Magnetics Business & Technology - Summer 2012 - (Page 18)

FEATURE ARTICLE The easiest one to tackle next is REuse. Although this is a very successful strategy in many industries, it is rare that permanent magnets find a second life. They are usually so deeply integrated into higher level assemblies, which are seldom designed to enable simple removal of the magnet components, that using them again for anything substantial is unusual. You can find any number of fairly trivial uses for magnets recovered from devices, but when you rule out the ones that involve holding notes to the fridge, the numbers decline dramatically. If anyone has examples of reuse in technical applications (other than sterilizing magnetic stirrers rather than throwing them away) I would love to hear about them. Then we get to REduce. This is the big one, and there can be all sorts of ways of reducing the amount, the waste and the impact of over specification. With RE metals, the area where true supply and demand pressures may come into play is with the so called “heavies”. With China now imposing separate export quotas for the heavies, and with new sources being several years away, it is wise to reduce the need for these metals. In the permanent magnet business, this really means Dysprosium (Dy), which is added to many of the NdFeB alloys to increase their temperature capability. Designing devices that run a little cooler, and not over specifying the grade of magnet material needed, just to be safe, will reduce cost significantly. Another aspect to consider in relation to Dy is that the bonded magnet world already seems to have solved the problems. The world’s largest supplier of powders, Magnequench, doesn’t use Dy in any of their regular powder grades, and yet achieve temperature stability that satisfies the auto industry. Another powder supplier, Aichi Steel, who make anisotropic powders for bonded magnets (Magfine) either had the foresight or the luck to replace their Dy diffusion process used in higher temperature grades, with a similar process but using a NdCuAl alloy, and brought this into production before the price spike last year. Many of the sintered NdFeB manufacturers are looking at similar Dy replacement efforts, but the diffusion processes do not work well on thick magnet sections, so this is a particularly good match for powders used in bonded magnets. So don’t over specify, and if you can bring operating temperatures down in devices that use sintered NdFeB, the reduced magnet costs will be significant. The next area where REduce is important is in the efficient use of expensive materials. Something that will probably not be apparent to the majority of magnet users is how efficiently the starting alloys are converted into finished product. When alloys are relatively cheap, this inefficiency in the conversion tends to be lost in the overall cost of production, and in the relative benefit of high performance that RE magnets can deliver. However, with the exposure that has been given to RE metal costs over the last twelve months, all levels of the supply chain are digging into the cost structure and asking awkward questions related to efficiency of material use. The standard method of production of RE magnets in China is to press and sinter large blocks of material, and then use wire cutting, slicing and grinding to create the final shape. What that shape is has a big impact on the utilization of the starting block. Obviously, square and rectangular blocks are created with good utilization of the starting block, but when you think about how arcs, discs, spheres and rings are made, cutting of these from large blocks can be horribly wasteful of the starting material. The picture below shows the progression of good to bad utilization of material, with respect to the part shape. This method of production is fine when material costs are relatively low but if you assume that the price of RE metals is not going to go back down to anything close to Q4 2010 prices, it makes a lot of sense to consider tooling so that parts can be pressed close to net shape. But beware – the alignment in tooled parts is going to be different, so performance can change (and not necessarily downwards) even when using the same grade of powder. Comparing the effective utilization of starting alloy in sintered and bonded products highlights another interesting difference. Production of pow- 18 Magnetics Business & Technology • Summer 2012 www.MagneticsMagazine.com http://www.eaglabs.com http://www.eaglabs.com http://www.MagneticsMagazine.com

Table of Contents for the Digital Edition of Magnetics Business & Technology - Summer 2012

Magnetics Business & Technology - Summer 2012
Editor's Choice
Injection Molded Magnets for Electrical Machines
The Process of Developing and Testing a New Transformer
Rare Earths & Corporate Social Responsibility
Research & Development
RE-use, RE-duce, RE-cycle, RE-place
Magnets • Materials • Measurement
Application • Component Developments
Industry News
Rare Earth Crisis Dissected: Securing the Future
Marketplace
Advertising Index
Spontaneous Thoughts: The End of Axial Pressing?

Magnetics Business & Technology - Summer 2012