Patent Description:
Continuing efforts to reduce weight and increase fuel efficiency have driven the automotive industry to develop metal with improved strength and ductility allowing the use of thinner gauges while still maintaining industrial safety standards. During production, these metals often start as metal blanks that are later stamped in to automotive parts. Depending on an end use, automotive parts require different levels of strength and ductility. For example, a part stamped for use in automobiles may be subjected to one type of stresses via rough driving surfaces, internal vibrations, and exposure to corrosive environments whereas a neighboring part may only be subjected to minimal stresses. Moreover, individual parts may be subjected to inconsistent stresses in localized areas. Because certain parts experience less hardship, they can be produced with lighter metals and metal alloys to satisfy specific strength or stiffness requirements. However, for those parts that are subjected the most stress, they are usually made of steel or steel alloy that is treated for optimized strength and ductility. These treatment methods typically involve some way of heating the part to temperatures at which the physical and sometimes chemical property of the underlying metal is changed. Depending on the constituents of the metal alloy used, when a part is heated to a certain temperature, the constituents can form an uninterrupted microstructure before being cooled. While these treated parts can be made at thinner gauges to reduce weight, treated parts have become so hard that they are difficult to shape and connect to other neighboring parts. In addition, oftentimes it is beneficial to develop a part with a localized area that is softer with increased ductility to improve absorption during an impact event.

Attempts to produce parts with improved workability having localized areas with different levels of ductility and strength have resulted in the development of several processes in which localized areas of a part can be treated. One popular method involves heating a die between the stamping of metal parts. During this process, the die is heated to a temperature high enough to change the physical characteristics of the metal being stamped. However, it is hard to accurately heat treat a small or complex-shaped localized area without excess heat creeping into nearby portions. Moreover, the localized areas that are heat treated have large transition zones between a tempered location and a non-tempered location. Further relevant prior art is described in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>.

Accordingly, there is a continuing desire to further develop and refine tempering processes to limit the size of transition zones.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims. 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. In order to solve the aforementioned problem, a hot stamping tool assembly, having the features defined in claim <NUM>, is provided. Further, a method of forming a part with tailor tempered properties and small transition zones, having the features defined in claim <NUM> is provided.

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:.

In general, the subject embodiments are directed to a hot stamp tool assembly and a method of forming a part with tailored temper properties. 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.

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the views, the hot stamp tool assembly and method of same ultimately provide a part with temper locations and non-temper locations and small transition zones between temper locations and non-temper locations.

Referring initially to <FIG>, the hot stamp tool assembly <NUM> is generally shown. The hot stamp tool assembly <NUM> may include at least one hot forming die <NUM> (see <FIG>) and at least one annealing die <NUM> (<FIG>). In some embodiments, the hot stamp tool assembly <NUM> includes a plurality of annealing dies <NUM>, for example, a first annealing die and second annealing die <NUM> and a plurality of hot forming dies <NUM>, for example, a first hot forming die and a second hot forming die <NUM>. A first transfer arm <NUM> is located on one side of the hot stamp tool assembly <NUM> and a second transfer arm <NUM> is located on an opposite side of the hot stamp tool assembly <NUM>. The first transfer arm <NUM> includes at least one blank holder <NUM>, such as a hydraulically operated clamp, an energized magnet, a suction device, or any other implements conventionally utilized for moving blanks between locations. In some embodiments, the at least one blank holder <NUM> may include a first blank holder and a second blank holder <NUM>. The second transfer arm <NUM> includes at least one shaped part holder <NUM>, such as a hydraulically operated clamp, an energized magnet, a suction device, or any other implements conventionally utilized for moving shaped blanks between locations. In some embodiments, the at least one shaped part holder <NUM> may include a first shaped part holder, a second first shaped part holder, a third shaped part holder, and a fourth shaped part holder <NUM>.

As illustrated by the arrows, the first transfer arm <NUM> connects to a pair of heated blanks 34A and removes them from a furnace <NUM> with a respective one of the first blank holders <NUM> and simultaneously places one heated blank 34A in the first hot forming die <NUM> and the other heated blank 34A in the second hot forming die <NUM>. Once the heated blanks 34A have been placed into the hot forming dies <NUM>, a stroke of the hot forming dies <NUM> stamps each of the blanks 34A into a shaped part 34B. While located in the hot forming dies <NUM>, the blanks may also be quenched. The combination of heating and rapidly cooling may change a microstructure of at least a portion of the shaped parts 34B. For example, the heating and quenching may result in the formation of martensitic in at least a portion of the shaped parts 34B. After shaped and quenched, the second transfer arm <NUM> removes the shaped parts 34B with two of the shaped part holders <NUM> and places one shaped part 34B in the first annealing die <NUM> and the other shaped part 34B in the second annealing die <NUM>. The shaped parts 34B then undergo an annealing process. For example, portions of the shaped parts <NUM> may be reheated to above a recrystallization temperature and then slowly cooled until they are annealed, thus becoming annealed parts 34C. While the shaped part 34B is located in the annealing die <NUM>, it may further be subjected to additional cooling on portions of the shaped part 34B adjacent to those portions of the shaped part 34B that are annealed. The second transfer arm <NUM> removes the annealed parts 34C with two of the other shaped part holders <NUM> that were not used in placing the shaped parts 34B into the annealing die <NUM>. In operation, the second transfer arm <NUM> may thus simultaneously connect to two or more shaped parts 34B and two or more annealed parts 34C with each of the shaped part holders <NUM> and move the shaped parts 34B between the forming dies <NUM> and the annealing dies <NUM> while removing the annealed parts 34C from the annealing dies <NUM> in one process step.

<FIG> is a cross-sectional side view of one of the hot forming dies <NUM> located within the hot stamp tool assembly <NUM>. Each of the hot forming dies <NUM> may include the same configuration and operational parameters. The hot forming die <NUM> includes a upper forming die <NUM> and a lower forming die <NUM> defining a forming cavity <NUM> therebetween. Inner surfaces of the upper forming die <NUM> and the lower forming die <NUM> may include topographical features to form the shaped part 34B into any number of shapes, including automotive components such as automotive pillars. The upper forming die <NUM> includes a series of upper forming die channels <NUM> located adjacent to the forming cavity <NUM> and the lower forming die <NUM> includes a series of lower forming die channels <NUM> located adjacent to the forming cavity <NUM>. The upper forming die channels <NUM> and the lower forming die channels <NUM> thus provide quenching of the shaped part 34B with liquid coolant that is circulated therein or static cooling devices that are located therein. In some embodiments, the quenching process in the hot forming dies <NUM> may thus circulate coolant and change the microstructure in at least a portion of the shaped part 34B (e.g., forming martensite). In some embodiments, the shaped part 34B is cooled at a rate of at least <NUM> per second and martensite may be formed between <NUM> and <NUM>. The upper forming die <NUM> and the lower forming die <NUM> may define a bend portion <NUM> of the cavity <NUM> that forms a stiffener flange <NUM> in the shaped part 34B. Cooling channels <NUM>, <NUM> may be located adjacent to the entire outline wherein the shaped part 34B will be located, including the bend portion <NUM> such that primarily the entire shaped part is quenched. In some embodiments, the coolant in the forming die <NUM> may include a liquid, such as water, circulated at a temperature between <NUM> and <NUM>.

<FIG> and <FIG> are cross-sectional side views of the annealing die <NUM> located within the hot stamp tool assembly <NUM>. Each of the annealing dies <NUM> may include the same configuration and operational parameters. The annealing die <NUM> includes an upper annealing die <NUM> and an lower annealing die <NUM> defining an annealing cavity <NUM> therebetween. Inner surfaces of the upper annealing die <NUM> and an lower annealing die may include topographical features similar to that of the hot forming dies <NUM>. The upper annealing die <NUM> includes a series of upper die channels <NUM> located adjacent to the annealing cavity <NUM> and the lower annealing die <NUM> includes a series of lower die channels <NUM> located adjacent to the annealing cavity <NUM>. The upper die channels <NUM> and the lower die channels <NUM> may provide continued cooling of the shaped part 34B with coolant that is circulated therein or static cooling materials that are located therein. The cooling operation in the annealing die <NUM> may cause further reduce the temperature of portions of the shaped part 34B to between <NUM> and <NUM>. In some embodiments, the coolant in the annealing die <NUM> may include a liquid, such as water, circulated at a temperature between <NUM> and <NUM>. In some embodiments, the shaped part 34B is placed in the annealing die <NUM> once it reaches a temperature below <NUM>.

The upper annealing die <NUM> may include at least one upper heating element, such as an upper induction coil <NUM> located adjacent to the annealing cavity <NUM> and the lower annealing die <NUM> may include at least one lower heating element, such as a lower induction coil <NUM>, located adjacent to the annealing cavity <NUM>. The at least one lower induction coil <NUM> may be disposed adjacent to and on an opposite side of the cavity <NUM> from the at least one upper induction coil <NUM>. In some embodiments, the upper annealing die <NUM> includes two upper induction coils <NUM> located in a spaced relationship, wherein the series of upper die channels <NUM> are located between each of the upper induction coils <NUM>. Similarly, the lower annealing die <NUM> may include two lower induction coils <NUM> located in a spaced relationship, wherein the series of lower die channels <NUM> are located between each of the lower induction coils <NUM>. In some embodiments, the die channels <NUM>, <NUM> are located on either side of the induction coils <NUM>, <NUM>. In some embodiments, the induction coils <NUM>, <NUM> are located at a trim location of the shaped part 34B. In operation, the induction coils <NUM>, <NUM> may rapidly heat and anneal the shaped part 34B at the trim location while the cooling channels <NUM>, <NUM> maintain a lower temperature on locations of the shaped part 34B adjacent to the induction coils <NUM>, <NUM>, thus decreasing the creeping effect of the heat transfer and a reducing the size of a transition zone between the annealed portions of the shaped part 34B and the non-annealed portions of the shaped portion 34B.

As best illustrated in <FIG>, the annealing die <NUM> may include a annealing die insert that includes an upper annealing die insert <NUM> and a lower annealing die insert <NUM> that can be moved independently of the upper annealing die <NUM> and the lower annealing die <NUM>. The upper and lower annealing die inserts <NUM>, <NUM> define an annealing insert cavity <NUM> with a bend <NUM> that accommodates the stiffener flange <NUM>. Both annealing inserts <NUM>, <NUM> are located on an outside portion of annealing die <NUM> from the induction coils <NUM>, <NUM>. As such, the quenched area is spaced from the stiffener flange <NUM> by a portion of the annealed part 34C which has been softened through annealing. The stiffener flange <NUM> can later be removed via cutting. No cooling channels may be necessary next to the stiffener flange <NUM> if it will be removed. However, the die channels <NUM>, <NUM> opposite the stiffener flange <NUM> hinder the transition zone from creeping into portions other than the annealed portion and the stiffener flange <NUM>. The stiffener flange <NUM> also prevents distortion of the annealed part 34C during the annealing process. However, in some embodiments it should be appreciated that the die channels <NUM>, <NUM> may be located on opposite sides of the induction coils <NUM>, <NUM>. For example, it may be beneficial to allow the stiffener flange <NUM> to be quenched such that a trimming operation on the annealed portion is modified. In some embodiments, the trim portion and/or trimming operation may include deforming, piercing, cutting, etc. without departure from the subject disclosure. As such, when the die channels <NUM>, <NUM> are located on opposite sides of the induction coils <NUM>, <NUM>, the annealed portion may be completely surrounded by the quenched portions. In some embodiments, the trim portion is inset from but outlines an entire or partial periphery of the annealed part 34C. In some embodiments, the upper and lower annealing die inserts <NUM>, <NUM> may perform the trimming operation.

<FIG> generally illustrates the control system <NUM> according to the principles of the present disclosure. The control system <NUM> may include a controller <NUM> and the controller <NUM> may include a processor <NUM> and a memory <NUM>. The processor <NUM> may include any suitable processor, such as those described herein. Additionally, or alternatively, the controller <NUM> may include any suitable number of processors, in addition to or other than the processor <NUM>. The memory <NUM> may comprise a single disk or a plurality of disks (e.g., hard drives), and includes a storage management module that manages one or more partitions within the memory <NUM>. In some embodiments, memory <NUM> may include flash memory, semiconductor (solid state) memory or the like. The memory <NUM> may include Random Access Memory (RAM), a Read-Only Memory (ROM), or a combination thereof. The memory <NUM> may include instructions that, when executed by the processor <NUM>, cause the processor <NUM> to, at least, perform the systems and methods described herein. The controller <NUM> may control operations of the forming die <NUM>, the annealing die <NUM>, the first transfer arm <NUM>, the second transfer arm <NUM>, and other features.

<FIG> is a series of top views of the hot stamp tool illustrating sequential steps of a process <NUM> of forming tailored temper properties in a part with small transition zones. Each step in the process <NUM> may be carried out by instructions from the memory executed by the processor. Each of the hot stamp tools illustrated in <FIG> is the same hot stamp tool as a function of time during the course of process <NUM>. The process <NUM> begins with providing <NUM> a hot stamp tool having a pair of annealing dies and a pair of hot forming dies, wherein the hot forming dies each include a blank and the annealing dies each include a shaped part (which was previously a blank formed in one of the hot forming dies). During a stroke <NUM> of the hot stamp tool, the hot forming dies shape <NUM> the blanks into a shaped part and may further include a quenching <NUM> step, such as by a series of cooling channels, wherein a hardened microstructure may be formed within the shaped part. During the stroke <NUM>, the annealing die simultaneously cools <NUM> and anneals <NUM> adjacent locations on the shaped part to form an annealed part. The step of annealing may include heating with an induction coil and the step of cooling may including cooling channels located adjacent to the induction coil. Next, the second transfer arm grabs <NUM> each of the shaped parts and each of the annealed parts and moves <NUM> the shaped parts to the annealing dies and moves <NUM> the annealed parts away from the hot stamp assembly. Once the shaped parts are moved <NUM>, the first transfer arm moves <NUM> additional heated blanks into the hot forming dies. The heated blanks may be moved directly from a furnace. Next, the second transfer arm moves <NUM> the annealed parts into an area for additional processing (such as material deformation, trimming, piercing, or material removal of the annealed portion) and returns <NUM> into a position for step <NUM>, wherein the process <NUM> repeats.

<FIG> show enlarged steps <NUM> through <NUM> of the process <NUM>. More particularly, <FIG> illustrates providing <NUM> a hot stamp tool having a pair of annealing dies and a pair of hot forming dies, wherein the hot forming dies each include a blank and the annealing dies each include a shaped part (which was previously a blank formed in one of the hot forming dies). <FIG> illustrates the second transfer arm grabbing <NUM> each of the shaped parts and each of the annealed parts and moving <NUM> the shaped parts to the annealing dies and moving <NUM> the annealed parts away from the hot stamp assembly. <FIG> illustrates the first transfer arm moving <NUM> additional heated blanks towards the hot forming dies from a furnace and the second arm moving the annealed parts away from the hot stamp assembly. <FIG> illustrates the first transfer arm moving <NUM> the additional heated blanks into the hot forming dies. <FIG> illustrates the second transfer arm moving <NUM> the annealed parts into an area for additional processing. <FIG> illustrates the second transfer arm returning <NUM> into a position for step <NUM>, wherein the process <NUM> repeats.

<FIG> illustrates a series of cross-sectional views of a part undergoing a process <NUM> of forming tailored temper properties with small transition zones. Each step in the process <NUM> may be carried out by instructions from the memory executed by the processor. The process <NUM> presented in <FIG> may be included with non-overlapping steps in process <NUM>, for example, between steps <NUM> through <NUM>. More particularly, the process begins by providing <NUM> a heated blank directly from a furnace. The heated blank is then placed <NUM> within a hot forming die, wherein it is shaped <NUM> and quenched <NUM> via cooling channels to from a shaped part with a hardened microstructure, e.g., higher levels of martensite. Next, the shaped part is placed <NUM> within an annealing die, wherein it continues to be cooled <NUM> via die channels and locally annealed <NUM> with induction coils that are adjacent to the die channels. The step of cooling may include cooling portions of the shaped part adjacent to the induction coils to a temperature between <NUM> and <NUM>. The portion of the shaped part that is cooled is entirely within the space between adjacent pairs of induction coils presented in <FIG> and <FIG>. The local annealing <NUM> step may include forming an annealed portion within or adjacent to a non-annealed portion, wherein a transition zone at least partially separates the annealed portion from the non-annealed portion and at least part, a majority, or substantially all the transition zone is less that <NUM>, less than <NUM>, approximately <NUM>, or less than <NUM>. Next, the part is moved <NUM> with the second transfer arm for later processing. The later processing includes deforming <NUM> the annealed portion. The step of deforming <NUM> may include one of cutting, riveting, bending, piercing, trimming to size, etc. The step of cutting may including laser cutting. The resulting part <NUM> may be a part of an automobile for example a pillar and more specifically a B-pillar.

<FIG> illustrates a part <NUM> having at least one non-annealed portion <NUM> with a small transition zone <NUM> that includes at least one deformation <NUM>. More particularly, the part <NUM> is illustrated as a B-pillar with a transition zone <NUM> forming an outer edge that includes a deformation <NUM> including a cut along a peripheral edge of the transition zone <NUM>.

<FIG> is a flowchart of a method <NUM> of forming a part with tailored temper properties and small transition zones. The method <NUM> begins by hot forming <NUM> and quenching <NUM> a blank in a hot forming die until it is a shaped part <NUM>. The step of quenching <NUM> may include changing the microstructure of the shaped part. The method <NUM> continues by placing <NUM> the shaped part in an annealing die wherein it is partially cooled <NUM> and partially heated <NUM>, simultaneously and at adjacent locations, until it is an annealed part <NUM> with a small transition zone between the annealed portions and the non-annealed portions. A portion of the annealed part that was heated <NUM> (i.e., an annealed portion of the annealed part) is then deformed <NUM>.

Claim 1:
A hot stamp tooling assembly (<NUM>) comprising:
at least one hot forming die (<NUM>) and at least one annealing die (<NUM>);
the at least one hot forming die (<NUM>) including an upper forming die (<NUM>) and a lower forming die (<NUM>) for shaping a blank into a shaped part;
the at least one annealing die (<NUM>) including an upper annealing die (<NUM>) and a lower annealing die (<NUM>) for receiving the shaped part;
the at least one annealing die (<NUM>) including at least one cooling element (<NUM>) and at least one heating element (<NUM>, <NUM>), the cooling element located adjacent to the heating element; and
wherein the at least one heating element (<NUM>, <NUM>) anneals a portion of the shaped blank and the at least one cooling element (<NUM>) simultaneously cools a portion of the shaped blank adjacent to the at least one heating element (<NUM>, <NUM>) to hinder heat transfer from the at least one heating element (<NUM>, <NUM>) to the cooled portion.