An argon-free protection-free austenitic stainless steel pipe welding method

Abstract

The present application relates to the technical field of welding, and discloses an argon-free protection austenitic stainless steel pipe welding method, which comprises the following steps: welding a sealing weld on a butt joint of a first austenitic stainless steel pipe and a second austenitic stainless steel pipe; blocking an end of the first austenitic stainless steel pipe or the second austenitic stainless steel pipe away from the butt joint; placing the first austenitic stainless steel pipe and the second austenitic stainless steel pipe in an inclined manner, so that the blocked end of the first austenitic stainless steel pipe or the second austenitic stainless steel pipe is located at the lower end; filling water into the inclined first austenitic stainless steel pipe and the second austenitic stainless steel pipe, and the water level is higher than the position of the butt joint; and welding the remaining weld of the butt joint. The present application can avoid internal argon filling during welding, save argon use cost, avoid oxidation caused by the contact between the high-temperature weld and the heat-affected zone in the steel pipe and air, shorten the cooling time between welds, reduce the dangerous temperature residence time, and effectively improve the welding construction quality and efficiency.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a welding method for austenitic stainless steel pipes that does not require argon gas protection. Background Technology

[0002] During the welding process of austenitic stainless steel pipes, the temperature of the weld and heat-affected zone must be strictly controlled to prevent the surface from being oxidized due to excessively high temperature or prolonged high-temperature residence time, which may even lead to coarse grains in the weld joint and excessive residence time in the dangerous temperature range (450℃~850℃) (excessive residence time in the dangerous temperature range is the main cause of intergranular corrosion).

[0003] Currently, when welding austenitic stainless steel pipes, such as Figure 1 As shown, an argon gas inlet pipe 30 is arranged inside the first austenitic stainless steel tube 10, and an argon gas exhaust pipe 40 is arranged inside the second austenitic stainless steel tube 20. A large flow rate of argon gas is continuously injected into the two austenitic stainless steel tubes for internal protection and cooling. Simultaneously, welding must be performed using low current, low voltage, and high welding speed, with strict control of welding heat input. Furthermore, the temperature of the austenitic stainless steel tubes during welding must be controlled by increasing the cooling dwell time between weld passes to ensure compliance with relevant technical requirements. However, this welding method requires a large internal argon gas flow rate, resulting in high argon consumption and construction costs. Moreover, it can only be performed using relatively small welding parameters, severely limiting welding heat input and resulting in low deposition efficiency. The long cooling dwell time between weld passes further reduces welding efficiency. Additionally, the use of gas for cooling and protection of the welding area is ineffective, and the inner surface of the stainless steel tube weld and the heat-affected zone are prone to oxidation due to high temperatures during the filling and capping layer welds. Summary of the Invention

[0004] In view of the above problems, the purpose of this invention is to provide a welding method for austenitic stainless steel pipes without argon purging, so as to avoid argon purging during the welding process of austenitic stainless steel pipes, improve the deposition efficiency and welding construction efficiency, and avoid oxidation of the inner surface of the weld and the heat-affected zone due to high temperature.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The argon-free welding method for austenitic stainless steel pipes of the present invention includes:

[0007] Step S1: Weld the bottom sealing weld of the butt joint between the first austenitic stainless steel tube and the second austenitic stainless steel tube.

[0008] Step S2: Seal the end of the first austenitic stainless steel tube or the second austenitic stainless steel tube that is away from the butt joint.

[0009] Step S3: Tilt the first austenitic stainless steel tube and the second austenitic stainless steel tube so that the sealing end of the first austenitic stainless steel tube or the second austenitic stainless steel tube is located at the lower end.

[0010] Step S4: Fill the tilted first austenitic stainless steel tube and the second austenitic stainless steel tube with water, and the water level is higher than the position of the butt joint.

[0011] Step S5: Weld the remaining weld of the butt joint.

[0012] Preferably, before step S1, the method further includes:

[0013] Assemble the first austenitic stainless steel tube and the second austenitic stainless steel tube.

[0014] Multi-point positioning welding was performed on the butt joint of the first austenitic stainless steel tube and the second austenitic stainless steel tube.

[0015] Preferably, after multi-point positioning welding, the front side of the positioning weld of each point is cleaned of slag, and the two ends of each positioning weld are ground and beveled.

[0016] Preferably, manual tungsten inert gas (TIG) welding is used for tack welding. The length of the tack weld is 15mm to 20mm, the thickness of the tack weld is 2mm to 3mm, the welding current is 80A to 100A, and the argon flow rate of the welding torch is 15L / min to 20L / min.

[0017] Preferably, both the bottom sealing weld and the positioning weld are single-sided welds with double-sided forming.

[0018] Preferably, step S2 includes:

[0019] Insert the plug into the end of the first or second austenitic stainless steel tube;

[0020] Use aluminum foil with sealant to stick at the connection between the plug head and the end of the corresponding first or second austenitic stainless steel tube.

[0021] Preferably, step S3 includes:

[0022] The first austenitic stainless steel tube and the second austenitic stainless steel tube are placed on the welding positioner and clamped.

[0023] The first austenitic stainless steel tube and the second austenitic stainless steel tube are tilted at a set angle.

[0024] Preferably, in step S5, the remaining weld of the butt joint is welded using tungsten inert gas welding or carbon dioxide gas shielded welding.

[0025] Preferably, after step S5, the method further includes:

[0026] Step S6: Set aside the first and second austenitic stainless steel tubes after welding until the weld area drops to the set temperature.

[0027] Step S7: Drain the water from the inside of the first and second austenitic stainless steel pipes and remove the seals.

[0028] Preferably, after step S7, step S8 is also included, in which the first austenitic stainless steel tube and the second austenitic stainless steel tube are placed for more than a set time, and then non-destructive testing is performed on the weld.

[0029] Compared with existing technologies, the argon-free welding method for austenitic stainless steel pipes according to embodiments of the present invention has the following advantages:

[0030] The argon-free welding method for austenitic stainless steel pipes according to this invention involves first performing a root pass weld on the butt joint of two austenitic stainless steel pipes, then sealing one end of one of the pipes, filling the pipe with water, and finally welding the remaining weld seam. By using water-filled cooling and protection inside the stainless steel pipe, argon filling during welding can be avoided, saving argon usage costs. Furthermore, this water-filled cooling method improves the cooling rate and the protection of the weld and heat-affected zone, preventing oxidation of the high-temperature weld and heat-affected zone from contact with air, appropriately increasing welding heat input and welding deposition efficiency, significantly shortening the cooling (construction pause) time between weld passes, reducing the time spent at dangerous temperatures, and effectively improving welding quality and efficiency. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of argon gas filling protection into the first and second austenitic stainless steel tubes in the prior art.

[0032] Figure 2 This is a schematic flowchart of the argon-free welding method for austenitic stainless steel pipes according to an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram showing the location of the positioning weld in an embodiment of the present invention;

[0034] Figure 4 This is a schematic diagram of the bottom sealing weld in an embodiment of the present invention;

[0035] Figure 5This is a schematic diagram of the end sealing of the second austenitic stainless steel tube in an embodiment of the present invention;

[0036] Figure 6 This is a schematic diagram of filling water into the first austenitic stainless steel tube and the second austenitic stainless steel tube in an embodiment of the present invention.

[0037] In the diagram, 10 is the first austenitic stainless steel tube; 20 is the second austenitic stainless steel tube; 30 is the argon gas inlet pipe; and 40 is the argon gas exhaust pipe.

[0038] 1. Bottom sealing weld; 2. Positioning weld; 3. Plug head; 31. Water pipe; 32. Switch; 4. Tin foil; 5. Water; 6. Positioner top pressure roller; 61. Positioner drive wheel. Detailed Implementation

[0039] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the 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, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0042] like Figure 2 - Figure 6 As shown in the figure, an argon-free welding method for austenitic stainless steel pipe according to an embodiment of the present invention includes the following steps:

[0043] Step S1: Weld the butt joint of the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 with a sealing weld 1, connecting the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 into a single integral tube (see...). Figure 4 );

[0044] Step S2: Seal the end of the first austenitic stainless steel tube 10 or the second austenitic stainless steel tube 20 away from the butt joint, so that the integral tube formed by the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 is sealed at one end and open at the other end.

[0045] Step S3: The integral tube formed by the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 is placed at an angle, so that the sealed end of the first austenitic stainless steel tube 10 or the second austenitic stainless steel tube 20 is located at the lower end and the open end is located at the upper end.

[0046] Step S4: Fill the tilted first austenitic stainless steel tube 10 and second austenitic stainless steel tube 20 with water 5, and make the water level higher than the joint, so that the water in the whole tube completely submerges the joint.

[0047] Step S5: Weld the remaining welds of the butt joint, specifically the welding of the filling weld and the cover weld, to achieve welding of the stainless steel pipe filling and cover welds under argon protection conditions.

[0048] This invention employs a method of internal water filling for cooling and protection within stainless steel pipes. Throughout the entire welding process, the steel pipes do not require argon gas purging, significantly reducing argon gas usage costs. Furthermore, this internal water filling cooling and protection method improves the cooling rate and the protection of the weld and heat-affected zone, preventing oxidation of the high-temperature weld and heat-affected zone from contact with air. It also appropriately increases welding heat input and welding deposition efficiency, significantly shortens the cooling (work pause) time between weld passes, reduces the time spent at dangerous temperatures, and effectively improves welding quality and efficiency.

[0049] During welding, the heat generated is promptly transferred to the tap water inside the stainless steel pipe. The tap water, through convection, rapidly and thoroughly cools the welding area, reducing the time spent in the dangerous temperature zone and improving welding quality. Simultaneously, the tap water blocks contact between the weld seam and heat-affected zone inside the stainless steel pipe and air, providing excellent protection for this area. Compared to argon gas protection, water cooling and protection are more thorough, preventing oxidation and discoloration on both sides of the weld (preventing a decline in its mechanical properties and corrosion resistance). This allows for a suitable increase in welding current and significantly shortens the cooling time (work pause) between weld passes, effectively improving welding efficiency. Furthermore, although the weld slag on the surface of the weld seam inside the stainless steel pipe will automatically detach, a small amount of slag may remain in the transition area between the weld seam and the base material. During welding, the high temperature of the weld seam transfers heat to the tap water, instantly causing the water near the weld seam surface to boil. This boiling process thoroughly removes any remaining slag, providing a certain degree of auxiliary slag removal.

[0050] In this embodiment, before step S1, the assembly further includes: assembling the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20, wherein the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 are pre-processed with welding bevels according to the drawing requirements; and performing multi-point positioning welding on the butt joint of the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 to facilitate the sealing welding of the butt joint.

[0051] like Figure 3 As shown, in this embodiment, four-point positioning welding is set, and the positioning welds 2 of each point are spaced apart along the circumferential direction of the butt joint. Further, manual tungsten inert gas (TIG) welding is used for positioning welding, specifically using self-shielded TIG welding wire (2.6mm diameter) for manual TIG welding, eliminating the need for argon filling inside the stainless steel tube. The positioning weld 2 is a single-sided weld with double-sided forming; the weld surface inside the stainless steel tube is covered with slag for protection, and the weld formation meets design requirements. The length of the positioning weld 2 is 15mm–20mm, the thickness is 2mm–3mm, the welding current is 80A–100A, and the argon flow rate of the welding torch is 15L / min–20L / min.

[0052] Furthermore, after multi-point positioning welding, the front side of the positioning weld 2 of each positioning weld is cleaned to remove slag, and the slag on the back side of the positioning weld 2 can be automatically removed; the two ends of each positioning weld 2 are ground and beveled to ensure the joint quality of the bottom sealing weld 1 at the positioning weld 2.

[0053] In step S1, manual tungsten inert gas (TIG) welding is used for the bottom sealing weld. Specifically, a self-shielded TIG welding wire (2.6mm diameter) is used for manual TIG welding, eliminating the need to fill the stainless steel tube with argon gas. During the bottom sealing weld construction, a welding positioner can be used to maintain the flat welding position, completing the welding of the entire circumference of the bottom sealing weld 1 while the stainless steel tube rotates.

[0054] In this embodiment, the bottom sealing weld 1 is a single-sided weld with double-sided forming. The surface of the weld inside the stainless steel pipe is covered with slag for protection, which automatically falls off after welding, and the weld formation meets the design requirements. Furthermore, after the bottom sealing weld 1 is welded, its front weld is thoroughly cleaned and inspected to ensure that there are no welding defects. If welding defects are found, they must be repaired in a timely manner.

[0055] like Figure 5As shown, in this embodiment, step S2 includes: inserting the plug 3 into the end of the first austenitic stainless steel tube 10 or the second austenitic stainless steel tube 20, so that the integral tube formed by the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 is sealed at one end and open at the other end; using aluminum foil 4 with sealant to stick at the connection between the plug 3 and the end of the corresponding first austenitic stainless steel tube 10 or second austenitic stainless steel tube 20 to improve the sealing performance. The combination of the plug 3 and the aluminum foil 4 achieves both temporary sealing of the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 and facilitates removal. Preferably, the plug 3 is a cork stopper, with a water pipe 31 installed in the middle of the cork stopper, and a switch 32 installed on the water pipe 31 to facilitate water flow 5 and drainage 5 in the stainless steel tube. The cork stopper and the water pipe 31 are sealed together.

[0056] like Figure 6 As shown, in this embodiment, step S3 includes: placing the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 on a welding positioner and clamping them; tilting the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 at a set angle so that the open end is at the upper end and the sealed end is at the lower end, facilitating water filling. Placing the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 on the welding positioner and clamping them with the positioner's top pressure wheel 6 and positioner drive wheel 61 not only facilitates the adjustment of the angle of the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20, but also allows the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 to rotate continuously during the welding process, which can change the inherent position of the weld seam, allowing welding to be carried out in the easier-to-weld position in the upper half of the circle, reducing the welding difficulty.

[0057] Optionally, in step S3, the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 can be placed on an inclined fixed fixture, and then water 5 can be filled into them. Welding can be carried out while the stainless steel tubes are fixed in place.

[0058] In this embodiment, in step S5, the remaining weld of the butt joint is welded using tungsten inert gas welding or carbon dioxide gas shielded welding. The heat generated during the welding process is promptly transferred to the tap water inside the stainless steel pipe, and the tap water continuously and thoroughly cools the welding area through convection.

[0059] In this embodiment, after step S5, the method further includes: step S6, setting aside the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 after welding until the weld area drops to a set temperature, which is room temperature; step S7, draining the water inside the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 and removing the seal.

[0060] Furthermore, following step S7, step S8 is also included, whereby after placing the first austenitic stainless steel tube 10 and the second austenitic stainless steel tube 20 for a set time, non-destructive testing is performed on the weld to ensure that there are no welding defects. The set time is 24 hours.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. An argon-free argon protection-free austenitic stainless steel pipe welding method characterized by, The application relates to a method for welding a butt joint of first and second austenitic stainless steel pipes. The method comprises the following steps: S1, welding a sealing weld on the butt joint of the first and second austenitic stainless steel pipes; S2, plugging an end of the first or second austenitic stainless steel pipe away from the butt joint; S3, placing the first and second austenitic stainless steel pipes in an inclined state, with the plugged end of the first or second austenitic stainless steel pipe being located at the lower end; S4, filling water into the first and second austenitic stainless steel pipes in the inclined state, with the water level being higher than the position of the butt joint; 2. The argon-free shielded welding method of the austenitic stainless steel pipe according to claim 1, characterized by, S5, welding the remaining weld of the butt joint. Before the step S1, the method further comprises the following steps: assembling the first and second austenitic stainless steel pipes; 3. The argon-free shielded welding method of the austenitic stainless steel pipe according to claim 2, characterized by, positioning and welding the butt joint of the first and second austenitic stainless steel pipes by using multiple spot positioning welds.

4. The argon-free back shielding-free welding method of an austenitic stainless steel pipe according to claim 2, characterized by, After the multiple spot positioning welds, the front surface of each spot positioning weld is subjected to slag removal treatment, and the two ends of each spot positioning weld are subjected to slope polishing treatment.

5. The argon-free back shielding-free welding method of an austenitic stainless steel pipe according to claim 2, characterized by, The spot positioning welds are welded by using a manual tungsten argon arc welding mode, the length of each spot positioning weld is 15-20 mm, the thickness of each spot positioning weld is 2-3 mm, the welding current is 80-100 A, and the argon flow rate of a welding torch is 15-20 L / min.

6. The argon-free back shielding-free welding method of an austenitic stainless steel pipe according to claim 1, characterized by, The sealing weld and the spot positioning welds are all single-sided welding double-sided forming welds. The step S2 comprises the following steps: inserting a plug head into the end of the first or second austenitic stainless steel pipe; 7. The argon-free back shielding-free welding method of an austenitic stainless steel pipe according to claim 1, characterized by, using tin foil paper with sealing glue to be attached to the connection between the plug head and the end of the first or second austenitic stainless steel pipe. The step S3 comprises the following steps: clamping the first and second austenitic stainless steel pipes on a welding positioner; 8. The argon-free back shielding-free welding method of an austenitic stainless steel pipe according to claim 1, characterized by, inclining the first and second austenitic stainless steel pipes to a set angle.

9. The argon-free back shielding-free welding method of an austenitic stainless steel pipe according to claim 1, characterized by, In the step S5, the remaining weld of the butt joint is welded by using a tungsten argon arc welding mode or a carbon dioxide gas shielded welding mode. After the step S5, the method further comprises the following steps: S6, placing the first and second austenitic stainless steel pipes after welding until the weld area is lowered to a set temperature; 10. The argon-free shielded austenitic stainless steel pipe welding method according to claim 9, characterized by, S7, discharging the water in the first and second austenitic stainless steel pipes and removing the plug. After the step S7, the method further comprises the following step S8: placing the first and second austenitic stainless steel pipes for more than a set time, and then performing nondestructive flaw detection on the weld.

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