The formation of internal cracks in as-cast billet is mainly attributed to the stress and strain states near the solidifying front. This study investigates the effect of chamfer configuration of as-cast billet on the maximal principal stress and the tensile stress during soft reduction process. The LIT and ZDT of GCr15 bearing steel are calculated by the solidification phase transformation model. What’s more, the 3D finite element models is established to investigate stress and strain states in the brittle temperature range. The relationships between chamfer angle and maximal principal stress, internal crack, as well as equivalent plastic strain are analyzed. Numerical results reveal that a chamfer configuration of as-cast billet is much more effective than a rectangular one on decreasing the risk of internal cracks.

The optimization method using the ON/OFF sensitivity analysis has an advantage hat an epoch-making construction of magnetic circuit may be obtained. Therefore, it is attractive for designers of magnetic devices. We have already developed the ON/OFF method for the optimization of a static magnetic field problem, and the effectiveness is verified by applying it to the optimization of magnetic recording heads. In this paper, the ON/OFF sensitivity method is extended to the optimization of the eddy current problem using the adjoint variable. The newly developed ON/OFF method is applied to the determination of the optimal topology of the yoke of the billet heater for rolling wire rod. As a result, the optimal shape of yoke, which we could not imagine beforehand can be obtained. It is shown that the local heating of the yoke was reduced without decreasing the heating efficiency.

The article presents the results of investigations performed on segregation of elements in the billets. The research were performed under standard industrial conditions, during high carbon steel production cycle. Probes (templates with the thickness of 20 mm) were taken from billets with square cross-section of 160 mm. Segregation of elements was determined based on the quantitative analysis of results performed by using spark spectrometry pursuant to PN-H-04045. Changes in concentrations of elements were analysed along two cross-sections. Element contents were performed at points distanced from each other by approx. 10 mm. The segregation of carbon, sulphur and phosphorus was determined for different billets.