Marine titanium-steel plasma hot wire efficient melt-brazing method and application thereof

Abstract

The invention discloses a marine titanium-steel plasma hot wire efficient melt-brazing method and application thereof, and belongs to the technical field of electric arc welding. According to the method, a silicon bronze welding wire serves as brazing filler metal, a plasma bypass hot wire melt-brazing connection mode is adopted, the electric arc of a plasma welding gun is arranged on the steel side in an offset mode, the steel side is subjected to fusion welding, the titanium side is subjected to brazing, and before the silicon bronze welding wire is fed into the electric arc, a hot wire system is adopted for conducting wire heating on the welding wire, so that titanium-steel dissimilar metal heat input is reduced. By introducing bypass shunting, decoupling between base metal heat input and welding wire cladding efficiency can be achieved, and the cladding efficiency and heat input accuracy and controllability in the welding process are both considered. S211 silicon bronze welding wires are adopted as middle filling materials to restrain generation of iron-titanium brittle intermetallic compounds at the joints, so that efficient and precise welding of the marine titanium alloy stainless steel plates with the thickness of 2-4 mm is achieved, and efficient and precise titanium-steel dissimilar metal welding is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of arc welding, and in particular relates to a ship-used titanium-steel plasma hot wire high-efficiency brazing method and application thereof. Background Art

[0002] At present, the welding of titanium and steel dissimilar metals will affect their performance due to the formation of iron-titanium intermetallic compounds (IMCs), and due to the large difference in the linear expansion coefficients between the two base materials, these intermetallic phases are very brittle, resulting in spontaneous cracking of the fusion welded joint. Therefore, inhibiting the formation of brittle intermetallic compounds (IMCs) is the key to achieving reliable connection. In order to change the interface microstructure and optimize the mechanical properties of the joint, introducing an intermediate transition layer metal to hinder the direct diffusion between Ti-Fe has become an important research direction. In recent years, filler metals such as Nb, Cu, Mg, and V have been widely used in the connection of titanium alloys and stainless steel.

[0003] Fusion welding refers to the process of applying a heat source to melt the middle filler wire and the base materials to be welded on both sides to form a molten pool at the joint. The corresponding components of the base materials on both sides and the welding wire fuse, and after cooling and crystallization, the welded workpieces form a solid whole. This welding method has a simple process and high welding quality, and is widely used in actual production and manufacturing. In recent years, domestic and foreign scholars have also conducted a series of research on the titanium steel dissimilar metal fusion welding method, mainly focusing on the control of the metallurgical behavior of the joint by different filler materials and different process parameters, and the influence of metal compounds produced at the interface on the related properties of the joint.

[0004] Adding a suitable intermediate layer metal can effectively avoid the contact between iron and titanium elements, thereby inhibiting the formation of iron-titanium intermetallic compounds and greatly improving the mechanical properties of the fusion welding joint. Among them, copper-based non-pure copper welding wire is a very suitable intermediate layer material; the use of high-energy beam welding can improve the welding effect and efficiency, and can realize the concentration and controllability of the energy beam, making the welding more efficient and precise; the welding nozzle is biased toward the stainless steel side to be melted to improve the weld formation. However, the use of a single fusion welding will melt the titanium side, forming a molten pool rich in iron and titanium elements in the middle gap, which is easy to generate brittle intermetallic compounds such as TiFe and TiFe2 under high-temperature catalysis, greatly reducing the physical properties of titanium-steel dissimilar metal joints and even cracking the joints. Therefore, a single fusion welding is not well suited for titanium-steel dissimilar metal welding. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies in the prior art and to achieve efficient, precise welding with high adaptability to working conditions. The present invention proposes a method for efficient brazing of marine titanium-steel plasma hot wire, providing a solution for achieving efficient and precise welding of marine titanium-steel dissimilar metals.

[0006] The invention provides a method for efficient melting brazing of titanium-steel plasma hot wire for ship use. The titanium-steel dissimilar metal weld is welded by a melting brazing method, a silicon bronze welding wire is used as a filling material of the titanium-steel dissimilar metal weld, the arc of a plasma welding gun is biased to the steel side, the steel side is melt-welded, and the titanium side is brazed; before the silicon bronze welding wire is fed into the arc, a hot wire system is introduced to heat the welding wire, and at the same time, the hot wire system reduces the heat input of the titanium-steel dissimilar metal by 40% to 50% through bypass shunting; the heat input is controlled so that the current flowing through the base material is shunted through a bypass hot wire power supply.

[0007] Furthermore, the method comprises the following steps:

[0008] Step 1: Pre-treat the titanium plate and the steel plate in the base material; reserve an assembly spacing of 1 to 3 mm between the titanium plate and the steel plate, and fix them with a fixture;

[0009] Step 2: Connect the welding device; place the base material on the workbench, connect the positive electrode of the plasma welding power supply to the base material, and the negative electrode to the tungsten electrode in the plasma welding gun; connect the positive electrode of the hot wire system power supply to the welding wire, and the negative electrode to the positive electrode of the plasma welding power supply. The plasma welding power supply is used as the main current, and the current flows back to the positive electrode of the plasma welding power supply through the bypass hot wire system power supply and the base material;

[0010] Step 3: Place the plasma welding gun on the positive surface of the weld on the steel plate side, feed the silicon bronze welding wire preheated by the hot wire power supply into the arc generated by the plasma welding gun through the wire feeder, and the welding wire is located at the edge of the weld on the steel plate side;

[0011] Step 4: Adjust welding process parameters; first turn on the shielding gas, ion gas and water cooling device of the plasma welding gun, then turn on the switches of other welding devices, the welding gun starts to move at a uniform speed along the welding direction, and welding begins;

[0012] Step 5: After welding is completed, turn off the switch of the welding device and release the fixture.

[0013] Furthermore, in step 3, the distance between the plasma welding gun and the surface of the steel plate is 4 to 6 mm; the distance between the welding wire and the surface of the steel plate is 2 to 3 mm, and the angle between the welding wire and the weld plane on the steel plate side is 15° to 45°.

[0014] Furthermore, in step 4, the current of the hot wire power supply is 40-60A, and the current of the plasma welding power supply is 120-140A.

[0015] Furthermore, in step 4, the shielding gas flow rate of the plasma welding gun is 15 to 20 L / min, and the ion gas flow rate is 0.5 to 0.7 L / min.

[0016] Furthermore, in step 4, the wire feeding speed of the wire feeder is 120-150 mm / min, and the travel speed of the workbench is 140-160 mm / min.

[0017] Furthermore, after welding using the method, the tensile strength of the titanium-steel dissimilar metal weld is 170-190 MPa, and the peak hardness of the corresponding joint is 500-700 HV.

[0018] The present invention further provides an application of a ship-based titanium-steel plasma hot wire high-efficiency brazing welding method, wherein the method is applied to ship-based titanium-steel dissimilar metal welding with a thickness of 2 to 4 mm.

[0019] The beneficial effects of the present invention are:

[0020] (1) The method of the present invention achieves precise and controllable heat input through a hot wire system, thereby solving the technical problem of arc welding of titanium steel. The melting efficiency of the welding wire is improved through hot wire technology, thereby increasing the welding efficiency and reducing the heat input acting on the base material per unit time.

[0021] (2) The plasma welding gun of the method of the present invention forms a main current through the ionization of the gas between the tungsten electrode and the base material, and part of the current flows back to the plasma welding power supply through the flow between the tungsten electrode and the welding wire. The technical advantage of bypass diversion while heating the wire realizes a lower heat input to the base material. At the same time, the heat of the arc is more efficiently utilized to melt the base material, which can further reduce the heat input of the main current. Through the integration and control of the integrated plasma hot wire power supply, the bypass current is adjusted in real time by the hot wire power supply to accurately control the utilization efficiency of the heat input in the dissimilar metal welding process.

[0022] (3) The method of the present invention achieves 4 mm titanium steel butt welding, breaking through the difficulty of welding thick dissimilar metal plates. By adjusting the assembly gap, process parameters, etc., effective connection of titanium steel is achieved. The feasibility of the scheme is verified by combining macro and micro testing.

[0023] (4) The present invention uses silicon bronze as the brazing material for titanium-steel dissimilar metal fusion brazing, which significantly improves the wettability of the brazing material to titanium and steel, promotes the spreading of the brazing material on the surface of the parent material, and forms a continuous and dense weld interface. The Cu in the silicon bronze reacts with Ti to form Cu-Ti intermetallic compounds (such as CuTi, CuTi2), while the reaction with Fe on the steel side is weak, avoiding the formation of brittle Ti-Fe phases (such as FeTi, Fe2Ti), thereby reducing the risk of interface brittleness. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The schematic diagram of the high-efficiency brazing method of plasma hot wire for marine titanium-steel of the present invention;

[0025] Figure 2The technical roadmap of the high-efficiency brazing method of plasma hot wire for marine titanium-steel of the present invention;

[0026] Figure 3 The microscopic SEM image and EDX element distribution map of a partial area of ​​the titanium-steel dissimilar metal weld of Example 1 of the present invention;

[0027] Figure 4 This is a macroscopic morphology of the titanium-steel dissimilar metal weld of Example 1 of the present invention.

[0028] The accompanying drawings are marked as follows: 1. hot wire power supply; 2. negative electrode of hot wire power supply; 3. positive electrode of hot wire power supply; 4. plasma welding power supply; 5. negative electrode of plasma welding power supply; 6. positive electrode of plasma welding power supply; 7. wire feeder; 8. wire feeder switch; 9. silicon bronze welding wire; 10. wire feeder guide wheel; 11. butt weld; 12. titanium alloy plate; 13. stainless steel plate; 14. plasma welding arc; 15. plasma welding gun; 16. copper nozzle of plasma welding gun; 17. butt assembly gap. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the accompanying drawings.

[0030] A method for high-efficiency brazing of titanium-steel plasma hot wire for shipbuilding, such as Figure 1 As shown, titanium and steel dissimilar metals are prone to generate brittle iron-titanium intermetallic compounds during welding. Since the two metals have quite different physical and chemical properties, their weldability is poor, and large residual stress is easily generated during welding, leading to weld cracking. Ti easily fuses with Cu and Si in the brazing material to generate a brittle phase, which reduces the mechanical properties of the joint. The plasma hot wire welding process (BC-PAW) is used to precisely control the heat input during welding. The fusion brazing process of steel-side fusion welding and titanium-side brazing is used to inhibit the fusion of titanium and iron elements, reduce the brittleness of the joint, and improve its mechanical properties, thereby achieving efficient and precise connection of marine titanium steel. The present invention has carried out research on titanium-steel dissimilar metal fusion brazing based on the BC-PAW welding process, such as Figure 2 As shown, the technical route is as follows:

[0031] (1) The BC-PAW welding experimental system was built, and the S211 silicon bronze welding wire was used to carry out the process test of stainless steel surface cladding. The influence of different process parameters on the welding wire cladding amount under the plasma hot wire brazing process was studied, and the optimal process parameter range suitable for titanium steel brazing was determined.

[0032] (2) S211 silicon bronze welding wire was used as the intermediate transition layer to butt weld a 4 mm thick Ti70 titanium alloy plate and a 304 stainless steel plate. The arc was biased to the steel side, and the connection mode was titanium side brazing-steel side fusion welding. The mechanical properties of the joint were analyzed.

[0033] (3) Observe and analyze the macroscopic morphology and microstructure of the joint, and explore the metallurgical behavior between the Ti and Cu transition layers in the joint structure and the diffusion behavior of each element in the fusion zone.

[0034] The invention discloses a marine titanium-steel plasma hot wire high-efficiency brazing method, comprising the following steps:

[0035] Step 1: Use plasma hot wire technology to achieve efficient and precise connection of titanium and steel dissimilar metals. The equipment used in the welding test is WC-100B plasma arc welding machine, T-550i plasma arc welding DC welding power supply, WF-007A automatic wire feeder, stepper motor controller, etc.

[0036] Step 2: Before the test, use laser cutting to obtain plates of corresponding sizes, and mechanically clean the titanium and steel plates, and polish the cut surfaces with #180 sandpaper to remove the remaining oxide layer, processing defects, etc. Then use acetone reagent to rinse the joints to remove residual stains, wipe with alcohol reagent and rinse with water, and finally use a hair dryer to clean the residual liquid and store it in a dust-free place.

[0037] Step 4: According to the BC-PAW welding system, the plasma arc welder, plasma welding power supply, automatic wire feeder, stepper motor controller and other welding equipment are assembled to obtain an integrated BC-PAW welding system; the BC-PAW welding system is that the positive electrode of the plasma welding power supply is connected to the base material, the negative electrode is connected to the tungsten electrode in the plasma welding gun, the positive electrode of the hot wire power supply is connected to the welding wire, and the negative electrode is connected to the positive electrode of the plasma arc welder. The ion power supply is used as the main current, and the current flows back to the welding machine through the bypass hot wire power supply and the base material, such as Figure 1 As shown; the base material is placed on the workbench, and the stepper motor controller controls the uniform movement of the workbench.

[0038] Step 5: Place the Ti70 titanium alloy plate and 304 stainless steel plate that have been pre-treated before welding on both sides of the central copper groove of the workbench, with a reserved assembly spacing of 3 mm, and fix them with a fixture, adjust the arc starting position, that is, the vertical plane formed by the welding wire and the center of the welding gun just acts on the edge of the steel plate to be welded; the distance between the plasma welding gun and the surface of the steel plate is 4 to 6 mm; the distance between the welding wire and the surface of the steel plate is 2 to 3 mm, and the angle between the welding wire and the weld plane on the steel plate side is 15° to 45°.

[0039] Step 6: According to the BC-PAW welding process requirements, set the welding process parameters such as plasma current, hot wire current, workbench travel mechanism speed, wire feeding speed, shielding gas flow rate, ion gas flow rate, etc.; the shielding gas flow rate of the plasma welding gun is 15-20L / min, and the ion gas flow rate is 0.5-0.7L / min; the wire feeding speed of the wire feeder is 120-150mm / min, and the workbench travel mechanism speed, i.e., the welding speed, is 140-160mm / min.

[0040] Step 7: Wear a protective mask strictly, turn on the front and back protective gas 5s in advance, make the welding joint a pure argon environment, and turn on the plasma welder and water cooling device; press the small arc start button, wait for a stable and bright small arc to be formed, turn on the main welding switch, and turn on the hot wire current, wire feeding and workbench travel switches at the same time. The welding gun starts to move at a uniform speed in the welding direction, and welding begins.

[0041] Step 8: After welding is completed, turn off the welding system switch and loosen the fixtures on both sides to avoid cracks or even breakage at the joint due to residual stress. Wait for the joint to cool down and remove the test workpiece.

[0042] Example 1

[0043] This embodiment discloses a method for efficient brazing of titanium-steel plasma hot wire for shipbuilding, comprising the following steps:

[0044] Step 1: The base materials used in the test are Ti70 titanium alloy and 304 stainless steel. The size of the Ti70 titanium alloy plate is 120mm×60mm×4mm, and the size of the 304 stainless steel plate is 120mm×80mm×4mm. A 1.2mm diameter S211 silicon bronze welding wire is used as the filler material of the weld, and a plasma hot wire welding process is used to perform a surfacing test on the substrate surface.

[0045] Step 2: Connect the cladding test device and set the brazing process parameters; the hot wire current is 40A, the plasma current is 130A, the workbench travel speed is 150mm / min, the wire feeding speed is 120mm / min, the shielding gas flow rate is 15L / min, and the ion gas flow rate is 0.7L / min;

[0046] Step 3: Turn on the plasma welding machine, shielding gas, ion gas, and water cooling device; then turn on other devices to start welding; after welding, cool and remove the workpiece.

[0047] The weld seam of this embodiment has a larger weld width, and the front side of the welded titanium-steel dissimilar metal weld has no obvious welding defects, and the back side weld seam is continuously and evenly formed, and the titanium steel is effectively connected; Figure 3As shown, from the scanning electron microscope image of the titanium-steel dissimilar metals welded in this embodiment, it can be seen that there is no obvious welding defect on the front side of the weld and it is continuous and uniform; the Ti element of the titanium-steel dissimilar metals is mainly distributed in the interface layer near the titanium side, and the Ti element content decreases sharply as it moves away from the fusion line, and the Ti element content in the brazing filler layer is extremely small; the Cu element is dispersed and evenly distributed in the entire titanium-copper interface layer, indicating that the brazing filler metal and the titanium base material are well fused; the Fe element is less distributed in the titanium-copper interface layer; and the Si element is less distributed in the brazing filler filling area.

[0048] like Figure 4 As shown, the upper surface of the titanium side base material of the titanium-steel dissimilar metal welded in this embodiment melts a small amount under the higher heat input of the plasma arc, and is divided into regions A, B and C along the thickness direction. It can be seen that the thickness of the fusion zone near the titanium side has no obvious change in the three regions A, B and C, the heat loss from region A to C is not large, the heat gradient of the specimen is not large, the back forming is more complete, the hot wire system reduces the heat input of the plasma welding gun, so that the heat input on the upper surface of the titanium side base material is reduced, the melting amount is relatively small, and there are no obvious defects in the front weld, and the forming is better.

[0049] The fracture positions of the titanium-steel dissimilar metal tensile tests welded in this embodiment all occurred at the titanium-copper interface layer, which was a brittle fracture with a maximum tensile strength of 181.81 MPa. The method of the present invention has an optimization effect on the brittleness of the titanium-steel joint, and the peak hardness of the corresponding joint is 650 HV.

[0050] Comparative Example 1

[0051] This comparative example discloses a method for efficient brazing of titanium-steel plasma hot wire for ship use, which is the same as that of Example 1, wherein the brazing process parameters are set in step 2, the hot wire current is 30A, and the plasma current is 140A; the parameters of the other steps are the same as those of Example 1;

[0052] The titanium-steel dissimilar metals welded in this comparative example obtained a well-formed butt weld. Inspection of the formation showed that the back side was well fused but the front side was not fully filled, so the plasma current should be reduced and the hot wire current increased.

[0053] Comparative Example 2

[0054] This comparative example discloses a method for efficient brazing of titanium-steel plasma hot wire for ship use, which is the same as that of Example 1, wherein the brazing process parameters are set in step 2, the hot wire current is 20A, and the plasma current is 150A; the parameters of the other steps are the same as those of Example 1;

[0055] In this comparative welding, some areas of the front side of the titanium-steel dissimilar metal weld collapsed due to excessive cladding, and the back residual height was too large. The larger amount of melting on the titanium side may form more iron-titanium intermetallic compounds. Therefore, the hot wire current should be increased to reduce heat input and increase the welding wire cladding efficiency.

[0056] Comparative Example 3

[0057] This comparative example discloses a method for efficient brazing of titanium-steel plasma hot wire for ship use, which is the same as that in Example 1, wherein the brazing process parameters are set in step 2, the hot wire current is 20A, and the plasma current is 140A; the parameters of the other steps are the same as those in Example 1;

[0058] The hot wire current of this comparative example is too small, and the weld width is too small, which is not conducive to weld formation.

[0059] Comparative Examples 4 and 5

[0060] This comparative example discloses a method for efficient brazing of titanium-steel plasma hot wire for ship use, which is the same as that in Example 1, wherein the brazing process parameters are set in step 2, the hot wire current is 30A, and the plasma current is selected as 130A and 150A respectively; the parameters of the other steps are the same as those in Example 1;

[0061] In comparative example 4, the plasma current is too small, and the welded titanium-steel dissimilar metal weld is unevenly formed; in comparative example 5, the plasma current is too large, and the welded titanium-steel dissimilar metal weld cannot be formed.

[0062] In summary, the ship-use titanium-steel plasma hot wire high-efficiency brazing method of the present invention uses S211 silicon bronze welding wire as brazing material and adopts plasma hot wire welding process to achieve effective connection of titanium-steel dissimilar metals. Under the premise of satisfying weld formation, the lowest welding heat input is adopted, plasma current 130A, hot wire current 40A, travel speed 150mm / min, wire feeding speed 120mm / min, shielding gas flow 15L / min, and ion gas flow 0.7L / min. Under this process parameter, the weld formation is optimal and titanium steel is effectively connected.

[0063] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for efficient brazing of titanium-steel plasma hot wire for shipbuilding, characterized in that: The titanium-steel dissimilar metal weld is welded by a fusion brazing method, and a silicon bronze welding wire is used as a filling material for the titanium-steel dissimilar metal weld. The arc of the plasma welding gun is biased to the steel side, and the steel side is fusion welded, and the titanium side is brazed. Before the silicon bronze welding wire is fed into the arc, a hot wire system is introduced to heat the welding wire, and at the same time, the hot wire system reduces the heat input of the titanium-steel dissimilar metal by 40% to 50% through bypass diversion.

2. The method for high-efficiency brazing of titanium-steel plasma hot wire for shipbuilding according to claim 1 is characterized in that: The method comprises the following steps: Step 1: Pre-treat the titanium plate and the steel plate in the base material; reserve an assembly spacing of 1 to 3 mm between the titanium plate and the steel plate, and fix them with a fixture; Step 2: Connect the welding device; place the base material on the workbench, connect the positive electrode of the plasma welding power supply to the base material, and the negative electrode to the tungsten electrode in the plasma welding gun; connect the positive electrode of the hot wire system power supply to the welding wire, and the negative electrode to the positive electrode of the plasma welding power supply. The plasma welding power supply is used as the main current, and the current flows back to the positive electrode of the plasma welding power supply through the bypass hot wire system power supply and the base material; Step 3: Place the plasma welding gun on the positive surface of the weld on the steel plate side, feed the silicon bronze welding wire preheated by the hot wire power supply into the arc generated by the plasma welding gun through the wire feeder, and the welding wire is located at the edge of the weld on the steel plate side; Step 4: Adjust welding process parameters; first turn on the shielding gas, ion gas and water cooling device of the plasma welding gun, then turn on the switches of other welding devices, the welding gun starts to move at a uniform speed along the welding direction, and welding begins; Step 5: After welding is completed, turn off the switch of the welding device and release the fixture.

3. The method for high-efficiency brazing of titanium-steel plasma hot wire for shipbuilding according to claim 2 is characterized in that: In step 3, the distance between the plasma welding gun and the surface of the steel plate is 4 to 6 mm; the distance between the welding wire and the surface of the steel plate is 2 to 3 mm, and the angle between the welding wire and the weld plane on the steel plate side is 15° to 45°.

4. The method for high-efficiency brazing of titanium-steel plasma hot wire for shipbuilding according to claim 2 is characterized in that: In step 4, the current of the hot wire power supply is 40-60A, and the current of the plasma welding power supply is 120-140A.

5. The method for high-efficiency brazing of titanium-steel plasma hot wire for shipbuilding according to claim 2 is characterized in that: In step 4, the shielding gas flow rate of the plasma welding gun is 15-20 L / min, and the ion gas flow rate is 0.5-0.7 L / min.

6. The method for high-efficiency brazing of titanium-steel plasma hot wire for shipbuilding according to claim 2 is characterized in that: In step 4, the wire feeding speed of the wire feeder is 120-150 mm / min, and the travel speed of the workbench is 140-160 mm / min.

7. The method for high-efficiency plasma hot wire brazing of titanium and steel for shipbuilding according to any one of claims 1 to 6, characterized in that: After welding by the method, the tensile strength of the titanium-steel dissimilar metal weld is 170-190 MPa, and the peak hardness of the corresponding joint is 500-700 HV.

8. An application of the method for high-efficiency plasma hot wire brazing of titanium-steel for shipbuilding as claimed in any one of claims 1 to 7, characterized in that: The method is applied to the welding of titanium-steel dissimilar metals with a thickness of 2 to 4 mm for shipbuilding.

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