Highlights:A new approach developed by a research group from Xi’an Jiaotong Universitytackles the long-standing problem in magnesium industry: stable, large-scaleand cost-effective production of high-quality magnesium.
High-endmagnesium alloys need high-purity and stable primary magnesium with affordableprice. However, current commercial primary magnesium either has poor quality(e.g. Mg9990) or is of high purity but with very high price. Prof. ZhiweiShan’s research group of Xi’an Jiaotong University (funded by a project fromFugu, Shaanxi province), has tackled this problem by developing a cost-effectivetechnology, being capable of large-scale production of high quality puremagnesium. They have built the first thousand-ton Mg9995A demonstration line inChina successfully, without reducing the total production or increasingoperational complexity. The popularization and application of this technologywill produce significant social and economic benefits.
Applicationsof Magnesium
Asthe lightest structural metal materials, magnesium and its alloys areattracting worldwide interests because of their potential to reduce energy costin aeronautics, astronautics and transportation industry. Magnesium also shows broadapplications in medical biological implant material, reducing agents fortitanium, zirconium and hafnium, considered as strategic materials, as well ashydrogen storage devices.
PrimaryMagnesium
Primarymagnesium is the feedstock for manufacturing magnesium products. China is thelargest producer of primary magnesium. Chinese primary magnesium production accountsfor more than 80% of the world’s total, while Shaanxi's primary magnesiumproduction takes up about 60% of the national total. Most of the primary magnesiumin China is produced by the Pidgeon process, which has long been consideredunable to produce high-quality magnesium stably and economically.
Strongdemand for high-quality primary magnesium
Manufacturinghigh-quality magnesium products requires high-quality primary magnesium since impuritiesin feedstock can be delivered into final products and cause serious problemslike fast corrosion. For example, the tolerance limit of Fe for corrosion in puremagnesium is only ~170 ppm, representing the corrosion rate of magnesium willdramatically increase when Fe content exceeds this value. If some Si exists inmagnesium, the corrosion rate will drastically increase by three orders ofmagnitude when the Fe content increases only from 3 ppm to 25 ppm. Acutally, asearly as 1942, it was pointed out that the excellent corrosion resistance ofmagnesium alloys is often masked because of their extreme sensitivity tocertain impurities and combinations of impurities (Hanawalt, et al., J. trans.AIME 147, 273–299, 1942). However, there is still no available technology to producehigh quality primary magnesium at affordable price. Most primary magnesium inuse today is usually of low purity, while further purification requiresadditional processes that are usually of very high cost, hindering the healthyand fast development of the entire magnesium industry.
Achievements
After8 years of research and development, Prof. Zhiwei Shan’s research groupdeveloped a cost-effective technology that is capable of producing large-scalehigh quality primary magnesium. They have built the first thousand-ton Mg9995Ademonstration line in China successfully, based on horizontal reduction retorts(the main equipment where magnesium is reduced and collected) that arecurrently widely employed by the factories. During a month’s trial period, thetotal yield of Mg9995A exceeded 90%. It is worth noting that the usage of thisnew technology will not reduce the total production or increase operationalcomplexity, which allows large-scale applications in the magnesium industry.
Acommittee composed of government personnel, chief engineers of magnesium enterprisesand senior researchers of research institutes highly praised and affirmed thisproject and made the comment that it paves a new way for producing high-qualityprimary magnesium, which is expected to benefit the entire magnesium industry.
