450 MPa级海底管线钢HIC试验裂纹分析研究

Analysis and research on cracks of 450 MPa subsea pipeline steel in HIC test

H_(2)S腐蚀问题在油气输送过程中十分重要,其破坏性和危害性极大,严重影响了油气输送管道的寿命,制约了油气输送管道材料的发展,因此抗H_(2)S腐蚀管道用钢成为其中一种发展趋势。本文采用经济型成分设计,开发出450 MPa级耐酸性海底管线钢,但HIC试验出现轻微的氢致裂纹。通过金相显微镜、扫描电镜、EDS等手段,分别对试验钢在HIC试验中产生裂纹的原因,从组织、杂物、元素偏析、硬度等方面进行分析研究,找出HIC试验出现裂纹的原因,来提高450 MPa级海底管线钢的耐HIC性能。研究结果表明:HIC试验中出现的裂纹不是由钢中异常夹杂物造成的,而是由于钢中的Mn偏析产生了硬相的微观组织引起的。

The problem of H_(2)S corrosion is very important in the process of oil and gas transportation,with great de-structive and harmful effects.It seriously affects the lifespan of oil and gas transportation pipelines and restricts the development of materials for oil and gas transportation pipelines.Therefore,steel for anti H_(2)S corrosion pipelines has become one of the development trends.This article adopts an economical composition design to develop 45o MPa grade acid resistant submarine pipeline steel,but slight hydrogen induced cracking occurred during HIC testing.By using metallographic microscopy,scanning electron microscopy,EDS and other methods,the causes of cracks in the test steel during HIC testing were analyzed and studied from the aspects of microstructure,impurities,element segregation,hardness,etc.,in order to identify the causes of cracks in HIC testing and improve the HIC resistance of 450 MPa grade submarine pipeline steel.The research results indicate that the cracks appearing in the HIC test are not caused by abnormal inclusions in the steel,but by the microstructure of the hard phase generated by Mn seg-regation in the steel.