Anti-oxidation girth welding method for inner container of stainless steel water tank
By combining precise tooling alignment with argon gas replacement and real-time monitoring and control, the problem of oxidation on the back of the weld seam of the stainless steel water tank inner liner was solved, achieving efficient anti-oxidation welding, improving welding quality and safety, and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PHNIX GUANGZHOU ELECTRICAL
- Filing Date
- 2026-03-02
- Publication Date
- 2026-05-12
AI Technical Summary
When welding the inner liner of a stainless steel water tank, oxidation on the back of the weld reduces its corrosion resistance. Existing shielding gas welding technology cannot effectively cover and synchronously follow the welding trajectory, leading to the risk of oxidation on the back of the weld. Furthermore, the introduction of high-flow gas increases costs and welding defects.
The tooling achieves precise docking between the inner liner and the end cap. The air in the inner liner is replaced from bottom to top by utilizing the density difference of argon gas. Combined with real-time monitoring by pressure and concentration detectors, the flow rate and outlet of argon gas are controlled to ensure that the concentration of protective gas is not lower than 99.5% during the welding process to prevent oxidation.
It effectively prevents oxidation on the back of the weld, improves the quality of weld formation, reduces gas consumption costs, ensures the consistency and safety of the welding process, and avoids overload of the internal pressure of the inner liner.
Smart Images
Figure CN122007692A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of protective gas welding technology, and more specifically, to a method for anti-oxidation circumferential welding of stainless steel water tank inner liner. Background Technology
[0002] When welding stainless steel, without protection, the high temperature can easily cause the stainless steel weld to react with oxygen in the air, resulting in a decrease in corrosion resistance. This severe degradation of performance makes the weld area a vulnerable point for corrosion in subsequent use, and it is easy for rust and leakage to start from the weld in the future. This is a fatal defect for stainless steel water tank liners that are in a state of high temperature and high pressure for a long time, and it must be prevented by strict welding protection process.
[0003] There are two existing processes for circumferential welding of stainless steel water tank inner liner: One involves inserting the end cap into the inner liner, forming a plug-in weld joint. This method presents two problems: gaps exist between the end cap and the inner liner, leading to crevice corrosion; additionally, the lack of gas protection on the back of the weld during welding causes oxidation, reducing the corrosion resistance of the inner liner. The second method involves butt-jointing the end cap and inner liner, forming a butt joint. A liner is added during assembly to ensure assembly accuracy and to provide a tight fit between the liner and the weld joint, reducing oxidation on the back of the weld. However, this method does not completely solve the problem of gaps between the inner liner and the circumferential weld leading to crevice corrosion, nor does it completely resolve the oxidation issue on the back of the weld.
[0004] To address the issue of oxidation on the back side of the weld during welding, existing processes typically require the use of a specialized protective cover. This cover is pre-filled with high-purity protective gas (inert gases such as argon and helium, or carbon dioxide and mixed gases) to purge the air inside. During welding, the protective cover slides synchronously with the position of the molten pool on the back side, precisely coordinating with the welding operation on the front side. This effectively protects the back side of the weld, preventing oxidation of the molten pool and heat-affected zone. However, this shielding gas welding technology has obvious limitations in its applicability to welding of the inner liner and the end cap: because the back side of the weld is not a smooth plane, the existing follow-type back shielding gas cover cannot move and seal in real time with the welding trajectory, resulting in the shielding gas not being able to effectively cover and synchronously follow the weld pool, causing discontinuous protection on the back side of the weld and forming an oxidation risk zone; if shielding gas is directly injected into the inner liner, due to its semi-enclosed structural characteristics, the injected shielding gas is easy to circulate with the outside air, making it difficult to form a stable and dense shielding gas curtain in the welding area, thus failing to guarantee the anti-oxidation effect of the weld; if shielding gas is continuously injected at a large flow rate during the welding process to isolate the air on the back side of the weld, it will not only increase the welding cost but also cause defects such as concave weld root due to airflow impact, seriously affecting the welding quality. Summary of the Invention
[0005] The purpose of this invention is to provide a method for anti-oxidation circumferential welding of stainless steel water tank inner liner, thereby solving the above-mentioned technical problems.
[0006] A method for anti-oxidation circumferential welding of stainless steel water tank inner liner, used for welding the stainless steel water tank inner liner, characterized by comprising the following steps: S1. Precise docking of inner tank body and end cap: The end cap is rounded by tooling, and the inner tank body is introduced at the same time to achieve precise docking of inner tank body and end cap, preventing cracks from occurring during welding. S2. Shielding gas filling: Stand the connected inner tank upright, close other openings, and only open the air inlet at the bottom and the air outlet at the top of the inner tank. Welding shielding gas is filled in from the air inlet at the bottom of the inner tank, and air is discharged from the air outlet at the top of the inner tank to prevent the weld of the stainless steel water tank inner tank from reacting with oxygen in the air during welding. S3. Protective gas monitoring and concentration control: A pressure detector is installed near the inner liner docking joint and a gas concentration detector is installed at the top vent to monitor the pressure and concentration of the protective gas inside the inner liner in real time during inflation. When the gas concentration detector detects that the protective gas concentration at the top vent of the inner liner is 99.5%, the control valve installed at the top vent of the inner liner is adjusted to reduce the vent size until it is closed, and the inflation flow rate is reduced at the same time. S4. Circumferential seam welding: During welding, under the monitoring of pressure detector and gas concentration detector, protective gas is continuously injected at a low flow rate to ensure that the protective gas concentration is not lower than 99.5% to prevent oxidation during welding; a small amount of gas is controlled to be released from the outlet to achieve real-time pressure relief and prevent the internal pressure of the inner tank from being overloaded due to the high temperature of welding, and finally achieve anti-oxidation circumferential seam welding of the stainless steel water tank inner tank.
[0007] As a preferred technical solution of the present invention, the protective gas is argon. At normal temperature (20°C) and standard atmospheric pressure (101.325 kPa), the density of argon is about 1.37 times that of air. Taking advantage of this density difference, the injected argon can naturally replace the air inside the inner liner, pushing the air out from the top vent, so that the argon concentration inside the inner liner reaches the welding requirement of 99.5%, providing a reliable anti-oxidation protective atmosphere for circumferential welding.
[0008] In summary, compared with the prior art, the beneficial effects of the present invention are: The anti-oxidation circumferential welding method for the stainless steel water tank inner liner of this invention can effectively prevent oxidation on the back of the weld during welding of the inner liner and the end cap, thus preventing a decrease in corrosion resistance. Specifically, it involves: using tooling to round the end cap, achieving precise alignment between the inner liner and the end cap, effectively controlling the assembly gap, and avoiding defects such as welding cracks caused by improper assembly of the inner liner and the end cap, thereby improving the weld formation quality; and scientifically designing the gas replacement path, selecting argon as the protective gas, and utilizing its greater density than air, placing the filling port at the bottom of the inner liner and the outlet at the top. This bottom-up gas replacement flow field design can efficiently remove air from the inner liner, ensuring that the protective gas concentration in the welding area meets process requirements and avoiding corrosion damage caused by improper assembly of the inner liner and the end cap. Residual air leads to oxidation; a phased flow control strategy is adopted, which uses a large flow rate to quickly replace the air before welding, and then switches to a small flow rate to maintain the concentration of protective gas in the inner liner during welding. This strategy saves gas consumption, reduces production costs, and avoids the back of the weld from being concave or poorly formed due to excessive gas flow during welding. The concentration and pressure of the protective gas in the cavity are monitored in real time by gas concentration detectors and pressure detectors, and the inlet flow rate and outlet control valve opening are dynamically adjusted accordingly to achieve closed-loop control of gas concentration and pressure during welding. This ensures that the protective gas concentration is always within an effective range and prevents the internal pressure of the inner liner from being overloaded due to welding heat input, further improving the consistency and safety of the welding process. Attached Figure Description
[0009] Figure 1 This is a schematic diagram of the tooling described in this invention; Figure 2 This is a schematic flowchart of the anti-oxidation circumferential weld method for the inner liner of a stainless steel water tank according to the present invention. Detailed Implementation
[0010] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments given herein are for illustration and explanation only and are not intended to limit the present invention.
[0011] like Figure 1 As shown in the diagram, a circular clamping fixture includes a frame 1, a pressing disc 2, and a fixing hoop 4. The stainless steel water tank inner liner is composed of an inner liner body 5 and a cap 3. The frame 1 vertically fixes the inner liner body 5, and the pressing disc 2 and the fixing hoop 4 round the cap 3 and tightly fit it with the inner liner body 5, preparing for the subsequent welding between the cap 3 and the inner liner body 5.
[0012] like Figure 2 As shown, the anti-oxidation circumferential welding method for stainless steel water tank inner liner, used for welding stainless steel water tank inner liner, includes the following steps: S1. Precise docking of inner tank body and end cap: The end cap is rounded by tooling, and the inner tank body is introduced at the same time to achieve precise docking of inner tank body and end cap, preventing cracks from occurring during welding. S2. Shielding gas filling: Stand the connected inner tank upright, close other openings, and only open the air inlet at the bottom and the air outlet at the top of the inner tank. Welding shielding gas is filled in from the air inlet at the bottom of the inner tank, and air is discharged from the air outlet at the top of the inner tank to prevent the weld of the stainless steel water tank inner tank from reacting with oxygen in the air during welding. S3. Protective gas monitoring and concentration control: A pressure detector is installed near the inner liner docking joint and a gas concentration detector is installed at the top vent to monitor the pressure and concentration of the protective gas inside the inner liner in real time during inflation. When the gas concentration detector detects that the protective gas concentration at the top vent of the inner liner is 99.5%, the control valve installed at the top vent of the inner liner is adjusted to reduce the vent size until it is closed, and the inflation flow rate is reduced at the same time. S4. Circumferential seam welding: During welding, under the monitoring of pressure detector and gas concentration detector, protective gas is continuously injected at a low flow rate to ensure that the protective gas concentration is not lower than 99.5% to prevent oxidation during welding; a small amount of gas is controlled to be released from the outlet to achieve real-time pressure relief and prevent the internal pressure of the inner tank from being overloaded due to the high temperature of welding, and finally achieve anti-oxidation circumferential seam welding of the stainless steel water tank inner tank.
[0013] In a preferred embodiment of the present invention, the protective gas is argon. At normal temperature (20°C) and standard atmospheric pressure (101.325 kPa), the density of argon is about 1.37 times that of air. Taking advantage of this density difference, the injected argon can naturally displace the air inside the inner liner, pushing the air out from the top vent, so that the argon concentration inside the inner liner reaches the welding requirement of 99.5%, providing a reliable anti-oxidation protective atmosphere for circumferential welding.
[0014] In this embodiment, the inner tank of the water tank has a capacity of 1000L, a diameter of 800mm, and a height of 1900mm. All other openings are closed, leaving only the drain hole at the bottom of the vertically standing inner tank as the argon gas filling port, and the hot water outlet at the top of the inner tank as the gas outlet. Before welding, pure argon gas is first filled into the inner tank at a flow rate of 150-200L / min. A pressure detector near the joint detects a filling pressure of 0.5-0.6MPa. After approximately 25 minutes of filling, a gas concentration detector at the top of the inner tank detects an argon gas concentration of 99.5% at the outlet. At this point, the filling flow rate is changed to 20L / min, and the control valve at the outlet is adjusted to control a small amount of gas output. During welding, based on real-time feedback data from the pressure detector and the gas concentration detector, the protective gas filling flow rate and the opening of the top outlet control valve are dynamically adjusted to ensure that the argon gas concentration inside the inner tank remains at no less than 99.5%. Under the premise of effectively avoiding the problem of increased internal pressure of the inner liner caused by high welding temperature, the weld seam is ultimately safe and oxidation-free.
[0015] It should be understood that the above embodiments are one or more embodiments of the present invention. There are many other embodiments and variations based on the present invention. Any variations and modifications made by those skilled in the art without making pioneering innovations are within the protection scope of the present invention.
Claims
1. A stainless steel water tank inner liner includes an inner liner body and an end cap; the stainless steel water tank inner liner anti-oxidation circumferential weld method is characterized by... Includes the following steps: S1. Precise docking of inner tank body and end cap: The end cap is rounded by tooling, and the inner tank body is introduced at the same time to achieve precise docking of inner tank body and end cap, preventing cracks from occurring during welding. S2. Shielding gas filling: Stand the connected inner tank upright, close other openings, and only open the air inlet at the bottom and the air outlet at the top of the inner tank. Welding shielding gas is filled in from the air inlet at the bottom of the inner tank, and air is discharged from the air outlet at the top of the inner tank to prevent the weld of the stainless steel water tank inner tank from reacting with oxygen in the air during welding. S3. Protective gas monitoring and concentration control: A pressure detector is installed near the inner liner docking joint and a gas concentration detector is installed at the top vent to monitor the pressure and concentration of the protective gas inside the inner liner in real time during inflation. When the gas concentration detector detects that the protective gas concentration at the top vent of the inner liner is 99.5%, the control valve installed at the top vent of the inner liner is adjusted to reduce the vent size until it is closed, and the inflation flow rate is reduced at the same time. S4. Circumferential seam welding: During welding, under the monitoring of pressure detector and gas concentration detector, protective gas is continuously injected at a low flow rate to ensure that the protective gas concentration is not lower than 99.5% to prevent oxidation during welding; a small amount of gas is controlled to be released from the outlet to achieve real-time pressure relief and prevent the internal pressure of the inner tank from being overloaded due to the high temperature of welding, and finally achieve anti-oxidation circumferential seam welding of the stainless steel water tank inner tank.
2. The protective gas according to claim 1, characterized in that, The protective gas is argon.