30MnSi管桩钢筋延迟脆断原因分析

Reason Analysis on Delay Brittle Fracture of 30MnSi Steel Bars for Pipe Piles

针对30MnSi管桩钢筋(PC钢棒)延迟脆断的现象,从力学性能、化学成分、显微组织、表面质量、断口形貌以及后续热处理工艺等方面对延迟脆断的原因进行了分析。结果表明:该管桩钢筋发生延迟脆断主要是由于其热处理过程中回火温度不稳定,使钢筋表面局部形成异常马氏体组织,这种组织形式自身存在着组织应力,而内氢的存在增加了管桩钢筋的内应力;当受外力作用时,外力和管桩钢筋自身的内应力经过一段时间逐渐集中于表面马氏体区,形成断裂源,从而导致管桩钢筋静置数日后突然脆断。

To solve the delay brittle fracture problem of 30MnSi steel bars for pipe piles （PC steel bars）, the fracture reasons were analyzed from mechanical properties, chemical compositions, microstructure, surface quality, fracture morphology and follow-up heat treatment processing technology and other aspects. The results show that the delay brittle fracture of the PC steel bars was mainly due to the unstable tempering temperature during the final heat treatment process which results in the formation of local abnormal martensite structure. Because of the existence of internal stress from the martensite structure and inside hydrogen, when receiving external force, fracture source would gradually form at the abnormal martensite zone over a period of time, and resulted in the sudden brittle fracture of the PC steel bars after being placed for a few days.