Influence of the filling gas mixture on the interruption capability of medium voltage load break switches

In today’s medium voltage switchgear SF6 is commonly used as insulating and arc quenching medium. Because of its high potential impact on the environment a substitution with an environmentally friendly alternative is pursued. In this paper the influence of the mixing ratio of carbon dioxide nitrogen mixtures as filling gas on the interruption capability in medium voltage load break switches is investigated. The interruption capability is regarded by means of the thermal interruption performance as well as the dielectric recovery of a model load break switch. The model load break switch allows an axial arc blowing with variable pressure and uses an exchangeable nozzle system.

The Quenching and Sonication Effect on the Mechanical Strength of Silver Nanowires Synthesized Using the Polyol Method

This study aims to determine the effect of fast cooling (quenching) on thermal properties, mechanical strength, morphology and size of the AgNWs. The synthesis of AgNWs was carried out at three different quenching-medium temperatures as follows: at 27 °C (ambient temperature), 0 °C (on ice), and −80 °C (in dry ice) using the polyol method at 130 °C. Furthermore, the AgNWs were sonified for 45 min to determine their mechanical strength. Scanning electron microscopy analysis showed that the quenched AgNWs had decreased significantly; at 27 °C, the AgNWs experienced a change in length from (40 ± 10) to (21 ± 6) µm, at 0 °C from (37 ± 8) to (24 ± 8) µm, and at −80 °C from (34 ± 9) to (29 ± 1) µm. The opposite occurred for their diameter with an increased quenching temperature: at 27 °C from (200 ± 10) to (210 ± 10) nm, at 0 °C from (224 ± 4) to (239 ± 8) nm, and at −80 °C from (253 ± 6) to (270 ± 10) nm. The lower the temperature of the quenching medium, the shorter the length and the higher the mechanical strength of AgNWs. The UV-Vis spectra of the AgNWs showed peak absorbances at 350 and 411 to 425 nm. Thermogravimetric analysis showed that AgNWs quenched at −80 °C have better thermal stability as their mass loss was only 2.88%, while at the quenching temperatures of 27 °C and 0 °C the mass loss was of 8.73% and 4.17%, respectively. The resulting AgNWs will then be applied to manufacture transparent conductive electrodes (TCEs) for optoelectronic applications.

Effect of austenitizing and tempering on impact resistance of a hot rolled high strength steel

The aim of this study is to investigate the effect of heat treatments on the impact properties of hot rolled high strength steel and describes the effect of tempering temperature and quenching media on the microstructure, hardness, and impact resistance of plates. In the present study a high strength steel was austenitized at 900 °C with different quenching medium and followed by tempering at 300 °C, 500 °C. After thermal treatments, the values of Charpy impact resistance, hardness, and microscopic structure were evaluated from mechanical and metallographic analysis of metals respectively. The change of mechanical properties and microstructure of the metal with the existence of heat treatment with the ballistic performance of high-strength steel. Experimental results showed that tempering at 500 °C for 2 hours after water quenching medium it provides the best mechanical properties in conjunct on with an improved in microstructure.

Study of α”-Martensitic Transformation in Ti35NbxSn Alloys Subjected to Cryogenic Heat Treatment

TiNbSn alloys have been extensively researched due to several properties they exhibit, including high mechanical strength, low elastic modulus, superelasticity, shape memory effect, biocompatibility. The present study evaluated the cryogenic heat treatment in the Ti35NbxSn alloys (x = 0.0; 2.5; 5.0; 7.5). The alloys were arc melted, cold formed and quenched in both water and liquid nitrogen at-198° C. The Ti35Nb2.5Sn alloy was also aged after exposed to both quenching medium. Microstructure and microhardness analyses were performed. Cryogenic treatment was not enough for transformation of primary β phase into martensitic α” in alloys containing 5 and 7.5% Sn. Cryogenic treatment provided β to α” transformation in alloys containing 0 and 2.5% Sn. The Sn-free alloy was more likely to α" transformation in both quenching medium. The alloys microhardness increased with decrease of both quenching temperature and Sn content. The increase of α" is also related to the increase of the alloy microhardness after aging.

Experimental Study on Heat Treatment of SS 420 and EN 24 Using Nanoparticulate Quenching Process

Heat transfer through nanotechnology is a current trend which occupies most research areas with improved results. Taking this concept, the present work has been focused on the analysis of quenching effect on steel such as EN 24 and SS 420 with nanoparticles dispersed in quenching medium. Quenching is the process of removing heat from the heat-treated elements which also take part in determining the hardness values depending on the heat transfer rate and quenching time. To ensure the outcome properties, different volume concentrations of nanofluids have been prepared by adding TiO2 nanoparticles with the average diameter of less than 20[Formula: see text]nm in synthetic oil. Here, it is planned to have four volume concentrations (0.25[Formula: see text]g/lit, 0.375[Formula: see text]g/lit, 0.5[Formula: see text]g/lit, 0.625[Formula: see text]g/lit) of nanofluids to be used in the experiment. The materials after facing heat treatment up to 850∘C (EN 24) and 980∘C (SS 420), are subjected to quenching by using nanofluid. The work has been carried out by altering the tempering temperature and volume of nanoparticles in the quenching medium. The outcome quality of the product desirably supports our expectations, such as improved hardness and reduced time consumption for quenching. Additionally, the comparative analysis shows an improvement in heat transfer characteristics as well as properties in quenched specimen with nanofluids.