A method for welding a diaphragm and a base of a capacitive metal vacuum gauge

Abstract

The application discloses a kind of welding methods of diaphragm and pedestal of capacitive metal vacuum gauge, belong to high-precision welding process technical field, comprising the following steps: diaphragm and pedestal are sequentially preheated stage, welding stage and stepped cooling stage;In the welding stage, multiple temperature adjusting devices are arranged around the welding area, the temperature gradient of welding area is monitored and locally adjusted in real time, to form predetermined temperature gradient distribution in welding area;The application is by setting multiple miniature heating rods and cooling pipes temperature adjusting devices around the welding area in the welding stage, the temperature gradient of welding area is monitored and locally adjusted in real time, to form predetermined temperature gradient distribution in welding area.Welding heat input is no longer passive dependent on the overall power of heating source, but can actively compensate local temperature difference according to weld geometry and heat dissipation conditions, effectively avoids the welding defects of incomplete fusion, overburning and hot cracking caused by uneven temperature distribution in traditional method.

Description

Technical Field

[0001] This invention relates to the field of high-precision welding technology, and in particular to a welding method for a capacitive metal vacuum gauge diaphragm and a base. Background Technology

[0002] A capacitive metal vacuum gauge is a high-precision sensor that measures vacuum based on the principle of capacitance change. Its core structure includes an elastically deformable metal diaphragm and a base that seals against it. The welding quality between the diaphragm and the base directly determines the gauge's sealing performance, long-term stability, and measurement accuracy. In practical applications, the welded joint must withstand not only static pressure but also maintain reliable sealing and elasticity under complex conditions such as temperature cycling and mechanical vibration. Therefore, developing a welding method that can precisely control the welding process, especially the temperature gradient, is of great significance for improving the overall performance of capacitive metal vacuum gauges.

[0003] Currently, the welding of diaphragms to substrates mainly employs traditional methods such as resistance welding, induction welding, or flame brazing. To control temperature during the welding process, existing technologies typically employ the following measures: first, relying on operator experience to manually adjust the heating power of the welding equipment; second, installing simple environmental control devices (such as fans and air conditioners) in the welding area to maintain a stable ambient temperature; and third, using a single-rate heating or cooling process. For example, operators judge the welding temperature visually or based on experience, manually adjusting the heating current or time; or, after welding, directly turning off the heating source and allowing the workpiece to cool naturally in the air.

[0004] However, the aforementioned existing technical solutions have significant technical problems in practical applications. First, traditional welding equipment has limited temperature control accuracy, typically achieving only ±5℃ or even coarser control precision, and lacks the ability to provide real-time feedback and adjustment of local temperatures in the welding area, resulting in large temperature fluctuations and poor weld quality consistency during welding. Second, existing methods often neglect the matching of the thermal expansion coefficients of the welding material and the base material, or rely solely on experience to select the welding material, leading to significant thermal stress during welding. After cooling, high residual stress remains inside the diaphragm, making it prone to zero-point drift or even diaphragm fatigue fracture during long-term use. Third, the welding environment (such as workshop temperature, humidity, and airflow) significantly affects weld quality. Existing technologies lack effective environmental isolation and compensation measures, making the welding process susceptible to external interference, especially in mass production, where significant differences in weld quality exist between different batches. Fourth, existing cooling methods are mostly natural cooling or single-stage forced cooling; a sudden temperature drop creates a severe temperature gradient inside the weld joint, further exacerbating the generation of residual stress.

[0005] In summary, existing welding methods for capacitive metal vacuum gauge diaphragms and bases have shortcomings in terms of temperature control accuracy, thermal stress suppression, and environmental adaptability. Therefore, developing a precise temperature gradient control welding method for capacitive metal vacuum gauge diaphragms and bases has significant practical importance and application value. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a welding method for capacitive metal vacuum gauge diaphragms and bases, aiming to solve the problems of poor temperature control accuracy, large thermal stress and residual stress, and weak environmental adaptability in the existing welding process of capacitive metal vacuum gauge diaphragms and bases.

[0007] To achieve the above-mentioned objective, the first aspect of this invention proposes a method for welding a capacitive metal vacuum gauge diaphragm to a base, comprising the following steps: The diaphragm and the base are subjected to a preheating stage, a welding stage, and a stepped cooling stage in sequence. During the welding stage, multiple temperature control devices are set up around the welding area to monitor and locally adjust the temperature gradient of the welding area in real time, so as to form a predetermined temperature gradient distribution in the welding area.

[0008] Optionally, the preheating stage includes heating the diaphragm and the base to 100°C at a heating rate of 5°C / min and holding for 20 minutes.

[0009] Optionally, the welding stage includes welding for 3 to 8 minutes at a welding temperature of 280°C to 320°C.

[0010] Optionally, the stepped cooling stage includes: first cooling to 200°C at a cooling rate of 3°C / min, and then cooling to room temperature at a cooling rate of 1°C / min.

[0011] Optionally, the temperature regulation device includes a miniature heating rod and a cooling pipe, and the real-time monitoring and local regulation includes: activating the cooling pipe to locally cool down when the local temperature is higher than the target value, and activating the heating rod to locally heat up when the local temperature is lower than the target value.

[0012] Optionally, the welding area is divided into a central area, an intermediate area, and an edge area. The target temperature of the central area is set to be higher than that of the intermediate area, and the target temperature of the intermediate area is set to be higher than that of the edge area. The junction of the intermediate area and the edge area forms a weld annular zone, which is the target area for temperature gradient control.

[0013] Optionally, the simulation optimization step is also included: before implementing the preheating, welding, and cooling steps, the temperature field of the welding process between the diaphragm and the base is simulated using computer simulation software. Material properties and welding process parameters are input, the welding stress distribution under different temperature gradients is simulated, the temperature gradient curve that minimizes residual stress is determined based on the simulation results, and the parameters of each stage are set according to the curve.

[0014] Optionally, welding materials that match the coefficient of thermal expansion of the diaphragm and the base can be selected for welding.

[0015] Optionally, the preheating stage, welding stage, and stepped cooling stage are all carried out in a constant temperature and humidity environment.

[0016] Optionally, the welding equipment used to perform the welding stage has a temperature control accuracy of ±1°C.

[0017] The beneficial effects of this invention are: 1. The welding method for the capacitive metal vacuum gauge diaphragm and substrate of the present invention utilizes a temperature regulation device consisting of multiple miniature heating rods and cooling pipes arranged around the welding area during the welding stage. This device monitors and locally adjusts the temperature gradient in the welding area in real time, thereby forming a predetermined temperature gradient distribution within the welding area. This eliminates the passive dependence of the welding heat input on the overall power of the heating source. Instead, it actively compensates for local temperature differences based on the weld geometry and heat dissipation conditions, effectively avoiding welding defects such as incomplete fusion, overheating, and hot cracking caused by uneven temperature distribution in traditional methods. Compared to existing technologies that rely on operational experience or simple environmental control, this solution significantly improves the control accuracy and batch consistency of welding temperature.

[0018] 2. The welding method for the capacitive metal vacuum gauge diaphragm and substrate of the present invention divides the welding process into a preheating stage, a welding stage, and a stepped cooling stage. In the preheating stage, the temperature is slowly raised to 100°C at a rate of 5°C / min and held for 20 minutes to ensure the material is heated sufficiently and uniformly, eliminating initial thermal stress. In the stepped cooling stage, the temperature is first lowered to 200°C at a rate of 3°C / min, and then lowered to room temperature at a rate of 1°C / min, avoiding drastic volume shrinkage caused by a sudden temperature drop. The synergistic effect of preheating and stepped cooling significantly reduces the peak thermal stress of the weld joint throughout the entire heating and cooling process, and the residual stress is reduced by approximately 40% compared to traditional methods, effectively reducing the risk of diaphragm deformation, warping, or microcracks.

[0019] 3. The welding method for the capacitive metal vacuum gauge diaphragm and base of the present invention fundamentally reduces the internal stress caused by inconsistent thermal expansion of the materials by selecting welding materials with thermal expansion coefficients that match those of the diaphragm and base. Simultaneously, computer simulation software is used to simulate the temperature and stress fields of the welding process. By simulating the residual stress distribution under different combinations of parameters such as heating rate, welding temperature, and cooling rate, the optimal temperature gradient curve is found before actual welding. This achieves scientific optimization of process parameters, avoiding the high cost and low efficiency of traditional trial-and-error methods.

[0020] 4. The welding method for the capacitive metal vacuum gauge diaphragm and base of the present invention places the entire process of preheating, welding, and cooling in a constant temperature and humidity environment, and uses temperature sensors to monitor the temperature of each zone in real time, forming a closed-loop feedback control: when the temperature is too high, the cooling pipe is activated to introduce coolant; when the temperature is too low, the heating rod is activated to compensate for heating. This design effectively isolates the welding process from the interference of external workshop airflow and environmental temperature fluctuations, enabling the method to achieve high-precision and highly repeatable welding quality even under ordinary production workshop conditions, greatly reducing the dependence on ultra-clean constant temperature workshops. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the welding area temperature gradient control timing of the welding method for welding the capacitive metal vacuum gauge diaphragm and the base of the present invention. Figure 2 This is a schematic diagram of the welding temperature gradient optimization control process for the welding method of the capacitive metal vacuum gauge diaphragm and the base of the present invention. Figure 3 This is a schematic diagram of the temperature control sequence for the welding process of the diaphragm of the capacitive metal vacuum gauge of the present invention to the substrate. Figure 4 This is a schematic diagram of the diaphragm welding temperature control sequence in the welding method of the capacitive metal vacuum gauge diaphragm and the base of the present invention. Figure 5 This is a schematic diagram of the temperature control device structure for the welding method of the capacitive metal vacuum gauge diaphragm and the base of the present invention.

[0022] Explanation of reference numerals in the attached figures: 101. Miniature heating rod; 102. Cooling pipe.

[0023] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0024] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0026] Please see Figures 1-5 This invention aims to provide a welding method for the diaphragm and substrate in a capacitive metal vacuum gauge, solving common technical problems in existing welding processes such as high thermal stress, easy damage to sensitive diaphragms, and poor process consistency. The core concept of this invention lies in employing a three-stage process path of "preheating-gradient temperature-controlled welding-slow cooling," and actively shaping and precisely maintaining a predetermined, non-uniform spatial temperature gradient field during the welding stage, thereby systematically suppressing the generation of residual welding stress. This concept is further illustrated below through several different embodiments.

[0027] Example 1 This embodiment describes a preferred implementation based on a conventional controllable heat source (such as resistance heating or induction heating). Please refer to... Figure 4 The core of this method lies in decomposing the welding process into three stages: preheating, gradient welding, and stepped cooling, and adding an active spatial temperature gradient adjustment mechanism in the welding stage.

[0028] 1. Preliminary process preparation First, a welding host with high-precision temperature control is required, ideally achieving a temperature control accuracy of ±1℃. The selection of welding materials is a crucial aspect of stress control; solder with a coefficient of thermal expansion (CTE) that matches the diaphragm and base materials should be chosen. Matching means that, within the expected operating temperature range of 20℃ to 300℃, the absolute value of the difference between the average linear expansion coefficient of the selected solder and the average linear expansion coefficient of the diaphragm material should not exceed ±2×10⁻⁻⁻⁴ ... 6 / K. For example, when both the diaphragm and the base are made of Invar alloy (whose average coefficient of linear expansion is approximately 1.2 × 10⁻⁻⁻⁴), 6 When the coefficient of linear expansion of the solder is / K), the average coefficient of linear expansion should be controlled within 0×10⁻. 6 / K to 3, 2×10⁻ 6 Within the range of / K. Practice has shown that using solder within this matching range can significantly reduce welding internal stress caused by the incompatibility of thermal expansion between dissimilar materials.

[0029] In addition, to ensure the stability of the process environment, a constant temperature and humidity control system should be activated within the welding area to lock the ambient temperature within 20±1℃ and control the relative humidity within 50%±10%. This is to eliminate potential interference from environmental fluctuations on precise temperature gradient control and provide a stable background field for the entire welding process.

[0030] 2. Preheating Stage: The diaphragm and base to be welded are clamped onto the worktable of the welding equipment in the predetermined positions. The preheating program is then initiated: the overall temperature of the workpiece is steadily increased from room temperature (approximately 25°C) to 100°C at a linear heating rate of 5°C / min, and held at this temperature for 20 minutes. The engineering significance of this slow heating process is that it allows sufficient time for the material to undergo thermal expansion and stress relaxation, resulting in a more uniform initial temperature distribution within the diaphragm, base, and solder. This effectively avoids initial thermal stress introduced by excessively rapid local temperature rise or large temperature differences.

[0031] It should be noted that the diaphragm and the base are coaxially assembled, and the weld seam annular band is located at the junction of the middle area and the edge area. This location is the target area for temperature gradient control in this invention.

[0032] 3. Welding Stage: After preheating, the system immediately enters the core welding stage. The key technical feature of this stage is that it no longer passively accepts the naturally formed, often uneven, temperature field, but actively intervenes to construct and maintain a preset, spatially non-uniformly distributed temperature gradient field in the welding area.

[0033] (1) To achieve precise temperature control, the welding area must first be geometrically divided into three concentric rings: the central zone, the intermediate zone, and the edge zone. Taking a typical circular diaphragm with a diameter of 30 mm as an example, the zoning scheme is as follows: the central zone is defined as a circular area with a radius of 0-5 mm; the intermediate zone is defined as an annular area with a radius of 5-12 mm; and the edge zone is defined as an annular area with a radius of 12-15 mm. It should be noted that the above specific dimensions are not fixed and can be adjusted proportionally according to the actual diameter of the diaphragm by those skilled in the art. The principle for setting the boundaries of the zoning is to ensure that the location of the final weld (usually near the junction of the intermediate zone and the edge zone) is in a transition zone of a gently changing temperature gradient. Based on this zoning, the target temperatures for each zone are set as follows: 350℃ for the central zone, 300℃ for the intermediate zone, and 250℃ for the edge zone. The non-uniform temperature distribution design with higher temperatures inside and lower temperatures outside aims to actively compensate for the natural heat loss effect from the high-temperature central zone to the low-temperature edge zone during welding, thereby forming a controllable and gentle temperature gradient throughout the weld area.

[0034] (2) To achieve the above temperature gradient, multiple micro-regulating devices with independent heating and cooling functions need to be arranged around the welding area. Specifically, micro heating rods (for local heating) and cooling pipes (for local cooling) are alternately arranged in each zone. For example, three heating rods and three cooling pipes can be evenly arranged circumferentially in the central zone; six sets can be arranged in the middle zone; and eight sets can be arranged in the edge zone. The micro heating rods are preferably embedded inside the base and as close as possible to the welding interface, while the cooling pipes can be attached to the outer wall of the base or machined in a dedicated cooling channel. The heating power and the flow rate of the cooling medium (such as water or silicone oil) in each zone are regulated by an independent PID controller in a closed loop.

[0035] Simultaneously, thermocouples with an accuracy of ±0.5℃ are deployed as temperature sensing elements within each zone. The control logic is as follows: when the real-time monitored temperature of a zone exceeds its target value, the controller automatically activates the corresponding cooling pipe for localized cooling; when the temperature falls below the target value, miniature heating rods are activated for localized reheating. Through rapid feedback adjustment, the actual temperature of each zone can be stabilized within ±2℃ of the target value. The engineering value of this step lies in actively shaping the temperature gradient, transforming the distribution of thermal stress during the welding process from uncontrollable to controllable, thus maximizing the protection of the structurally fragile vacuum gauge diaphragm.

[0036] 4. Stepped Cooling Stage: After the main welding operation is completed, the stepped cooling stage begins. This stage employs a multi-stage cooling strategy: First, the overall temperature of the workpiece is reduced from 300℃ to 200℃ at a rate of 3℃ / min; Subsequently, the cooling rate was further reduced to 1℃ / min, and cooling continued to room temperature (approximately 25℃). The entire cooling process was carried out in a constant temperature and humidity environment and continuously monitored by a temperature sensor to ensure a smooth cooling curve without abrupt changes. The function of this multi-stage slow cooling step is to control the stress release behavior of the welded joint during the transition from a plastic to an elastic state.

[0037] The beneficial effect is that it avoids the drastic volume shrinkage and thermal shock caused by rapid cooling (such as direct air cooling or water cooling), allowing the residual stress of welding to be released in a more gradual and sufficient manner, thereby significantly reducing the risk of microcracks or fatigue fractures inside the diaphragm.

[0038] Example 2 This embodiment adds a computer simulation optimization step to the first embodiment, aiming to achieve "a priori" selection of welding process parameters. It should be noted that this simulation optimization is not a necessary step to achieve the basic objective of this invention, but adding it as a preferred solution to the first, third, or fourth embodiment can further improve welding quality and process consistency.

[0039] Before performing any actual welding operations, it is recommended to perform the following simulation optimization process: Step 1: Establish a high-fidelity simulation model. Operators use commercial finite element analysis software (such as ANSYS, COMSOL Multiphysics, etc.) to establish a three-dimensional finite element model that perfectly matches the geometry and material properties of the actual diaphragm and base. The input material properties should be as complete as possible, including at least: density, specific heat capacity, thermal conductivity, Young's modulus as a function of temperature, Poisson's ratio, coefficient of thermal expansion, and yield strength. Initial welding process parameters can refer to the typical values ​​for preheating rate, welding temperature, and cooling rate given in the first embodiment.

[0040] Step Two: Simulate the evolution of welding stress under different temperature gradients. The simulation software first calculates the temperature field distribution inside the workpiece throughout the entire welding cycle based on transient heat conduction analysis. Then, using this temperature field as a thermal load, a thermo-mechanical coupling analysis is performed to calculate the dynamic welding stress and post-weld residual stress distribution inside the workpiece. The key to this step is the need to systematically traverse different combinations of process parameters. In this application, the heating rate can be selected from the range of 3℃ / min, 5℃ / min, and 7℃ / min; the welding temperature can be selected from the range of 280℃, 300℃, and 320℃; and the cooling rate can be selected from the range of "3+1"℃ / min and "2+0, 5"℃ / min. The residual stress distribution under each range combination is then simulated and recorded.

[0041] Step 3: Determine the optimal temperature gradient curve. After the simulation is completed, the software outputs the residual stress distribution cloud map and peak stress data for each parameter combination. In this embodiment, the optimization criterion is preferably "minimizing the maximum principal residual stress value on the upper surface of the diaphragm". By comparing the calculation results of each combination, the technicians select the set of process parameters with the minimum residual stress. The temperature distribution curve of this set of parameters over time and space is the optimal temperature gradient curve.

[0042] For example, simulation results might show that optimizing the preheating rate from 5℃ / min to 4℃ / min and lowering the target temperature in the center region of the welding stage from 350℃ to 340℃ can reduce the peak residual stress in the edge region by 15%. Subsequently, the actual welding process will strictly follow this optimized temperature gradient curve to set the control parameters for each stage.

[0043] In summary, this embodiment replaces a large number of trial-and-error physical experiments with virtual simulation, which not only saves a significant amount of R&D time and material costs, but more importantly, it can reveal the internal stress distribution that cannot be directly measured in the actual process, thereby obtaining the optimal process window that surpasses traditional empirical formulas, and greatly improving the scientificity and reliability of process design.

[0044] Example 3 This embodiment provides an implementation scheme using laser welding technology. The main difference from the first embodiment lies in the form of the heat source. Furthermore, due to the high precision controllability of the laser heat source, a simpler natural cooling method can be used during the cooling stage.

[0045] 1. Preparation Stage. Prepare a laser welding device with precise energy control capabilities, requiring its output power (energy density) to be continuously adjustable within the range of 0.5-2 kW / cm², and equipped with a programmable scanning galvanometer or precision motion platform to achieve rapid and accurate laser beam positioning. The selection and matching standards for welding materials are the same as in the first embodiment. Maintain an ambient temperature of 20±1℃ and a relative humidity of 50%±10%. In addition, arrange multiple non-contact infrared temperature sensors (accuracy ±1℃) above the welding area for real-time monitoring of the surface temperature of each zone.

[0046] 2. Preheating Stage. Place the workpiece on the worktable and activate the laser preheating mode. Use a low energy density (e.g., 0 or 1 kW / cm²) to perform large-area scanning heating on the workpiece, slowly raising the overall temperature to 100°C at a rate of 5°C / min, and holding at that temperature for 20 minutes. The control system dynamically adjusts the laser output power or scanning speed based on feedback from the infrared sensor to accurately follow the preset heating curve.

[0047] 3. Welding Stage. First, following the spatial zoning strategy of the first embodiment, the welding area is divided into a central area, a middle area, and an edge area, and the same target temperature (350℃ / 300℃ / 250℃) is set. Subsequently, the control system dynamically adjusts the energy density and dwell time of the laser beam according to the target temperature of each zone.

[0048] For example: in the central area, an energy density of 1.5 kW / cm² and a dwell time of 0.5 seconds per point are used; in the middle area, 1.0 kW / cm² and 0.3 seconds per point are used; and in the edge area, 0.6 kW / cm² and 0.2 seconds per point are used. The laser beam scans and heats the area according to a preset path (such as a spiral from the inside out), and infrared sensors provide real-time feedback on the temperature of each area. The control logic is as follows: if the measured temperature is too high, the laser energy in that area is reduced or the dwell time is shortened; conversely, it is increased if the temperature is too low. Ultimately, the temperature of each zone is stabilized within ±2℃ of the target value. The entire welding process lasts approximately 5 minutes.

[0049] The advantage of this embodiment is that the heat-affected zone of the laser heat source is extremely small, and the spatial resolution of the energy input is extremely high. It can create a steeper and more precise predetermined temperature gradient than traditional heat sources, and is especially suitable for ultra-thin films with a thickness of less than 0 or 1 mm.

[0050] 4. Cooling Stage. Immediately after welding, turn off the laser output and stop all active temperature control devices. Allow the workpiece to cool naturally to room temperature in still air. Cooling from approximately 300°C to room temperature typically takes 30-60 minutes. During this process, temperature is monitored only by an infrared sensor, without any active intervention. The significant advantage of natural cooling is that it completely avoids the secondary temperature gradient and additional thermal stress that may be introduced by forced cooling (such as air cooling or liquid cooling), allowing residual stress to be released autonomously and fully in a manner closest to ideal, thereby minimizing the risk of diaphragm deformation or cracking.

[0051] Example 4 This embodiment provides an implementation scheme using electron beam welding technology. This method utilizes high-speed electron beams to bombard the workpiece surface in a vacuum environment to generate heat for welding, offering significant advantages such as extremely high energy conversion efficiency, a large weld depth-to-width ratio, and an extremely narrow heat-affected zone.

[0052] 1. Preparation stage. Prepare a standard electron beam welding equipment, which should include an electron gun, vacuum chamber, precision worktable, electromagnetic deflection and focusing system, and overall control system.

[0053] Equipment parameter requirements: accelerating voltage adjustable from 30-150kV, beam current adjustable from 1-50mA, electron beam spot diameter focused to 0.1-1mm. The vacuum chamber must be able to be evacuated to 10⁻⁻⁻⁻⁶. 4 A high vacuum below Pa is maintained to ensure stable electron beam transmission and cleanliness of the welding area. The selection criteria for welding materials remain unchanged. Infrared temperature sensors or thermocouples are installed on the inner wall of the vacuum chamber for temperature monitoring.

[0054] 2. Preheating Stage. Clamp the workpiece onto the worktable inside the vacuum chamber, close the chamber door, and evacuate to the working vacuum level (e.g., 10⁻³ Pa). Activate the electron beam preheating mode: use a lower beam current (e.g., 5 mA) and an electromagnetic deflection system for high-speed, large-area scanning to achieve uniform heating of the workpiece. Heat the entire workpiece to 100°C at a rate of 5°C / min and hold for 20 minutes. Temperature sensors provide real-time feedback, and the control system maintains the heating curve by adjusting the beam current or scanning speed.

[0055] 3. Welding Stage. Welding begins after preheating. First, the spatial zoning and target temperature settings are identical to those in the first embodiment (350°C for the center zone, 300°C for the middle zone, and 250°C for the edge zone). The control system precisely controls the electron beam's incident position, scanning path, dwell time, and energy density (by adjusting the beam current) through an electromagnetic deflection system.

[0056] Typical parameters are: 15mA beam current and 0.4 seconds / point dwell time in the central region; 10mA beam current and 0.3 seconds / point dwell time in the middle region; and 6mA beam current and 0.2 seconds / point dwell time in the edge region. Closed-loop feedback control logic is also used to ensure that the real-time temperature of each zone remains stable within ±2℃ of the target value. The entire welding process lasts approximately 5 minutes.

[0057] The advantage of this embodiment is that electron beam welding is carried out in a vacuum, completely eliminating oxidation and interference from the external atmosphere. Furthermore, its extremely narrow heat-affected zone enables the highest precision temperature gradient control, which is particularly crucial for the manufacturing of high-end vacuum gauges that require extremely high cleanliness and extremely low stress.

[0058] 4. Cooling Stage. After welding, turn off the electron beam and stop all active heating. It is preferable to maintain a vacuum state within the vacuum chamber, allowing the workpiece to cool naturally to room temperature in a high-vacuum environment. Cooling from 300°C to room temperature typically takes 40-90 minutes. Natural cooling in a vacuum environment has unique advantages: since there is almost no air convection, heat dissipation relies entirely on radiation and solid-state heat conduction, further reducing localized temperature differences caused by uneven heat convection, making the release of residual stress more uniform and complete than in an atmospheric environment.

[0059] In summary, the various welding methods provided by this invention employ a technical approach of preheating homogenization, welding gradient, and slow-release cooling, and combine active spatial temperature gradient control with optional simulation optimization methods, systematically solving long-standing technical problems in existing technologies such as high welding thermal stress, low precision, and poor environmental adaptability.

[0060] Experiments show that the residual stress level of the diaphragm of the capacitive metal vacuum gauge welded using this method can be reduced by about 40% compared with the traditional whole heating or local welding methods; In a wide temperature range cycling test from -40℃ to 85℃, the product's zero-point drift was reduced by more than 60%, and the mean time between failures (MTBF) was significantly extended.

[0061] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for welding a capacitive metal vacuum gauge diaphragm to a base, characterized in that, Includes the following steps: The diaphragm and the base are subjected to a preheating stage, a welding stage, and a stepped cooling stage in sequence. During the welding stage, multiple temperature control devices are set up around the welding area to monitor and locally adjust the temperature gradient of the welding area in real time, so as to form a predetermined temperature gradient distribution in the welding area.

2. The welding method between the capacitive metal vacuum gauge diaphragm and the base according to claim 1, characterized in that, The preheating stage includes heating the diaphragm and the base to 100°C at a heating rate of 5°C / min and holding for 20 minutes.

3. The welding method between the capacitive metal vacuum gauge diaphragm and the base according to claim 1, characterized in that, The welding stage includes welding for 3 to 8 minutes at a welding temperature of 280℃ to 320℃.

4. The welding method between the capacitive metal vacuum gauge diaphragm and the base according to claim 1, characterized in that, The stepped cooling stage includes: first cooling to 200°C at a cooling rate of 3°C / min, and then cooling to room temperature at a cooling rate of 1°C / min.

5. The welding method between the capacitive metal vacuum gauge diaphragm and the base according to claim 1, characterized in that, The temperature regulation device includes a miniature heating rod and a cooling pipe. The real-time monitoring and local regulation includes: activating the cooling pipe to locally cool down when the local temperature is higher than the target value, and activating the heating rod to locally heat up when the local temperature is lower than the target value.

6. The welding method between the capacitive metal vacuum gauge diaphragm and the base according to claim 1, characterized in that, The welding area is divided into a central area, an intermediate area, and an edge area. The target temperature of the central area is set to be higher than that of the intermediate area, and the target temperature of the intermediate area is set to be higher than that of the edge area. The junction of the intermediate area and the edge area forms a weld annular zone, which is the target area for temperature gradient control.

7. The welding method between the capacitive metal vacuum gauge diaphragm and the base according to claim 1, characterized in that, It also includes a simulation optimization step: before implementing the preheating, welding, and cooling steps, the temperature field of the welding process between the diaphragm and the base is simulated using computer simulation software. Material properties and welding process parameters are input, the welding stress distribution under different temperature gradients is simulated, the temperature gradient curve that minimizes residual stress is determined based on the simulation results, and the parameters of each stage are set according to the curve.

8. The welding method between the capacitive metal vacuum gauge diaphragm and the base according to claim 1, characterized in that, Welding should be performed using welding materials whose coefficients of thermal expansion match those of the diaphragm and the base.

9. The welding method between the capacitive metal vacuum gauge diaphragm and the base according to claim 1, characterized in that, The preheating stage, welding stage, and stepped cooling stage are all carried out in a constant temperature and humidity environment.

10. The welding method between the capacitive metal vacuum gauge diaphragm and the base according to claim 1, characterized in that, The welding equipment used in performing the welding stage has a temperature control accuracy of ±1℃.

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