Method for Producing a Brake Element, Brake Element

Abstract

A method is disclosed for producing a brake element, in particular a brake disk or brake drum, which has a friction portion and a fastening portion, wherein a blank for at least the friction portion is produced by a casting method from gray cast iron with lamellar graphite, wherein the blank is subjected to austenitizing at a predefined austenitizing temperature, and wherein the austenitized blank is subjected to austempering at a predefined austempering temperature. The friction portion and the fastening portion is produced in one piece, and that the fastening portion is produced with a wall thickness of at least 1.5 and at most 4.5 mm.

Claims

1. A method for producing a brake element which has a friction portion and a fastening portion, comprising: (a) producing a blank for at least the friction portion by a casting method from gray cast iron with lamellar graphite; (b) subjecting the blank to a first austenitizing process at a first predefined austenitizing temperature so as to produce an intermediate austenitized blank; and (c) subjecting the intermediate austenitized blank to a second austenitizing process at a second predefined austenitizing temperature so as to produce the brake element, wherein step (a) includes (i) producing the friction portion and the fastening portion to be configured as one piece, and (ii) producing the fastening portion with a wall thickness of at least 1.5 and at most 4.5 mm.

2. The method according to claim 1, wherein step (a) further includes producing the fastening portion with a wall thickness of at least 2 mm and at most 4 mm.

3. The method according to claim 1, wherein the first austenitizing process has a duration of between 30 minutes to 120 minutes.

4. The method according to claim 1, wherein the first predefined austenitizing temperature is between 790° C. and 915° C.

5. The method according to claim 1, wherein the second austenitizing process has a duration of 2 hours to 5 hours.

6. The method according to claim 1, wherein the second predefined austenitizing temperature is between 260° C. and 350° C.

7. The method according to claim 1, wherein between step (a) and step (b) the following step is performed: quenching the austenitized blank.

8. The method according to claim 7, wherein the quenching step includes the step of quenching the austenitized blank at a cooling rate of between 30° C. per minute and 50° C. per minute.

9. The method according to claim 1, wherein after step (c) the following step is performed: applying a wear-protection layer to at least a friction face of the friction portion.

10. The method according to claim 1, wherein after step (c) the following step is performed: abstaining from applying a wear-protection layer to at least a friction face of the friction portion so that the brake element is free of a wear-protection layer.

11. A brake element which is produced by the method set forth in claim 1, wherein the brake element is at least substantially free of perlite after step (c).

12. The method according to claim 1, wherein the brake element is a brake disk or brake drum.

13. The method according to claim 2, wherein step (a) further includes producing the fastening portion with a wall thickness of at least 2.5 mm.

14. The method according to claim 5, wherein the second austenitizing process has a duration of between 3 to 4 hours.

15. A method for producing a brake element which has a friction portion and a fastening portion, comprising: (a) producing a blank for at least the friction portion by a casting method from gray cast iron with lamellar graphite; (b) subjecting the blank to a first austenitizing process at a first predefined austenitizing temperature so as to produce an intermediate austenitized blank; (c) quenching the austenitized blank after step (b) and before step (d) so that formation of perlite is essentially avoided between step (b) and step (d); and (d) subjecting the intermediate austenitized blank to a second austenitizing process at a second predefined austenitizing temperature after step (c) so as to produce the brake element, wherein step (a) includes (i) producing the friction portion and the fastening portion to be configured as one piece, and (ii) producing the fastening portion with a wall thickness of at least 1.5 and at most 4.5 mm.

16. The method according to claim 15, wherein: the first austenitizing process has a duration of between 30 minutes to 120 minutes, and the second austenitizing process has a duration of 2 hours to 5 hours.

17. The method according to claim 16, wherein: the first predefined austenitizing temperature is between 790° C. and 915° C., and the second predefined austenitizing temperature is between 260° C. and 350° C.

18. The method according to claim 15, wherein the quenching step includes the step of quenching the austenitized blank at a cooling rate of between 30° C. per minute and 50° C. per minute.

19. The method according to claim 15, wherein after step (d) the following step is performed: applying a wear-protection layer to at least a friction face of the friction portion.

20. The method according to claim 15, wherein after step (d) the following step is performed: abstaining from applying a wear-protection layer to at least a friction face of the friction portion so that the brake element is free of a wear-protection layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The disclosure will be explained in more detail hereunder by way of the drawings in which:

[0019] FIG. 1 shows a brake element in a perspective illustration; and

[0020] FIG. 2 shows a method for producing the brake element.

DETAILED DESCRIPTION

[0021] FIG. 1 in a perspective illustration shows a brake element 1 which is configured as a brake disk 1. The brake element 1 has a friction portion 2 which is configured so as to be annular such that the friction portion 2 is a friction ring 2. The friction ring 2 has a friction face 3 and a further friction face which is opposite the friction face 3 so that the further friction face cannot be seen in FIG. 1. When the brake disk 1 is used according to the intended use in a brake system, brake members of the brake system are pressed against the friction faces of the brake disk 1 in order to generate a frictional brake torque.

[0022] The brake disk 1 moreover has a fastening portion 4. The fastening portion 4 is that part of the brake disk 1 by way of which the brake disk 1 can be fastened to a wheel hub of a vehicle. The fastening portion 4 here is configured as a brake cover 4. The brake cover 4 has a plurality of axial holes 5 for fastening means to pass through in order for the brake disk 1 to be fastened to the wheel hub by means of the brake cover 4.

[0023] The friction portion 2 and the fastening portion 4 are configured so as to be formed in one piece. The friction portion 2 as well as the fastening portion 4 are produced from bainite. By virtue of being produced from bainite, the brake disk 1 has a high tensile strength as well as a high degree of inherent damping. By virtue of the high tensile strength, the brake disk 1 can be produced with a minor wall thickness. The friction portion 2 as well as the fastening portion 4 here have a wall thickness of presently 2 to 4 mm.

[0024] A method for producing the brake disk 1 will be explained in more detail hereunder with reference to FIG. 2. To this end, FIG. 2 shows a diagram wherein the time t is illustrated on an abscissa of the diagram, and the temperature T is illustrated on an ordinate of the diagram.

[0025] A blank for the brake disk 1 is produced prior to a first temporal point t1. A one-piece blank is thus produced for the friction portion 2 and the fastening portion 4. The blank herein is produced or cast, respectively, by a casting method from gray cast iron with lamellar graphite.

[0026] Between the first temporal point t1 and a second temporal point t2, the blank is heated from room temperature to an austenitizing temperature of 850° C. A furnace or an inductive heating installation is used for heating the blank, for example.

[0027] Austenitizing of the blank commences as the austenitizing temperature is reached, thus at the second temporal point t2. The material of the blank is thus converted to austenite. During the austenitizing, the temperature of the blank is constantly maintained at the austenitizing temperature. The blank presently is austenitized for a duration of 60 minutes. Particularly advantageous austenitizing of the blank is achieved when the duration is between 30 minutes and 120 minutes.

[0028] The duration for the austenitizing ends at a third temporal point t3. The blank which now is austenitized is quenched following the third temporal point t3. To this end, the austenitized blank is cooled at a cooling rate of approximately 40° C. per minute. Liquid salt, water or oil is used as a coolant herein, for example. It is avoided that perlite is formed on account of the austenitized blank being quenched.

[0029] At a fourth temporal point t4, the austenitized blank has a temperature of 260° C. This temperature hereunder is referred to as the austempering temperature. The austenitized blank is in particular quenched in a salt bath and subsequently impinged with the austempering temperature for a duration of approximately 4 hours. The austenitized blank is austempered on account of being stored at the austempering temperature. The austenite of the austenitized blank is thus converted to bainite such that the blank subsequent to being stored at the austempering temperature for the duration of approximately 4 hours is at least substantially composed of bainite.

[0030] The duration of 4 hours ends at a fifth temporal point t5. The blank which now is austempered is cooled to room temperature following the fifth temporal point t5.

[0031] In order for the brake disk 1 illustrated in FIG. 1 to be produced, the austempered blank is ground and balanced. Subsequently to being ground and balanced, the brake disk 1 is optionally provided with a wear-protection layer. The wear-protection layer is preferably applied at least to the friction faces. According to a further exemplary embodiment, the wear-protection layer is alternatively dispensed with such that the brake disk, in particular the friction faces of the brake disk, is/are configured so as to be free of a wear-protection layer. The advantageous production of the brake disk described above already guarantees sufficient protection against wear for most applications.