Direct connection method of heat treatment and residual heat expansion for large thin-walled titanium alloy ring

Abstract

The application discloses a kind of directly connected methods of large thin-walled titanium alloy ring piece heat treatment-waste heat bulging, comprising the following steps: step 1: before heat treatment starts, complete bulging combined die, bulging equipment, material receiving station, hoisting path and the preparation of landing area;Step 2: keep heat treatment curve and record;Step 3: after workpiece is discharged, complete lifting, transport, landing, unhooking and machine in preset waste heat connection time window, so that workpiece directly enters bulging station;Step 4: bulging correction is implemented under waste heat state, to complete size adjustment and roundness correction under hot state condition.The application establishes quick transfer connection between heat treatment and bulging process, so that ring piece directly enters bulging process with heat treatment waste heat state, which avoids energy consumption and time loss of secondary heating after cooling, shortens manufacturing cycle, reduces the number of repeated heat cycles experienced by material, and reduces the difficulty of organization performance control and size modification.

Description

Technical Field

[0001] This invention belongs to the field of metal pressure processing, and specifically relates to a direct connection method for heat treatment and residual heat expansion of large thin-walled titanium alloy rings. Background Technology

[0002] Large thin-walled titanium alloy cylindrical rings are key load-bearing components in high-end equipment fields such as aerospace and deep-sea equipment. Their manufacturing process usually includes key processes such as ring rolling, heat treatment and microstructure control, and bulging and rounding. Ultimately, they must meet strict dimensional accuracy and geometric tolerance requirements.

[0003] Currently, the industry commonly uses a forging residual heat bulging process for conventional round rolled rings to correct dimensional deviations caused by hot working. This process can meet basic accuracy requirements for rings of ordinary specifications. However, for titanium alloy cylindrical rings with large height and thin wall thickness, due to their inherent structural characteristics and process characteristics such as large height-to-diameter ratio, thin wall thickness, and weak structural rigidity, the conventional bulging process cannot guarantee the dimensional compliance rate and performance stability of the final product. Specifically, the following technical problems exist: (1) Such high-height thin-walled rings have insufficient overall rigidity under the conditions of large height-to-diameter ratio and thin wall thickness. During the heating and cooling process of heat treatment, the internal thermal stress and structural stress of the workpiece are unevenly distributed. Even if equal height pads are used for horizontal mounting, it is still difficult to avoid thermal deformation such as excessive ellipticity, end face warping and generatrix straightness deviation, resulting in unqualified workpiece dimensions and a high risk of scrapping.

[0004] (2) Regarding the dimensional deviations caused by heat treatment, the existing production mode usually involves cooling the workpiece to room temperature and then performing a second independent heating before bulging and shaping. This mode has the following shortcomings: First, the bulging with residual heat from the forging process can only correct the initial deformation caused by ring rolling and cannot offset the secondary deformation induced by subsequent heat treatment. It has limited effect on the final dimensional accuracy control and the bulging process is redundant. Second, the large amount of high-temperature residual heat on the workpiece after heat treatment is not effectively utilized. After cooling, it is reheated and bulged, which not only causes significant energy waste but also adds an extra heating process, greatly extending the manufacturing cycle. At the same time, it continuously occupies the capacity of the heating furnace equipment, resulting in slow production cycle and low equipment utilization.

[0005] (3) Titanium alloy materials are highly sensitive to thermal cycling processes. After undergoing multiple thermal cycles of "heat treatment heating - cooling - secondary expansion heating - re-cooling", abnormal grain growth and decreased microstructure uniformity are easily induced, which significantly increases the complexity of microstructure performance control, is not conducive to the stable control of product performance consistency between batches, and also increases the difficulty of subsequent quality control.

[0006] Furthermore, for large, thin-walled ring-shaped components, improper operation or excessively slow transfer speed during inter-process transfer often leads to excessive heat loss from the workpiece and a reduced bulging effect. In such cases, secondary heating and re-performing the bulging process are necessary. Currently, in conventional bulging processes, workpiece transfer is mostly accomplished using a material handling machine, but controlling heat loss during the transfer process remains challenging. Summary of the Invention

[0007] This invention provides a direct connection method for heat treatment and residual heat expansion of large thin-walled titanium alloy rings. By establishing a rapid transfer connection between the heat treatment and expansion processes, the rings can directly enter the expansion process in the residual heat state of the heat treatment. This avoids the energy and time loss of secondary heating after cooling, shortens the manufacturing cycle, reduces the number of repeated thermal cycles that the material undergoes, and reduces the difficulty of microstructure and property control and dimensional modification.

[0008] The main technical solution adopted in this invention is as follows: A direct joining method for large thin-walled titanium alloy rings, involving heat treatment and residual heat expansion, includes the following steps: Step 1: Before the heat treatment begins, prepare the bulging combination mold, bulging equipment, receiving station, hoisting path and placement area, and mark the position of the hook and the position of the ring material transfer. Step 2: Complete the heat treatment process according to the preset heat treatment regime, and retain the heat treatment curve and records; Step 3: After the workpiece comes out of the furnace, it is lifted, transferred, placed, unhooked and put on the machine within the preset residual heat connection time window, so that the workpiece can directly enter the bulging station; the residual heat connection time window is the available time interval after the workpiece comes out of the furnace to meet the thermal state required for subsequent hot bulging. Step 4: After the workpiece enters the bulging station, bulging correction is carried out under residual heat to complete the dimensional adjustment and roundness correction under hot conditions.

[0009] Preferably, the waste heat connection time window is predetermined based on heat treatment records, hot component transfer records, trial production process or historical production statistics, and the key nodes of furnace exit, hoisting, placement, unhooking and machine loading are used as time verification benchmarks.

[0010] Preferably, in step 4, the workpiece temperature during bulging correction is between 600°C and 750°C.

[0011] Preferably, the method further includes step 5, in which, after completing the hot bulging correction in step 4, the relative posture of the workpiece is changed and hot bulging is performed again.

[0012] Preferably, in step 5, the workpiece is rotated 45° around the central axis and then subjected to hot expansion again, with a holding time of 18s to 30s.

[0013] Preferably, the large thin-walled titanium alloy ring is a cylindrical ring with an inner diameter of φ5100mm~φ5200mm, a wall thickness of 70mm~80mm, and a height of 1300mm~1400mm.

[0014] Preferably, in step 1, the hook includes a main structure, three sets of cantilever arms evenly radially distributed along the circumference of the main structure, and claws disposed at the ends of the cantilever arms for lifting the end face of the ring component.

[0015] Preferably, the cantilever is provided with multiple adjustment holes along the radial direction to accommodate rings of different diameters.

[0016] Preferably, the bulging mold assembly includes a support base, multiple first molds, and multiple second molds; wherein, The support base is provided with a plurality of rollers spaced apart along its circumference, and the rotation axis of each roller is arranged along the radial direction of the support base. Each of the first molds has an arc-shaped working surface, and the bottom surface of each first mold is a flat surface; Each of the second molds has an arc-shaped working surface, and the arc of the arc-shaped working surface of the second mold is the same as the arc of the arc-shaped working surface of the first mold; each of the second molds has an arc-shaped cavity on its bottom surface, which is used to avoid the corresponding roller and to provide the roller with an installation gap and movement avoidance space; Multiple first molds and multiple second molds are arranged on the support base at preset positions, together forming an bulging cavity; and the second molds avoid the location of the rollers through the arc-shaped concave cavity.

[0017] Beneficial effects: This invention provides a direct connection method for large thin-walled titanium alloy rings through heat treatment and residual heat expansion, which has the following advantages: (1) The present invention utilizes the residual heat after the titanium alloy ring is heat-treated and directly expands it without the need for secondary independent heating, which reduces energy consumption and eliminates the need for additional heating processes, significantly shortening the manufacturing cycle. Compared with the traditional secondary heating expansion method, the final size correction after heat treatment is combined into one step, effectively simplifying the process chain.

[0018] (2) In this invention, the workpiece only undergoes one complete thermal cycle, avoiding the problems of abnormal grain growth and decreased uniformity of structure that may be caused by repeated thermal cycles. This is conducive to ensuring the consistency of structure properties and quality control. The material has good plasticity and low springback at high temperature, resulting in low correction resistance and more thorough repair. This significantly improves the shape accuracy and first-pass yield, and is especially suitable for the large deformation correction needs of high-height thin-walled ring parts.

[0019] (3) In view of the residual heat window period after heat treatment, the present invention has constructed a supporting rapid transfer, clamping and bulging process system. By optimizing the transfer process, it ensures that the workpiece can directly enter the bulging station within the effective residual heat temperature to complete the rounding and shaping, thus fundamentally solving the contradiction between heat treatment deformation correction and residual heat waste and repeated heat cycle. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the first mold of the present invention; Figure 2 This is a schematic diagram of the structure of the second mold of the present invention; Figure 3 This is a schematic diagram of the structure of the support base of the present invention; Figure 4 This is a schematic diagram of the structure of the adjustable ring lifting device with three radial arms according to the present invention; In the diagram: Support base 1, roller 1-1, locking block 1-2, first mold 2, slot 2-1, second mold 3, arc-shaped cavity 3-1, hook 4, main structure 4-1, cantilever 4-2, claw 4-3, adjustment hole 4-4. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application are clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application. Example 1

[0022] Taking a large thin-walled titanium alloy ring as an example, the material is TC4 titanium alloy. The cold-state dimensions after ring rolling are as follows: inner diameter is φ5100mm~φ5200mm, wall thickness is 70mm~80mm, height is 1300mm~1400mm, and weight is 10000kg~10100kg.

[0023] This embodiment provides a direct joining method for large thin-walled titanium alloy rings through heat treatment and residual heat expansion, including the following steps: Step 1: Before the heat treatment begins, prepare the bulging combination mold, bulging equipment, material receiving station, hoisting path and placement area, and mark the position of the hook and the position of the ring material transfer.

[0024] Step 1-1: Install the bulging mold assembly of the 4000T bulging equipment into place. (For example...) Figure 1-3As shown, the bulging mold assembly includes a support base 1, multiple first molds 2, and multiple second molds 3. Multiple rollers 1-1 are spaced circumferentially on the support base 1, with the rotation axis of each roller 1-1 arranged radially along the support base 1. Each of the first molds 2 has an arc-shaped working surface, and the bottom surface of each first mold 2 is a flat surface. Each of the second molds 3 has an arc-shaped working surface, the curvature of which is the same as that of the first molds 2. Each second mold 3 has a circular arc-shaped cavity 3-1 on its bottom surface, which is used to avoid the corresponding roller 1-1 and provides installation clearance and movement clearance space for the roller 1-1. The multiple first molds 2 and the multiple second molds 3 are arranged in preset positions on the support base 1, together forming a bulging cavity. The second molds 3 avoid the positions of the rollers 1-1 through the circular arc-shaped cavity 3-1. The forging can be driven by rollers 1-1 to rotate circumferentially during the bulging process, meeting the process requirements of periodic reversing bulging. For example... Figure 1-3 As shown, the first mold 2 and the second mold 3 can be installed by engaging with the locking block on the support base 1 through the locking slot.

[0025] In this embodiment, both the first mold 2 and the second mold 3 are made of mold steel (grade 5CrNiMo). The molds can be stacked in 19 layers radially from the inside to the outside, and the size of the bulging combination mold matches the inner diameter of the workpiece φ5100mm~φ5200mm.

[0026] Steps 1-2: Confirm that the receiving station is in place, the hoisting path is unobstructed, and the placement area is cleared. Steps 1-3: Mark the hook position and ring material transfer position using a high-temperature resistant marker to shorten the time spent on hooking and transfer. In this embodiment, a three-radial-arm adjustable ring lifting device is used to replace the traditional radial clamping method for lifting and transferring the workpiece, such as... Figure 4 As shown, the adjustable ring lifting device with three radial arms includes a main structure 4-1, three sets of cantilever arms 4-2 evenly radially distributed along the circumference of the main structure 4-1, and claws 4-3 located at the ends of the cantilever arms 4-2 for lifting the end face of the ring. The claws 4-3 can be L-shaped.

[0027] To quickly adapt to different diameter specifications, each cantilever is equipped with multiple adjustment holes 4-4, which can quickly adapt to rings of different diameter specifications. The adjustable diameter range is 3000~6000mm, covering the hoisting needs of the full range of titanium alloy rings in the 5m class.

[0028] In this embodiment, the preparatory work for the bulging station is arranged to be completed before the heat treatment begins. On the one hand, this avoids temporary coordination and equipment adjustment after the heat treatment is completed, eliminating waiting time. On the other hand, it allows the workpiece to directly enter the target station along the predetermined hoisting path after it comes out of the furnace, ensuring efficient connection of residual heat.

[0029] Step 2: Complete the heat treatment process according to the preset heat treatment regime, and retain the heat treatment curve and records.

[0030] The heat treatment process used in this embodiment is as follows: heating to 750℃±10℃, holding for 120 minutes, cooling in the furnace to 600℃, and then air cooling. Complete heat treatment curves and records are maintained during the heat treatment process, including parameters such as heating rate, holding time, and cooling rate, to provide a basis for determining the residual heat window and process transitions.

[0031] Step 3: After the workpiece is taken out of the furnace, it is lifted, transferred, placed, unhooked and put on the machine within the preset residual heat connection time window, so that the workpiece can directly enter the expansion station without being reheated independently.

[0032] The residual heat connection time window is the usable time interval after the workpiece has exited the heat treatment furnace, ensuring it remains in the thermal state required for subsequent hot forming. This residual heat connection time window can be determined based on existing heat treatment records, hot part transfer records, trial production processes, or historical production statistics, with key nodes such as furnace exit, lifting, placement, unhooking, and machine mounting serving as verification benchmarks. By limiting the duration of these nodes, excessive heat dissipation of the workpiece during waiting and temporary coordination can be avoided, thus ensuring the feasibility of directly using residual heat for forming.

[0033] In this embodiment, the time taken for each step is as follows, starting from the moment the workpiece exits the heat treatment furnace: the ring is lifted out of the furnace (0 min), the hook position is determined according to the marked location and the hooking is completed (1 min 30 s), the workpiece is transferred from the heat treatment furnace area to the forming station (1 min 45 s), and the workpiece is placed in the forming station and unhooked and installed on the machine (4 min). Temperature measurement shows that the workpiece's body temperature is between 620℃ and 680℃ after being installed on the machine, meeting the temperature requirements for hot forming (600℃ to 750℃). The workpiece does not undergo any form of reheating during the entire transfer process.

[0034] In this embodiment, the workpiece is directly transferred to the bulging station within the residual heat window after heat treatment. Its advantages are as follows: First, by utilizing the existing residual heat of the workpiece for bulging, an independent reheating process can be saved, reducing energy consumption and equipment and process waiting time. At the same time, it avoids the workpiece undergoing a complete heating process after heat treatment, which helps to simplify the process chain and reduce the structural complexity and dimensional correction difficulty caused by repeated thermal cycles. Second, dimensional correction and rounding are performed directly under hot conditions, which is conducive to connecting the thermal history after heat treatment with the subsequent bulging action and reducing the process complexity caused by process interruption.

[0035] Step 4: After the workpiece enters the bulging station, bulging correction is carried out under residual heat to complete the dimensional adjustment and roundness correction under hot conditions.

[0036] Step 4-1: Start the 4000T bulging equipment. The bulging combination mold expands evenly outward along the radial direction, and the bulging force is applied from the inner wall of the ring to bulge the inner diameter of the ring to the hot dimension inner diameter of the product. Step 4-2: After the bulging is completed, maintain the pressure for 20 minutes to allow the material to undergo full plastic flow at high temperature, releasing and redistributing stress to ensure the stability of the bulging dimensions; Step 4-3: After the pressure holding is completed, the expansion mold shrinks back to its original position, completing the unloading.

[0037] After testing, the roundness deviation of the workpiece after bulging is ≤20mm, which meets the requirements for subsequent machining. In this embodiment, no re-bulging operation is performed. After the workpiece is cooled under pressure, the machining allowance distribution can be guaranteed to meet the machining requirements of the finished product.

[0038] The process parameters of this embodiment are compared with those of the existing secondary heating expansion technology (comparative example) as shown in Table 1.

[0039] Table 1 Comparison of key process indicators between Example 1 and the comparative example

[0040] The comparative results show that this embodiment directly utilizes the residual heat from the heat treatment furnace before bulging, eliminating the need for secondary heating. The total time from the end of heat treatment to the completion of bulging is reduced from 50 minutes in the comparative example to 25 minutes, and the equipment cycle time is reduced from 24-28 hours to 12-14 hours (a reduction of approximately 50%). The roundness deviation after bulging is controlled within ≤20mm, and the correction accuracy of both is comparable. This indicates that the present invention significantly reduces energy consumption, shortens the production cycle, and improves equipment turnover efficiency while ensuring the same roundness quality as bulging with secondary heating. Example 2

[0041] This embodiment, based on Embodiment 1, adds a step 5 after completing the hot bulging correction in step 4: performing hot bulging again after changing the relative orientation of the workpiece. The specific steps are as follows: Step 5-1: Using the arc-shaped cavity 3-1 on the bottom surface of the second mold 3 and the support base 1 with rollers 1-1, rotate the workpiece 45° around its central axis. Step 5-2: Restart the bulging equipment and perform bulging again to bulge the inner diameter of the ring to the hot dimension inner diameter of the product; Step 5-3: After holding the pressure for 20 seconds, the expansion mold shrinks back to its original position.

[0042] After re-expansion, the workpiece roundness deviation was ≤20mm (ellipticity accounted for only 0.3% of the inner diameter), which met the requirements for subsequent machining.

[0043] In this embodiment, the initial hot expansion utilizes the residual heat of the workpiece to complete the main dimensional correction; if necessary, rotational expansion can be performed to further compensate for local roundness deviations or dimensional inconsistencies. The mating structure between the arc-shaped cavity 3-1 of the second mold 3 and the support base 1 with rollers 1-1 provides convenient operating conditions for rotational expansion, allowing workpiece posture adjustment to be completed without additional lifting equipment.

[0044] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A direct connection method for large thin-walled titanium alloy rings, characterized in that, Includes the following steps: Step 1: Before the heat treatment begins, prepare the bulging combination mold, bulging equipment, receiving station, hoisting path and placement area, and mark the position of the hook and the position of the ring material transfer. Step 2: Complete the heat treatment process according to the preset heat treatment regime, and retain the heat treatment curve and records; Step 3: After the workpiece comes out of the furnace, it is lifted, transferred, placed, unhooked and put on the machine within the preset residual heat connection time window, so that the workpiece can directly enter the bulging station; the residual heat connection time window is the available time interval after the workpiece comes out of the furnace to meet the thermal state required for subsequent hot bulging. Step 4: After the workpiece enters the bulging station, bulging correction is carried out under residual heat to complete the dimensional adjustment and roundness correction under hot conditions.

2. The direct connection method for heat treatment-residual heat expansion of large thin-walled titanium alloy rings according to claim 1, characterized in that, The waste heat connection time window is predetermined based on heat treatment records, hot component transfer records, trial production process or historical production statistics, and the key nodes of furnace exit, hoisting, placement, unhooking and machine installation are used as time verification benchmarks.

3. The direct connection method for heat treatment-residual heat expansion of large thin-walled titanium alloy rings according to claim 1, characterized in that, In step 4, the workpiece temperature during bulging correction is between 600℃ and 750℃.

4. The direct connection method for heat treatment-residual heat expansion of large thin-walled titanium alloy rings according to claim 1, characterized in that, It also includes step 5, which involves changing the relative posture of the workpiece after completing the hot bulging correction in step 4 and then performing hot bulging again.

5. The direct connection method for heat treatment-residual heat expansion of large thin-walled titanium alloy rings according to claim 4, characterized in that, In step 5, the workpiece is rotated 45° around the central axis and then subjected to hot expansion again, with a holding time of 18s to 30s.

6. The direct connection method for heat treatment-residual heat expansion of large thin-walled titanium alloy rings according to claim 1, characterized in that, The large thin-walled titanium alloy ring is a cylindrical ring with an inner diameter of φ5100mm~φ5200mm, a wall thickness of 70mm~80mm, and a height of 1300mm~1400mm.

7. The direct connection method for heat treatment-residual heat expansion of large thin-walled titanium alloy rings according to claim 1, characterized in that, In step 1, the hook includes a main structure, three sets of cantilever arms evenly radially distributed along the circumference of the main structure, and claws set at the ends of the cantilever arms for lifting the end face of the ring component.

8. The direct connection method for heat treatment-residual heat expansion of large thin-walled titanium alloy rings according to claim 7, characterized in that, The cantilever is provided with multiple adjustment holes along the radial direction to accommodate rings of different diameters.

9. The direct connection method for heat treatment-residual heat expansion of large thin-walled titanium alloy rings according to claim 1, characterized in that, The bulging mold assembly includes a support base, multiple first molds, and multiple second molds; wherein... The support base is provided with a plurality of rollers spaced apart along its circumference, and the rotation axis of each roller is arranged along the radial direction of the support base. Each of the first molds has an arc-shaped working surface, and the bottom surface of each first mold is a flat surface; Each of the second molds has an arc-shaped working surface, and the arc of the arc-shaped working surface of the second mold is the same as the arc of the arc-shaped working surface of the first mold; each of the second molds has an arc-shaped cavity on its bottom surface, which is used to avoid the corresponding roller and to provide the roller with an installation gap and movement avoidance space; Multiple first molds and multiple second molds are arranged on the support base at preset positions, together forming an bulging cavity; and the second molds avoid the location of the rollers through the arc-shaped concave cavity.

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