Polishing method for eccentric double-junction spiral fireproof butterfly valve suitable for ultra-low temperature

Abstract

This invention relates to the field of cryogenic valve grinding technology, and particularly to a grinding method for eccentric wafer-type spiral fireproof butterfly valves suitable for cryogenic applications. The method includes: adjusting the first cryogenic time based on a residual austenite content in the valve plate exceeding a preset value, according to a first cryogenic time adjustment amount corresponding to the excess content; determining the total semi-finishing grinding amount based on a first dimensional change rate of the valve plate after the first cryogenic treatment; adjusting the second cryogenic time based on a half-height / width value exceeding a preset half-height / width, according to a second cryogenic time adjustment amount corresponding to the excess width; and adjusting the first cryogenic time adjustment amount based on a first correction coefficient corresponding to the excess change rate, based on a comprehensive change rate exceeding a preset change rate. This invention comprehensively regulates product quality stability and improves product precision by introducing a dynamically adjusted cryogenic treatment process during the graded grinding process.

Description

Technical Field

[0001] This invention relates to the field of ultra-low temperature valve grinding technology, and in particular to a grinding method for eccentric clamping spiral fireproof butterfly valves suitable for ultra-low temperatures. Background Technology

[0002] Valves are pipeline accessories used to control the opening and closing of pipelines and the direction of fluid flow. They generally have various functions such as guiding, shutting off, throttling, checking back, and relieving pressure. Currently, as control components in fluid transportation systems, valves have extremely high requirements for precision and corrosion resistance. In particular, some valves used in ultra-low temperature environments need to ensure dimensional stability and accuracy under ultra-low temperature conditions. Therefore, after the valve is formed, it usually needs to be polished.

[0003] Chinese Patent Publication No. CN118061020A discloses a valve grinding machine and its grinding method, which consists of a processing table, a clamping device, and a grinding device. In order to enable the grinding machine to grind the inner and outer walls of the valve body, the clamping device of the invention is configured as an inner ring clamping module and an outer ring clamping module. The outer ring clamping module and the inner ring clamping module can fix the valve body and grind the inner wall. Therefore, when grinding the valve body, the outer and inner walls of the valve body can be ground without changing the equipment, thereby improving production efficiency.

[0004] Therefore, it can be seen that the valve grinding machine and its grinding method have the following problems: it is difficult to comprehensively regulate the quality stability of the product and improve the product precision by introducing a dynamically adjusted cryogenic treatment process during the graded grinding process. Summary of the Invention

[0005] To address this, the present invention provides a grinding method for eccentric wafer spiral fireproof butterfly valves suitable for ultra-low temperatures, thereby overcoming the problem in the prior art that it is difficult to comprehensively regulate the quality stability of products and improve product precision by introducing a dynamically adjusted cryogenic treatment process during the graded grinding process.

[0006] To achieve the above objectives, the present invention provides a grinding method for eccentric wafer-type spiral fireproof butterfly valves suitable for cryogenic applications, comprising:

[0007] The first cryogenic duration is adjusted according to the first cryogenic duration adjustment amount corresponding to the excess content value, based on the residual austenite content value of the valve plate being greater than the preset content value. The excess content value is determined based on the residual austenite content value and the preset content value.

[0008] The total amount of semi-finishing grinding is determined based on the first dimensional change rate of the valve plate after the first cryogenic treatment.

[0009] Based on the fact that the half-width value is greater than the preset half-width, the second cryogenic duration is adjusted according to the second cryogenic duration adjustment amount corresponding to the width excess value. The half-width value is determined based on the diffraction pattern data of the valve plate surface after semi-fine polishing, and the width excess value is determined based on the difference between the half-width value and the preset half-width.

[0010] Based on the fact that the overall change rate is greater than the preset change rate, the first cryogenic duration adjustment amount is adjusted according to the first correction coefficient corresponding to the change excess value. The overall change rate is determined based on the second size change rate of the valve plate after the second cryogenic treatment and the first size change rate. The change excess value is determined based on the overall change rate and the preset change rate.

[0011] The total amount of fine grinding is determined based on the second dimensional change rate;

[0012] In response to a micro-strain value exceeding a preset strain value, the total amount of semi-finish grinding is adjusted according to the grinding correction coefficient corresponding to the strain excess value.

[0013] The micro-strain value is determined based on the lattice micro-strain of the valve plate surface after fine grinding, and the strain excess value is determined based on the micro-strain value and the preset strain value.

[0014] Furthermore, in response to the residual austenite content value being greater than the preset content value, the first cryogenic duration is increased by adjusting the first cryogenic duration based on the first cryogenic duration adjustment amount combined with the preset first cryogenic duration, wherein the first cryogenic duration adjustment amount is positively correlated with the content exceeding the value.

[0015] Furthermore, in response to determining the total amount of semi-finishing based on the first dimensional change rate, the total amount of semi-finishing is negatively correlated with the first dimensional change rate.

[0016] Furthermore, in response to adjusting the second cryogenic duration, the second cryogenic duration is increased according to the second cryogenic duration adjustment amount corresponding to the width excess value, wherein the second cryogenic duration adjustment amount is positively correlated with the width excess value.

[0017] Furthermore, in response to adjusting the first cryogenic duration adjustment amount, the first cryogenic duration adjustment amount is increased according to a first correction coefficient corresponding to the change exceeding the value, wherein the first correction coefficient is positively correlated with the change exceeding the value.

[0018] Furthermore, in response to determining the total amount of fine grinding based on the second dimensional change rate, the total amount of fine grinding is negatively correlated with the second dimensional change rate.

[0019] Furthermore, in response to the micro-strain value being greater than the preset strain value, the third cryogenic duration is increased according to the third cryogenic duration adjustment amount corresponding to the strain excess value, wherein the third cryogenic duration adjustment amount is positively correlated with the strain excess value.

[0020] Furthermore, in response to the micro-strain value being greater than the preset strain value, the total amount of semi-finishing grinding is increased according to the grinding correction coefficient, wherein the grinding correction coefficient is positively correlated with the strain exceeding the value.

[0021] Furthermore, in response to the microscopic strain value being greater than the preset strain value, the adjustment amount of the second cryogenic duration is increased according to the second correction coefficient corresponding to the strain excess value, wherein the second correction coefficient is positively correlated with the strain excess value.

[0022] Furthermore, based on the fact that the first cryogenic duration is greater than the critical cryogenic duration, the preset second cryogenic duration is increased according to the deviation value of the first cryogenic duration, wherein the deviation value of the first cryogenic duration is determined based on the first cryogenic duration and the critical cryogenic duration.

[0023] Compared with the prior art, the beneficial effect of the grinding processing method of the present invention for eccentric wafer spiral fireproof butterfly valves at ultra-low temperatures is that by introducing a dynamically adjusted cryogenic treatment process during the graded grinding process, the quality stability of the product is comprehensively adjusted and the precision of the product is improved.

[0024] Furthermore, by introducing a dynamic control mechanism for residual austenite content detection, the dimensional stability and process reliability of cryogenic valve manufacturing are improved. The residual austenite content of the valve plate is precisely measured using X-ray diffraction and compared with a preset threshold to determine dimensional stability. The cryogenic treatment duration is dynamically adjusted based on the content exceeding the threshold, achieving precise control of the material microstructure to ensure product dimensional stability. Introducing cryogenic treatment between multiple grinding processes effectively eliminates newly formed residual austenite generated by the reverse phase transformation induced by the thermo-mechanical coupling effect during grinding. This fundamentally avoids problems such as volume expansion, dimensional deformation, and sealing failure caused by the transformation of residual austenite to martensite at -269℃ cryogenic environment. It ensures the reliability of butterfly valve opening and closing and sealing performance under extreme working conditions. It also avoids the energy consumption and time waste caused by over-processing through differentiated deep cryogenic duration control. It achieves dynamic optimization of organizational stability, processing efficiency and cost control, ensures reliable grinding of key valves for ultra-low temperature hydrogen transport ships, increases the stability and accuracy of grinding processing dimensions, and meets the performance requirements of products under ultra-low temperature conditions.

[0025] Furthermore, a hierarchical control mechanism for cryogenic treatment duration was established. By judging whether the first cryogenic treatment duration exceeds the critical duration, the duration of the subsequent second cryogenic treatment is dynamically adjusted accordingly, enhancing the closed-loop control capability of microstructure stability during multi-stage grinding. When the first cryogenic treatment duration exceeds the critical value, the marginal effect of cryogenic treatment on the transformation of retained austenite is significantly reduced. At this point, by compensating for the deviation of the first cryogenic treatment duration in the second cryogenic treatment, the residual austenite and dimensional stability risks that may have been caused by insufficient cryogenic treatment in the early stage can be effectively compensated, preventing the unstable state from continuing into the fine grinding stage. This avoids process redundancy caused by excessive cryogenic treatment in a single stage, strengthens the synergistic effect of cryogenic treatment between each processing stage, and ensures that the material microstructure always converges towards a stable state during multiple grinding and cryogenic alternation processes, thereby guaranteeing the dimensional accuracy and sealing reliability of the final product under extreme low-temperature conditions.

[0026] Furthermore, by introducing a dynamic control mechanism for the total semi-finishing grinding amount based on the dimensional change rate after the first cryogenic treatment, a precise match between cryogenic treatment and subsequent machining is achieved. Contour data before and after cryogenic treatment are obtained using 3D scanning to quantify the first dimensional change rate, and the total semi-finishing grinding amount is adjusted accordingly. This effectively solves the problem of insufficient final finishing allowance if the material shrinkage caused by cryogenic treatment is still processed according to the original allowance. Integrating the dimensional changes brought about by cryogenic treatment into the machining allowance allocation allows the semi-finishing grinding stage to remove allowance differentially based on the actual shrinkage of the material. This avoids dimensional deviations caused by over-grinding and ensures sufficient and uniform machining allowance in the finishing grinding stage, thereby significantly improving the dimensional consistency, machining success rate, and final product accuracy of cryogenic valve products in complex process chains.

[0027] Furthermore, by introducing a dynamic stress state assessment based on the full width at half maximum (HWHM) value and a second cryogenic treatment duration control mechanism, accurate identification and targeted treatment of the stress state of the material microstructure after semi-finish grinding were achieved. X-ray diffraction pattern data of the valve plate surface after semi-finish grinding were obtained using an X-ray diffractometer. The HWHM value was used as a quantitative indicator of stress state and microstructure stability, and compared with a preset threshold. When the stress state was deemed unqualified, the second cryogenic treatment duration was dynamically increased based on the width exceeding the value, effectively addressing the problems of reverse phase transformation, newly formed retained austenite, and stress concentration induced by grinding heat and mechanical action during semi-finish grinding. By unifying stress reduction and retained austenite control through differentiated adjustment of cryogenic treatment duration, it is ensured that even with excessive grinding or process fluctuations, extended cryogenic treatment can still effectively eliminate new stress, promote the transformation of retained austenite to martensite, and achieve uniform stress distribution. This prevents quality risks such as microcracks, excessive surface hardening, deformation, and potential breakage, rapid wear, or seal failure during subsequent use, thereby improving the service reliability and precision of grinding processes for products suitable for ultra-low temperature environments.

[0028] Furthermore, by constructing a closed-loop feedback mechanism based on the comprehensive change rate, the quantitative verification of the effect of the first cryogenic treatment and the dynamic optimization of process parameters were achieved. 3D scanning was used to acquire dimensional change data before and after the two cryogenic treatments. The ratio of the second dimensional change rate to the first dimensional change rate was used as the comprehensive change rate to accurately assess the material microstructure stability and the sufficiency of the retained austenite phase transformation. When the comprehensive change rate exceeded a preset threshold, the adjustment amount of the first cryogenic duration was dynamically corrected based on the excess value, thus reinforcing the initial cryogenic treatment intensity and compensating for the process defect of insufficient retained austenite phase transformation from the previous cryogenic treatment. The dimensional stability performance of subsequent cryogenic treatments was used as the optimization basis for preceding processes, forming a cross-process self-learning and adaptive capability. This effectively avoided the chain risk of large dimensional changes in the second cryogenic treatment stage due to insufficient first cryogenic treatment, which in turn affected the overall processing accuracy. This ensured that the dimensions of the cryogenic valve tended to converge and stabilize in the complex process chain of multiple cryogenic treatments and grinding, providing a systematic process guarantee for high-reliability manufacturing under extreme conditions.

[0029] Furthermore, by introducing a dynamic control mechanism for the total amount of fine grinding based on the dimensional change rate after the second cryogenic treatment, precise matching between the final fine grinding allowance and the stable state of the material microstructure is achieved. The dimensional shrinkage after cryogenic treatment is quantified using the second dimensional change rate, and the total amount of fine grinding is adjusted accordingly. This effectively avoids dimensional deviations such as insufficient allowance or overcutting during the fine grinding stage caused by the cumulative dimensional changes from multiple cryogenic treatments. The dimensional evolution law of the material during the microstructure stabilization process is proactively integrated into the fine grinding allowance allocation strategy, enabling differentiated removal based on the actual shrinkage of the material during the fine grinding stage. This ensures that while maintaining the machining accuracy of the sealing surface and mating parts, sufficient correction allowance is reserved for the final product. Through grinding, products suitable for ultra-low temperature environments achieve dimensional and performance stability, avoiding economic losses caused by decreased product accuracy or dimensional non-compliance due to machining errors during grinding, resulting in excessive product defect rates.

[0030] Furthermore, by introducing a fine grinding quality assessment based on micro-strain values ​​and a reverse correction mechanism for semi-fine grinding parameters, a closed-loop optimization system from fine grinding quality feedback to preceding processes was constructed. X-ray diffraction was used to obtain the lattice micro-strain values ​​of the surface after fine grinding, precisely quantifying the degree of lattice distortion, stress concentration state, and depth of the processing damage layer. When the micro-strain value exceeds a preset threshold, the grinding quality is deemed unqualified, and the total amount of semi-fine grinding is dynamically increased through a grinding correction coefficient. This strengthens the control of allowances from upstream processes, avoiding excessive lattice distortion and dislocation accumulation caused by excessive grinding force, insufficient cooling, or tool passivation during the fine grinding stage. Linking the microstructure of the fine-ground surface with the process parameters of the semi-fine grinding stage allows the preceding processes to reserve sufficient space for microstructure control in subsequent cryogenic treatment and stress homogenization. This effectively prevents the risk of brittle surface hardened layers, microcracks, and dimensional instability under ultra-low temperature service conditions caused by high strain conditions, ensuring long-term stable dimensional accuracy, surface integrity, and microstructure reliability of the sealing surface in a -269℃ hydrogen energy environment.

[0031] Furthermore, by introducing a dynamic control mechanism for the third cryogenic treatment duration based on microscopic strain values, a precise match between the surface microstructure after fine grinding and the final cryogenic treatment is achieved. The degree of lattice distortion, stress concentration level, and residual austenite content caused by fine grinding are quantified using microscopic strain values. When the strain exceeds a preset threshold, the duration of the third cryogenic treatment is dynamically increased based on the strain exceeding the threshold. Since the newly added residual austenite is mainly distributed on the material surface, targeted control of the surface layer microstructure is achieved with appropriate duration increments, avoiding energy consumption and wasted time caused by excessive cryogenic treatment. Matching the fine grinding quality assessment with the final stabilization treatment depth ensures that even under process fluctuations such as excessive grinding force, insufficient cooling, or tool passivation, the differentially extended cryogenic treatment can still effectively eliminate surface stress concentration, promote the transformation of residual austenite to martensite, and achieve uniform stress distribution. This effectively guarantees the dimensional stability, microstructural reliability, and long-term sealing performance of the cryogenic valve sealing surface.

[0032] Furthermore, by constructing a dynamic correction mechanism for the second cryogenic treatment duration based on microscopic strain values, a cross-process closed-loop optimization of the surface stress state after fine grinding and the preceding cryogenic treatment process was achieved. When the microscopic strain value exceeds a preset threshold, it indicates that the current stress concentration may stem from insufficient effect of the second cryogenic treatment. At this point, the second cryogenic treatment duration is dynamically increased based on the strain exceeding the threshold. By transmitting the microstructure of the fine-ground surface to the cryogenic treatment stage after semi-fine grinding, the stress reduction and residual austenite phase transformation effect are enhanced from the source. This breaks the limitation of independent control of a single process, making the subsequent fine grinding quality the basis for optimizing the parameters of the preceding cryogenic process, effectively compensating for the potential strength deficiency in the second cryogenic treatment, and preventing the stress concentration state from continuing to the final product. Through cross-process parameter linkage correction, it is ensured that the stress of the material gradually converges and the microstructure remains stable in the complex process chain of multiple cryogenic and grinding cycles, providing a systematic process guarantee for the dimensional accuracy, sealing reliability, and long-term service safety of cryogenic valves under extreme conditions of -269℃. Attached Figure Description

[0033] Figure 1 This is a flowchart of a grinding process for an eccentric wafer-type spiral fireproof butterfly valve applicable to ultra-low temperatures, according to an embodiment of the present invention.

[0034] Figure 2 This is a flowchart illustrating the determination of dimensional stability in an embodiment of the present invention;

[0035] Figure 3 This is a flowchart illustrating the process of determining the suitability of the stress state according to an embodiment of the present invention;

[0036] Figure 4 This is a flowchart for determining the material structure stability according to an embodiment of the present invention. Detailed Implementation

[0037] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0038] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0039] Please see Figure 1 The diagram shown is a flowchart of a grinding process for an eccentric wafer-type spiral fireproof butterfly valve suitable for cryogenic applications, according to an embodiment of the present invention.

[0040] This invention relates to a grinding method for cryogenic eccentric wafer-type spiral fireproof butterfly valves, comprising:

[0041] Step S1: Based on the fact that the residual austenite content of the valve plate is greater than the preset content value, the first cryogenic duration is adjusted according to the first cryogenic duration adjustment amount corresponding to the excess content value, wherein the excess content value is determined based on the residual austenite content value and the preset content value.

[0042] Please see Figure 2 As shown, it is a flowchart for determining dimensional stability in an embodiment of the present invention;

[0043] X-ray diffractometer is used to measure the residual austenite content of the valve plate, determine the residual austenite content value, and compare the residual austenite content with the preset content value to determine the dimensional stability.

[0044] If the residual austenite content is less than or equal to the preset content value, the dimensions are considered stable.

[0045] If the residual austenite content is greater than the preset content value, the dimensions are determined to be unstable.

[0046] Taking austenitic stainless steel as the valve plate material as an example, 304 austenitic stainless steel is preferred. The outer diameter of the valve plate of the target product is 153mm, the structural length is 52mm, the residual austenite content is less than 3%, and the target use environment is -269℃ ultra-low temperature hydrogen energy transportation.

[0047] The initial outer diameter of the valve plate before semi-finishing is 156.94 mm, the initial structural length is 53.34 mm, and the initial retained austenite content is 16%.

[0048] The final product after grinding is designed for cryogenic operation, primarily for use in -269°C cryogenic hydrogen transport vessels. In this environment, commonly used valve materials undergo a residual austenite-to-martensite phase transformation, leading to volume expansion and dimensional deformation, thus affecting the valve's sealing performance and reliability. Therefore, during grinding, multiple cryogenic treatments must be performed to gradually remove residual austenite and stress changes from the material. This prevents excessive residual austenite and stress from repeated grinding, which could cause dimensional deformation in cryogenic environments. Because of the large amount of residual austenite and stress present during rough machining, and the instantaneous high temperatures generated by friction in localized areas of the material surface during grinding (reaching hundreds or even thousands of degrees Celsius), this thermo-mechanical coupling effect can induce a reverse phase transformation from martensite to austenite in stainless steel or nickel-based alloys containing austenitic structures. When the temperature rises above the austenitizing temperature, the original martensite or residual austenite may undergo a reverse transformation to form new austenite. However, during grinding... Subsequently, rapid cooling of the material may prevent the newly formed austenite from completely transforming into martensite, resulting in residual austenite and again triggering the risk of dimensional instability. Therefore, after each grinding process, appropriate cryogenic treatment is required to ensure the dimensional stability of the product and avoid situations where the butterfly valve cannot open or close during ultra-low temperature hydrogen transportation. Furthermore, during the grinding process, many products are used in environments different from those at room temperature, requiring dimensional stability at conditions such as -80℃ and -150℃. Therefore, introducing cryogenic treatment between adjacent grinding processes during multiple grinding processes can effectively ensure that the product meets the performance requirements of subsequent usage environments.

[0049] Based on the principles of materials science and the microstructural evolution characteristics of stainless steel or nickel-based alloys commonly used in cryogenic valves, the retained austenite content is typically controlled within the range of 1% to 5%. If the retained austenite content is below 1%, it may lead to over-processing, increasing costs without significant benefits; if the retained austenite content is above 5%, there is a possibility of microstructural instability and a significantly increased risk of dimensional changes. Therefore, a target retained austenite content of 3% is selected. A 3% retained austenite content ensures the stability of the material's microstructure at -269℃, avoiding dimensional changes caused by martensitic phase transformation, while also preventing a significant increase in energy consumption and processing time due to excessive cryogenic treatment.

[0050] To ensure dimensional stability, the material requires multiple cryogenic treatments of varying durations. For the cryogenic treatment prior to semi-finishing, a preset first cryogenic duration is set to fully facilitate the phase transformation of retained austenite. A preset content value of 10% is used. After multiple experiments with valve plates containing 8%, 9%, 10%, 11%, 12%, 13%, and 14% retained austenite, respectively, were cryogenically treated with liquid nitrogen followed by liquid helium for 120 minutes, then restored to room temperature. The retained austenite content was then measured, ultimately yielding data of 10%-12% for 30... 4. The residual austenite content of the austenitic stainless steel valve plate is less than 5%. The residual austenite content of the 304 austenitic stainless steel valve plate is less than 4% for those with less than 10%, while the residual austenite content of the 304 austenitic stainless steel valve plate with more than 12% varies, with some having less than 5% and others having more than 5%. Materials with a residual austenite content of 10%-12% can achieve a residual austenite content of less than 5% under the condition of a preset first cryogenic treatment time. Therefore, 10% is selected as the preset content value to ensure that the dimensional stability can be achieved after cryogenic treatment when the preset first cryogenic treatment time is followed.

[0051] The preset first cryogenic duration is determined based on the segmented cooling of the material from room temperature to -269°C at different cooling rates and the duration of cooling. The cooling rate is 2-4°C / min when cooling from room temperature to -80°C, 5°C / min when cooling from -80°C to -180°C, and 2°C / min when cooling from -180°C to -269°C. The cooling method adopts a combination of liquid nitrogen cryogenic treatment followed by liquid helium cryogenic treatment.

[0052] The preset first cryogenic duration is 120 minutes;

[0053] When the residual austenite content is less than or equal to the preset content value, and the material is determined to be dimensionally stable, it indicates that the residual austenite content in the current material is close to the dimensionally stable state of the material. It is not necessary to perform deep cryogenic treatment for an excessively long time. Deep cryogenic treatment according to the preset first deep cryogenic time can transform the residual austenite into martensite and achieve the purpose of dimensional stability.

[0054] Specifically, in response to a residual austenite content value exceeding a preset content value, the first cryogenic duration is increased based on the first cryogenic duration adjustment amount combined with the preset first cryogenic duration, wherein the first cryogenic duration adjustment amount is positively correlated with the content exceeding the value.

[0055] When the retained austenite content exceeds a preset value, indicating dimensional instability, it signifies that the retained austenite content in the current material tends to exceed the expected dimensional stability achieved after cryogenic treatment for a preset first cryogenic duration. Therefore, the first cryogenic duration of the first cryogenic treatment is increased according to the adjustment amount corresponding to the excess content value. The excess content value is the difference between the retained austenite content and the preset value. Based on different excess content values, the first cryogenic duration of the first cryogenic treatment is increased by different adjustment amounts corresponding to the excess content values ​​to enhance the chemical transformation of retained austenite to martensite during cryogenic treatment. The free energy difference allows the retained austenite to fully transform into martensite. In the initial stage of cryogenic treatment, the retained austenite content decreases rapidly. However, as the retained austenite content decreases, the rate of reduction slows down, gradually decreasing by about 2% per hour. After 8 hours, the retained austenite content stabilizes. Therefore, the first cryogenic treatment duration adjustment is set to 30 minutes. Whenever the content exceeds the limit by 1%, the first cryogenic treatment duration is increased by one adjustment amount based on the preset duration. For the portion exceeding the limit by less than 1%, it is calculated as 1%. Based on an initial retained austenite content of 16%, the first cryogenic treatment duration is determined to be 300 minutes by adding 6 adjustment amounts to the preset duration of 120 minutes.

[0056] This invention improves the dimensional stability and process reliability of cryogenic valve manufacturing by introducing a dynamic control mechanism for residual austenite content detection. The residual austenite content of the valve plate is precisely measured using X-ray diffraction and compared with a preset threshold to determine dimensional stability. The cryogenic treatment duration is dynamically adjusted based on the content exceeding the threshold, achieving precise control of the material microstructure to ensure product dimensional stability. Introducing cryogenic treatment between multiple grinding processes effectively eliminates newly formed residual austenite generated by the inverse phase transformation induced by the thermo-mechanical coupling effect during grinding. This fundamentally avoids problems such as volume expansion, dimensional deformation, and sealing failure caused by the transformation of residual austenite to martensite in a -269℃ cryogenic environment. This ensures the opening and closing reliability and sealing performance of the butterfly valve under extreme operating conditions. Furthermore, differentiated cryogenic treatment duration control avoids energy consumption and time waste caused by over-treatment, achieving dynamic optimization of microstructure stability, processing efficiency, and cost control. This ensures reliable grinding of key valves for cryogenic hydrogen transport vessels, increases the dimensional stability and accuracy of grinding processes, and meets the performance requirements of products under cryogenic conditions.

[0057] Specifically, based on the fact that the first cryogenic duration is greater than the critical cryogenic duration, the preset second cryogenic duration is increased according to the deviation value of the first cryogenic duration, wherein the deviation value of the first cryogenic duration is determined based on the first cryogenic duration and the critical cryogenic duration.

[0058] The critical cryogenic duration is 8 hours. When the first cryogenic duration exceeds the critical cryogenic duration, the effect of continued cryogenic treatment on the material properties is not significant. Therefore, the preset second cryogenic duration is increased, and the preset second cryogenic duration is increased by the deviation value of the first cryogenic duration. This ensures that the second cryogenic treatment can compensate for the dimensional instability caused by the insufficiency of the first cryogenic treatment, and avoid the dimensional instability affecting the final fine grinding process, thus affecting the size and performance of the final product. Several 304 austenitic stainless steels with different residual austenite contents (15%, 18%, 20%, 22%, 25%, 26%, 30%, 35%, and 38%) were subjected to cryogenic treatment in actual experiments. The results were recorded. Following a predetermined cryogenic treatment sequence of liquid nitrogen followed by liquid helium, the treatment was completed every 30 minutes after 120 minutes. The materials were then allowed to return to room temperature, and the change in residual austenite content over time was analyzed. The results showed that initially, the residual austenite content decreased rapidly, by about 1% every 30 minutes. After about 2 hours, the rate of decrease slowed down, and after about 5-6 hours, the rate of decrease slowed again, finally stabilizing after 8 hours.

[0059] This invention further establishes a hierarchical control mechanism for cryogenic treatment duration. By judging whether the first cryogenic treatment duration exceeds the critical duration, the duration of the subsequent second cryogenic treatment is dynamically adjusted accordingly, enhancing the closed-loop control capability of microstructure stability during multi-stage grinding. When the first cryogenic treatment duration exceeds the critical value, the marginal effect of cryogenic treatment on the transformation of retained austenite is significantly reduced. At this point, by compensating for the deviation of the first cryogenic treatment duration in the second cryogenic treatment, the residual austenite and dimensional stability risks that may have been caused by insufficient cryogenic treatment in the early stage can be effectively compensated, preventing the unstable state from continuing into the fine grinding stage. This avoids process redundancy caused by excessive cryogenic treatment in a single stage, strengthens the synergistic effect of cryogenic treatment between each processing stage, and ensures that the material microstructure always converges towards a stable state during multiple grinding and cryogenic alternation processes, thereby guaranteeing the dimensional accuracy and sealing reliability of the final product under extreme low-temperature conditions.

[0060] Step S2: Determine the total amount of semi-finishing grinding based on the first dimensional change rate of the valve plate after the first cryogenic treatment.

[0061] Specifically, in response to determining the total amount of semi-finishing based on the first dimensional change rate, the total amount of semi-finishing is negatively correlated with the first dimensional change rate.

[0062] The contour data of the valve plate before and after the first cryogenic treatment is obtained by 3D scanning. The first dimensional change rate is determined based on the contour data. Based on the first dimensional change rate, the total amount of semi-finishing is reduced.

[0063] The total amount of semi-finish grinding is adjusted according to the first dimensional change rate. After the first cryogenic treatment, the size of the valve plate shrinks. To prevent the total amount of semi-finish grinding from exceeding expectations and resulting in insufficient grinding allowance during subsequent fine grinding, the total amount of semi-finish grinding is reduced according to the first dimensional change rate. For example, if the first dimensional change rate after cryogenic treatment is 2% (size shrinkage), the total amount of semi-finish grinding is reduced by 2%. Before semi-finish grinding, the initial outer diameter of the valve plate was 156.94 mm, the initial structural length was 53.34 mm, and the initial retained austenite content was 16%. After the first cryogenic treatment, the outer diameter of the valve plate was 153.88 mm, and the structural length was 52.30 mm. The first dimensional change rate was 1.95%. The original total amount of semi-finish grinding was a diameter reduction of 0.605 mm and a structural length reduction of 0.206 mm. After adjustment according to the first dimensional change rate, the total amount of semi-finish grinding was a diameter reduction of 0.593 mm and a structural length reduction of 0.202 mm. The valve plate, after semi-precision grinding, has an outer diameter of 153.287 mm and a structural length of 52.098 mm.

[0064] This invention achieves precise matching between cryogenic treatment and subsequent machining by introducing a dynamic control mechanism for the total semi-finishing grinding amount based on the dimensional change rate after the first cryogenic treatment. Contour data before and after cryogenic treatment are obtained using 3D scanning to quantify the first dimensional change rate and adjust the total semi-finishing grinding amount accordingly. This effectively solves the problem of insufficient final finishing allowance if the material shrinkage caused by cryogenic treatment is still processed according to the original allowance. By integrating the dimensional changes brought about by cryogenic treatment into the machining allowance allocation, the semi-finishing grinding stage can differentiate the removal of allowance based on the actual shrinkage of the material. This avoids dimensional deviations caused by over-grinding and ensures sufficient and uniform machining allowance in the finishing grinding stage, thereby significantly improving the dimensional consistency, processing success rate, and final product accuracy of cryogenic valve products in complex process chains.

[0065] Step S3: Based on the fact that the half-width value is greater than the preset half-width, the second cryogenic duration is adjusted according to the second cryogenic duration adjustment amount corresponding to the width excess value. The half-width value is determined based on the diffraction pattern data of the valve plate surface after semi-fine polishing, and the width excess value is determined based on the difference between the half-width value and the preset half-width. The width excess value is the difference between the half-width value and the preset half-width.

[0066] Specifically, in response to adjusting the second cryogenic duration, the second cryogenic duration is increased according to the second cryogenic duration adjustment amount corresponding to the width excess value, wherein the second cryogenic duration adjustment amount is positively correlated with the width excess value.

[0067] Please see Figure 3 As shown, it is a flowchart for determining the passability of stress state according to an embodiment of the present invention;

[0068] Based on the diffraction pattern data of the valve plate surface after semi-fine grinding, the half-width at half maximum (WHM) value is determined, and the WHM value is compared with the preset WHM value to determine the qualification of the stress state.

[0069] If the half-width value is less than or equal to the preset half-width, the stress state is deemed acceptable.

[0070] If the half-width value is greater than the preset half-width, the stress state is deemed unqualified.

[0071] X-ray diffraction was used to measure the diffraction pattern data of the valve plate surface after semi-finish grinding, and the full width at half maximum (FWHM) values ​​were calculated and output. During semi-finish grinding, frictional heat generated during the grinding process causes the processed surface of the material to reach a high instantaneous temperature, which can reach hundreds or even thousands of degrees Celsius. For stainless steel or nickel-based alloys containing austenitic structures, this thermo-mechanical coupling effect can induce a reverse phase transformation from martensite to austenite. When the temperature rises above the austenitizing temperature, the original martensite structure or retained austenite may undergo a reverse transformation to form new austenite. However, the rapid cooling of the material after grinding may prevent this newly formed austenite from completely transforming into martensite. The grinding process introduces new stresses into the grinding area, and the newly formed austenite becomes unstable, resulting in new retained austenite. The full width at half maximum (FWHM) value determined by the diffraction pattern data of the valve plate surface can fully indicate the stress state of the grinding area. The greater the grinding amount in semi-finish grinding, the greater the stress; the faster the grinding speed, the higher the heat generated, the greater the thermal stress, the higher the retained austenite content, and the longer the second cryogenic treatment time is required. To achieve the expected state after semi-finish grinding, the FWHM value obtained from the diffraction pattern data should be less than or equal to 2.5°. 2.5° is set as the preset FWHM.

[0072] When the half-width value is less than or equal to the preset half-width, and the stress state is deemed acceptable, it indicates that the material is being semi-finished according to the expected state and no situation exceeding the expected grinding state has occurred. Therefore, only the second cryogenic treatment according to the preset second cryogenic duration is needed to reduce the residual austenite content and reduce stress to achieve the purpose of valve plate dimensional stability, stress reduction and uniform distribution. This prevents dimensional instability caused by newly added residual austenite, and prevents microcracks, deformation, and excessive surface hardening caused by unreduced and undispersed stress, which could lead to product breakage, rapid wear or poor sealing during subsequent use.

[0073] When the half-width to half-height value exceeds the preset half-width to half-height, and the stress state is deemed unqualified, it indicates that the current semi-finished grinding state of the material exceeds expectations. This may be due to excessive grinding speed or excessive single grinding depth, leading to sudden stress changes at the grinding location, excessive temperature rise, and an increased risk of unexpected increase in retained austenite content. This also exceeds the ability of the material to maintain dimensional stability by reducing retained austenite content during the second cryogenic treatment beyond the preset second cryogenic duration, and thus exceeds the stress reduction capacity. In this case, it is necessary to adjust the second cryogenic treatment duration according to the width excess value and the corresponding second cryogenic duration adjustment amount. Extending the second cryogenic treatment duration will more effectively reduce retained austenite. Simultaneously, through the phase transformation of retained austenite to martensite within the material, the material's properties are altered. While reducing stress, this ensures uniform stress distribution and prevents the continuous occurrence of stress concentration, which could affect product quality.

[0074] After semi-finish grinding, residual austenite and stress appear on the surface of the ground area due to grinding and friction heating. Further deep cryogenic treatment is needed to induce a phase transformation in the residual austenite and to achieve a more uniform stress distribution through changes in the material's microstructure, thereby mitigating the risks of stress concentration and dimensional instability. For example, when the detected half-width at half-maximum (FWHM) value is 2.8°, it indicates that the expected state of semi-finish grinding has not been achieved; stress concentration and the increased content of residual austenite both exceed expectations. The extent to which the semi-finish grinding exceeds expectations needs to be assessed based on the excess width value. The preset second cryogenic treatment time is adjusted beyond the acceptable limit to fully mitigate the risks of residual austenite content and stress concentration. Based on the preset second cryogenic treatment time, an adjustment amount corresponding to the width excess is added to increase the total second cryogenic treatment time. The preset second cryogenic treatment time is determined based on the stress concentration and residual austenite content when the half-width is equal to the preset half-width. Under normal conditions, after semi-finish grinding, the second cryogenic treatment with the preset second cryogenic treatment time can achieve the desired results. The desired residual austenite content is below 3%, the stress state is uniformly distributed, and the half-width at half-maximum (WHM) is less than 1.5°. The preset second cryogenic treatment time is 120 minutes. Stress concentration and increased residual austenite content during semi-finish grinding are mainly concentrated on the surface of the grinding location or adjacent surfaces. Unlike the first cryogenic treatment, it is not necessary to consider the overall material reaching ultra-low temperatures. Therefore, the second cryogenic treatment time is adjusted to 20 minutes. Whenever the width exceeds the value by 0.5°, the second cryogenic treatment time is increased by 20 minutes; if the width exceeds the value by less than 0.5°, the second cryogenic treatment time is increased by 20 minutes. The ° part is calculated as 0.5°. The adjustment amount of the second cryogenic treatment time is positively correlated with the width excess value, so as to fully reduce the residual austenite increased by semi-finish grinding while ensuring uniform stress distribution through ultra-low temperature cryogenic treatment. The valve plate outer diameter after semi-finish grinding is 153.287mm, the structural length is 52.098mm, and the half-height-width value is 2.8°. The total time of the second cryogenic treatment is determined to be 140min based on the preset second cryogenic treatment time of 120min plus the second cryogenic treatment time corresponding to the width excess value of 0.3° by 20min.

[0075] This invention achieves precise identification and targeted treatment of the stress state of materials after semi-finish grinding by introducing a dynamic stress state assessment based on the full width at half maximum (HWHM) value and a second cryogenic treatment duration control mechanism. X-ray diffraction pattern data of the valve plate surface after semi-finish grinding is obtained using an X-ray diffractometer. The HWHM value is used as a quantitative indicator of stress state and microstructure stability and compared with a preset threshold. When the stress state is deemed unqualified, the second cryogenic treatment duration is dynamically increased based on the width exceeding the value, effectively addressing the problems of reverse phase transformation, newly formed retained austenite, and stress concentration induced by grinding heat and mechanical action during semi-finish grinding. By unifying stress reduction and retained austenite control through differentiated adjustment of cryogenic treatment duration, it is ensured that even with excessive grinding or process fluctuations, extended cryogenic treatment can still effectively eliminate new stress, promote the transformation of retained austenite to martensite, and achieve uniform stress distribution. This prevents quality risks such as microcracks, excessive surface hardening, deformation, and potential breakage, rapid wear, or seal failure during subsequent use, thereby improving the service reliability and precision of grinding processes for products suitable for ultra-low temperature environments.

[0076] Step S4: Based on the fact that the comprehensive change rate is greater than the preset change rate, the first cryogenic duration adjustment amount is adjusted according to the first correction coefficient corresponding to the change excess value. The comprehensive change rate is determined based on the second size change rate of the valve plate after the second cryogenic treatment and the first size change rate. The change excess value is determined based on the comprehensive change rate and the preset change rate.

[0077] Specifically, in response to adjusting the first cryogenic duration adjustment amount, the first cryogenic duration adjustment amount is increased according to a first correction coefficient corresponding to the excess value of the change, wherein the first correction coefficient is positively correlated with the excess value of the change.

[0078] Please see Figure 4 As shown, it is a flowchart for determining the material structure stability according to an embodiment of the present invention;

[0079] The comprehensive change rate is determined based on the second size change rate and the first size change rate. The comprehensive change rate is compared with the preset change rate to determine the material microstructure stability.

[0080] If the overall rate of change is less than or equal to the preset rate of change, the material structure is considered stable.

[0081] If the overall rate of change is greater than the preset rate of change, the material structure is determined to be unstable.

[0082] Change exceeding the limit = Overall change rate - Preset change rate;

[0083] The overall change rate = second dimension change rate / first dimension change rate; the first dimension change rate is 1.95%, the outer diameter of the valve plate after the second cryogenic treatment is 153.264 mm, the structural length is 52.09 mm, the second dimension change rate is 0.015%, and the overall change rate is 0.00769.

[0084] The preset change rate ranges from 0.05 to 0.10. Based on the operating environment of the butterfly valve for ultra-low temperature hydrogen transport ships at -269℃, and adhering to the principle of safety first, the preset change rate is set to 0.05.

[0085] Contour data of the valve plate before and after the second cryogenic treatment are obtained through 3D scanning. The second dimensional change rate is determined based on this data. Generally, the valve plate undergoes two cryogenic treatments before and after semi-finishing grinding, resulting in stable dimensional regions, especially after the second cryogenic treatment. The dimensional change trend before and after the two cryogenic treatments verifies the phase transformation effect of the residual austenite during the first cryogenic treatment. The overall change rate, determined by dividing the second dimensional change rate by the first dimensional change rate, verifies the effect of the first cryogenic treatment. If the effect of the first cryogenic treatment meets expectations, the second dimensional change rate is small, typically less than 0.02%, and the determined overall change rate should meet expectations, being less than 0.05% of the preset change rate. If the effect of the first cryogenic treatment does not meet expectations, the first dimensional change rate is typically less than 1%, while the second cryogenic treatment effectively stabilizes the dimensions, resulting in a larger second dimensional change rate, typically greater than 0.5%. If the determined overall change rate exceeds the expected 0.05, the first cryogenic duration adjustment amount is adjusted according to the first correction coefficient corresponding to the excess value. Whenever the excess value is greater than 0.2, the first cryogenic duration adjustment amount is increased by 10 minutes. The part less than 0.2 is calculated as 0.2. For example, if the first dimensional change rate is 0.8% and the second dimensional change rate is 0.6%, then the overall change rate = 0.6% / 0.8% = 0.75, and the excess value = 0.75 - 0.05 = 0.7. Whenever the excess value increases by 1%, the first cryogenic duration is increased by one first cryogenic duration adjustment amount based on the preset first cryogenic duration. At this time, the single first cryogenic duration adjustment amount is adjusted from 30 minutes to 70 minutes to extend the first cryogenic duration to ensure that the residual austenite fully undergoes phase transformation during the first cryogenic treatment to achieve the expected effect, ensure the dimensional stability of the material, and avoid a large second dimensional change rate, which would affect the overall accuracy of the grinding process. The outer diameter of the valve plate after the second cryogenic treatment was found to be 153.264 mm, and the structural length was 52.09 mm. The second dimensional change rate was 0.015%, and the overall change rate was 0.00769. It was determined that the material structure was stable and no adjustment of the first cryogenic treatment duration was required.

[0086] This invention achieves quantitative verification of the effect of the first cryogenic treatment and dynamic optimization of process parameters by constructing a closed-loop feedback mechanism based on the comprehensive change rate. 3D scanning is used to acquire dimensional change data before and after two cryogenic treatments. The ratio of the second dimensional change rate to the first dimensional change rate is used as the comprehensive change rate to accurately assess the material microstructure stability and the sufficiency of the retained austenite phase transformation. When the comprehensive change rate exceeds a preset threshold, the first cryogenic duration is dynamically adjusted based on the excess value, thus reinforcing the initial cryogenic treatment intensity and compensating for the process defect of insufficient retained austenite phase transformation from the previous cryogenic treatment. The dimensional stability performance of subsequent cryogenic treatments is used as the optimization basis for preceding processes, forming a cross-process self-learning and self-adaptive capability. This effectively avoids the chain risk of large dimensional changes in the second cryogenic treatment stage due to insufficient first cryogenic treatment, which in turn affects the overall processing accuracy. This ensures that the dimensions of the cryogenic valve tend to converge and stabilize in the complex process chain of multiple cryogenic treatments and grinding cycles, providing a systematic process guarantee for high-reliability manufacturing under extreme conditions.

[0087] Step S5: Determine the total amount of fine grinding for the fine grinding process based on the second dimensional change rate;

[0088] Specifically, in response to determining the total amount of fine grinding based on the second dimensional change rate, the total amount of fine grinding is negatively correlated with the second dimensional change rate.

[0089] The total amount of fine grinding is adjusted according to the second dimensional change rate. When the second dimensional change rate is 0.6%, the total amount of fine grinding is reduced by 0.6% to avoid exceeding the dimensional limit during fine grinding. Testing showed that the second dimensional change rate of the valve plate after the second cryogenic treatment was 0.015%. The original total amount of fine grinding was 0.264 mm in diameter and 0.09 mm in structural length. The adjusted total amount of fine grinding was 0.2639 mm in diameter and 0.0899 mm in structural length. The outer diameter of the valve plate after fine grinding is 153.0001 mm, and the structural length is 52.0001 mm.

[0090] This invention achieves precise matching between the final grinding allowance and the material's stable microstructure by introducing a dynamic control mechanism for the total grinding volume based on the dimensional change rate after the second cryogenic treatment. By quantifying the dimensional shrinkage after cryogenic treatment using the second dimensional change rate and adjusting the total grinding volume accordingly, it effectively avoids dimensional deviations such as insufficient allowance or overcutting during the grinding stage caused by accumulated dimensional changes from multiple cryogenic treatments. The dimensional evolution law of the material during microstructure stabilization is proactively integrated into the grinding allowance allocation strategy, enabling differentiated removal based on the actual shrinkage of the material during the grinding stage. This ensures sufficient correction allowance for the final product while maintaining the machining accuracy of the sealing surface and mating parts. The grinding process ensures dimensional and performance stability for products suitable for ultra-low temperature environments, avoiding economic losses caused by decreased product accuracy or dimensional non-compliance due to machining errors during grinding, resulting in excessively high defect rates.

[0091] Step S6: In response to the micro-strain value being greater than the preset strain value, adjust the total amount of semi-finish grinding according to the grinding correction coefficient corresponding to the strain excess value.

[0092] The micro-strain value is determined based on the lattice micro-strain of the valve plate surface after fine grinding, and the strain excess value is determined based on the micro-strain value and the preset strain value.

[0093] Specifically, in response to a micro-strain value exceeding a preset strain value, the total amount of semi-finishing grinding is increased according to a grinding correction coefficient, wherein the grinding correction coefficient is positively correlated with the strain exceeding the value.

[0094] Based on the lattice microstrain of the valve plate surface, the microstrain value is determined, and the microstrain value is compared with the preset strain value to determine the passability of the grinding quality.

[0095] If the micro-strain value is less than or equal to the preset strain value, the grinding quality is deemed acceptable.

[0096] If the micro-strain value is greater than the preset strain value, the grinding quality is deemed unqualified.

[0097] X-ray diffraction was used to obtain the lattice microstrain of the valve plate surface and determine the microstrain value. This value reflects the microscopic state of the material after fine grinding, whether the dimensions meet the expected state, and the stress state of the fine-ground surface, whether it meets the expected requirements of the product. The microstrain value reflects the degree of lattice micro-distortion on the surface of the material after fine grinding, directly characterizing the stress state, depth of the processing damage layer, and microstructure stability of the fine-ground surface. When the microstrain value exceeds 0.2%, it indicates that excessive grinding force, insufficient cooling, or passivation of the grinding wheel during the fine grinding process has led to excessive lattice distortion and dislocation accumulation. The high strain state causes stress concentration and an overly brittle surface hardened layer, resulting in the risk of inducing microcracks or dimensional instability during ultra-low temperature service. Based on engineering experience that the micro-strain of stainless steel after precision grinding is usually controlled within the range of 0.1% to 0.3%, the preset strain value is set at 0.2%. According to the principle of safety first, the more stringent value is selected. At this time, it can effectively identify whether the precision grinding quality meets the stringent requirements of ultra-low temperature valves for surface integrity. It can also leave a controllable window for subsequent third cryogenic treatment and stress homogenization, ensuring that the sealing surface of the final product has long-term stable dimensional accuracy and reliability in a hydrogen energy environment of -269℃.

[0098] When the micro-strain value is less than or equal to the preset strain value, and the grinding quality is deemed qualified, a third cryogenic treatment is performed according to the preset third cryogenic treatment duration. The third cryogenic treatment ensures that the stress concentration generated by the fine grinding process reaches a uniform stress state, and also ensures that the newly added retained austenite can fully transform into martensite to ensure dimensional stability. The preset third cryogenic treatment duration is 90 minutes, which can fully complete the phase transformation of retained austenite into martensite and achieve uniform stress distribution through changes in microstructure.

[0099] When the micro-strain value exceeds the preset strain value, and the grinding quality is deemed unqualified, it indicates that excessive grinding force, insufficient cooling, or wear of the grinding wheel during the fine grinding process has led to excessive lattice distortion and dislocation accumulation. The high strain state causes stress concentration and excessive brittleness of the surface hardened layer, while also increasing the content of residual austenite. At this point, it is necessary to increase the duration of the third deep cryogenic treatment to give the material more time to stabilize its dimensions and achieve uniform stress distribution through microstructural changes during the phase transformation process.

[0100] This indicates that the stress state, depth of the processing damage layer, and microstructure stability of the fine-ground surface exceeded expectations, possibly due to an excessively large amount of fine grinding. In this case, it is necessary to adjust the total amount of semi-fine grinding during the next material's semi-fine grinding process to reduce the total amount of fine grinding, ensuring the reliability and stability of the fine grinding process. The total amount of semi-fine grinding is increased by 0.5% whenever the strain exceeds the limit by 0.05%, thus reducing the total amount of fine grinding and ensuring that stress concentration, increased retained austenite content, and excessively deep processing damage layer depth do not occur during fine grinding. The microscopic strain value after fine grinding was measured to be 0.17%, lower than the preset strain value. Therefore, it is not necessary to adjust the total amount of semi-fine grinding based on the grinding correction coefficient corresponding to the strain excess value, nor is it necessary to increase the total amount of semi-fine grinding based on the grinding correction coefficient, nor is it necessary to increase the third cryogenic duration based on the third cryogenic duration adjustment amount corresponding to the strain excess value.

[0101] This invention constructs a closed-loop optimization system from fine grinding quality feedback to preceding processes by introducing a fine grinding quality assessment based on micro-strain values ​​and a reverse correction mechanism for semi-fine grinding parameters. X-ray diffraction is used to obtain the lattice micro-strain values ​​of the surface after fine grinding, accurately quantifying the degree of lattice distortion, stress concentration state, and depth of the processing damage layer. When the micro-strain value exceeds a preset threshold, the grinding quality is deemed unqualified, and the total amount of semi-fine grinding is dynamically increased through a grinding correction coefficient. This strengthens the control of allowance from the upstream of the process, avoiding excessive lattice distortion and dislocation accumulation caused by excessive grinding force, insufficient cooling, or tool passivation during the fine grinding stage. Linking the microstructure of the fine-ground surface with the process parameters of the semi-fine grinding stage allows the preceding processes to reserve sufficient space for microstructure control in subsequent cryogenic treatment and stress homogenization. This effectively prevents the risk of brittle surface hardened layers, microcracks, and dimensional instability under ultra-low temperature service conditions caused by high strain conditions, ensuring that the sealing surface maintains long-term stable dimensional accuracy, surface integrity, and microstructure reliability in a -269℃ hydrogen energy environment.

[0102] Specifically, in response to a microscopic strain value exceeding a preset strain value, the third cryogenic duration is increased according to a third cryogenic duration adjustment amount corresponding to the strain exceeding the value, wherein the third cryogenic duration adjustment amount is positively correlated with the strain exceeding the value.

[0103] The greater the micro-strain value exceeds the preset strain value, the more severe the stress concentration and the higher the content of retained austenite. Since the retained austenite is increased due to fine grinding, it is distributed on the surface of the material. Therefore, it is not necessary to consider whether the material interior needs to undergo uniform cryogenic treatment at ultra-low temperatures. Thus, excessive cryogenic treatment time is not required. Whenever the strain exceeds the preset strain value by 0.05%, the third cryogenic treatment time is increased by a third cryogenic treatment time adjustment. At this time, the single third cryogenic treatment time adjustment is set to 10 minutes. The third cryogenic treatment time is increased from 90 minutes to 100 minutes. Any part less than 0.05% is calculated as 0.05% to ensure that the third cryogenic treatment effect exceeds the expected material requirements, thereby ensuring that the product's dimensional stability, sealing, and stress uniformity meet the expected requirements.

[0104] This invention achieves precise matching between the surface microstructure after fine grinding and the final cryogenic treatment by introducing a dynamic control mechanism for the third cryogenic treatment duration based on microscopic strain values. The microscopic strain values ​​quantify the degree of lattice distortion, stress concentration level, and residual austenite content caused by fine grinding. When the strain exceeds a preset threshold, the duration of the third cryogenic treatment is dynamically increased based on the strain excess. Since the newly added residual austenite is mainly distributed on the material surface, the appropriate duration increment achieves targeted control of the surface layer microstructure, avoiding energy consumption and wasted time caused by excessive cryogenic treatment. Matching the fine grinding quality assessment with the final stabilization treatment depth ensures that even under process fluctuations such as excessive grinding force, insufficient cooling, or tool passivation, the differentially extended cryogenic treatment can still effectively eliminate surface stress concentration, promote the transformation of residual austenite to martensite, and achieve uniform stress distribution. This effectively guarantees the dimensional stability, microstructural reliability, and long-term sealing performance of the cryogenic valve sealing surface.

[0105] Specifically, in response to a microscopic strain value exceeding a preset strain value, the adjustment amount of the second cryogenic duration is increased according to a second correction coefficient corresponding to the strain excess value, wherein the second correction coefficient is positively correlated with the strain excess value.

[0106] This indicates that the current stress concentration exceeds expectations. This stress concentration may be due to an unsatisfactory second cryogenic treatment effect. Therefore, the second cryogenic duration is adjusted according to the strain excess value. A corresponding second correction coefficient is set based on the strain excess value exceeding the preset strain value. If the strain excess value is less than 0.05%, the second correction coefficient is set to 10 minutes. If the strain excess value is greater than or equal to 0.05%, the second correction coefficient increases by 15 minutes for every 0.05% excess. Amounts less than 0.05% are calculated as 0.05%. That is, when the strain excess value is 0.05%, the correction coefficient is calculated as follows: When the strain exceeds 8%, the second correction factor is 30 min. When the strain exceeds 0.11%, the second correction factor is 45 min. The original adjustment amount for the second cryogenic treatment time is 20 min. When the width exceeds 0.5°, the second cryogenic treatment time is adjusted by increasing the original adjustment amount by 20 min. If the strain exceeds 0.08%, the second correction factor is 30 min, and the adjustment amount for the second cryogenic treatment time increases to 50 min. Whenever the width exceeds 0.5°, the second cryogenic treatment time is increased by a newly determined adjustment amount of 50 min. After testing, the valve plate outer diameter after the third cryogenic treatment is 152.999 mm, the structural length is 52 mm, and the retained austenite content is 1.9%, meeting product requirements.

[0107] This invention achieves cross-process closed-loop optimization of the surface stress state after fine grinding and the preceding cryogenic treatment process by constructing a dynamic correction mechanism based on the adjustment of the second cryogenic duration according to the micro-strain value. When the micro-strain value exceeds a preset threshold, it indicates that the current stress concentration may be due to insufficient effect of the second cryogenic treatment. At this time, the adjustment of the second cryogenic duration is dynamically increased according to the strain exceeding the value. By feeding back the microstructure of the fine-ground surface to the cryogenic treatment stage after semi-fine grinding, the stress reduction and residual austenite phase transformation effect are strengthened from the source. This breaks the limitation of independent control of a single process, making the subsequent fine grinding quality the basis for optimizing the parameters of the preceding cryogenic process, effectively compensating for the potential strength deficiency problem of the second cryogenic treatment, and preventing the stress concentration state from continuing to the final product. Through the linkage correction of process parameters across processes, it ensures that the stress of the material gradually converges and the microstructure remains stable in the complex process chain of multiple cryogenic and grinding cycles, providing a systematic process guarantee for the dimensional accuracy, sealing reliability and long-term service safety of cryogenic valves under extreme conditions of -269℃.

[0108] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A polishing method for eccentrically double-jacked helical fireproof butterfly valve suitable for ultra-low temperature, characterized in that, include, The first cryogenic duration is adjusted according to the first cryogenic duration adjustment amount corresponding to the excess content value, based on the residual austenite content value of the valve plate being greater than the preset content value. The excess content value is determined based on the difference between the residual austenite content value and the preset content value. The total amount of semi-finishing grinding is determined based on the first dimensional change rate of the valve plate after the first cryogenic treatment. Based on the fact that the half-width value is greater than the preset half-width, the second cryogenic duration is adjusted according to the second cryogenic duration adjustment amount corresponding to the width excess value. The half-width value is determined based on the diffraction pattern data of the valve plate surface after semi-fine polishing, and the width excess value is determined based on the difference between the half-width value and the preset half-width. Based on the fact that the overall change rate is greater than the preset change rate, the first cryogenic duration adjustment amount is adjusted according to the first correction coefficient corresponding to the change excess value. The overall change rate is determined based on the second size change rate of the valve plate after the second cryogenic treatment and the first size change rate. The change excess value is determined based on the overall change rate and the preset change rate. The total amount of fine grinding is determined based on the second dimensional change rate; In response to a micro-strain value exceeding a preset strain value, the total amount of semi-finish grinding is adjusted according to the grinding correction coefficient corresponding to the strain excess value. The micro-strain value is determined based on the lattice micro-strain of the valve plate surface after fine grinding, and the strain excess value is determined based on the micro-strain value and the preset strain value.

2. The grinding method for an eccentric wafer-type spiral fireproof butterfly valve suitable for ultra-low temperatures according to claim 1, characterized in that, In response to a residual austenite content value exceeding a preset value, the first cryogenic duration is increased based on the first cryogenic duration adjustment amount combined with the preset first cryogenic duration, wherein the first cryogenic duration adjustment amount is positively correlated with the content exceeding the value.

3. The grinding method for an eccentric wafer-type spiral fireproof butterfly valve suitable for ultra-low temperatures according to claim 1, characterized in that, In response to determining the total amount of semi-finishing based on the first dimensional change rate, the total amount of semi-finishing is negatively correlated with the first dimensional change rate.

4. The grinding method for an eccentric wafer-type spiral fireproof butterfly valve suitable for ultra-low temperatures according to claim 1, characterized in that, In response to the adjustment of the second cryogenic duration, the second cryogenic duration is increased according to the second cryogenic duration adjustment amount corresponding to the width excess value, wherein the second cryogenic duration adjustment amount is positively correlated with the width excess value.

5. The grinding method for an eccentric wafer-type fireproof butterfly valve suitable for ultra-low temperatures according to claim 1, characterized in that, In response to adjusting the first cryogenic duration adjustment amount, the adjustment amount of the first cryogenic duration is increased according to a first correction coefficient corresponding to the excess value of the change, wherein the first correction coefficient is positively correlated with the excess value of the change.

6. The grinding method for an eccentric wafer-type spiral fireproof butterfly valve suitable for ultra-low temperatures according to claim 1, characterized in that, In response to determining the total amount of fine grinding based on the second dimensional change rate, the total amount of fine grinding is negatively correlated with the second dimensional change rate.

7. The grinding method for an eccentric wafer-type spiral fireproof butterfly valve suitable for ultra-low temperatures according to claim 1, characterized in that, In response to a microscopic strain value exceeding a preset strain value, the third cryogenic duration is increased according to a third cryogenic duration adjustment amount corresponding to the strain exceeding the value, wherein the third cryogenic duration adjustment amount is positively correlated with the strain exceeding the value.

8. The grinding method for an eccentric wafer-type spiral fireproof butterfly valve suitable for ultra-low temperatures according to claim 1, characterized in that, In response to a micro-strain value exceeding a preset strain value, the total amount of semi-finishing grinding is increased according to a grinding correction coefficient, wherein the grinding correction coefficient is positively correlated with the strain exceeding the value.

9. The grinding method for an eccentric wafer-type spiral fireproof butterfly valve suitable for ultra-low temperatures according to claim 1, characterized in that, In response to a microscopic strain value exceeding a preset strain value, the adjustment amount of the second cryogenic duration is increased according to a second correction coefficient corresponding to the strain excess value, wherein the second correction coefficient is positively correlated with the strain excess value.

10. The grinding method for an eccentric wafer-type spiral fireproof butterfly valve suitable for cryogenic applications according to claim 1, characterized in that, Based on the fact that the first cryogenic duration is greater than the critical cryogenic duration, the preset second cryogenic duration is increased according to the deviation value of the first cryogenic duration, wherein the deviation value of the first cryogenic duration is determined based on the first cryogenic duration and the critical cryogenic duration.

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