A two-phase columnar solidification model is used to study the principle of mechanical soft reduction (MSR) for the reduction of centerline segregation in slab casting. The two phases treated in the model are the bulk/interdendritic melt and the columnar dendrite trunk. The morphology of the columnar dendrite trunk is simplified as stepwise growing cylinders, with growth kinetics governed by the solute diffusion in the interdendritic melt around the growing cylindrical columnar trunk. The solidifying strand shell moves with a predefined velocity and the shell deforms as a result of bulging and MSR. The motion and deformation of the columnar trunks in response to bulging and MSR is modeled following the work of Miyazawa and Schwerdtfeger from the 1980s. Melt flow, driven by feeding of solidification shrinkage and by deformation of the strand shell and columnar trunks, as well as the induced macrosegregation are solved in the Eulerian frame of reference. A benchmark slab casting (9-m long, 0.215-m thick) of plain carbon steel is simulated. The MSR parameters influencing the centerline segregation are studied to gain a better understanding of the MSR process. Two mechanisms in MSR modify the centerline segregation in a slab casting: one establishes a favorable interdendritic flow field, whereas the other creates a non-divergence-free deformation of the solid dendritic skeleton in the mushy region. The MSR efficiency depends not only on the reduction amount in the slab thickness direction but also strongly on the deformation behavior in the longitudinal (casting) direction. With enhanced computation power the current model can be applied for a parameter study on the MSR efficiency of realistic continuous casting processes.

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Laser metal deposition (LMD) is utilized to clad the surface of a miniaturized test roll (Ø 40 mm) of tool steel. The cladding consists of two layers: a nickel alloy as intermediate layer deposited onto the surface of the steel substrate, and a metal matrix composite (MMC) as top layer consisting of spherical tungsten carbide particles embedded into the nickel alloy matrix. The thermomechanical wear behavior of the cladding is investigated on a test rig, where the test roll is pressed against an inductively heated load roll. Multiple test runs up to several hours simulating industrial loading conditions are performed. The presented testing procedure enables predicting the time-dependent abrasive wear behavior of the cladding, in particular for hot rolling mill applications. After testing for 8 h at temperature of 650 C and at contact pressure of approximately 1 GPa, the maximum depth of the wear mark is about 0.12 mm. Partial cracking, debonding and dissolution of the tungsten carbide particles, as well as formation of iron and chromium oxides at the surface of the wear marks occur. However, as low abrasive wear is observed, the investigated MMC may potentially be applicable for cladding rolls in steel hot rolling mills.