DE102010025950A1 - Improving wear resistance of a forming tool, preferably a heat forming tool useful for manufacturing press-hardened components, comprising providing forming tool with a protective layer made of a powdered coating material by welding - Google Patents

Abstract

Improving wear resistance of a forming tool (1.1), preferably a heat forming tool, comprises providing the forming tool with a protective layer (13) made of a powdered coating material by welding. At least one of at least two iron-containing components of composite powder mixture is applied on the forming tool and is melted by a welding beam, preferably laser welding beam. The application amount of at least one powdery mixture is adjusted in such a manner that the thickness of the final protective layer is 1-6 mm, preferably 2-4 mm. Improving wear resistance of a forming tool (1.1), preferably a heat forming tool, comprises providing the forming tool with a protective layer (13) made of a powdered coating material by welding. At least one of at least two iron-containing components of composite powder mixture is applied on the forming tool and is melted by a welding beam, preferably laser welding beam, where a first of at least two iron-containing components has (in wt%): carbon (0.2-0.8), chromium (2.0-9.0), molybdenum (1.0-5.0), tungsten (0.5-5.0), vanadium (0.2-2.0) and iron (balance) and unavoidable impurities. The second of at least two iron-containing components has (in wt.%): carbon (0.005-0.2), chromium (10.0-20.0), molybdenum (0.5-3.5), nickel (5.0-15.0), silicon (0.5-3.5) and iron (balance) and unavoidable impurities. The application amount of at least one powdery mixture is adjusted in such a manner that the thickness of the final protective layer is 1-6 mm, preferably 2-4 mm. An independent claim is also included for the heat forming tool comprising the protective layer which increase the wear resistance of the heat forming tool, where the protective layer has (in wt.%): carbon (0.1-0.6), chromium (7.5-8.0), nickel (1.5-10.5), molybdenum (0.4-3.0), tungsten (0.2-2.5), silicon (0.2-2.5), vanadium (0.1-1.4), iron (balance) and unavoidable impurities, where the protective layer exhibits a thickness of 1-6 mm, preferably 2-4 mm.

Description

The invention relates to a method for improving the wear resistance of a forming tool, in particular hot forming tool, in which the forming tool is provided by build-up welding with a protective layer made of a powdery coating material. Furthermore, the invention relates to a hot forming tool with a wear resistance increasing its, generated by build-up welding protective layer.

It is known to coat metallic components and tools that are exposed to high abrasive stress with a wear-resistant protective layer. One known method in this regard is laser deposition welding using an iron-containing coating material. Such a method is for example from the DD 273 458 A1 known. The method described there is essentially characterized in that a martensite-forming coating material is melted onto a metallic substrate, for example an industrial knife with a high energy source, in particular a laser under the condition that the temperature of the substrate is always lower than the martensite transformation temperature of the coating material. The coating material is an Fe-C alloy with 0.2% to 1.5% C, up to 1.5% Si, up to 1.0% Mn, up to 20% Cr, up to 20% Mo, up to 10% V to 10% Co and to 2.5% B by mass.

Hot forming tools for the production of press-hardened components, such as bumpers, body roof frames or B-pillars made of coated sheets, are subjected to high abrasive stress. The respective tool concept is crucial in order to use efficient forming tools for hot forming. The achievement of high cooling capacities in the forming tools is particularly influenced by the design of these tools, in particular by the position and the cross sections of the cooling channels in the respective tool. Another important influencing factor is a high thermal conductivity of the material used for the production of the forming tool. Furthermore, for a high performance of a hot forming tool, the complete positive engagement of the molds involved in the forming process is important. Because achieving the highest possible surface pressure improves heat dissipation. The maintenance of a complete positive engagement of the molds involved in the forming process, however, counteracts the wear of the forming tool.

There is the problem of achieving a high thermal conductivity on the one hand and a high wear resistance of the hot forming tools on the other hand against a very abrasive stress by the coatings of hot-forming sheets. High wear resistance can only be achieved with a corresponding hardness and heat resistance of the tool material. However, a high thermal conductivity is not consistent with a high wear resistance, since the thermal conductivity of a tool steel decreases with increasing hardness of the material, or the thermal conductivity of a tool steel is reduced in particular by its hardness.

The present invention has for its object to provide a hot forming tool with high thermal conductivity and improved wear resistance and to provide a method for its production.

This object is achieved by a method having the features of claim 1 or by a hot forming tool having the features of claim 7.

The method according to the invention is essentially characterized in that at least one pulverulent mixture composed of at least two iron-containing components (alloys) is applied to the forming tool and melted by means of a welding beam, preferably a laser welding beam, wherein a first of the at least two iron-containing components has the following composition: C: 0.2-0.8% by weight, Cr: 2.0-9.0% by weight, Not a word: 1.0-5.0 wt%, W: 0.5-5.0% by weight, V: 0.2-2.0% by weight, The remainder being iron and unavoidable impurities, the second of the at least two iron-containing components having the following composition: C: 0.005-0.2% by weight, Cr: 10.0-20.0% by weight, Not a word: 0.5-3.5% by weight, Ni: 5.0-15.0% by weight, Si: 0.5-3.5% by weight, Residual iron and unavoidable impurities, and wherein the application amount of the at least one powdery mixture is adjusted so that the thickness of the finished protective layer in the range of 1 mm to 6 mm, preferably in the range of 2 mm to 4 mm.

Due to the special layer structure, the hot forming tool according to the invention is optimized in terms of thermal conductivity and wear resistance. The upper hard layer is bonded to the tool base material by a powder build-up welding process, preferably a laser powder build-up welding process. In this way, a relatively thin, uniform protective layer is achieved. As a result, only the relatively thin protective layer of the forming tool has a comparatively poor thermal conductivity due to its hardness, while the base of the forming tool, i. H. the base material of the forming tool minus the protective layer is still kept at a high level of heat conduction, since the base material is not or not appreciably hardened and thus not reduced in its thermal conductivity.

The hardness and the toughness of the protective layer of the hot forming tool according to the invention can be adjusted by the welded-on filler material (powder mixture). The powder mixture used consists of at least two iron-containing components containing certain selected alloying elements.

The C content of the first of the at least two iron-containing components of the powder mixture is in the range of 0.2-0.8% by weight, preferably in the range of 0.3-0.7% by weight. Carbon forms carbide or carbides with one or more of the other alloying elements. Carbides are resistant to acids and usually harder than the pure metal components. Carbides are characterized in particular by a high heat resistance with respect to abrasion. If the carbon content is too low, this has a negative effect on the bond between the protective layer and the base material of the forming tool. The carbon content of the first of the at least two iron-containing components should therefore not fall below 0.2% by weight. On the other hand, the toughness of the protective layer decreases with too high a carbon content; Therefore, the carbon content of the first of the at least two iron-containing components should not exceed 0.8 wt .-%.

The chromium content of the first of the at least two iron-containing components of the powder mixture is 2.0-9.0% by weight, preferably 3.0-6.0% by weight. Chromium forms carbide in conjunction with the carbon present and causes an increase in the Softening resistance accompanied by high hardness at high process temperature. In particular, chromium improves the hot strength and corrosion resistance. To ensure these properties, the chromium content should not be less than 2.0% by weight. However, if the chromium content is too high, it will adversely affect the toughness, machinability and crack resistance of the protective layer. Therefore, the chromium content of the first iron-containing component should not be more than 9.0 wt .-%.

Molybdenum forms carbide in combination with carbon and improves the high-temperature strength of the protective layer, thereby improving the wear resistance, toughness and softening resistance. On the other hand, molybdenum can easily cause cracks in build-up welding if its content in the powder mixture is too high. Therefore, the molybdenum content of the first of the at least two iron-containing components of the powder mixture is in the range of 1.0-5.0 wt%, preferably in the range of 2.0-4.0 wt%.

Tungsten forms carbide in conjunction with the existing carbon and causes strengthening of the solid solution of the base material as well as an increase in the hot hardness. With regard to a sufficient high-temperature wear resistance, the tungsten content of the first of the at least two iron-containing components of the powder mixture is adjusted to a value of at least 0.5% by weight, preferably at least 1.0% by weight. However, since the flowability of build-up welding deteriorates and also the mechanical workability of the protective layer is made more difficult when the tungsten content is too high, it is increased to a maximum of 5.0% by weight, preferably to a maximum of 3.5% by weight. % limited.

Vanadium serves to produce stable high-strength carbides, to control hardness by precipitation hardening when heated to high temperature, and to ensure high wear resistance. Vanadium also increases the toughness of the protective layer. In order to utilize these effects, the vanadium content is at least 0.2% by weight, preferably at least 0.5% by weight in the first of the at least two iron-containing components of the powder mixture. On the other hand, the mechanical workability of the protective layer is made more difficult and its toughness is lowered when the vanadium content is too high. Therefore, the vanadium content of the first iron-containing component should not be more than 2.0% by weight, preferably not more than 1.5% by weight.

The carbon content of the second of the at least two iron-containing components of the powder mixture is in the range of 0.005-0.2 wt .-%. It has been found that the protective layer has a high heat resistance to abrasion when the carbon content of the second iron-containing component is set lower than that of the first iron-containing component of the powder mixture. At the same time, the toughness of the Protective layer can be improved. Preferably, the carbon content of the second component of the powder mixture is in the range of 0.01-0.05 wt%.

Silicon increases the oxidation resistance of the protective layer at high temperatures and improves the flowability and adhesion in build-up welding. It acts in particular as a deoxidizer during the melting of the powder mixture. In order to achieve these effects, the silicon content of the second iron-containing component of the powder mixture is adjusted to at least 0.5% by weight, preferably at least 1.0% by weight. On the other hand, silicon may reduce the toughness as well as the hot crack resistance of the protective layer if its content in the at least one second iron-containing component or in the powder mixture is too high. Therefore, the silicon content of the second iron-containing component of the powder mixture is limited to a maximum of 3.5 wt .-%, preferably to a maximum of 3.0 wt .-%.

As mentioned above, chromium in combination with existing carbon forms carbide and causes an increase of the softening resistance accompanied by high hardness at high temperature. In addition, chromium improves the heat resistance and corrosion resistance. In order to achieve these effects, the chromium content in the second iron-containing components of the powder mixture is adjusted to at least 10% by weight, preferably at least 12% by weight. However, if the chromium content in the second iron-containing component of the powder mixture is too high, this has a negative effect on the toughness, the machinability and the crack resistance of the protective layer. Therefore, the chromium content of the second iron-containing component should not be more than 20.0% by weight, preferably not more than 18.0% by weight.

As noted above, molybdenum forms carbide in conjunction with the existing carbon and improves the high temperature wear resistance of the protective layer. It has been found that it has a positive effect on the hardness, toughness and impact resistance of the protective layer of the hot forming tool when the molybdenum content of the at least one second iron-containing component is set slightly lower than that of the first iron-containing component of the powder mixture. In order to obtain advantageous hardness, toughness and impact resistance, the molybdenum content of the at least one second iron-containing component is adjusted to a value in the range of 0.5-3.5 wt .-%, preferably in the range of 1.0-3.0 wt .-% adjusted.

Nickel is not a carbide-forming element. Nevertheless, it improves the toughness and crack resistance of the protective layer. In order to optimize the toughness and crack resistance of the protective layer, the nickel content in the at least one second iron-containing component of the powder mixture is in the range of 5.0-15.0 wt.%, Preferably in the range of 8.0-14.0 % By weight.

The hardness of the protective layer depends on the mixing ratio of the iron-containing components (iron-base alloys). In order to achieve a high wear resistance, preferably a hardness in the range of 56 to 64 HRC, more preferably in the range of 60 to 64 HRC is set. The hardness or wear resistance of the protective layer produced according to the invention is optimal when the first component and the second component of the at least two iron-containing components in a mixing ratio in the range of 30:70 and 70:30, preferably in the range of 40:60 and 60:40 be mixed.

An advantageous embodiment of the method according to the invention is characterized in that the protective layer is built up from a plurality of layers of different hardness, wherein the uppermost layer has the highest hardness of the differently hard layers. This makes it possible to achieve optimum wear resistance of the protective layer and a particularly reliable cohesive connection of the same with the forming tool.

A further advantageous embodiment of the method according to the invention provides that 1 mm to 3 mm are removed from the forming tool in the region of the protective layer to be produced by milling prior to build-up welding. As a result, the forming tool is optimally prepared and achieved a particularly reliable cohesive connection of the protective layer to the forming tool.

So that the sheet metal components produced with the hot forming tool have a high surface quality, the protective layer should be smoothed. Accordingly, a further embodiment of the method according to the invention provides for a subsequent machining of the protective layer. The smoothing of the protective layer can be done for example by milling and / or grinding.

A further advantageous embodiment of the method according to the invention is that by the laser powder deposition welding a low heat input into the base material of the forming tool takes place. As a result, the set material properties of the forming tool remain largely unchanged and there are only very low stresses (delay) of Forming tool, so that the Nachbearbeitungsaufwand by milling and grinding is minimized.

The protective layer of the hot forming tool according to the invention has the following composition: C: 0.1-0.6 wt%, Cr: 7.5-18.0% by weight, Ni: 1.5-10.5% by weight, Not a word: 0.4-3.0% by weight, W: 0.2-2.5% by weight, Si: 0.2-2.5% by weight, V: 0.1-1.4% by weight, Remaining iron and unavoidable impurities, wherein the thickness of the protective layer in the range of 1 mm to 6 mm, preferably in the range of 2 mm to 4 mm.

As known per se, the hot forming tool is provided with at least one cooling channel. The cooling channel is arranged so that the shortest distance between the protective layer and the cooling channel is in the range of 15 mm to 35 mm, preferably in the range of 20 mm to 30 mm.

The hot forming tool according to the invention is preferably designed in segment, crown or shell construction. The tool body (base body) located below the protective layer is made of one or more materials (cast or forged steel) with a thermal conductivity of preferably at least 30 W / mK, particularly preferably at least 40 W / mK.

Further preferred and advantageous embodiments of the hot forming tool according to the invention are specified in the subclaims.

The invention will be explained in more detail with reference to a drawing illustrating several embodiments.

They show schematically:

1 a vertical cross-sectional view of a portion of a forming tool for hot working and press hardening of metal sheets at the beginning of the forming process;

2 the forming tool the 1 at the end of the forming process;

3 a stamp of the forming tool the 1 , in side view; and

4 a section of another hot forming tool according to the invention, in sectional view.

That in the 1 and 2 shown forming tool is used for hot forming and press hardening of sheet metal, preferably boron-alloyed steel sheet. The forming tool (pressing tool) is made of a stamp 1 and a die 2 built up. The Stamp 1 is inside a machine frame 5 arranged on the upper side holder 6 for holding the reshaped sheet metal blank 7 are mounted.

The matrix 2 has a movable bottom part 2.1 on that between side tool parts (blocks) 2.2 . 2.3 the die is arranged. In the open position of the hot forming tool is the movable bottom part 2.1 with his the stamp 1 facing mold surface against the molding surfaces of the lateral tool parts 2.2 . 2.3 the template in front. The movable floor part 2.1 serves as a counterpressure element for the stamp 1 and thus optimizes its positional fixation during the forming process by clamping the sheet metal blank.

The tool parts (blocks) 2.2 . 2.3 are with a base part serving as support (substructure) 2.4 the matrix 2 releasably connected. The blocks 2.2 . 2.3 and the bottom part 2.1 the matrix 2 as well as the stamp 1 have cooling channels 8th . 9 . 10 on, by the cooling liquid, such as cold water, for rapid cooling of the previously heated in a heat treatment plant austenitizing temperature sheet steel plate 7 is directed.

The hot forming tool is in the areas where it is subjected to a high abrasive stress, with the wear resistance increasing protective layers 11 . 12 . 13 . 14 Mistake. The respective protective layer 11 . 12 . 13 . 14 is made by laser cladding using a powdery mixture (powder mixture).

One advantage of laser deposition welding is, inter alia, the low heat input into the tool, so that the distortion of the tool remains low. This is particularly advantageous in terms of the cost of post-processing by milling and grinding, which can thus be kept low.

The powdery mixture is composed of two iron-containing components (iron-based alloys). The first component has the following composition: C: 0.2-0.8% by weight, Cr: 2.0-9.0% by weight, Not a word: 1.0-5.0 wt%, W: 0.5-5.0% by weight, V: 0.2-2.0% by weight, Remaining iron and unavoidable impurities.

The second component, however, has the following composition: C: 0.005-0.2% by weight, Cr: 10.0-20.0% by weight, Not a word: 0.5-3.5% by weight, Ni: 5.0-15.0% by weight, Si: 0.5-3.5% by weight, Remaining iron and unavoidable impurities.

The hardness and thus the wear resistance of the finished protective layer 11 . 12 . 13 . 14 depend in particular on the mixing ratio of the two iron-containing components (iron-based alloys). The mixing ratio is adjusted to be in the range of 30:70 and 70:30, preferably in the range of 40:60 and 60:40. This sets a hardness in the range of 56 to 64 HRC.

The powder mixture is applied by means of a suitable device to one or more areas of the hot forming tool and melted by means of a laser. The application rate of the mixture is adjusted so that the thickness of the finished protective layer 11 . 12 . 13 . 14 in the range of 1 mm to 6 mm, preferably in the range of 2 mm to 4 mm.

The protective layer can be composed of one or more layers. In the in the 1 and 2 The exemplary embodiment shown is an example of the tool parts (blocks). 2.2 . 2.3 the matrix with a two-layer protective layer 11 respectively. 12 Mistake. Will the protective layer of several layers 11.1 . 11.2 . 12.1 . 12.2 constructed, they preferably have different by adjusting the mixing ratio of the iron-based alloys different hardnesses. The layer structure is chosen so that the top layer 11.2 . 12.2 the protective layer 11 respectively. 12 the highest hardness of the different hard layers 11.1 . 11.2 . 12.1 . 12.2 having.

In 3 is the stamp 1 of the hot forming tool the 1 and 2 shown in side view. The Stamp 1 is segmented into several tool parts. It can be seen that on a stamp substructure 1.2 different tool parts 1.11 . 1.12 . 1.13 . 1.14 . 1.15 . 1.16 are mounted flush to each other. The tool parts 1.11 . 1.12 . 1.13 . 1.14 . 1.15 . 1.16 of the stamp 1 have according to the tool parts of the die 2 drilled cooling channels (in 3 not shown) extending along the molding surface (pressing surface). Areas of the tool parts 1.11 . 1.12 . 1.13 . 1.14 . 1.15 . 1.16 , which are subjected to a high abrasive stress during the forming process, are provided with a wear-resistant protective layer 13 provided in 3 is marked by a dot area. The protective layer 13 is prepared by laser cladding using the above powder mixture.

In 4 is another embodiment of a hot forming tool according to the invention 1' represented, which is executed in shell construction.

The tool 1' has a core 1.2 'and a related bowl-shaped body 1.1 on. The core 1.2 'and the bowl-shaped body 1.1 are formed complementary to each other. The main body 1.1 is preferably made of a ductile steel, for example a cast steel or a forged steel. In the core facing the inside of the body 1.1 are groove-shaped cooling channels 4 educated. The cooling channels 4 For example, by milling in the body 1.1 be incorporated. The main body (tool body) 1.1 has a thermal conductivity of at least 30 W / mK, preferably at least 40 W / mK.

On the forming the sheet metal blank facing active surface of the body 1.1 is in turn by means of laser powder deposition welding a protective layer 13 applied, which has a high hardness and wear resistance. The powder used for this purpose is the above-mentioned mixture of two iron-containing components (iron-based alloys). The mixing ratio is adjusted so that the finished protective layer 13 has a hardness in the range of 56 to 64 HRC. The mixing ratio can be varied between 30:70 and 70:30. The thickness of the hard protective layer 13 is in the range of 1 mm to 6 mm, with a thickness in the range of 2 mm to 4 mm being particularly preferred.

The shortest distance A between the protective layer 13 and the respective cooling channel 4 is in the range of 15 mm to 35 mm, preferably in the range of 20 mm to 30 mm. Due to the coating according to the invention of the shell-shaped base body 1.1 will significantly improve the wear resistance of the hot forming tool 1' reached. As the bowl-shaped body 1.1 itself is essentially not cured, this retains its relatively high thermal conductivity.

The method according to the invention can be used both in the production of new forming tools and in the repair of worn forming tools. As a repair technology laser powder deposition welding according to the invention can be used to eliminate wear-related erosion of hot forming tools, so that a good fit and thus a high cooling rate is restored. In both cases (production of new tools and repair of worn hot forming tools), the protective layer (s) to be produced in the area (s) 11 . 12 . 13 . 14 prior to powder build-up welding, a surface area of the tool 1 . 2.1 . 2.2 . 2.3 respectively. 1.1 removed by machining, for example by milling. The depth or the extent of the removal is preferably about 1 mm to 3 mm. After laser deposition welding of the powder mixture, the desired geometry of the hot forming tool 1 . 2.1 . 2.2 . 2.3 respectively. 1.1 produced. Therein, the thinning of the formed sheet 7 taken into account compared with the original sheet thickness in the incorporation of the tool gap.

The embodiment of the invention is not limited to the embodiments described above. Rather, numerous variants are possible, which make use even with fundamentally different design of the invention specified in the appended claims.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DD 273458 A1 [0002]

Claims (13)

Method for improving the wear resistance of a forming tool ( 1 . 2.1 . 2.2 . 2.3 . 1.1 ), in particular hot forming tool, in which the forming tool is produced by build-up welding with a protective layer made of a powdery coating material ( 11 . 12 . 13 . 14 ), characterized in that at least one powdery mixture composed of at least two iron-containing components is applied to the forming tool ( 1 . 2.1 . 2.2 . 2.3 respectively. 1.1 ) and is melted by means of a welding beam, preferably a laser welding beam, wherein a first of the at least two iron-containing components has the following composition: C: 0.2-0.8% by weight, Cr: 2.0-9.0% by weight, Not a word: 1.0-5.0 wt%, W: 0.5-5.0% by weight, V: 0.2-2.0% by weight, The remainder being iron and unavoidable impurities, the second of the at least two iron-containing components having the following composition: C: 0.005-0.2% by weight, Cr: 10.0-20.0% by weight, Not a word: 0.5-3.5% by weight, Ni: 5.0-15.0% by weight, Si: 0.5-3.5% by weight, Residual iron and unavoidable impurities, and wherein the application amount of the at least one powdery mixture is adjusted so that the thickness of the finished protective layer ( 11 . 12 . 13 . 14 ) in the range of 1 mm to 6 mm, preferably in the range of 2 mm to 4 mm. A method according to claim, characterized in that the first of the at least two iron-containing components has the following composition: C: 0.3-0.7% by weight, Cr: 3.0-6.0 wt%, Not a word: 2.0-4.0% by weight, W: 1.0-3.5% by weight, V: 0.2-1.9% by weight, Remainder iron and unavoidable impurities, and / or wherein the second of the at least two iron-containing components has the following composition: C: 0.01-0.1% by weight, Cr: 12.0-18.0% by weight, Not a word: 1.0-3.0% by weight, Ni: 8.0-14.0% by weight, Si: 1.0-3.0% by weight, Remaining iron and unavoidable impurities. A method according to claim 1 or 2, characterized in that the first component and the second component of the at least two iron-containing components in a mixing ratio in the range of 30:70 and 70:30, preferably in the range of 40:60 and 60:40 are mixed , Method according to one of claims 1 to 3, characterized in that the protective layer ( 11 . 12 ) of several different hard layers ( 11.1 . 11.2 ; 12.1 . 12.2 ), wherein the topmost layer ( 11.2 . 12.2 ) the highest hardness of the differently hard layers ( 11.1 . 11.2 ; 12.1 . 12.2 ) having. Method according to one of claims 1 to 4, characterized in that before the build-up welding of the forming tool ( 1 . 2.1 . 2.2 . 2.3 . 1.1 ) 1 mm to 3 mm in the region of the protective layer to be produced ( 11 . 12 . 13 . 14 ) are removed by milling. Method according to one of claims 1 to 5, characterized in that the protective layer ( 11 . 12 . 13 . 14 ) is post-machined after the build-up welding. Hot forming tool ( 1 . 2.1 . 2.2 . 2.3 . 1.1 ) with a wear-resistance-increasing protective layer produced by build-up welding, characterized in that the protective layer ( 11 . 12 . 13 . 14 ) has the following composition: C: 0.1-0.6 wt%, Cr: 7.5-18.0% by weight, Ni: 1.5-10.5% by weight, Not a word: 0.4-3.0% by weight, W: 0.2-2.5% by weight, Si: 0.2-2.5% by weight, V: 0.1-1.4% by weight, Remaining iron and unavoidable impurities, the protective layer ( 11 . 12 . 13 . 14 ) has a thickness in the range of 1 mm to 6 mm, preferably in the range of 2 mm to 4 mm. Hot forming tool according to claim 7, characterized in that the protective layer ( 11 . 12 ) of several different hard layers ( 11.1 . 11.2 . 12.1 . 12.2 ), wherein the uppermost layer ( 11.2 . 12.2 ) the highest hardness of the differently hard layers ( 11.1 . 11.2 . 12.1 . 12.2 ) having. Hot forming tool according to claim 7 or 8, characterized in that the protective layer ( 11 . 12 . 13 . 14 ; 11.2 . 12.2 ) has a hardness in the range of 56 to 64 HRC, preferably in the range of 60 to 64 HRC. Hot forming tool according to one of claims 7 to 9, characterized in that the surface of the protective layer ( 11 . 12 . 13 . 14 ; 11.2 . 12.2 ) is ground. Hot forming tool with at least one cooling channel ( 4 ) according to one of claims 7 to 10, characterized in that the shortest distance (A) between the protective layer ( 13 ) and the cooling channel ( 4 ) in the range of 15 mm to 35 mm, preferably in the range of 20 mm to 30 mm. Hot forming tool ( 1 ; 1.1 ) according to one of claims 7 to 11, characterized in that it is designed in segment, crown or shell construction. Hot forming tool according to one of claims 7 to 12, characterized in that the below the protective layer ( 13 ) located tool body ( 1.1 ) is made of one or more materials having a thermal conductivity of at least 30 W / mK, preferably at least 40 W / mK.

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