Patent Application
20250066868
The present disclosure relates to press hardened steel used in vehicle structural and body members.
Press hardened steel is used in vehicle designs including but not limited to automobiles, trucks, vans, sport utility vehicles, autonomous vehicles, battery electric vehicles, farm or construction equipment, railway vehicles and the like to provide regional or local increased material strength in load-bearing components, in particular to mitigate against material collapse in impact zones of vehicle bodies such as door panels and body pillars. Previous work for induction hardening of steel not done on 22MnB5 American Iron and Steel Institute (AISI) materials was typically done on higher carbon steels. Current press hardened steel (PHS) is entirely formed in a furnace. A coating layer such as zinc is applied to the steel prior to heating for cathodic protection to improve corrosion resistance. In the furnace, a heating rate and final heating temperature must be carefully controlled to avoid melting the coating layer or generation of excess surface oxides defining scale on outer surfaces of the PHS may be formed which must be subsequently removed using a process such as shot-blasting.
Material properties of presently prepared PHS are uniform throughout a blank and throughout a finished form of the item. Uniform material properties which are increased to maximize material strength, for example in vehicle crush zones and pillars, increase an overall component weight and cost and may not allow a desired deformation of the component under impact loading to allow localized absorption and dispersion of the impact loading.
Thus, while current systems and methods to produce and utilize press hardened steel achieve their intended purpose, there is a need for a new and improved system and method to produce and use press hardened steel.
According to several aspects, a method to achieve variable properties of a vehicle component using a coating free press hardened steel (CFPHS) comprises: transferring a blank of a CFPHS material having base blank properties into a heating unit having multiple induction heating coils; heating the blank within the heating unit to create a modified blank having differing modified blank properties throughout the modified blank compared to the base blank properties; moving the modified blank out of the heating unit into a die; and forming a shaped part by operation of the die creating a finished CFPHS part.
In another aspect of the present disclosure, the method further includes tailoring mechanical and surface qualities of the finished CFPHS part using a localized heating.
In another aspect of the present disclosure, the method further includes performing the localized heating employing one a uniform heating rate and a tailored or a variable heating rate to achieve a desired temperature profile.
In another aspect of the present disclosure, the method further includes uniformly heating across the blank or in predetermined areas within the blank to enable a selective mechanical and surface property profile defining the modified blank.
In another aspect of the present disclosure, the method further includes energizing the induction heating coils using a variable power supply having a variable frequency device.
In another aspect of the present disclosure, the method further includes generating varying and localized current intensities within the heating unit and across the blank.
In another aspect of the present disclosure, the method further includes: generating variable heating rates using the variable power supply; and providing zoned hold temperatures for the blank.
In another aspect of the present disclosure, the method further includes operating a multi-axis transfer device to manipulate the blank within the heating unit to create the modified blank.
In another aspect of the present disclosure, the method further includes creating the CFPHS material by: incorporating carbon (C) in an alloy matrix having a C concentration of greater than or equal to about 0.05% to less than or equal to about 0.35 wt. %; including chromium (Cr) at a Cr concentration of greater than or equal to about 1 wt. % to less than or equal to about 9 wt. %; including silicon (Si) at a Si concentration of greater than or equal to about 0.5 wt. % to less than or equal to about 2 wt. %; including Manganese (Mn) at a Mn concentration of greater than or equal to about 0.5 wt. % to less than or equal to about 2.5 wt. %; and providing a balance of iron (Fe).
In another aspect of the present disclosure, the method further includes creating the CFPHS material by: including with the alloy matrix martensite greater than or equal to about 95 vol. %; disposing a first layer directly on the alloy matrix, the first layer being continuous, and having a thickness of greater than or equal to about 0.01 μm to less than or equal to about 10 μm; and enriching with Cr and Si.
According to several aspects, a method to achieve variable properties of a component using a coating free press hardened steel, comprising: transferring a blank of a coating free press hardened steel (CFPHS) material into a heating unit having multiple induction heating coils; energizing the induction heating coils using a variable power supply; generating varying and localized current intensities within the heating unit and across the blank by operating predetermined ones of the induction heating coils; heating the blank within the heating unit to create a modified blank having differing modified blank properties throughout the modified blank compared to properties of the blank prior to transferring the blank into the heating unit; and operating a multi-axis transfer device to manipulate the blank within the heating unit when heating the blank to create the modified blank.
In another aspect of the present disclosure, the method further includes operating a variable frequency device together with the variable power supply.
In another aspect of the present disclosure, the method further includes: moving the modified blank out of the heating unit into a die using the multi-axis transfer device; and forming a shaped part including operating the die to create a finished CFPHS part.
In another aspect of the present disclosure, the method further includes forming a shaped part by operation of the die creating a finished CFPHS part.
In another aspect of the present disclosure, the method further includes tailoring mechanical properties of the modified blank via operation of the induction heating coils to achieve an austenitization temperature in at least one zone of the modified blank and heating the modified blank to sub-critical temperatures in areas other than the at least one zone to achieve tailored mechanical properties within the modified blank.
In another aspect of the present disclosure, the method further includes: mitigating an edge effect of overheating risk of the modified blank by tuning a current input and a frequency input to the induction heating coils or controlling a distance from one coil of the multiple induction heating coils for heating; and varying an energy into the induction heating coils to vary material properties throughout a modified blank thickness.
In another aspect of the present disclosure, the method further includes tailoring an oxide layer of the CFPHS material to provide an optimal thickness ranging between a no oxide layer to a maximum allowable oxide layer in differing areas of the modified blank.
According to several aspects, a method to achieve variable properties of a component using a coating free press hardened steel comprises: transferring a blank of a coating free press hardened steel (CFPHS) material into a heating unit having multiple induction heating coils, the blank having one of multiple shapes including but not exclusive to flat, rod, wire, coil and bar; energizing the induction heating coils using a variable power supply; generating varying and localized current intensities within the heating unit and across the blank by operating predetermined ones of the induction heating coils to create multiple induction heating patterns across the blank to achieve targeted zones of surface properties of the blank; and completing heating of the blank within the heating unit to create a modified blank having differing modified blank properties throughout the modified blank compared to properties of the blank prior to transferring the blank into the heating unit.
In another aspect of the present disclosure, the method further includes: operating a multi-axis transfer device to manipulate the blank within the heating unit during modification of the blank into the modified blank; moving the modified blank out of the heating unit into a die; and forming a shape of the modified blank defining a finished CFPHS material component in the die.
In another aspect of the present disclosure, the method further includes: heating the blank within the heating unit from a room temperature up to a range including approximately 500° C. to approximately 950° C.; and applying a heating rate of approximately 20° C./second up to approximately 500° C./second when heating the blank.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
When a component, element or layer is referred to as being “on”, “engaged to”, “connected to”, or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other component, element, or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on”, “directly engaged to”, “directly connected to”, or “directly coupled to” another element or layer, there may be in intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion, such as “between” versus “directly between”, “adjacent” versus “directly adjacent”, and the like. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Referring to
A material of the CFPHS blank 12 provides an alloy matrix including carbon (C) at a concentration of greater than or equal to 0.05% to less than or equal to about 0.35 wt. %, chromium (Cr) at a concentration of greater than or equal to about 1 wt. % to less than or equal to about 9 wt. %, silicon (Si) at a concentration of greater than or equal to about 0.5 wt. % to less than or equal to about 2 wt. %, including Manganese (Mn) at a Mn concentration of greater than or equal to about 0.5 wt. % to less than or equal to about 2.5 wt. %, and a balance of iron (Fe). The alloy matrix is greater than or equal to about 95 vol. % martensite, a first layer disposed directly on the alloy matrix, the first layer being continuous, having a thickness of greater than or equal to about 0.01 μm to less than or equal to about 10 μm, and including an oxide enriched with Cr and Si, and a second layer disposed directly on the first layer, the second layer including an oxide enriched with Fe.
According to several aspects the heating unit 14 defines an induction heating oven whose features are further defined in reference to
Referring to
According to several aspects, induction heating is used for heat treatment of the CFPHS base material defining the blank 12. The blank 12 is transferred for example by a roller set 30 into the heating unit 14. The heating unit 14 may include at least one and according to several aspects, multiple induction heating coils 32. The induction heating coils 32 are energized using a variable power supply 34 which may include a variable frequency device 36. Using the variable power supply 34 with the variable frequency device 36, varying and localized current intensities may be generated within the heating unit 14 and across the blank 12 by energizing or varying a power supplied to predetermined ones of the multiple induction heating coils 32. Using the variable power supply 34 variable heating rates may be provided and zoned hold temperatures may also be provided for the blank 12. An edge effect of overheating risk is mitigated via use of the multiple induction heating coils 32, by fine tuning a current and a frequency input or controlling a distance from an exemplary coil 38 of the multiple induction heating coils 32 and/or a coil edge 40 for heating. According to several aspects, the blank 12 is induction heated within the heating unit 14 from room temperature up to a range including approximately 500° C. to approximately 950° C. According to several aspects, a heating rate of approximately 20° C./second up to approximately 500° C./second is used.
With continuing reference to
Induction heating achieves targeted surface oxide layer properties within the CFPHS material. Mechanical properties may be varied via induction heating through the CFPHS blank thickness 50. Varying mechanical properties are also produced using induction heating across the CFPHS blank surface. Using induction heating to target different locations within the CFPHS blank or component further achieves variable surface characteristics. Induction heating permits targeting different locations within a CFPHS component to achieve variable mechanical properties. It is noted an initial material form of the blank 12 is not limited to flat blanks as shown. Other product shapes may be used, for example but not exclusive to: rod, wire, coil, bar and the like within the scope of the present disclosure.
According to several aspects, the method to achieve variable properties of a component using coating free press hardened steel (CFPHS) 10 of the present disclosure provides variable properties within a CFPHS blank and in a finished component using localized variable heating methods such as induction heating. The method to achieve variable properties of a component using coating free press hardened steel (CFPHS) 10 of the present disclosure allows tailoring a CFPHS oxide layer for optimal thickness from a no oxide layer to a maximum allowable oxide layer in different areas of a component. The use of induction heating on CFPHS to achieve desired press hardened properties is enabled using CFPHS material of the present disclosure. The method to achieve variable properties of a component using coating free press hardened steel (CFPHS) 10 of the present disclosure renders conventional furnace heating unnecessary due to use of induction heating to achieve the desired heat treatment of CFPHS. It is noted the desired press hardened properties of the present disclosure cannot be achieved using conventional American Iron and Steel Institute (AISI) coated press hardened steel of any base grade, nor with bare (uncoated) press hardened steel without detrimental effects on a surface quality of the component or other necessary subsequent or preceding operations, such as shot blast for bare material and pre-diffusion for AISI coated material.
The method to achieve variable properties of a component using coating free press hardened steel (CFPHS) 10 of the present disclosure permits tailored mechanical properties to be accomplished via induction heating, for example, to the austenitization temperatures in one or more areas of the component and wherein the component is heated to sub-critical temperatures in other areas to achieve tailored mechanical properties within the component. This is not achievable by using only a conventional furnace. As used herein, austenitization defines a heat treatment process for steel and other ferrous alloys where a material is heated above its critical temperature and transformed from ferrite to an austenite crystal structure which allows the austenite to absorb carbon from the iron carbides in a carbon steel. When followed by a quenching process, the austenitized material becomes hardened.
Using induction heating, multiple zones of varying mechanical properties may be achieved in the component using induction coils. Current specialized non-induction coil furnaces typically produce this effect with limitations of a number of zones possible. This effect is not achievable using only a conventional furnace.
Using induction heating, targeted zones of desired surface properties may be achieved by varying an induction heating pattern. Varying an induction heating pattern is not achievable using only a conventional furnace. A CFPHS without a coating and with a stable oxide layer enables induction hardening without the risk of melting or excess surface oxide (scale).
A method to achieve variable properties of a component using coating free press hardened steel (CFPHS) 10 of the present disclosure offers several advantages. These include using induction heating to heat treat CFPHS components to reduce a cost of capital investment due to a more compact nature of induction hardening equipment and a reduced complexity of induction tooling over furnace heating. Maintenance of the induction equipment may be less expensive and involved than furnace equipment, leading to cost reduction for the component producer. Varying mechanical properties within a CFPHS blank and a finished component reduces the complexity of an assembly with multiple components of separate material grades. Using induction heating on a CFPHS component may reduce product cost and may increase performance of the component and provide a complexity reduction. Varying an oxide layer in selected areas of the CFPHS component also allows for improved joining in predetermined areas which allows an assembly to be stronger and better integrated.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023110864536 | Aug 2023 | CN | national |
