CN-122007562-A - Single-sided welding double-sided forming manual argon arc welding method for stainless steel thin-wall pipeline

Abstract

The invention relates to the technical field of stainless steel pipeline welding, and particularly discloses a single-sided welding double-sided forming manual argon arc welding method for a stainless steel thin-wall pipeline, which comprises the following steps of cleaning and assembling the stainless steel pipeline, and sealing to form a closed cavity; the method comprises the steps of arranging an input interface and an exhaust hole at two ends of a pipeline, inputting argon, carrying out pre-filling, regulating the flow of the argon, stably controlling the dynamic pressure in a closed cavity, confirming that the argon continuously and stably flows out of the exhaust hole, starting welding, adopting manual tungsten argon arc welding, carrying out self-fluxing welding on butt welding seams of the outer wall of the pipeline under the condition that welding wires are not added by adopting a blunt tungsten electrode, and after the welding is finished, delaying to close an air source under the condition that the back protection argon continuously flows. Therefore, the automatic welding machine has the flexibility of manual welding and the quality stability of the inner wall of automatic welding, so that the whole pipeline structure meets the regulation and process requirements, and the sanitary safety and process stability of medicine production are ensured.

Inventors

• ZHANG QING
• KANG ZHIBIN
• ZHANG LI
• XIONG YAN

Assignees

• 四川科伦药业股份有限公司

Dates

Publication Date

20260512

Application Date

20260324

Claims (10)

1. 1. The manual argon arc welding method for single-sided welding and double-sided molding of the stainless steel thin-wall pipeline is characterized by comprising the following steps of: S1, cleaning a groove of a stainless steel pipeline to be welded and the inner side and the outer side of the groove, then performing butt-joint assembly, controlling the amount of misalignment, and detachably sealing the two ends of the pipeline to form a closed cavity, wherein the wall thickness of the stainless steel pipeline is not more than 3mm; S2, establishing an argon input interface at one end of a pipeline, and arranging an exhaust hole with the aperture of 1-3mm at the other end of the pipeline far away from the interface; s3, adjusting the flow of argon, controlling the dynamic pressure in the closed cavity to be between 0.1bar and 0.2bar stably, and starting welding after confirming that the argon continuously and stably flows out of the exhaust hole; S4, manual argon tungsten-arc welding is adopted, a blunt tungsten electrode is used, self-fluxing welding is carried out on butt welding seams of the outer walls of the pipelines under the condition that welding wires are not added, the arc length is kept stable during welding, and single-sided welding and double-sided forming are realized; and S5, after welding is finished, the gas source is delayed to be closed under the state that the back protection argon is kept to continuously flow, and after the welding line is cooled, the internal and external forming quality of the welding line is checked.
2. 2. The method for single-sided welding, double-sided molding, manual argon arc welding of stainless steel thin-walled pipes according to claim 1, characterized in that in step S1, the cleaning comprises wiping the groove and both sides at least in a 20mm range with a special solvent free of chloride ions to remove oil and impurities.
3. 3. The single-sided welding double-sided molding manual argon arc welding method for a stainless steel thin-walled pipe according to claim 1, characterized in that in step S1, a cover plate with an O-ring is used to seal the pipe end, and the input port and the exhaust hole are integrated on the cover plate.
4. 4. The method for single-sided welding and double-sided forming of a thin-walled stainless steel pipe according to claim 1, wherein in step S3, the dynamic pressure is monitored and adjusted by a precision pressure gauge connected in parallel to the argon gas feeding line in combination with an adjustable pressure reducing valve.
5. 5. The single-sided welding double-sided molding manual argon arc welding method for the stainless steel thin-walled pipeline according to claim 1 is characterized in that in the step S4, the welding current and the welding speed are selected according to the matching of the pipeline wall thickness, and the following relation is satisfied, when the wall thickness is 1.5mm, the welding current is 35-40A, and the welding speed is 80-130mm/min; when the wall thickness is 2.0mm, the welding current is 40-45A, and the welding speed is 100-150mm/min.
6. 6. The single-sided welding double-sided forming manual argon arc welding method for the stainless steel thin-wall pipeline according to claim 1, wherein in the step S4, an included angle between a tungsten electrode of a welding gun and a tangential direction of a welding bead is 70-85 degrees, and a straight line or small-amplitude transverse swing arc conveying method is adopted.
7. 7. The single-sided welding double-sided molding manual argon arc welding method for a stainless steel thin-walled pipe according to claim 1, wherein in step S4, the tip taper angle of the blunt tungsten electrode is 30 ° -45 °, and the tungsten electrode diameter is 1.6mm or 2.4mm.
8. 8. The single-sided welding double-sided molding manual argon arc welding method for stainless steel thin-walled pipes according to claim 1, characterized in that in step S4, for the weld with longer circumference, a segmented back welding method is adopted for welding, and each welding length is not more than 1/4 of the circumference of the pipe, and the interlayer temperature is controlled below 50 ℃.
9. 9. The method for single-sided welding, double-sided molding, manual argon arc welding of a thin-walled stainless steel pipe according to claim 1, wherein the time for delaying the closing of the gas source in step S5 is the time required for the weld metallic color to disappear to a temperature lower than 100 ℃ and is not less than 30 seconds.
10. 10. The single-sided welding double-sided molding manual argon arc welding method for a stainless steel thin-walled pipe according to claim 1, characterized by further comprising the step of performing an acid pickling passivation treatment on the weld and the heat affected zone to restore and enhance the corrosion resistance thereof after the inspection of step S5.

Description

Single-sided welding double-sided forming manual argon arc welding method for stainless steel thin-wall pipeline Technical Field The invention relates to the technical field of stainless steel pipeline welding, in particular to a single-sided welding double-sided forming manual argon arc welding method for a stainless steel thin-wall pipeline. Background In the pharmaceutical, biological and high-end food industries, the delivery lines for fluid materials (e.g., medical fluids, purified water, water for injection, dry powders, etc.) must meet extremely high standards of hygiene and safety. Such pipes are typically manufactured from austenitic stainless steel (e.g., 304, 316L) with internal surface smoothness, cleanliness and weld quality related to the quality of the final product and patient safety. The current pharmaceutical production quality control Specification (GMP) and related industry standards clearly require that the inner wall of a fluid conveying pipeline should be smooth, free of dead corners, free of weld flash, easy to clean and free of residues, so as to prevent absorption, precipitation, microorganism breeding and metal ion pollution of liquid medicine components. At present, welding of stainless steel sanitary pipelines in the industry mainly depends on automatic or semi-automatic track type argon arc welding equipment. The technology can realize high-quality and good-repeatability welding seams by accurately controlling welding parameters and welding gun movements, and the inner wall forming is generally smooth. However, the automatic welding technology has high requirements on the assembly precision of the pipeline and the position of the welded junction, and is difficult to be suitable for a complex space structure of an installation site. For limited small spaces such as a tee joint, the vicinity of an elbow, a valve assembly and the like, or special-shaped pipe fittings and non-standard parts, automatic welding equipment cannot reach or cannot stably run. For small-batch, multi-specification or maintenance replacement scenes, large-scale automatic welding equipment is poor in economy and long in preparation time, and operation flexibility is lacked. When automatic welding cannot be performed, the site is usually replaced with a conventional manual argon arc welding for the supplementary work. However, the traditional manual argon arc welding faces serious challenges when realizing single-sided welding and double-sided forming (especially for thin-wall pipelines with the wall thickness less than or equal to 3 mm). The operator needs to melt the base material by arc heat alone to form the back weld bead without adding a welding wire (self-fluxing) by a pure-done technique. The process is extremely prone to various defects caused by improper parameter control, improper handling or poor backside protection, which may result in sagging, undercut, or more commonly, formation of protruding "flash" in the backside bead. The inner wall bulges can seriously damage the smoothness and streamline of the inner wall of the pipeline to form fluid dead angles, so that not only is the conveying resistance increased and the component layering possibly caused by turbulence increased, but also the inner wall bulges become high-risk areas with residual liquid medicine, incomplete cleaning and microorganism breeding, and the GMP core principle is violated. Although argon filling protection can be adopted in the pipeline to improve the metal performance of the back weld joint and prevent oxidation, the argon filling cannot ensure that the geometric shape of the back weld joint meets the requirement of smoothness and flatness. The argon arc welding method can deal with various complex working conditions, but is difficult to stably and reliably produce the inner wall forming quality meeting the extremely high sanitary standard in the pharmaceutical industry, while the automatic welding technology can ensure the inner wall forming quality, but cannot flexibly adapt to narrow space and special-shaped parts, so that a welded junction which cannot be welded and cannot be welded in place exists in the process of pipeline installation, transformation and maintenance, thereby becoming a weak point of the whole fluid structure and influencing engineering efficiency and product quality. Therefore, the welding mode of the current pipeline is optimized and improved, so that the welding mode has the flexibility of manual welding and the quality stability of the inner wall of automatic welding, the welding difficulty in a specific scene is solved, the whole pipeline structure meets the regulation and process requirements, and the sanitary safety and the process stability of medicine production are further ensured. Disclosure of Invention The invention aims to provide a single-sided welding double-sided forming manual argon arc welding method for a stainless steel thin-wall pipeline, so that the manual welding flexibility