RU2787134C1 - Pressing systems and methods - Google Patents

Abstract

FIELD: metals processing.

SUBSTANCE: invention relates to the processing of metals by pressure and can be used in the production of hot-formed structural elements. The device contains a fixed lower and movable upper working parts, a cooling tool and a press die. The die is located downstream of the cooling tool. A mechanism for transporting the workpiece from the cooling tool to the press die is provided. The cooling tool comprises an upper gas cooling tool connected to the movable upper working part and/or a lower gas cooling tool connected to the stationary lower working part. The press die contains an upper pressing die connected to the upper working part and a lower pressing die connected to the lower working part.

EFFECT: shortening the time of transportation of the workpiece from the cooling tool to the press die and constant uniform cooling of the workpiece during the production process are ensured.

15 cl, 4 dwg

Description

The present application claims the priority of European Patent Application No. 19382899.3, filed October 14, 2019. The present invention relates to press systems for the production of hot-formed structural elements and methods for doing so.

State of the art

In the field of vehicle manufacturing, the design and implementation of lightweight materials or components is becoming more and more important in order to meet the criteria for lightweight construction. The requirement for weight reduction is largely driven by the goal of reducing CO ₂ emissions. The growing concern for occupant safety is also leading to the use of materials that enhance vehicle crash integrity while also increasing energy absorption.

A process known as cold die quenched hot forming (HFDQ) (also known as hot forging or press quenching) uses boron steel sheets to produce forged components with ultra high strength steel (UHSS) properties with a tensile strength of, for example, 1500 MPa or even up to 2000 MPa or more. The increase in strength compared to other materials allows the use of a thinner material, resulting in a reduction in weight compared to mild steel components made by conventional cold forming.

Steel sheets can be coated or uncoated. However, to improve corrosion protection, coatings can be applied before, during or after the hot forming process. For example, the use of Al-Si coatings or Zn coatings is known.

Depending on the composition of the base steel material, hardening (i.e., rapid cooling) of the blanks may be required to achieve high tensile strengths. Quenching may involve a cooling rate above the critical cooling rate of the material used (eg, approximately 30 ºC/s). Other steel materials may have relatively low critical cooling rates. Examples of steel materials are known that can be quenched at room temperature with air cooled at a relatively low cooling rate.

The hot stamping process can be carried out in such a way that the workpiece to be hot formed is heated to a predetermined temperature, for example, to or above the austenitization temperature, by means of, for example, a furnace system, so as to reduce strength, i.e., to facilitate the hot stamping process. The preform to be hot-formed can be molded by a pressing system having a low temperature compared to the preform (for example, room temperature) and a temperature control means, thus a molding and heat treatment process using a temperature difference can be carried out.

Known multi-stage pressing system for the production of hot-formed elements. Multi-stage pressing systems may include a plurality of tools configured to simultaneously perform various operations on the blanks. With such configurations, a plurality of blanks simultaneously go through different stages of production at each cycle using tools that form a multi-stage pressing system. An aspect of using such a multi-stage pressing system is that the output can be high.

The multi-stage pressing system may include a conveyor or transport device that transports the heated preform to a press die that is configured to compress the preform. Additional tools that can be included in a multi-stage pressing system can be, for example, a punching tool, a calibration tool, a cutting tool, an edge trimming tool, a second press die, etc. In addition, a furnace system that heats and releases the preform to be thermoformed may be provided upstream of the multi-stage system or compression device.

Generally, such systems use an external pre-cooling tool to pre-cool the preform to be thermoformed. For example, zinc-coated steel billets may typically require cooling prior to the hot forming process to reduce or minimize problems such as microcracks. After the billet has been cooled, it is transported from the external pre-cooling tool to the multi-stage device or pressing system.

EP3067128 describes press systems for the production of hot formed structural elements. The systems comprise a fixed lower working part, a movable upper working part and a mechanism capable of providing the movement of the press up and down the movable upper working part relative to the fixed lower working part. The system additionally comprises a cooling tool configured to cool the preheated billet, which comprises: upper and lower mating dies, wherein the lower die is connected to the lower working part using one or more lower displacement elements and/or the upper die is connected to the upper working part with using one or more upper bias elements. The system further comprises a press die configured to pull the workpiece, the press die being located downstream of the cooling tool.

The system described in EP3067128 is designed to speed up the manufacturing process. To ensure this, the cooling tool is designed to cool the workpiece sufficiently rapidly. The cooling tool "closes" before the die closes because the biasing elements that bring the upper and lower coolant dies into contact with the workpiece close before the die. Thus, the dies of the cooling tool can be in contact for a sufficient amount of time to properly cool the workpiece. And by incorporating the tools in the same press, the transport time from the cooling tool to the drawing tool can be shortened, so the process can be optimized and productivity can be increased while still maintaining a satisfactory formability that does not lead to cracks in the workpiece or the like.

However, contact plate cooling tools require a great deal of maintenance. In addition, it makes it difficult to ensure uniform and constant cooling during the manufacturing process. In particular, when restarting a production process after an interruption, such as when starting with a new batch of product or at the start of a work day, a relatively long time (and a corresponding loss of production) is required before the required cooling is consistently achieved.

The present invention is intended to provide improvements in multi-step processes and systems.

Brief description of the invention

In the first aspect, a pressing device is proposed for the production of hot-formed structural elements. The pressing device comprises a fixed lower working part, a movable upper working part and a mechanism capable of providing the movement of the press up and down the movable upper working part relative to the fixed lower working part. The device further comprises a cooling tool configured to cool the preheated workpiece, and a press die capable of pulling the workpiece, and which is located downstream from the cooling tool, and a workpiece transport mechanism for transporting the workpiece from the cooling tool to the press die.

Herein, the cooling tool comprises an upper gas cooling tool connected to a movable upper working part and/or a lower gas cooling tool connected to a stationary lower working part. The press die also contains an upper pressing die connected to the upper working part and a lower pressing die connected to the lower working part.

In accordance with this aspect, a multi-stage pressing apparatus is provided that combines a cooling tool and a press die. This can speed up the production process and ensure high output. By incorporating tools into the same press, the transport time from the cooling tool to the drawing tool can be shortened, so the process can be optimized and productivity can be increased while still maintaining a satisfactory formability that does not lead to cracks in the workpiece or similar.

An aspect of gas refrigeration applications is that it requires relatively minor maintenance. It is also relatively easy to ensure a constant uniform cooling process by means of gas cooling. Therefore, gas cooling is usually not subject to the disadvantages that occur when using contact plates.

Providing a gas cooling tool in a multi-stage device also provides versatility. For example, for relatively thin workpieces, only the lower gas cooling tool can be used. For the same process with thicker workpieces, an upper gas cooling tool can be added. In such a case, the cycle time can remain short. Depending on the needs, cooling tools as described in this document allow flexibility in cooling parameters, including cooling time, cooling gas temperature, cooling flow, etc.

In some examples, one cooling tool is provided. For example, only a lower cooling tool connected to a fixed lower working part may be provided. In this case, the pressing device can have increased reliability and be relatively economical. In other examples, only an upper cooling tool connected to a movable upper working part may be provided. In this case, the upper cooling tool can be connected to the movable upper working part using biasing elements that push the upper cooling tool towards the fixed lower working part.

Thanks to the biasing members, the upper and lower gas cooling tool can reach the appropriate position relative to the workpiece to be cooled before the drawing/pressing with the press die takes place. Therefore, within the same pressing device, within one cycle, the cooling cycle can be longer than the pull cycle.

In still other examples, the upper gas coolant is connected to the movable upper working part and the lower gas coolant is connected to the stationary lower working part. In these cases, one or more upper bias members may connect the movable upper working portion to the upper gas coolant tool. The upper displacement elements displace the upper gas cooling tool from the movable upper working part. The lower gas coolant tool may be connected to the fixed lower working part by means of one or more lower biasing members which bias the lower gas coolant away from the fixed lower working part.

In some examples, at the bottom of the press cycle, the upper gas coolant is at a predetermined first distance from the workpiece and the lower gas coolant is at a predetermined second distance from the workpiece. Efficient and most predictable gas cooling can be achieved when air is blown onto the workpiece from a predetermined range of distances relative to the workpiece. At the bottom of the pressing cycle, it is required to maintain a distance between the cooling tool(s) and the workpiece.

The predetermined first distance may be equal to the predetermined second distance so that essentially the same cooling conditions can be provided for both the top and bottom surfaces of the workpiece.

In some examples, the cooling tool may include stops that maintain a minimum distance between the upper gas cooling tool and the workpiece (or the lower gas cooling tool supporting the workpiece).

In some examples, restraints may be provided on the upper gas coolant tool, the restraints being positioned to contact the lower gas coolant tool (or lower stationary workpiece) to generate a force opposing the biasing elements. This force, opposing the biasing elements, ensures that the distance is maintained as the pressing cycle continues. As the movable upper work portion continues to move towards the lower fixed work portion, the biasing members can be compressed and the distance between the gas cooling tools and the workpiece can be maintained.

In some examples, the restraints may be rods or bars.

In some examples, the apparatus may be configured to start a refrigeration cycle upon reaching a minimum distance between the upper gas cooling tool and the lower gas cooling tool. Uniform cooling on both sides can be achieved if the air flow on both sides is essentially the same and is supplied from the same distance. Increased cooling for e.g. thin headers can be achieved with top and bottom cooling tools. Refrigeration cycles in these examples may be intermittent. Such intermittent refrigeration cycles can also be used in examples where only the lower gas cooling tool or only the upper gas cooling tool is provided. Once the preform is in the desired position, the cooling cycle can be started.

In other examples, the cooling may be substantially continuous. Therefore, the flow of the cooling gas can be constant and thus the cooling can start when the workpiece is transported to the cooling tool. This can be implemented both in the case of using one gas cooling tool, and in the case of using two gas cooling tools.

In some examples, the bias elements may include one or more springs. In some examples, the bias elements may comprise hydraulic or pneumatic actuators.

In some examples, the upper gas cooler and/or the lower gas cooler comprise a plurality of slots connected to a compressed gas reservoir, the system further comprising a control to control the flow of gas from the reservoir through the slots. The cooling rate and temperature to be achieved can be controlled by the gas volume flow, the gas temperature, and the slot-to-work distance. In some examples, the system may further comprise means for controlling the temperature of the compressed gas in the reservoir.

In some examples, the slots may be directed substantially perpendicular to the workpiece.

In some examples, the gas may be air, which may be at substantially room temperature. In this aspect, an economical system can be proposed.

In some examples, the upper and/or lower press die of the press die includes channels that conduct coolant or coolant air. In some examples, the preform material and the desired microstructure of the resulting component is such that a high cooling rate is necessary or desirable. The press die can be controlled by the temperature to provide a correspondingly high or correspondingly low cooling rate. The cooling rate may also be different for one part of the workpiece as opposed to another part of the same workpiece. Therefore, the resulting microstructure for these different parts may differ.

In some examples, the temperature in the upper and/or lower pressing die is controlled based on the temperature on the working surface of one of the dies. The pressing device may include one or more thermocouples on the working surface of one of the pressing dies.

In some examples, the pressing device may be a mechanical press. In some examples, the pressing device may be a servo-mechanical press. In still other examples, the pressing device may be a hydraulic press. The methods and systems described herein may be implemented in various types of compression apparatus. A mechanical and servo-mechanical press device can achieve high output because the bias elements in the device provide some flexibility in adjusting the refrigeration cycle.

In some examples, the compression device may further comprise a first post-treatment tool configured to perform the first post-treatment, wherein the first post-treatment tool is located downstream of the compression device and includes: upper and lower dies of the first post-treatment tool, wherein the upper the die of the first postoperative tool is connected to the upper working part, and the lower die of the first postoperative tool is connected to the lower working part. Herein, the workpiece transport mechanism is further configured to transport the workpiece from the die to the first finishing tool.

Many steps and processes can be added to the same pressing device. Operations performed after drawing the workpiece are referred to herein as "post-operative" processing.

In some examples, the first post-processing includes trimming and cutting the workpiece, while the upper and/or lower dies of the first post-processing tool may contain one or more cutting blades.

To control temperature during the process, the upper and/or lower die of the first finishing tool may include one or more heaters or hot fluid passages. To maintain some formability and to facilitate cutting, edge trimming, or other machining, it may be beneficial to maintain a minimum workpiece temperature. In this way, the wear of postoperative instruments can be reduced.

To this end, in some examples, the heaters or hot fluid passages may be configured to maintain the workpiece temperature above 200°C based on the temperature measured on the dies of the first finishing tool.

In some examples, the top and/or bottom die of the first post-treatment tool may include channels that conduct coolant, optionally coolant water. In some examples, the temperature in the upper and/or lower die of the first post-processing tool can be controlled based on the temperature on the working surface of one of the dies. Optionally, thermocouples may be provided on the working surface of one of the dies of the first post-processing tool.

In some examples, the compression device may further comprise a second post-treatment tool, wherein the second post-treatment tool is located downstream of the first post-treatment tool. The workpiece transport mechanism can be further configured to transport the workpiece from the first post-processing tool to the second post-work tool, wherein the upper die of the second post-work tool is connected to the upper working part, and the lower die of the second post-work tool is connected to the lower working part.

In some examples, the second finishing tool is configured to trim edges and/or punch holes.

In some examples, the second post-processing tool may be calibrated. In these cases, the second finishing tool may include an adjusting device configured to adjust the distance between the upper and lower dies of the second finishing tool so as to deform the workpiece, and the adjusting device is controlled based on a sensor system configured to determine the thickness of the workpiece. .

The temperature control means in the second post-treatment tool may be the same or similar to the temperature control means in the first post-treatment tool.

In a further aspect, a method for hot forming a preform is provided. The method includes providing a pressing device according to any of the examples described herein and providing a billet to be hot formed made of ultra high strength steel (UHSS) having a zinc coating. The method further includes heating the workpiece; placement of the workpiece in the cooling tool; and cooling the workpiece, while ensuring the movement of the press down the movable upper working part relative to the fixed lower working part. The method then further comprises performing an upward movement of the press on the movable upper working part relative to the stationary lower working part; installation in the required position of the workpiece in the press die; and pulling out the workpiece by performing a downward and upward motion of the press on the movable upper working part relative to the stationary lower working part.

In some examples, the workpiece can be heated above the UHSS austenitization temperature. The preform can be heated to a temperature above Ac1, and, in some examples, the preform can be heated to a temperature above Ac3.

In some examples, the workpiece can be heated to a temperature of 860-910 ºC.

In some examples, UHSS may contain in mass fractions: 0.20-0.50% C, 0.75-1.5% Si and 1.50-2.50% Mn. Preferably, UHSS contains in percentage mass fractions: 0.21-0.25% C, 1.05-1.33% Si, 2.06-2.34% Mn. More preferably, the UHSS may contain, by weight, approximately: 0.22% C, 1.2% Si, 2.2% Mn. UHSS is of such a composition that it can be quenched by air cooling. Optionally, the UHSS further comprises Mn, Al, Ti, B, P, S, N.

UHSS can be offered with a protective coating to improve corrosion protection before, during or after the hot forming process. This coating may be a zinc coating or a silicon aluminum coating.

In some examples, the workpiece can be cooled in a cooling tool to a temperature of 400-600 ºC. For zinc coated UHSS, cooling to this temperature range before drawing can prevent cracking. The temperature range is such as to still maintain good formability for the subsequent drawing process.

Silicon aluminum coated UHSS blanks can be used in such a way as to eliminate the need for shot peening to remove some or all of the zinc oxide layer after the hot stamping process. The use of a multi-stage device can improve plant performance.

In some examples, the method may further include cooling the preform during drawing. In some examples, the billet can be cooled during drawing to a temperature of 320-280 ºC.

In some examples, the temperature of the workpiece can be maintained above 200 ºC in the first and optionally also in the second finishing tool.

In some examples, blanks may be made from UHSS containing, in percentage by weight: 0.15-0.25% C, maximum 0.5% Si, maximum 2.5% Mn, 0.002-0.005% B, and maximum 0.05 %Cr. In some examples, the UHSS may further contain Al, Ti, P, and Mo.

In some examples, blanks can be made from UHSS containing, in percentage by weight: 0.15-0.25% C, maximum 1% Si, 2.5% Mn, 0.002-0.005% B and 0.5-0.7 %Cr. Preferably the UHSS material contains in percentage by weight: 0.15-0.25% C, maximum 0.5% Si, maximum 2.5% Mn, 0.002-0.005% B and maximum 0.5% Cr. In some examples, the UHSS may further contain Al, Ti, P, and Mo.

In an alternative example, the UHSS material contains in percentage by weight: 0.15-0.25% C, maximum 0.5% Si, maximum 2.5% Mn, 0.002-0.005% B and maximum 0.5% Cr, preferably approximately 0.3%Cr. In some examples, the UHSS may further contain Al, Ti, P, and Mo.

UHSS with compositions according to the preceding paragraphs is not air-quenchable and may instead require a higher cooling rate to obtain a martensitic microstructure.

In some examples, steel that does not harden when cooled in ambient air may be 22MnB5 steel. An example of 22MnB5 steel is Usibor® 1500P. The composition of Usibor® is given below in percentage by weight (the rest is iron (Fe) and unavoidable impurities):

After a hot forging process with cold die quenching, Usibor® 1500P can have a yield strength of, for example, 1100 MPa and an ultimate tensile strength of 1500 MPa.

Usibor® 2000 is another boron steel with even higher strength. After the hot stamping process with cold die quenching, the yield strength of ^Usibor® 2000 can be 1400 MPa or more, and the ultimate tensile strength can be higher than 1800 MPa. The composition of Usibor ^® 2000 contains in mass fractions: a maximum of 0.37% carbon, a maximum of 1.4% manganese, a maximum of 0.7% silicon and a maximum of 0.005% boron.

For UHSS without ambient air quench capability, the first cooling of the workpiece before drawing the workpiece may be from a temperature above the austenitizing temperature to 600-800ºC, optionally 650-700ºC. Subsequently, during molding, the temperature of the preform can be reduced to, for example, 450-250 ºC, optionally 320-280 ºC.

Brief description of the drawings

Non-limiting examples of the present invention will be described below with reference to the accompanying drawings, in which:

in fig. 1 is a schematic representation of a multi-stage pressing system according to the example;

in fig. 1A-1F schematically illustrate the sequence of steps during the process of cooling and molding a preform using the multi-stage pressing system according to FIG. 1;

in fig. 2A is a schematic representation of another example of a multi-stage pressing system;

in fig. 2B schematically illustrates an upper gas cooling tool according to the example shown in FIG. 2A;

in fig. 3A-3F schematically illustrate the sequence of states occurring in the process of cooling and molding blanks, in accordance with the example; and

in fig. 4 schematically illustrates yet another example of a multi-stage pressing system.

Detailed description of examples

In FIG. 1A is a schematic representation of an example of a multi-stage pressing apparatus. The device 1 contains a fixed lower working part 2, a movable upper working part 3 and a mechanism (not shown) configured to ensure the movement of the press up and down the movable upper working part 3 relative to the fixed lower working part 2.

The fixed lower working part 2 can be a large metal plate. In this particular example, the fixed lower working part 2 may be stationary. In some examples, a die damper (not shown) may be provided built into the fixed lower working portion 2. The damper may be configured to receive and control forces acting on the workpiece holder. The movable upper working part 3 can also be a single piece of metal. The movable upper working part 3 can provide a tact cycle (moving up and down).

The pressing system may be configured to perform approximately 30 cycles per minute, so one stroke cycle may last approximately 2 seconds. In the following examples, the tact cycle may be different.

The press mechanism can be driven mechanically, hydraulically or servo-mechanically. The movement of the movable upper working part 3 relative to the fixed lower working part 2 can be determined by the mechanism. In this particular example, the press may be a servo-mechanical press, so that a constant pressure force can be provided during the cycle. In a servo-mechanical press, an unlimited possibility of controlling the speed and position of the sliding (power cylinder) can be provided. The servo-mechanical press can also be provided with a wide range of pressure forces in any sliding position, thus achieving high press flexibility. Servo-driven presses may have opportunities to improve the conditions and productivity of the metal forming process. The press may have a pressure force of, for example, 2000 Tn.

In some examples, the press may be a mechanical press, so the movement of the pressure force to the fixed lower working part 2 may depend on the drive and the hinge system. In this way, mechanical presses can achieve more cycles in a unit of time. Alternatively, hydraulic presses can also be used.

A cooling tool 10 configured to cool a preheated workpiece 80 is shown in FIG. 1. Cooling tool 10 may include a lower gas cooler 12. This lower cooling tool may contain air knives. The lower cooling tool 12 may include a compressed air plenum containing a series of holes or continuous slots through which the compressed air exits, and preferably with a laminar flow pattern.

The air that comes out of the slots or holes acts on the heated workpiece 80. In this way, the workpiece 80 is cooled.

The lower gas cooling tool may contain various control mechanisms. For example, it is possible to control the temperature of the gas in a pressure chamber with compressed air. As an alternative or additional option to control the flow of air towards the workpiece, one or more valves may be included.

The advantage of using gas cooling is that the cooling profile (temperature versus time) can be precisely controlled. It is also relatively easy to maintain uniform cooling over the course of a production cycle, such as a day.

In examples, centering elements such as pins, workpiece holders 16 and/or guides may be provided in the cooling tool.

The pins or holders 16 support the workpiece 80 at a distance d1 from the lower gas cooling tool 12 at any time.

This example also provides a press die 20 configured to form or stretch a blank and is integrated into a multi-stage pressing device. The press die 20 is located downstream of the cooling tool 10. The press die 20 contains the upper 21 and lower 22 mating dies. "Coupled" as used herein means that the dies have complementary shapes so as to deform the workpiece placed between them as the upper press die 21 moves towards the lower press die 22.

In this particular case, the blank 70 is shown to go through a molding or stretching step in the next pressing cycle. It is obvious that the workpiece 70 in the previous cycle has undergone a cooling process in the cooling tool 10.

The upper die 21 may include an upper working surface 23 which, in use, faces the blank to be thermoformed. The lower die 22 may include a lower working surface 24 which, in use, faces the preform to be thermoformed. The side or part of the upper die opposite the upper working surface 23 can be connected to the upper working part 3, and the side or part of the lower die opposite the lower working surface 22 can be connected to the lower working part 2.

The upper 21 and lower 22 mating dies may include cold fluid channels such as water and/or cold air passing through the channels provided in the dies. In the water channel, the water circulation rate in the channels may be high so that water evaporation can be prevented. Additionally, a control system for controlling the temperature of the dies may be provided.

In examples, the pressing system 20 may be provided with a workpiece holder 25 configured to hold the workpiece and place the workpiece on the lower die 22. The workpiece holder may be provided with one or more biasing elements configured to move the workpiece holder to a position at a predetermined distance from lower stamp 22.

A first post-processing tool 30 capable of performing trimming and/or punching operations may be provided. In this particular example, billet 60 undergoes a trimming or cutting operation on the next press cycle. It is clear that the blank 60 has previously been subjected to a cooling process in a cooling tool 10 and a molding process in a die 20.

The first finishing tool 30 is located downstream of the press die 20. The first finishing tool 30 may comprise top 32 and bottom 31 dies. The upper die 32 may comprise an upper work surface 33 and the lower mating die 31 may comprise a lower work surface 34. In use, both work surfaces face the work piece 60.

The side of the upper die 32 opposite the upper working surface 33 may be fixed to the upper working part 3, and the side of the lower die 31 opposite the lower working surface 34 can be fixed to the lower working part 2. The dies may contain one or more knives or cutting blades (not shown) located on the working surfaces.

The first finishing tool 30 may include one or more electrical heaters or hot fluid passages and temperature sensors to control the temperature of the dies. The sensors may be thermocouples. In some examples, it is preferable to maintain the temperature of the workpiece located between the upper and lower dies, in case of use at or near a given temperature, for example, above 200 ºC, above 250 ºC or above 300 ºC.

In some instances, the upper 32 and lower 31 mating dies may include cold fluid channels such as water and/or cold air passing through the channels provided in the dies.

In the examples, the first post-processing tool 30 may be provided with a workpiece holder (not shown) configured to hold the workpiece and place the workpiece on the lower die 31. The workpiece holder may also be provided with one or more bias elements configured to bias the workpiece holder. to a position at a predetermined distance from the lower die.

In the example shown in FIG. 1, a second post-treatment tool 40 is provided. The second finishing tool 40 may also be configured to perform additional trimming and/or punching operations. The second post-treatment tool 40 is located downstream of the first post-treatment tool 30. The second finishing tool 40 may comprise an upper die 42 and a lower die 41. The upper mating die 42 may comprise an upper work surface 43 and the lower mating die 41 may comprise a lower work surface 44. In use, both work surfaces may be facing the workpiece to be hot forming. The work surfaces may be irregular in shape, for example, they may contain protrusions or indentations.

The side of the upper die 42, opposite to the working surface 43, can be connected to the upper working part 3. The side of the lower die 41, opposite to the working surface 44, is connected to the lower working part 2.

The dies may contain one or more knives or cutting blades located on the working surfaces.

In some examples, an adjustment device (not shown) may be provided to adjust the distance between the top 42 and bottom 41 dies. Thus, the blank 50 located between the top 42 and bottom 41 dies can be deformed along the working surfaces of each top and bottom dies in use.

After adjusting the distance between the upper 42 and lower 41 deformation dies (and thus sizing the blank), the tolerances of the hot formed blank can be reduced. In some examples, the preform to be thermoformed may have an area of non-optimized thickness, such as a thickness that is greater in one part of the preform than in any other part, thus the thickness is to be optimized.

With this arrangement of irregularly shaped work surfaces, the distance in selected parts of the work surfaces (for example, near the radius in the workpiece) can be adjusted in or near the non-optimized thickness area, thus the material can be deformed, i.e. extruded to fill the zones adjacent with a non-optimized thickness area, so that a constant thickness can be achieved throughout the workpiece.

In the examples, the control device can be controlled based on a sensor system configured to determine the thickness of the workpiece.

In some examples, the second post-processing tool 40 may be provided with a workpiece holder (not shown) configured to hold the workpiece and position the workpiece on the lower die 41. The workpiece holder may also be provided with one or more biasing elements configured to the possibility of shifting the workpiece holder to a position at a given distance from the lower die.

In the following examples, other ways of matching tool dies for operation at lower or higher temperatures may also be envisaged.

It should be understood that although the figure shows dies having a substantially square or rectangular shape, the blocks may be of any other shape and may even have partially rounded shapes.

Also, for transporting workpieces between tools, an automatic transport device (not shown), for example, a plurality of industrial robots or a conveyor, can be provided.

In all examples, temperature sensors and control systems may be provided in any of the tools or in the transport system to control the temperature. Tools with additional cooling systems, workpiece holders, etc. can also be provided.

In FIG. 1A-1F schematically illustrate the sequence of states that occur during the process of cooling and molding blanks, in accordance with the example. Like elements are designated by like reference numerals.

For the sake of simplicity, references to the corners of the pressing cycle are sometimes included in descriptions with respect to FIGS. 1A (and subsequent figures). Angle references can be used to indicate the approximate positions of the top work piece relative to the bottom work piece. Thus, for example, reference can be made to the top work piece 1 being at 0º relative to the bottom work piece, which indicates that the top work piece is at the highest position relative to the bottom work piece, and the 180º position indicates that the upper working part is in the lowest position (full contact position) relative to the lower working part. Then 360º again refers to the upper working part, which is at the highest point, and the process cycle is completed.

In FIG. 1A, a hot-formed blank 80 made of ultra-high strength steel (UHSS) can be provided. In this particular example, billet 80 may be zinc coated. In some examples, UHSS may contain, for example, approximately 0.22% C, 1.2% Si, 2.2%. Predetermined amounts of Si and Mn can ensure that the workpiece is quenched at room temperature, and thus rapid quenching can be avoided (and thus pressing time in the production of the workpiece can be reduced). The workpiece material may further contain Mn, Al, Ti, B, P, S, N in different proportions.

Ultra high strength steel (UHSS) with these characteristics can have an Ac3 transformation temperature (austenitic transformation temperature, hereinafter referred to as "Ac3 temperature") of 860-870 ºC. For the above steel composition, Ac3 can be approximately 867 ºC. The transformation temperature Ms (martensitic transformation start temperature, hereinafter referred to as "Ms temperature") can be 380-390 ºC. For the above steel composition, Ms can be approximately 386 ºC. The transformation temperature Mf (martensitic transformation end temperature, hereinafter referred to as "Mf temperature") may be equal to or close to 270 ºC.

You can use different compositions of steel. In particular, the steel compositions described in EP 2735620 A1 can be considered suitable. Specific reference may be made to Table 1 and paragraphs 0016-0021 of EP 2735620, as well as to the ideas in paragraphs 0067-0079.

Billet 80 may be heated to achieve at least the austenitizing temperature. The heating may be carried out in a heating device (which is not shown), such as an oven. In this particular example, the maximum temperature for heating the preform may be determined by the coating. The melting temperature (and thus vaporization temperature) of zinc can be equal to or close to 910 ºC, thus the maximum temperature for heating the billet 80 in the heating device can be chosen below about 910 ºC. Billet 80 can be heated to a temperature above Ac3 but below the zinc vaporization temperature of 910 ºC or close to it. In addition, heating can be carried out in the range of 867-910 ºC, in particular at a temperature equal to or close to 890 ºC (for the above steel composition). The heating time period may be approximately 6 minutes, but it depends on the thickness of the workpiece, for example.

After the billet 80 has been heated to the desired temperature for a sufficiently long time, the billet 80 can be transported to the cooling tool 10. This can be done by an automatic transport device (not shown), such as a plurality of industrial robots or a conveyor. The transport time of the workpiece between the furnace (not shown) and the cooling tool 10 can be 2-3 seconds.

In some examples, a centering element may be provided, such as pins and/or guides upstream of the cooling tool, so that the workpiece can be properly centered. Workpiece 80 may be positioned on workpiece pins or holders 16 that maintain a minimum distance between lower gas coolant tool 12 and workpiece 80.

The upper working part 3 of the press can be placed in the open position (position 0º). The workpiece 80 is then positioned on the gas cooling tool 11. In some examples, the workpiece may be positioned on a workpiece holder.

As commented above, the bias elements may comprise, for example, a spring, such as a mechanical spring or a pneumatic spring, although some other bias elements may possibly be, for example, a hydraulic mechanism. The hydraulic mechanism may be a passive or active mechanism.

In FIG. 1B, the press has started moving the press down the movable upper working part 1 relative to the fixed lower working part 2. In this particular example, the cooling has already begun. However, it is noted that in other examples, the cooling cycles may be continuous, and thus the cooling may begin as soon as the workpiece 80 is positioned in the cooling tool.

A stream of compressed cooling gas (which may be air) may be applied to the workpiece. The gas flow can be controlled based on flow meter measurements. The gas pressure may be, for example, about 2 bar. The required gas flow, gas temperature and cooling time may vary depending on the thickness of the preform, for example. A thicker billet will require more cooling until the gas temperature drops and/or the gas flow increases.

Slots or holes through which gas can flow to the preform may be located substantially perpendicular to the front surfaces of the preforms.

In FIG. 1C, for example, in the range of 130-180º, deformation may start in the press die.

In FIG. 1D after reaching the desired end position (position 180º), the movement of the press upwards of the upper working part by means of the press mechanism can be provided. The end of the cooling cycle can be in the range of positions 210-270º of the upper working part (and thus the upper die) relative to the lower working part.

As commented above, during the pressing of the billet 80, the billet can be cooled by using cooling equipment in the press dies. It has been found that zinc-coated ultra-high-strength steel (UHSS) can develop microcracks at die temperatures above 600ºC. In this way, the preform can be cooled down to temperatures below 600 ºC, in particular 500-600 ºC, and preferably to a temperature equal to or close to 550 ºC, before being transported to the press die.

As already commented, billet 80 may be preheated to a temperature equal to or close to 890 ºC, i.e. heated in an oven. The workpiece can be transported to the cooling tool 10, so during the transport period the temperature can be reduced to 850-800 ºC or 750 ºC. The workpiece can then be cooled down to approximately 550 ºC.

By using a cooling tool 10 built into the pressing system or device, the time for cooling the workpiece can be optimized since additional movement for transporting the workpiece from an external cooling tool can be eliminated. It can also save time. In addition, movements of the workpiece between tools can be limited, so that the cooling rate can be easily controlled.

In FIG. 1E, the billet 80 may already be cooled, and thus ready for transport from the cooling tool 10 to the press die 20. The transport may be performed by an automatic transport device (not shown), such as a plurality of industrial robots or a conveyor. As commented above, the billet can be transported at or near 550ºC. Due to the transport time, the billet 80 can be cooled before it reaches the forming tool.

While blank 80 is subjected to the process described above, other blanks 50, 60, 70 may be subjected to other processes. Blank 70 is pulled while blanks 50 and 60 are post-processed.

When forming, the last full contact between the working surface of the upper die of the forming tool and the workpiece (and thus the end of the pull operation) can be in the 180-210º position. The last contact between the workpiece and the workpiece holder in this example may be in the position 210-270º, for example.

The temperature of the preform 70 can be reduced during molding until a temperature of 300-400 ºC is reached, in particular approximately 350-370 ºC. The press die may be provided together with a cooling system. The cooling system can be controlled by a controller so that the temperature of the work piece 70 can be lowered and maintained at the desired temperature.

The blank 60 has already been drawn and transported from the die 20 to the first post-processing tool 30, for example for punching holes or trimming edges. The transport may be performed by an automatic transport device (not shown), such as a plurality of industrial robots or a conveyor. As commented above, billet 60 may exit die 20 at temperatures above 300 ºC, and in particular at 350-370 ºC. Thanks to the transport time, workpiece 60 can be cooled down a little further. The blank 100 may be placed on the lower die 31 and between the lower die 31 and the upper die 32.

The workpiece 60 has been transported or located on the lower die 31, and the automatic transport system can be configured to feed the workpiece 200 to the press die 20 and feed the workpiece 300 to the cooling tool 10. As a result, the cooling tool 10 can start the operation of cooling the workpiece 300, as commented higher. At the same time, the press die 20 may start the drawing and cooling operation of the billet 300, as also commented above.

In the first finishing tool, the upper die 32 can only contact the workpiece 60 located between the upper die 32 of the press die and the lower die 31 of the press die when the desired end position (equal to or close to 180º of the press cycle) has been reached.

While the press is in contact with the workpiece 60, the hole punching operation can be performed using cutting blades or other cutting elements. After the hole punching operation is completed, the edge trimming operation can be performed. In alternative examples, the trimming operation may be performed first, and the trimming operation may also be performed after the trimming operation is completed. Edge trimming and hole punching can also be performed substantially simultaneously.

While the workpiece 60 is being post-processed, the workpiece may be heated using the heating equipment discussed above to maintain a minimum temperature of the workpiece and ensure workpiece deformability.

After reaching the desired end position (pressing cycle position 180º), the upward movement of the press can be carried out. The last full contact between the working surface of the top die 32 and the workpiece 100 (and thus the end of the operation) can be in the 180-210º position. The last contact between the workpiece and the workpiece holder (if provided in finishing tools) can be observed in the range of 210-270º of the pressing cycle.

Finally, in this particular example, a second post-processing tool is included in the pressing device. Obviously, in the following example, a post-treatment tool may be omitted, or more than two post-treatment tools may be included in the compression device.

In this example, the second finishing tool can be used to punch holes or trim edges. In addition, a calibration operation can be performed, thus manufacturing tolerances can be reduced. To this end, the distance between the upper die 42 and the lower die 41 can be adjusted using an adjusting device. The control device can be controlled based on a sensor system (not shown) capable of detecting the thickness of the workpiece 100. In the following example, the workpiece can be pressed by the upper 42 and lower 41 dies, thus a constant thickness of the workpiece can be achieved. In the same way as the die temperature of the first post-processing tool (and thus the temperature of the workpiece) can be controlled, it is also possible, in particular, to ensure the minimum temperature of the workpiece.

After completion of the operation of the second finishing tool, the workpiece can be transported and quenched at room temperature.

In some examples, depending on the desired shape of the final component, additional drawing and other operations, such as punching holes and/or trimming edges, may be provided. In the following examples, the order of post-processing may be changed (eg, first cutting, then calibration, or vice versa).

In FIG. 2A shows another example of a multi-stage pressing device. In this example, the cooling tool 10 contains both an upper cooling tool 11 and a lower gas cooling tool 12.

In this specific example, the upper gas cooling tool 11 is connected to the movable upper working part 1 by means of one or more biasing elements. The biasing element pushes the upper gas cooling tool from the movable upper working part 1 to the stationary lower working part 2. The biasing element in this example may be springs, such as mechanical springs or air springs, but other biasing elements can be used in other examples. Such alternative biasing elements may include, for example, a hydraulic mechanism for pushing the cooling tool towards the opposite cooling tool.

In other examples, the lower gas cooling tool 12 may be connected to the stationary lower working part 1 by means of biasing elements. The principle of operation will be the same as described in this document for the upper gas cooling tool. In some examples, both the upper gas coolant tool 11 and the lower gas coolant tool 12 may be provided with biasing elements.

By inserting the upper and/or lower biasing elements, the cooling time can be adjusted and increased during the tact cycle (up and down movements of the movable upper working part 1 relative to the lower working part 2).

Thanks to the bias elements in the cooling tool, cooling can begin before the press dies of the forming tool (and downstream downstream tools) make contact.

Limiters 14 are provided in the upper gas cooling tool. These are also illustrated in FIG. 2b. The stops 14 may be in the form of a rod and may come into contact with the lower gas cooling tool 12 (or the fixed lower working part) when the movable upper working part 1 moves down. Limiters 14 may maintain a distance between the upper and lower gas cooling tool. This also means that the distance between the upper gas cooling tool 11 and the workpiece 80 is maintained.

The size and shape of the stops may be chosen such that the distance from the upper gas cooler 11 to the billet 80 is also maintained at a distance d1 (distance between the lower air cooler 12 and the billet 80) for the part of the pressing cycle when cooling takes place.

With reference to FIG. 2B, an example of a possible arrangement of a plurality of stops 14 can be seen. In this example, the stops 14 are typically straight bars. The distal ends 14A of the stops may be flat, and in this example a contact surface may be provided for the lower gas cooling tool. As mentioned above, the function of the upper and lower gas cooling tools may be opposite. The bars 14 are attached to the side surfaces 19 of the upper gas cooling tool 11. Also in FIG. 1B shows a plurality of straight slots 18 through which pressurized cooling gas can exit and flow to the workpiece.

The upper gas cooling tool 11 can be located at a predetermined distance relative to the upper working part 2 using the upper displacement elements 13.

In FIG. 3A-3F illustrate a sequence of steps similar to that of FIG. 1A–1F. However, in contrast to the previous example, the cooling tool in this example contains both the upper gas cooling tool 11 and the lower gas cooling tool 12.

In FIG. 3A shows the multi-stage pressing device shown in FIG. 2A before the press starts moving, for example at 0º press cycle.

In FIG. 3B, the pressing device began the downward movement of the press of the movable upper working part 1 relative to the stationary lower working part 2, thus the upper gas cooling tool 11 moved to the lower die 12 (and thus the workpiece 80 was located on the lower tool 11).

The upper gas coolant tool 14 moves the stops 14 which extend to the lower gas coolant tool. In the case shown in FIG. 3B, the stops 14 are near the position to come into contact with the lower gas coolant tool 12.

In FIG. 3C, for example in the range of 90º-150º of the press cycle, the stops 14 come into contact with the lower gas coolant tool. The billet 80 is then at a predetermined distance from the upper gas cooling tool. The workpiece is also at a predetermined distance from the lower gas cooling tool. The workpiece can be located at an equal distance from the upper and lower gas cooling tool. With the correct determination of the distances from the workpiece to the upper and lower gas cooling tool, controlled cooling can take place.

As the movement of the press continues, the distance between the upper and lower cooling tools and between the cooling tools and the workpiece can be maintained as the biasing elements are compressed.

A stream of compressed cooling gas (which may be air) may be applied to the workpiece. As stated above, the gas flow can be controlled based on flow meter measurements. The gas pressure may be, for example, about 2 bar. The required gas flow and gas temperature may vary, for example, depending on the thickness of the preform. A thicker billet will require more cooling until the gas temperature drops and/or the gas flow increases. Using both the bottom and top gas cooling tool can provide a relatively short cooling cycle even for thicker workpieces.

In FIG. 3D, after reaching the desired end position (position 180º), the movement of the press upwards of the upper working part can be provided by means of the press mechanism. The end of the cooling cycle can be in the range of positions 210-270º of the upper working part (and thus the upper die) relative to the lower working part. The top bias elements 13, which can be seen still partially compressed in the case of FIG. 3D may begin to return to their original position or configuration. By appropriately arranging the biasing elements, the cooling period can be longer than the compression period and the cooling cycle can last, for example, in the range of 0.33-1 second.

Fig. 3E and FIG. 3F are basically the same as those illustrated in FIG. 2E and 2F.

In the example described herein, gas cooling begins when the workpiece is positioned at a specific predetermined distance from the upper and lower air-cooling tools. Obviously, in other examples, gas cooling may begin before such a point and may also be prolonged.

In FIG. 4 schematically illustrates yet another example of a multi-stage pressing device. In this example, the cooling tool 10 does not contain a lower cooling tool, but only contains an upper gas cooling tool 11. The upper gas cooling tool 11 can be connected to a movable upper working part 1 with upper displacement elements 13.

The upper gas cooling tool may contain restrictors 14 as shown above. As in the previous example, the combination of offset elements 13 and stops allows you to quickly reach the minimum distance between the cooling tool and the workpiece, and then maintain this minimum distance. Thus, the cooling cycle may be longer than the molding cycle.

For completeness, various aspects of the present invention are set forth in the following numbered paragraphs:

Clause 1. A pressing device for the production of hot-formed structural elements, comprising: a fixed lower working part, a movable upper working part and a mechanism configured to ensure the movement of the press up and down the movable upper working part relative to the fixed lower working part, while the device contains:

a cooling tool configured to cool the preheated workpiece, and

a press die configured to pull the workpiece and which is located downstream of the cooling tool, and

a workpiece transport mechanism for transporting the workpiece from the cooling tool to the press die,

wherein the cooling tool comprises an upper gas cooling tool connected to the movable upper working part, and/or a lower gas cooling tool connected to the fixed lower working part,

wherein the press die comprises an upper pressing die connected to the upper working part and a lower pressing die connected to the lower working part.

Claim 2. The pressing device according to claim 1, wherein the pressing device is configured such that the cooling time exceeds the pulling time in the pressing cycle.

Item 3. The pressing device according to item 1 or 2, containing the lower gas cooling tool connected to the stationary lower working part.

Item 4. The pressing device according to item 1 or 2, comprising an upper gas cooling tool connected to the movable upper working part by means of one or more upper biasing elements that displace the upper gas cooling tool from the movable upper working part.

Item 5. The pressing device according to item 1 or 2, where the cooling tool comprises an upper gas cooling tool connected to a movable upper working part, and a lower gas cooling tool connected to a fixed lower working part,

wherein the upper gas cooling tool is connected to the movable upper working part by means of one or more upper displacement elements that displace the upper gas cooling tool from the movable upper working part, and/or the lower gas cooling tool is connected to the fixed lower working part by means of one or more lower displacement elements which displace the lower gas cooling tool from the stationary lower working part.

Item 6. The pressing device of item 4 or 5, wherein at the bottom of the pressing cycle, the upper gas coolant is at a predetermined first distance from the workpiece and the lower gas coolant is at a predetermined second distance from the workpiece.

Item 7. The pressing device according to item 6, wherein the predetermined first distance is equal to the predetermined second distance.

Item 8. The pressing device according to any one of items 4-7, wherein the cooling tool contains stops that maintain a minimum distance between the upper gas cooling tool and the workpiece.

Claim 9. The pressing apparatus of claim 8, wherein stops are provided on the upper gas coolant tool, wherein the stops are positioned to contact the lower gas coolant tool to generate a force opposing the biasing elements.

Item 10. The pressing device according to item 9, where the limiters are rods or bars.

Item 11. The pressing device according to any one of items 8-10, where the device is configured to start a cooling cycle when a minimum distance between the upper gas cooling tool and the workpiece is reached.

Item 12. The pressing device according to any one of items 4-11, where the bias elements contain one or more springs.

Claim 13. The pressing system according to any one of claims 1-12, wherein the upper gas cooling tool and/or the lower gas cooling tool comprise a plurality of slots connected to a compressed gas reservoir, the system further comprising a control for controlling the flow of gas from the reservoir through slots.

Item 14. The pressing system of item 13, where the slots are directed essentially perpendicular to the workpiece.

Item 15. The pressing system of item 14, wherein the gas is air at room temperature.

Item 16. The compression system according to any one of items 13-15, further comprising means for controlling the temperature of the compressed gas in the reservoir.

Item 17. The pressing device according to any one of items 1 to 16, wherein the upper and/or lower pressing die of the pressing die includes channels that conduct coolant or cooling air.

Claim 18. The pressing apparatus of claim 17, wherein the temperature in the upper and/or lower press ram is controlled based on the temperature on the working surface of one of the dies.

Item 19. The pressing device of item 18, further comprising one or more thermocouples on the working surface of one of the pressing dies.

Claim 20. A pressing device according to any one of paragraphs 1-19, wherein the pressing device is a mechanical press.

Item 21. The pressing device according to any one of paragraphs 1-19, where the pressing device is a servo-mechanical press.

Claim 22. A pressing device according to any one of paragraphs 1-19, wherein the pressing device is a hydraulic press.

Item 23. The pressing device according to any one of items 1-22, further comprising a first post-treatment tool configured to perform a first post-treatment, wherein the first post-treatment tool is located downstream of the press die and includes:

upper and lower dies of the first postoperative tool, while

the upper die of the first finishing tool is connected to the upper working part, and the lower die of the first finishing tool is connected to the lower working part, and at the same time

the workpiece transport mechanism is further configured to transport the workpiece from the press die to the first post-processing tool.

Item 24. The pressing device of item 23, wherein the first post-processing includes trimming and/or cutting the workpiece, and

the upper and/or lower dies of the first postoperative tool comprise one or more cutting blades.

Item 25. The pressing device of item 23 or 24, wherein the upper and/or lower die of the first post-treatment tool comprises one or more heaters or hot fluid passages.

Claim 26. The pressing apparatus of Claim 25, wherein the heaters or hot fluid passages are configured to maintain the temperature of the workpiece above 250 ºC or 300 ºC based on the temperature measured on the dies of the first finishing tool.

Item 27. The pressing device according to any one of items 23-26, wherein the upper and/or lower die of the first finishing tool comprises channels that conduct coolant, optionally coolant water.

Item 28. The pressing device according to any one of items 25-27, wherein the temperature in the upper and/or lower die of the first finishing tool is controlled based on the temperature on the working surface of one of the dies.

Item 29. The pressing device of item 28, further comprising one or more thermocouples on the working surface of one of the dies of the first post-processing tool.

Claim 30. The pressing apparatus of any one of Claims 23-29, further comprising a second post-treatment tool, wherein the second post-treatment tool is located downstream of the first post-treatment tool, and the workpiece transport mechanism is further configured to transport the workpiece away from the first post-treatment tool. treatment to the second postoperative instrument, and at the same time

the upper die of the second finishing tool is connected to the upper working part, and the lower die of the second finishing tool is connected to the lower working part.

Item 31. The pressing device of item 30, wherein the second finishing tool is configured to trim edges and/or punch holes.

Item 32. The pressing device of item 31, wherein the second finishing tool comprises upper and lower dies of the second finishing tool, wherein

the first and/or second postoperative tool comprises one or more cutting blades.

Item 33. The pressing device according to any one of items 30-32, wherein the second finishing tool comprises an adjusting device configured to adjust the distance between the upper and lower dies of the second finishing tool so as to deform the workpiece, and wherein the adjusting device is operated on the basis of a sensor system configured to determine the thickness of the workpiece.

Item 34. The pressing device according to any one of items 30-33, wherein the temperature in the upper and/or lower die of the first finishing tool is controlled based on the temperature on the working surface of one of the dies.

Item 35. The pressing device of item 34, further comprising one or more thermocouples on the working surface of one of the dies of the first post-processing tool.

Item 36. A method for hot forming a preform, including:

- provision of a pressing device according to any of paragraphs 1-35;

- providing a billet to be hot formed, made of ultra-high strength steel (UHSS), having a zinc coating;

- heating the workpiece;

- placement of the workpiece in the cooling tool;

- cooling the workpiece, while ensuring the movement of the press down the movable upper working part relative to the fixed lower working part;

- moving the press upwards of the movable upper working part relative to the fixed lower working part;

- installation in the required position of the workpiece in the press die; and

- pulling the workpiece by moving the press down and up the movable upper working part relative to the fixed lower working part.

Item 37. The method of item 36, wherein the preform is heated to a temperature that is higher than the UHSS austenitization temperature.

Item 38. The method according to item 37, in which the workpiece is heated to a temperature of 860-910 ºC.

Item 39. The method of any one of items 36-38, wherein the UHSS contains about 0.22% C, 1.2% Si, 2.2% Mn.

Item 40. The method of item 39, wherein the UHSS further comprises Mn, Al, Ti, B, P, S, N.

Item 41. A method according to any one of items 36-40, wherein the workpiece is cooled in a cooling tool to a temperature of 500-600 ºC.

Item 42. The method of any one of items 36-41, further comprising cooling the workpiece during drawing.

Item 43. The method of item 42, in which the preform is cooled during drawing to a temperature of 400-300 ºC.

Item 44. The method of any one of items 36-43, wherein the pressing device comprises a first finishing tool comprising upper and lower dies of the first finishing tool containing cutting blades, wherein

the upper die of the first finishing tool is connected to the upper working part, and the lower die of the first finishing tool is connected to the lower working part, and

the method further includes punching holes and/or trimming the edges of the workpiece by

transporting the workpiece from the press die to the first post-processing tool; and

ensuring the movement of the press down and up the movable upper working part relative to the fixed lower working part.

Item 45. The method according to item 44, wherein the temperature of the workpiece located in the first finishing tool is maintained above 200 ºC, in particular above 300 ºC.

Item 46. The method of any one of items 44 or 45, wherein the pressing device comprises a second finishing tool comprising upper and lower dies of the second finishing tool, wherein

the upper die of the second finishing tool is connected to the upper working part, and the lower die of the second finishing tool is connected to the lower working part, and

the method further includes:

transporting the workpiece from the first finishing tool to the second finishing tool; and

ensuring the movement of the press down and up the movable upper working part relative to the fixed lower working part.

While only a few examples are disclosed herein, other alternatives, modifications, uses, and/or equivalents are possible. In addition, all possible combinations of the described examples are also covered. Thus, the scope of the present invention should not be limited to specific examples, but should be determined only by careful reading of the following claims.

Claims (32)

1. A pressing device for the production of hot-formed structural elements, comprising: a fixed lower working part, a movable upper working part and a mechanism configured to ensure that the movable upper working part moves up and down under pressure relative to the fixed lower working part, characterized in that the device contains : a cooling tool configured to cool the preheated workpiece, and a press die configured to pull the workpiece and which is located downstream of the cooling tool, and a workpiece transport mechanism for transporting the workpiece from the cooling tool to the press die, wherein the cooling tool comprises an upper gas cooling tool connected to the movable upper working part, and/or a lower gas cooling tool connected to a fixed lower working part, while the upper gas cooling tool and/or the lower gas cooling tool are configured to provide a flow compressed cooling gas to act on the workpiece, and wherein the press die comprises an upper pressing die connected to the movable upper working part and a lower pressing die connected to the fixed lower working part. 2. Pressing device according to claim 1, characterized in that the pressing device is designed in such a way that the cooling time exceeds the pulling time in the pressing cycle. 3. Pressing device according to claim 1 or 2, comprising a lower gas cooling tool connected to a fixed lower working part. 4. Pressing device according to claim 1 or 2, comprising an upper gas cooling tool connected to the movable upper working part by means of one or more upper biasing elements that displace the upper gas cooling tool from the movable upper working part. 5. The pressing device according to claim 1 or 2, characterized in that the cooling tool comprises an upper gas cooling tool connected to the movable upper working part, and a lower gas cooling tool connected to the fixed lower working part, wherein the upper gas cooling tool is connected to the movable upper working part by means of one or more upper displacement elements that displace the upper gas cooling tool from the movable upper working part, and/or the lower gas cooling tool is connected to the fixed lower working part by means of one or more lower displacement elements which displace the lower gas cooling tool from the stationary lower working part. 6. Pressing device according to claim 4 or 5, characterized in that at the bottom of the pressing cycle, the upper gas cooling tool is at a predetermined first distance relative to the workpiece, and the lower gas cooling tool is at a predetermined second distance relative to the workpiece, and optionally the first distance is equal to the given second distance. 7. Pressing device according to any one of paragraphs. 4-6, characterized in that the cooling tool contains stops that maintain a minimum distance between the upper gas cooling tool and the workpiece. 8. Pressing device according to claim 7, characterized in that limiters are provided on the upper gas coolant tool, wherein the limiters are arranged to come into contact with the lower gas coolant tool to create a force opposite to the biasing elements. 9. Pressing device according to any one of paragraphs. 4-8, characterized in that the bias elements contain one or more springs. 10. The pressing device according to any one of paragraphs. 1-9, characterized in that the upper gas cooling tool and/or the lower gas cooling tool contain a plurality of slots connected to the reservoir with compressed gas, while the system further comprises a control to control the flow of gas from the reservoir through the slots. 11. Pressing device according to claim 10, characterized in that the slots are directed perpendicular to the workpiece. 12. The pressing device according to any one of paragraphs. 1-11, characterized in that the upper and/or lower pressing die of the pressing die comprises channels conducting coolant or cooling air. 13. The pressing device according to any one of paragraphs. 1-12, characterized in that the pressing device is a mechanical press or a servomechanical press. 14. The pressing device according to any one of paragraphs. 1-13, further comprising a first post-treatment tool configured to perform a first post-treatment, wherein the first post-treatment tool is located downstream of the press die and comprises: upper and lower dies of the first postoperative tool, while the upper die of the first finishing tool is connected to the upper working part, and the lower die of the first finishing tool is connected to the lower working part, and at the same time the workpiece transport mechanism is further configured to transport the workpiece from the press die to the first post-processing tool. 15. A method for hot forming a workpiece, including: providing a pressing device according to any one of paragraphs. 1-14; providing a billet to be hot formed made of ultra high strength steel (UHSS) having a zinc coating; heating the workpiece; placement of the workpiece in the cooling tool; cooling the workpiece to ensure downward movement under pressure of the movable upper working part relative to the fixed lower working part; performing an upward movement under pressure of the movable upper working part relative to the fixed lower working part; installation in the required position of the workpiece in the press die; and pulling the workpiece by performing a downward and upward movement under pressure of the movable upper working part relative to the fixed lower working part.

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