EP2257651B1 - Method for shaping from a blank of a hardening material with differential cooling - Google Patents

Abstract

The invention relates to a drawing tool (1) for shaping and cooling a steel part from a blank (6), said tool including: at least one punch (2); and at least one matrix (3); the punch and the matrix each including: at least a first portion (21, 31) corresponding to a hot area (11) of the drawing tool; and at least a second portion (22, 32) corresponding to a cold area (12) of the drawing tool; in the cold area, the second part of the punch and the second part of the matrix are brought into contact with the blank when the drawing tool is closed; characterized in that, in the hot area of the drawing tool, a heating means are provided for heating said hot area to a temperature higher than about 400° C., and in that, in said hot area, a distance (L) on top of the blank thickness (e) is provided between the punch and the matrix when the drawing tool is closed, is related to the temperature (T) of the hot area, and is given by the formula T=100·(6-L), with L>0.2 and 400@T<600; L being in mm and T in ° C.

Description

The present invention relates to hot forming processes with cooling. More particularly, the present invention relates to hot forming processes from blank of quenching material with differential cooling.

A tool according to the preamble of claim 1 and a method according to the preamble of claim 7.

Such a tool and such a method are described in the document WO-A-2006038868 .

A stamping process with quenching of a piece of material dipping in the same tool is known and is described in document JP 2005-205416 . In this process, a blank is shaped by a stamping tool. After stamping, while the piece is still held in the tool, quenching is performed by contact between the tool and the stamped blank. In addition to this contact is made a cold water circulation in pipes provided for this purpose in the stamping tool which accelerates the cooling.

However, for certain steel parts, it would be useful to be able to temper only part of the part. For example, in the automotive field, it would be advantageous to be able to make a foot-medium having areas with different mechanical characteristics. Thus some areas can be made ductile or preserved to improve shock absorption during a collision.

Today, this type of parts is made in two or more parts by different forming and cooling processes. The two or more parts are then bonded by welding techniques well known to those skilled in the art.

The method used today is therefore expensive in time and equipment. In addition, the weld portion is an area of weakness presenting a risk to the user during an impact.

The document US 5,916,389 also discloses such a method wherein a steel object is obtained. This steel object is composed of different parts whose material is in different structural states; some parts are hardened, others remain ductile.

• des éléments de chauffe peuvent être prévus dans un poinçon et une matrice d'un outil d'emboutissage ; ou
• des renfoncements sont prévus dans le poinçon et la matrice de l'outil d'emboutissage, de sorte que lorsque le poinçon et la matrice viennent au contact du flan en acier, il n'y a pas de contact là où il y a des renfoncements ; c'est-à-dire là où l'acier doit rester ductile.

In order to maintain a more ductile structure of the steel in some places, several possibilities are proposed:

• heating elements may be provided in a punch and a die of a stamping tool; or
• recesses are provided in the punch and die of the stamping tool, so that when the punch and die come into contact with the steel blank, there is no contact where there are recesses ; that is, where the steel must remain ductile.

However, the mechanical properties at the end of manufacture depend closely on the cooling rate. The use of the heating means alone or the use of the recesses alone does not make it possible to obtain the expected results on the mechanical properties.

The document US 2002/0104591 discloses a method in which a foot-medium is formed with two parts having different mechanical properties. A first part corresponding to the upper part of the foot-medium has a martensitic structure with a mechanical strength beyond 1400N / mm ² . A second portion corresponding to the lower part of the foot-medium has a ferritic-pearlitic structure and a mechanical strength of less than 850N / mm ² (about 500N / mm ² ) and an elongation of less than 25% (preferably 20%) .

In order to obtain a foot-medium having two parts with different mechanical properties, the lower part to remain ductile is protected from heat when heated to austenitic temperature. Thus, the lower part of the foot-medium is not in an austenitic state at the end of the heating and therefore can not be tempered to obtain a martensitic structure.

This method has the following disadvantage: when the blank remains in the oven longer than the required time (even a time slightly longer), the transition zone between the hardened and unhardened parts may widen.

• une première variante consiste à réaliser à peu de choses près le même procédé que celui décrit dans le document US 2002/0104591 ;
• une deuxième variante consiste à utiliser un outil d'emboutissage présentant des moyens de refroidissement là où une trempe est souhaitée ;
• dans une troisième variante, l'outil d'emboutissage présente différentes parties en matériaux différents, ayant des valeurs de conductivité thermique différentes.

The document US 2002/0113041 discloses a heat-forming method with differential cooling, having several variants:

• a first variant consists in practically producing the same method as that described in the document US 2002/0104591 ;
• a second variant consists in using a stamping tool having cooling means where a quenching is desired;
• in a third variant, the stamping tool has different parts made of different materials, having different thermal conductivity values.

The inventors have tried to obtain hardened steel parts having the desired mechanical properties using low conductivity materials (eg concrete having a conductivity of about 2W.m ^-1 .K ^-1) for stamping tool. The results obtained were not convincing. Also, a low conductivity of the material does not prevent the first parts in production from being quenched since they are in contact with the cold tool.

The document DE 10 2006 019 395 A1 discloses a method, wherein the stamping tool comprises a die, a punch and a blank holder. The three elements of the stamping tool can be heated to different temperatures. Nevertheless only examples where the three parts are heated to an identical temperature are given. The method consists in heating the stamping tool to a temperature of between 200 and 650 ° C.

For a temperature below 200 ° C, the elongation A ₈₀ is about 5%, and the mechanical strength above 1500 MPa. For a temperature above 200 ° C, the elongation A ₈₀ is greater than 5.8% and mechanical strength below 1500 MPa. For a temperature of 400 ° C., the mechanical strength is 820 MPa and the elongation A _{80 is} 10%.

When there is a temperature drop from 790 ° C to 390 ° C, a cooling rate of about 80 to 115 K / s is measured (it would appear that this is valid for a tool temperature above 200 ° C). The structure of the steel is then martensitic with fine grain. For a tool temperature below 200 ° C, a cooling rate of about 80 to 480 K / s is measured. In this case, the steel structure is martensitic to coarse grain.

Nevertheless, the conditions under which these tests were carried out do not make it possible to obtain the desired mechanical properties, namely an elongation A ₈₀ greater than about 15% and a mechanical strength R _m greater than 500 MPa.

It is only at the cost of a selection of cooling conditions that the inventors have succeeded in obtaining a hardened steel object whose mechanical properties are satisfactory.

The inventors have filed a patent application on ¹ August 2007 under number 07/56863 and published under the number FR-A-2919512 . In this application is described a hot forming process with differential quenching from tube, wherein, a tube is heated up to an austenitization temperature and then formed and cooled in a stamping tool, having heating means by injecting a coolant through the tube cavity. These heating means used to prevent, in some places, the material to become martensitic.

This method, although operating for the tubes, is not applicable to the forming of a blank because of the difference in geometry.

An object of the present invention is to provide a method for obtaining a stamped piece from a steel blank and whose mechanical characteristics can cover a range of possible mechanical characteristics between those of untreated steel and those hardened steel.

Another object of the present invention is to provide a method that does not require a traditional step of tempering a stamped and tempered part.

Another auxiliary object of the present invention is to confer different properties of mechanical strength and elongation of the material to different parts of the same room, as sought by those skilled in the art.

• au moins un poinçon ; et
• au moins une matrice ;
  le poinçon et la matrice comprenant chacun :
• au moins une première partie correspondant à une zone chaude de l'outil d'emboutissage ; et
• au moins une deuxième partie correspondant à une zone froide de l'outil d'emboutissage ;

dans la zone froide, la deuxième partie du poinçon et la deuxième partie de la matrice venant au contact du flan quand l'outil d'emboutissage est fermé ; et
caractérisé en ce que, dans la zone chaude de l'outil d'emboutissage, sont prévus des moyens de chauffe aptes à porter cette zone chaude à une température au-dessus d'environ 400°C ; et en ce que dans la zone chaude, une distance en sus d'une épaisseur flan est prévue entre le poinçon et la matrice quand l'outil d'emboutissage est fermé, est liée à la température (T) de la zone chaude et est donnée par la formule : $$\mathbf{T}=100.\left(6-\mathbf{L}\right),$$

avec L > 0,2 et 400 ≤ T < 600 ; L étant exprimé en mm et T en °C.For this purpose, the present invention provides a stamping tool for forming and cooling a steel part from a blank, the tool comprising:

• at least one punch; and
• at least one matrix;
  the punch and the die each comprising:
• at least a first portion corresponding to a hot zone of the stamping tool; and
• at least a second portion corresponding to a cold zone of the stamping tool;

in the cold zone, the second part of the punch and the second part of the die coming into contact with the blank when the stamping tool is closed; and
characterized in that, in the hot zone of the stamping tool, heating means are provided capable of carrying this hot zone to a temperature above about 400 ° C; and in that in the hot zone, a distance in excess of a blank thickness is provided between the punch and the die when the stamping tool is closed, is related to the temperature (T) of the hot zone and is given by the formula: $$\mathbf{T}=100.\left(6-\mathbf{The}\right),$$

with L > 0.2 and 400 ≤ T <600; L being expressed in mm and T in ° C.

• sur une face de formage de la première partie du poinçon est prévue au moins une saillie ;
• sur une face de formage de la première partie de la matrice est prévue au moins une saillie ;
• dans la première partie du poinçon, sont prévus au moins en partie les moyens de chauffe ;
• dans la première partie de la matrice, sont prévus au moins en partie les moyens de chauffe ;
• l'outil d'emboutissage présente un jeu d'air entre la zone froide et la zone chaude.

Other preferred but non-limiting characteristics of this stamping tool are:

• on one forming face of the first part of the punch is provided at least one projection;
• on one forming face of the first part of the matrix is provided at least one projection;
• in the first part of the punch are provided at least in part the heating means;
• in the first part of the matrix are provided at least in part the heating means;
• the stamping tool has an air gap between the cold zone and the hot zone.

The present invention also provides a method of forming and cooling according to the features of independent claim 7.

• la température de chauffe de la zone chaude de l'outil d'emboutissage est en dessous d'environ 600°C ;
• dans la zone chaude, un refroidissement est effectué à une vitesse comprise entre environ 5°C/sec et environ 15°C/sec ;
• dans la zone froide, un refroidissement est effectué à une vitesse comprise entre environ 27°C/sec et environ 100°C/sec.

Other preferred but nonlimiting features of this process are:

• the heating temperature of the hot zone of the stamping tool is below about 600 ° C;
• in the hot zone, cooling is carried out at a rate of between about 5 ° C / sec and about 15 ° C / sec;
• in the cold zone, cooling is carried out at a rate of between about 27 ° C / sec and about 100 ° C / sec.

• la figure 1 est une représentation schématique en perspective d'un outil d'emboutissage selon la présente invention ;
• la figure 2 est une vue schématique en coupe transversale d'une première partie de l'outil d'emboutissage comprenant des moyens de chauffe ;
• la figure 3 est une vue schématique en coupe transversale d'une deuxième partie de l'outil d'emboutissage ;
• la figure 4 est une vue schématique d'un pied-milieu réalisé conformément à l'invention.

Other characteristics, objects and advantages will appear on reading the description which follows and based on the drawings given by way of example, among which:

• the figure 1 is a schematic perspective representation of a stamping tool according to the present invention;
• the figure 2 is a schematic cross-sectional view of a first part of the stamping tool comprising heating means;
• the figure 3 is a schematic cross-sectional view of a second portion of the stamping tool;
• the figure 4 is a schematic view of a foot-medium made according to the invention.

In the remainder of the description, the elongation values at break are understood as test values obtained on a specimen A ₈₀ .

With reference to the figure 1 will be described below a stamping tool 1 according to the invention.

The stamping tool 1 comprises a set of punches 2 and a set of dies 3 . The set of punches 2 and the set of dies will hereinafter be called punch 2 and die 3, respectively .

The matrix 3 has a recess generally complementary to a relief of the punch 2 . The complementarity of this recess and the relief gives a heated blank 6 a specific shape.

The punch 2 and the die 3 comprise at least two parts 21, 22; 31, 32 corresponding to at least two zones: a hot zone 11 and a cold zone 12.

In the remainder of the description, the expression air gap is understood to mean a distance L in addition to a thickness of the blank 6 between the die 3 and the punch 2. That is to say, if the thickness of the blank 6 is e, a distance d between the die and the punch when the stamping tool 1 is closed is: $$\mathbf{d}\mathbf{=}\mathbf{The}\mathbf{+}\mathbf{e}\mathbf{.}$$

Also, it will be considered later that there is air gap when the distance L is greater than a machining tolerance value necessary for the punch 2 and the matrix 3 since to be stamped. This tolerance is a maximum of 0.2 mm. A set of air then corresponds to a distance L greater than 0.2 mm.

It will be said, moreover, that there is contact between the stamping tool 1 and the blank 6 if L is less than 0.2 mm.

In a first portion 21 of the punch 2 corresponding to the hot zone 11 are provided heating elements 4.

Alternatively, in a first portion 31 of the die 3 corresponding to the hot zone 11 are also provided heating elements 4.

The heating elements 4 are therefore provided either only in the punch 2, or only in the die 3, or in both at once.

These heating elements 4 make it possible to bring the hot zone 11 to a temperature greater than 400 ° C. and preferably below 600 ° C.

The heating elements 4 are chosen from heating cartridges, induction heating devices and thermal sheaths.

The use of heat cartridges is mainly well suited for straight stamping tools without much curve.

Thermal ducts and induction heaters can conform to curved shapes.

With reference to the figure 2 , will be described hereinafter the first parts (respectively 21 and 31 ) of the punch 2 and the die 3 corresponding to the hot zone 11.

In a first variant, the punch 2 and the die 3 each have a forming face (respectively 21f and 31f ). The forming face 21f of the punch 2 is not complementary to the forming face 31f of the die 3 so as to leave an air gap 7, defining a distance L between the punch 2 and the blank 6 and between the die 3 and the blank 6. This air gap 7 is less than about 2 mm.

The punch 2 then has on the forming face 21f at least one projection 211 which abuts against the forming face 31f of the die 2 (as shown in FIG. figure 2 ). This projection 211 has a maximum height of about 2 mm maximum.

Sub-variant, this projection 211 may be present not on the forming face 21f of the punch 2 but on that 31f of the die 3.

As a further subvariant, at least one protrusion 211 is present both on the forming face 21f of the punch 2 and 31f of the matrix 3. These projections 211 are then facing one opposite the other or no.

In a second variant, the punch 2 and the die 3 have forming faces 21f, 31f substantially complementary to one another. Thus, if for example the forming face 21f of the punch 2 has a surface of which a section has a substantially Ω shape, the forming face 31f of the die 3 also has a surface of which a section has a substantially Ω shape, so that the punch 2 can be inserted into the die 3. When the stamping tool 1 is closed, there remains only a reduced space whose thickness is filled by the blank 6 during forming.

In parts 22 and 32, respectively of the punch 2 and the die 3, corresponding to the cold zone 12, the punch 2 and the die 3 have substantially complementary shapes (as illustrated in FIG. figure 3 ). That is to say that the punch 2 and the die 3 each have a forming face 21f, 31f complementary to that 31f, 21f of the other, to the nearest thickness.

Sub-variant, in the second parts 22, 32 of the punch 2 and the matrix 3, are provided cooling systems, for example water circulation circuits.

When the stamping tool 1 is closed on the blank 6 to be formed, there is no clearance present between the blank on one side and the second parts 22, 32 of the punch 2 and the die 3 of another side.

Hereinafter is described a method according to the invention.

The blank to be formed 6 is made of steel, for example a boron steel (NF EN 10083-1, -2 and -3 standards). But the material of the blank 6 is not limited to boron steels, it can be any type of steel suitable for the manufacture of the workpiece.

The blank 6 is raised to a temperature beyond which the steel structure becomes austenitic. Then the blank 6 is placed in the stamping tool 1 for forming.

During forming, the stamping tool 1 is closed on the blank 6 making contact, at least partially, the blank 6, the punch 2 and the die 3.

• entre le flan 6 et le poinçon 2 là où il y a une saillie 211 ; et/ou
• entre le flan 6 et la matrice 3 là où il y a une saillie 211 ; et/ou
• entre le flan et la face 31f de formage de la matrice 3 ; et/ou
• entre le flan et la face 21f de formage du poinçon 2 ;

selon la sous-variante de réalisation de la zone chaude 11 de l'outil d'emboutissage 1 employée ; et il ne peut y avoir contact à la fois entre le flan 6 et la totalité de la face de formage 21f du poinçon 2 et entre le flan 6 et la totalité de la face de formage 31f de la matrice 3. In the first variant, there is contact only:

• between the blank 6 and the punch 2 where there is a projection 211; and or
• between the blank 6 and the die 3 where there is a projection 211; and or
• between the blank and the forming face 31f of the die 3; and or
• between the blank and the forming face 21f of the punch 2;

according to the sub-variant embodiment of the hot zone 11 of the stamping tool 1 used; and there can not be contact both between the blank 6 and the entire forming face 21f of the punch 2 and between the blank 6 and the entire forming face 31f of the die 3.

In this first variant, the hot zone 11 of the stamping tool 1 is brought to a temperature above about 400 ° C. and below about 600 ° C.

avec L > 0,2 et 400 ≤ T < 600 ; L étant exprimé en mm et T en °C.The necessary air gap 7 is connected to the temperature T of the hot zone 11 by the following formula: $$\mathbf{T}=100.\left(6-\mathbf{The}\right),$$

with L > 0.2 and 400 ≤ T <600; L being expressed in mm and T in ° C.

The heating of the hot zone 11 of the stamping tool 1 as well as the air gap 7 contribute to a descent in temperature at a speed of between about 5 ° C./sec and about 15 ° C./sec. from a start temperature of about 900 ° C and an end temperature of from about 400 ° C to about 600 ° C. The structure of the steel of the blank 6 therefore does not become hard (martensitic) but ductile with a mechanical strength of between about 450 MPa and about 800 MPa; and an elongation greater than about 15%.

In the second variant, there is contact between the hot zone 11 of the stamping tool 1 and the blank 6, and it is brought to a temperature of about 600 ° C. When the stamping tool 1 is brought to this temperature, the steel of the blank does not become hard (martensitic) but ductile with a mechanical strength of between about 450 MPa and about 800 MPa; and an elongation of from about 15% to about 20%.

In the cold zone 12, the blank 6 is formed by the closure of the stamping tool 1; the punch 2 and the die 3 coming into contact with the blank 6 on their respective forming face 21f, 31f . Quenching is carried out, that is, cooling with a temperature drop of between about 27 ° C / sec and about 100 ° C / sec, between a start temperature of about 900 ° C. and an end temperature of about 250 ° C. The cold zone is maintained at a temperature of at least the forming time. In this cold zone 12, the mechanical strength is between about 1200 MPa and about 1700 MPa; and the elongation is from about 3% to about 7%.

Tests carried out by the inventors of the invention have shown that a stamping of a blank 6 with differentiated quenching, in which the stamping tool is brought to a temperature of 250 ° C. and comprises an air gap. of 2 mm, gives the forced room a mechanical strength of about 770 MPa and an elongation A ₈₀ of about 10.5%.

A stamping of a blank 6 with differentiated quenching, in which the stamping tool is heated to a temperature of 400 ° C. and comprises an air gap 7 of 2 mm, gives the forced part a mechanical strength of about 610 MPa and an elongation a ₈₀ of about 19.4%.

A stamping of a blank 6 with differentiated quenching, in which the stamping tool is heated to a temperature of 500 ° C. and comprises an air gap 7 of 1 mm, gives the forced part a mechanical strength of about 570 MPa and an ₈₀ % elongation of about 21%.

Alternatively, between the cold zone 12 and the hot zone 11 of the stamping tool 1 is provided an air gap 8 less than 2 mm At this zone 8, the formed part has a transition zone in which the hardness of the material goes from 250 Hv (hot zone) to 450 Hv (cold zone).

This transition zone on the final piece is of the order of 20 mm.

The stamping tool 1 is kept closed long enough (pressing time) for the structure of the material to undergo the desired transformation.

The pressing time is equivalent to the time required for quenching the cold part; i.e., between about 5 and about 15 seconds.

Other operations are possible in the stamping tool at the same time as forming and cooling: trimming (cutting of the part in the press tool), calibration (finishing in order to obtain the right shape).

An example of application is given below, purely for illustrative purposes. A foot-medium is formed from a blank 6 of steel.

A foot-medium 9 is a part having a generally I-shaped shape (with wheelbase) intended to be placed between the front door and the rear door of a vehicle. Specifically, the foot-medium 9 has a central portion 9a extending generally vertically and two ends (upper 9b and lower 9c ), each ending with a T (T tumbled for the lower end). The foot-medium 9 has a cross section generally in Ω.

It is advantageous for the safety of a user of the vehicle that the foot-medium 9 does not have homogeneous mechanical characteristics. Preferably, it is sought to give a first upper portion 92, said cold portion, a high mechanical strength (between about 1200 MPa and about 1700 MPa) and a low elongation (between about 3% and about 7%) to obtain anti-intrusion properties (to protect the passenger); and a second bottom portion 91, said hot portion, a lower mechanical strength (about 450 MPa to about 800 MPa) and greater elongation (greater than about 15%, to obtain absorbing properties of energy in case of shock.

Thus, during a collision between vehicles or during a collision between the vehicle and an obstacle, the hot part 91 of the foot-medium 9 deforms and absorbs the energy of the shock.

Today, in order to obtain such a foot-medium, an automobile manufacturer manufactures the part in two parts separately having different mechanical properties as described above with two different manufacturing processes. The two parts are then joined together, thus creating a

zone of fragility between the two parties. With the tool and the method of the present invention, the foot-medium 9 can be made in one piece, which avoids the need for assembly, for example by laser, and thus eliminates this area of weakness.

A blank 6 of steel is heated to an austenitic temperature and then placed in the stamping tool 1. The punch 2 and the die 3 have forming faces 21f, 31f capable of conferring the shape of the foot-medium 9 finished to the blank 6 steel.

The punch 2 and the die 3 are made in two zones ( 11, 21, 31; 12, 22, 32 ). The cold zone 12 corresponds to the upper part 92 of the central foot 9, the hot zone 11 corresponds to the lower part 91 of the central foot 9.

où L est le jeu d'air 7 et e l'épaisseur du flan 6. When the drawing tool 1 is completely closed on the blank 6 for forming, the distance d 2 punch die 3 is defined in the hot zone according to the first variant of the invention by: $$\mathbf{d}\mathbf{=}\mathbf{The}\mathbf{+}\mathbf{e}\mathbf{,}$$

where L is the air gap 7 and e is the thickness of the blank 6.

In the cold zone 12, there is contact between the punch 2 and the blank 6 and between the die 3 and the blank 6. The temperatures of the hot 11 and cold zones 12 are respectively between about 400 ° C. and about 600 ° C. ° C and between about 50 ° C and about 150 ° C.

According to the second variant of the invention, there is contact between the punch 2 and the blank 6 and between the die 3 and the blank 6 in the two zones. Hot zone 11 is then maintained at about 600 ° C and cold zone 12 between about 50 ° C and about 150 ° C.

Closing the stamping tool 1 on the blank 6 causes the cooling of the steel.

In cold zone 12, the cooling rate is between about 27 ° C / sec and about 100 ° C / sec.

In the hot zone 11, the cooling rate is between about 5 ° C / sec and about 15 ° C / sec.

Between the two zones 11, 12 of the stamping tool 1 is provided an air gap 8 less than 2 mm. This zone corresponds to a transition zone 93 of the formed part not exceeding 450Hv. This area has a length of about 20mm (this area is exaggerated on the figure 4 ). In this transition zone 93, the hardness of the material goes from about 250 Hv near the hot portion 91 to about 450 Hv near the cold portion 92.

The hot part 91 has a mechanical strength of between about 450 MPa and about 800 MPa; and an elongation greater than 7% and preferably above about 15%.

The cold part 92 has a mechanical strength of between about 1200 MPa and about 1700 MPa; and an elongation of from about 3% to about 7%.

The use of the invention is not limited to the production of foot-media. Thus, the invention can also be used to obtain stamped parts having parts that have different mechanical properties (anti-intrusion and energy absorption). Also, the method according to the invention eliminates the traditional step of income after stamping.

Of course, the present invention is not limited to the embodiments described above, but the skilled person will make many variations or modifications while remaining within the scope of the claims.

Claims (10)

1. A drawing tool (1) for shaping and cooling a steel piece from a blank (6), the tool comprising:

   - at least one punch (2); and

   - at least one matrix (3);
   the punch and the matrix each comprising:

   - at least a first portion (21, 31) corresponding to a hot area (11) of the drawing tool; and

   - at least a second portion (22, 32) corresponding to a cold area (12) of the drawing tool;

   wherein, in the cold area, the second portion of the punch and the second portion of the matrix are brought into contact with the blank when the drawing tool is closed; and
   characterized in that, in the hot area of the drawing tool, heating means (4) are provided for heating said hot area to a temperature higher than about 400° C; and in that, in the hot area, a distance (L) on top of the blank thickness (e) is provided between the punch and the matrix when the drawing tool is closed, is related to the temperature (T) of the hot area, and is given by the formula: $$\mathbf{T}=100.\left(6-\mathbf{L}\right),$$

   

   
   with L > 0.2 and 400 ≤ T < 600, L being expressed in mm and T in °C.
2. The drawing tool according to the preceding claim, characterized in that on one shaping surface (21f) of the first portion of the punch, at least one protrusion (211) is provided.
3. The drawing tool according to any one of the preceding claims, characterized in that on one shaping surface (31f) of the first portion of the matrix, at least one protrusion (211) is provided.
4. The drawing tool according to any one of the preceding claims, characterized in that, in the first portion of the punch, the heating means are at least partially provided.
5. The drawing tool according to any one of the preceding claims, characterized in that, in the first portion of the matrix, the heating means are at least partially provided.
6. The drawing tool according to any one of the preceding claims, characterized in that it has air play (8) between the cold area and the hot area.
7. A shaping and cooling method, characterized in that it uses the drawing tool according to any one of the preceding claims, the method comprising the steps consisting of:

   - heating the blank to an austenitic temperature;

   - placing the blank into the drawing tool;

   - closing the drawing tool onto the blank; and

   - removing the shaped piece from the drawing tool;
   wherein the hot area of the drawing tool is brought to a temperature above 400°C using the heating means
8. The method according to the preceding claim, characterized in that the heating temperature of the hot area of the drawing tool is below about 600°C.
9. The method according to one of claims 7 or 8, characterized in that, in the hot area, cooling is done at a speed between about 5°C/sec and about 15°C/sec.
10. The method according to one of claims 7 to 9, characterized in that, in the cold area, cooling is done at a speed between about 27°C/sec and about 100°C/sec.

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