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SiC-TiB2 composite ceramics of the solid-state has stable property in high temperature with wide application. In the paper, SiC-TiB2 composite ceramics was prepared by spark plasma sintering with 50 MPa pressure and heat preservation for 10 min at 1750 ℃, and the effect of TiB2 content (0 vo l%-20 vol%) on microstructure and mechanical properties of SiC composite ceramics by solid-state spark plasma sintering was investigated. The experimental results show that the grain growth of SiC is inhibited with the increase of TiB2 content. When TiB2 content is 20 vol%, TiB2 promotes the decomposition of SiC into Si, which is located in the grain boundaries of SiC and TiB2 to reduce mechanical properties of composite ceramics. SiC-15 vo l%TiB2 composite ceramics have the preferable comprehensive mechanical properties with relative density, Vickers hardness, bending strength and fracture toughness of 98.8%, 27.2 GPa, 431 MPa and 5.24 MPa • m1/2, respectively. [ABSTRACT FROM AUTHOR]

A three-dimensional model is established to investigate the effect of argon injection mode, argon flow rate and casting speed on the gas–liquid two-phase flow behavior inside a slab continuous casting mold. The Eulerian–Eulerian model is employed to simulate the gas–liquid flow, and the population balance model is applied to describe the bubble breakage and coalescence process in the mold. The numerical simulation results of the bubble size distribution are verified using the water model experiment. The results show that the flow field and bubble distribution are similar between the argon injection at the upper submerged entry nozzle (SEN) and tundish upper nozzle (TUN), while the number density is larger for the argon injection of TUN. The coalescence rate of bubbles and the bubble size inside the mold increase with increasing argon flow rate. When the argon flow rate exceeds 4 L/min, the flow pattern of liquid steel changes from double-roll flow to complex flow, with aggravation of the level fluctuation of the top surface near the SEN. When the casting speed increases, the bubble breakup rate increases and results in a decrease in the size of bubbles inside the mold. At a high casting speed, the flow pattern tends to form double-roll flow, and the liquid level at the narrow face of the top surface increases. [ABSTRACT FROM AUTHOR]

In order to improve the inclusion removal property of the tundish, the mathematic model for simulation of the flow field sourced from inner-swirl-type turbulence controller (ISTTC) was developed, in which there were six blades arranged with an eccentric angle (θ) counterclockwise. Based on the mathematical and water model, the effect of inclusion removal in the swirling flow field formed by ISTTC was analyzed. It was found that ISTTC had got the better effect of inhibiting turbulence in tundish than traditional turbulence inhibitor (TI). As the blades eccentric angle (θ) of ISTTC increasing, the intensity of swirling flow above it increased. The maximum rotate speed of fluid in swirling flow band driven by ISTTC (θ=45°) was equal to 25 rmp. Based on the force analysis of inclusion in swirling flow sourced from ISTTC, the removal effect of medium size inclusion by ISTTC was attributed to the centripetal force (Fct) of swirling flow, but removal effect of ISTTC to small size inclusion was more depend on its better turbulence depression behavior.

The surface quality of slabs is closely related with the initial solidification at very first seconds of molten steel near meniscus in mold during continuous casting. The solidification, structure, and free deformation for given steels have been investigated in droplet experiments by aid of Laser Scanning Confocal Microscope. It is observed that the appearances of solidified shells for high carbon steels and some hyper-peritectic steels with high carbon content show lamellar, while that for other steels show spherical. Convex is formed along the chilling direction for most steels, besides some occasions that concave is formed for high carbon steel at times. The deformation degree decreases gradually in order of hypo-peritectic steel, ultra-low carbon steel, hyper-peritectic steel, low carbon steel, and high carbon steel, which is consistent with the solidification shrinkage in macroscope during continuous casting. Additionally, the microstructure of solidified shell of hypo-peritectic steel is bainite, while that of hyper-peritectic steel is martensite.

Based on the calculation results of the two-dimensional unsteady heat transfer model for continuous slab casting with soft reduction process, a coupled thermo-elastic-plastic mathematical model has been developed to study the effects of the reduction amount and solid phase fraction in slab centerline on the deformation behavior of solidification shell in this paper. The calculated results show that the displacement along thickness direction of slab changes little in width center region of slab when the reduction amount keeps constant, then it increases and a peak of displacement appears in 0.075 m whose distance is far from the slab narrow face, finally, it decreases severely near the narrow face of slab. When the solid phase fraction is the same, the displacement of solidification shell toward to the width and thickness direction of slab increases with the increasing of reduction amount. When the solid phase fraction is 0.3, the reduction amount in reduction subzone is 0.15 mm and 0.25 mm, respectively, the effective reduction efficiency decreases from 0.463 to 0.436. When the total reduction amount is 5 mm, the solid phase fraction varies from 0.3 to 0.7, the accumulated displacement of solidification front increases from 0.238 mm to 0.805 mm, the reduction efficiency decreases from 0.46 to 0.32.

Argon stirring is one of the most widely used metallurgical methods in the secondary refining process as it is economical and easy, and also an important refining method in clean steel production. Aiming at the issue of poor homogeneity of composition and temperature of a bottom argon blowing ladle molten steel in a Chinese steel mill, a 1:5 water model for 110 t ladle was established, and the mixing time and interface slag entrainment under the different conditions of injection modes, flow rates and top slag thicknesses were investigated. The flow dynamics of argon plume in steel ladle was also discussed. The results show that, as the bottom blowing argon flow rate increases, the mixing time of ladle decreases; the depth of slag entrapment increases with the argon flow rate and slag thickness; the area of slag eyes decreases with the decrease of the argon flow rate and increase of slag thickness. The optimum argon flow rate is between 36–42 m3/h, and the double porous plugs injection mode should be adopted at this time. [ABSTRACT FROM AUTHOR]

Background: Aberrant apoptosis in nucleus pulposus (NP) cells is the primary cause of intervertebral disc degeneration (IDD). In contrast, a large number of studies have confirmed that autophagy may protect NP cells from apoptosis. Sinomenine is an alkaloid monomer, which has been reported to stimulate cell autophagy. Therefore, the aim of the present study was to investigate the effects of sinomenine on IDD., Methods: The effects of sinomenine on the proliferation and apoptosis of NP cells were evaluated with the CCK-8 assay and Annexin V/PI staining, respectively., Results: The data obtained from the present study demonstrated that sinomenine could notably reverse TBHP-induced growth inhibition and apoptosis in rat NP cells. In addition, sinomenine significantly induced autophagy in rat NP cells, which was completely inhibited by 3-methyladenine (3MA). In addition, the protective effect of sinomenine against TBHP in rat NP cells was abolished following treatment with 3MA. Finally, an in vivo study further confirmed that sinomenine could ameliorate rat IDD., Conclusion: Taken together, the results of the present study indicated sinomenine could ameliorate rat IDD via induction of autophagy in vitro and in vivo . These findings suggest the therapeutic potential of sinomenine in the prevention of IDD., Competing Interests: None., (AJTR Copyright © 2019.)