Welding process for butt joint of surfacing pipes through argon arc welding

Abstract

According to the welding method, the mode that the surfacing layer covers the width of the whole pipe before butt welding of the pipe is adopted, so that the problem that in the prior art, a gap is reserved for two sections of the pipe, and manual surfacing is carried out after butt welding is solved; primary protection is generated for the pipe base material through formation of the base layer welding seam consistent with the pipe base material, the filling layer welding seam is welded through the welding wire matched with the pipe base material after the base layer welding seam is welded, the filling layer welding seam is used for preventing the nickel-based alloy layer which is subjected to surfacing finally from entering the base layer welding seam, and secondary protection is generated for the pipe base material.

Description

Technical Field

[0001] The invention relates to the field of serpentine pipe welding, and in particular to a welding process for argon arc welding butt joint of cladding pipes. Background Art

[0002] The serpentine tube is a structure often used in the convection heating surface devices of boilers such as economizers, superheaters and reheaters. The commonly used serpentine tube structure has a total length of more than 30 meters and needs to be welded from multiple tubes. In order to improve the overall efficiency and quality, the tubes are usually welded by argon arc welding and automatically transported to the bending equipment for serpentine tube bending. Figure 1 It is a schematic diagram of the structure of the serpentine tube and the location diagram of the butt weld.

[0003] Since economizers, superheaters and reheaters are running in boilers, ordinary carbon steel or alloy steel pipes are corroded by high-temperature corrosive gases, and the pipe walls are easily thinned, resulting in leakage. Therefore, it is common practice to weld corrosion-resistant nickel-based alloys on the outer wall of the pipes.

[0004] When cladding pipes are butt welded, the corresponding carbon steel or alloy steel welding consumables are used for the parent materials of carbon steel or alloy steel pipes. During welding, if the nickel-based alloy of the cladding layer is integrated into the carbon steel or alloy steel weld, it will cause welding cracks and affect the welding quality. Therefore, the current mainstream solution is to leave about 30-50mm of the parent material to be butted at both ends when cladding pipes are clad. After the automatic butt welding and pipe bending are completed, the remaining parent material is covered with nickel-based alloy by manual cladding method, and attached Figure 2 It is a schematic diagram of butt welding two pipes after surfacing welding in the prior art, Figure 3 The invention is a specific process flow for butt welding two pipes in the prior art.

[0005] It can be seen from the prior art that although the pipe cladding of the prior art occurs before the butt welding of the two pipes, in order to prevent the nickel-based alloy of the cladding layer from being integrated into the carbon steel and alloy steel welds, the automatic cladding cannot cover the entire pipe, and the butt surface needs to be left unwelded, and the reserved gap is manually clad after the butt welding is completed. This firstly causes the complexity of the process, that is, it is necessary to complete the process of cladding-butt welding-cladding. Secondly, because the reserved pipe gap is too narrow, manual cladding can only be performed after the butt welding is completed. The efficiency of manual cladding is very low, and manual cladding is very unstable, which will cause the nickel-based alloy of the cladding layer to be uneven. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a process for automatic butt welding of nickel-based alloy cladding pipes, which can ensure the welding quality and beautiful appearance of the automatic butt welding without leaving a bare cladding pipe at the end of the cladding pipe.

[0007] A process for automatically butting a nickel-based alloy cladding pipe, comprising the following steps:

[0008] 1. Prepare the pipes according to the drawing.

[0009] 2. Overlay welding on the pipe; the overlay welding layer covers the entire width of the pipe.

[0010] 3. Process the groove of the cladding pipe according to the drawing. The end of the pipe should be flat and processed with a groove angle of 35° and a blunt edge of 0-0.5mm.

[0011] 4. Use automatic argon arc welding system for welding. During welding, the welding gun is located at the top of the pipe within the range of ±5°.

[0012] 4.1. Assemble the pipes through the automatic argon arc welding system to ensure zero gap.

[0013] 4.2. Use the method of self-melting the base material without adding wire to weld the base weld. The welding gun should not swing during the welding process. The base weld should be 5-15mm longer than the inner diameter of the pipe to ensure that the arc closing and arc starting points are staggered.

[0014] 4.3. Use welding wire that matches the base material of the pipe to weld the filler layer weld. The welding gun should not swing during the welding process. The number of welding layers should be set according to the thickness of the base material. Through preliminary process testing, it is ensured that the base layer weld is 0.5-1mm lower than the surface of the base material to ensure that the nickel-based alloy metal of the cladding layer will not invade the base layer weld. The filler layer weld should be 5-15mm longer than the inner diameter circumference of the pipe to ensure that the arc closing and arc starting points are staggered.

[0015] 4.4. Use cladding nickel-based alloy metal welding wire for cladding filling and capping layer welding. During welding, the welding gun swings and the welding wire needs to be heated to above 300°C by resistance heating. Depending on the thickness requirements of the cladding layer, the cladding filling layer welds are welded for more than one layer. When welding the cladding filling layer and cladding capping layer welds, the arc is continuously welded between each layer. The capping layer weld should be 10-15mm longer than the first layer of the filling layer weld to ensure that the arc closing and arc starting points are staggered.

[0016] 5. Perform RT nondestructive testing on the pipe.

[0017] 6. Pipe bending processing.

[0018] 7. Carry out subsequent processes.

[0019] The above-mentioned cladding process adopts a method in which the cladding layer covers the entire width of the pipe before the butt welding of the pipe, thereby preventing the problem of manual cladding after butt welding with a gap left between the two sections of the pipe in the prior art, and adopts a method of welding the base material without adding wire to the base material by self-melting, thereby generating primary protection for the base material of the pipe, and by welding the filling layer weld with a welding wire matching the base material of the pipe after welding the base material weld, the last cladding nickel-based alloy layer is prevented from entering the base material weld through the filling layer weld, thereby generating secondary protection for the base material of the pipe, and even if the nickel-based alloy layer can enter the filling layer weld during cladding, it will not enter the base material weld, and even if the problem of the welding process causes the nickel-based alloy layer to enter the base material weld during cladding, it will not enter the base material; the secondary protection mechanism effectively protects the base material of the pipe, and the welding gun swings when cladding the nickel-based alloy layer to prevent the nickel-based alloy weld layer from accumulating and entering the filling layer weld. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attached Figure 1 Schematic diagram of the structure of the serpentine tube.

[0021] Attached Figure 2 The diagram is a schematic diagram of butt welding two pipes after surfacing welding in the prior art.

[0022] Attached Figure 3 The present invention is a specific process flow chart of butt welding two pipes in the prior art.

[0023] Attached Figure 4 The specific process flow chart of butt welding two pipes of the present invention is shown in FIG.

[0024] Attached Figure 5 It is a schematic diagram of butt welding two pipes after surfacing welding according to the present invention.

[0025] Attached Figure 6 Schematic diagram of welding the butt ends of two cladding pipes.

[0026] Specific implementation cases:

[0027] 1. Receive pipes: receive 16Mo3 pipes with specifications of Φ60.3*6.3 and polish and sandblast them.

[0028] 2. Pipe cladding: Use nickel-based welding wire ERN i CrMo-3 to clad the pipe surface with a thickness of 2 mm.

[0029] 3. Beveling processing: First, the butt joint of the cladding pipe is flattened on the beveling machine so that the butt joint is perpendicular to the central axis of the cladding pipe. Then, the butt joint of the cladding pipe is beveled so that the bevel angle of each butt joint of the cladding pipe is 35°, and the welding bevel angle of the two butt joints of the cladding pipe is 70°.

[0030] Welding process: firstly butt the two butt joints of the butt joint to make the butt joint gap zero, and then use self-melting welding to weld the first circle of the butt joint. The welding degree of the first layer of welding is 375°. The welding gun does not swing during the welding process. When the welding gun of the first layer of welding reaches the arc-ending point, the welding gun is moved away from the arc-ending point. When the temperature of the weld is cooled to no more than 50℃, the second layer of welding is started. 1.2mm welding wire is used for filling. The first layer of welding is at a welding angle of 375°. The welding gun does not swing during the welding process. When the welding gun of the first layer of the circle reaches the arc-ending point, the welding gun is moved away from the arc-ending point. When the temperature of the weld is cooled to no more than 50°C, replace the nickel-based cladding wire. 1.2mm welding wire, start welding the third and fourth layers, welding process: a. The welding gun swings along the groove width and stays for 0.2s when it reaches the edge of the groove; b. Turn on the hot wire function and adjust the hot wire current to 5A; c. The third and fourth layers of welding are not interrupted and welding is continuous. During the welding process of the welding gun, the temperature distribution of the weld and its surrounding area is calculated using the following formula:

[0031]

[0032] Wherein, W(x,y,z,t) represents the temperature distribution of the weld and its vicinity, x represents the x-axis coordinate of the temperature distribution corresponding point coordinate (x,y,z), y represents the y-axis coordinate of the temperature distribution corresponding point coordinate (x,y,z), z represents the z-axis coordinate of the temperature distribution corresponding point coordinate (x,y,z), t represents time, R represents welding heat input, π represents pi, ρ represents the thermal diffusivity of the cladding pipe, x0 represents the x-axis coordinate of the welding gun position coordinate (x0,y0,z0), y0 represents the y-axis coordinate of the welding gun position coordinate (x0,y0,z0), z0 represents the z-axis coordinate of the welding gun position coordinate (x0,y0,z0), u represents a time variable that changes with time, and du represents the differential of the time variable u. According to the temperature distribution, the welding stress of the cladding pipe is calculated using the following formula:

[0033]

[0034] Among them, F(x,y,z) represents the welding stress of the weld and its vicinity, W(x,y,z) represents the temperature distribution of the weld and its vicinity, x represents the x-axis coordinate of the temperature distribution corresponding point coordinate (x,y,z), y represents the y-axis coordinate of the temperature distribution corresponding point coordinate (x,y,z), z represents the z-axis coordinate of the temperature distribution corresponding point coordinate (x,y,z), M represents the elastic modulus of the cladding pipe, α represents the thermal expansion coefficient, and β represents the Poisson's ratio. According to the welding stress, the welding control in the welding process is optimized to ensure the welding quality.

[0035] Perform RT nondestructive testing on the butt weld of the cladding pipe to obtain quality characteristics, calculate characteristic parameters of the quality characteristics, and calculate the weld quality of the cladding pipe using the following formula based on the characteristic parameters:

[0036]

[0037] Where D represents the weld quality, i represents the i-th quality feature, n represents the total number of quality features, Q i represents the weight of the i-th quality feature, E i represents the characteristic parameter of the i-th quality feature, and b represents the error.

[0038] The pipe is automatically transported to the automatic pipe bending machine through the motion mechanism and bent according to the drawings and procedures.

[0039] Carry out subsequent processing work.

[0040] Furthermore, when the first circle welding is performed on the butt joint by self-fusion welding, since the welding gun is stationary, the speed of parallel rotation of the cladding pipe 1 around the pipe is set to V1, and the speed of parallel rotation of the cladding pipe 2 around the pipe is set to V2, and V2>V1.

[0041] Furthermore, assuming that the inner diameter of the cladding pipe is Φ1 and the outer diameter of the cladding pipe is Φ2, then T1 = πΦ1 / V1, T2 = πΦ1 / V2, and T1 and T2 satisfy (T1-T2) / T2>0.2.

[0042] Furthermore, when starting the third and fourth layer welding, the width of the groove is set to L, and the width of the groove is set to three parts, the middle third of the groove is L1, the right edge of the groove to the right edge of the middle groove L1 is L2, and the left edge of the groove to the left edge of the middle groove L1 is L3.

[0043] Furthermore, the welding gun swings along the groove width, the swinging speed in L1 is V1, the swinging speed in L2 is V2, the swinging speed in L3 is V3, and V1>V2=V3.

[0044] Furthermore, L1 / V1=t1, L2 / V2=t2, (t2-t1) / t1>δ+0.2.

[0045] The parameters in step 4 are shown in the following table:

[0046] Table 1

[0047]

[0048] Compared with the prior art, the above-mentioned process of welding the butt joint ends of two cladding pipes is performed with groove processing on the ends of the two butt joint pipes, which is different from the direct alignment welding method of the two pipes in the prior art, so that the welding groove angle of the butt joint ends of the two cladding pipes is 70°, which is convenient for welding multiple layers of welds in the groove. By welding multiple layers of welds in the groove, that is, the first layer of welds and the base layer weld of the cladding pipe adopt the same self-melting welding of the pipe base material, that is, a self-melting base layer weld is formed in the groove of the butt joint of the two pipes, and the second layer of welding adopts 1.2mm welding wire is cooled to 50℃ after welding at 375°, forming the filler layer weld at the groove, and then the nickel-based cladding wire is welded 1.2mm welding layer, this method of opening a groove on the butt pipe and welding the base layer weld and the filling layer weld in the groove before welding the nickel-based cladding layer prevents the nickel-based cladding layer from entering the weld of the two pipes butting each other, and the method of welding the two pipes with grooves and the cladding layer covering the entire width of the pipe before butt welding is combined so that the base layer weld and the filling layer weld can cover the entire serpentine pipe. After welding according to this cladding process, the chemical composition performance of the nickel-based alloy weld can meet the requirements of corrosion-resistant cladding, effectively solving the problems in the prior art.

Claims

1. A welding process for argon arc welding of cladding pipes, comprising the following steps: 1: Prepare the pipe according to the drawing; 2: Perform cladding welding on the pipe; the cladding layer covers the entire width of the pipe; 3: Process the groove of the cladding pipe according to the drawing. The end of the pipe should be flat and processed with a groove angle of 35° and a blunt edge of 0-0.5mm; 4: Use automatic argon arc welding system for welding, and the welding gun is located at the top of the pipe within ±5°; 4.1: Assemble the pipes through the automatic argon arc welding system; 4.2: Use the method of self-melting the base material without adding wire to weld the base weld; 4.3: Use welding wire that matches the pipe base material to weld the filler layer weld; 4.4: Use cladding nickel-based alloy metal welding wire for cladding filler cap layer welding, welded on the filler layer weld.

2. The welding process for argon arc welding butt welding of cladding pipe according to claim 1 is characterized in that: In step 4.2, the welding torch does not swing during the welding process. The base weld should be 5-15mm longer than the inner diameter of the pipe to ensure that the arc end and arc start points are staggered.

3. The welding process of argon arc welding butt welding of cladding pipe according to claim 1 is characterized in that: In step 4.3, the welding gun does not swing during the welding process; the number of welding layers is set according to the thickness of the base material.

4. The welding process for argon arc welding butt welding of cladding pipe according to claim 1 is characterized in that: In step 4.3, the base layer weld is 0.5-1 mm below the surface of the parent material, and the filler layer weld is 5-15 mm longer than the inner diameter circumference of the pipe.

5. The welding process for argon arc welding butt welding of cladding pipe according to claim 1 is characterized in that: In step 4.4, during welding, the welding gun swings and the welding wire needs to be heated to above 300°C by resistance heating.

6. The welding process for argon arc welding butt welding of cladding pipe according to claim 1 is characterized in that: In step 4.4, according to the different requirements of the thickness of the cladding layer, the cladding filling layer weld is welded for more than one layer, and the cladding filling layer and the cladding cover layer weld are welded continuously without stopping the arc between each layer.

7. The welding process for argon arc welding butt welding of cladding pipe according to claim 1 is characterized in that: In step 4.4, the cap layer weld is 10-15 mm longer than the filler layer weld.

8. The welding process for argon arc welding butt welding of cladding pipe according to claim 1 is characterized in that: In step 2, the groove angle of each butt joint port of the cladding pipe is 35°, and the welding groove angle of the butt joint ports of the two cladding pipes is 70°.

9. The welding process for argon arc welding butt welding of cladding pipe according to claim 1, characterized in that: Perform RT nondestructive testing on the butt welds of cladding pipes to ensure weld quality.

10. The welding process for argon arc welding butt welding of cladding pipe according to claim 1, characterized in that: The pipe is automatically transported to the automatic pipe bending machine through the motion mechanism and bent according to the drawings and procedures.

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