A method for controlling the shape of a large and complex forged part

Abstract

The present application relates to a kind of large complex forgings shape control method, belong to technical material hot working technical field, the shape control method includes: after forging forming, the forging is taken out from die;Heating the forging taken out from die, and the die is cooled by cleaning die;After heating, the forging is placed in the die cavity of cooling die and is pressed for second time;After second pressing, the forging is taken out from die and placed in sand pit and is air cooled;After air cooling, the forging is heat treated, to ensure that the forging is in vertical state during heat treatment;The flash of the forging after heat treatment is cut off.By the above method, the probability and degree of warping deformation of the forging can be effectively reduced.

Description

Technical Field

[0001] This invention belongs to the field of hot working technology of technical materials, and specifically relates to a method for controlling the shape of large and complex forgings. Background Technology

[0002] Large and complex forgings, as key components in high-end equipment manufacturing, play a vital role in national economic and defense construction. The conventional production process for large and complex forgings is "forging → deburring → heat treatment → subsequent machining." Due to uneven plastic deformation and temperature changes during the forging process, localized stress concentrations can occur. If the internal stress exceeds the material's tensile strength, cracks will form in the forging; otherwise, it will accumulate as residual stress. The distribution of residual stress within the forging varies depending on the degree of deformation unevenness; it may be tensile stress on the surface and compressive stress in the core, or vice versa. The traditional method of deburring before heat treatment causes a sudden release of residual stress in the forging, increasing the likelihood of warping.

[0003] During the heat treatment process before machining, forgings are susceptible to the effects of unstable support forces during heating, clamping forces during transport, the flatness of the furnace bottom plate, and the weight of the forgings themselves. Large and complex forgings, especially thin-web and high-rib forgings, often warp and deform, resulting in reduced dimensional accuracy and uneven mechanical properties, which seriously affect the quality of forgings and subsequent production.

[0004] Chinese patent CN102121085A discloses a method for preventing warping deformation of titanium alloy thin-web forgings during hot working. This method mainly includes: using a support fixture to suspend the forging longitudinally for air cooling, followed by placing a pressure block on top of the forging and placing it flat on a pad to prevent warping deformation. While this method has some effect in preventing warping during hot working, the longitudinal suspension cooling method is only suitable for shorter forgings and requires specialized tooling and pads, making the operation relatively complex and lacking versatility.

[0005] Chinese patent CN222250850U discloses a special tooling for preventing heat treatment warping of long, thin-walled forgings with curvature. Its main purpose is to solve the problem of heat treatment warping in long, thin-walled forgings with curvature. However, since different methods are used to control warping deformation of forgings of different shapes, this method is not very effective when applied to controlling warping of other complex and large forgings.

[0006] Therefore, a universal control method applicable to the precise shape control of complex and large forgings is urgently needed. Summary of the Invention

[0007] The application provides a shape control method for large complex forgings, which is used for reducing the probability of warping of the large complex forgings during forging, thereby achieving the purpose of controlling the shape of the forged forgings.

[0008] The application is achieved by the following technical scheme: a shape control method for large complex forgings, comprising the following steps:

[0009] Step 1: after the forging is formed by forging, the forging is taken out of the mold;

[0010] Step 2: the forging taken out of the mold is heated, and the mold is cleaned to cool the mold;

[0011] Step 3: the heated forging is placed in the mold cavity of the cooled mold for secondary pressing;

[0012] Step 4: the forging after secondary pressing is taken out of the mold and placed in a sand pit for air cooling;

[0013] Step 5: the forging after air cooling is completed is heat treated, and the forging is ensured to be in a vertical state during the heat treatment;

[0014] Step 6: the flash of the forging after heat treatment is cut off.

[0015] Further, in order to better achieve the application, in the step 2, the specific method for heating the forging taken out of the mold is as follows:

[0016] The forging is loaded into a heating furnace with a set temperature of 800-1150 DEG C for heating.

[0017] Further, in order to better achieve the application, the heating time of the forging in the heating furnace with a temperature of 800-1150 DEG C is 20-30 minutes.

[0018] Further, in order to better achieve the application, in the step 2, the specific method for cleaning the mold to cool the mold is as follows:

[0019] The mold cavity is blown by a normal-temperature medium to cool the mold temperature to below 400 DEG C.

[0020] Further, in order to better achieve the application, the normal-temperature medium is compressed air or a mixture of compressed air and water.

[0021] Further, in order to better achieve the application, in the step 3, the load condition of the secondary pressing is 30000-40000 tons.

[0022] Further, in order to better achieve the application, in the step 4, when the forging is placed in the sand pit for air cooling, the lower surface of the forging is ensured to be completely in contact with the sand, and the forging is ensured to be completely placed in the sand pit.

[0023] Further, in order to better realize the present application, the time for the forging to be air-cooled in the sand pit is at least 2 hours.

[0024] Further, in order to better realize the present application, in step 5, the specific method for ensuring that the forging is in a vertical state during the heat treatment process is that:

[0025] During the heat treatment process, the forging is loaded in the "Y" type tooling for heating and cooling.

[0026] Further, in order to better realize the present application, the "Y" type tooling comprises a bottom beam, two vertical columns and two diagonal braces, the bottom ends of the two vertical columns are fixedly connected to the bottom beam, and a placing space is formed between the two vertical columns, and each of the vertical columns is fixedly connected with the bottom beam through a diagonal brace;

[0027] The specific method for loading the forging in the "Y" type tooling is that the forging is vertically inserted into the placing space so that the bottom end of the forging is overlapped on the bottom beam, and a plurality of the "Y" type tooling are used to support different parts of the forging respectively.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] (1) The method provided by the present application can effectively reduce the warping deformation of large and complex forgings. Through the post-forging secondary pressing and the heat treatment with flash, not only the warping deformation of the forgings caused by the sudden release of residual stress of the forgings after the flash is immediately cut off after forging, but also the adverse effects of factors such as unstable supporting force, clamping force, flatness of the furnace bottom plate of the heat treatment furnace during the heat treatment process are avoided. The warping deformation of the forgings can be reduced by at least 50%;

[0030] (2) The method provided by the present application can effectively reduce the material cost of the forgings. Since the warping deformation of large and complex forgings is difficult to control, in order to avoid the situation that the subsequent local machining allowance is not enough due to the warping of the forgings, the warping of the forgings is usually considered in the design of the forgings, which will increase the design allowance of the forgings, thereby increasing the material cost of the forgings. By using the method involved in the present application, the warping deformation of large and complex forgings can be controlled within the normal design allowance, thereby reducing the material cost of the forgings by 5%-10%;

[0031] (3) The method provided by the present application can significantly improve the production efficiency and reduce the energy consumption. Different from the traditional heat treatment method of flat loading and small quantity loading of the furnace, the present application uses special heat treatment tooling and adopts the vertical loading heat treatment method with flash, which can increase the loading quantity of each furnace cycle, and the loading quantity can be increased by more than 50%, thereby improving the production efficiency and reducing the energy consumption;

[0032] (4) The method provided by the application is different from the conventional production path of "forging -> trimming -> heat treatment -> subsequent machining" or the method of additionally adding a straightening process after heat treatment, and has the advantages of high implementation efficiency, strong universality, good repeatability and operability, and can effectively solve the problem of warping deformation of large complex forgings. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0034] Figure 1 is a flow chart of the shape control method of the large complex forging provided by embodiment 1 of the present application;

[0035] Figure 2 is a structural schematic diagram of the "industry" type tooling in the embodiment of the present application;

[0036] Figure 3 is a structural schematic diagram of the asymmetric single-sided rib type titanium alloy forging standing on the "industry" type tooling in embodiment 2 of the present application;

[0037] Figure 4 is a structural schematic diagram of the thin plate type steel forging standing on the "industry" type tooling in embodiment 3 of the present application.

[0038] In the drawings:

[0039] 1 - asymmetric single-sided rib type titanium alloy forging, 2 - thin plate type steel forging, 3 - flash, 4 - "industry" type tooling. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present application more clear, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of the present application.

[0041] Embodiment 1

[0042] The embodiment provides a shape control method of a large complex forging as shown in Figure 1 The method specifically includes the following steps:

[0043] Step 1: After forging, the forging is removed from the mold. It is worth noting that the forging in this step refers to the final forging of the forging. This is easily understood as the first pressing occurring during the final forging process.

[0044] Step 2: Immediately heat the forging removed from the mold and clean the mold to allow it to cool down. In this step, the forging is heated by placing it in a furnace set at 800-1500℃ for 20-30 minutes. The mold is cleaned by blowing a room-temperature medium into the mold cavity. This not only cleans the cavity but also rapidly cools the mold to below 400℃. The room-temperature medium can be compressed air or a mixture of compressed air and water.

[0045] Step 3: Place the heated forging into the cooled mold cavity for secondary pressing. The load condition for secondary pressing is 30,000-40,000 tons. This secondary pressing allows the forging shape to match the mold cavity a second time, eliminating warping that occurred during the first demolding (i.e., removing the forged forging from the mold as described in Step 1). Since the mold temperature is lowered to below 400℃ before secondary pressing, the effectiveness of secondary pressing and pressure holding is guaranteed. Furthermore, during the secondary pressing process, the low temperature of the mold accelerates the overall cooling rate of the forging and allows for more uniform cooling across all areas. This drastically reduces the forging's thermoplasticity, thereby increasing its strength and preventing warping due to insufficient strength.

[0046] Step 4: Remove the forging from the mold after secondary pressing and place it in a sand pit for air cooling. Before using the sand pit, ensure its surface is flat, that the lower surface of the forging is in complete contact with the sand without gaps, and that the forging is completely immersed in the sand pit. The forging should be air-cooled in the sand pit for at least 2 hours. This allows the forging to cool slowly in the sand pit, reducing the temperature difference between the inside and outside of the forging during cooling. This ensures uniform volume contraction throughout the forging during cooling, allowing the stress generated during cooling to be released slowly and evenly, thereby reducing warping deformation.

[0047] Step 5: Perform heat treatment on the forging after air cooling, ensuring that the forging remains in an upright position during the heat treatment process. The specific method to ensure the forging remains in an upright position during heat treatment is as follows: During heat treatment, the forging is placed inside a "Y"-shaped fixture 4 for heating and cooling. Specifically, the "Y"-shaped fixture 4 is as follows... Figure 2As shown, it comprises a bottom beam, two columns and two inclined braces, the bottom ends of the two columns are fixedly connected to the bottom beam, and a placing space is formed between the two columns, and each column is fixedly connected with the bottom beam. The specific method of placing the forging in the "industry" shaped tool 4 is: the forging is inserted vertically into the placing space, so that the bottom end of the forging overlaps on the bottom beam, and a plurality of "industry" shaped tools 4 are used to support different parts of the forging respectively.

[0048] During the heat treatment process, the vertical furnace loading method of the forging through the "industry" shaped tool 4 not only avoids the deformation caused by improper support during heating or improper clamping during cooling, but also reduces the thermal stress and deformation caused by the uneven heating and cooling speed of the forging due to the large contact area between the forging and the furnace bottom plate.

[0049] Step 6: cutting off the flash 3 of the forging after heat treatment. That is, the forging is retained with the flash 3 during the post-forging heat treatment. Due to the uneven plastic deformation and temperature change during the forging forming process, local stress concentration of the forging will occur, which will accumulate into residual stress. The distribution of residual stress in the forging is different under the condition of uneven deformation, which may be tensile stress on the surface and compressive stress in the center, or tensile stress on the surface and compressive stress in the center. The traditional method of cutting off the flash before heat treatment will cause the sudden release of residual stress of the forging, which will eventually increase the warping deformation of the forging. Since the thickness of the flash 3 of the forging is relatively thin, the cooling speed is faster than that of the body of the forging, the volume shrinkage of the flash 3 is large, and the periphery of the forging is subjected to uniform tensile stress. With the continuous cooling, the tensile stress on the periphery of the forging still exists and hinders the warping deformation of the body of the forging due to the cooling and volume shrinkage. Therefore, the warping deformation of the forging with flash 3 during heat treatment is smaller.

[0050] Compared with the conventional large complex forging production path, the method provided by the present application can effectively reduce the warping deformation of large complex forgings. Through the post-forging secondary pressing and heat treatment with flash 3, not only the warping deformation of the forging caused by the sudden release of residual stress of the forging due to the immediate cutting off of the flash 3 after forging is avoided, but also the adverse effects of factors such as unstable supporting force, clamping force and flatness of the furnace bottom plate during heat treatment are eliminated. The warping deformation of the forging can be reduced by at least 50%;

[0051] Moreover, the method provided by the present application can also effectively reduce the material cost of the forging. Since the warping deformation of large complex forgings is difficult to control, in order to avoid the situation that the local machining allowance is not enough due to the warping of the forging, the warping of the forging is usually considered in the design of the forging, which will increase the design allowance of the forging, thereby increasing the material cost of the forging. By using the method involved in the present application, the warping deformation of large complex forgings can be controlled within the normal design allowance, thereby reducing the material cost of the forging by 5%-10%.

[0052] And, the method provided by the application can also significantly improve production efficiency and reduce energy consumption, which is different from the traditional hot treatment mode of flat packing and small quantity packing of the furnace. The application invests in a special hot treatment tooling and adopts a 3 -stand edge hot treatment mode to increase the loading capacity of each furnace, which can be increased by more than 50%, thereby improving production efficiency and reducing energy consumption.

[0053] In addition, the method provided by the application has the advantages of high implementation efficiency, strong universality, good repeatability and operability, and is suitable for popularization and application.

[0054] Embodiment 2

[0055] This embodiment is a specific implementation of embodiment 1. This embodiment is used for shape control of the final forging of the asymmetric single-sided rib titanium alloy forging 1. The specification of the asymmetric single-sided rib titanium alloy forging 1 is 2906mmx745mmx288mm, and the production quantity is 8. Embodiment 2 includes the following steps:

[0056] Step 1: After the asymmetric single-sided rib titanium alloy forging 1 is completed by the final forging, the ejection force is applied to the ejection rod to eject it from the mold cavity, and then the ejection machine is used to take it out of the mold cavity;

[0057] Step 2: Put the asymmetric single-sided rib titanium alloy forging 1 into the heating furnace with a set temperature of 950℃ again, heat for 20 minutes, at the same time, use compressed air to blow the mold cavity, so that the mold temperature is reduced to below 400℃;

[0058] Step 3: Put the heated asymmetric single-sided rib titanium alloy forging 1 into the mold cavity after cooling, use the tonnage of 35000 tons to keep pressure for 30 seconds, and perform the second pressing pressure holding;

[0059] Step 4: Make the asymmetric single-sided rib titanium alloy forging 1 after the second pressing demolding, and then transfer the asymmetric single-sided rib titanium alloy forging 1 to the sand pit for air cooling;

[0060] Step 5: Place the asymmetric single-sided rib titanium alloy forging 1 vertically in the placement space of the plurality of "industry" type toolings 4 (as shown in detail in Figure 3 Subsequently, place it in the heating furnace, so that the asymmetric single-sided rib titanium alloy forging 1 remains in a vertical state for heat treatment and cooling after heat treatment.

[0061] Step 6: Cut off the flash 3 of the asymmetric single-sided rib titanium alloy forging 1 and then perform subsequent processes. The warping value of the asymmetric single-sided rib titanium alloy forging 1 after heat treatment is shown in Table 1.

[0062] Comparative Example 1:

[0063] Comparative Example 1 is a comparative embodiment of Example 2, and specifically, Comparative Example 1 is also used for controlling the shape of the asymmetric single-sided rib-shaped titanium alloy forge piece 1 formed by final forging, the specification of the asymmetric single-sided rib-shaped titanium alloy forge piece 1 is 2906mm x 745mm x 288mm, and the production quantity of the asymmetric single-sided rib-shaped titanium alloy forge piece 1 is 8 pieces. Comparative Example 1 includes the following steps:

[0064] Step 1: After the asymmetric single-sided rib-shaped titanium alloy forge piece 1 is completed by final forging, the ejection force is applied by the ejector rod to eject it from the mold cavity, and then it is taken out from the mold cavity by the discharging machine;

[0065] Step 2: The asymmetric single-sided rib-shaped titanium alloy forge piece 1 is transferred to the cooling rack for cooling, ensuring that the asymmetric single-sided rib-shaped titanium alloy forge piece 1 is in contact with the rack at least at multiple points to ensure stable placement;

[0066] Step 3: After the asymmetric single-sided rib-shaped titanium alloy forge piece 1 is cooled, the flash is cut off;

[0067] Step 4: The asymmetric single-sided rib-shaped titanium alloy forge piece 1 is placed on the heat treatment rack in a flat manner supported by the pad, and heat treatment is performed;

[0068] Step 5: After the heat treatment is completed, the asymmetric single-sided rib-shaped titanium alloy forge piece 1 is cooled, and then the subsequent process is performed. The warping value of the asymmetric single-sided rib-shaped titanium alloy forge piece 1 after heat treatment is shown in Table 1.

[0069] Example 3:

[0070] This embodiment is another specific embodiment of Example 1, and this embodiment is used for controlling the shape of the thin plate-shaped steel forge piece 2 formed by final forging, the specification of the thin plate-shaped steel forge piece 2 is 2544mm x 537mm x 250mm, and the production quantity of the thin plate-shaped steel forge piece 2 is 8 pieces. Example 3 includes the following steps:

[0071] Step 1: After the thin plate-shaped steel forge piece 2 is completed by final forging, the ejection force is applied by the ejector rod to eject it from the mold cavity, and then it is taken out from the mold cavity by the discharging machine;

[0072] Step 2: The thin plate-shaped steel forge piece 2 is again loaded into the heating furnace set at a temperature of 1050℃ for 20 minutes, and at the same time, the mold cavity is purged with a mixture of compressed air and water to reduce the mold temperature to below 400℃;

[0073] Step 3: The heated thin plate-shaped steel forge piece 2 is repositioned in the cooled mold cavity, and a tonnage of 40000 tons is used for 35 seconds of pressure retention for the second pressure retention;

[0074] Step 4: Demold the sheet steel forging 2 after secondary pressing, and then transfer the sheet steel forging 2 to a sand pit for air cooling.

[0075] Step 5: Place the thin plate steel forging 2 upright in the placement space of multiple "Y"-shaped tooling 4 (specifically as follows). Figure 4 As shown in the figure, it is then placed in a heating furnace, so that the thin plate steel forging 2 is kept in a vertical position for heat treatment and cooling after heat treatment.

[0076] Step 6: Remove the flash 3 from the sheet steel forging 2 before proceeding to subsequent processes. The warpage value of the sheet steel forging 2 after heat treatment is shown in Table 1.

[0077] Comparative Example 2:

[0078] Comparative Example 2 is a comparative implementation of Example 3. Specifically, this comparative example is also used to control the shape of the thin plate steel forging 2, which has a size of 2544mm × 537mm × 250mm and a production quantity of 8 pieces. Comparative Example 2 includes the following steps:

[0079] Step 1: After the thin plate steel forging 2 completes the final forging, it is ejected from the mold cavity by applying an ejector force through an ejector rod, and then removed from the mold cavity by a discharge machine;

[0080] Step 2: Transfer the thin plate steel forging 2 to the cooling rack for cooling, ensuring that the thin plate steel forging 2 should be in contact with the rack at least at multiple points to ensure stable placement;

[0081] Step 3: After the thin plate steel forging 2 has cooled, remove the burrs;

[0082] Step 4: Place the thin plate steel forging 2 on the heat treatment tray using a flat mounting method supported by pads, and perform heat treatment;

[0083] Step 5: After heat treatment, wait for the thin plate steel forging 2 to cool before proceeding with subsequent processes. The warpage value of the thin plate steel forging 2 after heat treatment is shown in Table 1.

[0084]

[0085] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope described in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for controlling the shape of large and complex forgings, characterized in that, including: Step 1: After the forging is formed, take the forging out of the mold. Step 2: Heat the forging taken out of the mold and clean the mold to cool down the mold. Step 3: Put the heated forging into the cooled mold cavity for secondary pressing. Step 4: Take out the forging after secondary pressing from the mold and place it in a sand pit for air cooling. Step 5: Perform heat treatment on the forging after air cooling is completed, ensuring that the forging is in a vertical state during the heat treatment process. Step 6: Cut off the flash (3) of the forging after heat treatment is completed.

2. The method for controlling the shape of large and complex forgings according to claim 1, characterized in that, In the said Step 2, the specific method for heating the forging taken out of the mold is: Put the forging into a heating furnace set at a temperature of 800 - 1150 °C for heating.

3. The shape control method for large and complex forgings according to claim 2, wherein: The heating time of the forging in the heating furnace at 800 - 1150 °C is 20 - 30 minutes.

4. The method for controlling the shape of large and complex forgings according to claim 1, characterized in that, In the said Step 2, the specific method for cleaning the mold and cooling down the mold is: Use a normal temperature medium to blow the mold cavity to cool the mold temperature below 400 °C.

5. The shape control method for large and complex forgings according to claim 4, wherein: The normal temperature medium is compressed air or a mixture of compressed air and water.

6. The shape control method for large and complex forgings according to claim 1, wherein: In the said Step 3, the load condition for the secondary pressing is 30000 - 40000 tons.

7. The shape control method for large and complex forgings according to claim 1, wherein: In the said Step 4, when placing the forging in the sand pit for air cooling, ensure that the lower surface of the forging is in full contact with the sand and ensure that the forging is completely placed in the sand pit.

8. The shape control method for large and complex forgings according to claim 7, wherein: The air cooling time of the forging in the sand pit is at least 2 hours.

9. The method for controlling the shape of large and complex forgings according to claim 1, characterized in that, In the said Step 5, the specific method for ensuring that the forging is in a vertical state during the heat treatment process is: During the heat treatment process, place the forging in a "industry" - shaped tooling (4) for heating and cooling.

10. The shape control method for large and complex forgings according to claim 9, wherein: The "industry" - shaped tooling (4) includes a bottom beam, two columns and two diagonal braces. The bottom ends of the two columns are fixedly connected to the bottom beam, and a placement space is formed between the two columns. One diagonal brace is fixedly connected between each column and the bottom beam; The specific method for placing the forging in the "industry" - shaped tooling (4) is: insert the forging vertically into the placement space, make the bottom end of the forging lap on the bottom beam, and use multiple "industry" - shaped toolings (4) to support different parts of the forging respectively.

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