Method for replacing ship rudder horn

Abstract

The invention discloses a method for replacing a ship rudder horn, which comprises the following steps of: measuring rudder blade gap data, measuring old rudder horn data as an original record, so that a new rudder horn is measured and compared again after being installed, and a center line of a guyed rudder system is established; hoisting a new rudder horn in place, adjusting the position of the rudder horn by taking the center line of the steering engine as a reference, assembling the new rudder horn and a ship body structure together, symmetrically welding, and performing ultrasonic flaw detection and magnetic powder flaw detection on a welding seam; boring the new rudder horn by taking the center line of the guyed rudder system as a reference; and a rudderstock lower cloth and a rudder pintle cloth of the rudder horn are machined, and the steering engine, the rudder blade, the rudderstock and the rudder pintle are installed back. According to the replacement method of the ship rudder horn, the parameters of the old rudder horn are collected to serve as the positioning parameters of the new rudder horn, accurate replacement of the rudder horn can be achieved, accurate folding of the replaced new rudder horn and the ship body is facilitated, and the installation accuracy of the rudder horn can be improved by establishing the center line of the guyed rudder system.

Description

Technical Field

[0001] The invention relates to the technical field of ship repair and construction, and in particular to a method for replacing a ship rudder arm. Background Art

[0002] The ship's rudder arm is an important component in the ship's rudder system. It connects the rudder stock and the rudder blade to ensure that the rudder system can work effectively and stably. The rudder arm is a structural component connecting the rudder stock and the rudder blade. It is usually made of high-strength materials (such as cast steel or forged steel) to withstand the torque and stress generated by the rudder system during operation.

[0003] During the ship repair process, cracks appear in the stress concentration area of ​​the ship's rudder arm (usually an integral steel casting), which seriously affects the safety of the ship's navigation. The classification society surveyor usually requires the shipowner to replace the rudder arm, because the classification society usually does not accept the repair of the rudder arm by welding. The replacement of the ship's rudder arm is a relatively complicated process, involving cutting and welding of the hull structure, lifting operations, boring of the rudder bearing, replacement of the bearing sleeve, more processes, high welding quality requirements, long cycle and high price.

[0004] In view of the above, it is necessary to propose a method for replacing a ship rudder arm to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects in the prior art and provide a method for replacing a ship rudder arm.

[0006] To achieve the above object, the technical solution of the present invention is as follows: A method for replacing a ship rudder arm comprises the following steps: S1: Rudder blade clearance data measurement. Before removing the rudder blade, measure and record the clearance between the rudder blade and the upper and lower planes of the old rudder arm, as well as the clearance between the rudder blade and the shape of the old rudder arm; then remove the rudder blade, steering gear, rudder stock, and rudder pintle; S2: Measure the data of the old rudder arm, set up the upper cable rack in the steering gear room, set up the lower cable rack on the dock deck, pull the steel wire between the two cable racks, and establish the center line of the cable rudder system based on the steering gear center line and the lower rudder pintle boss body hole, and position the steel wire properly; measure the rudder stock lower boss body hole, lower rudder pintle boss hole, rudder stock sealing stuffing box body hole, steering gear base friction plate inner hole, and the distance from the front, back, left and right four points to the steel wire, and issue a measurement report as the original record; S3: After the rudder blade is removed and before the old rudder arm is cut off, measure and record the distances from the flange surfaces of the rudder pintle bushing holes and the flange surfaces of the rudder stock bushing holes on the upper and lower parts of the old rudder arm to the plane of the steering gear base, so as to compare them when locating the height position of the new rudder arm; measure all dimensions of the new rudder arm parts, confirm that the outer dimensions are consistent with the old ones and that there is enough machining allowance for the inner holes and planes of the rudder pintle bushing and rudder stock bushing; cut off the old rudder arm; S4: Hoist the new rudder arm into place, take the center line of the steering gear as the reference, pull the steel wire through the rudder stock lower bushing hole and the rudder pintle bushing hole of the rudder arm, and extend it downward to the dock deck; adjust the position of the rudder arm to ensure that the front, back, left, and right distances of the steel wire in the hole are basically uniform, with a difference of less than 2mm, and control the distances from the flange surface of the rudder pintle bushing hole of the rudder arm and the flange surface of the rudder stock bushing hole to the plane of the steering gear base to meet the old size requirements; S5: Assemble the new rudder arm and the hull structure together, weld symmetrically, and perform ultrasonic and magnetic particle testing on the welds after completion; S6: Boring the new rudder arm based on the centerline of the cable rudder system; S7: Process the lower thread of the rudder stock and the thread of the rudder pintle of the rudder arm, and reinstall the servo, rudder blade, rudder stock and rudder pintle.

[0007] Furthermore, the center line of the cable rudder system is directly above the steering gear, and the upper cable rack is installed on the top of the steering gear room. Directly below the steering gear, a support column is welded on the dock deck, the height of which is the same as the bottom baseline of the ship, and the lower cable rack is installed on the top of the column. A steel wire with a diameter of 0.75mm is stretched between the two cable racks, and the hanging weight is greater than 25kg.

[0008] Furthermore, in step S5, welding is performed according to the welding process and symmetrically to reduce the deformation of the centerline axis of the rudder system caused by welding. During the welding process, the change of the distance between the rudder system steel wire and the front and rear left and right points of the rudder arm rudder rod cloth and the rudder pin cloth is detected, and the difference is required to be no more than 3mm, otherwise the electric welding is suspended for half an hour before the electric welding is carried out.

[0009] Furthermore, in the step S6, marks are drawn on the front and rear left and right planes of the lower bushing hole of the rudder stock and the rudder pintle bushing hole of the new rudder hanging arm, and foreign punch holes are punched as boring references, and the lower bushing hole of the rudder stock and the rudder pintle bushing hole of the rudder hanging arm, as well as the flange plane, are bored to the designed size.

[0010] Furthermore, after the rudder blade is installed, the distance from the hull shell is at least 25 mm and the installation gap between the rudder blade and the rudder arm is appropriate.

[0011] Furthermore, in the step S7, the rudder stock lower fabric and the rudder pintle fabric are provided by the ship, and the fabric processing dimensions are designed according to the installation measurement dimensions, the outer circle interference, the inner hole clearance and the water expansion coefficient; after the fabric processing, the fabric is frozen with liquid nitrogen and installed in the rudder stock lower fabric hole and the rudder pintle fabric hole of the rudder arm.

[0012] Furthermore, the welding process includes: 20mm of the welding surface needs to be cleaned to remove moisture, rust and grease; all connecting plates must be welded continuously without intermittent welding; the welding sequence is arranged as follows: first weld the butt joints of the outer plate, then weld the butt joints of the internal components, and finally weld the fillet welds connecting the components and the plates.

[0013] Furthermore, the welding order of butt welds is: first weld the flat butt weld, then weld the horizontal butt weld, and finally weld the vertical butt weld. The welding order of fillet welds is: first weld the vertical fillet weld, then weld the flat fillet weld. The joints with grooves are welded first, and the joints without grooves are welded later. For the welding of fillet welds, an even number of welders are arranged to weld symmetrically from the middle to the left and right, front and back, so that the structural parts can shrink evenly.

[0014] Furthermore, the welding area is preheated to ensure uniform preheating within 100mm around the welded area. The preheating temperature is not less than 120℃, the interlayer temperature is 120-250℃, and the temperature is confirmed and recorded on site using a thermometer; in order to prevent cold cracks, after welding, the electric heating block is covered on the weld area and wrapped with ceramic wool, heated to a temperature range of 200~250℃ for 40 minutes; slowly cooled to room temperature; and flaw detection is performed 24 hours after welding.

[0015] The advantages and beneficial effects of the present invention are as follows: a method for replacing a ship's rudder arm of the present invention can realize accurate replacement of the rudder arm by collecting parameters of an old rudder arm as positioning parameters of a new rudder arm, and is convenient for accurate closing of the replaced new rudder arm with the hull, and establishing the center line of the wire rudder system can improve the installation accuracy of the rudder arm, meet the requirements for the installation accuracy of the rudder arm, and improve the maintenance efficiency of the ship; and the designed welding process effectively overcomes the deformation of the hull caused by welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the longitudinal section of the axis of the ship's rudder arm; Figure 2 It is a schematic diagram of the internal structure of the ship at the rudder arm; Figure 3 It is an axonometric view of the new rudder arm; Figure 4 is a side view of the bracket arm; Figure 5 It is a schematic diagram of the longitudinal section of the rudder arm; Figure 6 It is a schematic diagram of the connection relationship between the rudder pin bushing of the rudder arm and the rudder blade; Figure 7 It is a schematic diagram of the connection relationship between the bushing hole of the rudder stock hanging the rudder arm and the rudder blade; Figure 8 It is a schematic diagram of the joint welding sequence; Fig. 9 It is a schematic diagram of the internal structure welding; Fig.10 It is a schematic diagram of the symmetrical welding sequence; In the figure: 1. rudder blade; 2. rudder arm; 3. hull; 4. steering gear; 5. rudder stock; 6. rudder pintle; 7. flange surface of rudder pintle hole; 8. flange surface of rudder stock hole; 9. steering gear room; 10. upper cable rack; 11. dock deck; 12. lower cable rack; 13. rudder pintle hole; 14. rudder stock hole; 15. steel wire; 16. center line of cable rudder system; 17. body hole of rudder stock sealing stuffing box; 18. inner hole of friction plate of steering gear base; 19. plane of steering gear base; 20. hydraulic nut. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0018] During the ship repair process, cracks appear in the stress concentration area of ​​the ship's rudder arm 2 (generally an integral steel casting), which seriously affects the safety of the ship's navigation. The classification society surveyor usually requires the shipowner to replace the rudder arm 2. Specifically, taking a bulk carrier as an example, the bulk carrier has a total length of 190m, a width of 30m, a depth of 15m, a designed draft of 9.5m, a maximum draft of 10.70m, and a light tonnage of 10092.9t. According to the shipowner's requirements, the rudder arm 2 was replaced because of cracks, and the rudder arm 2 will not be replaced without removing the tail shaft, intermediate shaft and propeller, and the new rudder arm 2 will be aligned using the center line of the old rudder system as a reference. Specifically, the old rudder arm 2 with cracks is replaced by the following rudder arm 2 replacement process.

[0019] The construction method is as follows: 1. Before removing the rudder blade 1, measure and record the clearance between the upper and lower planes of the rudder blade 1 and the old rudder arm 2 (i.e. the clearance between the upper and lower flange surfaces where the rudder blade 1 is connected to the rudder arm 2 and the flange surfaces 7 of the rudder pintle bushing and the flange surfaces 8 of the rudder stock bushing), as well as the clearance between the rudder blade 1 and the outer shape of the old rudder arm 2 (i.e. the distance between the outer wall of the rotation axis of the rudder blade 1 and the rudder arm 2) so as to compare the dimensions after reinstallation. Then remove the rudder blade 1, steering gear 4, rudder stock 5, rudder pintle 6, as shown in the figure below. Figure 1 , 2 shown.

[0020] 2. Install the steering gear 4 back. Install the upper cable rack 10 on the top of the steering gear room 9, just above the steering gear 4. Weld a support column on the dock deck 11, just below the steering gear 4, with the height equal to the base line of the ship bottom. Install the lower cable rack 12 on the top of the column. Pull a steel wire 15 with a diameter of φ0.75mm between the two cable racks to establish the center line 16 of the cable rudder system. The weight is greater than 25kg. Figure 2As shown. With the center line of the steering gear 4 and the lower pintle bushing hole 13 as the reference, the steel wire 15 is properly positioned. Measure the lower pintle bushing hole 13, the rudder stock lower bushing body hole, the rudder stock sealing stuffing box body hole 17, the inner hole 18 of the friction plate of the steering gear base, and the distances from the steel wire 15 at four points in front, back, left and right, and issue a measurement report as the original record so that the new rudder arm 2 can be measured and compared again after installation.

[0021] 3. After the rudder blade 1 is removed and before the old rudder arm 2 is cut off, measure and record the distance between the upper and lower planes of the old rudder arm 2 and the plane 19 of the steering gear base, so as to compare when locating the height position of the new rudder arm 2. Measure all dimensions of the new rudder arm 2 parts, confirm that the outer dimensions are consistent with the old ones and that the rudder pintle bushing hole 13 and the rudder stock bushing hole 14 and the plane have sufficient machining allowances. Cut off the old rudder arm 2.

[0022] 4. Hoist the new rudder arm 2 into place, take the center line of the steering gear 4 as the reference, pull a steel wire 15 with a diameter of 0.75mm, pass through the rudder bar wiring hole 14 and the rudder pintle wiring hole 13 of the rudder arm 2, and extend downward to the lower cable rack 12 on the dock deck 11, with a hanging weight greater than 25kg; adjust the position of the rudder arm 2 with reference to the center line 16 of the cable rudder system, and ensure that the front, back, left and right distances of the steel wire 15 in the rudder bar wiring hole 14 and the rudder pintle wiring hole 13 of the new rudder arm 2 are basically uniform. For specific adjustment parameters, refer to the adjustment of the old rudder arm in step 2. The data measured on the arm 2 are controlled to be within 2mm, so as to facilitate the subsequent boring process, so that the new rudder arm 2 is positioned in the horizontal direction with reference to the axis of the old rudder arm 2, so that the new rudder arm 2 is consistent with the old rudder arm 2 to the greatest extent in the horizontal direction; and in the vertical direction, the distance between the rudder pin bushing flange surface 7 and the rudder bar bushing flange surface 8 of the rudder arm 2 and the steering gear base plane 19 is controlled to meet the old size requirements, and the specific adjustment parameters are adjusted with reference to the parameters measured on the old rudder arm 2 in step 3. In this way, the alignment degree between the rudder arm 2 and the propeller shaft can be kept in compliance with the requirements without dismantling the tail shaft, the intermediate shaft and the propeller;

[0023] 5. Assemble the new rudder arm 2 and the hull 3 structure together. Figure 3-5As shown, the new rudder arm 2 is made of cast steel, with the following dimensions: length L2780*width W1800*height H4216; weight 18700 kg; in step 4, after the new rudder arm 2 is adjusted in the vertical and horizontal directions, the new rudder arm 2 and the hull 3 are first tack welded, and then submitted to the shipowner for ship inspection, and then welded according to the welding process, symmetrical welding, minimize the deformation of the rudder system centerline axis caused by welding, and detect the change of the rudder system steel wire 15 from the rudder arm 2 rudder bar cloth hole 14 and the rudder pin cloth hole 13 before and after the welding process, requiring the difference not to exceed 3mm, otherwise the electric welding is suspended for half an hour before the electric welding. The completed welds are 100% ultrasonically inspected and magnetically inspected, and submitted to the shipowner for ship inspection.

[0024] 6. Taking the center line 16 of the wire rudder system as the reference, mark the front and rear left and right planes of the rudder bar bushing hole 14 and the rudder pintle bushing hole 13 of the new rudder arm 2, and punch the holes as the boring reference. The rudder bar bushing hole 14 and the rudder pintle bushing hole 13 of the rudder arm 2, as well as the flange plane, are bored to the designed size. Because the deformation of the rudder arm 2 after welding is very difficult to control, if the deformation of the rudder arm 2 after welding exceeds the design range, it will be adjusted by processing the holes and planes of the rudder arm 2 and even the base of the steering gear 4 to meet the installation requirements, so as to ensure that the distance between the rudder blade 1 and the shell of the hull 3 is at least 25mm after installation and the installation gap between the rudder blade 1 and the rudder arm 2 is appropriate.

[0025] 7. Process the lower rudder stock fabric and the pintle fabric of the rudder arm 2. The materials are provided by the ship, and the shipyard provides the installation measurement dimensions. The lower rudder stock fabric and the pintle fabric are both composite materials. The dimensions of the lower rudder stock fabric are Φ422*Φ371.5*400; the dimensions of the pintle fabric are: Φ450*Φ406.5*400; The service engineer designs the processing dimensions of the bushing according to the outer circle interference, inner hole clearance and water expansion coefficient. After the bushing is processed, it is frozen with liquid nitrogen and installed in the bushing hole 14 of the rudder arm 2 and the bushing hole 13 of the rudder pintle. The pressing distance of the rudder stock 5 is 5.911-6.958mm. The rudder stock 5 and the rudder pintle 6 are both installed with hydraulic nuts 20. Figure 6 , 7 As shown, the pressing force of the rudder stock 5 is 2700-3800 KN; the pressing distance of the rudder pintle 6 is 0.37-5 mm, and the pressing force of the rudder pintle 6 is 101-3000 KN; the pressing distance of the steering gear 4 is 7.44 mm.

[0026] 8. Install the steering gear 4, rudder blade 1, rudder stock 5 and rudder pintle 6 back into place according to the above requirements.

[0027] 9. Experiment: During the rudder test in the dock, there should be no abnormal noise, and the rudder blade 1 should rotate smoothly. According to the shipowner's requirements, after the construction is completed, the main engine mooring test and navigation test are carried out to check whether the rudder system works normally.

[0028] The welding process includes: the welding surface 20mm needs to be cleaned to remove moisture, rust and grease; all connecting plates must be welded continuously without interruption; the welding sequence is arranged as follows: Figure 8 As shown, first weld the outer plate butt joint ①, then weld the internal component butt joint ②, and finally weld the fillet weld ③ connecting the component and the plate. The number of positioning welds should be minimized, and the positioning weld should have sufficient length, not less than 50mm.

[0029] The schematic diagram of the internal structure welding sequence is as follows Fig. 9 shown.

[0030] Furthermore, the welding sequence of butt welds is: first weld the flat butt weld, then weld the horizontal butt weld, and finally weld the vertical butt weld. The welding sequence of fillet welds is: first weld the vertical fillet weld, then weld the flat fillet weld. The joints with grooves are welded first, and the joints without grooves are welded later. For the welding of fillet welds, an even number of welders are arranged to weld symmetrically from the middle to the left and right, front and back, so that the structural parts shrink evenly, such as Fig.10 shown.

[0031] Furthermore, the welding area can be preheated by ceramic electric heating or flame heating to ensure uniform preheating within 100mm around the welding area. The preheating temperature is not less than 120℃, the interlayer temperature is 120-250℃, and the temperature is confirmed and recorded on site by a thermometer; in order to prevent cold cracks, after welding, the electric heating block is covered on the weld area and wrapped with ceramic cotton, heated to 200~250℃ and maintained for 40 minutes; slowly cooled to room temperature; flaw detection is performed 24 hours after welding; 100% UT and 100% MT are required for the welding area.

[0032] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for replacing a ship's rudder arm, characterized in that: The following steps are involved: S1: Measuring the clearance data of the rudder blade (1). Before removing the rudder blade (1), measure and record the clearance between the rudder blade (1) and the upper and lower planes of the old rudder arm (2), as well as the clearance between the rudder blade (1) and the outer shape of the old rudder arm (2); then remove the rudder blade (1), the steering gear (4), the rudder stock (5), and the rudder pintle (6); S2: Measure the data of the old rudder arm (2), set up the upper cable rack (10) in the steering gear room (9), set up the lower cable rack (12) on the dock deck (11), and pull the steel wire (15) between the two cable racks. Take the center line of the steering gear (4) and the main body hole of the lower rudder pintle as the reference, establish the center line of the cable rudder system (16), and properly position the steel wire (15); measure the main body hole of the lower rudder pintle, the main body hole of the lower rudder pintle (13), the main body hole of the rudder stock sealing stuffing box (17), the inner hole of the friction plate of the steering gear base (18), and the distances of the four points from the steel wire (15) to the front, back, left and right, and issue a measurement report as the original record; S3: After the rudder blade (1) is removed and before the old rudder arm (2) is cut off, measure and record the distances from the upper and lower rudder pintle bushing flange surfaces (7) and the rudder stock bushing flange surfaces (8) of the old rudder arm (2) to the steering gear base plane (19) for comparison when locating the height position of the new rudder arm (2); measure all dimensions of the new rudder arm (2) parts to confirm that the outer dimensions are consistent with the old ones and that the inner holes and planes of the rudder pintle bushing and rudder stock bushing have sufficient machining allowances; cut off the old rudder arm (2); S4: hoist the new rudder arm (2) into place, and with the centerline of the steering gear (4) as the reference, pull the steel wire (15), pass through the rudder stock bushing hole (14) and the rudder pintle bushing hole (13) of the rudder arm (2), and extend it downward to the dock deck (11); adjust the position of the rudder arm (2) to ensure that the front, rear, left and right distances of the steel wire (15) in the hole are basically uniform, with a difference of less than 2 mm, and control the distances from the rudder pintle bushing hole flange surface (7) and the rudder stock bushing hole flange surface (8) of the rudder arm (2) to the steering gear base plane (19) to meet the old size requirements; S5: Assemble the new rudder arm (2) and the hull (3) structure together, weld them symmetrically, and perform ultrasonic and magnetic particle inspection on the welds after completion; S6: Boring the new rudder arm (2) based on the centerline (16) of the cable rudder system; S7: Process the lower thread of the rudder stock and the thread of the rudder pintle that hangs on the rudder arm (2), and reinstall the steering gear (4), rudder blade (1), rudder stock (5), and rudder pintle (6).

2. A method for replacing a ship rudder arm (2) according to claim 1, characterized in that: The center line (16) of the cable rudder system is directly above the steering gear (4), and the upper cable frame (10) is installed on the top of the steering gear room (9). A supporting column is welded on the dock deck (11) directly below the steering gear (4), and the height is the same as the bottom baseline of the ship. The lower cable frame (12) is installed on the top of the column. A steel wire (15) with a diameter of 0.75 mm is stretched between the two cable frames, and the hanging weight is greater than 25 kg.

3. A method for replacing a ship rudder arm (2) according to claim 1, characterized in that: In the step S5, welding is performed according to the welding process and symmetrically to reduce the deformation of the centerline axis of the rudder system caused by welding. During the welding process, the change of the distance between the rudder system steel wire (15) and the front and rear left and right points of the rudder arm (2) rudder bar cloth and the rudder pintle cloth is detected. The difference is required to be no more than 3 mm. Otherwise, the electric welding is suspended for half an hour before the electric welding is carried out again.

4. A method for replacing a ship rudder arm (2) according to claim 1, characterized in that: In the step S6, marks are drawn on the front and rear left and right planes of the end faces of the rudder stock bushing hole (14) and the rudder pintle bushing hole (13) of the new rudder hanging arm (2), and foreign punch holes are punched as a boring reference, and the rudder stock bushing hole (14) and the rudder pintle bushing hole (13) of the rudder hanging arm (2), as well as the flange plane, are bored to the designed size.

5. A method for replacing a ship rudder arm (2) according to claim 4, characterized in that: After the rudder blade (1) is installed, the distance between it and the outer shell of the hull (3) is at least 25 mm, and the installation clearance between it and the rudder arm (2) is appropriate.

6. A method for replacing a ship rudder arm (2) according to claim 1, characterized in that: In the step S7, the rudder stock lower fabric and the rudder pintle fabric are made of materials supplied by the ship, and the fabric processing dimensions are designed according to the installation measurement dimensions, the outer circle interference, the inner hole clearance and the water expansion coefficient; after the fabric processing, the fabric is frozen with liquid nitrogen and installed in the rudder stock fabric hole (14) and the rudder pintle fabric hole (13) of the rudder hanging arm (2).

7. A method for replacing a ship rudder arm (2) according to claim 3, characterized in that: The welding process includes: 20mm of the welding surface needs to be cleaned to remove moisture, rust and grease; all connecting plates must be welded continuously without discontinuous welding; the welding sequence is arranged as follows: first weld the butt joints of the outer plate, then weld the butt joints of the internal components, and finally weld the fillet welds connecting the components and the plates.

8. A method for replacing a ship rudder arm (2) according to claim 7, characterized in that: The welding sequence of butt welds is: first weld the flat butt weld, then weld the horizontal butt weld, and finally weld the vertical butt weld. The welding sequence of fillet welds is: first weld the vertical fillet weld, then weld the flat fillet weld. The joints with grooves are welded first, and the joints without grooves are welded later. For the welding of fillet welds, arrange an even number of welders to weld symmetrically from the middle to the left and right, front and back, so that the structural parts can shrink evenly.

9. A method for replacing a ship rudder arm (2) according to claim 8, characterized in that: Preheat the welding area to ensure uniform preheating within 100mm around the welded area. The preheating temperature is not less than 120℃, the interlayer temperature is 120-250℃, and the temperature is confirmed and recorded on site using a thermometer; in order to prevent cold cracks, after welding, the electric heating block is covered on the weld area and wrapped with ceramic wool, heated to a temperature range of 200~250℃ for 40 minutes; slowly cooled to room temperature; and flaw detection is performed 24 hours after welding.

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