Resistance welding method and device for titanium alloy aircraft with large-curved-surface narrow-wave-pitch structure

Abstract

The invention discloses a resistance welding method and device for a titanium alloy aircraft with a large-curved-surface narrow-wave-pitch structure. The resistance welding device comprises a linear upper electrode, a spherical lower electrode, a V-shaped upper roller and a V-shaped lower roller, wherein the linear upper electrode and the spherical lower electrode are used for spot welding, and the V-shaped upper roller and the V-shaped lower roller are used for seam welding. According to the method, the fitting gap of the part to be welded is controlled before welding, a special spot welding electrode tip and a welding wheel end face structure are matched, a pulse current mode is adopted during welding, the'small-pressure, small-current and long-time 'welding specification is debugged, large-flow external cooling water is used, and cooling water protection is adopted for the back face of a welding seam, so that stable welding seam quality is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy welding technology, in particular to a resistance welding method and device for titanium alloy large-curved surface narrow-pitch structure aircraft. Background Art

[0002] Titanium and titanium alloys have the characteristics of low density, high specific strength, and strong corrosion resistance, and have been widely used in the aerospace field. The raw material of an aviation radiator product is titanium alloy, and the overall structure is a cylindrical rotating body. The outer layer of the product is designed with corrugated structural parts, and the corrugated structural parts are mainly connected to the cylinder after assembly by resistance spot welding and seam welding. Due to the performance design requirements of the product, the corrugated structural parts are narrow pitch structures, and the straight edge of the assembly welding with the cylinder is no more than 2mm. The axial corrugated channels of this part are distributed in 49 places. When the product is working, the corrugated channels need to withstand high temperature and high pressure gas, so the sealing and stability of the weld quality are required to be high.

[0003] The welding process control requirements for titanium and titanium alloy products are relatively high. On the one hand, titanium and titanium alloys are more active in the hot state. When welding titanium and titanium alloy components without protection, the base material begins to absorb hydrogen at 200°C, oxygen at 400°C, and nitrogen at 600°C. The presence of elements such as hydrogen, oxygen, and nitrogen will make the weld brittle and reduce the load-bearing capacity of the weld. On the other hand, titanium and titanium alloys have low thermal conductivity, and heat is easily concentrated in the weld and heat-affected area during welding. If the heat output of the equipment during welding is unstable or the heat is too concentrated, the weld will be locally overheated, resulting in welding burns, breakdown, and cracks. The weld structure has coarse grains, which reduces the mechanical properties of the weld.

[0004] The resistance spot welding and seam welding process requires a certain electrode pressure to be applied on the workpiece surface. The elongation of titanium and titanium alloys at room temperature is only 12%, which is only 1 / 4 of austenitic stainless steel. Therefore, titanium and titanium alloys have poor plasticity at room temperature. Since the parts are narrow-pitch structures, the electrode width of the pressure surface during welding is only 2mm, and the force-bearing surface of the parts is small. Excessive electrode pressure is prone to deep local indentations or even local ruptures; when the electrode pressure is small, the resistance of the weld will increase, resulting in breakdown of the workpiece.

[0005] In summary, in order to ensure the welding quality of titanium and titanium alloy narrow-pitch structural aircraft and meet the high temperature and high pressure working requirements under its operating conditions, it is necessary to adopt a resistance welding process that meets its specific structure. Summary of the invention

[0006] The present invention aims to provide a resistance welding method and device for a titanium alloy large-curved narrow-pitch structure aircraft, which can meet the welding quality requirements of its narrow-pitch structure while stabilizing the welding process and controlling the final welding quality.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A resistance welding device for a titanium alloy large curved surface narrow pitch structure aircraft, comprising:

[0009] The electrode head comprises an upper electrode and a lower electrode, the welding working end of the upper electrode is in a straight line shape, and the edges of the straight line welding working end are all rounded, and the welding working end of the lower electrode is a spherical surface;

[0010] The welding wheel comprises an upper welding wheel and a lower welding wheel, the welding working end of the upper welding wheel is V-shaped, so that the contact area between the welding working end of the upper welding wheel and the part to be welded is smaller than the contact area between the welding working end of the lower welding wheel and the part to be welded, and the edges on both sides of the welding working end of the upper welding wheel are blunt.

[0011] As a solution:

[0012] The length of the welding working end face of the upper electrode is twice the wave pitch size of the welded part;

[0013] The end face width of the welding working end of the upper electrode is 0.8 to 0.85 times the wave pitch size of the welded part.

[0014] As a solution:

[0015] The width of the end face of the welding working end of the upper welding wheel is 0.85 to 0.90 times the wave pitch size of the welded part;

[0016] The width of the end face of the welding working end of the lower welding wheel is 2.5 to 5 times the width of the end face of the welding working end of the upper welding wheel.

[0017] As a solution, the edge profile of the end surface of the welding working end of the upper electrode is rectangular, and the welding working end is a plane or an ellipsoidal surface.

[0018] A resistance welding method for a titanium alloy large-curved narrow-pitch structure aircraft adopts the above-mentioned resistance welding device and comprises the following steps:

[0019] S1, assemble the corrugated plate and the cylinder, and control the fitting gap between the corrugated plate and the cylinder at the welding point to be no more than 0.5mm;

[0020] S2, spot welding positioning of the corrugated plate and the cylinder, using the upper electrode and the lower electrode to perform spot welding positioning between the corrugated plate and the cylinder;

[0021] S3, seam welding positioning corrugated plate and cylinder, using upper welding wheel and lower welding wheel to seam weld corrugated plate and cylinder, and adopt pulse current mode during seam welding, and use cooling water to cool the upper welding wheel, lower welding wheel and the outer surface of the welded part during seam welding. Before seam welding, coolant is passed into the corrugated channel so that the back of the welded part is immersed in cooling water.

[0022] Furthermore, in S3, a welding specification of low pressure, low current and long time is adopted.

[0023] Furthermore, in S3, the weld of the seam welding completely covers the welding point during the spot welding positioning, and the welding point cannot exceed the edge of the weld of the seam welding.

[0024] Furthermore, in S2, before spot welding the corrugated plate and the cylinder, the assembled corrugated plate and the cylinder are pickled.

[0025] Furthermore, in S3, welding is started from the middle of the cylinder curved surface, and then welding is performed toward both axial sides of the cylinder.

[0026] Furthermore, the resistance welding method for titanium alloy large-curved narrow-pitch structure aircraft also includes S4, grinding the welding surface after the seam welding is completed to remove the surface oxide scale.

[0027] The key to quality control of resistance welding of titanium alloy large-surface narrow-pitch structure aircraft is to control the gap between parts to be welded before welding, design appropriate spot welding electrode head and welding wheel end face structure, use pulse current mode during welding, adjust the welding specification of "low pressure, low current, long time", and use large-flow external cooling water and cooling water protection on the back of the weld to obtain stable weld quality.

[0028] Compared with the prior art, the present invention has the following characteristics:

[0029] (1) The raw material of the titanium alloy large curved surface narrow wave pitch structure aircraft is titanium alloy, which is partially or entirely curved and is obtained by hot forming. The titanium alloy large curved surface narrow wave pitch structure aircraft is a narrow wave pitch corrugated structure, and the adjacent wave pitch size is not greater than 2mm. For the aircraft, the present invention discloses a processing method for the titanium alloy large curved surface narrow wave pitch structure aircraft, which is specifically a resistance welding method, including spot welding and seam welding. When seam welding, spot welding positioning is first used, and then specific welding parameters are used to complete the seam welding processing.

[0030] (2) The present invention adopts a special electrode structure, that is, a combination of a straight spot welding upper electrode and a spherical lower electrode, and a seam welding adopts a combination of a V-shaped upper welding wheel and a conventional lower welding wheel.

[0031] (3) The present invention realizes quality control by controlling the assembly gap between the corrugated plate and the cylinder, the welding parameter setting during seam welding, and the cooling method during seam welding. Selecting the pulse current welding mode during seam welding can effectively control heat input, refine the weld grains, promote molten pool stirring, avoid the impact of component segregation on weld quality, reduce the impact of temperature gradient, reduce welding stress, and generally improve weld quality. During seam welding, cooling water is directly introduced into the inner cavity of the corrugation to achieve timely cooling of the parts while isolating the air to prevent the titanium alloy from being contaminated by impurities in the air in the hot state. (4) The present invention changes the traditional idea of ​​welding the corrugated plate and the cylinder, which is to first perform low current hot pressing and then use high current welding. It directly uses one welding parameter (referring to the welding parameter during seam welding) to weld in one step, and compensates for each other through pressure, current and time, and adjusts to obtain the welding parameters for seam welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of titanium alloy large curved surface narrow wave pitch structure aircraft welding;

[0033] Figure 2 It is a schematic diagram of the welding between the corrugated plate and the cylinder;

[0034] Figure 3 Schematic diagram of the electrode head structure;

[0035] Figure 4 is a schematic diagram of the welding wheel structure;

[0036] Figure 5 Schematic diagram of the structure of the upper welding wheel;

[0037] Figure 6 is a structural schematic diagram of the lower welding wheel;

[0038] In the figure, 1-upper electrode, 2-upper welding wheel, 3-lower welding wheel, 4-first cooling water pipe, 5-second cooling water pipe, 6-inner cavity channel. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above-mentioned technical ideas of the present invention, various modifications, substitutions and changes made according to the common technical knowledge and customary means in the field are included in the scope of the present invention.

[0040] like Figure 2 As shown, it is the welding structure of corrugated plate and cylinder. Figure 2 Position A is the 2mm narrow pitch resistance welding weld, position B is the large curved surface of the cylinder (specifically the cylindrical curved surface), and position C is the inner cavity channel of the corrugated plate. In order to solve the welding problem of titanium alloy large curved surface narrow pitch structure aircraft, the present invention adopts the idea of ​​spot welding first and then seam welding, as follows:

[0041] (1) The gap between the corrugated plate and the cylinder to be welded should be no more than 0.5 mm.

[0042] (2) Figure 3 When spot welding is positioned, a modified special electrode head structure is selected. The electrode head includes an upper electrode 1 and a lower electrode. The end face of the upper electrode 1 is in a "straight shape". After a large number of orthogonal tests and test data fitting, it is concluded that the end face length of the upper electrode 1 is designed to be 2 times the wave pitch size of the weld, and the end face width of the upper electrode 1 is designed to be 0.8 to 0.85 times the wave pitch size of the weld. At the same time, the sharp edges are blunted to avoid the formation of sharp angles, and the lower electrode is designed to be spherical.

[0043] (3) Figures 4 to 6 During seam welding, the end face of the upper welding wheel 2 is designed to be a tapered "V" structure (thin near the edge of the upper welding wheel 2, thick near the center), the end face of the upper welding wheel 2 is designed to be 0.85 to 0.90 times the wave pitch size of the welding point, and the sharp edges on both sides of the end face are blunted, and the end face of the lower welding wheel 3 is designed to be 2.5 to 5 times the width of the end face of the upper welding wheel 2. The lower welding wheel 3 is a roller structure with a smaller diameter than the upper welding wheel 2. The end face of the lower welding wheel 3 is designed to be flat, and the end faces on both sides are inverted to prevent scratching the inner wall of the part. The upper welding wheel 2 is designed to be a "V" shaped structure mainly due to the narrow wave pitch of the corrugated plate (the effective welding surface is only 2mm). Another reason is to stabilize the welding heat and avoid the offset of the molten core during the welding process. In addition, the end face of the lower welding wheel 3 is in direct contact with the inner wall of the part to avoid scratching the inner wall of the part.

[0044] (4) Equipment parameter setting: pulse current mode is used for seam welding. During the pulse welding process, energy is applied to the welding area in the form of pulses. During the pulse action, the welding energy melts the weld metal; during the pulse interval, the heat is rapidly dissipated and the weld metal cools rapidly. This periodic heating and cooling process limits the growth time of the grains. Compared with traditional continuous welding, the weld metal is not in a high temperature state for a long time, thereby inhibiting the excessive growth of the grains and promoting the formation of a fine grain structure.

[0045] (5) Turn on the external cooling water to fully cool the upper welding wheel 2, the lower welding wheel 3 and the outer surface of the welded area. During seam welding, the cooling water is sprayed synchronously.

[0046] (6) Pour cooling water into the corrugated channel ( Figure 1 The inner cavity channel 6 is shown in the figure, so that the back of the welding part is fully immersed in the liquid surface. The cooling water in (5) and (6) is used to cool the parts during welding and take away excess heat, and on the other hand, it is used to isolate the air. The two sides of the inner cavity channel 6 are connected, so the cooling water is introduced before welding and continues to be introduced during the welding process.

[0047] (7) Adjust the welding parameters and adopt the welding specifications of "small pressure, small current, and long time". During the seam welding process, it is necessary to ensure that the weld completely covers the spot welding positioning weld point, and the weld point cannot exceed the edge of the seam welding weld. Since titanium alloy has low cold plasticity and is prone to cracking under external force, small pressure is used; titanium alloy has low thermal conductivity and is prone to overheating and burning during welding, resulting in coarse grains, and in severe cases, directly piercing the workpiece, so a small current is used. The long time is to obtain a better weld joint, and the welding heat can ensure that the weld nugget size that meets the standard requirements is obtained. (8) After welding, use a special grinding tool to clean the oxide scale on the workpiece surface.

[0048] A resistance welding method for a titanium alloy large-curved surface narrow-pitch structure aircraft comprises the following steps:

[0049] 1) Control the assembly surface size of the corrugated plate and the cylinder to ensure that the gap between the parts to be welded is no more than 0.5mm;

[0050] 2) Pickling treatment of corrugated plates and cylinders. Pickle the corrugated plates and cylinders to be welded according to standard requirements, and check that there is no oil, rust or other excess material attached to the surface of the parts after pickling;

[0051] 3) Spot welding positioning. Design a special "straight-shaped" upper electrode 1, use machining milling or sheet metal grinding to round the edges of the welding surface, and touch it with your hand to make sure there are no sharp edges. Then spot weld the area to be welded, and the offset of each adjacent positioning welding point should not exceed 0.5mm to avoid pressure waves;

[0052] 4) Seam welding parameter setting. Debug the pulse current mode and debug the welding parameters according to the welding specification of "low pressure, low current, long time";

[0053] 5) Turn on the cooling water. Set the first cooling water pipe 4 and the second cooling water pipe 5 on the outer sides of the upper welding wheel 2 and the lower welding wheel 3 of the seam welding machine respectively, spray cooling the upper welding wheel 2, the lower welding wheel 3 and the welding surface. Fill the corrugated channel of the corrugated plate with cooling water before welding ( Figure 1 The inner cavity channel 6) in the welding joint is completely immersed in the liquid surface;

[0054] 6) Test welding of test pieces. Use test pieces of the same material and specifications for test welding, and conduct appearance and tear inspection. Only after passing the inspection can the product be welded;

[0055] 7) Formal welding: Use the welding parameters that have passed the test welding to weld the product. Start welding from the middle of the cylinder surface and weld to both sides of the axial direction.

[0056] 8) Post-weld inspection: After welding is completed, the weld is inspected with a 5-10x magnifying glass, X-ray flaw detection or sealing inspection. No welding defects (breakdown, burns, cracks and welding spatter) are allowed.

[0057] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A resistance welding device for titanium alloy large curved surface narrow pitch structure aircraft, characterized in that: include: An electrode head, the electrode head comprising an upper electrode (1) and a lower electrode, the welding working end of the upper electrode (1) being in a straight line shape, and the edges of the straight line welding working end are all rounded, and the welding working end of the lower electrode is a spherical surface; The welding wheel comprises an upper welding wheel (2) and a lower welding wheel (3), the welding working end of the upper welding wheel (2) is V-shaped, so that the contact area between the welding working end of the upper welding wheel (2) and the part to be welded is smaller than the contact area between the welding working end of the lower welding wheel (3) and the part to be welded, and the edges on both sides of the welding working end of the upper welding wheel (2) are blunt.

2. The resistance welding device for titanium alloy large curved surface narrow pitch structure aircraft according to claim 1, characterized in that: The length of the end face of the welding working end of the upper electrode (1) is twice the wave pitch size of the welded part; The width of the end face of the welding working end of the upper electrode (1) is 0.8 to 0.85 times the wave pitch size of the welded part.

3. The resistance welding device for titanium alloy large curved surface narrow pitch structure aircraft according to claim 1, characterized in that: The width of the end face of the welding working end of the upper welding wheel (2) is 0.85 to 0.90 times the wave pitch size of the welded part; The width of the end face of the welding working end of the lower welding wheel (3) is 2.5 to 5 times the width of the end face of the welding working end of the upper welding wheel (2).

4. The resistance welding device for titanium alloy large curved surface narrow pitch structure aircraft according to claim 1, characterized in that: The edge profile of the end surface of the welding working end of the upper electrode (1) is rectangular, and the welding working end is a plane or an ellipsoidal surface.

5. A resistance welding method for titanium alloy large curved surface narrow pitch structure aircraft, characterized in that: Using the resistance welding device of claim 1, and The following steps are involved: S1, assemble the corrugated plate and the cylinder, and control the fitting gap between the corrugated plate and the cylinder at the welding point to be no more than 0.5mm; S2, spot welding the corrugated plate and the cylinder, using the upper electrode (1) and the lower electrode to perform spot welding between the corrugated plate and the cylinder; S3, seam welding the corrugated plate and the cylinder to position them, using an upper welding wheel (2) and a lower welding wheel (3) to cooperate with each other to seam weld the corrugated plate and the cylinder, and using a pulse current mode during seam welding. During the seam welding process, cooling water is used to cool the upper welding wheel (2), the lower welding wheel (3) and the outer surface of the welded part. Before seam welding, cooling water is passed into the corrugated channel so that the back of the welded part is immersed in the cooling water.

6. The resistance welding method for titanium alloy large curved surface narrow pitch structure aircraft according to claim 5, characterized in that: In S3, a welding specification of low pressure, low current and long time is adopted.

7. The resistance welding method for titanium alloy large curved surface narrow pitch structure aircraft according to claim 5, characterized in that: In S3, the weld of the seam welding completely covers the welding point when the spot welding is positioned, and the welding point cannot exceed the edge of the weld of the seam welding.

8. The resistance welding method for titanium alloy large curved surface narrow pitch structure aircraft according to claim 5, characterized in that: In S2, before spot welding the corrugated plate and the cylinder, the assembled corrugated plate and the cylinder are pickled.

9. The resistance welding method for titanium alloy large curved surface narrow pitch structure aircraft according to claim 5, characterized in that: In S3, welding is started from the middle of the cylinder curved surface, and then welding is performed toward both axial sides of the cylinder.

10. The resistance welding method for titanium alloy large curved surface narrow pitch structure aircraft according to claim 5, characterized in that: It also includes S4, which is to grind the weld surface after seam welding to remove the surface oxide scale.

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