EP4151756A1

EP4151756A1 - Method of manufacturing an areal component of an age-hardenable aluminium alloy, corresponding process line and areal component

Info

Publication number: EP4151756A1
Application number: EP21197222.9A
Authority: EP
Inventors: Thorbjoern Hoeiland
Original assignee: Raufoss Development AS
Current assignee: Raufoss Development AS
Priority date: 2021-09-16
Filing date: 2021-09-16
Publication date: 2023-03-22

Abstract

The invention relates to a method of manufacturing an areal component made of one piece from an areal semi-finished part of an age-hardenable aluminium alloy, the method comprising an age-hardening treatment wherein the alloy is, subsequent to a solution heat treatment of the semi-finished part, cooled down in a quenching process to a first temperature allowing cold-working and a natural and/or artificial aging of the age-hardening treatment is performed after optional cold-working steps, wherein a warm sheet-forming process of the semi-finished part is inserted amid the quenching process, splitting the quenching process in at least two quenching regions, one above a second temperature at which the warm sheet-forming process begins and another one above the first temperature, the second temperature being not higher than the maximum of 320°C and 85% of the recrystallization temperature of the alloy and not lower than the minimum of 120°C and 30% of the recrystallization temperature.

Description

The invention relates to a method of manufacturing an areal component made of one piece from an areal semi-finished part of an age-hardenable aluminium alloy, the method comprising an age-hardening treatment wherein the alloy is, subsequent to a solution heat treatment of the semi-finished part, cooled down in a quenching process to a first temperature allowing cold-working and a natural and/or artificial aging of the age-hardening treatment is performed after optional cold-working steps, as well as a corresponding process line to perform a method and components manufactured by said method.
Such methods are well known in the art, f.i. from the manufacturing of components for the automotive industry where light-weight parts but still with sufficient strength are desired. The condition of light-weight materials is met by using an aluminium alloy having lower weight as compared to components made of steel, while the condition of higher strength is realized by age-hardening.
Important for the age-hardening treatment is that, inbetween natural and/or artificial aging and the previous solution heat treatment of the age-hardening treatment, a cooling process is performed sufficiently rapidly to allow the increase of mechanical properties as strength in the age-hardening treatment by the subsequent aging process. To this end, the skilled person may use continuous cooling precipitation (CCP) diagrams for the respectively selected alloy, giving information about linear cooling conditions for the quenching from solution heat treatment temperature down to about room temperature.
While WO 01/32979 A1 discloses the production of a control arm for use in the wheel suspension of a car of high-strength aluminium and produced by a cold forming process, WO 2016/009185 discloses a technique named HFQ utilizing solution heat treatment, hot-forming and cold-dye quenching, that is a technique in which quenching is made in the forming tool of the hot-forming process hot-forming the part right after solution heat treatment. Thereto, heat loss from the blank should be minimized by transferring the blank intermediately to the press of the hot-forming process. In particular, WO 2016/009185 uses different speeds for the closing of the press dyes. Then, the press is maintained in the closed position and the formed component is quenched, and natural aging is performed once the component is sufficiently cooled and removed from the press, optionally followed by artificial aging. Such process HFQ has found broad acceptance in the field of aluminium components manufacturing.
It is an object of the present invention to further improve a method as initially introduced, in particular in terms of higher flexibility regarding process and equipment.
This object is solved by the invention by a further development of a method as initially introduced, which is essentially characterized in that a warm sheet-forming process of the semi-finished part is inserted amid the quenching process, splitting the quenching process in at least two quenching regions, one above a second temperature at which the warm sheet-forming process begins and another one below said second temperature and above the first temperature, the second temperature being not higher than the maximum of 320°C and 85% of the recrystallization temperature of the alloy and not lower than the minimum of 120°C and 30% of the recrystallization temperature.
That is, the invention completely leaves the conventional view of a continuous quenching process by typical continuous linear cooling in accordance with typical cooling curves of continuous cooling precipitation (CCP) diagrams and the insertion splits the quenching process in two quenching regions, due to performing a warm sheet-forming process with a forming tool. Said forming tool could be held at or close to the second temperature, however in other preferred embodiments, the forming tool is temperature controlled by temperature control to a temperature not higher than the second and above the first temperature, for instance within the interval 90°C to 200°C. In particular for high speed production, the lower value for said interval may be lower, such as 80°C, 70°C, 60°C, 50°C, 40°C or even room temperature. The upper limit might reach up to the second temperature.
Although additional cold-working steps, in particular cold-forming steps may be additionally performed (at a lower first temperature allowing cold-working), preferably the major part of the forming in terms of material flow is done within the warm-forming process beginning at the second temperature. That is, said forming process beginning at second temperature is a warm-forming process where the formed semi-finished part reaches the forming temperature after having been subject to only the partly quenching process in the one (first) quenching region, that is after having been subject to a temperature difference (gradient) of easily 100°K or more, or even 140°K or more or 180°K or more.
It is, thus, a warm-working inserted amid the quenching process and performed above the temperature range of cold-working, but quite below the temperature range of hot-forming as taught by the WO 2016/009185 .
The warm-forming process performed as sheet-forming process does not intend to means or to require (flat) sheets of uniform thickness as starting material (sheet-forming is to be seen in counter-correlation to bulk-forming, that is the semi-finished part is an areal part having a thickness of at least a magnitude lower than its areal extensions).
The second temperature is preferably not higher than 320°, more preferably not higher than 300°, in particular not higher than 280°. Moreover, the second temperature is preferably not higher than 85% of the recrystallization temperature of the alloy, more preferably not higher than 80% thereof, in particular not higher than 75% thereof.
Moreover, it is preferred that the second temperature is not lower than 120°, more preferably not lower than 150°, even more preferably not lower than 180°, and in particular not lower than 210°, and/or not lower than 30% of the recrystallization temperature of the alloy, more preferably not lower than 40% thereof, even more preferably not lower than 50% thereof, in particular not lower than 60% thereof.
This gives a suitable weight distribution to the respective quenching regions before and after the forming process. Moreover, it provides for a reasonable relation between ductility of the material and durability of the warm-forming tool.
Regarding the solution heat treatment, it is, in some embodiments, preferably performed by heating the alloy to at least its solvus temperature and to maintain the temperature of the solution heat treatment until the desired amount of the alloying element or elements responsible for precipitation or solution hardening have entered solution. The solvus temperature (often in the range 500°C to 595°C) itself obviously depends on the underlying alloy. However, the temperature of the solution heat treatment does not necessarily fully reach the solvus temperature, the skilled person readily understands that the temperature of the solution heat treatment and soaking time may be varied within typical ranges used by the person skilled in the art well knowing solution heat treatments.
Also the aging process completing the age-hardening treatment is not particularly restricted by the subject invention, the skilled person may use for natural/artificial aging typical temperature and duration as used for the subject alloy, f.i. room storage from about 20° to 150° from ten minutes up to three days regarding the natural aging and/or an artificial aging from 2 to about 10 hours of temperatures in the region of 150°C to 200°C. Regarding the aluminium alloy, also here the invention is not particularly restricted. Required are age-hardenable aluminium alloys, preferably a 6xxx alloy or also a 7xxx alloy.
In case of a 6xxx alloy, it is preferred that the Cu-content thereof is not more than 1%, preferably not more than 0.8%, in particular not more than 0.6%. In case of use of an 7xxx alloy, it is preferred that the Cu-content is not more than 0.5%, preferably not more than 0.4%, in particular not more than 0.3%.
This gives a reasonable combination with the splitted quenching in terms of reducing or avoiding later stress corrosion cracking.
Via the second quenching region, the quenching process reaches temperatures allowing cold-working. As commonly understood, cold-working is not a process limited to room temperature, but can be also somewhat higher, the ductility of the metal being, however, limited with respect to warm-working/forming. In preferred embodiments, cold-working steps are taken subsequent to warm-forming and quenching in the other (second) quenching region. The second quenching region may have a first part cooling down to a first cold forming temperature of a first cold working, in particular above 60°C and a second part cooling further down to a second cold forming temperature for a second or more other cold working steps, in particular below 60°C. There can preferably be a cooling rate of 30-200 K/s in the first and of 10-40 K/s in the second part. The cooling down to the first cold forming temperature may partly occur also during the warm-forming process.
Preferably, cold-working steps may include lateral/cross forming or punching steps, other than possible trimming steps or cutting steps. In comparison between the shape of the areal component of the semi-finished part prior to warm-forming and the final part of the areal component, it is preferred that the major part of the forming involving material flow is performed by the warm-forming process. Preferably, the first temperature is not higher than 150°C, further preferably not higher than 120°C, in particular not higher than 90°C. Further, in preferred embodiments, the first temperature is lower than the temperature of the nose of the GP-zone (Guinier-Preston-zone) for the underlying alloy in the TTT-diagram (time-temperature-transformation). The "nose" means the portion of the GP-zone extending most to the left with respect to the time axis (lowest time).
In a preferred embodiment, the quenching in the other (second) quenching region is done partly outside the forming tool of the warm sheet-forming process. Preferably, it is done in another tool for a cold-working step. Said other tool is preferably a cold tool, contrary to the forming tool of the warm-forming process being preferably temperature-controlled. That is, for the second quenching, an in-tool quenching is preferred, the quenching being, however, temporarily before the forming in said other cold-working/forming tool.
In a further highly preferred aspect, the quenching in the one (first) quenching region is done mostly or even fully outside the forming tool of the warm-sheet forming process. It is preferably done at least in part in an intermediate zone handling the semi-finished part locally between the zone of the solution heat treatment (furnace) and the forming tool of the warm sheet-forming process. Transport from the intermediate zone to the warm-forming tool can be made by usual means (and may consist of stroke motion in tacted common device), however, due to the later explained preferred embodiment of the semi-finished part having topological profile, the stiffness caused by topology of the semi-finished part renders transport handling thereof easier and may attribute to a reduction of the transport time facilitating the keeping of desired quenching rates. The process being a highly dynamical process, it is clear that there might still be some temperature losses between the quenching in the intermediate zone and the warm-forming or even during the warm-forming (depending on the temperature control of the tool) itself, however, these are at significant lower rates than in the first quenching region. That is, by the insertion of the warm-forming, there will be, in the log-scaled diagram as usually used for CCP-diagrams, a flip in curvature from curving to the right to curving to the left, preferably also followed by a re-flip from curving to the left to curving to the right, resulting in behavior during the warm-forming process heavily slowing down quenching. Here, it is preferred that the temperature gradient between start and end of the warm-forming process is at most 100 K, preferably at most 80 K, in particular at most 60 K.
In a preferred embodiment, the solution heat-treated semi-finished part is subject to lubrication in the intermediate zone. The time for quenching in the first quenching region is, thus, used for providing the part with lubrication for the subsequent warm-forming process, such that preferably no lubrication steps need to be taken before the solution heat treatment. A wider range of lubrication agents can be used due to the warm-forming process being at second temperature and descending, such that there are easier conditions for tool protection with respect to hot-forming. As an example, Wisura ZO 3373 or Lubrodal F 25 AL could be used for lubrication.
In a preferred embodiment, a shift of the time-temperature-transformation (TTT) curve towards coarse-quenched induced precipitation, the shift caused by said insertion of the warm-forming process is counteracted to keep the TTT curve within a set region, by a second control of the cooling rate in the second quenching region with reference to the required cooling rate according to continuous cooling precipitation diagram for the alloy for staying within the set region, and/or by first cooling control for a counter-shift of the crossover between the first quenching region and the warm-forming. Thereby, notwithstanding the "lost time" for cooling caused by the influence of the quenching by the forming process, quenching results otherwise obtained by continued quenching with essentially kept cooling rate can be at least partly safeguarded.
This is in particular when the said region is set to pass by the nose of β" formation in the TTT-diagram, and the counteraction is preferably by first cooling control. Preferably, also the time between the end of the first quenching region and the end of warm-forming is not larger than 133% of the difference between the time interval between said β" nose and said crossover and the time interval between said β" nose and the nose of the GP-zone in the TTT diagram for the alloy, preferably not larger than 125% thereof, in particular not larger than 110% thereof. In one, preferably both quenching regions, the cooling rates are preferably at least the respective UCCR (upper critical cooling rate), preferably more rapid by 5% or more, preferably by 10% or more.
For the cooling rate of the one quenching region before warm-forming, one uses preferably rates of at least 120 K/s, more preferably at least 150 K/s, in particular also more than 180 K/s, depending on the respectively used alloy. Moreover, it can be controlled to even several hundreds K/s, as 300 K/s to 800 K/s, for example.
By "sneaking below the noses of formation of β" (Mg₅Si₆) and of the GP-zone (GPI), which are the pre-stage and "nucleation" for hardening phases, course-quenched induced precipitation can be reduced and even avoided, such as to most benefit from the age-hardening treatment effects.
To this end, it is also preferred that the said region is set such that the curve at most crosses the GP-zone of the alloy, preferably passing by the nose of the GP-zone in the TTT-diagram.
Regarding the quenching in the first quenching region in the intermediate zone, preferably within a cooling and lubrication device, preferably oil or water quenching is done. Moreover, it is preferred that combination of conduction and convection quenching is applied. The temperature control of said cooling and lubrication device is independent of that of the warm-forming tool.
For the second quenching region, air or water cooling is preferably used. In case that quenching is already continued during warm-forming, a ratio of the cooling rate during warm-forming and that of the first quenching zone is lower than1/2, preferably lower than 1/3, in particular lower than 1/4 and even than 1/5. The warm-forming tool is preferably coated, DLC coatings can be used as an example.
As already mentioned before, contrary to typical starting points of semi-finished parts with uniform thickness, according to a preferred embodiment, the semi-finished part is formed to have a thickness increase of a first portion thereof with respect to a second portion thereof of at least 20%, preferably at least 40%, and/or of at least 0.4 mm, preferably at least 1 mm, in particular at least 2 mm. However, it is also envisaged that said thickness increase may at least partly reach 60% or more, even 80% or 100% or more. Thereby, a suitable pre-distribution of weight and stiffness can be attributed, facilitating the forming process.
This aspect is also considered protection-worthy and disclosed as such irrespective of the relation between forming steps and quenching. That is, the invention discloses independently and provides a method of manufacturing an areal component made of one piece from an areal semi-finished part of an age-hardenable aluminium alloy, the method comprising an age-hardening treatment wherein the alloy is, subsequent to a solution heat treatment of the semi-finished part, cooled down in a quenching process to a first temperature allowing cold-working and a natural and/or artificial aging of the age-hardening treatment is performed after optional cold-working steps, wherein at least one sheet-forming process is performed between the end of the solution heat treatment and the aging process, which is essentially characterized in that the semi-finished part, which is preferably an extruded part, already has a thickness increase of a first portion thereof with respect to a second portion thereof of at least 20%, preferably at least 40%, and/or of at least 0.4 mm, preferably at least 1 mm, in particular at least 2 mm.
In a further preferred aspect, the semi-finished part is formed by an extrusion process/is (already) an extruded part, and has in particular a non-flat profile. That is, the subject invention preferably departs from an extruded topological profile. By deviation from a flat sheet like semi, part of the extension in width dimension is shifted to an extension direction orthogonal to the areal extension, which gives advantages regarding the construction of the forming tools. In particular, it is envisaged to have a ratio of extension in said orthogonal direction with respect to width and/or length direction of the areal extension of at least 3%, preferably at least 6%, in particular at least 9%.
Moreover, according to an even more preferred embodiment, the component has topological profile portions, and the extruded semi-finished, but not yet warm-formed part already has topological profile portions corresponding to those of the component and matching these after the forming processes of the method.
Thereby, weight of forming work including in particular material flow is shifted from the warm-forming process to the provision of the semi, increasing more the flexibility of the method due to less restraints for their forming processes.
In terms of a process line, the invention provides a process line for manufacturing an areal component made of one piece from an areal semi-finished part of an age-hardenable aluminium alloy, the process line comprising a furnace for performing a solution heat treatment of the semi-finished part, a cooling arrangement to cool down the alloy in a quenching process to a first temperature alloying cold-working and an arrangement to perform natural and/or artificial aging of the age-hardening treatment, which is essentially characterized by a forming tool for a warm sheet-forming process performed beginning at a second temperature, the warm sheet-forming process of the forming tool being inserted amid the quenching process thereby splitted into at least two quenching regions, a first quenching region above the second temperature and locally in an intermediate zone between the furnace and the warm-forming tool and another at least partly in a second intermediate zone outside the forming tool and in particular another tool for a cold-working step between the warm-forming tool and the aging arrangement or additional tools for additional cold-working steps, the second temperature being not higher than the maximum of 320°C and 85% of the recrystallization temperature of the alloy and not lower than the minimum of 120° and 30% of the recrystallization temperature, the process line being controlled in accordance with a method according to any of the preceding aspects.
The advantages of said process line result from the above-described advantages of the method.
Further, the invention provides an areal semi-finished part of an age-hardenable aluminium alloy in the state after the warm-forming process and before the other quenching region according to the method aspects described before, and an areal component made of one piece and of an age-hardenable aluminium alloy, manufactured in accordance with one of the above-described method aspects.
Preferably, the areal component is a structural component in particular for the automotive industry, in particular a part for a wheel suspension, such as a spring link. However, it is understood that the invention is not limited to parts for the automotive industry, and can be used also for components or parts in other fields, where in particular both light-weight and high-strength parts are desired. The weight of the part may preferably be within the range of 2 kg to 5 kg. In width direction (profile direction perpendicular to extrusion direction), extensions between 150 mm and 600 mm are preferred.
Further features, details and advantages of the invention result from the subsequent description of preferred embodiments in relation to the attached figures, wherein

Fig. 1 shows a semi-finished part (Fig. 1A), a warm- and cold-formed component (Fig. 1C) and an intermediate step after warm-forming (Fig. 1B),
Fig. 2 shows a cross-section of Fig. 1A and Fig. 1C along line II-II of Fig. 1C,
Fig. 3 shows a cross-section of Fig. 1A and Fig. 1C along line III-III of Fig. 1C,
Fig. 4 shows a cross-section of Fig. 1A and Fig. 1C along line IV-IV of Fig. 1C,
Fig. 5 shows schematically a process line,
Fig. 6 shows schematically the quenching process in a TTT-representation with inserted warm-forming process slowing down quenching.

Fig. 1c shows (upside-down) a spring link 10f for a vehicle suspension as an example for an areal component made from an aluminium alloy. The exemplary alloy is a 6xxx Al alloy with Cu-content of less than 1%, but other age-hardenable aluminium alloys could be used. In Fig. 1c, the person skilled in the art recognizes some typical features of spring links, as the generally U-shaped form (see cross-sections of Figs. 2 to 4), the representation of Fig. 1c being upside down with respect to that of Figs. 2 to 4. Further, one recognizes an outwardly bulged middle portion and flange portions axially running around the bulged middle portion with a shape provided by the manufacturing process, and wheelside and vehicle-side mounting portions at respective axial end portions of the spring link 10f. However, the spring link 10f being only an example and other types of areal components can be manufactured by the herein-described method details of the components regarding shape and other details are omitted.
The manufacture of spring link 10f does not depart from a (flat) sheet of rolled aluminium alloy, which is the typically used starting point for sheet-forming processes, but departs from an areal semi-finished part in form of an extruded profile 10. The extruded profile 10 has a topological profile in form of roughly a wave structure. In more detail, as can be taken from the cross-section of extruded profile 10 in Fig. 2, the extrusion 10 has a central plateau region 1 from which the profile rises to both sides to an adjacent hill 2, to then descend to a valley 3.
The extruded profile 10 has not only a topological structure, here the shown doublewave-wing structure, but also deviates from a uniform thickness as typically provided for semi-finished parts before starting a forming process.
The thickness of the areal extruded profile 10 is not uniform and, in the present example, has portions of relatively higher thickness, as in the plateau region 1 and at the bottom of valleys 3, and relatively thinner regions as in particular the hills 2 and the crossover from hills 2 to valleys 3.
From Fig. 2 it becomes clear that, axially in the region of the outwardly bulged middle portion of the extruded profile 10, the shape already roughly matches that of the spring link 10 of the extruded profile 10 in single regions, as for instance the valley region 3/3f, the hills 2/2f and the plateau region 1, and in order to form the extruded profile 10 into the shape of spring link 10f in that regions more a bending is required rather than deep drawing due to the pre-formed portions matching with the corresponding portions of the spring link 10f. Moreover, there is already a secondary match of the respective portions regarding thickness distribution, such that also less material flow is required during the forming operation to establish the thickness profile of the areal finished parts, that is the spring link 10f, at least in part.
Fig. 1b shows the situation after a warm forming process of extruded profile 10, wherein the main part of the forming is done, resulting in the shown warm-formed profile 10w. The warm-forming is done during an interruption of the quenching process (involving change of location of the semi from intermediate zone to warm-forming tool) after solution heat treatment of the extruded profile 10. Steps to work the warm-formed extruded profile 10w into the shape of the spring link 10f are done in cold-working steps, including forming, but also trimming and punching steps after reaching cold-forming temperatures as room temperature or somewhat higher by a second part of the quenching process after begin of warm-forming. However, the predominant part of the forming process regarding material flow is done in the warm-forming process.
Said quenching in the second quenching region is partly done within the tool for the first cold-working steps after the warm-forming and starts already in the warm-forming tool. Although in Fig. 1 no intermediate situation between Fig. 1b and Fig. 1c is shown, the cold-working steps between the situation of the warm-formed part 10w and the spring link 10f may comprise more than only one cold-working step, and in particular several cold-working steps. On the other hand side, for the present embodiment, the warm-forming process to arrive at extruded profile 10 after solution heat treatment and quenching in the first quenching zone is done in one forming step made in one forming tool.
The quenching in the first quenching zone before starting warm-forming is, however, not done in the tool of the warm forming process, but in an intermediate zone between the zone of solution heat treatment and the warm forming tool. This spatial configuration is shown in the schematically drawn process line 1000 of Fig. 5.
The extruded profile 10 enters furnace 100 for solution heat treatment. In the subject embodiments, one reaches metal temperatures of about 570° C, for other alloys of the 7xxx family, lower values of for instance 520°C or even lower can be used. After solution heat treatment, the solution-heat treated profiles 10 are brought to cooling and lubrication device 200 within transport step TS1. In cooling and lubrication device 200, the solution-heat treated profiles 10 are lubricated and cooled in a first quenching region the quenching being, however, slowed down due to transport to and warm-forming in warm-forming tool 300. The lubricated solution-heat treated profiles 10 are rapidly transported in transportation step TS2 (f.i. batching motion) to the warm-forming tool 300, providing for said influence of the quenching process, while quenching is continued in the second quenching region part in tool 300 and in part in cold-working-forming tool 401 of cold working arrangement 400, to which the warm-formed profiles 10w are transported after warm-forming in warm-forming tool 300 in transport step TS3. The dashed line around device 200 and tool 300 therein indicates that these do not need to be fully separated devices but may be different stations of a common arrangement.
In said (first) cold-working tool 401, which is here for instance a cold tool contrary to the temperature-controlled tool 300, a first step of the remaining cold-working in cold working arrangement 400 to arrive at the final areal component, here spring link 10f, is performed.
From Fig. 1 it is clear that there might be parallel forming of more than one piece in the respective steps, final separation cutting would be along line C shown in Fig. 1, preferably as cold process.
The areal component, here in the example the spring link 10f, is then subjected to natural aging, which could be during room storage at room temperature or higher for a period which may be short on the minute scale of even reach up to a few days, followed by artificial aging in furnace 500 with set temperature for artificial aging, according to the usual artificial aging parameters known by the skilled person for the respective alloy type, for instance between 150 and 200°C for 2 to 10 h.
Fig. 6 (log scale in the sense of having increments for the t-axis of 10^-2, 10^-1, 10°, 10¹) shows merely schematically the cooling process of the solution-heat treated profile 10 in the first quenching region 61 from about the solution-heat treatment temperature down to the warm-forming temperature. First quenching is performed and the profiles 10 are lubricated. The quenching is slowed down in the second quenching region reaching from about warm-forming temperature to the cold-forming temperatures of the cold-forming in cold-forming arrangement 400. During said influence of the quenching process in region 62 at about the warm-forming temperature, warm-forming is performed to obtain the warm-formed profile 10w from solution heat-treated and then lubricated profiles 10 (Fig. 1b).
The purely schematical representation in Fig. 6 is that of a TTT-diagram, one recognizes that notwithstanding the influenced quenching due to zone 62, the TTT-curve passes by the nose of the β" zone, and the TTT-curve also passes by the nose of the GP-zone. One understands that the curve depends on the warm-forming temperature decisive for the level of turning from right into left curvature in the diagram, several possibilities are displayed in Fig. 6 as 62a to 62e before terminating quenching in region 63.

Claims

Method of manufacturing an areal component (10f) made of one piece from an areal semi-finished part (10) of an age-hardenable aluminium alloy, the method comprising an age-hardening treatment wherein the alloy is, subsequent to a solution heat treatment of the semi-finished part (10), cooled down in a quenching process to a first temperature allowing cold-working and a natural and/or artificial aging of the age-hardening treatment is performed after optional cold-working steps,
characterized in that a warm sheet-forming process of the semi-finished part (10) is inserted amid the quenching process, splitting the quenching process in at least two quenching regions (61, 63), one (61) above a second temperature at which the warm sheet-forming process (62) begins and another one (63) above the first temperature, the second temperature being not higher than the maximum of 320°C and 85% of the recrystallization temperature of the alloy and not lower than the minimum of 120°C and 30% of the recrystallization temperature.
Method according to claim 1, wherein quenching in the other quenching region (63) is done at least partly outside the forming tool of the warm sheet-forming process and preferably in another tool (401) for a cold-working step which in particular includes a cold-forming step.
Method according to claim 1 or 2, wherein quenching in the one quenching region (61) is done mostly outside the forming tool (300) of the warm sheet-forming process and at least in part in an intermediate zone (200) handling the semi-finished part (10) locally between the zone (100) of the solution heat treatment and the forming tool (300) of the warm sheet-forming process.
Method according to claim 3, wherein the solution heat-treated semi-finished part is subject to lubrication in the intermediate zone (200), and preferably no lubrication steps for the part are taken before the solution heat treatment.
Method according to any of the preceding claims, wherein a shift of the time-temperature-transformation (TTT) curve towards coarse-quenched induced precipitation caused by said insertion amid the cooling process is counteracted to keep the TTT curve within a set region, by a second control of the cooling rate in the second quenching region (63) with reference to the required cooling rate according to continuous cooling precipitation diagram for the alloy for staying within the set region, and/or by first cooling control for a counter-shift of the crossover between the first quenching region (61) and the warm-forming.
Method according to claim 5, wherein the set region is set to pass by the nose of β" formation in the TTT diagram, and the counteraction is preferably by first cooling control.
Method according to claim 6, wherein the time between the end of the first quenching region (61) and the end of the warm-forming is not larger than 133% of the difference between the time interval between said β" nose and said crossover and the time interval between said β" nose and the nose of the GP-zone in the TTT diagram for the alloy, preferably not larger than 125% thereof, in particular not larger than 110% thereof.
Method according to any of the claims 5 to 7, wherein the set region is set to at most cross the GP-zone of the alloy, preferably passing by the nose of the GP-zone in the TTT diagram.
Method according to any of claims 3 to 8, wherein a combination of conduction and convection quenching is applied for the first quenching region in the intermediate zone.
Method according to any of the preceding claims, wherein the semi-finished part (10) is formed to have a thickness increase of a first portion thereof with respect to a second portion thereof of at least 20%, preferably at least 40%, and/or of at least 0.4 mm, preferably at least 1 mm, in particular at least 2 mm.
Method according to any of the preceding claims, wherein the semi-finished part (10) is formed by an extrusion process and has in particular a non-flat profile.
Method of claim 11, wherein the component has topological profile portions (2f, 3f), and the extruded semi-finished, but not yet warm-formed part already has topological profile portions (2, 3) corresponding to those of the component and matching these after the forming processes of the method.
Process line (1000) for manufacturing an areal component (10f) made of one piece from an areal semi-finished part (10) of an age-hardenable aluminium alloy, the process line comprising a furnace (100) for performing a solution heat treatment of the semi-finished part, a cooling arrangement (200, 300, 401) to cool down the alloy in a quenching process to a first temperature alloying cold-working and an arrangement (500) to perform natural and/or artificial aging of the age-hardening treatment,
characterized by a forming tool (300) for a warm sheet-forming process performed beginning at a second temperature, the warm sheet-forming process of the forming tool (300) being inserted amid the quenching process thereby splitted into at least two quenching regions (61, 63), a first quenching region (61) above the second temperature and locally in an intermediate zone between the furnace and the warm-forming tool and another (63) at least partly in a second intermediate zone outside the forming tool (300) and in particular another tool (402) for a cold-working step between the warm-forming tool (300) and the aging arrangement or additional tools (401) for additional cold-working steps, the second temperature being not higher than the maximum of 320°C and 85% of the recrystallization temperature of the alloy and not lower than the minimum of 120° and 30% of the recrystallization temperature, the process line being controlled in accordance with a method according to any of the preceding claims.
Areal semi-finished part (10w) of an age-hardenable aluminium alloy in the state after the warm-forming process of the method of any of claims 1 to 12.
Areal component (10f) made of one piece and of an age-hardenable aluminium alloy, manufactured in accordance with a method of any of claims 1 to 12.