Interim temper process

A method for forming a structure using an interim temper process is provided. A metal material is partially-aged to a stable temper that does not require cold storage. The partially-aging step is completed at a supplier facility prior to the metal material being received by the manufacturer. Once received by the manufacturer, the partially-aged metal material is heated to a first temperature to perform retrogression. A structure is formed from the partially-aged metal material after performing the retrogression. The structure is shaped and inspected. The structure is then heated to a second temperature in an age oven to reach its final aged state. The final aged state may be close to, meet, or exceed a T6 temper.

BACKGROUND INFORMATION

Field

The present disclosure relates generally to manufacturing metal structures. More specifically, the present disclosure relates to an interim temper process for partially aging and subsequently roll forming metal structures for aircraft applications.

Background

Although manufacturers have increasingly turned to composite materials for use in aircraft and automotive applications, metal structures are still viable options to provide structural support for these platforms. Manufacturers may use roll forming techniques to fabricate such metal structures.

Prior to roll forming, metal materials are subjected to a number of different manufacturing processes. These processes alter the properties of the metal material to make it more desirable for roll forming. Numerous processing steps require manpower, resources, equipment, time and floor space that often reduce the efficiency and increase the cost of the overall fabrication process more than desired.

Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above, as well as other possible issues.

SUMMARY

An illustrative embodiment of the present disclosure provides a method for forming a structure. A partially-aged metal material is heated to a first temperature to perform retrogression. A structure is roll formed from the partially-aged metal material after performing the retrogression. The partially-aged metal material is not placed in cold storage before roll forming. All partially-aging is done off-site. The structure is heated to a second temperature to reach a final aged state. The final aged state may meet or exceed a T6 temper.

Another illustrative embodiment of the present disclosure provides a method for forming a structure for an aircraft. A metal material, such as 7000 series aluminum, is solution heat-treated. The metal material is then partially-aged either by heating it to a temperature of 170-190 degrees Fahrenheit for approximately four hours or less or naturally aging the metal material for up to 40 hours. The partially-aged metal material is not stored in a freezer. Instead, it remains exposed to room temperature. The partially-aged metal material is heated to a temperature between 350- and 410-degrees Fahrenheit to perform retrogression. The structure is roll formed from the partially-aged metal material after performing the retrogression. The structure is heated to reach a final aged state. The structure may be heated for approximately eighteen hours at a temperature of 250-degrees Fahrenheit.

A further illustrative embodiment of the present disclosure provides a manufacturing system comprising a heating system, a roll forming system, and an age oven. The heating system is configured to heat a partially-aged metal material to a first temperature to perform retrogression. The roll forming system is configured to roll form a structure from the partially-aged metal material after performing the retrogression. The partially-aged metal material is not placed in cold storage before roll forming. The aging oven is configured to heat the structure to a second temperature to reach a final aged state for the structure.

DETAILED DESCRIPTION

The illustrative embodiments recognize and take into account one or more different considerations. For example, the illustrative embodiments recognize and take into account that the manufacturing process for roll forming aluminum stringers is often more expensive and time consuming than desired. Prior to roll forming, metal material in its annealed condition is corrugated, solution heat-treated, quenched, and held in a freezer. Current solutions employ an on-site solution heat-treating and cold storage process that requires holding freshly quenched material in freezers at −10 degrees Fahrenheit before forming the stringer. Cold storage slows the natural aging process of the metal, aging that would occur if it was stored at room temperature. Therefore, it is important to limit the time the metal material is exposed to room temperature before the roll forming process starts to maintain a desired strength level that still allows formability.

Additionally, the solution heat-treating, quenching, and freezing steps make the entire process take longer and cost more than desired. Having a simpler process would save in manpower and storage costs.

Thus, the disclosed embodiments relate to a method for forming a structure. A metal material is partially-aged to a stable temper that does not require cold storage. Ideally, the metal is partially-aged offsite by a supplier. Once at the manufacturing facility, the partially-aged metal material is heated to a first temperature to perform retrogression. A structure is formed from the partially-aged metal material after performing the retrogression. The structure is shaped and inspected as usual. The structure is then heated to a second temperature in an age oven to reach its final aged state. The final aged state may be close to a T6 temper. Using the method described herein, the final aging step may be completed in less time than with currently used processes.

With reference now to the figures and, in particular, with reference toFIG.1, an illustration of an aircraft is depicted in accordance with an illustrative embodiment. In this illustrative example, aircraft100has wing102and wing104attached to fuselage106.

Turning now toFIG.2, an illustration of a block diagram of a manufacturing environment is depicted in accordance with an illustrative embodiment. Manufacturing environment200is an environment where components within manufacturing system202may be used to form structure204.

Structure204is a structure made from metal material206and configured for use in platform208. Metal material206may comprise at least one of an aluminum, an aluminum alloy, or some other suitable type of material. Specifically, metal material206may be a 7000-series aluminum alloy such as, for example, without limitation, 7075 aluminum alloy. Metal material206is in its annealed condition in this illustrative example.

For example, “at least one of item A, item B, or item C” may include, without limitation, item A, item A and item B, or item B. This example also may include item A, item B, and item C, or item B and item C. Of course, any combination of these items may be present. In other examples, “at least one of” may be, for example, without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or other suitable combinations.

Platform208may be, for example, without limitation, a mobile platform, a stationary platform, a land-based structure, an aquatic-based structure, or a space-based structure. More specifically, platform208may be an aircraft, a surface ship, a tank, a personnel carrier, a train, a spacecraft, a space station, a satellite, a submarine, an automobile, a power plant, a bridge, a dam, a house, a manufacturing facility, a building, and other suitable platforms.

Platform208takes the form of aircraft210in this illustrative example. When structure204is manufactured for aircraft210, structure204may be, for example, without limitation, a fuselage stringer, a frame, a skin panel, a skin doubler, or some other suitable structure configured for use in aircraft210. In this illustrative example, structure204takes the form of stringer212. Stringer212is a fuselage stringer in this illustrative example. One of stringers122shown inFIG.1may be a physical implementation for stringer212.

Metal material206goes through a partial-aging process prior to being formed into structure204. In this depicted example, the partial-aging process occurs at supplier facility213. However, the partial-aging process also may be completed at the manufacturing facility in some illustrative examples.

In some illustrative examples, partial-aging includes natural aging processes. For instance, metal material206may be solution heat-treated and then allowed to naturally age at room temperature to reach a desired Rockwell hardness.

Partial-aging system214comprises a number of components configured to solution heat treat and age metal material206to form partially-aged metal material216. As used herein, “a number of” when used with reference to items means one or more items. Thus, a number of components is one or more components.

Partial-aging system214ages metal material206to interim temper218in various ways. For example, without limitation, metal material206may be solution heat treated and aged by exposure to temperatures between 170- and 190-degrees Fahrenheit. Exposure to such temperatures may be for less than four hours. Preferably, metal material206may be exposed to such temperatures for two to four hours. Of course, other temperatures and time intervals may be implemented. For instance, metal material206may be exposed to 170-degrees Fahrenheit for up to 24 hours or more, depending on the particular implementation. This aging process may be referred to as an “interim aging process” or “interim temper aging” or “pre-aging” throughout this disclosure.

Interim temper218is a stable temper at which partially-aged material216can be stored at room temperature without substantially affecting the formability of partially-aged material216, therefore eliminating the need for cold storage220. As an example, interim temper218is lower than T6 temper222of structure204in final aged state224of structure204. Interim temper218develops a yield strength that is intermediate between as-quenched (prior art) and fully aged conditions.

In other illustrative examples, metal material206is not partially-aged through heating. Instead, metal material206is naturally aged at room temperature. Natural aging can occur for approximately four to twenty-four hours or more. In some illustrative examples, metal material206is naturally aged for up to forty hours or more. In other words, in the case of natural aging, metal material206is exposed to a temperature of 170- and 190-degrees Fahrenheit for zero hours.

As depicted, partially-aged metal material216has properties226. Properties226may comprise at least one of Rockwell hardness, ultimate tensile strength, elongation, tensile yield stress, and other desirable properties to ensure that partially-aged metal material216can be roll formed into structure204without failure.

For example, without limitation, after the interim aging process, partially-aged metal material216comprises a yield stress between 32 and 50 ksi and an elongation value of between 20 and 25 ksi. Preferably, partially-aged metal material216has a yield stress of between 45 and 49 ksi prior to retrogression.

Partially-aged metal material216also may have a difference in value of ultimate tensile strength (UTS) and tensile yield strength (TYS), i.e, UTS-TYS, of 25 to 30 ksi. Properties226differ based on how long metal material206is partially-aged. The values disclosed herein for yield stress, UTS-TYS ratio, and other properties226are just examples of some desirable ranges.

Once partially-aged metal material216is formed, it is transported to a manufacturing facility that will fabricate structure204using manufacturing system202. Partially-aged metal material216is never placed in cold storage220.

As depicted, manufacturing system202comprises heating system228, roll forming system230, inspection system232, age oven234, monitoring system236, and controller238. Manufacturing system202may comprises a number of additional components as well, depending on the particular implementation.

In this illustrative example, heating system228performs retrogression240on partially-aged metal material216when received from supplier facility213. Specifically, heating system228is configured to heat partially-aged metal material216to first temperature242to perform retrogression240. For example, without limitation, heating system228may include a hot plate, a thermal heater, a conduction heating device, or some other suitable device.

First temperature242is selected such that partially-aged metal material216has forming properties244after retrogression240. First temperature242may be approximately 400 degrees Fahrenheit in this illustrative example. Partially-aged metal material216may be exposed to first temperature242for any amount of time less than five minutes, depending on the exact aged state of interim temper218. For example, without limitation, partially-aged metal material216may be exposed to first temperature242(400 degrees Fahrenheit) for a few seconds to five minutes. Retrogression240may be achieved almost instantaneously in some illustrative examples. Other temperatures and time periods also may be used, depending on the particular implementation. For example, partially-aged metal material216may reach desired parameters after a matter of seconds exposed to 300-degrees, 330-degrees, 340-degrees Fahrenheit, or some other temperature.

In this illustrative example, forming properties244are selected to optimize formability of partially-aged metal material216. Forming properties244may comprise at least one of Rockwell hardness, ultimate tensile strength, elongation, tensile yield stress, and other desirable properties. In this depicted example, it is desirable for partially-aged metal material216to comprise a yield stress between 32 and 45 ksi after retrogression240. Preferably, partially-aged metal material216comprises a yield stress of between 40 and 42 ksi after retrogression240, compared to approximately 32 ksi with freshly quenched metal material. In this manner, retrogression240decreases yield stress.

As another example, it may be desirable for partially-aged metal material216to comprise a UTS-YTS of between 25 and 30 ksi after retrogression240. Retrogression240is utilized such that forming properties244of partially-aged metal material216are as close to the as-quenched condition as possible, or, in some cases, more optimal than the as-quenched condition.

Various aging techniques influence the Rockwell hardness of partially-aged metal material216as compared to as-quenched material (prior art). As-quenched material may have a Rockwell hardness of approximately 40 HRB immediately after quenching. If partially-aged material216is naturally aged, it may have a Rockwell hardness of approximately 53 HRB after four hours and approximately 65 HRB after twenty-four hours. Using partial-aging system214, partially-aged metal material216may have a Rockwell hardness of approximately 71 HRB after one-hour exposure to 170-degrees Fahrenheit and approximately 75 HRB after two-hour exposure to 170-degrees Fahrenheit. Retrogression240decreases Rockwell hardness to a value ideal for roll forming.

After retrogression, partially-aged metal material216is roll formed into structure204using roll forming system230. Roll forming system230may comprises a number of components configured to shape, cut, trim, contour, or otherwise fabricate structure204from partially-aged metal material216.

Inspection system232is configured to inspect structure204after roll forming and before being placed in age oven234. Inspection system232may comprise mechanical, electrical, computer-controlled or human components.

After inspection, structure204is placed in age oven234. Age oven234comprises heating components configured to heat structure204to second temperature246for a period of time to reach final aged state224for structure204.

In this illustrative example, second temperature246may be a temperature between 200- and 300-degrees Fahrenheit. Because the material used for structure204has been partially-aged as described herein, final aging time can be reduced. For example, without limitation, age oven234may be configured to heat structure204at 250-degrees Fahrenheit for 18 hours, as opposed to 23 hours as with currently used systems, to reach final age state224. Final age state224may be close to, meet, or exceed the properties for T6 temper222.

In some illustrative examples, monitoring system236is associated with heating system228. Monitoring system236comprises a number of components and sensors which monitor state of aging248of partially-aged metal material216. Information from monitoring system236is transmitted to controller238. Controller238is configured to determine cycle time250for retrogression240based on state of aging248of partially-aged metal material216to optimize the parameters for forming properties244. Controller238may be part of an integrated controller that controls other processes in manufacturing system202or may be a separate component. In some illustrative examples, monitoring system236is absent.

With an illustrative embodiment, manufacturing structure204using partially-aged metal material216may take less time than with traditional techniques. Because metal material206is interim aged at supplier facility213, manufacturers must complete fewer steps to form structure204, and cold storage220is eliminated.

FIG.3AandFIG.3Bhighlight the differences between currently used techniques and the method described inFIG.2.FIG.3Ais an illustration of a flowchart of a roll forming process in accordance with the prior art, whileFIG.3Bis an illustration of a flowchart of a roll forming process in accordance with an illustrative embodiment.

InFIG.3A, material is received from the supplier in the annealed state. The material is taper milled (operation300) before being corrugated, heat treated, quenched, and held in a freezer (operations302-308). Only when fabrication is about to take place does the manufacturer pull the material out of the freezer and complete the roll forming process (operation310). Once the structure is formed, it may go through a variety of additional processes such as cutting, flange trimming, hole making, joggling, and contouring (operations312-320) before being inspected (operation322), and loaded on racks which are delivered to the age oven (operation324). The structure is then aged to its final state (operation326). Typically, the final aging process takes twenty hours or more.

InFIG.3B, material is received in the partially-aged condition, thus eliminating the need for operations302-308. All other operations are performed in the same manner as inFIG.3Aexcept for final aging (operation326). When the partially-aging process is completed using the solution heat treating method, the length of final aging is reduced. When the partially-aging process is done using natural aging at room temperature, the final aging process may not be reduced; however, the elimination of operations302-308improves cycle time and allows structure204to be fabricated much more quickly than before. In addition, the processes described herein contemplate a final aged state that is close to or exceeds a T6 temper, which produces substantially the same result as with the quenching process.

Turning now toFIG.4, an illustration of a graph showing various properties of a partially-aged metal material is depicted in accordance with an illustrative embodiment.FIG.4shows the properties of 7075 aluminum alloy after different processes have been performed.FIG.4illustrates a side-by-side comparison of data taken in the as-quenched condition, after partially-aging, and after retrogression as described with reference toFIG.2. Properties400include yield stress402, elongation404, and UTS-TYS406. UTS-TYS406represents the difference in ultimate tensile strength and tensile yield stress.

With reference next toFIG.5, an illustration of a graph showing various properties of a partially-aged metal material is depicted in accordance with an illustrative embodiment.FIG.5shows properties of 7075 aluminum alloy after different processes have been performed.FIG.5also illustrates a side-by-side comparison of data taken in the as-quenched condition, after partially-aging, and after retrogression as described with reference toFIG.2. InFIG.5, properties400are shown after 7075 aluminum has been partially-aged at approximately 170-degrees Fahrenheit for four hours.

Turning next toFIG.6, an illustration of a flowchart of a process for roll forming a structure is depicted in accordance with an illustrative embodiment. The method depicted inFIG.6may be used to form structure204using manufacturing system202shown inFIG.2.

The process begins by receiving a partially-aged metal material from a supplier (operation600). Next, the partially-aged metal material is taper milled (operation602). The process then heats the partially-aged metal material to a first temperature to perform retrogression on the material (operation604).

Next, a structure is roll formed from the partially-aged and retrogressed metal material (operation606). The structure is then heated to a second temperature to reach a final aged state (operation608), with the process terminating thereafter. After reaching the final aged state at the desired temper, the structure is air cooled.

FIG.7illustrates another flowchart of a process for roll forming a structure in accordance with an illustrative embodiment. The method depicted inFIG.7may be used to form structure204with manufacturing system202shown inFIG.2. This method provides an alternative embodiment wherein the interim aging step is completed at the manufacturing facility.

The process begins by solution heat treating a metal material (operation700). A partially-aged material is formed by naturally aging the solution treated material (operation702). The partially-aged metal material is taper milled without being placed in cold storage (operation704). The process then performs retrogression on the partially-aged metal material (operation706).

Next, a structure is roll formed from the partially-aged and retrogressed metal material (operation708). The structure is then heated to a second temperature to reach a final aged state (operation710), with the process terminating thereafter.

With reference next toFIG.8, an illustration of a flowchart of a process for monitoring retrogression of a partially-aged metal material is depicted in accordance with an illustrative embodiment. The method depicted inFIG.8may be used to monitor state of aging248of partially-aged metal material216during retrogression240shown inFIG.2. The process may be implemented during operation604inFIG.6or operation706inFIG.7.

The process begins by collecting information about a state of aging of the material (operation800). This information may include properties, temperature, precipitate state, or other desired information.

The information is sent to a controller (operation802), where it is compared to a desired state of aging for the material (operation804). A determination is made as to whether the current state of aging matches the desired state of aging (operation806). If the current state of aging matches the desired state of aging, retrogression is terminated (operation808), thus terminating the process. If the current state of aging does not match the desired state of aging, the process returns to operation800. In this manner, manufacturing system202with monitoring system236and controller238can give real time feedback to manipulate cycle time250for retrogression240inFIG.2.

Illustrative embodiments of the disclosure may be described in the context of aircraft manufacturing and service method900as shown inFIG.9and aircraft1000as shown inFIG.10. Turning first toFIG.9, an illustration of a block diagram of an aircraft manufacturing and service method is depicted in accordance with an illustrative embodiment. During pre-production, aircraft manufacturing and service method900may include specification and design902of aircraft1000inFIG.10and material procurement904.

During production, component and subassembly manufacturing906and system integration908of aircraft1000inFIG.10takes place. Thereafter, aircraft1000inFIG.10may go through certification and delivery910in order to be placed in service912. While in service912by a customer, aircraft1000inFIG.10is scheduled for routine maintenance and service914, which may include modification, reconfiguration, refurbishment, and other maintenance or service.

Manufacturing system202fromFIG.2and the components within manufacturing system202may be used to fabricate structure204from partially-aged metal material216during component and subassembly manufacturing906, after partially-aged metal material216is received from supplier facility213. In addition, manufacturing system202may be used for parts made for routine maintenance and service914as part of a modification, reconfiguration, or refurbishment of aircraft1000inFIG.10.

With reference now toFIG.10, an illustration of a block diagram of an aircraft is depicted in which an illustrative embodiment may be implemented. In this example, aircraft1000is produced by aircraft manufacturing and service method900inFIG.9and may include airframe1002with plurality of systems1004and interior1006. Examples of systems1004include one or more of propulsion system1008, electrical system1010, hydraulic system1012, and environmental system1014. Any number of other systems may be included. Although an aerospace example is shown, different illustrative embodiments may be applied to other industries, such as the automotive industry.

Apparatuses and methods embodied herein may be employed during at least one of the stages of aircraft manufacturing and service method900inFIG.9. In one illustrative example, components or subassemblies produced in component and subassembly manufacturing906inFIG.9may be fabricated or manufactured in a manner similar to components or subassemblies produced while aircraft1000is in service912inFIG.9. As yet another example, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during production stages, such as component and subassembly manufacturing906and system integration908inFIG.9. One or more apparatus embodiments, method embodiments, or a combination thereof may be utilized while aircraft1000is in service912, during maintenance and service914inFIG.9, or both. The use of a number of the different illustrative embodiments may substantially expedite the assembly of aircraft1000, reduce the cost of aircraft1000, or both expedite the assembly of aircraft1000and reduce the cost of aircraft1000.

The illustrative embodiments decrease fabrication times for structures used in aircraft and automotive applications. The reduction in manpower and equipment, as well as the elimination of processing steps, promotes efficiency and saves money for manufacturers. With the use of an illustrative embodiment, no cold storage is needed. Final aging cycle time is reduced in some cases, thus making it faster and easier to produce structural components for aircraft.