Stainless steel pipe L-shaped groove welding method

Abstract

The invention discloses a welding method for an L-shaped groove of a stainless steel pipe, which relates to the technical field of welding and comprises the following steps of: blanking the pipe according to a construction drawing and actual on-site surveying and mapping conditions; an L-shaped groove is cut in the pipe; the pipes are assembled in pairs; according to the diameter of the pipe, the L-shaped groove is welded, and a welding seam is formed; the quality of the welding seam is checked; and if the welding defect is detected, rectifying the welding defect. By the adoption of the L-shaped groove, on the premise that the welding quality is guaranteed, the using amount of filling materials can be effectively reduced, the welding cost is reduced, and meanwhile it is guaranteed that the interior of a welding seam is in smooth transition, a heat affected zone is small, and welding deformation is relatively small. In addition, the welding quality is ensured by checking the pipes before blanking and detecting and rectifying the quality of welding seams after welding.

Description

Technical Field

[0001] The invention relates to the technical field of welding, in particular to a method for welding an L-shaped groove of a stainless steel pipe. Background Art

[0002] In modern industrial manufacturing, welding, as a key joining technology, is widely used across various industries, from construction and machinery manufacturing to aerospace and automotive manufacturing. With the rapid development of industry, the requirements for welding quality, efficiency, and cost are also increasing. Stainless steel, with its excellent corrosion resistance, high strength, and good processability, has become an indispensable material in many industrial scenarios. Stainless steel L-shaped grooves, as a common welding groove form, play a vital role in connecting various stainless steel structural components.

[0003] In recent years, with the continued growth in welding demand, traditional welding processes and groove forms have become increasingly difficult to meet the increasingly stringent quality and performance requirements. For example, in the manufacture of some high-cleanliness piping systems, the strength and fluidity requirements of welded joints are extremely high, and any minor welding defect can cause pipeline failure. Summary of the Invention

[0004] The main purpose of this application is to provide a stainless steel pipe L-shaped groove welding method, aiming to optimize the welding process and improve the quality and efficiency of L-shaped groove welding.

[0005] To achieve the above objectives, the present application proposes a stainless steel pipe L-shaped groove welding method, comprising the following steps:

[0006] Cut the pipes according to the construction drawings and actual on-site surveying and mapping conditions;

[0007] Cutting an L-shaped groove on the pipe;

[0008] Pairing the pipes;

[0009] Welding the L-shaped groove according to the diameter of the pipe to form a weld;

[0010] Inspecting the quality of the weld;

[0011] If welding defects are detected, the welding defects are rectified.

[0012] In one embodiment, the step of “cutting the pipes according to the construction drawings and the actual on-site surveying and mapping” includes:

[0013] Check the pipe blanking size, cut verticality and pipe mouth roundness;

[0014] Cleaning the burrs on the pipe mouth;

[0015] Cleaning the inner wall surface of the pipe;

[0016] Clean the outer wall of the pipe.

[0017] In one embodiment, the tubing includes pipes and pipe fittings;

[0018] The step of “cutting an L-shaped groove on the pipe” comprises:

[0019] Determining whether the pipe is a pipe or a pipe fitting;

[0020] If the pipe is a pipeline, trim the outer wall of the pipeline and process the pipe opening into an L-shaped groove;

[0021] If the pipe is a pipe fitting, clamp one end of the pipe fitting, trim the outer peripheral wall of the other end of the pipe fitting, and process the pipe end of the other end of the pipe fitting into an L-shaped groove;

[0022] Clean the impurities within 40mm on each side of the pipe groove;

[0023] Protect the groove.

[0024] In one embodiment, the step of “assembling the pipes” includes:

[0025] Align and connect the two pipes;

[0026] Detecting the concentricity of the two pipes;

[0027] Fixing the butt joint of the pipe opening;

[0028] Spot welding is performed on at least one location of the pipe opening joint;

[0029] After spot welding is completed, the dimensions of the pipe joints shall be reviewed;

[0030] Detecting the gap between the two pipes;

[0031] If the pairing gap is less than or equal to 0.1 mm, it is determined that the pairing is completed.

[0032] In one embodiment, the step of “spot welding at least one point of the pipe opening joint” includes:

[0033] Provide a high-frequency argon arc welder to perform spot welding symmetrically at four locations on the butt joint of the pipe orifice, and control the current of the high-frequency argon arc welder to be between 50A and 110A and / or control the spot welding depth to be between 0.5mm and 1.5mm;

[0034] Spot welding is performed symmetrically at four locations on the butt joint of the pipe mouth;

[0035] Inspecting and analyzing the stress on the pipe joint;

[0036] Add welds to stress concentration areas;

[0037] Wherein, the high-frequency argon arc welding machine needs to keep the arc extinguished for 3 to 5 seconds after each spot welding to perform delayed protection cooling on the welding point.

[0038] In one embodiment, the weld includes a first layer, a second layer, and a third layer extending radially outward from the pipe in sequence;

[0039] The step of “welding the L-shaped groove according to the pipe diameter to form a weld” includes:

[0040] Measuring the diameter and wall thickness of the pipe;

[0041] If the pipe diameter is greater than 80 mm and the wall thickness is greater than 2 mm, the first layer is primed with autogenous welding using a motorized welder, the second layer is filled with argon arc welding using a motorized welder, and the third layer is filled with argon arc welding or electric welding using a motorized welder;

[0042] If the pipe diameter is greater than 80 mm and the wall thickness is less than or equal to 2 mm, use motorized autogenous welding for welding;

[0043] If the pipe diameter is less than or equal to 80 mm and the wall thickness is greater than 2 mm, the first layer is primed with autogenous welding using a closed welding machine, the second layer is filled with manual argon arc welding, and the third layer is filled with manual argon arc welding or electric welding;

[0044] If the pipe diameter is less than or equal to 80 mm and the wall thickness is less than or equal to 2 mm, autogenous welding is used for welding using a closed welding machine.

[0045] In one embodiment, after the step of “welding the L-shaped groove according to the diameter of the pipe to form a weld”, the method further includes:

[0046] Aim the welding torch airflow direction at the weld to perform surface gas shielding for 3 to 5 seconds, until the weld temperature drops below the interlayer temperature of 150°C;

[0047] Continue to circulate argon until the metal weld at the welding point cools down.

[0048] In one embodiment, before the step of "spot welding at least one point of the pipe joint", the step further includes circulating argon gas into the pipe;

[0049] After the step of "assembling the pipes", the process also includes: sealing the welding end with a silicone plug or other clean material, and then opening the argon filling valve to replace the protective gas; setting the protective gas pressure in the pipe to be greater than the outside air pressure, and confirming whether the purge level is appropriate by observing the purge flow rate.

[0050] In one embodiment, before the step of “aligning the centers of the two pipes and then butting them together”, the method further includes:

[0051] A silicone plug is provided in at least one of the pipes near the joint of the pipe opening to separate the gas on both sides of the silicone plug.

[0052] In one embodiment, the step of "inspecting the quality of the weld" includes: inspecting whether there are the impurities or holes, and whether the arc closure work is completed in the middle of the weld.

[0053] Check the inner surface of the pipe under lighting conditions and compare the color with that of qualified samples;

[0054] Check whether the welding pool and weld bead width are uniform, and the error between the welding pool and weld bead width and the preset value is less than or equal to 2mm, and the weld bead distortion does not exceed 25% of the weld bead width;

[0055] It is clear that the weld reinforcement is less than or equal to 0.5mm, the reinforcement difference is less than or equal to 0.1mm and not lower than the parent material, and the width difference is less than or equal to 0.5mm.

[0056] One or more technical solutions proposed in this application have at least the following technical effects:

[0057] In an embodiment of the present invention, the stainless steel pipe L-shaped groove welding method includes the following steps: cutting the pipe according to the construction drawings and the actual situation of on-site surveying and mapping; cutting the L-shaped groove on the pipe; assembling the pipe; welding the L-shaped groove according to the pipe diameter to form a weld; inspecting the quality of the weld; and rectifying the weld defect if any. By adopting the L-shaped groove, the amount of filler material used can be effectively reduced, the welding cost can be reduced, and the welding deformation is relatively small while ensuring the welding quality. In addition, the welding quality is ensured by inspecting the pipe before cutting and inspecting and rectifying the weld quality after welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0059] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0060] Figure 1This is a flow chart of a stainless steel pipe L-shaped groove welding method;

[0061] Figure 2 for Figure 1 Flowchart of step S10;

[0062] Figure 3 for Figure 1 Flowchart of step S20;

[0063] Figure 4 for Figure 1 Flowchart of step S30;

[0064] Figure 5 for Figure 1 Flowchart of step S40;

[0065] Figure 6 for Figure 1 Flowchart of step S50 in FIG.

[0066] The purpose, features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0067] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0068] It should be noted that if a directional indication is involved in an embodiment of the present invention, the directional indication is only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0069] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0070] The main solution of this application is: cutting pipes according to construction drawings and actual on-site surveying and mapping; cutting L-shaped grooves on the pipes; assembling the pipes; welding the L-shaped grooves according to the pipe diameters to form welds; inspecting the quality of the welds; and rectifying any welding defects found.

[0071] Promoting Industrial Production: In industrial production, welding quality is directly related to product performance and service life. Research on stainless steel L-shaped grooves can optimize welding processes and reduce welding defects such as porosity, cracks, and lack of fusion, thereby improving the strength, sealing, and corrosion resistance of welded joints. This not only improves product quality and reliability, reduces product failure rates and repair costs, but also extends product service life and enhances a company's market competitiveness.

[0072] Optimizing the design and welding process for stainless steel L-grooves can reduce production costs. On the one hand, reducing weld defects and improving weld quality can reduce scrap and rework, lowering raw material and labor costs. On the other hand, improving welding efficiency and adopting more energy-efficient welding processes can reduce energy consumption and equipment operating costs. For example, using the appropriate groove form and welding parameters can achieve faster welding speeds and reduce welding time, thereby improving production efficiency and reducing production costs.

[0073] It should be noted that the L-shaped groove of stainless steel pipe is a special groove formed at the weld joint, and its shape resembles a capital letter "L". It usually consists of a vertical surface and an inclined surface, with the angle between the two surfaces generally being 90°. In practical applications, the dimensional parameters of the L-shaped groove mainly include groove depth, groove width, blunt edge size, and root gap.

[0074] Groove depth refers to the vertical distance from the weld surface to the bottom of the groove, which directly affects the weld penetration and weld strength. Generally speaking, thicker stainless steel plates require a larger groove depth to ensure complete penetration during welding. Groove width refers to the lateral dimension of the groove on the weld surface, which determines the amount of filler material used during welding and the width of the weld. The blunt edge refers to a straight edge reserved at the root of the groove. Its function is to prevent the root from burning through during welding and also reduce the amount of filler material used. The root gap refers to the gap reserved at the root of the groove between the two weldments during assembly of the welded joint. It helps to ensure root fusion and the quality of the weld.

[0075] Secondly, the implementation body of this embodiment is pipes. The present invention does not limit the specific pipes. The pipes can be pipes or pipe fittings, where pipes refer to tubular objects used to transport fluids, usually long strips with fixed length and diameter; and pipe fittings refer to components used to connect pipes, change pipe direction, branch or control fluid flow, common ones include elbows, tees, crosses, flanges, valves, etc., which are small and irregular in size.

[0076] See also Figure 1 The embodiment of the present application provides a stainless steel pipe L-shaped groove welding method, including steps S10 to S60:

[0077] Step S10: Cutting pipes according to the construction drawings and actual on-site surveying and mapping conditions;

[0078] It should be noted that the construction drawings and actual on-site surveys include pipe cutting dimensions, cutout verticality, and pipe end roundness. The data on the drawings and the cutting dimension list are compared with the actual measurements to determine the pipe cutting dimensions and then cut the pipe. Blanking refers to the process of cutting or separating raw materials into blanks or semi-finished products that meet design requirements according to specific sizes and shapes. It is the first step in manufacturing and a critical step in transforming raw materials into finished parts. The quality and accuracy of blanking directly impact the efficiency of subsequent processing steps and the quality of the final product.

[0079] Step S20: cutting an L-shaped groove on the pipe;

[0080] Step S30: grouping the pipes;

[0081] It should be noted that pairing refers to aligning and positioning two pipes in accordance with design requirements and welding process standards to ensure that the pipes are in the correct relative position and posture during welding.

[0082] Step S40: welding the L-shaped groove according to the diameter of the pipe to form a weld;

[0083] Step S50: inspecting the weld quality;

[0084] Step S60: If welding defects are detected, the welding defects are rectified.

[0085] In an embodiment of the present invention, the stainless steel pipe L-shaped groove welding method includes the following steps: cutting the pipe according to the construction drawings and actual on-site surveying and mapping; cutting the L-shaped groove on the pipe; assembling the pipe; welding the L-shaped groove according to the pipe diameter to form a weld; inspecting the weld quality; and rectifying any weld defects if detected. By adopting the L-shaped groove, the amount of filler material used can be effectively reduced, welding costs can be lowered, and welding deformation can be relatively small while ensuring welding quality. In addition, welding quality is ensured by inspecting the pipe before cutting and inspecting and rectifying the weld quality after welding.

[0086] See also Figure 2 In a feasible implementation, step S10 may include steps S11 to S14:

[0087] Step S11: Checking the pipe blanking size, the verticality of the cut, and the roundness of the pipe mouth;

[0088] In this embodiment, the pipe blanking dimensions include the pipe length and pipe diameter. For curved pipe fittings, the blanking dimensions also include the bending radius, and the bending radius should meet the minimum bending radius requirements of the material, generally 1-2 times the outer diameter of the pipe. The cutout perpendicularity refers to the perpendicularity between the side of the cutout and the surface of the cut material, that is, the perpendicularity of the angle formed by the plane where the pipe cutout is located and the tangent plane of the outer wall of the pipe. By confirming the cutout perpendicularity, the occurrence of undercuts during welding is avoided. The pipe mouth roundness refers to the circularity of the cross-section of the pipe end, that is, whether the pipe mouth is close to a perfect circle. By confirming the pipe mouth roundness, the quality of the weld during subsequent welding is improved. It is understood that the present invention does not limit the specific measurement method, and the measurement can be performed according to the actual tools available. In this embodiment, the blanking dimensions are measured by a tape measure, the cutout perpendicularity is measured by using a square on a work platform, and the pipe mouth roundness is measured by comparing the outer diameter of the pipe in different directions. The dimensional error in each direction should be less than 0.5 mm.

[0089] Step S12: cleaning the burrs on the pipe mouth;

[0090] It is understandable that after cutting, burrs will inevitably appear on the pipe ends. Therefore, these burrs need to be cleaned. In this embodiment, a plate file is used to clean the pipe ends. It should be noted that to improve the verticality of the cut and enhance the quality of subsequent welding, a pipe cutter should be used when cutting each pipe. After cutting, a dedicated flattener should be used to smooth the cut surface, with the pipe ends facing downward. A file should then be used to remove burrs, with the pipe ends facing downward.

[0091] Step S13: cleaning the inner wall surface of the pipe;

[0092] Step S14: cleaning the outer wall surface of the pipe.

[0093] It is understandable that when the pipe mouth is cut, iron slag and other cutting impurities will adhere to the inner wall of the pipe and need to be cleaned; and impurities such as oil, rust, dust and other impurities on the outer wall of the pipe and the incision will affect the welding quality. These impurities may cause defects such as pores and slag inclusions in the weld during the welding process, reducing the strength and performance of the weld. Anhydrous alcohol or acetone can be used for cleaning. Alcohol and acetone have good dissolving power and can effectively remove oil, dust and other organic impurities to ensure a clean welding surface.

[0094] See also Figure 3 In a feasible implementation manner, the step S20 includes steps S21 to S25:

[0095] Step S21: determining whether the pipe is a pipe or a pipe fitting;

[0096] Step S22: If the pipe is a pipeline, trimming the outer peripheral wall of the pipeline and processing the pipe opening into an L-shaped groove;

[0097] Step S23: If the pipe is a pipe fitting, clamp one end of the pipe fitting, trim the outer peripheral wall of the other end of the pipe fitting, and process the pipe end of the other end of the pipe fitting into an L-shaped groove;

[0098] Step S24: cleaning impurities within 40 mm on each side of the pipe groove;

[0099] Step S25: protecting the groove.

[0100] It's understandable that pipes and fittings need to be fixed during cutting, and because of their different shapes, the fixing methods vary. For pipes, first use an external turning tool to correct the outer wall of the pipe. Then, switch the tool and use a grooving tool to process the pipe into an L-shaped groove. Oil, paint, scale, rust, burrs, and other defects within 40mm on each side of the groove must be removed, and there must be no defects such as cracks or interlayers. Acetone or alkaline cleaning agents can be used for cleaning. After cleaning, the groove should be protected from dust, oil, and other impurities. For pipe fittings, a simple fixture is first made to secure one end of the elbow or other fitting. The tool is then fixed to a rotatable chuck, and the elbow or other fitting is then beveled.

[0101] See also Figure 4 In a feasible implementation manner, the step S30 includes steps S31 to S37:

[0102] Step S31: aligning and butting the two pipes;

[0103] Step S32: detecting the concentricity of the two pipes;

[0104] Step S33: fixing the butt joint of the pipe orifice;

[0105] Step S34: spot welding at least one of the joints of the pipe orifices;

[0106] Step S35: After spot welding is completed, the dimensions of the pipe joint are reviewed;

[0107] Step S36: detecting the gap between the two pipes;

[0108] Step S37: If the pairing gap is less than or equal to 0.1 mm, it is determined that the pairing is completed.

[0109] After the groove processing is completed, when the pipes and pipes, and pipes and pipe fittings are assembled, the pipe ends are directly butted together without leaving any gaps. After alignment, the concentricity of the two pipes is checked, and the pipes at both ends are fixed with pipe butt clamps, and spot welding is performed at least at one point at the butt joint of the pipe ends, thereby pre-fixing the two pipes.

[0110] It's important to note that the dimensions of the pipe joint primarily include the concentricity and perpendicularity of the two pipes. The gap refers to the axial spacing between the two pipes when they are joined. To ensure joint quality, the dimensions of the pipe joint must be reviewed after spot welding, and the gap between the two pipes must be checked. The ends must be flush, and the pipes or fittings on both sides of the joint must maintain concentricity and perpendicularity. The maximum allowable gap during joining must not exceed 0.1mm.

[0111] Furthermore, in a feasible implementation manner, step S34 includes steps S341 to S344:

[0112] Step S341: providing a high-frequency argon arc welder to perform spot welding symmetrically at four locations on the butt joint of the pipe orifice, controlling the current of the high-frequency argon arc welder to be between 50A and 110A and / or controlling the spot welding depth to be between 0.5mm and 1.5mm;

[0113] Step S342: spot welding the pipe orifice at four symmetrical locations;

[0114] Step S343: inspecting and analyzing the stress on the pipe joint;

[0115] Step S344: adding welding points to the stress concentration area;

[0116] Wherein, the high-frequency argon arc welding machine needs to keep the arc extinguished for 3 to 5 seconds after each spot welding to perform delayed protection cooling on the welding point.

[0117] Among them, the current of the argon arc welding machine is controlled between 50A and 110A. Through the higher current, the surface of the pipe is heated up quickly and fused instantly. It should be noted that it is strictly forbidden to stay for a long time during spot welding to avoid the pipe wall being penetrated. In addition, it is not advisable to move the welding gun directly after the arc is extinguished. A 3-5 second lag protection cooling must be maintained to prevent the weld from coming into contact with the air at high temperature and absorbing oxygen quickly, resulting in yellowing, blueing, or oxidation of the weld surface. It can be understood that the positions of the electric welding are symmetrical, such as Figure 5 As shown, the pipe is fixed by spot welding at the 3, 6, 9, and 12 o'clock positions of the pipe mouth. Alternatively, the number of spot welds can be adjusted to 2 or 8, evenly spaced around the pipe mouth joint. Subsequently, based on force analysis and process requirements, additional welds can be added to key locations or stress concentration areas, shortening the distance between welds to ensure more uniform force distribution across the welded areas.

[0118] In addition, in a feasible embodiment, before step S34, the step S331 is further included: circulating argon gas into the pipe;

[0119] After the step of "assembling the pipes", steps S38 to S39 are also included:

[0120] Step S38: sealing the pipe orifice and opening the argon filling valve to replace the protective gas;

[0121] In this example, argon gas is introduced into the pipe in advance and exhausted to meet welding conditions, thereby improving welding quality. Furthermore, after the intersection of the two pipe ends is rounded, argon is pre-filled for 1.5-2 minutes to fully exhaust the air in the pipe.

[0122] Step S39: Set the shielding gas pressure inside the pipe to be greater than the outside air pressure, and confirm whether the purge level is appropriate by observing the purge flow rate.

[0123] In this embodiment, the shielding gas pressure inside the pipe is set to be greater than the outside air pressure to prevent outside air from entering the pipe. The appropriate purge level can be confirmed by observing the purge flow rate. This can also prevent excessive purge levels and reduce protector waste. It will be appreciated that the shielding gas is typically helium, but other inert gases such as neon may also be used. The present invention does not limit the specific type of shielding gas.

[0124] Furthermore, in a feasible embodiment, before the step of "aligning the centers of the two pipes and then docking them", it also includes: setting a silicone plug in at least one of the pipes near the docking point of the pipe mouth to separate the gas on both sides of the silicone plug.

[0125] Specifically, a silicone plug is first attached to the entire inner wall 100mm away from the joint of each pipe opening to separate the gas on both sides of the silicone plug. In this way, the hydrogen filling space can be minimized, ensuring the quality of argon filling while saving the time required for argon filling and the amount of argon used. The silicone plug can also be a water-soluble paper or degradable plastic film that fits the inner wall of the pipe. While being able to isolate the air, it does not need to be removed after welding. The silicone plug can be set on one of the inner walls of the pipe, or on the inner wall of each pipe, thereby further reducing the argon filling space.

[0126] See also Figure 5 In a feasible embodiment, the weld includes a first layer, a second layer, and a third layer arranged radially outward from the pipe;

[0127] The step S40 includes steps S41 to S45:

[0128] Step S41: measuring the diameter and wall thickness of the pipe;

[0129] Step S42: If the pipe diameter is greater than 80 mm and the wall thickness is greater than 2 mm, the first layer is primed with autogenous welding using a motorized welder, the second layer is filled with argon arc welding using a motorized welder, and the third layer is filled with argon arc welding or electric welding using a motorized welder;

[0130] Step S43: If the pipe diameter is greater than 80 mm and the wall thickness is less than or equal to 2 mm, welding is performed using motorized autogenous welding;

[0131] Step S44: If the pipe diameter is less than or equal to 80 mm and the wall thickness is greater than 2 mm, the first layer is primed with autogenous welding using a closed welding machine, the second layer is filled with manual argon arc welding, and the third layer is filled with manual argon arc welding or electric welding;

[0132] Step S45: If the pipe diameter is less than or equal to 80 mm and the wall thickness is less than or equal to 2 mm, autogenous welding is performed using a closed welding machine.

[0133] By using two advanced pipeline welding machines, motorized welding machine and closed welding machine, for pipes of different diameters, the labor cost is greatly reduced and the work efficiency is improved.

[0134] It should be noted that a weld is the joint formed by joining two or more separate metals through the welding process. Autogenous welding is a welding technique that uses an arc or other heat source to heat the base metal, causing it to partially melt and form the weld, without the need for welding wire.

[0135] In addition, different welding methods are required for different pipe diameters. For pipes with a diameter greater than 80mm, automatic welding machines can be used for welding with high welding precision. For pipes with a diameter less than 80mm, the diameter is too small to be welded automatically. Therefore, closed welding machines can be used for autogenous welding. In a closed environment, the rotating tungsten needle in the welding clamp surrounds the pipe weld seam. The inner and outer walls are protected by argon gas. Autogenous welding without welding wire or welding slag can achieve single-sided welding and double-sided forming. The tungsten rod is The WCe-20 tungsten rod is connected with DC positive polarity, the welding technique is the hand crank 8-shaped or crescent-shaped method, and the weld width is controlled at 4mm.

[0136] To ensure welding quality for L-shaped grooves, one embodiment of the present invention employs three-layer welding. First, autogenous welding is used for the base layer, allowing the base material to be used as the filler. Furthermore, by controlling the gap between the two welds during assembly and combining appropriate welding process parameters, a weld head that meets the requirements can be obtained after welding, with the weld backside height less than 0.5 mm and the weld inner surface relatively smooth. The second layer is welded using wire-added argon arc welding to prevent arc welding, which could damage the original weld formation due to excessive current. The third and subsequent layers can be welded using wire-added argon arc welding or electric welding. It is understood that the number of weld layers can be increased to more layers as needed, and argon arc welding or electric welding can be used to improve weld strength.

[0137] In addition, it can be understood that when the wall thickness of the pipe is small, the two pipes can be welded together with fewer weld layers, and there is no need to continue to fill more layers of welds. Specifically, when the wall thickness of the pipe is less than 2 mm, the weld of the first layer of autogenous welding can meet the conditions and no welding material needs to be filled.

[0138] In one embodiment, the welding process parameters of the first layer autogenous welding are shown in Table 1 below:

[0139] Table 1

[0140] Current 80-90A Voltage 20-24v Welding speed 50-60mm / min Argon flow rate 8-10L / min Shielding gas flow 10-12L / min Tungsten electrode extension length 6-8mm

[0141] In a feasible implementation, after step S40, steps S46 to S47 are further included.

[0142] Step S46: Align the welding torch airflow direction with the weld bead for surface gas shielding for 3 to 5 seconds until the weld temperature drops below the interlayer temperature of 150°C;

[0143] Step S47: Continue to circulate the argon gas until the metal weld at the welding location cools down.

[0144] After welding is complete, the torch should not be removed directly. Instead, the torch should be aligned with the weld bead to provide surface gas shielding for 3-5 seconds, until the weld temperature drops below 150°C between passes. This is to prevent the weld from rapidly absorbing oxygen when exposed to air at high temperatures, which can cause the weld surface to turn yellow, blue, or oxidize. Even after welding is complete and the torch can be removed, continue circulating argon gas until the metal weld cools down to reduce the risk of contamination.

[0145] See also Figure 6 In a feasible implementation manner, the step S50 includes steps S51 to S54:

[0146] Step S51: Check whether there are impurities or holes, and whether the arc closure work is completed in the middle of the weld.

[0147] Step S52: Check the inner surface of the pipe under lighting conditions and compare the color with the qualified sample

[0148] Step S53: Check whether the welding pool and the weld bead width are uniform, and whether the error between the welding pool and the weld bead width and the preset value is less than or equal to 2 mm, and the weld bead distortion does not exceed 25% of the weld bead width.

[0149] Step S54: Check whether there are any undercuts, unfused or concave defects. The excess height of the surface molding shall not exceed 20% of the wall thickness of the pipe and shall not be greater than 2 mm.

[0150] Among them, the welding quality is ensured by inspecting these key items.

[0151] Step S60: If welding defects are detected, the welding defects are rectified.

[0152] Specifically, in a feasible implementation manner, welding defects and their causes and prevention methods are shown in Table 2 below:

[0153] Table 2

[0154]

[0155]

[0156] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent processing scope of the present application.

Claims

1. A stainless steel pipe L-shaped groove welding method, characterized in that: The stainless steel pipe L-shaped groove welding method comprises the following steps: Cut the pipes according to the construction drawings and actual on-site surveying and mapping conditions; Cutting an L-shaped groove on the pipe; Pairing the pipes; Welding the L-shaped groove according to the diameter of the pipe to form a weld; Inspecting the quality of the weld; If welding defects are detected, the welding defects are rectified.

2. The stainless steel pipe L-shaped groove welding method according to claim 1, characterized in that: The step of "cutting pipes according to the construction drawings and actual on-site surveying and mapping" includes: Check the pipe blanking size, cut verticality and pipe mouth roundness; Cleaning the burrs on the pipe mouth; Cleaning the inner wall surface of the pipe; Clean the outer wall of the pipe.

3. The stainless steel pipe L-shaped groove welding method according to claim 1, characterized in that: The pipes include pipes and pipe fittings; The step of "cutting an L-shaped groove on the pipe" includes: Determining whether the pipe is a pipe or a pipe fitting; If the pipe is a pipeline, trim the outer wall of the pipeline and process the pipe opening into an L-shaped groove; If the pipe is a pipe fitting, clamp one end of the pipe fitting, trim the outer peripheral wall of the other end of the pipe fitting, and process the pipe end of the other end of the pipe fitting into an L-shaped groove; Clean the impurities within 40mm on each side of the pipe groove; Protect the groove.

4. The stainless steel pipe L-shaped groove welding method according to claim 1, characterized in that: The step of "assembling the pipes" includes: Align and connect the two pipes; Detecting the concentricity of the two pipes; Fixing the butt joint of the pipe opening; Spot welding is performed on at least one location of the pipe opening joint; After spot welding is completed, the dimensions of the pipe joints shall be reviewed; Detecting the gap between the two pipes; If the pairing gap is less than or equal to 0.1 mm, it is determined that the pairing is completed.

5. The stainless steel pipe L-shaped groove welding method according to claim 4, characterized in that: The step of "spot welding at least one point of the pipe opening joint" includes: Provide a high-frequency argon arc welder to perform spot welding symmetrically at four locations on the butt joint of the pipe orifice, and control the current of the high-frequency argon arc welder to be between 50A and 110A and / or control the spot welding depth to be between 0.5mm and 1.5mm; Spot welding is performed symmetrically at four locations on the butt joint of the pipe mouth; Inspecting and analyzing the stress on the pipe joint; Add welds to stress concentration areas; Wherein, the high-frequency argon arc welding machine needs to keep the arc extinguished for 3 to 5 seconds after each spot welding to perform delayed protection cooling on the welding point.

6. The stainless steel pipe L-shaped groove welding method according to claim 1, characterized in that: The weld includes a first layer, a second layer, and a third layer extending radially outward from the pipe in sequence; The step of "welding the L-shaped groove according to the pipe diameter to form a weld" includes: Measuring the diameter and wall thickness of the pipe; If the pipe diameter is greater than 80 mm and the wall thickness is greater than 2 mm, the first layer is primed with autogenous welding using a motorized welder, the second layer is filled with argon arc welding using a motorized welder, and the third layer is filled with argon arc welding or electric welding using a motorized welder; If the pipe diameter is greater than 80 mm and the wall thickness is less than or equal to 2 mm, use motorized autogenous welding for welding; If the pipe diameter is less than or equal to 80 mm and the wall thickness is greater than 2 mm, the first layer is primed with autogenous welding using a closed welding machine, the second layer is filled with manual argon arc welding, and the third layer is filled with manual argon arc welding or electric welding; If the pipe diameter is less than or equal to 80 mm and the wall thickness is less than or equal to 2 mm, autogenous welding is used for welding using a closed welding machine.

7. The stainless steel pipe L-shaped groove welding method according to claim 1, characterized in that: After the step of "welding the L-shaped groove according to the diameter of the pipe to form a weld", the method further includes: Aim the welding torch airflow direction at the weld to perform surface gas shielding for 3 to 5 seconds, until the weld temperature drops below the interlayer temperature of 150°C; Continue to circulate argon until the metal weld at the welding point cools down.

8. The stainless steel pipe L-shaped groove welding method according to claim 4, characterized in that: Before the step of "spot welding at least one point of the pipe joint", the step further includes circulating argon gas into the pipe; After the step of "assembling the pipes", the following steps are also included: sealing the welding end with a silicone plug or other clean material, and then opening the argon filling valve to replace the protective gas; setting the protective gas pressure in the pipe to be greater than the outside air pressure, and confirming whether the purge level is appropriate by observing the purge flow rate.

9. The stainless steel pipe L-shaped groove welding method according to claim 8, characterized in that: Before the step of "aligning the centers of the two pipes and then butting them together", the method further includes: A silicone plug is provided in at least one of the pipes near the joint of the pipe opening to separate the gas on both sides of the silicone plug.

10. The stainless steel pipe L-shaped groove welding method according to claim 1, characterized in that: The step of "inspecting the weld quality" includes: Check whether there are the aforementioned impurities or holes, and whether the arc closure is completed in the middle of the weld; Check the inner surface of the pipe under lighting conditions and compare the color with that of qualified samples; Check whether the welding pool and weld bead width are uniform, and the error between the welding pool and weld bead width and the preset value is less than or equal to 2mm, and the weld bead distortion does not exceed 25% of the weld bead width; It is clear that the weld reinforcement is less than or equal to 0.5mm, the reinforcement difference is less than or equal to 0.1mm and not lower than the parent material, and the width difference is less than or equal to 0.5mm.

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