GB/T 20892-2020Praseodymium-neodymium metal (English PDF)

1 Scope

China's national product standard for praseodymium-neodymium metal. It specifies the technical requirements, the test methods, the inspection rules, and the marks, packaging, transport, storage and quality certificate, and it applies to praseodymium-neodymium metal produced from praseodymium-neodymium raw material. This is the single most commercially important rare earth metal product there is, and the reason is the magnet. A sintered neodymium-iron-boron magnet is the strongest permanent magnet available, and it is what makes a traction motor, a wind turbine generator, a hard disk actuator, a loudspeaker and a hundred smaller devices as small as they are. The magnet does not need pure neodymium: praseodymium substitutes for it almost perfectly in the crystal lattice and behaves nearly identically, so the mixed didymium metal is used directly. That matters enormously in practice, because praseodymium and neodymium are adjacent lanthanides and separating them from one another is the most expensive step in the whole separation chain. Not doing it, where the application does not require it, removes that cost entirely. So what the standard specifies is the total praseodymium and neodymium content and the ratio between them - since the magnet alloy is formulated on that ratio - along with the limits on the other rare earths, which dilute without contributing, and on the non-rare-earth impurities. Iron, oxygen, carbon, nitrogen and silicon are the ones that matter, because they form inclusions and grain boundary phases that degrade the coercivity of the finished magnet at concentrations measured in hundreds of parts per million. Issued on 19 November 2020 and in force since 1 October 2021, it replaces GB/T 20892-2007.

This Standard specifies the technical requirements, test methods, inspection rules, marks, packaging, transportation, storage and quality certificates of praseodymium- neodymium metal. This Standard applies to the praseodymium-neodymium metal, that uses praseodymium neodymium oxide as the raw material, is produced by the molten salt electrolysis method and is used as magnetic materials.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 8170, Rules of rounding off for numerical values & expression and judgement of limiting values

GB/T 12690 (all parts), Chemical analysis methods for non-rare earth impurities of rare earth metals and their oxides

GB/T 14635, Rare earth metals and their compounds - Determination of total rare earth content

GB/T 17803, Designation system for rare earth products

GB/T 26417, Chemical analysis methods of praseodymium-neodymium alloy and the compounds - Determination of REO relative contents

3 Technical requirements

3.1 Product classification The products are divided into six designations according to chemical composition: PrNd-80NdA, PrNd-80NdB, PrNd-75NdA, PrNd-75NdB, PrNd-70NdA, PrNd-70NdB. The method of product designation representation shall comply with the provisions of GB/T 17803.