Heat exchanger tube plate and barrel welding seam welding process

Abstract

The invention discloses a heat exchanger tube plate and barrel welding seam welding process. The process comprises the following steps of A, preparation before welding; b, the aluminum gasket is machined; c, assembling an aluminum gasket; d, a plurality of rigid fixing blocks are welded to the outer edges of the two tube plates; e, the two tube plates are arranged between the two barrels and assembled in pairs; f, the two tube plates and the two barrels are subjected to manual arc welding and tack welding; g, preheating before welding; h, manual argon tungsten-arc welding backing weld bead welding; i, manual arc welding filling cosmetic welding bead welding is conducted; J, after welding seams are cooled, all rigid fixing blocks are polished and removed, and welding scars are polished to be flush with base metal; k, polishing and removing all defects on two sides of the weld to ensure that the weld surface must be in smooth transition with the outer surfaces of the tube plate and the cylinder; and L, nondestructive testing. By means of the welding process, the welding quality is stable and reliable during large-diameter heat exchanger tube plate welding, and component welding deformation can be controlled within the design requirement range.

Description

Technical Field

[0001] The invention relates to the technical field of welding, and in particular to a welding process for a heat exchanger tube sheet and a cylinder weld. Background Art

[0002] In the process of modular production of chemical production lines, the multiple equipment contained in the chemical production line will be divided in the factory to form multiple modules. Each module is produced, welded and assembled in the factory, and then transported to the production workshop for assembly and splicing between modules. The assembly and welding between the tube sheet and the cylinder of the heat exchanger is often encountered in modular production.

[0003] At present, the welding technology for the weld between the tube sheet and the cylinder of the heat exchanger is very difficult, and the component quality requirements are high. In particular, the welding technology for the large-diameter heat exchanger tube sheet weld is more difficult. The single weld design is asymmetric, the weld cladding metal filling volume is large, the welding product deformation requirements are high, the welding is continuous, and the working cycle is long. These characteristics make it impossible for conventional welding methods and processes to complete normal welding work, and welding deformation is prone to occur. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a heat exchanger tube sheet and cylinder weld welding process, which can handle large diameter heat exchanger tube sheet weld welding with stable and reliable weld quality, and the component welding deformation can be controlled within the design requirements.

[0005] In order to solve the above technical problems, the technical solution of the present invention is: a heat exchanger tube sheet and cylinder weld welding process, comprising the following steps:

[0006] A. Preparation before welding, including the following steps:

[0007] a1) Determine the execution standards of welding projects;

[0008] a2) Check whether the specifications, grades, welding materials and gas of tube sheets and aluminum gaskets meet the standards;

[0009] a3) Selection tools;

[0010] a4) Acceptance inspection of tools;

[0011] a5) Process the bosses on the two tube sheets to be welded according to the design parameters, and the height of the bosses is 3.0-3.5mm;

[0012] a6) Processing grooves on the two cylinder end faces to be welded, the grooves are single V-shaped grooves, the angle between the groove surface and the vertical direction is 45±2.5°, and the blunt edge is 0-1mm;

[0013] a7) Remove all debris within 20mm of the inner and outer surfaces of the groove to reveal the metallic luster;

[0014] a8) Check that the welder is equipped with the corresponding welding qualification certificate;

[0015] B. For the processing of aluminum gasket, aluminum material with material grade 5083 is selected for processing. The diameter and thickness of the aluminum gasket are the same as the diameter and thickness of the cylinder. The width of the aluminum gasket is 25-30mm; the roughness of the contact surface of the aluminum gasket is Rz6.3;

[0016] C. Assemble aluminum gasket

[0017] The aluminum gasket is installed between two tube sheets, and the aluminum gasket is clamped between the two tube sheets by bolts evenly distributed around the circumference;

[0018] D. Weld multiple rigid fixing blocks on the outer edges of the two tube sheets. The rigid fixing blocks are evenly distributed around the circumference, and each rigid fixing block is located between adjacent bolts. The fillet welds between the outer edges of the two tube sheets and the rigid fixing blocks are welded first, and the center symmetry method and manual arc welding are used;

[0019] E. Place two tube sheets between two cylinders and assemble them;

[0020] F. Spot weld the two tube sheets and the two cylinders by hand arc welding and assemble them with spot welding blocks, including the following steps:

[0021] f1) Divide the entire circumference of the circumferential weld between the tube sheet and the cylinder into twelve equal parts, and select eight point fixing blocks to be arranged at ①, ②, ④, ⑤, ⑦, ⑧, ⑩, Point location;

[0022] f2) Place the spot fixing block on the groove surface, spot fix the fillet weld in a single pass, the length of the single-sided single pass of the spot fix fillet weld is greater than 15mm, and the thickness is greater than 3mm;

[0023] f3) Check the quality of spot welding;

[0024] G. Preheating before welding: when the room temperature is greater than ≥15℃, preheating is not required; when the room temperature is -20℃ to 15℃, preheating to ≥15℃ is required;

[0025] H. Manual tungsten inert gas arc welding for base weld

[0026] When the cylinder and the tube sheet are fixed horizontally, the horizontal position 5G welding is adopted, and the welding is performed symmetrically in sections; when the cylinder and the tube sheet are installed horizontally, the horizontal rotation position 1G welding is adopted, and the left welding method and pressure pass welding are adopted; the two welds of the two tube sheets are symmetrical and welded at the same time, and the welding process, welding sequence, welding direction and welding parameters are the same; the root is welded through, and the base weld is welded in two layers, one pass per layer, the interpass temperature is ≤250℃, and the joints between layers are staggered;

[0027] I. Manual arc welding for filling and capping welds: When welding in the horizontal fixed position 5G, adopt segmented symmetrical welding; when welding in the horizontal rotating position 1G, adopt the left welding method and pressure welding; the two welds of the two tube sheets are symmetrical and welded at the same time, and the welding process, welding sequence, welding direction and welding parameters are the same;

[0028] Among them, the order and direction of the 5G manual arc welding filling and capping welds in the horizontal fixed position are the same as those of the base welds. The first layer of the manual arc welding filling and capping welds is one pass, and the second and subsequent layers are multi-pass welds;

[0029] The welding sequence of the 1G manual arc welding filling and capping weld in the horizontal rotation position is the same as that of the base weld. The first layer of the manual arc welding filling and capping weld is one pass, and the second and subsequent layers are multi-pass welds;

[0030] Linear welding and pressure welding are used; the swing width of the welding torch shall not exceed 3 times the diameter of the welding rod; the interlayer temperature shall be less than 250℃; the interlayer joints shall be staggered by more than 20mm; the welding rod shall be a basic welding rod with a diameter of 3.2mm or 4.0mm. When a welding rod with a diameter of 3.2mm is used, the thickness of each weld bead shall be 3-5mm; when a welding rod with a diameter of 4.0mm is used, the thickness of each weld bead shall be 5-7mm; the weld surface excess height shall be less than 2.5mm; single layer single pass During welding, the arc first melts the base metal on the cylinder groove surface, and then changes the electrode angle to melt the base metal on the tube sheet side; when welding single-layer with two passes, the first weld pass is arranged on the base metal side of the cylinder groove surface, and the second weld pass is arranged between the weld cladding metal and the tube sheet base metal; when welding single-layer with multiple passes, the first weld pass is arranged on the base metal side of the cylinder groove surface, and the second weld pass is next to the first weld pass, and the last weld pass is arranged between the weld cladding metal and the tube sheet base metal;

[0031] J. After the weld has cooled, grind and remove all rigid fixing blocks, and grind the weld scar until it is flush with the parent material;

[0032] K. Grind and remove all defects on both sides of the weld to ensure that the weld surface has a smooth transition with the tube sheet and the outer surface of the cylinder;

[0033] L. Nondestructive testing.

[0034] Preferably, the specific welding method of step H, manual tungsten inert gas arc welding for the base weld is:

[0035] h1) Manual tungsten inert gas arc horizontal fixed position 5G weld root pass welding:

[0036] h11) Manual tungsten inert gas arc horizontal fixed position 5G weld base weld first layer welding, determine the segmented symmetrical welding sequence and arc starting position: the first group of welding sequence; according to the clock position ⑥→⑤, ③→②, ⑧→⑨; ⑥→⑦, ④→③, ⑨→⑩ in sequence; ⑥→⑤, is a set of symmetrical welding sections, ③→②, ⑧→⑨ is a set of symmetrical welding sections, ⑥→⑦, It is a group of symmetrical welding sections, ④→③, ⑨→⑩ are a group of symmetrical welding sections; the welding direction is the forward direction; when welding ⑥→⑤, ③→②, ⑨→⑩, the arc is started from 10mm in front of points ⑥, ③, and ⑨ respectively, and then it turns back to 10-20mm behind points ⑥, ③, and ⑨ to start welding, and the arc is closed 10mm in front of the point solid block at points ⑤, ②, and ⑩; when welding ⑥→⑦, the arc is started from 10mm in front of the gentle slope of the front section weld joint near point ⑥, and then it turns back to the gentle slope of the front section weld joint to start welding, and the arc is closed 10mm in front of the point solid block at point ⑦; welding ④→③, ⑧→⑨ The arcs are started 20mm in front of the point blocks at points ④, ①, and ⑧, and then folded back to Weld from 10mm in front of the spot fixing block at points ④, ①, and ⑧ until ③、 ⑨Re-weld the arc at the gentle slope joint near the position and the end of the previous weld;

[0037] h12) The second welding sequence: ⑦→⑧, ②→①; ⑤→④, Sequential welding; among which ⑤→④, It is a symmetrical welding section, ⑦→⑧, ②→① are a symmetrical welding section; when welding each welding section, first grind off the spot blocks at both ends of the welding section, then grind off the weld scars, grind until it is flush with the surface of the parent material, then start the arc from the starting clock position of the welding section, then turn back to the gentle slope welding joint at the end of the previous section of the weld, then move forward to the gentle slope joint of the previous welding section and the end of the weld, then re-weld and close the arc;

[0038] h13) Manual tungsten inert gas arc welding horizontal fixed position 5G weld base weld second layer welding, welding sequence and direction are the same as steps h11) and h12); determine the segmented symmetrical welding sequence and arc starting position: the first group of welding sequence is according to the clock position ⑥→⑤→④→③, Welding in the following order: ⑥→⑤→④→③, It is a set of symmetrical welding sections; the welding direction is the forward direction; welding ⑥→⑤→④→③, The arc is started from 20mm before points ⑥ and ⑨, and then the arc is turned back to 10mm before points ⑥ and ⑨ to weld. The arc is welded to points ③ and ⑨. Re-weld near the point to close the arc; grind the two ends of the weld metal into a gentle slope;

[0039] h14) The second welding sequence: according to ⑥→⑦→⑧→⑨, Sequential welding: ⑥→⑦→⑧→⑨, It is a symmetrical welding section; the welding direction is the forward direction; welding ⑥→⑦→⑧→⑨, The arc is started from 10mm in front of the gentle slope of the weld end near points ⑥ and ③, and then the arc is turned back to the gentle slope of points ⑥ and ③ to start welding, and the arc is welded to points 9 and Near the point position, re-weld and close the arc after the gentle slope joint at the end of the weld; Grind and clean the excessive height to strengthen the height;

[0040] h2) Manual tungsten inert gas arc welding in horizontal rotation position 1G weld root pass welding

[0041] h21) For the first layer of the manual tungsten inert gas argon arc horizontal rotation position 1G weld, the left welding method is used to determine the segmented symmetrical welding sequence and arc starting position: the first group of welding sequence; according to the clock position ④→③→②, ⑩→⑨→⑧; ⑦→⑥→⑤, The sequence of welding is as follows; ④→③→②, ⑩→⑨→⑧ are a set of symmetrical welding sections, ⑦→⑥→⑤, It is a set of symmetrical welding sections; the welding direction is the forward direction; when welding ④→③→②, ⑩→⑨→⑧, the arc is started from 20mm in front of points ④ and ⑩ respectively, and then it turns back to 10mm in front of the point fixing block at points ④ and ⑩ respectively to start welding, and the arc is closed 10mm in front of the point fixing block at points ② and ⑧; when welding ⑦→⑥→⑤, When welding, start the arc from 20mm before point ⑦ and ① respectively, then turn back to 10mm before point ⑦ and ① respectively, until ⑤, The arc is closed 10mm before the point fixing block at the point position;

[0042] h22) The second welding sequence: ②→①, ⑧→⑦; ⑤→④, Sequential welding; ②→①, ⑧→⑦ are a symmetrical welding section, ⑤→④, It is a symmetrical welding section. When welding each welding section, first grind away the point blocks at both ends of the welding section, then grind away the weld scars, grind until it is flush with the surface of the parent material, and then grind from point ②, point ⑧, point ⑤, The arc starts at the point position, and the arc bends back to the gentle slope welding joint at the end of the previous weld, and then welds to the vicinity of point ①, point ⑦, point ④, and point ⑩, and then re-welds and closes the arc after the gentle slope joint at the end of the previous weld;

[0043] h23) For the second layer of the manual tungsten argon arc welding of the 1G weld seam with horizontal rotation position, the left welding method is adopted. The arc is started at a position 100mm away from any weld joint position, and then it is turned back 10mm to start welding. Before one welding wire is used up, the arc is re-welded to close the arc; the end of the weld is ground to a gentle slope; after changing the welding wire, the arc is started 10mm before the gentle slope of the weld end, and the arc is turned back to the joint on the gentle slope to start welding. The tire rotation drives the tube sheet and the cylinder to start rotating, and the entire weld is welded in sequence;

[0044] h3) Manual tungsten inert gas arc welding is performed in 2 layers, with 1 pass in each layer. The joints between layers are staggered by more than 20mm. The welding wire is φ1.6mm or φ2.4mm. The welding pass is linear. The swing width of the welding torch does not exceed 3 times the diameter of the welding wire. The excess height of the back of the weld relative to the inner wall of the cylinder is less than 3mm. The temperature between layers is controlled in the range of <250℃.

[0045] Preferably, the G preheating before welding includes the following steps:

[0046] g1) Fix the thermocouples at the tube sheet and the cylinder at points ⑥ and Point position, the thermocouple measuring end is 40mm-50mm away from the outer edge of the weld groove;

[0047] g2) The thermocouple is wrapped with an electric heating belt, and the measuring end of the thermocouple is 0-5mm away from the edge of the electric heating belt. It is wrapped and tied with insulation cotton. The area between the measuring ends of the thermocouple is 50-70mm for the weld and splash area. The weld, splash area, the edge of the tube sheet, the bolts and nuts, and the rigid fixing blocks are wrapped and insulated with insulation cotton blankets; both ends of the cylinder are sealed with insulation cotton blankets;

[0048] g3) Power on for preheating, use a digital point thermometer to measure the groove surface temperature regularly, and control the preheating temperature of the groove surface in the range of 15℃-75℃;

[0049] g4) After preheating meets the requirements, remove the insulation blankets from the weld and spatter areas.

[0050] Preferably, the step E of arranging two tube sheets between two cylinders and assembling them comprises the following steps:

[0051] e1) Confirm that the fixtures, point fixing blocks, tube sheets and cylinders used for assembly are of the same material or the same group;

[0052] e2) Assemble the two tube sheets and the cylinder horizontally with a gap of 0-1mm.

[0053] Preferably, in step D, the fillet weld between the end width of the rigid fixing block in the length direction and the tube sheet is 40 mm long, single-pass hand arc welding is used, the fillet weld length is 25-35 mm, the weld angle height is 8-9 mm, and the weld toe line is within the thickness edge line of the tube sheet; the fillet weld is welded using center-symmetrical welding.

[0054] After adopting the above technical scheme, the effect of the present invention is as follows: in the welding process, the tube sheet is first rigidly fixed by a rigid fixing block, and then respectively assembled with two cylinders to form two axially symmetrical butt welds, and then the symmetrical welds are divided into twelve equal parts, and manual tungsten inert gas arc welding is used for base welding and manual arc welding is used for filling and capping welding and symmetrical welding. Therefore, welding can be completed in groups, and personnel can be replaced after welding each section to ensure continuous welding, reduce the labor intensity of welders, and also reduce welding deformation and crack tendency, thereby ensuring welding quality; using argon arc welding Primer can ensure root penetration and weld inner surface forming; use rigid fixing blocks for fixing, axially symmetrical welding in the same direction, control the same welding process parameters, reasonably arrange the distribution of manual arc welding passes and welding sequence, and the welding process of the latter weld is essentially a normalizing heat treatment of the previous adjacent weld, which reduces the lateral shrinkage stress of the weld cladding metal. The left welding method is used for welding, and the rigid fixing blocks are removed after the weld is cooled. The above measures effectively control welding stress and deformation, so that the deformation quality of the weld and tube sheet meets the requirements of the process design indicators of the heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0056] Figure 1 It is a partial axial structural cross-sectional view of the tube sheet and the cylinder assembly at the groove of the embodiment of the invention;

[0057] Figure 2 is a partial structural cross-sectional view between the tube sheet and the rigid fixing block of an embodiment of the invention;

[0058] Figure 3 It is a partial view of the point fixing block of the tube sheet and the cylinder groove assembly of the embodiment of the invention;

[0059] Figure 4 yes Figure 3 An enlarged schematic diagram at A;

[0060] Figure 5 is a schematic diagram of welding sequence and direction of an embodiment of the invention;

[0061] Figure 6 It is a groove weld welding method and weld bead arrangement diagram of an embodiment of the invention;

[0062] In the attached figure: 1, cylinder; 2, tube sheet; 3, groove; 31, blunt edge; 4, bolt; 5, rigid fixing block; 6, aluminum gasket; 7, boss; 8, point fixing block. DETAILED DESCRIPTION

[0063] The present invention is further described in detail below through specific examples.

[0064] like Figures 1 to 6As shown, a welding process for the weld seam between the tube sheet 2 and the cylinder 1 of a heat exchanger comprises the following steps:

[0065] A. Preparation before welding, including the following steps:

[0066] a1) Determine the implementation standard of the welding project; in this embodiment, the implementation standard is: "ASME Boiler and Pressure Vessel Code Volume IX Welding, Brazing and Bonding Qualification-Welding, Brazing and Bonding Process, Welder, Brazer and Welding, Brazing and Bonding Operator Qualification Standard" 2023 Edition; "ASME Boiler and Pressure Vessel Code Volume VIII-1 Pressure Vessel Construction Rules"

[0067] 2023 edition;

[0068] a2) Check whether the specifications, grades, welding materials and gas of the tube sheet 2 and aluminum gasket 6 meet the standards;

[0069] In this embodiment, the tube sheet 2 is made of SA-516 70N, with a specification diameter of φ1220×38.1mm and the cylinder 1 is made of SA-516 70N, with a specification diameter of φ1220×14mm as examples. Table 1 records the specifications, grades, and process parameters of the main and auxiliary materials involved in the manufacture of the heat exchanger.

[0070] type Brand Specifications / Thickness Implementation Standards Tube sheet 2 SA-516 70N φ1220×38.1 ASME SA-516 Cylinder 1 SA-516 70N φ1220×14 ASME SA-516 Carbon steel covered welding rod E7018S φ3.2 / φ4.0 AWS A5.1 Carbon steel solid welding wire ER 70S-6 φ1.6 / φ2.4 AWS A5.18 Argon Ar 99.997％ GB / T10624-1995

[0071] Table 1

[0072] a3) Select tools; the welding equipment required include: inverter DC argon arc / manual arc welding machine WS-400E or similar arc welding power source, argon gas pressure reducing gauge, welding rod drying box, welding rod insulation barrel, heat treatment equipment TCS-1 or similar equipment, thermocouple, spot temperature meter and groove 3 processing equipment, non-destructive and physical and chemical testing equipment, etc.

[0073] It is required that the ammeter, voltmeter, argon gas pressure reducing meter and the above corresponding equipment of the inverter DC argon arc / manual arc welding machine WS-400E have been calibrated and are within the calibration validity period.

[0074] The main tools and machines required include: angle grinder, grinding disc, cutting disc, wire brush, slag cleaning hammer, half-circular file, flashlight, weld inspection ruler, acetone, cotton yarn and labor protection supplies, thermal insulation cotton, and thermal insulation quilt.

[0075] a4) Inspection of tools; check whether the purity of argon gas is 99.997%, check whether the surface of welding wire used in argon arc welding torch is clean, and check whether the physical and chemical parameters of tube sheet 2 and cylinder 1, welding wire used in argon arc welding torch and manual arc welding rod are qualified;

[0076] a5) The two tube sheets 2 to be welded are processed with bosses 7 according to the design parameters. The height of the bosses 7 is 3.0-3.5 mm. In this embodiment, the height of the bosses 7 is 3.2 mm.

[0077] a6) processing grooves 3 on the end faces of the two cylinders 1 to be welded, wherein the grooves 3 are single V-shaped grooves 3, the angle between the groove 3 surface and the vertical direction is 45±2.5°, and the blunt edge 31 is 0-1mm;

[0078] a7) Remove all debris within 20mm of the inner and outer surfaces of the three grooves to reveal the metallic luster; such as oil, rust, oxide scale, etc., and scrub with acetone if necessary.

[0079] a8) Check that the welder is equipped with the corresponding welding qualification certificate;

[0080] B. Processing of aluminum gasket 6: Aluminum material with grade 5083 is selected for processing. The diameter and thickness of aluminum gasket 6 are the same as the diameter and thickness of cylinder 1. The width of aluminum gasket 6 is 25-30mm. The roughness of the contact surface of aluminum gasket 6 is Rz6.3.

[0081] C. Assemble aluminum gasket 6

[0082] Install the aluminum gasket 6 between the two tube sheets 2, and fix the aluminum gasket 6 between the two tube sheets 2 by bolts 4 evenly distributed around the circumference; the nut should be evenly stressed, and the torque value should be checked with a torque wrench if necessary;

[0083] D. Weld a plurality of rigid fixing blocks 5 on the outer edges of the two tube sheets 2. The rigid fixing blocks 5 are evenly distributed around the circumference, and each rigid fixing block 5 is located between adjacent bolts 4; Figure 1 and Figure 2 As shown, in this embodiment, a total of twenty-four rigid fixing blocks 5 are evenly distributed on the outer edges of the two tube sheets 2.

[0084] The length of the fillet weld between the rigid fixing block 5 and the tube sheet 2 is 40mm, and the hand arc welding is single-pass. The fillet weld length is 25-35mm, the weld angle height is 8-9mm, and the weld toe line is within the thickness edge line of the tube sheet 2. The fillet weld adopts central symmetric welding. In this way, after the rigid fixing block 5 is removed, the weld scar is polished to be flush with the surface of the parent material, and the appearance of the product can be maintained. The fillet weld adopts central symmetric welding to make the overall welding stress and deformation uniform.

[0085] E. Place two tube sheets 2 between two cylinders 1 and assemble them;

[0086] like Figure 3As shown, the E sets two tube sheets 2 between two cylinders 1 and assembles them, including the following steps: e1) confirming that the tooling fixtures and point fixing blocks 8 used for assembly are of the same material or the same group as the tube sheets 2 and the cylinder 1; e2) aligning the two tube sheets 2 and the cylinder 1 horizontally, with an assembly gap of 0-1mm.

[0087] F. Spot-weld the two tube sheets 2 and the two cylinders 1 by hand arc welding and assemble them using spot-weld blocks 8, including the following steps:

[0088] f1) The entire circumference of the circumferential weld between the tube sheet 2 and the cylinder 1 is evenly divided into twelve equal parts, and eight point fixing blocks 8 are selected and arranged at ①, ②, ④, ⑤, ⑦, ⑧, ⑩, Point location;

[0089] f2) placing the spot-fixing block 8 on the three sides of the groove, spot-fixing the fillet weld in a single pass, the length of the single-sided single-pass weld of the spot-fixing fillet weld is greater than 15 mm, and the thickness is greater than 3 mm;

[0090] f3) Check the quality of spot welding;

[0091] G. Preheating before welding: when the room temperature is greater than or equal to 15°C, no preheating is required; when the room temperature is between -20°C and 15°C, preheating to ≥15°C is required; the G preheating before welding includes the following steps;

[0092] g1) Fix the thermocouples at points ⑥ and ⑥ of the tube sheet 2 and the cylinder 1 respectively. Point position, the thermocouple measuring end is 40mm-50mm away from the outer edge of the weld groove 3;

[0093] g2) The thermocouple is wrapped with an electric heating belt, the measuring end of the thermocouple is 0-5mm away from the edge of the electric heating belt, and is wrapped and tied with insulation cotton. The area between the measuring ends of the thermocouple is 50-70mm for the weld and splash area. The weld, splash area, the edge of the tube sheet 2, the bolts 4, the nuts, and the rigid fixing blocks 5 are wrapped and insulated with insulation cotton quilts; both ends of the cylinder 1 are sealed with insulation cotton quilts;

[0094] g3) Power on for preheating, use a digital point thermometer to measure the temperature of the three surfaces of the groove regularly, and control the preheating temperature of the three surfaces of the groove within the range of 15℃-75℃;

[0095] g4) After preheating meets the requirements, remove the insulation blankets from the weld and spatter areas.

[0096] H. Manual tungsten inert gas arc welding for base weld

[0097] When the cylinder 1 and the tube sheet 2 are fixed horizontally, the horizontal position 5G welding is adopted, and the welding is performed symmetrically in sections; when the cylinder 1 and the tube sheet 2 are installed in a horizontal rotation, the horizontal rotation position 1G welding is adopted, and the left welding method and pressure pass welding are adopted; the two welds of the two tube sheets 2 are symmetrical and welded at the same time, and the welding process, welding sequence, welding direction and welding parameters are the same; the root is welded through, and the bottom pass is welded in two layers, one pass per layer, the interpass temperature is ≤250℃, and the interlayer joints are staggered;

[0098] The specific welding method of step H, manual tungsten inert gas arc welding for the base weld is:

[0099] h1) Manual tungsten inert gas arc horizontal fixed position 5G weld root pass welding:

[0100] h11) Manual tungsten inert gas arc horizontal fixed position 5G weld base weld first layer welding, determine the segmented symmetrical welding sequence and arc starting position: the first group of welding sequence; according to the clock position ⑥→⑤, ③→②, ⑧→⑨; ⑥→⑦, ④→③, ⑨→⑩ in sequence; ⑥→⑤, is a set of symmetrical welding sections, ③→②, ⑧→⑨ is a set of symmetrical welding sections, ⑥→⑦, It is a group of symmetrical welding sections, ④→③, ⑨→⑩ are a group of symmetrical welding sections; the welding direction is the forward direction; when welding ⑥→⑤, ③→②, ⑨→⑩, the arc is started from 10mm in front of points ⑥, ③, and ⑨ respectively, and then it turns back to 10-20mm behind points ⑥, ③, and ⑨ to start welding, and the arc is closed 10mm in front of the point-fixing block 8 at points ⑤, ②, and ⑩; when welding ⑥→⑦, the arc is started from 10mm in front of the gentle slope of the front section weld joint near point ⑥, and then it turns back to the gentle slope of the front section weld joint to start welding, and the arc is closed 10mm in front of the point-fixing block 8 at point ⑦; welding ④→③, ⑧→⑨ The point fixing block 8 at the ④, ①, and ⑧ positions starts arcing 20mm in front of the point fixing block 8, and then folds back to the Weld from 10mm in front of the spot fixing block 8 at points ④, ①, and ⑧ until ③、 ⑨Re-weld the arc at the gentle slope joint near the position and the end of the previous weld;

[0101] h12) The second welding sequence: ⑦→⑧, ②→①; ⑤→④, Sequential welding; among which ⑤→④, It is a symmetrical welding section, ⑦→⑧, ②→① are a symmetrical welding section; when welding each welding section, first grind and remove the spot fixing blocks 8 at both ends of the welding section, then grind and remove the weld scars, grind until it is flush with the surface of the parent material, then start the arc from the starting clock position of the welding section, then turn back to the gentle slope welding joint at the end of the previous section of the weld, then move forward to the gentle slope joint of the previous welding section and the end of the weld, and then re-weld and close the arc;

[0102] h13) Manual tungsten inert gas arc welding horizontal fixed position 5G weld base weld second layer welding, welding sequence and direction are the same as steps h11) and h12); determine the segmented symmetrical welding sequence and arc starting position: the first group of welding sequence is according to the clock position ⑥→⑤→④→③, Welding in the following order: ⑥→⑤→④→③, It is a set of symmetrical welding sections; the welding direction is the forward direction; welding ⑥→⑤→④→③, The arc is started from 20mm before points ⑥ and ⑨, and then the arc is turned back to 10mm before points ⑥ and ⑨ to weld. The arc is welded to points ③ and ⑨. Re-weld near the point to close the arc; grind the two ends of the weld metal into a gentle slope;

[0103] h14) The second welding sequence: according to ⑥→⑦→⑧→⑨, Sequential welding: ⑥→⑦→⑧→⑨, It is a symmetrical welding section; the welding direction is the forward direction; welding ⑥→⑦→⑧→⑨, The arc is started from 10mm in front of the gentle slope of the weld end near points ⑥ and ③, and then the arc is turned back to the gentle slope of points ⑥ and ③ to start welding, and the arc is welded to points 9 and Near the point position, re-weld and close the arc after the gentle slope joint at the end of the weld; Grind and clean the excessive height to strengthen the height;

[0104] h2) Manual tungsten inert gas arc welding in horizontal rotation position 1G weld root pass welding

[0105] h21) For the first layer of the manual tungsten inert gas argon arc horizontal rotation position 1G weld, the left welding method is used to determine the segmented symmetrical welding sequence and arc starting position: the first group of welding sequence; according to the clock position ④→③→②, ⑩→⑨→⑧; ⑦→⑥→⑤, The sequence of welding is as follows; ④→③→②, ⑩→⑨→⑧ are a set of symmetrical welding sections, ⑦→⑥→⑤, It is a set of symmetrical welding sections; the welding direction is the forward direction; when welding ④→③→②, ⑩→⑨→⑧, the arc is started from 20mm in front of points ④ and ⑩ respectively, and then it turns back to 10mm in front of the point fixing block 8 at points ④ and ⑩ respectively, and the arc is closed at 10mm in front of the point fixing block 8 at points ② and ⑧; when welding ⑦→⑥→⑤, When welding, start the arc from 20mm before point ⑦ and ① respectively, then turn back to 10mm before point ⑦ and ① respectively, until ⑤, The arc is closed 10mm in front of the point fixing block 8 at the point position;

[0106] h22) The second welding sequence: ②→①, ⑧→⑦; ⑤→④, Sequential welding; ②→①, ⑧→⑦ are a symmetrical welding section, ⑤→④, For a symmetrical welding section; when welding each welding section, first grind away the point blocks 8 at both ends of the welding section, then grind away the weld scars, grind until it is flush with the surface of the parent material, and then grind from point ②, point ⑧, point ⑤, The arc starts at the point position, and the arc bends back to the gentle slope welding joint at the end of the previous weld, and then welds to the vicinity of point ①, point ⑦, point ④, and point ⑩, and then re-welds and closes the arc after the gentle slope joint at the end of the previous weld;

[0107] h23) The welding of the second layer of the base weld of the manual tungsten argon arc at the horizontal rotation position 1G is carried out by the left welding method. The arc is started at a position 100mm away from any weld joint, and then it is turned back 10mm to start welding. Before one welding wire is used up, the arc is re-welded to close the arc; the end of the weld is ground to a gentle slope; after changing the welding wire, the arc is started 10mm before the gentle slope of the end of the weld, and the arc is turned back to the joint on the gentle slope to start welding. The tire rotation drives the tube sheet 2 and the cylinder 1 to start rotating, and the entire weld is welded in sequence;

[0108] h3) Manual tungsten inert gas arc welding is performed in 2 layers, with 1 pass in each layer. The joints between layers are staggered by more than 20mm. The welding wire is φ1.6mm or φ2.4mm. It is a linear weld. The swing width of the welding torch does not exceed 3 times the diameter of the welding wire. The excess height of the back of the weld relative to the inner wall of the cylinder 1 is less than 3mm. The temperature between layers is controlled in the range of <250℃.

[0109] I. Manual arc welding for filling and capping welds: When welding at the horizontal fixed position 5G, adopt segmented symmetrical welding; when welding at the horizontal rotating position 1G, adopt the left welding method and press weld; the two welds of the two tube sheets 2 are welded symmetrically and simultaneously, and the welding process, welding sequence, welding direction and welding parameters are the same;

[0110] Among them, the order and direction of the 5G manual arc welding filling and capping welds in the horizontal fixed position are the same as those of the base welds. The first layer of the manual arc welding filling and capping welds is one pass, and the second and subsequent layers are multi-pass welds;

[0111] The welding sequence of the 1G manual arc welding filling and capping weld in the horizontal rotation position is the same as that of the base weld. The first layer of the manual arc welding filling and capping weld is one pass, and the second and subsequent layers are multi-pass welds;

[0112] Linear welding and pressure welding are used; the swing width of the welding torch shall not exceed 3 times the diameter of the welding rod; the interlayer temperature shall be less than 250℃; the interlayer joints shall be staggered by more than 20mm; the welding rod shall be alkaline welding rod with a diameter of 3.2mm or 4.0mm. When using a welding rod with a diameter of 3.2mm, the thickness of each weld bead shall be 3-5mm; when using a welding rod with a diameter of 4.0mm, the thickness of each weld bead shall be 5-7mm; the weld surface excess height shall be less than 2.5mm; when welding single-layer single-pass welding, the electric The arc first melts the base metal on the three sides of the cylinder 1 groove, and then changes the electrode angle to melt the base metal on the tube sheet 2 side; when single-layer two-pass welding is performed, the first weld pass is arranged on the base metal side of the three sides of the cylinder 1 groove, and the second weld pass is arranged between the weld cladding metal and the base metal of the tube sheet 2; when single-layer multi-pass welding is performed, the first weld pass is arranged on the base metal side of the three sides of the cylinder 1 groove, and the second weld pass is next to the first weld pass, and the last weld pass is arranged between the weld cladding metal and the base metal of the tube sheet 2;

[0113] like Figure 3 As shown, the following steps are included: e1) confirming that the tooling fixture, the point fixing block 8, the tube sheet 2 and the cylinder 1 are of the same material or the same group; e2) aligning the two tube sheets 2 and the cylinder 1 horizontally, with an aligning gap of 0-1 mm;

[0114] F. The two tube sheets 21 and the cylinder 12 are spot welded by hand arc welding and assembled using spot welding blocks 8, including the following steps:

[0115] f1) Divide the entire circumference of the girth weld into 12 equal parts. Figure 4 As shown, the hour positions ③, ⑥, ⑨, No point fixing block 8 is set at the position, and eight point fixing blocks 8 are arranged at ①, ②, ④, ⑤, ⑦, ⑧, ⑩, Point location;

[0116] f2) placing the spot fixing block 8 on the groove 3, and welding the corner weld 9 of the spot fixing block 8 in a single pass, with the length of each section of the corner weld 9 of the spot fixing block 8 being greater than 15 mm and the thickness being greater than 3 mm;

[0117] f3) Check the quality of the corner weld 9 of the spot fixing block 8. If the quality is unqualified, repair welding is required;

[0118] G. Preheating before welding: when the room temperature is greater than ≥15℃, preheating is not required; when the room temperature is -20℃ to 10℃, preheating to ≥15℃ is required. Preheating includes the following steps;

[0119] g1) Fix the thermocouples at points 6 and 7 on the tube sheet 2 and the shell 1 respectively. Point position, the thermocouple measuring end is 40mm-50mm away from the outer edge of the weld groove 3;

[0120] g2) The thermocouple is wrapped with an electric heating tape, and the measuring end of the thermocouple is 0-5mm away from the edge of the electric heating tape. It is wrapped and tied with insulation cotton. The area between the measuring ends of the thermocouple is 50mm-70mm for the weld and splash area. The weld, splash area, the edge of the tube sheet 2, the bolts 4 nuts and 24 rigid fixed connecting plates are wrapped with insulation cotton for insulation; both ends of the cylinder 1 are sealed with insulation cotton;

[0121] g3) Power on for preheating, use a digital point thermometer to measure the temperature of the three surfaces of the groove regularly, and control the preheating temperature of the three surfaces of the groove within the range of 15℃-75℃;

[0122] g4) After preheating meets the requirements, remove the insulation blankets in the weld and splash areas;

[0123] H. Manual tungsten inert gas arc welding base weld 10 welding, such as Figure 6 When welding at the horizontal fixed position 5G, the welding is performed symmetrically in sections; when welding at the horizontal rotating position 1G, the left welding method and pressure pass welding are used; the two welds of the two tube sheets 2 are symmetrical with the parallel planes in the middle of the two tube sheets 2 as the axis, and are welded at the same time, and the welding process, welding sequence, welding direction and welding parameters are the same;

[0124] h1) Manual tungsten inert gas arc horizontal fixed position 5G weld root weld 10

[0125] h11) Manual tungsten inert gas arc horizontal fixed position 5G weld base weld first layer welding, determine the segmented symmetrical welding sequence and arc starting position: the first group of welding sequence; according to the clock position ⑥→⑤, ③→②, ⑧→⑨; ⑥→⑦, ④→③, ⑨→⑩; among which ⑥→⑤, is a pair of symmetrical welding sections, ③→②, ⑧→⑨ is a pair of symmetrical welding sections, ⑥→⑦, It is a pair of symmetrical welding sections, ④→③, ⑨→⑩ are a pair of symmetrical welding sections; the welding direction is the forward direction; when welding ⑥→⑤, ③→②, ⑨→⑩, the arc is started from 10mm in front of points ⑥, ③, and ⑨ respectively, and then it turns back to 10-20mm behind points ⑥, ③, and ⑨ to start welding, and the arc is closed 10mm in front of the point-fixing block 8 at points ⑤, ②, and ⑩; when welding ⑥→⑦, the arc is started from 10mm in front of the gentle slope of the front section weld joint near point ⑥, and then it turns back to the gentle slope of the front section weld joint to start welding, and the arc is closed 10mm in front of the point-fixing block 8 at point ⑦; welding ④→③, ⑧→⑨ The point fixing block 8 at the ④, ①, and ⑧ positions starts arcing 20mm in front of the point fixing block 8, and then folds back to the Weld from 10mm in front of the spot fixing block 8 at points ④, ①, and ⑧ until ③、 ⑨Re-weld the arc at the gentle slope joint near the position and the end of the previous weld;

[0126] h12) The second welding sequence: ⑦→⑧, ②→①; ⑤→④, Sequential welding; among which ⑤→④, It is a symmetrical welding section, ⑦→⑧, ②→① are a symmetrical welding section; when welding each welding section, first grind and remove the spot fixing blocks 8 at both ends of the welding section, then grind and remove the weld scars, grind until it is flush with the surface of the parent material, then start the arc from the starting clock position of the welding section, then turn back to the gentle slope welding joint at the end of the previous section of the weld, then move forward to the gentle slope joint of the previous welding section and the end of the weld, and then re-weld and close the arc;

[0127] h13) Manual tungsten inert gas arc welding horizontal fixed position 5G weld base weld 10 second layer welding, welding sequence and direction are roughly the same as h11) and h12). Determine the segmented symmetrical welding sequence and arc starting position: the first group of welding sequence is according to the clock position ⑥→⑤→④→③, Welding in the following order: ⑥→⑤→④→③, It is a pair of symmetrical welding sections; the welding direction is the forward direction; welding ⑥→⑤→④→③, The arc is started from 20mm before points ⑥ and ⑨, and then the arc is turned back to 10mm before points ⑥ and ⑨ to weld. The arc is welded to points ③ and ⑨. Re-weld near the point to close the arc; grind the two ends of the weld metal into a gentle slope;

[0128] h14) The second welding sequence: according to ⑥→⑦→⑧→⑨, Sequential welding: ⑥→⑦→⑧→⑨, It is a symmetrical welding section; the welding direction is the forward direction; welding ⑥→⑦→⑧→⑨, The arc is started from 10mm in front of the gentle slope of the weld end near points ⑥ and ③, and then the arc is turned back to the gentle slope of points ⑥ and ③ to start welding, and the arc is welded to points 9 and Near the point position, re-weld and close the arc after the gentle slope joint at the end of the weld; Grind and clean the excessive height to strengthen the height;

[0129] h2) Manual tungsten inert gas arc horizontal rotation position 1G weld root weld 10 welding

[0130] h21) For the first layer of the manual tungsten inert gas argon arc horizontal rotation position 1G weld, the left welding method is used to determine the segmented symmetrical welding sequence and arc starting position: the first group of welding sequence; according to the clock position ④→③→②, ⑩→⑨→⑧; ⑦→⑥→⑤, The welding sequence is as follows: ④→③→②, ⑩→⑨→⑧ are a pair of symmetrical welding sections, ⑦→⑥→⑤, It is a pair of symmetrical welding sections; take the welding direction as the forward direction; when welding ④→③→②, ⑩→⑨→⑧, start the arc from 20mm in front of point ④ and ⑩ respectively, then turn back to 10mm in front of the point fixing block 8 at point ④ and ⑩ respectively, and end the arc at 10mm in front of the point fixing block 8 at point ② and ⑧; when welding ⑦→⑥→⑤, When welding, start the arc from 20mm before point ⑦ and ① respectively, then turn back to 10mm before point ⑦ and ① respectively, until ⑤, The arc is closed 10mm in front of the point fixing block 8 at the point position;

[0131] h22) The second welding sequence: ②→①, ⑧→⑦; ⑤→④, Sequential welding; ②→①, ⑧→⑦ are a symmetrical welding section, ⑤→④, It is a symmetrical welding section; when welding each welding section, first grind off the point fixing blocks 8 at both ends of the welding section, then grind off the weld scars, grind until it is flush with the surface of the parent material, and then start the arc from the positions of points ②, ⑦, ⑤, and ⑩. The arc is turned back to the end of the previous weld and the welding joint is started with a gentle slope, and then welded to points ①, ⑧, ④, Near the point position, re-weld and close the arc after the gentle slope joint with the end of the previous weld;

[0132] h23) For the second layer of the manual tungsten argon arc horizontal rotation position 1G weld, use the left welding method, select a place 100mm away from any weld joint to start the arc, then turn back 10mm to start welding, and re-weld and close the arc before one welding wire is used up. The tire stops rotating. Grind the weld end to a gentle slope. After changing the welding wire, the arc starts 10mm before the gentle slope of the weld end, and the arc turns back to the joint on the gentle slope to start welding. The tire starts rotating and the entire weld is welded in sequence.

[0133] h3) Manual tungsten inert gas arc welding pass 10 is welded in 2 layers, 1 pass per layer, the joints between layers are staggered more than 20mm, the welding wire is φ1.6 or φ2.4, the welding pass is linear, the torch swing width does not exceed 3 times the diameter of the welding wire, the excess height of the back of the weld relative to the inner wall of the cylinder 1 is less than 3mm, and the interlayer temperature is controlled in the range of <250℃;

[0134] I. Manual arc welding for filling and capping welds: When welding at the horizontal fixed position 5G, adopt segmented symmetrical welding; when welding at the horizontal rotating position 1G, adopt the left welding method and press weld; the two welds of the two tube sheets 2 are welded simultaneously with the parallel plane at the middle position of the two tube sheets 2 as the axis symmetry, and the welding process, welding sequence, welding direction and welding parameters are the same;

[0135] I1) Horizontal fixed position 5G manual arc welding filling and capping weld

[0136] I1)1 Horizontal fixed position 5G Manual arc welding fill cap weld The welding order and direction are roughly the same as h13)h14). The first layer of manual arc welding fill cap weld is one layer, and the second and subsequent layers are multi-pass welds;

[0137] I2) Horizontal rotation position 1G manual arc welding filling cap weld

[0138] I21) The welding sequence and direction of the 1G manual arc welding filler and capping weld in the horizontal fixed position are roughly the same as h23). The first layer of the manual arc welding filler and capping weld is one layer at a time, and the second and subsequent layers are multi-pass welds;

[0139] I3) Manual arc welding for filling and capping welds: The two axially symmetrical butt welds of the tube sheet 2 and the cylinder 1 are welded by two people in each group at the same time, with the same welding parameters and in the same direction; linear welds and pressure welds are used; the torch swing width does not exceed 3 times the electrode diameter; the interlayer temperature is <250℃; the interlayer joints are staggered by more than 20mm; the welding rods are φ3.2 or φ4.0 basic welding rods. When φ3.2 welding rods are used, the thickness of each layer is 3-5mm, and when φ4.0 welding rods are used, the thickness of each layer is 5-7mm; the weld surface excess height is less than 2.5mm;

[0140] In single-layer single-pass welding, the arc first melts the base metal on the three sides of the cylinder 1 groove, and then changes the electrode angle to melt the base metal on the tube sheet 2 side; in single-layer two-pass welding, the first weld pass is arranged on the base metal side of the three sides of the cylinder 1 groove, and the second weld pass is arranged between the weld cladding metal and the base metal of the tube sheet 2; in single-layer multi-pass welding, the first weld pass is arranged on the base metal side of the three sides of the cylinder 1 groove, and the second weld pass is next to the first weld pass, and the last weld pass is arranged between the weld cladding metal and the base metal of the tube sheet 2;

[0141] Compared with the right welding method, the left welding method has a shallower welding penetration, lower welding heat input, smaller welding stress and deformation; the linear weld has a lower heat input than the swing weld, which is more conducive to reducing welding stress and welding deformation; the manual arc welding weld arrangement starts from the parent material on the cylinder 1 side and gradually welds to the tube sheet 2 side, that is, the cladding metal of the last weld is fused with the parent material of the tube sheet 2, that is, only the transverse tensile stress of the weld of the last weld acts on the parent material of the tube sheet 2, which relatively reduces the inward bending deformation value caused by the transverse tensile stress of the weld in the edge area of ​​the tube sheet 2.

[0142] During the welding process, each weld should be 100% visually inspected, and any defects should be promptly polished and removed. Grinding and removing defects should be done carefully to avoid overheating. The weld surface should be continuous, uniform in thickness, and have a uniform transition with the surface of the adjacent weld. Welding operations should be avoided under adverse climatic conditions. Screens should be set up in the workplace to reduce the impact of airflow on arc stability. The welding rod should be dried and insulated as required to avoid defects such as pores during welding. So far, Table 2 is a table of welding process parameters for the base weld and the filling and capping weld:

[0143]

[0144]

[0145] Table 2

[0146] J. After the weld has cooled down to room temperature, grind and remove all the rigid fixing blocks 5, and grind the weld scar to be flush with the base material; after cooling down to room temperature, remove the rigid fixing blocks 5 again, so that the internal stresses of the tube sheet 2, weld and cylinder 1 metal due to thermal expansion and contraction are balanced, and relatively reduce the inward bending deformation value caused by the internal stress in the edge area of ​​the tube sheet 2.

[0147] K. Grind and remove all defects on both sides of the weld to ensure that the weld surface has a smooth transition with the outer surface of the tube sheet 2 and the cylinder 1;

[0148] L. Nondestructive testing: Finally, the geometric dimension inspection can be carried out: the flatness of the tube sheet 2 in the example meets the design pipeline requirements.

[0149] The above-described embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Various modifications and alterations to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A heat exchanger tube sheet and cylinder weld welding process, characterized in that: The following steps are involved: A. Preparation before welding, including the following steps: a1) Determine the execution standards of welding projects; a2) Check whether the specifications, grades, welding materials and gas of tube sheets and aluminum gaskets meet the standards; a3) Selection tools; a4) Acceptance inspection of tools; a5) Process the bosses on the two tube sheets to be welded according to the design parameters, and the height of the bosses is 3.0-3.5mm; a6) Processing grooves on the two cylinder end faces to be welded, the grooves are single V-shaped grooves, the angle between the groove surface and the vertical direction is 45±2.5°, and the blunt edge is 0-1mm; a7) Remove all debris within 20mm of the inner and outer surfaces of the groove to reveal the metallic luster; a8) Check that the welder is equipped with the corresponding welding qualification certificate; B. For the processing of aluminum gasket, aluminum material with material grade 5083 is selected for processing. The diameter and thickness of the aluminum gasket are the same as the diameter and thickness of the cylinder. The width of the aluminum gasket is 25-30mm; the roughness of the contact surface of the aluminum gasket is Rz6.3; C. Assemble aluminum gasket The aluminum gasket is installed between two tube sheets, and the aluminum gasket is clamped between the two tube sheets by bolts evenly distributed around the circumference; D. Weld multiple rigid fixing blocks on the outer edges of the two tube sheets. The rigid fixing blocks are evenly distributed around the circumference, and each rigid fixing block is located between adjacent bolts. The fillet welds between the outer edges of the two tube sheets and the rigid fixing blocks are welded first, and the center symmetry method and manual arc welding are used; E. Place two tube sheets between two cylinders and assemble them; F. Spot weld the two tube sheets and the two cylinders by hand arc welding and assemble them with spot welding blocks, including the following steps: f1) Divide the entire circumference of the circumferential weld between the tube sheet and the cylinder into twelve equal parts, and select eight point fixing blocks to be arranged at ①, ②, ④, ⑤, ⑦, ⑧, ⑩, Point location; f2) Place the spot fixing block on the groove surface, spot fix the fillet weld in a single pass, the length of the single-sided single pass of the spot fix fillet weld is greater than 15mm, and the thickness is greater than 3mm; f3) Check the quality of spot welding; G. Preheating before welding: when the room temperature is greater than ≥15℃, preheating is not required; when the room temperature is -20℃ to 15℃, preheating to ≥15℃ is required; H. Manual tungsten inert gas arc welding for base weld When the cylinder and the tube sheet are fixed horizontally, the horizontal position 5G welding is adopted, and the welding is performed symmetrically in sections; when the cylinder and the tube sheet are installed horizontally, the horizontal rotation position 1G welding is adopted, and the left welding method and pressure pass welding are adopted; the two welds of the two tube sheets are symmetrical and welded at the same time, and the welding process, welding sequence, welding direction and welding parameters are the same; the root is welded through, and the base weld is welded in two layers, one pass per layer, the interpass temperature is ≤250℃, and the joints between layers are staggered; I. Manual arc welding for filling and capping welds: When welding in the horizontal fixed position 5G, adopt segmented symmetrical welding; when welding in the horizontal rotating position 1G, adopt the left welding method and pressure welding; the two welds of the two tube sheets are symmetrical and welded at the same time, and the welding process, welding sequence, welding direction and welding parameters are the same; Among them, the order and direction of the 5G manual arc welding filling and capping welds in the horizontal fixed position are the same as those of the base welds. The first layer of the manual arc welding filling and capping welds is one pass, and the second and subsequent layers are multi-pass welds; The welding sequence of the 1G manual arc welding filling and capping weld in the horizontal rotation position is the same as that of the base weld. The first layer of the manual arc welding filling and capping weld is one pass, and the second and subsequent layers are multi-pass welds; Linear welding and pressure welding are used; the swing width of the welding torch shall not exceed 3 times the diameter of the welding rod; the interlayer temperature shall be less than 250℃; the interlayer joints shall be staggered by more than 20mm; the welding rod shall be a basic welding rod with a diameter of 3.2mm or 4.0mm. When a welding rod with a diameter of 3.2mm is used, the thickness of each weld bead shall be 3-5mm; when a welding rod with a diameter of 4.0mm is used, the thickness of each weld bead shall be 5-7mm; the weld surface excess height shall be less than 2.5mm; single layer single pass During welding, the arc first melts the base metal on the cylinder groove surface, and then changes the electrode angle to melt the base metal on the tube sheet side; when welding single-layer with two passes, the first weld pass is arranged on the base metal side of the cylinder groove surface, and the second weld pass is arranged between the weld cladding metal and the tube sheet base metal; when welding single-layer with multiple passes, the first weld pass is arranged on the base metal side of the cylinder groove surface, and the second weld pass is next to the first weld pass, and the last weld pass is arranged between the weld cladding metal and the tube sheet base metal; J. After the weld has cooled, grind and remove all rigid fixing blocks, and grind the weld scar until it is flush with the parent material; K. Grind and remove all defects on both sides of the weld to ensure that the weld surface has a smooth transition with the tube sheet and the outer surface of the cylinder; L. Nondestructive testing.

2. A heat exchanger tube sheet and cylinder weld welding process according to claim 1, characterized in that: The specific welding method of step H, manual tungsten inert gas arc welding for the base weld is: h1) Manual tungsten inert gas arc horizontal fixed position 5G weld root pass welding: h11) Manual tungsten inert gas arc horizontal fixed position 5G weld base weld first layer welding, determine the segmented symmetrical welding sequence and arc starting position: the first group of welding sequence; according to the clock position ⑥→⑤, ③→②, ⑧→⑨; ⑥→⑦, ④→③, ⑨→⑩ in sequence; ⑥→⑤, is a set of symmetrical welding sections, ③→②, ⑧→⑨ is a set of symmetrical welding sections, ⑥→⑦, It is a group of symmetrical welding sections, ④→③, ⑨→⑩ are a group of symmetrical welding sections; the welding direction is the forward direction; when welding ⑥→⑤, ③→②, ⑨→⑩, the arc is started from 10mm in front of points ⑥, ③, and ⑨ respectively, and then it turns back to 10-20mm behind points ⑥, ③, and ⑨ to start welding, and the arc is closed 10mm in front of the point solid block at points ⑤, ②, and ⑩; when welding ⑥→⑦, the arc is started from 10mm in front of the gentle slope of the front section weld joint near point ⑥, and then it turns back to the gentle slope of the front section weld joint to start welding, and the arc is closed 10mm in front of the point solid block at point ⑦; welding ④→③, ⑧→⑨ The arcs are started 20mm in front of the point blocks at points ④, ①, and ⑧, and then folded back to Weld from 10mm in front of the spot fixing block at points ④, ①, and ⑧ until ③、 ⑨Re-weld the arc at the gentle slope joint near the position and the end of the previous weld; h12) The second welding sequence: ⑦→⑧, ②→①; ⑤→④, Sequential welding; among which ⑤→④, It is a symmetrical welding section, ⑦→⑧, ②→① are a symmetrical welding section; when welding each welding section, first grind off the spot blocks at both ends of the welding section, then grind off the weld scars, grind until it is flush with the surface of the parent material, then start the arc from the starting clock position of the welding section, then turn back to the gentle slope welding joint at the end of the previous section of the weld, then move forward to the gentle slope joint of the previous welding section and the end of the weld, then re-weld and close the arc; h13) Manual tungsten inert gas arc welding horizontal fixed position 5G weld base weld second layer welding, welding sequence and direction are the same as steps h11) and h12); determine the segmented symmetrical welding sequence and arc starting position: the first group of welding sequence is according to the clock position ⑥→⑤→④→③, Welding in the following order: ⑥→⑤→④→③, It is a set of symmetrical welding sections; the welding direction is the forward direction; welding ⑥→⑤→④→③, The arc is started from 20mm before points ⑥ and ⑨, and then the arc is turned back to 10mm before points ⑥ and ⑨ to weld. The arc is welded to points ③ and ⑨. Re-weld near the point to close the arc; grind the two ends of the weld metal into a gentle slope; h14) The second welding sequence: according to ⑥→⑦→⑧→⑨, Sequential welding: ⑥→⑦→⑧→⑨, It is a symmetrical welding section; the welding direction is the forward direction; welding ⑥→⑦→⑧→⑨, The arc is started from 10mm in front of the gentle slope of the weld end near points ⑥ and ③, and then the arc is turned back to the gentle slope of points ⑥ and ③ to start welding, and the arc is welded to points 9 and Near the point position, re-weld and close the arc after the gentle slope joint at the end of the weld; Grind and clean the excessive height to strengthen the height; h2) Manual tungsten inert gas arc welding in horizontal rotation position 1G weld root pass welding h21) For the first layer of the manual tungsten inert gas argon arc horizontal rotation position 1G weld, the left welding method is used to determine the segmented symmetrical welding sequence and arc starting position: the first group of welding sequence; according to the clock position ④→③→②, ⑩→⑨→⑧; ⑦→⑥→⑤, The sequence of welding is as follows; ④→③→②, ⑩→⑨→⑧ are a set of symmetrical welding sections, ⑦→⑥→⑤, It is a set of symmetrical welding sections; the welding direction is the forward direction; when welding ④→③→②, ⑩→⑨→⑧, the arc is started from 20mm in front of points ④ and ⑩ respectively, and then it turns back to 10mm in front of the point fixing block at points ④ and ⑩ respectively to start welding, and the arc is closed 10mm in front of the point fixing block at points ② and ⑧; when welding ⑦→⑥→⑤, When welding, start the arc from 20mm before point ⑦ and ① respectively, then turn back to 10mm before point ⑦ and ① respectively, until ⑤, The arc is closed 10mm before the point fixing block; h22) The second welding sequence: ②→①, ⑧→⑦; ⑤→④, Sequential welding; ②→①, ⑧→⑦ are a symmetrical welding section, ⑤→④, It is a symmetrical welding section. When welding each welding section, first grind away the point blocks at both ends of the welding section, then grind away the weld scars, grind until it is flush with the surface of the parent material, and then grind from point ②, point ⑧, point ⑤, The arc starts at the point position, and the arc bends back to the gentle slope welding joint at the end of the previous weld, and then welds to the vicinity of point ①, point ⑦, point ④, and point ⑩, and then re-welds and closes the arc after the gentle slope joint at the end of the previous weld; h23) For the second layer of the manual tungsten argon arc welding of the 1G weld seam with horizontal rotation position, the left welding method is adopted. The arc is started at a position 100mm away from any weld joint position, and then it is turned back 10mm to start welding. Before one welding wire is used up, the arc is re-welded to close the arc; the end of the weld is ground to a gentle slope; after changing the welding wire, the arc is started 10mm before the gentle slope of the weld end, and the arc is turned back to the joint on the gentle slope to start welding. The tire rotation drives the tube sheet and the cylinder to start rotating, and the entire weld is welded in sequence; h3) Manual tungsten inert gas arc welding is performed in 2 layers, with 1 pass in each layer. The joints between layers are staggered by more than 20mm. The welding wire is φ1.6mm or φ2.4mm. The welding pass is linear. The swing width of the welding torch does not exceed 3 times the diameter of the welding wire. The excess height of the back of the weld relative to the inner wall of the cylinder is less than 3mm. The temperature between layers is controlled in the range of <250℃.

3. A heat exchanger tube sheet and cylinder weld welding process as claimed in claim 2, characterized in that: The G pre-welding preheating comprises the following sub-steps: g1) Fix the thermocouples at the tube sheet and the cylinder at points ⑥ and Point position, the thermocouple measuring end is 40mm-50mm away from the outer edge of the weld groove; g2) The thermocouple is wrapped with an electric heating belt, the measuring end of the thermocouple is 0-5mm away from the edge of the electric heating belt, and is wrapped and tied with thermal insulation cotton. The area between the measuring ends of the thermocouple is 50-70mm for the weld and splash area. The weld, splash area, the edge of the tube sheet, the bolts and nuts, and the rigid fixing blocks are wrapped and insulated with thermal insulation quilts; Both ends of the cylinder are sealed with thermal insulation blankets; g3) Power on for preheating, use a digital point thermometer to measure the groove surface temperature regularly, and control the preheating temperature of the groove surface in the range of 15℃-75℃; g4) After preheating meets the requirements, remove the insulation blankets from the weld and spatter areas.

4. A heat exchanger tube sheet and cylinder weld welding process as claimed in claim 3, characterized in that: The step E of arranging two tube sheets between two cylinders and assembling them comprises the following steps: e1) Confirm that the fixtures, point fixing blocks, tube sheets and cylinders used for assembly are of the same material or the same group; e2) Assemble the two tube sheets and the cylinder horizontally with a gap of 0-1mm.

5. A heat exchanger tube sheet and cylinder weld welding process as claimed in claim 4, characterized in that: In step D, the fillet weld between the end width of the rigid fixing block in the length direction and the tube sheet is 40 mm long, single-pass hand arc welding is used, the fillet weld length is 25-35 mm, the weld angle height is 8-9 mm, and the weld toe line is within the thickness edge line of the tube sheet; the fillet weld is welded symmetrically.

Images