JP2022549682A - Aluminum manufacturing method - Google Patents

Abstract

A method of forming a part from an aluminum blank workpiece to a target shape is disclosed by (a) cold forming an aluminum blank workpiece between a set of dies to fully or partially form a target shape; and (b) heating to or above a solution heat treatment (SHT) temperature and substantially maintaining that temperature until the SHT is complete. solution heat treating the formed component, thereby producing a solution heat treated fully or partially formed component; In between, the solution heat treated fully or partially formed component is quenched and held between dies to provide additional shaping as well as quenching to fully form into the target shape. and generating a component.

Description

The present invention relates to a method for forming components from aluminum workpieces and components produced by said method.

The current trend to achieve vehicle weight reduction in the automotive, rail and aerospace industries has led to an increase in attempts to form panels or components for such vehicles from aluminum, such as aluminum alloy sheets. . Reducing vehicle weight is particularly important to reduce fuel consumption and minimize carbon dioxide air pollution. The use of lightweight components can also provide other benefits, such as improved handling performance in automotive applications and the ability to carry heavier loads in aerospace applications. For these reasons, it is desirable to make components for such applications from lightweight alloys such as aluminum alloys. Maintaining and improving occupant safety standards is important in reducing the weight of vehicles, and parts and parts made using new lightweight materials such as aluminum have the same strength as the materials they replace. is required.

Methods of forming parts from lightweight alloys, such as aluminum alloys, are less researched or developed than methods of forming parts from materials such as steel. Steel and light alloys such as aluminum alloys have very different microstructural development mechanisms, so the steel forming process is generally the same as how light alloys are used to effectively form components. method cannot be applied. A difficulty encountered in forming aluminum alloys is their generally poor formability (ductility) at room temperature (approximately 20-25° C.), which limits the complexity of the formed parts that can be formed. The low formability (low ductility) of aluminum alloys at room temperature results in aluminum alloy constituents made from crushed solid blocks of processed aluminum alloys, which result in a high percentage of the alloy being wasted and thus high resulted in manufacturing costs.

WO2008/059242 discloses a method of forming aluminum alloy sheets into complex shaped components. The method disclosed in WO 2008/059242 includes the following general steps.

(i) heating the aluminum alloy sheet to its solution heat treatment (SHT) temperature and maintaining that temperature until SHT is complete; (iii) immediately closing the cold dies to form the sheet into the component; (iv) during cooling of the formed component, holding the component formed in the closed mold.

SHT dissolves certain constituent alloying elements (precipitates) into solid solution within the aluminum, and cooling in step (iv) quenches the aluminum, preventing precipitation of constituents during quenching and thermal distortion of the formed part. . After SHT, the material is in a soft form suitable for molding. Although this method has certain advantages over previous methods, it also has certain disadvantages. For example, for this method to be successful, the forming must occur before the sheet cools. Since the sheet tends to cool rapidly (thin, low specific heat capacity, high thermal conductivity), shaping must be done very quickly. This is a problem in that molding requires very rapid pressing. Such presses are expensive and have short tool life due to high temperatures and high friction. It is also difficult to form composite parts because the sheet tends to cool before the composite part is fully formed.

Similarly, heating aluminum alloys to temperatures well above room temperature, but below the SHT temperature, has been found to improve the formability of certain alloys and aid in the formation of parts having complex geometries. . Also, if such heating is combined with the forming step prior to SHT and subsequent further forming, or occurs prior to the forming step (i.e., a hot forming process is performed), complex parts may be reduced. It was found to be easier to form. Aluminum alloys in specific temper states (e.g., T4 or T6 temper states) are preferred, and several different states, such as the O condition state (annealed alloys) undergoing the same process, result in formed parts with poor mechanical properties. As such, it is used almost exclusively in these types of processes involving pre-hot forming followed by SHT.

O condition aluminum alloys have relatively high formability (ductility), generally compared to other aluminum alloys typically used in hot forming/SHT processes (e.g., T4 and T6 tempered aluminum alloys). are inexpensive at room temperature, but have low strength at room temperature to adequately reduce or avoid thermal distortion of the molded part over the relatively long times required for SHT and then allow good mechanical properties of the molded part. It is not commonly used in such processes because it is difficult to achieve rapid cooling in the process.

SUMMARY OF THE INVENTION The present invention seeks to provide alternative and/or improved methods for forming components from aluminum metal, such as aluminum alloy sheets.

SUMMARY OF THE INVENTION In a first aspect of the present invention, a method is provided for forming a component (element, part) into a target shape from an aluminum blank workpiece, the method comprising: (a) forming an aluminum blank workpiece between a set of dies; (b) heating above a solution heat treatment (SHT) temperature and reducing that temperature until the SHT is complete; solution heat treating the fully or partially formed component by substantially maintaining, thereby producing a solution heat treated fully or partially formed component; (c) quenching the solution heat-treated fully or partially formed component while held between a set of dies; providing additional shaping to produce a fully formed component in the target shape.

This method is for forming a part into a target shape (predetermined shape) molded part. Cold forming, i.e. forming an aluminum workpiece at a temperature below its recrystallization temperature, strain hardens the aluminum alloy, which inhibits local thinning during forming, resulting in greater deformation (greater geometric complexity). properties), increases the static and dynamic strength of the molded component, and generally reduces the likelihood of tearing or cracking in the workpiece during the molding process.

It has been found that cold forming in step (a), in combination with steps (b) and (c), advantageously allows for the effective formation of a wider range of aluminum alloys. The method of the first aspect can be effectively used with aluminum alloys in the O condition for strain hardening due to cold forming. Cold forming is less complex and requires less energy than hot forming and therefore offers cost savings over warm/hot forming processes in terms of energy usage. Molds used for cold forming are easier to control than hot molds because they eliminate heating that can impart defects such as distortion and poor surface quality to the part. It is understood that cold forming may use lower forming speeds compared to hot forming and therefore the life of tools used in the cold mold process is longer than that of the hot forming process. be.

If sufficient alloying elements are in solution after the quenching in step (c), SHT is completed in step (b) and optional aging treatment is performed to obtain a precipitation hardened and tempered material of the required strength. It is formed. The time required for SHT completion depends on the material being formed and the temperature to which it is exposed, but can be determined experimentally using known techniques.

In step (c) the quenching of the solution heat treated fully or partially formed component is noted that quenching may be performed on the solution heat treated formed component after step (b). means. Quenching and quenching the fully or partially formed component by holding it between a set of dies (a closed set of dies) in step (c) is performed after the quenching step. Any distortion in the formed components of is advantageously minimized.

The combination of steps described in the method according to the first aspect allows the design of complex target geometries with little springback in materials with a metallurgical structure containing little or no precipitates. It was found that

The low ductility of aluminum alloys at cold forming temperatures can lead to imperfect formed parts formed in step (a). Depending on the target shape of the formed component, the cold forming step (a) may or may not result in a component conforming to the target shape. Advantageously, if the target shape is not achieved in step (a), it is achieved in step (c). Thus, the component formed in step (a) may be fully formed to the target shape of the formed component, or partially to a shape part way toward the target shape of the formed component. may be formed in Step (a), if present, advantageously reduces the forming burden in step (c). Preferably, if the target shape is fully achieved in the forming of step (a), but springback is exhibited in the workpiece (perhaps as a result of SHT step (b)), the secondary forming process is reduced to springback. A quenching step (c) may be used to eliminate the effect.

In step (a), the aluminum workpiece may be cold formed at a temperature of 0-100°C, preferably 15-50°C, most preferably 15-30°C.

The temperature of the cold forming step (a) may be controlled by a set of molds and/or temperature treatment of the aluminum blank workpiece in steps prior to cold forming in step (a).

The part formed in step (a) is 20% to 100% of the target forming part shape (target shape), such as 20% to 60% of the target forming part shape, 30% to 70% of the target forming part shape, or It may be formed from 80% to 100%. Part forming may be advantageously used prior to SHT processing to avoid any possible failures resulting from tight bending of the workpiece in the initial press.

A set of dies, i.e. a set of dies in step (a) and/or a set of dies in step (c), is placed on the workpiece during forming when the workpiece is positioned between the dies. A grip comprising one or more protrusions configured to grip the piece may be provided, and step (a) and/or step (c) use the grip to grip the workpiece during molding further including The use of grips and protrusions advantageously controls the flow of the aluminum blank workpiece into the mold during forming and prevents wrinkling in the component while reducing the likelihood of tearing or cracking of the component. is known. One or more protrusions may be referred to as a drawbead. The method may further include providing the grip with recesses configured to receive the protrusions and grip the workpiece between the protrusions when the grip grips the workpiece.

The mold set used in step (a) may be a first set of molds and the set of molds used in step (c) is a second set of molds. There may be (ie different molds may be used for the molds in steps (a) and (c)). Alternatively, the molds used in steps (a) and (c) may be the same mold (ie, the same mold).

If the molds in step (a) and step (c) are the same mold, the drawbeads (if present) are more likely to spread during the first forming step (a) and more during step (c). It can be removable or adjustable so that it does not.

The aluminum blank workpiece used in step (a) may be an aluminum sheet workpiece. The aluminum blank workpiece used in step (a) may be annealed or may be in any temper condition state such as temper conditions T3, T4-T6, T7, O, F or W, and step ( The aluminum blank workpiece used in a) may be fully or partially annealed, or in a T4 or T6 temper condition, but is not so limited. The aluminum blank workpiece used in step (a) may be fully annealed. Preferably, the aluminum blank workpiece used in step (a) is not fully strain hardened.

The aluminum blank workpieces used may be aluminum alloys or formable aluminum alloys. The aluminum blank workpiece used may be a heat treatable aluminum alloy or a non-heat treatable aluminum alloy, but is preferably a heat treatable aluminum alloy. If the aluminum blank workpiece is a non-heat treatable aluminum alloy, the solution heat treatment step (b) is fully or partially formed below the metallurgically stable temperature so that the metallographic structure remains stable. step (c) includes quenching the heated fully or partially formed component from step (b).

The aluminum blank workpiece may be AA2XXX, A6XXX, or AA7XXX series alloys. The aluminum alloy may alternatively be an AA5XXX series alloy.

Preferably, the aluminum blank workpiece used is an O-state annealed aluminum alloy sheet (eg, AA6082 aluminum alloy).

The solution heat treatment step (b) may comprise heating the fully or partially formed component to a temperature within the range of 450-600°C.

In step (c), preferably within 1 to 20 seconds, more preferably within 3 to 10 seconds, upon completion of the solution heat treatment for the solution heat treated fully or partially formed component Transfer to molds, preferably rapidly to a set of molds. This timeframe (rapid timeframe) is used to prevent any adverse cooling effects, such as the formation of precipitates, that may occur in the solution heat treated formed component before the quenching in step (c) is performed. It is enough.

In step (c), the set of molds may be maintained at a temperature of 0-250°C, such as 15-60°C, or 20-25°C. Preferably, the set of molds in step (c) is maintained at a temperature below 150°C.

The temperature of the pair of molds in step (c) increases as heat energy is transferred from the solution heat treated molded parts held therebetween. By maintaining the temperature of a set of molds between 0 and 250° C., preferably below 150° C., the molds can be sufficiently cooled to achieve a quench microstructure suitable for precipitation aging. .

In step (c), the solution heat treated molded part undergoes localized cooling (which cools certain parts of the part) to ensure temperature consistency and thus a substantially homogeneous metal crystalline structure within the part. can do. A set of molds can be configured to provide localized cooling. In step (c), if the material is a heat treatable aluminum alloy, the quenching may be performed at a temperature below the artificial aging temperature of the material. Alternatively, in step (c), if the material is a non-heat treatable aluminum alloy, the quenching may be performed at a temperature below the metallurgical stability temperature of the material, whereby the microstructure of the alloy remains stable. guaranteed to be.

In step (c), quenching (quenching) may be performed at a rate of 15° C./s or more and 200° C./s or less, e.g., the temperature of the solution heat-treated fully or partially formed component is , 16° C./second or higher, 20° C./second or higher, 30° C./second or higher, and the like. The quenching (quenching) described herein advantageously ensures that the proper metallurgical microstructure is achieved in the final product and the adverse effects associated with low quench rates, such as low strength or low corrosion performance. Avoid impact.

Step (c) of the method may further comprise providing the formed component with insulation configured to protect said component from any adverse cooling effects during quenching.

The method may further comprise step (d) of artificially aging the formed component to obtain improved mechanical properties.

The method further comprises using a lubricant to lubricate the set of dies and/or the interface between the set of dies and the part in step (a) and/or step (c). can contain.

Lubrication can be used to advantageously reduce interfacial friction between the mold and workpiece to improve formability.

A second aspect of the present invention provides a component formed by a method according to the first aspect described herein.

These and other aspects of the invention are described below, by way of example, with reference to the accompanying drawings.
1 shows a set of molds suitable for using the present invention in the closed position; 1 shows a set of molds suitable for using the present invention in the open position; 1 shows a temperature-time profile of an aluminum alloy workpiece formed in accordance with one example of the present invention;

For a detailed description of an exemplary method of the first aspect, refer to FIG. 1, a target-shaped component is formed from a blank of fully annealed aluminum alloy sheet (hereinafter referred to as the "workpiece") in the O state. given in relation to forming. Although the detailed examples below describe forming fully annealed aluminum blanks, the methods disclosed herein are made from partially annealed aluminum blanks or other aluminum alloys. It can also be effectively used to form a blank.

A workpiece is first received by a first mold tool. The workpiece may be supplied to the first mold tool from a roll of annealed aluminum alloy sheet, whereby blanks are produced by cutting the sheet to the appropriate dimensions when the mold tool receives the sheet. It may be formed or pre-cut to the desired dimensions.

The first mold tool may be a conventional forming mold tool for cold forming, such as that shown generally in FIGS. 1a and 1b in item 100. FIG. Figures 1a and 1b show the molding die tool in open and closed positions, respectively, in which corresponding punch plate 102 and cavity (mold) plate 104 components are mated in male and female relationship, respectively. When these parts are pressed together (as shown in FIG. 1b) against the workpiece 112 by the pressing part, the parts are formed out of the workpiece 112 leaving the intermediate part It is designed to form.

The mold tool comprises one or more grip sets, indicated generally at item 106, configured to grip the workpiece during the molding process. The grip set 106 controls the flow of metal during forming and helps prevent or at least minimize wrinkling of the workpiece 112 during forming. Grip set 106 is provided in two parts 106 a and 106 b positioned around the edges of plates 102 and 104 and above and below workpiece 112 . When brought together, parts 106 a and 106 b are configured such that they clamp and grip workpiece 112 . Grip set 106 may include a draw bead set that assists grip set 106 in gripping workpiece 112 during molding. The draw bead set protrusions 108 enter the recesses 110 (shown in FIG. 1b) as they clamp the workpiece 112, trapping the workpiece 112 therebetween and forming a tortuous path to retain the workpiece 112. are configured to protrude from the grip so as to enhance grip on the workpiece 112 . The intermediate component formed in the first step may or may not be conformal in shape to the desired target shape, i.e., the component formed in the first step is the target It may be fully or partially formed into shape. The first mold tool 100 may or may not have a liquid cooling system to maintain the desired temperature of the punch and cavity plate components.

The first step in the method is the cold forming step, shown generally in item (1) of FIG. 2, and is carried out under typical cold forming conditions. The cold forming step is performed at a cold forming temperature, such as room temperature (approximately 20° C.). An O-condition annealed aluminum alloy is used as the work, and the forming speed ranges from 1 mm/sec to 200 mm/sec. Any conventional lubricant of a type suitable for the cold forming process can be used in this cold forming process.

The intermediate part is removed from the first mold tool and in a second step (generally indicated by item (2) in FIG. 2) the SHT of the material (450-600° C. for annealed aluminum alloy ) and soaked at that temperature until SHT is complete and a solution heat treated intermediate part is formed. Immersion times at temperatures for solution treatment depend on the type of alloy and can be determined experimentally using known techniques. There are no special requirements for the transfer time between removing the intermediate part formed by the first mold tool in the first step and heating the intermediate part in the second step.

Once the SHT is complete, the solution heat treated intermediate part is transferred and closed in a second mold tool for quenching in a third step, shown generally in item (3) of FIG. positioned between the mold and the second molding step.

The solution heat treated intermediate part is transferred to the second mold tool as quickly as possible, eg within 1-10 seconds, as soon as heat is no longer applied. Forming speeds in the third step range from 50 mm/sec to 500 mm/sec. Pressures for holding a set of molds range from 1 megapascal to 30 megapascals. The holding time (ie, the time the workpiece is held between the closed mold stool with the required pressure) ranges from 2 seconds to 15 seconds.

The temperature of the punch and cavity plate portions of the second mold tool is room temperature when the solution heat treated intermediate part is placed between them. Thermal energy will be transferred from the solution heat treated intermediate part to the second mold tool when it is between the closed second mold tools. The second mold tool is configured such that the temperature of the part contacting the intermediate part remains below 150°C. Liquid cooling may be employed by the second mold tool to control its temperature. The solution heat treated intermediate part is cooled rapidly, preferably at a rate greater than 15°C/sec, to prevent the formation of rough phases when held between the sealed second mold tools. be. In other words, the part formed inside the second mold tool is quenched. Alternatively, the solution heat treated intermediate component may be rapidly cooled after the second step (after SHT and before entering the second mold tool). Precise control of the cooling rate is not necessary as long as it exceeds 15°C per second. Factors to consider that can affect the cooling rate are blank size, blank thickness, holding pressure, and the like. The second mold tool can be provided with grips according to those described above in relation to the grips of the first mold tool. A particular quench rate should preferably be selected based on the particular alloy used and the ultimate mechanical and corrosion requirements of its constituents. For example, 2XXX or 7XXXX alloys such as 2024 may require quenching of about 50 degrees Celsius per second or about 200 degrees Celsius per second to achieve good corrosion resistance. Alternatively, less sensitive alloys such as 7020 may be quenched slower to allow for lower quench forces, or allow less precise or simpler tooling to be used. . To improve formability, a lubricant may be applied to the first and/or second mold tools to reduce interfacial friction between the mold and the workpiece. The lubricant for the first mold tool can be any lubricant suitable for use in the cold forming process and for the second mold tool any lubricant suitable for use at high temperatures. It may be a lubricant, and when received by the second mold tool, the workpiece is initially received by the second mold tool and is at the quench temperature of the quench process.

As a finishing step for heat treatable aluminum alloy parts, an additional artificial aging step (not shown in FIG. 2) is introduced at the end of the process to allow precipitation hardening, thereby achieving increased hardness and strength. be able to.

The shapes of the first and second mold tools (ie, the shape of the punch plate and the cavity (mold) plate) may be substantially identical to each other, or they may differ in shape. Shape differences may be used to facilitate partial forming in the first cold forming step, for example, the shape of the first mold tool may be 20-100% towards the target shape. , producing a partially formed intermediate part, the shape of the second mold tool may conform to the target shape (ie, 100% of the target shape). If the first and second mold tools are the same, partial forming in the first forming step can be achieved by varying forming variables such as forming force and time. A second mold tool may be shaped to "overform" the solution heat treated intermediate part to take into account any distortion effects that may occur after forming. In this way, an intermediate part is produced that is 20-100% towards the target shape for the part formed in the first (cold) forming step, and for the part formed in the second forming step: The same mold tool or different mold tools can be used to achieve a molded part that is 100% of the target shape. The method by which the degree of shaping (percentage towards the target shape) in the first mold tool and/or the second mold tool is determined is not limited, for example by measuring dimensions using a 3D scanner. , and then comparing the measured values to corresponding values of the target shape.

The methods disclosed herein are a significant departure from conventional methods of forming aluminum alloys. Those skilled in the art will appreciate that the methods disclosed herein teach by way of example and not by way of limitation. Therefore, the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims encompass all general and specific features described herein and all statements of scope of method that may be said, as a matter of language, to lie therebetween. is intended.

Claims (23)

A method of manufacturing aluminum for forming a component in a target shape from an aluminum blank workpiece, comprising:
step (a) of cold forming said aluminum blank workpiece between a set of dies to produce said component fully or partially formed into said target shape;
solution heat treating the fully or partially formed component by heating to or above a solution heat treating (SHT) temperature and substantially maintaining that temperature until SHT is complete; (b) producing said fully or partially formed component;
quenching the solution heat treated fully or partially formed component while held between the pair of dies; and (c) providing additional shaping to produce said component fully formed to said target shape. The aluminum manufacturing method according to claim 1, wherein in step (a), the aluminum blank workpiece is cold-formed at a temperature of 0-100°C, preferably 15-30°C. the temperature of cold forming in step (a) is controlled by temperature treatment of the set of molds and/or the aluminum blank workpiece in a step prior to cold forming in step (a); The method for producing aluminum according to claim 1 or 2. the component formed in step (a) is partially formed with respect to the target shape;
4. The method of claim 1, wherein the partially formed component is fully formed to the target shape in step (c). 5. The aluminum manufacturing method according to any one of claims 1 to 4, wherein in said step (a), said component is formed to 20 to 100% of said target shape. The set of molds is provided with grips having one or more protrusions configured to grip the aluminum blank workpiece during forming and to control the flow of the aluminum blank workpiece during forming. ,
6. The method of any one of claims 1 to 5, further comprising using the grips to grasp the aluminum blank workpiece during forming when steps (a) and (c) are present. Aluminum manufacturing method. The set of molds used in step (a) is a first set of molds and the set of molds used in step (c) is a second set of molds. A set of molds,
or,
The set of molds used in step (a) and the set of molds used in step (c) are identical according to any one of claims 1-6. aluminum manufacturing method. The method of manufacturing aluminum according to any one of claims 1 to 7, wherein the aluminum blank workpiece is an aluminum sheet workpiece. Aluminum fabrication according to any one of the preceding claims, wherein the aluminum blank workpiece is annealed or is in any temper condition state such as temper conditions T3, T4-T6, T7, F or W. Method. The aluminum blank workpiece is fully or partially annealed or is in a T4 or T6 temper condition, preferably the aluminum blank workpiece is fully annealed. 1. The method for producing aluminum according to claim 1. The method of manufacturing aluminum according to any one of claims 1 to 10, wherein the aluminum blank workpiece is an aluminum alloy. Process for producing aluminum according to any one of the preceding claims, wherein the aluminum blank workpiece is a heat treatable or non-heat treatable aluminum alloy, preferably a heat treatable aluminum alloy. The method of manufacturing aluminum according to any one of claims 1 to 12, wherein the aluminum blank workpiece is AA2XXX, A6XXX, or AA7XXX series alloy. The method of manufacturing aluminum according to any one of claims 1 to 12, wherein the aluminum blank workpiece is an AA5XXX series alloy. The aluminum manufacturing method of any one of claims 1 to 14, wherein the aluminum blank workpiece is an O-state annealed aluminum alloy sheet (eg, AA6082 aluminum alloy). 16. The method of any one of claims 8 to 15, wherein step (b), wherein a solution heat treatment is performed, heats the component formed in step (a) to a temperature within the range of 450-600°C. The described method for producing aluminum. In step (b), the fully or partially formed component that has been solution heat-treated is subjected to the step (c), preferably within 1-20 seconds, more preferably within 3-10 seconds. The method for producing aluminum according to any one of claims 1 to 16, wherein the aluminum is transferred to the mold at . Process for producing aluminum according to any one of the preceding claims, wherein in step (c) the set of molds is maintained at a temperature between 0 and 250°C, preferably below 150°C. In step (c), if the aluminum blank workpiece is a heat treatable aluminum alloy, the quenching is performed at a temperature below the artificial aging temperature; The method for producing aluminum according to any one of claims 13 to 18, which is carried out at a temperature equal to or lower than the stable temperature. The method for producing aluminum according to any one of claims 1 to 19, wherein in step (c), rapid cooling is performed at a rate of 15°C/sec or more and 200°C/sec or less. A method of manufacturing aluminum according to any preceding claim, further comprising the step of artificially aging the formed component to obtain improved mechanical properties. 22. Any of claims 1-21, wherein in step (a) and/or step (c), a lubricant is used to lubricate the interface between the set of molds and/or the component. 1. The method for producing aluminum according to claim 1. A component formed by the aluminum manufacturing method of any one of claims 1-22.

Images