WO2017085267A1

WO2017085267A1 - Method and device for partial hardening of sheet steel components

Info

Publication number: WO2017085267A1
Application number: PCT/EP2016/078158
Authority: WO
Inventors: Andreas Sommer; Reiner Kelsch; Tobias HÄGELE; Cornelius Fink
Original assignee: Voestalpine Metal Forming Gmbh
Priority date: 2015-11-20
Filing date: 2016-11-18
Publication date: 2017-05-26
Also published as: DE102016109095B4; DE102016109095A1

Abstract

The invention relates to a method for partial hardening of sheet steel components, wherein sheet steel components (3) are guided through a furnace (1) and at least parts thereof are heated in the furnace (1) to a temperature > Ac₃, wherein the sheet steel components (3) are guided in steps through the furnace (1), wherein the regions of the components which are not to be heated to a temperature > Ac₁ or > Ac₃ are introduced or pushed into a thermo box (10) in the conveying direction (6) between two conveying steps, in which the regions which are not to be heated > Ac₁ or > Ac₃ are acted on for cooling, such that there the component temperature is kept below the austenite starting temperature (Ac) or the austenitising temperature (Ac₃).

Description

Method and device for partial hardening of sheet steel components

The invention relates to a method and a device for partial hardening of sheet steel components.

The partial hardening of sheet steel components, in particular of body components, is known.

In principle, a steel strip is in such processes hot- and cold-rolled and then optionally provided with egg ^¬ ner Korrosionsschut zbeschichtung. Such a corrosion protection coating is, for example, an aluminum coating, an aluminum-silicon coating, a zinc coating or a zinc alloy coating. Such coatings protecting be placed in so-called hot-dip process on ^¬, in which the hot and cold rolled steel strip, for example with thicknesses of 0.5 mm to 4 mm, by a FLÜS ^¬ Siges metal strip runs, adhering the metal to the steel strip and, optionally, excess liquid metal is stripped with a scraper, so that a predetermined Di ^¬ bridge of the coating metal can be adjusted.

Subsequently, the steel strips with the coating can still be subjected to an annealing treatment. A known Tem ^¬ treatment is z. B. the Galvannealing, in which a

Zinc coating is heated again on a steel strip, namely up to 700 ° C to the zinc and including lie ^¬ constricting iron together to form a zinc-iron alloy umzuwan ^¬ spindles. If individual boards are punched for the production of steel components made of such a steel strip, either cold worked at ^¬ closing, then heated and inserted in a form hardening tool, in which they, if necessary, even partially, with a speed which is above the critical hardening speed , Is cooled to reach a hardened sheet metal component. This process is called mold hardening. In this method, very complex shapes can be produced from the steel strip in a conventional, for example, five-stage, deep-drawing process.

Another possibility is to ne a Stahlblechplati-, the WUR punched out of the steel strip or cut to bring ^¬ en, to a necessary for the curing temperature, warm convert to ^¬ closing in a one step process and at the same time deter the hot forming tool and här ^¬ th This process is called press hardening. In this process, only relatively simple geometries can be produced compared to hot stamping, but the process Weni ^¬ ger is expensive.

For partial curing, it is known to lead the component areas that are to remain cold, either with insulation through a heating furnace, or, for. B. in Berei ^¬ chen, which should remain cold, a relatively large absorption ^¬ mass to create or keep slightly spaced, which absorbs the heat acting on the sheet and thus ensures that in these areas, the sheet is not ^necessary for hardening ^¬ low austenite start temperature (temperature> Aci) or austenitizing temperature (ie a temperature> Ac ₃ ). In the attachment of insulation to such components is a disadvantage that it is relatively expensive to install the insulation and then, before hardening or pressing hardening ^¬ decrease again. In addition, is removed via the Iso-regulation ^¬ enthalpy from the oven, because the insulation must then be cooled down again.

Absorption masses have proven themselves, they are applied to the furnace carrier or integrated into the furnace carrier with which such components are passed through the furnace. However, an absorption mass also carries enthalpy from the furnace and ensures that the furnace support alone with the absorption mass or the absorption mass must be strongly cooled.

Another variant, for example, storage temperature heat components only in the austenite or the austenitizing and then to bring the areas that gehär ^¬ tet to be targeted with spotlights to a temperature above AC3. Such a method allows a very accurate heating of the areas to be cured, but has the disadvantage that only thin components can be heated quickly. Also, the arrangement of spotlights in the oven ensures that the oven for other products must first be converted.

The object of the invention is to provide a method for the partial hardening of sheet steel components, which enables a reliable only partial hardening with great flexibility.

The object is achieved with a method having the features of at ^¬ claim 1. Advantageous developments are characterized in the dependent claims.

It is a further object of the invention to provide a device for partial hardening of sheet steel components, which can produce both partially and fully hardened ^¬ te components or different partially cured components with great flexibility and is variable with respect to the cycle times. The object is achieved with a device having the features of claim 6.

Advantageous developments are characterized in the dependent claims.

The inventive method provides sheet metal components of a hardenable steel sheet, in particular a curable boron-manganese steel, such as. As a 22MnB5, or similar steels to pass through a heating furnace, wherein in the heating furnace, the steel component or parts of the steel component are heated to a temperature above AC ₃ , then to bring about by quenching cooling curing.

A sheet-steel component may be, for example, a substantially planar board which has been cut from a steel strip or an already formed component such as a B-pillar.

Preferably, the steel components are thereby cyclically moved through the furnace, wherein the furnace is preferably a Hubschrittför- furnace. A heating of the steel components to temperatures up to about 600 ° C to 700 ° C is not critical, because it is not necessary for the Här ^¬ tion structural change is achieved. According to the invention, in the regions of the furnace in which the steel components reach these temperatures, that region of the components which is not to be hardened is transferred into a region integrated in the furnace wall in which heat sinks are present, the cooling bodies being actively or passively cooled ,

According to the invention these areas are formed moboxen as drawers or thermo- that can be pushed to the side of the furnace wall forth in the furnace space, wherein the heat sink are preferably tuned by the contour of the cooling area from ^¬ and are themselves cooled actively or passively, ,

By pushing in and out of the drawers or thermoboxes can be achieved according to the invention that can be reacted very flexibly to different components, even on construction ^¬ parts that are to be fully cured. In this case, the method provides for the thermoboxes to be completely withdrawn from the oven ^cavity . Since the steel components are gradually transported through the oven, a plurality of drawers / thermoboxes nachei ^{¬ one} another arranged so that a steel component passes with each step in a new drawer or a new thermobox. The drawers or thermal boxes are designed such that they have a region which is not to be hardened, to shield a ^¬ hand against the heat radiation overlying thermal radiator and on the other hand, shield the heat sink contained in the RTD on the one hand, on the other hand the cooling body of the furnace outer side at ^¬ game as air, pressurized with a cooling medium. The air can be passed through the interior of such a heat sink to dissipate the heat absorbed to the outside.

The drawers or thermoboxes can in this case be designed so that the steel components with each step, with which they are transported, are simultaneously introduced into such a thermobox or drawer raised from below.

In order to obtain a thermal separation between the drawer / thermobox and the furnace chamber, wherein the furnace chamber ^{beispielswei ¬} se 900 ° C to 1000 ° C is hot, while the component in the soft range should not have more than 700 ° C, below the thermobox or drawer ceramic sheets be integrated, which form a thermal separation between ^¬ 900 ° C furnace atmosphere and 700 ° C furnace zone below the thermoboxes during the cooling position. In addition, the thermoboxes can be formed at their outer periphery with nozzles such that an air curtain between ^¬ rule the interior of the thermoboxes and the furnace atmosphere consists. Preferably, the individual drawers or thermal boxes are monitored by thermal sensors and adapted to the cooling capacity to which it ^¬ ford variable cooling capacity.

During transport through the oven the Bautei- le of RTD to RTD in the 900 ° C hot oven thus be moved, but be ^¬ sit in the area covered by the thermoboxes areas only a maximum of 700 ° C. Should it come to standstill during production, the components can remain locally in the thermoboxes and the soft component area is cooled accordingly.

The invention is exemplified erläu tert ^¬ reference to a drawing it in which:

1 shows a furnace for heating steel sheet components with different temperature ranges and highly specific ^¬ matically indicated thermal boxes;

Figure 2 is a partially cutaway cross-sectional view of a furnace according to Figure 1 with a lifting and by sliding device for steel sheet components and a retracted ther- mobox in a lowered state of the Stahlblechbau ^¬ part;.

. 3 shows the apparatus of Figure 2 in a raised state of the steel component to be ^¬;

Figure 4 is a Doppelthermobox in a longitudinally cut at ^¬ view with respect to the furnace axis with an active cooling component;

Figure 5: a thermobox with a passive component cooling.

A furnace 1 for heating sheet steel components is a forth ^¬ kömmlicher, particularly Hubschrittförderofen, z. B. a Hub ^¬ beam furnace, in which resting on furnace supports 2 Stahlblechbau ^¬ parts 3 of a furnace inlet 4 to a furnace exit 5 ent ^¬ long a conveying direction 6 moves.

Alternatively, it can also be provided that no oven supports are used, in particular in the case of planar sinkers. In such a procedure, the flat board is conveyed without oven ^¬ carrier or goods carrier through the oven chains.

In the furnace 1, the steel sheet components 3 are heated by means of gas burners, gas burners sheathed in jet pipes 7 or other suitable heating devices.

The heating takes place in such a way that the Stahlblechbautei ^¬ le 3 can be at least partially heated to a temperature at which their steel structure is present in an austenitic state, ^¬ that means that the temperature is greater than about 900 ° C. Thus, the components are at least teilbe ^¬ richly heated to a temperature> Ac ₃ . For this purpose, the sheet steel ^components are made of a hardenable steel ^¬ alloy, in particular, the Stahlblechbautei ^¬ le 3 of a boron-manganese steel, such as. As a 22MnB5 or comparable curable boron-manganese steels formed. In a first region 8 after the oven inlet 4, the components reach a temperature of about 700 ° C, which is a tempera ^ture below AC ₃ , optionally also below Aci. In ^¬ insofar as the components can be heated here uncritically to this tempera ^ture .

In a further, subsequent heating zone 9, both the furnace atmosphere and the components reach temperatures higher Tempe ^¬ so that thermal boxes according to the invention 10 are provided in this area. 9

The first heating area 8 is thus a preheating area and the second heating area 9 serves as an austenitizing area. The thermoboxes 10 can be provided as individual thermoboxes 10 or as double thermoboxes 10 (FIG. 1).

The thermoboxes 10 according to the invention each have at least one guide rail 11, on which the thermoboxes 10 extend transversely to the

The conveying direction 6 of the furnace 1 laterally from a furnace wall 12 ago in the inner region 13 of a furnace 1 are inserted. In the furnace 1 is each a lifting and transporting device 14 is provided, wherein the lifting and conveying device 14 in a known per se is adapted to move the furnace carrier 2 with a aufzu ^¬ heating unit load through the furnace 1 and reported.

The thermoboxes 10 are preferably box-like with side walls 15, wherein the side walls 15 pass through the furnace wall 12. In addition, the thermoboxes have 10 De ^¬ Ckenwandungen 16th

To seal the oven to the outside, the thermoboxes 10 have respective backside walls (not shown) or are fitted into the furnace wall 12 so as to be sealed to the outside.

Within the RTD 10 16 cooling means 17 are at at least one of the Wandun ^¬ gene 15 present.

The cooling means 17 may be air-carrying plates or boxes, for example, which are connected to respective outlet nozzles 18 or ^¬ formed outlet geometries 18, can be printed from de ^¬ NEN air or other suitable cooling gas onto the component 3 overall.

Additionally or alternatively, the cooling devices 17 may themselves be cooled components which absorb and dissipate heat acting on the component 3 by radiation (FIG. 5). Here, it is advantageous if these corresponding Küh ^¬ Ironing Facilities 17 are adapted to the contour of the component to be cooled ^¬ the art that, of all surfaces of the component 3 z. B. a distance of 20 mm to 30 mm is maintained. DEM according to the cooling means 17 have a contour that says the component contour as far as possible ent ^¬ in this case.

In order to achieve a shielding of the component also down, may on the furnace support 2 and below the component 3 sheet or plate-like so-called ceramic sheets 19 be present, which shield the area of the thermobox 10 down and inward toward the furnace 1 and thus the Facilitate cooling of the component. The ceramic sheets 19 may be integrated in the furnace saddle 20.

The ceramic sheets 19 preferably have ei ^¬ ne contour to the component, which also corresponds to the component contour from the bottom as possible or this is so far approximated that the strongest possible shielding is achieved.

Additionally or alternatively (not shown), the thermobox to the furnace atmosphere both down and to Ofenmit ^¬ te out have air curtains, which by blowing in air and possibly also by the suction of the cooler area within the thermobox (about 700 ° C) ge ^¬ gen shield the hotter oven atmosphere (about 900 ° C).

The inventive method provides to take the corresponding preformed steel sheet components 3 on a furnace support 2 au ^¬ ßerhalb of the furnace 1 and then the steel sheet components to combine 3 to the furnace carrier 2 with the lifting and transporting device 14 so that the furnace carrier 2 with the steel sheet ^¬ 3 components clocked in the oven 1 are introduced. By doing Preheating 8, the sheet steel components by means of geeig ^¬ ned heating devices to a temperature of 700 ° C ge ^{¬ introduced} . Reach the steel sheet components 3 in a second Austenitisierungsbereich 9 - wherein the transition of the Vorheizbe ^¬ Reich 8 for Austenitisierungsbereich 9 is fluid or

can be flowing - the component areas that are not austenitized are moved under a suitable thermobox 10 and then raised so that these component areas are within the thermobox 10, where they are shielded from further heating and either ak ^¬ tively with Air or a suitable other cooling gas to be flowed or the heat from cooled cooling devices 17 from ^sorbiert and is derived. While the remaining area of the component 3 is now slowly heated to the austenitizing temperature, the components 3 are moved stepwise through the furnace 1, being lowered from a thermobox 10, led to the next thermobox 10 and raised there again ^¬ to continue to prevent the component 3 is overheated there too.

At the furnace exit 5, the components are then extracted 3 with the tempered under ^¬ areas differently from the furnace 1 and supplied to the further processing.

The ceramic sheets 19 to shield the components down to the furnace and towards the center Face Absorptionsmas ^¬ sen only a very small mass and is place at the end of the furnace little enthalpy from the furnace off.

An example of a possible steel sheet component 3 at ^¬ play, a body B-column, wherein the foot region, for example, is not to be hardened and soft remains, so that the foot region is guided in the area of thermo boxes. In the invention, it is advantageous that each m ther- mobox forms a separate small furnace atmosphere, which is monitored by means of thermocouple ^¬ and means Kühlmediumdurch- flow rate in the desired range of about 700 ° C.

The lifting of the components in the thermoboxes is done by the Hubschrittferördertechnik in the oven, this being particularly simple and safe.

In the raised state, the thermal separation of the small furnace atmosphere takes place in the thermoboxes through the integrated in the carrier or furnace saddle ceramic sheets, which also partially preferably have the component contour.

The component is not completely heated in the invention and then locally cooled, which means a loss of energy, but the soft component areas are locally prevented from further heating in the oven and kept only at temperature. Only the later, hard component area is controlled via the AC ₃ -

Temperature warmed up.

In the invention also is of advantage that, depending on the thermal drawers or thermal boxes can be drawn from the furnace interior to the exterior of the component geometry and corresponding spre ^¬ accordingly, the cooling devices 17 are interchangeable in order to be adapted to other component contours.

If a batch is to be completely ^cured with the oven 1 according to the invention, the thermal drawers or

Thermoboxes pulled in a simple manner from the furnace interior to the furnace ^¬ outer, so that the radiation of gas burners or other radiation devices in the oven is not hindered by Ther ^¬ moschubladen or thermoboxes. As a result, the oven according to the invention is extremely flexible. By a double-cycle mode and possibly double vor ^¬ existing thermoboxes the life in the thermoboxes ver ^¬ double and the number of Umsetzvorgänge is halved.

If due to stagnation in further processing, the material must remain in the oven, the soft Be ^¬ rich remain in the thermoboxes and their temperature is maintained there, so that the Committee sinks.

List of reference numbers:

1 oven

2 oven carriers

3 sheet steel component

4 oven entrance

5 oven exit

6 conveying direction

7 gas burners

8 first heating area

9 second heating area

10 thermobox

11 guide rail

12 furnace wall

13 indoor area

14 lifting and transport device

15 side wall

16 ceiling wall

17 cooling device

18 outlet nozzles

19 ceramic sheet

20 oven saddle

Claims

claims

A method for partial hardening of steel sheet metal components, said steel sheet parts or a flat board (3) through a furnace (1) are held and in the furnace (1) at least in partial areas are heated to a temperature> Ac ₃ who, ^¬ wherein

the steel sheet components or the planar board (3) step ^¬, by the furnace (1) are passed, wherein the device areas that should not be heated to a temperature> Aci or> Ac ₃ between two conveyor ^¬ steps in the conveying direction (6) be in a thermo box (10) placed a ^¬ or hoisted, in which, acted cow ^¬ lend the preparation ^¬ che, which should not be heated> Aci or> Ac _3, so that there the component temperature un ^¬ ter the austenite start temperature ( Aci) or the austenitizing temperature (Ac ₃ ).

A method according to claim 1, characterized in that the components (3) in the thermobox (10) are actively cooled by flowing against a cooling medium.

A method according to claim 1 or 2, characterized in that the components (3) are cooled in the thermobox (10) by cooled cooling means (17), such as plates or the like, by the absorption of heat radiation.

A method according to claim 3, characterized in that the components (3) are ge ^¬ into contact with the cooling means (17) or held at a small distance to the Küh ^¬ Ironing Facilities (17). Method according to one of the preceding claims, characterized in that the oven support (2) means (19) are present, which, when the component (3) and the furnace ^¬ carrier (2) are lifted into the thermobox (10), the construction ^¬ part (3) downwards and towards the middle of the furnace in such a way from the rest of the furnace atmosphere or the inside of the furnace (13) abschirm ^¬ men that within the thermobox (10) own Ofenat ^¬ atmosphere is formed, which is cooler than the Ofenat ^¬ atmosphere inside the oven (13).

Apparatus for the partial hardening of sheet steel components, in particular apparatus for carrying out the method according to one of claims 1 to 5, characterized in that a furnace (1) is provided, wherein the furnace (1) has a lifting and transporting device (14), with the parts to be heated or the planar board (3) are passed stepwise through the furnace (1), wherein in the oven suitable heating devices (7) are present and the Erhit ^¬ tion devices (7) acting on the parts to be heated (3) are formed, said furnace (1) via thermo boxes (10), wherein the thermal boxes (10) so attached are ^¬ arranged that the to be heated parts or the planar board (3) along a conveying direction (6) between two conveying steps under a thermobox (10) and the thermobox (10) can be raised, so that in the thermobox (10) raised component areas are shielded from the rest of the furnace atmosphere.

Device according to claim 6, characterized in that the furnace (1) has furnace supports (2), the parts (3) to be heated on them being passed through the furnace (1) in a stepwise manner.

8. Apparatus according to claim 6 or 7, characterized in that the thermoboxes (10) laterally from a furnace wall (12) in the furnace interior (13) are arranged slidably.

9. Apparatus according to claim 6 to 8, characterized in that in the thermoboxes (10) cooling means (17) are IN ANY ^¬ the, wherein the cooling means (17) on a in the thermobox (10) lifted arranged component area active by flowing with a Cooling medium or passive by ge ^¬ cooled plates, the component areas cooling acting from ^¬ formed.

10. Device according to one of claims 6 to 9, characterized ge ^¬ indicates that the cooling means (17) with respect to ih ^¬ rer to the component facing contour of the contour of the component following or are formed approximately.

11. Device according to one of claims 6 to 10, characterized ge ^¬ indicates that the thermoboxes (10) downwards, ie to the raisable and lowerable kiln supports (2) and the furnace ^¬ center (13) out with movable shielding (19 ) are shielded.

12. Device according to one of claims 6 to 11, characterized ge ^¬ indicates that the shielding means (19) on the furnace ^¬ carrier (2) or furnace caliper (20) are arranged.

13. Device according to one of claims 6 to 12, characterized ge ^¬ indicates that the thermoboxes (10) have air or gas curtains, wherein the air or gas curtains the atmosphere within the thermobox (10) of the atmosphere in the furnace interior (13), whereby the air curtains are blown in by air blowing on the outside of the thermobox (10). and possibly formed by suction of the same.