METHOD AND SYSTEM FOR USING AIR GAPS IN HOT-STAMPING TOOLS TO FORM TAILOR TEMPERED PROPERTIES

- MAGNA INTERNATIONAL INC.

A sheet metal blank is hot-stamped between first and second tool surfaces of first and second die tools, respectively, to form a hot-stamped product. That product is then heat treated between the first and second tool surfaces. An actively cooled portion of the tool surfaces quenches part of the hot-stamped product to form a hardened zone. An actively heated portion of the tool surfaces slows heat transfer from the hot-stamped product to the heated portion, which causes the hot-stamped product to have a soft zone. A matrix of insulating gaps is formed in the heated portion to further slow the rate of heat transfer from the hot-stamped product to the heated portion. The insulating gaps may facilitate the use of a lower-temperature heated portion, which may consequently save energy and result in the heated portion having greater wear resistance and longer life.

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Description
CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. Provisional Patent Application No. 62/805,232, filed on Feb. 13, 2019, which is hereby expressly incorporated by reference in its entirety.

BACKGROUND 1. Field of the Invention

Various embodiments relate generally to a hot forming system and method for producing vehicle parts.

2. Description of Related Art

Vehicle manufacturers strive to provide vehicles that are increasingly strong, light and inexpensive. One process used to form vehicle body parts is a hot-forming method in which heated blanks of steel are hot-stamped and quenched (for rapid cooling and hardening) in a hot forming die. A pre-heated sheet stock may be typically introduced into a hot forming die, formed to a desired shape and quenched subsequent to the forming operation while in the die to thereby produce a heat treated product. The known hot forming dies for performing the stamping and quenching steps typically employ water cooling passages (for circulating cooling water through the hot forming die) that are formed in a conventional manner. In some applications, it may be desirable to cool certain portions of the stamped metal at a slower rate than other portions. Such portions of the stamped part are heated by the stamping die so that the rate of cooling is slowed relative to the portions of the part that are exposed to portions of the die that receive cooling fluid. The more slowly cooled portions of the part will remain softer (more ductile) than the portions of the part subject to rapid cooling (quenching). To heat portions of the die, cartridge heaters can be provided within a form block of the die so that heat is applied to areas of a product being stamped.

SUMMARY

One or more non-limiting embodiments provide a hot-stamping apparatus and hot stamping method through which a sheet metal blank is hot-stamped between first and second tool surfaces of first and second die tools, respectively, to form a hot-stamped product. That hot-stamped product is then heat treated between the first and second tool surfaces. An actively cooled portion of the tool surfaces quenches part of the hot-stamped product to form a hardened zone. An actively heated portion of the tool surfaces slows heat transfer from the hot-stamped product to the heated portion, which causes the hot-stamped product to have a soft zone. A matrix of insulating gaps is formed in the heated portion to further slow the rate of heat transfer from the hot-stamped product to the heated portion. The insulating gaps may facilitate the use of a lower-temperature heated portion, which may consequently save energy and result in the heated portion having greater wear resistance and longer life.

The below-listed claims disclose additional non-limiting embodiments.

One or more of these and/or other aspects of various embodiments, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. In one embodiment, the structural components illustrated herein are drawn to scale. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. In addition, it should be appreciated that structural features shown or described in any one embodiment herein can be used in other embodiments as well. As used in the specification and in the claims, the singular form of “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

All closed-ended (e.g., between A and B) and open-ended (greater than C) ranges of values disclosed herein explicitly include all ranges that fall within or nest within such ranges. For example, a disclosed range of 1-10 is understood as also disclosing, among other ranges, 2-10, 1-9, 3-9, etc. Similarly, where multiple parameters (e.g., parameter C, parameter D) are separately disclosed as having ranges, the embodiments disclosed herein explicitly include embodiments that combine any value within the disclosed range of one parameter (e.g., parameter C) with any value within the disclosed range of any other parameter (e.g., parameter D).

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of various embodiments as well as other objects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:

FIG. 1 is a perspective view of a lower die of a hot stamping system;

FIG. 2 is a perspective view of a hot-stamped product manufactured by the hot stamping system in FIG. 1;

FIG. 3 is a perspective view of a heated portion of the lower die in FIG. 1;

FIG. 4 is a top view of the heated portion shown in FIG. 3;

FIG. 5 is an enlarged top view of the portion 5-5 in FIG. 4;

FIG. 6 is a cross-sectional view of the heated portion of the lower die in FIG. 5, taken along the line 6-6 in FIG. 5;

FIG. 7 is a cross-sectional view of the heated portion of the hot stamping system in FIG. 1;

FIG. 8 is an enlarged cross-sectional view of the portion 8-8 shown in FIG. 7; and

FIG. 9 is a further enlarged cross-sectional view of FIG. 8.

 DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

This disclosure relates to a hot-stamping system 10 and method for producing a hot-stamped product 20 with tailored properties. Such hot-stamped products 20 may include a vehicle body member or panel, or a pillar of an automobile. Forming “tailored” properties of products or parts using the system 10 and method herein described provides shaped parts that have regions of high strength and hardness as well as other regions of reduced strength, ductility, and hardness. When the herein described forming system 10 is used as part of a method of forming such a tailored product or part, such as vehicle pillars (A or B pillars), the resulting vehicle structure has a complex configuration that includes regions that are engineered to deform in a predetermined manner upon receiving a force resulting from a vehicular crash, for example.

As shown in FIGS. 1 and 7, the system 10 comprises upper and lower dies 30, 40 having upper and lower die tool surfaces 30a, 40a, respectively. FIG. 1 illustrates the lower die 30 and lower tool surface 30a. It should be understood that the upper die 40 and upper tool surface 40 generally has a mating structure and surface. The upper and lower dies 30, 40 are shaped and configured to mate with each other to form a die cavity therebetween. The dies 30, 40 receive therebetween and hot stamp a workpiece/metal blank (e.g., a piece of hot sheet metal, e.g., steel such as press hardened steel (PHS), boron steel, with or without coatings (e.g., aluminum coating)).

As shown in FIG. 1, the lower tool surface 30a is divided into heated and cooled portions 50a, 60a. As shown in FIG. 1, the cooled portions 60a and heated portion 50a may be formed by discrete die portions 60, 50, respectively, of the lower die 30 that fit together to define the overall die 30. FIGS. 3 and 4 illustrate the heated lower die portion 50 that defines the heated portion 50a of the lower tool surface 50a.

As shown in FIG. 7, the heated die portion 50 of the lower die 30 (as well as the corresponding heated upper die portion shown in FIG. 7) includes one or more heaters 70 that are positioned and configured to heat the heated tool surface portion 50a. In the illustrated embodiment, the heater 70 comprise cartridge heaters, but could alternatively comprise any other type of suitable heater (e.g., passages through which heated fluid passes). The cooled die portions 60 of the lower die 30 (as well as the corresponding cooled upper die portions of the upper die 40) include one or more coolers (e.g., coolant passages through which an actively cooled (e.g., via a refrigeration system) coolant flows).

In the illustrated embodiment, the upper and lower dies surfaces 30a,40a in the heated portion 50a of the dies 30, 40 are both heated. However, according to alternative embodiments, only the upper die 40 or only the lower die 30 could be heated. Similarly, in the illustrated embodiment, the upper and lower tool surfaces 60a in the cooled portions 60 of the dies 30, 40 are both cooled. However, according to alternative embodiments, only the upper die 40 or only the lower die 30 could be cooled.

In the illustrated embodiment, the dies 30, 40 form one continuous cooled portion and one continuous heated portion. However, according to various alternative embodiments, additional and/or fewer heated and/or cooled portions may be provided to accommodate the particular hardness and ductility requirements of any desired product (e.g., alternating hard and soft portions of a work piece to provide an accordion crumple zone; a plurality of soft portions surrounded by a large hardened portion, etc.).

As shown in FIGS. 3-9, a matrix 90 of insulating gaps 100 is formed in the heated surface portions 50a of the tool surfaces 30a, 40a of the upper and lower dies 30, 40. The matrix 90 divides the heated surface portion 50a into (1) a non-contact surface area formed by the insulating gaps 100, and (2) a contact surface area 110 where the gaps 100 are not disposed. The contact area 110 is shaped and configured to contact the blank during hot forming and contact the resulting hot-stamped product during heat treating. In contrast, the non-contact area formed by the gaps 100 is shaped and configured to not contact the blank during hot forming and not contact the hot-stamped product during heat treating.

As used herein, the area of any surface is its actual surface area. Thus, the depth and shape of the depressions that form the gaps 100 will slightly impact the area of the gaps 100.

As shown in FIGS. 6 and 9, the gaps 100 create depressions relative to the contact area 110 surrounding the gaps 100. As shown in FIG. 6, the gaps 100 have a maximum depth d relative to the surface of the contact area 110. According to various embodiments, the maximum depth d of at least a D number of the air gaps 100 is (a) at least 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and/or 5.0 mm, (b) less than 20, 15, 10, 7.5, 5.0, 4.5, 4.0, 3.5, 3.0, 2.5, 2.0, 1.5, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, and/or 0.2 mm, and/or (c) between any two such upper and lower values (e.g., between 0.01 and 20 mm, between 0.05 and 1.0 mm, between 0.1 and 0.5 mm, etc.). According to various embodiments, the depth d is about 0.25 mm for at least 10 of the gaps 100. According to various embodiments, D is (a) at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, and/or 100, (b) less than 1000, 500, 400, 300, 200, 150, 100, 90, 80, 70, 60, 50, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, and/or 6, and/or (c) between any two such values (e.g., between 2 and 1000, between 5 and 500, etc.). The depths d of different air gaps 100 may differ, even within a single embodiment.

According to various embodiments, gaps 100 each have an area a as viewed in a direction perpendicular to the contact area 110 surrounding the gap 100. According to various embodiments, the area a of an A number of the gaps 100 is (a) at least 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1250, 1500, 2000, 2500, 3000, 3500, 4000, 5000, 7500, and/or 10000 mm2, (b) less than 10000, 7500, 5000, 4000, 3000, 2500, 2000, 1500, 1250, 1000, 900, 800, 700, 600, 500, 400, 300, 200, 100, 90, 80, 70, 60, 50, 40, 35, 30, 25, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, and/or 6 mm2, and/or (c) between any two such upper and lower values (e.g., between 5 and 10000 mm2, between 10 and 1000 mm2, between 15 and 200 mm2, between 200 and 1000 mm2). According to various embodiments, A is (a) at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, and/or 100, (b) less than 1000, 500, 400, 300, 200, 150, 100, 90, 80, 70, 60, 50, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, and/or 6, and/or (c) between any two such values (e.g., between 2 and 1000, between 5 and 500, etc.).

As shown in FIGS. 4-5, the area a of an A number of the gaps 100 is generally rectangular, with the rectangular gaps 100 arranged in a rectilinear grid of gaps 100. According to one or more embodiments and as shown in FIG. 5, the gaps 100 may comprise 20 m×20 mm squares on a 25 mm pitch, which results in 5 mm wide contact surfaces 110 separating adjacent gaps 100. As shown in FIGS. 3-4, others of the gaps 100 have an area formed by different shapes. According to yet other embodiments, an area a of an A number of the gaps 100 may have any other suitable shape (e.g., triangles or hexagons) and be laid out in any suitable matrix (e.g., a hexagonal or triangular grid, a matrix of mixed polygonal gaps 100, a matrix of irregular gaps 100 having a variety of different shapes and areas).

According to various embodiments, a shape and size of the gap(s) 100 and contact surface(s) 110 is chosen so as to the contact surface(s) 110 are sufficiently spread out over the heated portion 50a that they support the blank during said hot-stamping and substantially prevent the blank from moving into the volume of the air gap(s) 100 during the hot-stamping. According to various embodiments, overlaying a circle with a diameter c onto anywhere within the heated portion 50a results in the circle overlaying at least a portion of the contact surface(s) 110. According to various embodiments, the diameter c is (a) less than 10000, 7500, 5000, 4000, 3000, 2000, 1000, 900, 800, 700, 600, 500, 400, 300, 250, 200, 150, 100, 90, 80, 70, 60, 50, 40, 30, 20, and/or 10 mm and (b) greater than 0, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, and/or 100 mm.

According to various embodiments, the cumulative contact surface 110 area within the heated portion 50 may comprise at least (a) 20, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80% of the area of the heated portion 50, (b) less than 20, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80% of the area of the heated portion 50, and/or (c) between any two such upper and lower values (e.g., between 25 and 80%, between 26 and 50%, etc.). According to one or more embodiments, the contact surface comprises about 36% of an area of the heated portion 50.

According to various embodiments, a surface area of the heated portion 50a (including both the contact surface area 110 and a surface area of the gaps 100) is (1) at least 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1250, 1500, 2000, 2500, 3000, 4000, 5000, 7500, 10000, 15000, 20000, 30000, 40000, 50000, 75000, and/or 100000 mm2, (2) less than 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1250, 1500, 2000, 2500, 3000, 4000, 5000, 7500, 10000, 15000, 20000, 40000, 50000, 60000, 75000 mm2, and/or (3) between any two such upper and lower values (e.g., between 100 and 100000 mm2, between 200 and 20000 mm2). According to various embodiments, the surface area of the heated portion 50a is the same as the and surface area of the corresponding soft zone 20a.

In the illustrated embodiment, each air gap 100 is isolated from every other gap 100 by the contact surface 110. According to various embodiments, each gap 100 is completely surrounded by the contact surface 110. However, according to alternative embodiments, some or all of the gaps 100 may be interconnected (e.g., by a break in the contact surface 110 that separates two adjacent gaps 100). According to some embodiments, such interconnection may result in isolated islands of contact surface 110 surrounded completely by one or more gaps 100 (e.g., a matrix/grid of contact surfaces 110 separated by gaps 100, for example formed by reversing the relative positions of the gaps 100 and contacts surfaces 110 in FIG. 5).

According to various embodiments, the matrix extends over multiple gaps 100 in orthogonal directions. For example, with respect to a matrix comprising a rectilinear grid as shown in FIG. 5, the matrix creates a rectilinear grid having x rows and y columns, where x and y are each at least 2.

According to various embodiments, the gaps 100 each have a volume v. According to various embodiments, the volume v of a V number of the gaps 100 is (a) at least 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1250, 1500, 2000, 2500, 3000, 3500, 4000, 5000, 7500, 10000, 12500, 15000, 17500, and/or 20000 mm3, (b) less than 20000, 17500, 15000, 12500, 10000, 7500, 5000, 4000, 3000, 2500, 2000, 1500, 1250, 1000, 900, 800, 700, 600, 500, 400, 300, 200, 100, 90, 80, 70, 60, and/or 50 mm3, and/or (c) between any two such upper and lower values (e.g., between 20 and 20000 mm3, between 100 and 10000 mm3, etc.). According to various embodiments, V is (a) at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, and/or 100, (b) less than 1000, 500, 400, 300, 200, 150, 100, 90, 80, 70, 60, 50, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, and/or 6, and/or (c) between any two such values (e.g., between 2 and 1000, between 5 and 500, etc.).

According to various embodiments, A, D, and V may be the same or different from each other.

According to various embodiments, the gaps 100 may be formed by any suitable manufacturing method, including, without limitation, material removal methods (e.g., machining/drilling/abrading the gaps 100 into the surface of the dies), additive manufacturing (e.g., building up the contact surfaces adjacent to the gaps 100 (e.g., via 3D printing) to form the gaps 100), casting or forging the gaps 100 into the surface of the dies (e.g., at the same time as the contact surfaces are formed, or thereafter), etc.

While the matrix of gaps 100 has been described in detail with respect to the lower die 30, it should be understood that a mirror-image (or non mirror-image) matrix of gaps 100 may also be formed on the upper die 40, as shown in FIGS. 7-9. The corresponding portions of the upper die 40 may also be heated via heaters. Similarly, portions of the upper die 40 that mate with the cooled portions 60 may also be cooled.

As shown in FIG. 9, the matrix of insulating gaps 100 are shaped and configured to create a clearance between the hot-stamped product 20 and the heated portions 50a in the area of each of the insulating gaps 100 during the hot-stamping and heat-treating. According to various embodiments, the gaps 100 may be filled with air or another insulator (e.g., ceramic with a low heat conductivity). Consequently, the gaps 100 slow heat transfer from the hot-stamped product 20 to the heated portion 50a.

The cooled portion 60 causes heat to quickly flow from the corresponding zone 20b of the product 20 to the cooled portion 60 during the heat-treating, which results in quenching and the formation of a hardened zone 20b (shown in FIG. 2) in the product 20.

While the heated portion 50 is heated, the temperature of the heated portion 50 is still lower than the temperature of the blank/product 20 when the hot-stamping process begins, which causes heat to flow from the product 20 to the heated portion 50 during the hot-stamping and, to a greater extent, during heat-treating. As a result, the heating of the heated portion 50 causes heat to transfer more slowly from the hot-stamped product 20 to the heated portion 50. Additionally, the insulating gaps 100 slow the transfer of heat from the hot-stamped product 20 to the heated portion 50 via the gaps 100. Heating the heated portion 50 and providing the matrix of insulating gaps 100, causes a corresponding zone 20a of the hot-stamped product 20 that is pressed between the heated portions 50 of the die to be cooled relatively slowly, which results in a soft zone 20a of the hot-stamped product 20 that is relatively softer and more ductile than the hardened zone 20b of the product 20 and contains less martensite than the hardened zone 20b.

The rate of heat transfer from the hot-stamped product 20 to the heated portion 50 is a function of the temperature gradient between the two. Heating the heated portion 50 reduces the temperature gradient, which slows heat transfer and results in a softer, more ductile zone 20a in the product 20. However, increasing the temperature of the heated portion 50 to reduce that gradient can be expensive due to energy costs and can detrimentally increase wear on the dies 30, 40 because hotter tools wear more easily than lower temperature tools.

The heat transfer rate from the hot-stamped product 20 to the heated portion 50 is also a function of the heat transfer coefficient of the gaps 100. The air gaps 100 provide insulation, which slows the transfer of heat from the hot-stamped product 20 to the heated portion 50. This slowing of the heat transfer rate facilitates the counterbalancing use of a larger temperature gradient between the hot-stamped product 20 and heated portion 50, while still providing a soft zone 20a. That larger temperature gradient means that the temperature of the heated portion 50 can be lower, which reduces energy cost and increases the working lifespan of the heated portions 50 of the dies 30, 40. According to various embodiments, the working lifespan of the heated portions 50a may be extended by at least 5000, 10000, 15000, and/or 20000 hot-stamping cycled between repair/resurfacing.

According to various embodiments, during the hot stamping and heat treating, a maximum temperature of one or more of the heated portions 50a of the tool surface (and/or a maximum temperature within the core of one or more of the heated portions 50 of the die) is (a) at least 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100° C. cooler than a red hardness temperature of the tool material that forms the heated portion 50a and/or 50, (b) less than 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300° C. cooler than a red hardness temperature of the tool material that forms the heated portion 50a or 50, and/or (c) between 1 and 300° C. cooler than a red hardness temperature of the tool material that forms the heated portions 50a and/or 50, between 5 and 150 ° C. cooler than a red hardness temperature of the tool material that forms the heated portions 50a and/or 50, and/or between 10 and 100° C. cooler than a red hardness temperature of the tool material that forms the heated portions 50a and/or 50. According to various embodiments keeping the heated portion 50a of the surface of the die 50 below (and preferably well below) its red hardness temperature will reduce wear and tear on the die portion 50, 50a. According to various embodiments, keeping the core of the heated portion 50 of the die below (and preferably well below) its red hardness temperature tends to reduce the thermal-expansion-caused deformation of the die (and resulting shape errors in the stamped part). Despite this relatively lower maximum temperature of the tool material that forms the heated portions 50a, the air gaps 100 slow the rate of cooling of the hot stamped product sufficiently that the a hardness throughout the resulting soft zone 20a of the heat treated product (i.e., upon completion of the heat treatment) is advantageously low, e.g., y, wherein y is (a) less than 400, 350, 300, 250, 240, 230, 220, 210, 200, and/or 190 Hv, (b) at least 100, 120, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 300, 350, and/or 400 Hv, and/or (c) between any two such values (e.g., between 100 and 400 Hv, between 140 and 300 Hv, between 150 and 250 Hv, between 180 and 220 Hv).

According to various embodiments, the blank material and cooled portion 60 result in a hardened zone 20b with a hardness, h, wherein h is (a) greater than or equal to 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, 500, 525, 550, 575, 600, 625, 650, 675, and/or 700 Hv, (b) less than or equal to 700, 675, 650, 635, 600, 575, 550, 525, 500, 475, and/or about 450 Hv, and/or (c) between any two such upper and lower valued (e.g., between 225 and 600 Hv, between 250 and 550 Hv, between 350 and 600 Hv, between 400 and 550 Hv, etc.).

According to various embodiments, the tool material that forms the heated portion 50a may comprise any suitable material: W360 steel, which has a red hardness of 580° C.; S600 with a red hardness of 610° C., Revolma with a red hardness of 630° C. There is a tradeoff between the advantageous higher red hardness temperatures of tool materials such as S600 or Revolma, and their correspondingly increased brittleness.

The foregoing illustrated embodiments are provided to illustrate the structural and functional principles of various embodiments and are not intended to be limiting. To the contrary, the principles of the present invention are intended to encompass any and all changes, alterations and/or substitutions thereof (e.g., any alterations within the spirit and scope of the following claims).

Claims

1. A hot-stamping method comprising:

hot-stamping a metal blank between first and second tool surfaces of first and second die tools, respectively, to form a hot-stamped product; and
heat treating the hot-stamped product between the first and second tool surfaces, said heat treating comprises: using an actively cooled portion of at least one of the first and second tool surfaces to form a first zone in the hot-stamped product, and using an actively heated portion of at least one of the first and second tool surfaces to form a second zone in the hot-stamped product, wherein the heated portion is heated by a heater that is thermally connected to the heated portion,
wherein the heated portion comprises a combination of (1) one or more insulating gaps that cumulatively define a non-contact surface area of the heated portion, wherein the non-contact surface area does not contact the hot-stamped product during the heat treating and (2) one or more contact surfaces that define a contact surface area of the heated portion and contact the hot-stamped product during the heat treating,
wherein the one or more insulating gaps slow heat transfer from the hot-stamped product to the heated portion during said heat treating, and
wherein the heat treating results in a hardness throughout the second zone of less than y Hv, wherein y is 350 Hv.

2. The method of claim 1, wherein a maximum temperature of the heated portion during said hot-stamping and heat treating is at least x° C. cooler than a red hardness temperature of a tool material that forms the heated portion, wherein x is 1.

3. The method of claim 2, wherein x is 25 and y is 220.

4. The method of claim 3, wherein the heat treating results in a hardness in the first zone of at least 350 Hv.

5. The method of claim 3, wherein the heat treating results in a hardness in the first zone of at least 400 Hv.

6. The method of claim 3, wherein:

the tool material comprises W360; and
the maximum temperature of the heated portion during said hot-stamping is less than 600° C.

7. The method of claim 1, wherein the heat treating results in a hardness in the second zone of less than 220 Hv and a hardness in the first zone of at least 400 Hv.

8. The method of claim 1, wherein a maximum temperature in a core of the first and second die tools during said hot-stamping and heat treating is at least x° C. cooler than a red hardness temperature of a tool material that forms the first and second die tools, wherein x is 1.

9. The method of claim 1, wherein:

an area of the heated portion is at least 10000 mm2;
the contact surface area occupies less than 50% of the area of the heated portion; and
the contact and non-contact surface area is shaped such that overlaying a circle with a diameter c onto anywhere within the area of the heated portion results in the circle overlaying at least a portion of the contact surface area, wherein c is less than 75 mm.

10. The method of claim 1, wherein the heat treating results in a hardness throughout the second zone of between 180 and 220 Hv.

11. The method of claim 10, wherein the heat treating results in a hardness in the second zone of at least 350 Hv.

12. The method of claim 1, wherein the insulating gaps each comprise air gaps.

13. The method of claim 1, wherein the heated portion comprises a matrix of (1) said one or more insulating gaps or (2) said one or more contact surfaces.

14. The method of claim 13, wherein the matrix comprises a grid of (1) said one or more insulating gaps or (2) said one or more contact surfaces.

15. The method of claim 13, wherein:

the heated portion comprises first and second heated portions of the first and second tool surfaces, respectively; and
the matrix comprises first and second matrices formed in the first and second heated portions, respectively.

16. The method of claim 1, wherein each of at least 5 of said insulating gaps occupies an area of at least 20 mm2.

17. The method of claim 1, wherein each of at least 5 of said insulating gaps are at least 0.1 mm deep.

18. The method of claim 1, wherein each of at least 5 of said insulating gaps have a volume of at least 100 mm3.

19. The method of claim 1, wherein, during said heat treating, active heating of the actively heated portion slows a transfer of heat from the hot-stamped product to at least one of the first and second die tools.

20. A hot-stamping system comprising:

a first die having a first tool surface;
a second die having a second tool surface, the first and second dies being configured to mate with each other so that the first and second tool surfaces form a die cavity therebetween so as to receive a metal blank therein and hot-stamp the metal blank into a hot-stamped product;
a cooler positioned and configured to cool a cooled portion of at least one of the first and second tool surfaces;
a heater positioned and configured to heat a heated portion of at least one of the first and second tool surfaces; and
the heated portion comprises a matrix of (1) insulating gaps separated by contact surfaces, or (2) contact surfaces separated by insulating gaps,
wherein the insulating gaps are shaped and configured to create a clearance between the hot-stamped product and the heated portion in the area of each of the insulating gaps after the metal blank is hot-stamped,
wherein the contact surfaces are shaped and configured to contact the hot-stamped product after the metal blank is hot-stamped,
wherein the insulating gaps are shaped and configured to slow heat transfer from the hot-stamped product to the heated portion.

21. The hot-stamping system of claim 20, wherein the insulating gaps each comprise air gaps.

22. The hot-stamping system of claim 20, wherein:

the hot-stamping system is shaped and configured to heat treat the hot-stamped product between the first and second tool surfaces;
the hot-stamping system is shaped and configured to use the cooled portion to form a first zone in the hot-stamped product during the heat treating;
the hot-stamping system is shaped and configured to use the heated portion to form a second zone in the hot-stamped product; and
the first zone is harder than the second zone.

23. The hot-stamping system of claim 22, wherein the heated portion is divided into (1) a non-contact area that is formed by the insulating gaps and is configured not to contact the hot-stamped product during said heat treating, and (2) a contact area that is shaped and configured to contact the hot-stamped product during said heat treating.

24. The hot-stamping system of claim 22, the heater is positioned and configured to slow a transfer of heat from the hot-stamped product to at least one of the first and second die tools during the heat treating.

25. The hot-stamping system of claim 20, wherein the matrix comprises a grid.

26. The hot-stamping system of claim 20, wherein each of at least 5 of said insulating gaps occupies an area of at least 20 mm2.

27. The hot-stamping system of claim 20, wherein each of at least 5 of said insulating gaps occupy a volume of at least 100 mm3.

28. The hot-stamping system of claim 20, wherein each of at least 5 of said insulating gaps are at least 0.1 mm deep.

29. The hot-stamping system of claim 20, wherein:

the heated portion comprises first and second heated portions of the first and second tool surfaces, respectively; and
the matrix comprises first and second matrices formed in the first and second heated portions, respectively.
Patent History
Publication number: 20220105553
Type: Application
Filed: Feb 4, 2020
Publication Date: Apr 7, 2022
Applicant: MAGNA INTERNATIONAL INC. (Aurora, ON)
Inventors: Kyle Daniel FAIRBARN (Aurora), David Camil POLSONI (Aurora), Leslie George SHUMAN (Aurora)
Application Number: 17/428,761
Classifications
International Classification: B21D 22/20 (20060101); B21D 37/16 (20060101); C21D 8/02 (20060101); C21D 7/13 (20060101);