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The fastening bolts of high speed railway brake discs are required to display tempering stability to resist soften lower than demand tensile strength £¨that is tempering resistance£©once the temperature reaches up to 400 degree celsius. Meanwhile, the brake disc fastening bolts must display qualified comprehensive mechanical property at a low temperature of -40 degree celsius to resisit severe environments such as shock and vibration of brittle fracture, damp, acid corrosion, sand, etc.
In domestic usage, current brake disc fastening bolts of high speed trains are imported non-standard bolts. This type of bolts is not only expensive with long delivery cycle, but also the tensile strength is not adequate to meet the requirement of class 10.9 standard specified in ISO898-1: 2009, according to the third-party test result of China National Product Quality Supervision and Inspection Center for Iron and Steel Material. At the same time, some imported bolts of brake disc were found with fractures when unloaded after having served a distance of 300,000 km. Due to the above reasons, we are are currently working on the research, development, innovation, and production of new brake disc fastening bolts with a reasonable cost, safety and a high quality.
We began to research, design, and develop the high-speed rail wheel brake bolts in 2012. December of the same year, we produced hundreds of samples of class 10.9 bolts. The T1 samples were sent for mechanical performance test to China National Product Quality Supervision and Inspection Center for Iron and Steel Material by our customer at the same time. The tensile strength reached and exceeded 860 MPA under a high temperature of 400 degree celsius. At -40 degree celsius, the result of Akv2 exceeded 80J. The above samples were installed for test running by the terminal customer and were unloaded for examination every 100,000 km untll reached 600,000 km. None of the sample displayed fracture. Later, we produced four small batches of the bolts in September and November 2013, as well as in February and March 2014. The terminal customer varified that 100% of our products are with stable and reliable quality.
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