HEAT TREATMENT INSTALLATION FOR PRODUCING SHAPED COMPONENTS

Abstract

There are disclosed a heat treatment installation and a method of producing shaped components having at least two microstructural regions of different ductility or strength from semi-finished products of hardenable steel, using a continuous furnace which permits heating of the semi-finished products to a first temperature in a first region and permits heating of the semi-finished products to a second temperature, which differs from the first temperature, in a second region. The two regions are separated from one another by partition walls extending in the transport direction, and the continuous furnace includes a lifting-step chain conveyor as a transport device.

Claims

1. A heat treatment installation for the production of shaped components from semi-finished products of hardenable steel, the components having at least two microstructural regions of different ductility or strength, the heat treatment installation comprising: a continuous furnace comprising a lifting-step chain conveyor for transporting semi-finished products in a transport direction through a furnace chamber, said lifting-step chain conveyor defining a lower supporting surface for said semi-finished products; at least one upper partition wall extending in said transport direction at least along a part of said furnace chamber; at least one lower partition wall extending in said transport direction at least along a part of said furnace chamber, said upper and lower partition walls dividing said furnace chamber into a first sub-chamber and into a second sub-chamber thermally divided from said first sub-chamber; a heating system being configured for heating said first and second sub-chambers to different temperatures; and a final treatment station configured for hot-forming or hardening semi-finished products after heating within said furnace chamber; wherein said at least one lower partition wall ends at a distance of a maximum of 10 mm below said lower supporting surface.

2. The heat treatment installation of claim 1, further comprising a first zone without any partition walls being configured for austenitizing said semi-finished products, and a second zone, wherein said first and second sub-chambers are provided separated from one another by said partition walls.

3. The heat treatment installation of claim 1, wherein said at least one upper partition wall is adjustable in height.

4. The heat treatment installation of claim 1, wherein said heating system is configured for heating and cooling said first and second sub-chambers.

5. The heat treatment installation of claim 4, wherein said heating system comprises jacket radiant tubes being configured for heating and cooling said first and second sub-chambers.

6. The heat treatment installation according to claim 1, wherein said at least one lower partition wall is adjustable in height.

7. The heat treatment installation of claim 1, wherein said lifting-step chain conveyor comprises transport chains which are mounted displaceably on rollers, wherein said transport chains define said lower supporting surface, and further comprises punches arranged displaceably in a vertical direction for holding semi-finished products at an elevated level during a return movement of said transport chains.

8. The heat treatment installation of claim 1, wherein said at least one lower partition wall ends upwardly substantially at a level of a supporting surface of said lifting-step chain conveyor drive.

9. A heat treatment installation for the production of shaped components from semi-finished products of hardenable steel, the components having at least two microstructural regions of different ductility or strength, the heat treatment installation comprising: a continuous furnace comprising a lifting-step chain conveyor for transporting semi-finished products in a transport direction through a furnace chamber; at least one partition wall extending in said transport direction at least along a part of said furnace chamber, said partition wall dividing said furnace chamber into a first sub-chamber and into a second sub-chamber thermally divided from said first sub-chamber; a heating system being configured for heating and cooling said first and second sub-chambers to different temperatures; and a final treatment station configured for hot-forming or hardening semi-finished products after heating within said furnace chamber.

10. The heat treatment installation of claim 9, further comprising a first zone being configured for austenitizing the semi-finished products without any partition walls, and a second zone, wherein said first and second sub-chambers are provided separated from one another by said partition walls.

11. The heat treatment installation of claim 9, wherein said first and second sub-chambers are separated from each other by upper and lower partition walls extending in said transport direction, between which a gap remains for passing semi-finished products therethrough.

12. The heat treatment installation of claim 11, wherein said at least one upper partition wall is adjustable in height.

13. The heat treatment installation of claim 11, wherein said at least one lower partition wall ends at a distance of no more than 5 mm below a level of a lower supporting surface of said lifting-step chain conveyor.

14. The heat treatment installation of claim 11, wherein said at least one lower partition wall ends upwardly substantially at a level of a supporting surface of said lifting-step chain conveyor drive.

15. The heat treatment installation according to claim 11, wherein said at least one lower partition wall is adjustable in height.

16. The heat treatment installation of claim 9, wherein said heating system comprises jacket radiant tubes being configured for heating and cooling said first and second sub-chambers.

17. The heat treatment installation of claim 9, wherein said lifting-step chain conveyor comprises transport chains which are mounted displaceably on rollers, and further comprises punches arranged displaceably in a vertical direction for holding semi-finished products at an elevated level during a return movement of said transport chains.

18. A heat treatment installation for the production of shaped components from semi-finished products of hardenable steel, the components having at least two microstructural regions of different ductility or strength, the heat treatment installation comprising: a continuous furnace comprising a lifting-step chain conveyor for transporting semi-finished products in a transport direction through a furnace chamber; at least one partition wall extending in said transport direction at least along a part of said furnace chamber, said partition wall dividing said furnace chamber into a first sub-chamber and into a second sub-chamber thermally divided from said first sub-chamber; a heating system being configured for heating said first and second sub-chambers to different temperatures; and a final treatment station configured for hot-forming or hardening semi-finished products after heating within said furnace chamber.

19. The heat treatment installation of claim 18, further comprising a first zone being configured for austenitizing the semi-finished products without any partition walls, and a second zone, wherein said first and second sub-chambers are provided separated from one another by said partition walls.

20. The heat treatment installation of claim 18, wherein said first and second sub-chambers are separated from each other by upper and lower partition walls extending in said transport direction, between which a gap remains for passing semi-finished products therethrough, wherein at least one of said at least one upper and lower partition walls is adjustable in height.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Further features and advantages of the invention will be apparent from the following description of an embodiment with reference to the drawings. In the drawings show:

[0051] FIG. 1 an overall view of a heat treatment system according to the invention;:

[0052] FIG. 2 a section through the continuous furnace according to FIG. 1 along line II-II;

[0053] FIG. 3 a section through the continuous furnace according to FIG. 1 along the line III-Ill; and

[0054] FIG. 4 a detailed view of FIG. 3, from which the height-adjustable accommodation of the upper partition wall in the ceiling of the furnace can be seen.

EMBODIMENTS

[0055] A heat treatment installation according to the invention is shown in FIG. 1 and designated overall by the numeral 10. The heat treatment installation 10 comprises a continuous furnace 12, as well as an associated hardening station 18, which is designed as a press hardening station.

[0056] The continuous furnace 12 has a continuous lift-step chain conveyor, the structure of which is explained in more detail below with reference to FIG. 3.

[0057] The continuous furnace 12 further has a first zone 14, which is provided for austenitization and which is followed by a second zone 16, in which two different regions or sub-chambers are created by thermally insulating partition walls running in the transport direction, so that different temperatures can be set in these sub-chambers.

[0058] FIG. 2 shows a section through the continuous furnace 12 in the region of the first zone 14 along line II-II. In this region, the continuous furnace is not divided by thermally insulating partition walls in the transport direction or longitudinal direction. Thus, the furnace interior in this region can be heated continuously by means of suitable heating devices 26, for example gas or oil burners, to as uniform a temperature as possible, which is used for austenitizing. In FIG. 2, tubular heating elements 26 are indicated by dashed lines. The temperature in question for austenitizing depends, of course, on the material used in each case, on the throughput time, and also on the desired microstructure.

[0059] Generally, a range between 900° C. and 930° C. is preferred.

[0060] The furnace chamber 13 is bounded at the lower end by a furnace floor 36, at the upper end by a furnace roof 34, and at the sides by corresponding side walls 35 and 37. The conveyor 20 is designed as a lifting step chain conveyor of a basically known design, similar to that known, for example, from WO 2018/019920 A1.

[0061] The lifting-step chain conveyor 20 has transport chains 56 which are displaceably mounted on associated slide rails 54, wherein punches 58 which are displaceable in the vertical direction are provided for holding the semi-finished products during a return movement of the transport chains 56. The semi-finished products are moved by linear displacement over a step length in each case in the transport direction by means of the transport chains 58. Thereafter, the semi-finished products are lifted by means of the punches 58 movable in the vertical direction and the transport chains 58 are retracted to their initial position. Then the semi-finished products are lowered onto the transport chains 56 and transported further in a further transport step.

[0062] FIG. 3 shows a cross-section through the continuous furnace 12 in zone III-III according to FIG. 1. This is the second zone 16 of the continuous furnace, in which a separation in the transport direction is provided by thermally insulating partition walls for division into two different zones.

[0063] In FIG. 3, upper partition walls 30 and lower partition walls 32 can be seen. Exemplarily, a semi-finished product 28 in the form of a steel plate is shown resting on the lifting step chain conveyor 20 and extending through a gap formed between the upper partition walls 30 and the lower partition walls 32 into the two regions 48 on one side 48 and 50 on the other side.

[0064] In this regard, the lower partition wall 32 preferably extends to the level of the transport chains 58 so that the thermal separation between the two regions 48 and 50 extends from below directly to an overlying semi-finished product 28. The upper partition walls 30 are accommodated within the furnace roof 34 in a height-adjustable manner, as will be explained in more detail below with reference to FIG. 4.

[0065] Jacketed radiant tubes 38, 40, which project into sub-chamber 50 from one side, and 42, 44, which project into sub-chamber 48 from the other side, are used for heating.

[0066] These jacketed jet tubes 38, 40 and 42, 44, respectively, can be used for both heating and cooling. For cooling, a suitable cooling medium, e.g. cooling air, is passed therethrough.

[0067] By means of a combined heating or cooling option, a particularly precise temperature control can be ensured by means of the jacketed jet tubes 38, 40, 42, 44.

[0068] Preferably, one of the two regions, such as sub-chamber 48, continues to be maintained at austenitizing temperature, which can be approximately in the range of 870° C. to 950° C. The other sub-chamber 50 is used to cool the semi-finished products 28 to a temperature for bainite formation. The preferred temperature here is between 200° C. and 600° C., preferably in the range 450° C. to 600° C. The tubular elements 38, 40 in question are thus used in cooling mode in this range 50.

[0069] The upper partition walls 30 are accommodated within the furnace ceiling 34 so as to be adjustable in the vertical direction, as will be briefly explained in more detail with reference to FIG. 4. Since the furnace ceiling 34 has a thickness of the order of about 40 cm due to the thermal insulation, the upper end of the upper partition walls 30 can be suitably guided here, for example between a roller guide 60. In this way, an adjustability of the upper partition walls 30 of about just under 30 cm is made possible. Furthermore, suitable fixing means are provided to fix the upper partition walls 30 at a desired height (not shown).

[0070] In FIG. 4, the upper partition 30 is shown in its upper end position. From here, a downward displacement of the upper partition 30 in the direction of the arrow 62 is enabled.