TY - JOUR

T1 - Protecting molten magnesium and its alloys

AU - Hort, Norbert

AU - Wiese, Burkhard

AU - Dieringa, Hajo

AU - Kainer, Karl Ulrich

N1 - cited By 2

PY - 2016/6

Y1 - 2016/6

N2 - Magnesium is having a high affinity to oxygen in the molten state and unlike other metals it is not forming a stable protecting film on the surface of melts. To avoid burning it is therefore necessary to protect molten Mg and its alloys. To achieve this, nowadays mostly SF6 is used in combination with carrier gases like dry air, N2, CO2, or even Ar. However, SF6 has been identified as a highly potent greenhouse gas with a global warming potential > 23,000 more than CO2. Moreover, SF6 is cracked at temperatures higher than 750 °C and toxic fluorine is set free. Fortunately fluorine immediately reacts with Mg vapour and forms stable MgF2. Due to the different threats caused by SF6 the European Union (EU) will ban the use of SF6 for high pressure die casting of magnesium alloys as of January 1st, 2018. Alternatives are already available. But most of them are fluorinated hydrocarbons or other fluorinated chemicals. They are also under discussion in the EU due to the risk that comes with fluorine. SO2 is already recommended as a possible SF6 replacement but is also having its own restrictions with maximum working space concentrations. It might be necessary to reuse again fluxes, but they also have limitations. If magnesium and its alloys shall be further used and processed in the EU, alternative ways of magnesium melt protection need to be established within the near future. This contribution will discuss available methods to protect molten Mg and their consequences.

AB - Magnesium is having a high affinity to oxygen in the molten state and unlike other metals it is not forming a stable protecting film on the surface of melts. To avoid burning it is therefore necessary to protect molten Mg and its alloys. To achieve this, nowadays mostly SF6 is used in combination with carrier gases like dry air, N2, CO2, or even Ar. However, SF6 has been identified as a highly potent greenhouse gas with a global warming potential > 23,000 more than CO2. Moreover, SF6 is cracked at temperatures higher than 750 °C and toxic fluorine is set free. Fortunately fluorine immediately reacts with Mg vapour and forms stable MgF2. Due to the different threats caused by SF6 the European Union (EU) will ban the use of SF6 for high pressure die casting of magnesium alloys as of January 1st, 2018. Alternatives are already available. But most of them are fluorinated hydrocarbons or other fluorinated chemicals. They are also under discussion in the EU due to the risk that comes with fluorine. SO2 is already recommended as a possible SF6 replacement but is also having its own restrictions with maximum working space concentrations. It might be necessary to reuse again fluxes, but they also have limitations. If magnesium and its alloys shall be further used and processed in the EU, alternative ways of magnesium melt protection need to be established within the near future. This contribution will discuss available methods to protect molten Mg and their consequences.

KW - Engineering

KW - carbon dioxide

KW - Die casting

KW - Fluorine

KW - Fluxes

KW - Global warming

KW - Greenhouse gases

KW - Hydrocarbons

KW - magnesium

KW - Magnesium alloys

KW - sulfur dioxide

KW - sulfur hexafluoride

UR - https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009350842&partnerID=40&md5=7f13c727d70555a5a890fbf38af7bf60

M3 - Journal articles

VL - 108

SP - 105

EP - 108

JO - Metallurgia Italiana

JF - Metallurgia Italiana

SN - 0026-0843

IS - 6

ER -