High volume manufacturing method for forming high strength aluminum components

Abstract

The present disclosure relates generally to "high volume manufacturing methods for forming high strength aluminum components." The methods include obtaining a material blank made of a 7xxx series aluminum alloy, heating the blank to a solvus temperature of the material, and stamping and quenching the heated blank to form a plurality of components. During the quenching operation, the components are cooled to a second temperature that is less than the solvus temperature. The methods also include performing one or more structural modifications to the components within a set period of time that is less than or equal to 24 hours. The methods also include shelfing the components, wherein a gap is defined between two adjacent components; artificially aging the components with an industrial furnace; and pre-treating the components with a chemical solution.

Description

Technical Field

[0001] This disclosure relates to a method for mass production of stamped metal parts. Background Technology

[0002] The descriptions in this section are provided only as background information in relation to this disclosure and may not constitute prior art.

[0003] Various industries, such as the automotive and aerospace industries, are shifting from heavy materials such as steel to lighter materials, such as 5xxx and 6xxx series aluminum alloys, which can be formed or shaped using methods similar to those used for steel.

[0004] Aluminum alloys are typically identified using the International Alloy Nomenclature System, which assigns a four-digit number to each alloy. The first digit indicates the primary alloying element. If the second digit is not zero, it indicates a variation in the alloy, and the third and fourth digits identify a specific alloy within the series. For example, 5xxx series alloys are alloys with magnesium, and 6xxx series alloys are alloys with both magnesium and silicon.

[0005] 7xxx series aluminum alloys are cast with zinc and possess strength similar to high-strength and ultra-high-strength steels. However, compared to low-carbon steel or other types of aluminum alloys, 7xxx series alloys are not formable at room temperature, making them difficult to implement in mass production. The teachings of this disclosure address this and other problems. Summary of the Invention

[0006] This section provides a general overview of this disclosure and is not a full disclosure of the entire scope or all features of this disclosure.

[0007] In one form, this disclosure relates to a mass production method for forming high-strength aluminum components. The method includes obtaining a material blank and heating the blank to the material's melt temperature using a first industrial furnace. The method further includes stamping and quenching the heated blank to form a plurality of components, and cooling these components to a second temperature below the melt temperature. The method also includes performing one or more structural modifications on the plurality of components within a set time period following the stamping and quenching of the heated material blank. The set time period is set to be less than or equal to 24 hours. The method further includes racking the plurality of components, wherein a gap is defined between two adjacent components; artificially aging the plurality of components using a second industrial furnace; and pretreating the plurality of components with chemicals.

[0008] In another form, one or more structural modifications are made to multiple components at room temperature.

[0009] In another form, the method further includes performing low-temperature aging of the plurality of components prior to performing the one or more structural modifications.

[0010] In one form, the one or more structural modifications include at least one of trimming, perforating, and bending the plurality of components.

[0011] In another form, the method further includes using multiple machines positioned in series for the stamping and quenching of the heated material, and for the one or more structural modifications of the multiple components.

[0012] In another form, the one or more structural modifications are completed within 8 hours after the stamping and quenching of the material blank.

[0013] In one embodiment, the method also includes cleaning multiple components before artificially aging them.

[0014] In another form, heating the billet to the melting point also includes transferring the material billet to one or more furnaces.

[0015] In another form, the stamping and quenching, the execution of one or more structural modifications, and the placement of the plurality of parts are completed within 24 hours.

[0016] In one form, the material blank is made of 7xxx series aluminum alloy.

[0017] In one form, this disclosure relates to a mass production method for forming high-strength aluminum components. The method includes unpacking a batch of material blanks made of 7xxx series aluminum alloys, heating the material blanks to their melting point temperature, and stamping and quenching the heated material blanks to form multiple components. The components are then cooled to a second temperature below the melting point temperature. The method further includes performing one or more structural modifications on the multiple components within a set time period following the stamping and quenching of the heated material blanks, wherein the set time period is less than or equal to 24 hours. The method also includes cleaning the multiple components to remove foreign matter, artificially aging the multiple components in an industrial furnace, and pretreating the multiple components in a chemical solution.

[0018] In another form, the method also includes caching multiple components in a staging area prior to the artificial aging of multiple components.

[0019] In another form, the method also includes performing low-temperature aging of multiple components before implementing one or more structural modifications.

[0020] In one form, one or more structural modifications include at least one of trimming and perforating multiple components.

[0021] In another form, the one or more structural modifications are completed within 8 hours after the stamping and quenching of the material blank.

[0022] In another form, the method further includes: transferring at least one blank to a stamping press at a time via a first automated machine for stamping and quenching of the heated blank; transferring one part at a time from the stamping press to one or more part forming machines via a second automated machine to perform the one or more structural modifications; and placing the part according to the one or more structural modifications, wherein a gap is defined between two adjacent parts.

[0023] In one embodiment, the stamping and quenching, the execution of one or more structural modifications, and the placement of multiple components are completed within 24 hours.

[0024] In one form, this disclosure relates to a hot stamping method for mass production. The method includes obtaining a material blank made from 7xxx series aluminum molten metal; heating the blank to the melting point of the material; stamping and quenching the heated batch to form multiple parts; continuously forming multiple features on the parts over a maximum of 24 hours during the stamping and quenching process using multiple machines positioned in series; artificially aging the parts; and pretreating the parts with a chemical solution.

[0025] In another form, at least one feature is formed continuously within 8 hours after the material blank is stamped and quenched.

[0026] In another form, the method further includes placing the components in a fixing device after one or more structural modifications, wherein a gap is defined between two adjacent components.

[0027] Further applicability will become apparent from the description provided herein. It should be understood that the descriptions and specific examples are intended for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0028] To facilitate a good understanding of this disclosure, its various forms will now be described by way of example with reference to the accompanying drawings, in which:

[0029] Figure 1 Several stampings that can be formed from 7xxx series aluminum alloys according to the teachings of this disclosure are shown;

[0030] Figure 2 This is a flowchart of a mass production routine for forming high-strength aluminum parts from 7xxx series aluminum alloy blanks, based on the teachings of this disclosure.

[0031] Figure 3A and Figure 3B It is a graph of the expected tensile stress and yield stress of stamped and quenched parts according to the teachings of this disclosure; and

[0032] Figure 4 An exemplary mass production layout for forming high-strength aluminum parts is shown in accordance with the teachings of this disclosure.

[0033] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure in any way. Detailed Implementation

[0034] The following description is exemplary in nature only and is not intended to limit this disclosure, its application, or its use. It should be understood that throughout the accompanying drawings, corresponding reference numerals indicate similar or corresponding parts and features.

[0035] Reference Figure 1 This disclosure generally relates to a mass production method 100 that transforms a blank 102 made of 7xxx series aluminum alloys into high-strength aluminum components, such as hinge pillars 104A, side beam reinforcements 104B, B-pillar reinforcements 104C, or other suitable components. The mass production method includes solution heat treatment of the blank 102, stamping and a quenching process to rapidly reduce the temperature of the blank 102, and a series of structural modifications to form additional features on the component within a specific time period defined by the formability characteristics of the material. The method described herein outlines a value stream process for hot stamping 7xxx series aluminum alloys, which can be implemented in various manufacturing industries, such as the automotive and aerospace industries. This method can be implemented to form various components, such as B-pillars, rockers, hinge pillars, and components within assemblies such as seat frames requiring strength and load-bearing capacity.

[0036] Reference Figure 2An exemplary mass production routine 200 for forming parts from 7xxx series aluminum alloy blanks is provided. At 202, one or more blanks are taken from a stack of blanks, and at 204, the blanks undergo solution heat treatment. That is, in order to form stamps from 7xxx series aluminum alloys, the blanks undergo a heating process, such as solution heat treatment, before being stamped. For example, U.S. Patent No. 8,496,764 (which is incorporated herein by reference) outlines a system and method for forming blanks from manufactured (F-temper) 7xxx series aluminum alloys. The outlined method provides that a blank made of 7xxx series aluminum alloys is heated to a predetermined temperature, such as a solution temperature or solidus temperature, by a heating device (e.g., an industrial furnace). The solution temperature of 7xxx series aluminum alloys is approximately 460°C to 490°C, which is the temperature range that enhances the solute in solution (single phase). The solidus temperature is a specific temperature on a phase diagram curve below which the material is completely solid. At the solidus temperature, the heated material exists between a solid and a liquid phase, and is therefore solid to facilitate billet processing and can be formed due to its liquid or partially liquid properties. In one form of AA7075, solution heat treatment is a temperature range above the melt line temperature, between 460°C and 490°C, which heats the billet to a single-phase field but holds it below the solidus temperature, in this case 490°C, to prevent initial melting. Both the melt line and the solidus line are temperatures dependent on the chemical properties of the alloy. Typically, the melt line is a line on the phase diagram that separates the homogeneous solid state of the material from the lower-temperature unstable multiphase state.

[0037] After heating, routine 200 proceeds to 206, where the blank is transferred to the die set, or in other words, to a stamping press, which simultaneously stamps and quenches the heated blank to form a part. In one form, as described in U.S. Patent No. 8,496,764, the stamping press includes a holding device that positions the blank between and spaced apart from the dies, and inhibits conductive heat transfer between the blank and the dies. In one form, the stamping press is a standard hydraulic press. In another form, the stamping press is a servo-mechanical press with a servo-valve-controlled hydraulic cushion for quenching control. The slide of the servo-mechanical press is driven by an electric servo motor that provides dynamic and fine control over the speed and position of the master slide during its stroke. The master slide moves to the upper half of the die. The lower half of the die can be pushed upwards with a control force relative to the upper slide. This allows for control of the forming and quenching pressures. The servo-valve-controlled hydraulic cushion dynamically controls the hydraulic cushion force throughout the entire stamping stroke. This system dynamically controls the position and pressure of the hot stamping to optimize press cycle time and control quenching during the stroke. The billet is cooled to, for example, room temperature by the die of the stamping press. The press travel speed is between 200 mm / s and free fall to maximize the cooling rate, thereby ensuring the desired final strength and corrosion resistance characteristics of the part are achieved. For example, the billet can be cooled at a first quenching rate greater than or equal to 150 °C / s during its cooling from 400 °C to 290 °C, and then at a second quenching rate (e.g., 50 °C / s) during its cooling to its final temperature (e.g., 25 °C).

[0038] After stamping and quenching, routine 200 proceeds to 208, where one or more structural modifications are performed within a set time period. More specifically, the stamped part begins to age over time (i.e., natural aging), causing its yield strength and ultimate tensile strength to increase, and thus becoming less formable over time. For example, Figure 3A and Figure 3B The expected tensile and yield stresses of a 2 mm 7075 aluminum alloy sample after quenching are shown. The initial tensile and yield stresses of the sample show little or no change, and then begin to increase after approximately 100 minutes, indicating that the material becomes less formable. Therefore, when forming parts from 7xxx series aluminum, any subsequent structural modifications (where one or more features are formed on the part) will be completed within a set time period (i.e., the formability time period) defined by the formability properties of the material. For example, in one form, the set time period after stamping and quenching is less than or equal to 24 hours. In another form, the set time period after stamping and quenching is less than or equal to 8 hours.

[0039] In one form, subsequent structural modifications are performed at room temperature and include one or more cutting operations, such as trimming and perforation, and / or bending operations. For example, Figure 2 This includes trimming and / or piercing operations at 208A, and bending operations at 208B. Structural modifications can be performed using one or more machines arranged in series with the stamping press (e.g., die flanging, trimming tools, piercing tools, secondary molding, etc.) to minimize delays in part formation. Other suitable operations involving structural modifications to the part can also be implemented as part of the method for creating the part, provided the modifications are performed within a set time period.

[0040] In one form, after receiving further structural modifications at 208, each component is cleaned at 210 to remove foreign matter. For example, lubricant may be applied to the blank prior to the solution heat treatment operation, or lubricant may be applied to the stamping die at 204 and removed at 210. The component is then positioned, or in other words, rested at 212 with one or more other components, wherein a gap is defined between two adjacent components. More specifically, in one form, multiple components may be rested in a fixture (not shown) configured to provide a gap between two adjacent components to prevent components from nesting together. The fixture is also configured to hold the components in position such that it prevents the components from shifting during subsequent operations. In one form, the fixture may be a stainless steel SMF component support for optimal heat treatment response.

[0041] In cases where multiple components are arranged together, artificial aging is performed at 214 to increase the yield strength of the components, and a chemical pretreatment is performed at 216. In one form, the artificial aging is performed in an industrial furnace to obtain a high-strength state, such as T6 or T7x. For example, for the T6 state, the component is aged at 110°C for two hours and then aged at 165°C for another two hours. Further details regarding the artificial aging are provided in U.S. Publication Application 2015 / 0101718, which is incorporated herein by reference. Additionally, other artificial aging specifications / standards may be used, such as those provided by the American Society for Metals (ASM) and the U.S. Military Standards (MIL). In one form, the time interval between the stamping and quenching operation at 206 and the artificial aging at 214 is less than 24 hours. That is, the natural aging that occurs between these two operations is less than 24 hours.

[0042] In one form, for chemical pretreatment, the batch of components is immersed in a chemical solution provided in a tank. For example, the fixtures holding the components are immersed in the tank by a forklift to allow the components to be fully coated. Gaps provided between the components allow the chemical solution to flow between them to completely coat each component. Pretreatment may include titanium zirconium, allodine, or electrochemical treatments to provide a stable oxide conversion coating to promote the bond strength and durability of structural adhesives. Chemical pretreatment allows the components to receive and retain adhesives, coatings, or other chemicals as part of downstream assembly processes. After chemical pretreatment, the batch of components is transferred to a holding area at point 218.

[0043] Mass production routine 200 may include additional processing steps, and some steps may be performed in a different order. For example, before performing structural modifications at step 208, the stamped parts may undergo a low-temperature aging process for 20 to 60 minutes using a conveyor or roll furnace at, for example, 120°C. The low-temperature aging process is considered in relation to the set time period discussed above. In other words, if implemented, the low-temperature aging and structural modifications will be completed within the set time period (i.e., the formability time period). The routine may also include a step of caching or stacking parts between structural modifications and artificial aging. In another variation, parts may be placed before cleaning. In yet another variation, batch pretreatment is performed before artificial aging.

[0044] Reference Figure 4 This provides an example implementation of a high-volume manufacturing production line based on the teachings of this disclosure. Section 402 includes two stockpiles arranged in parallel and identified as 4041 and 4042. The stockpiles are depilated one after another by automated machines 4061 and 4062, respectively. In one form, automated machines 4061 and 4062 are robotic devices, each moving one stockpile at a time to section 408.

[0045] In one configuration, a solution heat treatment (SHT) operation is performed at section 408. Section 408 comprises two stacked convection furnaces 4101 and 4102, which are configured to heat multiple billets at once. For example, furnaces 4101 and 4102 include multiple shelves for holding multiple billets, and automated machines 4061 and 4062 transfer one billet at a time to each shelf of the respective furnace 4101 and 4102. Here, furnaces 4101 and 4102 perform solution heat treatment as discussed above.

[0046] As described above, after the solution heat treatment operation, the billet is transferred to section 412 for a stamping-quenching operation. Automated machines 4141 and 4142 transfer the heated billet from furnaces 4101 and 4102 to a stamping press 415, where the billet is stamped into parts and rapidly cooled to room temperature. Automated machine 416 transfers the parts from the stamping press 415 to section 418 for a cryogenic aging operation performed by a conveyor furnace 420. In another embodiment, the cryogenic aging operation can be omitted, and the parts can proceed directly to sections 422 or 424 for additional processing.

[0047] Section 422 is a holding area for accumulating or buffering parts before they enter a series of forming operations in section 424. Although not shown, another automated machine can be used to move the parts from the cryogenic aging operation to the holding area. In another form, parts from the cryogenic aging operation can bypass the holding area and be transferred directly to the series of forming operations in section 424.

[0048] Part 424 includes a plurality of machines 4261 and 4262 arranged in series with each other, and a stamping press 414 for performing one or more structural modifications on the part. Machines 4261 and 4262 may include any suitable cutting and / or bending machines for performing one or more structural modifications as described above. In one form, automated machine 428 transfers the part from one machine to another.

[0049] With structural modifications, the components are cleaned by the washer 432 in section 430 and then placed in section 434 by the automated machine 436. Although not shown, an additional automated machine can be used to transfer the components from machine 4262 to the washer 432 and from the washer 432 to section 434 for placement. Alternatively, the components can be placed manually.

[0050] After a batch of components is placed in section 434, it is transferred to section 437 for an artificial aging operation performed by a conveyor furnace 438. In one embodiment, the batch of components is transferred via an operator-operated elevator. In another embodiment, the batch of components is transferred by an automated machine. The batch of components is then transferred from the conveyor furnace 438 to section 440 for chemical pretreatment. For example, using an elevator, the batch of components is placed in a tank 442 filled with a chemical solution. After chemical pretreatment, the batch of components is removed from tank 442 and placed in a holding area (not shown).

[0051] Figure 4The manufacturing layout described herein is merely one example implementation of the mass production method of this disclosure. The layout can be constructed in other suitable ways for implementation. For example, instead of two stockpiles in section 402, one stockpile may be sufficient based on the time allocated for solution heat treatment, stamping-quenching operations, and structural modifications. Other suitable variations are also within the scope of this disclosure.

[0052] This disclosure describes a mass production method / routine for forming high-strength aluminum parts using 7xxx series aluminum alloys. The method minimizes the delay between stamping and heat treatment of the parts, ensuring that the natural aging of the parts after quenching does not exceed 24 hours. The method also includes room temperature forming following quenching (i.e., structural modification) within 8 hours of quenching, cleaning, and chemical pretreatment. Therefore, this disclosure outlines a method for forming high-strength aluminum parts using 7xxx series aluminum.

[0053] The description in this disclosure is exemplary in nature only, and therefore, any modifications intended without departing from the spirit and scope of this disclosure are intended to fall within its scope. Such modifications should not be considered as departing from the spirit and scope of this disclosure.

[0054] According to the present invention, a method for mass production of high-strength aluminum components includes: obtaining a material blank; heating the blank to the melting point temperature of the material using a first industrial furnace; stamping and quenching the heated blank to form a plurality of components, wherein the components are cooled to a second temperature below the melting point temperature; performing one or more structural modifications on the plurality of components within a set time period following the stamping and quenching of the heated material blank, wherein the set time period is set to be less than or equal to 24 hours; placing the plurality of components, wherein a gap is defined between two adjacent components; artificially aging the plurality of components using a second industrial furnace; and pretreating the plurality of components with a chemical solution.

[0055] According to one embodiment, one or more structural modifications are performed on the plurality of components at room temperature.

[0056] According to one embodiment, the invention is further characterized by performing low-temperature aging of the plurality of components before implementing the one or more structural modifications.

[0057] According to one embodiment, the one or more structural modifications include at least one of trimming, perforating, and bending the plurality of components.

[0058] According to one embodiment, the invention is further characterized by using a plurality of machines positioned in series for the stamping and quenching of the heated material, and for the one or more structural modifications of the plurality of components.

[0059] According to one embodiment, the one or more structural modifications are completed within 8 hours after the stamping and quenching of the material blank.

[0060] According to one embodiment, the invention is further characterized by cleaning the plurality of components before artificially aging them.

[0061] According to one embodiment, heating the billet to the melting point temperature also includes transferring the material billet to one or more furnaces.

[0062] According to one embodiment, the stamping and quenching, the implementation of one or more structural modifications, and the placement of the plurality of components are completed within 24 hours.

[0063] According to one embodiment, the material blank is made of 7xxx series aluminum alloy.

[0064] According to the present invention, a method for mass production of high-strength aluminum components includes: unpacking a batch of material blanks, wherein the material blanks are made of 7xxx series aluminum alloys; heating the material blanks to their melting point temperature; stamping and quenching the heated material blanks to form a plurality of components, wherein the components are cooled to a second temperature below the melting point temperature; performing one or more structural modifications on the plurality of components within a set time period following the stamping and quenching of the heated material blanks, wherein the set time period is less than or equal to 24 hours; cleaning the plurality of components to remove foreign matter; artificially aging the plurality of components in an industrial furnace; and pretreating the plurality of components with a chemical solution.

[0065] According to one embodiment, the invention is further characterized by caching the plurality of components in a temporary storage area prior to the artificial aging of the plurality of components.

[0066] According to one embodiment, the invention is further characterized by performing low-temperature aging of the plurality of components before implementing the one or more structural modifications.

[0067] According to one embodiment, the one or more structural modifications include at least one of trimming and perforating the plurality of components.

[0068] According to one embodiment, the one or more structural modifications are completed within 8 hours after the stamping and quenching of the material blank.

[0069] According to one embodiment, the invention is further characterized by: transferring a blank to a stamping press at one time via a first automated machine for stamping and quenching of the heated blank; transferring a part from the stamping press to one or more part forming machines in succession via a second automated machine to perform the one or more structural modifications; and placing the part according to the one or more structural modifications, wherein a gap is defined between two adjacent parts.

[0070] According to one embodiment, the stamping and quenching, the implementation of one or more structural modifications, and the placement of the plurality of components are completed within 24 hours.

[0071] According to the present invention, a hot stamping method for mass production includes: obtaining a material blank made of 7xxx series aluminum solution; heating the blank to the melting point temperature of the material; stamping and quenching the heated batch to form multiple parts; continuously forming multiple features on the parts by means of multiple machines positioned in series for a maximum of 24 hours during the stamping and quenching; artificially aging the parts; and pretreating the parts with a chemical solution.

[0072] According to one embodiment, at least one feature is formed continuously within 8 hours after the material blank is stamped and quenched.

[0073] According to one embodiment, the invention is further characterized in that, after one or more structural modifications, the components are placed in a fixing device, wherein a gap is defined between two adjacent components.

Claims

1. A method for mass production of high-strength aluminum components, the method comprising: Obtain material blanks; The billet is heated to the melting point of the material using a first industrial furnace; The heated blank is stamped and quenched to form multiple parts, wherein the multiple parts are cooled to a second temperature below the melt line temperature; The components are aged at low temperature in a conveyor furnace or a rotary furnace; One or more structural modifications are performed on the plurality of components after low-temperature aging within a set time period following the stamping and quenching of the heated material blank, wherein the set time period is set to be less than or equal to 24 hours. The plurality of components with the modified placement structure, wherein a gap is defined between two adjacent components; The aforementioned components were artificially aged and placed in a second industrial furnace; as well as The artificially aged components are pretreated with a chemical solution.

2. The method of claim 1, wherein the one or more structural modifications to the plurality of components are performed at room temperature.

3. The method of claim 1, further comprising cleaning the plurality of components prior to the artificial aging of the plurality of components.

4. The method of claim 1, wherein heating the billet to the melting point further comprises transferring the material billet to one or more furnaces.

5. The method of claim 1, wherein the low-temperature aging process is performed for 20 to 60 minutes.

6. The method of claim 1, further comprising caching the plurality of components in a temporary storage area prior to the artificial aging of the plurality of components.

7. The method of claim 1, wherein the one or more structural modifications include at least one of trimming, perforating, and bending the plurality of components.

8. The method of claim 1, further comprising using a plurality of machines positioned in series for the stamping and quenching of the heated blank, and for the one or more structural modifications of the plurality of components.

9. The method of claim 1, further comprising: A first automated machine transfers one billet at a time to a stamping press for stamping and quenching of the heated billet; as well as A second automated machine continuously transfers one part at a time from the stamping press to one or more part forming machines to perform the one or more structural modifications.

10. The method of claim 1, wherein performing one or more structural modifications further comprises forming a plurality of features on the part by means of a plurality of machines positioned in series, during a maximum of 24 hours of stamping and quenching.

11. The method according to any one of claims 1 to 10, wherein the material blank is made of 7xxx series aluminum alloy.

12. The method of any one of claims 1 to 10, wherein the one or more structural modifications are completed within 8 hours after the stamping and quenching of the material blank.

13. The method of claim 12, wherein the material blank is made of 7xxx series aluminum alloy.

14. The method of any one of claims 1 to 10, wherein the stamping and quenching, the execution of one or more structural modifications, and the placement of the plurality of parts are completed within 24 hours.

15. The method of claim 14, wherein the material blank is made of 7xxx series aluminum alloy.

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