Journal of Liaoning Petrochemical University

Journal of Liaoning Petrochemical University ›› 2005, Vol. 25 ›› Issue (1): 64-66.

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Analysis of Mesh Dehiscence of 904L Used in MEK Uni t

  

  1. No .2 Plant of Fushun Petrochemical Company , Fushun Liaoning 113004 , P .R .China
  • Received:2004-06-17 Published:2005-03-20 Online:2017-04-14

904L 在甲乙酮生产装置中开裂原因分析

张玉光   

  1. 抚顺石油化工公司石化二厂, 辽宁抚顺113004
  • 作者简介:张玉光(1957 -), 男, 辽宁抚顺市, 高级工程师, 在读工程硕士

Abstract:

        The on -the -spot research and observation of corrosive shape w ere made for mesh dehiscence of water hat screen cloth in 904L under the working conditions of 6 MPa , 155 ℃, pH 37 using H type resin catalyst for producing me thyl-ethyl-ketone .The mesh crack w as found to be belonged to stress corrosion cracking through analyzing and observing alloy agent mass fraction, corrosive media test, inner material impurity , mesh residual stress resource , and crack shape of 904L.And also the expatiating was made for the main reason causing SCC ;lack of Ni, Mo and Cu content in the materials, excess of C and inner material impurities, much residual stress, and the damage to the inactivited surface during transportantion and installation.The process of SCC is that catalyst and mesh surface form the gap , and it is quickly acidificated.When pH falls to activating value of 904L , passivating film is destroyed in the gap because of reducing reaction .The macro corrosive battery is formed among metal inter surface , electrolyte solution and outer surface.When the corrosive depth develops to a certain value , it causes stress concentration resulting in cracking .The crack is vertical to the mesh circle and develops along with the mesh radius.When it reaches to the neutral surface of the mesh, the cracking disappears.There is no crack in the internal pressure area of neutral surface .Therefore , the crack can' t be found in the deeper corrosive pit of mesh surface .

Key words: Stainless steel, Cataly st , Anode , Stress cor rosion cracking

摘要:         在6 MPa 、155 ℃, pH 值为3~ 7 , 使用氢型树脂催化剂生产甲乙酮的环境中, 对904L 制水帽筛网网丝开裂失效进行了现场调研和腐蚀形态观测。通过904L 合金元素质量分数、腐蚀介质的测定和材料内部夹杂物、网丝残余应力来源、裂纹形态等分析与观察认为网丝开裂属于应力腐蚀开裂。阐述了材料内Ni 、Mo 、Cu 合金元素用量不足、C 含量超标、内部夹杂物多和残余应力高, 以及安装、运输过程中损伤钝化表面是应力腐蚀开裂失效的主要原因。说明了发生应力腐蚀开裂的过程是:催化剂与网丝表面形成缝隙, 缝隙内急速酸化, 当pH值降到904L 去钝化要求的值时, 缝隙内发生钝化膜全面的还原性破坏。构成了由缝隙内金属表面(活性区)-电解质溶液-缝隙外金属表面(钝化区)组成的宏观腐蚀电池。当缝隙内达到一定腐蚀深度时产生应力集中引发裂纹, 发生应力腐蚀开裂。裂纹垂直于网丝圆周方向并沿网丝径向发展, 达到网丝中性面时裂纹消失, 中性面内压应力区没有裂纹。因此, 网丝外表面深度较大的腐蚀坑内看不到裂纹。

关键词: 不锈钢,  催化剂,  阳极,  应力腐蚀开裂

Cite this article

ZHANG Yu -guang. Analysis of Mesh Dehiscence of 904L Used in MEK Uni t[J]. Journal of Liaoning Petrochemical University, 2005, 25(1): 64-66.

张玉光. 904L 在甲乙酮生产装置中开裂原因分析[J]. 辽宁石油化工大学学报, 2005, 25(1): 64-66.

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