KR20130064712A - Plant and method for hot forming blanks - Google Patents

Abstract

PURPOSE: A method and a facility for hot-forming blanks are provided for a unit to move flame of a burner. CONSTITUTION: A facility for hot-forming blanks includes a unit for moving a flame of a burner or a burner(1) is provided. The unit for moving the flame of the burner and/or the burner comprises a robot. The burner is implemented as a hydrogen - oxygen burner, a fuel - oxygen burner, and an acetylene burner. The burner is implemented as a back up mixing burner.

Description

Method and equipment for hot forming blanks {PLANT AND METHOD FOR HOT FORMING BLANKS}

FIELD OF THE INVENTION The present invention relates to a heating device for a plant for hot forming blanks, in particular an austenitizing device, the heating device being embodied for local heating of the blanks, in particular austenitizing and comprising at least one burner. do. The invention also relates to a corresponding installation for hot forming blanks and a corresponding method for hot forming a blank, in which case one or more zones of the blank are locally heated, in particular austenitized, by pressing Molded.

Hot forming of metal sheets is a relatively new development trend, especially in the manufacture of components for vehicle bodies. In the context of this field, according to the use of well-established representations in the field of shaping techniques, the metal sheets used thereby are thus also identified as "blanks". In principle, the blanks are correspondingly cut, die cut, bonded and / or preformed metal sheets. However, the measures according to the invention can be used not only in the case of correspondingly produced metal sheets, but also in the case of the base materials respectively used. The present invention thus extends to each and every workpiece or semifinished parts, which can be shaped by a corresponding molding process, such as pressing and / or deep drawing.

Hot forming makes it possible to produce components comprising complex geometries and high stability without elasticity, and for car bodies manufactured by hot forming a significant weight reduction, for example as well as for example of the passengers of the corresponding vehicle, Enable increased safety.

In particular, with the increasing demands of stiffness and stability of structural components in vehicles, high strength and highest strength steels are increasingly used. Increased stability provides a reduction in vehicle weight, which in particular provides reduced pollutant emissions and fuel consumption. In the case of current vehicle models, the use of hot formed components can save up to 25 kg in weight.

In essence, hot forming methods are combined with forming and curing and tempering techniques. For example, by using corresponding steels, such as manganese-boron steels, stability above 1,500 MPa can thereby be achieved. Press-curing methods include, for example, heating the blanks to a temperature above the complete austenitization temperature, such as above 850 ° C., and thereafter rapid cooling of the blank in the tool. The desired martensitic structure with the desired stability is formed therethrough. The combination of molding by quenching in the tool is sometimes also identified as press- or mold-hardening.

In principle, so-called roller hearth furnaces are used to preheat blanks in response to hot forming of the highest strength materials for automotive bodies. The heating of these furnaces is usually effected by steel pipes which are heated electrically or by gas burners. In order to get the process cycle times as short as possible, a certain "supply" of preheated components is needed in the installation. The heat treatment period for temperature control of the steel represents a significant parameter that defines the visual cycle of the corresponding press. However, due to the low grade of efficiency at temperatures below 600 ° C., the efficiency of roller hearth furnaces is small. Roller hearth furnaces require lengths of up to 50 meters and thus require corresponding structural conditions, including efficient loss of excess heat. Drum melting furnaces, which are used as an alternative to roller hearth furnaces to preheat components, also include corresponding drawbacks. They are also heated by steel pipes and are unsatisfactory in terms of their efficiency rating.

Press hardened components are characterized by their high stability and stiffness. As mentioned, metal sheet thicknesses can be reduced by press hardening and the weight can thus be saved. However, low final deformation of the press hardened components is a problem, which can lead to the formation of tears in the case of subsequent production operations, for example welding of other parts. For this reason, certain areas of the vehicle body are embodied to be press-cured, for example, and other areas are embodied such that they contain higher ductility and thus absorb more energy by plastic deformation.

Current approaches, which are used to generate these locally different features, so-called "fitting properties", have the specific effect of the alloying elements of the corresponding semi-finished parts, so-called "custom welded blanks", and thus different materials Fabrication of the blanks joined from them, partial (local) heating by inductive or conductive heating techniques, partial temperature control of certain areas of the press hardening tools by local heating, heating in the corresponding roller hearth furnace (and thus auster) Nitriding), including partial tempering of press hardened components and shielding of certain component regions. However, these methods are extensive and the results are often unsatisfactory and they often incur excessive costs.

Accordingly, there is a need for improved possibilities for providing blanks comprising locally different features.

In view of the above, the instant invention proposes a heating device, in particular an austenitizing device and a corresponding installation, for hot forming blanks, the heating device being embodied for locally heating the blanks, in particular austenitizing zones. Means comprising at least one burner and provided with means for moving the burner and / or flame of the burner into zones where local heating is provided.

A method for hot forming the blank is also proposed, in which case one or more zones of the blank are locally heated, in particular austenitized, formed by pressing, and the zones of the blanks being heated are heated by one or more burners. And the flame of the burner and / or burner in the zone to be heated is moved.

Preferred embodiments are the subject matter of the following description as well as the dependent claims.

The measures proposed in accordance with the invention provide a means for moving the flame of the burner and / or the burner to a zone in which local heating is provided, in a heating device for a plant for hot forming blanks, in particular in an austenitizing device. Wherein the heating device is implemented for local heating of the zones of the blanks, in particular austenitization, and comprises one or more burners.

As mentioned above, the term "blanks" in the context of the present application should be understood in a comprehensive manner. The term includes metal sheets, semi-finished parts, combined and / or preformed components that are hot formed, in particular press hardened, in the corresponding installation.

An important aspect of the present invention is the use of burners and / or means for moving the flames of the burners. Only such use makes it possible to specifically heat only certain areas of the blanks continuously, without heating the entire blank. Means for moving the burner or burner flame allow for accurate local heating of the blank with high spatial resolution. Compared to fixed burners, movable burners or movable burners each have the advantage of increased variability. In addition, the burner can be moved very precisely to the position to be heated.

According to the invention, it is possible to move one or a plurality of burners comprising a relatively low flame and / or narrow focus of flame over the zone to be heated so that the zone is heated evenly in all positions. Because of the high focusing of the burner flame, the invention, on the other hand, also enables heating of small zones. However, for defined burners, continuous heating requires the use of a larger flame, which covers the entire area to be heated, but this includes the disadvantage that small zones cannot be heated correctly. This is in turn the reason why a plurality of smaller burners are used, and the area between the individual burner flames will be heated less than the areas directly affected by the flames.

The heating device, in particular an austenitization device, according to the invention is implemented for partial heating, in particular for austenitization, and therefore for heating or austenitizing certain regions or localized regions of the blanks, respectively. One or more burner flames of the burner can thereby be oriented in the zone (s) provided for partial heating, in particular austenitization. The corresponding burner arrangement thus provides, in particular, the defined local austenitization of the zones, and high local stability can be achieved as a result, for example by press hardening. However, higher swelling and lower hardness of the material are ensured in the non-austenitized areas after press hardening.

Means for moving the burner or burners preferably comprise a robot. The term “robot” is in particular a machine or industry which can be programmed and / or controlled and which can move the burner or tilt or rotate the burner to the desired positions so as to affect the area where the flames of the burner are heated. It is understood as a robot. The movement of the burner is caused by a program sequence provided by the robot, or the robot is equipped with sensors or supplies the information required to move the burner or the robot is connected to the sensor. The robot may be provided with a robotic arm, a gripper or other burner holder and control.

The means for moving the robot and generally the burner can be implemented such that the burner can be moved, rotated and / or tilted in all three dimensions. However, as a means for the movement of the burner, it provides one or two linear guides or linear portals, which enable the movement of the burner in one dimension (linear) or in two dimensions (two dimensions). Is often enough.

In a preferred embodiment of the invention, hydrogen-oxygen burners, fuel-oxygen burners, in particular fuel gas-oxygen burners or acetylene burners are used. Such burner types are known in principle from DE 103 45 411 A1, for example. The term acetylene burners includes acetylene-oxygen burners and acenylene-air burners.

It is particularly advantageous to use premix burners. Premixed fuel gas-oxygen burners are also used, for example, for the so-called flame polishing of glass parts, in particular lead crystal or soda-lime glass. At least part of the surface of the glass piece is here heated and melted by a burner flame. Corresponding burners are also known as so-called hydropox burners and are sold under this brand name by the applicant.

Premixed fuel gas-oxygen burners, especially hydrogen-oxygen burners, are characterized by exceptionally high heat transfer efficiency. In contrast to the so-called external mixing burners, the gas mixture of oxygen and fuel gas is already supplied to the burner head of the premixed fuel gas-oxygen burner instead of first being generated in the corresponding burner head. The premix burners produce particularly strong flames, which are suitable for melting larger areas, which may also include recesses or other irregularities. As known in accordance with the invention, this has a significant advantage compared to external mixing burners. Only weak flames, which cannot penetrate into corners, holes or recesses of the surface, can be produced in the external mixing burners. The use of a premix burner thus provides for local heating, in particular of regions of corresponding blanks, in particular of differently shaped regions. It is possible to reach high temperatures by heating by an external mixing burner for a long period of time, but there is a risk that the blank is heated not only in the desired areas, but in the whole. The burners used according to the invention may also be arranged downstream from the installation in the installation or between the downstream pressing tool and the installation.

It has been found to be advantageous to provide a burner comprising a plurality of nozzle openings in which a fuel-oxygen or hydrogen-oxygen mixture or an acetylene-air or acetylene-oxygen mixture leaks to locally heat the blanks. In a preferred embodiment, the burner has 100 to 1000 nozzle openings. Very continuous heating of the zone to be heated is obtained in this way.

The nozzle openings are distributed in the region of the burner head, having a width of 50 to 400 mm. The area of the burner or burner head, covered by the nozzle openings, is each selected preferably as a function of the size of the zones to be heated.

Advantageously, the burner has a plurality of nozzle openings, including a relatively small diameter, arranged close to each other. A very continuous heating of the blanks or the zones of the blanks to be heated can each be obtained in this way. Advantageously, the diameter of the nozzle openings is less than 2 mm or less than 1.5 mm. For example, nozzle openings comprising a diameter of 0.5 mm to 1.3 mm are selected. The nozzle openings are preferably arranged densely, ensuring a very continuous heating. Depending on the size of the nozzle openings, the distance of two adjacent nozzle openings is between 1 mm and 4 mm.

In a preferred embodiment of the invention, the burner or heating device comprising burners has an output of 50 to 500 kPa. Typically, the output of one burner is 30 to 150 mW. Depending on the requirements, one or a plurality of burners are installed. The output of the burner or burners is distributed to the plurality of nozzle openings so that the burner output for each nozzle opening remains relatively low and the local heating of the blank, which is too high, is thus avoided.

According to a particularly preferred embodiment of the invention, the heating device is implemented as an austenitizing device. By using a premixed hydrogen-oxygen burner or a premixed fuel-oxygen burner, local austenitization is particularly possible in a particularly efficient manner. Full austenitization of the blank can also be provided in a particularly fast and energy efficient manner.

It is also pointed out in this context that partial maceration of regions of the blank is also possible by implementing a heating device with a movable burner. For this purpose, for example, the heating device should ensure that only the corresponding areas of the blank are heated to a temperature below the austenitization temperature.

Preferred heating devices, in particular corresponding austenitization devices, are provided for the local heating of the blanks in particular to temperatures of 750 to 1,050 ° C, in particular 800 to 1,000 ° C, such as 850 to 950 ° C. The corresponding temperature depends on the respective materials and exceeds the austenitization temperature. In the case of manganese-boron steels, for example, the austenitization temperature is approximately 850 ° C. If the corresponding blank is preheated to a temperature just below the austenitization temperature, the austenitization temperature can be reached or exceeded rapidly, respectively, by a corresponding burner, which can be predetermined, in particular in the areas of the blank. have.

The installation according to the invention for hot forming blanks has a heating device as described above for locally heating the blanks and a pressing device for forming the heated blanks.

Advantageously, this installation further comprises one or more loading devices for loading the installation and / or one or more delivery devices for delivering the blanks into one or more pressing devices of the installation. By means of the corresponding devices, the operation of the corresponding installation is made possible, which can be caused by faster visual cycles due to the efficient heating by the movable burner proposed in accordance with the invention, which is the This is because the limited step, ie the heating of the blanks, is significantly reduced in time.

The visual cycle can be further reduced in particular in that a preheating device is provided upstream of the heating device. The blanks first pass through a preheating device where they are completely heated. Certain zones of the blanks are subsequently heated again or further heated with the aid of the heating device according to the invention.

Advantageously, the at least one preheating device comprises at least one patterner furnace. For example, vertical patternoster furnaces, which include improved energy efficiency and, in particular, offer the advantage of replacing large roller hearth furnaces with a large design, such as those mentioned above, and thus requiring corresponding structural conditions, In principle it can be used as known patternoster furnaces. For example, the patternor furnaces can be heated electrically or by fuel and can be operated in corresponding temperature ranges, ensuring efficient and reliable heating.

Advantageously, the corresponding equipment comprises a preheating device, which is provided for preheating the blanks at a temperature of 450 to 850 ° C., in particular 600 to 800 ° C., for example 650 to 750 ° C. In another embodiment, the preheating device serves to preheat the blanks at a temperature of 450 ° C to 550 ° C. Advantageously, the corresponding preheating temperatures are just below the lower limit of the austenitization temperature of the corresponding materials or below a certain degree of lower limit, so that complete austenitization of the materials is still not obtained by preheating of the blanks. Each temperature used depends on the material of the respective blanks. As mentioned, the complete austenitization temperature of manganese-boron steels is, for example, 850 ° C. One skilled in the art can simply derive the corresponding temperatures from the main values of the available materials. Because of only a relatively small degree up to the austenitization temperature, the corresponding preheating is subsequently partially austenitized in a short period of time in an energy efficient manner, especially in the (defined) regions of the blanks that can be predetermined. To provide. As mentioned, partial softening of the corresponding blank material may also be provided in response to heating to a temperature below the austenitization temperature.

It has been found advantageous to implement such a preheating device having at least one premixed hydrogen-oxygen burner or fuel gas-oxygen burner. Very efficient, in particular also area preheating per area of the blanks, is also possible by this.

Advantageously, heating devices, in particular austenitizing devices, and preheating devices are combined in the form of structural units. This provides compact installations that have a small design and can be worked in an energy efficient manner, eg requiring thermal or temperature insulation respectively.

It has been found advantageous to provide a heating device with a housing. The heat loss during the local heating of the blank is reduced in this way and the degree of efficiency is thus improved.

The invention is used for the manufacture of motor vehicle body components of motor vehicles, for example B-pillars of motor vehicle cells, in a particularly advantageous manner. Special requirements are made for these automotive body components in terms of hardness, material stability and expansion characteristics. In particular, the blanks used for this purpose should not be too brittle, as otherwise a tear may be formed in the material in response to the forming and welding processes necessary for the fabrication of automotive body components. .

According to the invention, the burners or burners used for heating, in particular austenitization, produce water or steam containing exhaust gases. When these water containing exhaust gases reach the preheating device, a significant dew point occurs in the preheating device, which can lead to an increased portion of diffusible hydrogen in the metallic structure of the blanks. The blanks thus become more brittle and may cause material tearing (“slowed rupture”) as described above.

Thus, preferably, means are provided for preventing exhaust gas from reaching the preheating device from the burner or burners of the heating device. In a preferred embodiment, an intake device for extracting exhaust gas from the housing is provided for this purpose. For this purpose, the housing comprises one or a plurality of vents, which are connected to the extraction device. Exhaust gas not only flows out of the vents, but is actively removed. The vents are not the same as the inlet or outlet openings for conveying or ejecting the blank into and out of the housing.

Preferably, the vents are arranged so that a flow that keeps the exhaust gas away from the inlet opening is implemented in the housing to prevent the exhaust gas from reaching the preheating device connected upstream of the inlet opening through the inlet opening. In addition, the inlet opening can be provided with a gas veil, in particular a nitrogen veil. Gas, such as nitrogen, is blown into the housing in the region of the inlet opening, forming a gas barrier against the leaking exhaust gas. It is also possible to close the inlet opening by means of a slide, flap or other mechanical means, instead of or in addition to the gas bale, to prevent leakage of exhaust gas.

If other processing steps that can be found in relation to humidity or other components or features of the exhaust gas continue downstream from the housing, the housing has a corresponding protection to prevent leakage of the exhaust gas through the outlet opening of the housing. It can also be found to provide sex measures.

The method according to the invention for hot forming the blank comprises the zone of the blank being heated by one or more burners, the burner and / or the flame of the burner being moved towards the zone of the blank being heated, and the blank is then subjected to pressing. It is characterized by being molded by.

In an embodiment, the blanks are loaded into a plant according to the invention, preheated to a preheating temperature by a preheating device of the plant, and at least locally heated or austenitized, respectively, by a heating device, in particular an austenitizing device, It is shape | molded by pressing by a pressing apparatus. As described, the pressing method may be a press cure method.

The plant according to the invention for hot forming blanks, the heating device according to the invention for the partial austenitization of such plant blanks as well as the method according to the invention for hot forming and partial austenitization are described above. Similarly beneficial from these advantages.

It is needless to say that the features and features mentioned previously, which are described below, can be used in each particular combination, as well as in other combinations or alone, without departing from the scope of the instant invention.

The invention is schematically illustrated in the drawings by way of example embodiments and will be described in detail below with reference to the drawings.

1 is a schematic illustration of a plant for hot forming blanks according to a preferred embodiment of the invention,
2 is a schematic illustration of burner heads used in accordance with an embodiment of the present invention and the state of the art;
3 is a diagram illustrating in a flowchart form a method for hot forming blanks according to an embodiment of the invention.

In the drawings, the same elements or elements having the same effect, if applicable, have the same reference numerals and will not be described again for the sake of clarity.

1 is a view showing a facility for hot forming blanks according to a preferred embodiment of the present invention. The installation is identified by reference numeral 10 as a whole. This installation has a loading device 3, in which corresponding blanks P, for example punched metal sheet pieces, can be loaded into the corresponding installation in the direction of the arrow (lower horizontal arrow). A preheating device 4 is provided, schematically shown here as a patterner furnace. The blanks P flow into the lower region of the preheating device 4 in the direction of the arrow, rise upwards (shown by the vertical arrows) and are continuously heated during the rise. Reference is made to the above information on the temperatures used in the preheating device 4.

In the upper region of the preheating device 4, the blanks P leave the preheating device in the direction of the arrow (upper horizontal arrow). They then pass through an austenitization device 2 comprising a burner 1, symbolized here as a burner 1 of three flames. Burner 1 may comprise any number of burner flames. The burner 1 may also be spherical so as to be able to move and affect different areas of the blank P in succession. For this purpose, corresponding exercise devices can be provided, which can also be controlled fully automatically, for example by using a corresponding control. The blanks P pass through the austenitizing device 2 in the direction of the arrow, where it is heated in at least predetermined locally defined regions to a temperature exceeding the austenitization temperature of the corresponding material.

The blanks P are then reached into the delivery device 5 where it is delivered to a pressing tool, for example not shown in FIG. 1.

A preferred embodiment of the burner head, which can be used according to the invention, is shown in FIG. 2 (right). To further illustrate, a burner head for use according to the state of the art is shown in FIG. 2 (left).

A so-called external mixing burner head for use according to the state of the art is identified with reference 21 and a premix burner head, which can be used according to the invention, is identified with reference 22.

For example, the external mixing burner head 21 has a line 212 located on the outside for providing oxygen and a line 211 located on the inside for providing fuel gas, in particular hydrogen. . Mixing of gases provided through both channels takes place first in the region of the burner nozzles 213. As established, the corresponding so-called external mixing burners generate relatively weak flames, which are only conditionally suitable for the purpose according to the invention. The minimum distance between the two burner nozzles 213 is also defined by the dimensions of the fuel gas supply line 211 and the oxygen supply line 212. This means that the distance of the fuel nozzles 213 among the fuel nozzles cannot drop below a certain minimum distance, whereby the number of the fuel nozzles 213 for each length is limited upward or vice versa.

Stronger burner flames, which ensure improved energy transfer, are generated by the premixed hydrogen-oxygen burners, which are used according to the invention and have a common channel 221 where the hydrogen-oxygen mixture is fed to the burner head 22. Can be. In particular, areas, embodied in recesses or more complex shapes, can be affected by the heat required, for example in a more reliable manner. The corresponding gas mixture already flows out of the nozzles 223 as a mixture and is ignited here. In addition, burner nozzles 223 may be arranged more densely than in the case of embodiments in an external mixing burner. The compact arrangement of burner nozzles 223 provides a significantly more uniform heating of the blank.

3 shows schematically a flowchart of a method according to a particularly preferred embodiment of the invention. In the first method step 101, the corresponding blanks P are punched out of the metal sheet. In a second method step 102, these blanks are loaded into a hot forming facility according to the invention, for example by means of a loading device. This can happen continuously. In step 103 the blanks P are preheated in the installation, and the means described previously for this purpose can be used. In step 104, in particular partial austenitization takes place as described above. After austenitization, the blanks P are transferred into the pressing tool by the delivery device in step 105 where it is pressed, for example press hardened, in step 106. After quenching in the pressing tool, blanks comprising regions with different coupling features are thus available.

1 burner
2 heating devices (austenitic devices)
3 loading device
4 preheating device
5 transmission device
10 Plants for hot forming
21 burner head
22 burner head
100 method for hot forming
101 stamping
102 loading
103 Preheat
104 Austenitic
105 delivery
106 pressing
211 hydrogen supply line
212 oxygen supply line
214 fuel nozzle
221 Mixture Supply Line
223 fuel nozzle
P blank

Claims (18)

Heating device, in particular austenitizing device 2, for installation 10 for hot forming blanks P, which is embodied for local heating of zones of blanks P, in particular austenitization and comprising one or more burners ),
Means are provided for moving the burner and / or flame of the burner to said zones where local heating is provided,
Heating apparatus for installations for hot forming blanks.
The method of claim 1,
The means for moving the burner and / or the flame of the burner comprises a robot,
Heating apparatus for installations for hot forming blanks.
3. The method according to claim 1 or 2,
The burner is characterized in that implemented as a hydrogen-oxygen burner, fuel-oxygen burner or acetylene burner,
Heating apparatus for installations for hot forming blanks.
The method according to any one of claims 1 to 3,
The burner is characterized in that it is implemented as a premix burner,
Heating apparatus for installations for hot forming blanks.
The method according to any one of claims 1 to 4,
For local heating of the blanks in particular to a temperature of 750 to 1050 ° C., in particular to a temperature of 800 to 1000 ° C., for example 850 to 950 ° C.,
Heating apparatus for installations for hot forming blanks.
6. The method according to any one of claims 1 to 5,
The burner comprises between 100 and 1000 nozzle openings,
Heating apparatus for installations for hot forming blanks.
7. The method according to any one of claims 1 to 6,
The burner comprises nozzle openings, the diameter of the nozzle openings being less than 2 mm, preferably less than 1.5 mm, particularly preferably between 0.5 mm and 1.3 mm and / or the distance between two adjacent nozzle openings between 1 mm and 4 mm. It is between mm,
Heating apparatus for installations for hot forming blanks.
The method according to any one of claims 1 to 7,
Characterized in that the heating device has an output of 50 to 500 kW,
Heating apparatus for installations for hot forming blanks.
The method according to any one of claims 1 to 8,
The heating device is characterized in that the housing is provided,
Heating apparatus for installations for hot forming blanks.
The method of claim 9,
The housing is provided with a suction device for extracting the exhaust gas from the housing,
Heating apparatus for installations for hot forming blanks.
In the plant (10) for hot forming blanks (P) comprising a heating device for locally heating the blanks and a pressing device for forming the heated blanks,
The heating device 2 is characterized in that it is implemented according to any one of claims 1 to 10,
Facility for hot forming blanks.
The method of claim 11,
One or more loading devices 3 for loading the blanks into the installation 10 and / or one or more delivery devices 5 for delivering the blanks P into the pressing device of the installation 10 are provided. Characterized in that
Facility for hot forming blanks.
13. The method according to claim 11 or 12,
The at least one preheating device 4 is characterized in that it is arranged upstream of the heating device 2,
Facility for hot forming blanks.
The method of claim 13,
Wherein the at least one preheating device 4 comprises at least one patterner furnace,
Facility for hot forming blanks.
The method according to claim 13 or 14,
The at least one preheating device 4 is provided for preheating the blanks at a temperature of 450 to 850 ° C., in particular 600 to 800 ° C., for example 650 to 750 ° C.,
Facility for hot forming blanks.
16. The method according to any one of claims 13 to 15,
Wherein the preheating device comprises at least one premixed hydrogen-oxygen burner or one premixed fuel-oxygen burner,
Facility for hot forming blanks.
In a method 100 for hot forming a blank P, wherein at least one zone of the blank P is locally heated, in particular austenitized and formed by pressing,
Wherein the zone of the blank to be heated is heated by one or more burners and the flame of the burner and / or burner is moved to the zone of the blank to be heated,
Method for hot forming blanks.
The method of claim 17,
The coated blanks are hot formed, in particular the blanks coated with aluminum silicon or zinc are hot formed,
Method for hot forming blanks.

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