Patent Application
20210079492
The present disclosure relates to methods of manufacturing components of an automotive vehicle frame, for example, components of a frame for a body-on-frame vehicle.
Many automotive vehicles include a frame that provides a structure to which various vehicle components can be mounted. For a variety of reasons, at least certain portions of that frame may require high levels of strength and/or stiffness. As such, the frame, or at least certain components thereof, may be formed of a high strength material, such as, for example, Advanced High Strength Steel (AHSS). Frame components formed of AHSS are typically manufactured using a cold forming process and then portions of the frame component requiring additional strength and/or stiffness may be reinforced by arc welding one or more separately-manufactured reinforcement elements to the cold-formed body of the component at the appropriate location(s).
Components formed of AHSS add a significant amount of weight to the vehicle. Additionally, local reinforcement of portions of the frame component require the separate production of reinforcements that have to be welded to the already-formed frame body of the frame component, resulting in, for example, additional cost and complexity to the manufacturing process. Further, the cold forming process used to manufacture frame components out of AHSS typically has larger than desired geometric tolerances presenting additional manufacturing difficulties.
In at least some implementations, a method of manufacturing a component of an automotive vehicle frame comprises heating a blank comprised of ultra high strength steel to at least a predetermined temperature, forming with a forming tool the heated blank into a desired shape for the vehicle frame component, and then cooling or allowing the formed component to cool until it reaches a predetermined state.
In at least some implementations, a method of manufacturing a component of an automotive vehicle frame comprises welding a reinforcement element to a blank comprised of ultra high strength steel and then heating the blank and reinforcement element to at least a predetermined temperature. Once the blank and reinforcement element are heated to at least the predetermined temperature, the method comprises transferring the heated blank and reinforcement element to a forming tool, forming with the forming tool the blank and reinforcement element into a desired shape for the vehicle frame component, and then cooling or allowing the formed component to cool until it reaches a predetermined state.
In at least some implementations, a component of an automotive vehicle frame comprises a body formed of ultra high strength steel and a reinforcement element, wherein when the component is formed, the body and the reinforcement element are of a unitary construction. The component further includes a first portion comprising a first portion of the body and having a first thickness and a second portion comprising a second portion of the body and the reinforcement element and having a second thickness greater than the first thickness.
Further areas of applicability of the present disclosure will become apparent from the detailed description, claims and drawings provided hereinafter. It should be understood that the summary and detailed description, including the disclosed embodiments and drawings, are merely exemplary in nature intended for purposes of illustration only and are not intended to limit the scope of the invention, its application or use. Thus, variations that do not depart from the gist of the disclosure are intended to be within the scope of the invention.
Referring in more detail to the drawings,
The method 10 is a departure from conventional vehicle frame component manufacturing processes that utilize cold forming processes to manufacture frame components out of advanced high strength steel (AHSS), and that require post-formation reinforcement of portions of the component by arc welding one or more separately-manufactured reinforcement elements to that or those portions of the body of the component.
As shown in
In addition to the above, step 12 may also include heating the blank at the predetermined temperature for a predetermined period of time to ensure the austenitization of the blank. As with the predetermined temperature, the particular value of this predetermined period of time may be dependent upon a number of factors including, for example, the particular type of UHSS that is being used. Accordingly, it will be appreciated that the predetermined period of time is an empirically-derived value that is determined prior to the performance of method 10 and that is dependent upon the particular material being used. By way of example, however, for at least certain types of steel (e.g., 22MnB5 steel) the predetermined period of time is typically between 4-10 minutes.
Step 12 may be performed in a number of ways. One way is by placing the blank into a suitable heating device, for example, an oven or furnace, that is configured to heat blanks formed of UHSS to the required predetermined temperature or temperature range. It will be appreciated, however, that any suitable means for heating UHSS blanks to at least a predetermined temperature may be used, and thus, the present disclosure is not limited to any particular way(s) of performing step 12.
Following step 12, the method 10 may proceed to a step 14 of forming the heated blank into a desired shape for the vehicle frame component being manufactured. More specifically, a forming tool, such as, for example, a die of a press machine may be used to form the heated blank into the desired shape. In an embodiment, step 14 is performed while the blank is in the austenitic condition and may be performed while the heated blank is still in the oven or furnace or, alternatively, after it has been removed from the oven or furnace.
In an instance where the heated blank is formed while in the oven or furnace, the blank may be loaded onto a die of a press either before or after the heating process, and then after the blank is heated to at least the desired predetermined temperature, the press may be operated to form the heated blank into the desired shape.
On the other hand, in an instance where the heated blank is formed after it has been removed from the oven or furnace, the method 10 may include one or more additional steps prior to the forming step 14. For example, and as illustrated in
Once the heated blank has been formed into the desired shape for the frame component being manufactured, the method 10 may proceed to a step 18 of cooling the formed component until it has reached a predetermined state. In an embodiment, the predetermined state corresponds to the completion of the phase transformation of the material that began when the blank was heated in step 12. Completion of the phase transformation can be determined by detecting or determining that the temperature of the formed component has reached or fallen below a predetermined temperature. In an embodiment, this temperature is the Martensite Finish temperature for the particular material being formed. In other embodiments, the predetermined temperature is a temperature value at least a certain amount below the Martensite Finish temperature, for example, 100-200° C. below the Martensite Finish temperature. As with the predetermined temperature discussed with respect to step 12, the particular value of the predetermined temperature used to determine the completion of the phase transformation process in step 18 may be dependent upon a number of factors including, for example, the particular type of UHSS that is being used. Accordingly, it will be appreciated that the predetermined temperature is an empirically-derived temperature value that is determined prior to the performance of method 10 and that is dependent upon the particular material being used. For purposes of illustration, however, in an embodiment when 22MnB5 steel is used, the predetermined temperature may be in the range of 635-735° C.
In any event, the formed component may be cooled in a number of ways. In an instance where a cooled die is used in the forming step 14, the component may be held in the die and the die may contribute to the cooling of the component. In other embodiments, however, alternative or additional external cooling means may be used to cool the component. Regardless of the particular way in which the component is cooled, the component may be cooled at particular rate that may be dependent upon one or more factors such as, for example, the particular material being used to form the component. For purposes of illustration, however, in at least some embodiments the rate may be on the order of 25-100° C./s, and in at least one embodiment, at approximately 25-30° C./s (e.g., 27° C./s).
Depending on the particular component being manufactured, portions of the component may require greater strength and/or stiffness than other portions of the component. To account for this, rather than forming the entirety of the component to meet these increased strength and/or stiffness requirements or targets (and thereby using an unnecessary amount of material that adds costs and weight to the vehicle), local reinforcements may be used to increase the strength and/or stiffness of the relevant portion(s) of the component. In an embodiment wherein reinforcement is needed, the method 10 may include one or more steps performed prior to the heating step 12, forming step 14, and/or cooling step 18.
More particularly, and as shown in
Joining the reinforcement element(s) with the blank prior to the heating and forming steps provides a number of advantages over the reinforcement techniques utilized for vehicle frame components manufactured from AHSS using conventional cold forming processes. More specifically, in conventional cold-forming manufacturing processes, separate reinforcement elements have to be produced and then arc welded onto the formed body of the component after the completion of the cold forming process. Not only does this increase the cost and complexity of the manufacturing process, but the arc welds create heat affected zones (HAZ) that must be considered when designing for strength and/or durability.
By joining the reinforcement elements to the blank prior to the heating and forming steps of the method 10, the welds between the reinforcement element and the blank are annealed and hardened during the heating, forming, and cooling steps of the method 10 thereby eliminating, or at least mitigating, the formation of HAZ and negative effects on material properties. Improved geometric tolerances provided using the hot forming methodology described above also allow greater control over weld gaps, simplifying assembly of the component with other components of the vehicle frame. Additionally, a wider range of thickness ratios between the non-reinforced and reinforced portions of the component are possible using the above-described methodology because relatively thin reinforcement elements can be joined to the blank (e.g., thickness ratio of 1:2 or less), which is difficult to do using the conventional cold forming process and post-formation reinforcement technique since relatively thin reinforcement elements cannot be reliably arc welded to thicker materials.
The method 10 described above may be used to manufacture any number of vehicle frame components, such as, for example and without limitation, rails or beams or cross members or kick-up/kick-down assemblies. And because the methodology can be performed using UHSS which is stronger, lighter, and has a greater formability than AHSS, stronger components that have a smaller mass and, in some instances, relatively small radii and tight tolerances can be manufactured using the method 10.
For purposes of illustration,
