All-position argon arc welding method for semiconductor-grade ultra-pure stainless steel pipeline

Abstract

The invention discloses an all-position argon arc welding method for a semiconductor-grade ultra-high-purity stainless steel pipeline, and relates to the technical field of semiconductor-grade ultra-high-purity stainless steel pipeline welding.The method comprises the steps that firstly, the pipe end of a to-be-welded pipeline is subjected to ultra-high cleanliness pretreatment, and groove forming and oxidation film removing are completed; pipeline coaxiality assembly is completed in a clean environment, and a pipeline inner and outer double-layer high-purity argon laminar flow protection system is built; a partition welding parameter matrix is constructed based on all stations of all-position welding, pipeline circular seam continuous welding is completed through low-heat input pulse tungsten electrode argon arc welding, and welding parameters are dynamically and finely adjusted in the whole welding process; and after welding, carrying out in-situ passivation treatment on a welding seam and the inner wall of the pipeline. Uniform forming of all-position welding of the semiconductor-grade ultra-pure stainless steel pipeline can be achieved, welding seam oxidation, forming defects and intergranular corrosion risks are effectively controlled, the cleanliness of the inner wall of the pipeline and the corrosion resistance of welding seams are guaranteed, and the strict use requirement for semiconductor ultra-pure medium conveying is met.

Description

Technical Field

[0001] This invention relates to the field of semiconductor-grade ultra-high purity stainless steel pipe welding technology, and in particular to an all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes. Background Technology

[0002] In semiconductor chip manufacturing, the stable delivery of media such as ultra-high purity specialty gases, ultra-high purity water, and chemical reagents is a core element in ensuring chip production yield and process stability. Semiconductor-grade ultra-high purity stainless steel pipes, as the core carriers for these media, directly determine the cleanliness, corrosion resistance, and long-term operational stability of the media delivery system through the quality of their welded joints. All-position argon arc welding is the most widely used circumferential welding process in the on-site installation of semiconductor pipelines. Pipeline circumferential welding requires continuous coverage of multiple different positions, including flat welding, vertical-up welding, overhead welding, and vertical-down welding. The control of process parameters, cleanliness, and weld protection during the welding process directly determines the weld formation quality, inner wall cleanliness, and resistance to intergranular corrosion. The semiconductor industry's requirements for pipeline welds not only need to meet conventional mechanical performance indicators but also impose far more stringent requirements on the degree of oxidation of the weld inner wall, surface roughness, residual particulate contaminants, and corrosion resistance than those for conventional industrial pipelines. This places higher standards on the entire process control of all-position welding of pipelines.

[0003] Existing all-position TIG welding processes are mostly designed for welding stainless steel pipes in conventional industrial applications. They lack a comprehensive cleanliness control system tailored to the requirements of semiconductor-grade ultra-high purity pipes. Pre-treatment standards for pipe ends are unclear, and the processes of inner wall polishing, degreasing, cleaning, and drying lack specific control. This can easily introduce contaminants such as grease, metal debris, and solid particles into the pipe before welding, resulting in post-weld cleanliness that fails to meet semiconductor industry standards. Furthermore, existing all-position welding processes often use uniform welding parameters for the entire circumferential weld, without differentiated parameter design based on the stress state and forming characteristics of the molten pool at different welding positions. This easily leads to defects such as uneven weld formation, incomplete penetration, weld beads, and undercut during all-position welding. The lack of precise quantitative control over welding heat input can result in coarse grains in the weld and heat-affected zone, significantly increasing the risk of intergranular corrosion during use and making them unsuitable for the long-term stable delivery of ultra-high purity media in semiconductor pipelines.

[0004] Current welding processes often rely solely on external gas protection during the welding process, while internal pipe protection typically employs a fixed-flow, continuous argon flow. This approach fails to dynamically adjust the shielding gas flow and pressure based on real-time changes at the welding station, leading to issues like disruption of the shielding gas laminar flow and intrusion of external air in overhead and vertical welding positions. This results in defects such as oxidation discoloration and oxide inclusions on the weld inner wall, directly compromising its cleanliness and corrosion resistance. Furthermore, current post-weld passivation processes often utilize offline passivation of the entire pipeline, failing to provide precise in-situ passivation for the weld area. This results in uneven passivation film thickness and insufficient density in the weld region, causing a significant difference in corrosion resistance between the weld area and the base pipe material. During long-term transport of ultra-high-purity corrosive media, preferential corrosion and particle shedding in the weld area can occur, impacting the long-term operational stability of the semiconductor media transport system. Summary of the Invention

[0005] This invention proposes an all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes to solve the problems mentioned in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for all-position argon arc welding of semiconductor-grade ultra-high purity stainless steel pipes, wherein the pipe ends of the semiconductor-grade ultra-high purity stainless steel pipes to be welded are subjected to ultra-high cleanliness pretreatment, and the pipe end face flat processing, inner wall electrolytic polishing, degreasing and decontamination, ultrapure water rinsing and dust-free drying are completed in sequence, and the precision forming of the welding bevel and the removal of the oxide film on the bevel surface are completed simultaneously, thereby controlling the core indicators of roughness and cleanliness of the inner wall of the pipe end; Complete the high-precision assembly and pre-weld system protection of the pipeline to be welded, complete the coaxiality assembly of the pipeline in a Class 1000 clean environment, control the assembly gap and misalignment, build a double-layer high-purity argon laminar flow protection system on the inner and outer walls of the pipeline simultaneously, complete the oxygen content replacement and sealing pressure maintenance inside the pipeline before welding, and ensure that the oxygen content in the pipeline is lower than the preset safety threshold throughout the welding process. Based on four welding positions for all-position pipeline welding—flat welding, vertical upward welding, overhead welding, and vertical downward welding—an all-position zoned welding parameter matrix is ​​constructed. Matching parameters for welding pulse current base value and peak value, pulse frequency, wire feed speed, welding travel speed, and internal and external shielding argon flow rate are set for different positions. At the same time, a smooth transition range of parameters between each position is set. Low heat input pulsed tungsten inert gas welding process is used to perform continuous welding in all positions. The pipe circumferential weld is completed in one continuous welding according to the preset partition parameter matrix. The molten pool temperature, weld formation state and shielding gas purity are monitored in real time throughout the welding process. Based on the monitoring data, the welding parameters are dynamically fine-tuned in a closed loop to control the range of the weld heat-affected zone and the welding line energy input. After welding, the weld and the inner wall of the pipe are subjected to in-situ passivation treatment. High-purity nitrogen atomized electronic grade passivation liquid is used to complete the uniform passivation of the weld area. Simultaneously, ultrapure water circulation rinsing and dust-free drying are completed after passivation, forming a uniform and dense corrosion-resistant passivation film on the weld surface.

[0007] Furthermore, it also includes a precise control step for the welding line energy in all positions. During the construction of the welding parameter matrix, a welding line energy calculation formula is introduced for different welding stations to precisely quantify and control the welding heat input at each station. The calculation formula is as follows: ; in For the corresponding welding line energy of the welding station, The thermal efficiency coefficient of tungsten inert gas welding. For welding arc voltage, This is the effective value of the welding current. This refers to the welding travel speed.

[0008] Furthermore, it also includes a dynamic control step for laminar flow protection of high-purity argon gas inside the pipe. Throughout the welding process, the flow rate and pressure of the protective argon gas inside the pipe are dynamically adjusted according to the real-time changes of the welding position. In the overhead welding position, the static pressure of the argon gas inside the pipe is increased to counteract the effect of gravity falling of the molten pool. In the flat welding position, a stable laminar flow state is maintained to prevent the intrusion of external air.

[0009] Furthermore, it also includes a pre-welding cleanliness classification and control step. For semiconductor-grade ultra-high purity stainless steel pipes of different specifications and application scenarios, corresponding pre-treatment cleanliness levels are set to control the amount of residual grease, the number of particulate contaminants, and the core indicators of surface roughness on the inner wall of the pipe. After the pre-treatment is completed, the pipe port is sealed and protected in a Class 100 clean environment.

[0010] Furthermore, in the pipe assembly step, the coaxiality misalignment of the pipes to be welded is controlled within 5% of the pipe wall thickness, the assembly gap is controlled between 0.5mm and 2mm, and after assembly, a stainless steel positioning clamp with a cleanliness standard is used to temporarily fix the pipes. The positioning weld points are set on the outer wall of the pipes and are completely within the bevel range of the subsequent welding.

[0011] Furthermore, in the aforementioned double-layer high-purity argon laminar flow protection system, the outer wall protection adopts a welding torch nozzle with a gas lens structure, which achieves uniform and stable delivery of argon through a laminar flow rectification structure. The inner wall protection adopts a double-sided adjustable gas plug structure, forming a sealed protective gas chamber in the pipes on both sides of the weld. Before welding, the air in the gas chamber is replaced by continuously introducing high-purity argon. The oxygen content in the gas chamber is continuously monitored throughout the welding process.

[0012] Furthermore, in the in-situ passivation treatment step, a passivation film uniformity evaluation calculation formula is introduced for the passivation effect in the weld area, and the passivation treatment process parameters are optimized and adjusted in a closed loop. The calculation formula is as follows: ; in The uniformity coefficient of the passivation film in the weld area is given. This represents the total number of passivation film thickness detection points. For the first The measured thickness of the passivation film at each test point This is the arithmetic mean of the passivation film thickness at all detection points.

[0013] Furthermore, in the all-position welding parameter matrix, the peak welding current for the flat welding station is set to 80A to 120A, the peak welding current for the vertical upward welding station is set to 100A to 140A, the peak welding current for the overhead welding station is set to 70A to 100A, and the peak welding current for the vertical downward welding station is set to 90A to 130A. The pulse frequency for each station is set to 30Hz to 80Hz, the base current is 30% to 40% of the peak current, and a parameter transition range of 10° to 15° is set between adjacent stations. Within the range, the welding parameters adopt a linear smooth adjustment mode.

[0014] Furthermore, in the pre-treatment step of the pipe end before welding, the inner wall of the pipe end is treated with precision electrolytic polishing process, degreasing and decontamination are carried out by ultrasonic cleaning with electronic grade anhydrous ethanol for a duration of not less than 15 minutes, ultrapure water rinsing is carried out by circulating electronic grade ultrapure water, and after rinsing, high-purity nitrogen with a cleanliness level of 100 is used for constant temperature and dust-free drying, and immediately after drying, a clean dustproof plug is used to double-seal the pipe end for protection.

[0015] Furthermore, this includes non-destructive testing and systematic verification of cleanliness and corrosion resistance of the completed pipe welds. This involves sequentially performing radiographic non-destructive testing, internal wall roughness testing, particle size testing, and intergranular corrosion testing. The radiographic non-destructive testing must meet the Class I weld requirements of NB / T 47013.2 "Non-destructive testing of pressure equipment - Part 2: Radiographic testing". The internal wall particle size testing requires that the number of solid particles larger than 0.1 μm in the pipe does not exceed the limit specified in SEMI F72 standard. The intergranular corrosion test adopts the oxalic acid etching method in GB / T 4334-2020 "Corrosion of metals and alloys - Test method for intergranular corrosion of austenitic and ferritic-austenitic (duplex) stainless steel". After the test, there should be no intergranular corrosion grooves or cracks in the weld and heat-affected zone. At the same time, the inner wall of the weld is inspected for oxidation color.

[0016] Compared with existing technologies, the beneficial effects of this invention are: This method, designed for the usage characteristics and requirements of semiconductor-grade ultra-high purity stainless steel pipes, establishes a comprehensive process control system covering pre-treatment of pipe ends before welding, pipe assembly protection, all-position welding implementation, post-weld in-situ passivation, and verification of weld performance and cleanliness. It can achieve uniform and stable forming of all-position welding of pipe circumferential seams, effectively control the generation of weld forming defects, and ensure the overall mechanical properties and consistency of all-position forming of the weld.

[0017] This method utilizes an ultra-high cleanliness pretreatment and a graded cleanliness control system to specifically remove contaminants such as grease, oxide film, and solid particles from the inner wall of the pipeline. It strictly controls the roughness and cleanliness indicators of the inner wall of the pipe end. Combined with a double-layer high-purity argon laminar flow protection system throughout the welding process, it can achieve effective protection of both sides of the weld, control the generation of oxidation defects on the inner wall of the weld, and ensure that the cleanliness indicators of the inner wall of the pipeline after welding meet the usage requirements of the semiconductor industry.

[0018] This method, through the construction of a full-position zoned welding parameter matrix and the precise quantitative control of welding line energy, can match the molten pool formation characteristics of different welding stations, achieve a smooth transition of welding parameters between stations, and strictly control the heat input and interpass temperature throughout the welding process. This effectively reduces the range of the weld heat-affected zone, avoids the problem of coarse grains in the weld and heat-affected zone, reduces the risk of intergranular corrosion during the use of the weld, and ensures that the corrosion resistance of the weld area is consistent with that of the pipeline base material.

[0019] This method utilizes a post-weld in-situ passivation process to precisely and uniformly passivate the weld area, forming a dense and continuous passivation film on the weld surface. This further enhances the corrosion resistance of the weld area. Simultaneously, a systematic weld performance and cleanliness verification system has been established to comprehensively verify the mechanical properties, internal defects, inner wall cleanliness, and corrosion resistance of the weld. This ensures strict quality control of the welded products and guarantees that the welded pipeline products meet the requirements for transporting semiconductor-grade ultra-high purity media.

[0020] The process steps of this method are standardized and controllable, and it can be adapted to the on-site all-position welding construction of semiconductor-grade ultra-high purity stainless steel pipelines of different specifications and materials. All parameters and test data of the process are fully traceable, which can effectively improve the stability of the welding process and the pass rate of the welded products, and provide standardized process support for the on-site installation and construction of semiconductor ultra-high purity media transportation pipelines. Attached Figure Description

[0021] Figure 1 This is a schematic block diagram of an all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes proposed in this invention. Figure 2 Detailed sub-flowchart of ultra-high cleanliness pretreatment of pipe ends before welding; Figure 3 Flowchart for the construction and dynamic control of a double-layer high-purity argon laminar flow protection system; Figure 4 Logic diagram for constructing and implementing the all-position zone welding parameter matrix; Figure 5 This is a quality control chart for post-weld in-situ passivation treatment and system verification. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The invention will now be described in further detail with reference to the accompanying drawings.

[0025] Reference Figures 1 to 5 A method for all-position argon arc welding of semiconductor-grade ultra-high purity stainless steel pipes. The pipe ends of the semiconductor-grade ultra-high purity stainless steel pipes to be welded undergo ultra-high cleanliness pretreatment, which includes the following steps: pipe end face flat processing, inner wall electrolytic polishing, degreasing and decontamination, ultrapure water rinsing, and dust-free drying. Simultaneously, the precision forming of the welding bevel and the removal of the oxide film on the bevel surface are completed, and the core indicators of pipe end inner wall roughness and cleanliness are strictly controlled. Complete the high-precision assembly and pre-weld system protection of the pipeline to be welded, complete the coaxiality assembly of the pipeline in a Class 1000 clean environment, accurately control the assembly gap and misalignment, build a double-layer high-purity argon laminar flow protection system on the inner and outer walls of the pipeline simultaneously, complete the oxygen content replacement and sealing pressure maintenance inside the pipeline before welding, and control the oxygen content in the pipeline to be lower than the preset safety threshold throughout the welding process. Based on four welding positions for all-position pipeline welding—flat welding, vertical upward welding, overhead welding, and vertical downward welding—an all-position zoned welding parameter matrix is ​​constructed. Matching parameters for welding pulse current base value and peak value, pulse frequency, wire feed speed, welding travel speed, and internal and external shielding argon flow rate are set for different positions. At the same time, a smooth transition range of parameters between each position is set. Low-heat-input pulsed tungsten inert gas welding (TIG) process is used to perform continuous welding in all positions. The circumferential weld of the pipeline is completed in one continuous welding process according to the preset partition parameter matrix. The temperature of the molten pool, the weld formation state and the purity of the shielding gas are monitored in real time throughout the welding process. The welding parameters are dynamically fine-tuned in a closed loop based on the monitoring data, and the range of the heat-affected zone of the weld and the welding line energy input are strictly controlled.

[0026] This invention also includes a step for precise control of welding line energy in all positions. During the construction of the welding parameter matrix, a welding line energy calculation formula is introduced for different welding stations to precisely quantify and control the welding heat input of each station. The calculation formula is as follows: ; in For the corresponding welding line energy of the welding station, The thermal efficiency coefficient of tungsten inert gas welding. For welding arc voltage, This is the effective value of the welding current. To optimize welding speed, the upper limit of heat input for each welding station can be precisely limited through quantitative calculation of line energy, matching the molten pool formation requirements of different stations. Simultaneously, the line energy fluctuation of all-position welding is controlled within a preset range. Considering the intergranular corrosion-sensitive temperature range of 316L and 316LMOD ultra-high purity stainless steel, line energy thresholds and interpass temperature control limits are set for each station. The timing of pulse current base peak values ​​is matched to the molten pool solidification rate. In the overhead welding station, the line energy fluctuation range is further narrowed to counteract the influence of molten pool gravity. In the vertical welding station, dynamic fine-tuning of line energy matches the molten pool spreading and solidification rhythm, controlling the risk of coarse weld grains and intergranular corrosion caused by excessive welding heat input, ensuring uniform and consistent metallographic structure of welds in all positions.

[0027] This invention also includes a dynamic control step for laminar flow protection of high-purity argon gas inside the pipe. Throughout the welding process, the flow rate and pressure of the protective argon gas inside the pipe are dynamically adjusted according to the real-time changes in the welding position. In the overhead welding position, the static pressure of the argon gas inside the pipe is increased to counteract the effect of gravity falling on the molten pool. In the flat welding position, a stable laminar flow state is maintained to prevent the intrusion of external air. By controlling the Reynolds number of the protective argon gas, the laminar flow state inside the pipe is ensured to be maintained at all times, eliminating the influence of external air brought in by eddies. Simultaneously, the protective argon gas inside the pipe is preheated at a constant temperature to eliminate the problem of sudden local temperature changes and molten pool protection failure caused by cold argon gas entering the molten pool area. After the welding arc leaves the corresponding weld area, the argon gas protection state inside the pipe is maintained until the temperature on the back side of the weld drops below the intergranular corrosion sensitive temperature range. After welding is completed, high-purity argon gas is continued to be introduced to complete the back side protection of the weld cooling process. Throughout the welding process, the weld area inside the pipe is always under the complete coverage and protection of high-purity argon gas, eliminating oxidation and discoloration defects on the inner wall of the weld.

[0028] This invention includes a pre-welding cleanliness classification and control step. For semiconductor-grade ultra-high purity stainless steel pipes of different specifications and application scenarios, corresponding pre-treatment cleanliness levels are set. The amount of residual grease, the number of particulate contaminants, and the surface roughness of the pipe inner wall are controlled separately. Differentiated pre-treatment process standards are formulated for high-purity special gas pipes, ultra-high purity water pipes, and bulk inert gas pipes used in chip manufacturing. During pre-treatment, the amount of residual grease and the number of particulate contaminants are monitored in real time using online detection equipment. After pre-treatment, the pipe ports are double-sealed in a Class 100 clean laminar flow hood environment. A vacuum nitrogen-filled protection mode is used during pipe transportation to eliminate secondary contamination during transportation and storage. This controls the cleanliness of the pipe inner wall before welding, matching the usage requirements for semiconductor-grade ultra-high purity media transportation.

[0029] In the pipe assembly process of this invention, the coaxiality misalignment of the pipes to be welded is controlled within 5% of the pipe wall thickness, and the assembly gap is controlled between 0.5mm and 2mm. Before assembly, the non-contact coaxiality pre-calibration of the pipes to be welded is completed using a laser alignment instrument. Differentiated assembly gaps are set according to the differences in pipe wall thickness and welding positions. The assembly gap range is narrowed for thin-walled pipes, and the assembly gap is appropriately widened for thick-walled pipes, and the parameters are matched with multi-layer and multi-pass welding parameters. After assembly, a passivated stainless steel positioning fixture with a cleanliness standard is used for temporary fixation. The contact parts between the positioning fixture and the pipe are isolated with non-metallic clean gaskets to eliminate iron ion contamination and surface scratches. The positioning weld point is set on the outer wall of the pipe and is completely within the bevel range of the subsequent welding. During the positioning welding process, double-layer argon gas protection is activated on both sides to ensure that the positioning weld point is free of oxidation defects and is completely integrated into the subsequent formal weld. The entire assembly process is completed in a Class 1000 cleanroom to eliminate the problem of environmental pollutants entering the pipe interior.

[0030] In this invention's double-layer high-purity argon laminar flow protection system, the outer wall protection uses a welding torch nozzle with a gas lens structure. A multi-layer sieve-type laminar flow rectification structure ensures uniform and stable argon delivery. The nozzle diameter is matched to the pipe diameter and bevel size, and the ratio of the tungsten electrode extension length to the nozzle inner diameter is controlled to ensure the effective range of laminar flow protection. The purity of the argon gas used is not less than 99.999%. The inner wall protection uses adjustable gas plugs with multi-hole flow equalization structures on both sides, forming a sealed protective gas chamber within the pipes on both sides of the weld. The multi-hole flow equalization structure enables uniform axial laminar flow of the protective gas within the pipes, eliminating the influence of local eddies. Before welding, high-purity argon gas is continuously introduced to replace the air in the gas chamber. Throughout the welding process, an online oxygen analyzer monitors the oxygen content, water content, and argon purity in the gas chamber in real time. A multi-pipeline closed-loop control system dynamically adjusts the flow rate of the inner and outer protective argon gases in real time according to the welding speed, ensuring that the oxygen content remains below 50 ppm.

[0031] In the in-situ passivation process of this invention, a passivation film uniformity evaluation formula is introduced to evaluate the passivation effect in the weld area, and the passivation process parameters are optimized and adjusted in a closed loop. The calculation formula is as follows: ; in The uniformity coefficient of the passivation film in the weld area is given. This represents the total number of passivation film thickness detection points. For the first The measured thickness of the passivation film at each test point The arithmetic mean of the passivation film thickness at all detection points is used. By quantitatively calculating the uniformity coefficient, the overall distribution of the passivation film can be accurately evaluated. This allows for the optimization of core process parameters such as passivation solution concentration, atomization pressure, and passivation time. Before passivation, the weld area is purged non-contactly with constant-temperature high-purity nitrogen at a cleanliness level of Class 100 to remove welding fumes and dust from the weld surface. During passivation, the temperature of the passivation solution is precisely controlled in a closed loop to achieve a uniform and stable passivation reaction rate. After passivation, electronic-grade ultrapure water with a resistivity of not less than 18.2 MΩ·cm is used for circulating turbulent rinsing. The resistivity and pH value of the rinsing water are monitored online throughout the process to eliminate any passivation solution residue. After rinsing, high-purity nitrogen with a dew point below -70℃ is used for gradient heating and dust-free drying. Finally, a uniform and dense passivation film is formed in the weld area, improving the intergranular corrosion resistance of the weld area and ensuring that its corrosion resistance is consistent with that of the pipe base material.

[0032] In the all-position welding parameter matrix of this invention, the peak welding current is set to 80A to 120A for the flat welding position, 100A to 140A for the vertical upward welding position, 70A to 100A for the overhead welding position, and 90A to 130A for the vertical downward welding position. The pulse frequency for each position is set to 30Hz to 80Hz, and the base current is 30% to 40% of the peak current. A parameter transition range of 10° to 15° is set between adjacent positions. Within the range, the welding parameters adopt a linear smooth adjustment mode to control weld formation defects caused by sudden parameter changes. Meanwhile, different wire feeding modes are set for different welding positions. The flat welding position adopts the early wire feeding mode to ensure the filling amount of the molten pool. The overhead welding position adopts the delayed wire feeding mode to eliminate the problem of molten pool sagging. The vertical welding position adopts the intermittent wire feeding mode synchronized with the pulse current. The wire is fed synchronously when the peak current is output and stops when the base current is output, matching the melting and solidification rhythm of the molten pool. The arc length is controlled in a closed loop through real-time feedback of arc voltage throughout the welding process. The tungsten electrode height is dynamically adjusted to ensure the stability of the welding arc length. Different welding layers and single-pass weld penetration control parameters are set for pipes with different wall thicknesses to achieve uniform penetration and consistent formation of welds in all positions.

[0033] In the pre-treatment step of the pipe end before welding in this invention, the pipe end flat-end machining adopts a chip-free cold working process to eliminate the problem of metal debris remaining inside the pipe. The inner wall of the pipe end is treated with a precision electrolytic polishing process. Different electrolytic polishing voltage, current density and polishing time are set for stainless steel pipes of different initial states (EP grade, BA grade) and pipes of different materials (316L, 316LMOD). The inner wall roughness is controlled within Ra 0.2μm. Degreasing and decontamination are performed by constant temperature ultrasonic cleaning with electronic grade anhydrous ethanol, and the ultrasonic cleaning time is not less than During the 15-minute cleaning process, the oil content of the cleaning solution is monitored in real time. Ultrapure water rinsing is performed using electronic-grade ultrapure water with a resistivity of not less than 18.2 MΩ·cm under high pressure and turbulent circulation. The rinsing time is dynamically adjusted according to the pipe diameter and length to ensure that there are no contaminant residues on the inner wall of the pipe. After rinsing, high-purity nitrogen with a cleanliness level of 100 is used for gradient heating and dust-free drying. The dew point value of the nitrogen at the outlet is monitored throughout the drying process to ensure that there is no moisture residue on the inner wall of the pipe. After drying, a clean dustproof plug is immediately used to double-seal the pipe ends for protection.

[0034] This invention also includes non-destructive testing and systematic verification of cleanliness and corrosion resistance of pipeline welds. After welding, the weld and the inner wall of the pipeline are subjected to in-situ passivation treatment. High-purity nitrogen atomized electronic-grade passivation liquid is used to achieve uniform passivation of the weld area. Simultaneously, ultrapure water circulation rinsing and dust-free drying are performed after passivation to form a uniform and dense corrosion-resistant passivation film on the weld surface. The completed pipeline welds are subjected to non-destructive testing and systematic verification of cleanliness and corrosion resistance. Radiographic non-destructive testing of the weld, inner wall roughness testing, particle size testing, and intergranular corrosion testing are performed in sequence to comprehensively verify the mechanical properties of the weld and the cleanliness of the pipeline, matching the usage requirements of semiconductor-grade ultra-high purity media transportation. Radiographic non-destructive testing must meet the Class I weld requirements in NB / T47013.2 "Non-destructive testing of pressure equipment - Part 2: Radiographic testing". The inner wall particle size testing must ensure that the number of solid particles larger than 0.1 μm in the pipeline does not exceed the limit specified in SEMI F72 standard. The intergranular corrosion test adopts GB / T The oxalic acid etching method in 4334-2020 "Corrosion of Metals and Alloys - Test Method for Intergranular Corrosion of Austenitic and Ferritic-Austenitic (Duplex) Stainless Steel" was used. After the test, the weld and heat-affected zone were controlled to be free of intergranular corrosion grooves and cracks. At the same time, the inner wall of the weld was inspected for oxidation color to ensure that there was no oxidation discoloration on the inner wall of the weld and heat-affected zone. The metallographic structure of the weld was also tested simultaneously to ensure that the grain size of the weld and heat-affected zone was consistent with the base material, and no coarse columnar grains or Widmanstätten structure were generated. The self-corrosion potential of the weld area was verified to be within the preset range by polarization curve electrochemical testing. The weld sealing was tested by helium mass spectrometry to ensure that there were no micro-leakage defects in the weld. The welding parameters, environmental cleanliness parameters, shielding gas parameters, and test data of the entire welding process are traceable and archived throughout the process, which fully ensures that the welded finished product meets the stringent requirements for semiconductor-grade ultra-high purity media transportation.

[0035] The following two examples further illustrate the specific implementation of this system: Example 1

[0036] Implementation of all-position argon arc welding for high-purity specialty gas transportation in semiconductor chip factories using EP-grade stainless steel pipelines. This embodiment is applied to a high-purity corrosive specialty gas delivery system in a 12-inch chip manufacturing plant. The pipe to be welded is a 316L MODEP-grade semiconductor ultra-high purity stainless steel pipe with an outer diameter of 12.7mm and a wall thickness of 1.24mm. It is used for delivering electronic-grade specialty gases such as high-purity chlorine and hydrogen chloride. The core requirements are that the inner wall of the weld is free of oxidation, meets the cleanliness standard, and has excellent resistance to intergranular corrosion. The welding operation is completed in a Class 1000 cleanroom welding workshop in the plant. The pipe circumferential weld is a fixed-position weld. This embodiment completely covers all technical solutions of the method, and all steps correspond completely to the overall design of the method, with no technical content exceeding the design scope.

[0037] This embodiment employs an all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes. First, the pipe ends undergo ultra-high cleanliness pretreatment. The pipe end is machined using a chip-free cold working process, simultaneously completing the precision forming of a V-shaped welding bevel. The bevel angle is controlled between 35° and 40° to remove the original oxide film from the bevel surface. The inner wall of the pipe end is treated with a precision electropolishing process. Corresponding electropolishing parameters are set for EP-grade pipes, controlling the inner wall roughness to within Ra0.2μm. Degreasing and cleaning are performed using electronic-grade anhydrous ethanol for constant-temperature ultrasonic cleaning for 20 minutes. During the cleaning process, the grease content of the cleaning solution is monitored in real-time using online detection equipment. Ultrapure water rinsing uses electronic-grade ultrapure water with a resistivity of not less than 18.2 MΩ·cm for high-pressure turbulent circulation rinsing. The rinsing time is dynamically adjusted according to the pipeline length. After rinsing, high-purity nitrogen with a cleanliness level of 100 is used for gradient heating and dust-free drying. The dew point value of the outlet nitrogen is monitored throughout the drying process to ensure that there is no moisture residue on the inner wall of the pipeline. After drying, a clean dustproof plug is immediately used to double-seal the pipe ends for protection.

[0038] Following this, high-precision assembly of the pipes to be welded and pre-welding system protection were completed. The assembly operation was performed in a Class 1000 cleanroom environment. Before assembly, a laser alignment instrument was used to perform non-contact coaxiality pre-calibration of the pipes to be welded. The coaxiality misalignment of the pipes to be welded was controlled within 5% of the pipe wall thickness, and the assembly gap was controlled between 0.5mm and 1mm. After assembly, passivated clean stainless steel positioning clamps were used for temporary fixation. Non-metallic clean gaskets were used to isolate the positioning clamps from the pipe contact area to eliminate iron ion contamination and surface scratches. The positioning weld points were set on the outer wall of the pipe and were completely within the bevel range for subsequent welding. During the positioning welding process, double-layer argon gas protection was simultaneously activated on both sides to ensure that the positioning weld points were free of oxidation defects and completely integrated into the subsequent formal weld. A dual-layer high-purity argon laminar flow protection system is simultaneously constructed on the inner and outer walls of the pipeline. The outer wall protection uses a welding torch nozzle with a gas lens structure, and the uniform and stable delivery of argon is achieved through a multi-layer sieve-type laminar flow rectification structure. The inner wall protection uses adjustable gas plugs with multi-hole flow equalization structures on both sides, forming a sealed protective gas chamber in the pipeline on both sides of the weld. Before welding, the air in the gas chamber is replaced by continuously introducing high-purity argon with a purity of not less than 99.999%. Throughout the welding process, the oxygen content in the gas chamber is monitored in real time by an online oxygen analyzer, and the oxygen content is controlled to always be below 50 ppm.

[0039] Subsequently, based on the four welding stations for all-position welding of pipelines, an all-position zoned welding parameter matrix was constructed. The peak welding current for the flat welding station was set to 85A, for the vertical upward welding station to 105A, for the overhead welding station to 75A, and for the vertical downward welding station to 95A. The pulse frequency for each station was set to 50Hz, and the base current was 35% of the peak current. A 12° parameter transition interval was set between adjacent stations, and the welding parameters within the interval adopted a linear smooth adjustment mode. At the same time, differentiated wire feeding modes were set for different welding stations. The flat welding station adopted an early wire feeding mode to ensure the amount of molten pool filling, the overhead welding station adopted a delayed wire feeding mode to eliminate the problem of molten pool sagging, and the vertical welding station adopted an intermittent wire feeding mode synchronized with the pulse current to match the melting and solidification rhythm of the molten pool. During the welding process, precise quantitative control of welding line energy is carried out for different workstations. The line energy threshold and interpass temperature control upper limit are set for each workstation. The solidification rate of the molten pool is matched by the timing switching of the pulse current base peak value to control the risk of weld grain coarsening and intergranular corrosion caused by excessive welding heat input.

[0040] Subsequently, a low-heat-input pulsed tungsten inert gas (TIG) welding process was employed to perform continuous welding in all positions. Following a pre-defined matrix of zoned parameters, the circumferential weld seam was continuously welded in one pass. Throughout the welding process, the molten pool temperature, weld formation, and shielding gas purity were monitored in real time. Based on the monitoring data, welding parameters were dynamically adjusted in a closed-loop manner to strictly control the heat-affected zone (HAZ) of the weld. Throughout the welding process, the flow rate and pressure of the shielding argon gas inside the pipe were dynamically adjusted according to the real-time changes in the welding position. In the overhead welding position, the static pressure of the argon gas inside the pipe was increased to counteract the effect of gravity-induced molten pool descent. In the flat welding position, a stable laminar flow was maintained to prevent external air intrusion. After the welding arc left the corresponding weld area, the argon gas shielding was maintained until the temperature on the back side of the weld dropped below the intergranular corrosion-sensitive temperature range. After welding, high-purity argon gas was continuously introduced to complete the back side protection during weld cooling.

[0041] After welding, in-situ passivation treatment is performed on the weld and the inner wall of the pipe. Before passivation, the weld area is purged non-contactly with constant-temperature high-purity nitrogen gas of Class 100 cleanliness to remove welding fumes and dust from the weld surface. Electronic-grade nitric acid passivation solution atomized with high-purity nitrogen is used to uniformly passivate the weld area. During passivation, the temperature of the passivation solution is precisely controlled in a closed loop to achieve a uniform and stable passivation reaction rate. After passivation, electronic-grade ultrapure water with a resistivity of not less than 18.2 MΩ·cm is used for circulating turbulent rinsing. The resistivity and pH value of the rinsing water are monitored online throughout the process to eliminate any passivation solution residue. After rinsing, high-purity nitrogen gas with a dew point below -70℃ is used for gradient heating and dust-free drying to form a uniform and dense corrosion-resistant passivation film on the weld surface.

[0042] Finally, the completed pipe welds are subjected to non-destructive testing and system verification of cleanliness and corrosion resistance. The welds are subjected to radiographic non-destructive testing, internal wall roughness testing, particle size testing, and intergranular corrosion testing in sequence. The weld metallographic structure testing, polarization curve electrochemical testing, and helium mass spectrometry leak detection are completed simultaneously. The welding parameters, environmental cleanliness parameters, shielding gas parameters, and test data of the entire welding process are traceable and archived throughout, which fully ensures that the welded products meet the stringent requirements of semiconductor-grade high-purity special gas transportation.

[0043] Table 1. Performance Comparison of This Method and Traditional Welding Methods for High-Purity Special Gas Pipelines Table 1 visually demonstrates the comprehensive advantages of this method in welding high-purity specialty gas pipelines for semiconductors. Traditional welding methods lack a comprehensive cleanliness control system, resulting in a high incidence of oxidation defects on the weld inner wall. The lack of differentiated design of welding parameters across all positions leads to uneven weld formation, insufficient heat input control results in a high risk of intergranular corrosion, and significant differences in corrosion resistance between the weld and the base material, failing to meet the stringent requirements for specialty gas transportation. This method, through comprehensive cleanliness control, multi-position zoning parameter design, dual-layer dynamic argon protection, and precise heat input control, achieves oxidation-free weld inner walls and uniform weld formation, significantly reducing the risk of intergranular corrosion and ensuring that the pipeline's cleanliness and corrosion resistance meet semiconductor industry standards. Example 2

[0044] All-position argon arc welding implementation of BA-grade stainless steel pipelines for ultra-high purity water transportation in semiconductor plant area This embodiment is applied to an ultra-high purity water delivery system in a semiconductor plant. The pipe to be welded is a 316LBA-grade semiconductor ultra-high purity stainless steel pipe with an outer diameter of 50.8 mm and a wall thickness of 2.11 mm. It is used for delivering electronic-grade ultra-high purity water with a resistivity of not less than 18.2 MΩ·cm. The core requirements are low roughness of the weld inner wall, no solid particle residue, and excellent resistance to long-term water erosion. The welding operation is completed in a Class 1000 cleanroom within the plant. The pipe circumferential seam is a field-installed, all-position fixed-joint weld. This embodiment completely covers all technical solutions of the method, and all steps correspond completely to the overall design of the method, with no technical content exceeding the design scope.

[0045] This embodiment employs an all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes. First, ultra-high cleanliness pretreatment of the pipe ends is performed. A corresponding cleanliness level is set for the application scenario of ultra-high purity water pipes, and differentiated pretreatment process standards are established. The pipe end flat-end machining adopts a chip-free cold working process, simultaneously completing the precision forming of the V-shaped welding bevel. The bevel angle is controlled between 30° and 35° to remove the original oxide film on the bevel surface. The inner wall of the pipe end is treated with a precision electrolytic polishing process. Corresponding electrolytic polishing parameters are set for BA-grade pipes, controlling the inner wall roughness to within Ra0.2μm. Degreasing and decontamination are performed using electronic-grade anhydrous ethanol for constant-temperature ultrasonic cleaning. The ultrasonic cleaning time is set to 15 minutes, and the change in grease content of the cleaning solution is monitored in real time during the cleaning process. Ultrapure water rinsing uses electronic-grade ultrapure water with a resistivity of not less than 18.2 MΩ·cm for high-pressure turbulent circulation rinsing. The rinsing time is dynamically adjusted according to the pipe diameter and length. After rinsing, high-purity nitrogen with a cleanliness level of 100 is used for gradient heating and dust-free drying. After drying, the pipe ends are immediately sealed with clean dustproof plugs for double protection. During pipeline transportation, a vacuum nitrogen-filled protection mode is used to eliminate secondary pollution problems during transportation and storage.

[0046] Following this, high-precision assembly of the pipes to be welded and pre-welding system protection were completed. The assembly operation was performed in a Class 1000 cleanroom environment. Before assembly, a laser alignment instrument was used to perform non-contact coaxiality pre-calibration of the pipes to be welded. The coaxiality misalignment of the pipes to be welded was controlled within 5% of the pipe wall thickness, and the assembly gap was controlled between 1mm and 2mm, matching the parameter design for multi-layer, multi-pass welding of thick-walled pipes. After assembly, passivated clean stainless steel positioning clamps were used for temporary fixation. The contact points between the positioning clamps and the pipes were isolated using non-metallic clean gaskets. The positioning weld points were set on the outer wall of the pipes and were completely within the bevel range for subsequent welding. During the positioning welding process, double-layer argon gas protection was simultaneously activated on both sides. A dual-layer high-purity argon laminar flow protection system is simultaneously constructed on the inner and outer walls of the pipeline. The outer wall protection uses a large-diameter welding torch nozzle with a gas lens structure. The nozzle diameter is matched to the corresponding specification according to the pipeline diameter, and the ratio of the tungsten electrode extension length to the nozzle inner diameter is controlled to ensure the effective range of laminar flow protection. The inner wall protection uses adjustable gas plugs with multi-hole flow equalization structures on both sides to form a sealed protective gas chamber in the pipeline on both sides of the weld. Before welding, high-purity argon with a purity of not less than 99.999% is continuously introduced to replace the air in the gas chamber. Throughout the welding process, the oxygen content, water content and argon purity in the gas chamber are monitored in real time by an online oxygen analyzer. A multi-pipeline closed-loop control system dynamically adjusts the flow rate of the inner and outer protective argon in real time according to the welding progress speed to control the oxygen content to always be below 50ppm.

[0047] Subsequently, based on the four welding stations for all-position welding of pipelines, an all-position zoned welding parameter matrix was constructed. Two welding passes were set for thick-walled pipelines, with welding parameters specifically set for the root pass and the fill / cap pass. The peak welding current for the root pass (flat welding station) was set to 110A, for the vertical upward welding station to 130A, for the overhead welding station to 95A, and for the vertical downward welding station to 120A. The peak current for each station in the fill / cap pass was correspondingly reduced by 10%. The pulse frequency for each station was set to 40Hz, and the base current was 40% of the peak current. A 15° parameter transition interval was set between adjacent stations, within which the welding parameters were adjusted linearly and smoothly. During the welding process, precise quantitative control of the welding heat input was implemented for different stations. A heat input threshold and an upper limit for interpass temperature control were set for each station. The timing of the pulse current base peak value was matched to the molten pool solidification rate to control the risk of weld grain coarsening and intergranular corrosion caused by excessive welding heat input.

[0048] Subsequently, a low-heat-input pulsed tungsten inert gas (TIG) welding process was employed for continuous all-position welding. Following a pre-defined matrix of zoned parameters, continuous welding of the root pass and filler / cap coat was completed. Throughout the welding process, the molten pool temperature, weld formation, and shielding gas purity were monitored in real-time. Based on the monitoring data, welding parameters were dynamically adjusted in a closed-loop manner. Arc length control was achieved through real-time feedback of the arc voltage, and the tungsten electrode height was dynamically adjusted to ensure stable arc length. The heat-affected zone (HAZ) and single-pass weld penetration were strictly controlled. Throughout the welding process, the flow rate and pressure of the shielding argon gas inside the pipe were dynamically adjusted according to real-time changes in the welding position, ensuring that the weld area inside the pipe was always completely covered and protected by high-purity argon gas. After welding, high-purity argon gas was continuously introduced to provide back-side protection for the entire weld cooling process.

[0049] After welding, the weld and the inner wall of the pipe are subjected to in-situ passivation treatment. Before passivation, the weld area is purged non-contactly with constant temperature high-purity nitrogen with a cleanliness level of Class 100. Electronic-grade passivation liquid atomized with high-purity nitrogen is used to complete the uniform passivation of the weld area. During the passivation process, the temperature of the passivation liquid, the atomization pressure, and the passivation time are precisely controlled in a closed loop. After passivation, electronic-grade ultrapure water with a resistivity of not less than 18.2 MΩ·cm is used for circulating turbulent rinsing. The resistivity and pH value of the rinse water are monitored online throughout the process to eliminate the problem of passivation liquid residue. After rinsing, high-purity nitrogen with a dew point of less than -70℃ is used for gradient heating and dust-free drying to form a uniform and dense corrosion-resistant passivation film on the weld surface.

[0050] Finally, the welded pipe seams are subjected to non-destructive testing and system verification of cleanliness and corrosion resistance. The weld seams are subjected to radiographic non-destructive testing, internal wall roughness testing, particle size testing, and intergranular corrosion testing in sequence. The weld seams are also subjected to metallographic structure testing and helium mass spectrometry leak detection at the same time. All parameters and test data of the entire welding process are traceable and archived, which fully ensures that the welded finished products meet the requirements for semiconductor-grade ultrapure water transportation.

[0051] Table 2. Performance Comparison of This Method and Traditional Welding Method for Ultra-High Purity Water Pipelines Table 2 clearly demonstrates the comprehensive advantages of this method in the welding of semiconductor ultrapure water pipelines. Traditional welding methods, designed for all-position welding of thick-walled pipelines without layered parameter design, are prone to uneven weld penetration and poor weld uniformity. The lack of targeted control over pre-weld treatment and post-weld passivation results in high weld inner wall roughness and a large amount of solid particle residue, posing a high risk of water erosion during long-term use and failing to meet the requirements for ultrapure water transportation. This method, through layered welding parameter design for thick-walled pipelines, graded cleanliness control throughout the entire process, and precise in-situ passivation treatment, achieves uniform weld penetration and consistent weld uniformity in all positions, effectively controls weld inner wall roughness and particle residue, reduces the risk of long-term water erosion, and ensures that pipeline cleanliness meets industry standards for semiconductor ultrapure water transportation.

[0052] Reference Figure 1 This diagram outlines the complete workflow of all-position TIG welding for semiconductor-grade ultra-high purity stainless steel pipes. The process begins with rigorous pretreatment of the pipe ends in a cleanroom, followed by assembly, positioning, and the establishment of a double-layer high-purity argon gas protection system. The core step involves low-heat-input pulsed TIG welding, performing continuous circumferential welding based on an all-position zoning parameter matrix, with precise control of heat input during the process. Immediately after welding, in-situ passivation is performed to restore corrosion resistance. Finally, systematic verification through X-ray inspection, internal wall particle size analysis, and intergranular corrosion testing ensures that the weld performance and pipe cleanliness fully meet the standard requirements for semiconductor ultra-high purity media transport.

[0053] Reference Figure 2 This diagram details the ultra-cleaning and surface treatment sub-process for the ends of semiconductor-grade stainless steel pipes, aiming to thoroughly remove contaminants and strictly control the inner wall roughness. The process begins with precision flat-end machining of the pipe ends to be welded, followed by core precision electrolytic polishing of the inner wall (Ra≤0.2μm). Next, degreasing and decontamination are achieved through ultrasonic cleaning with electronic-grade anhydrous ethanol, followed by circulating rinsing with electronic-grade ultrapure water. The drying process is completed at a constant temperature using high-purity nitrogen with a Class 100 cleanliness level. Immediately after all steps are completed, the pipe ends are double-sealed to prevent secondary contamination during transport, providing a clean base material for subsequent high-quality welding.

[0054] Reference Figure 3 This diagram illustrates the robust gas protection logic established during welding to prevent oxidation and discoloration of the inner wall. The process is divided into two stages: pre-weld replacement and dynamic control during welding. Before welding, a sealed chamber is established using adjustable gas plugs on both sides, continuously introducing high-purity argon gas with a purity of no less than 99.999% until the oxygen content is monitored to be below a preset threshold of 50 ppm. After welding begins, the welding torch side utilizes a gas lens to achieve laminar flow protection on the outer wall; the inner wall side is dynamically adjusted according to the real-time changes in the welding position: for example, in the overhead welding position, the internal pressure is appropriately increased to counteract the influence of gravity on the molten pool. Closed-loop monitoring is implemented throughout the process to ensure that the inner wall weld area is always completely covered, eliminating oxidation discoloration defects.

[0055] Reference Figure 4 This figure illustrates the intelligent control logic of pulsed TIG welding parameters for 360-degree all-position welding of pipelines. The system first divides the circumferential weld seam into four main welding zones: flat welding, vertical upward welding, overhead welding, and vertical downward welding. Based on the physical characteristics of each zone, an initial parameter matrix including pulse current, wire feed speed, and shielding gas flow rate is constructed. The core implementation process involves closed-loop fine-tuning: the system collects the molten pool temperature and weld formation status in real time and automatically corrects the parameters. Simultaneously, smooth transition intervals are set between adjacent zones, and a linear smooth adjustment mode is used to change the parameters, effectively avoiding weld formation defects caused by sudden parameter changes and ensuring uniform weld quality in all positions.

[0056] Reference Figure 5 This diagram illustrates the logic control block diagram for the final quality inspection and performance recovery phases of the welding method. After welding, the system performs in-situ passivation treatment on the weld and its inner wall. By introducing quantitative calculations for passivation film uniformity evaluation (Cv coefficient), the passivation solution concentration and atomization pressure are optimized in a closed loop to ensure the formation of a uniform and dense corrosion-resistant film on the weld surface. The system then undergoes a rigorous verification phase: sequentially performing radiographic non-destructive testing (Level I), inner wall roughness and particle size detection, visual inspection of inner wall oxide color, and intergranular corrosion testing. Through multi-dimensional, comprehensive verification of metallographic structure and cleanliness, the system ensures that the final delivered pipeline meets the standards for semiconductor-grade ultra-high purity media transportation.

[0057] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for all-position argon arc welding of semiconductor-grade ultra-high purity stainless steel pipes, characterized in that, Includes the following steps: The pipe ends of semiconductor-grade ultra-high purity stainless steel pipes to be welded undergo ultra-high cleanliness pretreatment, which sequentially completes pipe end face flat processing, inner wall electrolytic polishing, degreasing and decontamination, ultrapure water rinsing, and dust-free drying. Simultaneously, the precision forming of the welding bevel and the removal of the oxide film on the bevel surface are completed, controlling the core indicators of pipe end inner wall roughness and cleanliness. Complete the high-precision assembly and pre-weld system protection of the pipeline to be welded, complete the coaxiality assembly of the pipeline in a Class 1000 clean environment, control the assembly gap and misalignment, build a double-layer high-purity argon laminar flow protection system on the inner and outer walls of the pipeline simultaneously, complete the oxygen content replacement and sealing pressure maintenance inside the pipeline before welding, and ensure that the oxygen content in the pipeline is lower than the preset safety threshold throughout the welding process. Based on four welding positions for all-position pipeline welding—flat welding, vertical upward welding, overhead welding, and vertical downward welding—an all-position zoned welding parameter matrix is ​​constructed. Matching parameters for welding pulse current base value and peak value, pulse frequency, wire feed speed, welding travel speed, and internal and external shielding argon flow rate are set for different positions. At the same time, a smooth transition range of parameters between each position is set. Low heat input pulsed tungsten inert gas welding process is used to perform continuous welding in all positions. The pipe circumferential weld is completed in one continuous welding according to the preset partition parameter matrix. The molten pool temperature, weld formation state and shielding gas purity are monitored in real time throughout the welding process. Based on the monitoring data, the welding parameters are dynamically fine-tuned in a closed loop to control the range of the weld heat-affected zone and the welding line energy input. After welding, the weld and the inner wall of the pipe are subjected to in-situ passivation treatment. High-purity nitrogen atomized electronic grade passivation liquid is used to complete the uniform passivation of the weld area. Simultaneously, ultrapure water circulation rinsing and dust-free drying are completed after passivation, forming a uniform and dense corrosion-resistant passivation film on the weld surface.

2. The all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes according to claim 1, characterized in that, It also includes a step for precise control of welding line energy in all positions. During the construction of the welding parameter matrix, a welding line energy calculation formula is introduced for different welding stations to precisely quantify and control the welding heat input of each station. The calculation formula is as follows: ； in For the corresponding welding line energy of the welding station, The thermal efficiency coefficient of tungsten inert gas welding. For welding arc voltage, This is the effective value of the welding current. This refers to the welding travel speed.

3. The all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes according to claim 1, characterized in that, It also includes a dynamic control step for laminar flow protection of high-purity argon gas inside the pipe. Throughout the welding process, the flow rate and pressure of the protective argon gas inside the pipe are dynamically adjusted according to the real-time changes of the welding position. In the overhead welding position, the static pressure of the argon gas inside the pipe is increased to counteract the effect of gravity falling of the molten pool. In the flat welding position, a stable laminar flow state is maintained to prevent the intrusion of external air.

4. The all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes according to claim 1, characterized in that, It also includes a pre-welding cleanliness classification and control step, which sets corresponding pre-treatment cleanliness levels for semiconductor-grade ultra-high purity stainless steel pipes of different specifications and application scenarios, and controls the amount of grease residue, particulate contaminants and surface roughness core indicators on the inner wall of the pipe respectively. After the pre-treatment is completed, the pipe port is sealed and protected in a Class 100 clean environment.

5. The all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes according to claim 1, characterized in that, In the pipeline assembly step, the coaxiality misalignment of the pipeline to be welded is controlled within 5% of the pipeline wall thickness, and the assembly gap is controlled between 0.5mm and 2mm. After the assembly is completed, a stainless steel positioning clamp with a cleanliness standard is used to temporarily fix it. The positioning weld point is set on the outer wall of the pipeline and is completely within the bevel range of the subsequent welding.

6. The all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes according to claim 1, characterized in that, In the aforementioned double-layer high-purity argon laminar flow protection system, the outer wall protection adopts a welding torch nozzle with a gas lens structure, which achieves uniform and stable delivery of argon through a laminar flow rectification structure. The inner wall protection adopts a double-sided adjustable gas plug structure, forming a sealed protective gas chamber in the pipes on both sides of the weld. Before welding, the air in the gas chamber is replaced by continuously introducing high-purity argon. The oxygen content in the gas chamber is continuously monitored throughout the welding process.

7. The all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes according to claim 1, characterized in that, In the in-situ passivation step, a passivation film uniformity evaluation formula is introduced to assess the passivation effect in the weld area. This formula is used to perform closed-loop optimization and adjustment of the passivation process parameters. ； in The uniformity coefficient of the passivation film in the weld area is given. This represents the total number of passivation film thickness detection points. For the first The measured thickness of the passivation film at each test point This is the arithmetic mean of the passivation film thickness at all detection points.

8. The all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes according to claim 1, characterized in that, In the all-position welding parameter matrix, the peak welding current for the flat welding station is set to 80A to 120A, the peak welding current for the vertical upward welding station is set to 100A to 140A, the peak welding current for the overhead welding station is set to 70A to 100A, and the peak welding current for the vertical downward welding station is set to 90A to 130A. The pulse frequency for each station is set to 30Hz to 80Hz, the base current is 30% to 40% of the peak current, and a parameter transition range of 10° to 15° is set between adjacent stations. Within the range, the welding parameters adopt a linear smooth adjustment mode.

9. The all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes according to claim 1, characterized in that, In the pre-treatment step of the pipe end before welding, the inner wall of the pipe end is treated with precision electrolytic polishing process, and degreasing and decontamination are carried out by ultrasonic cleaning with electronic grade anhydrous ethanol for a duration of not less than 15 minutes. Ultrapure water rinsing is carried out by circulating electronic grade ultrapure water. After rinsing, high-purity nitrogen with a cleanliness level of 100 is used for constant temperature and dust-free drying. After drying, the pipe end is immediately sealed with a clean dustproof plug for double protection.

10. The all-position argon arc welding method for semiconductor-grade ultra-high purity stainless steel pipes according to claim 1, characterized in that, This also includes non-destructive testing and cleanliness and corrosion resistance system verification of the completed pipe welds. The process involves sequentially performing radiographic non-destructive testing, internal wall roughness testing, particle size testing, and intergranular corrosion testing. The radiographic non-destructive testing must meet the Class I weld requirements in NB / T 47013.2 "Non-destructive testing of pressure equipment - Part 2: Radiographic testing". The internal wall particle size testing requires that the number of solid particles larger than 0.1 μm in the pipe does not exceed the limit specified in SEMI F72 standard. The intergranular corrosion test adopts the oxalic acid etching method in GB / T 4334-2020 "Corrosion of metals and alloys - Test method for intergranular corrosion of austenitic and ferritic-austenitic (duplex) stainless steel". After the test, there should be no intergranular corrosion grooves or cracks in the weld and heat-affected zone. At the same time, the inner wall of the weld is inspected for oxidation color.

Images