Transformation of cross cracks of continuously casted billet in rolled product

Increased requirements to the surface quality of hot-rolled products used in automobiles manufacturing and endeavor to decrease t rejections of the metal with surface defects, stipulate the necessity to increase the quality of the initial continuously casted billet (CCB). Cracks, formed in the process of crystallization, which are transformed into surface defects of rolled products during hot deformation are attributed to the surface defects of CCB. Classification of defects presented, reasons of cross cracks on CCB and their locations considered. In the course of the experiment the samples, cut from two CCBs in the place, where cross cracks were visually revealed after shot blasting and hot etching in the 50% solution of chloric acid. The cross cracks on the surface of a sample were revealed in the zone of the big side, and the other – on a rib. The longitudinal polished sections were cut from the place of cross cracks location. At the study of the polished sections multiple cracks were discovered. The width of cracks opening was different – from 0.01 up to 0.3 mm, depth in the section of the study – up to 10 mm. The locations of the cross cracks on the billets were marked by notches from two sides (method of “marked” defects). After that the billets were rolled at a one-stand reversible mill 850 for the diameter of 100 mm. At the visual inspection of the rolled product surface, obtained from the defect CCB, surface defects in the form of discontinuity flaws were discovered. The discontinuity flaws looked as metal ruptures of longitudinal and cross orientation and sometimes having a form of tongue. The degree of defects development depends on the depth and the crack location on the initial CCB. The defects which location corresponds to the CCB side have less opening, and defects which location corresponds to the initial billet rib looked as a rough fissure. Cross samples were cut in the places of defects locations on the surface of rolled product for metal science study. At the cross polished sections the defect cavity have several branches, the cavity walls are twisting, around the cavity branches and next to them, aggregation of small globular oxides and massive decarburization were observed. The defects of rolled products surface were classified as rolled-out cracks (cross orientation). The cracks depth in the section under study was 0.6–3.5 mm. Based on the results of the study the surface defects of rolled products were properly classified and reasons of their arising revealed, that will allow avoiding their formation in the future. Based on the proper classification and avoiding of the surface defects reasons, the rolled products rejects by surface defects will be considerably decreased.

Bayesian MRF Modeling and Graph Cuts for Phase Unwrapping with Discontinuity Phase Flaws：A Comparative Study

Phase unwrapping (PU) is a difficult task commonly found in applications involving interferometric synthetic aperture radar (InSAR), magnetic resonance imaging (MRI) and optical surface profile measurements; all of which involve mathematically ill-posed problems. Conventional algorithms exhibit strong shortcomings in PU when phase discontinuity flaws exist. To simulate these situations, we are custom-designed test data with a phase discontinuity flaw. This simulated data is a 3D Gaussian distribution with an arc-shaped notch as a phase flaw. PU is carried out by Bayesian inference and MRF (Markov Random Field) modeling. A graph cut algorithm is employed for optimization with respect to energy minimization. Three other conventional algorithms are also employed and their PU performance is compared. The results show the good performance and effectiveness of the Bayesian MRF modeling method. These experimental results are important references for phase unwrapping problems when phase discontinuities exist.

Measures of Ductility for UFG Materials Obtained by SPD

It is shown that for ultrafine grained materials obtained with severe plastic deformation methods, the value of elongation up to fracture does not determine ductility, while the reduction of area up to fracture does determine it. The latter characteristic gives information about how an alloy structure resists the formation of discontinuity flaws under deformation in a hard stress state. We show that for a commercial grade titanium that underwent Twist Extrusion (TE), the value of , and thus ductility, is higher in the UFG state than in the coarse-grained state.