In order to provide the mechanism of nozzle clogging, recovered nozzles for high strength steel grade were examined carefully after continuous casting. The thickness of clogged material in SEN is increased in the following order: from the bottom to the top of the nozzle, upper part of slag line, and the pouring hole. Nozzle clogging material begins to form due the adhesion of metal to nozzle wall, the decarburization, and reduction of oxide in the refractory by Al and Ti in the melt. The reduction of oxide in the refractory by Al and Ti improves the wettability of the melt on the refractory and forms a thin Al-Ti-O layer. Metal containing micro alumina inclusions is solidified on the Al-Ti-O layer, and the solid layer grows due to the heat evolution through the nozzle wall. Thermodynamic calculation has been made for the related reactions. The effect of superheat to the nozzle clogging is discussed on ultra low carbon steel and low carbon steel.
Around the world, silicon carbide (SiC) is used as a raw material in several engineering applications because of its various beneficial properties. Currently, though the Acheson method is one of the most emblematic to manufacture SiC, the direct carbonization of metallic silicon is simple and beneficial. In this reaction, silicon wafer cutting sludge can be used as an alternative silicon source material. The silicon wafer sludge contains silicon, ethylene glycol, cooling water, and a small amount of impurities. In this study, SiC was synthesized using silicon wafer sludge by a carbothermal process. In a typical experiment, the silicon sludge was mixed with carbon at different molar ratios. Then, the mixture was turned into pellets, which were placed in alumina crucibles and heat-treated at a temperature from 1400 °C to 1600 °C to fabricate SiC. To deduce the optimum condition for the synthesis of SiC, an investigation was carried out on the effects of different mixing ratios, temperatures, and heating times. To ensure sufficient carbonization, excess carbon was mixed, and the synthesized SiC was characterized by X-ray diffraction (XRD). Subsequently, purification of the synthesized SiC products by oxidation of excess carbon was performed. The removal of extra carbon could be confirmed by XRD and attenuated total reflectance (ATR) spectroscopy. This process can give basic information for the development of a technology to produce SiC using recycling Si wafer cutting sludge waste.
Cu-Be alloy (C17200) rod having diameter of 23.5mm was produced by a vacuum continuous casting method at furnace temperature range of from 1240°C to 1260°C with casting speed range of from 35mm/min to 103mm/min. When the furnace temperature was 1240°C and 1250°C, Cu-Be alloy rod without fracture could successfully produced at high casting speed of 103mm/min. However, when the furnace temperature was 1260°C, the breakout occurred at casting speed faster than 78mm/min. Surface roughness (Ra) increased with increasing not only a furnace temperature but also a casting speed.
With an increased production of Printed Circuit Boards (PCBs) in electronic equipment, the consumption of solder alloys is growing globally. Recently, increasing importance of recycling solder scrap has been recognized. Generally, solder scrap contains many impurities such as plastics and other metals. Hazardous components must be eliminated for recycling solder scrap. The present work studied pretreatment for reuse of solder scrap alloys. An experiment was conducted to enhance the cleanliness of solder scrap melt and eliminate impurities, especially lead. Physical separation with sieving and magnetic force was made along with pyrometallurgical methods. A small decrease in lead concentration was found by high temperature treatment of solder scrap melt. The impurities were removed by filtration of the solder scrap melt, which resulted in improvement of the melt cleanliness. A very low concentration of lead was achieved by a zone melting treatment with repeated passage. This study reports on a pretreatment process for the reuse of solder scrap that is lead free.
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