Stress regulation and control method for diffusion welding of miniature proportional valve body

Abstract

The invention discloses a stress regulation and control method for diffusion welding of a miniature proportional valve body. The stress regulation and control method comprises the following steps of material pretreatment, wherein precise polishing and plasma cleaning are conducted on the contact face of a stainless steel base body and a ceramic coating; performing multi-stage variable-temperature and variable-pressure diffusion welding by using a diffusion welding machine; in a low-temperature pre-pressing stage, eliminating interface microcosmic unevenness through low pressure; a gradient heating and pressurizing stage: feeding back strain in real time based on a laser displacement sensor, dynamically adjusting pressure, and matching thermal expansion difference of the heterogeneous material; in the steady-state diffusion stage, a metallurgical bonding layer with the thickness of 1-3 microns is formed; post-welding non-thermal stress elimination is conducted, specifically, zirconia ceramic particles are adopted for conducting micro shot blasting treatment on the surface of the valve body; and low-temperature aging treatment: preserving heat for 2-4 hours in an environment of 150-200 DEG C, and homogenizing stress distribution through a dislocation climbing mechanism. According to the method, the problems of microcrack leakage, insufficient fatigue life, non-uniform interface bonding strength of heterogeneous materials and the like caused by residual stress concentration in diffusion welding of the valve body of the micro proportional valve can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of precision manufacturing of micro proportional valves, and more particularly to a stress control method for diffusion welding of a micro proportional valve body. Background Art

[0002] In the manufacturing of micro proportional valves, diffusion welding technology is widely used in the precision connection of valve body and valve seat due to its advantages such as low heat input and high bonding strength.

[0003] However, existing technologies have significant drawbacks: First, the constant temperature-pressure loading mode leads to concentrated residual stress at the weld interface, causing microcrack leakage and insufficient fatigue life; second, a single welding parameter is difficult to adapt to the thermal-mechanical properties of heterogeneous materials, resulting in fluctuations in interface bonding strength and localized overheating defects; third, while post-weld high-temperature annealing can eliminate stress, it damages the acid- and alkali-resistant coating and causes micron-scale deformation. To address these issues, existing improvements include gradient heating, which reduces thermal stress but only improves bonding strength to a limited extent; vibration-assisted welding, which can easily lead to resonant deformation in thin-walled structures; and laser annealing, which is a complex and costly process.

[0004] Therefore, providing a stress control method for diffusion welding of a micro proportional valve body is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a stress control method for diffusion welding of a micro proportional valve body to solve the problems of micro crack leakage, insufficient fatigue life and uneven interface bonding strength of heterogeneous materials caused by residual stress concentration in diffusion welding of a micro proportional valve body.

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

[0007] A stress control method for diffusion welding of a micro proportional valve body comprises the following steps:

[0008] 1) Material pretreatment: Precision polishing and plasma cleaning of the contact surface between the stainless steel substrate and the ceramic coating;

[0009] 2) Use a diffusion welding machine to perform multi-stage variable temperature and pressure diffusion welding:

[0010] Ⅰ: Low temperature pre-pressing stage: eliminating interface micro roughness through low pressure;

[0011] II: Gradient heating and pressurization stage: Based on the real-time strain feedback of the laser displacement sensor, the pressure is dynamically adjusted to match the thermal expansion difference of heterogeneous materials;

[0012] III: Steady-state diffusion stage: a metallurgical bonding layer with a thickness of 1 to 3 μm is formed;

[0013] 3) Post-weld non-thermal stress relief:

[0014] Ⅰ: The valve body surface is micro shot peened with zirconium oxide ceramic particles;

[0015] II: Low temperature aging treatment: Keep the temperature at 150-200℃ for 2-4 hours to homogenize the stress distribution through the dislocation climb mechanism.

[0016] Furthermore, during the gradient heating and pressurizing stage and the steady-state diffusion stage, high-frequency vibration is applied to the welding interface through the piezoelectric ceramic driver, while avoiding the natural frequency of the thin-wall structure of the valve body.

[0017] Furthermore, after the precision polishing in step 1), the roughness of the contact surface between the stainless steel substrate and the ceramic coating is Ra≤0.1 μm.

[0018] Furthermore, in the low-temperature pre-pressing stage, the temperature is set to 300-400°C, the pressure is set to 0.5-2 MPa, and the time is set to 10-20 minutes; in the gradient heating and pressurization stage, the heating rate is 5-10°C / min until the temperature reaches 800-850°C; in the steady-state diffusion stage, the temperature is set to 850°C±5°C, the pressure is set to 4-6 MPa, and the time is set to 30-60 minutes.

[0019] Furthermore, the diffusion welding machine is a vacuum diffusion welding machine with a vacuum degree of ≤5×10 -3 Pa, and equipped with a multi-zone independent temperature control system.

[0020] Furthermore, the frequency of the high-frequency vibration is 20 to 50 kHz, and the amplitude is ≤ 5 μm.

[0021] Furthermore, the vibration parameters are monitored and fed back in real time by a laser interferometer to control the amplitude deviation to ≤0.2μm; the vibration direction is precisely adjusted by a six-axis robot; and the vibration energy is concentrated on the interface atomic layer.

[0022] Furthermore, in step 3), the shot peening pressure is 0.1-0.3 MPa, and the coverage is 200%-300%.

[0023] It can be seen from this that the present invention provides a stress control method for diffusion welding of a micro proportional valve body. Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) Effectively solve the problem of welding stress concentration and significantly improve sealing performance and pressure resistance:

[0025] Through the synergistic effect of a multi-stage dynamic temperature and pressure change process and high-frequency micro-amplitude vibration, the thermal-mechanical response of the interface between heterogeneous materials is precisely controlled, the residual stress concentration caused by differences in thermal expansion coefficients is eliminated, and the generation of microcracks is fundamentally suppressed. Combined with non-thermal stress relief technology, while ensuring the integrity of the acid and alkali resistant coating, the micro valve body achieves high sealing performance under high-pressure conditions, completely eliminating the leakage risk caused by residual stress in traditional processes and meeting the needs of long-term stable operation in complex media environments.

[0026] 2) Ensure material performance and assembly accuracy, and enhance environmental adaptability:

[0027] A combined low-temperature aging and micro-shot peening process replaces high-temperature annealing to prevent high-temperature oxidation or phase change of the acid- and alkali-resistant coating, ensuring stable corrosion resistance in extreme environments with a pH range of 2 to 10. High-frequency vibration and deformation feedback control suppress welding deformation to the submicron level, meeting the stringent dimensional tolerance requirements of precision assembly, significantly improving product yield and batch consistency, and meeting the high reliability requirements of core components for scientific instruments.

[0028] 3) The process is efficient and controllable, suitable for low-cost batch manufacturing:

[0029] Based on the multi-parameter dynamic matching mechanism of the intelligent optimization system, closed-loop control of core process parameters such as temperature, pressure, and vibration is achieved, which greatly shortens the welding cycle and reduces energy consumption; the introduction of non-heat treatment technologies such as micro-shot peening simplifies the post-processing process, and the manufacturing cost of a single piece is only 1 / 6 of the traditional laser annealing process. Combined with modular equipment design, it can be quickly expanded to large-scale production of thousands of pieces per year, providing a manufacturing solution with both high performance and low cost for the domestic replacement of micro proportional valves. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0031] Figure 1 The accompanying drawing is a flow chart of a stress control method for diffusion welding of a micro proportional valve body provided by the present invention. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] like Figure 1 As shown, an embodiment of the present invention discloses a stress control method for diffusion welding of a micro proportional valve body, comprising the following steps:

[0034] 1) Material pretreatment: Precision polishing and plasma cleaning of the contact surface between the stainless steel substrate and the ceramic coating; after precision polishing, the roughness of the contact surface between the stainless steel substrate and the ceramic coating is Ra ≤ 0.1 μm;

[0035] 2) Use a diffusion welding machine to perform multi-stage variable temperature and pressure diffusion welding:

[0036] Ⅰ: Low temperature pre-pressing stage: the temperature is set to 300-400℃, the pressure is set to 0.5-2MPa, and the time is set to 10-20 minutes to eliminate the microscopic roughness of the interface through low pressure;

[0037] II: Gradient heating and pressurization stage: The heating rate is 5-10°C / min until the temperature reaches 800-850°C. Based on the real-time strain feedback of the laser displacement sensor (accuracy 0.1μm), the pressure (2-8MPa) is dynamically adjusted to match the thermal expansion difference of the heterogeneous materials.

[0038] III: Steady-state diffusion stage: the temperature is set at 850°C ± 5°C, the pressure is set at 4-6 MPa, and the time is set at 30-60 minutes to form a metallurgical bonding layer with a thickness of 1-3 μm;

[0039] 3) Post-weld non-thermal stress relief:

[0040] Ⅰ: Micro-shot peening of the valve body surface using zirconium oxide ceramic particles; in this embodiment, the shot peening pressure is 0.1-0.3 MPa, and the coverage rate is 200%-300%. The shot peening trajectory is planned by the robot to achieve uniform coverage;

[0041] II: Low-temperature aging treatment: Keep the temperature at 150-200°C for 2-4 hours to homogenize stress distribution through dislocation climb. This process avoids the coating oxidation temperature (≥250°C) and the temper brittleness zone of stainless steel (300-450°C) throughout the process to ensure stable material properties.

[0042] Specifically, during the gradient heating and pressurization phase and the steady-state diffusion phase, high-frequency vibration is applied to the weld interface via a piezoelectric ceramic driver. The frequency of the high-frequency vibration is 20 to 50 kHz, and the amplitude is ≤5 μm to avoid the natural frequency of the thin-walled structure of the valve body (first-order mode ≈65 kHz). The vibration parameters are monitored and fed back in real time by a laser interferometer, controlling the amplitude deviation to ≤0.2 μm; the vibration direction is precisely adjusted by a six-axis robot; the vibration energy is concentrated on the atomic layer at the interface, and combined with the fast response of the piezoelectric ceramic driver (frequency adjustment accuracy of ±0.1 kHz), it promotes atomic migration and dislocation movement while suppressing macrostructural deformation.

[0043] In order to further optimize the technical solution of the present invention, the diffusion welding machine is a vacuum diffusion welding machine with a vacuum degree of ≤5×10 -3 Pa, to prevent oxidation, and equipped with a multi-zone independent temperature control system (accuracy ± 3 ° C).

[0044] The present invention uses a multi-stage variable temperature and pressure process to accurately match the thermal-mechanical response characteristics of heterogeneous materials such as stainless steel-ceramic composite coatings, combines high-frequency micro-vibration to promote atomic diffusion and inhibit structural deformation, and simultaneously adopts surface micro-plastic deformation treatment instead of high-temperature annealing. While eliminating welding residual stress, ensuring the performance of acid and alkali resistant coatings and micron-level assembly accuracy, it significantly improves the valve body's pressure resistance and fatigue life, and reduces energy consumption by 30% through coordinated optimization of process parameters, meeting the needs of high-precision, low-cost batch manufacturing of micro proportional valves.

[0045] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0046] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A stress control method for diffusion welding of a micro proportional valve body, characterized in that: The following steps are involved: 1) Material pretreatment: Precision polishing and plasma cleaning of the contact surface between the stainless steel substrate and the ceramic coating; 2) Use a diffusion welding machine to perform multi-stage variable temperature and pressure diffusion welding: Ⅰ: Low temperature pre-pressing stage: eliminating interface micro roughness through low pressure; II: Gradient heating and pressurization stage: Based on the real-time strain feedback of the laser displacement sensor, the pressure is dynamically adjusted to match the thermal expansion difference of heterogeneous materials; III: Steady-state diffusion stage: a metallurgical bonding layer with a thickness of 1 to 3 μm is formed; 3) Post-weld non-thermal stress relief: Ⅰ: The valve body surface is micro shot peened with zirconium oxide ceramic particles; II: Low temperature aging treatment: Keep the temperature at 150-200℃ for 2-4 hours to homogenize the stress distribution through the dislocation climb mechanism.

2. The stress control method for diffusion welding of a micro proportional valve body according to claim 1, characterized in that: During the gradient heating and pressurization stage and the steady-state diffusion stage, high-frequency vibration is applied to the welding interface through the piezoelectric ceramic driver, avoiding the natural frequency of the valve body's thin-wall structure.

3. The stress control method for diffusion welding of a micro proportional valve body according to claim 1, characterized in that: After precision polishing in step 1), the roughness of the contact surface between the stainless steel substrate and the ceramic coating is Ra≤0.1 μm.

4. The stress control method for diffusion welding of a micro proportional valve body according to claim 1, characterized in that: In the low-temperature pre-pressing stage, the temperature is set to 300-400°C, the pressure is set to 0.5-2MPa, and the time is set to 10-20 minutes; in the gradient heating and pressurization stage, the heating rate is 5-10°C / min until the temperature reaches 800-850°C; in the steady-state diffusion stage, the temperature is set to 850°C±5°C, the pressure is set to 4-6MPa, and the time is set to 30-60 minutes.

5. The stress control method for diffusion welding of a micro proportional valve body according to claim 1, characterized in that: The diffusion welding machine is a vacuum diffusion welding machine with a vacuum degree of ≤5×10 -3 Pa, and equipped with a multi-zone independent temperature control system.

6. The stress control method for diffusion welding of a micro proportional valve body according to claim 2, characterized in that: The frequency of high-frequency vibration is 20 to 50 kHz, and the amplitude is ≤ 5 μm.

7. The stress control method for diffusion welding of a micro proportional valve body according to claim 6, characterized in that: The vibration parameters are monitored and fed back in real time by a laser interferometer, and the amplitude deviation is controlled to be ≤0.2μm; The vibration direction is precisely adjusted by a six-axis robot; the vibration energy is concentrated on the interface atomic layer.

8. The stress control method for diffusion welding of a micro proportional valve body according to claim 1, characterized in that: In step 3), the shot peening pressure is 0.1-0.3 MPa, and the coverage is 200%-300%.

Images