saabinski

Is Reynolds 953 magnetic? I know some types of stainless steel are I but wasn't sure about 953. Anyway a magnet sticks to mine.

Thanks,
b

unterhausen

yes, it is

Scooper

Eric's right; 953 is magnetic. Curiously, my early 2007 953 frame has seat stays that aren't magnetic (all the main tubes and the chain stays are). I know Reynolds has several seat stay tubes in the 953 range (GS4650, GS4652, GS4670, and GS4671), but maybe they weren't available when my frame was made.

The Spot Rot separates from the seat tube at a little over 8 on the magnetic attraction scale, which is about the same as unpainted 4130.

fietsbob

Non steel alloys like Monel are going to have to be thicker wall than the Bike Biz wants to use ..

perfect for MINE sweepers ridding a Harbor of Magnetic Mines , Though.

long john

Iron, nickel, and cobalt are the three elements ferromagnetic at room temperature

Falanx

Iron, nickel, cobalt and gadolinium are the four elements that are ferromagnetic at room temperature. Bear in mind that paramagnetic materials can be attracted to a magnet, too, and there's bloody hundreds of them, including liquid oxygen.

ftwelder

Nickel? Oxygen? Really now?.

I have no argument but would a magnet really attract to liquid oxygen?

That spot rot tool is pretty neat.

Italuminium

Another high school maxim busted! But since Stan came up with that awesome tool, could it (or a different version which can measure to a finer degree) be used as a way to tell tubing apart, or are the main kinds of tubing used too much alike in this department?

Falanx

Yep, seen it done. You pour out enough LOX into a boiling tube to chill and fill it, so there's no losses, suspended from something like a bench clamp with a bit of string and bring a strong magnet near it, it will pull towards the magnet. Oxygen is a diatomic gas, with a double bond, so that's four valence electrons used up between two atoms. That leaves two unbonded pairs of electrons on each atom (oxygen is 1s2,2s2,2p2 = 6, but a full 1 and 2 shell is 8 electrons). And unbonded pairs give fun electric behaviour, like paramagnetism. There's hundreds, if not thousands of compounds and materials with paramagnetic behaviour, just because certain electron configurations allow for it.

With iron and iron alloys specifically, magnetism is a function mostly of how much body centred (alpha- and delta- ferrite, or alpha- or epsilon- martensite) crystal there is there. Austenite does have a Curie point, but it's so far below zero you're essentially never going to see it, and some austenitic steels are metastable, so they transform to martensite long before they get that cold anyways. A magnet would give you some feel for how much of various crystal structures you had in your sample, but 50% martensite-50% ferrite is basically the same no matter what it's composition (within reason*), and the same for x% austenite-y% ferrite-z% martensite microstructures.

* Discounting strange alloys with huge amounts of cobalt, aluminium, tungsten, nickel and carbon, 'cause they were bred for magnetism and pretty much suck at being engineering alloys.

Scooper

The original Spot Rot gauge sold for about $12 IIRC, but it hasn't been available for several years. The company that made them now sells the "PRO Gauge II" that is advertised as reading paint or powder coat thickness directly from .001" to .015" with an accuracy of ±.001". It sells for $80 instead of $12, though (a bit too expensive IMHO).

PRO Gauge II

Road Fan

Ok, but isn't iron the most ferromagnetic element, especially per dollar? So much so that for practical purposes (transformer and inductor design, lifting magnets, usefulness of permanent magnets) the others are not significant players in the marketplace, and that if a steel tube is responding to a magnet, it's mainly due to the Fe, not the Ni.

Falanx

Absolutely. 953 is only ~10% nickel, so the 75% iron in the alloy is the source of most of the energy product. My statement concerned the crystallography, not the composition of the steel.

bsektzer

FWIW, gaseous oxygen is paramagnetic too. There are medical oxygen analyzers that use this property to determine the % of oxygen in a gas sample.

long john

wow

Falanx

I did say that earlier :-p