A method for welding a large diameter tube sheet with a stainless steel corrosion resistant layer

Abstract

The application discloses a method for surfacing a large-diameter tube plate with a stainless steel anticorrosive layer, which sequentially surfs a transition layer, a surface layer and a corrosion-resistant layer on the surface of the tube plate to solve the problems of tube plate deformation, out-of-tolerance of the flatness of the tube plate and uneven thickness of the anticorrosive layer after surfacing. The transition layer, the surface layer and the corrosion-resistant layer are sequentially surfaced on the tube plate, which can ensure full penetration of the surfacing weld and completely avoid defects such as slag inclusion, incomplete penetration and cracks of the surfacing weld. The method can refine grains, make stress distribution uniform, avoid large deformation of the tube plate, enhance the strength of the tube plate and thus ensure the mechanical properties and processing performance of the tube plate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of welding technology, in particular to a method for welding a large-diameter tube plate with a stainless steel corrosion-resistant layer. BACKGROUND

[0002] With the advancement of manufacturing power to manufacturing country, the chemical industry is also more and more common to use large-diameter tube shell heat exchanger. Tube plate, which is a kind of round steel with holes drilled on a round steel plate and slightly larger than the outer diameter of the tube, is used to fix the tube and seal the medium in the heat exchanger. The tube is inserted into the tube plate and welded to fix it. It is a kind of accessory that plays such a role. It is mainly used in chemical containers, such as tube heat exchanger, pressure vessel, boiler, condenser, central air conditioning, evaporator, seawater desalination, which plays the role of supporting and fixing the tube. The metal material not only has strong rigidity, but also has good heat conduction performance. Different materials are used according to different use environments. Generally, Q345R container plate is used, such as primary and secondary pressure vessels, which do not flow through corrosive medium, and carbon steel composite plate can be used. In the presence of strong acid, high pressure and high temperature, nuclear energy and other environments, stainless steel, 16 manganese, titanium alloy and other corrosion-resistant materials are required. When in use, the tube plate part is generally in contact with industrial cooling water, and impurities, salts, gases and microorganisms in the industrial cooling water can cause corrosion to the tube plate.

[0003] Most large heat exchanger tube plates adopt the structure of welding a stainless steel corrosion-resistant layer. Due to the large diameter and thin thickness of the tube plate, it is easy to cause deformation of the tube plate, out-of-tolerance of the flatness of the tube plate, and uneven thickness of the corrosion-resistant layer after welding. The method of tube plate welding and the treatment of tube plate deformation after welding are the difficulties in manufacturing heat exchangers.

[0004] Patent 201210536810.X discloses a large heat exchanger tube plate corrosion-resistant layer welding method, which comprises the following steps: a, cleaning the impurities on the tube plate to be welded; b, setting the arc voltage, welding speed and wire dry extension value of the electric welding machine, adding flux, and using submerged arc automatic welding to weld the two cleaned tube plates to form a transition layer, then welding a corrosion-resistant layer on the transition layer to obtain a finished product; c, cleaning the finished product after welding and checking; d, non-destructive testing of the finished product. However, the existing technology of welding a corrosion-resistant layer on the transition layer is easy to cause migration of carbon elements, resulting in defects such as slag inclusion, incomplete penetration and cracks in the weld between the transition layer and the corrosion-resistant layer. The final result is that the grain becomes coarse, the stress distribution is uneven, the tube plate deforms greatly, and the strength of the tube plate is reduced, thereby reducing the mechanical properties and processing performance of the tube plate. SUMMARY

[0005] In view of the above prior art, the purpose of the present application is to provide a method for welding a large-diameter tube plate with a stainless steel corrosion-resistant layer.

[0006] To achieve the above object, the present application adopts the following technical solutions:

[0007] The present application provides a method for welding a large-diameter tube sheet with a stainless steel corrosion-resistant layer, comprising the following steps:

[0008] (1) Pre-treatment: grooves are machined on the welding surfaces of the first and second tube sheets; the first and second tube sheets are tightly attached back to back, and the first and second tube sheets are fixed together by using arc-shaped plate clamps;

[0009] (2) Welding of transition layer: welding of transition layer in the groove of the first tube sheet, turning over, welding of transition layer in the groove of the second tube sheet;

[0010] (3) Welding of surface layer: welding of surface layer in the groove of the second tube sheet, turning over, welding of surface layer in the groove of the first tube sheet;

[0011] (4) Welding of corrosion-resistant layer: welding of corrosion-resistant layer in the groove of the first tube sheet, turning over, welding of corrosion-resistant layer in the groove of the second tube sheet;

[0012] (5) Post-treatment: removing the arc-shaped plate clamps and rough turning the surface of the tube sheet.

[0013] Preferably, the bottom of the groove in step (1) has a protrusion, the distance from the top of the protrusion to the upper surface of the tube sheet is 9-11 mm, and the distance from the edge of the groove to the upper surface of the tube sheet is 12-14 mm. The groove is machined to leave a deformation allowance and a machining allowance. After welding is completed, the clamps are loosened, and the periphery is raised upward, because the back also has a relatively large machining allowance, thereby ensuring that the final size can still be met when the back is machined.

[0014] Preferably, in step (1), arc-shaped plate clamps are welded on the top edges of the first and second tube sheets, lugs are welded at the midpoints of the sides of the arc-shaped plate clamps, and the lugs of the first and second tube sheets are connected by bolts and nuts; the arc-shaped plate clamps are obtained by cutting a circular ring into four arcs of the same size, a total of 8 arc-shaped plate clamps and 8 lugs are welded. The arc-shaped plate clamps have the advantage of tube sheet expansion allowance compared with the circular ring clamps, thereby reducing stress concentration.

[0015] As more preferably, the welding mode between the arc-shaped plate clamp and the tube plate in step (1) is fillet welding, and the welding is preheated to ≥100℃, φ4.0mm J507 electrode is used, welding current is 140-180A, welding voltage is 24-26V, welding speed is 10-16cm / min, welding temperature is ≤250℃, and welding length is at least 250mm; the welding mode between the lug and the arc-shaped plate clamp is fillet welding, and the welding is preheated to ≥100℃, φ4.0mm J507 electrode is used, welding current is 140-180A, welding voltage is 24-26V, welding speed is 10-16cm / min, and welding temperature is ≤250℃; and the post-welding is subjected to hydrogen elimination heat treatment, temperature is 250-350℃, and time is 20-40min.

[0016] As preferably, the thickness of the transition layer in step (2) is 3-4mm, and the first tube plate and the second tube plate are preheated to ≥80℃ before surfacing; the surfacing is from the center to the edge of the tube plate, and the surfacing mode is stick manual welding, φ4.0mm A302 electrode is used, welding current is 110-160A, welding voltage is 24-26V, welding speed is 10-16cm / min, and welding temperature is ≤150℃; the first tube plate and the second tube plate are subjected to hydrogen elimination heat treatment after surfacing, temperature is 200-300℃, and time is 0.05-1h; and stress relief heat treatment is performed, temperature is increased to 400℃ at a speed of 100-150℃ / h, then increased to 600-640℃ at a speed of 150-200℃ / h, kept for 200-220min, and decreased to 400℃ at a speed of 200-260℃ / h, and air-cooled below 400℃.

[0017] As preferably, the thickness of the surface layer in step (3) is 4-4.5mm, and the surfacing is from the edge to the center of the tube plate, and the surfacing mode is manual arc welding, φ4.0mm A102 electrode is used, welding current is 110-160A, welding voltage is 24-26V, welding speed is 10-16cm / min, and welding temperature is ≤150℃; the first tube plate and the second tube plate are subjected to stress relief heat treatment after surfacing, temperature is increased to 400℃ at a speed of 100-150℃ / h, then increased to 600-640℃ at a speed of 150-200℃ / h, kept for 200-220min, and decreased to 400℃ at a speed of 200-260℃ / h, and air-cooled below 400℃.

[0018] The transition layer and the corrosion-resistant layer are welded from inside to outside, while the surface layer is welded from outside to inside. Because the transition layer and the corrosion-resistant layer have relatively thick welds, the welding stress will be pushed outward when welded from inside to outside, and will not be concentrated; the surface layer has relatively thin welds, and the welding stress is relatively small, and will not be concentrated, so welding from outside to inside is adopted.

[0019] Preferably, the top of the corrosion-resistant layer in step (4) is flush with the upper surface of the tube sheet; the tube sheet is built up from the center to the edge by manual welding with a φ4.0mm A102 electrode, a welding current of 110-160A, a welding voltage of 24-26V, a welding speed of 10-16cm / min, and a welding temperature of ≤150℃; after the first and second tube sheets are built up, stress relief heat treatment is performed at a temperature rising rate of 100-150℃ / h to 400℃, then at a temperature rising rate of 150-200℃ / h to 600-640℃, and held for 200-220min, and then at a temperature falling rate of 200-260℃ / h to 400℃, and then air-cooled below 400℃.

[0020] The present application builds up a transition layer, a surface layer and a corrosion-resistant layer on the tube sheet in sequence, which can ensure full penetration of the built-up weld, and completely avoid defects such as slag inclusion, incomplete penetration and cracks in the built-up weld. The present application can refine the grains, make the stress distribution uniform, avoid large deformation of the tube sheet, enhance the strength of the tube sheet, and thus ensure the mechanical properties and processing properties of the tube sheet.

[0021] However, the number of built-up layers is not the more the better. When the number of built-up layers is too large, the grains of the corrosion-resistant layer will become large due to overburning, the stress distribution will be uneven, the tube sheet will have large deformation, the strength of the tube sheet will be reduced, the plasticity will be reduced, the impact value will not meet the requirements, and the tube sheet will suddenly break in use; in addition, the large grains will make it difficult to detect defects.

[0022] The surface layer acts as an isolation layer and a protective layer, can prevent the adverse effects of the base material on the weld metal, and thus ensure the performance and quality of the welded joint. The present application can avoid migration of carbon elements during welding, enhance the corrosion resistance of the tube sheet, and minimize the deformation of the tube sheet.

[0023] The surface layer acts as an isolation layer and a protective layer.

[0024] After the transition layer is welded, many grooves are formed on the welding surface. The present application uses the welding of the surface layer to fill the grooves with a smaller current in the opposite direction to the welding of the transition layer. This can maximize the prevention of migration of carbon elements and avoid the entry of carbon elements into the corrosion-resistant layer.

[0025] The current problems in building up a stainless steel corrosion-resistant layer on a tube sheet with a Q345R base layer include the following two aspects: first, the tube sheet has a large diameter, and the heat distribution is uneven during welding, which can easily cause the stress of the tube sheet to be too concentrated and the deformation of the tube sheet to be large; second, the corrosion-resistant layer is relatively thin, which can easily cause the thickness to be uneven during welding, and the thin places can be easily damaged during machining, and thus the corrosion resistance cannot be achieved. Generally, a jig is used to prevent deformation and change the welding method to solve the problems of too concentrated stress and large deformation of the tube sheet.

[0026] The beneficial effects of the present application are as follows:

[0027] The present application solves the problems of deformation of the tube plate, out-of-tolerance of the flatness of the tube plate, and uneven thickness of the corrosion-resistant layer after surfacing by sequentially surfacing the transition layer, the surface layer, and the corrosion-resistant layer on the surface of the tube plate.

[0028] The present application sequentially surfsaces the transition layer, the surface layer, and the corrosion-resistant layer on the tube plate, which can ensure full penetration of the surfacing weld, completely avoid defects such as slag inclusion, incomplete penetration, and cracks in the surfacing weld, refine the grains, make the stress distribution uniform, avoid large deformation of the tube plate, enhance the strength of the tube plate, and thus ensure the mechanical properties and processing performance of the tube plate.

[0029] In the present application, the transition layer and the corrosion-resistant layer are welded from the inside to the outside, while the surface layer is welded from the outside to the inside. A smaller current is used to fill the gullies formed by welding the transition layer in the opposite direction to welding the transition layer. This can maximize the prevention of the migration of carbon elements and avoid the entry of carbon elements into the corrosion-resistant layer. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 : The recess processing schematic diagram in step (1) of the present application;

[0031] Figure 2 : The schematic diagram of the tube plate, the arc-shaped plate clamp, and the lifting lug in step (2) of the present application;

[0032] Figure 3 : The top view of the arc-shaped plate clamp and the lifting lug in step (2) of the present application;

[0033] Figure 4 : The schematic diagram of the fixed tube plate in step (2) of the present application;

[0034] Figure 5 : The schematic diagram of the first tube plate surfacing the transition layer in step (3) of the present application;

[0035] Figure 6 : The schematic diagram of the second tube plate surfacing the transition layer in step (3) of the present application;

[0036] Figure 7 : The schematic diagram of the second tube plate surfacing the surface layer in step (4) of the present application;

[0037] Figure 8 : The schematic diagram of the first tube plate surfacing the surface layer in step (4) of the present application;

[0038] Figure 9 : The schematic diagram of the first tube plate surfacing the corrosion-resistant layer in step (5) of the present application;

[0039] Figure 10The schematic diagram of the second tube plate in step (5) of the application for welding the corrosion-resistant layer;

[0040] Figure 11 The schematic diagram of the tube plate after welding the corrosion-resistant layer of the application;

[0041] Figure 12 The temperature curve of the stress relief heat treatment in step (3) of the application;

[0042] Figure 13 The temperature curve of the stress relief heat treatment in step (4) of the application;

[0043] Figure 14 The temperature curve of the stress relief heat treatment in step (6) of the application;

[0044] The figure shows: 1. first tube plate, 2. second tube plate, 3. lug, 4. arc-shaped plate clamp, 5. bolt, 6. nut, 7. corrosion-resistant layer, 8. surface layer, 9. transition layer. DETAILED DESCRIPTION

[0045] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0046] As described in the background, based on this, the application provides a method for welding a large-diameter tube plate with a stainless steel corrosion-resistant layer, comprising the following steps:

[0047] (1) Pretreatment: grooves are machined on the welding surfaces of the first tube plate and the second tube plate, respectively, the bottom of the groove has a protrusion, the top of the protrusion is 9-11 mm away from the upper surface of the tube plate, and the edge of the groove is 12-14 mm away from the upper surface of the tube plate.

[0048] The first tube plate and the second tube plate are tightly attached back to back, arc-shaped plate clamps are welded on the top edges of the first tube plate and the second tube plate, respectively, lugs are welded at the midpoints of the sides of the arc-shaped plate clamps, and the lugs of the first tube plate and the second tube plate are connected by bolts and nuts; the arc-shaped plate clamps are obtained by cutting a circular ring into four arc-shaped pieces of the same size, a total of 8 arc-shaped plate clamps and 8 lugs are welded.

[0049] The welding mode of the arc-shaped plate clamp and the tube plate is fillet welding, and the welding is preheated to ≥100℃, a J507 welding rod with a diameter of 4.0 mm is used, the welding current is 140-180 A, the welding voltage is 24-26 V, the welding speed is 10-16 cm / min, the welding temperature is ≤250℃, and the welding length is at least 250 mm; the welding mode of the lug and the arc-shaped plate clamp is fillet welding, and the welding is preheated to ≥100℃, a J507 welding rod with a diameter of 4.0 mm is used, the welding current is 140-180 A, the welding voltage is 24-26 V, the welding speed is 10-16 cm / min, and the welding temperature is ≤250℃; and after welding, the hydrogen elimination heat treatment is performed at a temperature of 250-350℃ for 20-40 min.

[0050] (2) build-up welding of the transition layer: the transition layer is built up in the groove of the first tube plate, and then the transition layer is built up in the groove of the second tube plate;

[0051] The thickness of the transition layer is 3-4 mm, and the first tube plate and the second tube plate are preheated to ≥80℃ before welding; the welding is performed from the center of the tube plate to the edge, the welding mode is manual welding with a welding rod, a A302 welding rod with a diameter of 4.0 mm is used, the welding current is 110-160 A, the welding voltage is 24-26 V, the welding speed is 10-16 cm / min, and the welding temperature is ≤150℃; after the welding of the first tube plate and the second tube plate is completed, the hydrogen elimination heat treatment is performed at a temperature of 200-300℃ for 0.05-1 h; the stress relief heat treatment is performed at a speed of 100-150℃ / h to 400℃, then at a speed of 150-200℃ / h to 600-640℃, and the temperature is kept for 200-220 min, and then the temperature is decreased to 400℃ at a speed of 200-260℃ / h, and the temperature is air-cooled below 400℃.

[0052] (3) build-up welding of the surface layer: the surface layer is built up in the groove of the second tube plate, and then the surface layer is built up in the groove of the first tube plate;

[0053] The thickness of the surface layer is 4-4.5 mm, and the welding is performed from the edge of the tube plate to the center, the welding mode is manual welding with a welding rod, a A102 welding rod with a diameter of 4.0 mm is used, the welding current is 110-160 A, the welding voltage is 24-26 V, the welding speed is 10-16 cm / min, and the welding temperature is ≤150℃; after the welding of the first tube plate and the second tube plate is completed, the stress relief heat treatment is performed at a speed of 100-150℃ / h to 400℃, then at a speed of 150-200℃ / h to 600-640℃, and the temperature is kept for 200-220 min, and then the temperature is decreased to 400℃ at a speed of 200-260℃ / h, and the temperature is air-cooled below 400℃.

[0054] (4) build-up welding of the corrosion-resistant layer: the corrosion-resistant layer is built up in the groove of the first tube plate, and then the corrosion-resistant layer is built up in the groove of the second tube plate;

[0055] The top of the corrosion-resistant layer is flush with the upper surface of the tube sheet; welding is carried out from the center of the tube sheet to the edge, and the welding method is manual welding with φ4.0mm A102 welding rods, welding current of 110-160A, welding voltage of 24-26V, welding speed of 10-16cm / min, and welding temperature ≤150℃; after the first and second tube sheets are welded, stress relief heat treatment is carried out, heating to 400℃ at a rate of 100-150℃ / h, then heating to 600-640℃ at a rate of 150-200℃ / h, holding for 200-220min, cooling to 400℃ at a rate of 200-260℃ / h, and air cooling below 400℃.

[0056] (5) Post-processing: Remove the arc plate fixture and rough machine the surface of the tube plate.

[0057] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0058] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0059] Example

[0060] The tube sheet base material is Q345R normalized steel plate. The tube sheet requires a stainless steel anti-corrosion layer of S30408. The thickness of the first and second tube sheets is 110mm, and the diameter is 3000mm. The stainless steel anti-corrosion layer is welded according to the following steps:

[0061] (1) Pre-treatment: A groove for welding is machined on the weld overlay surface of the tube sheet. The bottom of the groove has a protrusion, the distance from the top of the protrusion to the upper surface of the tube sheet is 10mm, and the distance from the edge of the groove to the upper surface of the tube sheet is 13mm. Figure 1 As shown.

[0062] Two tube sheets are placed back-to-back and pressed tightly together. The ring is cut into four identical arc shapes to obtain arc-shaped plate clamps. Arc-shaped plate clamps are welded to the top edges of the two tube sheets, for a total of eight clamps. Lifting lugs are welded to the midpoints of the sides of the arc-shaped plate clamps, for a total of eight lugs. Figure 2 , 3 As shown; the lifting lugs of the first and second tube sheets are connected with bolts and nuts, thereby fixing the first and second tube sheets together, as follows. Figure 4 As shown.

[0063] The arc-shaped plate clamp and the tube sheet are welded by fillet weld. Preheating to 100℃ is used before welding. Use φ4.0mm J507 welding rod, welding current of 160A, welding voltage of 25V, welding speed of 15cm / min, welding temperature of 250℃, and welding length of 250mm. The lifting lug and the arc-shaped plate clamp are welded by fillet weld. Preheating to 100℃ is used before welding. Use φ4.0mm J507 welding rod, welding current of 160A, welding voltage of 25V, welding speed of 15cm / min, and welding temperature of 250℃.

[0064] After welding, a hydrogen removal heat treatment is performed at 300℃ for 30 minutes. The weld is then cleaned and ground, and subjected to metallographic inspection (MT) with a pass level of NB / T47013.4-2015, Grade I.

[0065] (2) Welding transition layer: Preheat the first tube sheet and the second tube sheet to 80°C, and weld a transition layer in the groove of the first tube sheet, such as... Figure 3 As shown, flip the tube sheet over and weld a transition layer inside the groove of the second tube sheet, as shown. Figure 4 As shown; the thickness of the transition layer is 3.5 mm;

[0066] Welding was performed from the inside out, with the center of the tube sheet as the center. The welding method was manual welding with φ4.0mm A302 welding rods, a welding current of 150A, a welding voltage of 25V, a welding speed of 15cm / min, and a welding temperature of 150℃. After the transition layer between the first and second tube sheets was welded, hydrogen removal heat treatment was performed at 250℃ for 1 hour. Then, stress relief heat treatment was performed in a furnace, with the temperature increased to 400℃ at a rate of 100℃ / h, then increased to 600℃ at a rate of 150℃ / h, held for 210 minutes, and then decreased to 400℃ at a rate of 230℃ / h. Air cooling was then performed below 400℃. The heat treatment curve is shown below. Figure 12 As shown; after the tube sheet is taken out of the furnace, it is slowly cooled to room temperature and the weld overlay surface is polished; non-destructive testing is performed, NB / T47013.5-2015,PT,100%, Class I, NB / T47013.3-2015,UT,100%, Class I.

[0067] (3) Weld overlay layer: A weld overlay layer is applied in the groove of the second tube sheet, such as... Figure 5 As shown, flip the tube sheet over and deposit a surface layer within the groove of the first tube sheet, as... Figure 6 As shown; the thickness of the surface layer is 4mm;

[0068] The surfacing is performed from the edge to the center of the tube sheet, the surfacing mode is manual welding with a welding rod, a A102 welding rod with a diameter of 4.0 mm is used, the welding current is 150 A, the welding voltage is 25 V, the welding speed is 15 cm / min, and the welding temperature is 150 ℃; after the surface welding of the first tube sheet and the second tube sheet is completed, stress relief heat treatment is performed in the furnace, the temperature is increased to 400 ℃ at a speed of 100 ℃ / h, then the temperature is increased to 600 ℃ at a speed of 150 ℃ / h, the temperature is kept for 210 min, the temperature is decreased to 400 ℃ at a speed of 230 ℃ / h, and the temperature is air-cooled below 400 ℃, and the heat treatment curve is as shown in Figure 13 After the tube sheet is taken out of the furnace, it is slowly cooled to room temperature, the surfacing surface is polished, nondestructive testing is performed, NB / T47013.5-2015, PT, 100%, I level, NB / T47013.3-2015, UT, 100%, I level.

[0069] (4) The corrosion-resistant layer is surfaced in the groove of the first tube sheet, as shown in Figure 7 , the first tube sheet is turned over, the corrosion-resistant layer is surfaced in the groove of the second tube sheet, as shown in Figure 8 , and the top of the corrosion-resistant layer is flush with the upper surface of the tube sheet.

[0070] The surfacing is performed from the inside to the outside with the center of the tube sheet as the center, the surfacing mode is manual welding with a welding rod, a A102 welding rod with a diameter of 4.0 mm is used, the welding current is 150 A, the welding voltage is 25 V, the welding speed is 15 cm / min, and the welding temperature is 150 ℃; stress relief heat treatment is performed in the furnace, the temperature is increased to 400 ℃ at a speed of 100 ℃ / h, then the temperature is increased to 600 ℃ at a speed of 150 ℃ / h, the temperature is kept for 210 min, the temperature is decreased to 400 ℃ at a speed of 230 ℃ / h, and the temperature is air-cooled below 400 ℃, and the heat treatment curve is as shown in Figure 14 After the tube sheet is taken out of the furnace, it is slowly cooled to room temperature, the surfacing surface is polished, nondestructive testing is performed, NB / T47013.5-2015, PT, 100%, I level, NB / T47013.3-2015, UT, 100%, I level.

[0071] (5) Post-processing: the arc-shaped plate clamp is removed from the tube sheet using a polishing machine, the surface of the tube sheet is roughly machined, and the thickness of the tube sheet is roughly machined to 100 mm, as shown in Figure 11 .

[0072] Comparative Example

[0073] The base layer material of the tube sheet is a Q345R normalized steel plate, the tube sheet requires surfacing of a corrosion-resistant layer S30408, the thicknesses of the first tube sheet and the second tube sheet are both 110 mm, the diameter is 3000 mm, and the stainless steel corrosion-resistant layer is surfaced according to the following steps:

[0074] (1) Pretreatment: grooves for surfacing are processed on the surfacing surface of the tube sheet, the bottom of the groove has a protrusion, the top of the protrusion of the groove is 10 mm away from the upper surface of the tube sheet, and the edge of the groove is 13 mm away from the upper surface of the tube sheet, as shown in Figure 1 .

[0075] The two tube sheets are tightly attached back to back, the circular ring is cut into four arc-shaped plates of the same size, and the arc-shaped plate clamps are obtained, the arc-shaped plate clamps are welded at the top edges of the two tube sheets respectively, a total of 8 arc-shaped plate clamps are welded, and lifting lugs are welded at the midpoints of the sides of the arc-shaped plate clamps, a total of 8 lifting lugs are welded, as shown in Figure 2 , 3 ; the lifting lugs of the first tube sheet and the second tube sheet are connected by bolts and nuts, so that the first tube sheet and the second tube sheet are fixed together, as shown in Figure 4 .

[0076] The welding mode of the arc-shaped plate clamp and the tube sheet is fillet welding, and the welding is preheated to 100°C before welding, a J507 welding rod with a diameter of 4.0 mm is used, the welding current is 160 A, the welding voltage is 25 V, the welding speed is 15 cm / min, the welding temperature is 250°C, and the welding length is 250 mm; the welding mode of the lifting lug and the arc-shaped plate clamp is fillet welding, and the welding is preheated to 100°C before welding, a J507 welding rod with a diameter of 4.0 mm is used, the welding current is 160 A, the welding voltage is 25 V, the welding speed is 15 cm / min, and the welding temperature is 250°C;

[0077] After welding, hydrogen removal heat treatment is performed at a temperature of 300°C for 30 min. The weld is cleaned and polished, and MT inspection is performed, and the qualified level is NB / T47013.4-2015, Grade I.

[0078] (2) Surfacing transition layer: the first tube sheet and the second tube sheet are preheated to 80°C, the transition layer is surfaced in the groove of the first tube sheet, and the transition layer is surfaced in the groove of the second tube sheet by turning over; the thickness of the transition layer is 3.5 mm;

[0079] The transition layer is surfaced from the inside to the outside with the center of the tube sheet as the center, the surfacing mode is manual welding with a welding rod, a A302 welding rod with a diameter of 4.0 mm is used, the welding current is 150 A, the welding voltage is 25 V, the welding speed is 15 cm / min, and the welding temperature is 150°C; after the transition layer of the first tube sheet and the second tube sheet is welded, hydrogen removal heat treatment is performed at a temperature of 250°C for 1 h; then stress relief heat treatment is performed in the furnace, the temperature is increased to 400°C at a speed of 100°C / h, then the temperature is increased to 600°C at a speed of 150°C / h, the temperature is kept for 210 min, the temperature is decreased to 400°C at a speed of 230°C / h, and the temperature is air-cooled below 400°C, and the heat treatment curve is as shown in Figure 12After the tube sheet is taken out of the furnace, it is slowly cooled to room temperature, the surfacing surface is polished, nondestructive testing is performed, NB / T47013.5-2015, PT, 100%, Class I, NB / T47013.3-2015, UT, 100%, Class I.

[0080] (3) Surfacing a corrosion-resistant layer in the groove of the first tube sheet, turning over, and surfacing a corrosion-resistant layer in the groove of the second tube sheet; the top of the corrosion-resistant layer is flush with the upper surface of the tube sheet;

[0081] The surfacing is performed from inside to outside with the center of the tube sheet as the center, the surfacing mode is manual welding with a welding rod, a φ4.0mm A102 welding rod is used, the welding current is 150A, the welding voltage is 25V, the welding speed is 15cm / min, and the welding temperature is 150℃; stress relief heat treatment is performed by entering the furnace, the temperature is raised to 400℃ at a speed of 100℃ / h, then the temperature is raised to 600℃ at a speed of 150℃ / h, the temperature is kept for 210min, the temperature is reduced to 400℃ at a speed of 230℃ / h, and the temperature is air-cooled below 400℃, and the heat treatment curve is as shown in Figure 14 After the tube sheet is taken out of the furnace, it is slowly cooled to room temperature, the surfacing surface is polished, nondestructive testing is performed, NB / T47013.5-2015, PT, 100%, Class I, NB / T47013.3-2015, UT, 100%, Class I.

[0082] (4) Post-processing: the arc-shaped plate clamp is removed from the tube sheet using a polishing machine, the surface of the tube sheet is roughly turned, and the thickness of the tube sheet is roughly turned to 100mm.

[0083] The comparative example does not have the step of surfacing a surface layer compared with the example.

[0084] Experimental example

[0085] The flatness, corrosion resistance,

[0086] The test is performed according to B method in GB / T 4334-2008 “Stainless Steel Sulfuric Acid-Copper Sulfate Corrosion Test Method”.

[0087] Tolerance in flatness / mm Corrosion rate / g.m -2 ·h -1 ]]> Deformation phenomenon Example 1 0.0002 No Comparative example 2.3 0.0104 Yes

[0088] The present application solves the problems of deformation of the tube sheet after surfacing, out-of-tolerance of the flatness of the tube sheet, and uneven thickness of the corrosion-resistant layer after surfacing by sequentially surfacing a transition layer, a surface layer, and a corrosion-resistant layer on the surface of the tube sheet.

[0089] The present application sequentially surfacing a transition layer, a surface layer, and a corrosion-resistant layer on the tube sheet, which can ensure full penetration of the surfacing weld, completely avoid defects such as slag inclusion, incomplete penetration, and cracks of the surfacing weld, refine the grains, make the stress distribution uniform, avoid large deformation of the tube sheet, enhance the strength of the tube sheet, and thus ensure the mechanical properties and processing performance of the tube sheet.

[0090] The above descriptions are only the preferred embodiment of the present application, but not for limiting the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for overlaying a stainless steel anti-corrosion layer onto a large-diameter tube sheet, characterized in that, Includes the following steps: (1) Pretreatment: Grooves are machined on the weld overlay surfaces of the first tube sheet and the second tube sheet respectively; the first tube sheet and the second tube sheet are placed back to back and tightly pressed together, and the first tube sheet and the second tube sheet are fixed together using an arc plate clamp; (2) Welding transition layer: Welding transition layer in the groove of the first tube sheet, flipping it over, and welding transition layer in the groove of the second tube sheet. (3) Weld overlay layer: Weld overlay layer in the groove of the second tube sheet, flip it over, and weld overlay layer in the groove of the first tube sheet. (4) Welding corrosion resistant layer: Welding corrosion resistant layer in the groove of the first tube sheet, flipping it over, and welding corrosion resistant layer in the groove of the second tube sheet. (5) Post-processing: Remove the arc plate fixture and rough machine the tube plate surface; In step (2), the thickness of the transition layer is 3-4 mm. Before welding, the first tube sheet and the second tube sheet are preheated to ≥80℃. Welding is performed from the center of the tube sheet to the edge. The welding method is manual welding with welding rods. A302 welding rods with a diameter of φ4.0 mm are used. The welding current is 110-160A, the welding voltage is 24-26V, the welding speed is 10-16cm / min, and the welding temperature is ≤150℃. After the first tube sheet and the second tube sheet are welded, hydrogen removal heat treatment is performed at a temperature of 200-300℃ for 0.05-1h. Stress relief heat treatment is performed by raising the temperature to 400℃ at a rate of 100-150℃ / h, then raising the temperature to 600-640℃ at a rate of 150-200℃ / h, holding for 200-220min, and cooling down to 400℃ at a rate of 200-260℃ / h. Air cooling is performed below 400℃. In step (3), the thickness of the surface layer is 4-4.5mm. Welding is carried out from the edge of the tube sheet to the center. The welding method is manual welding with welding rods. A102 welding rods with a diameter of φ4.0mm are used. The welding current is 110-160A, the welding voltage is 24-26V, the welding speed is 10-16cm / min, and the welding temperature is ≤150℃. After the first tube sheet and the second tube sheet are welded, stress relief heat treatment is carried out. The temperature is raised to 400℃ at a rate of 100-150℃ / h, and then raised to 600-640℃ at a rate of 150-200℃ / h. The temperature is held for 200-220min, and then cooled to 400℃ at a rate of 200-260℃ / h. The temperature is then air-cooled below 400℃.

2. The method for overlaying a stainless steel anti-corrosion layer onto a tube sheet according to claim 1, characterized in that, The bottom of the groove in step (1) has a protrusion, the distance from the top of the protrusion to the upper surface of the tube sheet is 9-11 mm, and the distance from the edge of the groove to the upper surface of the tube sheet is 12-14 mm.

3. The method for overlaying a stainless steel anti-corrosion layer onto a tube sheet according to claim 1, characterized in that, In step (1), arc-shaped plate clamps are welded to the top edges of the first tube sheet and the second tube sheet respectively, and lifting lugs are welded at the midpoint of the side of the arc-shaped plate clamps. The lifting lugs of the first tube sheet and the second tube sheet are connected with bolts and nuts. The arc-shaped plate clamps are obtained by cutting a ring into four arcs of the same size. A total of 8 arc-shaped plate clamps and 8 lifting lugs are welded.

4. The method for overlaying a stainless steel anti-corrosion layer onto a tube sheet according to claim 3, characterized in that, In step (1), the arc plate clamp and the tube sheet are welded by fillet weld. Before welding, the temperature is preheated to ≥100℃. Use φ4.0mm J507 welding rod, welding current is 140-180A, welding voltage is 24-26V, welding speed is 10-16cm / min, welding temperature is ≤250℃, and welding length is at least 250mm. The lifting lug and the arc plate clamp are welded by fillet weld. Before welding, the temperature is preheated to ≥100℃. Use φ4.0mm J507 welding rod, welding current is 140-180A, welding voltage is 24-26V, welding speed is 10-16cm / min, and welding temperature is ≤250℃. After welding, hydrogen removal heat treatment is performed at a temperature of 250-350℃ for 20-40min.

5. The method for overlaying a stainless steel anti-corrosion layer onto a tube sheet according to claim 1, characterized in that, In step (4), the top of the corrosion-resistant layer is flush with the upper surface of the tube sheet; welding is carried out from the center of the tube sheet to the edge. The welding method is manual welding with welding rods. A102 welding rods with a diameter of φ4.0mm are used. The welding current is 110-160A, the welding voltage is 24-26V, the welding speed is 10-16cm / min, and the welding temperature is ≤150℃. After the first tube sheet and the second tube sheet are welded, stress relief heat treatment is carried out. The temperature is raised to 400℃ at a rate of 100-150℃ / h, and then raised to 600-640℃ at a rate of 150-200℃ / h. The temperature is held for 200-220min, and then cooled to 400℃ at a rate of 200-260℃ / h. The temperature is then air-cooled below 400℃.

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