Device and method for welding stainless steel pipe joint of staggered joint structure

Abstract

The invention provides a device and a method for welding a stainless steel pipe joint with a staggered joint structure. The device comprises a guide hole shaft and a guide column shaft, the guide hole shaft and the guide column shaft are stepped shafts, a first threaded hole is machined in the end face of the small-diameter section of the guide hole shaft, and a guide hole is machined in the end face of the large-diameter section of the guide hole shaft. The small-diameter section of the guide pillar shaft is inserted into the guide hole, and a second threaded hole is formed in the end face of the large-diameter section of the guide pillar shaft; the outer diameter size of the large-diameter section of the guide hole shaft is matched with the size of an inner hole of the welding large-aperture joint; and the outer diameter size of the large-diameter section of the guide post shaft is matched with the size of an inner hole of the welding small-aperture joint. The mandrel positioning device is designed according to the structure and the size of the joint to be welded, alignment of the two joints can be accurately achieved before welding, the problem that alignment is difficult in manual butt welding is effectively solved, and the defects of undercut, air holes, incomplete penetration and the like are reduced.

Description

Technical Field

[0001] This invention relates to the field of pipe joint welding technology, and in particular to an apparatus and method for welding stainless steel pipe joints with misaligned joints. Background Technology

[0002] In structures such as pipes and containers, misalignment (i.e., the inner and outer walls of two joints are not aligned) often occurs due to design or manufacturing errors. Traditional welding methods rely on manual alignment or simple tooling, which makes it difficult to ensure coaxiality and easily leads to problems such as weld misalignment and stress concentration. At the same time, in fields such as aerospace and shipbuilding, the weld grade must reach level two or above, with extremely high requirements for coaxiality error (usually ≤0.1mm).

[0003] For the welding of multi-variety, small-batch misaligned pipe joints, there are currently two common welding methods.

[0004] One method involves manual, assisted positioning and welding, where operators use tools to clamp the stainless steel pipe fittings for butt welding. During the welding process, the operator's experience and skill are crucial for controlling the alignment of the fittings and the welding parameters. The other method uses a turntable to clamp the two fittings. A guide rail moves two concentric turntables on either side, clamping and fixing the two fittings to be welded. The rotation of the turntable, in conjunction with the welding equipment, enables circumferential welding of the fittings. Specifically:

[0005] Manual butt welding: Stainless steel has unique physical and chemical properties, making it difficult to achieve a weld grade of II or higher during argon arc welding. Furthermore, the misalignment of the inner and outer diameters of the two joints, coupled with the lack of precise positioning and fixing devices in manual clamping, makes accurate alignment of the two joints during butt welding difficult. This easily leads to undercut, i.e., a depression forming on the base metal at the weld edge; porosity is also common, as gases in the weld pool fail to escape in time during solidification and remain in the weld, forming pores; incomplete penetration is also prone to occur, meaning the weld metal does not completely fill the gap at the joint root, resulting in incomplete fusion at the joint root. These defects severely affect the welding quality of stainless steel pipe joints, reducing their performance and reliability.

[0006] Turntable clamping method: Welding the two joints using a turntable requires specialized turntable equipment, which significantly increases welding costs. Furthermore, the large size of the turntable equipment presents numerous inconveniences when operating in an argon atmosphere. An argon atmosphere requires a relatively enclosed space to ensure the shielding gas concentration in the welding area; however, large turntable equipment is difficult to set up and operate in an argon atmosphere, not only occupying a significant amount of space but also potentially affecting the effective coverage of the argon gas, thus impacting welding quality. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide an apparatus and method for welding stainless steel pipe joints with misaligned joints.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] Option 1: A device for welding stainless steel pipe joints with misaligned joints, comprising: a guide shaft and a guide post shaft coaxially arranged on the left and right sides; both the guide shaft and the guide post shaft are stepped shafts, with a first threaded hole machined on the end face of the small-diameter section of the guide shaft and a guide hole machined on the end face of the large-diameter section of the guide shaft; the small-diameter section of the guide post shaft is inserted into the guide hole, and a second threaded hole is machined on the end face of the large-diameter section of the guide post shaft; the outer diameter of the large-diameter section of the guide shaft matches the inner diameter of the welded large-diameter joint; the outer diameter of the large-diameter section of the guide post shaft matches the inner diameter of the welded small-diameter joint; both the guide shaft and the guide post shaft are made of T3 grade copper; the small-diameter section of the guide post shaft has a transition fit with the guide hole.

[0010] Option 2: The method for welding the staggered stainless steel pipe joint of the present invention includes the following steps:

[0011] Step 1: Slowly insert the guide shaft into the large-diameter connector, ensuring a tight connection without any movement. Then, insert the guide post shaft into the small-diameter connector, ensuring a tight connection without any movement. Next, insert the small-diameter section of the guide post shaft into the guide hole for connection and assembly, achieving coaxial alignment of the large-diameter and small-diameter connectors. Step 2: Use clamps to fix the two ends of the large-diameter connector with the guide shaft and the small-diameter connector with the guide post shaft. Step 3: Place the large-diameter and small-diameter connectors in a working environment with uniform argon gas coverage. Step 4: Operate the welding equipment to weld the circumferential weld. Step 5: After welding, wait for the weld to cool to room temperature and then turn off the argon gas supply system. Screw the screw into the first and second threaded holes, and apply tension by rotating the screw to pull the guide shaft and guide post shaft out of the large-diameter and small-diameter connectors.

[0012] Compared with existing technologies, the advantages of this invention are as follows: This invention, through the cooperative design of the guide post shaft and guide hole shaft, after being embedded in the inner hole of the joint, utilizes a stepped structure to achieve forced alignment of the welding bevel, reducing the impact of misalignment on welding quality. The device of this invention features simple structure, low cost, and convenient operation, enabling rapid and precise alignment and fixation of two stainless steel pipe joints, ensuring welding concentricity, thereby effectively reducing welding defects, consistently obtaining weld quality of grade II or higher, and is particularly suitable for welding environments with limited space. Specifically:

[0013] 1. Significantly improved welding quality: The precise alignment of the mandrel positioning device effectively reduces welding defects such as undercut, porosity, and incomplete penetration, enabling high-quality welding of Class II and above weld seams, and improving the welding strength and reliability of stainless steel pipe joints.

[0014] 2. Cost Reduction: This device eliminates the need for large, specialized turntable equipment, utilizing common materials and a simple structure, thus reducing equipment procurement and maintenance costs. Furthermore, improved welding quality minimizes rework and scrap due to welding defects, further lowering production costs.

[0015] 3. Easy to operate and highly adaptable: The device is compact in size, making it easy to set up and operate in an argon atmosphere, without being limited by site space. Moreover, the mandrel positioning device can be customized to fit joints of different structures and sizes, exhibiting strong adaptability and meeting the welding requirements of various misaligned stainless steel pipe joints.

[0016] 4. Improved production efficiency: Precise alignment reduces preparation time before welding and adjustment time during welding, while high-quality welding reduces post-weld processing steps, thereby improving overall production efficiency. Attached Figure Description

[0017] Figure 1 This is an overall structural diagram of the present invention;

[0018] Figure 2 This is an exploded view of the present invention.

[0019] In the diagram: 1. Large-diameter connector; 2. Small-diameter connector; 3. First threaded hole; 4. Guide shaft; 5. Guide hole; 6. Small-diameter section; 7. Guide post shaft; 8. Second threaded hole. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0021] Example 1

[0022] This embodiment provides a device for welding stainless steel pipe joints with misaligned joints, comprising: a guide shaft 4 and a guide post shaft 7 coaxially arranged on the left and right sides; both the guide shaft 4 and the guide post shaft 7 are stepped shafts, with a first threaded hole 3 machined on the end face of the small-diameter section of the guide shaft 4, and a guide hole 5 machined on the end face of the large-diameter section of the guide shaft 4; the small-diameter section 6 of the guide post shaft 7 is inserted into the guide hole 5, and a second threaded hole 8 is machined on the end face of the large-diameter section of the guide post shaft 7; the outer diameter of the large-diameter section of the guide shaft 4 matches the inner diameter of the welded large-diameter joint 1; the outer diameter of the large-diameter section of the guide post shaft 7 matches the inner diameter of the welded small-diameter joint 2; both the guide shaft 4 and the guide post shaft 7 are made of T3 grade copper; the small-diameter section 6 of the guide post shaft 7 is fitted with the guide hole 5.

[0023] Example 2

[0024] This embodiment provides a method for welding stainless steel pipe joints with misaligned joints, including the following steps:

[0025] Step 1: Slowly insert the guide shaft 4 into the large-diameter connector 1, ensuring a tight connection between the guide shaft 4 and the large-diameter connector 1 without any shaking; then insert the guide post shaft 7 into the small-diameter connector 2, ensuring a tight connection between the guide post shaft 7 and the small-diameter connector 2 without any shaking; then insert the small-diameter section 6 of the guide post shaft 7 into the guide hole 5 for connection and assembly, achieving coaxial alignment of the large-diameter connector 1 and the small-diameter connector 2;

[0026] Step 2: Use clamps to fix the two ends of the large-diameter joint with the guide hole shaft and the small-diameter joint with the guide post shaft to prevent the joint from moving during welding and ensure the stability of the welding.

[0027] Step 3: Place the above-mentioned large-diameter joint and small-diameter joint in a working environment with argon gas evenly covered to form a good protective atmosphere and prevent air from entering during the welding process, which would affect the welding quality;

[0028] Step 4: Operate the welding equipment to weld the circumferential weld. During the welding process, maintain stable welding parameters to ensure that the weld is uniform and continuous.

[0029] Step 5: After welding is completed, wait for the weld to cool to room temperature and then turn off the argon gas supply system. Screw the screw into the first threaded hole and the second threaded hole, and apply tension by rotating the screw to pull the guide shaft and guide post shaft out of the large-diameter joint and the small-diameter joint.

[0030] The present invention has been described in detail above. However, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, any modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. An apparatus for welding stainless steel pipe joints with misaligned joints, characterized in that, include: A guide shaft (4) and a guide post shaft (7) are coaxially arranged on the left and right sides; both the guide shaft (4) and the guide post shaft (7) are stepped shafts. The end face of the small diameter section of the guide shaft (4) is machined with a first threaded hole (3), and the end face of the large diameter section of the guide shaft (4) is machined with a guide hole (5); the small diameter section (6) of the guide post shaft (7) is inserted into the guide hole (5), and the end face of the large diameter section of the guide post shaft (7) is machined with a second threaded hole (8); the outer diameter of the large diameter section of the guide shaft (4) matches the inner diameter of the welded large diameter joint (1); the outer diameter of the large diameter section of the guide post shaft (7) matches the inner diameter of the welded small diameter joint (2).

2. The apparatus for welding stainless steel pipe joints with misaligned joints according to claim 1, characterized in that, The guide shaft (4) and guide post shaft (7) are both made of T3 grade copper.

3. The apparatus for welding stainless steel pipe joints with misaligned joints according to claim 1, characterized in that, The small-diameter section (6) of the guide shaft (7) is fitted with the guide hole (5).

4. A method for welding stainless steel pipe joints with staggered joints, characterized in that: Includes the following steps: Step 1: Slowly insert the guide shaft (4) into the large-diameter connector (1) to ensure that the guide shaft (4) and the large-diameter connector (1) are tightly connected without any shaking; then insert the guide post shaft (7) into the small-diameter connector (2) to ensure that the guide post shaft (7) and the small-diameter connector (2) are tightly connected without any shaking; then insert the small-diameter section (6) of the guide post shaft (7) into the guide hole (5) for connection and assembly to achieve coaxial alignment of the large-diameter connector (1) and the small-diameter connector (2); Step 2: Use a clamp to fix the two ends of the large-diameter connector (1) with the guide shaft (4) and the small-diameter connector (2) with the guide post shaft (7); Step 3: Place the large-diameter connector (1) and the small-diameter connector (2) in a working environment with argon gas evenly distributed; Step 4: Operate the welding equipment to weld the circumferential weld; Step 5: After welding is completed, wait for the weld to cool to room temperature and turn off the argon supply system; screw the screw into the first threaded hole (3) and the second threaded hole (8), apply tension by rotating the screw, and pull the guide shaft (4) and guide post shaft (7) out of the large-diameter joint (1) and the small-diameter joint (2) respectively.

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