Environmentally Assisted Cracking: Theory and Practice: Poster Session
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Bai Cui, University of Nebraska Lincoln; Raul Rebak, GE Global Research; Srujan Rokkam, Advanced Cooling Technologies, Inc.; Jenifer Locke, Ohio State University
Monday 5:30 PM
February 24, 2020
Room: Sails Pavilion
Location: San Diego Convention Ctr
Session Chair: Bai Cui, University of Nebraska-Lincoln
C-11 (Invited): Corrosion is Metallurgy’s Waterloo: Raul Rebak1; 1GE Research
Corrosion is an often ignored process in spite it costs about 4% of nations’ gross national product. Corrosion is a natural process by which materials (e.g. alloys) go back to their original state as minerals. Metallurgy is the engineering practice by which minerals are processed to become metals and alloys. There are engineering ways by which this ultimately unavoidable corrosion progression can be delayed, minimized, managed, or controlled. Since industrial engineers generally perceive corrosion as a nuisance, corrosion is frequently ignored when they are designing their beautiful shiny creations. The wisdom and advice of corrosion experts is often overlooked because no one wants to associate rot and decay with new designs. Therefore, corrosion related failures (many of them catastrophic) still occur all over the world. Eventually corrosion will destroy all metallurgical creations, a final and decisive defeat like the one in Waterloo. Corrosion deserves respect.
Cancelled
C-12: Fracture Failure Analysis on 20MnTiB Steel High-strength Bolt Used in Bridge: Lan Liu1; Juan Wen2; QingCai Liu1; Lin Chen1; 1Chongqing University; 2Chongqing Cheng Tou Road and Bridge Administration Co.Ltd
The fracture failure of 20MnTiB steel high-strength bolts in some bridges occurred. To reveal the reason for the fracture failure of the high-strength bolts, macroscopic analysis, chemical analysis, phase analysis, microscopic analysis and metallographic analysis were carried out on one of the failed high-strength bolts. The results show that the corrosion products on the fracture surface of the failed high-strength bolt are mainly composed of SiO2, Fe2O3 and Al2O3, and contain the elements S and Cl by energy spectrum analysis. The fracture analysis of the failed high-strength bolt show that it had two crack sources, one was outward expansion caused by the notch, and the final fracture turned out tongue pattern, while the other was outward expansion in the form of branches, and the final fracture turned out intergranular fracture morphology. It can be deduced that the main cause of the high-strength bolt fracture is machining defects and stress corrosion.
Cancelled
C-13: Fracture Failure Analysis on 35VB Steel High-strength Bolt Used in Bridge: Lin Chen1; Juan Wen2; Qingcai Liu1; Lan Liu1; 1Chongqing University; 2Chongqing Cheng Tou Road and Bridge Administration Co.Ltd
The failure of 35VB steel high-strength bolts used in some bridge occurred. EDS,SEM, XRD and optical microscope were used on one of the failed bolts to investigate the reasons for its failure. The results showed that the main corrosion product on the fracture surface was Fe3O4, and contained the elements S and Cl. The fracture analysis showed that the crack extended outward from the crack source in a dendritic form, and the final fracture occurred at the tear zone accompanied by the shear lip. The micromorphology of the failed bolt was mainly dimple, while grain boundary cracks appeared in the expansion zone. The metallographic structure of the failed bolt was mainly composed of tempered sorbite with martensitic orientation plus a part of ferrite. It can be deduced that the main causes of 35VB steel high-strength bolt failure are heat treatment process defect and stress corrosion.