Quasi-Symmetric Transfer Behavior in an Asymmetric Two-Strand Tundish with Different Turbulence Inhibitor

The task of the tundish is to supply and distribute the molten steel with the similar temperature and the similar inclusion mass concentration to the continuous casting mold. But it is difficult for the asymmetric tundish to accomplish this task. Thus, the scheme about the asymmetric turbulence inhibitor and the baffle wall with guided holes is proposed to optimize the tundish. In order to have a deep insight into the metallurgical behavior in the asymmetric tundish, numerical simulation is applied to describe the fluid flow, the heat transfer, RTD (residence time distribution) curve, and inclusion collision aggregation behavior. Numerical results show that the predicted temperature and inclusion concentration agree with the industrial experimental data. In the asymmetric two-strand tundish, the asymmetric turbulence inhibitor and the baffle wall with guided holes can extend the mean residence time at the left outlet, reduce the temperature difference between the two outlets, and prompt the inclusion removal rate at the left outlet.

Пороги инициирования и динамические характеристики взрыва для тонких образцов композитов ТЭН-Al при лазерном воздействии

In this paper, we measured thresholds H _cr of explosive decomposition of thin ( h = 1 mm) samples of PETN-Al composites with densities in the range of ρ = 0.9–1.7 g/cm^3 and variations in the concentration of aluminum inclusions in the range of 0.025–1.0 wt % upon exposure to pulses of a neodymium laser (λ = 1064 nm, 14 ns). For each ρ, inclusion concentrations n _opt, at which the threshold for explosive decomposition of H _cr is minimal, are obtained. The velocities of air shock waves (ASWs) were determined depending on sample density ρ, and the times of the start of explosive decomposition were determined depending on the inclusion concentration. The amplitude (in relative units) and time shift of the maximal pressure of an ASW at the piezodetector are determined depending on sample density. It is concluded that the explosion is governed by the SW mechanism at high densities. As sample ρ decreases, the completeness of the explosion increases, with the most likely mechanism for small ρ being explosive burning. The efficiency of explosive decomposition is higher for samples with lower densities.

Numerical Simulation of Inclusion Capture in the Slab Continuous Casting Considering the Influence of the Primary Dendrite Arm Spacing

In the present work, a coupled three-dimensional numerical model of fluid flow, heat transfer, and inclusion motion during the solidification of molten steel in slab continuous casting mold has been developed. Based on the model, this paper has studied the inclusion capture during the process. The influence of the primary dendrite arm spacing on inclusion capture has been considered. The inclusion distributions, total masses, and average diameters at different depth from the slab surface have been given out in the present paper. The simulation results revealed the inclusion concentration existed in the solidification process, and the inclusion capturing area varies with the depth from the slab surface.

Field Synergy Analysis for Inclusion Removal in the Continuous Casting Tundish

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

Effects of Electromagnetic Purification on Properties of Al-RE Rod for Electrical Purpose

An electromagnetic purification system was installed to process molten aluminum in an Al-RE rod continuous casting and hot rolling line. The variation of inclusion concentration in rod samples with and without electromagnetic purification was detected via quantitative metallography. The tensile strength and electrical resistivity of as-rolled rods as well as subsequently cold drawn wires were also tested. Results show that a 61% additional improvement of removal efficiency was achieved by electromagnetic purification other than ceramic foam filtration. The inclusion concentration in the rods has negligible impact on electrical resistivity of samples and the deformation restricts the fluctuation of electrical properties apparently. The UTS of drawn wires with electromagnetic purification improves by 3%-5% as compared with those with filtration only, while the variation of inclusion concentrations has little influence on the UTS of as-rolled rods. A negative linear relationship between the logarithm of UTS and the logarithm of inclusion area fraction for cold-drawn samples is also obtained.

Original Position Statistic Distribution Analysis for Al Inclusion in Continuous-Casting Thin Slab

Single discharge analysis and comparison of signals of multi-channels, two kinds of technique of Original position statistic distribution analysis, were used to analyze and evaluate the Al inclusion in continuous-casting thin slab. The samples are continuous casting slab . Datum of Al inclusions such as average concentration and concentration distribution , types of inclusion, concentration of the different type of Al inclusion, size distribution are obtained on different sect of cross section and the whole cross section of the sample.

Correlation Analysis of MnS Inclusion Composition Using Original Position Statistic Distribution Analysis

In the process of Original Position Statistic Distribution Analysis, many abnormal higher spark signals exist. They are believed as inclusion signals. Analyzing the time sequence and position of the abnormal spark, It is found that the higher spark signals for S and Mn will appear simultaneously . The reason is that MnS inclusion caused the element concentration enrichment at these zone. Mixing some pure MnS crystal in pure iron powder and pressed by Heat Isostatic Pressing technology, reference samples of MnS inclusion were made . Criteria of abnormal higher spark signals for Mn and S is the measured value from the “blank sample ”.After analyzing the spark behavior of these reference samples using OPA instrument, we can calculate the MnS inclusion concentration through such method. steel samples were analyzed and results is satisfactory.