Preparation method for titanium-steel composite welded pipe

Abstract

The invention discloses a preparation method, particularly discloses a preparation method for a titanium-steel composite welded pipe, and belongs to the technical field of titanium composite steel pipe production and manufacturing processes. According to the preparation method for the titanium-steel composite welded pipe, the operation difficulty is remarkably reduced, and the welding quality can be effectively guaranteed. According to the preparation method, the butt-welded titanium-steel composite welded pipe with the mechanical property and the corrosion resistance meeting the specified requirements is obtained through the steps of precise blanking, precise forming and assembling, controllable welding and pressure shaping and titanium covering layer assembling and welding, a titanium covering layer within the specified width near a welding groove is removed while precise blanking is conducted, during precise forming and assembling, precise butt joint is achieved in the process that a titanium steel composite plate is rolled into a round pipe through a concave-convex die bending method, and precise forming and assembling work is completed; the round pipe steel base body layer is welded firstly, and then pressure shaping is conducted on weld joints in the pipe.

Description

Technical Field

[0001] The invention relates to a preparation method, in particular to a preparation method for a titanium-steel composite welded pipe, and belongs to the technical field of titanium composite steel pipe production and manufacturing process. Background Art

[0002] Titanium or titanium alloys have excellent corrosion resistance in seawater and common acidic and alkaline media, and are therefore often used in important occasions in the fields of chemical industry, energy, marine engineering, etc. However, titanium and titanium alloys are expensive, usually dozens of times the price of steel. In order to reduce costs, titanium alloys are often used in the form of titanium / steel composite plates, that is, titanium alloy is used as the composite layer in contact with the medium to provide the corrosion resistance of the composite material, while steel with excellent mechanical properties is used as the matrix material to provide the mechanical properties of the composite material.

[0003] The most promising application areas for titanium steel composite plate materials are pipes for oil and gas transmission, chemical solutions or seawater transmission. As mentioned above, the welded pipes made of titanium steel composite plates with steel outer layer and titanium inner wall have both pressure resistance and excellent corrosion resistance, which can prevent the failure of the pipeline due to corrosion of the medium in the pipe during long-term service. However, at present, although titanium steel composite plate materials have been applied in various industries such as coking, chemical industry, and marine engineering, they are still limited to the preparation of large-diameter pipes and containers, and are difficult to promote in huge market areas such as oil and gas pipelines and seawater pipelines. The reason is that the preparation of titanium steel composite welded pipes is difficult, and the most critical problem is welding.

[0004] The use of composite plates to prepare welded pipes involves welding of longitudinal weld plates. The difficulty lies in that if iron and titanium are mixed during welding, a brittle intermetallic compound phase will be formed, resulting in cracking while welding and difficulty in forming the weld; even a small amount of mixed melting will damage the mechanical properties and corrosion resistance of the joint. Therefore, when welding steel, the titanium layer near the weld must be removed, otherwise the titanium element will enter the weld, causing the weld to become brittle; when welding the titanium layer, iron must be prevented from entering the weld, otherwise the corrosion resistance of the weld will be seriously reduced.

[0005] At present, the cover plate lap welding process is usually used in industrial production to weld titanium steel composite plates: before coiling the pipe, in the process of cutting the titanium steel composite plate, first remove the titanium coating near the two sides; after coiling the pipe, weld the steel butt layer; then, use the titanium strip as a cover plate to cover the top of the steel weld, and use the lap weld method to complete the welding of the two welds of the titanium strip cover plate and the titanium layer of the composite plate. There are major disadvantages in cover plate welding: the cover plate forms a bulge on the inner wall of the pipe, and its existence will cause the weldment, especially for the most commonly used small-diameter pipes, to reduce the cross-sectional area of ​​the medium passing through, resulting in the pipe fittings not meeting the industry standard application requirements. In particular, pipe fittings for oil and gas transmission require inspection by ball test, and welded pipes prepared by cover plate lap welding are difficult to pass the inspection.

[0006] For this kind of titanium-steel composite welded pipe that requires ball test inspection, butt welding must be used for preparation. Various butt welding methods have been studied, such as the transition layer welding method, that is, first welding the steel butt layer or the titanium butt layer, then welding, depositing or cold spraying V, Nb, Cu and other Cu welding wires, nickel welding wires, etc. at the titanium-steel interface, and finally welding the titanium butt layer or the steel butt layer to avoid direct melting of titanium and steel. In this welding method, the V and Nb used are expensive, and the brittle layer cannot be completely avoided. The transition layer welding operation is difficult. If the process is improper or unstable, it is very likely to cause the mechanical properties and corrosion resistance of the joint to be damaged at the same time. The titanium-steel composite plate butt welding process using the transition layer has not yet been widely used. Other butt welding methods, including direct butt welding, flat plate butt welding, and bent plate butt welding, use the careful design of the groove and the precise control of the welding process to avoid welding through the titanium coating and to weld through as much as possible. The operation is difficult and the welding quality is extremely unstable. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a preparation method for titanium-steel composite welded pipe, which has significantly reduced operation difficulty and can effectively ensure welding quality.

[0008] The technical solution adopted to solve the above technical problems is: a method for preparing titanium-steel composite welded pipes, wherein the preparation method obtains titanium-steel composite welded pipes with qualified mechanical properties and corrosion resistance and capable of passing ball inspection through the steps of precise blanking, precise forming and assembly, steel matrix welding and weld shaping, and titanium cladding assembly and welding.

[0009] Among them, the titanium coating within the specified width near the welding groove is removed while accurately cutting the material.

[0010] During precision forming and assembly, the concave and convex die bending method is used to roll the titanium steel composite plate into a round tube to achieve precise docking and complete the precision forming and assembly work.

[0011] When welding the steel matrix and shaping the weld, the steel matrix layer of the round tube is welded first and then the weld inside the tube is remelted and shaped.

[0012] Furthermore, during precise cutting, the titanium steel composite plate is first cut into a rough slab of a specified width by laser cutting, water jet cutting, plasma cutting or wire cutting, and then milling or planing and finally grinding are used to obtain a precise slab with a straight side surface and a plate width of W = 3.14D-δ+δ, wherein D is the outer diameter of the welded pipe, δ is the wall thickness of the pipe, and the plate width W has a tolerance of ±0.2 mm.

[0013] The preferred embodiment of the above scheme is that the rough slab is obtained by cutting by laser cutting or water jet cutting, and the finishing and trimming is carried out by milling.

[0014] Furthermore, when removing the titanium coating, after fine machining and trimming, the titanium coating is first cut off using a precision cutting machine with a diamond cutting blade as a cutting tool, and then the titanium coating is torn off from the steel substrate layer to complete the removal of the titanium coating near the welding groove. The width w of the removed titanium coating is 5 to 30 ± 0.2 mm on a single side, and the cutting depth during cutting is the thickness of the titanium coating δ-0.1 to 0.2 mm.

[0015] The preferred method of the above scheme is that during precision forming and assembly by the concave and convex die bending method, before bending, a steel needle is used to mark the side edge as a reference, and a positioning line is drawn every 5° corresponding to the cross-sectional circle of the pipe. The parallelism between the positioning line and the side edge and between the positioning lines is ±0.2mm; during bending, the center of the bottom of the punch is aligned with the positioning line.

[0016] Furthermore, the titanium steel composite plate is formed by bending and rolling in the concave and convex dies and then seamed and spot welded in the pipe seaming machine. The specific process is as follows:

[0017] First, use anhydrous ethanol or acetone to clean the oil stains on the surface near the weld, transfer the rolled tube blank into the mold of the seaming machine, and use the hydraulic mechanism to seam together; when seaming, the two sides of the weld are completely fitted, the gap is between 0-0.5mm, and the misalignment does not exceed 0.5mm; then use the two-protection welding method for spot welding, and the distance between two adjacent welding points is 200±5mm.

[0018] The preferred embodiment of the above scheme is that after the spot welding is completed, the plasma wire-filling welding method is used to carry out the butt welding of the steel matrix layer inside the pipe, and the welding parameters should ensure full penetration; the wire feeding parameters ensure that the height of the top of the weld is 0 to 3 mm above the outer surface of the pipe; the covering layer material of the titanium cladding group is annealed TA1 or TA2 pure titanium strip, and the width of the annealed TA1 or TA2 pure titanium strip is 3.14wD-2δ / Wk, where the k value is 0.1-0.5mm, and the strip width tolerance is 0.2mm; the thickness is 0.3-0.6mm.

[0019] Furthermore, after the steel matrix layer in the pipe is welded, the argon arc welding remelting method is used to shape the excess height at the bottom of the weld. The specific process is as follows:

[0020] The argon arc welding gun driven by the linear guide slide module is used to remelt the excess height of the weld of the steel matrix layer in the pipe to ensure that the excess height of the weld after remelting is less than 0.5mm.

[0021] The preferred method of the above scheme is that when the titanium cladding in the tube is paired, at least two layers of annealed TA1 or TA2 pure titanium strips are arranged in an overlapping manner above the weld of the steel matrix layer in the tube, and both sides of each layer of the overlapping annealed TA1 or TA2 pure titanium strips are aligned with the existing titanium cladding in the tube, and then each layer of the annealed TA1 or TA2 pure titanium strips is pressed with a copper bar so that the compacted thickness of each layer of the annealed TA1 or TA2 pure titanium strips is greater than the thickness of the existing titanium cladding, and then each layer of the annealed TA1 or TA2 pure titanium strips is spot welded to the existing titanium cladding on the corresponding side to firmly complete the pairing of the titanium cladding in the tube.

[0022] Among them, spot welding is carried out using a argon arc welding gun driven by a linear guide slide module. The spot welding sequence is to first spot weld the longitudinal midpoint of the weld, then spot weld the longitudinal 1 / 4 and 3 / 4 lengths of the weld and both ends, then continue spot welding at intervals of no more than 300mm, and finally drive the argon arc welding gun to complete the welding of the entire weld.

[0023] Furthermore, the spot welding process parameters are 60-100A, the spot welding time is 0.3-0.8s, and the shielding gas flow rate is 5-10L / min; the full weld welding process parameters are tungsten needle diameter 2.0-4.0mm, tungsten needle tip angle 30-45°, tungsten needle tip aligned with the side of the groove, tungsten needle tip height 1-3mm, welding current 150-250A, welding wire diameter 1.0-1.6mm, welding speed 2-5mm / s, wire feeding speed 10-25mm / s, welding gun shielding gas flow rate 5-10L / min, the drag hood protection range is at least 50mm in length directly behind the welding gun and 10mm in width on both sides of the weld, and the drag hood gas flow rate is 20-30L / min.

[0024] The beneficial effects of the present invention are as follows: the technical solution provided in the present application obtains a titanium-steel composite welded pipe with qualified mechanical properties and corrosion resistance and can pass the ball inspection through the steps of precise cutting, precise forming and assembly, steel matrix welding and weld shaping, and titanium coating assembly and welding, and removes the titanium coating within a specified width near the welding groove while precisely cutting the material, and then leaves a titanium coating removal groove of a specified width during precise forming and assembly, and then covers the titanium coating in the groove and welds it. In this way, since the preparation method of the present application not only realizes the independent welding of the steel base layer and the titanium coating, but also realizes the titanium coating inside the tube by docking and welding the titanium coating, it solves the technical problem that the flow area is reduced when overlapping is used in the prior art, and the ball detection cannot be passed. Since the technical scheme of the present application first welds the steel base layer independently, and then assembles and welds the titanium coating inside the tube, the welding of the two is carried out independently, thereby effectively avoiding titanium mixing into the steel weld and iron mixing into the titanium weld, which not only significantly reduces the difficulty of the operation, but also effectively guarantees the welding quality, and easily obtains welds with stable welding quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the automatic welding device inside the pipe involved in the preparation method of the titanium-steel composite welded pipe of the present invention;

[0026] Figure 2 for Figure 1 Side sectional view of .

[0027] Marked in the figure are: titanium coating 1, steel base layer 2, annealed TA1 or TA2 pure titanium strip 3, linear guide slide module 4, copper bar 5, argon arc welding gun 6, steel base layer weld 7. DETAILED DESCRIPTION

[0028] like Figure 1 , Figure 2 The present invention provides a method for preparing titanium-steel composite welded pipes with significantly reduced difficulty and effective welding quality. The preparation method obtains a butt-welded titanium-steel composite welded pipe with qualified mechanical properties and corrosion resistance and can pass the ball inspection through the steps of precise blanking, precise forming and assembly, steel matrix welding and weld shaping, and titanium coating assembly and welding. The titanium coating 1 within a specified width near the welding groove is removed while the material is precisely blanked. During precise forming and assembly, the titanium-steel composite plate is rolled into a round tube by a concave-convex die bending method to achieve precise docking and complete precise forming and assembly. During steel matrix welding and weld shaping, the steel matrix layer 2 of the round tube is first welded and then the weld in the tube is remelted and shaped. The technical solution provided in the present application obtains a butt-welded titanium-steel composite welded pipe whose mechanical properties and corrosion resistance meet the specified requirements through the steps of precise cutting, precise forming and assembly, steel matrix welding and remelting shaping, and titanium coating assembly and welding. The titanium coating within a specified width near the welding groove is removed during precise cutting, and then a titanium coating removal groove of a specified width is reserved during precise forming and assembly, and then the titanium coating is covered in the groove and welded. In this way, since the preparation method of the present application not only realizes the independent welding of the steel base layer and the titanium coating, but also realizes the titanium coating inside the tube by docking and welding the titanium coating, it solves the technical problem that the flow area is reduced when overlapping is used in the prior art, and the ball detection cannot be passed. Since the technical scheme of the present application first welds the steel base layer independently, and then assembles and welds the titanium coating inside the tube, the welding of the two is carried out independently, thereby effectively avoiding titanium mixing into the steel weld and iron mixing into the titanium weld, thereby significantly reducing the difficulty of the operation, and at the same time effectively ensuring the welding quality, and easily obtaining welds with stable welding quality.

[0029] Accordingly, combined with the actual situation of the production site, the present application first uses laser cutting, water jet cutting, plasma cutting or wire cutting to cut the titanium steel composite plate into a rough slab of a specified width during precise cutting, and then uses milling or planing and finally grinding to obtain a precise slab with a straight side surface and a plate width of W = 3.14D-δ + δ, where D is the outer diameter of the welded pipe, δ is the wall thickness of the pipe, and the plate width W tolerance is ±0.2mm. The preferred method is that the rough slab is obtained by cutting by laser cutting or water jet cutting, and the finishing trimming is milling. When removing the titanium coating 1, after finishing and trimming, the titanium coating 1 is first cut off by a precision cutting machine using a diamond cutting blade as a cutting tool, and then the titanium coating 1 is torn off from the steel substrate layer 2 to complete the removal of the titanium coating 1 near the welding groove. The width of the removed titanium coating 1 is 5 to 30 ± 0.2 mm on a single side, and the cutting depth during cutting is the thickness of the titanium coating 1 δ-0.1 to 0.2 mm.

[0030] Furthermore, when the present application adopts the concave-convex die bending method for precision forming and assembly, before bending, a steel needle is used to mark the side as a reference, and a positioning line is drawn every 5° corresponding to the cross-section circle of the pipe. The parallelism between the positioning line and the side, and between the positioning lines are both ±0.2mm; when bending, the center of the bottom of the punch is aligned with the positioning line. After the titanium-steel composite plate is rolled and formed in the concave-convex die, it is then seamed and spot welded in a pipe seaming machine. The specific process is that first, anhydrous ethanol or acetone is used to clean the oil stains on the surface near the weld, and the rolled tube blank is transferred into the seaming machine mold, and the hydraulic mechanism is used for seaming; when seaming, the two sides of the weld are completely fitted, the gap is between 0-0.5mm, and the misalignment does not exceed 0.5mm; then the two-protection welding method is used for spot welding, and the spacing between two adjacent welding points is 200±5mm. After the spot welding is completed, the plasma wire-filling welding method is used to butt weld the steel matrix layer 2 in the pipe. The welding parameters should ensure full penetration; the wire feeding parameters ensure that the height of the top of the weld is 0 to 3 mm above the outer surface of the pipe; the covering layer material of the titanium cladding 1 group is annealed TA1 or TA2 pure titanium strip 3, the width of the annealed TA1 or TA2 pure titanium strip 3 is 3.14wD-2δ / Wk, where the k value is 0.1-0.5mm, the strip width tolerance is 0.2mm; the thickness is 0.3-0.6mm. More specifically, after the welding of the steel matrix layer 2 in the pipe is completed, the argon arc welding remelting method is used to shape the excess height of the bottom of the weld. The specific process is to use the argon arc welding gun driven by the linear guide slide module 4 to remelt the excess height of the weld of the steel matrix layer 2 in the pipe, and ensure that the excess height of the weld after remelting is less than 0.5mm.

[0031] As a critical step in the preparation method of the present application, when the titanium coating 1 in the tube is assembled, at least two layers of annealed TA1 or TA2 pure titanium strips 3 are overlapped and arranged above the weld bead 7 of the steel matrix layer in the tube, and the two sides of each overlapping layer of annealed TA1 or TA2 pure titanium strips 3 are aligned with the existing titanium coating in the tube, and then the copper strips 5 are used to press each layer of annealed TA1 or TA2 pure titanium strips 3, so that the compacted thickness of each layer of annealed TA1 or TA2 pure titanium strips 3 is The thickness of the titanium coating 1 is greater than that of the existing titanium coating 1, and then each layer of annealed TA1 or TA2 pure titanium strip 3 is spot welded to the existing titanium coating 1 on the corresponding side to firmly complete the assembly of the titanium coating in the tube, wherein the spot welding is carried out by using a linear guide slide module 4 to drive an argon arc welding gun 6, and the spot welding sequence is to first spot weld the longitudinal midpoint of the weld, then spot weld the longitudinal 1 / 4 and 3 / 4 lengths of the weld and both ends, and then continuously spot weld at intervals not exceeding 300 mm, and finally drive the argon arc welding gun 6 to complete the welding of the entire weld. Correspondingly, the spot welding process parameters are 60-100A, the spot welding time is 0.3-0.8s, and the shielding gas flow rate is 5-10L / min; the full weld welding process parameters are as follows: tungsten needle diameter 2.0-4.0mm, tungsten needle tip angle 30-45°, tungsten needle tip aligned with the side of the groove, tungsten needle tip height 1-3mm, welding current 150-250A, welding wire diameter 1.0-1.6mm, welding speed 2-5mm / s, wire feeding speed 10-25mm / s, welding gun shielding gas flow rate 5-10L / min, the drag hood protection range is at least 50mm in length directly behind the welding gun and 10mm in width on both sides of the weld, and the drag hood gas flow rate is 20-30L / min.

[0032] In summary, the principle of the preparation method of the present application is to use the precise design of the cutting procedure of titanium steel composite plate and titanium strip, the rolling tube and the steel layer welding procedure, and the use of the characteristics of pure titanium thin strips being soft and easy to deform, and use multi-layer titanium strips to fill the grooves in the tube, which provides conditions for the precise assembly and welding of the titanium strips and the titanium cladding butt welds on the inner wall of the welded tube. After the composite plate is cut, the dimensional accuracy is high, and the size of the welded tube is precisely controllable; based on the side of the plate, the precision cutting, after removing the titanium cladding for the subsequent welded tube, the groove width is precisely controllable; the precise positioning during the tube forming process can prevent the weld from being skewed; after the two-protection welding method is spot-welded, the steel butt layer is welded by plasma welding, and the weld is welded through once to prevent deformation, misalignment, and incomplete penetration defects. The back excess height of the butt weld of the steel is remelted by argon arc welding to prevent the excessive excess height from hindering the titanium strip. The titanium strip is pressed by a copper strip, and its fast thermal conductivity can be used to prevent the thin titanium strip from curling after being heated by the arc. The linear guide slide module and the argon arc welding gun are small in size and can realize arc spot welding and welding in small-diameter pipes; argon arc welding is a precision welding process that can ensure that the weld depth is controllable, and it will not burn through the steel butt layer, and can ensure that when the thickness of the titanium coating is 1-3mm, the weld depth reaches 80-90% of the thickness of the titanium coating. Under the condition of proper inert gas protection measures, the titanium molten pool has good fluidity, the weld surface is smooth, and the excess height is small. By adopting the method provided by the present invention, a titanium-steel composite welded pipe with no obvious protrusions on the inner wall of the pipe, qualified size and shape, and excellent mechanical properties and corrosion resistance can be obtained.

[0033] The technical solution of the present application is further described below through specific embodiments:

[0034] The present invention provides a method for preparing a titanium-steel composite welded pipe. The procedure of the welded pipe preparation method comprises the following steps:

[0035] (1) Material preparation: Cutting and finishing of plates. Remove a certain width of titanium coating near the groove. Prepare thin titanium strips for butt welding. (2) Rolling: Roll the plate into a tube. (3) Seam joining and welding: Butt, spot weld and fix the longitudinal seam of the tube in the mold to complete the steel layer butt weld. (4) Finishing of the weld inside the tube: Remove the excess height on the back of the steel layer weld inside the tube. (5) Titanium layer butt welding: Put the titanium strip into the groove on the inner wall of the tube, and butt its two sides with the titanium coating of the plate to complete the titanium layer welding inside the tube.

[0036] The procedure of the welded pipe preparation method, in step (1), the plate blanking method is laser cutting, or water jet cutting, or plasma cutting, or wire cutting, and then the side edge is finished by milling, planing and grinding to make the side edge surface straight and ensure its width W = 3.14 (D-δ) + δ, where D is the outer diameter of the welded pipe, δ is the wall thickness of the pipe, and the tolerance is 0.2 mm. Preferably, the composite plate for pipe making is prepared by laser cutting or water jet cutting, followed by milling and finally grinding.

[0037] The procedure of the welded pipe preparation method, in step (1), the width w of the titanium coating removed near the groove is 5-30 mm, with a tolerance of 0.2 mm. The method for removing the titanium coating is to cut the titanium coating with a precision cutting machine using a diamond cutting blade under water cooling, with the cutting depth being the thickness of the titanium coating minus 0.1-0.2 mm, and after cutting, tear the titanium coating off the steel plate.

[0038] The procedure of the welded pipe preparation method, in step (1), the titanium strip for butt welding is annealed TA1 or TA2 pure titanium strip, with a width of 3.14w(D-2δ) / Wk, wherein the k value is 0.1-0.5mm, the tolerance is 0.2mm, and the thickness is 0.3-0.6mm. Laser cutting is adopted.

[0039] In the procedure of the welded pipe preparation method, in step (2), the pipe rolling method is a bending method using a concave and convex die. Before bending, a steel needle is used to mark the side edge as a reference, and a positioning line is drawn every 5° corresponding to the cross-section circle of the pipe. The parallelism between the positioning line and the side edge and the positioning line is 0.2 mm. During bending, the center of the bottom of the convex die is aligned with the positioning line.

[0040] The procedure of the welded pipe preparation method, in step (3), seaming is performed in a pipe seaming machine. First, use anhydrous ethanol or acetone to clean the surface oil near the seam. Transfer the pipe into the seaming machine mold and use a hydraulic mechanism to seam the pipe. After seaming, the two sides of the seam are completely fitted together, with no obvious gap and no obvious misalignment. Spot welding is performed using the two-protection welding method. One welding point is made every 200mm. After spot welding is completed, the steel butt layer is welded using a plasma wire filling welding method. The welding parameters should ensure full penetration; the wire feeding parameters should ensure that the weld top excess height, that is, the height of the weld above the outer surface of the pipe is 0-3mm.

[0041] In the procedure of the welded pipe preparation method, in step (4), the method for removing the excess height at the bottom of the weld bead of the steel layer in the pipe is argon arc welding remelting. The argon arc welding gun driven by the linear guide slide module is used to remelt the excess height of the weld bead of the steel layer in the pipe. The remaining height of the remelted weld bead is less than 0.5 mm.

[0042] The procedure of the welded pipe preparation method, in step (5), the butt welding method of the titanium layer in the pipe is to stack multiple thin titanium strips into the groove of the inner wall of the pipe, the total thickness of which is ≥ the thickness of the titanium coating, and the two sides of the strips are aligned with the two sides of the groove of the inner wall of the pipe, and the gaps on both sides are of equal size, and then a copper strip is pressed on the thin titanium strip to fix it. The width of the copper strip ensures that the distance between its side and the weld seam on both sides is 5-10mm. The linear guide slide module is placed above the copper strip, and the argon arc welding gun is moved by the module to spot weld and fix the multi-layer thin titanium strips to the titanium coating. The spot welding sequence is to first spot weld the longitudinal midpoint of the weld, then spot weld the longitudinal 1 / 4 and 3 / 4 length of the weld, then spot weld the two ends, and then continuously spot weld at intervals of 300mm. Then, the argon arc welding gun is moved by the module to complete the welding of the entire weld. The spot welding process parameters are 60-100A, spot welding time 0.3-0.8s, and shielding gas flow rate 5-10L / min. Full weld welding process parameters: tungsten needle diameter 2.0-4.0mm, tungsten needle tip angle 30-45°, tungsten needle tip aligned with the side of the groove, tungsten needle tip height 1-3mm, welding current 150-250A, welding wire diameter 1.0-1.6mm, welding speed 2-5mm / s, wire feeding speed 10-25mm / s, welding gun shielding gas flow 5-10L / min, the drag hood protection range is at least 50mm in length behind the welding gun and 10mm in width on both sides of the weld, and the drag hood gas flow is 20-30L / min.

[0043] Embodiment 1

[0044] The titanium-steel composite welded pipe preparation method proposed in the present invention is used to prepare a titanium-steel composite pipe with an outer diameter of 273 mm and a wall thickness of 9.2 mm (the steel layer is Q235 carbon steel with a thickness of 8 mm, and the titanium coating is TA1 pure titanium with a thickness of 1.2 mm). The method comprises the following steps: (1) Material preparation: cutting and finishing of the plate. Remove the titanium coating of a certain width near the groove. Prepare thin titanium strips for butt welding. (2) Tube rolling: roll the plate into a tube. (3) Seam joining and welding: butt the longitudinal seams of the tube in the mold, spot weld and fix them, and weld them to complete the butt weld of the steel layer. (4) Finishing of the weld inside the tube: remove the excess height on the back of the steel layer weld inside the tube. (5) Titanium layer butt welding: put the titanium strip into the groove on the inner wall of the tube, and butt its two sides with the titanium coating of the plate to complete the welding of the titanium layer inside the tube.

[0045] In step (1), the plate cutting method is water jet cutting, and then the side edge is finished by milling and grinding to make the side edge surface straight. According to the width calculation formula W = 3.14 (D-δ) + δ, where D is the outer diameter of the welded pipe, δ is the wall thickness of the pipe, and its value is 835.82mm; after inspection, the tolerance is 0.1mm.

[0046] In step (1), the width w of the titanium coating removed near the groove is set to 20 mm. The method for removing the titanium coating is to adjust the position of the cutting machine guide rail based on the side of the plate, cut the titanium coating under water cooling by using a precision cutting machine with a diamond cutting blade, and set the cutting depth to the thickness of the titanium coating minus 1.9 mm. After cutting, a hydraulic press is used to tear the titanium coating off the steel plate. After inspection, the width of the removed titanium coating is 20 mm, and its tolerance is 0.2 mm.

[0047] In step (1), the butt welding titanium strip used is an annealed TA1 pure titanium strip with a thickness of 0.5 mm. According to the width calculation formula 6.28w(D-2δ) / Wk, where the k value is 0.2 mm, the value is 37.5 mm. Laser cutting is used. After inspection, the width tolerance is 0.05 mm.

[0048] In step (2), the titanium steel composite tube is rolled by a concave and convex die bending method. Before bending, a steel needle is used to mark the side edge as a reference, and a positioning line is drawn every 5° corresponding to the cross-section circle of the tube. The parallelism between the positioning line and the side edge and the positioning line is 0.2 mm. During bending, the center of the bottom of the convex die is aligned with the positioning line.

[0049] In step (3), the seaming is performed in a pipe seaming machine. First, anhydrous ethanol is used to clean the oil stains on the surface near the seam. The pipe is transferred to the seaming machine mold and the pipe is seamed using a hydraulic mechanism. After the seaming, the two sides of the seam are completely fitted, with no obvious gap and no obvious misalignment. The spot welding is performed using the double-protection welding method. A carbon steel welding wire with a diameter of 1.2 mm is used, and the welding current is 120A; one welding spot is used every 200 mm. After the spot welding is completed, the steel butt layer is welded using a plasma filling wire welding method. The welding process parameters are: welding current 195A, plasma gas 2.8L / min, travel speed 0.5m / min, wire feeding speed 3.0m / min. After the welding is completed, the weld is inspected to determine that the back of the weld, i.e., the weld surface inside the pipe, is fully welded; the excess height at the top of the weld is about 2mm.

[0050] In step (4), the method for removing the excess height at the bottom of the steel layer weld in the pipe is argon arc welding remelting. The argon arc welding gun driven by the linear guide slide module is used to remelt the excess height of the steel layer weld in the pipe. The remelting current is 100A, the tungsten needle tip angle is 30°, the tungsten needle tip height is 2mm, and the welding gun travel speed is 3mm / s. After inspection, the remelted weld has a total weld length and a residual height of less than 0.5mm.

[0051] In step (5), when the titanium layer in the tube is butt-welded, multiple thin titanium strips are stacked into the groove of the inner wall of the tube, and the total thickness is equal to the thickness of the titanium coating. The two sides are aligned with the two sides of the groove of the inner wall of the tube, and the gaps on both sides are of equal size. Then, a copper strip is pressed on the thin titanium strip to fix it. The copper strip width is 25mm, ensuring that the distance between its side and the weld seam on both sides is about 6-7mm. The linear guide slide module is placed above the copper strip, and the argon arc welding gun is moved by the module to spot weld and fix the multi-layer thin titanium strip to the titanium coating. The spot welding sequence is to first spot weld the longitudinal midpoint of the weld, then spot weld the longitudinal 1 / 4 and 3 / 4 length of the weld, then spot weld the two ends, and then spot weld continuously at intervals of 300mm. Then, the argon arc welding gun is moved by the module to complete the welding of the entire weld. The spot welding process parameters are 80A, spot welding time 0.5s, and shielding gas flow rate 7L / min. Full weld welding process parameters: tungsten needle diameter 3.0mm, tungsten needle tip angle 30°, tungsten needle tip aligned with the side of the groove, tungsten needle tip height controlled at 1-2mm, welding current 180A, welding wire diameter 1.2mm, welding speed 3mm / s, wire feeding speed 18mm / s, welding gun shielding gas flow 7L / min, drag hood protection range is 60mm length behind the welding gun and 10mm width on both sides of the weld, and the drag hood gas flow is 25L / min.

[0052] Through the precise design of the titanium-steel composite plate and titanium bar cutting procedure, tube coiling and steel layer welding procedure, the characteristics of pure titanium thin strips being soft and easy to deform are utilized, and multi-layer titanium bars are used to fill the grooves in the tube, so as to realize the precise assembly of the titanium bar and the titanium cladding butt weld of the inner wall of the welded tube. It is observed that after the titanium bar is pressed by the copper bar, its side is closely attached to the side of the groove, and its bottom is closely attached to the bottom of the groove, ensuring that there is no obvious bulge after the titanium bar is welded. From the process inspection results, the dimensional accuracy of the composite plate and titanium bar after cutting is high, and the size of the welded tube is precisely controllable; with the side of the plate as the reference, the groove width is precisely controllable after the titanium cladding is removed for subsequent welding; the precise positioning during the tube forming process can prevent the weld from being skewed; after the two-protection welding method is spot-welded, the steel butt layer is welded by plasma welding, and the weld is welded through once to prevent deformation, misalignment, and incomplete penetration defects. The back excess height of the butt weld of the remelted steel is used for argon arc welding to prevent the excessive excess height from hindering the titanium bar. The above measures ensure the size of the groove and titanium strip, preventing the width of the titanium strip from being larger than the groove and forming a bulge after welding, and preventing the width of the titanium strip from being too narrow, so that the gap between its side and the side of the groove is too large after pressing. The copper strip is used to press the titanium strip, and its fast thermal conductivity is used to prevent the thin titanium strip from curling after being heated by the arc. The linear guide slide module and the argon arc welding gun are small in size, realizing arc spot welding and welding in small-diameter pipes. The characteristics of the argon arc welding precision welding process are used to ensure that the weld depth is controllable and does not burn through the steel butt layer. After inspection, the four layers of strips at the weld are melted, and the weld depth exceeds 80%. Due to the effect of the filler wire, a residual height of about 0.8-1mm is formed at the weld. A weld with no obvious bulge on the inner wall of the pipe and qualified size and shape is obtained. Non-destructive testing shows that the steel layer weld has no defects such as incomplete penetration, pores, cracks, etc., and the mechanical properties are guaranteed. The titanium butt weld has no defects such as undercut and burn-through, and the corrosion resistance is also guaranteed. A titanium-steel composite welded pipe with excellent performance was obtained.

[0053] Embodiment 2

[0054] The titanium-steel composite welded pipe preparation method proposed in the present invention is used to prepare a titanium-steel composite pipe with an outer diameter of 273 mm and a wall thickness of 10 mm (the steel layer is Q235 carbon steel with a thickness of 8 mm, and the titanium coating is TA1 pure titanium with a thickness of 2 mm). The method comprises the following steps: (1) Material preparation: cutting and finishing of the plate. Remove the titanium coating of a certain width near the groove. Prepare thin titanium strips for butt welding. (2) Tube rolling: roll the plate into a tube. (3) Seam joining and welding: butt the longitudinal seams of the tube in the mold, spot weld and fix them, and weld them to complete the butt weld of the steel layer. (4) Finishing of the weld inside the tube: remove the excess height on the back of the steel layer weld inside the tube. (5) Titanium layer butt welding: put the titanium strip into the groove on the inner wall of the tube, and butt its two sides with the titanium coating of the plate to complete the welding of the titanium layer inside the tube.

[0055] In step (1), the plate cutting method is laser cutting, and then the side edge is finished by milling and grinding to make the side edge surface straight. According to the width calculation formula W = 3.14 (D-δ) + δ, where D is the outer diameter of the welded pipe, δ is the wall thickness of the pipe, and its value is 837.53mm; after inspection, the tolerance is about 0.1mm.

[0056] In step (1), the width w of the titanium coating removed near the groove is set to 25 mm. The method for removing the titanium coating is to adjust the position of the cutting machine guide rail based on the side of the plate, cut the titanium coating under water cooling by using a precision cutting machine with a diamond cutting blade, and set the cutting depth to the thickness of the titanium coating minus 1.1 mm. After cutting, a hydraulic press is used to tear the titanium coating off the steel plate. After inspection, the width of the removed titanium coating is 25 mm, and its tolerance is 0.15 mm.

[0057] In step (1), the butt-welded titanium strip used is an annealed TA2 pure titanium strip with a thickness of 0.5 mm. According to the width calculation formula 6.28w(D-2δ) / Wk, where the k value is 0.23 mm, the value is 47.5 mm. Laser cutting is used. After inspection, the width tolerance is 0.05 mm. Three pure titanium strips are used.

[0058] In step (2), the titanium steel composite tube is rolled by a concave and convex die bending method. Before bending, a steel needle is used to mark the side edge as a reference, and a positioning line is drawn every 5° corresponding to the cross-section circle of the tube. The parallelism between the positioning line and the side edge and the positioning line is 0.2 mm. During bending, the center of the bottom of the convex die is aligned with the positioning line.

[0059] In step (3), the seaming is performed in a pipe seaming machine. First, acetone is used to clean the oil stains on the surface near the seam. The pipe is transferred to the seaming machine mold and the pipe is seamed using a hydraulic mechanism. After the seaming, the two sides of the seam are completely fitted together, with no obvious gap and no obvious misalignment. The spot welding is performed using the double-protection welding method. A carbon steel welding wire with a diameter of 1.2 mm is used, and the welding current is 120A; one welding spot is used every 200 mm. After the spot welding is completed, the steel butt layer is welded using a plasma wire filling welding method. The welding process parameters are: welding current 190A, plasma gas 2.7L / min, travel speed 0.5m / min, wire feeding speed 2.8m / min. After the welding is completed, the weld is inspected to determine that the back of the weld, i.e., the weld surface inside the pipe, is fully welded; the excess height at the top of the weld is about 1.8mm.

[0060] In step (4), the method for removing the excess height at the bottom of the steel layer weld in the pipe is argon arc welding remelting. The argon arc welding gun driven by the linear guide slide module is used to remelt the excess height of the steel layer weld in the pipe. The remelting current is 80A, the tungsten needle tip angle is 30°, the tungsten needle tip height is 2mm, and the welding gun travel speed is 3.5mm / s. After inspection, the remelted weld has a total weld length and a residual height of less than 0.5mm.

[0061] In step (5), when the titanium layer in the tube is butt-welded, multiple thin titanium strips are stacked into the groove of the inner wall of the tube, and the total thickness is equal to the thickness of the titanium coating. The two sides are aligned with the two sides of the groove of the inner wall of the tube, and the gaps on both sides are of equal size. Then, a copper strip is pressed on the thin titanium strip to fix it. The copper strip width is 30mm, ensuring that the distance between its side and the weld seam on both sides is about 9-10mm. The linear guide slide module is placed above the copper strip, and the argon arc welding gun is moved by the module to spot weld and fix the multi-layer thin titanium strip to the titanium coating. The spot welding sequence is to first spot weld the longitudinal midpoint of the weld, then spot weld the longitudinal 1 / 4 and 3 / 4 length of the weld, then spot weld the two ends, and then spot weld continuously at intervals of 300mm. Then, the argon arc welding gun is moved by the module to complete the welding of the entire weld. The spot welding process parameters are 80A, spot welding time 0.6s, and shielding gas flow rate 7L / min. Full weld welding process parameters: tungsten needle diameter 3.0mm, tungsten needle tip angle 30°, tungsten needle tip aligned with the side of the groove, tungsten needle tip height controlled at 1-2mm, welding current 200A, welding wire diameter 1.2mm, welding speed 3.5mm / s, wire feeding speed 17mm / s, welding gun shielding gas flow 9L / min, drag hood protection range is 60mm length behind the welding gun and 10mm width on both sides of the weld, and the drag hood gas flow is 20L / min.

[0062] Through the precise design of the titanium-steel composite plate and titanium bar cutting procedure, tube coiling and steel layer welding procedure, the characteristics of pure titanium thin strips being soft and easy to deform are utilized, and multi-layer titanium bars are used to fill the grooves in the tube, so as to realize the precise assembly of the titanium bar and the titanium cladding butt weld of the inner wall of the welded tube. It is observed that after the titanium bar is pressed by the copper bar, its side is closely attached to the side of the groove, and its bottom is closely attached to the bottom of the groove, ensuring that there is no obvious bulge after the titanium bar is welded. From the process inspection results, the dimensional accuracy of the composite plate and titanium bar after cutting is high, and the size of the welded tube is precisely controllable; with the side of the plate as the reference, the groove width is precisely controllable after the titanium cladding is removed for subsequent welding; the precise positioning during the tube forming process can prevent the weld from being skewed; after the two-protection welding method is spot-welded, the steel butt layer is welded by plasma welding, and the weld is welded through once to prevent deformation, misalignment, and incomplete penetration defects. The back excess height of the butt weld of the remelted steel is used for argon arc welding to prevent the excessive excess height from hindering the titanium bar. The above measures ensure the size of the groove and titanium strip, preventing the width of the titanium strip from being larger than the groove and forming a bulge after welding, and preventing the width of the titanium strip from being too narrow, so that the gap between its side and the side of the groove is too large after pressing. The copper strip is used to press the titanium strip, and its fast thermal conductivity is used to prevent the thin titanium strip from curling after being heated by the arc. The linear guide slide module and the argon arc welding gun are small in size, realizing arc spot welding and welding in small-diameter pipes. The characteristics of the argon arc welding precision welding process are used to ensure that the weld depth is controllable and does not burn through the steel butt layer. After inspection, the three layers of strips at the weld are melted, and the weld depth exceeds 80%. Due to the effect of the filler wire, a residual height of about 1mm is formed at the weld. A weld with no obvious bulge on the inner wall of the pipe and qualified size and shape is obtained. Non-destructive testing shows that the steel layer weld has no defects such as incomplete penetration, pores, cracks, etc., and the mechanical properties are guaranteed. The titanium butt weld has no defects such as undercut and burn-through, and the corrosion resistance is also guaranteed. A titanium-steel composite welded pipe with excellent performance was obtained.

Claims

1. A method for preparing a titanium-steel composite welded pipe, characterized in that: The preparation method obtains a titanium-steel composite welded pipe having qualified mechanical properties and corrosion resistance and capable of passing the ball inspection through the steps of precise blanking, precise forming and assembly, steel matrix welding and weld shaping, and titanium cladding assembly and welding. In this process, the titanium coating (1) within a specified width near the welding groove is removed while accurately cutting the material. During precision forming and assembly, the concave and convex die bending method is used to roll the titanium steel composite plate into a round tube to achieve precise docking and complete the precision forming and assembly work. When welding the steel matrix and shaping the weld, the steel matrix layer (2) of the round tube is welded first and then the weld inside the tube is remelted and shaped.

2. The method for preparing a titanium-steel composite welded pipe according to claim 1, characterized in that: When cutting materials precisely, the titanium steel composite plate is first cut into rough slabs of specified width by laser cutting, water jet cutting, plasma cutting or wire cutting, and then milling, planing and finally grinding are used to obtain precise slabs with straight side surfaces and a plate width of W = 3.14 (D-δ) + δ, where D is the outer diameter of the welded pipe, δ is the wall thickness of the pipe, and the plate width W tolerance is ±0.2mm.

3. The method for preparing a titanium-steel composite welded pipe according to claim 2, characterized in that: The raw slab is obtained by cutting using laser cutting or water jet cutting, and the finishing and trimming is done by milling.

4. The method for preparing a titanium-steel composite welded pipe according to claim 1, 2 or 3, characterized in that: When removing the titanium coating (1), after fine processing and trimming, the titanium coating (1) is first cut off by a precision cutting machine using a diamond cutting blade as a cutting tool, and then the titanium coating (1) is torn off from the steel base layer (2) to complete the removal of the titanium coating (1) near the welding groove. The width w of the removed titanium coating (1) is (5 to 30) ± 0.2 mm on a single side, and the cutting depth during cutting is the thickness of the titanium coating (1) δ - (0.1 to 0.2) mm.

5. The method for preparing a titanium-steel composite welded pipe according to claim 4, characterized in that: During precision forming and assembly using the concave and convex die bending method, before bending, a steel needle is used to mark the side edge as a reference, and a positioning line is drawn every 5° corresponding to the cross-sectional circle of the pipe. The parallelism between the positioning line and the side edge, and between the positioning lines, is ±0.2mm; during bending, the center of the bottom of the punch is aligned with the positioning line.

6. The method for preparing a titanium-steel composite welded pipe according to claim 5, characterized in that: The titanium steel composite plate is rolled and formed in the concave and convex molds, and then seamed and spot welded in the pipe seaming machine. The specific process is as follows: First, use anhydrous ethanol or acetone to clean the oil stains on the surface near the weld, transfer the rolled tube blank into the mold of the seaming machine, and use the hydraulic mechanism to seam together; when seaming, the two sides of the weld are completely fitted, the gap is between 0-0.5mm, and the misalignment does not exceed 0.5mm; then use the two-protection welding method for spot welding, and the distance between two adjacent welding points is 200±5mm.

7. The method for preparing a titanium-steel composite welded pipe according to claim 6, characterized in that: After the spot welding is completed, the steel matrix layer (2) in the pipe is butt welded by plasma wire welding. The welding parameters should ensure full penetration. The wire feeding parameters should ensure that the height of the top of the weld is 0 to 3 mm above the outer surface of the pipe. The covering layer material of the titanium coating (1) group is annealed TA1 or TA2 pure titanium strip (3). The width of the annealed TA1 or TA2 pure titanium strip (3) is 3.14w (D-2δ) / Wk, where the k value is 0.1-0.5 mm, and the strip width tolerance is 0.2 mm; the thickness is 0.3-0.6 mm.

8. The method for preparing a titanium-steel composite welded pipe according to claim 4, characterized in that: After the steel matrix layer (2) in the pipe is welded, the argon arc welding remelting method is used to shape the excess height at the bottom of the weld. The specific process is as follows: An argon arc welding gun driven by a linear guide rail slide module (4) is used to remelt the excess height portion of the weld of the steel matrix layer (2) in the pipe, ensuring that the excess height of the weld after remelting is less than 0.5 mm.

9. The method for preparing a titanium-steel composite welded pipe according to claim 8, characterized in that: When assembling the titanium coating (1) in the pipe, at least two layers of annealed TA1 or TA2 pure titanium strips (3) are overlapped and arranged above the weld bead (7) of the steel base layer in the pipe, and both sides of each layer of the overlapped annealed TA1 or TA2 pure titanium strips (3) are aligned with the existing titanium coating in the pipe, and then each layer of the annealed TA1 or TA2 pure titanium strips (3) is pressed with a copper bar (5) so that the compacted thickness of each layer of the annealed TA1 or TA2 pure titanium strips (3) is greater than the thickness of the existing titanium coating (1), and then each layer of the annealed TA1 or TA2 pure titanium strips (3) is spot welded to the existing titanium coating (1) on the corresponding side to firmly complete the assembly of the titanium coating in the pipe. The spot welding is performed by using an argon arc welding gun (6) driven by a linear guide slide module (4), and the spot welding sequence is: first, spot welding the longitudinal midpoint of the weld, then spot welding the longitudinal 1 / 4 and 3 / 4 lengths of the weld and both ends, then continuous spot welding at intervals not exceeding 300 mm, and finally driving the argon arc welding gun (6) to complete the welding of the entire weld.

10. The method for preparing a titanium-steel composite welded pipe according to claim 9, characterized in that: The spot welding process parameters of the titanium clad butt weld are 60-100A, spot welding time 0.3-0.8s, and shielding gas flow rate 5-10L / min; the full weld welding process parameters are tungsten needle diameter 2.0-4.0mm, tungsten needle tip angle 30-45°, tungsten needle tip aligned with the side of the groove, tungsten needle tip height 1-3mm, welding current 150-250A, welding wire diameter 1.0-1.6mm, welding speed 2-5mm / s, wire feeding speed 10-25mm / s, welding gun shielding gas flow rate 5-10L / min, the drag hood protection range is at least 50mm in length directly behind the welding gun and 10mm in width on both sides of the weld, and the drag hood gas flow rate is 20-30L / min.

Images