Patent ID: 12208433

DETAILED DESCRIPTION OF THE DRAWINGS

FIG.1shows a hot forming system10for producing a vehicle body assembly or a vehicle body member. Referring toFIG.1, the hot forming system10includes a first die12, a second die14, and a cooling system38operatively associated with the first die12and the second die14.

In illustrative embodiment, the first die12is shown as a lower die. In another embodiment, the first die12may be an upper die. The first die12has a first die body18and a first die surface20. In one embodiment, the first die body18may be formed of a heat conducting material such as tool steel, in particular DIEVAR®, which is marketed by Bohler-Uddeholm Corporation of Rolling Meadows, Ill., or commercially available H-11 or H-13. In one embodiment, the first die surface20may include a complex forming die surface. The first die body18may also include a plurality of cooling channels22in at least a portion thereof.

In illustrative embodiment, the second die14is shown as an upper die. In another embodiment, the second die14may be a lower die. In one embodiment, the second die14may include a second die body24that may be formed of a tool steel, such as DIEVAR® or commercially available H-11 or H-13, a second die surface26and a plurality of cooling channels28in at least a portion thereof. In one embodiment, the second die surface26may include a complex forming die surface.

As used herein, the term “die surface” refers to the portion of the exterior surface of a die that forms a hot formed component. Moreover, the term “complex die surface” as used in this description means that the die surface has a three-dimensionally contoured shape.

The hot forming die set12and14may be mounted in a stamping press34and may be coupled to the cooling system38. In one embodiment, the stamping press34may be configured to close the first and second dies12and14in a die action direction to deform a workpiece30received between the first and second dies12and14so as to form and optionally trim a hot formed member36. In one embodiment, the stamping press34may be configured to maintain the dies12and14in a closed relationship for a predetermined amount of time to permit the hot formed member36to be cooled to a desired temperature.

The cooling system38may include a source of cooling fluid. In one embodiment, cooling fluid may include water, gas or other fluid medium. Cooling fluid, provided by the cooling system38, may be continuously circulated through the cooling channels22and28to cool the dies12and14, respectively. In one embodiment, the cooling system38may include a reservoir/chiller and a fluid pump. It may be appreciated that circulating cooling fluids cools the dies12and14and that the dies12and14quench and cool the hot formed member36.

In one embodiment, the cooling channels22,28may be formed by techniques such as gun drilling that yield straight channels extending through the respective die bodies. In one embodiment, the cooling channels22,28are formed by gun drilling the cooling channels through one or two sides of the respective die bodies.

In one embodiment, each cooling channel22may be offset from the die surface20by a first predetermined distance and this distance may be consistent along the length of the cooling channels22. Similarly, each cooling channel28may be offset from the die surface26by a second predetermined distance, which may be different from the first predetermined distance, and this distance may be consistent along the length of the cooling channels28. In another embodiment, the second predetermined distance may be the same as the first predetermined distance.

The first and the second die surfaces20and26are configured to cooperate to form a die cavity39therebetween so as to receive the workpiece30therein. In one embodiment, the die cavity39is configured to have a shape that corresponds to a final shape of the workpiece after the hot forming operation/procedure.

In one embodiment, the workpiece30may be a blank, which may be formed of a heat-treatable steel, such as boron steel. In another embodiment, the workpiece30may be stamped from a sheet of hardenable steel, such as Usibor®1500P or Usibor® 1500, boron steel or any suitable hot stamp press hardened material. In one embodiment, the workpiece30may be pre-shaped specifically for producing a desired shaped hot formed product, such as, for example, by an additional cutting procedure or an additional cold forming procedure. In one embodiment, the additional cutting procedure or additional cold forming procedure may be optional.

In one embodiment, the hot formed member36is a vehicle body member or vehicle body assembly. In one embodiment, the vehicle body component that is formed or produced by the system ofFIG.1may include a B column or B pillar for a vehicle. Of course, other types of members may be produced in a similar fashion, and the example of the B pillar is provided merely for illustrative purposes and in order to facilitate a better understanding of the embodiments of the present patent application.

Referring toFIG.3, a laser cladding process is generally used to form a single pass thin coating layer on each of the first and the second die surfaces20and26. The coating includes the prior art/unmodified/existing S390 powder. The prior art/unmodified/existing S390 powder is a high speed steel. This is manufactured by Bohler and marketed under the name Bohler S390. The details about the prior art/unmodified/existing S390 powder can be found in http://www.bohler.ca/media/productdb/downloads/S390DE.pdf. The coating layer thickness is approximately 1 millimeter at the valley bottom of the cladding lines. No obvious crack can be seen on top surface. One hot tear was found at the root of one cladding track (pass). The core microstructure was found to comprise of martensite with small carbides and presumed retained austenite arranged in a columnar and dendritic pattern. It was found that this single layer coating of the S390 material can be produced without obvious cracks. It was also found that a defect-free S390 material coating layer can be achieved more readily for thinner coating layers having thickness less than 1 millimeter.FIG.2shows a table with hardness measurement values of the coating layer with the prior art/unmodified/existing S390 material, hardness measurement values at the fusion line and hardness measurement values at the heat-affected zone. The average hardness in the coating layer is about 64 HRC.

Applicant of the present patent application has found that the unmodified/existing S390 powder/material does not allow for more than one coating layer (e.g., multiple layer coating configuration) deposited via the laser cladding procedure. That is, if a single layer coating/deposit is formed using the unmodified/existing S390 powder/material, the structure of the coating/deposit has no issues. Multiple layer cladding of the unmodified/existing S390 powder/material includes dual layer cladding to approximately a thickness of 2 millimeters. Multiple cracks & porosity are visible in the second layer of the coating with the unmodified/existing S390 powder after the top surface of the coating layer is ground. That is, once a second coating layer and/or a thicker (i.e., more than 1 millimeter thickness) coating layer is applied using the unmodified/existing S390 powder, the resultant structure provides cracking and/or porosity. This ultimately results in de-layering or flaking of the deposit/coating.

The present patent application provides an improved/modified S390 powder/material that includes mechanical properties similar to that of the S390 powder while minimizing cracking and porosity. That is, the improved/modified S390 powder of the present patent application is configured to reduce cracking & porosity in a multilayer structure/configuration. The improved/modified S390 powder of the present patent application is also configured to optimize the single pass process by extending the maximum possible cladding thickness. In one embodiment, the clad layer thickness is configured to be controlled by process speed and powder feed rate. The improved/modified S390 powder/material of the present patent application is described in detail below.

Referring toFIGS.1and12, in one embodiment, the present patent application provides the forming system10. The forming system10includes the first die12having the first die surface20and the second die14having the second die surface26. The first and the second die surfaces20and26are configured to cooperate to form the die cavity39therebetween so as to receive the workpiece30therein. Coatings50are formed on opposing portions of the first and second die surfaces20and26. The coatings50on the opposing portions of the first and the second die surfaces20and26cooperate to be on opposite sides of the workpiece30received in the die cavity39.

In one embodiment, a ratio of Vanadium to Tungsten in the coatings50is in the range between 0.31 and 0.45. In one embodiment, each of the coatings50includes at least two layer configuration. In another embodiment, each of the coatings50includes a predetermined thickness. In one embodiment, the predetermined thickness of each of the coatings50is at least 2 millimeters. In one embodiment, the predetermined thickness of each of the coatings50is in the range between 0.75 millimeters and 1.25 millimeters thickness. In one embodiment, the coatings50includes a predetermined width. In one embodiment, the predetermined width of each of the coatings50is in the range between 3 millimeters and 5 millimeters.

For example,FIG.12shows dies12,14of the forming system10with modified/improved S390 material coatings50thereon, wherein the coatings50have a predetermined thickness.FIG.13shows dies12,14of the forming system10with modified/improved S390 material coatings50thereon, wherein the coatings50have at least two layer configuration.

In one embodiment, in the two layer coating configuration, each layer of the coating includes the same material. In one embodiment, in the two layer coating configuration, each layer of the coating is deposited layer by layer, that is, one layer at a time. In one embodiment, the deposited first layer of the two layer coating configuration is cured, dried or cooled before applying the second layer of the two layer coating configuration. In one embodiment, there is no time lapse between two layers. That is, as soon as one layer is complete, the next layer is applied from the same starting point as the first layer. In one embodiment, there is no cooling of the first layer before applying the second layer of the two layer coating configuration.

In one embodiment, the coatings50formed on the opposing portions of the first and second die surfaces20,26form a relatively high wear resistance die region, a relatively high surface hardness die region, a relatively high toughness die region and/or a relatively high compressive strength die region. In one embodiment, the coatings50formed on the opposing portions of the first and second die surfaces20,26provide high impact resistance, high strength, high toughness and/or high wear resistance to the respective die. In one embodiment, the coatings50formed on the opposing portions of the first and second die surfaces20,26substantially prolong the service life of the die.

In general, mechanical friction between the die surface(s) and the workpiece, during the hot forming procedures, leads to die wear. In one embodiment, some portions of the first and second die surfaces20,26are prone to higher wear than other portions of the first and second die surfaces20,26. In one embodiment, the coatings50are only formed on those portions of the first and second die surfaces20,26that are subject to high wear during a hot forming procedure. In one embodiment, the coatings50are formed on those portions of the first and second die surfaces20,26that are subject to high contact stresses and pressures during a hot forming procedure. In one embodiment, the coatings50are formed on the entire first and second die surfaces20,26.

In one embodiment, the coatings may be laser clad on opposing portions of the first and second die surfaces20and26. In another embodiment, the coatings may be laser sintered on opposing portions of the first and second die surfaces20and26. In yet another embodiment, the coatings may be formed or deposited, using an additive manufacturing procedure on opposing portions of the first and second die surfaces20and26.

In one embodiment, the coatings may have powdered material configuration. In one embodiment, the coatings may be sprayed on to the die bodies. In one embodiment, the coatings may be in the form of a clad material. In one embodiment, the coatings may include a spray multilayer coating.

In one embodiment, the coatings may be formed on the die bodies using a laser cladding procedure. In one embodiment, a laser cladding process is generally used to form a single pass thin coating layer on each of the first and the second die surfaces20and26. The procedure also includes binding the material together to form the desired geometry of the coatings. In one embodiment, the desired geometry of the coatings is formed (i.e., built up additively) layer by layer.FIG.15shows an exemplary laser cladding procedure/process.FIG.15shows a workpiece having a cladding overlay thereon when the workpiece is being moved in a cladding direction under a laser cladding system. The laser cladding system includes a laser optics head, a powder injection head, and a laser beam.FIG.15also shows melt pool and powder jet.

In one embodiment, the coatings may be formed on the die bodies using a laser sintering procedure. The laser sintering procedure is an additive manufacturing procedure in which a laser device is used as the power source to sinter powdered coatings. The procedure also includes binding the material together to form the desired geometry of the coatings. In one embodiment, the desired geometry of the coatings is formed (i.e., built up additively) layer by layer. In one embodiment, the laser sintering procedure may be selective laser sintering or direct metal laser sintering.

In another embodiment, the coatings may be formed on the die bodies using a laser metal deposition procedure. The laser metal deposition procedure generally uses a laser device as the power source to form a melt pool on a substrate material (e.g., metallic substrate). The improved/modified S390 material (e.g., powder) is fed into the melt pool and is absorbed into the melt pool to form a deposit/coating that is fusion bonded to the substrate material. Like the laser sintering procedure, the laser metal deposition procedure is an additive manufacturing procedure in which the desired geometry of the coating is formed (i.e., built up additively) layer by layer.

In other embodiments, other additive manufacturing procedures, which are similar to the laser metal deposition procedure and the laser sintering procedure (described above), may be used in the present patent application. In one embodiment, the additive manufacturing procedure may generally refer to a procedure in which the coatings are formed on the respective die surface(s) by adding layer-upon-layer of the improved/modified S390 material of the present patent application. In one embodiment, the additive manufacturing procedure is configured to provide a uniform molecular thermal bond between the coating and its respective die bodies, for example, without air pockets or weld slag. In one embodiment, laser melting procedure may be used to deposit or form coating layer(s) on the respective die surface(s).

In one embodiment, the improved/modified S390 powder/material of the present patent application is a high speed steel material produced by powder-metallurgy methods. In one embodiment, the improved/modified S390 powder/material of the present patent application is referred to as power-metallurgy material.

In one embodiment, the improved/modified S390 powder of the present patent application, because of its properties, retains its hardness at high temperatures. This property (i.e., retains its hardness at high temperatures) is ideal as a powder/material is used in a laser cladding process to repair badly worn Dievar Form Steels in a Hot Stamp Production Environment.

In another embodiment, the improved/modified S390 powder/material of the present patent application is used as a means to enhance the life cycle of our Hot Stamp Form Steels. This is done by adding the modified/improved S390 powder/material to the high wear areas via the laser cladding, prior to final machining. This procedure is configured to increase resistance to wear during stamping process.

In one embodiment, the improved/modified S390 powder of the present patent application is a derivative alloy of the S390 powder and is configured to enable multi-layer deposition in the laser cladding process. The existing S390 powder is not capable of multi-layer deposition. The improved S390 powder of the present patent application has multi-layer deposition capabilities.

In one embodiment, the improved/modified S390 powder of the present patent application is a derivative alloy of the S390 powder and is configured to enable formation of a coating having a thickness of at least 2 millimeters.

In one embodiment, the formulation of the improved S390 powder of the present patent application has no significant impact on the cost of the improved S390 powder.

Deposition of the S390 powder on the die surfaces is configured to allow for repair of hot stamp form steel. Current wear values require 2 to 3 millimeters of the coating material deposits with minimal cracking and porosity.

In one embodiment, the improved/modified S390 powder of the present patent application includes modified chemical composition of the existing S390 powder so as to enable hot stamp facilities to perform repairs on worn hot stamp form steels without de-layering of the cladding material.

In one embodiment, the improved/modified S390 powder of the present patent application is configured to suppress cracks.FIG.4Ashows a two layer structure of the existing/unmodified S390 powder, whileFIG.4Bshows a two layer structure of the improved/modified S390 powder of the present patent application. As shown inFIG.4A, severe crack occurs after application of second layer of cladding using the existing/unmodified S390 powder. Referring toFIG.4B, no visible cracks are observed in any application layers when the improved S390 powder of the present patent application is used. Thus, the crack suppression for the two layer cladding of S390 powder is achieved by modifying chemistry of the S390 powder.

FIG.5shows different views of a double layer structure of the coating including the modified/improved S390 material.FIG.5shows the cross section of clad double layer using the modified/improved S390 material. There is no obvious change in microstructure in comparison to the cladding with the pure prior art/unmodified S390 powder. For example, the core microstructure was found still to be martensite with fine carbides and possible retained austenite along dendritic patterns.

FIG.6shows a table with hardness measurement values of the modified/improved S390 material coating/layer in accordance with an embodiment of the present patent application, and hardness measurement values at the fusion line. As can be seen fromFIG.6, the hardness measurement values of the modified/improved S390 material coating/layer remained high or remained the same (as that for the thicknesses below 1 millimeter) when the thickness of the modified/improved S390 material coating/layer was increased to be more than 1 millimeter (i.e., when the thickness of the modified/improved S390 material coating/layer is between 1 millimeter and 2.5 millimeters).

FIG.7shows a table with three different compositions of the modified/improved S390 material in accordance with one embodiment of the present patent application. In one embodiment, successful cladding is achieved by modifying the ratio of Vanadium and Tungsten in the alloy composition. In one embodiment, all the value listed in the table ofFIG.7are percentages.

In one embodiment, all the three different compositions of the modified/improved S390 material include mechanical properties that are similar to the prior art/unmodified S390 material. In one embodiment, each of the three different compositions of the modified/improved S390 material has the same Red Hardness, the same wear resistance, the same toughness, the same grindability and the same compressive strength for multiple layer deposit configuration as is with a single layer deposit of the unmodified/prior art S390 material.

In one embodiment, each of the three different compositions of the modified/improved S390 material produced/formed a laser clad multi-layer material coating configuration without cracks. In one embodiment, each of the three different compositions of the modified/improved S390 material produced/formed a laser clad coating having a thickness of at least 2 millimeters without cracks. In one embodiment, each of the three different compositions of the modified/improved S390 material has no significant impact on the powder cost.

FIG.8shows a table with hardness measurement values of the three different compositions of the modified/improved S390 material coating layer in accordance with an embodiment of the present patent application, hardness measurement values at the fusion line, and hardness measurement values at the heat-affected zone.

FIG.9shows different views of a double layer structure of the coating including the modified/improved S390 material in accordance with one embodiment of the present patent application. That is,FIG.10shows the double layer structure of the coating including the modified/improved S390 material having a composition of powder mix E as shown inFIG.7. The core microstructure was found to be comprised of martensite with retained austenite arranged in a columnar and dendritic pattern. Minor gas porosity was observed and tended to be located at the edges of adjacent cladding passes. Also, a grey phase is visible, which is likely comprised of carbide.

FIG.10shows different views of a double layer structure of the coating including the modified/improved S390 material in accordance with another embodiment of the present patent application. That is,FIG.10shows the double layer structure of the coating including the modified/improved S390 material having a composition of powder mix H as shown inFIG.7. The microstructure was found to comprised of martensite and potential retained austenite. A large gas porosity was observed on this plane cross-sectioned. Porosity tended to be located at the edges of adjacent passes. A grey phase was sometimes observed and likely comprised of carbide.

FIG.11shows different views of a double layer structure of the coating including the modified/improved S390 material in accordance with yet another embodiment of the present patent application. That is,FIG.10shows the double layer structure of the coating including the modified/improved S390 material having a composition of powder mix K as shown inFIG.7. The microstructure was found to comprised of martensite and potential retained austenite and was found to be similar to that of Mix E and Mix H. Gas porosity was also observed and tended to be located at the edges of adjacent cladding passes. A grey phase is visible, which is likely comprised of carbide.

FIG.14shows a method1400of forming a die12,14in accordance with an embodiment of the present patent application. The method1400comprises forming a die12,14having a die surface20,26at procedure1402; and applying coatings50on the die surface of the die12,14using a laser cladding procedure at procedure1404. The coatings50includes a predetermined thickness, and a ratio of Vanadium to Tungsten in the coatings is in the range between 0.31 and 0.45. In one embodiment, the coatings50includes at least two layer configuration. In one embodiment, the predetermined thickness of the coating50is at least 2 millimeters. In one embodiment, the predetermined thickness of each of the coatings50is in the range between 0.75 millimeters and 1.25 millimeters thickness. In one embodiment, the coatings50includes a predetermined width. In one embodiment, the predetermined width of each of the coatings50is in the range between 3 millimeters and 5 millimeters. In one embodiment, the coating is formed on portions of the die surface that is subject to high wear during a hot forming procedure.

In one embodiment, the die surface20of the die12is configured to cooperate with a second die surface26of a second die14to form a die cavity39therebetween so as to receive a workpiece30therein. In one embodiment, the die cavity39is configured to have a shape that corresponds to a final shape of the workpiece30after a hot forming procedure.

In one embodiment, the automotive rear rails are made in the forming system of the present patent application. In another embodiment, various other automotive components are made in the forming system of the present patent application.

In one embodiment, the forming system of the present patent application may be used to form products having tailored tempered properties (TTP). For example, such products may include regions of reduced hardness, reduced strength and/or high ductility/yield/elongation in products. In one embodiment, the system of the present patent application may be used to form vehicle body pillars, vehicle rockers, vehicle roof rails, vehicle bumpers and vehicle door intrusion beams. In another embodiment, the system of the present patent application may be used to form customer required hot stamp structural components. In one embodiment, the hot formed member or component may be referred to as a hot stamped member or a hot shaped member. For example, hot stamping allows for the forming of complex part geometries with the final product achieving ultra-high strength material properties.

Although the present patent application has been described in detail for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that the present patent application is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. In addition, it is to be understood that the present patent application contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.