Research And Development Of Automobile Brake Drum With Inproved Properties

According to the practice situation of the automobile brake drum life and safety sharply decreasing, which caused by automobile burden, speed, load imbalance and frequent brake, combining with the means of modern analysis and test to find out the defects reasons of the brake drum castings under the new service conditions, through optimizing the design and selecting the material composition, organizational performance, smelting and casting process to improve the integrated performance and service life of the development brake drum significantly. Conclusions are as follows:(1) For the composition, we selected the high-carbon alloy firstly to breakthrough the designed restricted area of the previous drum brake materials. High-carbon selection is based on the following considerations: the thermal fatigue resistance is most related to the number of graphite, which is largely depends on the carbon content. Therefore, the choice of high-carbon (C > 3.4%) as the composition of brake drum materials should be first determined. Concerning the strength of cast iron decrease with the increase of carbon content, we can add alloy element to improve the strength and hardness of the casting without damaging the thermal fatigue. The details are: 3.4～3.6C%, 1.7～1.9Si%, 0.7～0.9Mn%, 0.2～0.4Cr%, 0.2～0.4Cu% and 0.1～0.2Mo%.(2) According to the typical failure and use condition of the drum brake, we adopted a pearlite matrix, A-type graphite organizations. Thereinto, the pearlite content is large than 95%, the graphite is A-type with lengths of 4 to 6. This design is based on the following considerations: first of all, the pearlite can obtain moderate hardness and strength, the material of the brake drum is too soft(Ferrite), easily wearing and too hard(Bainite or Martensite) will cause brake abnormal sound and poor processing. Secondly, A -type graphite organizations will improve the alloy thermal fatigue resistance.(3) The technics design adopted advanced smelting and casting equipment as well as the appropriate process to achieve organizational and component design.(4) The mechanical properties of high-performance automobile brake drum castings are: strength of 240-280MPa, Brinell hardness 190-210HB.The System test results show that the new brake drum design alloy materials achieved the expected goals with a good performance. The new material brake drum loading by the use of a few years indicates that the service life up to 60000 km. which has obvious economic and social benefits.