X56管线钢的腐蚀疲劳寿命试验研究

STUDY ON CORROSION FATIGUE LIFE IN X56 STEEL

采用不同应力比在不同环境下对Ｘ５６管线钢进行疲劳试验。结果表明，对称循环时腐蚀环境下的Ｓ－Ｎ曲线的斜率要比空气中的大，低应力下腐蚀疲劳寿命比在空气中低得多，应力越低降低幅度越大。在空气中有疲劳极限存在，而在腐蚀环境中不存在疲劳极限。在高应力区两曲线有相交点，腐蚀疲劳寿命甚至比空气中时还要长。当应力比为０．２时，两曲线的斜率几乎相同。所不同的仅是有无疲劳极限之分。即在较高频率下腐蚀损伤只在低应力区有效，在高应力区作用并不明显。文中借助于应变电极的实验结果，对腐蚀疲劳破坏形式与机理进行了讨论和解释。

The corrosion fatigue tests of X56 pipeline steel in 3.5%NaCl solution were carried out at differ-ent stress ratios。The results showed that the corrosion fatigue life was lower than that in air at small stress duringfully reversed cycling,the smaller the stress was,the more the fatigue life decreased.And the slopes of S-Ncurve in the solution was bigger than that in air,There existed fatigue limit in air,but there was no fatigue limitin corrosion environment. At higher frequency,corrosion damage affected more in low stress field,less in highstress field.