Welding method for butt joint of carbon steel continuous pipe and dissimilar metal 20CrMo tool cylinder

Abstract

The invention discloses a welding method for butt joint of a carbon steel continuous pipe and a dissimilar metal 20CrMo tool cylinder. The welding method comprises the steps that firstly, the tool cylinder is annealed; 2, the continuous pipe is straightened, cut off and fixed; 3, cleaning the inner surface and the outer surface of the opening edge, and performing groove machining; 4, pipe end assembling and positioning welding are carried out; 5, the cooling block and the heat preservation cotton are clamped; step 6, welding; and step 7, weld joint treatment. According to the method, a plurality of gas lifting tool positions are preset in advance and are welded and fixed according to the condition in a well, a continuous pipe and tool welding integrated product can be provided for an oil field customer, the original continuous pipe gas lifting operation process of an oil field is improved, all continuous pipes can be put into the well at a time, segmented gas lifting at the design position of the continuous pipe is achieved, and the wellhead pressure is reduced; the liquid discharge amount is increased, and the construction cost of gas lift operation is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of welding and relates to a welding method for butting a carbon steel continuous pipe against a dissimilar metal 20CrMo tool cylinder. Background Art

[0002] Coiled Tubing (CT), also known as flexible tubing, serpentine tubing or coiled tubing, is a high-strength, high-plasticity continuous welded steel pipe produced using special micro-alloy materials and unique manufacturing processes. A single tube can be up to tens of thousands of meters long. The finished product is wound on a reel for transportation and delivery. It is mainly used in oil and gas field workover, logging, drilling, completion, oil and gas transportation and other operations.

[0003] There are two existing lifting methods for coiled tubing gas lift operations: one is to inject gas through the annulus between the coiled tubing and the production tubing to lift the production fluid from the coiled tubing to the ground; the other is to inject gas through the coiled tubing to lift the production fluid from the annulus between the coiled tubing and the production tubing to the ground. Both gas lift methods lower the coiled tubing below the static liquid level in the well, which requires continuous multiple trips down the well. Single-stage gas lift has problems such as long operation time, high operation cost, and increased fatigue of the coiled tubing. The multi-stage gas lift process refers to the design and welding of gas lift tools at different positions on a single-disc coiled tubing for gas lift operations. The gas lift tool is fixed by segmented welding, and the "coiled tubing + tool" welding integrated product can be directly used in the well at a later stage, realizing multi-stage gas lift operations in a single trip down the well, solving many problems of the current single-stage gas lift operation, such as long operation time and high wellhead pressure.

[0004] When delivering continuous tubing products to customers, no circumferential welds are allowed in the middle of the entire coil of tubing. This is because during the use of the continuous tubing, the tubing must withstand severe tests in complex environments such as tension, compression, bending, and corrosion, which place very stringent requirements on welds and conventional welding methods are difficult to meet the requirements. Summary of the invention

[0005] The purpose of the present invention is to provide a method for welding a carbon steel coiled tube to a dissimilar metal 20CrMo tool barrel, which solves the problems in the prior art of single-stage gas lift operation, long operation time, high wellhead pressure, particularly great difficulty in processing and manufacturing, and difficulty in meeting the requirements of conventional welding methods.

[0006] The technical solution adopted by the present invention is a method for welding a carbon steel continuous pipe to a dissimilar metal 20CrMo tool cylinder, which is implemented according to the following steps:

[0007] Step 1, annealing the tool barrel;

[0008] Step 2, straightening, cutting and fixing the coiled tube;

[0009] Step 3: Clean the inner and outer surfaces of the butt joint and process the groove;

[0010] Step 4, performing pipe end assembly and positioning welding;

[0011] Step 5, clamping the cooling block and the insulation cotton;

[0012] Step 6, welding;

[0013] Step 7, weld processing.

[0014] The beneficial effect of the present invention is that the method of the present invention can preset multiple gas lift tool positions in advance according to the situation in the well, and weld and fix them, so as to provide oil field customers with an integrated welding product of "coiled tubing + tool", improve the original coiled tubing gas lift operation process of the oil field, and can lower all the coiled tubing into the well at one time, realize segmented gas lift at the designed position of the coiled tubing, reduce the wellhead pressure, increase the discharge volume, and reduce the construction cost of the gas lift operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the preset position of the workpiece during welding according to the method of the present invention;

[0016] Figure 2 It is a welding process flow chart of the method of the present invention;

[0017] Figure 3 This is a radiographic inspection photograph 1 of Example 1 of the present invention;

[0018] Figure 4 This is the second radiographic detection photograph of Example 1 of the present invention;

[0019] Figure 5 This is a radiographic inspection photograph 1 of Example 2 of the present invention;

[0020] Figure 6 This is the second radiographic inspection photograph of Example 2 of the present invention;

[0021] Figure 7 This is a radiographic inspection photograph 1 of Example 3 of the present invention;

[0022] Figure 8 This is the second radiographic inspection photograph of Example 3 of the present invention;

[0023] Fig. 9 This is a radiographic inspection photograph 1 of Example 4 of the present invention;

[0024] Fig.10 This is the second X-ray detection photo of Example 4 of the present invention.

[0025] In the figure, 1. coiled tubing, 2. tool cylinder. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Reference Figure 1 When the welding method of the present invention is implemented, the coiled tube 1 and the tool barrel 2 are connected end to end in sequence. The material of the coiled tube 1 is CT80 grade carbon steel, and the material of the tool barrel 2 is 20CrMo, a dissimilar metal. The weld seam at the joint between the coiled tube 1 and the tool barrel 2 has very strict requirements, and conventional welding methods are difficult to meet the requirements. It is necessary to use the method of the present invention for welding.

[0028] Reference Figure 2 The welding method of the carbon steel coiled tube butting the dissimilar metal 20CrMo tool barrel of the present invention mainly comprises the following steps: annealing the tool barrel 2 - straightening the coiled tube 1 at the predetermined welding position - cutting at the predetermined position - grinding and groove processing of the tube end - positioning welding of the assembly - water cooling of the coiled tube end and insulation of the tool barrel end - welding - grinding of the outer weld - radiographic inspection - delivery to the customer after passing the test, which is specifically implemented in the following steps:

[0029] Step 1, annealing the tool barrel 2;

[0030] Before welding, the tool barrel 2 made of 20CrMo material is annealed to reduce the material strength of the tool barrel 2 so as to match the strength of the continuous tube 1 made of CT80 material.

[0031] Step 2, straightening, cutting and fixing the coiled tube 1;

[0032] First, the straightening equipment is used to complete the straightening operation within 3 meters of the predetermined position of the coiled tubing 1 (oil tubing). After straightening, the straightness B of the coiled tubing 1 within 1.5 meters is required to be less than 2mm; and the coiled tubing 1 is cut by the pipe cutting equipment.

[0033] Step 3: Clean the inner and outer surfaces of the butt joint and process the groove;

[0034] First, use an internal grinder and an angle grinder to clean the oil stains within 15mm of the inner surface of the butt joint of the coiled tube 1 and the tool tube 2 and within 25mm of the outer surface of the butt joint until the ends of the coiled tube 1 and the tool tube 2 are both exposed to metallic luster; the internal grinder uses an 80-100 mesh internal grinder head, and the angle grinder uses a 120-150 mesh angle grinding disc;

[0035] Then, a mechanical beveling machine is used to bevel the butt joint ends of the coiled tube 1 and the tool tube 2, and the bevel angles after processing are both 37°;

[0036] Step 4, performing pipe end assembly and positioning welding;

[0037] Clamp the continuous tube 1 port and the tool tube 2 port to be welded on the welding assembly stand, adjust the relative positions of the two ports to make the pipe mouth assembly straight, and the assembly gap is 2.2-2.5mm. Use a ruler and a level to measure the vertical and horizontal directions of the pipe end to ensure that the continuous tube 1 and the tool tube 2 are assembled without misalignment, and position the welding at the 3, 9 and 12 o'clock positions of the weld respectively.

[0038] Step 5, clamping the cooling block and the insulation cotton;

[0039] At one end of the coiled tube 1 to be welded, clamp a water-cooled copper block 10-15mm away from the welding groove; at one end of the tool tube 2 to be welded, clamp a heat-insulating cotton 10-15mm away from the welding groove;

[0040] Step 6, welding;

[0041] First, manual tungsten inert gas arc welding is used, and the welding position is 5G full-position welding, and three-point positioning welding is performed at the 12 o'clock, 3 o'clock, and 9 o'clock positions of the weld respectively;

[0042] Then adopt a two-layer multi-stage welding method, with a base welding current of 65A and a cover welding current of 80A, and keep the tool cylinder 2 warm for 5 minutes;

[0043] Then, use a wire brush to clean between the layers until the metallic luster is revealed;

[0044] Step 7, weld processing;

[0045] After completing the cover welding, remove the water-cooled copper block, first use an 80-100 mesh elastic grinding wheel for coarse grinding, and then use a 120-150 mesh elastic grinding wheel for fine grinding. Grind the weld until it is flush with the parent material, and the grinding direction is parallel to the axial direction of the pipe body.

[0046] The subsequent step is to perform radiographic inspection on the weld positions of the finished products in accordance with the standard Q / SY BG 1023-2022.

[0047] Example 1

[0048] The material of the coiled tube 1 is CT80 grade carbon steel, and the material of the tool barrel 2 is a dissimilar metal 20CrMo. The following steps are implemented:

[0049] Step 1, annealing the 20CrMo tool barrel;

[0050] Before welding, the 20CrMo tool barrel is annealed to improve various structural defects and residual stress caused during the welding process;

[0051] Step 2, straightening, cutting and fixing the pipe ends;

[0052] First, use the straightening equipment to complete the straightening operation within 3 meters of the predetermined position of the coiled tubing 1 (oil tubing). After straightening, the straightness B of the coiled tubing 1 within 1.5 meters is required to be less than 2mm;

[0053] Then the coiled tube 1 is cut, and the cut coiled tube 1 and the tool tube 2 are placed on the welding assembly stand and fixed securely;

[0054] Step 3, surface cleaning and groove processing;

[0055] First, use an internal grinder and an angle grinder to clean the oil stains within 15mm of the inner surface of the butt joint of the coiled tube 1 and the tool tube 2 and within 25mm of the outer surface of the butt joint until the ends of the coiled tube 1 and the tool tube 2 are both metallic in appearance; the internal grinder uses an 80-mesh internal grinder head, and the angle grinder uses a 120-mesh angle grinder;

[0056] Then, a mechanical beveling machine is used to bevel the butt joint ends of the coiled tube 1 and the tool tube 2, and the bevel angles after processing are both 37°;

[0057] Step 4, pairing the pipe ends;

[0058] Clamp the coiled tube 1 port and tool tube 2 port to be welded on the welding assembly stand, adjust the relative positions of the two ports to make the pipe ends straight, with an assembly gap of 2.2mm, and use a ruler and a level to measure the vertical and horizontal directions of the pipe ends to ensure that the coiled tube 1 and tool tube 2 are assembled without misalignment;

[0059] Step 5, clamping the cooling block and the thermal insulation cotton;

[0060] At one end of the coiled tube 1 to be welded, clamp a water-cooled copper block 10 mm away from the welding groove; at one end of the tool tube 2 to be welded, clamp a heat-insulating cotton 10 mm away from the welding groove;

[0061] Step 6, performing welding;

[0062] First, manual tungsten inert gas arc welding is used, and the welding position is 5G full-position welding, and three-point positioning welding is performed at the 12 o'clock, 3 o'clock, and 9 o'clock positions of the weld respectively;

[0063] Then adopt two-layer multi-stage welding, the base welding current is 65A, the cover welding current is 80A, and the tool cylinder 2 is kept warm after welding for 5 minutes;

[0064] Then use a wire brush to clean between the layers until the metallic luster is revealed;

[0065] Step 7, weld processing;

[0066] After completing the cover welding, remove the water-cooled copper block, first use an 80-mesh elastic grinding wheel for coarse grinding, and then use a 120-mesh elastic grinding wheel for fine grinding. Grind the weld until it is flush with the parent material, with the grinding direction parallel to the axial direction of the pipe body.

[0067] The weld position of the finished product is radiographically inspected according to the standard Q / SY BG 1023-2022.

[0068] The relevant data and test results of Example 1 are shown in Table 1.

[0069] Example 2

[0070] The material of the coiled tube 1 is CT80 grade carbon steel, and the material of the tool barrel 2 is a dissimilar metal 20CrMo. The following steps are implemented:

[0071] Step 1, annealing the 20CrMo tool barrel;

[0072] Before welding, the 20CrMo tool barrel is annealed to improve various structural defects and residual stress caused during the welding process;

[0073] Step 2, straightening, cutting and fixing the pipe ends;

[0074] First, use the straightening equipment to complete the straightening operation within 3 meters of the predetermined position of the coiled tubing 1 (oil tubing). After straightening, the straightness B of the coiled tubing 1 within 1.5 meters is required to be less than 2mm;

[0075] Then the coiled tube 1 is cut, and the cut coiled tube 1 and the tool tube 2 are placed on the welding assembly stand and fixed securely;

[0076] Step 3, surface cleaning and groove processing;

[0077] First, use an internal grinder and an angle grinder to clean the oil stains within 15mm of the inner surface of the butt joint of the coiled tube 1 and the tool tube 2 and within 25mm of the outer surface of the butt joint until the ends of the coiled tube 1 and the tool tube 2 are both exposed to metallic luster; the internal grinder uses a 100-mesh internal grinder head, and the angle grinder uses a 150-mesh angle grinding disc;

[0078] Then, a mechanical beveling machine is used to bevel the butt joint ends of the coiled tube 1 and the tool tube 2, and the bevel angles after processing are both 37°;

[0079] Step 4, pairing the pipe ends;

[0080] Clamp the coiled tube 1 port and tool tube 2 port to be welded on the welding assembly stand, adjust the relative positions of the two ports to make the pipe ends straight, with an assembly gap of 2.5mm, and use a ruler and a level to measure the vertical and horizontal directions of the pipe ends to ensure that the coiled tube 1 and tool tube 2 are aligned without misalignment;

[0081] Step 5, clamping the cooling block and the thermal insulation cotton;

[0082] At one end of the coiled tube 1 to be welded, clamp a water-cooled copper block 15 mm away from the welding groove; at one end of the tool tube 2 to be welded, clamp a heat-insulating cotton 15 mm away from the welding groove;

[0083] Step 6, welding;

[0084] First, manual tungsten inert gas arc welding is used, and the welding position is 5G full-position welding, and three-point positioning welding is performed at the 12 o'clock, 3 o'clock, and 9 o'clock positions of the weld respectively;

[0085] Then adopt two-layer multi-stage welding, the base welding current is 65A, the cover welding current is 80A, and the tool cylinder 2 is kept warm after welding for 5 minutes;

[0086] Then use a wire brush to clean between the layers until the metallic luster is revealed;

[0087] Step 7, weld processing;

[0088] After completing the cover welding, remove the water-cooled copper block, first use a 100-mesh elastic grinding wheel for coarse grinding, and then use a 150-mesh elastic grinding wheel for fine grinding. Grind the weld until it is flush with the parent material, with the grinding direction parallel to the axial direction of the pipe body.

[0089] The weld position of the finished product is radiographically inspected according to the standard Q / SY BG 1023-2022.

[0090] The relevant data and test results of Example 2 are shown in Table 1.

[0091] Example 3

[0092] The material of the coiled tube 1 is CT80 grade carbon steel, and the material of the tool barrel 2 is a dissimilar metal 20CrMo. The following steps are implemented:

[0093] Step 1, annealing the 20CrMo tool barrel;

[0094] Before welding, the 20CrMo tool barrel is annealed to improve various structural defects and residual stress caused during the welding process;

[0095] Step 2, straightening, cutting and fixing the pipe ends;

[0096] First, use the straightening equipment to complete the straightening operation within 3 meters of the predetermined position of the coiled tubing 1 (oil tubing). After straightening, the straightness B of the coiled tubing 1 within 1.5 meters is required to be less than 2mm;

[0097] Then the coiled tube 1 is cut, and the cut coiled tube 1 and the tool tube 2 are placed on the welding assembly stand and fixed securely;

[0098] Step 3, surface cleaning and groove processing;

[0099] First, use an internal grinder and an angle grinder to clean the oil stains within 15mm of the inner surface of the butt joint of the coiled tube 1 and the tool tube 2 and within 25mm of the outer surface of the butt joint until the ends of the coiled tube 1 and the tool tube 2 are both metallic in luster; the internal grinder uses a 90-mesh internal grinder head, and the angle grinder uses a 140-mesh angle grinding disc;

[0100] Then, a mechanical beveling machine is used to bevel the butt joint ends of the coiled tube 1 and the tool tube 2, and the bevel angles after processing are both 37°;

[0101] Step 4, pairing the pipe ends;

[0102] Clamp the coiled tube 1 port and tool tube 2 port to be welded on the welding assembly stand, adjust the relative positions of the two ports to make the pipe ends straight, with an assembly gap of 2.4mm, and use a ruler and a level to measure the vertical and horizontal directions of the pipe ends to ensure that the coiled tube 1 and tool tube 2 are aligned without misalignment;

[0103] Step 5, clamping the cooling block and the thermal insulation cotton;

[0104] At one end of the coiled tube 1 to be welded, clamp a water-cooled copper block 12 mm away from the welding groove; at one end of the tool tube 2 to be welded, clamp a heat-insulating cotton 12 mm away from the welding groove;

[0105] Step 6, welding;

[0106] First, manual tungsten inert gas arc welding is used, and the welding position is 5G full-position welding, and three-point positioning welding is performed at the 12 o'clock, 3 o'clock, and 9 o'clock positions of the weld respectively;

[0107] Then adopt two-layer multi-stage welding, the base welding current is 65A, the cover welding current is 80A, and the tool cylinder 2 is kept warm after welding for 5 minutes;

[0108] Then use a wire brush to clean between the layers until the metallic luster is revealed;

[0109] Step 7, weld processing;

[0110] After completing the cover welding, remove the water-cooled copper block, first use a 90-mesh elastic grinding wheel for coarse grinding, and then use a 130-mesh elastic grinding wheel for fine grinding. Grind the weld until it is flush with the parent material, with the grinding direction parallel to the axial direction of the pipe body.

[0111] The weld position of the finished product is radiographically inspected according to the standard Q / SY BG 1023-2022.

[0112] The relevant data and test results of Example 3 are shown in Table 1.

[0113] Example 4

[0114] The material of the coiled tube 1 is CT80 grade carbon steel, and the material of the tool barrel 2 is a dissimilar metal 20CrMo. The following steps are implemented:

[0115] Step 1, annealing the 20CrMo tool barrel;

[0116] Before welding, the 20CrMo tool barrel is annealed to improve various structural defects and residual stress caused during the welding process;

[0117] Step 2, straightening, cutting and fixing the pipe ends;

[0118] First, use the straightening equipment to complete the straightening operation within 3 meters of the predetermined position of the coiled tubing 1 (oil tubing). After straightening, the straightness B of the coiled tubing 1 within 1.5 meters is required to be less than 2mm;

[0119] Then the coiled tube 1 is cut, and the cut coiled tube 1 and the tool tube 2 are placed on the welding assembly stand and fixed securely;

[0120] Step 3, surface cleaning and groove processing;

[0121] First, use an internal grinder and an angle grinder to clean the oil stains within 15mm of the inner surface of the butt joint of the coiled tube 1 and the tool tube 2 and within 25mm of the outer surface of the butt joint until the ends of the coiled tube 1 and the tool tube 2 are both metallic in appearance; the internal grinder uses an 80-mesh internal grinder head, and the angle grinder uses a 150-mesh angle grinding disc;

[0122] Then, a mechanical beveling machine is used to bevel the butt joint ends of the coiled tube 1 and the tool tube 2, and the bevel angles after processing are both 37°;

[0123] Step 4, pairing the pipe ends;

[0124] Clamp the coiled tube 1 port and tool tube 2 port to be welded on the welding assembly stand, adjust the relative positions of the two ports to make the pipe ends straight, and the assembly gap is 2.3mm; and use a ruler and a level to measure the vertical and horizontal directions of the pipe ends to ensure that the coiled tube 1 and tool tube 2 are aligned without misalignment;

[0125] Step 5, clamp the cooling block and insulation cotton,

[0126] At one end of the coiled tube 1 to be welded, clamp a water-cooled copper block 15 mm away from the welding groove; at one end of the tool tube 2 to be welded, clamp a heat-insulating cotton 10 mm away from the welding groove;

[0127] Step 6, performing welding;

[0128] First, manual tungsten inert gas arc welding is used, and the welding position is 5G full-position welding, and three-point positioning welding is performed at the 12 o'clock, 3 o'clock, and 9 o'clock positions of the weld respectively;

[0129] Then adopt two-layer multi-stage welding, the base welding current is 65A, the cover welding current is 80A, and the tool cylinder 2 is kept warm after welding for 5 minutes;

[0130] Then use a wire brush to clean between the layers until the metallic luster is revealed;

[0131] Step 7, weld processing;

[0132] After completing the cover welding, remove the water-cooled copper block, first use a 100-mesh elastic grinding wheel for coarse grinding, and then use a 120-mesh elastic grinding wheel for fine grinding. Grind the weld until it is flush with the parent material, with the grinding direction parallel to the axial direction of the pipe body.

[0133] The weld position of the finished product is radiographically inspected according to the standard Q / SY BG 1023-2022.

[0134] The relevant data and test results of Example 4 are shown in Table 1.

[0135] Table 1, Comparison of relevant data of four embodiments

[0136]

[0137] See the X-ray inspection photos of Example 1. Figure 3 and Figure 4 , see the X-ray detection photos of Example 2 Figure 5 and Figure 6 , see the X-ray detection photos of Example 3 Figure 7 and Figure 8 , see the X-ray detection photos of Example 4 Fig. 9 and Fig.10 .

[0138] According to the above four embodiments shown in Table 1, in response to the needs of customers, the welding method of the present invention is used to successfully weld the carbon steel coiled tubing 20CrMo tool barrel and complete the downhole operation. The method of connecting the 20CrMo tool barrel on the coiled tubing by welding is the first in the country.

Claims

1. A method for welding a carbon steel coiled tube to a dissimilar metal 20CrMo tool cylinder, characterized in that: Follow these steps to implement: Step 1, annealing the tool barrel; Step 2, straightening, cutting and fixing the coiled tube; Step 3: Clean the inner and outer surfaces of the butt joint and process the groove; Step 4, performing pipe end assembly and positioning welding; Step 5, clamping the cooling block and the insulation cotton; Step 6, welding; Step 7, weld processing.

2. The method for welding carbon steel coiled tube to dissimilar metal 20CrMo tool cylinder according to claim 1 is characterized in that: In step 1, the specific process is: Before welding, the tool barrel made of 20CrMo material is annealed to reduce the material strength of the tool barrel so that it matches the strength of the continuous tube made of CT80 material.

3. The method for welding carbon steel coiled tube to dissimilar metal 20CrMo tool cylinder according to claim 1, characterized in that: In step 2, the specific process is: First, use the straightening equipment to complete the straightening operation within 3 meters of the predetermined position of the coiled pipe end. After straightening, the straightness B of the coiled pipe within 1.5m is required to be less than 2mm; The continuous pipe is cut by pipe cutting equipment.

4. The method for welding carbon steel coiled tube to dissimilar metal 20CrMo tool cylinder according to claim 1, characterized in that: In step 3, the specific process is: First, use an internal grinder and an angle grinder to clean the oil within 15mm of the inner surface of the joint edge of the continuous tube and the tool barrel and within 25mm of the outer surface of the edge until the ends of the continuous tube and the tool barrel are both exposed to metallic luster; the internal grinder uses an 80-100 mesh internal grinder head, and the angle grinder uses a 120-150 mesh angle grinding disc; Then, a mechanical beveling machine was used to bevel the butt joints of the coiled tube and the tool barrel, and the bevel angles after processing were all 37°.

5. The method for welding carbon steel coiled tube to dissimilar metal 20CrMo tool cylinder according to claim 1, characterized in that: In step 4, the specific process is: Clamp the continuous pipe port and tool barrel port to be welded on the welding assembly stand, adjust the relative positions of the two ports to make the pipe mouth assembly straight, and the assembly gap is 2.2-2.5mm. Use a ruler and a level to measure the vertical and horizontal directions of the pipe end to ensure that the continuous pipe and tool barrel are assembled without misalignment, and position the welding at the 3, 9, and 12 o'clock positions of the weld respectively.

6. The method for welding carbon steel coiled tube to dissimilar metal 20CrMo tool cylinder according to claim 1, characterized in that: In step 5, the specific process is: At one end of the continuous pipe to be welded, clamp the water-cooling copper block 10-15mm away from the welding groove; at one end of the tool tube to be welded, clamp the insulation cotton 10-15mm away from the welding groove.

7. The method for welding carbon steel coiled tube to dissimilar metal 20CrMo tool cylinder according to claim 1, characterized in that: In step 6, the specific process is: First, manual tungsten inert gas arc welding is used, and the welding position is 5G full-position welding, and three-point positioning welding is performed at the 12 o'clock, 3 o'clock, and 9 o'clock positions of the weld respectively; Then adopt two-layer multi-stage welding method, the base welding current is 65A, the cover welding current is 80A, and the tool barrel is kept warm for 5 minutes; Then, use a wire brush to clean between the layers until the metallic luster is revealed.

8. The method for welding carbon steel coiled tube to dissimilar metal 20CrMo tool cylinder according to claim 1, characterized in that: In step 7, the specific process is: After completing the cap welding, remove the water-cooled copper block, first use an 80-100 mesh elastic grinding disc for coarse grinding, and then use a 120-150 mesh elastic grinding disc for fine grinding. Grind the weld until it is flush with the parent material, and the grinding direction is parallel to the axial direction of the pipe body.

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