Novel cast steel brake disc and heat treatment process

Abstract

The invention relates to a novel cast steel brake disc and a heat treatment process, the brake disc is formed by integrally casting a steel material with a plurality of alloy elements, and the brake disc comprises a connecting area and a brake area; the braking area is provided with two groups of braking surfaces, and the distance between the two groups of braking surfaces is 40-50mm; the brake surface is a semimetal brake surface or a powder metallurgy brake surface; after the cast steel brake disc is integrally cast and formed, heat treatment is carried out, specifically, firstly, the cast steel brake disc formed through casting is heated to 900-920 DEG C for oil quenching treatment, and after the cast steel brake disc is cooled to the room temperature, the cast steel brake disc is heated to 500-600 DEG C for tempering treatment; compared with a conventional gray iron brake disc, the cast steel brake disc has the advantages that the creep resistance, the tensile strength and the thermal fatigue strength of the cast steel brake disc are remarkably improved by analyzing the types and the components of various alloy elements through a proper ratio and optimal heat treatment process parameters, the strength decline is less under a high-temperature condition, the reliability is high, the abrasion loss is reduced, and the brake noise is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of automobile parts, and in particular to a novel cast steel brake disc and a heat treatment process. Background Art

[0002] The brake disc is the main component of the disc brake. It and the brake lining serve as a pair of friction pairs. The friction lining clamps and rubs the brake disc to slow down or stop the vehicle. The brake disc must withstand the axial clamping force of the friction lining and the friction between the two. The greater the vehicle's weight and load, and the faster the speed, the greater the force on the brake disc during deceleration and braking. Every time the vehicle brakes during driving, the driving kinetic energy is converted into heat energy, of which 90% of the heat is absorbed by the brake disc body. Tests have verified that the high temperature of a single brake is as high as 500°C. In the condition of continuous descent of a long slope, frequent braking is required, and the temperature of the friction surface of the brake disc that rubs against the brake lining will continue to rise.

[0003] Whether it is a light vehicle or a heavy vehicle, the brake disc breaks and fails due to thermal fatigue of the material. Especially for heavy trucks, which have long continuous driving distances, heavy loads, complex road conditions, and long continuous working hours of the brake disc, the brake disc of the disc brake is more prone to cracking and failure. Not only is the service life of the brake disc short, but the after-sales replacement of the brake disc maintenance process is complicated and difficult, the maintenance cost is high, and most importantly, it will affect the driving safety of the entire vehicle.

[0004] Due to the good thermal conductivity of graphite contained in the brake disc matrix, the most commonly used materials for brake discs are gray cast iron and ductile iron. Gray cast iron is a brittle material, and the graphite in it is in the form of flakes, which has a splitting effect on the matrix, so its tensile strength is low. The tip or edge of the flake graphite is prone to stress concentration, causing brittle cleavage or interface fracture, which becomes the root of the crack. This physical property of gray cast iron determines that it is difficult to meet the high reliability requirements of brake discs and has a low service life. Ductile iron graphite is spherical, which reduces the splitting effect of graphite balls on the matrix, and the utilization rate of the matrix strength can reach 70% to 90%, so its mechanical properties at room temperature and high temperature are significantly better than those of gray cast iron, and its fatigue strength is also much better than that of gray cast iron. However, since the thermal conductivity of ductile iron is worse than that of gray cast iron, and its linear expansion coefficient and elastic modulus are higher than those of gray cast iron, it has poor creep resistance at high temperatures and a strong tendency to deform. Under the condition of restraint, it will lead to greater internal stress, which will promote the generation and expansion of cracks. Therefore, the service life of high-speed and high-load vehicle brake discs made of ductile iron is not significantly better than that of gray cast iron under the conditions of hot and cold cycles, especially under rapid cooling and heating.

[0005] Therefore, in order to improve the reliability of brake discs, extend the life of brake discs, and reduce after-sales maintenance costs, it is necessary to develop a brake disc with superior performance to cope with high-speed and heavy-load driving conditions and enhance product competitiveness. Summary of the invention

[0006] The purpose of the present invention is to provide a new type of cast steel brake disc and heat treatment process to address the deficiencies of the prior art. Through appropriate proportions of various alloy elements and heat treatment processes, its creep resistance, tensile strength and thermal fatigue strength are significantly improved, the strength decay under high temperature conditions is less, the reliability is high, the wear is reduced, and the brake noise is reduced.

[0007] The present invention is achieved by adopting the following technical solutions:

[0008] A new type of cast steel brake disc, which is integrally cast by a steel material of several alloy elements, including a connection area and a brake area;

[0009] The components of the alloy elements and the contents of each component are: carbon 0.15-0.25%; silicon 0.2-0.5%; manganese 0.7-1.1%; chromium 0.7-1.2%; molybdenum 0.5-0.7%; nickel 0.7-1.2%; the balance is iron.

[0010] Furthermore, the braking area is provided with two sets of braking surfaces, and the distance between the two sets of braking surfaces is 40-50 mm.

[0011] Furthermore, the braking surface is a semi-metallic braking surface or a powder metallurgy braking surface.

[0012] Furthermore, the end surface of the connection area is provided with bolt holes, and the number of the bolt holes is 8-12.

[0013] A novel heat treatment process for cast steel brake discs is applied to the novel cast steel brake discs as described above. After the cast steel brake discs are integrally cast and formed, heat treatment is performed:

[0014] First, the cast steel brake disc is heated to 900-920°C for oil quenching, and then heated to 500-600°C for tempering after cooling to room temperature.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects:

[0016] 1. By analyzing the types and components of various alloy elements, and through appropriate proportions and optimal heat treatment process parameters, the cast steel brake disc of the present invention has significantly improved creep resistance, tensile strength and thermal fatigue strength compared with conventional gray iron brake discs, less strength decay under high temperature conditions, high reliability, reduced wear and reduced braking noise;

[0017] 2. By optimizing the brake disc material and adjusting the distance between the two braking surfaces to 40-50mm, and using semi-metallic friction pads or powder metallurgy friction pads for braking, the temperature resistance is improved and the heat crack resistance life of the brake disc is increased by more than 3 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the present invention;

[0019] Figure 2 It is a cross-sectional view of the present invention.

[0020] Reference numerals

[0021] 1. Brake; 2. Connection area; 3. Braking surface. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0023] A new type of cast steel brake disc, the brake disc is integrally cast by a steel material of several alloy elements, including a connection area 2 and a brake area 1;

[0024] The components of the alloy elements and the contents of each component are: carbon 0.15-0.25%; silicon 0.2-0.5%; manganese 0.7-1.1%; chromium 0.7-1.2%; molybdenum 0.5-0.7%; nickel 0.7-1.2%; the balance is iron.

[0025] The braking area 1 is provided with two sets of braking surfaces 3, and the distance between the two sets of braking surfaces 3 is 40-50 mm.

[0026] The braking area 1 can be equipped with a semi-metallic braking surface or a powder metallurgy braking surface for braking, and the braking surface 3 with a spacing of 40-50mm can effectively improve the braking stability of the brake disc under high temperature conditions. At 500°C, the friction coefficient can still be stabilized at around 0.35, and the friction performance is stable and reliable.

[0027] The braking surface 3 is a semi-metallic braking surface or a powder metallurgy braking surface.

[0028] The end surface of the connection area 2 is provided with bolt holes, and the number of the bolt holes is 8-12.

[0029] The connection area 2 is provided with bolt holes for connecting and fixing the cast steel brake disc.

[0030] A new heat treatment process for cast steel brake discs is applied to the new cast steel brake discs as described above. After the cast steel brake discs are integrally cast and formed, heat treatment is performed:

[0031] First, the cast steel brake disc is heated to 900-920°C for oil quenching, and then heated to 500-600°C for tempering after cooling to room temperature.

Claims

1. A new type of cast steel brake disc, characterized in that: The brake disc is integrally cast by a steel material of several alloy elements, and comprises a connection area (2) and a brake area (1); The components of the alloy elements and the contents of each component are: carbon 0.15-0.25%; silicon 0.2-0.5%; manganese 0.7-1.1%; chromium 0.7-1.2%; molybdenum 0.5-0.7%; nickel 0.7-1.2%; the balance is iron.

2. The novel cast steel brake disc according to claim 1 is characterized in that: The braking area (1) is provided with two groups of braking surfaces (3), and the distance between the two groups of braking surfaces (3) is 40-50 mm.

3. The novel cast steel brake disc according to claim 1 is characterized in that: The braking surface (3) is a semi-metallic braking surface or a powder metallurgy braking surface.

4. The novel cast steel brake disc according to claim 1 is characterized in that: The end surface of the connection area (2) is provided with bolt holes, and the number of the bolt holes is 8-12.

5. A novel heat treatment process for cast steel brake disc, applied to the novel cast steel brake disc according to claim 1, characterized in that: After the cast steel brake disc is integrally cast, it is heat treated: First, the cast steel brake disc is heated to 900-920°C for oil quenching, and then heated to 500-600°C for tempering after cooling to room temperature.

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