Stone D.H.,Engineering Systems Inc. |
Iwand H.C.,Engineering Systems Inc. |
Kristan J.,EVRAZ North America |
Lehnhoff G.R.,EVRAZ North America
Journal of Failure Analysis and Prevention | Year: 2015
A number of electric flash butt rail welds fractured vertically through the cross section of the rail. The fractures initiated in the web near the bending neutral plane in a region where high-carbon-content liquid was identified to have been produced during the welding process, resulting in a brittle cementite (ledeburite) network structure that reduced the load carrying capacity of the weld. Fracture initiation near the neutral plane was encouraged due to longitudinal stresses in the continuously welded rail from thermal contraction at colder temperatures. Additionally, residual stresses induced by flash butt welding could have contributed to fracture initiation. © 2015, ASM International.
Collins L.E.,EVRAZ North America |
Rashid M.,EVRAZ North America
Proceedings of the Biennial International Pipeline Conference, IPC | Year: 2014
The tensile properties of line pipe are usually determined using a flattened strap tensile sample which is obtained by cutting a long transverse sample from the pipe and then flattening it prior to machining the final tensile coupon. Although, several documents have been published to standardize this test, variability in the reported yield stress for the same material tested by different labs continues to be an issue particularly in high strength line pipe (X70 and X80). Pipe properties are influenced by the pipe forming operations which introduce plastic strain into the steel. As well, the flattening of the tensile blank reverses the deformation and leads to Bauchinger effects which further alter the tensile properties of the material. There is no standard available for the flattening process and pipe manufacturers and operators continue to seek a best practice for the process. In addition, other factors such as placement of extensometer on a flattenend tensile specimen during the tensile testing have been considered a source of variation in the results. Several projects were conducted to identify the source of variability and to standardize the flattening and testing process among the Evraz QA Labs. These initiatives included: a round robin tensile testing program in which tensile tests were performed on flat plates and subsequently on flattened strap specimens produced from a sister plate; examination of a 2-step flattening procedure against a 1-step method, and investigation of the extensometer placement (ID, OD or side mounted ) on the recorded stress-strain behaviour. The flattening process was found to be the main source of variability of yield stress. No real trend was observed resulting from extensometer position. Other testing practices such as specimen gripping, zeroing the load and positioning at the start of the test, and the dimensional variability within the reduced section of a specimen were also found to contribute to yield stress variability. Best practices for determination of yield stress using flattened strap tensile samples are discussed. Copyright © 2014 by ASME.
Chen S.,EVRAZ North America |
D'Souza C.,EVRAZ North America |
Evans D.,EVRAZ North America |
Dunnett K.,EVRAZ North America |
And 3 more authors.
Iron and Steel Technology | Year: 2013
To control tundish superheat in a desired range, an in-house, on-line superheat model was developed and implemented at EVRAZ Regina Steel. Over the past year, a series of analyses and modifications were made to the model and practices, such as: •Additions of dynamic cascade effect, dynamic hang time effect and flying tundish effect. •Upgrades of the slab holding program and user interfaces. •Optimization of the aim superheat control ranges by considering susceptibilities of various product grades to slab defects. These enhancements have improved the model accuracy and superheat control performance by more than 40%. The slab hold ratio due to low/high superheat has been significantly reduced from above 12% to around 7%, leading to substantial slab quality and operational benefits. It is believed that further improvements can be achieved by more closely following the model recommendations, better controlling and maintaining stable and proper tundish levels, ensuring accurate temperature measurements, and continuing to optimize the aim superheat ranges.