EH690超高强海洋装备用钢盐雾腐蚀前后疲劳性能研究

Study on Fatigue Properties of EH690 Ultra-high Strength Steel for Marine Equipment before and after Salt Spray Corrosion Testing

为了研究EH690超高强海洋装备用钢腐蚀前后疲劳性能的变化,采用淬火+回火工艺制备了50 mm厚EH690试验钢,观察了试验钢的金相显微组织和腐蚀前后表面形态,对比了盐雾腐蚀前后的疲劳性能,分析了腐蚀后疲劳试样典型断口形貌。结果表明,EH690试验钢组织为回火马氏体,晶粒度等级约为7.5级,盐雾腐蚀后的腐蚀产物主要是α-FeOOH、γ-FeOOH以及Fe_(3)O_(4)等。腐蚀后,材料的平均疲劳寿命大幅下降。断口分析显示,腐蚀导致的表面缺陷是材料疲劳性能下降的主要原因之一,腐蚀造成的表面点蚀坑会导致严重的应力集中,从而提升材料表面裂纹萌生的几率,降低海工钢的疲劳寿命。

In order to study the changes of fatigue properties of the EH690 ultra-high strength steel for marine equipment before and after corrosion testing,the 50 mm thick EH690 testing steel was prepared by quenched and tempered(Q&T)process.After that,the metallographic micro-structures and surface morphology of the tested steel before and after corrosion testing were observed,and the fatigue properties before and after salt spray corrosion testing were compared,and at last the typical fracture morphology of the corroded fatigue samples was analyzed.The tested results showed that the microstructures in the EH690 tested steel was composed of tempered martensite,and the grain size grade was about 7.5.While the corrosion products after salt spray corrosion testing were mainlyα-FeOOH,γ-FeOOH and Fe_(3)O_(4) and so on.After corrosion,the average fatigue life of the mentioned steel material was greatly reduced.So according to the analysis of fractures,the surface defect caused by corrosion was one of the main causes leading to the declining of fatigue performance of the steel material,meanwhile the surface corrosive pitting pits caused by corrosion would lead to serious stress concentration,thus resulting in increasing probability of surface crack initiation,which would reduce the fatigue life of the steel for ocean engineering.