Patent Application
20250144692
This U.S. Patent application claims the benefit of CN patent application Serial No. 2023114557749 filed on Nov. 3, 2023 and titled “METHOD AND FIXTURE FOR LOCAL SOFTENING OF HOT STAMPED MEMBER”, the entire disclosures of which are hereby incorporated by reference.
The present invention relates to the technical field of hot stamping, and in particular to a method and fixture for local softening of a hot stamped member.
At present, the use of lightweight materials such as high-strength hot stamping steel in place of conventional steel materials has become an important way to reduce the weight of automobiles. However, since the hardness of base materials of high-strength hot stamped parts is too high, the problem of riveting difficulty is present in vehicle body assembly and the like. In order to solve this problem, it is generally necessary to perform softening treatment at a connection position on a corresponding hot stamped part, so as to lower material hardness, thereby facilitating riveting without affecting the overall performance of the part. In addition, a softened region of a hot stamped part also has a good energy-absorbing effect in the event of a vehicle collision, thereby reducing the impact on passengers within the vehicle. Therefore, hot stamped parts for vehicles often need to be locally softened. A softened region may have microstructures including ferrite and pearlite, and ferrite and pearlite have lower yield strength and greater ductility than martensite.
Existing local soft region techniques are as follows: (1) Tailor welding is performed by using ductibor 500 or ductibor 1000 and a conventional special stamping 1500 Mpa material. (2) A die soft region technique: ultra-high-strength steel is heated to the austenization temperature, and the die temperature in a region to be softened is 400° C. during thermoforming, so that the soft region structure is gradually cooled to obtain bainite, ferrite, and pearlite structures, thereby obtaining a soft region having a hardness lower than that of a fully martensitic base material. (3) Local heating and softening techniques, such as the induction heating disclosed in the patent for invention with the publication number CN 106466695 B, and the laser heating disclosed in the patent for invention with the publication number CN 116590499 A, etc. (4) A technique of performing heating per region in a heating furnace: for example, the following is disclosed in the patent for invention with the publication number CN 107552622 B: a movable shielding portion is provided in a heating furnace, so that the heating furnace is configured to heat a plurality of portions of a blank at different temperatures to form a softened region in a selected position in the blank.
In the above methods, it is difficult to control the costs incurred from tailor-welding materials. The die soft region technique has high die costs, and has high die maintenance costs at later stages. For the local heating and softening techniques of dies, the dimensional precision of parts is low, and it is difficult to control the temperature. In addition, implementation on hot stamped parts is not sufficiently flexible. For the technique of performing heating per region in a heating furnace, the one-time investment of process equipment is high, and different process equipment needs to be purchased separately for different products. Therefore, development of a more advantageous local softening technique for a hot stamped member is an urgent technical problem that needs to be solved.
In view of the above defects in the prior art, one aspect of the present invention is a method and fixture for local softening of a hot stamped member. According to the method, a hot stamping blank is subjected to local temperature control during heating to form a hot stamping blank having soft and hard regions, so that a hot stamped member that is locally softened can be formed in one step without the need for tailor welding. Therefore, die costs can be reduced, and the dimensional precision of obtained parts is high.
In order to achieve the above objective, in one aspect, the present invention provides a method for local softening of a hot stamped member, comprising the following steps:
In the local softening method, the heat-absorbing plates are used to absorb heat during the heating process and the heat-insulating blankets cover the region to be softened of the hot stamping blank to perform heat insulation, which together ensure that the temperature of a local region of the hot stamping blank is lower than the austenization temperature of other regions, so that the local region does not form martensite during rapid cooling of the part, and therefore does not become a soft region.
Further, in step S106, a heating rate of the heating furnace is 115 to 546° C./min. This feature allows the heating rate of the region to be softened of the hot stamping blank in the heating furnace to be further controlled, thereby satisfying application requirements.
Further, the heat preservation time in step S107 is determined according to the thickness of the hot stamping blank and performance requirements of the region to be softened, and is 100 s to 475 s. This feature allows the temperature eventually reached at the region to be softened of the hot stamping blank in the heating furnace to be effectively controlled, thereby satisfying application requirements.
Further, step S101 to step S109 are all performed on a conveyor belt, and the first heat-absorbing plate is laid flat on the conveyor belt. This feature facilitates improvement in efficiency of machining processes and reduction in labor costs.
Further, step S101 to step S105 and step S108 are all implemented by means of a manipulator. This feature facilitates improvement in efficiency of machining processes and reduction in labor costs.
According to another aspect, the present invention provides a fixture for local softening of a hot stamped member, comprising a hot stamping blank to be stamped, wherein a first heat-insulating blanket and a first heat-absorbing plate are sequentially stacked below a region to be softened of the hot stamping blank, and a second heat-insulating blanket and a second heat-absorbing plate are sequentially stacked thereabove.
Further, the thickness of the first heat-insulating blanket or the second heat-insulating blanket is 0.4 to 10 mm. In one aspect, this feature allows the temperature eventually reached at the region to be softened of the hot stamping blank in the heating furnace to be effectively controlled, thereby satisfying application requirements. In another aspect, spatial requirements of a heating device are not high.
Further, the thickness of the first heat-absorbing plate or the second heat-absorbing plate is 0.4 to 10 mm. This feature allows the region to be softened to have an increased thickness, and can effectively lower the core temperature during heating, thereby ensuring that the temperature of the hot stamping blank is effectively controlled.
Further, the material of the first heat-insulating blanket or the second heat-insulating blanket comprises, but is not limited to, one or a mixture of currently known materials capable of heat preservation and insulation, such as ceramic and quartz fibers, etc.
Further, the material of the first heat-absorbing plate or the second heat-absorbing plate comprises, but is not limited to, one or a mixture of currently known metal and alloy plates capable of heat transfer.
Compared with the prior art, one or more aspects of the present invention can provide the following advantages or beneficial effects:
(1) According to the present invention, the fixture can be provided so that the temperature of a local region of a hot stamping blank is effectively controlled during heating to form a hot stamping blank having soft and hard regions. Therefore, a hot stamped member that is locally softened can be formed in one step without the need for tailor welding.
(2) According to the present invention, a conventional fully-cool die can be used, thereby reducing die costs and achieving safety and reliability.
(3) According to the present invention, the size of a region to be softened can be controlled by the shape and size of a heat-insulating assembly, thereby facilitating operation, and achieving high control precision, high adaptability, and high dimensional precision of a resulting product region.
(4) The present invention can be implemented without custom modification of a heating device, thereby reducing equipment investment costs. The fixture can be reused, thereby reducing implementation costs.
The present invention and the features, the shape, and advantages thereof will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following accompanying drawings. The same reference numerals refer to the same parts throughout the accompanying drawings. The accompanying drawings are not completely drawn to scale, and the focus is to show the substance of the present invention.
Exemplary embodiments of the present disclosure will be described in further detail below with reference to the accompanying drawings. It should be understood that all of these described exemplary embodiments are merely part of rather than all of the embodiments and examples of the present invention. Instead, these exemplary embodiments are provided so that those skilled in the art can more thoroughly understand the present disclosure, and the technical content of the present disclosure can be more completely conveyed to those skilled in the art.
Furthermore, the terms “first” and “second” are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined by “first” or “second” may explicitly or implicitly include one or more of the described features.
Referring to
In the present embodiment, the heating rate of the heating furnace in step S106 may be 115 to 546° C./min, so that the heating rate of the region to be softened of the hot stamping blank in the heating furnace is further controlled, thereby satisfying application requirements. The heat preservation time in step S107 may be determined according to the thickness of the hot stamping blank and performance requirements on the region to be softened, and is 100 s to 475 s, so that the temperature eventually reached at the region to be softened of the hot stamping blank in the heating furnace is effectively controlled, thereby satisfying application requirements. Step S101 to step S109 may all be performed on a conveyor belt, and the first heat-absorbing plate 1 is laid flat on the conveyor belt 6. Step S101 to step S105 and step S108 may all be implemented by means of a manipulator.
In the local softening method provided in the present embodiment, the heat-absorbing plates are used to absorb heat during the heating process and the heat-insulating blankets cover the region to be softened of the hot stamping blank to perform heat insulation, which together ensure that the temperature of a local region of the hot stamping blank in the heating furnace is lower than the austenization temperature of other regions, so that said region does not form martensite during rapid cooling of the part, and therefore does not become a soft region.
Referring to
In the present embodiment, the thickness of the first heat-insulating blanket 2 or the second heat-insulating blanket 4 may be 0.4 to 10 mm. In one aspect, this allows the temperature eventually reached at the region to be softened of the hot stamping blank in the heating furnace to be effectively controlled, thereby satisfying application requirements. In another aspect, spatial requirements of a heating device are not high. The thickness of the first heat-absorbing plate 1 or the second heat-absorbing plate 5 may be 0.4 to 10 mm. Due to this feature, a portion to be softened of a part is not austenitized, and forms a soft region after cooling. The material of the first heat-insulating blanket 2 or the second heat-insulating blanket 4 may be one or a mixture of ceramic and quartz fibers. The material of the first heat-absorbing plate 1 or the second heat-absorbing plate 5 may be one or a mixture of metal and alloy plates.
It can be understood that the number of layers in the heat-absorbing plates and the heat-insulating blankets is not specifically defined as long as the heat transfer effect is not affected, and so may be one or more.
In order to further facilitate understanding of the technical solution of the present invention, the technical solution of the present invention is described in further detail below by using specific implementation examples.
A local softening process of a hot stamped member was as follows:
In summary, the present application provides a method and a fixture for the local softening of a hot stamped member. According to the method, a local region to be softened of a hot stamping blank is covered by a heat-insulating layer, and the heat-insulating layer is covered by a heating layer. After the hot stamping blank is fed into a heating furnace, a local temperature difference is generated, thereby forming a soft region. Then, the hot stamping blank having soft and hard regions is fed into a thermoforming machine so as to be machined into a hot stamped member. According to the present invention, a hot stamping blank is subjected to local temperature control during heating to form a hot stamping blank having soft and hard regions, so that a hot stamped member that is locally softened can be formed in one step without the need for tailor welding. Therefore, die costs can be reduced, and the dimensional precision of obtained parts is high.
Standard parts used in the present application document can be directly purchased from the market, and non-standard structural components recited in the specification can also be obtained without any doubt by performing machining directly according to common technical knowledge in the prior art. In addition, the parts and components are connected by using conventional means well established in the prior art, and all the machines, parts, and devices (for example, the hot stamping blank, the heat-absorbing plates, and the heat-insulating blankets) are conventional types in the prior art. Therefore, details will not be described herein.
The preferred embodiments of the present invention have been described above. It is to be understood that the present invention is not limited to the particular embodiments described above, and that devices and structures not described in detail should be understood to be implemented using common means in the art. Any person skilled in the art can make many possible variations and modifications to the technical solution of the present invention by using the above-disclosed methods and technical contents without departing from the scope of the technical solution of the present invention, or change the same into equivalent embodiments of equivalent variations, without affecting the substance of the present invention. Therefore, any simple changes, equivalent variations, or modifications made to the above embodiments according to the technical substance of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023114557749 | Nov 2023 | CN | national |
