S. Timur

Beneficiation of brass ashes

Abstract Slags formed during brass smelting contain a significant amount of metallic value. The glassy and oxidized portion of the ground slag, usually referred to as “brass ash”, consists of compounds such as ZnO, ZnO·SiO 2 , Cu-Zn, CuO, Cu and Zn/Cu/B oxide, and its colored-metal content may vary between 28÷52% Zn and 8÷16% Cu. These ashes are classified as harmful wastes, due to their high Zn content, and are considered to be secondary raw materials that should be treated accordingly, from an economical viewpoint. The aim of this experimental study is to investigate the possibilities of beneficiating brass ashes by treating it with H 2 SO 4 or (NH 4 ) 2 CO 3 + NH 4 OH mixtures. Effects of temperature, air sparging and addition of oxidizing agents, such as MnO 2 and Fe 2 (SO 4 ) 3 , are investigated on copper and zinc leaching recovery. As a result of both acidic and alkaline leaching experiments, it is observed that more than 90% of Zn and more than 65% of Cu was leached out. Two separate process flow sheets are proposed for the possible treatment of brass ashes.

Effects of electrochemical boriding process parameters on the formation of titanium borides

In this study, the boriding of titanium via molten salt electrolysis was investigated in borax based electrolyte at various current densities (50–700 mA/cm2), temperatures (900–1200°C) and process durations (1 min-4 h). Thin film XRD results revealed that two main titanium boride phases TiB2 and TiB was formed even after 1 minute of process time. Scanning electron microscopy (SEM) images conducted on the cross-sections demonstrated a bilayer boride structure composed of a continuous uniform TiB2 phase and TiB whiskers that grew below the TiB2 layer toward the substrate. Dependence of boride layer thickness and morphology on the process parameters was evaluated. The results of the study showed that temperature of boriding was the most critical parameter both on boriding rate and morphology of the boride layer. It was possible to grow 8 μm thick TiB2 layer on titanium in 30 minutes of boriding at 1200°C.

Enhanced Surface Hardness by Boron Diffusion in Martensitic Stainless Steel via Cathodic Reduction and Thermal Diffusion Based Boriding (CRTD-Bor)

In this study, a developed new boriding method called as “Cathodic Reduction and Thermal Diffusion based Boriding” (CRTD-Bor) was applied to increase the surface hardness of 400 series steels. The cross-sectional examination of borided steel revealed that the boride layers consisted of single phase Fe2B. A dense and continuously 25μm thick Fe2B layer could be formed after 20 minutes of CRTD-Bor. The grown boride layer exhibited 1500±200 HV on top, and gradually decreased to the matrix (325 ± 25 HV).