METHOD FOR HEATING A BLANK AND HEATING SYSTEM

Abstract

A method for manufacturing a steel component from a blank is provided. Firstly, a blank is placed in a conveyor system. Then, at least a preselected zone of the blank is preheated while the blank is retained at a predetermined preheating location. Finally, the blank is conveyed through a furnace. A preheating system for heating blanks in a production line is also provided.

Claims

1. A method for manufacturing a steel component from a blank, the method comprising: placing a blank in a conveyor system; preheating at least a preselected zone of the blank; and conveying the blank through a furnace, and wherein the preheating comprises retaining the blank at a predetermined preheating location.

2. The method according to claim 1, wherein the blank is retained at the predetermined preheating location by stopping elements.

3. The method according to claim 2, wherein the stopping elements are retractable pins configured to be displaceable in an up-and-down motion for retaining the blank in the preheating location.

4. The method according to claim 2, wherein the stopping elements are elevating bars configured to lift the blank perpendicularly to a conveying direction.

5. The method according to claim 1, wherein the blank is retained at the predetermined preheating location by stopping the conveyor system for a predetermined period of time.

6. The method according to claim 1, wherein the preheating step comprises preheating at least a thickest zone of the blank.

7. The method according to claim 1, wherein the preheating step comprises preheating the whole blank.

8. The method according to claim 7, wherein the preheating step comprising comprises: preheating the whole blank to a first temperature; and preheating at least a thickest zone of the blank to a second temperature, wherein the second temperature is higher than the first temperature.

9. The method according to claim 1, wherein the preheating step comprises heating at least the preselected zone of the blank below an Ac3 temperature.

10. The method according to claim 1, wherein the preheating is done in 25 seconds or less.

11. The method according to claim 1, further comprising: transferring the heated blank to a press tool; hot deforming the blank; and quenching the blank.

12. A heating system for heating blanks in a production line, the heating system comprising: a furnace; a conveyor system for conveying the blanks through the furnace; and a preheating system for preheating at least a preselected zone of a blank, wherein the conveyor system is configured to temporarily retain the blank in a predetermined preheating location upstream from the furnace.

13. The heating system according to claim 12, wherein the heating system comprises stopping elements to retain the blank at the predetermined location.

14. The heating system according to claim 12, wherein the preheating system comprises: a base; at least one heating element; and a support structure.

15. The heating system according to claim 14, wherein the at least one heating element comprises an infrared, an induction, a flame, a fluid or an electric heater.

16. The method according to claim 9, wherein the temperature is between 300-820 C.

17. The method according to claim 9, wherein the temperature is between 500-700 C.

18. The method according to claim 10, wherein the preheating is done in 10 seconds or less.

19. The heating system according to claim 13, wherein the stopping elements are retractable pins configured to be displaceable in an up-and-down motion for retaining the blank at the predetermined location.

20. The heating system according to claim 13, wherein the stopping elements are elevating bars configured to lift the blank perpendicularly to a conveying direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which:

[0041] FIG. 1 schematically illustrates a side view of a production line according to an example;

[0042] FIGS. 2a-2d schematically illustrate different examples for retaining a blank in a predetermined preheating location;

[0043] FIGS. 3a-3c schematically illustrate various blanks heated according to different examples;

[0044] FIGS. 4a and 4b schematically illustrate examples of a preheating system; and

[0045] FIG. 5 schematically illustrates an example of a method for manufacturing a blank.

DETAILED DESCRIPTION

[0046] FIG. 1 shows a blank 1 in a production line 100. The production line 100 may be e.g. a hot deformation or hot stamping production line which may comprise a conveyor system 120 to transport the blank 1 though the production line 100.

[0047] The conveyor system 120 may comprise e.g. a plurality of conveyor rollers, parallel conveyor belts or walking beams. The conveyor system 120 in such a case may be driven using e.g. motors. In this case, the speed of the conveyor system 120 may be controlled by controlling the speed of the motors.

[0048] According to an example, the conveyor system 120 may comprise a feeding system and a furnace conveyor system to transport the bank through the furnace.

[0049] The blank 1 may be placed in the conveyor system 120 by e.g. an industrial transfer robot (not shown) e.g. after being cut from a steel coil, and may be conveyed to a preheating system 110.

[0050] The preheating system 110 may comprise a plurality of heating elements 111 arranged in a base 112 to preheat the blank 1 before entering the furnace. The base 112 of the preheating system 110 may be of any suitable size and shape, which may be determined e.g. by the dimensions of the blank. Accordingly, the number, size and shape of heating elements 111 may vary depending on e.g. the blank size or the desired blank configuration. A further support structure 113 may be used to fix the base 112 of the preheating system 110 to the floor. In other examples the support structure may be e.g. be coupled to the conveyor system, suspended from the ceiling or anchored to a wall.

[0051] The blank 1 may then be conveyed into the furnace 130 where it may be heated to a predetermined temperature, e.g. above an austenization temperature, so as to prepare the blank 1 for subsequent processes. In particular, the blank may be heated to Ac3 or above.

[0052] Depending on the blank material and the coating, the furnace temperature and the time that the blank remains in the furnace can vary. When the blank has been subjected to a preheating process as described before, the time in the furnace may be reduced compared to the time in the furnace of those blanks without a preheating process.

[0053] The heated blank 1 may exit the furnace 130 through a door (not shown) configured to open when the blank 1 arrives, and to close again when the blank 1 has left the furnace 130. The blank 1 may be transported by a conveyor system 120, e.g. a conveyor belt or a roller conveyor, to a centering system 140, e.g. a centering table, to be correctly positioned for subsequent processing.

[0054] A centering table 140 may comprise a plurality of centering pins 141 which can be passive or can be actively moved to correctly position and center the blank 1.

[0055] After being centered and correctly positioned, the blank 1 may be transferred to a press tool 150 for deforming and quenching. The blank 1 may be transferred to the press tool 150 by a transferring system (not shown), e.g. an industrial transfer robot, which may pick up the blank 1 from the conveyor system 120 and may place it on the pressing tool 150. The transfer robot may comprise a plurality of gripping units to grab and pick up the blank 1 from the conveyor means 120.

[0056] The pressing tool 150 may be provided with cooling means (not shown) e.g. water supplies or any other suitable means, to quench the blank 1 simultaneously to the hot deforming process. The cooling or quenching may be done homogeneously for the whole blank 1. Typically, channels may be provided in the dies of the press tool through which cold water or other liquid may be conducted. This cools the contact surfaces of the press tool so that the blank is quenched.

[0057] FIGS. 2a-2d show the blank 1 in a predetermined preheating location, e.g. under the preheating system, in which the blank 1 may be subjected to a preheating process. The blank 1 may be retained in the predetermined preheating location e.g. where the preheating system overlaps substantially the whole blank or at least the preselected zone to be preheated, during the entire preheating process. The blank 1 may be preheated about 15 seconds or less at a temperature between 600-700 C. During the preheating process the blank 1 may still in the predetermined preheating location.

[0058] In the example shown in FIG. 2a, the blank 1 is retained in a predetermined preheating location by stopping the conveyor system 120 e.g. a conveyor belt. According to this example, the blank 1 would firstly be conveyed to the predetermined preheating location. Secondly, the blank would be retained in that position, i.e. predetermined preheating location, by stopping the conveyor system e.g. stopping the motion of the conveyor belt(s). The blank would then be preheated, and finally, once the preheating process has finished, the blank would be conveyed to the furnace.

[0059] A conveyor system comprising conveyor rollers o walking beams may alternatively be used. In these examples, the conveyor system is stopped by avoiding the upward and forward movement of the walking beams or the rotation of the conveyor rollers.

[0060] The conveyor system 120 may be programmed to stop its movement when the blank is detected in the appropriate position e.g. by using sensors. In other examples the conveyor system may be programmed to stop periodically e.g. every 15-30 seconds.

[0061] FIGS. 2b and 2c show a lateral view and a top view respectively of a conveyor system 120, e.g. conveyor rollers or walking beams, which may comprise at least a stopping element configured to retain the blank in the predetermined preheating location. Such stopping elements may be retractable pins 122.

[0062] The retractable pins 122 may be configured to be up-and-down displaceable for retaining the blank 1 in a predetermined preheating location i.e. avoiding its forward movement in the conveying direction (indicated by the x axis). A difference between this example and the example of FIG. 2a is that the conveyor system 120 of FIGS. 2b and 2c may be operating at a substantially constant speed. As only the blank that is preheated is stopped, there is no need to interrupt the operation of the other blanks.

[0063] The retractable pins 122 may be retracted e.g. under the conveyor system 120, until the blank 1 is detected e.g. by sensors. The retractable pins 122 may be configured to move up to retain the blank 1 when the blank 1 is detected in an adequate location, i.e. a predetermined preheating location. The retractable pins 122 may be in the up position, i.e. totally protruding, before and during the preheating process. In the same way, the retractable pins 122 may be configured to retract after the preheating process has finished, and so, the blank 1 may be conveyed to the furnace.

[0064] FIG. 2d shows another example to retain the blank 1 in a predetermined preheating location. In the example of FIG. 2d, the stopping elements or stops may be elevating bars 123 configured to displace the blank 1 perpendicularly to a conveying direction x. The elevating bars 123 may be located interleaved with the conveyor system 120 e.g. a plurality of conveyor belts or conveyor rollers, so as to avoid blocking the movement of the conveyor system 120.

[0065] The elevating bars 123 may be configured to be perpendicularly displaceable (indicated by the y axis) to the conveying direction when the bank 1 is detected, e.g. by sensors, in a predetermined preheating location. According to this example, the elevating bars 123 may be hidden, i.e. retracted, until the blank 1 is in a predetermined preheating location. At that time, the elevating bars 123 would project outwardly and the blank 1 would therefore be perpendicularly displaced from the conveyor system 120 i.e. it would be elevated above the conveyor system (while the conveyor continues operating). The blank 1 may then be subjected to a preheating process. After the preheating process, the elevating bars 123 may be retracted and thus, the blank 1 may be placed onto the conveyor system 120 to be conveyed to the furnace.

[0066] FIG. 3a depicts a rectangular blank 300 which has been preheated at T.sub.1 temperature, e.g. 630 C. When heating a blank (with or without zones of different thickness), it may be desirable to increase the efficiency of the heating process e.g. reducing the heating time. By preheating the blanks (or at least certain zones of the blank) the heating process may be optimized as the blanks may stay less time in the furnace. Moreover, as the time in the furnace may be reduced, the furnace length may be decreased which, at least, reduces the energy consumption and the space taken up by the furnace.

[0067] FIG. 3b shows a rectangular blank, the central zone 310 of which has been preheated to T.sub.1 temperature. The preheated zone 310 may correspond to e.g. the thickest zone of the blank. By preheating the thick zone of a blank, a homogeneous heating e.g. above Ac3, of the whole blank may be assured in a subsequent heating process.

[0068] Additionally, in a blank with zones of different thickness and/or different materials, e.g. a TWB, each zone may be preheated at a different temperature. FIG. 3c illustrates a rectangular blank with three zones of different thicknesses, and wherein the temperature at which each zone has been preheated is different. A first zone 320 may be preheated at T.sub.1, a second zone 330 which may correspond to the thickest zone of the blank, may be heated at T.sub.2 e.g. between 600-700 C. and finally, a third zone 340, which may correspond to the thinner zone of the blank, may not be heated. Temperature T.sub.2 corresponding to the second zone, i.e. the thickest zone of the blank is therefore higher than the T.sub.1 corresponding to the first zone.

[0069] In other examples, the whole blank may be preheated at T.sub.1 while a predetermined zone, e.g. the thickest zone of the blank, may be preheated at T.sub.2, wherein T.sub.2 is higher than T.sub.1.

[0070] In some examples, the blank may be made of different materials (e.g. different types of steels) which may e.g. have different thermal conductivities. Each material may therefore need to be heated for a specific heating time to reach a predetermined temperature. In such cases the different material areas may be heated at different temperatures.

[0071] FIGS. 4a depicts a preheating system 110 comprising a rectangular base 112 and heating elements 111a arranged on it. In the depicted example, all the heating elements 111a are switched on, and therefore the whole blank would be preheated (see FIG. 3a).

[0072] In other examples, the blank may be selectively preheated. FIG. 4b shows an example of a preheating system 110 wherein the heating elements 111a, 111b may be configured to selectively turn on and off for locally preheating only preselected zones of the blank, and thereby a heating pattern is created. In the example of FIG. 4b only a central zone of the blank would be preheated (see FIG. 3b).

[0073] The pattern may be formed by arranging the heating elements 111a, 111b in a predetermined manner (not shown) or it may be created by selectively switching off certain heating elements 111b while leaving other heating elements 111a switched on as shown in FIG. 4b. The switched on heating elements 111a preheat preselected zones of the blank at a desired temperature, for example at a temperature between 600-700 C.

[0074] In further examples, the amount of heat delivered by the heating elements 111a that are switched on may be regulated, e.g. controlling the power of the heating elements, so that different temperatures may be achieved.

[0075] By switching the heating elements on or off and/or by controlling the output power of the heating elements a tailored heating pattern taking into account e.g. the dimensions of the blank and/or the position of the preselected zone of the blank to be preheated, can be provided.

[0076] In some examples, the heating elements 111a, 111b may be infrared heaters, particularly infrared heating lamps. In other examples, induction heaters, flame or hot air directed to the blank may be used. In other examples, the blank may be heated by contacting a heating plate which is heated by electric heaters embedded in the heating plate or by a hot fluid, e.g. water, oil, etc., flowing through channels.

[0077] FIG. 5 shows a method to manufacture a steel component from a blank with zones of different thickness according to an example. Firstly, a blank may be placed 510 in a conveyor system e.g. by an industrial transfer robot. Optionally, if the blank has not been positioned in a predetermined preheating location the blank may be then conveyed 520 to a suitable preheating location, i.e. in a proper position with respect to a preheating system. Once in the predetermined preheating location, the blank may be retained 530 in such position e.g. by stopping the conveyor system or by stops or stopping elements as described before. The blank, or at least a preselected zone of the blank and in particular a zone of the blank that has increased thickness, may then be preheated 540 e.g. at a temperature of about 600-700 C. during less than 15 seconds.

[0078] When the preheating process is ended, the blank may be conveyed through the furnace 550 to be heated e.g. at a temperature above Ac3. The blank may be in the furnace for about 3 minutes. After the heating process, the heated blank may exit the furnace and may be centered and correctly positioned in a centering system e.g. centering table, arranged downstream. The blank may then be transferred to a press tool e.g. by an industrial transfer robot, where it may be hot deformed to obtain (almost) the final shape. The blank may also be entirely or partially quenched in the press tool e.g. by supplying cold water. Optionally the blank may further be subjected to post processing steps such as e.g. cutting, trimming, and/or joining to further components using e.g. welding.

[0079] Although only a number of examples have been disclosed herein, other alternatives, modifications, uses and/or equivalents thereof are possible. Furthermore, all possible combinations of the described examples are also covered. Thus, the scope of the present disclosure should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow.