A heat treatment processing method for controlling deformation of flat plate type aluminum alloy castings

Abstract

The application discloses a kind of heat treatment processing methods of controlling flat plate type aluminum alloy castings deformation, solve the secondary defects such as the problem that existing flat plate type aluminum alloy castings production process easily causes casting cracking, surface scratch, internal organization damage etc..The core process of the present application is "solution → accurate correction → aging", combined with the heating rate design of flat plate type castings special heat treatment, accurate correction process is carried out immediately after solution treatment and before aging treatment, using the characteristics of low hardness and high plasticity of aluminum alloy after solution treatment to complete correction, avoid the difficulty of correction and secondary defects caused by the increase of hardness after aging;Among them, after solution treatment, deformation measurement, tool adjustment, pressure correction and correction detection are carried out in turn combined with correction tool, the deformation amount of the castings before aging is stably controlled to be ≤2mm, and aging treatment is the only strengthening process after correction, to ensure that the final casting deformation still maintains ≤2mm.The method can greatly improve the product pass rate, reduce the correction energy consumption and production cost.

Description

Technical Field

[0001] This invention relates to a heat treatment process for aluminum alloys, specifically a heat treatment process for controlling the deformation of flat aluminum alloy castings. Background Technology

[0002] The increasingly complex structure of aluminum alloy castings presents significant challenges to the manufacturing process. Due to their flat structure, flat aluminum alloy castings are highly susceptible to complex deformations such as warping, dents, and wavy shapes during the solution treatment and aging stages of heat treatment. These deformations are caused by multiple factors, including uneven stress release within the material, differences in temperature field distribution, fluctuations in cooling rate, and improper heating rate. These factors severely affect the assembly accuracy and performance of the products.

[0003] The current mainstream heat treatment process is "solution treatment → aging → correction", which means that solution strengthening and age hardening are completed first, and then the deformed casting is corrected. However, after aging treatment, the hardness of aluminum alloy castings will increase by 40% to 60%, while the plasticity will decrease by more than 40% simultaneously. This results in the need to apply greater external force (usually 15 to 25 MPa) during correction, which not only significantly increases energy consumption, but also easily causes secondary defects such as casting cracking, surface scratches, and internal structural damage. The overall deformation is difficult to control within 2 mm, and the product qualification rate is low, sometimes only around 50%.

[0004] The reasons for the above phenomena are as follows: First, the process logic is reversed. After aging, the internal stress has formed a "lock-in effect." Correction can only achieve surface morphology correction and cannot completely release the internal stress. Secondary deformation may still occur during subsequent use. Second, the correction tooling has structural deficiencies. Existing tooling is mostly an integral rigid structure or uses a single-spacing support point design, which has poor versatility and low adjustment accuracy (only able to achieve adjustments above 1mm). It cannot accurately match the stress distribution characteristics of different specifications of flat castings and is difficult to perform targeted correction of local deformation. Third, the thermal conductivity characteristics of flat castings have not been taken into account, and there is a lack of dedicated heating rate design. The heating rate of existing processes is mostly designed for frame-type and curved surface castings. This process easily leads to a large temperature gradient between the surface and the interior of flat castings, thereby causing planar warping deformation.

[0005] To address this, existing technologies attempt to adjust the process sequence, but due to the lack of precise calibration fixtures adapted to the process and the failure to optimize the heat treatment heating rate parameters, intermediate calibration is only performed through simple pressurization, resulting in unstable deformation control and insufficient calibration accuracy. Therefore, the problem has not been fundamentally solved.

[0006] For example, Chinese invention patent CN105506522A discloses a method for correcting deformation during heat treatment of frame-type aluminum alloy castings. The method employed is "solution treatment → straightening → aging," but it is only suitable for frame-type castings (with localized bending deformation). Its adjustable fixture is a molded part adaptation structure consisting of an upper forming plate and segmented fastening bolts, which can only achieve localized straightening of frame-type castings and cannot adapt to the overall planar warping / concave deformation of flat-plate castings. Furthermore, this correction method lacks a standardized method for measuring planar deformation, and its adjustment accuracy is at the "molded part level," failing to achieve the micron-level precision required for flat-plate castings.

[0007] For example, Chinese invention patent CN115090715A discloses a hot mechanical correction device and method for aluminum alloy castings with high strength and toughness and complex curved surface structure. Because it is adapted to complex curved surface structure, the correction device used is a complex curved surface adaptation structure of "conformal pressure block + positioning frame". This structure is cumbersome and has poor versatility. It is not suitable for local correction of curved surface castings and does not meet the flat surface support requirements of flat castings. In addition, it does not have a precise height adjustment component or optimize the heating rate. Therefore, it cannot achieve uniform support and thermal stress control for flat structures.

[0008] In summary, there is an urgent need for an integrated solution that combines "process route optimization + dedicated heating rate design + specialized tooling collaboration" to control the deformation of flat aluminum alloy castings at the source, improve correction accuracy, and simultaneously balance production efficiency and overall product performance. Summary of the Invention

[0009] The purpose of this invention is to solve the technical problem that the existing production process of flat aluminum alloy castings is prone to secondary defects such as casting cracking, surface scratches and internal structural damage, and to provide a heat treatment processing method for controlling the deformation of flat aluminum alloy castings.

[0010] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0011] A heat treatment method for controlling the deformation of flat aluminum alloy castings, characterized by the following steps:

[0012] Step 1, Preparation

[0013] Prepare semi-finished castings; the semi-finished castings are flat aluminum alloy castings that have not undergone heat treatment;

[0014] Step 2, solution treatment

[0015] The semi-finished casting is placed in a heat treatment furnace and heated from room temperature to 535±5℃ at a heating rate of 200~250℃ / h. After holding at this temperature for 5~6h, it is quenched to obtain the solid solution of the casting.

[0016] Step 3, Deformation Measurement

[0017] The deformation of the solid solution in the casting is measured by using a calibration fixture combined with a multi-point measurement method. It is determined whether the deformation is ≤2mm and whether there are obvious defects on the surface. If not, the deformation location and degree of the solid solution in the casting are determined according to the test results, and step 4 is executed; if yes, step 7 is executed.

[0018] Step 4, Tooling Adjustment

[0019] Adjust the correction tooling according to the location and degree of deformation so that the correction amount of the casting at the deformation location corresponds to the degree of deformation.

[0020] Step 5, Pressure Calibration

[0021] The solid solution of the casting, together with the correction fixture, is placed in the working area of ​​the press. The solid solution of the casting is pressure-corrected by pressing the correction fixture with the press.

[0022] Step 6, Calibration and Detection

[0023] Using a calibration fixture combined with a multi-point measurement method, the deformation of the solid solution in the casting is measured again, and it is determined whether the deformation is ≤2mm and whether there are no obvious defects on the surface. If not, the deformation location and degree of the solid solution in the casting are determined according to the test results, and the process returns to step 4; if yes, step 7 is executed.

[0024] Step 7, Time-sensitive processing

[0025] The solid solution of the casting is placed in a heat treatment material frame, and the temperature is raised from room temperature to 185±5℃ at a heating rate of 150~200℃ / h, and then held for 6.5~8h to obtain a flat aluminum alloy casting.

[0026] Furthermore,

[0027] In step 2, the quenching treatment refers to immersing the semi-finished casting in water at 60-80°C within 10-20 seconds after the heat preservation is completed, and obtaining the solid solution of the casting after 10-15 minutes.

[0028] Furthermore, in step 3, the calibration fixture includes a base plate, a support assembly, and an upper pressure plate;

[0029] The base plate and the upper pressure plate are arranged in parallel, and the support assembly is located between them;

[0030] The support assembly includes a plurality of lower push rods and a plurality of upper push rods in a one-to-one correspondence; each lower push rod is vertically installed on the upper surface of the base plate to support the lower surface of the casting; each upper push rod is vertically installed on the lower surface of the upper pressure plate at the corresponding position to support the upper surface of the casting; the positions of the lower and upper push rods are arranged according to the planar stress distribution characteristics of the casting to achieve symmetrical support of the stress concentration area of ​​the casting from top to bottom;

[0031] At least one U-shaped shim is provided at the connection between each lower push rod and the base plate, and at the connection between each upper push rod and the upper pressure plate, for adjusting the support height of the corresponding lower or upper push rod.

[0032] Furthermore, in step 3, the calibration fixture also includes at least two locating pins mounted on the base plate, the upper end faces of the two locating pins cooperating with the positions of the locating holes on the casting to position the casting in the horizontal direction.

[0033] Each locating pin has a boss at its bottom, and a connecting flange is located near the boss. The connecting flange has flange holes around its circumference.

[0034] The base plate is provided with a countersunk platform corresponding to the boss and a fixed threaded hole corresponding to the flange hole.

[0035] Furthermore, in step 3, the edges of the base plate and the upper pressure plate are respectively provided with lifting lugs or lifting rings;

[0036] The top of the locating pin is chamfered.

[0037] Furthermore, in step 3, both the base plate and the upper pressure plate are made of high-strength wear-resistant alloy steel, with a flatness error ≤0.03mm and a parallelism error ≤0.05mm.

[0038] The thickness of the U-shaped gasket is 0.1~0.5mm;

[0039] The lower and upper push rods are both cylindrical structures with a height of 100-120mm and a diameter of 30-40mm; the lower and upper push rods are respectively provided with mounting holes along the radial direction.

[0040] Furthermore, in step 3, the measurement of the deformation of the solid solution in the casting is specifically carried out by positioning the solid solution in the casting using the positioning pin on the base plate and placing it at the top of the lower push rod, and then measuring the deformation of the solid solution in the casting using a multi-point measurement method.

[0041] Furthermore, in step 3, the multi-point measurement method refers to measuring the deformation at at least 4 points on the edge of the solid solution of the casting and at least 2 points at the center, and then taking the average value.

[0042] Further, step 4 specifically involves adjusting the number of U-shaped shims on the corresponding upper and lower push rods according to the deformation location and degree of deformation, so as to determine the height of each upper push rod and each lower push rod, thereby making the correction amount of the casting at the deformation location correspond to the degree of deformation, and then placing the solid solution of the casting horizontally between the lower push rod and the upper push rod.

[0043] Furthermore, in step 5, during the process of pressure correction of the solid solution of the casting by pressing and correcting the tooling, the deformation of the solid solution of the casting is monitored in real time. When the deformation correction amount is reached, the pressure is held for 1 minute and then slowly released.

[0044] The beneficial effects of this invention are as follows:

[0045] 1. High precision in deformation control, significantly improving product qualification rate: This invention breaks through the traditional process logic, precisely placing the correction process after solution treatment and before aging treatment. Combined with a unique heating rate design, it reduces thermal stress from the source of heat conduction. Utilizing the characteristics of flat aluminum alloy castings at this stage—low hardness (30%~50% lower than after aging) and good plasticity (more than 40% higher than after aging)—the correction difficulty is greatly reduced, avoiding secondary defects such as cracking and surface damage that are prone to occur during correction after aging. At the same time, correction after solution treatment can completely release the internal stress of the casting, and there is no secondary deformation during the aging treatment stage. The product qualification rate can be significantly increased from about 50% in the existing technology to over 99%.

[0046] 2. Significantly improved production efficiency, suitable for large-scale production: Compared with the traditional "solution treatment → aging → correction" process, this invention eliminates the complex correction process for high-strength castings after aging (the traditional correction process takes up 40% to 50% of the total processing time). The correction process of this invention is simple to operate and time-saving. The matching correction fixture is quickly positioned by positioning pins and adjusted by standardized U-shaped shims, which is suitable for flat aluminum alloy castings of different specifications (thickness 20 to 50 mm, surface area 0.2 to 0.5 m²). There is no need to frequently change the fixture, and the heat treatment processing time of a single casting is reduced by 30% to 40%.

[0047] 3. Significantly reduced production costs and overall benefits: (1) Reduced scrap and rework costs: The product qualification rate is increased to over 99%, significantly reducing scrap rate and rework costs; (2) Reduced equipment and labor costs: The dedicated calibration tooling has a simple structure and low manufacturing cost (only 1 / 3 to 1 / 2 of the existing complex calibration tooling), strong versatility, and no need to invest in other calibration equipment; The simplified process reduces labor input by 30%, and the tooling operation does not require professional technicians, reducing labor training costs; Overall, this invention can reduce production costs by 25% to 35%.

[0048] 4. The calibration fixture is innovative and practical, and easy to operate: The calibration fixture designed in this invention eliminates the defects of existing fixtures that are complex and cumbersome to adjust. It consists only of a base plate, support components, U-shaped shims, upper pressure plate and positioning pins. The structure is simple and the manufacturing cost is low. With the positioning pins, it can be quickly positioned and is easy to operate. Ordinary workers can operate it proficiently after simple training, reducing the dependence on manpower.

[0049] 5. The matching design of the calibration fixture provides targeted support and precise calibration: This invention adopts a structural design of "upper and lower push rods arranged according to the planar stress distribution + U-shaped shims". During the calibration process, the positions of the upper and lower push rods are arranged according to the planar stress distribution of flat castings, which can ensure the accuracy of support; the U-shaped shims adopt a standardized design with a thickness of 0.1~0.5mm, which can achieve micron-level adjustment and high adjustment accuracy; the whole can achieve targeted support and precise calibration of the deformation position, and stably control the deformation of the casting within 2mm. Attached Figure Description

[0050] Figure 1 This is a reference diagram showing the usage state of the calibration tooling in an embodiment of the present invention.

[0051] Figure 2 This is a top view of the base plate structure of the calibration fixture in an embodiment of the present invention.

[0052] Figure 3 This is a schematic diagram (partial cross-section) of the base plate structure of the calibration fixture in an embodiment of the present invention.

[0053] Figure 4 This is a bottom view of the upper pressure plate structure of the calibration fixture in an embodiment of the present invention.

[0054] Figure 5 This is a schematic diagram of the lower push rod structure of the calibration fixture in an embodiment of the present invention.

[0055] Figure 6 This is a schematic diagram of the U-shaped shim structure of the calibration fixture in an embodiment of the present invention.

[0056] Figure 7 This is a schematic diagram of the positioning pin structure of the calibration fixture in an embodiment of the present invention.

[0057] Figure 8 for Figure 7 Top view.

[0058] The attached figures are labeled as follows:

[0059] 1-Base plate, 11-Counterpart, 12-Fixing threaded hole, 13-Lifting lug threaded hole, 14-Lower push rod threaded hole, 2-Lower push rod, 21-Assembly hole, 3-Upper push rod, 4-Upper pressure plate, 41-Elongated hole, 42-Upper push rod threaded hole, 5-U-shaped gasket, 6-Locking pin, 61-Boss, 62-Connecting flange, 63-Flange hole. Detailed Implementation

[0060] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0061] This embodiment provides a heat treatment method for controlling the deformation of flat aluminum alloy castings. The specific operation steps are performed in the following order, and the steps cannot be reversed.

[0062] Step 1, Prepare semi-finished castings

[0063] The semi-finished casting described in this embodiment is an untreated ZL101A flat aluminum alloy casting (distinguished from frame-type, complex curved surface, irregularly shaped subframe, and end frame castings), with a thickness of 20~50mm and a surface area of ​​0.2~0.5m². 2 .

[0064] Step 2, solution treatment

[0065] The semi-finished casting is placed in a heat treatment furnace and heated from room temperature to 535±5℃ at a rate of 200~250℃ / h. After holding at this temperature for 5~6 hours, the semi-finished casting is transferred to water for quenching within 10~20 seconds. The water temperature for quenching is controlled at 60~80℃, and the solid solution is obtained after 10~15 minutes. This process ensures that the precipitated phases in the aluminum alloy are fully dissolved, resulting in a homogeneous solid solution. Furthermore, the low hardness and high plasticity of the aluminum alloy after solution treatment lay the foundation for subsequent precise correction.

[0066] Step 3, Deformation Measurement

[0067] The deformation of the solid solution in the casting is measured by using a calibration fixture combined with a multi-point measurement method. It is then determined whether the deformation is ≤2mm and whether there are obvious defects such as scratches or indentations on the surface. If not, the deformation location and degree of the solid solution in the casting are determined based on the test results, and step 4 is executed; if yes, step 7 is executed.

[0068] like Figure 1As shown, the calibration fixture used in this embodiment is a symmetrical precision support calibration structure, which is used to adapt to the stress distribution characteristics of aluminum alloy castings of different specifications and to achieve accurate identification and calibration of deformation positions. The calibration fixture includes a base plate 1, a support component, an upper pressure plate 4, and a positioning pin 6.

[0069] Both the base plate 1 and the upper pressure plate 4 are made of high-strength wear-resistant alloy steel and are arranged in parallel, with the support components located between them.

[0070] The support assembly includes multiple lower push rods 2 and multiple upper push rods 3, each corresponding to the other. Each lower push rod 2 is vertically installed on the upper surface of the base plate 1 to support the lower surface of the casting. Each upper push rod 3 is vertically installed on the lower surface of the upper pressure plate 4 at the corresponding position to support the upper surface of the casting. The positions of the lower push rods 2 and upper push rods 3 are arranged according to the planar stress distribution characteristics of the casting to achieve symmetrical support for the stress concentration areas of the casting. At least one U-shaped shim 5 is provided at the connection between each lower push rod 2 and the base plate 1, and at the connection between each upper push rod 3 and the upper pressure plate 4, to adjust the support height of the corresponding lower push rod 2 or upper push rod 3.

[0071] Specifically, refer to Figures 1 to 3 As shown, the base plate 1 is horizontally set and fixed on the base of the press, used to support the positioning points on the lower surface of the casting, with a flatness error ≤0.03mm. The base plate 1 is provided with threaded holes 14 for lower push rods, with a thread diameter of M16~M20. The positions of the threaded holes 14 correspond one-to-one with the positioning points on the lower surface of the casting, used for threaded connection with the lower push rod 2. Simultaneously, threaded holes 13 for lifting lugs are provided on both sides of the base plate 1, used to fix lifting lugs or lifting rings for easy lifting. A countersunk platform 11 is formed on the upper surface of the base plate 1. Threaded holes 12 for fixing positioning pins 6 are formed along the circumferential direction on the outer side of the countersunk platform 11 at set intervals. The countersunk platform 11 and the threaded holes 12 cooperate to fix the positioning pins 6.

[0072] Reference Figure 1 and Figure 4 As shown, the upper pressure plate 4 is parallel to the base plate 1 and their dimensions are perfectly matched. The upper pressure plate 4 is fixed to the press head of the press and located directly above the base plate 1. It is used to apply uniform pressure to the casting in conjunction with the base plate 1. The flatness error of the upper pressure plate 4 is ≤0.03mm, and the parallelism error with the base plate 1 is ≤0.05mm. The upper pressure plate 4 has threaded holes 42 for the upper push rod and threaded holes 13 for the lifting lugs. The thread diameter is M16~M20. The position of the threaded holes 42 for the upper push rod corresponds one-to-one with the positioning points on the upper surface of the casting and is used for threaded connection with the upper push rod 3. The threaded holes 13 for the lifting lugs are located on both sides of the upper pressure plate 4 and are used to fix the lifting lugs or lifting rings for easy lifting. At the same time, an elongated hole 41 is also provided in the center of the upper pressure plate 4, which is detachably connected to the press head of the press by bolts.

[0073] Reference Figure 5 As shown, both the lower ejector rod 2 and the upper ejector rod 3 are cylindrical structures made of high-strength alloy structural steel, with a height of 100-120mm and a diameter of 30-40mm. The bottom of the lower ejector rod 2 and the top of the upper ejector rod 3 are fitted with standard M16-M20 threads, the thread length of which is less than the thickness of the base plate 1 and the upper pressure plate 4, facilitating threaded connection between the ejector rods and the base plate 1 and the upper pressure plate 4. Furthermore, assembly holes 21 are provided at the center of the sides of the lower ejector rod 2 and the upper ejector rod 3 for easy assembly and disassembly. The lower ejector rod 2 and the upper ejector rod 3 are respectively threaded to the upper surface of the base plate 1 and the lower surface of the upper pressure plate 4, with each rod corresponding to the other. In actual use, the central axes of the lower ejector rod 2 and the corresponding upper ejector rod 3 coincide, thus forming a symmetrical upper and lower support for the casting.

[0074] Reference Figure 6 As shown, U-shaped shims 5 are installed at the connection points of each lower push rod 2 and the base plate 1, and at the connection points of each upper push rod 3 and the upper pressure plate 4. At least one shim is installed at each connection point, serving as the sole adjusting component for adjusting the height of the lower push rod 2 and the upper push rod 3 during the calibration process. The thickness of a single U-shaped shim 5 is 0.1~0.5mm, enabling micron-level precise adjustment of the corresponding push rod height. The width of the U-shaped groove on the U-shaped shim 5 is smaller than the diameter of the corresponding push rod, ensuring the stability of the fit between the U-shaped shim 5 and the corresponding push rod. In actual adjustment, the height of the corresponding push rod can be precisely adjusted by increasing / decreasing the number of U-shaped shims 5, thereby achieving targeted support for the deformation location of the casting.

[0075] Reference Figure 7 and Figure 8 As shown, the locating pin 6 is fixed at the recessed platform 11 of the base plate 1. Its position is arranged according to the rectangular surface contour of the flat casting (such as four-corner positioning + center auxiliary positioning) to achieve rapid and accurate positioning of the casting on the tooling, avoiding the surface displacement of the casting during the calibration process from affecting the calibration accuracy. The bottom of the locating pin 6 is provided with a boss 61. After the boss 61 is inserted into the recessed platform 11, it is fixed by engaging with the fixing threaded hole 12 on the base plate 1 through the flange hole 63 on the connecting flange 62 of the locating pin 6. The top of the locating pin 6 is provided with a 5×45° chamfer to facilitate the rapid placement and positioning of the casting.

[0076] Based on the aforementioned calibration fixture, the measurement of the deformation of the casting solid solution specifically involves positioning the casting solid solution using the positioning pins 6 on the base plate 1 and quickly placing it on the top of the lower push rod 2 of the base plate 1. Then, a multi-point measurement method is used to measure the deformation of the casting solid solution. The multi-point measurement method involves measuring the deformation at at least four points on the edge of the casting solid solution and at least two points at the center using a dial indicator, measuring each selected key point three times and taking the average value. This allows for accurate measurement of the deformation at each key point of the casting, clearly identifying the location (dent / warping / protrusion) and degree of deformation.

[0077] Step 4, Tooling Adjustment

[0078] Based on the deformation location and degree measured in step 3, the height of the upper push rod 3 and lower push rod 2 at corresponding positions on the base plate 1 and upper pressure plate 4 are adjusted. The adjustment method is only to add or remove the detachable U-shaped shims 5 on the corresponding push rods, without any other adjustment operations. Specifically: for the warped and protruding parts on the upper surface of the casting: add U-shaped shims 5 at the corresponding upper push rod 3 (i.e., raise the upper push rod 3), and remove U-shaped shims 5 at the corresponding lower push rod 2 (i.e., lower the lower push rod 2), forming a reverse pressing space to flatten the protrusion; for the concave parts on the upper surface of the casting: remove U-shaped shims 3 at the corresponding upper push rod 3 (i.e., lower the upper push rod 3), and add U-shaped shims 5 at the corresponding lower push rod 2 (i.e., raise the lower push rod 2). During pressure correction, the concave parts are flattened by the supporting force of the lower push rod 2.

[0079] Step 5, Pressure Calibration

[0080] The adjusted calibration fixture and the solid solution of the casting are placed in the working area of ​​the press. Uniform pressure is applied to the upper pressure plate 4 on the solid solution using the press head to perform pressure calibration, ensuring complete contact between the casting surface and the upper ejector rod 3 and lower ejector rod 2. During the pressure calibration process, the deformation of the solid solution is monitored in real time. When the required deformation is reached, the pressure is held for 1 minute, and then the press head is slowly released to ensure that the casting deformation is ≤2mm.

[0081] Step 6, Calibration and Detection

[0082] After the pressure holding period ends, turn off the press and, following the method in step 3, use a combination of calibration fixtures and multi-point measurement to measure the deformation of the solid solution in the casting again. Determine whether the deformation is ≤2mm and whether there are no obvious defects such as scratches or indentations on the surface. If not, determine the deformation location and degree of the solid solution in the casting based on the test results and return to step 4; if yes, proceed to step 7.

[0083] Step 7, Time-sensitive processing

[0084] The qualified castings are stacked in a heat treatment container for aging treatment. Specifically, the temperature is increased from room temperature to 185±5℃ at a rate of 150~200℃ / h, and then held for 6.5~8h to obtain flat aluminum alloy castings. In this embodiment, the aging treatment is the only strengthening process after the correction is qualified. No correction operation is performed during the aging treatment. The deformation of the casting is maintained at ≤2mm after aging treatment by effectively releasing the internal stress of the casting after correction.

[0085] In summary, this embodiment designs specific heating rate parameters for the planar thermal conductivity characteristics of flat aluminum alloy castings to avoid thermal stress deformation caused by uneven local temperature distribution.

[0086] Solution treatment heating rate: The heating rate from room temperature to solution temperature (535±5℃) is controlled at 200~250℃ / h to ensure that the surface and internal temperature of flat castings rise synchronously, reducing surface warping caused by temperature gradient.

[0087] Aging treatment heating rate: The heating rate from room temperature to aging temperature (185±5℃) is controlled at 150~200℃ / h to avoid secondary deformation caused by thermal stress accumulation during aging.

[0088] The following explanation uses the machining of a 400mm×300mm×40mm ZL101A flat aluminum alloy casting as an example:

[0089] 1. Solution treatment: Place the ZL101A flat aluminum alloy casting with dimensions of 400mm×300mm×40mm into a heat treatment furnace, raise the temperature from room temperature to 535℃ at a heating rate of 200℃ / h, and hold for 5h; after the holding period, quench in 70℃ water for 10min within 15s to obtain a uniform solid solution of the casting.

[0090] 2. Deformation Measurement: After the solid solution of the casting is cooled to room temperature, it is quickly placed on the base plate 1 of the calibration fixture using the positioning pin 6 on the base plate 1, so that the lower surface of the solid solution of the casting is in close contact with the top of the lower push rod 2 on the base plate 1. Using the multi-point measurement method of "4 points at the edge + 2 points at the center", the deformation of each point is measured 3 times with a dial indicator and the average value is taken. The maximum deformation of the solid solution of the casting is 4.2 mm. The specific deformation characteristics of the solid solution of the casting are: the edge is warped and raised, and the center is slightly concave.

[0091] 3. Tooling Adjustment: Based on the deformation characteristics of the casting solid solution, where the edges curve upwards and the center is concave, adjust the support height of the upper ejector rod 3 and lower ejector rod 2 at each position. The adjustment method is to increase or decrease the number of U-shaped shims 5 between the corresponding ejector rod and the base plate 1 or upper pressure plate 4, as detailed below:

[0092] (1) For the warped and protruding parts at the edge: reduce the number of U-shaped shims 5 with a thickness of 0.2mm on the lower push rod 2 at the corresponding position, so that the top support height of the lower push rod 2 is reduced by 0.4mm, leaving room for deformation to be corrected downwards at the edge; add two U-shaped shims 5 with a thickness of 0.2mm on the upper push rod 3 at the corresponding position, so that the bottom pressure height of the upper push rod 3 is increased by 0.4mm, and a downward correction force is applied to the warped and protruding parts during pressure correction.

[0093] (2) For the central recessed area: Add 3 U-shaped shims 5 with a thickness of 0.2mm to the lower push rod 2 at the corresponding position, so that the top support height of the lower push rod 2 is increased by 0.6mm, providing upward support force for the central recessed area; reduce 3 U-shaped shims 5 with a thickness of 0.2mm to the upper push rod 3 at the corresponding position, so that the bottom pressure height of the upper push rod 3 is reduced by 0.6mm, and an upward correction force is applied to the recessed area during pressure correction.

[0094] After adjustment, the height distribution of the upper push rod 3 and the lower push rod 2 is adapted to the deformation profile of the casting. During the pressure correction process, they can fit evenly with the corresponding parts of the casting to achieve targeted reverse correction.

[0095] 4. Pressure calibration: Place the adjusted tooling and the solid solution of the casting in the working area of ​​the press. Apply uniform pressure to the upper pressure plate 4 through the press head so that the surface of the solid solution of the casting is completely in contact with the upper push rod 3 and the lower push rod 2. Hold the pressure for 1 minute and then slowly release the press head.

[0096] 5. Calibration and Inspection: After loosening the press head, use the same measurement method as described above to inspect the casting. The maximum deformation of the casting is 1.5mm≤2mm, and there are no scratches or indentations on the surface. The calibration is qualified.

[0097] 6. Aging treatment: Place the qualified ZL101A castings in the heat treatment material frame according to the specifications, put them into the heat treatment furnace, and raise the temperature from room temperature to 185℃ at a heating rate of 150℃ / h, and hold for 6.5h. No correction operation is performed during the aging treatment, and the stability of the casting shape is ensured by the effective release of the internal stress of the casting.

[0098] 7. Test results: After aging treatment, the deformation and mechanical properties of the casting were tested. The maximum deformation of the casting was still 1.5mm≤2mm, the tensile strength of the casting was ≥190MPa, and the surface hardness was ≥80HB, which fully met the technical requirements of the product.

[0099] This invention addresses the challenge of controlling planar deformation in ZL101A flat aluminum alloy castings, a problem that existing technologies cannot solve. It abandons the traditional "solution treatment → aging → correction" process route and adopts a core route of "solution treatment → precise correction → aging." A precise correction process based on specialized correction fixtures is added after solution treatment and before aging treatment. Combined with a heat treatment heating rate design specific to flat castings, this provides a collaborative "process-tooling-heating rate" anti-deformation processing method. Utilizing the low hardness and high plasticity of the aluminum alloy after solution treatment, and combining the targeted support and correction of deformation locations by the correction fixtures, the deformation of the casting is stably controlled within 2mm. Aging treatment then enhances performance, ultimately yielding products with regular shape and excellent performance. This method not only improves the product qualification rate of flat castings but also reduces production costs, meeting the needs of large-scale, high-precision, collinear heat treatment production of flat aluminum alloy castings.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, and such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A heat treatment method for controlling the deformation of flat aluminum alloy castings, characterized in that, Includes the following steps: Step 1, Preparation; Prepare semi-finished castings; the semi-finished castings are flat aluminum alloy castings that have not undergone heat treatment; Step 2, solution treatment; The semi-finished casting is placed in a heat treatment furnace and heated from room temperature to 535±5℃ at a heating rate of 200~250℃ / h. After holding at this temperature for 5h~6h, it is quenched to obtain the solid solution of the casting. Step 3, Deformation measurement; The deformation of the solid solution in the casting is measured by using a calibration fixture combined with a multi-point measurement method. It is determined whether the deformation is ≤2mm and whether there are obvious defects on the surface. If not, the deformation location and degree of the solid solution in the casting are determined according to the test results, and step 4 is executed. If so, proceed to step 7; Step 4, tooling adjustment; Adjust the correction tooling according to the location and degree of deformation so that the correction amount of the casting at the deformation location corresponds to the degree of deformation. Step 5, pressure calibration; The solid solution of the casting, together with the correction fixture, is placed in the working area of ​​the press. The solid solution of the casting is pressure-corrected by pressing the correction fixture with the press. Step 6, Calibration and Testing; Using a calibration fixture combined with a multi-point measurement method, the deformation of the solid solution in the casting is measured again, and it is determined whether the deformation is ≤2mm and whether there are no obvious defects on the surface. If not, the deformation location and degree of the solid solution in the casting are determined according to the test results, and the process returns to step 4. If so, proceed to step 7; Step 7, Time-sensitive processing; The solid solution of the casting is placed in a heat treatment material frame, and the temperature is raised from room temperature to 185±5℃ at a heating rate of 150~200℃ / h, and then held for 6.5h~8h to obtain a flat aluminum alloy casting.

2. The heat treatment method for controlling the deformation of flat aluminum alloy castings according to claim 1, characterized in that: In step 2, the quenching treatment refers to immersing the semi-finished casting in water at 60-80°C within 10-20 seconds after the heat preservation is completed, and obtaining the solid solution of the casting after 10-15 minutes.

3. The heat treatment method for controlling the deformation of flat aluminum alloy castings according to claim 1, characterized in that: In step 3, the calibration fixture includes a base plate (1), a support assembly, and an upper pressure plate (4). The base plate (1) and the upper pressure plate (4) are arranged in parallel, and the support component is located between them; The support assembly includes a plurality of lower push rods (2) and a plurality of upper push rods (3) that correspond one-to-one; each lower push rod (2) is vertically installed on the upper surface of the base plate (1) to support the lower surface of the casting; each upper push rod (3) is vertically installed on the lower surface of the upper pressure plate (4) at the corresponding position to support the upper surface of the casting; the positions of the lower push rods (2) and the upper push rods (3) are arranged according to the planar stress distribution characteristics of the casting to achieve symmetrical support of the stress concentration area of ​​the casting from top to bottom; At least one U-shaped pad (5) is provided at the connection between each lower push rod (2) and the base plate (1), and at the connection between each upper push rod (3) and the upper pressure plate (4), for adjusting the support height of the corresponding lower push rod (2) or upper push rod (3).

4. The heat treatment method for controlling the deformation of flat aluminum alloy castings according to claim 3, characterized in that: In step 3, the calibration fixture also includes at least two positioning pins (6) installed on the base plate (1). The upper end faces of the two positioning pins (6) are matched with the positions of the positioning holes on the casting to position the casting in the horizontal direction. Each locating pin (6) has a boss (61) at its bottom and a connecting flange (62) near the boss (61). The connecting flange (62) has a flange hole (63) in its circumference. The base plate (1) is provided with a countersunk (11) corresponding to the boss (61) and a fixed threaded hole (12) corresponding to the flange hole (63).

5. The heat treatment method for controlling the deformation of flat aluminum alloy castings according to claim 4, characterized in that: In step 3, the edges of the base plate (1) and the upper pressure plate (4) are respectively provided with lifting lugs or lifting rings; The top of the positioning pin (6) is chamfered.

6. The heat treatment method for controlling the deformation of flat aluminum alloy castings according to claim 5, characterized in that: In step 3, the base plate (1) and the upper pressure plate (4) are both made of high-strength wear-resistant alloy steel, with a flatness error of ≤0.03mm and a parallelism error of ≤0.05mm. The thickness of the U-shaped gasket (5) is 0.1~0.5mm; The lower push rod (2) and the upper push rod (3) are cylindrical structures with a height of 100~120mm and a diameter of 30~40mm. The lower push rod (2) and the upper push rod (3) are respectively provided with assembly holes (21) along the radial direction.

7. The heat treatment method for controlling the deformation of flat aluminum alloy castings according to claim 6, characterized in that: In step 3, the deformation of the solid solution in the casting is measured by positioning the solid solution in the casting through the positioning pin (6) on the base plate (1) and placing it on the top of the lower push rod (2). Then, the deformation of the solid solution in the casting is measured by the multi-point measurement method.

8. The heat treatment method for controlling the deformation of flat aluminum alloy castings according to claim 7, characterized in that: In step 3, the multi-point measurement method refers to measuring the deformation at at least 4 points on the edge of the solid solution of the casting and at least 2 points at the center, and then taking the average value.

9. The heat treatment method for controlling the deformation of flat aluminum alloy castings according to claim 8, characterized in that: Step 4 specifically involves adjusting the number of U-shaped shims (5) on the corresponding upper push rod (3) and lower push rod (2) according to the deformation location and degree of deformation, in order to determine the height of each upper push rod (3) and each lower push rod (2), so that the correction amount of the casting at the deformation location corresponds to the degree of deformation. Then, the solid solution of the casting is placed horizontally between the lower push rod (2) and the upper push rod (3).

10. The heat treatment method for controlling the deformation of flat aluminum alloy castings according to claim 1, characterized in that: In step 5, during the pressure correction of the solid solution of the casting by pressing the correction fixture with a press, the deformation of the solid solution of the casting is monitored in real time. When the deformation correction amount is reached, the pressure is held for 1 minute and then slowly released.

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