CN105506522B - A kind of frame clsss aluminium alloy castings heat treatment deformation bearing calibration - Google Patents

Abstract

The invention discloses a method for correcting heat treatment deformation of frame-type aluminum alloy castings, which is used to solve the technical problem that the existing heat treatment deformation control methods of aluminum alloy castings are poor in practicability. The technical solution is to fix the front end, the middle part of the casting and the rear end of the casting with adjustable tooling before the heat treatment of the aluminum alloy casting to prevent the deformation of the aluminum alloy casting during solid solution and water entry. In the middle area of the casting, the load is applied to cause deformation in the middle of the casting in the direction of the reverse bending stress, and then the aluminum alloy casting is subjected to artificial aging, so that the deformed area of the aluminum alloy casting returns to the size error under the action of the bending stress generated by the structural gravity of the aluminum alloy casting itself Within the control range, the heat treatment deformation control of aluminum alloy castings is realized, thereby effectively avoiding the bending deformation of aluminum alloy castings, and making the aluminum alloy castings meet the requirements of mechanical properties and dimensions.

Description

A heat treatment deformation correction method for frame-type aluminum alloy castings

technical field

The invention relates to a method for correcting heat treatment deformation of an aluminum alloy casting, in particular to a method for correcting heat treatment deformation of a frame-type aluminum alloy casting.

Background technique

In the field of aerospace, with the deepening of the design concept of integration, integration, light weight and precision, some frame-type aluminum alloy castings with the characteristics of large size, complex shape structure, thin wall and high performance requirements are getting more and more attention. Wide range of applications. However, due to the complex structure and uneven wall thickness of such castings, large-scale shape deformation and partial complex deformation are prone to occur during heat treatment, which brings difficulties to the subsequent casting and use. Therefore, it must be carried out during the heat treatment of castings. Certain fixation and orthopedics prevent casting deformation.

The document "Application Publication No. CN103834883A Chinese Invention Patent" discloses a heat treatment deformation control method for thin-walled saddle-shaped aluminum alloy castings. According to the characteristics of the casting, this method installs the blocking plate and the clamp on the casting before heating, and puts the thicker side of the casting into the furnace vertically, and heats it in stages to reduce the thermal stress during heating. The shape of the adjustable tooling can reduce the deformation during quenching, and the pre-tightening force will continue to be applied during the aging stage to maintain the binding force of the tooling. This method solves the deformation problem of castings caused by the difference of solid solution into water at the front and rear ends of the castings during the heat treatment process, and is suitable for cylindrical or saddle-shaped castings with relatively simple structures or relatively symmetrical shapes. However, for some complex frame-type aluminum alloy castings, in addition to the deformation caused by the difference of solid solution into water during the heat treatment process, the stress concentration is locally formed due to the structure of the casting itself, which leads to the bending deformation of the casting during the heat treatment process, especially for the average Large-scale frame-type aluminum alloy castings with a wall thickness of only 3 to 5mm have large dimensions, complex structures, and greater deformation.

Contents of the invention

In order to overcome the disadvantage of poor practicability of the existing heat treatment deformation control methods of aluminum alloy castings, the present invention provides a correction method for heat treatment deformation of frame-type aluminum alloy castings. In this method, before the heat treatment of aluminum alloy castings, adjustable tooling is used to fix the front end of the casting, the middle of the casting and the rear end of the casting to prevent the deformation of the aluminum alloy casting during solid solution and water entry. In the middle area of the casting, a load is applied to cause deformation in the middle of the casting in the direction of the reverse bending stress, and then the aluminum alloy casting is subjected to artificial aging, so that the deformed area of the aluminum alloy casting is restored to the dimensional error control under the action of the bending stress generated by the gravity of the aluminum alloy casting itself Within the scope, the heat treatment deformation control of aluminum alloy castings is realized, thereby effectively avoiding the bending deformation of aluminum alloy castings, and making the aluminum alloy castings meet the requirements of mechanical properties and dimensions.

The technical solution adopted by the present invention to solve the technical problem: a method for correcting heat treatment deformation of a frame-type aluminum alloy casting, which is characterized in that it includes the following steps:

The first step is to install front-end adjustable tooling 4 near the front end 1 of the casting, install rear-end adjustable tooling 6 near the rear end 3 of the casting, and install middle adjustable tooling 5 at the middle part 2 of the casting. The positioning bolts 10 on the three adjustable tooling constrain and fasten the width direction of the casting, and maintain the same fastening force of the inner and outer bolts of the casting; The castings in the middle part 2 and the rear end 3 of the casting are placed in the same shape and size as the adjustable tooling, and the upper pressing plate 9, the upper forming plate 8 and the casting 12 are compressed and fixed by fastening bolts 7 .

The second step is to put the fixed casting into the heat treatment furnace and place it horizontally, and use refractory bricks to pad the front end 1 of the casting and the rear end 3 of the casting.

Step 3: The casting is heated with the furnace, and the temperature is raised to 500-510°C at a rate of 50-80°C/h, kept for 0.5-1h, heated to 530-540°C at a rate of 0.5-1°C/min, and held for 8-5 18h.

The fourth step is to take out the casting within 10-15 seconds, immerse the casting vertically in water for quenching, the water temperature is required to be 25-50°C, and the casting stays in the water for 5-10 minutes.

Step 5: Take the casting out of the water, place it on the cast iron platform 14, place the front backing plate 13 and the rear backing plate 15 at the bottom of the front adjustable tooling 4 and the rear adjustable tooling 6 respectively, and remove the middle adjustable tooling 5, the pre-tightening force of the fastening bolt 7 on the middle adjustable tooling 5, and a jack is used to apply a uniform load in the direction of the bending stress 16 on the upper platen 9 of the middle adjustable tooling 5, so that the central area of the casting is deformed under the action of this external force. Overcorrection is completed within 1 to 3 hours after solution treatment.

Step 6: Remove the three adjustable toolings from the overcorrected casting, and place it horizontally in a heat treatment furnace for aging treatment. The aging temperature is 160-180°C, the holding time is 12-18 hours, and the casting is cooled with the furnace. As the casting cools and shrinks, the size of the overcorrected part returns to within the size error range due to the bending stress generated by the weight of the front and rear ends of the casting at the original excessive deformation.

The beneficial effects of the present invention are: before the heat treatment of the aluminum alloy casting, the method adopts adjustable tooling to fix the front end, the middle part of the casting and the rear end of the casting, so as to prevent the deformation of the aluminum alloy casting during the process of solid solution and water entry. Finally, in the central area of the casting where the bending stress is concentrated, a load is applied to cause deformation in the middle of the casting in the direction of the reverse bending stress, and then the aluminum alloy casting is artificially aged, so that the deformed area of the aluminum alloy casting is within the bending stress generated by the gravity of the aluminum alloy casting itself. Under the action, it returns to the range of size error control, and realizes the heat treatment deformation control of aluminum alloy castings, thereby effectively avoiding the bending deformation of aluminum alloy castings, and making aluminum alloy castings meet the mechanical properties and size requirements.

The invention adopts the shape of the inner cavity of the adjustable tooling upper plate to match the shape of the casting, which can quickly realize the fastening constraint on the casting, not only saves the time for shape correction, but also avoids the phenomenon of cracking and deformation of the casting caused by local stress concentration.

Utilizing the stress characteristics of the casting structure itself, the overcorrection is applied to the easily deformable area, so that the casting will automatically return to the original shape in the subsequent aging stage, and the reliable control of the deformation process can be realized.

Utilizing the characteristics of low tensile strength, good elongation and easy correction after solution treatment and before aging treatment of castings, overcorrection is carried out to avoid cracking of castings caused by external force correction.

The distribution of residual stress inside the casting after heat treatment is reduced, and the deformation or fracture of the casting due to the influence of residual stress in the future use process is avoided.

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

Fig. 1 is a structural schematic diagram of a frame-type aluminum alloy casting and a schematic diagram of the installation position of an adjustable tooling for which the method for correcting heat treatment deformation of a frame-type aluminum alloy casting according to the present invention is.

Fig. 2 is a left sectional view of Fig. 1 .

Fig. 3 is a schematic diagram of the process of applying external force to the casting in the method of the present invention.

In the figure, 1-front end of the casting, 2-middle part of the casting, 3-rear end of the casting, 4-adjustable tooling at the front end, 5-adjustable tooling at the middle part, 6-adjustable tooling at the rear end, 7-fastening bolts, 8-upper Shaped plate, 9-upper plate, 10-locating bolt, 11-bottom plate, 12-casting, 13-front backing plate, 14-cast iron platform, 15-back backing plate, 16-reverse bending stress direction.

detailed description

The following examples refer to Figures 1-3.

Take the heat treatment deformation control of a large frame-type cast aluminum alloy component in the aviation field as an example. It has a rectangular frame structure with complex curved surfaces and many internal ribs. The rear end is connected with a U-shaped large plane and tilted upwards. The local wall thickness is 12mm. The total length of the casting is 2930mm, the width is 1250mm, and the height is 420mm. The average wall thickness is 5mm. The alloy material is ZL114A. Since the front and rear ends of the casting are curved upwards, the middle part of the casting is easily deformed by the upward bending stress, which is also a difficult point in the anti-deformation control of this type of casting during casting and subsequent heat treatment. This piece is formed by gypsum mold combined with vacuum pressurized casting method, which not only requires high dimensional accuracy and surface roughness during casting, but also requires strict control of casting deformation during heat treatment, and the dimensional control accuracy requirements of key parts in the length direction of casting Within the range of 0.1-1.8mm, the dimensional accuracy in the width direction is required to be within the range of 3.5-6.3mm. Performance requirements σb≥320MPa, δ5≥8% requirements.

Example 1:

In the first step, the front end 1 of the casting, the middle part 2 of the casting, and the rear end 3 of the casting are the key dimension control parts of the casting. The front end adjustable tooling 4 is installed at a distance of 810mm from the end of the front end 1 of the casting, and 620mm from the end of the rear end 3 of the casting. The rear adjustable tooling 6 is installed at the middle part of the casting 2, and the middle adjustable tooling 5 is installed at the middle part of the casting. The distance between the front adjustable tooling 4 and the rear end adjustable tooling 6 is 700mm; Forming plate 8, upper pressing plate 9, fastening bolts 10 and lower bottom plate 11, the positioning bolts 10 are used to constrain and fasten the width direction of the casting, and maintain the same fastening force of the inner and outer bolts of the casting; the upper forming plate in the adjustable tooling The shape of the inner cavity of 8 is consistent with the outline of the casting where the adjustable tooling is placed at the front end 1 of the casting, the middle part 2 of the casting, and the rear end 3 of the casting, and the upper pressing plate 9, the upper forming plate 8 and the casting 12 are pressed tightly by fastening bolts 7 fixed.

In the second step, the fixed casting is put into the heat treatment furnace, the casting is placed horizontally, and the front end 1 and the rear end 3 of the casting are padded with refractory bricks.

In the third step, the casting is heated with the furnace, and the temperature is raised to 510°C at a rate of 50°C/h, kept for 0.5h, heated to 540°C at a rate of 0.5°C/min, and kept for 18h.

The fourth step is to take out the casting within 15 seconds, immerse the casting vertically in water for quenching, the water temperature is required to be 50°C, and the casting stays in the water for 10 minutes.

The fifth step is to take the casting out of the water, place it on the cast iron platform 14, place the front backing plate 13 and the rear backing plate 15 with a thickness of 8mm on the bottom of the front adjustable tooling 4 and the rear adjustable tooling 6 respectively, and remove the middle part The pre-tightening force of the fastening bolt 7 on the adjustable tooling 5, and a jack is used to apply a uniform load in the direction of the bending stress 16 on the upper platen 9 of the adjustable tooling 5 in the middle, so that the central area of the casting will produce 4mm under the action of this external force. amount of deformation. The amount of deformation depends on the length of the casting and the magnitude of the bending stress generated by the self-weight of the warping parts at both ends in the middle of the casting, which can be determined according to the deformation law of the casting.

The overcorrection is completed within 3 hours after the solution treatment. Since the casting has just finished solution treatment at this time, the tensile strength is low and the elongation is good, and it is easy to produce elastic-plastic deformation, which is convenient for overcorrection.

The sixth step is to remove the adjustable tooling from the overcorrected casting and place it horizontally in a heat treatment furnace for aging treatment. The aging temperature is 180°C and the holding time is 12 hours. The casting is cooled with the furnace. As the casting cools and shrinks, at the place where the original excessive deformation is applied, due to the bending stress generated by the weight of the front and rear ends of the casting, the size of the excessive orthopedic part returns to the range of dimensional error within 1mm, which meets the dimensional accuracy control requirements of the casting. The mechanical properties of castings also meet the technical requirements.

Example 2:

In the first step, the front end 1 of the casting, the middle part 2 of the casting, and the rear end 3 of the casting are the key dimension control parts of the casting. The front end adjustable tooling 4 is installed at a distance of 810mm from the end of the front end 1 of the casting, and 620mm from the end of the rear end 3 of the casting. The rear adjustable tooling 6 is installed at the middle part of the casting 2, and the middle adjustable tooling 5 is installed at the middle part of the casting. The distance between the front adjustable tooling 4 and the rear end adjustable tooling 6 is 700mm; Forming plate 8, upper pressing plate 9, fastening bolts 10 and lower bottom plate 11, the positioning bolts 10 are used to constrain and fasten the width direction of the casting, and maintain the same fastening force of the inner and outer bolts of the casting; the upper forming plate in the adjustable tooling The shape of the inner cavity of 8 is consistent with the outline of the casting where the adjustable tooling is placed at the front end 1 of the casting, the middle part of the casting 2, and the rear end 3 of the casting, and the upper pressing plate 9, the upper forming plate 8 and the casting 12 are pressed tightly by fastening bolts 7 fixed.

In the second step, the fixed casting is put into the heat treatment furnace, the casting is placed horizontally, and the front end 1 and the rear end 3 of the casting are padded with refractory bricks.

In the third step, the casting is heated with the furnace, and the temperature is raised to 500°C at a rate of 80°C/h, kept for 1 hour, heated to 530°C at a rate of 1°C/min, and held for 8 hours.

The fourth step is to take out the casting within 10 seconds, immerse the casting vertically in water for quenching, the water temperature is required to be 25°C, and the casting stays in the water for 5 minutes.

The fifth step is to take the casting out of the water, place it on the cast iron platform 14, place the front backing plate 13 and the rear backing plate 15 with a thickness of 8mm on the bottom of the front adjustable tooling 4 and the rear adjustable tooling 6 respectively, and remove the middle part The pre-tightening force of the fastening bolt 7 on the adjustable tooling 5, and a jack is used to apply a uniform load in the direction of the bending stress 16 on the upper platen 9 of the adjustable tooling 5 in the middle, so that the central area of the casting produces 3.5 The amount of deformation in mm. The overcorrection is completed within 1 hour after the solution treatment.

The sixth step is to remove the adjustable tooling from the overcorrected casting, and place it horizontally in a heat treatment furnace for aging treatment. The aging temperature is 160°C, the holding time is 18 hours, and the casting is cooled with the furnace. As the casting cools and shrinks, at the place where the excessive deformation was originally applied, due to the bending stress generated by the weight of the front and rear ends of the casting, the size of the excessive orthopedic part returns to within the range of dimensional error of 1mm, which meets the dimensional accuracy control requirements of the casting. The mechanical properties of castings also meet the technical requirements.

Example 3:

In the first step, the front end 1 of the casting, the middle part 2 of the casting, and the rear end 3 of the casting are the key dimension control parts of the casting. The front end adjustable tooling 4 is installed at a distance of 810mm from the end of the front end 1 of the casting, and 620mm from the end of the rear end 3 of the casting. The rear adjustable tooling 6 is installed at the middle part of the casting 2, and the middle adjustable tooling 5 is installed at the middle part of the casting. The distance between the front adjustable tooling 4 and the rear end adjustable tooling 6 is 700mm; Forming plate 8, upper pressing plate 9, fastening bolts 10 and lower bottom plate 11, the positioning bolts 10 are used to constrain and fasten the width direction of the casting, and maintain the same fastening force of the inner and outer bolts of the casting; the upper forming plate in the adjustable tooling The shape of the inner cavity of 8 is consistent with the outline of the casting where the adjustable tooling is placed at the front end 1 of the casting, the middle part of the casting 2, and the rear end 3 of the casting, and the upper pressing plate 9, the upper forming plate 8 and the casting 12 are pressed tightly by fastening bolts 7 fixed.

In the second step, the fixed casting is put into the heat treatment furnace, the casting is placed horizontally, and the front end 1 and the rear end 3 of the casting are padded with refractory bricks.

In the third step, the casting is heated with the furnace, and the temperature is raised to 505°C at a rate of 70°C/h, kept for 1 hour, heated to 530°C at a rate of 1°C/min, and held for 12 hours.

The fourth step is to take out the casting within 10 seconds, immerse the casting vertically in water for quenching, the water temperature is required to be 30°C, and the casting stays in the water for 8 minutes.

The fifth step is to take the casting out of the water, place it on the cast iron platform 14, place the front backing plate 13 and the rear backing plate 15 with a thickness of 8mm on the bottom of the front adjustable tooling 4 and the rear adjustable tooling 6 respectively, and remove the middle part The pre-tightening force of the fastening bolt 7 on the adjustable tooling 5, and a jack is used to apply a uniform load in the direction of the bending stress 16 on the upper platen 9 of the adjustable tooling 5 in the middle, so that the central area of the casting produces 3.5 The amount of deformation in mm. The overcorrection is completed within 2 hours after the solution treatment.

The sixth step is to remove the adjustable tooling from the overcorrected casting and place it horizontally in a heat treatment furnace for aging treatment. The aging temperature is 170°C and the holding time is 16 hours. The casting is cooled with the furnace. As the casting cools and shrinks, at the place where the excessive deformation was originally applied, due to the bending stress generated by the weight of the front and rear ends of the casting, the size of the excessive orthopedic part returns to within the range of dimensional error of 1mm, which meets the dimensional accuracy control requirements of the casting. The mechanical properties of castings also meet the technical requirements.

Claims (1)

1. A method for correcting heat treatment deformation of a frame type aluminum alloy casting, characterized in that it comprises the following steps: The first step is to install the front adjustable tooling (4) near the front end (1) of the casting, install the rear adjustable tooling (6) near the rear end (3) of the casting, and install the middle adjustable tooling in the middle of the casting (2). tooling (5); the positioning bolts (10) on the three adjustable toolings constrain and fasten the width direction of the casting, and maintain the same fastening force of the inner and outer bolts of the casting; The shape of the cavity is consistent with the casting profile size at the front end of the casting (1), the middle part of the casting (2), and the rear end of the casting (3). Plate (8) and casting (12) are compressed and fixed; The second step is to put the fixed casting into the heat treatment furnace and place it horizontally, and use refractory bricks to pad the front end (1) and the rear end (3) of the casting; Step 3: The casting is heated with the furnace, and the temperature is raised to 500-510°C at a rate of 50-80°C/h, kept for 0.5-1h, heated to 530-540°C at a rate of 0.5-1°C/min, and held for 8-5 18h; Step 4: Take out the casting within 10-15 seconds, immerse the casting vertically in water for quenching, the water temperature is required to be 25-50°C, and the casting stays in the water for 5-10 minutes; Step 5: Take the casting out of the water, place it on the cast iron platform (14), place the front backing plate (13) and the rear backing plate on the bottom of the front adjustable tooling (4) and the rear adjustable tooling (6) respectively (15), remove the pretightening force of the fastening bolts (7) on the middle adjustable tooling (5), and apply a reverse bending stress direction ( 16) The uniform load causes the central area of the casting to produce deformation under the action of the external force; the overcorrection is completed within 1 to 3 hours after the solution treatment; The sixth step is to remove the three adjustable toolings from the overcorrected casting, and place it horizontally in a heat treatment furnace for aging treatment. The aging temperature is 160-180°C, and the holding time is 12-18 hours. The casting is cooled with the furnace; The cooling shrinkage of the casting, at the place where the original excessive deformation is applied, due to the bending stress generated by the weight of the front and rear ends of the casting, the size of the excessive orthopedic part returns to the size error range.