DE102017116218A1 - WATER-BASED LUBRICATION FOR WARM FORMING - Google Patents

Abstract

A manufacturing control system is configured to cause an aluminum alloy blank to be heated at least to its solvus temperature, to cause a molding set to be sprayed with a lubricant formulation containing water, lubricant and a surfactant to cause the blank to be blown in the mold Form set during heating is placed so that the blank does not touch the mold set, and to cause the mold set is closed on the blank to form the blank into a part while the part is quenched.

Description

TECHNICAL AREA

The present disclosure relates to hot working aluminum alloy parts and lubricant formulations used therefor.

BACKGROUND

Automotive body panels have long been made of structural steels. Aluminum alloy body panels, however, are gaining in popularity due to their low weight. Aluminum alloys of the 5xxx and 6xxx series, which are aluminum-magnesium and aluminum-magnesium-silicon alloys, are of interest in this regard as they can be formed and processed by methods similar to structural steel.

7xxx series aluminum-zinc alloys have strengths of T6 or T7x hardness similar to those of high-strength and ultra-high-strength steels, and can achieve strengths exceeding 400 MPa. T6 and T7x tempered aluminum-zinc alloys, however, can not be conventionally embossed since these alloys exhibit little to no formability at room temperature.

SUMMARY

In one embodiment, a method includes heating an aluminum alloy blank at least to its solvus temperature, spraying sections of a die set with a lubricant formulation containing water, lubricant, and a surfactant, placing that blank in the die set during heating in such a manner, that the blank does not touch the die set, and closing the die set on the blank to form a part of the blank while the part is quenched.

In another embodiment, a manufacturing system includes a smelting furnace or furnace configured to heat an aluminum alloy ingot at least to its solvus temperature, a die set, a nozzle assembly adapted to form portions of the die set with a lubricant formulation containing water, lubricant and a surfactant contains, to spray. The system further includes a transfer mechanism configured to place the blank in the die set during heating so that the blank does not contact the die set, and an actuator configured to close the die set on the blank To form a blank into a part while the part is quenched.

In another embodiment, a manufacturing control system includes one or more controllers. The one or more controllers are configured to heat an aluminum alloy blank via a heater to at least its solvus temperature, to spray portions of a die set via a nozzle with a lubricant formulation containing water, lubricant, and a surfactant, the blank in the die set during heating via a transfer mechanism so that the blank does not touch the die set and to close the die set on the blank via an actuator to form the blank into a part while the part is quenched.

BRIEF DESCRIPTION OF THE DRAWINGS

1 a perspective view of a hot forming station.

2 is a block diagram of the hot forming station off 1 ,

3 FIG. 10 is a flowchart of an algorithm for hot working an aluminum alloy blank.

DETAILED DESCRIPTION

Here, embodiments of the present disclosure are described. It should be understood, however, that the disclosed embodiments are merely examples and other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be enlarged or reduced to show details of particular components. Thus, specific details of structure and function disclosed herein are not intended to be limiting, but merely representative of the teachings of teaching a person skilled in the art to various uses of the present invention.

One of ordinary skill in the art appreciates that various features illustrated and described with respect to any of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described are. The illustrated combinations of features provide representative embodiments for typical applications. Various combinations and modifications of features consistent with the teachings of the present disclosure; however, may be desirable for certain applications or implementations.

The so-called "hot forming" is used for molding, for example, blanks of aluminum alloy series 6xxx or 7xxx s with F-hardness for automotive components. In one example, an F-durometer series 7xxx aluminum alloy is heated at least to its solvus temperature and then placed in a mold set without touching the mold set. The mold set is then closed to form the blank while also being quenched.

Lubricants are often used in sheet metal forming applications. They can reduce the friction between the blank and the mold, allowing a fluid and controlled flow of metal. In addition, they can help with partial removal, remove unwanted heat and extend the life of the mold. However, the choice and application of the lubricant associated with hot forging operations of aluminum alloys may be more complicated compared to the hot forging operations of aluminum alloys because of the high blanks temperatures achieved prior to hot working. (These temperatures may exceed 250 ° C - a temperature at which certain lubricants can no longer work.) Here, certain formulation lubricants are applied to molds for hot forming stations, as explained in more detail below.

In relation to 1 includes a manufacturing system 10 to form a blank 12 a heater 14 , a transfer mechanism 16 and a formal sentence 18 , In one example, the blank is 12 around a blank made of aluminum alloy series 7xxx with F-hardness. However, other alloys are also provided. The heater 14 heated, as the name suggests, the blank 12 and may be an industrial melting furnace or furnace capable of producing internal temperatures high enough to contain the blanks disposed therein 12 to a predetermined temperature, for example, a solution temperature of the blanks 12 to heat up. Under certain circumstances, the heater heats up 14 the blanks 12 but not above its liquidus (enamel) temperature.

The solution temperature for a 7xxx series aluminum alloy may be about 450 ° C to 490 ° C. The solution temperature (or solid solution temperature) is the temperature at which a substance is readily miscible, which is the property of the materials to combine in all proportions to form a homogeneous solution.

The solidus temperature is the collection of temperatures in a phase diagram under which a certain substance is completely solid. The solidus temperature quantifies the temperature at which the melting of a substance can begin, but not the temperature at which the substance has completely melted. For some materials, there may be a phase existence between the solidus and the liquidus temperatures, so that the substance consists of a solid and a liquid phase at the same time. The closer the material temperature is to the solidus temperature, the more the material is in a solid phase. The closer the material temperature is to the liquidus temperature, the more the material is in a liquid phase. Therefore, the blank can 12 at least to its solvus temperature, but heated to less than its solidus temperature to provide a substantially solid blank to allow for machining and transportation with easier formability. The solvus temperature indicates the solubility limits for the hardening of alloying elements in the aluminum matrix. Above the solvus temperature for any alloy is the mixed crystal temperature range.

The transfer mechanism 16 may be designed to the blank 12 to move and to arrange. In the transfer mechanism 16 In some examples, it may be a manipulator such as a robotic, arm, or conveyor belt arrangement. The transfer mechanism 16 may be designed to the blank 12 quickly out of the heater 14 in the formula sentence 18 to convict the likelihood of loss of heat from the blank 12 to reduce. For example, the system can 10 and the transfer mechanism 16 be designed so that the temperature of the blank 12 not at or below its critical quench temperature - the temperature at which quenching must be started to ensure proper quenching of the material - drops. For example, the critical quench temperature for most 7xxx series aluminum alloys is about 400 ° C.

The formula sentence 18 is provided to the blank 12 to form a part with a predetermined shape. The formula sentence 18 includes a first form in some examples 20 , a second form 22 , at least one actuating element 24 and a staging device 26 , The first and / or the second form 20 . 22 are designed to be the blank 12 to form the predetermined form. The actuator 24 press the first form 20 and / or the second form 22 to each other or away from each other and provides a force for the formation of the blank 12 ready. The actuator 24 may be of any suitable type, for example hydraulic, pneumatic, mechanical, electromechanical type or combinations thereof. The formula sentence 18 and the actuator 24 together can also be referred to as a machine press, embossing press or quenching press.

The staging device 26 can be used to arrange the blank 12 between the first and the second form 20 . 22 and be provided spaced therebetween. In itself, the staging device 26 a heat transfer by conduction between the blank 12 and the sentence 18 inhibit, thereby helping the blank 12 at or above its critical quench temperature. The staging device 26 can the blank 12 from the transfer mechanism 16 received and the blank 12 solve while the first form 20 and / or the second form 22 be closed and the blank 12 engage. In addition, the system can 10 be designed so that the blank 12 between removal of the heater 14 and closing the formula set 18 little heat loses. In one example, the temperature of the blank 12 decrease by more than 10 ° C. The blank 12 could, assumed the blank 12 is heated to 490 ° C and the critical quenching temperature is 400 ° C but will be subject to greater temperature loss, for example up to 90 ° C.

The formula sentence 18 can be a piping 28 comprising cooling the first and / or the second mold 20 . 22 and a quenching of the blank 12 molded part allows. In the piping 28 they may be cavities or channels that are in the mold set 18 are formed, or any combination of externally connected piping and channels. The piping 28 may be connected to a cooling source and receive a heat transfer medium, for example a fluid, from the cooling source around the die set 18 to a desired temperature (eg 1 ° C to 30 ° C) to cool. The formula sentence 18 may be cooled in a manner that inhibits condensation on one or more surfaces thereon. In a mass production environment, the temperature of the formulation may be 18 Be cooled to the predetermined temperature range before a blank is formed and quenched to remove heat, possibly from a previous blank to the mold set 18 was transferred.

Shaping the heated blank 12 to some extent may occur at the same time as quenching the part. The quench rate affects the final degree of hardness, the ultimate strength, and the ultimate corrosion behavior of the material. For example, in some embodiments, the quench rate for an aluminum alloy while transitioning from 400 ° C to 290 ° C may be equal to or greater than 150 ° C per second. The part can be further cooled to a final temperature between 200 ° C and 25 ° C before the part of the set 18 is removed to provide dimensional stability during further processing.

The system 10 may be configured to be operated continuously with a plurality of blanks heated in series or in parallel by one or more heaters and then transferred to at least one mold set for molding and quenching. At least one of the molding sets may become hotter than 30 ° C during or after the molding of the blank.

The part can be from the formula set 18 through the transfer mechanism 16 , another transfer device or removed by hand. The part then passes on to further processing, which may include crimping, deburring and cold aging and / or aging, to bring the aluminum alloy part to a high strength degree of hardness, for example T6 or T7x.

In order to improve the quenching and metal flow behavior during molding, a water-based solvent is applied to the molds 20 . 22 applied (eg sprayed) before the formula set 18 around the blank 12 closed (for example, in front of the transfer mechanism, the blank between the molds 20 . 22 arranges). As most production molding kits require maintenance and anti-corrosion treatments such as the molding kit 18 various oils and greases thereon, a surfactant is added to the lubricant formulation to maintain the weight of the locally applied coating prior to hot stamping.

Because the lubricant formulation is water-based, it does not build up to the same extent on the surface of the molds 20 . 22 Like non-water based formulations, the fronts remain relatively clean and do not require frequent cleaning. Further advantages are that (i) the forms 20 . 22 (ii) the water may contain a base or acid concentrate to assist proper preparation of the surface for subsequent pre-treatment and dyeing processes; (iii) solvent-based Volatile organic compounds or smoke are generated during the quenching process, (iv) the coating weight and the lubricant concentration at different areas of the molds 20 . 22 can be varied by spot application to aid the ductility and effectiveness of quenching; and (v) the process window and robustness can be increased by more uniform quench rates and higher overhangs of the mold fronts.

For example, the lubricant is a lubricant that is normally used for forging applications (eg, FORGE EASE AL 278). It was originally found that this lubricant performs well when used with isopropyl alcohol (IPA) at a concentration of 1: 3 (lubricant: IPA) and applied to aluminum alloy blanks prior to warm forging. Therefore, this formulation was sought in the context of hot working. However, due to the high temperatures of the blanks associated with hot working, the lubricant formulation was applied to the mold set rather than the blanks. Although favorable results were obtained, it was found that IPA may be inflammatory. Thus, an alternative to IPA was sought.

A surfactant, which is a combination of acetylenediol and an alcohol ethoxylate (e.g., DYNOL 800), has been found to be a suitable replacement for IPA. That is, it is believed that nonionic surfactants are preferable to anionic or cationic surfactants. In one example, a water to solvent to surfactant ratio of 90% water, 10% lubricant, and 3% surfactant addition has been found to be effective. For example, if the water / lubricant mixture were 3000 ml, the amount of water would be 2700 ml, the amount of lubricant would be 300 ml and the amount of surfactant 93 ml.

This lubricant formulation could be applied evenly, without streaks or excessive film residue. Since the formulation is primarily water, the quenching efficiency associated with the hot forming process is improved.

With reference to 2 is the system 10 as one or more controls 30 in conjunction with the heater 14 , the transfer mechanism 16 , the actuator 24 and a spray nozzle assembly 32 and operatively arranged to control this. At the controls 30 it can be a distributed processor group or processor, and so on. With further reference to 3 can the controls 30 to process 34 the heater 14 instructing to heat an aluminum alloy blank at least to its solvus temperature. At process 36 can the controls 30 the spray nozzle assembly 32 instruct the forms 20 . 22 with a lubricant formulation such as those set forth herein. As mentioned above, the lubricant concentration can be varied to solve different tasks in terms of formability and quenching efficiency. For example, a lubricant formulation that relatively contains more lubricant may be initially from the spray can assembly 32 on certain sections of the forms 20 . 22 while another lubricant formulation containing relatively fewer lubricants is subsequently applied by the spray nozzle assembly 32 (or other spray nozzle assembly) on other portions of the molds 20 . 22 can be applied. At process 38 can the controls 30 the transfer mechanism 16 instruct the blank during heating in the molds 20 . 22 arrange so that the blanks are not in contact with the molds 20 . 22 come. Besides, the controls can 30 at operation 40 the actuator 24 instruct the forms 20 . 22 close to form a part while the part is quenched.

The processes, methods, logic, or strategies disclosed herein may be deliverable to and / or implemented by a processing device, controller, or computer that may include existing programmable electronic control units or an associated electronic control unit. Likewise, the processes, methods, logic, or strategies may be stored as data and instructions executable by a controller or computer in many forms including, but not limited to, information that is permanently in various ways of manufacturing articles including non-writable storage media such as ROM devices, and information changeably stored on recordable storage media such as floppy disks, magnetic tapes, compact discs, RAM devices, and other magnetic and optical media. The processes, methods, logic or strategies may also be implemented in a software executable object. Alternatively, they may be used in whole or in part using appropriate hardware components such as application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), state machines, controllers or other hardware components or devices, or a combination of Be formed hardware, software and firmware components.

Rather, the terms used in the specification are descriptive terms rather than limiting terms, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments may be combined to form further embodiments of the invention, which may not be explicitly described or illustrated. While various embodiments may be described as offering advantages or being preferred over other prior art embodiments or implementations with respect to one or more desired properties, it will be apparent to one of ordinary skill in the art that one or more features may be used or multiple properties can be challenged to achieve the desired overall attributes of the system, depending on the particular application and implementation. These attributes may include, but are not limited to, cost, strength, life, life cycle cost, marketability, appearance, packaging, size, operability, weight, manufacturability, ease of assembly, and the like. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more features are not outside the scope of the disclosure and may be desirable for particular applications.

Claims (10)

 Method, comprising: Heating an aluminum alloy blank at least to its solvus temperature; Spraying a portion of a molding kit with a lubricant formulation containing water, lubricant and a surfactant; Placing the blank in the mold set during heating so that the blank does not touch the mold set; and Closing the die set on the blank to form the blank into a part while quenching the part.  The method of claim 1, wherein the surfactant contains acetylenediol.  The method of claim 1, wherein the surfactant contains alcohol ethoxylate.  The method of claim 1, wherein the lubricant formulation contains more water per volume than lubricant and surfactant.  The method of claim 1, wherein the lubricant formulation contains less than 5% surfactant per volume.  The method of claim 1, wherein the aluminum alloy blank is a F-grade aluminum alloy blank.  The method of claim 6, wherein the aluminum alloy blank is a 6xxx aluminum alloy blank of F-hardness.  The method of claim 6, wherein the blank of aluminum alloy is a 7xxx aluminum alloy blank with F-hardness.  The method of claim 1, further comprising cooling the formulation to a temperature between 1 ° C and 30 ° C.  The method of claim 1, wherein the solvus temperature is at least 450 ° C.

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