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柴油机气阀扇形掉块断裂是指:在气阀面上开始形成径向裂纹,作弦向发展,最后导致阀盘边缘成块脱落的一种断裂形式。其裂纹的发展情况如图1所示。扇形掉块断裂在进气阀和排气阀上均有发生,而以排气阀上为多。扇形掉块断裂会引起严重的机破事故,影响行车安全。我们对一批破损的12V175型柴油机气阀进行了检验、分析,提出了防止断裂的措施。一、实验方法共搜集了28个有扇形掉块和有裂纹而未脱落的破损气阀。这些阀体所用的材料为4Crl4Ni14W2Mo耐热钢,阀面均堆焊硬质合金,其成份为钴—铬—钨和铁—镍—硼—硅,后者为修复阀面时所用的成份。从破损气阀中取得24个断口,对阀面状态和断面进行了宏观低倍检查,并用透射电
Diesel valve fan-shaped block rupture refers to the beginning: the formation of radial cracks in the valve surface, as the chord to development, and finally led to the valve plate into a block off the form of a fracture. The development of the crack shown in Figure 1. Fan-shaped block fracture in the intake valve and exhaust valve have occurred, while the exhaust valve is more. Fan-shaped broken block will cause serious machine broken accident, affecting traffic safety. We tested a group of damaged 12V175 diesel valve, analysis, put forward measures to prevent fracture. First, the experimental methods were collected a total of 28 fan-shaped block and cracked and not broken off the valve. The materials used for these bodies are 4Crl4Ni14W2Mo heat-resistant steels, which are hard alloyed on the valve surface and are made of cobalt-chromium-tungsten and iron-nickel-boron-silicon, the latter used to repair valve surfaces. Twenty-four fractures were taken from the damaged gas valve and the macroscopic low magnification inspection of the valve surface state and the section was carried out.