EP3408417A1

EP3408417A1 - Heat treatment method and heat treatment device

Info

Publication number: EP3408417A1
Application number: EP17703346.1A
Authority: EP
Inventors: Andreas Reinartz
Original assignee: Schwartz GmbH
Current assignee: Schwartz GmbH
Priority date: 2016-01-25
Filing date: 2017-01-25
Publication date: 2018-12-05
Anticipated expiration: 2037-01-25
Also published as: JP2019506531A; CN109072325B; BR112018015072A2; BR112018015072B1; PT3408417T; US11359254B2; CN109072325A; AT15722U1; MX2018009036A; ES2920485T3; JP6940509B2; HUE059496T2; EP3408417B1; DE202016104191U1; US20190032163A1; KR20180117111A; DE102016201024A1; EP3851546A1; PL3408417T3; CN206204366U

Abstract

The invention relates to a method and to a device for the heat treatment of steel components directed specifically at individual zones of the component. In one or more first regions of the steel component, a predominantly austenitic structure can be adjusted, from which, by way of quenching, a mainly martensitic structure is educible. In one or more second regions of the steel component, there is a mainly bainitic structure, wherein the metal component is initially heated in a first furnace to a temperature above the AC3 temperature. Subsequently, the steel component is transferred into a treatment station, wherein the steel component can cool down during the transfer. In the treatment station, the one or more second regions of the steel component are cooled down to a cooling stop temperature ϑ2 during a treatment period. Subsequently, said metal component is transferred to a second furnace, wherein the temperature of the one or more second regions increases again to a temperature below the AC3 temperature.

Description

Heat treatment method and heat treatment apparatus Description:

The invention relates to a method and a device for targeted

Component zone-specific heat treatment of a steel component.

In the art, in many applications in different industries there is a desire for high strength sheet metal parts with low part weight.

For example, in the automotive industry, it is the endeavor that

To reduce fuel consumption of motor vehicles and to reduce CO ₂ emissions, while at the same time to increase occupant safety. There is therefore a rapidly increasing demand for body components with a favorable

Ratio of strength to weight. These components include in particular A and B pillars, side impact protection in doors, sills, frame parts,

Bumper, cross member for floor and roof, front and rear

Side members. In modern motor vehicles, the raw ka rosse with a safety cage usually consists of a hardened steel sheet with about 1, 500 MPa strength. In many cases Al-Si-coated steel sheets are used. For the production of a component from hardened steel sheet the process of the so-called press hardening was developed. This steel sheets are first on

Warmed austenitemperatur, then placed in a press tool, quickly formed and rapidly through the water-cooled tool to less than

M a rt a itsta rstem pera tu r deterred. This creates hard, solid

Martensitic structure with approx. 1 .SOOMPa strength. However, such a hardened steel sheet has only a small elongation at break. The kinetic energy of a

Impact can therefore not be sufficiently converted into deformation heat. For the automotive industry, it is therefore desirable to be able to produce body components that have several different expansion and strength zones in the component, so that more solid areas (hereinafter, first areas) on the one hand and rather expandable areas (hereinafter second areas) on the other hand present in a component. On the one hand, components with high strength are basically desirable in order to obtain components of high mechanical strength with low weight. On the other hand, even high-strength components should be able to have partially soft areas. This brings the desired, partially increased

Deformability in the event of a crash This is the only way to reduce the kinetic energy of an impact, thus minimizing the acceleration forces on the occupants and the rest of the vehicle. In addition, modern joining methods require de-consolidated points, which allow the joining of identical or different materials. Often, for example, crimping or riveting joints have to be used, which presuppose deformable areas in the component.

The general demands on a production plant should continue to be respected: so there should be no cycle time loss at the press hardening plant, the entire system should be universally used without restrictions and can be retrofitted quickly product specific. The process should be robust and economical and the production plant need only minimal space. The shape and edge accuracy of the component should be high. In all known methods, the targeted heat treatment of the component takes place in a time-consuming treatment step, which has a significant influence on the cycle time of the entire heat treatment device.

The object of the invention is therefore to provide a method and a device for targeted component zone-specific heat treatment of a steel component, wherein areas of different hardness and ductility can be achieved, in which the influence on the cycle time of the entire heat treatment apparatus is minimized.

According to the invention, this object is achieved by a method having the features of independent claim 1. Advantageous developments of the method will become apparent from the dependent claims 2 to 6. The object is further by a Device according to claim 8 solved. Advantageous embodiments of the device will become apparent from the dependent claims 7 to 15.

The steel component is first heated to above Austenitisierungstemperatur AC3, so that the structure can completely convert into austenite. In a subsequent hardening process, for example, the press hardening process is then quenched so fast that primarily forms martensitic microstructure and strengths of about 1, 500MPa be achieved. The quenching takes place advantageously from the fully austenitized microstructure. This must be

at the latest after falling below the structural transformation start temperature θι, at which microstructural transformations can start, with at least the lower critical

Cooling rate to be cooled. For example, at the

commonly used for press hardening material 22MnB5 around 660 ° C as limit d- _{\ are} considered. An at least partially martensitic microstructure may still arise if the quenching starts at a lower temperature, but then a reduced strength of the component in this area is to be expected.

This temperature profile is common in the press hardening process especially for fully hardened components.

A second area or a plurality of second areas are also initially heated to above the austenitizing temperature AC3, so that the structure can completely transform into austenite. Thereafter, it is cooled down as rapidly as possible within a treatment time t _B to a cooling stop temperature # 2. For example, the martensite start temperature for 22MnB5 is around 410 ° C. A slight settling in temperature ranges below the martensite start temperature is also possible. Subsequently, it is not cooled further quickly, so that bainitic structure is formed in the majority. These

Microstructure transformation does not happen abruptly, but requires a treatment time. The conversion is exothermic. Leaving this transformation in a heated environment with a similar temperature as the existing at the cooling end Component temperature, the Abkühlstopptemperatur θ ₂ , take place, you can clearly see the caused by the recalescence increase in temperature in the component. By adjusting the cooling rate and / or the temperature to be cooled to, as well as the residence time to the pressing of the component, can be

basically set the desired strength and elongation values that are between the maximum achievable strength of the structure in the first range and the values of the untreated component. Investigations have shown that suppression of the temperature increase due to recalescence by further, forced cooling is rather disadvantageous for the achievable elongation values. An isothermal hold on the cooling temperature therefore does not seem to be advantageous. On the other hand, reheating is advantageous.

In one embodiment, the second region or the second regions are additionally actively heated in this phase. This can be done, for example

Heat radiation done.

In one embodiment, the cooling stop temperature θ _{2 is selected} above the martensite start temperature M _s . In an alternative embodiment, the cooling stop temperature θ ₂ below the martensite start temperature M _{s is} selected.

The heat treatment of the first and second regions is in principle

different, wherein primarily the treatment of the second area or the second areas has a dependence on the duration of treatment. According to the invention second areas in a first furnace to achieve the

Austenitization temperature downstream treatment station within a treatment time t _B of a few seconds partially cooled to Abkühlstopptemperatur d ₂ . In this treatment station, the first area or areas are not treated particularly. Optionally, the treatment station can also be heated for this purpose. For this example, the heat input via convection or heat radiation can be used. According to the components after a few seconds in the

Treatment station, which may also have a positioning device to ensure the accurate positioning of the different areas, transported in a second oven, which preferably has no special devices for different treatment of the different areas. It is only a furnace temperature θ ₄ , ie a substantially homogeneous temperature θ ₄ in the entire furnace chamber, set, which is usually between the

Austenitizing temperature AC3 and the minimum quenching temperature is. An advantageous size is for example between 660 ° C and 850 ° C. Thus, the different temperature ranges approach 9 _{4 of} the second furnace. If the temperature losses in the first regions during the stay in the treatment station for the second regions are so low that the temperature does not fall lower than the temperature 9 _{4 of} the second furnace, this approaches

Temperature profile of the first regions Type of temperature 0 _{4 of} the second furnace from above. In an advantageous embodiment, the minimum

Cooling temperature, ie the Abkühlstopptemperatur d2 in the areas of the second type lower than the selected temperature 0 _{4 of} the second furnace. In this respect, the temperature profile of the second regions approaches the temperature 9 of the second furnace from below. Through this process, the temperatures of the differently treated areas approach each other

The first or the first regions emit heat in the second furnace when they enter the second furnace at a higher temperature than the internal temperature 9 of the second furnace. The second or second areas receive heat in the second oven. All in all, this requires only a relatively small amount of heating power in the second furnace. Optionally, during the

Production process to be completely dispensed with further heating. So this treatment step is particularly energy efficient As a first furnace, for example, a continuous furnace or a batch furnace, such as a chamber furnace may be provided. Continuous furnaces usually have a large capacity and are particularly well suited for mass production, since they can be fed and operated without much effort.

According to the invention, the treatment station has a device for rapid cooling of one or more second regions of the steel component. In a preferred embodiment, the device has a nozzle for blowing the or the second regions of the steel component with a gaseous fluid,

For example, air or a protective gas, such as nitrogen.

In a further advantageous embodiment of the method, the blowing of the second or the second regions takes place by blowing with a gaseous fluid, wherein the gaseous fluid water, for example in fogged form, is attached. For this purpose, in an advantageous embodiment, the device has one or more nebulizing nozzles. By blowing with the gaseous fluid mixed with water, the heat removal from or from the second regions is increased. With the evaporation of the water on the steel component, a large heat dissipation and a high energy transport is achieved.

For example, a continuous furnace or a batch furnace, for example a chamber furnace, can also be provided as the second furnace. In a further embodiment, the second or the second regions are cooled via heat conduction, for example by contacting them with one or more punches, which has or have a significantly lower temperature than the steel component. For this purpose, the stamp can be made of a good heat-conducting material and / or be cooled directly or indirectly. A combination of the types of cooling is conceivable. It has proven to be advantageous if measures are taken in the treatment station for reducing the temperature losses of the first or the first regions. Such measures can be, for example, the attachment of a heat treatment ref l e k to rs and / or the isolation of surfaces of the treatment station in the region of the first or the first areas.

With the method according to the invention and the invention

Heat treatment device can be stamped steel components with one or more first and / or second areas, which may also be complex shaped, economically a corresponding temperature profile, as the different areas contour sharp very quickly to the necessary

Process temperatures can be brought. Clearly contoured boundaries of the individual areas can be realized between the two areas, and the low temperature difference minimizes distortion of the components. Small spreads in the temperature level of the component have an advantageous effect on further processing in the press. The necessary residence times for the second region or the second regions can, for example, be realized in a continuous furnace as a function of the component length via the setting of the conveying speed and the design of the furnace length. Influencing the cycle time of the heat treatment apparatus is thus minimized, it can even be avoided altogether.

According to the invention it is with the method shown and with the

Heat treatment apparatus according to the invention possible to set almost any number of second areas, which in addition to each other within a steel component still different Festig keits- and elongation values may have. Also, the selected geometry of the sections is freely selectable. Point or line-shaped areas as well as eg large area areas can be displayed. The location of the areas is irrelevant. The second areas may be completely enclosed by first areas or located at the edge of the steel component. Even a full-surface treatment is conceivable. A special orientation of the Steel component to the passage direction is for the purpose of the invention

Method for the targeted component zone-specific heat treatment of a

Steel component not required. A limitation of the number of simultaneously treated steel components is possibly given by the press hardening tool or the conveying technique of the entire heat treatment apparatus. The

Application of the method to already preformed steel components is also possible. Due to the three-dimensionally shaped surfaces of already preformed steel components, only a higher constructive effort for the representation of the mating surfaces results.

Furthermore, it is advantageous that already existing

Heat treatment systems can be adapted to the method according to the invention. For this purpose, in a conventional heat treatment device with only one oven behind this only the treatment station and the second oven must be installed. Depending on the design of the existing furnace, it is also possible to divide this, so that from the original one furnace, the first and the second furnace arise.

Further advantages, features and expedient developments of the invention will become apparent from the dependent claims and the following description of preferred embodiments with reference to the drawings.

1 shows a typical temperature curve during the heat treatment of a steel component with a first and a second region

Fig. 2 shows a thermal heat treatment apparatus according to the invention in a plan view as a schematic drawing

Fig. 3 shows a further inventive thermal heat treatment apparatus in a plan view as a schematic drawing 4 is a schematic plan view of a further thermal heat treatment device according to the invention in a plan view; FIG. 5 is a schematic plan view of a further thermal heat treatment device according to the invention

6 shows a further inventive thermal heat treatment device in a plan view as a schematic drawing.

7 shows a further inventive thermal heat treatment device in a plan view as a schematic drawing

1 is a typical temperature curve in the heat treatment of a steel component 200 having a first region 210 and a second region 220 according to the inventive method. The steel component 200 is in the first furnace 1 10 according to the schematically drawn temperature run θ ₂ οο, ι ιο during the residence time in the first furnace t _{1 10} heated to a temperature above the AC3 temperature. Subsequently, the steel component 200 is transferred to the treatment station 150 with a transfer time t ₁₂ o. The steel component loses heat. In the treatment station, a second region 220 of the steel component 200 is rapidly cooled, wherein the second region 220 rapidly according to the drawn

Course θ ₂ 2ο, ΐ δο loses heat. The cooling ends after the expiry of the

Treatment time t _B , which is only a few seconds, depending on the thickness of the steel component 200, the desired material properties and the size of the second region 220. In a first approximation, the treatment time t _{B is} equal to the residence time t ₁₅₀ in the treatment station 150. The second area 220 has now reached the cooling stop temperature d ₂ above the martensite start temperature M _s . At the same time, the temperature of the first region 210 in the

Treatment station 150 has fallen in accordance with the plotted temperature profile 210.150, wherein the first region 210 is not in the region of the Kühlhleirichtung. After expiration of the treatment time t _B , the steel component 200 during the Transfer time t ₁₂ i transferred to the second furnace 130, wherein it further loses heat, provided that its temperature is greater than the internal temperature 0 _{4 of} the second furnace 130. In the second furnace 130, the temperature of the first region 210 of the steel component 200 changes according to the schematically drawn temperature curve θ ₂ ιο, ο 3ο during the residence time t ₁₃₀ , ie the temperature of the first region 210 of the steel component 200 continues to decrease slowly. In this case, the temperature of the first region 210 of the steel component 200 may fall below the AC3 temperature, but this does not necessarily have to occur. On the other hand, the temperature of the second region 220 of the steel member 200 increases according to FIG

plotted temperature curve $ 220,130 during the dwell time t ₁₃₀ again, without reaching the AC3 temperature. The second furnace 130 has no special devices for different treatment of the different areas 210, 220. It is only a furnace temperature θ ₄ , ie one in the

Substantially homogeneous temperature throughout the interior of the second furnace 130, set between the austenitizing temperature AC3 and the

Abkühlstopptemperatur Q ₂ , for example between 660 ° C and 850 ° C. Thus, the various regions 210, 220 approach the internal temperature 0 _{4 of} the second furnace 130. If the temperature losses in the first region 210 during the dwell time t ₁₅₀ in the second zone treatment station 150 are so low that the temperature does not fall lower than the second furnace 130 temperature θ ₄ , the temperature profile approaches $ 210, 130 first range of temperature 0 _{4 of} the second furnace 130 from above. The

Cooling stop temperature $ 2 is lower than the selected temperature θ _{4 of} the second furnace 130 in this embodiment. The temperature profile $ 220,130 of the second region approximates the temperature 9 _{4 of} the second furnace 130 from below. The temperature of the region 210 does not fall below the

Microstructure transformation start temperature $ _! , Due to the small temperature difference between the two areas 210, 220, clearly contoured delimitations of the individual areas 210, 220 can be realized and the distortion of the steel component 200 is minimized. Small spreads in the temperature level of the steel component 200 have an advantageous effect on further processing in the press-hardening tool 160. The necessary residence time t ₁₃₀ for the second area 220 may depend on be realized by the length of the steel component on the setting of the conveying speed and the design of the length of the second furnace 130. A

Influencing the cycle time of the heat treatment apparatus 100 is thus minimized, it can even be avoided altogether. The first region 220 of the steel component 200 emits heat in the second furnace 130. The second region 220 of the steel component 200 absorbs heat in the second furnace 130, the heat absorption being limited by the heat released in the recalescence of the microstructure in the second region 220 of the steel component 200. This requires the sum of only a relatively small demand for heating power in the second furnace 130. Optionally, can be completely dispensed with an additional heating of the second furnace 130. So this treatment step is particularly energy efficient.

After completion of the residence time t _{130 of} the steel component 200 in the second furnace 130, it is transferred during the transfer time t ₁₃₁ in a press-hardening tool 160, where it is transformed and cured during the residence time t ₁₆ o.

FIG. 2 shows a heat treatment device 100 according to the invention in a 90 ° arrangement. The heat treatment device 100 has a loading station 101, via which steel components are fed to the first furnace 110. Furthermore, the heat treatment device 100, the treatment station 150 and in

Main flow direction D behind arranged the second furnace 130. Next in the main flow direction D arranged behind it is a removal station 131, which is equipped with a positioning device (not shown). The

Main flow direction now bends substantially 90 ° to a

Press hardening tool 160 in a press (not shown), in which the steel component 200 is press-hardened. In the axial direction of the first furnace 1 10 and the second furnace 130, a container 161 is arranged, can be spent in the rejects. The first furnace 110 and the second furnace 120 are at this

Arrangement preferably as continuous furnaces, for example, roller hearth furnaces executed.

FIG. 3 shows a heat treatment apparatus 100 according to the invention in a straight arrangement. The heat treatment apparatus 100 has a loading station 101 on, the steel components to the first furnace 1 10 are supplied. Furthermore, the heat treatment device 100, the treatment station 150 and in

Main flow direction D behind arranged the second furnace 130. Next in the main flow direction D arranged behind it is a removal station 131, which is equipped with a positioning device (not shown). Further, in a further straight main flow direction, a press hardening tool 160 follows in a press (not shown) in which the steel component 200 is press-hardened. in the

Substantially in 90 ° to the removal station 131, a container 161 is arranged, can be spent in the rejects. The first furnace 110 and the second furnace 120 are also preferably designed as continuous furnaces, for example roller hearth furnaces, in this arrangement.

Fig. 4 shows a further variant of an inventive

Heat treatment apparatus 100. The heat treatment apparatus 100 again has a loading station 101, via which steel components are fed to the first furnace 110. The first furnace 1 10 is again preferably designed as a continuous furnace in this embodiment. Furthermore, the heat treatment apparatus 100 has the treatment station 150, which in this embodiment is combined with a removal station 131. The removal device 131 can

For example, have a gripping device (not shown). The

Removal station 131 removes, for example by means of the gripping device, the steel components 200 from the first furnace 1 10. The heat treatment with the

Cooling of the second and second regions 220 is carried out and the steel components or the steel components 200 are inserted into a second furnace 130 arranged essentially at 90 ° to the axis of the first furnace 110. This second furnace 130 is preferably provided in this embodiment as a chamber furnace, for example with a plurality of chambers. After expiration of the residence time t _{130 of} the steel components 200 in the second furnace 130, the steel components 200 are removed via the removal station 131 from the second furnace 130 and inserted into an opposite, in a press (not shown) installed press hardening tool 160. For this purpose, the removal station 131 may have a positioning device (not shown). In the axial direction of the first furnace 1 10 is behind the Removal station 131 a container 161 arranged, can be spent in the rejects. The main flow direction D describes at this

Embodiment, a deflection of substantially 90 °. In this

Embodiment, no second positioning system for the treatment station 150 is required. Moreover, this embodiment is advantageous when in

Axial direction of the first furnace 1 10 not enough space, for example, in a production hall is available. The cooling of the second regions 220 of the steel component 200 in this embodiment can also take place between the removal station 131 and the second furnace 130, so that no stationary treatment station 150 is required. For example, a cooling device, for example a

Blowing nozzle to be integrated in the gripping device. The removal device 131 ensures the transfer of the steel component 200 from the first furnace 110 into the second furnace 130 and into the press-hardening tool 160 or into the container 161. Also in this embodiment, the position of the press-hardening tool 160 and container 161 can be reversed, as seen in FIG. The

Main flow direction D describes two in this embodiment

Deflections of substantially 90 °. If the space for installation of the heat treatment device is limited, a heat treatment device according to FIG. 6 is suitable: In comparison to the embodiment shown in FIG. 4, the second furnace 130 is offset in a second plane above the first furnace 110. Also in this embodiment, the cooling of the second regions 220 of the steel component 200 can also take place between the removal station 131 and the second furnace 130, so that no stationary treatment station 150 is required. Again, it is advantageous to run the first furnace 1 10 as a continuous furnace and the second furnace 120 as a chamber furnace, possibly with multiple chambers. Finally, FIG. 7 shows a final embodiment of the invention

Heat treatment device shown schematically. Compared to that in FIG. 6 In the embodiment shown, the positions of the press-hardening tool 160 and container 161 are reversed.

The embodiments shown herein are only examples of the present invention and therefore should not be considered as limiting. Alternative embodiments contemplated by one skilled in the art are

equally within the scope of the present invention.

LIST OF REFERENCE NUMBERS

100 heat treatment device

1 10 first oven

130 second oven

131 removal station

150 treatment station

160 press hardening tool

161 containers

200 steel component

210 first area

220 second area

D Main flow direction

M _s martensite start temperature

t _B treatment time

t _{1 10} residence time in the first oven

t ₁₂ o Transfer time of steel component in treatment station

t ₁₂ i Transfer time steel component in second furnace

t ₁₃₀ residence time in the second oven

t ₁₃₁ Transfer time of steel component in press hardening tool

tiso residence time in treatment station

t ₁₆₀ residence time in the press hardening tool

Structural transformation starting temperature

d ₂ cooling stop temperature

# 3 internal temperature first oven

# ₄ internal temperature second oven

) 200.1 10 Temperature profile of the steel component in the first furnace

# 210,150 Temperature profile of the first area of the steel component in the

treatment station

# 220,150 Temperature profile of the second area of the steel component in the

treatment station $ 210,130 Temperature profile of the first area of the steel component in the second

oven

# 220,130 Temperature profile of the second area of the steel component in the second

oven

# 200,160 Temperature profile of the steel component in the press hardening tool

Claims

claims:

1. A method for targeted component zone-specific heat treatment of a

Steel component (200), wherein in the steel component (200) in one or more first regions (210) a predominantly austenitic structure is adjustable, from which a majority martensitic structure can be represented by quenching, and in one or more second regions (220) the majority of bainitic structure is adjustable,

characterized,

that the steel component (200) is first heated in a first furnace (110) to a temperature above the AC3 temperature, the steel component (200) is subsequently transferred to a treatment station (150), where it can cool during the transfer, and the treatment station (150) the one or more second regions (220) of the steel component (200) are cooled to a cooling stop temperature $ 2 during a treatment time t _B , then transferred to a second furnace, wherein the temperature of the one or more second regions ( 220) rises again to a temperature below the AC3 temperature.

2. The method according to claim 1,

characterized,

that the cooling stop temperature θ ₂ above the martensite start temperature M _{s is} selected.

3. The method according to claim 1,

characterized,

the cooling stop temperature θ ₂ below the martensite start temperature M _{s is} selected.

4. Method according to one of the preceding claims,

characterized,

in the second oven, the one or more first regions (210) except for a temperature above the microstructure transformation start temperature θι

cooling down.

5. Method according to one of the preceding claims,

characterized,

in that the re-heating of the second region or regions (220) in the second furnace is assisted by the supply of heat.

6. The method according to any one of the preceding claims,

characterized,

the internal temperature in the second furnace 9 _{4 is} greater than the cooling-down stop temperature d ₂ .

7. A heat treatment device (100), comprising a first furnace (110) for heating a steel component (200) to a temperature above AC3

Temperature,

characterized,

that the heat treatment device (100) further comprises a

Treatment station (150) and a second oven, wherein the

Treatment station (150) has a device for rapid cooling of one or more second regions (220) of the steel component (200).

8. A heat treatment device (100) according to claim 7,

characterized,

that the device for rapid cooling of one or more second

Areas (220) of the steel component (200) has a nozzle for blowing the or the second regions (220) of the steel component (200) with a gaseous fluid.

9. A heat treatment device (100) according to one of claims 7 or 8, characterized in that:

that the device for rapid cooling of one or more second Areas (220) of the steel component (200) has a nozzle for blowing the second or regions (220) of the steel component (200) with a gaseous fluid, the water is mixed.

10. A heat treatment device (100) according to any one of claims 7 to 9, d a d e c e c e c e n e c e n e,

in that the device for rapid cooling of one or more second regions (220) of the steel component (200) has punches for contacting the second region or regions (220) of the steel component (200).

11. A heat treatment device (100) according to claim 10,

characterized,

the stamp is designed to be coolable for contacting the second region or regions (220) of the steel component (200).

12. A heat treatment device (100) according to any one of claims 7 to 11, d a d u c h e c e n e c e n e,

the treatment station (150) has a positioning device.

13. A heat treatment device (100) according to any one of claims 7 to 12, d a d e c o v e c e n e c e n e,

that the second furnace (130) is heated to a substantially homogeneous temperature.

14. A heat treatment device (100) according to any one of claims 7 to 13, d a d e c e c e s e c e n e c e,

the treatment station (150) has heat reflectors.

15. A heat treatment apparatus (100) according to any one of claims 7 to 14, d a d e c o v e c e n e c e n e,

the treatment station (150) has heat-insulated walls.