排气歧管是发动机排气系统中的重要零件之一,是多管口的薄壁异形管件。蠕墨铸铁的排气歧管在进行开裂试验时,运行250个循环后,出现微裂纹。通过工艺验证,铸造中局部冷却速度过快,形成较多条块状碳化物从而降低蠕化率,是导致出现微裂纹的根本原因。 Exhaust manifold exhaust system is one of the important parts of the engine, is a multi-nozzle thin-walled shaped tube. Compacted graphite cast iron exhaust manifold cracking test carried out after 250 cycles of operation, the emergence of micro-cracks. Through the process verification, the local cooling rate in casting is too fast, more massive carbides are formed to reduce the creep rate, which is the root cause of microcracks.