Method for welding weld joint between heat exchange tube and tube plate in horizontal direction

Abstract

The invention belongs to the technical field of heat exchange tube and tube plate welding, and discloses a method for welding a weld joint between a heat exchange tube and a tube plate in a horizontal direction, which comprises the following steps of: preparing and assembling an outer-layer heat exchange tube and an outer-layer heat exchange tube plate, and forming a weld joint between the outer-layer heat exchange tube and the outer-layer heat exchange tube plate; an automatic argon arc welding wire matched with the base metal is selected and installed; welding equipment is installed and debugged, specifically, a full-automatic argon arc welding machine without a positioning core rod is adopted, a welding gun of the welding machine is vertically arranged downwards, welding seams of the outer-layer heat exchange tube and the outer-layer heat exchange tube plate are welded in the horizontal direction, and welding parameters are set on the welding machine; installing a tungsten electrode, and adjusting a wire feeding angle, wherein the tip of the tungsten electrode points to a gap between the outer-layer heat exchange tube and the outer-layer heat exchange tube plate; in the welding process, a welding machine visually recognizes and records the positions of the heat exchange tube and the tube hole of the tube plate, and a welding gun automatically moves to the position of the tube hole to achieve automatic welding; and quality detection. Welding quality is improved, welding seam strength is enhanced, and stability and reliability in the welding process are guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of heat exchange tube and tube sheet welding, and relates to a method for horizontally welding a heat exchange tube and a tube sheet weld. Background Art

[0002] In the traditional heat exchanger manufacturing process, such as Figure 1 As shown, the welding of heat exchange tubes and tube sheets is usually carried out in a vertical position on the tube sheet surface, which is usually called full-position welding. The welding method is usually automatic or semi-automatic argon arc welding, and the welding gun generally has a positioning core rod inserted into the heat exchange tube to fix the welding gun. This welding method has the following disadvantages:

[0003] Uneven weld formation: During the welding process, the molten pool is affected by gravity, surface tension, and arc blowing force. All-position welding includes different positions such as flat welding, uphill welding, downhill welding, and overhead welding. During the welding process, except for the constant influence of gravity, the directions of the other two forces are always changing. Therefore, it is difficult to ensure the uniformity of weld formation during all-position welding;

[0004] Difficulty in adjusting welding parameters: Since the direction of force on the molten pool is constantly changing during the full-position welding of the heat exchange tube and the tube sheet, the penetration and forming of the weld in different directions are different. Therefore, the welding current, voltage, wire feeding speed, etc. need to be adjusted at each rotation angle of full-position welding to ensure root penetration and weld size at each position and obtain the appropriate weld forming effect. Existing methods generally divide the weld into multiple intervals according to the angle, and set different welding parameters for each interval, which makes it difficult to adjust the welding parameters;

[0005] Risk of incomplete penetration at the root: In order to meet the regulatory requirements for the minimum leakage diameter of the heat exchange tube and tube sheet weld, the designer will increase the depth of the groove of the heat exchange tube and tube sheet joint, which increases the difficulty of welding and causes incomplete penetration. Especially in the downhill welding position, the molten pool flows downward severely during welding, reducing the penetration depth and increasing the risk of incomplete penetration at the root;

[0006] It is difficult to control the shrinkage of the tube mouth: for example, in the overhead welding position, the liquid metal is easy to fall under the action of gravity, causing the weld of the tube mouth to invade the heat exchange tube. Especially when the groove is large and the molten pool size is large, the shrinkage inside the tube mouth exceeds the tolerance, which will affect the penetration of the expander during the subsequent expansion;

[0007] The inner wall of the heat exchange tube is easily scratched: In the traditional semi-automatic welding method, in order to ensure that the welding gun is in the center of the heat exchange, it is necessary to insert a positioning core rod into the heat exchange tube during welding to position and fix the welding gun, but the positioning core rod may scratch the inner wall of the heat exchange tube, affecting the service life of the heat exchange tube. Especially in special heat exchangers, scratches on the inner wall are not allowed.

[0008] Especially in the shell and tube heat exchanger with double-layer heat exchange tubes, since the inner heat exchange tube is also sheathed in the outer heat exchange tube, the channel between the weld between the outer heat exchange tube and the tube sheet and the outer wall of the inner heat exchange tube is an important dimension, which seriously affects the cross-sectional area of ​​the heat exchange channel. When the weld between the heat exchange tube and the tube sheet is uneven, the width is greatly different, and the shrinkage value is uneven, it will cause irregular flow size, affect the flow rate of the heat exchange medium, etc., and cause the heat exchange effect to fail to meet the design requirements.

[0009] In order to solve the above problems, it is necessary to develop a method that can improve the roundness and forming uniformity of the weld. Summary of the invention

[0010] In order to solve at least one of the above technical problems, the present invention provides a method for horizontally welding the welds between heat exchange tubes and tube sheets, which can improve welding quality, enhance weld strength, and ensure the stability and reliability of the welding process.

[0011] In order to achieve the above object, the technical solution of the present invention is to provide a method for horizontally welding the weld between a heat exchange tube and a tube sheet, comprising the following steps:

[0012] Prepare and clean the outer heat exchange tubes and outer heat exchange tube sheets;

[0013] Assemble the outer heat exchange tube and the outer heat exchange tube sheet, and position and expand the tube, with a weld between the two;

[0014] Select and install automatic argon arc welding wire that matches the parent material;

[0015] Install and debug the welding equipment: use a fully automatic argon arc welding machine without a positioning core rod, with the welding gun of the welding machine set vertically downward, weld the weld between the outer heat exchange tube and the outer heat exchange tube sheet in a horizontal position, and set the welding parameters on the welding machine;

[0016] Install the tungsten electrode and adjust the wire feeding angle: the tip of the tungsten electrode points to the gap between the outer heat exchange tube and the outer heat exchange tube sheet; weld the weld in a horizontal position: during the welding process, the welding machine visually identifies and records the positions of the heat exchange tube and the tube sheet holes, and the welding gun automatically moves to the tube hole position to achieve automatic welding;

[0017] Quality inspection.

[0018] According to the present invention, further, the heat exchanger is placed in a vertical position, with the outer heat exchange tube plate surface facing the horizontal direction and the weld facing the welding gun.

[0019] According to the present invention, further, the plate holes of the outer layer heat exchange tube sheet are formed with 0-3mm chamfered grooves.

[0020] According to the present invention, further, the positioning expansion tube adopts mechanical expansion tube.

[0021] According to the present invention, further, the parameters for adjusting the wire feeding angle are: the welding wire is located 1.5-2 mm below the tip of the tungsten electrode and is offset outward by 0.3-0.5 mm.

[0022] According to the present invention, further, the diameter of the automatic argon arc welding wire is φ0.6mm, φ0.8mm or φ1.0mm.

[0023] According to the present invention, further, the quality inspection includes visual inspection and penetration inspection of the weld seam after welding;

[0024] Visual inspection: Check whether there are cracks, incomplete penetration, lack of fusion, pores and weld nodules on the weld surface; Penetrant inspection: Ensure that there is no indication on the weld surface.

[0025] The beneficial effects of the present invention are:

[0026] 1. Improve welding quality: Horizontal welding eliminates the change in the force direction of the molten pool during welding, makes the weld uniform, ensures the penetration depth in all directions (angles), significantly reduces the difficulty of adjusting welding parameters, and can obtain a uniform shrinkage size after welding.

[0027] 2. Improve the operation quality of the heat exchanger: Stable penetration depth and good weld formation ensure the strength of the weld, avoid the insufficient weld size that may exist in a certain direction (angle) in traditional welding, improve the safety and stability of the heat exchanger in operation, reduce the risk of leakage, and ensure the operation quality of the heat exchanger.

[0028] 3. The present invention adopts a positioning-free core rod welding gun, which avoids possible scratches on the inner wall of the heat exchange tube, improves the welding quality of the heat exchange tube, and meets the design requirements.

[0029] 4. The roundness of the weld of the present invention is significantly improved, the width of the weld is relatively uniform, and the flow channel size is relatively uniform, ensuring that the heat exchange channel size between the outer heat exchange tube and the tube sheet weld and the outer wall of the inner heat exchange tube in the shell and tube heat exchanger of the double-layer heat exchange tube is uniform, thereby ensuring the heat exchange effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of all-position welding in the prior art;

[0031] Figure 2 It is a schematic diagram of the heat exchange tube and tube sheet structure in the shell and tube heat exchanger of the double-layer heat exchange tube of the present invention;

[0032] Figure 3 It is a schematic diagram of the welding seam of the horizontally welded heat exchange tube and tube sheet of the present invention.

[0033] In the accompanying drawings,

[0034] 1-outer heat exchange tube; 2-outer heat exchange tube sheet; 3-weld; 4-inner heat exchange tube; 5-inner heat exchange tube sheet; 6-fluid heat exchange channel; 7-tungsten electrode; 8-positioning-free core rod welding gun. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0036] See also Figure 2 and Figure 3 The embodiment of the present application discloses a method for welding a heat exchange tube and a tube sheet weld in a horizontal position, which is used for welding a heat exchange tube and a tube sheet weld of a shell and tube heat exchanger with double-layer heat exchange tubes. The heat exchanger includes an inner heat exchange tube 4 and an outer heat exchange tube 1 sleeved on the outer periphery of the inner heat exchange tube 4, and a fluid heat exchange channel 6 for medium circulation is formed between the two; the length of the outer heat exchange tube 1 is shorter than that of the inner heat exchange tube 4; the outer periphery of the inner heat exchange tube 4 is fixedly welded with an inner heat exchange tube sheet 5, and the outer periphery of the outer heat exchange tube 1 is fixedly welded with an outer heat exchange tube sheet 2, and a weld 3 is formed at the welding point between the two. Preferably, the heat exchange tube and the tube sheet can be made of carbon steel, stainless steel and titanium alloy.

[0037] In order to improve the welding quality of the weld 3, the following steps are included:

[0038] Step 1: Prepare and clean the heat exchange tubes and tube sheets;

[0039] Clean the surface of the heat exchange tube and tube sheet to ensure that there is no oil stain or rust, so as to provide good surface conditions for subsequent welding; Step 2, assemble the outer heat exchange tube 1 and the outer heat exchange tube sheet 2, and perform positioning and tube expansion. During the positioning and tube expansion process, control the position of the heat exchange tube or scrape the longer part of the heat exchange tube after positioning and expansion;

[0040] Among them, the plate hole of the outer heat exchange tube sheet 2 forms a 0-3mm chamfer groove, and the outer heat exchange tube 1 is flush with the outer heat exchange tube sheet 2 or shrinks inward to be flush with the inner side of the chamfer; the positioning expansion tube adopts mechanical expansion tube, which is used to eliminate the gap between the heat exchange tube and the inner wall of the tube sheet hole and fix the position of the two, ensuring the stability of the heat exchange tube position during welding, and the heat exchange tube and the tube hole are concentric;

[0041] Use the tooling to place the heat exchanger in a vertical position, ensuring that the tube sheet faces the horizontal direction;

[0042] Step 3: Select and install the automatic argon arc welding wire that matches the base material;

[0043] The common diameters of the automatic argon arc welding wires for the weld between the outer heat exchange tube 1 and the outer heat exchange tube sheet 2 are φ0.6mm, φ0.8mm, and φ1.0mm. The matching welding wires are selected according to the parent material and welding requirements to ensure the welding quality and weld performance;

[0044] Step 4: Install and debug the welding equipment;

[0045] The welding equipment is a dedicated fully automatic argon arc welding machine without a positioning core rod for flat welding of tubes and tube sheets. The welding gun of the equipment is a positioning core rod-free welding gun, which is set vertically downward and can weld the weld between the outer heat exchange tube and the outer heat exchange tube sheet in a horizontal position 3. Set the welding parameters on the equipment; install the tungsten electrode and adjust the wire feeding angle.

[0046] The welding process parameters include shielding gas, welding speed, welding current, welding voltage, etc. Since welding is performed in a flat welding position, the force direction of the molten pool remains unchanged during the welding process. Except for arc starting and arc ending, the welding parameters of the entire circle are consistent; the tip of the tungsten electrode points to the gap between the heat exchange tube and the tube sheet to ensure that the root of the weld is melted through; the wire feeding angle is adjusted so that the welding wire is 1.5-2mm below the tip of the tungsten electrode and offset outward by about 0.5mm to ensure a stable welding process and good weld formation;

[0047] Step 5, welding the heat exchange tube-tube sheet weld in a horizontal position;

[0048] During the welding process, the welding machine visually identifies and records the positions of the heat exchange tubes and tube sheet holes, and the welding gun automatically moves to the tube hole position to achieve automatic welding.

[0049] After one pipe opening is welded, the welding gun automatically moves to the remaining unwelded pipe holes according to the program to continue welding.

[0050] Among them, because visual recognition positioning is used, positioning is no longer dependent on the positioning core rod, so the inner wall of the heat exchange tube will not be scratched, the risk of corrosion during product operation is reduced, and the service life of the heat exchange tube is increased;

[0051] Step 6: Quality inspection;

[0052] Conduct visual inspection and penetration inspection on the completed welds;

[0053] Visual inspection: Check whether there are defects such as cracks, incomplete penetration, lack of fusion, pores and weld bumps on the weld surface; Penetrant testing: Ensure that there is no display on the weld surface, further verify the weld quality, and ensure the safe and reliable operation of the heat exchanger.

[0054] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and equivalent changes made by using the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for horizontally welding a heat exchange tube and a tube sheet weld, characterized in that: The method comprises the following steps: preparing and cleaning the outer heat exchange tube and the outer heat exchange tube sheet; Assemble the outer heat exchange tube and the outer heat exchange tube sheet, and position and expand the tube, with a weld between the two; Select and install automatic argon arc welding wire that matches the parent material; Install and debug the welding equipment: use a fully automatic argon arc welding machine without a positioning core rod, with the welding gun of the welding machine set vertically downward, weld the weld between the outer heat exchange tube and the outer heat exchange tube sheet in a horizontal position, and set the welding parameters on the welding machine; Install the tungsten electrode and adjust the wire feeding angle: the tip of the tungsten electrode points to the gap between the outer heat exchange tube and the outer heat exchange tube sheet; weld the weld in a horizontal position: during the welding process, the welding machine visually identifies and records the positions of the heat exchange tube and the tube sheet holes, and the welding gun automatically moves to the tube hole position to achieve automatic welding; Quality inspection.

2. The method for horizontally welding the weld between the heat exchange tube and the tube sheet according to claim 1, characterized in that: The heat exchanger is placed in a vertical position, with the outer heat exchange tube plate facing the horizontal direction and the weld facing the welding gun.

3. The method for horizontally welding the weld between the heat exchange tube and the tube sheet according to claim 1, characterized in that: The plate holes of the outer layer heat exchange tube sheet are formed with 0-3mm chamfered grooves.

4. The method for horizontally welding a heat exchange tube and a tube sheet weld according to claim 1, characterized in that: The positioning expansion tube adopts mechanical expansion tube.

5. The method for horizontally welding the weld between the heat exchange tube and the tube sheet according to claim 1, characterized in that: The parameters for adjusting the wire feeding angle are as follows: the welding wire is located 1.5-2 mm below the tip of the tungsten electrode and is offset outward by 0.3-0.5 mm.

6. The method for horizontally welding a heat exchange tube and a tube sheet according to claim 1, characterized in that: The diameter of the automatic argon arc welding wire is φ0.6mm, φ0.8mm or φ1.0mm.

7. The method for horizontally welding a heat exchange tube and a tube sheet weld according to claim 1, characterized in that: The quality inspection includes visual inspection and penetration inspection of the completed welds; Visual inspection: Check the weld surface for cracks, incomplete penetration, lack of fusion, pores and weld bumps; Penetrant testing: Ensures that there is no indication on the weld surface.

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