Influence of copper on quality of hot strips by EAF-CSP process

Electron microscopy and X-ray Energy Dispersive Spectroscopy (XEDS) study on influence of Cu on low carbon hot strips produced by CSP (Compact Strip Production) process has been carried out. The results indicated that copper segregation and enrichment at interfacial layer between oxidized surface and steel matrix is the key factor, which results in microcracks and edge flaws on the strips. The primary considerations to prevent detrimental effects from Cu include controlling copper content in proper level, higher soaking temperature and non-oxidizable atmosphere during soaking. Copper sulfide precipitates with nanometers in size were observed, they may be beneficial to the properties of CSP products, and influence of Cu on quality of CSP hot strips is discussed.

Analysis of stress and failure in rock specimens with closed and open flaws on the surface

The influence of closed and open surface flaws on the stress distribution and failure in rock specimens is investigated.Heterogeneous finite element models are developed to simulate the compression tests on flawed rock specimens.The simulated specimens include those with closed flaws and those with open flaws on the surface.Systematic analyses are conducted to investigate the influences of the flaw inclination,friction coefficient and the confining stress on failure behavior.Numerical results show significant differences in the stress,displacement,and failure behavior of the closed and open flaws when they are subjected to pure compression;however,their behaviors under shear and tensile loads are similar.According to the results,when compression is the dominant mode of stress applied to the flaw surface,an open flaw may play a destressing role in the rock and relocate the stress concentration and failure zones.The presented results in this article suggest that failure at the rock surface may be managed in a favorable manner by fabricating open flaws on the rock surface.The insights gained from this research can be helpful in managing failure at the boundaries of rock structures.

Influence of copper on quality of hot strips by EAF-CSP process

Electron microscopy and X-ray Energy Dispersive Spectroscopy (XEDS) study oninfluence of Cu on low carbon hot strips produced by CSP (Compact Strip Production) process has beencarried out. The results indicated that copper segregation and enrichment at interfacial layerbetween oxidized surface and steel matrix is the key factor, which results in microcracks and edgeflaws on the strips. The primary considerations to prevent detrimental effects from Cu includecontrolling copper content in proper level, higher soaking temperature and non-oxidizable atmosphereduring soaking. Copper sulfide precipitates with nanometers in size were observed, they may bebeneficial to the properties of CSP products, and influence of Cu on quality of CSP hot strips isdiscussed.

APPLICATION OF SINTAP TO THE SAFETY ASSESSMENT OF X65 PIPELINE STEEL

The recently developed European flaw assessment procedure, structural integrity assessment procedure（SiNTAP） is applied to assessment for welded joints of the API 5L X65 pipeline steel with an assumed embedded flaw and surface flaw at the weld toe. As one of the basic input data, fracture toughness crack tip opening displacement （CTOD） tests are conducted at 0℃ and performed according to the requirements of the standard of BS7448. For the heat affected zone （HAZ） specimens, the microstructure observation is performed to insure that the tip of the crack is located in the coarse grain zone. The result explains the dispersity of the test values. In structural integrity assessment procedure-fracture assessment diagram（SINTAP FAD） method, the failure curves of welded joints at level 1 and 3 are derived from the tensile test results. The results of the assessment show that all assessment points are located within the failure lines of analysis level 1 and 3. So the welded joint of the pipeline is safe. This study laid the foundation of application of SINTAP to pipeline structure assessment.