A method for controlling springback deformation of an aluminum alloy thin-walled die casting

Abstract

The application discloses a kind of control methods of springback deformation of aluminum alloy thin-wall die casting, comprising the following steps: step 1, furnace: workers according to the effective volume in furnace, the aluminum alloy die casting to be processed is appropriately loaded into furnace;Step 2, equipment inspection: workers check the parts in processing furnace and electric heating element, ensure that it has no contact with aluminum alloy die casting;A kind of control method of springback deformation of aluminum alloy thin-wall die casting of the application, the springback deformation of aluminum alloy die casting is controlled by pretreatment, mold structure and process flow three aspects, step 1 to step 5 by annealing treatment to the profile to be stamped, reduce its hardness to control reduce the springback deformation when die casting;Step 6 to step 9 by changing mold structure, make the springback trend of inside and outside mutually offset, to reduce springback;Step 10 and step 11 by increasing compensation correction process or taking tensile casting process to reduce the springback deformation of whole.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aluminum alloy die casting, in particular to a control method for springback deformation of aluminum alloy thin-wall die casting. BACKGROUND

[0002] Aluminum alloy material is prone to large springback deformation behavior during stamping forming, and size out-of-tolerance, cracking, thinning rate out-of-tolerance, wrinkling and other phenomena are prone to occur during stamping process. The special material properties of aluminum parts have brought great difficulties to process analysis, springback analysis and production debugging. SUMMARY

[0003] The purpose of the present application is to provide a control method for springback deformation of aluminum alloy thin-wall die casting, to solve the problem of large springback deformation behavior of existing aluminum alloy material during stamping forming, size out-of-tolerance, cracking, thinning rate out-of-tolerance, wrinkling and other phenomena during stamping process, which brings great difficulties to process analysis, springback analysis and production debugging.

[0004] To achieve the above purpose, the present application provides the following technical scheme: a control method for springback deformation of aluminum alloy thin-wall die casting, comprising the following steps:

[0005] Step 1, furnace loading: the workers load the aluminum alloy die casting to be processed into the furnace according to the effective volume in the furnace;

[0006] Step 2, equipment inspection: the workers inspect the parts and electric heating elements in the furnace to ensure that they are not in contact with the aluminum alloy die casting;

[0007] Step 3, parameter configuration: the workers set the heating speed and holding time in the furnace according to the hardness of the aluminum alloy die casting to be detected;

[0008] Step 4, power-on temperature rising: the workers turn on the furnace power to heat the aluminum alloy die casting to be processed inside, and hold the temperature at a specified temperature;

[0009] Step 5, cooling treatment: the workers pour poor heat-conducting medium into the furnace to slowly cool the aluminum alloy profile at an appropriate speed;

[0010] Step 6, compensation processing: the workers use the characteristics that the springback directions of different parts of the bending piece are opposite, correct the shape and size of the working part of the convex and concave dies according to the estimated or tested springback amount, and compensate the springback amount of the aluminum alloy die casting by springback in the opposite direction;

[0011] Step 7, correction processing: change the structure of the punch to concentrate the correction force on the die casting deformation area, increase the change degree of the stress and strain state of the aluminum alloy die casting deformation area, force the inside and outside of the aluminum profile to be tangential compressive stress and tangential tensile strain, so that the rebound trends of the inside and outside cancel each other out;

[0012] Step 8, longitudinal pressure: after the die casting is completed, the staff uses the shoulder of the mold to longitudinally press the end of the aluminum alloy die casting, so that the deformation area is subjected to compressive stress on the cross section, and when the aluminum alloy profile is unloaded, the rebound trends of the inside and outside are opposite, thereby reducing the rebound force, and the method can obtain a larger bending size, but the blank precision requirement is higher;

[0013] Step 9, upgrade processing: use a polyurethane concave die instead of a rigid metal concave die for processing, and when die casting, the aluminum profile gradually enters the polyurethane concave die with the punch, and the increased bending force will change the stress and strain state of the material in the fillet deformation area, achieving a similar correction bending, thereby reducing the rebound;

[0014] Step 10, compensation correction: after processing, the staff applies a larger correction pressure to the die casting to change the stress and strain state of the deformation area to control the rebound amount;

[0015] Step 11, tensile casting: adopt the draw bending process, the aluminum profile is subjected to tangential tensile force during bending deformation, the applied drawing force should make the combined stress in the deformation area greater than the yield limit of the material, the inside compressive strain in the neutral layer is converted into tensile strain, that is, the entire cross section of the aluminum profile is in the range of plastic drawing deformation, and after unloading, the rebound trends of the inside and outside cancel each other out, thereby reducing the rebound.

[0016] As a preferred technical solution of the present application, the effective volume of the profile loaded into the furnace in step 1 is less than half of the volume of the furnace, so as to avoid incomplete heating.

[0017] As a preferred technical solution of the present application, in step 3, the hardness of the aluminum alloy die casting is detected by a Rockwell hardness tester, so as to set a reasonable critical temperature.

[0018] As a preferred technical solution of the present application, in step 3, when different thickness parts are loaded into the same treatment furnace, the heating and holding time should be determined according to the maximum thickness, and the aluminum profiles with a thickness difference greater than 10 mm should not be treated in the same furnace.

[0019] As a preferred technical solution of the present application, in step 4, the furnace door should not be opened arbitrarily during the power feeding and temperature rising operation of the aluminum alloy die casting to be processed.

[0020] Compared with the prior art, the beneficial effects of the present application are: the overall springback deformation of the aluminum alloy die casting is controlled through three aspects of pretreatment, mold structure and process flow, steps 1 to 5 are to anneal the to-be-stamped profile, slowly cool it to obtain a stable organization close to the equilibrium state, reduce its hardness to control the reduction of the springback deformation during die casting, and then quench after die casting; steps 6 to 9 are to change the mold structure to offset the springback trend of the inner and outer sides, thereby reducing the springback; and steps 10 and 11 are to increase the compensation correction process or adopt the tension casting process to reduce the overall springback deformation force. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0022] The present application provides a control method for springback deformation of an aluminum alloy thin-wall die casting, comprising the following steps:

[0023] Step 1, furnace loading: the workers load the to-be-processed aluminum alloy die casting into the furnace according to the effective volume in the furnace, and the to-be-processed aluminum alloy die casting is loaded in an appropriate amount. When loading, it must be handled with care to prevent the profile from being scratched and deformed;

[0024] Step 2, equipment inspection: the workers check the parts and electric heating elements in the treatment furnace to ensure that they are not in contact with the aluminum alloy die casting. When the aluminum alloy die casting pieces are stacked, point and less line contact is allowed, and surface contact is avoided. The stacking gap is not less than 10 mm;

[0025] Step 3, parameter configuration: the workers set the heating speed and holding time in the furnace according to the hardness of the to-be-tested aluminum alloy die casting;

[0026] Step 4, power-on temperature rising: the workers turn on the power of the furnace body to heat the to-be-processed aluminum alloy die casting in the furnace, and heat it to a specified temperature for holding;

[0027] Step 5, cooling treatment: the workers pour poor heat-conducting medium into the furnace to slowly cool the aluminum alloy profile at an appropriate speed. When the furnace is discharged after cooling, special care should be taken to try to vertically hang heating in the furnace, or a special heat treatment clamp, protective cover or frame tooling can be designed to prevent deformation;

[0028] Step 6, compensation processing: the workers use the characteristics of the opposite springback directions of different parts of the bending piece to correct the shape and size of the working part of the punch and the die according to the springback amount obtained by estimation or test, and compensate the springback amount of the aluminum alloy die casting by the springback in the opposite direction. The springback angle is made on the die, so that the working part of the die has a certain slope. When double-angle bending is performed, the springback angle on both sides of the bending punch is removed, and the single-face gap of the bending die is kept equal to the material thickness, so as to make the aluminum alloy profile adhere to the punch, and the springback of the aluminum alloy profile on both sides is vertical after the die is opened;

[0029] Step 7, correction processing: change the structure of the punch to concentrate the correction force in the die casting deformation area, and increase the change degree of the stress and strain state of the deformation area of the aluminum alloy die casting. The premise is that when the material thickness is more than 0.8 mm and the plasticity is good, and the bending fillet radius is not large, the structure of the punch is changed.

[0030] Step 8, longitudinal pressure: after the die casting is completed, the workers use the shoulder of the die to longitudinally press the end of the aluminum alloy die casting, so that the deformation area is subjected to compressive stress on the cross section, and the springback trends of the inside and outside of the aluminum alloy profile are opposite when unloaded, thereby reducing the springback force. By using this method, the bending size can be obtained, but the precision of the blank is required to be higher;

[0031] Step 9, upgrading processing: using a polyurethane die instead of a rigid metal die for processing; when bending, the metal sheet gradually enters the polyurethane die with the punch, and the increased bending force will change the stress and strain state of the material in the fillet deformation area, so as to achieve a similar correction bending, thereby reducing the springback;

[0032] Step 10, compensation correction: after processing, the workers apply a large correction pressure to the die casting to change the stress and strain state of the deformation area to control the springback amount. Generally, when the correction compression amount of the material in the bending deformation area is 2% to 5% of the plate thickness, a good stress and strain state is obtained.

[0033] Step 11, tensile casting: using the draw bending process, the aluminum profile is subjected to tangential drawing force during the bending deformation process. The drawing force should be applied to make the combined stress in the deformation area greater than the yield limit of the material, and the compressive strain inside the neutral layer is converted into tensile strain, that is, the entire cross section of the aluminum profile is in the range of plastic drawing deformation, and the springback trends of the inside and outside are offset to each other after unloading, thereby reducing the springback.

[0034] Preferably, the effective volume of each profile loaded into the furnace in step 1 is less than half of the volume in the furnace.

[0035] Preferably, the hardness of the aluminum alloy pressure casting is detected by a Rockwell hardness tester in step 3, so that a reasonable critical temperature is set. When the same processing furnace is loaded with parts of different thicknesses in step 3, the heating and holding time should be determined according to the maximum thickness. The parts to be pressure cast with a thickness difference of more than 10 mm should not be processed in the same furnace.

[0036] Preferably, the furnace door should not be opened arbitrarily during the power-on heating operation of the aluminum alloy pressure casting to be processed in step 4.

[0037] The application in use: first, the aluminum alloy profile is annealed by the treatment furnace, the workers according to the effective volume in the furnace, the aluminum alloy die casting parts to be processed are loaded in the furnace, the die casting parts must be handled with care when loading, to prevent the profile from being scratched and deformed, the workers check the parts and electric heating elements in the treatment furnace, to ensure that they have no contact with the aluminum alloy die casting parts, the aluminum alloy die casting pieces are allowed to have point and less line contact when stacking, to avoid surface contact, the stacking gap is not less than 10mm, the workers set the heating speed and holding time in the furnace according to the hardness of the aluminum alloy die casting parts to be detected, the workers turn on the power of the furnace body, so that the internal aluminum alloy die casting parts to be processed are heated, and the temperature is kept at a specified temperature, the workers pour poor heat-conducting medium into the furnace, so that the aluminum alloy profile is slowly cooled at an appropriate speed, and special care should be taken when the furnace is discharged after cooling, the aluminum alloy profile should be vertically hung in the furnace as much as possible, or a special heat treatment clamp, protective cover or frame tool can be designed to prevent deformation, after the annealing treatment is completed, the structure of the die casting mold is modified, the workers use the characteristics that the rebound directions of different parts of the bending piece are opposite, according to the rebound amount obtained by pre-estimation or test, when double-angle bending, the rebound angle of both sides of the bending punch is removed, and the single-face gap of the bending mold is kept equal to the thickness of the material, to make the aluminum alloy profile stick to the punch, after the mold is opened, the aluminum alloy profile rebounds vertically on both sides, the shape and size of the working part of the punch and the die are corrected, the rebound amount of the aluminum alloy die casting parts is compensated by the rebound in the opposite direction, the structure of the punch is changed, the correction force is concentrated in the die casting deformation area, the change degree of the stress and strain state of the aluminum alloy die casting deformation area is increased, the premise is that when the material thickness is 0.8mm or more, the plastic is better, and the bending radius is not large, the punch structure is changed, the springback amount is reduced, after the die casting is completed, the staff uses the shoulder of the die to press the end of the aluminum alloy die casting longitudinally, so that the deformation area is subjected to compressive stress on the cross section, and the springback trend of the aluminum alloy profile inside and outside is opposite when unloading, thereby reducing the springback force, and the bending size can be obtained by using this method, but the blank precision is required to be higher, the polyurethane concave die is used instead of the rigid metal concave die for processing, and the aluminum alloy profile gradually enters the polyurethane concave die with the punch during die casting, the bending force will change the stress and strain state of the material in the corner deformation area, and the correction bending is similar, so as to reduce the springback, after the overall processing is completed, the staff applies a large correction pressure to the die casting to change the stress and strain state of the deformation area, so as to control the springback amount, or the casting method is changed, the aluminum alloy profile is subjected to tangential drawing force during bending deformation through the drawing bending process, the drawing force should be applied to make the composite stress in the deformation area greater than the yield limit of the material, the compressive strain inside the neutral layer is converted into tensile strain, that is, the entire cross section of the aluminum alloy profile is in the range of plastic drawing deformation, and the springback trends of the inner and outer sides are offset to each other after unloading, thereby reducing the springback, the drawing bending of the large curvature radius bending piece is carried out on the drawing bending machine, and the sequence of bending deformation and drawing has a certain influence on the springback amount during drawing bending, and the bending first and then drawing is better than the drawing first and then bending, but the bending first and then drawing will increase the friction between the bent blank and the die, and the drawing force is difficult to be effectively transmitted to each part, therefore, the "drawing+bending+drawing" composite process method is adopted in actual production, for general small bending stamping parts, the straight edge part of the blank can be pressed to limit the flow of the material in the non-deformation area, or the gap between the punch and the concave die is reduced, so that the material in the deformation area is subjected to thin extrusion drawing, so as to increase the tensile strain in the deformation area.

[0038] Although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments, or make equivalent replacement to part of the technical features, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of controlling springback deformation of an aluminum alloy thin-walled die casting, characterized by, It comprises the following steps: Step 1, furnace loading: the workers load the aluminum alloy die castings to be processed into the furnace according to the effective volume in the furnace; Step 2, equipment inspection: the workers inspect the parts and electric heating elements in the processing furnace to ensure that they are not in contact with the aluminum alloy die castings; Step 3, parameter configuration: the workers set the heating speed and holding time in the furnace according to the hardness of the aluminum alloy die castings to be detected; Step 4, power-on heating: the workers turn on the power of the furnace body to heat the aluminum alloy die castings to be processed inside to the specified temperature for holding; Step 5, cooling treatment: the workers pour poor heat-conducting medium into the furnace to slowly cool the aluminum alloy profile at an appropriate speed; Step 6, compensation processing: the workers use the feature that the rebound directions of different parts of the bent piece are opposite, and correct the shape and size of the working part of the male and female dies according to the rebound amount obtained by pre-estimation or test, to compensate for the rebound amount of the aluminum alloy die castings in the opposite direction; Step 7, correction processing: change the structure of the male die to concentrate the correction force in the die casting deformation area, and increase the change degree of the stress and strain state of the deformation area of the aluminum alloy die castings; Step 8, longitudinal pressure: after the die casting is completed, the workers use the shoulder of the die to longitudinally press the end of the aluminum alloy die castings, so that the deformation area is subjected to compressive stress on the cross section, and the rebound trends of the inside and outside of the aluminum alloy profile are opposite when unloaded, thereby reducing the rebound force; Step 9, upgrading processing: use a polyurethane female die to replace a rigid metal female die for processing; Step 10, compensation correction: after processing, the workers apply a large correction pressure to the die castings to change the stress and strain state of the deformation area to control the rebound amount; Step 11, tensile casting: adopt the draw bending process, the aluminum alloy profile is subjected to tangential drawing force during bending deformation, the drawing force applied should make the combined stress in the deformation area greater than the yield limit of the material, the compressive strain inside the neutral layer is converted into tensile strain, that is, the entire cross section of the aluminum alloy profile is in the range of plastic drawing deformation, and the rebound trends of the inside and outside are offset to each other after unloading, thereby reducing the rebound.

2. The method of claim 1, wherein the aluminum alloy thin-walled die casting is a wheel. The effective volume of each profile loaded in the furnace in step 1 is less than half of the volume in the furnace.

3. The method of claim 1, wherein the aluminum alloy thin-walled die casting is a wheel. In step 3, the hardness of the aluminum alloy die castings is detected by a Rockwell hardness tester to set a reasonable critical temperature.

4. The method of claim 1, wherein the method is characterized by: In step 3, when different thickness parts are loaded in the same processing furnace, the heating and holding time should be determined according to the maximum thickness, and the aluminum alloy profiles with a thickness difference greater than 10 mm should not be processed in the same furnace.

5. The method of claim 1, wherein the method is characterized by: In step 4, the processing furnace should not be opened arbitrarily during the power-on heating operation of the aluminum alloy die castings to be processed.