Corrosivity of HFC125 as Shielding Gas for Magnesium Melt under High Temperature

Abstract

HFC125 is a potential substitutive to SF 6 in terms of its protective effectiveness, reduced GWP and cost. In the present study, corrosivity of HFC125 containing nitrogen atmosphere to the medium-carbon steel of C45E4 was examined by systematic experiments under the temperatures and HFC125 concentrations commonly used in Mg die-casting practice. For comparison, the corrosivity of SF 6 containing nitrogen atmosphere was examined in the identical conditions, followed by X-ray diffraction and X-ray fluorescence characterization of the corrosion products. The results show that the HFC125 containing nitrogen atmosphere was less corrosive to C45E4 than SF 6 containing one in long-playing corrosion under identical conditions. Oxidation was the major cause of the corrosion to C45E4 and HFC125 or SF 6 was of secondary contribution. HFC125 or its decomposition was deduced to corrode C45E4 to produce fluorides; SF 6 or its decomposition was deduced to react with C45E4 to produce sulfides.

The Effects of Settling Time on the Quality of Fluxless Mg–Nd–Zn–Zr Melt Preparation

“…The melt of MgNdZnZr tend to lose rare earth element neodymium (Nd) when utilizing flux purification, 9) because Nd reacts with the magnesium chloride (MgCl 2 ) in fluxes. In view of the loss of Nd and MgCl 2 , and other disadvantages of flux technology, fluxless technology (like gas shielding, 10) filtration 11) and gas bubbling 1215) ) is gaining an increasing interest. 15) Though fluxless MgNdZnZr melt preparation avoids the drop of Nd, but the undesirable phenomena of the zirconium (Zr) loss, still exists; undissolved Zr particles in MgNdZnZr melt are easy to settle to the melt bottom due the higher density compared to Mg melt, which is a characteristic of the melt of Zr alloying Mg alloys.…”