Materials Science Forum Vols. 704-705

Abstract: Steady increase of requirements to quality an axial zone continuously cast blooms stimulated in last time development of principles of its deformation at the end of solidifications with the purpose of suppression of axial porosity and segregation: soft reduction or mechanical soft reduction. The technology of soft reduction is one of the most effective ways of improvement quality of internal layers continuously cast blooms. In this case the central part of section of continuously cast blooms is in liquid or liquid-solid condition (mushy zone). At the same time, in practice now there are, at least, some original technical decisions for realization of this method.

Abstract: Al₂O₃-TiC particles reinforced iron matrix functionally gradient material is successfully fabricated by combining the methods of self-propagating high-temperature synthesis (SHS) with casting. The SHS products are analyzed by SEM and XRD and EDS. The results show that the grain size of the particle is round 1μm~3μm, the composition of the Al₂O₃-TiC/ Fe surface composite takes on a gradient distribution from outside to inside, and transforms gradually to the matrix metal. The hardness below 0.5mm from exterior surface of the functionally gradient materials increases dramatically and gradually changes to the hardness of the matrix. Key words: In situ generation; SHS; Casting; Surface composite material; FGM

Abstract: In this paper, a formula for the calculation of carbon content during austenitizing of cast iron was deduced, considering the effect of silicon content. According to this formula, carbon content of austenite at a certain austenization temperature for a cast iron with given composition can be easily calculated, and the austenization temperature for getting the expected carbon content in the austenite can also be determined. Besides, according to the relationship between austenization temperature T_x and the according carbon content C_ax, and considering the effect of silicon content, the carbon content of the austenite in the commonly used cast iron during heat treatment was calculated. The formula can be as a theoretical basis for determined austenization temperature and carbon content in austenite during heat treatment of cast iron, in particular, can play an important role in heat treatment of austempered ductile iron. Keywords: cast iron heat treatment; diffusion of carbon; carbon content in austenite

Abstract: The field synergy principle has been successfully used for optimization design of heat transfer exchanger. In this subject, the field synergy between the molten steel flow field and the inclusion concentration distribution is analyzed based on the mass transfer equations and removal mechanisms of inclusions. Then, inclusions removals of different particle sizes are numerically calculated for a two-strand tundish. The results show the large particle size inclusions are removed mainly by Stokes floatation and the removal efficiency has no obvious relationship on flow field. The small size inclusions removal efficiency is influenced by the synergy between the velocity vectors and the inclusion concentration gradients. So, changing the flow field mainly promotes the removal efficiency of small size inclusions. For the selected two-strand tundish, flow controls should be set for removing those inclusions which particle sizes are less than 100μm,. When the inclusion particle size is less than 10μm, the overall maximum removal efficiency is no more than 25%. So some new metallurgy techniques should be developed to improve the removal efficiency of small size inclusions. Keywords: Continuous tundish; Inclusion removal; Field synergy

Abstract: In this paper ,the WC and high-Cr Cast Iron layer were obtained on the surface of ZG30Cr steel by casting-penetrating process, the organization and wear properties of penetrating layer were studied.The results show that the layer is dense, without pores, slag and other defects, the penetrating layer and substrate are metallurgical bonding. When 30 %WC and 70 % Cr-Fe with 100～120 mesh are added to permeability agent ,the penetrating layer has the best wear resistance, is 6.8 times the matrix materials. Keywords: The layer structure; Particle size; Wear resistance

Abstract: The Shrinkage and porosity of ZL101A alloy mechanism box prepared by sand gravity casting process was investigated. The solidification process was simulation analysis by using InteCAST software and the original casting process was optimized based on the above simulated results. The results showed that the shrinkage and porosity defects’ position of ZL101A alloy mechanism box were accurately predicted by the analysis procedure which was from liquid distribution to shrinkage formation and then to Niyama shrinkage porosity. The shrinkage and porosity of the ZL101A alloy mechanism box prepared by optimized process were clearly reduced and the distribution of them was reasonable. Keywords: InteCAST software;ZL101A; Mechanism box; Shrinkage and porosity; Numerical simulation

Abstract: In the gaps between cells within continuous groups of rolling mills, as a result of local temperature and mechanical factors, longitudinal elastic stress may arise in the strip; this stress is the sum of uniform and self-balancing components. These components affect metal flow in the deformation source. According to the St Venant principle, the influence of the self-balancing component declines with increasing distance from the point of action. The longitudinal and transversal distribution of the self-balancing elastic stress in the strip was analyzed as well as the maximum distance between the deformation source and the point of elastic stress in the strip at which the self-balancing component still affects the plastic deformation of the metal, i.e., the extent of the influence zone of the self-balancing component. The results of this analysis will be useful for a design of new flatness control methods and devices.

Abstract: The numerical simulation of temperature gradient in the solidification process for large bushing castings of zinc-base alloy was made with HUAZHU CAE/Inte-CAST10.0 software in this paper. Tendency and the position of shrinkage were predicted,and the effect of cooling water rate and cooling time on temperature gradient and shrinkage during the molten metal solidification was discussed. The results show that:seting chilled iron at bottom of bearing bush and using water-cooling metal core in inner cavity of casting simultaneously, can eliminated shrinkage hole and porosity.

Abstract: The strength ratio, thickness ration of blanks and the microstructure of weld seam play important role in the formability of tailor welded blanks (TWB). With numeric simulation technology in different conditions such as different thickness and different strength combination of TWB’s materials, the forming limit depth (FLD) of tailor welded blanks is analyzed. The affect of the thickness ratio and strength ratio on forming limit depth is investigated, the laws influencing the formability of TWB square box are summarized, and approaches are presented to increase the FLD. The results of simulation and practice indicate that reducing the difference of the thickness ratio, choosing lower strength material for thicker blank, and adopting right heat treatment can improve the forming limit depth. Keywords: Tailor Welded Blanks; Forming Limit Depth; Thickness Ratio; Strength Ratio