 1020°C for graded heating.

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

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

[0022] More preferably, the water cooling temperature is controlled at 25-60°C, 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 box is not greater than ±2°C; the cold treatment is to reduce the temperature to -80°C within 10 to 30 minutes and then keep it warm for 60 minutes.

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

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

[0026] The present invention uses martensite-strengthened stainless steel and successfully prepares high-precision torque sensor elastomers that can meet different specifications and large sizes by means of three-level hot and cold processing processes, namely heat treatment aging, cold treatment aging and external field vibration aging. The material structure has low residual stress and stability; high precision, good matching of strength and toughness, small thermal expansion coefficient and excellent comprehensive performance. The core steps include heat treatment process, cryogenic treatment process and stress relief technology. The elastomer prepared by this method has excellent comprehensive performance and can meet the needs of torque sensor elastomers of different sizes and specifications in certain special occasions. DETAILED DESCRIPTION

[0027] In order to make the present invention more clearly understood, preferred embodiments are described in detail as follows.

[0028] Example 1

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

[0030] The preparation method is as follows:

[0031] Step 1: using a vacuum arc furnace melting method to make the raw material into an elastic material that meets the composition requirements and forging requirements;

[0032] Step 2: Use forging hot working to change the shape of the billet, normalize after forging + high temperature tempering to optimize the microstructure and homogenize the grain size; 860℃ normalizing + 620℃ tempering;

[0033] Step 3, perform rough processing according to the size of the sensor elastic body;

[0034] Step 4: Place the forged elastomer in a vacuum gas quenching heating furnace, heat it to 1020°C in stages and keep it warm for 70 minutes; then quench it with liquid nitrogen high pressure gas to room temperature; then temper it at 260°C, the tempering holding time is not less than 300 minutes, and then cool it to room temperature with water, and the water temperature is controlled at 25-60°C;

[0035] Step 5, placing the quenched elastomer into a cold treatment box for cold treatment, and returning the temperature to room temperature in the air after the cold treatment; during the cold treatment, the temperature is reduced to -80°C within 30 minutes; the cold treatment insulation time is 60 minutes;

[0036] Step 6: Perform fine processing according to the size requirements of the sensor elastic parts;

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

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

[0039] Example 2

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

[0041] The preparation method is as follows:

[0042] Step 1: using a vacuum arc furnace melting method to make the raw material into an elastic material that meets the composition requirements and forging requirements;

[0043] Step 2: Use forging hot working to change the shape of the billet, normalize after forging + high temperature tempering to optimize the structure and homogenize the grain; 880℃ normalizing + 600℃ tempering;

[0044] Step 3: Rough machining is performed based on the size of the sensor elastic body and the allowance is added;

[0045] Step 4: Place the forged elastomer in a vacuum gas quenching heating furnace, heat it to 1020°C in stages and keep it warm for 80 minutes; then quench it with liquid nitrogen high pressure gas to room temperature; then temper it at 250°C, the tempering holding time is not less than 300 minutes, and then cool it to room temperature with water, and the water temperature is controlled at 25-60°C;

[0046] Step 5, placing the quenched elastomer in the effective area of ​​the cold treatment box for cold treatment, and returning the temperature to room temperature in the air after the cold treatment; the temperature uniformity of the effective area of ​​the cold treatment box is less than or equal to ±2°C; during the cold treatment, the temperature is reduced to -80°C within 10-30 minutes; the cold treatment insulation time is 60 minutes;

[0047] Step 6: Perform fine processing according to the size requirements of the sensor elastic parts;

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

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

Claims

1. A large-size high-precision torque sensor elastic body, characterized in that: The composition includes, 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.

2. A method for preparing a large-size high-precision torque sensor elastomer according to claim 1, characterized in that: The following steps are involved: Step 1), vacuum arc furnace melting process: using a vacuum arc furnace melting method to make the raw material into an elastic material that meets the composition requirements and forging requirements; Step 2), forging and post-forging normalizing and high-temperature tempering process: forging hot processing is used to change the shape of the billet, eliminate the defects of the metal produced during the smelting process, and post-forging normalizing and high-temperature tempering are used to optimize the microstructure and homogenize the grains; Step 3), rough processing process: rough processing the blank according to the size requirements of the sensor elastic body to obtain a rough elastic body product; Step 4), quenching and tempering heat treatment process: the crude elastomer is placed in a vacuum gas quenching heating furnace for heating and heat preservation treatment, and then high-pressure gas quenching is performed to room temperature; Step 5), cold treatment process: put the elastomer after quenching and tempering heat treatment into the effective area of ​​the cold treatment box for cold treatment, and return the temperature to room temperature in the air after the cold treatment; Step 6), finishing process: finishing the elastic body according to the part size requirements of the sensor elastic body; Step 7), vibration aging stress relief process: use a residual stress analyzer to monitor the residual stress in all directions, and use vibration aging stress relief equipment to relieve stress.

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

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

5. The preparation method according to claim 2, characterized in that: In the step 4), the temperature uniformity of the vacuum air quenching heating furnace is less than ±5°C. After the blank is placed in the effective zone of the vacuum air quenching heating furnace, the temperature is sequentially increased to 650°C and 850°C for insulation and then increased to 1020°C for staged heating.

6. The preparation method according to claim 2, characterized in that: In the step 4), the high pressure gas quenching is performed at 250° C., the tempering holding time is not less than 300 minutes, and then the steel is water-cooled to room temperature.

7. The preparation method according to claim 6, characterized in that: The cooling medium of the high-pressure gas quenching is an inert gas, and the gas cooling pressure is not greater than 15Pa.

8. The preparation method according to claim 6, characterized in that: The water cooling temperature is controlled at 25-60°C, 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 box is not greater than ±2°C; the cold treatment is to reduce the temperature to -80°C within 10 to 30 minutes and then keep it warm for 60 minutes.

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