Shape of slab solidification end under non-uniform cooling and its influence on the central segregation with mechanical soft reduction

In order to study the effect of continuous casting process parameters on the shape of slab solidification end under non-uniform cooling,a solidification model of a continuous-cast slab with non-uniform cooling condition was established with ProCAST software.The model was verified by the results of nail shooting tests and the infrared temperature measurement equipment.Four characteristic parameters were defined to evaluate the uniformity of the shape of slab solidification end.The results showed that the nonuniformity at the beginning and end of solidification,the solidification end length,and the solidification unevenness increased with the rise of casting speed.For each 10°C increase of superheat,the solidification unevenness increased by about 0.022.However,the effect of superheat on the solidification end length can be ignored.The secondary cooling strength showed minimal effect on the nonuniformity at the beginning and end of solidification.With the increase in secondary cooling intensity,the solidification end length decreased,but the solidification unevenness increased.In addition,the central segregation of the slab produced with and without the mechanical soft reduction(MSR)process was investigated.The transverse flow of molten steel with low solid fraction influenced the central segregation morphology under MSR.

Mechanism of fluidized chlorination reaction of Kenya natural rutile ore

In this paper, the thermodynamics and kinetics of nature rutile carbochlorination in a fluidized-bed were investigated. The thermodynamic calculations of TiO2-C- C12 system show that when C is excess in the solid phase, titanium tetrachloride and carbon monoxide can exist sta- bly. At high temperature, the reaction with CO as the product is the dominant reaction. The appropriate reaction conditions are as follows： reaction temperature of 950 ℃, reaction time of 40 min, carbon ratio of 30 wt% of rutile, natural rutile particle size of -96 μm, petroleum coke size of -150 μm, and chlorine flow of 0.036 m3.h-1. Under the above conditions, the reaction conversion rate of TiO2 can reach about 95 %. This paper proposed a reaction rate model, and got a rutile chlorination rate formula, which is generally consistent with the experimental data. For the TiO2-C-C12 system, the reaction rate is dependent on the initial radius of rutile particle, density, and the partial pressures of C12. From 900 to 1,000 ℃, the apparent activation energy is 10.569 kJ.mo1-1, and the mass diffu- sion is found to be the main reaction-controlling step. The expression for the chlorine reaction rate in the C-C12 sys- tem is obtained, and it depends on the degree of reaction, the partial pressure of C12, and the size of rutile particle.

Flow field, heat transfer and inclusion behavior in a round bloom mold under effect of a swirling flow submerged entry nozzle

Flow field,heat transfer and inclusion behavior in a 700 mm round bloom mold under the effect of a swirling flow submerged entry nozzle(SEN)were investigated with the aim to enhance the casting process.The results indicate that the impinging flow phenomenon,which is commonly observed in conventional single-port SEN casting,was completely suppressed by the swirling flow SEN coming from a novel swirling flow generator design in tundish.Steel from the SEN port moved towards the mold wall in 360 direction,leading to a uniform temperature distribution in the mold.Compared to a conventional single-port SEN casting,the steel super-heat was decreased by about 5 K at the mold center,and the temperature was increased by around 3.5 K near the meniscus.In addition,the removal ratio of inclusions to the mold top surface in the swirling flow SEN casting was found to be increased.Specifically,the removal ratio of spherical inclusions with diameters of 1,10,50 and 100μm was increased by 18.2%,18.5%,22.6% and 42.7%,respectively.Furthermore,the ratio was raised by 18.2%,20.8%,21.5% and 44.1%for non-spherical inclusions,respectively.

Special issue on numerical simulation of multiphase and multiscale metallurgical processes

Steel production process is a multiphase and multiscale high-temperature metallurgical process involving complex physical behaviours and chemical reactions.The movement of high-temperature melts closely affects the cleanliness,homogenization,and refinement of high-quality steel.However,due to the high temperature,invisibility,and difficult quantification of metallurgical process,the data that can be measured in high-temperature melts during production process are limited.

Special issue on continuous casting

Continuous casting is considered to be one of the most important innovations in steel industry since it is first propagated by Henry Bessemer in 1846.It has many benefits,including(Ⅰ)increased yield,(Ⅱ)improved product quality,(Ⅲ)energy saving,(Ⅳ)less pollution,(Ⅴ)reduced costs,(Ⅵ)better working conditions,etc.Nowadays,more than 98% of crude steel output in the world is produced through the continuous casting process.