Iron content in "Alloy-steel" bolts?

chicagomoon · Aug 8, 2019

Hey guys,

I know this is a bit of an odd question. For one of my projects, I need to make a very efficient electromagnet (actually a dozen of them). Everything I've read says that the electromagnet should have an "Iron Core" and that other core materials don't work nearly as well.

I want to use an off-the-shelf M4 or M5 bolt for this. On mcmaster-carr there are a lot of different options for bolts. Actually now that I drill down into the specs, it seems like the finish/treatment is different and there's really only two different ones in the sizes I require:

Material Black-Oxide Alloy Steel
Fastener Strength Grade/Class Class 12.9
Tensile Strength 170,000 psi
Hardness Rockwell C37

Material Black-Oxide Alloy Steel
Fastener Strength Grade/Class Class 8.8
Hardness Rockwell C20
Tensile Strength 110,000 psi

Does the class, hardness or tensile strength give any indicators on the actual composition of these fasteners? Now that I realize there's only 2 different ones, I should probably just order both and use the one that works better eh?

thermite · Aug 8, 2019

chicagomoon said:
Hey guys,

I know this is a bit of an odd question. For one of my projects, I need to make a very efficient electromagnet (actually a dozen of them). Everything I've read says that the electromagnet should have an "Iron Core" and that other core materials don't work nearly as well.

I want to use an off-the-shelf M4 or M5 bolt for this. On mcmaster-carr there are a lot of different options for bolts. Actually now that I drill down into the specs, it seems like the finish/treatment is different and there's really only two different ones in the sizes I require:

Material Black-Oxide Alloy Steel
Fastener Strength Grade/Class Class 12.9
Tensile Strength 170,000 psi
Hardness Rockwell C37

Material Black-Oxide Alloy Steel
Fastener Strength Grade/Class Class 8.8
Hardness Rockwell C20
Tensile Strength 110,000 psi

Does the class, hardness or tensile strength give any indicators on the actual composition of these fasteners? Now that I realize there's only 2 different ones, I should probably just order both and use the one that works better eh?

You should "probably just order" the "I" section of proper Silicon-Iron alloy stampings as used to close the open side with "E" shaped laminations for building proper transformer cores. They are in the market. Bobbins and wire as well. Even ready-made goods that only need the wires connected.

The way you are headed, the product will be a "very inefficient electromagnet" and an even less efficient HEATER, as it will try to do some of each. Successfully, even.

"Very efficient electromagnets" BTW.. use superconductors. Unfortunately, not yet the "room temperature" ones. CERN's Large Hadron Collider uses them:

LHC Magnet Program | Superconducting Magnet Division

Either settle for commercial goods. Or figure out how to go away and get really, really RICH first to fund yer dream! That could be fun. More fun than messing with bolt-magnets even.

Especially if you can DO it! The wealth. Not the bolts.

Milland · Aug 8, 2019

You really should use something like this: Soft Iron Rod | $3.99

Soft iron is typically used for the cores of electromagnets, and the link above is even the right OD for your needs. If you really need it threaded you can add M5 threads to the OD.

Limy Sami · Aug 8, 2019

A little tip (born of years of experience) for the OP, …...unless its for some obscure reason, use off the shelf parts & material, don't try and re-invent the wheel.

thermite · Aug 8, 2019

Limy Sami said:
A little tip (born of years of experience) for the OP, …...unless its for some obscure reason, use off the shelf ^^^ New, Old Stock, surplus ^^^ parts & material, don't try and re-invent the wheel.

Really.

We live in SUCH a technical society, the cast-offs and leftovers are a treasure for DIY re-purposing on the cheap of components one can usually download a spec sheet for from some online source. Not a lot of research needed to know in advance what will work, and how well. Because it already has done.

Limy Sami · Aug 8, 2019

As usual, Thermite put it better than I.

thermite · Aug 8, 2019

Limy Sami said:
As usual, Thermite put it better than I.

Routine teamwork.

Thank John Hookham Frere, PC.

Our North Atlantic link has even been set to music. Cue John Philip Sousa; "Hands Across The Sea".

YouTube

Caveat: Often LOUD music, actually... but PM is good with that, too!

jim rozen · Aug 8, 2019

chicagomoon said:
Hey guys,

I know this is a bit of an odd question. For one of my projects, I need to make a very efficient electromagnet ...

For a merely very efficient electromagnet either of those bolts will work. If you want a super-duper magnet then
probably do a cursory wikipedia search on magentic properties of materials.

Efficiency might be how rapidly and inexpensively you can make one of these. Quick trip to HD for inexpensive
steel bolts and wire....

crossthread · Aug 8, 2019

"Very efficient" is pretty relevant here. You can make a fairly good magnet with any piece of steel regardless of alloy. How "very efficient" do you need it to be? When I was a kid we made electromagnets out of old horseshoes. If you think you may have a bar with high iron content, you can hold it in one hand oriented North and South and hit the end hard with a hammer. It should attract a compass needle.

johnoder · Aug 8, 2019

Iron Content

Lets say 0.4% carbon, 1.5% manganese, 0.2% moly and 0.9% chromium

The rest is iron - 97 % - or near that

chicagomoon · Aug 8, 2019

johnoder said:
Lets say 0.4% carbon, 1.5% manganese, 0.2% moly and 0.9% chromium

The rest is iron - 97 % - or near that

Thanks for the answers so far guys. Basically I don't want to have an electro-magnet that could have been twice as powerful if I just chose a different bolt for the core. If it's a +/- 10-20% difference, I don't care.. but if it's orders of magnitude difference, then I'd like to be using the right stuff.

So the Soft Iron rod posted by Milland is 1008 Carbon Steel = ~99.5% Iron content. If my Alloy Steel bolt is ~97.5% Iron.. am I in the same ballpark?

thermite · Aug 8, 2019

crossthread said:
"Very efficient" is pretty relevant here. You can make a fairly good magnet with any piece of steel regardless of alloy. How "very efficient" do you need it to be? When I was a kid we made electromagnets out of old horseshoes. If you think you may have a bar with high iron content, you can hold it in one hand oriented North and South and hit the end hard with a hammer. It should attract a compass needle.

Bandages as well, my damned luck.

crossthread · Aug 8, 2019

Thermite....you've got to learn to control yourself.

Milland · Aug 8, 2019

crossthread said:
Thermite....you've got to learn to control yourself.

It's fascinating how he goes off at the least little spark. He should have changed his name to Tungsten. It's hard, brittle, and dense...

thermite · Aug 8, 2019

Milland said:
It's fascinating how he goes off at the least little spark. He should have changed his name to Tungsten. It's hard, brittle, and dense...

NFW!

Osmium.... yah cheapskate.

YouTube

NRDock · Aug 8, 2019

One should guess that lower strength bolts will contain less of the alloying elements that contribute to higher strength.

Milland · Aug 8, 2019

thermite said:
NFW!

Osmium.... yah cheapskate.

YouTube

Hey, I did a whole treatise on osmium a week or so ago: Material for counterwieht post #46

thermite · Aug 8, 2019

Milland said:
Hey, I did a whole treatise on osmium a week or so ago: Material for counterwieht post #46

"Treatist" are ye, now?

Rather suspected there was sumthin' Bolsheviki-flavoured 'bout yer political gleanings!

Mind, that post was right frugal compared to "Free Bankruptcy for all" as is lately being touted as the next best HealthScare plan.

First imtro to Osmium was on phonograph needle tips, 78 RPM era, then fountain pen nib tips.

But that latter one was just on paper...

Milland · Aug 8, 2019

thermite said:
"Treatist" are ye, now?

Rather suspected there was sumthin' Bolsheviki-flavoured 'bout yer political gleanings!

I lean left, but dress right...

thermite · Aug 8, 2019

Milland said:
I lean left, but dress right...

Back before it became so very-damned polically incorrect, even African Americans had been know to trap black agitators in cruelly confined spaces. Worse -give them food and water as seldom as but once a week - worse-yet - try to shift the blame and shame of it onto transgendered folk.

"Speed Queen" label on our one, back in the day.

Gone to agitating Hispanics more recently with a "Cabrio" label on the current one. No visible agitator either. The movement patiently works its way up from the bottom, reliably accomplishes its goals with minimal fuss, almost never gets out of balance even under rude overloading.

Iron content in "Alloy-steel" bolts?

Plastic

Diamond

Diamond

Diamond

Diamond

Diamond

Diamond

Diamond

Titanium

Diamond

Plastic

Diamond

Titanium

Diamond

Diamond

Cast Iron

Diamond

Diamond

Diamond

Diamond

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