Talk:Alnico

Missing units in property table

Can we get some units in there? — Preceding unsigned comment added by 190.212.255.132 (talk) 16:25, 9 April 2015 (UTC)

ALNICO

Acronym in caps?? — Preceding unsigned comment added by 98.109.7.254 (talk) 17:59, 24 November 2011 (UTC)

In technical literature, it seems to appear most often as a proper noun, in lower case with the first letter capitalized 1, 2, 3, 4, 5; or less often as a common noun 6, 7, 8; or occasionally in camel case ("AlNiCo") 9 but not in all caps. --Chetvorno^TALK 01:31, 27 November 2011 (UTC)

Shielding

I remember hearing somewhere that nice watches sometimes have AlNiCo shield plates to keep them from being magnetized. However, mu metal claims that hard magnetic materials don't work as shield materials. I imagine that an "unmagnetized" block of material would keep its random local fields in the face of fields lower than its coercivity, and would work as a shield, but perhaps I'm wrong.

Any thoughts?--Joel 21:29, 8 May 2007 (UTC)

How are they nescient? You are. But yes, if you unmagnetized a AlNiCo magnèt, it would be such a shield. -lysdexia 04:23, 21 June 2009 (UTC) —Preceding unsigned comment added by 69.225.250.5 (talk)

Alternate Name

Years ago, I ran across a book at my junior high school's library describing several small motors ("mini", "midi", and "maxi"), many of which were based around Alnico magnets (very small bar magnets, perhaps 1.5 cm long). The book, and the store I bought them from, referred to these as "hot pad" magnets as well as the "Alnico" moniker. I can no longer find any references to this book (I can't even find the *name* of it), nor any connection to phrase "hot pad", but I know they exist. Can someone shed some light on this? Vanessaezekowitz (talk) 19:20, 27 August 2009 (UTC)

I remember they used to sew little magnets about that long into kitchen hot pads so they could be stuck on refrigerator doors. Don't know about the book, though. --Chetvorno^TALK 07:47, 18 July 2011 (UTC)

The book is "How to Make and Use Electric Motors" by Al G. Renner It was published by G.P. Putnam's Sons, New York — Preceding unsigned comment added by 24.143.49.170 (talk) 00:09, 18 September 2012 (UTC)

Coercivity

I just removed a cite needed dealing with coercivity. While AlNiCo magnets have lower coercivity than other types of synthetic magnets, they have extremely high corecivity compared to most natural materials. In this instance, I felt that there was sufficient information in the article that an additional cite was not warranted. Also, I found nothing on this page with British spelling, so I removed that as well. Msaunier (talk) 06:13, 18 July 2011 (UTC)

However, the page currently states that Alnico has both a high coercivity and a low coercivity (in the sidebox on magnet keepers) — Preceding unsigned comment added by 195.64.89.205 (talk) 12:13, 31 May 2014 (UTC)

• This has surfaced again, in relation to a bunch of reversions. I've moved some user page stuff over, because it belongs here, not there.

According to Coercivity, it's measured in Oersteds, not Tesla. Alcio comes in at the high end 380–6,030, comapred to e.g. Iron's 2. The source you've found doesn't agree with the majority of other sources used on the majority of related articles. OrangeDog (τ • ε) 16:23, 3 January 2019 (UTC)

If you're talking about Teslas, then that's probably in relation to remanence, not coercivity. Both are relevant here.

GliderMaven started broadly right here (well, not here), although it's still not clearly worded. Alnico (not Alcio, not alcino, not Al Pacino) has high coercivity, in comparison to other magnets of its era. It is low compared to modern magnets, even some of the 1960s magnet alloys before modern neodymium. This means that it can make useful magnets, but also that it's prone to losing this magnetic field – hence the need for keepers.

But the problem with the article is that Alnico wasn't useful for its coercivity, but for its remanence. These are different things: if you like, remanence is 'useful' in a permanent magnet, coercivity is the 'cost' of achieving this: the applied field needed to make it. It's the high remanence which made Alnico valuable, not anything about its coercivity. It's coercivity isn't that high, and what really matters for the "Does it need a keeper?" question is $BH_{max}$ the energy product (in Gauss-Oersteds). Which for Alnico is so low that it is indeed "infamous" for needing a keeper to avoid self demagnetisation. Andy Dingley (talk) 17:08, 3 January 2019 (UTC)

I don't mind saying "moderately high coercivity" or that Alnico has lower coercivity than other magnet families. But this sentence is in the introduction, which is going to be read by general readers who know nothing about metal and magnets. We are describing an iron alloy. It is important to tell readers that Alnico alloys are used for magnets because, like all magnet alloys, they have higher coercivity than other iron alloys used for other things. Coercivity of Alnico: 700 Oe. Coercivity of pure iron: 1 Oe. Here are some sources:

• "Permanent magnet materials are differentiated from the softer substances more particularly by their high coercivity" Heck, Magnetic Materials, p.238
• "They [Alnico alloys] are characterized by high remanence and available energy and moderately high coercivity" Laughlin, Warne, Electrical Engr's Reference Book, p.8-14
• "A major breakthrough came in 1931 with the discovery of the ... high coercive field of the...aluminum-nickel-cobalt-iron alloys (Alnico alloys). With these alloys the coercive field was increased by an order of magnitude compared to the old tungsten and chromium steels" Gerber, Wright, Asti, Applied Magnetism, p.335
• "[Alnico] exhibited coercivity of over 30kA/m, which was almost double that of the best steel magnets then available. Until the development of the rare earth magnets...alnico was the main hard [high coercivity] magnetic material" Tumanski, Handbook of Magnetic Measurements, p.146
• "Hard magnetic materials are usually classified as having coercivities over 10kA/m (125 Oe)... Alnico...has 56 kA/m (700 Oe)"

--Chetvorno^TALK 17:37, 3 January 2019 (UTC)

• It is important to tell readers... That depends which section, of which articles. This spills across magnet keeper too. Also the Alnico article also needs to address that. Not up front, along with the basic issue of high remanence, but somewhere.

In fact, I'd take issue with the whole issue of coercivity, and mentioning it so often before remanence. No-one buys a magnet because of its high coercivity, that's just sometimes easier to measure, but because of its remanence. What does, "Alnico alloys can be magnetised to produce strong magnetic fields and have a high coercivity (resistance to demagnetization), thus making strong permanent magnets." mean anyway? We can argue whether coercivity is high or low here, but Alnico does not have anything which can be presented as "resistance to demagnetization" and if "strong permanent magnets" is presented like this, in that particular sentence (where it's contrasted to the magnetic field), it's implying robust magnets rather than powerful magnets, which is quite wrong for Alnico. Andy Dingley (talk) 17:58, 3 January 2019 (UTC)

Classified as strategic material years ago?

I remember that Alnico material became quite expensive and somewhat scarce as a result of the US government placing restrictions on it, because they thought the material would become important in a war effort. Can anyone write more on this subject? Amclaussen. — Preceding unsigned comment added by 192.100.180.19 (talk) 17:11, 23 January 2014 (UTC)

Alnico was vital to the war effort for WW2. It was used in Sherman and M-3 tanks, as well as to produce proximity fuse magnet assemblies for motor and anti-aircraft shells. --74.8.36.5 (talk) 16:18, 9 February 2018 (UTC)

References

Chemistry

Alnico 119.2.125.133 (talk) 16:54, 18 July 2022 (UTC)