Artificial Inclusion Environments—Replicating Industry in the Laboratory

The authors present a series of complementary test methods which were developed and used to investigate reactions between high aluminium steel and silica rich inclusions. Non-metallic inclusions (NMIs) cause many defects in the final steel product, therefore the ability to track their size, morphology and composition and correlate this with fundamental reaction kinetics provides important knowledge to support the production of clean quality steel products. Novel steel grades such as TRIP, TWIP and low-density steels have high aluminium contents; aluminium is a readily oxidisable species presenting the potential for instability and excessive reaction with commonly used mould powders that contain silica. A novel combination of techniques including HT-CLSM (High-Temperature Confocal Laser Scanning Microscope), XCT (X-ray computed tomography) and SEM/EDS (scanning electron microscopy/electron dispersive spectroscopy) have been used to study the interaction of entrained mould powder inclusions with steel at high temperatures simulating industrial conditions. This report presents a discussion on the development of techniques and samples to achieve representative and repeatable results that can provide information on the complex chemical and physical interaction phenomena with confidence. Each experimental technique had its own learning points and consequent results. Outcomes presented include possible confirmation of the chemical reaction rate controlling step being aluminium mass transfer; heterogeneous local environmental conditions including fluidity and chemical composition; and occurrence of spontaneous emulsification where the mould powder inclusion breaks apart into a cloud of smaller fragments.

Optimization of Chemical Composition of the Mould Powder for Casting Ø 170 mm Billets from C45 Steel

Physico-chemical properties of mould powders and assumed casting parameters for the particular steel grade influence the way of lubricating the surface of the skin of concast billets formed in the mould, as well as heat transfer along its circumference. The paper presents research which main aim was to improve the surface quality of continuous casting round billets (Ø 170 mm) cast from C45 steel. Improvement of the surface quality can be obtained by designing the chemical composition of mould powder for local casting conditions and the technical and technological parameters of CC equipment. Based on the experimental casting from C45 medium carbon steel it was found that there are relationships between the physicochemical properties of mould powder and intensity of skin lubrication and heat transmission to the mould wall.

Characterization of diatomite from Sig region (West Algeria) for industrial application

Purpose – Diatomite also known Kieselguhr, is a non-metallic mineral composed of the skeletal remains of microscopic single-celled aquatic algae called diatoms. The purpose of this paper is to test and to evaluate the diatomite of Sig region (West Algeria) to substitute the main mould powder used in continuous casting of steel for thermal insulation and lubrication. Design/methodology/approach – To assess the behavior of diatomite at different temperatures, a combination of simultaneous scanning calorimetric and thermogravimetric testing was used and to evaluate the structure of diatomite, the scanning microscopy method was applied. Findings – The results showed different endothermic and exothermic peaks, mainly at 84.7°C and 783.5°C for endothermic peaks and 894.9°C for exothermic peak. The scanning microscopy method was used and a large porosity was observed. The trial industrial in continuous casting of steel showed a weak loss temperature of steel. Originality/value – This product may be used for thermal insulation in continuous casting of steel. Also the characterization showed the hot behavior of this product with the various transformations and could give the possibility to other use.

The Study of Surface Longitudinal Crack on SPA-H Steel Slab by CSP

By the means of Metallographic analysis, scanning electron microscope (SEM), and energy spectrum analysis, the development of SPA-H surface middle longitudinal crack was studied. To find out the causes of the longitudinal crack, statistical method was adopted. The result shows that, the generating process of longitudinal crack was: the changing of mould powder owing to Ti and Al element, low overheating degree, and bad slag smelting, which leading to bad transfer heat of slab and depression. For the thermal stress of solidifying contraction, molten steel static pressure, and mould friction, the stress concentration was produced in the weak place of solidified shell, for example, in the small equiaxial crystal less than 1mm. the cracking occurred when the stress more than allow strength of high temperature slab.