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CN-121976015-A - Method for treating brake disc by enhanced ferrite nitrocarburizing and oxidizing towards European seven emission standard

CN121976015ACN 121976015 ACN121976015 ACN 121976015ACN-121976015-A

Abstract

The invention provides a method for treating a brake disc by enhanced ferrite nitrocarburizing and oxidizing and a brake disc manufactured by the method, the key parameters such as process temperature, atmosphere concentration and treatment duration of each stage are regulated and controlled by carrying out stress relief annealing, multi-stage pre-oxidation treatment, multi-stage nitriding treatment, multi-stage post-oxidation treatment and cooling treatment on the brake disc. The brake disc manufactured by the treatment has obviously improved wear resistance, enhanced rust resistance and corrosion resistance, and uniform and consistent white brightness layer thickness. The brake disc treated by the method successfully passes through the European seven standard brake particulate matter emission test, and the dual advantages of the brake disc in the aspects of environmental protection performance and braking performance are proved.

Inventors

  • LIN XINHONG
  • ZHAO YONG
  • ZHANG YUANLI

Assignees

  • 重庆三友未来汽车技术服务有限公司

Dates

Publication Date
20260505
Application Date
20260203

Claims (10)

  1. 1. A method for treating a brake disc by enhanced ferrite nitrocarburizing and oxidizing is characterized by comprising the following steps: annealing the brake disc casting blank; carrying out multi-stage pre-oxidation treatment on the annealed brake disc, wherein the multi-stage pre-oxidation treatment comprises at least two stages of pre-oxidation; Nitriding, namely nitriding the brake disc subjected to multi-stage pre-oxidation treatment, and nitrocarburizing to generate a white bright layer; post-oxidation treatment, namely oxidizing the brake disc subjected to nitriding treatment to generate an oxide layer; And cooling, namely cooling the oxidized brake disc.
  2. 2. The method for treating a brake disc by enhanced ferritic nitrocarburizing and oxidizing according to claim 1, wherein the at least two-stage pre-oxidizing comprises a first-stage pre-oxidizing temperature of 450 ℃ to 540 ℃ and a treatment time of 0.5 to 2 hours, and a second-stage pre-oxidizing temperature of 550 ℃ to 650 ℃ and a treatment time of 0.5 to 3 hours.
  3. 3. The method for reinforcing a ferritic nitrocarburizing oxidation process for brake disks according to any one of claims 1-2, wherein the nitriding treatment is a multi-stage nitriding treatment comprising subjecting the brake disk subjected to the multi-stage pre-oxidation treatment to at least two-stage nitriding treatments.
  4. 4. The method for treating the brake disc by enhanced ferritic nitrocarburizing and oxidizing process according to claim 3, wherein the nitriding treatment in at least two stages comprises the steps of nitriding treatment in the first stage at 600 ℃ to 650 ℃ for 7 to 9 hours, ammonia gas and nitrogen gas in a concentration ratio of 4:1 to 5:1 and nitrogen gas and carbon dioxide in a concentration ratio of 3:1 to 2:1, nitriding treatment in the second stage at 600 ℃ to 650 ℃ for 3 to 5 hours, ammonia gas and nitrogen gas in a concentration ratio of 4:1 to 3:1 and nitrogen gas and carbon dioxide in a concentration ratio of 2.5:1 to 1.5:1.
  5. 5. The method for reinforcing a ferritic nitrocarburizing oxidation process for brake disks according to any one of claims 1 to 2, wherein the post-oxidation treatment comprises a multi-stage oxidation treatment, and the brake disk after the multi-stage nitriding treatment is subjected to at least two stage oxidation treatments.
  6. 6. The method for treating a brake disc by enhanced ferritic nitrocarburizing and oxidizing according to claim 5, wherein the at least two-stage oxidizing treatment comprises a first-stage oxidizing temperature of 450 ℃ to 550 ℃ for 0.2 to 1 hour, and a second-stage oxidizing temperature of 400 ℃ to 600 ℃ for 0.2 to 1 hour.
  7. 7. The method for treating the brake disc by enhanced ferritic nitrocarburizing and oxidizing is characterized by comprising the steps of carrying out non-oxidation stress relief annealing treatment on a brake disc casting blank, wherein the annealing temperature is 530-570 ℃, the treatment time is not less than 4.5 hours, cooling comprises a slow cooling zone and a water cooling zone, nitrogen is adopted as a protective atmosphere, the temperature of the slow cooling zone is 400-420 ℃, the treatment time is 0.2-0.4 hours, the temperature of the water cooling zone is 180-210 ℃, and the treatment time is 0.3-0.5 hours.
  8. 8. A brake disc obtainable by treatment according to the method of any one of claims 1 to 7.
  9. 9. A brake disc according to claim 8, wherein the brake disc is formed in a multi-layer structure comprising, in order from the outside to the inside, an oxide layer, a white bright layer, and a base gray cast iron layer, the white bright layer having a hardness of greater than 800HV.
  10. 10. The brake disc of any of claims 8-9, wherein the brake disc passes the European seven standard brake particulate emissions test.

Description

Method for treating brake disc by enhanced ferrite nitrocarburizing and oxidizing towards European seven emission standard Technical Field The invention relates to the technical field of manufacturing of automobile brake discs, in particular to a method for treating a brake disc by enhanced ferrite nitrocarburizing and oxidizing and a brake disc manufactured by the method. Background At present, the traditional brake disc manufactured by adopting the ferrite nitrocarburizing FNC (Ferritic Nitrocarburizing) technology can cause the disc surface to rust after being used for a period of time, thereby causing the problems of increased thickness Variation difference DTV (DISC THICKNESS Variation), brake shake, noise generation and the like of the brake disc. In severe cases, even if the brake disc breaks due to the above problems, the brake disc breaks in emergency braking situations can seriously endanger the life safety of passengers. Although the traditional FNC process has certain rust resistance and wear resistance, researches and experiments show that the brake disc manufactured by the traditional FNC process has the rust resistance for 24 hours, and obvious defects and defects in the aspects of rust resistance and wear resistance exist in the FNC process. CN 106011736A patent discloses a surface improvement method of an automobile brake disc, which comprises the steps of stress relief annealing, repeated vacuumizing, pre-oxidation, soft nitriding, post-oxidation, cooling and the like, specifically, the pre-oxidation treatment is carried out on the brake disc for 45-55 minutes at the temperature of 380-420 ℃, and the soft nitriding treatment is carried out at the temperature of 540-590 ℃ and under the furnace pressure of 15-20 kPa. Although the hardness, the wear resistance and the corrosion resistance of the brake disc can be improved to a certain extent by the manufacturing process, the pre-oxidation treatment at a certain fixed temperature is difficult to control gradually according to the oxidation degree of the brake disc, and the nitriding treatment at the same temperature and the same atmosphere concentration has certain limitation on the characteristics of the white and bright layer generated by the nitriding effect. In general, brake discs manufactured according to the method in CN 106011736A still have a lack of performance in terms of wear resistance, corrosion resistance, hardness, etc. European countries are concerned with environmental ecology, promulgated European regulations relating to European standard brake particulate emissions tests, limiting automobile exhaust emissions, and prescribing PM10 brake emission particulate weights as shown in Table 1. Currently, european countries tend to use a laser cladding (LASER CLADDING) process in the field of automotive brake discs to enhance the wear and corrosion resistance of the brake discs by spraying alloy materials on the brake disc surfaces. However, the technology has the following problems that firstly, the cost of metal powder used by laser cladding is extremely high, the high manufacturing cost limits mass production on a large scale, and secondly, the mode of laser cladding (LASER CLADDING) has certain defects, such as that the coating of an alloy material is rusted, the rust prevention treatment is needed to be further sprayed with paint, the production cost is increased due to the improper use of laser cladding, the cracking risk is generated due to the fact that the alloy material is not sprayed in a cooling rib of a brake disc, the thickness of the laser cladding coating is uneven, dynamic balance measurement is needed after grinding, the beat time is long, and if the dynamic balance does not meet the requirement, the balance milling is needed to be further carried out. The brake disc manufactured by the traditional FNC technology including the brake disc improvement method disclosed in the CN 106011736A patent has defects in rust resistance and wear resistance, and the brake disc manufactured by the FNC technology is matched with a friction plate to perform a European seven test, and the test results fail, so that the traditional FNC technology cannot meet the European seven emission requirement. Table 1 ohseven brake emission standard The European seven brake emission standard specification number EU 2024/1257, set forth in Table 1, was tested in compliance with the requirements of the national Global System for technology (UN GTR) No. 24. The categories that are internationally classified according to automotive use and load carrying capacity are included in table 1, wherein class M vehicles are primarily concerned with passenger transportation, while class N is focused on cargo transportation. Specifically, M1 refers to a small-sized passenger car with a seat number of not more than 9 and including a driver seat, and a total design mass of not more than 5000kg, and N1 corresponds to a cargo vehicle with a maximum design total ma