WO2017129602A1

WO2017129602A1 - Heat treatment method and heat treatment device

Info

Publication number: WO2017129602A1
Application number: PCT/EP2017/051510
Authority: WO
Inventors: Andreas Reinartz
Original assignee: Schwartz Gmbh
Priority date: 2016-01-25
Filing date: 2017-01-25
Publication date: 2017-08-03
Also published as: PL3408416T3; JP7261267B2; AT15624U1; PT3408416T; DE102016201025A1; CN108884508A; JP2019506532A; CN108884508B; HUE057631T2; JP2021179012A; MX2018008998A; KR20180119580A; BR112018014947B1; US20190032164A1; ES2904571T3; EP3408416B1; JP7168450B2; BR112018014947A2; DE202016104194U1; EP3408416A1

Abstract

The invention relates to a method and to a device for the heat treatment of a steel component directed specifically at individual zones of the component. In one or more first regions of the steel component a primarily austenitic structure can be set, from which, by quenching, a predominantly martensitic structure can be produced, and in one or more second regions of the steel component there is a predominantly ferritic-pearlitic structure. The steel component is first of all heated in a first furnace to a temperature below the AC3 temperature, and the steel component is then transferred into a handling station. During the transfer the steel component can cool, and in the handling station one or more second regions of the steel component are cooled within a residence time t₁₅₀to a final cooling temperature ϑ_S, and is then transferred to a second furnace, in which heat is delivered to the steel component. The temperature of the one or more second regions increases again during the residence time t₁₃₀ to a temperature below the AC3 temperature, whilst the temperature of the one or more first regions is heated in the same residence time t₁₃₀ to a temperature above 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

Martensite start temperature quenched. 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 1 the desired, partially increased

Deformability in the event of a crash. This is the only way to reduce the kinetic energy of an impact and minimize 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 regions 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 5. The object is further by a Device according to claim 8 solved. Advantageous embodiments of the device will become apparent from the dependent claims 6 to 15.

A steel component is first heated to below the austenitizing temperature AC3.

Subsequently, the steel component is transferred to a treatment station. Here, the second or the second areas as soon as possible within a

Treatment time t _B cooled. In a preferred embodiment of

Heat treatment device, the treatment station a

Positioning on, with the help of the exact positioning of the individual areas is ensured. The rapid cooling of the second or the second regions takes place in a preferred embodiment of the method

Blowing with a gaseous fluid, such as air or an inert gas. In an advantageous embodiment, the treatment station has a device for blowing on the second region (s). This device may, for example, have one or more nozzles. In an advantageous embodiment of the method, the blowing of the second or the second regions is carried out by blowing with a gaseous fluid, wherein the gaseous fluid water, for example in nebulized 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. After the treatment time t _B has expired, the second area or the second areas have reached a cooling stop temperature ds. The

Treatment time t _B usually moves in the range of a few seconds. In this case, the second or the second regions can also be cooled to well below the martensite start temperature M _s . The martensite start temperature M _s is, for example, for the frequently used

Bodybuilder 22MnB5 at about 410 ° C. The first area or areas are not subjected to any special treatment in the treatment station, ie they are not blown on or on any other special Measures heated or cooled. The first or the first areas cool slowly in the treatment station, for example, via natural convection. It has proven to be advantageous if in the treatment station measures for reducing the temperature losses of the first or the first

Areas are hit. Such measures can be, for example, the attachment of a heat radiation reflector and / or the isolation of surfaces of the treatment station in the region of the first or the first regions. Subsequently, ie after the end of the treatment time t _B , the steel component is transferred to a second furnace. In this second furnace, the entire steel component is heated. The heating can be done for example by thermal radiation. In this case, the steel component remains during a residence time t ₁₃₀ in the second furnace, which is dimensioned such that the temperature of the first or the first regions above the AC3 temperature increases. Because the second or the second

Areas from the previous process steps at the beginning of the residence time t _{130 have} a significantly lower temperature than the or the first areas, they have not reached the end of the residence time t ₁₃₀ in the second furnace, the AC3 temperature. Subsequently, the steel component in a

Press hardening tool are transferred, wherein the first and the first areas are completely austenitized, while the second and the second areas are not austenitized, so that form by quenching in a subsequent press hardening of the first and the first areas martensitic structure with high strength values. Because the second

and / or the second regions were not austenitized at any time in the process, they exhibit, after the press-hardening step, ferritic-pearlitic microstructure with only low strength values at high ductility.

According to the components after a few seconds in the

Treatment station, which may also have a positioning device to ensure the exact positioning of the different areas, transported in a second oven, which preferably no special devices for owns different treatment of different areas. In a

Embodiment, only a furnace temperature 0 ₄ , ie a substantially homogeneous temperature in the entire furnace chamber, set above the

Austenitizing temperature AC3 is. Clearly contoured boundaries of the individual areas can be realized, and the low temperature difference between the two areas minimizes distortion of the components. Small spreads in the temperature level of the component have an advantageous effect on the other

Processing in the press. Advantageously, in one embodiment, a continuous furnace is provided as the first furnace. 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. But even a batch oven, such as a chamber oven, can be used as the first oven.

Advantageously, in one embodiment, the second furnace is a continuous furnace.

If both first and second furnaces are designed as continuous furnaces, the necessary residence times for the first or second regions can be realized as a function of the length of the component via the adjustment of the conveying speed and the design of the respective furnace length. An influencing of the cycle time of the entire production line with heat treatment device and press for a subsequent press hardening is thus avoidable. In an alternative embodiment, the second oven is a batch oven,

for example, a chamber furnace

In a preferred embodiment, the treatment station has a

Device for rapid cooling of one or more second regions of the steel component. In an advantageous embodiment, the device has a nozzle for blowing the second part or regions of the steel component with a gaseous fluid, for example air or an inert gas such as, for example Nitrogen, up. 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.

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.

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.

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. The second or the second areas were never austenitized during the course of the process and, even after being pressed off, have low strength values similar to the original strengths of the untreated steel component. 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 regions may be completely enclosed by first regions or located at the edge of the steel component. Even a full-surface treatment is conceivable. A particular orientation of the steel component to the passage direction is for the purpose of the method according to the invention for specific component zone-specific Heat treatment of a steel component is not required. A limitation of the number of simultaneously treated steel components is at most by the

Press hardening tool or the conveyor technology of the entire

Heat treatment device given. 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.

From the pictures shows:

Fig. 1 is a typical temperature curve in the heat treatment of a steel component having 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 shows a further inventive thermal heat treatment device in a plan view as a schematic drawing

Fig. 5 shows another thermal treatment device according to the invention in a plan view as a schematic drawing

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 heated in the first furnace 1 10 according to the schematically drawn temperature run θ ₂ οο _, ι ιο during the residence time t _{1 10} in the first furnace to a temperature below 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 member 200 is rapidly cooled, wherein the second area 220 loses ^its heat according to the drawn curve £ 220.150. The blowing ends after the treatment time t _{B has} elapsed, which is only a few seconds depending on the thickness of the steel component 200 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 ds. At the same time, the temperature of the first region 210 in the treatment station 150 has also fallen according to the temperature curve $ 210,150 plotted, wherein the first region 210 is not located in the region of the cooling device. After expiration of

Treatment time t _B , the steel member 200 is transferred during the transfer time t ₁₂ i in the second furnace 130, wherein it continues to lose heat. In the second oven 130 changes the temperature of the first portion 210 of the steel member 200 according to the schematically drawn temperature profile θ ₂ ιο, ο 3ο during the residence time t ₁₃₀ , ie the temperature of the first portion 210 of the steel member 200 is heated to a temperature above the AC3 temperature. Also the

Temperature of the second region 220 of the steel component 200 increases according to the plotted temperature profile $ 220.130 during the residence time t ₁₃₀ , without reaching the AC3 temperature. The second furnace 130 has no special devices for different treatment of the different areas 210, 220. Only one furnace temperature θ ₄ , ie a substantially homogeneous temperature θ ₄ in the entire interior of the second furnace 130, is set which is above the austenitizing temperature AC3 lies. Since the second or the second regions have a significantly lower temperature than the first region (s) at the beginning of the residence time t ₁₃₀ in the second furnace 130 and both regions are heated equally in the second furnace 130, they also have a different temperature at the end of the residence time ti ₃₀ on. The residence time t _{130 of} the steel component 200 in the second furnace 130 is so dimensioned that the first region or the first regions at the end of the residence time t _{130 have} a temperature above the AC3 temperature, while the second

or the second areas have not yet reached the AC3 temperature at this time.

Subsequently, the steel component during a transfer time t ₁₃₁ in a

Press hardening tool 160, which is installed in a press, not shown, to be transferred. During the transfer time t ₁₃₁ , the steel component 200 loses heat again so that the temperature of the first region (s) may also fall below the AC 3 temperature. This or these spaces but substantially completely austenitized, when they leave the second furnace 130 so that they t by a deterrent for a residence time in ₁₆₀

Press hardening train 160 undergoes a transformation into hard martensitic structure. Clearly contoured delimitations of the individual regions 210, 220 can be realized between the two regions 210, 220 and can be realized by the small ones

Temperature difference, the delay of the steel member 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 of} the steel component 200 in the second furnace 130 can be realized depending on the length of the steel component 200 via the adjustment 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.

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 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). Continue in Further, in the straight main flow direction, a press hardening tool 160 in a press (not shown) in which the steel member 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 device 100.

The heat treatment device 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 may 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. Die

Heat treatment with the cooling of the second and the second regions 220 is performed 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 t130 of the steel components 200 in the second furnace 130, the steel components 200 are removed from the second furnace 130 via the removal station 131 and inserted into an opposed press-hardening tool 160 installed in a press (not shown). For this purpose, the removal station 131 may have a positioning device (not shown). In the axial direction of the first furnace 1 10, a container 161 is arranged behind the removal station 131, can be spent in the rejects. The

Main flow direction D describes in this embodiment, a deflection of substantially 90 °. In this embodiment, no second

Positioning system for the treatment station 150 required. In addition, it is This embodiment is advantageous if in the 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 can in this

Embodiment also take place between removal station 131 and second furnace 130 so that it does not require a stationary treatment station 150.

For example, a cooling device, for example a blowing nozzle, can be integrated into 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 with 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 the embodiment shown in FIG. 6, the positions of the press-hardening tool 160 and the container 161 are reversed. The embodiments shown here are only examples of the present invention

Invention is therefore not restrictive to be understood. 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

135 removal station

150 treatment station

152 punctiform infrared radiator

153 heating field

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

ti2o transfer time steel component in treatment station

ti 2i 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

t ₁₅₀ residence time in treatment station

tieo dwell time in the press hardening tool

#s Cooling stop temperature

θ ₃ internal temperature of the first furnace

θ ₄ internal temperature of the second furnace

1) 200.1 10 Temperature profile of the steel component in the first furnace

# 210.150 Temperature profile of the first region of the metallic 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

$ 2oo _, i 6o 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) majority feritisch- perlitisches structure is adjustable,

characterized,

that the steel component (200) first in a first furnace (110) on a

Temperature is heated below the AC3 temperature, the steel component (200) is then transferred to a treatment station (150), where it can cool during the transfer, and in the treatment station (150), the one or more second portions (220) of the steel component (200) are cooled within a dwell time t ₁₅₀ to a cooling stop temperature ds, then transferred to a second furnace 130, in which the

Heat is supplied to the steel component (200), wherein the temperature of the one or more second regions (220) during the residence time t ₁₃₀ again rises to a temperature below the AC3 temperature, while the

Temperature of the one or more first regions (210) in the same residence time t ₁₃₀ are heated to a temperature above the AC3 temperature.

2. The method according to claim 1,

characterized,

that the heat supply in the second furnace (130) is achieved by heat radiation.

3. The method according to claim 1 or 2,

characterized,

that the one or more second regions (220) of the steel component (200) in the treatment station (150) within a residence time t ₁₅₀ are blown for cooling with a gaseous fluid.

Method according to claim 3,

characterized,

that the gaseous fluid contains water.

Method according to one of the preceding claims,

characterized,

that the cooling of the one or more second regions (220) of the

Steel component (200) in the treatment station (150) within a residence time t ₁₅₀ via heat conduction takes place.

Method according to claim 5,

characterized,

the one or more second regions (220) of the steel component (200) in the treatment station (150) are brought into contact with a stamp for cooling within a residence time t ₁₅₀ , the stamp having a lower temperature than the second region (s) ( 220).

Method according to one of the preceding claims,

characterized,

the internal temperature θ ₄ in the second furnace (130) is greater than the AC3 temperature.

A heat treatment apparatus (100) comprising a first furnace (110) for heating a steel component (200) to a temperature below the AC3 temperature,

characterized,

that the heat treatment device (100) further comprises a

Treatment station (150) and a second oven (130), wherein the treatment station (150) comprises a device for rapid cooling of one or more a plurality of second regions (220) of the steel component (200) and the second furnace (130) having means for introducing heat, with which at least the first or the first regions (210) of the steel component (200) to a temperature greater than AC3 temperature is heatable.

A heat treatment apparatus (100) according to claim 8,

characterized,

in that the device for rapid cooling of one or more second regions (220) of the steel component (200) has a nozzle for blowing on the second region (220) of the steel component (200) with a gaseous fluid.

10. A heat treatment device (100) according to claim 8 or 9, wherein:

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. 11. The heat treatment device (100) according to claim 8, wherein:

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).

12. Heat treatment apparatus (100) according to claim 1,

characterized,

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

13. A heat treatment device (100) according to any one of claims 8 to 12, d a d e c e c e s e c e n e c e,

the treatment station (150) has a positioning device. 14. A heat treatment apparatus (100) according to any one of claims 8 to 13, d a d e c e c e s e c e n e c e,

that the second furnace (130) is heated to a substantially homogeneous temperature 9 ₄ . 15. Heat treatment device (100) according to one of claims 8 to 14, characterized

the treatment station (150) has heat reflectors.

16. A heat treatment device (100) according to any one of claims 8 to 15, d a d e c o v e c e n e c e n e,

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