A three-layer intermediate transition layer of a welded titanium / steel clad plate and a welding method

Abstract

The application discloses a three-layer intermediate transition layer of a welded titanium / steel composite plate and a welding method, and relates to the technical field of welding.The application aims to solve the problems of excessive melting of a titanium / steel interface area and penetration cracks between a copper transition layer and steel in the welding of a titanium / steel composite plate transition layer.The transition layer is pure nickel, pure copper and pure niobium at the titanium / steel interface, and copper is used as a transition layer for welding in the transverse direction of the titanium / steel interface.The thickness of the titanium coating layer in the titanium / steel composite plate is greater than or equal to 1mm, and the thickness of the steel coating layer is greater than or equal to 7mm.The method comprises the following steps: assembling, opening a groove of a test piece, stacking a pure copper cladding layer, and welding in the order of self-fluxing backing welding-steel base plate welding-nickel transition layer welding-copper transition layer welding-niobium transition layer welding-titanium transition layer welding.The application precisely (in a small range) and effectively (with low heat input) protects the titanium / steel interface, and isolates the copper and the steel.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of welding, and particularly relates to a transition welding method of a longitudinal three-layer transition matching horizontal transition layer of a titanium / steel composite plate. BACKGROUND

[0002] The titanium / steel composite plate has the advantages of titanium alloy and steel, has high strength, excellent corrosion resistance, and lower cost than titanium alloy, and has a wide application prospect in the fields of petrochemical equipment and pressure vessels. From the requirement of process adaptability, the fusion welding process is the most suitable welding process for the titanium / steel composite plate. At present, the welding of the titanium / steel composite plate mainly adopts titanium plate lap welding and butt welding, and composite plate transition welding process. The lap structure has problems such as bulky structure and obvious gap between the cover plates; the butt welding process developed on this basis overcomes the problem of unreasonable joint structure; and the transition layer welding can solve the above problems, but also faces more metallurgical problems.

[0003] When the titanium / steel composite plate is subjected to fusion welding, a series of problems exist. On the one hand, the physical properties such as linear expansion coefficient and thermal conductivity of titanium and steel are greatly different, and when the two are directly welded, large stress and deformation will occur; on the other hand, the metallurgical compatibility of titanium and steel is very poor, and the mutual dissolution of titanium and steel in the welding process will lead to the generation of brittle intermetallic compounds TiFe and TiFe2, which seriously reduces the mechanical properties of the joint.

[0004] Some scholars have carried out relevant research on the above problems, and the patent with publication number CN102699484B discloses a welding method for titanium / steel composite plate welding using pure niobium as a transition layer, the groove is a V-shaped groove, the transition layer and the titanium cladding layer are both welded using inert gas shielded welding, and the welding sequence is steel layer-transition layer-titanium layer; the patent with publication number CN103785962B discloses a welding method for titanium / steel composite plate welding using pure vanadium as a transition layer, the titanium side is opened with a rectangular groove, the steel side is directly butt-jointed and assembled, the steel side is welded through using plasma welding, and after a 0.5-1 mm thick vanadium layer is built up using tungsten inert gas welding, a titanium layer is built up using shielded metal arc welding; the patent with publication number CN106112263B discloses a titanium / steel composite plate welding method using T2 red copper as a transition layer, a V-shaped groove is opened and the titanium layer has a short side, laser welding is used during welding, and the welding sequence is titanium layer-transition layer-steel layer; the patent with publication number CN108067732A discloses a titanium / steel composite plate welding method using molybdenum as a transition layer, the groove form and the welding sequence are similar to those of CN106112263B, and the transition layer uses molybdenum as a transition layer; the patent with publication number CN107984054B discloses a titanium / steel composite plate welding method using nickel and nickel-based alloy as a transition layer, the method all adopts tungsten inert gas welding, a V-shaped groove is opened and a platform is left on the titanium side, a nickel isolation layer is built up on the surface of the titanium side groove first, then the nickel is used to fill the groove, and then the titanium cover is welded.

[0005] The patent with publication number CN113145994A discloses a titanium / steel composite plate welding method using a double transition layer of copper and nickel, an X-shaped groove is opened, the titanium side welding method is all tungsten inert gas welding, and the welding sequence is steel base layer-copper layer-nickel layer-titanium cover; the patent with publication number CN113319405B discloses a double-wire shielded metal arc welding method for titanium / steel composite plate using copper vanadium or copper niobium as a transition layer, the method all adopts shielded metal arc welding, including CMT and pulse two modes, adopts a double-wire welding mode and a combination of the two modes, an X-shaped groove is opened, and the welding sequence is steel backing-copper layer-niobium layer-titanium layer-steel base layer, the copper layer welding is performed after the steel side backing welding, and the titanium / steel interface is covered using double-wire CMT / pulse MIG; An Tongbang of the Iron and Steel Research Institute proposes a titanium / steel composite plate welding method using copper niobium as a transition layer, the method opens an X-shaped groove and leaves a platform on the titanium side, the welding sequence is copper transition-niobium layer-titanium layer-steel layer. The welding method all adopts tungsten inert gas welding, a copper transition layer is welded on the surface of the groove after assembly, the niobium layer is welded to fill the groove below the platform, the copper layer is not fully covered, and then the welding of other layers is completed in sequence.

[0006] CN110238504B discloses a titanium alloy and steel high-strength diffusion bonding method, which uses nickel, copper and niobium as a composite interlayer for vacuum diffusion bonding of titanium alloy and steel, thereby improving the bonding strength of titanium alloy and steel. The diffusion welding process method proposed in this patent is only suitable for the welding of single dissimilar metals and cannot be used for the welding of titanium / steel composite plates.

[0007] In summary, the current transition layer welding of titanium / steel composite plates can be divided into single-layer transition welding and double-layer transition welding. In single-layer transition welding, whether copper transition layer welding or niobium transition layer welding is used, a large number of brittle intermetallic compounds are easily generated on one side of the titanium side or the steel side, which causes the mechanical properties of the joint to decrease or even cracks to occur. In double-layer transition welding, copper / niobium double-metal transition welding is used, and the metallurgical properties during titanium welding are improved. However, during the welding of the copper layer after assembly, the arc deviates due to the angle of the groove, causing the titanium cladding layer at the groove to melt and flow downward, which causes a large amount of titanium elements to be mixed into the copper layer, generating a large number of brittle intermetallic compounds. At the same time, when copper and steel are welded, the melting points of copper and steel differ greatly, and penetration cracks are easily generated during welding, which also leads to a decrease in joint performance.

[0008] In addition to the longitudinal transition form, the lateral transition at the titanium / steel interface of the titanium / steel composite plate is also particularly important. The metals at the interface of the titanium / steel composite plate have a risk of melting, and existing methods only consider the perspective of separating titanium and steel from the longitudinal direction to design transition layer materials. However, the existing methods do not protect the "dangerous point" - the interface of the titanium / steel composite plate. Under the influence of the welding heat source, titanium and iron at this point are prone to mutual diffusion to form a compound layer, and there is an interaction between the transition layer and the base material at this point, which causes element mixing and the formation of brittle intermetallic compounds, which greatly reduces the mechanical properties of the joint. The overall isolation method fully covers the groove, although it protects the interface area, but the transition layer material and the titanium and steel base material are in contact under the large heat input of tungsten inert gas welding, which also causes metallurgical compatibility problems. SUMMARY

[0009] The purpose of the present application is to solve the problems of excessive melting of the "dangerous point" - the titanium / steel interface area and penetration cracks between the copper transition layer and the steel in the transition layer welding of titanium / steel composite plates. An improved titanium / steel composite transition layer material design and welding process is provided, and a precise (small range) and effective (low heat input) protection strategy for the titanium / steel interface and a measure for isolating copper and steel are proposed.

[0010] To achieve the above-mentioned purposes, the technical solution of the present application is:

[0011] Before assembling the specimen to be welded, first adjust the welding surface of the specimen with the opened groove to the flat welding position by means of the clamp, and use the CMT welding method to weld the pure copper cladding layer, the thickness of the cladding layer is 1-3mm, the width is 2-4mm, and the cladding layer is ensured to cover the titanium / steel interface.

[0012] Assemble the specimen to be welded, and weld in the order of self-fluxing backing welding-steel base plate welding-nickel transition layer welding-copper transition layer welding-niobium transition layer welding-titanium transition layer welding.

[0013] First, use the TIG welding method to weld the steel base plate. After completing the backing welding and filling welding of the steel base plate, use the TIG welding method to weld a thin layer of nickel on the surface of the steel backing welding, the thickness of the nickel layer is 1-2mm, and the nickel transition layer is ensured to cover the steel base plate below the titanium / steel interface after welding. Then, use pure copper welding wire to use the CMT welding method to swing weld the pure copper transition layer, the swing frequency is 1-10Hz, the swing amplitude is 1-2mm, and the edge of the copper welding bead is 1-2mm away from the surface of the titanium cladding plate. When welding the niobium transition layer, the first layer uses the small specification TIG welding method to weld a thin layer of niobium to avoid excessive melting of the copper layer, and the second layer uses the normal specification TIG welding method to weld a thicker niobium layer to further isolate the copper element. Finally, use pure titanium welding wire to use the TIG welding method to weld the titanium cover layer.

[0014] The three-layer intermediate transition layer of the titanium / steel composite plate according to the present application, the transition layer at the titanium / steel interface is pure nickel, pure copper and pure niobium, and copper is used as the transition layer for welding in the transverse direction at the titanium / steel interface; the thickness of the titanium cladding layer in the titanium / steel composite plate is 1mm or more, and the thickness of the steel cladding layer is 7mm or more.

[0015] Further, the titanium cladding layer is a TA2 titanium cladding layer, and the steel cladding layer is a low-carbon steel cladding layer.

[0016] The welding method of the three-layer intermediate transition layer of the titanium / steel composite plate according to the present application, the welding method comprises the following steps:

[0017] 1) Before assembling the specimen to be welded, first adjust the welding surface of the specimen with the opened groove to the flat welding position by means of the clamp, and weld a pure copper cladding layer on the welding surface of the specimen, the thickness of the cladding layer is 1-3mm, the width is 2-4mm, and the cladding layer is ensured to cover the titanium / steel interface;

[0018] 2) Assemble the specimen to be welded, and weld in the order of self-fluxing backing welding-steel base plate welding-nickel transition layer welding-copper transition layer welding-niobium transition layer welding-titanium transition layer welding;

[0019] The nickel transition layer welding is realized by the following way: after the steel base plate is completed with the backing welding and the filling welding, a layer of nickel is welded on the surface of the steel backing welding by using the TIG welding method, the thickness of the nickel layer is 1-2mm, and the nickel transition layer is ensured to cover the steel base plate below the titanium / steel interface after welding;

[0020] The pure copper transition layer welding is realized by the following way: the pure copper transition layer is welded by using the pure copper welding wire, the swing frequency is 1-10Hz, the swing amplitude is 1-2mm, and the distance between the edge of the copper welding bead and the surface of the titanium cover plate is 1-2mm;

[0021] The niobium transition layer welding is realized by the following way: the niobium transition layer welding is two layers of welding, the first layer adopts the TIG welding condition: the welding current is 130-140A, the welding speed is 2-3mm / s, the wire feeding speed is 5-6mm / s, and the welding thickness of the niobium layer is less than or equal to 1mm; the second layer adopts the TIG welding condition: the welding current is 140-160A, the welding speed is 2-3mm / s, the wire feeding speed is 6-7mm / s, and the welding thickness of the niobium layer is 1.5-2.5mm.

[0022] The self-melting backing welding is realized by the following way: first, the point solid welding of the two ends of the weld is carried out by using the TIG welding method, and then the backing welding of the bevel without filling wire butt joint is carried out by using the TIG welding method.

[0023] The steel base plate welding is realized by the following way: the CMT welding method is used to carry out the swing welding of a forming by using the steel welding wire.

[0024] The titanium transition layer welding is realized by the following way: the pure titanium welding wire is used to weld the titanium cover layer by using the TIG welding method.

[0025] Further, the bevel is an X-shaped bevel with a blunt edge or a V-shaped bevel.

[0026] Further, the intersection point of the X-shaped bevel is 1-3mm below the titanium / steel interface, a 0.5-1mm blunt edge is left, the bevel angle of the titanium side is 80-90°, and the bevel angle of the steel side is 60-90°; the V-shaped bevel is processed to the steel side, and a 1-2mm blunt edge is left on the steel side.

[0027] Further, the CMT is used for welding the copper layer in step 1).

[0028] Further, the thickness of the welded copper layer is 1-2mm.

[0029] Further, the welding current of the first layer of the niobium transition layer is 130-140 A, the welding speed is 2-3 mm / s, and the wire feeding speed is 5-6 mm / s; the welding current of the second layer is 140-160 A, the welding speed is 1-2 mm / s, and the wire feeding speed is 6-7 mm / s.

[0030] Further, the pure copper transition layer is welded by adopting a CMT welding method, a swing welding or a single-layer single-pass forming.

[0031] Further, the thickness of the first layer of the niobium transition layer is less than 1 mm, and the thickness of the second layer of the niobium transition layer is 1.5-2.5 mm.

[0032] The present application has the following beneficial effects,

[0033] (1) Nickel is used as the first layer transition layer to isolate copper from iron, which can effectively isolate the penetration cracks generated when copper is directly welded with iron, and significantly improve the strength of the weld. Figure 5 As can be seen, when nickel is not used as a transition layer for isolation, several penetration cracks with a length of about 0.1 um are generated; when nickel is used as a transition layer for isolation, no penetration cracks are generated.

[0034] (2) Niobium is used as the third layer transition layer to isolate copper from titanium, the thin layer of niobium laid in the first layer can have a preliminary isolation effect on copper, the smaller heat input reduces the amount of copper melted into the niobium layer, and the thicker niobium layer welded in the second layer can further prevent the diffusion of copper elements and prevent them from contacting titanium, thereby reducing the titanium-copper compounds generated by the mutual contact of titanium and copper. Figure 6 As shown, when a single layer of niobium process is used, several cracks with a length of 0.3-0.8 mm are generated; when a double-layer niobium process is used, no cracks are generated.

[0035] (3) Copper is used as the second layer intermediate transition layer, copper has good metallurgical compatibility with nickel and niobium, and does not produce brittle hard compounds with both of them, the weld structure is good, and the copper layer as a soft metal can alleviate the deformation and residual stress in the joint.

[0036] (4) The CMT welding method is used to cover the copper layer, which accurately (small range) and effectively (low heat input) protects the "dangerous point" - the titanium / steel interface area. On the one hand, by changing the angle of the test plate for welding the copper layer, the downward flow of the titanium layer caused by the deviated arc is avoided; on the other hand, by using CMT to weld the two pre-assembled plates, the heat input is greatly reduced. Figure 4It can be seen that the number of compounds in the copper-clad layer welded by the above CMT welding process is small, and the size is small; and there are a large number of compounds with large size in the copper-clad layer welded by the TIG welding process. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of the groove structure of the present application, including an X-type groove and a large V-type groove;

[0038] Figure 2 is a schematic diagram of the copper-clad weld enlargement structure of the present application and an optical microscope photograph;

[0039] Figure 3 is an optical microscope photograph of the copper-clad weld enlargement structure of the present application;

[0040] Figure 4 is a comparison diagram of TIG welding copper-clad (upper) and CMT welding copper-clad (lower);

[0041] Figure 5 is a comparison diagram of weld effects with and without nickel layer transition, without nickel layer transition (left), with nickel layer transition (right);

[0042] Figure 6 is a comparison diagram of single-layer niobium and double-layer niobium crack conditions, single-layer niobium transition (left), double-layer niobium transition (right);

[0043] Figure 7 is a schematic diagram of the fixture for welding the copper-clad layer of the present application;

[0044] Figure 8 is a schematic diagram of the X-type groove and the large V-type groove weld of the present application;

[0045] Meaning of each reference numeral in the drawings: 1 - copper-clad weld at the interface, 2 - nickel weld, 3 - steel weld, 4 - copper weld, 5 - niobium weld, 6 - titanium weld, 7 - titanium plate, 8 - steel plate. DETAILED DESCRIPTION

[0046] The present application will be described in detail below with reference to the accompanying drawings of the specification, but it should be pointed out that the embodiments of the present application are not limited to the following embodiments.

[0047] Reference Figure 1 , the titanium / steel composite plate groove structure designed by the present application, reference Figure 2 and 3 , the method for three-layer intermediate layer transition welding of a titanium / steel composite plate described in the present application, the titanium / steel composite plate composed of a TA2 titanium cladding layer with a thickness of 1-3 mm and a low-carbon steel with a thickness of 7-10 mm is welded, nickel, copper and niobium are used for transition welding at the titanium / steel interface, and the welding method includes the following steps:

[0048] 1) Process X type or large V type welding groove, the intersection of X type groove is about 1-3mm below the titanium / steel interface, leave 0.5-1mm root face, the groove angle of titanium side is 60-90°, the groove angle of steel side is 60-90°; Process large V type groove to steel side, leave 1-2mm root face on steel side. Clean the groove and the area near the groove, the cleaning range should be not less than 15mm from the edge of the groove, the area after cleaning should not have oil, water, rust, oxide layer, etc., the surface should expose metal luster.

[0049] The design of the size and angle range of the groove can ensure the accessibility of the welding gun during the welding process of the transition layer, while not reducing the welding efficiency; cooperating with the process parameters in the patent, the designed effect of the three-layer transition of nickel, copper and niobium can be achieved.

[0050] 2) Place the two plates on the clamp with adjustable angle in turn for welding, keep the titanium / steel interface horizontal by adjusting the angle, then use pure copper welding wire for CMT welding, the welding gun is about 0.1mm close to the titanium side at the titanium / steel interface, the welding current is 70-90A, the welding speed is 130-150cm / min, the wire feeding speed is 15-25cm / min, complete the welding of the copper layer at the interface in turn, the thickness of the copper cladding layer is 1-2mm.

[0051] The CMT copper cladding layer welding with the welding condition can effectively reduce the melting at the titanium / steel interface, so that only slight melting occurs at the titanium / steel interface, further reducing the generation of brittle and hard intermetallic compounds at the titanium / steel interface. The horizontal welding angle also avoids the downward flow of titanium layer metal mixed into the copper cladding layer caused by the deflection of the arc.

[0052] 3) Assemble the composite plate, the longitudinal gap error should not exceed 0.1mm, form V type groove after assembly. Use tungsten argon arc welding to point solid at both ends of the groove, then use tungsten argon arc welding for self-melting backing welding, the welding current is 100-130A, the welding speed is 2-4mm / s, single-sided welding with double-sided forming.

[0053] 4) Use angle grinding to clean the back, and use industrial alcohol to wipe the inside and outside wall of the groove, use H08Mn2Si welding wire for CMT swing welding, the welding current is 130-150A, the welding speed is 3-5mm / s, the wire feeding speed is 6-8mm / s, for X type groove, weld once to form and fill the groove, the excess height is less than 1mm; for large V type groove, the welding parameters are the same as above, the steel weld surface after welding should be below 1-2mm below the titanium / steel interface.

[0054] Using CMT to weld the steel base layer effectively reduces the number of welding passes (TIG needs multiple passes), reduces the heat input during welding, and effectively reduces the stress and deformation during welding.

[0055] 5) Clean the titanium side groove, and use pure nickel welding wire as a transition layer to perform tungsten inert gas welding of the first layer of the transition layer. Weld one pass, and ensure that the tungsten electrode is less than 1 mm from the surface of the base material to ensure the spreading of the nickel, the welding current is 150-170 A, the welding speed is 0.5-2 mm / s, and the wire feeding speed is 4-6 mm / s, and the nickel should be spread below the titanium / steel interface.

[0056] The nickel is used for transition, and has good metallurgical properties with the two side metals (copper and steel), thereby avoiding the penetration crack between the copper and the steel as described in the present application. The welding process parameters improve the flowability of the nickel, and the nickel can achieve good spreading under the parameters.

[0057] 6) Perform flattening treatment on the nickel intermediate layer, and clean the surface and the welding groove by using an angle grinder, and then wipe the polished surface with industrial alcohol.

[0058] 7) Perform CMT oscillation welding by using pure copper welding wire, the welding current is 150-170 A, the welding speed is 6-8 mm / s, the wire feeding speed is 6-8 mm / s, the oscillation frequency is 4-6 Hz, and the oscillation amplitude is 1-2 mm. Weld one pass, and the weld is 1-2 mm below the surface of the titanium layer and covers the copper welding pass.

[0059] The CMT oscillation welding process can greatly reduce the heat input during the welding process of the pure copper layer, avoid the generation of a large heat-affected zone on the titanium / steel interface, reduce the number of welding passes, and improve the welding efficiency.

[0060] 8) Perform flattening treatment on the copper intermediate layer, and clean the surface and the welding groove by using an angle grinder, and then wipe the cleaned surface with industrial alcohol.

[0061] 9) Perform tungsten inert gas welding by using pure niobium welding wire, and the niobium layer is required to cover the copper layer during welding, the first layer has a small heat input, the welding current of each pass is 130-140 A, the welding speed is 1-2 mm / s, and the wire feeding speed is 5-6 mm / s; the second layer has a large heat input, the welding current of each pass is 140-160 A, the welding speed is 2-3 mm / s, and the wire feeding speed is 6-7 mm / s, and the interlayer temperature is strictly controlled, and the surface is cleaned and flattened after each welding pass.

[0062] The first layer has a small heat input, the small heat input reduces the amount of molten copper, and reduces the copper element molten into the niobium layer; the second layer of the thick niobium layer can further prevent the diffusion of the copper element, prevent the copper element from contacting the titanium, and reduce the titanium-copper compound generated by the mutual contact of the titanium and the copper.

[0063] 10) using pure titanium welding wire for tungsten argon arc welding, titanium layer to ensure corrosion resistance should be welded at least two layers, welding current 130-150A, welding speed 1-3mm / s, wire feed speed 5-7mm / s, gas flow 10-20L / min, titanium layer after welding excess height should be less than 2mm, weld forming uniform, dense, no cracks, undercut, lack of fusion and other defects.

[0064] Case 1:

[0065] Suitable for welding on 2mm+8mm TA2 / Q235 titanium steel composite plate, the specific welding process is as follows:

[0066] 1) processing X-type welding groove, the intersection point of the groove is 3mm below the titanium / steel interface, leaving 1mm bevel, the titanium side groove is treated with 2mm round corner, the titanium side groove angle is 90°, the steel side groove angle is 90°. Clean the groove and the area around the groove, the cleaning range should be not less than 15mm from the edge of the groove, the area after cleaning should not have oil, water, rust, oxide layer, etc., the surface should expose metal luster.

[0067] 2) place the two plates in turn on the adjustable angle clamp for welding, adjust the angle to keep the titanium / steel interface level, then use pure copper welding wire for CMT welding, the welding gun is close to the titanium side about 0.1mm at the titanium / steel interface, welding current 70A, welding speed 140cm / min, wire feed speed 20cm / min, complete the welding of copper layer at the interface in turn, the copper layer thickness is 2mm.

[0068] 3) assemble the composite plate, the longitudinal gap error should not exceed 0.1mm, after assembly, the two sides form a V-shaped groove. Use tungsten argon arc welding to point solid at both ends of the groove, then use tungsten argon arc welding for self-melting backing welding, welding current 120A, welding speed 2mm / s, single-sided welding double-sided forming.

[0069] 4) use angle grinding to clean the back, and use industrial alcohol to wipe the inside and outside of the groove, use H08Mn2Si welding wire for CMT swing welding, welding current 140A, welding speed 4.6mm / s, wire feed speed 6.67mm / s, weld once to form and fill the groove, the excess height is less than 1mm.

[0070] 5) clean the titanium side groove, use pure nickel welding wire as the transition layer for the first layer of tungsten argon arc welding. Welding once, the tungsten electrode distance from the base material surface is less than 1mm to ensure the spread of nickel, welding current 160A, welding speed 1.5mm / s, wire feed speed 5mm / s, which should ensure that the nickel spreads below the titanium / steel interface.

[0071] 6) Smooth the nickel interlayer and clean the surface and welding groove with an angle grinder, then wipe it with industrial alcohol.

[0072] 7) Use pure copper welding wire for CMT oscillation welding, welding current 160 A, welding speed 6.67 mm / s, wire feeding speed 6.67 mm / s, oscillation frequency 5 Hz, oscillation amplitude 1.5 mm. Weld one pass, and the weld after welding is 2 mm below the surface of the titanium layer.

[0073] 8) Smooth the copper interlayer and clean the surface and welding groove with an angle grinder, then wipe it with industrial alcohol.

[0074] 9) Use pure niobium welding wire for tungsten argon arc welding, and the niobium layer should cover the copper layer during welding. The welding current of the first layer is 130 A, the welding speed is 2 mm / s, and the wire feeding speed is 5 mm / s. The second layer uses large heat input, the welding current of each pass is 160 A, the welding speed is 3 mm / s, and the wire feeding speed is 6 mm / s. The interlayer temperature is strictly controlled, and each pass is cleaned and smoothed after welding.

[0075] 10) Use pure titanium welding wire for tungsten argon arc welding. In order to ensure corrosion resistance, at least two layers of titanium should be welded. The welding current is 140 A, the welding speed is 2 mm / s, the wire feeding speed is 6.67 mm / s, and the gas flow is 15 L / min. The titanium layer after welding should have a height of less than 2 mm, and the weld should be uniform, dense, and free of defects such as cracks, undercut, and incomplete fusion.

[0076] Case 2:

[0077] It is suitable for welding on (2 mm + 9 mm) TA2 / Q235 titanium steel composite plate with large V-shaped groove, and the specific welding process is as follows:

[0078] 1) Process large V-shaped welding groove, the intersection point of the groove is on the steel side, the blunt edge is 1-2 mm, the groove angle is 90°, and the groove and the plane are connected with 2-3 mm round corner treatment. Clean the groove and the area near the groove, the cleaning range should be not less than 15 mm from the edge of the groove, and the area after cleaning should be free of oil, water, rust, oxide layer, etc., and the surface should be exposed to metal luster.

[0079] 2) Place the two pieces of welding test plate on the adjustable clamp in turn for welding, adjust the angle to keep the titanium / steel interface level, then use pure copper welding wire for CMT welding, the welding gun is about 0.1 mm close to the titanium side at the titanium / steel interface, the welding current is 60 A, the welding speed is 140 cm / min, and the wire feeding speed is 20 cm / min. Complete the welding of the copper layer at the interface in turn, and the copper coating thickness is 1.5 mm.

[0080] 3) Assemble the composite plate, the longitudinal gap error should not exceed 0.1mm, after assembly, the titanium side forms a V-shaped groove, and the steel side is directly butt jointed. Use tungsten argon arc welding to point solid at both ends of the groove, and then use tungsten argon arc welding to self-melt and weld, the welding current is 160A, the welding speed is 2mm / s, and single-sided welding is formed on both sides.

[0081] 4) Use an angle grinder to clean the back, and use industrial alcohol to wipe the inside and outside of the groove. Use H08Mn2Si welding wire to perform CMT swing welding, the welding current is 130A, the welding speed is 5mm / s, and the wire feeding speed is 5.7mm / s. After welding, the steel weld thickness is about 4mm, and is below 2mm at the titanium / steel interface.

[0082] 5) Clean the titanium side groove, and use pure nickel welding wire as a transition layer to perform tungsten argon arc welding of the first layer of transition layer. Weld one pass, and ensure that the tungsten electrode is less than 1mm from the base material surface to ensure nickel spreading, the welding current is 160A, the welding speed is 1.5mm / s, and the wire feeding speed is 5mm / s. Ensure that the nickel spreads to below the titanium / steel interface.

[0083] 6) Perform flat treatment on the nickel intermediate layer, and use an angle grinder to clean the surface and welding groove.

[0084] 7) Use pure copper welding wire to perform CMT swing welding, the welding current is 140A, the welding speed is 8mm / s, the wire feeding speed is 5.2mm / s, the swing frequency is 5Hz, and the swing amplitude is 1.5mm. Weld one pass to form, and the weld after welding is below 2mm on the surface of the titanium layer and covers the copper weld.

[0085] 8) Perform flat treatment on the copper intermediate layer, and use an angle grinder to clean the surface and welding groove, and then use industrial alcohol to wipe it after cleaning.

[0086] 9) Use pure niobium welding wire to perform tungsten argon arc welding, and the niobium layer should cover the copper layer during welding. The first layer has small heat input, the welding current of each pass is 130A, the welding speed is 1.5mm / s, and the wire feeding speed is 5mm / s. The second layer uses large heat input, the welding current of each pass is 150A, the welding speed is 2mm / s, and the wire feeding speed is 6mm / s. The interlayer temperature is strictly controlled, and each pass after welding is cleaned and flattened.

[0087] 10) Use pure titanium welding wire to perform tungsten argon arc welding. In order to ensure corrosion resistance, the titanium layer should be welded at least two layers, the welding current is 130A, the welding speed is 2mm / s, the wire feeding speed is 6.67mm / s, and the gas flow is 10L / min. The titanium layer after welding should have a height of less than 2mm, the weld should be uniform, dense, and free of defects such as cracks, undercuts, and incomplete fusion.

[0088] Figure 3 These are optical microscope images of Examples 1 and 2, obtained by... Figure 3 The magnified optical microscope images of the copper-clad weld bead show that the copper-clad interface has good coverage and that there is not much melting at the titanium / steel interface.

[0089] Figure 4 (Below) is a diagram showing the copper plating effect of Example 1. Figure 4 The comparison between TIG soldered copper and CMT soldered copper shows that using the above-mentioned CMT soldering process to solder the copper layer can effectively reduce the number and size of brittle intermetallic compounds in the copper layer.

[0090] Figure 5 (Right) is a weld seam effect diagram of Example 2, through... Figure 5 The comparison of weld effects without nickel transition layer shows that the nickel transition layer can effectively prevent penetration cracking caused by direct welding of copper and steel. The weld with nickel as the intermediate transition layer between copper and steel has good structure and no penetration cracking.

[0091] Figure 6 These are comparison images of cracks during welding of Example 2 (double-layer niobium) and single-layer niobium. Figure 6 The comparison of crack patterns between single-layer and double-layer niobium shows that double-layer niobium can effectively avoid the problem of excessive copper elements mixing in during the welding of single-layer niobium, which leads to the formation of titanium-copper compounds and cracks. No cracks are generated under the double-layer niobium process.

Claims

1. A three-layer intermediate transition layer of a welded titanium / steel clad plate, characterized by, The transition layer at the titanium / steel interface is pure nickel, pure copper and pure niobium, and copper is used as the transition layer for welding transversely at the titanium / steel interface; the titanium cladding layer in the titanium / steel composite plate is more than 1mm thick, and the steel cladding layer is more than 7mm thick; The welding method of the three-layer intermediate transition layer of the welded titanium / steel composite plate is as follows: 1) Before assembling the welding test piece, first adjust the welding surface of the prepared test piece to the flat welding position by means of a clamp, and use CMT to build up a pure copper cladding layer on the welding surface of the test piece, with a cladding layer thickness of 1-3mm and a width of 2-4mm, so as to ensure that the cladding layer covers the titanium / steel interface; 2) Assemble the test piece to be welded, and weld in the order of self-fluxing backing welding-steel base plate welding-nickel transition layer welding-copper transition layer welding-niobium transition layer welding-titanium transition layer welding; The nickel transition layer welding is realized by the following method: after completing the backing welding and filling welding of the steel base plate, a layer of nickel is welded on the surface of the steel backing welding by TIG welding, with a nickel layer thickness of 1-2mm, so as to ensure that the nickel transition layer covers the steel base plate below the titanium / steel interface after welding; The copper transition layer welding is realized by the following method: a copper transition layer is welded using a pure copper welding wire, with a swing frequency of 1-10Hz and a swing amplitude of 1-2mm, and the distance between the edge of the copper welding bead and the surface of the titanium cladding plate is 1-2mm; The niobium transition layer welding is realized by the following method: the niobium transition layer welding is performed in two layers, the first layer is welded by TIG with a welding current of 130-140A, a welding speed of 2-3mm / s and a wire feeding speed of 5-6mm / s, and the welding thickness of the niobium layer is less than or equal to 1mm; the second layer is welded by TIG with a welding current of 140-160A, a welding speed of 2-3mm / s and a wire feeding speed of 6-7mm / s, and the welding thickness of the niobium layer is 1.5-2.5mm.

2. The three-layer intermediate transition layer of claim 1, wherein, The titanium cladding layer is a TA2 titanium cladding layer, and the steel cladding layer is a low-carbon steel cladding layer.

3. The three-layer intermediate transition layer of claim 1, wherein, The bevel is an X-type bevel with a land or a V-type bevel.

4. The three-layer intermediate transition layer of claim 3, wherein, The intersection point of the X-type bevel is 1-3mm below the titanium / steel interface, with a land of 0.5-1mm, a titanium side bevel angle of 80-90° and a steel side bevel angle of 60-90°; the V-type bevel is processed to the steel side, with a land of 1-2mm on the steel side.

5. The three-layer intermediate transition layer of claim 1, wherein, The thickness of the copper transition layer is 1-2mm.

6. The three-layer intermediate transition layer of claim 1, wherein, In the niobium transition layer welding, the welding current of the first layer is 130-140A, the welding speed is 2-3mm / s and the wire feeding speed is 5-6mm / s; the welding current of the second layer is 140-160A, the welding speed is 1-2mm / s and the wire feeding speed is 6-7mm / s.

7. The three-layer intermediate transition layer of claim 1, wherein, The copper transition layer welding adopts CMT welding method, swing welding or single-layer single-pass forming.

8. The three-layer intermediate transition layer of claim 1, wherein, The thickness of the first layer of the niobium transition layer is less than 1mm, and the thickness of the second layer of the niobium transition layer is 1.5-2.5mm.

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