Aluminum-steel dissimilar metal pipe joint inertia friction welding method

Abstract

The application discloses an inertia friction welding method for aluminum-steel dissimilar metal pipe joints, and comprises the following steps: S1, designing the joint structure of a welding part 1 and a welding part 2 before welding, welding tool structure and processing, then assembling the welding tool on the welding part 1 and the welding part 2 respectively, the welding part 1 is a steel end of the aluminum-steel dissimilar metal pipe joint, the welding part 2 is an aluminum end of the aluminum-steel dissimilar metal pipe joint, then mounting the assembled welding part 1 and the welding part 2 on the rotating end and the fixed end of the inertia friction welding equipment respectively; S2, welding according to the inertia friction welding equipment operation program and the set welding process parameters, the welding process parameters are as follows: moment of inertia 50-500 Kg.m 2 , flywheel rotating speed 800-1200 r / min, welding upset force 80-200 bar, upset pressure maintaining time 10-30 s. The method can effectively control the inertia friction welding defects of the aluminum-steel dissimilar metal, especially the large-diameter thick-wall aluminum-steel dissimilar metal, and improves the welding qualified rate, joint quality and performance.

Description

Technical Field

[0001] This invention belongs to the field of welding technology and relates to an inertial friction welding method for aluminum-steel dissimilar metal pipe joints. Background Technology

[0002] Aluminum-steel dissimilar metal pipe connection structures combine the advantages of aluminum alloys (low specific gravity, excellent electrical conductivity, and good corrosion resistance) with the high strength of steel, making them highly practical and increasingly widely used. This is especially true in piping systems in industries such as aerospace and air separation, where structural requirements necessitate the use of aluminum-steel dissimilar metal pipe joints. Furthermore, with the increasing scale of high-end equipment in aerospace and other fields, the demand for welding connections of large-diameter, thick-walled aluminum-steel pipe joints (Φ150mm and above) is gradually increasing.

[0003] Inertial friction welding is an effective joining process for dissimilar metals such as aluminum and steel. However, the significant differences in the physicochemical properties of aluminum and steel make it easy for hard and brittle intermetallic compounds to form at the joint, resulting in low performance and easy cracking. Furthermore, Fe and Al do not dissolve in each other under both liquid and solid conditions. This means that aluminum and steel must form an intermetallic compound at the joint interface to achieve a welded connection. This also makes aluminum-steel welding prone to defects such as voids and incomplete fusion. Therefore, the biggest challenge in achieving high-quality and high-performance welding of dissimilar metals such as aluminum and steel is to achieve a welded connection through intermetallic compounds while also addressing the impact of intermetallic compounds on the quality and performance of the joint.

[0004] Currently, the technical research and engineering applications of inertial friction welding of aluminum and steel dissimilar metals are mainly focused on small-sized joints with a welding diameter of less than 150mm and a welding wall thickness of less than 10mm. For large-diameter thick-walled joints with a diameter of more than 150mm and a wall thickness of more than 10mm, as the diameter and wall thickness of the workpiece to be welded increase, the superposition of the dissimilar material properties of aluminum and steel and the workpiece size effect significantly increases the difficulty of controlling the welding quality and performance of the joint. Meanwhile, inertial friction welding of large-size aluminum-steel joints generally requires tens of tons, hundreds of tons, or even greater welding upsetting forces. After welding, the joint area has a large amount of flash and plastic deformation layer. It is necessary to use a tube blank with a thickness greater than that of the product for welding and then machining to form the final product structure. During the welding process, the temperature of the aluminum-steel interface of the joint rises sharply under the action of frictional heat, which greatly reduces the strength and rigidity of the aluminum-steel in the joint welding area. In order to prevent the joint area from being crushed under the action of large upsetting forces and failing to form an effective connection, the welding thickness of the tube blank actually used needs to be further increased to ensure the rigidity of the joint area during the welding process. This makes the actual welding tube blank thickness much larger than the product thickness, which significantly increases the requirements of inertial friction welding equipment and also significantly increases the residual stress after welding of aluminum-steel joints. As a result, the residual stress makes the current aluminum-steel joints prone to cracking during the machining process after welding.

[0005] The above factors make the current aluminum-steel dissimilar metal inertial friction welding method demanding on equipment, difficult to control welding defects, and prone to cracking during post-weld joint processing, resulting in low welding pass rate, joint quality, and performance. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an inertial friction welding method for aluminum-steel dissimilar metal pipe joints.

[0007] To achieve the above objectives, the present invention employs the following technical solutions:

[0008] A method for inertial friction welding of aluminum-steel dissimilar metal pipe joints includes the following steps:

[0009] S1. Design and process the pre-welding joint structure and welding fixture structure of weldment 1 and weldment 2. Then, assemble the welding fixtures onto weldment 1 and weldment 2 respectively. Finally, install the assembled weldment 1 and weldment 2 onto the rotating end and the fixed end of the inertial friction welding equipment respectively. There are no restrictions on whether weldment 1 and 2 are installed on the rotating end or the fixed end, and it does not affect the setting of subsequent welding programs and welding parameters.

[0010] S2. Weld according to the operating procedure and set welding process parameters of the inertial friction welding equipment. The welding process parameters are: rotational inertia 50-500 kg / m. 2 Flywheel speed 800-1200 r / min, welding upsetting force 80-200 bar, upsetting holding time 10-30 s.

[0011] Based on the dimensions of the aluminum-steel dissimilar metal pipe joint product, the pre-welding pipe blank welding joint structure is designed. The joint includes weldment 1 and weldment 2, both of which are circular pipe structures. Weldment 1 is the steel end, and weldment 2 is the aluminum end. The welding parts of weldment 1 and weldment 2 adopt a joint structure with a small welding thickness. That is, the outer wall of the welding part of weldment 1 has a welding bevel and the inner wall is designed as a stepped structure. The outer wall of the welding part of weldment 2 is designed as a stepped structure and the inner wall has a welding bevel. The stepped structures of the two are used to place the internal support and the external welding fixture, respectively.

[0012] Welding part 1 has an outer diameter D1, an inner diameter D2, an outer wall welding bevel angle α, a welding bevel minor diameter D3, an inner wall step diameter D4, and a step height H1; Welding part 2 has an outer diameter D5, an inner diameter D6, a welding bevel surface that coincides with welding part 1 (i.e., its inner wall welding bevel angle is α), a welding bevel major diameter that is consistent with the outer diameter D1 of welding part 1, and a minor diameter D6 that is consistent with the welding bevel minor diameter D3 of welding part 1, an outer wall step diameter D7, and a step height H2.

[0013] D1, D2, D5, and D6 are the dimensions of the workpiece. The welding bevel angle is 80°≤α≤100° (preferably 90°), 30mm≤D1-D3≤40mm, 10mm≤D3-D4≤15mm, 10mm≤H1≤30mm, 5mm≤D5-D7≤10mm, and 50mm≤H2≤70mm.

[0014] The welding fixture includes an inner support fixture and an outer hoop fixture. The inner support fixture acts on the weldment 1 and includes wedge 1, wedge 2 and connecting bolts. Among them, the wedge 1 adopts a segmented structure to enhance the adaptability of the internal support. It is composed of no less than 4 wedge-shaped equal segments according to the inner diameter of the weldment 1. Each equal segment is an L-shaped structure with through holes. After the equal segments are assembled into the wedge 1, in the free state, the relationship between the outer diameter D8 of its small end and the inner diameter D2 of the weldment 1 is 2mm≤D2-D8≤4mm, the relationship between the outer diameter D9 of its large end and the inner wall step diameter D4 of the weldment 1 is 0.5mm≤D9-D4≤1mm, the inner hole included angle β is 15°≤β≤20°, and the inner hole large end diameter D10 is determined according to the outer diameter D8 and the pressure borne by the equal segments of the wedge 1 during the welding process to ensure that its rigidity is sufficient and does not deform. The relationship between the height H3 of its internal support area and the height H1 of the inner wall step of the welded part of the weldment 1 is H3=H1, and the relationship between the total height H4 and H3 is 20mm≤H4-H3≤25mm.

[0015] Wedge 2 is an integral T-shaped frustum structure. To ensure that after it is pressed into wedge 1, the outer diameter D1 of the welded part of weldment 1 is increased by 0.5-1mm and sufficient rigidity is guaranteed, the matching relationship between wedge 2 and wedge 1 is as follows: the cone angle of the frustum is consistent with the included angle β of the inner hole of wedge 1, the large end diameter D13=D8, the height H5 of the frustum and the total height H4 of wedge 1 satisfy the relationship 0≤H5-H4≤5mm, the total height H6 is 20mm≤H6-H5≤40mm, the small end diameter D12 and the small end diameter D11 of the inner hole of wedge 1 satisfy the relationship D12-D11≥2mm and satisfy the relationship D12=D10-2×H5×tan(β / 2) with the large end diameter D10 of the inner hole of wedge 1.

[0016] Before welding, equal-divided blocks are placed sequentially on the inner wall steps of weldment 1 to form wedge 1. Then, wedge 2 is pressed into the inner hole of wedge 1, causing the equal-divided blocks of wedge 1 to expand outwards and elastically deform the welding area of ​​weldment 1. The outer diameter D1 of the welding area of ​​weldment 1 is increased by 0.5-1mm by controlling the depth of wedge 2 pressed into the inner hole of wedge 1. Finally, wedge 1 and wedge 2 are connected and locked using bolts. To ensure the positional relationship of the bolt connection holes after wedge 2 is pressed into the inner hole of wedge 1, the diameter of the through hole of the equal-divided block of wedge 1 is 2mm larger than the major diameter of the threaded hole of wedge 2, to compensate for the positional deviation of the connection holes caused by the 0.5-1mm expansion of the inner diameter of wedge 1. Wedge 1 and wedge 2 are made of stainless steel.

[0017] The outer hoop fixture, acting on weldment 2, is a ring-shaped structure. Its inner diameter D14 is related to the outer wall step diameter D7 of weldment 2 in the condition 0 ≤ D7 - D14 ≤ 0.05 mm. Its outer diameter D15 satisfies 30 mm ≤ D15 - D14 ≤ 40 mm. Its height H7 is related to the outer wall step height H2 of weldment 2 in the condition H2 - H7 = 5 mm. The material is stainless steel. Before welding, the outer hoop fixture is installed at the outer wall step of weldment 2.

[0018] The present invention has the following advantages:

[0019] 1. The method of this invention includes a matching aluminum-steel welded joint structure, an inner support and outer hoop tooling structure, and welding process parameters. One of the key features is the use of a joint structure with a smaller weld thickness to achieve inertial friction welding of large-diameter aluminum-steel workpieces. By adopting a bevel and step structure on the aluminum-steel welding end face, the effective contact area of ​​the welding part is minimized. This allows the use of relatively small-capacity inertial friction welding equipment to achieve the welding of large-diameter aluminum-steel structures. At the same time, the use of a joint structure with a smaller weld thickness reduces post-weld residual stress, which helps prevent cracking caused by residual stress during post-weld joint processing.

[0020] 2. Another key aspect of this invention is the design of an internal support fixture at the stainless steel end welding area and the control of the outer diameter expansion of the stainless steel end welding area by 0.5-1mm. Additionally, an external clamping fixture is designed at the aluminum alloy end welding area and its interference fit with the aluminum alloy end welding area is controlled at 0-0.05mm. This ensures appropriate rigidity of the joint welding area, controls the degree of deformation of the joint welding area during the welding process, and prevents excessive deformation, especially at the aluminum alloy end, from causing crushing and ineffective connection under large upsetting forces and frictional heat, or from insufficient deformation leading to defects due to insufficient friction at the joint interface. This significantly improves the quality and performance of aluminum-steel welding.

[0021] 3. Another key aspect of this invention is the matching of the joint structure, welding fixtures, and welding process parameters. This enables high-quality, high-performance welding of aluminum-steel joints with large spans of diameter Φ100mm-Φ500mm and wall thickness 15mm-50mm using the same inertial friction welding equipment. (If the method of this invention is not used, to achieve the welding of aluminum-steel parts with the above-mentioned size span, the stability of the welding process is affected by the limitations of inertia and rotation speed matching. Two inertial friction welding equipment are required to weld aluminum-steel parts with a minimum diameter of Φ100mm and a minimum wall thickness of 15mm and a maximum diameter of Φ500mm and a maximum wall thickness of 50mm, respectively.) This significantly improves equipment compatibility, reduces equipment investment, and thus reduces production costs. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the joint structure of the weldment 1 of the present invention;

[0023] Figure 2 This is a schematic diagram of the joint structure of the weldment 2 of the present invention;

[0024] Figure 3 This is a schematic diagram of the internal support tooling structure of the present invention;

[0025] Figure 4 This is a schematic diagram of the wedge-shaped component 1 of the internal support tooling of the present invention;

[0026] Figure 5 This is a schematic diagram showing the dimensions of the wedge-shaped component 1 of the internal support tooling of the present invention;

[0027] Figure 6 This is a schematic diagram of the wedge-shaped component 2 of the internal support tooling of the present invention;

[0028] Figure 7 This is a schematic diagram showing the dimensions of the wedge-shaped component 2 of the internal support tooling of the present invention;

[0029] Figure 8 This is a schematic diagram showing the assembly relationship between the internal support tooling and the weldment 1 of the present invention;

[0030] Figure 9 This is a schematic diagram of the outer hoop tooling structure of the present invention;

[0031] Figure 10 This is a schematic diagram of the dimensions of the outer hoop tooling of the present invention;

[0032] Figure 11 This is a schematic diagram showing the assembly relationship between the outer hoop tooling and the weldment 2 of the present invention;

[0033] Figure 12 This is a schematic diagram of the assembly relationship between the pre-welding joint, inner support, and outer hoop tooling in the method of the present invention.

[0034] In the figure: 1—Welding part 1, 2—Welding part 2, 3—Outer hoop fixture, 4—Wedge-shaped part 1 of the inner support fixture, 5—Bolt, 6—Wedge-shaped part 2 of the inner support fixture. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings.

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0037] Example:

[0038] A method for inertial friction welding of aluminum-steel dissimilar metal pipe joints is disclosed. The joint product has an outer diameter of 414 mm, a wall thickness of 5 mm, and is made of 2219 aluminum alloy and 0Cr18Ni9 stainless steel. After welding, the joint structure is machined to meet the following requirements: no fluorescence detection on the joint surface and no internal defects detected by ultrasonic testing; leak detection is performed using room temperature vacuum helium mass spectrometry for at least 5 minutes, with a single-hole leak rate ≤1×10⁻⁶. -10 Pa·m 3 / s; Conduct a hydraulic burst test, pressurize to 2MPa, hold for 5 minutes, and do not allow damage or significant deformation. Continue pressurizing until bursting. The crack location should be the tooling weld or the aluminum alloy base material. If the crack location is at the inertial friction weld, the breaking pressure value should not be less than 4MPa. The method steps are as follows:

[0039] (1) Welded joint structure design

[0040] Based on the dimensions of the aluminum-steel dissimilar metal pipe joint product, the pre-welding pipe blank welding joint structure is designed. The joint includes weldment 1 and weldment 2, both of which are circular pipe structures. Weldment 1 is the steel end, and weldment 2 is the aluminum end. Weldment 1 has an outer diameter D1 = 428 mm, an inner diameter D2 = 316 mm, an outer wall welding bevel angle α = 90°, a welding bevel minor diameter D3 = 390 mm, an inner wall step diameter D4 = 378.5 mm, and a step height H1 = 25 mm. Weldment 2 has an outer diameter D5 = 450 mm, an inner diameter D6 = 390 mm, and a welding bevel surface that coincides with that of weldment 1, i.e., its inner wall welding bevel angle is α = 90°, the welding bevel major diameter is the same as the outer diameter D1 of weldment 1, and the minor diameter D6 is the same as the welding bevel minor diameter D3 of weldment 1. The outer wall step minor diameter D7 = 445 mm, and the step height H2 = 65 mm.

[0041] (2) Design of welding fixture for internal bracing and external hoop

[0042] The internal support fixture acts on weldment 1 and includes wedge 1, wedge 2, and connecting bolts. Wedge 1, designed according to the inner diameter of weldment 1, consists of 12 equally spaced wedge-shaped blocks. Each block is L-shaped with through holes. When the blocks are assembled into wedge 1, in its free state, its small end outer diameter D8 = 314 mm, large end outer diameter D9 = 379 mm, large end inner diameter D10 = 220 mm, small end inner diameter D11 = 203.5 mm, and inner hole included angle β = 16°. The height of its internal support area is H3 = 25 mm, and the total height is H4 = 48 mm. Wedge 2 is an integral T-shaped frustum structure. The cone angle of the frustum is the same as the included angle of the inner hole of wedge 1, i.e., 16°. Its large end diameter is D13 = 314 mm, frustum height H5 = 50 mm, total height H6 = 90 mm, and small end diameter D12 = 206 mm. Before welding, equal blocks are placed sequentially on the inner wall steps of weldment 1 to form wedge 1. Then, wedge 2 is pressed into the inner hole of wedge 1, causing the equal blocks of wedge 1 to expand outward and produce elastic deformation at the welding part of weldment 1. By controlling the depth of wedge 2 pressed into the inner hole of wedge 1, the outer diameter D1 of the welding part of weldment 1 is increased by 0.6mm. Finally, wedge 1 and wedge 2 are connected and locked with bolts. Wedge 1 and wedge 2 are made of 304 stainless steel.

[0043] The outer hoop fixture acts on weldment 2 and has a ring-shaped structure with an inner diameter of... Its outer diameter D15 = 480mm, and its height H7 = 60mm; the material is 304 stainless steel. Before welding, the outer hoop fixture is installed on the outer wall step of weldment 2.

[0044] (3) Welding and process parameters

[0045] Using the aforementioned joint structure and assembling the welding fixture onto weldment 1 and weldment 2, the assembled weldment 1 and weldment 2 are then installed on the rotating and fixed ends of the inertial friction welding equipment. The welding areas of weldment 1 and weldment 2 are cleaned of surface oxide film and oil stains using common pre-welding grinding methods, and wiped with acetone or alcohol. Welding is then performed according to the operating program and set welding process parameters of the inertial friction welding equipment. The welding process parameters are: rotational inertia 436 kg·m. 2 The flywheel speed is 880 r / min, the welding upsetting force is 185 bar, and the upsetting holding time is 30 s.

[0046] After welding, the joint structure was machined without cracking. Surface fluorescence and ultrasonic testing of the joint revealed no visible defects or internal flaws. Room temperature vacuum helium mass spectrometry was used for leak detection, with a detection time of 5 minutes and a single-hole leak rate ≤1×10⁻⁶. -12 Pa·m 3 / s; The two ends of the pipe joint are sealed by welding, and a hydraulic burst test is performed. The pressure is increased to 2MPa and held for 5 minutes. If the joint shows no damage or obvious deformation, the pressure is continued until bursting. The crack location is at the weld of the sealing tool. All of the above tests meet or exceed the corresponding index requirements, indicating that the method of the present invention is effective.

[0047] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A method for inertial friction welding of aluminum-steel dissimilar metal pipe joints, applicable to aluminum-steel dissimilar metal pipe joints with diameters of Φ100mm-Φ500mm and wall thicknesses of 15mm-50mm, characterized in that, Includes the following steps: S1. Design the pre-welding joint structure and welding fixture structure of weldment 1 and weldment 2 and process them. Then, assemble the welding fixtures onto weldment 1 and weldment 2 respectively. Weldment 1 is the steel end of the aluminum-steel dissimilar metal pipe joint and weldment 2 is the aluminum end of the aluminum-steel dissimilar metal pipe joint. Then, install the assembled weldment 1 and weldment 2 onto the rotating end and fixed end of the inertial friction welding equipment respectively. The welding fixtures include internal support fixtures and external hoop fixtures; The internal support tooling assembly weldment 1 includes wedge 1, wedge 2 and connecting bolts. Wedge 1 is composed of no less than 4 wedge-shaped equal blocks, which are L-shaped and have through holes. Wedge 2 is an integral T-shaped frustum structure. The equal blocks are placed sequentially on the inner wall steps of the weldment 1 to form wedge 1. Then, wedge 2 is pressed into the inner hole of wedge 1, causing the equal blocks of wedge 1 to expand outward and causing elastic deformation of the welded part of the weldment 1. The outer diameter D1 of the welded part of the weldment 1 is increased by 0.5-1mm by controlling the pressing depth of wedge 2. Then, wedge 1 and wedge 2 are connected and locked by connecting bolts to achieve quantitative preloading. The outer hoop fixture is a ring structure and is installed on the outer wall step of weldment 2. Its inner diameter D14 and the outer wall step diameter D7 of weldment 2 satisfy the micro interference constraint of 0≤D7-D14≤0.05mm. S2. Weld according to the operating procedure of the inertial friction welding equipment and the set welding process parameters. The welding process parameters are: moment of inertia 50-500Kg.m², flywheel speed 800-1200r / min, welding upsetting force 80-200bar, and upsetting holding time 10-30s.

2. The method for inertial friction welding of aluminum-steel dissimilar metal pipe joints according to claim 1, characterized in that: In step S1, the outer wall of the welding part of weldment 1 has a welding bevel and the inner wall is designed as a stepped structure, and the outer wall of the welding part of weldment 2 has a stepped structure and the inner wall has a welding bevel.

3. The method for inertial friction welding of aluminum-steel dissimilar metal pipe joints according to claim 2, characterized in that: The outer wall of weldment 1 has a welding bevel angle of α and a minor diameter of D3, an inner wall step diameter of D4 and a step height of H1; the inner wall of weldment 2 has a welding bevel angle of α, a major diameter of welding bevel that is the same as the outer diameter D1 of weldment 1, a minor diameter D6 that is the same as the minor diameter D3 of welding bevel of weldment 1, an outer wall step diameter of D7 and a step height of H2.

4. The method for inertial friction welding of aluminum-steel dissimilar metal pipe joints according to claim 3, characterized in that: 80°≤α≤100°, 30mm≤D1-D3≤40mm, 10mm≤D3-D4≤15mm, 10mm≤H1≤30mm, 5mm≤D5-D7≤10mm, 50mm≤H2≤70mm.

5. The method for inertial friction welding of aluminum-steel dissimilar metal pipe joints according to claim 1, characterized in that: In the free state, the wedge 1 has the following relationships: the outer diameter D8 of the small end is 2mm ≤ D2 - D8 ≤ 4mm; the outer diameter D9 of the large end is 0.5mm ≤ D9 - D4 ≤ 1mm; the included angle β of the inner hole is 15° ≤ β ≤ 20°; the height H3 of the inner support area is H3 = H1; and the total height H4 is 20mm ≤ H4 - H3 ≤ 25mm.

6. The method for inertial friction welding of aluminum-steel dissimilar metal pipe joints according to claim 1, characterized in that: The cone angle of the frustum of the wedge 2 is consistent with the included angle β of the inner hole of the wedge 1. The large end diameter D13 is equal to the small end outer diameter D8 of the wedge 1. The height H5 of the frustum and the total height H4 of the wedge 1 satisfy the relationship 0≤H5-H4≤5mm. The total height H6 is 20mm≤H6-H5≤40mm. The small end diameter D12 and the small end diameter D11 of the inner hole of the wedge 1 satisfy the relationship D12-D11≥2mm and the large end diameter D10 of the inner hole of the wedge 1 satisfy the relationship D12=D10-2×H5×tan(β / 2).

7. The method for inertial friction welding of aluminum-steel dissimilar metal pipe joints according to claim 1, characterized in that: The outer diameter D15 of the outer hoop fixture satisfies 30mm≤D15-D14≤40mm, and the relationship between the height H7 of the outer hoop fixture and the step height H2 of the outer wall of weldment 2 is H2-H7=5mm.

8. The method for inertial friction welding of aluminum-steel dissimilar metal pipe joints according to any one of claims 1-7, characterized in that: In step S2, before welding, the welding parts of weldment 1 and weldment 2 are cleaned of surface oxide film and oil stains by pre-welding grinding method, and wiped with acetone or alcohol.

Images