A welding method for improving the proportion of precipitated phase and mechanical properties of duplex titanium alloy
By altering the electron beam welding path and frequency using a sawtooth wave scanning mode, the problem of fewer precipitates in duplex titanium alloy joints was solved, achieving efficient deep penetration welding and improving the mechanical properties and welding efficiency of the joints.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INST OF METAL RESEARCH - CHINESE ACAD OF SCI
- Filing Date
- 2023-06-12
- Publication Date
- 2026-07-21
AI Technical Summary
Existing electron beam welding technology produces fewer precipitates in duplex titanium alloy joints, which affects the mechanical properties of the joints. Furthermore, conventional welding is slow, has high residual stress, and produces coarse grains, which reduces welding efficiency and joint performance.
By employing a sawtooth wave scanning mode to alter the electron beam's path and stirring frequency, the molten pool can be brought to a stable state earlier, thereby controlling the morphology of the precipitated phase, promoting the nucleation and growth of the α phase, and improving the mechanical properties of the joint.
Deep penetration welding of duplex titanium alloys was achieved, with good weld surface formation and excellent joint performance. This eliminated the need for pre-welding beveling, simplified process assembly, and improved welding efficiency and overall joint performance.
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Figure CN117123905B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of titanium alloy welding technology, specifically to a welding method for improving the proportion of precipitated phases and mechanical properties of duplex titanium alloys. Background Technology
[0002] Titanium alloys are widely used in important industrial fields such as aerospace, automotive, and shipbuilding due to their high strength, good corrosion resistance, and high temperature resistance. Among them, duplex (α+β) titanium alloys, with their high strength, high hardenability, and excellent weldability, have attracted widespread attention in large engineering equipment such as aircraft fuselages and aerospace load-bearing structural components. In aircraft structural components, duplex titanium alloys can replace high-strength steel of the same thickness, reducing weight by almost 10% to 20%. With the widespread application of duplex titanium alloys in industry, welding issues inevitably arise.
[0003] Currently, welding technologies for duplex titanium alloys mainly focus on argon arc welding and electron beam welding. However, in argon arc welding, it is necessary to first bevel the plate to be welded, followed by multi-layer, multi-pass welding. Moreover, multi-layer, multi-pass welding results in slow welding speed, high residual stress, and coarse grains, reducing welding efficiency and joint performance.
[0004] Compared to argon arc welding, electron beam welding, as a high-energy beam welding technology, has advantages such as fast welding speed, no need for beveling, concentrated energy, and small welding deformation, and has been successfully applied to the welding of titanium alloys. However, in the conventional circular wave scanning mode of electron beam welding, the weld temperature is too high, exceeding the β phase transformation temperature, resulting in the formation of coarse metastable β phases during solidification. Simultaneously, due to the excessively rapid cooling rate, the scanning trajectories in the conventional circular wave scanning mode overlap, causing secondary heat input to the previous trajectory. This results in a short stabilization time for the molten pool, preventing the precipitates within the β phase from nucleating and growing, thus reducing the mechanical properties of the joint.
[0005] In summary, if the molten pool can be brought to a stable state earlier and the fluctuations reduced by changing the electron beam's path and stirring frequency during electron beam welding, the morphology of the precipitated phases can be controlled. At the same time, the nucleation and growth of the precipitated phases can be promoted, thereby improving the mechanical properties of the joint. This is of great significance for promoting the engineering application of electron beam welding technology in the field of titanium alloy welding. Summary of the Invention
[0006] To address the problems existing in the prior art, this invention proposes a welding method to improve the proportion of precipitates and mechanical properties of duplex titanium alloys. This method solves the problem that existing electron beam welding technology results in fewer precipitates in duplex titanium alloy joints, which significantly affects the joint's mechanical properties. By changing the electron beam's motion path and stirring frequency, the molten pool can reach a stable state earlier, reducing molten pool fluctuations and thus controlling the morphology of the precipitates. At the same time, it promotes the nucleation and growth of precipitates, improving the joint's mechanical properties and advancing its engineering applications, which is of great significance.
[0007] To achieve the aforementioned objective, the technical solution adopted by the present invention is as follows:
[0008] A welding method for improving the proportion of precipitated phases and mechanical properties of duplex titanium alloys, the method comprising the following steps:
[0009] (1) Electron beam welding of dual-phase titanium alloy is performed using sawtooth wave scanning mode to achieve deep penetration welding of dual-phase titanium alloy.
[0010] (2) Fine α phases are precipitated in the fusion zone of the electron beam welding head in the sawtooth wave scanning mode, and the proportion of α phases formed is greater than 30%, thereby improving the mechanical properties of the joint.
[0011] In step (1), during the electron beam welding of the duplex titanium alloy plate, the scanning amplitude of the sawtooth wave is 0.05 to 5 mm.
[0012] The sawtooth wave scanning amplitude is within this range primarily to ensure stable energy transmission during the sawtooth wave scanning process, maintaining a stable molten pool under electron beam stirring, thereby achieving a good connection. However, if the amplitude is too small, the scanning effect will be insignificant, and the increase in the proportion of precipitated phases will not be significant; if the amplitude is too large, it will cause increased molten pool oscillation and disturbance, resulting in poor weld formation.
[0013] In step (1), the duplex titanium alloy sheet is particularly suitable for duplex near-β alloys.
[0014] Because the second phase is difficult to precipitate during rapid cooling of near-β duplex alloys, the weld strength decreases. The sawtooth wave design of this invention improves the mechanical properties of the joint by increasing the precipitation of the second phase.
[0015] In step (1), during the electron beam welding of the duplex titanium alloy plate, the scanning frequency of the sawtooth wave is 60-150 Hz.
[0016] The scanning frequency of the sawtooth wave is 60-150 Hz. This range is mainly to ensure stable energy transmission in the area swept by the waveform and to avoid instability of the molten pool under electron beam stirring, thereby achieving a good connection. However, although scanning frequencies that are too low or too high achieve deep penetration welding of duplex titanium alloys, the weld surface formation is poor, and undercut defects exist.
[0017] In step (1), the electron beam welding process is performed with a welding vacuum of 10. -5 ~10 -2 Pa.
[0018] The welding vacuum level within this range is primarily to ensure the quality of the weld surface formation, prevent surface oxidation, and avoid reactions with impurity elements. Too low a vacuum level will result in the presence of atmospheric elements such as hydrogen, oxygen, and nitrogen. Since titanium alloys are highly sensitive to these elements, they easily react chemically with them at high temperatures, reducing the overall performance of the joint. Too high a vacuum level produces essentially the same welding effect as the range, but ultra-high vacuum environments require longer vacuuming times and are more costly.
[0019] In step (1), the thickness of the duplex titanium alloy to be welded is greater than 10 mm.
[0020] The selected thickness within this range is primarily for conventional circular wave welding of medium-thick and thick duplex titanium alloys. Due to the plate thickness, achieving deep penetration welding requires a high heat input, and during rapid cooling, it easily leads to significant unevenness of precipitates along the weld penetration direction. Furthermore, the problems of insufficient growth time and low quantity of precipitates in the weld are more pronounced. Conversely, for plate thicknesses smaller than this range, achieving deep penetration welding requires a lower heat input, resulting in an increase in the number of precipitates and a more uniform distribution.
[0021] In step (1), during the electron beam welding process, the welding current is 20-80 mA and the welding speed is 100-800 mm / min.
[0022] Deep penetration welding of duplex titanium alloys can be achieved with welding currents within this range, resulting in well-formed joints and no obvious welding defects on the surface. There is a certain matching relationship between welding current and welding speed. Welding current and welding speed that are too low will produce welding defects such as incomplete penetration and lack of fusion; while welding current and welding speed that are too high will cause the surface of the plate to collapse, resulting in poor weld surface formation, wider welds, and reduced mechanical properties of the joint.
[0023] In step (2), after electron beam welding of the duplex titanium alloy plate, the width of the joint fusion zone is 2 to 10 mm and the width of the heat-affected zone is 1 to 4 mm.
[0024] The width of the fusion zone and heat-affected zone within this range mainly ensures the mechanical properties of the joint. When the width is too small, nail-point defects are easily generated at the weld root, significantly reducing the overall performance of the joint; when the width is too large, the required welding heat input is also large, resulting in coarse weld grains, which also reduces the mechanical properties of the joint.
[0025] In step (2), needle-like α phases with a thickness of 50 to 500 nanometers were precipitated in the joint fusion zone of the sawtooth wave scanning mode.
[0026] The thickness of the acicular α phase within this range primarily ensures the mechanical properties of the joint. Under sawtooth wave scanning, the precipitated acicular α phase is most abundant within this range, resulting in excellent joint performance. When the thickness is too small, a lower heat input is required, and some precipitated phases nucleate but do not have enough time to grow, reducing joint performance; when the thickness is too large, a higher heat input is required, resulting in coarser grains and affecting the joint strength.
[0027] The hardness of the dual-phase titanium alloy obtained after electron beam welding is 280-380 HV.
[0028] In some implementations...
[0029] After electron beam welding, the hardness of most duplex titanium alloy joints decreases. However, after sawtooth wave scanning welding, the number of precipitated phases increases, and the joint hardness increases.
[0030] Electron beam welding technology using sawtooth wave scanning mode can promote the precipitation of more α phase in duplex titanium alloys, providing a new method for the engineering application of electron beam welding of titanium alloys.
[0031] The design mechanism of the method of this invention is as follows:
[0032] This invention promotes the nucleation and growth of precipitates by altering the electron beam path and scanning frequency, thereby increasing the proportion of the α phase, based on the conventional circular wave scanning method. Firstly, in the conventional circular wave scanning mode, during electron beam welding, as the heat source migrates, the electron beam travels along the same waveform, causing partial overlap between subsequent and preceding scan trajectories, which in turn affects the preceding trajectory. This overlap is equivalent to an additional heat input, causing a secondary temperature increase or even secondary melting in that region. During cooling, coarse metastable β phases are formed. Furthermore, in the circular wave scanning mode, the overlapping regions of the scan trajectories, under the influence of this secondary heat input, cause the precipitates generated by the previous scan trajectory to remelt, resulting in a shorter stabilization time for the molten pool. This hinders the sufficient nucleation and growth of the precipitates, reducing the proportion of the α phase within the β phase.
[0033] When using the sawtooth wave scanning mode, the electron beam's path is altered during electron beam welding, ensuring it moves in a single direction with unconnected or overlapping scan trajectories. This allows the molten pool to stabilize earlier, reducing molten pool fluctuations and resulting in a uniform, near-parallel weld. Simultaneously, the non-overlapping electron beam heat source prevents secondary remelting of the materials to be welded. Consequently, a large number of α-phase nucleates under the high cooling rate after electron beam welding. Subsequently, the sawtooth wave's stirring effect prevents the scan trajectories from interfering with each other, allowing sufficient time for the α-phase to grow. Ultimately, a large number of needle-like α-phase precipitates within the β-phase, enhancing the α / β interface strengthening effect and improving the joint's mechanical properties.
[0034] The advantages of this invention are:
[0035] By optimizing welding process parameters and employing a sawtooth wave scanning method, electron beam deep-penetration welding of duplex titanium alloys was achieved. However, compared with conventional circular wave scanning welding, the sawtooth wave joint exhibited excellent near-parallel welds, avoiding the influence of the weld root on the joint performance.
[0036] Compared with the conventional circular wave scanning mode, the sawtooth wave scanning mode designed in this invention changes the movement path of the electron beam, making the electron beam move in a single direction; at the same time, it can make the molten pool enter a stable state earlier, reduce molten pool fluctuations, and allow the precipitated phase to grow more fully, forming a large number of needle-like α phases inside the β phase, thereby improving the mechanical properties of the joint.
[0037] It eliminates the need for pre-welding beveling and requires no external auxiliary field. It also features simple assembly, convenient and reliable welding process, and high overall joint performance, thus having broad industrial application prospects. Attached Figure Description
[0038] Figure 1 This is a schematic diagram of the welding process and scanning waveforms used in a welding method for improving the proportion of precipitated phases and mechanical properties of duplex titanium alloys according to the present invention; wherein: (a) welding process; (b) circular wave; (c) sawtooth wave;
[0039] Figure 2 Schematic diagrams of conventional circular wave and sawtooth wave scanning mechanism of the present invention; wherein: (a) and (b) circular wave; (c) and (d) sawtooth wave;
[0040] Figure 3The images show macroscopic surface formation micrographs of a 30mm thick biphase titanium alloy electron beam welded head obtained under conventional circular wave and sawtooth wave scanning modes of the present invention; where: (a) circular wave; (b) sawtooth wave; it can be seen that both scanning modes achieve deep penetration welding of biphase titanium alloy by electron beam, and the joint of the sawtooth wave scanning mode exhibits excellent near-parallel weld.
[0041] Figure 4 The images show the weld microstructure morphology of conventional circular wave and sawtooth wave scanning mode of the present invention; where (a) is a circular wave and (b) is a sawtooth wave; it can be seen that the joint precipitates in the sawtooth wave scanning mode are more numerous and more densely distributed;
[0042] Figure 5 The hardness distribution is shown in both the conventional circular wave and the sawtooth wave scanning mode of this invention; it can be seen that the designed sawtooth wave scanning mode results in a higher joint hardness. Detailed Implementation
[0043] The present invention will be further explained below with reference to specific implementation schemes, but this explanation does not limit the invention. The structures, proportions, sizes, etc., shown in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention. At the same time, terms such as "upper," "lower," "front," "rear," and "middle" used in this specification are only for clarity of description and are not intended to limit the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.
[0044] Example 1
[0045] Select a pair of 30 mm thick duplex titanium alloy plates, place an 8 mm thick backing plate of the same material as the plates to be welded underneath, and remove dust and oil from the surface of the plates and the mating surfaces to keep the mating surfaces clean.
[0046] A set of plates to be welded are butt-jointed, with the joining gap required to be smaller than the diameter of the electron beam heat source spot, and placed horizontally. Then, the scanning mode is selected as sawtooth wave scanning mode, and the sawtooth wave electron beam heat source is used to weld them to achieve butt welding of the duplex titanium alloy, such as... Figure 2 As shown. The process parameters are as follows: vacuum degree is 10. -5The welding parameters were: welding voltage 140 kV, welding current 49 mA, welding speed 400 mm / min, focusing current 1972 mA, scanning frequency 100 Hz, and scanning amplitude 0.2 mm. The weld joint fusion zone width was 3.5 mm, and the heat-affected zone width was 1.2 mm. The α phase accounted for over 30% of the fusion zone, with a thickness of 100–500 nm. The hardness of the fusion zone was 320–350 HV.
[0047] The joint cross-sectional morphology, microstructure, and mechanical properties of the duplex titanium alloy obtained through the welding process are as follows: Figure 3 , 4 As shown in Figure 5, the sawtooth wave electron beam welding achieved deep penetration welding of dual-phase titanium alloys, and the joint exhibited excellent near-parallel welds with good joint quality. Moreover, a large number of needle-like α phases precipitated in the fusion zone of the joint, and the proportion of α phases formed was greater than 30%, which improved the mechanical properties of the joint.
[0048] Comparative Example 1
[0049] Select a pair of 30 mm thick duplex titanium alloy plates, place an 8 mm thick backing plate of the same material as the plates to be welded underneath, and remove dust and oil from the surface of the plates and the mating surfaces to keep the mating surfaces clean.
[0050] The plates to be welded are butt-jointed, with the joining gap required to be smaller than the diameter of the electron beam heating source spot, and placed horizontally. Then, a conventional circular wave electron beam heating source is used to weld them to achieve butt welding of the duplex titanium alloy, such as... Figure 2 As shown. The process parameters are as follows: vacuum degree is 10. -5 The welding parameters were: welding voltage 140 kV, welding current 49 mA, welding speed 400 mm / min, focusing current 1972 mA, scanning frequency 100 Hz, and scanning amplitude 0.2 mm. The weld joint fusion zone width was 3 mm, and the heat-affected zone width was 1.6 mm. The α phase accounted for less than 10% of the fusion zone, and the α phase thickness was 50–200 nm. Figure 4 As shown; the hardness of the fusion zone is 280–295 HV ( Figure 5 ).
[0051] The joint cross-sectional morphology and microstructure of the duplex titanium alloy obtained through the welding process are as follows: Figure 3 and 4 As shown in the figure, conventional circular wave electron beam welding achieved deep penetration welding of dual-phase titanium alloys, but the weld root width was small, affecting the joint performance. Furthermore, only a small amount of needle-like α-phase precipitates were found in the joint fusion zone, resulting in low hardness.
[0052] Example 2
[0053] Determination of docking parameters: Select a 15 mm thick plate as a reference part and weld it by surface overlay welding. Place an 8 mm thick backing plate with the same material as the plate to be welded on the bottom.
[0054] A sawtooth wave electron beam heat source was used for surface surfacing welding of duplex titanium alloy, and the welding current and welding speed were determined. A cross-section of the joint was taken, and the parameters at which the weld penetration reached exactly 15 mm of the duplex titanium alloy reference plate were determined as the process parameters for butt welding of the duplex titanium alloy: welding current of 20 mA, welding speed of 100 mm / min, and vacuum degree of 10... -5 The welding voltage was 140 kV, the focusing current was 1972 mA, the scanning frequency was 100 Hz, and the scanning amplitude was 0.2 mm.
[0055] Technical effects and analysis: Under the aforementioned parameters, deep penetration welding of 15 mm thick duplex titanium alloy can be achieved. With good matching of welding current and welding speed, the weld formation is good and the joint is defect-free. The parameters at this time are determined as the process parameters for butt welding of duplex titanium alloy.
[0056] Comparative Example 2
[0057] Determination of butt welding parameters: Select a 15 mm thick plate as a reference part and weld it by surface overlay welding. Place an 8 mm thick backing plate with the same material as the plate to be welded underneath.
[0058] A sawtooth wave electron beam heat source was used, with a welding current of 15 mA, a welding speed of 90 mm / min, and a vacuum degree of 10. -5 Under the parameters of 140 kV welding voltage, 1972 mA focusing current, 100 Hz scanning frequency, and 0.2 mm scanning amplitude, surface overlay welding was performed on duplex titanium alloy, and the cross-section of the joint was cut.
[0059] Technical results and analysis: Under the parameters described, there were no obvious welding defects on the weld surface, but the penetration depth was only 10 mm, failing to achieve deep penetration welding of a 15 mm thick duplex titanium alloy.
[0060] Example 3
[0061] Determination of butt welding parameters: Select a 40 mm thick plate as a reference part and weld it by surface overlay welding. Place an 8 mm thick backing plate with the same material as the plate to be welded underneath.
[0062] A sawtooth wave electron beam heat source was used for surface surfacing welding of duplex titanium alloy, and the welding current and welding speed were determined. A cross-section of the joint was taken, and when the penetration depth reached 40 mm of the duplex titanium alloy reference plate, the parameters at this point were determined as the process parameters for butt welding of the duplex titanium alloy: welding current of 80 mA, welding speed of 800 mm / min, and vacuum degree of 10... -5 The welding voltage was 140 kV, the focusing current was 1972 mA, the scanning frequency was 100 Hz, and the scanning amplitude was 0.2 mm.
[0063] Technical effects and analysis: Under the parameters described, deep penetration welding of 40 mm thick duplex titanium alloy can be achieved, with good weld formation, no welding defects in the joint, and excellent near-parallel welds. The parameters at this time are determined as the process parameters for butt welding of duplex titanium alloy.
[0064] Comparative Example 3
[0065] Determination of butt welding parameters: Select a 40 mm thick plate as a reference part and weld it by surface overlay welding. Place an 8 mm thick backing plate with the same material as the plate to be welded underneath.
[0066] A sawtooth wave electron beam heat source was used, with a welding current of 90 mA, a welding speed of 900 mm / min, and a vacuum degree of 10. -5 Under the parameters of 140 kV welding voltage, 1972 mA focusing current, 100 Hz scanning frequency, and 0.2 mm scanning amplitude, surface overlay welding was performed on duplex titanium alloy, and the cross-section of the joint was cut.
[0067] Technical results and analysis: Under the parameters described, deep penetration welding of 40 mm thick duplex titanium alloy plates was achieved. However, due to the large heat input, the plate surface collapsed, the weld surface formation was poor, and the weld was wide.
[0068] Example 4
[0069] Determination of welding parameters: Based on the optimal welding parameters described in Example 1, the frequency of the scanning waveform is determined; a 30 mm thick plate is selected as a reference part, and welding is performed by surface overlay welding, with an 8 mm thick backing plate of the same material as the plate to be welded placed underneath.
[0070] A sawtooth wave electron beam heat source was used to perform surface overlay welding on duplex titanium alloy. A cross-section of the joint was taken. When the weld surface formed well and the penetration depth reached 30 mm on the duplex titanium alloy reference plate, the parameters at this point were determined as the scanning frequency for butt welding of the duplex titanium alloy, i.e., a scanning frequency of 60 Hz and a vacuum degree of 10. -5The welding voltage was 140 kV, the welding current was 49 mA, the welding speed was 400 mm / min, the focusing current was 1972 mA, and the scanning amplitude was 0.2 mm.
[0071] Technical effects and analysis: Under the parameters described, deep penetration welding of 30 mm thick duplex titanium alloy can be achieved, and the weld surface has good formation and the joint is free of welding defects.
[0072] Comparative Example 4
[0073] Determination of butt welding parameters: Select a 30 mm thick plate as a reference part and weld it by surface overlay welding. Place an 8 mm thick backing plate with the same material as the plate to be welded underneath.
[0074] A sawtooth wave electron beam heat source was used, with a scanning frequency of 50 Hz and a vacuum degree of 10. -5 Under the following parameters: welding voltage of 140 kV, welding current of 49 mA, welding speed of 400 mm / min, focusing current of 1972 mA, and scanning amplitude of 0.2 mm, surface overlay welding was performed on duplex titanium alloy, and the cross-section of the joint was cut.
[0075] Technical effects and analysis: Under the parameters described, although deep penetration welding of 30 mm thick duplex titanium alloy was achieved, the low scanning frequency resulted in poor weld surface formation and undercut defects.
[0076] Example 5
[0077] Determination of welding parameters: Based on the optimal welding parameters described in Example 1, the frequency of the scanning waveform is determined; a 30 mm thick plate is selected as a reference part, and welding is performed by surface overlay welding, with an 8 mm thick backing plate of the same material as the plate to be welded placed underneath.
[0078] A sawtooth wave electron beam heat source was used to perform surface overlay welding on duplex titanium alloy. A cross-section of the joint was taken. When the weld surface formed well and the penetration depth reached 30 mm on the duplex titanium alloy reference plate, the parameters at this point were determined as the scanning frequency for butt welding of the duplex titanium alloy, i.e., a scanning frequency of 150 Hz and a vacuum degree of 10. -5 The welding voltage was 140 kV, the welding current was 49 mA, the welding speed was 400 mm / min, the focusing current was 1972 mA, and the scanning amplitude was 0.2 mm.
[0079] Technical effects and analysis: Under the parameters described, deep penetration welding of 30 mm thick duplex titanium alloy can be achieved, and the weld surface has good formation and the joint is free of welding defects.
[0080] Comparative Example 5
[0081] Determination of butt welding parameters: Select a 30 mm thick plate as a reference part and weld it by surface overlay welding. Place an 8 mm thick backing plate with the same material as the plate to be welded underneath.
[0082] A sawtooth wave electron beam heat source was used, with a scanning frequency of 160 Hz and a vacuum degree of 10. -5 Under the following parameters: welding voltage of 140 kV, welding current of 49 mA, welding speed of 400 mm / min, focusing current of 1972 mA, and scanning amplitude of 0.2 mm, surface overlay welding was performed on duplex titanium alloy, and the cross-section of the joint was cut.
[0083] Technical effects and analysis: Under the parameters described, although deep penetration welding of 30 mm thick duplex titanium alloy was achieved, the high scanning frequency resulted in large heat input, severe spatter, poor weld surface formation, wide weld, and reduced joint mechanical properties.
[0084] Example 6
[0085] Determination of welding parameters: Determine the amplitude of the sawtooth wave scan; Select a 30 mm thick plate as a reference part and weld it by surface overlay welding. Place an 8 mm thick backing plate with the same material as the plate to be welded on the bottom.
[0086] A sawtooth wave electron beam heat source was used to perform surface surfacing welding on duplex titanium alloy. The weld surface was observed. When the weld surface was well formed and the penetration depth reached 30 mm of the duplex titanium alloy reference plate, the parameters at this time were determined as the sawtooth wave scanning amplitude for butt welding of duplex titanium alloy, that is, the scanning amplitude was 0.05 mm, the welding voltage was 140 kV, the welding current was 49 mA, the welding speed was 400 mm / min, the focusing current was 1972 mA, and the scanning frequency was 100 Hz.
[0087] Technical results and analysis: Under the parameters described, deep penetration welding of 30 mm thick duplex titanium alloy was achieved, and the weld pool was stable, the weld surface was well formed, and the joint was free of welding defects.
[0088] Comparative Example 6
[0089] Determination of welding parameters: Determine the amplitude of the sawtooth wave scan; Select a 30 mm thick plate as a reference part and weld it by surface overlay welding. Place an 8 mm thick backing plate with the same material as the plate to be welded on the bottom.
[0090] A sawtooth wave electron beam heat source was used to perform surface surfacing welding on duplex titanium alloy. The weld surface was observed. When the penetration depth reached 30 mm on the duplex titanium alloy reference plate, the parameters at this point were determined as the sawtooth wave scanning amplitude for butt welding of duplex titanium alloy, namely, a scanning amplitude of 0.02 mm, a welding voltage of 140 kV, a welding current of 49 mA, a welding speed of 400 mm / min, a focusing current of 1972 mA, and a scanning frequency of 100 Hz.
[0091] Technical effects and analysis: Under the parameters described, although deep penetration welding of 30 mm thick duplex titanium alloy was achieved, the scan amplitude was too small, resulting in an insignificant scanning effect, a negligible increase in the proportion of precipitated phases, and no significant improvement in joint performance.
[0092] Example 7
[0093] Determination of welding parameters: Determine the amplitude of the sawtooth wave scan; Select a 30 mm thick plate as a reference part and weld it by surface overlay welding. Place an 8 mm thick backing plate with the same material as the plate to be welded on the bottom.
[0094] A sawtooth wave electron beam heat source was used to perform surface surfacing welding on duplex titanium alloy. The weld surface was observed. When the weld surface was well formed and the penetration depth reached 30 mm of the duplex titanium alloy reference plate, the parameters at this time were determined as the sawtooth wave scanning amplitude for butt welding of duplex titanium alloy, that is, the scanning amplitude was 5 mm, the welding voltage was 140 kV, the welding current was 49 mA, the welding speed was 400 mm / min, the focusing current was 1972 mA, and the scanning frequency was 100 Hz.
[0095] Technical results and analysis: Under the parameters described, deep penetration welding of 30 mm thick duplex titanium alloy was achieved, and the weld pool was stable, the weld surface was well formed, and the joint was free of welding defects.
[0096] Comparative Example 7
[0097] Determination of welding parameters: Determine the amplitude of the sawtooth wave scan; Select a 30 mm thick plate as a reference part and weld it by surface overlay welding. Place an 8 mm thick backing plate with the same material as the plate to be welded on the bottom.
[0098] A sawtooth wave electron beam heat source was used to perform surface surfacing welding on duplex titanium alloy. The weld surface was observed. When the penetration depth reached 30 mm on the duplex titanium alloy reference plate, the parameters at this point were determined as the sawtooth wave scanning amplitude for butt welding of duplex titanium alloy, namely, a scanning amplitude of 6 mm, a welding voltage of 140 kV, a welding current of 49 mA, a welding speed of 400 mm / min, a focusing current of 1972 mA, and a scanning frequency of 100 Hz.
[0099] Technical effects and analysis: Under the parameters described, although deep penetration welding of 30 mm thick duplex titanium alloy was achieved, the excessively large scanning amplitude caused increased oscillation and disturbance of the molten pool, resulting in poor weld formation and reduced mechanical properties of the joint.
[0100] Matters not covered in this invention are common knowledge.
[0101] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A welding method for improving the proportion of precipitated phases and mechanical properties of duplex titanium alloys, characterized in that: Includes the following steps: (1) Electron beam welding of dual-phase titanium alloy is performed using sawtooth wave scanning mode to achieve deep penetration welding of dual-phase titanium alloy; (2) In the fusion zone of the electron beam welding head in the sawtooth wave scanning mode, needle-like α phase is precipitated, accounting for more than 30%, thereby improving the mechanical properties of the joint; the scanning amplitude of the sawtooth wave is 0.05~5 mm; the titanium alloy plate is a two-phase near-β alloy; In step (1), during the electron beam welding of the dual-phase titanium alloy plate, the sawtooth wave scanning frequency is 60-150 Hz. In step (1), during electron beam welding, the welding current is 20~80 mA and the welding speed is 100~800 mm / min; In step (2), needle-like α phases with a thickness of 50~500 nanometers were precipitated in the fusion zone of the sawtooth wave joint.
2. The welding method for improving the proportion of precipitated phases and mechanical properties of duplex titanium alloys according to claim 1, characterized in that: In step (1), the thickness of the titanium alloy is greater than 10 mm.
3. The welding method for improving the proportion of precipitated phases and mechanical properties of duplex titanium alloys according to claim 1, characterized in that: In step (1), the electron beam welding process takes place in a vacuum environment with a vacuum level of 10. -5 ~10 -2 Pa.
4. The welding method for improving the proportion of precipitated phases and mechanical properties of duplex titanium alloys according to claim 1, characterized in that: In step (2), after electron beam welding of the duplex titanium alloy plate, the width of the fusion zone is 2~10 mm and the width of the heat-affected zone is 1~4 mm.
5. The welding method for improving the proportion of precipitated phases and mechanical properties of duplex titanium alloys according to claim 1, characterized in that: In step (2), the hardness of the duplex titanium alloy joint obtained after electron beam welding is 280~380 HV.