OF HIGH PRESSURE DIE CAST ALUMINUM

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This PCT International Patent Application claims the benefit of and priority to U.S. Provisional Patent Application Serial No. 62/711,437 filed on July 27, 2018, titled “Method for Low Cost Joining of High Pressure Die Cast Aluminum,” the entire disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0002] The present invention relates to a component and a method of adhesively bonding the component that includes a first part and second part wherein one of the parts is aluminum or aluminum alloy. More particularly, the present invention relates to utilizing an adhesive with a degreasing agent and a passivation agent.

2. Related Art

[0003] This section provides background information related to the present disclosure which is not necessarily prior art.

[0004] Automobiles are the subject of many different types of stresses, such as rough driving surfaces, internal vibrations, and exposure to corrosive environments.

Various components of vehicles experience these hardships more than others and the malfunction of one component oftentimes leads to the damage of interrelated parts.

[0005] In attempts to balance strength and weight, components that include more than one part are oftentimes adhesively bonded together, thus reducing weight requirements and the risks of galvanic or bimetallic corrosion associated with fasteners and welding. However, in order to effectively bond two parts with adhesive, surfaces of the two parts that will be interfaced have conventionally required a time and material consuming pretreatment. Generally speaking, pretreatment is critical to the removal of impurities from a surface so that the bonded joint of two parts meet quality requirements, particularly in the automobile industry, as the presence of impurities between parts can greatly reduce the strength of a bond. One method involves passivating the surface to remove impurities to improve the adhesive bonding strength. Various other pretreatment methods have been developed with significant time and effort, notably when at least one of the two parts to be adhesively bonded is aluminum or aluminum alloy. These pretreatment methods typically include some form of degreasing, abrading, and/or depositing a thin film on the surface chemically. While many of these pretreatment methods have proven effective in strengthening adhesively bonded joints, they are time consuming and expensive. One common characteristic of these pretreatment methods is that they require multiple, complicated steps that are often outsourced to specialized facilities, incurring additional shipping and handling costs. Currently, known pretreatments are time consuming, require considerable floor space and also require expensive machinery and/or chemicals. In addition, the chemicals used in these pretreatment methods have limited quantity and cannot be reused, thus creating a substantial amount of chemical waste. Moreover, the chemicals used are often times hazardous to the environment and operators and thus must be shipped, stored, and used according certain regulations.

[0006] Accordingly, there is a continuing desire to develop bonded joints that are lightweight, strong, and simple to construct.

SUMMARY OF THE INVENTION

[0007] This section provides a general summary of the disclosure and is not to be interpreted as a complete and comprehensive listing of all of the objects, aspects, features and advantages associated with the present disclosure. [0008] In accordance with one aspect, the subject invention provides a method of adhesively bonding a first part to a second part comprising numerous steps. The method includes providing a first part of a first aluminum material that has not undergone any pretreatment processes, providing a second part of a steel material, and providing an adhesive. The next step includes placing the adhesive on the first aluminum material and simultaneously degreasing and passivating the first aluminum material with the adhesive. The method continues by pressing the first part and second part together and allowing the adhesive to cure and bond the first part to the second part.

[0009] According to another aspect, the subject invention provides an automotive component with a bonded joint that comprises a first part of a first aluminum material, a second part of a steel material, and a layer of adhesive between the first part and the second part. The layer of adhesive includes a passivation additive and a degreasing agent.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings described herein are for illustrative purposes only of selected embodiments and are not intended to limit the scope of the present disclosure. The inventive concepts associated with the present disclosure will be more readily understood by reference to the following description in combination with the accompanying drawings wherein:

[0011] Figure 1 A is a perspective view of a component assembled out of a first part of aluminum and a second part of steel that are bonded together with an adhesive with self piercing rivets and/or flow drilled screws;

[0012] Figure 1B is a cross-sectional view of the component from Figure 1 A;

[0013] Figure 1C is a view of the aluminum component being joined to the steel rail from Figure 1A; [0014] Figure 1D illustrates an assembled component in accordance with another embodiment of the invention that includes an adhesive bond between cast aluminum front shock towers and a stamped steel rail of an automobile, the adhesive includes an additive that simultaneously degreases and passivates bonded surfaces;

[0015] Figure 1E illustrates several parts arranged to be adhesively bonded without pretreatment;

[0016] Figure 2A graphically illustrates Lap Sheer ratings of parts bonded in accordance with various pretreatment methods;

[0017] Figure 2B graphically illustrates the Lap Sheer ratings of parts bonded without pretreatment in accordance with the subject disclosure;

[0018] Figure 2C graphically compares Lap Sheer ratings of parts bonded with pretreatment and parts bonded without pretreatment in accordance with the subject disclosure;

[0019] Figure 2D graphically compares the Lap Sheer ratings of parts bonded without any pretreatment to parts bonded with pretreatment, wherein two specific adhesives have been used;

[0020] Figure 3A is a flow chart illustrating a method of forming a component with an adhesively bonded joint in accordance with the subject disclosure; and

[0021] Figure 3B is a flow chart illustrating additional method steps of forming the component in Figure 3 A.

DESCRIPTION OF THE ENABLING EMBODIMENT

[0022] Example embodiments will now be described more fully with reference to the accompanying drawings. In general, the subject embodiments are directed to a component and a method of adhesively bonding the component that includes a first part and second part wherein at least one of the parts is aluminum or aluminum alloy. However, the example embodiments are only provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0023] Referring to the Figures, wherein like numerals indicate corresponding parts throughout the views, the component 20 and method 100 of assembling same is intended for increasing the efficiency of adhesively bonding parts at a bonded joint, which has conventionally required a multi-step pretreatment process. As it will be appreciated with further reading, the elimination of the pretreatment requirement can be accomplished without negative impacts to Lap Sheer ratings of the adhesively bonded joint.

[0024] The component 20 with an adhesively bonded joint is shown in Figures 1A through 1D in accordance with one embodiment of the invention. The component 20 includes a first part 22 and a second part 24. At least one of the first part 22 and second part 24 is casted of aluminum or aluminum alloy (“aluminum material”). These parts 22, 24 can be formed of dissimilar materials, such as a first part 22 formed of aluminum material and a second part 24 formed of steel or steel alloy (“steel material”). Alternatively, these parts 22, 24 could be both formed of the same or different aluminum material. The first part 22 includes an interfacing first surface 28 and the second part 24 includes an interfacing second surface 30. The first part 22 and second part 24 are joined along a bonded joint 26 at an overlap between the interfacing first surface 28 and the interfacing second surface 30, at least one of which having been degreased and passivated. The bonded joint 26 includes an adhesive 32 that includes a degreasing agent 34 such as amine additive that degreases the surface of application and a passivation additive 36 that can also include the amine additive forming a protective layer 38 that passivates the surface of application. The passivation additive 36 can also include an acid, such as nitric or citric acid. A mechanical connection 42 can also be seen, which would generally include rivets or flow drill screws. Figure 1 is a cross-sectional view illustrating the layers connecting the first part 22 and the second part 24 via adhesive 32 with the passivation additive 36 and the protective layer 38.

[0025] The quality of a bond can be measured in micro bonds per surface area or more pragmatically through quality testing to determine sheer strength (“Lap Sheer Test”). With this in mind, when an interfacing surface 28, 30 is not properly degreased the bonds per surface area are reduced as a result of loose impurities taking up surface space. In addition, when an interfacing surface 28, 30 is passivated, an outer layer 38 is created to shield the underlying material so that it is less susceptible to environmental damage. In the specific application of aluminum material, pure aluminum forms a naturally occurring layer 38 of aluminum oxide upon exposure to the atmosphere but is still subject to certain environmental damage. Moreover, certain aluminum alloys do not naturally oxidize and are thus even more susceptible to environmental damages such as corrosion. Accordingly, as the adhesive 32 dries or cures, trace amounts the passivation additive 36 are left, forming the protective layer 38.

[0026] Figure 1D illustrates another embodiment of the subject disclosure. The component 20’ includes a first part 22’, shock towers formed from a die casted aluminum material, connected a second part 24’, a front rail 40 constructed of steel alloy. A bonded joint 26’ connects the first part’ 22 to the second parts 24’ with adhesive 32. The adhesive 32 includes a degreasing agent 34 and a passivation additive 36. The bonded joint 26 is also shown to include a mechanical connection 42 in the form of rivets and/or flow drill screws. Figure 1C is a view of the aluminum component being joined to the steel rail via adhesive and a clamp 25. The adhesive 32 may be applied in flow holes drilled into one of the parts 22, 24. Once the adhesive 32 is placed and the parts 22, 24 are brought together, the parts 22, 24 may be clamped together until the adhesive 32 is fully cured or partially cured.

[0027] In accordance with another aspect of the subject disclosure, Figure 1D illustrates several example parts 22”, 24” illustrated as castings, wherein at least one of the parts 22”, 24” comprise aluminum material. While not limited hereto, the aluminum material of one or both parts could include Aural ® 2, Aural ® 5S, Silifont 36, C65K, and C611. In addition, the second part can include dual-phase steel alloy. It is preferable, however, that the materials used are high pressure die cast aluminum alloys and are used to make structural body castings. Some example preferred compositions will be presented below.

[0028] Figures 2A and 2C illustrate lap sheer ratings of conventional components having adhesive bonds between parts subjected to several conventional pretreatment methods which have traditionally been required. These pretreatment methods typically fall into two categories, one category involves subjecting a part to several baths and the other category involves subjecting a part to laser etching. After these pretreatment methods, these parts were bonded with adhesive. Lap Sheer tests were completed on bonded joints with a part comprising preheated aluminum alloy bonded to a part comprising steel alloy. These alloys are described in greater detail below.

[0029] Looking first to a first method (designated“Method 1” in Figures 2A and

2C), the pretreatment process was completed with a part of aluminum material such that after pretreatment the part had a polymer layer, a monolayer, and a metal surface. The first method has been tested to have up to 10 ¹⁵ nano molecular bonds per square centimeter [0030] Looking now a second method (designated“Method 2” in Figures 2 A and

2C), the pretreatment process was completed with a part of aluminum material that included at least four distinct steps that include dipping the material in proprietary blends between rinses.

[0031] Data was also drawn from a third method (designated“Method 3” in Figures

2A and 2C), this pretreatment process was also completed with a part of aluminum material, which included two degreasing steps followed by three rinsing steps before applying a deoxidizing blend. After deoxidizing, the material is rinsed three more times and dried.

[0032] Lap Sheer testing was also performed with a fourth method (designated

“Method 4” in Figures 2A and 2C). The fourth method included laser etching on aluminum material. During treatment, the laser etches the surface of the casting by partially remelting and rapidly resolidifying the surface of the aluminum part.

[0033] A fifth method is also presented (designated“Method 5” in Figures 2A and

2C), the pretreatment process was also completed with a part of aluminum material, which included a seven-step pretreatment method that includes dipping the material in active chemicals three times and rinsing the material four times.

[0034] In a sixth method (designated“Method 6” in Figures 2A and 2C), the pretreatment process was again completed with a part of aluminum material, which included at least five distinct steps, including application of active chemicals followed by three rinsing steps.

[0035] The Lap Sheer data gathered from each of these pretreatment methods was compared to Lap Sheer data taken from the method of the subject invention that does not require pretreatment (Figures 2B and 2C). As shown in Figure 2A, the results of the Lap Sheer tests with each pretreatment method are all between l2000MPa and l4000MPa. The pretreatment and bonding methods include (from left to right): The first method, the second method, the third method, the fourth method, the fifth method, and the sixth method. As described above, each of these pretreatment methods were completed with parts that include aluminum alloy that were bonded to a dual-phase steel alloy substrate. Specific details of these alloys will be presented below.

[0036] For comparison, the Lap Sheer data shown in Figure 2B quantifies the strength of bonded joints 26, bonded with the adhesive 32 in accordance with the subject invention that does not require pretreatment. From left to right the aluminum castings tested included two types of aluminum alloy with different ranges of heat treatment tempers selected based on the amount of debris left on the surface.

[0037] Figure 2D graphically compares the Lap Sheer ratings of parts bonded without pretreatment to Lap Sheer ratings of parts that have undergone the second method of pretreatment, wherein the same adhesive has been used in both. More particularly, the first two bars on the left utilize Betamate ® 73326/7332 adhesive and the two bars on the right utilize Betamate ® 1486 adhesive. Of note, lap sheer values in Figures 2A through 2D were tested on parts joined via adhesive only.

[0038] The first part 22 is preferably made of an aluminum material. Several primary preferred aluminum materials were used in carrying out Lap Sheer testing. A first aluminum material was used in all of the pretreatment tests and one of the subject adhesive tests. The first aluminum material comprises, in weight percent (wt.%) based on the total weight of the alloy: Silicon (minimum 9.5 wt.%, maximum 11.5 wt.%); Iron (no minimum, maximum 0.25 wt.%); Manganese (minimum 0.30 wt.%, maximum 0.70 wt.%);

Magnesium (minimum 0.1 wt.%, maximum 0.6 wt.%); Titanium (no minimum, maximum 0.10 wt.%); Strontium (minimum 0.01 wt.%, maximum 0.03 wt.%); other elements each at a maximum .05 wt.% or an aggregated maximum 0.15 wt.%; and the remaining balance being Aluminum. [0039] A second primarily preferred aluminum material for the first part 22 is a second aluminum alloy that comprises, in weight percent (wt.%) based on the total weight of the alloy: Silicon (minimum 6.0 wt.%, maximum 8.0 wt.%); Iron (no minimum, maximum 0.25 wt.%); Manganese (minimum 0.30 wt.%, maximum 0.60 wt.%);

Magnesium (minimum 0.1 wt.%, maximum 0.6 wt.%); Titanium (no minimum, maximum 0.15 wt.%); Strontium (minimum 0.01 wt.%, maximum 0.03 wt.%); other elements each at a maximum 0.05 wt.% or an aggregated maximum .15 wt.%; and the remaining balance being Aluminum.

[0040] A third primary preferred aluminum material for the first part 22 is a third aluminum alloy that comprises, in weight percent (wt.%) based on the total weight of the alloy: Silicon (minimum 6.0 wt.%, maximum 8.0 wt.%); Iron (no minimum, maximum 0.25 wt.%); Manganese (minimum 0.30 wt.%, maximum 0.60 wt.%); Magnesium (minimum 0.10 wt.%, maximum 0.50 wt.%); Zinc (maximum 0.70 wt.%); Titanium (no minimum, maximum 0.15 wt.%); Strontium (no minimum, maximum 0.03 wt.%); and the remaining balance being Aluminum.

[0041] The aluminum materials selected for the first part 22 are tempered based on the amount of debris left on the surface and the type of adhesive 32 applied. Thus, castings illustrated throughout the figures that are designated“F Temper” or“T5, T6, T7, etc.”. During testing, the adhesive 32 was applied in either a water based spray or a water free lubrication and allowed to cure and/or dry in conjunction with tempering the aluminum die casting and/or during the die cast process. As such, additional time and energy is saved because the heat required during the tempering or casting process can also serve to cure the adhesive. Looking specifically the temper designations, castings designated“F Temper” are provided directly from a foundry as casted and have not undergone heat treatment. Parts provided directly from the foundry have very dirty surfaces as most of the die spray (release agent) that is used during forming the part is still typically present during the time of applying the adhesive. Adhesive 32 in the form of water free lubricant is preferably used with alloys designated“F Temper” or“as cast.” The temper designation“T7” is a temper process preferably selected for the cleanest surfaces as die spray has been burned off during heat treatment and the material is artificially aged. More specifically, the“T7” alloys are solutionized at 465°C, air quenched, and artificially aged from 2l5°C to over 225°C from a “T4” condition. Alloys subjected the“T7” treatment are not as strong but are shown to have improved ductility, as such“T7” is a preferred treatment for alloys that are strong.

The designation“T5” is the preferred tempering process for materials which have undergone artificial aging at 2l5°C as casted, this stabilization treatment is used to prevent changes in mechanical properties during service. The designation“T6” is a preferred tempering process for materials that have been heat treated with forced air quenching and artificially aged. It is preferable that adhesives 32 can be applied via a water based spray in designations T6-T7 but in water free lubricant for T5 or below.

[0042] As described above, the second part 24 can either be aluminum material or steel material. For example, one preferred steel material is a dual-phase steel alloy comprising, in weight percent (wt.%) based on the total weight of the alloy: Carbon (maximum 0.12 wt.%); Silicon (maximum 1.5 wt.%); Manganese (maximum 1.5 wt.%); Phosphorous (maximum 0.03 wt.%); Aluminum (minimum 0.02 wt.%, maximum 0.06 wt.%); Chromium plus Molybdenum (maximum 1.0 wt.%); and the balance being Iron.

The example bonds presented in Figure 2B and 2C include the second material being dual phase steel alloy.

[0043] A graph comparing the Lap Sheer values of the parts bonded without pretreatment in accordance with the subject invention and parts bonded with conventional pretreatment methods is shown in Figure 2C. As it should be appreciated, the Lap Sheer values in MPa are all within a l2000MPa to l4000MPa range with no noticeable regression in strength resulting from using the adhesive 32 in accordance with the subject invention that eliminates the conventional pretreatment methods.

[0044] As explained previously, the adhesive 32 could be water based or lubrication based and includes a degreasing agent 34 such as amine additive that simultaneously degreases and a passivation additive 36 that can also include the amine additive forming a protective layer 38 that passivates the interfacing surfaces. In addition, the adhesive may be applied in separate layers, include first applying a resin layer that degreases and passivates followed by a hardening layer that cures the resin layer. One example adhesive, currently available in the market is a two part adhesive known by the tradename Betamate ®

73326/7332. The adhesive low modulus, low strength with high ductility. Another example is the Betamate ® 1486 which is a high modulus, high strength with low ductility adhesive.

[0045] It should be appreciated that the subject component includes a method of assembly 100 as presented in the flow chart in Figure 3 A. The method begins by providing a first part comprising aluminum material and a second part comprising aluminum material or steel material 110. At least the first part is casted 120 such that the first part and second part each include corresponding interfacing surfaces. The casting 120 step preferably includes high pressure vacuum die casting. Adhesive is applied 130 to at least the interfacing surface of the first part. The interfacing surfaces of the first part and second part are then pressed together 140. The interfacing surface of the first part is then degreased and a passivation layer is formed in the joint between the first and second parts 150 by the adhesive. After degreasing and forming the passivation layer 150, mechanical fasteners such as self-piercing rivets or flow drill screws are used to further connect the parts 160.

The adhesive is then completely dried and/or cured 170 adhering to both the first and second parts to form a bonded joint. The component is then prepared 180 for subsequent processing such as reinforcement with mechanical fasteners, shipping, or incorporation into a larger system like being moved from a casting location to a body-in-white (BIW) location where the component is incorporated into the frame of an automobile. Looking now to Figure 3B, after application of the adhesive 130, at least one of the steps designated with numerals 140-170 could be completed in conjunction with additional steps includes tempering the aluminum die casting 190 and die cast processing 200 with water free lube. As discussed above, the heat required for tempering and die casting can be used to expedite curing the adhesive. In addition, during or after drying and/or curing the adhesive, the first and second part can be mechanically connected 210, which could include self-piercing rivets, flow drill screws, etc. An additional step of heating 220 the at least one part of aluminum material could also be applied after casting 120.

[0046] As described above and presented in Figures 1D and 1E, this method can be utilized in bonding a die casted aluminum shock tower castings to Steel alloy front rails. However, it should also be appreciated that this method can be applied to various other automotive parts and structures with at least two metal parts that are bonded together.

[0047] It should be appreciated that the foregoing description of the embodiments has been provided for purposes of illustration. In other words, the subject disclosure it is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varies in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of disclosure.